Acid-free epoxidation of soybean oil with hydrogen peroxide to epoxidized soybean oil over titanium silicalite-1 zeolite supported cadmium catalysts

Abstract

Titanium silicalite-1 (TS-1) zeolite was successfully synthesized by hydrothermal method in the presence of the tetrapropylammonium hydroxide (TPAOH) template, and a series of TS-1 supported cadmium with different Cd loading (xCd/TS-1) catalysts were carefully prepared to produce epoxidized soybean oil (ESO) through the acid-free catalytic epoxidation of soybean oil (SO) with H2O2. These catalysts were fully characterized using various modern techniques and further evaluated systematically in this epoxidation reaction to understand the relationship between catalytic activity and structure of active components. The results show that the highly dispersed Cd species are introduced on the TS-1 support without affecting the coordination environment of tetrahedral Ti (framework Ti). Furthermore, the Cd species are coordinated with tetrahedral Ti species via O atom resulting in the weakness of the Ti–O bonds and facile attack of the Ti–O bonds by alcohol and H2O2, which can easily form the five-membered intermediate and promote the SO epoxidation process. Furthermore, the deactivation and regeneration behaviors of 2%Cd/TS-1 catalyst in SO epoxidation were also investigated, which reveal that the catalyst deactivation of coke deposition is due to the strong adsorption of the catalysts and SO molecules. But the spent 2%Cd/TS-1 can be completely regenerated by calcination method.