Fischer-Tropsch synthesis over reduced and unreduced iron oxide catalysts

Journal Article · Wed Jan 01 04:00:00 EST 1986 · J. Catal.; (United States)

DOI:https://doi.org/10.1016/0021-9517(86)90043-6· OSTI ID:5297988

Dictor, R A; Bell, A T

An investigation has been carried out of Fischer-Tropsch synthesis over potassium-promoted and unpromoted iron oxide catalysts. The distribution of products over reduced and unreduced Fe/sub 2/O/sub 3/ are similar. The primary products are methane and linear, terminal olefins. Some C/sub 2//sup +/ paraffins are produced in parallel with olefins, but most result from hydrogenation of the olefins. Isomerization of terminal to internal olefins also occurs as a secondary reaction. The Anderson-Schulz-Flory distribution of products is characterized by two branches differing in the value of ..cap alpha... The average molecular weight of the product increases with decreasing temperature, decreasing H/sub 2/ partial pressure, and increasing CO partial pressure. Methanol is the only oxygenated product formed over unpromoted Fe/sub 2/O/sub 3/. Promotion of Fe/sub 2/O/sub 3/ with potassium suppresses the rates of olefin hydrogenation and isomerization, and the rate of methanol formation, but enhances the rates of formation of C/sub 2//sup +/ hydrocarbons, branched hydrocarbons, and aldehydes. The kinetics for the synthesis of C/sub 1/-C/sub 7/ hydrocarbons were determined for both promoted and unpromoted catalysts. The data show that in general the kinetics of formation of an individual product cannot be represented by simple power-law rate expressions. Based on X-ray diffraction analyses of used catalysts, it is concluded that the phase of iron active for Fe/sub 2/O/sub 3/ Fischer-Tropsch synthesis is a mixture of chi- and epsilon'-iron carbides, and a small amount of ..cap alpha..-iron. 39 references.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5297988
• Journal Information: J. Catal.; (United States), Journal Name: J. Catal.; (United States) Vol. 97:1; ISSN JCTLA
• Country of Publication: United States
• Language: English

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