Methylcyclopentenyl Cations Linking Initial Stage and Highly Efficient Stage in Methanol-to-Hydrocarbon Process

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.