Effect of Oxalic Acid on the Structure and Catalytic Performance of Sb-V-O Catalyst for Propane Ammoxidation

VSb3 mixed oxide catalyst samples for propane ammoxidation were prepared by a coprecipitation method with the vanadium starting materials treated with different amounts of oxalic acid in the preparation process. The VSb3 mixed oxide catalyst prepared with vanadium starting materials treated with nitric acid and the catalyst without treatment were also prepared for comparison. The effects of the oxalic acid amount on the physicochemical properties of the VSb3 mixed oxide catalyst were investigated by low-temperature N-2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, and H-2 temperature-programmed reduction, and its catalytic performance for propane ammoxidation to acrylonitrile was tested. The results showed that the addition of oxalic acid in preparation process can keep V at a low valence, which generates a greater amount of SbVO4 phase that is vital active sites for propane ammoxidation. In the catalyst prepared with the oxalic acid/V molar ratio of 3, more SbVO4 phase can be formed, and Sb and V with suitable valence and appropriate concentration could disperse on the catalyst surface, resulting in better balance between oxidation and reduction capability. Therefore, both the conversion of propane and the selectivity for acrylonitrile can be obviously enhanced over the VSb3 mixed oxide catalyst prepared by treating vanadium starting materials with oxalic acid.