Selective Alkylation of Benzene with Propane over Bifunctional Pt-Heteropoly Acid Catalyst

The alkylation of benzene with propane to yield isopropylbenzene proceeds with high selectivity over bifunctional metal acid catalysts comprising Pt and Keggin heteropoly acid in a fixed-bed reactor at 250-350 degrees C and 1 bar pressure. Most efficiently the reaction occurs over Pt/H4SiW12O40/SiO2 catalyst at 300 degrees C, giving isopropylbenzene with 90-93% selectivity at 6-8% benzene conversion, significantly exceeding the efficiency of previously reported Pt/HZSM-5 catalyst. The alkylation proceeds through bifunctional reaction pathway including dehydrogenation of propane to propene (1) on Pt sites followed by benzene alkylation with propene (2) on acid sites. At Pt loadings above 0.5%, step 1 is at fast quasi-equilibrium and step 2 is the rate-limiting one.