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Investigation of the active Bronsted acid site for the DME carbonylation reaction in chabazite-type zeolites

Lusardi, Marcella and Davis, Mark EDWARD (2019) Investigation of the active Bronsted acid site for the DME carbonylation reaction in chabazite-type zeolites. In: 258th ACS National Meeting & Exposition, 25-29 August 2019, San Diego, CA.

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Chabazite-type (CHA) zeolites (SSZ-13s) are active acid catalysts in the carbonylation of di-Me ether (DME), an important C-C bond forming reaction involved in the conversion of syngas derivs. to valuable chem. intermediates. We observe a max. in the formation rate of Me acetate, the target product, as a function of Si/Al in the SSZ-13s that cannot be explained from the standpoint of total acid site d. While the active sites for this reaction have been better studied in other zeolite topologies (MOR, FER), to date, the origin of activity in CHA remains unclear. To investigate this issue, we synthesized SSZ-13s with a range of Si/Al (5 < Si/Al < 75) to vary both Bronsted acid site d. and siting (e.g., paired vs. isolated), and evaluated the impact of these parameters on the DME carbonylation activity. Further, because the CHA structure has only one T-site, differentiating Bronsted acid sites via 1H NMR may be feasible. Three possible extraframework, monovalent cation sites exist. Only two of these sites are accessible by reactants, reducing the active Bronsted acid site candidates to the proton that sits in the 6-membered ring (MR) window, and the one oriented in the 8MR window. We detect three distinct resonances in the high-spin 1H NMR spectra on dehydrated SSZ-13s. From the reactivity and NMR analyses, coupled with divalent cation exchange expts. for specific titrn. of paired (framework Al sepd. by no more than 3 Si-O units) acid sites, we developed a model for the location of the active site in CHA. Given the unique framework topol. of CHA compared to other active, DME carbonylation zeolite topologies, this investigation provides further insights into this useful C-C bond forming reaction.

Item Type:Conference or Workshop Item (Paper)
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URLURL TypeDescription Website
Lusardi, Marcella0000-0002-7002-4257
Davis, Mark EDWARD0000-0001-8294-1477
Additional Information:© 2019 American Chemical Society.
Record Number:CaltechAUTHORS:20190812-135709922
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:97787
Deposited By: Tony Diaz
Deposited On:12 Aug 2019 21:00
Last Modified:09 Mar 2020 13:19

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