Method of separation and cleaning of para-aminobenzoic acid

FIELD: separation and cleaning of para-aminobenzoic acid.

SUBSTANCE: proposed method consists in increasing the concentration of salts of para-nitrobenzoic acid in reaction mass by obtaining the following ratio of sodium and ammonium salts: Na-salt : NH4-salt = 7.5-8.0 : 2.5-2.0 mole; acidation of solution of para-aminobenzoic acid is carried out with the aid of nitric acid at concentration of 20-25%. Novelty of invention consists in setting the required ratio of sodium and ammonium salts of para-nitrobenzoic acid and use of nitric acid for separation of para-aminobenzoic acid from solution.

EFFECT: increased productivity of equipment; high concentration of salts of para-nitrobenzoic acid; high purity of target product.

2 cl, 1 tbl, 4 ex

 

The invention relates to the isolation and purification of p-aminobenzoic acid (ABA).

Closest to the proposed method is a method of extraction and purification of benzoic acids obtained by catalytic regeneration of the respective nitromist in aqueous solutions of their salts with hydrogen in the presence of hydrogenation catalysts, by acidification filtered from the catalyst solution of alkaline salts of benzoic acids with hydrochloric acid to pH 4-5, the processing hydrosulfite sodium and charcoal when heated to 80-90°With, by filtration of the hot solution from coal, cooling, separation, washing and drying the precipitate. [1].

The disadvantages of this method include relatively low concentrations in the reaction of the salt mass source NSC and the target of ABA (17-18 wt.%), relatively high values of the residue on ignition (as sulphate) - 0.03%.

The purpose of the invention is the provision of a higher concentration of salts NSC in the reaction mass and the achievement of higher purity target of ABA.

This goal is achieved by isolation and purification of ABA, which consists in the fact that to increase the concentration of salts NSC in the reaction mass ratio of sodium and ammonium salts comprising Na-salt: NH4salt=7.5-8.0:2.5-2.0 mol, and the acidification of a solution of ABA spend nitrogen is acid with a concentration of 20-25%.

Example 1. The solution obtained after hydrogenation with hydrogen in the presence of 25 g of Raney Nickel in an autoclave a mixture of 167 g (1 mol) of p-nitrobenzoic acid (NSC), 680 ml of water, 32 g (0.8 mol) of NaOH, 15.5 ml (13.6 g, 0.2 mol) of 25%aqueous ammonia, acidified at room temperature 20%nitric acid to pH 4.5, heated to 90°add 20 g of activated charcoal and 0.2 g of hydrosulfite sodium. The solution is filtered from coal and cooled to 5-10°C. the precipitation was separated, washed on the filter with 30 ml of cold water and dried in vacuum at 50-60°C. Receive 130.7 g (95.4% of theory) of p-aminobenzoic acid is a white crystalline powder with TPL 187-188°C. the Content of the basic substance (according to the potentiometric titration) - 99.9%, residue on ignition (as sulphate) - 0.01%.

Examples 2-4. The process is carried out analogously to Example 1, the results are presented in the table.

Table
Experience No.The ratio of salt NSC-Na:NH4, molThe concentration of HNO3, %The output of the ABA, %The content of basic substance, %Residue on ignition (as sulphate), %
28:22595.299.80.006
3 7.5:2.52095.399.90.007
4*9:136.5 (HCl)95.099.90.030
* Example comparison

Sources of information

1. A.S. 586164 of the USSR (1977), MKI 07 With 101/54. BI, 1977, No. 48.

The isolation and purification of p-aminobenzoic acid by acidification filtered from the catalyst solution of alkaline salts of p-aminobenzoic acid to a pH of 4-5, the processing hydrosulfite sodium and charcoal when heated to 80-90°With, by filtration of the hot solution from coal, cooling, separation, washing and drying the precipitate, characterized in that the ratio of sodium and ammonium salts of p-nitrobenzoic acid is Na-salt:NH4salt=7,5-8,0:2,5-2,0, mol, and the acidification of a solution of salts of p-aminobenzoic acid is carried out with nitric acid with a concentration of 20-25%.



 

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