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Method for producing isocyanates

A technology of isocyanate and product flow, which is applied in the preparation of isocyanic acid derivatives, purification/separation of isocyanic acid derivatives, and preparation of chlorides, etc., which can solve the problems of increased demand for sodium hydroxide solution and high cost

Active Publication Date: 2013-06-05
COVESTRO DEUTSCHLAND AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

The hydrochloric acid formed in this way must subsequently be dissociated in a complex manner into hydrogen chloride gas and water, which entails considerable costs
[0028] In short, it is still necessary to say that the CO-containing 2 The non-selective uptake of chlorine in the purge stream results in an increased demand for sodium hydroxide solution, whereas known prior art methods for removing CO containing 2 The method of selectively absorbing chlorine in the purge stream has many other disadvantages

Method used

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  • Method for producing isocyanates
  • Method for producing isocyanates
  • Method for producing isocyanates

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0125] Example 1 (according to the invention)

[0126] figure 2 It is the basis of simulation.

[0127] By means of stream P16, phosgene in excess of 100% compared to the stoichiometric amount of the primary amine toluene diamine (TDA) contained in stream E1 is fed to reactor A. The reaction for the production of toluene diisocyanate (TDI) was carried out at 150°C and a pressure of 2.6 bar. Most of the unreacted phosgene is taken out as stream P1 together with solvent (o-dichlorobenzene, ODB), TDI and by-product HCl, and cooled to 35°C in B1. The product TDI is withdrawn from B1 in liquid form together with stream P2, and HCl, phosgene and other components leave section B1 in gaseous form with stream P3a. P3a is in contact with stream E7 containing fresh ODB in absorber section B2. In this process, most of the phosgene contained in P3a is absorbed. HCl leaves the absorber in gaseous form together with stream P3b. Among other things, P3b still contains approximately 0.23vol% p...

Embodiment 2

[0134] Example 2 (according to the invention)

[0135] image 3 It is the basis of simulation.

[0136] Example 2 includes the same steps as Example 1, but an additional part of HCl gas is transferred from the absorber B2 and directed to the HCl absorber (not shown). A part of the stream leaving the condensation step I in gaseous form and containing excess CO is further recycled to the reactor H.

[0137] Segments A, B1 and B2 operate as described in Example 1. HCl leaves the absorber in gaseous form together with stream P3b. Among other things, P3b still contains about 0.24vol% of phosgene and about 1.2vol% of N 2 And trace amounts of solvent ODB, etc., where N 2 From the process used to inertize or maintain pressure. However, its CO 2 The content is 1.5 vol%, which is now significantly higher than that of Example 1, because the amount of flushing out of it by returning the material in the condensation step I1 / I2 is less and therefore aggregation occurs. On the other hand, there...

Embodiment 3

[0143] Example 3 (comparative example)

[0144] Figure 4 It is the basis of simulation.

[0145] Example 3 contains the same steps as Example 1, but E is now configured as a distillation column, the purpose is to avoid CO 2 The liquid chlorine and dissolved oxygen are removed from it.

[0146] Segments A, B1, B2, B3, and B4 operate as described in Example 1. HCl leaves absorber B2 in gaseous form together with stream P3b. P3b still contains about 0.22vol% of phosgene and about 1.2vol% of N 2 And trace amount of solvent ODB, etc., where N 2 From the process used to inertize or maintain pressure. Its CO 2 And CO content 0.15vol% (CO 2 ) And 0.03vol% (CO) are much lower than in Example 1, which is due to the distillation of liquid chlorine, which is basically no CO 2 It is sent to step H of phosgene preparation together with stream P9 without oxygen.

[0147] The gas stream P3b is compressed to 6 bar in the compressor B3 and introduced into the purification section B4 as a stream P3c....

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Abstract

The invention relates to a process for the preparation of isocyanates in a system network comprising an isocyanate production plant, a chlorine production plant and a phosgene production plant, in which carbon dioxide formed as a by-product is partially to completely condensed out with the gaseous chlorine formed in the chlorine production plant and enters into the phosgene preparation process and, after the preparation of phosgene, the predominant part of the carbon dioxide formed is thereby sluiced out of the system network in gaseous form.

Description

Technical field [0001] The present invention relates to a method for preparing isocyanate, and more specifically to a method for preparing isocyanate in a system network. Background technique [0002] The present invention relates to a method for preparing isocyanate in a system network, which includes isocyanate production equipment, chlorine production equipment, and phosgene production equipment, in which carbon dioxide formed as a by-product is partially to completely formed from the chlorine production equipment The gaseous chlorine is condensed out and enters the phosgene preparation process. After the phosgene is prepared, the main part of the formed carbon dioxide is flushed out of the system network in gaseous form. [0003] In the process of preparing isocyanates by phosgenation of the corresponding primary amines, hydrogen chloride gas is formed as a by-product. Hydrogen chloride gas usually carries gaseous material pollutants from phosgene synthesis or other process st...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07C263/10C07C265/14C01B7/04
CPCC07C263/10C07C265/12C07C263/18C07C265/14
Inventor J.金特鲁普P.莱纳E.雅各布斯A.佐佩K.维尔纳
Owner COVESTRO DEUTSCHLAND AG
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