Method for producing platinum group metals and method for recovering platinum group metals

Abstract

To provide a method for producing platinum group metals from organic compounds of platinum group metals with high yield, and a method for efficiently recovering platinum group metals from organic compounds of platinum group metals.SOLUTION: There is provided a method for producing platinum group metals comprising: heating an organic compound of a platinum group metal in the presence of oxygen to T2°C or higher, which satisfies the following formula (1), where T1°C is the lowest peak temperature among the peak temperatures in the range of 300°C to 600°C when the organic compound of a platinum group metal is measured by DSC in the atmosphere at a heating rate of 5°C / min. T2=T1-30...(1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a platinum group metal from an organic compound containing the platinum group metal, and more particularly to a method for producing a platinum group metal by heat-treating an organic compound of the platinum group metal under predetermined temperature conditions. The present invention also relates to a method for recovering platinum group metals from organic compounds of platinum group metals. [Background technology]

[0002] Platinum group metals are transition metals belonging to groups 8, 9, and 10 of the periodic table, and are a collective term for six metals: platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), and osmium (Os). Platinum group metals have electrons in the d orbitals, the outermost shell of the atom, that form covalent bonds with hydrogen and oxygen. Because of this, catalysts using platinum group metals are known to exhibit high activity in oxidation and reduction reactions. They are also chemically stable, highly resistant to acids and alkalis, and have high melting points, giving them excellent heat resistance. Because of these advantages, catalysts using platinum group metals are used in a variety of industries. For example, platinum group metals are used as catalysts for chemical reactions in the fields of fine chemicals, such as petroleum refining, petrochemicals, medicines, fragrances, and foods, etc. In these fields, catalysts containing platinum group metals are used in various chemical reactions, such as hydrogenation reactions, dehydrogenation reactions, oxidation reactions, coupling reactions, olefin metathesis reactions, and polymerization reactions.

[0003] These platinum group metals are also known as electrode catalysts used in electrodes of polymer electrolyte fuel cells, polymer electrolyte water electrolysis devices, soda industrial electrolytic cells, chemical sensors, and the like. These applications often involve the use of organic compounds of platinum group metals, which are important catalysts for the hydrogenation of olefins and the industrial synthesis of acetic acid. Because of their wide range of applicable reactions, they have also attracted academic attention for their use in fine chemical synthesis.

[0004] In recent years, platinum group metals have also been used in phosphorescent materials, which are one of the light-emitting materials used in television and smartphone displays, and organometallic compounds of iridium, ruthenium, and platinum are widely known as phosphorescent materials. In particular, iridium complexes for organic EL devices, in which the platinum group metal is iridium, are known to have luminous efficiency three to four times higher than that of organic EL devices using conventional fluorescent materials.

[0005] However, since platinum group metals are produced in unevenly distributed areas and their supply is unstable, if it were possible to recover used catalysts and phosphorescent materials and re-produce platinum group metals from the recovered organic compounds of platinum group metals, this would lead to a more stable supply of platinum group metals and also to cost reductions for the various products obtained from organic compounds of platinum group metals.

[0006] Methods for separating and recovering platinum group metals from alloys containing platinum group metals or mixtures of platinum group metals with metallic and / or inorganic materials include dry methods (e.g., Patent Documents 1 and 2), in which the alloy or mixture containing the platinum group metal is dissolved in a metal called a collector metal, such as iron or copper, at high temperature to recover the platinum group metal (see, for example, Patent Documents 1 and 2), and solution methods (e.g., Patent Documents 3, 4, and 5), in which the platinum group metal-containing mixture is dissolved in an acid, such as aqua regia, and the platinum group metal is ionized in the solution and extracted. Additionally, various methods have been proposed for recovering platinum group metals from acidic solutions, such as sulfuric acid and hydrochloric acid, that contain platinum group metals (see, for example, Patent Document 6). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2022-157581 [Patent Document 2] WO2015 / 030243 [Patent Document 3] Patent Publication No. 2022-135956 [Patent Document 4] Patent No. 5984020 [Patent Document 5] Patent No. 6399352 [Patent Document 6] WO2021 / 153710 Summary of the Invention [Problem to be solved by the invention]

[0008] However, all of the methods described in the above patent documents are directed to recovering platinum group metals from metal mixtures containing platinum group metals or inorganic compounds of platinum group metals. As mentioned above, organic compounds of platinum group metals have been widely used in recent years as catalysts and phosphorescent materials, and therefore recovering organic compounds of platinum group metals and producing platinum group metals from them has been a major challenge for platinum group metals, which are limited in resource amount. However, until now, no industrially significant method for recovering platinum group metals from organic compounds of platinum group metals has been known. That is, an object of the present invention is to provide a method for producing platinum group metals from organic compounds of platinum group metals. It is a further object of the present invention to provide a method for recovering platinum group metals from organic compounds of platinum group metals. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems and have completed the present invention.

[0010] [1] A method for producing a platinum group metal, comprising heating an organic compound of a platinum group metal in the presence of oxygen to T2°C or higher that satisfies the following formula (1), where T1°C is the lowest peak temperature among the peak temperatures in the range of 300°C or higher and 600°C or lower when the organic compound of a platinum group metal is measured in air by differential scanning calorimetry at a heating rate of 5°C / min: T2=T1-30 (1) [2] The method according to item [1], wherein the organic compound of a platinum group metal is heated in the presence of oxygen within a temperature range of T4°C or less that satisfies the following formula (2), where T3°C is the highest peak temperature among the peak temperatures in the range of 300°C or more and 600°C or less when measured by differential scanning calorimetry. T4=T3+340 (2) [3] The method according to [1] or [2] above, wherein the heating is carried out for 1 hour or more and 20 hours or less. [4] The method according to any one of [1] to [3] above, wherein the heating is carried out at a constant temperature. [5] The method according to any one of [1] to [4] above, wherein the organic compound of a platinum group metal is a compound represented by the following general formula (IV) or (V): [ka] [ka] [6] The method according to [5] above, wherein M in the general formula (IV) or (V) is iridium or ruthenium.

[0011] The present invention also has the following aspects. [7] A method for recovering platinum group metals, comprising heating an organic compound of a platinum group metal in the presence of oxygen to a temperature range of T2 or higher that satisfies the following formula (3), where T1°C is the lowest peak temperature among the peak temperatures in the range of 300°C or higher and 600°C or lower when the organic compound of a platinum group metal is measured in air by differential scanning calorimetry at a heating rate of 5°C / min: T2=T1-30 (3) [8] The method according to item [7], wherein the organic compound of a platinum group metal is heated in the presence of oxygen within a temperature range of T4°C or less that satisfies the following formula (4), where T3°C is the highest peak temperature among the peak temperatures in the range of 300°C or more and 600°C or less when measured by differential scanning calorimetry. T4=T3+340 (4) [9] The method for recovering the product according to [7] or [8], wherein the heated product is further reduced while being heated in the range of 500°C or higher and 700°C or lower. [Effects of the Invention]

[0012] The present invention provides a method for producing platinum group metals from organic compounds of platinum group metals, and a method for recovering platinum group metals from organic compounds of platinum group metals. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing differential scanning calorimetry of an organic compound of a platinum group metal used in the present invention. [Figure 2] 1 is a differential scanning calorimetry measurement chart of tris(2-phenylpyridinato)iridium (hereinafter also referred to as "Ir(ppy)3"). [Figure 3] 1 is a differential scanning calorimetry measurement chart of tri(benzoquinone)iridium (hereinafter also referred to as "Ir(bzq)3"). DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. In the production method of the present invention (hereinafter also referred to as "this production method"), when an organic compound of a platinum group metal is measured in air by differential scanning calorimetry (hereinafter also referred to as "DSC") at a heating rate of 5°C / min, the lowest peak temperature among peak temperatures in the range of 300°C to 600°C is defined as T1°C, and the production method of the present invention comprises heating the organic compound of a platinum group metal in the presence of oxygen to a temperature range of T2°C or higher that satisfies the following formula (1): T2=T1-30 (1) The organic compound of a platinum group metal used in this production method is represented by the following general formula (I). L n MX m (I) In the general formula (I), M represents a platinum group metal, L represents a ligand having at least one carbon atom coordinated to M, and X represents a ligand other than L. m is an integer of 0 or greater and represents the number of X atoms coordinated to M, n is an integer of 1 or greater and represents the number of L atoms coordinated to M, and m+n represents the valence of M. M is directly bonded to at least one carbon atom in L. The direct bond may be either a covalent bond or a coordinate bond between carbon and metal. L has carbon and may contain heteroatoms other than carbon such as hydrogen, oxygen, sulfur, phosphorus, nitrogen, etc. X is, for example, a halogen atom, oxygen, acetylacetonate, etc. When there are a plurality of L's, the plurality of L's may be the same or different. When there are a plurality of X's, the plurality of X's may be the same or different.

[0015] Examples of L include a ligand containing a carbonyl group, a linear or branched alkyl group, an alkenyl group, an alkynyl group, a monocyclic or polycyclic cycloalkyl group, a cycloalkenyl group, and an aromatic ring. The carbon atoms in these groups and aromatic rings may be substituted with at least one atom selected from the group consisting of oxygen, sulfur, phosphorus, and nitrogen, and the hydrogen atoms in these groups and aromatic rings may be substituted with functional groups containing oxygen, sulfur, phosphorus, and nitrogen. Furthermore, L may be a combination of at least two of the above groups, aromatic rings, heterocycles, and functional groups to form a single ligand. Acetylacetonate is not included in L.

[0016] Examples of the ligand include the ligands described in paragraphs 0027 and 0029 of JP-A-2004-52264 (excluding acetylacetonate), the ligands described in [Chemical Formula 5] of WO2005 / 097944, the ligands described in paragraph 0052 of JP-A-2018-142707, the ligands described in paragraph 0093 of JP-A-2015-120717, and the ligands described in paragraph 0052 of JP-A-2016-129232.

[0017] The organic compound of a platinum group metal used in this production method may be a mixture of multiple metals, or a mixture of multiple organic compounds of the same metal but with different ligands. From the viewpoint of separating the resulting platinum group metals, the organic compound of a platinum group metal used in this production method is preferably a mixture of organic compounds of the same platinum group metal.

[0018] From the viewpoint of increasing the yield of platinum group metals by this production method, organic compounds of platinum group metals having a phenylpyridine derivative represented by the following general formula (II) as a ligand, and organic compounds of platinum group metals having a benzoquinone derivative represented by the following general formula (III) as a ligand are preferred. [ka] In the general formula (II), M is the same as above, R1 and R2 are each a hydrogen atom or a linear or It represents a branched alkyl group, an alkenyl group, an alkynyl group, a monocyclic or polycyclic cycloalkyl group, a cycloalkenyl group, or an aromatic ring. The carbon atoms in these groups and aromatic rings may be substituted with at least one atom selected from the group consisting of oxygen, sulfur, phosphorus, and nitrogen, to form a heterocycle, or the hydrogen atoms in these groups and aromatic rings may be substituted with a functional group containing oxygen, sulfur, phosphorus, or nitrogen. n1 and n2 represent integers of 1 to 4, and when there are a plurality of R1s and R2s, they may be the same or different, and may combine with other R1s or R2s to form a ring. L1 represents a ligand different from a phenylpyridine derivative, the total number of m1 and l is the same as the valence of the platinum group metal M, m1 represents an integer of 1 or more, and l represents 0 or an integer of 1 or more.

[0019] [ka]

[0020] In the general formula (III), M is the same as defined above, and R3 to R5 each represent a hydrogen atom, a linear or branched alkyl group, an alkenyl group, an alkynyl group, a monocyclic or polycyclic cycloalkyl group, a cycloalkenyl group, or an aromatic ring. Carbon atoms in these groups and aromatic rings may be heterocycles substituted with at least one atom selected from the group consisting of oxygen, sulfur, phosphorus, and nitrogen, or hydrogen atoms in these groups and aromatic rings may be substituted with functional groups containing oxygen, sulfur, phosphorus, and nitrogen. n3 and n5 represent integers of 1 to 3, and n4 represents an integer of 1 or 2. When there are a plurality of R3 to R5, they may be the same or different, and may combine with at least one other R3 to R5 to form a ring. L2 represents a ligand different from a benzoquinone derivative, the total number of m2 and l' is the same as the valence of the platinum group metal M, m2 represents an integer of 1 or more, and l' represents 0 or an integer of 1 or more.

[0021] From the viewpoint of increasing the yield of platinum group metals by the present production method, organic compounds of platinum group metals represented by the following general formulas (IV) and (V) are more preferred. [ka] In the general formula (IV), M is the same as defined above.

[0022] [ka] In the general formula (V), M is the same as defined above.

[0023] In this production method, since an organic compound of a platinum group metal is heated in the presence of oxygen, platinum group metal oxides may be generated when the platinum group metal is generated. From the viewpoint of suppressing the generation of such platinum group metal oxides, M in the general formulas (II) and (III) is preferably iridium or ruthenium, and M in the general formulas (IV) and (V) is more preferably iridium or ruthenium.

[0024] Although there are no particular limitations on the shape of the organic compound of a platinum group metal used in this production method, a particulate form is preferred from the viewpoint of ease of handling.Furthermore, from the viewpoint of the production efficiency of platinum group metals, a powdered organic compound of a platinum group metal with an average particle size of 1 mm or less is preferred. The average particle size is usually the volume average particle size. The volume average particle size is the D50 value, which can be measured using a laser diffraction particle size analyzer or the like. D50 can be measured by dynamic light scattering using a laser particle size analyzer or the like. The volume average particle size of particles is the particle size at which the cumulative volume distribution curve reaches 50% of the cumulative volume when plotted from the small diameter side in the particle size distribution.

[0025] This production method is suitable for use in a variety of applications and for subsequent recovery of organic compounds of platinum group metals. Depending on the application, the recovered organic compounds of platinum group metals may be recovered in a state where they are attached to an organic or inorganic substance such as a substrate or carrier, or in a state where they are mixed with an organic or inorganic substance. Therefore, it is preferable to remove the organic or inorganic substances from the recovered organic compound of a platinum group metal by washing, pulverizing, classifying, dissolving, melting, or other treatment, and then subject the platinum group metal compound to the present production method.

[0026] In this production method, when the organic compound of a platinum group metal is subjected to DSC measurement in air at a heating rate of 5°C / min, the lowest peak temperature among the peak temperatures in the range of 300°C to 600°C is defined as T1°C, and the organic compound of a platinum group metal is heated in the presence of oxygen to a temperature range of T2°C or higher that satisfies the following formula (1): T2=T1-30 (1) The relationship between T1 and T2 is shown in Figure 1. Figure 1 shows a schematic DSC chart obtained when an organic compound of a platinum group metal is subjected to DSC measurement in air at a heating rate of 10°C / min. The horizontal axis of Figure 1 represents temperature (°C), and the vertical axis represents heat flow (mW).

[0027] As shown in Figure 1, DSC measurements of organic compounds of platinum group metals usually show multiple endothermic peaks in the range of 300°C to 600°C. T1 is the peak temperature of the peak that appears at the lowest temperature above 300°C, and is the peak top temperature. The peak top temperature is generally displayed by the DSC measurement device, but the peak top temperature can also be read from the DSC chart. It should be noted that FIG. 1 is a schematic illustration of a DSC chart, and the number of peaks and the shape of the peaks are not limited to this.

[0028] Heating breaks the bonds between platinum group metals and carbon, and the molecules of organic compounds of platinum group metals decompose, producing platinum group metals. If the heating temperature is below T2°C, the production of platinum group metals will not proceed smoothly, and it will take a long time to produce platinum group metals, which is industrially disadvantageous.

[0029] The upper limit of the heating temperature is usually 1000°C. If the temperature exceeds 1000°C, the platinum group metals produced may volatilize. Furthermore, in this production method, heating is performed in the presence of oxygen as described below, which may result in the production of platinum group metal oxides. From the viewpoint of suppressing the production of platinum group metal oxides, it is preferable to heat the organic compound of a platinum group metal in the presence of oxygen at a temperature of T4°C or lower that satisfies the following formula (2), where T3°C is the highest peak temperature among the peak temperatures in the range of 300°C to 600°C in the DSC measurement: T4=T3+340 (2) As shown in Figure 1, among the multiple endothermic peaks in the range of 300°C to 600°C, T3 is the peak temperature of the peak that appears at the highest temperature below 600°C, and is the peak top temperature. The peak top temperature can be determined in the same manner as above.

[0030] From the viewpoint of suppressing the generation of platinum group metal oxides, it is more preferable to heat the organic compound of a platinum group metal in the presence of oxygen within a temperature range of T5° C. or less that satisfies the following formula (5). T5=T3+300 (5)

[0031] The heating time can be set appropriately by checking the conversion amount of the organic compound of the platinum group metal, which is the raw material, while performing analysis, etc. during heating. The heating time is usually 1 hour or more, and from the viewpoint of the yield of the platinum group metal, 2 hours or more is preferred, and 3 hours or more is more preferred. The heating time is set appropriately depending on the heating temperature, but from the viewpoint of suppressing the production amount of platinum group metal oxide and suppressing the volatilization of the platinum group metal, 20 hours or less is preferred, and 15 hours or less is more preferred. From the viewpoint of suppressing the production amount of platinum group metal oxide and suppressing the volatilization of the platinum group metal, a shorter heating time is more preferred when the heating temperature is high.

[0032] The heating temperature does not need to be constant during the heating time, and may vary during the heating time, for example, as long as it is equal to or higher than T2°C. When the heating temperature is T2° C. or higher and T4° C. or lower, or T5° C. or lower, the heating temperature may vary during the heating period as long as it is within this temperature range. It is preferable that the heating temperature be constant during the heating time from the viewpoint of the yield of platinum group metals.

[0033] When the heating is carried out in a batch system, the heating may be carried out in a commonly used heat treatment furnace. There are no particular limitations on the heat treatment furnace, but a muffle furnace or a tubular furnace that can be heated up to about 1000°C in the atmosphere is preferably used. When the heating is carried out continuously, the heating may be carried out by flowing a gaseous fluid heated to a predetermined temperature and contacting the organic compound of a platinum group metal with the gaseous fluid for a predetermined period of time.

[0034] The heating may be carried out in an inert gas, but since, as mentioned above, the generation of platinum group metals requires that platinum group metal-carbon bonds be cleaved and that molecular decomposition of the organic compound of the platinum group metal proceed, the heating is carried out in the presence of oxygen in this production method to facilitate these processes. Furthermore, when the ligands of the organic compound of the platinum group metal are decomposed and removed as carbon dioxide, nitrogen oxides, etc., it is preferable that a sufficient amount of oxygen is present.

[0035] When the heating is carried out batchwise, the oxygen concentration in the heating atmosphere is preferably 5 vol% or more, more preferably 10 vol% or more, from the viewpoint of the amount of platinum group metal produced, and is preferably 50 vol% or less, more preferably 30 vol% or less, from the viewpoint of suppressing the production of platinum group metal oxides. When heating is carried out in a batch manner, it is preferable to carry out the heating in a crucible having a capacity sufficient for the organic compound of a platinum group metal.

[0036] When the heating is carried out continuously, the oxygen concentration in the gaseous fluid is preferably 5 vol% or more, more preferably 10 vol% or more, from the viewpoint of the amount of platinum group metal produced, and is preferably 50 vol% or less, more preferably 30 vol% or less, from the viewpoint of suppressing the production of platinum group metal oxides.

[0037] The heating produces platinum group metal and, as a by-product, platinum group metal oxide. The resulting platinum group metal has a valence of zero. The produced platinum group metal oxide can be reduced to platinum group metal by the reduction method described below. Therefore, the platinum group metal oxide produced by this production method can be considered a precursor of platinum group metal, and the amount of platinum group metal produced by this production method can be considered to include the amount of platinum group metal oxide produced and be used to determine the yield of platinum group metal. The yield of platinum group metal, including the amount of platinum group metal in the platinum group metal oxide, is preferably 80% by mass or more, more preferably 90% by mass or more. The yield is expressed as a percentage by dividing the total mass of the platinum group metal obtained by this production method and the platinum group metal in the platinum group metal oxide by the mass of the platinum group metal in the raw material organic compound of the platinum group metal.

[0038] The amount of platinum group metal oxide produced is preferably small, and the amount of platinum group metal is preferably 70 at% or more, more preferably 80 at% or more, and even more preferably 90 at% or more, where the total of the produced platinum group metal and the platinum group metal in the platinum group metal oxide is 100 at%. The platinum group metals can be qualitatively and quantitatively determined by X-ray diffraction (hereinafter also referred to as "XRD") or the like.

[0039] The produced platinum group metal oxide can be reduced, for example, by a reduction method using a reducing agent such as lithium aluminum hydride or sodium borohydride, or by a reduction method in which the oxide is directly reduced with hydrogen. The produced platinum group metal oxide may be separated from the platinum group metal obtained by this production method and then subjected to the reduction method described above to obtain the platinum group metal, or the mixture of platinum group metal and platinum group metal oxide may be subjected to the reduction method described above to obtain the platinum group metal from the platinum group metal oxide. When a platinum group metal oxide is obtained by this production method, it is preferable to subsequently convert the platinum group metal oxide into platinum group metal by the reduction method described above while the mixture of platinum group metal and platinum group metal oxide is still in this state, as this increases the yield of platinum group metal.

[0040] Therefore, from the viewpoint of improving the yield of platinum group metals, it is preferable to further reduce the mixture of platinum group metals and platinum group metal oxides produced in this production method. The produced platinum group metal oxides can be reduced with hydrogen at a temperature in the range of 500°C to 700°C to obtain platinum group metals. The reduction is preferably carried out while heating in the range of 400° C. to 900° C. The heating temperature is more preferably 500° C. to 800° C. The reduction may be carried out in a batch or continuous manner.

[0041] The reduction may be carried out by contacting with the reducing agent, but from the viewpoint of reducing power, it is preferable to carry out the reduction directly with hydrogen. When the reduction is carried out in a batch system, the hydrogen concentration in the heated atmosphere is preferably 25 vol% or more, more preferably 35 vol% or more, from the viewpoint of reducing power, and is preferably 80 vol% or less, more preferably 70 vol% or less, from the viewpoint of safety.

[0042] When the reduction is carried out continuously, the reduction can be carried out by contacting a gaseous fluid containing a predetermined hydrogen concentration at a predetermined temperature with a mixture of a platinum group metal and a platinum group metal oxide for a predetermined time. When the reduction is carried out continuously, from the viewpoint of reducing power, the hydrogen concentration in the gaseous fluid is preferably 25 vol% or more, more preferably 35 vol% or more. Furthermore, from the viewpoint of suppressing the production of platinum group metal oxide, the hydrogen concentration is preferably 80 vol% or less, more preferably 70 vol% or less.

[0043] It is preferable to dilute hydrogen with an inert gas so that the concentration falls within the above range. Examples of the inert gas include rare gases such as helium and argon, and nitrogen. The reduction time with hydrogen is usually 2 hours or more, preferably 4 hours or more. The end point of the reduction may be determined by quantifying the platinum group metal produced by the above method, but the reduction time is usually 9 hours or less, preferably 7 hours or less.

[0044] As described above, the present production method makes it possible to produce platinum group metals in high yield from organic compounds of platinum group metals, particularly from recovered organic compounds of platinum group metals.

[0045] The present invention also provides a method for recovering platinum group metals (hereinafter also referred to as "the present recovery method") by heating an organic compound of a platinum group metal in the presence of oxygen within a temperature range of T2°C or higher that satisfies the following formula (3), where T1°C is the lowest peak temperature among peak temperatures in the range of 300°C or higher and 600°C or lower when the organic compound of a platinum group metal is measured in air at a heating rate of 5°C / min: T2=T1-30 (3)

[0046] In this recovery method, the organic compounds of platinum group metals are the same as those described in this production method, and the preferred compounds are also the same. T1 and T2 are the same as those described in this production method.

[0047] In this recovery method, the upper limit of the heating temperature is usually 1000°C. When the highest peak temperature among the peak temperatures in the range of 300°C to 600°C inclusive in the DSC measurement is defined as T3°C, it is preferable to heat the organic compound of a platinum group metal in the presence of oxygen at a temperature of T4°C or lower that satisfies the following formula (4): T4=T3+340 (4) T3 and T4 are the same as those explained in this manufacturing method.

[0048] In this recovery method, as in the production method, it is more preferable to heat the organic compound of a platinum group metal in the presence of oxygen within a temperature range of T5° C. or less that satisfies the following formula (6): T5=T3+300 (6)

[0049] In this recovery method, the heating time, oxygen concentration, etc. are the same as in the above-mentioned production method. In this recovery method, as in the above-described production method, platinum group metal oxides are also recovered at the same time, and therefore, in this recovery method, it is also preferable to reduce the mixture of recovered platinum group metal and platinum group metal oxide from the viewpoint of improving the recovery rate of the platinum group metal. The reduction is also the same as in the present production method.

[0050] As described above, the present recovery method makes it possible to efficiently recover platinum group metals from organic compounds of platinum group metals, particularly from recovered organic compounds of platinum group metals.

[0051] Although the present manufacturing method and recovery method have been described above, the present invention is not limited to the configurations of the above-described embodiments. For example, in the configurations of the present manufacturing method and the present recovery method of the above embodiment, any other steps may be added, or any steps that produce the same effect may be substituted. [Example]

[0052] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0053] Synthesis Example 1 <Synthesis of Ir(ppy)3> Into a flask with a side tube, 133.5 g of iridium chloride (iridium concentration: 51.77 wt%), 503 g of 2-phenylpyridine, and 670 mL of ethylene glycol were charged, and the air in the flask was replaced with argon. A dropping funnel was installed on the side tube, and 164 g of triethanolamine and 240 mL of ethylene glycol were charged into the dropping funnel, and the air in the dropping funnel was replaced with argon. The solution was dropped while heating to 220 °C. After dropping, it was cooled and filtered, and further washed twice with 50 mL of methanol and four times with 200 mL of pure water. After washing, it was dried with a rotary evaporator to obtain 228 g of Ir(ppy)3 represented by the general formula (VI). The yield was 96.8%. After drying the Ir(ppy)3 obtained above, sublimation purification was carried out to obtain high-purity Ir(ppy)3.

[0054] The identification of the obtained Ir(ppy)3 was carried out by proton nuclear magnetic resonance (hereinafter also referred to as " 1 1H-NMR") and high performance liquid chromatography (hereinafter also referred to as "HPLC") measured under the following conditions. 1 In 1H-NMR, tetramethylsilane (hereinafter also referred to as "TMS") was used as a reference substance and identified by the chemical shift value of H shown in Table 1. The content of iridium in Ir(ppy)3 was 29.35 wt%. The content of iridium in Ir(ppy)3 was determined by inductively coupled plasma optical emission spectrometry (hereinafter also referred to as "ICP-OES").

[0055]

Chemical formula

[0056] Synthesis Example 2 <Synthesis of Ir(bzq)3> (i) Purification of 10-hydroxybenzo[h]quinoline A flask was charged with 250 g of 10-hydroxybenzo[h]quinoline and enough methanol to wet the 10-hydroxybenzo[h]quinoline, followed by a small amount of pure water. 172 g of 36% HCl was added to dissolve the 10-hydroxybenzo[h]quinoline, and then pure water was added to a total volume of 2.5 L to prepare a 10-hydroxybenzo[h]quinoline solution. The above 10-hydroxybenzo[h]quinoline solution was placed in a separatory funnel, and 400 mL of dichloromethane was then added. After the lower phase of the solution in the separatory funnel was drained, NaOH solution was added to the remaining liquid, and it was confirmed to be alkaline using pH test paper. 500 mL of dichloromethane was added to the separatory funnel to extract 10-hydroxybenzo[h]quinoline, and 300 mL of dichloromethane was added to the separatory funnel to extract 10-hydroxybenzo[h]quinoline again. The extracted solution was collected using a chromatographic column containing alumina soaked in dichloromethane, and the collected liquid was concentrated using a rotary evaporator to purify 10-hydroxybenzo[h]quinoline.

[0057] (ii) Synthesis of dibenzoquinone iridium dichloride (hereinafter also referred to as “[Ir(bzq)Cl]”) A reaction flask was charged with 136 g of the 10-hydroxybenzo[h]quinoline purified in (i), 132 g of iridium chloride, 2000 mL of dimethylformamide, and 290 mL of pure water, and the air inside the flask was replaced with argon. The solution was reacted in a microwave reactor while maintaining the temperature at -2°C using a reflux condenser. The reaction mixture was then filtered, washed with 300 mL of methanol, and then washed five times with 300 mL of pure water. The mixture was then washed five times with 300 mL of methanol and dried on a rotary evaporator to obtain [Ir(bzq)Cl].

[0058] (iii) Synthesis of Ir(bzq)3 A reaction flask was charged with 148 g of the 10-hydroxybenzo[h]quinoline purified in (i) above, 55 g of [Ir(bzq)Cl] synthesized in (ii) above, 200 mL of ethylene glycol, and 18.6 g of 36.6% HCl. 3000 mL of ethylene glycol was then added, and the air inside the flask was replaced with argon. The solution was reacted in a microwave reactor while maintaining the temperature at -2°C using a reflux condenser. Ir(bzq) was synthesized, represented by general formula (VII). The product was then filtered, washed with 300 mL of methanol, and washed five times with 300 mL of pure water.

[0059] (iv) Purification of Ir(bzq) A flask was charged with 145 g of Ir(bzq)3 synthesized in (iii) above and 2000 mL of ethylene glycol, and the air inside the flask was replaced with argon. The solution was reacted in a microwave reactor while maintaining the temperature at -2°C using a reflux condenser, and then filtered and washed with methanol. The Ir(bzq)3 was purified by washing five times with 300 mL of methanol and then drying on a rotary evaporator. 150 g of purified Ir(bzq)3 and 1500 mL of methanol were placed in a flask and subjected to ultrasonic cleaning, followed by filtration and washing with methanol seven times. After drying and sublimation purification, Ir(bzq)3 with a purity of over 99.5% was obtained.

[0060] The identification of the obtained Ir(bzq)3 was performed under the following conditions: 1 H-NMR and HPLC were performed. 1 In H-NMR, TMS was used as the reference substance and the compounds were identified by the H chemical shift values ​​shown in Table 1. The iridium content in Ir(bzq)3 was 26.01 wt%. The iridium content in Ir(bzq)3 was determined by ICP-OES.

[0061] [ka]

[0062]

Table 1

[0063] <DSC Measurement> Under the following conditions, DSC measurements were performed on 6.30 mg of Ir(ppy)3 synthesized in Synthesis Example 1 (1.85 mg in terms of iridium) and 7.60 mg of Ir(bzq)3 synthesized in Synthesis Example 2 (1.98 mg in terms of iridium).

[0064] DSC measuring device: Thermo plus EVO2 DSC manufactured by Rigaku Corporation, Vesta Co., Ltd. Measurement conditions: In an air atmosphere, the temperature was raised from room temperature to 600 °C at a heating rate of 5 °C / min to obtain a DSC chart. Schematic diagrams of the DSC measurement charts are shown in Figures 2 and 3 based on the DSC measurement results. Also, the respective T1, T2, T3, and T4 (all in °C) obtained from the measurement results are shown in Table 2.

[0065] < 1 <1H-NMR Measurement> Under the following conditions, 1H-NMR measurements of the above Ir(ppy)3 and Ir(bzq)3 were performed. 1 1H-NMR measurement was carried out. NMR measuring device: Fourier transform nuclear magnetic resonance of Agilent Technologies, Inc. (resonance frequency 400 MHz) Measurement conditions: Solvent: Dimethyl sulfoxide (DMSO)-d6 Measured nuclear: 1 1H

[0066] <HPLC Measurement> Under the following conditions, HPLC measurements of the above Ir(ppy)3 and Ir(bzq)3 were performed. HPLC measuring device: Agilent 1200 of Agilent Technologies, Inc. HPLC measurement conditions: Solvent: Dimethylformamide, Tetrahydrofuran Developing solvent: Hexane:Tetrahydrofuran = 5:5 Column used: Agilent Technologies ZORBAX RX-SIL 4.6 x 180 mm

[0067] [Table 2]

[0068] Example 1 1.0 g (0.29 g in terms of iridium) of Ir(ppy)3 synthesized in Synthesis Example 1 was weighed out and heated in a muffle furnace in the atmosphere for 12 hours at 350°C, which was above the T2°C obtained from the DSC measurement results, and incinerated. After cooling, the residue was recovered and its mass was measured, and the iridium yield was calculated using the following equation (7). The results are shown in Table 3.

[0069]

number

[0070] (Examples 2 to 12) Heating was carried out in the same manner as in Example 1, except that the heating temperature and heating time were changed as shown in Table 3. The results are shown in Table 3.

[0071] (Comparative Example 1) Heating was carried out in the same manner as in Example 1, except that the heating temperature and heating time were changed as shown in Table 3. The results are shown in Table 3.

[0072] Examples 13 to 22 Heating was carried out in the same manner as in Example 1, except that Ir(ppy) was replaced with Ir(bzq) synthesized in Synthesis Example 2, and the heating temperature and heating time were changed as shown in Table 4. The results are shown in Table 4.

[0073] (Comparative Example 2) Heating was carried out in the same manner as in Example 1, except that Ir(ppy)3 was changed to the above-mentioned Ir(bzq)3 and the heating temperature and heating time were changed as shown in Table 4. However, decomposition of the raw material Ir(bzq)3 was insufficient, and almost no iridium or iridium oxide was obtained.

[0074] The quantitative determination and recovery rate of iridium were determined by the following method. The mass ratio of iridium to iridium oxide was determined by XRD, and the purity of iridium was determined by ICP-OES. The measurement conditions for XRD and ICP-OES were as follows:

[0075] XRD measurement conditions Model name: Rigaku Corporation Ultima IV Measurement conditions: X-ray output: 40kV, 50mA Scan axis: 2θ / ω Entrance slit: 1 / 2° Scan speed: 30.0 deg / min Scan range: 5.0-90.0deg Step width: 0.2 deg

[0076] ICP-OES measurement conditions Model name: Agilent Technologies 5800 ICP-OES Measurement conditions: RF power: 1.2kW Nebulizer flow rate: 0.7 L / min Plasma flow rate: 12 L / min Observation mode: Axial

[0077] The mass of iridium oxide was determined from the mass of iridium determined by ICP-OES and the mass ratio of iridium to iridium oxide determined by XRD. The recovery rates of iridium in Tables 3 and 4 are values ​​expressed as percentages obtained by dividing the total mass of iridium obtained above and iridium in iridium oxide by the mass of iridium in the raw material iridium compound. In addition, the iridium and iridium oxide in Tables 3 and 4 are values ​​expressed as percentages of the mass ratio of iridium to iridium oxide determined by the XRD.

[0078] [Table 3]

[0079] [Table 4]

[0080] As is clear from the above results, according to this production method, iridium can be produced in good yield from an iridium complex, which is an organic compound of a platinum group metal, so long as the heating temperature is equal to or higher than T2. ​​It is also clear that as the heating temperature increases, the production rate of iridium oxide, which is an oxide of a platinum group metal, increases, and at relatively high temperatures, the production rate of iridium oxide also increases as the heating time increases. Therefore, it is believed that platinum group metals can be produced in good yield by this production method. Similarly, according to the present recovery method, iridium can be efficiently recovered from iridium complexes, which are organic compounds of platinum group metals. [Explanation of symbols]

[0081] T1: Minimum peak temperature T2:T1-30 T3: Maximum peak temperature T4:T3+340

Claims

1. The lowest peak temperature among the peak temperatures in the range of 300°C to 600°C when an organic compound of a platinum group metal is measured by differential scanning calorimetry in air at a temperature rise rate of 5°C / min is defined as T １ ° C., T satisfies the following formula (1): ２ The method for producing a platinum group metal comprises heating the organic compound of the platinum group metal at 0.5° C. or higher in the presence of oxygen. T ２ =T １ -30 (1)

2. The highest peak temperature among the peak temperatures in the range of 300°C to 600°C measured by the differential scanning calorimetry analysis is defined as T ３ ° C., T satisfies the following formula (2): ４ 2. The method according to claim 1, wherein the organic compound of a platinum group metal is heated in the presence of oxygen at a temperature in the range of 0.1 to 1.0°C or less. T ４ =T ３ +340 (2)

3. The method according to claim 1 or 2, wherein the heating is carried out for 1 hour or more and 20 hours or less.

4. 3. The method according to claim 1, wherein the heating is carried out at a constant temperature.

5. 3. The method according to claim 1, wherein the organic compound of a platinum group metal is a compound represented by the following general formula (IV) or (V): 【Chemical 1】 【Chemistry 2】

6. 6. The method according to claim 5, wherein M in the general formula (IV) or (V) is iridium or ruthenium.

7. The lowest peak temperature among the peak temperatures in the range of 300°C to 600°C when an organic compound of a platinum group metal is measured by differential scanning calorimetry in air at a temperature rise rate of 5°C / min is defined as T １ ° C., T satisfies the following formula (3): ２ A method for recovering platinum group metals, comprising heating the organic compound of a platinum group metal in the presence of oxygen within the above temperature range. T ２ =T １ -30 (3)

8. The highest peak temperature among the peak temperatures in the range of 300°C to 600°C measured by the differential scanning calorimetry analysis is defined as T ３ ° C., T satisfies the following formula (4): ４ 8. The method according to claim 7, wherein the organic compound of a platinum group metal is heated in the presence of oxygen at a temperature in the range of 0.1 to 1.0°C or less. T ４ =T ３ +340 (4)

9. 9. The method according to claim 7, wherein the heated product is further reduced while being heated at a temperature in the range of 500° C. to 700° C.

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