2741.     PRETTRE, M.  [Methane:  Reagent for Hydrocarbon Synthesis.]  Conf. réunion soc. beige étude pétrole, dérivés et succédanés, Brussels, 1947, 16 pp.; Rev. inst. franc, pétrole et Ann. combustibles liquides, vol. 2, 1947, pp. 131-140, 195-200; Jour. Inst. Petrol., vol. 33, 1947, . 308A; Chem. Abs., vol. 42, 1948, p. 6084.

        Two aspects of the kinetics of contact catalysis are examined:  Adsorption and reactions in the adsorbed phase.  By interrupting a normal catalytic reaction, cooling the catalyst zone in the presence of the reactants and transferring the cold catalyst, with exclusion of air, to a special apparatus (not described), it is possible to study the gases given off on desorption as the temperature rises, the most loosely adsorbed products being evolved first.  A study of the catalyst in the course of catalytic cracking with hydrogenation showed a high concentration of CH₄, although none of this material was present in the feed and only a small amount in the product.  It is, therefore, concluded that the adsorbed phase has a high concentration of CH₃, CH₂, and CH radicals; the isomerization process can thus be considered as being one of methylation.  In seeking to find a reaction in which the role of CH₄ could be experimentally demonstrated, thermodynamic considerations pointed to the Fischer-Tropsch synthesis as being one in which this effect ought to be evident at atmospheric pressure.  Experimental addition of CH₄ to synthesis gas shows that it participates in the reaction.  The use of CH₄ decreases the induction period of the Fischer-Tropsch catalyst (during which large quantities of CH₄ are normally produced); a similar effect is obtained by the dilution of the synthesis gas with an inert material, such as N₂.  It is considered that the large initial formation of CH₄ normally observed is due to the heating up of fresh catalyst; if the temperature is kept low, then condensable aliphatic hydrocarbons can be obtained almost immediately.