Kinetics and diffusion studies on the deactivation of ZSM-5 catalysts containing metals for toluene alkylation

The deactivation of catalysts containing HZSM-5, P,Cr-P, Ni- P and Sr on HZSM-5 catalysts were studied during the Alkylation of toluene in a fixed bed reactor at 673K and liquid hour space velocity (LHSV) of 4g toluene/h g catalyst under atmospheric pressure. The experimental data were examined for fit with three derived kinetic models to obtain the best fit. HZSM-5 & Sr/ZSM-5 catalysts obey 1st order deactivation, while the P/ZSM-5 and Cr-P/ZSM-5 catalysts obey 2 n d order deactivation but the Ni-P/ZSM-5 catalyst obeys 3 r d order deactivation Kinetics. Diffusion studies were carried out to estimate the Thiele modulus and effectiveness factor of the catalyst deactivation. The highest fraction of active sites poisoned was 0,25 for Sr/ZSM-5 catalyst after 2hr operation; HZSM-5 catalyst has a fraction of 0.1 and the other three catalysts have fractions of 0.01.