DE1273499B - Process for the regeneration of work solutions for the production of hydrogen peroxide by the anthraquinone process - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

COIb

German: 12 i- 15/02

Number: 1273499

File number: P 12 73 499.5-41 (D 45054)

Filing date: Wed 28, 1964

Opening day: July 25, 1968

The known process for producing hydrogen peroxide by reducing anthraquinone and oxidizing the resulting hydroquinone is subject to complications due to the constant reduction and oxidation process, which result in a number of more or less known undesirable by-products. It has been shown that some of these by-products can be regenerated into H2O2-forming material, ie to anthraquinone or partially hydrogenated anthraquinone, while another part of the by-products is lost for the M2O & - formation process. Accordingly, a number of methods are also known in the extensive patent literature for the regeneration of the damaged working solution. So you can find z. B. Indications to treat the working solution, which contains the reaction carrier anthraquinone and / or tetrahydroanthraquinone, with oxides of various metals, which should result in a conversion of the regenerable degradation products into reactive anthraquinone or tetrahydroanthraquinone. British patent specification 928 784 describes the treatment of the alkyl anthraquinone working solution with silicates of metals of the second group of the periodic table. According to British Patent 838 939, the used working solution is regenerated with calcium hydroxide or with calcium oxide. Furthermore, the French patent specification 1 305 640 describes the treatment of working solutions with solid substances which have previously been treated with an aqueous alkaline solution. In particular, it is pointed out in the description of this patent specification that the regeneration of working solutions in the oxidized state gives the best results, while the treatment in the reduced or partially reduced state gives poor results. In addition, a partial stream of the not yet extracted hydrogen peroxide-containing solution is fed to the oxidized solution before the regeneration, ie an oxidizing agent (hydrogen peroxide) is also used. Likewise, according to German patent specification 1030 314, the working solution is treated in the oxidized state with non-basic oxides.

It was found that these processes for regeneration do not lead to the goal in all cycle processes for the production of H2O2 by the anthraquinone process. It would be found, surprisingly, that in certain cases the main degradation product of the reaction carrier is almost a process for the regeneration of
Working solutions for the manufacture of
Hydrogen peroxide after
Anthraquinone process

Applicant:

German gold and silver refinery

formerly Roessler,

6000 Frankfurt, Weißf rauenstr. 9

Named as inventor:
DipL-Chem. Dr. Gerd Schreyer,
6454 Grossauheim;
DipL-Chem. Dr. Otto Weiberg,
DipL-Chem. Dr. Günter Giesselmann,
6078 Neu-Isenburg

Quantitatively, it can be converted back into active, workable quinone if the working solution is exclusively in the reduced or partially reduced form treated with catalytic amounts of alkaline substances.

In certain cases, the main breakdown products are the epoxides of alkyltetrahydroanthraquinone, z. B. when using practically alcohol-free working solutions and / or when using of hydrogenation catalysts which are either unsupported or applied to an inert support material. This inert carrier material does not affect the process.

Apart from these main breakdown products, other breakdown products of the process are only completely subordinate Quantities are present that are negligibly small. One treatment of these epoxies in one oxidized working solution gives poor results, as is clear from Examples 1, 2 and 4.

When using the originally used 2-ethylanthraquinone, the epoxide is formed of 2-ethyl-5,6,7,8-tetrahydroanthraquinone of the following formula:

C ₂ H ₅

Mp. 81 to 82 ° C, white crystals.

»MM7 / 508

The situation is quite analogous for other anthraquinones as reaction carriers, e.g. B. with tert-butyl anthraquinone, i-propyl anthraquinone, amyl anthraquinone. These epoxies can be found under the Working conditions of the redox cycle do not reduce to the corresponding hydroquinones and are thus real sources of loss for the reaction carrier.

These epoxides, which are the main degradation products, can be converted into alkyltetrahydroanthraquinone in relatively short times with alkyl anthrahydroquinones and / or ring-hydrogenated alkyl anthrahydroquinones in the presence of catalytic amounts of alkaline substances, i.e. into reaction carriers which are fully functional again. Examples of alkaline substances are: alkali hydroxides, alkaline earth hydroxides, alkali silicates, alkaline earth silicates, alkali aluminum silicates, ammonia, amines, quaternary ammonium bases, basic ion exchangers. The rate of regeneration, ie the conversion of the epoxides into tetrahydroanthraquinones, is generally a function of the reaction time and the temperature. The regeneration can therefore be achieved over longer times even at lower temperatures, for example between 20 and 50 ^° C .; on the other hand leads to the same result at elevated temperatures, for example above 5O ⁰ C, within a short time. The speed of regeneration also depends on the alkalinity of the substance used. The amount of alkaline compounds to be used is not critical as far as regeneration is concerned. With regard to the other process steps, however, only small amounts of alkaline substances are used. With the high conversion rate of regeneration, catalytic amounts are sufficient. The process according to the invention can be carried out batchwise or, with particular advantage, continuously in the circuit apparatus for generating hydrogen peroxide. It has proven advantageous here to connect a tower with regeneration agent between hydrogenation and oxidation, optionally in a partial flow.

The following selection of implementations may serve as an explanation, starting with the implementations be contrasted with oxidized solutions.

For experiments with oxidized or partial The following solvent mixtures and working solutions were used for reduced working solutions:

A. A solution of 5 g of tetrahydroethyl anthra -quinone epoxide in 30 g of trioctyl phosphate and 65 g of tetramethylbenzenes.

B. A working solution which, after prolonged use, contains 50 g of tetrahydroethyl anthraquinone epoxide, 49 g of tetrahydroethylanthraquinone and 54 g of ethylanthraquinone per liter of a solvent mixture from kogasin, dimethylnaphthalene and trioctyl phosphate. In the trials in the hydrogenated form, this working solution was hydrogenated to 40% and then with those given in the table below Treated catalysts.

C. A working solution which, in one liter of a mixture of trioctyl phosphate and tetramethylbenzenes, contains 15 g of tetrahydroethylanthraquinone epoxide, 48 g of tetrahydroethylanthraquinone and 64 g of ethylanthraquinone in dissolved form was used when hydrogenating conditions were used hydrogenated to 50% and treated with the specified catalysts.

The following comparison shows the superiority of the method according to the invention:

example solution State
the solution catalyst temperature
⁰ C regeneration
after 1 hour 1
2,
■ 3
4th
5 A.
B.
B.
C.
C. oxidized
reduced
oxidized
reduced 10% Al ₂ O ₃ + 0.75% Na ₂ O
0.1% NaOH
0.1% NaOH
10% sodium aluminum silicate with 0.8% NaOH
10% sodium aluminum silicate with 0.8% NaOH 120
120
120
120
120 0
15%
99%
0
97%

The other examples are intended to provide a better understanding of the concept of the invention.

Example 6

In a working solution which, after prolonged use, contained 50 g of tetrahydroethyl anthraquinone epoxide, 49 g of tetrahydroethyl anthraquinone and 54 g of ethyl anthraquinone per liter of a solvent mixture of cogasin, dimethylnaphthalene and trioctyl phosphate, 40% of the quinone were hydrogenated to hydroquinone with 10% of the weight of the solution sodium aluminum silicate, treated with 0.8 weight percent sodium hydroxide filterable, at 100 ⁰ C. After 1 hour, 97% of the epoxide had been converted to tetrahydroethyl anthraquinone. ,;

Example 7

An older working solution, which contained 15 g of tetrahydroethylanthraquinone epoxide, 48 g of tetrahydroethylanthraquinone and 64 g of ethylanthraquinone dissolved in a mixture of trioctyl phosphate and tetramethylbenzenes, was hydrogenated to such an extent that 50% of the quinone. was present as hydroquinone. 11 of this reduced solution was ^{treated at 90 °} C. with 100 g of a basic aluminum oxide with a content of 0.75% Na ₂ O, ie 0.025 equivalents of basic substance per liter of working solution. After 1 hour 73%, after 3 hours 77% and after 20 hours 88% of the epoxide had regenerated to active quinone.

Example 8

A working solution, in addition to 38 g of tetrahydroethyl anthraquinone and 25 g of ethyl anthraquinone, 17 g

Tetrahydroethylanthraquinone epoxide per liter of a mixture of methylcyclohexyl acetate and alkylated Benzene contained, had after 1 hour treatment at 90 ° C of the 50% hydrogenated solution with 10% of their weight of sodium aluminum silicate, the 0.8% by weight of titratable sodium hydroxide contained a 30% decrease in epoxide and a corresponding increase in tetrahydroethyl anthraquinone to be recorded.

Example 9

A working solution composed as in Example 1 was hydrogenated to such an extent that 40% of the quinone had been reduced to the hydroquinone. An addition of 0.1% sodium hydroxide, based on the total solution, resulted in ^{a regeneration of the epoxide of 70% after a treatment at 40 °} C. after 1 hour and of 97% to active quinone after 3 hours.

Example 10

A working solution containing 55 g of tert-butyl anthraquinone, 45 g of tert-butyl tetrahydroanthraquinone and 33 g of tert-butyltetrahydroanthraquinone epoxide in a mixture of xylene and trioctyl phosphate was hydrogenated to such an extent that 40% of the quinone were reduced to hydroquinone. A subsequent treatment of the working solution with 10%

ίο basic aluminum oxide with a content of 0.75% NaOH at 70 ⁰ C resulted in a regeneration of the epoxide to tert-butyltetrahydro-

. anthraquinone to 58%, after 3 hours to 85% and after 5 hours to 92%.

A compilation of further experiments can be found in the following, which contain Examples 11 to 19 Tabel. The regenerations were carried out using the working solution mentioned in Example 6 carried out in which the total quinone was 40% hydrogenated.

catalyst temperature ⁰ I. 1 hour ■ 3.5 ο regeneration after 20 hours example ⁰ C 20th 91 72 10% basic alumina 40 3 hours 11 with 1.5% Na ₂ O 13th 45. 35 10% basic alumina 40 26th 12th with 0.75% Na ₂ O 91 5 29 - the same 120 27 51 13th the same 60 49 95 78 14th 7% calcium silicate with 2.0% Na ₂ O 120 . 35 15th = 0.064 equivalents per liter 67 Work solution 22nd 10% Al ₂ O ₃ with 2% Ba (OH) ₂ 60 16 10% basic ion exchanger 120 7.3 17th = about 0.16 equivalents per liter 97 Work solution 76 the same 90 30th 18th the same 60 42 19th 15th

It has been found to be particularly expedient and simple in terms of process technology to add it to the circulating stream immediately after the catalytic hydrogenation of the working solution, d. H. after filtering off of the catalyst to incorporate a reaction path with a basic lumpy alkali compound. Granulates of basic aluminum oxide, sodium aluminum, can advantageously be used here Use silicate, alkaline-reacting calcium silicate.

55 Example 23

Regeneration in the cycle

A working solution which, after prolonged use, contained 42 g of ethyl anthraquinone and 48 g of tetrahydroethyl anthraquinone, 30 g of tetrahydroethyl anthraquinone epoxide per liter of a solvent mixture of 70 percent by volume of a high-boiling aromatic hydrocarbon and 30 percent by volume of trioctyl phosphate, was used in a circulatory apparatus to generate hydrogen peroxide using the known method of catalytic conversion hydrogenated and then oxidized with air. The hydrogen peroxide formed in the oxidation was extracted from the working solution with water in the next process step. By installing a regeneration tower between hydrogenation and oxidation, which was charged with 1%, based on the total circulating working solution, of a basic aluminum oxide with a content of 0.75% Na2Ü (this corresponds to 0.0025 equivalents of alkaline substance per liter of working solution) to regenerate at a working temperature of 70 ⁰ C within 4 days, the solution so far that the epoxide content after this time now 5 g, while had increased the content of 2-Äthyltetrahydroanthrachinon to the equivalent amount per liter was. Such a regeneration can also be realized with particular advantage using a partial flow.

By varying the working conditions, i. H. corresponding enlargement of the regeneration distance, increase in temperature or increase the alkalinity, conducting the regeneration in a partial stream of the hydrogenated solution, the epoxide can practically quantitatively converted into tetrahydroethylanthraquinone. With particular advantage can

a partial flow of the hydrogenated solution corresponding to the exercise of this cycle process from the outset are subjected to the process according to the invention and thus the formation of the undesired Epoxies are prevented. The expenditure on regeneration agent is very low, so that the process works very economically.

Claims (6)

Patent claims: 1. Process for regenerating -of working solutions for the production of hydrogen peroxide according to such anthraquinone processes in which the working solution is tetrahydroanthraquinone epoxides as the main breakdown products contains, with alkaline substances, characterized in that the regeneration of the working " solution in the reduced or partially reduced form and with catalytic amounts alkaline active substances is carried out. 2. The method according to claim 1, characterized in that that 0.0075 to 0.15% alkali oxide, 0.075 to 0.1% alkali hydroxide or 0.2% alkaline earth hydroxide, based on the working solution. 3. The method according to claim 1, characterized in that 10% of a basic ion exchanger, based on the working solution. 4. The method according to claim 1 to 3, characterized ■ that the working solution at temperatures of 20 to 160 ⁰ C, preferably 40 to 120 ⁰ C, treated. 5. The method according to claim 1 to 4, characterized in that the working solution treated between hydrogenation and oxidation. 6. The method according to claim 1 to 5, characterized in that the regeneration in Circular process between hydrogenation and oxidation takes place in a partial flow. Considered publications:
German interpretative document No. 1 081 432.