CS261310B1 - Method of 2-naphthol-6,8-disulphonic acid's insulation - Google Patents

Abstract

Method for isolating 2-naphthol-6,8-disulfoacid from the reaction product formed by sulfonating 2-naphthol oleol so that it reacts the product is diluted with water if necessary or the filtrates from the previous operation are neutralized with potassium hydroxide in an amount 20 to 160 g and ammonia at 10 to 10 g 150 g per 1000 g of undiluted reaction product and the ammonium potassium salt obtained 2-Naphthol-6,8-disulfoacid is isolated filtration or centrifugation associated with optional washing the product with water or brine, or by dissolving the isolated product in water and subsequent filtration.

Description

The invention relates to a process for the isolation of 2-naphthol-6,8-disulfonic acid (the so-called G-acid) from the reaction product formed by sulfonation of 2-naphthol with oleo. It is based on the fact that 2-naphthol-6,8-disulfoacid is isolated after the partial neutralization of the reaction product with ammonia and potassium hydroxide in the form of the ammonium potassium 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, and isomers can be obtained by appropriate selection of the sulfonating agent, its amount and the temperature mode of the reaction. 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-naphtholsulfo-acid 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 select processes that produce poorly soluble compounds of the desired 2-naphtholsulfoacid in the environment, whereas the 2-naphtholsulfoacid side-compounds are more soluble under the given conditions and therefore either remain in the crystalline filtrate or be removed from the isolated 2- naphthosulfoacids by washing. For example, 2-naphthol-3,6-disulfoacid is isolated as the disodium salt, 2-naphthol-6-sulfoacid is ammonium salt. The 2-naphthol-6,8-disulfoacid can be isolated either in the form of the dipotassium salt (AO 246 653) or by the classical dipotassium salt procedure. Both of these approaches have their drawbacks ^'-' in the isolation of the dipotassium salt product is formed in a form difficult to filter, the cost of potassium hydroxide is very high, the isolation of diammonium salts often occurs znečiětování side product 2-naphthol-6-sulphonic acid.

The disadvantages of the above methods of isolation of 2-naphthol-6,8-disulfoic acid can be overcome by the isolation process in the form of the ammonium potassium salt. The present invention provides a process for the isolation of 2-naphthol-6,8-disulfoacid from the reaction product formed by sulfonation of 2-naphthol with oil, wherein the reaction product is neutralized with potassium hydroxide in an amount of 20 to 160 g and ammonia in the amount of 10 to 150 g per 1000 g of undiluted reaction product and the obtained ammonium potassium salt of 2-naphthol-6,8-disulfoic acid is isolated by filtration or centrifugation associated with optional washing of the product with water or brine or washing of the isolated product in water and subsequent filtration.

The product obtained is isolated in yield and purity comparable to isolation in the form of barium and dipotassium salts, the product is deposited in a very filterable form and does not contaminate it with unwanted 2-naphthol-6-sulfoacid or other unwanted isomers.

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

He did

In a 10 L glass flask equipped with a stirrer, thermometer, and lance, 3400 g of water was charged, to which 4250 g of 2-naphthol-olefin sulfonation product containing 36% 2-naphthol-6,8-disulfoacid was added under cooling, 7% of 2-naphthol-3,6-disulfoic acid,

2.1% 2-naphthol-3,6,8-trisulfoacid and 1.6% 2-naphthol-6-sulfoacid. After cooling the undiluted mixture to 30 ° C, 895 g of a 46% aqueous KOH solution was added with cooling such that the temperature did not exceed 60 ° C. Then 273 g of liquid ammonia was added so that the temperature did not exceed 95 ° C.

After cooling the product to 25 ° C, the ammonium potassium salt of 2-naphthol-6,8-disulfoic acid was isolated on a Biichner funnel, and the product was washed with 1,400 g of water. 1,970 g of a paste containing 68% of 2-naphthol-6,8-disulfoic acid as ammonium salt were obtained, followed by 0.4% of 2-naphthol-3,6-disulfoic acid, 0.3% of 2-naphthol-3,6 , 8-trisulfoacid and 0.1% 2-naphthol-6-sulfoacid in the form of salts.

Example 2

To a 10 L glass flask used in Example 1 was charged 2,500 g of water and 2,000 g of wash water from Example 1. 4,250 g of 2-naphthol oleol sulfonation product of Example 1 were added under cooling. 606 g of liquid ammonia were added to the mixture at 35 ° C while cooling so that the temperature did not exceed 70 ° C. Thereafter 220 g of a 46% aqueous KOH solution were added while cooling so that the temperature did not exceed 100 ° C. After cooling the product to 30 ° C, the ammonium potassium salt of 2-naphthol-6,8-disulfoic acid was isolated by filtration on a Biichner funnel, and the product was washed with 1550 ml of water. 1,990 g of a paste containing 68% of 2-naphthol-6,8-disulfoacid in the form of the ammonium potassium salt was obtained, followed by 0.3% of 2-naphthol-3,6-disulfoic acid, 0.2% of 2-naphthol-3,6 , 8-trisulfoacid and less than 0.1% of 2-naphthol-6-sulfoacid in the form of salts.

Example 3

To a 10 L glass flask used in Example 1 was charged 2,500 g of water and 1,950 g of wash water from Example 2. 4,250 g of 2-naphthol oleol sulfonation product of Example 1 were added with cooling. 80 g of liquid ammonia was added to the mixture at 35 ° C while cooling so that the temperature did not exceed 70 ° C. Subsequently, 1,400 g of a 46% aqueous KOH solution were added while cooling so that the temperature did not exceed 100 ° C. After cooling the product to 30 ° C, the ammonium potassium salt of 2-naphthol-6,8-disulfoic acid was isolated by centrifugation, the product was triturated in 1,650 ml of 2% brine and isolated by filtration on a Buchner funnel. 1,900 g of a paste containing 71% of 2-naphthol-6,8-disulfoic acid as ammonium potassium salt were obtained, followed by 0.2% of 2-naphthol-3,6-disulfoic acid, 0.3% of 2-naphthol-3,6 , 8-trisulfoacid and 0.1% 2-naphthol-6-sulfoacid in the form of salts.

Claims (1)

object of the invention Process for the isolation of 2-naphthol-6,8-disulfoacid from the reaction product resulting from the sulphonation of 2-naphthol by oleum, characterized in that the reaction product is neutralized with 20 to 160 g of potassium hydroxide and ammonia in the amount of 10 to 150 g per 1000 g of undiluted reaction product and the obtained ammonium potassium salt of 2-naphthol-6,8-disulfoic acid is isolated by filtration or centrifugation by combined washing of the product with water or brine, or by washing of the isolated product in water and subsequent filtration.