WO2021109333A1

WO2021109333A1 - Method for preparing monodisperse diesel emulsion

Info

Publication number: WO2021109333A1
Application number: PCT/CN2020/073463
Authority: WO
Inventors: 景文珩; 黄辉辉; 李世龙; 倪迎香; 邢卫红
Original assignee: 南京工业大学
Priority date: 2019-12-06
Filing date: 2020-01-21
Publication date: 2021-06-10
Also published as: CN112280602B; CN112280602A

Abstract

Provided is a method for preparing a monodisperse diesel emulsion: taking a two-dimensional MXene-modified hydrophobic ceramic membrane as an emulsification medium, using water as the dispersed phase, and using diesel fuel having added emulsifier as the continuous phase; the dispersed phase passing through a ceramic membrane tube under a certain transmembrane pressure difference; under the effect of a continuous-phase shear force, the dispersed phase leaving the surface of the membrane tube and entering the continuous phase, causing the water and diesel to be fully miscible to form a monodisperse diesel emulsion. The two-dimensional nanochannel structure formed by means of the MXene-modified membrane extends the conventional straight-through milking means to a vertical-horizontal channel milking means, preventing the occurrence of agglomeration during the formation of the emulsion, such that the dispersed phase can directly prepare a monodisperse emulsion under a certain transmembrane pressure difference.

Description

Method for preparing monodisperse diesel emulsion

Technical field

The invention relates to a preparation method of a monodisperse diesel emulsion, in particular to the preparation of an MXene modified hydrophobic membrane, and its application in the preparation of a monodisperse emulsion, and is mainly used in improving the fuel utilization rate of diesel engines and improving catalytic cracking, etc. , Belongs to the field of petroleum processing.

Background technique

Diesel engines are by far one of the most effective and reliable energy conversion devices. Diesel engines form an integral part of global transportation and industrial infrastructure due to their high thermal efficiency and durability, especially in heavy-duty applications such as trucks, buses, agricultural equipment, locomotives, and ships. However, pollutants emitted from diesel engines into the atmosphere, such as: hydrocarbons (HC), carbon monoxide (CO), carbon dioxide (CO ₂ ), especially harmful nitrogen oxides (NO _x ), and particulate matter (PM) , Not only harms our ecology, but also threatens human health.

Without engine modification, emulsified diesel fuel is used as feed. The small water droplets in the emulsified diesel are heated to gasify and expand, instantly atomizing the oil droplets. The contact surface between the atomized oil droplets and the air is increased, thereby improving the combustion rate and combustion efficiency. In addition, the spontaneous explosion of fine droplets forms high-pressure steam and exerts additional pressure on the top of the piston, so the engine torque is increased and the performance is improved. Emulsion fuel capacity of NO _x reduction can be attributed to the evaporation of water, which suppresses the local adiabatic flame temperature, thereby significantly reducing the NO _x emissions. Its smoke reduction ability can be explained by a better air-fuel mixing process, which is due to the feature of enhanced atomization after micro-explosion. In addition, water decomposition can form hydroxyl radicals during the combustion process, which helps to oxidize soot, thereby reducing soot emissions.

At present, there are two main methods for preparing monodisperse emulsions: one is high-energy emulsification method based on high-pressure homogenization method and high-speed shear emulsification method, and the other is phase transition temperature method and phase transition component method. Mainly low-energy emulsification method. Among them, the energy consumption required by the high-energy emulsification method is about 10 ⁵ to 10 ⁷ times that of the low energy consumption. Such high energy consumption makes it impossible to prepare monodisperse emulsions on a large scale in industry, and the low energy consumption milking method also has certain limitations in industrial applications.

Membrane emulsification technology is a newly developed emulsification technology, mainly used for the preparation of microemulsions. This technology is more and more favored by researchers due to its simple device, low energy consumption, low shear force, small amount of surfactant required, and ease of industrialization.

In the process of membrane emulsification, especially the preparation of monodisperse emulsions, a membrane material that is not wettable with the dispersed phase must be selected as the emulsification medium. Therefore, generally hydrophilic membranes are suitable for the preparation of O/W emulsions, while hydrophobic membranes are suitable for the preparation of O/W emulsions. The membrane is more suitable for the preparation of W/O emulsion. Since the surface of the inorganic ceramic membrane is a high-energy hydrophilic surface, when it is directly used in the membrane emulsification process to prepare a monodisperse water-in-diesel emulsion, it is easy to cause the phenomenon of emulsion aggregation. Existing commercial ceramic membranes are difficult to prepare monodisperse emulsions due to the actual application and sintering preparation process of the ceramic membranes during the emulsification process. Commercial ceramic membranes tend to have higher porosity due to practical applications, and the higher porosity during the emulsification process easily leads to the occurrence of emulsion aggregation during the milking process. In the traditional membrane emulsification mechanism, the dispersed phase passes through the emulsifying medium to the membrane surface in a straight-through form, and leaves the membrane surface to form an emulsion under the action of shearing force. This traditional emulsification behavior tends to cause the emulsion to coalesce when it leaves the film surface, and this traditional emulsification behavior tends to cause the emulsion to have a large particle size and exhibit polydispersity.

CN 102794119 A proposes a method for preparing a monodisperse emulsion in a sleeve-type annular microchannel reactor. The method uses the annular microchannel between the inner and outer tubes of the reactor as the emulsification channel, and mainly adjusts the inner and outer tubes of the reactor. A monodisperse emulsion is prepared with a fluid flow rate of, but the particle size of the emulsion prepared by this method is large, and the maximum particle size can reach 20 μm. A method for preparing monodisperse W/O emulsion with hydrophilic ceramic membrane is reported in the literature (Desalination, 191(1-3):219-222.), and the flux can reach 140.6L·m ^-2 ·h ^-1 , The average particle size of the emulsion is 1～2μm.

Summary of the invention

The purpose of the present invention is to overcome the defect that the existing ceramic membrane emulsification technology is difficult to prepare nano-level monodisperse emulsions, and to provide a method for preparing a monodispersed diesel emulsion with low energy consumption and higher flux.

The technical scheme of the present invention is: by constructing a two-dimensional MXene modified film, the straight-through milking method in the traditional film emulsification process is changed, the two-dimensional nanochannel is used for milking, and the surface of the modified film is hydrophobically modified. Effectively prevent the emulsion from coalescing, thereby preparing a nano-level monodisperse diesel emulsion. The continuous phase is driven by the circulating pump to flow through the membrane surface at a certain flow rate. Under the action of the fluid shearing force, the dispersed phase emulsion droplet membrane surface enters the continuous phase to form an emulsion. When the pressure difference across the membrane increases, the membrane flux also increases, and the speed at which the dispersed phase forms emulsion droplets at the exit of the membrane pores increases. This method is suitable for the industrial production of monodisperse emulsions. As long as the dispersed phase is continuously squeezed through the membrane pores, the emulsion can be formed uninterruptedly.

To prepare the monodisperse W/O emulsion, we uniformly deposit the two-dimensional MXene on the inner surface of the ceramic membrane through an external pressure device. Construct a two-dimensional MXene modified layer on the surface of the ceramic membrane, and use the special properties of the two-dimensional material to construct a two-dimensional nanochannel, thus changing the straight-through milking method in the traditional emulsification process, using two-dimensional nanochannels A vertical-horizontal milking method is formed, which can effectively prevent the emulsion from coalescing during the milking process, so as to achieve the preparation of monodisperse emulsions.

The specific technical scheme of the present invention is: a preparation method of monodisperse diesel emulsion, which is characterized in that the two-dimensional MXene modified hydrophobic ceramic membrane is used as the emulsifying medium, water is used as the dispersed phase, and the diesel oil added with emulsifier is used as the continuous phase. The phase passes through the ceramic membrane tube under a certain transmembrane pressure difference. Under the action of the continuous phase shear force, the dispersed phase leaves the membrane tube surface and enters the continuous phase, so that water and diesel oil are fully miscible to form a monodisperse diesel emulsion.

Preferably, the above-mentioned emulsifying medium is prepared by the following method: dispersing MXene nanosheets in an aqueous solution, depositing MXene on the inner membrane of the ceramic membrane tube using a nitrogen external pressure device, controlling the pressure, and sintering the formed MXene modified ceramic membrane to obtain Two-dimensional MXene modified ceramic membrane; then the two-dimensional MXene modified ceramic membrane is modified with a hydrophobic modifier to obtain a two-dimensional MXene modified hydrophobic ceramic membrane.

Preferably, the size of MXene nanosheets is 200-500nm; the MXene nanosheets are dispersed in the aqueous solution to control the concentration of MXene at 0.2×10 ^-4 ～1.0×10 ^-4 mg/ml; the control pressure is at 0.1～0.5MPa; the sintering temperature It is 200～400℃.

Preferably, the ceramic membrane tube is a single-channel ceramic membrane tube, a multi-channel ceramic membrane tube or a hollow fiber ceramic membrane tube; the pore diameter of the ceramic membrane is 50-300nm; the ceramic membrane is an inorganic ceramic membrane, and the material is ZrO ₂ , Al ₂ O _3. One or more of SiC, TiO ₂ or SiO _{2 is compounded.}

Preferably, the hydrophobic modifier used above is hexadecyltrimethoxysilane, octyltrimethoxysilane, polydimethylsiloxane or trimethylchlorosilane; the concentration of the modifier is 0.01-0.2mol/L; The modification time is 3-24h.

Preferably, the added emulsifier is one or more of span 20, span 60, span 80, tween 20 or tween 80; wherein the mass fraction of the emulsifier in the continuous phase is 0.5-10 wt%; the dispersed phase is deionized water .

It is preferable to control the dispersed phase to pass through the ceramic membrane tube under the transmembrane pressure difference of 0.05-0.4MPa, and control the continuous phase with a flow rate of 0.1-0.5 m/s to flow across the membrane surface, so that the dispersed phase enters the continuous phase in the form of small droplets to complete the emulsification process.

The particle size of the diesel emulsion prepared by the invention is determined by the membrane tube aperture, the deposition amount of MXene, the hydrophobicity of the membrane surface, the water flux of the dispersed phase and the shear force. The prepared diesel emulsion has a small particle size and a monodisperse distribution; The volume content of water is preferably 1% to 40%.

Beneficial effects:

1. In the process of modifying the surface of the membrane tube, the two-dimensional MXene nanosheet constructs a longitudinal-horizontal two-dimensional nanoemulsification channel, which changes the traditional membrane emulsification method and is conducive to the formation of monodisperse emulsions.

2. After pressure deposition, the two-dimensional MXene nanosheets can be firmly bonded to the ceramic membrane after a high temperature sintering, and are insoluble in water and oil, so that continuous production can be sustained and stably without causing modification The damage of the layer may even fall off.

3. In this method, the two-dimensional MXene modified ceramic membrane is hydrophobically modified. When preparing the W/O emulsion, the water droplets will not spread on the surface of the membrane tube when entering the continuous phase through the membrane tube, which can effectively prevent Emulsion polymerization occurs and a monodisperse W/O type emulsion is prepared.

4. Membrane emulsification due to its simple technology, low energy consumption, less surfactant requirements, and the resulting emulsion has a small particle size (nano-level), uniform particle size, and good stability.

5. The selected ceramic membrane is resistant to high temperature, high pressure, acid and alkali, and pollution, so that it can adapt to most harsh emulsification environments.

6. This method uses MXene modified ceramic hydrophobic membrane as the emulsification medium. This method has large flux, fast emulsification, uniform particle size, simple operation, easy to scale up, and can be applied on a large scale to industrial fine monodisperse emulsions. preparation.

Description of the drawings

Figure 1 is a schematic diagram of the device process of membrane emulsified diesel; A is the feed port of the dispersed phase, B is the feed port of the continuous phase; 1 is a high-pressure advection pump, 2 is a stainless steel liquid storage tank, 3 is a peristaltic pump, 4 is Rotameter, 5 is a pressure gauge, v1, v2, v3, v4, v5 are the first valve, second valve, third valve, fourth valve, and fifth valve respectively, and 6 is MXene hydrophobic modified membrane;

Figure 2 is a schematic diagram of the process of forming an emulsion by the dispersed phase through a two-dimensional nanochannel; (a) is a schematic diagram of the membrane emulsification process of MXene modified membrane, (b) is the membrane emulsification process;

Figure 3 is the pore size distribution diagram of the ceramic membrane tube in Example 1; (a) is the pore size distribution diagram of the single-channel Al ₂ O ₃ ceramic membrane tube with a nominal pore size of 100 nm in Example 1, and (b) is Example 1 The pore size distribution map of the ceramic membrane tube after MXene is deposited in the medium;

Figure 4 is an SEM image of the two-dimensional MXene prepared in the laboratory in Example 1;

Figure 5 is the original MXene in Example 1 and the XRD pattern after high temperature sintering at 300°C;

Figure 6 is the original MXene in Example 1 and the TEM images after high temperature sintering at 300°C; (a) and (b) are the TEM images of the original MXene after vacuum drying, and (c) and (d) are the TEM images of the original MXene after 300 ℃ sintering. TEM image after sintering at ℃;

Figure 7 is the SEM of the inner membrane of the ceramic membrane tube in Example 1; where a is the SEM of the inner membrane of the single-channel Al ₂ O ₃ ceramic membrane tube in Example 1 with a nominal pore diameter of 100 nm, and b is the two-dimensional in Example 1 SEM image of MXene deposited on the inner membrane of the ceramic membrane tube;

8 is a diagram of the contact angle of the surface of the membrane tube after hydrophobic modification in Example 1;

Figure 9 is a graph showing the stability of the two-dimensional MXene modified ceramic membrane tested in water and oil;

Figure 10 is a metallographic microscope image of the monodisperse emulsion prepared in Example 1 when the water content is 10%;

Fig. 11 is a metallurgical microscope image of a W/O emulsion prepared after hydrophobic modification using a 100 nm original tube in Comparative Example 1.

Detailed ways

The embodiment of the present invention will be further explained:

The preparation process of a monodisperse diesel emulsion is shown in Figure 1. The specific operation process is as follows: (1) Install the MXene modified hydrophobically modified membrane into module 6, close the fourth and fifth valves v4, v5 to check the air tightness and adjust until the device does not leak; (2) open the third valve v3, add diesel to the diesel storage tank 2, open the second valve v2, and circulate through the peristaltic pump 3, adjust the speed of the peristaltic pump to control a certain membrane surface flow rate; (3) open the fifth valve v5 and pass the plunger pump 1 Press deionized water into the membrane tube, adjust the pressure parameters of the plunger pump, and control the pressure of the dispersed phase during the emulsification process. (4) After controlling the water content of a certain volume ratio, the fifth valve v5 is closed to complete the emulsification, and the emulsion is discharged from the first valve v1.

Figure 2 is a schematic diagram of the emulsification process of MXene modified hydrophobic membrane. From Figure 2(b), it can be seen that the special properties of the two-dimensional material itself construct a two-dimensional nanochannel, and the two-dimensional nanochannel is used to form a vertical-horizontal type. The way of milking.

Example 1

The raw material components for preparing the emulsion are: No. 0 diesel oil, deionized water, the emulsifier is selected as span 80, and the mass fraction of the emulsifier in the continuous phase is 1%. Add the emulsifier to the diesel oil and heat and stir for 5 hours for later use. Use a single-channel Al ₂ O ₃ tubular ceramic membrane with a nominal pore size of 100 nm as the modified carrier, configure 500ml with a concentration of 0.35×10 ^-4 mg/ml, and use nitrogen outside The pressure device deposits MXene in the solution on the inner membrane of the ceramic membrane, and the pressure is controlled to 0.1MPa, and the ceramic membrane tube on which MXene is deposited is sintered at a high temperature of 300°C. The MXene modified membrane tube was immersed in the ethanol solution of hexadecyltrimethoxysilane with a concentration of 0.05 mol/L for 6 hours, and then taken out and washed and dried with absolute ethanol for use. Figure 3(a) is the pore size distribution diagram of the original 100nm ceramic membrane tube, and Figure 3(b) is the pore size distribution diagram after depositing MXene. Comparing the two figures, it can be seen that the modified ceramic membrane after depositing MXene does not change the membrane tube. The average pore diameter. Figure 4 is the SEM image of two-dimensional MXene nanosheets prepared in the laboratory. Figure 5 is the XRD image of MXene after heating to 300℃ in air. It can be seen from the figure that MXene still has MXene after heating at 300℃ in air. The characteristic peak is not converted to titanium oxide. Figure 6(a)(b) is the TEM image of the original MXene after vacuum drying, and Figure 6(c)(d) is the TEM image of the MXene after sintering at 300℃. It can be seen from the figure that the MXene after high temperature sintering does not Obviously converted to TiO ₂ and still a complete two-dimensional sheet structure, which is also very consistent with our XRD results. _{Figure 7(a) is an SEM image of the inner membrane of a single-channel Al 2} O ₃ ceramic membrane tube with a nominal pore size of 100 nm, and Figure 7(b) is an SEM image of a two-dimensional MXene uniformly deposited on the inner membrane of the ceramic membrane tube. It can be seen that MXene can be uniformly deposited on the Al ₂ O ₃ ceramic inner film. Figure 8 is a diagram of the contact angle of the surface of the membrane tube after hydrophobic modification. Figure 9 is the test of the stability of the two-dimensional MXene modified ceramic membrane in water and oil respectively. It can be seen from the figure that the MXene modified membrane can be well stabilized in water and oil, so as to meet the long-term operation of industrial membrane emulsification. . The modified ceramic membrane tube is used as the emulsifying medium, and a high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase, but not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to 0.35m /s. Control the dispersed phase to permeate the membrane tube at a pressure of 0.05MPa, and the prepared diesel emulsion has a water content of 10%. Figure 10 is a metallographic microscope image of a monodisperse emulsion with a water content of 10% (volume content).

Comparative example 1

_{A single-channel Al 2} O ₃ ceramic membrane tube with a nominal pore diameter of 100 nm is used. Without MXene modification, the original tube is immersed in a hexadecyltrimethoxysilane ethanol solution with a concentration of 0.05 mol/L for 6 hours. Water ethanol washing and drying are used for later use, and the other control steps and parameters are the same as those in the first embodiment. The difference between Comparative Example 1 and Example 1 is that the ceramic membrane tube is not modified with two-dimensional MXene in Comparative Example 1. Figure 11 is the emulsion prepared under the conditions of this comparative example. The metallographic microscope image of the emulsion with a water content of 20%. Although the hydrophobic ceramic membrane is more suitable for preparing W/O emulsions, the emulsions prepared are still polydisperse micro The main reason for the emulsion is that the traditional straight-through membrane emulsification method easily causes the polymerization of the emulsion during the milking process to form a polydispersed emulsion. This also precisely illustrates the importance of our work.

Example 2

_{A single-channel Al 2} O ₃ tubular ceramic membrane with a nominal pore size of 50 nm was used as the modified carrier, with a 500ml concentration of 0.2×10 ^-4 mg/ml, and a nitrogen external pressure device to deposit MXene in the solution on the ceramic membrane On the inner membrane, the pressure is controlled to 0.2MPa, and the ceramic membrane tube on which MXene is deposited is sintered at a high temperature of 200°C. The MXene modified membrane tube was immersed in the octyltrimethoxysilane hydrophobic modification solution with a concentration of 0.01 mol/L for 24 hours, and the tube was taken out to be washed and dried with absolute ethanol for use. The raw material components for preparing the emulsion are: No. 0 diesel oil, deionized water, and 1 wt% of compound emulsifier (span 60: tween 20 = 1:1). A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to 0.35m/s. The dispersed phase is controlled to permeate the membrane tube at a pressure of 0.05 MPa, and the water content (volume content) of 1% is controlled. The particle size of the prepared emulsion is uniform, and the average particle size is about 300 nm.

Comparative example 2

_{A single-channel Al 2} O ₃ tubular ceramic membrane with a nominal pore diameter of 50 nm was used as the modified carrier, and a 500ml concentration of 0.2×10 ^-4 mg/ml was used to deposit MXene in the solution in the ceramic membrane using a nitrogen external pressure device On the membrane, the pressure is controlled to 0.2MPa, and the ceramic membrane tube with MXene deposited on it is sintered at a high temperature of 200°C. The control other steps and parameters are the same as in Example 2. The difference between Comparative Example 2 and Example 2 is that the two-dimensional MXene modified membrane is not hydrophobically modified in Comparative Example 2. The particle size of the prepared emulsion is polydisperse.

Example 3

A multi-channel SiC tubular ceramic membrane with a nominal pore size of 200nm was used as the modified carrier, and a 500ml concentration of 0.5×10 ^-4 mg/ml was used. A nitrogen external pressure device was used to deposit MXene in the solution on the inner membrane of the ceramic membrane. The pressure was controlled to 0.3MPa, and the ceramic membrane tube deposited on MXene was sintered at a high temperature of 400℃. The MXene modified membrane tube was immersed in a polydimethylsiloxane hydrophobic modification solution with a concentration of 0.2 mol/L for 3 hours, and was taken out to be washed and dried with absolute ethanol for use. The raw material components for preparing the emulsion are: No. 0 diesel oil, deionized water, and 3 wt% of compound emulsifier (span20: tween 80=1:1). A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to 0.35m/s. The dispersed phase is controlled to permeate the membrane tube at a pressure of 0.05 MPa, and the water content (volume content) of 30% is controlled, and the particle size of the prepared emulsion is uniform, and the average particle size is about 600 nm.

Example 4

_{A single-channel Al 2} O ₃ tubular ceramic membrane with a nominal pore size of 100 nm was used as the modified carrier, and a 500ml concentration of 1.0×10 ^-4 mg/ml was configured. The MXene in the solution was deposited in the ceramic membrane using a nitrogen external pressure device On the membrane, the pressure is controlled to 0.5MPa, and the ceramic membrane tube with MXene deposited on it is sintered at a high temperature of 300°C. The MXene modified membrane tube was immersed in a trimethylsilyl chloride hydrophobic modification solution with a concentration of 0.01 mol/L for 24 hours, and then washed and dried with absolute ethanol for use. The raw material components for preparing the emulsion are: No. 0 diesel oil, deionized water, and 5 wt% of compound emulsifier (span 20: span 80=1:1). A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to 0.1m/s. The dispersed phase is controlled to pass through the membrane tube at a pressure of 0.1 MPa, and the water content (volume content) of 20% is controlled. The particle size of the prepared emulsion is uniform, and the average particle size is about 800 nm.

Comparative example 4

A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to be 0.5m/s. Control other steps and parameters are the same as in Example 4. The prepared emulsion has a uniform particle size and an average particle size of about 400 nm.

Example 5

_{A single-channel Al 2} O ₃ tubular ceramic membrane with a nominal pore size of 100 nm was used as the modified carrier, and a 500ml concentration of 0.3×10 ^-4 mg/ml was used to deposit MXene in the solution in the ceramic membrane using a nitrogen external pressure device On the membrane, the pressure is controlled to 0.5MPa, and the ceramic membrane tube with MXene deposited on it is sintered at a high temperature of 300°C. The MXene modified membrane tube was immersed in the hexadecyltrimethoxysilane hydrophobic modification solution with a concentration of 0.05 mol/L for 6 hours, and then washed and dried with absolute ethanol for use. The raw material components for preparing the emulsion include: No. 0 diesel oil, deionized water, and 10 wt% of compound emulsifier (span 20: span 80=1:1). A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to 0.4m/s. The dispersed phase is controlled to permeate the membrane tube at a pressure of 0.2 MPa, and the water content (volume content) of 20% is controlled. The particle size of the prepared emulsion is uniform, and the average particle size is about 800 nm.

Example 6

_{A single-channel Al 2} O ₃ tubular ceramic membrane with a nominal pore size of 100 nm was used as the modified carrier, and a 500ml concentration of 0.3×10 ^-4 mg/ml was used to deposit MXene in the solution in the ceramic membrane using a nitrogen external pressure device On the membrane, the pressure is controlled to 0.5MPa, and the ceramic membrane tube with MXene deposited on it is sintered at a high temperature of 300°C. The MXene modified membrane tube was immersed in the hexadecyltrimethoxysilane hydrophobic modification solution with a concentration of 0.05 mol/L for 6 hours, and then washed and dried with absolute ethanol for use. The raw material components for preparing the emulsion include: No. 0 diesel oil, deionized water, and 10 wt% of compound emulsifier (span 20: span 80=1:1). A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to be 0.5m/s. The dispersed phase is controlled to permeate the membrane tube at a pressure of 0.4 MPa, and the water content (volume content) of 20% is controlled. The particle size of the prepared emulsion is uniform, and the average particle size is about 1.5 μm.

Example 7

_{A hollow fiber Al 2} O ₃ tubular ceramic membrane with a nominal pore diameter of 300 nm was used as the modified carrier, and a 500ml concentration of 0.5×10 ^-4 mg/ml was used to deposit MXene in the solution in the ceramic membrane using a nitrogen external pressure device On the membrane, the pressure is controlled to 0.1MPa, and the ceramic membrane tube with MXene deposited on it is sintered at a high temperature of 300°C. , The MXene modified ceramic membrane was immersed in a hexadecyltrimethoxysilane hydrophobic modification solution with a concentration of 0.05 mol/L for 6 hours, and then washed and dried with absolute ethanol for use. The raw material components for preparing the emulsion include: No. 0 diesel oil, deionized water, and a compound emulsifier 0.5 wt% (span 20: span 80=1:1). A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to 0.35m/s. The dispersed phase is controlled to permeate the membrane tube at a pressure of 0.1 MPa, and the water content (volume content) of 20% is controlled. The particle size of the prepared emulsion is uniform, and the average particle size is about 900 nm.

Example 8

_{A single-channel Al 2} O ₃ -SiO ₂ -TiO ₂ tubular ceramic membrane with a nominal pore diameter of 100 nm was used as the modified carrier, and a 500ml concentration of 0.5×10 ^-4 mg/ml was used. MXene is deposited on the inner membrane of the ceramic membrane, the pressure is controlled to 0.1MPa, and the ceramic membrane tube on which MXene is deposited is sintered at a high temperature of 300°C. The MXene modified ceramic membrane was immersed in a hexadecyltrimethoxysilane hydrophobic modification solution with a concentration of 0.05 mol/L for 6 hours, and then washed and dried with absolute ethanol for use. The raw material components for preparing the emulsion are: No. 0 diesel oil, deionized water, and 10 wt% of compound emulsifier (span 20: span 80=1:1). A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to 0.35m/s. The dispersed phase is controlled to permeate the membrane tube at a pressure of 0.05 MPa, and the water content (volume content) of 40% is controlled. The particle size of the prepared emulsion is uniform, and the average particle size is about 500 nm.

Example 9

_{A single-channel ZrO 2} tubular ceramic membrane with a nominal pore size of 200nm was used as the modified carrier, and a 500ml concentration of 0.5×10 ^-4 mg/ml was used to deposit MXene in the solution on the inner membrane of the ceramic membrane using a nitrogen external pressure device , The pressure is controlled to 0.1MPa, and the ceramic membrane tube deposited on MXene is sintered at a high temperature of 300°C. , The MXene modified ceramic membrane was immersed in a hexadecyltrimethoxysilane hydrophobic modification solution with a concentration of 0.05 mol/L for 6 hours, and then washed and dried with absolute ethanol for use. The raw material components for preparing the emulsion are: No. 0 diesel oil, deionized water, and 2 wt% of compound emulsifier (span 80: tween 80 = 1:1). A high-pressure constant-flow pump is used to provide a certain pressure difference across the membrane for the dispersed phase but is not limited to this. A peristaltic pump is used to provide the membrane surface shearing force, and the membrane surface flow rate is controlled to 0.35m/s. The dispersed phase is controlled to permeate the membrane tube at a pressure of 0.05 MPa, and the water content (volume content) of 20% is controlled, and the particle size of the prepared emulsion is uniform, and the average particle size is about 600 nm.

Claims

A preparation method of monodisperse diesel emulsion, which is characterized in that a two-dimensional MXene modified hydrophobic ceramic membrane is used as the emulsifying medium, water is used as the dispersed phase, and diesel fuel with emulsifier is added as the continuous phase, and the dispersed phase is at a certain transmembrane pressure difference. Under the action of the continuous phase shear force, the dispersed phase leaves the surface of the membrane tube and enters the continuous phase through the ceramic membrane tube, so that the water and diesel are fully miscible to form a monodispersed diesel emulsion.
The preparation method according to claim 1, wherein the emulsifying medium is prepared by the following method: dispersing MXene nanosheets in an aqueous solution, using a nitrogen external pressure device to deposit MXene on the inner membrane of the ceramic membrane tube, and controlling The formed MXene-modified ceramic membrane is sintered under pressure to obtain a two-dimensional MXene-modified ceramic membrane; then the two-dimensional MXene-modified ceramic membrane is modified with a hydrophobic modifier to obtain a two-dimensional MXene-modified hydrophobic ceramic membrane.
The preparation method according to claim 2, characterized in that the size of the MXene nanosheets is 200-500nm; the MXene nanosheets are dispersed in an aqueous solution to control the concentration of MXene to be 0.2×10 -4 to 1.0×10 -4 mg/ml; control pressure is 0.1～0.5MPa; sintering temperature is 200～400℃.
The preparation method according to claim 2, wherein the ceramic membrane tube is a single-channel ceramic membrane tube, a multi-channel ceramic membrane tube or a hollow fiber ceramic membrane tube; the pore size of the ceramic membrane is 50-300 nm; the ceramic membrane is Inorganic ceramic membrane, the material is a composite of one or more of ZrO 2 , Al 2 O 3 , SiC, TiO 2 or SiO 2.
The preparation method according to claim 2, wherein the hydrophobic modifier is hexadecyltrimethoxysilane, octyltrimethoxysilane, polydimethylsiloxane or trimethylchlorosilane ; Modifier concentration is 0.01～0.2mol/L; modification time is 3～24h.
The preparation method according to claim 1, wherein the emulsifier is one or more of span 20, span 60, span 80, tween 20 or tween 80; wherein the quality of the emulsifier in the continuous phase The fraction is 0.5-10wt%; the dispersed phase is deionized water.
The preparation method according to claim 1, characterized in that the dispersed phase is controlled to pass through the ceramic membrane tube under a transmembrane pressure difference of 0.05-0.4 MPa, and the continuous phase with a flow rate of 0.1-0.5 m/s is controlled to flow across the membrane surface.
The preparation method according to claim 1, characterized in that the volume content of water in the monodisperse diesel emulsion is 1%-40%.