Process for separating acetic acid from DMAC azeotrope

Abstract

The invention relates to a purification and recovery process of a dimethylacetamide (DMAC), and aims to provide a process which is characterized by simple process, lower treatment cost and effectively usable recovered substances. The technical scheme is as follows: the process for separating acetic acid from DMAC azeotrope comprises the following steps that: (1) weak alkaline resin is adopted to absorb the acetic acid; absorbent resin DMAC eluting water is added into the DMAC azeotrope material to be diluted to the material which contains 5 to 90 percent of water, and then injected into a columnar container filled with weak alkaline resin to absorb the acetic acid therein; (2) the content of the acetic acid of the water containing DMAC, and if the acid is removed by more than 95 percent relative to the DMAC azeotrope material, the material is conveyed to a distillation tower to be refined and recovered and the other material is absorbed again to remove the acetic acid until 95 percentof acid is removed, and the material is conveyed to the distillation tower to be refined and recovered; and (3) according to different groups contained in the weak alkaline resin, different regeneration methods are adopted; and the resin after regeneration is used for absorbing acetic acid again in step (1).

Description

technical field [0001] The invention relates to a process for purifying and recovering solvents, in particular to a process for purifying and recovering dimethylacetamide (DMAC). Background technique [0002] DMAC (dimethylacetamide) is recycled as a solvent in the production of spandex (the production process uses a distillation tower to recover), and its decomposition product, acetic acid, will slowly accumulate until it becomes the highest azeotrope (about 15% of acetic acid, dimethylacetamide DMAC waste in the state of amide about 85%). The treatment of these wastes has always been a difficult point, because the existing distillation and refining equipment cannot be used for separation, and usually these wastes can only be discharged and discarded as fuel. There are also some manufacturers who add a large amount of water to the waste to dilute it to 60-80% of the water content, add sodium hydroxide to neutralize the pH, and then enter the vacuum evaporator with stirring...

AI Technical Summary

Problems solved by technology

The treatment of these wastes has always been a difficult point, because the existing distillation and refining equipment cannot be used for separation, and usually these wastes can only be discharged and discarded as fuel

There are also some manufacturers who add a large amount of water to the waste to dilute it to 60-80% of the water content, add sodium hydroxide to neutralize the pH, and then enter the vacuum evaporator with stirring to evaporate and recover the water-containing DMAC. At the same time, it will produce DMAC containing more The gray-black anhydrous sodium acetate powder of impurities; however, these sodium acetates cannot be recycled and must be paid for by a professional environmental protection company; and during neutralization, it is difficult to control the acid content of 0.2-1.0% at the end point, and the partial acid removal effect is not good. Good (acid removal is not complete, only 95-70%), alkaline DMAC decomposes more, increasing the difficulty of refining; in addition, the equipment processing capacity is low; steam consumption is large, and the processing cost is high