Methylcyclopentenyl Cations Linking Initial Stage and Highly Efficient Stage in Methanol-to-Hydrocarbon Process
Wenna Zhang, Mozhi Zhang, Shutao Xu, Shushu Gao, Yingxu Wei, Zhongmin Liu
Abstract
In the conversion of methanol to hydrocarbon (MTH), hydrocarbon pool (HCP) species have been observed and demonstrated as important intermediates for efficient formation of olefins in the steady-state stage. However, in situ observation on the formation and evolution of the hydrocarbon pool species at the initial stage is still a huge challenge. In this contribution, experimental and theoretical evidence on the origin and conversion of the methylcyclopentenyl cations (MCP+) were obtained directly at the initial period of the MTH reaction. In situ solid-state NMR spectroscopies revealed that MCP+ was formed preferentially than polymethylbenzenes (PMBs) species when the HCP species began to accumulate at the transition stage. Additionally, the relationship between MCP+ and PMBs species was established by 13C-isotope tracing experiments and theoretical calculations. Importantly, this contribution highlights the importance of the MCP+ species in the whole methanol conversion process. Besides acting as an important active intermediate species for formation of olefins at the steady-state stage, MCP+ species play a crucial role in bridging the direct mechanism at the inefficient initial stage and the highly efficient steady-state stage following the indirect pathway for methanol conversion.