Extracting agent and application thereof in extraction of lithium element in oilfield brine

Abstract

The invention relates to the technical field of oil field brine metal recovery, and discloses an extraction agent and application thereof in extraction of lithium element in oil field brine. The extraction agent contains supercritical carbon dioxide, a chelating agent, a synergistic extraction agent, a transition metal source and a chlorine source; the volume ratio of the chelating agent to the synergistic extraction agent is 1: (0.1-0.3). The extraction agent disclosed by the invention is high in extraction efficiency of the lithium element and convenient to operate, carbon dioxide is easy to obtain as a solvent and can be recycled, generation of waste acid, waste alkali and organic waste liquid in the extraction process is avoided, and the extraction agent is green, environment-friendly, low in cost and free of secondary pollution to the environment.

Description

Technical Field

[0001] This invention relates to the field of oilfield brine metal recovery technology, specifically to an extractant and its application in extracting lithium from oilfield brine. Background Technology

[0002] Lithium is widely used in national defense, aerospace, energy, and various civilian industries, and is one of my country's important strategic metals, with demand increasing year by year. my country is rich in brine resources, which are rich in inorganic metal ions such as sodium, potassium, lithium, magnesium, and calcium, as well as various trace elements. Collecting and industrializing the lithium resources abundant in brine is of significant strategic importance. As the difficulty of material extraction and separation increases, and the requirements for greener, more diversified, and more refined processes become more stringent, various new extraction methods, such as ionic liquids, supercritical fluids, aqueous two-phase systems, electric field enhancement, and microwave enhancement, have emerged. These extraction methods have greatly broadened the application scope of extraction and separation technologies.

[0003] Substances exhibit different physical states under different temperatures and pressures. When the temperature and pressure of a fluid exceed its corresponding critical temperature and pressure, the fluid in this state is called a supercritical fluid (SCF). Supercritical fluid extraction, as an emerging technology, has attracted considerable attention in recent years due to its unique extraction characteristics and high efficiency. The most widely used SCF is supercritical carbon dioxide (SC-CO2). Carbon dioxide, at its critical temperature (Te = 31.06℃, near room temperature) and critical pressure (Pc = 7.38MPa, relatively low), exhibits high density, high diffusivity, and low viscosity, displaying excellent supercritical state similar to gas diffusion and liquid dissolution, thus possessing excellent solubility. Therefore, supercritical carbon dioxide fluid is widely used as a superior process extraction carrier in enhanced process separation fields, such as the pharmaceutical and food industries. Since SC-CO2 is a non-polar solvent, when extracting polar substances such as metal ions and inorganic metal compounds, a significant polarity difference exists between the solute and solvent. In such cases, chelating agents are needed to achieve charge neutrality and alter the polarity of the solute and solvent, thereby facilitating solvent-solute interactions. With the aid of chelating agents, supercritical carbon dioxide, as a superior extraction technology, can effectively recover high-value-added heavy metal elements from metal-containing waste oilfield brine, while reducing potential environmental risks. Compared to traditional pyrometallurgical and hydrometallurgical techniques, it reduces process requirements, thereby lowering energy consumption and pollution control costs, making it more readily accepted by the public. It also offers advantages such as ease of operation. Because carbon dioxide is readily available, inexpensive, and recyclable, it effectively addresses the high energy consumption and environmental risks associated with the recovery process, avoiding the generation of waste acid and alkali, and eliminating concerns about secondary environmental damage such as chemical precipitation and the production of large amounts of harmful wastewater. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of low extraction efficiency in the prior art and to provide an extractant that has high extraction efficiency, low cost and does not cause secondary pollution to the environment.

[0005] To achieve the above objectives, the present invention provides an extractant containing supercritical carbon dioxide, a chelating agent, a co-extracting agent, a transition metal source, and a chlorine source; wherein the volume ratio of the chelating agent to the co-extracting agent is 1:0.1-0.3.

[0006] Preferably, the chelating agent is selected from one or more of neutral organophosphorus compounds, β-diketones, dithiocarbamates, and crown ethers.

[0007] Preferably, the chelating agent is selected from one or more of the following: tributyl phosphate, Cyanex 272, Cyanex 301, acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, sodium dithiocarbamate, potassium dithiocarbamate, and 18-crown ether 6.

[0008] Preferably, the molar ratio of the chlorine source to the transition metal source is ≥3, wherein the chlorine source is calculated as chlorine element and the transition metal source is calculated as metal.

[0009] Preferably, the metal in the transition metal source is selected from at least one of iron, copper, zinc, and cobalt.

[0010] Preferably, the co-extractant is selected from one or more of water, monohydric alcohol, monoketone, hexane, chloroform, dichloromethane, toluene, and tetrahydrofuran.

[0011] A second aspect of the present invention provides the application of the above-mentioned extractant in the treatment of oilfield brine.

[0012] A third aspect of the present invention provides a method for separating lithium from oilfield brine, the method comprising: extracting the oilfield brine with the above-mentioned extractant, then separating the lithium-containing phase under reduced pressure, and finally back-extracting the lithium-containing phase with a back-extractant;

[0013] The extraction conditions include a pressure of 7.5-9 MPa and a temperature of 45-55°C; the back-extraction agent is selected from one or more of water, inorganic acid solution and inorganic salt solution.

[0014] Preferably, the molar ratio of lithium element in the oilfield brine to the chelating agent is 1:2-4.

[0015] Preferably, the molar ratio of lithium to transition metal source in the oilfield brine is 1:0.5-3, wherein the transition metal source is calculated as metal.

[0016] Preferably, the volume ratio of the supercritical carbon dioxide to the weight ratio of lithium in the oilfield brine is ≥50 mL / g.

[0017] Preferably, the extraction conditions also include a time of 25-30 minutes.

[0018] Preferably, the conditions for depressurization separation include: a pressure of 4-6 MPa and a temperature of 35-45°C.

[0019] Preferably, the volume ratio of the lithium-containing phase to the stripping agent is 1:2-4.

[0020] Preferably, the inorganic acid solution is selected from water, hydrochloric acid, and / or sulfuric acid.

[0021] Preferably, the inorganic salt solution is selected from one or more of potassium sulfate solution, potassium chloride solution, sodium sulfate solution and sodium chloride solution.

[0022] Preferably, the back-extraction conditions include a temperature of 20-25°C and a time of 0.5-1 h.

[0023] Preferably, the method is carried out in an extraction system;

[0024] The extraction system includes an extraction unit, a separation unit, and a back-extraction unit connected in sequence.

[0025] Preferably, the extraction unit includes at least two extraction vessels.

[0026] Preferably, the separation unit includes at least one separation vessel.

[0027] Preferably, the back-extraction unit includes at least one back-extraction vessel.

[0028] Preferably, the extraction system further includes a mixer connected to the extraction unit, the mixer being used to mix liquid carbon dioxide, a chelating agent, a co-extracting agent, a transition metal source, and a chlorine source.

[0029] Preferably, the extraction system further includes a carbon dioxide storage unit;

[0030] The carbon dioxide storage unit is connected to the mixer;

[0031] The carbon dioxide storage unit is connected to the separation unit.

[0032] Preferably, the carbon dioxide storage unit includes a carbon dioxide cylinder, a purifier, a cold box, and a liquid carbon dioxide storage tank connected in sequence.

[0033] The liquid carbon dioxide storage tank is connected to the mixer;

[0034] The carbon dioxide cylinder is connected to the separation unit.

[0035] Preferably, the extraction system further includes a first storage tank; the first storage tank is used to store the chelating agent and the co-extracting agent;

[0036] The first storage tank is connected to the mixer;

[0037] The first storage tank is connected to the back-extraction unit.

[0038] Preferably, the extraction system further includes a second storage tank; the second storage tank is used to store a transition metal source and a chlorine source;

[0039] The second storage tank is connected to the mixer.

[0040] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0041] (1) The extractant described in this invention has high extraction efficiency for lithium and is low in cost and will not cause secondary pollution to the environment.

[0042] (2) The method for separating lithium from oilfield brine described in this invention can achieve directional extraction of lithium, and the separated lithium-containing product has high purity. At the same time, the operation is convenient, and carbon dioxide as a solvent is easy to obtain and can be recycled, avoiding the generation of waste acid, waste alkali and organic waste liquid during the extraction process, which is green and environmentally friendly. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of an extraction system according to a specific embodiment of the present invention.

[0044] Explanation of reference numerals in the attached figures

[0045] 1 First storage tank 3 Mixer

[0046] 7 Second Storage Tank

[0047] 21 Carbon dioxide cylinders 22 Air purifiers

[0048] 23 Cold Box 24 Liquid Carbon Dioxide Storage Tank

[0049] 41 First extraction vessel 42 Second extraction vessel

[0050] 43 Third Extraction Vessel 44 Fourth Extraction Vessel

[0051] 45 Fifth Extraction Vessel 51 First Separation Vessel

[0052] 52 Second Separation Unit 61 Back-Extraction Unit Detailed Implementation

[0053] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0054] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0055] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating relative importance or implying the number of technical features indicated. Therefore, unless otherwise stated, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature; "multiple" means two or more. The term "comprising" and any variations thereof mean non-exclusive inclusion, where one or more other features, integers, steps, operations, units, components, and / or combinations thereof may be present or added.

[0056] Furthermore, terms such as "upper," "lower," "inner," and "outer" indicating orientation or positional relationships are based on the orientation or relative positional relationships shown in the accompanying drawings. They are merely simplified descriptions for the convenience of describing this application and do not indicate that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0057] Furthermore, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0058] In one aspect, the present invention provides an extractant containing supercritical carbon dioxide, a chelating agent, a co-extracting agent, a transition metal source, and a chlorine source; wherein the volume ratio of the chelating agent to the co-extracting agent is 1:0.1-0.3.

[0059] In a specific embodiment, the volume ratio of the chelating agent and the co-extractant can be 1:0.1, 1:0.2, or 1:0.3.

[0060] In a preferred embodiment, the chelating agent is selected from one or more of neutral organophosphorus compounds, β-diketones, dithiocarbamates, and crown ethers.

[0061] In a preferred embodiment, in order to improve the chelating effect between the chelating agent and lithium metal, the chelating agent is selected from one or more of the following: tributyl phosphate, Cyanex 272, Cyanex 301, acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, sodium dithiocarbamate, potassium dithiocarbamate, and 18-crown ether 6.

[0062] In this invention, there are no special requirements for the chlorine source, as long as it can provide chloride ions.

[0063] In this invention, there are no special requirements for the molar amount of the chlorine source, as long as it is far in excess of the metal in the transition metal source. In a preferred embodiment, the molar ratio of the chlorine source to the transition metal source is ≥3, wherein the chlorine source is calculated as chlorine element and the transition metal source is calculated as metal. Based on this, a high concentration of chloride ion environment can be provided, which is conducive to the formation of metal complexes.

[0064] In a preferred embodiment, in order to further improve the chelating effect of the chelating agent and increase the extraction efficiency, the metal in the transition metal source is selected from at least one of iron, copper, zinc and cobalt; more preferably, the metal in the transition metal source is iron.

[0065] In a specific implementation, when the transition metal source contains chlorine, the transition metal source containing chlorine is simultaneously a transition metal source and a chlorine source; when the chlorine source contains a transition metal, the chlorine source containing the transition metal is also simultaneously a transition metal source and a chlorine source. For example, when the transition metal source or chlorine source is ferric chloride, ferric chloride is simultaneously a transition metal source and a chlorine source.

[0066] In a preferred embodiment, in order to improve the solubility of the metal complex in supercritical carbon dioxide and improve the extraction efficiency, the co-extractant is selected from one or more of water, monohydric alcohol, monoketone, hexane, chloroform, dichloromethane, toluene and tetrahydrofuran.

[0067] The extractant described in this invention exhibits excellent extraction efficiency for metallic lithium, primarily due to its ability to extract lithium at high Cl concentrations. - Under certain conditions, metal ions R in transition metal sources n+ With Cl - Combine to form complex anions [RCl4] n-4 ], complexed anion [RCl4 n-4 [Can be used for Li] + Surrounding water molecules undergo displacement, complexing with anions [RCl4] n-4 Replacing water molecules can indirectly enhance the chelating agent and Li. + The ability to form complexes, and simultaneously complex anions [RCl4] n-4 It can exist in large quantities in the chelating agent in an ionic state, thereby significantly improving the chelating agent's affinity for Li. + chelation efficiency.

[0068] A second aspect of the present invention provides the application of the above-mentioned extractant in the treatment of oilfield brine.

[0069] A third aspect of the present invention provides a method for separating lithium from oilfield brine, the method comprising: extracting the oilfield brine with the above-mentioned extractant, then separating the lithium-containing phase under reduced pressure, and finally back-extracting the lithium-containing phase with a back-extractant;

[0070] The extraction conditions include a pressure of 7.5-9 MPa and a temperature of 45-55°C; the back-extraction agent is selected from one or more of water, inorganic acid solution and inorganic salt solution.

[0071] In the method described in this invention, oilfield brine can be extracted by adhering to a matrix such as diatomaceous earth, or it can be extracted directly in solution form.

[0072] In a preferred embodiment, in order to improve the extraction efficiency of lithium in oilfield brine by the extractant, the molar ratio of lithium in oilfield brine to the chelating agent is 1:2-4; specifically, the molar ratio of lithium in oilfield brine to the chelating agent can be 1:2, 1:3 or 1:4.

[0073] In a preferred embodiment, in order to enhance the complexation of the anion [RCl4] n-4 [Regarding Li] + The displacement effect of surrounding water molecules further improves the extraction efficiency of the extractant for lithium in oilfield brine. The molar ratio of lithium to transition metal source in oilfield brine is 1:0.5-3, where the transition metal source is calculated as metal. Specifically, the molar ratio of lithium to transition metal source in oilfield brine can be 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5 or 1:3.

[0074] In this invention, there are no special requirements for the amount of supercritical carbon dioxide used, as long as it is in excess relative to the weight of lithium in the oilfield brine; in a preferred embodiment, the volume ratio of the supercritical carbon dioxide to the weight ratio of lithium in the oilfield brine is ≥50mL / g.

[0075] In a preferred embodiment, in order to improve extraction efficiency, the extraction conditions further include: a time of 25-30 min; specifically, the time can be 25 min, 26 min, 27 min, 28 min, 29 min, or 30 min.

[0076] In a preferred embodiment, in order to further improve the extraction efficiency of lithium and the recovery rate of carbon dioxide, the conditions for vacuum separation include: a pressure of 4-6 MPa and a temperature of 35-45°C; specifically, the pressure is 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa or 6 MPa; and the temperature can be 35°C, 40°C or 45°C.

[0077] In a preferred embodiment, in order to improve the back-extraction efficiency of lithium, the volume ratio of the lithium-containing phase to the back-extraction agent is 1:2-4; specifically, the volume ratio of the lithium-containing phase to the back-extraction agent can be 1:2, 1:3 or 1:4.

[0078] In a preferred embodiment, in order to separate high-purity lithium products of lithium chloride or lithium sulfate, the inorganic acid solution is selected from hydrochloric acid solution and / or sulfuric acid solution.

[0079] In a preferred embodiment, the inorganic salt solution is selected from one or more of potassium sulfate solution, potassium chloride solution, potassium carbonate, sodium carbonate, sodium sulfate solution, and sodium chloride solution.

[0080] In a preferred embodiment, in order to further improve the efficiency and purity of lithium extraction by the back-extraction agent, the back-extraction conditions include: a temperature of 20-25°C and a time of 0.5-1h; specifically, the temperature can be 20°C, 21°C, 22°C, 23°C, 24°C or 25°C; and the time can be 0.5h, 0.6h, 0.7h, 0.8h, 0.9h or 1h.

[0081] In a preferred embodiment, the method is performed in an extraction system;

[0082] The extraction system includes an extraction unit, a separation unit, and a back-extraction unit connected in sequence.

[0083] In this invention, the extraction unit is used to extract lithium from oilfield brine. The extractant and the oilfield brine are in full contact within the extraction unit, and a high concentration of Cl is achieved. - Under certain conditions, metal ions R in transition metal sources n+ With Cl - Combine to form complex anions [RCl4] n-4 ], complexed anion [RCl4 n-4 [Can be used for Li] + Surrounding water molecules undergo displacement, complexing with anions [RCl4] n-4 After replacing water molecules, the chelating agent and Li are strengthened. + The system utilizes the ability to form complexes, allowing lithium in oilfield brine to chelate with the chelating agent in the extractant to form metallic lithium complexes that dissolve in supercritical carbon dioxide. The co-extracting agent further enhances the solubility of the metallic lithium complexes in supercritical carbon dioxide, thereby achieving the extraction of lithium from the oilfield brine. The supercritical carbon dioxide containing the dissolved metallic lithium complexes and co-extracting agent enters the separation unit, where it is depressurized and cooled to form carbon dioxide gas and a lithium-containing phase, achieving separation of the carbon dioxide gas and the lithium-containing phase. The lithium-containing phase then enters the back-extraction unit, where different lithium-containing products are separated through back-extraction under the action of different back-extraction agents. Using this extraction system can improve extraction efficiency and the purity of lithium-containing products.

[0084] In a preferred embodiment, to further improve extraction efficiency, the extraction unit includes at least two extraction vessels connected in parallel.

[0085] In a specific embodiment, each extraction vessel has an extractant inlet, an oilfield brine inlet, a waste oilfield brine outlet, and a solvent outlet; the extractant enters the extraction vessel through the extractant inlet, and the oilfield brine enters the extraction vessel through the oilfield brine inlet, and the two are in full contact within the extraction vessel, under high concentration Cl... - Under certain conditions, metal ions R in transition metal sources n+ With Cl - Combine to form complex anions [RCl4] n-4 ], complexed anion [RCl4 n-4 [Can be used for Li] + Surrounding water molecules undergo displacement, complexing with anions [RCl4] n-4 After replacing water molecules, the chelating agent and Li are strengthened. + The ability to form complexes allows lithium in oilfield brine to chelate with the chelating agent in the extractant to form a metallic lithium complex, which then dissolves in supercritical carbon dioxide. The co-extracting agent further enhances the solubility of the metallic lithium complex in supercritical carbon dioxide, thereby achieving the extraction of lithium from the oilfield brine. The supercritical carbon dioxide containing the dissolved metallic lithium complex and co-extracting agent is discharged from the solvent outlet, and the waste oilfield brine is discharged from the waste oilfield brine outlet for recycling.

[0086] In a preferred embodiment, the separation unit includes a separation vessel; the separation vessel is connected to all the extraction vessels.

[0087] In a specific embodiment, the separation vessel has a solvent inlet, a gas phase outlet, and a lithium-containing phase outlet; supercritical carbon dioxide, which dissolves lithium metal complexes and co-extractants, enters the separation vessel through the solvent inlet and is cooled and depressurized to form carbon dioxide gas and a lithium-containing phase, thereby achieving the separation of the two. The carbon dioxide gas is discharged from the gas phase outlet, and the lithium-containing phase is discharged from the lithium-containing phase outlet.

[0088] In a more preferred embodiment, the separation unit includes a plurality of separation vessels connected in series.

[0089] In a preferred embodiment, the back-extraction unit includes a back-extraction vessel; the back-extraction vessel is connected to all the separation vessels.

[0090] In a specific embodiment, the back-extraction vessel has a lithium-containing phase inlet, a back-extraction agent inlet, a lithium-containing aqueous phase outlet, and an organic phase outlet. The lithium-containing phase enters the back-extraction vessel from the lithium-containing phase inlet, and the back-extraction agent enters the back-extraction vessel from the back-extraction agent inlet. Under specific back-extraction conditions, lithium elements are transferred from the lithium-containing phase to the aqueous phase to form a lithium-containing aqueous phase and an organic phase. The lithium-containing aqueous phase is discharged from the aqueous phase outlet, and the organic phase chelating agent and co-extraction agent are discharged from the organic phase outlet.

[0091] In a more preferred embodiment, the back-extraction unit includes a plurality of back-extraction vessels connected in parallel.

[0092] In a preferred embodiment, the extraction system further includes a mixer 3 connected to the extraction unit. The mixer 3 is used to mix liquid carbon dioxide, chelating agent, co-extracting agent, transition metal source and chlorine source. Under heating and pressurization, the liquid carbon dioxide is made into a supercritical state and together with the chelating agent, co-extracting agent, transition metal source and chlorine source to form the extractant of the present invention.

[0093] In a preferred embodiment, the extraction system further includes a carbon dioxide storage unit connected to the mixer 3. The carbon dioxide storage unit is used to store carbon dioxide and add it to the mixer 3.

[0094] In a specific embodiment, the carbon dioxide storage unit includes a carbon dioxide cylinder 21, a purifier 22, a cold box 23, and a liquid carbon dioxide storage tank 24 connected in sequence; the liquid carbon dioxide storage tank 24 is connected to the mixer 3; the carbon dioxide cylinder 21 is used to store and supply gaseous carbon dioxide, which is purified by the purifier 22 to remove impurities such as moisture, and then enters the cold box 23 to be cooled and liquefied into liquid carbon dioxide, and then enters the liquid carbon dioxide storage tank 24, and supplies liquid carbon dioxide to the mixer 3.

[0095] In a preferred embodiment, the carbon dioxide storage unit is connected to the separation unit.

[0096] In a specific implementation, the carbon dioxide cylinder 21 is connected to the gas phase outlet of the separation unit, thereby realizing the recycling of carbon dioxide.

[0097] In a preferred embodiment, the extraction system further includes a first storage tank 1; the first storage tank 1 is connected to a mixer 3; the first storage tank 1 is used to store chelating agents and co-extracting agents and to add the chelating agents and co-extracting agents to the mixer 3.

[0098] In a preferred embodiment, the first storage tank 1 is connected to the back-extraction unit; in a specific embodiment, the first storage tank 1 is connected to the organic phase outlet of the back-extraction unit, thereby realizing the recycling of the organic phase chelating agent and the co-extracting agent.

[0099] In a preferred embodiment, the extraction system further includes a second storage tank 7; the second storage tank 7 is connected to the mixer 3; the second storage tank 7 is used to store the transition metal source and the chlorine source and to add the transition metal source and the chlorine source to the mixer 3.

[0100] In a preferred embodiment, the extraction system includes a first storage tank 1, a carbon dioxide storage unit, a mixer 3, a second storage tank 7, an extraction unit, a separation unit, and a back-extraction unit;

[0101] The first storage tank 1 is connected to the mixer 3;

[0102] The second storage tank 7 is connected to the mixer 3;

[0103] The carbon dioxide storage unit includes a carbon dioxide cylinder 21, a purifier 22, a cold box 23, and a liquid carbon dioxide storage tank 24 connected in sequence; the liquid carbon dioxide storage tank 24 is connected to the mixer 3.

[0104] The mixer 3 is connected to the extraction unit;

[0105] The extraction unit includes multiple extraction vessels connected in parallel; each extraction vessel has an extractant inlet, an oilfield brine inlet, a waste oilfield brine outlet, and a solvent outlet; the extractant inlet of each extraction vessel is connected to a mixer 3;

[0106] The separation unit includes multiple separation vessels connected in sequence; each separation vessel has a solvent inlet, a gas phase outlet, and a lithium-containing phase outlet.

[0107] The back-extraction unit includes a back-extraction vessel, which has a lithium-containing phase inlet, a back-extraction agent inlet, a lithium-containing aqueous phase outlet, and an organic phase outlet; the lithium-containing phase inlet of the back-extraction vessel is connected to the lithium-containing phase outlet of each separation vessel; the organic phase outlet of the back-extraction vessel is connected to the first storage tank 1.

[0108] The specific process for preparing lithium-containing products using the above extraction system includes:

[0109] The chelating agent and co-extractant stored in the first storage tank 1 are added to the mixer 3; the transition metal source and chlorine source stored in the second storage tank 7 are added to the mixer 3; the gaseous carbon dioxide stored in the carbon dioxide cylinder 21 enters the purifier 22, where it is purified to remove impurities such as moisture, and then enters the cold box 23 to be cooled and liquefied into liquid carbon dioxide, which then enters the liquid carbon dioxide storage tank 24. The liquid carbon dioxide stored in the liquid carbon dioxide storage tank 24 is added to the mixer 3. The chelating agent, co-extractant, transition metal source, chlorine source and liquid carbon dioxide are mixed in the mixer 3. Under specific pressure and temperature, the liquid carbon dioxide becomes supercritical carbon dioxide and together with the chelating agent, co-extractant, transition metal source and chlorine source to form the extractant.

[0110] The extractant enters multiple extraction vessels through the extractant inlet, and the oilfield brine enters multiple extraction vessels through the oilfield brine inlet. Extraction occurs in each extraction vessel, with high-concentration Cl₂. - Under certain conditions, metal ions R in transition metal sources n+ With Cl -Combine to form complex anions [RCl4] n-4 ], complexed anion [RCl4 n-4 [Can be used for Li] + Surrounding water molecules undergo displacement, complexing with anions [RCl4] n-4 After replacing water molecules, the chelating agent and Li are strengthened. + The ability to form complexes allows lithium in oilfield brine to chelate with the chelating agent in the extractant to form a metallic lithium complex, which then dissolves in supercritical carbon dioxide. The co-extracting agent further enhances the solubility of the metallic lithium complex in supercritical carbon dioxide, thereby achieving the extraction of lithium from the oilfield brine. The supercritical carbon dioxide containing the dissolved metallic lithium complex and co-extracting agent is discharged from the solvent outlet, and the waste oilfield brine is discharged from the waste oilfield brine outlet for recycling.

[0111] Supercritical carbon dioxide containing dissolved lithium metal complex and co-extractant enters multiple separation vessels through the solvent inlet of the separation vessel. After being depressurized and cooled in the separation vessel, it is separated into gaseous carbon dioxide and lithium-containing phase. The gaseous carbon dioxide is discharged through the gaseous outlet into carbon dioxide cylinder 21, realizing the recycling of carbon dioxide.

[0112] The lithium-containing phase enters the back-extraction vessel through the lithium-containing phase inlet, and the back-extraction agent enters the back-extraction vessel through the back-extraction agent inlet. The two are back-extracted in the back-extraction vessel. Under specific back-extraction conditions, lithium elements are transferred from the lithium-containing phase to the aqueous phase, forming a lithium-containing aqueous phase and an organic phase. The lithium-containing aqueous phase is discharged from the lithium-containing aqueous phase outlet as a lithium-containing product for utilization. The organic phase chelating agent and co-extraction agent are discharged from the organic phase outlet into storage tank 1, realizing the recycling of the chelating agent and co-extraction agent.

[0113] The following examples further illustrate the extractant of the present invention and its application in extracting lithium from oilfield brine. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0114] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.

[0115] All embodiments were carried out in the following extraction system, in conjunction with reference to [reference needed]. Figure 1 The extraction system includes a first storage tank 1, a carbon dioxide storage unit, a mixer 3, a second storage tank 7, an extraction unit, a separation unit, and a back-extraction unit;

[0116] The first storage tank 1 is connected to the mixer 3;

[0117] The second storage tank 7 is connected to the mixer 3;

[0118] The carbon dioxide storage unit includes a carbon dioxide cylinder 21, a purifier 22, a cold box 23, and a liquid carbon dioxide storage tank 24 connected in sequence; the liquid carbon dioxide storage tank 24 is connected to the mixer 3.

[0119] The mixer 3 is connected to the extraction unit;

[0120] The extraction unit includes a first extraction vessel 41, a second extraction vessel 42, a third extraction vessel 43, a fourth extraction vessel 43, and a fifth extraction vessel 45, which are connected in parallel. The first extraction vessel 41 has a first oilfield brine inlet, a first waste oilfield brine outlet, a first extractant inlet, and a first solvent outlet. The second extraction vessel 42 has a second oilfield brine inlet, a second waste oilfield brine outlet, a second extractant inlet, and a second solvent outlet. The third extraction vessel 43 has a third oilfield brine inlet, a third waste oilfield brine outlet, a third extractant inlet, and a third solvent outlet; the fourth extraction vessel 44 has a fourth oilfield brine inlet, a fourth waste oilfield brine outlet, a fourth extractant inlet, and a fourth solvent outlet; and the fifth extraction vessel 45 has a fifth oilfield brine inlet, a fifth waste oilfield brine outlet, a fifth extractant inlet, and a fifth solvent outlet. The first, second, third, fourth, and fifth extractant inlets are all connected to the mixer 3.

[0121] The first separation vessel 51 has a first solvent inlet, a first gas phase outlet, and a first lithium-containing organic phase outlet; the second separation vessel 52 has a second solvent inlet, a second gas phase outlet, and a second lithium-containing organic phase outlet; the first solvent inlet of the first separation vessel 51 is connected to the first solvent outlet, the second solvent outlet, the third solvent outlet, the fourth solvent outlet, and the fifth solvent outlet; the first gas phase outlet of the first separation vessel is connected to the second solvent inlet of the second separation vessel; the second gas phase outlet of the second separation vessel 52 is connected to the carbon dioxide cylinder 21.

[0122] The back-extraction unit includes a back-extraction vessel 61, which has a lithium-containing phase inlet, a back-extraction agent inlet, a lithium-containing aqueous phase outlet, and an organic phase outlet. The lithium-containing phase inlet of the back-extraction vessel 61 is connected to the first lithium-containing organic phase outlet and the second lithium-containing organic phase outlet. The organic phase outlet of the back-extraction vessel 61 is connected to the first storage tank 1.

[0123] The types and contents of metals in the oilfield brine of Examples 1-9 and Comparative Examples 1-4 are shown in Table 1.

[0124] Table 1

[0125] Element types Lithium (mg / L) Potassium (mg / L) Sodium (mg / L) Calcium (mg / L) Magnesium (mg / L) Element content 254 7660 84920 15750 1380

[0126] Example 1

[0127] The specific process for separating lithium-containing product S1 includes:

[0128] The chelating agent tributyl phosphate and the co-extractant anhydrous ethanol stored in the first storage tank 1 are added to the mixer 3; wherein the volume ratio of the chelating agent tributyl phosphate to the co-extractant anhydrous ethanol is 9:1. The transition metal source FeCl3 and the chlorine source AlCl3 stored in the second storage tank 7 are added to the mixer 3; wherein the molar ratio of metallic Fe in the transition metal source FeCl3 and chlorine in the chlorine source (FeCl3 and AlCl3) is 1:6. The gaseous carbon dioxide stored in the carbon dioxide cylinder 21 enters the purifier 22, where it is purified to remove moisture and other impurities, and then enters the cold box 23 for cooling. The carbon dioxide is converted into liquid phase carbon dioxide and then enters the liquid phase carbon dioxide storage tank 24. The liquid phase carbon dioxide stored in the liquid phase carbon dioxide storage tank 24 is added to the mixer 3. The chelating agent tributyl phosphate, the co-extracting agent anhydrous ethanol, the transition metal source FeCl3, the chlorine source (FeCl3 and AlCl3) and the liquid phase carbon dioxide are mixed in the mixer 3. Under the conditions of 8 MPa pressure and 40°C, the liquid phase carbon dioxide becomes supercritical carbon dioxide and forms extractant A1 together with the chelating agent tributyl phosphate, the co-extracting agent anhydrous ethanol, the transition metal source FeCl3 and the chlorine source (FeCl3 and AlCl3).

[0129] Extractant A1 enters the first extraction vessel 41, the second extraction vessel 42, the third extraction vessel 43, the fourth extraction vessel 43, and the fifth extraction vessel 45 through the first, second, third, fourth, and fifth extractant inlets, respectively. 1L of oilfield brine enters the first, second, third, fourth, and fifth extraction vessels 45 in equal amounts through the first, second, third, fourth, and fifth oilfield brine inlets, respectively. Extractant A1 and oilfield brine are mixed in the first extraction vessel... Extraction was carried out in extraction vessels 41, 42, 43, 44, and 45. In each extraction vessel, the molar ratio of lithium in the oilfield brine to the chelating agent tributyl phosphate in extractant A1 was 1:4, and the molar ratio of lithium in the oilfield brine to metallic Fe in the transition metal source FeCl3 was 1:1.5. The volume ratio of supercritical carbon dioxide in extractant A1 to the weight ratio of lithium in the oilfield brine was 100 mL / g in each extraction vessel. Extraction was performed at 8 MPa and 50 °C for 30 min. The Fe ions in the transition metal source FeCl3 were extracted. 3+ With Cl - Combine to form complex anions [FeCl4] - ], complexed anion [FeCl4- [Can be used for Li] + Surrounding water molecules undergo displacement, complexing with anions [FeCl4] - After replacing water molecules, the chelating agent tributyl phosphate and Li + The ability to form complexes is achieved by chelating lithium elements in oilfield brine with tributyl phosphate, a chelating agent in the extractant, to form a metallic lithium complex, which is then dissolved in supercritical carbon dioxide. Anhydrous ethanol, a co-extractant, further enhances the solubility of the metallic lithium complex in supercritical carbon dioxide, thereby realizing the extraction of lithium elements from oilfield brine. Waste oilfield brine is discharged from the waste oilfield brine outlet for recycling.

[0130] Supercritical carbon dioxide containing dissolved lithium metal complex and co-extractant anhydrous ethanol enters the first separation vessel 51 and the second separation vessel 52 through the first solvent inlet of the first separation vessel 51. After being depressurized and cooled in the first separation vessel 51 and the second separation vessel 52, it is separated into gaseous carbon dioxide and lithium-containing phase. The pressure in each separation vessel is 6 MPa and the temperature is 40°C. The gaseous carbon dioxide is discharged through the second gaseous outlet into the carbon dioxide cylinder 21, realizing the recycling of carbon dioxide.

[0131] The lithium-containing phase enters the back-extraction vessel 61 through the lithium-containing phase inlet, and the back-extraction agent water enters the back-extraction vessel 61 through the back-extraction agent inlet. The two are back-extracted in the back-extraction vessel 61 to transfer lithium from the lithium-containing phase to the aqueous phase, forming a lithium-containing aqueous phase and an organic phase. The back-extraction temperature is 20°C and the time is 0.5 h. The volume ratio of the lithium-containing phase to the back-extraction agent water is 1:2. The lithium-containing aqueous phase is discharged from the lithium-containing aqueous phase outlet as the lithium-containing product S1 (LiCl) for utilization. The organic phase is discharged from the organic phase outlet into the first storage tank 1, realizing the recycling of the chelating agent tributyl phosphate and the co-extraction agent anhydrous ethanol.

[0132] Example 2

[0133] The procedure was carried out in accordance with Example 1, except that the chelating agent was acetylacetone.

[0134] Example 3

[0135] The procedure was carried out as described in Example 1, except that the volume ratio of the chelating agent tributyl phosphate to the co-extracting agent anhydrous ethanol was 1:0.25.

[0136] Example 4

[0137] The implementation was carried out in accordance with Example 1, except that the transition metal source was CuCl2.

[0138] Example 5

[0139] The procedure was carried out in accordance with Example 1, except that the co-extractant was acetone.

[0140] Example 6

[0141] The implementation was carried out in accordance with Example 1, except that the molar ratio of lithium to tributyl phosphate chelating agent in the oilfield brine was 1:2.

[0142] Example 7

[0143] The implementation was carried out in accordance with Example 1, except that the molar ratio of lithium in the oilfield brine to metallic Fe in the transition metal source FeCl3 was 1:1.

[0144] Example 8

[0145] The implementation was carried out in accordance with Example 1, except that the molar ratio of lithium to tributyl phosphate chelating agent in the oilfield brine was 1:1.

[0146] Example 9

[0147] The implementation was carried out in accordance with Example 1, except that the molar ratio of lithium in the oilfield brine to metallic Fe in the transition metal source FeCl3 was 1:0.25.

[0148] Comparative Example 1

[0149] The procedure was carried out in accordance with Example 1, except that the volume ratio of the chelating agent tributyl phosphate and the co-extractant anhydrous ethanol was 1:0.05.

[0150] Comparative Example 2

[0151] The procedure was carried out in accordance with Example 1, except that the extractant did not contain the transition metal source FeCl3.

[0152] Comparative Example 3

[0153] The procedure was carried out in accordance with Example 1, except that the extractant did not contain the chlorine source AlCl3, and an equimolar amount of ferric sulfate was used to replace FeCl3.

[0154] Comparative Example 4

[0155] The procedure was carried out in accordance with Example 1, except that the extraction pressure was 10 MPa and the temperature was 40°C.

[0156] Test case

[0157] The types and contents of metals in the lithium-containing products separated in the examples and comparative examples were determined and analyzed, and the results are shown in Table 3.

[0158] Table 3

[0159]

[0160]

[0161] As can be seen from the results in Table 1, the extraction agent and method described in this invention are used to extract and separate lithium-containing products from oilfield brine. The extraction efficiency is high and the product purity is high. Under preferred implementation conditions, the extraction efficiency is as high as 80% or more.

[0162] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An extractant, characterized in that, The extractant contains supercritical carbon dioxide, a chelating agent, a co-extracting agent, a transition metal source, and a chlorine source; the volume ratio of the chelating agent to the co-extracting agent is 1:0.1-0.

3.

2. The extractant according to claim 1, characterized in that, The chelating agent is selected from one or more of neutral organophosphorus compounds, β-diketones, dithiocarbamates, and crown ethers.

3. The extractant according to claim 1 or 2, characterized in that, The chelating agent is selected from one or more of the following: tributyl phosphate, Cyanex 272, Cyanex 301, acetylacetone, trifluoroacetylacetone, hexafluoroacetylacetone, sodium dithiocarbamate, potassium dithiocarbamate, and 18-crown ether 6.

4. The extractant according to any one of claims 1-3, characterized in that, The molar ratio of chlorine source to transition metal source is ≥3, wherein the chlorine source is calculated as chlorine element and the transition metal source is calculated as metal.

5. The extractant according to claim 4, characterized in that, The metal in the transition metal source is selected from at least one of iron, copper, zinc and cobalt.

6. The extractant according to claim 5, characterized in that, The co-extractant is selected from one or more of water, monohydric alcohol, monoketone, hexane, chloroform, dichloromethane, toluene, and tetrahydrofuran.

7. The application of the extractant according to any one of claims 1-6 in the treatment of oilfield brine.

8. A method for separating lithium from oilfield brine, characterized in that, The method includes: extracting oilfield brine with the extractant described in any one of claims 1-6, then separating the lithium-containing phase under reduced pressure, and finally back-extracting the lithium-containing phase with a back-extractant; The extraction conditions include a pressure of 7.5-9 MPa and a temperature of 45-55°C; the back-extraction agent is selected from one or more of water, inorganic acid solution and inorganic salt solution.

9. The method according to claim 8, characterized in that, The molar ratio of lithium to the chelating agent in the oilfield brine is 1:2-4.

10. The method according to claim 8 or 9, characterized in that, The molar ratio of lithium to transition metal source in oilfield brine is 1:0.5-3, where the transition metal source is calculated as metal.

11. The method according to claim 10, characterized in that, The volume ratio of supercritical carbon dioxide to the weight ratio of lithium in the oilfield brine is ≥50 mL / g.

12. The method according to any one of claims 8-11, characterized in that, Extraction conditions also include a time of 25-30 minutes.

13. The method according to claim 12, characterized in that, The conditions for pressure reduction separation include: pressure of 4-6 MPa and temperature of 35-45℃.

14. The method according to claim 13, characterized in that, The volume ratio of the lithium-containing phase to the stripping agent is 1:2-4.

15. The method according to claim 14, characterized in that, The inorganic acid solution is selected from water, hydrochloric acid, and / or sulfuric acid; Preferably, the inorganic salt solution is selected from one or more of potassium sulfate solution, potassium chloride solution, sodium sulfate solution and sodium chloride solution.

16. The method according to claim 8 or 15, characterized in that, The conditions for back-extraction include a temperature of 20-25℃ and a time of 0.5-1h.

17. The method according to any one of claims 8-16, characterized in that, This method is performed in an extraction system; The extraction system includes an extraction unit, a separation unit, and a back-extraction unit connected in sequence.

18. The method according to claim 17, characterized in that, The extraction unit includes at least two extraction vessels.

19. The method according to claim 17, characterized in that, The separation unit includes at least one separation vessel.

20. The method according to any one of claims 17-19, characterized in that, The back-extraction unit includes at least one back-extraction vessel.

21. The method according to claim 20, characterized in that, The extraction system also includes a mixer (3) connected to the extraction unit, the mixer (3) being used to mix liquid carbon dioxide, chelating agent, co-extracting agent, transition metal source and chlorine source.

22. The method according to claim 21, characterized in that, The extraction system also includes a carbon dioxide storage unit; The carbon dioxide storage unit is connected to the mixer (3); The carbon dioxide storage unit is connected to the separation unit.

23. The method according to claim 22, characterized in that, The carbon dioxide storage unit includes a carbon dioxide cylinder (21), a purifier (22), a cold box (23), and a liquid carbon dioxide storage tank (24) connected in sequence. The liquid carbon dioxide storage tank (24) is connected to the mixer (3); The carbon dioxide cylinder (21) is connected to the separation unit.

24. The method according to claim 23, characterized in that, The extraction system further includes a first storage tank (1); the first storage tank (1) is used to store chelating agents and co-extracting agents; The first storage tank (1) is connected to the mixer (3); The first storage tank (1) is connected to the back-extraction unit.

25. The method according to claim 24, characterized in that, The extraction system further includes a second storage tank (7); the second storage tank (7) is used to store a transition metal source and a chlorine source; The second storage tank (7) is connected to the mixer (3).

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