Method for synthesizing 4,6-diamino resorcinol dihydrochloride (DAR)

Abstract

The invention discloses a method for synthesizing 4,6-diamino resorcinol dihydrochloride (DAR). The method for generating and producing DAR comprises four links of nitratlon reaction, alcoholysis, reduction and acidification, and the purity of products can meet the synthesis of PBO (poly (p-phenylenebenzobisoxazole) fiber. Compared with the prior art, the invention has the advantages of simpleness of synthesis and high reaction efficiency. A cheap selenium catalyst is adopted in the step with greatest difficulty and highest reaction cost, the selectivity of reaction is as high as 99 percent, and the reaction yield in the step is almost quantified. Crucially, the catalyst can realize multiple circulations by simple filtration. The production of by-products and isomers is reduced in the reaction process, and the purity of a final target compound 4,6-diamino resorcinol reaches 99,9 percent. The method disclosed by the invention has the advantages of simple whole process and low cost, meets the requirement of industrial production and is expected to realize industrialized application.

Description

technical field [0001] The invention relates to a method for synthesizing 4,6-diaminoresorcinol hydrochloride. Background technique [0002] 4,6-Diaminoresorcinol and its salts (abbreviated as DAR) are the starting materials required for the synthesis of poly-p-phenylenebenzobisoxazole (abbreviated as PBO) (see Macromolecules 1981, 14, 915). PBO can be processed into high-strength fibers with high elastic modulus. Because of its good heat resistance, high strength and good wear resistance, it is widely used in heat-resistant reinforced materials and textiles, military supplies, aerospace, industrial Production, sports equipment and other fields. PBO fiber is known as "the super fiber of the 21st century", the tensile strength can reach 5.8GPa, the tensile modulus is 380GPa, and the density is only 1.56g / cm 3 , The thermal decomposition temperature reaches 670 degrees. The structural formula of DAR is as follows: [0003] [0004] So far, there are many methods for syn...

AI Technical Summary

Problems solved by technology

Among them, the overwhelming majority of this step of nitro reduction is to use noble metal reducing agents (such as patents CN1074410C, CN101279924A, CN1762981A, CN101092367A, CN1450050A, CN101250118A, US5371291, US5399768, US5414130, US6222074B1), Pt / C / C / C Ru / C, etc., here not only has the disadvantages of high catalyst cost, but also involves the issue of how to effectively recycle the catalyst

Especially for molecules containing chlorine, it is necessary to add certain dechlorination accelerators in the reduction step, such as ammonium acetate or ammonium formate (such as patent CN1762981A), which further increases the cost of the reaction

The difference is that the patent CN101100654A involves the use of engineering bacteria to catalyze DAR. Although this reaction route avoids the use of noble metal catalysts and autoclave devices, it has high environmental requirements for large-scale production and is difficult to industrialize.

US5892118 mentions that the final product is obtained by forming hydroxime followed by Beckmann rearrangement reaction, but the cost of the reagents used in the reaction is relatively high, and the yield of the reaction is low, so it is difficult to apply to industrial production

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