Patent ID: 8530714

Claim:
A method for producing lower olefins comprising: introducing a feed gas, which is composed of a feedstock gas containing dimethyl ether and an additive gas containing steam in which the ratio of steam in the total amount of feed gas is 5 to 30% by volume, into an olefin synthesis reactor, bringing the feedstock gas into contact with a zeolite catalyst in the reactor to produce a hydrocarbon product containing C 2 -C 5 olefins, separating and recovering propylene from the hydrocarbon product, and using at least a part of the remainder after the separation as at least a part of the additive gas, wherein said method comprises multiple reactors connected in parallel, or connected in a combination of series and parallel, wherein the additive gas contains C 4 and/or C 5 olefins derived from the remainder after separating propylene from the hydrocarbon product, the ratio of the total amount of the C 4 and/or C 5 olefins in the additive gas to the total amount of methanol and dimethyl ether in the feedstock gas is 0.3 to 5.0 by molar ratio on a carbon basis, and the ratio of an additive gas excluding steam to the feedstock gas introduced into the olefin synthesis reactor (the number of moles of the additive gas excluding steam:the number of moles of the feedstock gas on a carbon basis) is in the range of 0.2 to 5.0.