Patent ID: 7132580
Filing Date: 2006-11-07
Classification: C07C,Y02P

Abstract:
1. A method of selective recovery of a DME-containing recycle stream and a DME-lean, methanol-lean and light olefin-rich product stream from the effluent stream from a MTO conversion zone wherein the effluent stream contains water, methanol, DME, ethylene, propylene and C 4 to C 6 olefins, which method comprises the steps of: (a) cooling and separating at least a portion of the effluent stream into an aqueous liquid stream containing methanol and DME, a hydrocarbon liquid stream containing methanol, DME and C (b) stripping DME from at least a portion of the liquid hydrocarbon stream separated in step (a) in a DME stripping zone operated at stripping conditions effective to produce an overhead vapor stream containing DME, methanol, ethylene and propylene and a liquid hydrocarbon bottom stream containing C (c) combining at least a portion of the hydrocarbon vapor stream separated in step (a) with at least a portion of the overhead vapor stream produced in step (b) to form a DME-rich light hydrocarbon vapor stream; (d) charging the resulting DME-rich light hydrocarbon vapor stream to a primary DME absorption zone and therein contacting this vapor stream with a DME selective solvent containing methanol at scrubbing conditions effective to produce (1) a liquid solvent bottom stream containing methanol, DME, water and substantial and undesired amounts of ethylene and propylene and (2) a light olefin-rich, DME-lean overhead vapor stream containing methanol; (e) passing at least a portion of the liquid bottom stream recovered from step (d) to a light olefin stripping zone operated at stripping conditions effective to strip at least a substantial portion of the ethylene and propylene contained in the liquid bottom stream without stripping any significant portion of the methanol therefrom to produce a stripper overhead stream containing DME, methanol, ethylene and propylene and a liquid bottom stream containing DME, methanol, water and reduced amounts of light olefins relative to the light olefin content of the liquid solvent bottom stream charged to this step; (f) recycling at least a portion of the liquid bottom stream recovered from step (e) to the MTO conversion zone thereby selectively providing additional oxygenate reactants thereto; and (g) charging at least a portion of the stripper overhead stream from step (e) and at least a portion of the light olefin-rich, DME-lean overhead vapor stream from step (d) to a secondary DME absorption zone wherein these streams are countercurrently contacted with an aqueous solvent at scrubbing conditions selected to produce a DME-lean and methanol-lean overhead vapor product stream rich in ethylene and propylene and a bottom liquid stream containing DME, methanol and the aqueous solvent.