PURPOSE: To produce a hydrocarbon mixture rich in 4-12 C isoparaffins in a high yield by bringing a gaseous mixture containing CO and H2 into contact with a specified catalyst mixture.
CONSTITUTION: The 1st catalyst containing at least one kind of element selected among Co, Fe, Lu and Ni and having capacity to synthesize hydrocarbon from synthesis gas if mixed with the 2nd catalyst in 3:1-1:5 ratio to obtain a catalyst mixture. The 1st catalyst includes molten iron. The 2nd catalyst is produced by supporting at least one kind of element selected among Fe, Co, Ni, Lu, Rh, Pd, Os, Ir, Pt, Cu, V, Cr, Mo and W on a zeolite carrier having 8-13 Angstrom pore diameter. A gaseous mixture containing CO and H2 in 4-0.5 molar ratio of H2/CO is brought into contact with the catalyst mixture under the conditions of atmospheric pressure - 40kg/cm2, 100-20,000 1/hr space velocity and 160-300oC.