A phosgenation reactor and a method for preparing isocyanates using the reactor

Abstract

The invention discloses a phosgenation reactor and a method for preparing isocyanate monomer by using the reactor. The reactor comprises an inner feeding pipe, an outer feeding pipe, a mechanical stirring shaft, a rotating area and a kettle body, and the rotating area Including the support structure, the packing block in the rotating area, the upper discharge device, and the lower discharge device; among them, the inner feed pipe and the outer feed pipe are arranged coaxially from the inside to the outside, and the upper and lower discharge devices are arranged in parallel and pass through the support structure connected with each other, and communicated with the outer and inner feed pipes respectively, the filling block in the rotating area is filled between the upper and lower dischargers, the upper discharger is connected with the mechanical stirring shaft, and the kettle body is provided with a gas phase outlet, a liquid Phase outlet, gas phase inlet, liquid phase inlet. Through the pretreatment of the hydrochloride solution in the reactor, the salt concentration and the quality of the hydrochloride solution are improved, and at the same time, the rapid removal of hydrogen chloride gas during the phosgenation process is achieved, effectively reducing the generation of chlorinated by-products , to reduce the difficulty of product separation.

Description

technical field [0001] The invention relates to a phosgenation reactor and a method for preparing isocyanate using the reactor, more specifically, to a phosgenation reactor and using the reactor to prepare isocyanate monomers through high-temperature salt-forming phosgenation Methods. Background technique [0002] In the prior art, the phosgenation method of preparing isocyanates by reacting organic primary amines with phosgene in an inert solvent is well known. For existing methods, chlorobenzene or o-dichlorobenzene is usually used as a solvent, which is widely used because of its good inertness and solvency, and is very suitable for recovering excess phosgene and separating hydrogen chloride produced . However, amines with high melting points generally have poor solubility in the above solvents, resulting in lower reaction concentrations. In addition, some isocyanate polymers and chlorinated by-products will be produced during the reaction, which will not only reduce t...

AI Technical Summary

Problems solved by technology

However, amines with high melting points generally have poor solubility in the above solvents, resulting in lower reaction concentrations

In addition, some isocyanate polymers and chlorinated by-products will be produced during the reaction, which will not only reduce the yield of the product, but also increase the difficulty of product purification and increase production costs.

[0003] U.S. Patent US2015246873 (A1) provides a method for preparing isocyanate by liquid phase method. High melting point isocyanate is prepared by cold and hot phosgenation. It uses a dynamic mixer to mix amine and solvent to form a suspension and control the particle size. , strengthen the dispersion, thereby reducing the occurrence of side reactions and increasing the yield, but the rapid mixing of solid or liquid suspensions is more difficult, and the minimization of by-products cannot be guaranteed

[0004] Chinese patent CN101638372A uses salt-forming phosgenation to prepare p-phenylene diisocyanate, but its hydrochloric acid needs to be specially prepared, and when forming a salt, it is necessary to dissolve all the amine in a solvent and then pass in hydrogen chloride gas, which can easily cause the amine to be wrapped by hydrochloride , reducing the yield

However, in order to solve the clogging problem and enhance the mixing effect in the process of application, the process needs to be operated at an extremely low concentration of xylylenediamine hydrochloride, and the overall energy consumption is relatively high.

[0006] In the Chinese patent CN102070491A, a centrifugal device is used to concentrate the low-concentration hydrochloride solution for phosgenation reaction, but the salt-forming reaction is still carried out at a low concentration, and the space-time yield of the salt-forming reaction is not improved; in order to reduce the phosgene The hydrogen chloride content in the process is reduced by reducing the reaction pressure, which has no obvious removal effect on hydrogen chloride dissolved in the solvent, and there is a risk of internal leakage blockage, which is not conducive to the long-term stable operation of the device

[0007] Problems existing in the prior art: (1) the salt-forming concentration of amines with high melting point is low, generally between 5wt~15wt%, and the obtained hydrochloride particles are easy to agglomerate, resulting in relatively low space-time yields of salt-forming and phosgenation reactions. Low; (2) due to the presence of hydrogen chloride gas, it is not conducive to the reaction of carbamoyl chloride cracking to generate isocyanate, and will cause the increase of chlorinated by-products, which will not only reduce the reaction yield but also increase the difficulty of product purification in the later stage

[0008] It is necessary to find a way to solve the problems of low salt-forming concentration and easy agglomeration of the obtained hydrochloride solution in the process of preparing isocyanate by salt-forming phosgenation of high-melting point amines. In addition, it is not conducive to the reaction of carbamoyl chloride cracking to generate isocyanate, which also leads to the increase of chlorinated by-products, reduces the reaction yield and increases the difficulty of product purification.

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