催化学报

催化学报 ›› 2007, Vol. 28 ›› Issue (11): 980-986.

• 研究论文 • 上一篇    下一篇

含钨SBA-15介孔分子筛催化剂的表面酸性和羟基分布

胡林华,季生福,刘倩倩,吴平易,朱吉钦,李成岳   

  1. 北京化工大学化工资源有效利用重点实验室, 北京 100029
  • 收稿日期:2007-11-25 出版日期:2007-11-25 发布日期:2011-10-13

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

HU Linhua, JI Shengfu*, LIU Qianqian, WU Pingyi, ZHU Jiqin, LI Chengyue   

  1. State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
  • Received:2007-11-25 Online:2007-11-25 Published:2011-10-13

PDF

1018

被引次数

24

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.

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

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