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Title: Water-gas shift reaction on alumina-supported Pt-CeO x catalysts prepared by supercritical fluid deposition

Abstract

Alumina-supported platinum catalysts, both with and without ceria, were prepared by supercritical fluid deposition and evaluated for activity for water-gas shift reaction. The organometallic precursor, platinum(II) acetylacetonate, was deposited from solution in supercritical carbon dioxide. Analysis of the catalysts by high resolution scanning transmission electron microscopy indicated that platinum was present in the form of highly dispersed metal nanoparticles. Pretreatment of the alumina-supported ceria in hydrogen prior to the deposition of the platinum precursor resulted in more platinum nucleated on ceria than non-pretreated alumina-supported ceria but varied in both particle size and structure. The ceria-containing catalyst that was not pretreated exhibited a more uniform particle size, and the Pt particles were encapsulated in crystalline ceria. Reaction rate measurements showed that the catalyst was more active for water-gas shift, with reaction rates per mass of platinum that exceeded most literature values for water-gas shift reaction on Pt-CeO x catalysts. The high activity was attributed to the significant fraction of platinum/ceria interfacial contact. We found that these results show the promise of supercritical fluid deposition as a scalable means of synthesizing highly active supported metal catalysts that offer efficient utilization of precious metals.

Authors:
 [1];  [1];  [1];  [2]; ORCiD logo [1]
  1. Univ. of South Alabama, Mobile, AL (United States). Dept. of Chemical and Biomolecular Engineering
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS)
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1349599
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Supercritical Fluids
Additional Journal Information:
Journal Volume: 119; Journal Issue: C; Journal ID: ISSN 0896-8446
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Supercritical; CO2; Platinum; Gas-shift; Wgs; Wgsr; Catalyst; Catalysis; Alumina; Hydrogen; Fuel cell; Reaction

Citation Formats

Deal, Jacob W., Le, Phong, Corey, C. Blake, More, Karren, and West, Christy Wheeler. Water-gas shift reaction on alumina-supported Pt-CeOx catalysts prepared by supercritical fluid deposition. United States: N. p., 2016. Web. doi:10.1016/j.supflu.2016.08.016.
Deal, Jacob W., Le, Phong, Corey, C. Blake, More, Karren, & West, Christy Wheeler. Water-gas shift reaction on alumina-supported Pt-CeOx catalysts prepared by supercritical fluid deposition. United States. doi:10.1016/j.supflu.2016.08.016.
Deal, Jacob W., Le, Phong, Corey, C. Blake, More, Karren, and West, Christy Wheeler. 2016. "Water-gas shift reaction on alumina-supported Pt-CeOx catalysts prepared by supercritical fluid deposition". United States. doi:10.1016/j.supflu.2016.08.016. https://www.osti.gov/servlets/purl/1349599.
@article{osti_1349599,
title = {Water-gas shift reaction on alumina-supported Pt-CeOx catalysts prepared by supercritical fluid deposition},
author = {Deal, Jacob W. and Le, Phong and Corey, C. Blake and More, Karren and West, Christy Wheeler},
abstractNote = {Alumina-supported platinum catalysts, both with and without ceria, were prepared by supercritical fluid deposition and evaluated for activity for water-gas shift reaction. The organometallic precursor, platinum(II) acetylacetonate, was deposited from solution in supercritical carbon dioxide. Analysis of the catalysts by high resolution scanning transmission electron microscopy indicated that platinum was present in the form of highly dispersed metal nanoparticles. Pretreatment of the alumina-supported ceria in hydrogen prior to the deposition of the platinum precursor resulted in more platinum nucleated on ceria than non-pretreated alumina-supported ceria but varied in both particle size and structure. The ceria-containing catalyst that was not pretreated exhibited a more uniform particle size, and the Pt particles were encapsulated in crystalline ceria. Reaction rate measurements showed that the catalyst was more active for water-gas shift, with reaction rates per mass of platinum that exceeded most literature values for water-gas shift reaction on Pt-CeOx catalysts. The high activity was attributed to the significant fraction of platinum/ceria interfacial contact. We found that these results show the promise of supercritical fluid deposition as a scalable means of synthesizing highly active supported metal catalysts that offer efficient utilization of precious metals.},
doi = {10.1016/j.supflu.2016.08.016},
journal = {Journal of Supercritical Fluids},
number = C,
volume = 119,
place = {United States},
year = 2016,
month = 8
}

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  • The water-gas shift reaction was investigated on alkali-promoted alumina catalysts prepared by mixing alumina with various alkali metal salts. Results showed that the activity for the CO + H/sub 2/O reaction increased with the concentration of promoter until the surface was almost saturated by the alkali metal ions. At the same concentration of metal ions, the efficiency of promotion was in the order Cs > K > Na > Li. The addition of alkali salts also increased the catalyst activity for the CO/sub 2/ + H/sub 2/ reaction at high temperatures. Although the promoters showed similar effect of concentration andmore » tendency for the efficiency, the results were not as clear as those for the CO + H/sub 2/O reaction. The kinetics of the water-gas shift reaction was studied on a potassium-promoted alumina in an infrared cell used as a flow-type reactor with the simultaneous spectroscopy of surface species. It was thus found that formate ion was formed during the CO + H/sub 2/O reaction and that the reaction rate was proportional to the surface concentration of the formate ions. A reaction mechanism through formate was proposed and physical and chemical factors contributing to the promotion were discussed based on this mechanism.« less
  • The kinetics of the WGS reaction as catalyzed by alumina-supported Group VIIB, VIII, and IB metals are examined. For several metals a strong effect of support on metal activity is observed. For example, the turnover number (rate per surface metal atom) of Pt supported on Al/sub 2/O/sub 3/ is an order of magnitude higher than the turnover number of Pt on SiO/sub 2/. The turnover numbers (at 300/sup 0/C) of the various alumina-supported metals studied for WGS decrease in the order Cu, Re, Co, Ru, Ni, Pt, Os, Au, Fe, Pd, Rh, and Ir. For these metals the range ofmore » activity varies by more than three orders of magnitude. It is shown that a volcano-shaped correlation exists between the activities of these metals and their respective CO heats of adsorption. The partial pressure dependencies of the reactants on these metals are reported for the first time. Over most metals the CO order of reaction is near zero and the H/sub 2/O order of reaction is near 1/2. A reaction sequence including formic acid as an intermediate is proposed in order to account for the apparent bifunctionality of the supported catalyst systems. This approach leads to a power rate law, r = kP/sub CO/sup x/P/sub H2O/sup 1-X)/2//, an expression shown to be consistent with the experimental parameters obtained in these kinetic studies.« less