A multidimensional synergistic composite promoter for CO2 hydrate formation and its preparation method

Abstract

This invention discloses a multidimensional synergistic composite promoter for CO2 hydrate formation and its preparation method. The multidimensional synergistic composite promoter provided by this invention comprises the following components: a nanofluid dynamics promoter and an ionic liquid thermodynamic promoter; the nanoparticles in the nanofluid are one or more of silica, graphite, and graphene oxide; in the ionic liquid, the cation is a nitrogen-containing organic base, and the anion is a weak acid containing a carboxyl functional group or its derivative. This invention constructs a multidimensional synergistic composite promoter by ultrasonically dispersing and mixing the above two promoters. This promoter can effectively reduce the gas-liquid interfacial tension, increase CO2 solubility and diffusion coefficient, and provide a large number of nucleation sites and enhance heat transfer, thereby significantly shortening the CO2 hydrate formation induction time and increasing the formation rate and gas storage capacity.

Description

Technical Field

[0001] This invention relates to the field of CO2 hydrate preparation technology, specifically to a multidimensional synergistic composite promoter for CO2 hydrate generation and its preparation method. Background Technology

[0002] Currently, carbon sequestration technologies are mainly divided into geological sequestration and marine sequestration. Among them, marine solid CO2 sequestration technology based on hydrate method has gradually become the research focus in this field because of its wide distribution of sequestration sites and the good stability, high mechanical strength and extremely high gas storage density of the generated CO2 hydrate itself.

[0003] Solid-state hydrate storage technology is a highly promising and environmentally friendly green process. Theoretically, 1m 3 Hydrates can store 170m 3 Using this gas for marine CO2 sequestration can greatly improve sequestration efficiency. However, the actual formation of CO2 hydrates is hampered by the required low-temperature and high-pressure conditions, as well as problems such as strong randomness in nucleation, long induction time, and slow growth rate, which seriously hinder its industrial application.

[0004] Traditional methods for promoting CO2 hydrate formation include stirring, aeration, spraying, and adding accelerators. While these methods are effective, their high energy consumption, complex operation, and significant environmental impact make them unsuitable for practical application.

[0005] Current research mainly focuses on the kinetics and thermodynamics of CO2 hydrate formation. By adding kinetic and thermodynamic promoters, the microstructure of the aqueous solution is altered, and gas-liquid contact is promoted at the molecular scale, thereby enhancing the formation of CO2 hydrate.

[0006] CN119020078A discloses a promoter for rapid phase transition of gas hydrates composed of dimethylcyclohexane and sodium dodecyl sulfate. However, dimethylcyclohexane, as a thermodynamic promoter, may participate in the hydration reaction as a second guest, which may reduce the gas storage capacity of the hydrate. Sodium dodecyl sulfate, as a kinetic promoter, generates a large amount of persistent foam during the gas recovery process, causing environmental pollution problems, and has poor reusability, making it unsuitable for large-scale engineering applications. CN120361712A discloses a promoter composed of water, sucralose, and graphene oxide dispersion. However, graphene oxide is prone to agglomeration, which reduces the gas-liquid contact area and covers nucleation sites, thereby reducing mass transfer efficiency and promoting effect. Furthermore, excessively high sucralose concentrations can lead to increased solution viscosity, increasing gas diffusion resistance, which is detrimental to hydrate formation. CN116656319A discloses the use of tetrafluoroethane (R134a) as a promoter, but all its embodiments are carried out at low temperatures of -2 to 3°C. Maintaining this temperature in actual industrial scale would consume extremely high energy, be economically unfeasible, and have an unclear promoting effect on CO2 hydrates.

[0007] It is evident that existing methods for sequestering carbon dioxide using hydrates suffer from problems such as long nucleation induction time, slow growth rate, low sequestration capacity, and the high cost, complex preparation process, and significant environmental impact of existing promoters. Therefore, in order to form hydrates more quickly and achieve stable and large-scale sequestration of CO2 in the ocean, it is particularly urgent to develop novel green and environmentally friendly composite promoters that combine thermodynamic and kinetic advantages. Summary of the Invention

[0008] The purpose of this invention is to provide a multidimensional synergistic composite promoter for carbon dioxide hydrate that combines thermodynamic and kinetic advantages and is environmentally friendly. This composite promoter can shorten the induction time for CO2 hydrate formation and improve the growth rate and CO2 sequestration capacity of CO2 hydrate.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] In a first aspect, the present invention provides a multidimensional synergistic composite promoter for CO2 hydrate generation, comprising the following components: a nanofluid dynamics promoter and an ionic liquid thermodynamics promoter; The nanofluid dynamics promoter is a dispersion of nanoparticles; The nanoparticles are one or more of silicon dioxide, graphite, and graphene oxide. The ionic liquid thermodynamic accelerator is a solution containing cations and anions; The cation donor is a nitrogen-containing organic base; The anion donor is a weak acid containing a carboxyl functional group or its derivative.

[0011] In this invention, the nanofluid dynamics promoter provides additional heterogeneous nucleation sites without participating in the CO2 hydrate formation reaction itself, reduces gas-liquid interfacial tension, increases solubility and diffusion coefficient in the liquid phase, and promotes gas-liquid contact at the molecular scale, thereby significantly shortening the induction time for CO2 hydrate formation. Furthermore, its excellent thermal conductivity can promptly remove the heat released during CO2 hydrate formation, further accelerating its formation. The ionic liquid thermodynamic promoter, by occupying the cavities of the CO2 hydrate cage structure, can shift the phase equilibrium curve to lower pressures and higher temperatures, fundamentally altering the phase equilibrium conditions of CO2 hydrate and allowing it to form under milder conditions.

[0012] The particle size of the nanoparticles is 20~100 nm; specifically, it can be 60 nm.

[0013] The mass fraction of nanoparticles in the nanofluid dynamics promoter is 0.3~1.0 wt%. Specifically, it can be 0.7 wt%.

[0014] The nitrogen-containing organic base is one or more of tetraethylammonium hydroxide, choline, and 1-methylimidazole; The weak acid containing a carboxyl functional group and its derivatives are one or more of aspartic acid, alanine, and trifluoroacetic acid. The molar ratio of the cation to the anion is 1:1.

[0015] The mass ratio of the nanofluid dynamics promoter to the ionic liquid thermodynamics promoter is 1:(3-9), preferably 1:5.

[0016] Secondly, the present invention provides a method for preparing the above-mentioned multidimensional synergistic composite promoter, comprising the following steps: S1. Add nanoparticles to water and disperse them to obtain a nanofluid dynamics promoter; S2. Mix the anion donor and the cation donor to obtain the ionic liquid thermodynamic promoter; S3. Mix and disperse the nanofluid dynamics promoter with the ionic liquid thermodynamics promoter to obtain a multidimensional synergistic composite promoter.

[0017] In step S1, the dispersion is ultrasonic dispersion; the conditions for ultrasonic dispersion are: power of 1000w, ultrasonic setting of 2s on and 5s off, and ultrasonic time of 5~45min.

[0018] In step S2, the mixing process includes: adding anion donor dropwise to a solvent containing cation donor under ice-water bath conditions, stirring, and obtaining a crude product; and rotary evaporating the crude product under reduced pressure to obtain an ionic liquid thermodynamic promoter. The solvent is anhydrous ethanol; The stirring conditions are: temperature 20~30℃, speed 100~250 rpm, and time 5~6h.

[0019] The conditions for vacuum rotary evaporation are: vacuum degree of 0.05~0.1 MPa, temperature of 60~80℃, rotation speed of 80~150 rpm, and time of 2~5 h.

[0020] In step S3, the conditions for ultrasonic dispersion are: ultrasonic setting is 2s on and 5s off, and ultrasonic time is 30~60min.

[0021] Thirdly, the present invention provides a method for sequestering carbon dioxide using marine hydrates, employing the aforementioned multidimensional synergistic composite promoter.

[0022] The conditions for sealing are: temperature 0~15℃ and pressure 3~15 MPa.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) This invention prepares a multidimensional synergistic composite promoter by selecting nanofluids with good surface effects, size effects and adsorption properties, and modifying them with novel ionic liquids prepared with different anions and cations. The promoter can regulate the interaction between CO2 molecules and H2O molecules, thereby forming crystal nuclei exceeding the critical size to induce CO2 hydrate nucleation, further shortening the induction time of CO2 hydrate formation, and improving the growth rate of CO2 hydrate and the amount of CO2 sequestered.

[0024] (2) In the composite promoter of this invention, the kinetic promoter promotes gas-liquid contact at the molecular scale by providing additional heterogeneous nucleation sites, while the thermodynamic promoter fundamentally changes the phase equilibrium conditions of CO2 hydrate by occupying the cavity of the hydrate cage structure, allowing it to be generated under milder conditions. The multidimensional synergistic composite promoter formed by the coupling of the two achieves synergistic effect, which can shorten the CO2 hydrate induction time by more than 36% compared with the pure water system and increase the CO2 hydrate gas storage capacity by more than 21%.

[0025] (3) The nanofluid materials and ionic liquid raw materials selected in this invention are widely available and inexpensive, with low production costs and potential for large-scale application; at the same time, they also have good biocompatibility and biodegradability, are environmentally friendly, and the entire system does not produce toxic or harmful substances during preparation and use, which meets the requirements of green chemistry and has significant environmental friendliness.

[0026] (4) The carbon dioxide hydrate multidimensional synergistic composite promoter of the present invention can still maintain a high-efficiency promoting effect under the conditions of 0~15℃ and 3~15 MPa, which is in line with the marine environment for large-scale and stable CO2 sequestration. Moreover, its components are compatible with the marine environment and will not introduce additional ecological risks, providing a reliable technical solution for safe and efficient CO2 marine sequestration. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0029] Unless otherwise specified, all reagents, materials, instruments, etc. used in the following examples are commercially available.

[0030] Example 1 This embodiment provides a method for preparing a multidimensional synergistic composite promoter for carbon dioxide hydrate, the specific preparation steps of which are as follows: S1. Accurately weigh 0.5 g of hydrophilic SiO2 nanoparticles with a particle size of 60 nm, add 99.5 g of deionized water, mix and place in an ultrasonic instrument, sonicate for 30 min in a pulse mode with 2 s working and 5 s intermittent, to obtain nano-SiO2 fluid.

[0031] S2. Accurately weigh 13.31 g of aspartic acid and place it in a round-bottom flask. Add an appropriate amount of deionized water and stir until completely dissolved. Add a magnetic stir bar. Measure 58.90 g of tetraethylammonium hydroxide and transfer it to a constant-pressure dropping funnel for later use.

[0032] S3. Place the round-bottom flask in a container containing an ice-water mixture for an ice-water bath; fix the container above the magnetic stirrer and install a constant-pressure dropping funnel above the round-bottom flask.

[0033] S4. Turn on the magnetic stirrer and control the speed at 300 rpm to mix the liquid evenly. Add tetraethylammonium hydroxide to aspartic acid dropwise.

[0034] S5. After the addition is complete, rinse the inner wall of the dropping funnel 5 times with deionized water to ensure that all reactants are transferred to the reaction system.

[0035] S6. After the reaction system gradually returns to room temperature (20℃), continue stirring for 6 hours to obtain a crude ionic liquid.

[0036] S7. Maintain the vacuum degree of the rotary evaporator at 0.08 MPa, then perform reduced pressure rotary evaporation at 65℃ for 5 h, controlling the rotation speed at 120 rpm to remove solvent and water, to obtain tetraethylammonium hydroxide aspartate ([N 2222 [Asp]) Ionic liquids.

[0037] S8. Take the [N] prepared above. 2222 2.5 g of [Asp] ionic liquid was added to nano-SiO2 fluid. The mixture was placed in an ultrasonic instrument and ultrasonically treated for 30 min in a pulse mode with a 2 s working time and a 5 s interval, finally obtaining 0.5 wt% 60 nm SiO2 and [N 2222 [Asp] A multidimensional synergistic composite promoter composed of ionic liquids.

[0038] Preparation of CO2 hydrate: The reactor lining was washed three times with deionized water to ensure it was clean and dry. The aforementioned multidimensional synergistic composite promoter was then added, the reactor lid was closed, and a tight seal was maintained to ensure good airtightness. Gas was injected to 0.5 MPa and then depressurized. The air inside the reactor was purged three times, and a vacuum was continuously applied for 5 minutes. Once the temperature inside the reactor dropped to the set reaction temperature of 3°C, this temperature was maintained constant for 3 hours. When injecting CO2 gas, the pressure at both ends was kept equal or differed by 0.1–0.2 MPa. Once the pressure inside the reactor reached 5 MPa, this pressure was maintained constant. The synthesis was considered complete when the reaction lasted for 5 hours (pressure drop rate ≤ 0.1 MPa / h), the experiment was stopped, and the data were recorded.

[0039] Example 2 This embodiment provides a method for preparing a multidimensional synergistic compound promoter for carbon dioxide hydrate. Unlike Example 1, the ionic liquid cation donor in this embodiment is choline, and the anion donor is alanine. The specific preparation steps are as follows: S1. Accurately weigh 0.5 g of hydrophilic SiO2 nanoparticles with a particle size of 60 nm, add 99.5 g of deionized water, mix them in an ultrasonic instrument, and ultrasonically treat them for 30 min in a pulse mode with a 2 s working time and a 5 s interval to obtain nano-SiO2 fluid.

[0040] S2. Accurately weigh 8.91 g of alanine and place it in a round-bottom flask. Add an appropriate amount of deionized water and stir until completely dissolved. Add a magnetic stir bar. Measure 41.67 g of choline and transfer it to a constant-pressure dropping funnel for later use.

[0041] S3. Place the round-bottom flask in a container containing an ice-water mixture for an ice-water bath; fix the container above the magnetic stirrer and install a constant-pressure dropping funnel above the round-bottom flask.

[0042] S4. Turn on the magnetic stirrer and control the speed at 300 rpm to mix the liquid evenly. Add choline to the lysine slowly dropwise.

[0043] S5. After the addition is complete, rinse the inner wall of the dropping funnel 5 times with deionized water to ensure that all reactants are transferred to the reaction system.

[0044] S6. After the reaction system gradually returns to room temperature (20℃), continue stirring for 6 h to obtain crude ionic liquid.

[0045] S7. Maintain the vacuum of the rotary evaporator at 0.06 MPa, and then perform reduced pressure rotary evaporation at 60℃ for 4 h, with the rotation speed controlled at 150 rpm to remove solvent and water, to obtain choline alanine salt ([Ch][Ala]) ionic liquid.

[0046] S8. Take 2.5 g of the [Ch][Ala] ionic liquid prepared above and add it to the nano-SiO2 fluid. Place the mixture in an ultrasonic instrument and sonicate it for 35 min in a pulse mode with a 2 s working time and a 5 s interval. Finally, a multidimensional synergistic composite promoter composed of 0.5 wt% 60 nm SiO2 and [Ch][Ala] ionic liquid is obtained.

[0047] Preparation of CO2 hydrate: The reactor lining was washed three times with deionized water to ensure it was clean and dry. After loading the aforementioned multidimensional synergistic composite promoter, the reactor lid was closed and tightly sealed to ensure good airtightness. Gas was injected to 0.5 MPa and then depressurized. The air inside the reactor was purged three times, and a vacuum was continuously applied for 5 minutes. Once the temperature inside the reactor dropped to the set reaction temperature of 3°C, this temperature was maintained constant for 3 hours. When injecting CO2 gas, the pressure at both ends was kept equal or the phase difference between the two ends was 0.1–0.2 MPa. Once the pressure inside the reactor reached 5 MPa, the pressure was kept constant. The synthesis was considered complete when the reaction lasted for 5 hours (pressure drop rate ≤ 0.1 MPa / h), the experiment was stopped, and the data were recorded.

[0048] Example 3 This embodiment provides a method for preparing a multidimensional synergistic composite promoter for carbon dioxide hydrate. Unlike Example 1, the ionic liquid cation donor in this embodiment is tetraethylammonium hydroxide, and the anion donor is aspartic acid. The specific preparation steps are as follows: S1. Accurately weigh 0.5 g of hydrophilic SiO2 nanoparticles with a particle size of 60 nm, add 99.5 g of deionized water, mix them in an ultrasonic instrument, and ultrasonically treat them for 30 min in a pulse mode with a 2 s working time and a 5 s interval to obtain nano-SiO2 fluid.

[0049] S2. Accurately weigh 11.40 g of trifluoroacetic acid and place it in a round-bottom flask. Add an appropriate amount of deionized water and stir until completely dissolved. Add a magnetic stir bar. Measure 8.21 g of 1-methylimidazole and transfer it to a constant-pressure dropping funnel for later use.

[0050] S3. Place the round-bottom flask in a container containing an ice-water mixture for an ice-water bath; fix the container above the magnetic stirrer and install a constant-pressure dropping funnel above the round-bottom flask.

[0051] S4. Turn on the magnetic stirrer and control the speed at 300 rpm to mix the liquid evenly. Add 1-methylimidazole to trifluoroacetic acid by slow dropwise addition.

[0052] S5. After the addition is complete, rinse the inner wall of the dropping funnel 5 times with deionized water to ensure that all reactants are transferred to the reaction system.

[0053] S6. After the reaction system gradually returns to room temperature (20℃), continue stirring for 5 h to obtain crude ionic liquid.

[0054] S7. Maintain the vacuum of the rotary evaporator at 0.09 MPa, and then perform reduced pressure rotary evaporation at 70°C for 4 h, with the rotation speed controlled at 100 rpm to remove solvent and water, to obtain 1-methylimidazolium trifluoroacetate ([MIM][TFA]) ionic liquid.

[0055] S8. Take 2.5 g of the [MIM][TFA] ionic liquid prepared above and add it to the nano-SiO2 nanofluid. Place the mixture in an ultrasonic instrument and sonicate it for 40 min in a pulse mode with a 2 s working time and a 5 s interval. Finally, a multidimensional synergistic composite promoter composed of 0.5 wt% 60 nm SiO2 and [MIM][TFA] ionic liquid is obtained.

[0056] Preparation of CO2 hydrate: The reactor lining was washed three times with deionized water to ensure it was clean and dry. After loading the aforementioned multidimensional synergistic composite promoter, the reactor lid was closed and tightly sealed to ensure good airtightness. Gas was injected to 0.5 MPa and then depressurized. The air inside the reactor was purged three times, and a vacuum was continuously applied for 5 minutes. Once the temperature inside the reactor dropped to the set reaction temperature of 3°C, this temperature was maintained constant for 3 hours. When injecting CO2 gas, the pressure at both ends was kept equal or the phase difference between the two ends was 0.1–0.2 MPa. Once the pressure inside the reactor reached 5 MPa, the pressure was kept constant. The synthesis was considered complete when the reaction lasted for 5 hours (pressure drop rate ≤ 0.1 MPa / h), the experiment was stopped, and the data were recorded.

[0057] Example 4 This embodiment provides a method for preparing a multidimensional synergistic composite promoter for carbon dioxide hydrate. Unlike Example 1, the SiO2 nanofluid in this embodiment has a mass fraction of 0.3 wt%. The specific preparation steps are as follows: S1. Accurately weigh 0.3 g of hydrophilic SiO2 nanoparticles with a particle size of 60 nm, add 99.7 g of deionized water, mix them in an ultrasonic instrument, and ultrasonically treat for 30 min in a pulse mode with a 2 s working time and a 5 s interval to obtain nano-SiO2 fluid.

[0058] S2. Accurately weigh 13.31 g of aspartic acid and place it in a round-bottom flask. Add an appropriate amount of deionized water and stir until completely dissolved. Add a magnetic stir bar. Measure 58.90 g of tetraethylammonium hydroxide and transfer it to a constant-pressure dropping funnel for later use.

[0059] S3. Place the round-bottom flask in a container containing an ice-water mixture for an ice-water bath; fix the container above the magnetic stirrer and install a constant-pressure dropping funnel above the round-bottom flask.

[0060] S4. Turn on the magnetic stirrer and control the speed at 300 rpm to mix the liquid evenly. Add tetraethylammonium hydroxide to aspartic acid dropwise.

[0061] S5. After the addition is complete, rinse the inner wall of the dropping funnel 5 times with deionized water to ensure that all reactants are transferred to the reaction system.

[0062] S6. After the reaction system gradually returns to room temperature (20℃), continue stirring for 6 h to obtain crude ionic liquid.

[0063] S7. Maintain the vacuum degree of the rotary evaporator at 0.08 MPa, then perform reduced pressure rotary evaporation at 65℃ for 5 h, controlling the rotation speed at 120 rpm to remove solvent and water, to obtain tetraethylammonium hydroxide aspartate ([N 2222 [Asp]) Ionic liquids.

[0064] S8. Take the [N] prepared above. 2222 2.5 g of [Asp] ionic liquid was added to nano-SiO2 fluid. The mixture was placed in an ultrasonic instrument and ultrasonically treated for 30 min in a pulse mode with a 2 s working time and a 5 s interval, finally obtaining 0.3 wt% 60 nm SiO2 and [N 2222 A multidimensional promoting system composed of [Asp] ionic liquids.

[0065] Preparation of CO2 hydrate: The reactor lining was washed three times with deionized water to ensure it was clean and dry. After loading the aforementioned multidimensional synergistic composite promoter, the reactor lid was closed and tightly sealed to ensure good airtightness. Gas was injected to 0.5 MPa and then depressurized. The air inside the reactor was purged three times, and a vacuum was continuously applied for 5 minutes. Once the temperature inside the reactor dropped to the set reaction temperature of 3°C, this temperature was maintained constant for 3 hours. When injecting CO2 gas, the pressure at both ends was kept equal or the phase difference between the two ends was 0.1–0.2 MPa. Once the pressure inside the reactor reached 5 MPa, the pressure was kept constant. The synthesis was considered complete when the reaction lasted for 5 hours (pressure drop rate ≤ 0.1 MPa / h), the experiment was stopped, and the data were recorded.

[0066] Example 5 This embodiment provides a method for preparing a multidimensional synergistic composite promoter for carbon dioxide hydrate. Unlike Example 1, the SiO2 nanofluid in this embodiment has a mass fraction of 0.7 wt%. The specific preparation steps are as follows: S1. Accurately weigh 0.7 g of hydrophilic SiO2 nanoparticles with a particle size of 60 nm, add 99.3 g of deionized water, mix them in an ultrasonic instrument, and ultrasonically treat them for 30 min in a pulse mode with a 2 s working time and a 5 s interval to obtain nano-SiO2 fluid.

[0067] S2. Accurately weigh 13.31 g of aspartic acid and place it in a round-bottom flask. Add an appropriate amount of deionized water and stir until completely dissolved. Add a magnetic stir bar. Measure 58.90 g of tetraethylammonium hydroxide and transfer it to a constant-pressure dropping funnel for later use.

[0068] S3. Place the round-bottom flask in a container containing an ice-water mixture for an ice-water bath; fix the container above the magnetic stirrer and install a constant-pressure dropping funnel above the round-bottom flask.

[0069] S4. Turn on the magnetic stirrer and control the speed at 300 rpm to mix the liquid evenly. Add tetraethylammonium hydroxide to aspartic acid dropwise.

[0070] S5. After the addition is complete, rinse the inner wall of the dropping funnel 5 times with deionized water to ensure that all reactants are transferred to the reaction system.

[0071] S6. After the reaction system gradually returns to room temperature (20℃), continue stirring for 6 h to obtain crude ionic liquid.

[0072] S7. Maintain the vacuum degree of the rotary evaporator at 0.08 MPa, then perform reduced pressure rotary evaporation at 65℃ for 5 h, controlling the rotation speed at 120 rpm to remove solvent and water, to obtain tetraethylammonium hydroxide aspartate ([N 2222 [Asp]) Ionic liquids.

[0073] S8. Take the [N] prepared above. 2222 2.5 g of [Asp] ionic liquid was added to SiO2 nanofluid. The mixture was placed in an ultrasonic instrument and ultrasonicated for 30 min in a pulse mode with a 2 s working time and a 5 s interval, finally yielding 0.7 wt% 60 nm SiO2 and [N 2222 A multidimensional promoting system composed of [Asp] ionic liquids.

[0074] Preparation of CO2 hydrate: The reactor lining was washed three times with deionized water to ensure it was clean and dry. After loading the aforementioned multidimensional synergistic composite promoter, the reactor lid was closed and tightly sealed to ensure good airtightness. Gas was injected to 0.5 MPa and then depressurized. The air inside the reactor was purged three times, and a vacuum was continuously applied for 5 minutes. Once the temperature inside the reactor dropped to the set reaction temperature of 3°C, this temperature was maintained constant for 3 hours. When injecting CO2 gas, the pressure at both ends was kept equal or the phase difference between the two ends was 0.1–0.2 MPa. Once the pressure inside the reactor reached 5 MPa, the pressure was kept constant. The synthesis was considered complete when the reaction lasted for 5 hours (pressure drop rate ≤ 0.1 MPa / h), the experiment was stopped, and the data were recorded.

[0075] Table 1. Mass ratio of nanofluids to ionic liquids

[0076] Comparative Example 1 The difference from the CO2 hydrate generation system in Example 1 is that pure water is used instead of the multidimensional synergistic compound promoter.

[0077] Comparative Example 2 The difference from the CO2 hydrate formation system in Example 1 is that a kinetic promoter is used instead of a multidimensional synergistic composite promoter, and steps S2-S8 are omitted.

[0078] The specific preparation steps are as follows: Accurately weigh 0.5 g of hydrophilic SiO2 nanoparticles with a particle size of 60 nm and add 99.5 g of deionized water. Mix and place in an ultrasonic instrument, and ultrasonically treat for 30 min in a pulse mode with a 2 s working time and a 5 s interval to obtain 0.5 wt% 60 nm SiO2 nanohydrodynamic promoter.

[0079] Preparation of CO2 hydrate: The reactor lining was washed three times with deionized water to ensure it was clean and dry. After loading the sample, the reactor lid was closed and tightly sealed to ensure good airtightness. Gas was injected to 0.5 MPa and then depressurized. The air inside the reactor was purged three times, and a vacuum was continuously applied for 5 minutes. After the temperature inside the reactor dropped to the set reaction temperature of 3°C, the temperature was maintained constant for 3 hours. When injecting CO2 gas, the pressure at both ends was kept equal or the phase difference between the two ends was 0.1~0.2 MPa. After the pressure inside the reactor reached 5 MPa, the pressure inside the reactor was kept constant. When the reaction lasted for 5 hours (pressure drop rate ≤ 0.1 MPa / h), the synthesis was considered complete, the experiment was stopped, and the data were recorded.

[0080] Comparative Example 3 The difference from the CO2 hydrate formation system in Example 1 is that a thermodynamic promoter is used instead of a multidimensional synergistic composite promoter, and step S1 in Example 1 is omitted.

[0081] The specific preparation steps are as follows: S1. Accurately weigh 13.31 g of aspartic acid and place it in a round-bottom flask. Add an appropriate amount of deionized water and stir until completely dissolved. Add a magnetic stir bar. Measure 58.90 g of tetraethylammonium hydroxide and transfer it to a constant-pressure dropping funnel for later use.

[0082] S2. Place the round-bottom flask in a container containing an ice-water mixture for an ice-water bath; fix the container above the magnetic stirrer and install a constant-pressure dropping funnel above the round-bottom flask.

[0083] S3. Turn on the magnetic stirrer and control the speed at 300 rpm to mix the liquid evenly. Add tetraethylammonium hydroxide to aspartic acid dropwise.

[0084] S4. After the addition is complete, rinse the inner wall of the dropping funnel 5 times with deionized water to ensure that all reactants are transferred to the reaction system.

[0085] S5. After the reaction system gradually returns to room temperature (20℃), continue stirring for 6 h to obtain crude ionic liquid.

[0086] S6. Maintain the vacuum degree of the rotary evaporator at 0.08 MPa, then perform reduced pressure rotary evaporation at 65℃ for 5 h, controlling the rotation speed at 120 rpm to remove solvent and water, to obtain tetraethylammonium hydroxide aspartate ([N 2222 [Asp]) Ionic liquids.

[0087] Preparation of CO2 hydrate: The reactor lining was washed three times with deionized water to ensure it was clean and dry. After loading the sample, the reactor lid was closed and tightly sealed to ensure good airtightness. Gas was injected to 0.5 MPa and then depressurized. The air inside the reactor was purged three times, and a vacuum was continuously applied for 5 minutes. After the temperature inside the reactor dropped to the set reaction temperature of 3°C, the temperature was maintained constant for 3 hours. When injecting CO2 gas, the pressure at both ends was kept equal or the phase difference between the two ends was 0.1~0.2 MPa. After the pressure inside the reactor reached 5 MPa, the pressure inside the reactor was kept constant. When the reaction lasted for 5 hours (pressure drop rate ≤ 0.1 MPa / h), the synthesis was considered complete, the experiment was stopped, and the data were recorded.

[0088] Effect verification 1. The induction time of CO2 hydrate formation in Examples 1-5 and Comparative Examples 1-3 was determined and compared with that of nano-alumina (Al2O3), nano-copper oxide (CuO), nano-zinc oxide (ZnO), and 1,3-dioxolane solution (DIOX) as promoters. The results are shown in Table 2.

[0089] Table 2. Induction time of CO2 hydrate formation under different promoting systems

[0090] 2. The formation rate of CO2 hydrate in Examples 1-5 and Comparative Examples 1-3 was determined and compared with that of nano-alumina (Al2O3), nano-copper oxide (CuO), nano-zinc oxide (ZnO), and 1,3-dioxolane solution (DIOX) as promoters. The results are shown in Table 3.

[0091] Table 3. CO2 hydrate formation rate under different promoting systems

[0092] 3. The gas storage capacity of CO2 hydrate in Examples 1-5 and Comparative Examples 1-3 was determined and compared with that of nano-alumina (Al2O3), nano-copper oxide (CuO), nano-zinc oxide (ZnO), and 1,3-dioxolane solution (DIOX) as promoters. The results are shown in Table 4.

[0093] Table 4. Gas storage capacity of CO2 hydrate under different promoting systems

[0094] Based on the above data comparison, it can be seen that the multidimensional synergistic composite promoter for carbon dioxide hydrate provided by the present invention shows significant advantages in promoting CO2 hydrate formation.

[0095] The systems constructed in Examples 1-5 showed a reduction in induction time of approximately 36% or more compared to Comparative Example 1 (pure water system), and an increase in CO2 hydrate gas storage capacity of over 21%. Furthermore, compared to single-promoter systems (Comparative Examples 2 and 3) and traditional systems using nano-alumina (Al2O3), nano-copper oxide (CuO), nano-zinc oxide (ZnO), and 1,3-dioxolane solution (DIOX), the multidimensional promoting system described in this invention exhibits significant advantages in terms of reduced induction time, increased generation rate, and gas storage capacity, demonstrating a remarkable synergistic promoting effect.

[0096] In this invention, the combination of SiO2 nanofluid and ionic liquid not only improves the nucleation rate but also enhances the system's heat and mass transfer capabilities, thereby achieving efficient and stable CO2 hydrate formation. This system enables efficient CO2 sequestration and has advantages such as mild operating conditions, long-lasting promoting effect, environmental friendliness, and low cost, making it suitable for the widespread application of large-scale CO2 hydrate sequestration technology.

[0097] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A multidimensional synergistic composite promoter for CO2 hydrate formation, characterized in that, It comprises the following components: nanofluid dynamics promoter and ionic liquid thermodynamic promoter; The nanofluid dynamics promoter is a dispersion of nanoparticles; The nanoparticles are one or more of silicon dioxide, graphite, and graphene oxide. The ionic liquid thermodynamic accelerator is a solution containing cations and anions; The cation donor is a nitrogen-containing organic base; The anion donor is a weak acid containing a carboxyl functional group or its derivative.

2. The multidimensional synergistic composite promoter according to claim 1, characterized in that, The nanoparticles have a particle size of 20~100 nm; The nanoparticles in the nanofluid dynamics promoter have a mass fraction of 0.3~1.0 wt%.

3. The multidimensional synergistic composite promoter according to claim 1, characterized in that, The nitrogen-containing organic base is one or more of tetraethylammonium hydroxide, choline, and 1-methylimidazole; The weak acid containing a carboxyl functional group and its derivatives are one or more of aspartic acid, alanine, and trifluoroacetic acid. The molar ratio of the cation to the anion is 1:

1.

4. The multidimensional synergistic composite promoter according to claim 1, characterized in that, The mass ratio of the nanofluid dynamics promoter to the ionic liquid thermodynamics promoter is 1:(3-9).

5. The method for preparing the multidimensional synergistic composite promoter according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Add nanoparticles to water and disperse them to obtain a nanofluid dynamics promoter; S2. Mix the anion donor and the cation donor to obtain the ionic liquid thermodynamic promoter; S3. Mix and disperse the nanofluid dynamics promoter with the ionic liquid thermodynamics promoter to obtain a multidimensional synergistic composite promoter.

6. The preparation method according to claim 5, characterized in that, In step S1, the dispersion is ultrasonic dispersion; the conditions for ultrasonic dispersion are: power of 1000w, ultrasonic setting of 2s on and 5s off, and ultrasonic time of 5~45min.

7. The preparation method according to claim 5, characterized in that, In step S2, the mixing process includes: adding anion donor dropwise to a solvent containing cation donor under ice-water bath conditions, stirring, and obtaining a crude product; and rotary evaporating the crude product under reduced pressure to obtain an ionic liquid thermodynamic promoter. The stirring conditions are: temperature 20~30℃, speed 100~250 rpm, and time 5~6h; The conditions for vacuum rotary evaporation are: vacuum degree of 0.05~0.1 MPa, temperature of 60~80℃, rotation speed of 80~150 rpm, and time of 2~5 h.

8. The preparation method according to claim 5, characterized in that, In step S3, the conditions for ultrasonic dispersion are: ultrasonic setting is 2s on and 5s off, and ultrasonic time is 30~60min.

9. A method for sequestering carbon dioxide using marine hydrates, characterized in that, Carbon dioxide is sequestered using the multidimensional synergistic compound promoter according to any one of claims 1-4.

10. The method according to claim 9, characterized in that, The conditions for sealing are: temperature 0~15℃ and pressure 3~15 MPa.

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