Effect of Titania Polymorphs on the Structure and Catalytic Performance of the Pt-WOx/TiO2 Catalyst in Glycerol Hydrogenolysis to 1,3-Propanediol

Catalytic hydrogenolysis of biomass-derived glycerol to 1,3-propanediol (1,3-PDO) represents an important process for the sustainable production of value-added chemicals. However, there is a dearth of understanding of the effect of the polymorph of the support on this reaction. Herein, two Pt-WOx/TiO2 catalysts supported on rutile TiO2 (r-TiO2) and anatase TiO2 (a-TiO2) polymorphs were prepared to investigate the crystal phase effect of TiO2 on the structural property and catalytic performance in glycerol hydrogenolysis. The TiO2 polymorph was identified to impose profound effects on the size of the Pt nanoparticles (NPs) and the dispersion and location of the WOx species, which originated from the discrepancies in the crystal structures between the PtO2 and the TiO2 polymorphs and the discrepancies in the interactions of WOx with different TiO2 polymorphs. In glycerol hydrogenolysis, the Pt-WOx/r-TiO2 catalyst gave a 1,3-PDO selectivity of 51.2% at a glycerol conversion to liquid products of 74.5%, yielding 38.1% of 1,3-PDO. In contrast, the Pt-WOx/a-TiO2 catalyst showed much inferior glycerol conversion and 1,3-PDO selectivity, yielding only 1.0% of 1,3PDO under identical reaction conditions. The superior catalytic performance of the Pt-WOx/r-TiO2 catalyst is attributed to the rTiO2 polymorph that facilitates a faster hydrogen spillover than the a-TiO2 polymorph from the Pt NPs to the reaction intermediate on the WOx species, which is substantiated by an even higher 1,3-PDO yield of 44.8% over the physically mixed Pt/r-TiO2 + WOx/r-TiO2 catalyst. This work demonstrates the critical role of the polymorph of the TiO2 support in the design of efficacious Pt-WOx- based catalysts for glycerol hydrogenolysis to 1,3-PDO.