Heptamethylbenzenium cation formation and the correlated reaction pathway during methanol-to-olefins conversion over DNL-6

• Formation of heptamethylbenzenium ion during MTO reaction was definitely confirmed by combination of NMR with GC–MS measurements.
• The high reactivity of HMMC/heptaMB+ was further evidenced and correlated with the variation of methanol conversion.
• Side chain methylation mechanism was suggested to be the main reaction route for methanol conversion over DNL-6.

Methanol conversion over SAPO molecular sieve DNL-6 was investigated from the view point of the reaction mechanism. The organic materials confined in the cavities of DNL-6 were mostly polymethylbenezenes. By combination of in situ NMR study with ex situ GC–MS measurements, the structure of heptamethylbenzenium ion (heptaMB+) formed during MTO reaction was definitely confirmed. Further evidences from the mass spectra and 13C solid-state NMR spectra in the isotopic switch experiments showed that the side chain methylation mechanism was the main reaction route for olefin formation from hydrocarbon pool species.

Figure optionsDownload high-quality image (136 K)Download as PowerPoint slide