固体酸催化剂SO_4^(2-)/SiO_2-TiO_2的制备及其催化酯化性能  

Preparation of Solid Acid SO^(2-)_4/SiO_2-TiO_2 and Its Catalytic Activity for Esterification

作　　者：张琦[1] 常杰[1] 王铁军[1] 徐莹[1] 

机构地区：[1]中国科学院广州能源研究所

出　　处：《催化学报》2006年第11期1033-1038,共6页

基　　金：国家自然科学基金(50476090);广东省自然科学基金(04000378)资助项目.

摘　　要：分别以机械混合法和浸渍法制备了SO42-/SiO2-TiO2固体酸催化剂,以乙醇和乙酸的酯化反应为模型反应考察了不同SiO2含量及不同温度焙烧的催化剂的活性.结果表明,机械混合法制备的400℃焙烧的SO42-/40%SiO2-TiO2催化剂活性最高,部分回流时,乙酸几乎全部转化,全回流反应100min时,其乙酸转化率达到84%.X射线衍射分析表明,SiO2抑制了硫酸氧钛的形成;催化剂的活性组分包括一定量的四方晶锐钛矿型TiO2、正交晶硫酸氧钛、少量立方晶金属钛和高比表面积的SiO2.红外光谱分析表明,添加SiO2后催化剂形成Ti-O-Si键,进而使SO42-与样品表面产生强相互作用;结合的SO42-主要以无机螯合状双配位和有机硫酸酯两种结构形式存在.热重-示差扫描量热分析表明,SiO2的添加使SO42-不易脱除,同时使锐钛矿TiO2向金红石相的转变温度降低.Solid acid catalysts SO4^2-/SiO2-TiO2 with different SiO2/TiO2 ratios and calcined at different temperatures were prepared by mechanical mixing and impregnation methods. The catalysts were used for esterification of ethanol and acetic acid. SO4^2-/SiO2-TiO2 prepared by mechanical mixing and calcination at 400 ℃ exhibited the highest activity, and the acetic acid conversion was nearly 100 % in partial reflux rectifying esterification and up to 84% in total reflux esterification, which was close to the chemical equilibrium composition. X-ray diffraction patterns indicated that SiO2 inhibited the excessive formation of titanium oxide sulfate. The combination of tetragonal crystal anatase TiO2, orthorhombic crystal titanium oxide sulfate, and cubic crystal titanium with high surface area SiOa ensured the high activity of the catalysts. Infrared spectra showed that the addition of SiO2 helped the formation of Ti-O-Si linkage which enhanced the strong bonding of SO4^2- with the catalyst surface. The sulfate species bonded were in bidentately chelating and covalent sulfate structures. Thermogravimetrlc-differential scanning calorimetry proved that SO4^2- was hardly removed with the addition of SiO2 and the temperature for ,ransformation of anatase to rutile was lowered.

关 键 词：硫酸 氧化硅 氧化钛 固体酸催化剂 生物油 乙酸 乙醇 酯化 

分 类 号：O643.36[理学—物理化学]