Vibrational Spectra of Hydrocarbons Adsorbed on Metals

Sheppard, N.; Cruz, Carlos de la

doi:10.1016/s0360-0564(08)60629-x

Cited by 111 publications

(83 citation statements)

References 397 publications

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“…[17] The TPD spectra for pentene on both Pd(111) and the supported Pd nanoparticles show that the molecules desorb intact at temperatures below 280 K (Figure 2). In analogy to other alkene molecules previously studied, [9][10][11][12] we have assigned the desorption peaks at about 130 K to a condensed layer, at around 170 K to p-bonded and at approximately 260 K to s-bonded pentene molecules. Upon further heating, the chemisorbed molecules dehydrogenate in a stepwise manner, as shown by hydrogen evolution extending to 800 K (cf.…”

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confidence: 89%

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Hydrogenation on Metal Surfaces: Why are Nanoparticles More Active than Single Crystals?

Doyle¹,

Shaikhutdinov²,

Jackson³

et al. 2003

Angew Chem Int Ed

300

243

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Hydrogenation of unsaturated hydrocarbons occurs efficiently on noble-metal catalysts, such as platinum, rhodium, and palladium.[1] The reaction mechanism first proposed by Horiuti and Polanyi [2] in 1934 proceeds by a) hydrogen dissociation on the metal surface, b) alkene adsorption, c) subsequent hydrogen addition to alkene and, finally, d) desorption of the product (alkane). Real hydrogenation catalysts represent very complex systems for studying reaction mechanisms at the molecular level. Therefore, model systems with a reduced complexity have been invoked ranging from single crystals to metal particles deposited on oxide films. [3][4][5][6][7][8] The conclusions regarding reaction mechanism and structural sensitivity are often based upon experiments on single metal crystals.[3] In particular, hydrogenation of alkenes has been shown to be structure insensitive.Herein, we report results showing that alkene hydrogenation reaction under low-pressure conditions, which does not occur on Pd(111) single crystal, proceeds efficiently on palladium nanoparticles. We show that the formation of weakly bound "subsurface" hydrogen is a key factor for hydrogenation to occur efficiently. The subsurface hydrogen exists in both Pd systems. However, the nanoparticle dimensions are such that this hydrogen is accessible to the adsorbed alkene, and hydrogenation occurs. In contrast, for crystals, the hydrogen atoms diffuse so deep into the bulk that they are not accessible to an adsorbed alkene, and therefore hydrogenation does not occur.We have studied the surface chemistry of ethene and different pentene isomers on both Pd(111) single crystal and Pd particles deposited on a thin alumina film (Figure 1). The particles studied are approximately 5 nm in diameter and consist primarily (% 90 %) of (111) facets [8] (% 10 % are (100) facets). The experiments were performed in ultrahigh vacuum on clean and well-defined systems. Using the temperatureprogrammed desorption (TPD) technique, we have observed that a number of hydrocarbon transformations, such as dehydrogenation and H-D exchange, occur on both palla-

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confidence: 89%

“…[9,10] There is considerably less data on the interaction of higher hydrocarbons. [11][12][13][14] Madix and co-workers studied the adsorption of various alkenes and dienes on the clean and hydrogen (deuterium) precovered Pd(111) and Pd(100) surfaces by TPD.…”

mentioning

confidence: 99%

Hydrogenation on Metal Surfaces: Why are Nanoparticles More Active than Single Crystals?

Doyle¹,

Shaikhutdinov²,

Jackson³

et al. 2003

Angew Chem Int Ed

300

243

View full text Add to dashboard Cite

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“…Higher hydrocarbons can be dehydrogenated to form carbon deposits and, thus, deactivate the catalyst [44][45][46][47][48][49]. Di-σ-bonded acetylene and ethylene as well as vinylidene and ethylidyne species have been proposed as precursors for the acetylene oligomerisation.…”

Section: Increased Selectivity and Stability Of Pdga And Pd 3 Gamentioning

confidence: 99%

Palladium–gallium intermetallic compounds for the selective hydrogenation of acetylenePart II: Surface characterization and catalytic performance

Osswald

Kovnir

Armbrüster

et al. 2008

Journal of Catalysis

308

234

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The structurally well-defined intermetallic compounds PdGa and Pd 3 Ga 7 constitute suitable catalysts for the selective hydrogenation of acetylene. The surface properties of PdGa and Pd 3 Ga 7 were characterized by X-ray photoelectron spectroscopy, ion scattering spectroscopy and CO chemisorption. Catalytic activity, selectivity and long-term stability of PdGa and Pd 3 Ga 7 were investigated under different acetylene hydrogenation reaction conditions, in absence and in excess of ethylene, in temperature-programmed and isothermal long-term experiments. Chemical treatment with ammonia solution -performed to remove the gallium oxide layer introduced during the milling procedure from the surface of the intermetallic compounds -yielded a significant increase in activity. Compared to Pd/Al 2 O 3 and Pd 20 Ag 80 reference catalysts, PdGa and Pd 3 Ga 7 exhibited a similar activity per surface area, but higher selectivity and stability. The superior catalytic properties are attributed to the isolation of active Pd sites in the crystallographic structure of PdGa and Pd 3 Ga 7 according to the active-site isolation concept.

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“…1,2,3,4,5,6 and references therein. The most significant attention was paid to investigation of ethylene adsorption, 7,8,9,10,11,12,13,14,15,16,17 because it is the simplest alkene containing an isolated carbon-carbon double bond.…”

Section: Introductionmentioning

confidence: 99%

Adsorption of Ethylene on Neutral, Anionic, and Cationic Gold Clusters

Lyalin

Taketsugu

2010

J. Phys. Chem. C

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The adsorption of ethylene molecule on neutral, anionic and cationic gold clusters consisting of up to 10 atoms has been investigated using density-functional theory. It is demonstrated that C 2 H 4 can be adsorbed on small gold clusters in two different configurations, corresponding to the π-and di-σ -bonded species. Adsorption in the π-bonded mode dominates over the di-σ mode over all considered cluster sizes n, with the exception of the neutral C 2 H 4 −Au 5 system. A striking difference is found in the size-dependence of the adsorption energy of C 2 H 4 bonded to the neutral gold clusters in the π and di-σ configurations. The important role of the electronic shell effects in the di-σ mode of ethylene adsorption on neutral gold clusters is demonstrated. It is shown that the interaction of C 2 H 4 with small gold clusters strongly depends on their charge. The typical shift in the vibrational frequencies of C 2 H 4 adsorbed in the π-and the di-σ configurations gives a guidance to experimentally distinguish between the two modes of adsorption.

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Vibrational Spectra of Hydrocarbons Adsorbed on Metals

Cited by 111 publications

References 397 publications

Hydrogenation on Metal Surfaces: Why are Nanoparticles More Active than Single Crystals?

Hydrogenation on Metal Surfaces: Why are Nanoparticles More Active than Single Crystals?

Palladium–gallium intermetallic compounds for the selective hydrogenation of acetylenePart II: Surface characterization and catalytic performance

Adsorption of Ethylene on Neutral, Anionic, and Cationic Gold Clusters

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