Kinetic rate parameters

The field of chemical reaction engineering (CRE) is intimately and uniquely connected with the design and scale-up of chemical reacting systems. To achieve the latter, two essential elements must be combined. First, a detailed knowledge of the possible chemical transformations that can occur in the system is required. This information is represented in the form of chemical kinetic schemes, kinetic rate parameters, and thermodynamic databases. In recent years, considerable progress has been made in this area using computational chemistry and carefully... 

The solution of problems in chemical reactor design and kinetics often requires the use of computer software. In chemical kinetics, a typical objective is to determine kinetics rate parameters from a set of experimental data. In such a case, software capable of parameter estimation by regression analysis is extremely usefiil. In chemical reactor design, or in the analysis of reactor performance, solution of sets of algebraic or differential equations may be required. In some cases, these equations can be solved an-... 

The simulated C02 fugacity matches the initial reservoir C02 content and indicates that the pH is buffered by C02-calcite equilibrium. Further modelling was carried out using the Geochemists Workbench React and Tact modules with the thermodynamic database modified to reflect the elevated P conditions and kinetic rate parameters consistent with the Waarre C mineralogy. The Waarre C shows low reactivity and short-term predictive modelling of the system under elevated C02 content changes little with time (Fig. 1). 

E. B. Ledesma, N. D. Marsh, A. K.Sandrowitz, and M. J. Womat, Global kinetic rate parameters for the formation of polycycUc aromatic hydrocarbons [PAH] from die pyrolysis of catechol A model compound representative of soUd fuel moieties. Energy Fuels 16(6), 1331—1336... 

The kinetic rate parameters, k, of many chemical processes obey the Arrhenius relation... 

The solid lines in Figs. 25 to 28 are the result of model predictions of metal deposition based on porphyrin reaction pathways. Curves are generated using intrinsic kinetic rate parameters and effective diffusion coefficients for the metal species on the order of 10 6 cm2/sec. These values are similar to diffusion coefficients measured in the independent studies referenced. 

Figure 4. The effect of asphaltene source on the global kinetic rate parameters for the pathways illustrated in Figure 3 (7).

Three-dimensional CFD-coupled with radiation field modeling and photocatalytic reaction dynamics was employed by Salvado-Estivill et al. (2007b) to model the decomposition of TCE in a flat-plate, single-pass photocatalytic reactor containing immobilized P25. The outcome was pollutant-specific kinetic rate parameters, which were independent of the reactor geometry, radiation field, and fluid dynamics. This was followed by... 

Once a catalyst that meets the minimum required performance standards is identified, the research effort is then shifted from discovery toward a development type of activity as shown in the middle cycle. Hence, more detailed evaluation of the catalyst candidates is conducted using a more sophisticated reactor system. This system should be designed so it can provide experimental data that can be used as the basis for discrimination between various proposed kinetic mechanisms and the associated kinetic rate parameters. It should also be crqrable of providing information on catalyst activity versus time-on-stream for quantifrcation of catalyst deactivation. Since the cost of periodic catalyst replacement or regeneration to maintain plant productivity can have a significant impact on process economics, information on catalyst activity and the catalyst performance parameters over a range of activities is critical for identifying more precise catalyst research milestones. If the minimum required level of catalyst performance versus time-on-stream is not attained, it may be necessary for additional discovery work to be undertaken. 

Generally, adsorption steps were taken as temperature independent, whereas the rate parameters of surface reactions and desorption steps were described by Arrhenius equations. The kinetic rate parameters for CO oxidation (steps 1-10) and the catalyst properties were taken from [24] with minor adaptation as mentioned. The rate parameters, e.g. activation energies and pre-exponential factors, for steps 11-28 were determined by non-linear regression. It was found [25] that the rates for NO reactions on ceria are independent of the oxidation state of ceria, so the rate parameters for the corresponding steps were taken as the same (i.e. steps 11 and 12 for oxygen, steps 25-28 for NO). 

Table 2, Estimates of the kinetic rate parameters obtained by the simultaneous regression of the cyclic feeding experiments at 523, 548, and 573 K, and a forcing frequency of 1/10 Hz for the nitric oxide reduction by carbon...

As for pharmacokinetics and reaction kinetics, rate parameters can be defined for sterilisation processes, such as the first-order reaction rate constant (k) with the dimension reciprocal time and the half-life (ti/a). However, more commonly the term decimal reduction time or D-value is used. The D-value is the time required to inactivate 90 % of the present micro-organisms. 

In the present work, propane-propylene mixtures with various ratios were pyrolyzed at temperatures near 900°C and at an atmospheric pressure in an annular flow reactor. Hydrogen was used as a diluent. Under these experimental conditions, it was rather difficult to maintain an uniform temperature throughout the reactor since the reaction rate was high, and consequently, thermal effects due to the heat reaction were significant. In this work, therefore, experimental data at the initial stage of decomposition were analyzed using the effective temperature method to obtain kinetic rate parameters, activation energy and frequency factor, for propane and propylene decompositions. From the relations between... 

Plot of ln[fi/2] versus ln[C2io] for estimation of kinetic rate parameters. So, the reaction order n = 3... 

The microwave and thermal cure processes for the epoxy-amine systems (epoxy resin diglycidyl ether of bisphenol A, DGEBA) with 4,4 -diaminodiphenyl sulfone (DDS) and 4,4 -diaminodiphenyl methane (DDM) were investigated for 1 1 stoichiometries by using fiber-optic FT-NIR spectroscopy. The kinetic rate parameters for the consumption of amines were determined by a least squares curve fit to a model for epoxy/amine cure. The activation energies for the polymerization of the DGEB A/DDS system were determined for both cure processes and found to be 66 and 69 kJ/mol for the microwave and thermal cure processes, respectively. No evidence was found for any specific effect of the microwave radiation on the rate parameters, and the systems were both found to be characterized by a negative substitution effect [99]. 

Control and optimization of the grafting process can be achieved once the kinetic rate parameters are known. This can be illustrated with data for VP graft polymer-... 

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