EP3221458A2

EP3221458A2 - Method and apparatus for converting carbon dioxide

Info

Publication number: EP3221458A2
Application number: EP15817753.5A
Authority: EP
Inventors: Lars KRÜGER; Christoph Herz; Martin Schönhoff
Original assignee: Gensoric GmbH
Current assignee: METHANOLOGY AG
Priority date: 2014-11-17
Filing date: 2015-11-17
Publication date: 2017-09-27
Also published as: WO2016078649A2; WO2016078649A3; US20170327959A1; WO2016078649A8; JP2017536845A; CN107429264A; DE102014016894A1

Abstract

The invention relates to a method for producing a hydrocarbon by the reduction of CO2, wherein CO2 is reduced to a hydrocarbon using a directly heated electrode. The invention also relates to an apparatus for carrying out a corresponding method, a corresponding power plant and a system comprising such a power plant and a vehicle with an internal combustion engine. The system and apparatuses can be used, for example, as a micro-energy system for local power supply.

Description

Process and apparatus for converting gaseous carbon compounds

The invention relates to a process for the preparation of a hydrocarbon by reducing C0 ₂ , in which C0 _{2 is} reduced by means of a directly heated electrode to a hydrocarbon. The invention also provides a device for carrying out a corresponding method, a corresponding power plant and a system comprising this power plant and a vehicle with an internal combustion engine. The methods and devices can be used, for example, as a micro-energy system for decentralized energy supply.

Our Vision - Independence, Decentralization and Commercial Profitability

Over the next 5 to 7 years, our solution will allow every household to contribute to a C0 ₂ -free economy and achieve energy independence from external gas or energy supplies for heating homes or buildings. This will be achieved through the use of alternative fuels and energy efficient energy storage systems based on the use of C0 ₂ conversion to chemical conversion approaches.

However, a structural change of existing infrastructure is not necessary for this goal. In fact, our system will preferably be compatible with existing heating systems and use educts that are largely available at low cost: ambient air, water, and surplus renewable energy.

Desired result of the project - a micro-energy system for decentralized, domestic use

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

The invention therefore relates in particular to a process for preparing a hydrocarbon by reducing C0 ₂ , comprising steps in which C0 _{2 is} reduced to a hydrocarbon by means of a directly heated electrode. The reduction can be enzymatic.

The reduction can be carried out in several steps, wherein the reduction in at least one, preferably all, steps is catalyzed by an enzyme which is associated with a directly heated electrode.

Enzyme immobilizations, on the one hand, help to better position the enzymes on electrode surfaces for better electron uptake, thus enabling improved activities and product formation rates. On the other hand, immobilization also stabilizes the enzymes. The macromolecules are always subject to conformational changes, which contribute to a certain extent to their catalytic activity. However, external influences (eg temperature or radiation) can also cause irreversible states of conformation, it can lead to the aggregation of the enzymes, whereby the function of the biocatalyst is disabled. Immobilization helps to bind the enzymes locally so that inactive conformational states are no longer taken and prevent aggregation.

For example, an enzyme in alginate can be immobilized on a carbon tissue and used on a working electrode to reduce C0 ₂ to formic acid (Wagner A. Enzyme Immobilization on Electrodes for C0 ₂ Reduction, 2013. Institute of Physical Chemistry). Alginate immobilization stabilizes the enzymes, but their positioning relative to the electrode is undirected.

Alternatives to alginate immobilization for better positioning of the enzymes on electrodes include immobilization on carbon nanotubes via functional enzyme groups, on gold surfaces via covalent sulfur bridges, or on Ni materials via histidine residues on the enzyme. For this purpose, the enzymes could be attached during production corresponding amino acids that bind directly to substrates of the heated electrodes.

Several, preferably all, steps of enzymes can be catalysed, which are each associated with an electrode which is heated directly to a temperature which is optimal for the respective reaction. Preferably, the temperature of the respective electrode is optimized with regard to the substance conversion of the respective enzyme, but it is also possible to choose a lower temperature, if otherwise a sufficient stability is not guaranteed by one or more of the enzymes. Unless all reactions require a higher temperature than the ambient temperature or reactor temperature for good overall conversion, it is also possible that one or more of the enzymes are not associated with a heated electrode. For example, the temperature of an electrode, with the formate dehydrogenase from Candida spp. is to be set to 35-40 ° C, in particular about 37-38 ° C.

Also, several, preferably all, steps of enzymes associated with the same directly heated electrode can be catalyzed. Preferably, the temperature of this electrode is optimized in terms of total substance conversion, but it is also possible to choose a lower temperature, unless otherwise sufficient stability of one or more of the enzymes is not guaranteed.

The reduction can be carried out in several steps, wherein the reduction in at least one, preferably all, steps is catalyzed in each case by an enzyme which thereby oxidizes a cofactor which is regenerated on a directly heated electrode, wherein the cofactor is selected from a group comprising NADH, NADPH, and FADH.

The reduction can be catalyzed by formate dehydrogenase, aldehyde dehydrogenase and / or alcohol dehydrogenase.

Although isolated enzymes are commercially available, they can be further optimized (Fielber S., Optimization of NAD-dependent formate dehydrogenase from Candida boidinii for use in biocatalysis, 2001). As formate dehydrogenase, e.g. an enzyme from Candida spp., in particular Candida biodinii (for example from Sigma-Adrich), which shows a temperature maximum of 35-40 ° C and works with NADH as cofactor. An enzymatic regeneration of the cofactor NADH on a directly heated electrode is optionally possible.

With regard to a further bio-electrocatalytic synthesis of methanol from formic acid, for example, an aldehyde dehydrogenase from Pseudomonas sp. and an alcohol dehydrogenase from Saccharomyces sp. Those used with the formate dehydrogenase from Candida spp. combine well, especially because so these Enzymes are NADH dependent. For example, a diaphorase from Pyrococcus sp. be used.

In this case, C0 ₂ can be converted by a carbonic anhydrase to bicarbonate, wherein the carbonic anhydrase is optionally associated with a directly heated electrode.

Alternatively, the reduction may be nonenzymatic on a heated electrode, the electrode preferably comprising a material selected from the group consisting of platinum, copper, titanium, ruthenium, and combinations thereof.

Different directly heatable electrodes, in which the heating element consists of the electrode, ie the temperature increase only starts from the electrode and is not transferred from the electrolyte to the electrode, are known from the prior art.

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

In the method according to the invention, the directly heated electrode can be shaped as a spiral or helix or net or surface, in particular as disclosed in DE 10 2014 114 047.

Suitable directly heated electrodes can be obtained, for example, from Gensoric GmbH (Rostock, DE). The directly heated electrode consists of an electrode material which is selected from the group comprising carbon, in particular glassy carbon or graphite, a noble metal, in particular gold or platinum, an optically transparent conductive material, in particular indium-doped tin oxide, copper, stainless steel and nickel.

The invention also relates to a device in which a method according to one of the preceding claims expires or can run, characterized in that it consists of two electrodes and a membrane for the separation of the anodic and cathodic reaction or comprises these.

A variety of reaction vessels can be connected in parallel and produce the total reaction product.

The device may be constructed and used as a disposable or recyclable reactor.

The invention also provides a device for producing a hydrocarbon by fixing C0 ₂ , comprising a) a directly heated electrode, with which preferably at least one enzyme is associated, which can catalyze a step of reducing C0 ₂ to a hydrocarbon, or with preferably, at least one cofactor which is capable of interacting with an enzyme capable of catalyzing a step of reducing C0 ₂ to a hydrocarbon and b) a device for introducing gaseous C0 ₂ which is capable of producing C0 ₂ in to introduce a reaction space in which it can come into contact with the directly heated electrode.

This device generally comprises a further electrode and a membrane for separating the anodic and cathodic reactions.

A device according to the invention may comprise 1-10,000 reaction spaces according to the invention with directly heated electrodes, preferably 100-5,000 or 500-2,000 or 800-1,200 Reaction vessels. A large number of reaction vessels can therefore be connected in parallel and produce the total of the reaction product.

The device can be constructed as a one-way reactor or as a recyclable reactor and used.

The gaseous CO ₂ can be used or purified from ambient air or used in concentrated form, for example from a gas bottle.

The invention also provides a power plant for the provision of energy in the form of electricity and / or a hydrocarbon, comprising i) an energy source, preferably a regenerative energy source based for example on photovoltaic, hydropower or wind power, preferably photovoltaic, ii) the device according to the invention, wherein for the production of one

Hydrocarbon necessary energy from the energy source i) comes from, iii) a hydrocarbon storage, and iv) optionally, a hydrocarbon fuel cell for the production of electricity, or v) optionally a device for the combustion of hydrocarbon for

Production of hot water or heat energy for heating buildings or apartments.

The invention also provides a system comprising a power plant according to the invention and a vehicle selected from the group comprising cars, buses and motorcycles, the vehicle being equipped with an engine which is suitable, preferably optimized, for the combustion of a hydrocarbon, preferably methanol , is.

According to the invention, the hydrocarbon is selected from the group comprising methanol and methane and formic acid and formaldehyde, preferably methanol. Not only for the owners of homes, who want to be more independent of the centralized energy supply and make their existing renewable energy system (RES) more cost-effective in an environment with uncertain prices and incentives, the project result is a micro-energy System (MES), which helps to save the surplus energy of the RES and to ensure the supply of energy mainly for heating on a small scale. Unlike other C0 ₂ uses and energy-to-X memory strategies, this application is especially suited for domestic applications as it runs in mild environmental conditions (no high pressure, no high temperatures). Due to the selectivity of the basic new electro-enzymatic approach, there is no need for the electrolytic production of H ₂ . In fact, all starting materials can be used directly from the environment (ambient air, tap water).

In the project, the key process is the electro-biocatalytic conversion of C0 ₂ and electricity through a cascade of enzymatic reactions to methanol. The resulting methanol is used as fuel for the heating system. No external storage or infrastructure is needed.

Commercial profitability

For the end user, our system becomes an attractive alternative to centralized gas or energy supply. The target annual cost structure for the system and consumables should be comparable to the cost of annual gas consumption (reference 10 Ct / KwH natural gas in Germany in about 5-10 years). In addition, our solution enables the efficient storage of energy produced by renewable sources (such as solar).

For distributors, ie strategic partners, the need for recurring purchases of consumables (enzyme reactor) offers an attractive sales potential in addition to the retail sale of the MES, which amounts to € 1 billion p.a. in Germany.

In the context of the invention, "a" means "one or more", unless otherwise specified. Fig. 1 Extent of the project. Energy: Energy, Enzymes: Enzymes, Enzyme reactor: Enzyme reactor, Separation unit: Separation unit, storage: Storage.

Fig. 2 Planned result of project activity: improvement of enzyme productivity and stability

Fig. 3 Core Technology - Electro-enzymatic reactor in which C0 ₂ , H _{2 is converted} from H ₂ O and electricity into high quality fuels such as CH 3 OH (methanol).

Examples

Proiektbeschreibung

1. Development activities in key technology I - electro-enzymatic reactions

Our key reaction involves the electrochemical formation of an organic Cl molecule such as methanol (CH ₃ OH) in an enzymatic cascade over several steps, performed on conducting and directly heated electrodes.

Scheme 1: Key reaction (cascading electro-biocatalytic reduction)

This approach is e.g. because of the following features:

Mild conditions - no high pressure or high temperatures needed

High selectivity through enzymatic conversion;

^■ No cleaning / concentration of high volume ambient air flows;

^■ No electrolysis on H ₂ O conversion to form H ₂ directly from water (giving 0 ₂ ); Higher reaction rate, higher conversions without significant or no degradation of enzymes by using directly heated electrodes compared to unheated electrodes; and or

Direct control of turnover and enzyme activity through integrated electrochemical conversion and temperature measurements is possible.

These features distinguish our approach from other C0 ₂ usage techniques, making it particularly suitable for small scale applications.

Key activities in the project are aimed at improving enzyme yields and stability, i. Extension of the service life. The current status and scheduled results are shown in FIG.

The planned activities to achieve these goals are

Improved enzyme stability and activity (by factors of 100 and 30)

Reduced production costs of the enzyme (target: <10 € / g)

Similar procedures have been successful in previous projects of 3 years duration.

There are examples of scientifically proven developments in which enzymes have been improved by using heated electrodes or heated reaction media. These enzymes are normally derived from thermophilic organisms and catalyze the partial reaction within the NADH cycle [McPherson, I.J. and Vincent, K.A .; Electrocatalysis by hydrogenases: lessons for building bio-inspired device. Journal of the Brazilian Chemical Society, 2014].

2. Development activities in key technology II - electro-enzymatic reactor

The key reaction cascade is carried out in a specially designed reactor. Because of our planned economic model, the main goal in this project is the development and realization of a disposable electro-enzymatic reactor in a cost-effective way (assembly, enzyme placement, wiring). It can, however a recyclable reactor can be used in which, for example, after the efficiency has lessened after purification, new enzymes are associated with the electrodes.

The reactor will comprise directly heated electrodes on which the enzymes are immobilized in a way that allows electrons to be transferred from the electrical energy source to the electrobiocatalytic reaction. This is achieved by using large area electrodes in the beaker or by modifying the inside of the tube reactors.

3. Development activities in key technology HI - system integration

According to the overall objective of the project, the key technologies are preferably integrated into a standalone system that can be integrated into existing domestic heating infrastructure.

The basic function of the system: an optimized enzyme cascade is able to produce x grams of product within y hours using z milligrams of catalyst. It is our goal to produce 5 kg of methanol per day for use in existing infrastructure, such as heating systems. Because of the complexity of scale-up of biocatalytic reactions, we will focus on a discrete scale-up strategy: "simply" increase the number of parallel (disposable) electro-biocatalytic reactors. "According to current designs, 1000 parallel reactors are capable of achieving the desired amount to produce energy / fuel per day.

The reaction medium is separated from the product methanol e.g. separated by using a pervaporation method. The reaction medium is pumped in a loop while the methanol is produced and stored within the device.

4. Comparative Experiments Bioelectrocatalysis with unheated electrode

Before an optimization of bioelectrocatalysis was carried out on HF Thermalab® (Gensoric, Rostock, DE), preliminary tests were carried out for the reduction of C0 ₂ to formic acid with a non-heatable enzyme alginate electrode. For the production of this electrode 75 mg of processed preparation of formate dehydrogenase from Candida spp. (Candida boidinii) (Sigma Aldrich). The enzyme was immobilized in alginate on a carbon cloth and used as a working electrode for the reduction of C0 ₂ to formic acid (Wagner A. Enzyme Immobilization on Electrodes for CO ₂ Reduction, 2013. Institute of Physical Chemistry). The reference electrode used was a silver-silver chloride electrode (Ag / AgCl) with 3 M KCl and, as counterelectrode, a 2 mm graphite rod. All reactions were performed at room temperature in 20 mL of an aqueous buffered electrolyte solution (0.05 M TRIS, pH 7.7) in a 100 mL reactor. For the bioelectrocatalytic synthesis of formic acid, the reactor was continuously gassed with C0 ₂ . Control experiments were carried out in argon-saturated electrolyte solutions without C0 ₂ . The functionality of the enzyme-alginate electrode was first checked by cyclic voltammetry and the reduction peak of C0 ₂ was determined at about -0.8 V.

Subsequently, the synthesis of formic acid was carried out by means of chronoamperometry (Table 1).

Table 1: Bioelectrocatalytic synthesis of formic acid from CO 2 by means of

Chronoamperometry.

In a first preliminary experiment, a total of 0.15 mg formic acid could be obtained bioelectrocatalytically from C0 ₂ at a voltage of -IV and at room temperature. The quantification was carried out by an enzymatic assay of the sample and by HPLC. In a second preliminary test, a voltage of -0.8 V was applied. A similar yield was obtained with 0.14 mg of formic acid from C0 ₂ .

5. Optimization of bioelectrocatalysis on heated electrodes

In the further course of the experiments, the bioelectrocatalytic reduction of C0 ₂ on heated electrodes was to be optimized. In this case, the effect of the temperature on the catalytic properties of the immobilized enzymes should be controlled by heating the electrodes analyzed and thus optimal parameters for the enzyme-catalyzed reaction can be found. For the experiments the system HF Thermalab ™ from Gensoric was used.

1 mg of enzyme (formate dehydrogenase from Candida sp.) Was immobilized on a heated microelectrode using alginate suspension. With this a series of chronoamperometric measurements at different temperatures (22 ° C 30 ° C, 35 ° C, 40 ° C, 45 ° C) were performed. As reference and counter electrode, the electrodes from the comparative experiments were used. Each experiment was preceded by the addition of 1 mg of regenerated cofactor NADH and a test of the enzyme microelectrode for bioelectrocatalytic activity with C0 ₂ at room temperature. In each case, this test was between -320 μΑ and -330 μΑ of a 2-3 minute chronoamperogram performed at -0.8 V. During the experiments, the temperature of the electrolyte in the reactor was measured. The negative control was an experiment with alginate without enzyme on the microelectrode.

In the comparative experiments, voltages of -1, 0 V and -0.8 V were used. Since there was a difference in the yields of less than 10% and the energy input into the reactor to avoid overpotentials should be kept as low as possible, was incorporated with a voltage of -0.8 V (vs. Ag / AgCl, 3 M).

In all chronoamperometric measurements, an increased current flow was observed at the beginning of the measurements, which decreased to a constant level after approx. 3 h. The current flow of the reaction at an electrode temperature of 40 ° C was highest compared to other experiments both at the beginning and in the further course of the reaction, which allowed conclusions on comparatively high reduction rates. In contrast, the chronoamperogram at 22 ° C had the lowest current flows on an enzyme electrode. The control course without enzyme barely showed a current flow of about -30 μΑ, which decreased even further towards 0 μΑ in the course of the reaction. During the chronoamperometric measurements, samples were taken from the reactor after 3 h and after 9 h, respectively, which were analyzed by HPLC for synthesized formic acid (Table 2). In all experiments with heated enzyme microelectrode, formic acid was already detected after 3 hours from the reactor gassed continuously with CO ₂ , with the amount approximately doubling after 9 hours. The highest amount of formic acid was measured at an electrode temperature of 40 ° C, while less formic acid was obtained in experiments with other electrode temperatures (22 ° C, 30 ° C, 35 ° C, 45 ° C). With the exception of the experiment at 45 ° C, the yield of product increased in proportion to the temperature of the electrode. While The experiments continuously monitored the temperature of the electrolyte solution in the reactor. Even at the highest applied heat output at 45 ° C electrode temperature, the electrolyte solution in the reactor remained constant at 22 ° C (Table 2).

Table 2: Bioelectratic synthesis of formic acid from CO 2 at different temperatures on heated electrodes.

* N. d .: not detected

discussion

In comparative experiments, the synthesis of 0.15 mg of formic acid from C0 _{2 was} demonstrated by chronoamperometry (-1 V, vs. Ag / AgCl, 3 M C1-) within 9 h at room temperature in a 100 mL reactor. The selective catalytic properties of the electroenzymes enabled the application of a low voltage (-0.8 V, vs. Ag / AgCl, 3 M C1-) for almost identical synthesis performance (0.14 mg formic acid in 9 h). In subsequent experiments, the synthesis of 0.05 mg of formic acid was achieved under similar conditions. A significant difference between comparative experiments and the first subsequent experiment at room temperature was the amount of enzymes used and the nature of the electrode material. While in the comparative experiment a total of 75 mg of enzyme was immobilized as a bioelectrocatalyst on carbon fabric, subsequent experiments were carried out with a heatable microelectrode from Gensoric, in which only 1 mg of enzyme was immobilized due to the significantly lower electrode surface. Accordingly, the yield with the heatable microelectrode with respect to the use of the catalyst with 0.05 mg of formic acid per mg of enzyme was significantly higher in comparison to the comparative experiment with about 0.002 mg of formic acid per mg of enzyme.

The advantage of using heated electrodes lies in the fact that temperatures can be set directly on the electrode surface for optimum reaction conditions and it is not necessary to temper the entire electrolyte solution of a reactor, which improves the energy balance of electrocatalytic processes of any kind. The temperature in the reactor was continuously monitored during bioelectrocatalytic syntheses. The temperature remained constant at 22 ° C. On the one hand, this could be due to the continuous mixing of the electrolyte due to the continuous gassing of the electrolyte and the transport of heat to the environment being promoted. On the other hand, some of the heat from the heated electrodes could also have been conducted directly to the immobilized enzymes, which were thereby increasingly excited to conformational changes.

In further experiments, the rate of synthesis of formic acid was optimized by directly heating the enzyme microelectrodes. The highest synthesis rates of 0.02-0.03 mg / h (based on a constant rate of synthesis according to Chronoamperogramm after the first 3 hours of the reaction) took place at 35 ° C and 40 ° C. In comparison, the rate of synthesis of formic acid decreased both when the electrode temperature decreased to 22 ° C and when it increased to 45 ° C. Probably, both substrate uptake and product delivery to the enzyme microelectrode, as well as changes in conformational states of the immobilized enzyme necessary for the catalytic reaction mechanism proceeded optimally between 35 ° C and 40 ° C, a sixfold increase in conversion over room temperature (22 ° C). Interestingly, in the literature, reaction optima of the same enzyme are indicated in solution at temperatures around 60 ° C (Tishkov V et al, Catalytic Mechanism and Application of Formated Dehydrogenase, Biochemistry (Moscow), 2004, 69 (11): 1252-1267).

Overall, the strongest current flows were measured at the beginning of each experiment, indicating that most of the electrode reaction occurred in the first few hours. This was confirmed by measurements of the formic acid concentration. After 3 h, therefore, already about half of the formic acid was synthesized, which was present in the respective experiment after another 6 h. The decrease in reaction rates can be explained by the increasing product concentration in the bioelectrocatalysts. Thus, diffusion effects are responsible for an initial accelerated reaction. In addition, the regeneration of NADH is probably a limiting factor for bioelectric catalysis. Since there was still sufficient cofactor for CC reductions at the beginning, the reactions were the fastest. In the further course, the cofactor was no longer reduced to isomers that could be used for enzymatic reactions, which led to slower reactions. An effective regeneration of the cofactor, for example also enzymatically, can therefore improve the reaction efficiency.

Since the experiments were carried out at different temperatures with the same enzyme microelectrode, it can be assumed that the bioelectrocatalytic synthesis of formic acid continues to increase constantly over the 9 h, since in the tests before each experiment a degeneration of the immobilized material over a period of time of one week was not observed.

Claims

claims

1. A process for producing a hydrocarbon by the reduction of C0 _2, comprising steps in which is reduced C0 ₂ by means of a directly heated electrode to a hydrocarbon.

2. The method according to claim 1, characterized in that the reduction is enzymatic.

3. The method according to any one of the preceding claims, characterized in that the reduction is carried out in several steps, wherein the reduction in at least one, preferably all, steps is catalyzed by an enzyme which is associated with a directly heated electrode.

4. The method according to claim 3, characterized in that several, preferably all steps of enzymes are catalyzed, which are each associated with an electrode which is heated directly to an optimum temperature for the respective reaction.

5. The method according to claim 3, characterized in that several, preferably all steps of enzymes are catalyzed, which are associated with the same directly heated electrode.

6. The method according to any one of claims 1 or 2, characterized in that the reduction is carried out in several steps, wherein the reduction is catalyzed in at least one, preferably all, steps in each case by an enzyme which thereby oxidizes a cofactor which on a regenerated directly heated electrode, wherein the cofactor is selected from a group comprising NADH, NADPH, and FADH.

7. The method according to any one of the preceding claims, characterized in that the reduction is catalyzed by formate dehydrogenase, aldehyde dehydrogenase and / or alcohol dehydrogenase.

8. The method according to any one of the preceding claims, characterized in that C0 _{2 is converted} by a carbonic anhydrase to bicarbonate, wherein the carbonic anhydrase is optionally associated with a directly heated electrode.

9. The method according to claim 1, characterized in that the reduction proceeds non-enzymatically on a heated electrode, wherein the electrode preferably comprises a material which is selected from the group comprising platinum, copper, titanium, ruthenium and combinations thereof.

10. The method according to any one of the preceding claims, characterized in that the directly heated electrode is formed as a spiral or helix or mesh or surface.

11. The method according to any one of the preceding claims, characterized in that the directly heated electrode consists of an electrode material which is selected from the group comprising carbon, in particular glassy carbon or graphite, a noble metal, in particular gold or platinum, an optically transparent conductive material, in particular indium-doped tin oxide, copper, stainless steel and nickel.

12. Device in which a method according to one of the preceding claims expires or which is suitable, characterized in that it comprises two electrodes and a membrane for separating the anodic and cathodic reaction.

13. The apparatus according to claim 12, characterized in that a plurality of reaction vessels are connected in parallel and in total can produce the reaction product.

14. The device according to claim 12, characterized in that it is constructed as a disposable or recyclable reactor.

15. A device for producing a hydrocarbon by fixing C0 ₂ , comprising c) a directly heated electrode, with which preferably at least one enzyme is associated, which comprises a step of reducing C0 ₂ to a hydrocarbon or at least one cofactor is associated, which may interact with an enzyme which can catalyze a step of reducing C0 ₂ to a hydrocarbon, and d) a device for introducing gaseous C0 ₂ which is suitable therefor to introduce the C0 ₂ in a reaction space in which it can come into contact with the directly heated electrode, wherein the device is optionally a device according to any one of claims 12-14.

16. Power plant for providing energy in the form of electricity and / or a hydrocarbon, comprising

i) an energy source, preferably a regenerative energy source based, for example, on photovoltaics,

ii) the device according to any one of claims 12-15, wherein the energy necessary for the production of a hydrocarbon originates from the energy source i),

iii) a hydrocarbon reservoir, and

iv) optionally, a hydrocarbon fuel cell for the production of electricity, or v) optionally a device for the combustion of hydrocarbons for

Production of hot water or heat energy for heating buildings or homes.

17. System of a power plant according to claim 16 and a vehicle selected from the group comprising car, bus and motorcycle, wherein the vehicle is equipped with an engine which is suitable for the combustion of a hydrocarbon, preferably, methanol, preferably, preferably optimized ,

18. A method, apparatus, power plant or system according to any one of the preceding claims, characterized in that the hydrocarbon is selected from the group comprising methanol and methane and formic acid and formaldehyde.