Hydrocarbons from carbon monoxide hydrogen-steam mixtures, unusual product distributions and mechanistic implications

Over recent years, considerable interest has developed in hydrocarbon synthesis via direct processing of H/sub 2/-lean synthesis gases which are produced by the ''second generation'' of thermally efficient coal gasifiers. To directly process gases with a H/sub 2//CO ratio less than 0.5, requires that water be mixed with the reactor feed gas so that additional H/sub 2/ is generated in-situ via the water-gas-shift (WGS) reaction. This obviously requires the use of catalysts which are active for both the synthesis and WGS reactions. The fact that most Group VIII metals are active for both reactions is well demonstrated by the development of the Kolbel-Engelhardt (KE) synthesis in which all the H/sub 2/ is formed in-situ. The authors previously examined the effect of H/sub 2//CO/H/sub 2/2O feed ratios on CO conversion rates (4); the present report concerns its effect upon hydrocarbon product distributions. In the experiments described, as the H/sub 2//CO ratio was reduced from 2.0 (Typical Fischer-Tropsch (FT) conditions), sufficient H/sub 2/O was added to compensate for the H/sub 2/ deficiency based on the assumption that all added H/sub 2/O was converted to H/sub 2/ via the WGS reaction.