System and method for co-production of dimethyl carbonate and dihydric alcohol

Abstract

The invention relates to a system and a method for co-production of dimethyl carbonate and dihydric alcohol. A methanol and dimethyl carbonate azeotrope material at the top of a reactive distillation column enters a first azeotropic distillation column, and a material extracted from the bottom of the reactive distillation column enters a methanol, dihydric alcohol and catalyst separation unit; a material at the bottom of the first azeotropic distillation column enters a second azeotropic distillation column, a first stream of steam material, a second stream of steam material and a third stream of steam material which are rich in methanol are extracted from the top of the first azeotropic distillation column, the first stream of steam material enters the reactive distillation column, the second stream of steam material enters a reboiler at the bottom of the reactive rectifying tower, and the third stream of steam material enters a reboiler at the bottom of the reactive distillation column; a third stream of steam material enters a reboiler at the bottom of the second azeotropic distillation column; and a DMC product is obtained at the tower bottom of the second azeotropic distillation column. Through the structural design, latent heat of high-pressure steam at the top of the first azeotropic distillation column is fully utilized, the energy efficiency is improved to the maximum extent, and the equipment investment is reduced.

Description

technical field [0001] The invention belongs to the technical fields of chemical industry, material and environmental protection, and in particular relates to a system and method for co-producing dimethyl carbonate and glycol. Background technique [0002] Dimethyl Carbonate (Dimethyl Carbonate, DMC for short, also known as dimethyl carbonate) is an environmentally friendly organic chemical product and an important organic synthesis intermediate. Its molecular structure contains functional groups such as carbonyl, methyl and methoxy groups, and has a variety of reactivity; it is also a green, non-toxic solvent that can replace aromatic hydrocarbons and acetate solvents, and it can also be used as an oxygen-containing solvent for gasoline. Additive, replaces MTBE. At present, DMC is mainly used as an electrolyte solvent for lithium-ion batteries, and the annual demand exceeds 1 million tons. Glycols mainly include ethylene glycol and propylene glycol, which are important or...

AI Technical Summary

Problems solved by technology

[0009] However, the current separation process of methanol and DMC binary azeotrope has the problem of high energy consumption, and the production cost of DMC is relatively high, which is not competitive compared with other process routes.

The main reasons are in two aspects: First, the amount of methanol circulation is very large. 1 mol of DMC product produced in the reactive distillation process under normal pressure needs 6.5 mol of methanol to be distilled out together, and a large amount of methanol needs to be distilled out again in the pressurized rectification tower; Secondly, in industrial practice, a large amount of high-concentration methanol at the top of the pressurized rectification tower is passed into the atmospheric separation tower for separation. -The relative volatility of the DMC azeotrope and the bottom methanol is very low, the reflux ratio is high, the steam energy consumption is also high, and the equipment is huge

[0010] Paper (Study on New Technology of Pressurized Separation of Methanol and Dimethyl Carbonate Azeotrope, 2001, Anhui Chemical Industry, 2-3) for the first time disclosed the separation of methanol and dimethyl carbonate by combining a pressurized rectification tower and an atmospheric rectification tower Experimental research, but there is no coupled utilization of energy, and the energy efficiency is low; the paper (Phase Equilibrium and Process Simulation of Pressure-Atmospheric Distillation Separation of Methanol-Dimethyl Carbonate, 2003, Journal of Process Engineering, 453-458) published Similar research work does not involve the comprehensive utilization of energy; the paper (Novel Procedure for the Synthesis of Dimethyl Carbonate by ReactiveDistillation, Ind.Eng.Chem.Res.2014, 3321-3328) studies the atmospheric pressure reactive distillation column + Combined technology of pressure azeotropic distillation column + atmospheric distillation column, dimethyl carbonate is extracted from the pressurized distillation column, methanol is extracted from the atmospheric pressure distillation column, the energy consumption is high, and the equipment is huge; the paper (Optimization and control of a reactive distillation process for the synthesis of dimethyl carbonate, Chinese Journal of Chemical Engineering, 2017, 1079–1090) studied the process of atmospheric pressure reactive distillation column + pressurized azeotropic distillation column, dimethyl carbonate from the pressure column output at the bottom, methanol at the top of the tower is circulated into the reactive distillation tower, and the energy consumption is also high; the paper (Process Simulation and System Analysis, Chinese Journal of Process Engineering, 2018, 1308-1313) studied the process of atmospheric reactive distillation tower+high pressure azeotropic distillation tower+atmospheric distillation, and the product dimethyl carbonate was extracted from the bottom of the atmospheric tower, although using The thermal coupling of steam at the top of the pressurized distillation column is used as the heat source of the reboiler of the reactive distillation column and the atmospheric column, but the high-pressure energy has not been utilized, and the concentration of dimethyl carbonate in the circulating methanol is high, so the energy consumption is still large; the paper (Study on process optimization and heat integration of reactive distillation synthesis of dimethyl carbonate, Modern Chemical Industry, 2020, 226-229) studied the process of reactive distillation + pressurized distillation + atmospheric distillation, dimethyl carbonate from pressurized The bottom of the rectification tower is extracted, and heat integration technology has been studied, but due to the extraction of methanol from the atmospheric column, the energy consumption is still relatively large

Patent document 200610137892 discloses a comprehensive energy utilization technology in the process of producing dimethyl carbonate by transesterification. The pressurized rectification tower overhead is used as the heat source of the atmospheric reaction rectification tower and the atmospheric rectification tower, but the energy The utilization efficiency is not high, and the equipment investment is relatively large; patent document 201310692281 discloses an energy-saving process for the production and separation of dimethyl carbonate and methanol, the energy consumption of the reactive distillation column is large, and the energy utilization efficiency of the pressurized distillation column is not high. Equipment investment is also large; patent document 201410755182 discloses a method for the continuous production of dimethyl carbonate and co-production of 1,2 propanediol by transesterification, including an atmospheric pressure reactive distillation column and a high-pressure azeotropic distillation column, and azeotropic distillation The product dimethyl carbonate is obtained at the bottom of the tower, and the methanol-rich material is obtained at the top of the tower. This material then enters the subsequent atmospheric azeotropic distillation tower, and the methanol obtained at the bottom of the tower is recycled to the reactive distillation tower for recycling, and the energy consumption is high. Equipment investment is also relatively large; patent document 201810706120 discloses a device and method for the co-production of ethylene glycol and dimethyl carbonate, which adopts pressurized rectification and separation to obtain dimethyl carbonate from the bottom of the tower, and the top material enters the subsequent methanol Atmospheric pressure separation tower, high-purity methanol is obtained at the bottom of the tower, with high energy consumption and huge equipment; patent document 202011484989 discloses a production device and its use method of transesterification dimethyl carbonate, using a method similar to 201410755182 and 201810706120 , there is also the problem of large energy consumption

[0011] In short, there is still a lot of room for improvement and improvement in the existing technology in terms of energy consumption and equipment optimization

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