Al_2(SO_4)_3/SiO_2催化甲醇脱水合成二甲醚  

Dehydration of Methanol to Dimethyl Ether over Al_2(SO_4)_3/SiO_2 Catalysts

作　　者：杨海霞[1] 孙清[1] 傅玉川[1] 沈俭一[1] 

机构地区：[1]南京大学化学化工学院,江苏南京210093

出　　处：《分子催化》2009年第2期139-144,共6页Journal of Molecular Catalysis(China)

基　　金：国家自然科学基金项目(20673055);国家973项目(2005CB221400)

摘　　要：采用浸渍法制备了不同负载量的Al2(SO4)3/SiO2催化剂.使用BET、XRD、FT-IR、异丙醇探针反应、NH3吸附量热和NH3吸附红外等手段对催化剂进行了表征,并测试了其在甲醇脱水合成二甲醚反应中的活性.BET、XRD和FT-IR结果表明,载体SiO2的表面积较高,随着Al2(SO4)3负载量的增加,样品的表面积逐渐降低,当Al2(SO4)3负载量高于20%时,样品表面开始出现晶相Al2(SO4)3.NH3吸附量热和NH3吸附红外结果表明,载体SiO2的酸性很弱,负载了Al2(SO4)3后,样品酸性大大增强,且酸性随着Al2(SO4)3负载量的增加先增强后减弱.样品表面同时存在B酸中心和L酸中心,但以B酸中心为主.Al2(SO4)3负载量为3%的样品的表面酸性最强,因而在甲醇脱水反应中表现出最高的反应活性,533K,甲醇转化率为83.5%,二甲醚选择性100%.The Al2（SO4）3/SiO2 catalysts were prepared via an incipient wetness impregnation method. The physical and chemical properties, in especial the surface acidity of the catalysts were characterized by the techniques of BET, XRD, FT-IR, isopropanol probe reaction, microcalorimetry and FT-IR for NH3 adsorption. The catalytic activities of the catalysts were evaluated in the reaction of methanol dehydration to dimethyl ether. The results from BET, XRD and FT-IR verified that the specific surface areas of the supported catalysts decreased with the increase of Al2（SO4）3 loading. Above 20% Al2（SO4）3 loading, crystalline Al2（SO4）3 was detected for the supported samples. It could be concluded from the results of microcalorimetry and FT-IR for NH3 adsorption, that, upon the loading of Al2（SO4）3, the supported catalysts exhibited much higher surface acidity than the SiO2 support, on which the surface acidity was first enhanced and then weakened with the continuous increase of Al2（SO4）3 loading. In addition, both Bronsted （B） and Lewis （L） acid sites exist on the surface of the supported samples with B predominantly. The catalyst with 3% Al2（SO4）3 loading exhibited the strongest surface acidity and thus acid sites possessed the highest catalytic activity in methanol dehydration. At 533 K, 83.5% conversion of methanol with 100% selectivity to dimethyl ether was achieved on the 3Al2（SO4）3/SIO2 catalyst.

关 键 词：Al2(SO4)3/SiO2 甲醇脱水 二甲醚合成 酸性 

分 类 号：O643.32[理学—物理化学]