Ethylene hydrogenation on Ni(1 0 0) surface

Egawa, Chikashi; Osawa, Shinji; Oki, Shoichi

doi:10.1016/s0039-6028(03)00265-6

Cited by 7 publications

(3 citation statements)

References 26 publications

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“…Surface-chemisorbed H thus clearly enhances the catalyst’s selectivity for the hydrogenation reaction. A similar suppression of olefin decomposition by coadsorbed hydrogen has been reported on Ni surfaces. , Besides weakening the olefin–Pd interaction, as proposed in section , it is conceivable that such a reduction of the butene decomposition results from a site blocking effect . Decomposition of C 4 H 8 is initiated by dehydrogenation to butadiene, which requires two empty sites to deposit the emitted H atoms.…”

Section: Discussionsupporting

confidence: 73%

Mechanism of Olefin Hydrogenation Catalysis Driven by Palladium-Dissolved Hydrogen

et al. 2016

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The Pd-catalyzed hydrogenation of CC double bonds is one of the most important synthetic routes in organic chemistry. This catalytic surface reaction is known to require hydrogen in the interior of the Pd catalyst, but the mechanistic role of the Pd-dissolved H has remained elusive. To shed new light into this fundamental problem, we visualized the H distribution near a Pd single crystal surface charged with absorbed hydrogen during a typical catalytic conversion of butene (C4H8) to butane (C4H10), using H depth profiling via nuclear reaction analysis. This has revealed that the catalytic butene hydrogenation (1) occurs between 160 and 250 K on a H-saturated Pd surface, (2) is triggered by the emergence of Pd bulk-dissolved hydrogen onto this surface, but (3) does not necessarily require large stationary H concentrations in subsurface sites. Even deeply bulk-absorbed hydrogen proves to be reactive, suggesting that Pd-dissolved hydrogen chiefly acts by directly providing reactive H species to the surface after bulk diffusion rather than by indirectly activating surface H through modifying the surface electronic structure. The chemisorbed surface hydrogen is found to promote hydrogenation reactivity by weakening the butene-Pd interaction and by significantly reducing the decomposition of the olefin.

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Section: Discussionsupporting

confidence: 73%

Mechanism of Olefin Hydrogenation Catalysis Driven by Palladium-Dissolved Hydrogen

et al. 2016

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“…It was obvious that as the temperature increased, the rate of the reaction of ethylene hydrogenation with the formation of ethane sharply increased with a significant excess of hydrogen. The metallic surface of nickel was catalytically active in both reactions of the 1,2-DCE hydrodechlorination and the ethylene hydrogenation to form ethane [44,45]. As follows from the presented data, the value of the equilibrium constant (K p ) exceeds 1 at temperatures above 450 • C. This means that nickel chloride should undergo a reduction with the formation of metal at such temperatures that consequently stabilizes the operation of the catalyst under the conditions of a lack of hydrogen.…”

Section: (Hydro)dechlorination Of C2h4cl2mentioning

confidence: 60%

“…It was obvious that as the temperature increased, the rate of the reaction of ethylene hydrogenation with the formation of ethane sharply increased with a significant excess of hydrogen. The metallic surface of nickel was catalytically active in both reactions of the 1,2-DCE hydrodechlorination and the ethylene hydrogenation to form ethane [44,45]. It should be noted that with an increase in the reaction temperature, the selectivity for methane rose noticeably, from 1% at 350 °C to 86% at 650 °C (Figure 3).…”

Section: (Hydro)dechlorination Of C 2 H 4 Clmentioning

confidence: 98%

Two Scenarios of Dechlorination of the Chlorinated Hydrocarbons over Nickel-Alumina Catalyst

et al. 2020

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Dechlorination processes attract great interest since they are involved in environmental protection and waste disposal technologies. In this paper, the process of gas-phase dechlorination of 1,2-dichloroethane, chloroform, and chlorobenzene over Ni/Al2O3 catalyst (90 wt% Ni) prepared by a coprecipitation technique was investigated. The reduction behavior of the oxide precursor NiO/Al2O3 was studied by thermogravimetric analysis in a hydrogen medium. A thermodynamic assessment of the conditions under which metallic nickel undergoes deactivation due to the formation of nickel chloride was performed. The dechlorination of chlorinated substrates was studied using a gravimetric flow-through system equipped with McBain balances in a wide range of temperatures (350–650 °C) and hydrogen concentrations (0–98 vol%). The impact of these parameters on selectivity towards the products of hydrodechlorination (C2H4, C2H6, and C6H6) and catalytic pyrolysis (carbon nanomaterial and CH4) was explored. The relationship between the mechanisms of the catalytic hydrodechlorination and the carbide cycle was discussed, and the specific reaction conditions for the implementation of both scenarios were revealed. According to the electron microscopy data, the carbonaceous products deposited on nickel particles during catalytic pyrolysis are represented by nanofibers with a disordered structure formed due to the peculiarity of the process including the side carbon methanation reaction.

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