A carbon dioxide and water co-permeable membrane, its preparation method and application

Abstract

The present invention belongs to the technical field of inorganic membranes, and particularly relates to a high-temperature carbon dioxide and water co-permeable membrane, its preparation method and application. At 500 - 600 °C, the porous proton conductor framework is impregnated in molten carbonate, taken out after heat preservation for 1 - 2 h, and a mixed proton-carbonate ion conductor membrane is obtained. The conductor membrane prepared by the present invention can directly capture carbon dioxide and water from high-temperature flue gas. On the one hand, pure carbon dioxide can be obtained through the condensation process to achieve carbon capture. On the other hand, the carbon dioxide and water permeated at high temperature can be used to obtain syngas through co-electrolysis or methane reforming, etc., and then high-value chemicals can be produced to realize the resource utilization of carbon dioxide.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic membranes, and in particular relates to a carbon dioxide and water co-permeation membrane and a preparation method and application thereof. Background Art

[0002] With the development of society, people's demand for fossil energy is increasing, leading to an annual increase in atmospheric carbon dioxide levels. Coal-fired power plant exhaust (flue gas) is the primary source of carbon dioxide emissions caused by human activities. Therefore, capturing carbon dioxide from flue gas is one of the current effective ways to address the greenhouse effect. Flue gas mainly consists of ~13% CO2, ~3% O2, ~73% N2, ~10% H2O, and ~1% other gases. Its temperature generally ranges from several hundred degrees to 1000°C, depending on the location. It is generally believed that high-temperature carbon dioxide capture can improve the operating efficiency of carbon capture coal-fired power generation technology and reduce separation costs. At the same time, high-temperature carbon capture facilitates the in-situ conversion of carbon dioxide to produce high-value chemicals (such as methane and synthesis gas), which has unique advantages. Existing carbon capture technologies mainly use organic amine aqueous solutions for absorption at low temperatures, which consumes a lot of energy.

[0003] Membrane separation technology has attracted widespread attention due to its advantages such as high throughput, low energy consumption, and high efficiency. Among them, the mixed oxygen ion-carbonate ion conductor (MOCC) membrane is a high-temperature carbon dioxide separation technology developed in recent years (Prog. Energy Combust. Sci. 2021, 82, 100888). Its theoretical selectivity for CO2 is 100%, but since the conductivity of oxygen ion conductor materials is generally low (for example, the conductivity of Sm-doped CeO2 at 500°C is 0.002S cm -1 Energy Environ. Sci. 2012, 5, 8310-8317), which limits its CO2 permeation rate. Furthermore, flue gas typically contains approximately 10% water. If water and CO2 can be separated together at high temperatures, pure CO2 can be obtained through a simple condensation process, utilizing waste heat and achieving carbon capture. Furthermore, it can be directly connected to a high-temperature solid oxide electrolysis cell or coupled with a methane reforming reaction to produce a syngas with an H2 / CO2 ratio, which is beneficial for downstream FT synthesis and realizes the resource utilization of CO2. Summary of the Invention

[0004] In view of the above problems, the present invention provides a carbon dioxide and water co-permeation membrane and a preparation method and application thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] On the one hand, the present invention provides a method for preparing a mixed proton-carbonate ion conductor membrane, which method is as follows: at 500-600 °C, impregnate a porous proton conductor framework in molten carbonate, take it out after heat preservation for 1-2 h, to obtain a mixed proton-carbonate ion conductor membrane.

[0007] In the above technical solution, the pore diameter of the porous proton conductor framework structure is 0.1-50 μm.

[0008] In the above technical solution, the method for preparing the porous proton conductor framework includes the following steps:

[0009] (1) Mix and ball-mill a proton conductor material powder, a pore-forming agent and ethanol, and the volume ratio of the pore-forming agent is 30-70%;

[0010] (2) Subject the powder after the above ball-milling to dry pressing and casting forming, and then sinter at a temperature of 900-1500 °C for heat preservation for 5-20 h to obtain a porous proton conductor framework structure.

[0011] In the above technical solution, the proton conductor material includes BaCe 1-x M x O3 (M = Zr, Y, Yb, 0 ≤ x ≤ 1), BaZr 1-x M x O3 (M = Ce, Y, Yb, 0 ≤ x ≤ 1), SrCe 1-x M x O3 (M = Zr, Y, Yb, 0 ≤ x ≤ 1), LiAl 1-x Co x O2 (0 ≤ x ≤ 1), LiNi 1-x Co x O2 (0 ≤ x ≤ 1).

[0012] In the above technical solution, the pore-forming agent is graphite, carbon black, starch or polymethyl methacrylate.

[0013] In the above technical solution, the method for preparing the molten carbonate is as follows: after mixing and ball-milling the carbonate, place it in a high-temperature muffle furnace, heat it to 500-600 °C, keep it warm for 2 h, and obtain the molten carbonate after cooling.

[0014] In the above technical solution, the carbonate is two or three of Li2CO3, Na2CO3 and K2CO3.

[0015] On the other hand, the present invention provides a mixed proton-carbonate ion conductor membrane prepared by the above preparation method.

[0016] On yet another aspect, the present invention provides the application of the above mixed proton-carbonate ion conductor membrane in carbon dioxide separation.

[0017] In the above technical solution, the application method is as follows: carbon dioxide and water are directly separated from flue gas under the condition of 400 - 900 °C.

[0018] The working principle of the mixed proton-carbonate ion conductor membrane prepared by the present invention is as Figure 1 shown. On the surface of the membrane supply side, CO2 reacts with H2O to generate H + and CO3 2- , and H + and CO3 2- then diffuse through the proton conductor phase and the molten carbonate phase respectively to the membrane permeation side surface, and react on the permeation side to obtain CO2 and H2O.

[0019] The beneficial effects of the present invention are as follows:

[0020] In the present invention, a material with proton conduction ability is prepared into a porous framework structure, and after impregnating molten carbonate therein, a dense biphasic mixed conductor membrane is formed. This membrane can directly capture carbon dioxide and water from high-temperature flue gas. On the one hand, pure carbon dioxide can be obtained through the condensation process to achieve carbon capture; on the other hand, the carbon dioxide and water permeating at high temperature can be used to obtain syngas through co-electrolysis or methane reforming, etc., and then high-value chemicals can be produced to realize the resource utilization of carbon dioxide. The design and preparation of this type of carbon dioxide and water co-permeation membrane provide a new design idea for the "dual carbon" goal. Description of the Drawings

[0021] Figure 1 is a schematic diagram of the working principle of the mixed proton-carbonate ion conductor membrane of the present invention;

[0022] Figure 2 is a chemical compatibility test chart of BaZr 0.85 Y 0.15 O 3-δ with (Li 0.425 Na 0.325 K 0.250 )2CO3 molten carbonate;

[0023] Figure 3 is a permeation performance test chart of the mixed proton-carbonate ion conductor membrane of the present invention. Specific Embodiments

[0024] The following further describes the present invention in combination with embodiments. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments.

[0025] In the present invention, the shape of the mixed proton-carbonate ion conductor membrane can be designed as a sheet membrane or a tubular membrane according to production requirements.

[0026] Example 1

[0027] Weigh BaZr 0.85 Y 0.15 O 3-δ (BZY)-corresponding BaCO3, ZrO2, and Y2O3 powders in stoichiometric ratios, add ethanol and ball mill for 24 h. After drying, grind the powders thoroughly, place them in a crucible, and keep them at 1400 °C for 5 h to obtain pure-phase BZY powders. Mix the obtained powders with ethanol and ball mill for 12 h. After drying, dry-press the BZY powders at 100 MPa to form a sheet with a diameter of 20 mm and a thickness of 1 mm. Then place it in a high-temperature box furnace, slowly heat it to 1450 °C, and calcine it for 12 h to obtain a porous proton conductor framework structure with pore sizes of 1 - 3 μm. Then weigh the carbonates corresponding to (Li 0.425 Na 0.325 K 0.250 )2CO3 in stoichiometric ratios, mix and grind the carbonates evenly, place them in a crucible, keep them at 600 °C for 2 h, and after cooling, obtain molten carbonate (MC) powders. Mix the BZY powders and MC powders with a volume ratio of 1:1 evenly, dry-press them at 100 MPa, place them in a muffle furnace, keep them at 700 °C for 2 h, and after cooling, obtain a mixed proton-carbonate ion conductor membrane sample.

[0028] Grind the obtained sample, perform XRD characterization, and analyze the chemical compatibility of the two materials. The test results are as Figure 2 shown. The BZY-MC sample only shows the peaks of BZY and MC, indicating that BZY and MC have good chemical compatibility.

[0029] Example 2

[0030] Place the BZY porous framework structure in Example 1 and an appropriate amount of molten carbonate powder in a crucible, immerse it at 600 °C for 1 h and then take it out to obtain a dense BZY-MC biphasic mixed conductor membrane. After cooling, sand the excess carbonates on both sides of the BZY-MC biphasic membrane, and then seal it on an alumina tube with silver paste. After keeping it at 600 °C for 2 h, introduce a wet carbon dioxide and nitrogen mixture (50 mL min -1 CO2, 50 mL min -1 N2, 3 mL min -1 H2O) into the supply side, and introduce helium at 100 mL min -1 passing through room-temperature water into the permeation side as a purge gas. Test the carbon dioxide permeation performance of the biphasic mixed conductor membrane between 600 - 800 °C. The results are as Figure 3 shown. The carbon dioxide permeation rate of this mixed conductor membrane is 0.07 mL min -1 cm -2Increased to 0.30 mL min at 800 °C -1 cm -2 .

Claims

1. Application of a mixed proton-carbonate ion conductor membrane in carbon dioxide separation, characterized in that, The preparation method of the mixed proton-carbonate ion conductor membrane is as follows: at 500-600 °C, immerse the porous proton conductor framework in molten carbonate, take it out after heat preservation for 1-2 h to obtain the mixed proton-carbonate ion conductor membrane; The preparation method of the porous proton conductor framework includes the following steps: (1) Mix the proton conductor material powder, pore former, and ethanol and ball mill them. The volume ratio of the pore former is 30% to 70%; the proton conductor material is BaZr 1-x M x O3 (M = Y, 0 ≤ x ≤ 1); (2) Subject the above-mentioned ball-milled powder to dry pressing and casting, and then sinter at a temperature of 900-1500 °C for 5-20 h to obtain the porous proton conductor framework; The preparation method of the molten carbonate is as follows: after mixing and ball-milling the carbonate, place it in a high-temperature muffle furnace, heat it to 500-600 °C, keep it warm for 2 h, and obtain the molten carbonate after cooling; the carbonate is two or three of Li2CO3, Na2CO3, and K2CO3.

2. The application according to claim 1, characterized in that, The pore diameter of the porous proton conductor framework structure is 0.1-50 μm.

3. The application according to claim 1, characterized in that The pore-forming agent is graphite, carbon black, starch, or polymethyl methacrylate.

4. The application according to claim 1, characterized in that The application method is as follows: directly separate carbon dioxide and water from flue gas under the condition of 400-900 °C.

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