Electrochemical conversion of carbon dioxide to 1,2-dibromoethane

Abstract

The present disclosure provides a method to form 1,2-dibromoethane in an electrochemical reactor system. The electrochemical reactor system comprises an electrochemical cell having an anode, an anolyte, a cathode, a catholyte and a membrane, an anode compartment and a cathode compartment, wherein the anolyte is an aqueous solution comprising at least 20 mM bromide salt. The method comprises the steps of introducing carbon dioxide into the cathode compartment; applying a potential to the cathode, and allowing an electrochemical reaction to proceed forming reduction products at the cathode and oxidation products at the anode; and bringing the reduction products in contact with the oxidation products externally from the electrochemical cell and allowing the reduction products to react with the oxidation products to form 1,2-dibromoethane.

Description

[0001] Electrochemical conversion of carbon dioxide to 1,2-dibromoethane

[0002] Field of the invention

[0003] The present disclosure relates to the field of alternative methods to form 1,2-dibromoethane.

[0004] Background of the invention

[0005] Electrochemical reduction of carbon dioxide into useful chemicals is considered a promising approach to decrease the carbon dioxide concentration in the earth's atmosphere. Typically, the main products of these reactions are limited to hydrocarbons and oxygenates.

[0006] Ethylene dibromide, also known as 1,2-dibromoethane, is an industrially important compound and is for instance used as a reactant in the production of various commodity chemicals. Traditional methods to form 1,2-dibromoethane rely on feedstocks from steam cracking of natural gas which are accompanied with various environmental impacts.

[0007] Therefore, there are drawbacks accompanied with traditional methods to produce 1,2-dibromoethane.

[0008] Summary of the invention

[0009] The objective of the present disclosure is to overcome one or more drawbacks of the prior art and / or to improve the methods for producing 1,2-dibromoethane.

[0010] Itemized embodiments

[0011] According to a first aspect there is provided a method to form 1,2-dibromoethane in an electrochemical reactor system. The electrochemical reactor system comprises an electrochemical cell having an anode, an anolyte, a cathode, a catholyte and a membrane, wherein the membrane physically separates the electrochemical cell into an anode compartment and a cathode compartment, wherein the membrane is configured to allow ionic conductivity between the anolyte and the catholyte, and wherein the anolyte is an aqueous solution comprising at least 20 mM bromide salt. The method comprises the steps of introducing carbon dioxide into the cathode compartment; applying a potential of at least -0.6

[0012] V versus reversible hydrogen electrode to the cathode, but wherein the potential applied to the cathode is less than -2.0 V versus reversible hydrogen electrode, such as by applying a potential of -1.2

[0013] V versus reversible hydrogen electrode to the cathode, and allowing an electrochemical reaction to proceed forming reduction products at the cathode and oxidation products at the anode; and bringing the reduction products in contact with the oxidation products externally from the electrochemical cell and allowing the reduction products to react with the oxidation products to form 1,2-dibromoethane.

[0014] In some embodiments according to the first aspect, there is provided a method wherein in the step of applying a potential to the cathode, the applied potential is at least -0.7 V versus reversible hydrogen electrode, preferably at least -0.9 V versus reversible hydrogen electrode, but wherein the applied potential is less than -1.4 V versus reversible hydrogen electrode, more preferably less than -1.3 V versus reversible hydrogen electrode.

[0015] According to a second aspect there is provided a method to form 1,2-dibromoethane in an electrochemical reactor system. The electrochemical reactor system comprises an electrochemical cell having an anode, an anolyte, a cathode, a catholyte and a membrane, wherein the membrane physically separates the electrochemical cell into an anode compartment and a cathode compartment, wherein the membrane is configured to allow ionic conductivity between the anolyte and the catholyte, and wherein the anolyte is an aqueous solution comprising at least 20 mM bromide salt. The method comprises the steps of introducing carbon dioxide into the cathode compartment; applying a potential in a range of -2 V to -0.6 V versus reversible hydrogen electrode to the cathode, and allowing an electrochemical reaction to proceed forming reduction products at the cathode and oxidation products at the anode; and bringing the reduction products in contact with the oxidation products externally from the electrochemical cell and allowing the reduction products to react with the oxidation products to form 1,2-dibromoethane.

[0016] In some embodiments according to the first aspect, there is provided a method wherein in the step of applying a potential to the cathode, the applied potential is in a range of -1.4 V to -0.7 V versus reversible hydrogen electrode, preferably in a range of -1.3 V to -0.9 V versus reversible hydrogen electrode.

[0017] In some embodiments according to any aspect, there is provided a method wherein the catholyte is an aqueous solution.

[0018] In some embodiments according to any aspect, there is provided a method wherein the anolyte comprises at least 100 mM bromide salt, preferably at least 200 mM bromide salt, more preferably at least 500 mM bromide salt.

[0019] In some embodiments according to any aspect, there is provided a method wherein the membrane is a cation exchange membrane, an anion exchange, or a bipolar membrane, preferably wherein the membrane is a cation exchange membrane.

[0020] In some embodiments according to any aspect, there is provided a method wherein the cathode is a gas diffusion electrode and wherein the cathode compartment comprises a gas compartment, wherein the gas diffusion electrode is arranged at an interphase between the catholyte and the gas compartment; and wherein the step of bringing the reduction products in contact with the oxidation products is performed externally from the electrochemical cell by bringing the reduction products from the gas compartment in contact with the oxidation products from the anolyte.

[0021] In some embodiments according to any aspect, there is provided a method wherein the cathode comprises a transition metal, preferably wherein the cathode comprises copper.

[0022] In some embodiments according to any aspect, there is provided a method wherein the anolyte has a pH below 11, preferably below 9, more preferably pH below 8.

[0023] In some embodiments according to any aspect, there is provided a method wherein the electrochemical cell is an electrochemical flow cell.

[0024] Detailed description of the invention

[0025] The present patent disclosure relates to the field of methods to form 1,2-dibromoethane. More specifically, the present patent disclosure relates to methods in electrochemical reactor systems. A electrochemical reactor system according to the present disclosure comprises an electrochemical cell having an anode, an anolyte, a cathode, a catholyte and a membrane. The membrane physically separates the electrochemical cell into an anode compartment and a cathode compartment, wherein the membrane is configured to allow ionic conductivity between the anolyte and the catholyte, and wherein the anolyte is an aqueous solution comprising at least 20 mM bromide salt.

[0026] The method comprises according to a first aspect the steps of i) introducing carbon dioxide into the cathode compartment; ii) applying a potential of at least -0.6 V versus reversible hydrogen electrode to the cathode, but wherein the potential applied to the cathode is less than -2.0 V versus reversible hydrogen electrode, and allowing an electrochemical reaction to proceed forming reduction products at the cathode and oxidation products at the anode, and iii) bringing the reduction products in contact with the oxidation products externally from the electrochemical cell and allowing the reduction products to react with the oxidation products to form 1,2-dibromoethane.

[0027] The method comprises according to a second aspect the steps of i) introducing carbon dioxide into the cathode compartment; ii) applying a potential in a range of -2 V to -0.6 V versus reversible hydrogen electrode to the cathode, and allowing an electrochemical reaction to proceed forming reduction products at the cathode and oxidation products at the anode, and iii) bringing the reduction products in contact with the oxidation products externally from the electrochemical cell and allowing the reduction products to react with the oxidation products to form 1,2-dibromoethane.

[0028] A membrane that is configured to allow ionic conductivity between the anolyte and the catholyte according to the present invention may be a porous or a semipermeable polymer film that allow ionic conduction of ions in the anolyte and / or in the catholyte. Furthermore, the membrane may facilitate that the reduction products from the catholyte are brought in contact with oxidation products in the anolyte externally from the electrochemical cell.

[0029] The method according to the present disclosure results in the formation of 1,2-dibromoethane.

[0030] It is apparent to those skilled in the art that the application of a potential to the cathode may be performed for example by including a reference electrode to measure / control the potential of the cathode and / or anode during the application of a potential to the cathode.

[0031] Alternatively, those skilled in the art understand that the application of a potential to the cathode may also be performed by using a separate experiment to measure the cathode and anode potentials at relevant reaction conditions, and applying a potential between the cathode and the anode resulting in an applied potential of at least -0.6 V versus reversible hydrogen electrode to the cathode, but wherein the potential applied to the cathode is less than -2.0 V versus reversible hydrogen electrode.

[0032] Alternatively, those skilled in the art understand that the application of a potential to the cathode may also be performed by using a separate experiment to measure the cathode and anode potentials at relevant reaction conditions, and applying a potential between the cathode and the anode resulting in an applied potential in a range of -2 V to -0.6 V versus reversible hydrogen electrode to the cathode.

[0033] Application of a potential in a range of -2 V to -0.6 V versus reversible hydrogen electrode to the cathode results in the formation of reduction products at the cathode and oxidation products at the anode.

[0034] Application of a potential of at least -0.6 V versus reversible hydrogen electrode to the cathode, but wherein the potential applied to the cathode is less than -2.0 V versus reversible hydrogen electrode, results in the formation of reduction products at the cathode and oxidation products at the anode. In some embodiments, in the step of applying a potential to the cathode, the applied potential is at least -0.7 V versus reversible hydrogen electrode. This improves the yield of 1,2-dibromoethane. In some embodiments, in the step of applying a potential to the cathode, the applied potential is at least -0.9 V versus reversible hydrogen electrode. This further improves the yield of 1,2-dibromoethane. In some embodiments, in the step of applying a potential to the cathode, the applied potential is less than -1.4

[0035] V versus reversible hydrogen electrode. This further improves the yield of 1,2-dibromoethane. In some embodiments, in the step of applying a potential to the cathode, the applied potential is less than -1.3

[0036] V versus reversible hydrogen electrode. This further improves the yield of 1,2-dibromoethane.

[0037] In some embodiments, in the step of applying a potential to the cathode, the applied potential is in a range of -1.4 V to -0.7 V versus reversible hydrogen electrode which further improves the yield of 1,2- dibromoethane. In some embodiments, in the step of applying a potential to the cathode, the applied potential is preferably in a range of -1.3 V to -0.9 V versus reversible hydrogen electrode which further improves the yield of 1,2-dibromoethane.

[0038] In some embodiments according to the present disclosure the catholyte is an aqueous solution. An aqueous catholyte increase the ionic conductivity between the cathode and the anode, in turn resulting in lower resistance and higher efficiency for the formation of 1,2-dibromoethane.

[0039] In some embodiments according to the present disclosure the anolyte comprises at least 100 mM bromide salt. Increasing the concentration of bromide salt in the anolyte increases the yield of 1,2- dibromoethane. Preferably the concentration of bromide salt in the anolyte is at least 200 mM bromide salt, more preferably at least 500 mM bromide salt.

[0040] In some embodiments according to the present disclosure the membrane is a cation exchange membrane, an anion exchange, or a bipolar membrane. The use of these membranes further increases the yield of 1,2-dibromoethane. It may be, without being bound by theory, due to the separation of reduction products from the anode and avoiding oxidation of the reduction products, as well as separation of the oxidation products from the cathode and avoiding reduction of the oxidation product, and that the reduction products are brought in contact with the oxidation products externally from the electrochemical cell. Preferably the membrane is a cation exchange membrane. This further improves the ionic conductivity across the membrane resulting in lower resistance and higher efficiency for the formation of 1,2-dibromoethane.

[0041] In some embodiments according to the present disclosure the cathode is a gas diffusion electrode and the cathode compartment comprises a gas compartment. The gas diffusion electrode is arranged at an interphase between the catholyte and the gas compartment. In some embodiments according to the present disclosure the step of bringing the reduction products in contact with the oxidation products is performed by bringing the reduction products from the gas compartment in contact with the oxidation products from the anolyte. The use of a gas diffusion electrode enhances mass transport of carbon dioxide to and reduction products from the cathode, thereby increasing the yield of 1,2-dibromoethane.

[0042] In some embodiments according to the present disclosure the cathode comprises a transition metal. Cathodes comprising transition metals improves the yield of 1,2-dibromoethane. Preferably the cathode comprises copper. This further improves the yield of 1,2-dibromoethane.

[0043] In some embodiments according to the present disclosure the anolyte has a pH below 11. This further improves the yield of 1,2-dibromoethane. Preferably the anolyte has a pH below 9, more preferably pH below 8. This further improves the yield of 1,2-dibromoethane. In some embodiments according to the present disclosure the electrochemical cell is an electrochemical flow cell. The use of an electrochemical flow cell enhances mass transport of carbon dioxide to and reduction products from the cathode as well as reactants to and oxidation products from the anode. The use of an electrochemical flow cell further allows the reactants and products to flow through the electrochemical cell allowing the reduction products to react with the oxidation products externally from the electrochemical cell, thereby increasing the yield of 1,2-dibromoethane.

[0044] Brief description of figures

[0045] The accompanying drawings are used to illustrate presently preferred non-limiting exemplary embodiments of devices used for the method according to the present disclosure. The above and other advantages of the features and objects of the disclosure will become more apparent, and the aspects and embodiments will be better understood from the following detailed description when read in conjunction with the accompanying drawings, in which:

[0046] Figure 1 is a schematic drawing of an electrochemical reactor system according to some embodiments of the present disclosure.

[0047] Figure 2 is a schematic drawing of an electrochemical reactor system according to some embodiments of the present disclosure.

[0048] Figure 3 is a schematic drawing of an electrochemical reactor system according to some embodiments of the present disclosure.

[0049] Detailed description of preferred embodiments

[0050] Figure 1 is a schematic drawing of an electrochemical reactor system 11 according to some embodiments of the present disclosure. In some embodiments, the electrochemical reactor system 11 comprises an electrochemical cell 51 comprising an anode 700, an anolyte 100, a cathode 500, a catholyte 200 and a membrane 400. The membrane 400 physically separates the electrochemical cell 51 into an anode compartment and a cathode compartment 101.

[0051] In some embodiments the cathode 500 is a gas diffusion electrode wherein the cathode compartment 101 comprises a gas compartment 300, wherein the gas diffusion electrode is arranged at the interphase between the catholyte 200 and the gas compartment 300.

[0052] In some embodiments, the gas diffusion electrode is a carbon-based material, such as a non-woven carbon paper treated with polytetrafluoroethylene, comprising a transition metal.

[0053] In some embodiments, the anode is a titanium frit comprising platinum or a carbon paper. In some embodiments, the electrochemical cell 51 comprises an anolyte inlet 110, and anolyte outlet 120, a catholyte inlet 210, a catholyte outlet 220, a gas inlet 310, a gas outlet 320, and valves 61.

[0054] In some embodiments, the gas outlet 320 is connected to 53 the anolyte outlet 120 externally from the electrochemical cell 51, and the electrochemical reactor system 11 comprises a section 55 arranged to bring the reduction products in contact with the oxidation products.

[0055] In some embodiments, a potential is applied between a cathode contact 550 and an anode contact 750.

[0056] Figure 2 is a schematic drawing of an electrochemical reactor system 21 according to some embodiments of the present disclosure. In some embodiments, the electrochemical cell 52 is an electrochemical flow cell. In some embodiments, carbon dioxide is introduced to the gas compartment 300 continuously through the gas inlet 310, and gas is withdrawn continuously from the gas outlet 320.

[0057] In some embodiments, anolyte is introduced to the anolyte compartment 100 continuously through the anolyte inlet 110, and anolyte is withdrawn continuously from the anolyte outlet 120.

[0058] In some embodiments, catholyte is introduced to the catholyte compartment 200 continuously through the catholyte inlet 210, and catholyte is withdrawn continuously from the catholyte outlet 220.

[0059] Figure 3 is a schematic drawing of an electrochemical reactor system 31 according to some embodiments of the present disclosure. In some embodiments, the electrochemical cell 50 is an electrochemical flow cell comprising valves 61.

[0060] In some embodiments, the volume occupied by the catholyte is minimized, i.e. the cathode 500 is in contact with the membrane 400, and the cathode 500 is a gas diffusion electrode wherein the cathode compartment 103 comprises a gas compartment 300. The cathode 500 is arranged at the interphase between the catholyte and the gas compartment 300.

[0061] In some embodiments, the volume occupied by the anolyte between the anode and the membrane is minimized, i.e. the anode is in contact with the membrane 400.

[0062] As apparent to those skilled in the art, movement of ions between the cathode 500 and the anode 700 is required for the completion of the internal circuit of the electrochemical cell 50. The catholyte is the substance that allows the movement of ions between the cathode 500 and the membrane 400. Similarly, the anolyte 100 is the substance that allows the movement of ions between the anode 700 and the membrane 400. The anolyte 100 is an aqueous solution comprising at least 20 mM bromide salt. In some embodiments, with reference to Figure 3, the membrane 400 may be an ion exchange membrane, such as a persulfonic acid membrane in its protonic form, and the cathode 500 may be a gas diffusion electrode, such as a non-woven carbon paper, wherein the gas diffusion electrode is arranged in contact with the membrane 400, and the anolyte 100 is an aqueous solution comprising at least 20 mM bromide salt. In such arrangement, the permeability of water through the membrane 400 would lead to water (moisture) between the cathode 500 and the membrane 400 in the cathode compartment 103. The water between the membrane 400 and the cathode 500 would for such setup be the catholyte.

[0063] In some embodiments, with reference to Figure 3, the anode 700 may be a non-woven carbon paper, wherein the anode 700 is arranged in contact with the membrane 400, and the anolyte 100 is an aqueous solution comprising at least 20 mM bromide salt is soaked through the pores of the nonwoven carbon paper serving as the anode 700.Although the present disclosure has been described with reference to specific embodiments also shown in the appended drawings, it will be apparent to those skilled in the art that many variations and modifications may be done within the scope of the present disclosure as described in the specification and defined with reference to the claims below.

[0064] For instance, it is apparent to those skilled in the art that features found in a specific embodiment referred to in Figure 1, Figure 2 or Figure 3 may be used in combination with and / or replace features found in another specific embodiment referred to in Figure 1, Figure 2 or Figure 3.

[0065] Examples

[0066] Example 1

[0067] Gas diffusion electrode was pretreated by electrochemical deposition of Cu on a microporous layer of a gas diffusion electrode (Sigracet 39 BB, Fuel Cell Store: a non-woven carbon paper with treated with 5 wt-% polytetrafluoroethylene (PTFE) with a 0.315 mm thickness and an air permeability of 1.5 Gurley sec). An electrochemical flow cell was assembled comprising inlet and outlet for gas, anolyte and catholyte, respectively.

[0068] An anolyte compartment was separated from the catholyte compartment by a proton exchange membrane, the proton exchange membrane employed was a 170 pm thick perfluorsulfonic acid membrane in its protonic form (PFSA D170-U Proton Exchange Membrane, Fuel Cell Store). A 1 cm2piece of platinized titanium frit was arranged in the anolyte compartment and employed as an anode. A Ag / AgCI was employed as a reference electrode inserted in the catholyte compartment. A 1 cm2piece of the gas diffusion electrode was employed as a cathode and separated the catholyte from the gas compartment. Aqueous solutions of 1 M KBr (aq.) with pH 2, pH 3, and pH 4 (adjusted with solution of HBr), pH 6, as well as pH 8, and pH 12 (adjusted with solution of KOH) were employed as anolytes. The anolyte compartment was filled with 30 mL of the anolyte and anolyte was flowed through the electrochemical flow cell at a rate of 4 mL / min.

[0069] An aqueous solution of 1 M KBr (aq.) with pH 6 was employed as a catholyte. The catholyte compartment was filled with 20 mL of the catholyte and catholyte was flowed through the electrochemical flow cell at a rate of 4 mL / min.

[0070] Carbon dioxide was introduced to the gas compartment at a flow rate of 5 mL / min.

[0071] A potential of -1.2 V vs. RHE was applied to the cathode for 10 minutes.

[0072] The outlet from the gas compartment and the outlet from the anolyte compartment were connected to a single 5 m long polytetrafluoroethylene (PTFE) tube with inner diameter of 1.5 mm. The PTFE tube was arranged to bring the reduction products from the gas compartment in contact with the oxidation products from the anolyte compartment in contact.

[0073] Additionally, one electrochemical cell without proton exchange membrane was assembled, that is without separation of the anolyte and the catholyte but instead a common electrolyte. The electrolyte employed in this experiment was 1 M KBr (aq.) with pH 6.

[0074] Example 2

[0075] A gas diffusion electrode (GDE) (10 cm2, 3.33 x 3.33 cm) was prepared according to example 1, by electrochemical deposition of Cu onto the microporous layer of a gas diffusion electrode (Sigracet 39 BB, Fuel Cell Store). The GDE consisted of a non-woven carbon paper treated with 5 wt-% polytetrafluoroethylene (PTFE), with a thickness of 0.315 mm and an air permeability of 1.5 Gurley sec.

[0076] The GDE was positioned in contact with a proton exchange membrane. The proton exchange membrane employed was a 170 pm thick perfluorosulfonic acid membrane in its protonic form (PFSA D170-U Proton Exchange Membrane, Fuel Cell Store).

[0077] The opposite side of the proton exchange membrane was in contact with two layers of carbon paper (AvCarb MGL-370, Fuel Cell Store), each having a surface area of 10 cm2(3.33 x 3.33 cm) serving as the anode.

[0078] An aqueous solution of 1 M KBr at pH 2 was employed as the anolyte. The anolyte compartment was filled with 30 mL of the anolyte, which was circulated through the electrochemical flow cell at a flow rate of 4 mL / min. Carbon dioxide (CO2) was introduced into the gas compartment at a flow rate at a flow rate of 20 mL / min. A total cell potential of 4.0 V was applied for 10 minutes. The outlets from both the gas compartment and the anolyte compartment were connected to a single 5 m long polytetrafluoroethylene (PTFE) tube with an inner diameter of 1.5 mm. The PTFE tube was arranged to facilitate contact between the reduction products from the gas compartment and the oxidation products from the anolyte compartment.

[0079] Results

[0080] Results from example 1:

[0081] The exhaust gas from the gas compartment was analyzed with solid phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS).

[0082] Additionally, the outputs from the PTFE tube were analyzed with solid phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS).

[0083] Results are summarized in the table below.

[0084] Table 1. The areas of 1,2-dibromoethane and of tribromomethane peaks at different pH of the anolyte as well as the yield of 1,2-dibromoethane.

[0085] The analysis of the amount of ethylene in the exhaust gas and the amount of ethylene in the output from the PTFE tube showed quantitative transformation of the ethylene.

[0086] Results from example 2:

[0087] The output from the PTFE tube was analyzed by solid-phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS). SPME GC-MS revealed the formation of 13.4 mg of dibromoethane, with a Faradaic efficiency of 46%. T e present disclosure comprises the following embodiments:

[0088] 1. A method to form 1,2-dibromoethane in an electrochemical reactor system; wherein the electrochemical reactor system comprises an electrochemical cell having an anode, an anolyte, a cathode, a catholyte and a membrane, wherein the membrane physically separates the electrochemical cell into an anode compartment and a cathode compartment, wherein the membrane is configured to allow ionic conductivity between the anolyte and the catholyte, and wherein the anolyte is an aqueous solution comprising at least 20 mM bromide salt; and wherein the method comprises the steps of: i) introducing carbon dioxide into the cathode compartment; ii) applying a potential of at least -0.6 V versus reversible hydrogen electrode to the cathode, but wherein the potential applied to the cathode is less than -2.0 V versus reversible hydrogen electrode, and allowing an electrochemical reaction to proceed forming reduction products at the cathode and oxidation products at the anode, and iii) bringing the reduction products in contact with the oxidation products externally from the electrochemical cell and allowing the reduction products to react with the oxidation products to form 1,2-dibromoethane.

[0089] 2. A method according to embodiment 1, wherein in the step of applying a potential to the cathode, the applied potential is at least -0.7 V versus reversible hydrogen electrode, preferably at least -0.9 V versus reversible hydrogen electrode, but wherein the applied potential is less than -1.4 V versus reversible hydrogen electrode, more preferably less than -1.3 V versus reversible hydrogen electrode.

[0090] 3. A method according to any one of the preceding embodiments, wherein the catholyte is an aqueous solution.

[0091] 4. A method according to any one of the preceding embodiments, wherein the anolyte comprises at least 100 mM bromide salt, preferably at least 200 mM bromide salt, more preferably at least 500 mM bromide salt. 5. A method according to any one of the preceding embodiments, wherein the membrane is a cation exchange membrane, an anion exchange, or a bipolar membrane, preferably wherein the membrane is a cation exchange membrane.

[0092] 6. A method according to any one of the preceding embodiments, wherein the cathode is a gas diffusion electrode and wherein the cathode compartment comprises a gas compartment, wherein the gas diffusion electrode is arranged at an interphase between the catholyte and the gas compartment; and wherein the step of bringing the reduction products in contact with the oxidation products is performed by bringing the reduction products from the gas compartment in contact with the oxidation products from the anolyte.

[0093] 7. A method according to anyone of the preceding embodiments, wherein the cathode comprises a transition metal, preferably wherein the cathode comprises copper.

[0094] 8. A method according to any one of the preceding embodiments, wherein the anolyte has a pH below 11, preferably below 9, more preferably pH below 8.

[0095] 9. A method according to any one of the preceding embodiments, wherein the electrochemical cell is an electrochemical flow cell.

Claims

Claims1. A method to form 1,2-dibromoethane in an electrochemical reactor system (11, 21, 31); wherein the electrochemical reactor system (11, 21, 31) comprises an electrochemical cell (51, 52, 50) having an anode (700), an anolyte (100), a cathode (500), a catholyte (200) and a membrane (400), wherein the membrane (400) physically separates the electrochemical cell (51, 52, 50) into an anode compartment and a cathode compartment (101, 103), wherein the membrane (400) is configured to allow ionic conductivity between the anolyte (100) and the catholyte (200), and wherein the anolyte (100) is an aqueous solution comprising at least 20 mM bromide salt; and wherein the method comprises the steps of: i) introducing carbon dioxide into the cathode compartment (101, 103); ii) applying a potential in a range of -2 V to -0.6 V versus reversible hydrogen electrode to the cathode, and allowing an electrochemical reaction to proceed forming reduction products at the cathode (500) and oxidation products at the anode (700), and iii) bringing the reduction products in contact with the oxidation products externally from the electrochemical cell (51, 52, 50) and allowing the reduction products to react with the oxidation products to form 1,2-dibromoethane.

2. A method according to claim 1, wherein in the step of applying a potential to the cathode (500), the applied potential is in a range of -1.4 V to -0.7 V versus reversible hydrogen electrode, preferably in a range of -1.3 V to -0.9 V versus reversible hydrogen electrode.

3. A method according to any one of the preceding claims, wherein the catholyte (200) is an aqueous solution.

4. A method according to any one of the preceding claims, wherein the anolyte (100) comprises at least 100 mM bromide salt, preferably at least 200 mM bromide salt, more preferably at least 500 mM bromide salt.

5. A method according to any one of the preceding claims, wherein the membrane (400) is a cation exchange membrane, an anion exchange, or a bipolar membrane, preferably wherein the membrane (400) is a cation exchange membrane.

6. A method according to any one of the preceding claims, wherein the cathode (500) is a gas diffusion electrode and wherein the cathode compartment (101, 103) comprises a gas compartment (300), wherein the gas diffusion electrode is arranged at an interphase between the catholyte (200) and the gas compartment (300); and wherein the step of bringing the reduction products in contact with the oxidation products is performed by bringing the reduction products from the gas compartment (300) in contact with the oxidation products from the anolyte (100).

7. A method according to any one of the preceding claims, wherein the cathode (500) comprises a transition metal, preferably wherein the cathode (500) comprises copper.

8. A method according to any one of the preceding claims, wherein the anolyte (100) has a pH below 11, preferably below 9, more preferably pH below 8.

9. A method according to any one of the preceding claims, wherein the electrochemical cell (51, 52, 50) is an electrochemical flow cell.

Images