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Title: In Situ Elucidation of the Active State of Co–CeO x Catalysts in the Dry Reforming of Methane: The Important Role of the Reducible Oxide Support and Interactions with Cobalt

The activation of methane and its dry reforming with CO 2 was systematically studied over a series (2–30 wt %) of Co (~5 nm in size) loaded CeO 2 catalysts, with an effort to elucidate the interplay between Co and CeO 2 during the catalytic process using in situ methods. The results of in situ time-resolved X-ray diffraction (TR-XRD) show a strong interaction of methane with the CoOx–CeO 2 systems at temperatures between 200 and 350 °C. The hydrogen produced by the dissociation of C–H bonds in methane leads to a full reduction of Co oxide, Co 3O 4 → CoO → Co, and a partial reduction of ceria with the formation of some Ce 3+. Upon the addition of CO 2, a catalytic cycle for dry reforming of methane (DRM) was achieved on the CoOx–CeO 2 powder catalysts at temperatures below 500 °C. A 10 wt % Co–CeO 2 catalyst was found to possess the best catalytic activity among various cobalt loading catalysts, and it exhibits a desirable stability for the DRM with a minimal effect of carbon accumulation. The phase transitions and the nature of active components in the catalyst were investigated under reaction conditions by in situmore » time-resolved XRD and ambient-pressure X-ray photoelectron spectroscopy (AP-XPS). These studies showed dynamic evolutions in the chemical composition of the catalysts under reaction conditions. CO 2 attenuated the reducing effects of methane. Under optimum CO- and H 2-producing conditions, both XRD and AP-XPS indicated that the active phase involved a majority of metallic Co with a small amount of CoO, both supported on a partially reduced ceria (Ce 3+/Ce 4+). Finally, we identified the importance of dispersing Co, anchoring it onto the ceria surface sites, and then utilizing the redox properties of CeO 2 for activating and then oxidatively converting methane while inhibiting coke formation. Furthermore, a synergistic effect between cobalt and ceria and likely the interfacial sitee are essential to successfully close the catalytic cycle.« less
Authors:
 [1] ; ORCiD logo [2] ;  [1] ;  [1] ;  [2] ; ORCiD logo [3] ;  [3] ;  [2] ; ORCiD logo [4] ; ORCiD logo [5] ;  [6] ; ORCiD logo [6] ;  [7] ; ORCiD logo [8] ;  [1] ; ORCiD logo [1] ; ORCiD logo [2]
  1. Stony Brook Univ., NY (United States). Materials Science and Chemical Engineering Dept.
  2. Brookhaven National Lab. (BNL), Upton, NY (United States). Dept. of Chemistry
  3. Stony Brook Univ., NY (United States). Dept. of Chemistry
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). Dept. of Chemistry; Stony Brook Univ., NY (United States). Dept. of Chemistry
  5. Technical Univ. of Catalonia, Barcelona (Spain). Inst. of Energy Technologies, Dept. of Chemical Engineering and Barcelona Research Center in Multiscale Science and Engineering
  6. Seoul National Univ. (Korea, Republic of). School of Chemical and Biological Engineering, Inst. of Chemical Processes
  7. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS), X-ray Science Division
  8. Stony Brook Univ., NY (United States). Materials Science and Chemical Engineering Dept.; Brookhaven National Lab. (BNL), Upton, NY (United States). Dept. of Chemistry
Publication Date:
Report Number(s):
BNL-207864-2018-JAAM
Journal ID: ISSN 2155-5435
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
ACS Catalysis
Additional Journal Information:
Journal Volume: 8; Journal Issue: 4; Journal ID: ISSN 2155-5435
Publisher:
American Chemical Society (ACS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AP-XPS; ceria; cobalt; in situ XRD; methane dry reforming
OSTI Identifier:
1462401