Mechanism of byproducts formation in the isobutane/butene alkylation on HY zeolites

Submicron-size HY zeolites with a particles size of 200–700 nm were synthesized employing a crystal precipitation method in this study. The catalytic activity for the isobutane/butene alkylation was evaluated. The results indicated that butene conversion was above 90% and the selectivity of expected products (C8) was nearly at 90% within 72 h. The micropores-blocking and coverage of acid sites resulting from high hydrocarbons increased the difficulty for the diffusion of products to the bulk and inhibited the adsorption of reactant on activity sites, which caused deactivation of catalyst. The ultimate C12 content in alkylate oil, stemmed from trimerization of butene, was reduced via the addition reaction with butene to C16 and the cracking to C5–C7. The formation mechanisms and transformation processes of byproducts in alkylate oil revealed that the source of C9–C11 switched from cracking of C16+ to the addition of C5–C7 carbocations with butene when acid sites concentration was reduced by accumulating oligomers.