Pt–WOx on monoclinic or tetrahedral ZrO2: Crystal phase effect of zirconia on glycerol hydrogenolysis to 1,3-propanediol

Abstract

The effects of the crystal phases of ZrO2 in the Pt–WOx/ZrO2 catalysts on glycerol hydrogenolysis to 1,3-propanediol (1,3-PDO) were comparatively studied. Pt and WOx were sequentially deposited on monoclinic (m-ZrO2) and tetragonal (t-ZrO2) ZrO2 supports with similar surface areas by the wetness impregnation method. On both catalysts, sub-nanosized Pt particles were well dispersed on the supports, and the WOx species were mainly in the monomeric state and partly covered the Pt particles. The Pt–WOx/m-ZrO2 catalyst had larger Pt particle size and less Brønsted acid sites than the Pt–WOx/t-ZrO2 catalyst. In glycerol hydrogenolysis, the glycerol conversion and 1,3-PDO selectivity on the Pt–WOx/m-ZrO2 catalyst were less than one half of those on the Pt–WOx/t-ZrO2 catalyst. The Pt–WOx/t-ZrO2 catalyst exhibited a high 1,3-PDO yield of 49.4%, an excellent 1,3-PDO productivity of 5.10ggPt−1h−1, and good recyclability. The superiority of the Pt–WOx/t-ZrO2 catalyst in glycerol hydrogenolysis to 1,3-PDO is attributed to the better synergy between smaller Pt particles in affording hydrogen atoms and more Brønsted acid sites in converting glycerol to the intermediate suitable for the formation of 1,3-PDO.