WOx/ZrO2 is effective in the hydrogenolysis of cellulose to C3 products but the active sites on the W–Zr interfaces are hardly controlled. Herein, we prepared WOx/ZrO2 catalysts with active WOx species by simply varying the reduction temperatures, which selectively achieved C3 alcohol formation. A series of characterizations showed that increased reduction temperatures (400–600 °C) led to the formation of more dispersed WOx, while higher reduction temperatures (>600 °C) contributed to producing aggregated WO3 and W2C. At 600 °C, the dispersity of WOx peaked with a W5+/∑Wn+ ratio of 19%, providing abundant Lewis acid sites and oxygen vacancies (Vo), which were the active sites for glucose isomerization to fructose and C–C cleavage of fructose. A selectivity of 48% for C3 alcohols was obtained over the optimized WOx/ZrO2(600 °C) + Ru/AC catalyst.
In this study, a tungstated zirconia (WOx/ZrO2) catalyst was developed for the continuous synthesis of adiponitrile (ADN) by gas-phase nitrilation of dimethyl adipate (DMA) with NH3. The highest TOFADN could be reached on WOx/ZrO2 bearing ∼1D WOx species (highly dispersed and discontinuous status) at the surface, which, however, delivered the poorest selectivity toward nitrilation (SADN+MCP). In comparison, both efficient and selective transformation of DMA to ADN was achieved by fabricating WOx/ZrO2 with continuously distributed oligomeric WOx species (∼2D) at the surface, either by varying the dosage of the W-reagent in the preparation of WOx(m)/ZrO2 or by doping a proper amount of the Mn element into WOx(5.0)/ZrO2, bearing WO3 NPs. Furthermore, the in situ diffuse reflectance infrared Fourier transform spectroscopy investigations of both independent and competitive adsorptions of ester functionality and NH3 over W–O–Zr, W–O–W, and Zr–O–Zr boundaries at the surface clarified the synergistic effect of these species in the activation of DMA/NH3 and thereby nitrilation.
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