JPH0147554B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to an electrochemical redox method for producing benzoanthrone at the cathode and simultaneously a planar polycyclic aromatic oxy compound at the anode in an electrolytic cell separated by a diaphragm into a cathode chamber and an anode chamber. . The oxy compound obtained by this invention has conventionally been
Often produced by reduction or oxidation reactions,
For large-scale production, various high-valent heavy metals or heavy metal salts are used. Therefore, after this treatment, a dilute heavy metal salt solution remains, causing serious ecological problems. For example, metals such as iron, zinc, aluminum or copper have been used to reductively convert anthraquinone to the semiquinone form in concentrated sulfuric acid. Such a method is particularly known in US Pat. No. 1,896,147 (reducing agent
Fe), US Patent No. 2034485 and USSR Patent No.
No. 401130 (Reducing agents Fe and Cu), AMLahin,
Zhur.Obschei Khim. 18 , 308 (1948), CA 44 ,
1079b (reducing agents Zn, A, CuSO ₄ ) and in US Pat. No. 1,791,309 (reducing agents Zn and A). Among these, iron has the greatest practical value as a reducing agent. However, the use of iron as a reducing agent involves major industrial and ecological disadvantages, since 2 moles of iron must be used for every mole of anthraquinone. This means, for example, that for every mole of benzantrone produced, 2.0 moles of iron sulfate, or for every 1000 g of benzantrone produced, at least 1320 g of iron sulfate are produced as a by-product. Furthermore, in order to isolate the produced benzanthrone, the sulfuric acid must be diluted to about 20%, resulting in a large amount of waste sulfuric acid, which then has to be converted into concentrated sulfuric acid again, wasting energy, or Its removal also poses environmental problems. Oxidation of polycyclic aromatic compounds has conventionally often been carried out in acidic media using high-valent metal salts. In this case, in order to separate the organic oxidation product from the reduced metal salt after the reaction, the reaction solution is sufficiently diluted with water and the organic product is separated or extracted with a solvent. Significant ecological problems arise here as well due to removal and dissolved metal salts. Thus, for example, when producing 500 kg of dihydroxybiolanthrone, 1200 kg of MnSO ₄ are produced in approximately 30,000 kg of 10% sulfuric acid. The treatment of this mixture is uneconomical, and the problems of gypsum conversion of sulfuric acid and treatment of gypsum remain. An alternative to the use of environmentally problematic reducing or oxidizing agents is to carry out environmentally friendly electrochemical reactions. For example, the following electrochemical process for producing benzantrone starting from anthraquinone and glycerin is known from European Patent Application No. 22062. Anthraquinone is reduced at the cathode in an acidic medium in an electrolytic cell and converted to the semiquinone form, ie, oxanthrone, which undergoes a ring-closing reaction with glycerin to form benzaanthrone. However, this method does not utilize the oxidation potential of the anode. Therefore, an object of the present invention is to develop a method for the already known electrochemical redox method in which the reduction reaction proceeding at the cathode is combined with the oxidation reaction occurring simultaneously at the anode. From US Pat. No. 1,544,357 an electrochemical process is known for producing benzidine from azoxybenzene and anthraquinone from anthracene. In this case, azoxybenzene and anthracene are converted at the cathode and anthracene at the anode, respectively, to the products mentioned above. Both reactions proceed simultaneously in an electrolytic cell separated by a diaphragm into a cathode and anode chamber. In the electrolytic cell, Cr() salt is dissolved on the cathode side, and Cr() salt is dissolved on the anode side.
Salt and sulfuric acid are added which are dissolving the Cr() salt. Although this known electrochemical method simultaneously performs reduction at the cathode and oxidation at the anode, benzaanthrone synthesis is inhibited by Cr() ions, so it is not useful for solving the previous problem. Furthermore, when using sulfuric acid with a concentration of 75% or more as an electrolyte, Cr described in the US patent
The oxidation of () to Cr() could not be processed later. Surprisingly, it has become clear that benzanthrone can be obtained on the cathode side and polycyclic aromatic oxy compounds such as dioxobiolanthrone can be obtained on the anode side without using a metal salt in the cathode chamber. Ta. That is, in this case,
The use of metal ions in the cathode compartment can be stopped when simultaneously utilizing the electrochemical potentials of the anode and cathode. Furthermore, transition metal ions such as the elements manganese, cerium or cobalt have proven suitable on the anode side. The method of this invention is performed in an electrolytic cell containing an acid that is separated into a cathode chamber and an anode chamber by a diaphragm, and in which the following formula is applied in the cathode chamber. [In the formula, the benzene rings of A and B may be substituted. ] The anthraquinone represented by is electrochemically converted into the semiquinone form, and this is reacted with glycerin to form the following formula: At the same time, the transition metal salt in the low oxidation state is converted to the high oxidation state in the anode chamber, and this metal ion is converted into the corresponding oxy compound by chemically oxidizing the planar polycyclic aromatic compound. By using this method, benzanthrone and a polycyclic planar aromatic oxy compound can be simultaneously produced electrochemically. Preferably, unsubstituted anthraquinone is used as the raw material for the production of benzaanthrone, which is an important intermediate product for useful vat dyes, carried out in the cathode chamber. or anthraquinones having two or more are also used: alkyl (C ₁ -C ₄ ) such as methyl or ethyl groups, and also alkoxy (C ₁ -C ₄ ) such as methoxy, ethoxy, n- and iso-propoxy, n-, iso- and tert-butoxy group; further substituents include hydroxyl group and chlorine, bromine and iodine. Polycyclic planar aromatic compounds which are converted into corresponding oxy compounds in the anode chamber according to the invention are, for example, those of the anthraquinone series, benzanthrone series and pyrene series. Such starting compounds may have, for example, alkyl side chains that are ultimately oxidized to aldehydes or acids. As an example of a chemical oxidation reaction in the anode chamber, 4.
Conversion of 4'-bibenzanthrone to dioxobiolanthrone is mentioned. Dioxobioleanthrone is easily reduced to dihydroxybioleanthrone, which is a useful intermediate in vat dye synthesis. In this case, in order to recycle the anolyte, the reduction of dioxobiolanthrone to dihydroxybiolanthrone is preferably carried out using SO ₂ - gas. Surprisingly, poorly soluble and large aromatic molecules such as 4,4'-bibenzanthrone or bioluanthrone are easily oxidized by this new method. In this case, the oxidation can be carried out directly in the anode chamber using as oxidizing agent an anolyte containing less than the stoichiometrically required amount of metal salt and preferably more than the stoichiometric amount of the metal salt. This can be done using a salt-containing anolyte as the oxidizing agent and separating it from the anode chamber. The electrolytic cell can be any cell equipped with a diaphragm that is resistant to concentrated and dilute mineral acids such as sulfuric and phosphoric acids, and to organic acids such as acetic acid. There must be. The material constituting the diaphragm is, for example, glass, porcelain, porous polytetraethylene or a polyfluorinated hydrocarbon polymer in the form of an ion exchange membrane. The pore size of the diaphragm is 1-300μ. The cathode chamber can be treated with a protective gas atmosphere so that oxidative side reactions do not occur. For this purpose, it is sufficient to supply, for example, a small amount of nitrogen gas to the reaction vessel on a horizontal surface. Suitable cathodes include the customary technical materials for electrochemical reactions, such as metals, metal alloys, activated metals, metal oxide electrodes, carbon electrodes or electrodes made of glassy sintered carbon. Anodes include platinum, glassy carbon electrodes, and PbO ₂ on titanium. on titanium
PbO ₂ is particularly suitable for in situ reaction in the anode chamber. Acidic media include in particular mineral acids with a pK _s <2, such as sulfuric acid or phosphoric acid. Particularly suitable is sulfuric acid with a concentration of 60-98%, especially 80-95%. The electrolytic solution can contain an organic solvent inert to the reaction as a solvent together with the acid. Electrochemical synthesis is carried out at temperatures of 50-150 °C.
In order to be able to process the quinoid compounds at industrially meaningful concentrations,
For example, from the viewpoint of solubility or suspension in a sulfuric medium, a treatment temperature of about 80 to 120°C, particularly 90 to 105°C is selected. The oxidation of the planar polycyclic aromatic compounds to the corresponding oxy compounds takes place in the anolyte with transition metal ions having an oxidation potential in acidic solution of at least +0.5 V. Metal ions useful as oxidizing agents are therefore generated electrolytically in the anode chamber according to the following equation: Me ⁿ⁺ −xe ⁻ →Me ^(n+x)+ Me=metal ion n+x=number of charges, x is 1 to 5, preferably 1e ⁻
=electron In other words, metal ions are converted from a low oxidation state to a high oxidation state at the anode. Especially suitable is an oxidation potential of +0.5 to +2.5V.
is a transition metal-oxidation-reduction pair, and specifically includes the following. Mn ²⁺ /Mn ³⁺ +1.51V;Ce ³⁺ /Ce ⁴⁺ +1.44V;
Co ²⁺ /Co ³⁺ +1.842V (in 3n HNO ₃ ); and Ag ⁺ /
Ag ²⁺ +1.987V (in 4n HCO ₄ ); measured against a hydrogen standard electrode. In this case, a second redox couple may be present in the anode chamber, one being used in a catalytic amount, i.e. in a molar ratio of 1:100 to 1:1000. The component used at a lower concentration, more specifically, the component used at a concentration of 1 to 10 mmol per mole of transition metal sulfate, is silver sulfate (), which is oxidized at the anode during the reaction to form silver sulfate ( )become.)
It is preferred to use a redox pair mixture which is a silver() salt such as. Addition of a catalytic amount of silver salt increases the yield of conversion of the transition metal salt to a higher valence state. In the case of oxidation of manganese() to manganese(), the yield of manganese() increases by about 20-50% depending on the current density. Electrochemically produced transition metal ions in a high valence state react in situ with the planar polycyclic aromatic compound dissolved in the anolyte, oxidizing it to the corresponding oxy compound, which itself is obtained, changes to a low valence state again, and is further reoxidized at the anode to become a new oxidizing agent. In this way, the oxidizing agent is introduced into a circulating process, so that less than the stoichiometric amount required to oxidize the organic feed compound in the anode compartment is sufficient. In a preferred variant of the invention, the anode chamber does not contain any organic compounds other than the metal salt or salt mixture when energized. In this case, the electrolysis is stopped when almost all of the main components of the metal salt or salt mixture have been converted to a high valence state. This salt solution or suspension is now removed from the anode chamber and used to oxidize the planar polycyclic aromatic compound in a separate reaction vessel. Since the consumed oxidizing agent is not regenerated in this case, the stoichiometric ratio of oxidizing agent and aromatic compound must be maintained. The oxidizing agent consumed at the end of the chemical oxidation reaction, i.e., the metal salt solution in a low oxidation state, is purified after separating the aromatic oxy compounds, optionally with activated carbon, concentrated, and returned to the anode chamber, where it is returned to the anode chamber. Newly oxidized electrolytically. The product obtained is treated with catholyte (Katho) in the usual manner.
-lyten) as well as from the anolyte. If sulfuric acid is used as the reaction medium, either it is diluted, for example to 60%, the precipitated product is separated and washed until neutral, or the product is extracted from the 60% sulfuric acid using a commercially available solvent. . After isolating the product, the anolyte is concentrated to its original concentration and used for the next oxidation cycle. However, it is also possible to oxidize with a dilute solution and then return the oxidized anolyte to its original concentration. High-boiling inert organic solvents, especially halogenated hydrocarbons, in particular chlorobenzenes such as monochlorobenzene, are suitable for extraction and isolation by phase separation of the reaction products formed. Extraction temperature (dissolution of product in organic solvent) is 70~
The temperature is 110°C, preferably 90-100°C. The most important advantages of the method according to the invention are listed below. a. The cathode chamber and the anode chamber are used to carry out redox reactions simultaneously; b. By using a transition metal salt mixture in the anode chamber, the reaction Me ⁿ⁺ →Me ^(n+x)+ of oxidation yields are obtained; c. the anolyte, after separation of the aromatic oxidation products, can be optionally purified, concentrated and reused, and thus does not pose ecological problems; The invention will be illustrated by the following examples. Example 1 In an electrolyzer with a carbon-cathode, a platinum-anode and a magnetic diaphragm, 88% on the cathode side.
Anthraquinone 46.8g (0.225mol) in 1300g sulfuric acid
Dissolve and drop 31.05g of glycerin during electrolysis. The anode side of the electrolytic cell contains 10g of MnSO ₄ H ₂ O.
(0.059 mol) suspended in 88% sulfuric acid. 51700 coulombs (3.5V, 3A,
5 hours). After precipitation and crystallization of crude benzanthrone from the catholyte, 44.0 g of benzantrone are isolated. melting point
171−173℃. This corresponds to a yield of 85% of the theoretical amount,
The current yield of the cathode is 71.4%. After electrolysis, put the anolyte into a beaker and add 4,4'-
10.0 g (0.021 mol) of bibenzanthrone are mixed and the reaction mixture is stirred at 30° C. for 4 hours. The formed dioxobiolanthrone is reduced in situ to dihydroxybiolanthrone by dropwise addition of 400 ml of 40% sodium bisulfite solution. The precipitate of dihydroxybiol anthrol is then separated, washed and dried. Dihydroxybiolanthrone yield 11.0
g, yield 76.4%. Dihydroxybiolanthrone has the following formula It is useful as an intermediate for the synthesis of vat dyes shown in This dye is obtained by methylation of dihydroxybiolanthrone. When using electrochemically produced dihydroxybiolanthrone, the yield is about 99.5%. Examples 2-5 In the examples below, instead of the anthraquinone in the same electrolytic cell as described in Example 1, the substituted anthraquinones listed below are first electrochemically converted to the semiquinone form, which is then reacted in situ with glycerin. to the corresponding substituted benzantrone.

【table】

[Table] Example 6 In an electrolyzer with a carbon cathode, an anode made of glassy sintered carbon, and a porcelain diaphragm, 46.8 g of anthraquinone in 1300 g of 88% sulfuric acid on the cathode side.
(0.225 mol) and when energized, glycerin 31.05
Drop g. The anode side of the electrolytic cell is also MnSO ₄ H ₂ O (0.59 mol)
It has 1300 g of 88% sulfuric acid suspended in 100 g. 95℃
51600 coulombs (3.5V, 3A, 5
time). After suspension and crystallization of crude benzanthrone from the catholyte, 37.08 g of benzantrone are isolated. melting point
171−173℃. This corresponds to a yield of 71.6% based on the theoretical amount, and the current yield of the cathode is 60%. After the completion of electrolysis, the anolyte was prepared as described in Example 1.
Used in the oxidation of 4'-bibenzanthrone. Examples 7-13 Treated as described in Example 6, changing the anthraquinone/glycerin ratio in the catholyte and the cation pair on the anode side, and using a platinum electrode as the anode,
The following results are obtained regarding the benzantrone yield.

[Table] Example 14 An electrolyzer as described in Example 1, using a Ti/PbO ₂ anode instead of a Pt anode. Replace the porcelain diaphragm with an ion exchange membrane made of polyfluorinated hydrocarbon polymer. The cathode reaction and the anode reaction proceed simultaneously. Cathode benzanthrone synthesis is performed as described in Example 5. The yield of crystallized benzanthrone was 83.5%. Melting point 170-172℃. Add MnSO ₄ H ₂ O 2 to 130 g of 88% sulfuric acid in the anode chamber.
After a while after the start of electrolysis, the colorless solution turns pale purple (Mn ²⁺ → Mn ³⁺ ), and then 5 g of 4,4'-bibenzaanthrone is added to the anolyte heated to 95°C.
Dissolve (0.011mol). 51500 coulombs (7.5V,
2A, 7.5 hours), stop electrolysis. The current yield is 70.2% of the theoretical amount. Dilute the anolyte to 60% with water, separate the dihydroxybiolanthrone produced, wash until neutral, and dry. Yield 2.1g, yield 39.28%. Dihydroxybiolantrone is reduced to dihydroxybiolantrone by a conventional method. Example 15 In an electrolyzer with carbon-cathode, Pt-anode and porcelain diaphragm, 88% on the cathode side
Anthraquinone 46.8g (0.225mol) in 1300g sulfuric acid
Dissolve and drop 31.05g of glycerin while energizing. The anode side of the electrolytic cell contains 80g of MnSO ₄ H ₂ O.
(0.47 mol) Ag ₂ SO ₄ 0.62 g (2 mmol) is suspended or dissolved in 600 g of 88% sulfuric acid. 51700 coulombs (3.5V,
3A, 5 hours). After precipitation and crystallization of crude benzanthrone from the catholyte, 44 g of benzantrone are isolated. melting point
171−173℃. This corresponds to a product yield of 85% relative to theory and a current yield of 71%. The anolyte contains 25g of 4,4'-bibenzanthrone after electrolysis.
(0.055 mol) and stirred at 30°C for 4 hours. After diluting the reaction with 640 ml of water, the formed dioxoleanthrone was dissolved in situ at 60°C in SO ₂ 2.24
(0.1 mol) is reduced to dihydroxybiolanthrone. The precipitate of dihydroxybiolanthrone is separated, washed and dried. The yield of dihydroxybiolanthrone is
24.1g (0.049mol), yield 90%, total current yield is
It is 73.4%. Example 16 Add 5.02 g of bibenzanthrone (titration concentration 90%) to 145 ml of anolyte containing 0.086 mol of Mn ³⁺ .
React for 1.5 hours at 30°C (conversion rate of Mn ³⁺ →Mn ²⁺ 85%). Next, add 145 ml of water to the reaction mixture and add 60 ml of water.
Heat to 5.36 °C and SO ₂ within 45 minutes while stirring
Inject g. Of the amount injected, 0.694g is used to reduce the generated dioxobioleanthrone.
The reaction mixture was heated at 90 °C for 2 h and excess SO ₂
is expelled by nitrogen gas. The reaction product is separated off through a semi-molten glass filter and the mother liquor is concentrated again under vacuum (1-5 mm Hg). The reaction product was washed with water until it became neutral,
dry. The yield of dihydroxybiolanthrone was 4.85 g, yield 90.67%. The collected volume of concentrated mother liquor was 116 ml, and sulfuric acid and Mn ²⁺ were
Contains 198.4g. This mother liquor is adjusted to 145 ml with 98% sulfuric acid and water and placed in the anode chamber to repeat the anode oxidation cycle. After 5 cycles, the Mn()-containing sulfuric acid is purified by adding 1 g of activated carbon after separating the product, then warming to 40° C. and filtering. The purified anolyte is still pale yellow and can be enriched and used for further oxidation cycles. The current yield for the reoxidation of manganese sulfate ( ) to manganese sulfate ( ) is positively influenced by the catalytic amount of silver ions and is also influenced by the current density and the conversion rate.

Table Example 17 In the electrolyzer described in Example 1, a Ti/PbO ₂ anode is used instead of the Pt anode. Replace the porcelain diaphragm with a polyfluorinated hydrocarbon polymer. The cathode reaction and the anode reaction proceed simultaneously within the electrolytic cell. Cathode benzanthrone synthesis is performed as described in Example 1. The yield of crystallized benzanthrone was 81.5%. Melting point 171-172℃. Cathode current yield 68.4%. In the anode chamber, add 130g of 88% sulfuric acid.
Dissolve MnSO ₄ H ₂ O2 g, and after a while after electrolysis starts, the colorless solution turns pale purple (Mn ²⁺ → Mn ³⁺ )
After that, 2g (0.0058mol) of tetrachloropyrene
Dissolve in the anolyte solution warmed to 95℃. Stop electrolysis after passing 51600 coulombs (7.0V, 4A, 4 hours). The anolyte is diluted with water to 50% _H2SO4 , the solid residue _is separated off, washed to neutrality and dried. Crude yield after drying: 2.4g. The dry residue contains naphthalenetetracarboxylic anhydride as a product, naphthalenetetracarboxylic acid, and some amount of raw material tetrachloropyrene, according to mass spectrometry analysis. Example 18 In an electrolytic cell with a carbon cathode, a Pt anode and a porcelain diaphragm, 46.8 g of anthraquinone was added to 1300 g of 88% sulfuric acid on the cathode side as described in Example 1.
Mix g, dissolve anthraquinone, 3.5V
After applying a voltage of 31.05g of glycerin was added dropwise. The anode side of the electrolyzer contains 130 g of 88% sulfuric acid with 10 g of MnSO ₄ .H ₂ O suspended. 51900 coulombs (3.5V,
3A, 5 hours). After treatment of the cathode chamber, the yield of benzanthrone is 79.4%. Melting point 173-174℃. The current yield of the cathode is 83.7%. The anolyte is tetrachloropyrene 14.0g (0.04mol)
and stirred at 30°C for 6 hours. The product obtained is diluted with 300 ml of water, filtered, washed to neutrality and dried. Crude yield after drying: 13.5g. The dry residue contains the product naphthalene tetracarboxylic anhydride along with a small amount of raw material according to mass spectrometry analysis. Example 19 0.09 mol of manganese sulfate () obtained by electrochemical oxidation of manganese sulfate () according to Example 6
200 g of 90% sulfuric acid containing is mixed with 1.54 g (0.01 mol) of acenaphthene with stirring at room temperature. At this time, the temperature increases by about 2°C. After stirring for 5 hours at room temperature, the reaction mixture is diluted to a sulfuric acid concentration of 55% and undissolved organic residues are separated off. Wash the residue with water and dry. Yield of crude material 1 g (after drying). Mass spectrometry analysis shows that the residue contains 1,8-naphthalene dicarboxylic anhydride. Example 20 1.28g of naphthalene instead of acenaphthene
(0.01 mol) and otherwise treated as described in Example 19 to produce a dry residue shown to be phthalic anhydride by mass spectrometry.
Obtain 0.5g. Example 21 Malachite green leuco base 10g
(0.03 mol) is mixed with 0.09 mol of manganese sulfate () dissolved in 200 g of 90% sulfuric acid and oxidized as in Example 19. - Manganese sulfate () solution, Example 6
Obtained by electrochemical oxidation of manganese sulfate () according to. Within 10 minutes the solution turns dark and the temperature rises to 53°C. After 1.5 hours oxidation is complete, do not dilute 90
% sulfuric acid was filtered through a glass filter.
54.4 g of MnSO ₄ xnH ₂ SO ₄ are recovered. mother liquor with sulfuric acid
Dilute this solution to 55% with 30% NaOH
Adjust to PH3. Malachide _green is then precipitated as dark green shiny crystals with the composition _C23H25N2 ⁽⁺⁾ _. ( _SO42 ^- ) _{/ 2xnNa2SO4} . Dry yield 19g.

Claims (1)

[Scope of Claims] 1. In an electrolytic cell containing acid, which is separated by a diaphragm into a cathode chamber and an anode chamber, the following formula is applied in the cathode chamber. [In the formula, the benzene rings of A and B may be substituted. ] The anthraquinone represented by is electrochemically converted into the semiquinone form, and this is reacted with glycerin to form the following formula: At the same time, the transition metal salt in the low oxidation state is converted to the high oxidation state in the anode chamber, and this metal ion is converted into the corresponding oxy compound by chemically oxidizing the planar polycyclic aromatic compound. 1. An electrochemical method for producing benzaanthrone and a planar polycyclic aromatic oxy compound, characterized in that the resulting product is separated into a catholyte and an anolyte. 2 Rings A and B are alkyl (C ₁ -
The method according to claim ₁ , characterized in that the raw material is an anthraquinone having one or more of C4), alkoxy ( _C1 - _C4 ), hydroxy, or halogen. 3. The method according to claim 1, characterized in that anthraquinone is reduced to oxyanthrone at the cathode, and this is ring-closed by reaction with glycerin to form benzanthrone. 4. The method according to claim 1, characterized in that 4,4'-bibenzanthrone is chemically oxidized to dioxobiolanthrone in the anolyte during or after electrolysis. 5. The method according to claim 1, characterized in that an electrolytic cell equipped with a diaphragm having a pore size of 1 to 300 μm is used. 6. Process according to claim 1, characterized in that a mineral acid with a pK _s <2 is used. 7. The method according to claim 6, characterized in that sulfuric acid with a concentration of 60 to 98% is used. 8. The method according to claim 6, characterized in that sulfuric acid with a concentration of 80 to 95% is used. 9. Process according to claim 1, characterized in that the treatment is carried out at a temperature of 50 to 150°C. 10. Process according to claim 1, characterized in that the treatment is carried out at a temperature of 80 to 120°C. 11. Process according to claim 1, characterized in that the treatment is carried out at a temperature of 90-105°C. 12. A method according to claim 1, characterized in that transition metal ions are oxidized at the anode to obtain a redox couple with a potential of +0.5 to +2.5V. 13 In the anode chamber, the following redox couple: Mn ²⁺ /
13. Process according to claim 12, characterized in that one of Mn ³⁺ , Ce ³⁺ /Ce ⁴⁺ , Co ²⁺ /Co ³⁺ , Ag ⁺ /Ag ²⁺ is present. 14 The anode chamber contains manganese sulfate (),
14. Process according to claim 13, characterized in that it is oxidized to manganese sulphate () during electrolysis. 15. Process according to claim 13, characterized in that the second redox couple mixture is present in the anode compartment in a molar ratio of 1:100 to 1:1000. 16. Process according to claim 1, characterized in that the anode oxidation is carried out in the presence of a catalytic amount of silver() salts. 17 Silver sulfate () as a silver salt transition metal salt 1
17. Process according to claim 16, characterized in that it is used in a concentration of 1 to 10 mmol mole. 18. Claim 1, characterized in that after carrying out the electrochemical redox reaction of the electrolytic cell, the contents of the cathode chamber and the anode chamber are transferred to separate reaction vessels for carrying out the chemical reaction. Method described. 19 The anolyte consumed in the chemical oxidation reaction is purified, concentrated, and returned to the anode chamber of the electrolytic cell, where transition metal ions are electrochemically oxidized anew. A method according to claim 18. 20 Anthraquinone is reduced cathodically in 80-90% sulfuric acid, and at the same time glycerin is reduced at 1:1.1-
Add at a molar ratio of 1:1.2, and add 60% sulfuric acid after the reaction is complete.
2. A method according to claim 1, characterized in that the precipitated benzantrone is isolated. 21 Manganese sulfate () is oxidized in the presence of 4,4'-bibenzaanthrone at the anode in 80-90% sulfuric acid to form manganese sulfate () that acts as an oxidizing agent at that location, and 4,4'-bibenzanthrone is produced. 2. A method according to claim 1, characterized in that the method comprises converting the dioxobioleanthrone into dioxobioleanthrone. 22 Manganese sulfate () is oxidized to manganese sulfate () with an anode in 80-90% sulfuric acid, and then the anolyte is oxidized to 4,4'-bibenzanthrone to dioxobiolanthrone in a separate reaction vessel. Claims 1, 18 or 1, characterized in that the anolyte is returned to the anode chamber for reoxidation after product isolation.
The method described in Section 9.