Mechanism of alkane H/D exchange over zeolite H-ZSM-5 at low temperature: a combined computational and experimental study
Mechanism of alkane H/D exchange over zeolite H-ZSM-5 at low temperature: a combined computational and experimental study
复制标题
低温下 H-ZSM-5 沸石上烷烃 H/D 交换机理：计算与实验相结合的研究
DOI：
10.1039/c6cy00467a
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发表时间：
2016-01-01
影响因子：
5
通讯作者：
Deng, Feng
中科院分区：
文献类型：
--
作者：
Chu, Yueying;Xue, Nianhua;Deng, Feng
理论计算为异丁烷与H-ZSM-5分子筛在室温下H/D交换反应的可能途径提供了基础性的认识。从理论上证明，无论是直接交换机制还是间接的双分子氢化物转移机制，是一个有效的途径，异丁烷活化由于高活化势垒，这可能会阻止H/D交换在低温下。结果表明，微量的烯烃杂质可以大大加速烷氧基中间体的形成，这是参与双分子氢化物转移机制。一旦从烯烃杂质产生烷氧基中间体，催化循环就可以自我维持。另一方面，理论计算也表明脱铝沸石中的骨架外铝（EFA 1）物种对H/D交换没有明显的促进作用。此外，我们的计算也与实验结果一致。
Theoretical calculations have provided fundamental insights into the possible pathways for the H/D exchange of isobutane with H-ZSM-5 zeolite at room temperature. It is theoretically demonstrated that neither the direct exchange mechanism nor the indirect bimolecular hydride transfer mechanism is an efficient route for isobutane activation due to high activation barriers, which possibly prohibit H/D exchange at low temperatures. It is revealed that a trace of olefin impurities can considerably accelerate the formation of an alkoxyl intermediate which is involved in the bimolecular hydride transfer mechanism. Once the alkoxyl intermediate is generated from the olefin impurities, the catalytic cycle is self-sustaining. On the other hand, the theoretical calculations also illustrate that the extra-framework aluminum (EFAl) species in the dealuminated zeolite has no obvious promotional effect on the H/D exchange. Furthermore, our calculations are also consistent with the experimental results.