Structure oriented dispersant, flaky magnesium hydroxide nanomaterial and preparation and application thereof

Abstract

The application discloses a structure guiding dispersant, a flaky magnesium hydroxide nanometer material and a preparation and application thereof, and a preparation method of the structure guiding dispersant comprises the following steps: S1, placing sodium alkyl benzene sulfonate in a reaction container, and adding methanol as a solvent; S2, slowly adding formaldehyde under a certain reflux temperature and a certain rotating speed to carry out reaction; and S3, removing the solvent through vacuum drying and reduced pressure distillation after the reaction is completed. The structure guiding dispersant can assist the formation of a two-dimensional flaky structure of the nanometer material in the process of preparing the nanometer magnesium salt by a coprecipitation method, meanwhile, the structure guiding dispersant and the flaky magnesium salt nanometer material can form a synergistic effect, can effectively reduce the oil-water interfacial tension, and can be applied to oil reservoir development as an oil displacement system. The preparation process is simple, raw materials are widely sourced, and production cost is low, and the prepared flaky magnesium hydroxide nanometer material has good oil-water interfacial activity, can effectively reduce the oil-water interfacial tension, and can improve the oil recovery rate.

Description

Technical Field

[0001] This invention relates to a structure-directed dispersant, sheet-like magnesium hydroxide nanomaterials, their preparation and application. Background Technology

[0002] With the increasing severity of energy issues, the development of low-permeability reservoirs has become a key research focus in the oilfield field. However, due to the complex pore-throat structure, small pore size, and large specific surface area of ​​low-permeability reservoirs, conventional oil displacement agents face difficulties in injection. Furthermore, the development of natural fractures in these reservoirs results in severe heterogeneity, making it difficult to effectively utilize remaining oil. This also hinders the successful development of conventional surfactant flooding and polymer flooding technologies in low-permeability reservoirs.

[0003] Nanomaterials have demonstrated excellent injection capabilities in the exploitation of low-permeability pores. Furthermore, they can effectively improve microscopic oil washing efficiency by altering reservoir wettability, reducing interfacial tension, and stripping interfacial oil films. Oil displacement technology systems based on nanomaterials are crucial for improving the recovery rate of low-permeability reservoirs and are of paramount importance for oil and gas extraction.

[0004] Traditional nanomaterials research mainly focuses on one-dimensional spherical nanoparticles (such as SiO2, TiO2, Al2O3, CuO, ZnO, etc.). Spherical nanoparticles usually have advantages such as simpler manufacturing process and lower cost, but they also have disadvantages such as easy aggregation and blockage, low contact efficiency with oil-water interface, small specific surface area, few active sites, and low modification efficiency.

[0005] New research has discovered that two-dimensional sheet-like nanomaterials possess advantages such as large specific surface area, numerous active sites, and high efficiency in contacting the oil-water interface. However, current nanosheet oil displacement agents primarily utilize sheet-like nanomaterials such as molybdenum disulfide and graphene oxide. The preparation of these nanomaterials is often accompanied by complex processes and high costs, lacking industrial viability. Compared to sheet-like nanomaterials such as graphene and molybdenum disulfide, sheet-like magnesium salts are relatively cheaper and have higher industrial application value. Currently, sheet-like magnesium salts are mainly prepared via hydrothermal and co-precipitation methods: the hydrothermal method requires sophisticated equipment, involves complex processes, and requires high temperatures, resulting in high reaction costs; while the conventional co-precipitation method, although simple to operate and low in cost, produces nanomaterials with irregular shapes and wide particle size distributions, making it impossible to stably and efficiently obtain sheet-like nanomaterials. Summary of the Invention

[0006] This invention was made to achieve stable preparation of sheet-like nanomaterials using a co-precipitation method under low-cost conditions.

[0007] As a first aspect of the present invention, a structure-directed dispersant having the following structural formula is involved:

[0008]

[0009] Wherein, R is an aliphatic hydrocarbon with 8 to 18 carbon atoms.

[0010] As a second aspect of the present invention, a method for preparing the above-described structure-directed dispersant is provided, the method comprising:

[0011] S1: Place sodium alkylbenzene sulfonate in a reaction vessel and add methanol as a solvent;

[0012] S2: Formaldehyde is slowly added dropwise at a certain reflux temperature and a certain rotation speed to carry out the reaction;

[0013] S3: After the reaction is complete, the solvent is removed by vacuum distillation and vacuum drying to obtain the structure-directed dispersant.

[0014] Further, the sodium alkylbenzene sulfonate in S1 is at least one of sodium dodecylbenzene sulfonate, sodium tetradecylbenzene sulfonate, sodium hexadecylbenzene sulfonate, and sodium octadecylbenzene sulfonate.

[0015] Furthermore, the molar mass ratio of sodium alkylbenzene sulfonate and formaldehyde in S1 is 1.0:2.0 to 3.0.

[0016] Furthermore, the reflux temperature in S2 is 65–80°C, the rotation speed is 300 r / min, and the reaction time is 5 h.

[0017] Furthermore, the formaldehyde in S2 is added at a rate of 2–4 mL / min.

[0018] As a third aspect of the present invention, there is a relation to sheet-like magnesium hydroxide nanomaterials, which are prepared from a magnesium source under alkaline conditions in the presence of the aforementioned structure-directing dispersant.

[0019] As a fourth aspect of the present invention, a method for preparing the above-described sheet-like magnesium hydroxide nanomaterials is provided, the method comprising:

[0020] A1: Dissolve the structure-directing dispersant and magnesium source in deionized water;

[0021] A2: Under a certain temperature and stirring speed, ammonia water is slowly added dropwise to adjust the pH of the solution, resulting in a suspension;

[0022] A3: The suspension obtained in A2 is continuously stirred and reacted at a certain temperature for a period of time, and then purified and dried to obtain the sheet-like magnesium hydroxide nanomaterial.

[0023] Furthermore, the mass ratio of the structure-directed dispersant to the magnesium source in A1 is 1.0:1.0 to 6.0.

[0024] Furthermore, the magnesium source in A1 is magnesium chloride.

[0025] Furthermore, the stirring temperature in A2 is 35–50°C, and the stirring speed is 300–500 r / min.

[0026] Furthermore, the pH value of A2 is 9 to 10.

[0027] Furthermore, the ammonia solution in A2 is added at a rate of 1.5 mL / min.

[0028] Furthermore, the stirring temperature in A3 is 35–50°C, and the stirring time is 180–300 min.

[0029] As a fifth aspect of the invention, there is a system for displacing oil, which comprises the flake-shaped magnesium hydroxide nanomaterials described above.

[0030] As a sixth aspect of the present invention, it relates to the application of the above-described oil displacement agent system in oilfield development.

[0031] The structure-directed dispersant provided by this invention, when applied to the preparation of magnesium hydroxide by co-precipitation, serves two purposes. First, as a dispersant, it enhances steric hindrance, preventing the aggregation of nanomaterials and thus controlling the particle size of magnesium hydroxide nanomaterials. Second, as a structure-directing agent, it directly guides the growth of magnesium hydroxide. The hydroxyl groups on the structure-directed dispersant form coordination bonds with magnesium ions, allowing the dispersant to adsorb onto the surface of magnesium hydroxide. The presence of benzene rings and long carbon chains on the dispersant inhibits the longitudinal growth of magnesium hydroxide crystals, thereby guiding the formation of flake-like morphology in magnesium hydroxide. This achieves a stable method for preparing flake-like magnesium hydroxide nanomaterials.

[0032] The flake-shaped magnesium hydroxide nanomaterials provided by this invention exhibit good dispersibility in solution and possess strong interfacial tension reduction and automatic adsorption functions at the oil-water interface. Furthermore, the structure-directed dispersant provided by this invention itself possesses surfactant properties, which can synergistically enhance the synthesized flake-shaped magnesium hydroxide nanomaterials. The nanomaterial system and surfactant system can be compounded simultaneously during the synthesis of the flake-shaped magnesium hydroxide nanomaterials. Simple dilution of the reaction system forms a high-performance nano-oil displacement agent system, which effectively reduces oil-water interfacial tension and improves oil recovery.

[0033] The method for preparing sheet-like magnesium hydroxide nanomaterials according to the present invention is simple and stable, with a wide range of raw material sources and low production costs, and has industrial value. Attached Figure Description

[0034] Figure 1SEM images of the sheet-like magnesium hydroxide nanomaterials prepared in Example 5;

[0035] Figure 2 This is a SEM image of the sheet-like magnesium hydroxide nanomaterials prepared in Example 8. Detailed Implementation

[0036] The embodiments of the present invention are described in detail below: The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0037] The endpoints and any values ​​of the ranges disclosed in this invention 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 in this invention.

[0038] Example 1

[0039] Sodium dodecylbenzenesulfonate (3.48 g) and formaldehyde (0.6 g) were weighed in a molar ratio of 1:2. The weighed sodium dodecylbenzenesulfonate was placed in a 250 mL three-necked flask, and 50 mL of methanol was added as solvent. Formaldehyde was added dropwise at a stirring rate of 2.5 mL / min at a reflux temperature of 65 °C for 5 h. After the reaction was complete, the solvent was removed by vacuum distillation and vacuum drying to obtain a viscous solid, which is the structure-directed dispersant.

[0040] Example 2

[0041] Sodium tetradecylbenzenesulfonate (3.76 g) and formaldehyde (0.75 g) were weighed according to a molar ratio of 1:2.5. The weighed sodium tetradecylbenzenesulfonate was placed in a 250 mL three-necked flask, and 50 mL of methanol was added as solvent. Formaldehyde was added dropwise at a stirring rate of 3 mL / min at a reflux temperature of 70 °C for 5 h. After the reaction was complete, the solvent was removed by vacuum distillation and vacuum drying to obtain a viscous solid, which is the structure-directed dispersant.

[0042] Example 3

[0043] Sodium hexadecylbenzenesulfonate (4.04 g) and formaldehyde (0.6 g) were weighed in a molar ratio of 1:2. The weighed sodium hexadecylbenzenesulfonate was placed in a 250 mL three-necked flask, and 50 mL of methanol was added as solvent. Formaldehyde was added dropwise at a stirring rate of 3.5 mL / min at a reflux temperature of 75 °C for 5 h. After the reaction was complete, the solvent was removed by vacuum distillation and vacuum drying to obtain a viscous solid, which is the structure-directed dispersant.

[0044] Example 4

[0045] Sodium octadecylbenzenesulfonate (4.32 g) and formaldehyde (0.9 g) were weighed out in a molar ratio of 1:3. The weighed sodium octadecylbenzenesulfonate was placed in a 250 mL three-necked flask, and 50 mL of methanol was added as solvent. Formaldehyde was added dropwise at a stirring rate of 300 rpm (4 mL / min) under reflux at 80 °C for 5 h. After the reaction was complete, the solvent was removed by vacuum distillation and vacuum drying to obtain a viscous solid, which is the structure-directed dispersant.

[0046] Example 5

[0047] Take a 250ml beaker and add 0.5g of the structure-directed dispersant prepared in Example 1, 2.0g of MgCl2, and 100ml of deionized water. Form a dispersion by ultrasonic vibration. Adjust the pH of the dispersion to 9 using ammonia. Pour the pH-adjusted dispersion into a 250ml flask and slowly add 4g of ammonia solution (dropping rate 1.5mL / min) dropwise in a 35℃ water bath while stirring at 300r / min. A suspension is obtained after the addition is complete. The suspension is kept at 300r / min and 35℃ for 180min until the reaction is complete. Centrifuge the obtained product, wash it multiple times with ethanol, and dry it to obtain a dry powder product, i.e., flake-shaped magnesium hydroxide nanomaterials.

[0048] Example 6

[0049] Take a 250ml beaker and add 0.5g of the structure-directed dispersant prepared in Example 2, 2.25g of MgCl2, and 100ml of deionized water. Form a dispersion by ultrasonic vibration. Adjust the pH of the dispersion to 9 using ammonia. Pour the pH-adjusted dispersion into a 250ml flask and slowly add 4g of ammonia solution (dropping rate 1.5mL / min) dropwise in a 40℃ water bath while stirring at 400r / min. After the addition is complete, a suspension is obtained. The suspension is kept at 400r / min and 40℃ for 240min to maintain the reaction. The reaction is complete after centrifugation. The product is washed multiple times with ethanol and dried to obtain a dry powder product, i.e., flake-shaped magnesium hydroxide nanomaterials.

[0050] Example 7

[0051] Take a 250ml beaker and add 0.5g of the structure-directed dispersant prepared in Example 3, 2.5g of MgCl2, and 100ml of deionized water. Form a dispersion by ultrasonic vibration. Adjust the pH of the dispersion to 10 using ammonia. Pour the pH-adjusted dispersion into a 250ml flask and slowly add 4g of ammonia solution (dropping rate 1.5mL / min) dropwise in a 45℃ water bath while stirring at 450r / min. A suspension is obtained after the addition is complete. The suspension is kept at 450r / min and 45℃ for 240 minutes to allow the reaction to proceed. Centrifuge the product, wash it multiple times with ethanol, and dry it to obtain a dry powder product, i.e., flake-shaped magnesium hydroxide nanomaterials.

[0052] Example 8

[0053] Take a 250ml beaker and add 0.5g of the structure-directed dispersant prepared in Example 4, 3.0g of MgCl2, and 100ml of deionized water. Form a dispersion by ultrasonic vibration. Adjust the pH of the dispersion to 10 using ammonia. Pour the pH-adjusted dispersion into a 250ml flask and slowly add 4g of ammonia solution (dropping rate 1.5mL / min) dropwise in a 50℃ water bath while stirring at 500r / min. A suspension is obtained after the addition is complete. The suspension is kept at 500r / min and 50℃ for 300min until the reaction is complete. Centrifuge the obtained product, wash it multiple times with ethanol, and dry it to obtain a dry powder product, i.e., flake-shaped magnesium hydroxide nanomaterials.

[0054] Comparative Example 1

[0055] Take a 250ml beaker and add 0.5g sodium dodecylbenzenesulfonate, 2.0g MgCl2, and 100ml deionized water. Form a dispersion by ultrasonic vibration. Adjust the pH of the dispersion to 9 using ammonia. Pour the pH-adjusted dispersion into a 250ml flask and slowly add 4g of ammonia solution (dropping rate 1.5mL / min) dropwise in a 35℃ water bath while stirring at 300r / min. After the addition is complete, a suspension is obtained. Continue the reaction at 300r / min and 35℃ for 180min until the reaction is complete. Centrifuge to separate the product, wash repeatedly with ethanol, and dry to obtain a dry powder product, namely magnesium hydroxide nanomaterials.

[0056] Comparative Example 2

[0057] Take a 250ml beaker and add 0.5g of polyethylene glycol 20000, 3.0g of MgCl2, and 100ml of deionized water. Form a dispersion by ultrasonic vibration. Adjust the pH of the dispersion to 10 using ammonia. Pour the pH-adjusted dispersion into a 250ml flask and slowly add 4g of ammonia solution (dropping rate 1.5mL / min) dropwise in a 50℃ water bath while stirring at 500r / min. After the addition is complete, a suspension is obtained. Continue the reaction at 500r / min and 50℃ for 300min until the reaction is complete. Centrifuge the obtained product, wash it multiple times with ethanol, and dry it to obtain a dry powder product, namely magnesium hydroxide nanomaterials.

[0058] Test Example 1

[0059] The microstructure of magnesium hydroxide nanomaterials prepared in Examples 5-8 and Comparative Examples 1 and 2 was observed using environmental scanning electron microscopy. The results are shown in Table 1. The SEM image of the magnesium hydroxide nanomaterial in Example 5 is shown below. Figure 1 As shown, it exhibits a well-defined lamellar structure with a particle size of approximately 97 nm; the SEM image of the magnesium hydroxide nanomaterial in Example 8 is shown below. Figure 2 As shown, it exhibits a well-defined lamellar structure with a particle size of approximately 74 nm.

[0060] Table 1. Characterization results of nanomaterial morphology and particle size.

[0061] name Example 5 Example 6 Example 7 Example 8 Comparative Example 1 Comparative Example 2 Appearance flakes flakes flakes flakes acicular block Particle size 97nm 89nm 91nm 74nm / / thickness 4.11nm 4.26nm 4.41nm 3.74nm / /

[0062] As shown in Table 1, the magnesium hydroxide nanomaterials prepared in Examples 5 to 8 are all sheet-like structures, while the magnesium hydroxide nanomaterials in Comparative Examples 1 and 2 are needle-like and block-like, respectively.

[0063] Test Example 2

[0064] The interfacial tension properties of magnesium hydroxide nanomaterials prepared in Examples 5-8 and Comparative Examples 1 and 2 were tested using an SVT20N interfacial tension meter.

[0065] First, the sample cell was filled with magnesium hydroxide nanomaterials prepared in Examples 5-8, Comparative Examples 1 and 2 to prepare a dispersion with a magnesium hydroxide nanomaterial mass concentration of 0.1 wt%. Then, a certain volume of crude oil (Daqing Oilfield) was injected into the center of the sample cell using a micro-syringe. The rotation speed was adjusted to 6000 rpm, and the change in oil droplet morphology over time was captured using an image acquisition system. The oil-water interfacial tension at different times was calculated based on the oil droplet morphology. The oil-water interfacial tension at oil droplet equilibrium was obtained after the oil-water interface stabilized. The method was referenced to the industry standard SYT5370-1999, "Methods for Determination of Surface and Interfacial Tension". Simultaneously, a 0.1 wt% aqueous solution of sodium dodecylbenzenesulfonate was used as a control group. The test results are shown in Table 2.

[0066] Table 2. Results of interfacial tension test

[0067]

[0068] As shown in Table 2, the sheet-like magnesium hydroxide nanomaterials prepared in Examples 5-8 can all reduce the interfacial tension to 10. -1 The magnesium hydroxide nanomaterials prepared in Examples 5-8 exhibited interfacial activity on the order of mN / m, while those prepared in Comparative Examples 1 and 2 could only reduce the oil-water interfacial tension to 7.29 mN / m and 10.41 mN / m, respectively. Meanwhile, the sodium dodecylbenzenesulfonate in the control group could reduce the oil-water interfacial tension to 1.91 mN / m. The magnesium hydroxide nanomaterial dispersions prepared in Examples 5-8 showed stronger interfacial activity.

[0069] Test Example 3

[0070] Oil displacement experiments were conducted on the magnesium hydroxide nanomaterials prepared in Examples 5-8 and Comparative Examples 1 and 2:

[0071] Using artificial rock cores Oil displacement comparative experiments were conducted. The core porosity was approximately 25%, and the permeability was approximately 30 mD. Saturated crude oil (viscosity 3.5 mPa·s, 25℃) was saturated with water and aged for 7 days before the displacement experiment was performed. The mother liquor of nanosheets prepared in Examples 5, 6, 7, 8, Comparative Example 1, and Comparative Example 2 was diluted to a dispersion with a nanosheet mass concentration of 0.1 wt% and used as an oil displacement agent. At the same time, a 0.1 wt% aqueous solution of sodium dodecylbenzenesulfonate surfactant was used as a control group.

[0072] Water was driven at a rate of 0.1 mL / min until the water cut reached 98%. Then, 0.3 PV of oil displacement agent solution was injected into the core at a rate of 0.1 mL / min. Subsequent water drive was carried out at a rate of 0.1 mL / min until the water cut reached 98%. The oil recovery rate enhancement of the oil displacement agent was calculated based on the difference between the final oil recovery rate and the water drive recovery rate. The oil recovery rate enhancement of different oil displacement agents is shown in Table 3.

[0073] Table 3 Results of Enhanced Oil Recovery (Oil Displacement Agent Mass Fraction: 0.1 wt%)

[0074]

[0075] As can be seen from Table 3, the nano-dispersions prepared from the flake magnesium hydroxide nanomaterials obtained in Examples 5-8 exhibit a higher enhanced oil recovery rate, indicating that under the same experimental conditions, the flake magnesium hydroxide nanomaterials prepared in Examples 5-8 have better oil displacement performance than Comparative Example 1, Comparative Example 2 and sodium dodecylbenzenesulfonate when applied as an oil displacement agent.

[0076] Although specific embodiments of the invention have been described in detail, those skilled in the art will understand that various modifications and substitutions can be made to those details based on all the teachings disclosed, and all such changes are within the scope of protection of this invention. The full scope of this invention is given by the appended claims and any equivalents thereof.

Claims

1. A method for preparing sheet-like magnesium hydroxide nanomaterials, characterized in that, The method includes: A1: Dissolve the structure-directing dispersant and magnesium source in deionized water; A2: Under certain temperature and stirring speed, ammonia water is slowly added dropwise to adjust the pH of the solution to weak alkalinity, thus obtaining a suspension; A3: The suspension obtained in A2 is continuously stirred and reacted at a certain temperature for a period of time, and then purified and dried to obtain the sheet-like magnesium hydroxide nanomaterial. The structure-directed dispersant has the following structural formula: ， In the formula, R is an aliphatic hydrocarbon with 8 to 18 carbon atoms.

2. The method as described in claim 1, characterized in that, The mass ratio of the structure-directed dispersant to the magnesium source in A1 is 1.0:1.0~6.

0.

3. The method as described in claim 1, characterized in that, The magnesium source in A1 is magnesium chloride.

4. The method as described in claim 1, characterized in that, The stirring temperature in A2 is 35~50℃, and the stirring speed is 300~500r / min.

5. The method as described in claim 1, characterized in that, The pH value of A2 is 9-10.

6. The method as described in claim 1, characterized in that, The ammonia solution in A2 is added at a rate of 1.5 mL / min.

7. The method as described in claim 1, characterized in that, The stirring temperature in A3 is 35~50℃, and the stirring time is 180~300min.

8. An oil displacement agent system, characterized in that, The oil displacement agent system comprises the sheet-like magnesium hydroxide nanomaterials prepared by the method according to any one of claims 1-7.

9. The application of the oil displacement agent system according to claim 8 in oilfield development.

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