We demonstrate efficacy of a bifunctional strategy to improve the lifetime of CHA zeotypic materials (4x increase in turnover number) for the conversion of methanol-to-olefins (MTO) via physical addition of Y2O3 without disrupting the high selectivity to ethylene and propylene. We also reveal that the efficacy of this strategy increases with increasing proximity between the rare-earth metal oxide surface and acid sites inside the zeotypic material. This strategy is the result of our mechanistic inquiries about the identity and involvement of plausible intermediates and steps in MTH deactivation and the kinetic coupling made possible by the presence of acid and base catalytic functions within molecular diffusion distances. This strategy exploits: (i) The scavenging of formaldehyde, derived in methanol dehydrogenation events, that reacts in Prins-type alkylation chemistries to transform active olefin- and aromatic- chain carriers in the dual-cycle ‘hydrocarbon pool’ mechanism that describes propagation events in MTO to unreactive polycyclic species; (ii) The previously unrecognized ability of Y2O3 and more generally of rare-earth oxides to selectively and catalytically decompose formaldehyde to COx in presence of unconverted methanol/DME reactants and methanol homologation products; and (iii) The crucial role of formaldehyde transport between and within zeotypic domains in determining lifetime for MTO.

Bifunctional strategy coupling Y2O3 catalyzed alkanal decomposition with methanol-to-olefins catalysis for enhanced lifetime

254th National Meeting (2017)

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