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Title: Enhanced Hydrodeoxygenation of m -Cresol over Bimetallic Pt–Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway

Abstract

Supported bimetallic catalysts consisting of a noble metal (e.g., Pt) and an oxophilic metal (e.g., Mo) have received considerable attention for the hydrodeoxygenation of oxygenated aromatic compounds produced from biomass fast pyrolysis. Here, we report that PtMo can catalyze m-cresol deoxygenation via a pathway involving an initial tautomerization step. In contrast, the dominant mechanism on monometallic Pt/Al 2O 3 was found to be sequential Pt-catalyzed ring hydrogenation followed by dehydration on the support. Bimetallic Pt 10Mo 1 and Pt 1Mo 1 catalysts were found to produce the completely hydrogenated and deoxygenated product, methylcyclohexane (MCH), with much higher yields than monometallic Pt catalysts with comparable metal loadings and surface areas. Over an inert carbon support, MCH formation was found to be slow over monometallic Pt catalysts, while deoxygenation was significant for PtMo catalysts even in the absence of an acidic support material. Experimental studies of m-cresol deoxygenation together with density functional theory calculations indicated that Mo sites on the PtMo bimetallic surface dramatically lower the barrier for m-cresol tautomerization and subsequent deoxygenation. The accessibility of this pathway arises from the increased interaction between the oxygen of m-cresol and the Mo sites in the Pt surface. This interaction significantly alters the configurationmore » of the precursor and transition states for tautomerization. Lastly, a suite of catalyst characterization techniques including X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR) indicate that Mo was present in a reduced state on the bimetallic surface under conditions relevant for reaction. Overall, these results suggest that the use of bifunctional metal catalysts can result in new reaction pathways that are unfavorable on monometallic noble metal catalysts.« less

Authors:
 [1];  [2];  [3];  [2];  [2];  [2];  [2];  [1]
  1. Univ. of Colorado, Boulder, CO (United States). Chemical and Biological Engineering Dept.
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States). National Bioenergy Center
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Chemical Sciences and Engineering Division
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Bioenergy Technologies Office; National Science Foundation (NSF); Department of Education (DOE'd)
OSTI Identifier:
1271939
Report Number(s):
NREL/JA-5100-66831
Journal ID: ISSN 2155-5435
Grant/Contract Number:  
AC36-08GO28308; MCB-090159; CHE-1149752; AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 6; Journal Issue: 7; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; bimetallic; biomass; catalytic fast pyrolysis; hydrodeoxygenation; molybdenum; oxophilic promoter; platinum

Citation Formats

Robinson, Allison, Ferguson, Glen Allen, Gallagher, James R., Cheah, Singfoong, Beckham, Gregg T., Schaidle, Joshua A., Hensley, Jesse E., and Medlin, J. Will. Enhanced Hydrodeoxygenation of m -Cresol over Bimetallic Pt–Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway. United States: N. p., 2016. Web. doi:10.1021/acscatal.6b01131.
Robinson, Allison, Ferguson, Glen Allen, Gallagher, James R., Cheah, Singfoong, Beckham, Gregg T., Schaidle, Joshua A., Hensley, Jesse E., & Medlin, J. Will. Enhanced Hydrodeoxygenation of m -Cresol over Bimetallic Pt–Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway. United States. https://doi.org/10.1021/acscatal.6b01131
Robinson, Allison, Ferguson, Glen Allen, Gallagher, James R., Cheah, Singfoong, Beckham, Gregg T., Schaidle, Joshua A., Hensley, Jesse E., and Medlin, J. Will. Thu . "Enhanced Hydrodeoxygenation of m -Cresol over Bimetallic Pt–Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway". United States. https://doi.org/10.1021/acscatal.6b01131. https://www.osti.gov/servlets/purl/1271939.
@article{osti_1271939,
title = {Enhanced Hydrodeoxygenation of m -Cresol over Bimetallic Pt–Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway},
author = {Robinson, Allison and Ferguson, Glen Allen and Gallagher, James R. and Cheah, Singfoong and Beckham, Gregg T. and Schaidle, Joshua A. and Hensley, Jesse E. and Medlin, J. Will},
abstractNote = {Supported bimetallic catalysts consisting of a noble metal (e.g., Pt) and an oxophilic metal (e.g., Mo) have received considerable attention for the hydrodeoxygenation of oxygenated aromatic compounds produced from biomass fast pyrolysis. Here, we report that PtMo can catalyze m-cresol deoxygenation via a pathway involving an initial tautomerization step. In contrast, the dominant mechanism on monometallic Pt/Al2O3 was found to be sequential Pt-catalyzed ring hydrogenation followed by dehydration on the support. Bimetallic Pt10Mo1 and Pt1Mo1 catalysts were found to produce the completely hydrogenated and deoxygenated product, methylcyclohexane (MCH), with much higher yields than monometallic Pt catalysts with comparable metal loadings and surface areas. Over an inert carbon support, MCH formation was found to be slow over monometallic Pt catalysts, while deoxygenation was significant for PtMo catalysts even in the absence of an acidic support material. Experimental studies of m-cresol deoxygenation together with density functional theory calculations indicated that Mo sites on the PtMo bimetallic surface dramatically lower the barrier for m-cresol tautomerization and subsequent deoxygenation. The accessibility of this pathway arises from the increased interaction between the oxygen of m-cresol and the Mo sites in the Pt surface. This interaction significantly alters the configuration of the precursor and transition states for tautomerization. Lastly, a suite of catalyst characterization techniques including X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR) indicate that Mo was present in a reduced state on the bimetallic surface under conditions relevant for reaction. Overall, these results suggest that the use of bifunctional metal catalysts can result in new reaction pathways that are unfavorable on monometallic noble metal catalysts.},
doi = {10.1021/acscatal.6b01131},
url = {https://www.osti.gov/biblio/1271939}, journal = {ACS Catalysis},
issn = {2155-5435},
number = 7,
volume = 6,
place = {United States},
year = {2016},
month = {5}
}

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