Method for promoting generation of carbon dioxide hydrate

Abstract

The invention belongs to the technical field of gas hydrate generation, and provides a carbon dioxide hydrate generation promoting method which comprises the following steps: adding an accelerant system containing modified nanoparticles into a carbon dioxide-water mixed system, and carrying out hydrate generation reaction under the conditions of 2-15 DEG C and 3-10 MPa, wherein the accelerant system is formed by compounding an amino acid derivative, a surfactant and metal salt according to the mass ratio of 1: (0.5-2): (0.1-0.8), and the modified nanoparticles are silicon dioxide nanoparticles treated by a silane coupling agent. Through multi-component synergistic effect and process parameter optimization of the composite accelerant system, rapid generation and high-density storage of the carbon dioxide hydrate are realized under low-temperature and low-pressure conditions, meanwhile, energy consumption is reduced, and environmental pollution is avoided.

Description

Technical Field

[0001] The present invention belongs to the technical field of gas hydrate formation, and particularly relates to a method for promoting the formation of carbon dioxide hydrate. Background Art

[0002] Carbon dioxide hydrate is a cage-like crystal structure formed by carbon dioxide molecules and water molecules under low temperature and high pressure conditions, and has important application values in gas storage, industrial refrigeration and natural gas hydrate exploitation. However, in the traditional process of carbon dioxide hydrate formation, there are problems such as slow kinetics and harsh thermodynamic conditions, which limit the industrial application. In the prior art, the formation conditions of hydrate are often improved by adding chemical promoters. For example, surfactants, nanoparticles or amino acids are used to reduce the reaction activation energy.

[0003] There are still obvious defects in the existing promoters in practical applications. For example, although a single surfactant can reduce the interfacial tension, it is easy to aggregate and fail under high pressure, and the residues may cause environmental pollution. Although the nanoparticle promoter can provide nucleation sites, the particle dispersibility is poor, and it is easy to deposit and block the equipment after long-term use. Although the amino acid-based promoter has good environmental friendliness, its promoting effect is unstable under low temperature conditions. In addition, most of the prior art uses a single type of promoter, and the synergistic effect between different substances is not fully utilized, resulting in limited promotion efficiency.

[0004] Some studies have tried to improve the performance by compounding multiple promoters, but there are problems such as unreasonable ratio and unclear action mechanism. For example, when a surfactant and nanoparticles are simply mixed, the system may become unstable due to charge repulsion. Another solution proposes to modify the promoter structure by metal ions, but the matching relationship between the ion concentration and temperature parameters is not optimized, and uneven crystal growth is likely to occur in practical applications. In terms of process parameters, most of the existing methods use fixed temperature or pressure conditions, without considering the different thermodynamic condition requirements of different promoter systems, resulting in high energy consumption.

[0005] Therefore, a method for promoting the formation of carbon dioxide hydrate needs to be designed. Summary of the Invention

[0006] In order to overcome the defects in the prior art, a method for promoting the formation of carbon dioxide hydrate is provided.

[0007] In order to achieve the above object, the present invention provides the following technical solutions: A method for promoting the formation of carbon dioxide hydrate, which comprises the following steps: adding a promoter system containing modified nanoparticles to a carbon dioxide-water mixed system, and carrying out a hydrate formation reaction under the conditions of 2-15 °C and a pressure of 3-10 MPa, wherein the promoter system is compounded from an amino acid derivative, a surfactant and a metal salt according to a mass ratio of 1:0.5-2:0.1-0.8, and the modified nanoparticles are silica nanoparticles treated with a silane coupling agent; The amino acid derivative is a condensate of L-arginine and maleic anhydride, with a substitution degree of 60-85% and a molecular weight of 800-2000 Da; the metal salt is a mixture of magnesium chloride and copper nitrate, wherein the molar ratio of magnesium ions to copper ions is 1:0.05-0.2.

[0008] The surfactant includes sodium dodecyl sulfate and polyoxyethylene lauryl ether, and the mass ratio of sodium dodecyl sulfate to polyoxyethylene lauryl ether is 1:0.3-1.2.

[0009] The preparation method of the modified nanoparticles includes: dispersing silica with a particle size of 50-100 nm in an ethanol-water mixed solvent, adding γ-aminopropyltriethoxysilane, refluxing and reacting at 60-80 °C for 3-6 hours, centrifuging, washing and drying to obtain silica nanoparticles grafted with amino groups on the surface, which are the modified nanoparticles.

[0010] The volume fraction of ethanol in the ethanol-water mixed solvent is 70-90%, and the addition amount of the silane coupling agent is 10-25% of the mass of silica.

[0011] The addition amount of the promoter system is 0.5-3% of the mass of the carbon dioxide-water mixed system, and it is added in two times: 60-80% is added for the first time in the precooling stage, and the remaining part is added after the pressure rises to 5 MPa; The promoter system further contains a polysaccharide thickener, and the polysaccharide thickener is 0.01-0.1% of the total mass of the promoter system. The polysaccharide thickener is a mixture composed of xanthan gum and gellan gum according to a mass ratio of 1:0.5-1.5.

[0012] The polysaccharide thickener is carboxymethylated with a substitution degree of 0.3-0.7. The modification method includes: dispersing the polysaccharide in an alkaline solution, adding sodium chloroacetate, and reacting at 40-60 °C for 4-8 hours. The obtained product is the polysaccharide thickener.

[0013] The hydrate formation reaction is carried out in a vertical tubular reactor. The temperature of the circulating coolant in the jacket layer is 2-5 °C lower than the reaction temperature, and the flow rate is 0.5-1.2 m / s; during the hydrate formation reaction, ultrasonic waves with a frequency of 20-50 kHz are applied, and the ultrasonic power density is 50-150 W / m³.

[0014] An organic amine buffer is added to the carbon dioxide-water mixed system at a concentration of 0.05 - 0.3 mol / L. The organic amine buffer is a mixture composed of triethanolamine and diethanolamine at a molar ratio of 1:0.8 - 1.5.

[0015] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. The technical solution of this application significantly improves the formation efficiency of carbon dioxide hydrate through the synergistic effect of multiple components. The amino acid derivative and the surfactant form a composite micelle structure. The L-arginine derivative forms zwitterionic characteristics through the amino group in the molecule and the carboxyl group of maleic anhydride, and forms an oriented arrangement at the gas-liquid interface, effectively reducing the interfacial tension. Sodium dodecyl sulfate and polyoxyethylene lauryl ether in the surfactant form a mixed micelle. The former stabilizes the surface of the bubble through electrostatic interaction, and the latter prolongs the bubble lifetime through the steric hindrance effect of the polyoxyethylene chain. The synergistic effect of the two synchronously improves the carbon dioxide solubility and the interfacial contact area.

[0016] 2. The introduction of metal salts in this application enhances the ionic strength of the system. Magnesium chloride changes the solution dielectric constant through hydration, and the trace addition of copper nitrate forms metal coordination sites on the surface of nanoparticles. The dual action promotes the arrangement of water molecules towards the cage structure. The amino-functionalized surface of the modified nanoparticles forms a hydrogen bond network, which not only serves as a physical nucleation site to accelerate the formation of crystal nuclei, but also fixes carbon dioxide molecules through chemical adsorption, solving the problem of easy agglomeration and failure of traditional nanoparticles. The organic-inorganic hybrid interface formed by silane coupling agent treatment significantly improves the dispersion stability of the particles under high-pressure conditions.

[0017] 3. The staged addition strategy of this application realizes dynamic regulation. The high-concentration promoter in the precooling stage quickly establishes a nucleation environment, and the supplementary addition operation after the pressure increases targets the requirements of the crystal growth stage to supplement the consumed active components. The carboxymethylated polysaccharide thickener constructs a three-dimensional network structure through the entanglement of molecular chains, which not only inhibits the excessive aggregation of surfactant micelles, but also prolongs the crystal growth time through the space confinement effect, making the hydrate structure more dense and stable.

[0018] 4. The enhanced heat transfer design of the vertical tube reactor and the ultrasonic cavitation effect form microscale turbulence, effectively eliminating the local concentration gradient. The precise temperature control of the circulating coolant keeps the system in the metastable region. The microjet generated by ultrasonic waves not only accelerates the gas-liquid mass transfer, but also breaks large crystals to maintain a uniform particle size distribution.

[0019] 5. The organic amine buffer maintains a weakly alkaline environment in the system through the proton transfer mechanism, which not only protects the active groups of amino acid derivatives, but also promotes the existence of metal ions in a suitable valence state, avoiding the interference of hydroxide precipitation on the reaction process.

[0020] 6. Through the synergistic optimization of intermolecular forces and macroscopic processes, the composite promotion system of this application breaks through the efficiency bottleneck of traditional methods while reducing energy consumption. The multi-level synergy of each component at the gas-liquid interface, solution bulk, and crystal growth interface realizes the synchronous improvement of the nucleation site density, molecular diffusion rate, and crystal growth kinetics, forming an overall chain optimization from microscopic molecular arrangement to macroscopic process parameters.

[0021] 7. This method uses a promoter system that combines amino acid derivatives, surfactants, and metal salts, combined with modified nanoparticles and polysaccharide thickeners, to significantly improve the formation rate and stability of carbon dioxide hydrate under optimized temperature and pressure conditions. At the same time, ultrasonic waves are used to enhance mass transfer and organic amine buffers are used to regulate the pH value to achieve an efficient and controllable hydrate formation process. Detailed implementation manners

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative work belong to the scope of protection of the present invention.

[0023] In this application, the sources of various raw materials are briefly described as follows: Carbon dioxide: Supplied by Shenzhen Changdali Welding Materials Co., Ltd., CAS number is 124-38-9, and the purity grade is SFC grade.

[0024] L-arginine maleic anhydride condensate: Purchased from J&K Scientific Ltd.

[0025] Sodium dodecyl sulfate: Sangon Biotech Co., Ltd., CAS number is 151-21-3, molecular biology grade, purity ≥99%, product number A100227.

[0026] Polyoxyethylene lauryl ether: Purchased from Tokyo Chemical Industry Co., Ltd., Japan.

[0027] Magnesium chloride: J&K Scientific Ltd., CAS number may be 7786-30-3, and the specific model needs to be consulted for its inorganic reagent series.

[0028] Copper nitrate: Strem Chemicals, CAS number is 10031-43-3, purity 99.9%, product number 44-1200.

[0029] Silica nanoparticles: Xi'an Ruixi Biotechnology Co., Ltd., particle size 50-100nm, product form is white powder, specific surface area is about 800m² / g.

[0030] γ-aminopropyltriethoxysilane: Xi'an Ruixi Biotechnology Co., Ltd., CAS No. 919-30-2, used for surface modification, purity ≥98%.

[0031] Xanthan gum: Purchased from Zhejiang Institute of Ocean Development, AS No. 11138-66-2.

[0032] Gellan gum: Purchased from Zhejiang Institute of Ocean Development, CAS No. 71010-52-1.

[0033] Triethanolamine: Dow Chemical Company, CAS No. 102-71-6, purity ≥99%.

[0034] Diethanolamine: Dow Chemical Company, CAS No. 111-42-2, purity ≥99%.

[0035] Sodium chloroacetate: Amethyst brand of J&K Scientific Ltd., CAS No. 3926-62-3, analytical reagent grade.

[0036] Absolute ethanol: SuperDry series of J&K Scientific Ltd., CAS No. 64-17-5, purity 99.9%, product number 954403.

[0037] A method for promoting the formation of carbon dioxide hydrate, the method comprising the following steps: adding a promoter system containing modified nanoparticles to a carbon dioxide-water mixed system, and carrying out a hydrate formation reaction at 2-15 °C and a pressure of 3-10 MPa, wherein the promoter system is compounded from an amino acid derivative, a surfactant and a metal salt according to a mass ratio of 1:0.5-2:0.1-0.8, and the modified nanoparticles are silica nanoparticles treated with a silane coupling agent.

[0038] The amino acid derivative is a condensate of L-arginine and maleic anhydride, with a substitution degree of 60-85% and a molecular weight of 800-2000 Da.

[0039] The surfactant includes sodium dodecyl sulfate and polyoxyethylene lauryl ether, and the mass ratio of sodium dodecyl sulfate to polyoxyethylene lauryl ether is 1:0.3-1.2.

[0040] The metal salt is a mixture of magnesium chloride and copper nitrate, and the molar ratio of magnesium ions to copper ions is 1:0.05-0.2.

[0041] The preparation method of the modified nanoparticles includes: dispersing silica with a particle size of 50-100 nm in an ethanol-water mixed solvent, adding γ-aminopropyltriethoxysilane, refluxing and reacting at 60-80 °C for 3-6 hours, centrifuging, washing and drying to obtain silica nanoparticles grafted with amino groups on the surface, which are the modified nanoparticles.

[0042] The volume fraction of ethanol in the ethanol-water mixed solvent is 70 - 90%, and the addition amount of the silane coupling agent is 10 - 25% of the mass of silica.

[0043] The addition amount of the promoter system is 0.5 - 3% of the mass of the carbon dioxide-water mixed system, and it is added in two times: 60 - 80% is added for the first time in the pre-cooling stage, and the remaining part is added after the pressure rises to 5 MPa; The promoter system also contains a polysaccharide thickener, the polysaccharide thickener is 0.01 - 0.1% of the total mass of the promoter system, and the polysaccharide thickener is a mixture composed of xanthan gum and gellan gum according to a mass ratio of 1:0.5 - 1.5.

[0044] The polysaccharide thickener is carboxymethylated and modified with a substitution degree of 0.3 - 0.7. The modification method includes: dispersing the polysaccharide in an alkaline solution, adding sodium chloroacetate, and reacting at 40 - 60 °C for 4 - 8 hours. The obtained product is the polysaccharide thickener.

[0045] The hydrate formation reaction is carried out in a vertical tubular reactor. The temperature of the circulating coolant in the jacket is 2 - 5 °C lower than the reaction temperature, and the flow rate is 0.5 - 1.2 m / s; during the hydrate formation reaction, ultrasonic waves with a frequency of 20 - 50 kHz are applied, and the ultrasonic power density is 50 - 150 W / m³.

[0046] An organic amine buffer with a concentration of 0.05 - 0.3 mol / L is added to the carbon dioxide-water mixed system, and the organic amine buffer is a mixture composed of triethanolamine and diethanolamine according to a molar ratio of 1:0.8 - 1.5.

[0047] Through the multi-component synergistic effect of the composite promoter system and the optimization of process parameters, this application realizes the rapid formation and high-density storage of carbon dioxide hydrate under low-temperature and low-pressure conditions, while reducing energy consumption and avoiding environmental pollution.

[0048] The technical solutions of the present invention are further described below through examples and comparative examples, but the protection scope of the present invention is not limited thereto.

[0049] Example 1 Disperse silica nanoparticles with a particle size of 100 nm in an ethanol-water mixed solvent with an ethanol volume fraction of 90%. Add γ-aminopropyltriethoxysilane, which is 25% of the mass of silica, and reflux at 80 °C for 6 hours. After centrifugation, washing, and drying, amino-modified nanoparticles are obtained. The promoter system is composed of an L-arginine-maleic anhydride condensate (substitution degree 85%, molecular weight 2000 Da), sodium dodecyl sulfate and polyoxyethylene lauryl ether (mass ratio 1:1.2), and magnesium chloride and copper nitrate (magnesium ion to copper ion molar ratio 1:0.2) compounded in a mass ratio of 1:2:0.8. The promoter system is added in two portions at 3% of the mass of the carbon dioxide-water mixed system - 80% of the promoter is added during the first pre-cooling stage, and the remaining 20% is added after the pressure rises to 10 MPa. A carboxymethylated xanthan gum-gellan gum mixture (mass ratio 1:1.5, substitution degree 0.7) is added as a thickener to the system, and the addition amount is 0.1% of the total mass of the promoter. The reaction is carried out in a vertical tube reactor. The temperature of the coolant in the jacket is 5 °C lower than the reaction temperature, with a flow rate of 1.2 m / s. At the same time, 50 kHz ultrasonic waves (power density 150 W / m³) are applied. A 0.3 mol / L triethanolamine-diethanolamine buffer (molar ratio 1:1.5) is added to the carbon dioxide-water mixed system, and the reaction temperature is controlled at 2 °C and the pressure at 10 MPa.

[0050] Example 2 In this example, the same parts as in Example 1 will not be elaborated again, and the differences are described as follows: Silica nanoparticles with a particle size of 50 nm are used. A silane coupling agent, which is 10% of the mass of silica, is added in a solvent with an ethanol volume fraction of 70%, and the modified particles are prepared by refluxing at 60 °C for 3 hours. The promoter system is composed of an amino acid derivative with a substitution degree of 60% and a molecular weight of 800 Da, a surfactant (sodium dodecyl sulfate and polyoxyethylene lauryl ether mass ratio 1:0.3), and a metal salt (magnesium to copper ion ratio 1:0.05) compounded in a mass ratio of 1:0.5:0.1. The total addition amount is 0.5% of the mass of the system. When added in stages, 60% is added during the first pre-cooling stage, and the remaining 40% is added after the pressure rises to 3 MPa. The thickener used is a carboxymethylated polysaccharide with a substitution degree of 0.3 (xanthan gum and gellan gum mass ratio 1:0.5), and the addition amount is 0.01%. The temperature difference of the reactor coolant is set at 2 °C, the flow rate is 0.5 m / s, and the ultrasonic frequency is 20 kHz (power density 50 W / m³). The buffer concentration is 0.05 mol / L (triethanolamine and diethanolamine molar ratio 1:0.8), and the reaction temperature is 15 °C and the pressure is 3 MPa.

[0051] Example 3 In this example, the same parts as in Example 1 will not be elaborated again, and the differences are described as follows: Silica particles with an intermediate particle size of 75nm were selected, and 15% silane coupling agent was added to a solvent with an ethanol volume fraction of 80%, and the modified particles were obtained by reacting at 70℃ for 4.5 hours. The amino acid derivative has a substitution degree of 72% and a molecular weight of 1400Da, and is compounded with a surfactant (mass ratio of 1:0.75) and a metal salt (magnesium-copper ion ratio of 1:0.12) at a mass ratio of 1:1.25:0.45. The total amount of accelerator added is 1.75%, and 70% is added in the precooling stage when added twice, and the remaining 30% is added after the pressure rises to 6.5MPa. The thickener is a carboxymethylated polysaccharide with a substitution degree of 0.5 (mass ratio of 1:1), and the addition amount is 0.055%. The reactor cooling temperature difference is 3.5℃, the flow rate is 0.85m / s, and the ultrasonic parameters are 35kHz / 100W / m³. The buffer concentration is 0.175mol / L (molar ratio 1:1.15), the reaction temperature is 8.5℃, and the pressure is 6.5MPa.

[0052] Comparative Example 1 In this comparative example, the same points as Example 1 are not repeated here, and the differences are as follows: No carboxymethylated polysaccharide thickener is used.

[0053] Comparative Example 2 In this comparative example, the same points as Example 2 are not repeated here, and the differences are as follows: The phased addition strategy was cancelled and all accelerators were added at once during the precooling stage.

[0054] Comparative Example 3 In this comparative example, the same points as Example 3 are not repeated here, and the differences are as follows: The metal salt was replaced with magnesium chloride alone.

[0055] Comparative Example 4 In this comparative example, the same points as Example 1 are not repeated here, and the differences are as follows: Remove ultrasonic treatment from the system.

[0056] Comparative Example 5 In this comparative example, the same points as Example 1 are not repeated here, and the differences are as follows: Unmodified silica particles were used instead of the amino-modified particles of Example 1.

[0057] Performance test results and analysis The carbon dioxide hydrate formation was promoted according to the parameters of the embodiment and the comparative example, and the results were tested. The test results are specifically shown in Table 1.

[0058] As can be seen from Table 1, the ultra-short induction time of 8.2 minutes in Example 1 is due to the synergistic effect of the amino-modified nanoparticles and the zwitterionic amino acid derivatives. The hydrogen bond network formed by the amino groups on the surface of the modified particles accelerates the induction of The amphiphilic structure of the amino acid derivative forms a directional arrangement at the gas-liquid interface, reducing the nucleation barrier. Compared with 27.6 minutes for the unmodified particles in comparative example 5, the silane coupling treatment is confirmed to improve the dispersibility of the particles.

[0059] The 143v / v gas storage density of Example 1 breaks through the upper limit of the traditional system, mainly due to the synergistic effect of the phased addition strategy and the polysaccharide thickener. The high concentration of promoter in the precooling stage establishes dense nucleation points, and the supplementary addition after the pressure increase maintains the concentration gradient required for crystal growth. The three-dimensional network structure constructed by carboxymethylated polysaccharides delays excessive crystal growth and makes the cage structure more complete. Compared with the 117v / v added at one time in Comparative Example 2, the effectiveness of the dynamic regulation strategy is proved.

[0060] The uniform particle size distribution (D90) of 85 μm in Example 1 relies on the coupling of ultrasonic cavitation effect and vertical reactor design. The micro jet generated by 50kHz ultrasonic wave breaks up large crystals, while the sleeve-type heat transfer is enhanced to avoid local overheating. After the ultrasonic wave is removed in Comparative Example 4, the D90 increases to 210 μm, and obvious crystal agglomeration occurs.

[0061] The energy consumption of 18.5kW·h / m³ in Example 1 is more than 40% lower than that of the traditional method. The key lies in the synergistic effect of the metal salt ion strength regulation and the buffer. Magnesium chloride changes the dielectric constant of the solution to reduce the phase change enthalpy, and copper nitrate stabilizes the nanoparticles through coordination. The two work together to reduce the energy loss of the system. When a single metal salt is used in Comparative Example 3, the energy consumption rises to 25.9kW·h / m³, confirming the complementary effect of the dual metal ions.

[0062] No accumulation of accelerator degradation products was detected in all the example systems after 200 hours of continuous operation, and the combination of organic amine buffer and bio-based polysaccharide achieved environmental friendliness. However, the lack of thickener in comparative example 1 resulted in excessive residual surfactant, confirming the necessity of carboxymethylation modification for micelle stability.

[0063] Table 1 Analysis and test results The test results show that ethanol and specific amino acid promoters can significantly shorten the induction time of carbon dioxide hydrate, increase the generation rate and gas storage density at appropriate concentrations, while the synergistic effects of staged pressurization, low temperature (below freezing point) and polysaccharide thickeners can further optimize crystal stability.

[0064] The above are the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for promoting the formation of carbon dioxide hydrate, characterized in that, The method comprises the following steps: adding a promoter system containing modified nanoparticles into a carbon dioxide-water mixed system, and carrying out a hydrate formation reaction under the conditions of 2-15 °C and a pressure of 3-10 MPa, wherein the promoter system is compounded from an amino acid derivative, a surfactant and a metal salt according to a mass ratio of 1:0.5-2:0.1-0.8, and the modified nanoparticles are silica nanoparticles treated with a silane coupling agent; the amino acid derivative is a condensate of L-arginine and maleic anhydride, with a degree of substitution of 60-85% and a molecular weight of 800-2000 Da; the metal salt is a mixture of magnesium chloride and copper nitrate, wherein the molar ratio of magnesium ions to copper ions is 1:0.05-0.

2.

2. The method for promoting the formation of carbon dioxide hydrate according to claim 1, characterized in that: The surfactant includes sodium dodecyl sulfate and polyoxyethylene lauryl ether, and the mass ratio of sodium dodecyl sulfate to polyoxyethylene lauryl ether is 1:0.3-1.

2.

3. The method for promoting the formation of carbon dioxide hydrate according to claim 1, characterized in that: The preparation method of the modified nanoparticles includes: dispersing silica with a particle size of 50-100 nm in an ethanol-water mixed solvent, adding γ-aminopropyltriethoxysilane, refluxing and reacting at 60-80 °C for 3-6 hours, centrifuging, washing and drying to obtain silica nanoparticles grafted with amino groups on the surface, which are the modified nanoparticles.

4. The method for promoting the formation of carbon dioxide hydrate according to claim 3, characterized in that: In the ethanol-water mixed solvent, the volume fraction of ethanol is 70-90%, and the addition amount of the silane coupling agent is 10-25% of the mass of silica.

5. The method for promoting the formation of carbon dioxide hydrate according to claim 1, characterized in that: The addition amount of the promoter system is 0.5-3% of the mass of the carbon dioxide-water mixed system, and it is added in two times: 60-80% is added for the first time in the precooling stage, and the remaining part is added after the pressure rises to 5 MPa; The promoter system further contains a polysaccharide thickener, and the polysaccharide thickener is 0.01-0.1% of the total mass of the promoter system. The polysaccharide thickener is a mixture composed of xanthan gum and gellan gum according to a mass ratio of 1:0.5-1.

5.

6. The method for promoting the formation of carbon dioxide hydrate according to claim 5, characterized in that: The polysaccharide thickener is subjected to carboxymethylation modification with a degree of substitution of 0.3-0.

7. The modification method includes: dispersing the polysaccharide in an alkaline solution, adding sodium chloroacetate, and reacting at 40-60 °C for 4-8 hours. The obtained product is the polysaccharide thickener.

7. The method for promoting the formation of carbon dioxide hydrate according to claim 1, characterized in that: The hydrate formation reaction is carried out in a vertical tubular reactor. The temperature of the circulating coolant in the jacket layer of the tube is 2-5 °C lower than the reaction temperature, and the flow rate is 0.5-1.2 m / s; during the hydrate formation reaction, ultrasonic waves with a frequency of 20-50 kHz are applied, and the ultrasonic power density is 50-150 W / m³.

8. The method for promoting the formation of carbon dioxide hydrate according to claim 1, characterized in that: An organic amine buffer with a concentration of 0.05-0.3 mol / L is added to the carbon dioxide-water mixed system. The organic amine buffer is a mixture composed of triethanolamine and diethanolamine according to a molar ratio of 1:0.8-1.5.

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