Method for recovering DMF from trichloroethane

Abstract

The invention relates to a method for recovering DMF from trichloroethane. The method comprises the following steps: layering a neutralized and desolventized trichloroethane mixed solvent; subjectingDMF and water at an upper layer to DMF rectification to recover DMF; feeding a lower trichloroethane layer into a rectifying tower, condensing a trichloroethane gas phase at the top of the tower intoa liquid state, and feeding the liquid trichloroethane into a condensation reflux tank; partially extracting a part of liquid for reflux, controlling the temperature of the top of the rectifying towerto be no more than 39 DEG C, and extracting trichloroethane with a purity of 99%, a DMF content of less than or equal to 0.5% and a water content of about 1000-5000 ppm from the top of the tower; directly sending the extracted trichloroethane to a dehydration tower for water removal, and after the water content is less than or equal to 300 ppm, directly extracting trichloroethane as a finished product, cooling trichloroethane to normal temperature and returning trichloroethane to a chlorination process for reuse; and extracting and cooling materials at the bottom of the rectifying tower, adding 10% of water, conducting layering, removing DMF from an upper DMF water layer, carrying out rectifying to recover DMF, and returning trichloroethane at a lower layer to the rectifying tower for rectification. According to the invention, trichloroethane recovery efficiency is high, water washing in a traditional process is avoided, the generation amount of wastewater is reduced, steam consumption is reduced, and a large amount of the valuable solvent DMF can be recovered.

Description

technical field [0001] The invention belongs to the technical field of chemical production, and in particular relates to a method for recovering DMF from trichloroethane in the production of sucralose. Background technique [0002] Sucralose is a fresh sweetener, its sweetness is 600-800 times that of sucrose, and its sweetness is similar to that of sucrose. Sucralose is not absorbed by the human body, has no bioaccumulation, and has high safety. The sucrose industry developed rapidly, the number of production enterprises gradually increased, and the output continued to increase. In the production process of sucralose, a large amount of trichloroethane is used as a solvent for the chlorination reaction. As the output increases, the usage of trichloroethane also increases. In the traditional process of sucralose production, the reacted trichloroethane needs to be washed with 1 / 2 of its volume of water, and it needs to be washed three times to remove the DMF and some impuriti...

AI Technical Summary

Problems solved by technology

In the traditional process of sucralose production, the reacted trichloroethane needs to be washed with 1 / 2 of its volume of water, and it needs to be washed three times to remove the DMF and some impurities, until the purity of trichloroethane reaches the requirement Finally, the complex process of dehydrating and rectifying trichloroethane will inevitably produce a large amount of waste water containing low-concentration DMF, and cause waste of valuable solvent DMF

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