A method for preparing porous supported materials for solar fuel production

Abstract

This invention discloses a method for preparing porous supported materials for solar fuel production, belonging to the field of fuel synthesis from cracked CO2 and H2O. This invention aims to provide a porous oxygen-carrying composite material with high cycle stability and high CO2 conversion rate for the synthesis of solar thermochemical fuels. This invention synthesizes a porous ceramic framework material and loads it with an oxygen-carrying material via a template impregnation method. This invention also synthesizes Ni by doping with Co. 0.8 Co 0.2 Fe2O4 exhibits high stability in the solar thermochemical reduction of CO2.

Description

Technical Field

[0001] This invention belongs to the field of solar thermochemistry and solar photothermal chemical cracking of CO2 and H2O to synthesize fuels. Specifically, it relates to a method for preparing porous supported materials for solar fuel preparation. Background Technology

[0002] Oxygen-carrying materials can decompose CO2 and H2O into CO and H2 at high temperatures, thus showing great promise for applications in solar thermal utilization and high-temperature waste gas recovery, effectively mitigating the greenhouse effect and energy crisis. The thermochemical conversion of CO2 under concentrated solar power can decompose CO2 in industrial waste gas into CO fuel, and the decomposition temperature of the two-step CO2 process is much lower than that of direct conversion. However, existing oxygen-carrying material systems typically suffer from low CO2 conversion rates, poor recycling capacity, and low energy conversion efficiency. Researchers have proposed numerous performance enhancement methods, with perovskite or spinel oxygen carriers being common examples. Doping or lattice substitution can improve recycling capacity or lower the temperature required for thermal reduction. Nickel-based ferrites exhibit high performance in fuel production and chemical stability, but the characteristic mechanisms by which various transition metal elements synergistically participate in the thermochemical CO2 conversion process, particularly the thermal oxidation-reduction (reduction and oxidation) performance of Fe-Ni-Co nanocomposite oxide materials under different ratios and preparation methods, have not been further investigated.

[0003] Directly filling the oxygen carrier material into the reactor can easily lead to sintering, resulting in a large amount of material failing to perform as intended and reducing stability. Summary of the Invention

[0004] The purpose of this invention is to provide a porous oxygen-supported composite material with high cycle stability and high CO2 conversion rate for the synthesis of solar thermochemical fuels. This invention relates to Co 2+ and Ni 2+ with Fe 3+ When used in conjunction with CO2 conversion, the microscale heat transfer, mass transfer, and cycling performance of ferrite are significantly improved. The porous silicon carbide prepared by the method of this invention has high thermal conductivity, high solar light absorption performance, and high thermal stability, making it the optimal framework material for preparing shaped load materials.

[0005] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a method for preparing porous supported materials for solar fuel production, comprising the following steps:

[0007] Step 1, according to Ni 0.8 Co 0.2The stoichiometric proportions of Fe2O4 were determined by weighing out Fe(NO3)3, Ni(NO3)2, and Co(NO3)2 hydrates, adding deionized water, and stirring until homogeneous. A chelating agent was then added and stirred again until homogeneous. The mixture was then stirred at 95°C for a period of time, followed by the addition of a gelation accelerator. Stirring continued at 95°C until a colloid was formed. The mixture was then heated at 110°C until the gel showed a clear and deeper color. Further heating at 110°C continued until numerous pores appeared. Calcination was then performed until all gases were released. The mixture was then pulverized and ground to obtain Ni. 0.8 Co 0.2 Fe2O4 powder;

[0008] Step 2: Soak the polyurethane foam in sodium hydroxide solution for 3 hours, then heat in a water bath at 60°C to remove the membranes in the middle of the polyurethane foam mesh. (The membranes are septa in the middle of the polyurethane foam skeleton that block some of the pores and need to be removed; heating and soaking are done simultaneously.)

[0009] SiC or Si3N4 powder is added to the binder solution to prepare a slurry.

[0010] The treated polyurethane foam is immersed in the slurry, then repeatedly squeezed and blown out excess slurry to ensure that the pores are visible and that no slurry flows out. Then it is dried, sintered in stages, and cooled to room temperature in the furnace to obtain a porous ceramic skeleton material.

[0011] Step 3: Take the Ni obtained in Step 1 0.8 Co 0.2 Fe2O4 powder is added to water and stirred continuously to form a suspension, which is then impregnated and loaded onto a porous framework. After drying, the porous loaded material is obtained.

[0012] In step two, the adhesive solution consists of 10% (by mass) aluminum dihydrogen phosphate, 0.5% (by mass) PVA, 0.5% (by mass) CMC, and water.

[0013] Further specifying, the chelating agent is citric acid, and the gelation promoter is polyethylene glycol PEG-400.

[0014] Further specifying, in step one, calcination is carried out at 950℃ for 4 hours.

[0015] Further specifying, the total molar number of cations of the three metal ions in step one is in a molar ratio of 1:2.5 to the chelating agent.

[0016] Further specifying, the pore size of the polyurethane foam in step two is 10 PPI, and the mass percentage concentration of the sodium hydroxide solution is 20%.

[0017] Further specifying, in step two, the slurry is prepared by adding 34 mL of binder solution to 60 g of SiC (or Si3N4) powder.

[0018] Further specifying, in step two, the solid-liquid mass ratio is 7:4, in which the treated polyurethane foam is immersed in the slurry.

[0019] Further specifying the staged sintering process in step two: holding at 1℃ / min to 600℃ for 60 min, holding at 3℃ / min to 1050℃, holding at 1℃ / min to 1300℃ for 30 min, and holding at 4℃ / min to 1500℃ for 120 min.

[0020] Further specifying step three, the Ni obtained in step one is mixed at a solid-liquid ratio of 1:2. x Co 1-x Fe2O4 powder is added to water.

[0021] The above method is used to prepare porous supported materials for solar thermochemical and solar photothermal chemical cracking of CO2 and H2O.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) A stable porous ceramic framework material is used to load an oxygen carrier material that can react with CO2 and is filled in a reactor for experimental testing.

[0024] (2) Improve the thermochemical stability of CO2-reduced oxygen carrier materials. Attached Figure Description

[0025] Figure 1 The curves showing the temperature and products changing over time in a solar thermochemical reduction experiment of CO2 using a cobalt-doped nickel ferrite oxygen carrier material.

[0026] Figure 2 The curves show the temperature and products changing over time in a solar thermochemical reduction experiment of CO2 using nickel ferrite oxygen carrier material.

[0027] Figure 3 This is a comparison of CO production in solar thermochemical experiments using oxygen carrier materials synthesized by sol-gel method and solid-state grinding method. Detailed Implementation

[0028] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0029] Example 1: Preparation of Ni oxygen carrier in this example 0.8 Co 0.2The specific steps for preparing Fe2O4 are as follows: Weigh out 0.6893g of Fe(NO3)3·9H2O hydrate, 0.1985g of Ni(NO3)2·6H2O hydrate, and 0.0497g of Co(NO3)2·6H2O, and pour them into a beaker. Add 10mL of deionized water and stir to mix the solution. Then add citric acid monohydrate as a chelating agent and stir to ensure that the total molar ratio of the three metal ions to citric acid is approximately 1:2.5. Stir at 95℃ for a period of time in a heating stage, and then add polyethylene glycol (PEG-400) as a gelation promoter. If the amount prepared is less than 200mg, ensure that the molar ratio of PEG-400 to citric acid is 1.5:1. If the amount prepared is increased, appropriately reduce the amount of PEG-400 according to the amount of sample prepared, and still ensure that the mixture is stirred at 95℃ for a period of time until the water evaporates and a colloid is formed. If the sample preparation volume is small, it needs to be poured into a crucible, while for larger sample preparations, it remains in a beaker. The furnace preset temperature can be adjusted to 110℃, and preparation can continue until the gel shows a clear and deepened color. Then, the preset temperature is adjusted to 130℃, and preparation continues until numerous pores appear, forming a dry gel. Afterward, it is calcined in a muffle furnace at 950℃ for 4 hours along with the crucible to ensure complete removal of the generated gases. The calcined powder is then pulverized and ground to obtain the final Ni. x Co 1-x Fe2O4 powder. Furthermore, physically doped materials are mixed and ground by weighing according to a specified oxide molar ratio. For example, 20% CoO-doped NiFe2O4 is mixed in a CoO:NiFe2O4 ratio of 1:4.

[0030] The specific steps for preparing oxygen-supported porous ceramic materials are as follows: First, take a polyurethane foam with a diameter of 60 mm, a thickness of 40 mm, and a density of 10 PPI, soak it in a 20% sodium hydroxide solution for 3 hours, and simultaneously heat it in a water bath at 60°C to remove the diaphragm. Add 60 g of SiC to 34 mL of binder (10% (mass) aluminum dihydrogen phosphate, 0.5% (mass) PVA, 0.5% (mass) CMC) solution to prepare a slurry with a solid-liquid mass ratio of 7:4. Immerse the polyurethane foam in the slurry, repeatedly squeeze it, and blow out excess slurry to ensure that the pores are visible and that the slurry does not flow out. The block material was placed in a drying oven and dried at 100°C for 24 hours. After drying, it was placed in a muffle furnace for sintering to form a porous ceramic material. The heating process was as follows: 1°C / min to 600°C and held for 60 minutes, 3°C / min to 1050°C, 1°C / min to 1300°C and held for 30 minutes, 4°C / min to 1500°C and held for 120 minutes. Finally, it was cooled to room temperature with the furnace to obtain the porous ceramic skeleton material.

[0031] Nano-sized iron-cobalt-nickel oxygen carriers were added to water and continuously stirred to form a suspension with a solid-liquid ratio of 1:2. This suspension was then impregnated onto a porous framework and dried in a drying oven at 100°C for 24 hours to obtain a porous supported material, Ni, for solar fuel preparation. 0.8 Co 0.2 Fe2O4@SiC.

[0032] Porous ceramics supported on an oxygen carrier are placed in a solar thermochemical reactor to convert CO2 to CO in a two-step process at high temperature. This is compared to NiFe2O4 and Ni... 0.8 Co 0.2 The test results of Fe2O4 loading on SiC porous framework materials are as follows: Figure 1 and 2 As shown in the figure, it can be seen that as the number of cycles increases, the load Ni... 0.8 Co 0.2 The CO yield of Fe2O4 oxygen carrier material does not decrease significantly, and it also has a high CO yield at high cycle numbers. Figure 3 Two materials synthesized by physical milling and sol-gel methods were described, along with their oxidation process with CO2 after high-temperature reduction. CO production was calculated by integration. The highest cycle CO production was 312 mL, with an average CO2 conversion rate of 5.2% per cycle. Ni 0.8 Co 0.2 The relatively similar CO yields per cycle in the Fe2O4 material indicate the stability of the oxygen carrier material synthesized by the sol-gel method in thermocatalytic CO2 conversion.

Claims

1. A method for preparing a porous supported material for solar fuel production, characterized in that, Includes the following steps: Step 1: According to Ni 0.8 Co 0.2 The stoichiometric proportions of Fe2O4 were determined by weighing out Fe(NO3)3, Ni(NO3)2, and Co(NO3)2 hydrates, adding deionized water, and stirring until homogeneous. A chelating agent was then added and stirred again until homogeneous. The mixture was then stirred at 95°C for a period of time, followed by the addition of a gelation accelerator. Stirring continued at 95°C until a colloid was formed. The mixture was then heated at 110°C until the gel showed a clear and deeper color. Further heating at 110°C continued until numerous pores appeared. Calcination was then performed until all gases were released. The mixture was then pulverized and ground to obtain Ni. 0.8 Co 0.2 Fe2O4 powder; Step 2: Soak the polyurethane foam in sodium hydroxide solution for 3 hours, then heat in a water bath at 60°C to remove the diaphragm in the middle of the mesh polyurethane foam. SiC or Si3N4 powder is added to the binder solution to prepare a slurry. The treated polyurethane foam is immersed in the slurry, then repeatedly squeezed and blown out excess slurry to ensure that the pores are visible and that no slurry flows out. Then it is dried, sintered in stages, and cooled to room temperature in the furnace to obtain a porous ceramic skeleton material. Step 3: Take the Ni obtained in Step 1 0.8 Co 0.2 Fe2O4 powder is added to water and stirred continuously to form a suspension, which is then impregnated and loaded onto a porous framework. After drying, the porous loaded material is obtained. In step two, the adhesive solution consists of 10% aluminum dihydrogen phosphate, 0.5% PVA, 0.5% CMC, and water.

2. The method according to claim 1, characterized in that, The chelating agent is citric acid, and the gelation promoter is polyethylene glycol PEG-400.

3. The method according to claim 1, characterized in that, In step one, calcination is carried out at 950℃ for 4 hours.

4. The method according to claim 1, characterized in that, In step one, the total molar number of the three metal ions cations and the molar ratio of the chelating agent are 1:2.

5.

5. The method according to claim 1, characterized in that, The polyurethane foam in step two has a pore size of 10 PPI, and the sodium hydroxide solution has a mass percentage concentration of 20%.

6. The method according to claim 1, characterized in that, In step two, the slurry is prepared by adding 60g of SiC or Si3N4 powder to 34mL of binder solution.

7. The method according to claim 1, characterized in that, In step two, the solid-liquid mass ratio is 7:4, and the treated polyurethane foam is immersed in the slurry.

8. The method according to claim 1, characterized in that, Step 2 involves a phased sintering process: holding at 1℃ / min up to 600℃ for 60 min, holding at 3℃ / min up to 1050℃, holding at 1℃ / min up to 1300℃ for 30 min, and holding at 4℃ / min up to 1500℃ for 120 min.

9. The method according to claim 1, characterized in that, Step 3: Mix the Ni obtained in Step 1 with a solid-liquid ratio of 1:

2. 0.8 Co 0.2 Fe2O4 powder is added to water.

10. A porous supported material prepared by the method of any one of claims 1-9 for use in solar thermochemical and solar photothermal chemical cracking of CO2 and H2O.

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