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 (SiO 2 /Al 2 O 3 = 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 CH 2 ) −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 (C 2 −C 4 olefins, C 2 −C 4 paraffins, methane, and C 5 −C 10 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 C 5 −C 10 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 C 2 −C 4 olefins, the yield is limited to 12%, at 550 °C.