A method of regulating the formation of a sparingly soluble gas hydrate

Abstract

The present application relates to the field of gas hydrate, and particularly to a method for regulating the formation of a poorly soluble gas hydrate; the method regulates the hydrophilic and hydrophobic properties of the attached solid surface, controls the influence of the surface on the growth rate of the gas hydrate; by regulating the hydrophilic and hydrophobic properties of the solid surface and controlling the particles in the gas and solution, the growth rate of the gas hydrate can be regulated; the solid is a fused quartz material; the regulation specifically controls the area ratio of the hydrophobic region and the hydrophilic region of the solid surface to be 1:1.75; the present application combines the advantages of both, optimally designs the area ratio of the hydrophobic small region and the hydrophilic small region, so that the nucleation of the hydrophobic region and the material migration can be achieved, and the adjacent hydrophilic region can also be used as a crystallization site to shorten the time required for the growth of the gas hydrate, which is conducive to promoting the generation of the gas hydrate in different application environments.

Description

Technical Field

[0001] This invention belongs to the field of gas hydrates, and specifically provides a method for regulating the formation of sparingly soluble gas hydrates. Background Technology

[0002] Natural gas hydrates are crystalline compounds formed by water (host) molecules and methane (guest) molecules under high pressure and low temperature conditions. They are clean, efficient, abundant, and sustainable alternative energy sources that can meet the growing global energy demand as traditional fossil fuels decline. Natural gas hydrates are widely distributed in permafrost and deep-sea continental margins. Extensive work has been done in the past few decades to address the development and production of natural gas. However, due to a relatively insufficient understanding of the hydrate formation mechanism, the commercial development of natural gas hydrates is still immature. Natural gas hydrates have also attracted much attention due to their potential significance for many practical problems, such as preventing the formation of natural gas hydrates in gas pipelines, global warming, carbon dioxide sequestration, hydrogen storage, marine geological hazards, and seawater desalination. These problems also require a correct understanding of the hydrate formation mechanism at the microscopic level. To date, many molecular dynamics (MD) simulations have been conducted, providing molecular-level insights into these mechanisms. Current simulation studies on the formation process of methane hydrates mainly focus on homogeneous nucleation of artificially supersaturated methane solutions in a volumetric liquid.

[0003] However, the hydrate formation mechanisms occurring in these solutions may differ from those in real-world solutions. Under actual conditions, hydrate nucleation occurs via heterogeneous nucleation, where the surface plays a crucial role. Furthermore, since natural gas hydrates can form under diverse geological conditions, understanding their nucleation mechanisms on hydrophobic or hydrophilic surfaces is essential. Numerous molecular dynamics (MD) simulations have been conducted on the behavior and microstructure of natural gas hydrates in the presence of hydrophobic or hydrophilic solid surfaces. However, despite the similarities in the systems studied in these works, the observed variety of mechanisms highlights the complexity of the problem. Some currently controversial issues include: whether hydrate formation occurs near the surface or in the bulk phase; whether hydroxylation of the surface triggers or inhibits hydrate formation; whether sparingly soluble gases are concentrated on hydrophobic or hydrophilic surfaces; and whether hydrophobic or hydrophilic surfaces provide nucleation nodes, among others. Summary of the Invention

[0004] The purpose of this invention is to propose a method for regulating the growth of interfacial gas hydrates by controlling the properties of the solid surface to influence the growth of gas hydrates.

[0005] This invention modulates the hydrophilicity and hydrophobicity of the attached solid surface, controlling its influence on the growth rate of gas hydrates. Under actual conditions, hydrate nucleation occurs through heterogeneous nucleation, in which the gas-liquid surface and the surface of the attached solid play crucial roles.

[0006] Therefore, by controlling the hydrophilic and hydrophobic properties of solid surfaces and the particles in gases and solutions, the growth rate of gas hydrates can be regulated.

[0007] A method for regulating the formation of sparingly soluble gas hydrates, characterized in that the growth of gas hydrates is influenced by regulating the hydrophilicity and hydrophobicity of the solid surface.

[0008] Preferably, the solid is fused silica material.

[0009] Preferably, the regulation specifically involves controlling the area ratio of the hydrophobic region to the hydrophilic region on the solid surface to be 1:1.75.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] Based on our macroscopic and microscopic experiments on the growth of gas hydrates on solid-liquid surfaces, we concluded that hydrophobic interfaces are conducive to gas nucleation and migration but unfavorable to crystal growth; hydrophilic interfaces are conducive to the adhesion of microcrystals but unfavorable to migration and mass transport, also hindering crystal growth. This invention combines the advantages of both, optimizing the area ratio of hydrophobic and hydrophilic microregions. This allows for the utilization of hydrophobic regions for nucleation and mass migration, as well as the use of adjacent hydrophilic regions as crystallization sites, shortening the time required for gas hydrate growth and facilitating the formation of gas hydrates under various application environments. Attached Figure Description

[0012] Figure 1 The graph shows the SFG signal of a semi-hydrophilic and semi-hydrophobic surface versus the SFG signal of a hydrophobic surface (representing the area ratio of the hydrophobic region).

[0013] Figure 2 A, B, and C are images of the contact angles of ultrapure water droplets on a highly hydrophobic OTS coating, a partially hydrophobic OTS coating, and a hydrophilic silica surface, respectively.

[0014] Figure 2 Image D of water droplets before hydrate crystallization in regions (1)(2)(3) when t=0s;

[0015] Figure 2 When t0 = 0s, E first forms a nucleation image at random locations around the water droplets in region (2);

[0016] Figure 2When t1 = 60s, the hydrated crystals in region (2) grow, forming a polycrystalline layer covering the original water droplet;

[0017] Figure 2 G is the image of hydrates exceeding the original water boundary in region (2) when t2 = 240s, and hydrates beginning to form in region (1);

[0018] Figure 2 H. Comparison of hydrate crystal growth in region (1) and region (2) on the covered surface when t3 = 270s;

[0019] Figure 2 Image of water droplet surface in region (3) where hydrate crystals begin to form at t4 = 405s;

[0020] Figure 2 J is the image of the hydrate front in region (3) reaching one end of the water droplet and advancing towards the other end when t5 = 420s;

[0021] Figure 2 When t6 = 450s, the hydrated crystals in region (3) grow, forming a layer covering the surface of the water droplet. Detailed Implementation

[0022] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0023] Example 1

[0024] This embodiment provides a method for pre-experimental treatment of windows with different hydrophilicity, hydrophobicity, and semi-hydrophobicity.

[0025] (1) Hydrophilic window. Infrared grade fused silica window is used. It is cleaned with ultraviolet ozone for 1 hour, soaked in concentrated sulfuric acid-Nochromix mixed solution for 6 hours, ultrasonically rinsed with deionized water for 30 minutes, and then baked until dry.

[0026] (2) Hydrophobic window. The fused silica window is cleaned through the above process. A mixed solution of 80% hexadecane, 12% carbon tetrachloride (CCl4) and 8% chloroform is prepared. A low concentration of trichlorooctadecylsilane organic molecules (OTS) is added. A dense monomolecular film with stable surface properties and uniform structure is grown on the surface of the window by the self-assembly of OTS molecules, so that the surface of the window is hydrophobic.

[0027] (3) Semi-hydrophilic and semi-hydrophobic window. The OTS molecular layer firmly covering the surface of the window can only be removed by UV cleaning. Based on the prepared window with OTS covering the surface, a UV ozone cleaning machine was used to remove some of the OTS after about 30 minutes, reducing the surface coverage. This resulted in a fused silica window with surface hydrophilic and hydrophobic properties between hydrophilic and completely hydrophobic.

[0028] (4) Three regions—hydrophilic, hydrophobic, and semi-hydrophilic / semi-hydrophobic—are simultaneously formed on the same window. The preparation method involves immersing half of the window in a mixed solution of 80% hexadecane, 12% carbon tetrachloride (CCl4), and 8% chloroform during OTS growth, and then adding a low-concentration solution of trichlorooctadecylsilane organic molecules (OTS). Consequently, the OTS coverage at the liquid surface is lower, thus forming a semi-hydrophilic / semi-hydrophobic region. The immersed and unimmersed portions are the hydrophilic and hydrophobic regions, respectively.

[0029] like Figure 2 The image shows a series of photographs of water droplet crystallization on a silica surface in a strongly hydrophobic region (1) with no hydrate formation history, a partially hydrophobic region (OTS coating) (2), and a hydrophilic region (3). The elapsed time is shown below each photograph. The experimental conditions were T = -13℃ and P = 7.0 MPa.

[0030] On a macroscopic level, we can directly obtain experimental results by taking photographic images (see...). Figure 2 DK) studied the formation of natural gas (methane) hydrates on three different hydrophilic fused silica surfaces using our self-made optical system.

Claims

1. A method for regulating the formation of methane gas hydrate, characterized in that, The growth of methane gas hydrates can be influenced by controlling the hydrophilicity and hydrophobicity of the fused silica window surface; Specifically, the regulation involves controlling the area ratio of hydrophobic micro-regions to hydrophilic micro-regions on the surface of the fused silica window to be 1:1.75; The methods for preparing hydrophobic and hydrophilic microregions on the surface of fused silica windows are as follows: (1) The OTS molecular layer on the surface of the fused silica window is treated with an ultraviolet ozone cleaner to remove some of the OTS, thereby reducing its surface coverage. This results in a fused silica window with surface hydrophilic and hydrophobic properties between hydrophilic and completely hydrophobic. The area ratio of the hydrophobic micro-region to the hydrophilic micro-region in the fused silica window is 1:1.75.

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