Directed transforming of coke to active intermediates in methanol-to-olefins catalyst to boost light olefins selectivity

Abstract

Methanol-to-olefins (MTO), the most important catalytic process producing ethylene and propylene from non-oil feedstocks (coal, natural gas, biomass, CO 2 , etc.), is hindered by rapid catalyst deactivation due to coke deposition. Common practice to recover catalyst activity, i.e. removing coke via air combustion or steam gasification, unavoidably eliminates the active hydrocarbon pool species (HCPs) favoring light olefins formation. Density functional theory calculations and structured illumination microscopy reveal that naphthalenic cations, active HCPs enhancing ethylene production, are highly stable within SAPO-34 zeolites at high temperature. Here, we demonstrate a strategy of directly transforming coke to naphthalenic species in SAPO-34 zeolites\xa0via steam cracking. Fluidized bed reactor-regenerator pilot experiments show that an unexpectedly high light olefins selectivity of 85% is achieved in MTO reaction with 88% valuable CO and H 2 and negligible CO 2 as byproducts from regeneration under industrial-alike continuous operations. This strategy significantly boosts the economics and sustainability of MTO process. Methanol-to-olefins is hindered by rapid catalyst deactivation due to coke deposition. Here the authors demonstrate an approach of directly transforming coke to active intermediates to simultaneously recover catalyst activity and boost light olefins selectivity.