A kind of preparation method of dl-p-hydroxydihydantoin

Abstract

The invention discloses a preparation method of DL-p-hydroxytrihydantoin. Phenol, sulfuric acid with a mass concentration of 98% and water were added to the reactor, and a certain concentration of sulfuric acid aqueous solution was used to catalyze the para-activity of phenol, then the catalyst with a total molar weight of 1 / 3 was added after heating, and urea was added. Add a certain amount of water; slowly add the total molar amount of 1 / 3 glyoxylic acid aqueous solution, the dropwise addition is completed, add the remaining total molar amount of 2 / 3 catalyst, after stirring, the reaction temperature is increased, and the remaining total molar amount is added dropwise. The molar weight is 2 / 3 glyoxylic acid aqueous solution, the dropwise addition is completed and the insulation is completed, and after cooling, the insulation is centrifugal suction filtration to retain the solid; the surface of the solid material is washed with hot water, washed to neutral pH, and dried. The invention improves the product yield and purity, reduces the phenol content in the mother liquor, reduces the amount of waste water, relieves the pressure of environmental protection, effectively suppresses the generation of the largest single impurity, and improves the product yield and quality.

Description

technical field [0001] The invention relates to the technical field of DL-p-hydroxydihydantoin, in particular to a preparation method of DL-p-hydroxydihydantoin. Background technique [0002] At present, most of the domestic DL-p-hydroxybenzene hydantoin production process adopts the hydrochloric acid synthesis process route, which has the following defects: 1. High temperature reaction is required in the production process, which produces a large amount of harmful HCL gas, which causes corrosion to production equipment , the maintenance cost is high. The poor operating environment of workers causes great pressure on environmental protection. 2. Hydrogen chloride gas is easy to volatilize, resulting in unstable concentration of hydrochloric acid in the reaction solution, and large fluctuations in product content and yield. 3. The amount of wastewater is large, and the cost of subsequent wastewater treatment is high. [0003] There are patent reports that the dilute sulfur...

AI Technical Summary

Problems solved by technology

[0002] At present, most of the domestic DL-p-hydroxyphenylhydantoin production process adopts the hydrochloric acid synthesis process route, which has the following defects: 1. High temperature reaction is required in the production process, and a large amount of harmful HCL gas is produced, which causes corrosion to production equipment , high maintenance cost

Poor operating environment for workers causes great pressure on environmental protection

2. Hydrogen chloride gas is easy to volatilize, causing the concentration of hydrochloric acid in the reaction solution to be unstable, and the product content and yield fluctuate greatly

3. The amount of wastewater is large, and the cost of subsequent wastewater treatment is high

And many patents also mention that the reaction yield can be improved by adding some catalysts, such as adding solid acid, addition phase transfer catalyst, etc., which are only reflected in the dilute sulfuric acid or dilute hydrochloric acid system, and have not solved the problem of large amount of wastewater from the root cause. question