Reaction between hydrogen and carbon monoxide on catalysts derived from Mo(CO)/sub 6//Al/sub 2/O/sub 3/

Journal Article · Sun Jun 01 00:00:00 EDT 1980 · J. Catal.; (United States)

OSTI ID:6992434

Bowman, R G; Burwell, Jr, R L

If Mo(CO)/sub 6//(dehydroxylated alumina, ..gamma..- + delta-Al/sub 2/O/sub 3/) is activated in helium to 500/sup 0/C, clusters of Mo about 4nm in diameter are formed. They are contaminated with some retained carbon which is essentially completely removed as methane by hydrogen at 650/sup 0/C. The average oxidation number of the molybdenum is about +0.3 and it is suggested that the clusters consist of Mo/sup 2 +/ plus Mo(0) in which the charge is delocalized and balanced by Al-O/sup -/ groups at the surface. The clusters are not identical with metallic molybdenum since they do not chemisorb nitrogen. Materials so prepared exhibit a turnover frequency for formation of methane at 300/sup 0/C of about 0.04 sec/sup -1/ per surface atom of molybdenum in flowing hydrogen plus carbon monoxide (mole ration = 5). Smaller amounts of ethane and propane are also formed. Activation at 300 to 500/sup 0/C in helium or hydrogen leads to similar turnover frequencies and selectivities. Activation of Mo(CO)/sub 6//(alumina dehydroxylated at 475/sup 0/C) at 300/sup 0/C in hydrogen or helium results in a material in which Mo is ionic and highly dispersed. Turnover frequencies for formation of methane at 300/sup 0/C are about 0.001 sec/sup -1/ per atom of molybdenum and selectivities are about the same as for the catalyst on dehydroxylated alumina. Activation in hydrogen results in formation of about 1.4 molecules of methane per molecule of Mo(CO)/sub 6/ and the resulting water, in essence, further oxidizes the molybdenum beyond the Mo/sup 2 +/ formed initially by reaction of Mo(0) with surface hydroxyl groups, Mo + 2Al-OH/sub 8/ ..-->.. Mo/sup 2 +/ + H/sub 2/ + 2Al-O/sub 8//sup -/. 4 figures, 2 tables.

• Research Organization: Northwestern Univ., Evanston, IL
• OSTI ID: 6992434
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 63:2; ISSN JCTLA
• Country of Publication: United States
• Language: English

Related Subjects

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ACTIVATION ENERGY
ALKANES
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
ENERGY
ETHANE
HIGH TEMPERATURE
HYDROCARBONS
HYDROGEN
HYDROGEN COMPOUNDS
METALS
METHANATION
METHANE
MOLYBDENUM
MOLYBDENUM COMPOUNDS
NONMETALS
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PROPANE
REFRACTORY METALS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
WATER