Gas separation membrane

Abstract

A gas separation membrane comprises a carbon molecular sieve layer and an organosilicon layer disposed on the surface of the carbon molecular sieve layer. The organosilicon layer is formed by a polycondensation reaction of a silicon precursor layer formed by an organosilicon casting solution. The organosilicon casting solution includes organosilicon sol, and the content of organosilicon sol ranges from 1.9 to 35 wt% based on 100 wt% of the total amount of the organosilicon casting solution. The organosilicon sol is formed by a hydrolysis-condensation reaction of a mixture comprising polyhedral oligomeric half-silsesquioxanes having polyethylene glycol segments, wherein the weight-average molecular weight of the polyethylene glycol segments in the polyhedral oligomeric half-silsesquioxanes is less than 2000 g / mole. This gas separation membrane exhibits high selectivity for carbon dioxide gas and is therefore suitable for carbon dioxide separation.

Description

Technical Field

[0001] The present invention relates to a gas separation technology, in particular to a gas separation membrane used for gas separation. Prior Art

[0002] The Republic of China's patent publication TW202302723A discloses an organic silicon film. The organic silicon film includes an organic silicon material. The organic silicon material is formed by a hydrolysis polymerization reaction of an organic siloxane composition and a calcination treatment. The organic siloxane composition includes tetraethoxysilane, a polyhedral oligomeric half-siloxane material having an epoxy group, and an organic siloxane component. The polyhedral oligomeric half-siloxane material having an epoxy group is a polyhedral oligomeric half-siloxane having an epoxy propyl group. Summary of the invention

[0003] Therefore, the object of the present invention is to provide a novel gas separation membrane.

[0004] Therefore, the gas separation membrane of the present invention comprises a carbon molecular sieve layer and an organic silicon layer disposed on the surface of the carbon molecular sieve layer, wherein the organic silicon layer is formed by a polycondensation reaction of a silicon precursor layer formed by an organic silicon casting liquid, wherein the organic silicon casting liquid comprises an organic silicon sol, and the content of the organic silicon sol ranges from 1.9 wt % to 35 wt % based on the total amount of the organic silicon casting liquid as 100 wt %, and the organic silicon sol is formed by a hydrolysis condensation reaction of a mixed liquid, wherein the mixed liquid comprises a polyhedral oligomeric half siloxane having a polyethylene glycol chain segment, and the weight average molecular weight of the polyethylene glycol chain segment in the polyhedral oligomeric half siloxane having a polyethylene glycol chain segment is less than 2000 g / mole.

[0005] The effect of the present invention is that the gas separation membrane of the present invention permeates the polyhedral oligomeric half siloxane with polyethylene glycol segments, especially the weight average molecular weight of the polyethylene glycol segments in the polyhedral oligomeric half siloxane with polyethylene glycol segments is less than 2000 g / mole, and the organic silicon layer formed by cooperating with the organic silicon sol in the organic silicon casting liquid in a content range of 1.9wt% to 35wt%, and also permeates the organic silicon layer and the carbon molecular sieve layer, so that the gas separation membrane of the present invention has high selectivity for carbon dioxide gas and is suitable for carbon dioxide separation. Implementation

[0006] The gas separation membrane of the invention comprises a carbon molecular sieve layer, an organic silicon layer arranged on the surface of the carbon molecular sieve layer, and an aluminum oxide substrate arranged on the surface of the carbon molecular sieve layer opposite to the organic silicon layer.

[0007] The carbon molecular sieve layer has a microporous and ultramicroporous structure, and the carbon molecular sieve layer provides a gas transmission channel and has a sieving ability for gas. The carbon molecular sieve layer is formed by carbonizing a polymer precursor membrane formed by a polymer casting liquid. The polymer casting liquid includes a polymer and a good solvent for the polymer. The polymer is selected from at least one of the group consisting of polyimide, cellulose and polyetherimide. The good solvent for the polymer is, for example, but not limited to, N-methylpyrrolidone. Taking the total amount of the polymer casting liquid as 100wt%, the content of the polymer is 10wt%, and the content of the good solvent for the polymer is 90wt%.

[0008] The organic silicon layer is formed by a polycondensation reaction of a silicon precursor layer formed by an organic silicon casting film liquid. The organic silicon casting film liquid includes an organic silicon sol and a good solvent for the organic silicon sol. The good solvent for the organic silicon sol is, for example, but not limited to, ethanol. The organic silicon sol is formed by a hydrolysis condensation reaction of a mixed liquid, and the mixed liquid includes a polyhedral oligomeric half-siloxane with a polyethylene glycol chain segment, an alcohol solvent, an acid catalyst, and water. The weight average molecular weight of the polyethylene glycol segments in the polyhedral oligomeric half siloxane with polyethylene glycol segments is less than 2000 g / mole, which can make the organic silicon layer have a higher diffusion rate and solubility for carbon dioxide gas, thereby having a higher permeability to carbon dioxide gas, and then the gas separation membrane has a high carbon dioxide selectivity; preferably, the weight average molecular weight of the polyethylene glycol segments is 499 g / mole to less than 2000 g / mole; in some embodiments of the present invention, the weight average molecular weight of the polyethylene glycol segments in the polyhedral oligomeric half siloxane with polyethylene glycol segments is 499 g / mole. In some embodiments of the present invention, the polyhedral oligomeric half siloxane with polyethylene glycol segments also has a methoxy group. The alcohol solvent is, for example, but not limited to, ethanol. The acid catalyst is, for example, but not limited to, nitric acid. In some embodiments of the present invention, the molar ratio of the polyhedral oligomeric half siloxane having polyethylene glycol segments, the alcohol solvent, the acid catalyst and the water is 1:11.05:0.34:5.82. And based on the total amount of the organic silicon casting liquid as 100wt%, the content of the organic silica sol ranges from 1.9wt% to 35wt%, which can make the organic silicon layer have better selectivity for carbon dioxide gas, and then make the gas separation membrane have a high carbon dioxide selectivity. Based on the total amount of the organic silicon casting liquid as 100wt%, the content of the good solvent of the organic silica sol ranges from 65wt% to 98.1wt%.

[0009] In some embodiments of the present invention, the polymer casting liquid is coated on the surface of the aluminum oxide substrate by spin coating, chemical vapor deposition or dip coating to form the polymer precursor layer, and then the polymer precursor layer is carbonized to form the carbon molecular sieve layer by, for example but not limited to, heating from room temperature (25°C) to 240°C at a heating rate of 5°C / min in a vacuum or inert atmosphere, holding the temperature for 6 hours, and then heating to 600°C. Then, the organic silicon casting liquid is coated on the carbon molecular sieve layer by spin coating, chemical vapor deposition or dip coating to form the silicon precursor layer, and a precursor body comprising the aluminum oxide substrate, the carbon molecular sieve layer and the silicon precursor layer stacked in sequence is obtained. The precursor is then heated using heating conditions such as, but not limited to, heating from room temperature to 240°C at a heating rate of 0.5°C / min in a nitrogen atmosphere and maintaining the temperature for 3 hours, so that the silicon precursor layer undergoes a polycondensation reaction to form the organic silicon layer, thereby obtaining the gas separation membrane of the present invention comprising the aluminum oxide substrate, the carbon molecular sieve layer and the organic silicon layer stacked in sequence.

[0010] The present invention will be further described with reference to the following examples. However, it should be understood that the examples are only for illustration and should not be construed as limiting the implementation of the present invention.

[0011] [Example 1]

[0012] Polyetherimide (brand: Sigma-Aldrich Co., USA, model: 700193) is dissolved in N-methylpyrrolidone to form a polymer casting solution, and based on the total amount of the polymer casting solution being 100wt%, the content of the polyetherimide is 10wt%.

[0013] First, 11.05 mol of ethanol, 0.34 mol of nitric acid and 5.82 mol of water are placed in a serum bottle at room temperature and mixed uniformly. Then, the serum bottle is placed in an ice bath, and 1 mol of methoxy PEG-10 polyhedral oligomeric half siloxane (Methoxy PEG-10 Polysilsesquioxane, brand: Hybrid Plastics, model: PG1190, weight average molecular weight: 4878.21 g / mol, weight average molecular weight of the polyethylene glycol segment in the methoxy PEG-10 polyhedral oligomeric half siloxane: 499 g / mol) is added dropwise into the serum bottle, and stirred continuously for several minutes to uniformly disperse the methoxy PEG-10 polyhedral oligomeric half siloxane, so as to obtain a mixed solution. Then, the serum bottle is moved to a 60°C water bath, heated and stirred continuously for 1.5 hours, so that the mixed solution undergoes a hydrolysis condensation reaction. Then the serum bottle is moved back to the ice bath to terminate the hydrolysis condensation reaction, and the organosilicon sol is obtained. Finally, the serum bottle is placed in a refrigerator for standby use.

[0014] The polymer casting liquid is coated on the surface of an aluminum oxide substrate by a spin coating method to form a polymer precursor layer, and then the polymer precursor layer is heated from room temperature to 240°C at a heating rate of 5°C / min in a vacuum or inert atmosphere by a high-temperature furnace and kept at the temperature for 6 hours, and then heated from 240°C to 600°C at a heating rate of 5°C / min to carbonize the polymer precursor layer to form a carbon molecular sieve layer. The organic silicon sol is taken from the serum bottle and added to ethanol for dilution to obtain an organic silicon casting liquid, and the content of the organic silicon sol in the organic silicon casting liquid is 1.9wt% based on the total amount of the organic silicon casting liquid being 100wt%. Then, the organic silicon casting liquid is coated on the carbon molecular sieve layer by a spin coating method to form a silicon precursor layer, and a precursor body including the aluminum oxide substrate, the carbon molecular sieve layer and the silicon precursor layer stacked in sequence is obtained. The precursor is then placed in the high-temperature furnace, heated from room temperature to 240°C at a heating rate of 0.5°C / min in a nitrogen atmosphere and maintained at this temperature for 3 hours, so that the silicon precursor layer undergoes a polycondensation reaction to form an organic silicon layer, thereby obtaining a gas separation membrane comprising the aluminum oxide substrate, the carbon molecular sieve layer and the organic silicon layer stacked in sequence.

[0015] [Examples 2 to 4]

[0016] The difference between Examples 2 to 4 and Example 1 is that Example 2 uses an organic silicon casting film liquid with an organic silicon sol content of 3.7wt% to form a silicon precursor layer, Example 3 uses an organic silicon casting film liquid with an organic silicon sol content of 6.8wt% to form a silicon precursor layer, and Example 4 uses an organic silicon casting film liquid with an organic silicon sol content of 35wt% to form a silicon precursor layer.

[0017] [Comparative Example 1]

[0018] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not use an organic silicon casting liquid to form a silicon precursor layer, so the gas separation membrane of Comparative Example 1 does not contain an organic silicon layer, and the gas separation membrane of Comparative Example 1 is composed of an aluminum oxide substrate and a carbon molecular sieve layer stacked on each other.

[0019] [Gas permeation flux and gas selectivity of gas separation membranes]

[0020] The following uses the gas separation membrane of Example 1 as an example to illustrate the measurement method of gas permeation flux and gas selectivity. The gas separation membranes of Examples 2 to 4 and the gas separation membrane of Comparative Example 1 are measured in the same manner.

[0021] The gas separation membrane of Example 1 is placed in a measuring device, and then the measuring device is evacuated, and then a test gas (hydrogen, carbon dioxide, oxygen, nitrogen or methane) with a pressure of 2 bar and a purity of 99.999% is introduced into the measuring device, and the gas permeation pressure generated by the test gas passing through the gas separation membrane of Example 1 and entering the permeation end of the measuring device is measured using the pressure sensor of the measuring device, and a graph of the gas permeation pressure and time is drawn, and a slope value is calculated based on the graph, and the slope value is substituted into the formula The gas permeation flux of the gas separation membrane of Example 1 to the test gas is calculated. In the formula, dp / dt is the slope of the pressure to time in the pseudo-steady state (unit: cmHg / sec), V is the volume of the permeation end of the measuring device (unit: cm3), Δp is the pressure difference on both sides of the gas separation membrane (unit: cmHg), A is the area of ​​the gas separation membrane for the gas to be tested to permeate (unit: cm2), P0 is 76 cmHg, T0 is 273K, and T is the test temperature 298K.

[0022] Table 1 Example Comparative Example 1 2 3 4 1 Gas permeation flux (10 -10mol m -2s -1Pa -1) H2 332.32±34.37 474.23±75.17 293.90±58.06 78.19±58.22 343.35±92.59 CO 2 125.49±10.89 179.93±20.50 131.32±58.26 51.29±14.94 411.60±182.09 N 2 2.28±0.30 2.85±1.14 2.51±1.31 1.34±0.54 12.75±7.39 CH 4 1.31±0.10 1.37±0.50 1.21±0.47 0.74±0.34 6.83±3.81 Gas selectivity H2 / CO2 2.65±0.15 2.64±0.32 2.42±0.89 1.41±0.65 1.00±0.59 H2 / N2 144.97±4.01 195.92±118.81 136.83±58.49 53.97±18.58 38.12±29.00 H2 / CH4 252.21±14.27 393.28±215.19 265.09±86.38 99.56±36.72 67.47±46.38 CO2 / N2 54.74±2.98 71.52±33.78 55.63±5.78 38.01±7.97 35.11±7.37 CO 2 / CH 4 95.24±0.30 144.25±59.47 111.57±16.31 72.91±15.35 63.70±10.50 Gas selectivity of H 2 / CO 2: permeation flux of H 2 / permeation flux of CO 2. Gas selectivity of H 2 / N 2: permeation flux of H 2 / permeation flux of N 2. Gas selectivity of H 2 / CH 4: permeation flux of H 2 / permeation flux of CH 4. Gas selectivity of CO 2 / N 2: permeation flux of CO 2 / permeation flux of N 2. Gas selectivity of CO 2 / CH 4: permeation flux of CO 2 / permeation flux of CH 4.

[0023] Referring to the gas selectivity in Table 1, it can be seen that the gas separation membranes of Examples 1 to 4 have high selectivity for carbon dioxide gas, proving that the gas separation membrane of the present invention has a high carbon dioxide selectivity.

[0024] In summary, the gas separation membrane of the present invention cooperates with the organic silicon layer and the carbon molecular sieve layer, especially the organic silicon layer is made of a specific polyhedral oligomeric half siloxane material (i.e., the polyhedral oligomeric half siloxane having a polyethylene glycol segment, and the weight average molecular weight of the polyethylene glycol segment in the polyhedral oligomeric half siloxane having a polyethylene glycol segment is less than 2000 g / mole) and is matched with an organic silicon casting solution with a specific organic silicon sol content (i.e., the content of the organic silicon sol in the organic silicon casting solution ranges from 1.9 wt % to 35 wt %), so the gas separation membrane of the present invention has a high selectivity for carbon dioxide gas and is suitable for carbon dioxide separation, and thus can indeed achieve the purpose of the present invention.

[0025] However, what is described above is only an embodiment of the present invention and should not be used to limit the scope of implementation of the present invention. All simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the patent specification are still within the scope covered by the patent of the present invention.

Claims

1. A gas separation membrane comprising: a carbon molecular sieve layer; and an organosilicon layer disposed on the surface of the carbon molecular sieve layer, the organosilicon layer being formed by a polycondensation reaction of a silicon precursor layer formed by an organosilicon casting solution, the organosilicon casting solution comprising organosilicon sol, and the content of organosilicon sol ranging from 1.9 wt% to 35 wt% based on a total amount of 100 wt% of the organosilicon casting solution, the organosilicon sol being formed by a hydrolysis-condensation reaction of a mixture comprising a polyhedral oligomeric half-siloxane having polyethylene glycol segments, and the weight average molecular weight of the polyethylene glycol segments in the polyhedral oligomeric half-siloxane having polyethylene glycol segments being less than 2000 g / mole.

2. The gas separation membrane as claimed in claim 1, wherein, The weight-average molecular weight of the polyethylene glycol segment ranges from 499 g / mole to less than 2000 g / mole.

3. The gas separation membrane as claimed in claim 2, wherein, The weight-average molecular weight of this polyethylene glycol segment is 499 g / mole.

4. The gas separation membrane as claimed in claim 1, wherein, This polyhedral oligomeric half-siloxane with polyethylene glycol segments also has methoxy groups.

5. The gas separation membrane as claimed in claim 1, wherein, The mixture also includes an alcohol solvent, an acid catalyst, and water, and the molar ratio of the polyhedral oligomeric half-siloxane with polyethylene glycol segments, the alcohol solvent, the acid catalyst, and the water is 1:

1. 11.05：0.34：5.82。 6. The gas separation membrane as claimed in claim 1, wherein, The carbon molecular sieve layer is formed by carbonizing a polymer precursor membrane formed by a polymer casting solution, wherein the polymer casting solution includes a polymer selected from at least one of the group consisting of polyimide, cellulose and polyetherimide.

7. The gas separation membrane as claimed in claim 6, wherein, Assuming the total amount of the polymer casting solution is 100wt%, the content of the polymer is 10wt%.

8. The gas separation membrane of claim 1 further comprises an alumina substrate disposed on the surface of the carbon molecular sieve layer opposite to the organosilicon layer.