Abstract: A series of SBA-15 mesoporous silica catalysts containing tungsten oxide were prepared by impregnation and hydrothermal methods, respectively. After temperature-programmed carburization in flowing CH4/H2, the SBA-15 mesoporous silica catalysts containing tungsten oxide are converted to the corresponding catalysts containing tungsten carbides. The surface acidity and hydroxyl groups of the catalysts were characterized using NH3-TPD and FT-IR spectroscopy, respectively. The NH3-TPD results show that the SBA-15 mesoporous silica catalysts containing tungsten oxide prepared by the impregnation method have weak acid sites of SBA-15 mesoporous silica, whereas the SBA-15 mesoporous silica catalysts containing tungsten carbides have strong acid sites of W2C besides the weak acid sites of SBA-15. However, the SBA-15 mesoporous silica catalysts containing tungsten oxide prepared by the hydrothermal method have increasing weak acid sites of SBA-15, whereas the SBA-15 mesoporous silica catalysts containing tungsten carbides have strong acid sites of W2C with lower W contents and strong acid sites of W2C and WC with higher W contents. The results of FT-IR show that there are α-, β-, and γ-hydrogen bond hydroxyl groups besides free silica hydroxyl groups in the SBA-15 mesoporous silica catalysts containing tungsten oxide and tungsten carbides. Moreover, the distribution of hydrogen bond hydroxyl groups is dependent upon the preparation process and tungsten content of the catalysts.

Key words: SBA-15 mesoporous silica, tungsten oxide, tungsten carbide, temperature-programmed desorption of ammonia, Fourier transform infrared spectroscopy