Photochemical kettle for refluxing phosgene at bottom and method for preparing hexamethylene diisocyanate

Abstract

The invention relates to production equipment and a method for fat diisocyanate, in particular to production equipment and a method for preparing hexamethylene diisocyanate by using a phosgene method. A photochemical kettle for refluxing phosgene at bottom is characterized in that a phosgene condensate reflux pipeline enters from the bottom of a reaction kettle, wherein a check valve (4) is additionally arranged on the inlet part; all the condensed liquid-phase phosgene refluxes into a reaction liquid system from the bottom of a thermal photochemical kettle (2) through the check valve (4); only the material in the reflux pipeline can enter the reaction kettle, but the material in the reaction kettle cannot enter the reflux pipeline, so that reaction is prevented from occurring in the pipeline. The phosgene consumption after improvement is 1.5-2 times the theoretical using amount of the phosgene in photochemical synthesis reaction. The method can be applied to a chemical device of which an excess amount of low boiling point substance participates in reaction, the reaction system temperature is relatively higher and an excess amount of substance is required to be recovered and fed back for recycling.

Description

technical field [0001] The present invention relates to the production equipment and method of aliphatic diisocyanate, in particular to the production equipment and method of preparing hexamethylene diisocyanate by phosgene method. Background technique [0002] As an important class of organic chemical intermediates, isocyanates are widely used in industry, agriculture, medicine and health. These compounds are widely used in the synthesis of polyisocyanates, polyurethanes, polyureas, polymer adhesives, insecticides, herbicides, etc. Hexamethylene diisocyanate (1,6-hexamethylene diisocyanate, English abbreviation HDI) is the aliphatic isocyanate with the largest demand in the polyurethane industry at present, and has become the successor toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI ), polymethyl polyphenylene isocyanate (PAPI), isocyanate species with large demand, mainly used in the production of automotive OEM coatings and repair paints, aircraft OEM coati...

AI Technical Summary

Problems solved by technology

Usually, the condensed reflux liquid is designed to enter from the top of the reactor. In this case, the problem is that the gas phase of the reactor has a certain temperature, especially the temperature of the thermal photochemical reactor is higher, and the boiling point of phosgene is low, so it flows back into the reactor quickly. vaporized

As a result, on the one hand, the amount of phosgene that actually enters the reaction liquid phase for circulation is small, and on the other hand, the vaporized phosgene enters the condenser, and this cycle increases the load of the condenser and reduces the condensation efficiency. As a result, a large amount of excess phosgene is pumped into the tail gas treatment system for destruction treatment together with hydrogen chloride, which leads to a large consumption of phosgene and an increase in cost

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