A silicon dioxide hydrophobic oleophilic separation membrane based on stainless steel mesh and a preparation method thereof

Abstract

This invention relates to a silica oil-water separation membrane based on stainless steel mesh and its preparation method, which is applied to oil-water separation in oil fields and belongs to the field of oil-water separation. Preparation method: (1) The stainless steel mesh is completely immersed in a 5% NaOH aqueous solution by mass and ultrasonically treated. Then it is cleaned with acetone, ethanol and deionized water respectively; (2) The stainless steel mesh obtained in step (1) is etched with hydrofluoric acid solution, then ultrasonically cleaned with acetone, ethanol and deionized water respectively, and dried; (3) A mixed sol of anhydrous ethanol, deionized water, ammonia and tetraethoxysilane is prepared; (4) An appropriate amount of methyltriethoxysilane is added dropwise to the mixed sol; (5) The silica sol obtained in step (4) is aged, and then the stainless steel mesh treated in step (2) is immersed in the sol for about 5 min, taken out and dried, and the cycle is repeated 4 times; (6) The stainless steel mesh obtained in step (5) is treated at 400℃ for 2 hours. The prepared oil-water separation membrane has hydrophobic and oleophilic properties.

Description

Technical Field

[0001] This invention designs a silica hydrophobic and oleophilic membrane based on stainless steel mesh and its preparation method, which is applied to oil-water separation in oil fields and belongs to the field of oil-water separation in oil fields. Background Technology

[0002] Oil-water separation is a crucial step in oilfield development, permeating the entire process of oilfield development and industrial oily wastewater treatment. Incomplete oil-water separation within pipelines and treatment equipment can lead to high-water-content crude oil or stable emulsions hindering oil and gas transport, reducing production efficiency, and causing a decline in yield. In severe cases, it can result in excessively high water content in exported crude oil, even forcing wells to reduce or cease production, leading to significant economic losses.

[0003] Oilfield produced fluids typically contain crude oil, water, and various surfactants. After undergoing high-speed flow, throttling, and pump shearing in wellbores and surface pipelines, they readily form stable oil-water emulsions. When temperature, pressure, flow rate, or chemical environment changes, or when the conditions for aging or demulsification of the emulsion are not met, oil droplets and water struggle to coalesce and separate, remaining suspended as tiny droplets for extended periods, resulting in an emulsion state that is difficult to separate. Incomplete oil-water separation in oilfields can lead to the formation of emulsion layers or mixed liquid zones in wellbores, surface separators, electrostatic precipitators, and wastewater pipelines. This results in decreased efficiency of separation equipment, blurred oil-water interfaces, and electric field breakdown in electrostatic precipitators, causing excessive water content in exported crude oil that fails to meet refinery processing requirements. Furthermore, excessively high oil content in oily wastewater can clog formation pores and reduce water injection efficiency if directly reinjected. Emulsions increase fluid viscosity and flow resistance, raising pumping energy consumption and demulsifier usage. They also easily cause under-deposit corrosion, microbial growth, and filter clogging, exacerbating equipment and tubing damage, shortening equipment lifespan, and severely impacting the economic viability and safety of oilfield development, thus hindering efficient oil and gas extraction and waterflooding.

[0004] Current oil-water separation technologies can be broadly categorized into physical and chemical methods. Physical oil-water separation technologies include gravity sedimentation, flotation, cyclone separation, coalescence separation, and membrane separation, while chemical oil-water separation technologies primarily utilize demulsifiers and flocculants. Chemical oil-water separation is more widely used, but the type, concentration, and treatment time of the reagents need precise control depending on the oil properties, water content, and emulsification level of the produced fluids from different oilfields. Furthermore, some chemical residues can cause secondary pollution. While physical oil-water separation equipment is relatively simple to operate and maintain, gravity sedimentation technology requires a large footprint and has low separation efficiency; flotation separation technology requires continuous aeration, resulting in high energy consumption; cyclone separation technology is sensitive to fluctuations in flow rate and pressure difference, limiting its separation accuracy; coalescence separation technology is susceptible to clogging by suspended solids; and membrane separation technology suffers from membrane fouling, requiring regular cleaning or replacement, leading to high operating costs.

[0005] Silica oil-water separation membranes based on stainless steel mesh refer to functional materials that achieve efficient separation of oil-water mixtures by loading silica nanoparticles onto the surface of a stainless steel mesh and modifying it with specific functional groups. The principle is mainly based on a special wettability design, utilizing the synergistic effect of surface chemical composition and microstructure to preferentially wet one phase of oil or water and allow it to permeate through the membrane pores, while the other phase is selectively retained. When the oil-water mixture contacts the membrane surface, the micro-nano rough structure constructed by silica and the grafted hydrophobic or hydrophilic molecular layers cause extreme contact angle differences between oil droplets and water droplets at the membrane interface, resulting in opposite two-phase permeation behaviors. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of commonly used oil-water separation technologies by providing a silica oil-water separation membrane based on stainless steel mesh and its preparation method. The oil-water separation membrane developed in this invention possesses excellent hydrophobic and oleophilic properties, and can be used for the efficient separation of oilfield produced fluids, industrial oily wastewater, etc.

[0007] By constructing a rough silica structure on the surface of stainless steel mesh and performing hydrophobic modification, the high strength and good permeability of stainless steel mesh can be retained while taking into account the hydrophobic properties and anti-fouling ability imparted by silica.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A silica oil-water separation membrane based on stainless steel mesh, wherein the oil-water separation membrane uses 316 stainless steel mesh with 25μm sieve openings as a substrate and a silica film modified with methyltriethoxysilane is loaded on the surface.

[0010] This invention provides a method for preparing a silica oil-water separation membrane based on a stainless steel mesh, comprising the following steps:

[0011] (1) Cut the stainless steel mesh into 4mm×5mm rectangles and immerse it completely in a 5% NaOH aqueous solution. Sonicate the solution at 55-60℃ for 15 minutes to remove surface grease, rolling oil, wax, and other organic contaminants. Then, ultrasonically clean the mesh for 5-10 minutes each with acetone, ethanol, and deionized water.

[0012] (2) The stainless steel mesh obtained in step (1) is etched with a 40% hydrofluoric acid solution, then ultrasonically cleaned with acetone, ethanol and deionized water for 5 min each, and dried at 60℃ for 10-20 min for later use.

[0013] (3) Preparation of silica sol: 100 mL of anhydrous ethanol, 9 mL of deionized water, 5 mL of ammonia and 7 mL of tetraethoxysilane (TEOS) were added in sequence and mixed rapidly under mechanical stirring. The mixture was reacted at 60 °C for 90 minutes.

[0014] (4) Add 4.2 mL of methyltriethoxysilane (MTES) dropwise to the mixture obtained in step (3) and stir continuously at 60°C for 19 hours to avoid gel formation. The resulting silica sol will not turn into a gel within one week.

[0015] (5) The silica sol obtained in step (4) is aged at room temperature and pressure for 3 days. Then the stainless steel mesh treated in step (2) is immersed in the sol for about 5 minutes. After taking it out, it is dried at 110°C for 30 minutes. This dip-coating-drying process is repeated 4 times to obtain a silica film with sufficient roughness.

[0016] (6) The stainless steel mesh loaded with silica film obtained in step (5) is treated at 400°C for 2 hours to finally achieve hydrophobic-oleophilic properties.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] This study provides a novel material design approach for oil-water separation, validating the excellent superhydrophobic-superoleophilic separation performance of silica membranes based on stainless steel mesh. It also offers new application directions for functional silica coatings. Alkaline chemical degreasing treatment of the stainless steel mesh removes organic contaminants from its surface, preventing membrane layer adhesion and peeling. By combining the stainless steel mesh substrate with a silica coating, the good mechanical strength and permeability of the stainless steel mesh can be preserved, meeting the application requirements of various scenarios. Attached Figure Description

[0019] Figure 1 This is an image showing the contact angle between the silica film on the stainless steel surface and water in Embodiment 1 of the present invention.

[0020] Figure 2 This is a picture showing the contact angle between the silica film on the stainless steel surface of the stainless steel mesh (without alkaline chemical degreasing treatment) and water, which is the subject of Comparative Example 1 of this invention.

[0021] Figure 3 This is a microscopic SEM image of the silica film on the stainless steel surface processed in Example 1 of the present invention.

[0022] Figure 4 This is a microscopic SEM image of the silica film on the surface of stainless steel without alkaline chemical degreasing treatment, as shown in Comparative Example 1 of this invention. Specific implementation methods

[0023] The present invention will be further described in detail below with reference to specific implementation schemes. It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Example 1

[0025] (1) Cut the stainless steel mesh into a rectangle of 4mm×5mm and immerse it completely in a 5% NaOH aqueous solution. Sonicate it at 60℃ for 15 minutes, and then ultrasonically clean it with acetone, ethanol and deionized water for 5 minutes respectively.

[0026] (2) The stainless steel mesh obtained in step (1) is etched with a 40% hydrofluoric acid solution, then ultrasonically cleaned with acetone, ethanol and deionized water for 5 min each, and dried at 60℃ for 20 min.

[0027] (3) Preparation of silica sol: 100 mL of anhydrous ethanol, 9 mL of deionized water, 5 mL of ammonia and 7 mL of tetraethoxysilane (TEOS) were added in sequence and mixed rapidly under mechanical stirring. The mixture was reacted at 60 °C for 90 minutes.

[0028] (4) Add 4.2 mL of methyltriethoxysilane (MTES) dropwise to the mixture obtained in step (3) and stir continuously at 60 °C for 19 hours;

[0029] (5) The silica sol obtained in step (4) is aged at room temperature and pressure for 3 days, and then the stainless steel mesh treated in step (2) is immersed in the sol for 5 minutes. After taking it out, it is dried at 110°C for 30 minutes. This dip-coating-drying process is repeated 4 times to obtain a silica film with sufficient roughness.

[0030] (6) The stainless steel mesh loaded with silica film obtained in step (5) was treated at 400°C for 2 hours. The contact angle between the resulting silica film and water was 143.84°.

[0031] (7) Mix 10 mL of water and 90 mL of liquid paraffin and stir for 5 min. Use the stainless steel mesh with silica film obtained in step (6) to separate the oil-water mixture by gravity. The oil flux can reach 510.34 L·m -2 ·h -1 The oil-water separation efficiency can reach 95.67%.

[0032] Comparative Example 1

[0033] (1) Cut the stainless steel mesh into a rectangle of 4mm×5mm, etch it with a 40% hydrofluoric acid solution, then clean it with acetone, ethanol and deionized water for 5 minutes each, and dry it at 60℃ for 20 minutes.

[0034] (2) Preparation of silica sol: 100 mL of anhydrous ethanol, 9 mL of deionized water, 5 mL of ammonia and 7 mL of tetraethoxysilane (TEOS) were added in sequence and mixed rapidly under mechanical stirring. The mixture was reacted at 60 °C for 90 minutes.

[0035] (3) Add 4.2 mL of methyltriethoxysilane (MTES) dropwise to the mixture obtained in step (2) and stir continuously at 60 °C for 19 hours;

[0036] (4) The silica sol obtained in step (3) is aged at room temperature and pressure for 3 days, and then the stainless steel mesh treated in step (1) is immersed in the sol for 5 minutes. After taking it out, it is dried at 110°C for 30 minutes. This dip-coating-drying process is repeated 4 times to obtain a silica film with sufficient roughness.

[0037] (5) The stainless steel mesh loaded with silica film obtained in step (4) was treated at 400°C for 2 hours. The contact angle between the resulting silica film and water was 138.18°.

[0038] (6) Mix 10 mL of water and 90 mL of liquid paraffin and stir for 5 min. Use the stainless steel mesh with a silica film loaded in step (5) to separate the oil and water mixture by gravity. The oil flux can reach 475.54 L·m -2 ·h -1 The oil-water separation efficiency can reach 94.44%.

[0039] Oil-water separation experiments were conducted on Example 1 and Comparative Example 1. Through... Figure 1 It can be seen that the silica film on the surface of stainless steel mesh treated with alkaline chemical degreasing has a larger contact angle with water and better hydrophobicity.

[0040] This invention prepares a silica hydrophobic and oleophilic film based on stainless steel mesh, which retains the high strength and good permeability of stainless steel mesh while possessing the hydrophobic properties and anti-fouling ability imparted by silica.

[0041] Although preferred experimental cases have been listed and described in detail here, those skilled in the art will recognize that various improvements, additions, substitutions, etc., can be made without departing from the spirit of the invention, and these are all considered to be within the scope of the invention as defined by the patent claims.

Claims

1. A silica film based on stainless steel mesh, characterized in that, The pretreatment of the stainless steel mesh is divided into two steps: alkaline chemical degreasing treatment followed by etching treatment.

2. A method for preparing a silica film on a stainless steel mesh according to claim 1, characterized in that, Includes the following steps: (1) Cut the stainless steel mesh into 4mm×5mm rectangles and immerse it completely in a 5% NaOH aqueous solution. Sonicate the solution at 55-60℃ for 15 minutes to remove surface grease, rolling oil, wax, and other organic contaminants. Then, ultrasonically clean the mesh for 5-10 minutes each with acetone, ethanol, and deionized water. (2) The stainless steel mesh obtained in step (1) is etched with a 40% hydrofluoric acid solution, then ultrasonically cleaned with acetone, ethanol and deionized water for 5 min each, and dried at 60℃ for 10-20 min for later use.

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