Rate-limiting cumene adsorption

To answer this question we shall assume that the adsorption of cumene is indeed rate-limiting, derive the corresponding rate law, and then check to see if it is consistent with experimental observation. By assuming that this (or any other) step is rate-limiting, we are considering that the reaction rate constant of this step (in this ease k/ ) is small with respeet to the specific rates of the other steps (in this case ks and The rate of adsorption is... 

Combining Equations (10-41) and (10-37), we find that the rate law for the catalytic decompositon of cumene, assuming that the adsorption of cumene is the rate-limiting step, is... 

If the cumene dccompostion is adsorption rate limited, then the initial rale will be linear with the initial partial pressure of cumene as shown in Figure 10-16. 

Advantage can be drawn from the positive effect of phenol on PA transformation into p-HAP to improve the yield and selectivity of p-HAP production.[82 84] Thus, with a HBEA zeolite the yield and selectivity for p-HAP passes from ca. 5 and 28 % respectively with cumene solvent to 24 and 60% with phenol as a solvent .[84] Again sulfolane was shown to have a very positive effect on the selectivity for p-HAP and limits the catalyst deactivation. To explain these observations as well as the effect of P and PA concentrations on the reaction rates, it was proposed that sulfolane plays two independent roles in phenol acylation solvation of acylium ion intermediates and competition with P and PA for adsorption on the acid sites.1831... 

Cumene is cracked in a recycle reactor over commercial H-ZSM5 extrudates during a pulse experiment. The results are compared to those obtained from steady state measurements. A linear model for diffusion, adsorption and reaction rate is applied to reactants and products. In contrast to literature it is shown that if the Thiele modulus is greater than 5, the system becomes over parameterised. If additionally adsorption dynamics are negligible or not measurable, only one lumped parameter can be extracted, which is the apparent reaction constant found from steady state experiments. The pulse experiment of cumene is strongly diffusion limited showing no adsorption dynamics of cumene. However, benzene adsorbed strongly on the zeolite and could be used to extract transient model parameters. 

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