Superparamagnetic composite magnetic material as well as preparation method and application thereof

Abstract

The invention relates to the field of magnetic nano materials, in particular to a superparamagnetic composite magnetic material and a preparation method and application thereof. The superparamagnetic composite magnetic material is of a jujube cake structure in which superparamagnetic nanoparticles are dispersed and embedded in a polymer matrix. The superparamagnetic composite magnetic material with the jujube cake structure has high saturation magnetization intensity; according to the preparation method disclosed by the invention, the superparamagnetic nano-particles can be prepared into the superparamagnetic composite magnetic material with a larger size, the prepared superparamagnetic composite magnetic material is high in saturation magnetization intensity, and the limitation of the size of the superparamagnetic nano-particles on the magnetic intensity is broken through; the superparamagnetic composite magnetic nano material with the jujube cake structure is suitable for preparing a demulsifier in oilfield development.

Description

Technical Field

[0001] This invention relates to the field of magnetic nanomaterials, specifically to a superparamagnetic composite magnetic material, its preparation method, and its applications. Background Technology

[0002] Magnetic nanoparticles possess both magnetic and nanoscale (small size) properties, giving them significant scientific value and broad application prospects. These properties make them promising for applications in magnetic recording materials, magnetic fluids, catalysis, and biomedicine. Particularly in biomedicine, magnetic nanoparticles have already been used as drug delivery carriers, in thermotherapy, as contrast agents in magnetic resonance imaging (MRI), and for the labeling and separation of cells and proteins. Currently, their practical application is primarily in fields like pharmaceuticals and electronics, where the usage volume is small and the unit price is high. This is largely due to the relatively high cost of modified magnetic nanoparticles. However, as the preparation and modification technologies for magnetic nanoparticles mature, their cost continues to decrease. They will find increasing application in production and daily life sectors with large usage volumes and stringent cost requirements.

[0003] Superparamagnetic particles have attracted considerable attention from researchers across various fields. Superparamagnetic nanoparticles possess unique magnetic properties. They exhibit magnetism in the presence of an external magnetic field, and their magnetism disappears when the field is absent. When magnetic, the particles interact with each other, exhibiting a tendency to aggregate. When non-magnetic, they tend to disperse due to thermal motion. Therefore, magnetic fields can be used to regulate and control the aggregation and dispersion of nanoparticles. Furthermore, the interaction between an external magnetic field and magnetic particles can be utilized to promote particle migration and enrichment. This technology has already found applications in the enrichment and purification of biomolecules.

[0004] In addition, the application of superparamagnetic magnetic nanoparticles in oil and gas fields has also attracted attention. As more and more oil fields worldwide enter their late-stage development phases, enhanced oil recovery (EOR) technologies using various chemical agents are widely applied to extract as much residual oil as possible from the formation. However, the extracted crude oil is often severely emulsified, causing significant problems for storage and transportation. To achieve rapid demulsification, the demulsification system often needs to be heated while adding demulsifiers, which not only consumes a large amount of energy but also poses safety hazards. Those skilled in the art have attempted to use magnetic nanoparticles or derivatives modified with magnetic nanoparticles for low-temperature (room-temperature) demulsification. Current research is still in its initial stages; although some progress has been made, it is still a long way from field application (see Adewunmi, AA, MS Kamal, and T.I. Solling, Journal of Petroleum Science and Engineering, 2021, 196).

[0005] Current research on the demulsification mechanism of low-temperature magnetic nanoparticle demulsifiers suggests that the surface properties of magnetic nanoparticles allow them to disperse well in the continuous phase of emulsions. Their high surface energy enables them to readily replace emulsifier molecules on the oil-water interface film after adsorption, forming a mixed film structure where the original surfactant and magnetic nanoparticles coexist. Under the influence of a magnetic field, the magnetic nanoparticles can attract droplet migration, accelerate droplet sedimentation, and promote film structure rupture, thereby destabilizing the emulsion. Summary of the Invention

[0006] One drawback currently hindering the practical application of nanoparticle demulsifiers is that the magnetism exhibited by superparamagnetic nanoparticles in the presence of an external magnetic field is not strong enough. Particularly in some high-viscosity liquids, the migration of superparamagnetic nanoparticles is extremely difficult. If applied to W / O emulsions, if the crude oil viscosity is high, the enrichment process of water droplets by the nanoparticle demulsifier under the influence of an external magnetic field will be very slow, failing to effectively utilize the unique advantages of magnetic nanoparticles.

[0007] Existing research clearly shows that the superparamagnetism of Fe3O4 nanoparticles originates from the particle size. When the size is reduced to a certain level, the magnetic nanoparticles become single-domain particles, and the coercivity increases significantly. When the size is further reduced to less than 15 nm, they become superparamagnetic particles, with both coercivity and remanence being zero. Methods to improve the magnetic force experienced by superparamagnetic Fe3O4 nanoparticles in an external magnetic field have been almost never reported.

[0008] The purpose of this invention is to overcome the problems of weak saturation magnetization and slow migration in high-viscosity liquids in existing technologies for superparamagnetic nanoparticles, and to provide a superparamagnetic composite magnetic material, its preparation method and application. This superparamagnetic composite magnetic material has the characteristics of high saturation magnetization and rapid migration in high-viscosity liquids.

[0009] To achieve the above objectives, the first aspect of the present invention provides a superparamagnetic composite magnetic material, which has a jujube cake structure in which superparamagnetic magnetic nanoparticles are dispersed and embedded in a polymer matrix.

[0010] The second aspect of the present invention provides a method for preparing the superparamagnetic composite magnetic material described in the first aspect, the method comprising the following steps: S1, preparation of superparamagnetic magnetic nanoparticles; S2, mixing and reacting a polymer precursor, an alkaline catalyst and superparamagnetic magnetic nanoparticles under organic solvent conditions, followed by separation and washing.

[0011] The third aspect of this invention provides an application of the superparamagnetic composite magnetic material described in the first aspect in the preparation of demulsifiers during oilfield development.

[0012] Through the above technical solution, the present invention has the following advantages:

[0013] This invention relates to a superparamagnetic composite magnetic material with a jujube cake structure, exhibiting high saturation magnetization. The preparation method of this invention enables the fabrication of large-sized superparamagnetic composite magnetic materials from superparamagnetic magnetic nanoparticles, resulting in high saturation magnetization and overcoming the limitation imposed by the size of superparamagnetic nanoparticles on magnetic strength. This jujube cake-structured superparamagnetic composite magnetic nanomaterial is suitable for use in the preparation of demulsifiers in oilfield development. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the jujube cake structure of a superparamagnetic composite magnetic material according to a preferred embodiment of the present invention. Detailed Implementation

[0015] 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.

[0016] This invention provides a superparamagnetic composite magnetic material, such as Figure 1 As shown, the superparamagnetic composite magnetic material exhibits a jujube cake structure in which superparamagnetic magnetic nanoparticles are dispersed and embedded in a polymer matrix.

[0017] The present invention relates to a superparamagnetic composite magnetic material with a date cake structure, which has a high saturation magnetization intensity.

[0018] According to a preferred embodiment of the present invention, the average particle size of the superparamagnetic nanoparticles is 4-15 nm, for example, it can be 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, and 15 nm, preferably 5-15 nm. By adopting the aforementioned technical solution, the saturation magnetization of the superparamagnetic composite magnetic material can be further improved.

[0019] According to a preferred embodiment of the present invention, the size of the superparamagnetic composite magnetic material is 20-2000 nm, for example, it can be 20 nm, 50 nm, 80 nm, 100 nm, 130 nm, 170 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 900 nm, 1000 nm, 1200 nm, 1400 nm, 1600 nm, 1800 nm, and 2000 nm, preferably 300-2000 nm. By adopting the aforementioned technical solution, the saturation magnetization of the superparamagnetic composite magnetic material can be further improved.

[0020] According to a preferred embodiment of the present invention, the polymer matrix is ​​a polysiloxane matrix and / or a polyacrylate matrix, preferably a polysiloxane matrix. By adopting the aforementioned technical solution, the saturation magnetization of the superparamagnetic composite magnetic material can be further improved.

[0021] According to a preferred embodiment of the present invention, the polymer molecules in the polymer matrix contain one or more of hydroxyl, C1-C4 hydrocarbon, phenyl, amino, and mercapto groups, preferably one or more of hydroxyl, amino, and alkenyl groups. By adopting the aforementioned preferred embodiment, the saturation magnetization of the superparamagnetic composite magnetic material can be further improved.

[0022] In this invention, the content of the superparamagnetic nanoparticles can be selected within a wide range, and commonly used content ranges can achieve the purpose of this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the content of the superparamagnetic nanoparticles, based on the total mass of the superparamagnetic composite magnetic material, is 0.1-70 wt%, for example, 0.3 wt%, 0.5 wt%, 0.7 wt%, 0.9 wt%, 1 wt%, 10 wt%, 20 wt%, 30 wt%, 40 wt%, 50 wt%, 60 wt%, and 65 wt%, preferably 0.2-50 wt%.

[0023] In this invention, the content of the polymer matrix can be selected within a wide range, and commonly used content ranges can achieve the purpose of this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the content of the polysiloxane matrix, based on the total mass of the superparamagnetic composite magnetic material, is 30-99.9% wt, for example, 35 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, 90 wt%, 95 wt%, 98 wt%, and 99 wt%, preferably 50-99.8 wt%.

[0024] In this invention, the type of superparamagnetic nanoparticles can be a conventional choice in the art. According to a preferred embodiment of this invention, the general formula of the superparamagnetic nanoparticles is M. Ⅱ Fe Ⅲ 2O4, where M is one or more of Mn, Mg, Zn, Co, Fe, and Ni, more preferably Fe. By adopting the aforementioned preferred scheme, the saturation magnetization of the superparamagnetic composite magnetic material can be further improved.

[0025] Any superparamagnetic composite magnetic material that meets the foregoing requirements of this invention can achieve the purpose of this invention. There are no special requirements for its preparation method. The following is an illustrative description, but it does not limit the scope of this invention. This invention provides a method for preparing the superparamagnetic composite magnetic material, which includes the following steps: S1, preparation of superparamagnetic magnetic nanoparticles; S2, under organic solvent conditions, mixing and reacting polymer precursor, alkaline catalyst and superparamagnetic magnetic nanoparticles, followed by separation and washing.

[0026] The preparation method of this invention can prepare superparamagnetic magnetic nanoparticles into large-sized superparamagnetic composite magnetic materials. The superparamagnetic composite magnetic materials have high saturation magnetization, breaking through the limitation of the size of superparamagnetic nanoparticles on magnetic strength.

[0027] Superparamagnetic nanoparticles that meet the foregoing requirements of this invention can achieve the purpose of this invention. There are no special requirements for their preparation methods. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, step S1 includes: reacting in an aqueous phase under an optional inert atmosphere, where a superparamagnetic nanoparticle precursor compound, an optional surfactant, an optional hydrophobic agent, and a precipitant react to obtain superparamagnetic nanoparticles.

[0028] In this invention, there are no particular restrictions on the method of feeding the reactants in step S1, and it can be a conventional choice in the art. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the method of feeding the reactants in step S1 includes: preparing an aqueous solution containing a superparamagnetic nanoparticle precursor compound and a solution containing a surfactant and a hydrophobic agent; then adding the aqueous solution containing the superparamagnetic nanoparticle precursor compound dropwise to the solution containing the surfactant and the hydrophobic agent, while simultaneously introducing an inert atmosphere for protection; after the dropwise addition is completed, heating to the reaction temperature, and then slowly adding a precipitant at a rate of, for example, 4 g / h; and after the precipitant is added, dynamic mixing is performed.

[0029] In this invention, there are no particular restrictions on the feeding method of the reactants in step S2, and it can be a conventional choice in the art. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, in step S2, the superparamagnetic nanoparticles are first prepared into an alcohol solution, and then a polymer precursor and an alkaline catalyst are added for mixing and reaction, followed by separation and washing.

[0030] In this invention, step S1 further includes: adding acid, such as acetic acid, to the material after the contact reaction to adjust it to neutral, followed by separation and washing.

[0031] In this invention, the washing methods in steps S1 and S2 can be conventional methods in the art, such as separation by adding alcohol for magnetic separation and / or centrifugation, with the number of washing cycles being 1-5. In step S2 of this invention, dispersion is achieved by ultrasonic oscillation during washing.

[0032] In this invention, the frequency of ultrasonic oscillation is a conventional choice in the art, for example, the frequency of ultrasonic oscillation is 28 kHz and / or 40 kHz.

[0033] In this invention, there are no special requirements on the amount of alcohol used in the washing process, as long as the purpose of this invention can be achieved. In this invention, the amount of alcohol used is 50 grams to illustrate the advantages of the technical solution of this invention.

[0034] According to a preferred embodiment of the present invention, the superparamagnetic nanoparticle precursor compound is a metal salt of Mn, Mg, Zn, Co, Fe and Ni, preferably an iron salt.

[0035] In this invention, there are no special requirements for the type of surfactant. As long as it can achieve the purpose of this application, it is illustrative but does not limit the scope of the invention. According to a preferred embodiment of the invention, the surfactant is selected from at least one of sodium (-2-ethylhexyl) succinate sulfonate (AOT), octadecyltrimethylammonium chloride, sorbitan monooleate and fatty alcohol polyoxyethylene ether, preferably sodium (-2-ethylhexyl) succinate sulfonate and / or fatty alcohol polyoxyethylene ether.

[0036] In this invention, the type of hydrophobic agent is not particularly required, as long as it can achieve the purpose of this application. This is an illustrative example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the hydrophobic agent is selected from at least one of white oil, cyclohexane, kerosene, benzene, toluene or xylene, preferably cyclohexane and / or benzene.

[0037] In this invention, the precipitant is an alkaline substance. According to a preferred embodiment of this invention, the alkaline substance is selected from at least one of ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide, more preferably ammonia and / or cesium hydroxide.

[0038] In this invention, the alkaline substance is added in the form of a solution, which is illustrative but does not limit the scope of the invention. According to a preferred embodiment of the invention, the concentration of the alkaline substance is 0.1-50% wt.

[0039] In this invention, the organic solvent is an alcohol solution. According to a preferred embodiment of this invention, the alcohol in the alcohol solution is a C1-C4 alcohol, preferably methanol and / or ethanol.

[0040] According to a preferred embodiment of the present invention, the polymer precursor includes at least one of tetraalkoxysilane, a silane coupling agent, and an acrylate. By employing the aforementioned preferred embodiment, the saturation magnetization of the superparamagnetic composite magnetic material can be further improved.

[0041] In this invention, common tetraalkoxysilanes can be used in this invention. This is an illustrative example, but does not limit the scope of the invention. According to a preferred embodiment of the invention, the tetraalkoxysilane includes at least one of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, preferably at least one of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane.

[0042] In this invention, common silane coupling agents can be used, which are illustrated by way of example but do not limit the scope of the invention. According to a preferred embodiment of the invention, the silane coupling agent is at least one of KH540, KH550, KH570, KH580, KBM-602, KBM-603, Nanda-42, Nanda-73, A-1110, A-1120 and A-1130, preferably at least one of KH540, KH550, KH570, A-1110, A-1120 and A-1130.

[0043] In this invention, the alkaline catalyst is an alkaline compound. According to a preferred embodiment of this invention, the alkaline compound is at least one selected from ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide, preferably ammonia.

[0044] In this invention, the alkaline compound is fed in the form of a solution, which is illustrative but does not limit the scope of the invention. According to a preferred embodiment of the invention, the concentration of the alkaline compound is 0.1-50% wt.

[0045] According to a preferred embodiment of the present invention, in step S1, the mass ratio of the superparamagnetic nanoparticle precursor compound, water, optionally a surfactant, optionally a hydrophobic agent, and a precipitant is 1-10:2-20:0-30:0-100:0.1-10, for example 1-10:2-20:5-30:5-100:0.1-10, 1-8:2-15:5-25:5-80:1-10, 2-8:2-10:5-20:8-70:3-8, 3-7:3-8:8-15:10-50:4-8, and 4-7:4-8:10-15:20-50:5-8, preferably 1-10:2-20:5-30:6-100:2-10, and more preferably 1-5:5-15:5-20:20-100:5-10.

[0046] In this invention, the mass ratio of the polymer precursor to the alcohol and superparamagnetic nanoparticles in step S2 can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, in step S2, the mass ratio of the polymer precursor to the alcohol and superparamagnetic nanoparticles is 0.5-25:1-50:1, for example, 0.6-25:1-45:1, 1-20:1-40:1, 2-20:5-40:1, 4-20:8-40:1, 4-15:15-40:1, 5-10:20-40:1, 6-10:25-40:1 and 6-8:25-35:1, preferably 0.8-25:5-40:1, and more preferably 1-10:20-40:1.

[0047] In this invention, the mass ratio of the polymer precursor to the alkaline catalyst in step S2 can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, in step S2, the mass ratio of the polymer precursor to the alkaline catalyst is 1:0.01-1, for example, 1:0.01, 1:0.03, 1:0.05, 1:0.07, 1:0.09, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8 and 1:0.9.

[0048] According to a preferred embodiment of the present invention, the inert atmosphere is at least one of nitrogen atmosphere, helium atmosphere and argon atmosphere.

[0049] In this invention, the range of selectable conditions for the contact reaction in step S1 is relatively wide. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the conditions for the contact reaction include: a reaction temperature of 5-95°C, for example, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 95°C; and a reaction time adjusted according to the reaction temperature, for example, 0.1-30 hours.

[0050] According to a preferred embodiment of the present invention, the conditions for the mixing reaction in step S2 include: a reaction temperature of 5-95°C, for example, 5°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, and 95°C, preferably 20-60°C. By adopting the aforementioned preferred embodiment, the saturation magnetization of the superparamagnetic composite magnetic material can be further improved.

[0051] In this invention, there are no special requirements for the reaction time in step S2, as long as the reaction is sufficient. According to a preferred embodiment of this invention, the reaction time is 0.2-5 hours.

[0052] This invention provides an application of the superparamagnetic composite magnetic material described above in the preparation of demulsifiers for oilfield development.

[0053] The superparamagnetic composite magnetic nanomaterial with a date cake structure of the present invention is suitable for the preparation of demulsifiers in oilfield development.

[0054] The present invention will be described in detail below through examples. In the following examples, the average particle size of the superparamagnetic nanoparticles was measured by scanning electron microscopy, transmission electron microscopy, or Malvern particle size analyzer; the size of the superparamagnetic composite magnetic material was measured by scanning electron microscopy; the saturation magnetization was measured by the patch method; unless otherwise specified, the raw materials are all commercially available products.

[0055] The present invention will be described in detail below through embodiments.

[0056] Example 1

[0057] 1.27 g of ferrous chloride and 3.25 g of ferric chloride were dissolved in 10.5 g of deoxygenated deionized water. 2 g of AOT and 84.5 g of cyclohexane were transferred to a 250 mL four-necked flask and stirred until completely dissolved. The dissolved ferrous chloride and ferric chloride solution was then added dropwise to the flask under nitrogen protection. After the addition was complete, the system temperature was raised to 40 °C. 4 g of concentrated ammonia (25% wt) was slowly added dropwise over approximately one hour. After stirring at 40 °C for 24 hours, 3.5 g of acetic acid was added to neutralize the ammonia in the reaction solution, resulting in magnetite nanoparticles with an average particle size of 10 nm. 50 g of methanol was added to the reaction solution, and the mixture was stirred. The product was concentrated to one side of the flask using a magnet, and the clear solution in the flask was then discarded. This washing process was repeated three times to obtain a methanol solution of superparamagnetic nanoparticles.

[0058] Add 10 g of tetramethoxysilane to a methanol solution. After stirring until homogeneous, add 5 g of concentrated ammonia (25% wt) and stir at 25°C for 2 hours. Then, use a magnet to concentrate the magnetic material to one side of the flask, and then pour off the material and solvent that were not attracted by the magnet. Remove the magnet, add 50 g of methanol, and sonicate for 3 minutes. Then, use a magnet to concentrate the magnetic nanoparticles to one side of the flask, and then pour off the methanol. Repeat this washing process three times to obtain the structure shown below. Figure 1 The superparamagnetic composite nanomaterial shown has a size of 300 nm. The content of superparamagnetic magnetic nanoparticles is 18.8 wt% and the content of polysiloxane matrix is ​​81.2 wt% based on the total mass of the superparamagnetic composite magnetic material.

[0059] Example 2

[0060] 1.27 g of ferrous chloride and 3.25 g of ferric chloride were dissolved in 10.5 g of deoxygenated deionized water. 4 g of AOT and 84.5 g of cyclohexane were transferred to a 250 mL four-necked flask and stirred until completely dissolved. The dissolved ferrous chloride and ferric chloride solution was then added dropwise to the flask under nitrogen protection. After the addition was complete, the system temperature was raised to 40 °C. 4 g of cesium hydroxide solution (25% wt) was slowly added dropwise over approximately one hour. After stirring at 40 °C for 24 hours, 3.5 g of acetic acid was added to neutralize the ammonia in the reaction solution, resulting in magnetite nanoparticles with an average particle size of 5 nm. 50 g of methanol was added to the reaction solution, and the mixture was stirred. The product was concentrated to one side of the flask using a magnet, and the clear solution in the flask was then discarded. This washing process was repeated three times to obtain a methanol solution of superparamagnetic nanoparticles.

[0061] Add 20 g of KH540 to the methanol solution. After stirring evenly, add 25 g of concentrated ammonia (25% wt) and stir at 45°C for 2 hours. Then, use a magnet to concentrate the magnetic material to one side of the flask, and then pour off the material and solvent that were not attracted by the magnet. Remove the magnet, add 50 g of methanol, sonicate for 3 minutes, and then use the magnet to concentrate the magnetic nanoparticles to one side of the flask, and then pour off the methanol. Repeat this washing process 3 times to obtain a superparamagnetic composite nanomaterial with a size of 450 nm, similar in structure to Example 1. The content of superparamagnetic magnetic nanoparticles is 10.4 wt%, and the content of polysiloxane is 89.6 wt%, based on the total mass of the superparamagnetic composite magnetic material.

[0062] Example 3

[0063] 1.27 g of ferrous chloride and 3.25 g of ferric chloride were dissolved in 30 g of deoxygenated deionized water. 20 g of hexadecyl polyoxyethylene ether (n=5) and 40 g of benzene were transferred to a 250 mL four-necked flask and stirred until completely dissolved. The dissolved ferrous chloride and ferric chloride solution was then added dropwise to the flask and stirred until homogeneous. Nitrogen gas was used for protection during the addition. After the addition was complete, the system temperature was raised to 40 °C. 10 g of ammonia (25% wt) was slowly added dropwise over approximately one hour. After stirring at 40 °C for 24 hours, 10 g of acetic acid was added to neutralize the ammonia in the reaction solution, resulting in magnetite nanoparticles with an average particle size of 9 nm. 50 g of methanol was added to the reaction solution, and the mixture was stirred. The product was concentrated to one side of the flask using a magnet, and the clear solution in the flask was then discarded. This washing process was repeated three times to obtain a methanol solution of superparamagnetic nanoparticles.

[0064] Add 50 g of KH570 to the methanol solution. After stirring evenly, add 35 g of ammonia (25% wt) and stir at 25°C for 2 hours. Then, use a magnet to concentrate the magnetic nanoparticles to one side of the flask, and then pour off the magnetic nanoparticles and solvent that were not attracted by the magnet. Remove the magnet, add 50 ml of methanol, sonicate for 3 minutes, and then use the magnet to concentrate the magnetic nanoparticles to one side of the flask, and then pour off the methanol. Repeat this washing process 3 times to obtain a superparamagnetic composite nanomaterial with a size of 2000 nm, similar in structure to Example 1. The content of superparamagnetic magnetic nanoparticles is 4.4 wt%, and the content of polysiloxane matrix is ​​95.6 wt%, based on the total mass of the superparamagnetic composite magnetic material.

[0065] Example 4

[0066] Following Example 1, the difference is that the reaction temperature for preparing the superparamagnetic composite nanomaterial was 10°C, resulting in a superparamagnetic composite nanomaterial with a size of 130 nm and a structure similar to that in Example 1.

[0067] Example 5

[0068] According to Example 1, except that 1.27 g of ferrous chloride was replaced with 1.26 g of manganese chloride tetrahydrate, a superparamagnetic composite nanomaterial with a size of 300 nm with a structure similar to that in Example 1 was obtained.

[0069] Example 6

[0070] Following Example 1, except that tetramethoxysilane was replaced with tetrabutoxysilane, a superparamagnetic composite nanomaterial with a size of 210 nm with a structure similar to that of Example 1 was obtained.

[0071] Example 7

[0072] According to Example 1, the difference is that 4 grams of AOT and 20 grams of cyclohexane were added, and the average particle size of the obtained magnetite magnetic nanoparticles was 4 nm.

[0073] Example 8

[0074] According to Example 1, the difference is that 30 grams of deoxygenated deionized water, 30 grams of AOT and 40 grams of cyclohexane were added, and the average particle size of the obtained iron oxide magnetic nanoparticles was 5 nm.

[0075] Example 9

[0076] According to Example 1, except that 2 grams of AOT were replaced with 20 grams of hexadecyl polyoxyethylene ether (n=5), and 30 grams of deoxygenated deionized water and 40 grams of cyclohexane were added, the average particle size of the obtained magnetite magnetic nanoparticles was 7 nm.

[0077] Example 10

[0078] According to Example 1, the difference is that 2 grams of AOT is replaced with 20 grams of hexadecyl polyoxyethylene ether (n=5), 84.5 grams of cyclohexane is replaced with 40 grams of benzene, and 30 grams of deoxygenated deionized water is added, resulting in magnetic nanoparticles of iron oxide with an average particle size of 11 nm.

[0079] Example 11

[0080] According to Example 1, the difference is that in the preparation process of the magnetite magnetic nanoparticles, 2 g of AOT was replaced with 20 g of hexadecyl polyoxyethylene ether (n=5), 84.5 g of cyclohexane was replaced with 40 g of benzene, 30 g of deoxygenated deionized water and 10 g of concentrated ammonia (25% wt) were added, and the mixture was stirred at a constant temperature of 65°C. The average particle size of the obtained magnetite magnetic nanoparticles was 13 nm.

[0081] Example 12

[0082] 1.26 g of ferrous chloride and 3.25 g of ferric chloride were dissolved in 10.5 g of deoxygenated deionized water. 2 g of AOT and 84.5 g of cyclohexane were transferred to a 250 mL four-necked flask and stirred until completely dissolved. The dissolved ferrous chloride and ferric chloride solution was then added dropwise to the flask under nitrogen protection. After the addition was complete, the system temperature was raised to 40 °C. 4 g of concentrated ammonia (25% wt) was slowly added dropwise over approximately one hour. After stirring at 40 °C for 24 hours, 3.5 g of acetic acid was added to neutralize the ammonia in the reaction solution, resulting in magnetite nanoparticles with an average particle size of 10 nm. 50 g of methanol was added to the reaction solution, and the mixture was stirred. The product was concentrated to one side of the flask using a magnet, and the clear solution in the flask was then discarded. This washing process was repeated three times to obtain a methanol solution of superparamagnetic nanoparticles. The methanol was evaporated to obtain nanoparticle powder.

[0083] Nanoparticle powder was added to 10g of methyl acrylate monomer and stirred until homogeneous. Then, 0.2g of benzoyl peroxide was added and stirred until dissolved. The mixture was heated to 80℃ and reacted for 30 minutes to form a solid superparamagnetic composite nanomaterial. The solid superparamagnetic composite nanomaterial was then pulverized into particles with a particle size of 200nm using a pulverizer.

[0084] Example 13

[0085] Following Example 1, except that AOT was replaced with hexadecyl polyoxyethylene ether (n=5), the average particle size of the obtained magnetite nanoparticles was 15 nm. However, a small portion of the obtained superparamagnetic composite nanomaterial product precipitated and could not be dispersed in methanol.

[0086] Comparative Example 1

[0087] 1.27 g of ferrous chloride and 3.25 g of ferric chloride were dissolved in 10.5 g of deoxygenated deionized water. 2 g of AOT and 84.5 g of cyclohexane were transferred to a 250 mL four-necked flask and stirred until completely dissolved. The dissolved ferrous chloride and ferric chloride solution was then added dropwise to the flask under nitrogen protection. After the addition was complete, the system temperature was raised to 40 °C. 4 g of concentrated ammonia (25% wt) was slowly added dropwise over approximately one hour. After stirring at 40 °C for 24 hours, 3.5 g of acetic acid was added to neutralize the ammonia in the reaction solution, resulting in magnetite nanoparticles with an average particle size of 10 nm. 50 g of methanol was added to the reaction solution, and the mixture was stirred. The product was concentrated to one side of the flask using a magnet, and the clear solution in the flask was then discarded. This washing process was repeated three times to obtain a methanol solution of superparamagnetic nanoparticles.

[0088] Test case

[0089] The superparamagnetic composite nanomaterials or magnetic nanoparticles were added to 30 ml of a 2 wt% HPAM aqueous solution and stirred until homogeneous. Then, these samples were placed in the same magnetic field, and the time it took for all the magnetic nanoparticles to accumulate on one side of the sample vial was recorded, as shown in Table 1 below.

[0090] Table 1

[0091] Sample source Size / Average Particle Size (nm) Enrichment time (s) Example 1 300 37 Example 2 650 25 Example 3 2000 19 Example 4 130 45 Example 5 300 46 Example 6 210 44 Example 7 300 43 Example 8 300 40 Example 9 300 39 Example 10 300 35 Example 11 300 32 Example 12 200 45 Example 13 300 29 Comparative Example 1 10 61

[0092] 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 combinations of 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. A superparamagnetic composite magnetic material, characterized in that, The superparamagnetic composite magnetic material exhibits a jujube cake structure in which superparamagnetic magnetic nanoparticles are dispersed and embedded in a polymer matrix.

2. The superparamagnetic composite magnetic material according to claim 1, wherein, The superparamagnetic nanoparticles have an average particle size of 4-15 nm, preferably 5-15 nm; and / or The superparamagnetic composite magnetic material has a size of 20-2000 nm, preferably 300-2000 nm.

3. The superparamagnetic composite magnetic material according to claim 1 or 2, wherein, The polymer matrix is ​​a polysiloxane matrix and / or a polyacrylate matrix, preferably a polysiloxane matrix; and / or The polymer matrix contains one or more of the following molecules: hydroxyl, C1-C4 hydrocarbon, phenyl, amino, and mercapto; preferably, it contains one or more of the following: hydroxyl, amino, and alkenyl.

4. The superparamagnetic composite magnetic material according to any one of claims 1-3, wherein, Based on the total mass of the superparamagnetic composite magnetic material, The content of the superparamagnetic nanoparticles is 0.1-70 wt%, preferably 0.2-50 wt%; and / or The content of the polymer matrix is ​​30-99.9% wt, preferably 50-99.8% wt.

5. The superparamagnetic composite magnetic material according to any one of claims 1-4, wherein, The general formula of the superparamagnetic nanoparticles is M Ⅱ Fe Ⅲ 2O4, where M is one or more of Mn, Mg, Zn, Co, Fe and Ni, more preferably Fe.

6. A method for preparing the superparamagnetic composite magnetic material according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: S1, Preparation of superparamagnetic nanoparticles; S2. Under organic solvent conditions, the polymer precursor, alkaline catalyst, and superparamagnetic nanoparticles are mixed and reacted, then separated and washed. Preferably, step S1 includes: reacting in an aqueous phase, optionally under an inert atmosphere, a superparamagnetic nanoparticle precursor compound, optionally a surfactant, optionally a hydrophobic agent and a precipitant to obtain superparamagnetic nanoparticles.

7. The preparation method according to claim 6, wherein, In step S1, The superparamagnetic nanoparticle precursor compound is one or more metal salts of Mn, Mg, Zn, Co, Fe, and Ni, preferably an iron salt; and / or The surfactant is selected from at least one of sodium (-2-ethylhexyl)succinate sulfonate, octadecyltrimethylammonium chloride, sorbitan monooleate, and fatty alcohol polyoxyethylene ether, preferably sodium (-2-ethylhexyl)succinate sulfonate and / or fatty alcohol polyoxyethylene ether; and / or The hydrophobic agent is selected from at least one of white oil, cyclohexane, kerosene, benzene, toluene, and xylene, preferably cyclohexane and / or benzene; and / or The precipitant is an alkaline substance, preferably at least one of ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide, more preferably ammonia and / or cesium hydroxide; and / or In step S2, The organic solvent is an alcohol, preferably a C1-C4 alcohol, more preferably methanol and / or ethanol; and / or The polymer precursor comprises at least one of tetraalkoxysilane, a silane coupling agent, and an acrylate; preferably, the tetraalkoxysilane comprises at least one of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, and more preferably at least one of tetramethoxysilane, tetraethoxysilane, and tetrapropoxysilane; and / or the silane coupling agent is at least one of KH540, KH550, KH570, KH580, KBM-602, KBM-603, Nanda-42, Nanda-73, A-1110, A-1120, and A-1130, and more preferably at least one of KH540, KH550, KH570, A-1110, A-1120, and A-1130; and / or The alkaline catalyst is an alkaline compound, preferably at least one selected from ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide, rubidium hydroxide, and cesium hydroxide, and more preferably ammonia.

8. The preparation method according to claim 6 or 7, wherein, In step S1, the mass ratio of the superparamagnetic nanoparticle precursor compound, water, optionally a surfactant, optionally a hydrophobic agent, and a precipitant is 1-10:2-20:0-30:0-100:0.1-10, preferably 1-10:2-20:5-30:6-100:2-10, more preferably 1-5:5-15:5-20:20-100:5-10; and / or In step S2, the mass ratio of the polymer precursor to alcohol and superparamagnetic nanoparticles is 0.5-25:1-50:1, preferably 0.8-25:5-40:1, more preferably 1-10:20-40:1; and / or the mass ratio of the polymer precursor to alkaline catalyst is 1:0.01-1.

9. The preparation method according to any one of claims 6-8, wherein, In step S1, the conditions for the contact reaction include: a reaction temperature of 5-95℃; and / or a reaction time of 0.1-30h; and / or In step S2, the conditions for the mixing reaction include: a reaction temperature of 5-95℃, preferably 20-60℃; and / or a reaction time of 0.2-5h.

10. The application of the superparamagnetic composite magnetic material according to any one of claims 1-5 in the preparation of demulsifiers during oilfield development.

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