Method for synthesizing 3,5-diamido benzoic acid by industrial continuous hydrogenation

Abstract

The invention discloses a method for synthesizing 3,5-diamido benzoic acid by industrial continuous hydrogenation. The method comprises the following steps: by taking m-dinitrobenzoic acid and hydrogen as raw materials and water as a reaction solvent, adding water and a catalyst in a reduction kettle, in addition, respectively adding the raw material, namely m-dinitrobenzoic acid and hydrogen for reduction reaction; carrying out further reaction on a reaction liquid in second and third reduction kettles until the conversion rate of the raw materials reaches 100%; and then crystallizing the reaction liquid so as to obtain the product 3,5-diamido benzoic acid. In the method, three reduction kettles which are successively connected are adopted so as to complete the reduction reaction, the contact time of the raw materials is long, the conversion rate of the raw materials can reach 100%, the appearance of the obtained product is of grey white powder, the chromatograph purity of the product is above 99%, the content of the product is above 95%, and the yield of the product is above 97%.

Description

technical field [0001] The invention relates to a preparation method of 3,5-diaminobenzoic acid, in particular to a method for industrial continuous hydrogenation synthesis of 3,5-diaminobenzoic acid, which belongs to the technical field of organic synthesis chemistry. Background technique [0002] 3,5-Diaminobenzoic acid is an important class of dyes and pharmaceutical intermediates. Many high value-added downstream products can be developed using it as raw materials. A series of yellow reactive dyes derived from it can be used as deep yellow dyes or as yellow components in black dyes, and are currently in great demand in the market. 3,5-diaminobenzoic acid is generally obtained from 3,5-dinitrobenzoic acid through reduction reaction. There are three ways to prepare 3,5-diaminobenzoic acid by reducing 3,5-dinitrobenzoic acid in the literature: iron powder reduction, hydrazine reduction and hydrogenation reduction. The production of 3,5-diaminobenzoic acid by the iron powd...

AI Technical Summary

Problems solved by technology

Although it is recorded in the description that the product purity is as high as 95%, and the yield is as high as more than 96%, there is no sufficient record in the examples of this patent on the use of activated carbon catalysts to prepare the relevant data of m-diaminobenzoic acid, and the description does not disclose this technology. The detailed substantive content of the scheme, and the method recorded in this patent is only in the small test stage and is not suitable for industrialized large-scale production

In addition, this patent also has the following deficiencies: 1. The batch production process is adopted, and the operation procedure is cumbersome, and the operator must be on site at all times, so there are human safety hazards, and the batch production needs to be replaced every time, and the replacement needs to consume a certain amount of nitrogen and hydrogen. , and part of the solvent will be brought into the air, resulting in pollution; 2. The use of organic solvents such as methanol or ethanol, which are extremely volatile, flammable and explosive solvents, have certain pollution to the air or surface water, and the product purity and yield relatively low

The compatibility of this material with organic solvents (methanol or ethanol) is not good, and it cannot be completely dissolved, and this material is acidic, with a pH of about 1-3, which affects the activity of nickel-based catalysts. Realize industrial production

If the pH is adjusted to make the material into a salt, it will be almost insoluble with organic solvents, and the reaction situation cannot be verified.

Images