Simultaneous production of 1,3-propylene glycol and 1-propanol trough glycerol hydrogenolysis: Pt catalysts supported on heteropolyacids-modified mesoporous silica

Abstract

In this work, Pt catalysts were prepared using a sol-gel synthesized SiO2 modified by inclusion of tungstophosphoric acid (TPA) and tungstosilicic acid (TSA), which were evaluated in the glycerol hydrogenolysis in liquid phase to obtain 1,3-propylene glycol (1,3-PG) and 1-propanol (1-POH). The results showed that the SiO2 presents a mesoporous and amorphous structure which, modified by inclusion of TPA and TSA, exhibits [H3-xPW12O40]x- (x = 0–3) and [H4-xSiW12O40]x- (x = 0–4) anions with Keggin structure type. The inclusion of TPA or TSA generates strong acid sites and enhances Pt dispersion in the Pt/SiO2-TPA and Pt/SiO2-TSA catalysts, which have smaller and similar particle sizes ranging from 1.5 to 2.9 nm depending on the heteropolyacid content. On their surface, the Pt/SiO2-TPA catalysts present a low number of strong acid sites composed by [W2O7]2- and W2O5 species while the Pt/SiO2-TSA catalysts present a greater number of sites, but with lower acid strength, composed mainly by [W2O6]2-, H4SiW12O40 and [W7O24]−6 species. The Pt/SiO2-TPA catalysts were more active but less stable than the Pt/SiO2-TSA catalysts, both series being selective to 1,3-PG and 1-POH. The sintering of the support, the adsorption of glycerol molecules and the leaching of W were identified as the main causes of deactivation.