Method for preparing isocyanate by means of atomizing type gas-liquid two-phase phosgenation

Abstract

The invention belongs to the technical field of chemical products and relates to a method for preparing isocyanate by means of atomizing type gas-liquid two-phase phosgenation. The method includes: feeding liquid-phase amine and high-temperature gas-phase phosgene into a reactor, heating to an overheat temperature of 5-50 DEG C before mixing, mixing and reacting to obtain a mixture; quenching the mixture with inert solvent, and entering an atomizing type reactor for reacting to generate isocyanate, wherein liquid amine or mixture solution can be quickly dispersed into liquid drops with the diameter of 0.01-3mm by the reactor, a nozzle of the reactor is in a venture or laval structure, and the liquid-phase amine enters from the nozzle or a lateral annular clearance of the nozzle; and finally the generated isocyanate is subjected to removal of phosgene, HCl and solvent and rectification and purification to obtain the product isocyanate. The process is scientific and reasonable in step and reliable in principle, and equipment is simple in structure, low in manufacturing cost, safe and reliable in operation, high in production efficiency and environment-friendly in production.

Description

Technical field: [0001] The invention belongs to the technical field of chemical product preparation, and relates to a method for preparing isocyanate, in particular to a method for preparing isocyanate by spray-type gas-liquid two-phase phosgenation. Background technique: [0002] At present, the industrial production of isocyanate is obtained by reacting amine with excess phosgene in the presence of an inert solvent, that is, phosgenation reaction; phosgenation can be divided into liquid-phase phosgenation and gas-phase phosgenation. The so-called liquid phase method and gas phase method are classified according to the phase state of the amine material before entering the reactor. The process of TDA in the supercooled liquid state of the reactor is called the liquid phase phosgene method, and the process of entering the reactor in the gas state is called the gas phase. Phosgenation. Liquid phase phosgenation is currently the most common isocyanate production process, but ...

AI Technical Summary

Problems solved by technology

Liquid phase phosgenation is currently the most common isocyanate production process, but the liquid phase phosgenation production method has two disadvantages: one is the use of highly toxic phosgene, especially the large excess of phosgene in the production process, which makes The safety of the process is reduced, and there are potential safety hazards; the second is the existence of excess solvent and phosgene, which makes the energy consumption of the whole process very high, which increases the product cost and pollutes the environment, which is not conducive to energy saving and emission reduction; in order to solve The disadvantage of high energy consumption in the liquid phase method, people only proposed the gas phase phosgenation method, the material residence time of the gas phase reaction is shorter, which can increase the output per unit time, obtain a greater space-time yield, thereby reducing investment costs; EPA593334 patent A process is disclosed for the preparation of aromatic diisocyanates in the gas phase by reacting diamines with phosgene in a tubular reactor which has no dynamic components and whose walls taper along the longitudinal axis; the reactor in this process has no Moving parts can reduce the leakage of phosgene; EPA699657 patent discloses a method for preparing aromatic isocyanate in the gas phase. The reaction of appropriate diamine and phosgene is completed in two parts. The first part accounts for 20% of the total reaction volume. - 80% mixed system, the second part is a reaction system close to plug flow accounting for 80-20% of the total reaction volume; EP289840 patent discloses the preparation of diisocyanates by phosgenation in the gas phase

The microstructure mixer can strengthen the mixing reaction of amine and phosgene, but this microstructure mixer may block the mixer even if a very small solid; CN101429138A patent discloses a method for preparing isocyanate, which method comprises primary amine, light The gas and the inert gas are preheated to a temperature 5-100°C higher than the boiling point of the primary amine, and then the preheated primary amine and the inert gas are mixed to obtain a primary amine mixed gas, and the primary amine mixed gas and phosgene are mixed in the mixer Mix and carry out a preliminary reaction to obtain a preliminary reaction mixture, and the preliminary reaction mixture enters a tubular reactor for further reaction; gas-phase phosgenation has its own disadvantages: one is that the large-scale vaporization process of amine consumes a lot of energy and also causes amine Second, because the gas phase reaction speed is very fast and the temperature is very high, coke residue is often generated during the reaction process, which reduces the reaction yield and may block the equipment; the third is the high temperature gas phase reactant after the reaction Requires rapid condensation into a liquid phase, requires the addition of an inert solvent and consumes cooling capacity

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