WO2024213538A1

WO2024213538A1 - Particle electrode system and particle electrode reactor

Info

Publication number: WO2024213538A1
Application number: PCT/EP2024/059609
Authority: WO
Inventors: Matthias Franzreb; André Tschöpe; Michael ABT
Original assignee: Karlsruher Institut für Technologie
Priority date: 2023-04-11
Filing date: 2024-04-09
Publication date: 2024-10-17
Also published as: DE102023109066A1

Abstract

The invention relates to a new particle electrode system having a particle electrode and at least one counter electrode arranged within the particle electrode. The invention also relates to the particle electrode and the counter electrodes themselves and to a reactor comprising the new particle electrode system, the particle electrode and/or the counter electrodes. Furthermore, the invention relates to the use of the particle electrode system and reactor described herein in electrochemical or electrobiotechnological methods and to a method for continuously operating an electrochemical or electrobiotechnological reactor with the particle electrode system described herein.

Description

PARTICLE ELECTRODE SYSTEM AND PARTICLE ELECTRODE REACTOR

INTRODUCTION

The present invention relates to a new particle electrode system with a particle electrode and at least one counter electrode arranged within the particle electrode. The invention also relates to the particle electrode and the counter electrodes themselves and to a reactor comprising the new particle electrode system, the particle electrode and/or the counter electrodes. Furthermore, the invention relates to the use of the particle electrode system or reactor described herein in electrochemical or electrobiotechnological processes and to a process for the continuous operation of an electrochemical or electrobiotechnological reactor with the particle electrode system described herein.

BACKGROUND

Electrochemical and electrobiotechnological processes take place primarily at the interface between the electrode and the surrounding solution. In order to achieve high conversion rates, the ratio of electrode surface to solution volume must be maximized. Particle electrodes in the form of fixed or fluidized bed electrodes are an efficient way of maximizing the available electrode surface per reactor volume. Electrochemical reactions are an essential component of many technical production processes. The best-known example is chlor-alkali electrolysis. Electrochemical reactions are also increasingly used in inorganic and organic synthesis reactions and in connection with enzymatic reactions. Finally, electrochemical reactions offer an efficient way to detoxify or destroy contaminants in wastewater treatment plants or the treatment of process water.

In the case of electrobiotechnological processes, particle electrodes offer the additional advantage, in addition to a high specific electrode surface, that the biocatalysts required for the reactions, e.g. whole-cell catalysts or enzymes, can be immobilized on the particles of the particle electrode. This means that in a continuous process, i.e. with a constant or intermittent flow through the electrode space (process space), discharge or flushing out and thus a decrease in the expensive biocatalysts can be avoided. In addition, the spatial proximity of the electrochemical and biocatalytic reactions, for example, requires short material transport paths and thus accelerated reaction kinetics. In electrochemical reactors with immobilized biocatalysts, however, the problem often arises that the stability, ie the possible operating time, of these biocatalysts is limited and is often only hours to a few days. As a result, the process, which is intended to be continuous, must be stopped, the electrode particles that have ceased to function, together with the biocatalysts immobilized on them, must be removed, and the reactor must be filled with fresh electrode particles. In classic electrochemical reactors, abrasion, corrosion, or gradual "poisoning" of the electrode surface by undesirable components in the feed solution (reaction solution) regularly lead to a functional impairment of the electrode particles, so that they must be regularly exchanged and replaced with new ones.

The use of other types of electrode, such as stacks of electrode plates, expanded metal mesh or carbon fabrics, does not provide a solution to this problem. If biocatalysts are immobilized on such types of electrodes, the described time-dependent functional losses and the need to replace the electrodes also occur. This is often more complex and time-consuming for permanently installed plates or grids than in the case of a particle electrode. The same applies to such types of electrodes with regard to the potential problems of classic electrochemical reactions such as abrasion, corrosion or poisoning, which also require electrode replacement.

There is therefore great interest in electrochemical reactor types based on particle electrodes, which are characterized by optimized charge transport and thus fast reaction kinetics and which enable simple and fast, partial or complete replacement of the particle electrode. Such electrochemical reactor types are of particular interest for industrial use, so that scalability to the industrial scale and thus a high degree of variability in the design is desirable. For efficient operation on an industrial scale, the possibility of continuous process control is also a key criterion and interruption of reactor operation for replacing the electrode particles or reaction solution should be minimized as far as possible and any necessary replacement should be as simple and quick as possible.

STATE OF THE ART

In the field of electrochemical processes, electrochemical reactors based on particle electrodes have already been developed. For example, magnetically induced fluidized bed reactors for electrochemical wastewater treatment or magnetically induced electrochemical fluidized bed reactors for electroenzymatic synthesis processes based on a fluidized particle electrode made of magnetizable conductive particles were developed. In these, the electrical contact could be achieved by magnetically stabilizing the fluidized particle bed. the particle electrode can be improved [Tschöpe, A., et al., A magnetically induced fluidized-bed reactor for intensification of electrochemical reactions. Chemical Engineering Journal, 2020. 385; Tschöpe, A., et al., Electrical conductivity of magnetically stabilized fluidized-bed electrodes - Chronoamperometry and impedance studies. Chemical Engineering Journal, 2020. 396; Tschöpe, A. and M. Franzreb, Influence of non-conducting suspended solids onto the efficiency of electrochemical reactors using fluidized bed electrodes. Chemical Engineering Journal, 2021. 424],

The reactor systems described therein consist of two concentric cylinders, the inner working electrode chamber with the particle electrode and an annular gap-shaped counter electrode chamber that surrounds it. The inner electrode chamber (working electrode chamber) is separated from the outer counter electrode chamber by a cation exchange membrane. For this purpose, the cylinder wall of the inner cylinder chamber has round openings. A stationary electrode made of platinized titanium is used to electrically contact the working electrode chamber. The electrode particles are held within the working electrode chamber via a built-in PTFE filter. A platinized titanium electrode made of expanded metal is placed in the outer cylinder chamber (counter electrode chamber), which serves as the counter electrode of the reaction system. Depending on the area of application, this type of reactor can also have an additional gas input into the working electrode chamber. This type of reactor is therefore characterized by the fact that the particle electrode is arranged within a counter electrode that surrounds it.

Similar systems to those described above are widespread in the literature. An example is the reactor according to EP0171478A2, in which the reactor has a cylindrical electrolysis cell main body which is divided by a diaphragm into a main electrode chamber and a counter electrode chamber. In the main electrode chamber there is a particle electrode on which, for example, dissolved metals are electrolytically deposited or on which organic substances are electrolytically decomposed. An electrolyte is continuously fed into the main electrode chamber, which keeps the particle electrode in suspension. The counter electrode separated by the diaphragm is porous and is designed, for example, as expanded metal. Gas formed on the counter electrode can penetrate through the pores into the interior of the porous counter electrode and rise there. The diaphragm surrounding the counter electrode chamber is open at the top to allow gas to escape. In a variant of the reactors described therein, a particle bed is also provided in the inner region of the counter electrode, which serves to build up a flow resistance to avoid short-circuit flows of the supplied electrolyte. In the known particle electrodes, the current is usually supplied to the particle electrode via a simple metal rod or an arrangement of rods.

US4206020 also describes such reactor types in the classic design of an electrochemical fluidized bed electrode, in which a cylindrical particle electrode is arranged within a cylindrical counter electrode. In a variant of the reactors described here, the current is additionally supplied via an extension of the contact in the form of a vertically extending cylindrical network at the edge of the particle electrode.

However, such reactor types cannot be scaled to an industrial scale or are characterized by insufficient efficiency above a certain size, since the resulting electron transport paths between the working and counter electrodes increase rapidly with increasing reactor diameter, and the voltage losses therefore become too great for economical operation. If, for example, the reactor type according to US4206020 is scaled in all directions, the result is an increasingly longer path from the inner area of the working electrode to the outer annular gap of the counter electrode. With the longer path, the resistance increases and the efficiency decreases.

US4183792 describes a process for the oxidation of Ni(OH)2 in a reactor which is equipped with a stationary particle bed electrode, a bed of nickel pellets, as the working electrode (anode), and in which the counter electrode is designed in the form of a large number of individual cylindrical elements which are immersed vertically in the particle bed of the particle electrode. Simple, solid stainless steel rods are used for the counter electrodes, which are coated with a non-conductive porous layer to prevent an electrical short circuit with the particle bed. The particle bed is contacted with a contacting electrode in the form of a wire mesh arranged at the bottom of the particle bed.

US3180810 describes a variant of a reactor structure in which the particle electrode is formed in a housing which has a plurality of recesses and in which counter electrodes are arranged in these recesses, so that several counter electrodes extend into the particle bed at different locations, virtually shielded by the housing recesses.

The reactor designs described in US4183792 and US3180810 also result in long electron transport paths within the particle bed from the bottom of the reactor to the upper filling level of the particle bed, which severely limits the scaling of the reactor height for these reactor types. In such reactor designs, the undesirable occurrence of gas bubbles at the counter electrodes can also occur. From CN207596570 U a reactor system is known in which a cathode chamber with a vertical cathode is arranged within an anode chamber surrounding the cathode chamber and in which the anode electrode is arranged on the inside of the outer wall of the anode chamber. The cathode chamber is surrounded by a permeable cation exchange membrane and a three-dimensional particle electrode is provided between the anode electrode and this permeable membrane. Due to the fact that the particle bed is only contacted at the edge, this arrangement also results in long paths for the charge flow through the particle bed, which has a detrimental effect on resistance and efficiency in scaled systems.

Another reactor variant with electrodes arranged vertically in a particle bed is described in W02023/094503. The reactors shown therein can be in the form of several cells packed with particles arranged in a honeycomb shape, which form a so-called biocathode. Within the particle bed of these cells, vertically inserted anodes are provided, which are shielded from the particle bed by an ion exchange membrane and which have current collectors on their outer surface, which extend vertically along the anode wall through the particle bed. The inner walls of the honeycomb-shaped cells also have internal current collectors, which also extend vertically along the outer edges of the particle beds. The individual honeycombs can be separated from one another by internal current collectors in the form of partitions extending vertically through the cells.

From the publications US4,016,044 and FR1,445,756, reactors with particle electrodes are known, in which one or both electrodes are designed in such a way that an at least partial horizontal extension into a particle bed is made possible, for example by attaching rectangular or radial sheets or nets to an electrode extending vertically through a particle bed.

Another fundamental problem in large reactors is the cooling of the reactor volume. Cooling usually takes place via the reactor outer shell or the reactor lid. With such externally supplied cooling, uniform and constant cooling of the entire reactor is difficult to achieve and temperature regulation inside the reactor is sluggish due to long distances to the inside of the reactor. This problem becomes more and more relevant as the reactor size increases, so that reactors with external cooling are also limited in terms of scaling. US3287249 describes a reactor with an integrated cooling circuit and bundled tubular electrodes, each of which forms a complete electrochemical module with its own working electrode and counter electrode. The structure of these modules is designed in such a way that the working electrode, designed as a long, narrow particle bed, is located in the center and is surrounded by an insulating diaphragm, a helical support structure and finally by a cylindrical counter electrode on the outside. A bundle of such electrochemical modules is arranged in a common reactor housing through which a coolant flows. In a reactor with an arrangement according to US 3287249, the reaction takes place in the area of the working electrode, designed as a particle electrode, which forms the core of the tubular modules.

An overview of electrochemical reactors with particle electrodes is also provided in a review article from 2021 [Li, H. T., et al., Three-dimensional particle electrode system treatment of organic wastewater: A general review based on patents. Journal of Cleaner Production, 2021. 308].

TASK

Based on this prior art, the object of the present invention was to provide a new, improved particle electrode system and a new, improved reactor for electrochemical or electrobiotechnological processes that do not have the disadvantages of the prior art. In particular, the object of the present invention was to provide an improved particle electrode system that is characterized by short electron transport paths through the entire particle electrode and thus enables optimized charge transport and fast reaction kinetics, thus making it possible to improve efficiency, even when scaled up to an industrial scale. In a further aspect of the invention, a further object was to provide a particle electrode system that enables improved cooling of the reactor. Improved cooling should be characterized, for example, by the possibility of uniform and constant cooling of the entire electrode chamber or the entire particle electrode or the entire reactor. Improved cooling should reduce or avoid temperature gradients between the outside and inside of the reactor. Improved cooling should be characterized by rapid and uniform temperature control and improve or avoid sluggish temperature adjustment between the outside and inside of the reactor. An improved cooling system should also be characterized by the fact that the above-mentioned advantageous improved cooling performance (uniform, constant and quickly adjustable temperature control) is possible even in large reactors on an industrial scale. In a further aspect of the invention, a further object was to provide a To provide a particle electrode system in which the undesirable occurrence of gas bubbles on the counter electrodes can be reduced or there is a possibility of simply removing such undesirable gas bubbles on the counter electrodes. In a further aspect of the invention, a further object was to provide a particle electrode system which enables a simple and quick, partial or complete replacement of the particle electrode or used electrode particles. A further object of the invention was therefore to provide a particle electrode system or a reactor which is suitable for particularly efficient operation on an industrial scale and offers the possibility of continuous process control, and with which an interruption of reactor operation for an exchange of the electrode particles or the reaction solution can be minimized as far as possible. The exchange of the electrode particles or the reaction solution should be as trouble-free, simple and quick as possible in continuous operation. In addition, the particle electrode systems should offer the greatest possible variability and flexibility with regard to the inlet and outlet systems so that they can be combined with a large number of differently designed external additional components. A particular aspect of the invention was to provide improved particle electrode systems that are suitable for sizes ranging from laboratory plants to miniplants and pilot plants, as well as for industrial scale, i.e. that are easily and reliably scalable and are characterized by a high degree of variability in design.

DESCRIPTION OF THE INVENTION

The new particle electrode system of the present invention is distinguished from those known from the prior art in particular by a special design of the electrical contact in the particle electrode. The electrical contact of the particle electrode is designed according to the invention in the form of an arrangement that extends evenly distributed throughout the entire volume of the electrode particles in the particle electrode chamber. The at least one counter electrode is arranged inside the particle electrode. This minimizes the electron transport paths and makes them more uniform throughout the entire volume of the particle electrode (working electrode). The electrode arrangement according to the invention can be scaled as required without the maximum distance between a point in the working electrode and the next counter electrode increasing. The electron transport paths can thus be kept constant even in up-scaling and in large reactors on an industrial scale. The system according to the invention can therefore be scaled as required in principle without any loss of efficiency. The new particle electrode system of the present invention is also characterized by a new, more advantageous design of the counter electrodes, which on the one hand enables a significant improvement in the cooling of the electrodes or the reactor and on the other hand enables a quick and easy replacement of used electrode particles and reaction solution from the particle electrode during operation without having to dismantle the reactor or partially rebuild it. The new design of the counter electrodes also surprisingly makes it possible to quickly, easily and continuously remove gas bubbles that appear at the counter electrodes from the system or to allow the introduction of gaseous components if required.

The present invention solves the above-described disadvantages of the prior art through the novel, almost three-dimensionally interwoven arrangement and design of the working electrode chamber with the particle electrode and the novel design of the counter electrode chamber, in which the counter electrodes serve as multifunctional elements that, in addition to electron transport, also fulfill functions for particle transport/exchange as well as for cooling and, if necessary, gas introduction. The novel arrangement and design makes it possible for the first time to realize a reactor system with a particle electrode that can be scaled almost as desired.

The present invention is described in more detail below and particularly includes the following embodiments:

Electrode system comprising an electrode chamber (1) with

(a) a particle electrode (2) comprising a-i. electrode particles (2a) distributed in the volume of the electrode chamber and a-ii. one or more power supply lines (7) and a-iii. one or more conductive elements (8), wherein the power supply lines (7) and the conductive elements (8) are in direct contact with one another and together form an arrangement which extends through the filling level (2b) and the horizontal extent (2c) of the electrode particles in the electrode chamber; and

(b) at least one counter electrode (18) comprising bi. a conductive rod or wire (19a), b-ii. an outer casing (19b) which is arranged at a distance from the outer surface of the rod or wire (19a) such that b-iii. an annular gap (26) which runs circularly around the rod or wire (19a) is formed between the casing (19b) and the outer surface of the rod or wire (19a), and which b-iv. has an inlet opening (13) and an outlet opening (14) through which counter electrode electrolyte solution is passed through the annular gap (26) surrounding the rod or wire (19a), and bv. an electrical contact (9); wherein the at least one counter electrode (18) is arranged within the particle electrode (2) and wherein the conductive elements (8) extending through the particle bed of the electrode chamber have recesses (8a) within which the counter electrodes (18) are arranged.

The aforementioned electrode system, wherein two or more conductive elements (8) extending through the electrode chamber are provided, which are each arranged parallel to one another and evenly distributed in the electrode chamber (1).

One of the aforementioned electrode systems, wherein the conductive elements (8) extending through the electrode chamber are in the form of conductive sheets, strips, wires, grids or porous nets.

One of the aforementioned electrode systems, wherein the conductive elements (8) extending through the electrode chamber and the at least one counter electrode (18) are arranged such that the at least one counter electrode penetrates the recesses (8a) of the conductive elements (8) extending through the electrode chamber and thus forms a three-dimensionally interlocking arrangement with them.

One of the aforementioned electrode systems, wherein the conductive rod or wire (19a) of the at least one counter electrode (18) is in the form of a hollow rod.

One of the aforementioned electrode systems, which has at least two counter electrodes (18) in the form of a hollow rod (19a), wherein

(i) at least one counter electrode is designed as a cooling counter electrode (18a) which has a drain device (10) and an inlet device (12) through which coolant is passed through the hollow inner region (27) of the hollow rod counter electrode (18a), and

(ii) at least one counter electrode is designed as a distribution counter electrode (18b) which has a device (11, 20) for supplying and removing electrode particles into the electrode chamber via the hollow inner region (27) of the hollow rod counter electrode (18b).

One of the aforementioned electrode systems, further comprising

(c) Devices for supplying and removing reaction solutions from the particle electrode, which may comprise drain openings (4, 17) and inlet openings (5, 15) as well as chambers for distributing (21), collecting (23) and compensating the expansion volume of the particle electrode (22). One of the aforementioned electrode systems, which has more than one counter electrode (18) designed as cooling counter electrodes (18a).

One of the aforementioned electrode systems, wherein a number of distribution and cooling counter electrodes are provided in a ratio of distribution counter electrode(s) (18b): cooling counter electrodes (18a) of 1:4 to 1:20, preferably 1:6.

One of the aforementioned electrode systems, wherein the counter electrodes (18) are arranged evenly and symmetrically distributed within the particle electrode (2).

One of the aforementioned electrode systems, wherein the particle electrode is designed as a fluid bed particle electrode.

One of the aforementioned electrode systems, wherein the particle electrode is designed as a fixed bed particle electrode.

One of the aforementioned electrode systems, wherein the electrode particles have a diameter of 5 to 5,000 pm, preferably 100 to 1,000 pm.

One of the aforementioned electrode systems, wherein the electrode particles have catalytically active functionalities and/or magnetic properties immobilized on their surface.

One of the aforementioned electrode systems, wherein the conductive elements (8) extending through the electrode chamber are designed in the form of conductive grids or porous nets which are permeable to the electrode particles (2a) and have a mesh size which is a multiple of the size of the electrode particles (2a).

One of the aforementioned electrode systems, wherein the conductive elements (8) extending through the electrode chamber are dimensioned such that they extend over the entire cross-sectional area up to the edges of the electrode chamber (1) and wherein the recesses (8a) are designed and positioned in the elements (8) such that elements (8) arranged parallel to one another each have recesses (8a) positioned parallel to one another through which the counter electrodes are introduced into the electrode chamber (1) and are thereby circularly enclosed by the conductive elements (8).

One of the aforementioned electrode systems, wherein the sheath (19b) of the counter electrodes (18) is formed of materials which allow the passage of charge and prevent the passage and penetration of electrode particles (2a) into the annular gap (26).

One of the aforementioned electrode systems, wherein the sheath (19b) of the counter electrodes (18) is formed from materials selected from the group comprising micro- or nanoporous polymer networks and membranes, as well as ion exchange membranes.

One of the aforementioned electrode systems, wherein the counter electrodes (18) are designed in the form of hollow rods which have an electrically non-conductive coating on the inner surface of their hollow space (27).

One of the aforementioned electrode systems, wherein at least one counter electrode is provided in the form of a distribution counter electrode (18b), which has a non-conductive distributor piece (29) and supply and removal devices (11, 20) for the exchange of electrode particles between the particle electrode and the hollow inner region (27) of the distribution counter electrode (18b).

One of the aforementioned electrode systems, wherein the distributor piece (29) of the distributor counter electrode (18b) is designed such that several separate sub-channels (32) in the form of separate sub-segments of the annular gap enable the counter electrode electrolyte to flow through the annular gap (26) and openings (20) are provided between these sub-channels, which connect the hollow inner region (27) of the distributor counter electrode (18b) to the particle electrode and through which the electrode particles can be exchanged between the inner region of the distributor counter electrode (18b) and the particle electrode.

One of the aforementioned electrode systems, wherein at least one counter electrode in the form of an inflow or return flow counter electrode (18c) is provided, which is designed such that an internal supply or return of electrolyte solution takes place to the region in which the associated inlet opening of the electrolyte is located, so that inlet and outlet connections for the electrolyte are on the same side of the reactor.

One of the aforementioned electrode systems, wherein at least one counter electrode has devices for the continuous flow of electrolyte solution, gases or other reaction solutions, which can comprise valves, inlet and outlet openings (3, 6), lines (30, 32) and chambers for distribution (24) and collection (25), as well as coupling devices for connection to external components. Particle electrode (2) comprising in a housing (1a) electrode particles (2a) dispersed in a working electrolyte solution, and one or more power leads (7) and one or more conductive elements (8), wherein the power leads (7) and the conductive elements (8) are in direct contact with one another and together form an arrangement which extends through the filling level (2b) and the horizontal extent (2c) of the electrode particle dispersion in the electrode chamber and wherein the conductive elements (8) extending through the particle bed of the electrode chamber have recesses (8a) within which counter electrodes can be arranged.

The aforementioned particle electrode, which also has one or more of the following features:

■ in the particle electrode, two or more of the conductive elements (8) extending through the electrode chamber are provided and these are arranged parallel to one another and evenly distributed in the electrode chamber (1);

■ the conductive elements (8) extending through the electrode chamber are in the form of conductive sheets, strips, wires, grids or porous nets;

■ the conductive elements (8) extending through the electrode chamber are arranged such that when at least one counter electrode is introduced within the recesses (8a) of the conductive elements (8) extending through the electrode chamber, the at least one counter electrode forms a three-dimensionally interlocking arrangement with these;

■ the conductive elements (8) extending through the electrode particle dispersion are designed in the form of conductive grids or porous nets which are permeable to the electrode particles (2a),

■ the conductive elements (8) extending through the electrode particle dispersion are designed in the form of conductive grids or porous nets which have a mesh size which is a multiple of the size of the electrode particles (2a),

■ the conductive elements (8) extending through the electrode particle dispersion are dimensioned such that they extend over the entire cross-sectional area up to the edges of the housing (1a) and have recesses (8a), preferably circular recesses, which are positioned in the elements (8) such that elements (8) arranged parallel to one another have recesses positioned parallel to one another (8a) through which counter electrodes, preferably rod-shaped counter electrodes, particularly preferably those in the form of a hollow rod, can be inserted into the housing (1a) and are thus circularly enclosed by the conductive elements (8);

■ the particle electrode is designed as a fluid bed particle electrode or as a fixed bed particle electrode;

■ the electrode particles have a diameter of 5 to 5,000 pm, preferably 100 to 1,000 pm;

■ the electrode particles have catalytically active functionalities immobilized on their surface;

■ the electrode particles have magnetic properties.

Counter electrode (18) comprising a conductive rod or wire (19a) which is designed in the form of a hollow rod, an outer insulating sheath (19b) which is arranged at a distance from the outer surface of the rod or wire (19a) such that an annular gap (26) which runs circularly around the rod or wire (19a) is formed between the sheath (19b) and the outer surface of the rod or wire (19a), and which has an inlet opening (13) and an outlet opening (14) through which counter electrode electrolyte solution can be passed through the annular gap (26) surrounding the rod or wire (19a), and an electrical contact (9).

The aforementioned counter electrode, wherein the sheath (19b) is formed of materials which allow the passage of charge and prevent the passage and penetration of electrode particles (2a) into the annular gap (26).

One of the aforementioned counter electrodes, wherein the sheath (19b) is formed from materials selected from the group comprising micro- or nanoporous polymer networks and membranes, as well as ion exchange membranes.

One of the aforementioned counter electrodes, which has devices for the continuous flow of counter electrode electrolyte through the annular gap (26), which can comprise inlet and outlet openings (3, 6), lines (30, 32) and chambers for distribution (24) and collection (25).

One of the aforementioned counter electrodes, which has devices for the continuous flow of electrolyte solution, gases or other reaction solutions through the hollow inner region (27) of the hollow rod counter electrode, which supply and Drainage openings, pipes and chambers for distribution and collection, as well as connections to external components.

One of the aforementioned counter electrodes, which is designed in the form of a cooling counter electrode (18a) and has a drain device (10) and an inlet device (12) through which coolant can be passed through the hollow inner region (27) of the hollow rod counter electrode (18a).

One of the aforementioned counter electrodes, which is designed in the form of a distribution counter electrode (18b) and has a non-conductive distribution piece (29) and a device for supplying and removing (11, 20) electrode particles via the hollow inner region (27) of the distribution counter electrode (18b).

One of the aforementioned counter electrodes, wherein the distributor piece (29) is designed such that several separate partial channels (32) in the form of separate partial segments of the annular gap enable the counter electrode electrolyte to flow through the annular gap (26) and openings (20) are provided between these partial channels, which connect the hollow inner region (27) of the distribution counter electrode (18b) with the external environment and through which electrode particles can be exchanged between the inner region of the distribution counter electrode (18b) and the external environment.

One of the aforementioned counter electrodes, which is designed in the form of an inflow or return flow counter electrode (18c), which is designed such that a supply or return or diversion of electrolyte solution takes place through the counter electrode into the reactor system or to selected positions with inlet or outlet connections or collection or distribution chambers in the reactor.

Reactor comprising one of the aforementioned electrode systems, one of the aforementioned particle electrodes, one or more of the aforementioned counter electrodes or combinations thereof.

The aforementioned reactor, which comprises a particle electrode with electrode particles with magnetic properties and provides magnets outside the electrode housing which enable the application of magnetic fields in the particle electrode.

Use of one of the aforementioned electrode systems, one of the aforementioned particle electrodes, one of the aforementioned counter electrodes and/or the aforementioned reactor in electrochemical or electrobiotechnological processes comprising electrochemical reaction and synthesis processes, electroenzymatic reaction and synthesis processes, electromicrobial reaction and synthesis processes

Method for the continuous operation of an electrochemical or electrobiotechnological reactor, comprising

(A) the provision of one of the abovementioned reactors with one of the abovementioned electrode systems,

(B) feeding the particle electrode (2) of the electrode system for operation as a fluid bed particle electrode or as a fixed bed particle electrode,

(C) continuous or cyclic pumping of a cooling solution from an external cooling water system through a counter electrode of the electrode system designed as a cooling counter electrode (18a) for temperature control in the electrode chamber,

(D) cyclic or continuous exchange of counter electrode electrolyte through the annular gap (26) of the counter electrodes (18),

(E) if necessary, replacement of the electrode particles (2a) in the electrode system by

Throttling or closing the drain device (4) of the reaction solution of the particle electrode and

Opening the supply and discharge device (11) of the distribution counter electrode (18b) and allowing reaction solution to flow via the supply devices (5, 15) through the opening (20) of the distributor piece (29) into the interior of the distribution counter electrode (18b) and

- Removal of the entrained electrode particles from the reactor via the feed and discharge device (11), subsequent feeding of fresh electrode particles into the reactor via the feed and discharge device (11) into the interior of the distribution counter electrode (18b) and through the opening (20) into the particle electrode, wherein the exchange of the electrode particles takes place during ongoing reactor operation.

The aforementioned method for the continuous operation of an electrochemical or electrobiotechnological reactor, further comprising the supply or return or diversion of electrolyte solution through the counter electrode designed as an inflow or return flow counter electrode (18c) into the reactor system or to selected positions with inflow or outflow connections or collection or distribution chambers in the reactor. Counter electrode electrolyte solution and Particle electrode electrolyte solution is passed separately through different inflow or return current counter electrodes (18c).

The aforementioned method for the continuous operation of an electrochemical or electrobiotechnological reactor, further comprising gassing the reactor and/or supplying further reaction solutions, each through one or more counter electrodes.

The present invention will be described in detail below.

DETAILED DESCRIPTION OF THE INVENTION

To solve the above-described disadvantages of the prior art, the inventors of the present invention have developed a new particle electrode system which comprises a novel particle electrode and novel counter electrodes and is characterized by a special arrangement of the components.

The electrode system according to the invention (also referred to herein as particle electrode system) comprises a particle electrode (2) and at least one counter electrode (18) in an electrode chamber (1), wherein the at least one counter electrode (18) is arranged within the particle electrode (2).

The elements of the electrode systems according to the invention are described in detail below.

particle electrode

A particle electrode according to the invention (also referred to herein as a working electrode) can basically be based on any conventional particle electrode. In particle electrodes, electrode particles (2a) are dispersed in an electrolyte solution (working electrolyte solution) in a container or housing, also referred to as an electrode chamber. The electrode particles dispersed in the working electrolyte solution are also referred to herein together as an electrode particle dispersion. A current supply leads through the bed of electrode particles. Examples of particle electrodes that can be designed according to the present invention include particles made of the materials gold, platinum, copper, steel, activated carbon and graphite. Composite particles consisting of at least two materials can also be used as particle electrodes, such as graphite particles with a magnetite core. If the material density of the electrode particles is lower than the density of the fluid flowing through, a particle electrode can be produced on the basis of a so-called "inverse fluid bed". In the particle electrode according to the invention, these basic elements of a particle electrode are designed in such a way that one or more power leads (7) are provided, which are directly connected to one or more conductive elements (8) and thus form a current-conducting arrangement (also referred to herein as "electrical contacting of the particle electrode"). This current-conducting arrangement of current leads (7) and conductive elements (8) are arranged in the electrode particles of the particle electrode in such a way that they extend on the one hand at one or more points in the electrode chamber through the filling level (2b) of the electrode particles and on the other hand also at several levels of the electrode chamber through the electrode particles in their horizontal extension (2c) in the electrode chamber. The filling volume of the particle electrode is thus derived from the filling level and the (horizontal) cross-sectional area of the electrode chamber.

The number of power supply lines (7) and conductive elements (8) extending through the electrode chamber varies with the size of the electrode chamber or the reactor. For smaller reactor diameters, for example those on a laboratory scale, a single power supply line (7) may be sufficient, which extends through the entire filling height (2b) of the electrode particles and which is connected to several conductive elements (8) arranged parallel to one another and distributed over different levels. In such an exemplary embodiment, the conductive elements (8) arranged parallel to one another extend at different levels of the filling height of the electrode particles, quasi horizontally, through the electrode chamber. In such embodiments, the length of the horizontally extending conductive elements (8) is ideally selected so that they extend as far as possible from the connected power supply line (7) to the points in the electrode chamber that are furthest away from it. In principle, such an arrangement can also be designed tilted by 90°, in which the power supply (7) then extends horizontally through the electrode particles and, starting from this, the connected conductive elements (8) extend at various points through the filling level of the electrode particles, quasi vertically, in the electrode chamber. As a result, in the arrangements according to the invention, the conductive elements (8) with the recesses (8a) provided therein extend horizontally through the particle bed, i.e. in the horizontal extension (2c) of the electrode particles in the electrode chamber, or horizontally through the electrode particle dispersion. If reference is made here to an "extension through the electrode chamber", this means an extension through the particle bed or the electrode particle dispersion in the electrode chamber due to the structure according to the invention. Such an arrangement and connection of power supply(s) and conductive elements can in principle be freely varied with regard to their geometric or spatial design and can be freely adapted to the geometry of the electrode chamber or the reactor. In principle, it is possible to connect one or more power supplies to the outer Edges of the electrode chamber to be placed vertically in the particle bed and from there the conductive elements to extend towards the interior of the electrode chamber. Such a horizontal extension can be extended as desired, for example to the center of the reactor or to the opposite edge of the electrode chamber. It is also possible to have one or more power leads immersed vertically in the particle electrode bed at one or more points away from the outer edge of the electrode chamber and to have the conductive elements extend horizontally from there towards the outer edge or to the center of the electrode chamber. An arrangement with conductive elements extending in a star shape in different horizontal directions is also possible. In embodiments of such arrangements tilted at 90°, the power supply lines can run horizontally through the electrode chamber at different heights or levels of the filling level of the electrode particles and the conductive elements connected to them extend from there either also horizontally in other directions of the electrode chamber (almost forming an arrangement extending in two dimensions in a cross or star shape) or they extend vertically through the filling level of the electrode particles. The decisive factor in the selected design of the arrangement that forms the electrical contact of the particle electrode is that conductive elements extend evenly through all areas of the electrode chamber and thus ensure an even distribution of even and short electron transport paths.

In preferred embodiments of the invention, several conductive elements (8) are arranged parallel to one another along a power supply line (7). Parallel conductive elements then extend through the electrode chamber on different horizontal planes or vertically spaced from one another.

The conductive elements (8) extending through the electrode chamber can in principle be designed in all conceivable, sufficiently thin, geometric shapes that allow an extension through the particle electrode bed. The conductive elements are preferably in the form of conductive sheets, strips, wires, disks, grids or porous nets. Conductive sheets, strips, wires, grids or porous nets are preferred. Grids or porous nets are particularly preferred. Such power supplies (7) and/or conductive elements (8) can basically be formed from any conventional and known conductive materials. Examples include materials made of titanium, steel, nickel, gold, platinum, silver, copper, tungsten, zirconium, tantalum, graphite, activated carbon and from materials with conductive surfaces made of e.g. gold, platinum, graphite, ruthenium oxide, iridium oxide. The conductive elements (8) extending through the electrode chamber (ie through the particle bed) have recesses (8a) within which the counter electrodes (18) are arranged. In the case of wires, such recesses can be formed in the form of bends, such bends being designed in such a way that they enable the contact-free reception and partial enclosure of the counter electrodes. In the case of sheets, strips, disks, grids or porous nets, the recesses are usually in the form of cutouts or holes which depict the shape of the counter electrodes to be accommodated therein and are large enough to receive them contact-free and to completely (or partially) enclose them all around.

In a preferred embodiment of the invention, the conductive elements (8) extending through the electrode chamber (i.e. through the particle bed) are designed in the form of conductive grids or porous nets. Such grids or nets are preferably dimensioned such that they extend over an entire plane (e.g. the entire cross section) of the electrode chamber, in the case of a horizontal arrangement in the electrode chamber, for example over the entire horizontal cross-sectional area from the outer edge to the respective opposite outer edge or in the case of a vertical arrangement in the electrode chamber, for example over the entire vertical cross-sectional area from one outer edge to the opposite outer edge and over the entire filling height. In such embodiments in which the conductive elements have a large area, they must be permeable to the electrode particles (2a). If the conductive elements are designed in the form of grids or nets, they preferably have a mesh size which is a multiple of the size of the electrode particles (2a).

In a particularly preferred embodiment of the invention, the conductive elements (8) extending through the electrode chamber are dimensioned such that they extend over the entire (horizontal or vertical) cross-sectional area (i.e. through the entire particle bed) to the outer edges of the electrode chamber (1). In such large-area conductive elements, the recesses (8a) are designed in the form of holes which are positioned in the elements (8) such that elements (8) arranged parallel to one another each have recesses (8a) positioned parallel to one another through which the counter electrodes are introduced into the electrode chamber (1) and are thereby circularly enclosed by the conductive elements (8) at different levels. If rod-shaped counter electrodes are used, the recesses are circular. The size of the recess should be selected so that contact-free insertion of the counter electrodes is possible. Furthermore, devices for supplying and removing reaction solutions from the particle electrode can be provided, which can comprise drain openings (4, 17) and inlet openings (5, 15) as well as chambers for distributing (21), collecting (23), and compensating the expansion volume of the particle electrode (22).

It is also possible to provide devices for the supply and removal of gases for the purpose of gassing the system. Such devices can either feed gases directly into selected areas of the electrode system via separate feed lines or they can be fed in via the counter electrodes, for example via the inner cavity in hollow rod counter electrodes or via the annular gap.

The particle electrodes of the present invention can be operated as a fluid bed particle electrode or as a fixed bed particle electrode. Particularly preferred are flow-through fixed bed particle electrodes and conventional or inverse fluid bed particle electrodes with a low expansion of the fluid bed of 1 to 30%, preferably 2 to 10%.

The particle electrodes of the present invention generally have a diameter of 5 to 5,000 pm, preferably 100 to 1,000 pm.

The electrode particles of the particle electrodes of the present invention can be surface-functionalized, i.e. functional groups can be immobilized on their surface, which provide the electrode particles with additional functional properties. Examples include functionalizations for immobilizing enzymes and microorganisms, e.g. affinity tag-based groups and covalent groups, as well as structures for immobilization by inclusion or adsorption.

Preferred examples include electrode particles that have catalytically active functionalities immobilized on their surface and/or that have magnetic properties. Examples of surface functionalizations include doping with nano/microparticles and foreign atoms, coatings and composite structures to improve the electrocatalytic properties, immobilized synthetic or biological enzymes and whole-cell catalysts. In contrast to such surface functionalizations, magnetism is not a surface property but a property of the volume of the particles. In the case of magnetic electrode particles, the magnetic properties therefore result from the use of a magnetic material or composite materials with a magnetic component.

In principle, conventional electrodes could also be used as counter electrodes in the particle electrode systems according to the invention, such as conventional solid or hollow rod electrodes. In order to achieve the particular advantages according to the invention described herein, however, special counter electrodes are used which comprise a conductive rod or wire (19a) which has an outer sheath (19b) which is arranged at a distance from the outer surface of the rod or wire (19a) such that an annular gap (26) which runs circularly around the rod or wire (19a) is formed between the sheath (19b) and the outer surface of the rod or wire (19a). This annular gap has an inlet opening (13) and an outlet opening (14) through which counter electrode electrolyte solution can be passed through the annular gap (26) surrounding the rod or wire (19a). The counter electrode also has an electrical contact (9).

Because the counter electrodes are surrounded at a certain distance by the sheath (19b), for example a fabric or a membrane, the electrode particles of the working electrode are prevented from coming into direct contact with the outer surface of the counter electrodes, which would lead to an electrical short circuit. The constant distance between the sheath and the surface of the counter electrode can be achieved by an open-mesh, non-conductive spacer. A separate electrolyte solution can be pumped through the annular gap, i.e. the gap provided between the sheath and the outer surface of the counter electrode.

The counter electrode electrolyte in this separated annular gap area can be cyclically or continuously exchanged or circulated via a separate fluidic system. This allows, for example, undesirable gas bubbles formed on the counter electrode surface to be quickly and continuously removed from the system. The fluidic system of the counter electrode is guided through the annular gap (26) via devices for the continuous flow of counter electrode electrolyte. Such devices include, for example, inlet and outlet openings (3, 6), lines (30, 32) and chambers for distributing (24) and collecting (25) the counter electrode electrolyte. These devices enable the counter electrode electrolyte of the fluidic system of the counter electrodes to flow through the inlet and outlet openings and the distribution and collection chambers through the annular gap that surrounds the counter electrodes.

The casing (19b) of the counter electrodes (18) is formed from materials that allow the passage of charge and prevent the passage and penetration of electrode particles (2a) into the annular gap (26). Preferably, the casing (19b) of the counter electrodes (18) is formed from materials that are selected are selected from the group comprising micro- or nanoporous polymer networks and membranes, as well as ion exchange membranes.

If the sheath (19b) is made of fabric such as non-conductive, fine-meshed polymer fabric, the sheath serves exclusively to prevent direct contact between the particle electrode and the counter electrode and to form an annular gap between the sheath and the surface of the counter electrode, which can be flushed with a counter electrode electrolyte. If the sheath (19b) is an ion exchange membrane, it also serves as a semi-permeable separating layer that allows either cations or anions to pass through and at the same time prevents the oppositely charged ion type from passing through.

The sheath can also be designed in the form of a porous, non-conductive diaphragm, which is supported by a coarse-mesh structure (spacer), so that the diaphragm maintains the desired distance from the conductive rod of the counter electrode to form the annular gap, even under the weight pressure of the particle electrode.

Examples of non-conductive polymer fabric coverings include extruded or sintered separators, nonwovens, membranes, fine-pored grids and fabrics.

Examples of ion exchange membrane coatings include cation exchange membranes, anion exchange membranes, bipolar membranes and chlor-alkali membranes.

In a preferred embodiment of the invention, the conductive rod or wire (19a) of the counter electrodes according to the invention is designed in the form of a hollow rod. The inner surface of such hollow counter electrodes is electrically insulated by a coating or an installation. Hollow rod counter electrodes preferably have an electrically non-conductive coating on the inner surface of their cavity (27). The inner region or inner cavity (27) of such hollow rod counter electrodes is fluidically separated from the counter electrode electrolyte that flows through the annular gap.

In further aspects of the invention, the inventors of the present invention have developed special designs of counter electrodes in the form of hollow rods, which enable further special advantages for the particle electrode systems according to the invention. By using the inner cavity (27) of the counter electrodes in different ways, in special designs of the particle electrode systems according to the invention Counter electrodes specific counter electrode types can be provided in the particle electrode system. On the one hand, a novel cooling system can be integrated into the particle electrode systems according to the invention by means of a so-called cooling counter electrode (18a) and on the other hand, a novel system for exchanging used electrode particles can be integrated by means of a so-called distribution counter electrode (18b). In addition, the cavity of the counter electrodes can be used to pass through other components, for example for introducing gases or other reaction solutions (educts) or for the purpose of return flow or the return or diversion of electrolyte solutions through the reactor system.

cooling counter electrodes

In particle electrode systems according to the invention with cooling counter electrodes, the hollow rod of the counter electrode penetrates all chambers of the particle electrode system or the reactor and thus, in addition to the function as a counter electrode, simultaneously also fulfills the function of cooling the interior of the reactor.

The cooling counter electrodes are connected to an external cooling water system via inlet and outlet openings. By using a separate cooling circuit that is fluidically decoupled from the electrolyte circuits of the particle electrode and the counter electrodes, the residence time of the cooling medium in the reactor can be regulated so that only a small temperature difference occurs between the inlet and outlet. The local cooling capacity and thus also the temperature within the working electrode volume can thus be kept almost constant over the reactor height in a range that is optimal for the reaction. This is particularly important for electroenzymatic reactions, as these are very sensitive to reaction differences and temperatures that are too high quickly lead to enzyme inactivation.

A counter electrode according to the invention, which is designed as a cooling counter electrode (18a), has a drain device (10) and an inlet device (12), through which coolant can be passed through the hollow inner region (27) of the hollow rod counter electrode (18a).

By pumping a cooling solution through the interior of a large part of the counter electrodes, the reactor volume can be cooled directly from the inside. By evenly distributing several such cooling counter electrodes within the electrode chamber, a uniform and continuous temperature control can be achieved within the entire reactor. By introducing several such cooling counter electrodes, the distances between such cooling units can also be kept sufficiently small so that rapid temperature control can be achieved and the cooling effect achieved with external cooling systems The associated inertia during temperature adjustments is prevented right into the interior of the reactor due to long distances for temperature equalization.

The number, spatial distribution and spacing of such cooling counter electrodes in an electrode chamber can be selected and variably adjusted depending on the size of the electrode chamber or reactor and the reaction carried out therein or the heat development associated with the respective reaction type. This new type of counter electrode is therefore characterized by a high degree of variability in terms of possible applications.

Such a cooling concept based on the cooling counter electrodes according to the invention is, in contrast to conventional cooling via the reactor jacket or, for example, the reactor cover, practically independent of the reactor dimensions and freely scalable.

A specific embodiment of such a cooling counter electrode is described in detail below by way of example.

distribution counter electrodes

In particle electrode systems according to the invention with distribution counter electrodes, the counter electrode hollow rod ends within the working electrode volume just above the bottom. The end piece of a distribution counter electrode is specially designed to enable the continuous supply and removal of electrode particles from the electrode chamber.

A counter electrode according to the invention, which is designed as a distribution counter electrode (18b), thus has a device (11, 20) for supplying and removing electrode particles into the electrode chamber via the hollow inner region (27) of the hollow rod counter electrode (18b).

In particular, a counter electrode according to the invention in the form of a distribution counter electrode has a non-conductive distribution piece (29) and supply and discharge devices (11, 20) for exchanging electrode particles between the particle electrode and the hollow inner region (27) of the distribution counter electrode (18b). The distribution piece (29) of the distribution counter electrode (18b) is preferably designed such that several separate sub-channels (32) in the form of separate sub-segments of the annular gap enable the counter electrode electrolyte to flow through the annular gap (26) and openings (20) are provided between these sub-channels, which connect the hollow inner region (27) of the distribution counter electrode (18b) to the particle electrode, through which the electrode particles can be exchanged between the inner region of the distribution counter electrode (18b) and the particle electrode. In a specific In an embodiment of a distribution counter electrode according to the invention, the distribution piece (29) is designed such that several separate partial channels (32) in the form of separate partial segments of the annular gap enable the counter electrode electrolyte to flow through the annular gap (26) and openings (20) are provided between these partial channels, which connect the hollow inner region (27) of the distribution counter electrode (18b) with the external environment, through which electrode particles can be exchanged between the inner region of the distribution counter electrode (18b) and the external environment.

Such an inventive design makes it possible to form a fluidic connection that is sealed against the working electrode. The opening that forms the end piece connects the interior of the counter electrode with the particle bed of the working electrode. To ensure that no electrical short circuit occurs between the working and counter electrodes during reactor operation, the inner wall of the counter electrode hollow rods is electrically insulated by a coating or insert, as already mentioned above. During regular reactor operation, the distribution counter electrode is closed so that the liquid rests inside the distribution counter electrode and no particles are fed into or removed from the working electrode space. If a decreasing catalytic activity or, for example, contamination requires the electrode particles to be replaced, the drainage system can be set so that solution flowing in at high speed via the inlet and distribution openings flows into the interior of the distribution counter electrode, thus carrying along a high concentration of electrode particles, which can then be removed from the reactor. In this way, the electrode particles can be completely discharged if necessary. By adjusting the feed system, new (e.g. unused) particles can then be pumped into the working electrode chamber of the reactor in the form of a slurry or particle suspension, where it is distributed across the cross-section. Excess solution supplied with the particle suspension can be discharged via other devices (collection openings, inlet and outlet systems). The undesired discharge of particles can be prevented by installing fine-mesh grids, nets or membranes.

This specific design of counter electrodes means that electrode particles whose functionality has been exhausted can be removed or fresh electrode particles can be added via the distribution counter electrodes, purely via pumping or targeted flow processes, without the need to open the reactor housing or loosen mechanical connections. As described above for cooling via cooling counter electrodes, particle exchange using the distribution counter electrodes evenly distributed over the entire reactor cross-section is also much more homogeneous and scalable than would be possible with a conventional particle removal system attached to the side of the reactor wall. A specific embodiment of such a distribution counter electrode is described in detail below by way of example.

inflow or reverse flow counter electrodes

In order to allow the electrolyte solutions to flow through the reactor system in a targeted manner, one or more counter electrodes can be designed as so-called inflow or return flow counter electrodes (18c). Such inflow or return flow counter electrodes (18c) can be used, for example, if external components are to be connected to the system which, due to their predetermined design and geometry, have connections for the inflow or outflow at positions that can be reached more easily by redirecting the electrolyte solutions to other positions in the electrode system or reactor. This makes it possible to bring about a targeted (re)direction of electrolyte solution flows through the counter electrodes designed as hollow rods into or through the reactor system, for example to selected positions in the reactor structure with inflow or outflow connections or collection or distribution chambers. This can also enable, for example, an internal return of electrolyte from the collection chamber in which the electrolyte is collected after flowing through the reactor. An electrolyte circuit can be implemented with only one supply and discharge of a partial flow, whereby a pump must also be connected to the reactor to keep the circuit running. However, it is also possible to provide only a single flow through, in the sense of a diversion or return of electrolyte, which can be used to (re)direct the electrolyte to desired positions in the reactor. If, for example, the inlet and outlet devices are on the same side of the reactor (e.g. on the top), this can be implemented by directing the electrolyte to the corresponding adjacently positioned devices through such a single flow through the inflow or return flow counter electrodes (18c).

It is possible and advantageous according to the invention that different solutions can be passed separately from one another through different counter electrodes to different positions through the electrode system. This makes the system according to the invention highly variable and compatible with a large number of external components.

Basically, a counter electrode according to the invention, which is designed as an inflow or return current counter electrode (18c), also has devices (11, 20) for supplying and removing the electrolyte solution(s) passed through the hollow inner region (27) of the hollow rod counter electrode (18c). Such inflow or return current counter electrodes can also have devices, for example Fasteners, coupling pieces or adapters for connection to external components.

If the term "inflow or return flow counter electrodes" is used here, this means that a counter electrode is designed either as an inflow or as a return flow counter electrode. For the sake of clarity, it should be noted that this does not mean that only one of the two variants ("or") is provided. The system can have one or more inflow counter electrodes as well as one or more return flow counter electrodes, or only one or more inflow counter electrodes or only one or more return flow counter electrodes are provided. This can be freely selected depending on requirements and reactor design, which further characterizes the high variability of the system according to the invention. There is also free variability with regard to the number of inflow and return flow counter electrodes.

A particle electrode system in the sense of the present invention refers to an arrangement comprising, in an electrode chamber (1), a particle electrode as described in detail above and at least one counter electrode as described in detail above, wherein the at least one counter electrode is arranged within the particle electrode. The latter means that one or more counter electrodes are introduced into a continuous particle electrode comprising the entire electrode space or the entire reactor diameter. The electrode systems according to the invention thus differ from conventional electrode systems or reactors in which the counter electrode(s) is arranged outside the particle electrode, i.e. is not surrounded by the particle bed of the particle electrode, such as in the conventional electrode systems described above, in which in cylindrical arrangements an inner electrode chamber (working electrode chamber) is usually arranged within a counter electrode chamber, separated by an ion exchange membrane.

The particle electrode system in turn forms the core component of a reactor in which the electrochemical or electrobiotechnological processes are carried out using the particle electrode system according to the invention.

In a preferred embodiment, the electrode system according to the invention has at least two counter electrodes in the form of a hollow rod. At least one of the counter electrodes is designed as a cooling counter electrode and at least one of the counter electrodes is designed as a distribution counter electrode, the cooling and distribution counter electrodes each being described in detail above. Depending on the size of the electrode system, it is preferred that it has more than one counter electrode designed as a cooling counter electrode.

Basically, the type and number of the respective functional counter electrodes must be selected depending on the size of the electrode chamber or reactor and the reactions carried out therein.

The novel structure according to the invention, with the three-dimensionally interwoven arrangement of working and counter electrodes, enables electrode operation in which the maximum current path length covered within the particle bed and the electrolyte is only a few centimeters. The modular and variably combinable components of the electrode system make it possible to equip reactors regardless of the reactor dimensions and to combine them with a large number of external parts and components. By integrating the necessary reactor cooling into the concept of the modular counter electrode structure, the cooling power introduced per reactor volume is also independent of the scaling, so that there is no risk of overheating even for large reactor volumes with high energy input. This is an important advantage, especially in the case of electrochemical reactors with temperature-sensitive, immobilized biocatalysts. Finally, the modular counter electrode concept according to the invention also offers the advantage of simple and uniform handling of the electrode particles, especially those with immobilized biocatalysts. The number of positions in the reactor at which electrode particles can be exchanged can be easily expanded by scaling the reactor, without additional design measures being required. The simple and, if necessary, continuous renewal of electrode particles with exhausted biocatalysts makes it possible to use biocatalysts with a service life of a few days or even hours. This also opens up applications in which the biocatalyst can be regenerated in external reaction vessels under changed conditions that cannot be realized in the actual synthesis reaction and can be returned to the electrochemical reactor.

It has been found to be advantageous that in an electrode system according to the invention the number of distribution and cooling counter electrodes is selected such that they are used in a ratio of distribution counter electrodes to cooling counter electrodes of 1:4 to 1:20, preferably 1:6.

The counter electrodes are preferably arranged evenly and symmetrically distributed within the particle electrode. It is important that the selected distribution enables uniform and continuous electron transport paths as well as a uniform and sufficiently homogeneous temperature setting. The distance between the central axes of the counter electrodes is ideally between 1 to 30 cm, preferably between 2 to 10 cm.

In a particularly preferred embodiment of an electrode system according to the invention, the conductive elements (8) extending through the electrode chamber (i.e. through the particle bed) with the recesses (8a), as described in detail above, and the counter electrodes in the electrode chamber are arranged such that the counter electrodes penetrate the recesses of the conductive elements extending through the electrode chamber or are partially or completely circularly enclosed by them, as described in more detail above, so that a three-dimensionally interlocking arrangement of counter electrodes and conductive elements or electrical contacting of the particle electrode or is formed.

Such a three-dimensional contact system, which is formed from the arrangement of the power supply (7) and the conductive elements (8) connected to it, enables almost any scaling of particle electrodes to an industrial scale. Fillings made of conductive materials have a significantly lower conductivity than, for example, a continuous metal wire, which means that a power line in pure particle fillings leads to considerable energy losses due to ohmic losses after just a few centimeters of line length. The three-dimensional electrical contacting of the particle electrode according to the invention enables efficient electrical contacting of the particle electrode over the entire working electrode volume.

As already explained above and as can be seen from the following descriptions of specific preferred embodiments of electrode systems according to the invention, these can also have devices for the supply and removal of reaction solutions, or dispersing or working solution from the particle electrode or working chamber, as well as counter electrode electrolyte and/or coolant and/or gases. Such devices include, for example, drain openings, inlet openings, chambers for distributing and collecting reaction solutions, dispersing solution, electrolyte solution or coolant, chambers that enable compensation of the expansion volume of the particle electrode, as well as other devices for protection against undesired particle discharge, shut-off devices, valves, pumps, etc. reactor

The present invention also includes a reactor operated using the electrode system described herein with the particle electrode described herein and the counter electrodes described herein.

In a particular embodiment, a reactor according to the invention can also have magnets outside the electrode housing, via which magnetic fields can be applied in the particle electrode. Such magnets can be magnetic coil(s) or permanent magnet(s). Such a design is suitable for versions in which the reactor or the particle electrode installed therein is to be operated with electrode particles with magnetic properties.

Applying a magnetic field then leads to a magnetization of the electrode particles. The magnetized electrode particles form a local magnetic north or south pole on opposite sides. As a result, the electrode particles are magnetically attracted to one another, resulting in the formation of particle chains. The intensive mutual contact of the particles in such chains can further improve the electrical conductivity within the particle bed by reducing the voltage drop within the particle bed and thus ultimately improving the performance efficiency of the electrochemical reactor.

The electrode system according to the invention and the reactor with the components or modules described herein, such as the particle electrode according to the invention and the counter electrodes according to the invention, are suitable for use in electrochemical or electrobiotechnological processes. These include in particular electrochemical reaction and synthesis processes, electroenzymatic reaction and synthesis processes and electromicrobial reaction and synthesis processes. Specific examples include electroenzymatic co-factor regeneration, substitution by direct and indirect electron transfer and the electrochemical generation of substrate for enzymes. In combination with an aerobic or anaerobic microorganism, a direct electron transfer between the particle electrode and a mediated electron transport via electrochemically generated substrates such as hydrogen and formate are included. Purely electrochemical processes include electrosorption, electrodeposition and the removal of organic and metallic contaminants.

The present invention also includes a method for the continuous operation of an electrochemical or electrobiotechnological reactor, comprising

(A) providing a reactor as described herein equipped with an electrode system as described herein which in particular, it is equipped with one or more of the cooling and distribution counter electrodes described herein, and optionally with one or more inflow and/or return flow counter electrodes;

(B) feeding the particle electrode of the electrode system for operation as a fluidized bed particle electrode or as a fixed bed particle electrode;

(C) continuous or cyclic pumping of a cooling solution from an external cooling water system through the cooling counter electrode(s) of the electrode system to control the temperature in the electrode chamber (particle bed);

(D) cyclic or continuous exchange of counter electrode electrolyte through the annular gap of the counter electrodes;

(E) if necessary, replacement of the electrode particles in the electrode system by

Throttling or closing the drain device for the reaction solution of the particle electrode and

Opening the supply and discharge device of the distribution counter electrode and allowing reaction solution to flow via the supply devices through the opening in the distribution piece of the distribution counter electrode into the interior of the distribution counter electrode; and

- Removal of the entrained electrode particles from the reactor via supply and removal devices, subsequent feeding of fresh electrode particles into the reactor via supply and removal devices into the interior of the distribution counter electrode and through openings in the particle electrode, whereby the exchange of the electrode particles takes place during ongoing reactor operation.

The method according to the invention can also comprise the supply, return or diversion of electrolyte solution through the counter electrodes designed as inflow or return flow counter electrodes, for example for supplying, returning or diverting components to selected inlets or outlets or connection points to connected components or external components.

The process according to the invention can also comprise gassing the reactor and/or supplying further reaction solutions, each through one or more counter electrodes.

Such supply, return or diversion as well as such gassing can also take place continuously and during ongoing reactor operation. It should be noted for the sake of clarity that, in the sense of the present invention, a continuous process or continuous operation of a reactor is also referred to as continuous if the flow is throttled or the flow direction is reversed in order to exchange the used particles. On the one hand, the conditions in the reactor are not strictly stationary during a (partial) particle exchange. On the other hand, the process and reactor system according to the invention can be operated in such a way that the supply of electricity and solution does not have to be completely stopped, which is a particular advantage of the present invention. Accordingly, a process and reactor operation according to the invention can be referred to as continuous.

In principle, the components described above and the process steps of the aforementioned process are not to be understood as an exhaustive list, but the individual modules or components described here, such as particle electrodes, counter electrodes, electrode systems or reactors, can of course include further components that are required for their operation and are generally known to a person skilled in the art. This also applies to the process sequence shown, which can be supplemented by further steps or process components if the process management requires this or makes sense.

DESCRIPTION OF THE FIGURES

Fig. 1 schematic representation of the basic structure of a reactor according to the invention

Fig. 2 Cross-sectional view of the reactor at the level of the axis A - A of Figure 1

Fig. 3 Detailed view of the lower area of a distribution counter electrode according to the invention

Fig. 4 Cross-sectional view at the level of line B - B of Figure 3

Fig. 5 schematic representation of an embodiment of a reactor according to the invention with magnets

Fig. 6 Details of a digital reactor twin of a reactor according to the invention created in COMSOL

Fig. 7 Current density distributions within a reactor in the simulation test

Fig. 8 schematic representation of an internal supply of

(1) Working electrode electrolyte into the working electrode chamber and

(2) Counter electrode electrolyte in the annular gap via counter electrodes in operation as inflow counter electrodes (18c)

REFERENCE SIGN

(1) (Working) electrode chamber / working electrode

(1a) Housing of the electrode chamber

(2) Particle electrode (2a) Electrode particles

(2b) Filling level of the electrode particles in the electrode chamber

(2c) (horizontal) extension (cross-sectional area) of the electrode particles in the electrode chamber

(3) Drain for counter electrode electrolyte to be drained from the upper distribution chamber (25)

(4) Outlet opening from the collection chamber (23) for the reaction solution of the particle electrode to be discharged

(5) Inlet for reaction solution of the particle electrode

(6) Inlet for fluidic system / counter electrode electrolyte of the counter electrode (18)

(7) Power supply(s)

(8) conductive elements in contact with the power supply (7), which extend from a power supply (7) into the working electrode space

(8a) Recesses in a conductive element (8)

(9) electrical contact of the counter electrode (18)

(10) Drain for coolant from the cooling counter electrode (18a)

(11) upper opening of the distribution counter electrode (18b) for removing used or supplying fresh electrode particles via the cavity of the distribution counter electrode (18b)

(12) Inlet for coolant from the cooling counter electrode (18a)

(13) (Inlet) opening(s) for counter electrode electrolyte from the lower distribution chamber (24) into the annular gap (26)

(14) (Drain) opening(s) for counter electrode electrolyte from the annular gap (26) from the upper distribution chamber (25)

(15) Inlet opening(s) between distribution chamber (21) and particle electrode chamber of the working electrode (1)

(16) Covering devices (e.g. grids, nets or membranes)

(17) Outlet opening(s) between free liquid area (22) and collection chamber (23) for escaping reaction solution of the particle electrode

(18) Counter electrode(s) / counter electrode module(s)

(18a) Cooling counter electrode(s)

(18b) Distribution counter electrode(s)

(18c) Inflow or return current counter electrode(s)

(19a) conductive rod or wire of the counter electrode(s)

(19b) Sheath of the counter electrode(s) / sheath structure around the counter electrode(s) (18)

(20) Opening at the end piece of the distribution counter electrode (18b) between the cavity of the distribution counter electrode and the particle bed of the working electrode (1)

(21) Distribution chamber for reaction solution of the particle electrode

(22) free liquid area to compensate for the expansion volume of the particle electrode (23) Collection chamber for reaction solution of the particle electrode

(24) lower distribution chamber for fluidic system / counter electrode electrolyte of the counter electrode (18)

(25) upper distribution chamber for fluidic system / counter electrode electrolyte of the counter electrode (18)

(26) Annular gap between counter electrode (18) and sheath (19b)

(27) Interior / cavity of hollow rod counter electrode(s)

(28) (tightly closing) end piece for receiving the distribution counter electrode (18b) and the sheath structure (19b)

(29) non-conductive distributor of the distribution counter electrode (18b)

(30) non-conductive tube for fixing the distributor (29) and for supplying counter electrode electrolyte

(31) Bottom of the particle electrode chamber

(32) Partial channels in the form of an annular gap segment within the distributor piece (29) for supplying counter electrode electrolyte from the tube (30) into the annular gap (26)

(33) Magnets (e.g. magnetic coil(s) or permanent magnet(s))

EXAMPLES

The invention is described in more detail by the following exemplary embodiments, without being limited thereto.

Construction of an electrochemical reactor with scalable

Figure 1 shows a section through an exemplary basic structure of a possible embodiment of an electrochemical reactor system according to the invention.

In the cylindrical housing (1a) of the working electrode chamber (1), an example of a rod-shaped power supply (7) (several can be provided) is shown, to which conductive elements (8) in the form of coarse-mesh metal grids are attached at regular intervals. The mesh size of the metal grids (8) is a multiple of the particle size of the particles (2a) of the particle electrode (2). This allows the particles of the particle electrode (2) to pass through the metal grids (8) practically unhindered during a particle exchange. Nevertheless, the metal grids (8) enable efficient electrical contact of the particle electrode (2) over the entire working electrode volume.

In the exemplary embodiment shown, several conductive elements (8) in the form of metal grids are arranged parallel to each other on different levels of the particle electrode (stacked one on top of the other) and each extend across the entire cross-sectional area of the electrode chamber through the particle bed. The conductive elements (here the metal grids) have circular recesses (8a) at regular intervals, which are each positioned on the grids in such a way that they are positioned parallel one above the other. Before the particle electrode is filled with the electrode particles, rod-shaped counter electrodes (18) are pushed through these recesses (8a), which extend through the entire filling height (2b) of the electrode. This ensures that even with large working electrode volumes, the current paths within the particle bed that are also required for current conduction are also kept short everywhere. The interlocking three-dimensional arrangement of conductive elements for contacting the particle electrode (here the metal grids), particle electrode and counter electrode modules evenly distributed within the particle electrode results in local current paths between the working and counter electrodes of a maximum of a few centimeters, even for working electrode volumes of, for example, several cubic meters.

Construction of a working electrode chamber (particle electrode)

The working electrode space is delimited on two sides (here at the bottom and top) by fluidic distribution and collection chambers through which the reaction solution for the redox reaction at the working electrode is supplied and removed. The reaction solution flows through the inlet (5) into the distribution chamber (21) and from here through numerous inlet openings (15) into the volume of the working electrode (2). To ensure that no electrode particles can sediment downwards through the inlet openings (15), these are covered by a fine-mesh cover, e.g. a grid (16). At the upper end of the particle bed (2) there is a free liquid area (22) which, if required, enables the particle bed (2) to expand slightly during reactor operation and serves as a kind of compensation chamber. When flowing through the working electrode, the reaction solution leaves this area via outlet openings (17), collects in a collection chamber (23) and leaves the reactor via the outlet opening (4).

Structure of the counter electrode modules (cooling and distribution counter electrode)

In the embodiment shown here, the counter electrode modules (18) comprise the actual counter electrode, designed as a hollow rod in the form of a conductive rod (19a), an electrical contact (9) of the counter electrode and a sheath (19b), e.g. a fabric, that envelops the counter electrode (18) at a certain distance in a circular manner. The constant distance between the sheath (19b) and the surface of the conductive counter electrode rod (19a) can be achieved by an open-mesh, non-conductive spacer (not shown in Figure 1). The sheath (19b) can be, for example, non-conductive, fine-mesh polymer fabric or ion exchange membranes. The sheath prevents direct contact between the particle electrode (2) and the conductive Counter electrode rod (19a). The annular gap (26) formed by the distance between the casing (19b) and the counter electrode rod (19a) is flushed through by the counter electrode electrolyte. If an ion exchange membrane is used as the casing (19b), this also fulfils the function of a semi-permeable separating layer that allows either cations or anions to pass through and at the same time prevents the oppositely charged ion type from passing through. The counter electrode electrolyte in this separated annular gap (26) can be cyclically or continuously exchanged or circulated via its own fluidic system. This allows, for example, unwanted gas bubbles formed on the surface of the counter electrode rod to be quickly removed from the system. The counter electrode fluidic system enters the electrode system at the inlet opening (6) in a second, lower distribution chamber (24). The counter electrode electrolyte then flows through the openings (13) into the annular gap (26) that surrounds the conductive counter electrode rods (19a). At the upper end of the reactor, the counter electrode electrolyte flows from the openings (14) into a second, upper collection chamber (25) and leaves the reactor via the drain (3).

In preferred embodiments of the invention, the counterelectron modules (18) are designed as hollow rod counterelectrodes, which have a hollow inner region (27) that is fluidically separated from the counterelectrode electrolyte in the annular gap (26). According to the invention, this hollow inner region can be used for additional functionalization of the counterelectrodes, depending on the design.

In an embodiment of a so-called cooling counter electrode (18a) according to the invention, the hollow rod (19a) of the counter electrode (18a) penetrates all chambers of the reactor and, in addition to functioning as a counter electrode, also enables cooling of the reactor interior. The inner cavity (27) of the cooling counter electrodes is connected to an external cooling water system through inlet openings (12) and outlet openings (10). This makes it possible to integrate a separate cooling circuit into the reactor that is fluidically decoupled from the electrolyte circuits, via which the residence time of the cooling medium in the reactor can be regulated so that only a small temperature difference occurs between the inlet and outlet. The local cooling capacity and thus also the temperature within the working electrode volume (in the particle bed) can thus be kept almost constant over the entire reactor height and over the entire reactor cross-section in a range that is optimal for the reaction. This is particularly important for electroenzymatic reactions, since these react very sensitively to reaction differences and temperatures that are too high quickly lead to enzyme inactivation.

In an embodiment according to the invention of a so-called distribution counter electrode (18b), the conductive counter electrode hollow rod (19a) ends within the working electrode volume just above the floor formed by the lower distribution chamber (21). The end piece is designed in such a way that, on the one hand, a fluidic connection to the lower distribution chamber (24) is formed which is sealed against the working electrode. On the other hand, the end piece also has an opening (20) which connects the interior of the counter electrode (27) with the particle bed of the working electrode (2). To ensure that no electrical short circuit occurs between the working and counter electrodes during reactor operation, the inner wall of the counter electrode hollow rods (19a) is electrically insulated by a coating or an insert. During normal reactor operation, the upper opening (11) of the distribution counter electrodes (18b) is closed. Accordingly, the liquid rests inside the distribution counter electrode (18b) and no electrode particles (2a) are fed into or removed from the working electrode space. If a decrease in catalytic activity or, for example, contamination or other inactivation of the electrode particles requires the particles to be replaced, the outlet (11) from the interior of the distribution counter electrodes (18b) can be opened and the outlet (4) of the upper collection chamber (23) can be throttled or closed completely. As a result, the solution flowing in via the inlet (5) and the distribution openings (15) flows at high speed through the opening (20) into the interior of the distribution counter electrode (18b), entraining a high concentration of electrode particles (2a) which leave the reactor via the outlet (11). This makes it possible to completely remove the electrode particles (2a) if necessary. New particles can then be pumped into the reactor in the form of a slurry, in this case using the opening (11) as the inlet. The particle suspension passes through the opening (20) into the working electrode chamber and is distributed there over the cross-section. The solution supplied with the particle suspension is discharged via the collection openings (17) and the drain (4), whereby a covering device in the form of a fine-mesh grid (16) in front of the collection openings (17) prevents an undesired discharge of particles.

Figure 2 shows a view of the reactor cross-section at the level of the axis A - A in Figure 1.

The position of the cross-section was chosen so that it shows one of the conductive elements (8), which are designed here as a coarse-meshed metal grid. These serve to evenly contact the particle electrode (2) over the entire reactor cross-section. The metal grids (8) have circular recesses (8a) for introducing the counter electrodes (18) into the area of the particle electrode (2), the diameter of which is approximately 5 mm larger than the outer diameter of the counter electrodes, so that the counter electrodes can be guided through the conductive elements without contact. The metal grids are connected to the power source by the current guides (7), e.g. in the form of solid metal rods. The counter electrode modules (18) are arranged evenly distributed over the reactor cross-section (2c), whereby Both cooling counter electrodes (18a) and distribution counter electrodes (18b) are provided. The respective number can be freely varied depending on the size of the reactor and the desired cooling and particle exchange performance. In the example shown, an arrangement with only one central distribution counter electrode (18b) and six cooling counter electrodes (18a) distributed symmetrically and evenly around it was shown as an example and for the sake of clarity. Such arrangements can be used, for example, in small pilot reactors with a working electrode volume of approx. 1 L. Larger reactors accordingly have a large number of distribution counter electrodes (18b) and cooling counter electrodes (18a), which are distributed in a uniform pattern across the reactor cross-section.

In the embodiment shown here, the counter electrodes (18) have the following concentric structure, viewed from the outside inwards. The boundary (separation) from the particle electrode (2) is formed by the casing (19a). This can be designed, for example, in the form of a porous, non-conductive diaphragm, which is supported by a coarse-mesh structure, so that the diaphragm maintains the desired distance from the metal hollow rod (19a), the outer surface of which forms the actual counter electrode, even under the weight pressure of the particle electrode. The counter electrode electrolyte flows upstream through the annular gap (26) formed by the casing, possibly with a support structure, whereby any gas bubbles formed on the counter electrode (18) are quickly removed. The inner region (27) of the counter electrode, which is designed as a hollow rod, is separated from the fluid region of the counter electrode electrolyte and can take on separate functions that are essential for scaling and operation of the reactor. In the case of functionalization as a cooling counter electrode (18a), a cooling medium is passed through this inner region, which evenly dissipates the heat energy generated in particular by ohmic losses in the reactor. In the case of functionalization as a distribution counter electrode (18b), used, dirty or inactive electrode particles (2a) can be removed via the inner region and fresh electrode particles (2a) can be added in a second step.

Figure 3 shows a detailed view of the lower area of the distribution counter electrode (18b), which, due to its special design according to the invention, allows electrode particles to be removed or added and at the same time counter electrode electrolyte to be added without the working electrode and counter electrode electrolyte mixing. Figure 3 shows the upper area of the shortened lower area of the conductive counter electrode hollow rod (19a), which ends just above the bottom (31) of the particle electrode area in a cylindrical, non-conductive distribution piece (29). Just like the conductive hollow rod (19a), the shortened casing (diaphragm) (19b) of the distribution counter electrode (18b) also ends in a tightly closing end piece (28). At the lower end of the distribution piece (29) is connected to a non-conductive pipe (30) which projects through the base (31). This pipe (30) serves to fix and position the distributor piece (29) and to supply the counter electrode electrolyte. In the schematic representation in Figure 3, the vertical section runs centrally through the distributor counter electrode (18b) and thus through the area of the opening segments (20). As a result, the distributor piece (29) is interrupted in the view in the representation and the continuous material area behind the cutting plane is indicated by dashed lines.

Figure 4 illustrates the geometric structure of the distributor (29) using a cross-sectional view at the level of line B - B in Figure 3. Figure 4 shows that in the middle area the distributor (29) consists of four partial channels (32) which have the shape of an annular gap segment. The counter electrode electrolyte is guided from the tube (30) through these completely closed partial channels (32) into the annular gap (26) of the distributor counter electrode (18b), which is formed by the counter electrode hollow rod (19a) and the casing (diaphragm) (19b) (as shown in Figure 3). Between the partial channels (32) are the openings (20) which connect the particle electrode area (2) with the inner area of the hollow rod (27). Electrode particles (2a) can be conveyed into the inner area of the hollow rod (27) through these openings (20). By reversing the flow direction in the interior of the hollow rod (27), electrode particles (2a) can also be pumped from a reservoir into the area of the working electrode.

Figure 5 shows a schematic representation of another possible embodiment of the reactor according to the invention. This embodiment is suitable for particle electrodes which are operated with electrode particles (2a) with high magnetizability. In this embodiment, the reactor housing (1a) in the area of the particle electrode (2) is surrounded by one or more magnetic coils (33) or an arrangement of one or more permanent magnets, by means of which the area of the particle electrode can be superimposed with a magnetic field.

The remaining components in this exemplary embodiment correspond to those of the reactor described in Example 1.

3 - Preliminary study

For a preliminary study, a design of a particle electrode with conductive elements (8) in the form of coarse-mesh contact grids was realized on a laboratory scale.

The following aspects were examined: (i) Is it possible to handle a particle electrode even in the presence of the contact grid or does blockages or local clearances occur despite the size of the grid mesh?

(ii) Does the introduction of the conductive grid lead to the predicted uniform contacting and an increase in efficiency?

For the preliminary study, a contact grid was used that consisted of four round-shaped titanium expanded metal disks that were welded to a common titanium wire at a distance of 1 cm each. The expanded metals had a mesh size of 5 mm. The electrode particles used were composite particles of activated carbon and magnetite and 5% polymer binder. The particles had a particle size distribution of 50 - 400 pm, with an average particle size of 170 pm. A platinum-plated titanium sheet was used as the counter electrode. The two electrode compartments of the working and counter electrode compartment were separated by a cation exchange membrane. A 3 mM solution of the oxidized form of potassium hexacyanoferrate was fed into the particle-filled working electrode compartment and a 3 mM solution of the reduced form of potassium hexacyanoferrate was fed into the counter electrode compartment at a constant flow rate of 1 and 4 ml/min, respectively. The electrolyte of both chemical solutions consisted of a 1 M potassium chloride solution. Optionally, a magnetic field with a magnetic flux density of 20 mT could be superimposed on the reactor using a Helmholtz coil. The reactor wall was made of transparent 3D-printed material, so that optical observation of the behavior of the particle bed was possible.

(i) Hydrodynamic behavior:

Filling and operation of the reactor showed that the electrode particles passed through the multi-layer contact grid without observable impairment and reached the bottom of the reactor through sedimentation in the working electrode chamber, which was initially filled with liquid. During operation, the working electrode chamber was supplied with a flow rate that led to an approx. 10% expansion of the particle electrode, i.e. the particle electrode was operated as a fluid bed. Even when the fluidized state was set, the contact grid showed no negative effects.

(ii) Electrochemical efficiency:

By applying a voltage of -0.2 to -0.8 V to an Ag/AgCI reference electrode adjacent to the working electrode, the reduction of potassium ferricyanide to potassium ferrocyanide took place on the particles in the working electrode chamber. In contrast to contacting the particle bed with only one expanded metal disc on the reactor floor, the use of the four-layer contact grid with otherwise the same reaction conditions resulted in an increase in current flow of 300%. This enabled the conversion of the incoming potassium hexacyanoferrate solution to be increased from 25% with an expanded metal disc to approximately 80% when using the contact grid.

Example 4 - Digital twin of the reactor structure

Based on the experimental results of the preliminary study from Example 3, the average conductivities of a particle bed made of the composite particles described in Example 3 and of a particle bed made of graphite particles with a diameter of approximately 600 pm could be calculated. In addition, the specific surface areas of the respective particle bed and the electrolyte conductivity were measured. Data for the membrane resistance and the specific conductivity of the titanium current leads were taken from literature data. Using the finite element multiphysics software COMSOL 6.0, a detailed three-dimensional simulation model for an electrochemical reaction system constructed according to the invention was then created. The simulated reaction system comprises a working electrode volume of 1 L, which is contacted via an arrangement of 10 expanded metal discs at a distance of 15 mm. The working electrode space has a diameter of 100 mm and a height of 200 mm, of which 160 mm are filled with the particle electrode in the sedimented state. Seven counter electrode modules are immersed within the working electrode volume, a central distribution counter electrode module and six cooling counter electrode modules arranged in a hexagonal pattern. The hollow rods of the counter electrodes have an outer diameter of 20 mm. The outer diameter of the annular gap for the counter electrode electrolyte formed by the membrane is 24 mm. Figure 6 shows a series of images with various details (shaded in grey) of the digital reactor twin created in COMSOL.

Simulation results for a potassium hexacyanoferrate concentration of 30 mM with a particle bed of graphite particles show the current density distributions achieved in the feed within the reactor. The cross sections show maximum current densities of over 250,000 A/m ³ and an average current density of over 100,000 A/m ³ . In the longitudinal section, it can be seen that the current density drops between the contact grids. From this it can be concluded that for the selected type of electrode particles, a reduction in the distance between the planes of the contact grid could achieve a further increase in the average current density. The cross section at half the reactor height shows a relatively homogeneous current density distribution in the reactor area between the counter electrode modules. In the edge area of the reactor, triangular zones of lower current density occur, but these result from the fact that there is no additional counter electrode module further out at these points. For a reaction system scaled to larger dimensions with a hexagonal counter electrode pattern, the current density is almost the same. The largely homogeneous current density distribution shown in the interior can be assumed in the edge area. The calculated average current density of over 100,000 A/m ³ is a very good value for an incoming reactant concentration of only 30 mM, which reflects the efficient use of the high specific surface area of the particle electrode.

Example 5

Figure 8 shows a schematic representation of another possible embodiment of the reactor according to the invention based on a partial section of an electrode system according to the invention, in which an internal supply of working electrode electrolyte into the working electrode chamber and of counter electrode electrolyte into the annular gap of the counter electrode takes place via counter electrodes in operation as inflow counter electrodes (18c). This internal supply allows the correspondingly diverted electrolyte solutions to be fed into the system via selected inflow positions. By reversing the direction of the electrolyte flow and the targeted selection of the flow direction, a discharge of electrolyte solution at specifically selected positions in the reactor can also be made possible, for example by using suitable pumps and valves.

In the case of simultaneous gas supply or formation, a flow from bottom to top in the chambers offers advantages, which is why a design as illustrated in Figure 8 is particularly suitable if all external connections are arranged on the upper reactor cover. The electrolytes are then first fed through the interior of inflow or return flow counter electrode hollow rods into the lower area of the reactor. There they are then distributed into the particle-filled working electrode chamber or the annular gaps of the counter electrodes and flow through them from bottom to top.

Claims

PATENT CLAIMS

[1] Electrode system comprising an electrode chamber (1) with

(b) at least one counter electrode (18) comprising b-i. a conductive rod or wire (19a), b-ii. an outer casing (19b) which is arranged at a distance from the outer surface of the rod or wire (19a) such that b-iii. an annular gap (26) which runs circularly around the rod or wire (19a) is formed between the casing (19b) and the outer surface of the rod or wire (19a), and which b-iv. has an inlet opening (13) and an outlet opening (14) through which counter electrode electrolyte solution is passed through the annular gap (26) surrounding the rod or wire (19a), and b-v. an electrical contact (9); wherein the at least one counter electrode (18) is arranged within the particle electrode (2), and wherein the conductive elements (8) extending through the particle bed of the electrode chamber have recesses (8a) within which the counter electrodes (18) are arranged.

[2] Electrode system according to claim 1, wherein two or more conductive elements (8) extending through the electrode chamber are provided, which are each arranged parallel to one another and evenly distributed in the electrode chamber (1), and wherein the conductive elements (8) extending through the electrode chamber are designed in the form of conductive sheets, strips, wires, grids or porous nets.

[3] Electrode system according to claim 1 or 2, wherein the conductive elements (8) extending through the electrode chamber and the at least one counter electrode (18) are arranged such that the at least one counter electrode penetrates the recesses (8a) of the conductive elements (8) extending through the electrode chamber and thus forms a three-dimensionally interlocking arrangement with them.

[4] Electrode system according to claim 1, 2 or 3, which has at least two counter electrodes (18) in the form of a hollow rod (19a), wherein

(ii) at least one counter electrode is designed as a distribution counter electrode (18b) which has a device (11, 20) for supplying and removing electrode particles into the electrode chamber via the hollow inner region (27) of the hollow rod counter electrode (18b), and

(iii) optionally has at least one counter electrode in the form of a hollow rod (19a) with devices for the continuous flow of electrolyte solution, gases or other reaction solutions, which may comprise valves, inlet and outlet openings (3, 6), lines (30, 32) and chambers for distribution (24) and collection (25), as well as coupling devices for connection to external components.

[5] Electrode system according to one of claims 1 to 4, which has at least one counter electrode in the form of an inflow or return flow counter electrode (18c), which is designed such that a supply, return or diversion of electrolyte solution takes place within the reactor system.

[6] Electrode system according to one of claims 1 to 5, wherein the counter electrodes (18) are arranged evenly and symmetrically distributed within the particle electrode (2).

[7] Electrode system according to one of claims 1 to 6, wherein the conductive elements (8) extending through the electrode chamber are dimensioned such that they extend over the entire cross-sectional area up to the edges of the electrode chamber (1) and wherein the recesses (8a) are designed and positioned in the elements (8) such that elements arranged parallel to one another

(8) have recesses (8a) positioned parallel to one another, through which the counter electrodes are introduced into the electrode chamber (1) and are thereby circularly enclosed by the conductive elements (8).

[8] Electrode system according to one of claims 1 to 7, wherein the sheath (19b) of the counter electrodes (18) is formed from materials which allow the passage of charge and prevent the passage and penetration of electrode particles (2a) into the annular gap (26), preferably selected from the group comprising micro- or nanoporous polymer networks and membranes, as well as ion exchange membranes.

[9] Electrode system according to one of claims 1 to 8, wherein at least one counter electrode is designed in the form of a distribution counter electrode (18b) which has a non-conductive distribution piece (29) and supply and discharge devices (11, 20) for exchanging electrode particles between the particle electrode and the hollow inner region (27) of the distribution counter electrode (18b), wherein the distribution piece (29) of the distribution counter electrode (18b) is preferably designed such that several separate partial channels (32) in the form of separate partial segments of the annular gap enable the counter electrode electrolyte to flow through the annular gap (26) and openings (20) are provided between these partial channels which connect the hollow inner region (27) of the distribution counter electrode (18b) to the particle electrode and through which the electrode particles can be exchanged between the inner region of the distribution counter electrode (18b) and the particle electrode.

[10] Particle electrode (2) comprising in a housing (1a) electrode particles (2a) dispersed in a working electrolyte solution, and one or more power supply lines (7) and one or more conductive elements (8) which have one or more recesses (8a) within which counter electrodes (18) can be arranged, wherein the power supply lines (7) and the conductive elements (8) are in direct contact with one another and together form an arrangement which extends through the filling level (2b) and the horizontal extent (2c) of the electrode particle dispersion in the electrode chamber, wherein the particle electrode can also have one or more of the following features:

■ the conductive elements (8) extending through the electrode particle dispersion are designed in the form of conductive grids or porous nets which are permeable to the electrode particles (2a);

■ the conductive elements (8) extending through the electrode particle dispersion are designed in the form of conductive grids or porous nets, which have a have a mesh size which is a multiple of the size of the electrode particles (2a);

■ the conductive elements (8) extending through the electrode particle dispersion are dimensioned such that they extend over the entire cross-sectional area up to the edges of the housing (1a) and have recesses (8a), preferably circular recesses, which are positioned in the elements (8) such that elements (8) arranged parallel to one another each have recesses (8a) positioned parallel to one another, through which counter electrodes, preferably rod-shaped counter electrodes, particularly preferably those in the form of a hollow rod, are inserted into the housing (1a) and are thus circularly enclosed by the conductive elements (8);

■ the electrode particles have magnetic properties.

[11] Counter electrode (18) comprising a conductive rod or wire (19a) which is designed in the form of a hollow rod, an outer insulating sheath (19b) which is arranged at a distance from the outer surface of the rod or wire (19a) such that an annular gap (26) which runs circularly around the rod or wire (19a) is formed between the sheath (19b) and the outer surface of the rod or wire (19a), and which has an inlet opening (13) and an outlet opening (14) through which counter electrode electrolyte solution can be passed through the annular gap (26) surrounding the rod or wire (19a), and an electrical contact (9), wherein the counter electrode can also have one or more of the following features: the sheath (19b) is made of materials which allow the passage of charge and prevent the passage and penetration of electrode particles (2a) into the annular gap (26), preferably selected from the Group comprising micro- or nanoporous polymer networks and membranes, as well as ion exchange membranes; it also has devices for the continuous flow of counter electrode electrolyte through the annular gap (26), which can comprise inlet and outlet openings (3, 6), lines (30, 32) and chambers for distribution (24) and collection (25); it has devices for the continuous flow of electrolyte solution, gases or other reaction solutions, which can comprise valves, inlet and outlet openings (3, 6), lines (30, 32) and chambers for distribution (24) and collection (25), as well as coupling devices for connection to external components.

[12] Counter electrode according to claim 11, which is designed in the form of a cooling counter electrode (18a) and has a drain device (10) and an inlet device (12) through which coolant can be passed through the hollow inner region (27) of the hollow rod counter electrode (18a), and/or which is designed in the form of a distribution counter electrode (18b) and has a non-conductive distributor piece (29) and a device for supplying and removing (11, 20) electrode particles via the hollow inner region (27) of the distribution counter electrode (18b), and wherein preferably the distributor piece (29) is designed such that several separate partial channels (32) in the form of separate partial segments of the annular gap enable the counter electrode electrolyte to flow through the annular gap (26) and openings (20) are provided between these partial channels, which open the hollow inner region (27) of the distribution counter electrode (18b) with the external environment and through which electrode particles can be exchanged between the interior of the distribution counter electrode (18b) and the external environment.

[13] Reactor comprising the electrode system according to one of claims 1 to 9, a particle electrode according to claim 10, one or more of the counter electrodes according to claim 11 or 12 or combinations thereof, wherein the reactor may further comprise magnets outside the electrode housing which enable the application of magnetic fields in the particle electrode.

[14] Use of the electrode system according to one of claims 1 to 9, a particle electrode according to claim 10, one or more of the counter electrodes according to claim 11 or 12 and/or the reactor according to claim 13 in electrochemical or electrobiotechnological processes comprising electrochemical reaction and synthesis processes, electroenzymatic reaction and synthesis processes, electromicrobial reaction and synthesis processes.

[15] A method for the continuous operation of an electrochemical or electrobiotechnological reactor, comprising

(A) providing a reactor according to claim 13 having an electrode system according to any one of claims 1 to 9;

(B) feeding the particle electrode (2) of the electrode system for operation as a fluid bed particle electrode or as a fixed bed particle electrode, (C) continuous or cyclic pumping of a cooling solution from an external cooling water system through counter electrodes of the electrode system designed as cooling counter electrodes (18a) for temperature control in the electrode chamber;

(D) cyclic or continuous exchange of counter electrode electrolyte through the annular gap (26) of the counter electrodes (18);

- Removal of the entrained electrode particles from the reactor via the feed and discharge device (11), then feeding fresh electrode particles into the reactor via the feed and discharge device (11) into the interior of the distribution counter electrode (18b) and through the opening (20) into the particle electrode, if necessary continuous flow of electrolyte solution, gases or other reaction solutions through one or more of the counter electrodes designed as hollow bodies, whereby the exchange of the electrode particles takes place while the reactor is in operation.