Bifunctional hydrate inhibitor and preparation method thereof

Abstract

This invention discloses a bifunctional hydrate kinetic inhibitor of Formula I with an average number-average molecular weight of 1000-10000, its preparation method, and its application. The bifunctional hydrate kinetic inhibitor is an amphiphilic block copolymer, which, compared to conventional inhibitors, exhibits higher supercooling, better inhibition effect, and requires a smaller dosage (typically 0.1-0.5 wt%). It also possesses anti-agglomeration properties, preventing the aggregation of already formed hydrates and reducing the risk of blockage. It is suitable for three-phase systems (oil, gas, and water) or two-phase systems (oil-water or gas-water), and can be applied to inhibit hydrate formation during oil and gas extraction, processing, and transportation, showing broad application prospects. R1 is (CH2)m1, where m1 is an integer, m1 = 1-5; R2 is (CH2)m2, where m2 is an integer, m2 = 1-4; m and n are integers, m = 10-50, n = 10-200.

Description

Technical fields:

[0001] This invention relates to the field of hydrate inhibitor technology, specifically to a novel bifunctional hydrate inhibitor and its preparation method. Background technology:

[0002] Natural gas hydrates are non-stoichiometric cage-like complexes, resembling ice in appearance. The formation of gas hydrates during natural gas transportation and processing can cause a series of hazards, such as clogging gas pipelines, blocking blowout preventers and damaging deep-sea mining platform facilities. In extreme cases, it can even cause pipeline rupture, leading to significant casualties, economic losses, and environmental damage. Therefore, effectively preventing hydrate formation and avoiding flow safety accidents caused by hydrate blockage is a crucial and urgent issue for the entire oil and gas industry.

[0003] Currently, injecting additives into pipelines is a relatively effective and economical method for preventing hydrate formation. These chemical additives are therefore called hydrate inhibitors. Thermodynamic inhibitors (THIs) prevent hydrate formation by altering the thermodynamic conditions of hydrate formation, such as lowering the hydrate formation temperature or increasing the formation pressure. They can disrupt the hydrogen bonding interactions in hydrate formation. However, THIs need to be injected at a concentration of 10%-50% to be effective, which is not only costly but also severely environmentally damaging. In addition, THIs are usually volatile and enter oil and gas, increasing refining costs and chemical losses. Based on environmental, technological, and economic considerations, THIs are gradually being replaced by new low-dose hydrate inhibitors (including kinetic inhibitors and anti-polymerization agents).

[0004] Anti-agglomeration agents (AAs) disperse hydrate particles and prevent their aggregation, allowing them to exist in a flowable slurry state within pipelines, thus achieving hydrate control. However, the limited dispersibility and environmental toxicity of AAs restrict their industrial application. Kinetic inhibitors, on the other hand, do not alter the thermodynamic conditions for hydrate formation. They achieve their inhibitory effect by delaying or preventing hydrate nucleation or growth, ensuring sufficient time for the pipeline fluid to traverse the hydrated zone.

[0005] Kinetic inhibitors are typically water-soluble polymers, some of which are already in industrial use, including polyvinylpyrrolidone (PVP) and polyvinylcaprolactam (PVCap), and are often used as a standard for evaluating the performance of other inhibitors. Although they can effectively inhibit the formation or growth of hydrates, their application is not widespread because: 1. they are not suitable for environments with high supercooling; 2. they cannot effectively prevent hydrate aggregation after formation. Therefore, modifying them to improve their inhibitory and anti-aggregation properties is a pressing issue. The applicant's previous research, CN 118165155 A, discloses a novel hydrate kinetic inhibitor that is an amphiphilic block copolymer, synthesized from a hydrophilic segment of an alkylamide and a hydrophobic segment of a lactone / lactide monomer; the molar ratio of alkylamide to lactone / lactide monomer used in the synthesis of the novel hydrate kinetic inhibitor is 1:1; the average molecular weight of the novel hydrate kinetic inhibitor, Mn, is 1000–10000; the novel hydrate kinetic inhibitor has the following structure: However, further improvements are needed. Summary of the Invention:

[0006] The purpose of this invention is to provide a novel bifunctional hydrate inhibitor and its preparation method.

[0007] The present invention is achieved through the following technical solutions:

[0008] Equation I represents bifunctional hydrate kinetic inhibitors with average number-average molecular weights ranging from 1000 to 10000:

[0009]

[0010] Where R1 is (CH2)m1, m1 is an integer, m1 = 1 to 5; R2 is (CH2)m2, m2 is an integer, m2 = 1 to 4; m and n are integers, m = 10 to 50, n = 10-200.

[0011] The bifunctional hydrate kinetic inhibitor is an amphiphilic block copolymer comprising a hydrophilic lactam polymer segment and a hydrophobic lactone / lactolide polymer segment, wherein the hydrophilic lactam polymer segment and the hydrophobic lactone / lactolide polymer segment communicate with each other via... The molar ratio of lactam monomer to lactone / lactide monomer for synthesizing bifunctional hydrate kinetic inhibitors was 1:1-4.

[0012] The preparation method of the bifunctional hydrate kinetic inhibitor includes the following steps:

[0013] 1) The vinyl lactam monomer, chain initiator azobisisobutyronitrile, and mercaptoethanol were stirred and mixed and dissolved in a solvent. The mixture was reacted at 30-90°C for 6-40 hours under a nitrogen atmosphere, dried by rotary evaporation, and cooled to room temperature. The product was dissolved in tetrahydrofuran and then precipitated with n-hexane. The precipitate was washed with a large amount of anhydrous diethyl ether, filtered, and dried to obtain hydroxyl-terminated polyvinyl lactam.

[0014] 2) Hydroxyl-terminated modified polyvinyl lactam, lactone / lactolide, and stannous octoate catalyst were dissolved in a solvent under stirring and reacted at 110–130 °C for 6–40 hours under a nitrogen atmosphere. The reaction solution was then dried by rotary evaporation and cooled to room temperature. The resulting product was dissolved in tetrahydrofuran and precipitated with n-hexane. The precipitate was washed with a large amount of anhydrous diethyl ether, filtered, and dried to obtain a novel inhibitor. The molar ratio of lactam monomer to lactone / lactolide monomer in the synthesis of the bifunctional hydrate kinetic inhibitor was 1:1–4.

[0015] Preferably, in step 1), the amount of chain initiator is 0.5wt% to 2.0wt% of the amount of solvent, the amount of solvent is 1 to 20 times the volume of the vinyl lactam monomer, and the solvent is isopropanol.

[0016] Preferably, in steps 1) and 2), the amount of n-hexane used is 2 to 10 times the volume of tetrahydrofuran.

[0017] Preferably, in step 2), the amount of stannous octoate is 0.5wt% to 2.0wt% of the amount of solvent used, the amount of solvent is 1 to 20 times the volume of the vinyl lactam monomer, and the solvent is toluene.

[0018] This invention also protects the application of the bifunctional hydrate kinetic inhibitor, which is used to inhibit the formation of hydrates in three-phase systems of oil, gas, and water, or two-phase systems of oil, water, or gas and water. In use, it is first prepared as an aqueous solution with a concentration of 0.1 wt% to 0.5 wt%, applicable pressure of 1 to 25 MPa, and temperature of -25 to 25°C.

[0019] The beneficial effects of this invention are as follows: This invention is a novel bifunctional hydrate inhibitor, which has a higher supercooling degree and better inhibition effect compared with general traditional inhibitors. It requires a smaller dosage, generally about 0.1 to 0.5 wt%. It also has anti-agglomeration properties, which can prevent the aggregation of formed hydrates and reduce the risk of blockage. The dosage is much smaller than that of traditional thermodynamic inhibitors, which greatly reduces reagent costs. It is suitable for three-phase systems of oil, gas and water or two-phase systems of oil and water or gas and water. It can be used to inhibit the formation and aggregation of hydrates in the process of oil and gas extraction, processing and transportation, and has broad application prospects. Attached image description:

[0020] Figure 1This is an example diagram of the time-temperature and time-pressure curves during the hydrate formation process in Example 1 of the present invention, using a 0.5wt% PVCAP-b-PVL solution.

[0021] Figure 2 This is an example diagram of the time-torque curve during the hydrate formation process in Example 1 of the present invention, using a 0.5wt% PVCAP-b-PVL solution. Detailed implementation method:

[0022] The following is a further description of the invention, but not a limitation thereof.

[0023] The experimental equipment of this invention is a visual high-pressure stirring test device, mainly composed of a sapphire high-pressure reactor, a mechanical stirrer, a torque detector, a low-temperature air bath, temperature and pressure sensors, a vacuum pump, a high-pressure gas cylinder, and a data acquisition system. The sapphire high-pressure reactor has a maximum working pressure of 11 MPa and a working temperature range of -30 to 80°C. The pressure inside the sapphire high-pressure reactor can be freely adjusted via a gas valve. The low-temperature air bath provides a temperature environment of -30 to 80°C for the reactor jacket. The data acquisition system collects and stores parameters such as pressure, temperature, torque, and rotation speed inside the reactor in real time. The formation of hydrates can be judged by sudden changes in temperature or pressure during the reaction or directly observed. After the reaction begins, the point where the pressure inside the reactor drops sharply (i.e., the pressure decreases deviates from the original trend) is the starting point of hydrate formation. The maximum supercooling is the temperature corresponding to this point minus the thermodynamic equilibrium temperature of the hydrate corresponding to this pressure. A constant stirring rate is maintained. When the temperature inside the sapphire high-pressure reactor is constant, methane gas is introduced until the pressure inside the reactor reaches the set value, at which point the inlet valve is closed. Then, the temperature inside the reactor is lowered to below the hydrate formation temperature at that pressure using a constant cooling rate (e.g., 1°C / h). The maximum supercooling the solution can withstand is the hydrate formation temperature minus the corresponding thermodynamic equilibrium temperature during this process. The effectiveness of the novel inhibitor can be quantified based on the maximum supercooling that the solution with the inhibitor added can withstand. The greater the maximum supercooling, the better the inhibitory effect.

[0024] The anti-polymerization experimental equipment was the aforementioned visual high-pressure stirring test device, which used a motor for high-intensity stirring and was equipped with a torque detector. The reactor was first cooled to the experimental temperature and a certain amount of methane gas was introduced. This temperature was then maintained while stirring continued until hydrates began to form. At this point, the pressure decreased and the torque increased. The longer the time it took for hydrates to form, the better the inhibitor's effect; the smaller the torque after hydrate formation, the better the inhibitor's anti-polymerization effect.

[0025] Specific implementation process:

[0026] Before the experiment, the reactor was thoroughly cleaned with deionized water three to five times, and then the reactor and experimental piping system were purged with nitrogen to ensure the system was dry. The reactor was then evacuated, and 40 mL (approximately 1 / 3 of the sapphire reactor's volume) of deionized water or a novel inhibitor solution was introduced. To remove air from the reactor, 1 MPa of 99.99% pure methane gas was introduced, followed by evacuation, repeating this process three times. A constant stirring rate of 800 rpm was maintained. When the temperature inside the sapphire high-pressure reactor reached 20°C, methane gas was introduced until the pressure inside the reactor reached a constant 10.0 MPa, at which point the inlet valve was closed. Then, the temperature inside the reactor was lowered from 20°C to -10°C at a rate of 1°C / h. Temperature and pressure change curves were used to determine whether hydrates were formed.

[0027] Before the anti-polymerization experiment, the reactor was thoroughly cleaned with deionized water three to five times, followed by purging of the reactor and experimental piping system with nitrogen to ensure the system was dry. The reactor was then evacuated, and 40 mL (approximately 1 / 3 of the sapphire reactor's volume) of an oil-water mixture (7:3 oil-water ratio, inhibitor concentration 0-0.5% of the aqueous phase volume) was introduced. To remove air from the reactor, 1 MPa of 99.99% pure methane gas was introduced, followed by evacuation, repeating this process three times. A constant stirring speed of 800 rpm was maintained. When the temperature inside the sapphire high-pressure reactor reached 3°C, methane gas was introduced until the pressure inside the reactor reached a constant 8.0 MPa, at which point the inlet valve was closed. Then, mechanical stirring was started at 800 rpm, maintaining the reactor temperature at 3°C. Changes in gas pressure and torque were observed to determine whether hydrates were formed.

[0028] Example 1: Preparation of PVCAP-b-PVL, an amphiphilic block copolymer hydrate kinetic inhibitor

[0029] The PVCAP-b-PVL structure is shown below:

[0030]

[0031] Includes the following steps:

[0032] 0.719 mmol of chain initiator azobisisobutyronitrile, 71.9 mmol of vinylcaprolactam, and 3.6 mmol of mercaptoethanol were weighed and dissolved in 100 mL of isopropanol. The solution was added to a 250 mL three-necked flask, stirred until dissolved, sealed with a rubber stopper, and then evacuated under vacuum and nitrogen gas three times. The reaction was then carried out at 85 °C for 20 hours under a nitrogen atmosphere. The reaction solution was dried by rotary evaporation at 50 °C and cooled to room temperature. The resulting product was dissolved in tetrahydrofuran and then precipitated with n-hexane. The precipitate was washed with a large amount of anhydrous diethyl ether, filtered, and dried to obtain hydroxyl-terminated modified polyvinylcaprolactam.

[0033] Weigh 1 mmol of hydroxyl-terminated modified polyvinylcaprolactam, 1 mmol of γ-valerate, and 10 mmol of stannous octoate, dissolve them in toluene, add the solution to a 250 mL three-necked flask, stir until dissolved, seal with a rubber stopper, and evacuate under nitrogen three times. React at 110 °C for 24 hours under a nitrogen atmosphere. Dry the reaction solution by rotary evaporation and cool to room temperature. Dissolve the obtained product in tetrahydrofuran, precipitate with n-hexane, wash the precipitate with a large amount of anhydrous diethyl ether, filter, and dry to obtain a novel inhibitor.

[0034] Detection and determination: The above inhibitors were prepared into aqueous solutions of 0.1 wt%, 0.25 wt%, and 0.5 wt%. The maximum supercooling degree of hydrate formation and the maximum torque during hydrate formation were determined in the inhibitor-containing system. The experimental results are shown in Table 4.

[0035] The gel permeation chromatography (GPC) data of the novel bifunctional hydrate inhibitor PVCAP-b-PVL are shown in Table 1:

[0036] Table 1 Number-mean molecular weight and polydispersity index

[0037]

[0038] Example 2: Preparation of PVP-b-PVL, an amphiphilic block copolymer hydrate kinetic inhibitor

[0039] The PVP-b-PVL structure is shown in the figure below.

[0040]

[0041] The preparation method is the same as in Example 1, except that the hydrophilic monomer vinylcaprolactam is replaced with vinylpyrrolidone. The gel permeation chromatography (GPC) data of the novel bifunctional hydrate inhibitor PVP-b-PVL are shown in Table 2.

[0042] Table 2 Number-mean molecular weight and polydispersity index

[0043]

[0044] Detection and determination: The above-mentioned inhibitors were prepared into aqueous solutions of 0.1 wt%, 0.25 wt%, and 0.5 wt%. The maximum supercooling degree of hydrate formation and the maximum torque during hydrate formation were determined in the inhibitor-containing system. The experimental results are shown in Table 4.

[0045] Comparative Example 1: Preparation of Unmodified Polyvinylcaprolactam (PVCAP)

[0046] Includes the following steps:

[0047] 0.719 mmol of azobisisobutyronitrile (AIBN), 71.9 mmol of vinylcaprolactam (VCL), and 100 mL of isopropanol were weighed sequentially into a 250 mL three-necked flask. The mixture was stirred until dissolved, sealed with a rubber stopper, and then evacuated under vacuum and nitrogen gas three times. The reaction was carried out at 85 °C for 20 hours under a nitrogen atmosphere. The reaction solution was dried by rotary evaporation at 50 °C and cooled to room temperature. The resulting product was dissolved in tetrahydrofuran and then precipitated with n-hexane. The precipitate was washed with a large amount of anhydrous diethyl ether, filtered, and dried to obtain PVCAP.

[0048] Detection and determination: The above inhibitors were prepared into aqueous solutions of 0.1 wt%, 0.25 wt%, and 0.5 wt%. The maximum supercooling degree of hydrate formation and the maximum torque during hydrate formation were determined in the inhibitor-containing system. The experimental results are shown in Table 4.

[0049] Comparative Example 2:

[0050] Pure water was added to the reactor, and the maximum supercooling and maximum torque of hydrate formation in the additive-free system were measured.

[0051] Comparative Example 3:

[0052] Preparation of amphiphilic block copolymer (PMAM-b-PCL)

[0053] The preparation method is the same as in Example 1, except that the hydrophilic monomer vinylcaprolactam is replaced with methacrylamide and γ-valerolactone is replaced with ε-caprolactone.

[0054] Includes the following steps:

[0055] 0.719 mmol of chain initiator azobisisobutyronitrile, 71.9 mmol of methacrylamide, and 3.6 mmol of mercaptoethanol were weighed and dissolved in 100 mL of isopropanol. The solution was added to a 250 mL three-necked flask, stirred until dissolved, sealed with a rubber stopper, and then evacuated under vacuum and nitrogen gas three times. The reaction was then carried out at 85 °C for 20 hours under a nitrogen atmosphere. The reaction solution was dried by rotary evaporation at 50 °C and cooled to room temperature. The resulting product was dissolved in tetrahydrofuran and then precipitated with n-hexane. The precipitate was washed with a large amount of anhydrous diethyl ether, filtered, and dried to obtain hydroxyl-terminated modified polymethacrylamide.

[0056] Weigh 1 mmol of hydroxyl-terminated modified polymethacrylamide, 1 mmol of ε-caprolactone, and 10 mmol of stannous octoate, dissolve them in toluene, add the solution to a 250 mL three-necked flask, stir until dissolved, seal with a rubber stopper, and evacuate under nitrogen three times. React at 110 °C for 24 hours under a nitrogen atmosphere. Dry the reaction solution by rotary evaporation and cool to room temperature. Dissolve the obtained product in tetrahydrofuran, precipitate with n-hexane, wash the precipitate with a large amount of anhydrous diethyl ether, filter, and dry to obtain a novel inhibitor.

[0057] The gel permeation chromatography (GPC) data of the novel hydrate kinetic inhibitor PMAM-b-PCL are shown in Table 3:

[0058] Table 3 Number-mean molecular weight and polydispersity index

[0059]

[0060] Detection and determination: The above inhibitors were prepared into aqueous solutions of 0.25 wt%, 0.5 wt%, and 1 wt%, and the maximum supercooling of hydrate formation in the inhibitor-containing system was determined. The experimental results are shown in Table 4.

[0061] Table 4 Comparison of Concentration, Maximum Subcooling Temperature, and Maximum Torque

[0062]

[0063]

[0064] The above specific embodiments are merely explanations of the present invention and are not intended to limit the present invention. After reading this specification, those skilled in the art can make modifications to these embodiments without contributing any inventive step, but as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. The application of the bifunctional hydrate kinetic inhibitor shown in Formula I, with an average number-average molecular weight of 1000–10000, characterized in that, It is used to suppress the formation of hydrates in three-phase oil-gas-water systems and two-phase oil-water or gas-water systems; Where R1 is (CH2)m1, m1 is an integer, m1 = 1 to 5; R2 is (CH2)m2, m2 is an integer, m2 = 1 to 4; m and n are integers, m = 10 to 50, n = 10-200.

2. The application of the bifunctional hydrate kinetic inhibitor according to claim 1, characterized in that, When using, first prepare an aqueous solution. The concentration of the bifunctional hydrate kinetic inhibitor is 0.1wt% to 0.5wt%, the applicable pressure is 1 to 25 MPa, and the temperature is -25 to 25℃.

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