Acetylene and Ethylene Hydrogenation on Alumina Supported Pd-Ag Model Catalysts

Khan, Neetha A.; Shaikhutdinov, Shamil K.; Freund, Hans‐Joachim

doi:10.1007/s10562-006-0041-y

Cited by 254 publications

(201 citation statements)

References 28 publications

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“…The hydrogenation pathway from acetylene to ethylene and further to ethane (reactions 1-3) does not require assemblies of active sites in contrast to the oligomerisation reaction (4) leading to higher hydrocarbons [15,42,43]. Higher hydrocarbons can be dehydrogenated to form carbon deposits and, thus, deactivate the catalyst [44][45][46][47][48][49].…”

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

312

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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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

312

234

View full text Add to dashboard Cite

show abstract

Section: Introductionmentioning

confidence: 99%

“…The hydride has higher mobility than the surface hydrogen and can hydrogenate surface adsorbates upon emerging to the surface [3]. Thus, the amount of bulk-dissolved hydrogen seriously affects the activity and selectivity of structure-sensitive hydrogenation reactions [4].Geometrical and electronic information of palladium nano-particles and of palladium hydride can be obtained from X-ray absorption spectroscopy (XAS) at the K and L edges [5,6]. At the Pd K edge XAS, the formation of palladium hydrides was generally deduced from an increased interatomic distance in EXAFS analysis [5].…”

mentioning

confidence: 99%

Distinguishing surface adsorbed hydrogen from bulk-dissolved hydrogen in supported Pd nanoparticles using in situ Pd L₃-edge XANES

Tew¹,

Miller²,

Bokhoven³

2009

J. Phys.: Conf. Ser.

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Abstract. In situ X-ray absorption spectroscopy at the Pd L 3 edge was applied to determine the particle size effect on the formation of palladium hydride and on surface hydrogen adsorption at room temperature. Pd L 3 edge XANES spectra allow direct detection of hydride formation via a characteristic spectral feature caused by the formation of a Pd-H anti-bonding state. This feature showed strong particle size dependence. The L 3 edge spectra were reproduced using full multiple scattering analysis and density of states calculations and the contributions of bulkdissolved and surface hydrogen to the XANES spectra could be distinguished. The ratio of hydrogen on the surface versus that in the bulk increased with decreasing particle size, and smaller particles dissolved less hydrogen. IntroductionThe particle size and support effects on catalytic performance are two well-known factors that affect the activity and selectivity of a reaction. For hydrogenation reaction catalyzed by palladium catalysts, the particle size effect can be critical because the formation of palladium hydride is particle size dependent. The amount of hydride that forms decreases with increasing dispersion of palladium in supported catalysts [1]. In contrast to the bulk metal, palladium particles smaller than 2.6 nm have been suggested to not form a hydride phase, even at high hydrogen pressures (P H2 =1 atm and T =298 K) [2]. The hydride has higher mobility than the surface hydrogen and can hydrogenate surface adsorbates upon emerging to the surface [3]. Thus, the amount of bulk-dissolved hydrogen seriously affects the activity and selectivity of structure-sensitive hydrogenation reactions [4].Geometrical and electronic information of palladium nano-particles and of palladium hydride can be obtained from X-ray absorption spectroscopy (XAS) at the K and L edges [5,6]. At the Pd K edge XAS, the formation of palladium hydrides was generally deduced from an increased interatomic distance in EXAFS analysis [5]. In contrast, Pd L 3 edge XANES allows the direct detection of palladium hydride via a signature peak at ~6 eV above the Fermi level, caused by the formation of a Pd-H anti-bonding state [6]. This ~6 eV peak can be theoretically simulated [7]. Distinction of bulkdissolved hydrogen from surface hydrogen in a palladium-catalyzed process remains challenging. It was recently reported that nuclear reaction analysis can distinguish surface adsorbed and bulkdissolved hydrogen on or in palladium nanocrystals on Al 2 O 3 NiAl (110) [8]. We performed XAS at the Pd L 3 edge to determine the electronic structural changes that occur in supported nano-sized

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“…Some Pd facets (e.g., 111) are not prone to carbon dissolution, so hydrogen dissolved in the nanoparticle leads to unselective full hydrogenation. Temperature-programmed desorption (TPD) studies have confirmed that sub-surface hydrogen species lead to non-selective hydrogenation, while surface ones selectively hydrogenate alkynes to alkenes [32]. In addition, according to DFT calculations, the carbide phase affects reaction energeticsonly surface hydrogen adsorption is exothermic, but bulk hydrogen dissolution is suppressed in the presence of Pd-C [33].…”

Section: Figurementioning

confidence: 99%

“…These catalysts produced no alkanes at all, but, instead, significant amounts (up to 70%) of undesired oligomers were formed. Ota et al [25] compared Pd [39,40]. The intermetallic catalyst showed a selectivity of 70% as opposed to 20% for Pd catalyst.…”

Section: Gas-phase Hydrogenationmentioning

confidence: 99%

The Reduction of Alkynes Over Pd-Based Catalyst Materials - A Pathway to Chemical Synthesis

Ao¹,

Sk²

2017

J Chem Eng Process Technol

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Many reactions, including selective hydrogenation of alkynes, take place on solid surfaces. These reactions are vital in many areas of industry including the manufacture of polymers and fine chemicals such as vitamins, fragrances, and drugs. The choice of a catalyst is a trade-off between activity, selectivity and costs. Palladium-based heterogeneous catalysts are traditionally used for these processes as they provide the activation of hydrogen at room temperatures and offers reasonable selectivity, but these catalysts have a number of practical drawbacks. This review discusses recent research work in the selective hydrogenation of alkynes on palladium-based catalysts, emphasises the mechanism and catalytic materials and important applications including alkyne removal from gasphase alkene precursors for polymer synthesis and liquid phase selective hydrogenation for the synthesis of fine chemicals. Langmuir-Hinshelwood reaction kinetic models, reaction intermediates, formation of carbonaceous layer, the nature of active sites and the effects of reversible and irreversible adsorbates over Pd surface are discussed as well as the factors affecting catalyst activity and selectivity and how these can be optimised in synthetic protocols for these reactions.

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Acetylene and Ethylene Hydrogenation on Alumina Supported Pd-Ag Model Catalysts

Cited by 254 publications

References 28 publications

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

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

Distinguishing surface adsorbed hydrogen from bulk-dissolved hydrogen in supported Pd nanoparticles using in situ Pd L₃-edge XANES

The Reduction of Alkynes Over Pd-Based Catalyst Materials - A Pathway to Chemical Synthesis

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Acetylene and Ethylene Hydrogenation on Alumina Supported Pd-Ag Model Catalysts

Cited by 254 publications

References 28 publications

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

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

Distinguishing surface adsorbed hydrogen from bulk-dissolved hydrogen in supported Pd nanoparticles using in situ Pd L3-edge XANES

The Reduction of Alkynes Over Pd-Based Catalyst Materials - A Pathway to Chemical Synthesis

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Distinguishing surface adsorbed hydrogen from bulk-dissolved hydrogen in supported Pd nanoparticles using in situ Pd L₃-edge XANES