Insight into the nature of Brönsted acidity of Pt-(WOx)n-H model catalysts in glycerol hydrogenolysis

Abstract

In glycerol hydrogenolysis, the conventional preparation methods for Pt-WOx catalysts on active supports usually result in the coexistence of various active sites, causing complex reaction network and declining the atom efficiency of W toward 1,3-propanediol (1,3-PDO) production. Herein, we report Pt-(WOx)n-H model catalyst prepared via strong metal–oxide interaction (SMOI) behavior on inert SiO2 support, which shows both high performance and W efficiency for 1,3-PDO. The W efficiency as high as 5.786 h−1 was obtained on 2W4Pt/SiO2 at 160 °C under 8.0 MPa. Furthermore, these model catalysts also give the advantage in revealing the Brönsted acidity of Pt-(WOx)n-H sites. Structure characterizations and DFT calculation confirm the Brönsted acid strength of Pt-(WOx)n-H is significantly sensitive to both the polymerization and reduction degree of WOx domains. The high catalytic efficiency of 2W4Pt/SiO2 originates from the strong Brönsted acidity and its synergism with Pt metal. The correlation between Brönsted acidity and electronic state of Pt-(WOx)n-H is also discussed by electron density difference analysis and XPS.