EP4165236B1 - Method for the electrochemical preparation of alkanedicarboxylic acids by ring-opening oxidation using a doped ni(o)oh foam electrode - Google Patents

Method for the electrochemical preparation of alkanedicarboxylic acids by ring-opening oxidation using a doped ni(o)oh foam electrode Download PDF

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EP4165236B1
EP4165236B1 EP21727488.5A EP21727488A EP4165236B1 EP 4165236 B1 EP4165236 B1 EP 4165236B1 EP 21727488 A EP21727488 A EP 21727488A EP 4165236 B1 EP4165236 B1 EP 4165236B1
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hydrogen
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EP4165236A1 (en
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Frank Weinelt
Franz-Erich Baumann
Siegfried R. Waldvogel
Anna-Lisa RAUEN
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Evonik Operations GmbH
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    • 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
    • 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
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • 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
    • C25B11/042—Electrodes formed of a single material
    • C25B11/047—Ceramics
    • 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
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/13—Single electrolytic cells with circulation of an electrolyte
    • C25B9/15—Flow-through cells

Definitions

  • the invention relates to a process for the electrochemical production of alkylenedicarboxylic acids by ring-opening oxidation using a doped Ni(O)OH foam electrode in an aqueous alkaline solution.
  • BV Lyalin and VA Petrosyan disclose the production of unsubstituted adipic acid and the oxidation of carbohydrates.
  • EP 2907898 A1 ( US 2015/0225861 A1 ) discloses the use of nickel foam at reaction temperatures of 80 ° C for the oxidative ring cleavage of 3,3,5-trimethylcyclohexanol in one embodiment variant. The reaction was carried out in a highly diluted solution with low yields.
  • Schmitt et al. (Beilstein J. Org. Chem., 2015, 11, 473-480 ) reveal the cleavage of lignin into various oxo-substituted aromatics using different electrodes. The oxidation to the corresponding acids was not successful.
  • Another advantage is the high yield of the process according to the invention.
  • the present invention thus opens up for the first time the possibility of developing a technically relevant continuous process for obtaining alkanedicarboxylic acids without the use of aggressive chemicals and still in high yields.
  • R 1 , R 2 , R 3 can be the same or different, hydrogen or alkyl radical with 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, linear or branched, where at least one of the radicals R 1 , R 2 , R 3 is an alkyl radical.
  • radicals R 1 , R 2 , R 3 are particularly preferably hydrogen and R 2 is an alkyl radical with 1 to 4 carbon atoms.
  • the process according to the invention is preferably carried out according to scheme (IV).
  • A is a hydrocarbon with 4 to 9 carbons, all ring carbons of A in the cyclic starting material of scheme (IV) carrying at least one hydrogen substituent, A has at least 2 ring carbon atoms, more preferably 3 to 9 ring carbon atoms.
  • the process according to the invention is preferably carried out according to at least one of the schemes (II), (III) or (IV).
  • Isomers are known to those skilled in the art; reference is made in particular to the definitions by Prof. Kazmaier of Saarland University, e.g. E.g. http://www.uni-saarland.de/fak8/kazmaier/PDF_files/vorlesungen/Stereochemie%20Strassb%20V orlage.pdf.
  • the doping content information relates to the elementary state of the doping based on the mass of the metal of the electrode.
  • the Ni(O)OH foam electrode preferably has 3 to 9% by weight of phosphorus and more preferably 4 to 9% by weight; phosphorus is considered an element and is based on the metal mass of the electrode.
  • the content determination of the phosphorus doping is preferably carried out in accordance with DIN EN ISO 5427, Appendix D.1.
  • the Ni(O)OH foam electrode preferably has a thickness of several millimeters, more preferably more than 3 mm, more preferably more than 5 mm and particularly preferably equal to or thicker than 6 mm.
  • the Ni(O)OH foam electrode preferably contains at least 90% by weight of metal, more preferably at least 95, 98, 99% by weight, more preferably at least 99.9, particularly preferably at least 99.99% by weight. Nickel, based on the total metal content.
  • Ni(O)OH foam electrode can contain other metals besides nickel.
  • Preferred other metals are Co, Fe and Cu.
  • Content of other metals in the Ni(O)OH foam electrode is preferably equal to or less than 10% by weight, more preferably 5% by weight, more preferably 2% by weight, particularly preferably less than or equal to 1% by weight based on the total metal content.
  • the Ni(O)OH foam electrode preferably contains a maximum of 5% by weight, preferably 2% by weight, more preferably 1% by weight and particularly preferably 0.5% by weight and particularly preferably a maximum of 0.1% by weight.
  • % iron or iron compounds where the content information relates to the element in relation to the total metal content.
  • the Ni(O)OH foam electrode preferably contains a maximum of 1% by weight, preferably 0.1% by weight and more preferably a maximum of 0.01% by weight of V, Wo and Mo; These metals are subject to corrosion in an alkaline-aqueous medium, which can have an unfavorable effect on the process according to the invention.
  • any metal that is inert to the reaction medium can be used as a cathode material.
  • cosolvents can be alcohols or DMSO. Up to 30% by volume of a cosolvent is preferably present, more preferably 1 to 20% by volume, based on the sum of the solvents, more preferably the solvent consists of water.
  • alkaline additives are suitable as alkaline additives.
  • Alkaline metal hydroxides such as LiOH, NaOH, KOH, and soluble alkaline earth metal hydroxides are preferred in the process according to the invention.
  • Sodium hydroxide is particularly preferably used according to the invention.
  • the concentration of the alkaline additive is preferably 0.5 to 2 mol/l based on the aqueous alkaline solution, more preferably 0.8 to 1.5 mol/l and particularly preferably 1 mol/l with a possible deviation of up to 10% , preferably a deviation of up to 5% of the molarity.
  • the concentration of the starting materials according to scheme (I) is preferably 0.06 to 0.5 mol/l, more preferably 0.08 to 0.3 and particularly preferably 0.09 to 0.11 mol/l.
  • the total current that leads to the reaction according to the invention according to schemes (II) and (III) is 8 F.
  • 8 to 10 F are used, more preferably 8.5 to 9 F.
  • 6 F are required for implementation according to scheme (IV).
  • 6 to 8 F are used, more preferably 6.5 to 7 F.
  • the method according to the invention is preferably carried out with a current density of 2 to 10 mA/cm 2 , more preferably 2.5 to 7.5 mA/cm 2 and particularly preferably 3.3 to 6 mA/cm 2 .
  • the area specification refers to the geometric area without taking the inner surface of the foam into account.
  • This current density information refers to the largest area on one of the sides and is therefore independent of the flow direction in the case of the flow cell.
  • the process according to the invention can be carried out discontinuously, for example in a batch electrolysis cell or continuously in an electrolysis cell through which flow occurs, preferably in an electrolysis cell through which flow is continuous.
  • the process according to the invention is preferably carried out at temperatures of 20 - 70°C, preferably 30 - 60°C, more preferably 35 - 50°C.
  • the method according to the invention is carried out using a doped Ni(O)OH foam electrode, the doping being selected from phosphorus, arsenic, selenium and sulfur, the concentration of alkali being 0.8 to 1.5 mol/l and the concentration of starting material according to scheme (I) is 0.08 to 0.3 mol/l.
  • the method according to the invention is carried out using a Ni(O)OH foam electrode doped with phosphorus, the concentration of alkali being 0.8 to 1.5 mol/l and the current density being 2 to 10 mA/cm 2 .
  • the method according to the invention is carried out using a Ni(O)OH foam electrode doped with phosphorus according to scheme (IV).
  • A is a hydrocarbon with 4 to 9 carbons, all ring carbons of A in the cyclic starting material of scheme (IV) carrying at least one hydrogen substituent, preferably A has at least 2 ring carbon atoms, more preferably 3 to 9 ring carbon atoms.
  • the method according to the invention is more preferably carried out using a phosphorus-doped Ni(O)OH foam electrode in a flow cell, the concentration of alkali being 0.8 to 1.5 mol/l and the concentration of starting material according to scheme (I). is 0.08 to 0.3 mol/l.
  • the method according to the invention is particularly preferably carried out using a phosphorus-doped Ni(O)OH foam electrode in a flow cell, the concentration of alkali being 0.8 to 1.5 mol/l, whereby the Concentration of starting material according to scheme (I) is 0.08 to 0.3 mol/l and the flow rate of the reaction medium in the anode space is at least 5 cm/min, preferably at least 8 cm/min, more preferably at least 10 cm/min .
  • Figure 1 shows the schematic structure with a reaction cell with continuous flow
  • Figure 2 shows the temperature dependence of the yield of the reaction according to Table 1, entry 1, for the doped anode in the batch test.
  • All anodes used had dimensions of length 60 mm, width 20 and thickness 6 mm. In the batch process, however, only half of the surface (length 30 mm) was immersed to carry out the process according to the invention.
  • the cathodes have the same surface area as the anodes, but are made of sheet metal. The thickness does not play a significant role, especially in the flow process only one surface is exposed to the reaction medium.
  • the nickel foam electrodes had a density of 0.35 to 0.44 g/cm 3 . This corresponds to a porosity of 95 to 96%.
  • the phosphorus-doped electrodes were purchased from Aqua Titan, Dortmund.
  • Ni(O)OH layer of the anodes was carried out in 280 ml of a solution of 0.1 mol/l NiSO 4 * 6H 2 O, 0.1 mol/l NaOAc * 3H 2 O, 0.005 mol/l NaOH in carried out with distilled water.
  • the electrodes were completely immersed and coated with a pole change (10 s) at 150 coulombs and 10 mA/cm 2 at room temperature. After the reaction was complete, the electrodes were rinsed and then dried.
  • the reaction cell was filled (25 ml) with water and sodium hydroxide dissolved therein (1 mol/l) and the substance to be oxidized (educt according to scheme (I)). The concentration of starting material was 0.1 mol/l. The stirred solution was then tempered. The electrooxidation was carried out under galvanostatic conditions.
  • the doped Ni(O)OH foam electrode prepared above was used as the anode in the experiments according to the invention; in the experiments not according to the invention, electrodes of basically the same construction and not doped with phosphorus were used and stainless steel sheet electrodes were used as cathodes.
  • the solution was discharged quantitatively (with rinsing using demineralised water and dichloromethane (20 ml each)) and extracted with dichloromethane (volume ratio: water to organic solvent approximately 2 to 1).
  • the remaining aqueous phase was adjusted to pH 1 with 50% sulfuric acid and extracted four times with diethyl ether (volume ratio: water to organic solvent approximately 2 to 1).
  • the organic phases were dried separately over sodium sulfate and the solvent was then removed on a rotary evaporator.
  • the doped Ni(O)OH foam electrode produced above was installed in a multilayer Teflon block in such a way that it was completely flowed through; the entry area was 6 mm * 20 mm, i.e. the flow direction was in the longitudinal axis of the electrode.
  • the cathode was separated by a slot plate at a distance of less than a millimeter.
  • the chamber was flowed through from bottom to top in an upright position.
  • a Ritmo ® 05 from Fink Chem+Tec GmbH & Co. KG was used as the pump.
  • reaction solutions were carried out as in the batch process.
  • the workup was carried out as in the batch process.
  • DC6 octanedioic acid

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Ceramic Engineering (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)

Description

Die Erfindung bezieht sich auf ein Verfahren zur elektrochemischen Herstellung von Alkylendicarbonsäuren durch ringöffnende Oxidation mittels einer dotierten Ni(O)OH Schaumelektrode in wässriger alkalischer Lösung.The invention relates to a process for the electrochemical production of alkylenedicarboxylic acids by ring-opening oxidation using a doped Ni(O)OH foam electrode in an aqueous alkaline solution.

Johannes Kaulen und Hans-Jürgen Schäfer (Tetrahedron 1982, 38(22), 3299 - 3308 ) offenbaren die Umsetzung von unsubstituiertem Cyclohexanol zu unsubstituierter Adipinsäure an einer Ni(O)OH Elektrode. Diese Elektrode war als Plattenelektrode ausgebildet. Die Produkte wurden in keinem Fall tatsächlich isoliert. Zu gleichen Ergebnissen kam auch Hans-Jürgen Schäfer (Topics in Current Chemistry, 1987, 142, 101-129 ). Johannes Kaulen and Hans-Jürgen Schäfer (Tetrahedron 1982, 38(22), 3299 - 3308 ) disclose the conversion of unsubstituted cyclohexanol to unsubstituted adipic acid on a Ni(O)OH electrode. This electrode was designed as a plate electrode. In no case were the products actually isolated. The same results were also achieved Hans-Jürgen Schäfer (Topics in Current Chemistry, 1987, 142, 101-129 ).

Johannes Kaulen ("Oxidation von Diolen und sekundären Alkoholen an der Nickelhydroxid-Elektrode. Anwendung zur selektiven Oxidation von Hydroxysteroiden", Dissertation Universität Münster 1981 ) offenbart Untersuchungen zur elektrochemischen Oxidation von Cyclohexanol. Nennenswerte Umsätze erzielte er an Nickelhydroxidelektroden bei höheren Temperaturen zum Teil unter ringspaltender Bildung von Adipinsäure. Johannes Kaulen ("Oxidation of diols and secondary alcohols on the nickel hydroxide electrode. Application for the selective oxidation of hydroxysteroids", dissertation University of Münster 1981 ) discloses studies on the electrochemical oxidation of cyclohexanol. He achieved significant sales on nickel hydroxide electrodes at higher temperatures, sometimes with the ring-splitting formation of adipic acid.

B.V. Lyalin und V.A. Petrosyan (Russian Journal of Electrochemistry, 2010, 46(11), 1199-1214 offenbaren die Herstellung von unsubstituierter Adipinsäure und die Oxidation von Kohlenhydraten. BV Lyalin and VA Petrosyan (Russian Journal of Electrochemistry, 2010, 46(11), 1199-1214 disclose the production of unsubstituted adipic acid and the oxidation of carbohydrates.

Dieselben Autoren offenbaren in " Electrosynthesis of adipic acid by undivided cell electrolysis" (Russian Chemical Bulletin, International Edition, Vol. 53 No. 3 pp. 688-692, March, 2004 ) die ringspaltende elektrochemische Oxidation von Cyclohexanol zu Adipinsäure an Nickelhydroxid-Elektroden. In der Veröffentlichung ist eine maximale Ausbeute an Adipinsäure von 46,7 % bei gleichzeitiger Stromausbeute von 11,5 % angegeben. Nebenprodukte bei der Umsetzung sind Bernsteinsäure und Glutarsäure, die mit einer Ausbeute von 6,3 % bzw. 11,5 % gebildet werden. Diese Komponenten entstehen durch oxidative Abspaltung von CH2-Gruppen aus dem C6-Grundkörper von Cyclohexanol.The same authors reveal in " Electrosynthesis of adipic acid by undivided cell electrolysis" (Russian Chemical Bulletin, International Edition, Vol. 53 No. 3 pp. 688-692, March, 2004 ) the ring-splitting electrochemical oxidation of cyclohexanol to adipic acid on nickel hydroxide electrodes. The publication states a maximum yield of adipic acid of 46.7% with a simultaneous current efficiency of 11.5%. By-products of the reaction are succinic acid and glutaric acid, which are formed with a yield of 6.3% and 11.5%, respectively. These components are formed by oxidative elimination of CH 2 groups from the C6 base of cyclohexanol.

EP 2907898 A1 ( US 2015/0225861 A1 ) offenbart zur oxidativen Ringspaltung von 3,3,5-Trimethylcyclohexanol in einer Ausführungsvariante die Verwendung von Nickelschaum bei Reaktionstemperaturen von 80°C. Die Umsetzung erfolgte in stark verdünnter Lösung mit geringen Ausbeuten. EP 2907898 A1 ( US 2015/0225861 A1 ) discloses the use of nickel foam at reaction temperatures of 80 ° C for the oxidative ring cleavage of 3,3,5-trimethylcyclohexanol in one embodiment variant. The reaction was carried out in a highly diluted solution with low yields.

Schmitt et al. (Beilstein J. Org. Chem., 2015, 11, 473-480 ) offenbaren die Spaltung von Lignin in diverse Oxo-substituierte Aromaten unter Verwendung unterschiedlicher Elektroden. Die Oxidation zu den entsprechenden Säuren gelang nicht. Schmitt et al. (Beilstein J. Org. Chem., 2015, 11, 473-480 ) reveal the cleavage of lignin into various oxo-substituted aromatics using different electrodes. The oxidation to the corresponding acids was not successful.

Weiterer Stand der Technik findet sich in CN 109 837 555 A und CN 111 229 267 A .Further state of the art can be found in CN 109 837 555 A and CN 111 229 267 A .

Gegenstand der vorliegenden Erfindung ist ein Verfahren zur elektrochemischen Herstellung von Alkandicarbonsäuren durch ringöffnende Oxidation mittels einer mit Elementen der 5. und/oder 6. Hauptgruppe dotierten Ni(O)OH Schaumelektrode in wässriger alkalischer Lösung,

  • wobei die Ni(O)OH Schaumelektrode 2 bis 10 Gew.-% Phosphor aufweist, hierbei wird Phosphor als Element betrachtet und auf die Metallmasse der Elektrode bezogen,
  • gemäß Schema (I)
    Figure imgb0001
    • wobei
      Figure imgb0002
      eine Einfach- oder Doppelbindung darstellt, entsprechend ist R vorhanden oder nicht,
    • wobei R Wasserstoff oder ein Acylrest ist, wobei der Acylrest der Rest einer aliphatischen Monocarbonsäure mit 2 bis 8 Kohlenstoffatomen ist und wobei A ein Kohlenwasserstoff mit 4 bis 30 Kohlenstoffen ist, wobei alle Ringkohlenstoffe von A im cyclischen Edukt des Schemas (I) mindestens einen Wasserstoffsubstituenten tragen.
The subject of the present invention is a process for the electrochemical production of alkanedicarboxylic acids by ring-opening oxidation using a Ni(O)OH foam electrode doped with elements of the 5th and/or 6th main group in an aqueous alkaline solution,
  • where the Ni(O)OH foam electrode has 2 to 10% by weight of phosphorus, here phosphorus is considered an element and is based on the metal mass of the electrode,
  • according to scheme (I)
    Figure imgb0001
    • where
      Figure imgb0002
      represents a single or double bond, correspondingly R is present or not,
    • where R is hydrogen or an acyl radical, where the acyl radical is the radical of an aliphatic monocarboxylic acid with 2 to 8 carbon atoms and where A is a hydrocarbon with 4 to 30 carbons, all ring carbons of A in the cyclic starting material of scheme (I) having at least one hydrogen substituent carry.

Das erfindungsgemäße Verfahren wird nachfolgend beispielhaft beschrieben, ohne dass die Erfindung auf diese beispielhaften Ausführungsformen beschränkt sein soll. Sind nachfolgend Bereiche, allgemeine Formeln oder Verbindungsklassen angegeben, so sollen diese nicht nur die entsprechenden Bereiche oder Gruppen von Verbindungen umfassen, die explizit erwähnt sind, sondern auch alle Teilbereiche und Teilgruppen von Verbindungen, die durch Herausnahmen von einzelnen Werten (Bereichen) oder Verbindungen erhalten werden können. Werden im Rahmen der vorliegenden Beschreibung Dokumente zitiert, so soll deren Inhalt vollständig zum Offenbarungsgehalt der vorliegenden Erfindung gehören. Werden nachfolgend %-Angaben gemacht, so handelt es sich, wenn nicht anders angegeben, um Angaben in Gewichts-%. Bei Zusammensetzungen beziehen sich die %-Angaben, wenn nicht anders angegeben auf die Gesamtzusammensetzung. Werden nachfolgend Mittelwerte angegeben, so handelt es sich, wenn nicht anders angegeben, um Massenmittel (Gewichtsmittel). Werden nachfolgend Messwerte angegeben, so wurden diese Messwerte, wenn nicht anders angegeben, bei einem Druck von 101325 Pa und einer Temperatur von 25 °C ermittelt.The method according to the invention is described below by way of example, without the invention being limited to these exemplary embodiments. If ranges, general formulas or compound classes are given below, these should include not only the corresponding ranges or groups of compounds that are explicitly mentioned, but also all sub-ranges and sub-groups of compounds that are obtained by removing individual values (ranges) or compounds can be. If documents are quoted in the context of the present description, their content should belong entirely to the disclosure content of the present invention. If percentage information is given below, unless otherwise stated, it is information in percent by weight. For compositions, the percentages refer to the total composition unless otherwise stated. If average values are given below, they are mass averages (weight averages), unless otherwise stated. If measured values are given below, these measured values were determined at a pressure of 101325 Pa and a temperature of 25 °C, unless otherwise stated.

Vorteil dieses Verfahrens gegenüber chemischen Oxidationsverfahren ist die Vermeidung des Einsatzes von chemischen Oxidationsmitteln wie z.B. Sal petersäure.The advantage of this process over chemical oxidation processes is that it avoids the use of chemical oxidizing agents such as nitric acid.

Ein weiterer Vorteil ist die hohe Ausbeute des erfindungsgemäßen Verfahrens.Another advantage is the high yield of the process according to the invention.

Die Ausführung in einer Durchflusszelle ist technisch einfacher und robuster als alle Ausführungen des Standes der Technik. Alle mechanisch aufwendigen Prozesse, wie z.B. Rührprozesse, können entfallen.The design in a flow cell is technically simpler and more robust than all prior art designs. All mechanically complex processes, such as stirring processes, can be omitted.

Damit eröffnet die vorliegende Erfindung erstmals die Möglichkeit der Entwicklung eines technisch relevanten kontinuierlichen Prozesses zur Gewinnung von Alkandicarbonsäuren ohne die Verwendung von aggressiven Chemikalien und trotzdem in hohen Ausbeuten.The present invention thus opens up for the first time the possibility of developing a technically relevant continuous process for obtaining alkanedicarboxylic acids without the use of aggressive chemicals and still in high yields.

Bevorzugt werden im erfindungsgemäßen Verfahren Alkandicarbonsäuren (DC) gemäß Schema (I) hergestellt

Figure imgb0003

  • wobei
    Figure imgb0004
    eine Einfach- oder Doppelbindung darstellt, entsprechend ist R vorhanden oder nicht,
  • wobei R Wasserstoff oder ein Acylrest ist, wobei der Acylrest der Rest einer aliphatischen Monocarbonsäure mit 2 bis 5 Kohlenstoffatomen, besonders bevorzugt ein Acetyl ist, und
  • wobei A ein Kohlenwasserstoff mit 4 bis 30 Kohlenstoffen ist, wobei alle Ringkohlenstoffe von A im cyclischen Edukt des Schemas (I) mindestens einen Wasserstoffsubstituenten tragen, A weist mindestens 2 Ringkohlenstoffatome auf, mehr bevorzugt 3 bis 9 Ringkohlenstoffatome.
Alkanedicarboxylic acids (DC) according to scheme (I) are preferably produced in the process according to the invention
Figure imgb0003
  • where
    Figure imgb0004
    represents a single or double bond, correspondingly R is present or not,
  • where R is hydrogen or an acyl radical, the acyl radical being the radical of an aliphatic monocarboxylic acid with 2 to 5 carbon atoms, particularly preferably an acetyl, and
  • where A is a hydrocarbon with 4 to 30 carbons, all ring carbons of A in the cyclic starting material of scheme (I) carrying at least one hydrogen substituent, A has at least 2 ring carbon atoms, more preferably 3 to 9 ring carbon atoms.

Für den Fall dass

Figure imgb0005
gleich einer Einfachbindung und R gleich Wasserstoff ist (Cycloalkanole), wird das erfindungsgemäße Verfahren bevorzugt nach Schema (II) durchgeführt.
Figure imgb0006
 In case that
Figure imgb0005
is a single bond and R is hydrogen (cycloalkanols), the process according to the invention is preferably carried out according to scheme (II).
Figure imgb0006

R1, R2, R3 können gleich oder verschieden sein, Wasserstoff oder Alkylrest mit 1 bis 8 Kohlenstoffatomen bevorzugt 1 bis 5 Kohlenstoffatomen, linear oder verzweigt, wobei mindestens einer der Reste R1, R2, R3 ein Alkylrest ist.R 1 , R 2 , R 3 can be the same or different, hydrogen or alkyl radical with 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, linear or branched, where at least one of the radicals R 1 , R 2 , R 3 is an alkyl radical.

Mehr bevorzugt ist nur einer der Reste R1, R2, R3 ein Alkylrest mit 1 bis 4 Kohlenstoffatomen. Besonders bevorzugt sind die Reste R1 und R3 Wasserstoff und R2 ein Alkylrest mit 1 bis 4 Kohlenstoffatomen.More preferably, only one of the radicals R 1 , R 2 , R 3 is an alkyl radical with 1 to 4 carbon atoms. The radicals R 1 and R 3 are particularly preferably hydrogen and R 2 is an alkyl radical with 1 to 4 carbon atoms.

Für den Fall dass

Figure imgb0007
gleich einer Einfachbindung und R gleich ein Acylrest ist (Acylcycloalkanole), wird das erfindungsgemäße Verfahren bevorzugt nach Schema (III) durchgeführt.
Figure imgb0008

  • wobei der Acylrest ein Acetyl ist, und
  • A ein Kohlenwasserstoff mit 4 bis 9 Kohlenstoffen ist, wobei alle Ringkohlenstoffe von A im cyclischen Edukt des Schemas (III) mindestens einen Wasserstoffsubstituenten tragen, A weist mindestens 3 Ringkohlenstoffatome auf (Acylhexanole), mehr bevorzugt 3 bis 9 Ringkohlenstoffatome.
In case that
Figure imgb0007
is a single bond and R is an acyl radical (acylcycloalkanols), the process according to the invention is preferably carried out according to scheme (III).
Figure imgb0008
  • where the acyl radical is acetyl, and
  • A is a hydrocarbon with 4 to 9 carbons, all ring carbons of A in the cyclic starting material of scheme (III) carrying at least one hydrogen substituent, A has at least 3 ring carbon atoms (acylhexanols), more preferably 3 to 9 ring carbon atoms.

Für den Fall dass

Figure imgb0009
gleich einer Doppelbindung und R nicht vorhanden ist (Cycloalkanone), wird das erfindungsgemäße Verfahren bevorzugt nach Schema (IV) durchgeführt.
Figure imgb0010
 wobei A ein Kohlenwasserstoff mit 4 bis 9 Kohlenstoffen ist, wobei alle Ringkohlenstoffe von A im cyclischen Edukt des Schemas (IV) mindestens einen Wasserstoffsubstituenten tragen, A weist mindestens 2 Ringkohlenstoffatome auf, mehr bevorzugt 3 bis 9 Ringkohlenstoffatome.In case that
Figure imgb0009
equal to a double bond and R is not present (cycloalkanones), the process according to the invention is preferably carried out according to scheme (IV).
Figure imgb0010
 where A is a hydrocarbon with 4 to 9 carbons, all ring carbons of A in the cyclic starting material of scheme (IV) carrying at least one hydrogen substituent, A has at least 2 ring carbon atoms, more preferably 3 to 9 ring carbon atoms.

Bevorzugt wird das erfindungsgemäße Verfahren nach mindestens einem der Schemas (II), (III) oder (IV) durchgeführt.The process according to the invention is preferably carried out according to at least one of the schemes (II), (III) or (IV).

Wo immer Moleküle beziehungsweise Molekülfragmente ein oder mehrere Stereozentren aufweisen oder aufgrund von Symmetrien in Isomere unterschieden werden können oder aufgrund anderer Effekte z.B. eingeschränkter Rotation in Isomere unterschieden werden können, sind alle möglichen Isomere von der vorliegenden Erfindung mit eingeschlossen.Wherever molecules or molecular fragments have one or more stereocenters or are differentiated into isomers based on symmetries can be or can be differentiated into isomers due to other effects, for example limited rotation, all possible isomers are included in the present invention.

Isomere sind dem Fachmann bekannt, in besonderer Weise wird auf die Definitionen von Prof. Kazmaier der Universität des Saarlandes verwiesen, z. B. http://www.uni-saarland.de/fak8/kazmaier/PDF_files/vorlesungen/Stereochemie%20Strassb%20V orlage.pdf verwiesen.Isomers are known to those skilled in the art; reference is made in particular to the definitions by Prof. Kazmaier of Saarland University, e.g. E.g. http://www.uni-saarland.de/fak8/kazmaier/PDF_files/vorlesungen/Stereochemie%20Strassb%20V orlage.pdf.

Die Gehaltsangaben der Dotierung beziehen sich auf den Elementarzustand der Dotierung bezogen auf die Masse des Metalls der Elektrode.The doping content information relates to the elementary state of the doping based on the mass of the metal of the electrode.

Bevorzugt weist die Ni(O)OH Schaumelektrode 3 bis 9 Gew.-% Phosphor und mehr bevorzugt 4 bis 9 Gew.-% auf, hierbei wird Phosphor als Element betrachtet und auf die Metallmasse der Elektrode bezogen.The Ni(O)OH foam electrode preferably has 3 to 9% by weight of phosphorus and more preferably 4 to 9% by weight; phosphorus is considered an element and is based on the metal mass of the electrode.

Die Gehaltsbestimmung der Phosphordotierung wird bevorzugt gemäß DIN EN ISO 5427, Anhang D.1 durchgeführt.The content determination of the phosphorus doping is preferably carried out in accordance with DIN EN ISO 5427, Appendix D.1.

Bevorzugt weist die Ni(O)OH Schaumelektrode eine Dicke von mehreren Millimetern auf, mehr bevorzugt von mehr als 3 mm, weiter mehr bevorzugt mehr als 5 mm und insbesondere bevorzugt gleich oder dicker als 6 mm.The Ni(O)OH foam electrode preferably has a thickness of several millimeters, more preferably more than 3 mm, more preferably more than 5 mm and particularly preferably equal to or thicker than 6 mm.

Die Ni(O)OH Schaumelektrode enthält als Metall bevorzugt mindestens zu 90 Gew.-%, mehr bevorzugt mindestens 95, 98, 99 Gew.-%, weiter mehr bevorzugt mindestens 99,9, insbesondere bevorzugt mindestens 99,99 Gew.-% Nickel, bezogen auf den Gesamtmetallgehalt.The Ni(O)OH foam electrode preferably contains at least 90% by weight of metal, more preferably at least 95, 98, 99% by weight, more preferably at least 99.9, particularly preferably at least 99.99% by weight. Nickel, based on the total metal content.

Die Ni(O)OH Schaumelektrode kann außer Nickel weitere Metalle enthalten. Bevorzugte weitere Metalle sind Co, Fe und Cu.The Ni(O)OH foam electrode can contain other metals besides nickel. Preferred other metals are Co, Fe and Cu.

Gehalt anderer Metalle in der Ni(O)OH Schaumelektrode ist bevorzugt gleich oder kleiner als 10 Gew.-%, mehr bevorzugt 5 Gew.-%, weiter mehr bevorzugt 2 Gew.-%, insbesondere bevorzugt kleiner oder gleich 1 Gew.-% bezogen auf den Gesamtmetallgehalt.Content of other metals in the Ni(O)OH foam electrode is preferably equal to or less than 10% by weight, more preferably 5% by weight, more preferably 2% by weight, particularly preferably less than or equal to 1% by weight based on the total metal content.

Bevorzugt enthält die Ni(O)OH Schaumelektrode maximal 5 Gew.-%, bevorzugt 2 Gew.-%, mehr bevorzugt 1 Gew.-% und besonders bevorzugt 0,5 Gew.-% und insbesondere bevorzugt maximal 0,1 Gew.-% Eisen oder Eisenverbindungen, wobei die Gehaltsangaben auf das Element in Bezug auf den Gesamtmetallgehalt bezogen sind.The Ni(O)OH foam electrode preferably contains a maximum of 5% by weight, preferably 2% by weight, more preferably 1% by weight and particularly preferably 0.5% by weight and particularly preferably a maximum of 0.1% by weight. % iron or iron compounds, where the content information relates to the element in relation to the total metal content.

Bevorzugt enthält die Ni(O)OH Schaumelektrode maximal je 1 Gew.-%, bevorzugt je 0,1 Gew.-% und mehr bevorzugt maximal je 0,01 Gew.-% an V, Wo und Mo; diese Metalle unterliegen in alkalisch-wässrigen Medium einer Korrosion, dies kann sich ungünstig auf das erfindungsgemäße Verfahren auswirken.The Ni(O)OH foam electrode preferably contains a maximum of 1% by weight, preferably 0.1% by weight and more preferably a maximum of 0.01% by weight of V, Wo and Mo; These metals are subject to corrosion in an alkaline-aqueous medium, which can have an unfavorable effect on the process according to the invention.

Als Kathodenmaterial kommt prinzipiell jedes gegenüber dem Reaktionsmedium inerte Metall in Frage. Bevorzugt wird erfindungsgemäß Edelstahl, Platin oder Nickel oder eine Mischung eingesetzt.In principle, any metal that is inert to the reaction medium can be used as a cathode material. According to the invention, preference is given to using stainless steel, platinum or nickel or a mixture.

Das erfindungsgemäße Verfahren wird in wässriger alkalischer Lösung durchgeführt. Bevorzugte Cosolventien können Alkohole oder DMSO sein. Bevorzugt sind bis zu 30 Vol.-% eines Cosolvenzes anwesend, mehr bevorzugt 1 bis 20 Vol.-%, bezogen auf die Summe der Lösungsmittel, mehr bevorzugt besteht das Lösungsmittel aus Wasser.The process according to the invention is carried out in an aqueous alkaline solution. Preferred cosolvents can be alcohols or DMSO. Up to 30% by volume of a cosolvent is preferably present, more preferably 1 to 20% by volume, based on the sum of the solvents, more preferably the solvent consists of water.

Als alkalische Zusätze eignen sich im Prinzip alle bekannten anorganischen Basen. Bevorzugt werden im erfindungsgemäßen Verfahren Alkalimetallhydroxide, wie LiOH, NaOH, KOH, und lösliche Erdalkalimetallhydroxide. Besonders bevorzugt wird erfindungsgemäß Natriumhydroxid eingesetzt. Bevorzugt liegen keine weiteren Anionen von Basen vor.In principle, all known inorganic bases are suitable as alkaline additives. Alkaline metal hydroxides, such as LiOH, NaOH, KOH, and soluble alkaline earth metal hydroxides are preferred in the process according to the invention. Sodium hydroxide is particularly preferably used according to the invention. Preferably there are no further anions of bases present.

Die Konzentration des alkalischen Zusatzes beträgt bevorzugt 0,5 bis 2 mol/l bezogen auf die wässrige alkalische Lösung, mehr bevorzugt 0,8 bis 1,5 mol/l und insbesondere bevorzugt 1 mol/l mit einer möglichen Abweichung von bis zu 10%, bevorzugt einer Abweichung von bis zu 5% der Molarität.The concentration of the alkaline additive is preferably 0.5 to 2 mol/l based on the aqueous alkaline solution, more preferably 0.8 to 1.5 mol/l and particularly preferably 1 mol/l with a possible deviation of up to 10% , preferably a deviation of up to 5% of the molarity.

Bevorzugt beträgt im erfindungsgemäßen Verfahren die Konzentration der Edukte gemäß Schema (I) 0,06 bis 0,5 mol/l, mehr bevorzugt 0,08 bis 0,3 und insbesondere bevorzugt 0,09 bis 0,11 mol/l.In the process according to the invention, the concentration of the starting materials according to scheme (I) is preferably 0.06 to 0.5 mol/l, more preferably 0.08 to 0.3 and particularly preferably 0.09 to 0.11 mol/l.

Der Gesamtstrom, der zur erfindungsgemäßen Umsetzung nach Schema (II) und (III) führt, beträgt gemäß der Theorie 8 F. Bevorzugt werden 8 bis 10 F eingesetzt, mehr bevorzugt 8,5 bis 9 F.According to theory, the total current that leads to the reaction according to the invention according to schemes (II) and (III) is 8 F. Preferably 8 to 10 F are used, more preferably 8.5 to 9 F.

Die Einheit F steht für Faraday, welche definiert ist als Produkt aus Avogadrokonstante und Elementarladung eines Elektrons: F = NA * e.The unit F stands for Faraday, which is defined as the product of Avogadro's constant and the elementary charge of an electron: F = N A * e.

Zur Umsetzung gemäß Schema (IV) werden theoretisch 6 F benötigt. Bevorzugt werden 6 bis 8 F eingesetzt, mehr bevorzugt 6,5 bis 7 F.Theoretically, 6 F are required for implementation according to scheme (IV). Preferably 6 to 8 F are used, more preferably 6.5 to 7 F.

Bevorzugt wird das erfindungsgemäße Verfahren mit einer Stromdichte von 2 bis 10 mA/cm2, mehr bevorzugt 2,5 bis 7,5 mA/cm2und insbesondere bevorzugt 3,3 bis 6 mA/cm2 ausgeführt. Die Flächenangabe bezieht sich auf die geometrische Fläche ohne Berücksichtigung der inneren Oberfläche des Schaumes. Diese Angaben zur Stromdichte beziehen sich auf die größte Fläche einer der Seiten und sind damit im Fall der Durchflusszelle unabhängig von der Fließrichtung.The method according to the invention is preferably carried out with a current density of 2 to 10 mA/cm 2 , more preferably 2.5 to 7.5 mA/cm 2 and particularly preferably 3.3 to 6 mA/cm 2 . The area specification refers to the geometric area without taking the inner surface of the foam into account. This current density information refers to the largest area on one of the sides and is therefore independent of the flow direction in the case of the flow cell.

Das erfindungsgemäße Verfahren kann diskontinuierlich zum Beispiel in einer Batch-Elektrolysezelle oder kontinuierlich in einer durchströmbaren Elektrolysezelle erfolgen, bevorzugt in einer kontinuierlich durchströmten Elektrolysezelle.The process according to the invention can be carried out discontinuously, for example in a batch electrolysis cell or continuously in an electrolysis cell through which flow occurs, preferably in an electrolysis cell through which flow is continuous.

Das erfindungsgemäße Verfahren wird bevorzugt bei Temperaturen von 20 - 70°C, bevorzugt von 30 - 60°C, mehr bevorzugt von 35 - 50°C durchgeführt.The process according to the invention is preferably carried out at temperatures of 20 - 70°C, preferably 30 - 60°C, more preferably 35 - 50°C.

Weiter bevorzugt wird das erfindungsgemäße Verfahren unter Verwendung einer dotierten Ni(O)OH-Schaumelektrode durchgeführt, wobei die Dotierung ausgewählt ist aus Phosphor, Arsen, Selen und Schwefel, wobei die Konzentration an Alkali 0,8 bis 1,5 mol/l beträgt und die Konzentration an Edukt gemäß Schema (I) 0,08 bis 0,3 mol/l beträgt.More preferably, the method according to the invention is carried out using a doped Ni(O)OH foam electrode, the doping being selected from phosphorus, arsenic, selenium and sulfur, the concentration of alkali being 0.8 to 1.5 mol/l and the concentration of starting material according to scheme (I) is 0.08 to 0.3 mol/l.

Weiter bevorzugt wird das erfindungsgemäße Verfahren unter Verwendung einer mit Phosphor dotierten Ni(O)OH-Schaumelektrode durchgeführt, wobei die Konzentration an Alkali 0,8 bis 1,5 mol/l beträgt und die Stromdichte von 2 bis 10 mA/cm2 beträgt.More preferably, the method according to the invention is carried out using a Ni(O)OH foam electrode doped with phosphorus, the concentration of alkali being 0.8 to 1.5 mol/l and the current density being 2 to 10 mA/cm 2 .

Weiter mehr bevorzugt wird das erfindungsgemäße Verfahren unter Verwendung einer mit Phosphor dotierten Ni(O)OH-Schaumelektrode nach Schema (II) durchgeführt

Figure imgb0011

  • wobei R1, R2, R3 gleich oder verschieden sind, Wasserstoff oder Alkylrest mit 1 bis 8 Kohlenstoffatomen bevorzugt 1 bis 5 Kohlenstoffatomen, linear oder verzweigt, wobei mindestens einer der Reste R1, R2, R3 ein Alkylrest ist,
  • wobei mehr bevorzugt nur einer der Reste R1, R2, R3 ein Alkylrest mit 1 bis 4 Kohlenstoffatomen ist und besonders bevorzugt sind die Reste R1 und R3 Wasserstoff und R2 ein Alkylrest mit 1 bis 4 Kohlenstoffatomen.
More preferably, the method according to the invention is carried out using a Ni(O)OH foam electrode doped with phosphorus according to scheme (II).
Figure imgb0011
  • where R 1 , R 2 , R 3 are the same or different, hydrogen or alkyl radical with 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, linear or branched, where at least one of the radicals R 1 , R 2 , R 3 is an alkyl radical,
  • where more preferably only one of the radicals R 1 , R 2 , R 3 is an alkyl radical with 1 to 4 carbon atoms and particularly preferably the radicals R 1 and R 3 are hydrogen and R 2 is an alkyl radical with 1 to 4 carbon atoms.

Weiter mehr bevorzugt wird das erfindungsgemäße Verfahren unter Verwendung einer mit Phosphor dotierten Ni(O)OH-Schaumelektrode nach Schema (IV) durchgeführt

Figure imgb0012
wobei A ein Kohlenwasserstoff mit 4 bis 9 Kohlenstoffen ist, wobei alle Ringkohlenstoffe von A im cyclischen Edukt des Schemas (IV) mindestens einen Wasserstoffsubstituenten tragen, bevorzugt weist A mindestens 2 Ringkohlenstoffatome auf, mehr bevorzugt 3 bis 9 Ringkohlenstoffatome.More preferably, the method according to the invention is carried out using a Ni(O)OH foam electrode doped with phosphorus according to scheme (IV).
Figure imgb0012
 where A is a hydrocarbon with 4 to 9 carbons, all ring carbons of A in the cyclic starting material of scheme (IV) carrying at least one hydrogen substituent, preferably A has at least 2 ring carbon atoms, more preferably 3 to 9 ring carbon atoms.

Das erfindungsgemäße Verfahren wird mehr bevorzugt unter Verwendung einer mit Phosphor dotierten Ni(O)OH-Schaumelektrode in einer Durchflusszelle durchgeführt, wobei die Konzentration an Alkali 0,8 bis 1,5 mol/l beträgt und die Konzentration an Edukt gemäß Schema (I) 0,08 bis 0,3 mol/l beträgt.The method according to the invention is more preferably carried out using a phosphorus-doped Ni(O)OH foam electrode in a flow cell, the concentration of alkali being 0.8 to 1.5 mol/l and the concentration of starting material according to scheme (I). is 0.08 to 0.3 mol/l.

Das erfindungsgemäße Verfahren wird besonders bevorzugt unter Verwendung einer mit Phosphor dotierten Ni(O)OH-Schaumelektrode in einer Durchflusszelle durchgeführt, wobei die Konzentration an Alkali 0,8 bis 1,5 mol/l beträgt, wobei die Konzentration an Edukt gemäß Schema (I) 0,08 bis 0,3 mol/l beträgt und wobei die die Strömungsgeschwindigkeit des Reaktionsmediums im Anodenraum mindestens 5 cm/min beträgt, bevorzugt mindestens als 8 cm/min, mehr bevorzugt mindestens 10 cm/min.The method according to the invention is particularly preferably carried out using a phosphorus-doped Ni(O)OH foam electrode in a flow cell, the concentration of alkali being 0.8 to 1.5 mol/l, whereby the Concentration of starting material according to scheme (I) is 0.08 to 0.3 mol/l and the flow rate of the reaction medium in the anode space is at least 5 cm/min, preferably at least 8 cm/min, more preferably at least 10 cm/min .

Figur 1 zeigt den schematischen Aufbau mit einer kontinuierlich durchströmten Reaktionszellezelle
Figur 2 zeigt die Temperaturabhängigkeit der Ausbeute der Reaktion gemäß Tabelle 1, entry 1, für die dotierte Anode im Batchversuch. Figure 1 shows the schematic structure with a reaction cell with continuous flow
Figure 2 shows the temperature dependence of the yield of the reaction according to Table 1, entry 1, for the doped anode in the batch test.

ElektrodenElectrodes

Alle verwendeten Anoden hatten die Abmessungen Länge 60 mm, Breite 20 und Dicke 6 mm. Im Batchverfahren wurde jedoch zur Durchführung des erfindungsgemäßen Verfahrens nur die Hälfte der Fläche (Länge 30mm) eingetaucht. Die Kathoden haben die gleichen Flächenausdehnungen wie die Anoden, jedoch als Blech ausgearbeitet. Die Dicke spielt keine wesentliche Rolle, insbesondere im Durchflussverfahren ist lediglich eine Oberfläche dem Reaktionsmedium ausgesetzt.All anodes used had dimensions of length 60 mm, width 20 and thickness 6 mm. In the batch process, however, only half of the surface (length 30 mm) was immersed to carry out the process according to the invention. The cathodes have the same surface area as the anodes, but are made of sheet metal. The thickness does not play a significant role, especially in the flow process only one surface is exposed to the reaction medium.

Die Nickelschaumelektroden hatten eine Dichte von 0,35 bis 0,44 g/cm3. Das entspricht einer Porosität von 95 bis 96%.The nickel foam electrodes had a density of 0.35 to 0.44 g/cm 3 . This corresponds to a porosity of 95 to 96%.

Die Phosphor-dotierten Elektroden wurden von der Firma Aqua Titan, Dortmund bezogen.The phosphorus-doped electrodes were purchased from Aqua Titan, Dortmund.

Die Ausbildung der Ni(O)OH-Schicht der Anoden wurde in 280 ml einer Lösung aus 0,1 mol/l NiSO4 * 6H2O, 0,1 mol/l NaOAc * 3H2O, 0,005 mol/l NaOH in destilliertem Wasser durchgeführt. Die Elektroden wurden vollständig eingetaucht und unter Polwechsel (10 s) bei 150 Coulomb und 10 mA/cm2 bei Raumtemperatur beschichtet. Die Elektroden wurden nach beendeter Reaktion abgespült und anschließend getrocknet.The formation of the Ni(O)OH layer of the anodes was carried out in 280 ml of a solution of 0.1 mol/l NiSO 4 * 6H 2 O, 0.1 mol/l NaOAc * 3H 2 O, 0.005 mol/l NaOH in carried out with distilled water. The electrodes were completely immersed and coated with a pole change (10 s) at 150 coulombs and 10 mA/cm 2 at room temperature. After the reaction was complete, the electrodes were rinsed and then dried.

Ringöffnende ElektrooxidationRing-opening electrooxidation a) Batchverfahrena) Batch process

Zur Elektrooxidation wurde die Reaktionszelle mit Wasser sowie darin gelöstem Natriumhydroxid (1 mol/l) und der zu oxidierenden Substanz (Edukt nach Schema (I)) befüllt (25ml). Die Konzentration an Edukt betrug 0,1 mol/l. Anschließend wurde die gerührte Lösung temperiert. Die Elektrooxidation wurde unter galvanostatischen Bedingungen durchgeführt. Als Anode wurde in den erfindungsgemäßen Versuchen die oben hergestellte dotierte Ni(O)OH Schaumelektrode verwendet, in den nicht erfindungsgemäßen Versuchen wurden prinzipiell baugleiche nicht mit Phosphor dotierte Elektroden verwendet und als Kathoden dienten Edelstahlblechelektroden.For electrooxidation, the reaction cell was filled (25 ml) with water and sodium hydroxide dissolved therein (1 mol/l) and the substance to be oxidized (educt according to scheme (I)). The concentration of starting material was 0.1 mol/l. The stirred solution was then tempered. The electrooxidation was carried out under galvanostatic conditions. The doped Ni(O)OH foam electrode prepared above was used as the anode in the experiments according to the invention; in the experiments not according to the invention, electrodes of basically the same construction and not doped with phosphorus were used and stainless steel sheet electrodes were used as cathodes.

Nach Beendigung der Reaktion wurde die Lösung quantitativ (mit Nachspülen mittels VE-Wasser und Dichlormethan (jeweils 20 ml)) ausgetragen und mit Dichlormethan (Volumenverhältnis: Wasser zu org. Lösemittel etwa 2 zu 1) extrahiert. Die verbliebene wässrige Phase wurde mit 50%-iger Schwefelsäure auf pH 1 eingestellt und viermal mit Diethylether (Volumenverhältnis: Wasser zu org. Lösemittel etwa 2 zu 1) extrahiert. Die organischen Phasen wurden beide (Dichlormethan/Diethylther) getrennt voneinander über Natriumsulfat getrocknet und anschließend das Lösungsmittel am Rotationsverdampfer entfernt.After the reaction had ended, the solution was discharged quantitatively (with rinsing using demineralised water and dichloromethane (20 ml each)) and extracted with dichloromethane (volume ratio: water to organic solvent approximately 2 to 1). The remaining aqueous phase was adjusted to pH 1 with 50% sulfuric acid and extracted four times with diethyl ether (volume ratio: water to organic solvent approximately 2 to 1). The organic phases (dichloromethane/diethyl ether) were dried separately over sodium sulfate and the solvent was then removed on a rotary evaporator.

b) Durchflussverfahrenb) Flow method

In einem mehrschichtigen Teflonblock wurde die oben hergestellte dotierte Ni(O)OH Schaumelektrode so eingebaut, dass sie vollständig durchflossen wurde, die Eintrittsfläche war 6 mm * 20 mm groß, die Fließrichtung also in Längsachse der Elektrode. Die Kathode war durch eine Schlitzplatte getrennt im Abstand von weniger als einem Millimeter angebracht. Die Kammer wurde aufrechtstehend von unten nach oben durchströmt. Als Pumpe wurde eine Ritmo® 05 der Fink Chem+Tec GmbH & Co. KG verwendet.The doped Ni(O)OH foam electrode produced above was installed in a multilayer Teflon block in such a way that it was completely flowed through; the entry area was 6 mm * 20 mm, i.e. the flow direction was in the longitudinal axis of the electrode. The cathode was separated by a slot plate at a distance of less than a millimeter. The chamber was flowed through from bottom to top in an upright position. A Ritmo ® 05 from Fink Chem+Tec GmbH & Co. KG was used as the pump.

Die Reaktionslösungen waren wie im Batch-Verfahren ausgeführt.The reaction solutions were carried out as in the batch process.

Die Aufarbeitung wurde wie im Batch-Verfahren durchgeführt.The workup was carried out as in the batch process.

NMR-SpektroskopieNMR spectroscopy

1H- und 13C-NMR-Spektren wurden an einem Multikernresonanzspektrometer des Typs AC 300 und AC II 400 der Firma Bruker Analytische Messtechnik, Karlsruhe vorgenommen. Als Lösungsmittel diente CDCl3. Die chemischen Verschiebungen sind dabei in ppm angegeben und beziehen sich auf das Protonensignal des deuterierten Lösungsmittels. Die Zuordnung der Signale erfolgte dann unter zur Hilfenahme von H-COSY, H,C-HSQC sowie H,C-HMBC-Experimenten, wobei die letztendliche Auswertung der Spektren mit dem Programm MestReNova (Version: 7.01-8414) durchgeführt wurde. 1 H and 13 C NMR spectra were recorded on an AC 300 and AC II 400 multinuclear resonance spectrometer from Bruker Analytische Messtechnik, Karlsruhe performed. CDCl 3 served as the solvent. The chemical shifts are given in ppm and refer to the proton signal of the deuterated solvent. The signals were then assigned with the help of H-COSY, H,C-HSQC and H,C-HMBC experiments, with the final evaluation of the spectra being carried out using the MestReNova program (version: 7.01-8414).

Die in den Tabellen angegebenen Ausbeuten wurden mittels Integration der Signale im 13C-NMR (inverse gated) gegen den Standard Trimethoxybenzol bestimmt. Die Ausbeuten sind molar bezogene Angaben. Tabelle 1: Umsetzungsbespiele unterschiedlicher Alkylcycloalkanole (CH) zu Alkandicarbonsäuren (DC) entry Alkylcycloalkanol (CH) Alkandicarbonsäuren (DC) 1

Figure imgb0013
Figure imgb0014
 2
Figure imgb0015
Figure imgb0016
 3
Figure imgb0017
Figure imgb0018
 4
Figure imgb0019
Figure imgb0020
 5
Figure imgb0021
Figure imgb0022
 6
Figure imgb0023
Figure imgb0024
 Tabelle 2: Umsetzungsbespiele unterschiedlicher Alkylcycloalkanone (CO) zu Alkandicarbonsäuren (DC) entry Alkylcycloalkanone (CO) Alkandicarbonsäuren (DC) 7
Figure imgb0025
Figure imgb0026
 8
Figure imgb0027
Figure imgb0028
 9
Figure imgb0029
Figure imgb0030
 Tabelle 3: Effekt der Phosphordotierung auf die Ausbeute diverser Alkylcycloalkanole (CH) gemäß Tabelle 1; undotierte Anode ist nicht anspruchsgemäß (Batch), dotierte Anode (Batch) und Durchfluss (dotierte Anode) sind anspruchsgemäß Entry undotierte Anode dotierte Anode Durchfluss Ausbeute [%] Temperatur; Stromdichte, Ladungsmenge Ausbeute [%] Temperatur; Stromdichte, Ladungsmenge Ausbeute [%] 1 53 20°C; 5 mA/cm2, 8,5 F 63 20°C; 2,5 mA/cm2, 8 F 63 2 44 50°C; 2,5 mA/cm2, 8,5 F 54 3 36 50°C; 2,5 mA/cm2, 8,5 F 66 4 30 50°C; 2,5 mA/cm2, 8,5 F 42 45°C; 2,5 mA/cm2, 8 F 43 5 18 50°C; 2,5 mA/cm2, 8,5 F 43 20°C; 5 mA/cm2, 8 F 6 60 45°C; 2,5 mA/cm2, 8 F Tabelle 4: Abhängigkeit der Ausbeute von der Durchflussgeschwindigkeit; Umsetzung in der Durchflusszelle (dotierte Anode) (CH1 zu DC1); 60 mA, 8 F, 20°C entry Flow rate [ml/min] DC1 [%] 1a 0,47* 10 E-3 51 1b 0,1 53 1c 1,0 56 1d 7,5 60 1e 10,0 62 1f 12,5 64 Tabelle 5: Abhängigkeit der Ausbeute vom Alkali (1 M = 1 mol/l) und vom Lösungsmittel (Verhältnis bezogen auf das Volumen), Umsetzung im Batchverfahren mit dotierter Anode, CH1 zu DC1 entry Lösungsmittel Alkalizusatz DC 1 [%] 1-1 H2O 0,1 M NaOH 20 1-2 H2O 0,5 M NaOH 45 1-3 H2O 1,0 M NaOH 51 1-4 H2O 2,0 M NaOH 45 1-5 H2O 5,0 M NaOH 16 1-6 H2O 1,0 M K2CO3 3 1-7 H2O 1,0 M KOH 50 1-8 H2O/tBuOH (3:7) 1,0 M NaOH 1 1-9 H2O/ tBuOH (2:1) 0,25 M NaOH 26 1-10 H2O/ tBuOH (1:1) 0,18 M KOH 7 1-11 H2O/PE (1:1) 1,0 M NaOH 16 1-12 H2O/DMSO (1:1) 1,0 M NaOH 7 1-13 H2O/ tAmylOH (2:1) 1,0 M NaOH 27 tBuOH = tert. Butanol, PE = Petrolether, DMSO = Dimethylsulfoxid, tAmylOH = tert. Amylalkohol (2-Methyl-2-butanol); 30 mA, 8 F, 20°C Tabelle 6: Umsetzung von Alkylcycloalkanonen (CO) zu Alkandicarbonsäuren (CD); Umsetzung im Batch-Verfahren mit dotierter Anode Entry dotierte Anode Ausbeute [%] Temperatur; Stromdichte, Ladungsmenge 7 61 20°C; 2,5 mA/cm2, 6 F 8 66 20°C; 2,5 mA/cm2, 6 F 9 64 40°C; 2,5 mA/cm2, 6 F Cyclooctanol-Essigsäureester wurde im Batch-Verfahren an der dotierten Anode bei 20°C, 5 mA/cm2 und 8 F in 30% Ausbeute zur Octandisäure (DC6) umgesetzt. The yields given in the tables were determined by integrating the signals in 13 C-NMR (inverse gated) against the standard trimethoxybenzene. The yields are molar-related data. Table 1: Reaction examples of different alkylcycloalkanols (CH) to form alkanedicarboxylic acids (DC) entry Alkylcycloalkanol (CH) Alkanedicarboxylic acids (DC) 1
Figure imgb0013
Figure imgb0014
 2
Figure imgb0015
Figure imgb0016
 3
Figure imgb0017
Figure imgb0018
 4
Figure imgb0019
Figure imgb0020
 5
Figure imgb0021
Figure imgb0022
 6
Figure imgb0023
Figure imgb0024
 entry Alkylcycloalkanones (CO) Alkanedicarboxylic acids (DC) 7
Figure imgb0025
Figure imgb0026
 8th
Figure imgb0027
Figure imgb0028
 9
Figure imgb0029
Figure imgb0030
 Entry undoped anode doped anode flow Yield [%] Temperature; Current density, amount of charge Yield [%] Temperature; Current density, amount of charge Yield [%] 1 53 20°C; 5 mA/cm 2 , 8.5 F 63 20°C; 2.5 mA/cm 2 , 8 F 63 2 44 50°C; 2.5 mA/cm 2 , 8.5 F 54 3 36 50°C; 2.5 mA/cm 2 , 8.5 F 66 4 30 50°C; 2.5 mA/cm 2 , 8.5 F 42 45°C; 2.5 mA/cm 2 , 8 F 43 5 18 50°C; 2.5 mA/cm 2 , 8.5 F 43 20°C; 5 mA/cm 2 , 8 F 6 60 45°C; 2.5 mA/cm 2 , 8 F entry Flow rate [ml/min] DC1 [%] 1a 0.47*10E-3 51 1b 0.1 53 1c 1.0 56 1d 7.5 60 1e 10.0 62 1f 12.5 64 entry solvent Alkaline additive DC 1 [%] 1-1 H2O 0.1M NaOH 20 1-2 H2O 0.5M NaOH 45 1-3 H2O 1.0M NaOH 51 1-4 H2O 2.0M NaOH 45 1-5 H2O 5.0M NaOH 16 1-6 H2O 1.0 MK2CO3 3 1-7 H2O 1.0M KOH 50 1-8 H2O / tBuOH (3:7) 1.0M NaOH 1 1-9 H2O / tBuOH (2:1) 0.25M NaOH 26 1-10 H2O / tBuOH (1:1) 0.18M KOH 7 1-11 H2O /PE (1:1) 1.0M NaOH 16 1-12 H2O /DMSO (1:1) 1.0M NaOH 7 1-13 H2O /tAmylOH (2:1) 1.0M NaOH 27 t BuOH = tert. Butanol, PE = petroleum ether, DMSO = dimethyl sulfoxide, t AmylOH = tert. amyl alcohol (2-methyl-2-butanol); 30mA, 8F, 20°C Entry doped anode Yield [%] Temperature; Current density, amount of charge 7 61 20°C; 2.5 mA/cm 2 , 6 F 8th 66 20°C; 2.5 mA/cm 2 , 6 F 9 64 40°C; 2.5 mA/cm 2 , 6 F Cyclooctanol acetic acid ester was converted into octanedioic acid (DC6) in a batch process at the doped anode at 20 ° C, 5 mA / cm 2 and 8 F in 30% yield.

Claims (14)

  1. Method for the electrochemical preparation of alkanedicarboxylic acids by ring-opening oxidation in aqueous alkaline solution, characterized in that the oxidation is carried out at a Ni(O)OH foam electrode doped with elements of main group 5 and/or 6, wherein the Ni(O)OH foam electrode comprises 2 to 10% by weight phosphorus, phosphorus here being considered as an element, and based on the metal mass of the electrode, according to scheme (I)
    Figure imgb0035
    where
    Figure imgb0036
    represents a single or double bond, R accordingly being present or not,
    where R is hydrogen or an acyl radical, wherein the acyl radical is the radical of an aliphatic monocarboxylic acid having 2 to 8 carbon atoms and where A is a hydrocarbon having 4 to 30 carbon atoms, in which all ring carbons of A in the cyclic reactant of scheme (I) bear at least one hydrogen substituent.
  2. Method according to Claim 1, characterized in that the Ni(O)OH foam electrode comprises 3 to 9% by weight and preferably 4 to 9% by weight, phosphorus here being considered as an element and based on the metal mass of the electrode.
  3. Method according to Claims 1 to 2, characterized in that the Ni(O)OH foam electrode is two or more millimetres thick, preferably more than 3 mm, more preferably more than 5 mm and especially preferably equal to or thicker than 6 mm.
  4. Method according to at least one of Claims 1 to 3, characterized in that the Ni(O)OH foam electrode comprises nickel as metal to an extent of at least 80% by weight, preferably at least 90, 95, 98, 99% by weight, more preferably at least 99.9, especially preferably at least 99.99% by weight.
  5. Method according to at least one of Claims 1 to 4, characterized in that the aqueous solution signifies that up to 30% by volume of a cosolvent may be present in the solution.
  6. Method according to at least one of Claims 1 to 5, characterized in that the alkaline additive to the aqueous solution is lithium hydroxide, sodium hydroxide or potassium hydroxide, preferably no further anions of the bases are present.
  7. Method according to at least one of Claims 1 to 6, characterized in that the concentration of the alkaline additive is 0.5 to 2 mol/l, based on the aqueous alkaline solution, preferably 0.8 to 1.5 mol/l and particularly preferably 1 mol/l with a possible deviation of up to 10%, preferably a deviation of up to 5% in the molarity.
  8. Method according to at least one of Claims 1 to 7, characterized in that the concentration of the cycloalkanols, i.e. R = hydrogen and
    Figure imgb0037
    is a single bond in scheme (I), is 0.06 to 0.5 mol/l, preferably 0.08 to 0.3 and particularly preferably 0.09 to 0.11 mol/l.
  9. Method according to at least one of Claims 1 to 8, characterized in that the method according to
    Figure imgb0038
     is carried out,
    where R1, R2, R3 are the same or different, hydrogen or alkyl radical having 1 to 8 carbon atoms, preferably 1 to 5 carbon atoms, linear or branched, wherein at least one of the radicals R1, R2, R3 is an alkyl radical, wherein more preferably only one of the radicals R1, R2, R3 is an alkyl radical having 1 to 4 carbon atoms and particularly preferably the radicals R1 and R3 are hydrogen and R2 is an alkyl radical having 1 to 4 carbon atoms.
  10. Method according to Claim 9, wherein the total amount of electrons applied is 8 to 10 F, more preferably 8.5 to 9 F, where F is the Faraday unit.
  11. Method according to at least one of Claims 1 to 9, characterized in that the method is carried out at a current density of 2 to 10 mA/cm2, more preferably 2.5 to 7.5 mA/cm2 and especially preferably 3.3 to 6 mA/cm2, the area referring to the geometric area without consideration of the inner surface area of the foam.
  12. Method according to at least one of the preceding claims, characterized in that the electrolysis is carried out in a batch electrolytic cell or in a continuous flow electrolytic cell, preferably in a continuous flow electrolytic cell.
  13. Method according to at least one of the preceding claims, characterized in that the cathode material used is stainless steel, platinum or nickel or a mixture.
  14. Method according to at least one of the preceding claims, characterized in that the electrolysis is carried out at temperatures of 20 - 70°C, preferably 30 - 60°C, more preferably 35 - 50°C.
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