CN106975370A - Ionic liquid/transition metal dichalcogenide gas separation membrane and its application are prepared using capillary effect - Google Patents

Abstract

The invention discloses a method for preparing an ionic liquid/transition metal disulfide gas separation membrane by using capillary effect and its application. The steps of the method are as follows: 1) prepare transition metal disulfide nanosheet dispersion liquid, take quantitative dispersion liquid and vacuum filter to obtain transition metal disulfide film; 2) drop quantitative ionic liquid on transition metal disulfide film, use Capillary effect yields ionic liquid/transition metal dichalcogenide gas separation membranes. The invention realizes the combination of the transition metal disulfide film and the ionic liquid by using the capillary effect vacuum filtration method, and introduces the ionic liquid into the two-dimensional layered film in situ, thereby restricting the ionic liquid; and then using the ionic liquid to The difference in solubility and diffusion coefficient of different gases realizes gas separation. The composite membrane prepared by the invention has high application value in gas separation, the preparation process is fast and efficient, the required amount of ionic liquid is small, and the cost is saved.

Description

Fabrication of Ionic Liquids/Transition Metal Disulfides for Gas Separation Using Capillary Effect Membranes and their applications

technical field

The invention relates to the preparation and application of a gas separation composite membrane, in particular to an ionic liquid/transition metal disulfide gas separation membrane and its application.

Background technique

Membrane-based gas separation technology has become an indispensable part of industrial reduction and purification of gases. Gas separation membranes are widely used in many production processes, such as separation of H ₂ from biochemicals, separation of CO ₂ from natural gas, enrichment of water vapor and so on. As early as the 1970s, polymer membranes have been commercially used as gas separation membranes. However, the disadvantages of polymer films, such as low flux and poor stability, also greatly limit its application. Two-dimensional layered materials such as graphene and graphene oxide have unique nanoscale channels, which make gas separation membranes have new possibilities in the field of gas separation. A large number of studies have shown that graphene and graphene oxide have good selectivity, but their flux still needs to be further improved; while graphene-like two-dimensional materials are rarely studied as thin film materials.

Transition metal dichalcogenides such as molybdenum disulfide and tungsten disulfide can be prepared by simple chemical exfoliation to obtain graphene-like two-dimensional materials. And studies have shown that defects in molybdenum disulfide strongly interact with carbon dioxide, making it an ideal material for separating carbon dioxide gas. So far, there are few studies on the separation effect of molybdenum disulfide and tungsten disulfide gas separation membranes. Only some studies have shown that the efficiency of single molybdenum disulfide and tungsten disulfide gas separation membranes for gas separation is low, and there is a lot of room for improvement. Therefore, it can be modified by compounding with other materials to prepare composite membranes, so as to try to improve its gas separation efficiency.

As a new type of molten salt substance, ionic liquid is a new type of green solvent with low vapor pressure, good thermal stability, large electrochemical window, and its properties can be adjusted by designing and changing anion, cation, and alkyl substituents. It can be regulated to meet different functional requirements, so it has a very wide range of applications. In common gases, ionic liquids have a higher solubility for carbon dioxide than ordinary gases, so it has great application potential in the separation and enrichment of carbon dioxide. However, because ionic liquids are in a liquid state and have strong fluidity, they have poor stability in separating carbon dioxide. The invention restricts the flow of the ionic liquid through the lamellar gap of the transition metal disulfide two-dimensional layered material, so as to solve the problem of its stability. The gas separation effect of the prepared composite membrane has also been greatly improved.

Contents of the invention

The invention provides a method for preparing an ionic liquid/transition metal disulfide gas separation membrane by using the capillary effect and its application in gas separation. The ionic liquid and the transition metal disulfide are compounded by vacuum filtration and capillary effect. It realizes the simple and convenient introduction of ionic liquid into the middle of the sheet of transition metal disulfide under the conditions of normal temperature, low energy consumption and no pollution, so that the two materials can be compounded and optimized, and the gas separation has been greatly improved. The concrete technical scheme that the present invention adopts is as follows:

The method for preparing ionic liquid/transition metal disulfide gas separation membrane by capillary effect comprises the following steps:

1) Prepare transition metal disulfide nanosheet dispersion liquid, take quantitative dispersion liquid and vacuum filter to obtain transition metal disulfide film;

2) A quantitative ionic liquid is added dropwise on the transition metal disulfide thin film, and the ionic liquid/transition metal disulfide gas separation membrane is prepared under the action of the capillary effect.

The principle of the preparation method of the present invention is as follows: after the transition metal disulfide nano-sheets are vacuum-filtered, a layered structure is obtained as a basic support; since there is a gap between the layers, after the ionic liquid is dripped on the nano-sheets, , the ionic liquid will be subjected to a large capillary force, and will enter between the transition metal dichalcogenide sheets through the capillary effect; under the action of negative pressure, the interlamellar distance will be further reduced, and the ionic liquid will be confined in the middle of the sheet, which has a confinement and the confinement effect of ionic liquids will greatly increase the stability of ionic liquids; ionic liquids themselves have higher solubility to carbon dioxide than other gases, such as hydrogen and methane, and the confined ionic liquids are The separation performance of the gas in the confinement state will be further improved; thus, the prepared ionic liquid/transition metal dichalcogenide gas separation membrane has significant gas separation performance.

Preferably, the transition metal disulfide nanosheet dispersion is a molybdenum disulfide nanosheet dispersion with a concentration of 0.1-1 mg/mL; the molybdenum disulfide nanosheets Layer dispersion liquid suction filtration makes molybdenum disulfide film on polycarbonate porous film or inorganic aluminum oxide porous film; Described ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim] [BF ₄ ]); add the ionic liquid dropwise on the molybdenum disulfide film, and use the capillary effect to prepare the [Bmim][BF ₄ ]/molybdenum disulfide gas separation membrane.

Preferably, the transition metal disulfide nanosheet dispersion is a tungsten disulfide nanosheet dispersion with a concentration of 0.1-1 mg/mL. Under a negative pressure of 50-90KPa, the tungsten disulfide nanosheet dispersion is suction-filtered onto a polycarbonate porous membrane or an inorganic alumina porous membrane to prepare a tungsten disulfide film; the ionic liquid is 1-butyl- 3-Methylimidazolium tetrafluoroborate ([Bmim][BF ₄ ]); the ionic liquid is added dropwise on the tungsten disulfide film, and the capillary effect is used to prepare [Bmim][BF ₄ ]/tungsten disulfide gas separation membrane.

Based on the above two preferred schemes, further, the capillary effect film forming process can be kept at a negative pressure not lower than 50KPa.

Based on the above two preferred solutions, further: after the ionic liquid/transition metal disulfide gas separation membrane is formed, the mass percentage of the ionic liquid is 30%-80%.

The ionic liquid/transition metal disulfide gas separation membrane prepared according to any of the above technical schemes can be applied to separate carbon dioxide and hydrogen, carbon dioxide and methane. During the separation process, the applicable pressure is 0.01MPa～0.2MPa. No matter from the flux difference of single gas or the direct separation of mixed gas, it shows excellent effect.

Compared with the prior art, the present invention has the following advantages: the transition metal disulfide sheet is used as the basic support, and the ionic liquid is confined in the middle of the sheet, which greatly increases the stability of the ionic liquid, and is limited by The gas separation performance of the confined ionic liquid in the confinement state has also been greatly improved, making the prepared ionic liquid/transition metal disulfide gas separation membrane have significant gas separation performance, greatly improving the performance of the transition metal disulfide The gas separation performance of the gas separation membrane.

Description of drawings

Fig. 1 is the scanning electron microscope figure of the molybdenum disulfide film surface and section prepared in embodiment 1;

Fig. 2 is the scanning electron micrograph of [Bmim] [BF4]/molybdenum disulfide gas separation membrane surface and section prepared in embodiment 1;

Fig. 3 is the scanning electron micrograph of the tungsten disulfide film surface and section prepared in embodiment 2;

4 is a scanning electron microscope image of the surface and section of the [Bmim][BF4]/tungsten disulfide gas separation membrane prepared in Example 2.

detailed description

The present invention will be further elaborated and illustrated below in conjunction with the accompanying drawings and embodiments.

Example 1

1) 3ml of molybdenum disulfide nanosheet dispersion with a concentration of 0.5mg/mL was directly vacuum-filtered on the inorganic alumina porous membrane to form a molybdenum disulfide membrane, as shown in Figure 1. Wherein the inorganic aluminum oxide porous membrane has a diameter of 2.5 cm, a pore diameter of 200 nm, and a porosity of 25-50%. The surface of the molybdenum disulfide film shown in Figure 1 is dense, the film is continuous without cracks, and its cross-sectional layered structure is obvious, which can be seen to be formed by stacking molybdenum disulfide sheets layer by layer. The large gap between the sheets also makes the performance of pure MoS2 membrane as a gas separation membrane poor.

2) Under a negative pressure of 90KPa, 0.5mL of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF ₄ ]) was evenly added dropwise on the molybdenum disulfide film, under the capillary effect [Bmim][BF ₄ ] gradually entered the middle of the molybdenum disulfide nanosheets, and finally a uniform [Bmim][BF ₄ ]/molybdenum disulfide gas separation membrane was obtained, as shown in Figure 2. The surface of the [Bmim][BF ₄ ]/MoS2 gas separation membrane shown in Figure 2 is dense, and the film is continuous without cracks. Compared with pure MoS2, the ionic liquid is filled between the MoS2 sheets, and the film thickness is The layered structure on the cross-section is not obvious, and there is no obvious gap, which shows that [Bmim][BF ₄ ] is fully filled in the middle of the molybdenum disulfide sheet, and the two form a composite structure.

3) The separation performance of the prepared molybdenum disulfide film was tested for binary mixed gas. The experimental results show that the separation ratio of CO ₂ /CH ₄ is 0.47 and the separation ratio of CO ₂ /H ₂ is 0.28 at 0.06 MPa. At 0.08MPa, the separation ratio of CO ₂ /CH ₄ is 0.50, and the separation ratio of CO ₂ /H ₂ is 0.30.

4) The prepared [Bmim][BF ₄ ]/molybdenum disulfide gas separation membrane was tested for the separation performance of binary mixed gas. The experimental results showed that at 0.06MPa, the separation ratio of CO ₂ /CH ₄ reached 13.9, CO The separation ratio of ₂ /H ₂ reaches 10.22. The separation ratios of CO ₂ /CH ₄ and CO ₂ /H ₂ are 29.6 and 36.5 times that of pure MoS ₂ films, respectively. At 0.08MPa, the separation ratio of CO ₂ /CH ₄ reaches 28.3, and the separation ratio of CO ₂ /H ₂ reaches 15.4. The separation ratios of CO ₂ /CH ₄ and CO ₂ /H ₂ are 56.6 and 51.3 times that of pure MoS ₂ films, respectively.

Example 2

1) Vacuum filter 3ml of tungsten disulfide nanosheet dispersion with a concentration of 0.5mg/mL directly on the inorganic alumina porous membrane to form a tungsten disulfide membrane, as shown in Figure 3. Wherein the inorganic aluminum oxide porous membrane has a diameter of 2.5 cm, a pore diameter of 200 nm, and a porosity of 25-50%. The surface of the tungsten disulfide film shown in Figure 3 is dense, the film is continuous without cracks, and its cross-sectional layered structure is obvious, which can be seen to be formed by stacking tungsten disulfide sheets layer by layer. The large gap between the sheets also makes the pure tungsten disulfide membrane have poor performance as a gas separation membrane.

2) Under a negative pressure of 90KPa, 0.5mL of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF ₄ ]) was evenly added dropwise on the tungsten disulfide film, under the capillary effect [Bmim][BF ₄ ] gradually entered the middle of the tungsten disulfide nanosheets, and finally a uniform [Bmim][BF ₄ ]/tungsten disulfide gas separation membrane was obtained, as shown in Figure 4. The surface of the [Bmim][BF ₄ ]/tungsten disulfide gas separation membrane shown in Figure 4 is dense and continuous without cracks. The layered structure on the cross-section is not obvious, and there is no obvious gap, which shows that [Bmim][BF ₄ ] is fully filled in the middle of the tungsten disulfide sheet, and the two form a composite structure.

3) The separation performance of the prepared tungsten disulfide film was tested for binary mixed gas. The experimental results show that the separation ratio of CO ₂ /CH ₄ is 0.37 and the separation ratio of CO ₂ /H ₂ is 0.32 at 0.06 MPa. At 0.08MPa, the separation ratio of CO ₂ /CH ₄ is 0.41, and the separation ratio of CO ₂ /H ₂ is 0.35.

4) The prepared [Bmim][BF ₄ ]/tungsten disulfide gas separation membrane was tested for the separation performance of binary mixed gas. The experimental results showed that the separation ratio of CO 2 /CH 4 reached 26.1 at 0.06 MPa, and the CO ₂ /CH ₄ separation ratio reached 26.1. The separation ratio of ₂ /H ₂ reaches 9.4. The separation ratios of CO ₂ /CH ₄ and CO ₂ /H ₂ are 70.5 and 29.4 times that of pure WS ₂ films, respectively. At 0.08MPa, the separation ratio of CO ₂ /CH ₄ reaches 25.9, and the separation ratio of CO ₂ /H ₂ reaches 11.2. The separation ratios of CO ₂ /CH ₄ and CO ₂ /H ₂ are 63.2 and 32 times that of pure MoS ₂ films, respectively.

The above-mentioned embodiment is only a preferred solution of the present invention, but it is not intended to limit the present invention. Various changes and modifications can be made by those skilled in the relevant technical fields without departing from the spirit and scope of the present invention. Therefore, all technical solutions obtained by means of equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

Claims (8)

1. a kind of utilization capillary effect prepares the method for ionic liquid/transition metal dichalcogenide gas separation membrane, its feature It is, comprises the following steps：

1) transition metal dichalcogenide nanoscale twins dispersion liquid is prepared, takes quantitative dispersion liquid vacuum filtration to obtain the sulphur of transition metal two Compound film；

2) quota ion liquid is added dropwise on transition metal dichalcogenide film, in the presence of capillary effect, prepares Ionic liquid/transition metal dichalcogenide gas separation membrane.

2. prepare ionic liquid/transition metal dichalcogenide gas separation membrane using capillary effect as claimed in claim 1 Method, it is characterised in that described transition metal dichalcogenide nanoscale twins dispersion liquid is that molybdenum disulfide nano sheet layer is scattered Liquid, its concentration is 0.1~1mg/mL；Under the negative pressure for being not less than 50KPa by molybdenum disulfide nano sheet layer dispersion liquid suction filtration to gather Molybdenum disulfide film is made on carbonic ester perforated membrane or inorganic oxide aluminium perforated membrane；Described ionic liquid is 1- butyl -3- Methyl imidazolium tetrafluoroborate；Ionic liquid is added drop-wise on molybdenum disulfide film, using capillary effect, is made as 1- fourths Base -3- methyl imidazolium tetrafluoroborates/molybdenum disulfide gas separation membrane.

3. prepare ionic liquid/transition metal dichalcogenide gas separation membrane using capillary effect as claimed in claim 1 Method, it is characterised in that described transition metal dichalcogenide nanoscale twins dispersion liquid is that tungsten disulfide nano slices layer is scattered Liquid, its concentration is 0.1~1mg/mL.Under the negative pressure for being not less than 50KPa by tungsten disulfide nano slices layer dispersion liquid suction filtration to gather Tungsten disulfide film is made on carbonic ester perforated membrane or inorganic oxide aluminium perforated membrane；Described ionic liquid is 1- butyl -3- Methyl imidazolium tetrafluoroborate；Ionic liquid is added drop-wise on tungsten disulfide film, using capillary effect, is made as 1- fourths Base -3- methyl imidazolium tetrafluoroborates/tungsten disulfide gas separation membrane.

4. prepare ionic liquid/transition metal dichalcogenide gas separation using capillary effect as claimed in claim 2 or claim 3 The method of film, it is characterised in that be maintained at using capillary effect film-forming process under the negative pressure for being not less than 50KPa.

5. prepare ionic liquid/transition metal dichalcogenide gas separation using capillary effect as claimed in claim 2 or claim 3 The method of film, it is characterised in that ionic liquid/transition metal dichalcogenide gas separation membrane is after film forming, shared by ionic liquid Mass percent be 30%~80%.

6. the ionic liquid prepared such as any methods described of Claims 1 to 5/transition metal dichalcogenide gas separation Film.

7. the application of ionic liquid as claimed in claim 6/transition metal dichalcogenide gas separation membrane, it is characterised in that institute The ionic liquid of preparation/transition metal dichalcogenide gas separation membrane can be applied to separation carbon dioxide and hydrogen, carbon dioxide And methane.

8. application as claimed in claim 7, it is characterised in that in separation process, applicable pressure for 0.01MPa~ 0.2MPa。