CN111606822A

CN111606822A - Method for recovering acidic DMF (dimethyl formamide) in sucralose production

Info

Publication number: CN111606822A
Application number: CN202010447899.7A
Authority: CN
Inventors: 孙多龙; 王玉斌; 石剑; 刘学立
Original assignee: Anhui Jinhe Industrial Co Ltd
Current assignee: Anhui Jinhe Industrial Co Ltd
Priority date: 2020-05-25
Filing date: 2020-05-25
Publication date: 2020-09-01

Abstract

The invention relates to a method for recovering acidic DMF in sucralose production, which is characterized by comprising the following steps: (1) introducing acidic DMF and ethanol into a reactor according to the flow ratio of 1:0.3 for reaction at the temperature of 83-85 ℃, and then, carrying out the reaction until the pH value is 6.0-6.4; (2) feeding the mixture into a primary separation tower at a feed rate of 0.8-1m³H, reflux ratio 1:3, the kettle temperature is 78-80 ℃, the top temperature is 48-50 ℃, and the negative pressure is-0.07 to-0.08 MPa; (3) rectifying the mixture at the bottom of the primary separation tower at the kettle temperature of 90-95 ℃ and the top temperature of 78-80 ℃ under normal pressure, wherein the reflux ratio is 1:1, obtaining high-purity DMF at the bottom of the tower, removing light components to obtain ethyl acetate, and recycling; (4) distilling the mixture of the first-separating tower top liquid at 73-75 deg.C under normal pressure, returning the ethanol from the tower top to the reactor for reuse, and treating the acid-containing wastewater from the tower bottom. The invention has the advantages that: ethanol is adopted to replace dimethylamine for reaction, so that the yield of DMF products is high, side reactions are few, and the rectification waste liquid and residues are few; compared with dimethylamine, the ethanol has lower raw material cost, can save 100 ten thousand yuan per year, and reduces the treatment cost.

Description

Method for recovering acidic DMF (dimethyl formamide) in sucralose production

Technical Field

The invention belongs to the technical field of chemical engineering, and relates to a method for recovering acidic DMF (dimethyl formamide) in sucralose production.

Background

Sucralose is a fresh sweetener, the sweetness of which is 800 times of that of sucrose, and the sweetness of which is pure and similar to that of sucrose, and sucralose is not absorbed by human body, has no bioaccumulation and high safety, so that the sucralose industry is rapidly developed in this year, production enterprises are gradually increased, and the yield is continuously improved. DMF is largely used as acidity in the production process of sucralose, and the usage amount of DMF is increased along with the increase of yield.

Patent publication No. CN109503410A provides a treatment method of performing neutralization reaction by dimethylamine and acidic DMF, and then performing rectification, which has the disadvantages that DMF is decomposed under strong alkaline conditions, DMF is lost, and complicated operation processes such as distillation, crystallization and filtration are performed after neutralization, and a large amount of solid salt slag which is difficult to treat is generated.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the method for recovering the acidic DMF in the sucralose production, which has the advantages of simple operation, high efficiency, high recovery rate and low cost.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a method for recovering acidic DMF in sucralose production is characterized by comprising the following steps:

(1) introducing acidic DMF and ethanol into a reactor according to the flow ratio of 1:0.3 for esterification reaction at the reaction temperature of 83-85 ℃, wherein the pH value after the reaction is 6.0-6.4;

(2) the mixture after reaction is sent into a primary separation tower (a rectifying tower) for separation operation, and the feeding amount is 0.8-1m³H, reflux ratio 1:3, the kettle temperature is 78-80 ℃, the top temperature is 48-50 ℃, and the negative pressure is-0.07 to-0.08 Mpa, a mixture of acetic acid, ethanol and water is obtained at the top of the primary separation tower, and a mixture of ethyl acetate and DMF is obtained at the bottom of the primary separation tower;

(3) performing rectification separation operation on a mixture (ethyl acetate and DMF) at the bottom of the primary separation tower, rectifying at the kettle temperature of 90-95 ℃ and the top temperature of 78-80 ℃ under normal pressure at a reflux ratio of 1:1, and recycling ethyl acetate obtained by removing light components from the DMF obtained at the bottom of the rectification tower to a sucralose system for reuse;

(4) distilling the mixture (acetic acid, ethanol and water) at the top of the primary separating tower at normal pressure, controlling the temperature at 73-75 ℃, recycling the ethanol at the top of the tower to the reactor for reuse, and treating the acid-containing wastewater at the bottom of the tower.

Further, the mass fraction of carboxylic acid in the acidic DMF in the step (1) is 5-40%.

Furthermore, the mass percent of DMF in the high-purity DMF in the step (1) is more than or equal to 99.5 percent, the water content is less than 500ppm, and the acid content is less than 500 ppm.

Compared with the prior art, the invention has the following advantages:

1. the invention adopts ethanol to replace dimethylamine for neutralization reaction, has high yield of DMF products (improved from 92 percent to 99.5 percent), less side reactions, less rectification waste liquid and residue (reduced from 500 kg/day to 200 kg/day, and can save cost by 90 ten thousand yuan per year);

2. compared with dimethylamine, the ethanol has lower raw material cost, can save 100 ten thousand yuan per year, and reduces the treatment cost; and the byproduct ethyl acetate can be used for sucralose, the dimethylamine smell problem of the existing project tail gas is difficult to treat, the dimethylamine smell problem of the existing project tail gas is easy to treat, and only one set of condensing device is needed, so that the environmental influence can not be generated.

Drawings

FIG. 1 is a schematic diagram of the recovery process of acidic DMF in sucralose production.

Detailed Description

The invention is further illustrated with reference to fig. 1:

a method for recovering acidic DMF in sucralose production comprises the following specific implementation steps:

example 1

(1) Adding 3000L of acidic DMF (acetic acid 5wt%, DMF80 wt%) into a reactor, adding 300L of ethanol for reaction, and reacting at 85 ℃ to ensure that the pH value of the mixture after reaction is 6.0;

(2) reaction ofThe mixture is input into a rectifying tower, and the operating conditions of the rectifying tower are as follows: the feed rate was 0.9m³The reflux ratio is 1:3, the kettle temperature is 80 ℃, the top temperature is 50 ℃, and the negative pressure is-0.08 Mpa; a mixture containing DMF and ethyl acetate is obtained at the bottom of the tower, and a mixture containing ethanol, acetic acid and water is obtained at the top of the tower;

(3) and (2) rectifying the mixture at the bottom of the tower in a light component removal tower, rectifying and separating the mixture at the bottom of the tower (ethyl acetate and DMF) at the operating kettle temperature of 95 ℃, rectifying the mixture at the top temperature of 80 ℃ under normal pressure at the reflux ratio of 1:1, returning the high-purity DMF obtained at the bottom of the rectifying tower to a sucralose system for recycling the separated light component ethyl acetate, drying and dehydrating the ethyl acetate, and returning the ethyl acetate to the sucralose production for use, wherein the mass fraction of the separated heavy component DMF is 99.5%, the water content is 480ppm, the acid content is 490ppm, and the DMF recovery rate is 95%.

(4) And distilling the mixture of the acetic acid, the ethanol and the water at the tower top under normal pressure, controlling the temperature at 75 ℃, recycling the ethanol at the tower top into the reactor for reuse, and treating the acid-containing wastewater at the tower bottom.

Example 2

(1) Adding 3000L of acidic DMF (acetic acid 12wt%, DMF80 wt%) into a reactor, adding 500L of ethanol, reacting at 85 deg.C to obtain a mixture with pH of 6.3;

(2) inputting the reaction mixture into a rectifying tower, wherein the operating conditions of the rectifying tower are as follows: feed rate 1m³The reflux ratio is 1:3, the kettle temperature is 78 ℃, the top temperature is 48 ℃, and the negative pressure is-0.07 Mpa; a mixture containing DMF and ethyl acetate is obtained at the bottom of the tower, and a mixture containing ethanol, acetic acid and water is obtained at the top of the tower;

(3) the mixture at the bottom of the tower is sent into a light component removal tower for rectification, the mixture at the bottom of the tower (ethyl acetate and DMF) is rectified and separated, the temperature of an operation kettle is 93 ℃, the top temperature is 78 ℃, the normal pressure rectification is carried out, the reflux ratio is 1:1, the high-purity DMF obtained at the bottom of the rectification tower is obtained, the ethyl acetate obtained by light component removal returns to a sucralose system for recycling the separated light component ethyl acetate, then the ethyl acetate is dried and dehydrated and then returns to the sucralose production for use, the mass fraction of the separated heavy component DMF is not less than 99.6%, the moisture content is 490ppm, the acid content is less than 485ppm, and the DMF recovery rate is 96.5;

(4) and distilling the mixture of the acetic acid, the ethanol and the water at the tower top under normal pressure, controlling the temperature at 73 ℃, recycling the ethanol at the tower top into the reactor for reuse, and treating the acid-containing wastewater at the tower bottom.

It should be noted that, although the above embodiments have been described herein, the invention is not limited thereto. Therefore, based on the innovative concepts of the present invention, the technical solutions of the present invention can be directly or indirectly applied to other related technical fields by making changes and modifications to the embodiments described herein, or by using equivalent structures or equivalent processes performed in the content of the present specification and the attached drawings, which are included in the scope of the present invention.

Claims

1. A method for recovering acidic DMF in sucralose production is characterized by comprising the following steps:

(2) the mixture after reaction is sent into a primary separation tower for separation operation, and the feeding amount is 0.8-1m³H, reflux ratio 1:3, the kettle temperature is 78-80 ℃, the top temperature is 48-50 ℃, and the negative pressure is-0.07 to-0.08 Mpa, a mixture of acetic acid, ethanol and water is obtained at the top of the primary separation tower, and a mixture of ethyl acetate and DMF is obtained at the bottom of the primary separation tower;

(3) performing rectification separation operation on the mixture at the bottom of the primary separation tower, rectifying the mixture at the kettle temperature of 90-95 ℃ and the top temperature of 78-80 ℃ under normal pressure at a reflux ratio of 1:1, and recycling the high-purity DMF obtained at the bottom of the rectification tower and the ethyl acetate obtained by light component removal to a sucralose system for reuse;

(4) and distilling the mixture of the liquid at the top of the primary separating tower at normal pressure, controlling the temperature at 73-75 ℃, recycling the ethanol at the top of the tower to the reactor for reuse, and treating the acid-containing wastewater at the bottom of the tower.

2. The method according to claim 1, wherein the acidic DMF is recovered from the sucralose production process, and the method comprises the following steps: the mass fraction of carboxylic acid in the acidic DMF in the step (1) is 5-40%.

3. The method according to claim 1, wherein the acidic DMF is recovered from the sucralose production process, and the method comprises the following steps: in the high-purity DMF in the step (1), the mass percent of DMF is more than or equal to 99.5%, the water content is less than 500ppm, and the acid content is less than 500 ppm.