Differences in acid and catalytic properties of W incorporated spherical SiO2 and 1%Al-doped SiO2 in propene metathesis

Abstract

Propene self-metathesis to ethylene and 2-butene was investigated over tungsten-based catalysts (9 wt.% W) supported on silica and 1%Al-doped SiO2, prepared by different processes. On pure SiO2, incorporating WOx improved tungsten dispersion and formation of active tetrahedral WOx species, compared to the impregnated ones. However, negative effect was found when tungsten was incorporated in the 1%Al-doped SiO2 as the catalysts contained more crystalline WOx, lower tetrahedral species, and lower Lewis acid sites, compared to the W-imp 1Al2O3/SiO2 prepared by impregnation. Incorporating both W and Al in the SiO2 by sol-gel method may lead to suppression of bridge hydroxyl Si(OH)Al group, as a consequence more crystalline WOx was formed. Nevertheless, the abundance of Bronsted and Lewis acid was found to play important role in the propene metathesis and the secondary metathesis of 1-butene reactions than surface silanol and the presence of tetrahedral tungsten oxide species on the 1%Al-doped SiO2 supported catalysts.