催化学报

催化学报 ›› 2007, Vol. 28 ›› Issue (7): 627-634.

• 研究论文 • 上一篇    下一篇

SO2-4/SiO2表面酸性的红外光谱和密度泛函理论研究

郭岱石1,马紫峰1,蒋淇忠1,叶伟东2,李春波2   

  1. 1 上海交通大学化学工程系, 上海 200240; 2 浙江医药股份有限公司新昌制药厂, 浙江新昌 312500
  • 收稿日期:2007-07-25 出版日期:2007-07-25 发布日期:2011-07-25

FT-IR and Density Functional Theory Studies on Surface Acidity of SO2-4/SiO2

GUO Daishi1, MA Zifeng1*, JIANG Qizhong1, YE Weidong2, LI Chunbo2   

  1. 1 Department of Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China; 2 Xinchang Pharmaceutical Factory, Zhejiang Medicine Co.Ltd, Xinchang 312500, Zhejiang, China
  • Received:2007-07-25 Online:2007-07-25 Published:2011-07-25

PDF

1175

被引次数

25

摘要： 对介孔SiO2及硫酸根促进的SiO2样品进行了原位吡啶吸附红外光谱测试,分别建立了硫酸根促进前后的SiO2表面原子簇模型,用密度泛函理论对其吡啶吸附行为进行了计算,分析了SO2-4/SiO2表面酸性产生的机理. 实验和计算结果表明, SO2-4/SiO2表面不存在Lewis酸中心,原位红外谱图中表征Lewis酸性的特征峰对应于氢键吸附吡啶的环振动,这种氢键作用因SiO2表面的硫酸根促进而得到加强. HSO-4螯合结构为SO2-4/SiO2表面Bronsted酸中心,其酸强度强于表面磺酸基团修饰的介孔SiO2材料SO3H-MSU, 而弱于HZSM-5. SO2-4/SiO2的酸催化活性源于其表面的Bronsted酸性.

关键词: 二氧化硅, 硫酸根, 表面酸性, 吡啶吸附, 红外光谱, 密度泛函理论

Abstract: Silica MCM-41 without and with sulfuration treatment was measured by in situ pyridine adsorption infrared spectroscopy. Cluster models of pure SiO2 and SO2-4/SiO2 were built up, and density functional theory calculations on pyridine adsorption were carried out to analyze the surface acidity of SO2-4/SiO2. The combined results of experimental and theoretical studies showed that there were no Lewis acid sites on the surface of SO2-4/SiO2. The IR frequencies assignable to Lewis acidity corresponded to the enhanced hydrogen-bonded adsorption of pyridine by sulfuration treatment. The chelating structure of HSO-4 acts as Brnsted sites on the surface of SO2-4/SiO2, with an acid strength higher than that of sulfonic group-functionalized silica SO3H-MSU but weaker than that of HZSM-5. The acid catalytic activity of SO2-4/SiO2 results from the Bronsted acidity.

Key words: silica, sulfate anion, surface acidity, pyridine adsorption, infrared spectroscopy, density functional theory