2055.     ---------------.  [LANE, J. C. AND WEIL, B. H.]  Synthine Process.  II.  Catalytic Synthesis, Including Catalysts and Reaction Mechanisms.  Petrol. Refiner, vol. 25, 1946, pp. 423-434; Chem. Abs., vol. 42, 1948, p. 9118.

Two main reactions take place in the synthine process, the predominant one depending chiefly on the ratio of H₂:CO and the type of catalyst used:  (1) nCO+(2n+1)H₂→C_nH_2n±₂+nH₂O; (2) nCO+2nH₂→C_nH_2n+nH₂O.  Since the reaction is exothermic and involves a reduction in volume, relatively low temperatures and elevated pressures favor the reaction.  Temperatures range from 375° with Ni or Co catalysts to 465° with Fe catalysts, and pressures vary from atmospheric pressure to 150 p.s.i.  The synthesis gas is passed through reaction chambers in 1 or more stages, with or without recycle of the unconverted portion.  The heavier products are condensed from the residual gas, and the lighter products are adsorbed on charcoal or in oil.  Most theories of the reaction mechanism stipulate the intermediate formation of carbides of the catalyst metals.  By hydrogenation of these unstable carbides, CH₂ groups are produced, but there are various theories as to the method of producing them.  Both polymerization and hydrogenation then occur to produce hydrocarbons of higher molecular weight.  Catalysts consist of Fe and Co alone, or in mixtures with Ni.  They are supported on an inert carrier (kieselguhr), or used as all alloy-skeleton type catalysts, or fluid catalysts.  The German commercial operation is described.  The various modifications in the process that will produce branched-chain hydrocarbons, alcohols, aromatic hydrocarbons, or CH₄ are all discussed in detail.