Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoOx/Al2O3 Catalysts

Chakrabarti, Anisha; Wachs, Israel E.

doi:10.1021/acs.jpcc.9b02426

Title: Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoO_x/Al₂O₃ Catalysts

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Abstract

The activation of supported MoO_x/Al₂O₃ catalysts and the resulting surface intermediates were examined with in situ DRIFTS during olefin metathesis reaction conditions, aided by C₃D₆-C₃H₆ isotopically labeled switching, C₂H₄-C₄H₈ titration, and temperature programmed reaction experiments. The studies shows that activation by propylene of the surface MoO_x sites on Al₂O₃ initiates by forming surface isopropoxide species that subsequently dehydrogenate to acetone and surface Mo-OH. Desorption of acetone from the catalyst surface reduces the Mo⁺⁶ sites to Mo⁺⁴ sites, creating a vacancy for coordination of the next CH₂=CHCH₃ molecule. Oxidative addition from subsequent adsorption of propylene on the surface Mo⁺⁴ sites results in formation of surface Mo=CH₂ and Mo=CHCH3 reactive intermediates, oxidizing the reduced surface molybdena sites back to Mo⁺⁶. This study demonstrates the activation mechanism and surface intermediates during olefin metathesis by supported MoO_x/Al₂O₃ catalysts under reaction conditions.

Authors:

Chakrabarti, Anisha ^[1];

^[2]

Lehigh Univ., Bethlehem, PA (United States); Honeywell UOP, Des Plaines, IL (United States)
Lehigh Univ., Bethlehem, PA (United States)

Publication Date:: Mon Apr 29 00:00:00 EDT 2019

Research Org.:: Lehigh Univ., Bethlehem, PA (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:: 1510503

Grant/Contract Number:: SC0014510

Resource Type:: Accepted Manuscript

Journal Name:: Journal of Physical Chemistry. C

Additional Journal Information:: Journal Volume: XXXX; Journal Issue: XXX; Journal ID: ISSN 1932-7447

Publisher:: American Chemical Society

Country of Publication:: United States

Language:: English

Subject:: 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

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                    Chakrabarti, Anisha, and Wachs, Israel E. Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoOx/Al2O3 Catalysts.  United States: N. p., 2019. 
Web.  doi:10.1021/acs.jpcc.9b02426.

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                    Chakrabarti, Anisha, & Wachs, Israel E. Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoOx/Al2O3 Catalysts.  United States.  https://doi.org/10.1021/acs.jpcc.9b02426

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                    Chakrabarti, Anisha, and Wachs, Israel E. Mon .  
"Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoOx/Al2O3 Catalysts".  United States.  https://doi.org/10.1021/acs.jpcc.9b02426.  https://www.osti.gov/servlets/purl/1510503.

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@article{osti_1510503,

  title        = {Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoOx/Al2O3 Catalysts},

  author       = {Chakrabarti, Anisha and Wachs, Israel E.},

  abstractNote = {The activation of supported MoOx/Al2O3 catalysts and the resulting surface intermediates were examined with in situ DRIFTS during olefin metathesis reaction conditions, aided by C3D6-C3H6 isotopically labeled switching, C2H4-C4H8 titration, and temperature programmed reaction experiments. The studies shows that activation by propylene of the surface MoOx sites on Al2O3 initiates by forming surface isopropoxide species that subsequently dehydrogenate to acetone and surface Mo-OH. Desorption of acetone from the catalyst surface reduces the Mo+6 sites to Mo+4 sites, creating a vacancy for coordination of the next CH2=CHCH3 molecule. Oxidative addition from subsequent adsorption of propylene on the surface Mo+4 sites results in formation of surface Mo=CH2 and Mo=CHCH3 reactive intermediates, oxidizing the reduced surface molybdena sites back to Mo+6. This study demonstrates the activation mechanism and surface intermediates during olefin metathesis by supported MoOx/Al2O3 catalysts under reaction conditions.},

  doi          = {10.1021/acs.jpcc.9b02426},

  journal      = {Journal of Physical Chemistry. C},

  number       = XXX,

  volume       = XXXX,

  place        = {United States},

  year         = {Mon Apr 29 00:00:00 EDT 2019},

  month        = {Mon Apr 29 00:00:00 EDT 2019}

}

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Title: Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoOx/Al2O3 Catalysts

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Title: Activation Mechanism and Surface Intermediates during Olefin Metathesis by Supported MoO_x/Al₂O₃ Catalysts