Understanding the zeolites catalyzed isobutane alkylation based on their topology effects on the reactants adsorption

Abstract

The easy deactivation of zeolites catalyzed isobutane alkylation, originated from the preferential adsorption of olefin against isobutane, limits their industrial applications. In this work, the adsorption properties of zeolites towards isobutane and 1-butene with different topologies and Si/Al ratios were investigated using CBMC simulations. Based on the calculated Henry coefficient and adsorption heat, the adsorption affinity decreases with the increase of Si/Al ratio in FAU-type zeolites, while for 1-butene the decrease is more obvious. The adsorption capacity of zeolites towards isobutane and 1-butene depends on the interaction between adsorbents and adsorbates at low pressures, while on the effective void volume of adsorbents at high pressures. A satisfactory relationship between the adsorption selectivity (SI/O) and catalytic stability of zeolites for isobutane alkylation was found. Compared to FAU and LTL zeolites with expansions in pores or channels, BEA-15 and MTW-39 zeolites exhibit a much higher SI/O and catalytic stability.