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Title: Elucidation of the Reaction Mechanism for High-Temperature Water Gas Shift over an Industrial-Type Copper–Chromium–Iron Oxide Catalyst

Abstract

The water gas shift (WGS) reaction is of paramount importance for the chemical industry, as it constitutes, coupled with methane reforming, the main industrial route to produce hydrogen. Copper–chromium–iron oxide-based catalysts have been widely used for the high-temperature WGS reaction industrially. The WGS reaction mechanism by the CuCrFeOx catalyst has been debated for years, mainly between a “redox” mechanism involving the participation of atomic oxygen from the catalyst and an “associative” mechanism proceeding via a surface formate-like intermediate. In the present work, advanced in situ characterization techniques (infrared spectroscopy, temperature-programmed surface reaction (TPSR), near-ambient pressure XPS (NAP-XPS), and inelastic neutron scattering (INS)) were applied to determine the nature of the catalyst surface and identify surface intermediate species under WGS reaction conditions. The surface of the CuCrFeOx catalyst is found to be dynamic and becomes partially reduced under WGS reaction conditions, forming metallic Cu nanoparticles on Fe3O4. Neither in situ IR not INS spectroscopy detect the presence of surface formate species during WGS. TPSR experiments demonstrate that the evolution of CO2 and H2 from the CO/H2O reactants follows different kinetics than the evolution of CO2 and H2 from HCOOH decomposition (molecule mimicking the associative mechanism). Steady-state isotopic transient kinetic analysis (SSITKA)more » (CO + H216O → CO + H218O) exhibited significant 16O/18O scrambling, characteristic of a redox mechanism. Computed activation energies for elementary steps for the redox and associative mechanism by density functional theory (DFT) simulations indicate that the redox mechanism is favored over the associative mechanism. The combined spectroscopic, computational, and kinetic evidence in the present study finally resolves the WGS reaction mechanism on the industrial-type high-temperature CuCrFeOx catalyst that is shown to proceed via the redox mechanism.« less

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3]; ORCiD logo [3]; ORCiD logo [3]; ORCiD logo [4];  [4];  [4];  [1]; ORCiD logo [5]; ORCiD logo [5]; ORCiD logo [6]; ORCiD logo [1]
  1. Chemical Sciences Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
  2. Chemical Sciences Division and Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States; Department of Chemistry, University of California, Riverside, California 92521, United States
  3. Departments of Chemical Engineering and Chemistry, The University of Kansas, Lawrence, Kansas 66047, United States
  4. Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
  5. Operando Molecular Spectroscopy &, Catalysis Laboratory, Department of Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, United States
  6. Department of Chemistry, University of California, Riverside, California 92521, United States
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
OSTI Identifier:
1542620
DOE Contract Number:  
AC02-05CH11231; AC05-00OR22725
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 141; Journal Issue: 19; Journal ID: ISSN 0002-7863
Country of Publication:
United States
Language:
English

Citation Formats

Polo-Garzon, Felipe, Fung, Victor, Nguyen, Luan, Tang, Yu, Tao, Franklin, Cheng, Yongqiang, Daemen, Luke L., Ramirez-Cuesta, Anibal J., Foo, Guo Shiou, Zhu, Minghui, Wachs, Israel E., Jiang, De-en, and Wu, Zili. Elucidation of the Reaction Mechanism for High-Temperature Water Gas Shift over an Industrial-Type Copper–Chromium–Iron Oxide Catalyst. United States: N. p., 2019. Web. doi:10.1021/jacs.9b03516.
Polo-Garzon, Felipe, Fung, Victor, Nguyen, Luan, Tang, Yu, Tao, Franklin, Cheng, Yongqiang, Daemen, Luke L., Ramirez-Cuesta, Anibal J., Foo, Guo Shiou, Zhu, Minghui, Wachs, Israel E., Jiang, De-en, & Wu, Zili. Elucidation of the Reaction Mechanism for High-Temperature Water Gas Shift over an Industrial-Type Copper–Chromium–Iron Oxide Catalyst. United States. doi:10.1021/jacs.9b03516.
Polo-Garzon, Felipe, Fung, Victor, Nguyen, Luan, Tang, Yu, Tao, Franklin, Cheng, Yongqiang, Daemen, Luke L., Ramirez-Cuesta, Anibal J., Foo, Guo Shiou, Zhu, Minghui, Wachs, Israel E., Jiang, De-en, and Wu, Zili. Thu . "Elucidation of the Reaction Mechanism for High-Temperature Water Gas Shift over an Industrial-Type Copper–Chromium–Iron Oxide Catalyst". United States. doi:10.1021/jacs.9b03516.
@article{osti_1542620,
title = {Elucidation of the Reaction Mechanism for High-Temperature Water Gas Shift over an Industrial-Type Copper–Chromium–Iron Oxide Catalyst},
author = {Polo-Garzon, Felipe and Fung, Victor and Nguyen, Luan and Tang, Yu and Tao, Franklin and Cheng, Yongqiang and Daemen, Luke L. and Ramirez-Cuesta, Anibal J. and Foo, Guo Shiou and Zhu, Minghui and Wachs, Israel E. and Jiang, De-en and Wu, Zili},
abstractNote = {The water gas shift (WGS) reaction is of paramount importance for the chemical industry, as it constitutes, coupled with methane reforming, the main industrial route to produce hydrogen. Copper–chromium–iron oxide-based catalysts have been widely used for the high-temperature WGS reaction industrially. The WGS reaction mechanism by the CuCrFeOx catalyst has been debated for years, mainly between a “redox” mechanism involving the participation of atomic oxygen from the catalyst and an “associative” mechanism proceeding via a surface formate-like intermediate. In the present work, advanced in situ characterization techniques (infrared spectroscopy, temperature-programmed surface reaction (TPSR), near-ambient pressure XPS (NAP-XPS), and inelastic neutron scattering (INS)) were applied to determine the nature of the catalyst surface and identify surface intermediate species under WGS reaction conditions. The surface of the CuCrFeOx catalyst is found to be dynamic and becomes partially reduced under WGS reaction conditions, forming metallic Cu nanoparticles on Fe3O4. Neither in situ IR not INS spectroscopy detect the presence of surface formate species during WGS. TPSR experiments demonstrate that the evolution of CO2 and H2 from the CO/H2O reactants follows different kinetics than the evolution of CO2 and H2 from HCOOH decomposition (molecule mimicking the associative mechanism). Steady-state isotopic transient kinetic analysis (SSITKA) (CO + H216O → CO + H218O) exhibited significant 16O/18O scrambling, characteristic of a redox mechanism. Computed activation energies for elementary steps for the redox and associative mechanism by density functional theory (DFT) simulations indicate that the redox mechanism is favored over the associative mechanism. The combined spectroscopic, computational, and kinetic evidence in the present study finally resolves the WGS reaction mechanism on the industrial-type high-temperature CuCrFeOx catalyst that is shown to proceed via the redox mechanism.},
doi = {10.1021/jacs.9b03516},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 19,
volume = 141,
place = {United States},
year = {2019},
month = {4}
}