负载型KNO_3固体碱对环戊二烯甲基化反应的催化作用  

Catalytic Performance of Supported KNO_3 Solid Bases for Methylation of Cyclopentadiene

作　　者：孙林兵[1] 吴正颖[1] 寇佳慧[2] 淳远[1] 王英[1] 朱建华[1] 邹志刚[2] 

机构地区：[1]南京大学化学化工学院,江苏南京210093 [2]南京大学环境材料与再生能源研究中心,江苏南京210093

出　　处：《催化学报》2006年第8期725-731,共7页

基　　金：国家自然科学基金资助项目(20343027和20203010)

摘　　要：考察了负载型KNO3固体碱对环戊二烯(CPD)和甲醇的甲基化制备甲基环戊二烯(MCPD)反应的催化性能.通过X射线衍射和低温氮吸附等手段研究了载体的表面性质和KNO3在不同载体表面的分解情况,并用非水溶液Hammett指示剂法测定了各固体碱的碱强度.结果表明,KNO3负载在不同的氧化物载体上后其碱强度表现出极大的差异,负载在ZrO2,-γAl2O3,水滑石(HT)和MgO上能检测到H-为27.0的碱强度,这些碱性位可视为固体超强碱;而负载在SiO2和TiO2上仅检测到了H-为9.3的碱强度,这与载体本身的表面性质密切相关.碱强度较低的KNO3/SiO2和KNO3/TiO2以及氧化物载体本身在CPD甲基化反应中表现出较差的活性,说明催化剂应具有一定的碱强度,但是催化剂的酸性和比表面积也会对其催化活性产生一定的影响.在所考察的催化剂中,KNO3/-γAl2O3和KNO3/HT的催化性能最好,在450℃时就能催化转化约32%的CPD,MCPD的选择性可达86%左右,高于传统固体碱MgO在500℃时的活性.The catalytic performance of a series of supported KNO3 solid bases for the synthesis of methylcyclopentadiene via cyclopentadiene methylation with methanol was investigated. X-ray diffraction and N2 adsorption were applied to study the characteristics of different supports and the decomposition of KNO3 on them. The base strength of samples was measured using Hammett indicator. Significant difference in base strength of different oxides-supported KNO3 was observed. A base strength （ H- ） of 27.0 was detected in KNO3 supported on ZrO2,γ-Al2O3, hydrotalcite （HT）, and MgO, which showed the characteristics of solid superbases; while a base strength （H-） of only 9.3 was examined in SiO2- and TiO2- supported KNO3. Such difference in base strength could be ascribed to the differences in surface nature of supports. A suitable basicity was necessary for catalyzing the methylation of cyclopentadiene with methanol, since only small amounts of cyclopentadiene molecules were converted over catalysts with low basicity, such as KNO3/SiO2 and KNO3/TiO2 as well as most oxide supports. However, the acidity and surface area of catalysts also had certain effects on the reaction. The conversion of cyclopentadiene and selectivity for methylcyclopentadiene were around 32 % and 86 % , respectively, over KNO3/γ-Al2O3 and KNO3/HT at 450℃ . Such catalytic activity was higher than that on MgO.

关 键 词：固体碱 硝酸钾 负载型催化剂 碱强度 环戊二烯 甲基化 甲基环戊二烯 

分 类 号：O643.32[理学—物理化学]