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

Abstract

The invention discloses a method for recovering phosgene in continuous production process of toluene di-isocyanate, comprising the following steps: importing a gas stream with an absolute pressure of0.08-0.2 MPa, which is generated in a preparation process of the toluene di-isocyanate, into the bottom of a first phosgene absorption tower and leading inert organic solvent into the first phosgene absorption tower to absorb; leading part of tower bottom absorption liquid in the first phosgene absorption tower into a second phosgene absorption tower after being boosted by a tower bottom liquid pump; importing another gas stream with the absolute pressure of 0.5-0.8 MPa, which is generated in the preparation process of the toluene di-isocyanate, into the second phosgene absorption tower, and continuing absorbing through adding the inert organic solvent from the top of the second phosgene absorption tower; and reusing the phosgene inert solvent solution acquired from the bottom of the second phosgene absorption tower in the continuous production process of the toluene di-isocyanate. The method avoids using large-sized compressors, reduces the cost on operation and maintenance and achieves the purpose for recovering the phosgene at lower cost.

Description

technical field [0001] The invention relates to a method for recovering phosgene in the continuous preparation process of toluene diisocyanate. Background technique [0002] Polyurethane materials have the characteristics of convenient modification, easy processing and molding, and simple construction. They are 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 applied 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 isocyanate, and ...

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 brought by 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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