A viscoelastic solution formed from a double-tailed surfactant and its lubricating and fracturing applications

Abstract

The present application discloses a kind of double-head double-tail type surfactant formed viscoelastic solution and its lubrication and fracturing application.The present application obtains new surfactant containing double-head double-tail through a series of synthesis steps.The Krafft point of the surfactant is lower than 1 ℃.Self-assembly wormlike micelles and rare ring micelles are formed in water at a certain concentration, and the diameter of the ring micelles is as small as 30 nm.The surfactant dissolved in water can form a high-efficiency viscoelastic solution with good lubricating performance.In addition, when the concentration of the surfactant is only 5 mmol / L, the viscosity of the solution can be increased by about 600 times by adding a small amount of inorganic salt, which greatly reduces the use cost.The viscoelastic solution can be used as a water-based lubricant with good performance, and also can be used as oilfield fracturing fluid, which has significant application potential.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of double-head double-tail type surfactant formed viscoelastic solution and its lubrication and fracturing application, belongs to surfactant application field. BACKGROUND

[0002] Surfactants have a wide range of applications in people's lives. It can be adsorbed to the interface of two phases, and can also form various aggregates in the bulk phase, such as spherical micelles, worm-like micelles, vesicles and liquid crystals. These supramolecular aggregates give surfactant solutions significant viscoelasticity through intermolecular or inter-aggregate interactions. Surfactant viscoelastic solutions have shown broad application prospects in personal care products, oil field fracturing fluids, fluid drag reducers and other fields.

[0003] Surfactants with specific structures form various aggregates in the bulk phase through intermolecular weak interactions such as hydrophobic interaction, electrostatic interaction, hydrogen bonding and π-π stacking, among which hydrophobic interaction is the main driving force. When linear aggregate structures are formed in the solution, the solution can have certain viscoelasticity, and have wide applications in EOR, fracturing, drag reduction and lubrication. Generally speaking, the larger the volume of the hydrophobic group of surfactants, the easier it is to form linear aggregates such as worm-like micelles. However, surfactants containing larger hydrophobic groups have poor solubility and cannot effectively self-assemble in solution, such as dihexadecyldimethylammonium bromide, which has a solubility of less than 1 mmol / L at room temperature [Colloids and Surfaces A, 1995, 98(1-2), 107-115.]. To increase the solubility of long-chain surfactants in water, one feasible method is to introduce a hydrophilic head group into the molecule. For example, Yoshimura et al. synthesized a single-chain double-head quaternary ammonium salt surfactant C 18-2Am, although it has good water solubility, cannot form a high-efficiency viscoelastic aqueous solution [Journal of Colloid and Interface Science 2012, 374(1), 157-163]. In addition, the double-chain surfactants such as didodecyldimethylammonium bromide [Colloids and Surfaces A, 2022, 652, 129822], ditetradecyldimethylammonium bromide [Langmuir, 1988, 4, 1363-1367], and dihexadecyldimethylammonium bromide [Langmuir, 2008, 24, 6509-6520] cannot significantly change the viscoelasticity of the aqueous solution within the soluble concentration range. Therefore, how to provide a surfactant through organic synthesis, which has excellent solubility and can form a viscoelastic solution within the soluble concentration range, and broaden the application field of such surfactants, is a problem to be solved in the field. SUMMARY

[0004] TECHNICAL PROBLEM

[0005] The double-chain surfactant contains two alkyl tail chains, and thus has stronger hydrophobicity, which is conducive to the self-assembly of the molecules in water. How to increase the solubility of the double-chain surfactant through organic synthesis, form a viscoelastic solution within the soluble concentration range, and broaden the application field of such surfactants is a technical problem faced by the field.

[0006] TECHNICAL SCHEME

[0007] The first object of the present application is to provide a novel double-head and double-tail containing quaternary ammonium salt surfactant, which has the following structural formula:

[0008]

[0009] The second object of the present application is to provide a preparation method of the compound.

[0010] In an embodiment, the synthesis route of the novel double-head and double-tail containing quaternary ammonium salt surfactant is as follows:

[0011]

[0012] In an embodiment, the synthesis steps of the novel double-head and double-tail containing quaternary ammonium salt surfactant (Di-C12-N2) include:

[0013] (1) Diethyl malonate reacts with 1-bromododecane under the catalysis of sodium hydride to obtain compound 1;

[0014] (2) Compound 1 reacts with 1-bromododecane in the presence of sodium hydride to obtain compound 2;

[0015] (3) Compound 2 is subjected to saponification reaction with sodium hydroxide, and then is neutralized with hydrochloric acid and subjected to decarboxylation reaction to obtain compound 3;

[0016] (4) Compound 3 reacts with thionyl chloride to obtain compound 4;

[0017] (5) Compound 4 reacts with 3-dimethylaminopropylamine to obtain compound 5;

[0018] (6) Compound 5 reacts with 3-bromo-propyl trimethylammonium bromide to obtain a novel gemini surfactant with double head and double tail, which is denoted as Di-C12-N2.

[0019] In an embodiment, in step (1), the molar ratio of diethyl malonate to 1-bromododecane is (0.8-1.5):1.

[0020] In an embodiment, in step (1), the molar ratio of diethyl malonate to sodium hydride is (0.7-1.5):1.

[0021] In an embodiment, in step (1), the reaction temperature is 50-80°C, and the reaction time is 3-10h.

[0022] In an embodiment, step (1) specifically comprises the following process:

[0023] Sodium hydride is added into a three-necked flask, washed with petroleum ether for several times, and then tetrahydrofuran is added. Diethyl malonate is added dropwise at room temperature, and the reaction is carried out for 3h. Then 1-bromododecane is added, and the reaction is carried out at 70°C for 6h. The mixture is washed with citric acid solution once, and then washed with deionized water twice until the pH value is 7. The organic layer is dried over anhydrous magnesium sulfate, and then filtered. The filtrate is subjected to rotary evaporation to remove tetrahydrofuran, and then subjected to reduced pressure distillation to obtain pure compound 1.

[0024] In an embodiment, in step (2), the molar ratio of compound 1 to 1-bromododecane is (0.8-1.5):1.

[0025] In an embodiment, in step (2), the molar ratio of compound 1 to sodium hydride is (0.7-1.5):1.

[0026] In an embodiment, in step (2), the reaction temperature is 50-80°C, and the reaction time is 3-10h.

[0027] In an embodiment, step (2) specifically comprises the following process:

[0028] Sodium hydride was added into a three-necked flask and washed with petroleum ether several times. Tetrahydrofuran was added, and compound 1 was added dropwise at 60°C for 3h, and 1-bromododecane was added, and the reaction was continued at 72°C for 6h. The mixture was washed with citric acid solution once and deionized water twice until pH=7. The organic layer was dried over anhydrous magnesium sulfate, and then filtered under suction. The filtrate was rotary evaporated to remove tetrahydrofuran, and then distilled under reduced pressure to obtain pure compound 2.

[0029] In an embodiment, in step (3), the molar ratio of compound 2 to sodium hydroxide is 1:(3-5).

[0030] In an embodiment, in step (3), the temperature of the saponification reaction is 50-80°C, and the time is 15-30h.

[0031] In an embodiment, step (3) specifically includes the following process:

[0032] Compound 2, sodium hydroxide and ethanol were placed in a three-necked flask and reacted at 70°C for 24h. After the reaction was completed, the solvent was removed by rotary evaporation, and the residue was adjusted to pH=2 with hydrochloric acid solution. The mixture was refluxed at 150°C for 72h. After cooling to room temperature, the aqueous phase was removed, and anhydrous diethyl ether was added. The mixture was washed with deionized water several times, dried over anhydrous magnesium sulfate, and filtered under suction. The filtrate was rotary evaporated to remove diethyl ether, and recrystallized with petroleum ether. After drying, pure compound 3 was obtained.

[0033] In an embodiment, in step (4), the molar ratio of compound 3 to thionyl chloride is 1:(1-2).

[0034] In an embodiment, step (4) specifically includes the following process:

[0035] Compound 3 was placed in a three-necked flask, a few drops of DMF were added, and thionyl chloride was slowly added dropwise at 60°C. The acidic gas generated was absorbed with sodium hydroxide solution, and the reaction was continued until the system became a clear liquid. After the reaction was completed, the excess thionyl chloride was removed by distillation under reduced pressure to obtain pure compound 4.

[0036] In an embodiment, in step (5), the molar ratio of compound 4 to 3-dimethylaminopropylamine is 1:(0.8-1.2).

[0037] In an embodiment, in step (5), triethylamine is also added to the reaction, and the molar ratio of compound 4 to triethylamine is 1:(2-3).

[0038] In an embodiment, step (5) specifically includes the following process:

[0039] Compound 4 is slowly dripped into the three-necked flask containing triethylamine and 3-dimethylaminopropylamine under ice-bath cooling, and the dripping is completed at room temperature for 6 hours; after the reaction is completed, dichloromethane is added for extraction, and the pH is adjusted to strong alkalinity by using NaOH aqueous solution, methanol is added for recrystallization, and the compound 5 is obtained after drying.

[0040] In one embodiment, the molar ratio of compound 5 to 3-bromo-propyl trimethylammonium bromide in step (6) is 1:(0.8-1.2).

[0041] In one embodiment, the reaction temperature in step (6) is 90-100℃, and the reaction time is 48-72 hours.

[0042] In one embodiment, step (6) specifically includes the following process:

[0043] Compound 5, 3-bromo-propyl trimethylammonium bromide and ethanol are placed in a single-necked flask, and the reaction is carried out at 92℃ for 48-72 hours; after cooling to room temperature, the solvent is removed by distillation under reduced pressure, and recrystallization is carried out three times using ethanol and ethyl acetate, and the Di-C12-N2 is obtained after drying.

[0044] The third object of the present application is to provide the use of the above-mentioned novel double-head-and-double-tail-containing quaternary ammonium salt surfactant in the preparation of a viscoelastic solution.

[0045] The fourth object of the present application is to provide a viscoelastic aqueous solution with excellent performance, which is formed by dissolving Di-C2-N2 in water.

[0046] In one embodiment, the concentration of Di-C2-N2 is 70-90 mmol / L.

[0047] In one embodiment, the viscoelastic aqueous solution contains highly curved circular micelles and worm-like micelles.

[0048] In one embodiment, the diameter of the circular micelles is as small as 30 nm.

[0049] The fifth object of the present application is to provide a viscoelastic aqueous solution containing an inorganic salt and the above-mentioned novel double-head-and-double-tail-containing quaternary ammonium salt surfactant.

[0050] In one embodiment, the inorganic salt includes any one or more of sodium chloride, potassium chloride, calcium chloride, lanthanum chloride, sodium bromide, potassium bromide, sodium iodide and potassium iodide.

[0051] In one embodiment, the molar ratio of the novel double-head-and-double-tail-containing quaternary ammonium salt surfactant to the inorganic salt ranges from 1:2 to 1:8.

[0052] In one embodiment, the concentration of the novel double-headed and double-tailed quaternary ammonium salt surfactant in the viscoelastic aqueous solution is 5-90 mmol / L.

[0053] A fifth object of the present application is to provide a water-based lubricant containing the above-mentioned novel double-headed and double-tailed quaternary ammonium salt surfactant.

[0054] A sixth object of the present application is to provide the use of the above-mentioned novel double-headed and double-tailed quaternary ammonium salt surfactant in personal care products, oilfield fracturing fluids, fluid drag reducers.

[0055] Advantages:

[0056] A novel double-headed and double-tailed quaternary ammonium salt surfactant is obtained by using diethyl malonate as a raw material through a series of synthesis steps. The solubility in water at room temperature can reach 90 mmol / L, and the Krafft point is lower than 1℃, breaking through the conventional performance of double-chain surfactants. When the concentration of its aqueous solution is 40 mmol / L, it self-assembles into worm-like micelles and rare ring-like micelles in water, among which the ring-like micelles have a diameter as small as 30 nm, and there is currently no report on surfactants forming ring-like micelles with such a small size in water. The ring-like micelles and worm-like micelles formed in the bulk phase endow the aqueous solution with obvious viscoelasticity, and the high-efficiency viscoelastic solution formed has good lubricating performance. The friction coefficient of an 80 mM aqueous solution is reduced by 35% compared with pure water. In addition, when the concentration of the surfactant is only 5 mmol / L, the addition of inorganic salt with a concentration of 40 mmol / L can increase the viscosity of the solution by 1000 times, which greatly reduces the use cost of the surfactant and increases its application potential in the fields of tertiary oil recovery and cosmetics. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 The molecular structure is Di-C12-N2.

[0058] Figure 2 The hydrogen nuclear magnetic resonance spectrum is that of Di-C12-N2.

[0059] Figure 3 The appearance photos are of aqueous solutions of Di-C12-N2 at different concentrations.

[0060] Figure 4 The steady shear graphs are of aqueous solutions of Di-C12-N2 at different concentrations.

[0061] Figure 5 The in-situ freeze transmission electron microscopy graph is of an aqueous solution of Di-C12-N2 with a concentration of 40 mmol / L.

[0062] Figure 6 The friction curve graph is of an aqueous solution of Di-C12-N2 with a concentration of 80 mmol / L and pure water.

[0063] Figure 7 Zero shear viscosity plot of 5 mmol / L Di-C12-N2 solution with different sodium chloride concentration.

[0064] Figure 8 Steady shear rheology comparison plot of 40 mmol / L Di-C12-N2 aqueous solution and single-tailed gemini quaternary ammonium surfactant C18-3-2N aqueous solution.

[0065] Figure 9 Steady shear rheology comparison plot of 5 mmol / L Di-C12-N2 and single-tailed gemini quaternary ammonium surfactant C18-3-2N aqueous solution mixed with 40 mmol / L NaCl respectively. DETAILED DESCRIPTION

[0066] Example 1: Synthesis of compound 1

[0067] Sodium hydride (31.3 g, 0.78 mol) was added into a three-necked flask and washed with petroleum ether for three times. 500 mL of tetrahydrofuran was added, and diethyl malonate (125.3 g, 0.78 mol) was slowly added dropwise at room temperature. After the addition was completed, the system was stirred for 6 h until it turned light yellow. 1-bromododecane (150 g, 0.60 mol) was added, and the reaction was continued at 70 °C for 6 h. After cooling to room temperature, the mixture was first washed with a citric acid solution once, and then washed with deionized water twice until the pH was 7. The organic layer was dried over anhydrous magnesium sulfate, and then filtered under suction. The filtrate was rotary evaporated to remove tetrahydrofuran, and then distilled under reduced pressure to obtain compound 1.

[0068] Example 2: Synthesis of compound 2

[0069] Sodium hydride (17 g, 0.43 mol) was added into a three-necked flask and washed with petroleum ether for three times. 600 mL of tetrahydrofuran was added, and compound 1 (105.8 g, 0.32 mol) was slowly added dropwise at 60 °C. After the addition was completed, the system was stirred for 3 h. 1-bromododecane (84.3 g, 0.34 mol) was added, and the reaction was continued at 72 °C for 6 h. After cooling to room temperature, the mixture was first washed with a citric acid solution once, and then washed with salt water twice until the pH was 7. The organic layer was dried over anhydrous magnesium sulfate, and then filtered under suction. The filtrate was rotary evaporated to remove tetrahydrofuran, and then distilled under reduced pressure to obtain compound 2.

[0070] Example 3: Synthesis of compound 3

[0071] Compound 2 (72.3 g, 0.15 mol), sodium hydroxide (23.3 g, 0.58 mol) and 300 mL of ethanol were placed in a three-necked flask and reacted at 70°C for 24 h. After the reaction was completed, the solvent was removed by rotary evaporation, and the residue was added to a small amount of deionized water and then adjusted to pH = 2 with concentrated hydrochloric acid. The mixture was refluxed at 150°C for 72 h. After cooling to room temperature, the aqueous phase was removed, anhydrous diethyl ether was added, and the mixture was washed several times with deionized water, dried over anhydrous magnesium sulfate, and filtered under suction. The filtrate was rotary evaporated to remove diethyl ether, and recrystallized from petroleum ether. After drying, compound 3 was obtained.

[0072] Example 4: Synthesis of compound 4

[0073] Compound 3 (33.7 g, 0.08 mol) was placed in a three-necked flask, a few drops of DMF were added, and thionyl chloride (12.1 g, 0.10 mol) was slowly added dropwise at 60°C. The generated acidic gas was absorbed with an aqueous sodium hydroxide solution, and the reaction was continued until the system became a clear liquid and no bubbles were generated in the aqueous sodium hydroxide solution. After the reaction was completed, the excess thionyl chloride was removed by distillation under reduced pressure to obtain compound 4.

[0074] Example 5: Synthesis of compound 5

[0075] Triethylamine (25.8 g, 0.26 mol) and 3-dimethylaminopropylamine (9.6 g, 0.09 mol) were placed in a three-necked flask, and compound 4 (35.3 g, 0.09 mol) was slowly added dropwise under ice bath. After the dropwise addition was completed, the reaction was continued at room temperature for 6 h. After the reaction was completed, an appropriate amount of dichloromethane was added for extraction, and the pH was adjusted to strong alkalinity with an aqueous NaOH solution. After recrystallization from methanol, compound 5 was obtained after drying.

[0076] Example 6: Synthesis of Di-C12-N2

[0077] Compound 5 (25.5 g, 0.053 mol) and 3-bromo-propyltrimethylammonium bromide (12.6 g, 0.048 mol) were placed in a single-necked flask with 200 mL of ethanol, and the mixture was reacted at 92°C for 48-72 h. After cooling to room temperature, the solvent was removed by distillation under reduced pressure, and recrystallization was performed three times with ethanol and ethyl acetate. After drying, white powdery Di-C12-N2 was obtained.

[0078] Example 7: Preparation of a viscoelastic aqueous solution

[0079] 3 mL of deionized water was taken, and Di-C12-N2 was added to it to obtain a surfactant concentration of 10, 15, 30, 35, 40, 45, 50, 60, 70, 80, and 90 mmol / L, respectively. The solution was heated to 70°C and mixed uniformly by shaking to ensure complete dissolution of the solution. The solution was allowed to stand at 25°C, and the state of the solution was observed.

[0080] Figure 3 The photos show the appearance of aqueous solutions of Di-C12-N2 at different concentrations. As can be seen from the photos, the Di-C12-N2 solution can support its own gravity when the concentration of Di-C12-N2 is only 70 mmol / L, and has the feature of not flowing when inverted, which illustrates the high efficiency of the viscoelasticity of the system.

[0081] Example 8: Determination of the solubility of Di-C12-N2

[0082] The solubility of the surfactant was determined by observation. A certain amount of surfactant was weighed into a 10 mL cylindrical vial, 5 mL of ultrapure water was added, and the vial was heated to clarity in a dry bath at 65°C, then it was placed in a 25°C constant temperature oven for 48 h, and the phenomenon was observed. If no solid precipitated, the sample was added to the solution, and the above steps were repeated until a small amount of solid precipitated at 25°C; if solid precipitated, the solvent was added until it completely dissolved. Thus the solubility of the surfactant was obtained.

[0083] The solubility of Di-C12-N2 in water at room temperature reached 90 mmol / L, breaking through the conventional performance of double-chain surfactants.

[0084] Example 9: Determination of the Krafft point of Di-C12-N2

[0085] An aqueous solution of Di-C12-N2 with a mass concentration of 1.0 wt.% was prepared, and the solution was placed in a refrigerator at 1°C for at least 3 days. If no solid precipitated, it indicated that the Krafft point of the surfactant was lower than 1°C. If precipitation occurred, the conductivity of the sample was measured after removal using a METTLER TOLEDO conductivity meter, and the conductivity of the sample was measured every 2°C, with 3 parallel tests at each temperature point, and the temperature was gradually increased until the precipitation in the system completely dissolved. The Krafft point was the temperature corresponding to the turning point of the conductivity-temperature curve.

[0086] Although the hydrophobic group of Di-C12-N2 contains 32 carbon atoms, its Krafft point is lower than 1°C, greatly expanding its application field.

[0087] Example 10: Measurement of the viscoelasticity of aqueous solutions of Di-C12-N2 at different concentrations

[0088] Aqueous solutions of Di-C12-N2 at different concentrations were prepared, and were placed at 25°C for 24 h, and the steady-state rheological properties were tested at 25°C.

[0089] Figure 4The steady shear graph of different concentrations of Di-C12-N2 aqueous solution can be seen from the figure. When the concentration is 40 mmol / L, the viscosity of Di-C12-N2 aqueous solution (0.029 Pa·s) is 30 times larger than that of pure water solvent (0.0010 Pa·s).

[0090] Example 11: Micro-morphology measurement of 40 mmol / L Di-C12-N2 aqueous solution

[0091] The sample preparation was carried out by using a low-temperature sample preparation device Cryoplunge TM3 with controllable environment, and the environmental temperature was controlled at 25°C. The relative humidity in the cavity of the device was adjusted to more than 90%, about 5 μL of sample was taken to the micro-grid by using a pipette, and then the sample on the micro-grid was absorbed by using filter paper to obtain an extremely thin liquid film. Then the sample was quickly inserted into liquid ethane cooled by liquid nitrogen. The frozen sample was transferred to a sample rod cooled by liquid nitrogen, and finally into a transmission electron microscope for observation, and the operating voltage was 120 kV.

[0092] Figure 5 The in-situ cryogenic transmission electron microscopy image of 40 mmol / L Di-C12-N2 aqueous solution can be seen. Di-C12-N2 self-assembles in water to form worm-like micelles and rare ring-like micelles, wherein the diameter of the ring-like micelles is as small as 30 nm, and there is no report about surfactants forming ring-like micelles with such small size in water. The ring-like micelles and worm-like micelles formed in the bulk phase endow the aqueous solution with obvious viscoelasticity.

[0093] Example 12: Friction coefficient measurement of 80 mmol / L Di-C12-N2 aqueous solution and pure water solvent

[0094] The friction performance test of Di-C12-N2 aqueous solution was carried out by using MFT-5000 friction and wear tester (Rtec Instruments, USA) under ball-disc friction pair. Steel ball (GCr15, diameter 9.56 mm) and steel disc (45 steel, diameter 50.80 mm, thickness 6 mm) were selected for friction test. Before the friction test, the steel ball and the steel disc were placed in anhydrous ethanol for ultrasonic cleaning for 10 min. After cleaning, the steel ball and the steel disc were dried in DZF-6 050 vacuum drying oven and then used.

[0095] Figure 6 The friction coefficient graph of Di-C12-N2 aqueous solution and pure water solvent can be seen from the figure. The friction coefficient of 80 mmol / L Di-C12-N2 aqueous solution is reduced by 35% compared with pure solvent, which shows that Di-C12-N2 has good anti-friction performance and can be applied in the field of lubrication.

[0096] Example 13: Preparation of mixed solution of 5 mmol / L Di-C12-N2 and different concentrations of sodium chloride

[0097] Take 3 mL of deionized water, add Di-C12-N2 and NaCl to it, the concentration of Di-C12-N2 is fixed at 5 mmol / L, the molar ratio of Di-C12-N2 and NaCl is 1:2, 1:2.5, 1:3, 1:3.2, 1:3.4, 1:3.6, 1:4, 1:5, 1:5.3, 1:5.6, 1:6, 1:7, 1:8, heat the solution to 70°C, ensure that the solution is completely dissolved and mixed uniformly, and observe the solution state at 25°C.

[0098] Example 14: Zero shear viscosity of mixed solution of 5 mmol / L Di-C12-N2 and different concentrations of sodium chloride

[0099] Prepare a mixed solution of 5 mmol / L Di-C12-N2 and different concentrations of sodium chloride, stand at 25°C for 24h, and test the steady-state rheological properties at 25°C.

[0100] As can be seen from Figure 7 , the viscosity of the mixed solution increases with the increase of the concentration of added NaCl. When the concentration of added NaCl is 40 mmol / L, the viscosity of the mixed solution (viscosity is 0.94 Pa·s) is 1000 times larger than that of 5 mmol / L Di-C12-N2 aqueous solution (viscosity is 9.8E-4 Pa·s), which greatly reduces the cost of preparing viscoelastic solution of surfactant and is conducive to its better industrial application.

[0101] Comparative Example 1

[0102] Preparation of single-tailed double-headed quaternary ammonium salt surfactant:

[0103] The synthetic route is as follows:

[0104]

[0105] Pour 0.88 mol of tetradecanoic acid and 5.27 mol of methanol into a 2000 mL three-necked flask, add 3 mL of concentrated sulfuric acid as catalyst, and reflux in a 70°C oil bath for 5-6h. After the reaction is completed, add 100 mL of dichloromethane, wash with 50 mL of deionized water and separate. Add 100 g of anhydrous magnesium sulfate to the oil phase, stand for 30 min, then filter, remove the dichloromethane and other residual solvents from the obtained organic phase under reduced pressure. Purify the remaining liquid by reduced pressure distillation to obtain intermediate A.

[0106] Put 0.63 mol of intermediate A and 1.90 mol of 3-dimethylamino propylamine into a 1000 mL three-necked flask, add 1 g of KOH as catalyst, and react at 100°C for 48 h. After the reaction is completed, put the mixture into a 1000 mL beaker, and recrystallize three times with acetone and ethanol to obtain intermediate B.

[0107] Put 0.05 mol of intermediate B and 0.05 mol of (3-bromopropyl) trimethylammonium bromide into a 500 mL single-necked flask, add 80 mL of ethanol, and react at 85°C for 48 h. After the reaction is completed, remove the ethanol under reduced pressure, and recrystallize the residue three times with a mixture of acetone and ethanol. Dry in a vacuum drying oven to obtain the final product, single-tailed double-headed quaternary ammonium salt surfactant.

[0108] Viscosity test of 40 mmol / L aqueous solution of single-tailed double-headed quaternary ammonium salt surfactant:

[0109] Take 3 mL of deionized water, add the above single-tailed double-headed quaternary ammonium salt surfactant to it, and the surfactant concentration is 40 mmol / L. Heat the solution to 70°C and shake to mix evenly, ensure that the solution is completely dissolved, and stand at 25°C to observe the solution state. The viscosity of the aqueous solution is 0.0012 Pa·s.

[0110] Figure 8 A steady-state rheological comparison chart of 40 mmol / L Di-C12-N2 aqueous solution and single-tailed double-headed quaternary ammonium salt surfactant C18-3-2N aqueous solution is shown. The viscosity of the Di-C12-N2 solution (0.029 Pa·s) is 24 times that of C18-3-2N (0.0012 Pa·s), and Di-C12-N2 is more likely to form a viscoelastic solution.

[0111] Zero-shear viscosity test of 5 mmol / L single-tailed double-headed quaternary ammonium salt surfactant C18-3-2N mixed solution with 40 mmol / L sodium chloride:

[0112] Prepare a 5 mmol / L single-tailed double-headed quaternary ammonium salt surfactant mixed solution with 40 mmol / L sodium chloride, stand at 25°C for 24 h, and test the steady-state rheological properties at 25°C. The viscosity of the mixed solution is 0.0016 Pa·s.

[0113] Figure 9The steady-state rheological comparison of Di-C12-N2 / NaCl and C18-3-2N / NaCl aqueous solutions at equal concentrations is shown. The C18-3-2N / NaCl system behaves as a Newtonian fluid within the tested concentration range, while the Di-C12-N2 / NaCl solution behaves as a non-Newtonian fluid, indicating that the aggregate size formed in the latter system is larger than that in the former. The viscosity of the Di-C12-N2 / NaCl solution (0.94 Pa-s) is 588 times that of the C18-3-2N / NaCl (0.0016 Pa-s).

Claims

1. A novel double-head and double-tail containing quaternary ammonium salt surfactant, whose molecular structure is as follows: ###0001### Di-C12-N2.

2. A novel quaternary ammonium surfactant containing double head and double tail according to claim 1, characterized in that, The synthesis method comprises the following steps: It comprises: (1) Diethyl malonate reacts with 1-bromododecane under the catalysis of sodium hydride to obtain compound 1; (2) Compound 1 reacts with 1-bromododecane under the action of sodium hydride to obtain compound 2; (3) Compound 2 is subjected to saponification reaction with sodium hydroxide, and then is neutralized with hydrochloric acid and subjected to decarboxylation reaction to obtain compound 3; (4) Compound 3 reacts with sulfoxide chloride to obtain compound 4; (5) Compound 4 reacts with 3-dimethylaminopropylamine to obtain compound 5; (6) Compound 5 reacts with 3-bromo-propyl trimethyl ammonium bromide to obtain the novel double-head and double-tail containing quaternary ammonium salt surfactant, which is denoted as Di-C12-N2.

3. The application of the novel double-head and double-tail containing quaternary ammonium salt surfactant in the preparation of viscoelastic solution.

4. A viscoelastic aqueous solution, characterized by, It is formed by dissolving the novel double-head and double-tail containing quaternary ammonium salt surfactant in water.

5. The viscoelastic aqueous solution according to claim 4, characterized in that, The concentration of the novel double-head and double-tail containing quaternary ammonium salt surfactant is 70-90 mmol / L.

6. A viscoelastic aqueous solution containing inorganic salt and the novel double-head and double-tail containing quaternary ammonium salt surfactant.

7. The viscoelastic aqueous solution according to claim 6, characterized in that, The inorganic salt comprises any one or more of sodium chloride, potassium chloride, calcium chloride, lanthanum chloride, sodium bromide, potassium bromide, sodium iodide and potassium iodide.

8. The viscoelastic aqueous solution according to claim 6, characterized in that, The molar ratio of the novel double-head and double-tail containing quaternary ammonium salt surfactant to the inorganic salt ranges from 1:2 to 1:8; the concentration of the novel double-head and double-tail containing quaternary ammonium salt surfactant in the viscoelastic aqueous solution is 5-90 mmol / L.

9. A water-based lubricant characterized by, The novel double-head and double-tail containing quaternary ammonium salt surfactant or the viscoelastic aqueous solution.

10. The application of the novel double-head and double-tail containing quaternary ammonium salt surfactant or the viscoelastic aqueous solution in personal care products, oil field fracturing fluid and fluid drag reducer.

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