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Method for continuous removal of phosgene in small-variety isocyanate preparation process

A technology for isocyanate and preparation process, which is applied in the field of continuous removal of phosgene in the preparation process of small varieties of isocyanate, can solve the problems of increasing the load of phosgene removal tower, long operation period, and unstable system, so as to facilitate automatic control and reduce Effects of production cost and shortened operation cycle

Active Publication Date: 2015-02-04
QINGDAO UNIV OF SCI & TECH +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This method has a long operation period, low production efficiency, large energy consumption, and cannot be automatically controlled. The phosgene purged out is not easy to recover, resulting in low phosgene utilization rate, and the purged phosgene directly enters the phosgene absorption tower, which may Break down the tower, causing system instability
Chinese patent CN103073452A discloses a method for removing phosgene in the process of preparing toluene diisocyanate. This method is suitable for a pressurized operating system, but not for a normal-pressure operating system. HCL or CO will increase the load of the phosgene removal tower, making the subsequent phosgene recovery process more difficult, and HCL may also react with isocyanate to form acid chlorides, increasing the generation of by-products

Method used

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  • Method for continuous removal of phosgene in small-variety isocyanate preparation process

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preparation example Construction

[0009] In the preparation process of the small variety of isocyanate in this embodiment, the photochemically reacted material produced by the liquid phase phosgenation reaction of amine and excess phosgene in the photochemical reactor 1, the photochemically reacted material is passed through the phosgene The side or top of the phosgene removal tower 2 is continuously passed into the phosgene removal tower 2 for rectification. The phosgene removal tower 2 is operated at normal pressure (0.8-1.2 bar) and comes out from the top of the phosgene removal tower 2. The mixed gas of solvent and phosgene enters the tower top condenser 3, and the temperature of the tower top condenser 3 is 40°C-60°C, and the non-condensable phosgene and HCL enter the phosgene recovery device 5, and the phosgene recovered by the phosgene recovery device 5 Return to the photochemical reactor for recycling, and the separated HCL is discharged through the tail gas device 6; after the solvent is condensed by t...

Embodiment 1

[0012] This embodiment continuously removes phosgene in the production process of 3-chloro, 4-methylphenylisocyanate, the concentration is 16.7%, the flow rate is 80kg / h amine and toluene mixed solution, and temperature is-10 ℃, flow rate 66kg / h of phosgene is used for cold and hot photochemical reaction. The reacted material contains 3-chloro, 4-methylphenylisocyanate, toluene, phosgene and HCL. The temperature is 105°C and the flow rate is 124kg / h. The phosgene content is 1.3%, and the isocyanate content is 12.1%. The phosgene removal tower 2 continuously enters the phosgene removal tower 2 from the top of the phosgene removal tower 2, and the phosgene removal tower 2 selects normal pressure operation; the temperature control of the top condenser 3 The temperature of the tower kettle 4 is controlled at 115°C; the phosgene separated by the tower top condenser 3 is returned to the photochemical reactor 1 through the phosgene recovery device 5, and the HCL is discharged into the...

Embodiment 2

[0014] In this embodiment, for the continuous removal of phosgene in the production process of n-butyl ester, the mixed solution of amine and xylene with a concentration of 16% and a flow rate of 1670kg / h is mixed with a light solution with a temperature of -10°C and a flow rate of 1680kg / h. The gas is subjected to cold and heat photochemical reaction, and the reacted material contains n-butyl ester, xylene, phosgene and HCL, the temperature is 105°C, the flow rate is 4420kg / h, the content of phosgene is 2.1%, and the content of isocyanate is 8%. The chemical liquid enters the phosgene removal tower 2 continuously from the upper part of the phosgene removal tower 2, and the phosgene removal tower 2 operates under normal pressure; the temperature of the top condenser 3 is controlled at 50°C, and the temperature of the tower kettle 4 is controlled at 139°C The phosgene separated by the overhead condenser 3 is returned to the photochemical reactor 1 through the phosgene recovery d...

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Abstract

The invention belongs to the phosgene removing technical field, and relates to a method for continuous removal of phosgene in a small-variety isocyanate preparation process. A material after a photochemical reaction is continuously introduced into a phosgene removing tower through the side or the tower top of the phosgene removing tower and is rectified, a solvent and phosgene mixed gas going out of the tower top of the phosgene removing tower go into a tower top condenser, phosgene and HCL which cannot be condensed go into a phosgene recycling device, the phosgene recycled by the phosgene recycling device returns to a photochemical reactor for cycle use, and separated HCL is discharged by a tail gas device; the solvent is condensed through the tower top condenser, then reflows to the phosgene removing tower and goes into a reboiler; an ester solution having the phosgene removed in the reboiler is subjected to product synthesis; after the synthesized product is separated, the solvent is distilled and then is recycled for preparing an amine solution. The whole process has the advantages of simple operation, easy control, and convenient realization of automatization control, and reduces the production cost.

Description

Technical field: [0001] The invention belongs to the technical field of phosgene removal, and relates to a method for continuously removing phosgene during the preparation of isocyanate, in particular to a method for continuously removing phosgene during the preparation of small-species isocyanate. Background technique: [0002] Small variety of isocyanate is an important class of organic reaction intermediates, it has a very wide range of uses in industry, agriculture, medicine and health, etc. Small variety of isocyanate includes 3,4-dichlorophenyl isocyanate, 3,5-dichlorophenyl isocyanate, Chlorophenyl isocyanate, 3-chloro, 4-methylphenyl isocyanate, isopropylphenyl isocyanate or n-butyl ester, etc., the existing industrial production of small varieties of isocyanate mainly adopts liquid phase phosgenation method, that is, amine and Excess phosgene reacts in the liquid phase, and excess phosgene needs to be separated for recycling. The traditional phosgene removal method...

Claims

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Application Information

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IPC IPC(8): C07C265/12C07C263/20
Inventor 毕荣山谭心舜郑世清葛纪军曾民成韩传贵张波赵超
Owner QINGDAO UNIV OF SCI & TECH