A mixed conductor carbon dioxide separation membrane and its preparation method and application

Abstract

The present invention belongs to the field of inorganic membranes, and specifically relates to a mixed conductor carbon dioxide separation membrane and its preparation method and application. The mixed conductor carbon dioxide separation membrane is obtained by impregnating a molten carbonate into a porous skeleton by an impregnation method; the preparation method of the molten carbonate is as follows: component I is mixed and ground, heated to 500-600°C, kept warm for 2h, and then component II is added to obtain a molten carbonate; component I is two or three of lithium carbonate, sodium carbonate and potassium carbonate, and component II is one or more of lithium carbonate, barium carbonate, calcium carbonate, strontium carbonate and magnesium carbonate, and the addition amount of component II is 0.01-50mol%. The present invention achieves a significant improvement in the permeability and stability of the mixed conductor carbon dioxide separation membrane by adding lithium, barium, calcium, strontium and magnesium ions to traditional molten carbonates. The method is simple in process and opens up a new research direction for studying this type of mixed conductor carbon dioxide separation membrane.

Description

Technical Field

[0001] The invention belongs to the field of inorganic membranes, and in particular relates to a mixed conductor carbon dioxide separation membrane and a preparation method and application thereof. Background Art

[0002] Carbon dioxide capture is of great significance for achieving the goals of "carbon peak" and "carbon neutrality". Existing carbon dioxide capture technology is mainly based on the absorption of organic amine aqueous solutions, but this method has high energy consumption, complex processes and high costs. Membrane separation technology has received widespread attention due to its advantages such as high processing capacity, low cost and high efficiency, but traditional carbon dioxide separation membranes (such as zeolite membranes and MOF membranes) are limited by the "Robinson effect" and it is difficult to simultaneously obtain high permeation rate and high selectivity.

[0003] Hybrid electron-carbonate ion conductor membrane is a new carbon dioxide separation technology developed in recent years. It consists of a porous skeleton structure that can conduct electrons and a molten carbonate phase that can conduct carbonate ions. It separates carbon dioxide through an electrochemical process at high temperatures (400-900°C) and can directly separate carbon dioxide from high-temperature simulated flue gas (the main source of industrial carbon emissions). According to the reaction process on the membrane surface (CO3 2- =CO2+1 / 2O2+2e - ), a CO2 / O2 mixed gas can be obtained on the membrane permeation side, which can be used in the following three aspects: 1) converted into CO2 and H2O through the synthesis gas combustion process, and pure CO2 can be obtained after condensation, and the heat generated can be used for power generation; 2) the captured high-temperature CO2 / O2 mixed gas is directly used in the oxygen-enriched combustion process; 3) directly coupled chemical reactions at high temperatures to prepare high-value chemicals, such as methane reforming to produce synthesis gas, ethane oxidative dehydrogenation to produce ethylene, and methane oxidative coupling to produce ethylene. Therefore, the development of a high-permeability mixed electron-carbonate ion conductor membrane is of great significance in carbon capture.

[0004] At present, the research on the membrane is mainly focused on the skeleton material of the membrane, such as improving the permeability and stability by optimizing the microstructure of the membrane skeleton (J.Membr.Sci.2017,523,439-445), modifying the surface of the skeleton structure by atomic layer deposition (Chem.Commun.2016,52,9817-9820) and vapor deposition (J.Membr.Sci.2014,453,36-41) and other technologies to improve its thermal stability and wettability with molten carbonate, reducing the bulk diffusion resistance by reducing the thickness of the membrane, and improving its permeation rate, etc. These optimization methods for skeleton materials generally have the problems of complex process and high cost. Summary of the invention

[0005] In view of the above problems, the present invention provides a mixed conductor carbon dioxide separation membrane and a preparation method and application thereof. The carbon dioxide permeation rate and stability of the membrane are improved by adding single metal ions of lithium, barium, calcium, strontium, magnesium or a combination thereof to the molten carbonate phase in the mixed conductor carbon dioxide separation membrane. The method has a simple process and opens up a new research direction for studying this type of mixed conductor carbon dioxide separation membrane.

[0006] In order to achieve the above object, the present invention adopts the following technical scheme:

[0007] In one aspect, the present invention provides a method for preparing a mixed conductor carbon dioxide separation membrane, the method comprising: impregnating a molten carbonate into a porous skeleton by an impregnation method to obtain a mixed conductor carbon dioxide separation membrane;

[0008] The preparation method of the molten carbonate is:

[0009] Component I is mixed and ground, heated to 500-600°C, kept warm for 2 hours, and then component II is added to obtain molten carbonate;

[0010] The component I is two or three of lithium carbonate, sodium carbonate and potassium carbonate, and the component II is one or more of lithium carbonate, barium carbonate, calcium carbonate, strontium carbonate and magnesium carbonate, wherein the addition amount of component II is 0.01-50 mol%.

[0011] In the above technical solution, the immersion temperature is 400-600° C., and the immersion time is 0.5-2 h.

[0012] In the above technical solution, the porous skeleton includes metallic silver, nickel oxide, and lithium nickelate.

[0013] In the above technical solution, the pore diameter of the porous skeleton is 0.1 to 50 microns.

[0014] In the above technical solution, the porous skeleton is in sheet or tube type.

[0015] Another aspect of the present invention provides a mixed conductor carbon dioxide separation membrane prepared by the above preparation method.

[0016] In another aspect, the present invention provides an application of the above separation membrane, wherein the mixed conductor carbon dioxide separation membrane has an operating temperature of 400-900°C.

[0017] The beneficial effects of the present invention are:

[0018] The present invention achieves a significant improvement in the permeability and stability of a mixed conductor carbon dioxide separation membrane by adding lithium, barium, calcium, strontium and magnesium ions to traditional molten carbonate. The method is simple in process and opens up a new research direction for studying this type of mixed conductor carbon dioxide separation membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The microscopic morphology of the mixed conductor carbon dioxide separation membrane of the present invention, wherein a is a porous skeleton structure, and b is a two-phase dense membrane after being impregnated with molten carbonate;

[0020] Figure 2 The effect of lithium ion addition on carbon dioxide permeability in Comparative Example 1 and Example 1;

[0021] Figure 3 The effect of adding barium and calcium ions on the carbon dioxide permeability in Comparative Example 1 and Example 2;

[0022] Figure 4 These are the stability test results of the mixed conductor membrane in Example 5. DETAILED DESCRIPTION

[0023] The present invention is further described below in conjunction with embodiments. The described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments.

[0024] The shape of the mixed conductor membrane described in the present invention can be designed as a sheet membrane or a tubular membrane according to production requirements.

[0025] Comparative Example 1

[0026] The nickel oxide powder was dry pressed under a pressure of 100 MPa and sintered at 950 °C to obtain a porous skeleton. Figure 1 As shown in a; lithium carbonate and sodium carbonate are mixed and ground in a molar ratio of 52:48, and treated at 600℃ for 2h to form molten carbonate. The porous nickel oxide skeleton is immersed in the molten carbonate for 1h, and a dense two-phase mixed conductor membrane is obtained after cooling and taking out. Figure 1 As shown in b, the mixed conductor membrane was sealed on the alumina tube with glass / silver paste; at 850°C, 100 mL min was introduced into the supply side. -1 A mixture of carbon dioxide, oxygen and nitrogen (15% CO2, 10% O2, 75% N2) was introduced into the permeate side at a rate of 100 mL / min. -1 With helium as the purge gas, the permeation rates of carbon dioxide and oxygen were 0.80 and 0.40 mL min, respectively. -1 cm -2 .

[0027] Example 1

[0028] The nickel oxide powder was dry pressed under a pressure of 100 MPa, and a porous skeleton was obtained after high-temperature sintering at 950 ° C. Lithium carbonate and sodium carbonate were mixed and ground in a molar ratio of 52:48, and after being treated at 600 ° C for 2 hours, 30 mol% of lithium carbonate was added to form a lithium-rich molten carbonate. The porous nickel oxide skeleton was immersed in the lithium-rich molten carbonate for 1 hour, and a dense two-phase mixed conductor membrane was obtained after cooling and taking out. The mixed conductor membrane was sealed on the alumina tube with glass / silver paste. At 850 ° C, 100 mL min was passed into the supply side. -1 A mixture of carbon dioxide, oxygen and nitrogen (15% CO2, 10% O2, 75% N2) was introduced into the permeate side at a rate of 100 mL min -1 Helium was used as the purge gas. The permeation rates of carbon dioxide and oxygen were 1.38 and 0.67 mL min, respectively. -1 cm -2 .

[0029] Example 2

[0030] Nickel oxide powder was dry pressed under a pressure of 100 MPa, and a porous skeleton was obtained after high-temperature sintering at 950°C. Lithium carbonate and sodium carbonate were mixed and ground in a molar ratio of 52:48, and after being treated at 600°C for 2 hours, 2 mol% of barium carbonate and 2 mol% of calcium carbonate were additionally added to form a molten carbonate containing lithium, sodium, barium and calcium ions. The porous nickel oxide skeleton was immersed in the molten carbonate for 1 hour, and a dense two-phase mixed conductor membrane was obtained after cooling and taking out; the mixed conductor membrane was sealed on the alumina tube with glass / silver paste; at 850°C, 100 mL min was passed through the supply side. -1 A mixture of carbon dioxide, oxygen and nitrogen (15% CO2, 10% O2, 75% N2) was introduced into the permeate side at a rate of 100 mL min -1 With helium as the purge gas, the permeation rates of carbon dioxide and oxygen were 1.17 and 0.59 mL min, respectively. -1 cm -2 .

[0031] Example 3

[0032] Nickel oxide powder was dry pressed under a pressure of 100 MPa, and a porous skeleton was obtained after high-temperature sintering at 950°C; lithium carbonate and sodium carbonate were mixed and ground in a molar ratio of 52:48, and after being treated at 600°C for 2 hours, 40 mol% of lithium carbonate was additionally added to form a lithium-rich molten carbonate, and the porous nickel oxide skeleton was immersed in the lithium-rich molten carbonate for 1 hour, and a dense two-phase mixed conductor membrane was obtained after cooling and taking out; the mixed conductor membrane was sealed on the alumina tube with glass / silver paste; 100 mL min was passed through the supply side at 850°C. -1A mixture of carbon dioxide, oxygen and nitrogen (15% CO2, 10% O2, 75% N2) was introduced into the permeate side at a rate of 100 mL min -1 With helium as the purge gas, the permeation rates of carbon dioxide and oxygen were 0.77 and 0.39 mL min, respectively. -1 cm -2 .

[0033] Example 4

[0034] Nickel oxide powder is dry-pressed under a pressure of 100 MPa, and a porous skeleton is obtained after high-temperature sintering at 950°C; lithium carbonate and sodium carbonate are mixed and ground in a molar ratio of 52:48, and after being treated at 600°C for 2 hours, 40 mol% of lithium carbonate, 2 mol% of barium carbonate and 2 mol% of lithium calcium carbonate are additionally added to form a molten carbonate rich in lithium and containing barium and calcium ions, and the porous nickel oxide skeleton is immersed in the molten carbonate for 1 hour, and a dense two-phase mixed conductor membrane is obtained after cooling and taking out; the mixed conductor membrane is sealed on an alumina tube with glass / silver paste; 100 mL min is passed through the supply side at 850°C. -1 A mixture of carbon dioxide, oxygen and nitrogen (15% CO2, 10% O2, 75% N2) was introduced into the permeate side at a rate of 100 mL min -1 With helium as the purge gas, the permeation rates of carbon dioxide and oxygen were 1.17 and 0.58 mL min, respectively. -1 cm -2 .

[0035] Example 5

[0036] The two-phase mixed conductor membranes in Example 3 and Example 4 were heated to 850°C and 100 mL / min was introduced into the supply side. -1 A mixture of carbon dioxide, oxygen and nitrogen (15% CO2, 10% O2, 75% N2) was introduced into the permeate side at a rate of 100 mL min -1 Helium was used as the purge gas. The long-term stability of the two membranes was tested.

[0037] Figure 1 a is the porous skeleton structure of the mixed conductor carbon dioxide separation membrane, Figure 1 b is a dense mixed conductor carbon dioxide separation membrane.

[0038] Figure 2 This is the effect of adding lithium ions in molten carbonate on the permeability of mixed conductor carbon dioxide separation membrane. It can be seen that the permeation rates of carbon dioxide and oxygen have been significantly improved.

[0039] Figure 3This is the effect of adding barium and calcium ions in molten carbonate on the permeability of the mixed conductor carbon dioxide separation membrane. It can be seen that the addition of barium and calcium ions also significantly improves the permeation rate of carbon dioxide and oxygen.

[0040] Figure 4 This is a stability test of whether barium and calcium ions are added to the molten carbonate. It can be seen that the addition of barium and calcium ions significantly improves the stability of the mixed conductor carbon dioxide separation membrane.

Claims

1. A method for preparing a mixed conductor carbon dioxide separation membrane, characterized in that: The method comprises: impregnating molten carbonate into a porous framework by an impregnation method to obtain a mixed conductor carbon dioxide separation membrane; The immersion temperature is 400-600°C and the immersion time is 0.5-2 h; The preparation method of the molten carbonate is: Component I is mixed and ground, heated to 500-600 °C, kept warm for 2 hours, and then component II is added to obtain molten carbonate; The component I is two or three of lithium carbonate, sodium carbonate and potassium carbonate, and the component II is one or more of lithium carbonate, barium carbonate, calcium carbonate, strontium carbonate and magnesium carbonate, wherein the addition amount of component II is 0.01-50 mol; The porous skeleton is nickel oxide, and the pore diameter of the porous skeleton is 0.1-50 μm.

2. The preparation method according to claim 1, characterized in that: The porous skeleton is in sheet or tube form.

3. A mixed conductor carbon dioxide separation membrane prepared by the preparation method according to any one of claims 1 to 2.

4. An application of the mixed conductor carbon dioxide separation membrane according to claim 3, characterized in that: The mixed conductor carbon dioxide separation membrane has an operating temperature of 400-900°C.

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