Rate laws catalyst decay

The rate of catalyst decay, can be expressed in a rate law analogous to Equation (10-93) ... 

Catalytic deactivation adds another level of complexity to sorting out the reaction rate law parameters and pathways. In addition, we need to make adjustments for the decay of the catalysts in the design of catalytic reactors. This adjustment is usually made by a quantitative specification of the catalyst s activity, a(t), In analyzing reactions over decaying catalysts we divide the reactions into two categories separable kinetics and nonseparable kinetics. In separable kinetics, we separate the rate law and activity ... 

The activity, as before, is a function of the time the catalyst has been in contact with the reacting gas stream. The decay rate law is... 

The catalytic deactivation is independent of gas-phase concentration and follows a first-order decay rate law, with a decay constant of 0.72 reciprocal minutes. The feedstream is diluted with nitrogen so that as a first approximation, volume changes can be neglected with reaction. The reactor contains 22 kg of catalyst that moves through the reactor at a rate of lOkg/min. The gas oil is fed at a rate of 30mol/min at a concentration of 0.075 mol/dm, Determine the conversion that can be achieved in this reactor. 

P10-25c The decomposition of spartanol to wulfrene and CO2 is often carried out at high temperatures [/ Theor. Exp., 15, 15 (2014)]. Consequently, the denominator of the catalytic rate law is easily approximated as unity, and the reaction is first-order with an activation energy of 150kJ/mol. Fortunately, the reaction is irreversible. Unfortunately, the catalyst over which the reaction occurs decays with time on stream. The following conversion-time data were obtained in a differential reactor ... 

The decompositon of cumene is carried out over a LaY zeolite catalyst, and deactivation is found to occur by coking. Determine the decay law and rate law and use these to design a STTR. 

The activity of a fluidized CSTR is maintained constant ly feeding fresh catalyst and removing spent catalyst at constant rate. Using the RTD data above, what is the mean catalytic activity if the catalyst decays according to the rate law... 

Oscilloscope traces obtained from a 10 3M Ph2C-0 solution are displayed in Fig. 7.4. In catalyst-free solution, the 550-nm absorption of the ketyl decays as expected according to a second-order rate law. The rate constant obtained from the kinetic analysis if 8.5 x 10sM-1s 1 in agreement with published literature values. At the low laser intensity applied, this decay is barely visible on the 10-/is/division time scale in Fig. 7.4 a. Addition of catalyst, 8 mg of Pt/100 ml of solution as determined by atomic absorption spectroscopy, sharply enhances the absorption decay. This process follows approximately first-order kinetics, the half-life time being 40 /is. The decay is attributed to the reaction... 

Write out the general algorithm and derive an expression for conversion as a function of time, the reactor parameters, and the catalyst parameters. Fill in the following algorithm Mole balance Rate law Decay law Stoichiometry ... 

Szepe and Levenspiel (1971) showed that many of the rate laws proposed can be readily derived by assuming that the rate of decay is a function of the number of active sites. The general equation for aging by coke deposition on a catalyst of homogeneous surface can be written as a function of the fraction of active sites or as a combined function of the fraction of active sites and the concentration of gas oil to the power two ... 

From the above results, it is clear that the rate decay must be attributed to a chemical deactivation of the polymerization centers with time. Different mathematical expressions have been proposed, for those catalyst systems most widely studied in the literature, in order to express the law of the decay. For propylene polymerization with TiCyMgCl2—AlEt3/EB or with TiCyEB/MgCl2 - Al Et3/EB, Spitz 45-97) proposed an expression of the following type ... 

In this case, no back reaction occurs since Ru(bipy)3+ is reduced to the 2 + state by EDTA. While in the absence of catalyst the MV+ absorption is stable, addition of collodal Pt induces a decay of the signal, the rate of which increases sharply with Pt concentration. From a fitting of the absorbance decay curves to an exponential time law, one obtains the rate constants which are plotted as a function of Pt concentration in the lower part of Fig. 7.3. The ascent of the curve is steeper than linear, indicating that the reaction order is greater than one with respect to the Pt concentration. At a concentra-... 

The kinetic values obtained using the power law decay function show similar trends as discussed above concerning order of reactivity among the oil lumps and catalyst effects. It is noted however that the three light oil lumps show approximately the same cracking rates. Furthermore, the 95% confidence intervals for the parameter estimates are of similar magnitude showing that either decay model is appropriate for use in the model for the reaction conditions used in this study. 

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