CS246653B1 - Method Isolation of 2-naphthol-6,8-disulfoacid - Google Patents

Abstract

The method of isolating 2-naphthol-6,8-disulfonic acid from the reaction product formed by the sulfonation of 2-naphthol with oleum consists in neutralizing the reaction product, optionally after dilution with water, with gaseous, liquid ammonia or its aqueous solution. Ammonia is used in an amount of 40 to 200 g per 1 kg of undiluted reaction product. The obtained ammonium salt of 2-naphthol-6,8-disulfonic acid is then isolated by filtration or centrifugation with optional washing with water or brine.

Description

The present invention relates to a process for the isolation of 2-naphthol-6,8-disulfonic acid from the reaction product of sulfonation of 2-naphthol with oil. It is based on the fact that 2-naphthol-6,8-disulfoacid is isolated after partial neutralization of the reaction product with ammonia in the form of an ammonium salt.

Sulfo acids derived from 2-naphthol are among the important intermediates for the preparation of organic dyes. They are produced predominantly by sulfonation of 2-naphthol, with the appropriate choice of the sulfonating agent, the amount thereof, and the temperature mode of the reaction to obtain the desired isomers. However, in addition to these isomers, other 2-naphtholsulfoacids differ from the desired isomer by the position or number of sulfo groups.

Isolation of the 2-naphtholsulfoacids produced from the reaction products is difficult since the content of the 2-naphtholsulfoacid side products in the products produced is extremely undesirable in most applications.

In the production of each of the 2-naphtholsulfoacids, a special isolation process must be chosen which must provide high yields and meet demanding quality requirements. This means that it is necessary to choose processes that produce poorly soluble compounds of the desired 2-naphtholsulfoacid in the environment, while the 2-naphtholsulfoacid side-compounds are more soluble under the given conditions and therefore either remain in the mother filtrate during crystallization or can be removed from the isolated 2-Naphthosulfoacids by washing.

For example, 2-naphthol-3,6-sulfoacid is isolated as the sodium salt, 2-naphthol-6,8-disulfoic acid is isolated as the potassium salt. In the production of 2-naphthol-6-sulfoacid, ammonium salt isolation can then be used (USSR AO 925 945), since the ammonium salt of 2-naphthol-6-sulfoacid is so low soluble in the diluted sulfonation product of 2-naphthol that it allows a high yield. isolating the sulfoacid, wherein the ammonium salts of the 2-naphtholsulfoacids (e.g., 2-naphthol-3,6- and -6,8-disulfoacids) are substantially more soluble under the given conditions and are therefore not precipitated in solid form.

Surprisingly, it has now been found that by suitable selection of the ammonia amount, conditions can also be achieved in which 2-naphthol-6,8-disulfoacid can also be isolated in the form of the ammonium salt by using ammonia undiluted with water or washing waters.

The process according to the invention for the isolation of 2-naphthol-6,8-disulfoacid from the reaction product formed by sulphonation of 2-naphthol with oil is neutralized with ammonia gas, liquid or its aqueous solution in an amount of 40 to 200 g of ammonia per kg of undiluted reaction product and the obtained 2-naphthol-6,8-aisulfoacid ammonium salt is isolated by filtration or centrifugation, optionally combined with washing the product with water or brine.

The use of the process according to the invention eliminates the disadvantages of the potassium salt isolation process used hitherto, in that it is difficult to filter the product causing considerable operational complications, further reducing the amount of waste produced in the production of 2-naphthol-6,8-disulfoacid products. Furthermore, isolation of 2-naphthol-6,8-disulfoacid in the form of an ammonium salt is much less expensive than isolation in the form of a potassium salt, since the price of ammonia is lower than the price of potassium hydroxide.

The product obtained is isolated in yield and purity comparable to that of the potassium salt, and the filtration time of the product is reduced by up to one half.

The isolation procedure of the invention can be illustrated by the examples below.

Example 1: i '.... 3k /.

The mixer was mixed with 0.8 kg of the reaction product resulting from sulfonation of 2-naphthol with 20% ole at 80 ° C and 0.6 kg of water containing

1.2% wt. 2-na-tol-3,6,8-trisulfoacid

1.1% wt. 2-Naphthol-6-sulfoacids

4.7 wt. Of 2-naphthol-3,6-disulfoacid

18.4% wt. Of 2-naphthol-6,8-disulfoacid

37.0% wt. sulfuric acid

To the flask was added 60 g of ammonia gas from the cylinder over 20 minutes, increasing the temperature from the original 20 to 80 ° C. After cooling the partially neutralized product to 30 ° C, 310 g of a paste containing 71.5 wt.% Was obtained by filtration and washing with 0.15 L of water. 2-naphthol-6,8-disulfoacid, 0.2 wt. 2-naphthol-6-sulfoacids, less than 0.2 wt. 2-naphthol -3,6-disulfoacid and 0.2 wt. Of 2-naphthol-3,6,8-trisulfoacid.

Example 2

In the apparatus described in Example 1, 1 l of the raw material of the composition of Example 1 was introduced.

To the flask was added 50 g of ammonia as a 25% aqueous solution over 10 minutes. After cooling the partially neutralized product to 20 ° C, 290 g of a paste containing 70.9 wt. 2-naphthol-6,8-disulfoic acid, 0.25 wt. 2-naphthol-6-sulfoacids, 0.1 wt. % Of 2-naphthol-3,6-disulfoacid and 0.25 wt. Of 2-naphthol-3,6,8-trisulfoacid.

Example 3

The apparatus described in Example 1 was charged with 1.4 kg of a mixture of 0.8 kg of the reaction product resulting from sulfonation of 2-naphthol with 20% ole at 80 ° C and 0.6 kg of the ammonium salt isolation filtrate of Example 1 containing

1.4 % hm 1.3 % hm 4.9 % hm 19.3 % hm 39.0 % hm.

2-Naphthol-3,6,8-trisulfoic acid 2-Naphthol-6-sulfoic acid 2-Naphthol-3,6-disulfoic acid 2-Naphthol-6,8-disulfoic acid

125 g of liquid ammonia was added to the flask over a 25 minute period. After cooling the partially neutralized product to 30 ° C, 335 g of a paste containing 71.0 wt. 2-naphthol-6,8-disulfoacid, 0.2 wt. 2-naphthol-6-sulfoacids, 0.1 wt. % Of 2-naphthol-3,6-disulfoacid and 0.3 wt. Of 2-naphthol-3,6,8-trisulfoacid.

Claims (1)

Process for the isolation of 2-naphthol-6,8-disulfoacid from the reaction product formed by sulfonation of 2-naphthol with oil, characterized in that the reaction product is neutralized with ammonia gas, liquid or an aqueous solution thereof in an amount of 40 to 200 g of ammonia per kg of undiluted reaction product and the resulting 2-naphthol-6,8-disulfoic acid ammonium salt is isolated by filtration or centrifugation, accompanied by optional washing of the product with water or brine.