TITLE: Mechanisms of Fischer-Tropsch Synthesis.

AUTHOR: A. T. Bell.

INST.  AUTHOR: California Univ., Berkeley. Lawrence Berkeley Lab.

SPONSOR: Department of Energy, Washington, DC.

LANGUAGE: English

PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Department of Energy [DE],  Apr 84,  23p.

NOTES: ANS student/professional conference on nuclear science and engineering, College Station, TX, USA, 6 Apr 1984.

ABSTRACT:

Both H sub 2 and CO in the gas phase are virtually in equilibrium with adsorbed H atoms and CO. The dissociation of CO is on activated process on Ru but is essentially irreversible. The dissociation of CO is on activated process on Ru but is essentially irreversible. The carbon atoms released by CO dissociation react very rapidly via a reversible sequence of steps to form CH/sub x/ (x=1-3) groups. Carbon-carbon bonds appear to be formed via alkyl group migration to methylene groups and insertion of the latter species into the metal-carbon bond of the alkyl. Termination of chain growth can occur by beta -hydrogen elimination to form 1-olefins or by reductive elimination to form 1-olefins or by reductive elimination to form normal paraffins. The extension of the proposed scheme to account for the formation of branched hydrocarbons and oxygenated products can readily be envisioned. Branching can result from isomerization of the growing chain. The insertion of CO into the metal-carbon bond of a surface alkyl group will produce an acyl group which is then a precursor to the formation of an aldehyde or alcohol. While the discussion has been limited to Ru, the same chemistry is expected to occur on other Group VIII metals.  Consistent with this, several recent studies of Fischer-Tropsch synthesis over Ni, Fe, and Co have proposed equivalent reaction mechanisms. The observed differences in reaction kinetics and product distribution are, therefore, very likely due to differences in the rate and equilibrium parameters associated with individual reaction steps. (ERA citation 09:037404)

REPORT  NUMBER: LBL-17789;   CONF-840484-1

CONTRACT  NUMBER: AC03-76SF00098