Both a new modeling approach and new experimental data for the sediment build-up in centrifuges are presented. In semibatch apparatus, the suspension is continuously fed to the centrifuge, separating the particles inside the rotor and discharging the clarified liquid. The solid phase is removed once the capacity of the centrifuge is reached. The solids fraction of the sediment depends on the rheological properties of the cake. The sediment growth and consolidation throughout the process can be calculated using a pseudo two-dimensional approach that takes into account particle-size dependent settling, sediment compressibility, the centrifugal force field, and the geometry of the bowl. The predictions of the separation behavior and the particle-size distributions of the sediment and overflow are compared with experimentally obtained results, showing improved accuracy when compared to simpler models. The model presented is applicable to all solid-bowl centrifuges without conveying systems. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Highly crystalline exfoliated MFI-nanosheets can pave the way for large-scale deployment of sub-500-nm zeolite membranes due to their processing and packing advantages. Exfoliated MFI-nanosheets prepared by melt compounding contain a large amount of polymer and unexfoliated particles which are detrimental to the fabrication of ultrathin zeolite membranes. Complete removal of polystyrene from the nanosheet suspension in toluene is demonstrated by centrifugation of the suspension across chlorobenzene as confirmed by thermogravimetric analysis (TGA) data and transmission electron microscopy (TEM) images. Rate-zonal centrifugation in a nonlinear density gradient fractionated exfoliated MFI-nanosheets from unexfoliated particles. The purified nanosheets were highly crystalline as indicated by high-resolution TEM (HRTEM) and electron diffraction (ED). Coating of purified MFI-nanosheets on a smooth α-alumina support, fabricated by filtration of α-alumina suspension, led to a compact, b-oriented, 80-nm-thick film. A mild hydrothermal treatment of the film led to a 200-nm-thick membrane, which demonstrated molecular sieving properties. © 2013 American Institute of Chemical Engineers AIChE J, 2013

5-hydroxymethylfurfural (HMF) can be produced from the acid-catalyzed dehydration of fructose, but its yield is limited due to subsequent HMF degradation to side products. A reactive adsorption process is proposed to improve the yield to HMF. Separate experimental single-component isotherms of fructose, HMF, formic acid, and levulinic acid on carbon BP2000 and reaction kinetics of the fructose dehydration to HMF in aqueous solution of HCl are presented to develop empirical isotherms and kinetic rate constants, respectively. These submodels are subsequently integrated in an adsorptive reactor at a range of temperatures (100–150^°C) with different loadings of adsorbent. It is shown that the adsorbent improves HMF yield compared to the single-solution phase (adsorbent-free case). Low temperatures and high-adsorbent loadings improve HMF yield. Under certain conditions both reactive adsorption and the commonly used reactive extraction can result in a similar improvement in HMF yield. HMF recovery from the solid adsorbent has been identified as a major challenge that can be ameliorated through adsorbent and solvent selection. The framework outlined here can be applied to any aqueous phase chemistry where the desired product is an intermediate in a reaction cascade. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The design of an effective plant-wide control strategy is a key challenge for the development of future continuous pharmaceutical processes. This article presents a case study for the design of a plant-wide control structure for a system inspired by an end-to-end continuous pharmaceutical pilot plant. A hierarchical decomposition strategy is used to classify control objectives. A plant-wide dynamic model of the process is used to generate parametric sensitivities, which provide a basis for the synthesis of control loops. Simulations for selected disturbances illustrate that the critical quality attributes (CQAs) of the final product can be kept close to specification in the presence of significant and persistent disturbances. Furthermore, it is illustrated how selected CQAs of the final product can be brought simultaneously to a new setpoint while maintaining the remaining CQAs at a constant value during this transition. The latter result shows flexibility to control CQAs independently of each other. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A tubular ceramic-based multilayer composite nanofiltration membrane has been developed for dye desalination. Poly(acrylic acid)(PAA)/poly(vinyl alcohol)(PVA)/glutaraldehyde(GA) was dynamically assembled on to the inner surfaces of tubular ceramic microporous substrates which had been pretreated using dynasylan ameo silane coupling agents. Subsequently, the composite membranes were thermally crosslinked to form covalent ester bonds. Experimental results proved that the composite membrane had good nanofiltration performance for dye desalination. The (GA/PVA/PAA)₃/ceramic multilayer membrane shows over 96% retention of Congo red and less than 3% NaCl retention using a permeate flux of about 25 L/(m²·h). An investigation of membrane performance as a function of operating conditions suggested that the covalent crosslinking multilayer membrane possessed much higher stability compared to other, electrostatically assembled, multilayer membranes. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A new framework to automate, augment, and accelerate steps in computer-aided molecular design is presented. The problem is tackled in three stages: (1) composition design, (2) structure determination, and (3) extended design. Composition identification and structure determination are decoupled to achieve computational efficiency. Using approximate group-contribution methods in the first stage, molecular compositions that fit design targets are identified. In the second stage, isomer structures of solution compositions are determined systematically, and structure-based property corrections are used to refine the solution pool. In the final stage, the design is extended beyond the scope of group-contribution methods by using problem-specific property models. At each design stage, novel optimization models and graph theoretic algorithms generate a large and diverse pool of candidates using an assortment of property models. The wide applicability and computational efficiency of the proposed methodology are illustrated through three case studies. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Selective capture of H₂S from gas mixture is essential to reduce its undesirable high corrosiveness and toxicity. Ionic liquids have been proposed as a promising material, and there is a need to clarify the capture mechanisms and search for optimal combination of cation and anion for application. This work aims to elucidate the interactions between H₂S and nonfluorous imidazolium ionic liquids (NIILs) at a molecular level. The effects of hydroxyl group on the tail of alkyl chain, and combinations of imidazolium cations and nonfluorous anions on H₂S capture are explored using quantum chemistry calculations. Furthermore, molecular dynamics simulations are used to explore the microstructural features of NIIL–H₂S–CH₄ mixture systems. It is found that the hydroxyl groups in the cations is essential in governing the absorption properties of NIILs, including the interaction sites for hydrogen bonding, interaction geometries and energies, diffusion coefficients, and organization of H₂S and CH₄ around cations and anions. A molecular viewpoint to design appropriate ionic liquids for promoting their applications for H₂S capture is provided. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A process integration approach has been applied to integrate a traditional steelmaking plant with a polygeneration system to increase energy efficiency and suppress carbon dioxide emissions from the system. Using short-cut models and empirical equations for different units and available technologies for gas separation, methane gasification, and methanol synthesis, a mixed integer nonlinear model is applied to find the optimal design of the polygeneration plant and operational conditions of the system. Due to the complexity of the blast furnace (BF) operation, a surrogate model technique is chosen based on an existing BF model. The results show that from an economic perspective, the pressure swing adsorption process with gas-phase methanol unit is preferred. The results demonstrate that integration of conventional steelmaking with a polygeneration system could decrease the specific emissions by more than 20 percent. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Novel glucose-sensitive systems for the release of insulin from poly(diethylaminoethyl methacrylate) (PDEAEM) microparticles and nanoparticles decorated with glucose oxidase and catalase enzymes have been developed. The effect of polymer composition and loading conditions on the insulin loading efficiency and release was studied. The optimal conditions for loading insulin into PDEAEM microparticles were found to be at a loading pH of 5.6, particle to insulin mass ratio of 7:1, a concentration of 1.0 mg/mL insulin, and a collapsing pH of approximately 9.5. Microparticles exhibited a responsive (pH) or intelligent (glucose) release of insulin from a stimulus. Microparticles that had a nominal crosslinking ratio of 10% released a third of the insulin payload after a single stimulus, compared to nearly 70% for microparticles with a 3% crosslinking ratio. PDEAEM microparticles of 150 μm diameter showed promise as components of a system of automated, intelligent delivery method for insulin to type I diabetics. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The design of fragranced products is a combination of art, technology, and scientific knowledge, although the former still predominates in the industry. For that reason, a theoretical model to assess their performance considering the release and diffusion together with the predicted odor intensity over time and distance from the source was developed and validated. Diffusion profiles were experimentally measured in a diffusion tube, similar to the Stefan tube, and predicted with a model for pure fragrance chemicals, binary, quaternary, and multicomponent (11 chemicals) mixtures. A very good agreement between our purely predictive model and experimental concentration data was observed. Fragrance concentrations in air were then converted into odor intensities using models from psychophysics, making it possible to evaluate the evolution of the odor with time and distance using a performance plot. Accordingly, the performance of these mixtures was modeled and experimentally validated, which constitutes a landmark for fragrance design. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Hydrophobic zeolites, including Ti- and Sn-beta, have been found to adsorb and isomerize glucose into fructose. An experimental question has been the significance of the entropic contribution to the free energy of transfer of glucose from solution to zeolite. We here perform Gibbs ensemble Monte Carlo calculations to quantify the enthalpy, entropy, and free energy of transfer of glucose from the aqueous phase to the zeolite phase. We find that the entropic contribution is large and positive, nearly compensating for an unfavorable enthalpy of transfer in all-silica zeolite beta. A significant component of the positive entropy of transfer from the aqueous phase to zeolite is the unstructuring of first coordination shell waters around glucose as it leaves the solution. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

Ordered mesoporous carbons (OMCs) were used as supports to prepare Wacker-type catalysts for diethyl carbonate (DEC) synthesis by oxidative carbonylation of ethanol in a gas-phase reaction. The effect of support structure on the dispersion of the active species and catalytic properties were investigated. Nitrogen sorption, X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the active components have encapsulated in pore channels of OMCs. Characterizations of the catalysts, such as TEM, scanning electron microscope (SEM) and XRD, indicated that active components supported on OMCs have better dispersion compared to activated carbon (AC). The ethanol conversion of the catalysts was improved by ∼65% using OMCs as the catalyst support than AC. The stability of the catalytic activity can also be enhanced through surface modification of OMCs. Surface oxygen-containing groups (OCGs) on OMCs before and after surface modification were characterized by transmission IR spectra and the Beohm titration. The relationship between surface OCGs and anchor ability of OMCs was studied. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

The development of a novel composite two-phase method to predict the thermodynamic physical properties of carbon dioxide (CO₂) above and below the triple point, applied herein in the context of Reynolds-Averaged Navier–Stokes computational modeling has been detailed here. A number of approaches have been combined to make accurate predictions in all three phases (solid, liquid, and gas) and at all phase changes for application in the modeling of releases of CO₂ at high pressure into the atmosphere. Predictions of a free release of CO₂ into the atmosphere from a reservoir at a pressure of 10 MPa and a temperature of 283 K, typical of transport conditions in carbon capture and storage scenarios, is examined. A comparison of the results shows that the sonic CO₂ jet that forms requires a three-phase equation of state including the latent heat of fusion to realistically simulate its characteristics. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

A novel efficient agent-based method for scheduling network batch processes in the process industry is proposed. The agent-based model is based on the resource-task network. To overcome the drawback of localized solutions found in conventional agent-based methods, a new scheduling algorithm is proposed. The algorithm predicts the objective function value by simulating another cloned agent-based model. Global information is obtained, and the solution quality is improved. The solution quality of this approach is validated by detailed comparisons with the mixed-integer programming (MIP) methods. A solution close to the optimal one can be found by the agent-based method with a much shorter computational time than the MIP methods. As a scheduling problem becomes increasingly complicated with increased scale, more specifications, and uncertainties, the advantages of the agent-based method become more evident. The proposed method is applied to simulated industrial problems where the MIP methods require excessive computational resources. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

A new methodology that includes process synthesis and control structure decisions for the optimal process and control design of dynamic systems under uncertainty is presented. The method integrates dynamic flexibility and dynamic feasibility in a single optimization formulation, thus, reducing the costs to assess the optimal design. A robust stability test is also included in the proposed method to ensure that the optimal design is stable in the presence of magnitude-bounded perturbations. Since disturbances are treated as stochastic time-discrete unmeasured inputs, the optimal process synthesis and control design specified by this method remains feasible and stable in the presence of the most critical realizations in the disturbances. The proposed methodology has been applied to simultaneously design and control a system of CSTRs and a ternary distillation column. A study on the computational costs associated with this method is presented and compared to that required by a dynamic optimization-based scheme. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

Quantitative methods for individualizing and optimizing the dosage regimen and clinically monitoring each patient are desirable to insure that each patient can obtain effective therapeutic benefit while minimizing undesirable side effects. This is of special concern for medicines that are expensive or whose toxic side effects are severe (e.g., oncological agents). The optimal dosage regimen for an individual is a combination of dose amount and/or dosing interval (i.e., time between doses) which minimizes the risk that the drug exposure deviates from the desired therapeutic window. The therapeutic window is defined as the range of drug exposure (e.g., blood concentration, area under the curve concentration-time) which is below a threshold defining an acceptable toxic side effect and above a threshold defining a minimum acceptable level of therapeutic efficacy. In this work, the dosage regimen optimization problem defined in terms of general pharmacometric models (i.e., described by differential-algebraic equations) is presented and a solution approach outlined which uses a scenario-based stochastic optimization formulation that minimizes a risk metric. The scenarios are derived from the posterior joint probability distribution of the individual's pharmacometric parameters which is obtained following an approximate Bayesian inference approach. A Smolyak rule is used for the selection of the scenarios (i.e., combination of pharmacometric parameters) to be considered and for computing the approximation to the risk metric. Two case studies, gabapentin and cyclophosphamide, are presented to elucidate the advantages and limitations of the proposed approach. The numerical results demonstrate that low risk optimal solutions can be generated via the proposed stochastic optimization; while significantly reducing the computational burden in comparison with the conventional Markov chain Monte Carlo—grid search approach. This partially alleviates implementation issues preventing the deployment of dosage regimen individualization in clinical practice. Since stochastic optimization has been extensively used in other domains, the approach for uncertainty characterization proposed in this work may have general relevance beyond the pharmacometrics domain. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

The spectral properties of the discrete and continuous convection and convection-diffusion operators with loop or recycle boundary condition are analyzed. It is shown that the spectral properties of these nonsymmetric operators are closely related to the theory of circulant (Toeplitz) matrices and the complex Fourier series, respectively. Although there may be many complex eigenvalues, the smallest eigenvalue is real and approaches zero as the loop circulation or recycle ratio increases. This property is used to simplify nonlinear diffusion-convection-reaction models of loop and recycle reactors to obtain two-mode low-dimensional averaged models that are accurate in the limit of large recycle ratio. Explicit expressions for the two mixing coefficients that relate the two concentration modes and their dependence on various inlet conditions are also derived. Finally, the application of the low-dimensional models to determine the impact of macromixing on the conversion, yield, and selectivity for the case of nonlinear kinetics is illustrated. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Conditional volume averaging is used to develop a model capable of simulating two-phase flows of viscoelastic fluids with surface tension effects. The study is started with the single-phase mass and momentum balances, which are subsequently conditionally volume averaged. In doing so, In doing so, we arrive at a set of equations having unclosed interfacial terms, for which closure relations for viscoelastic fluids are presented. The resulting equations possess a structure similar to the single-phase equations; however, separate conservation equations are solved for each phase. As a result, each phase has its own pressure and velocity over the entire domain. Next, our numerical implementation is briefly outlined. We find that a Poiseuille single-phase flow is predicted correctly. The closure terms are examined by considering a two-phase shearing flow and a quiescient cylinder with surface tension. A convergence analysis is performed for a steady stratified two-phase flow with both phases being viscoelastic. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Expanding the chemical diversity of microbial fermentation products enables green production of fuel, chemicals, and pharmaceuticals. In recent years, coenzyme A (CoA) dependent chain elongation, resembling the reversed β-oxidation pathway, has attracted interest for its use in producing higher alcohols, fatty acids, and polyhydroxyalkanoate. To expand the chemical diversity of this pathway, we metabolically engineered Escherichia coli to produce 2-pentanone, which is not a natural fermentation product of E. coli. We describe the first demonstration of 2-pentanone synthesis in E. coli by coupling the CoA-dependent chain elongation with the acetone production pathway. By bioprospecting for enzymes capable of efficient hydrolysis of 3-keto-hexanoyl-CoA, production of 2-pentanone increased 20 fold, reaching a titer of 240 mg/L. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A novel method to simultaneously simulate particle motion and its breakage in a dry impact pulverizer was developed. The motion of particles in the pulverizer was calculated using a discrete phase model (DPM)-computational fluid dynamics (CFD) coupling model. When the particle impacts against a vessel wall, impact stress acting on the particle is calculated from Hertz's theory as a function of the impact velocity. At the same time, the particle strength as a function of the particle size is calculated from Griffith's theory. If the impact stress is larger than the particle strength, the particle is broken and replaced with smaller fragments. The size distribution of the fragments is obtained from a breakage function proposed. The motion of the fragments is calculated again by using the DPM-CFD coupling model. By repeating the above calculations over the whole particles, the grinding phenomenon can be simulated. The calculated results showed good agreement with the experimental one, and validity of the proposed method was confirmed. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The optimization of the composition of the algae for the simultaneous production of bioethanol and biodiesel is presented. We consider two alternative technologies for the biodiesel synthesis from algae oil, enzymatic or homogeneous alkali catalyzed that are coupled with bioethanol production from algae starch. In order to determine the optimal operating conditions, we not only couple the technologies, but simultaneously optimize the production of both biofuels and heat integrate them while optimizing the water consumption. Multi-effect distillation is included to reduce the energy and cooling water consumption for ethanol dehydration. In both cases, the optimal algae composition results in 60% oil, 30% starch, and 10% protein. The best alternative for the production of biofuels corresponds to a production price of 0.35 $/gal, using enzymes, with energy and water consumption values (4.00 MJ/gal and 0.59 gal/gal). © 2013 American Institute of Chemical Engineers AIChE J, 2013

Simulations and experiments were carried out to explore the solvent extraction of ethanol from aqueous solution using a series of seven 10-carbon alcohols. It is shown that configurational-bias Monte Carlo simulations in the Gibbs ensemble coupled with the TraPPE-UA force field can be utilized for predictive screening of the different extraction abilities (in terms of capacity factor and selectivity) of these alcohols. Analysis of the simulation trajectories indicates that extraction capacity is connected to the stabilization of larger ethanol/water cluster in the organic solvent, whereas selectivity is improved when smaller ethanol/water clusters are more prevalent. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A solution strategy for designing flexible process flow sheets with a large number of uncertain parameters is presented. The basic mathematical formulation is a two-stage stochastic program transformed into its multi-scenario deterministic equivalent. The main feature of the proposed approach is a tremendous reduction in scenarios to a smaller number of those critical ones. This reduction is achieved through simple sensitivity analyses that identify those uncertain parameters that are critical for feasibility and those that are involved in a stochastic approximation of the objective value. Through the application of this strategy, it is possible to solve the problems with several tens or even hundred uncertain parameters, assuming weak interactions between them. Feasible designs are obtained for a fixed degree of flexibility, while the expected objective function is approximated fairly well. The strategy is applied to two flow sheet examples. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The solubility of the major constituents of natural gas in ionic liquids (ILs) can be used to identify their potential for acid gas removal from a producing gas stream. We have developed models for the solubility of H₂S, CH₄, and C₂H₆ in ILs at typical conditions encountered in natural gas treatment. In this work, a conductor-like screening model for realistic solvation was used to predict the activity coefficients for solutes in ILs and a cubic EOS was used for vapor-phase corrections from ideality. Empirical correlations were developed to extrapolate solubilities where experimental data are not available at desired conditions; targeted in this study at 298.15 K and 2000 kPa. Over 400 possible ILs were ranked based on the higher selectivity of absorption of CO₂ and H₂S over CH₄ and C₂H₆. The best 15% (58) of promising ILs for sour gas treatment predominantly contain the anions BF₄, NO₃, and CH₃SO₄ and the cations N₄₁₁₁, pmg, and tmg. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The problem of driving a batch process to a specified product quality using data-driven model predictive control (MPC) is described. To address the problem of unavailability of online quality measurements, an inferential quality model, which relates the process conditions over the entire batch duration to the final quality, is required. The accuracy of this type of quality model, however, is sensitive to the prediction of the future batch behavior until batch termination. In this work, we handle this “missing data” problem by integrating a previously developed data-driven modeling methodology, which combines multiple local linear models with an appropriate weighting function to describe nonlinearities, with the inferential model in a MPC framework. The key feature of this approach is that the causality and nonlinear relationships between the future inputs and outputs are accounted for in predicting the final quality and computing the manipulated input trajectory. The efficacy of the proposed predictive control design is illustrated via closed-loop simulations of a nylon-6,6 batch polymerization process with limited measurements. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A modeling approach to identify sets of culture conditions to promote homogeneous growth of cells in perfusion bioreactors equipped with regular shape scaffolds is proposed. We identify cases in which dynamic culturing is necessary using a zero-dimensional mass transport and reaction model. Then, based on the three-dimensional (3-D) rendering of the flow field inside the bioreactor, we identify regions where cellular growth may become critical; finally, using a 1-D mass transport and reaction model, we calculate the minimal perfusion flow necessary to maintain the cellular growth rate above a target threshold. The developed approach is used to analyze culturing conditions inside an indirect perfusion bioreactor equipped with a lattice scaffold. Regions where the perfusion flow is inadequate to foster cellular growth at the desired rate are identified. The perfusion flow required to maintain the target growth rate inside the bioreactor is calculated. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Rigid particles transported through a pinched-flow fractionation (PFF) device are simulated using boundary-integral methods (BIM). The PFF device separates particles by size using a bifurcated microfluidic channel. The critical flow ratio of the two input channels required to achieve complete separation of large and small particles decreases with increasing diameter of the larger particles relative to the pinch height, and is nearly independent of the smaller particle size. A narrow pinch with a square exit was shown to have the lowest critical flow ratio and was selected as the model device to be fabricated. Experiments conducted using this device confirm that the larger particles exit further from the top wall than do the smaller particles, due to steric exclusion, and the final exit positions are within a few percent of the simulation results. It is shown that BIM is a valuable tool in the design of microfluidic devices. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A stochastic formulation for the description of cooling-antisolvent mediated crystal growth processes based on the Fokker-Planck equation is discussed. Previous results are further extended to include not only the additional degree of freedom (temperature) in the approach, but also to formulate the model parameters dependencies with the input manipulated variables (antisolvent flow rate and temperature) toward a global model to be used within all possible operating regimes. The obtained global models are used to define, for the first time, an operating map of the crystallization process, where asymptotic isomean and isovariance curves are reported in an antisolvent flow-rate-temperature plane. Input multiplicities are identified and validated both numerically and experimentally for the NaCl-water-ethanol nonisothermal antisolvent crystallization system. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Microbioreactors with multioptical sensors have become increasingly important because of their small working volumes, high degree of parallelization and the available robotics. A novel hydrophobic luminescent copolymer P(Pt-TPP-TFEMA) along with reference P(Pt-TPP-EMA) containing the pendant group of 5,10,15,20-tetraphenylporphyrin (TPP) moiety as low-cost dissolved oxygen (DO) chemosensor film for high-throughput microbioreactors is designed. Its sensor film exhibits fast response to DO with good stability and fatigue resistance, being capable of applying as a low-cost DO indicator for high-throughput bioprocess measurement. Results show that the quenching response of DO increases with the enhancement in the copolymeric hydrophobicity using the presented hybrid fluorinated ethyl methacrylate. Furthermore, the long emission band at 650 nm of chromophore TPP with large Stoke's shift about 250 nm brings several advantages, such as low scattering, deep penetration, and minimal interferences of absorption and fluorescence from the fermentation system, which shows high-promising application in bioprocess monitoring. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Excellent desulfurization is achieved via reactive adsorption using Friedel-Crafts acylation materials, that is, acylating reagents and Lewis acids, such as acetyl chloride (AC) and AlCl₃, being named as acylation desulfurization (ACDS). For model oil, thiophenic compounds, namely, dibenzothiophene, benzothiophene, and thiophene, are removed completely by AC–AlCl₃ within 30 min at room temperature. In this process, thiophenic compounds are acylated by AC under the catalysis of AlCl₃, and the acylated derivatives are stronger base than original ones due to incorporation of O-containing carbonyl group (CO) and, thus, adsorbed more easily by AlCl₃ via Lewis acid–base complexation. Further, ACDS mechanism is identified by acylated product characterization and quantum chemistry calculation. Satisfactorily, ACDS is still effective for toluene-rich and real oils, and real oil quality is improved with desulfurization proceeding. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The vapor recompression (VRC) distillation scheme is examined and compared with conventional distillation in an analysis spanning fundamental thermodynamics, high-level calculations, and rigorous simulation. The purpose of this article is three-fold: first, it provides greater insight into VRC distillation. Second, it provides a process synthesis tool to rapidly assess whether VRC is likely to be more thermodynamically favorable than conventional distillation for a given split. Third, it may be used to determine if VRC can be implemented practically. The tool presented in the article is consolidated in the form of a single chart, for which only the top and bottom product temperatures are required to determine the outcome. Using this chart, first-pass estimates can be obtained with no calculations whatsoever. The tool, which appears to be the first of its kind in this context, is validated with examples and rigorous simulation. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The evaluation of foam and spray granulation mechanisms and their performances in achieving uniform liquid distribution in a high-shear mixer-granulator is presented. A regime map is presented to describe the granulation mechanisms for the foam and spray systems. Foam and spray granulation are shown to successfully create granules of well-distributed moisture at the end of wet massing despite there was a deviation from the theoretical moisture content at the end of binder addition. In the wetting and nucleation regime, spray granulation involves drop penetration nucleation outside of the drop-controlled regime, whereas foam granulation operates favorably in the mechanical dispersion regime. For foam granulation, mechanical dispersion produces more uniform granule-size distributions below the overwetting limit. Spray granulation exhibits steady granule growth, whereas foam granulation shows induction granule growth followed by rapid granule growth. The regime map provides a basis to customize formulations and compare the different foam and spray granulation mechanisms. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Platinum-deposited titanium nitride (Pt/TiN) nanoparticle aggregates with high porosities were successfully prepared via a self-assembly-assisted spray pyrolysis method. The addition of formic acid (HCOOH) had a significant influence on the process, promoting the simultaneous formation of metallic Pt and reduction on the surface of the TiN support material. Complete reduction of the Pt/TiN nanoparticle aggregates improved the catalytic activity. The electrochemical surface area (ECSA) of Pt/TiN with HCOOH (Pt/TiN_w/HCOOH) was 87.15 m²/g-Pt, which was higher than that of Pt/TiN without HCOOH (Pt/TiN_w/o-HCOOH). The catalytic durability of Pt/TiN_w/HCOOH was twice that of Pt/TiN_w/o-HCOOH. An effective strategy for obtaining carbon-free catalysts with high activities and durabilities was identified. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Porous electrode theory was used to model performance of the convection battery using lithium iron-phosphate chemistry. The model results and underlying equations were able to quantify and extend previous interpretations of laboratory validation studies. These analyses substantiated the following conclusions on the performance of the convection battery: (a) flow in the convection battery can reduce concentration overpotentials by 99.9%, (b) both the ionic and electron conductivities of solid phases can have a major impact on convection battery performance, and (c) the solid-phase ionic conductivity of a porous separator is an important design parameter and is not considered by porous electrode theory as published to date. In view of the ability of the convection battery to overcome both bulk diffusion and liquid-phase effective conductivity limitations; the convection battery has an unprecedented potential to redefine the performance of large batteries. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

In this contribution, the direct vapor recompression approach is introduced in a batch distillation operated at an unsteady state condition. This vapor recompressed batch distillation (VRBD) accompanies an isentropic compressor that runs at a fixed as well as variable speed. Aiming to ensure the optimal use of internal heat source, an open-loop control policy is proposed for the VRBD that adjusts either the overhead vapor splitting or the external heat supply to the reboiler. Again, the variable speed VRBD additionally involves the manipulation of compression ratio. Developing two alternative configurations of VRBD column, the best heat integrated scheme is attempted to identify in the aspects of energy efficiency and total annualized cost for further advancement. A closed-loop control algorithm for the best performing variable speed VRBD aiming to meet the end objective of relatively high-purity product discharged at a constant composition is developed. The separation of a reactive system is considered to illustrate these results and demonstrate the effectiveness of the novel VRBD scheme. Performing simulation tests, it is investigated that the closed-loop control operation substantially improves not only the distillate purity but also the total amount of product. Achieving significant improvement in thermodynamic efficiency and cost by the controlled heat integrated scheme over its conventional counterpart, finally the attractiveness of the VRBD column by investigating its potential to reduce the greenhouse gas (i.e., CO₂) emissions is shown. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A multi-scale approach with the combination of computational fluid dynamic (CFD) and macroscopic calculation methods has been proposed to predict the hydrodynamics behavior in the corrugated structured packing column. On the basis of the concept of the representative unit, the three-dimensional (3-D) volume of fluid (VOF) model of the structured packing is applied in the small scale simulation, and the stream split fraction coefficients and effective wetted area ratio are calculated. The unit network model, which is a mechanistic model, is applied in large scale calculation basing on the small scale results. The liquid holdup distribution in the entire column can be available by this multi-scale method. A comparison between the simulation results and the experimental data of our previous work is given to validate the present model. The multi-scale model is proved to be prospective to assist the analysis and design of structure packing columns in chemical engineering. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The dissolution of solid lime particles into liquid slags at high temperatures was evaluated by means of confocal scanning laser microscopy. An additional solid layer around the lime particle was observed at the intermediate stage of the dissolution into CaOAl₂O₃SiO₂ slags. The dissolution rate was decelerated due to the existence of the additional layer and the dissolution profile could be clearly distinguished into three stages, that is, an early, intermediate, and late stage. By adding 10 wt % MgO, this layer could be effectively eliminated and the slope of the whole dissolution profile kept relatively constant. The dissolution path and mechanisms were subsequently evaluated by incorporating thermodynamic calculations. Both direct and indirect dissolutions could be distinguished. It was realized that the decrease in composition range for solid precipitating after adding MgO could significantly reduce the interfacial reaction (IR) layer formation. Post-mortem analyses on quenched samples were further carried out to confirm the theoretical calculations. It was found that the solid layer in slags without MgO was (CaO)₂·SiO₂ and (CaO)₃·SiO₂ which is in line with the thermodynamic calculations. However, only (CaO)₂·SiO₂ was noticed in slags with MgO which both (CaO)₂·SiO₂ and MgO phases should be present according to the calculations. The nonequilibrium during dissolution may play an important role on phase transformation and MgO particles in much smaller quantity may have dissolved into (CaO)₂·SiO₂ phase. The diffusion of CaO in both slags with and without MgO was additionally investigated. The local CaO concentration distributions from the direct dissolution phase to the slag bulk could be well fitted with the theoretical model proposed via Fick's second law. As a result, the local diffusion coefficient in the dissolution region was obtained and the effect of MgO addition on diffusion could be assessed. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

An experimental examination of a novel device for enhancing the gas absorption into an aqueous absorbent flowing down the outer wall of a vertical cylinder was reported. This device utilizes flexible strings tightly wound around the cylinder, taking the form of a multiple helix. The absorbent flows along parallel channels partitioned by the strings, maintaining mutual contact with the surrounding gas for a longer time than it would when it flows down the same cylinder wall in the absence of such strings. Both flow-observation experiments and absorption experiments using water as the absorbent flowing along a single helical channel and carbon dioxide as the gas to be absorbed were carried out. The effectiveness of the helical-flow device for promoting the absorption was recognized at water flow rates high enough to induce an oscillatory flow mode accompanied by periodical liquid−gas interface deformation. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A novel mass-transfer intensified approach for CO₂ capture with ionic liquids (ILs) using rotating packed bed (RPB) reactor was presented. This new approach combined the advantages of RPB as a high mass-transfer intensification device for viscous system and IL as a novel, environmentally benign CO₂ capture media with high thermal stability and extremely low volatility. Amino-functionalized IL (2-hydroxyethyl)-trimethyl-ammonium (S)−2-pyrrolidinecarboxylic acid salt ([Choline][Pro]) was synthesized to perform experimental examination of CO₂ capture by chemical absorption. In RPB, it took only 0.2 s to reach 0.2 mol CO₂/mol IL at 293 K, indicating that RPB was kinetically favorable to absorption of CO₂ in IL because of its efficient mass-transfer intensification. The effects of operation parameters on CO₂ removal efficiency and IL absorbent capacity were studied. In addition, a model based on penetration theory was proposed to explore the mechanism of gas–liquid mass transfer of ILs system in RPB. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

We study the mixing structure, mixing performance, and short term dynamics in round bottomed laminar tanks agitated by an eccentrically located angled disc. We define eccentricity (E = e/R) as the ratio of the distance of the axis of rotation from the center line of the tank (e) and the tank radius (R). The structural and dynamic features observed at different eccentricity values were compared using planar laser-induced fluorescence techniques and computational fluid dynamics calculations. A Poincaré analysis demonstrates the chaotic nature of the flow induced by eccentricity. Practically globally chaotic conditions are observed for E = 0.42 and E = 0.50, with mixing times of 5–8 min at Re = 416. We study the effect of different injection points on the short-term mixing dynamics and we calculate axial flow rates and Power numbers. Stirred tanks agitated by an eccentrically located angled disc are a simple and cost effective system for laminar mixing applications. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

Fault-tolerant control methods have been extensively researched over the last 10 years in the context of chemical process control applications, and provide a natural framework for integrating process monitoring and control aspects in a way that not only fault detection and isolation but also control system reconfiguration is achieved in the event of a process or actuator fault. But almost all the efforts are focused on the reactive fault-tolerant control. As another way for fault-tolerant control, proactive fault-tolerant control has been a popular topic in the communication systems and aerospace control systems communities for the last 10 years. At this point, no work has been done on proactive fault-tolerant control within the context of chemical process control. Motivated by this, a proactive fault-tolerant Lyapunov-based model predictive controller (LMPC) that can effectively deal with an incipient control actuator fault is proposed. This approach to proactive fault-tolerant control combines the unique stability and robustness properties of LMPC as well as explicitly accounting for incipient control actuator faults in the formulation of the MPC. Our theoretical results are applied to a chemical process example, and different scenaria were simulated to demonstrate that the proposed proactive fault-tolerant model predictive control method can achieve practical stability and efficiently deal with a control actuator fault. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

A novel sulfonated polyphenylsulfone (sPPSU)/polyphenylsulfone (PPSU)-based dual-layer hollow fiber membrane with a nanometric thin skin layer has been designed for biofuel dehydration via pervaporation. The thickness of skin selective layer is in the range of 15–90 nm under different spinning conditions measured by positron annihilation spectroscopy (PAS) coupled with a mono-energetic positron beam. The effects of outer-layer dope properties, coagulation temperature, and dope flow rate during spinning were systematically investigated. By tuning these spinning parameters, a high performance sPPSU/PPSU-based dual-layer hollow fiber membrane with desirable morphology was successfully obtained. Particularly owing to its nanometric thin skin layer, a high flux of 3.47 kg/m²h with a separation factor of 156 was achieved for dehydration of an 85 wt % isopropanol aqueous solution at 50°C. After post thermal treatment at 150°C for 2 h, the separation factor was dramatically improved to 687 while flux dropped to 2.30 kg/m²h, which make it comparable to the inorganic membranes. In addition, excellent correlations were found among the results from field emission scanning electron microscopy, PAS spectra, and separation performance. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

The synthesis and application of bifunctional mesoporous Al-P-V—O catalysts with both acidic and redox sites for selective oxidation of methanol to dimethoxymethane (DMM) is described. The catalysts were characterized by N₂ adsorption/desorption, X-ray diffraction, temperature-programmed desorption, X-ray photoelectron spectroscopy, and infrared spectroscopy. It is shown that porosity; redox property and surface acidity of the catalysts were greatly influenced by the Al/V/P ratio. The synergistic effect of phosphorus and vanadium was investigated. Al-P-V—O catalysts exhibited good catalytic activity because of the controlled reducibility and the acidic sites. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

Reverse roll coating is probably the most widely used coating operation, much less investigated than its counterpart and inherently unstable forward roll coating. A new data to complement earlier work which was limited to large gaps and thus “thick” films is presented. The intention is to assess the feasibility of reverse roll coating to yield very thin films (<10 μm) at high speeds (>1 m/s) for application in the newer technologies, such as the production of solar cells and plastic electronics. The data obtained demonstrate this is possible but at the lowest permissible gap (25–50 μm) with low-viscosity fluids (∼7 mPa s). The study also developed a new understanding of how instabilities are controlled. It was seen that the size of the inertia forces generated by the applicator roller in relation to surface tension, as expressed by the Weber number and not the applicator Capillary number (viscous forces/surface tension) which is the critical parameter. © 2013 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2013

The design of adsorption-based separation processes using novel adsorbents requires reliable data for the adsorption of fluid mixtures on candidate adsorbents. Due to the difficulty of generating sufficient data across possible operating conditions, process designs generally rely on interpolation of pure-component data using a model, most commonly ideal adsorbed solution theory (IAST), and related theories. There are many cases where IAST fails to provide an adequate description of mixture adsorption, usually due to the fact that practical adsorbents do not have uniform surfaces. We have evaluated the use of a segregated version of IAST, where competition is assumed to occur at isolated adsorption sites. This simple modification can provide the correct description of adsorption across a large range of pressures using ideal isotherm models. We also demonstrate the importance of identifying multiple sites even for weakly adsorbing components to provide the correct behavior at high pressure. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A CFD model was developed with the aim at simulating the turbulent flow field induced by dust feeding and dispersion within the 20 L bomb, and the associated effects on the distribution of dust concentration. The model was validated considering a set of data (pressure time histories and root mean square velocity) available in the literature. The time sequences of velocity vector and kinetic energy maps have shown that multiple turbulent vortex structures are established within the sphere. These vortices generate dead volumes for the dust which is pushed toward the walls of the sphere. The obtained results are relevant to the practice of dust explosion testing and the interpretation of test results and, then, they should be taken as reference to improve the conditions for standard tests. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Ash-related problems are often the main reason for entrained-flow gasifiers and boilers unscheduled shut downs. Thus, understanding the high-temperature physical properties of molten coal ash slag may enable an accurate description of the condition of ash deposition in the gasifier and boiler. The evolution of the time dependence of rheological behaviors, including the viscosity and yield stress of the molten coal ash slag containing 0–35.51 vol % crystals at decreasing temperatures (1400–1280°C) and within 1.05 × 10⁵ s, were investigated. Non-Newtonian behaviors, including shear thinning, become obvious with an increasing crystal contents. The trends in the change of crystal nucleation rate in molten coal ash slag are similar with those of the growth rate. Finally, the experimental results and the crystal-size distribution method are used to develop a semiempirical parameterization that describes the complex non-Newtonian rheology of crystal-bearing molten coal ash slag. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Based on the Gibbs-Tolman-Koenig formalism, we considered the Tolman correction to the free energy barrier of bubble nucleation in polymer-gas binary mixtures. For this class of systems, the correction may be estimated with a reasonable accuracy using experimentally accessible macroscopic thermodynamic quantities only. Although the Tolman correction is applicable only in the low supersaturation regime, a simple ansatz regarding the supersaturation dependence of the Tolman length can be made to extend the usefulness of this approach and to yield the free energy barrier that vanishes at the mean-field spinodal as demanded by thermodynamic considerations. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A simple correction to the infinite dilution activity coefficient computed via molecular simulation for a nonelectrolyte solid solute in solution is proposed. The methodology adopts the concept that the activity coefficient may be fundamentally interpreted as a product of a residual and combinatorial term. The residual contribution is assumed to be insensitive to concentration, and the combinatorial term is modeled using the athermal Flory–Huggins theory. The proposed method uses only properties for the solute computed at infinite dilution to estimate solution-phase properties at finite concentrations. Properties of the pure solid solute are estimated using the group contribution method of Gani and coworkers, allowing for efficient blind solubility predictions to be made. The method is applied to predict the solubility of solid phenanthrene in 17 different solvents. For all cases, the combinatorial correction lowers the predicted solubility relative to the infinite dilution approximation, and in general, improves agreement with experiment. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The issue of chemical process optimization when at the operation stage the design specification should be met with some probability and the control variables can be changed has been considered. A common approach for solving the broad class of optimization problems with normally distributed uncertain parameters were developed. This class includes the one-stage and two-stage optimization problems with chance constraints. This approach is based on approximate transformation of chance constraints into deterministic ones. © 2013 American Institute of Chemical Engineers AIChE J, 2013

In this work, the modeling and control of a batch crystallization process used to produce tetragonal hen egg white lysozyme crystals are studied. Two processes are considered, crystal nucleation and growth. Crystal nucleation rates are obtained from previous experiments. The growth of each crystal progresses via kinetic Monte Carlo simulations comprising of adsorption, desorption, and migration on the (110) and (101) faces. The expressions of the rate equations are similar to Durbin and Feher. To control the nucleation and growth of the protein crystals and produce a crystal population with desired shape and size, a model predictive control (MPC) strategy is implemented. Specifically, the steady-state growth rates for the (110) and (101) faces are computed and their ratio is expressed in terms of the temperature and protein concentration via a nonlinear algebraic equation. The MPC method is shown to successfully regulate both the crystal size and shape distributions to different set-point values. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The effects of interactions between nonlinear subprocesses on the stabilizability of plantwide systems via the concept of dissipative systems are studied. Conditions for which controlled variables of each interconnected subprocess can be driven to and maintained at their desired values are established through the application of interconnection decoupling techniques. The resulting decoupling feedback law encodes the interaction effects between subprocesses and determines the required information structure for achieving desired control performance using distributed control laws. The proposed constructive approach leads to new criteria for the selection of manipulated and controlled variables that guarantee plantwide stability. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Theoretical modeling coupled with an experimental study is presented for the preparation and characterization comparison of the amphiphilic copolymers of 2, 2, 3, 3, 4, 4, 4-heptafluorobutyl methacrylate (HFBMA) and 2-hydroxyethyl methacrylate (HEMA) to achieve a multiscale generalization of the polymeric system. A series of amphiphilic copolymers having different chain structures with HFBMA as the hydrophobic component and HEMA as the hydrophilic component was first synthesized through atom transfer radical copolymerization (ATRcoP) or model-based semibatch ATRcoP. Theoretical modeling is used to optimize the macromolecular structure and experimental approaches that are used to prepare copolymers of HFBMA and HEMA with some tailor-made polymer properties. Furthermore, a systematic comparison of major properties (i.e., thermal, micellization, and surface properties) of these fluorinated copolymers (i.e., random, block, linear gradient, and inverse linear gradient copolymers) was carried out. The results show that these fluorinated copolymers with different chain structures have dissimilar properties. The results also demonstrate that the approach of coupling theoretical modeling with an experimental study can be used to guide a multiscale generalization of the polymeric system for practical application. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Direct interfacial molecular dynamics simulations are used to obtain the phase behavior and interfacial tension of CO₂–H₂O–NaCl mixtures over a broad temperature and pressure range (50°C ≤ T ≤ 250°C, 0 ≤ P ≤ 600 bar) and NaCl concentrations (1–4 mol/kg H₂O). The predictive ability of several existing water (SPC and TIP4P2005), carbon dioxide (EPM2 and TraPPE), and sodium chloride (SD and DRVH) models is studied and compared, using conventional Lorentz–Berthelot combining rules for the unlike-pair parameters. Under conditions of moderate NaCl molality (∼1 mol/kg H₂O), the predictions of the CO₂ solubility in the water-rich and CO₂-rich phase resemble those in the CO₂–H₂O system [Liu et al., J Phys Chem B. 2011;115:6629–6635]. Consistent with our previous work, the TraPPE/TIP4P2005 model combination gives the best overall performance in predicting coexistence composition and pressure in the water-rich phase. Critical assessments are also made on the ranges of temperature and pressure where particular model combinations work better. The dependence of the interfacial tension on temperature and pressure is better predicted by the TraPPE/TIP4P2005 and EPM2/SPC models, whereas the EPM2/TIP4P2005 model overestimates this property by 10–20%, possibly due to the inadequacy of the combining rules. It is also found that the interfacial tension increases with salt concentration, consistent with experimental observations. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A Particle-in-Cell simulation with Monte Carlo collisions was used to study electron and ion energy distributions (IEDs) in low-pressure (2.67 Pa) direct-current (dc)/radio-frequency (rf) hybrid capacitively-coupled Ar plasmas. One electrode (dc/rf electrode) of the parallel plate diode was powered by a 13.56 MHz source, and a negative dc bias voltage, whereas the opposite (substrate) electrode was grounded. Secondary electrons emitted from the dc/rf electrode accelerated in the adjacent sheath and entered the plasma, yielding a high-energy tail of the electron energy distribution. For given dc bias voltage, the plasma density increased as the secondary electron emission yield due to ion bombardment increased. A fraction of the secondary electrons were energetic enough to overcome the sheath potential barrier on the substrate electrode and bombard the substrate. The electron angular distribution on the substrate electrode had a peak of directional electrons superimposed on a typical cosine distribution. The mean energy and angular spread of directional electrons could be controlled by varying the dc bias voltage. However, as the dc bias became more negative, the dc/rf sheath expanded at the expense of the bulk plasma, reducing the plasma density, in agreement with published data. The IED on the substrate electrode exhibited a dominant bimodal feature with multiple shoulder peaks due to ion-neutral charge exchange collisions. The average ion energy decreased as the dc voltage became more negative, also in agreement with data. Pulsing the plasma power enhanced the tail of the electron energy distribution in the early activeglow (power ON), and yielded a distinct ballistic electron flux on the substrate with energy equal to the applied dc bias. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Eighteen kinds of porous materials from carbons, zeolites, and metal organic frameworks (MOFs) have been extensively investigated for desulfurization and decarburization of the biogas, natural gas, and flue gas by using a molecular modeling approach. By considering not only the selectivity but also capacity, Na-5A, zeolite-like MOF (zMOF), and Na-13X, MIL-47 are screened as the most promising candidates for removal of sulfide in the CH₄CO₂H₂S and N₂CO₂SO₂ systems, respectively. However, for simultaneous removal of sulfide and CO₂, the best candidates are zMOF for the natural gas and biogas (i.e., CH₄CO₂H₂S system) and MOF-74-Zn for the flue gas (i.e., N₂CO₂SO₂ system). Moreover, the regeneration ability of the recommended adsorbents is further assessed by studying the effect of temperature on adsorption. It is found that compared to the zMOF and MIL-47 MOFs, the Na-5A and Na-13X zeolites are not easily regenerated due to the difficulty in desorption of sulfide at high temperature, which results from the stronger adsorbent–adsorbate interactions in zeolites. The effect of sulfide concentration on the adsorption properties of the recommended adsorbents is also explored. We observe that the zMOF and MIL-47 are also superior to the Na-5A and Na-13X for desulfurization of gas mixtures containing high sulfide concentration. This is because MOFs with larger pore volume lead to a greater sulfide uptake. The effects of porosity, framework density, pore volume, and accessible surface area on the separation performance are analyzed. The optimum porosity is about 0.5–0.6, to meet the requirements of both high selectivity and uptake. It is expected this work provides a useful guidance for the practical applications of desulfurization and decarburization. © 2013 American Institute of Chemical Engineers AIChE J, 2013

When particles are transported in pipelines, they acquire electrostatic charges as they come into contact with the pipe wall. Charged particles can cause problems such as particle agglomeration, blockage, and explosion. Understanding the particle charge can help to prevent these issues. This study investigates a technique for predicting the particle charge in a straight pipe of any given length, as well as the pipe length at which electrostatic equilibrium occurs, through experimentation in a short 1-m pipe section. Experimentation with five different types of particles and four pipe wall materials at longer pipe lengths were used to validate the technique. This predictive technique is applicable to a range of particle shapes and sizes under the restriction that charge transfer is due to impact charging. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A shape coefficient is introduced to quantify droplet shape by measuring its similarity to a desired shape to enable the study of droplet shape evolution upon impingement on a solid surface. Parametric simulations are performed with an experimentally validated numerical model to determine the impact conditions to maximize the shape coefficient. Results show that the Weber number is the controlling factor that determines the maximum achievable shape coefficient and the time instant when it is achieved for small Ohnesorge numbers, whereas the Reynolds number becomes the key parameter defining the optimal shape when the Ohnesorge number is large. A regime map is also developed to define the regions where a desired droplet shape can be achieved without splash. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The integration in a natural gas combined cycle (NGCC) of a novel process for H₂ production using a chemical Ca–Cu loop was proposed. This process is based on the sorption-enhanced reforming process for H₂ production from natural gas with a CaO/CaCO₃ chemical loop, but including a second Cu/CuO loop to regenerate the Ca-sorbent. An integration of this system into a NGCC was proposed and a full process simulation exercise of different cases was carried out. Optimizing the operating conditions in the Ca–Cu looping process, 8.1% points of efficiency penalty with respect to a state-of-the-art NGCC are obtained with a CO₂ capture efficiency of 90%. It was demonstrated that the new process can yield power generation efficiencies as high as any other emerging and commercial concepts for power generation from NGCC with CO₂ capture, but maintaining competing advantages of process simplification and compact pressurized reactor design inherent to the Ca–Cu looping system. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Batch process monitoring is a challenging task, because conventional methods are not well suited to handle the inherent multiphase operation. In this study, a novel multiway independent component analysis (MICA) mixture model and mutual information based fault detection and diagnosis approach is proposed. The multiple operating phases in batch processes are characterized by non-Gaussian independent component mixture models. Then, the posterior probability of the monitored sample is maximized to identify the operating phase that the sample belongs to, and, thus, the localized MICA model is developed for process fault detection. Moreover, the detected faulty samples are projected onto the residual subspace, and the mutual information based non-Gaussian contribution index is established to evaluate the statistical dependency between the projection and the measurement along each process variable. Such contribution index is used to diagnose the major faulty variables responsible for process abnormalities. The effectiveness of the proposed approach is demonstrated using the fed-batch penicillin fermentation process, and the results are compared to those of the multiway principal component analysis mixture model and regular MICA method. The case study demonstrates that the proposed approach is able to detect the abnormal events over different phases as well as diagnose the faulty variables with high accuracy. © 2013 American Institute of Chemical Engineers AIChE J, 2013

We have recently demonstrated that boric acid (H₃BO₃, BA) is a promising additive to decrease onset temperature as well as to enhance hydrogen release kinetics for thermolysis of ammonia borane (NH₃BH₃, AB). The observations suggest that tetrahydroxyborate ion released by heating BA serves as Lewis acid and catalyzes AB dehydrogenation. Using this approach, we obtained high H₂ yield at 85°C, along with rapid kinetics. Various operating conditions were investigated, such as reactor temperature, AB wt %, and particle size of BA. Even in the presence of 10 wt % BA, high H₂ yield (13 wt %) and trace amount of ammonia (10–20 ppm) were obtained at 80°C, proton exchange membrane (PEM) fuel cell operating temperature. To our knowledge, such H₂ yield value is higher than from any other method using AB with additive or catalyst at PEM fuel cell operating temperatures. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Product shortages, which cause backlogging and/or lost sales costs commonly occur in the chemical industries, especially in the commodity polymer business. Shortage costs in a supply chain optimization model are studied under the framework of a generalized batch-storage network. A classical economic order quantity model with backlogging costs suggested an optimal time delay and final product delivery lot size. A product shortage can be mitigated by advancing production/transportation or by purchasing a substitute product from a third party as well as by a product delivery delay in the supply chain network. Optimal solutions that consider all means for recovering shortage are more complicated than the classical case. Four solutions are identified depending on the parametric range and variable bounds. The optimal capacity for production/transportation processes associated with a product in shortage can differ from that of a product not in shortage. An illustrative example is presented in support of the analytical results. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Ionic liquids (ILs) are innovative solvents for chemical processing. In this work, a database on activity coefficients of organic solutes at infinite dilution in ILs was collected from literature sources. The activity coefficients have been correlated by activity coefficient model for the regular solution and have been used to estimate the solubility parameter of ILs. The solubility parameters of ILs have been further correlated based on a concept of the group contribution method. Through the analysis of the database and the prediction results of selectivities, it was shown here that as compared with conventional organic solvents, higher selectivity can be achieved by using ILs as working solvents for separation of alkane/aromatic, aromatic/aromatic hydrocarbon mixtures via extraction or supported liquid membrane. © 2013 American Institute of Chemical Engineers AIChE J, 2013

This work considers the problem of designing an active fault-isolation scheme for nonlinear process systems subject to uncertainty. The faults under consideration include bounded actuator faults and process disturbances. The key idea of the proposed method is to exploit the nonlinear way that faults affect the process evolution through supervisory feedback control. To this end, a dedicated fault-isolation residual and its time-varying threshold are generated for each fault by treating other faults as disturbances. A fault is isolated when the corresponding residual breaches its threshold. These residuals, however, may not be sensitive to faults in the operating region under nominal operation. To make these residuals sensitive to faults, a switching rule is designed to drive the process states, upon detection of a fault, to move toward an operating point that, for any given fault, results in the reduction of the effect of other faults on the evolution of the same process state. This idea is then generalized to sequentially operate the process at multiple operating points that facilitate isolation of different faults for the case where the residuals are not simultaneously sensitive to faults at a single operating point. The effectiveness of the proposed active fault-isolation scheme is illustrated using a chemical reactor example and demonstrated through application to a solution copolymerization of methyl methacrylate and vinyl acetate. © 2013 American Institute of Chemical Engineers AIChE J, 2013

An accurate prediction of the dry pressure drop is very important for consideration of valve trays and for calculations in distillation field. Therefore, in this article, a series of hydraulic experiments were first conducted to reveal that the intermediate state during the valve opening process is closely related to the dry tray pressure drop under great valve weight. Then, a rigorous force analysis was made to show that Euler number is related only to the valve's position at the balance points for a certain valve type. Third, a new model for prediction of the dry tray pressure drop—which considers for the first time the influence of the intermediate state—was developed and then simplified for the purpose of convenient utilizations. Finally, the new model and its simplified form were tested by comparisons with the experimental results. The agreements are good, with the mean deviations being <5%. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Induction time distributions for gas hydrate formation were measured for gas mixtures of methane + propane at pressures up to 11.3 MPa using a high-pressure automated lag time apparatus (HP-ALTA). Measurements were made at subcooling temperatures between 4.3 and 13.5 K and, while isothermal induction times between 0 and 15,000 s were observed, the median isothermal induction times for the distributions ranged from 100 to 4000 s. A hyperbolic relationship between median induction time and subcooling was used to correlate the data. A graphical interpretation is presented that relates the two types of data that can be acquired by using the HP-ALTA in one of two modes to study hydrate formation: induction time distributions at constant subcooling and formation temperature distributions observed during linear cooling ramps. The equivalence of these two modes provides a robust method for studying the variation of formation phenomena in different hydrate systems. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Phase Doppler anemometry was used to quantify the flow characteristic of a three phases (liquid, solid, and bubbles) cylindrical bubble column driven by a point air source made of a 30-mm diameter perforated air stone centrally mounted at the bottom. The cylindrical bubble column had an inner diameter of 152 mm and was filled with liquid up to 1 m above the point source. Acrylic beads with a nominal diameter of 3 mm were used as the solid phase. To match the density of the solid phase which was 1.05 kg/m³, the liquid density was raised to about 1.0485 kg/m3 by added salt. The bubble diameters generated were within the range of 600–2400 µm. The detailed turbulent characteristics of the liquid-phase velocity, bubble diameter, bubble velocity, and solid velocity were measured at three different air rates, namely 0.4, 0.8, and 1.2 L/min (corresponding to average gas volume fraction of 0.0084, 0.0168, and 0.0258, respectively) for the homogeneous bubble column regime. With the addition of the solid phase, the flow field was found to be relatively steady compared to the two-phase column referencing the probability density functions for both the liquid and bubble velocities. An analysis based on the determination of the drag forces and transversal lift forces was performed to examine the flow stability in the three-phase bubble column. The analysis illustrated that how the added solid phase effectively stabilized the flow field to achieve a steady circulation in the bubble column and a generalized criterion for the flow stability in the three-phase bubble column was derived. Further investigation for the transition and the heterogeneous bubble column regime with air rates at 2.0 and 4.0 L/min shown that this criterion can also be used as a general prediction of flow stability in this three-phase bubble column. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A reactor model for the single-phase rotor–stator spinning disk reactor based on residence time distribution measurements is described. For the experimental validation of the model, the axial clearance between the rotor and both stators is varied from 1.0 × 10⁻³ to 3.0 × 10⁻³ m, the rotational disk speed is varied from 50 to 2000 RPM, and the volumetric flow rate is varied from 7.5 × 10⁻⁶ to 22.5 × 10⁻⁶ m³ s⁻¹. Tracer injection experiments show that the residence time distribution can be described by a plug flow model in combination with 2–3 ideally stirred tanks-in-series. The resulting reactor model is explained with the effect of turbulence, the formation of Von Kármán and Bödewadt boundary layers, and the effect of the volumetric flow rate. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Modeling the operation of spiral-wound membrane modules is essential for their successful design and optimization. Such models must include the main types of membrane fouling, degrading desalination plant performance, including scaling due to sparingly soluble salts. Unfortunately, the complexity of underlying physicochemical processes and the coexistence of several spatial and temporal scales render intractable modeling of membrane scaling based on first principles. Therefore, a suitable (albeit simplified) framework is developed for incorporating scaling dynamics into a fluid flow model formulated at an intermediate (i.e., mesoscopic) length scale of membrane operation. The general mesoscopic approach involves integration of spatially distributed submodels, thereby allowing predictions at the large (entire membrane sheet) scale; these submodels comprise constitutive laws and kinetic rate expressions derived at fine scales. A submodel for the effect of pre-existing bulk particles on scale formation is developed herein. Several numerical results are presented to exemplify the potential of the proposed framework. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The results of catalytic treatment of vapors exiting a g/min pyrolysis unit before product condensation to the liquid phase using a Ru/TiO₂ catalyst for oak and switchgrass pyrolysis are reported. The pyrolysis is conducted at 500°C and the catalysis at 400°C at atmospheric pressure with a hydrogen partial pressure of 0.58 atm. It is found that the catalytic treatment provides significant conversion of light oxygenates to larger, less oxygenated, molecules and, simultaneously, bio-oil phenolics are also converted to less oxygenated phenolics with methoxy methyl groups transferred to the ring. The activity of the catalyst gradually diminished with increasing biomass fed to the system. Untreated pyrolysis oil forms a single liquid phase with some tarry material, consistent with the literature, whereas the treated liquid product forms separate oil and aqueous phases, the latter of which is about 80% water. The oil from the treated vapors has a lower initial viscosity with only a small increase upon accelerated aging compared to the untreated product oil, which has a dramatic increase in viscosity after aging. This is indicative of poor oil stability for untreated oil that is further confirmed by large increases in molecular weight, while the treated oil has a small increase in molecular weight after accelerated aging. In an effort to understand compatibility with refinery streams, the solubility of the oils in tetralin was examined. The untreated oil was found to have very limited solubility in tetralin, whereas the treated oil phase was completely soluble except for a small aqueous phase that appeared. There are a number of challenges in developing a high yield process for pyrolysis based conversion of biomass to transportation fuels. The Ru/TiO₂ catalyst used here shows promise for conducting multiple types of favorable reactions in the presence of the full spectrum of primary pyrolysis products that creates significant product stability under mild conditions. This could lead to higher liquid yields of stable, refinery compatible, product oil. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Microreactors are very promising tools for the design of future chemical processes. For example, emulsions of very narrow size distribution are obtained at much lower energy consumption than the one spent with usual processes. Micromixers play thereby an eminent role. The goal of this study is to better understand the hydrodynamic properties of a split-and-recombine Caterpillar micromixer (CPMM) specially with regard to handling viscoelastic fluids, a topic hardly addressed so far in the context of micromixers in general, although industrial fluids like detergent, cosmetic, or food emulsions are non-Newtonian. Friction factor was measured in a CPMM for both Newtonian and non-Newtonian fluids. For Newtonian fluids, the friction factor in the laminar regime is f/2 = 24/Re. The laminar regime exists up to Reynolds numbers of 15. For shear-thinning fluids like Carbopol 940 or viscoelastic fluids like Poly Acryl Amide (PAAm) aqueous solutions, the friction factor scales identically within statistical errors up to a generalized Reynolds number of 10 and 0.01, respectively. Above that limit, there is an excess pressure drop for the viscoelastic PAAm solution. This excess pressure drop multiplies the friction factor by more than a decade over a decade of Reynolds numbers. The origin of this excess pressure drop is the high elongational flow present in the Caterpillar static mixer applied to a highly viscoelastic fluid. This result can be extended to almost all static mixers, because their flows are generally highly elongational. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A new approach for the incorporation of safety criteria into the selection, location, and sizing of a biorefinery is introduced. In addition to the techno-economic factors, risk metrics are used in the decision-making process by considering the cumulative risk associated with key stages of the life cycle of a biorefinery that includes biomass storage and transportation, process conversion into biofuels or bioproducts, and product storage. The fixed cost of the process along with the operating costs for transportation and processing as well as the value of the product are included. An optimization formulation is developed based on a superstructure that embeds potential supply chains of interest. The optimization program establishes the tradeoffs between cost and safety issues in the form of Pareto curves. A case study on bio-hydrogen production is solved to illustrate the merits of the proposed approach. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A systematic top-down procedure to design an effective plantwide control system for economically (near) optimum process operation over a wide throughput range is developed. The proposed procedure focuses on devising a control system for optimal operation at maximum throughput, where usually the highest number of constraints is active and the economic benefits of improved operation are the greatest. To do so, loops for tight control of all the active constraints and economically sound controlled variables (CVs) corresponding to unconstrained degrees of freedom are first implemented (Step 1) followed by a consistent inventory control system (Step 2). This control system is adapted with setpoints that become unconstrained at lower throughputs taking up additional economic CV control or throughput manipulation (Step 3). Iteration between the three steps may be necessary to eliminate fragile/unconventional inventory loops (Step 4). The application of the methodology is demonstrated on three realistic example processes. © 2013 American Institute of Chemical Engineers AIChE J, 2013

In this study, Cu-loaded Santa Barbara amorphous (SBA)-15 catalysts were synthesized by impregnation method and further used for catalytic wet peroxidation (CWPO) of pyridine from aqueous solution using hydrogen peroxide as oxidant. The synthesized catalysts have been characterized by Brunauer–Emmett–Teller surface area: temperature-programmed reduction, H₂-chemisorption, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. Characterization results indicate good dispersion of Cu species inside the porous structure of SBA-15. The effect of various parameters such as Cu loading on SBA-15, pH, catalyst dose, H₂O₂ concentration, and temperature have been studied for their effect on CWPO of pyridine. More than 97% pyridine removal and 92% total organic carbon removal was achieved at optimum condition. Cu/SBA-15 showed stable performance during reuse for six cycles with negligible copper leaching. © 2013 American Institute of Chemical Engineers AIChE J, 2013

In this article, multiscale simulation methods were used to study structural and transport properties of Nafion–ionic liquid composite membranes that are novel proton conducting materials for fuel cells. Coarse-grained model for 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) ionic liquid was first developed in the framework of BMW-MARTINI force field. Coarse-grained simulation results of bulk [bmim][BF₄] ionic liquid show good agreement with all-atom simulation results and experimental data. Nafion–[bmim][BF₄] composite membranes were then simulated using all-atom and coarse-grained models. Ionic liquid cluster formation inside Nafion was revealed by coarse-grained simulations. Diffusion coefficients of both [bmim]⁺ cations and anions are reduced by one to two orders of magnitude depending on their concentrations in Nafion membrane. [Bmim]⁺ cations have faster self-diffusion coefficient than anions, while this phenomenon is more pronounced when ionic liquids are confined in Nafion. This work provides molecular basis for understanding Nafion–ionic liquid composite membranes. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Systematic molecular dynamics simulations have been performed to illustrate the roles of guest molecules played in the process of hydrate growth at vapor-liquid interfaces. In our simulations, guest molecules are represented by a commonly used single-site Lennard–Jones model, and the roles of guest molecules on hydrate growth have been investigated separately from the effect of water–guest molecule attractive interaction ε and that of molecular size σ, respectively. Our simulation results demonstrate that the water-guest molecule attraction regulates the pathway and rate of nucleus growth, whereas the size of guest molecules determines the dynamically preferable structure. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A series of active oxygen material Ce_xZr_1−xO₂-supported NiCo bimetallic nanosized catalysts were prepared by coprecipitation method, which is simple and fit for industrial use with lower cost than other methods. The effect of CeO₂/ZrO₂ mole ratio, Co metal addition, and PEG-6000 addition were investigated. The catalysts were characterized through X-ray diffraction, H₂ thermal-programmed reduction, N₂ adsorption, Raman spectroscopy, CO pulse chemisorption, X-ray photoelectron spectroscopy, oxygen storage capacity, and transmission electron microscopy-energy dispersive X-ray analysis. Modifications of the structural and redox properties of these materials were evaluated in relation to their catalytic performances. Particularly, the relationship between the active oxygen sites of the catalysts and their catalytic performances was investigated. The interaction between active metals (Ni and Co) and Ce_xZr_1−xO₂ support was found to be very important for catalytic performance. The active oxygen site of Ce_xZr_1−xO₂ can considerably improve catalytic performance. Appropriate Co metal addition also remarkably enhanced the catalytic stability and activity. Moreover, PEG-6000 addition can improve the Brunauer–Emmett–Teller surface area and active metal dispersion of catalysts to improve their performances. The nanosized catalyst 15 wt % Ni-5 wt % Co/Ce_0.25Zr_0.75O₂ prepared by adding 5 wt % PEG-6000 achieved almost 85% CO₂ conversion and 98% selectivity to methane at 280°C when the gas hourly space velocity was 10,000 h⁻¹. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The phase behavior for a series of poly(1,4-isoprene-b-DL-lactide) diblock copolymers characterized by a relatively large Flory–Huggins segment–segment interaction parameter (χ) and low degrees of polymerization (N) over a range of compositions was reported. Ordered-state morphologies were deduced from small-angle x-ray scattering (SAXS) measurements, and χ(T) was determined from order-disorder transition temperatures (T_ODT's) associated with the compositionally symmetric specimens and assuming the mean-field theory, that is, (χN)_ODT=10.5. The ODT was determined by differential scanning calorimetry, SAXS, and dynamic mechanical spectroscopy, and shown to be weakly first-order, with latent heats of transition that vary strongly with composition. We interpret this behavior in terms of the mean and Gauss interfacial curvature of the ordered-state morphologies and with respect to composition fluctuations in the disordered state. These results offer a fresh strategy for investigating weakly first-order phase transitions within the Brazovskii universality class. © 2013 American Institute of Chemical Engineers AIChE J, 2013

An efficient decomposition method to solve the integrated problem of scheduling and dynamic optimization for sequential batch processes is proposed. The integrated problem is formulated as a mixed-integer dynamic optimization problem or a large-scale mixed-integer nonlinear programming (MINLP) problem by discretizing the dynamic models. To reduce the computational complexity, we first decompose all dynamic models from the integrated problem, which is then approximated by a scheduling problem based on the flexible recipe. The recipe candidates are expressed by Pareto frontiers, which are determined offline by using multiobjective dynamic optimization to minimize the processing cost and processing time. The operational recipe is then optimized simultaneously with the scheduling decisions online. Because the dynamic models are encapsulated by the Pareto frontiers, the online problem is a mixed-integer programming problem which is much more computationally efficient than the original MINLP problem, and allows the online implementation to deal with uncertainties. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A continuum gas–solid model that includes descriptions for solid frictional stress and a turbulent gas phase is evaluated against published experimental measurements of mean and fluctuating velocity inside the jet plume region of a bubbling fluidized bed with a high-speed vertical jet injection. The main uncertainties in closure relations necessary in the continuum model are first identified and then determined using available experimental data. The overall model shows good agreement with both the gas and particle experimental velocity profiles. The trends in the centerline mean and fluctuating velocity with change in the fluidized state of the emulsion are also captured favorably. Main deviations between the model and experiment are noted and possible reasons for the mismatch are discussed. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The guaranteed cost distributed fuzzy (GCDF) observer-based control design is proposed for a class of nonlinear spatially distributed processes described by first-order hyperbolic partial differential equations (PDEs). Initially, a T–S fuzzy hyperbolic PDE model is proposed to accurately represent the nonlinear PDE system. Then, based on the fuzzy PDE model, the GCDF observer-based control design is developed in terms of a set of space-dependent linear matrix inequalities. In the proposed control scheme, a distributed fuzzy observer is used to estimate the state of the PDE system. The designed fuzzy controller can not only ensure the exponential stability of the closed-loop PDE system but also provide an upper bound of quadratic cost function. Moreover, a suboptimal fuzzy control design is addressed in the sense of minimizing an upper bound of the cost function. The finite difference method in space and the existing linear matrix inequality optimization techniques are used to approximately solve the suboptimal control design problem. Finally, the proposed design method is applied to the control of a nonisothermal plug-flow reactor. © 2013 American Institute of Chemical Engineers AIChE J, 2013

HZSM-5 (SiO₂/Al₂O₃=280 mol/mol) is used to produce hydrocarbons from reagent-grade isopropanol and mixed alcohols made from lignocellulosic biomass (waste office paper and chicken manure) using the MixAlco™ process. All studies were performed at 101 kPa (abs). The experiments were conducted in two sets: (1) vary temperature (300–T_max°C) at weight hourly space velocity (WHSV)=1.31 h^–1, and (2) vary WHSV (0.5–11.5 h^–1) at T=370°C. For isopropanol, T_max=450°C and for mixed alcohols T_max=520°C. For isopropanol, higher temperatures produced more gaseous products and more aromatics. High WHSV gives high concentration of C6+ olefins, whereas low WHSV gives high concentrations of C9 aromatics. For mixed alcohols, changes in temperature affected the product distribution similar to isopropanol. In contrast, WHSV did not affect the concentration of reaction products; only dehydration products were observed. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Conversion of carbohydrates to 5-hydroxymethylfurfural (HMF) will provide a new step toward achieving renewable biomass-based chemicals and fuels platform. Recently, the excellent yield of HMF (91.0%) in dimethyl sulfoxide (DMSO) catalyzed by sulfonated carbon was demonstrated, but the separation of HMF from the reaction mixture remains challenging because of the high boiling point of DMSO. As a solution, herein, low boiling point solvent tetrahydrofuran (THF) mixed with DMSO was used for the fructose dehydration and high yield of HMF (98.0%) was still obtained. Besides, the stability of the sulfonated carbonaceous catalyst was also confirmed. More importantly, HMF from the reaction solution was successfully separated by using simple extraction method, and high purity of HMF (ca. 96.4%) was obtained. Compared with pure DMSO solvent, the combination of low boiling point THF with DMSO not only gives higher yield of HMF, but also improves the separation efficiency and reduces environmental risk. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Zeolites confine active sites within void spaces of molecular dimension. The size and shape of these voids can be tuned by changing framework topology, which can influence catalytic reactivity and selectivity via coupled reaction-transport phenomena that exploit differences in transport properties among reactants and/or products that differ in size and shape. The polarity and solvating properties of intrazeolite void environments can be tuned by changing chemical composition and structure, ranging from hydrophobic defect-free pure-silica surfaces to silica surfaces containing hydrophilic defect sites and/or heteroatoms. Here, we discuss how the polarity of zeolite voids influences catalytic reactivity and selectivity via the partitioning of reactant, product, and solvent molecules between intrazeolitic locations and external fluid phases. These findings provide a conceptual basis for developing selective catalytic processes in aqueous media using hydrophobic zeolites that are able to adsorb organic reactants while excluding liquid water from internal void spaces. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Micrometer–nanometer hydrophobic titania–fluoroalkylsilane composite coatings were prepared on substrates based on liquid-phase deposition. Coatings and crystallization forms were characterized with instruments of surface analyses. Experimental facilities of pool boiling were established to evaluate heat and mass transfer on coated surfaces in deionized water and saturated calcium carbonate solution. Obvious pool boiling enhancement was observed on thinner microscale–nanoscale hydrophobic titania–fluoroalkylsilane composite films at higher heat fluxes compared to that on thicker titania–fluoroalkylsilane coatings or on titania coatings and stainless steel surfaces. Lower fouling resistance was obtained on titania–fluoroalkylsilane coatings in pool boiling of saturated calcium carbonate solution and crystal form was aragonite, which was different from calcite on titania coatings. Results of inhibition of fouling and enhancement of heat transfer on titania–fluoroalkylsilane coatings were contributed to special surface microscale–nanoscale structure and material wettability. Asymptotic model was used to fit experimental data of fouling resistance, and reasonable agreement was obtained. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The pore diffusion model that describes unsteady-state adsorption, diffusion, and reaction in a porous catalyst is in the form of a parabolic partial differential equation. To relieve computational loads, approximate ordinary differential equations are often used and they can be derived from the transfer function between the surface and average concentrations in the particle. The transfer function shows half-order behaviors at the high-frequency range. The rational transfer functions cannot describe well this half-order behavior. Here, introducing the half-order term to rational transfer function candidates for approximation, models valid throughout low- and high-frequency ranges are derived. Since the proposed approximate models are valid globally, they can be applied to reactive porous catalysts easily. They can also be used for noninteger shape factors that will show better performances for adsorbents different from ideal geometries of infinite slab, infinite cylinder and sphere, and for biporous adsorbents. © 2013 American Institute of Chemical Engineers AIChE J, 2013

A novel networked process monitoring, fault propagation identification, and root cause diagnosis approach is developed in this study. First, process network structure is determined from prior process knowledge and analysis. The network model parameters including the conditional probability density functions of different nodes are then estimated from process operating data to characterize the causal relationships among the monitored variables. Subsequently, the Bayesian inference-based abnormality likelihood index is proposed to detect abnormal events in chemical processes. After the process fault is detected, the novel dynamic Bayesian probability and contribution indices are further developed from the transitional probabilities of monitored variables to identify the major faulty effect variables with significant upsets. With the dynamic Bayesian contribution index, the statistical inference rules are, thus, designed to search for the fault propagation pathways from the downstream backwards to the upstream process. In this way, the ending nodes in the identified propagation pathways can be captured as the root cause variables of process faults. Meanwhile, the identified fault propagation sequence provides an in-depth understanding as to the interactive effects of faults throughout the processes. The proposed approach is demonstrated using the illustrative continuous stirred tank reactor system and the Tennessee Eastman chemical process with the fault propagation identification results compared against those of the transfer entropy-based monitoring method. The results show that the novel networked process monitoring and diagnosis approach can accurately detect abnormal events, identify the fault propagation pathways, and diagnose the root cause variables. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The combination of reduced oxygen tension and flow perfusion bioreactor culture is investigated for its effect on the proliferation, glycosaminoglycan production, and chondrogenic gene expression of bovine articular chondrocytes on porous polymer scaffolds. It was hypothesized that the combination of such factors would more closely replicate the in situ environment of these cells, leading to improvements in the cell phenotype. Chondrocytes were seeded onto electrospun poly(ε-caprolactone) scaffolds and cultured in static or perfusion culture in either normoxic or hypoxic conditions for 6days. Results demonstrated that the combination of hypoxic and perfusion culture led to an increase in chondrocyte proliferation and glycosaminoglycan production, as well as an improvement in the ratio of collagen II/I gene expression over perfusion culture alone. The results demonstrate the need to combine multiple signals in vitro, in order to improve tissue growth by more closely replicating the native environment of cells. © 2013 American Institute of Chemical Engineers AIChE J, 2013

Soft sensors are used widely to estimate a process variable which is difficult to measure online. One of the crucial difficulties of soft sensors is that predictive accuracy drops due to changes of state of chemical plants. It is called as the degradation of soft sensor models. In this study, we attempted to classify this degradation of models in terms of changes in an explanatory variable and an objective variable, and the rapidity of the changes. Moreover, we discussed characteristics of adaptive soft sensor models, based on the classification results. By analyzing simulated data sets and a real industrial data set, we could obtain knowledge and information on appropriate adaptive models for each type of the degradation. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The increasing demand for optically pure compounds stimulates the development of new chiral separation processes on an industrial scale. The enantioselective liquid–liquid extraction (ELLE) of phenylsuccinic acid (PSA) enantiomers using hydrophilic hydroxyphenyl-β-CD as extractant (C) was studied experimentally in a countercurrent cascade of 10 centrifugal contactor separators at 293 K. Based on a single-stage equilibrium model and the law of conservation of mass, a multistage equilibrium model of ELLE was developed to investigate the influence of changes in the process parameterssuch as phase ratios and concentrations on extraction efficiency. The multistage equilibrium model was verified experimentally with a good agreement. The model was applied to predict the symmetrical separation of PSA enantiomers. By modeling, optimal process parameters for the symmetrical separation of PSA enantiomers can beachieved. The minimum number of stages was determined at 22 and 24 for ee_eq>98% and ee_eq>99%, respectively. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The synthesis and utilization of mesoporous Cu-MCM-41 catalysts for hydrogenation of dimethyl oxalate to ethylene glycol is described in this article. Physicochemical properties of these Cu-MCM-41 catalysts have been investigated by N₂-physisorption, X-ray diffraction, inductively coupled plasma, N₂O titration, transmission electron microscopy, temperature programmed reduction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. It was found that the copper loading significantly influenced the pore structure and copper surface area of the catalyst. High catalytic performance is obtained over a 20Cu-MCM-41 catalyst with a full DMO conversion and EG yield of 92% at a LHSV of 3.0 h⁻¹. The catalytic performance of optimized 20Cu-MCM-41 catalyst could be attributed to the fine copper dispersion and large copper surface areas. © 2013 American Institute of Chemical Engineers AIChE J, 2013

The authors review and project their group's work in reaction engineering, electrokinetics, thin-film lubrication/wetting, biosensing, mass spectrometry, etc., that share one common mathematical underpinning: singularities. These can be geometric singularities of actual surfaces or objects, where focused electrical, acoustic, optical and shear-stress fields produce anomalous physical phenomena that have been explored mathematically with a spectral theory or exploited for specific applications. They are also singularities of mathematical manifolds, such as solution branches and Riemann manifolds, defined by abstract mathematical formulations, so that they can be used to design optical sensors, and understand nonlinear dynamical behavior that is relevant to system control and surface characterization. The common mathematical framework for these diverse topics underscores how mathematics can reveal, organize and inspire real and industrially relevant problems in chemical engineering. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1830–1843, 2013

The kinetic parameters of ferrous iron oxidation, covering both lag and growth phases at low pH, were determined using a free suspended culture of the bacterium Leptospirillum ferriphilum. A mathematical model was developed to simulate the dynamics of a continuous bioreactor used for operation of a novel hybrid Fe(II)/Fe(III) redox flow fuel cell system. By changing the current load within a predefined range, three runs were performed to predict time-varying ferrous iron concentration, bacterial cell concentration, and pH as the major output variables of simulation program. The model was experimentally validated through three runs. It was found out that the key variable in dynamic analysis of the bioreactor was the current load applied. To optimize the bioreactor and the fuel cell conditions for a normal-steady-state operation, the optimal current profile for a transient phase was determined. A selected optimal policy was also implemented and validated during the mini-pilot-scale system experiments. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1844–1854, 2013

Based on chemical modeling of phase equilibria for the NH₄Cl-MgCl₂-AlCl₃-H₂O system, a practical approach to produce Mg-Al spinel (MgAl₂O₄) (widely used as refractory brick, supports in catalysts, and inert material for oxygen carriers) is proposed and proven feasible. This novel process includes coprecipitation of Mg₄Al₂(OH)₁₄·3H₂O from the NH₃-MgCl₂-AlCl₃-H₂O system; calcination of Mg₄Al₂(OH)₁₄·3H₂O to obtain Mg-Al spinel and recovery of NH₄Cl from NH₄Cl-rich solutions by feeding MgCl₂-AlCl₃. A MSMPR reactor was applied to investigate the effect of temperature, feed concentration, and NH₄Cl addition on coprecipitation of precursor Mg₄Al₂(OH)₁₄·3H₂O from MgCl₂-AlCl₃ solutions with Mg/Al ratio = 2 through gradual addition of NH₄OH. The phase equilibria of the NH₄Cl-MgCl₂-AlCl₃-H₂O system were determined over the temperature range 283.2 to 363.2 K using dynamic method. The experimental solubilities were regressed to obtain new Bromley-Zemaitis model parameters. These newly obtained parameters were verified by predicting the quaternary system. A chemical model for the NH₄Cl-MgCl₂-AlCl₃-H₂O system has been established with the OLI platform. All the results generated from this study will provide the theoretical basis for Mg-Al spinel production. The high quality Mg-Al spinel was prepared by calcination of precursor from 773.2 to 1273.2 K, and the NH₄Cl was successfully recovered through the common ion effect of MgCl₂-AlCl₃ addition. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1855–1867, 2013

Controlled release poly(lactic-co-glycolic acid) microparticles for use as active pharmaceutical ingredient carriers were prepared by the emulsion extraction method. Particle formation experiments were carried out in a stirred vessel. The local flow conditions in these experiments, that is, local shear rates and dissipation rates, and the extraction rate of the organic solvent were examined by a computational fluid dynamics (CFD) simulation. The local flow conditions in the stirred tank reactor have a significant influence on the final properties, specific surface area, skeletal density, organic solvent content, and size of the microparticles. We determined nondimensional correlations for predicting these particle properties as functions of the process parameters as, for example, the stirrer speed, emulsion injection point, and oil droplet size in the initial emulsion. The results demonstrate that CFD simulations offer insight into the particle formation process for different batch sizes and provide a basis for scale-up and optimization of the process. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1868–1881, 2013

An annular granular jet surrounding an air jet at its core is studied experimentally using high-speed digital photography. The experimental results show that particle bubbles in a periodic manner are formed whether the central air is swirling or not. This flow feature is induced by the intense interaction between the central air jet and the annular granular jet, and it is important for the dispersion of particles by the air jet in the near field. The interaction between the two phases is mainly intensified by higher superficial air jet velocity and the addition of swirl to the central air jet. The bubbling frequency, bubble size, bubble shape, and bubble growth rate are investigated by analyzing a large number of images. In addition, the dispersion angle of granular jet is found to be mainly governed by the radial growth rate of the bubble. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1882–1893, 2013

The mechanisms of segregation in solids mixing, even in simple rotating drums, are not clearly understood. Although most past studies have focused on binary mixtures, this work investigates the effect of polydispersity on granular flow, mixing, and segregation in a rotating drum operated in rolling regime through particle trajectories obtained from the radioactive particle tracking technique. Velocity profiles, radial segregation, and axial dispersion coefficients for monodisperse and polydisperse systems of glass beads are analyzed with respect to rotational speed and particle size. A model is introduced to predict the residence times along streamlines and evaluate the rate at which the material renews at the free surface and within the inner layers of the bed. Our results reveal similar velocity profiles and residence times for monodisperse and polydisperse systems. They also indicate that the particles distribute along the radial direction of the drum, although not necessarily in a core/shell configuration. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1894–1905, 2013

A discrete element method (DEM) study is conducted to investigate the mixing and heat-transfer characteristics of steel spherical particles under various rotation speeds and flow regimes of a rotating tumbler. The mixing degree, weighted temperature, temperature discrepancy at the mixing interface, temperature radial distribution, and information entropy are used to analyze the effect of mixing structure and evolution duration on the heat-transfer characteristics. The results under the same revolution and the same evolution time are compared to show the effects of evolution time and mixing structure on thermal conduction. After a detailed analysis, the joint contribution of mixing degree and duration to granular heat transfer is explained, and the different approaches in static thermal conduction and dynamic mixing are shown. Moreover, a new method is proposed using the mean increase rate of temperature information entropy to determine the most effective operating condition for thermal conduction in granular particles. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1906–1918, 2013

Deposition of particles in selective catalytic reduction DeNO_x monolithic catalysts was studied by low-dust pilot-scale experiments. The experiments showed a total deposition efficiency of about 30%, and the deposition pattern was similar to that observed in full-scale low-dust applications. On extended exposure to the dust-laden flue gas, complete blocking of channels was observed, showing that also in low-dust applications soot blowing is necessary to keep the catalyst clean. A particle deposition model was developed in computational fluid dynamics, and simulations were carried out assuming either laminar or turbulent flow. Assuming laminar flow, the accumulated mass was underpredicted with a factor of about 17, whereas assuming turbulent flow overpredicted the experimental result with a factor of about 2. The simulations showed that turbulent diffusion in the monolith channels and inertial impaction and gravitational settling on the top of the monolith were the dominating mechanisms for particle deposition on the catalyst. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1919–1933, 2013

Three-dimensional (3-D) gas-liquid–solid flow and mixing behaviors in microchannels were simulated by coupled volume of fluid and discrete phase method and simulations were validated against observations. The detachment time and length of gas slug are shortened in liquid–solid flow, compared with those in liquid flow due to higher superficial viscosity of liquid–solid mixture, which will move the bubble formation toward the dripping regime. Solid particles mainly distribute in liquid slug and particle flow shows obvious periodicity. With the increase of contact angle of the inner wall, gas slug (0–50°), stratified (77–120°), and liquid drop (160°) flows are observed. The residence time distributions of solid and liquid phases are similar because particles behave as tracers. The backmixing of solid and liquid phases in liquid drop flow is the weakest among the three flow patterns, and the backmixing of gas phase in slug flow is weaker than that in both stratified and liquid drop flows. The results can provide a theoretical basis for the design of microreactors. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1934–1951, 2013

The desulfurization process to a two-dimensional (2-D) and three-dimensional (3-D) Eulerian–Eulerian computational fluid dynamic (CFD) model of a coal bubbling fluidized gasifier is introduced. The desulfurization process is important for the reduction of harmful SO_x emissions; therefore, the development of a CFD model capable of predicting chemical reactions involving desulfurization is key to the optimization of reactor designs and operating conditions. To model the process, one gaseous phase and five particulate phases are included. Devolatilization, heterogeneous, and homogeneous chemical reactions as well as calcination and desulfurization reactions are incorporated. A calcination-only model and a calcination plus desulfurization model are simulated in 2-D and 3-D and the concentrations of SO₂ leaving the reactors are compared. The simulated results are assessed against available published experimental data. The influence of the fluidized bed on the desulfurization is also considered. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1952–1963, 2013

The purification reuse/recycle is one effective resource conservation strategy. In this article, a novel conceptual method is proposed to identify the optimal purification feed flow rate (PFFR) and the corresponding maximum hydrogen utility savings (HUS) of the hydrogen network with purification reuse/recycle. In this method, the sources and sink-tie-lines are divided into three regions according to the purified product and purification feed. The quantitative relationship between the HUS and the PFFR is analyzed for the sink-tie-lines and sources of each region. With the quantitative relationship line between the HUS and the PFFR of each source plotted, the quantitative relationship diagram can be obtained and can be used to identify the pinch point and the HUS for a given PFFR. Furthermore, the optimal PFFR and the maximum HUS can be identified easily. Three cases are studied to illustrate the applicability of the proposed method. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1964–1980, 2013

The online redesign of experiments for parameter determination of nonlinear dynamic systems has been studied recently by different research groups. In this article, this technique is assessed in a real case study for the first time. The presented algorithm adopts well-known concepts from model-based control. Compared to previous studies, special attention is given to the efficient treatment of the underlying nonlinear and possibly ill-conditioned parameter estimation and experiment design problems. These problems are solved with single shooting and gradient-based nonlinear programming (NLP) solvers. We use an initial value solver, which generates first- and second-order sensitivities to compute exact derivatives of the problem functions. As a special feature, we propose the integration of a local parameter identifiability analysis and a corresponding algorithm that generates well-conditioned problems. The practical applicability is demonstrated by experimental application to a chromatography column system where A, D, and E optimal experiments are performed. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1981–1995, 2013

Systematic plantwide control system design for economically optimal operation of the ethyl benzene process over a large throughput range is studied. As throughput is increased, constraints progressively become active with the highest number of active constraints at maximum throughput. An economic plantwide control system (CS1) is designed for operation at this most constrained operating point using a novel “top-down” pairing approach with higher prioritization to the economic objectives over regulatory objectives. This structure is adapted for near optimal low throughput operation with constraints that go inactive taking up additional economic variable control. For comparison, a conventional plantwide control structure (CS2) with the throughput manipulator at a fresh feed and “bottom-up” pairing for the control objectives is also synthesized. Four overrides are needed in CS2 to handle the hard equipment capacity constraints at maximum throughput. Rigorous dynamic simulations show that CS1 is dynamically and economically significantly superior to CS2. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1996–2014, 2013

The synthesis and design of reactive distillation columns separating reacting mixtures with the most unfavorable relative volatilities (i.e., the reactants are the heaviest and lightest components with the products being the intermediate ones) are described. The unfavorable thermodynamics poses great difficulties in combining the reaction operation and the separation operation involved and limits severely the potential of reactive distillation columns in the reduction of capital investment (CI) and operating cost. To remove the limitation, we propose two strategies for facilitating the synthesis and design of this kind of reactive distillation columns in this article. One is to arrange prudentially the reactive section so as to strengthen internal energy integration between the reaction operation and the separation operation involved; that is, while the reactive section should be placed at the bottom of the reactive distillation columns separating exothermic reactions, it should be at the top of the reactive distillation columns separating endothermic reactions. The other is to introduce an external recycle flow between the two ends of the reactive distillation columns to reinforce internal mass integration and internal energy integration between the reaction operation and the separation operation involved; that is, whereas the external recycle flow should be directed from the top to bottom of the reactive distillation columns separating exothermic reactions, it should be from the bottom to top of the reactive distillation columns separating endothermic reactions. Separation of four hypothetical ideal (i.e., two quaternary and two ternary systems, respectively) and two real nonideal (i.e., two quaternary systems) reacting mixtures is chosen to evaluate the proposed strategies. The results show that they can considerably lower energy requirement besides a further reduction in CI. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2015–2032, 2013

A guaranteed cost control scheme is proposed for batch processes described by a two-dimensional (2-D) system with uncertainties and interval time-varying delay. First, a 2-D controller, which includes a robust feedback control to ensure performances over time and an iterative learning control to improve the tracking performance from cycle to cycle, is formulated. The guaranteed cost law concept of the proposed 2-D controller is then introduced. Subsequently, by introducing the Lyapunov–Krasovskii function and adding a differential inequality to the Lyapunov function for the 2-D system, sufficient conditions for the existence of the robust guaranteed cost controller are derived in terms of matrix inequalities. A design procedure for the controller is also presented. Furthermore, a convex optimization problem with linear matrix inequality (LMI) constraints is formulated to design the optimal guaranteed cost controller that minimizes the upper bound of the closed-loop system cost. The proposed control law can stabilize the closed-loop system as well as guarantee H_∞ performance level and a cost function with upper bounds for all admissible uncertainties. The results can be easily extended to the constant delay case. Finally, an illustrative example is given to demonstrate the effectiveness and advantages of the proposed 2-D design approach. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2033–2045, 2013

Soft sensors are widely used to estimate process variables that are difficult to measure online. By using soft sensors, analyzer faults can be detected by estimation errors. However, it is difficult to detect abnormal data and determine the reasons because estimation errors increase not only due to analyzer faults but also due to variations caused by changes in the state of chemical plants. To separate those factors, we previously proposed to construct the relationships between distances to soft sensor models (DMs) and the accuracy of prediction of the models quantitatively and estimate the prediction accuracy of new data online. In this article, we used a one-class support vector machine (OCSVM) to estimate data density and the output of an OCSVM as a DM. The proposed method was applied to real industrial data and the superiority of the proposed DM to the traditional ones was demonstrated by comparing their results. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2046–2050, 2013

Microchannel reactors are a promising route for monetizing distributed natural gas resources. However, intensification and miniaturization represent a significant challenge for reactor control. Focusing on autothermal methane-steam reforming reactors, a novel microchannel reactor temperature control strategy based on confining a layer of phase-change material (PCM) between the reactor plates is introduced. Melting-solidification cycles, which occur with latent heat exchange at constant temperature, allow the PCM layer to act as an energy storage buffer—a “thermal flywheel”—constituting a distributed controller that mitigates temperature excursions caused by fluctuations in feedstock quality. A novel stochastic optimization algorithm for selecting the PCM layer thickness (i.e., distributed controller “tuning”) is introduced. Furthermore, a hierarchical control structure, whereby the PCM layer is complemented by a supervisory controller that addresses persistent disturbances, is proposed. The proposed concepts are illustrated in a comprehensive case study using a detailed two-dimensional reactor model. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2051–2061, 2013

The energy needs of the world continue to grow, as does the resulting environmental impact. Policy makers continue to call for alternative energies to replace today's petroleum-based liquid fuels. However, liquid fuels have significant advantages, and it is probably unwise to abandon the existing infrastructure without appropriately exploring alternatives to lessen the environmental burden of producing liquid fuels. Biomass and coal are often proposed as alternatives to petroleum-based carbon sources, but those processes lose a significant amount of their potential product to unwanted carbon dioxide emissions. However, combining biomass and coal with cleaner natural gas yields processes with less environmental impact to produce liquid fuels with small, zero, or even negative carbon dioxide emissions. Our process synthesis approach is applied to commonly encountered liquid fuel production methods to identify promising routes and to establish feasibility limits on those less promising alternatives. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2062–2078, 2013

A novel production of biobased p-xylene from hydroxymethylfurfual has been investigated and presented. This is an important part of a process for the production of aromatics from lignocellulosic biomass. The detailed flow sheets are designed based on laboratory experiments by Leshkov et al. and William et al. and economic analysis has been performed. The minimum biobased p-xylene cost is estimated as $3,962/metric ton, of which the main contribution comes from the HMF cost. Sensitivity analysis has been used to assess the impact of uncertainties of economic parameters and also to determine the most significant reaction factor in the technological development, i.e., selectivity and conversion. It has been shown that high selectivity is favored at the same yield. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2079–2087, 2013

A counter-intuitive decanter level control structure was reported in an earlier article which the aqueous level controller had to use reverse action for stable control. The Aspen model used in this study was the simple Decanter model, which assumes that there are only two liquid phases and pressure remains constant. This article presents results when the alternative Flash3 model is used. The aqueous level controller with direct action works well. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2088–2095, 2013

Biomass as a source for chemicals production attracts growing attention due to the decreasing storage of fossil fuels and global warming caused by emission of CO₂. In this study, conversion of glucose with copper oxide (CuO) was studied under alkaline hydrothermal conditions using a batch reactor and continuous flow reactor. CuO, as an oxidant, greatly improves the yields of lactic acid (LA) and acetic acid from glucose and was reduced into Cu₂O and Cu. Selective production of LA with the highest yield of 59% and acetic acid with the highest yield of 32% can be achieved by controlling reaction time, temperature, and addition of CuO. A possible mechanism of conversion of glucose with CuO was proposed. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2096–2104, 2013

Sorption-enhanced glycerol reforming, an integrated process involving glycerol catalytic steam reforming and in situ CO₂ removal, offers a promising alternative for single-stage hydrogen production with high purity, reducing the abundant glycerol by-product streams. This work investigates this process in a fixed-bed reactor, via a two-scale, nonisothermal, unsteady-state model, highlighting the effect of key operating parameters on the process performance. CO₂ adsorption kinetics was investigated experimentally and described by a mathematical reaction-rate model. The integrated process presents an opportunity to improve the economics of green hydrogen production via an enhanced thermal efficiency process, the exothermic CO₂ adsorption providing the heat to endothermic steam glycerol reforming, while reducing the capital cost by removing the processing steps required for subsequently CO₂ separation. The operational time of producing high-purity hydrogen can be enhanced by increasing the adsorbent/catalyst volume ratio, by adding steam to the reaction system and by increasing the inlet reactor temperature. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2105–2118, 2013

Coal pyrolysis to acetylene in hydrogen plasma is carried out under ultrahigh temperature and milliseconds residence time. To better understand the complex gas-particle reaction behavior, a comprehensive computational fluid dynamics with discrete phase model has been established, with special consideration of the particle-scale physics such as the heat conduction inside particle. The improved chemical percolation devolatilization model that incorporates the tar cracking reactions is adopted. The model predictions are in good agreement with the performances of two pilot-plant reactors. The simulations reveal the detailed unmeasurable information of gas phase and particle-scale behaviors, then point out the facts that coal devolatilization almost finishes in the first 100 mm of the reaction chamber and the optimal particle diameter is suggested to be 20–50 μm. The different reactor performances during the scale-up from 2- to 5-MW unit are analyzed based on the detailed simulation results in combination with the operational experience. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2119–2133, 2013

A simple route has been developed to prepare well-aligned TiO₂ nanotube arrays, which is based on outward coating of TiO₂ and inward etching of Cu(OH)₂ nanorod templates. Effects of annealing temperature and time on the crystal size and crystallinity of TiO₂ nanotube arrays and photocatalytic activities of TiO₂ nanotube arrays for degradation of Rhodamine B in aqueous solution have been investigated. The results indicate that the TiO₂ nanotube arrays annealed at 500°C for 2 h possessed an enhanced photocatalytic activity in comparison with the TiO₂ nanotube arrays without post heating and commercial anatase TiO₂ nanoparticle film and presented a good life cycle performance. Scale-up of the process has also been demonstrated. Our work opens a new avenue to fabricate free-standing TiO₂ nanotube arrays and demonstrates an excellent photocatalytic performance of the anatase TiO₂ nanotube arrays for wastewater treatment. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2134–2144, 2013

The initial thickness of methane hydrate film was directly measured by suspending a single methane bubble in water at 274.0, 276.0, and 278.0 K. The results show that the initial hydrate film thickness decreases from tens of micrometers to about 10 µm with the subcooling increased from 0.5 K to about 3 K. When subcooling is higher than 1.0 K, all initial film thickness data measured under different temperatures vary inversely with the subcooling. Notable three-dimensional growths of hydrate crystals of different sizes and shapes at film front and emergence of new crystal were clearly observed at lower subcooling that resulting in the rougher surface of hydrate film and uncertainty of initial thickness measurement under lower subcooling. The hydrate film growth was dominated by film growth in thickness, not by lateral growth at low subcooling. The growth in thickness of hydrate shell covering one whole bubble surface was also investigated. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2145–2154, 2013

A calibration protocol to quantify the compositional information of gas hydrates using Raman spectroscopy is proposed. Structure I pure CH₄-, CO₂- and C₂H₆-hydrates in their deuterated and hydrogenated forms with known cage occupancies were investigated by Raman spectroscopy. Raman scattering cross sections of CH₄ in the large and small cages were found to be very similar, but not identical. Some C₂H₆ bands of C₂H₆-hydrate were tentatively reassigned or newly reported and assigned. Our results show that the relative cross sections of guest vibrational modes in the deuterated hydrate are in agreement with those in the hydrogenated hydrate, whereas they are considerably different from those in fluid phase. Using our Raman quantification factors, the relative cage occupancies can now be determined more reliably in CH₄-hydrates. Moreover, with additional assumptions, the absolute cage occupancies, the bulk guest composition and hydration number of pure or mixed gas hydrates become accessible by Raman spectroscopy. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2155–2167, 2013

The goal of this study is to evaluate the performance of a fixed valve tray column designed to remove fly-ash particles. A series of experiments were carried out at room temperature to demonstrate the collection efficiency of a fixed valve tray column at different gas and liquid superficial velocities. The fly-ash particles removal characteristics of the fixed valve tray column were evaluated by measuring variations of concentration and size distribution of particles in the outlet. The mechanism of particle removal in this turbulent dispersion system was theoretically analyzed on the basis of diffusion, interception, sedimentation and impaction, and a model was proposed to predict the collection efficiency. The results show that the simulation results agree well with the experimental data. In contrast to most of the conventional models, the present model is capable of evaluating the effects of bubble hydrodynamics, system property, and operation conditions on the collection efficiency. The model is expected to guide effectively the design and operation of valve tray washing columns, which is widely applied nowadays. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2168–2178, 2013

The effect of the gas molecular size and its affinity to the pore surface on gas permeation properties through the ceramic membranes was studied by both the gas permeation experiments and gas permeation simulations using a nonequilibrium molecular dynamics (MD) technique. A modified gas permeation model equation based on the gas translation (GT) mechanism was presented. MD simulation revealed that the effective diffusion length in a micropore depended on the gas molecular size, and the pre-exponential coefficient of a modified GT model equation showed good correlation with the kinetic diameter of the gas molecules. Also presented is a simple method to estimate the mean pore size of microporous membranes. The estimated pore sizes were consistent with observed kinetic diameter dependencies of gas permeance for real silica membranes. The pore size of a Deca-Dodecasil 3R (DDR) zeolite membrane was also reasonably estimated at ∼0.4 nm from the reported gas permeation data. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2179–2194, 2013

Imidazolate framework ZIF-8 is modified via postsynthetic method using etheylenediamine to improve its adsorption performance toward CO₂. Results show that the BET surface area of the modified ZIF-8 (ED-ZIF-8) increases by 39%, and its adsorption capacity of CO₂ per surface area is almost two times of that on ZIF-8 at 298 K and 25 bar. H₂O uptake on the ED-ZIF-8 become obviously lower compared to the ZIF-8. The ED-ZIF-8 selectivity for CO₂/N₂ adsorption gets significantly improved, and is up to 23 and 13.9 separately at 0.1 and 0.5 bar, being almost twice of those of the ZIF-8. The isosteric heat of CO₂ adsorption (Q_st) on the ED-ZIF-8 becomes higher, while Q_st of N₂ gets slightly lower compared to those on the ZIF-8 Furthermore, it suggests that the postsynthetic modification of the ZIF-8 not only improves its adsorption capacity of CO₂ greatly, but also enhances its adsorption selectivity for CO₂/N₂/H₂O significantly. ©2013 American Institute of Chemical Engineers AIChE J, 59: 2195–2206, 2013

High-temperature CO₂ selective membranes offer potential for use to separate flue gas and produce a warm, pure CO₂ stream as a chemical feedstock. The coupling of separation of CO₂ by a ceramic–carbonate dual-phase membrane with dry reforming of CH₄ to produce syngas is reported. CO₂ permeation and the dry reforming reaction performance of the membrane reactor were experimentally studied with a CO₂–N₂ mixture as the feed and CH₄ as the sweep gas passing through either an empty permeation chamber or one that was packed with a solid catalyst. CO₂ permeation flux through the membrane matches the rate of dry reforming of methane using a 10% Ni/γ-alumina catalyst at temperatures above 750°C. At 850°C under the reaction conditions, the membrane reactor gives a CO₂ permeation flux of 0.17 mL min⁻¹ cm⁻², hydrogen production rate of 0.3 mL min⁻¹ cm⁻² with a H₂ to CO formation ratio of about 1, and conversion of CO₂ and CH₄, respectively, of 88.5 and 8.1%. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2207–2218, 2013

Annular centrifugal contactors were developed as single, compact units utilized to transfer desired species between immiscible fluid phases. Critical to understanding the mass-transfer characteristics in the annular mixing region is a clear picture of the distribution of droplet sizes of the fluids involved. To date, very little experimental data appears in the literature. We fill that void by using laser fluorescence and optical methods to directly observe and measure drop-size distributions for a silicone oil/water system in a centrifugal contactor. The shape and characteristics of the log-normal distributions, including the Sauter mean diameter and distribution means, are elucidated in terms of rotor speed and organic phase fraction. The size distribution of entrained air bubbles is also examined. The results presented here will be invaluable in validating and expanding the predictive capacity of the many models that have been developed to describe the flow within these devices. Published 2013 American Institute of Chemical Engineers AIChE J, 59: 2219–2226, 2013

Solubilities of H₂S in five 1-alkyl-3-methylimidazolium carboxylates ionic liquids (ILs) have been measured at temperatures from 293.15 to 333.15 K and pressures up to 350 kPa. It is shown that these ILs have significantly larger absorption capacities for H₂S than those common ILs reported in the literature. The solubility is found to increase dramatically with the increasing alkalinity of the anions and slightly with the increasing length of the alkyl chains on the cations. It is further demonstrated that the absorption isotherms are typically nonideal. With the assumption of complex formation between H₂S and ILs, a reaction equilibrium thermodynamic model is developed to correlate the experimental solubilities. The model favors a reaction mechanism of AB₂ type that two IL molecules interact with one H₂S molecule. Thermodynamic parameters such as Henry's law constants, reaction equilibrium constants, and heat of complex formation are also calculated to evaluate the absorption process of H₂S in these ILs. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2227–2235, 2013

The gas solubility of pure oxygen and of pure carbon dioxide as well as of their gaseous mixture are measured in the ternary liquid mixture cyclohexane + cyclohexanone + cyclohexanol at 313.6 K with a high-pressure view-cell technique using the synthetic method. The new experimental data are used to assess the capability of molecular simulation and conductor-like screening model (COSMO)-SAC to predict multicomponent fluid-phase coexistence behavior. These methods are also compared systematically on the basis of experimental binary fluid-phase coexistence data. In that comparison also the Peng–Robinson (PR) equation of state is included as a reference. Molecular simulation and COSMO-SAC yield good results and are found to be far superior to the PR equation of state both in predictive and in adjusted mode. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2236–2250, 2013

The local shear rate generated in a cylindrical tank equipped with a Rushton turbine was investigated using particle image velocimetry in a shear-thinning fluid (Carbopol). This non-Newtonian fluid was used in an attempt to mimic fermentation broths. Three Reynolds numbers corresponding to the transition regime were investigated. The hydrodynamics is analyzed, and the velocity field is decomposed by proper orthogonal decomposition into mean flow, organized motion, and turbulence. Then, the contributions of each flow structure to the total dissipation of kinetic energy are presented. The spatial heterogeneity of shear rate is discussed and a new expression is proposed for shear rate. This work shows that the local shear rate is highly heterogeneous in a tank. Future works will need to focus on other types of stirrer and investigate the effect of scaling up reactors on the shear rate heterogeneity. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2251–2266, 2013