Efficient formation of propylene oxide under low hydrogen concentration in propylene epoxidation over Au nanoparticles supported on V-doped TS-1

Abstract

The direct epoxidation of propylene to propylene oxide (PO) represents a unique feature of gold nanoparticle catalysts. Different amounts of vanadium were introduced into TS-1 using a hydrothermal method to give V-TS-1, and the effect of various vanadium loadings on the catalytic performance of Au/V-TS-1 was investigated in the epoxidation of propylene under different reaction conditions. The obtained characterization results indicate that the molecular sieve pore structure and crystalline phase structure of TS-1 were maintained after vanadium incorporation, and vanadium was incorporated into the molecular sieve framework. The introduction of an appropriate amount of vanadium resulted in the homogeneous dispersion of gold particles with a small average particle size, which facilitated the epoxidation reaction. When V was introduced into TS-1, the propylene conversion decreased under the condition of 10 % H₂ concentration (C₃H₆/H₂ = 1/1) in the reaction atmosphere, but the PO selectivity was maintained. Interestingly, when the H₂ concentration in the reaction atmosphere was lowered to 2 % (C₃H₆/H₂ = 3/1), the propylene conversion in Au/TS-1 was significantly decreased compared to 10 % H₂ concentration condition, while in Au/V-TS-1, the propylene conversion was maintained in 2 % H₂ concentration condition compared to 10 % H₂. Au/V-TS-1 also maintained its selectivity for PO even when the H₂ concentration was lowered. Therefore, under low hydrogen concentration conditions, the PO formation rate of Au/V-TS-1 was much higher than that of Au/TS-1. More, the same trend was observed when Mo was added in place of V. Our strategy will guide the design of future catalysts as a way to utilize hydrogen more effectively while maintaining PO productivity.