Unraveling the promoting roles of sulfate groups on propane combustion over Pt-SO42−/ZrO2 catalysts

Pt-SO42−/ZrO2 catalysts with different SO42− contents were employed for propane combustion. Addition of SO42− significantly improved the catalytic activity for propane combustion, such as the Pt-5SO42−/ZrO2 catalyst gave the highest turnover frequency (TOF) of 0.56 s−1 at 200 °C, while the pristine Pt/ZrO2 catalyst gave a TOF of only 0.020 s−1. Strong coordination between Pt and SO42− species resulted in drastic suppression of CO adsorption capacity (from 36.8 to 6.0 μmol gcat−1), and increased Pt0 ratio in the spent Pt-SO42−/ZrO2 catalysts. The exposed Pt sites on the Pt/ZrO2 and Pt-SO42−/ZrO2 catalysts show comparable reactivity for C-H activation as evidenced by the methane combustion, and the sulfate species are not helpful in C-H bond cleavage. The enhanced catalytic activities on Pt-SO42−/ZrO2 catalysts for propane combustion are mainly ascribed to the higher reactivity for C-C bond activation promoted by the synergistic catalysis of Pt species with superacid sites. Whereas, such synergy is affected by the amount of SO42− because the excessive SO42− would reduce the exposed Pt sites.