1242.    ---------------.  [GREAT BRITAIN FUEL RESEARCH BOARD.] Synthesis of Hydrocarbons From Carbon Monoxide and Hydrogen.  Rept. for the Year Ended March 1939.  H. M. Sta. Office, London, pp. 151-176.

       Continuation of the investigations begun in 1937-38 gives further account of the operation of the plant and of the yields obtained during a run lasting more than 2 mo.  An important aspect of the process is the possibility of using certain fractions of the crude product for the preparation of lubricating oils.  During the most favorable stage of the run, the yield of recovered liquid hydrocarbons was over 90 gm. per N m.³ of synthesis gas and, in addition, about 10 gm. per m.³ of easily condensible hydrocarbons and 3 gm. per m.³ of hard wax.  The rate of input of synthesis gas was standardized at 120 cu. ft. per hr.  The normal synthesis was started at 186° and progressively raised to 215° as the activity of the catalyst diminished.  It was found necessary, at least at the end of each 24-hr. period and sometimes oftener, to revivify the catalyst by passing H₂ over it for 1 or 2 hr., after which a spurt in the activity occurred accompanied by the production of excessive amounts of CO₂.  To obtain the best results, a special “running-in” technique of the catalyst had to be observed.  Further data regarding the synthesis mechanism indicate that carbide is not formed on the catalyst in the usual way 2Co+CO→Co₂C+CO₂ but rather by 2Co+CO+H₂→Co₂C+H₂O.  These conclusions are confirmed and put on a quantitative basis by measuring the rates of the various reactions at a series of temperatures and so obtaining the corresponding energies of activation; that of (1) is 18,000 cal., that of (2) 9,500 cal., and that of the reduction of carbide Co₂C+2H₂→2Co+CH₄, 11,500 cal.  The results indicate that reaction (1) will not occur during the Fischer synthesis, and that the formation of carbide by reaction (2) will occur, followed by its reduction to CH₂ groups.  Previous work on the o-p-H₂ conversion has proved that in the presence of large amounts of chemisorbed H₂ these CH₂ groups are reduced further to give CH₄; when, however, the amounts of chemisorbed H₂ is small, they polymerize and give higher hydrocarbons.  It is reasonable to suppose that the larger numbers of CH₂ groups produced on the surface during the synthesis are equivalent to a macro-molecule from which fragments can be broken off to form the Fischer products.  If so, cracking of paraffin hydrocarbons should occur on the catalyst at 200° by interaction of the paraffin hydrocarbon with chemisorbed H₂, and hence in the Fischer synthesis the products actually obtained are hydrogenation-cracking products of the macro-molecules of CH₂ groups, caused by the presence of quite small amounts of chemisorbed H₂.  In the presence of larger amounts the hydrogenation-cracking is carried so far that CH₄ only is produced.