Acid strength and bifunctional catalytic behavior of alloys comprised of noble metals and oxophilic metal promoters

David Hibbitts; Qiaohua Tan; Matthew Neurock

doi:10.1016/j.jcat.2014.03.016

Acid strength and bifunctional catalytic behavior of alloys comprised of noble metals and oxophilic metal promoters

David Hibbitts, Qiaohua Tan, Matthew Neurock

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38 Scopus citations

Abstract

The promotion of metal catalysts with partially oxidized oxophilic MO _x species, such as ReO_x-promoted Rh, has been demonstrated to produce Brønsted acid sites that can promote hydrogenolysis of oxygenate intermediates such as those found in biomass-derived species. A wide variety of alloy compositions and structures are examined in this work to investigate strongly acidic promoters by using DFT-calculated deprotonation energies (DPE) as a measure of acid strength. Sites with the highest acid strength had DPE less than 1100 kJ mol^-1, similar to DPE values of heteropolyacids or acid-containing zeolites, and were found on alloys composed of an oxophilic metal (such as Re or W) with a noble metal (such as Rh or Pt). NH₃ adsorbs more strongly to sites with increasing acid strength and the activation barriers for acid-catalyzed ring opening of a furan ring decrease with increasing acid strength, which was also shown to be stronger for OH acid sites bound to multiple oxophilic metal atoms in a three-fold configuration rather than OH sites adsorbed in an atop configuration on one oxophilic metal, indicating that small MO_x clusters may yield sites with the highest acid strength.

Original language	English (US)
Pages (from-to)	48-58
Number of pages	11
Journal	Journal of Catalysis
Volume	315
DOIs	https://doi.org/10.1016/j.jcat.2014.03.016
State	Published - Jun 2014
Externally published	Yes

Bibliographical note

Funding Information:
The authors are grateful to the National Science Foundation for the financial support of this work under the NSF Award EEC-0813570 as part of the Center for Biorenewable Chemicals (CBiRC) at Iowa State University and the NSF award OISE 0730277 for the Partnership in International Research and Education (PIRE) and also kindly acknowledge access to the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy, Office of Biological and Environmental Research at the Pacific Northwest National Laboratory. The authors also kindly acknowledge the very helpful discussions with Robert J. Davis (University of Virginia), Craig Plaisance (University of Virginia), James A. Dumesic (University of Wisconsin) and Mei Chia (University of Wisconsin).

Keywords

DFT, bifunctional catalysis
Deprotonation energies
Hydrodeoxygenation
Hydrogenolysis
Hydroxymethyl tetrahydrofuran
Oxophilic metal promoters
Ring opening cyclic ethers

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title = "Acid strength and bifunctional catalytic behavior of alloys comprised of noble metals and oxophilic metal promoters",

abstract = "The promotion of metal catalysts with partially oxidized oxophilic MO x species, such as ReOx-promoted Rh, has been demonstrated to produce Br{\o}nsted acid sites that can promote hydrogenolysis of oxygenate intermediates such as those found in biomass-derived species. A wide variety of alloy compositions and structures are examined in this work to investigate strongly acidic promoters by using DFT-calculated deprotonation energies (DPE) as a measure of acid strength. Sites with the highest acid strength had DPE less than 1100 kJ mol-1, similar to DPE values of heteropolyacids or acid-containing zeolites, and were found on alloys composed of an oxophilic metal (such as Re or W) with a noble metal (such as Rh or Pt). NH3 adsorbs more strongly to sites with increasing acid strength and the activation barriers for acid-catalyzed ring opening of a furan ring decrease with increasing acid strength, which was also shown to be stronger for OH acid sites bound to multiple oxophilic metal atoms in a three-fold configuration rather than OH sites adsorbed in an atop configuration on one oxophilic metal, indicating that small MOx clusters may yield sites with the highest acid strength.",

keywords = "DFT, bifunctional catalysis, Deprotonation energies, Hydrodeoxygenation, Hydrogenolysis, Hydroxymethyl tetrahydrofuran, Oxophilic metal promoters, Ring opening cyclic ethers",

author = "David Hibbitts and Qiaohua Tan and Matthew Neurock",

note = "Funding Information: The authors are grateful to the National Science Foundation for the financial support of this work under the NSF Award EEC-0813570 as part of the Center for Biorenewable Chemicals (CBiRC) at Iowa State University and the NSF award OISE 0730277 for the Partnership in International Research and Education (PIRE) and also kindly acknowledge access to the Molecular Science Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy, Office of Biological and Environmental Research at the Pacific Northwest National Laboratory. The authors also kindly acknowledge the very helpful discussions with Robert J. Davis (University of Virginia), Craig Plaisance (University of Virginia), James A. Dumesic (University of Wisconsin) and Mei Chia (University of Wisconsin). ",

year = "2014",

month = jun,

doi = "10.1016/j.jcat.2014.03.016",

language = "English (US)",

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pages = "48--58",

journal = "Journal of Catalysis",

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AU - Hibbitts, David

AU - Tan, Qiaohua

AU - Neurock, Matthew

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N2 - The promotion of metal catalysts with partially oxidized oxophilic MO x species, such as ReOx-promoted Rh, has been demonstrated to produce Brønsted acid sites that can promote hydrogenolysis of oxygenate intermediates such as those found in biomass-derived species. A wide variety of alloy compositions and structures are examined in this work to investigate strongly acidic promoters by using DFT-calculated deprotonation energies (DPE) as a measure of acid strength. Sites with the highest acid strength had DPE less than 1100 kJ mol-1, similar to DPE values of heteropolyacids or acid-containing zeolites, and were found on alloys composed of an oxophilic metal (such as Re or W) with a noble metal (such as Rh or Pt). NH3 adsorbs more strongly to sites with increasing acid strength and the activation barriers for acid-catalyzed ring opening of a furan ring decrease with increasing acid strength, which was also shown to be stronger for OH acid sites bound to multiple oxophilic metal atoms in a three-fold configuration rather than OH sites adsorbed in an atop configuration on one oxophilic metal, indicating that small MOx clusters may yield sites with the highest acid strength.

AB - The promotion of metal catalysts with partially oxidized oxophilic MO x species, such as ReOx-promoted Rh, has been demonstrated to produce Brønsted acid sites that can promote hydrogenolysis of oxygenate intermediates such as those found in biomass-derived species. A wide variety of alloy compositions and structures are examined in this work to investigate strongly acidic promoters by using DFT-calculated deprotonation energies (DPE) as a measure of acid strength. Sites with the highest acid strength had DPE less than 1100 kJ mol-1, similar to DPE values of heteropolyacids or acid-containing zeolites, and were found on alloys composed of an oxophilic metal (such as Re or W) with a noble metal (such as Rh or Pt). NH3 adsorbs more strongly to sites with increasing acid strength and the activation barriers for acid-catalyzed ring opening of a furan ring decrease with increasing acid strength, which was also shown to be stronger for OH acid sites bound to multiple oxophilic metal atoms in a three-fold configuration rather than OH sites adsorbed in an atop configuration on one oxophilic metal, indicating that small MOx clusters may yield sites with the highest acid strength.

KW - DFT, bifunctional catalysis

KW - Deprotonation energies

KW - Hydrodeoxygenation

KW - Hydrogenolysis

KW - Hydroxymethyl tetrahydrofuran

KW - Oxophilic metal promoters

KW - Ring opening cyclic ethers

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SN - 0021-9517

VL - 315

SP - 48

EP - 58

JO - Journal of Catalysis

JF - Journal of Catalysis

ER -

Acid strength and bifunctional catalytic behavior of alloys comprised of noble metals and oxophilic metal promoters

Abstract

Bibliographical note

Keywords

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