Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B3/00—Electrolytic production of organic compounds

Definitions

• the present invention relates to an electrochemical redox process which is carried out in an electrolysis cell separated by a diaphragm in the cathode and anode compartments, cathodic benzanthrones and simultaneously anodically planar polycyclic aromatic oxy compounds being produced.
• the oxy compounds obtainable according to the present invention have hitherto often been produced by means of reduction or oxidation reactions, in which heavy metals or heavy metal salts of higher value are frequently used as industrial reducing or oxidizing agents. After working up, diluted metal salt solutions remain, the disposal of which poses considerable ecological problems.
• metals such as iron, zinc, aluminum or copper in concentrated sulfuric acid are used for the reductive conversion of anthraquinone into the semiquinone form.
• metals such as iron, zinc, aluminum or copper in concentrated sulfuric acid are used for the reductive conversion of anthraquinone into the semiquinone form.
• Such processes are described, inter alia, in US Pat. No. 1,896,147 (reducing agent Fe), US Pat. No. 2,034,485 and USSR Patent 401,130 (reducing agent Fe and Cu), AM Lahin, Zhur. Obschei Khim. 18, 308 (1948), see. CA 44, 1079b (reducing agent Zn, Al, CuS0 4 ) and U.S. Patent 1,791,309 (reducing agent Zn and Al).
• iron has gained the greatest practical importance as a reducing agent.
• iron as a reducing agent has major economic and ecological disadvantages, since at least 2 moles of iron must be used per mole of anthraquinone. This means that, for example, 2.0 moles of iron sulfate per mole of benzanthrone produced or at least 1320 g of iron sulfate per 1000 g of benzanthrone produced are produced as waste products.
• large amounts of waste sulfuric acid are produced, because in order to isolate the benzanthrone formed, the sulfuric acid has to be diluted to approx. 20%, which then either has to be regenerated to concentrated sulfuric acid in an energy-intensive manner or whose removal is also an environmental problem.
• the environmentally friendly electrochemical reaction procedure represents an alternative to the use of environmentally harmful reducing or oxidizing agents.
• the oxidation potential of the anode is not used in this method.
• the object of the invention is therefore to develop an electrochemical redox process which couples the already known reduction reaction taking place at the cathode with an oxidation reaction taking place simultaneously at the anode.
• the process according to the invention thus consists in the simultaneous production of benzanthrones and polycyclic planar aromatic oxy compounds electrochemically by working in an electrolysis cell which contains an acid and is separated by a diaphragm into a cathode and an anode compartment, an anthraquinone of the formula being used in the cathode compartment electrochemically converted into the semiquinone form and this with glycerin to the benzanthrone of the formula implemented, the benzene rings A and B can be substituted and at the same time the cations of a transition metal salt in the anode space from the lower to a higher oxidation state and uses these metal ions for the chemical oxidation of planar polycyclic aromatic compounds to the corresponding oxy compounds.
• the products are isolated from the catholyte and anolyte.
• Unsubstituted anthraquinone is preferably used as the starting material for the production of benzanthrones in the cathode compartment, which are important as vat dye intermediates, but also those anthraquinones whose rings A and B have one or more of the following substituents: alkyl (C l -C 4), such as methyl or ethyl, furthermore alkoxy (C 1 -C 4), such as the methoxy, ethoxy, n-and iso-propoxy and n-, iso- and tert . -Butoxy residue; Finally, the hydroxyl group and the halogen atoms, such as chlorine, bromine and iodine, come into consideration as substituents.
• Polycyclic planar aromatic compounds which correspond to the present invention in the anode compartment appropriate oxy compounds are, for example, those of the anthraquinone, benzanthrone and pyrene series.
• Such starting compounds can also have, for example, alkyl side chains which are terminally oxidized to the aldehyde or to the acid.
• An example of the chemical oxidative reaction in the anode compartment is the conversion of 4,4'-bibenzanthrone to dioxoviolanthrone.
• Dioxoviolanthrone can easily be reduced to dihydroxyviolanthrone, an important intermediate for the synthesis of vat dyes. It is advantageous for the recycling of the anolyte to carry out the reduction of dioxoviolanthrone to dihydroxyviolanthrone with SO Z gas.
• oxidation can be carried out either directly in the anode compartment with a smaller than stoichiometrically required amount of metal salt, or preferably separately from the anode compartment with an anolyte solution containing more than the stoichiometric amount of metal salt as the oxidizing agent.
• any cell with a diaphragm can be selected as the electrolysis cell, the diaphragm being acid-resistant and concentrated and dilute mineral acid, such as sulfuric acid, phosphoric acid, and against organic acids, such as acetic acid.
• Materials from which the diaphragm is made are, for example, glass, clay, porous polytetrafluoroethylene or polymeric perfluorinated hydrocarbons in the form of an ion exchange membrane.
• the pore size of the diaphragm is in the range of 1 to 300 u.
• Suitable cathodes are the materials customary for electrochemical reactions, such as metals, metal alloys, activated metals, metal oxide electrodes, carbon electrodes, or electrodes made of glass-like sintered carbon.
• electrodes made of sintered carbon and Pb0 2 on titanium are particularly suitable for in situ reactions in the anode compartment.
• the acidic reaction medium in particular mineral acids having a pK a ⁇ 2, such as sulfuric or phosphoric acid.
• Sulfuric acid with a concentration of 60 to 98% and especially a concentration of 80 to 95% is particularly suitable.
• the electrolyte can also contain reaction-inert organic solvents as solubilizers.
• the electrochemical synthesis takes place at a temperature between 50 and 150 ° C. Because of the solubility or However, in order to be able to work in technically interesting concentrations, operating temperatures in the range from about 80 to 120.degree. C., but in particular 90 to 105.degree. C., must be selected for suspending the quinoid compounds formed as an intermediate stage, for example in sulfuric acid electrolyte.
• Transition metal redox pairs with an oxidation potential between +0.5 and +2.5 volts are particularly suitable; are mentioned in detail: measured against hydrogen normal electrode.
• a mixture of two redox pairs can also be present in the anode compartment, one of the two being present in each case in catalytic amounts, namely with molar ratios of 1: 100 to 1: 1000.
• the component used in lower concentration namely 1 to 10 mmol per mole of transition metal sulfate
• a silver I salt for example silver I sulfate, which forms silver II sulfate during the reaction at the anode is oxidized.
• the addition of catalytic amounts of silver salt increases the yield when the transition metal salt is converted to its higher valence level.
• the yield of manganese III can be increased by 20 to 50%, depending on the current density.
• the electrochemically produced, higher-quality transition metal ions react in situ with the planar, polycyclic, aromatic compound dissolved in the anolyte and oxidize them to the corresponding oxy compounds, go back to the lower valence level even by taking up electrons, are finally reoxidized at the anode and stand again ready as an oxidizer.
• the oxidizing agent is conducted in a cyclic process, therefore a less than stoichiometric amount is sufficient to oxidize the organic starting compound in the anode compartment.
• the anode compartment contains no organic compound in addition to the metal salt or salt mixture when current is passed.
• the electrolysis is stopped when the metal salt or the main component of the salt mixture is almost completely converted to the higher valence level.
• This salt solution or suspension can now be removed from the anode compartment and used in a separate reaction vessel for the oxidation of planar polycyclic aromatics. Since the oxidizing agent used is not regenerated in this case, stoichiometric ratios are required between the oxidizing agent and aromatics.
• the oxidant consumed at the end of the chemical oxidation reaction i.e. the solution of the metal salt now present in the lower oxidation state, after separation of the aromatic oxy compound, clarification by means of activated carbon and concentration, if appropriate, can be returned to the anode compartment and is again electrolytically oxidized here.
• the products obtained can be isolated in the usual way from the catholyte, such as anolyte.
• sulfuric acid as the reaction medium, e.g. Diluted to 60%
• the precipitated product is filtered off and washed until neutral, or the product is extracted from the 60% sulfuric acid with a commercially available solvent.
• the anolyte is concentrated to the original concentration and used in the next oxidation cycle.
• the extraction temperature (absorption of the product in the organic solvent) is 70 to 110 ° C, advantageously 90 to 100 ° C.
• anthraquinone (0.225 mol) are dissolved in 1300 g of 88% strength sulfuric acid on the cathode side in an electrolysis apparatus with a carbon cathode, Pt anode and sound diaphragm, and 31.05 g of glycerol are added dropwise during the electrolysis.
• the anode side of the electrolysis cell contains 130 g of 88% strength sulfuric acid, in which 10 g of MnSO 4 .H 2 O (0.059 mol) are suspended. At 95 ° C 51 700 coulombs are used for electrolysis (3.5 V, 3A, 5 h).
• the anolyte is poured into a beaker, 10.0 g (0.021 mol) of 4,4'-bibenzanthrone are added, and the reaction mixture is stirred at 30 ° C. for 4 hours.
• the dioxoviolanthrone formed is reduced in situ by dropwise addition of 400 ml of 40% sodium bisulfite solution to dihydroxyviolanthrone.
• the dihydroxyviolanthrone precipitate is finally filtered off, washed and dried.
• Dihydroxyviolanthrone serves as an intermediate for the synthesis of the vat dye of the formula which is obtained by methylation of dihydroxyviolanthrone.
• the yield is approximately 99.5% when electrochemically represented dihydroxyviolanthrone is used.
• an anode made of sintered carbon and a clay diaphragm, 88.8% of 88.8% anthraquinone (0.225 mol) are dissolved in 1300 g of sulfuric acid on the cathode side, and 31.05 g of glycerin are added dropwise when the current is passed through.
• the anode side of the electrolysis cell also contains 1300 g of 88% strength sulfuric acid, in which 100 g of MnSO 4 .H 2 O (0.59 mol) are suspended. At 95 ° C 51 600 coulombs are used for electrolysis (3.5 V, 3 A, 5 h).
• the anolyte is used as described in Example 1 for the oxidation of 4,4'-bibenzanthrone.
• a Ti / Pb0 2 anode is used instead of a Pt anode.
• the clay diaphragm is replaced by an ion exchange membrane made of perfluorinated polymeric hydrocarbons.
• the cathodic reaction and the anodic reaction take place simultaneously.
• Dioxoviolanthrone can be reduced to dihydroxyviolanthrone as usual.
• anthraquinone (0.225 mol) are dissolved in 1300 g of sulfuric acid in 1300 g of sulfuric acid in an electrolysis apparatus with a carbon cathode, Pt anode and sound diaphragm on the cathode side, and 31.05 g of glycerol are added dropwise when the current is passed through.
• the anode side of the electrolytic cell contains 600 g of 88% sulfuric acid, in which 80 g of MnSO 4 .H 2 O (0.47 mol) and 0.62 g of Ag 2 S0 4 (2 mmol) are suspended or dissolved.
• the Mn-II-containing sulfuric acid is purified by adding 1 g of activated carbon, then heating to 40 ° C. and filtration.
• the clarified anolyte is light yellow again and can be used in further oxidation cycles after concentration.
• the current efficiency of the reoxidation of the manganese-II to manganese-III sulfate is influenced positively by catalytic amounts of silver ions and is also dependent on the current density and the degree of conversion.
• a Ti / Pb0 2 anode is used instead of a Pt anode.
• the clay diaphragm is replaced by an ion exchange membrane made of perfluorinated polymeric hydrocarbons. The cathodic reaction and the anodic reaction take place simultaneously in the electrolytic cell.
• the anolyte is diluted with water to 50% H 2 SO 4 and the solid residue is filtered off, washed neutral and dried. Yield raw, after drying: 2.4 g.
• this dry residue contains the product naphthalene tetracarboxylic anhydride, naphthalene tetracarboxylic acid, and some starting material, tetrachloropyrene.
• Example 1 in an electrolysis apparatus with carbon cathode, Pt anode and sound diaphragm on the cathode side 1300 g H 2 SO 4 88% with 88.8 g anthraquinone and after dissolving the anthraquinone and applying a voltage of 3, 5 V, 31.05 g of glycerin added dropwise.
• the anode side of the electrolytic cell contains 130 g of 88% strength sulfuric acid, in which 10 g of MnSO 4 .H 2 O are suspended.
• the dry residue contains naphthalene tetracarboxylic anhydride in addition to small amounts of starting material.
• the mass spectrometric analysis shows that the dry residue contains 1,8-naphthalenedicarboxylic acid anhydride.
• the solution darkens within 10 minutes and the temperature rises to 53 ° C.
• the oxidation is complete after 1.5 hours and the undiluted 90% sulfuric acid is filtered off with a glass frit; 54.4 g of MnS0 4 xn H 2 SO 4 , moist, are recovered.
• the mother liquor will diluted to 55% sulfuric acid and this solution adjusted to pH 3 with 30% NaOH. Malachite green precipitates in dark green shiny crystals of the composition C 23 H 25 N 2 (+) . (SO 4 2 -) / 2 xn Na 2 SO 4 .

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• 1982
  • 1982-03-02 US US06/354,109 patent/US4394227A/en not_active Expired - Fee Related
  • 1982-03-02 DE DE8282101587T patent/DE3278880D1/de not_active Expired
  • 1982-03-02 EP EP82101587A patent/EP0060437B1/fr not_active Expired

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