CN113430373B

CN113430373B - Method for separating rare earth elements

Info

Publication number: CN113430373B
Application number: CN202110733215.4A
Authority: CN
Inventors: 王艳良; 肖文涛; 吴玉远; 林锦池
Original assignee: Fujian Changting Jinlong Rare Earth Co Ltd
Current assignee: Fujian Jinlong Rare Earth Co ltd
Priority date: 2021-06-30
Filing date: 2021-06-30
Publication date: 2022-11-04
Anticipated expiration: 2041-06-30
Also published as: CN113430373A

Abstract

The invention provides a method for separating rare earth elements, which uses an N, N-dialkyl amino carboxylic acid compound as an extractant for separating the rare earth elements, and the extractant can separate and purify yttrium element from a mixed rare earth raw material; the method comprises the following steps: a) Mixing an extracting agent with an organic solvent to obtain an extracting agent solution; b) Mixing the extractant solution with an inorganic alkali solution, and saponifying to obtain a saponified extractant solution; c) And mixing the saponified extractant solution with a rare earth solution for extraction, wherein yttrium is enriched in a water phase, and yttrium-poor rare earth is enriched in an organic phase. The extractant has simple synthesis, low cost and good chemical stability as the extractant, and can tolerate strong acid and strong base without decomposition. The separation coefficient of lanthanide and yttrium is superior to that of naphthenic acid, so that it can be substituted for naphthenic acid, and has good application prospect.

Description

Method for separating rare earth elements

Technical Field

The invention relates to the technical field of separation and extraction in the field of hydrometallurgy, in particular to a method for separating rare earth elements.

Background

The rare earth elements refer to 15 lanthanide elements with atomic numbers of 57-71 in the periodic table of the elements, and 17 metal elements including No. 21 scandium and No. 39 yttrium with similar chemical properties. The rare earth element has unique magnetic, optical and electrical properties, is known as 'industrial vitamin', is widely applied to the fields of metallurgy, petrochemical industry, glass ceramics, energy materials, military industry and the like, and is an important fundamental raw material for the development of human society.

At present, the exploitation of rare earth ore in nature firstly needs to use a leaching agent to leach rare earth ions to obtain a rare earth leaching solution, and then the rare earth ions are extracted and separated one by one in a solvent extraction mode. The development of an extractant is the most central technology in the solvent extraction process, multiple factors such as extraction selectivity, extraction rate, extraction capacity, stability, solubility, back extraction performance, safety, synthesis method and source of a compound need to be considered in the rare earth metal extractant for industrial application, the excellent extractant can be called one of ten thousand, and the good extractant can simplify the production process, improve the separation efficiency, reduce the production cost and reduce the pollution emission.

Commercially available extractant products known in the art are mainly classified into organic phosphine extractants, carboxylic acid extractants and amine extractants, typical organic phosphine extractants include 2-ethylhexyl phosphonic acid mono (2-ethylhexyl) ester (P507), bis (2-ethylhexyl) phosphonic acid (P204), bis (2,4,4-trimethylpentyl) phosphinic acid (C272), tributyl phosphonate (TBP) and the like, amine extractants include tri-N-octylamine (N235), secondary carbon primary amine (N1923), methyltrioctylammonium chloride (N263) and the like, and carboxylic acid extractants include naphthenic acid, neodecanoic acid, secondary octylphenoxyacetic acid (CA-12) and the like.

The commercially available extractant still has some defects, for example, P507 is the one most widely used in the rare earth separation industry, but the separation coefficient of the extractant for adjacent rare earth elements is low, such as the separation coefficient of praseodymium-neodymium is only 1.4, which makes the praseodymium-neodymium element difficult to separate. Naphthenic acid is mainly used for separating and purifying yttrium oxide, but the naphthenic acid is a byproduct of petrochemical industry, has complex components, can extract rare earth under the condition of higher pH, and has easily changed components after long-term use, thereby reducing the concentration of an organic phase and influencing the stability of a separation process. CA-12 extractant has been tried to replace naphthenic acid, which can effectively separate yttrium from all lanthanides in rare earth element extraction separation process and overcome the problem of reduced organic phase concentration when the naphthenic acid is used for extracting and separating yttrium, but the separation coefficient of heavy rare earth and yttrium in the extraction system is low, which causes the heavy rare earth element and yttrium to be difficult to separate, thus more stages of extraction tanks are required to be designed to achieve separation effect.

In order to separate yttrium, a rare earth element more efficiently, it is necessary to develop a novel extractant having a higher separation coefficient than the prior art and capable of overcoming the disadvantages of the prior art, and an extractive separation method using the same.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to separate and purify the rare earth elements from the mixed rare earth feed liquid by adopting N, N-dialkyl amino carboxylic acid as an extracting agent for separating the rare earth elements.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a method for separating rare earth elements, wherein a compound having a structural formula I is used as an extractant to extract rare earth mixed liquor:

wherein R is ₁ And R ₂ And (e.g., can be C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C22, C24, C26, C28, C30, C35, C40, etc.) is independently (e.g., can be a C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C22, C24, C26, C28, C30, C35, C40, etc.).

R ₃ Is (for example, may be Cl, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C22, C24, C26, C28, C30, C35, C40, etc.) a straight or branched, substituted or unsubstituted, saturated or unsaturated hydrocarbon group.

X is H or OH; preferably, said X is H.

n is a natural number of 1 to 10 (for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc.); preferably, n is 1 to 6.

The invention provides an aminocarboxylic acid compound with a structure shown in formula I as a carboxylic acid type extracting agent for separating rare earth metal yttrium, which is used for separating element yttrium from rare earth mixed liquor. The compound as a metal extractant has a high separation coefficient for rare earth elements, particularly has high efficiency for separating heavy rare earth and yttrium elements, and can overcome the defects existing in the process of separating yttrium from naphthenic acid.

The hydrocarbyl is any one of substituted alkyl, substituted alkenyl and substituted alkynyl, and the substituents of the alkyl, the alkenyl and the alkynyl are respectively and independently selected from any one or the combination of at least two of halogen, hydroxyl, carboxyl, acyl, ester group, ether group, alkoxy, phenyl, phenoxy, amino, amide group, nitro, cyano, sulfydryl, sulfonyl, thiol group, imino, sulfonyl or sulfanyl; preferably, the substituent is halogen.

Preferably, said R is ₁ And R ₂ Independently is a C7 or higher linear or branched, saturated or unsaturated, unsubstituted hydrocarbon group, preferably a C7-C30 linear or branched, saturated or unsaturated, unsubstituted hydrocarbon group.

Preferably, said R is ₁ And R ₂ Independently a linear or branched and unsubstituted alkyl group, more preferably a C7-C30 linear or branched and unsubstituted alkyl group, further a C7-C30 branched and unsubstituted alkyl group.

Preferably, said R is ₁ And R ₂ Independently any one of the following groups, wherein,

represents the position of attachment of the group:

preferably, said R is ₃ Is a C6 or higher linear or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbon group, preferably a C6-C30 linear or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbon group.

Preferably, said R is ₃ Is a C6 or higher linear or branched, saturated or unsaturated, unsubstituted hydrocarbon group, preferably a C6-C30 linear or branched, saturated or unsaturated, unsubstituted hydrocarbon group.

Preferably, said R is ₃ Is a linear or branched unsaturated hydrocarbon group, preferably a C6-C30 or higher linear or branched, unsaturated and unsubstituted hydrocarbon group, and the unsaturated hydrocarbon group may specifically be a linear alkenyl group, more preferably a C6-C18 linear alkenyl groupAn alkenyl group.

Preferably, said R is ₃ Is C10-C18 straight-chain alkenyl.

Preferably, said R is ₃ Is any one of the following groups, wherein,

represents the position of attachment of the group:

preferably, n is a natural number from 1 to 6.

Preferably, X is H.

Preferably, the extractant is saponified to obtain saponified extractant solution; then extracting with mixed rare earth solution.

Preferably, the method for separating rare earth element yttrium comprises the following steps:

a) Mixing an extractant with an organic solvent to obtain an extractant solution;

b) Mixing the extractant solution with an inorganic alkali solution, and saponifying to obtain a saponified extractant solution;

c) And mixing the saponified extractant solution with a rare earth solution for extraction, wherein yttrium is enriched in a water phase, and yttrium-poor rare earth is enriched in an organic phase.

Preferably, the rare earth solution comprises one or more rare earth ions of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium;

the total concentration of rare earth ions in the rare earth solution is 0.05-1.5 mol/L, and the pH value of the rare earth solution is 1-7.

Preferably, the organic solvent is selected from one or more of toluene, xylene, octane, dichloromethane and kerosene.

Preferably, the mass ratio of the extractant to the organic solvent is: 1: 1 to 10, for example, 1: 1, 12, 1: 3, 1: 4, 1: 5, 1: 6, 1: 7, 1: 8, 1: 9, 1: 10, etc.

The present invention provides a method for preparing an N, N-dihydrocarbylaminocarboxylic acid as described in the first aspect, which comprises:

mixing N, N-dihydrocarbyl secondary amine shown in a formula II and dianhydride compound shown in a formula III for reaction to obtain N, N-dihydrocarbyl amide carboxylic acid shown in a formula IV, and reducing the N, N-dihydrocarbyl amide carboxylic acid with a reducing agent to obtain N, N-dihydrocarbyl amino carboxylic acid compound shown in a formula I, wherein the reaction formula is as follows:

wherein R is ₁ 、R ₂ 、R ₃ And the group defined in the first aspect, n is a natural number of 1 to 10.

Preferably, the molar ratio of the secondary N, N-dihydrocarbylamine of formula II to the dianhydride compound of formula III is 1: 1 (0.8-1.2), and can be, for example, 1: 0.8, 1: 0.9, 1: 1, 1: 1.1, 1: 1.2, etc.

Preferably, the temperature of the mixing reaction of the N, N-dihydrocarbyl secondary amine of formula II and the dianhydride compound of formula III is 0-125 deg.C, such as 0 deg.C, 5 deg.C, 10 deg.C, 15 deg.C, 20 deg.C, 25 deg.C, 30 deg.C, 35 deg.C, 40 deg.C, 50 deg.C, 60 deg.C, 70 deg.C, 80 deg.C, 90 deg.C, 100 deg.C, 105 deg.C, 110 deg.C, 115 deg.C, 120 deg.C, 125 deg.C, and the mixing reaction time is 0.5-4h, such as 0.5h, 0.6h, 0.8h, 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, etc.

Preferably, the mixing reaction of the N, N-dihydrocarbyl secondary amine shown in the formula II and the dianhydride compound shown in the formula III is carried out in the absence of a solvent; or in a solvent, which is an inert solvent.

In the present invention, it is worth mentioning that the reaction can also be carried out under the solvent-free condition, and the compound with the structure shown in formula II and the compound with the structure shown in formula III are directly mixed and reacted.

Preferably, the inert solvent is selected from any one of hexane, dichloromethane, petroleum ether, toluene, xylene or kerosene or a combination of at least two thereof.

Compared with the prior art, the invention has the following beneficial effects:

(1) The extractant adopted by the invention is used for enriching rare earth elements from low-concentration rare earth raw materials, separating and purifying yttrium elements from mixed rare earth raw materials, and removing elements such as aluminum, iron, radioactive thorium, radioactive uranium, actinium and the like from the mixed rare earth raw materials.

(2) The extractant used in the invention has good chemical stability, can resist strong acid and strong alkali without decomposition, and has a loss rate in a hydrochloric acid medium of below 0.05 percent; the loss rate in the liquid caustic soda medium is below 0.06 percent. 50mL of the extractant solution is mixed with 50mL of hydrochloric acid solution with the concentration of 6mol/L and stirred, and another 50mL of the extractant solution is mixed with 50mL of sodium hydroxide solution with the concentration of 6mol/L and stirred, the stirring is maintained for 15 days, and then the loss rate of the extractant is tested by nuclear magnetic detection.

Detailed Description

The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the specific embodiments are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The mixed rare earth solution in the following embodiments has the same components, and the specific components are as follows: lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium and yttrium, wherein the concentration of each element is 0.020mol/L.

β _Ln/Y Represents the relative separation coefficient of the rare earth ions (Ln) with respect to the yttrium ions (Y).

Example 1

a) Taking 5.51g of an extracting agent (the structural formula of the extracting agent is shown as I-1) and 18.5g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution; the concentration is 0.52mol/L;

b) Mixing the extractant solution with 0.96mL of 10.8mol/L sodium hydroxide aqueous solution, and saponifying at 25 deg.C for 5min to obtain saponified extractant solution with saponification degree of 80%;

c) Taking 25mL of saponified extractant solution, adding the saponified extractant solution, and extracting for 0.5h. The concentration of rare earth ions in the aqueous phase before and after extraction was measured, and the relative separation coefficient beta of each rare earth ion (Ln) with respect to yttrium ion (Y) was calculated _Ln/Y (ii) a The specific test results are shown in table 1.

Wherein, the synthetic route of the extracting agent I-1 is shown as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-diheptyldiamine represented by the formula II-1 (21.4g, 0.10 mol) in toluene (20 mL) to obtain a solution one; dissolving an octanenylglutaric anhydride compound (22.5 g,0.10 mol) represented by formula III-1 in toluene (30 mL) to obtain a solution II;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove the toluene to obtain a compound IV-1.

(3) Dissolving compound IV-1 in sodium borohydride (NaBH) ₄ ) And ZnCl ₂ Reducing in tetrahydrofuran solution to obtain the compound I-1.

The invention carries out nuclear magnetic resonance analysis on the compound I-1:

¹ H NMR(500MHz，CDCl3)，δ12.01(1H)，5.42(1H)，5.34(1H)，2.46(2H)，2.40(4H)，2.33(2H)，2.03(1H)，1.94(2H)，1.54(2H)，1.45(4H)，1.33(2H)，1.31(4H)，1.31(2H)，1.31(2H)，1.29(2H)，1.25(4H)，1.19(4H)，0.93(6H)，0.88(3H)，0.88(6H)。

¹³ C NMR(500MHz，CDCl3)，δ178.4，134.9，129.3，64.6，64.4(2C)，34.8(2C)，31.9，31.6，31.3(2C)，31.2，29.9，29.4，29.0(2C)，28.0，27.5，23.0(2C)，22.7，18.7(2C)，14.1，14.1(2C)。

example 2

a) Taking 6.24g of an extracting agent (the structural formula of the extracting agent is shown as I-2) and 18.8g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution with the concentration of 0.52mol/L;

b) Mixing the extractant solution with 0.96mL of 10.8mol/L sodium hydroxide aqueous solution, and saponifying at 25 ℃ for 5min to obtain a saponified extractant solution with a saponification degree of 80%;

c) Taking 25mL of mixed rare earth solution, adding the saponified extractant solution, and extracting for 0.5h at room temperature. The concentration of rare earth ions in the aqueous phase before and after extraction was measured, and the relative separation coefficient beta of each rare earth ion (Ln) with respect to yttrium ion (Y) was calculated _Ln/Y (ii) a The specific test results are shown in table 1.

Wherein, the synthetic route of the extracting agent I-2 is shown as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-diisooctylsecondary amine represented by formula II-2 (24.1g, 0.10mol) in toluene (20 mL) to obtain solution I; deckenylglutaric anhydride compound represented by formula III-2 (25.2 g,0.10 mol) was dissolved in toluene (30 mL) to give solution two;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 1h, and after the reaction is finished, concentrating in vacuum to remove toluene to obtain a compound IV-2.

(3) Dissolving compound IV-2 in sodium borohydride (NaBH) ₄ ) And ZnCl ₂ Reducing in tetrahydrofuran solution to obtain the compound I-2.

The invention carries out nuclear magnetic resonance analysis on the compound I-2:

¹ H NMR(500MHz，CDCl ₃ )，δ12.01(1H)，5.42(1H)，5.34(1H)，2.46(2H)，2.40(4H)，2.33(2H)，2.03(1H)，1.94(2H)，1.55(2H)，1.54(2H)，1.33(2H)，1.31(4H)，1.30(2H)，1.29(2H)，1.26(2H)，1.26(2H)，1.26(2H)，1.25(2H)，1.25(4H)，1.19(4H)，0.99(6H)，0.88(3H)，0.88(6H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，134.9，129.3，64.6，63.1(2C)，38.0(2C)，32.3(2C)，31.9，31.6，31.2，29.9，29.7，29.3，29.3(2C)，28.0，27.5，26.3(2C)，22.7，14.1，14.1(2C)，11.6(2C)。

example 3

a) Taking 8.08g of an extracting agent (the structural formula of the extracting agent is shown as I-3) and 16.9g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution with the concentration of 0.52mol/L;

Wherein, the synthetic route of the extracting agent I-3 is shown as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-diisodecylamine represented by the formula II-3 (29.8g, 0.10mol) in toluene (20 mL) to obtain a solution I; a dodecenylheptanedioic anhydride compound represented by the formula III-3 (32.2g, 0.10 mol) was dissolved in toluene (30 mL) to obtain a solution II;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 1h, and after the reaction is finished, concentrating in vacuum to remove toluene to obtain a compound IV-3.

(3) Dissolving compound IV-3 in sodium borohydride (NaBH) ₄ ) Reducing in tetrahydrofuran solution to obtain the compound I-3.

The invention carries out nuclear magnetic resonance analysis on the compound I-3:

¹ H NMR(500MHz，CDCl ₃ )，δ11.87(1H)，5.42(1H)，5.34(1H)，5.31(1H)，4.66(1H)，2.40(4H)，2.21(2H)，2.03(1H)，1.94(2H)，1.55(4H)，1.54(2H)，1.33(2H)，1.30(2H)，1.30(2H)，1.29(2H)，1.26(2H)，1.26(2H)，1.26(2H)，1.26(2H)，1.26(4H)，1.26(4H)，1.25(2H)，1.25(2H)，1.25(2H)，1.25(2H)，1.25(4H)，1.25(4H)，1.19(4H)，0.99(6H)，0.88(3H)，0.88(6H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，133.5，132.4，55.7(2C)，29.6，95.0，38.3(2C)，37.5，34.0，32.6(2C)，31.8(2C)，31.9，29.9，29.6(2C)，29.7，29.7，29.6，29.4，29.3，28.0，27.2，27.1(2C)，27.0，26.3(2C)，24.7，22.7(2C)，22.7，14.1(2C)，14.1，11.6(2C)。

example 4

a) Taking 6.89g of extractant (the structural formula of the extractant is shown as I-4) and 18.11g of toluene, mixing the extractant and the toluene to obtain extractant solution with the concentration of 0.52mol/L

c) Taking 25mL of mixed rare earth solution, adding the saponified extractant solution, and extracting for 0.5h at room temperature. Measuring the concentration of rare earth ions in the aqueous phase before and after extraction, and calculating the relative ratio of each rare earth ion (Ln)Relative separation coefficient beta in yttrium ion (Y) _Ln/Y (ii) a The specific test results are shown in table 1.

Wherein, the synthetic route of the extracting agent I-4 is as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-diisohydrocarbylsecondary amine represented by the formula II-4 (26.5g, 0.10mol) in toluene (20 mL) to obtain a solution I; a dodecenylglutaric anhydride compound represented by formula III-4 (28.0 g,0.10 mol) was dissolved in toluene (30 mL) to give a second solution;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove the toluene to obtain a compound IV-4.

(3) Dissolving compound IV-4 in sodium borohydride (NaBH) ₄ -ZnCl ₂ ) Reducing in tetrahydrofuran solution to obtain the compound I-4.

The invention carries out nuclear magnetic resonance analysis on the compound I-4:

¹ H NMR(500MHz，CDCl ₃ )，δ12.01(1H)，5.82(2H)，5.42(1H)，5.34(1H)，5.13(2H)，4.88(2H)，2.63(2H)，2.46(2H)，2.33(2H)，2.13(4H)，2.03(1H)，1.94(2H)，1.54(2H)，1.33(2H)，1.31(4H)，1.30(4H)，1.29(4H)，1.29(2H)，1.26(8H)，1.25(8H)，1.06(6H)，0.88(3H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，139.1(2C)，134.9，129.3，115.7(2C)，61.3(2C)，59.0，34.9(2C)，33.9(2C)，32.2，31.9，31.2，29.9，29.7(2C)，29.7，29.7，29.6(2C)，29.6，29.6，29.3，28.0，27.5，27.1(2C)，22.7，21.0(2C)，14.1。

example 5

a) Taking 6.54g of an extracting agent (the structural formula of the extracting agent is shown as I-5) and 18.46g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution with the concentration of 0.52mol/L;

c) Taking 25mL of mixed rare earth solution, adding the saponified extractant solution, and extracting for 0.5h at room temperature. The concentration of the rare earth ions in the aqueous phase before and after extraction was measured, and the relative separation coefficient beta of each rare earth ion (Ln) with respect to the yttrium ion (Y) was calculated _Ln/Y (ii) a The specific test results are shown in table 1.

Wherein, the synthetic route of the extracting agent I-5 is as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-diisohydrocarbylsecondary amine represented by the formula II-5 (26.5g, 0.10mol) in toluene (20 mL) to obtain a solution one; a hexaalkenylazelaic anhydride compound represented by formula III-5 (25.2g, 0.10 mol) was dissolved in toluene (30 mL) to give a solution II;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove the toluene to obtain a compound IV-5.

(3) Dissolving Compound IV-5 in sodium borohydride (NaBH) ₄ -ZnCl ₂ ) Reducing in tetrahydrofuran solution to obtain the compound I-5.

The invention carries out nuclear magnetic resonance analysis on the compound I-5:

¹ H NMR(500MHz，CDCl ₃ )，δ11.87(1H)，5.82(2H)，5.20(1H)，5.13(2H)，4.88(2H)，2.63(1H)，2.46(2H)，2.43(2H)，2.21(2H)，2.13(4H)，2.03(1H)，1.94(2H)，1.66(3H)，1.54(2H)，1.46(2H)，1.37(2H)，1.33(4H)，1.31(4H)，1.30(2H)，1.29(4H)，1.26(2H)，1.25(8H)，1.06(3H)，0.95(3H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，139.1(2C)，138.1，126.3，115.7(2C)，63.8，59.3，55.1，37.1，34.7，34.0，33.9(2C)，30.7，30.4，29.7，29.7，29.7，29.7，29.6(2C)，29.3，29.0，28.6，27.5，27.3，24.7，23.6，20.9，14.2，14.1。

example 6

a) Taking 6.6g of an extracting agent (the structural formula of the extracting agent is shown as I-6) and 18.4g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution with the concentration of 0.52mol/L;

Wherein, the synthetic route of the extracting agent I-6 is shown as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-diisohydrocarbylsecondary amine represented by the formula II-6 (18.1g, 0.10mol) in toluene (20 mL) to obtain a solution I; dissolving a dodecenyladipic anhydride compound represented by formula III-6 (18.4g, 0.10mol) in toluene (30 mL) to obtain a solution II;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove the toluene to obtain a compound IV-6.

(3) Dissolving compound IV-4 in sodium borohydride (NaBH) ₄ -ZnCl ₂ ) Reducing in tetrahydrofuran solution to obtain the compound I-6.

The invention carries out nuclear magnetic resonance analysis on the compounds 1-6:

¹ H NMR(500MHz，CDCl ₃ )，δ11.87(1H)，5.83(1H)，5.82(1H)，5.23(1H)，5.19(1H)，5.13(1H)，4.88(1H)，3.41(1H)，2.43(2H)，2.40(2H)，2.33(2H)，2.13(2H)，1.55(2H)，1.54(2H)，1.37(2H)，1.33(2H)，1.30(1H)，1.29(4H)，1.19(2H)，1.15(1H)，1.01(3H)，0.99(3H)，0.88(3H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，139.1，131.4，117.7，115.7，72.5，56.6，55.1，40.7，39.6，34.3，33.9，29.8，29.6，29.4，28.7，27.4，26.5，22.5，18.2，17.5，11.9。

example 7

a) Taking 7.2g of an extracting agent (the structural formula of the extracting agent is shown as I-7) and 17.8g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution with the concentration of 0.52mol/L;

Wherein, the synthetic route of the extracting agent I-7 is shown as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-dienyldiamine represented by the formula II-7 (12.5 g,0.10 mol) in toluene (20 mL) to obtain a first solution; a dianhydride compound represented by the formula III-7 (44.8g, 0.10mol) was dissolved in toluene (30 mL) to obtain a solution II;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove the toluene to obtain a compound IV-7.

(3) Dissolving compound IV-7 in sodium borohydride (NaBH) ₄ ) And ZnCl ₂ In tetrahydrofuran solution to obtain the compound I-7.

The invention carries out nuclear magnetic resonance analysis on the compound I-7, and the results are as follows:

¹ H NMR(500MHz，CDCl ₃ )，δ11.87(1H)，6.05(1H)，5.61(1H)，5.61(1H)，5.55(1H)，5.42(1H)，5.34(1H)，3.99(1H)，3.80(2H)，3.23(2H)，2.21(2H)，2.03(1H)，1.98(2H)，1.94(2H)，1.54(2H)，1.46(2H)，1.33(2H)，1.33(2H)，1.30(2H)，1.30(2H)，1.29(2H)，1.26(24H)，1.25(2H)，1.25(2H)，1.25(2H)，0.96(3H)，0.88(3H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，147.3，133.5，132.4，129.8，128.5，93.1，61.2，57.2，35.6，34.0，33.3，32.4，31.9，29.3，29.6(10C)，29.7，29.7，29.7，29.0，28.0，27.2，23.3，24.7，22.7，14.2，14.1。

example 8

a) Taking 9.3g of an extracting agent (the structural formula of the extracting agent is shown as I-8) and 15.73g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution with the concentration of 0.52mol/L;

Wherein, the synthetic route of the extracting agent I-8 is as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-dienyldiamine represented by the formula II-8 (12.5 g,0.10 mol) in toluene (20 mL) to obtain a first solution; a dianhydride compound represented by formula III-8 (61.6g, 0.10mol) was dissolved in toluene (30 mL) to give a solution II;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove toluene to obtain a compound IV-8.

(3) Dissolving compound IV-8 in sodium borohydride (NaBH) ₄ ) And ZnCl ₂ In tetrahydrofuran solution to obtain the compound I-8.

The invention carries out nuclear magnetic resonance analysis on the compound I-8, and the results are as follows:

¹ H NMR(500MHz，CDCl ₃ )，δ11.87(1H)，6.05(1H)，5.61(1H)，5.61(1H)，5.55(1H)，5.42(1H)，5.34(1H)，3.99(1H)，3.80(2H)，3.23(2H)，2.21(2H)，2.03(1H)，1.98(2H)，1.94(2H)，1.54(2H)，1.46(2H)，1.33(2H)，1.33(2H)，1.30(2H)，1.30(2H)，1.29(2H)，1.26(2H)，1.26(44H)，1.26(2H)，1.25(2H)，1.25(2H)，0.98(3H)，0.88(3H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，147.3，133.5，132.4，129.8，128.5，93.1，61.2，57.2，35.6，34.0，33.3，32.4，31.9，30.0，29.9，29.7，29.7，29.6(20C)，29.6，29.3，29.3，29.0，28.0，27.2，24.7，23.3，22.7，14.2，14.1。

example 9

a) Taking 5.1g of an extracting agent (the structural formula of the extracting agent is shown as I-9) and 19.9g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution with the concentration of 0.52mol/L;

Wherein, the synthetic route of the extracting agent I-9 is as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-dihydrocarbyldiamine represented by the formula II-9 (10.1g, 0.10mol) in toluene (20 mL) to obtain a solution I; the dianhydride compound represented by formula III-9 (30.6 g,0.10 mol) was dissolved in toluene (30 mL) to give a second solution;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove the toluene to obtain a compound IV-9.

(3) Dissolving compound IV-9 in sodium borohydride (NaBH) ₄ ) And ZnCl ₂ Reducing in tetrahydrofuran solution to obtain the compound I-9.

The invention carries out nuclear magnetic resonance analysis on the compound I-9, and the results are as follows:

¹ H NMR(500MHz，CDCl ₃ )，δ11.87(1H)，2.69(1H)，2.60(2H)，2.43(2H)，2.39(1H)，2.21(2H)，1.96(2H)，1.54(2H)，1.44(2H)，1.43(2H)，1.38(2H)，1.33(2H)，1.29(2H)，1.28(2H)，1.28(2H)，1.26(2H)，1.26(2H)，1.25(2H)，1.25(2H)，1.00(3H)，1.00(3H)，0.88(3H)，0.87(3H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，80.1，79.2，58.0，57.3，56.0，34.0，31.4，30.9，29.6，29.4，29.3，29.0，29.0，29.0，28.1，26.7，25.9，24.7，22.7，21.7，19.4，18.1，18.1，14.1，11.8。

example 10

a) 5.5g of an extractant (the structural formula of the extractant is shown as I-10) and 19.5g of toluene are taken, and the extractant and the toluene are mixed to obtain an extractant solution with the concentration of 0.52mol/L.

Wherein, the synthetic route of the extracting agent I-10 is as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-dihydrocarbyldiamine represented by the formula II-10 (10.1g, 0.10mol) in toluene (20 mL) to obtain a solution I; the dianhydride compound represented by formula III-10 (33.4g, 0.10 mol) was dissolved in toluene (30 mL) to give a second solution;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove the toluene to obtain a compound IV-10.

(3) Dissolving compound IV-10 in sodium borohydride (NaBH) ₄ ) Reducing in tetrahydrofuran solution to obtain the compound I-10.

The invention carries out nuclear magnetic resonance analysis on the compound I-10, and the results are as follows:

¹ H NMR(500MHz，CDCl ₃ )，δ11.87(1H)，5.31(1H)，4.6(1H)，2.69(1H)，2.43(2H)，2.39(1H)，2.21(2H)，1.96(2H)，1.54(2H)，1.44(2H)，1.43(2H)，1.38(2H)，1.33(2H)，1.30(2H)，1.29(2H)，1.28(2H)，1.28(2H)，1.26(2H)，1.26(2H)，1.26(2H)，1.25(2H)，1.25(2H)，1.00(3H)，1.00(3H)，0.88(3H)，0.87(3H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，90.3，80.1，79.2，53.6，49.8，34.0，32.0，30.9，29.6，29.6，29.6，29.3，29.0，29.0，29.0，28.1，26.2，25.2，24.7，22.7，22.0，21.8，21.8，19.4，14.1，11.8。

example 11

a) Taking 3.7g of an extracting agent (the structural formula of the extracting agent is shown as I-11) and 21.3g of toluene, and mixing the extracting agent and the toluene to obtain an extracting agent solution with the concentration of 0.52mol/L;

Wherein, the synthetic route of the extracting agent I-11 is shown as follows:

the synthesis method comprises the following steps:

(1) Dissolving N, N-dihydrocarbyldiamine represented by the formula II-11 (12.9 g,0.10 mol) in toluene (20 mL) to obtain a solution one; the dianhydride compound represented by formula III-11 (17.0 g,0.10 mol) was dissolved in toluene (30 mL) to give a second solution;

(2) Adding the solution I into the solution II, stirring the solution, raising the temperature to 80 ℃, maintaining the temperature for 2 hours, and after the reaction is finished, concentrating in vacuum to remove toluene to obtain a compound IV-11.

(3) Dissolving Compound IV-11 in sodium borohydride (NaBH) ₄ ) And ZnCl ₂ In tetrahydrofuran solution to obtain the compound I-11.

The invention carries out nuclear magnetic resonance analysis on the compound I-11, and the results are as follows:

¹ H NMR(500MHz，CDCl ₃ )，δ12.12(1H)，2.43(4H)，2.40(2H)，2.33(2H)，1.76(2H)，1.41(4H)，1.31(2H)，1.29(4H)，1.25(2H)，1.25(2H)，1.19(2H)，0.91(3H)，0.88(3H)。

¹³ C NMR(500MHz，CDCl ₃ )，δ178.4，62.4，57.2(2C)，35.2，32.3，31.2，30.5(2C)，29.3，29.2，23.0，20.4(2C)，14.1，13.8(2C)。

comparative example 1

a) Taking 3.7g of naphthenic acid (the purity of an extractant is 95 percent) and 21.3g of toluene, and mixing the extractant and the toluene to obtain an extractant solution with the concentration of 0.52mol/L;

c) Taking 25mL of mixed rare earth solution, adding the saponified extractant solution, and extracting for 0.5h at room temperature. Testing of rare earth ions in aqueous phase before and after extractionConcentration and calculating a relative separation coefficient beta of each rare earth ion (Ln) with respect to the yttrium ion (Y) _Ln/Y (ii) a The specific test results are shown in table 1.

(relative separation coefficient beta of rare earth ion (Ln) with respect to yttrium ion (Y)) _Ln/Y ) As shown in table 1:

TABLE 1

As can be seen from Table 1, the N, N-dihydrocarbylaminocarboxylic acid extractants of examples 1-11 have a separation coefficient (. Beta.) for lanthanides from yttrium _Ln/Y ) Separation coefficient (beta) superior to that of naphthenic acid extractant in comparative example 1 _Ln/Y ) The N, N-dialkyl amino carboxylic acid extracting agent can better separate and purify yttrium element from mixed rare earth raw materials.

The applicant states that the present invention is illustrated by the above examples of the N, N-dihydrocarbylaminocarboxylic acids, the preparation and use thereof, but the present invention is not limited to the above examples, which does not mean that the present invention must be practiced by relying on the above examples. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A method for separating rare earth elements is characterized in that a compound with a structural formula I is used as an extracting agent to extract rare earth mixed feed liquid;

wherein R is ₁ And R ₂ Independently a linear or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbyl group;

R ₃ is a linear or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbon group;

x is H or OH;

n is a natural number of 1 to 10.

2. The method for separating rare earth elements according to claim 1, wherein R is ₁ And R ₂ Independently a C7 or higher linear or branched, saturated or unsaturated, unsubstituted hydrocarbon group.

3. The method for separating rare earth elements according to claim 2, wherein R is ₁ And R ₂ Independently a C7-C30 linear or branched, saturated or unsaturated, unsubstituted hydrocarbon group.

4. The method for separating rare earth elements according to claim 1, wherein R is ₁ And R ₂ Independently a linear or branched and unsubstituted alkyl group.

5. The method for separating rare earth elements according to claim 4, wherein R is ₁ And R ₂ Independently a C7-C30 linear or branched, unsubstituted alkyl group.

6. The method for separating rare earth elements according to claim 5, wherein R is ₁ And R ₂ Independently a C7-C30 branched and unsubstituted alkyl group.

7. The method for separating rare earth elements according to claim 1, wherein R is ₃ Selected from linear or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbon groups of C6 or more.

8. The method for separating rare earth elements according to claim 7, wherein R is ₃ Is C6-C30 straight or branched, saturated or unsaturated, substituted or unsubstituted hydrocarbyl.

9. The method for separating rare earth elements according to claim 1, wherein R is ₃ Is C6 or above straight chain or branched chain, saturated or unsaturated, unsubstituted alkyl.

10. The method for separating rare earth elements according to claim 9, wherein R is ₃ Is a C6-C30 linear or branched, unsaturated and unsubstituted hydrocarbon group.

11. The method for separating rare earth elements according to claim 10, wherein R is ₃ Is C10-C18 straight-chain alkenyl.

12. The method for separating rare earth elements according to claim 1, wherein X is H.

13. The method for separating rare earth elements according to claim 1, wherein the extractant is first saponified to obtain a saponified extractant solution; then extracting with mixed rare earth solution.

14. The method for separating rare earth elements according to claim 1, comprising the steps of:

15. The method of separating rare earth elements according to claim 13 or 14, wherein the rare earth solution contains one or more rare earth ions of lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium;

16. The method for separating rare earth elements according to claim 14, wherein the organic solvent is one or more selected from toluene, xylene, octane, dichloromethane, kerosene.

17. The method of claim 16, wherein the mass ratio of the extractant to the organic solvent is 1: 1 to 10.