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Reaction Conversion (reaction + conversion)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

A two-phase model for variable-density fluidized bed reactors with generalized nonlinear kinetics

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2000
Zahra M. Tafreshi
Abstract A model based on the classical two-phase concept is developed for the simulation of variable-density reaction with generalized nonlinear kinetics in a bubbling fluidized bed. The influence of reaction density parameter on the fluidodynamics and performance of the reactor for four general types of reactions was explored. The results show that the expansion factor has a significant effect on both fluidodynamic characteristics and reaction conversion. In all types of reactions, higher values of hydro-dynamic variables were obtained when , , 0. Reaction conversion, however, dropped as the expansion factor increased. This trend was more pronounced for reaction orders higher than unity. This suggests that bubbling fluidized operations are probably not optimal and applicable for certain types of reactions. Comparative analysis between reaction type and implications for optimum fluidized bed reactor are discussed. On a mis au point un modèle basé sur le concept classique à deux phases pour la simulation de la réaction à densité variable avec les cinétiques non linéaires généralisées dans un lit fluidisé bouillonnant. L'influence du paramètre de densité de réaction sur la dynamique des fluides et la performance du réacteur a été étudiée pour quatre types généraux de réaction. Les résultats montrent que le facteur d'expansion a un effet significatif sur les caractéristiques de dynamique des fluides et la conversion de la réaction. Dans tous les types de réactions, de grandes valeurs de variables hydrodynamiques ont été obtenues pour , , 0. Cependant, la conversion de la réaction chute lorsque le facteur d'expansion augmente. Cette tendance est plus prononcée pour des ordres de réaction supérieurs à l'unite. Cela suppose que les opérations en lit fluidisé bouillonnant ne sont probablement pas optimales ni applicables à certains types de réaction. L'analyse comparative entre le type de réaction et les implications pour un réacteur à lit fluidisé bouillonnant est examinée. [source]

Photooxidation of Benzyl Alcohols with Immobilized Flavins

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
Harald Schmaderer
Abstract Benzyl alcohols are oxidized cleanly and efficiently to the corresponding aldehydes under irradiation using flavin photocatalysts and aerial oxygen as the terminal oxidant in homogeneous aqueous solution. Turnover frequencies (TOF) of more than 800,h,1 and turnover numbers (TON) of up to 68 were obtained. Several flavin photocatalysts with fluorinated or hydrophobic aliphatic chains were immobilized on solid supports like fluorous silica gel, reversed phase silica gel or entrapped in polyethylene pellets. The catalytic efficiency of the heterogeneous photocatalysts was studied for the oxidation of different benzyl alcohols in water and compared to the analogous homogeneous reactions. Removal of the heterogeneous photocatalyst stops the reaction conversion immediately, which shows that the immobilized flavin is the catalytically active species. The immobilized catalysts are stable, retain their reactivity if compared to the corresponding homogeneous systems and are easily removed from the reaction mixture and reused. TOF of up to 26,h,1, TON of 280 and up to 3 reaction cycles without loss of activity are possible with the heterogeneous flavin photocatalysts. [source]

A two-phase model for variable-density fluidized bed reactors with generalized nonlinear kinetics

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2000
Zahra M. Tafreshi
Abstract A model based on the classical two-phase concept is developed for the simulation of variable-density reaction with generalized nonlinear kinetics in a bubbling fluidized bed. The influence of reaction density parameter on the fluidodynamics and performance of the reactor for four general types of reactions was explored. The results show that the expansion factor has a significant effect on both fluidodynamic characteristics and reaction conversion. In all types of reactions, higher values of hydro-dynamic variables were obtained when , , 0. Reaction conversion, however, dropped as the expansion factor increased. This trend was more pronounced for reaction orders higher than unity. This suggests that bubbling fluidized operations are probably not optimal and applicable for certain types of reactions. Comparative analysis between reaction type and implications for optimum fluidized bed reactor are discussed. On a mis au point un modèle basé sur le concept classique à deux phases pour la simulation de la réaction à densité variable avec les cinétiques non linéaires généralisées dans un lit fluidisé bouillonnant. L'influence du paramètre de densité de réaction sur la dynamique des fluides et la performance du réacteur a été étudiée pour quatre types généraux de réaction. Les résultats montrent que le facteur d'expansion a un effet significatif sur les caractéristiques de dynamique des fluides et la conversion de la réaction. Dans tous les types de réactions, de grandes valeurs de variables hydrodynamiques ont été obtenues pour , , 0. Cependant, la conversion de la réaction chute lorsque le facteur d'expansion augmente. Cette tendance est plus prononcée pour des ordres de réaction supérieurs à l'unite. Cela suppose que les opérations en lit fluidisé bouillonnant ne sont probablement pas optimales ni applicables à certains types de réaction. L'analyse comparative entre le type de réaction et les implications pour un réacteur à lit fluidisé bouillonnant est examinée. [source]

Water gas shift reaction via Pd-based membranes

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009
Silvano Tosti
Abstract The water gas shift reaction has been studied in tubular Pd-based membranes: a thin walled dense tube and a composite Pd-ceramic tube have been considered. A computer code based on a finite element model has been developed for modelling the membrane reactor. The model accounts for the reaction kinetic, the hydrogen diffusion through the porous ceramic support and permeation through the PdAg membrane and for the partial pressure gradients of hydrogen generated at the permeate side of the membrane when a flow of purge gas is introduced. The code has been used to assess the influence of temperature, lumen pressure, presence of wall effects and sweep gas mode on the reaction conversion and hydrogen yield of the membrane reactors. At 200 kPa of lumen pressure and counter-current sweep mode, it was found that both reaction conversion and hydrogen yield increase with temperature: the dense and the composite membranes exhibit very close values of conversion (more than 99% at 400 °C) and hydrogen yield (96,97% at 400 °C). In co-current mode, the highest values of both reaction conversion and hydrogen yield have been assessed at 350 °C, while it was demonstrated that the beneficial effects of increasing the lumen pressure up to 400 kPa are maximum at 300 °C. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]