Chemisorption of methane

The species first to be expected from the chemisorption of methane on a metal surface is a surface-attached methyl group. If, as seems probable, the threefold axis of the CH3 group is perpendicular to the metal surface (C3v overall symmetry of the surface complex), the expected completely symmetrical modes are eCH3 s, <5CH3 s, and eCM (M = metal). According... 

The dissociative adsorption of alkanes on Ir(l 1 0) surface was investigated in a series of studies performed by the Madix group [13, 32, 33]. A study performed by Hamza et al. [32] probed the dynamics of the dissociative chemisorption of methane, ethane, propane, and n-butane on the Ir(l 1 0)-(l x 2) surface. These investigations were complemented by a later study of propane dissociation on the Ir(l 1 0)-(l x 2) surface by Soulen and Madix [13]. Shown in Figs 6 and 7 are plots of S0 vs. E obtained for propane at various surface temperatures [32] and a plot of experimental and theoretical values of S0 for propane (at an incident translational energy of 50kcal/mol) on Ir(l 1 0)-(l x 2) as a function of surface temperature [13]. 

A quantum tunneling mechanism was proposed by Yerhoef et al. to describe these trends, and an attempt was made to develop a tunneling model to predict the chemisorption of methane and ethane over the entire range of normal incident energies studied. This was accomplished by modeling the... 

This model generalizes an early proposal made by Frennet and Lienard (55-57) for methane adsorption. These authors studied the surface composition of carbon and hydrogen atoms during the chemisorption of methane on metal films and found that the results were best explained by assuming that methane was adsorbed according to a bimolecular reaction between methane and adsorbed hydrogen ... 

The results of these experiments form a picture of the dominant features of the methane-nickel surface interaction potential that control the mechanism of the dissociation of methane. We will find that there is indeed a barrier to the dissociative chemisorption of methane and that translational and vibrational energy of the incident methane molecule are effective in overcoming 1t. The identification of this barrier along the dissociative reaction coordinate allows the establishment of a link between low pressure, ultrahigh vacuum surface science and high pressure catalysis (ref. 3). 

The present observation supports the conclusion that the barrier to dissociative chemisorption of methane arises largely from the energy required to deform the molecule so that the attractive interaction between the carbon atom and the Ni surface becomes sufficiently large to result in Ni-C bond formation. 

Jackson B, Nave S (2011) The dissociative chemisorption of methane on Ni(lOO) Reaction path description of mode-selective chemistry. J Chem Phys 135 114701... 

The chemisorption of methane on nickel involves the breakage of a C-H bond (Ceyer et al., 1987) and this requires that the molecule has sufficient energy to overcome a barrier of about 52 kJ/mol (Beebe et al., 1987 and Chorkendorff et al., 1990) and that it hits a free nickel site with free neighbor sites (Alstrup et al., 1990). The rate of adsorption is an order of magnitude higher on the open (110) nickel surface plane than on the dense (111) surface plane. The activated chemisorption of methane is the rate determining step in steam reforming (Rostrup-Nielsen,... 

The chemisorption of methane on a metal surface requires that one of the C-H bonds of CH4 is broken... 

RW Verhoeff, D Kelly, CB Mullins, WH Weinberg. The direct dissociative chemisorption of methane and ethane on Ir(llO) isotope effects and vibrationally assisted chemisorption. Proceedings of 8th International Conference on Solid Surfaces, The Hague, 1992. 

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