2871.     ---------------.  [ROELEN, O.]  [Cobalt and Nickel Catalysts for the Hydrogenation of Carbon Monoxide.]  Angew. Chem., vol. 61, 1949, p. 448.

        Paper presented at the annual meeting of the German Chemical Society in September 1949.  The best method for producing highly active catalysts from Co is by precipitation of the carbonate from boiling nitrate solution upon kieselguhr.  Newly roasted kieselguhr from finely divided crude kieselguhr with a minimum amount of impurities makes the best carrier.  The particle size of the carrier influences the boiling properties of the products and the paraffin deposition on the catalyst.  The 3 best activators for Co are Th, Mg, and Mn.  Th and Mn promote the formation of high-molecular hydrocarbons and the deposition of paraffin on the catalyst, whereas Mg has the opposite effect.  Further specific effects were determined.  The technically best catalyst contains both Th and Mg.  The highest activity, measured by the temperature, is shown by Mn with complete conversion already at 160°.  Co oxide can, under the best conditions, be reduced below 250°; at 400° complete reduction occurs in 1 min.  The mechanism of the poisoning of the catalyst by impurities was explained; it occurs only in the afterheating period of reduction, neither before nor after.  The Co solution must contain no Cu, Fe, Al, and Ca.  These metals are removed by wet regeneration.  The temporary disabling of the catalyst because of paraffin deposition can be removed through destructive hydrogenation or extraction.  C deposition was acknowledged as the reason for any remaining poisoning rather than recrystallization or the like.  Dry regeneration by removing the deposited C by means of H₂ at 400° gave complete reactivation.  Repeated dry regeneration produced operating periods of over 2 yr. without exhaustion of the catalyst.  Highly active Co catalysts decompose CO at temperatures as low as 30°.  Mg is able to activate Ni catalysts also.  The first technical methanation was realized with a Ni-Mg-kieselguhr catalyst.