Mesoporous Zirconium Oxide Prepared by Anchoring W, Mo, Nb, Ta Using Peroxo Precursors: Influence of the Oxoanions on the Pores Size and the Hydrothermal Catalysts Stability for Cellulose Conversion

Efficient and sustainable cellulose conversion into chemicals requires the design of heterogeneous catalysts with controlled acid-base properties, mesoporosity and excellent stability in hydrothermal conditions. To this end, modified zirconia with anchored W, Mo, Ta and Nb oxoanions were prepared by ionic exchange using peroxo precursors of the selected transition metals. Modified zirconia samples were characterized by X-ray diffraction, N-2 isotherms, FTIR of pyridine adsorption and microcalorimetry of ammonia adsorption. If the nature of the oxoanion tunes slightly the catalysts Lewis acid strength or density, it influences strongly their mesoporosity with mesopores in the range of 10 nm for ZrTa and ZrNb. Upon Pt loading, all the Pt-modified zirconia are effective to catalyze C-C and C-O cleavage during cellulose hydrogenolysis leading to PG as main short polyols with the co-formation of 2,5-hexanedione over ZrNb and ZrTa. Most important, ZrNb and ZrTa exhibit excellent water tolerance without any leaching nor structure modification. Combined to their mesoporosity, these features make ZrNb and ZrTa, true solid Lewis acids with high potential in the frame of bulky biomass conversion in hot waterier [GRAPHICS]