Electrolyte solution and method for producing same

Abstract

The electrolyte solution contains an electrolyte solution in which the amount of the electrolyte solution used is between 1 wt% and 10 wt% of the weight of the electrolyte solution, an ionic liquid in which the amount of the ionic liquid used is between 1 wt% and 5 wt% of the weight of the electrolyte solution, and a solvent in which the solvent is used in an amount of 75 wt% to 99 wt% of the weight of the electrolyte solution.

Description

[Technical Field]

[0001] The present invention relates to an electrolyte solution and a method for producing the same, and more particularly to an electrolyte solution used in a forward osmosis-electrolytic accumulation process. [Background technology]

[0002] Water electrolysis is a method for producing hydrogen because it uses renewable water and produces pure oxygen as a by-product. The electrolysis process uses an electric current to split water (H2O) into hydrogen (H2) and oxygen (O2). Alkaline water electrolysis is a type of industrial electrolysis.

[0003] The most common electrolyte for alkaline water electrolysis is potassium hydroxide (KOH) because it has the best electrical conductivity within the temperature range of 50 to 80 °C. Another aspect is the solubility of the product gas in the electrolyte, as this affects the purity of the final product gas.

[0004] Another approach is to use ionic liquids as electrolytes or additives, thanks to their excellent performance. Their negligible vapor pressure, non-flammability, and thermal stability are compelling reasons for their application in water electrolysis. Furthermore, ionic liquids can be used in a wide electrochemical window. They also enable highly efficient water electrolysis at low temperatures. However, splitting water into hydrogen and oxygen requires a large amount of energy, which also leads to higher energy consumption.

[0005] Therefore, it is necessary to determine an electrolyte solution containing a mixture of electrolyte and ionic liquid so that the yield of hydrogen and oxygen can be improved under low energy consumption. DETAILED DESCRIPTION OF THE INVENTION

[0006] The present invention includes the use of an electrolyte in an amount of 1 wt% to 10 wt% of the weight of the electrolyte solution, the use of an ionic liquid in an amount of 1 wt% to 5 wt% of the electrolyte solution, and the use of a solvent in an amount of 75 wt% to 99 wt% of the electrolyte solution.

[0007] Other aspects, features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the drawings and preferred embodiments of the invention. Abbreviation details Emim.MeSO3: 1-Ethyl-3-methylimidazolium methanesulfonate Emim.Otf: 1-ethyl-3-methylimidazolium trifluoromethanesulfonate H2: Hydrogen KOH: Potassium hydroxide NaCl: Sodium chloride NaOH: Sodium hydroxide NaSc: sodium saccharin Details of the invention Detailed descriptions of preferred embodiments of the present invention are disclosed. However, it should be understood that these embodiments are merely examples of the present invention, and that the present invention can be embodied in various forms. Therefore, the details disclosed herein are not limiting, but should be construed only as a basis for the claims and used to teach the present invention to those skilled in the art. Numerical data or ranges used in the specification should not be construed as limiting.

[0008] The present invention relates to electrolyte solutions and methods for making same, and more particularly to electrolyte solutions used in forward osmosis and electrolysis processes. For purposes of this invention and the appended claims, the term "liquid feed stream" refers to any feed stream that contains water, such as, but not limited to, wastewater, brine, seawater, groundwater, tap water, and stormwater.

[0009] A first aspect of the present invention is an electrolyte solution comprising: The amount of electrolyte used is 1 wt% to 10 wt% of the electrolyte solution, preferably 8 wt%, and the electrolyte is selected from the group consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH), sodium chloride (NaCl) and mixtures thereof, preferably KOH, The ionic liquid is selected from the group consisting of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (Emim.Otf), 1-ethyl-3-methylimidazolium methanesulfonate (Emim.MeSO3) and mixtures thereof, preferably Emim.Otf, and The amount of solvent used is 75 wt% to 99 wt% of the electrolyte solution, preferably 78 wt%. The solvent is deionized water. The electrolyte solution further contains an additive in an amount of 0 wt % to 10 wt % of the electrolyte solution, preferably 10 wt %, and the additive is saccharin sodium.

[0010] Table 1 shows the chemical components and their compositions used in the electrolyte solution of the present invention. Table 1: Chemical components and their composition used in the electrolyte solution of the present invention

[0011] [Table 1]

[0012] The additive is optional and is used in the integrated process of forward osmosis and electrolysis. If the electrolyte is used in a conventional electrolysis process, it may not contain any additive. The additive has an important effect in the integrated process of forward osmosis and electrolysis, as it increases the osmotic pressure and improves the yield of the target gases (hydrogen and oxygen), and the results are explained in the Examples section below.

[0013] A second aspect of the present invention discusses a method for preparing said electrolyte solution, said method comprising the steps of: i. Add the electrolyte to the container; ii. adding an ionic liquid via a pump to the vessel of step (i) to form a first mixture; iii. optionally, adding an additive to the first mixture obtained in step (ii) to form a second mixture; and iv. Add the solvent to the second mixture obtained in step (iii) under stirring at 25°C under a pressure of 1 atmosphere for 30 minutes or until the mixture is uniformly dissolved to produce the electrolyte solution of the present invention. Stirrs that can be used include, but are not limited to, a magnetic stirrer, a mechanical stirrer, and a stirrer.

[0014] With reference to the above method, step (ii) should be carried out using a fume hood or suction arm to prevent inhalation of the ionic liquid. A third aspect of the present invention contemplates the use of the electrolyte of the present invention in, but not limited to, forward osmosis and electrolysis integrated processes, alkaline water electrolysis, and other conventional electrolysis processes, such as plating and metal extraction. The electrolyte of the present invention is not suitable for acid water electrolysis.

[0015] The following embodiments are intended to illustrate the present invention in a non-limiting manner. Test results Using the components listed in Table 1, the electrolyte solution of the present invention is prepared using the method described in the second aspect of the present invention, and this is used in the method described in the fourth aspect of the present invention.

[0016] Electrolyte solution test results Different electrolytes are evaluated by cyclic voltammetry tests. Cyclic voltammetry tests are used to evaluate the electrochemical potential window of the electrolyte and the corresponding current density at each applied voltage. For the present invention, electrochemical impedance spectroscopy (EIS) tests are performed using 10 milliliters of electrolyte in a small container, employing a three-electrode system. The electrode system used consists of a platinum plate as the working electrode and a counter electrode, and a saturated mercury electrode as the reference electrode. The results for the composite electrolyte show the highest current density recorded for each substance based on response surface methodology (RSM).

[0017] In Table 2, Group 1 refers to a conventional electrolyte solution containing 10 wt% KOH and 90 wt% deionized water. Group 2 represents an electrolyte solution of the present invention, containing 4.29 wt% Emim.Otf, 8.31 wt% KOH, and 97.4 wt% deionized water. Group 3 represents an electrolyte solution of the present invention, containing 4.3 wt% Emim.Otf, 8.31 wt% KOH, 10 wt% NaSc, and 77.39 wt% deionized water.

[0018] Table 2 shows the cyclic voltammetry test results of the electrolytes of the present invention. Table 2: Cyclic voltammetry test results for electrolytes of the present invention

[0019] [Table 2]

[0020] From Table 2, it is clear that Groups 2 and 3 of the present invention can exhibit considerable current density values. It should be understood that the higher the current density, the higher the electrolysis rate and the yield of hydrogen and oxygen. It is also clear that Groups 2 and 3 of the present invention have higher current densities than Group 1, indicating that Groups 2 and 3 of the present invention provide higher hydrogen and oxygen yields during the electrolysis process.

[0021] In Table 3, Group 1 refers to a conventional electrolyte solution containing 10 wt% KOH and 90 wt% deionized water. Group 2 represents an electrolyte solution of the present invention, containing 5 wt% Emim.Otf, 10 wt% KOH, and 85 wt% deionized water. Group 3 represents an electrolyte solution of the present invention, containing 5 wt% Emim.Otf, 10 wt% KOH, 10 wt% NaSc, and 75 wt% deionized water.

[0022] Table 3 shows the results of H2 yield and current density and specific energy consumption of the corresponding electrolytes of the present invention. Table 3: H2 yield, current density and specific energy consumption results of the corresponding electrolytes of the present invention.

[0023] [Table 3]

[0024] According to Table 3, it is clear that Groups 2 and 3 of the present invention have higher current density and H yield under lower energy consumption compared to the conventional electrolyte solution (Group 1), which indicates that Groups 2 and 3 of the present invention are more efficient in producing H than the conventional electrolyte solution (Group 1).

[0025] Test results of the application of the electrolyte of the present invention using forward osmosis and electrolytic accumulation processes A method for generating hydrogen and oxygen from a liquid feed stream, achieved by an integrated forward osmosis and electrolysis system, said method comprising the steps of:

[0026] Water is pumped from a liquid feed stream in contact with one side of a forward osmosis membrane by forward osmosis due to the osmotic pressure difference between the liquid feed stream and the electrolyte solution and fed to the electrolyte solution; and • Applying a voltage to the electrolyte solution to produce hydrogen and oxygen, and the electrolyte solution contacts the other side of the forward osmosis membrane; The steps are performed simultaneously, and the electrolyte solution is as described in the first aspect of the present invention, and the electrolyte solution further comprises an additive. The method includes applying a voltage to the electrolyte solution, the applied voltage being in the range of 1.8 V to 2.4 V. The method further includes injecting water into the electrolyte solution through a forward osmosis membrane by forward osmosis, the forward osmosis membrane being wetted with ethanol at a concentration of 99% prior to use in the method.

[0027] The electrolyte solution of the present invention acts as an absorbent in a forward osmosis process, drawing water molecules from a liquid feed stream through the forward osmosis membrane, and simultaneously acts as an electrolyte in an electrolysis process, converting the water molecules into hydrogen and oxygen.

[0028] The osmolality of the electrolyte solution of the present invention is greater than the osmolality of the liquid feed stream. Also, the osmotic pressure of the electrolyte solution of the present invention is greater than the osmotic pressure of the liquid feed stream. Because the osmotic pressure and osmolality of the electrolyte solution of the present invention are greater than the osmotic pressure and osmolality of the liquid feed stream, water molecules pass from the liquid feed stream through the forward osmosis membrane into the electrolyte solution by forward osmosis. It should be understood that the higher the electrical conductivity of the aqueous solution, the higher the permeation molality and permeation pressure.

[0029] The conductivity of the electrolyte solution of the present invention is at least 36.67 mS / cm, preferably between 36.67 mS / cm and 323.42 mS / cm, and most preferably between 250 mS / cm and 323.42 mS / cm. The conductivity of the liquid feed stream is at least 0.001 mS / cm, preferably between 0.002 mS / cm and 0.01 mS / cm, and most preferably between 0.002 mS / cm and 0.005 mS / cm.

[0030] The conductivity difference between the liquid feed stream and the electrolyte solution of the present invention is at least 36.66 mS / cm, with the electrolyte solution having a higher conductivity than the liquid feed stream, preferably between 36.66 mS / cm and 323.23 mS / cm, and most preferably between 250 mS / cm and 323.23 mS / cm.

[0031] The electrolyte solution in contact with the other side of the forward osmosis membrane is contained in an electrochemical cell. The electrochemical cell includes an anode and a cathode that allow a voltage to be applied to the electrolyte solution. When a voltage is applied to the electrolyte solution, water molecules are converted to hydrogen gas and hydroxide ions at the anode, and the hydroxide ions are converted to oxygen gas and water molecules at the cathode.

[0032] The net reaction converting two water molecules into two hydrogen molecules and one oxygen molecule is:

[0033] [ka]

[0034] Table 4 shows the amount of hydrogen gas generated under a specific energy consumption when using a conventional electrolyte solution containing 10 wt% KOH and 90 wt% deionized water, and an electrolyte solution of the present invention containing 10 wt% KOH, 3.69 wt% Emim.Otf, and 86.31 wt% deionized water, obtained by applying the method described in the second aspect of the present invention.

[0035] Table 4: Hydrogen gas generation results under specific energy consumption in conventional electrolyte solution using KOH and the electrolyte solution of the present invention

[0036] [Table 4]

[0037] According to Table 4, the amount of hydrogen gas produced using the electrolyte solution of the present invention under a certain specific energy consumption is higher than the amount of hydrogen gas produced using the conventional electrolyte solution under a certain specific energy consumption, which indicates that energy consumption is reduced by applying the electrolyte solution of the present invention and the method described in the second aspect of the present invention.

[0038] Table 5 shows the water flow rates from wastewater through forward osmosis into an electrolyte solution of the present invention containing 10 wt% KOH, 3.69 wt% Emim.Otf, and 86.31 wt% deionized water, and into a conventional electrolyte solution containing 10 wt% KOH and 90 wt% deionized water.

[0039] Table 5: Water flow rate by forward osmosis from wastewater to KOH in conventional electrolyte solution and in the electrolyte solution of the present invention.

[0040] [Table 5]

[0041] According to Table 5, the water flux from wastewater to the electrolyte solution of the present invention by forward osmosis is higher than the water flux from wastewater to the conventional electrolyte solution by forward osmosis, indicating that the electrolyte solution of the present invention, which is the absorption liquid, increases the efficiency of the forward osmosis process.

[0042] Overall, the electrolyte solution of the present invention increases the rate of hydrogen and oxygen production with lower energy consumption. The terms used herein are used only to describe particular exemplary embodiments and are not intended to be limiting. As used herein, the singular forms "one," "one," and "it" can also include the plural unless the context clearly indicates otherwise. The terms "comprise," "including," and "having" are inclusive and thus specify the presence of features, integers, steps, operations, components, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, components, components, and / or groups thereof.

[0043] The method steps, processes, and operations described herein need not be construed as requiring execution in the particular order described or illustrated, unless an order of execution is explicitly identified. It should also be understood that additional or alternative steps may be employed. The use of the phrase "at least" or "at least one" implies the use of one or more elements, as in one embodiment, the use of the phrase may be to achieve one or more desired purposes or results.

Claims

1. An electrolyte solution comprising: An electrolyte in which the amount of electrolyte used is 1 wt % to 10 wt % of the electrolyte solution; an ionic liquid in an amount of 1 wt % to 5 wt % of the weight of the electrolyte solution; and 75 wt % to 99 wt % of the electrolyte solution is a solvent.

2. The electrolyte solution according to claim 1, further comprising an additive, the amount of the additive being 0 wt % to 10 wt % of the weight of the electrolyte solution.

3. 2. The electrolyte solution of claim 1, wherein the electrolyte is selected from the group consisting of potassium hydroxide, sodium hydroxide, sodium chloride, and mixtures thereof.

4. 2. The electrolyte solution according to claim 1, wherein the ionic liquid is 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium methanesulfonate (Emim. MeSO ３ ) and mixtures thereof.

5. 10. The electrolyte solution of claim 1, wherein the solvent is deionized water.

6. 3. The electrolyte solution of claim 2, wherein the additive is sodium saccharin.

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