阅读说明：本技术 一种三氯蔗糖生产中酸性dmf的回收方法 (Method for recovering acidic DMF (dimethyl formamide) in sucralose production ) 是由 孙多龙 王玉斌 石剑 刘学立 于 2020-05-25 设计创作，主要内容包括：本发明涉及一种三氯蔗糖生产中酸性DMF的回收方法,其特征在于：(1)将酸性DMF与乙醇按流量比1:0.3通入反应器进行反应,83-85℃,反应后pH值6.0~6.4；(2)混合物送入初分塔,进料量0.8-1m<Sup>3</Sup>/h,回流比1：3,釜温78-80℃,顶温48-50℃,负压-0.07~-0.08Mpa；(3)初分塔塔底混合物进行精馏,釜温90-95℃,顶温78-80℃,常压精馏,回流比1:1,塔底得到高纯度DMF,脱轻得乙酸乙酯,回用；(4)初分塔塔顶液混合物常压蒸馏,温度73-75℃,塔顶乙醇回反应器再用,塔底含酸废水送去处理。本发明优点：采用乙醇替代二甲胺反应,DMF产品收率高,副反应少,精馏废液及残渣少；乙醇相比于二甲胺,原料成本更低廉,每年可节约成本100万元,处理成本也降低。(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 0.8-1m 3 H, 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.)

1. 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 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.

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: