An accelerator for the preparation of gas hydrates and its application

Abstract

This invention provides a promoter for the preparation of gas hydrates and its application, comprising, by weight percentage, 0.1%–25% tetrafluoroethane and 75%–99.9% water. The inventors have discovered that using tetrafluoroethane as a promoter for gas hydrates can effectively improve the problems of long induction time, slow formation rate, and high phase equilibrium pressure of gas hydrates. Compared to existing surfactants, such as tetrahydrofuran, the tetrafluoroethane of this invention can effectively stabilize the cage-like structure of hydrates during gas hydrate formation, thereby reducing the induction time, increasing the formation rate, and effectively reducing the phase equilibrium pressure—lower than that achieved by existing surfactants—allowing for the consumption of more reactant gases.

Description

Technical Field

[0001] This invention relates to the field of gas hydrate technology, and more specifically to a promoter for the preparation of gas hydrates and its application. Background Technology

[0002] The current situation regarding CO2 emissions is extremely serious. Taking effective measures to control CO2 emissions is of great significance for addressing global warming and mitigating the intensifying greenhouse effect. In recent years, the technology of recovering and storing CO2 using gas hydrates has attracted the attention of international scholars.

[0003] The formation of gas hydrates is a complex gas-liquid-solid multiphase heat and mass transfer process. Improving the formation rate and gas storage density of hydrates, shortening the induction time, and reducing the phase equilibrium pressure are key to the efficient storage of CO2 gas.

[0004] Adding a suitable surfactant to the reaction system can effectively improve the surface tension of the gas-water system, accelerate the heat and mass transfer process, and promote hydrate formation. Currently discovered surfactants include tetrahydrofuran (THF), tetrabutylammonium bromide (TBAB), and sodium dodecyl sulfate (SDS). Among these, adding tetrahydrofuran (THF) can reduce the phase equilibrium conditions for hydrate formation; tetrabutylammonium bromide (TBAB) can reduce the conditions for hydrate formation; and sodium dodecyl sulfate (SDS) can effectively increase the hydrate formation rate.

[0005] However, the surfactants added above can only improve one aspect of the formation process, and the improvement effect is limited. They cannot simultaneously address the problems of long gas hydrate induction time, slow formation rate, and high phase equilibrium pressure. In view of this, it is indeed necessary to provide a technical solution to solve the above problems. Summary of the Invention

[0006] One of the objectives of this invention is to provide a promoter for the preparation of gas hydrates, addressing the shortcomings of existing technologies, so as to solve the problems that currently used surfactants cannot simultaneously improve the long induction time, slow formation rate, and high phase equilibrium pressure of gas hydrates.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An accelerator for the preparation of gas hydrates comprises, by weight percentage, 0.1% to 25% tetrafluoroethane and 75% to 99.9% water.

[0009] Preferably, by weight percentage, it comprises 1% to 10% tetrafluoroethane and 90% to 99% water.

[0010] Preferably, the applicable gas for preparation includes any one of methane, carbon dioxide, propane, ethane, and ethylene.

[0011] Preferably, the gas used for preparation is carbon dioxide, and the water is an aqueous solution containing a basic compound, wherein the basic compound is a basic compound that can react with carbonic acid to form a carbonate precipitate, and the basic compound accounts for 0.01 to 0.15% of the weight of the aqueous solution.

[0012] Preferably, the basic compound is calcium hydroxide and / or barium hydroxide; the basic compound accounts for 0.05 to 0.1% of the weight of the aqueous solution.

[0013] Preferably, the tetrafluoroethane content is 2% to 4% or 5% to 8% by weight.

[0014] The second objective of this invention is to provide an application of the promoter for gas hydrate preparation according to any one of the above claims in a gas hydrate preparation method. The gas hydrate preparation method is as follows: 75% to 99.9% water by weight is added to a reaction vessel, and 0.1% to 25% tetrafluoroethane by weight is introduced, while controlling the initial pressure of the reaction vessel to be 0.4 to 1 MPa; then, a reaction gas is introduced to carry out the gas hydrate synthesis reaction at a temperature of -2 to 3°C, and the gas hydrate preparation is completed when the pressure inside the reaction vessel no longer decreases.

[0015] Preferably, the synthesis reaction of gas hydrates is further aided by ultrasound and / or stirring.

[0016] Preferably, the reaction gas is carbon dioxide, and the preparation method of carbon dioxide hydrate is as follows: prepare an aqueous solution of a basic compound with a weight percentage of 0.01-0.15%; add 75%-99.9% of the aqueous solution of the basic compound by weight to the reaction vessel, introduce tetrafluoroethane with a weight percentage of 0.1%-25%, and control the initial pressure of the reaction vessel to 0.4-1 MPa; then introduce carbon dioxide and carry out the synthesis reaction of carbon dioxide hydrate at a temperature of -2-3℃. When the pressure in the reaction vessel no longer decreases, the preparation of carbon dioxide hydrate is completed.

[0017] Preferably, the pressure in the reactor after carbon dioxide is introduced is 2.4–10 MPa.

[0018] The beneficial effects of this invention are as follows: The inventors discovered that using tetrafluoroethane as a promoter for gas hydrate formation can effectively improve the problems of long induction time, slow formation rate, and high phase equilibrium pressure of gas hydrates. Compared with existing surfactants, such as tetrahydrofuran, the tetrafluoroethane of this invention can effectively stabilize the cage-like structure of hydrates during gas hydrate formation, thereby reducing the induction time, increasing the formation rate, and effectively reducing the phase equilibrium pressure, which is lower than that achievable by existing surfactants, allowing for the consumption of more reactant gases. Attached Figure Description

[0019] Figure 1 This is a photograph taken before the gas hydrate reaction in Example 1 of the present invention.

[0020] Figure 2 This is a photograph taken during the gas hydrate reaction in Example 1 of the present invention.

[0021] Figure 3 This is a photograph taken after the formation of gas hydrates in Example 1 of the present invention.

[0022] Figure 4 This is a photograph taken before the gas hydrate reaction in Example 6 of the present invention.

[0023] Figure 5 This is a photograph taken during the gas hydrate reaction in Example 6 of the present invention.

[0024] Figure 6 This is a photograph taken after the gas hydrate reaction in Example 6 of the present invention. Detailed Implementation

[0025] The formation of gas hydrates involves water molecules forming cage-like structures through hydrogen bonds to encapsulate the gas. These cage-like structures interlock to provide more enclosures for the gas molecules. The formation of gas hydrates is a complex gas-liquid-solid multiphase heat and mass transfer process, including induction, rapid formation, and the completion of phase equilibrium. The reaction time from induction to the completion of phase equilibrium is very long. Even with the addition of surfactants to accelerate the reaction, hydrate formation still requires at least 7 days, often resulting in low reaction efficiency, high phase equilibrium pressure, limited consumption of reactant gases, and loose, non-dense hydrates. Particularly for carbon dioxide hydrates, the long reaction time can easily cause swelling of the reactor gaskets, leading to carbon dioxide leakage.

[0026] Based on this, a first aspect of the present invention aims to provide an accelerator for the preparation of gas hydrates, comprising, by weight percentage, 0.1% to 25% tetrafluoroethane and 75% to 99.9% water.

[0027] Through extensive research, the inventors discovered that tetrafluoroethane (R134a) can lower the phase equilibrium conditions for hydrate formation. Within the timeframe for hydrate formation (taking 7 days as an example), hydrate synthesis can begin directly at 2.5 MPa. After consuming the reaction gas, the pressure drops below 2.5 MPa. In contrast, no hydrates are formed in a pure water system at 2.5 MPa. Even with the addition of existing surfactants such as THF or SDS, the pressure cannot be lowered from 2.5 MPa to achieve the hydrate synthesis conditions; at least 4 MPa is required. Furthermore, the tetrafluoroethane of this invention also reduces the hydrate induction time and increases the hydrate growth rate, resulting in more hydrates being generated within the same timeframe. These beneficial effects are mainly due to the fact that the presence of tetrafluoroethane effectively stabilizes the cage-like structure of the hydrate, ensuring that a large number of gas molecules are stably encapsulated within the cage, thus promoting the forward reaction.

[0028] In addition, controlling the weight percentage of tetrafluoroethane within the range of 0.1% to 25% can, on the one hand, avoid the tetrafluoroethane content being too low to effectively support the cage structure; on the other hand, it can also avoid the content being too high to hinder gas molecules from entering the cage structure and affecting the hydrate synthesis rate.

[0029] Specifically, the weight percentage of tetrafluoroethane can be 0.1%–1%, 1%–5%, 5%–10%, 10%–15%, 15%–20%, or 20%–25%. Preferably, the weight percentage of tetrafluoroethane is 0.5%–20%. More preferably, the weight percentage of tetrafluoroethane is 0.8%–15%. Even more preferably, the weight percentage of tetrafluoroethane is 1%–10%, specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0030] The water content is adjusted adaptively according to the tetrafluoroethane content. For example, when the weight percentage of tetrafluoroethane is 1% to 10%, the water content is 90% to 99%. The water can be pure water or an aqueous solution containing a compound. This compound should be one that enhances the heat and mass transfer of the system. The heat and mass transfer effect of the compound synergistically works with that of tetrafluoroethane, achieving not only a 1+1>2 effect, but under optimal conditions, a 1+1=4 effect. This can greatly improve the problems of long hydrate induction time, slow formation rate, and high phase equilibrium pressure.

[0031] The gases for which the gas hydrates described in this invention are applicable include any one of methane, carbon dioxide, propane, ethane, and ethylene. Carbon dioxide is preferred as an example, and the following embodiments also use carbon dioxide to verify the beneficial effects of this invention; however, the implementation of this invention is not limited to this.

[0032] Carbon dioxide hydrate (CO2·nH2O) is a non-stoichiometric cage-like compound formed by CO2 and water under certain temperature and pressure conditions. It is typically an SI-type hydrate, containing several small cages and several large cages formed by the combination of these small cages. Carbon dioxide gas molecules mainly occupy the small cages. The tetrafluoroethane of this invention primarily stabilizes the cage-like structure of the large cages. This facilitates more efficient capture of carbon dioxide gas molecules by the small cages, and the carbon dioxide gas molecules are firmly secured within the small cages, effectively promoting the forward reaction of the hydrate. The amount of carbon dioxide reacted is greatly increased. Under optimal conditions, the introduced carbon dioxide can be almost completely reacted, and the phase equilibrium pressure drops to 0.4 MPa–1 MPa.

[0033] In some embodiments, the water used is an aqueous solution containing a basic compound, which is a basic compound that can react with carbonic acid to form a carbonate precipitate, and the basic compound accounts for 0.01 to 0.15% of the weight of the aqueous solution.

[0034] Carbon dioxide's water solubility allows it to form carbonic acid in aqueous solutions. Utilizing this property, the inventors discovered that adding a basic compound to water, which reacts with carbonic acid to form a precipitate, can enhance heat and mass transfer during the precipitation and growth process, thus better promoting the formation of hydrates. Furthermore, its combined use with tetrafluoroethane can have a cumulative promoting effect, efficiently accelerating the formation of carbon dioxide hydrates. Under optimal conditions, the combined use of the two can achieve a 1+1=4 effect, greatly improving the problems of long induction time, slow formation rate, and high phase equilibrium pressure of carbon dioxide hydrates.

[0035] It should be noted that the inventors also conducted experiments using aqueous solutions containing only basic compounds as promoters, without tetrafluoroethane. The reaction conditions could not be started at 2.5 MPa; they had to be carried out at higher pressures, and the promoting effect on the formation of carbon dioxide hydrates was also very effective. Therefore, the present invention is a further improvement based on the premise of containing tetrafluoroethane.

[0036] Specifically, the weight percentage of the basic compound in water can be 0.01–0.02%, 0.02%–0.04%, 0.04%–0.06%, 0.06%–0.08%, 0.08–0.10%, 0.10%–0.12%, or 0.01%–0.15%. Preferably, the weight percentage of the basic compound in water can be 0.05–0.1%, specifically 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%.

[0037] In some embodiments, the basic compound is calcium hydroxide and / or barium hydroxide. The inventors further discovered that using these two basic compounds, with the tetrafluoroethane stabilizing the cage structure, and the presence of these basic compounds in the aqueous solution, effectively enhances heat and mass transfer, further promoting the formation of carbon dioxide hydrate. Calcium hydroxide is particularly preferred, as its low solubility results in small-scale calcium carbonate precipitates. This not only enhances heat and mass transfer but also allows the precipitates to grow to a size that just drives hydrate formation at the microscopic scale, significantly shortening the induction time and effectively promoting the growth rate of carbon dioxide hydrate. During the rapid reaction phase, the pressure of the hydrate drops dramatically, reducing the pressure of the residual gas in the reactor to below 1 MPa within 1000 minutes, an increase of 400-800% compared to the pure water system. Furthermore, a small amount of calcium carbonate is encapsulated within the cage by the hydrate, further stabilizing the cage structure. Combined with the effect of tetrafluoroethane, the resulting carbon dioxide hydrate is abundant and dense.

[0038] Preferably, the calcium hydroxide accounts for 0.05-0.1% of the weight of water. Specifically, it can be 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, or 0.1%. Calcium hydroxide itself is slightly soluble in water, and 0.15% is close to its maximum solubility. The resulting aqueous solution has a low concentration, which is more suitable for the temperature and pressure conditions required for the growth of carbon dioxide hydrates.

[0039] In some embodiments, tetrafluoroethane comprises 2% to 4% or 5% to 8% by weight, with the balance being water, which is an aqueous solution of calcium hydroxide, wherein the calcium hydroxide accounts for 0.05% to 0.1% of the weight of the water.

[0040] Further research by the inventors revealed that in the above embodiments, when the weight percentage of tetrafluoroethane is greater than 4% and less than 5%, the improvement in carbon dioxide hydrate induction time, growth rate, and phase equilibrium pressure is not as significant as when the percentage is in the range of 2%–4% or 5%–8%. This may be because the configuration of the generated carbon dioxide hydrate changes when the percentage is in the range of 4%–5%, thus having some impact.

[0041] In addition to the basic compounds listed above, the addition of other substances or external stimuli that can improve the heat and mass transfer of the system, provided that tetrafluoroethane is contained, also falls within the scope of protection of this invention.

[0042] The second aspect of this invention aims to provide the application of the above-mentioned promoter in a method for preparing gas hydrates. The method for preparing gas hydrates is as follows: 75% to 99.9% water by weight is added to a reaction vessel, and 0.1% to 25% tetrafluoroethane by weight is introduced, while controlling the initial pressure of the reaction vessel to be 0.4 to 1 MPa; then, a reaction gas is introduced to carry out the synthesis reaction of gas hydrates at a temperature of -2 to 3°C, and the reaction is completed when the pressure in the reaction vessel no longer decreases.

[0043] The hydrate preparation method provided by this invention, due to the addition of tetrafluoroethane, the promoter of this invention, allows the synthesis reaction to begin at 2.5 MPa after the reaction gas is introduced. While higher pressures can certainly facilitate hydrate formation, for industrial practicality, it is preferred to begin the synthesis reaction at 2.5 MPa. The reaction temperature can be adjusted according to different gases to meet the hydrate formation conditions, which will not be elaborated further here.

[0044] In some embodiments, ultrasound and / or stirring are also used as auxiliary processes during the synthesis of gas hydrates. Adding ultrasound or stirring can further increase the gas hydrate formation rate. However, it should be noted that the present invention, even without ultrasound or stirring, can effectively improve the problems of long induction time, slow formation rate, and high phase equilibrium pressure in current gas hydrate formation processes. Eliminating these processes avoids the energy consumption required for ultrasound or stirring, and the hydrate preparation cost is lower compared to existing surfactants. In addition to the ultrasound and stirring auxiliary processes listed above, adding other auxiliary processes that can improve hydrate formation under the premise of the present invention also falls within the scope of protection of the present invention.

[0045] In some embodiments, the reactant gas is carbon dioxide, and the preparation method of carbon dioxide hydrate is as follows: prepare an aqueous solution of a basic compound with a weight percentage of 0.01-0.15%; add 75%-99.9% of the aqueous solution of the basic compound by weight to a reaction vessel, introduce tetrafluoroethane with a weight percentage of 0.1%-25%, and control the initial pressure of the reaction vessel to 0.4-1 MPa; then introduce carbon dioxide and carry out the synthesis reaction of carbon dioxide hydrate at a temperature of -2-3°C. When the pressure in the reaction vessel no longer decreases, the preparation of carbon dioxide hydrate is completed.

[0046] In an aqueous solution supplemented with a basic compound, the initial pressure of the reactor can be 0.4–0.5 MPa, and the final pressure of the reactor can be reduced to 0.4–0.5 MPa during the time period when the hydrate is fully formed.

[0047] In some embodiments, the pressure in the reactor after introducing carbon dioxide is 2.4–10 MPa. The higher the pressure in the reactor after introducing carbon dioxide, the higher the carbon dioxide content. Existing surfactants require at least 4 MPa pressure to form hydrates, and even after a long reaction time, the pressure can only be reduced to a maximum of 1.5 MPa before hydrate formation ceases, leaving a large amount of carbon dioxide residue in the system, thus limiting carbon dioxide consumption. However, the tetrafluoroethane provided by this invention can not only reduce the pressure from a relatively high level to 0.4–1 MPa, but also directly start operation from the conventional phase equilibrium pressure of 2.4 MPa, reducing the pressure to 0.4–1 MPa, which is the initial pressure of the reactor. Therefore, this invention can essentially consume all the introduced carbon dioxide, and starting at a lower pressure is more suitable for industrial production applications, making it more feasible. The following examples also directly verify the beneficial effects of this invention from a phase equilibrium pressure of 2.4–2.5 MPa.

[0048] To make the technical solution and advantages of the present invention clearer, the present invention and its beneficial effects will be described in further detail below with reference to specific embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0049] Example 1

[0050] An accelerator for the preparation of gas hydrates comprises, by weight percentage, 3% tetrafluoroethane and 97% water.

[0051] This accelerator is used in the preparation of carbon dioxide hydrate. The preparation method is as follows: 300 mL of water is added to a 600 mL reactor, 9 g of tetrafluoroethane (R134a) (equivalent to 3%) is introduced into the reactor, and the initial pressure of the reactor is controlled at 0.5 MPa. Carbon dioxide (CO2) is continued to be introduced until the pressure of the reactor reaches 2.5 MPa. The temperature is -2℃, and the constant volume reaction is carried out for 1800 min until the gas pressure in the reactor tends to stabilize. The gas pressure drop in the reaction system is 320% higher than that in the pure water system without additives under the same conditions. (It should be noted that carbon dioxide hydrate will not be generated in the pure water system or the system containing other surfactants such as THF. Only the pressure drop caused by carbon dioxide dissolving in water will occur. However, the examples listed in this invention all generate carbon dioxide hydrate.)

[0052] Example 2

[0053] Unlike Example 1, the accelerator in this example contains 6.25% tetrafluoroethane by weight, with the remainder being water.

[0054] The rest of the settings are the same as in Example 1, and will not be repeated here.

[0055] In this embodiment, the gas pressure drop in the reaction system is 235% higher than that in a pure water system without additives under the same conditions.

[0056] Example 3

[0057] Unlike Example 1, the accelerator in this example contains 7.7% tetrafluoroethane by weight, with the remainder being water.

[0058] The rest of the settings are the same as in Example 1, and will not be repeated here.

[0059] In this embodiment, the gas pressure drop in the reaction system is 180% higher than that in a pure water system without additives under the same conditions.

[0060] Example 4

[0061] Unlike Example 1, the accelerator in this example contains 0.1% tetrafluoroethane by weight, with the remainder being water.

[0062] The rest of the settings are the same as in Example 1, and will not be repeated here.

[0063] In this embodiment, the gas pressure drop in the reaction system is 75% higher than that in a pure water system without additives under the same conditions.

[0064] Example 5

[0065] Unlike Example 1, the accelerator in this example contains 25% tetrafluoroethane by weight, with the remainder being water.

[0066] The rest of the settings are the same as in Example 1, and will not be repeated here.

[0067] In this embodiment, the gas pressure drop in the reaction system is 85% higher than that in a pure water system without additives under the same conditions.

[0068] Example 6

[0069] An accelerator for the preparation of gas hydrates comprises, by weight percentage, 3% tetrafluoroethane and 97% an aqueous solution of calcium hydroxide, wherein the calcium hydroxide accounts for 0.067% by weight in the aqueous solution.

[0070] This accelerator is used in the preparation of carbon dioxide hydrate. The preparation method is as follows: 300 mL of calcium hydroxide aqueous solution is added to a 600 mL reactor. 9 g of tetrafluoroethane (R134a) (equivalent to 3% by weight) is introduced into the reactor, and the initial pressure of the reactor is controlled at 0.5 MPa. Carbon dioxide (CO2) is continued to be introduced until the pressure in the reactor reaches 2.5 MPa. The temperature is -2℃, and the constant volume reaction is carried out. The pressure decreases to below 1 MPa within 1000 min. The experiment is stopped after 1800 min (the reaction can still continue). At this time, the gas pressure drop in the reaction system is 635% higher than the gas pressure drop in the pure water system without additives under the same conditions.

[0071] Example 7

[0072] An accelerator for the preparation of gas hydrates comprises, by weight percentage, 6.25% tetrafluoroethane and 93.75% an aqueous solution of calcium hydroxide, wherein the calcium hydroxide accounts for 0.067% by weight in the water.

[0073] This accelerator is used in the preparation of carbon dioxide hydrate. The preparation method is as follows: 300 mL of calcium hydroxide aqueous solution is added to a 600 mL reactor. 20 g of tetrafluoroethane (R134a) (equivalent to 6.25%) is introduced into the reactor, and the initial pressure of the reactor is controlled at 0.5 MPa. Carbon dioxide (CO2) is continued to be introduced until the pressure in the reactor reaches 2.5 MPa. The temperature is -2℃, and the constant volume reaction is carried out. Within 1000 min, the pressure decreases to below 1 MPa. After 1800 min, the gas pressure in the reactor tends to stabilize. At this time, the gas pressure drop in the reaction system is 415% higher than the gas pressure drop in the pure water system without additives under the same conditions.

[0074] Example 8

[0075] Unlike Example 7, the accelerator in this example contains 7.7% tetrafluoroethane by weight, with the remainder being an aqueous solution of calcium hydroxide.

[0076] The rest of the settings are the same as in Example 7, and will not be repeated here.

[0077] In this embodiment, the gas pressure inside the reactor tends to stabilize after 1800 minutes. At this point, the gas pressure drop in the reaction system is 350% higher than that in the pure water system without additives under the same conditions.

[0078] Example 9

[0079] Unlike Example 7, the accelerator in this example contains 4.5% tetrafluoroethane by weight, with the remainder being an aqueous solution of calcium hydroxide.

[0080] The rest of the settings are the same as in Example 7, and will not be repeated here.

[0081] In this embodiment, the gas pressure drop in the reaction system is 300% higher than that in a pure water system without additives under the same conditions.

[0082] Example 10

[0083] Unlike Example 7, the accelerator in this example contains 10% tetrafluoroethane by weight, with the remainder being an aqueous solution of calcium hydroxide.

[0084] The rest of the settings are the same as in Example 7, and will not be repeated here.

[0085] In this embodiment, the gas pressure drop in the reaction system is 315% higher than that in a pure water system without additives under the same conditions.

[0086] Example 11

[0087] Unlike Example 6, in this example, the accelerator contains 3% tetrafluoroethane by weight, with the remainder being an aqueous solution of calcium hydroxide, which accounts for 0.1% of the total aqueous solution.

[0088] The rest of the settings are the same as in Example 6, and will not be repeated here.

[0089] In this example, the gas pressure inside the reactor tends to stabilize after 1800 min. At this point, the gas pressure drop in the reaction system is 545% higher than that in the pure water system without additives under the same conditions.

[0090] Example 12

[0091] Unlike Example 8, in this example, the accelerator contains 7.7% tetrafluoroethane by weight, with the remainder being an aqueous solution of calcium hydroxide, which accounts for 0.1% of the total aqueous solution.

[0092] The rest of the settings are the same as in Example 8, and will not be repeated here.

[0093] In this embodiment, the gas pressure drop in the reaction system is 300% higher than that in a pure water system without additives under the same conditions.

[0094] Example 13

[0095] Unlike Example 6, in this example, the accelerator contains 3% tetrafluoroethane by weight, with the remainder being an aqueous solution of barium hydroxide, which accounts for 0.067% of the total aqueous solution.

[0096] The rest of the settings are the same as in Example 6, and will not be repeated here.

[0097] In this example, the gas pressure inside the reactor tends to stabilize after 1800 min. At this point, the gas pressure drop in the reaction system is 435% higher than that in the pure water system without additives under the same conditions.

[0098] Example 14

[0099] Unlike Example 7, the accelerator in this example contains 6.25% tetrafluoroethane by weight, with the remainder being an aqueous solution of barium hydroxide, which accounts for 0.067% of the total aqueous solution.

[0100] The rest of the settings are the same as in Example 7, and will not be repeated here.

[0101] In this embodiment, the gas pressure drop in the reaction system is 320% higher than that in a pure water system without additives under the same conditions.

[0102] The composition of the accelerators and the gas pressure drop results in Examples 1 to 14 above are summarized in Table 1 below.

[0103] Table 1

[0104]

[0105] As can be seen from the gas pressure drop ratios of Examples 1-14 above, during the constant volume reaction process (i.e., measuring the changes in gas pressure and temperature over time during hydrate formation in a closed reactor), under the same reaction conditions, the gas hydrate provided by this invention can begin to synthesize hydrates at a pressure of 2.5 MPa. However, hydrates cannot be generated in pure water systems or systems containing other surfactants such as THF at a pressure of 2.5 MPa, requiring higher pressures. It is evident that this invention reduces the phase equilibrium pressure for gas hydrate formation and also improves the formation rate. The gas pressure in the reactor tends to stabilize after 1800 min, and the gas hydrate formation reaction is basically completed.

[0106] Furthermore, a comparison between Examples 1-5 and Examples 6-14 shows that when a basic compound is added, i.e., under conditions of enhanced heat and mass transfer, the gas pressure drop ratio is higher compared to the pure water system. Specifically, in the scheme of Example 6, the pressure drops below 1 MPa within 1000 minutes, significantly shortening the induction time and leading to rapid hydrate formation. At 1800 minutes, the gas pressure drop in the reaction system is 635% higher than that in the pure water system without additives under the same conditions, and the reaction can continue. Within the time period for complete hydrate formation (taking 7 days as an example), the pressure inside the reactor can drop by 0.4 MPa, indicating that the introduced carbon dioxide has essentially reacted completely.

[0107] In addition, such as Figures 1-3 and Figures 4-6 The comparison shows that, compared to the beginning Figure 1 and Figure 4 , Figures 2-3 and Figures 5-6 Large amounts of carbon dioxide hydrate were subsequently generated. Furthermore, if we compare... Figure 2 and Figure 5 or Figure 3 and Figure 6 It can also be clearly seen that when basic compounds are added, the amount of carbon dioxide hydrate generated is greater and denser.

[0108] Furthermore, the comparison between Examples 6-7 and Examples 13-14 also shows that, compared with the combination of barium hydroxide aqueous solution and tetrafluoroethane, the combination of calcium hydroxide aqueous solution and tetrafluoroethane can consume a greater amount of carbon dioxide, and the gas pressure drop ratio is increased more under the same conditions and time.

[0109] In summary, using tetrafluoroethane as a promoter for gas hydrates according to the present invention can effectively improve the problems of long induction time, slow formation rate, and high phase equilibrium pressure of gas hydrates. In particular, when used in conjunction with aqueous solutions containing basic compounds, it can greatly improve the problems of long induction time, slow formation rate, and high phase equilibrium pressure of carbon dioxide hydrates. The preparation method is more convenient for industrial application and will not cause environmental pollution.

[0110] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A promoter for gas hydrate production, characterized by, The gas hydrate preparation method comprises the following steps: preparing a water solution of an alkali compound, wherein the alkali compound is an alkali compound which can form carbonate precipitate with carbonic acid, and the weight percentage of the alkali compound in the water solution is 0.01-0.15%; adding 75-99.9% of the water solution of the alkali compound into a reaction kettle; and introducing 0.1-25% of tetrafluoroethane into the reaction kettle, and controlling the initial pressure of the reaction kettle to be 0.4-1 MPa; then introducing carbon dioxide to carry out the synthesis reaction of the carbon dioxide hydrate at a temperature of-2-3 ℃, and the preparation of the carbon dioxide hydrate is completed when the pressure in the reaction kettle stops decreasing.

2. The promoter for gas hydrate production according to claim 1, characterized by, The gas hydrate preparation method comprises the following steps: preparing a water solution of an alkali compound, wherein the alkali compound is an alkali compound which can form carbonate precipitate with carbonic acid, and the weight percentage of the alkali compound in the water solution is 0.01-0.15%; adding 75-99.9% of the water solution of the alkali compound into a reaction kettle; and introducing 0.1-25% of tetrafluoroethane into the reaction kettle, and controlling the initial pressure of the reaction kettle to be 0.4-1 MPa; then introducing carbon dioxide to carry out the synthesis reaction of the carbon dioxide hydrate at a temperature of-2-3 ℃, and the preparation of the carbon dioxide hydrate is completed when the pressure in the reaction kettle stops decreasing.

3. The promoter for gas hydrate production according to claim 1, characterized by, The weight percentage of the alkali compound in the water solution is 0.05-0.1%.

4. The promoter for gas hydrate production according to claim 1, wherein The weight percentage of the tetrafluoroethane is 2-4% or 5-8%.

5. Use of a promoter for gas hydrate formation according to any one of claims 1 to 4 in a method for the production of gas hydrates, characterized in that, The reaction gas is carbon dioxide, and the preparation method of the carbon dioxide hydrate comprises the following steps: preparing a water solution of an alkali compound, wherein the weight percentage of the alkali compound is 0.01-0.15%; adding 75-99.9% of the water solution of the alkali compound into a reaction kettle; introducing 0.1-25% of tetrafluoroethane into the reaction kettle, and controlling the initial pressure of the reaction kettle to be 0.4-1 MPa; then introducing carbon dioxide to carry out the synthesis reaction of the carbon dioxide hydrate at a temperature of-2-3 ℃, and the preparation of the carbon dioxide hydrate is completed when the pressure in the reaction kettle stops decreasing.

6. Use according to claim 5, characterized in that, The synthesis reaction of the gas hydrate is assisted by ultrasonic and / or stirring.

7. Use according to claim 5, characterized in that, The pressure in the reaction kettle after the introduction of the carbon dioxide is 2.4-10 MPa.

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