Synthesis gas consisting of a mixture of CO and H2, if desired together with other gases, is passed at 1,000°-1,250° over bauxite in such a way that the gas remains 0.5 sec. in the hot zone. The gas is then freed from H2S by means of an Fe oxide purification mass and after cooling passed over a Co-Th oxide catalyst at ordinary pressure and at about 180°. The yield of liquid hydrocarbons produced amounts to 115 cc. per m.3 of CO-H2 mixture. Quartz can be used instead of bauxite.