PROCESS FOR THE PREPARATION OF AN OLEFINIC PRODUCT FROM AN OXYGENATE

摘要

The invention relates to a process for the preparation of ethylene and/or propylene comprising: (a) an oxygenate conversion step wherein a gaseous effluent comprising olefins is obtained; (b) subjecting the effluent to water removal and compression steps; (c) acid gas removal from the effluent obtained in step (b), wherein the gaseous effluent is treated with a caustic solution and a non-aqueous liquid stream comprising aromatic C7+ hydrocarbons is added to the caustic solution to control the formation of red oil, to obtain a treated gaseous effluent and a spent liquid phase comprising spent caustic solution, aromatic C7+ hydrocarbons and high molecular weight contaminants; and (d) separating an aqueous phase and a non-aqueous phase from the spent liquid phase; (e) purifying the non-aqueous phase by membrane separation using a hydrophobic non-porous or nano-porous membrane; and (f) separating the olefinic product from the treated gaseous effluent.

主权项

1. A process for the preparation of an olefinic product comprising ethylene and/or propylene from an oxygenate, the process comprising the following steps:
a) contacting an oxygenate feedstock in an oxygenate conversion reaction zone with a molecular sieve-comprising catalyst at a temperature in the range of from 350 to 1000° C. to produce an oxygenate conversion effluent comprising olefins, water, carbon dioxide and carbonyl compounds including C2+ aldehyde and/or ketone; b) subjecting the oxygenate conversion effluent to a water removal step followed by a compression step with optional recovery of any condensed hydrocarbons in the water removal step and/or in the compression step, to obtain a compressed water-depleted gaseous stream comprising olefins, carbon dioxide and carbonyl compounds; c) separating carbon dioxide from the compressed water-depleted gaseous stream by subjecting the gaseous stream to a caustic wash treatment in a caustic tower wherein the gaseous stream is countercurrently contacted with a caustic solution to obtain a washed gaseous stream comprising olefins, wherein a non-aqueous liquid stream comprising one or more aromatic C7+ hydrocarbons is added to the caustic solution prior to contacting the caustic solution with the gaseous stream and wherein a spent liquid phase comprising spent caustic solution, the one or more aromatic C7+ hydrocarbons and high molecular weight contaminants is discharged from the caustic tower; d) separating the spent liquid phase that is discharged from the caustic tower into an aqueous phase comprising spent caustic solution and a non-aqueous phase comprising the one or more aromatic C7+ hydrocarbons and the high molecular weight contaminants; e) separating the high molecular weight contaminants from the non-aqueous phase by contacting the non-aqueous phase with a hydrophobic non-porous or nano-porous membrane to obtain a purified non-aqueous stream as permeate and a stream comprising the high molecular weight contaminants as retentate; and f) subjecting the washed gaseous stream to one or more separation steps such that at least an olefin product stream comprising ethylene and/or propylene is obtained.