丙烷选择氧化制丙烯醛MoBiTeO/SiO_(2)催化剂中Te组分的作用

Role of Te on Selective Oxidation of Propane to Acrolein over MoBiTeO/SiO_2 Catalysts

用浸渍法制备了一系列不同Te含量的MoBiTeO/SiO_(2)催化剂,并用XRD、Raman、XPS、NH3-TPD、吡啶吸附FT-IR和催化剂性能评价等方法考察了Te组分对催化剂的结构、酸性及其丙烷选择氧化制丙烯醛性能的影响.结果表明,催化剂中Mo氧化物与Te氧化物之间发生了相互作用,通过形成Mo—O—Te桥氧键生成了Te多钼酸盐物种,在一定程度上分散了Mo-O活性中心,同时TeOx具有脱除丙烯α-H、插氧并将其转化为丙烯醛的功能,因此,在MoBiO/SiO2催化剂中添加Te组分使丙烯醛选择性有显著的提高.但是Te的加入同时也使催化剂中B酸增强,这不利于丙烯醛生成.因此,Te添加量有一最佳范围,nTe/nMo为0.05-0.1时催化剂具有较好的催化性能.

A series of MoBiTeO/SiO_(2) catalysts with different Te contents was prepared by impregnation method. Effect of Te on the catalysts'structure, acidity and catalytic performance for selective oxidation of propane to acrolein was investigated by XRD, Raman, XPS, NH3-TPD, FT-IR, and performance evaluation techniques. The results indicated that by forming Mo-O-Te bond with the Mo species, tellurium component in the catalyst improved the dispersion of Mo oxide species that would be favorable to the formation of isolate active sites on the catalysts. Besides, Te could be the centers for α-H abstraction of propene and O-insertion to allyl species. So, the addition of Te to MoBiO/SiO2 catalyst promoted the acrolein selectivity greatly. However, the addition of tellurium also could contribute the formation of B acid sites in MoBiTeO/SiO2 catalysts that had been proved to be harmful to the generation of acrolein. Therefore, there existed an optimal scale for the amount of Te-content in the MoBiTeO/SiO2 catalysts. When the nTe/nMo ratio was 0.05-0.1, the catalyst showed the best catalytic performance.