Specificity of sites within eight-membered ring zeolite channels for carbonylation of methyls to acetyls

Aditya Bhan, Ayman D. Allian, Glenn J. Sunley, David J. Law, Enrique Iglesia

Research output: Contribution to journalArticle

179 Scopus citations

Abstract

The acid-catalyzed formation of carbon-carbon bonds from C1 precursors via CO insertion into chemisorbed methyl groups occurs selectively within eight-membered ring (8-MR) zeolite channels. This elementary step controls catalytic carbonylation rates of dimethyl ether (DME) to methyl acetate. The number of O-H groups within 8-MR channels was measured by rigorous deconvolution of the infrared bands for O-H groups in cation-exchanged and acid forms of mordenite (M,H-MOR) and ferrierite (H-FER) after adsorption of basic probe molecules of varying size. DME carbonylation rates are proportional to the number of O-H groups within 8-MR channels. Na+ cations selectively replaced protons within 8-MR channels and led to a disproportionate decrease in carbonylation turnover rates (per total H+). These conclusions are consistent with the low or undetectable rates of carbonylation on zeolites without 8-MR channels (H-BEA, H-FAU, H-MFI). Such specificity of methyl reactivity upon confinement within small channels appears to be unprecedented in catalysis by microporous solids, which typically select reactions by size exclusion of bulkier transition states.

Original languageEnglish (US)
Pages (from-to)4919-4924
Number of pages6
JournalJournal of the American Chemical Society
Volume129
Issue number16
DOIs
StatePublished - Apr 25 2007

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