Dehydration method during production process of toluene diisocynate

Abstract

The invention belongs to the field of toluene diisocynate production technology and relates to a dehydration method during the production process of toluene diisocynate. Toluenediamine and phosgene have cold light gasification reaction to obtain a mixture flow of carbamyl chloride, amidogen hydrochloride and hydrogen chloride; the mixture flow flows into a phosgenation reaction tower; carbamyl chloride and amidogen hydrochloride react to produce toluene diisocynate and the by-product hydrogen chloride; at the bottom of a hydrogen chloride rectifying tower, the mixture flow of amidogen and hydrogen chloride is divided into two parts, most of the mixture flow returns to the top of the phosgenation reaction tower and serves as the backflow, and the rest of the mixture flow enters into a drain sump containing activated carbon as the catalyst; water and phosgene in the mixture flow react to produce hydrogen chloride and carbon dioxide to remove water in the mixture flow under the function of the activated carbon catalyst; the dehydrated mixture flow enters into the bottom of the phosgenation reaction tower for further rectification and is discharged from the bottom of the phosgenation reaction tower for next step. The dehydration technology is simple and environmentally friendly, the cost is low, and the dehydration effect is excellent.

Description

Technical field: [0001] The invention belongs to the technical field of toluene diisocyanate production, and relates to a process for removing trace water in the production process of toluene diisocyanate, in particular to a dehydration method in the process of producing toluene diisocyanate by high-pressure phosgenation. Background technique: [0002] Toluene diisocyanate (TDI) is an important isocyanate product, which is mainly used in the production of flexible polyurethane foam, polyurethane coating, adhesive, elastomer and polyurethane prepolymer. Most of the existing industrialized production of TDI is Phosgenation method, phosgenation method is divided into normal pressure method and high pressure method. In the high-pressure phosgenation method, toluenediamine and phosgene are first subjected to cold phosgenation reaction in a reactor in the presence of an inert solvent to generate carbamoyl chloride, amino hydrochloride and hydrogen chloride, and then the resulting ...

AI Technical Summary

Problems solved by technology

In the prior art, in order to reduce this kind of corrosion and increase the operating rate, the phosgenation reaction tower, the hydrogen chloride rectification tower and the corresponding pipelines are made of expensive Hastelloy alloys, but this method greatly increases the production cost and the economic benefits are not obvious

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