Method for recycling phosgene in continuous production process of toluene di-isocyanate

Abstract

The invention discloses a method for recycling phosgene in a continuous production process of toluene di-isocyanate, comprising the following steps: importing gas streams generated in the preparationprocess of the toluene di-isocyanate to the bottom of a first phosgene absorption tower and leading in inert organic solvent to the first phosgene absorption tower to absorb; separating the gas streams exhausted from the top of the first phosgene absorption tower by a phosgenation reaction flash separator lead in by a liquid ejector pump and leading the acquired gas streams into a second phosgeneabsorption tower; leading part of tower bottom absorption solution in the first phosgene absorption tower which is pressurized by the tower bottom liquid pump of the first phosgene absorption tower tothe second phosgene absorption tower and leading in inert organic solvent to the second phosgene absorption tower to absorb; and reusing the phosgene inert organic solvent solution acquired from thebottom of the second phosgene absorption tower to the continuous production process of the toluene di-isocyanate. The method reduces the investment on a large-scale compressor and reduces the cost onoperation and maintenance, thereby achieving the purpose of recycling the phosgene at a lower cost.

Description

technical field [0001] The invention relates to a method for recovering phosgene in the continuous production process of toluene diisocyanate. Background technique [0002] Polyurethane materials have the characteristics of convenient modification, easy processing and molding, and simple construction, and are extremely widely used in various fields such as heat insulation, shockproof, sound insulation, cushion materials, packaging, and light structures. Isocyanate is an important monomer raw material in the polyurethane industry. The method of preparing isocyanate by phosgenation of primary amine has been reported many times in patents, and has been carried out on a large scale in industry, especially aromatic isocyanate TDI (toluene diisocyanate), The reactions that may occur during its preparation are as follows: [0003] [0004] [0005] TDI+urea→TDI biuret (7) [0006] TDI+TDI biuret → polyurea (8) [0007] Reaction (1), (2) is the main reaction to generate iso...

AI Technical Summary

Problems solved by technology

However, due to the high excess rate of phosgene, resulting in a large flow of gas rich in phosgene, coupled with the complexity of the phosgenation reaction system and the high toxicity of phosgene itself, the selection of large compressors The harsh requirements of the operation and operation make the phosgene recovery process using the compressor high in cost, poor in operation stability and high in danger

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