Alloys hydrocarbon reaction model

D. A Speculative Model of Hydrocarbon Reactions on Metals and Alloys... 

Hj Dj exchange on, 26 39-43 heteropolyanion-supported, 41 230-231 high MiUer index, 26 12-15,35,36 -H-USY zeoUte, 39 186-187 hydrocarbons adsorption, 38 229-230 reactions of cyclopropane, cyclohexane, and n-heptane, 26 51-53 structural effects, 30 25-26 hydrogen adsorption on, 23 15 hydrogenation, 30 281-282 olefins, in ethanol, 30 352-353 in hydrogenation reaction, 33 101 -iron alloys, 26 75 isomerization, 30 2-3 isotope, NMR properties, 33 213,274 kinetic oscillations, 37 220-228 ball models of densely packed surfaces, 37 221-222... 

Early higher pressure reaction smdies over Pt-Sn model catalysts by Paffett [62,63] and Somorjai [64, 65] and their coworkers revealed new insights into hydrocarbon catalysis in such systems. Szanyi et al. [62] showed that n-butane hydrogenolysis under moderate pressures (1-200 Torr H3/butane=20) and temperatures (up to 650 K) could be carried out without disruption of the ordered Sn/Pt(lll) surface alloys. This established that such catalytic reactions could be studied while maintaining the composition and geometric structure of these alloys under reducing reaction conditions (but not catalytic oxidation due to the aggressive interaction of O3 with Sn). These ordered Sn/Pt surfaces are qualitatively different from those in many studies of promoters and poisons, or disordered alloys, e.g., Au-Pt, in which the quantitative information on ensemble sizes available for reactions is difficult to determine. 

The studies reviewed here focus on Sn/Pt because of the opportunity afforded by the ordered alloys formed in this system for improving our basic understanding, as well as the commercial importance of Pt-Sn catalysts in naphtha reforming and their potential for other selective hydrogenation and dehydrogenation reactions. These studies combined detailed structural characterization of the alloy surfaces with UHV studies of adsorption and reaction of hydrocarbons and other small molecules, and measurements of the rate and selectivity of catalytic reactions at atmospheric pressure over these model catalysts. 

Ni based amorphous alloy containing Pd in low concentration seems to be a good candidate for hydrocarbon oxidation as both metals are active in oxidation reactions [8]. In the present work from the possible Ni-based metal alloys the Ni5oNb50 composition has been selected as we have good deal of experience in its preparation. We replaced part of Nb by Pd and used Pd2Ni5oNb4g amorphous alloy ribbons as starting material for the oxidation of xylene. The latter reaction has been selected as a model reaction for the oxidation of unbumt hydrocarbons in automobile exlraust gases. 

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