Use of kinetic modeling

To rationally govern the selectivity of a catalytic process, the elementary reaction steps on real catalyst surfaces must be identified. The use of well-defined organometallic compounds (possible intermediates in surface reactions) can be very useful in the determination of these steps. The use of kinetic modelling techniques combined with statistical analysis of kinetic... 

But there is much more to be learned from this data. Now is the time to exploit the use of kinetic models. At this stage, there will be much about the kinetics that is not known, but there will be enough known that reasonable candidate models can be hypothesized. Here again the knowledge of the process chemist comes to the forefront in suggesting appropriate models to explore. From the initial studies, one can see that the rate of loss of A and B appeared to be equal and match the formation of C (see runs 1 and 5 in Fig. 1). C then appears to degrade as... 

Use of Kinetic Models for Solid State Reactions in Combustion Simulations... 

Most previous theoretical studies of dynamic operating reactors used kinetic expressions obtained under steady-state operation. These models do not account for the detailed dynamics of the adsorption and desorption rate processes, and they may lead to erroneous predictions in periodic operation of the reactor. Thus, simulations of periodic processes may require use of kinetic models that are much more detailed than those used for predicting steady-state operation. These dynamic models also need to account for the rate of adsorption, desorption, and adsorption capacity of the catalyst. As mentioned above, the hot-temperature zone in a cooled RFR may exhibit complex dynamic features under... 

There are typically several different product grades produced in a singlepolymerization reactor, and transitioning between these products in the minimum time maximizes production yield. Most PS producers rely on the use of kinetic modeling and computer simulation to aid in the manufacture of PS to minimize... 

The biological monitoring of lead exposure in paediatric and adult human populations has usually involved one of two approaches (1) measurement of the internal or systemic dose of lead itself in some indicator medium, or (2) quantification of some subcritical effect of lead. The extent to which biological monitoring in humans accurately states both exposure risk and relative health risk remains the subject of much research. Of particular interest are (1) the biokinetic characteristics of the common indicators of exposure, (2) the development and use of kinetic models of lead metabolism, and (3) the relative merits of the use of biological effect indicators versus measurement of the toxicant in some medium. 

The use of PB modeling by practitioners has been hmited for two reasons. First, in many cases the kinetic parameters for the models have been difficult to predict and are veiy sensitive to operating conditions. Second, the PB equations are complex and difficult to solve. However, recent advances in understanding of granulation micromechanics, as well as better numerical solution techniques and faster computers, means that the use of PB models by practitioners should expand. 

There are cases where non-regular lattices may be of advantage [36,37]. The computational effort, however, is substantially larger, which makes the models less flexible concerning changes of boundary conditions or topological constraints. Another direction, which may be promising in the future, is the use of hybrid models, where for example local attachment kinetics are treated on a microscopic atomistic scale, while the transport properties are treated by macroscopic partial differential equations [5,6]. 

The development of methods for the kinetic measurement of heterogeneous catalytic reactions has enabled workers to obtain rate data of a great number of reactions [for a review, see (1, )]. The use of a statistical treatment of kinetic data and of computers [cf. (3-7) ] renders it possible to estimate objectively the suitability of kinetic models as well as to determine relatively accurate values of the constants of rate equations. Nevertheless, even these improvements allow the interpretation of kinetic results from the point of view of reaction mechanisms only within certain limits ... 

Example 4.6 Use the kinetic model of Example 4.5 to determine the outlet concentration for the loop reactor if the operating conditions are the same as in Run 1. 

Chapter 10 begins a more detailed treatment of heterogeneous reactors. This chapter continues the use of pseudohomogeneous models for steady-state, packed-bed reactors, but derives expressions for the reaction rate that reflect the underlying kinetics of surface-catalyzed reactions. The kinetic models are site-competition models that apply to a variety of catalytic systems, including the enzymatic reactions treated in Chapter 12. Here in Chapter 10, the example system is a solid-catalyzed gas reaction that is typical of the traditional chemical industry. A few important examples are listed here ... 

We currently model, at least in simple fashion, all resins scaled-up which have an exothermic stage, in order to assess safety implications and utilise plant to its highest productivity regarding heat removal. The data generated is used in verification of kinetics models. 

The present chapter will focus on the practical, nuts and bolts aspects of this particular CA approach to modeling. In later chapters we will describe a variety of applications of these CA models to chemical systems, emphasizing applications involving solution phenomena, phase transitions, and chemical kinetics. In order to prepare readers for the use of CA models in teaching and research, we have attempted to present a user-friendly description. This description is accompanied by examples and hands-on calculations, available on the compact disk that comes with this book. The reader is encouraged to use this means to assimilate the basic aspects of the CA approach described in this chapter. More details on the operation of the CA programs, when needed, can be found in Chapter 10 of this book. 

Two kinetic experiments with different CD concentrations were used for kinetic modeling. In this simulation all of the rate constants not involved in the hydrogenation step were not altered. The calculated and simulated kinetic curves and optical yield-conversion dependencies are shown in Figure 9a and 9b. The results of kinetic modeling indicates that the whole kinetic curve and the optical yield - conversion dependencies can be well described by a kinetic model derived from the shielding effect model. 

However, there is little to choose between this model and a second-order model for both forward and reverse reactions, b. Now use the kinetic model to size a reactor to produce 10 tons per day of ethyl acetate. First, the conversion at equilibrium needs to be calculated. At equilibrium, the rates of forward and reverse reactions are equal ... 

In the presence of dibenzyl, octahydrophenanthrene undergoes both dehydrogenation and isomerization. In this study, we use the kinetic model (refer to Figure 1 for structures) ... 

The study did model and fit all data using a kinetic model given in Eqn. (5). The experimental data was fit to obtain values of a and (3. The utility of this model is limited because it is not based on independent parameters. However, the model does show how the desulfurization activity depends on the growth rate and cell density for various experimental conditions. 

The detailed composition, referring to classes of compounds, is shown for C6 in Figure 9.3 with and without precolumn hydrogenation. In addition to paraffins, there are olefins—mainly with terminal double bond—and small amounts of alcohols (and aldehydes). The low detection limit of gas chromatography (GC) analysis allows precise determination even of minor compounds and provides exhaustive composition data also for use in kinetic modeling. Because of the short sampling duration of ca. 0.1 s,8 time-resolved selectivity data are obtained. 

Complex I can be regulated by phosphorylation. Demin et al. [28] studied superoxide generation by Complex III using the kinetics model of electron transfer from succinate to cytochrome c. 

In this chapter we consider how to construct reaction models that are somewhat more sophisticated than those discussed in the previous chapter, including reaction paths over which temperature varies and those in which species activities and gas fugacities are buffered. The latter cases involve the transfer of mass between the equilibrium system and an external buffer. Mass transfer in these cases occurs at rates implicit in solving the governing equations, rather than at rates set explicitly by the modeler. In Chapter 16 we consider the use of kinetic rate laws, a final method for defining mass transfer in reaction models. 

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