A polymer nanomembrane and its application in oil dewatering

Abstract

The present invention discloses a polymer nanomembrane and its application in oil water removal, belonging to the field of nanomembrane technology. The polymer nanomembrane material of the present invention utilizes solvent polarity differences to control the emulsion particle size through ultrasonic waves. Electrospraying the polymer emulsion forms a fiber network with a uniform pore structure. This material exhibits the advantages of a continuous two-dimensional nanomesh, high coverage, and uniform mesh pores. The resulting nanomembrane has a high efficiency (>98%) in separating emulsified water from oil products. Furthermore, this technology does not rely on the complex external conditions imposed by electrospraying, resulting in a simple and controllable preparation process.

Description

Technical Field

[0001] The invention belongs to the technical field of nano-membrane, and in particular relates to a polymer nano-membrane and its application in oil product water removal. Background Art

[0002] During fuel production, distribution, and storage, the incorporation of water (known as emulsified water) is a common phenomenon. This incorporation can not only lead to incomplete combustion, affecting combustion efficiency, increasing soot and particulate matter emissions, and exacerbating air pollution, but can also generate corrosive compounds, accelerating corrosion of engines, fuel systems, pumps, and pipelines. It can even clog injectors due to microbial growth, disrupting engine operation. Emulsified water, due to its tiny particle size and difficulty settling, poses a challenge in fuel purification.

[0003] Currently, the removal of emulsified water from fuel relies primarily on filters in the engine's fuel supply system, a key component of which is fuel filter paper. This filter paper must possess fine pores to effectively intercept emulsified water, good chemical stability to ensure long-term use, and exhibit both hydrophobic and oleophilic properties. However, existing fuel filter materials, primarily meltblown nonwoven fabric / paper-based composite filter media, have coarse fibers (>2μm) and, consequently, large pores, resulting in low emulsified water separation efficiency (<92%).

[0004] In order to refine the fiber diameter and improve the emulsified water separation efficiency, ZL202210663134.6 discloses a fluffy nano-filter material and its preparation method and application, which is specifically obtained by hot-pressing a composite of an electrospun nanofiber layer and a non-woven fabric. However, the diameter of traditional electrospun nanofibers is relatively coarse (>100nm), resulting in a large pore size of the separation membrane (>2μm), making it difficult to achieve effective separation of emulsified water. CN103806221A discloses a method for preparing a multi-component mesh nanofiber membrane, which enhances the tip instability of the Taylor cone by introducing nanoparticles, further promotes the formation of tiny charged droplets, and obtains a two-dimensional nano-mesh / nanofiber composite material (fiber diameter in the mesh <50nm). However, the resulting nano-mesh is randomly interspersed and distributed in the traditional electrospun fiber membrane, resulting in large gaps between the meshes, which easily leads to leakage of emulsified water droplets and is difficult to apply to the separation of emulsified water in fuel. CN107476132A discloses a method for preparing a stacked spider web composite filter paper. Using hydrophobic paper coated with nanofibers as the substrate, ultrasonic pre-atomization technology is used to prepare a stacked spider web composite filter paper with micro-nano gradient pore knots. The average diameter of the fibers in the web is 20 to 100 nm, which is an order of magnitude lower than that of ordinary electrostatic fibers. However, since the preparation relies on ultrasonic pre-atomization and electric field secondary atomization technology, the size of the tiny charged droplets is uncontrollable and the droplet movement is uncertain, resulting in poor continuity of the nanonet, uneven mesh distribution, and low coverage. In addition, this technology also involves complex equipment and multi-step operations, including a composite process of bidirectional electric field drawing and spraying non-woven fabrics, which increases production costs and technical barriers, is difficult to simplify, and limits its service life in harsh industrial environments.

[0005] Although the above-mentioned existing technologies have produced nanomesh materials and reduced the fiber diameter in the mesh, they still have defects such as poor nanomesh continuity, uneven mesh distribution, insufficient functionality, and complex preparation process, which seriously limit the practical application of the material.

[0006] Therefore, there is an urgent need to develop polymer nanomesh materials for oil dewatering with good inter-mesh continuity, uniform mesh distribution, and simple preparation process. Summary of the Invention

[0007] [Technical Issues]

[0008] Nanomesh materials prepared by existing technologies still have defects such as poor nanomesh continuity, uneven mesh distribution, insufficient functionality, and complex preparation process, which seriously limit the practical application of this material in oil dewatering.

[0009] [Technical solution]

[0010] To address the above-mentioned technical problems, the present invention provides a polymer nanomembrane and its application in oil water removal. This polymer nanomembrane material utilizes solvent polarity differences to control the emulsion particle size through ultrasonic waves. Electrospraying the polymer emulsion forms a fiber network with a uniform pore structure. This nanomembrane exhibits the advantages of a continuous two-dimensional nanomesh, high coverage, and uniform mesh pores. The resulting nanomembrane achieves high efficiency (>98%) in separating emulsified water from oil products. Furthermore, this invention does not rely on the complex external conditions imposed by electrospraying, resulting in a simple and controllable preparation process.

[0011] In order to achieve the above objectives, the technical solutions provided are as follows:

[0012] A method for preparing a polymer nanomembrane, comprising the following steps:

[0013] (1) dissolving a hydrophobic and lipophilic polymer in a polar solvent A to obtain a solution B;

[0014] (2) ultrasonically dispersing the solution B obtained in step (1) in a non-polar solvent C to obtain a spunlace solution; wherein the solution B and the solvent C are immiscible;

[0015] (3) Electrostatically spraying the spraying solution obtained in step (2) to obtain a polymer nanomembrane.

[0016] In one embodiment, the hydrophobic and oleophilic polymer in step (1) is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polystyrene, polyvinyl chloride, polyetherimide, polychlorotrifluoroethylene, polysulfone, polycaprolactone, polymethyl methacrylate, polyvinyl pyrrolidone, and polyethylene terephthalate, or a mixture of any two or three of the above polymers.

[0017] In one embodiment, the molecular weight of the polyvinylidene fluoride is 300,000 to 800,000; the molecular weight of polyvinylidene fluoride-hexafluoropropylene is 300,000 to 700,000; the molecular weight of polystyrene is 150,000 to 700,000; the molecular weight of polyvinyl chloride is 20,000 to 99,000; the molecular weight of polyetherimide is 20,000 to 80,000; the molecular weight of polytrifluorochloroethylene is 100,000 to 200,000; the molecular weight of polysulfone is 35,000 to 80,000; the molecular weight of polycaprolactone is 36,000 to 100,000; the molecular weight of polymethyl methacrylate is 15,000 to 120,000; the molecular weight of polyvinyl pyrrolidone is 300,000 to 1,300,000; and the molecular weight of polyethylene terephthalate is 20,000 to 50,000.

[0018] In one embodiment, in the solution B of step (1), the mass fraction of the polymer is 5 to 20%.

[0019] In one embodiment, the polar solvent A in step (1) is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, dimethyl sulfoxide, ethanol, methanol, chloroform, dichloromethane, trifluoroacetic acid, ethylene glycol, tetrahydrofuran, methylpyrrolidone, and dimethylformamide.

[0020] In one embodiment, the ultrasonic dispersion in step (2) has a power of 500 to 2500W.

[0021] In one embodiment, the particle size of solution B in the spunlace solution in step (2) is 10 to 100 nm.

[0022] In one embodiment, the non-polar solvent C in step (2) is one or more of trichloroethane, carbon tetrachloride, carbon tetrafluoride, n-hexane, cyclohexane, isobutane, n-butane, methylcyclohexane, heptane, n-dodecane, n-tetradecane, hexadecane, and petroleum ether.

[0023] In one embodiment, the mass ratio of solution B to solvent C in step (2) is 1:99 to 20:80.

[0024] In one embodiment, the parameters of the electrostatic spraying described in step (3) are: temperature 10-30°C, relative humidity 20%-70%, perfusion rate 0.1-30 mL / h, voltage 5-60 kV, the distance between the receiving device and the spinneret is 10-30 cm, the slide distance is 0-10 cm, the receiving device is a metal roller, the temperature of the receiving device is 10-50°C, and the speed of the receiving device is 20-100 n / min.

[0025] The present invention also provides a polymer nanomembrane prepared by the above-mentioned preparation method.

[0026] The present invention also provides the use of the polymer nano-membrane in removing water from oil products.

[0027] In one embodiment, the application places the polymer nanomembrane in a dead-end filtration device to remove water from the oil.

[0028] The present invention also provides a method for improving the efficiency of water removal and separation in oil products, wherein the method uses the above-mentioned polymer nano-membrane as a filter membrane to remove water.

[0029] Beneficial effects:

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention utilizes ultrasonic dispersion of a polymer / polar solvent solution in a non-polar solvent to achieve the formation of tiny droplets of the polymer / polar solvent solution, and then utilizes the deformation and phase separation of these tiny droplets in an electric field to obtain a nanomembrane with a continuous two-dimensional network structure.

[0032] 2. The present invention uses emulsion electrospraying technology to achieve the preparation of polymer nanomesh, with simple, flexible steps and easy operation. Compared with existing technologies, this method has the advantages of high two-dimensional nanomesh coverage, good structural stability, and strong controllability.

[0033] 3. The polymer nanomembrane prepared by the present invention not only has the fine two-dimensional mesh structure unique to nanomembrane, but also has continuous mesh surfaces and uniform mesh size, which can significantly improve the oil removal performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 These are SEM images of polymer nanomembranes of Examples 1-4 of the present invention; (a) is Example 1; (b) is Example 2; (c) is Example 3; (d) is Example 4;

[0035] Figure 2 These are SEM images of the products prepared in Comparative Examples 1-3; (a) is Comparative Example 1; (b) is Comparative Example 2; and (c) is Comparative Example 3. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention. The following specific embodiments further describe the present invention.

[0037] The test method involved in the present invention is:

[0038] 1. Appearance

[0039] The morphology of the fiber membrane samples was characterized by scanning electron microscopy (SEM, SU-8010, Hitachi, Japan).

[0040] 2. Separation performance

[0041] Preparation of water-in-oil emulsion: water and oil are mixed in a volume ratio of 1:99, and ultrasonically treated at a power of 400 W for 30 minutes to prepare an oil-in-water emulsion. The oil can be diesel, gasoline, kerosene, or motor oil. The particle size of the emulsified water in the obtained water-in-oil emulsion is less than 1 μm.

[0042] The membrane was placed in a dead-end filtration device to conduct an emulsion separation experiment. The water content (W) of the emulsion and filtrate was tested, and the separation efficiency (%) of the membrane was calculated according to formula (1):

[0043]

[0044] Example 1

[0045] A method for preparing a polymer nanomembrane comprises the following steps:

[0046] (1) adding polyvinylidene fluoride with a molecular weight of 570,000 to an N,N-dimethylformamide solvent, wherein the mass percentage of the polyvinylidene fluoride is 16 wt %, and fully dissolving the polyvinylidene fluoride to prepare a uniform solution A;

[0047] (2) adding solution A to n-hexane solvent, wherein the mass ratio of solution A to n-hexane is 1:9, and ultrasonicating the solution A with an ultrasonic machine having a power of 1200 W until the solution A is completely emulsified and the particle size is 10 to 90 nm, thereby obtaining a spunlace emulsion;

[0048] (3) Under the conditions of humidity of 35% and ambient temperature of 30°C, the spunlace emulsion was added to the electrospinning device, and electrospinning was carried out under the conditions of static voltage of 20 kV, injection pump flow rate of 0.5 mL / h, and fiber receiving distance of 10 cm to obtain a polyvinylidene fluoride nanomesh, wherein the fiber diameter in the mesh was about 8 to 67 nm.

[0049] Example 2

[0050] A method for preparing a polymer nanomembrane comprises the following steps:

[0051] (1) adding polystyrene with a molecular weight of 400,000 to N,N-dimethylformamide to dissolve the polystyrene in a mass percentage of 14 wt %, and fully dissolving the polystyrene to prepare a uniform solution A;

[0052] (2) adding solution A to hexadecane solvent, wherein the mass ratio of solution A to hexadecane is 1:9, and ultrasonicating the solution A with an ultrasonic machine having a power of 1000 W until the solution A is completely emulsified and the particle size is 20 to 100 nm, thereby obtaining a spunlace emulsion;

[0053] (3) Under the conditions of humidity of 45% and ambient temperature of 25°C, the spunlace emulsion was added to the electrospinning device, and electrospinning was carried out under the conditions of static voltage of 30 kV, injection pump flow rate of 1 mL / h, and fiber receiving distance of 15 cm to obtain a polystyrene nanomesh, wherein the fiber diameter in the mesh was about 10 to 97 nm.

[0054] Example 3

[0055] A method for preparing a polymer nanomembrane comprises the following steps:

[0056] (1) adding polyetherimide with a molecular weight of 38,000 to dimethyl sulfoxide to dissolve the polyetherimide in a mass percentage of 12 wt %, and fully dissolving the polyetherimide to prepare a uniform solution A;

[0057] (2) adding solution A to petroleum ether solvent, wherein the mass ratio of solution A to petroleum ether is 1:8, and ultrasonicating with an ultrasonic machine having a power of 1000 W until solution A is completely emulsified and the particle size is 10 to 100 nm, thereby obtaining a spunlace emulsion;

[0058] (3) Under the conditions of humidity of 50% and ambient temperature of 23°C, the spunlace emulsion was added to the electrospinning device, and electrospinning was carried out under the conditions of static voltage of 25 kV, injection pump flow rate of 1.5 mL / h, and fiber receiving distance of 20 cm to obtain a polyetherimide nanomesh, wherein the fiber diameter in the mesh was about 10 to 48 nm.

[0059] Example 4

[0060] A method for preparing a polymer nanomembrane comprises the following steps:

[0061] (1) adding polymethyl methacrylate with a molecular weight of 35,000 to N,N-dimethylformamide to dissolve the polymethyl methacrylate in an amount of 18 wt % to fully dissolve the polymethyl methacrylate to prepare a uniform solution A;

[0062] (2) adding solution A to cyclohexane solvent in a mass ratio of 1:8, and ultrasonicating with an 800W ultrasonic machine until solution A is completely emulsified and the particle size is 10 to 100 nm, thereby obtaining a spunlace emulsion;

[0063] (3) Under the conditions of humidity of 40% and ambient temperature of 25°C, the spunlace emulsion was added to the electrospinning device, and electrospinning was carried out under the conditions of static voltage of 20 kV, injection pump flow rate of 1 mL / h, and fiber receiving distance of 25 cm to obtain polymethyl methacrylate nanomesh, wherein the fiber diameter in the mesh was about 8 to 81 nm.

[0064] Comparative Example 1

[0065] The only difference from Example 1 is that step (2) is omitted and solution A is directly used as the spinning solution for electrospinning. The rest is consistent with Example 1.

[0066] The SEM image of the product prepared in this comparative example is as follows Figure 2 As shown in a.

[0067] Depend on Figure 2It can be seen that compared with Example 1, the final sample obtained in Comparative Example 1 contains only nanofibers but no two-dimensional nanomesh. This is mainly because the spinning jet of the high-concentration polymer solution has difficulty overcoming surface tension in the electric field to atomize into droplets, resulting in difficulty in forming polymer droplets and, therefore, in forming a nanomesh film.

[0068] Comparative Example 2

[0069] The only difference from Example 1 is that step (2) only involves physical stirring without ultrasonic dispersion, and the resulting particle size is 5 to 8 mm. The rest is consistent with Example 1.

[0070] The SEM image of the product prepared in this comparative example is as follows Figure 2 As shown in b.

[0071] Depend on Figure 2 b It can be seen that: compared with Example 1, the sample finally obtained in Comparative Example 2 only has nanofibers, and no nanomesh is formed. This is mainly because the polymer droplets cannot be dispersed into nanosize under the action of physical stirring alone, and larger droplets are difficult to overcome surface tension in the electric field to form a nanomesh.

[0072] Comparative Example 3

[0073] (1) adding polyvinylidene fluoride to N,N-dimethylformamide solvent, wherein the mass percentage of the polyvinylidene fluoride is 16 wt %, and fully dissolving the polyvinylidene fluoride to prepare a uniform solution A;

[0074] (2) adding solution A to acetone solvent, wherein the mass ratio of solution A to acetone is 1:9; obtaining a spinning solution;

[0075] (3) Under the conditions of humidity of 35% and ambient temperature of 30°C, the spinning solution was added to the electrospinning device, and electrospinning was performed under the conditions of static voltage of 20 kV, injection pump flow rate of 0.5 mL / h, and fiber receiving distance of 10 cm.

[0076] Depend on Figure 2 As shown in Figure 3, compared with Example 1, the final sample obtained in Comparative Example 3 contained only microspheres but no two-dimensional nanomesh. This is because N,N-dimethylformamide and acetone are both polar solvents with good compatibility, resulting in the absence of tiny droplets in the spinning solution, making it difficult to form a nanomesh.

[0077] Performance Testing

[0078] Oil dewatering performance test:

[0079] Preparation of water-in-oil emulsion: Mix oil and water in a volume ratio of 99:1, and prepare the water-in-oil emulsion by ultrasonication at a power of 560W for 30 minutes. The oil can be diesel, gasoline, kerosene, or motor oil. The particle size of the emulsified oil in the obtained water-in-oil emulsion is less than 1μm.

[0080] The membrane materials prepared in the examples and comparative examples were placed in a dead-end filtration device for separation experiments. The water content in the emulsion and filtrate was measured using a coulometric Karl Fischer moisture meter, and the membrane separation efficiency (%) was calculated. The experimental results are shown in Table 1 below:

[0081] Table 1. Separation efficiency of membranes prepared in Examples and Comparative Examples (%)

[0082]

[0083]

[0084] In summary, the emulsion spraying technology of the present invention successfully realizes the preparation of nano-mesh membrane. This method has simple steps and flexible operation. The prepared material not only has structural characteristics such as high two-dimensional nano-mesh coverage, small mesh pore size, and large membrane porosity, but also shows high separation efficiency and high oil flux in the application field of oil water removal.

[0085] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a polymer nanomembrane, characterized in that: The preparation method comprises the following steps: (1) dissolving a hydrophobic and lipophilic polymer in a polar solvent A to obtain a solution B; the polar solvent A is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, acetone, dimethyl sulfoxide, ethanol, methanol, chloroform, dichloromethane, trifluoroacetic acid, ethylene glycol, tetrahydrofuran, methylpyrrolidone, and dimethylformamide; (2) ultrasonically dispersing the solution B obtained in step (1) in a non-polar solvent C to obtain a spunlace solution; wherein the solution B and the solvent C are immiscible; (3) The spunlace solution obtained in step (2) is subjected to electrostatic spunlace to obtain a polymer nanomembrane.

2. The preparation method according to claim 1, characterized in that The hydrophobic and oleophilic polymer in step (1) is at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polystyrene, polyvinyl chloride, polyetherimide, polychlorotrifluoroethylene, polysulfone, polycaprolactone, polymethyl methacrylate, polyvinyl pyrrolidone, and polyethylene terephthalate, or a mixture of any two or three of the above polymers.

3. The preparation method according to claim 1, characterized in that The particle size of solution B in the spunlace solution in step (2) is 10 to 100 nm.

4. The preparation method according to claim 1, characterized in that The non-polar solvent C in step (2) is one or more of trichloroethane, carbon tetrachloride, carbon tetrafluoride, n-hexane, cyclohexane, isobutane, n-butane, methylcyclohexane, heptane, n-dodecane, n-tetradecane, hexadecane, and petroleum ether.

5. The preparation method according to claim 1, characterized in that The parameters of the electrostatic spraying described in step (3) are: temperature 10-30°C, relative humidity 20%-70%, infusion rate 0.1-30 mL / h, voltage 5-60 kV, distance between the receiving device and the spinneret 10-30 cm, slide distance 0-10 cm, the receiving device is a metal roller, the temperature of the receiving device is 10-50°C, and the speed of the receiving device is 20-100 n / min.

6. The polymer nanomembrane prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the polymer nanomembrane according to claim 6 in removing water from oil products.

8. The use according to claim 7, characterized in that The polymer nano-membrane is placed in a dead-end filtration device to remove water from the oil.

9. A method for improving the efficiency of water removal and separation in oil products, characterized in that: The method is to use the polymer nanomembrane described in claim 6 as a filter membrane to remove water.

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