ELECTROCHEMICAL SYNTHESIS METHOD AND DEVICE

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), in which at least one educt reacts 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.

Claims

1. A process for producing at least one product by electrochemical synthesis on a directly electrically heated working electrode (1) in which at least one educt reacts on the heated working electrode (1) to the at least one product.

2. 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 on the heated working electrode (1) to the at least one product.

3. The process of claim 1, wherein the working electrode (1) is directly heated by means of a symmetrical arrangement with a heating current in the form of an alternating current, wherein the symmetrical contacting preferably occurs via a bridge circuit (2).

4. The process of claim 1, wherein the electrochemically active surface area of the working electrode (1) comprises at least 1×10.sup.−6 m.sup.2, preferably 1×10.sup.−5 m.sup.2 or 1×10.sup.−4 m.sup.2.

5. The process of claim 1, wherein the reaction is selected from the group consisting of oxidation, reduction, protonation, deprotonation, substitution, hydrogenation, dehydrogenation, condensation, hydrolysis, addition, cleavage, cyclization, dimerization, polymerization and elimination.

6. The process of claim 1, wherein the product is selected from the group consisting of a protein comprising a nitro group, gluconic acid, sorbitol, D-arabinose, adiponitrile, a regenerated cofactor such as NAD+ or NADP+ and a product which is unstable at the reaction temperature on the working electrode (1).

7. The process of claim 1, wherein the reaction of the at least one educt to the at least one product is enzymatically catalyzed, wherein optionally the enzyme and/or a cofactor is immobilized on the heated working electrode (1).

8. The process according to claim 1, wherein a heating current in the form of an alternating 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 for heating the working electrode (1), and/or wherein the temperature of the working electrode (1) is increased pulse-like for up to 250 ms above the boiling point of the electrolytes surrounding the electrode.

9. A device comprising two insulated conductors (3) which are connected to one another via a working electrode (1) which is thinner in relation to the conductors, wherein the working electrode is a wire of an electrode material selected from the group comprising gold, platinum, copper, nickel, stainless steel, lead, Hg-amalgams, indium-doped tin oxide and carbon, wherein the working electrode (1) has the form of a three-dimensional spiral.

10. The device according to claim 9, wherein the spiral forms a conical spiral, preferably a conical Archimedean spiral or an Archimedean spiral coil, a loxodrome or a section of such a spiral.

11. A device comprising two insulated conductors (3) which are connected to one another via a plurality of working electrodes which are thinner in relation to the insulated conductors, wherein the working electrodes (1) are composed of an electrode material selected from the group comprising gold, platinum, copper, nickel, noble steel, lead, Hg-amalgams, indium doped tin oxide and carbon, wherein the working electrodes (1) are arranged so that no vertical superimposition takes place and that they (a) are preferably essentially parallel to one another, and/or (b) preferably extend from a lower contact point (5) with one of the insulated conductors (3) to an upper contact point (6) offset vertically and optionally horizontally with the other insulated conductor (3), wherein the working electrodes (1) extend outwardly from the lower contact point (5), extend obliquely upwards in an intermediate section and extend inwards in an upper section towards the upper contact point (6), wherein the inclination in the middle section is arranged so that no vertical superimposition of the working electrode sections (1) or the working electrodes (1) occurs.

12. The device according to claim 9, wherein the working electrode (1) is stabilized by an insulating carrier (7), wherein the insulating carrier (7) is preferably a cage or a grid, and/or wherein the insulating carrier (7) is preferably made of an insulating material selected from the group comprising glass, ceramic or plastic, e.g. Polytetrafluoroethylene (PTFE).

13. The device according to claim 9, wherein the working electrode has a surface area of at least 1×10.sup.−5m.sup.2, preferably 5×10.sup.−5m.sup.2 or 7×10.sup.−5m.sup.2, and/or a diameter of 0.1-5 mm and/or a length of 2.5-100 mm and/or a resistance of 0.5-20 Ohm.

14. The device according to claim 9, wherein the working electrode (1) is directly heated by means of a symmetrical arrangement with a heating current in the form of an alternating current, wherein the symmetrical contacting preferably occurs via a bridge circuit (2).

15. The device according to claim 9, wherein the counterelectrode is arranged with a distance of at least 1 mm, preferably at least 5 mm, relative to the working electrode, such that the thermal convection around and above the working electrode does not lead to a mixing of the space around the counterelectrode, preferably the counterelectrode is located under the working electrode.

16. The process of claim 1, wherein the reaction proceeds at the directly heated working electrode of a device comprising two insulated conductors (3) which are connected to one another via a working electrode (1) which is thinner in relation to the conductors, wherein the working electrode is a wire of an electrode material selected from the group comprising gold, platinum, copper, nickel, stainless steel, lead, Hg-amalgams, indium-doped tin oxide and carbon, wherein the working electrode (1) has the form of a three-dimensional spiral.

17. A process for the synthesis or regeneration of a cofactor of an enzymatic reaction, wherein the synthesis or regeneration takes place on a directly electrically heatable working electrode, preferably on the directly heated working electrode of a device according to claim 9.

18. The use of claim 2, wherein the working electrode (1) is directly heated by means of a symmetrical arrangement with a heating current in the form of an alternating current, wherein the symmetrical contacting preferably occurs via a bridge circuit (2).

19. The use of claim 2, wherein the electrochemically active surface area of the working electrode (1) comprises at least 1×10.sup.−6 m.sup.2, preferably 1×10.sup.−5 m.sup.2 or 1×10.sup.−4 m.sup.2.

20. The use of claim 2, wherein the reaction is selected from the group consisting of oxidation, reduction, protonation, deprotonation, substitution, hydrogenation, dehydrogenation, condensation, hydrolysis, addition, cleavage, cyclization, dimerization, polymerization and elimination.

21. The use of claim 2, wherein the product is selected from the group consisting of a protein comprising a nitro group, gluconic acid, sorbitol, D-arabinose, adiponitrile, a regenerated cofactor such as NAD+ or NADP+ and a product which is unstable at the reaction temperature on the working electrode (1).

22. The use of claim 2, wherein the reaction of the at least one educt to the at least one product is enzymatically catalyzed, wherein optionally the enzyme and/or a cofactor is immobilized on the heated working electrode (1).

23. The use according to claim 2, wherein a heating current in the form of an alternating 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 for heating the working electrode (1), and/or wherein the temperature of the working electrode (1) is increased pulse-like for up to 250 ms above the boiling point of the electrolytes surrounding the electrode.

24. The use of claim 2, wherein the reaction proceeds at the directly heated working electrode of a device comprising two insulated conductors (3) which are connected to one another via a working electrode (1) which is thinner in relation to the conductors, wherein the working electrode is a wire of an electrode material selected from the group comprising gold, platinum, copper, nickel, stainless steel, lead, Hg-amalgams, indium-doped tin oxide and carbon, wherein the working electrode (1) has the form of a three-dimensional spiral.

Description

LEGENDS

[0049] FIG. 1 shows various forms of spirals. (A) conical Archimedean spiral (B) conical logarithmic spiral; in each case viewed 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 center of the spiral, (D) shows the insulated conductors (3) with one connected to the outer side of the spiral.

[0050] FIG. 2 shows a preferred embodiment of a device according to the invention, with a working electrode (1) shaped as a conical Achimedean spiral. The working electrode (1) is connected to insulated conductors (3) at a lower (5) and an upper (6) contact point. The working electrode (1) is directly electrically heatable via a symmetrical arrangement, with alternating current (AC), preferably at least 50 kHz, being used as the heating current. The symmetrical contacting is effected by means of a bridge circuit (2). A symmetrically arranged inductance is provided in the connection arms of the bridge circuit (7). By means of the bridge circuit, the working electrode (1) is or can be connected with a galvanostat or a potentiostat, a reference electrode (REF) and a counterelectrode (AU/AUX), which functions either as an anode or a cathode, depending on whether a reduction or an oxidation takes place at the working electrode. This galvanostat or potentiostat can also be a simple power supply device with a two-pole output, on whose displays merely the decomposition voltage between the working electrode and the counterelectrode, as well as the electrolytic current, are indicated.

EXAMPLES

Example 1

[0051] According to the invention, a large area of the directly heatable working electrode (1) for electrochemical synthesis can be achieved in that a very long wire e.g. out of platinum or gold, or else parallel thin carbon rods, can be used as working electrodes. The working electrode is contacted at the ends as in the prior art, whereby a heating current of preferably at least 1000 Hz frequency, advantageously at least 20 kHz, more preferably 50 kHz, is used so that a bridge circuit or a choke filter circuit known per se for separating the electrochemical circuit from the heating circuit can be used.

[0052] (A) A Pt wire of, for example, 5 cm in length and 0.1 mm in diameter can be spirally wound onto a cylindrical or preferably conical insulating cage made of glass, plastic or ceramic. Such a working electrode can be used, e.g. in a reagent glass, as a cell for electrochemical synthesis.

[0053] B) A working electrode of platinum has a resistance of 2 ohm and a length of 10 cm. Its diameter is 82.2 microns. The electrode surface area is 25.8 mm.sup.2 as the cylinder surface area.

[0054] C) With a diameter of 1 mm, the electrode length is 14.4 m, resulting in an electrode surface area of 446 cm.sup.2. This already allows for syntheses e.g. in a 10 to 100 L reactor, that is, in pilot-plant scale.

[0055] A wire e.g. of platinum of 1440 cm in length 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, e.g. in the pilot-plant scale. Advantageously, as the cage and the turns become smaller in diameter (conical rather than cylindrical), the working electrode thus has the shape of a conical spiral. This optimizes thermal convection and achieves a uniform temperature control of the working electrode. The electrochemical contact is located in the center, as shown in FIG. 2.

Example 2

[0056] A device according to the invention is used for

[0057] a) Selective oxidation of free amino groups to nitroso groups in proteins.

[0058] b) Oxidation of aldehyde groups in sugars to gluconic acid by an electrochemically prepared oxidizing agent (e.g., hypobromide of bromide), wherein e.g. heated carbon rod electrodes of graphite or glass-carbon can be used.

[0059] c) Coulometric tracking of the faraday mass conversion of a synthesis reaction by measuring the amount of electrolysis and calculating the charge quantity/substance quantity as an integral of the current over time.

[0060] d) For electrochemical recovery of chlorate from a solution of sodium chloride, the solution must be heated to effect the disproportionation of the primary hypochlorite. Classically, the entire electrolyte solution is heated for this purpose. According to the invention, only the working electrode is heated from directly heated glass carbon rods, wherein simultaneously the solution is thermoconvectively stirred. External stirring and heating are therefore not required. Yield and energy efficiency are improved.

Example 3

[0061] An array of electrolysis cells in combinatorial synthesis or parallel synthesis for the screening of active substances and tests of enzyme variants.

[0062] The electrolysis cells can be structurally separated from one another or can share a common cell space. The latter permits the simultaneous study of immobilized enzymes in biocatalytic electrosynthesis at the respective electrode temperature; the evaluation being carried out by means of the measurement and evaluation of the electrolysis current. Cooling from the outside is particularly important for small cell volumes, in order to keep the electrolyte temperature constant at the desired value. Active cooling by Peltier elements can be helpful. Coolers from above also support thermal convection.