FIELD: chemistry.
SUBSTANCE: claimed invention relates to method of selective isolation of recycling flow, which contains dimethyl ester (DME), from flow, which leaves zone of methanol conversion into olefins (MTO), where said leaving flow contains water, methanol, DME, ethylene, propylene, C4-C6-olefins. Claimed method includes stages: (a) cooling and separation of at least part of leaving flow into liquid flow, which contains methanol and DME, liquid hydrocarbon flow, which contains methanol, DME and C2-C6-olefins, and vaporous hydrocarbon flow, which contains DME, methanol, ethylene and propylene; (b) distillation of DME from at least part of liquid hydrocarbon flow, separated at stage (a) in zone of DME distillation, functioning in conditions of distillation, efficient for formation of vaporous main flow, which contains DME, methanol, ethylene and propylene, and liquid hydrocarbon bottom flow, which contains C4-C6-olefins; (c) mixing of at least part of vaporous hydrocarbon flow, separated at stage (a), with at least part of main vaporous flow, produced at stage (b), with formation of enriched DME vaporous flow of light hydrocarbons; (d) supply of formed enriched with DME vaporous flow of light hydrocarbons into zone of primary absorption of DME, where said vaporous flow is brought in contact with methanol-containing selective with respect to DME solvent in conditions of wet purification, which allows to form (1) liquid bottom solvent flow, containing methanol, DME, water and substantial and undesirable amount of ethylene and propylene, and (2) main vaporous flow of product, enriched with light olefins and depleted of DME; (e) directing of at least part of liquid bottom flow, separated at stage (d), into zone of light olefins distillation, functioning in conditions of distillation, efficient for distillation of at least considerable part of ethylene and propylene, contained in liquid bottom flow, without distilling from there any considerable part of methanol, which results in formation of main flow of distillation section, containing DME, ethylene and propylene, and liquid bottom flow, containing DME, methanol, water and light olefins in amount reduced in comparison with amount of light olefins in liquid bottom solvent flow, supplied to this stage, and (f) recycling of at least part of liquid bottom flow, separated at stage (e) into zone of conversion MTO, thus selectively introducing to it additional oxygenated reactants.
EFFECT: reduction of undesirable increase of C2 and C3-olefins in recycling DME flow.
10 cl, 4 tbl, 2 dwg, 2 ex
