甲苯与甲醇侧链烷基化X型沸石催化剂的吸附量热研究  

MICROCALORIMETRIC ADSORPTION INVESTIGATION OFTHE XTYPE ZEOLITE CATALYSTS FOR SIDE CHAINALKYLATION OF TOLUENE WITH METHANOL

作　　者：王文月[1] 沈俭一[1] 葛欣[1] 朱卫[2] 

机构地区：[1]南京大学化学系 [2]南京大学现代分析中心

出　　处：《催化学报》1998年第4期334-338,共5页

基　　金：国家自然科学基金

摘　　要：研究了甲苯与甲醇在用碱金属阳离子交换法及浸渍法添加ＫＯＨ所制得的几种Ｘ型沸石上的侧链烷基化反应．以ＮＨ３和ＣＯ２为探针分子，用微分吸附量热法表征了这一系列催化剂的酸碱性，并与催化活性关联．结果发现，甲苯与甲醇侧链烷基化活性并不与催化剂的强碱性成正比（如ＮａＸ），而是与催化剂上酸碱强度的匹配以及一定数目的酸碱中心有关．ＮａＸ的酸碱性都很强，具有较高的苯环烷基化活性．ＣｓＸ上酸碱中心数目较少，侧链反应活性较低．相比之下，ＫＸ具有适当的酸碱强度和酸碱中心数目（对ＮＨ３吸附，它的吸附热为５０ｋＪ／ｍｏｌ，吸附覆盖度为１２００μｍｏｌ／ｇ；对ＣＯ２吸附，它的吸附热为８５～５５ｋＪ／ｍｏｌ，吸附覆盖度为５０μｍｏｌ／ｇ），是所有催化剂中侧链反应活性最高的．The side chain alkylation of toluene with methanol over several Xtype zeolites, exchanged with alkali cations and/or further impregnated with KOH, was studied. The catalytic reactivity of these catalysts was correlated to their acidity and basicity, characterized by microcalorimetric adsorption of NH3 and CO2. It was found that the strong basicity (such as on the NaX) is not necessarily proportional to the activity of the side chain alkylation. It seems that the coordination of proper acidity and basicity in terms of strength and number is more important for the side chain alkylation. Both acidity and basicity on NaX are quite strong. This catalyst shows high activity for the ring alkylation. On the other hand, the CsX catalyst has fewer acid and base sites, and therefore it exhibits relatively low activity for the side chain alkylation reaction. In contrast, the KX seems to have proper acid and base sites in terms of strength and number (50 kJ/mol and 1200 μmol/g for NH3 adsorption, and 85～55 kJ/mol and 50 μmol/g for CO2 adsorption). This catalyst exhibits the highest activity for the side chain alkylation among the catalysts studied in this work.

关 键 词：X型沸石 催化剂 甲苯 甲醇 侧链烷基化 吸附量热 

分 类 号：O643.36[理学—物理化学] O625.11[理学—化学]