焙烧温度对Nb_2O_5/α-Al_2O_3催化剂结构及催化性能的影响

Effect of Calcination Temperature on Structure and Catalytic Performance of Nb_2O_5/α-Al_2O_3 Catalyst for Ethylene Oxide Hydration

制备了Nb2O5/α-Al2O3催化剂并用于环氧乙烷水合反应制乙二醇,采用X射线衍射,热重-差热分析,红外光谱,吸附氨的程序升温脱附,吸附环氧乙烷的程序升温脱附,扫描电镜和透射电镜研究了焙烧温度对催化剂物理化学性质及催化性能的影响.结果表明,焙烧温度明显影响氧化铌催化剂的结构、酸量及酸强度.催化剂的结构不同,环氧乙烷在催化剂表面的吸附强度存在明显差别,而催化剂的酸量和酸强度影响其催化性能.

The Nb2O5/α-Al2O3 catalyst was prepared by impregnation method and used for ethylene oxide （EO） hydration to form ethylene glycol. The effects of the calcination temperature on the structure, acidity, and the catalytic performance of the catalyst were investigated by using X-ray diffraction, thermogravimetry and differential thermal analysis, infrared spectroscopy, temperature-programmed desorption of NH3, temperature-programmed desorption of EO, scanning electron microscopy, and transmission electron microscopy. It was found that the crystal form of niobium oxide, the catalyst acidity, and the EO adsorption strength were markedly influenced by the calcination temperature, which resulted in the dependence of EO conversion and ethylene glycol selectivity on the calcination temperature. The reaction results were discussed in terms of the strength and density of acidity resulted from the different structure formed at various calcination temperature.