Investigation of vanadium-containing mixed oxides on the catalytic performance for 2, 6-dichlorotoluene ammoxidation

Vanadium composite different metal oxides such as VAlO, VTiO, VFeO and VWO were synthesized via a one-pot hydrothermal approach and subsequent annealing treatment, and used as catalysts for the ammoxidation of 2, 6-dichlorotoluene (DCT) to 2, 6-dichlorobenzonitrile (DCBN). XRD, SEM, TEM, XPS, FTIR, TPD, TPR and BET technologies were taken on to investigate the correlations between the physical-chemical characteristics and reactivities. The results have revealed that high vanadic reducibility of catalyst is beneficial to enhance the activity resulting in high conversion of DCT, but tends to total oxidation leading to low selectivity. The surface Lewis acid sites (containing strong and medium acidity) are helpful to increase the selectivity to DCBN. VFeO displays the best reducibility resulting in the highest conversion, but the least Lewis acid sites leading to the lowest selectivity, which is well contrary to VWO catalyst. VTiO showed the best catalytic properties in terms of yield, mainly attributed to its much larger specific surface area contributing to forming more moderate active sites with monolayer vanadia in tetracoordinated as well as abundant acid sites. This work provides valuable information for designing highly effective catalysts for the ammoxidation of DCT to DCBN.