| Minova, Ivalina B., Bühl, Michael, Matam, Santhosh K., Catlow, C. Richard A., Frogley, Mark D., Cinque, Gianfelice, Wright, Paul A. and Howe, Russell F. 2022. Carbene-like reactivity of methoxy groups in a single crystal SAPO-34 MTO catalyst. Catalysis Science & Technology 12 (7) , pp. 2289-2305. 10.1039/D1CY02361F |
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Abstract
Synchrotron FTIR microspectroscopy coupled with mass spectrometric analysis of desorbed products has been used to investigate the initial stages of the methanol to olefins (MTO) reaction in single crystals of SAPO-34. Surface methoxy groups (SMS) are key to initial dimethylether (DME) and subsequent carbon–carbon bond formation. Deprotonation of SMS is the critical first step in direct olefin formation at low temperatures and DME is not involved in the carbon–carbon forming step. Experiments with CD3OH confirm the deprotonation step and show an inverse kinetic isotope effect consistent with irreversible deprotonation. The subsequent formation of alkoxide species, which are the precursors of the olefinic hydrocarbon pool present in working MTO catalysts, is initiated via insertion of surface carbene-like species into adjacent SMS. The observed induction period for this process is determined by the limited mobility of SMS and/or carbene species. Olefins formed from cracking of the alkoxide species then transmit carbon–carbon bond formation through the SAPO-34 by rapid diffusion and reaction with further SMS. Acetyl species seen with methanol at higher temperatures support the insertion of CO into SMS suggested in the literature, but these species do not play a role in direct olefin formation.
| Item Type: | Article |
|---|---|
| Date Type: | Publication |
| Status: | Published |
| Schools: | Schools > Chemistry Research Institutes & Centres > Cardiff Catalysis Institute (CCI) Professional Services > Advanced Research Computing @ Cardiff (ARCCA) |
| Publisher: | Royal Society of Chemistry |
| ISSN: | 2044-4753 |
| Funders: | EPSRC |
| Date of First Compliant Deposit: | 11 April 2022 |
| Date of Acceptance: | 11 February 2022 |
| Last Modified: | 07 May 2023 15:00 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/149130 |
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