Epoxidation of Propylene with Air as Oxidant over Supported Gold Catalysts Prepared by Anion Adsorption

摘要

Propylene oxide is an important chemical intermediate whose production directly from propylene by epoxidation with air as oxidant has been the focus of research for many years. Highly dispersed Au/TiO_2, Au/TiO_2-MCM-48 catalysts prepared by deposition-precipitation method have shown an extraordinary selectivity in the epoxidation of propylene using a combination of H_2 and O_2 as oxidation mixture. A hydroperoxide-like intermediate has been proposed to be responsible for the selective epoxidation. This oxidizing species was said to be formed over gold and subsequently used for epoxidation over the Ti-containing support. SiO_2 is an industrially common support. But SiO_2-supported Au catalyst was not prepared by deposition-precipitation method due to its low point of zero charge. In this paper, SiO_2-, TiO_2-, and TiO_2/SiO_2-supported Au catalysts were prepared by a novel anion adsorption method and then evaluated their catalytic activities in the epoxidation of propylene.