Kinetic Modeling of n-Butane Cracking on HZSM-5 Zeolite Catalyst

A kinetic model of lumps has been established for n-butane cracking over HZSM-5 zeolite catalyst (SiO2/Al2O3 = 30) in the 400−550 °C range, based on the results obtained in a fixed bed reactor (space time, up to 2.4 (g of catalyst) h (mol CH2)−1; He/n-butane molar ratio in the feed, up to 6/1; time on stream, 5 h). The model allows quantifying the distribution of the lumps of products (C2−C4 olefins, C2−C4 paraffins, methane, and C5−C10 components) in a wide range of temperatures, partial pressures of hydrocarbons in the reaction medium, and space times. The kinetic model steps for the transformation of n-butane into olefins and of olefins into paraffins and C5−C10 are second order with respect to the reactant, whereas the remaining steps are first order with respect to each reactant. When the target is the production of C2−C4 olefins, the yield is limited to 12%, at 550 °C.