CS217523B1 - A method of separating aromatic sulfoacids - Google Patents

Abstract

Aromatic sulfonic acids, which are important intermediates, especially in the production of organic dyes, are produced by sulfonation of aromatic hydrocarbons. The invention relates to the separation of the obtained sulfonic acids, which contain an unequal number of sulfo groups, by liquid extraction using high molecular weight amines or their salts with acids in a suitable organic solvent.

Description

The invention relates to the separation of aromatic sulfo acids containing unequal amounts of sulfo groups by liquid extraction.

Aromatic sulfoacids are important intermediates, especially in the production of organic dyes. Most sulfoacids are produced by sulfonating the aromatic hydrocarbons with a suitable sulfonating agent and then separating the products of the reaction mixture. In most cases, the reaction mixture contains, in addition to the unreacted sulfonating agent, isomeric sulfo acids and sulfo acids with greater or lesser number of sulfo groups than the desired product. Separation of these reaction mixtures is most often carried out by salting-out, which utilizes the low solubility of sodium salts of sulfo acids which fall out of solution, while calcium sulfate remains in solution.

The solubility of the sodium salts of the various isomeric sulfoacids is in some cases quite different, which is used in fractional salting out, whereby sulfoacids can be obtained in a high degree of purity. In some cases, the different solubilities of the sodium and potassium salts of sulfoacids are used for separation, for example in the separation of the so-called R- and G-acids.

In another method, the so-called liming, first the sulfuric acid is removed from the sulphonation mixture in the form of a sparingly soluble calcium sulphate and then the calcium salts of the sulphonic acids are separated, for example by salting out.

A considerable disadvantage of these processes is their low yield. Due to the imperfection of these processes, there is a considerable leakage of sulfo acids or their salts into the waste water. Based on the available data, it can be estimated that the losses of basic raw materials (naphthalene, anthraquinone and their derivatives) are on average more than 50%. Thus, the imperfection of the insulation process causes considerable economic losses, in addition a large amount of inorganic waste is produced. The occurrence of sulfo acids and their salts in wastewater is extremely undesirable, as these substances are very difficult to biodegradable and often toxic or suspected of carcinogenic effects.

U.S. Pat. No. 3,179,703 discloses the separation of soluble aromatic sulfo acids (2-naphthol-8-sulfonic acid, toluene-4-sulfonic acid) * sulfuric acid by liquid extraction using tertiary higher molecular amines dissolved in a suitable solvent. The aromatic sulfoacid passes into the extract as an amine salt, while sulfuric acid remains largely in the raffinate. The free sulfoacid can be obtained from the raffinate by reextraction into an aqueous hydroxide solution.

We have now found a method for separating aromatic sulfo acids with different numbers of sulfo acids or their salts based on the principle of liquid extraction which according to the invention consists in subjecting an aqueous solution of a mixture of sulfo acids to extraction using amines and molecular weights above 100 or their salts with acids dissolved in an organic solvent, preferably chlorobenzene.

The invention is the result of the research that liquid extractions can be used not only for separating sulfo acids and sulfuric acid, but also advantageously for separating sulfo acids containing unequal numbers of sulfo groups, especially mono- and disulfo acids. High molecular weight amines dissolved in an organic solvent or salts of such amines (e.g., tri-n-octylamine hydrochloride) may also be used as the extraction agent for this purpose when the free acids, but their salts, are treated. The amine salts contained in the extract can be obtained into the aqueous solution in the form of the sodium salt by reextraction into the aqueous sodium hydroxide solution or by treatment with another alkaline agent. The main advantage of this process compared to the methods of separation (salting, liming) used so far is the minimization of product losses and waste production.

The extraction efficiencies of division represented by the separation factor, which can be identified with the first approach the equilibrium constant K exchange reaction as described for scheme one polybasic acid-dibasic equation (ϊα ₂₎ + _ε 2 X ~ <== ^ Yf- + 2 (XA) _e where

^2_ Y is the anion of a dibasic acid,

X 'denotes the anion of a monobasic acid,

YAg denotes an amine salt with a dibasic aromatic sulfoacid, XA denotes an amine salt with a monobasic aromatic sulfoacid, the index R is related to the raffinate, E "to the extract.

The equilibrium constant is then described by the relation

where the terms in parentheses indicate the concentrations of the individual substances.

The value of the separation factor K is closely related to the number of equilibrium steps required to separate the mixture. If the K-value is greater than 10, the desired degree of separation on a low-level device can usually be achieved.

The method for separating sulfo acids by liquid extraction is illustrated in the following examples.

Example 1 ml of an aqueous solution of 9,10-anthraquinone-2,6-disulfonic acid (ADSK) and 9,10-anthraquinone-2-sulfonic acid (ASK) containing both ADSK and ASK at the same concentration of 0.034 mol / l were shaken for 5 min at 100 ° C. ml separator with 50 ml tri-n-octylamine (TQA) in 0.05 mol / l chlorobenzene. After phase separation, the raffinate found to contain ADSK at 0.025 5 mol / l and only traces of ASK, extract ASK salt with TOA at 0.0334 0 mol / l, ADSK salt with TOA at 0.00β 5 mol / l.

Example 2

An aqueous solution containing 0.044 7 mol / l ASK and 0.028 6 mol / l ADSK was subjected to extraction under the conditions of Example 1. The raffinate analysis showed that it contained 0.002 3 mol / l ASK and 0.026 ADSK. 5 mol / l. The extract contained ASK salt with TOA concentration of 0.042 4 mol / l ADSK salt with TOA concentration of 0.002 1 mol / l. The separation factor K calculated from these data is 4 300.

Example 3

An aqueous solution containing 0.018 6 mol / L of benzene sulfonic acid (BOD) and 0.036 0 mol / L of benzene-1,3-disulfonic acid (BDSK) was subjected to extraction under the conditions of Example 1. The raffinate analysis showed that contains BOD at a concentration of 0.002 6 mol / l, BDSK at a concentration of 0.021 2 mol / l. The extract contained BOD salt with TOA concentration 0.016 0 mol / l, BDSK salt with TOA concentration 0.014 8 mol / l. The separation factor K calculated from these values is 54.

Claims (1)

SUBJECT OF THE INVENTION A method for separating aromatic sulfo acids having different numbers of sulfo groups or their salts, based on the principle of liquid extraction, characterized in that the aqueous solution of the mixture of sulfo acids is subjected to extraction using amines of molecular weight greater than 100 or their salts with acids dissolved in an organic solvent. preferably in chlorobenzene.