Multilayer electrocatalyst for the conversion of co 2 into ethylene glycol

Abstract

The invention relates to a multilayer electrocatalyst (2) for the electrochemical conversion of CO2 into ethylene glycol, comprising a first catalyst layer (4) for the electrochemical reduction of CO2 into CO, a second catalyst layer (6) for the conversion of CO into ethylene, and a third catalyst layer (8) for the electrocatalytic conversion of ethylene into ethylene glycol.

Description

[0001] Description

[0002] Multilayer electrocatalyst for the conversion of CO2 to ethylene glycol

[0003] The present invention relates to a multilayer electrocatalyst for the electrocatalyzed conversion of CO2 to ethylene glycol, a multilayer electrocatalyst system for the electrocatalyzed conversion of CO2 to ethylene glycol, a process for producing a multilayer electrocatalyst, and a process for the electrocatalyzed conversion of CO2 to ethylene glycol, in particular using a multilayer electrocatalyst.

[0004] To improve the overall CO2 balance in the automotive sector, sustainable materials, especially sustainable polymers, are increasingly being used today. The most relevant raw material sources for sustainable polymers include bio-based approaches based on renewable resources, recycled plastics, and CC>2-based polymer approaches.

[0005] Polymer classes produced via the first and second approaches have unfortunately proven to be less suitable for use in applications with demanding mechanical and thermal requirements, particularly since the manufacturing processes according to the first and second approaches do not yield a defined molecular weight, inevitably resulting in an undesirable variance in the physical, mechanical, and chemical properties of the produced polymers.

[0006] In contrast, CO2-based thermoplastic polymers possess a defined molecular weight distribution and thus a specific property profile tailored to the respective application. Furthermore, their greatest advantage over petrochemical polymer solutions is their improved CO2 balance.

[0007] Approaches for the electrochemical conversion of CO2 using catalysts are already known from the prior art, e.g., WO 2024 / 084288 A2. However, it is currently not possible to directly convert CO2, i.e., within a catalyst or system, into a desired polymer starting material such as ethylene glycol. The known solutions, on the other hand, generally lead to a multitude of byproducts that cannot be further utilized in the polymer chemical industry or can only be utilized with high energy input and further intermediate steps. In addition, the known solutions usually exhibit lower coulombic efficiencies (< 60%), which also results in increased energy consumption. It is therefore an object of the present invention to at least partially overcome the disadvantages described above.In particular, the object of the present invention is to provide a device and a method for the environmentally friendly and energy-efficient production of a polymer starting material, such as ethylene glycol, with which polymers for demanding mechanical and thermal requirements can be produced in a simple, fast and cost-effective manner.

[0008] The aforementioned problem is solved by the patent claims. Accordingly, the problem is solved by a multilayer electrocatalyst with the features of claim 1, a multilayer electrocatalyst system with the features of dependent claim 6, a method for producing a multilayer electrocatalyst with the features of claim 7, and a method for the electrochemical conversion of CO2 into ethylene glycol according to claim 11.

[0009] Further features and details of the invention will become apparent from the dependent claims, the description, and the drawings. Features and details described in connection with the multilayer electrocatalyst according to the invention naturally also apply in connection with the invention.

[0010] Multilayer electrocatalyst system and the inventive method and vice versa, so that with regard to the disclosure of the individual aspects of the invention, mutual reference is always made or can be made.

[0011] According to the invention, a multilayer electrocatalyst for the conversion of CO2 to ethylene glycol is provided. The multilayer electrocatalyst comprises a first catalyst layer for the electrochemical reduction of CO2 to CO, a

[0012] a second catalyst layer for the conversion of CO to ethene and a third catalyst layer for the electrocatalytic conversion of ethene to ethylene glycol.

[0013] According to the invention, the multilayer electrocatalyst of the present kind, in particular by virtue of its structure comprising a first catalyst layer for the electrochemical reduction of CO2 to CO, a second catalyst layer for the conversion of CO to ethene, and a third catalyst layer for the electrocatalytic conversion of ethene to ethylene glycol, is designed to convert CO2 "directly," i.e., within a single system, into a starting material for polymer production. The individual steps that take place within the first, second, and third catalyst layers can be considered, in particular, as intermediate steps of an overall process that occurs within a single system.Due to the low solubility of CO2, the multilayer electrocatalyst described can preferably be used in aqueous solution, particularly within a gas diffusion electrode, preferably in a (continuous) electrolysis setup where CO2 can be introduced in gaseous form or in aqueous solution containing one or more electrolytes, such as KHCO3 and KOH. For example, platinum with aqueous KOH can be used as the counter electrode. The base structure of the gas diffusion electrode can optionally be made of titanium or stainless steel alloys with a typical thickness of 2 mm, into which flow-optimized grooves with a depth of, for example, 0.8 mm can be incorporated. The ethylene glycol produced can then be used for the production of polymers, e.g.for the manufacture of continuous filaments, staple fibers, crimp fibers, felts or spinning cords for clothing fabrics, home textiles and industrial purposes, or in mixtures with other fibers such as cotton, wool, silk and synthetic fibers.

[0014] With a view to achieving the most effective conversion of CO2 to ethylene glycol, it may be advantageous to provide that the first catalyst layer and / or the

[0015] The second catalyst layer and / or the third catalyst layer comprise transition metals, wherein preferably the first catalyst layer and / or the second catalyst layer and / or the third catalyst layer comprise at least one of the following transition metals: Ag, Au, Pd, Pt, Zn, Co, Rh, Cr, Ni, Cu, and Fe. The combination of the individual catalyst layers can be in any order and comprise various configurations. The individual layers can be in the form of catalyst sheets, stacks, and particles, and can also include other catalytically used processes not further specified.

[0016] Similarly, with regard to the most effective conversion of CO2 to ethylene glycol, it may be advantageous to provide that the first catalyst layer and / or the

[0017] The second catalyst layer and / or the third catalyst layer differ in their layer composition, with the first catalyst layer preferably having Cu as the largest transition metal component by quantity and / or the

[0018] The second catalyst layer has Ag as the largest transition metal component by quantity and / or the third catalyst layer has Pd as the largest transition metal component by quantity. Preferably, the

[0019] A multilayer electrocatalyst comprises a first catalyst layer with Cu as the most abundant transition metal component, a second catalyst layer with Ag as the most abundant transition metal component, and a third catalyst layer with Pd as the most abundant transition metal component. Optionally, to increase selectivity and Coulombic efficiency and reduce the energy required for electrolysis, the individual layers can then contain one or more secondary catalysts from the group consisting of Ag, Au, Pd, Pt, Zn, Co, Rh, Cr, Ni, Cu, and Fe. It is understood, however, that the multilayer electrocatalyst also includes a first Cu catalyst layer, a

[0020] It may have a second Ag catalyst layer and a third Pd catalyst layer without secondary catalysts.

[0021] To ensure effective gas exchange for effective CO2 distribution within the multilayer electrocatalyst, it is advantageously further provided that a gas diffusion layer is included to accommodate the catalyst layers, wherein the gas diffusion layer preferably comprises a carbon-containing material, in particular in the form of a carbon cloth or carbon paper. Alternatively, the gas diffusion layer can also be formed from a metal foam.

[0022] To ensure the most efficient conversion of CO2 to ethylene glycol, it may be advantageous to provide that the first catalyst layer and / or the

[0023] second catalyst layer and / or the third catalyst layer in a ratio of 0.5 to 99 wt.%, based on the total mass of first catalyst layer,

[0024] second catalyst layer and third catalyst layer, preferably in a ratio of 33 wt.%.

[0025] The invention also relates to a multilayer electrocatalyst system for the electrochemical reduction of CO2 in ethylene glycol, comprising a plurality of interconnected multilayer electrocatalysts. The multilayer electrocatalyst system according to the invention thus offers the same advantages as those already described in detail with regard to the multilayer electrocatalyst according to the invention.

[0026] The invention also relates to a method for producing a multilayer electrocatalyst described above, comprising the steps of coating a gas diffusion layer with a first catalyst suspension to form a first catalyst layer, coating the first catalyst layer with a

[0027] The process involves the preparation of a second catalyst suspension to form a second catalyst layer, as well as the coating of the second catalyst layer with a third catalyst suspension to form a third catalyst layer. Thus, the inventive process for producing a multilayer electrocatalyst has the same advantages as those already described in detail with regard to the inventive multilayer electrocatalyst or the inventive multilayer electrocatalyst system. It is also understood here that individual, several, or all mandatory and / or optional steps of the inventive process can be carried out in the proposed sequence, but also in a different sequence. In particular, individual, several, or all mandatory and / or optional steps of the inventive process can be carried out repeatedly, e.g., cyclically.It is further understood that individual, several or all of the obligatory and optional steps of the method according to the invention can also be carried out at least partially automatically or in an automated and / or self-learning manner, in particular can be implemented by a computer, preferably via computer-implemented simulation methods.

[0028] With a view to the simplest and quickest possible production of a

[0029] A multilayer electrocatalyst can advantageously be provided such that the first catalyst suspension and / or the second catalyst suspension and / or the

[0030] The third catalyst suspension comprises a catalyst powder and a solvent. Suitable solvents include, for example, water, methanol, ethanol, isopropanol, or similar substances.

[0031] To simplify the coating process and increase electrical conductivity, it is advantageous to provide that the first catalyst suspension and / or the second catalyst suspension and / or the third catalyst suspension additionally contain a binder and / or conductive carbon black. Examples of binders that can be used include nitrate, PTFE, PFVD, or similar materials.

[0032] With a view to simple and effective application of the catalyst layers, it may advantageously be provided that the first catalyst suspension and / or the second catalyst suspension and / or the third catalyst suspension is applied by means of one of the following application methods: drop coating, spin coating, spray coating or screen printing.

[0033] The invention also relates to a process for the electrochemical conversion of CO2 to ethylene glycol, preferably using a multilayer electrocatalyst or a multilayer electrocatalyst system described above, comprising the steps of converting CO2 to CO by means of a first catalyst layer via electrochemical reduction, converting CO to ethene by means of a second catalyst layer, and converting ethene to ethylene glycol by means of a third catalyst layer via electrocatalytic conversion. The process according to the invention thus has the same advantages as already described in detail with regard to the process described above.

[0034] The multilayer electrocatalyst or the multilayer electrocatalyst system according to the invention and the method according to the invention for producing a multilayer electrocatalyst have been described.

[0035] It is understood here that individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out in the proposed sequence, but also in a different sequence. In particular, individual, several, or all mandatory and / or optional steps of the method according to the invention can be carried out repeatedly, e.g., cyclically. It is further understood that individual, several, or all of the mandatory and optional steps of the method according to the invention can also be carried out at least partially automatically or in a self-learning manner, in particular by a computer, preferably by computer-implemented simulation methods.

[0036] The invention also relates to ethylene glycol produced via a previously described process for the electrochemical conversion of CO2 into ethylene glycol, preferably by means of a previously described multilayer electrocatalyst.

[0037] Furthermore, the invention also relates to a polymer product made from ethylene glycol, which in turn is produced via a previously described process for the electrochemical conversion of CO2 into ethylene glycol, preferably by means of a previously described multilayer electrocatalyst.

[0038] Further advantages, features, and details of the invention will become apparent from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. The features mentioned in the claims and in the description can each be essential to the invention individually or in any combination.

[0039] They each show schematically:

[0040] Figure 1 shows a multilayer electrocatalyst according to the invention for the electrochemical conversion of CO2 into ethylene glycol, Figure 2 shows the individual steps of a process according to the invention for producing a multilayer electrocatalyst according to the invention for the electrochemical conversion of CO2 into ethylene glycol and

[0041] Figure 3 shows the individual steps of a process according to the invention for the electrochemical conversion of CO2 into ethylene glycol.

[0042] Figure 1 shows a multilayer electrocatalyst 2 according to the invention for the electrochemical conversion of CO2 into ethylene glycol.

[0043] As can be seen in Fig. 1, the multilayer electrocatalyst 2 according to the invention has a first catalyst layer 4 for the electrochemical reduction of CO2 to CO, a second catalyst layer 6 for the conversion of CO to ethene and a

[0044] third catalyst layer 8 for the electrocatalytic conversion of ethene to ethylene glycol.

[0045] In addition, the multilayer electrocatalyst 2 has a gas diffusion layer 10 made of carbon-containing material, onto which the catalyst layers 4, 6, 8 are applied.

[0046] A metal substrate 12 is also arranged at the end of the multilayer electrocatalyst 2 on the left side, forming the cathode together with the multilayer electrocatalyst 2. The cathode is separated from an anode 14 made of an iridium-containing material by a membrane M. The cathode compartment is purged with gaseous CO2, which can be pre-humidified and temperature-controlled. An aqueous phase is located between the catalyst layer 8 and the membrane M, in which ethylene glycol EG is carried out of the process (catholyte). A liquid anolyte is passed through the anode compartment. The anolyte can be an aqueous, organic, or ionic liquid, to which conductivity-enhancing additives such as KOH can also be added.

[0047] By applying a voltage to the anode and cathode, CO2 is converted into C2+ products, such as ethylene glycol as a starting material for polymer production, for example for the production of plastics or the production of fine chemicals.

[0048] Fig. 2 shows the individual steps of a process according to the invention for the production of a multilayer electrocatalyst according to the invention for the electrochemical conversion of CO2 into ethylene glycol.

[0049] As can be seen in Fig. 2, the method according to the invention comprises the steps of coating 100a a gas diffusion layer 10 with a first catalyst suspension to form a first catalyst layer 4, coating 200a the first catalyst layer 4 with a second catalyst suspension to form a

[0050] second catalyst layer 6 and of coating 300a the second catalyst layer 6 with a third catalyst suspension to form a third catalyst layer 8.

[0051] In the coating 100a of the gas diffusion layer 10 with a first catalyst suspension, 1.5 M Cu(NO2)2 is placed under an N2 atmosphere in deionized water and

[0052] 1.5 M NaOH is added dropwise before the solid (the resulting Cu(OH)₂) is filtered off and dried after 8 h. The solid is then mixed with ethanol and the suspension is applied to the gas diffusion layer 10 using a spray coating. The subsequent calcination of Cu(OH)₂ on the gas diffusion layer 10 takes place under electrical reduction at -0.35 V for 15 min or alternatively thermally at 550 °C for 90 min.

[0053] During the coating of the first catalyst layer 4 in 200a with the

[0054] In the second catalyst suspension, 400 mg of Ag nanoparticles (20–40 nm) are first suspended in 40 mL of deionized water and 40 mL of isopropanol, before 0.5 mL of an ionomer solution (5 wt%, e.g., Sustainion XA-9) is added to the suspension and the suspension is stirred for 60 min. The suspension is then spray-coated onto the complex consisting of the gas diffusion layer 10 and the first catalyst layer 4 and subsequently dried overnight at 70 °C.

[0055] When coating 300a the second catalyst layer 6 with the

[0056] In the third catalyst suspension, 1 mol of PdC₂ is dissolved in deionized water, and a hydrazine solution (N₂H₄ 30 mol, 0.08 g / mL) is added dropwise while stirring. The Pd catalyst is then washed in deionized water and dried overnight (70 °C). The Pd catalyst is dissolved in ethanol (1 mg / mL) and spray-coated onto the catalyst subsystem consisting of gas diffusion layer 10 with first and second catalyst layers 4, 6. The layer is then dried overnight at 70 °C.

[0057] Fig. 3 shows the individual steps of a process according to the invention for the electrochemical conversion of CO2 into ethylene glycol.

[0058] As shown in Fig. 3, the process according to the invention comprises the steps of converting 100b of CO2 to CO by means of a first catalyst layer 4 via electrochemical reduction, converting 200b of CO to ethene by means of a second catalyst layer 6, and converting 300b of ethene to ethylene glycol by means of a third catalyst layer 8 via electrocatalytic conversion. The preceding explanation of the embodiments describes the present invention exclusively by way of examples. Of course, individual features of the embodiments can be freely combined with one another, provided this is technically feasible, without departing from the scope of the present invention. List of reference numerals

[0059] 1 multilayer electrocatalyst system

[0060] 2 multilayer electrocatalyst

[0061] 4 first catalyst layer

[0062] 6 second catalyst layer

[0063] 8 third catalyst layer

[0064] 10 Gas diffusion layer

[0065] 12 Substrat

[0066] 14 Anode

[0067] 100a Coating a gas diffusion layer with a first catalyst suspension 200a Coating the first catalyst layer with a second catalyst suspension 300a Coating the second catalyst layer with a third catalyst suspension

[0068] 100b Conversion of CO2 to CO using a first catalyst layer

[0069] 200b Conversion of CO to ethene using a second catalyst layer

[0070] 300b Conversion of ethene to ethylene glycol using a third catalyst layer

[0071] M Membran

[0072] EC Ethylene glycol

Claims

Patent claims 1. Multilayer electrocatalyst (2) for the electrochemical conversion of CO2 to ethylene glycol, comprising: a first catalyst layer (4) for the electrochemical reduction of CO2 to CO, a second catalyst layer (6) for the conversion of CO to ethene and a third catalyst layer (8) for the electrocatalytic conversion of ethene to ethylene glycol.

2. Multilayer electrocatalyst (2) according to claim 1, characterized by that the first catalyst layer (4) and / or the second catalyst layer (6) and / or the third catalyst layer (8) comprise transition metals, wherein preferably the first catalyst layer (4) and / or the second catalyst layer (6) and / or the third catalyst layer (8) comprise at least one of the following transition metals: Ag, Au, Pd, Pt, Zn, Co, Rh, Cr, Ni, Cu and / or Fe.

3. Multilayer electrocatalyst (2) according to claim 1 or 2, characterized by that the first catalyst layer (4) and / or the second catalyst layer (6) and / or the third catalyst layer (8) differ in their layer composition, wherein preferably the first catalyst layer (4) has Cu as the largest transition metal component by quantity and / or the second catalyst layer (6) has Ag as the largest transition metal component by quantity and / or the third catalyst layer (8) has Pd as the largest transition metal component by quantity.

4. Multilayer electrocatalyst (2) according to one of the preceding claims, characterized in that that a gas diffusion layer (10) is provided for receiving the catalyst layers (4, 6, 8), wherein the gas diffusion layer preferably comprises a carbon-containing material, in particular in the form of a carbon cloth or carbon paper.

5. Multilayer electrocatalyst (2) according to one of the preceding claims, characterized in that that the first catalyst layer (4) and / or the second catalyst layer (6) and / or the third catalyst layer (8) is present in a ratio of 0.5 to 99 wt.%, based on the total mass of first catalyst layer (4), second catalyst layer (6) and third catalyst layer (8), preferably in a ratio of 33 wt.%.

6. Multilayer electrocatalyst system (1) for the electrochemical reduction of CO2 in ethylene glycol, comprising a plurality of interconnected Multilayer electrocatalysts (2) according to any one of the preceding claims.

7. Method for producing a multilayer electrocatalyst (2) according to any one of claims 1 to 5, comprising the steps: Coating (100a) a gas diffusion layer with a first catalyst suspension to form a first catalyst layer (4), coating (200a) the first catalyst layer (4) with a second catalyst suspension to form a second catalyst layer (6) and Coating (300a) the second catalyst layer (6) with a third catalyst suspension to form a third catalyst layer (8).

8. Method according to claim 7, characterized by that the first catalyst suspension and / or the second catalyst suspension and / or the third catalyst suspension comprises a catalyst powder and a solvent.

9. Method according to claim 8, characterized by that the first catalyst suspension and / or the second catalyst suspension and / or the third catalyst suspension additionally contains a binder and / or a conductive carbon black.

10. Method according to claim 8 or 9, characterized by that the first catalyst suspension and / or the second catalyst suspension and / or the third catalyst suspension is applied by one of the following application methods: drop coating, spin coating, spray coating or screen printing.

11. A method for the electrochemical conversion of CO2 to ethylene glycol, preferably using a multilayer electrocatalyst (2) according to any one of claims 1 to 5 or using a multilayer electrocatalyst system according to claim 6, comprising the steps: Conversion (100b) of CO2 to CO using a first catalyst layer (4) via electrochemical reduction, Conversion (200b) of CO to ethene using a second catalyst layer (6) and conversion (300b) of ethene to ethylene glycol using a third catalyst layer (8) via electrocatalytic conversion.

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