The effects of impregnation of precious metals on the catalytic activity of titanium silicate (TS-1) in epoxidation of propene using hydrogen peroxide

Abstract

Propene oxide is an important chemical intermediate and titanium silicalite (TS-1) has been widely investigated as a promising catalyst for the direct epoxidation of propene with ex-situ or in-situ produced hydrogen peroxide as an oxidant. In order to clarify the effects of the kind of precious metal and treatment process in the catalyst preparation on the propene epoxidation and the hydrogen peroxide decomposition, TS-1 was impregnated with gold and palladium via drying, calcination and reduction and the experiments to check its catalytic performance were conducted in a gas aspirating autoclave reactor in the absence of mass transfer limitations. The presence of precious metals vigorously catalyzed the side reactions and hydrogen peroxide decomposition. Some of the precious metal containing TS-1 catalysts showed high initial rates but there was no catalyst with a propene oxide yield after 5 h reaction time comparable to TS-1 alone because of the enhancement of side reactions by precious metals. The significant decline in the selectivity to propene oxide over the dried precious metal containing TS-1 catalysts was attributed to the leaching of precious metals into the reaction medium. Palladium containing TS-1 showed exceptionally high decomposition of hydrogen peroxide. Reduction and calcination increased the decomposition by forming metallic gold and palladium. Homogeneous dispersion of gold nanoparticles was achieved by a sol immobilization method which led to a decrease of propene oxide selectivity and an increase of hydrogen peroxide decomposition.

Epoxidation of propene in a confined Taylor flow (CTF) reactor at atmospheric pressure

“…The results of various analyses of TS-1 catalyst showed good agreement with the data indicated in the original patent [34] and were presented in our previous papers [33,36]. The BET analysis gave a specific surface area of 421 m 2 /g and a pore volume of 0.255 cm 3 /g, which are comparable to the values reported in the literature [4,12,33].…”

Comparison of a monolith and a confined Taylor flow (CTF) reactor for propene epoxidation

“…The TS-1 catalyst prepared was characterized using various analytical techniques and found to be in good agreement with the data provided in the original patent [35]. The analysis results of XRD, FT-IR, UV-vis, SEM, TEM, TGA and BET were presented in our previous papers [37,38]. An even distribution of TS-1 particles on the alumina rod and tube wall was achieved through the coating method and confirmed by a SEM image that was also shown in our previous paper [34].…”

Advances in Designing Au Nanoparticles for Catalytic Epoxidation of Propylene with H2 and O2

“…Interestingly, ILI could achieve an Au capture efficiency of 100 wt.%, which was higher than that of any other technique. In other studies, Shin et al successfully used tetrakis(hydroxymethyl)phosphonium chloride/NaOH for stabilizing the system [60].…”