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Method for treating waste DMF in sucralose production

A technology of sucralose and a treatment method, which is applied in chemical instruments and methods, preparation of organic compounds, chemical industry and other directions, can solve the problems of reduced DMF recovery, accelerated DMF decomposition, and high catalyst consumption, and achieves the promotion of positive progress, The effect of improving yield and high purity

Active Publication Date: 2021-11-12
ANHUI JINGHE IND
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] Patent Publication No. CN106831471A discloses the use of rectification towers to carry out reactive distillation to refine DMF, but the NKC-9 catalyst is used, which has the problem of easy catalytic deactivation
Patent Publication No. CN109503409A uses sulfuric acid as a catalyst, but sulfuric acid will accelerate the decomposition of DMF, and the dimethylamine produced will react with sulfuric acid to generate dimethylamine sulfate that does not have catalytic ability, resulting in more catalyst consumption, reduced DMF recovery and formation of useless waste salt

Method used

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  • Method for treating waste DMF in sucralose production
  • Method for treating waste DMF in sucralose production

Examples

Experimental program
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Effect test

Embodiment 1

[0022] In this embodiment, the vacuum rectification tower, the methanol rectification tower, and the reactive rectification tower all use single-column batch rectification, and the packing is 50 cm high, 4 cm in diameter, and filled with glass springs;

[0023] (1) Send 2500 mL of waste DMF (10% acetic acid, no more than 1% water, DMAC, and tetramethylurea, and the rest is DMF) discharged from the bottom of the deacidification tower in the sucralose DMF recovery section to vacuum distillation The tower is subjected to vacuum rectification, and the low-boiling impurities (methyl acetate, methanol) are distilled out under normal pressure. The temperature of the kettle remains unchanged, the pressure in the tower drops to 30 kPa, and the water is distilled out. The volume of low-boiling impurities and water is 21mL; Reduce the pressure to 7-9 kPa, control the top temperature of the vacuum distillation tower at 75-80°C to distill out a total of 1700 mL of product DMF (purity 99.8%)...

Embodiment 2

[0027] The bottoms of the reactive distillation tower in Example 1 are returned to the system to carry out rectification under reduced pressure again, and the specific operation steps are as follows:

[0028] Mix 1600mL of the bottom fraction of the reactive distillation tower and 1000mL of waste DMF discharged from the bottom of the deacidification tower and put it into the vacuum rectification tower, repeat the operation steps of Example 1 to obtain 130 mL of low-boiling impurities, which are combined into methanol and acetic acid Non-azeotropic mixture of methyl esters; distilled water 170 mL, product DMF 1750 mL (purity 99.72%), acidic azeotrope 650 mL, bottom liquid 70 mL.

[0029] The content (GC) of each step product of embodiment 2 is as follows:

[0030] Element Methyl acetate Methanol DMF DMAC Tetramethylurea Acetic acid retention time (min) 2.8 3.4 9.8 11.9 13.8 14.4 Waste DMF(%) 84.3 4.1 1.86 8.7 Reactive distillat...

Embodiment 3

[0032] In this embodiment, the vacuum rectification tower, the methanol rectification tower, and the reactive distillation tower all adopt continuous rectification, and the vacuum rectification tower is replaced by a light removal tower, a weight removal tower and a refining tower connected in sequence. The specific process see process figure 2 :

[0033] (1) The waste DMF discharged from the bottom of the deacidification tower in the sucralose DMF recovery section (9% acetic acid, water, DMAC, and tetramethylurea do not exceed 1%, and the rest is DMF) is mixed with the bottom fraction of the reactive distillation tower after 0.9 m 3 The amount per hour is pumped into the middle of the light removal tower (the theoretical plate number of the light removal tower is 25, and the feed position is the 18th plate), and the top temperature of the light removal tower is controlled at 85°C, the pressure inside the tower is 30 kPa, and the top temperature is 85°C. The reflux ratio is...

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Abstract

The invention relates to a method for treating waste DMF in sucralose production, and the method is characterized by comprising the following steps: (1) feeding waste DMF discharged from the bottom of a deacidification tower into a vacuum rectification tower for vacuum rectification, feeding non-condensable gas extracted from the top of the rectification tower into a methanol rectification tower for rectification again, and feeding methanol recovered by rectification into a reaction rectification tower for reaction; (2) feeding an acidic azeotrope extracted from the lower part of the reduced-pressure rectifying tower into a reactive rectifying tower; controlling the volume ratio of the acidic azeotrope to methanol to be 1: (0.9-1.5), returning reaction liquid at the bottom of the reactive distillation tower to the vacuum distillation tower, and returning a mixture of methanol and methyl acetate distilled from the top of the reactive distillation tower to the methanol distillation tower. The method has the advantages that the generated methyl acetate is removed through reactive distillation, the reaction is promoted to proceed forwards, and the yield is increased; acetic acid contained in the raw materials is used as a catalyst, so that the problem of inactivation does not need to be worried about, and excessive decomposition of DMF is avoided; the prepared methyl acetate is high in purity, the product DMF is high in purity, and the production cost of sucralose is reduced.

Description

technical field [0001] The invention belongs to the technical field of chemical production, and in particular relates to a treatment method for waste DMF in sucralose production. Background technique [0002] In the production process of sucralose, DMF (N,N-dimethylformamide) is used as a solvent in the chlorination process, and the Wich's reagent in the chlorination process of sucralose needs DMF to form, So DMF is also an indispensable participant in the chlorination process. Under the existing process conditions, it is inevitable that a large amount of waste DMF will be produced. The waste DMF discharged from the bottom of the deacidification tower in the sucralose DMF recovery section is also called acidic DMF because the important impurity acetic acid contained in it makes it acidic. Acetic acid and DMF can form an azeotropic mixture with a higher boiling point than pure DMF, so it cannot be separated simply by distillation. Waste DMF usually also contains a certain ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C231/24C07C233/03C07C67/08C07C67/54C07C69/14
CPCC07C231/24C07C67/08C07C67/54C07C233/03C07C69/14Y02P20/10
Inventor 张正颂沈东东仇鑫慈昊
Owner ANHUI JINGHE IND
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