Ruthenium and gold-doped M1 phase MoVNbTeO catalysts for propane ammoxidation to acrylonitrile

Ammoxidation of propane to acrylonitrile was investigated over the M1 phase MoVNbTeO catalysts doped with 5 wt.% Ru and Au, respectively. The MoVNbTeO mixed metal oxide catalyst was synthesized by a hydrothermal method, whereas ruthenium and gold were introduced by incipient wetness impregnation. The structures of the MoVNbTeO mixed metal oxide and ruthenium- and gold-doped catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD patterns of the original MoVNbTeO catalyst confirmed the formation of the orthorhombic M1 phase, while the XRD patterns of ruthenium- and gold-doped catalysts demonstrated that the presence of ruthenium and gold significantly affected the crystal structure of the MoVNbTeO M1 phase. The catalytic activity was studied in a tubular fixed-bed micro-reactor at atmospheric pressure and 360–445 °C. Ru- and Au-doped MoVNbTeO M1 catalysts showed lower ammoxidation activity than the original MoVNbTeO M1 catalyst. However, both doped catalysts were much more active in the oxidative dehydrogenation (ODH) of propane at relatively low temperature (< 400 °C) showing the selectivity to propylene of 85 and 73 mol.% for the Au- and Ru-doped catalysts, respectively. The significant enhancement of propane ODH activity may be due to the presence of gold nanoparticles or ionic gold and ruthenium. The morphology and crystal structures of the original MoVNbTeO M1 and Au-doped catalysts after catalytic testing remained essentially unchanged, whereas the MoVNbTeO M1 phase was significantly affected by the presence of the Ru dopants. Furthermore, the peaks corresponding to RuO2 was detected in the XRD patterns of the Ru-doped M1 catalyst after ammoxidation reaction.

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► Ru- and Au-doped MoVNbTeO M1 catalysts showed lower ammoxidation activity than the original MoVNbTeO M1 catalyst.
► Both Au- and Ru-doped catalysts were much more active than the original MoVNbTeO M1 catalyst in the oxidative dehydrogenation (ODH) of propane to propylene at relatively low temperature (< 400 °C).
► The morphology and crystal structure of the original MoVNbTeO M1 and Au-doped catalysts after catalytic testing remained essentially unchanged, whereas the Ru-doped M1 catalyst underwent phase transformation under ammoxidation reaction conditions.