Catalytic Properties of SiO_2-Supported Heteropolyacids for Alkylation of Isobutane with Butene II. Quantum Chemical Studies on Reaction Mechanism and Catalyst Deactivation

Quantum chemical calculations were carried out to investigate the isobutane/butene reaction system on the heteropolyacid catalyst. Optimum quantum structural parameters of isobutane and butene and thermal parameters of their adsorption, surface reaction and desorption were obtained. The calculation results indicated that activation energy was unnecessary for the butene adsorption on the solid acid catalyst, while isobutane could only adsorb on strong acid sites and then participate in the reaction. Large molecule olefins produced by the butene polymerization strongly adsorbed on the strong acid sites and the catalytic activity of the solid acid catalyst for the alkylation was decreased. So the deactivation of the solid acid catalyst for the alkylation cannot be avoided. The difference between liquid acid and solid acid catalysts for alkylation was compared. There were many benefits to use liquid acids as C 4 alkylation catalysts. It was suggested that developing a new liquid acid alkylation catalyst that is nontoxic, noncorrosive and environmentally friendly should be a subject of future research.