Phosgenation reactor and method for preparing isocyanate monomer by using phosgenation reactor

Abstract

The invention discloses a phosgenation reactor and a method for preparing an isocyanate monomer by using the phosgenation reactor. The phosgenation reactor comprises an inner material inlet pipe, an outer material inlet pipe, a mechanical stirring rotation shaft, a rotation area and a kettle body, wherein the rotation area comprises a support structure, a rotation area filler block, an upper material outlet device and a lower material outlet device, the inner material inlet pipe and the outer material inlet pipe are coaxially arranged from inside to outside, the upper material outlet device and the lower material outlet device are arranged in parallel, are connected through the support structure, and are respectively communicated to the outer material inlet pipe and the inner material inlet pipe, the rotation area filler block is filled between the upper material outlet device and the lower material outlet device, the upper material outlet device is connected to the mechanical stirringrotation shaft, and the kettle body is provided with a gas phase material outlet, a liquid phase material outlet, a gas phase material inlet and a liquid phase material inlet. According to the present invention, by pre-treating the hydrochloride solution in the reactor, the salt forming concentration and the quality of the hydrochloride solution are improved while the rapid removal of hydrogen chloride gas during the phosgenation is achieved, such that the generation of chlorination by-products is effectively reduced, and the product separation difficulty is reduced.

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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