Nickel single crystals, hydrogenation

Christmann K., Schober O., ErtI G., and Neuman M., Adsorption of hydrogen on nickel single crystal surfrces, J. Phys. Chem., 60 (1974) pp.4528-4540. 

Thus, for both reactions a catalytic specificity of the crystal planes was found. Cunningham and Gwathmey (36) studying ethylene hydrogenation on different planes of a nickel single crystal, also arrived at the conclusion that planes cut in different crystallographic directions exhibit different activities. 

K. Christman, O. Schober, G. Ertl and M. Neumann, Adsorption of hydrogen on nickel single crystal surfaces, J. Chem. Phys., 1974, 60, 4528. 

Goodman D W, Kelley R D, Madey T E and Yates J T Jr 1980 Kinetics of the hydrogenation of CO over a single crystal nickel catalyst J. Catal. 63 226... 

It is obvious that one can use the basic ideas concerning the effect of alkali promoters on hydrogen and CO chemisorption (section 2.5.1) to explain their effect on the catalytic activity and selectivity of the CO hydrogenation reaction. For typical methanation catalysts, such as Ni, where the selectivity to CH4 can be as high as 95% or higher (at 500 to 550 K), the modification of the catalyst by alkali metals increases the rate of heavier hydrocarbon production and decreases the rate of methane formation.128 Promotion in this way makes the alkali promoted nickel surface to behave like an unpromoted iron surface for this catalytic action. The same behavior has been observed in model studies of the methanation reaction on Ni single crystals.129... 

The above described experiments over atomically clean single crystal catalysts have been extended to studies of the kinetics of various catalytic reactions over chemically modified catalysts. Examples are recent studies Into the nature of poisoning by sulfur of the catalytic activity of nickel, ruthenium, and rhodium toward methana-tlon of CO (11,12) and CO2 (15). ethane (12) and cyclopropane (20) hydrogenolysls, and ethylene hydrogenation (21). 

Three slices of single-crystal nickel, 10 mm. in diameter and 2 mm. in thickness, respectively, parallel to the (110), (100), and (111) planes were prepared by S. Kaya and denoted, respectively, a, b, and c. They were studied by Matsuda (unpublished) about ten years ago with particular reference to the rates of recombination of hydrogen atoms and to the activation energies for the chemisorption of hydrogen. The latter had been theoretically estimated by Horiuti et ah, as mentioned elsewhere, as functions of the different arrangement of the nickel atoms on the three main crystal planes mentioned above. The relative rates of recombination on the electropolished surfaces of these specimens observed by Matsuda at room temperature followed the qualitative rule ... 

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