Process for preparing lower olefins from an oxygenate

A process for preparing lower olefins from an oxygenate, the process comprising the following steps:

• a) contacting the oxygenate with a molecular sieve-comprising catalyst, at a temperature in the range of from 350 to 1000° C. to obtain an olefinic product stream comprising ethylene, propylene and C4 hydrocarbons;
• b) separating ethylene and/or propylene and a fraction comprising C4 hydrocarbons including saturated and unsaturated C4 hydrocarbons, from the olefinic product stream;
• c) subjecting at least part of the fraction comprising C4 hydrocarbons to extractive distillation to obtain a stream enriched in unsaturated C4 hydrocarbons comprising isobutene and n-butenes, and a stream enriched in saturated C4 hydrocarbons;
• d) supplying at least part of the stream enriched in unsaturated C4 hydrocarbons obtained in step c) and an alcohol selected from the group consisting of methanol, ethanol and a mixture thereof, to an etherification reaction zone comprising an etherification catalyst and reacting, in the etherification reaction zone, at least part of the isobutene in the stream enriched in unsaturated C4 hydrocarbons with the alcohol to obtain an etherification product stream comprising alkyl tertiary butyl ether;
• e) separating the etherification product stream into an alkyl tertiary butyl ether-enriched stream and an isobutene-depleted unsaturated C4 hydrocarbon stream;
• and
• f) recycling at least part of the isobutene-depleted unsaturated C4 hydrocarbon stream and/or at least part of the alkyl tertiary-butyl ether to step a).