Chemical Engineering & Technology

The medium-temperature shift (MTS) catalyst is a new concept for the volume reduction of two-stage water-gas shift reactors. Studies are performed to develop advanced catalytic systems to convert CO in a single-stage MTS reactor. MTS catalysts and new modifications are reviewed.

A mixture of polypropy-lene and sawdust was chosen to study the effects of temperature on the oxidation performance of simulated medical waste in a packed-bed reactor. Detailed information in terms of product yields, compositions of liquid and gas products, and technical parameters is provided for a better understanding of the controlled air oxidation process.

Ionic liquid-coated Ni₂P/SiO₂ catalysts with different coating thicknesses were prepared in order to enhance the selectivity in selective hydrodesulfurization of gasoline. The selectivity factor was higher after the ionic liquid coating and presented a maximum of 16.7 at full monolayer coverage on the original Ni₂P/SiO₂ catalyst by the ionic liquid.

Using biomass as feedstock requires a re-development of the synthesis pathways via new intermediates to new end products as well as of the chemical processes. General principles are described, how the economic potential of synthesis pathways can be determined without having much detailed knowledge on the chemical processes by means of exergy balances.

The hydrodynamic, heat and mass transfer characteristics in a pressurized co-current gas-solid magnetically fluidized bed (MFB) were systematically investigated. It is shown that the pressurized MFB has the advantages of a wider operation range of the superficial gas velocity, a larger bed voidage, small pressure drop, and larger heat transfer efficiency, compared with the conventional fluidized bed.

The total annual cost of a glycerol etherification plant is minimized while taking into account the uncertainty of the design data and operability constraints. The solution is obtained by constructive nonlinear dynamics, using a reactor-separation-recycle model of the plant. The effectiveness of the approach is proved by dynamic simulation.

The mass transfer zone method for the analysis of adsorption kinetics from a fixed-bed breakthrough curve includes approxima-tions and estimation errors. A new analytical procedure for determining intraparticle diffusivity and the fluid-film mass transfer coefficient from an experimental breakthrough curve is described. The proposed method has the advantage of less trial and error and yields reliable results.

The effect of flue gas recirculation (FGR) by primary air mixed with FGR or nitrogen on NO_x emissions was evaluated. Bed temperature, stoichiometric oxygen ratio in the combustion chamber, and excess oxygen ratio were investigated in a vortexing fluidized-bed combustor. The results proved that the NO_x emissions can be effectively decreased with FGR.

A dynamic numerical computational fluid dynamics model was integrated into a commercial fluid dynamics simulator and validated to simulate the fluid flow and transport phenomena for separation of CO₂-CH₄ in a packed-bed adsorption column. The simulation results demonstrated a realistic pattern for the effects of operating parameters on adsorption dynamics.

Cellulose salt was hydrothermally treated by utilizing quartz capillaries as a convenient method to screen the reaction mechanisms over time and tempera-ture. Several products of cellulose decomposition were detected. The experiments give insights into the reaction mechanisms and the precursors of the products.

Evaporation rates of fuels covered with a film of aqueous film-forming foam (AFFF) were measured in order to evaluate the possibility to diminish evaporation losses of volatile hydrocarbons. Polyethylene glycol is able to modify the AFFF in a way that it can create a protective permanent film on the fuel surface, thus leading to reduced evaporation losses.

Direct gas phase ozonation at room temperature was utilized to modify the properties of multiwalled carbon nanotubes used as catalysts in the oxidative dehydro-genation of ethyl benzene to styrene. Catalysts treated at a high ozone concentration during their preparation are considered to be promising candidates due to their high conversion and selectivity of 80 % and 92 %, respectively.

An innovative porous copper fiber sintered felt (PCFSF) has been applied as catalyst support to construct a methanol steam reforming microreactor. The effects of varying porosities, catalyst loadings, and sintering temperatures were evaluated by ultrasonic water bath vibration, leading to optimized conditions for the catalyst.

The effects of temperatures, pressures, and times on the supercritical CO₂ regeneration of activated carbon loaded with cyclo-hexane were investigated. The process of regeneration was mathematically modeled via dynamic extraction by solving the differential material balances. The achievable maximum yield of regeneration was 68 % at 55 °C and 140 bar.

A new procedure is proposed to scale up T-jets mixers, based on the identification of a noncritical dimension that can be increased without changing the mixing scales. This novel scale-up does not affect micromixing and represents a favorable alternative to the traditional numbering-up of microreactors to increase the throughput of an installation.

The preparation and application of innovative organic-inorganic hybrid membranes using hollow hTiO₂ spheres as inorganic filler and chitosan (CS) as polymer matrix are described for isopropanol dehydration. A hTiO₂(6)-CS/polyacrylonitrile composite membrane offered the best pervaporation performance. This kind of composite membranes may find promising applications in the dehydration of alcohols.

The main aim of the work was to generate ethylene polymers having bimodal weight distributions. For this purpose new ansa-zirconocenes with functional side chains tethered to the Si-bridge were synthesized. They were activated by methylaluminoxane and used in solution polymerization. Experiments using Me₂SiCp₂ZrCl₂ formed products with unimodal weight distributions, indicating that the functionalized side chains of the new catalysts cause bimodal weight distributions.

A structure model of spray coating film was built, and it can be used to calculate the permeability coefficients of films using its structure parameters. The relationship between film structure, permeability coefficients of the film, and release characteristics of the coated urea were modeled for efficiently predicting the release characteristics.

Three advanced oxidation reactors, i.e., UV/H₂O₂, photo-Fenton reaction, and conductive diamond electrolysis, were built for the elimination of persistent organic pollutants and tested for their capacity to discolor indigo carmine. An energetic analysis on total energy consumption and effective electrical consumption after subtraction of non-process-related costs is performed.