Reactivity of adsorbed CO toward C2H4, H2, and NO on the surface of supported rhodium catalysts

Chuang, Steven S. C.; Krishnamurthy, R.; Tan, Eric C. D.

doi:10.1016/0927-7757(95)03312-7

Cited by 16 publications

(22 citation statements)

References 28 publications

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“…Combined, these pieces of evidence suggest that the SiO 2 support plays an important role in the CO insertion reaction to form propionaldehyde. This idea is consistent with observations of previous studies (17) indicating hydrogen present on the SiO 2 support may play a role in hydrogenating C 3 H 5 O acyl groups present on the Rh particle, a reaction step which has been thought to be the rate limiting step in propionaldehyde formation, under certain reaction conditions (14).…”

Section: Discussionsupporting

confidence: 81%

“…Insightful studies by Chuang and coworkers (14)(15)(16)(17) and others (18,19) have investigated C 2 H 4 hydroformylation on oxide supported Rh particles to gain information on the reaction mechanism and reactivity of various adsorbed CO surface species. Motivated by the desire to understand oxygenate reaction pathways in CO hydrogenation catalysis, investigators have utilized C 2 H 4 hydroformylation as a probe reaction to understand CO insertion into adsorbed surface ethyl species (R-C 2 H 5 ), without the complications of the CO dissociation step.…”

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confidence: 99%

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Planar oxide supported rhodium nanoparticles as model catalysts

McClure

Lundwall²,

Goodman³

2010

Proc. Natl. Acad. Sci. U.S.A.

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C 2 H 4 ∕CO∕H 2 reaction is investigated on Rh∕SiO 2 model catalyst surfaces. Kinetic reactivity and infrared spectroscopic measurements are investigated as a function of Rh particle size under near atmospheric reaction conditions. Results show that propionaldehyde turnover frequency (TOF) (CO insertion pathway) exhibits a maximum activity near hd p i ¼ 2.5 nm. Polarization modulation infrared reflection absorption spectroscopy under CO and reaction (C 2 H 4 ∕CO∕H 2 ) conditions indicate the presence of Rh carbonyl species (RhðCOÞ 2 , Rh(CO)H) on small Rh particles, whereas larger particles appear resistant to dispersion and carbonyl formation. Combined these observations suggest the observed particle size dependence for propionaldehyde production via CO insertion is driven by two factors: (i) an increase in propionaldehyde formation on undercoordinated Rh sites and (ii) creation of carbonyl hydride species (Rh(CO)H)) on smaller Rh particles, whose presence correlates with the lower activity for propionaldehyde formation for hd p i < 2.5 nm.Ethylene hydroformylation | CO insertion | polarization modulation infrared reflection absorption spectroscopy | Rh/SiO2 A complicating effect of understanding the structure-activity relationships of heterogeneous catalytic reactions at ambient pressures (near 1 atm or above) is the known ability of reactant gas environments to alter the morphology, particle dispersion, and even the types of adsorbates present on certain supported nanoparticle (NP) systems (1-4). For example, elevated pressure CO ambients have been shown to oxidatively disrupt and disperse Rh nanoparticles, creating highly dispersed gem-dicarbonyl species RhðCOÞ 2 on oxide supports (1-3, 5-8). Under elevated pressure (CO∕H 2 ) and (CO 2 ∕H 2 ) hydrogenation reaction conditions, Rh(CO)H carbonyl hydride species can also be formed (3, 9-12). The creation and stability of such carbonyl species (RhðCOÞ 2 , Rh(CO)H) can depend on particle size, gas pressure, and surface temperature. The cumulative effect of such factors could potentially have an important effect on the overall catalytic properties of the supported Rh NP surface, especially for catalytic reactions involving surface bound CO. Developing an understanding of how such factors can affect the catalytic properties of supported Rh NPs is important from a fundamental surface chemistry perspective. Unraveling these details will require the ability to conduct spectroscopic and kinetic investigations of an informative probe reaction (i) under near atmospheric reaction conditions and (ii) on supported Rh nanoparticles surfaces with well defined initial particle size distributions.CO insertion into adsorbed alkyl groups (R-C x H y ) to form oxygenates (e.g., alcohols, aldehydes) is an important reaction step in many heterogeneous catalytic reactions. For example, C 2 H 4 hydroformylation (C 2 H 4 þ CO þ H 2 ) is a well known reaction for the synthesis of aldehydes via the CO insertion reaction (13). Insightful studies by Chuang and coworkers (14-17) and others (...

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Section: Discussionsupporting

confidence: 81%

mentioning

confidence: 99%

Planar oxide supported rhodium nanoparticles as model catalysts

McClure

Lundwall²,

Goodman³

2010

Proc. Natl. Acad. Sci. U.S.A.

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“…It has been proposed that during heterogeneous C 2 H 4 hydroformylation on Rh surfaces, C 2 H 4 is hydrogenated to form a C 2 H 5 surface species, which then undergoes CO insertion to form a surface acyl species, followed by hydrogenation to form propionaldehyde [89,90]. As such, the C 2 H 4 hydroformylation reaction has been studied by several groups to investigate and understand the CO insertion reaction step under CO hydrogenation (CO/H 2 ) conditions on supported Rh surfaces, without the complications of the CO dissociation step [89][90][91][92][93][94].…”

Section: Characterization Of Surface Sites Under Uhvmentioning

confidence: 99%

Simulating the Complexities of Heterogeneous Catalysis with Model Systems: Case studies of SiO2 Supported Pt-Group Metals

McClure

Goodman

2011

Top Catal

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Model catalyst surfaces, consisting of vapordeposited metal nanoparticles supported on a planar oxide support, can help to link reactivity studies on well-defined single crystal surfaces with those conducted on high-surface area supported catalysts. When coupled with near atmospheric pressure kinetic and spectroscopic techniques, these well-defined model catalyst surfaces represent a useful approach to combine the power of surface analytical techniques with reactivity studies under relevant reaction conditions. Here, we review recent results of our investigations characterizing the physical and catalytic properties of Pt/SiO 2 and Rh/SiO 2 model catalyst surfaces. As will be discussed, the model catalyst approach can help simulate the complexities of catalytic reactions on supported catalysts, helping to provide insights into the role of particle size, particle morphology, and surface adsorbates in dictating the observed structure-sensitivity (activity and selectivity) during reactions at near atmospheric pressures.

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“…Indeed, a better view of the phenomena occurring during the reaction process should be provided by the knowledge of the adsorbed compounds, while the catalyst is working [33][34][35], since the surface of a working catalyst is usually strongly different from that of the fresh catalyst [36]. Therefore, we used the in situ DRIFTS technique, which allows studying the evolution of the adsorbed species, intermediates and products inside the cell, which acts as a reactor.…”

Section: Introductionmentioning

confidence: 99%