草酸处理对丙烷氨氧化催化剂Sb-V-O结构和催化性能的影响

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

以不同量的草酸处理钒的起始原料,采用共沉淀法制备了VSb3混合氧化物催化剂,运用N2低温吸附、X射线衍射、X射线光电子能谱和H2程序升温还原等方法对催化剂进行了表征,并考察了其在丙烷氨氧化反应中的催化性能.结果表明,草酸的处理可使所得样品中V处于较低的价态,从而有利于活性相SbVO4的生成.当草酸/V(摩尔比)为3时,所制VSb3混合氧化物中存在较多的活性相SbVO4,且其表面具有适量Sb和V的分布,使催化剂具有良好的氧化/还原性能平衡,因而在丙烷氨氧化反应中表现出更高的活性和丙烯腈选择性.

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 N2 adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, and H2 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.