ACID-CATALYZED ISOMERIZATION OF DIALKYLBENZENES
ACID-CATALYZED ISOMERIZATION OF DIALKYLBENZENES
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DOI：
10.1021/jo01263a026
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发表时间：
1969-01-01
影响因子：
3.6
通讯作者：
CSICSERY, SM
中科院分区：
文献类型：
--
作者：
CSICSERY, SM
异构化和烷基转移是1-甲基-2-乙基苯在二氧化硅-氧化铝裂化催化剂和部分多价阳离子交换、部分去阳离子的Y型八面沸石分子筛上的主要反应。异构化通过两种不同的机制进行。第一类由分子内1、2位移组成。反式烷基化中间体参与第二个反应。二甲苯和二乙苯可以由甲基乙苯通过相同类型的烷基转移中间体形成。我们建议将该反应命名为“烷基交换”。分子间异构化的程度可以根据烷基交换的水平来估计。分子间异构化的贡献随着温度的升高而降低。 300以上异构化主要通过分子内1、2位移发生。低于 200 的异构化主要是通过烷基转移中间体进行。在中间温度下，分子间和分子内过程对整体异构化的贡献程度相似。对于二烷基苯的酸催化异构化，提出了两种不同的机制。通常假设碳正离子参与两种异构化机制。根据 Olah 和他的同事 1 以及 Matsumoto 和 Morita 的说法，二烷基苯的异构化是通过一系列反应进行的。
Isomerization and transalkylation are the principal reactions of l-methyl-2-ethylbenzene over silica-alumina cracking catalyst and partially multivalent cation-exchanged, partially decationized Y-type faujasitemolecular sieves. Isomerization proceeds by two different mechanisms. The first type consists ofintramolecular 1, 2 shifts. Trans alkylated intermediates are involved in the second reaction. Xylenes and diethylbenzenes may be formed from methylethylbenzene by the same type of transalkylated intermediates. We suggest the name“alkyl ex-change” for this reaction. The extent of intermolecular isomerization may be estimated from the level of alkyl exchange. The contribution of intermolecular isomerization decreases with increasing temperature. Above 300 isomerization primarily occurs by intramolecular 1, 2 shifts. Below 200 isomerization via transalkylated intermediates predominates. At intermediate temperatures intermolecular and intramolecular processes con-tribute to over-all isomerization to a similar extent.Two different mechanisms have been proposed for the acid-catalyzed isomerization of dialkylbenzenes. Carbonium ion involvement in both isomerization mechanisms is commonly assumed. According to Olah and his coworkers1 and Matsumoto and Morita, 2 isomeriza-tion of dialkylbenzenes proceeds through a series of