Influence of WO Content in Phosphated Tungsten-Zirconium Oxide Catalysts on the Catalytic Pathways of Glycerol Transformation.

The catalytic performance of phosphate-stabilized WO-ZrO compositions in gas-phase glycerol dehydration has been investigated. Results show that varying WO concentrations direct the process towards either acrolein or allyl alcohol formation. Catalysts with low WO content exhibit strong Lewis acid sites (Zr and W), where these metal ions likely function as redox sites, facilitating glycerol hydrogenolysis to produce allyl alcohol. Higher WO concentrations (exceeding 20 wt %) lead to the shielding of some W and Zr sites by polytungstate surface complexes, which are strong Brønsted acid sites. This alteration promotes glycerol dehydration through the removal of two water molecules, thereby shifting the selectivity towards acrolein formation.