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Multiple isotope tracing of methanation over nickel and molybdenum sulfide catalysts

Thesis/Dissertation ·
OSTI ID:6805086

The methanation of mixtures of carbon monoxide and hydrogen over nickel and molybdenum sulfide catalysts was studied by a novel isotope transient tracing technqiue employing deuterium and /sup 13/C. In the case of both nickel and molybdenum sulfide catalysts, methanation of mixtures of carbon monoxide and hydrogen involves sequential conversion of CH/sub x/I (x = 0.3) species. Comparmental models of the data indicate that the CHI species is present at the highest concentration, where the symbol is used generally to identify sites for chemisorption. The CI species, sometimes designated as carbidic carbon is present at somewhat lower concentrations. Species CH/sub 2/I and CH/sub 3/I are also preset at much lower concentrations. For nickel, the concentration of all chemisorbed intermediates is much higher than for molybdenum sulfide. The rate of methanation is also correspondingly higher for nickel than for molybdenum sulfide. Nickel adsorbs carbon monoxide much more readily than molybdenum sulfide and this is the predominant adsorbed species in the case of nickel catalyst. The major surface species with molybdenum sulfide is chemisorbed hydrogen, with only extremely small concentration of adsorbed carbon monoxide.

OSTI ID:
6805086
Country of Publication:
United States
Language:
English