DE1668920A1 - Process for the production of hydroquinone - Google Patents

Description

297 «« »

DA-1973

description

to the Patent application

of

Instytut Przemysu Organicznego Warszawa / Poland,

concerning

Process for the production of hydroquinone

! • Priority 4 2.1967 - Poland - P 118 855 2. "24 6.1967 - - - P 121 332

The most common process used in industry to manufacture hydroquinone is based on the Oxidation of aniline in a sulfuric acid medium by adding MnOo and then reducing the preserved quinones. This method is the most economical and at the same time allows one to be obtained high purity product.

The separation of the quinones from the reaction mixture is particularly difficult in this process apart from the main product, there are also inorganic salts (mainly manganese and ammonium sulphate) and products of the by-products and Follow-up reactions as well as sludge, in which calibration is still un-

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reacted MnO "is located. The most common method used to obtain quinones is distillation with steam.

Although this method is technologically very tedious and associated with large losses of quinone, it is still used because it is a production of quinones in a pure state, freed from the other components of the reaction mixture, among which there is also MnO ”which is very difficult to separate off mechanically and with difficulty.

ΰβζ content of quinones in the mixture, which obtained by steam distillation is low, which means that the capacity of the apparatus in which quinone is reduced to hydroquinone and hydroquinone is separated off, can limit. The steam distillation is normally carried out in packed columns. These have to be cleaned often because of silt, what is very cumbersome.

The process according to the invention treats the conversion of the MnO ₂ , which is still present in the reaction mixture formed after the oxidation of the aniline, into soluble manganese salts by means of reducing substances.

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With these. Reducing agents are: ELOg solutions, sulfur compounds {sulfur valence below VI5 and nitrogen compounds (nitrogen value below V}, such as & .B. Alkali sulfites, hydrogen sulfites, dithionites, nitrites, etc.). The separation of the MnO “from the reaction vessel eliminates the greatest technical difficulties associated with the recovery of quinone by means of steam distillation. At the same time, this operation reduces the quinone losses which were caused by the action of MnO2 on quinone and the associated transformations of the quinone. The precipitation of MnOc enables quinone to be obtained more easily from the reaction gas (compared to the steam distillation process ^{ .

The apparatus becomes simpler and the whole process more economical if it is obtained by precipitation of the quinhydron, which is an addition compound of quinone with hydroquinone, takes place. The quinhydrone is separated off by filtration and becomes the hydroquinone reduced. The quinone recovery process based on the precipitation of quinhydrone enables an easy and fast

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quantitative separation of the quinones formed from the Re » action mixture in a particularly favorable form for further Processing. Since the impurities that adhere to the quinone are separated by this operation, the production of pure hydroquinone is no longer a problem.

The quinones are obtained from the reaction mixture as an addition compound with hydroquinone the reduction of part of the quinone or the addition of hydroquinone enables the precipitation of the quinone hydrons by reducing part of the quinone then gives the best yield when half of that in the mixture contained quinone is reduced.

If the addition compound is to be precipitated by adding hydroquinone, this must be achieved the hydroquinone can be added in a molar ratio of 1: 1 or with a small excess. It is possible, the hydroquinone in solid state or as a solution (e.g. to be added in the form of crystallization fibers}. The inventive Process can be used for reaction mixtures with b -

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any concentration can be used. Particularly advantageous Results are obtained using concentrated solutions.

You get better yields if you do the oxidation carried out in such a way that the aniline is added dropwise to an emulsion consisting of MnO «and sulfuric acid solution, instead of adding the aniline sulfate - as is customary with the known methods. This method allows for a reduction dos water content in the reaction mixture without reducing the quinone yield.

The process according to the invention enables a high yield and in comparison to the known methods also allows the capacity of the apparatus to be increased.

According to the method according to the invention, it is also possible to use the entire amount of manganese, which is used as brownstone was added to the reaction to recover as manganese (II) salts .

Example I.

To a 1 m large, with stirrer, thermometer

and cooling coil (for cooling brine) provided reactor

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add 400 1 V / water, 115 kg of conical sulfuric acid and 15 kg of manganese dioxide (MnO ₀ - content 85%).

The contents are cooled to 5 ° C. and the aniline is added at a rate of 10 kg per hour. The temperature in the reactor is kept between 5-8 ° C.

The reactor is charged with a total of 30 kg of aniline. At the same time as the aniline is added, 60 kg of manganese dioxide are also added (15 kg in portions in 30 bags each). The contents of the reactor are mixed ^{at a temperature of 5-10 °} C. for a further 7 hours after charging. With further stirring, 3.13 kg of perhydrol (calculated on 100% H ₉ O ₉ ) are added over the course of 30 minutes.

Then the reaction mixture is neutralized to a pH of 5-6 and with the aid of cast iron filings at 65-70 ⁰ C reduces as long has been to one-half of the quinone reduced to hydroquinone. The contents of the reactor are cooled to 10 ° C. and filtered.

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The precipitation also contains iron sludge 30 kg of quinhydrone, which has an 85% yield (calculated on aniline) corresponds to · The quinhydrone obtained in this way is converted into a aqueous solution reduced to hydroquinone, separated and purified by crystallization «The reduction process of quinhydrone takes place with a yield of over 95% and the crystallization of the hydroquinone * when used a rational lye cycle - over 92%.

Hydroquinone is obtained in such a degree of purity that the product can be used for photographic Purposes is possible.

Example II

A reaction mixture after oxidation of aniline and dissolution of MnO ₂ , which is prepared as under the conditions described in Example X, gives 31 kg of technical grade hydroquinone or crystallization liquor containing the appropriate amount of hydroquinone Mixed temperature below 20 ^{° C.} The ctinhydron is removed by filtration.

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BATH

separates · 60 kg of product are obtained (calculated on the dry product), which is reduced to the hydroquinone. The hydroquinone is obtained and purified by crystallization. A yield is achieved by this process of 75% photographic hydroquinone.

Example III

9 kg of sodium hydrogen sulfite are added to a mixture after oxidation of aniline, which is prepared under the conditions as described in Example I. After stirring for 2 hours at a temperature of 10 ^° C., the crystallization liquors, which contain 29.5 kg of hydroquinone, are added. The contents are stirred for one hour at a temperature below 15 ° C., then the precipitated quinhydrone is filtered off and reduced with cast iron powder in an aqueous solution. The hydroquinone is separated and purified by crystallization. The process proceeds with a 77% yield of photographic hydroquinone.

Claims

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Claims (1)

Claims 1. Process for the production of hydroquinone by Oxyda tion of aniline with the help of MnOg to quinone and reduction of quinone, characterized in that the unconverted MnO, which is still contained in the reaction mixture after the oxidation, becomes the soluble Mn (II) salt reduced and the quinone by steam distillation or separated by precipitation of its addition compound with hydroquinone and reduced to the hydroquinone 2 · The method according to claim 1, characterized in that the reducing agent, the MnOg convert into soluble Mn (II) salts, use HgOg solutions. 3 «The method according to claim 1, characterized in that the reducing agent _{converts the MnO 2} into soluble Mn (II) salts. Sulfur compounds (sulfur valency below V) or nitrogen compounds (nitrogen valence below V) or their mixtures are used. 109838/1609 - ίο - 4. The method according to any one of claims 1, 3, characterized in that one acts as reducing Sulfur compounds alkali sulfites, alkali hydrosulfites or Alkalidithionite used. 5. The method according to claim 1, characterized in that the quinone from the reaction mixture is salted after the conversion of MnOg into soluble Mn (II) wins by steam distillation or as an addition compound with hydroquinone. 6. The method according to claim and / or 5, characterized in that the addition compound of quinone with hydroquinone either by adding solid or dissolved hydroquinone to the reaction mixture or by partial reduction of the quinones. 7. The method according to any one of claims 1,5,6, characterized in that the addition of quinone with hydroquinone is precipitated by the Crystallization and refining processes obtained crystallization liquors are used. 109838/1609 - Ii - 8. The method according to claim 1, characterized net that one separated from the reaction mixture Quinone either in the pure state or as an addition compound with hydroquinone reduced to hydroquinone, which by Crystallization is brought to the required degree of purity. 109838/1609