Self-metathesis of 1-butene to propene over SBA-15-supported WO3

Abstract

A series of SBA-15-supported WO₃ catalysts was prepared by impregnating silicotungstic acid on SBA-15 (HSiW-SBA-15) and subsequently calcining at different temperatures. It shows higher catalytic activity and stability than the physical mixtures of SBA-15 and WO₃ in the self-metathesis of 1-butene to propene. The calcination temperature of HSiW-SBA-15 has a significant effect on its catalytic performance. The sample calcined at 700 °C gave a 1-butene conversion and a propene selectivity of 59.6% and 59.7%, respectively, at 350 °C. It was found that the metathesis of 1-butene to propene occurred via two steps. The first one was isomerization of 1-butene to 2-butene on both Brønsted and Lewis acid sites, and the second one was metathesis of 1-butene and 2-butene to propene via the formation of W-carbene species (WCHCH₃, WCH₂ and WCHCH₂CH₃). The Si–O–W–OH Brønsted acid sites play a decisive role in the formation of W-carbene species, and the pseudo-Wittig mechanism dominates the process.