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Title: In Situ UV-Visible Assessment of Iron-Based High-Temperature Water-Gas Shift Catalysts Promoted with Lanthana: An Extent of Reduction Study

Here, the extent of reduction of unsupported iron-based high-temperature water-gas shift catalysts with small (<5 wt %) lanthana contents was studied using UV-visible spectroscopy. Temperature- programmed reduction measurements showed that lanthana content higher than 0.5 wt % increased the extent of reduction to metallic Fe, while 0.5 wt % of lanthana facilitated the reduction to Fe 3O 4. In situ measurements on the iron oxide catalysts using mass and UV-visible spectroscopies permitted the quantification of the extent of reduction under temperature-programmed reduction and high-temperature water-gas shift conditions. The oxidation states were successfully calibrated against normalized absorbance spectra of visible light using the Kubelka-Munk theory. The normalized absorbance relative to the fully oxidized Fe 2O 3 increased as the extent of reduction increased. XANES suggested that the average bulk iron oxidation state during the water-gas shift reaction was Fe +2.57 for the catalyst with no lanthana and Fe +2.54 for the catalysts with 1 wt % lanthana. However, the UV-vis spectra suggest that the surface oxidation state of iron would be Fe +2.31 for the catalyst with 1 wt % lanthana if the oxidation state of iron in the catalyst with 0 wt % lanthana were Fe +2.57. The findings ofmore » this paper emphasize the importance of surface sensitive UV-visible spectroscopy for determining the extent of catalyst reduction during operation. Furthermore, the paper highlights the potential to use bench-scale UV-visible spectroscopy to study the surface chemistry of catalysts instead of less-available synchrotron X-ray radiation facilities.« less
Authors:
 [1] ;  [2] ;  [3] ;  [4] ; ORCiD logo [4]
  1. Brigham Young Univ., Provo, UT (United States); Phillips 66, Bartlesville, OK (United States)
  2. Brigham Young Univ., Provo, UT (United States); Micron Technology, Boise, ID (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
  4. Brigham Young Univ., Provo, UT (United States)
Publication Date:
Report Number(s):
BNL-205683-2018-JAAM
Journal ID: ISSN 2073-4344; CATACJ
Grant/Contract Number:
SC0012704
Type:
Accepted Manuscript
Journal Name:
Catalysts
Additional Journal Information:
Journal Volume: 8; Journal Issue: 2; Journal ID: ISSN 2073-4344
Publisher:
MDPI
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:
36 MATERIALS SCIENCE; iron water gas shift catalysts; extent of reduction; UV-visible spectroscopy; XANES
OSTI Identifier:
1438322