A γ-diketone lithium-ion extractant and extraction system

Abstract

This invention belongs to the field of lithium purification technology, and relates to a γ-diketone lithium-ion extractant and extraction system. The lithium-ion extractant comprises a γ-diketone compound, wherein the γ-diketone compound has the general formula shown in Formula I: where n = 2, and R1, R2, R3, and R4 are each independently H or C1-C8 alkyl, C6-C... 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 The heteroaryl group, R1, R2, R3, and R4 may be the same or different; and the γ-diketone compound is not of the following structure: The γ-diketone compound of the present invention can control the degree of unimolecular enolization, and achieve partial enolization to solve the problems of large alkali consumption, large dissolution loss of extractant, poor selectivity for potassium ions, and low removal rate in the prior art.

Description

Technical Field

[0001] This invention relates to the field of lithium purification technology, and in particular to a γ-diketone lithium ion extractant and extraction system. Background Technology

[0002] Current lithium purification technologies mostly employ extraction. In existing extraction systems, diketone extractants are used as lithium extractants, which has the following technical drawbacks: Firstly, to ensure lithium extraction efficiency in the solution (typically requiring a lithium concentration <10 mg / L), the pH value at extraction equilibrium is relatively high, requiring pH >12.5, leading to increased alkali consumption. Simultaneously, under high pH conditions, commonly used diketones (such as Lix54) experience significant dissolution losses, resulting in poor extractant stability and increasing the difficulty and cost of wastewater treatment. Secondly, existing technologies mostly use β-diketone-based extraction systems, some of which exhibit low selectivity for lithium, sodium, and potassium in the solution, especially low selectivity for potassium content, directly affecting the quality of the purified lithium product. Summary of the Invention

[0003] In view of the above analysis, the present invention aims to provide a γ-diketone lithium-ion extractant and extraction system to solve at least one of the problems in the prior art, namely, large alkali consumption, large dissolution loss of extractant, poor selectivity for potassium ions, and low impurity removal rate.

[0004] The objective of this invention is mainly achieved through the following technical solutions:

[0005] This invention provides a γ-diketone lithium-ion extractant having a γ-diketone compound with the general structural formula shown in Formula I:

[0006] Where n = 2, R1, R2, R3, and R4 are each independently H or C1-C8 alkyl, C6-C 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 Heteroaryl groups, where R1, R2, R3, and R4 may be the same or different;

[0007] Furthermore, the γ-diketone compound does not have the following structure:

[0008]

[0009] Preferably, the γ-diketone compound does not have any of the following structures:

[0010] 1-Benzoylacetone, 2-Thiophenecarboxyltrifluoroacetone, benzoyltrifluoroacetone, 1-(2-naphthoyl)-3,3,3-trifluoroacetone, 2-methoxy-5-nonylbenzoyltrifluoroacetone, acetylacetone, acetylacetone, acetylacetone, acetylacetone, hexafluoroacetylacetone, benzoyltrifluoroacetone, 2-Thiophenecarboxyltrifluoroacetone, 4,4,4-trifluoro-1-(2-furanyl)-1,3-butanedione, 4,4,4-trifluoro-1-(p-tolyl)-1,3-butanedione, (4-(1-(5-(tert-butyl)2-hydroxyphenyl)ethyl)phenyl)dioctylphosphine oxide, 4-(dioctylphosphoyl)1-(4-octylphenyl)butane-1,3-dione.

[0011] Preferably, the substituent group of the substituted phenyl group is C1-C2. 10 Alkyl, C3-C6 cycloalkyl, C1-C 10 Alkoxy, C1-C 10 One or more of alkyl halogens and halogens, and when there are multiple alkyl halogens, R1, R2, R3, and R4 may be the same or different;

[0012] And / or, the substituent group of the substituted aryl group is C1-C. 10 Alkyl, C3-C6 cycloalkyl, C1-C 10 Alkoxy, C1-C 10 One or more of alkyl halogens and halogens, and when there are multiple halogens, R1, R2, R3, and R4 may be the same or different.

[0013] Preferably, in the γ-diketone compound, the total number of hydrogen atoms m on the carbon atoms connected to the carbonyl group in R1, R2, R3 and R4 satisfies: 5≤m≤8.

[0014] Preferably, in the γ-diketone compound, R1, R2, R3, and R4 satisfy the following conditions: R1 and R2 are C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 The aryl group, or R1 and R2 are hydrogen atoms, or the carbon atom of R1 and R2 connected to the carbonyl group is either a tertiary carbon atom or a quaternary carbon atom; and R3 and R4 are either hydrogen atoms, methyl, or ethyl.

[0015] Preferably, the γ-diketone compound comprises any one of the structures shown in A024 to A035:

[0016]

[0017] Preferably, in the γ-diketone compound, the total number of hydrogen atoms m on the carbon atoms connected to the carbonyl group in R1, R2, R3 and R4 satisfies: 5≤m≤7.

[0018] Preferably, in the γ-diketone compound, R1, R2, R3, and R4 satisfy the following condition: at least one of R1 and R2 is C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 The substituted aryl or isopropyl group is used; and R3 and R4 are either hydrogen atoms, methyl or ethyl.

[0019] Preferably, the γ-diketone compound can be any of the following structures:

[0020]

[0021] An extraction system comprising the aforementioned lithium-ion extractant, further comprising: a co-extractant and a diluent.

[0022] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0023] (1) Compared with traditional β-diketone compounds, the γ-diketone compounds of the present invention, based on the special core architecture of γ-diketone and through the selection of substituents, can control the degree of enolization of a single molecule and achieve partial enolization. Therefore, while completing the extraction of lithium ions, they can maintain a small solubility in water, and thus the γ-diketone compounds in the extractant have a low dissolution loss.

[0024] (2) Compared with traditional β-diketone compounds, the γ-diketone compounds of the present invention can control the degree of unimolecular enolization and achieve partial enolization, thereby reducing the actual number of hydroxide ions required at the phase interface, reducing the amount of alkali used, and achieving enolization and lithium ion extraction in a milder environment.

[0025] (3) The γ-diketone compound of the present invention has a lower ring-forming angle and stress and better stability due to the steric hindrance of the β-substituents adjacent to the ketone carbonyl group and the ring-forming effect of the polycyclic ring. The distance between the two carbonyl oxygen atoms is smaller, making the γ-diketone compound more likely to bind lithium ions rather than larger sodium and potassium ions than traditional compounds. Therefore, the extractant has higher selectivity for lithium ion extraction and reduces the content of impurities sodium and potassium ions in the extraction product. Under alkaline conditions, the extractant of the present invention can have a high extraction rate and high lithium selectivity for salt lake brine or lithium precipitation mother liquor with different magnesium-lithium ratios.

[0026] (4) The extraction system of the present invention has strong acid resistance, alkali resistance and anti-aging properties, and remains stable after repeated use.

[0027] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages will become apparent from the description or may be learned by practicing the invention. Attached Figure Description

[0028] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0029] Figure 1 This is the hydrogen NMR spectrum of A033. Detailed Implementation

[0030] On one hand, the present invention discloses a γ-diketone lithium-ion extractant having a γ-diketone compound of the general formula shown in Formula I:

[0031] Where n = 2, R1, R2, R3, and R4 are each independently H or C1-C8 alkyl, C6-C 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 Heteroaryl groups, where R1, R2, R3, and R4 may be the same or different;

[0032] Furthermore, the γ-diketone compound does not have the following structure:

[0033]

[0034] Specifically, the γ-diketone compound does not have any of the following structures:

[0035] 1-Benzoylacetone, 2-Thiophenecarboxyltrifluoroacetone, benzoyltrifluoroacetone, 1-(2-naphthoyl)-3,3,3-trifluoroacetone, 2-methoxy-5-nonylbenzoyltrifluoroacetone, acetylacetone, acetylacetone, acetylacetone, acetylacetone, hexafluoroacetylacetone, benzoyltrifluoroacetone, 2-Thiophenecarboxyltrifluoroacetone, 4,4,4-trifluoro-1-(2-furanyl)-1,3-butanedione, 4,4,4-trifluoro-1-(p-tolyl)-1,3-butanedione, (4-(1-(5-(tert-butyl)2-hydroxyphenyl)ethyl)phenyl)dioctylphosphine oxide, 4-(dioctylphosphoyl)1-(4-octylphenyl)butane-1,3-dione.

[0036] Specifically, the substituent group of the substituted phenyl group is C1-C. 10Alkyl, C3-C6 cycloalkyl, C1-C 10 Alkoxy, C1-C 10 One or more of alkyl halogens and halogens, and when there are multiple alkyl halogens, R1, R2, R3, and R4 may be the same or different;

[0037] And / or, the substituent group of the substituted aryl group is C1-C. 10 Alkyl, C3-C6 cycloalkyl, C1-C 10 Alkoxy, C1-C 10 One or more of alkyl halogens and halogens, and when there are multiple halogens, R1, R2, R3, and R4 may be the same or different.

[0038] Preferably, in the γ-diketone compound, the total number of hydrogen atoms m on the carbon atoms connected to the carbonyl group in R1, R2, R3 and R4 satisfies: 5≤m≤8.

[0039] Preferably, in the γ-diketone compound, R1, R2, R3, and R4 satisfy the following conditions: R1 and R2 are C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 The aryl group, or R1 and R2 are hydrogen atoms, or the carbon atom of R1 and R2 connected to the carbonyl group is either a tertiary carbon atom or a quaternary carbon atom; and R3 and R4 are either hydrogen atoms, methyl, or ethyl.

[0040] Preferably, the γ-diketone compound can be any one of the structures shown in A024 to A035:

[0041]

[0042] Preferably, in the γ-diketone compound, the total number of hydrogen atoms m on the carbon atoms connected to the carbonyl group in R1, R2, R3 and R4 satisfies: 5≤m≤7.

[0043] Preferably, in the γ-diketone compound, R1, R2, R3, and R4 satisfy the following condition: at least one of R1 and R2 is C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 The substituted aryl or isopropyl group is used; and R3 and R4 are either hydrogen atoms, methyl or ethyl.

[0044] Preferably, the γ-diketone compound can be any of the following structures:

[0045]

[0046] It should be noted that this invention utilizes the enolization effect of γ-diketone compounds under alkaline conditions, where the generated active hydrogen exchanges with lithium ions, thereby completing the extraction. The applicant's research has found that the degree of enolization, substituent polarity, and steric hindrance of the γ-diketone compound collectively affect its solubility in aqueous solution, thus influencing its dissolution loss during use: the higher the degree of enolization in the γ-diketone compound molecule, the greater its solubility in aqueous solution, and the greater the loss of γ-diketone compound during extraction; the greater the polarity of the substituent at the γ-position adjacent to the ketone carbonyl group... The γ-substituent itself has difficulty transferring hydrogen to the ketone carbonyl group to undergo enolization. The lower the solubility of γ-diketoyl compounds in aqueous solution, the more difficult it is to achieve enolization. When one of the β-substituents adjacent to the ketone carbonyl group is a benzene ring, a quaternary carbon group, or other substituents, the enolization of the ketone carbonyl group can only rely on the inner β-carbon of the two ketone carbonyl groups or the outer carbon atom connected to the ketone carbonyl group to provide hydrogen atoms. At the same time, when the γ-substituent adjacent to the ketone carbonyl group is a secondary carbon, tertiary carbon group, or an aromatic group with significant steric hindrance, the presence of the substituent will also inhibit the enolization reaction. When multiple factors are present at the same time, the effect is difficult to predict.

[0047] Existing technologies commonly used enolization and extraction processes for β-diketone compounds satisfy the following:

[0048]

[0049] Among them, A and B are β-diketone compounds with active hydrogen atoms at both ends as substituents.

[0050] The difference is that, due to the steric hindrance of at least one substituent A or B, the γ-diketone compound of this invention can only undergo partial enolization. The enolization process and the extraction process satisfy the following:

[0051]

[0052] In this compound, A and B are the two end substituents of the γ-diketone compound, and at least one of the substituents in A and B is C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 The hydrogen required for enolization, either aryl or isopropyl, comes partly or entirely from the carbon atom between the two carbonyl groups or from another substituent.

[0053] As an example, in A030, one of the carbonyl groups has a benzene ring as an outer substituent. One of the substituents' β-carbons does not contain a directly bonded hydrogen atom, and the benzene ring has a strong steric hindrance effect. Therefore, the ketone carbonyl undergoes enolization. The ketone carbonyl, which can only be bonded to the benzene ring, can only rely on the inner β-carbon of the two ketone carbonyl groups or the outer carbon atom of the substituent on the other side bonded to the ketone carbonyl to provide hydrogen atoms, thus extracting lithium ions.

[0054]

[0055] Compared with the prior art, on the one hand, the γ-diketone compound of the present invention, compared with the traditional β-diketone compound, achieves partial enolization based on the special core architecture of γ-diketone and through substituent selection. Therefore, it can maintain its low solubility in water while completing the extraction of lithium ions, and thus the γ-diketone compound in the extractant has a low dissolution loss.

[0056] On the other hand, since extraction occurs at the interface between the aqueous solution and the extractant phase, the partial enolization of the γ-diketone compound reduces the actual number of hydroxide ions required at the interface, thus reducing the amount of alkali used and enabling enolization and lithium-ion extraction to be achieved in a milder environment.

[0057] Meanwhile, the γ-diketone compound of the present invention has a lower ring-forming angle and stress and better stability due to the steric hindrance of the β-substituents adjacent to the ketone carbonyl group and the cyclization effect of the polycyclic ring. The smaller distance between the two carbonyl oxygen atoms makes the γ-diketone compound more likely to bind lithium ions rather than larger sodium and potassium ions than conventional compounds. Therefore, the extractant has higher selectivity for lithium ion extraction and reduces the content of impurities such as sodium and potassium ions in the extraction product. Under alkaline conditions, the extractant of the present invention can have a high extraction rate and high lithium selectivity for salt lake brines or lithium precipitation mother liquor with different magnesium-lithium ratios.

[0058] On the other hand, this invention discloses a γ-diketone compound that satisfies any one of the following structures:

[0059]

[0060] On the other hand, this invention discloses a method for preparing a γ-diketone compound, used to synthesize the aforementioned γ-diketone compound. The specific steps include:

[0061] S001: Dissolve the first raw material containing the acyl halide and the catalyst in an anhydrous and oxygen-free organic solvent;

[0062] S002: Add the second raw material containing an enone to an organic solvent and react it under visible light for a certain time to prepare γ-diketone.

[0063] Specifically, the first raw material molecule can be any of the acyl halide compounds with different electronic and spatial structures;

[0064] The second raw material can be any of the enones with different electronic and spatial structures; the catalyst can be any of fac-Ir(ppy)3, Ru(bpy)3(PF6)2, Ir(ppy)2(dtbbpy)PF6, [Ru(bpy)3]Cl2, or Ir[dF(CF3)ppy]2(phen)PF6, and the reaction equation satisfies:

[0065] R5, R6, R7, and R8 can be selected according to actual needs.

[0066] As an example, using 2-fluorobenzoyl chloride as the first raw material, fac-Ir(ppy)3 as the catalyst, and hex-3-en-2-one as the second raw material, the reaction in SO02 satisfies:

[0067]

[0068] Specifically, the organic solvent in S001 can be any one of toluene, benzene, acetonitrile, tetrahydrofuran, or DMF.

[0069] Preferably, the organic solvent in S001 needs to be dehydrated and deoxygenated.

[0070] Specifically, the reaction temperature in SO02 is 0℃-100℃ and the time is 0.1h-24h. Under these reaction conditions, the target compound can be obtained in a high yield.

[0071] Preferably, quenching treatment is required after the SO02 reaction is complete.

[0072] Specifically, the quenching agent can be a saturated sodium bicarbonate solution.

[0073] Preferably, the reaction of SO02 is further followed by extraction and purification.

[0074] Specifically, the extraction reagent can be any one of ethyl acetate, dichloromethane, anisole, or tert-butyl methyl ether; the purification method can be column chromatography.

[0075] On the other hand, the present invention discloses a lithium-ion extractant comprising the above-mentioned γ-diketone compound.

[0076] On the other hand, the present invention discloses an extraction system that, in addition to the lithium-ion extractant mentioned above, includes a co-extractant and a diluent.

[0077] Specifically, the co-extractant is one or more of trioctylphosphine oxide (TOPO), tributylphosphine oxide (TBPO), and trialkylphosphine oxide (TRPO).

[0078] Specifically, the diluent is one or more of alkanes, benzenes, or alcohols; preferably, the diluent is one or more of No. 260 solvent oil, aviation kerosene, xylene, and octanol.

[0079] On the other hand, this invention discloses a method for extracting lithium from a low-lithium solution, comprising:

[0080] S101: Pretreatment of low-lithium solution with alkali;

[0081] S102: Add the pretreated lithium-containing feed liquid to the extraction system for extraction;

[0082] S103: Extract the extracted organic material by back-extraction to obtain a lithium-rich back-extraction solution.

[0083] Specifically, the low-lithium solution can be brine from a salt lake or lithium precipitation mother liquor.

[0084] Specifically, the low-lithium solution has a lithium content of 0.1 g / L to 2.5 g / L, and the main impurities are cations such as sodium, potassium, magnesium, and calcium, with sodium content ranging from 10 g / L to 130 g / L and potassium content ranging from 1 g / L to 70 g / L. The anions include chloride ions and sulfate ions, with chloride ion content ranging from 5 g / L to 200 g / L and sulfate ion content ranging from 1 g / L to 190 g / L.

[0085] This invention discloses a salt lake brine, wherein the lithium content of the salt lake brine is 0.1 g / L to 0.98 g / L, and the main impurities are cationic impurities such as sodium, potassium, magnesium, and calcium, wherein the sodium content is 10 g / L to 130 g / L, and the potassium content is 1 g / L to 70 g / L; the anions are chloride ions and sulfate ions, wherein the chloride ion content is 5 g / L to 200 g / L, and the sulfate ion content is 1 g / L to 10 g / L.

[0086] This invention discloses a lithium precipitation mother liquor, wherein the lithium content of the mother liquor is 1.5 g / L to 2.5 g / L, and the main impurities are cations such as sodium, potassium, magnesium, and calcium, wherein the sodium content is 50 g / L to 130 g / L, and the potassium content is 5 g / L to 50 g / L; the anions are chloride ions and sulfate ions, wherein the chloride ion content is 5 g / L to 100 g / L, and the sulfate ion content is 5 g / L to 190 g / L.

[0087] Specifically, the alkali added to S101 can be sodium hydroxide or sodium carbonate, and the pretreatment pH range is 8 to 9.

[0088] It should be noted that, on the one hand, an alkaline environment is conducive to removing high-valence and divalent ions from the solution; on the other hand, the extraction system's selectivity for monovalent metal ions allows for the selective extraction of lithium from high-concentration sodium-potassium solutions, consuming hydroxide ions during the extraction process.

[0089] Specifically, the extraction system in S102 contains γ-diketoyl compounds that satisfy the following general formula:

[0090] It has the general formula shown in Equation I:

[0091] Where n = 2, R1, R2, R3, and R4 are each independently H or C1-C8 alkyl, C6-C 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 Heteroaryl groups, where R1, R2, R3, and R4 may be the same or different;

[0092] Furthermore, the γ-diketone compound does not have the following structure:

[0093]

[0094] Specifically, the γ-diketone compound does not have any of the following structures:

[0095] 1-Benzoylacetone, 2-Thiophenecarboxyltrifluoroacetone, benzoyltrifluoroacetone, 1-(2-naphthoyl)-3,3,3-trifluoroacetone, 2-methoxy-5-nonylbenzoyltrifluoroacetone, acetylacetone, acetylacetone, acetylacetone, acetylacetone, hexafluoroacetylacetone, benzoyltrifluoroacetone, 2-Thiophenecarboxyltrifluoroacetone, 4,4,4-trifluoro-1-(2-furanyl)-1,3-butanedione, 4,4,4-trifluoro-1-(p-tolyl)-1,3-butanedione, (4-(1-(5-(tert-butyl)2-hydroxyphenyl)ethyl)phenyl)dioctylphosphine oxide, 4-(dioctylphosphoyl)1-(4-octylphenyl)butane-1,3-dione.

[0096] Specifically, the substituent group of the substituted phenyl group is C1-C. 10 Alkyl, C3-C6 cycloalkyl, C1-C 10 Alkoxy, C1-C 10 One or more of alkyl halogens and halogens, and when there are multiple alkyl halogens, R1, R2, R3, and R4 may be the same or different;

[0097] And / or, the substituent group of the substituted aryl group is C1-C. 10 Alkyl, C3-C6 cycloalkyl, C1-C 10Alkoxy, C1-C 10 One or more of alkyl halogens and halogens, and when there are multiple halogens, R1, R2, R3, and R4 may be the same or different.

[0098] Preferably, in the γ-diketone compound, the total number of hydrogen atoms m on the carbon atoms connected to the carbonyl group in R1, R2, R3 and R4 satisfies: 5≤m≤8.

[0099] Preferably, in the γ-diketone compound, R1, R2, R3, and R4 satisfy the following conditions: R1 and R2 are C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 The aryl group, or R1 and R2 are hydrogen atoms, or the carbon atom of R1 and R2 connected to the carbonyl group is either a tertiary carbon atom or a quaternary carbon atom; and R3 and R4 are either hydrogen atoms, methyl, or ethyl.

[0100] Preferably, the γ-diketone compound can be any one of the structures shown in A024 to A035:

[0101]

[0102] Preferably, in the γ-diketone compound, the total number of hydrogen atoms m on the carbon atoms connected to the carbonyl group in R1, R2, R3 and R4 satisfies: 5≤m≤7.

[0103] Preferably, in the γ-diketone compound, R1, R2, R3, and R4 satisfy the following condition: at least one of R1 and R2 is C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 The substituted aryl or isopropyl group is used; and R3 and R4 are either hydrogen atoms, methyl or ethyl.

[0104] Preferably, the γ-diketone compound can be any of the following structures:

[0105]

[0106] It should be noted that this invention utilizes the enolization effect of γ-diketone compounds under alkaline conditions, where the generated active hydrogen exchanges with lithium ions, thereby completing the extraction. The applicant's research has found that the degree of enolization, substituent polarity, and steric hindrance of the γ-diketone compound collectively affect its solubility in aqueous solution, thus influencing its dissolution loss during use: the higher the degree of enolization in the γ-diketone compound molecule, the greater its solubility in aqueous solution, and the greater the loss of γ-diketone compound during extraction; the greater the polarity of the substituent at the γ-position adjacent to the ketone carbonyl group... The γ-substituent itself has difficulty transferring hydrogen to the ketone carbonyl group to undergo enolization. The lower the solubility of γ-diketoyl compounds in aqueous solution, the more difficult it is to achieve enolization. When one of the β-substituents adjacent to the ketone carbonyl group is a benzene ring, a quaternary carbon group, or other substituents, the enolization of the ketone carbonyl group can only rely on the inner β-carbon of the two ketone carbonyl groups or the outer carbon atom connected to the ketone carbonyl group to provide hydrogen atoms. At the same time, when the γ-substituent adjacent to the ketone carbonyl group is a secondary carbon, tertiary carbon group, or an aromatic group with significant steric hindrance, the presence of the substituent will also inhibit the enolization reaction. When multiple factors are present at the same time, the effect is difficult to predict.

[0107] Existing technologies commonly used enolization and extraction processes for β-diketone compounds satisfy the following:

[0108]

[0109] Among them, A and B are β-diketone compounds with active hydrogen atoms at both ends as substituents.

[0110] The difference is that, due to the steric hindrance of at least one substituent A or B, the γ-diketone compound of this invention can only undergo partial enolization. The enolization process and the extraction process satisfy the following:

[0111]

[0112] In this compound, A and B are the two substituents at both ends of the γ-diketone compound, and one substituent of A and B is C6-C6. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 The hydrogen required for enolization, either aryl or isopropyl, comes partly or entirely from the carbon atom between the two carbonyl groups or from another substituent.

[0113] As an example, in A030, one of the carbonyl groups has a benzene ring as an outer substituent. One of the substituents' β-carbons does not contain a directly bonded hydrogen atom, and the benzene ring has a strong steric hindrance effect. Therefore, the ketone carbonyl undergoes enolization. The ketone carbonyl, which can only be bonded to the benzene ring, can only rely on the inner β-carbon of the two ketone carbonyl groups or the outer carbon atom of the substituent on the other side bonded to the ketone carbonyl to provide hydrogen atoms, thus extracting lithium ions.

[0114]

[0115] Compared with the prior art, on the one hand, the γ-diketone compound of the present invention, compared with the traditional β-diketone compound, achieves partial enolization based on the special core architecture of γ-diketone and through substituent selection. Therefore, it can maintain its low solubility in water while completing the extraction of lithium ions, and thus the γ-diketone compound in the extractant has a low dissolution loss.

[0116] On the other hand, since extraction occurs at the interface between the aqueous solution and the extractant phase, the partial enolization of the γ-diketone compound reduces the actual number of hydroxide ions required at the interface, thus reducing the amount of alkali used and enabling enolization and lithium-ion extraction to be achieved in a milder environment.

[0117] Meanwhile, the γ-diketone compound of the present invention has a lower ring-forming angle and stress and better stability due to the steric hindrance of the β-substituents adjacent to the ketone carbonyl group and the cyclization effect of the polycyclic ring. The smaller distance between the two carbonyl oxygen atoms makes the γ-diketone compound more likely to bind lithium ions rather than larger sodium and potassium ions than conventional compounds. Therefore, the extractant has higher selectivity for lithium ion extraction and reduces the content of impurities such as sodium and potassium ions in the extraction product. Under alkaline conditions, the extractant of the present invention can have a high extraction rate and high lithium selectivity for salt lake brines or lithium precipitation mother liquor with different magnesium-lithium ratios.

[0118] Preferably, the extraction system in S102 also includes a co-extractant.

[0119] Specifically, the co-extractant is one or more of trioctylphosphine oxide (TOPO), tributylphosphine oxide (TBPO), and trialkylphosphine oxide (TRPO).

[0120] Preferably, the extraction system in S102 also includes a diluent.

[0121] Specifically, the diluent is one or more of alkane, benzene, or alcohol compounds.

[0122] Preferably, the diluent is one or more of No. 260 solvent oil, aviation kerosene, xylene, and octanol.

[0123] Preferably, the mass percentage of the γ-diketone compound in the extraction system of S102 is 5-20%, and the mass percentage of the co-extractant is 5-40%.

[0124] More preferably, the mass percentage of the γ-diketone compound in the extraction system of S102 is 5-15%, and the mass percentage of the co-extractant is 5-20%.

[0125] It should be noted that temperature affects both the extraction mass transfer and separation effects. If the temperature is too low during the extraction process, it will affect the extraction mass transfer efficiency, i.e., the extraction rate will be low. It will also affect the phase separation rate, i.e., the separation of the organic phase and the aqueous phase will be incomplete, and the amount of entrainment between the two phases will be large, making the subsequent treatment of the organic phase and water difficult, and the feed liquid processing capacity cannot be increased, which will affect the production capacity. If the extraction temperature is too high, it will increase the volatilization loss of the extractant and increase the economic cost.

[0126] To ensure subsequent extraction efficiency and phase separation, the extraction temperature in S102 is between 10 and 50°C, preferably between 20 and 40°C.

[0127] Preferably, S102 and S103 further include washing and removing impurities from the extracted organic phase.

[0128] Specifically, pure water or a weakly acidic aqueous solution is used as a washing reagent to wash and remove impurities from the extracted organic phase.

[0129] Preferably, the amount of cleaning reagent used satisfies the following conditions: the volume ratio of the extracted organic phase to water (O / A) is 10 to 20:1, and the washing level can be selected from 1 to 5.

[0130] Preferably, the washing and impurity removal temperature is between 10 and 50°C, and can be 10°C, 12°C, 15°C, 18°C, 20°C, 22°C, 25°C, 28°C, 30°C, 33°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, or 50°C.

[0131] Preferably, a weakly acidic aqueous solution is used to wash and remove impurities from the extracted organic phase.

[0132] Specifically, the pH value of the weakly acidic aqueous solution is 0.5 to 2.0.

[0133] It should be noted that this invention utilizes the enolization effect of γ-diketone compounds in an alkaline environment, where the active hydrogen produced exchanges with lithium ions to complete the extraction; at the same time, a very small amount of sodium and potassium will be co-extracted (extraction rate less than 5%); the purpose of washing is to remove the sodium and potassium entrained during the extraction process and the small amount of co-extracted sodium and potassium; using a weakly acidic aqueous solution for washing can improve the washing efficiency.

[0134] Preferably, the solution after washing and impurity removal is returned to the extraction section to recover the lithium element washed out, which helps to improve the lithium yield.

[0135] Specifically, the back-extraction temperature in S103 is 10 to 50°C, which can be 10°C, 12°C, 15°C, 18°C, 20°C, 22°C, 25°C, 28°C, 30°C, 33°C, 35°C, 38°C, 40°C, 42°C, 45°C, 48°C, or 50°C.

[0136] Preferably, the amount of back-extraction reagent in S103 satisfies the following conditions: the volume ratio of the organic phase to water after extraction (O / A) is 10 to 30:1, and the number of back-extraction stages can be selected from 1 to 5.

[0137] It should be noted that an acidic environment facilitates the de-enolization of γ-diketone compounds, consuming hydrogen ions in the solution while simultaneously releasing the relative lithium ion adsorption state of organic matter, thus achieving relative lithium ion de-extraction of water.

[0138] The acid solution used can be sulfuric acid, hydrochloric acid, phosphoric acid, or similar acid solutions. The acid with the same anion can be selected according to the lithium salt anion requirements of the back-extraction solution, with a concentration range of 0.5 mol / L to 8 mol / L.

[0139] The lithium concentration in the lithium-rich solution is obtained to be 15-30 g / L, preferably 22-30 g / L, in which the separation effect of lithium from sodium and potassium is high, the mass ratio of lithium / sodium in the solution is >200, and the mass ratio of lithium / potassium is >500, which meets the requirements for direct lithium precipitation.

[0140] To better illustrate the present invention, the following preparation examples and comparative examples are provided:

[0141] Preparation Example

[0142] This preparation example discloses a method for preparing a γ-diketone compound, which uses a substitution reaction to prepare A033, including:

[0143] S001: Dissolve 0.1 mol of 2-fluorobenzoyl chloride, 0.01 mol of fac-Ir(ppy)3, and 0.1 mol of hex-3-en-2-one in 500 mL of anhydrous N,N-dimethylformamide. The reaction is completed after 8 hours at 25 degrees Celsius under visible light.

[0144] S002: The reaction was quenched by adding saturated sodium bicarbonate solution to the system, the reaction system was extracted with dichloromethane, the organic phases were combined and concentrated, and then purified by column chromatography to obtain the target product with a yield of 70%.

[0145] The target product is A033, such as Figure 1 As shown, A033 contains nine characteristic peaks around 7.88 PPM, 7.46 PPM, 7.33 PPM, 3.74 PPM, 2.71 PPM, 2.49 PPM, 2.11 PPM, 1.58 PPM, and 0.84 PPM, indicating that A033 contains nine different hydrogen atoms, consistent with the structure of A033.

[0146] γ-diketone compounds were prepared by adjusting the types of raw materials according to the above method.

[0147] The remaining compounds in A024 to A035 can be purchased as commercial products or prepared by substitution reaction according to known techniques.

[0148] Experimental Example

[0149] This embodiment discloses a method for extracting lithium from a low-lithium solution using a γ-diketone compound containing A024 to A035. Specific conditions and experimental results are shown in Tables 1-3, including:

[0150] S101: Pre-treat the low-lithium solution as a lithium-containing raw material solution by adding alkali;

[0151] S102: Add the pretreated lithium-containing feed liquid to the extraction system for extraction;

[0152] S103: The organic phase after lithium extraction is mixed and washed to remove impurities;

[0153] S104: The extracted organic phase is back-extracted to obtain a lithium-rich back-extract, and the back-extracted organic phase is recovered and recycled as an extractant.

[0154] Table 1 Composition of Lithium-Containing Feed Solution

[0155]

[0156]

[0157] Table 2 Process Parameters

[0158]

[0159]

[0160]

[0161]

[0162] Table 3. Experimental Results

[0163]

[0164]

[0165] The results show:

[0166] As shown in Examples 1-17, for low-lithium solutions with lithium content of 0.1 g / L to 2.5 g / L, and main impurities being cations such as sodium, potassium, magnesium, and calcium, with sodium content of 10 g / L to 130 g / L and potassium content of 1 g / L to 70 g / L; and anions including chloride and sulfate ions, with chloride ion content of 5 g / L to 200 g / L and sulfate ion content of 1 g / L to 190 g / L, the lithium extraction system and extraction method of the present invention can prepare lithium-rich solutions with lithium concentration of 15 to 30 g / L, lithium / sodium mass ratio > 220, and lithium / potassium mass ratio > 510, meeting the requirements for direct lithium precipitation.

[0167] As shown in Examples 1-12, the extraction system composed of extractants A024-A035 exhibits an extractant hydrolysis loss of less than 0.0022% during the first use, and less than 0.0025% after 100 recycling cycles. Compared to the commonly used extraction system in Comparative Example 5, the hydrolysis loss is significantly reduced (extractant hydrolysis loss of less than 0.0044% during the first use, and less than 0.005% after 100 recycling cycles). Furthermore, compared to the commonly used extraction system in Comparative Example 5, this invention demonstrates higher selectivity for lithium ion extraction in lithium-ion / potassium ion separation systems (the lithium extraction system and extraction method of this invention prepare a lithium-rich solution with a lithium / potassium mass ratio > 510, while the lithium-rich solution in Comparative Example 5 has a lithium-ion / potassium ion ratio < 460).

[0168] Understandably, since extraction occurs at the interface between the aqueous solution and the extractant phase, the partial enolization of the γ-diketone compound reduces the actual number of hydroxide ions required at the interface, thus reducing the amount of alkali used. Enolization and lithium-ion extraction can be achieved at a lower pH and in a milder environment.

[0169] Meanwhile, a comparison of Examples 1-12 with Comparative Examples 1 and 2 shows that the extractant outside the scope of the present invention exhibits significantly worse lithium ion extraction selectivity and hydrolysis loss after multiple recycling of the extractant in the lithium ion / potassium ion separation system compared to Examples 1-12.

[0170] As can be seen from Examples 12, 3, and 4, the extraction system of the present invention with defined components and proportions exhibits better performance in terms of lithium ion extraction concentration and lithium ion selectivity compared to extraction systems with components and proportions outside the defined range. Example 12 can prepare a lithium-rich solution with a lithium concentration of 27.9 g / L, a lithium / sodium mass ratio of 252, and a lithium / potassium mass ratio of 544. In contrast, the lithium concentration, lithium / sodium mass ratio, and lithium / potassium mass ratio of the lithium-rich solutions in Comparative Examples 3 and 4 are significantly lower than those in Example 12.

[0171] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a γ-diketone lithium-ion extractant, characterized in that, For lithium ion extraction, the γ-diketone lithium ion extractant has a γ-diketone compound of the general formula shown in Formula I: Where n=2, R3 and R4 are each independently H or C1-C8 alkyl, C6-C 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 heteroaryl groups, where R3 and R4 may be the same or different; Furthermore, the γ-diketone compound does not have the following structure: ； At least one substituent in R1 and R2 is C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 It can replace either aryl or isopropyl.

2. The application of the γ-diketone lithium-ion extractant according to claim 1, characterized in that, The γ-diketone compound does not have any of the following structures: 1-Benzoylacetone, 2-thiophenecarboxyltrifluoroacetone, benzoyltrifluoroacetone, 1-(2-naphthoyl)-3,3,3-trifluoroacetone, 2-methoxy-5-nonylbenzoyltrifluoroacetone, acetylacetone, acetylacetone, acetylacetone, hexafluoroacetylacetone, benzoyltrifluoroacetone, 2-thiophenecarboxyltrifluoroacetone, 4,4,4-trifluoro-1-(2-furanyl)-1,3-butanedione, 4,4,4-trifluoro-1-(p-tolyl)-1,3-butanedione, (4-(1-(5-(tert-butyl)2-hydroxyphenyl)ethyl)phenyl)dioctylphosphine oxide, 4-(dioctylphosphoyl)1-(4-octylphenyl)butane-1,3-dione.

3. The application of the γ-diketone lithium-ion extractant according to claim 2, characterized in that, The substituent group of the substituted phenyl group is C1-C. 10 Alkyl, C3-C6 cycloalkyl, C1-C 10 Alkoxy, C1-C 10 One or more of alkyl halogens and halogens, and when there are multiple alkyl halogens, R1, R2, R3, and R4 may be the same or different; And / or, the substituent group of the substituted aryl group is C1-C. 10 Alkyl, C3-C6 cycloalkyl, C1-C 10 Alkoxy, C1-C 10 One or more of haloalkyl groups and halogens, and when there are multiple haloalkyl groups, R1, R2, R3, and R4 may be the same or different.

4. The application of the γ-diketone lithium-ion extractant according to claim 3, characterized in that, In the γ-diketone compound, the total number of hydrogen atoms n on the carbon atoms connected to the carbonyl group in R1, R2, R3 and R4 satisfies: 5≤n≤8.

5. The application of the γ-diketone lithium-ion extractant according to claim 4, characterized in that, In the γ-diketone compound, R1, R2, R3, and R4 satisfy the following conditions: R1 and R2 are C6-C. 12 Phenyl, C6-C 12 Substituted phenyl, C6-C 20 Aryl, C6-C 20 Substituted aryl or C6-C 20 The aryl group, or R1 and R2 are hydrogen atoms, or the carbon atom of R1 and R2 connected to the carbonyl group is either a tertiary carbon atom or a quaternary carbon atom; and R3 and R4 are either hydrogen atoms, methyl, or ethyl.

6. The application of the γ-diketone lithium-ion extractant according to claim 5, characterized in that, The γ-diketone compound includes any one of the structures shown in A024 to A035: .

7. The application of the γ-diketone lithium-ion extractant according to claim 5, characterized in that, In the γ-diketone compound, the total number of hydrogen atoms m on the carbon atoms connected to the carbonyl group in R1, R2, R3 and R4 satisfies: 5≤m≤7.

8. The application of the γ-diketone lithium-ion extractant according to claim 7, characterized in that, R3 and R4 are any one of hydrogen atoms, methyl, and ethyl.

9. The application of the γ-diketone lithium-ion extractant according to claim 8, characterized in that, The γ-diketone compound is any one of the following structures: 。 10. An extraction system, characterized in that, Includes the γ-diketone lithium-ion extractant, co-extractant, and diluent as described in any one of claims 1-9.

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