Non-ASF product distributions due to secondary reactions during Fischer-Tropsch synthesis

Journal Article · Mon Jan 01 04:00:00 EST 1996 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1996.0028· OSTI ID:223990

Kuipers, E W; Scheper, C; Wilson, J H ^[1]

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1. Koninklijke/Shell Laboratorium Amsterdam (Netherlands); and others

Since Fischer-Tropsch (FT) synthesis is a chain growth reaction, its total product yield decreases exponentially with chain length forming a so-called Anderson-Schulz-Flory (ASF) distribution. Such a distribution is unselective toward middle distillates for all possible chain growth probabilities. Chain-length-dependent secondary reactions, however, cause deviations from the ASF-type distribution and can thus be used to improve the selectivity to the desired product range. To investigate secondary reactions the authors set out to study FT synthesis on flat model catalysts, a cobalt foil and cobalt particles on a SiO{sub 2} wafer, allowing a much better definition of the experiments than porous ones. On a Co foil olefin hydrogenation is the main chain-length-dependent secondary reaction, causing an exponential increase in the paraffin-to-olefin ratio with carbon number, but not resulting in a deviation from the ASF distribution. On Co/SiO{sub 2} model catalysts chain-length-dependent reinsertion of {alpha}-olefins into the chain growth process is the main secondary reaction, causing an increase of the growth probability with chain length. To a lesser extent, hydrogenolysis also plays a role, shortening long hydrocarbons by successive demethylation. On Co/SiO{sub 2} the interplay of chain-length-dependent reinsertion and hydrogenolysis results in sigmoid product distributions with a high selectivity to middle distillates. These product distributions can be fitted with a simple model in which a chain growth reaction is combined with chain-length-dependent secondary hydrogenation, reinsertion, and hydrogenolysis. 95 refs., 6 figs., 1 tab.

• OSTI ID: 223990
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 158; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
10 SYNTHETIC FUELS
40 CHEMISTRY
ALKENES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHEMICAL PREPARATION
CHEMICAL REACTION YIELD
COBALT
FISCHER-TROPSCH SYNTHESIS
HYDROCARBONS
HYDROGENATION
MATHEMATICAL MODELS
SILICA