Method for preparing 5-amino benzimidazolone with high purity by catalytic hydrogenation

Abstract

The invention discloses a method for preparing 5-amino benzimidazolone with high purity by catalytic hydrogenation. The method comprises the following steps of: sequentially adding 5-nitrobenzimidazole, methanol and a nickeliferous catalyst into a high-pressure reaction kettle; replacing gas in the reaction kettle with hydrogen three times; pressurizing the hydrogen to 0.1-4MPs; raising the temperature to 25-100 DEG C; continuously hydrogenating and reducing for 2 hours; filtering reaction liquid; recovering methanol and recrystallizing the reaction liquid to obtain 5-amino benzimidazolone of which the color ranges from white to creamy white. The method has the advantages of low pollution, short production cycle, low energy consumption and high quality, the yield of the product is more than 90 percent, and the quality is more than 99 percent.

Description

technical field [0001] The invention relates to a preparation method of benzimidazolone derivatives, in particular to a method for preparing high-purity 5-aminobenzimidazolone by catalytic hydrogenation. Background technique [0002] 5-aminobenzimidazolone, the molecular formula is C 7 h 7 N 3 O, usually a white crystal, will be slightly reddish in the air because the amino group is easily oxidized by the air. It is the main intermediate for the synthesis of benzimidazolone pigments. Benzimidazolone pigments are a widely used high-grade azo type Organic pigments with bright colors and high tinting strength. The 5-aminobenzimidazolone molecule contains cyclic phthaloamino group (-NHCONH-) which is easy to form intermolecular and intramolecular hydrogen bonds, so that the pigment has excellent performance and is used in paints, coatings and plastics industries. [0003] At present, industrial production of 5-aminobenzimidazolone is obtained by reducing 5-nitrobenzimidazolo...

AI Technical Summary

Problems solved by technology

[0003] At present, industrial production of 5-aminobenzimidazolone is obtained by reducing 5-nitrobenzimidazolone. The 5-nitrobenzimidazolone raw material will be added to the kettle, and iron powder or sodium sulfide will be used as a reducing agent. Under acidic conditions at 80-90°C, after reacting for 8-9h, alkalization, cooling and centrifugation to obtain the crude product, and finally recrystallization to obtain the fine product, the yield is about 80%, and the purity is 98%-99%. During the reduction reaction, a large amount of organic waste water and waste residue will be produced, which will cause difficulties in the separation and purification process of the subsequent target product