Mechanistic role of water in HSSZ-13 catalyzed methanol-to-olefins conversion. Issue 16 (24th July 2019)

• Record Type: Journal Article
• Authors: Bollini, Praveen; Chen, Thomas T.; Neurock, Matthew; Bhan, Aditya
• Is Part Of: Catalysis science & technology. Volume 9:Issue 16(2019)
• Page Start: 4374
• Page End: 4383
• Publication Date: 2019-07-24
• Subjects: Catalysis -- Periodicals; 541.395
• DOI: 10.1039/c9cy01015g
• Languages: English
• ISSNs: 2044-4753

Abstract

Abstract : Attenuation of chain initiation and termination rates and higher turnover capacities in methanol-to-olefins (MTO) conversion observed with water co-feeds are plausibly due to formaldehyde hydrolysis. Abstract : Co-feeding water leads to a simultaneous attenuation of chain initiation and chain termination rates in HSSZ-13 catalyzed methanol-to-olefins (MTO) conversion. Density functional theory calculations and transient stoichiometric experiments support the plausibility of formaldehyde hydrolysis occurring over zeolitic Brønsted acid sites at MTO-relevant temperatures. A monotonic decrease in MTO chain initiation and termination rates, and a concurrent monotonic increase in total turnovers as a function of water co-feed partial pressure are consistent with the occurrence and mechanistic relevance of formaldehyde hydrolysis effected by co-fed water. Initiation/termination rates and total turnovers normalized by their corresponding values in the absence of water co-feeds at the same temperature show the expected trends as a function of reaction temperature, assuming equilibrium between formaldehyde and methanediol. These results underscore the implications of formaldehyde hydrolysis chemistry when assessing the mechanistic role of water in methanol-to-olefins conversion specifically, and deactivation mechanisms in zeolite-catalyzed hydrocarbon conversion processes more generally.