Catalytic Kinetics and Dynamics

Rafael C. Catapan Matthew A. Christiansen Amir A. M. Oliveira , and Dionisios G. Vlachos  

Heterogeneous Catalysis at Nanoscale for Energy Applications, First Edition. Edited by Franklin (Feng) Tao, William F. Schneider, and Prashant V. Kamat. 2015 John Wiley Sons, Inc. Published 2015 by John Wiley Sons, Inc. 

FIGURE 8.1 Molecular-level overview of a catalytic chemical reaction. Selected elementary-like steps of the CO oxidation reaction CO adsorption, surface diffusion of CO, the TS of the C0 +0 surface reaction, the COj desorption, and various adsorbed species. 

Binding energy Adsorption properties calculation and zero point energy correction  

Rates at the macroscale Transition State Theory and Collision Theory 

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Weekman, V. W., Kinetics and dynamics of catalytic cracking selectivity in fixed-bed reactors, Ind. Eng. Chem. Process Des. Devel. 8, 385 (1969). 

Using Equation (23.27)-Equation (23.33), the mathematical simulation of steady-state and dynamic experiments was carried out. The results of calculation are represented in Figures 23.9, 23.10, 23.14, and 23.15 (lines — calculation, points — experiment). It is easily seen that the model demonstrates a good agreement with experiments in both steady-state and dynamic regimes. This confirms the interpretation of the experiments as the influence of capillary condensation on kinetics and dynamics of catalytic reaction. 

Geske M, Korup O, Horn R. Resolving kinetics and dynamics of a catalytic reaction inside a fixed bed reactor by combined kinetic and spectroscopic profiling. Catalysis Science Technology 2013 3 169-175. 

Choi JH, Kim YH, Nam SH, Shin ST, Kim M-J, Park J. Ami-nocyclopentadienyl ruthenium chloride catalytic racemization and dynamic kinetic resolution of alcohols at ambient temperature. Angew. Chem. Int. Ed. 2002 41 2373-2376. 

The reactivities of tlie species witliin tlie Wilkinson cycle are so great tliat tliey are not observed directly during tlie catalytic reaction ratlier, tliey are present in a delicate dynamic balance during tlie catalysis in concentrations too low to observe easily, and only tlie more stable species outside tlie cycle (outside tlie dashed line in figure C2.7.2 are tlie ones observed. Obviously it was no simple matter to elucidate tliis cycle tlie research required piecing it togetlier from observations of kinetics and equilibria under conditions chosen so tliat sometimes tlie cycle proceeded slowly or not at all. 

The chemistry at the electrified aqueous/metal interface is quite fascinating, as its structure, properties, and dynamics can significantly influence reaction energetics, dictate the kinetics that control catalytic selectivity, and open up novel reaction pathways and mechanisms. 

In terms of catalytic kinetics, the implications of the dynamic changes in catalyst morphology during methanol synthesis are dramatic. Figure 16a shows the agreement between the predictions of a static microkinetic model and the measured rates of methanol synthesis catalyzed by Cu/ZnO/A1203... 

Enzymes are biological catalysts. Without their presence in a cell, most biochemical reactions would not proceed at the required rate. The physicochemical and biological properties of enzymes have been investigated since the early 1800s. The unrelenting interest in enzymes is due to several factors— their dynamic and essential role in the cell, their extraordinary catalytic power, and their selectivity. Two of these dynamic characteristics will be evaluated in this experiment, namely a kinetic description of enzyme activity and molecular selectivity. 

We have used CO oxidation on Pt to illustrate the evolution of models applied to interpret critical effects in catalytic oxidation reactions. All the above models use concepts concerning the complex detailed mechanism. But, as has been shown previously, critical. effects in oxidation reactions were studied as early as the 1930s. For their interpretation primary attention is paid to the interaction of kinetic dependences with the heat-and-mass transfer law [146], It is likely that in these cases there is still more variety in dynamic behaviour than when we deal with purely kinetic factors. A theory for the non-isothermal continuous stirred tank reactor for first-order reactions was suggested in refs. 152-155. The dynamics of CO oxidation in non-isothermal, in particular adiabatic, reactors has been studied [77-80, 155]. A sufficiently complex dynamic behaviour is also observed in isothermal reactors for CO oxidation by taking into account the diffusion both in pores [71, 147-149] and on the surfaces of catalyst [201, 202]. The simplest model accounting for the combination of kinetic and transport processes is an isothermal continuously stirred tank reactor (CSTR). It was Matsuura and Kato [157] who first showed that if the kinetic curve has a maximum peak (this curve is also obtained for CO oxidation [158]), then the isothermal CSTR can have several steady states (see also ref. 203). Recently several authors [3, 76, 118, 156, 159, 160] have applied CSTR models corresponding to the detailed mechanism of catalytic reactions. 

In a recent survey [19] it was noted that a realistic model for catalytic oxidation reactions must include equations describing the evolution of at least two concentrations of surface substances and account for the slow variation in the properties of the catalyst surface (e.g. oxidation-reduction). For the synchronization of the dynamic behaviour for various surface domains, it is necessary to take into consideration changes in the concentrations of gas-phase substances and the temperature of the catalyst surface. It is evident that, in the hierarchy of modelling levels, such models must be constructed and tested immediately after kinetic models. On the one hand, the appearance of such models is associated with the experimental data on self-oscillations in reactors with noticeable concentration variations of the initial substances and products (e.g. ref. 74) on the other hand, there was a gap between the comprehensively examined non-isothermal models with simple kinetics and those for the complex heterogeneous catalytic reactions... 

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