水热条件下氧化硅-氧化铝载体结构、织构及表面性质的演变

series of silica-alumina materials with different Si content were prepared by impregnation method, using alumina as support and TEOS as Si source. The silica-alumina materials were hydrothermal treated, and the evolution of structure, texture and surface properties of silica-alumina under hydrothermal conditions was studied, using XRD, TG, Nitrogen-Adsorption, FT-IR and Py-IR methods. The results showed that the content of Si had a great influence on the stability of alumina under hydrothermal condition. During the hydrothermal time of 128 h, for silica-alumina sample with Si content lower than 3%, the specific surface increased first and then decreased, the average pore size decreased first and then increased, and the sample surface hydroxyl groups continued to increase; when the Si content reached 7%, no hydration of alumina was found, the specific surface area and average pore size was unchanged, the surface B acid site disappeared and L acid center was unchanged. That's because the Si-O-Al bond, showing high stability under hydrothermal condition, played a role of stabilizing trivalent Al atom, and effectively prevented the transformation of trivalent Al atom to form the surface hydroxyl species and the surface hydroxyl species to boehmite.