Bunting Rhys J, Thompson Jillian, Hu P
School of Chemistry and Chemical Engineering, Queen's University Belfast, David Keir Building, Stranmillis Road, Belfast BT9 5AG, UK.
Phys Chem Chem Phys. 2020 May 28;22(20):11686-11694. doi: 10.1039/d0cp01284j. Epub 2020 May 14.
The mechanism for the partial oxidation of methane to methanol on single atom rhodium supported on ZSM-5 is investigated by DFT. The most favoured mechanism for methane activation is shown to be via oxidative addition at an undercoordinated rhodium metal centre and not through a typical metal oxo intermediate. The formation of a C-OH bond, and not methane activation, is found to be the rate determining step. CO coordinated to the rhodium centre is observed to strongly promote this bond formation. Water is required in the system to help prevent catalyst poisoning by CO, which greatly hinders the methane activation step, and to protonate an intermediate RhOOH species. These results suggest that more focus is required on methyl-oxygen bond formation and that exclusive consideration of methane activation will not completely explain some methane partial oxidation systems.
采用密度泛函理论（DFT）研究了ZSM-5负载的单原子铑上甲烷部分氧化制甲醇的机理。结果表明，甲烷活化最有利的机理是通过在配位不足的铑金属中心进行氧化加成，而不是通过典型的金属氧中间体。发现形成C-OH键而非甲烷活化是速率决定步骤。观察到与铑中心配位的CO强烈促进该键的形成。体系中需要水来帮助防止CO使催化剂中毒，CO会极大地阻碍甲烷活化步骤，同时使中间体RhOOH物种质子化。这些结果表明，需要更多地关注甲基-氧键的形成，仅考虑甲烷活化并不能完全解释某些甲烷部分氧化体系。
