Patent ID: 6852897

Claim:
A process for producing lower olefins, comprising the steps of: (A) separating a mixed fluid (I) obtained when a gaseous mixture containing carbon monoxide and hydrogen is introduced into an oxygen-containing compound synthesis means for reacting carbon monoxide and hydrogen with each other and synthesizing methanol, and from the methanol, forming dimethyl ether and water, said mixed fluid (I) containing carbon monoxide and hydrogen and dimethyl ether and methanol in a dimethyl ether/methanol weight ratio of 25/75 to 95/5 into a gas component (II) and a liquid component (III) by a high-pressure gas-liquid separation means under high pressure, wherein a part of the gas component (II) is introduced into the oxygen-containing compound synthesis means as a recycle gas, together with the gaseous mixture containing carbon monoxide and hydrogen, then separating the gas component (II) into an off-gas and dimethyl ether, and allowing the separated dimethyl ether to join the liquid component (III) to obtain a liquid component (IV) having a dimethyl ether/methanol weight ratio of 30/70 to 90/10, and (B) releasing the pressure of the liquid component (IV), and then introducing the liquid component (IV) into an olefin production means to form a lower olefin fraction (V) containing ethylene and propylene.