含钨SBA-15介孔分子筛催化剂的表面酸性和羟基分布  

Surface Acidity and Hydroxyl Groups of SBA-15 Mesoporous Silica Catalysts Containing Tungsten Species

作　　者：胡林华[1] 季生福[1] 刘倩倩[1] 吴平易[1] 朱吉钦[1] 李成岳[1] 

机构地区：[1]北京化工大学化工资源有效利用重点实验室,北京100029

出　　处：《催化学报》2007年第11期980-986,共7页

基　　金：国家自然科学基金(20473009);国家重点基础研究发展计划(973计划;2006CB202503).

摘　　要：分别以浸渍法和水热晶化法制备了SBA-15介孔分子筛孔中插入氧化钨和碳化钨的催化剂,采用NH3-TPD测定了表面酸性和总酸量,并采用FT-IR研究了它们的表面羟基分布情况.NH3-TPD结果表明,浸渍法制备的含氧化钨的SBA-15介孔分子筛催化剂表面只有SBA-15介孔分子筛的弱酸位,而含碳化钨的SBA-15介孔分子筛催化剂表面还出现了W2C的强酸位.水热晶化法制备的含氧化钨的SBA-15介孔分子筛催化剂表面SBA-15介孔分子筛的弱酸位随W含量的增大略有增强,W含量较高时还出现了钨物种的强酸位;含碳化钨的SBA-15介孔分子筛催化剂表面除了SBA-15介孔分子筛的弱酸位外,W含量较低时有W2C的强酸位,W含量较高时有W2C和WC两种强酸位.傅里叶变换红外光谱结果表明,浸渍法和水热晶化法制备的含氧化钨和碳化钨的SBA-15介孔分子筛催化剂除表面自由硅羟基外,还存在着α,β和γ三种不同类型的氢键羟基,并且氢键羟基和催化剂的制备方法以及催化剂的W含量都有一定的关系.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 SBAd 5 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.

关 键 词：SBA-15介孔分子筛 氧化钨 碳化钨 氨程序升温脱附 傅里叶变换红外光谱 

分 类 号：O643.32[理学—物理化学]