PURPOSE: To attain an improvement in the yield and miniaturization of facilities for a two-step reaction system, by recovering dimethyl ether from a purge gas separated from an effluent from a 1st-step reactor and feeding the ether into a 2nd-step reactor during the synthesis of a hydrocarbon oil from a synthesis gas through a two-step process via dimethyl ether.
CONSTITUTION: Using the following process, a hydrocarbon oil is produced via dimethyl ether from a synthesis gas comprising carbon monoxide and hydrogen. That is, a synthesis gas 101 is contacted with a catalyst comprising a methanol synthesis catalyst and an acid dehydration catalyst at a temp. as high as 150-400oC (a 1st-step reactor 1), thereby preparing dimethyl ether. Gas-liquid separation (a separating tank 5) of an effluent 103 from the aforesaid catalyst is conducted to prepare a gas component 107. From the gas component, dimethyl ether 112 is recovered (a dimethyl ether recovery column 3). The recovered dimethyl ether 112 is mixed with the condensed dimethyl ether (mixture 115) which is a component of a liquid 109 from gas-liquid separating operation. The mixture is contacted with a crystalline transition metal silicate zeolite catalyst (a 2nd-step reactor 2) at a temp. as high as 250-500oC