Pre-Synthesized WO3 Nanosheets via New Modified Thermal Exfoliation as a Route to Decouple Crystallinity from Loading in Pt/WO3/Al2O3 Glycerol Hydrogenolysis Catalysts

The development of highly crystalline tungsten oxide nanomaterials remains challenging for catalytic applications due to the difficulty in achieving high phase purity without sacrificing metal oxide loading. This work addresses this limitation through an innovative fast hydrothermal synthesis at 100 °C for 4 h without autoclaves or surfactants, using citric acid as a critical structural directing agent. Such methodology reduces the synthesis time by 50–80% compared to existing hydrothermal routes. Citric acid was identified as the critical parameter controlling the nanosheet thickness (20 nm to 35 nm) and diameter (109 nm to 173 nm), acting as a coordinating ligand. The resulting nanosheets were used to prepare Pt/WO3/Al2O3 catalysts with well-defined crystalline monoclinic WO3 structures at 9.5% wt. loading. Normally, this phase is inaccessible by standard impregnation at equivalent loading. NH3-TPD characterization confirmed that crystalline WO3 generates strong acid sites absent in the reference wet impregnation catalyst. Glycerol hydrogenolysis tests revealed that the presence of monoclinic WO3 reduces the average glycerol conversion rate by a factor of 3.8 and systematically shifts selectivity toward over-hydrogenolysis products (1-propanol and 2-propanol), despite identical WO3 loading and surface densities below the literature optimum of 2.2 W atoms (Formula presented.). These results demonstrate that the WO3 crystalline phase is a primary determinant of catalytic performance, without taking into account increased loading. Such demonstration will be useful for the rational design of selective glycerol hydrogenolysis catalysts.