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Kwak, Ja Hun
Molecular Catalysis lab
Research Interests
  • Heterogeneous catalysis, molecular catalysis, ASlumima, zeolites

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CO2 reduction on supported Ru/Al2O3 catalysts: Cluster size dependence of product selectivity

Cited 3 times inthomson ciCited 2 times inthomson ci
Title
CO2 reduction on supported Ru/Al2O3 catalysts: Cluster size dependence of product selectivity
Author
Kwak, JahunKovarik, LiborSzanyi, János
Keywords
CO/CH4 selectivity; CO2 reduction; reaction mechanism; Ru dispersion; Ru/Al2O3
Issue Date
201311
Publisher
AMER CHEMICAL SOC
Citation
ACS CATALYSIS, v.3, no.11, pp.2449 - 2455
Abstract
The catalytic performance of a series of Ru/Al2O3 catalysts with Ru content in the 0.1-5% range was examined in the reduction of CO2 with H2. At low Ru loadings (≤0.5%) where the active metal phase is highly dispersed (mostly atomically) on the alumina support, CO is formed with high selectivity. With increasing metal loading, the selectivity toward CH4 formation increases, while that for CO production decreases. In the 0.1% Ru/Al2O3 catalyst, Ru is mostly present in atomic dispersion, as scanning transmission electron microscopy (STEM) images obtained from the fresh sample prior to catalytic testing reveal. STEM images recorded from this same sample, following the temperature programmed reaction test, clearly show the agglomeration of small metal particles (and atoms) into 3D clusters. The clustering of the highly dispersed metal phase is responsible for the observed dramatic selectivity change during elevated temperature tests: dramatic decrease in CO and large increase in CH4 selectivity. Apparent activation energies, estimated from the slopes of Arrhenius plots, of 82 and 62 kJ/mol for CO and CH 4 formation were determined, respectively, regardless of Ru loading. These results suggest that the formation of CO and CH4 follow different reaction pathways or proceed on active centers of a different nature. Reactions with CO2/H2 and CO/H2 mixtures (under otherwise identical reaction conditions) reveal that the onset temperature of CO2 reduction is about 150 C lower than of CO reduction.
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DOI
http://dx.doi.org/10.1021/cs400381f
ISSN
2155-5435
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