Copolymer, method for preparing the same, and use

Abstract

The present invention relates to the technical field of oil and gas extraction and transportation, and more specifically to copolymers, methods for preparing the same, and their use. The copolymer comprises structural unit A and structural unit B, wherein structural unit A is derived from an unsaturated monomer containing pyrimidone and multiple hydrogen bonds, and structural unit B is derived from an unsaturated monomer containing pyrrolidone, and the content of structural unit A is 0.5 to 10 wt% and the content of structural unit B is 90 to 99.5 wt% based on the total weight of the copolymer. The copolymer not only contains structural unit A and structural unit B in specific amounts, but structural unit A and structural unit B each contain specific structures, thereby the copolymer has excellent inhibitory properties against hydrate formation, specifically it can withstand greater supercooling degrees, and can effectively extend the hydrate induction time and slow down the hydrate formation rate at various supercooling degrees.

Description

Detailed description of the invention

[0001] [Cross-reference of related applications] This application claims the interests of Chinese Patent Application No. 202310340058.X, filed on 31 March 2023, the contents of which are incorporated herein by reference.

[0002] [Technical field] This invention relates to the technical field of oil and gas extraction and transportation, and more specifically to copolymers, methods for preparing the same, and their use.

[0003] [Background technology] Natural gas hydrates are cage-like substances formed under high pressure and low temperature conditions by water molecules and small molecule gases such as methane and ethane. Currently, there are three types of crystalline structures for hydrates: type I, type II, and type H. Gas hydrates are frequently generated during oil and gas field production and pipeline transportation. When large amounts of hydrates are formed, they are highly likely to cause blockages in equipment such as wells and pipelines, disrupting the normal operation of the equipment and leading to pipeline ruptures, flow safety accidents, and unbearable losses. Therefore, preventing and controlling hydrate formation is a constant challenge for the oil and gas industry.

[0004] The main methods for inhibiting hydrate formation are the addition of chemical inhibitors such as thermodynamic inhibitors (THIs) and low-dose kinetic inhibitors (LDHs). Thermodynamic inhibitors prevent hydrate formation by altering the thermodynamic equilibrium conditions so that the equilibrium pressure or temperature for hydrate formation is lower than the actual pressure or temperature in the pipeline. Thermodynamic inhibitors are widely used in oil and gas field production, but their usage is high (typically 10% to 60% of the aqueous phase), resulting in high economic costs and certain environmental pollution problems. Low-dose kinetic inhibitors do not alter the thermodynamic conditions for hydrate formation in the system, but they delay the hydrate nucleation time, slow down the hydrate crystal growth rate, and prevent hydrate crystal growth, thus avoiding problems such as pipeline clogging. Compared to conventional thermodynamic inhibitors, their usage is very low (typically less than 1%), offering economic and environmental benefits.

[0005] However, the inhibitory effect of low-dose kinetic inhibitors is greatly affected by the degree of supercooling of the system, and their low inhibitory activity limits their application to highly supercooled systems. Furthermore, kinetic inhibitors, such as N-vinylcaprolactam, have problems such as poor biodegradability, high synthesis costs, low inhibitory activity, and a narrow range of applications, making large-scale commercialization difficult.

[0006] Currently, CN108219762A discloses a novel hydrate kinetic inhibitor, which is phenylated poly-N-vinylpyrrolidone prepared by polymerization of ethylbenzene and N-vinylpyrrolidone monomers. CN113388379A provides hydrate kinetic inhibitors obtained by polymerization of vinylpyrrolidone, cyclohexyl vinyl ether, and acrylate monomers, as well as methods for their preparation and use. CN105859963A discloses hydrate inhibitor products obtained by free radical solution polymerization in a solvent using N-vinylpyrrolidone (NVP), N-vinylcaprolactam (NVCL), acrylamide (AM), and acrylonitrile (AN) as synthetic monomers, with ammonium persulfate and sodium bisulfite as initiators. CN104194756A discloses a novel hydrate kinetic inhibitor, as well as methods for its preparation and use. The main component is a polyhydroxy polymer obtained by the reaction of chlorophenol with N-vinylcaprolactam or N-vinylpyrrolidone. "Preparation and Characterization of Novel Natural Gas Hydrate Kinetic Inhibitors" (Chou, Shi, Dong et al., Petrochemical, 2017, 46(04):467-470) discloses the synthesis of a kinetic inhibitor using solution polymerization with N-vinylpyrrolidone as the monomer and hydrogen peroxide as the initiator, under the action of nitrogen. "Development and Characterization of Novel Natural Gas Hydrate Kinetic Inhibitors" (Liu, Shujie et al., Offshore Oil & Gas of China, 2015, 27(06):69-73) discloses a novel hydrate kinetic inhibitor, KHI-S, which adsorbs to the hydrate surface via a lactam ring to form a dense film, preventing further contact between the hydrate and gas or water molecules, thereby slowing the continuous growth of the hydrate. The hydrate kinetic inhibitors prepared in the above-mentioned patent and non-patent documents require improvement in their inhibitory properties against hydrates, making them difficult to apply on a large scale.

[0007] [Overview of the prefecture] [Problems the invention aims to solve] The object of the present invention is to overcome the problem of conventional hydrate kinetic inhibitors, which is the need to improve the inhibitory properties against hydrates, and to provide a copolymer, a method for preparing the copolymer, and a method for using the copolymer, which has excellent inhibitory properties against hydrates, specifically, can withstand greater supercooling degrees, and can effectively extend the hydrate induction time and slow down the hydrate formation rate at various supercooling degrees.

[0008] [Means for solving the problem] To achieve the above objective, a first aspect of the present invention provides a copolymer comprising structural unit A and structural unit B, wherein structural unit A is derived from an unsaturated monomer containing pyrimidone and multiple hydrogen bonds, and structural unit B is derived from an unsaturated monomer containing pyrrolidone. The copolymer is characterized in that, based on its total weight, the content of structural unit A is 0.5 to 10 wt%, and the content of structural unit B is 90 to 99.5 wt%.

[0009] A second aspect of the present invention provides a method for preparing a copolymer, the method comprising the steps of contacting compound A and compound B in the presence of a first solvent and an initiator to carry out a first reaction and obtain the copolymer, Compound A is an unsaturated monomer containing pyrimidone and multiple hydrogen bonds, and compound B is an unsaturated monomer containing pyrrolidone. Based on the total weight of compound A and compound B, the amount of compound A used is 0.5 to 10 wt%, and the amount of compound B used is 90 to 99.5 wt%, characterized in that.

[0010] A third aspect of the present invention provides a copolymer prepared by the preparation method described in the second aspect of the present invention.

[0011] A fourth aspect of the present invention provides the use of the copolymer described in the first or third aspect of the present invention as a hydrate kinetic inhibitor.

[0012] [Effects of the invention] By the above technical solution, the copolymer provided by the present invention, its preparation method and use achieve the following beneficial effects.

[0013] (1) The copolymer provided by the present invention not only contains a structural unit A with a specific content and a structural unit B with a specific content, but also the structural unit A and the structural unit B each contain a specific structure. As a result, the copolymer has excellent inhibition characteristics against hydrates. Specifically, it can withstand a larger degree of supercooling, and at various degrees of supercooling, it can effectively extend the hydrate induction time and slow down the hydrate formation rate.

[0014] (2) The preparation method of the present invention has the advantages that the polymerization process is simple and industrial production is easy.

[0015] (3) The copolymer provided by the present invention can be used in the extraction and transportation of oil and gas as a hydrate kinetic inhibitor, has advantages such as stable properties and a wide supercooling degree adaptation range, and the future of its application can be expected.

[0016] [Brief Description of Drawings] [Figure 1] Infrared spectrum of the copolymer S-1 prepared in Example 1.

[0017] [Figure 2] Proton nuclear magnetic resonance spectrum of the copolymer S-1 prepared in Example 1.

[0018] [Figure 3] Schematic diagram of the device for evaluating the properties of the hydrate inhibitor.

[0019] [Explanation of Signs] 1 Methane cylinder 2 Pressure regulating valve 3 PID valve 4 Motor 5 Torque sensor 6 Stirrer 7 Reactor 8 Temperature sensor 9 Pressure sensor 10 Case and data acquisition and processing system [Mode for Carrying Out the Invention] The endpoints and any values in the ranges disclosed in this specification are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. In the case of numerical ranges, by combining between the endpoint values of each range, between the endpoint value of each range and an individual dot value, and between individual dot values, one or more new numerical ranges can be obtained, and these numerical ranges are regarded as specifically disclosed herein.

[0020] The first aspect of the present invention provides a copolymer, the copolymer including a structural unit A and a structural unit B, the structural unit A being derived from an unsaturated monomer containing pyrimidone and multiple hydrogen bonds, and the structural unit B being derived from an unsaturated monomer containing pyrrolidone, Based on the total weight of the copolymer, the content of the structural unit A is 0.5 to 10 wt%, and the content of the structural unit B is 90 to 99.5 wt%, which is characterized by this.

[0021] In the present invention, the copolymer includes the structural unit A and the structural unit B containing specific groups. When the contents of the structural unit A and the structural unit B in the copolymer satisfy a specific range, the copolymer has excellent inhibition characteristics against hydrates. Specifically, it can withstand a larger degree of supercooling, and at various degrees of supercooling, it can effectively extend the hydrate induction time and slow down the hydrate formation rate.

[0022] Specifically, pyrrolidone contained in the structural unit B and pyrimidone contained in the structural unit A are adsorbed to the growth sites of hydrates, causing lattice mismatch and destroying the crystal structure, and it is possible to inhibit the growth of hydrate nuclei to a critical size. Due to the multiple hydrogen bonds contained in the structural unit A, the adsorption ability of the copolymer to the surface of the formed hydrate crystal nuclei can be improved, preventing the aggregation of hydrate crystal particles and inhibiting the growth of hydrate crystals.

[0023] In this invention, the content of structural unit A and structural unit B in the copolymer is measured by hydrogen nuclear magnetic resonance spectroscopy. Approximately 5 to 10 mg of the purified copolymer is weighed into a nuclear magnetic resonance tube, dissolved in deuterated chloroform, and the experiment is performed at room temperature using a nuclear magnetic resonance spectrometer. By comparing the hydrogen nuclear magnetic resonance spectrum of the copolymer of structural unit A and structural unit B with the hydrogen nuclear magnetic resonance spectrum of the raw material of structural unit B, the relative content of structural unit A and structural unit B in the copolymer can be obtained by calculating the integrated area of ​​the characteristic signal peaks, as shown in Figure 2.

[0024] Furthermore, when the content of structural unit A is preferably 1 to 3 wt% and the content of structural unit B is preferably 97 to 99 wt% based on the total weight of the copolymer, it is advantageous for further improving the inhibitory properties of the copolymer hydrate.

[0025] According to the present invention, structural unit A has a structure represented by formula (1), and structural unit B has a structure represented by formula (2).

[0026] [ka]

[0027] (Here, R1 is H or C1~C 10 R2 is an alkyl group, and R2 is an alkyl group of H or C1-C5. n is an integer from 1 to 10, and R3 to R8 are each independently H or C1 to C 10 It is an alkyl group. In the present invention, if structural units A and B in the copolymer have the above-described specific structures, the inhibitory properties against the hydrate of the copolymer can be further improved.

[0028] Furthermore, R1 is a C1-C5 alkyl group, R2 is a C1-C3 alkyl group, n is an integer from 2 to 5, and R3-R8 are each independently H or a C1-C5 alkyl group. If at least one of the above conditions is met, the inhibitory properties against the copolymer hydrate can be further improved.

[0029] In the present invention, the weight-average molecular weight of the copolymer is 5 to 500,000, preferably 110,000 to 200,000.

[0030] A second aspect of the present invention provides a method for preparing a copolymer, the method comprising the steps of contacting compound A and compound B in the presence of a first solvent and an initiator to carry out a first reaction and obtain the copolymer, Compound A is an unsaturated monomer containing pyrimidone and multiple hydrogen bonds, and compound B is an unsaturated monomer containing pyrrolidone. Based on the total weight of compound A and compound B, the amount of compound A used is 0.5 to 10 wt%, and the amount of compound B used is 90 to 99.5 wt%, characterized in that.

[0031] In the present invention, a copolymer obtained by polymerizing an unsaturated monomer containing pyrimidone and multiple hydrogen bonds with an unsaturated monomer containing pyrrolidone simultaneously possesses the five-membered ring structure of pyrrolidone, the six-membered ring structure of pyrimidone, and the multiple hydrogen bond structure. As a result, the copolymer can not only be adsorbed onto the hydrate growth site, causing lattice mismatch and disrupting the crystal structure, thereby inhibiting the growth of hydrate nuclei to critical size, but it can also improve the adsorption capacity of the copolymer to the surface of the formed hydrate crystal nuclei, preventing aggregation of hydrate crystal particles and inhibiting the growth of hydrate crystals. Consequently, the copolymer has excellent inhibitory properties against hydrates, specifically, it can withstand greater supercooling degrees and can effectively extend the hydrate induction time and slow down the hydrate formation rate at various supercooling degrees.

[0032] In particular, when the content of compound A and compound B is controlled to satisfy the above range, the resulting copolymer has excellent inhibitory properties against hydrates.

[0033] Furthermore, the method of the present invention has low synthesis costs and mild reaction conditions, making large-scale commercial production possible.

[0034] Furthermore, when the amount of compound A used is preferably 1 to 3 wt% and the amount of compound B used is preferably 97 to 99 wt%, based on the total weight of compound A and compound B, it is advantageous for further improving the inhibitory properties of the copolymer hydrate.

[0035] According to the present invention, compound A has the structure shown in formula (3), and compound B has the structure shown in formula (4).

[0036] [ka]

[0037] (Here, R1' is H or C1~C 10 R2' is an alkyl group, and R2' is an alkyl group of H or C1-C5. n' is an integer from 1 to 10, and R3' to R8' are each independently H or C1 to C 10 It is an alkyl group. Furthermore, R1' is a C1-C5 alkyl group, R2' is a C1-C3 alkyl group, n' is an integer from 2 to 5, and R3'-R8' are each independently C1-C5 alkyl groups. If one or more of the above conditions are met, the inhibitory properties against the copolymer hydrate can be further improved.

[0038] According to the present invention, the conditions for the first reaction include a reaction temperature of 40 to 70°C and a reaction time of 6 to 10 hours.

[0039] In the present invention, since the conditions for the first reaction satisfy the above range, the polymerization process is simple and industrial production is easy, which is an advantage.

[0040] Furthermore, the conditions for the first reaction include a reaction temperature of preferably 50-60°C and a reaction time of preferably 7-9 hours.

[0041] According to the present invention, the first solvent is at least one selected from deionized water, ethanol, and methanol.

[0042] In one specific embodiment of the present invention, the first solvent is a mixture of deionized water and alcohol. When the above type is satisfied, it has the advantages of being low cost and readily available. In the present invention, the ratio of deionized water to alcohol is not particularly limited, for example, the volume ratio of deionized water to alcohol is 1:2.5 to 3.5.

[0043] In the present invention, the volume ratio of compound B to the first solvent is 1:2.5 to 3.5, and when this range is satisfied, the inhibitory properties on the obtained copolymer hydrate are further improved.

[0044] According to the present invention, the initiator is at least one selected from potassium persulfate, ammonium persulfate, and sodium persulfate.

[0045] According to the present invention, the amount of the initiator used is 1 to 2 wt%, preferably 1.5 to 2 wt%, based on the total weight of compound A and compound B.

[0046] In the present invention, the reaction is carried out under the protection of nitrogen or an inert gas in order to prevent oxidation of the reactants. In one specific embodiment of the present invention, the introduction time of the nitrogen or inert gas is 20 to 30 minutes.

[0047] The present invention provides exemplary a method for preparing compound A, the method comprising the steps of contacting compound C and compound D in the presence of a second solvent to carry out a second reaction and obtain compound A, Compound C has the structure shown in formula (5), and compound D has the structure shown in formula (6).

[0048] [ka]

[0049] (Here, R1'' is H or C1~C 10 R2'' is an alkyl group, where R2'' is H or an alkyl group of C1-C5, and n'' is an integer from 1 to 10.

[0050] Furthermore, R1'' is an alkyl group from C1 to C5, R2'' is an alkyl group from C1 to C3, and n'' is an integer from 2 to 5. In the present invention, the conditions for the second reaction include a reaction temperature of 20 to 30°C and a reaction time of 1.5 to 3 hours.

[0051] In the present invention, the molar ratio of compound C to compound D is 1:0.8 to 1.2.

[0052] In the present invention, the type of the second solvent is not particularly limited, but is a common choice in the art. For example, it may be dimethyl sulfoxide (DMSO).

[0053] In the present invention, the amount of the second solvent used is not particularly limited; for example, the mass ratio of compound C to the second solvent is 1:90 to 110.

[0054] In the present invention, the method further includes the step of separating, washing, and drying the obtained compound A after the reaction is complete. In the present invention, the washing method is not particularly limited, and for example, it may be washed with anhydrous ethanol. In the present invention, the drying method is not particularly limited, and for example, it may be dried under vacuum conditions at 30 to 50°C for 3 to 5 hours.

[0055] In the present invention, the method of adding compound C, compound D, and the second solvent is not particularly limited, as long as the second solvent can dissolve compound C and compound D. In one specific embodiment of the present invention, compound C is added to the second solvent and stirred until completely dissolved, then compound D is added to carry out the second reaction, where the stirring temperature is 130 to 170°C and the stirring time is 0.1 to 0.5 hours.

[0056] A third aspect of the present invention provides a copolymer prepared by the preparation method described in the second aspect of the present invention.

[0057] A fourth aspect of the present invention provides the use of the copolymer described in the first or third aspect of the present invention as a hydrate kinetic inhibitor.

[0058] In the present invention, a specific method for using the copolymer as a hydrate kinetic inhibitor includes the following:

[0059] The copolymer is mixed with water to obtain an inhibitor solution, where the concentration of the copolymer in the inhibitor solution is 0.5-2 wt%. The process includes adding the inhibitor solution to an oil and gas production well or transport pipeline using a ground injection device to carry out the inhibitory reaction.

[0060] The copolymer of the present invention can be used as a hydrate kinetic inhibitor in the production and transportation of petroleum and gas. It has advantages such as stable properties and a wide range of supercooling tolerances, and its future application potential is promising.

[0061] The present invention will be described in detail below with reference to examples.

[0062] In the following examples and comparative examples, the specific structure of the raw materials is as follows.

[0063] In compound C-1, R1'' is -CH3, In compound C-2, R1'' is -C2H5. In compound D-1, R2'' is -CH3, and n'' is 2. In compound D-2, R2'' is -C2H5, and n'' is 3. In compound B-1, R3' to R8' are all H. In compound B-2, R5' is -CH3, and R3', R4', and R6'~R8' are all H. Vinylcaprolactam, branded LUVICAP-EG and labeled W-3, is purchased from BASF in the United States. Polyvinylpyrrolidone is purchased from BASF in the United States under the brand name K90, and is labeled as W-4.

[0064] The raw materials used in the following examples and comparative examples are all commercially available conventional products.

[0065] In the following examples, the content and weight-average molecular weight of each structural unit of the copolymer are calculated using hydrogen nuclear magnetic resonance spectroscopy.

[0066] 1. Preparation of Compound A Preparation Example 1 S1: 2g of compound C-1 was added to 198g of DMSO and stirred at 150°C for 10 minutes until completely dissolved. Then, the mixture was transferred to room temperature (20°C), 2.64g of compound D-1 was added, and the mixture was reacted for 2 hours to produce a white solid. The molar ratio of compound C-1 to compound D-1 was 1:1.

[0067] S2: The white solid was separated by suction filtration, washed with anhydrous ethanol, and vacuum dried at 40°C for 4 hours to obtain compound A-1. Here, R1' is -CH3, R2' is -CH3, and n' is 2.

[0068] Preparation Example 2 Compound A-2 was prepared according to the method of Preparation Example 1, except that compound C-1 was changed to compound C-2 and compound D-1 was changed to compound D-2. In compound A-2, R1’ is -C2H5, R2’ is -C2H5, and n’ is 2.

[0069] II. Preparation of Copolymer Example 1 1mL of compound B-1, 12mL of deionized water, and 36mL of ethanol were mixed, 0.32g of compound A-1 was added, and after dissolving with ultrasonic waves, 0.241g of potassium persulfate was added to the reaction system. After dissolution, nitrogen was introduced for 20 minutes and reacted at 55 °C for 8 hours. The reaction product was separated by suction filtration to obtain copolymer S-1, and the specific characteristics are shown in Table 2.

[0070] Here, based on the total weight of compound A-1 and compound B-1, the usage amount of compound A-1 is 2wt%, the usage amount of compound B-1 is 98wt%, the first solvent is a mixture of deionized water and ethanol, the volume ratio of deionized water to ethanol is 1:3, the volume ratio of compound B-1 to the first solvent is 1:3, and based on the total weight of compound A-1 and compound B-1, the usage amount of potassium persulfate is 1.5wt%.

[0071] As a result of measuring the structure of copolymer S-1 by infrared spectrum, as shown in Figure 1, at 3434 cm -1 there is a characteristic peak of the amide group, at 2924 cm -1 there is a characteristic peak of the methylene group, at 1724 cm -1 there is a characteristic peak of the carbonyl group in the ester group, at 1633 cm -1 there is a characteristic peak of the carbonyl group in the amide group, at 1535 cm -1The characteristic peak of the six-membered ring is present, indicating successful polymerization of compound A-1 and compound B-1. The hydrogen nuclear magnetic resonance spectrum of copolymer S-1 is shown in Figure 2, where Figure 2 (left) is the complete spectrum obtained in the experiment, and Figure 2 (right) is an enlarged view of the dotted line portion, which is the hydrogen nuclear magnetic resonance spectrum of copolymer S-1. From Figure 2 (right), the content of structural units A and B in copolymer S-1 can be calculated, and the results are shown in Table 2.

[0072] Examples 2-7 Copolymers S-2 to S-7 were prepared according to the method of Example 1, except that the reaction conditions differed from those of Example 1, and the details are shown in Table 1. The characteristics of copolymers S-2 to S-7 are shown in Table 2.

[0073] Example 8 Copolymer S-8 was obtained by replacing compound A-1 with compound A-2 and compound B-1 with compound B-2. Copolymer S-8 was prepared according to the method of Example 1, except that the details are shown in Table 1. The characteristics of copolymer S-8 are shown in Table 2.

[0074] Comparative Example 1 Copolymer S-1 was changed to LUVICAP-EG and labeled as W-1.

[0075] Comparative Example 2 Copolymer S-1 was changed to polyvinylpyrrolidone K90 (PVPk90) and labeled as W-2.

[0076] Comparative Example 3 When copolymer S-1 was replaced with compound B-1, and compound B-1 and compound B-1 were self-polymerized, the reaction did not occur.

[0077] Comparative Example 4 The reaction conditions differed from those of Example 1, and copolymer D-1 was prepared according to the method of Example 1, except that the details are shown in Table 1. The characteristics of copolymer D-1 are shown in Table 2.

[0078] Comparative Example 5 Copolymer D-2 was prepared according to the method of Example 1, but differed in that the equal mass fraction of N-(3-aminopropyl)acrylamide was replaced with compound A-1 to prepare copolymer D-2.

[0079] [Table 1]

[0080] [Table 2]

[0081] Test Example 1: Measurement of Maximum Supercooling (1) Experimental apparatus An apparatus for evaluating the inhibitory properties of copolymer hydrates is shown in Figure 3, and this apparatus includes a methane cylinder 1, a pressure regulating valve 2, a PID valve 3 for adjusting the inlet and outlet pressures to 0-16 MPa, a motor 4, a torque sensor 5, a stirrer 6 with a stirring speed of 0-1000 r / min, a reaction vessel 7 with a volume of 500 mL, a pressure resistance of 20 MPa, and an operating temperature of -20°C to 50°C, a temperature sensor 8 with a measurement range exceeding 600°C and an accuracy of 0.1°C, a pressure sensor 9 with a measurement range of 25 MPa and an accuracy of 0.25%, and a case and data acquisition and processing system 10.

[0082] (2) Test method The testing method includes the following steps:

[0083] S1: The compounds prepared in each example and comparative example were dissolved in deionized water to prepare solutions containing the inhibitors.

[0084] S2: 170 mL of inhibitor solution was added to reaction vessel 7, and it was filled with methane at 8 MPa. The magnetic stirrer was started and the rotation speed was adjusted to 300 r / min, controlling the initial temperature of reaction vessel 7 to 10°C, and the temperature was cooled at a rate of 1°C / d. During the cooling process, changes in temperature, pressure, and torque were monitored over time. When the torque increased rapidly, the temperature and pressure at that time were recorded and recorded as the production pressure P1 and production temperature T0, respectively. The phase equilibrium temperature T1 corresponding to the production pressure P1 was calculated based on the methane hydrate phase equilibrium curve. Maximum supercooling T e =T1-T0. Specific data is shown in Table 3.

[0085] The above process indicates that when the torque increased rapidly, a phase transition occurred in the solution containing the inhibitor, resulting in the formation of solid methane hydrate particles.

[0086] [Table 3]

[0087] The results in Table 3 show that the copolymer of the present invention can withstand a higher degree of supercooling as an inhibitor.

[0088] Test Example 2: Measurement of Induction Time The induction time was measured using the temperature-pressure-torque change method with the apparatus shown in Figure 3. Specifically, the following steps were taken.

[0089] S1: The compounds prepared in each example and comparative example were dissolved in deionized water to prepare a 1 wt% inhibitor solution.

[0090] S2: 170 mL of the inhibitor solution was placed in reaction vessel 7 and cooled to the specified experimental temperature (experimental temperature T = phase equilibrium temperature T0 corresponding to the initial pressure P0 - degree of supercooling). Once the temperature stabilized, methane gas was introduced into reaction vessel 7 and stirred at a rotational speed of 300 r / min after reaching the required experimental pressure (i.e., initial pressure P0). This time was recorded as time 0. Under constant temperature conditions, the change in torque over time was recorded, and the time at which the torque increased rapidly was recorded. This is the torque-temperature rapid change time (induction time T). The system pressure after 1000 min was recorded. This is the pressure P1 at the end of the experiment. The gas consumption n was calculated using PV=nRT, and the specific data is shown in Table 4.

[0091] In the process described above, when methane hydrate is formed, the original inhibitor solution undergoes a phase transition from liquid to solid-liquid phase, resulting in a rapid increase in torque. By measuring the timing of this rapid change in torque, the induction time for methane hydrate nucleation can be determined.

[0092] The amount of hydrate produced is proportional to the amount of gas consumed. The less gas consumed, the less hydrate is produced, resulting in superior inhibitory properties.

[0093] [Table 4]

[0094] The results in Table 4 show that, at various degrees of supercooling, the pressure drop within 1000 min (P1-P0) for each inhibitor system was lower than that of the pure water system, indicating that the addition of all inhibitors inhibited the growth of hydrates. Among these, the copolymer of the present invention exhibits superior growth inhibition properties for hydrates as an inhibitor. Furthermore, the torque-temperature rapid change time (induction time) for each inhibitor system was longer than that of the pure water system, and all showed a certain level of nucleation inhibition ability. Among these, when the copolymer of the present invention was used as the inhibitor, the system induction time was the longest, and it exhibited superior nucleation inhibition properties.

[0095] Furthermore, the experiment revealed that the pressure drop of each inhibitor system at low supercooling temperatures of 5.5°C and 6.5°C was significantly higher than at 7.5°C. This is because, at low supercooling temperatures, the hydrates grow in a funnel shape, making the hydrate film formed at the gas-liquid interface more fragile and thus weakening the effect of inhibiting mass transfer between gas and liquid. At high supercooling temperatures, the hydrate film formed at the gas-liquid interface becomes relatively strong, increasing the resistance of the gas entering the liquid and reducing the pressure drop.

[0096] In summary, the contents of Tables 3 and 4 show that the copolymer provided in this invention can withstand a maximum supercooling degree of 3°C or higher, significantly inhibit the growth of hydrates, and the gas consumption does not exceed 0.22 moles in any case.

[0097] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, several simple modifications can be made to the technical solutions of the present invention, including combining each technical feature in any other suitable manner, and these simple modifications and combinations should also be considered as part of the disclosure of the present invention and all fall within the scope of protection of the present invention. [Brief explanation of the drawing]

[0098] [Figure 1] This is the infrared spectrum of copolymer S-1 prepared in Example 1. [Figure 2] This is the hydrogen nuclear magnetic resonance spectrum of copolymer S-1 prepared in Example 1. [Figure 3] This is a schematic diagram of a device for evaluating the properties of hydrate inhibitors.

Claims

1. A copolymer, The copolymer comprises structural unit A and structural unit B, wherein structural unit A is derived from an unsaturated monomer containing pyrimidone and multiple hydrogen bonds, and structural unit B is derived from an unsaturated monomer containing pyrrolidone. A copolymer characterized in that, based on the total weight of the copolymer, the content of structural unit A is 0.5 to 10 wt%, and the content of structural unit B is 90 to 99.5 wt%.

2. The copolymer according to claim 1, wherein, based on the total weight of the copolymer, the content of structural unit A is 1 to 3 wt%, and the content of structural unit B is 97 to 99 wt%.

3. The copolymer according to claim 1 or 2, wherein the structural unit A has the structure shown in formula (1), and the structural unit B has the structure shown in formula (2). 【Chemistry 1】 (Here, R １ is H or C １ ~C １０ It is an alkyl group, R ２ is H or C １ ~C ５ It is an alkyl group, n is an integer from 1 to 10, and R ３ ~R ８ are each independently H or an alkyl group of C １ ~C １０ .)

4. R １ C １ ~C ５ It is an alkyl group, Preferably, R ２ C １ ~C ３ It is an alkyl group, Preferably, n is an integer between 2 and 5. Preferably, R ３ ~R ８ These are, independently, H or C １ ~C ５ The copolymer according to claim 3, characterized in that it is an alkyl group.

5. A method for preparing copolymers, The method includes the step of contacting compound A and compound B in the presence of a first solvent and an initiator to carry out a first reaction and obtain the copolymer. Compound A is an unsaturated monomer containing pyrimidone and multiple hydrogen bonds, and compound B is an unsaturated monomer containing pyrrolidone. A method for preparing a copolymer, characterized in that, based on the total weight of compound A and compound B, the amount of compound A used is 0.5 to 10 wt%, and the amount of compound B used is 90 to 99.5 wt%.

6. The preparation method according to claim 5, wherein, based on the total weight of compound A and compound B, the amount of compound A used is 1 to 3 wt%, and the amount of compound B used is 97 to 99 wt%.

7. The preparation method according to claim 5 or 6, wherein compound A has the structure shown in formula (3), and compound B has the structure shown in formula (4). 【Chemistry 2】 (Here, R １ ' is H or C １ ~C １０ It is an alkyl group, R ２ ' is H or C １ ~C ５ It is an alkyl group, n' is an integer from 1 to 10, and R ３ '~R ８ ' are, independently, H or C １ ~C １０ It is an alkyl group.

8. The preparation method according to any one of claims 5 to 7, characterized in that the conditions for the first reaction include a reaction temperature of 40 to 70°C, preferably 50 to 60°C, and a reaction time of 6 to 10 hours, preferably 7 to 9 hours.

9. The first solvent is at least one selected from deionized water, ethanol, and methanol. Preferably, the preparation method according to any one of claims 5 to 8, wherein the initiator is at least one selected from potassium persulfate, ammonium persulfate, and sodium persulfate.

10. The preparation method according to any one of claims 5 to 9, characterized in that the amount of the initiator used is 1 to 2 wt% based on the total weight of compound A and compound B.

11. A copolymer prepared by the preparation method described in any one of claims 5 to 10.

12. Use as a hydrate kinetic inhibitor of the copolymer according to any one of claims 1 to 4 and 11.

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