Methylcyclohexane transformation over HMCM22 zeolite : Mechanism and location of the reactions
Methylcyclohexane transformation over HMCM22 zeolite : Mechanism and location of the reactions
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DOI：
10.1016/j.jcat.2008.08.006
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发表时间：
2008-10
影响因子：
7.3
通讯作者：
P. Matias;J. M. Lopes;S. Laforge;P. Magnoux;P. Russo;M. Carrott;M. Guisnet;F. R. Ribeiro
中科院分区：
文献类型：
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作者：
P. Matias;J. M. Lopes;S. Laforge;P. Magnoux;P. Russo;M. Carrott;M. Guisnet;F. R. Ribeiro
在350 °C下，在HMWW沸石（Si/Al=14.5）上，甲基环己烷（mch）转化为四种类型的产物：异构体（I）、C1-C8脂肪族烃（C）、苯烃（A）和捕获的碳质化合物（焦炭）。通过两步方法建立了各种微孔所发挥的作用：通过焦化和通过2，4-二甲基喹啉对外半笼位点进行毒化使超笼失活。超过85%的mch转换发生在超笼中，约11%发生在外半笼中，只有<2%发生在正弦通道中，考虑到质子位点分布，对应的转换频率值为33，82和2 h−1。产物分布非常不同：I、C3-C5支链烷烃和焦炭的量相似;主要是I和C3-C8支链烷烃;并且主要是C1-C8和A产物。正碳离子链机制可以解释超笼和半笼中形成的产物，而质子水解机制在狭窄的正弦通道中起重要作用。在超笼中，焦化失活非常快，在其他位置可以忽略不计。
At 350 °C, over a HMWW zeolite (Si/Al=14.5), methylcyclohexane (mch) transforms into four types of products: isomers (I), C1–C8aliphatic hydrocarbons (C), benzenic hydrocarbons (A), and trapped carbonaceous compounds (coke). The role played by the various micropores was established through a two-step method: deactivation of supercages by coking and poisoning of the outer hemicage sites by 2,4-dimethylquinoline. More than 85% of mch transformation occurs in the supercages, ∼11% occurs in the outer hemicages, and only <2% occurs in the sinusoidal channels, which, considering the protonic site distribution, corresponds to turnover frequency values of 33, 82, and 2 h−1. The product distributions are very different: I, C3–C5branched alkanes, and coke in similar amounts; essentially I and C3–C8branched alkanes; and mainly C1–C8and A products. The carbenium ion chain mechanism can account for the products formed in supercages and hemicages, whereas protolytic mechanisms play an important role in the narrow sinusoidal channels. Deactivation by coking is very fast in supercages and negligible in the other locations.