Desalting purification method for water-washing extraction water phase in RT base production process

Abstract

The invention discloses a desalting purification method for a water-washing extraction water phase in an RT base production process, and belongs to the technical field of fine chemical engineering. The desalting purification method for the water-washing extraction water phase in the RT base production process comprises the following steps: adding aniline into the washing-extraction water phase inthe nitrobenzene method RT base production process, performing uniform mixing, standing the obtained solution for layering, and separating out the water phase; and carrying out reduced pressure distillation on the water phase separated after aniline extraction at 80 DEG C or below, stopping heating when fractions are basically not discharged, performing cooling recrystallization, carrying out solid-liquid separation to obtain needle-like tetramethylammonium hydroxide crystals, and finally adding distilled water into the tetramethylammonium hydroxide crystals to prepare a solution with the massfraction of 20-25% for recycling. Compared with existing treatment methods, the extraction, concentration and recrystallization method for desalting purification of the water-washing extraction waterphase (impurity-containing tetramethylammonium hydroxide aqueous solution) in the RT base production process has the advantages of effective reduction of the treatment difficulty, obvious desalting effect, no generation of waste residues, economical property and environmental protection.

Description

technical field [0001] The invention relates to the technical field of fine chemicals, in particular to a method for desalting and purifying the aqueous phase by washing and extracting water in the RT base production process. Background technique [0002] The production of 4-aminodiphenylamine (RT base) by the nitrobenzene method is the most widely used process at home and abroad at present, and it is a green and clean production process due to the substantial reduction of the three wastes. [0003] However, this method also has some disadvantages: [0004] 1) Tetramethylammonium hydroxide, an organic base catalyst commonly used in the condensation process in production, is easy to decompose when the temperature is higher than 80°C, and it will react with CO in the air 2 The reaction will generate carbonates. Excessive carbonate content in the system will cause more adverse effects on production. It is necessary to regularly deal with the carbonates in the water extraction ...

AI Technical Summary

Problems solved by technology

However, it is necessary to strictly control the amount of condensation and dehydration when using NaOH to desalt, otherwise sodium salt will be introduced into the system, causing blockage of the condensation system pipeline, increasing the specific gravity of the water in the washing process, and increasing the side reactions of the system; in addition, it is difficult to filter the condensation liquid after desalting with NaOH , cannot be carried out continuously, and the environment for cleaning filter residues is harsh

with Ca(OH) 2 The amount of desalination is relatively large, because Ca(OH) 2 Slightly soluble in water, it is difficult to reduce the carbonate content to less than 1% during production, and a large amount of lime waste residue will be generated after treatment, which is low in efficiency, and calcium salts will also be introduced into the system