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Evidence of Scrambling over Ruthenium-based Catalysts in Supercritical-water Gasification.
- Source :
- ChemCatChem; Aug2012, Vol. 4 Issue 8, p1185-1189, 5p
- Publication Year :
- 2012
-
Abstract
- Catalytic processes that employ Ru catalysts in supercritical water have been shown to be capable of converting organics, such as wood waste, into synthetic natural gas (CH<subscript>4</subscript>) with high efficiencies at relatively moderate temperatures of around 400 °C. However, the exact roles of the catalyst and the descriptors that would enable the search for other catalysts with high conversions have not been determined. In the current work, we use electronic structure calculations coupled with batch experiments to understand the interaction of methane (CH<subscript>4</subscript>) and water (H<subscript>2</subscript>O) with a common catalyst material, ruthenium, to understand the final steps of the methanation reaction. The calculations predict that when CH<subscript>4</subscript> and H<subscript>2</subscript>O react with the Ru surface, the species will undergo rapid scrambling; interchanging most of the hydrogens with the surface before escaping as CH<subscript>4</subscript> and H<subscript>2</subscript>O once again. We conducted experiments using CH<subscript>4</subscript> as a feedstock in supercritical D<subscript>2</subscript>O (deuterated water) in the presence of a commercially available carbon-supported Ru catalyst, and found this mechanism to be confirmed: nearly all reacted CH<subscript>4</subscript> was converted to the fully substituted CD<subscript>4</subscript> or the <superscript>3</superscript>/<subscript>4</subscript>-substituted CHD<subscript>3</subscript> isotopomers, with less significant production of the <superscript>1</superscript>/<subscript>4</subscript>- or <superscript>1</superscript>/<subscript>2</subscript>-substituted species CH<subscript>3</subscript>D and CH<subscript>2</subscript>D<subscript>2</subscript>. The experiment was repeated with an in-house impregnated RuO<subscript>2</subscript>-on-carbon catalyst, with similar results. Although other criteria such as the ability to cleave CC and CO bonds and resistance to poisoning will also prove important, this study suggests that a characteristic of an effective catalyst for supercritical water gasification to methane is its ability to promote rapid equilibria through scrambling mechanisms. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 18673880
- Volume :
- 4
- Issue :
- 8
- Database :
- Complementary Index
- Journal :
- ChemCatChem
- Publication Type :
- Academic Journal
- Accession number :
- 78142282
- Full Text :
- https://doi.org/10.1002/cctc.201100450