CS256050B1 - Process for preparing pure 1-naphthol - Google Patents

Abstract

The purpose of the solution is a method for preparing pure 1-naphthol from technical 1-naphthol by crystallization, which is achieved by solubilizing the technical product at a temperature of 50 to 100 °C in an aqueous dissociated solution of a substance of the general formula with a concentration of 80 to 250 § l"3;, followed by cooling to crystallize pure 1-naphthol, which is separated and washed. The mother liquor after crystallization is used for subsequent crystallizations.

Description

The invention relates to a process for preparing pure 1-naphthol by a crystallization process. The present method of technical cleaning

1-Naphthol by crystallization ^from an organic solvent carries with it technologically difficult elements such as filtration from the organic solvent, its recovery and removal from the melt crystals of 1-naphthol. The crystallization of technical 1-naphthol from an aqueous solution of a mixture of sodium and potassium l-naphthalenesulfonate can yield 1-naphthol of high concentration, but due to ecologically unacceptable waste mother liquors after crystallization, it is necessary to dispose of these by alkaline melting contaminated with higher contents

Of 2-naphthol.

It has now been found that high purity 1-naphthol can be prepared from the technical product by the process of the invention by solubilizing the product at a temperature of 50 to 100 ° C in an aqueous dissociated solution of the compound of the formula

OH

C00 having a concentration ranging from 80 to 250 g / l, then pure 1-naphthol crystallizes by cooling and is separated and washed. The mother liquor after crystallization is used for subsequent crystallizations. The mother liquor after subsequent crystallization is supercooled and the crystallized mixture of 1-naphthol and 2-naphthol is separated off and the thus recovered mother liquor is optionally added

258 050 was used for subsequent crystallization.

This material is recovered from the wash water by acidification and separation. The process described in this invention has advantages over the prior art processes in particular in the higher yield, purity and performance of the plant and further in that in the case of the recovery of mother liquors in a closed cycle, no liquid waste contaminated with organic substances is generated.

The process according to the invention provides 1-naphthol with a content of 0.05 to 0.5% by weight. 2-naphthol according to the crystallization process, with an average yield of 80 to 85% according to the desired purity.

Example 1

The beaker was charged with 250 mL HgO, 13 mL 10-N NaOH, 22 mL 10-N KOH and 47 g 100% 1-hydroxy-2-naphthoic acid was added. The contents are heated to 75 ° C with stirring, 100 g of technical 1-naphthol containing 5% 2-naphthol are added, which dissolve while stirring and heating. After dissolution, the solution was cooled and filtered at 32 ° C, washed with water and dried. 85.2 g of pure 1-naphthol having a content of 0.1% by weight are obtained. Of 2-naphthol.

Example 2

500 ml of water and 55 ml of 10N NaOH solution are introduced into the beaker, the contents are heated to 40 DEG C. and 100 g of 2-hydroxy-3-naphthoic acid are added, and after heating to 50 DEG C. of naphthol containing 5% of 2-naphthol and dissolved while stirring and heating. After cooling to 25 ° C, the precipitated amount of 1-naphthol was isolated by filtration, washed with water and dried. 82 g of pure 1-naphthol having a content of 0.1% by weight are obtained. Of 2-naphthol.

Example 3

A beaker was charged with 500 ml of water and 65 ml of 10N NaOH solution, heated to 40 ° C and 80 g of 2-hyd-255 650-roxi-1-naphthoic acid was added. After dissolution, 130 g of technical 1-naphthol are introduced with stirring and heating. After dissolution, the solution was allowed to cool slowly and at 32 ° C the crystallized 1-naphthol was isolated by filtration and washed with water and dried to give 111 g of 1-naphthol pure containing 0.15% by weight of 2-naphthol.

Example 4

Into the mother liquors, which are removed during filtration according to the example. 2, 100 g of technical 1-naphthol are added at 90 DEG C. with constant heating and stirring. After dissolution, the solution was cooled and the crystallized 1-naphthol was filtered at 32 ° C.

After washing with water, the filter cake is dried. 100 g of 1-naphthol technical containing 5 wt. Of 2-naphthol. After dissolution at 80 ° C, the entire contents were cooled and the crystallized 1-naphthol was isolated by filtration at 35 ° C.

After washing with water, the filter cake is dried. The dried 1-naphthol pure from both crystallizations was vacuum distilled to give 174 g of 1-naphthol pure containing 0.1 wt. Of 2-naphthol.

Example 5

The mother liquors resulting from the filtration of Example 4 are cooled to 20 DEG C., the crystals formed are filtered off and washed and, after drying, 25 g of 1-naphthol are removed having a content of 45% by weight. Of 2-naphthol. 3 g of 2-hydroxy-3-naphthoic acid, 2 ml of 10-N NaOH solution and 100 g of 1-naphthol are added to the resulting mother liquors with stirring and heating. After dissolution at 65 ° C, the solution is cooled and the crystallized 1-naphthol is filtered off at 32 ° C, washed with water and dried. 80 g of 1-naphthol pure having a content of 0.1% by weight are thus obtained. Of 2-naphthol.

Example 6

The washings leaving in accordance with Examples 2,4 and 5 are mixed and, after cooling to 25 DEG C. and acidification to cong

The filter cake containing 3 g of 100% 2-hydroxi-3-naphthoic acid and 0.5 g of naphthol is introduced into the mother liquors leaving out according to example 5. In the mother liquors 100 g of technical 1-naphthol are gradually introduced at 65 DEG C. with stirring and heating, the solution is cooled after dissolution and the crystallized 1-naphthol is filtered at 32 DEG C. and washed with water and dried to give 82 g. 1-naphthol pure containing 0.3% by weight of 2-naphthol.

The mother liquors were acidified to pH = 6 and cooled to 0 ° C, the resulting mixture of 1- and 2-naphthol was filtered off and washed with water to dry. This gives 45 g of waste 1-naphthol containing 46% by weight of 2-naphthol.

The mother liquors after filtration of the waste 1-naphthol are combined with the wash waters and acidified to a positive Congo red reaction. The liberated 2-hydroxy-3-naphthoic acid was isolated by filtration and washed with water to give 101.5 g of 2-hydroxy-3-naphthoic acid.

Claims (4)

SUBJECT OF THE INVENTION 256 050 Process for the preparation of pure 1-naphthol from technical 1-naphthol, characterized in that the technical product is solubilized at a temperature of 50 to 100 ° C in an aqueous medium of a dissociated solution of a compound of the formula of 80-250 g / l; After cooling, pure 1-naphthol crystallized, which was separated and washed. 2. Process according to claim 1f, characterized in that the mother liquor after crystallization is used for subsequent crystallizations. 3. The method according to claim 1 and _f 2, characterized in that the mother Lou ¹ subcooled and crystallized sgiěs 1- and 2-naphthol are separated and thus recovered mother liquor, optionally after addition of a substance of the formula OTO -coo used for subsequent crystallization. 4. A method according to claim 1 or 2 _being characterized in that the washing water from a compound of general formula OH COO 'is recovered by acidification and separation ·.