A theoretical investigation into thiophenic derivative cracking mechanism over acidic and cation-exchanged beta zeolites

作者：Mao, Xinfeng; Sun, Yingxin^*; Pei, Supeng

来源：Computational and Theoretical Chemistry, 2015, 1074: 112-124.

DOI：10.1016/j.comptc.2015.10.019

• Thiophene
• C-S bond cracking
• Beta zeolite
• Cation-exchanged zeolites
• Bimolecular mechanism

A two-layer ONIOM study has been carried out to investigate the unimolecular and bimolecular cracking mechanisms of thiophene catalyzed by acidic and metal cation-exchanged (Li+, Na+, K+, Cu+, and Ag+) beta zeolites. The unimolecular cracking reactions of 3,4-dimethylthiophene (3,4-DMT) and benzothiophene (BT) catalyzed by acidic beta zeolite are also calculated. It was found that the rate-determining steps in these two mechanisms are both C-S bond cracking. Furthermore, the activation energy of C-S bond cracking in bimolecular mechanism is lower than that in unimolecular mechanism, indicating that the bimolecular cracking process is more favorable. In addition, although the activation energies of C-S bond cleavage of 3,4-DMT and BT over H-beta zeolite are relatively lower than thiophene, the practical process would be difficult to occur due to still high energy barriers. A close analysis of activation energies over cation-exchanged zeolites suggests that the metal cations do not reduce and contrarily increase their difficulty of thiophene cracking reactions.

• 出版日期2015-12-15
• 单位上海应用技术大学