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Consecutive First-order Reactions (consecutive + first-order_reaction)
Selected AbstractsCFD Modeling of a Bubble Column Reactor Carrying out a Consecutive A , B , C ReactionCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2004J.M. van Baten Abstract In this paper, we develop a CFD model for describing a bubble column reactor for carrying out a consecutive first-order reaction sequence A , B , C. Three reactor configurations, all operating in the homogeneous bubbly regime, were investigated: (I) column diameter DT = 0.1 m, column height HT = 1.1 m, (II) DT = 0.1 m, HT = 2 m, and (III) DT = 1 m, HT = 5 m. Eulerian simulations were carried out for superficial gas velocities UG in the range of 0.005,0.04 m/s, assuming cylindrical axisymmetry. Additionally, for configurations I and III fully three-dimensional transient simulations were carried out for checking the assumption of cylindrical axisymmetry. For the 0.1 m diameter column (configuration I), 2-D axisymmetric and 3-D transient simulations yield nearly the same results for gas holdup ,G, centerline liquid velocity VL(0), conversion of A, ,A, and selectivity to B, SB. In sharp contrast, for the 1 m diameter column (configuration III), there are significant differences in the CFD predictions of ,G, VL(0), ,A, and SB using 2-D and 3-D simulations; the 2-D strategies tend to exaggerate VL(0), and underpredict ,G, ,A, and SB. The transient 3-D simulation results appear to be more realistic. The CFD simulation results for ,A and SB are also compared with a simple analytic model, often employed in practice, in which the gas phase is assumed to be in plug flow and the liquid phase is well mixed. For the smaller diameter columns (configurations I and II) the CFD simulation results for ,A are in excellent agreement with the analytic model, but for the larger diameter column the analytic model is somewhat optimistic. There are two reasons for this deviation. Firstly, the gas phase is not in perfect plug flow and secondly, the liquid phase is not perfectly mixed. The computational results obtained in this paper demonstrate the power of CFD for predicting the performance of bubble column reactors. Of particular use is the ability of CFD to describe scale effects. [source] Hard-modelled trilinear decomposition (HTD) for an enhanced kinetic multicomponent analysisJOURNAL OF CHEMOMETRICS, Issue 5 2002Yorck-Michael Neuhold Abstract We present a novel approach for kinetic, spectral and chromatographic resolution of trilinear data sets acquired from slow chemical reaction processes via repeated chromatographic analysis with diode array detection. The method is based on fitting rate constants of distinct chemical model reactions (hard-modelled, integrated rate laws) by a Newton,Gauss,Levenberg/Marquardt (NGL/M) optimization in combination with principal component analysis (PCA) and/or evolving factor analysis (EFA), both known as powerful methods from bilinear data analysis. We call our method hard-modelled trilinear decomposition (HTD). Compared with classical bilinear hard-modelled kinetic data analysis, the additional chromatographic resolution leads to two major advantages: (1) the differentiation of indistinguishable rate laws, as they can occur in consecutive first-order reactions; and (2) the circumvention of many problems due to rank deficiencies in the kinetic concentration profiles. In this paper we present the theoretical background of the algorithm and discuss selected chemical rate laws. Copyright © 2002 John Wiley & Sons, Ltd. [source] Modeling of Product Removal during Enzymatic Conversions by Using Affinity MoleculesBIOTECHNOLOGY PROGRESS, Issue 6 2007Daniël G. R. Halsema The feasibility of using magnetic particles for in-line product isolation during enzymatic conversion was studied. A comparison was made between a process based on magnetic particles and a conventional adsorption column. The enzymatic reaction was described by two consecutive first-order reactions (synthesis and subsequent hydrolysis), while the adsorption of substrate and product was described by multicomponent Langmuir isotherms. The yield as well as synthesis/hydrolysis ratio were calculated for various system characteristics. The results show that magnetic particles are very effective when the affinity with the particles is specific and for enzymatic conversions involving low ratios of the rate of synthesis versus the rate of hydrolysis. For slow conversions and for low specific affinity molecules column separations are more appropriate. [source] Effect of Amino Acids on Acrylamide Formation and Elimination KineticsBIOTECHNOLOGY PROGRESS, Issue 5 2005Wendie L. Claeys The effect of amino acids other than asparagine on acrylamide (AA) formation/elimination kinetics was studied in an asparagine-glucose model system (0.01 M, pH 6) heated at temperatures between 140 and 200 °C. Addition of cysteine or lysine to the model significantly lowered the AA yield, whereas addition of glutamine had a strong promoting effect and of alanine a rather neutral effect on the AA formation. This was also reflected by AA formation/elimination kinetics, which for all model systems studied could be modeled by two consecutive first-order reactions. The ratio of the elimination to the formation rate constant increased from the systems to which glutamine or alanine was added, over the control model system, to the model systems that contained lysine or cysteine. [source] | ||||||||||