CS212039B1 - The method of crystallization of benzantrone - Google Patents

Abstract

Crystallization of benzanthrone from the hot reaction mixture after completion of condensation. A solution of benzanthrone in hot sulfuric acid is diluted by the addition of hot distilled water, which leads to the gradual precipitation of the product in a crystalline, rapidly filtering form.

Description

The invention relates to a process for the crystallization of benzantrone from a hot reaction mixture after completion of the condensation.

Benzantrone is an important basic intermediate of a wide range of dyes of excellent quality and can be considered as a basic intermediate of benzanthrone chemistry. The preparation of penziantrone by the condensation of anthraquinone with glycerine in a sulfuric acid environment under the reducing action of iron is described in a number of papers and monographs in various modifications. At the same time, however, there are many works motivated to replace this technology with the use of tar-based intermediates, such as the addition of benzantrone from 1-benzoylnaphthol. However, benzantrone is industrially produced by conventional technology, where attention has so far been mainly focused on side reactions and unpleasant side effects such as foaming of the reaction mixture, intense hydrogen evolution, exhalation, viscosity, mixing. An important production step, namely the crystallization of the product from the reaction mixture after completion of the condensation, has not yet been paid attention. In the prior art process, upon completion of the condensation, the reaction mixture is diluted with a stream of cold water, thereby reducing the solubility of the benzantrone that is eliminated from the mixture. However, the product is obtained in an unsatisfactory sticky form which is difficult to filter and poorly washed, the dry matter content being small. Removing such a product from the nucleate is mechanically difficult and lossy.

These disadvantages are overcome by the process of crystallizing benzantrone from the hot reaction mixture after completion of the reaction by reducing its solubility in sulfuric acid by the addition of water and separating the precipitated benzantrone from the liquid phase, which consists in supplying the reaction mixture with 100 ° C, optionally in the form of steam or mist.

The beneficial effect of hot dispersed water on the crystallization of benzantrone can be explained by the slower saturation of the benzantrone solution in hot sulfuric acid due to the higher temperature of the reaction mixture, but also by the homogeneous saturation of the crystallizer content using dispersed hot water. The drops of hot water in the stirred crystallizer create relatively small and poorly stable local supersaturation zones, which are immediately disposed of by mixing and result in a continuous, controlled supersaturation, creating the basic conditions for sufficient crystal development. Another advantage is that the dispersed water acts as a shower and thus contributes to the purification of the atmosphere in the working environment around the crystallizer. The process according to the invention yields a crystalline benzantrone which is well filtered and washed. The crystallization rate was increased 5 to 20 times and the rate was consequently shortened, resulting in a wash of 3 to 10 times. The dry weight of the washed product is about 60%, while in the prior art it was about 20%. .Drying time leads to energy saving. Acceleration of filtration creates conditions -1 for intensification of production.

To illustrate the invention, an exemplary embodiment is given below:

Example:

Condensation: In a 5000 L vat 1600 L of concentrated sulfuric acid and enough water are added to give a final concentration of 87%. 400 kg of anthraquinone and 70 kg of copper sulphate are added, heated to 130 ° C and a reducing iron suspension in glycerine (221 kg of glycerin and 304 kg of dispersed iron) is added. After completion of the condensation, the reaction mixture constituted 2000 kg of a solution of benzantrone in sulfuric acid.

Crystallization: 1000 to 3000 L of hot water dispersion of 80 ° C is added to the reaction mixture after completion of the condensation with stirring over 0.5 to 4 hours. During the addition of hot water, the reaction mixture gradually becomes saturated and the benzantrone precipitates in a crystalline, well filtering form. After cooling to about 60 ° C, the suspension is filtered and washed on nuances. A benzantrone paste with a dry matter content of 60-70% is obtained.

Claims (1)

PŘEb.iMĚT A process for crystallizing benzantrone from a hot reaction mixture after completion of the reaction by reducing its solubility in sulfuric acid by adding water and separating the precipitated benzantronium tronium from the liquid phase, characterized in that, after completion of the reaction, dispersed water is supplied at 40 to 100 ° C or in the form of steam and / or mist.