CN116731266A - Graphene oxide nanosheet and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of nano-sheet material preparation, and particularly discloses a graphene oxide nano-sheet and a preparation method thereof. The graphene oxide nano sheet provided by the invention comprises a graphene oxide sheet, wherein one surface of the graphene oxide sheet is grafted with CB [ n ], and the other surface of the graphene oxide sheet is grafted with a styrene-methyl methacrylate copolymer. The graphene oxide nano-sheet provided by the invention has good temperature resistance and salt resistance, can be aggregated on an oil-water interface to form an interfacial film with viscoelasticity when being used as a displacement agent, has good interfacial film stability, and can obviously improve the oil displacement efficiency of nano-fluid under low concentration.

Description

Graphene oxide nanosheet and preparation method thereof

Technical field

The present invention relates to the technical field of nanosheet material preparation, in particular to a kind of graphene oxide nanosheet, and also relates to its preparation method.

Background technique

With the rapid development of economy, human beings' demand for petroleum energy is becoming more and more obvious. At present, it is increasingly difficult to develop large new oil and gas fields, so there is an urgent need to maximize oil recovery based on existing oil and gas fields. After the secondary oil recovery stage, tertiary oil recovery technology is crucial to further extract the remaining crude oil in low-permeability reservoirs. However, problems such as the degradation and adsorption of commonly used chemical displacing agents during forward migration limit chemical flooding. Use of substitutes. Therefore, there is an urgent need to provide new displacing agent materials for enhanced oil recovery.

The two sides of the Janus material are hydrophilic and hydrophobic respectively, that is, they have different properties at the interface of the same material. Among various Janus materials, two-dimensional (2D) Janus nanosheets have special wettability due to their highly anisotropic shape and asymmetric chemical properties. This amphiphilic Janus nanofluid can aggregate at the oil-water interface. It also forms a viscoelastic interface film to achieve intelligent and efficient oil search, thereby significantly improving oil displacement performance and reducing the amount of oil displacement agent. However, in the geological environment of high temperature and high salt content, the collision between the nanofluid and salt ions makes the currently used Janus material more prone to aggregation and precipitation, thereby reducing or even destroying the oil displacement performance.

In view of the above reasons, the present invention aims to provide a new two-dimensional (2D) Janus nanosheet material, that is, a graphene oxide nanosheet material, to obtain a stable displacing agent in a high-temperature and high-salt environment.

Contents of the invention

The main technical problem solved by the present invention is to provide a graphene oxide nanosheet and a preparation method of the graphene oxide nanosheet. The graphene oxide nanosheet provided by the present invention can be used in the field of tertiary oil recovery. Use of displacing agents.

In order to solve the above technical problems, in the first aspect, the present invention provides a graphene oxide nanosheet, including a graphene oxide sheet, one side of the graphene oxide sheet is grafted with CB[n], and the graphene oxide sheet is The other side of the graphene oxide nanosheet is grafted with styrene-methyl methacrylate copolymer, and the structure of the graphene oxide nanosheet includes: PS-co-PMMA/GO/CB[n].

As an embodiment of the present invention, wherein CB[n] is CB[6] or CB[7].

In a second aspect, the invention provides a method for preparing graphene oxide nanosheets, including the steps:

(1) Disperse graphene oxide sheets in NaCl aqueous solution to prepare dispersion 1;

Dissolve azobisisobutyronitrile, methyl methacrylate, and styrene in kerosene to prepare solution 2;

Dissolve cerium ammonium nitrate in water to make solution 3;

Dissolve CB[n]acrylamide in water to make solution 4;

(2) Under nitrogen protection, first add the solution 2 to the dispersion 1, then add solution 3, stir, then add solution 4, then react at 35-45°C for 10-15h, and then heat up to 70-70°C. Continue the reaction at 90°C for 5-10 hours. When the reaction is completed, the solid powder is collected. The solid powder is washed to obtain graphene oxide nanosheets.

As an embodiment of the present invention, the content of graphene oxide sheets in the dispersion 1 is 0.8-1.2g/L, and the concentration of NaCl in the NaCl aqueous solution is 10-15 g/L.

As an embodiment of the present invention, in the solution 2, the concentration of azobisisobutyronitrile is 0.015-0.030 mol/L, the concentration of methyl methacrylate is 1.2-2.0 mol/L, and the benzene The concentration of ethylene is 0.2-0.7mol/L.

As an embodiment of the present invention, in the solution 2, the molar ratio of the methyl methacrylate and the styrene is (2-9):1.

As an embodiment of the present invention, the concentration of the cerium ammonium nitrate in the solution 3 is 30-35g/L.

As an embodiment of the present invention, the concentration of CB[n]acrylamide in the solution 4 is 6-18g/L.

As an embodiment of the present invention, the CB[n]acrylamide is CB[6]acrylamide or CB[7]acrylamide.

As an embodiment of the present invention, the dispersion 1, solution 2, solution 3, and solution 4 are mixed in a volume ratio of (3-4): (1-1.5): (1-1.2): (1-1.2) reaction.

As a preferred embodiment of the present invention, the concentration of azobisisobutyronitrile in the solution 2 is 0.018-0.025 mol/L.

As an embodiment of the present invention, the dispersion 1, solution 2, solution 3, and solution 4 are mixed and reacted in a volume ratio of (3-4): (1-1.2): (1-1.1): 1.

In a third aspect, the present invention provides an application of graphene oxide nanosheets. The graphene oxide nanosheets of the present invention or the graphene oxide nanosheets prepared by the preparation method of the present invention are used as oil recovery displacing agents. , further preferably used as a tertiary oil recovery displacing agent.

In a fourth aspect, the present invention also provides an oil recovery displacing agent, including polyvinylpyrrolidone, poly(2-acrylamide-2-methylpropanesulfonic acid), and the graphene oxide nanosheets of the present invention, so The graphene oxide nanosheets, polyvinylpyrrolidone, and poly(2-acrylamide-2-methylpropanesulfonic acid) were mixed in a mass ratio of 10:1:1.

The graphene oxide nanosheet provided by the invention is a Janus graphene oxide (GO) nanosheet, which is prepared by in-situ free radical polymerization. Specifically, the hydrophobic polymer polystyrene-co-polymethane is realized in a Pickering emulsion environment. The surface of graphene oxide sheet (GO) was asymmetrically functionalized with methyl acrylate and cucurbit[n]uril (CB[n]), respectively, to prepare CB[n] grafted on one side and benzene grafted on the other side. Graphene oxide nanosheets of ethylene-methyl methacrylate copolymer, i.e., polystyrene-co-polymethyl methacrylate/graphene oxide/cucurbit[n]uril Janus nanosheets (PS-co-PMMA/GO /CB[n]).

In the preparation process of the graphene oxide nanosheets of the present invention, in the oil phase, methyl methacrylate and styrene monomer dissolved in the oil phase are initiated by azobisisobutyronitrile to perform in-situ free radical copolymerization. The hydrophobic monomer is grafted on one side of the graphene oxide; in the water phase, the acrylamide CB[n] monomer is polymerized through the initiation of Ce ⁴⁺ , and the CB[n] is grafted on the other side of the graphene oxide. one side. The prepared PS-co-PMMA/GO/CB[n] Janus nanosheets have two segment structures on the hydrophobic surface of graphene oxide due to the simultaneous addition of styrene and methyl methacrylate to the oil phase. It is beneficial to control the properties of the hydrophobic side; the other side of graphene oxide introduces CB[n]. Cucurbit[n]uril (CB[n]) is a macrocyclic compound with a rigid structure and has a hydrophobic cavity at both ends. Each has n terminal carbonyl groups. Therefore, CB[n] can not only accommodate molecules or ions of suitable size, but can also interact with charged metal ions, charged parts of organic molecules, or polar polarity through ion-dipole, hydrogen bonding, etc. Large molecules form complexes. Due to the supramolecular effect of CB[n], grafting rigid cucurbit[n]uril onto the surface of nanomaterials can effectively change the affinity of the material surface and the wetting properties of the material surface, which can improve The curling of nanofluid under high temperature and high salt conditions improves the temperature and salt resistance of the polymer. The graphene oxide nanosheets prepared by the present invention not only have good temperature resistance and salt resistance, but also have the ability of host-guest interaction due to the CB[n] cavity on the surface, which is conducive to regulating the interface properties through simple supramolecular modification, so that It shows excellent results in the field of tertiary oil recovery.

The graphene oxide nanosheets (PS-co-PMMA/GO/CB[n] Janus nanosheets) provided by the invention have good temperature resistance and salt resistance; when used as a displacing agent, they can accumulate at the oil-water interface, A viscoelastic interface film is formed, which has good stability and can significantly improve the oil displacement efficiency of nanofluids at low concentrations. Using the graphene oxide nanosheets (PS-co-PMMA/GO/CB[n] Janus nanosheets) provided by the present invention as a tertiary oil recovery displacing agent can effectively reduce the oil-water interfacial tension and change rock lubrication at low concentrations. The wetness significantly improves the oil displacement efficiency of nanofluids and reduces economic costs, so it has broad application prospects.

The graphene oxide nanosheets provided by the invention adopt in-situ copolymerization and grafting of polystyrene and polymethyl methacrylate during preparation, which can easily regulate the ratio of polystyrene and polymethyl methacrylate chain segments, thereby The controllable synthesis of the hydrophobic surface of graphene oxide is achieved; the preparation method of the present invention is simple to operate, has high modification efficiency, and can be synthesized on a large scale in the liquid phase.

Description of drawings

Figure 1 is the NMR spectrum of CB[6]acrylamide provided by the present invention;

Figure 2 is the NMR spectrum of CB[7]acrylamide provided by the present invention;

Figure 3 is the infrared spectrum of CB[6]-C1, CB[6]-S2, CB[6]-S3, and CB[6]-S4 provided by the present invention;

Figure 4 is the infrared spectrum of CB[6]-S4, CB[6]-S5, and CB[6]-S6 provided by the present invention;

Figure 5 is the infrared spectrum of CB[7]-S7 provided by the present invention;

Figure 6 is a contact angle diagram of the hydrophilic side and the hydrophobic side of the graphene oxide nanosheet CB[6]-S4 provided in Embodiment 3 of the present invention;

Figure 7 is a contact angle diagram of the hydrophilic side and the hydrophobic side of the graphene oxide nanosheet CB[7]-S7 provided in Example 6 of the present invention.

Detailed ways

The technical solution of the present invention will be described in detail below through specific embodiments.

When preparing graphene oxide nanosheets, the present invention first disperses graphene oxide sheets (GO) in a sodium chloride aqueous solution, and then adds dissolved styrene (St), methyl methacrylate (MMA) and azobis The kerosene solution of isobutyronitrile makes the oil-water system form a highly inward emulsion; then add the cerium ammonium nitrate aqueous solution, stir and then add the CB[n] acrylamide aqueous solution to form a reaction system; GO sheets are in the organic phase and water At the phase interface, the hydroxyl groups on the surface of the aqueous GO sheets and cerium ammonium nitrate form a redox initiating system, which can initiate CB[n] acrylamide monomer at a lower temperature and graft CB[n] to the graphene oxide sheets. On one side; in the organic phase, at a higher temperature, azobisisobutyronitrile decomposes, which can trigger in-situ free radical copolymerization of styrene and methyl methacrylate on the other side of GO, and combine styrene and methacrylic acid. The methyl ester copolymer was grafted on the other side of graphene oxide, and finally PS-co-PMMA/GO/CB[n] Janus nanosheets with excellent performance were obtained.

Among them, graphene oxide sheets (GO), styrene (St), methyl methacrylate (MMA), azobisisobutyronitrile, and cerium ammonium nitrate are all obtained through purchase.

CB[n]acrylamide is obtained by preparation, and the preparation process is as follows.

1. Preparation of CB[6]acrylamide

Dissolve 400 mg of HO-CB[6] in 12 mL of methanesulfonic acid, cool in an ice bath, add 6.4 mL of acrylonitrile and 3 mL of trifluoromethanesulfonic acid, and react at 50°C for 5 hours. After the reaction, it was precipitated with acetone, and the solid obtained was washed three times with acetone, and then dried in a vacuum drying oven for 12 hours to obtain CB[6]acrylamide. The NMR spectrum of CB[6]acrylamide is shown in Figure 1.

2. Preparation of CB[7]acrylamide

Dissolve 500 mg of HO-CB[7] in 12 mL of methanesulfonic acid, cool in an ice bath, add 7.0 mL of acrylonitrile and 3 mL of trifluoromethanesulfonic acid, and react at 50°C for 5 hours. After the reaction, it was precipitated with acetone, and the solid obtained was washed three times with acetone, and then dried in a vacuum drying oven for 12 hours to obtain CB[7]acrylamide. The NMR spectrum of CB[7]acrylamide is shown in Figure 2.

In the following examples, the equipment and reagents used are commercially available unless otherwise specified.

Example 1

This embodiment provides a graphene oxide nanosheet, and the preparation process is:

Add 50 mg of graphene oxide sheets (GO) and 0.6 g of NaCl to 50 mL of deionized water, and conduct ultrasonic treatment for 1 h to obtain dispersion 1;

Take 0.05g azobisisobutyronitrile, 2.4mL methyl methacrylate, 1.2mL styrene (the molar ratio of methyl methacrylate and styrene is 2.2:1), dissolve it in 12mL kerosene solution, and make Solution 2;

Weigh 0.5g of ceric ammonium nitrate and dissolve it in 15 mL of water to make solution 3;

Weigh 0.09g CB[6]acrylamide and dissolve it in 15 mL water to make solution 4;

Under nitrogen protection, add solution 2 to the prepared dispersion 1, stir with electric stirring, then add solution 3, stir for 2 minutes, then add solution 4, then react at 40°C for 12 hours with electric stirring, and then raise the temperature to 85 The reaction was continued for 8 hours at ℃, and the reaction was completed. Collect the solid powder and wash it three times with tetrahydrofuran to obtain graphene oxide nanosheets PS-co-PMMA/GO/CB[6]Janus nanosheets, recorded as CB[6]-S2.

Example 2

This embodiment provides a graphene oxide nanosheet, and the preparation process is:

Add 50 mg of graphene oxide sheets (GO) and 0.6 g of NaCl to 50 mL of deionized water, and conduct ultrasonic treatment for 1 h to obtain dispersion 1;

Take 0.05g azobisisobutyronitrile, 2.8mL methyl methacrylate, 0.8mL styrene (the molar ratio of methyl methacrylate and styrene is 3.8:1), dissolve it in 12mL kerosene solution, and make Solution 2;

Weigh 0.5g of ceric ammonium nitrate and dissolve it in 15 mL of water to make solution 3;

Weigh 0.09g CB[6]acrylamide and dissolve it in 15 mL water to make solution 4;

Under nitrogen protection, add solution 2 to the prepared dispersion 1, stir with electric stirring, then add solution 3, stir for 2 minutes, then add solution 4, then react at 40°C for 12 hours with electric stirring, and then raise the temperature to 85 The reaction was continued for 8 hours at ℃, and the reaction was completed. Collect the solid powder and wash it three times with tetrahydrofuran to obtain graphene oxide nanosheets PS-co-PMMA/GO/CB[6]Janus nanosheets, recorded as CB[6]-S3.

Example 3

This embodiment provides a graphene oxide nanosheet, and the preparation process is:

Add 50 mg of graphene oxide sheets (GO) and 0.6 g of NaCl to 50 mL of deionized water, and conduct ultrasonic treatment for 1 h to obtain dispersion 1;

Take 0.05g azobisisobutyronitrile, 3.1mL methyl methacrylate, 0.4mL styrene (the molar ratio of methyl methacrylate and styrene is 8.4:1), dissolve it in 12mL kerosene solution, and make Solution 2;

Weigh 0.5g of ceric ammonium nitrate and dissolve it in 15 mL of water to make solution 3;

Weigh 0.09g CB[6]acrylamide and dissolve it in 15 mL water to make solution 4;

Under nitrogen protection, add solution 2 to the prepared dispersion 1, stir with electric stirring, then add solution 3, stir for 2 minutes, then add solution 4, then react at 40°C for 12 hours with electric stirring, and then raise the temperature to 85 The reaction was continued for 8 hours at ℃, and the reaction was completed. Collect the solid powder and wash it three times with tetrahydrofuran to obtain graphene oxide nanosheets PS-co-PMMA/GO/CB[6]Janus nanosheets, recorded as CB[6]-S4.

Example 4

This embodiment provides a graphene oxide nanosheet. The difference from Example 3 is that the concentration of CB[6]acrylamide in solution 4 is 12g/L, and the preparation process is:

Add 50 mg of graphene oxide sheets (GO) and 0.6 g of NaCl to 50 mL of deionized water, and conduct ultrasonic treatment for 1 h to obtain dispersion 1;

Take 0.05g azobisisobutyronitrile, 3.1mL methyl methacrylate, 0.4mL styrene (the molar ratio of methyl methacrylate and styrene is 8.4:1), dissolve it in 12mL kerosene solution, and make Solution 2;

Weigh 0.5g of ceric ammonium nitrate and dissolve it in 15 mL of water to make solution 3;

Weigh 0.18g CB[6]acrylamide and dissolve it in 15 mL of water to make solution 4;

Under nitrogen protection, add solution 2 to the prepared dispersion 1, stir with electric stirring, then add solution 3, stir for 2 minutes, then add solution 4, then react at 40°C for 12 hours with electric stirring, and then raise the temperature to 85 The reaction was continued for 8 hours at ℃, and the reaction was completed. Collect the solid powder and wash it three times with tetrahydrofuran to obtain graphene oxide nanosheets PS-co-PMMA/GO/CB[6]Janus nanosheets, recorded as CB[6]-S5.

Example 5

This embodiment provides a graphene oxide nanosheet. The difference from Example 3 is that the concentration of CB[6]acrylamide in Solution 4 is 18g/L, and the preparation process is:

Add 50 mg of graphene oxide sheets (GO) and 0.6 g of NaCl to 50 mL of deionized water, and conduct ultrasonic treatment for 1 h to obtain dispersion 1;

Take 0.05g azobisisobutyronitrile, 3.1mL methyl methacrylate, 0.4mL styrene (the molar ratio of methyl methacrylate and styrene is 8.4:1), dissolve it in 12mL kerosene solution, and make Solution 2;

Weigh 0.5g of ceric ammonium nitrate and dissolve it in 15 mL of water to make solution 3;

Weigh 0.27g CB[6]acrylamide and dissolve it in 15 mL water to make solution 4;

Under nitrogen protection, add solution 2 to the prepared dispersion 1, stir with electric stirring, then add solution 3, stir for 2 minutes, then add solution 4, then react at 40°C for 12 hours with electric stirring, and then raise the temperature to 85 The reaction was continued for 8 hours at ℃, and the reaction was completed. Collect the solid powder and wash it three times with tetrahydrofuran to obtain graphene oxide nanosheets PS-co-PMMA/GO/CB[6]Janus nanosheets, recorded as CB[6]-S6.

Example 6

This embodiment provides a graphene oxide nanosheet, which is prepared using CB[7]acrylamide. The preparation process is:

Add 55 mg of graphene oxide sheets (GO) and 0.6 g of NaCl to 50 mL of deionized water, and conduct ultrasonic treatment for 1 h to obtain dispersion 1;

Take 0.05g azobisisobutyronitrile, 3.1mL methyl methacrylate, 0.4mL styrene (the molar ratio of methyl methacrylate and styrene is 8.4:1), dissolve it in 12mL kerosene solution, and make Solution 2;

Weigh 0.5g of ceric ammonium nitrate and dissolve it in 15 mL of water to make solution 3;

Weigh 0.21g CB[7]acrylamide and dissolve it in 15 mL water to make solution 4;

Under nitrogen protection, add solution 2 to the prepared dispersion 1, stir with electric stirring, then add solution 3, stir for 2 minutes, then add solution 4, then react at 40°C for 12 hours with electric stirring, and then raise the temperature to 85 The reaction was continued for 8 hours at ℃, and the reaction was completed. Collect the solid powder and wash it three times with tetrahydrofuran to obtain graphene oxide nanosheets PS-co-PMMA/GO/CB[7]Janus nanosheets, recorded as CB[7]-S7.

Comparative example 1

This comparative example provides a graphene oxide nanosheet, and the preparation process is:

Add 50 mg of graphene oxide sheets (GO) and 0.6 g of NaCl to 50 mL of deionized water, and conduct ultrasonic treatment for 1 h to obtain dispersion 1;

Take 0.05g azobisisobutyronitrile and 3.5mL methyl methacrylate and dissolve them in 12mL kerosene solution to make solution 2;

Weigh 0.5g of ceric ammonium nitrate and dissolve it in 15 mL of water to make solution 3;

Weigh 0.09g CB[6]acrylamide and dissolve it in 15 mL water to make solution 4;

Under nitrogen protection, add solution 2 to the prepared dispersion 1, stir with electric stirring, then add solution 3, stir for 2 minutes, then add solution 4, then react at 40°C for 12 hours with electric stirring, and then raise the temperature to 85 The reaction was continued for 8 hours at ℃, and the reaction was completed. Collect the solid powder and wash it three times with tetrahydrofuran to obtain graphene oxide nanosheets PMMA/GO/CB[6]Janus nanosheets, recorded as CB[6]-C1.

Comparative example 2

This comparative example provides a graphene oxide nanosheet, and the preparation process is:

Add 50 mg of graphene oxide sheets (GO) and 0.6 g of NaCl to 50 mL of deionized water, and conduct ultrasonic treatment for 1 h to obtain dispersion 1;

Dissolve 0.3g n-octylamine in 12.5mL kerosene solution to make solution 2;

Weigh 0.5g of ceric ammonium nitrate and dissolve it in 15 mL of water to make solution 3;

Weigh 0.003g of 2-acrylamide-2-methylpropanesulfonic acid and dissolve it in 15 mL of water to prepare a 0.2 g/L 2-acrylamide-2-methylpropanesulfonic acid aqueous solution to obtain solution 4;

Under nitrogen protection, add solution 2 to the prepared dispersion 1, stir with electric stirring, and react at 40°C for 18 hours to obtain n-octylamine single-sided grafted graphene oxide; then add solution 3 and stir for 2 minutes. , add solution 4, and then react under electric stirring at 40°C for 12 hours, and the reaction is completed. The solid powder was collected and washed three times with tetrahydrofuran to obtain n-octylamine/GO/poly-2-acrylamide-2-methylpropanesulfonic acid (OtcA/GO/PAMPS) Janus nanosheets, designated as PAMPS-C2.

FT-IR was used to characterize the nanosheet material synthesized in the present invention. The infrared spectra of CB[6]-C1, CB[6]-S2, CB[6]-S3, and CB[6]-S4 are shown in Figure 3. Among them, a represents CB[6]-S2, b represents CB[6]-S3, c represents CB[6]-S4, and d represents CB[6]-C1.

The infrared spectra of CB[6]-S4, CB[6]-S5 and CB[6]-S6 are shown in Figure 4, where a represents CB[6]-S4 and b represents CB[6]-S5. c represents CB[6]-S6. It can be seen from Figure 4 that as the CB[6] content increases, the intensity of the carbonyl absorption peak of CB[6] at 1736 cm ^-1 increases.

The infrared spectrum of CB[7]-S7 is shown in Figure 5. From the infrared spectrum 5, it can be seen that the carbonyl absorption peak of CB[7] is at 1713 cm ^-1 , and the characteristic absorption peak of GO is at 1207 cm ^-1 .

Test example 1

Contact angle test: The Janus nanosheets prepared in the present invention are dispersed on the interface between water and kerosene. After the kerosene evaporates, the films of the hydrophilic surface and the hydrophobic surface of the Janus nanosheets are obtained respectively through the vertical pulling method and the horizontal attachment method. Characterization tests were performed with a contact angle meter.

Among them, the contact angle diagrams of the hydrophilic side and the hydrophobic side of the graphene oxide nanosheet CB[6]-S4 obtained in Example 3 are shown in Figure 6, and the graphene oxide nanosheet CB[7]-S7 obtained in Example 6 The contact angle diagrams of the hydrophilic side and hydrophobic side are shown in Figure 7. In Figures 6 and 7, a represents the hydrophilic side and b represents the hydrophobic side.

It can be seen from the figure that the contact angles of the hydrophilic surfaces of the Janus nanosheets produced in the present invention are all less than 5 degrees, and the contact angles of the hydrophobic surfaces are all greater than 90 degrees. This shows that the Janus nanosheets prepared by the present invention have an amphiphilic Janus nanosheet structure.

Test example 2

The temperature and salt resistance properties of the Janus nanosheets prepared by the present invention were evaluated. The experimental process is as follows.

(1) Prepare simulated salt-containing mineralized water, its composition is shown in Table 1:

Table 1 Composition of inorganic salt ions of mineralized water

(2) Add the Janus nanosheet solid powder prepared in the examples of the present invention or the nanosheet solid powder prepared in the comparative example, polyvinylpyrrolidone, and poly(2-acrylamide-2-methylpropanesulfonic acid) into the simulated salt-containing solution. In mineralized water, the mass ratio of nanosheet solid powder, polyvinylpyrrolidone, and poly(2-acrylamide-2-methylpropanesulfonic acid) is 10:1:1, and the weight average molecular weight of polyvinylpyrrolidone is 78000g/mol. , the weight average molecular weight of poly(2-acrylamide-2-methylpropanesulfonic acid) is 67000g/mol;

Afterwards, magnetic stirring was carried out for 3 hours, ultrasonic for 15 minutes, and a dispersion of Janus nanosheets with a concentration of 100 g/L was prepared. It was heated at 80°C for 24 hours, and then the transmittance of the nanofluid was measured by a spectrophotometer. If the transmittance increases, it means that the nanoparticles have settled and the dispersion performance is not good. Then continue to place it at 80°C for 72 hours, and conduct another transmittance measurement.

The transmittance detection results of the Janus nanosheets prepared in various embodiments and comparative examples of the present invention are shown in Table 2. It can be seen from the data in Table 2 that the Janus nanosheets prepared in various embodiments of the present invention have good dispersion stability in mineralized water. After 72 hours, the transmittance only increases slightly, indicating that the settlement of the dispersion is relatively slow. ; In contrast, the transmittance of the comparative example increased significantly after being left for 72 hours, indicating significant sedimentation and poor dispersion stability.

Table 2

It can be seen from the above experiments that the Janus nanosheets prepared in the embodiments of the present invention have better temperature and salt resistance than the comparative examples, have good dispersion stability in high-temperature and high-salt environments, and are not prone to aggregation and precipitation.

Test example 3

The displacement performance of the Janus nanosheets prepared by the present invention was evaluated. The experimental process is as follows.

Core displacement performance evaluation: Use cylindrical artificial core (diameter 2.5cm, length 10.0cm, permeability 400mD) to carry out oil displacement experiments;

Experimental oil: crude oil at 80°C, viscosity is 6.3mPa·s, density is 0.87g/cm ³ ;

Experimental nanofluid: Add the Janus nanosheet solid powder prepared in the examples of the present invention or the nanosheet solid powder prepared in the comparative example and polyvinylpyrrolidone and poly(2-acrylamide-2-methylpropanesulfonic acid) into the simulation In salt-containing mineralized water, the mass ratio of Janus nanosheet solid powder, polyvinylpyrrolidone, and poly(2-acrylamide-2-methylpropanesulfonic acid) is 10:1:1, and the weight average molecular weight of polyvinylpyrrolidone is 78000g/mol, the weight average molecular weight of poly(2-acrylamide-2-methylpropanesulfonic acid) is 67000g/mol;

Afterwards, stir magnetically for 3 hours, ultrasonic for 15 minutes, and prepare a dispersion of Janus nanosheets with a concentration of 100g/L for later use;

Experimental water: simulated salt-containing mineralized water shown in Table 1;

The specific experimental steps are:

(1) Dry the core at 100°C for 24 hours;

(2) At 80°C, saturate mineralized water and crude oil in sequence, and then age the core at 80°C for 72 hours;

(3) First drive with water at a flow rate of 0.1mL/min until the water content is greater than 98%; then inject 0.3PV nanofluid at a flow rate of 0.1mL/min; and finally drive with water at a flow rate of 0.1mL/min until the water content is greater than 98%;

(4) Calculate water flooding recovery factor and nanofluid flooding enhanced recovery factor. The specific recovery factor results corresponding to Janus nanosheets prepared in various embodiments of the present invention and comparative examples are shown in Table 3.

table 3

It can be seen from the data in Table 3 that the Janus nanosheets prepared in various embodiments of the present invention have better displacement effect and high overall recovery rate.

Although the present invention has been described in detail with general descriptions and specific embodiments above, it is obvious to those skilled in the art that some modifications or improvements can be made based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims (10)

1. A graphene oxide nanosheet, characterized in that it includes a graphene oxide sheet, one side of the graphene oxide sheet is grafted with CB[n], and the other side of the graphene oxide sheet is grafted with styrene. -Methyl methacrylate copolymer, the structure of the graphene oxide nanosheets includes: PS-co-PMMA/GO/CB[n]. 2. A method for preparing graphene oxide nanosheets according to claim 1, characterized in that it includes the steps: (1) Disperse graphene oxide sheets in NaCl aqueous solution to prepare dispersion 1; Dissolve azobisisobutyronitrile, methyl methacrylate, and styrene in kerosene to prepare solution 2; Dissolve cerium ammonium nitrate in water to make solution 3; Dissolve CB[n]acrylamide in water to make solution 4; (2) Under nitrogen protection, first add the solution 2 to the dispersion 1, then add solution 3, stir, then add solution 4, then react at 35-45°C for 10-15h, and then heat up to 70-70°C. Continue the reaction at 90°C for 5-10 hours. When the reaction is completed, the solid powder is collected. The solid powder is washed to obtain graphene oxide nanosheets. 3. The preparation method according to claim 2, characterized in that, in the dispersion 1, the content of graphene oxide sheets is 0.8-1.2g/L, and the concentration of NaCl in the NaCl aqueous solution is 10-15 g. /L. 4. The preparation method according to claim 2, characterized in that, in the solution 2, the concentration of azobisisobutyronitrile is 0.015-0.030mol/L, and the concentration of the methyl methacrylate is 1.2- 2.0mol/L, the concentration of styrene is 0.2-0.7mol/L. 5. The preparation method according to claim 4, characterized in that, in the solution 2, the molar ratio of the methyl methacrylate and the styrene is (2-9):1. 6. The preparation method according to claim 2, characterized in that, in the solution 3, the concentration of the cerium ammonium nitrate is 30-35g/L. 7. The preparation method according to claim 2, characterized in that, in the solution 4, the concentration of the CB[n]acrylamide is 6-18g/L, and the CB[n]acrylamide is CB[ 6]acrylamide or CB[7]acrylamide. 8. The preparation method according to any one of claims 2 to 7, characterized in that the dispersion 1, solution 2, solution 3, and solution 4 are in a volume ratio (3-4): (1-1.5): (1-1.2): (1-1.2) perform a mixed reaction. 9. Application of the graphene oxide nanosheets according to claim 1 or the graphene oxide nanosheets prepared by the preparation method according to any one of claims 2 to 8 as an oil recovery displacing agent. 10. An oil recovery displacing agent, characterized by comprising polyvinylpyrrolidone, poly(2-acrylamide-2-methylpropanesulfonic acid), and the graphene oxide nanosheets of claim 1, wherein the oxidized graphene nanosheets Graphene nanosheets, polyvinylpyrrolidone, and poly(2-acrylamide-2-methylpropanesulfonic acid) were mixed at a mass ratio of 10:1:1.