Functional surfactant for oil and gas fields and preparation method thereof
By combining modified nanoparticles, nitrogen-containing heterocyclic alkanes, and organosilicon surfactants, functional surfactants for oil and gas fields are prepared, solving the problems of poor high and low temperature resistance and salt resistance in existing technologies. This achieves efficient reduction of oil-water interfacial tension and improved oil recovery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-11
- Publication Date
- 2026-04-17
AI Technical Summary
Existing surfactants have poor resistance to high and low temperatures and salt in oil and gas fields, resulting in low recovery rates.
A combination of modified nanoparticles, nitrogen-containing heterocyclic alkanes, and organosilicon surfactants was used to prepare functional surfactants for oil and gas fields via nucleophilic substitution reactions, forming a three-dimensional network structure that enhances temperature and salt resistance as well as rheological properties.
It improves the stability of surfactants and reduces the interfacial tension between oil and water, thereby enhancing oil recovery.
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Figure CN118995178B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of surfactant technology for oil and gas fields, and in particular to a functional surfactant for oil and gas fields and its preparation method. Background Technology
[0002] Petroleum, also known as crude oil, is an oily substance formed from organic matter deep within the Earth's crust under pressure and high temperatures over millions of years. It is a mixture of various alkanes, cycloalkanes, and aromatic hydrocarbons, and like coal, it belongs to fossil fuels. Crude oil extraction can be divided into three stages: ① The primary oil recovery stage, which is extracted by self-flowing under the pressure inside the formation. This stage is also the easiest to extract. ② The secondary oil recovery stage, which relies on water or gas injection to increase formation pressure. This stage can usually achieve a recovery rate of about 30%. ③ In order to effectively utilize the remaining reserves in the formation, scholars have proposed a tertiary oil recovery stage that relies on more advanced technologies such as chemical flooding, microbial flooding, and hybrid flooding. Among these, surfactant flooding technology in chemical flooding is currently the fastest developing and most promising research direction.
[0003] Surfactants play an important role in chemical flooding. By injecting surfactants into the reservoir, the interaction between crude oil and rock surface is changed, the interfacial tension between oil and water is reduced, crude oil migration is promoted, and the recovery rate is improved. Surfactants are mainly classified into anionic, cationic, amphoteric and nonionic surfactants, as well as other types of surfactants. Among anionic surfactants, sulfonate surfactants are inexpensive, have good water solubility, and exhibit good interfacial activity when used in combination. They can achieve low interfacial tension even at low concentrations, and are therefore widely used.
[0004] However, the surfactants in the existing technology have problems with poor resistance to high and low temperatures and salt, resulting in low recovery rates. Summary of the Invention
[0005] The purpose of this invention is to provide a functional surfactant for oil and gas fields and its preparation method. The prepared surfactant has good stability, good rheological properties, and good temperature and salt resistance. It can effectively reduce the interfacial tension between oil and water and improve the oil recovery rate.
[0006] To achieve the above objectives, the present invention provides a functional surfactant for oil and gas fields, comprising modified nanoparticles, nitrogen-containing heterocyclic alkanes, and organosilicon surfactants; the modified nanoparticles are sulfonic acid-modified nano-silica; the nitrogen-containing heterocyclic alkanes are macrocyclic alkanes composed of CN, CO, or CC bonds; the organosilicon surfactants are cage-type oligomeric silsesquioxanes, wherein the molar ratio of nitrogen-containing heterocyclic alkanes to organosilicon surfactants is 1:1 to 1:20, and the mass percentage of modified nanoparticles is 1 to 2 wt% based on the total mass of nitrogen-containing heterocyclic alkanes and organosilicon surfactants.
[0007] Preferably, the nitrogen-containing heterocyclic alkane is selected from one or more of 1,4,7-triazacyclononane, 1,4,7,10-tetraazacyclododecane, and 1,4,7,10,13-pentaazacyclopentadecanane.
[0008] Preferably, the cage-like oligomeric silsesquioxane is a monochloropropylheptaisobutyl oligomeric cage-like silsesquioxane.
[0009] The preparation method of the above-mentioned functional surfactants for oil and gas fields includes the following steps:
[0010] S1. Preparation of sulfonic acid-modified nano-silica;
[0011] S2. Dissolve nitrogen-containing heterocyclic alkanes in solvent one, then add alkali, and stir under nitrogen conditions to obtain a nitrogen-containing heterocyclic alkanes solution;
[0012] S3. Dissolve the cage-type oligomeric silsesquioxane in solvent one, then transfer it to a constant pressure dropping funnel and add it dropwise to the nitrogen-containing heterocyclic alkane solution in S2. After heating and reacting, filter and retain the filtrate. Wash the filtrate and concentrate it by rotation to obtain the concentrated solution.
[0013] S4. Add the sulfonic acid-modified nano-silica from S1 to the concentrate of S3 and react under ultrasonic stirring to obtain a functional surfactant for oil and gas fields.
[0014] Preferably, S1 includes the following steps:
[0015] S1.1 Preparation of amino-modified nano-silica
[0016] Nano-silica and aminosilane coupling agent were dissolved in solvent 2, ultrasonically dispersed, and then stirred and refluxed at a constant temperature. After cooling to room temperature, they were centrifuged to obtain amino-modified nano-silica.
[0017] S1.2, Modify amino-modified nano-silica with sulfonic acid groups.
[0018] Sodium 3-chloro-2-hydroxypropanesulfonate was dissolved in deionized water. After complete dissolution, amino-modified nano-silica prepared by S1.1 was added. After ultrasonic dispersion, the mixture was heated in an oil bath to obtain a dispersion of sulfonic acid-modified nano-silica. The dispersion of sulfonic acid-modified nano-silica was separated, purified, and vacuum dried to obtain sulfonic acid-modified nano-silica powder.
[0019] Preferably, in S1.1, the mass ratio of aminosilane coupling agent to nano-silica is 1:0.5-1.
[0020] Preferably, in S1.1, solvent two includes one or both of ethanol and toluene; the reaction temperature of the constant temperature stirring reflux reaction is 60-120°C, and the constant temperature reaction time is 18-24h.
[0021] Preferably, in S1.2, the ultrasonic dispersion time is 5 min, the oil bath heating reaction is carried out at 70℃ for 24 h, and the separation and purification are carried out by first performing rotary concentration and then purification using a dialysis bag.
[0022] Preferably, the solvent in both S2 and S3 is chloroform, and the base in S2 is sodium hydroxide.
[0023] Preferably, in S2, the stirring is carried out at room temperature for 30 minutes.
[0024] Preferably, in S3, the addition is completed slowly over 30 minutes; the heating reaction is carried out by stirring at room temperature for 15 minutes, then raising the temperature to 65°C and reacting for 16–32 hours; and the washing is performed by washing three times with distilled water to remove unreacted nitrogen-containing heterocyclic alkanes.
[0025] Preferably, in S3, the molar ratio of nitrogen-containing heterocyclic alkanes to cage-type oligomeric silsesquioxanes is 1 to 20:1.
[0026] Preferably, in S4, based on the concentrate, the mass percentage of sulfonic acid-modified nano-silica is 0.05–2.0 wt%.
[0027] Mechanism of the present invention
[0028] Nitrogen-containing heterocyclic alkanes contain lone pairs of electrons on their nitrogen atoms, making them easy to modify with other functional groups. Cage-type oligomeric silsesquioxanes, due to the stable bond energy, easy rotation, large bond angle, and long bond length of their silicon-oxygen bonds, exhibit high biocompatibility and surface activity, while also being resistant to high and low temperatures. Sulfonic acid-modified nano-silica, obtained through functionalization modification, demonstrates good anti-aggregation and anti-interference capabilities under high temperature and high salt conditions. This invention uses nitrogen-containing heterocyclic alkanes as hydrophilic groups and cage-type oligomeric silsesquioxanes as hydrophobic groups to prepare functional surfactants for oil and gas fields through nucleophilic substitution reactions. Simultaneously, sulfonic acid-modified nano-silica is introduced and grafted with both nitrogen-containing heterocyclic alkanes and cage-type oligomeric silsesquioxanes to form a three-dimensional network structure. This increases the rheological properties of the surfactant, enhances its resistance to high and low temperatures and salt, and effectively reduces the interfacial tension between oil and water.
[0029] The beneficial effects of this invention are:
[0030] This invention provides a functional surfactant for oil and gas fields, which has good stability, good rheological properties, temperature and salt resistance, good wettability to rocks, and can effectively reduce the interfacial tension between oil and water, thereby improving the recovery rate of oil.
[0031] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0032] Figure 1 This is the infrared spectrum of the functional surfactant for oil and gas fields in Example 1 of the present invention. Detailed Implementation
[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.
[0034] Example 1
[0035] This invention provides a functional surfactant for oil and gas fields, which is prepared through the following steps:
[0036] S1. Preparation of sulfonic acid-modified nano-silica
[0037] S1.1 Preparation of amino-modified nano-silica
[0038] 5g of nano-silica and 10g of KH-550 were dissolved in ethanol, ultrasonically dispersed, heated to 60℃, and stirred under reflux for 18h. Then, the mixture was cooled to room temperature and centrifuged to obtain amino-modified nano-silica.
[0039] S1.2, Modify amino-modified nano-silica with sulfonic acid groups.
[0040] Dissolve 7.9g of sodium 3-chloro-2-hydroxypropanesulfonate in 100mL of deionized water. After complete dissolution, add 2g of sodium 3-chloro-2-hydroxypropanesulfonate.
[0041] The amino-modified nano-silica obtained in S1.1 was ultrasonically dispersed for 5 min, and then heated in an oil bath to 70°C for 24 h to obtain a dispersion of sulfonic acid-modified nano-silica. The dispersion of sulfonic acid-modified nano-silica was first concentrated by rotary evaporation and then purified by dialysis bag. The solvent was then completely evaporated and vacuum dried to obtain sulfonic acid-modified nano-silica powder.
[0042] S2. Dissolve 1.723 g of 1,4,7,10-tetraazacyclododecane in 50 mL of chloroform, then add 0.8 g of sodium hydroxide, and stir under nitrogen for 30 min to obtain a nitrogen-containing heterocyclic alkane solution.
[0043] S3. Dissolve 0.525g of monochloropropylheptaisobutyl oligomeric silsesquioxane in 5mL of chloroform, then transfer it to a constant pressure dropping funnel and add it dropwise to the nitrogen-containing heterocyclic alkane solution in S2. The addition is completed slowly over 30min. After stirring at room temperature for 15min, the temperature is raised to 65℃ and the reaction is carried out for 16h. After the reaction is completed, filter and retain the filtrate. Wash the filtrate three times with distilled water to remove unreacted nitrogen-containing heterocyclic alkanes, and then concentrate by rotation to obtain the concentrated solution.
[0044] S4. Based on the total mass of nitrogen-containing heterocyclic alkanes and organosilicon surfactants, add 1.0 wt% of the sulfonic acid-modified nano-silica from S1 to the concentrate of S3 and react under ultrasonic stirring to obtain a functional surfactant for oil and gas fields.
[0045] Example 2
[0046] This invention provides a functional surfactant for oil and gas fields, which is prepared through the following steps:
[0047] S1. Preparation of sulfonic acid-modified nano-silica
[0048] S1.1 Preparation of amino-modified nano-silica
[0049] 8g of nano-silica and 15g of KH-550 were dissolved in toluene, ultrasonically dispersed, heated to 100℃, and stirred under reflux for 20h. Then, the mixture was cooled to room temperature and centrifuged to obtain amino-modified nano-silica.
[0050] S1.2, Modify amino-modified nano-silica with sulfonic acid groups.
[0051] Dissolve 7.9g of sodium 3-chloro-2-hydroxypropanesulfonate in 100mL of deionized water. After complete dissolution, add 2g of sodium 3-chloro-2-hydroxypropanesulfonate.
[0052] The amino-modified nano-silica obtained in S1.1 was ultrasonically dispersed for 5 min, and then heated in an oil bath to 70°C for 24 h to obtain a dispersion of sulfonic acid-modified nano-silica. The dispersion of sulfonic acid-modified nano-silica was first concentrated by rotary evaporation and then purified by dialysis bag. The solvent was then completely evaporated and vacuum dried to obtain sulfonic acid-modified nano-silica powder.
[0053] S2. Dissolve 1.292 g of 1,4,7-triazacyclononane in 50 mL of chloroform, then add 0.8 g of sodium hydroxide, and stir under nitrogen for 30 min to obtain a nitrogen-containing heterocyclic alkane solution.
[0054] S3. Dissolve 0.525g of monochloropropylheptaisobutyl oligomeric silsesquioxane in 5mL of chloroform, then transfer it to a constant pressure dropping funnel and add it dropwise to the nitrogen-containing heterocyclic alkane solution in S2. The addition is completed slowly over 30min. After stirring at room temperature for 15min, the temperature is raised to 65℃ and the reaction is carried out for 24h. After the reaction is completed, filter and retain the filtrate. Wash the filtrate three times with distilled water to remove unreacted nitrogen-containing heterocyclic alkanes, and then concentrate by rotation to obtain the concentrated solution.
[0055] S4. Based on the total mass of nitrogen-containing heterocyclic alkanes and organosilicon surfactants, at a mass percentage of 1.5 wt%, the sulfonic acid-modified nano-silica of S1 is added to the concentrate of S3 and reacted under ultrasonic stirring to obtain a functional surfactant for oil and gas fields.
[0056] Example 3
[0057] This invention provides a functional surfactant for oil and gas fields, which is prepared through the following steps:
[0058] S1. Preparation of sulfonic acid-modified nano-silica
[0059] S1.1 Preparation of amino-modified nano-silica
[0060] 10g of nano-silica and 20g of KH-550 were dissolved in a mixed solution of ethanol and toluene, ultrasonically dispersed, heated to 120℃, and stirred under reflux for 24h. Then the mixture was cooled to room temperature and centrifuged to obtain amino-modified nano-silica.
[0061] S1.2, Modify amino-modified nano-silica with sulfonic acid groups.
[0062] Dissolve 7.9g of sodium 3-chloro-2-hydroxypropanesulfonate in 100mL of deionized water. After complete dissolution, add 2g of sodium 3-chloro-2-hydroxypropanesulfonate.
[0063] The amino-modified nano-silica obtained in S1.1 was ultrasonically dispersed for 5 min, and then heated in an oil bath to 70°C for 24 h to obtain a dispersion of sulfonic acid-modified nano-silica. The dispersion of sulfonic acid-modified nano-silica was first concentrated by rotary evaporation and then purified by dialysis bag. The solvent was then completely evaporated and vacuum dried to obtain sulfonic acid-modified nano-silica powder.
[0064] S2. Dissolve 2.153 g of 1,4,7,10,13-pentazolidinyl pentadecane in 50 mL of chloroform, then add 0.8 g of sodium hydroxide, and stir under nitrogen atmosphere for 30 min to obtain a nitrogen-containing heterocyclic alkane solution.
[0065] S3. Dissolve 0.525g of monochloropropylheptaisobutyl oligomeric silsesquioxane in 5mL of chloroform, then transfer it to a constant pressure dropping funnel and add it dropwise to the nitrogen-containing heterocyclic alkane solution in S2. The addition is completed slowly over 30min. After stirring at room temperature for 15min, the temperature is raised to 65℃ and the reaction is carried out for 32h. After the reaction is completed, filter and retain the filtrate. Wash the filtrate three times with distilled water to remove unreacted nitrogen-containing heterocyclic alkanes, and then concentrate by rotation to obtain the concentrated solution.
[0066] S4. Based on the total mass of nitrogen-containing heterocyclic alkanes and organosilicon surfactants, at a mass percentage of 2.0 wt%, the sulfonic acid-modified nano-silica of S1 is added to the concentrate of S3 and reacted under ultrasonic stirring to obtain a functional surfactant for oil and gas fields.
[0067] Comparative Example 1
[0068] The substance was dodecyl betaine, which was purchased from Shandong Jiapeng New Materials Co., Ltd.
[0069] Performance testing
[0070] Figure 1 This is the infrared spectrum of the functional surfactant for oil and gas fields in Example 1 of the present invention, as shown in the figure. The infrared spectrum is at 3330 cm⁻¹. -1 An absorption peak for NH appeared at 2972 cm⁻¹. -1An absorption peak of -CH3 appeared at 1120 cm⁻¹. -1 An absorption peak of Si-O-Si appeared at 1190 cm⁻¹. -1 1093cm -1 617cm -1 535cm -1 The presence of an absorption peak for sulfonic acid groups indicates that Example 1 of this invention successfully synthesized the target product.
[0071] Salt resistance test
[0072] In the petroleum industry, local groundwater is often used to prepare crude oil displacement fluids due to cost constraints. However, NaCl in groundwater is often difficult to separate effectively. Therefore, the NaCl tolerance of surfactants is crucial for them to function properly in high-salinity crude oil displacement fluids. To investigate the effect of sodium chloride concentration on the ability of surfactants to reduce oil-water interfacial tension, salt tolerance tests were conducted.
[0073] The surfactants prepared in Examples 1-3 and Comparative Example 1 were added to NaCl solutions of different concentrations (10 g / L, 20 g / L, 30 g / L, 50 g / L) at 25 °C, and the surface tension of the system was tested. The test results are shown in Table 1.
[0074] Table 1. Interfacial tension of NaCl solutions of different concentrations after the addition of different surfactants (unit: mN / m)
[0075]
[0076] As shown in Table 1, in NaCl solutions of the same concentration, the surface tension of the surfactant systems of Examples 1-3 is lower than that of the surfactant systems of Comparative Example 1, indicating that the surfactants prepared in Examples 1-3 of this invention have a better ability to reduce interfacial tension than Comparative Example 1.
[0077] As the concentration of NaCl solution increased, the surface tension of the surfactant systems from Examples 1-3 did not change significantly and even showed a decreasing trend, indicating that the surfactants prepared in Examples 1-3 of this invention have good salt resistance. However, the surface tension of the surfactant system from Comparative Example 1 increased with increasing NaCl solution concentration, indicating that its salt resistance was poor.
[0078] Temperature resistance test
[0079] The surfactants of Examples 1-3 and Comparative Example 1 were prepared into solutions with a concentration of 5 g / L, and their surface tensions were tested at temperatures of 60°C, 70°C, 80°C, and 90°C, respectively. The test results are shown in Table 2.
[0080] Table 2. Interfacial tension of different surfactants at different temperatures (unit: mN / m)
[0081]
[0082]
[0083] As shown in Table 2, the surface tension of the surfactant systems from Examples 1-3 did not change significantly with increasing temperature, and even showed a decreasing trend, indicating that the surfactants prepared in Examples 1-3 of this invention have good high-temperature resistance. However, the surface tension of the surfactant system from Comparative Example 1 increased with increasing temperature, indicating that its high-temperature resistance was poor.
[0084] Test of ability to reduce interfacial tension
[0085] The surfactants of Examples 1-3 and Comparative Example 1 were prepared into solutions with a concentration of 5 g / L and then mixed with crude oil (the crude oil was provided by the No. 2 Oil Production Plant of Qinghai Oilfield). After standing for 30 minutes, the interfacial tension of the oil and water mixture was tested, and the results are shown in Table 3.
[0086] Table 3. Interfacial tension of oil and water after mixing with different surfactants (unit: mN / m)
[0087]
[0088] As shown in Table 3, the interfacial tension of the oil-water mixture after mixing with the surfactants prepared in Examples 1-3 of the present invention is much smaller than that of the oil-water mixture after mixing with Comparative Example 1, indicating that the surfactants prepared in Examples 1-3 of the present invention have a strong ability to reduce interfacial tension.
[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A functional surfactant for use in oil and gas fields, characterized by: The product comprises modified nanoparticles, nitrogen-containing heterocyclic alkanes, and organosilicon surfactants; the modified nanoparticles are sulfonic acid-modified nano-silica; the nitrogen-containing heterocyclic alkanes are selected from one or more of 1,4,7-triazacyclononane, 1,4,7,10-tetraazacyclododecane, and 1,4,7,10,13-pentaazacyclopentadecane; the organosilicon surfactants are cage-type oligomeric silsesquioxanes, wherein the molar ratio of nitrogen-containing heterocyclic alkanes to organosilicon surfactants is 1:1 to 1:20, and the mass percentage of modified nanoparticles is 1 to 2 wt% based on the total mass of nitrogen-containing heterocyclic alkanes and organosilicon surfactants; Sulfonic acid-modified nano-silica was prepared by the following methods, including: S1.1 Preparation of amino-modified nano-silica Nano-silica and aminosilane coupling agent were dissolved in solvent 2, ultrasonically dispersed, and then stirred and refluxed at a constant temperature. After cooling to room temperature, they were centrifuged to obtain amino-modified nano-silica. S1.2, Modify amino-modified nano-silica with sulfonic acid groups. Sodium 3-chloro-2-hydroxypropanesulfonate was dissolved in deionized water. After complete dissolution, amino-modified nano-silica prepared by S1.1 was added. After ultrasonic dispersion, the mixture was heated in an oil bath to obtain a dispersion of sulfonic acid-modified nano-silica. The dispersion of sulfonic acid-modified nano-silica was separated, purified, and vacuum dried to obtain sulfonic acid-modified nano-silica powder. The cage-like oligomeric silsesquioxane is a monochloropropylheptaisobutyl oligomeric cage-like silsesquioxane; The aforementioned functional surfactant for oil and gas fields is prepared by the following method, including: S1. Preparation of sulfonic acid-modified nano-silica; S2. Dissolve nitrogen-containing heterocyclic alkanes in solvent one, then add alkali, and stir under nitrogen conditions to obtain a nitrogen-containing heterocyclic alkanes solution; S3. Dissolve the cage-type oligomeric silsesquioxane in solvent one, then transfer it to a constant pressure dropping funnel and add it dropwise to the nitrogen-containing heterocyclic alkane solution in S2. After heating and reacting, filter and retain the filtrate. Wash the filtrate and concentrate it by rotation to obtain the concentrated solution. S4. Add the sulfonic acid-modified nano-silica from S1 to the concentrate of S3 and react under ultrasonic stirring to obtain a functional surfactant for oil and gas fields.
2. A method for preparing a functional surfactant for oil and gas fields as described in claim 1, characterized in that: Includes the following steps: S1. Preparation of sulfonic acid-modified nano-silica; S2. Dissolve nitrogen-containing heterocyclic alkanes in solvent one, then add alkali, and stir under nitrogen conditions to obtain a nitrogen-containing heterocyclic alkanes solution; S3. Dissolve the cage-type oligomeric silsesquioxane in solvent one, then transfer it to a constant pressure dropping funnel and add it dropwise to the nitrogen-containing heterocyclic alkane solution in S2. After heating and reacting, filter and retain the filtrate. Wash the filtrate and concentrate it by rotation to obtain the concentrated solution. S4. Add the sulfonic acid-modified nano-silica from S1 to the concentrate of S3 and react under ultrasonic stirring to obtain a functional surfactant for oil and gas fields.
3. The method for preparing a functional surfactant for oil and gas fields according to claim 2, characterized in that: In S1.1, solvent two includes one or both of ethanol and toluene; the reaction temperature of the constant temperature stirring reflux reaction is 60~120℃, and the reaction time is 18~24h.
4. The method for preparing a functional surfactant for oil and gas fields according to claim 2, characterized in that: In S1.2, the ultrasonic dispersion time is 5 min, the oil bath heating reaction is carried out at 70℃ for 24 h, and the separation and purification are carried out by first performing rotary concentration and then purification using a dialysis bag.
5. The method for preparing a functional surfactant for oil and gas fields according to claim 2, characterized in that: The solvent in both S2 and S3 is chloroform, and the base in S2 is sodium hydroxide.
6. The method for preparing a functional surfactant for oil and gas fields according to claim 2, characterized in that: In S2, stirring is performed at room temperature for 30 minutes.
7. The method for preparing a functional surfactant for oil and gas fields according to claim 2, characterized in that: In S3, the addition is done slowly over 30 minutes; the heating reaction is carried out by stirring at room temperature for 15 minutes, then raising the temperature to 65°C and reacting for 16-32 hours; the washing process involves washing three times with distilled water to remove unreacted nitrogen-containing heterocyclic alkanes.