A Novel Concept for the Mechanism of Higher Oxygenate Formation from Synthesis Gas over MnO-Promoted Rhodium Catalysts

Treviño, Horacio; Hyeon, Taeghwan; Sachtler, Wolfgang M.H.

doi:10.1006/jcat.1997.1756

Cited by 29 publications

(24 citation statements)

References 31 publications

(21 reference statements)

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“…Underwood and Bell concluded that the high stability of acetate groups on Lapromoted-Rh/SiO 2 made them likely to be spectators, and only result from an accumulation of reaction products like ethanol or acetaldehyde [36]. Work on MnO-promotedRh/NaY catalysts by Treviño et al suggested an alternative mechanism in which acetate groups located at the metalpromoter interface are likely to be intermediates that are hydrogenated in the formation of higher oxygenates due to their proximity to H-atom spillover [37]. Since C 2?…”

Section: Co Hydrogenation On Ferh/tio 2 and Ferh/ Ceomentioning

confidence: 95%

Infrared Spectroscopy Investigation of Fe-Promoted Rh Catalysts Supported on Titania and Ceria for CO Hydrogenation

Magee¹,

Palomino²,

White³

2016

Catal Lett

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The nature of the promotional effect of Fe addition to Rh/TiO 2 and Rh/CeO 2 catalysts for CO hydrogenation was investigated using FT-IR spectroscopy in an ultrahigh vacuum compatible transmission IR cell. CO adsorption experiments on Rh and FeRh showed vibrational signatures characteristic of linear and bridge bound CO on Rh 0 as well as geminal-dicarbonyl species associated with Rh ? . Compared to TiO 2 , the CeO 2 -supported catalysts show increased dispersion, reflected by decreased particle size, and a lower signal for linear versus geminal-dicarbonyl bonded CO . The absorption frequencies for CO on Rh/CeO 2 are also redshifted relative to Rh/ TiO 2 , which results from a weaker Rh-CO interaction, likely due to the increased reducibility of the CeO 2 support. Upon addition of Fe, a new spectral feature is observed and attributed to CO bound to Rh in close contact with Fe, likely as a surface alloy. CO hydrogenation on (Fe)Rh catalysts on both supports was also studied. Compared to bare Rh, Fe containing catalysts promote formate and methoxy species on the surface at lower temperature (180°C), which suggests an enhancement in methanol selectivity by Fe addition. At higher temperatures (220°C), the spectral features appear similar, further confirming the role of Fe as a disrupter of large Rh 0 crystallites and regulator of CO dissociation and CH 4 formation. Graphical Abstract

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Section: Co Hydrogenation On Ferh/tio 2 and Ferh/ Ceomentioning

confidence: 95%

Infrared Spectroscopy Investigation of Fe-Promoted Rh Catalysts Supported on Titania and Ceria for CO Hydrogenation

Magee¹,

Palomino²,

White³

2016

Catal Lett

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“…Moreover, it can be anticipated that the situation will become more complicated when promoters such as Mn, Li, and Zr are added to the Rh/SiO 2 catalyst. Mn is the most extensively studied promoter and is considered to enhance the activity of the Rh-based catalysts through at least three ways: (1) promoting the adsorption and dissociation of CO (2,3,24), (2) accelerating the hydrogenation steps (25), and (3) creating new active sites for the CO insertion reaction (26). No matter which interpretation is correct, new active sites do form on the Rh-Mn/SiO 2 catalyst, which is different from that on the sample without promoters.…”

Section: Introductionmentioning

confidence: 99%

Different Mechanisms for the Formation of Acetaldehyde and Ethanol on the Rh–Based Catalysts

Wang

Luo

Liang

et al. 2000

Journal of Catalysis

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“…When increasing the Mn-to-Ce ratio, the individual reduction processes of free Rh 2 O 3 and free surface Ceria shift to higher temperatures and diminish in intensity until they become undistinguishable, being observable an only broad peak due to the combined reduction of manganese, cerium and rhodium species. A similar behavior have been described early for Rh doped manganese alumina [73] and Ce-Mn mixed oxides [72,[74][75]. The TPRs shown in However the analysis of HRTEM images (Fig.…”

Section: Specific Surface Area and Porosity Measurementsmentioning

confidence: 60%

“…Besides this, the reduction of rhodium and manganese species overlaps, which imply that rhodium reduction is in fact, shifted to higher temperatures with respect to isolated Rh 2 O 3 in RhCe 50 Al. It has been described that the reduction of manganese supported alumina samples are generally described to proceed by two step reduction profiles in the 320-350°C and 400-500°C temperature ranges, due to the 13 sequential MnO 2 /Mn 2 O 3 → Mn 3 O 4 → MnO reduction [72][73]. The deeper reduction from MnO to Mn(0) is not produced even in contact with rhodium [73].…”

Section: Specific Surface Area and Porosity Measurementsmentioning

confidence: 99%

Synthesis and characterization of Rh/MnO 2 -CeO 2 /Al 2 O 3 catalysts for CO-PrOx reaction

Laguna

López-Cartés

2017

Molecular Catalysis

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Rh/MnO 2 -CeO 2 /Al 2 O 3 catalysts with different manganese-to-ceria ratios have been synthesized, characterized and tested in CO-PrOx reaction. The physicochemical properties of the solids were studied by XRD, Raman spectroscopy, BET surface area, H 2 -TPR, TGA-DTG and TEM. The differences observed in the textural, structural and redox properties were related to the Mn-toceria ratio of the samples. The segregation of Mn species was observed at high Mn-to-Ce ratios.In opposite way, MnO 2 -CeO 2 solid solutions were obtained at low Mn to Ce ones. In this last case, the physicochemical properties of the solids were favored by the intimate Rh-Ce-Mn contact. The effect of the Mn-Ce presence on Rh catalysts which promotes the catalytic behavior towards selective CO oxidation was observed to be better at low temperatures. At higher temperatures, Mn species promote the Reverse Water Gas Shift reaction, whilst ceria promotes the H 2 oxidation in the whole range of working temperatures.

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A Novel Concept for the Mechanism of Higher Oxygenate Formation from Synthesis Gas over MnO-Promoted Rhodium Catalysts

Cited by 29 publications

References 31 publications

Infrared Spectroscopy Investigation of Fe-Promoted Rh Catalysts Supported on Titania and Ceria for CO Hydrogenation

Infrared Spectroscopy Investigation of Fe-Promoted Rh Catalysts Supported on Titania and Ceria for CO Hydrogenation

Different Mechanisms for the Formation of Acetaldehyde and Ethanol on the Rh–Based Catalysts

Synthesis and characterization of Rh/MnO 2 -CeO 2 /Al 2 O 3 catalysts for CO-PrOx reaction

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