Structure-Activity Relationships of Pt-WO_x/Al₂O₃ Prepared with Different W Contents and Pretreatment Conditions for Glycerol Conversion to 1,3-Propanediol

Turning waste glycerol into a fundamental chemical used in the petrochemical industry offers an opportunity to reduce not only waste from biodiesel production but also the consumption of petroleum-based chemicals. In the present work, glycerol was converted to 1,3-propanediol over Pt-WO_x/Al₂O₃ catalysts, while focusing on the influence of W loading contents (10–20 wt.%) and catalyst pretreatment conditions, specifically the calcination temperatures of WO_x/Al₂O₃ (700–900 °C), calcination temperatures of Pt-WO_x/Al₂O₃ (350–450 °C) and reduction temperatures of Pt-WO_x/Al₂O₃ (300–400 °C). The characteristics of the catalysts were identified by applying N₂-sorption, XRD, Raman, CO pulse chemisorption, NH₃-TPD, H₂-TPR, H₂-TPD, SEM and TEM-EDS and XPS. The W loading contents and pretreatment conditions strongly affected the activity and products selectivity. The W content and calcination temperature of WO_x/Al₂O₃ at 15 wt.% and 800 °C, respectively, were evaluated as the most suitable in providing optimum W-O-W clusters to generate H^δ+ which was a key parameter for the generation of 1,3-propanediol. The calcination and reduction temperatures of Pt-WO_x/Al₂O₃ at 400 °C and 350 °C, respectively, were mandatory to sufficiently convert PtCl₂ to Pt₃O₄ and Pt₃O₄ to metallic Pt, respectively. The optimized Pt-WO_x/Al₂O₃ catalyst achieved a high glycerol conversion (44.7%) with high selectivity toward 1,3-propanediol (45.1%) under a reaction temperature and pressure of 220 °C and 60 bar, respectively.