A TiO 2 Janus nanoparticle oil-in-water type thickening emulsifier and preparation method thereof

Abstract

The present invention discloses a TiO2 Janus nanoparticle water-in-oil thickening emulsifier and a preparation method thereof, belonging to the technical field of oilfield chemistry. The preparation method of the nanoparticle emulsifier comprises the following steps: mixing spherical hydrophilic nano-TiO2 particles with liquid paraffin and stirring to form paraffin particles wrapped by nanoparticles; then grafting hydrophilic groups onto the nanoparticles; then dissolving the paraffin particles and grafting hydrophobic groups, i.e., octadecyl bromide and 1-bromodocosane, onto the nanoparticles. The emulsifier of the present invention can be uniformly dispersed in water, and a stable water-in-oil emulsion can be obtained after stirring. The emulsion belongs to a water-in-oil emulsion with a viscosity higher than that of crude oil. The viscosity of the emulsion can reach more than 25 times that of crude oil at a water cut of 80%. The emulsion has fine particle size and high emulsion stability. During the oil displacement process, it can block the preferential channels and activate the fine pore throats, thereby increasing the swept volume and achieving the effect of improving the oil recovery rate.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, and specifically to a TiO 2 Janus nanoparticle oil-in-water type thickening emulsifier and preparation method thereof. Background Art

[0002] Improving oil recovery by emulsification with emulsifiers is a common means of increasing production in oil fields and is also one of the important research contents of oilfield chemistry. Emulsifier flooding has the characteristics of low cost, low pollution, convenience and speed. Different emulsifiers can be used for oil fields with different water content periods: for heavy oil fields with low to medium water content periods, viscosity-reducing emulsifiers can be injected. The emulsifier contacts and shears with the crude oil, emulsifies in situ, forms water-in-oil emulsions, reduces the viscosity of the crude oil, and improves the efficiency of oil washing; and when the oil field reaches a high water saturation, a viscosity-increasing emulsifier can be added. Through contact, shearing, and in-situ emulsification with the crude oil, an oil-in-water emulsion is formed, which increases the viscosity of the crude oil to a certain extent, first emulsifies the dominant channel, blocks the dominant channel, starts the low permeability channel, improves the sweep efficiency, and improves the recovery rate. However, the traditional emulsifier has poor emulsion stability and large emulsion droplet size, and cannot achieve a good displacement effect for some smaller pore throats.

[0003] Studies have shown that the smaller the particle size of the emulsion droplets, the better the stability. For this reason, people use nanoparticles to prepare emulsifiers. Chinese invention patent CN114736664A discloses an emulsifier formed by branched hydrophobic monomers on nano-titanium dioxide. The emulsifier has high stability, but poor emulsification effect under high water content conditions. Therefore, it is necessary to develop a viscosity-enhancing emulsifier with good stability and emulsification effect to be suitable for emulsification flooding operations under high water content conditions. Summary of the invention

[0004] In view of this, in order to solve the above problems, the present invention provides a TiO 2 Janus nanoparticle oil-in-water emulsifier and preparation method thereof. The emulsifier can emulsify with crude oil to form fine oil-in-water emulsion in the period of high water content, increase the viscosity of crude oil, block the dominant channel, and thus further improve the recovery rate.

[0005] A TiO 2 The preparation method of Janus nanoparticle oil-in-water type thickening emulsifier comprises the following steps:

[0006] S1, spherical hydrophilic nano-TiO 2The particles and the dispersant are added to an ethanol solution, and then the solution is ultrasonically treated to obtain a uniformly dispersed nano-solution; in this step, the dispersant is an auxiliary additive and can be selected as needed, such as any one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, and octadecyltrimethylammonium bromide.

[0007] S2. Add the melted paraffin into the nano solution and continue stirring to obtain an oil-in-water emulsion. After cooling, filtering and drying the oil-in-water emulsion, paraffin particles wrapped by nanoparticles are obtained. This step is used to embed the nanoparticles on the paraffin particles. The paraffin melting temperature and stirring speed can be selected as needed. For example, stirring at 80°C and 10,000 to 15,000 rpm for 30 to 60 minutes can form an oil-in-water emulsion.

[0008] S3, dispersing the paraffin particles wrapped by the nanoparticles in an ethanol solution and adjusting the pH to 9-11 with a pH adjusting agent; adding a hydrophilic modifier and heating it to react with the nanoparticles, adding a first solvent to dissolve the paraffin particles after the reaction, washing and drying the dissolved solid product to obtain nanoparticles containing hydrophilic groups; in this step, the pH adjusting agent is used to adjust the pH value, and specifically sodium hydroxide, potassium hydroxide and the like can be used, and the first solvent is used to dissolve the paraffin, and specifically n-heptane and the like can be used; in this step, the pH value should be between 9 and 11. If the pH is less than 9, it is not conducive to the reaction of the hydrophilic modifier with the hydroxyl groups on the surface of the nanoparticles, and is not conducive to the grafting of hydrophilic groups.

[0009] S4. Dispersing the nanoparticles containing hydrophilic groups in an ethanol solution and adjusting the pH to between 9 and 11 with a pH adjuster; adding a long-chain halogenated alkane and heating it to react with the nanoparticles, then filtering, drying and crushing the filtered solid to obtain a TiO2Janus nanoparticle oil-in-water emulsifier; the long-chain halogenated alkane is one of bromooctadecane and 1-bromodocosane.

[0010] As a specific embodiment of the present invention, in step S3, the hydrophilic modifier is one of aminosulfonic acid, bromobenzoic acid, and sodium bromoethylsulfonate. When the hydrophilic modifier is aminosulfonic acid, the reaction temperature of step S3 is preferably 40-45°C; when the hydrophilic modifier is bromobenzoic acid or sodium bromoethylsulfonate, the reaction temperature of step S3 is preferably 63-65°C.

[0011] As a specific implementation of the present invention, the mass of the hydrophilic modifier is 40% to 60% of the mass of the spherical hydrophilic nano-TiO2 particles.

[0012] As a specific embodiment of the present invention, the reaction temperature of step S4 is preferably 63-65°C.

[0013] As a specific embodiment of the present invention, the long-chain halogenated alkane in step S4 is 1-bromooctadecane.

[0014] As a specific embodiment of the present invention, the mass of the long-chain halogenated alkane is 2 40% to 60% of the particle mass.

[0015] A TiO 2 Janus nanoparticle oil-in-water type thickening emulsifier is a thickening emulsifier prepared by any of the above methods.

[0016] The present invention is beneficial in that:

[0017] The present invention is in TIO 2 Nanoparticles simultaneously introduce lipophilic (bromooctadecane or 1-bromodocosane) and hydrophilic groups to generate Janus nanoparticles, and the TIO is improved by modifying specific monomers. 2 Emulsification effect and stability of nanoemulsifier. After the nanoparticles are injected into the formation and sheared, a very fine oil-in-water emulsion can be formed in the dominant channel. The emulsion has a high viscosity, which is conducive to blocking the dominant channel, activating the remaining oil in the fine pore throat, and improving the sweep efficiency, thereby improving the recovery rate. Experiments have shown that at a water content of 80%, the emulsion formed by the emulsifier of the present invention has a high degree of emulsification, the emulsion viscosity can reach more than 25 times the viscosity of crude oil, and the average emulsion particle size is 1.208μm, and the minimum particle size is 0.1μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a bar graph of the emulsification degree of emulsions formed by different emulsifiers at different water contents;

[0019] Figure 2 It is a bar graph of the viscosity of emulsions formed by different emulsifiers at different water contents;

[0020] Figure 3 is a microscopic image of emulsions of different substances at 80% water content, where Figure 3a This is a microscopic picture of CG-1 emulsion. Figure 3b This is a microscopic picture of CG-2 emulsion. Figure 3c This is a microscopic picture of CG-3 emulsion. Figure 3d For unmodified TIO 2 Microscopic picture, Figure 3e This is a microscopic picture of oil-water self-emulsification. Figure 3f This is the microscopic picture of D1 emulsion. Figure 3g This is the microscopic picture of D2 emulsion;

[0021] Figure 4 is a contact angle diagram of different oil displacement agents, where Figure 4a is the contact angle of CG-1 oil phase, Figure 4bis the water phase contact angle of CG-1; Figure 4c The middle is the contact angle of CG-2 oil phase, Figure 4d Middle is the contact angle of CG-2 water phase; Figure 4e The middle is the contact angle of CG-3 oil phase, Figure 4f Middle is the contact angle of CG-3 water phase; Figure 4g The middle is the contact angle of D1 oil phase, Figure 4h Middle is the contact angle of D1 water phase; Figure 4i The middle is the contact angle of D2 oil phase, Figure 4j Middle is the contact angle of D2 water phase; DETAILED DESCRIPTION

[0022] The present invention is further described below by specific examples, but is not limited thereto. The raw materials used in the examples are all conventional raw materials and can be obtained commercially; the methods described are all prior art unless otherwise specified.

[0023] (I) Preparation of products

[0024] Example 1

[0025] Take 1g of spherical hydrophilic nano-TiO 2 (particle size: 20 nm) and 0.005 g of dodecyltrimethylammonium bromide were added to 150 ml of 20 wt % ethanol solution and ultrasonically treated for 30 min to make it uniformly dispersed;

[0026] The uniformly dispersed nano-TiO 2 The solution was heated in a water bath at 80°C, and 6g of paraffin was heated to 80°C to melt it. After the paraffin was completely melted, it was added to the nano-TiO 2 The solution was stirred at 13000 rpm and 80°C for 40 min using a high-speed stirring device to prepare a Pickering emulsion (oil-in-water emulsion); the prepared Pickering emulsion was cooled at room temperature, and then washed and filtered with a 20wt% ethanol solution to obtain paraffin particles wrapped by nanoparticles, and the paraffin particles wrapped by the nanoparticles were placed in a beaker and dried in an oven at 35°C for 24 hours.

[0027] The paraffin particles wrapped by the nanoparticles were uniformly dispersed in 200 ml of 96 wt% ethanol solution, and the pH value was adjusted to 10 by titration with 10% sodium hydroxide solution; 0.5 g of aminosulfonic acid was added to 10 ml of deionized water, and ultrasonicated for 10 min to completely dissolve it to form an aminosulfonic acid solution, and then the aminosulfonic acid solution was added to the paraffin particle solution wrapped by the nanoparticles, and the reaction was carried out at 45 ° C and 1000 r / min for 24 h to make the aminosulfonic acid branch to the nano-TiO 2The particles are cooled to room temperature after the reaction is completed, and the filtered paraffin particles are washed with a 95w% ethanol solution; the filtered paraffin particles are added into a beaker and melted in an 80°C water bath, and after melting, 100ml of n-heptane is added to extract the paraffin to release the nanoparticles containing hydrophilic groups; the nanoparticles containing hydrophilic groups are washed and filtered with a 95wt% ethanol solution, and the nanoparticles containing hydrophilic groups are placed in a beaker and dried in an oven at 80°C for 24h.

[0028] The nanoparticles containing hydrophilic groups were uniformly dispersed in 180 ml of 96 wt% ethanol solution, and the pH was titrated to 10 with 10% sodium hydroxide; at the same time, 0.5 g of 1-bromooctadecane was uniformly dispersed in 20 ml of 96 wt% ethanol solution, and reacted at 65° C. and 1000 rpm for 24 hours; the mixture was washed several times with 95 wt% ethanol solution, and the filter cake was filtered and dried in an oven at 80° C. for 24 hours, and then ground with a mortar to obtain a viscosity-enhancing modified nanoemulsifier CG-1.

[0029] Example 2

[0030] Take 1.1g hydrophilic nano-TiO 2 (particle size: 20nm) and 0.006g of hexadecyltrimethylammonium bromide auxiliary agent were added to 150ml of 23wt% ethanol solution and ultrasonicated for 30min to make it uniformly dispersed.

[0031] The uniformly dispersed nano-TiO 2 The solution was heated at 82°C and 6.5 g of paraffin was melted at 82°C. After the paraffin was completely melted, the nano-TiO 2 The solution was stirred at 15000 rpm and 82°C for 35 min using a high-speed stirring device to prepare a Pickering emulsion; the Pickering emulsion was cooled at room temperature, and repeatedly washed and filtered with a 23wt% ethanol solution to obtain paraffin particles wrapped by nanoparticles, and the paraffin particles wrapped by nanoparticles were placed in a beaker and dried in an oven at 35°C for 24 hours.

[0032] The paraffin particles wrapped by the nanoparticles are uniformly dispersed in 200 ml of 95wt% ethanol, and the pH value is adjusted to 9 by titration with 10% sodium hydroxide solution; at the same time, 0.55 g of bromobenzoic acid is dissolved in 10 ml of deionized water, and ultrasonicated for 10 minutes to completely dissolve it, and then added to the paraffin particle solution uniformly dispersed with the nanoparticles, and reacted at 65°C and 1000r / min for 24 hours.

[0033] After the reaction is completed, the mixture is cooled to room temperature and washed several times with a 95wt% ethanol solution to filter out the paraffin particles. The paraffin particles are added to a beaker and melted in an 82°C water bath. After melting, 100ml of n-heptane is added to extract the paraffin to release the nanoparticles. The nanoparticles containing hydrophilic groups are obtained by repeatedly washing and filtering with a 95wt% ethanol solution. The nanoparticles containing hydrophilic groups are placed in a beaker and dried in an oven at 80°C for 24h.

[0034] The nanoparticles were uniformly dispersed in 180 ml of 95 wt% ethanol solution, and the pH was titrated to 9 with 10% sodium hydroxide; at the same time, 0.58 g of 1-bromooctadecane was added to the nanoparticle solution, and the reaction was carried out at 65°C and 1000 rpm for 24 hours. After the reaction was completed, the mixture was repeatedly washed with 95% ethanol solution, and the filter cake was filtered and dried in an oven at 80°C for 24 hours, and then ground with a mortar to obtain the thickening nanoemulsifier CG-2.

[0035] Preparation method Synthesis The synthesis route is as follows (taking CG-1 as an example).

[0036]

[0037] Example 3

[0038] Take 0.9g hydrophilic nano-TiO 2 (particle size: 20nm) and 0.005g of octadecyltrimethylammonium bromide auxiliary agent were added to 150ml of 22% ethanol solution and ultrasonicated for 30min to make it uniformly dispersed. 2 The solution was heated at 84°C; at the same time, 5.5 g of paraffin was melted at 84°C.

[0039] After the paraffin is completely melted, add it to the nano-TiO 2 The solution was stirred at 10000 rpm and 84°C for 60 min using a high-speed stirring device to prepare a Pickering emulsion; the Pickering emulsion was cooled at room temperature, and repeatedly washed and filtered with a 22% ethanol solution to obtain paraffin particles wrapped by nanoparticles, and the paraffin particles wrapped by nanoparticles were placed in a beaker and dried in an oven at 35°C for 24 hours.

[0040] The paraffin particles wrapped by the nanoparticles were uniformly dispersed in 200 ml of 94% ethanol, and the pH value was adjusted to 11 by titration with 10% sodium hydroxide solution; at the same time, 0.46 g of sodium bromoethylsulfonate was dissolved in 10 ml of deionized water, and ultrasonicated for 10 minutes to completely dissolve it, and then added to the paraffin particle solution uniformly dispersed with the nanoparticles, and reacted at 65°C and 1000 r / min for 24 hours.

[0041] After the reaction is completed, cool to room temperature, wash repeatedly with 94% ethanol solution several times to filter out the paraffin particles. Add the paraffin particles to a beaker and melt them in an 84°C water bath. After melting, add 100 ml of n-heptane to extract the paraffin and release the nanoparticles. Wash and filter repeatedly with 94% ethanol solution to obtain nanoparticles containing hydrophilic groups. Put the nanoparticles containing hydrophilic groups into a beaker and dry them in an oven at 80°C for 24 hours.

[0042] The nanoparticles were evenly dispersed in 180 ml of 94% ethanol solution, and the pH was titrated to 11 with 10% sodium hydroxide; at the same time, 0.43 g of 1-bromodocosane was added to the nanoparticle solution, and the reaction was carried out at 65°C and 1000 rpm for 24 hours. After the reaction was completed, the solution was repeatedly washed with 95% ethanol solution, and the filter cake was filtered and dried in an oven at 80°C for 24 hours, and then ground with a mortar to obtain the thickening nanoemulsifier CG-3.

[0043] Comparative Example 1 (Nano-TiO2 with branched dodecane bromide 2 Emulsifier

[0044] 3g of spherical hydrophilic nano-TiO 2 (particle size: 20nm) was added to 100g of anhydrous ethanol and ultrasonicated for 30min to prepare a dispersion; 0.3g of isopropyl tri(dioctyl pyrophosphate) titanate auxiliary agent was added to the dispersion, and then it was placed in an oil bath at 65°C and heated and stirred at 500rpm for 12 hours, followed by adding 3g of dodecane bromide and stirring evenly, and then placed in an oil bath at 65°C and heated and stirred for 12 hours. After the reaction was completed, the product was filtered and washed, and then dried and ground to obtain a nano solid particle emulsifier D1.

[0045] Comparative Example 2 (Branched dodecane bromide, hydrophilic group nano-TIO 2 Emulsifier

[0046] 1g of spherical hydrophilic nano-TiO 2(particle diameter: 20nm) particles add 30ml distilled water, ultrasonic dispersion 30min, add 6g melted solid paraffin, put into 80 ℃ water-baths subsequently, stir 15min with high-speed stirring homogenizer 13000rpm under paraffin molten state, cool to room temperature subsequently, separate the paraffin particles wrapped by nanoparticles, cold filtration. The paraffin particles wrapped by nanoparticles are dispersed with stirring in 100ml80wt% ethanol solution, adjust pH to 9, then dropwise add 0.5g of dodecane bromide, constant temperature 65 ℃ reaction 20h. Dissolve the paraffin particles with n-heptane subsequently to release the nanoparticles, then wash repeatedly with absolute ethanol and distillation for several times, and dry for 24h at 80 ℃ for standby use. The nanoparticles were ultrasonically dispersed in 100 ml of 80% ethanol solution, and 2 ml of 20% ammonia water was added and stirred evenly. Then 0.5 g of aminopropyltriethoxysilane was added dropwise and the mixture was reacted at a constant temperature of 40 ° C for 20 h. Then 0.5 g of succinic anhydride was dissolved in 100 ml of N, N-dimethylformamide and added. The mixture was reacted at a constant temperature of 40 ° C for 36 h, cooled and filtered, and dried at 80 ° C for 24 h to obtain the modified nanomaterial D2.

[0047] In order to illustrate the effect of the nano solid particle emulsifier prepared in the embodiment of the present invention, a performance test is conducted on it below.

[0048] (II) Product performance test

[0049] 1.TiO 2 Dispersion of Janus nanoparticles in oil-in-water emulsifier

[0050] Examples 1 to 3, Comparative Examples 1 to 2 and unmodified spherical hydrophilic nano-TiO 2 A solution with a mass concentration of 0.05% was prepared and its dispersion effect was observed.

[0051] Examples 1 to 3 (CG-1, CG-2, CG-3) had similar phenomena, showing that the nanoparticles floated on the water surface at the beginning, gradually settled to the bottom after 10 to 20 seconds, and formed a uniformly dispersed milky white dispersion after 1 minute of ultrasonic stirring. It was observed that the dispersion began to gradually precipitate after 4 minutes.

[0052] Unmodified spherical hydrophilic nano-TiO 2 After adding the aqueous solution, it sinks to the bottom of the water. After ultrasonication and stirring for 1 minute, a uniformly dispersed milky white dispersion can be formed. However, it is less stable than the modified nanomaterials, and the nanomaterials have obvious aggregation phenomenon. They precipitate quickly after dispersion. It was observed that the dispersion began to gradually precipitate after 2 minutes.

[0053] Comparative Example 1 (D1) floated on the water surface after being added to water. After ultrasonication and stirring for 3 minutes, a uniformly dispersed milky white dispersion was formed. The solution was relatively stable, but the entire dispersion process was slow. It was observed that the dispersion began to gradually precipitate after 2 minutes.

[0054] After adding comparative example 2 (D2) into water, it directly sank to the bottom. After ultrasonication and stirring for 1 minute, a uniform milky white dispersion was formed. However, the milky white dispersion was unstable and easy to precipitate. It was observed that the dispersion gradually precipitated in less than 2 minutes.

[0055] It can be seen that the TiO 2 Janus nanoparticles are oil-in-water emulsifiers with high dispersion and stability.

[0056] 2.TiO 2 Emulsification of Janus nanoparticles oil-in-water emulsifier at different water contents

[0057] The results of the experiments were performed on the samples of Examples 1-3 (CG-1, CG-2, CG-3), Comparative Examples 1-2 (D1, D2), oil-water self-emulsification (blank control group without emulsifier), unmodified spherical hydrophilic nano-TiO 2 The emulsion volume of the particles.

[0058] The test includes the following steps: prepare 10 ml of a solution with a specified water-to-oil ratio; add an emulsifier to the oil-water solution so that the mass concentration of the emulsifier is 0.05 wt% (no emulsifier is added to the blank control group); stir continuously for 30 minutes at room temperature (24°C) and 1000 rpm, and then observe the emulsification (the volume of the emulsion after emulsification). The specific test results are shown in Tables 1 and Figure 1 .

[0059] Table 1 Emulsion volume of each emulsifier at different water contents

[0060]

[0061]

[0062] From Table 1, Figure 1 It can be seen that with the increase of water content, the emulsion volume of all test cases gradually decreased, among which the emulsification degree of oil-water self-emulsification decreased most significantly, followed by the unmodified TiO 2 Among the modified nanomaterials, the emulsification degree of Examples 1 to 3 is the best. This is mainly because the water content increases, the crude oil volume decreases, and the percentage of self-emulsifying active ingredients in the crude oil to the total mass of the liquid decreases, so the self-emulsification effect becomes worse. At the same time, the unmodified nanomaterials cannot provide effective substances, so the emulsification degree is not high.

[0063] When the water content is higher than 90%, although the emulsification degree of comparative example D2 is slightly higher than that of the modified nanomaterial, Examples 1-3 and comparative example D1 can prepare water-in-oil emulsions, while the unmodified TiO 2 The emulsion prepared in comparative example D2 is an oil-in-water emulsion and is not suitable for oil displacement in high water content reservoirs.

[0064] Therefore, when the moisture content rises to more than 70%, the modified nano-TIO of the present invention 2 Compared with the unmodified nanomaterials and comparative examples D1 and D2, the particles have better emulsification effect and can achieve better displacement effect.

[0065] 3. Improvement in emulsion viscosity at different water contents.

[0066] The results of the experiments were performed on the samples of Examples 1-3 (CG-1, CG-2, CG-3), Comparative Examples 1-2 (D1, D2), oil-water self-emulsification (blank control group without emulsifier), unmodified spherical hydrophilic nano-TiO 2 Emulsion viscosity of particles.

[0067] The test includes the following steps: prepare 20 ml of a solution with a specified water-to-oil ratio; add an emulsifier to the oil-water solution so that the mass concentration of the emulsifier is 0.05 wt% (the blank control group does not add an emulsifier); stir continuously for 30 minutes at room temperature (24°C) and 1000 rpm, and then use a viscometer at room temperature (24°C) to measure the apparent viscosity. The specific test results are shown in Table 2.

[0068] Table 2 Emulsion viscosity of each emulsifier at different water contents

[0069]

[0070] Combining Table 1 and Table 2, it can be seen that when the water content is higher than 70%, the oil and water are almost not emulsified, the viscosity of crude oil is almost unchanged, and the CG-1, CG-2 and CG-3 modified nanomaterials can still form oil-in-water emulsions. The maximum viscosity of CG-1 can reach 980.6 MPa·s, which is 20 times the viscosity of crude oil; the maximum viscosity of CG-2 modified nanomaterial can reach 1247.8 MPa·s, which is more than 25 times the viscosity of crude oil; the maximum viscosity of CG-3 modified nanomaterial can reach 1096.6 MPa·s, which is more than 22 times the viscosity of crude oil; the maximum viscosity of comparative example D1 can reach more than 20 times; and when the water content of comparative example D2 is above 70%, obvious viscosity reduction phenomenon occurs; when the water content of unmodified nanomaterial is above 90%, viscosity reduction phenomenon also occurs.

[0071] Referring to Figure 3, Figure 3 is a microscopic image of the emulsions of each emulsifier prepared above at a water content of 80%. Although the viscosity increase of the emulsions prepared by the emulsifiers of Examples 1-3 is only slightly greater than that of Comparative Example D1, it can be seen from Figure 3 that the emulsions prepared using Examples 1-3 have smaller particle sizes. The particle size range of the CG-1 emulsion is mainly 0.1-2.4 μm, and the average particle size is 1.397 μm; the particle size range of the CG-2 emulsion is mainly 0.1-1.4 μm, and the average particle size is 1.208 μm; the particle size range of the CG-3 emulsion is mainly 0.1-1.15 μm, and the average particle size is 1.320 μm; the particle size range of the emulsion prepared by Comparative Example D1 is mainly 2-10 μm, and the average particle size is 6.035 μm; the particle size of Comparative Example D1 is significantly larger than the emulsions prepared by the emulsifiers of Examples 1-3. The smaller the emulsion particle size, the more stable the emulsion is, and the more conducive it is to mobilizing small pores, which shows that Examples 1-3 are more effective in improving sweep efficiency and increasing oil recovery.

[0072] 4. Wettability test.

[0073] The modified nanomaterials of Examples 1-3 and the nanomaterials of Comparative Examples D1 and D2 were evenly spread on a quartz glass slide, with air as the surrounding phase, and the three-phase contact angles of the nanomaterials were measured using a HARHE-SPCA contact angle meter (Haako, China), as shown in Figure 4. The water phase wetting contact angles of the modified nanomaterials of Examples 1, 2 and 3 were 72.5°, 76.3°, and 70.35°, respectively, and the oil phase wetting contact angles were 9.75°, 4.25°, and 25.05°, respectively; while the unmodified nanomaterials were strongly hydrophilic and wetting, and were directly and completely wetted during the measurement process, and the contact angle could not be measured; the water phase contact angles of Comparative Examples D1 and D2 were 139.35° and 25.9°, respectively, and the oil phase wetting contact angles were completely wetting (0°) and 92.55°, respectively. By comparison, it can be seen that the hydrophobicity of the nanomaterials is enhanced after modification, but at the same time CG-1, CG-2 and CG-2 have a certain hydrophilicity, which is important for preparing oil-in-water emulsions with fine particle size at high water content; the comparative example D1 has very strong hydrophobicity after modification, but the strong hydrophobicity is not conducive to improving the stability of the emulsion and the emulsification degree of the emulsion; although the comparative example D2 introduces hydrophobic and hydrophilic groups at the same time after modification, it is found through the wetting angle measurement that its hydrophilicity is stronger, which is not conducive to the preparation of oil-in-water emulsions.

[0074] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A TiO 2 Preparation method of Janus nanoparticle oil-in-water type thickening emulsifier, It is characterized in that The following steps are involved: S1, spherical hydrophilic nano-TiO 2 The particles and the dispersant are added into an ethanol solution, and then the solution is ultrasonically treated to obtain a uniformly dispersed nano-solution; S2, adding the melted paraffin wax into the nano-solution and continuously stirring to obtain an oil-in-water emulsion, and cooling, filtering and drying the oil-in-water emulsion to obtain paraffin wax particles wrapped by nano-particles; S3, dispersing the paraffin particles wrapped by the nanoparticles in an ethanol solution and adjusting the pH to 9-11 with a pH regulator; adding a hydrophilic modifier and heating it to react with the nanoparticles, adding a first solvent to dissolve the paraffin particles after the reaction, washing and drying the dissolved solid product to obtain nanoparticles containing hydrophilic groups; the hydrophilic modifier is one of aminosulfonic acid, bromobenzoic acid, and sodium bromoethylsulfonate, and the mass of the hydrophilic modifier is the spherical hydrophilic nano-TiO 2 40% to 60% of the particle mass; S4, dispersing the nanoparticles containing hydrophilic groups in an ethanol solution and adjusting the pH to 9-11 with a pH adjuster; adding bromooctadecane or 1-bromodocosane and heating to react with the nanoparticles, then filtering, drying and crushing the filtered solid to obtain TiO 2 Janus nanoparticle oil-in-water emulsifier; the mass of the brominated octadecane or 1-bromodocosane is the mass of the spherical hydrophilic nano-TiO 2 40% to 60% of the particle mass.

2. According to the preparation method described in claim 1, It is characterized in that When the hydrophilic modifier is aminosulfonic acid, the reaction temperature of step S3 is 40-45°C; when the hydrophilic modifier is bromobenzoic acid or sodium bromoethylsulfonate, the reaction temperature of step S3 is 63-65°C.

3. According to the preparation method described in claim 1, It is characterized in that The reaction temperature of step S4 is 63-65°C.

4. According to the preparation method described in claim 1, It is characterized in that In step S1, the dispersant is one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide and octadecyltrimethylammonium bromide.

5. A TiO 2 The Janus nanoparticle oil-in-water type thickening emulsifier is prepared by the method described in any one of claims 1 to 4.

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