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Title: Mechanistic Insights into the Hydrogenolysis of Levoglucosanol over Bifunctional Platinum Silica–Alumina Catalysts

Abstract

Herein, we report on the hydrogenolysis of the biorenewable intermediate levoglucosanol (Lgol) over bifunctional platinum catalysts supported on silica alumina in tetrahydrofuran solvent. C-13 radiolabeling is used to confirm the ring rearrangement forming tetrahydrofurandimethanol. The reaction rate and product selectivity are comparable between 1.1 and 5.3 wt % Pt loadings, indicating that, at these metal loadings, the rate-limiting step is acid catalyzed. The measured zero-order dependence in hydrogen indicates that a non-rate-determining hydrogenation step follows an acid-catalyzed irreversible rate-determining step. The measured first-order dependence in Lgol indicates that the acid sites are not highly covered by Lgol. A physical mixture of Pt/SiO2 and SiAl catalysts displayed product selectivity similar to that of the Pt/SiAl catalyst, indicating that nanoscale proximity of metal and acid sites is not required to carry out Lgol hydrogenolysis selectively. As the Pt loading in Pt/SiAl catalysts is decreased, or when the bare SiAl support is separated from a Pt/SiO2 catalyst in a dual-layer configuration, the selectivity toward identified products decreases. These results suggest that degradation reactions are avoided when the reactive intermediates formed over acid sites are rapidly hydrogenated over metal sites. First-principles simulations are performed to investigate the energetics of the proposed reaction pathway. Amore » detailed reaction mechanism for Lgol hydrogenolysis is proposed on the basis of a combination of the experimental and computational results. These findings provide a fundamental understanding of the catalytic conversion of levoglucosanol over bifunctional metal-acid catalysts, facilitating rationally designed processes to produce renewable chemicals from biomass-derived levoglucosenone.« less

Authors:
 [1]; ORCiD logo [2];  [1];  [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [1]
  1. Department of Chemical and Biological Engineering, University of Wisconsin—Madison, Madison, Wisconsin 53706, United States
  2. Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1463674
DOE Contract Number:  
AC02-06CH11357
Resource Type:
Journal Article
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 8; Journal Issue: 5; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
bifunctional; biomass; catalysis; heterogeneous; kinetics; levoglucosenone; mechanism

Citation Formats

Krishna, Siddarth H., Assary, Rajeev S., Rashke, Quinn A., Schmidt, Zachary R., Curtiss, Larry A., Dumesic, James A., and Huber, George W. Mechanistic Insights into the Hydrogenolysis of Levoglucosanol over Bifunctional Platinum Silica–Alumina Catalysts. United States: N. p., 2018. Web. doi:10.1021/acscatal.7b03764.
Krishna, Siddarth H., Assary, Rajeev S., Rashke, Quinn A., Schmidt, Zachary R., Curtiss, Larry A., Dumesic, James A., & Huber, George W. Mechanistic Insights into the Hydrogenolysis of Levoglucosanol over Bifunctional Platinum Silica–Alumina Catalysts. United States. doi:10.1021/acscatal.7b03764.
Krishna, Siddarth H., Assary, Rajeev S., Rashke, Quinn A., Schmidt, Zachary R., Curtiss, Larry A., Dumesic, James A., and Huber, George W. Fri . "Mechanistic Insights into the Hydrogenolysis of Levoglucosanol over Bifunctional Platinum Silica–Alumina Catalysts". United States. doi:10.1021/acscatal.7b03764.
@article{osti_1463674,
title = {Mechanistic Insights into the Hydrogenolysis of Levoglucosanol over Bifunctional Platinum Silica–Alumina Catalysts},
author = {Krishna, Siddarth H. and Assary, Rajeev S. and Rashke, Quinn A. and Schmidt, Zachary R. and Curtiss, Larry A. and Dumesic, James A. and Huber, George W.},
abstractNote = {Herein, we report on the hydrogenolysis of the biorenewable intermediate levoglucosanol (Lgol) over bifunctional platinum catalysts supported on silica alumina in tetrahydrofuran solvent. C-13 radiolabeling is used to confirm the ring rearrangement forming tetrahydrofurandimethanol. The reaction rate and product selectivity are comparable between 1.1 and 5.3 wt % Pt loadings, indicating that, at these metal loadings, the rate-limiting step is acid catalyzed. The measured zero-order dependence in hydrogen indicates that a non-rate-determining hydrogenation step follows an acid-catalyzed irreversible rate-determining step. The measured first-order dependence in Lgol indicates that the acid sites are not highly covered by Lgol. A physical mixture of Pt/SiO2 and SiAl catalysts displayed product selectivity similar to that of the Pt/SiAl catalyst, indicating that nanoscale proximity of metal and acid sites is not required to carry out Lgol hydrogenolysis selectively. As the Pt loading in Pt/SiAl catalysts is decreased, or when the bare SiAl support is separated from a Pt/SiO2 catalyst in a dual-layer configuration, the selectivity toward identified products decreases. These results suggest that degradation reactions are avoided when the reactive intermediates formed over acid sites are rapidly hydrogenated over metal sites. First-principles simulations are performed to investigate the energetics of the proposed reaction pathway. A detailed reaction mechanism for Lgol hydrogenolysis is proposed on the basis of a combination of the experimental and computational results. These findings provide a fundamental understanding of the catalytic conversion of levoglucosanol over bifunctional metal-acid catalysts, facilitating rationally designed processes to produce renewable chemicals from biomass-derived levoglucosenone.},
doi = {10.1021/acscatal.7b03764},
journal = {ACS Catalysis},
issn = {2155-5435},
number = 5,
volume = 8,
place = {United States},
year = {2018},
month = {3}
}