Modular continuous production concepts are already successfully applied in research, development, and piloting of a series of chemical compounds in the markets of fine chemistry and pharmaceutical products. Besides, first case studies for the application of those concepts in industrial scale are reported. Current European research projects focus to proof their applicability in a broader range. The elaborated know-how will be commercially used in a franchise between BTS, INVITE, Ehrfeld Mikrotechik BTS, and further partners in the product Flonamic®. One core element of these production concepts are micro- and milli-structured devices assisting continuous-flow processes due to their superior transport characteristics and small holdup. In small-scale production concepts, these special devices have to be considered together with conventional technology. The platform concept developed by TU Dortmund University for chemical manufacturing simplifies the scale-up process from lab to container scale and beyond on different levels in flow rate, temperature, or other process conditions.

Typical examples at Bayer Technology Services demonstrate the capability of continuous-flow production processes with micro-structured equipment in different production scales. The elaborated know-how is commercially used in a franchise between BTS, INVITE, Ehrfeld Mikrotechik BTS, and further partners in the product Flonamic^®.

The use of reactive gases for syntheses on small laboratory scale is often avoided due to safety concerns so that expensive alternatives are required. The recent development of gas-permeable membrane-based reactors offers new options for safe handling of these gases in a continuous-flow system. A prototype of a gas/liquid system was built to introduce gas in the microreactor. An integrated gas flow controller and inline FTIR analysis were used to safely handle the gas. With the system, the carboxylation of a Grignard reagent with carbon dioxide was chosen as a nonhazardous model reaction to validate the prototype reactor.

Gas-permeable membrane-based reactors offer safe handling of gases in a continuous-flow system. A prototype of a gas/liquid system was constructed to introduce gas in a microreactor. An integrated gas flow controller and inline FTIR analysis were used to safely handle the gas. Carboxylation of a Grignard reagent with CO₂ served as a nonhazardous model reaction.

Life cycle assessment (LCA) has become increasingly popular in chemical industry as a standardized methodology for analysis of the environmental impact of products during their whole life cycle. Changes in process design by novel approaches like micro reaction engineering and the respective influence on the use of life cycle assessment are reviewed. The available literature on LCA in early research and development is comprehensively explored for conventional chemical and micro reaction engineering.

Micro process engineering has initiated a rethinking in process design within the field of chemical process engineering. In order to demonstrate how these changes in process design influence the use of life cycle assessment (LCA), the available literature on LCA in early R&D for conventional chemical and micro reaction engineering is reviewed.

Microreactors have been used for acquiring process data while consuming significantly lower amounts of expensive reagents. In this article, the combination of microreactor technology and computational fluid dynamics (CFD) is shown to contribute significantly towards understanding the diffusional properties of the substrate and the product of a biocatalytic reaction. Such knowledge is then applied to design reactor configurations. It has been demonstrated that this kind of knowledge is crucial for the choice and design of reactors. In the discussion, it is highlighted how microreactor-based platforms with similar dimensions to the ones tested here can be used as a screening tool for screening biocatalyst and process alternatives.

The combination of microreactor technology and CFD is used to gain process understanding of the diffusional properties of the substrate and product of a biocatalytic reaction. Such knowledge is then applied to design reactor configurations. It has been demonstrated that this kind of knowledge is crucial for the choice and design of reactors.

A screen printing procedure was developed to deposit catalyst coatings into microchannels by wash-coating through a low-cost technique suited for mass production. The composition of the suspension was optimized regarding the choice of solvent, binder, and additive so as to achieve both optimum rheological properties for screen printing and catalyst adhesion. The feasibility of screen printing catalysts into arrays of plates carrying microchannels was demonstrated and the long-term durability of the catalytic performance of the screen-printed coatings was proven experimentally.

For deposition of catalyst coatings in microchannels by wash-coating, a novel low-cost screen printing procedure was developed which is suited for mass production. Rheological properties and adherence of catalyst suspensions were optimized, allowing the successful implementation of screen printing without impairing the catalytic performance.

An innovative concept for the characterization of situations or problems (drivers) where the application of continuous flow processing, microreactor and/or other intensification technologies lead to the desired solutions is presented. An overview of techniques and equipment (tools) currently available for developing intensified processes is given as well as some examples of how they can be implemented in the engineering of chemical plants in kilo-lab, pilot-, and full-size manufacturing scale. These drivers and tools are described and depicted by easy-to-understand icons, and strategies for the development of continuous processes are explained. Short summaries of three different case studies demonstrate the economic advantages and potentials of intensified flow processing in manufacturing scale. Finally, the current approach to avoid inflexibility of systems operated in continuous mode is reported and how pilot and manufacturing plants can be realized with a special focus on modularity and multi-purpose functionality.

Problems that can be solved by application of continuous flow processing, microreactor, or other intensification technologies are characterized by an innovative concept. Techniques and equipment presently available for developing intensified processes are summarized and examples for their successful implementation in the engineering of chemical plants are described.

The application of ultrasound during the batch-wise as well as continuous crystallization of lipid nanoparticles is reported. For the latter, a micro heat exchanger is modified, allowing the inline application of ultrasound to promote the α-to-β transformation of the lipid nanoparticles. Ultrasonication during batch crystallization is carried out in an ultrasonic bath. While for batch processing the application of ultrasound leads to an increase of the fraction of stable β-polymorph according to differential scanning calorimetry measurements, no significant increase is found for continuous operation. This is a result of one or both of the following effects: The residence time in the continuous micro heat exchanger is approximately 1 s and thus possibly too short for significant influences on the polymorphism or crystallization. Additionally, the ultrasound is induced indirectly to the product side and thus reduced.

As an alternative approach to thermal treatment, ultrasound during batch-wise and continuous crystallization of solid lipid nanoparticles is applied. The overlapping effects of ultrasound and the accompanying temperature increase in batch processing are separated using a modified micro heat exchanger with the option for inline ultrasonic treatment.

The velocity distribution among microchannels with rectangular manifolds at different entrance velocities and the influences of structural parameters and entrance velocity on flow uniformity are investigated. The flow uniformity of a microchannel plate with rectangular manifold decreases with higher entrance velocity. At relatively low entrance velocity, the velocity distribution of the microchannel plate with centrosymmetric manifold is approximately symmetric. The velocity distribution becomes monotonically increased in a plate with large inlet manifold, whereas it becomes monotonically decreased in the one with large outlet manifold. A relatively uniform flow distribution can be obtained by the following conditions: longer microchannel, smaller microchannel width, symmetric manifold structure, larger manifold area, and perpendicular direction of inlet/outlet to the microchannel plane.

The flow uniformity of parallel microchannels influences the reaction performance. The effects of structural parameters and entrance velocities on the velocity distribution in a microchannel plate with rectangular manifolds are investigated by a 3D CFD model in order to enhance the design and optimization process for micro-channel plates. Relevant factors for a uniform flow distribution are evaluated.

A dual-pipe-type microreactor was applied to the formation of nanoparticles at a very rapid reaction rate. As a representative example, zirconia particles were produced by supplying zirconium tetrabutoxide solutes and alcohol/water mixtures. The effects of the solvent and alcohol types and the residence time on the particle properties were examined. Zirconia particles were produced and grown in an inner fluid, and no precipitation of particles was observed at the wall in the outer fluid. When ethanol was used as a solvent for diluting water, the zirconia particles had a sharp narrow size distribution that could not be attained by means of a conventional batch method. The mean particle size was successfully controlled in the range of 4–600 nm merely by changing the mean residence time and the concentrations of zirconium tetrabutoxide and water in the presence of a dispersant, polyethyleneimine.

Experiments were performed to form zirconia fine particles using a concentric microreactor with an axle dual pipe. The particle size of zirconia particles was controlled by changing the mean residence time and the concentrations of zirconium tetrabutoxide and water in the presence of a dispersant. Primary nucleation and particle growth can be independently and precisely controlled.

The generation of gas-liquid-liquid three-phase microflows in a cross-junction microchannel device is experimentally analyzed. Three gas-phase and eight water-phase flow manners at the cross junction are described with oil phase as continuous phase. Comparing with the gas-liquid and liquid-liquid two-phase microflows, similar flow behaviors of dispersed phases exist in the three-phase processes but new capillary numbers as well as the phase ratio of dispersed phases need to be introduced in the flow maps to distinguish the complicated three-phase flow modes. Although the three-phase flows are mercurial at the channel junction, only six flow patterns are observed in the downstream microchannel. According to the experimental results, the effects of bubble/droplet generation manners on their size distributions are indicated. The generation mechanisms of bubbles and droplets are analyzed and correlated equations are established for their average volumes.

The generation of gas-liquid-liquid three-phase microflows in a cross-junction microchannel is investigated by testing different working systems with variations of three-phase flow rates, viscosities, and interfacial tensions. Volume variations and size distributions of bubbles and droplets are indicated according to their respective generation mechanisms.

Utilizing petroleum coke as fuel in an efficient and environmentally friendly way is a great challenge. Within the technological framework of chemical looping combustion, the reaction of the oxygen carrier CuFe₂O₄ with a typical high-sulfur petroleum coke (designated as JS) was performed, focusing on the conversion of the JS coke, the oxygen transfer from CuFe₂O₄, and the reaction characteristics involved. Simultaneously, the evolution of sulfur and minerals present in JS was also considered. Thermogravimetric analysis of the reaction of CuFe₂O₄ with JS demonstrated the reaction superiority of CuFe₂O₄, with its reactivity being close to that of CuO. The preferred CuFe₂O₄ oxygen excess number Φ for JS conversion was determined as unity. Furthermore, both the experimental means, including Fourier transform infrared spectroscopy, field scanning electron microscopy/energy-dispersive X-ray spectrometry and X-ray diffraction analysis, and the thermodynamic simulation of the reaction of CuFe₂O₄ with JS indicated that the main reduced counterparts of CuFe₂O₄ were Cu and Fe₃O₄. Most of the organic sulfur dominant in JS coke reacted with the reduced CuFe₂O₄ to form Cu₂S, and the side product Fe₂SiO₄ should also be noted for its detrimental effect on the reactivity of CuFe₂O₄.

The reaction of petroleum coke with CuFe₂O₄ as oxygen carrier was systematically investigated. The evolution of minerals and sulfur species contained in the petroleum coke and their interactions with the reduced CuFe₂O₄ were explored in detail.

The mechanism of the salt-to-free form drug transformation was explored by investigating the pH-solubility profiles of a model drug in a salt form and the nucleation of the free base from the salt solution when its pH was increasing. The transformation of the salt to the free base during wet massing in the presence of pharmaceutical excipients with different pH was studied. The nucleation of the free base occurred when the pH of the salt solution reached a certain level pH_metastable, which was related to the free energy penalty associated with the creation of a new solid phase. The nucleation of the free base happened readily and thus, the salt-to-free base transformation occurred rapidly during wet massing with the excipients with a pH above the pH_metastable. These results can support robust formulation design of solid dosage forms containing salts by optimal excipient selection.

The mechanisms of the transformation from salt to free form drug during processing of a model drug are investigated with special emphasis on the interplay of salt solubility and pH of the excipients. The obtained results can provide a reliable guidance for selecting excipients for robust formulation design of solid dosage pharmaceuticals in salt forms.

Surface structures with a well-defined shape and dimension in a staggered arrangement were evaluated in terms of their capability to improve the single-phase convective heat transfer in channels with small dimensions. Two evaluation criteria were used: (i) the thermal efficiency index, defined by the ratio of heat transfer enhancement and pressure drop increase, and (ii) the irreversible entropy generation which is determined by the entropy production rates through heat conduction and dissipation. Beside experimental measurements, parametric studies were performed using computational fluid dynamics to establish the entropy generation rates within the heated flow channel.

Microstructures with defined shape, dimensions, and arrangement were assessed in terms of their capability to improve convective heat transfer in microchannels. Overall efficiencies were determined experi-mentally and by computational fluid dynamics. As evaluation criteria served the thermal efficiency index and the irreversible entropy generation.

Significant process intensification was achieved for the continuously operated Kolbe-Schmitt synthesis of 2,4-dihydroxybenzoic acid (β-resorcylic acid) on laboratory scale by using different approaches opening novel process windows. The results of the optimal process variant, both from the economic and ecological view, were scaled up to the pilot scale. In a first step, the synthesis from resorcinol in aqueous potassium hydrogen carbonate solution was transferred from the capillary reactor to a tailor-made electrically heated microstructured reactor comprising 40 microchannels and enabling a 25-fold increase of the capacity. In a second step, a pilot plant comprising three of such reactors operated in parallel was built and successfully tested with the same reaction.

The Kolbe-Schmitt synthesis is a traditionally used carboxylation reaction for phenolic cores which enables the introduction of a carboxylic group by an electrophilic substitution. Process intensification results were transferred from the lab scale to pilot scale without a considerable loss of performance.

Among the different separation processes, liquid-liquid extraction especially benefits from microfluidics as the short molecular diffusion distance and large specific interfacial area in microchannels are advantageous for effective liquid/liquid contacting. An overview is given on different examples of continuous micro liquid-liquid extraction. As contacting of the two phases as well as phase separation strongly depend on the flow pattern, one chapter is devoted to each parallel flow, segmented flow, and emulsions. Advantages and disadvantages of the three flow patterns are compared to each other. Additionally, possibilities for scaling up microfluidic concepts for higher-throughput systems are presented.

Continuous microfluidics experienced a steep rise in attention during the last two decades and many unit operations have successfully been adapted to microreactors. Especially liquid-liquid extraction benefits from the small dimensions as the short molecular diffusion distance and large specific interfacial area in microchannels are advantageous for effective liquid/liquid contacting.

There are a number of challenges that need to be overcome in order to stimulate more synthesis chemists to adopt continuous-flow chemical processing techniques. By way of example, the use of cryogenic consumables to cool reactions is impractical on scale or over extended reaction times. Here, a solution to the problem is described with the development of a convenient laboratory device that offers chemists the benefits of continuous flow processing using an accurate thermal energy transfer block which provides long-term reaction stability and is free from water ingress.

In continuous-flow chemical processing techniques, the use of cryogenic consumables to cool reactions is impractical on scale or over extended reaction times. A solution to the problem is described with the development of a convenient laboratory device.

The synthesis of adipic acid by means of a direct oxidation of cyclohexene by hydrogen peroxide was carried out in a continuous-flow packed-bed microreactor. The reaction uses Na₂WO₄·2H₂O as a catalyst and [CH₃(n-C₈H₁₇)₃N]HSO₄ as a phase transfer catalyst without additional solvent. A parametric process optimization, such as glass beads size, residence time, concentration of hydrogen peroxide, addition of acid, reaction temperature, and molar ratios of reactants and catalysts, was performed. It is demonstrated that smaller glass beads result in a better yield of adipic acid and that the addition of acid plays an important role in the oxidation of cyclohexene to adipic acid. Based on the concept of Novel Process Windows, the influence of elevated temperatures is investigated.

A novel microflow process is described for the synthesis of adipic acid by means of direct oxidation of cyclohexene by hydrogen peroxide in a continuous-flow packed-bed microreactor. Parametric process optimization of appropriate reaction conditions is performed and applied. This direct oxidation process has a great potential in microreactor technology.

Ionic liquids (IL) are salts that have extraordinarly low melting points below 100 °C. While only a very limited number of possible IL can be synthesized directly, the vast majority is prepared via the synthesis of a precursor IL with the desired cation and a subsequent anion exchange. This paper presents the continuous anion exchange by Donnan dialysis in aqueous solution with anion exchange membranes. The retention of the anion exchange membranes used in this work for inorganic and IL cations was found to be R > 99 %. The average integral transport coefficients were determined for the exchange of chloride/acetate, chloride/hydroxide and bromide/hydroxide for various IL and classical salts. The values of the integral average transport coefficients were found to be independent of the investigated counterions. Process modeling was applied to optimize the flow conditions to reach an anion exchange > 98 %. Ultrapure hydroxide solutions and acetates of common classes of IL cations were prepared with a conversion of the reactant anions of > 99 % and cationic impurity contents of < 1 %.

A diffusion model-based approach is presented to model and optimize countercurrent Donnan dialysis. Integral transport coefficients were determined for several anions, with the objective to prepare task-specific ionic liquids (ILs) by continuous anion exchange. Anion conversions > 99 % were reached after model-based process optimization. Ultrapure IL were produced in long-term experiments for up to 130 h on stream.

The mixed-matrix membrane (MMM) is a new membrane material for gas separation and plays a vital role for the advancement of current membrane-based separation technology. Blending between inorganic fillers like carbon molecular sieves, zeolite, metal oxides, silica and silica nanoparticles, carbon nanotubes, zeolitic imidazolate framework, metal organic framework, and glassy and rubbery polymers etc. is possible. Due to mechanical, thermal, and chemical stability, these membranes achieve high permeability and selectivity as compared to pure polymeric materials. Despite of these advantages, the MMM performances are still below industrial expectations because of membrane defects and related processing problems as well as the nonuniform dispersion of fillers in MMMs. Material selection for organic and inorganic phases, preparation techniques, material advancements, and performance of MMMs are discussed. Issues and challenges faced during MMM synthesis as well as problem solutions are highlighted.

Mixed-matrix membranes (MMMs) are promising tools for gas separation due to their excellent physical and chemical properties as compared to organic and inorganic membranes but face some challenges regarding interfacial defects or adhesion between the organic and inorganic phases. Recent advances in material development for fabrication of MMMs are highlighted.

The simulation of fermentation product separation using nanoporous membranes is presented. The aim of the simulation was to predict the performance of an extraction process to remove compounds from aqueous solutions. The simulation was conducted using computational fluid dynamics techniques for the solution of governing equations. The system studied was a membrane-based extractor of acetone from aqueous solutions using near-critical CO₂ as solvent. The predicted extraction percentages obtained by the simulations were compared to experimental values reported in the literature and showed very good agreement. The simulation can predict the concentration profile of acetone in the membrane and also predicts the formation of a concentration boundary layer.

Fermentation product separation using nanoporous membranes was simulated using computational fluid dynamics. A mass transfer model was developed to describe the porocritical extraction using hollow-fiber membrane contactors. The predicted extraction percentages obtained by the simulations showed very good agreement with experimental values reported in the literature.

Biodiesel and valuable free lutein were demonstrated to be simultaneously produced from Chlorella vulgaris lipid extracts. The alkali catalyst used in the transesterification of triglycerides acted as a reactant in converting lutein fatty acid esters to free lutein. A maximum biodiesel yield of 33.6 % by weight of the algal lipids was obtained after a 4-h reaction with MeOH at the MeOH/biomass ratio of 16:1 using 6 % alkali catalyst. The excess of alkali and MeOH employed in the production of biodiesel ensured the complete saponification of all lutein fatty acid esters to free lutein, giving a maximum yield of 2.3 % by weight of the algal lipids. In addition, a process for the separation of the biodiesel and free lutein products from the reaction mixture is proposed. Finally, a preliminary economic assessment was conducted, the results of which suggest that the process for the simultaneous production of biodiesel and lutein from C. vulgaris may be economically feasible.

Microalgae are an interesting source for biodiesel production. The effects of key reaction parameters on the yields of biodiesel and free lutein from Chlorella vulgaris were investigated, including the amount of catalyst, the biomass-to-alcohol ratio, and the reaction time. In addition, a possible process for the separation of the biodiesel and lutein products from the reaction mixture is proposed.

Amine solutions were applied in carbon dioxide removal from a model mixture of biogas, carried out in a loop reactor system. In addition, the effect of CO₂ absorption acceleration in the presence of piperazine was confirmed and quantified, relating the obtained CO₂ loading with the piperazine concentration. Further, the interactions of CO₂ and water in aqueous amine solutions were discussed. The obtained acid gas loadings were accurately described taking into account the effect of the dissolved CO₂ on the equilibrium constant. A logarithmic absorption isotherm that follows from such considerations and a saturation-type isotherm were compared. In describing the experimental data, advantages and disadvantages of both approaches are discussed.

The absorption performance of piperazine-containing amine solutions to be used for biogas upgrading was investigated in terms of CO₂ capture. The suggested approach was utilized to describe the non-ideality of the absorption isotherms and proved to be suitable also for data reported by other research groups.

The potential of binderless briquetting as a means of transforming low-rank coals into low moisture high grade solid fuel products has been studied. Using two dried low-rank coals, binderless briquettes with high mechanical strength have been successfully produced through mechanical compression. An increase in heating value was achieved as a result of moisture reduction in the briquettes compared to as-received coals. The residue moisture content in the briquettes had a predominant effect on briquetting characteristics and there existed an optimum moisture content for the maximum briquettes strength. The chemical structure and wettability of binderless briquettes were analyzed using FTIR and contact angle measurement. The results showed that hydrophobicity and chemical structure significantly affected the briquette properties.

High mechanical strength binderless briquettes using two dried low-rank coals were successfully produced. Drying of low-rank coals prior to briquetting resulted in 30–50 % increase in calorific value. The optimum moisture content for high compressive strength was 12–15 %. The aromaticity of the briquettes was higher than raw coals as a result of decomposition of oxygen functionalities and aliphatic hydrogen groups.

Most investigations on heat exchanger network (HEN) synthesis which plays an important role in improving the efficiency of industrial plants, focus on deterministic conditions whereas operational flexibility and feasibility are less concerned. In the real industrial world, each system experiences various disturbances due to changes in stream temperature, flow rate, and other uncertain factors. An approach for flexible HEN synthesis under severe operation uncertainty is proposed, which is represented by the Probability bounds analysis (PBA) theory and is sampled by a double-loop sampling method. A case study, which generates a better solution with less total annual cost and good flexibility under severe uncertainty, demonstrates the capability of this simplified approach.

Since operational flexibility and feasibility of Heat Exchanger Network (HEN) design traditionally are less concerned, an approach for flexible HEN synthesis under severe operation uncertainty is proposed. A case study providing a better solution with less total annual cost and good flexibility proves the potential of this simplified approach.

An engineered process for scalable manufacture of a calcium aluminum carbonate CO₂ sorbent with production amounts of about 1000 g per hour has been developed. The process includes mixing and heating, solid-liquid separation, drying and extrusion, crushing and conveying, and calcined molding steps. The sorbent preparation involves the coprecipitation of Ca²⁺, Al³⁺, and CO₃^2– under alkaline conditions. By adjusting the Ca:Al molar ratio, a series of Ca-rich materials could be synthesized for use as CO₂ sorbents at 750 °C. A calcium acetate-derived sorbent exhibited better cyclic stability than sorbents originating from CaCl₂ and Ca(NO₃)₂. The initial sorption capacity increased with CaO concentration. High stability of more than 90 % was maintained by the Ca:Al sorbents after 40 looping tests.

The main advantages using CaO-based sorbents for high-temperature CO₂ capture are their high capacity and advanced CO₂ uptake characteristics. A novel process for scalable manufacture of a calcium aluminum carbonate CO₂ sorbent is introduced. Using this method, CO₂ sorbents with significantly improved performance can be produced in kg-batches.

Based on the experiments of pulverized coal pneumatic conveying using nitrogen as carrier, the influences of riser inlet height above the gas distribution plate, riser diameter, pulverized coal external moisture content, and supplemental gas flow rate on the conveying characteristics such as pulverized coal mass flow rate and solid-gas ratio were investigated in a laboratory-scale experimental setup of a top-discharge blow tank under atmospheric pressure. There exists an optimal riser inlet height for a given top-discharge blow tank. The supplemental gas is one of the critical factors affecting the conveying stability and continuity. A model for material mass flow rate prediction with errors ranging from –25 % to +15 % is presented.

Dense-phase pneumatic conveying of pulverized coal has been widely employed to feed coal to gasifiers. The blow tank is one of the most important instruments in a dense-phase conveying system. The influences of riser inlet height, riser diameter, pulverized coal external moisture content, and supplemental gas flow rate on the conveying characteristics are investigated.

In this work, advanced oxidation removal of nitric oxide (NO) from flue gas by homogeneous Photo-Fenton was investigated in a photochemical reactor and the effects of several influencing factors on NO removal were evaluated. The gas-liquid reaction products were determined. The reaction pathways of NO removal are also preliminarily discussed. It was found that with the increase of Fe²⁺ concentration, NO removal efficiency first increased and then decreased. Increasing H₂O₂ concentration and UV radiation intensity greatly increased NO removal efficiency, but the growth rates gradually became smaller. NO removal efficiency greatly reduced with the increase of gas flow and NO concentration, and only slightly decreased with the increase of solution temperature, but significantly increased with the increase of initial solution pH value. The main anion product in the liquid phase was NO₃^–. With respect to removal of NO using homogeneous Photo-Fenton, ·OH oxidation was the main reaction pathway, and H₂O₂ oxidation was the secondary reaction pathway.

The emission of NO_x and SO₂ into the atmosphere is a major environmental concern because of their detrimental effects. The removal of nitric oxide from flue gas using a homogeneous Photo-Fenton advanced oxidation process was investigated in a lab-scale photochemical reactor in respect to a number of factors, including reaction systems, UV radiation, gas flow, solution temperature and initial solution pH value.

In order to establish a realistic fibrous media structure, internal microscopic cross-sectional images were taken by scanning electron microscopy and then processed by Matlab. Finally, the 3D models of the fibrous media were reconstructed using Gambit software. The influences of structural parameters of the fibrous media on solid volume fraction and pressure drop were analyzed by response surface methodology, and the internal gas flow fields of the fibrous media were simulated using Ansys Fluent. The simulation results of the pressure drop are in good agreement with the Davies experimental correlation data.

Fibrous media exhibit higher filtration efficiencies than other filtration media and important perfor-mance indicators of fibrous media are mainly determined by the internal microstructure. Response surface methodology and numerical simulation were applied to study the influence of structural parameters of the fibrous media on solid volume fraction and pressure drop.

Metathesis between decene and ethene to propene over a WO₃/SiO₂ catalyst was studied. The dependency of the conversion of decene, selectivity to propene, and working lifetime of the catalyst on ethane-to-decene molar ratio and temperature was evaluated. Low temperature was found to be favorable to the production of C₆–C₉ olefins, while high temperature enhanced C₁₀₊ olefins. The working lifetime of the catalyst decreased with the weight hourly space velocity. The optimum reaction conditions for the metathesis process of decene and ethene to propene were determined. An obvious induction period was found to exist in the metathesis reaction.

Metathesis between decene and ethene to propene over a WO₃/SiO₂ catalyst is proposed as a new route for the production of propene. The effects of reaction conditions on the conversion of decene, selectivity to propene, and working lifetime of the catalyst were investigated. An obvious induction period for the metathesis reaction was found.

An ultrasonic enhanced salt-containing hydrodistillation (UESHD) method for separating essential oil from lavender (Lavandula angustifolia) flowers was investigated using response surface methodology (RSM). The experimental data obtained from a 27-run experiment were fitted to a second-order polynomial equation. The optimal conditions were determined by the 3D response surface and the contour plots derived from the models. The efficiency of UESHD and conventional hydrodistillation (HD) was compared. The extraction yield of UESHD was two-fold higher than that of HD. In addition, GC-MS results indicated some differences in composition and content between the two essential oils from UESHD and HD.

An ultrasonic enhanced salt-containing hydro-distillation (UESHD) method was developed to separate lavender essential oil. The extraction yield of the oil was optimized by statistical software, the separation conditions by the Box-Behnken design. UESHD enabled a more than two-fold yield of essential oil than conventional hydrodistillation.

The present work reports the effect of bentonite clay on methane hydrate formation and dissociation in synthetic seawater of salinity 3.55 % of total dissolved salts. Extensive observations of pressure-temperature equilibrium during formation and decomposition of methane hydrate under different conditions have been made. It is observed that phase equilibrium conditions of hydrate are affected on changing the concentration of bentonite clay in synthetic seawater. Induction time for hydrate nucleation has been measured under different concentrations of clay and subcooling conditions. The presence of bentonite clay in synthetic seawater reduces the induction time of hydrate formation. Enthalpy of hydrate dissociation is calculated by Clausius-Clapeyron equation using measured phase equilibrium data. The amount of gas consumed during hydrate formation has been calculated using real gas equation. It is found that a larger amount of gas is consumed upon addition of bentonite clay in synthetic seawater.

Bentonite clay has been used for methane hydrate formation in synthetic seawater. Reaction kinetics and hydrate formation pressure and temperature were studied under different conditions. Bentonite clay has furthermore been investigated in terms of surface morphology, chemical changes due to hydrate formation and particle size distribution in suspension.

In this work, a mathematical model based on axial dispersion has been suggested to simulate the behavior of a multistage bubble column reactor. A six-stage pilot-scale reactor with an inner diameter of 0.35 m and a height of 12 m was used for hydrogen peroxide production through the direct oxidation of isopropyl alcohol at isothermal condition. Steady-state and dynamic simulations were performed to predict the concentration of all the reactants in gas and liquid phases. It was observed that for steady state-conditions the simulation results were consistent with the experimental results. Dynamic models involving liquid back-mixing can be used for the simulation of start-up, shut-down or transition operations in this kind of a rector.

Currently, an accurate dynamic description of multistage bubble column reactors (MBCR) is still difficult. In this study, a mathematical model, based on time-dependent kinetic constants and axial dispersion coeffi-cient in liquid and gas phases, has been developed to simulate the MBCR under dynamic conditions and validated with available experimental data.

Design and control of an extractive distillation system for tetrahydrofuran (THF) dehydration with ethylene glycol as entrainer is investigated. The main module is a two-column system containing an extractive distillation column, whose top stream is the desired product THF, and an entrainer recovery column. Economic analysis with total annual cost as the objective function is developed. Two kinds of control strategies are explored for THF dehydration. The responses reveal that the control structure with fixed reflux ratio cannot maintain the bottom liquid level of the entrainer recovery column, while the control scheme with fixed reboiler heat duty/feed flow ratio exhibits good control performance in spite of large deviations in feed flow rate and feed composition.

THF dehydration is a process of economical concern, as the THF demand is increasing. A steady-state design of two-column extractive distillation for tetrahydrofuran-H₂O separation is introduced, and optimal conditions are evaluated by minimizing the total annual costs. Both a basic and an improved control strategy are devised.

Microscale studies, which can provide basic information for meso- and macroscale studies, are essential for the realization of flow characteristics of a packed bed. In the present study, the effects of gas velocity, liquid velocity, liquid-solid contact angle, and liquid viscosity on the flow behavior were parametrically investigated for gas-liquid two-phase flow around a spherical particle, using computational fluid dynamics (CFD) methodology in combination with the volume-of-fluid (VOF) model. The VOF model was first validated and proved to be in good agreement with the experimental data. The simulation results show that the film thickness decreases with increasing gas velocity. This trend is more obvious with increasing operating pressure. With increasing liquid velocity, the film thickness tends to be uniform on the particle surface. The flow regime can change from film flow to transition flow to bubble flow with increasing contact angle. In addition, only at relatively high values does the liquid viscosity affect the residence time of the liquid on the particle surface.

Gas-liquid two-phase flow around a spherical particle was investigated by computational fluid dynamics methodology. The results show that the film thickness decreases with increasing gas velocity, especially at high pressures, that the flow regime can be changed with increasing contact angle, and that the liquid viscosity, at relatively high values, affects the residence time of the liquid on the particle surface.

To simulate the centrifugal short-path distillation process, both two phases and interfacial transport are taken into account simultaneously for the first time. A new computational fluid dynamics model based on the volume-of-fluid and species transport methods is built up to analyze the detailed flow and transfer characteristics. A binary system with dibutyl phthalate-dibutyl sebacate (DBP-DBS) is used as an example for the investigation with both numerical and experimental methods. The residence time and the effects of operating parameters such as evaporator temperature and feed flow rate are explored comparatively. The simulation result for the liquid-film thickness shows a satisfactory agreement with literature data. On the basis of the simulation results, we may also obtain detailed characteristics of the heat and mass transfer such as gradients in temperature and concentration and the liquid overall mass transfer coefficient.

Up to now, very few works have been reported concerning the interfacial transfer in the short-path distillation process. A computational fluid dynamics (CFD) model based on the volume-of-fluid and species transport methods is proposed for the first time to investigate the characteris-tics of flow and transport processes during centrifugal short-path distillation.

The effect of pressure on the possible existence of multiple steady states in bubble column reactors is investigated. A mathematical model involving fast pseudo first-order kinetics is employed to describe the performance of non-isobaric, non-isothermal reactors. The numerical analysis reveals that the existence of multiplicity is sensitive to pressure variation, yet high-pressure operating conditions do not necessarily lead to a higher likelihood of multiplicity in these contactors.

Bubble column reactors are widely used in industry for a variety of gas-liquid and biochemical reactions. The occurrence of steady-state multiplicity in non-isobaric bubble column reactors is examined using a mathematical model and the sensitivity of the reactor performance to pressure variation is investigated.