Reaction Networks in Propane Ammoxidation to Acrylonitrile Over Orthorhombic Mo-V-Nb-Te-O Catalyst

We investigated propane ammoxidation to acrylonitrile over hydrothermal Mo-V-Nb-TeO catalyst containing the dominant M1 phase, recently proposed as active and selective in this selective ammoxidation reaction. The reaction kinetics was studied in a tubular quartz reactor at 600-700K operated in both differential and integral regimes at 5-60% propane conversion. The results obtained in this study were examined on the basis of two reaction networks involving propane transformation via (1) parallel routes to propylene, acrylonitrile and carbon oxides and (2) propylene as the reaction intermediate for acrylonitrile. The results obtained indicated only a slight preference for the reaction network involving the propylene intermediate, which may be explained on the basis of catalytic behavior of the M1 and M2 phases present in the hydrothermal Mo-V-Nb-Te-O catalyst. The dominant M1 phase was capable of catalyzing all of the above transformation steps, whereas the M2 impurity phase was only active in propylene ammoxidation to acrylonitrile. The contribution of the M2 phase to propylene ammoxidation is expected to be less significant at industrially relevant high propane conversions because of the improved ability of the M1 phase to covert propylene into acrylonitrile at longer residence times.