2879.     ROELEN, O., AND ROYEN, P.  [Mechanism of Carbon Dioxide Formation on Catalysts of the Fischer-Tropsch Synthesis.]  Erdöl u. Kohle, vol. 3, No. 1, 1950, p. 10.

        Paper presented at the 1949 meeting of the die deutsche Gesellschaft für Mineraloelwissenschaft und Kohlechemie.  It was already regarded in 1923, by Fischer and coworkers that CO₂ formation occurs on Fe catalysts of the hydrocarbon synthesis as a secondary reaction, which is identical with the known conversion of a mixture of CO and steam into CO₂ and H₂.  Finally in 1949, H. Kölbel on the strength of newer investigations has replaced this view.  According to older conceptions of Wieland in 1912, Fischer and Schrader in 1921 assumed that, by this conversion, CO and H₂O are together changed to formic acid, which then is split catalytically into CO and H₂.  It is known that addition of alkali compounds, especially in the form of hydroxides and carbonates, to the Fe and Co catalysts of the Fischer synthesis intensify the conversion.  Roelen and later independently Royen supposed that, in this case, a 2d mechanism in introduced consisting in an intermediate formation of potassium formate from potassium  hydroxide and carbon monoxide, a reaction that technically serves for the production of formic acid.  The potassium formate 1^st formed is split on the catalyst by means of adsorbed water vapor hydrolytically into potassium hydroxide and free formic acid.  Roelen has shown that sodium formate at 200°-230° in presence of active Fe or Co is decomposed by water vapor into CO₂ and H₂.  He found that formic acid is converted by Fe catalysts and very quickly into H₂ and CO₂.  In mutual tests, it was shown that these reactions occur also on alkalized Cu catalysts at 120°.  It is further shown that catalysts of active C with a few % of alkali hydroxide plainly perform the conversion at 140°.  By the conversion, the potassium hydroxide present on the catalyst goes over in great part into potassium formate.  Catalysts which were impregnated with potassium hydroxide-potassium formate mixtures in the proportion formed by the conversion, showed by the treatment with water vapor of the same partial pressure as by the conversion tests, CO₂ and H₂ concentrations in the residual gas of the same magnitudes as in the conversion.  It was shown, thus, that the formate mechanism with alkalized catalysts of the Fischer-Tropsch synthesis can supply an essential contribution to the conversion reaction.  This determination is supported also by several physical-chemical observations.