Method for achieving synergistic effect for improving thermodynamic stability of gas hydrates by using organic mixture as hybrid promoter

Abstract

The present application relates to a method for achieving a synergistic effect for improving the thermodynamic stability of gas hydrates by using an organic mixture as a hybrid promoter. The hybrid promoter according to embodiments of the present application can significantly reduce the energy and cost required for the overall process of forming, storing, and transporting CH4 hydrates, thereby achieving an energy-intensive, economical, and sustainable process.

Description

A method for achieving a synergistic effect in improving the thermodynamic stability of gas hydrates by using organic mixtures as hybrid promoters.

[0001] The present invention relates to a method for obtaining a synergistic effect in improving the thermodynamic stability of gas hydrates by using an organic mixture as a hybrid promoter.

[0002] As the world population continues to grow, global energy demand is steadily increasing, and natural gas demand has also been steadily increasing over the past several decades. Despite recent challenges, including COVID-19, rising prices due to war, increased investment in clean and renewable energy, and technological advancements, natural gas remains a vital energy source. By the early 2020s, it accounted for approximately 25% of primary energy consumption, a share expected to remain stable for the next several decades.

[0003] Given this importance, there is a growing need for sustainable, economical, and safe natural gas transportation. One notable approach is the storage of natural gas or pure CH4 in gas hydrates, a concept that has been studied for the past 30 years due to its potential as solid natural gas or hydrate-based energy storage (HBES), as described in the prior literature (JS Gudmundsson et al., "Storing natural gas as frozen hydrate", SPE Prod. Fac. 9 (1994) 69-73).

[0004] Gas hydrates are a type of material in which water molecules form cage structures through hydrogen bonding, with gas molecules trapped within them through van der Waals interactions. Pure CH4 hydrate can store approximately 170 times more CH4 gas than solid hydrate. Furthermore, its water-based composition makes it non-explosive and environmentally friendly, making it extremely safe. However, its storage capacity is relatively low compared to liquefied natural gas (LNG) or compressed natural gas (CNG). Therefore, minimizing energy consumption during the production, storage, and transportation of CH4 hydrate is crucial to compete with LNG or CNG in terms of energy density.

[0005] The thermodynamic stability of CH4 hydrate affects the entire process, including its production, storage, and transportation. Applying the self-preservation effect to pure CH4 hydrate allows for long-term storage at relatively high temperatures and low pressures. Since this method stores pure methane without any additional components, it offers superior CH4 storage capacity compared to methods where a thermodynamic promoter occupies part of the cage. However, the precise mechanism of self-preservation remains unknown, control is difficult, and the potential for CH4 loss is cited as a drawback. Therefore, rather than applying self-preservation to pure CH4 hydrate, which has low thermodynamic stability, using a thermodynamic promoter to significantly improve the thermodynamic stability of CH4 hydrate and thereby shift storage temperature and pressure to much milder conditions is expected to be more sustainable in terms of energy efficiency and economics.

[0006] Among the promoters reported to date, those with the highest thermodynamic promoting performance are tetrahydrofuran (THF), cyclopentane (CP), and 1,2-epoxycyclopentane (12ECP). THF and CP, well-known conventional promoters, can increase the equilibrium temperature of CH4 hydrate by ~20 K. In particular, THF is miscible with water and has been reported to function as a kinetic promoter, enabling the formation process without stirring. Meanwhile, 12ECP, although immiscible with water, has been reported to exhibit higher promoting ability than THF or CP.

[0007] Efforts to develop new promoters continue to this day, and a significant portion of currently commercialized compounds with molecular sizes suitable for sII or sH have been investigated. Therefore, the discovery of new promoters is expected to soon reach its limit, and attempts to synthesize new compounds that are not currently commercially available as promoters are considered impractical and uneconomical. Therefore, for the future commercialization of HBES technology, it is essential to achieve maximum promoter efficacy using existing, cost-effective promoters.

[0008] The present invention aims to provide a method for obtaining a synergistic effect in improving the thermodynamic stability of gas hydrates by using an organic mixture as a hybrid promoter.

[0009] However, the problems that the present invention seeks to solve are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0010] The first aspect of the present invention provides a hybrid promoter comprising a first promoter; and a second promoter different from the first promoter, wherein the first promoter is cycloheptanone or cyclooctanone, and the hybrid promoter imparts superior thermodynamic stability to gas hydrate compared to the first promoter and the second promoter.

[0011] A second aspect of the present invention provides a hydrate comprising a hybrid promoter according to the first aspect.

[0012] The third aspect of the present invention provides an sH-type thermodynamic promoter for cluster hydrate, which is cyclooctanone.

[0013] Hybrid promoters according to the embodiments of the present invention can exhibit superior performance compared to conventional single promoters.

[0014] The hybrid promoter according to the embodiments of the present invention can realize an energy-intensive process by significantly reducing the energy required for the overall process of CH4 hydrate formation, storage, and transport.

[0015] The hybrid promoter according to the embodiments of the present invention is cheaper than the cyclooctanone-only promoter, and thus can realize an economical process.

[0016] Figure 1 is a schematic structural formula of compounds (cyclooctanone, cycloheptanone, cyclooctane, methylcyclohexane, and 2,2-dimethylbutane) used in one embodiment of the present invention.

[0017] FIG. 2 is a drawing showing a device for producing CH4 hydrate by adding a single promoter and a hybrid promoter and measuring the phase equilibrium temperature-pressure conditions of the produced CH4 hydrate in one embodiment of the present invention.

[0018] Figure 3 is a PT curve of [cyclooctane (cOct, 1.5 mol%) + cyclooctanone (cOct=O, 1.5 mol%) + CH4] hydrate in one embodiment of the present invention.

[0019] Figure 4 is a PT curve of a promoter according to one embodiment of the present invention and a conventional promoter.

[0020] Figures 5a to 5c are high-resolution powder diffraction (HRPD) patterns measured at 150 K of [cOct (3.0 mol%) + CH4] hydrate, [cOct=O (3.0 mol%) + CH4] hydrate, and [cOct(1.5 mol%) + cOct=O(1.5 mol%) + CH4] hydrate, respectively, in one embodiment of the present invention.

[0021] Figures 6a to 6c are schematic diagrams of the sizes of cOct molecules and cOct=O molecules, respectively, and the sH phase formed by (cOct + cOct=O + CH4) hydrate in one embodiment of the present invention.

[0022] Figure 7 is a solid state of [cOct (3.0 mol%) + CH4] hydrate; [cOct=O (3.0 mol%) + CH4] hydrate; [cOct(1.5 mol%) + cOct=O(1.5 mol%) + CH4] hydrate measured at 210 K in one embodiment of the present invention. 13 This is a C NMR spectrum.

[0023] FIG. 8 is an equilibrium PT curve of [cOct (3.0 mol%) + CH4] hydrate; [cOct=O (3.0 mol%) + CH4] hydrate; and [cOct(1.5 mol%) + cOct=O(1.5 mol%) + CH4] hydrate in one embodiment of the present invention.

[0024] Figure 9 is an equilibrium PT condition curve of [cOct (1.5 mol%) + cOct=O (1.5 mol%) + CH4] hydrate measured five times over three years in one embodiment of the present invention.

[0025] Figures 10a and 10b are, in one embodiment of the present invention, an equilibrium PT curve according to the composition of cOct=O; and a T-x2 curve under isobaric conditions (x2 means mol% of cOct=O), respectively.

[0026] Figures 11a and b are PXRD patterns (150 K) and (cOct + cOct=O + CH4) hydrates of various compositions, respectively, in one embodiment of the present invention. 13 C NMR spectrum (210 K).

[0027] FIG. 12a is an equilibrium PT curve of CH4 hydrate including 22DMB, MCH, and [22DMB+MCH], respectively, in one embodiment of the present invention, and FIG. 12b is an equilibrium PT curve of CH4 hydrate including MCH, cOct, and [MCH+cOct=O], respectively, in one embodiment of the present invention.

[0028] FIG. 13a is an equilibrium PT curve of CH4 hydrate including 22DMB, cOct=O, and [22DMB+cOct=O], respectively, in one embodiment of the present invention, and FIG. 13b is an equilibrium PT curve of CH4 hydrate including MCH, cOct=O, and [MCH+cOct=O], respectively, in one embodiment of the present invention.

[0029] FIG. 14 is an equilibrium PT curve of CH4 hydrate, each including cyclooctane (cOct), cycloheptanone (cHpt=O), and [cOct+cHpt=O], in one embodiment of the present invention.

[0030] Hereinafter, with reference to the attached drawings, implementation examples and embodiments of the present invention will be described in detail so that those skilled in the art can easily practice the present invention. However, the present invention may be implemented in various different forms and is not limited to the implementation examples and embodiments described herein. In addition, in the drawings, parts irrelevant to the description have been omitted to clearly explain the present invention, and similar parts have been designated with similar drawing reference numerals throughout the specification.

[0031] Throughout this specification, when a part is said to be "connected" to another part, this includes not only cases where it is "directly connected" but also cases where it is "electrically connected" with another element in between.

[0032] Throughout this specification, when it is said that an element is "on" another element, this includes not only cases where the element is in contact with the other element, but also cases where another element exists between the two elements.

[0033] Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0034] The terms "about," "substantially," and the like used in this specification are used in a meaning that is at or close to the numerical value when manufacturing and material tolerances inherent in the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which exact or absolute values ​​are mentioned to aid understanding of the present application.

[0035] The terms “step of ~” or “step of ~” as used throughout this specification do not mean “step for ~.”

[0036] Throughout this specification, the term "combination(s) thereof" included in the expressions in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expressions in the Makushi format, and means including one or more selected from the group consisting of said components.

[0037] Throughout this specification, references to “A and / or B” mean “A or B, or A and B.”

[0038] Throughout this specification, the term "hybrid promoter" means a hybrid promoter that uses a mixture of a first promoter and a second promoter, thereby possessing unique properties other than those possessed by each of the first promoter and the second promoter.

[0039] Below, the implementation examples of the present invention are described in detail, but the present invention may not be limited thereto.

[0040] The first aspect of the present invention provides a hybrid promoter comprising a first promoter; and a second promoter different from the first promoter, wherein the first promoter is cycloheptanone or cyclooctanone, and the hybrid promoter imparts superior thermodynamic stability to gas hydrate than the first promoter and the second promoter.

[0041] In one embodiment of the present invention, the first promoter and the second promoter may be sI-type, sII-type, or sH-type thermodynamic promoters, and the first promoter and the second promoter may be thermodynamic promoters of the same type.

[0042] In one embodiment of the present invention, the second promoter may be an organic compound.

[0043] In one embodiment of the present invention, the second promoter may be a conventional promoter.

[0044] In one embodiment of the present invention, the second promoter comprises one or more C 1-4 C substituted or unsubstituted with an alkyl group 3-10 Alkane; C 5-10 Cycloalkanone; one or more C 1-4 C substituted or unsubstituted with an alkyl group 5-10 It may be selected from cycloalkane; tetrahydrofuran; tetrahydrothiophene; and tert-butyl methyl ether.

[0045] In one embodiment of the present invention, the second promoter is propane, butane, 2,2-dimethylbutane, pentane, hexane, heptane, octane, nonane, decane, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, cyclononanone, cyclodecanone, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, methylcyclohexane, tetrahydrofuran, tetrahydrothiophene, 2-methylbutane, 2,3-dimethylbutane, 2,2,3-dimethylbutane, 2,2-dimethylpentane, 2,3-dimethylpentane, 3,3-dimethylpentane, methylcyclopentane, ethylcyclopentane, It may be selected from 1,1-dimethylcyclohexane, 1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, ethylcyclohexane, and tert-butyl methyl ether.

[0046] In one embodiment of the present invention, the molar ratio of the first promoter and the second promoter (first promoter:second promoter) may be about 1:10 to about 5:1. In one embodiment of the present invention, the composition ratio of the first promoter and the second promoter may be about 1:10 to about 5:1, about 1:9 to about 5:1, about 1:8 to about 5:1, about 1:7 to about 5:1, about 1:6 to about 5:1, about 1:5 to about 5:1, about 1:5 to about 4:1, about 1:5 to about 3:1, about 1:5 to about 2:1, about 1:2 to about 5:1, about 1:2 to about 2:1. In one embodiment of the present invention, the composition ratio of the first promoter and the second promoter may be about 1:1.

[0047] A second aspect of the present invention provides a hydrate comprising a hybrid promoter according to the first aspect.

[0048] Detailed explanations of parts that overlap with the first aspect of the present application have been omitted, but the contents described in the first aspect of the present application may be equally applied even if the explanation is omitted in the second aspect of the present application.

[0049] In one embodiment of the present invention, the hydrate may have an sH structure.

[0050] In one embodiment of the present invention, the hybrid promoter may be included in an amount of about 1 mol% to about 6 mol%, but may not be limited thereto. In one embodiment of the present invention, the hybrid promoter may be present in an amount of about 1 mol% to about 6 mol%, about 1 mol% to about 5 mol%, about 1 mol% to about 4 mol%, about 1 mol% to about 3 mol%, about 1 mol% to about 2 mol%, about 2 mol% to about 6 mol%, about 2 mol% to about 5 mol%, about 2 mol% to about 4 mol%, about 2 mol% to about 3 mol%, about 3 mol% to about 6 mol%, about 3 mol% to about 5 mol%, about 3 mol% to about 4 mol%, about 4 mol% to about 6 mol%, about 4 mol% to about 5 mol%, or about 5 mol% to about 6 mol%, but may not be limited thereto. For example, when the first promoter and the second promoter are sH-type, the hybrid promoter may be included at about 3 mol%, and when the first promoter and the second promoter are sII-type, the hybrid promoter may be included at about 5 mol% to about 6 mol%, or about 5.6 mol.

[0051] The third aspect of the present invention provides an sH-type thermodynamic promoter for cluster hydrate, which is cyclooctanone.

[0052] Detailed descriptions of overlapping parts with the first and second aspects of the present application have been omitted, but the contents described for the first and second aspects of the present application may be equally applied even if the description is omitted in the third aspect of the present application.

[0053] Hereinafter, the present invention will be described in more detail using examples. However, the following examples are provided only to help understand the present invention, and the contents of the present invention are not limited to the following examples.

[0054] [Example]

[0055] <Materials used>

[0056] IUPAC Name Abbreviation CAS No. MW Supplier Product No. Purity Cyclooctanone cOct=O502-49-8126.20 Tokyo Chemical Industry (TCI) C050497+% Cyclooctane cOct 292-64-8112.17 Alfa Aesar) L1500099 + % Methylcyclohexane MCH 108-87-298.19 TCIM019099 + % 2,2-dimethylbutane 22DMB 75-83-286.18 TCID 068998 + % Cycloheptanone cHpt = O 502-42-1112.17 TCIC 046698 + % Water H2O 7732-18-518.02 Merck 115333 LC-MS Methane CH 474-82-816.04 Daesung Gas 99.95%

[0057] The chemicals used in this example are shown in Fig. 1 and Table 1 above. All chemicals were used as received without further purification.

[0058] <P-T 추적 곡선 도출>

[0059] The PT trace curve was obtained through the following process, and the equilibrium PT conditions were determined accordingly:

[0060] (1) 1.12 g of cOct, 1.26 g of cOct=O, and 1.19 g of cOct (1.5 mol%) + cOct=O (1.5 mol) were added to 6.12 g of H2O to make the total concentration of the sH former 2.9 mol% to 3.0 mol%. The mixture was placed in a high-pressure resistance cell (~100 mL), and CH4 gas was injected at the required pressure at ambient temperature (~290 K); (2) While stirring at 150 rpm, the temperature of the cell was raised to 313 K to make cOct and cOct=O completely liquid; (3) The cell was cooled to 263 K for 10 h (-5 K / h), then heated to 272 K and maintained there for 2 h (even slower cooling rates of -1 K / h or less cause a pressure drop around 273 K, but maintaining the temperature just below the freezing point (273 K) after sufficient supercooling takes much less time); (4) When there was no further pressure decrease, the temperature of the cell was lowered to 268 K to confirm that hydrate formation was complete; (5) The equilibrium PT condition was obtained by gradually increasing the temperature at a very slow rate of +0.15 K / h (+1 K / 6 h). P and T inside the cell were measured using a pressure transmitter (model A-10, WIKA, Germany) and a resistance temperature detector (Pt100-class B), respectively. The data of P and T were automatically recorded every minute until the temperature reached 293 K. In the above processes (2) to (5), the stirring speed was maintained at 150 rpm. The PT curve (Fig. 3) for this was consistent with the conventional PT curve (Fig. 4). Accordingly, the reliability of the measurement method and data of this example was confirmed.

[0061] Hydrate Analysis

[0062] After performing the above (1) to (4), a solid sample was rapidly collected from a cell immersed in liquid nitrogen. The sample was finely ground (d < 200 μm) and stored in liquid nitrogen until immediately before measurement. The crystal structure of the powder sample was analyzed using a synchrotron high-resolution powder diffraction (HRPD) instrument at Pohang Accelerator Laboratory (Beamline 9B) or a powder X-ray diffraction (PXRD) instrument at the KAIST Research Development Analysis Center (SmartLab, Rigaku). HRPD patterns were obtained in the range of 2θ = 5.0° to 125.0° using X-rays with λ = 1.5425 Å, with a measurement interval of 0.01° and a measurement time of 0.7 s. Solid state 13 C NMR experiments were performed to analyze the distribution of target molecules using a Bruker Avance II 400 MHz NMR instrument at the Korea Basic Science Institute (Seoul Western Center). 13 C High-power decoupling / magic-angle spinning (MAS) NMR spectra were obtained using a 4 mm OD zirconia rotor with a MAS speed of 5 kHz. A pulse length of 1.6 μs and a repetition delay time of 3 s were applied. The static spectroscopy of tetramethylsilane at room temperature 13 The C signal was used as the reference (0 ppm).

[0063] 1. High-resolution powder diffraction analysis (HRPD)

[0064] Referring to Fig. 5a, for the (cOct + CH4) hydrate, the sH structure (P6 / mmm) with lattice parameters of a = 12.275 Å and c = 9.982 Å was observed at 150 K, which closely matches the values ​​(a = 12.313 Å and c = 10.054 Å at 215 K) disclosed in the previous literature 'KA Udachin et al., "Transformation of the hexagonal-structure clathrate hydrate of cyclooctane to a low-symmetry from below 167 K", Angew. Chem. Int. Ed. 47 (2008) 9704-9707'. Referring to Fig. 5, since the molecular sizes of cOct and cOct=O are similar, cOct=O is also expected to form sH hydrate.

[0065] Referring to b in Fig. 5, for the (cOct=O + CH4) hydrate, the sH structure with lattice parameters a = 12.295 Å and c = 10.000 Å can be confirmed.

[0066] Referring to c in Fig. 5, for the [cOct (1.5 mol%) + cOct=O (1.5 mol%) + CH4] hydrate, the lattice parameters are a = 12.279 Å and c = 9.984 Å, which are intermediate values ​​between those of (cOct + CH4) and (cOct=O + CH4) hydrates. In particular, rather than (cOct + CH4) hydrate (having a relatively small lattice parameter) and (cOct=O + CH4) hydrate (having a relatively large lattice parameter) being formed separately, a uniform phase having one set of lattice parameters was formed.

[0067] 2. 13 C NMR

[0068] solid state 13As a result of C NMR analysis, referring to Figure 7, two distinct peaks are observed at approximately -4.6 ppm and -4.9 ppm, which correspond to CH4 trapped in the sH-S and sH-M cages, respectively, which are due to CH4 trapped in the sH-S cage and sH-M cage, respectively. The two peaks (A S / A M ) are 1.49, 1.47, and 1.58 for (cOct + CH4), (cOct=O + CH4), and (cOct + cOct=O + CH4) hydrates, respectively. These values ​​are similar to the theoretical value of 1.5 for sH hydrate. Since no peak attributed to CH4 is observed in the sH-L cage, it can be inferred that the sH-L cage is exclusively filled with cOct or cOct=O. Fig. 6c shows a uniform and homogeneous sH phase formed by (cOct + cOct=O + CH4) hydrate.

[0069] 3. Equilibrium PT curve

[0070] Referring to Fig. 8, the four-phase (L1-L2-HV) equilibrium PT conditions for the (cOct / cOct=O + CH4) hydrate system can be confirmed. When compared at a constant pressure of 50 bar, the addition of cOct increases the equilibrium temperature of CH4 hydrate by approximately 4.5 K (graph indicated by circles). Meanwhile, the addition of cOct=O increases the equilibrium temperature by approximately 6.0 K (graph indicated by triangles). This indicates that the novel sH former cOct=O exhibits superior promotion performance compared to the existing promoter cOct. On the other hand, when a 1:1 mixture of cOct and cOct=O was added, the equilibrium temperature increased by only 7.0 K (graph indicated by diamonds). In general, the addition of a mixture of two different promoters is expected to exhibit a promotion performance that is intermediate between the promotion performances of the two promoters. However, the mixture of cOct and cOct=O exhibits a better promotion performance than the effective promoter cOct=O alone. This suggests that cOct and cOct=O synergistically enhance the thermodynamic stability of CH4 hydrate.

[0071] Regarding the above phenomenon, there are two important considerations:

[0072] (1) Consideration of measurement error or reliability of equilibrium conditions

[0073] As described above, the equilibrium conditions for pure CH4 and (cOct + CH4) hydrate are in good agreement with previously reported data. Referring to Fig. 9, for (cOct + cOct=O + CH4) hydrate, five equilibrium curves were derived over a three-year period, and all equilibrium curves were identical, confirming that this synergistic promotion was not the result of measurement error.

[0074] (2) Consideration of the dissociation tendency of (cOct+cOct=O+ CH4) hydrate

[0075] As shown in Fig. 7, cOct and cOct=O have different promoting performances, but no distinct shoulder is observed during the dissociation process of (cOct+cOct=O+ CH4) hydrate (286 K to 290 K, indicated by a circle in the graph of Fig. 3). That is, (cOct=O+ CH4) hydrate does not dissociate first, followed by (cOct=O+ CH4) hydrate, but (cOct+cOct=O+ CH4) hydrate dissociates simultaneously. When these results are combined with the HRPD results, it can be determined that cOct and cOct=O behave as if they were a single type of promoter to form sH CH4 hydrate.

[0076] x2= 0x2= 0.5x2= 1.0x2= 1.5x2= 2.0x2= 2.5x2= 3.0T / KP / barT / KP / barT / KP / barT / KP / barT / KP / barT / KP / barT / KP / bar280.533.4282.932.9283.733.5283.834.6 282.432.4282.432.9282.933.2283.949.5285.845.3286.145.5285.543.0285.145.0284.844.0285.043.6286.0 64.6287.558.0287.658.2286.952.7286.958.0286.655.1286.150.5287.477.3289.071.0288.969.4288.666.3288.571.5288.168.3287.358.5290.384.6290.583.7290.281.2289.883.5289.983.3288.165.2289.577.129082.5

[0077] *x2 represents the mol% of cOct=O. The sum of the mol% of cOct and cOct=O is 3.0.

[0078] Table 2 above shows the equilibrium PT conditions measured with various compositions of cOct=O (x2) while maintaining the total fraction of cOct and cOct=O at 3.0 mol%. Referring to Fig. 10(a), the data of Table 2 are graphically plotted in an x2-TP diagram in the range of 40 bar to 80 bar. Referring to Fig. 10(b), the equilibrium curves depending on the mixing ratio of cOct and cOct=O under isobaric conditions are shown. The straight line connecting the T values ​​at x2= 0 (pure cOct) and x2= 3.0 (pure cOct=O) represents the expected dissociation temperature assuming an ideal mixing effect of cOct and cOct=O. At all pressures, cOct and cOct=O exhibit synergistic promotion, and the promotion performance is maximum when x2 is in the range of 0.5 mol% to 1.5 mol%. Within this composition range, the equilibrium T value showed a synergistic promotion performance that was approximately 2 K higher than that assuming an ideal mixing effect. In addition, it was approximately 1 K higher than the value of (cOct=O + CH4) hydrate (x2= 3.0 mol%). Referring to Fig. 11, the PXRD patterns of hydrates according to various composition ratios of cOct and cOct=O and 13 By analyzing the C NMR spectrum, it was confirmed that all hydrates in Figure 10 had the sH structure.

[0079] To determine whether the observed synergistic promotion is unique to the (cOct + cOct=O) system or a general phenomenon, the equilibrium curves of CH4 hydrate with three representative promoters (22DMB, MCH, and cOct) and their mixtures were analyzed (Fig. 12). Referring to Fig. 12a, a 1:1 mixture of 22DMB and MCH exhibited promotion performance comparable to that of the individual components. Similarly, referring to Fig. 12b, a 1:1 mixture of MCH and cOct also exhibited promotion performance similar to that of the individual components. None of the mixtures outperformed the performance of the individual components.

[0080] However, this is not a phenomenon observed only in the (cOct+cOct=O) system, and referring to Figure 13, synergistic promotion was observed when 22DMB was mixed with cOct=O. Although 22DMB has a lower promotion performance than cOct=O, a 1:1 mixture of 22DMB and cOct=O improved the equilibrium temperature by 1.1 K (at 50 bar) compared to cOct=O alone. Similarly, MCH has a lower promotion performance than cOct=O, but a 1:1 mixture of MCH and cOct=O improved the equilibrium temperature by 0.7 K (at 50 bar) compared to cOct=O alone. In addition, cOct and cHpt=O showed similar promotional performance when used as single promoters, but when they were mixed in a 1:1 (1.5 mol%:1.5 mol%) ratio, the equilibrium temperature was increased by 1.0 K to 1.5 K compared to when used alone, showing synergistic promotion (see Figure 14).

[0081] Economic Analysis

[0082] From an engineering point of view, these hybrid promoters are expected to be used in various fields of hydrate utilization. The promotion performance of cOct=O is higher than that of cOct. However, a 1:1, 2:1, or 5:1 mixture of cOct and cOct=O (i.e., x2 = 1.5 mol%, 1.0 mol%, or 0.5 mol%) shows a much higher promotion performance than cOct=O alone. In the range of 40 to 80 bar and 280 to 290 K, a 1 K increase in the equilibrium temperature means a 7 to 10 bar decrease in the equilibrium pressure, which ultimately means a 10 bar decrease in the pressure required for storing gas in the form of hydrate and for storing and transporting the produced hydrate.

[0083] Furthermore, as shown in Table 3 below, since cOct is significantly cheaper than cOct=O, the hybrid promoter is more economical than using cOct=O alone. For example, assuming that the price of cOct is 30% of the price of cOct=O (e.g., $300 / kg for cOct (Merck) and $964 / kg for cOct=O (ThermoFisher)), the 2:1 hybrid promoter is 50% cheaper than the cOct=O promoter alone. Therefore, the synergistic promotion performance by the hybrid promoter can realize sustainable hydrate-based gas storage (HBGS) by maximizing both energy efficiency and economic feasibility.

[0084] Where to buy: TCI ThermoFisher Merck cOct $27.0 / 25 mL $113 / 250 mL $630 / 2.5 L cOct=O $39.0 / 25 g $482 / 500 g $131 / 100 g (cOct / cOct=O) ratio ++ 82%56%23%

[0085] ++Price per kilogram considering the density of cOct as 0.84 kg / L.

[0086] The above description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0087] The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. The first promoter; and A second promoter different from the first promoter As a hybrid promoter comprising, The above first promoter is cycloheptanone or cyclooctanone, The above hybrid promoter provides superior thermodynamic stability to the gas hydrate than the first promoter and the second promoter. Hybrid promoter.

2. In paragraph 1, The first promoter and the second promoter are sI-type, SII-type, or sH-type thermodynamic promoters, A hybrid promoter, wherein the first promoter and the second promoter are thermodynamic promoters of the same type.

3. In paragraph 1, A hybrid promoter wherein the second promoter is an organic compound.

4. In paragraph 3, The second promoter comprises one or more C 1-4 C substituted or unsubstituted with an alkyl group 3-10 Alkane; C 5-10 Cycloalkanone; one or more C 1-4 C substituted or unsubstituted with an alkyl group 5-10 A hybrid promoter selected from cycloalkane; tetrahydrofuran; tetrahydrothiophene; and tert-butyl methyl ether.

5. In paragraph 3, The second promoter is propane, butane, 2,2-dimethylbutane, pentane, hexane, heptane, octane, nonane, decane, cyclopentanone, cyclohexanone, cycloheptanone, cyclooctanone, cyclononanone, cyclodecanone, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclononane, cyclodecane, methylcyclohexane, tetrahydrofuran, tetrahydrothiophene, 2-methylbutane, 2,3-dimethylbutane, 2,2,3-dimethylbutane, 2,2-dimethylpentane, 2,3-dimethylpentane, 3,3-dimethylpentane, methylcyclopentane, ethylcyclopentane, 1,1-dimethylcyclohexane, A hybrid promoter selected from 1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, ethylcyclohexane, and tert-butyl methyl ether.

6. In paragraph 1, A hybrid promoter, wherein the molar ratio of the first promoter and the second promoter (first promoter:second promoter) is 1:10 to 5:

1.

7. A hydrate comprising a hybrid promoter according to paragraph 1.

8. In paragraph 7, Hydrate, which is a sH structure.

9. In paragraph 7, Hydrate, wherein the above hybrid promoter is included in an amount of 1 mol% to 6 mol%.

10. Cyclooctanone, an sH-type thermodynamic promoter for cluster hydrate.

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