An alkylimine-type natural gas hydrate inhibitor, its preparation method and application
By reacting modified chitosan quaternary ammonium salt with fatty aldehydes to generate alkylimine-type chitosan quaternary ammonium salt Schiff base derivatives, the problems of high dosage and environmental pollution associated with existing natural gas hydrate inhibitors are solved. This achieves low-dose, high-efficiency inhibition of natural gas hydrate formation, ensuring the continuity and production efficiency of oil and gas extraction.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LIAONING UNIVERSITY OF PETROLEUM AND CHEMICAL TECHNOLOGY
- Filing Date
- 2026-01-20
- Publication Date
- 2026-06-02
AI Technical Summary
Existing natural gas hydrate inhibitors suffer from problems such as high dosage, high cost, environmental pollution risks, and narrow applicable temperature range. In particular, traditional alcohol inhibitors and amide polymer inhibitors are difficult to effectively control hydrate formation during oil and gas extraction.
An alkylimine-type natural gas hydrate inhibitor was used, which reacted modified chitosan quaternary ammonium salt with fatty aldehydes to generate alkylimine-type chitosan quaternary ammonium salt Schiff base derivatives. This disrupted the hydrogen bond structure of the hydrate crystals, slowed down the formation rate, and reduced the amount of hydrates formed.
It achieves low-dose, high-efficiency inhibition of natural gas hydrate formation, reduces reagent consumption, lowers environmental pollution risks, and ensures the continuity and efficiency of oil and gas extraction.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of natural gas hydrate inhibition, specifically relating to an alkylimine-type natural gas hydrate inhibitor, its preparation method, and its application. Background Technology
[0002] Natural gas hydrates are a class of ice-like crystalline compounds that form under specific pressure and temperature conditions. Their structural characteristics are: a polyhedral cage-like framework constructed by host water molecules linked by hydrogen bonds, with guest gas molecules (such as methane and ethane) enclosed within this cage-like structure. Based on the differences in the size of the guest molecules, natural gas hydrates mainly exist in three crystal structures: Structure I, Structure II, and Structure H.
[0003] In the entire process of oil and gas resource extraction, gathering, and transportation, the formation of hydrates can easily lead to pipeline blockage accidents, posing a serious threat to production safety. Since the first confirmation of the correlation between hydrate formation and pipeline blockage, the oil and gas industry has consistently listed the prevention and control of hydrates as a core technical challenge. To address the risk of hydrate blockage in pipelines, the industry has developed various mitigation and remedial technologies, such as pressure reduction, chemical inhibitor injection, and heating. Among these, chemical inhibitor injection has become the most mainstream application solution due to its ease of operation and wide applicability.
[0004] Traditional hydrate inhibitors are represented by alcohols such as methanol and ethylene glycol; these inhibitors are defined as thermodynamic hydrate inhibitors (THIs). Their mechanism of action is to achieve inhibition by altering the thermodynamic formation conditions of hydrates, but this requires relatively high dosages (typically 40-70% by mass). High dosages not only increase the cost of the reagents but also pose potential environmental risks due to reagent residues.
[0005] In recent decades, the research and application of low-dose hydrate inhibitors (LDHIs) have received widespread attention. Currently, LDHs are mainly divided into two categories: kinetic hydrate inhibitors (KHIs) and anti-agglomeration agents. Most commercially available or research-stage KHIs are amide polymers, which have significant limitations: low supercooling resistance (narrow applicable temperature range), poor biodegradability, and easy environmental pollution. Summary of the Invention
[0006] This invention provides an alkylimine-type natural gas hydrate inhibitor, its preparation method, and its application. It can inhibit the formation of natural gas hydrate, significantly reduce natural gas consumption, prolong the induction time of natural gas hydrate formation, and significantly improve the inhibitory effect on natural gas hydrate.
[0007] The technical solution of the present invention is as follows: An alkylimine-type natural gas hydrate inhibitor has the following monomeric structural formula: Where m is the degree of polymerization, ranging from 100 to 6500; B represents the alkyl chain introduced after the reaction with the aliphatic aldehyde, B= , where n=1, 2, 3.
[0008] Furthermore, the alkylimine-type natural gas hydrate inhibitor is prepared using chitosan, 3-chloro-2-hydroxypropyltrimethylammonium chloride, and fatty aldehydes as raw materials.
[0009] The preparation method of the above-mentioned alkylimine-type natural gas hydrate inhibitor includes the following steps: 1) Under alkaline conditions, chitosan is fully dissolved in a solubility regulator to obtain a chitosan solution; 2) Add 3-chloro-2-hydroxypropyltrimethylammonium chloride to the chitosan solution, and after heating and reaction, perform precipitation separation, purification and drying treatment to obtain chitosan quaternary ammonium salt; 3) Dissolve the chitosan quaternary ammonium salt in deionized water and stir for 20-30 minutes until completely dissolved to obtain a chitosan quaternary ammonium salt solution; 4) Slowly add fatty aldehyde to the chitosan quaternary ammonium salt solution, and use the unreacted amino-NH2 in the chitosan quaternary ammonium salt to react with the aldehyde group-CHO on the fatty aldehyde. Stir at 25-35℃ for 20-24h; add acetone solution to precipitate the product, filter, and freeze dry to constant weight to obtain alkylimine type chitosan quaternary ammonium salt Schiff base derivative. 5) Dissolve the alkylimine-type chitosan quaternary ammonium salt Schiff base derivative in deionized water to obtain an alkylimine-type natural gas hydrate inhibitor.
[0010] Furthermore, in the preparation method of the alkylimine-type natural gas hydrate inhibitor, in step 1), the temperature is raised to 50-60℃ and magnetically stirred for 3-5 hours.
[0011] Furthermore, in the preparation method of the alkylimine-type natural gas hydrate inhibitor, in step 2), the heating temperature is 65-75℃ and the reaction time is 12-16h.
[0012] Furthermore, in the preparation method of the alkylimine-type natural gas hydrate inhibitor, in step 2), after the reaction is completed, the solution is cooled to room temperature and its pH value is measured. If it is not neutral, a neutralization reaction is carried out. After neutralization, ethanol is added to precipitate and separate the product. The precipitated product is filtered, washed, and vacuum dried at 80°C to constant weight to obtain chitosan quaternary ammonium salt.
[0013] Furthermore, in the preparation method of the alkylimine-type natural gas hydrate inhibitor, the chitosan has a degree of deacetylation >80% and a viscosity of 100-300 mPa·s; the chitosan structure contains a large number of amino groups, which are highly active and readily undergo nucleophilic reactions; the solubility regulator is isopropanol; isopropanol can adjust the polarity of the reaction system, promote the dissolution of chitosan and 3-chloro-2-hydroxypropyltrimethylammonium chloride to ensure sufficient contact, and isopropanol can also reduce the viscosity of the system, facilitating subsequent separation; the concentration of 3-chloro-2-hydroxypropyltrimethylammonium chloride is 60-70%; and the purity of the fatty aldehyde is >90%.
[0014] Furthermore, in the preparation method of the alkylimine-type natural gas hydrate inhibitor, the degree of substitution of the chitosan quaternary ammonium salt is 25%-45%; the mass ratio of fatty aldehyde to chitosan quaternary ammonium salt is 1:0.1-8.
[0015] The application of the above-mentioned alkylimine-type natural gas hydrate inhibitor is carried out as follows: the alkylimine-type natural gas hydrate inhibitor is injected into the reactor at a temperature higher than 273.15K, natural gas is injected into the reactor until the pressure is greater than 2.5MPa, and magnetic stirring is turned on to carry out the reaction; the hydrate reaction time is set to 10-72h, and the constant temperature water bath temperature is set to -5-10℃.
[0016] The beneficial effects of this invention are as follows: 1. This invention modifies the functional groups in the molecular structure of chitosan, a natural product-based kinetic hydrate inhibitor, to disrupt the ordered arrangement of hydrate crystals, break the hydrogen bonds between water molecules, and affect its normal growth pattern, making it difficult for hydrates to form a stable cage-like structure, thereby achieving biodegradability, low dosage, and high-efficiency inhibition of the hydrate inhibitor.
[0017] 2. Compared to traditional hydrate inhibitors, the alkylimine-type natural gas hydrate inhibitor of this invention does not combine two single inhibitors to achieve kinetic and thermodynamic synergy. Instead, it adds 3-chloro-2-hydroxypropyltrimethylammonium chloride and fatty aldehydes under high-temperature conditions to react with the amino bonds in chitosan to break and recombine, thereby generating a modified chitosan quaternary ammonium salt derivative. This solves the problem of poor water solubility and mediocre inhibitory effect of single chitosan inhibitors. Furthermore, the modification of the amino groups on chitosan can improve the problem of poor water solubility of chitosan. On the other hand, by introducing a strongly polar matrix, it preferentially interacts with water molecules to form hydrogen bonds, thereby disrupting the stability of the hydrate crystal structure and slowing down the hydrate nucleation rate. This demonstrates the good inhibitory effect of the alkylimine-type natural gas hydrate inhibitor of this invention.
[0018] 3. The alkylimine-type natural gas hydrate inhibitor of this invention has two major advantages in applications that inhibit the formation of natural gas hydrates: firstly, it requires a low dosage, reducing reagent consumption and usage costs; secondly, it exhibits excellent biodegradability, significantly reducing the potential pollution to the ecological environment caused by reagent residues, aligning with the concept of green development. Furthermore, this alkylimine-type natural gas hydrate inhibitor not only effectively reduces the final amount of natural gas hydrates formed but also significantly slows down their formation rate, fundamentally reducing the risk of blockage caused by the aggregation and deposition of natural gas hydrates in pipelines, thereby ensuring the continuity of extraction operations and improving overall production efficiency.
[0019] 4. The preparation method of the alkylimine-type natural gas hydrate inhibitor in this invention is easy to operate, has a simplified process, and can effectively control production input costs, showing outstanding advantages and good development potential in large-scale industrial production. Detailed Implementation
[0020] Chitosan was selected from Shanghai Maclean Biochemical Technology Co., Ltd. (CAS No. 9012-76-4); 3-chloro-2-hydroxypropyltrimethylammonium chloride was selected from Shanghai Bid Pharmaceutical Technology Co., Ltd. (CAS No. 3327-22-8); and propionaldehyde was selected from Shanghai Aladdin Biochemical Technology Co., Ltd. (CAS No. 123-38-6). Example 1
[0021] The preparation method of alkylimine-type natural gas hydrate inhibitors includes the following steps: Measure 10g of 40wt% NaOH solution, weigh 4.0g of chitosan, and add 50ml of isopropanol to the reaction flask. Heat to 55℃ and stir magnetically for 4 hours until the chitosan is completely dissolved. Add 30 ml of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution to the reaction flask and stir magnetically at 70 °C for 15 h. After the reaction is complete, measure the pH value of the reactants in the reaction flask. If it is not neutral, proceed with a neutralization reaction. Ethanol was added to precipitate and separate the product. The precipitated product was filtered, washed, and vacuum dried at 80°C to constant weight to obtain chitosan quaternary ammonium salt. The obtained chitosan quaternary ammonium salt was dissolved in 60 ml of deionized water and magnetically stirred for 20 min until completely dissolved to obtain chitosan quaternary ammonium salt solution. Add 5 ml of propionaldehyde solution to the chitosan quaternary ammonium salt solution, stir for 15 min until homogeneous, heat the mixed solution to 30°C, and stir for 24 h to allow the reaction to proceed. After the heating reaction was completed, the solution was poured into 3 times the volume of acetone solution to precipitate, then the solid and liquid were separated by filtration, and finally freeze-dried to constant weight to obtain alkylimine type chitosan quaternary ammonium salt Schiff base derivative. Weigh 0.4g of alkylimine-type chitosan quaternary ammonium salt Schiff base derivative and add it to a prepared 500ml oil-water ratio of 8:2 solution. After thorough stirring, an alkylimine-type natural gas hydrate inhibitor with a concentration of 800ppm is obtained.
[0022] Application Experiment: This application experiment was conducted in a 1L reactor, using methane as the gas. Before the experiment, the reactor was repeatedly cleaned at least three times with deionized water and ethanol, and purged with gas to remove excess gas. The airtightness was then checked to ensure good airtightness. The prepared alkylimine-type natural gas hydrate inhibitor was injected into the reactor. The data acquisition system and the cryogenic bath were turned on, and temperature and pressure changes were recorded at 20-second intervals. When the reactor temperature reached 281.15K, methane gas was injected and pressurized to 6MPa. Magnetic stirring was then started at 500 rpm. Once the gas reached dissolution equilibrium, the reactor temperature decreased to the set temperature at a rate of 0.15K / min, and the experiment began.
[0023] Analysis of the experimental results shows that the alkylimine-type natural gas hydrate inhibitor prepared in this embodiment induces methane hydrate formation in 137 min in the methane hydrate formation kinetics experiment. Compared with the comparative example, the induction time is extended by nearly 8 times. Moreover, only a small amount of hydrate is formed in the reactor, with no obvious aggregation phenomenon, and it does not affect the normal flow of the oil-water system in the reactor. Example 2
[0024] The preparation method of alkylimine-type natural gas hydrate inhibitors includes the following steps: Measure 10g of 40wt% NaOH solution, weigh 4.0g of chitosan, and add 50ml of isopropanol to the reaction flask. Heat to 55℃ and stir magnetically for 4 hours until the chitosan is completely dissolved. Add 30 ml of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution to the reaction flask and stir magnetically at 70 °C for 15 h. After the reaction is complete, measure the pH value of the reactants in the reaction flask. If it is not neutral, proceed with a neutralization reaction. Ethanol was added to precipitate and separate the product. The precipitated product was filtered, washed, and vacuum dried at 80°C to constant weight to obtain chitosan quaternary ammonium salt. The obtained chitosan quaternary ammonium salt was dissolved in 60 ml of deionized water and magnetically stirred for 20 min until completely dissolved to obtain chitosan quaternary ammonium salt solution. Add 5 ml of propionaldehyde solution to the chitosan quaternary ammonium salt solution, stir for 15 min until homogeneous, heat the mixed solution to 30°C, and stir for 24 h to allow the reaction to proceed. After the heating reaction was completed, the solution was poured into 3 times the volume of acetone solution to precipitate, then the solid and liquid were separated by filtration, and finally freeze-dried to constant weight to obtain alkylimine type chitosan quaternary ammonium salt Schiff base derivative. Weigh 1.5g of alkylimine-type chitosan quaternary ammonium salt Schiff base derivative and add it to a prepared 500ml oil-water ratio of 2:8 solution. After thorough stirring, an alkylimine-type natural gas hydrate inhibitor with a concentration of 3000ppm is obtained.
[0025] Application experiment: Same as Example 1.
[0026] Analysis of the experimental results shows that the alkylimine-type natural gas hydrate inhibitor prepared in this embodiment did not produce any hydrates in the methane hydrate formation kinetics experiment, and its inhibitory effect was significantly better than that of the comparative example. Example 3
[0027] The preparation method of alkylimine-type natural gas hydrate inhibitors includes the following steps: Measure 10g of 40wt% NaOH solution, weigh 4.0g of chitosan, and add 50ml of isopropanol to the reaction flask. Heat to 55℃ and stir magnetically for 4 hours until the chitosan is completely dissolved. Add 30 ml of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution to the reaction flask and stir magnetically at 70 °C for 15 h. After the reaction is complete, measure the pH value of the reactants in the reaction flask. If it is not neutral, proceed with a neutralization reaction. Ethanol was added to precipitate and separate the product. The precipitated product was filtered, washed, and vacuum dried at 80°C to constant weight to obtain chitosan quaternary ammonium salt. The obtained chitosan quaternary ammonium salt was dissolved in 60 ml of deionized water and magnetically stirred for 20 min until completely dissolved to obtain chitosan quaternary ammonium salt solution. Add 5 ml of propionaldehyde solution to the chitosan quaternary ammonium salt solution, stir for 15 min until homogeneous, heat the mixed solution to 30°C, and stir for 24 h to allow the reaction to proceed. After the heating reaction was completed, the solution was poured into 3 times the volume of acetone solution to precipitate, then the solid and liquid were separated by filtration, and finally freeze-dried to constant weight to obtain alkylimine type chitosan quaternary ammonium salt Schiff base derivative. Weigh 3.0g of alkylimine-type chitosan quaternary ammonium salt Schiff base derivative and add it to a prepared 500ml oil-water ratio of 3:7 solution. After thorough stirring, an alkylimine-type natural gas hydrate inhibitor with a concentration of 6000ppm is obtained.
[0028] Application experiment: Same as Example 1.
[0029] Analysis of the experimental results shows that the alkylimine-type natural gas hydrate inhibitor prepared in this embodiment did not produce any hydrates in the methane hydrate formation kinetics experiment, and its inhibitory effect was significantly better than that of the comparative example. Example 4
[0030] The preparation method of alkylimine-type natural gas hydrate inhibitors includes the following steps: Measure 10g of 40wt% NaOH solution, weigh 4.0g of chitosan, and add 50ml of isopropanol to the reaction flask. Heat to 55℃ and stir magnetically for 4 hours until the chitosan is completely dissolved. Add 30 ml of 3-chloro-2-hydroxypropyltrimethylammonium chloride solution to the reaction flask and stir magnetically at 70 °C for 15 h. After the reaction is complete, measure the pH value of the reactants in the reaction flask. If it is not neutral, proceed with a neutralization reaction. Ethanol was added to precipitate and separate the product. The precipitated product was filtered, washed, and vacuum dried at 80°C to constant weight to obtain chitosan quaternary ammonium salt. The obtained chitosan quaternary ammonium salt was dissolved in 60 ml of deionized water and magnetically stirred for 20 min until completely dissolved to obtain chitosan quaternary ammonium salt solution. Add 5 ml of propionaldehyde solution to the chitosan quaternary ammonium salt solution, stir for 15 min until homogeneous, heat the mixed solution to 30°C, and stir for 24 h to allow the reaction to proceed. After the heating reaction was completed, the solution was poured into 3 times the volume of acetone solution to precipitate, then the solid and liquid were separated by filtration, and finally freeze-dried to constant weight to obtain alkylimine type chitosan quaternary ammonium salt Schiff base derivative. Weigh 4.5g of alkylimine-type chitosan quaternary ammonium salt Schiff base derivative, add it to 500ml of deionized water, and stir thoroughly to obtain an alkylimine-type natural gas hydrate inhibitor with a concentration of 9000ppm.
[0031] Application experiment: Same as Example 1.
[0032] Analysis of the experimental results shows that the alkylimine-type natural gas hydrate inhibitor prepared in this embodiment induces methane hydrate formation in 168 min in the methane hydrate formation kinetics experiment. Compared with the comparative example, the induction time is extended by nearly 10 times, and only a small amount of hydrate is formed in the reactor, which does not affect the normal flow of the medium in the reactor. Comparative Example
[0033] Application Experiment: No hydrate inhibitors were added. The experiment was conducted in a 1L reactor using methane as the gas. Before the experiment, the reactor was thoroughly cleaned at least three times with deionized water and ethanol, and purged with gas to remove excess gas. The airtightness was then checked to ensure good airtightness. 500ml of deionized water was injected into the reactor. The data acquisition system and the cryogenic bath were turned on, and temperature and pressure changes were recorded at 20s intervals. When the reactor temperature reached 281.15K, methane gas was injected and pressurized to 6MPa. Magnetic stirring was then started at 500r / min. Once the gas reached dissolution equilibrium, the reactor temperature decreased to the set temperature at a rate of 0.15K / min, and the experiment began.
[0034] Analysis of the experimental results shows that the induction time for methane hydrate formation in the pure water system during the methane hydrate formation kinetics experiment was 17 minutes, and there was obvious hydrate formation in the reactor, leading to blockage.
[0035] The comparison of the above experimental data shows that the modified alkylimine-type chitosan quaternary ammonium salt Schiff base derivative has a better inhibitory effect on natural gas hydrates than the pure water experiment.
[0036] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. An alkylimine-type natural gas hydrate inhibitor, characterized in that, Its single-unit structural formula is as follows: Where m is the degree of polymerization, ranging from 100 to 6500; B represents the alkyl chain introduced after the reaction with the aliphatic aldehyde, B= , where n=1, 2, 3.
2. The alkylimine-type natural gas hydrate inhibitor according to claim 1, characterized in that, It was prepared using chitosan, 3-chloro-2-hydroxypropyltrimethylammonium chloride and fatty aldehyde as raw materials.
3. The method for preparing the alkylimine-type natural gas hydrate inhibitor as described in claim 2, characterized in that, Includes the following steps: 1) Under alkaline conditions, chitosan is fully dissolved in a solubility regulator to obtain a chitosan solution; 2) Add 3-chloro-2-hydroxypropyltrimethylammonium chloride to the chitosan solution, and after heating and reaction, perform precipitation separation, purification and drying treatment to obtain chitosan quaternary ammonium salt; 3) Dissolve the chitosan quaternary ammonium salt in deionized water and stir for 20-30 minutes until completely dissolved to obtain a chitosan quaternary ammonium salt solution; 4) Slowly add fatty aldehyde to the chitosan quaternary ammonium salt solution and stir at 25-35℃ for 20-24h; add acetone solution to precipitate the product, filter, and freeze dry to constant weight to obtain alkylimine type chitosan quaternary ammonium salt Schiff base derivative. 5) Dissolve the alkylimine-type chitosan quaternary ammonium salt Schiff base derivative in deionized water to obtain an alkylimine-type natural gas hydrate inhibitor.
4. The method for preparing the alkylimine-type natural gas hydrate inhibitor according to claim 3, characterized in that, In step 1), the temperature is raised to 50-60℃ and magnetically stirred for 3-5 hours.
5. The method for preparing the alkylimine-type natural gas hydrate inhibitor according to claim 3, characterized in that, In step 2), the heating temperature is 65-75℃ and the reaction time is 12-16h.
6. The method for preparing the alkylimine-type natural gas hydrate inhibitor according to claim 3, characterized in that, In step 2), after the reaction is completed, the solution is cooled to room temperature and its pH value is measured. If it is not neutral, a neutralization reaction is carried out. After neutralization, ethanol is added to precipitate and separate the product. The precipitated product is filtered, washed, and vacuum dried at 80°C to constant weight to obtain chitosan quaternary ammonium salt.
7. The method for preparing the alkylimine-type natural gas hydrate inhibitor according to claim 3, characterized in that, The chitosan has a degree of deacetylation >80% and a viscosity of 100-300 mPa·s; the solubility modifier is isopropanol; the concentration of 3-chloro-2-hydroxypropyltrimethylammonium chloride is 60-70%; and the purity of the fatty aldehyde is >90%.
8. The method for preparing the alkylimine-type natural gas hydrate inhibitor according to claim 3, characterized in that, The degree of substitution of the chitosan quaternary ammonium salt is 25%-45%; the mass ratio of fatty aldehyde to chitosan quaternary ammonium salt is 1:0.1-8.
9. The method for preparing the alkylimine-type natural gas hydrate inhibitor according to claim 3, characterized in that, The concentration of the alkylimine-type natural gas hydrate inhibitor is between 100 ppm and 20,000 ppm.
10. The application of the alkylimine-type natural gas hydrate inhibitor as described in claim 2, characterized in that, The process is as follows: an alkylimine-type natural gas hydrate inhibitor is injected into the reactor at a temperature greater than 273.15 K. Natural gas is injected into the reactor until the pressure is greater than 2.5 MPa. Magnetic stirring is started to carry out the reaction. The hydrate reaction time is set to 10-72 h, and the constant temperature water bath temperature is set to -5-10℃.