Method for recycling chloroform in process of producing methyl isocyanate

Abstract

The invention provides a method for recycling chloroform in a process of producing methyl isocyanate. The methyl isocyanate is prepared by reacting phosgene with monomethylamine to generate methylaminoformyl chloride, and decomposing methylaminoformyl chloride by taking chloroform as a solvent. The method for recycling chloroform in the process of producing methyl isocyanate is characterized by comprising the following steps: cooling decomposed tail gas to 30-40 DEG C by a cooler, then introducing the tail gas into a layering device, layering chloroform and hydrochloric acid in the tail gas in the layering device, enabling chloroform with high specific gravity to flow into a chloroform receiving kettle, receiving and circulating the chloroform for producing methyl isocyanate, and independently recycling hydrochloric acid with low specific gravity. The tail gas generated in the process of producing methyl isocyanate firstly flows through a falling-film absorption tower, HCl is absorbed into water, and then chloroform is quickly precipitated in a hydrochloric acid solution, so that the layering of hydrochloric acid and chloroform in the layering device is facilitated, and further hydrochloric acid and chloroform can be independently recycled; the recycled chloroform can be used for producing methyl isocyanate again; plenty of cost can be reduced. The method is simple and high in practicability.

Description

technical field [0001] The invention relates to the field of methyl isocyanate production methods, in particular to a method for recovering chloroform in the process of producing methyl isocyanate. Background technique [0002] The domestic production method of methyl isocyanate is generally at a temperature of 250-260 °C, phosgene reacts with monomethylamine to generate methylcarbamoyl chloride CH 3 After NHCOCl, it is obtained by decomposing it with chloroform as a solvent. The equation of the decomposition reaction is as follows: [0003] [0004] This method needs to use a large amount of chloroform as solvent in the production process. A large amount of chloroform and hydrochloric acid are included in the tail gas after the reaction is completed. Because chloroform is easy to produce highly toxic phosgene when exposed to light, the existing tail gas treatment method generally uses water to dissolve HCl and destroy the generated phosgene, and only recycles HCl hydro...

AI Technical Summary

Problems solved by technology

Because chloroform is easy to produce highly toxic phosgene when exposed to light, the existing tail gas treatment method generally uses water to dissolve HCl and destroy the generated phosgene, and only recycles HCl hydrochloric acid aqueous solution

However, this method causes a large amount of waste of chloroform, and the amount of chloroform that needs to be used in the production of methyl isocyanate increases greatly

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