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
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
• • 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
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
• • 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
  • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
  • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
  • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
  • C25B11/054—Electrodes comprising electrocatalysts supported on a carrier
• • 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
  • C25B3/01—Products
  • C25B3/07—Oxygen containing compounds
• • 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
  • C25B3/20—Processes
  • C25B3/23—Oxidation

Definitions

• the present invention relates to a method for electrochemical oxidation of organic compounds.
• cathodes and anodes which are used preparatively, must have special electrochemical properties.
• the production of electrodes are often made by coating metallic or carbon-like carrier electrodes by appropriate coating methods such as Plasma spraying, soaking and baking, hot pressing, galvanic Deposits, etc., as described in EP-B 0 435 434.
• DE-A 199 117 46.2 describes the production of a diamond coated electrode and their use in oxidation reactions described organic compounds.
• EP-A 808,920 describes a process for reducing organic Compounds by contacting the organic compound with a Described cathode, wherein the cathode is a carrier from an electrical conductive material and one formed thereon by floating comprises electrically conductive, cathodically polarized layer. Oxidations are there not described.
• DE-A 199 543 23.2 relates to the oxidation of Phosphonomethyliminodiacetic acid to glyphosate.
• this invention lies Task based on a process for the oxidation of organic compounds to provide the high space / time yields, high selectivities at multiple oxidized compounds possible, which the oxidation of Solvent suppressed if possible, high current densities allowed and industrial is applicable.
• This object is achieved by a process for electrochemical oxidation at least one organic compound by contacting one organic compound with an anode, characterized in that the Anode a support made of electrically conductive material and an in situ on it formed by floating, electrically conductive, anodically polarized Layer comprises, wherein phosphonomethyliminodiacetic acid as organic Connection is excluded.
• the catalytic becomes in the operating state active electrode due to the pressure loss at the surface formed by precoat electrically conductive anodically polarized layer stabilized.
• the term "in situ” used according to the invention includes all variants of such a type Alluviation of the material for the anodically polarized layer, that is, before together with or after the reaction mixture has been introduced into the Reactor.
• the term “in situ” thus expresses that the anode in the Oxidation cell is formed, namely by floating The layer can be regenerated by canceling the pumping suspended and discharged by draining. So there are oxidations performed on a system that is capable of a catalytically active electrode in the process of forming and disassembling without opening the cell or Electrodes must be removed.
• Electrically conductive materials are used as carriers for the electrically conductive, anodically polarized layer. Compared to the reductive processes already described, the oxidative side places increased demands on the stability of the material.
• platinum or platinized metals such as. B. platinized titanium.
• the materials from which the carrier is made also depend on the solvent of the anolyte.
• Coated Ti, Ta and Nb carriers are preferably used. In particular, platinized or mixed oxides of IV. To VI.
• electrode carbon and graphite can also be used, from which suitable carrier materials can be provided by a new processing method, water jet cutting.
• fabric shapes made of graphite or carbon can be used, which are commercially available in the form of technical fabrics.
• These carriers are preferably in the form of permeable, porous materials.
• This can be in the form of commercially available filter mesh made of metal wires or graphite / carbon fibers, Graphite / carbon fabrics and graphite / carbon sponges.
• perforated metal foils can be metal felts, graphite felts, Edge filters, sieves or porous sintered bodies as large supports in the form of plates or candles.
• the pore size is in generally 5-300 ⁇ m, preferably 50-200 ⁇ m.
• usable carrier preferably at least about 3%, more preferably 5% and in particular approximately 10% free area, the free area is a maximum of approximately 50%.
• an electrically conductive material for the electrically conductive anodic Polarized layer can all be electrically conductive and partially conductive Materials are used for as long as possible from these Allowing to form a layer on the carrier defined above.
• This anodically polarized layer preferably contains at least one metal, at least one metal oxide or at least one carbon-like material, such as.
• B. Coal especially activated carbon, carbon black or graphite or mixtures of two or more of it.
• Preferred metals are classic metals and / or metal oxides can also be used for the oxidation, in particular Mn, Fe, Mo, Co, Ag, Ir, Pt, Os, Cu, Zn, Cr, Pd, V, W, Bi, Ce and / or their oxides or Mixtures or dopings thereof are used.
• Their salts can also be used in low concentration are used, which regeneratively oxidatively regenerates become.
• the metals or metal oxides used are preferably in finely divided and / or activated form.
• the anodically polarized layer can also be used alone Flooding of the carbonaceous material can be formed. Furthermore, can the anode can also be constructed in situ by using the above metals and Metal oxides on carbon-like materials, especially activated carbon as a carrier be washed ashore.
• the manufacture of e.g. B. in that described in DE-A-44 08 512 is on surfaces such. B. metals and carbonaceous materials to the Carrier washed up.
• the anodically polarized layer can be an electrically conductive
• B. magnetites and coal Activated carbon should be mentioned in particular.
• an anode used which is obtained by first the electrically conductive Auxiliary material is washed up on a carrier and then this Auxiliary material by in situ oxidation of metals, such as. B. Mn, Fe, Mo, Co, Ag, Ir, Cu, Zn, Cr, V, W, Bi the catalytically active layer is formed.
• the said Anode is generated so that the metals directly or after the application of the Auxiliary material washed up as a carrier.
• the average particle size of the particles forming the layer defined above, and the thickness of the layer is always chosen so that an optimal ratio of filter pressure loss and hydraulic throughput is guaranteed and a optimal mass transport is possible.
• the mean is Particle size about 1 to about 400 microns, preferably about 30 to 150 ⁇ m
• the thickness of the layer is generally about 0.5 to 20 mm, preferably 1 to about 5 mm.
• the Pore size of the carrier exceeds the average diameter of the particle, so that two or more particles during the formation of the layer on the support Form bridges over the gaps, which has the advantage that through education the layer on the carrier no significant flow obstruction for the Solution containing organic compound to be oxidized is formed.
• the pore size of the support is about two to about four times as large as the average particle size of the particles forming the layer.
• carriers can also be used in the context of this invention Pore sizes are used which are smaller than the average particle size of the Layer-forming particles are, however, then precisely on those of the forming layer outgoing flow obstruction.
• the anode used according to the invention becomes in situ by floating the constituents forming the layer on the electrical conductive carrier formed, wherein the particles forming the layer contained Solution flows through the carrier until the entire solid content of it Solution is washed up or held.
• the current densities in the process according to the invention are generally about 100 to about 10000 A / m 2 , preferably about 300 to 4000 A / m 2 .
• the throughput of the solution containing the organic compound to be oxidized is generally about 1 to 4000 m 3 / (m 2 xh), preferably about 50 to about 1000 m 3 / (m 2 xh).
• a system pressure of generally approximately 1x10 4 Pa (absolute) to approximately 4x10 6 Pa, preferably approximately 4x10 4 Pa to approximately 1x10 6 Pa the pressure loss in the layer at the flow rates used according to the invention is approximately 1x10 4 Pa to approximately 2x10 5 Pa, preferably about 2.5x10 4 Pa to about 7.5x10 4 Pa.
• the process according to the invention is generally carried out at temperatures between approximately -10 ° C to the boiling point of the used Solvent used, temperatures from 0 ° C to 70 ° C preferred are.
• the process according to the invention can be carried out as a function of the one to be oxidized Connection in acid, i.e. at a pH below 7, preferably at -2 to 3, more preferably 0 to 3, in neutral, i.e. at a pH of about 7 and in basic, i.e. at a pH above 7, preferably is 8-14 and especially 10-14, medium can be carried out.
• the reaction at normal pressure and at 20 to 50 ° C. is particularly preferred carried out.
• the type of used Cell type, the shape and arrangement of the electrodes are not decisive Influence, so that in principle all cell types common in electrochemistry can be used.
• Undivided cells with plane-parallel electrode arrangement or candle-shaped Electrodes are preferably used when neither educts nor Products are disruptively altered by the anode process or react with each other.
• the electrodes are preferably plane-parallel arranged because in this embodiment with a small electrode gap (1 mm up to 10 mm, preferably 3 mm) a homogeneous current distribution is given.
• Split cells with plane-parallel electrode arrangement or candle-shaped Electrodes are preferably used when the anolyte from Catholytes must be separated, e.g. B. chemical side reactions to exclude or to simplify the subsequent material separation.
• Separation medium can be ion exchange membranes, microporous membranes. Diaphragms, filter fabrics made of non-electron-conducting materials, glass frits as well as porous ceramics are used.
• the electrodes are arranged plane-parallel, as with this Embodiment and small electrode gaps (two gaps each 0 mm to 10 mm, preferably cathodic 0 mm and anodic 3 mm) a homogeneous Current distribution is given.
• the separation medium is preferably located directly on the Cathode.
• Electrode materials can generally be perforated materials such as Nets, expanded metal sheets, lamellas, profile webs, grids and smooth sheets use. In the case of the plane-parallel electrode arrangement, this takes place in the form flat surfaces, in the embodiment with candle-shaped electrodes in the form a cylindrical arrangement.
• the choice of the cathode material or its coating is such. T. depending on the desired cathode reaction.
• stainless steel, nickel, nickel-coated or precious metal-coated electrodes are used for the formation of hydrogen; for applications that require a high hydrogen overvoltage, Pb, Hg, Cd, alloys of Pb / Sn or other metals such as Cu, Ag, steel, Hastelloy® are used in question.
• graphite, conductive ceramics, such as. B. use TiO x compounds, Raney nickel, Pt, Pd / C.
• protic solvents i.e. Solvents that contain and can release protons and / or Can form hydrogen bonds, such as. B. water, alcohols, Amines, carboxylic acids etc., optionally in a mixture with aprotic polar ones Solvents such as B. THF to use in the inventive method. They are preferred because of the conductivity to be maintained lower alcohols such as methanol, ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, tert-butanol, ether, such as. B.
• diethyl ether, 1,2-dimethoxyethane, Furan, THF, MTBE and dimethylformamide used preferably one Mixture of these solvents or more preferably water without additives, provided there are no solubility problems of the substances to be reacted or formed is coming.
• carboxylic acids can also be used or amides are used.
• Preferred carboxylic acids are used formic acid, acetic acid, propionic acid and longer-chain branched like unbranched carboxylic acids, also sulfuric acid.
• the oxidation according to the invention is carried out in the presence of a Auxiliary electrolytes made.
• auxiliary electrolyte As a rule, one cannot do without an auxiliary electrolyte, it is used for Setting the conductivity of the electrolysis solution and / or for controlling the Selectivity of the reaction.
• the content of the auxiliary electrolyte is usually included a concentration of about 0.1 to about 10, preferably about 1 up to about 5 wt .-% each based on the reaction mixture.
• Auxiliary electrolyte come protonic acids, such as. B. organic acids, wherein Methanesulfonic acid, benzenesulfonic acid, acetic acid or toluenesulfonic acid can be called and mineral acids, such as. B. sulfuric acid and Phosphoric acid. Neutral salts can also be used as auxiliary electrolytes be used.
• Metal cations of lithium come as cations, Sodium, potassium but also tetralalkylammonium cations, such as B. Tetramethylammonium, tetraethylammonium, tetrabutylammonium and Dibutyldimethylammonium in question.
• anions fluoride, Tetrafluoroborate, sulfonates, such as. B. methyl sulfonate, benzenesulfonate, Toluenesulfonate, sulfates such as e.g. B.
• sulfate methyl sulfate, ethyl sulfate, phosphates, such as e.g. B. methyl phosphate, dimethyl phosphate, diphenyl phosphate, hexafluorophosphate, Phosphonates, e.g. B. methylphosphonate and Phenylphosphonate methyl ester, but also the halides chloride, bromide and Iodide.
• basic compounds such as. B. alkali or Alkaline earth metal hydroxides, carbonates, bicarbonates and alcoholates can be used, with alcoholate anions methylate, ethylate, butylate and isopropylate are preferably used.
• alcoholate anions methylate, ethylate, butylate and isopropylate are preferably used.
• Compounds again question the above cations.
• amines in aqueous solutions or in mixtures of water with organic solvents as auxiliary electrolyte such.
• this method cannot only using a homogeneous solution of the organic to be oxidized Compound can be carried out in a suitable solvent, but also in a two-phase system consisting of one phase containing at least one organic solvent as defined above and a second hydrated phase.
• the electrochemical oxidation according to the invention can either be continuous or be carried out discontinuously.
• an anode is shown in situ in that a catalytically active layer is formed by floating.
• the carrier as long as a suspension of the finely divided metal and / or Metal oxide and / or nanoclusters and / or the carbon-like material, that is Flow through the material that is to be washed up until it essentially the total amount of material contained in the suspension the carrier. Whether this is the case can be B. visually recognize that the cloudy suspension at the beginning of the precoat becomes clear.
• the Carrier through a suspension of the material forming the intermediate layer flows through until essentially the entire amount used on Carrier located.
• the anodic is then used to wash away the Proceed polarized layer forming material as described above.
• the oxidizing organic compound fed to the system and introduced a precisely defined amount of electricity is oxidized into the system.
• control the amount of electricity supplied It is also possible to isolate partially oxidized compounds.
• the selectivities are at least 50%, generally above 70% and, in the case of particularly smooth oxidations, greater than 90%.
• Catalyst can be replaced by the in the electrolytic cell Flow direction is reversed, whereby the stranded layer Loses contact with the wearer and z. B. by suction or filtration of this contained solution or suspension can be removed. After that, the Layer as described above and then new Educt supplied and implemented.
• the steps implementation (oxidation), renewal of the catalyst or renewed implementation of an educt can also be operated alternately by first, as described above, the anode is made by floating in situ is then fed and the organic compound to be oxidized is implemented, the flow direction within the Electrolysis cell is changed and the spent catalyst, for. B. by Filtering is removed, then the anode with again the fresh anodically polarized layer forming material and then is further oxidized.
• the electrolysis unit consists of at least one anode a common anolyte cycle stationary as homogeneously continuous Reactor operated. That means that after a single wash of the Catalyst a defined concentration level of starting materials and products is held.
• the reaction solution is constantly electrochemical active anode pumped in a circuit and the circuit continuously educt supplied, product being continuously removed from this cycle, so that the reactor content remains constant over time.
• the advantage of this process control compared to the discontinuous reaction procedure is the simpler Process management with less equipment.
• the reaction technology Disadvantage that either unfavorable concentration ratios (i.e. low Educt concentration and high product concentration at the end point of the reaction) or a higher separation effort during processing can be accepted must, with the following apparatus arrangement, which is particularly preferred, be encountered:
• At least two electrolysis units are connected in series, the first educt and the last unit the product is removed. This procedure ensures that in the first Electrolysis unit (s) worked with significantly cheaper concentration profiles as in the last unit (s). This means, on average, about everyone Electrolysis units, compared to a reaction in which the Electrolysis units are operated in parallel, higher space-time yields reached.
• Electrochemical oxidations preferred according to the invention are the formation of Alcohols, ethers, ketones, aldehydes, epoxides, carboxylic acids, esters, Olefins, amides, azo compounds and oxoamides. Also preferred is halogenation, especially fluorination, chlorination, bromination and particularly preferably bromination.
• a preferred method according to the invention is the oxidation of aromatics such as substituted benzenes, substituted toluenes and substituted or unsubstituted naphthalenes.
• the alkyl chains can be branched or unbranched.
• methods for alkoxylation preferably methoxylation of 4-methoxytoluene, p-xylene, p-tert-butyltoluene, 2-methylnaphthalene, anisole or hydroquinone dimethyl ether are particularly preferred.
• toluene and benzene derivatives such as. B. chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene and analogously the fluorinated, brominated and iodinated benzenes.
• substrates are fluoro-, chloro-, bromo- and iodotoluenes, which can be ortho-, meta- and para-substituted, as well as nitrobenzenes or nitrotoluenes, especially nitrobenzene, m-, o-, p-dinitrobenzene, m-, o- , p-nitrotoluene, 2,4- and 2,6-dinitrotoluene or monoacetyl- or bisacetyl-substituted toluenes and benzenes.
• the aforementioned organic compounds can by the method for electrochemical oxidation can also be acyloxylated, in particular there Acetic acid is used as a solvent.
• Another preferred method for electrochemical oxidation relates to the anodic dimerization of substituted and unsubstituted benzenes, toluenes and naphthalenes, the aforementioned organic compounds preferably being substituted by C 1 to C 5 alkyl chains.
• the process according to the invention can also advantageously be used for the alkoxylation, preferably methoxylation or hydroxylation, of carbonyl compounds, in particular cyclohexanone, acetone, butanone or substituted benzophenones.
• Another preferred method is the oxidation of alcohols or Carbonyl compounds to carboxylic acids, for example from butanediol Acetylenedicarboxylic acid or from propargyl alcohol to propiolic acid.
• the piston reaction is also preferred Decarboxylation of aliphatic carboxylic acids for coupling the Carboxylic acid residues, which can also be substituted, for the synthesis of alkanes or for the further synthesis of alcohols, ethers, diesters, mono- and Dicarboxylic acids and compounds induced by radicals.
• Another preferred method is the implementation of open chain and cyclic Hydrocarbons to allyl and double methoxylated Obtaining products, the synthesis is particularly preferred here starting from cyclohex-2-enylmethyl ether or 1,1-dimethoxy-2-cyclohexane of cyclohexane.
• the method can advantageously also be used for the functionalization of amides.
• Particularly suitable amides are shown in the general formula (I) wherein R 1 is a branched or linear C 1 to C 20 alkyl, cycloalkyl, aralkyl group, and R 2 or R 3 independently of one another represent a C 1 to C 20 alkyl group. Alkoxylation is the most preferred functionalization. Dimethylformamide is particularly preferably converted to N-monomethoxymethyl-N-methylformamide.
• the method according to the invention is also suitable for the oxidation of heterocycles.
• Preferred heterocycles have 3 to 7, preferably 4 to 6 and particularly preferably 4 to 5 carbon atoms.
• the heterocycles can have 1 to 3, preferably 1 to 2 and particularly preferably 1 hetero group or hetero atom.
• Preferred hetero groups or heteroatoms are those which have NH, O and S. It is further preferred that the heterocycles have at least one double bond, preferably two double bonds.
• the heterocycles can also be substituted, halogens and C 1 -C 20 -alkyl groups being particularly preferred substituents.
• Preferred electrochemical reactions on heterocycles are, in particular, the conversion of tetrahydrofuran to 2-monomethoxytetrahydrofuran and 2,5-dimethoxytetrahydrofuran or of furan to dimethoxydihydrofuran, and the conversion of N-methylpyrrolidone-2 to 5-methoxy-N-methylpyrrolidone-2.
• the oxidation of hydrazines to the corresponding azo compounds is further preferred; isopropyl, ethyl and tert-butyl hydrazodicarboxylate are particularly preferably converted to the corresponding azodicarboxylic acid esters.
• the electrochemical oxidation of metal salts which can be used in-cell or ex-cell as mediators is furthermore preferred, the use of the ion pair Ce 3 + / 4 + and / or Cr 3 + / 6 + being particularly preferred.
• the following compounds are oxidized: p-xylene, p-methoxytoluene, p.tert.-butyltoluene, p-chlorotoluene, p-isopropyltoluene; Acetone, methyl ethyl ketone, cyclohexanone, methyl glyoxaldimethyl acetal; Ethyl, isopropyl, tert-butyl hydrazodicarboxylate; Dimethyl sebacate; Ce 3 + / 4 + , Cr 3 + / 6 + .
• the electrolyte consisted of a mixture of 1166.7 g 7% Sodium methyl sulfate solution in methanol, 70 g p-methoxytoluene and 20 g BA 1200 graphite powder, 10 g Sigradur K (20-50 ⁇ m).
• the implementation was like carried out as follows:
• the cell was first filled and heated to 40 ° C., then the graphite material was added and pumped for about 10 minutes in order to obtain a filter layer as an electrode.
• the electrolysis was then carried out at a temperature of 40 ° C. with a current density of 300 A / m 2 at normal pressure.
• the electrolysis was ended after 4.5 F. After distilling off the solvent and distilling the product mixture, 79% anisaldehyde was obtained. The turnover was 90%.
• the electrolyte consisted of a mixture of 1281 methanol, 7 g water, 42 g Potassium iodide, 70 g methylglyoxaldimethylacetal and 20 g graphite powder BA 1200, 10 g Sigradur K (20-50 ⁇ m).
• the implementation was carried out as follows:
• the cell was first filled and heated to 40 ° C., then the graphite material was added and pumped for about 10 minutes in order to obtain a filter layer as an electrode.
• the electrolysis was then carried out at a temperature of 10 ° C. with a current density of 1000 A / m 2 at normal pressure.
• the electrolysis was ended after 3 F. 27% tetramethoxypropanol were obtained.
• the electrolyte consisted of a mixture of 1281 g methanol, 7 g water, 42 g potassium iodide, 70 g methylglyoxaldimethyl acetal, 600 mg nickel (II) sulfate, 20 g BA 1200 graphite powder, 10 g Sigradur K (20-50 ⁇ m).
• the implementation was like carried out as follows:
• the cell was first filled, then the graphite material was added and pumped for about 10 minutes in order to obtain a filter layer as an electrode.
• the electrolysis was then carried out at a temperature of 10 ° C. with a current density of 1000 A / m 2 at normal pressure.
• the electrolysis was ended after 3 F. 54% tetramethoxypropanol were obtained.

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• 1999
  • 1999-12-22 DE DE19962102A patent/DE19962102A1/de not_active Withdrawn
• 2000
  • 2000-12-18 EP EP00127271A patent/EP1111094A3/fr active Pending
  • 2000-12-22 US US09/742,537 patent/US6398938B2/en not_active Expired - Fee Related
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