WO2016045665A2

WO2016045665A2 - Electrochemical synthesis method and device

Info

Publication number: WO2016045665A2
Application number: PCT/DE2015/100403
Authority: WO
Inventors: Gerd-Uwe Flechsig
Original assignee: Universität Rostock
Priority date: 2014-09-26
Filing date: 2015-09-25
Publication date: 2016-03-31
Also published as: EP3198060B1; US20170335474A1; EP3198060A2; DE102014114047A1; WO2016045665A3

Abstract

The present invention relates to a method for producing at least one product by electrochemical synthesis on a directly electrically heated working electrode (1), at least one reactant reacting on the heated working electrode (1) to the at least one product. The invention also relates to the use of a directly electrically heated working electrode (1) for the electrochemical synthesis of at least one product. The invention relates in particular to a working electrode (1), particularly in the form of a three-dimensional, preferably conical spiral, designed for the electrochemical synthesis. Another object of the invention is the synthesis/regeneration of an enzymatic cofactor on a working electrode (1) according to the invention.

Description

Process and apparatus for electrochemical synthesis

The present invention relates to a process for the preparation of at least one product by electrochemical synthesis at a directly electrically heated working electrode (1), wherein at least one educt at the heated working electrode (1) reacts to the at least one product, or the use of a direct electrical heated working electrode (1) for the electrochemical synthesis of at least one product. The invention also relates to a working electrode (1) designed especially for electrochemical synthesis, in particular in the form of a three-dimensional, preferably conical spiral. The invention also relates to the synthesis / regeneration of an enyzmatic cofactor on a working electrode (1) according to the invention.

In the prior art are used for trace analysis in voltammetry, amperometry / coulometry and potentiometry heated working electrodes, which are to heat indirectly, for example, by means of alternating current directly or by means of AC or DC.

In an indirect heating, the working electrode may be constructed of a plurality of concentrically or parallel layers which are galvanically separated from one another, the outermost layer serving as an electrode and an inner layer as the heating element. Indirect heating by means of galvanically separated from the electrode heaters is disadvantageous because the structure of the sensors is more complicated, the temperature changes due to the thermal inertia (due to the heat capacity) of the different layers usually slower and the possibilities of miniaturization are limited.

Different directly heatable working electrodes, in which the heating current and the electrolysis current, in this case the current for the electrochemical measuring signal, jointly flow through the same conductor, are known from the prior art.

A direct electrical heating of the working electrode and simultaneously trouble-free electrochemical measurement can be made possible in the prior art by a so-called symmetrical arrangement or special filter circuits. A variant of the directly heated working electrode has a third contact for the connection to the electrochemical measuring device exactly in the middle between the two contacts for the supply of the heating current. By this arrangement disturbing influences of the heating current are suppressed to the measurement signals. The disadvantage here is especially the complex structure with three contacts per working electrode, the thermal disturbance by the heat dissipating third contact and the complicated miniaturization. In a preferred variant according to the invention, therefore, a symmetrical contacting takes place by means of a bridge circuit which enables direct heating (Wachholz et al., 2007, Electroanalysis 19, 535-540, in particular Fig. 3, Dissertation Wachholz 2009). In this case, the working electrode can be designed so that the temperature distribution at the surface of the working electrode is uniform (DE 10 2004 017 750). DE 10 2006 006 347 discloses advantageous directly electrically heatable electrodes.

In the prior art, there are various embodiments of directly heated working electrodes and arrays. The oldest variant of a single electrode relies on printed circuit boards, which have corresponding recesses (wide slots) and an electrical insulation with a paraffin-PE mixture. Here are typically soldered wire electrodes made of gold or platinum. The wire diameter is usually 25 micrometers (P. Gründler et al, Chem. Phys. Chem. 10 (2009) 559).

In addition, layered electrodes and arrays have been proposed. As substrates printed circuit boards, glass, plastic were specified.

In the case of all layered constructions, there is the disadvantage that the electrolyte solution can not circulate freely around the electrode (limited micromirror effect, temperature and diffusion field are deformed), and that a considerable part of the heat is used to heat the substrate and thus lost. This also leads by the heat capacity of the substrate to a slower heating and cooling of the working electrode.

The disadvantage of the previous wire electrodes was, above all, that either no microliter drops could be deposited thereon, or that a construction with an additional plastic web was used in which the electrode construction (with respect to the printed circuit board) had to be perpendicular. (Flechsig et al., Langmuir 21 (2005) 7848). An array construction was hardly conceivable in this way.

Another disadvantage was that previous electrode arrays of layered working electrodes always consisted of the same electrode material. A design of several different electrode materials (i.e., for example, gold, silver, and platinum working electrodes on an array) would require a lot of manufacturing effort (sputtering, vapor deposition, screen printing with many alternating masks).

According to the prior art, there are also array-like devices with a plurality of independently to be heated wire-shaped working electrodes, the trouble-free allow electrochemical measurement with simultaneous direct electrical heating of the electrodes, wherein the electrolyte solution can circulate freely around the electrodes. The materials of the working electrodes may vary within an array. Similar to a conventional flat array, microliter drops can be deposited on and surround the electrodes (WO 2013/017635).

In order to carry out electrochemical analyzes in the trace range, it is therefore possible to use microelectrodes heated in the prior art. The working electrode must be small in order to keep the metabolic rate negligibly small, thus avoiding changes in the analytical solution, which is a prerequisite in analytical voltammetry and amperometry, and also to keep the working range of the potentiostat galvanostat.

In order to perform electrochemical syntheses at elevated temperatures, usually electrochemical cells are used, which are brought by a thermostat with water as the heat transfer medium to the desired temperature. The entire amount of electrolyte is heated with it. The working electrode used here is generally a platinum mesh electrode, as a cylinder of 3 cm in diameter and 5 cm in length.

The expert in electrochemical syntheses has the problem that first of all a large amount of energy is needed to heat the entire solution, secondly that the temperature changes are very slow and thirdly sensitive substances in the electrolyte solution can be affected. The object of the invention is therefore to provide an apparatus and a method to enable a high-mass electrochemical synthesis which reduces or at least partially overcomes the problems mentioned.

This object is achieved by the present invention, in particular by the subject matter of the claims.

An object of the invention is a process for the preparation of at least one product by electrochemical synthesis at a directly electrically heated working electrode (1), in which at least one reactant reacts at the heated working electrode (1) to the at least one product. Likewise provided by the invention is the use of a directly electrically heated working electrode (1) for the electrochemical synthesis of at least one product in which at least one educt reacts at the heated working electrode (1) to the at least one product. The working electrode (1) can be directly heated by means of a symmetrical arrangement by means of a heating current designed as an alternating current, wherein the use of a bridge circuit, as explained above, is particularly advantageous. The symmetrical contacting and direct heating of the working electrode (1) can thus be effected by a bridge circuit, for example, in Wachholz et al., 2007, Electroanalysis 19, 535-540, in particular FIG. 3. In particular, the working electrode (1) can have a first and a second connection for the supply of the heating current, wherein the working electrode (1) is connected to a potentiostat via a third connection, wherein the connection of the third connection to the working electrode (1) via a Bridge circuit (2) which is connected to the first and second terminals is formed. Suitable circuits are disclosed, for example, in DE 2006 006 347.

For heating the working electrode, a heating current embodied as an alternating current can be used, in particular with a frequency of at least 1 kHz, preferably at least 20 kHz, more preferably at least 50 kHz or at least 100 kHz.

The electrochemically active surface of the working electrode (1) preferably comprises at least 1 × 10 ⁶ m ² , applicable for example for microscale synthesis, preferably 1 × 10 ⁵ m ² approximately on a half-scale or 1 × 10 ⁴ m ² on a larger laboratory scale to the area of one or more square meters are possible.

Of particular advantage in the method according to the invention is the fact that the volume elements of the electrolyte solution are only heated very briefly when they come into contact with the working electrode (1), wherein the reactants are reacted electrochemically at the desired elevated temperature. Even unwanted secondary reactions at high temperature can be so minimized by the rapid cooling of each volume element as a result of thermal convection. It is achieved that selectively only the electrochemical reaction proceeds at elevated temperature. There is a method of chemical reaction in the gas phase in a very limited very hot zone: cf. Arc combustion in the Birkeland-Eyde process (1904, US 775123), which takes into account similar considerations.

A process according to the invention can advantageously be used for various electrochemical syntheses, for example for oxidation, reduction, substitution, dehydrogenation, addition, cleavage, cyclization, dimerization, polymerization, protonation, deprotonation or elimination. The at least one product of the reaction may be, for example, a nitrosogroup protein, gluconic acid, sorbitol, D-arabinose, adiponitrile, a regenerated cofactor such as NAD ⁺ or NADP ⁺ . It is particularly advantageous to carry out the process according to the invention if the product of the synthesis is a product which is unstable at the reaction temperature at the working electrode (1), since in this case the product is exposed to this temperature only for a minimal time. After synthesis on the heated working electrode, the product diffuses in the electrolyte, which itself is not heated to the reaction temperature. Unstable means in this context that the stability at the reaction temperature is lower than the stability at a lower temperature (eg room temperature or 4 ° C), in particular at a triple or ten times lower stability based on the difference in the reaction rate. The stability can be analyzed eg as a half-life. It is possible to cool the electrolyte solution, if it promotes the stability of starting material or product or the course of the reaction.

In the context of the present invention, the indefinite article "a / a" always includes "two / more", unless this is clearly to be understood differently from the context. In particular, in an electrochemical synthesis it is of course also possible, e.g. a reaction of two reactants to one or two product (s) or from one reactant to one two products are carried out.

In a further advantageous embodiment, the reaction of the at least one starting material to the at least one product can also be catalyzed enzymatically, wherein optionally the enzyme and / or an optionally necessary cofactor is immobilized on the heated working electrode (1). However, starting material (s), enzyme and / or cofactor can also be homogeneously distributed in the electrolyte solution. In one embodiment, a synthesis reaction of at least one product catalyzed by an enzyme requiring a cofactor such as NAD + or NADP + takes place. The regeneration of the cofactor necessary for a continuation of the reaction takes place at the working electrode. Of course, the synthesis of a product which is unstable at the reaction temperature is also conceivable in enzymatic catalysis.

In one embodiment, which is particularly suitable for reactions in which thermally highly sensitive substances are involved, or in which reaction products otherwise deposit on the working electrode, the temperature of the working electrode can be pulsed for up to 300 ms, for example about 5-250 ms, 50-200 ms or 100-150 ms, but preferably shorter than 100 ms, be increased above the boiling point of the electrolyte surrounding the electrode. This has the advantage of getting only a small part of the solution for a short time Period is heated. The short thermal convection occurring after the heat pulse makes stirring the solution unnecessary. In addition, the short period of heating is positive for the stability of starting materials and products and possibly of enzymes that catalyze the reaction. For unstable educts or products, this advantage plays a special role. Furthermore, any deposits on the working electrode are removed so that it cleans itself.

The method according to the invention makes it possible to follow the substance conversion of the reaction coulometrically. In particular, coulometric observation of the faradaic conversion of a synthesis reaction by measurement of the electrolytic current strength and calculation of the amount of charge / amount of substance as integral of the current over time is possible.

An object of the invention is also a device comprising two insulated conductors (3) which are interconnected by a thinner working electrode (1) in relation to the conductors, the working electrode (1) being an anode made of an electrode material such as a wire from precious metal, in particular gold or platinum, or from a carbon pin, eg Graphite, boron-doped diamond or glassy carbon, or of optically transparent conductive material such as ITO (indium-doped tin oxide) (an electrode material), preferably gold or platinum, wherein the working electrode (1) is preferably in the form of a spiral, preferably a three-dimensional spiral. As the cathode, less noble metals such as copper, stainless steel or nickel can be used as electrode materials in addition to the materials mentioned.

The insulated conductors (3) may e.g. Copper pins or other good electrical conductors, e.g. are insulated by a glass tube or by a plastic coating, as well known in the art.

In a circular cylinder you can lay a plane Archimedean spiral on the ground and fit a screw (or helix) as a curve in the mantle. The superposition curve of spiral and screw is called a conical spiral or conical space spiral. In an Archimedean spiral, the distance to the center increases linearly with the increasing angle of its orbit. If this distance is projected as an angular distance to a pole on a spherical surface, an archimedian sphere spiral is created. It is a line of finite length, and is not identical to the loxodrome, which by its construction process resembles the logarithmic spiral (Source: Wikipedia, see also Fig. 1)). Through the center of the spiral, a central axis can be thought of.

These spiral shapes can be used in connection with the invention. Advantageously, the spiral is configured as a conical spiral, in particular a conical spiral Archimedean spiral or an Archimedean sphere spiral or a Loxodrom. A section of such a spiral is sufficient, in particular in the case of spherical spirals, it is even preferred that only a section increasing or decreasing in diameter (ie not first increasing and then decreasing) is used. Even irregular spiral shapes are possible. A particularly advantageous embodiment is shown in FIG.

In any case, a sufficient distance between sections of the working electrode (1) should be ensured to prevent short circuits. It is useful to have a distance of about 1 to about 20 mm, preferably about 5 to about 15 mm or about 8 to about 10 mm. The distance is preferably uniform within the spiral. The electrical contact points between working electrode (1) and insulated conductors (3) may be located approximately in the middle, that is on or near the central axis of the spiral. In this case, lower and upper contact point (5, 6) are preferably laterally slightly offset from each other. The contact point, which is connected to the outer, from the axis farthest side of the spiral, can also be guided along the outside of the spiral. If the connection of this point of contact is guided along the spiral, insulation can be achieved up to the point of contact on the outer side of the spiral, furthest away from the axis, to an even more uniform temperature v. A. at the nearest lower turn. Preferably, the three-dimensional spiral working electrode is oriented in relation to the insulated conductors and possibly the further structure of the device so that the diameter of the spiral decreases from bottom to top.

Preferred three-dimensional spiral shapes, when the spiral working electrode is vertically aligned along its central axis, cause the working electrode to barely or preferably not vertically overlap when using the electrochemical synthesis device, ie, not heated to above the heated electrode by the heating of the working electrode Sections of the working electrode hits and these additionally heated. This ensures a uniform temperature of the working electrode, which is important for the synthesis process.

The same effect can be achieved with a further device according to the invention comprising two insulated conductors (3), which are interconnected by a plurality of thinner working electrodes (1) in relation to the insulated conductors, the working electrodes (1) functioning as an anode a wire made of precious metal, in particular gold or platinum or else a pin of carbon, eg graphite, boron-doped diamond or glassy carbon, or of optically transparent conductive material, such as ITO (indium-doped tin oxide) (an electrode material). As a cathode, in addition to the materials mentioned also less noble metals such as copper, stainless steel or nickel can be used. Here, the working electrodes (1) are designed so that no vertical superimposition of the working electrodes (1) takes place and this

(a) preferably run substantially parallel to one another, and / or

(B) preferably from a lower contact point (5) with one of the insulated conductors (3) to a vertically and optionally horizontally offset upper contact point (6) with the other insulated conductor (3) extend, wherein the working electrodes (1) in a lower portion extending outwardly from the lower contact point (5), inclined upward in a central portion and inward in an upper portion toward the upper contact point (6), the inclination in the central portion being such that no vertical Overlaying the sections of the working electrodes (1) or the working electrodes (1) takes place.

One embodiment is particularly useful when using carbon as the electrode material, e.g. Glassy carbon or graphite, about in pen form, advantageous. In this case, the working electrode has essentially a stile-like shape, as in a wall bar, the spars of which form the insulated conductors (3), and which is obliquely positioned to prevent a vertical superposition of the working electrodes (rungs). It can be e.g. to act parallel glass or graphite pencils, which are ladder-like, but arranged obliquely. These parallel pins are connected by insulated conductors, resulting in a lattice-shaped working electrode. The pins may e.g. be attached to an insulating grid or cage. This may be a stretched, e.g. plane or e.g. cylindrical shape. Also, use of screen printing electrodes e.g. made of glassy carbon in parallel form is possible.

It may be useful to stabilize the working electrodes (1) in an inventive device by an insulating support (7). In this case, the insulating support (7) may e.g. be a cage or a grid. Preferably, a free circulation of the electrolyte by the carrier (7) is not severely restricted. The insulating support is preferably made of or comprises an insulating material, the material being glass, ceramic or plastic, e.g. Polytetrafluoroethylene (PTFE, Teflon®), can be. If sufficient stability is ensured by the material and the shape of the electrode (1), the use of a carrier is not necessary.

The use of a planar working electrode in the method according to the invention is also possible. Again, there is no vertical overlay, so that a uniform temperature distribution is possible. Preferably, the working electrode (1) a surface area of at least lxlO ^"6 m ^2, preferably lxl ^{0" 5} m ² or lxl 0 ^"4 m ^2. The diameter may for example, about 0.05-5 mm, preferably 0, 1- The length may be for example 2.5-100 cm, preferably 5-50 cm, 10-40 cm, 15-30 cm or 20-25 cm The length depends on the cross-sectional area and the resistivity of the The resistance between the two heating current contacts (5) and (6) should be, for example, about 0.5 to 20 ohms, preferably 1 to 10 ohms, so that on the one hand the voltage drop between the contacts will not too large, on the other hand, the resistance is still easily measured by electronics and thus the heating power automatically adjustable (Flechsig, Gründler, Wang, 2004, EP 1743173, DE 10 2004 017 750 B4).

Example: the working electrode made of platinum has a resistance of 2 ohms and a length of 10 cm. Then its diameter must be 82.2 microns. The electrode surface is then 25.8 mm ² as the cylinder jacket surface.

With a diameter of 1 mm, the electrode length would have to be 14.4 m, resulting in an electrode surface of 446 cm ² . That would be pilot scale.

Preferably, in the device according to the invention, the working electrode (1) can be directly heated by means of a symmetrical arrangement by means of a heating current designed as an alternating current. The symmetrical contacting preferably takes place via a bridge circuit (2), as explained above. In the connection arms of the bridge circuit in each case a symmetrically designed inductance is provided (7). Via the bridge circuit, the working electrode (1) can be provided with a galvanostat or a potentiostat, a reference electrode (REF) and a counterelectrode (AUX), which appears either as an anode or a cathode, depending on whether at the working electrode a reduction or an oxidation expires, be connected or connected to it. This galvanostat or potentiostat can also be a simpler power supply unit with a bipolar output, on whose displays only the decomposition voltage between working and counter electrode, as well as the electrolysis current are displayed.

In the apparatus according to the invention, the counterelectrode (AUX) is preferably arranged at a distance of at least 1 mm, preferably at least 5 mm, from the working electrode so that the thermal convection around and above the working electrode does not lead to mixing of the space around the counterelectrode it is below when used. This avoids that the reverse reaction of the product takes place to the educt at the counter electrode. It also prevents unwanted Move products from the counter electrode to the working electrode. Examples include, in particular, the halogens chlorine and bromine, but also oxygen and others. For example, it may be desirable to conduct cathodic reduction at a strongly negative potential in a chloride-containing solution. This would have the oxidation of the chloride to chlorine at the counter electrode as an anode and, depending on the pH value, the formation of hypochlorite. In this situation, it is advantageous if the two electrode spaces are separated from each other, for which membranes and diaphragms have hitherto been used. This is also possible within the scope of the invention. However, the use of the limited thermal convection according to the invention renders such separation by diaphragms or membranes superfluous, so that the device according to the invention preferably does not comprise any diaphragms or membranes.

For support one can still use a cooler, e.g. Arrange a cooling Peltier element on the bottom of the cell.

In the case of an embodiment of the working electrode (1) according to the invention, the device may comprise the components shown in FIG. 2 of the present application. It can also comprise the components shown in DE 10 2006 006 347, Fig. 1, Fig. 2, Fig. 3 or Fig. 4 (preferably Fig. 1) in a corresponding arrangement.

In a particularly preferred embodiment, in the method according to the invention, the reaction takes place at the directly heated working electrode of a device according to the invention, in particular a device which comprises two insulated conductors (3) which are interconnected via a thinner working electrode (1) in relation to the conductors are, wherein the working electrode (1) made of a wire of an electrode material such as gold, platinum and carbon (eg graphite, boron-doped diamond or glassy carbon) or ITO (as anode or cathode) or less noble metals such as copper, stainless steel or nickel (as Cathode), wherein the working electrode (1) has the shape of a spiral, preferably a three-dimensional spiral having.

The invention also relates in particular to a process for the synthesis or regeneration of a cofactor of an enzymatic reaction in which the synthesis or regeneration takes place at a directly electrically heatable working electrode, preferably at the directly heated working electrode of a device according to the invention. Again, the use of a device comprising two insulated conductors (3) interconnected by a thinner working electrode (1) relative to the conductors is preferred, the working electrode (1) being made of a wire of an electrode material such as gold, Platinum and carbon (eg graphite, boron-doped diamond or glassy carbon) or ITO (as Anode or cathode) or less noble metals such as copper, stainless steel or nickel (as a cathode), wherein the working electrode (1) has the shape of a spiral, preferably a three-dimensional spiral.

Legend

Fig. 1 shows various shapes of spirals. (A) conical Archimedean spiral (B) conical logarithmic spiral, view obliquely from the side. (C, D) View of a working electrode (1) in the form of a conical Archimedean spiral from above. The insulated conductors (3) are shown as thick dots. (C) shows both insulated conductors (3) in the middle of the spiral, (D) shows the insulated conductor (3) connected to the outer side of the spiral outside the spiral.

FIG. 2 shows a preferred embodiment of a device according to the invention, by way of example with a working electrode (1) shaped as a conical Archimedean spiral. The working electrode (1) is connected at a lower (5) and an upper (6) contact point with insulated conductors (3). The working electrode (1) can be directly electrically heated via a symmetrical arrangement, alternating current (AC), preferably at least 50 kHz, being used as the heating current. The symmetrical contacting takes place by means of a bridge circuit (2). In the connection arms of the bridge circuit in each case a symmetrically designed inductance is provided (7). Via the bridge circuit, the working electrode (1) with a galvanostat or a potentiostat, a reference electrode (REF) and a counter electrode (AU / AUX), which appears either as anode or cathode, depending on whether at the working electrode, a reduction or an oxidation takes place, be connected or connected to it. This galvanostat or potentiostat can also be a simpler Stromversorgunsgerät with two-pole output, on whose displays only the decomposition voltage between the working and counter electrode, and the electrolysis current are displayed.

Examples

example 1

According to the invention, a large area of the directly heatable working electrode (1) for electrochemical synthesis can be achieved by using a very long wire, for example of platinum or gold, or even parallel thin carbon pencils as working electrodes. The working electrode is contacted as in the prior art at the ends, wherein a heating current of preferably at least 1000 Hz frequency, advantageously at least 20 kHz, better 50 kHz is used, so that a known bridge circuit or Throttling filter circuit can be used to separate the electrochemical from the heating circuit.

A) A Pt wire, for example, 5 cm in length and 0, 1 mm diameter can be spirally wound on a cylindrical or preferably conical insulating cage made of glass, plastic or ceramic. Such a working electrode may e.g. be used in a test tube as a cell for electrochemical synthesis.

B) A working electrode made of platinum has a resistance of 2 ohms and a length of 10 cm. Its diameter is 82.2 microns. The electrode surface is as

Cylinder jacket surface 25.8 mm ² .

C) With a diameter of 1 mm, the electrode length is 14.4 m, which is a

Electrode surface of 446 cm ² result. This already allows syntheses, for example, in a 10 to 100 L reactor, ie on a pilot plant scale.

A wire, for example made of platinum 1440 cm long and 1 mm in diameter has an advantageous heating resistance of 1 to 20, preferably 2 to 10 ohms and can be used in a larger cell, such as in Technikumsmaßstab. Advantageously, the cage and the windings at the top are smaller in diameter (conical instead of cylindrical), so the working electrode has the shape of a conical spiral. This optimizes the thermal convection and achieves a uniform temperature control of the working electrode. The electrochemical contact is in the middle as shown in FIG.

Example 2

A device according to the invention is used for a) selective oxidation of free amino groups to nitroso groups in proteins. b) oxidation of aldehyde groups in sugars to gluconic acid by an electrochemically produced oxidizing agent (e.g., hypobromide of bromide), e.g. heated Kohlstift- electrodes made of graphite or glassy carbon can be used. c) Coulometric monitoring of the faradaic conversion of a synthesis reaction by measurement of the electrolysis current strength and calculation of the amount of charge / amount of substance as integral of the current over time. d) For the electrochemical recovery of chlorate from a sodium chloride solution, the solution must be heated to effect the disproportionation of the primary hypochlorite formed. Classically, the entire electrolysis solution is heated for this purpose. According to the invention, only the working electrode is heated from directly heated Glaskohlestiften, whereby the solution is simultaneously stirred thermoconvectively. External stirring and heating are not required. Yield and energy efficiency are improved.

Example 3

An array of electrolysis cells in combinatorial synthesis or parallel synthesis for the screening of drugs and testing of enzyme variants.

The electrolysis cells can be structurally separated, or share a common cell space. The latter allows the simultaneous study of immobilized enzymes in biocatalytic electrosynthesis at their own electrode temperature; the evaluation takes place via the measurement and evaluation of the electrolysis current. Especially with small cell volumes, external cooling is important to keep the electrolyte temperature constant at the desired value. Active cooling by Peltier elements can be helpful. Top-mounted coolers also support thermal convection.

Claims

claims

1. A process for the preparation of at least one product by electrochemical synthesis at a directly electrically heated working electrode (1), wherein reacts at least one reactant at the heated working electrode (1) to the at least one product.

2. Use of a directly electrically heated working electrode (1) for the electrochemical synthesis of at least one product in which at least one reactant reacts at the heated working electrode (1) to the at least one product.

3. The method of claim 1 or use according to claim 2, characterized in that the working electrode (1) is heated directly by means of a symmetrical arrangement by a heating current designed as alternating current, wherein the symmetrical contacting preferably via a bridge circuit (2).

4. The method according to claim 1 or 3 or use according to claim 2 or 3, characterized in that the electrochemically active surface of the working electrode (1)

6 2 5 2 4 2

at least 1x10 ^" m, preferably 1x10 ^" m or 1x10 ^" m.

5. The method according to claim 1 or 3-4 or use according to claim 2 or 3-4, characterized in that the reaction is selected from a group comprising oxidation, reduction, protonation, deprotonation, substitution, hydrogenation, dehydrogenation, condensation, hydrolysis, Addition, cleavage, cyclization, dimerization, polymerization and elimination.

6. The method of claim 1 or 3-5 or use according to claim 2 or 3-5, characterized in that the product is selected from a group consisting of a nitrosogroup comprising protein, gluconic acid, sorbitol, D-arabinose, adiponitrile, a regenerated cofactor such as NAD or NADP and at the reaction temperature at the working electrode (1) unstable product.

7. The method of claim 1 or 3-6 or use according to claim 2 or 3-6, characterized in that the reaction of the at least one reactant to the at least one product is enzymatically catalyzed, wherein optionally the enzyme and / or a cofactor on the heated working electrode (1) is immobilized.

8. The method according to claim 1 or 3-7 or use according to claim 2 or 3-7,

Characterized in that for heating the working electrode designed as an alternating current heating current with a frequency of at least 1 kHz, preferably at least 20 kHz, more preferably at least 50 kHz or at least 100 kHz is used, and / or

Characterized in that the temperature of the working electrode is pulsed for up to 250 ms above the boiling point of the electrolyte surrounding the electrode.

A device comprising two insulated conductors (3) interconnected by a thinner working electrode (1) in relation to said conductors, said working electrode (1) being made of a wire of an electrode material selected from the group consisting of which comprises gold, platinum, copper, nickel, stainless steel, lead, mercury amalgam, indium-doped tin oxide and carbon, characterized in that the working electrode (1) has the shape of a three-dimensional spiral.

10. The device according to claim 9, characterized in that the spiral forms a conical spiral, in particular a conical Archimedean spiral or an Archimedean spherical spiral, a Loxodrom or a section of such a spiral.

A device comprising two insulated conductors (3) which are interconnected by a plurality of thinner working electrodes (1) thinner relative to said insulated conductors, said working electrodes (1) being made of an electrode material selected from a group consisting of consisting of gold, platinum, copper, nickel, stainless steel, lead, Hg-amalgam, indium-doped tin oxide and carbon, wherein the working electrodes (1) are designed so that no vertical superposition of the working electrodes (1) takes place and this

(a) preferably run substantially parallel to one another, and / or

12. Device according to one of claims 9 to 1 1, characterized in that the working electrode (1) by an insulating support (7) is stabilized,

Wherein the insulating support (7) is preferably a cage or a grid, and / or

Wherein the insulating support (7) is preferably made of an insulating material selected from the group consisting of glass, ceramic or plastic, e.g. Polytetrafluoroethylene (PTFE).

13. The device according to any one of claims 9-12, characterized in that the working electrode (1) has a surface of at least lxlO ^"5 m ² , preferably 5xl0 ^{" 5} m ² or 7xl0 ^"5 m ² and / or a diameter of 0 , 1-5 mm and / or a length of 2.5-100 mm and / or has a resistance of 0.5-20 ohms.

14. Device according to one of claims 9-13, characterized in that the working electrode (1) by means of a symmetrical arrangement by a heating current formed as an alternating current is directly heated, wherein the symmetrical contacting preferably via a bridge circuit (2).

15. Device according to one of claims 9-14, characterized in that the counter electrode is arranged at a distance of at least 1 mm, preferably at least 5 mm to the working electrode, that the thermal convection around and above the working electrode not to a thorough mixing of Room leads around the counter electrode, preferably the counter electrode is located below the working electrode when used.

16. The method of claim 1 or 3-8 or use according to claim 2 or 3-8, characterized in that the reaction takes place at the directly heated working electrode of a device according to any one of claims 9-15.

17. A process for the synthesis or regeneration of a cofactor of an enzymatic reaction, characterized in that the synthesis or regeneration takes place at a directly electrically heated working electrode, preferably at the directly heated working electrode of a device according to any one of claims 9-15.