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Title: Steam Reforming of Ethanol over Pt/ceria with Co-Fed Hydrogen

Abstract

Metal/ceria catalysts are receiving great interest for reactions involving steam conversion, including CO for low-temperature water-gas shift, and the conversion of chemical carriers of hydrogen, among them methanol, and ethanol. The mechanism by which ROH model reagents are activated on the surface of the Pt/partially reduced ceria catalyst was explored using a combination of reaction testing and infrared spectroscopy. In this particular investigation, the activation and turnover of ethanol were explored and compared with previous investigations of methanol steam reforming and low-temperature water-gas shift under H2-rich conditions, where the surface of ceria is in a partially reduced state. Under these conditions, activation of ethanol was found to proceed by dissociative adsorption at reduced defect sites on ceria (i.e., Ce surface atoms in the Ce3+ oxidation state), yielding an adsorbed type II ethoxy species and an adsorbed H species, the latter identified to be a type II bridging OH group. In the presence of steam, the ethoxy species rapidly undergoes molecular transformation to an adsorbed acetate intermediate by oxidative dehydrogenation. This is analogous to the conversion of type II methoxy species to formate observed in previous investigations of methanol steam reforming. In addition, although formate then decomposes in steam to CO2more » and H2 during methanol steam reforming, in an analogous pathway for ethanol steam reforming, the acetate intermediate decomposes in steam to CO2 and CH4. Therefore, further H2 production requires energy-intensive activation of CH4, which is not required for methanol conversion over Pt/ceria.« less

Authors:
; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
959707
Report Number(s):
BNL-82693-2009-JA
Journal ID: ISSN 0021-9517; JCTLA5; TRN: US201016%%851
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Catalysis; Journal Volume: 245
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; 10 SYNTHETIC FUELS; ACETATES; ADSORPTION; ATOMS; CATALYSTS; DEFECTS; DEHYDROGENATION; ETHANOL; FORMATES; HYDROGEN; METHANOL; OXIDATION; PRODUCTION; SPECTROSCOPY; STEAM; TESTING; TRANSFORMATIONS; WATER GAS; national synchrotron light source

Citation Formats

Jacobs,G., Keogh, R., and Davis, B. Steam Reforming of Ethanol over Pt/ceria with Co-Fed Hydrogen. United States: N. p., 2007. Web. doi:10.1016/j.jcat.2006.10.018.
Jacobs,G., Keogh, R., & Davis, B. Steam Reforming of Ethanol over Pt/ceria with Co-Fed Hydrogen. United States. doi:10.1016/j.jcat.2006.10.018.
Jacobs,G., Keogh, R., and Davis, B. Mon . "Steam Reforming of Ethanol over Pt/ceria with Co-Fed Hydrogen". United States. doi:10.1016/j.jcat.2006.10.018.
@article{osti_959707,
title = {Steam Reforming of Ethanol over Pt/ceria with Co-Fed Hydrogen},
author = {Jacobs,G. and Keogh, R. and Davis, B.},
abstractNote = {Metal/ceria catalysts are receiving great interest for reactions involving steam conversion, including CO for low-temperature water-gas shift, and the conversion of chemical carriers of hydrogen, among them methanol, and ethanol. The mechanism by which ROH model reagents are activated on the surface of the Pt/partially reduced ceria catalyst was explored using a combination of reaction testing and infrared spectroscopy. In this particular investigation, the activation and turnover of ethanol were explored and compared with previous investigations of methanol steam reforming and low-temperature water-gas shift under H2-rich conditions, where the surface of ceria is in a partially reduced state. Under these conditions, activation of ethanol was found to proceed by dissociative adsorption at reduced defect sites on ceria (i.e., Ce surface atoms in the Ce3+ oxidation state), yielding an adsorbed type II ethoxy species and an adsorbed H species, the latter identified to be a type II bridging OH group. In the presence of steam, the ethoxy species rapidly undergoes molecular transformation to an adsorbed acetate intermediate by oxidative dehydrogenation. This is analogous to the conversion of type II methoxy species to formate observed in previous investigations of methanol steam reforming. In addition, although formate then decomposes in steam to CO2 and H2 during methanol steam reforming, in an analogous pathway for ethanol steam reforming, the acetate intermediate decomposes in steam to CO2 and CH4. Therefore, further H2 production requires energy-intensive activation of CH4, which is not required for methanol conversion over Pt/ceria.},
doi = {10.1016/j.jcat.2006.10.018},
journal = {Journal of Catalysis},
number = ,
volume = 245,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • No abstract prepared.
  • Overlayer Pt on Ni (Ni@Pt) or Co (Co@Pt) were synthesized and tested for H2 generation from APR of lactose. H2 chemisorption descriptor showed that Ni@Pt and Co@Pt overlayer catalysts had reduced H2 adsorption strength compared to a Pt only catalyst, which agree with computational predictions. The overlayer catalysts also demonstrated lower activity for ethylene hydrogenation than the Pt only catalyst, which likely resulted from decreased H2 binding strength decreasing the surface coverage of H2. XAS results showed that overlayer catalysts exhibited higher white line intensity than the Pt catalyst, which indicates a negative d-band shift for the Pt overlayer, furthermore » providing evidence for overlayer formation. Lactose APR studies showed that lactose can be used as feedstock to produce H2 and CO under desirable reaction conditions. The Pt active sites of Ni@Pt and Co@Pt overlayer catalysts showed significantly enhanced H2 production selectivity and activity when compared with that of a Pt only catalyst. The single deposition overlayer with the largest d-band shift showed the highest H2 activity. The results suggest that overlayer formation using directed deposition technique could modify the behavior of the surface metal and ultimately modify the APR activity.« less
  • The effects of ZnO facets on ethanol steam reforming (ESR) were investigated over Co/ZnO catalysts synthesized using ZnO with different fractions of (10-10) non-polar facet. Co supported on ZnO with a higher fraction of (10-10) non-polar facet shows higher C-C cleavage activity and higher selectivity to CO2 (lower selectivity to CO) compared with Co supported on ZnO with less (10-10) non-polar facet exposed. The improved ethanol steam reforming performances are attributed to the high fraction of metallic Co stabilized by the ZnO (10-10) non-polar facet, which enhanced C-C cleavage and water-gas-shift (WGS) activities.