Deactivation kinetics rate coefficients

Nitration by nitric acid in sulphuric acid has also been by Modro and Ridd52 in a kinetic study of the mechanism by which the substituent effects of positive poles are transmitted in electrophilic substitution. The rate coefficients for nitration of the compounds Pl CHi NMej (n = 0-3) given in Table 10 show that insertion of methylene groups causes a substantial decrease in deactivation by the NMej group as expected. Since analysis of this effect is complicated by the superimposed activation by the introduced alkyl group, the reactivities of the... 

The kinetic parameters are listed in Table 1. The linearity of lnAr l/r plot is revealed by the correlation coefficient. For all reactions but the deactivation, the rate constants follow the Arrhenius law satisfactorily, implying catalyst deactivation may involve more than one elementary steps. 

Bertole et al.u reported experiments on an unsupported Re-promoted cobalt catalyst. The experiments were done in a SSITKA setup, at 210 °C and pressures in the range 3-16.5 bar, using a 4 mm i.d. fixed bed reactor. The partial pressures of H2, CO and H20 in the feed were varied, and the deactivation, effect on activity, selectivity and intrinsic activity (SSITKA) were studied. The direct observation of the kinetic effect of the water on the activity was difficult due to deactivation. However, the authors discuss kinetic effects of water after correcting for deactivation. The results are summarized in Table 1, the table showing the ratio between the results obtained with added water in the feed divided by the same result in a dry experiment. The column headings refer to the actual experiments compared. It is evident that adding water leads to an increase in the overall rate constant kco. The authors also report the intrinsic pseudo first order rate-coefficient kc, where the overall rate of CO conversion rco = kc 6C and 0C is the coverage of active... 

Electronically excited ionic states, for which the transitions to the ground state are allowed, normally have very short radiative lifetimes, typically on the order of 10 nsec to 1 jLisec, Yet even these states are quite efficiently collisionally deactivated, particularly on interaction with the corresponding parent gases. Several such systems have been studied in detail, and the Stem-Volmer relation has been employed to determine rate coefficients for collisional deactivation.233-239 Some of these reactions and the pertinent kinetic data are displayed in the reactions that follow. 

Ion-molecule association reactions and the collisional deactivation of excited ions have been the subjects of recent reviews.244-246 Several systematic studies have been performed in which the relative deactivating efficiencies of various Mf species have been determined. By applying the usual kinetic formulations for the generalized reaction scheme of equation (11.31), and assuming steady-state conditions for (AB+), an expression for the low-pressure third-order rate coefficient can be derived ... 

Kinetic Modei of Non-Thermai Piasma Steriiization of Air Flow. Based on kinetic data presented in Table 12-1 and on comparison of experimental and simulation data on direct plasma deactivation of E. coli bacteria in air stream using a DBD discharge (Fig. 12-18), estimate reaction rate coefficient of plasma sterilization attributed to effect of charged particles. Assume that plasma density in the discharge is rig = lO cm, and that the charged particles are responsible for the discrepancy between experimental and simulation results presented in the Fig. 12-18. 

The general approach for modelling catalyst deactivation is schematically organised in Figure 2. The central part are the mass balances of reactants, intermediates, and metal deposits. In these mass balances, coefficients are present to describe reaction kinetics (reaction rate constant), mass transfer (diffusion coefficient), and catalyst porous texture (accessible porosity and effective transport properties). The mass balances together with the initial and boundary conditions define the catalyst deactivation model. The boundary conditions are determined by the axial position in the reactor. Simulations result in metal deposition profiles in catalyst pellets and catalyst life-time predictions. 

K , equilibrium constant of main reaction Ki adsorption constant of i component ki kinetic coefficient of poisoning rate, [eqn.(8)] k2 kinetic coefficient of deactivation rate, [eqn. (9)] kgi mass transfer coefficient of i component ko pre-exponential factor in eqn. (6)... 

Therefore, in biphasic systems the partition coefficient (a thermodynamic dimension) and the mass-transfer coefficient (a kinetic dimension) will dominate the cat of the enzyme. As a consequence, the overall reaction rate is mainly determined by the physical properties of the system (such as solubilities and stirring) and rally to a lesser extent by the enzyme s catalytic power. In other words, the enzyme could work faster, but is unable to get enough substrate. Enhanced agitatirai (stirring, shaking) would improve the mass transfer but, on the other hand, it increasingly leads to deactivation of the enzyme due to mechanical shear and chemical stress. 

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