Ion exchange filters useful for electrochemical systems
Patent Information
- Application Number
- KR1020267021794
- Authority / Receiving Office
- KR · KR
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-01-23
- Filing Date
- 2025-01-23
- Publication Date
- 2026-09-21
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Figure P1020267021794_ABST
Abstract
Description
Technology Field
[0001] Cross-reference regarding related applications
[0002] This application claims priority under 35 USC § 365(c) to European Patent Application No. 24305130 filed January 23, 2024, the entirety of which is incorporated herein by reference.
[0003] Technology field
[0004] The present invention relates to the field of ion exchange filters, particularly ion exchange filters having a mixed resin layer, and to the use of such ion exchange filters for purifying streams of aqueous fluids, such as coolant streams in fuel cells, batteries, or electrolytic cells. A method for purifying aqueous fluids using ion exchange filters is further provided. Background Technology
[0005] To more fully describe the latest technology related to the present invention, this specification incorporates several patents, patent applications, and publications. The full disclosures of each of these patents, patent applications, and publications are incorporated herein by reference.
[0006] Electrochemical systems involve converting chemical energy into electrical energy or vice versa through electrochemical reactions. Examples of electrochemical systems include batteries, battery chargers, fuel cells, and electrolyzers. These systems are widely used in various applications, such as portable electronic devices, electric vehicles, and renewable energy technologies.
[0007] A battery converts chemical energy into electrical energy through an electrochemical reaction process between two or more electrodes and an electrolyte. Inside the battery, chemical reactions occur, causing electrons to flow from the negative electrode (anode) to the positive electrode (cathode). This flow of electrons generates an electric current that can be used to power external devices. The electrolyte acts as a medium to transfer ions between the anode and the cathode. As the battery discharges, the chemical reactions that generate the current may begin to slow down, and the battery eventually becomes completely discharged. The battery can be recharged by a charger that applies an external current to reverse the electrochemical reaction.
[0008] Batteries and chargers require coolants to help manage their temperatures during charging and discharging. Batteries and chargers can generate excessive heat during operation, particularly during rapid discharge or charging. This heat can lead to a degradation in the performance and lifespan of the battery or charger, and in extreme cases, may cause safety issues such as thermal runaway or explosion. Coolants are used to help dissipate heat from the battery or charger by absorbing heat from internal elements—such as battery cells or plates—where energy is dissipated as heat rather than electrical potential, and transferring it away. Therefore, coolants help maintain the operating temperature of the battery or charger within a safe range. Additionally, coolants can help prevent the electrolyte from freezing or boiling in extreme temperature environments.
[0009] More specifically, electric vehicle chargers convert alternating current (AC) into direct current (DC) compatible with electric vehicle batteries. This conversion generates heat. For example, a typical 22 kW AC charger provides enough charge to add 200 km of driving range in 120 minutes. To reduce the charging time for 200 km of driving range to 16 minutes, a 150 kW DC charging station is required. According to a report by the U.S. Department of Energy, the temperature of a battery pack can rise to over 270°C during a 10-minute fast charge; therefore, an effective and improved thermal management system is necessary to prevent overheating at these power levels. For example, https: / / www.energy.gov / sites / prod / files / 2017 / 10 / f38 / Refer to the literature [Enabling Fast Charging: A Technology Gap Assessment, published by the Office of Energy Efficiency and Renewable Energy of the US Department of Energy] found in [Enabling Fast Charging: A Technology Gap Assessment, published by the Office of Energy Efficiency and Renewable Energy of the US Department of Energy].
[0010] Traditionally, air cooling has been the preferred solution, but liquid cooling has proven to be the most effective. The heat capacity of water—that is, the ratio of the amount of heat absorbed by water to the resulting temperature change—is 3,500 times greater than that of air. This is one of the reasons why water is up to 10 times more effective at dissipating heat from a source. Furthermore, liquid cooling enables operation using pre-charged systems, making maintenance easier, allowing for rapid replacement of any necessary parts, quick initial installation, and rapid upgrades. Therefore, liquid cooling can be applied without limitation to numerous applications, such as thermal battery packs, vehicle inverters, and charging station power electronics.
[0011] The coolant used for liquid cooling in fast chargers is typically a water / glycol mixture. Using a water / glycol mixture prevents the coolant from freezing and increases the boiling point compared to water alone.
[0012] It is evident that additional heat can be generated due to technical malfunctions of the battery charger. For example, if the voltage is unstable, overheating will occur in a charger programmed to maintain a constant charging rate. Furthermore, impurities will leach from metals originating from metal parts, such as coolers, as well as from plastic surfaces used in the cooling system. The non-conductive coolant itself undergoes thermal decomposition, releasing conductive components into the cooling loop. Glycol and formic acid are typical examples formed from the decomposition mechanism of ethylene glycol ("monoethylene glycol" or "MEG"), while lactic acid and acetic acid are formed from the decomposition mechanism of propylene glycol ("PG").
[0013] for example, https: / / doi.org / 10.1016 / 0165-1633(85)90016-4 AN INVESTIGATION OF THE DEGRADATION OF AQUEOUS ETHYLENE GLYCOL AND PROPYLENE GLYCOL SOLUTIONS USING ION CHROMATOGRAPHY Walter J. ROSSITER, Jr., McClure GODETTE, Paul W. BROWN and Kevin G. G. GALUK Building Materials Division, Center for Building Technology, National Bureau of Standards, Gaithersburg, MD 10899, USA; Received 17 May 1984; revised 30 August 1984, available online 5 March 2003; See Solar Energy Materials, Volume 11, Issues 5-6, January-February 1985, Pages 455-467.
[0014] A fuel cell system performs electrochemical oxidation by reacting a fuel, for example, hydrogen, with oxygen to produce electrical energy and water. The system may include, for example, several subsystems such as the following:
[0015] Subsystem for managing the flow of hydrogen and oxygen: This may include a gas compression and control system for delivering gas to the subsystem for electrical energy production. In some cases, hydrogen is produced on-site using a gas reformer that extracts hydrogen from hydrocarbons such as natural gas. Oxygen can be supplied directly from the air.
[0016] Subsystem for electrical energy production: This typically takes the form of a fuel cell stack containing multiple individual fuel cells. Each cell includes an anode and a cathode separated by an electrolyte and a proton-selective membrane. When hydrogen gas comes into contact with the anode, protons (H + It is split into ions and electrons. Protons pass through the electrolyte and the proton-selective membrane to the cathode, where they react with electrons and oxygen from the anode to generate electricity, heat, and water.
[0017] Subsystem for managing water flow: Water is produced as a product of the electrochemical oxidation of hydrogen in a fuel cell. This water can be released from the fuel cell stack in the form of steam, or it can be condensed and reused in the system, for example, as a humidifier or coolant for incoming air.
[0018] Liquid Coolant Subsystem: This generally includes the following:
[0019] o Means of exchanging heat via a liquid coolant: Fuel cells generate heat when performing electrochemical oxidation. Heat typically improves the efficiency of the fuel cell, which can be considered advantageous for operation. However, heat can degrade components such as ion exchange resins, electrolytes, and other constituent materials. Thermal management is critical to ensuring fuel cell performance and lifespan. Therefore, a cooling system is required to preserve and extend the operation of the electrochemical system. Cooling systems suitable for use with the ion exchange filters described herein are not particularly limited and typically include a coolant recirculated within pipes or tubing between a remote heat exchanger and the fuel cell. The heat exchanger may fluidly communicate with one or more of a radiator, a thermal regulator, or bypass means for optionally filtering the circulating coolant. Coolants suitable for use with the ion exchange filters described herein are not particularly limited but typically include fluids of low conductivity, such as purified water or aqueous alkylene glycol mixtures. Various additives may be included in the coolant. For example, other designs and coolants are well known and may also be suitable, including those described in EP1791206.
[0020] o Means for treating the above liquid coolant: During the circulation of the coolant, ions from metals or organic matter from plastic surfaces may diffuse into the coolant, glycols may be thermally decomposed into organic acids such as glycolic acid or formic acid, for example, or both of these phenomena may occur. Each of these mechanisms results in a gradual increase in electrical conductivity in the coolant liquid. Since this electrical conductance poses a risk to safety and reliability, the coolant must be treated to reduce or remove impurities. Such treatment is often performed using ion exchange resins.
[0021] Electrolyzers perform the electrochemical reduction of water to produce hydrogen and oxygen. Electrolytic systems may include, for example, several subsystems such as the following:
[0022] Subsystem for managing water flow: To provide a reliable water supply to the electrolytic cell, a pump and a water quality control system may be required.
[0023] Subsystem for electrical energy consumption: This is typically in the form of an electrolytic cell comprising an anode and a cathode separated by an electrolyte and an ion-selective membrane, such as a proton exchange membrane (PEM) in the case of protons. In the case of a proton-selective membrane, when water comes into contact with the anode, hydrogen ions (H₂ + It is split into ) and oxygen gas. Hydrogen ions move to the cathode through the electrolyte and proton-selective membrane, and are converted into hydrogen gas at the cathode. Oxygen gas is collected at the anode.
[0024] Subsystem for managing the flow of hydrogen and oxygen: This may include gas separation, purification, and compression systems, as well as a control system for delivering the gas to a destination.
[0025] Liquid Coolant Subsystem: This generally includes the following:
[0026] o Means of heat exchange via liquid coolant: Heat is generated in the electrolytic cell due to the resistance of the electrolyte solution to the passage of electricity. This heat typically improves the efficiency of the electrolysis process, which can be considered advantageous for operation. However, heat can degrade components such as ion exchange resins, electrolytic membranes, and other constituent materials. Therefore, a cooling system is required to preserve and extend the operation of the electrochemical system.
[0027] Some heat is absorbed by the water circulating through the electrolytic cell. Typically, not all of the water supplied to the electrolytic cell is converted into hydrogen and oxygen. A portion of the unconverted water can be treated with ion exchange resin to remove contaminants. The converted water can be replenished by a makeup water stream.
[0028] o Liquid cooling or air cooling may be additionally utilized. Cooling systems suitable for use with the ion exchange filters described herein are not particularly limited and typically include a coolant recirculated within pipes or tubing between a remote heat exchanger and an electrolytic cell. The heat exchanger may be fluidly connected to one or more of a plate heat exchanger, a heat regulator, or bypass means for optionally filtering the circulating coolant. The coolant system or loop, distinct from the loop containing the electrolytic feed and product streams, is not particularly limited but typically includes a fluid of low conductivity, such as purified water. Various additives may be included in the coolant. Other designs and coolants, including some designs and coolants similar to those described in EP1791206 in relation to fuel cells, are well known and may be used. Water is typically used to transfer heat from an electrolytic cell to one or more coolers.
[0029] Means for treating feedwater recirculated through the electrolytic cell or coolant stream, which may be contaminated by ions from metal surfaces, organic matter from plastic surfaces, other chemicals, or microorganisms, are often additionally included. Such contamination can reduce heat transfer efficiency or cause fouling, scaling, corrosion, or safety hazards. This treatment is often performed using ion exchange resins.
[0030] However, in all of these electrochemical systems, coolants containing impurities can cause short circuits due to conductance. Short circuits can simply lead to inefficiency or cause the complete failure of the system. They can also result in dangerous electrical fires. Alternatively, impurities can foul the anode, cathode, or membrane, leading to inefficient operation and shortening the system's lifespan. Therefore, it is evident that coolant purification is a critical aspect of many electrochemical systems.
[0031] One common method for removing contaminants from a coolant stream is ion exchange treatment. Several studies describe removing debris and contaminants from a coolant stream using ion exchange resins. For example, see US8808931; US7261816; US6673482; US6663993 and EP1791206. In particular, US8808931 describes treating a fuel cell coolant using a strong base anion (SBA) exchange resin of the HCO3 form. When using an HCO3 form anion resin, the thermal stability of the coolant increased compared to a coolant treated with a typically used OH form anion resin. However, when using HCO3 form SBA in a fuel cell coolant, the conductivity of the coolant also increased. As discussed above, increased conductivity is undesirable because it can lead to short circuits, other unsafe situations, and fuel cell shutdown.
[0032] US11165074 describes treating coolant streams using a combination of strong acid cations, strong basic anions, and weak basic anion exchange resins. It is hypothesized that weak basic anion resins may have higher thermal stability than strong basic anion resins. Nevertheless, there are limitations associated with weak basic anion resins. For example, in coolant loops for batteries and fuel cells for electric vehicles (EVs), the primary contaminants (weakly associated organic acids, mainly glycolic acid) are associated with the thermal decomposition of glycols. Weak basic anion resins containing secondary or tertiary amines would not be able to effectively remove weak acid ions, such as glycolic acid with a pKa of 3.83, from water using ion exchange at near-neutral or alkaline pH. Specifically, glycolic acid and its derivative impurities do not exist significantly in the form of free acids because the pH exceeds their pKa values. Therefore, under conditions of nearly neutral pH, the conjugate bases of glycolic acid and derivative acids cannot protonate secondary or tertiary amines, so glycolic acid and other acid impurities are not adsorbed onto the weak base resin. Therefore, when the pH of the coolant is nearly neutral or slightly alkaline, glycolic acid and related impurities will not be removed from the coolant stream by the weak base anion resin.
[0033] Consequently, there remains a need for ion exchange filters containing resins that improve thermal stability, produce an eluent with lower electrical conductivity, and generate an aqueous stream of excellent purity for use in various electrochemical systems.
[0034] Accordingly, electrochemical systems such as fuel cells, batteries, battery chargers, and electrolytic cells are provided herein, comprising an ion exchange filter having a mixed bed of a strong base anion resin of the OH form, a strong base anion resin of the H-form, a strong base anion resin of the HCO3 form, or a combination of these two types of strong base anion resins, together with a specific ratio of a strong acid cation resin of the H-form. A method for treating a cooling water stream, for example, a cooling water stream from an electrochemical system, using the ion exchange filter described herein is further provided. Brief explanation of the drawing
[0035] Figure 1 is a graph of conductivity versus the total amount of hydroxyglycolic acid (HGA) removed from a 0.1 M aqueous solution, showing the conductivity trends of product streams from various mixed layers used to treat contaminated coolant streams. Figure 2 is a graph of tolitriazole retention versus time for various mixed layers. Specific details for implementing the invention
[0036] A mixed-bed resin cartridge is typically used for processing coolant streams. Mixed-beds known in the art generally include an H-type cation resin and an OH-type anion resin.
[0037] The resin bead size is not particularly limited and can be selected depending on the operating conditions. The preferred bead diameter of the anion exchange resin is about 300 to 1000 microns. A uniform particle size (UPS) resin may be used, or a resin having mixed bead sizes, for example, a resin having a Gaussian particle size distribution may be used.
[0038] In the cooling circuit of an electrochemical system, high temperatures (approximately 60 to 105°C) will induce thermal decomposition of anionic functional groups in OH-type resins, thereby shortening the resin life. To minimize the effects of the thermal decomposition process, HCO3-type anionic resins may be used. However, if a mixed layer containing strong acid cations in the H form and strong base anions in the HCO3 form is used in the coolant loop, the conductivity baseline of the coolant shifts from less than 0.1 μS / cm to a range of 1.0 to 5 μS / cm or 0.3 to 5 μS / cm due to HCO3 equilibrium, which is undesirable. Conductivity is 0.1 cm when equipped with a conductivity probe WTWLR325 / 01 -1 It is measured with an inoLab™ Cond 7310P conductivity meter having a cell constant.
[0039] Surprisingly, it has been found that ion exchange filters containing a mixed layer of ion exchange resins solve thermal stability and conductivity problems while maintaining the high standard water resistivity required for use in electrochemical systems. Generally, water with a resistivity of 12, 15, 17, or 19 mOhm-cm or higher is considered to meet these standards. Since resistivity is the reciprocal of conductivity, it is determined by the same experimental method as conductivity. The mixed layer described herein contains a strong base anion resin of the OH form, a strong base anion resin of the H₂ form, a strong base anion resin of the HCO₃ form, or a combination of these two types of strong base anion resins in a specific ratio, together with a strong acid cation resin of the H₂ form.
[0040] Strong acid ion exchange resins and strong base ion exchange resins suitable for use in the present invention, and methods for synthesizing said resins are described in U.S. Patent No. 8,808,931 granted to Golz et al.; and U.S. Patent No. 6,784,213 granted to Rohrbach et al.; and references cited in these patents. Additionally, suitable acid resins and base resins are available for purchase, for example, from DuPont de Nemours, Inc. (hereinafter “DuPont”), Wilmington, Delaware, USA. Furthermore, those skilled in the art are well aware of the definitions of various terms used herein to describe ion exchange resins and their uses, such as “replenishment water,” “Type I resin,” “Type II resin,” “gel resin,” etc. These terms are also defined and used in product data sheets and other literature publicly provided by ion exchange resin manufacturers. For example, https: / / www.dupont.com / water / technologies / ion-exchange-ix.html Refer to .
[0041] Preferably, the strong acid ion exchange resin used herein is suitable for use in one or more of industrial utility makeup water applications, condensate polishing applications, and 18 MOhm-cm water production for the semiconductor industry. Also preferably, the strong acid cation resin is characterized by one or more of the following properties: it is a gel-type resin; it is a cross-linked copolymer of styrene and divinylbenzene; it is a sulfonated polymer; it is a protonated (H) form; it may have any particle size distribution, e.g., a uniform particle size or a Gaussian particle size distribution, or it may be sieved to achieve different types of particle size distributions; and the total ion exchange capacity is about 1.0 to about 2.65 equivalents, more preferably about 1.5 to about 2.65 equivalents, even more preferably about 1.8 to about 2.3 equivalents (eq / L) per liter of the H form resin. The term "total ion exchange capacity" is synonymous with and used interchangeably herein with the terms "total capacity of cation exchange resin," "total capacity of anion exchange resin," and "total capacity and salt splitting capacity of anion exchange resin," depending on the cationic or anionic nature of the resin under discussion. Total ion exchange capacity may be measured according to one or more of the methods set forth in ASTM Standard D2187-17 (Standard Test Methods and Practice for Evaluating Physical and Chemical Properties of Particulate Ion Exchange Resins) or by other suitable methods.
[0042] Preferably, the strong base ion exchange resin used herein is also suitable for use in one or more of industrial utility makeup water applications, condensate polishing applications, or 18 MOhm-cm water production for the semiconductor industry. Also preferably, the strong base anion resin is characterized by one or more of the following properties: it is a Type I resin; it is a gel resin; it is a cross-linked copolymer of styrene and divinylbenzene; it is in the OH form or HCO3 form; it has a uniform particle size or a Gaussian particle size distribution; and the total ion exchange capacity in the OH form is about 0.9 to about 1.8, more preferably about 0.9 to about 1.6, and even more preferably about 1.0 to about 1.4 eq / L.
[0043] The mixed layer described herein comprises a strong acid cation resin (SAC) of the H form and a strong base anion (SBA) of the OH form or of the OH and HCO3 forms. Specifically, when the electrochemical system is a fuel cell, a battery, or a battery charger, the mixed layer
[0044] a) H-type strong acid cation resin;
[0045] b) a strong base anion resin of the OH type; and
[0046] c) Includes a strong base anion resin of the HCO3 type.
[0047] However, if the electrochemical system is an electrolytic cell, the mixed layer is
[0048] a) H-type strong acid cation resin;
[0049] b) a strong base anion resin of the OH type; and optionally,
[0050] c) Includes a strong base anion resin of the HCO3 type.
[0051] The mixed layer is preferably dominated by anions. Alternatively, for a given volume of the mixed layer, the sum of the volumes of the OH-type strong base anion resin and the HCO3-type strong base anion resin is preferably greater than or equal to the volume of the H-type strong acid cation resin. Preferably, the volume of the cation resin is greater than 7.5 vol% and less than 25.0 vol%, greater than 10.3 vol% and less than 25.0 vol%, and greater than 15 vol% and less than 20 vol% based on the total volume of the mixed layer. Complementarily, the volume of the anion resin(s) is more preferably greater than 75.0 vol% and less than 92.5 vol%, greater than 75.0 vol% and less than 89.7 vol%, or greater than 80 vol% and less than 85 vol% based on the total volume of the mixed layer. The sum of the volume percentages of the resins in the mixed layer is 100 vol%. The term "complementary," used here alone or in derivative forms such as "complementarily," refers to percentages that add up to 100%, such as 10.3% and 89.7%.
[0052] Also preferably, in a given volume of an anion-dominant mixed layer, for every 1 equivalent of the total ion exchange capacity of the strong acid cation resin in the mixture, the total ion exchange capacity of the strong base anion resin is greater than 1 equivalent. For example: in a 100 ml mixed layer containing 75 ml of anion resin with an exchange capacity of 1.0 equivalent / L and 25 ml of cation resin with an exchange capacity of 2.0 equivalent / L, the volume of the mixture contains an anion capacity of 75 x 1 / 25 x 2 = 1.5 equivalents per equivalent of the cation capacity.
[0053] More preferably, in a given volume of an anion-dominant mixed layer, both of the following conditions are satisfied: the sum of the volume percentage(s) of strong base anion exchange resin(s) is greater than the volume percentage(s) of strong acid cation exchange resin(s) with respect to the total volume of the mixed layer; and the total ion exchange capacity(s) of the strong base anion exchange resin(s) is greater than the total ion exchange capacity of the strong acid cation exchange resin(s). Much more preferably, in a given volume of anion-dominant mixed layer, the number of moles of anion exchange sites exceeds the number of moles of cation exchange sites.
[0054] A design suitable for an ion exchange cartridge used to purify a fuel cell coolant stream is described, for example, in U.S. Patent No. 8,808,931. Similar design principles may be applied to adapt these systems for use in purifying coolant streams in other electrochemical systems, for example, batteries, battery chargers, and electrolyzers.
[0055] Coolants suitable for use in the electrochemical systems described herein are well known in the art. However, simply put, coolants generally comprise water, one or more glycols, or a combination of water and one or more glycols. Suitable glycols include alkylene glycols. The alkylene group may be linear or branched. Preferred alkylene groups comprise 2 to 10 carbon atoms, more preferably 2 to 4, and even more preferably 2 to 3 carbon atoms.
[0056] Additionally, suitable coolants may contain a number of additives or stabilizers that reduce or prevent the thermal or oxidative decomposition of glycol. Generally, the additive package is kept as a trade secret of the coolant manufacturer. Nevertheless, the coolant may contain one or more of, for example, heat stabilizers and corrosion inhibitors. Additive packages are typically divided into three groups: IAT (Inorganic Additive Technology), OAT (Organic Additive Technology), and HOAT (Hybrid OAT). OAT and HOAT types have the lowest conductivity and are primarily used in fuel cells and electric vehicles. Pure glycol itself is colorless, but it can be colored with dyes such as Rhodamine for liquid identification and leak detection. Therefore, the additive package may additionally contain dyes. Other suitable additives include heat stabilizers, often described as silica-based, and antifoaming additives, often described as silicone or polyglycol. Suitable corrosion inhibitors that prevent oxidative decomposition include azoles, carboxylates, and triazoles.
[0057] Suitable additives and stabilizers, and suitable amounts of these additives and stabilizers, are known in the art. For example, see the literature [Kirk-Othmer Encyclopedia of Chemical Technology] and PCT International Application Publication WO 2017080542. However, simply put, the total amount of additives and stabilizers in the coolant is preferably less than 5 weight%, less than 3 weight%, less than 2 weight%, or less than 1 weight% based on the total weight of the coolant.
[0058] If additives such as corrosion inhibitors and heat stabilizers remain in the coolant stream, the glycol-containing coolant will last longer and exhibit superior performance. However, glycols will decompose when exposed to high temperatures. The decomposition products include low molecular weight organic acids that can cause corrosion of metal surfaces present in the coolant loop, for example, in an aluminum-copper cooler. Since the dissolved or suspended metal, which is a corrosion product, catalyzes the decomposition of glycols in the coolant, it increases the rate of thermal decomposition of glycols and increases the formation of conductive organic acids that promote corrosion.
[0059] By maintaining optimal levels of stabilizers in the refrigerant, these negative feedback loops can be prevented or slowed down. For this reason, stabilized refrigerants are available for purchase, such as, for example, Glysantin™ FC G 20-00 / 50 suppressed, ready-to-use, low-conductivity glycol refrigerant from BASF SE, Ludwigshafen, Germany (hereinafter "BASF"). For an explanation of the effects of stabilizers, see, for example, the literature [Technische Information TI / EVO e for Refer to Glysantin™ FC G 20-00 / 50, published by BASF in January, 2016.
[0060] However, current state-of-the-art H / OH type ion exchange resins effectively remove these additives from glycol. This phenomenon is described, for example, in the literature cited above by Rossiter et al. In contrast, the mixed-layer ion exchange resin described herein surprisingly and advantageously does not remove additives such as corrosion inhibitors and stabilizers from the coolant stream, or removes them in smaller amounts, thereby extending the effective life of the coolant and the coolant loop.
[0061] Three preferred embodiments of the mixed-layer ion exchange filter provided herein are described below.
[0062] Embodiment 1 : The mixed layer comprises the entire layer of ion exchange resin. In this embodiment:
[0063] The mixed layer is preferably dominated by anions. Therefore, this can be explained as follows: the sum of the volume of the strong base anion resin in the OH form and the volume of the strong base anion resin in the HCO3 form is greater than the volume of the strong acid cation resin in the H form.
[0064] In the case of anion exchange resin, the proportion of the OH form should be in the range of 33 to 75 volume% of the total volume of the anion resin in the mixed layer. This can be further explained as follows: the volume of the strong base anion resin in the OH form is greater than 33% and less than 75% of the sum of the volume of the strong base anion resin in the OH form and the volume of the strong base anion resin in the HCO3 form.
[0065] Embodiment 2 : The layer of the ion exchange resin comprises a mixed layer section and a non-mixed layer section, wherein the non-mixed layer section is located above the mixed layer section. As used herein, the term "above" refers to an upstream position, and the term "below" refers to a downstream position. To apply these terms, the ion exchange filter does not need to be positioned vertically. For example, in this embodiment 2, the coolant flowing through the ion exchange filter first passes through the non-mixed layer section located above the mixed layer section. Complementarily, the mixed layer section is located below the non-mixed layer section, that is, the water passing through the mixed layer section has already passed through the non-mixed layer section. In this embodiment 2:
[0066] The mixed layer section is preferably dominated by anions. Therefore, this can be explained as follows: the sum of the volume of the strong base anion resin in the OH form and the volume of the strong base anion resin in the HCO3 form is greater than the volume of the strong acid cation resin in the H form.
[0067] The non-mixed layer section preferably consists of one or more strong basic anion resins of the OH type. This resin may be the same or different from the strong basic anion resin of the OH type in the mixed layer.
[0068] For the anion exchange resin in the mixed bed section, the proportion of the OH form should be in the range of 33 to 75 volume%. This can be further explained as follows: the volume of the strong base anion resin in the OH form is greater than 33% and less than 75% of the sum of the volume of the strong base anion resin in the OH form and the volume of the strong base anion resin in the HCO3 form.
[0069] The volume of the OH-type strong base anion resin in the mixed layer section is greater than 40% of the sum of the volumes of the OH-type strong base anion resin in the non-mixed layer section and the mixed layer section.
[0070] Embodiment 3 : The layer of the ion exchange resin comprises a mixed layer section and a non-mixed layer section, and the non-mixed layer section is located below the mixed layer section. In this embodiment:
[0071] The mixed layer section is preferably dominated by anions. Thus, this can be explained as follows: for a given volume of mixed layer resin, the sum of the volume of the strong base anion resin in the OH form and the volume of the strong base anion resin in the HCO3 form is greater than the volume of the strong acid cation resin in the H form.
[0072] The non-mixed layer section preferably consists of one or more strong basic anion resins of the OH type. This resin may be the same or different from the strong basic anion resin of the OH type in the mixed layer.
[0073] For the anion exchange resin in the mixed bed section, the proportion of the OH form should be in the range of 33 to 75 volume%. This can be further explained as follows: the volume of the strong base anion resin in the OH form is greater than 33% and less than 75% of the sum of the volume of the strong base anion resin in the OH form and the volume of the strong base anion resin in the HCO3 form.
[0074] The volume of the OH-type strong base anion resin in the mixed layer section is greater than 60% of the sum of the volumes of the OH-type strong base anion resin in the non-mixed layer section and the mixed layer section.
[0075] The following examples are provided to further explain the invention. These examples, representing specific embodiments and preferred aspects currently being considered for carrying out the invention, are intended to illustrate the invention and are not intended to limit it.
[0076] Examples
[0077] In the following set of experiments, the strong acid cation exchange resin was a sulfonated, divinylbenzene-crosslinked polystyrene gel polymer with a total ion exchange capacity of at least 2.05 equivalents per liter of the H form. The strong base anion exchange resin was a type 1, divinylbenzene-crosslinked polystyrene gel polymer with a total ion exchange capacity of at least 1.10 equivalents per liter of the OH form. These ion exchange resins represent a wide range of commercially available anion and cation resins, available for purchase, for example from DuPont, which feature different capacities but similar chemical compositions. The ultrapure water used in these sets of experiments has a resistivity of at least 17 MOhm-cm.
[0078] Experiment Set 1: Contamination removal using a completely mixed bed: strong acid cations (SAC) (H form), strong base anions (SBA) (OH and HCO3 forms)
[0079] Experiments were performed in a glass column with an inner diameter of 2 cm containing a total resin volume of 50 ml. A 380 ppm solution of monoglycolic acid (MGA; a known contaminant of the fuel cell coolant cycle loop) was prepared in ultrapure water.
[0080] The ratio of resin in the mixed layer was changed as described in Table 1.
[0081] 5 bed volume (BV; where, 5) before using the mixed layer It was rinsed with ultrapure water (50 ml = 250 ml). The MGA solution was injected into the top of the mixed layer at a flow rate of 1000 mL / hr (equivalent to 20 BV per hour). Injection was continued until the mixed layer resin was exhausted. Exhaustion was reached after approximately 150 layer volumes had passed through the resin; exhaustion is defined as the conductivity of the eluent being 5 μS / cm or higher. The first 3 bed volumes of the eluent are discarded and not included in this measurement.
[0082] The experimental results are shown in Table 1. The average weighted conductivity of the eluent is calculated by dividing the sum of the conductivity measured for each BV by the total number of BVs that passed through the mixing layer. The final value of the average weighted conductivity is reported when exhaustion is reached (i.e., when the conductivity of the eluent is 5 μS / cm). For example, if 0–10 BV = 10 μS at 1 μS and 10–20 BV = 20 μS at 2 μS, the average weight at 20 BV is (10+20 μS) / 20 BV = 1.5 μS. The conductivity of the 10th BV of the eluent was considered as the starting conductivity.
[0083] It was found that when the amount of OH-type resin in the mixed layer was 33 to 75 volume%, the average weighted conductivity remained low. Increasing the volume% of the OH-type resin in the mixed layer to more than 75 volume% did not further reduce the average weighted conductivity; however, these compositions are expected to reduce the thermal stability of the mixed layer.
[0084] [Table 1] Resin combinations used to process MGA streams (fully mixed layers)
[0085]
[0086] Experiment Set 2: Thermal stability of the resin in the mixed layer: SAC (H form), SBA (OH and HCO3 forms). The loss of resin capacity due to thermal aging is evaluated by calculating the difference between the total ion exchange capacity of the thermally aged ion exchange resin and the total ion exchange capacity of the same ion exchange resin before thermal aging, and reporting the difference as a percentage of the total exchange capacity of the original resin.
[0087] To measure the loss of resin capacity due to thermal aging, 200 mL of a mixed resin layer containing different amounts of OH and HCO3 resins was placed in a sealed glass vial and placed in a furnace at 90°C for 500 hours. After regenerating the thermally aged resins, they were tested to evaluate their ion exchange capacity. To regenerate the OH resins and HCO3 resins into the OH form, 10 mL of the OH form resin was stirred with 20 mL of 1N HCl for 10 minutes to react the corresponding OH sites with HCl. After a contact time of 10 minutes, 1N NaOH solution was added to the remaining supernatant HCl solution to adjust the pH to 7.0 (back titration). The strong acid cation resins were regenerated with 1N HCl to completely restore them to the H form, followed by rinsing with deionized water. Subsequently, 5 g of NaCl was added to release the H sites, and the resins were back-titrated with 1N NaOH solution to 7.0.
[0088] The volume of the mixed resin before thermal aging was calculated by weighting the initial volume of each individual resin in the mixture by its volume percentage. For example, the initial volume of the mixed resin in Test 1 was (55 (Initial capacity OH form) + 45 (Initial capacity in HCO3 form)) / 100, where the sum of the volume percentages of the OH resin and the HCO3 resin is 100 volume%. The initial heat capacity was also determined by the method described above. Specifically, the resin was not heated; after regeneration, the ion exchange capacity as an equivalent per liter of OH functional group was measured. The results are shown in Table 2. The loss of resin capacity due to thermal aging was greater when the volume% of the OH form exceeded 75 volume% at 90°C.
[0089] [Table 2] Thermal Stability Test Results
[0090]
[0091] Experiment Set 3: Contaminant removal using a partially mixed layer with unmixed OH resin on top: SAC (H form), SBA (OH form and HCO3 form)
[0092] Experiments were performed in a glass column with a 2 cm inner diameter containing a total resin volume of 50 ml. A 380 ppm solution of hydroxyglycolic acid (HGA, a known contaminant in fuel cell coolant cycle loops) was prepared in Glysantin™ FC G20 refrigerant, which is available from BASF and is believed to be a mixture containing 50% ethylene glycol and 50% deionized water.
[0093] The ratio of resin in the mixed layer was changed as described in Table 3.
[0094] The partial mixed layer was rinsed with 5 BV ultrapure water before use. HGA solution was injected into the top of the partial mixed layer at a flow rate of 1000 mL / hr (corresponding to 20 layer volumes per hour). As determined by the method described above in Experiment Set 1, the injection was continued until the mixed layer resin was exhausted.
[0095] The results are shown in Table 3. Performance was measured as the number of eluted layer volumes prior to the 5 μS / cm endpoint, which indicates that exhaustion was reached. The results indicate that up to 60 volume% of the OH form can remain in the non-mixed layer before performance degradation is observed, as a decrease in the volume of eluent processed through the column prior to exhaustion (or more than 40 volume% of the OH form must be present in the mixed layer).
[0096] [Table 3] Resin combinations used to process HGA streams (partially mixed layer under unmixed OH resin)
[0097]
[0098] Experiment Set 4: Contaminant removal using a partially mixed layer with unmixed OH resin at the bottom: SAC (H form), SBA (OH form and HCO3 form)
[0099] The experiment was performed in a glass column with an inner diameter of 2 cm containing a total resin volume of 50 ml. The HGA solution described in Experiment Set 3 was prepared.
[0100] The ratio of resin in the mixed layer was changed as described in Table 4.
[0101] The partial mixed layer was rinsed with 5 BV ultrapure water before use. HGA solution was injected into the top of the partial mixed layer at a flow rate of 1000 mL / hr (corresponding to 20 layer volumes per hour). Injection was continued until the mixed layer resin was depleted, as determined by the method presented in Experiment Set 1 above.
[0102] The results are shown in Table 4. Performance was measured as the number of layer volumes processed prior to 5 μS / cm, which indicates exhaustion was reached. The results indicate that up to 40 volume% of the OH form can remain in the unmixed layer of this composition before performance degradation is observed as a decrease in the volume of eluent processed through the column prior to exhaustion (or more than 60 volume% of the OH form must be present in the mixed layer).
[0103] In summary, these data indicate that there exists an optimal range of relative volumes of HCO3-type anion resin and OH-type anion resin that combines high thermal stability and good performance (measured by resin capacity loss due to thermal aging and average weighted conductivity). There also exists an optimal percentage range of mixed volume in which the OH resin maintains good performance (measured by removing a larger amount of impurities before depletion), which surprisingly depends on whether the unmixed layer of the OH-type resin is above or below the mixed layer.
[0104] [Table 4] Resin combination used to process the HGA stream (partially mixed layer over unmixed OH resin)
[0105]
[0106] Experiment Set 5: Contamination removal using a mixed bed: Strong acid cations in the form of H (SAC), weak base anions in the form of free bases (WBA)
[0107] This set of experiments was performed to provide comparative examples. Experiments were conducted in a glass column with an inner diameter of 2 cm containing a total resin volume of 400 ml. HGA solutions described in experiment sets 3 and 4 were prepared.
[0108] The ratio of resin in the mixed layer was 50% SAC and 50% WBA by volume.
[0109] The mixed layer was rinsed with 5 BV ultrapure water before use. HGA solution was injected into the top of the mixed layer at a flow rate of 600 layer volume. As described in Experiment Set 1 above, the injection was continued until the mixed layer resin was depleted.
[0110] The results are shown in Figure 1, which illustrates the conductivity profile as a function of the amount (in meq or mmol) of HGA removed (i.e. absorbed or "loaded") from the solution per liter of resin. The data in Figure 1 show that the mixed layer containing WBA exhibits an immediate increase in conductivity compared to a mixed layer containing 50V% SAC resin mixed with 50V% SBA resin of either the OH form or the HCO3 form. In contrast, the conductivity of the stream exiting the mixed layer containing OH form SBA begins to rise when the total loaded volume exceeds about 700 meq / L of HGA loading, and the conductivity of the stream exiting the mixed layer containing HCO3 form SBA begins to rise when the total loaded volume exceeds about 800 meq / L of loading. These results indicate that the effectiveness of using WBA resin in treating coolant streams contaminated with common products of glycol decomposition is limited.
[0111] Advantageously, the mixed resin layer described herein does not remove additives such as corrosion inhibitors and stabilizers from the coolant stream. In contrast, the strong acid cation / strong base anion (H / OH) mixed layer of the prior art completely or substantially completely removes additives.
[0112] In particular, the results illustrated in FIG. 2 indicate that the mixed layer of ion exchange resins as described herein (H-type SAC resin, HCO3-type SBA resin) does not completely remove the stabilizer or reduce its concentration below the operating level after 7 hours or more of operation under the following conditions:
[0113] Resin volume = 50mL mixed layer
[0114] Test hydraulic system = Hourly sampling for HPLC analysis during loop circulation of 1 L of tollytriazole aqueous solution (concentration 1.5 g / L) at a speed of 20 BV / h (feeding with stirring).
[0115] Coolant samples were analyzed by HPLC using a WATERS™ e2695 separation module equipped with an XSelect HSS T3 5μm column (available from Waters Corp, Milton, Massachusetts, USA) and operating at 25°C. The injection size was 10 μl, and the UV detection was 210 nm. The mobile phase was disodium hydrogen phosphate (Na2HPO4, 3.4 g / L (pH 2.7) in 20% acetonitrile (by weight or volume), remainder in water or deionized water).
[0116] In contrast, under the same conditions, a conventional mixed layer (SAC resin in the H form, SBA resin in the OH form) removes substantially all tolyriazole from the circulating solution after 1 hour.
[0117] Although specific preferred embodiments of the present invention have been described and specifically illustrated above, the invention is not intended to be limited to these embodiments. As set forth in the claims below, various modifications may be made without departing from the scope and spirit of the invention.
Claims
Claim 1 A device for processing a liquid stream in an electrochemical system, wherein the electrochemical system is a fuel cell or a battery or a battery charger, and the device comprises a mixed bed of ion exchange resin, wherein the ion exchange resin comprises a) a strong acid cation resin of the H form; b) a strong base anion resin of the OH form; and c) a strong base anion resin of the HCO3 form; wherein, for a given volume of the mixed bed resin, the sum of the volume of the strong base anion resin of the OH form and the volume of the strong base anion resin of the HCO3 form is greater than the volume of the strong acid cation resin of the H form; wherein the total ion exchange capacity of the strong base anion resin of the OH form and the strong base anion resin of the HCO3 form is 0.9 to 1.8 equivalents / L, and the total ion exchange capacity of the strong acid cation resin of the H form is 1.0 to 2.65 equivalents / L; and wherein the device optionally further comprises a non-mixed bed of ion exchange resin, wherein the non-mixed bed comprises a strong base anion exchange resin of the OH form. Claim 2 The apparatus of claim 1, wherein the mixed layer, the non-mixed layer, or both the non-mixed layer and the mixed layer are characterized by one or more conditions selected from the group consisting of: a) the volume of the OH-type strong base anion resin in the mixed layer is greater than 33% of the sum of the volume of the OH-type strong base anion resin and the volume of the HCO3-type strong base anion resin; b) the volume of the OH-type strong base anion resin is less than 75% of the sum of the volume of the OH-type strong base anion resin and the volume of the HCO3-type strong base anion resin; c) the total volume of the OH-type strong base anion resin and the HCO3-type strong base anion resin in the mixed layer and the non-mixed layer is greater than or equal to the volume of the H-type strong acid cation resin; d) the volume of the OH-type strong base anion resin in the mixed layer and the non-mixed layer is equal to the volume of the OH-type strong base anion resin in the mixed layer and the HCO3-type strong base e) The sum of the volumes of the anion resins exceeds 33% of the total volume; f) The sum of the volumes of the OH-type strong base anion resins in the mixed and non-mixed layers is less than 75% of the total volume of the OH-type strong base anion resins and the HCO3-type strong base anion resins in the mixed and non-mixed layers; f) The volume of the OH-type strong base anion resin in the mixed layer section exceeds 40% of the sum of the volumes of the OH-type strong base anion resins in the non-mixed layer section and the mixed layer section; and g) The volume of the OH-type strong base anion resin in the mixed layer section exceeds 60% of the sum of the volumes of the OH-type strong base anion resins in the non-mixed layer section and the mixed layer section. Claim 3 An apparatus according to claim 1 or 2, wherein the liquid stream comprises a mixture of glycol and water; the glycol comprises ethylene glycol, propylene glycol, or a combination of ethylene glycol and propylene glycol; and optionally, the liquid stream further comprises one or more additives selected from the group consisting of heat stabilizers, antifoamers, and corrosion inhibitors. Claim 4 An apparatus according to any one of claims 1 to 3, comprising a coolant loop, wherein the liquid stream is a coolant within the coolant loop. Claim 5 A device according to any one of paragraphs 1 to 4, wherein the non-mixed layer section is located above the mixed layer section. Claim 6 A device according to any one of paragraphs 1 to 4, wherein the non-mixed layer section is located below the mixed layer section. Claim 7 An apparatus for treating a liquid stream in an electrolytic cell, wherein the apparatus comprises a mixed layer of ion exchange resins, said mixed layer comprises a strong acid cation resin of the H form; and a strong base anion resin of the OH form; and optionally a strong base anion resin of the HCO3 form; for a given volume of the mixed layer resin, the volume of the strong base anion of the OH form or the sum of the volume of the strong base anion resin of the OH form and the volume of the strong base anion resin of the HCO3 form is greater than the volume of the strong acid cation resin of the H form; the total ion exchange capacity of the strong base anion resin of the OH form and the optional strong base anion resin of the HCO3 form is 0.9 to 1.8 equivalents / L, and the total ion exchange capacity of the strong acid cation resin of the H form is 1.0 to 2.65 equivalents / L; and the apparatus optionally further comprises a non-mixed layer of ion exchange resins, said non-mixed layer comprises a strong base anion exchange resin of the OH form. Claim 8 An apparatus according to claim 7, wherein the liquid stream comprises water and an anion-rich mixture of materials classified as total organic carbon; one or more organic acids; and at least one dissolved impurity selected from the group consisting of one or more ions selected from the group consisting of boron ions, silica ions, manganese ions, nickel ions, zinc ions, sodium ions, potassium ions, fluoride ions, chloride ions, bromide ions, nitrate ions, phosphate ions, and sulfate ions. Claim 9 An apparatus according to claim 7 or 8, comprising a coolant loop, wherein the liquid stream is a coolant within the coolant loop. Claim 10 An apparatus according to any one of claims 7, 8, or 9, wherein the volume of the strong base anion resin of the OH form is at least 3 times, or preferably at least 6 times, the volume of the strong acid cation resin of the H form. Claim 11 A method for processing a liquid stream in an electrochemical system, wherein the electrochemical system is a fuel cell or a battery, and the method comprises the steps of: providing an apparatus of any one of claims 1 to 6; and contacting the liquid stream with a mixed layer of ion exchange resin. Claim 12 A method for treating a liquid stream in an electrolytic cell, comprising the steps of: providing an apparatus of any one of claims 7, 8, 9, or 10; and bringing the liquid stream into contact with a mixed layer of ion exchange resin.