A Comparative Study of CO and CO2Hydrogenation over Rh/SiO2

Fisher, Ian A.; Bell, Alexis T.

doi:10.1006/jcat.1996.0259

Cited by 166 publications

(119 citation statements)

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“…On the larger Ru NPs, the selectivity is proposed to be controlled by a site blocking mechanism, where the active Ru surface is essentially covered by strongly adsorbed CO ad , preventing the dissociative adsorption of CO 2 , which corresponds to the previous ideas for the origin of the selectivity in the selective CO methanation over Ru catalysts [17,18]. As the CO concentration and hence the CO ad coverage decreases, CO 2 can adsorb on the resulting empty sites and dissociate to CO ad , which acts as intermediate for the CO 2 methanation [27, 49,50]. Therefore, the selectivity for CO methanation decreases with decreasing CO concentration in the feed gas.…”

Section: Kinetic Measurementssupporting

confidence: 66%

Influence of the catalyst loading on the activity and the CO selectivity of supported Ru catalysts in the selective methanation of CO in CO2 containing feed gases

Eckle

Augustin

Anfang³

et al. 2012

Catalysis Today

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We have investigated the methanation of CO and CO 2 over Ru/zeolite catalysts with different Ru loading in semi-realistic reformate gases by in situ X-ray absorption spectroscopy (XAS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and kinetic measurements. Increasing the Ru loading causes an increase of the mean particle size from 0.9 nm (2.2 wt.% Ru) to 1.9 nm (5.6 wt.% Ru). At the same time, also the activity for CO methanation increases, while the selectivity for CO methanation, which is constant at 100% for reformate gases with 0.6% CO, decreases at low CO contents. The latter findings are interpreted in terms of a change in the physical effects governing the selectivity for CO methanation with increasing Ru particle size, from an inherently low activity for CO 2 dissociation and subsequent CO ad methanation on very small Ru nanoparticles to a site blocking mechanism on larger Ru nanoparticles. In the latter mechanism, CO 2 methanation is hindered by a reaction inhibiting adlayer of CO at higher CO ad coverages, i.e., at not too low CO concentrations, but facile in the absence of a CO adlayer, at lower CO concentrations in the reaction gas mixture.

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Section: Kinetic Measurementssupporting

confidence: 66%

Influence of the catalyst loading on the activity and the CO selectivity of supported Ru catalysts in the selective methanation of CO in CO2 containing feed gases

Eckle

Augustin

Anfang³

et al. 2012

Catalysis Today

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“…After the adsorption of formaldehyde on Rh/ TiO 2 an absorption band was observed at 1727 cm )1 , which was assigned as m(CO) in HCHO (a) [36]. Fisher and Bell found that adsorbed CO and CO 2 could be hydrogenated to surface formaldehyde on Rh/SiO 2 [2], which absorbs at 1710 cm )1 . This species was observed rarely during the hydrogenation of CO or CO 2 because it decomposes under the reaction conditions, as was found on Rh/Al 2 O 3 [37].…”

Section: Surface Interaction Of H 2 and Co 2 On Rh/tiomentioning

confidence: 97%

“…It was demonstrated that the turnover rates for the CH 4 formation on alumina-supported noble metals decreased in the order Ru > Rh > Pt $ Ir $ Pd [1]. On supported Rh catalysts the rate of CO 2 hydrogenation to methane was higher and the activation energy for methane formation was lower than those of CO hydrogenation [1][2][3]. On Rh foil the hydrogenation of CO 2 produces exclusively methane with lower activation energy than for the CO + H 2 reaction [4].…”

Section: Introductionmentioning

confidence: 96%

Effect of H2S on the hydrogenation of carbon dioxide over supported Rh catalysts

et al. 2007

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The hydrogenation of CO 2 was studied on supported noble metal catalysts in the presence of H 2 S. In the reaction gas mixture containing 22 ppm H 2 S the reaction rate increased on TiO 2 and on CeO 2 supported metals (Ru, Rh, Pd), but on all other supported catalysts or when the H 2 S content was higher (116 ppm) the reaction was poisoned. FTIR measurements revealed that in the surface interaction of H 2 + CO 2 on Rh/TiO 2 Rh carbonyl hydride, surface formate, carbonates and surface formyl were formed. On the H 2 S pretreated catalyst surface formyl species were missing. TPD measurements showed that adsorbed H 2 S desorbed as SO 2 , both from TiO 2 -supported metals and from the support. IR, XP spectroscopy and TPD measurements demonstrated that the metal became apparently more positive when the catalysts were treated with H 2 S and when the sulfur was built into the support. The promotion effect of H 2 S was explained by the formation of new centers at the metal/support interface.

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“…39 The second mechanism involves the direct dissociation of CO 2 to CO(ads) and O(ads) on the metal surface, with CO(ads) being subsequently hydrogenated to CH 4 . 33,36,38,40 In our case the direct dissociation of CO 2 seems to be evidenced. We have confirmed experimentally that the first step in the mechanism by which the reaction occurs is dissociative adsorption of CO 2 on the surface of the catalyst.…”

Section: Ftir Resultsmentioning

confidence: 73%

Structure–function relationship during CO₂ methanation over Rh/Al₂O₃ and Rh/SiO₂ catalysts under atmospheric pressure conditions

Martin

Hemmingsson

Wang

et al. 2018

Catal. Sci. Technol.

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The effect of the support material and chemical state of Rh in Rh/A 2 O 3 and Rh/SiO 2 model catalysts during CO 2 hydrogenation were studied by a combined array of in situ characterisation techniques including diffuse reflectance infrared Fourier transform spectroscopy, energy-dispersive X-ray absorption spectroscopy and high-energy X-ray diffraction at 250-350°C and atmospheric pressure. CO 2 methanation proceeds via intermediate formation of adsorbed CO species on metallic Rh, likely followed by their hydrogenation to methane. The linearly-bonded CO species is suggested to be a more active precursor in the hydrogenation compared to the bridge-bonded species, which seems to be related to particle size effects: for larger particles mainly the formation of inactive bridge-bonded CO species takes place. Further, analysis of the chemical state of Rh under the reaction conditions reveal a minor formation of RhO x from dissociation of CO 2 , which is a consequence of the increased activity observed over the Rh/Al 2 O 3 catalyst.

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A Comparative Study of CO and CO2Hydrogenation over Rh/SiO2

Cited by 166 publications

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Influence of the catalyst loading on the activity and the CO selectivity of supported Ru catalysts in the selective methanation of CO in CO2 containing feed gases

Influence of the catalyst loading on the activity and the CO selectivity of supported Ru catalysts in the selective methanation of CO in CO2 containing feed gases

Effect of H2S on the hydrogenation of carbon dioxide over supported Rh catalysts

Structure–function relationship during CO₂ methanation over Rh/Al₂O₃ and Rh/SiO₂ catalysts under atmospheric pressure conditions

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A Comparative Study of CO and CO2Hydrogenation over Rh/SiO2

Cited by 166 publications

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Influence of the catalyst loading on the activity and the CO selectivity of supported Ru catalysts in the selective methanation of CO in CO2 containing feed gases

Influence of the catalyst loading on the activity and the CO selectivity of supported Ru catalysts in the selective methanation of CO in CO2 containing feed gases

Effect of H2S on the hydrogenation of carbon dioxide over supported Rh catalysts

Structure–function relationship during CO2 methanation over Rh/Al2O3 and Rh/SiO2 catalysts under atmospheric pressure conditions

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Structure–function relationship during CO₂ methanation over Rh/Al₂O₃ and Rh/SiO₂ catalysts under atmospheric pressure conditions