ChemInform Abstract: COMMENT ON MECHANISM OF ETHANE HYDROGENOLYSIS

Frennet, Alfred; Degols, L.; Liénard, Georges; Crucq, A.

doi:10.1002/chin.197452174

Cited by 8 publications

(15 citation statements)

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“…Use was made of the kinetic analysis proposed in 1954 by Cimino et al [32] for iron catalysts, and the rate determining step was assumed to be identical on all metals where the experimental order with respect to hydrogen is negative. In 1974, Frennet et al [33] suggested an alternative to this already well accepted interpretation.…”

Section: Exchange Reactions Where C-c Bond Ruptures Are Involved In Amentioning

confidence: 95%

“…[33], interpretation of ethane hydrogenolysis results considering that the carboncarbon bond breaking is rate determining on almost all studied metallic catalysts can be criticized. They suggested that the hydrogenating desorption of adsorbed C 1 fragments was rate controlling on several metals such as W, Ru and Rh.…”

Section: Exchange Reactions Where C-c Bond Ruptures Are Involved In Amentioning

confidence: 97%

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Site requirements in the kinetics of alkane transformations catalysed by metals

Garin

2006

Top Catal

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Hydrogen pressure is often found to cause an inhibiting effect on the kinetics of alkane reactions on metal surfaces. The most common interpretation of such results is focussed on the degree of dehydrogenation of the active surface intermediate following a dissociative mechanism. A series of arguments will be given in favour of an associative mechanism in which the hydrocarbon reacts with an adsorbed hydrogen atom. In this mechanism, the adsorption site or ''landing site'' is composed of a chemisorbed hydrogen atom associated with an ensemble of ''Z'' potential sites. These sites are associated with the hydrogen chemisorption site. The validity of H 2 adsorption to determine the metallic dispersion will be also discussed.

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Section: Exchange Reactions Where C-c Bond Ruptures Are Involved In Amentioning

confidence: 95%

Section: Exchange Reactions Where C-c Bond Ruptures Are Involved In Amentioning

confidence: 97%

Site requirements in the kinetics of alkane transformations catalysed by metals

Garin

2006

Top Catal

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“…A structure-sensitive reaction like hydrogenolysis requires a larger ensemble of platinum atoms than isomerization (55,56). Because of the high surface coverage of platinum by sulfur in both Pt(S)/H-LTL and Pt(S)/K-LTL, it is likely that the remaining, active platinum atoms are more isolated than in the sulfur-free catalysts.…”

Section: Catalytic Propertiesmentioning

confidence: 99%

The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL

Miller¹,

Koningsberger

1996

Journal of Catalysis

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The reactivity, structure, and sulfur tolerance is compared for platinum supported on acidic and alkaline LTL zeolite. In the absence of sulfur, EXAFS spectroscopy indicates that small metallic platinum particles of approximately 6 to 14 atoms/cluster are present. The TOF for neopentane hydrogenolysis and isomerization is ca 100 times higher on the acidic LTL due to the metalsupport interaction. Saturation of the platinum by H 2 S, results in the formation of surface Pt-S bonds with a bond length of 2.33Å. Comparison of the EXAFS results of the sulfur poisoned catalysts, indicates that the S to Pt ratio is lower for platinum on the acidic zeolite. Catalytically, the initial activity (per gram) of both catalysts is greatly reduced after sulfur poisoning due to the loss of exposed platinum, however, the initial neopentane TOFs are nearly unchanged. Because of its higher TOF, the catalytic activity (per gram) of sulfur poisoned, acidic Pt/LTL is comparable to that of nonsulfur poisoned alkaline Pt/LTL. In both sulfur poisoned catalysts the neopentane isomerization selectivity increases compared to the sulfur free catalyst. Although the initial TOFs of the nonsulfur poisoned and sulfur poisoned catalysts are the same, there is a rapid loss in activity due to coke formation in the sulfur poisoned, alkaline LTL, while rate of deactivation by coke in the sulfided, acidic LTL is much lower. The increased sulfur tolerance of acidic supported noble metal catalysts appears to result primarily from the higher intrinsic TOF. In addition, because of its resistance to coke deactivation, the acidic supported sulfur tolerant catalyst is able to maintain stable catalytic activity.

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“…Thus, one chemisorbed hydrogen atom can affect the surface properties of the catalyst over a relatively large area, making it energetically favourable for further hydrogen atoms t o stick t o the surface. Metal-hydrogen active sites, consisting of several surface atoms, have been proposed as " h d i n g sites" by Frennet et al [21]. We interpret these landing sites 2,s the delocalization of the hydrogen-metal bond in our exciton-like state extending to several atoms.…”

Section: Surface Catalystsmentioning

confidence: 94%

Subsurface hydrogen exciton‐like states in solid catalysts

Szász

Fabian

1989

Physica Status Solidi (b)

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Subsurface hydrogen electronic levels are discussed in terms of exciton-like states generated by vacancy-hydrogen interaction in transition-metal catalysts. Trapped hydrogen atoms have binding energies that depend exponentially on the density of electronic states a t the Fermi level.Die Elektronenniveaus von Sub-Oberflkichenwasserstoff werden mit Exziton-ahnlichen Zustanden diskutiert, die durch Leerstellen-Wasserstoff-Wechselwirkung in tfbergangsmetallkatalysatoren gebildet werden. Die angehafteten Wasserstoffatome haben Bindungsenergien, die exponentiell von der Dichte der Elektronenzustande am Ferminiveau abhgngen.

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ChemInform Abstract: COMMENT ON MECHANISM OF ETHANE HYDROGENOLYSIS

Cited by 8 publications

References 1 publication

Site requirements in the kinetics of alkane transformations catalysed by metals

Site requirements in the kinetics of alkane transformations catalysed by metals

The Origin of Sulfur Tolerance in Supported Platinum Catalysts: The Relationship between Structural and Catalytic Properties in Acidic and Alkaline Pt/LTL

Subsurface hydrogen exciton‐like states in solid catalysts

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