Carbene-like reactivity of methoxy groups in a single crystal SAPO-34 MTO catalyst

Ivalina B. Minova; Michael Bühl; Santhosh K. Matam; C. Richard A. Catlow; Mark D. Frogley; Gianfelice Cinque; Paul A. Wright; Russell F. Howe

doi:10.1039/d1cy02361f

Carbene-like reactivity of methoxy groups in a single crystal SAPO-34 MTO catalyst

Ivalina B. Minova, Michael Bühl, Santhosh K. Matam, C. Richard A. Catlow, Mark D. Frogley, Gianfelice Cinque, Paul A. Wright, Russell F. Howe^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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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.

Original language	English
Pages (from-to)	2289-2305
Number of pages	17
Journal	Catalysis Science and Technology
Volume	12
Issue number	7
Early online date	21 Feb 2022
DOIs	https://doi.org/10.1039/d1cy02361f
Publication status	Published - 7 Apr 2022

Bibliographical note

Funding Information:
IBM and PAW would like to thank the EPSRC and CRITICAT Centre for Doctoral Training for Financial Support (PhD studentship to IBM EP/I017008/1, and ESI equipment grant EP/L016419/1). The UK Catalysis Hub is thanked for resources and support provided via membership of the UK Catalysis Hub Consortium and funded by EPSRC (grants EP/I038748/1, EP/I019693/1, EP/K014706/1, EP/K014668/1, EP/K014854/1, EP/K014714/1 and EP/M013219/1). We thank the Diamond Light Source for provision of beam time and support facilities at the MIRIAM beamline B22 (Experiments SM18680-1, SM 20906-1, SM 22347-1, SM23081-1).

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Cite this

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title = "Carbene-like reactivity of methoxy groups in a single crystal SAPO-34 MTO catalyst",

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.",

author = "Minova, {Ivalina B.} and Michael B{\"u}hl and Matam, {Santhosh K.} and Catlow, {C. Richard A.} and Frogley, {Mark D.} and Gianfelice Cinque and Wright, {Paul A.} and Howe, {Russell F.}",

note = "Funding Information: IBM and PAW would like to thank the EPSRC and CRITICAT Centre for Doctoral Training for Financial Support (PhD studentship to IBM EP/I017008/1, and ESI equipment grant EP/L016419/1). The UK Catalysis Hub is thanked for resources and support provided via membership of the UK Catalysis Hub Consortium and funded by EPSRC (grants EP/I038748/1, EP/I019693/1, EP/K014706/1, EP/K014668/1, EP/K014854/1, EP/K014714/1 and EP/M013219/1). We thank the Diamond Light Source for provision of beam time and support facilities at the MIRIAM beamline B22 (Experiments SM18680-1, SM 20906-1, SM 22347-1, SM23081-1). ",

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AU - Minova, Ivalina B.

AU - Bühl, Michael

AU - Matam, Santhosh K.

AU - Catlow, C. Richard A.

AU - Frogley, Mark D.

AU - Cinque, Gianfelice

AU - Wright, Paul A.

AU - Howe, Russell F.

N1 - Funding Information: IBM and PAW would like to thank the EPSRC and CRITICAT Centre for Doctoral Training for Financial Support (PhD studentship to IBM EP/I017008/1, and ESI equipment grant EP/L016419/1). The UK Catalysis Hub is thanked for resources and support provided via membership of the UK Catalysis Hub Consortium and funded by EPSRC (grants EP/I038748/1, EP/I019693/1, EP/K014706/1, EP/K014668/1, EP/K014854/1, EP/K014714/1 and EP/M013219/1). We thank the Diamond Light Source for provision of beam time and support facilities at the MIRIAM beamline B22 (Experiments SM18680-1, SM 20906-1, SM 22347-1, SM23081-1).

PY - 2022/4/7

Y1 - 2022/4/7

N2 - 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.

AB - 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.

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DO - 10.1039/d1cy02361f

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AN - SCOPUS:85127034724

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JO - Catalysis Science and Technology

JF - Catalysis Science and Technology

IS - 7

ER -

Carbene-like reactivity of methoxy groups in a single crystal SAPO-34 MTO catalyst

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