X型沸石催化剂的甲苯甲醇侧链烷基化反应和吸附量热研究

STUDIES OF SIDE CHAIN ALKYLATION OF TOLUENE WITH METHANOL AND MICROCALORIMETRIC ADSORPTION OVER X TYPE ZEOLITE CATALYSTS

本文报道了以原粉ＮａＸ和成型ＮａＸ为前体分别通过离子交换法及浸渍法制得的几种碱金属阳离子Ｘ型沸石上甲苯甲醇侧链烷基化反应的活性和选择性。并以ＮＨ３和ＣＯ２的微分吸附量热表征了这些催化剂的酸碱性。结果表明，在所有催化剂中成型ＫＸ的侧链反应活性最高。该催化剂对ＮＨ３的微分吸附热为４５ｋＪ／ｍｏｌ左右，吸附覆盖度为３．３μｍｏｌ／ｍ２；对ＣＯ２的微分吸附热在１２８～６０ｋＪ／ｍｏｌ之间，吸附覆盖度为０．１６μｍｏｌ／ｍ２。对比其他三种酸性相近的催化剂，碱性更强（如Ｋ／ＫＸ（ｐ）和Ｋ／ＫＸ（ｃ））或更弱（如ＫＸ（ｐ））时，侧链反应活性都较差。看来，成型ＫＸ催化剂的表面酸碱性匹配对侧链烷基化反应比较有利。该结果进一步证明了在甲苯甲醇侧链烷基化反应中催化剂酸碱协同作用的重要性。

The side chain alkylation of toluene with methanol over several X type zeolites, using powder NaX or commercial NaX as the starting materials respectively, then exchanged with alkali cations and/or further impregnated with KOH, was studied The catalytic reactivities of these catalysts were correlated to their acidities and basicities, characterized by microcalorimetric adsorption of CO 2 and NH 3 It was found that of all the catalysts the commercial KX shows the highest activity The differential heat and coverage are 128￣65 kJ/mol and 0 16 μmol/m 2 for CO 2 adsorption; and 50 kJ/mol or so and 3 3 μmol/m 2 for NH 3 adsorption Comparing to the other catalysts with the same acidity, the activity of the side chain alkylation is worse when the catalyst has a stronger basicity (such as K/KX( c ) and K/KX( p )) or a weaker basicity (such as KX( p )) It seems that KX( c ) has a proper acidity and basicity which is more favorable to this reaction than other catalysts studied in this work This results further demonstrate that the coordination of acidity and bacisity on the catalyst is more important to the side chain alkylation of toluene with methanol