Li Lei, Gao Xianlong, Huang Fangtao, Miao Lei, Zhao Guoqing, Zhu Zhirong
School of Chemical Science and Engineering, Tongji University, Shanghai 200092, P. R. China.
Guangzhou Institute for Food Inspection, Guangzhou 510410, Guangdong, P. R. China.
Inorg Chem. 2025 Jan 13;64(1):11-24. doi: 10.1021/acs.inorgchem.4c04101. Epub 2024 Dec 23.
The vapor-phase alkylation of phenol with methanol was investigated on X zeolites and modified X zeolites. First, the difference of product distribution was tested between acid zeolite (HZSM-5, HX, HMCM-22, and Hβ) and basic zeolite X (KX and CsX). Then, X zeolites were modified with Li, K, Cs, Ca, Mg, La, and Ce ion exchange to adjust the acid-base properties of the zeolites. Finally, the type of acid sites and strength of acid-base sites on zeolite catalysts were determined by characterization techniques such as Py-IR and TPD, and the alkylation of phenol with methanol was tested. The results showed that O-alkylation products convert to the C-alkylation products on the B acid sites, which enhances the isomerization reaction, thereby increasing the proportion of -cresol in cresol. The results of TPD and IR indicated that weak basic sites on the zeolite promote the vertical adsorption of the aromatic ring and strong basic sites promote side-chain activation, while acid sites determine whether ring substitution or side-chain substitution occurs. During the reaction of phenol with methanol, the phenolic hydroxyl group strongly interacts with the surface of zeolites, leading to differences in the adsorption mode of the aromatic ring (vertical or parallel), which, in turn, alters the position of alkyl substitution. It is found that the proper acid-base property of X zeolites can selectively determine the desired alkylated products.
在X型沸石和改性X型沸石上研究了苯酚与甲醇的气相烷基化反应。首先，测试了酸性沸石（HZSM - 5、HX、HMCM - 22和Hβ）和碱性沸石X（KX和CsX）之间产物分布的差异。然后，用Li、K、Cs、Ca、Mg、La和Ce离子交换对X型沸石进行改性，以调节沸石的酸碱性质。最后，通过Py - IR和TPD等表征技术确定了沸石催化剂上酸位的类型和酸碱位的强度，并测试了苯酚与甲醇的烷基化反应。结果表明，O - 烷基化产物在B酸位上转化为C - 烷基化产物，这增强了异构化反应，从而提高了甲酚中对甲酚的比例。TPD和IR结果表明，沸石上的弱碱位促进芳环的垂直吸附，强碱位促进侧链活化，而酸位决定发生环取代还是侧链取代。在苯酚与甲醇的反应过程中，酚羟基与沸石表面强烈相互作用，导致芳环吸附模式（垂直或平行）的差异，进而改变烷基取代的位置。发现X型沸石适当的酸碱性质可以选择性地确定所需的烷基化产物。
