Preparation and Pore Structure of Copper-doped Silica Membranes

Copper-doped silica membranes were prepared via Sol-Gel process with tetraethylorthosilicate(TEOS) and copper nitrate as precursors. The status of copper in the membranes was detected by means of FT-IR, XPS, XRD and the pore structure was determined by N2 adsorption. The effects of copper dopant and H2O/TEOS molar ratio on the pore structure were investigated and the stability of the pore structure under hydrothermal conditions was studied in detail. The results show that when the molar ratio of TEOS to H2O is 0.5, it leads to microporous structure, with a pore volume of 0.155 cm3/g and a sharp pore size distribution centered at 0.5nm for the sample with a Cu/Si molar ratio of 0.8. A faction of copper is incorporated into silica framework by replacing silicon atoms, and the residual mainly exists as crystalline phase such as Cu and Cu2O outside the framework. The microporous structure of the doped samples could be preserved for a short time (240h) under hydrothermal conditions but finally collapsed after further hydrothermal treatment.