Hydrogen transfer reaction contributes to the dynamic evolution of zeolite-catalyzed methanol and dimethyl ether conversions: Insight into formaldehyde

Formaldehyde (HCHO), generating from hydrogen transfer (HT) of reactant, is significant for autocatalysis initiation and deactivation in methanol-to-olefins (MTO), but hitherto, its evolution throughout the reaction has not been thoroughly revealed. Herein, by established colorimetric analysis method, HCHO MTO dimethyl ether (DME)-to-olefins (DTO) reactions over SAPO-34 was situ quantitatively monitored, where detected slight conspicuous amounts at initial stages with semi-conversion, also when co-fed water or high-pressure H2. We reveal weak HT ability DME relative to methanol, which enables prominent olefins-based cycle suppresses reactant-induced DTO (which critical MTO). A complete dynamic network disclosed, constituting two simultaneous interplaying pathways: main olefin generation as open-line hidden-line. Especially, co-feeding H2 capacitating a long-term highly efficient operation modulating more moderate evolution, great potential industry application.