Adsorption, methanation and sulfur poisoning on nickel and ruthenium
The adsorption and methanation of CO and CO/sub 2/ in SiO/sub 2/- and Al/sub 2/O/sub 3/- supported Ni and Ru catalysts were studied with temperature-programmed desorption (TDS) and temperature-programmed reaction (TDR). S poisoning of the reactions was also studied with the same techniques. CO/sub 2/ adsorption on Ni/SiO/sub 2/ and Ru/SiO/sub 2/ was found to be very temperature dependent. On both catalysts CO/sub 2/ dissociated to CO and O atoms, and O atoms reacted with H/sub 2/ at room temperature. The CH/sub 4/ peak temperature did not change with initial coverage, indicating methanation is first order in CO coverage. Thus, following adsorption, CO and CO/sub 2/ methanation proceed by the same mechanism. On Ni/Al/sub 2/O/sub 3/, desorption and decomposition of CO and CO/sub 2/ and their hydrogenation to CH/sub 4/ were found to be influenced by metal-support interactions. Only one distinct CO binding state was present in Ni/Al/sub 2/O/sub 3/ and Ru/Al/sub 2/O/sub 3/, while more than one were observed on Ni/SiO/sub 2/ and Ru/SiO/sub 2/. CO disproportionation was slower on Ni/Al/sub 2/O/sub 3/ than Ni/SiO/sub 2/, but a much larger fraction of CO disproportionated on Ni/Al/sub 2/O/sub 3/. Methanation proceeded faster on Ni/Al/sub 2/O/sub 3/ than on Ni/SiO/sub 2/, but two CH/sub 4/ reaction states were observed on Ni/Al/sub 2/O/sub 3/. S poisoning of the CO and CO/sub 2/ reactions studied were examined as a function of surface coverage on Ni/SiO/sub 2/ and Ru/SiO/sub 2/. On Ni/SiO/sub 2/, S preferentially poisoned strongly-bound CO sites, but the specific rates of CO disproportionation and CO methanation remained unchanged on partially S-covered surfaces. Interaction between adsorbed CO and S on partially S-covered Ru/SiO/sub 2/ caused CO desorption, CO/sub 2/ formation, and methanation to occur at a lower specific rate than on clean Ru/SiO/sub 2/. A new method for preparing supported Ni catalysts by precipitation of Ni-dimethylglyoxime onto SiO/sub 2/ yielded catalysts that can be reduced at low temperature (498/sup 0/K) and have both high dispersions and high percentage reduction to elemental Ni is described.
- OSTI ID:
- 6222523
- Country of Publication:
- United States
- Language:
- English
Similar Records
Spillover sites on a 19% Ni/Al sub 2 O sub 3 catalyst
Carbon and carbon monoxide hydrogenation on nickel: support effects
Related Subjects
10 SYNTHETIC FUELS
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYST SUPPORTS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
METALS
METHANATION
MINERALS
NICKEL
NONMETALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
POISONING
RUTHENIUM
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SULFUR
TRANSITION ELEMENTS