Effects of particle structure on CO hydrogenation on Ni on SiO/sub 2/

Journal Article · Sun Jun 01 04:00:00 EDT 1986 · J. Catal.; (United States)

OSTI ID:5206057

Lee, C; Schmidt, L D; Moulder, J F; Rusch, T W

The effects of oxidation-reduction cycling on the morphology, surface composition, hydrogen uptake, and kinetics of CO hydrogenation over silica-supported Ni catalysts have been studied by hydrogen chemisorption, kinetics in a differential flow reactor, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) in a rapid transfer reactor system. When Ni particles (approx. 4% dispersion, approx. 250 A diameter) are oxidized at 460/sup 0/C and then reduced in H/sub 2/ at 300/sup 0/C, hydrogen chemisorption areas increase while methanation activities decrease. Heating progressively up to 650/sup 0/C produces a decrease in surface area and an increase in methanation activity. XPS confirms total oxidation and reduction of Ni by 350/sup 0/C. TEM shows that particles spread on the SiO/sub 2/ surface upon oxidation and form clusters of smaller Ni particles upon low-temperature reduction. These results show that solid-state redispersion occurs upon oxidation-reduction cycling but that the methanation activity is low on freshly reduced Ni. It is argued that the activity change is caused by a lower activity on high index planes of smaller particles of Ni which may be associated with preferential buildup of carbon on these planes. These transformations can be produced reversibly on fairly large particles, and these structures can be metastable for long times under reaction conditions.

• Research Organization: Univ. of Minnesota, Minneapolis (USA)
• OSTI ID: 5206057
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 99:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

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010408* -- Coal
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