CS217902B1 - Process for preparing naphthalene-1,3,6-trisulfonic acid monosodium salt - Google Patents

Abstract

Method for preparing naphthalene-1,3,6-trisulfonic acid in the form of monosodium salt by sulfonating sodium salt of 2-naphthalenesulfonic acid with 65% oleum, in such a way that the dried sodium salt of 2-naphthalenesulfonic acid is dissolved in 100% sulfuric acid and sulfonated at a temperature of 120 to 180 °C with 65% oleum, whereby after sulfonation a mixture of sodium salts of naphthalenetrisulfonic acids is obtained with a content of 74 to 75% by weight of naphthalene-1,3,6-trisulfonic acid

Description

The present invention provides the preparation of a monosodium salt of naphthalene-1,3,6-trisulfonic acid by sulfonation of the sodium salt of naphthalene-2-sulfoacid with oleum.

The main technological process for the preparation of naphthalene-1,3,6-trisulfoacid is currently trisulfonation of naphthalene. According to the procedure published in FIAT-Final Report No. 1016, p. 37, naphthalene-1,3,6-trisulfoacid was industrially produced by introducing a monohydrate (= 100% HgSO 4) cooled to 20 ° C into the sulfonation boiler and introducing ground naphthalene with stirring. Then the temperature of the reaction mixture was raised to 80-85 ° C and the mixture was recovered at this temperature for 1 hour. After this time, the temperature rose to 145 ° C with some delay.

Then the temperature was lowered to 85 ° C by cooling the reaction mixture, and the reaction mixture was diluted with monohydrate and then at 40 ° C 65% oleum was added, followed by further sulfonation. First, a major proportion of 65% oleate was added over 8 hours, then the temperature was raised to 145 ° C and maintained at that temperature for 2.5 hours. Then the reaction mixture was cooled to 60 ° C and the remaining amount of 65% olea was added at this temperature and kept at 150 to 155 ° C for 2-3 hours. The yield of naphthalene-1,3,6-trysulfoacid reached about 70-72% of the theory based on naphthalene. On this occasion it should be noted that the accurate determination of naphthalentrisulfoacid isomers was very inaccurate at the time.

Current production technologies are based on the above described technology, variously modified.

By analyzing this technology based on naphthalene, and based on new improved analytical methods, namely liquid chromatography, it has been concluded that direct trisulfonation of naphthalene may not always give the best results. Based on the technological condition that after the introduction of naphthalene at low temperature, which mainly produces 1-naphthalenesulfoacid, the temperature rises to 145 ° C, at which the sulfogroup rearrangement from position 1 to position 2 results in an equilibrium mixture which it has an approximate composition of 85 wt. 2-naphthalenesulfoacids, 10 wt. % Of 1-naphthalenesulfoacid, approx.

1,5-naphthalenedisulfoacids.

Further sulfonating this equilibrium mixture with oleo gives:

(a) 2-naphthalenesulfoacid

, Sat ₃ h

Olo

OlO s ₃ h ho ₃ s

(b) 1-naphthalenesulfoacid

The desired 1,3,6-isomer is obtained mainly from 2-naphthalenesulfoacid. The above overview shows that 1-naphthalenesulfoacid is not too suitable for the preparation of the 1,3,6-isomer. The products obtained from the sulfonation of the equilibrium mixture contain a considerable amount of ballast substances which are transferred to further processing steps, for example in the production of H-acid.

Based on preliminary theoretical considerations and experimental verification, it has now been found that a suitable starting material could be the sodium salt of 2-naphthalene sulfoacid, which is processed at considerable production capacities to produce β-naphthol. This acid, commonly called the beta salt, is virtually free of both 1-naphthalenesulfoacid and no further disulfoic acid or dinaphthylsulfones. Hydrolysis of the reaction mixture after sulphonation primarily results in the hydrolysis of 1-naphthalene-sulphonic acid, which decomposes into naphthalene and sulfuric acid. Naphthalene is recovered and can be used for further sulfonation. This reduces the loss of naphthalene which results from the sulfonation of the equilibrium mixture of the ballast. On the other hand, salting out the beta salt yields one purification step. The beta-salt after drying has been shown to be a very suitable starting material for the preparation of the desired naphthalene-1,3,6-trysulfoacid isomer. Sulfuric acid (monohydrate) is used as the sulfonation solvent, and 65% oleum is used as the sulfonating agent. The temperature for trisulfonation is 120 to 1 ° C (preferably 140 to 165 ° C). Sulfonation time ranging from 2 to 6 hours.

Upon sulfonation of the beta-salt, a 4-6% by weight higher naphthalene-1,3,6-trisulfoacid content (from the sum of the trisulfoacid isomers) is achieved compared to the direct trisulfonation of naphthalene. The advantage of this process is that as the resultant product of sulfonation of the beta-salt is the monosodium salt of naphthalentrisulfoacids, which results in further limestone savings in neutralizing and removing excess sulfuric acid and reducing waste.

The examples below illustrate embodiments of the process of the invention

Example, (comparative experiment)

A 500 ml five-necked flask equipped with a stirrer, a thermometer, a reflux condenser with a nitrogen lance and a metering device was charged with 133.6 parts by weight after the flask was flushed with nitrogen. 100% sulfuric acid. 102.5 parts by weight are added with cooling over 30 minutes with cooling. of naphthalene such that the temperature is raised uniformly from 40 ° C to 80 ° C over a given period. The temperature of the reaction mixture was then raised to 150 ° C and maintained at this temperature for 1.5 hours.

After this time, the reaction mixture was cooled to 100 ° C and the second part (98.4 parts by weight) was added.

100% sulfuric acid. The temperature of the reaction mixture was adjusted to 80 ° C and 245.6 parts by weight of the reaction mixture were added over 2 hours. 65% olee. The reaction mixture was then heated to 155 ° C and held at that temperature for 1 hour. A further portion of 65% olea, i.e. 49.6 parts by weight, was added over a further 15 minutes, and the reaction mixture was stirred at 155-160 ° C for 1 hour.

The reaction mixture, which contains isomers of naphthalentrisulfonic acids, is suitable for further processing up to H-acid.

The selectivity of sulfonation at 100% naphthalene conversion relative to naphthalene-1,3,6-trisulfonic acid was 71.35%.

The sulfonaol reaction mixture was analyzed by liquid chromatography and contains naphthalene-1,3,5,7-tetrasulfonic acid naphthalene-1,3,6-trisulfonic acid naphthalene-1,3,5-trisulfonic acid naphthalene-1,3,7 -trisulfonic acid sulfonated dinaphtylsulfone sulfuric acid

0.3 wt.

33.4 wt.

4.9 wt.

8.2 wt. about 1.5 wt. 52.0 wt.

Example 2

The sulfonation apparatus described in Example 1 was charged with 235.2 parts by weight. Of 100% sulfuric acid and 184.2 parts by wt. sodium salt of naphthalene-2-sulfonic acid, the temperature of the mixture rising to 50 ° C. 196.8 parts by weight are added to the resulting 50 ° C warm suspension. 65% olea so that the temperature of the mixture rises to a maximum of 90 ° C. The reaction mixture was then heated to 160 ° C and allowed to sulfonate at this temperature for 2 hours.

The resulting mixture of isomers of naphthalentrisulfonic acids in the form of monosodium salts is suitable for direct further processing,

The sulfonation selectivity at 100% conversion of the naphthalene-2-sulfonic acid sodium salt to naphthalene-1,3,6-trisulfonic acid is 75.3% ·

The reaction mixture after sulfonation was analyzed by liquid chromatography and contains naphthalene-1,3,5,7-tetrasulfonic acid naphthalene-1,3,6-trisulfonic acid naphthalene-1,3,5-trisulfonic acid naphthalene-1,3,7 -trisulfonic acid sulfonated dinaphtylsulfone sulfuric acid

0.1 wt.

36.1 wt.

3.7 wt.

8.1% wt.

1.5 wt. 50.5 wt.

Claims (1)

A process for the preparation of naphthalene-1,3,6-trisulfonic acid in the form of the monosodium salt by sulfonating the sodium salt of 2-naphthalenesulfonic acid with 65% oleem, characterized in that the sodium salt of 2-naphthalenesulfonic acid is dissolved in 100% sulfuric acid and sulfonated at 120 to 180 [deg.] C. 65% oleum, whereby after sulphonation a mixture of sodium salts of naphthalentrisulphonic acids having a content of 74 to 75% by weight is obtained. naphthalene-1,3,6-trisulfoacids.