Adjustment of W–O–Zr Boundaries Boosts Efficient Nitrilation of Dimethyl Adipate with Ammonia on WOx/ZrO2 Catalysts

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.