Process of producing liquid hydrocarbon oil or dimethyl ether from lower hydrocarbon gas containing carbon dioxide

A process for the production of dimethyl ether, comprising the steps of:

• (a) mixing a gas feed, containing a lower hydrocarbon having 1-4 carbon atoms and 30-70 mole % of CO2 based on a total mole of the CO2 and the lower hydrocarbon, with H2O to obtain a mixed gas having contents of the CO2, H2O and lower hydrocarbon satisfying the following condition:
• 0.5≦([CO2]+(H2O])/[C]≦2.5
• wherein [CO2] represents the moles of the CO2, [H2O] represents the moles of the H2O and [C] represents the moles of carbon of the lower hydrocarbon;
• (b) contacting said mixed gas with a catalyst at a temperature of 600-1,000° C. and a pressure of 10-75 atm to produce a synthesis gas with a synthesis gas production efficiency Yf of at least 80% and a carbon conversion efficiency Cf of at least 50%,
• said synthesis gas production efficiency Yf being represented by the following formula:
• Yf={[CO]+[H2])/([C]+[CO2]+[H2O])}×100%
• wherein [CO] represents the moles of CO in said synthesis gas, [H2] represents the moles of H2 in said synthesis gas, and [CO2], [H2] and [C] are as defined previously,
• said carbon conversion efficiency Cf being represented by the following formula:
• Cf={[CO]/([C]+[CO2])}×100%
• wherein [CO], [CO2] and [C] are as defined previously,
• said synthesis gas having a molar ratio of hydrogen to carbon monoxide of 0.5-1.5,
• said catalyst having a specific surface area of 5 m2/g or less and comprising a magnesium oxide-containing carrier and at least one catalytic metal selected from the group consisting of rhodium and ruthenium and supported on said carrier in an amount of 10-5,000 ppm, in terms of elemental metal, based on the weight of said carrier;
• (c) reacting said synthesis gas in the presence of one or more catalysts having activities of methanol synthesis, methanol dehydration and CO shift reaction to obtain a product containing dimethyl ether;
• and
• (d) separating said dimethyl ether from said product.