Recycling of catalyst coating film components

Abstract

A method for recycling a fluoropolymer from a membrane comprising the fluoropolymer, the fluoropolymer comprising a fluoropolymer backbone and a plurality of groups represented by the formula -SOZ, where Z is hydrogen, the method comprising: contacting the membrane with a reagent that provides a source of cations for forming a fluoropolymer salt, where Z is a cation, the reagent being maintained at a temperature low enough that the membrane remains in a solid, undispersed form; removing excess unreacted reagent from the solid fluoropolymer salt; and dispersing the solid fluoropolymer salt in a solvent after removing the excess reagent.

Description

[Technical Field]

[0001] This specification relates to a method for recycling components of catalyst coating films, such as those used in fuel cells and hydrogen water electrolyzers. [Background technology]

[0002] As investment in the global hydrogen economy increases, the production of fuel cells and hydrogen-generating water electrolyzers is set to grow rapidly. Catalyst coatings (CCMs) are a key functional component in both fuel cells and electrolyzers. Such CCMs generally consist of a conductive polymer membrane coated on both sides with a catalyst-containing layer. CCMs are configured to drive oxidation and reduction reactions and to support proton and electron transport, processes that are necessary for fuel cell and electrolyzer technologies to function.

[0003] While the materials and composition of CCM components vary according to the functional performance requirements of the end application, they generally contain several useful components, including one or more platinum group metal (PGM) catalysts and one or more proton-conducting polymers.

[0004] Typically, the film is formed from one or more ionomers, such as a perfluorosulfonic acid (PFSA) ionomer. The ionomer may also be provided in one or both of the catalyst layers. The ionomer in the catalyst layer may be the same as or different from the ionomer in the main film component and / or in the other catalyst layer.

[0005] The CCM may contain two different catalysts, one for driving an oxidation reaction on one side of the CCM and the other for driving a reduction reaction on the other side of the CCM. The CCM may also contain a recombination catalyst provided to catalyze the recombination of hydrogen and oxygen to form water, reducing the amount of hydrogen passing through the membrane and mixing with oxygen to form a potentially explosive mixture. The CCM may also contain a metal oxide (e.g., CeO2) as a peroxide scavenger to slow the decomposition of the CCM and extend its lifespan.

[0006] CCM catalysts can be based on platinum group metals such as platinum, ruthenium, iridium, palladium, or mixtures thereof. Platinum group metals may be provided in elemental (metallic) form, compound form (e.g., oxides such as iridium oxide catalysts), or PGM-based metal alloys (e.g., PtCo). Furthermore, the PGM catalyst material may be supported on a substrate material (e.g., carbon such as a platinum-supported carbon catalyst or PtCo-supported carbon containing carbon particles on which platinum is arranged).

[0007] A catalyst coating (CCM) can also be provided in combination with additional functional layers to form a multilayer electrode assembly (MEA). Such an MEA may have, for example, 3, 5, or 7 layers.

[0008] With the increasing production of CCMs for fuel cells and electrolytic cells, there is also a corresponding increase in CCM waste material, including the large amount of scrap material generated during CCM production (e.g., due to quality control failures), as well as an increase in end-of-life (EoL) CCMs. Since CCMs contain several rare and / or valuable components, including platinum group metals (particularly Pt, Pd, Ir, and Ru) and ionomers (in both membrane and catalyst layers), there is a growing demand for methods to recycle such components from scrap / waste CCM materials.

[0009] One current method for recovering PGMs from production scrap and end-of-life CCM materials involves incineration. The incineration process produces PGM-rich (typically Pt and Ir) ash that is processed through conventional PGM refining routes. However, the incineration process releases harmful and toxic gases such as CO2 and HF from the polymers that are part of the membrane. Both of these gases have adverse effects as they pollute the atmosphere, increase the greenhouse effect, and / or have harmful effects on human health. Therefore, cleaner processes that reduce or eliminate the release of these gases are needed.

[0010] In addition to the above, incineration methods destroy ionomer components, which are of equally important value. Therefore, it is desirable to provide a process that can recover both PGMs and ionomer components, as well as a cleaner, safer, and more environmentally friendly process. Processes for recovering perfluorosulfonic acid ionomers are known; see, for example, International Publication No. 2016 / 156815 and U.S. Patent No. 7255798. Furthermore, processes for recovering individual PGM catalyst components are known; see, for example, U.S. Patent No. 7709135. However, in order to enable fuel cells and electrolytic cells to become more sustainable technologies, there is a need for commercially viable and environmentally friendly routes for recovering, separating, and recycling both PGMs and ionomer components from waste CCM materials, including production scrap and end-of-life materials.

[0011] This specification relates to a method for recycling ionomer materials (perfluorosulfonic acid (PFSA) polymers) from ionomer membranes in fuel cells or electrolytic cells.

[0012] International Publication No. 2021250576 discloses a process for recycling ionomer material from ionomer membranes in fuel cells or electrolytic cells. The solubility of fluorinated polymers used in such membranes is described as decreasing when the fluorinated polymer is heat-treated, as can occur during the manufacture of membranes containing the fluorinated polymer. Specifically, fluorinated polymers having a fluorinated main chain and multiple groups represented by the formula -SO3H or salts thereof readily dissolve in water and alcohol mixtures when freshly prepared after being heated to a temperature of at least 100°C. These polymers are typically insoluble in water and water / alcohol mixtures under standard conditions. International Publication No. 2021250576 discloses that such heat-treated fluorinated polymers become soluble when heated in the presence of water and a base. Therefore, International Publication No. 2021250576 discloses a method comprising dissolving a fluorinated polymer membrane in water and a base to form a fluorinated polymer salt solution, and then converting the fluorinated polymer salt solution back into a fluorinated polymer solution by hydrogen cation exchange. The base has been shown to be typically an alkali metal hydroxide (e.g., lithium hydroxide, sodium hydroxide, or potassium hydroxide) or ammonium hydroxide. It has been further shown that the moles of the base used may be equivalent to the moles of the fluorinated polymer, or an excess of base (e.g., up to 100, 200, or 300 mole percent excess base relative to the fluorinated polymer) may be used.

[0013] The objective of this specification is to provide an improved process for the recovery of ionomers. [Overview of the Initiative]

[0014] This specification relates to the recovery of perfluorosulfonic acid (PFSA) polymers from scrap or spent membranes, such as membranes used in fuel cells or electrolytic cells. As described in International Publication No. 2021250576, it is recognized that the use of equivalent or excess bases may be advantageous in ensuring that all or substantially all of the fluorinated polymer is converted to salt form. Salt formation is advantageous in protecting the sulfonic acid groups during the recovery process, and therefore ensuring that all or substantially all of the sulfonic acid groups are converted to salt form during the process. However, it is also recognized that the use of bases such as hydroxides, as described in International Publication No. 2021250576, may cause some problems in further processing of ionomer materials, particularly when the material being processed also contains one or more platinum group metal catalysts, such as in catalyst coating membranes.

[0015] Excess base can lead to etching / corrosion problems in the equipment. Furthermore, excess base can cause problems in the speciation and extraction of other components, such as platinum group metal catalysts present in the catalyst coating of fuel cells or electrolytic cells. Additionally, any excess base must be recovered during the ion exchange process to convert fluorinated polymer salts back into protonated acid forms, which can negatively impact the overall balance of the materials. For example, if hydroxide is used as a base to convert fluorinated polymers into salt forms, excess hydroxide base is corrosive to metal and glass-lined vessels that may be used in subsequent high-temperature, high-pressure dispersion processes. Furthermore, excess hydroxide base can cause problems in the speciation and extraction of other components, such as platinum group metal catalysts present in the catalyst coating of fuel cells or electrolytic cells. Additionally, excess hydroxide base must be recovered during the ion exchange process to convert fluorinated polymer salts back into protonated acid forms, which can negatively impact the overall balance of the materials.

[0016] Therefore, it is recognized that if an excess base is added to a fluorinated polymer to ensure a substantially complete conversion of the fluorinated polymer to its salt form, the excess base should be substantially removed during or immediately after the conversion of the fluorinated polymer to its salt form. Removal of the excess base reduces etching / corrosion problems in the apparatus, reduces problems in the specification and extraction of other components such as platinum group metal components, and ensures that the excess base does not need to be recovered during the subsequent ion exchange process that converts the fluorinated polymer salt back to its acid form, thus improving the overall material balance. As described in International Publication No. 2021250576, when a membrane is heated in a basic solution to form a dispersion of the fluorinated polymer salt in a basic solution, it is difficult to separate the fluorinated polymer salt from the excess base. However, it has been found that the membrane material can be treated with a basic solution to form a salt without heating the membrane to a temperature at which it disperses in the basic solution. This allows the membrane to be retained in the form of a solid salt that is easily separated from the basic solution before further processing.

[0017] In addition to the above, while International Publication No. 2021250576 proposes the use of bases in the form of alkali metal hydroxides (e.g., lithium hydroxide, sodium hydroxide, or potassium hydroxide) or ammonium hydroxide, it has been found that other reagents can be used to convert fluorinated polymers into salt forms. For example, carbonates can be used, and thus the aforementioned problems associated with the use of hydroxide bases can be reduced or avoided. Therefore, in addition to removing excess salt-forming reagent when converting fluorinated polymers into salt forms, it may also be advantageous to use carbonates as salt-forming reagents in that they can remove carbon dioxide decomposition products generated during sulfonate formation as gaseous products, thus avoiding the generation of highly corrosive alkaline solutions and avoiding the need for considerable washing steps.

[0018] As a further alternative to using hydroxides and carbonates as salt-forming reagents for converting fluorinated polymers into salts, it has also been found that polymer salts can be produced using other reagents as cation sources. Such reagents include inorganic salts such as halide salts (e.g., chlorides, e.g., sodium chloride or metallic chlorides such as lithium chloride). Alternatively, polymer salts (e.g., formate (e.g., lithium formate), acetate, oxalate, citrate, or gluconate) can be produced using organic salts as cation sources. Furthermore, the cations can be inorganic cations (i.e., metallic cations) or NH4 + These may be organic cations such as [examples of organic cations]. Other options for the reagent include bicarbonates, carbamates, nitrates, phosphates, and sulfates, which may be, for example, in the form of metal salts or ammonium salts.

[0019] According to this specification, such reagents are added to the fluorinated polymer to convert it into a salt form without heating it to a temperature sufficient to disperse the film, so that the film maintains a solid, non-dispersible form. Then, before dispersing the solid polymer salt in a solvent, any excess unreacted reagent is removed from the solid polymer salt. Removal of excess unreacted reagent reduces etching / corrosion problems in the apparatus, reduces problems in the specification and extraction of other components such as platinum group metal components, and ensures that there is no need to recover excess reagent during the subsequent ion exchange process to convert the fluorinated polymer salt back into an acid form, thus improving the overall material balance.

[0020] Therefore, this specification relates to a method for recycling a fluorinated polymer from a film containing a fluorinated polymer, wherein the fluorinated polymer comprises a fluorinated polymer main chain and a plurality of groups represented by the formula -SO3Z (wherein Z is hydrogen), and the method is The process involves contacting a film with a reagent that provides a cation source for forming a fluorinated polymer salt in which Z is a cation, wherein the reagent is maintained at a temperature low enough that the film remains in a solid, non-dispersed state. Removing excess unreacted reagent from the solid fluorinated polymer salt, and after removing the excess reagent, dispersing the solid fluorinated polymer salt in a solvent, and providing a method.

[0021] For example, when the reagent is a base, the method is contacting the membrane with a basic aqueous solution containing water and a base to form a fluorinated polymer salt where Z is a cation, optionally providing a molar excess of base relative to the -SO3Z group, and maintaining the basic aqueous solution at a sufficiently low temperature such that the membrane remains in a solid, non-dispersed form, and removing the excess / unreacted base by separating the solid fluorinated polymer salt from the basic aqueous solution (e.g., by solid-liquid separation techniques), and after removing the excess base, dispersing the solid fluorinated polymer salt in a solvent, and including.

[0022] In another embodiment, the reagent is a carbonate, and the method is contacting the membrane with a carbonate aqueous solution containing water and a carbonate to form a fluorinated polymer salt where Z is a cation, optionally providing a molar excess of carbonate relative to the -SO3Z group to form the fluorinated polymer salt, and maintaining the carbonate aqueous solution at a sufficiently low temperature such that the membrane remains in a solid, non-dispersed form, and removing the excess / unreacted carbonate from the solid fluorinated polymer salt, and after removing the excess carbonate, dispersing the fluorinated polymer salt in a solvent, and including.

[0023] Optionally, after dispersing the solid fluorinated polymer salt in a solvent, the fluorinated polymer salt is converted back to a fluorinated polymer where Z is hydrogen by cation exchange. This can be done immediately after the dispersion step. Alternatively, the dispersed polymer salt can be dried and stored, and then, when needed for use, redispersed later and converted to the protonated form.

Brief Description of the Drawings

[0024] For a better understanding of the present invention and to illustrate how it can be implemented, specific embodiments of the present invention are described only as examples with reference to the accompanying drawings. [Figure 1] This is a flowchart of the process for recycling fluorinated polymer film materials. [Figure 2] This figure shows FTIR data for fluorinated polymer film materials, fluorinated polymer salt materials formed after treatment in water and a base, and fluorinated polymer salt materials formed after treatment in water and a base and subsequently washed with water. [Figure 3] This figure shows an example of a process step (before autoclaving) that includes refluxing a fluorinated polymer film in a basic LiOH solution to form a fluorinated polymer salt without dispersing the film, followed by washing with water. [Figure 4] These photographs show the membrane before (left) and after (right) the process of refluxing the membrane in a basic LiOH solution and washing it with water. [Figure 5] This figure shows a further step in which the membrane is autoclaved, following the processing steps shown in Figure 3, in order to disperse the membrane in water. [Figure 6] This figure shows a further ion exchange step (after autoclaving) to convert the dispersed polymer salt back into a protonated acid form. [Figure 7] This is a flowchart of a method for recycling fluorinated polymer film materials using a carbonate reagent instead of a hydroxide reagent, as in another example. [Figure 8] This figure shows an example of a process step (before film dispersion) that includes refluxing a fluorinated polymer film in a Li2CO3 solution to form a fluorinated polymer salt without dispersing the film, followed by washing with water. [Figure 9] This figure shows the FTIR ATR spectra of PFSA ionomer membranes receiving 1 and 2 molar equivalents of Na as Na2CO3 in response to SO3- in the membrane. [Modes for carrying out the invention]

[0025] As shown in Figure 1, this specification provides a method for recycling fluorinated polymers from a film containing a fluorinated polymer. The fluorinated polymer comprises a fluorinated polymer main chain and a plurality of groups represented by the formula -SO3Z. Z may be hydrogen or a cation, such as a metal cation, an alkali metal cation, or a quaternary ammonium cation (ammonium or alkylammonium cation). In an example of this method, in at least some of the -SO3Z groups, Z is hydrogen.

[0026] This method, The film is brought into contact with a reagent that provides a cation source for forming a fluorinated polymer salt in which Z is a cation, wherein the reagent is maintained at a sufficiently low temperature (e.g., below 150°C, 100°C, 80°C, 60°C, or 40°C, optionally above 5°C, 10°C, or 15°C) such that the film remains in a solid, non-dispersed state. To remove excess unreacted reagent from the solid fluorinated polymer salt (e.g., using solid-liquid separation techniques, optionally decantation and filtration), The method includes removing excess reagent and then dispersing the solid fluorinated polymer salt in a solvent (e.g., water). The ionomer can then be dried and stored as a salt that can be redispersed for later use. Alternatively, after dispersing the solid fluorinated polymer salt in a solvent, the fluorinated polymer salt may be converted back to a fluorinated polymer where Z is hydrogen by cation exchange.

[0027] Optionally, the reagent is provided in an equivalent or excess amount such that the reagent provides a molar equivalent or molar excess of cations relative to the -SO3Z group. The solid fluorinated polymer salt can be washed in the solvent, optionally in water, after separating the solid fluorinated polymer salt from the reagent and before dispersing the solid fluorinated polymer salt in the solvent. This ensures that all or substantially all of the excess unreacted reagent is removed from the film before dispersion in the solvent. The solid fluorinated polymer salt can then be dispersed in the solvent by heating the solid fluorinated polymer salt in the solvent to a temperature of at least 180°C, 200°C, 220°C, 240°C, or 250°C (optionally 500°C, 400°C, or 300°C or less) using, for example, an autoclave.

[0028] Reagents that provide cation sources for forming fluorinated polymer salts include bases, hydroxides, metal hydroxides, ammonium hydroxide, carbonates, metal carbonates, alkali metal carbonates, alkaline earth metal carbonates, ammonium carbonate, halides, metal halides, organic salts, formate salts, acetate salts, oxalates, citrate salts, gluconates, inorganic cation sources, metal cation sources, organic cation sources, and NH4. + The source may be selected from one or more of the following: bicarbonates, carbamates, nitrates, phosphates, and sulfates.

[0029] Examples in which the reagent is a base (e.g., hydroxide) According to certain embodiments, the reagent is a base, and the method involves contacting the film with a basic aqueous solution containing water and a base (e.g., an alkali metal hydroxide or a hydroxide such as ammonium hydroxide) to form a fluorinated polymer salt. The solid fluorinated polymer salt can then be dispersed in a solvent, and optionally, the fluorinated polymer salt can be converted back to a fluorinated polymer where Z is hydrogen by cation exchange. In the step of contacting the film with a basic aqueous solution to form a fluorinated polymer salt, a molar excess of base can be provided compared to the -SO3Z groups, and the excess base can be removed before dispersing the film and optionally converting the fluorinated polymer salt to a fluorinated polymer by cation exchange. As described in the summary section, according to this specification, the excess base is added to the fluorinated polymer to ensure that the fluorinated polymer is substantially completely converted to the salt form, but the excess base is substantially removed during or immediately after the conversion of the fluorinated polymer to the salt form. Removing excess / unreacted bases reduces etching / corrosion problems in the apparatus, mitigates issues in the specification and extraction of other components such as platinum group metal components, and ensures that there is no need to recover excess bases during the subsequent ion exchange process that converts fluorinated polymer salts back into acidic form, thus improving the overall material balance.

[0030] The basic aqueous solution is maintained at a sufficiently low temperature so that the membrane remains in a solid, non-dispersible form during the process of contacting the membrane with the basic aqueous solution to form a solid, non-dispersible form of fluorinated polymer salt. This is in contrast to conventional methods in which the membrane is heated in an aqueous basic solution to disperse it. It has been found that the fluorinated polymer membrane can be converted to salt form without dispersing the membrane. This is advantageous because excess base can be easily removed by separating the solid fluorinated polymer salt from the basic aqueous solution, for example, by solid-liquid separation techniques, optionally by decantation or filtration. The solid fluorinated polymer salt can then be dispersed in a (non-basic) solvent, optionally water, before converting the fluorinated polymer salt back into a fluorinated polymer by cation exchange. As previously shown, the removal of excess base in this manner reduces etching / corrosion problems in the apparatus, reduces problems in the specification and extraction of other components such as platinum group metal components, ensures that there is no need to recover excess base during the subsequent ion exchange process to convert the fluorinated polymer salt back into an acid form, and thus improves the overall material balance.

[0031] During the step of contacting the film with a basic aqueous solution to form a fluorinated polymer salt, the basic aqueous solution may be maintained at a temperature below 150°C, 100°C, 80°C, 60°C, or 40°C, optionally above 5°C, 10°C, or 15°C, optionally within a range defined by any of the aforementioned upper and lower limits (e.g., room temperature). The temperature may be low enough so that the conversion of the fluorinated polymer to the salt form is achieved without dispersing the fluorinated polymer film, which remains in a non-dispersible solid form.

[0032] After separating the solid fluorinated polymer salt from a basic aqueous solution, and before dispersing the solid fluorinated polymer salt in a solvent, the solid fluorinated polymer salt can be washed with a solvent, and optionally with water.

[0033] The solid fluorinated polymer salt can be dispersed in a solvent (e.g., water) by heating the solid fluorinated polymer salt in the solvent to a temperature of at least 180°C, 200°C, 220°C, 240°C, or 250°C (optionally 500°C, 400°C, or 300°C or lower) before forming the fluorinated polymer salt, optionally washing it, and converting the fluorinated polymer salt to a fluorinated polymer by cation exchange.

[0034] In the process described above, the fluorinated polymer film is converted to a salt form without dispersing the film. Dispersion is then achieved in a further process step without the use of a base.

[0035] The base used to form the fluorinated polymer salt may be a hydroxide. In some cases, the base is a metal hydroxide, optionally an alkali metal hydroxide (e.g., LiOH or NaOH), or ammonium hydroxide. The solid salt may be stored as an intermediate product until needed for use in the production of a new fluorinated polymer, or until immediately converted to a fluorinated polymer. In this regard, the fluorinated polymer salt can then be dispersed (e.g., by autoclaving in water) before the step of converting the fluorinated polymer salt to a fluorinated polymer by cation exchange. After the fluorinated polymer salt has been converted to a fluorinated polymer by cation exchange, the fluorinated polymer can be reused to produce a new film.

[0036] The membrane may be a catalyst coating membrane for a fuel cell or electrolytic cell. In this case, it is desirable to recycle the catalyst components and the polymer material of the membrane. For this reason, at least one catalyst material can be separated from the membrane before heating the membrane in the presence of water and a base to form a fluorinated polymer salt, and / or at least one catalyst material can be separated from the fluorinated polymer or fluorinated polymer salt after heating the membrane in the presence of water and a base to form a fluorinated polymer salt.

[0037] experiment The perfluorosulfonic acid ionomer film fragments were cut into pieces small enough to fit in the container. 6.0 g of anhydrous LiOH and 250 g of water were weighed, and the LiOH was dissolved in the water. The film fragments were submerged in the LiOH solution and heated under reflux for 1 hour. The resulting mixture was washed with 4 × 100 mL of water. The remaining water was decanted to leave the (moist) film fragments. 250 g of water was weighed and added to the (moist) film fragments, and heated under reflux for 1 hour. The water was then removed by decantation, and the solid product was dried under vacuum.

[0038] Figure 2 shows FTIR data indicating salt formation. FTIR data was collected for the untreated fluorinated polymer film material 301, the fluorinated polymer salt material 303 formed after treatment in an aqueous LiOH solution, and the fluorinated polymer salt material formed after treatment in an aqueous LiOH solution, followed by water washing 304.

[0039] Figure 3 shows an example of the process steps (before autoclaving). The film on a roll was cut, and then further cut or folded to size. The film was brownish in color, as shown in the figure. The film was then refluxed in a lithium hydroxide solution, at which point it became colorless and was converted to a salt form, as confirmed by spectroscopic analysis. The conversion was achieved without dispersing the film, which remained in a solid, non-disperse form.

[0040] It should be noted that a change in film color does not necessarily indicate a chemical change, and films can have different colors. However, in the exemplary examples, the chemical change of the polymer from the protonated form to the salt form was accompanied by a corresponding color change, as shown in the figure.

[0041] In the final step before autoclaving, as shown in Figure 3, the solid polymer salt film material was washed with water to remove all residual LiOH solution. Figure 4 shows photographs of the film before (left) and after (right) the process of refluxing the film in a basic LiOH solution and washing it with water, illustrating the change in film color from brown to colorless, and the fact that the film remains in a solid, non-dispersed state. Spectroscopic analysis confirmed that the colorless film was in salt form.

[0042] Figure 5 shows a further step of autoclaving the membrane following the processing steps shown in Figure 3, in order to disperse the membrane in water. A colorless, solid, non-dispersible polymer salt membrane was autoclaved in water under nitrogen at 250°C and a pressure of 40 bar / 4000 kPa. This yielded a (non-basic) aqueous dispersion of the polymer salt.

[0043] Figure 6 shows a further ion exchange step (after autoclaving) to convert the dispersed polymer salt back into a protonated acid form. An ion exchange column containing Amberlyst® 15(H) resin was used in this process step. The dispersion of (protonated)fluorinated polymer may be reused to produce a new membrane or may be dried and stored for future use.

[0044] Examples where the reagent is a carbonate Instead of using bases such as hydroxides as described above, other embodiments of this method use carbonates as reagents to convert the fluorinated polymer film into a salt form before dispersion.

[0045] As shown in Figure 7, this method also provides a method for recycling fluorinated polymers from a film containing a fluorinated polymer. The fluorinated polymer, again, comprises a fluorinated polymer main chain and a plurality of groups represented by the formula -SO3Z (wherein Z is hydrogen). This method involves contacting the film with an aqueous solution containing water and a carbonate (e.g., a metal carbonate, alkali metal carbonate, alkaline earth metal carbonate, or ammonium carbonate) to form a fluorinated polymer salt. The fluorinated polymer salt can then be dispersed in a solvent and optionally converted back to a fluorinated polymer where Z is hydrogen by cation exchange.

[0046] As described in the overview section, the use of carbonates (rather than hydroxides) that can remove carbon dioxide decomposition products generated during sulfonate formation as gaseous products avoids the generation of highly corrosive alkaline solutions and avoids the need for considerable washing steps.

[0047] Aqueous carbonate solutions can be degassed to remove carbon dioxide from the solution formed during the reaction between the carbonate and the -SO3Z group. Degassing can be achieved by heating the aqueous carbonate solution and / or reducing the pressure above it. Furthermore, the step of contacting the membrane with the carbonate solution to form a fluorinated polymer salt can be carried out in a container with atmosphere control, including a pressure relief regulator to ensure that the released carbon dioxide does not overpressure the container. Furthermore, after the step of contacting the membrane with the carbonate solution to form a fluorinated polymer salt, the atmosphere in the container can be replaced with an inert gas, optionally nitrogen. Instead of using a sealed container, the membrane can be contacted with the carbonate in an open container.

[0048] Accordingly, according to one embodiment of this specification, a PFSA membrane (e.g., scrap membrane material generated during the manufacture of membranes for fuel cells or electrolytic cells, or used / waste membranes from such equipment) is treated with a carbonate solution of sufficient concentration and volume to completely convert the sulfonic acid to the corresponding salt. These substances are thoroughly mixed for a sufficient amount of time (with heating optionally) to convert the sulfonic acid to the salt by ion exchange. The mixture can then be heated to replace carbon dioxide from the solution, and the pressure can optionally be reduced to facilitate degassing of the solution. The carbonate and ionomer may be added directly to an autoclave or pressure reactor equipped with atmosphere control and pressure release control to ensure that the released carbon dioxide does not overpressurize the vessel during sulfonate formation and that a change in atmosphere from carbon dioxide to nitrogen is allowed after the completion of sulfonate formation.

[0049] In the process of forming a fluorinated polymer salt by contacting a membrane with a carbonate solution, it is possible to provide a molar excess of carbonate compared to the -SO3Z groups, and the excess carbonate can be removed before dispersing the membrane and converting the fluorinated polymer salt back to a protonated fluorinated polymer by cation exchange. The excess carbonate can be added to the fluorinated polymer to ensure that the fluorinated polymer is substantially completely converted to the salt form, and the excess carbonate can be substantially removed during or immediately after the conversion of the fluorinated polymer to the salt form. The removal of excess carbonate reduces problems in the specification and extraction of other components such as platinum group metal components and ensures that there is no need to recover the excess carbonate during the subsequent ion exchange process that converts the fluorinated polymer salt back to an acid form, thus improving the overall material balance.

[0050] Advantageously, the carbonate aqueous solution is maintained at a sufficiently low temperature so that the membrane remains in a solid, non-dispersible form during the process of contacting the membrane with the carbonate aqueous solution to form a solid, non-dispersible form of the fluorinated polymer salt. This is in contrast to the conventional method of dispersing the membrane by heating it in an aqueous basic solution. It has been found that the fluorinated polymer membrane can be converted to a salt form using a carbonate reagent without dispersing the membrane. This is advantageous because excess carbonate can be easily removed by separating the solid fluorinated polymer salt from the carbonate aqueous solution by solid-liquid separation techniques, optionally decantation or filtration. Alternatively, the carbonate (e.g., ammonium carbonate) can be removed using heat treatment (note that ammonium carbonate, other organic carbonates, and / or other ammonium salts can be removed using heat treatment as an alternative to solid-liquid separation techniques such as filtration). The solid fluorinated polymer salt can then be dispersed in a (non-basic) solvent, optionally water, before converting the fluorinated polymer salt to a fluorinated polymer by cation exchange. As previously shown, the removal of excess carbonates reduces problems in the specification and extraction of other components, such as platinum group metal components, and ensures that there is no need to recover excess carbonates during the subsequent ion exchange process that converts the fluorinated polymer salts back into an acidic form, thus improving the overall material balance.

[0051] During the step of contacting the film with an aqueous carbonate solution to form a fluorinated polymer salt, the aqueous carbonate solution may be maintained at a temperature below 150°C, 100°C, 80°C, 60°C, or 40°C, optionally above 5°C, 10°C, or 15°C, optionally within a range defined by any of the aforementioned upper and lower limits (e.g., room temperature). The temperature may be low enough so that the conversion of the fluorinated polymer to the salt form is achieved without dispersing the fluorinated polymer film, which remains in a non-dispersible solid form.

[0052] After separating the solid fluorinated polymer salt from the carbonate aqueous solution, and before dispersing the solid fluorinated polymer salt in the dispersion solvent, the solid fluorinated polymer salt can be washed with a washing solvent, optionally water.

[0053] The solid fluorinated polymer salt can be dispersed in a solvent (e.g., water) by heating the solid fluorinated polymer salt in the solvent to a temperature of at least 180°C, 200°C, 220°C, 240°C, or 250°C before forming the fluorinated polymer salt, optionally washing it, and converting the fluorinated polymer salt to a fluorinated polymer by cation exchange.

[0054] In the preferred process described above, the fluorinated polymer film is converted to a salt form without dispersing the film. Dispersion is then achieved in a further process step without the use of a base / carbonate.

[0055] The solid salt may be stored as an intermediate product until it is needed for use in the production of a new fluorinated polymer or until it is immediately converted to a protonated fluorinated polymer. In this regard, the fluorinated polymer salt can then be dispersed (for example, by autoclaving in water) before the step of converting the fluorinated polymer salt to a fluorinated polymer by cation exchange. After the fluorinated polymer salt has been converted to a fluorinated polymer by cation exchange, the fluorinated polymer can be reused to produce a new film.

[0056] The membrane may be a catalyst coating membrane for a fuel cell or electrolytic cell. In this case, it is desirable to recycle the catalyst components and the polymer material of the membrane. Therefore, at least one catalyst material can be separated from the membrane before contacting the membrane with a carbonate solution to form a fluorinated polymer salt, and / or at least one catalyst material can be separated from the fluorinated polymer or fluorinated polymer salt after contacting the membrane with a carbonate solution to form a fluorinated polymer salt.

[0057] experiment Figure 8 shows an example of the process steps (before autoclaving). The film on a roll was cut, and then further cut or folded to size. The film was brownish in color, as shown in the figure. The film was then refluxed in a lithium carbonate solution, at which point it became colorless and was converted to a salt form, as confirmed by spectroscopic analysis. The conversion was achieved without dispersing the film, and the film remained in a solid, non-disperse form.

[0058] It should be noted that a change in film color does not necessarily indicate a chemical change, and films can have different colors. However, in the exemplary examples, the chemical change of the polymer from the protonated form to the salt form was accompanied by a corresponding color change, as shown in the figure.

[0059] In the final step before autoclaving, as shown in Figure 8, the solid polymer salt film material was washed with water to remove residual lithium carbonate solution. Spectroscopic analysis confirmed that the colorless film was in salt form.

[0060] In one example, sodium carbonate (0.73 g, 6.88 mmol) was dissolved in deionized water (200 mL). A portion of the perfluorosulfonic acid ionomer membrane (6.25 mmol SO3) was then dissolved. - The membrane was immersed in a portion of sodium carbonate solution (100 mL) for 1 hour and then boiled for another hour. The resulting membrane was washed with deionized water and dried under vacuum. The FTIR of the membrane before and after ion exchange (membrane receiving 1 equivalent of Na as Na2CO3, see Figure 9) was approximately 1050-1060 cm⁻¹.-1 The shift of the symmetric stretch of the sulfinate group (SO3 - ) is shown, indicating a change in the environment and interpreted as successful ion exchange. The basicity of the solution after ion exchange and boiling decreased from 0.04 M [OH - to 0.00 M [OH - upon titration with HCl.

[0061] The second example followed the same methodology but used twice the amount of sodium carbonate (1.46 g, 13.75 mmol). The FTIR of the membrane before and after ion exchange (membrane receiving 2 equivalents of Na as Na2CO3, see Figure 9) shows a similar shift in the symmetric stretch of the sulfinate group (SO3 - ). The basicity of the solution after ion exchange and boiling decreased from 0.06 M [OH - to 0.02 M [OH - , and the pH decreased from 11.1 to 8.4.

[0062] As previously described in the example of the hydroxide reagent with reference to Figure 5, the membrane can be dispersed in water using a further step of autoclaving the membrane following the process of Figure 8. The non-dispersed polymer salt film of the colorless solid can be autoclaved in water under nitrogen at 250 °C and a pressure of 40 bar (4000 kPa). This gives an (non-basic) aqueous dispersion of the polymer salt.

[0063] Furthermore, as previously described in the example of the hydroxide reagent with reference to Figure 6, a further step of ion exchange (after autoclaving) can be used to convert the dispersed polymer salt back to the protonated acid form. An ion exchange column containing Amberlyst™ 15(H) resin can be utilized in this process step. The dispersion of the (protonated) fluorinated polymer may then be reused to produce new membranes or dried and stored for future use.

[0064] Alternative salt-forming reagents Other reagents can be used to provide the cation source necessary to form a fluorinated polymer salt in which Z is a cation, while it has also been confirmed that the film remains in a solid, non-dispersed state. For example, metal chloride solutions have been used for this purpose.

[0065] Although the present invention has been specifically illustrated and described with reference to certain embodiments, it will be understood by those skilled in the art that various modifications in form and detail can be made without departing from the scope of the invention as defined by the appended claims. This disclosure may include the following: [Aspect 1] A method for recycling a fluorinated polymer from a film containing a fluorinated polymer, wherein the fluorinated polymer comprises a fluorinated polymer main chain and a fluorinated polymer of formula -SO 3 The method comprises a plurality of groups represented by Z (wherein Z is hydrogen), and the method is The process involves contacting the film with a reagent that provides a cation source for forming a fluorinated polymer salt in which Z is a cation, wherein the reagent is maintained at a sufficiently low temperature so that the film remains in a solid, non-dispersed state. To remove excess unreacted reagent from the solid fluorinated polymer salt, The present invention provides a method comprising removing the excess reagent and then dispersing the solid fluorinated polymer salt in a solvent. [Aspect 2] The method according to embodiment 1, further comprising dispersing the solid fluorinated polymer salt in the solvent, and then converting the fluorinated polymer salt back into a fluorinated polymer in which Z is hydrogen by cation exchange. [Aspect 3] The method according to embodiment 1 or 2, wherein the excess unreacted reagent is removed from the solid fluorinated polymer salt using solid-liquid separation techniques, optionally decantation and filtration. [Aspect 4] The method according to any one of embodiments 1 to 3, wherein the solvent used to disperse the solid fluorinated polymer salt after removing the excess base is water. [Aspect 5] The method according to any one of embodiments 1 to 4, wherein the reagent is maintained at a temperature of 150°C, 100°C, 80°C, 60°C, or less than 40°C during the step of contacting the film with the reagent to form the fluorinated polymer salt. [Aspect 6] The method according to any one of embodiments 1 to 5, wherein the solid fluorinated polymer salt is washed with a solvent, or optionally with water, after separating the solid fluorinated polymer salt from the reagent and before dispersing the solid fluorinated polymer salt in the solvent. [Aspect 7] The method according to any one of embodiments 1 to 6, wherein the solid fluorinated polymer salt is dispersed in the solvent by heating the solid fluorinated polymer salt in the solvent to a temperature of at least 180°C, 200°C, 220°C, 240°C, or 250°C. [Aspect 8] The reagent that provides the cation source for forming the fluorinated polymer salt includes bases, hydroxides, metal hydroxides, ammonium hydroxide, carbonates, metal carbonates, alkali metal carbonates, alkaline earth metal carbonates, ammonium carbonate, halides, metal halides, organic salts, formate salts, acetate salts, oxalates, citrate salts, gluconates, inorganic cation sources, metal cation sources, organic cation sources, and NH4. 4 + The method according to any one of embodiments 1 to 7, wherein the source is selected from one or more of bicarbonates, carbamates, nitrates, phosphates, and sulfates. [Aspect 9] The reagent is the -SO 3 The method according to any one of embodiments 1 to 8, which provides the cation in a molar equivalent or molar excess relative to the Z group. [Aspect 10] The method according to any one of embodiments 1 to 9, wherein the reagent is an aqueous solution. [Aspect 11] The method according to any one of embodiments 1 to 10, wherein the reagent is a base, or optionally a hydroxide. [Aspect 12] The method according to any one of embodiments 1 to 10, wherein the reagent is an aqueous carbonate solution, optionally a metal carbonate, an alkali metal carbonate, an alkaline earth metal carbonate, or ammonium carbonate. [Aspect 13] The carbonate aqueous solution is degassed, and the carbonate and the -SO 3 The method according to embodiment 12, wherein carbon dioxide formed during the reaction with the Z group is removed, and degassing is achieved by heating the carbonate aqueous solution and / or reducing the pressure on the carbonate aqueous solution. [Aspect 14] The method according to embodiment 12 or 13, wherein the step of contacting the membrane with the carbonate aqueous solution to form the fluorinated polymer salt is performed in a container having atmosphere control including a pressure relief regulating device to ensure that the released carbon dioxide does not overpressure the container. [Aspect 15] The method according to any one of embodiments 12 to 14, wherein, after the step of contacting the film with the carbonate aqueous solution to form the fluorinated polymer salt, the atmosphere inside the container is replaced with an inert gas, optionally nitrogen. [Aspect 16] The method according to any one of embodiments 1 to 15, wherein the fluorinated polymer salt is converted to a fluorinated polymer by cation exchange, and the fluorinated polymer is then reused to produce a new film. [Aspect 17] The method according to any one of embodiments 1 to 16, wherein the membrane is a catalyst coating membrane for a fuel cell or electrolytic cell. [Aspect 18] The method according to embodiment 17, wherein at least one catalyst material is separated from the membrane before the membrane is brought into contact with the reagent. [Aspect 19] The method according to embodiment 17 or 18, wherein at least one catalyst material is separated from the fluorinated polymer or the fluorinated polymer salt after the film has been brought into contact with the reagent.

Claims

1. A method for recycling a fluorinated polymer from a film containing a fluorinated polymer, wherein the fluorinated polymer comprises a fluorinated polymer main chain and a material of the formula -SO ３ The method comprises a plurality of groups represented by Z (wherein Z is hydrogen), and the method is The film is brought into contact with a reagent that provides a cation source for forming a fluorinated polymer salt in which Z is a cation, wherein the reagent is maintained at a sufficiently low temperature so that the film remains in a solid, non-dispersed state. To remove excess unreacted reagent from the solid fluorinated polymer salt, After removing the excess reagent, the solid fluorinated polymer salt is dispersed in the solvent. A method comprising dispersing the solid fluorinated polymer salt in the solvent, and then converting the fluorinated polymer salt back into a fluorinated polymer in which Z is hydrogen by cation exchange.

2. The method according to claim 1, wherein the excess unreacted reagent is removed from the solid fluorinated polymer salt using a solid-liquid separation technique.

3. The method according to claim 1, wherein the solvent used to disperse the solid fluorinated polymer salt after removing the excess base is water.

4. The method according to claim 1, wherein the reagent is maintained at a temperature of 150°C, 100°C, 80°C, 60°C, or less than 40°C during the step of contacting the film with the reagent to form the fluorinated polymer salt.

5. The method according to claim 1, wherein the solid fluorinated polymer salt is washed in a solvent after being separated from the reagent and before being dispersed in the solvent.

6. The method according to claim 1, wherein the solid fluorinated polymer salt is dispersed in the solvent by heating the solid fluorinated polymer salt in the solvent to a temperature of at least 180°C, 200°C, 220°C, 240°C, or 250°C.

7. The reagent that provides the cation source for forming the fluorinated polymer salt includes bases, hydroxides, metal hydroxides, ammonium hydroxide, carbonates, metal carbonates, alkali metal carbonates, alkaline earth metal carbonates, ammonium carbonate, halides, metal halides, organic salts, formate salts, acetate salts, oxalates, citrate salts, gluconates, inorganic cation sources, metal cation sources, organic cation sources, and NH ４ ＋ The method according to claim 1, wherein a source of nitrates is selected from one or more of bicarbonates, carbamates, nitrates, phosphates, and sulfates.

8. The reagent is the -SO ３ The method according to claim 1, which provides the cation in a molar equivalent or molar excess relative to the Z group.

9. The method according to claim 1, wherein the reagent is an aqueous solution.

10. The method according to claim 1, wherein the reagent is a base.

11. The method according to claim 1, wherein the reagent is an aqueous carbonate solution.

12. The carbonate aqueous solution is degassed, and the carbonate and the -SO ３ The method according to claim 11, wherein carbon dioxide formed during the reaction with the Z group is removed, and degassing is achieved by heating the carbonate aqueous solution and / or reducing the pressure on the carbonate aqueous solution.

13. The method according to claim 11, wherein the step of contacting the membrane with the carbonate aqueous solution to form the fluorinated polymer salt is performed in a container having atmosphere control including a pressure relief regulating device to ensure that the released carbon dioxide does not overpressure the container.

14. The method according to claim 13, wherein, after the step of contacting the film with the carbonate aqueous solution to form the fluorinated polymer salt, the atmosphere inside the container is replaced with an inert gas.

15. The method according to claim 1, wherein the fluorinated polymer salt is converted to a fluorinated polymer by cation exchange, and the fluorinated polymer is then reused to produce a new film.

16. The method according to claim 1, wherein the membrane is a catalyst coating membrane for a fuel cell or electrolytic cell.

17. The method according to claim 16, wherein at least one catalyst material is separated from the membrane before the membrane is brought into contact with the reagent.

18. The method according to claim 16, wherein at least one catalyst material is separated from the fluorinated polymer or the fluorinated polymer salt after the membrane has been brought into contact with the reagent.

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