EP0006177B1 - Bipolar electrode for electrochemical oxidation in diaphragmless cells and its utilisation - Google Patents
Bipolar electrode for electrochemical oxidation in diaphragmless cells and its utilisation Download PDFInfo
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- EP0006177B1 EP0006177B1 EP79101765A EP79101765A EP0006177B1 EP 0006177 B1 EP0006177 B1 EP 0006177B1 EP 79101765 A EP79101765 A EP 79101765A EP 79101765 A EP79101765 A EP 79101765A EP 0006177 B1 EP0006177 B1 EP 0006177B1
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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
- C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
- C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
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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
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- the invention relates to a bipolar electrode made of graphite or glassy carbon for the methoxylation of organic compounds.
- bipolar electrodes made of graphite plates are known, in which the graphite plates are provided with porous metal plates or metal grids which are screwed onto the anode plates in such a way that a small gap remains between the anode and the cathode.
- the surfaces of the anodes facing the cathodes are coated with iron and the surfaces of the cathodes are wetted with liquid metal, for example mercury, during operation.
- the invention thus relates to a multilayer, bipolar electrode made of carbon plates, in particular graphite or vitreous carbon, and metal grids or metal nets arranged between the plates, which is characterized in that the metal nets consist of materials which reduce hydrogen overvoltage and rest on the cathode surface.
- the invention furthermore relates to the use of such electrodes for carrying out anodic methoxylations of organic compounds in undivided electrolysis cells.
- the materials used for the metal meshes of the electrode according to the invention are mainly the metals of I. IV. V. VI. and VIII. Subgroup of the Periodic Table of the Elements in question. From an economic point of view, however, the base metals are preferred, e.g. Steel, nickel, copper, brass and titanium, especially stainless steel and nickel.
- the term metal mesh should be understood to mean nets or fabrics or expanded metals.
- Meter cross sections from 0.002 MM 2 to 9 MM 2 have proven to be usable. However, cross sections from 0.008 mm 2 to 9 mm 2 are preferred.
- the electrode according to the invention can have networks in one or more layers, depending on the requirements of the respective electrolysis, it only has to be ensured that the electric field cannot reach as far as the carbon plate. If several layers are used, the layers can consist of the same type or of different types.
- the mesh sizes and wire thicknesses of the metal nets or metal mesh are variable within wide limits, for example the wire thicknesses are between 0.05 mm and 1 mm, preferably between 0.1 and 0.4 mm diameter and the mesh sizes between 0.1 and 5 mm, preferably between 0.2 and 0.7 mm.
- the expanded metals can be made from 0.3 to 3 mm thick metal sheets. With web widths of 0.5 to 3 mm, the mesh widths are 0.5 to 4 mm and the mesh lengths are 1 to 6 mm.
- the electrodes according to the invention 2 to 3 layers of VA steel mesh with a mesh size of 0.5 mm and a wire thickness of 0.3 mm are combined, with a layer of fine metal mesh with a mesh size of 0.19 mm and a wire thickness of 0.1 mm encased and placed on the cathode sides of the plates made of glassy carbon or graphite.
- the electrode according to the invention is particularly characterized by a long service life. It also allows high, technically interesting electrolysis current densities of up to 1 A / cm 2 . The considerable amounts of heat developed at these current densities can be easily dissipated when using the electrode according to the invention if there are correspondingly thick layers of metal nets, metal meshes and / or expanded metals on the carbon plates and sufficient electrolyte volumes are passed between the electrode gaps. This also counteracts the risk of formation of heat pockets in the electrode gaps, so that work can be carried out with a minimized electrode spacing, to mention to avoid valuable energy losses in the electrolyte.
- An undivided cell with an anode made of vitreous carbon, a cathode made of nickel and in between two bipolar electrodes made of vitreous carbon was installed in a flow apparatus with circulation pump, heat exchanger and degassing vessel. Between the plates was a stack of nickel mesh (2 layers of 0.19 mm and 0.1 mm wire gauge and between 2 layers of 0.5 mm mesh and 0.3 mm gauge) and polyethylene mesh (1 layer of 0.9 mm mesh and the thread thickness 0.3 mm) so that the nickel fabric came to rest on the cathode sides of the carbon plates and the nickel electrode. Then the stack was pressed into the cell.
- All electrode plates were enclosed in a polyethylene frame which was 22 mm wide perpendicular to the flow direction of the electrolyte, 12 mm wide parallel to the flow direction and, like the plates, was approx. 2.5 mm thick.
- the effective electrode area of each anode was 255 cm 2 .
- the mixture of 3,220 g of benzene, 391 g of tetramethylammonium fluoride, 49 g of hydrogen fluoride and 10,340 g of methanol was electrolyzed at 51 A, 17.5 V to 18.9 V cell voltage and 35 ° C. for 17 hours and 45 minutes (corresponding to 2 120 Ah) .
- the electrolyte then contained 7.42 mol of p-benzoquinone tetramethyl ketal, corresponding to a current efficiency of 43.9% of theory. Th.
- the undivided cell was equipped with an electrode stack which consisted of an anode made of vitreous carbon, a nickel cathode and two bipolar electrodes made of vitreous carbon which were inserted between these outer electrodes.
- the bipolar electrodes like the outer electrodes, were enclosed in the polyethylene frames described in Example 1.
- Polyethylene nets (mesh size 3x5 mm, thread thickness 0.5 mm) served as spacers between the plates; thicker meshes with a larger mesh size were used, which made the free volumes between the plates comparable to those in Example 1.
- the resulting larger electrode spacing was compensated for by a higher conductive salt concentration and thus better conductivity of the electrolyte.
- the mixture of 1,050 g of benzene, 380 g of tetramethylammonium fluoride, 10 g of hydrogen fluoride and 4,340 g of methanol was electrolyzed for 12 hours at 50 A (corresponding to 1,800 Ah) and 19 to 22 V.
- the electrolyte then contained 0.40 mol of p-benzoquinone tetramethyl ketal, corresponding to a current yield of 3.6% of theory. Th.
- a stack of 6 round, bipolar switched graphite disks (type Diabon ( R ) N from Sigri in Meitingen; diameter 50 mm; thickness 21 mm) was installed in a glass tube with an inner diameter of 50 mm and a length of 138 mm, between each of which a nickel mesh (Mesh size 0.5 mm wire thickness 0.3 mm) and a polyethylene mesh (mesh size 1.8 mm, thread thickness 0.6 mm) were inserted so that the nickel meshes formed the cathode sides.
- the graphite disks had 56 holes 1.5 mm in diameter through which the electrolyte could flow.
- the glass tube was closed by similarly drilled graphite plates, which acted as contact electrodes.
- This cell was installed in a circulation apparatus with a circulation pump, heat exchanger and degassing vessel.
- the mixture of 350 g of o-chloroanisole, 139 g of tetramethylammonium fluoride, 3.17 g of hydrogen fluoride and 2 900 g of methanol was 4 hours and 50 minutes at 5 A (corresponding to 169 Ah), 37 to 43.4 V and 34- 35 ° C electrolyzed.
- the electrolyte then contained 181 g of chlorine-p-benzoquinone tetramethyl ketal, 71.1 g of chlorohydroquinone dimethyl ether and 124 g of unreacted starting product.
- Example 2 In the cell described in Example 2, the metal nets were removed and the mixture described there was electrolyzed twice in succession. After a total of 223 Ah, the cell voltage dropped from 38 V to 27 V. The electrolysis was stopped and the cell opened. Graphite particles had accumulated between two of the plates and caused short circuits.
- Example 1 In the cell and flow-through apparatus described in Example 1, the mixture of 4,800 g of 1-formylpiperidine, 13,600 g of methanol and 68 g of tetramethylammonium tetrafluoroborate at 27.5 A, 42 V cell voltage and 25 ° C. was used for 27 hours and 33 minutes (corresponding to 2,273 Ah) electrolyzed. After working up by distillation, 5 720 g of 1-formyl-2-methoxypiperidine were isolated, corresponding to a current efficiency of 89.6%.
- the undivided cell was equipped with an electrode stack consisting of an anode made of glassy carbon, a nickel cathode and two between these outer electrodes pushed bipolar electrodes made of glassy carbon. All four electrodes were enclosed in the polyethylene frame described in Example 1. Polyethylene nets (mesh size 3x5 mm, thread thickness 0.5 mm) served as spacers between the plates.
- the mixture of 4,800 g of 1-formylpiperidine, 13,600 g of methanol and 68 g of tetramethylammonium tetrafluoroborate was electrolyzed at 27.5 A, 45 V cell voltage and 25 ° C. for 27 hours and 33 minutes (corresponding to 2,273 Ah). After working up by distillation, 5 120 g of 1-formyl-2-methoxypiperidine were isolated, corresponding to a current efficiency of 80.3%.
- Example 2 In the cell described in Example 2, the metal nets were removed and then the mixture of 480 g of 1-formylpiperidine, 1 360 g of methanol and 6.80 g of tetramethylammonium tetrafluoroborate was 40 hours and 40 minutes at 1 A (corresponding to 285 Ah), 105 V cell voltage and 25 ° C electrolyzed.
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Description
Gegenstand der Erfindung ist eine bipolare Elektrode aus Graphit oder glasartigem Kohlenstoff für die Methoxylierung organischer Verbindungen.The invention relates to a bipolar electrode made of graphite or glassy carbon for the methoxylation of organic compounds.
Es ist bekannt, daß man anodische Oxydationen und Methoxylierungen in ungeteilten Zellen an Kohlenstoffelektroden durchführen kann [vgl. z.B. DE-A 25 02 167; DE-A 25 47 386; s. auch Acta Chem. Scand., B 29, 617-21 (1975) BE-A 836 949]. Benutzt man hierbei die Kohlenstoffelektroden in bipolarer Schaltung, um größere Substanzmengen mit technisch interessanten Raum/Zeit-Ausbeuten herzustellen, so tritt bei Verwendung von Graphit an den Kathoden durch den gebildeten Wasserstoff Erosin auf. Infolge dieser Erosion können durch von den Kathoden abgesprengte Graphitpartikel elektrische Kurzschlüsse in den engen Elektrodenspalten auftreten, wodurch neben Stromausbeuteverlusten erhebliche Störungen beim Zellenbetrieb verursacht werden. Verwendet man anstelle von Graphit glasartigen Kohlenstoff als Elektrodenmaterial so treten zwar keine Erosionen, dafür jedoch während der Elektrolyse zunehmende Stromausbeuteverluste auf.It is known that anodic oxidations and methoxylations can be carried out in undivided cells on carbon electrodes [cf. e.g. DE-A 25 02 167; DE-A 25 47 386; s. also Acta Chem. Scand., B 29, 617-21 (1975) BE-A 836 949]. If the carbon electrodes are used in a bipolar circuit in order to produce larger amounts of substance with technically interesting space / time yields, when hydrogen is used graphite on the cathodes is formed by the hydrogen formed. As a result of this erosion, electrical short circuits can occur in the narrow electrode gaps as a result of graphite particles being blasted off from the cathodes, which, in addition to losses in the efficiency of electricity, causes considerable disturbances in cell operation. If glass-like carbon is used as the electrode material instead of graphite, there are no erosions, but there are increasing losses in current efficiency during the electrolysis.
Nach der SU-A 186 981 sind bipolare Elektroden aus Graphitplatten bekannt, bei denen die Graphitplatten mit porösen Metallplatten oder Metallgittern versehen sind, die so auf die Anodenplatten geschraubt sind, daß zwischen Anode und Kathode ein kleiner Spalt verbleibt. Die den Kathoden zugewandten Oberflächen der Anoden sind mit Eisen beschichtet und die Oberflächen der Kathoden werden während des Betriebes mit flüssigem Metall, beispielsweise Quecksilber benetzt.According to SU-A 186 981, bipolar electrodes made of graphite plates are known, in which the graphite plates are provided with porous metal plates or metal grids which are screwed onto the anode plates in such a way that a small gap remains between the anode and the cathode. The surfaces of the anodes facing the cathodes are coated with iron and the surfaces of the cathodes are wetted with liquid metal, for example mercury, during operation.
Aufgabe der vorliegenden Erfindung ist es demnach, eine konstruktiv einfache bipolare Elektrode zu schaffen, bei der einerseits eine Zerstörung der Elektrode an der Kathode durch Wasserstoffentwicklung vermieden wird und andererseits die Stromausbeute während des Elektrolysevorgangs erhalten bleibt.It is therefore an object of the present invention to provide a structurally simple bipolar electrode in which, on the one hand, destruction of the electrode on the cathode by evolution of hydrogen is avoided and, on the other hand, the current efficiency is maintained during the electrolysis process.
Gegenstand der Erfindung ist somit eine mehrschichtige, bipolare Elektrode aus Kohlenstoffplatten, insbesondere aus Graphit oder glasartigem Kohlenstoff, und zwischen den Platten angeordneten Metallgittern oder Metallnetzen, die dadurch gekennzeichnet ist, daß die Metall-Netze aus wasserstoffüberspannungsherabsetzenden Materialien bestehen und auf der Kathodenoberfläche aufliegen.The invention thus relates to a multilayer, bipolar electrode made of carbon plates, in particular graphite or vitreous carbon, and metal grids or metal nets arranged between the plates, which is characterized in that the metal nets consist of materials which reduce hydrogen overvoltage and rest on the cathode surface.
Gegenstand der Erfindung ist weiterhin die Verwendung solcher Elektroden zur Durchführung anodischer Methoxylierungen organischer Verbindungen in ungeteilten Elektrolysezellen.The invention furthermore relates to the use of such electrodes for carrying out anodic methoxylations of organic compounds in undivided electrolysis cells.
Als die Wasserstoffüberspannung herabsetzende Materialien für die Metall-Netze der erfindungsgemäßen Elektrode kommen hauptsächlich die Metalle der I. IV. V. VI. und VIII. Nebengruppe des Periodensystems der Elemente in Frage. Aus wirtschaftlichen Gesichtspunkten sind darunter jedoch die Nichtedelmetalle bevorzugt wie z.B. Stahl, Nickel, Kupfer, Messing und Titan, insbesondere VA-Stahl und Nickel.The materials used for the metal meshes of the electrode according to the invention are mainly the metals of I. IV. V. VI. and VIII. Subgroup of the Periodic Table of the Elements in question. From an economic point of view, however, the base metals are preferred, e.g. Steel, nickel, copper, brass and titanium, especially stainless steel and nickel.
Unter dem Begriff Metall-Netz sollen Netze oder Gewebe oder Streckmetalle verstanden werden. Meterialquerschnitte von 0,002 MM 2 bis 9 MM 2 haben sich als brauch-bar erweisen. Bevorzugt werden jedoch Querschnitte von 0,008 mm2 bis 9 mm2. Die erfindungsgemäße Elektrode kann je nach den Erfordernissen der jeweiligen Elektrolyse Netze in einer oder mehreren Lagen aufweisen, dabei muß lediglich sichergestellt werden, daß das elektrische Feld nicht bis zur Kohlenstoffplatte durchgreifen kann. Bei Verwendung mehrerer Lagen können die Lagen aus der gleichen Sorte oder aus verschiedenen Sorten bestehen. Die Maschenweiten und Drahtstärken der Metallnetze oder Metallgewebe sind in weiten Grenzen variabel, beispielsweise liegen die Drahtstärken zwischen 0,05 mm und 1 mm, bevorzugt zwischen 0,1 und 0,4 mm Durchmesser und die Maschenweiten zwischen 0,1 und 5 mm, vorzugsweise zwischen 0,2 und 0,7 mm. Die Streckmetalle können aus 0,3 bis 3 mm dicken Blechen hergestellt sein. Bei Stegbreiten von 0,5 bis 3 mm betragen die Maschenweiten 0,5 bis 4 mm und die Maschenlängen 1 bis 6 mm. In einer besonders bevorzugten Ausführungsform der erfindungsgemäßen Elektroden werden 2 bis 3 Lagen aus VA-Stahinetz der Maschenweite 0,5 mm und der Drahtstärke 0,3 mm zusammengefaßt, mit einer Lage feinem Metallnetz der Maschenweite 0,19 mm und der Drahtstärke 0,1 mm umhüllt und auf die Kathodenseiten der Platten aus glasartigem Kohlenstoff oder Graphit aufgelegt. Die Figur gibt schematisch den Aufbau der erfindungsgemäßen Elektrode wieder mit der Kohlenstoffplatte 1, den kathodenseitigen Metallnetzen 2 und dem Abstandshalter aus isolierendem Material 3.The term metal mesh should be understood to mean nets or fabrics or expanded metals. Meter cross sections from 0.002 MM 2 to 9 MM 2 have proven to be usable. However, cross sections from 0.008 mm 2 to 9 mm 2 are preferred. The electrode according to the invention can have networks in one or more layers, depending on the requirements of the respective electrolysis, it only has to be ensured that the electric field cannot reach as far as the carbon plate. If several layers are used, the layers can consist of the same type or of different types. The mesh sizes and wire thicknesses of the metal nets or metal mesh are variable within wide limits, for example the wire thicknesses are between 0.05 mm and 1 mm, preferably between 0.1 and 0.4 mm diameter and the mesh sizes between 0.1 and 5 mm, preferably between 0.2 and 0.7 mm. The expanded metals can be made from 0.3 to 3 mm thick metal sheets. With web widths of 0.5 to 3 mm, the mesh widths are 0.5 to 4 mm and the mesh lengths are 1 to 6 mm. In a particularly preferred embodiment of the electrodes according to the invention, 2 to 3 layers of VA steel mesh with a mesh size of 0.5 mm and a wire thickness of 0.3 mm are combined, with a layer of fine metal mesh with a mesh size of 0.19 mm and a wire thickness of 0.1 mm encased and placed on the cathode sides of the plates made of glassy carbon or graphite. The figure schematically shows the structure of the electrode according to the invention again with the
Die erfindungsgemäße Elektrode zeichnet sich besonders durch eine hohe Lebensdauer aus. Sie erlaubt weiterhin hohe, technisch interessante Elektrolyse-Stromdichten von bis zu 1 A/cm2. Die bei diesen Stromdichten entwickelten beträchtlichen Wärmemengen lassen sich bei Verwendung der erfindungsgemäßen Elektrode dann leicht abführen, wenn sich entsprechend dicke Lagen an Metallnetzen, Metallgeweben und/oder Streckmetallen auf den Kohlenstoffplatten befinden und ausreichende Elektrolytvolumina zwischen den Elektrodenspalten hindurchgeführt werden. Hierdurch wird auch der Gefahr der Bildung von Wärmenestern in den Elektrodenspalten begegnet, so daß bei minimiertem Elektrodenabstand gearbeitet werden kann, um nennenswerte Energieverluste im Elektrolyten zu vermeiden.The electrode according to the invention is particularly characterized by a long service life. It also allows high, technically interesting electrolysis current densities of up to 1 A / cm 2 . The considerable amounts of heat developed at these current densities can be easily dissipated when using the electrode according to the invention if there are correspondingly thick layers of metal nets, metal meshes and / or expanded metals on the carbon plates and sufficient electrolyte volumes are passed between the electrode gaps. This also counteracts the risk of formation of heat pockets in the electrode gaps, so that work can be carried out with a minimized electrode spacing, to mention to avoid valuable energy losses in the electrolyte.
Im Folgenden wird die Wirkungsweise der erfindungsgemäßen Elektrode anhand von Beispielen näher erläutert:The mode of operation of the electrode according to the invention is explained in more detail below using examples:
In eine Durchflußapparatur mit Umwälzpumpe, Wärmeaustauscher und Entgasungsgefäß wurde eine ungeteilte Zelle mit einer Anode aus glasartigem Kohlenstoff, einer Kathode aus Nickel und dazwischen zwei bipolar geschalteten Elektroden aus glasartigem Kohlenstoff eingebaut. Zwischen die Platten wurde jeweils ein Stapel aus Nickelgewebe (2 Lagen der Maschenweite 0.19 mm und 0.1 mm Drahtstärke und dazwischen 2 Lagen der Maschenweite 0,5 mm und der Drahtstärke 0,3 mm) und Polyäthylengewebe (1 Lage der Maschenweite 0,9 mm und der Fadenstärke 0,3 mm) so eingeschoben, daß das Nickel-gewebe auf die Kathodenseiten der Kohleplatten und die Nickelelektrode zu liegen kam. Dann wurde der Stapel zusammengepreßt in die Zelle eingebaut. Alle Elektrodenplatten waren in einen Polyäthylenrahmen eingefaßt, der senkrecht zur Strömungsrichtung des Elektrolyten 22 mm breit, parallel zur Strömungsrichtung 12 mm breit und wie die Platten ca. 2,5 mm dick war. Die wirksame Elektrodenfläche jeder Anode betrug 255 cm2.An undivided cell with an anode made of vitreous carbon, a cathode made of nickel and in between two bipolar electrodes made of vitreous carbon was installed in a flow apparatus with circulation pump, heat exchanger and degassing vessel. Between the plates was a stack of nickel mesh (2 layers of 0.19 mm and 0.1 mm wire gauge and between 2 layers of 0.5 mm mesh and 0.3 mm gauge) and polyethylene mesh (1 layer of 0.9 mm mesh and the thread thickness 0.3 mm) so that the nickel fabric came to rest on the cathode sides of the carbon plates and the nickel electrode. Then the stack was pressed into the cell. All electrode plates were enclosed in a polyethylene frame which was 22 mm wide perpendicular to the flow direction of the electrolyte, 12 mm wide parallel to the flow direction and, like the plates, was approx. 2.5 mm thick. The effective electrode area of each anode was 255 cm 2 .
In dieser Zelle wurde die Mischung aus 3 220 g Benzol, 391 g Tetramethylammoniumfluorid, 49 g Fluorwasserstoff und 10 340 g Methanol bei 51 A, 17.5 V bis 18.9 V Zellspannung und 35°C 17 Stunden und 45 Minuten (entsprechend 2 120 Ah) elektrolysiert. Danach enthielt der Elektrolyt 7.42 Mol p-Benzochinontetramethylketal entsprechend einer Stromausbeute von 43.9% d. Th.In this cell, the mixture of 3,220 g of benzene, 391 g of tetramethylammonium fluoride, 49 g of hydrogen fluoride and 10,340 g of methanol was electrolyzed at 51 A, 17.5 V to 18.9 V cell voltage and 35 ° C. for 17 hours and 45 minutes (corresponding to 2 120 Ah) . The electrolyte then contained 7.42 mol of p-benzoquinone tetramethyl ketal, corresponding to a current efficiency of 43.9% of theory. Th.
In der in Beispiel 1 beschriebenen Anlage wurde die ungeteilte Zelle mit einem Elektrodenstapel bestückt, der aus einer Anode aus glasartigem Kohlenstoff, einer Nickel-kathode, sowie zwei zwischen diese Außenelektroden geschobenen bipolar geschalteten Elektroden aus glasartigem Kohlenstoff bestand. Die bipolar geschalteten Elektroden waren wie die Außenelektroden in die in Beispiel 1 beschriebenen Polyäthylenrahmen eingefaßt. Poly- äthylennetze (Maschenweite 3x5 mm, Fadenstärke 0,5 mm) dienten zwischen den Platten als Abstandshalter; und zwar wurden dickere Netze mit größerer Maschenweite verwendet, die die freien Volumina zwischen den Platten mit denen in Beispiel 1 vergleichbar machten. Der daraus entstehende größere Elektrodenabstand wurde durch eine höhere Leitsalzkonzentration und damit bessere Leitfähigkeit des Elektrolyten ausgeglichen. In der beschriebenen Zelle wurde die Mischung aus 1 050 g Benzol, 380 g Tetramethylammoniumfluorid, 10 g Fluorwasserstoff und 4 340 g Methanol 12 Stunden bei 50 A (entsprechend 1 800 Ah) und 19 bis 22 V elektrolysiert. Danach enthielt der Elektrolyt 0,40 Mol p-Benzochinontetramethylketal entsprechend einer Stromausbeute von 3,6% d. Th.In the system described in Example 1, the undivided cell was equipped with an electrode stack which consisted of an anode made of vitreous carbon, a nickel cathode and two bipolar electrodes made of vitreous carbon which were inserted between these outer electrodes. The bipolar electrodes, like the outer electrodes, were enclosed in the polyethylene frames described in Example 1. Polyethylene nets (mesh size 3x5 mm, thread thickness 0.5 mm) served as spacers between the plates; thicker meshes with a larger mesh size were used, which made the free volumes between the plates comparable to those in Example 1. The resulting larger electrode spacing was compensated for by a higher conductive salt concentration and thus better conductivity of the electrolyte. In the cell described, the mixture of 1,050 g of benzene, 380 g of tetramethylammonium fluoride, 10 g of hydrogen fluoride and 4,340 g of methanol was electrolyzed for 12 hours at 50 A (corresponding to 1,800 Ah) and 19 to 22 V. The electrolyte then contained 0.40 mol of p-benzoquinone tetramethyl ketal, corresponding to a current yield of 3.6% of theory. Th.
In ein Glasrohr mit 50 mm Innendurchmesser und 138 mm Länge wurde ein Stapel aus 6 runden, bipolar geschalteten Graphitscheiben (Typ Diabon(R) N der Fa. Sigri in Meitingen; Durchmesser 50 mm; Dicke 21 mm) eingebaut, zwischen die jeweils ein Nickelnetz (Maschenweite 0,5 mm Drahtstärke 0,3 mm) und ein Polyäthylennetz (Maschenweite 1,8 mm, Fadenstärke 0,6 mm) so eingeschoben waren, daß die Nickelnetze die Kathodenseiten bildeten. Die Graphitscheiben trugen 56 Bohrungen von 1,5 mm Durchmesser, durch die der Elektrolyt strömen konnte. Das Glasrohr war durch gleichartig durchbohrte Graphitplatten verschlossen, die als Kontaktelektroden fungierten. Diese Zelle war in eine Umlaufapparatur mit Umwälzpumpe, Wärmetauscher und Entgasungsgefäß eingebaut. In dieser Anlage wurde die Mischung aus 350 g o-Chloranisol, 139 g Tetramethylammoniumfluorid, 3,17 g Fluorwasserstoff und 2 900 g Methanol 4 Stunden und 50 Minuten bei 5 A (entsprechend 169 Ah), 37 bis 43,4 V und 34-35°C electrolysiert. Danach enthielt der Elektrolyt 181 g Chlor - p - benzochinontetramethylketal, 71,1 g Chlorhydrochinondimethyl- äther und 124 g an nicht umgesetztem Ausgangsprodukt.A stack of 6 round, bipolar switched graphite disks (type Diabon ( R ) N from Sigri in Meitingen; diameter 50 mm; thickness 21 mm) was installed in a glass tube with an inner diameter of 50 mm and a length of 138 mm, between each of which a nickel mesh (Mesh size 0.5 mm wire thickness 0.3 mm) and a polyethylene mesh (mesh size 1.8 mm, thread thickness 0.6 mm) were inserted so that the nickel meshes formed the cathode sides. The graphite disks had 56 holes 1.5 mm in diameter through which the electrolyte could flow. The glass tube was closed by similarly drilled graphite plates, which acted as contact electrodes. This cell was installed in a circulation apparatus with a circulation pump, heat exchanger and degassing vessel. In this plant, the mixture of 350 g of o-chloroanisole, 139 g of tetramethylammonium fluoride, 3.17 g of hydrogen fluoride and 2 900 g of methanol was 4 hours and 50 minutes at 5 A (corresponding to 169 Ah), 37 to 43.4 V and 34- 35 ° C electrolyzed. The electrolyte then contained 181 g of chlorine-p-benzoquinone tetramethyl ketal, 71.1 g of chlorohydroquinone dimethyl ether and 124 g of unreacted starting product.
In der in Beispiel 2 beschriebenen Zelle wurden die Metallnetze entfernt und zweimal nacheinander die dort beschriebene Mischung elektrolysiert. Dabei trat nach insgesamt 223 Ah ein Abfall der Zellspannung von 38 V auf 27 V ein. Die Elektrolyse wurde abgebrochen und die Zelle geöffnet. Zwischen zwei der Platten hatten sich Graphitpartikel angesammelt und zu Kurzschlüssen geführt.In the cell described in Example 2, the metal nets were removed and the mixture described there was electrolyzed twice in succession. After a total of 223 Ah, the cell voltage dropped from 38 V to 27 V. The electrolysis was stopped and the cell opened. Graphite particles had accumulated between two of the plates and caused short circuits.
In der in Beispiel 1 beschriebenen Zelle und Durchflußapparatur wurde die Mischung aus 4 800 g 1-Formylpiperidin, 13 600 g Methanol und 68 g Tetramethylammoniumtetrafluoroborat bei 27,5 A, 42 V Zellspannung und 25°C 27 Stunden und 33 Minuten (entsprechend 2 273 Ah) elektrolysiert. Nach destillativer Aufarbeitung wurden 5 720 g 1 - Formyl - 2 - methoxypiperidin entsprechend einer Stromausbeute von 89,6% isoliert.In the cell and flow-through apparatus described in Example 1, the mixture of 4,800 g of 1-formylpiperidine, 13,600 g of methanol and 68 g of tetramethylammonium tetrafluoroborate at 27.5 A, 42 V cell voltage and 25 ° C. was used for 27 hours and 33 minutes (corresponding to 2,273 Ah) electrolyzed. After working up by distillation, 5 720 g of 1-formyl-2-methoxypiperidine were isolated, corresponding to a current efficiency of 89.6%.
In der in Beispiel 1 beschriebenen Anlage wurde die ungeteilte Zelle mit einem Elektrodenstapel bestückt, der aus einer Anode aus glasartigem Kohlenstoff, einer Nickelkathode sowie zwei zwischen diese Außenelektroden geschobenen bipolar geschalteten Elektroden aus glasartigem Kohlenstoff bestand. Alle vier Elektroden waren in die in Beispiel 1 beschriebenen Polyäthylenrahmen eingefaßt. Poly- äthylennetze (Maschenweite 3x5 mm, Fadenstärke 0,5 mm) dienten zwischen den Platten als Abstandshalter. In der beschriebenen Zelle wurde die Mischung aus 4 800 g 1-Formylpiperidin, 13 600 g Methanol und 68 g Tetramethylammoniumtetrafluorborat bei 27,5 A, 45 V Zellspannung und 25°C 27 Stunden und 33 Minuten (entsprechend 2 273 Ah) elektrolysiert. Nach destillativer Aufarbeitung wurden 5 120 g 1 - Formyl - 2 - methoxypiperidin entsprechend einer Stromausbeute von 80,3% isoliert.In the system described in Example 1, the undivided cell was equipped with an electrode stack consisting of an anode made of glassy carbon, a nickel cathode and two between these outer electrodes pushed bipolar electrodes made of glassy carbon. All four electrodes were enclosed in the polyethylene frame described in Example 1. Polyethylene nets (mesh size 3x5 mm, thread thickness 0.5 mm) served as spacers between the plates. In the cell described, the mixture of 4,800 g of 1-formylpiperidine, 13,600 g of methanol and 68 g of tetramethylammonium tetrafluoroborate was electrolyzed at 27.5 A, 45 V cell voltage and 25 ° C. for 27 hours and 33 minutes (corresponding to 2,273 Ah). After working up by distillation, 5 120 g of 1-formyl-2-methoxypiperidine were isolated, corresponding to a current efficiency of 80.3%.
In der in Beispiel 2 beschriebenen Zelle und Anlage wurde die Mischung aus 480 g 1 - Formylpiperidin, 1 360 g Methanol, und 6.80 g Tetramethylammoniumtetrafluoroborat 34 Stunden und 15 Minuten bei 1 A (entsprechend 240 Ah), 98 V Zellspannung und 25°C elektrolysiert. Aus dem klaren Elektrolyt konnten durch destillative Aufarbeitung 577 g 1 - Formyl - 2 - methoxypiperidin entsprechend einer Stromausbeute von 90.2% d. Th. isoliert werden.In the cell and system described in Example 2, the mixture of 480 g of 1-formylpiperidine, 1,360 g of methanol and 6.80 g of tetramethylammonium tetrafluoroborate was electrolyzed for 34 hours and 15 minutes at 1 A (corresponding to 240 Ah), 98 V cell voltage and 25 ° C. . 577 g of 1-formyl-2-methoxypiperidine, corresponding to a current yield of 90.2% of theory, could be obtained from the clear electrolyte by working up by distillation. Th. Be isolated.
In der in Beispiel 2 beschriebenen Zelle wurden die Metallnetze entfernt und dann die Mischung aus 480 g 1 - Formyl - piperidin, 1 360 g Methanol und 6.80 g Tetramethylammoniumtetrafluorborat 40 Stunden und 40 Minuten bei 1 A (entsprechend 285 Ah), 105 V Zellspannung und 25°C elektrolysiert.In the cell described in Example 2, the metal nets were removed and then the mixture of 480 g of 1-formylpiperidine, 1 360 g of methanol and 6.80 g of tetramethylammonium tetrafluoroborate was 40 hours and 40 minutes at 1 A (corresponding to 285 Ah), 105 V cell voltage and 25 ° C electrolyzed.
Der anfangs wasserklare Elektrolyt nahm bereits nach kurzer Zeit eine im Laufe der Elektrolyse zunehmende Trübung an, die von feinem Graphitabrieb herrührte. Nach destillativer Aufarbeitung ließen sich 476 g 1 - Formyl - 2 - methoxy - piperidin entsprechend einer Stromausbeute von 62.7% isolieren.After a short time, the initially clear electrolyte assumed an increasing turbidity in the course of the electrolysis, which resulted from fine graphite abrasion. After working up by distillation, 476 g of 1-formyl-2-methoxy-piperidine could be isolated, corresponding to a current yield of 62.7%.
Claims (3)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19782825494 DE2825494A1 (en) | 1978-06-10 | 1978-06-10 | BIPOLAR ELECTRODE FOR ANODIC PROCESSES IN UNDIVIDED CELLS |
| DE2825494 | 1978-06-10 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0006177A1 EP0006177A1 (en) | 1980-01-09 |
| EP0006177B1 true EP0006177B1 (en) | 1982-08-11 |
Family
ID=6041489
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP79101765A Expired EP0006177B1 (en) | 1978-06-10 | 1979-06-05 | Bipolar electrode for electrochemical oxidation in diaphragmless cells and its utilisation |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US4404082A (en) |
| EP (1) | EP0006177B1 (en) |
| JP (1) | JPS54162682A (en) |
| BR (1) | BR7903636A (en) |
| DE (2) | DE2825494A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4370214A (en) * | 1980-04-25 | 1983-01-25 | Olin Corporation | Reticulate electrode for electrolytic cells |
| US5277767A (en) * | 1991-04-08 | 1994-01-11 | Eastman Kodak Company | Electrochemical synthesis of diaryliodonium salts |
| GB201309753D0 (en) * | 2013-05-31 | 2013-07-17 | Water Fuel Engineering Ltd | Electrolysis cell and electrode |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| YU245767A (en) * | 1967-12-16 | 1975-06-30 | Inst Za Hemijska Tehno I Metal | Postupak za elektrokataliticko poboljsanje katodnih polarizacionih svostava grafitnih elektroda |
| US3969215A (en) * | 1974-02-25 | 1976-07-13 | Industrial Filter & Pump Mfg. Co. | Process and apparatus for removing metallic ions from an electrolytic solution |
| DE2502167C2 (en) * | 1975-01-21 | 1982-09-23 | Basf Ag, 6700 Ludwigshafen | Electrochemical cell with bipolar electrodes |
| FR2343821A2 (en) * | 1975-03-21 | 1977-10-07 | Ugine Kuhlmann | PERFECTED ELECTROLYZER FOR THE INDUSTRIAL PREPARATION OF FLUORINE |
| US4071429A (en) * | 1976-12-29 | 1978-01-31 | Monsanto Company | Electrolytic flow-cell apparatus and process for effecting sequential electrochemical reaction |
-
1978
- 1978-06-10 DE DE19782825494 patent/DE2825494A1/en not_active Withdrawn
-
1979
- 1979-06-05 EP EP79101765A patent/EP0006177B1/en not_active Expired
- 1979-06-05 DE DE7979101765T patent/DE2963528D1/en not_active Expired
- 1979-06-07 US US06/046,494 patent/US4404082A/en not_active Expired - Lifetime
- 1979-06-08 JP JP7134879A patent/JPS54162682A/en active Pending
- 1979-06-08 BR BR7903636A patent/BR7903636A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DE2963528D1 (en) | 1982-10-07 |
| US4404082A (en) | 1983-09-13 |
| JPS54162682A (en) | 1979-12-24 |
| DE2825494A1 (en) | 1979-12-20 |
| EP0006177A1 (en) | 1980-01-09 |
| BR7903636A (en) | 1980-02-05 |
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