Calcium oxide / water foaming type porous ceramic as well as preparation method and application thereof

Abstract

The invention discloses calcium oxide / water foamed porous ceramic as well as a preparation method and application thereof. Belongs to the field of porous ceramics. The invention aims to solve the problems of low adsorption capacity, poor thermal stability and difficult regeneration of the existing carbon capture material and the problems of high cost, complex process and difficulty in considering high performance of the traditional porous ceramic preparation method. The porous ceramic disclosed by the invention is a three-dimensional communicated pore structure framework formed by taking silicon carbide (SiC) and aluminum oxide (Al2O3) as matrixes, wherein the mass ratio of the SiC to the Al2O3 is (1.5-1.2): 1; the carbon absorption active layer is distributed on the hole wall of the framework; the carbon absorption active layer is composed of residual calcium oxide (CaO) and loaded nano magnesium oxide (MgO), and the porous ceramic has high porosity, a three-dimensional communicated pore structure, good mechanical properties and efficient CO2 adsorption capacity, and is suitable for the fields of industrial tail gas carbon capture, building heat insulation and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of porous ceramics, and particularly relates to a calcium oxide / water foaming type porous ceramic and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of industrialization, a large amount of carbon dioxide (CO2) emission in industrial tail gas has become one of the main factors of global climate change. Carbon capture, utilization and storage technology is widely recognized as a key path to achieve carbon neutrality. The commonly used carbon capture materials currently include activated carbon, zeolite molecular sieve, metal organic framework material, etc., but these materials generally have problems of low adsorption capacity, poor thermal stability, difficult regeneration or high cost.

[0003] Porous ceramic materials exhibit good application prospects in high-temperature tail gas treatment due to their excellent thermal stability, chemical inertness, high specific surface area and controllable pore structure. However, traditional porous ceramic preparation methods such as particle packing method and foaming method often have difficulty in balancing high porosity, good connectivity and high strength, and most of the materials themselves do not have the ability to actively adsorb CO2.

[0004] In the prior art, patent CN 119869579 A discloses a porous ceramic loaded three-dimensional molybdenum disulfide composite catalytic material and a preparation method thereof. The material grows molybdenum disulfide nanoflowers on the porous ceramic through a hydrothermal method, and is used for photocatalytic degradation of organic matter, but it is mainly aimed at organic pollutant treatment and does not involve CO2 adsorption function, and the pore structure may lack selectivity for CO2 in high-temperature tail gas. In addition, patent CN 118724565 B discloses an alumina porous ceramic material and a preparation method and application thereof. The material is prepared by corundum sand, binder and pore former, and has the characteristics of controllable pore size, high strength and good adsorption performance, but is applied in the field of vacuum chuck, focuses on physically adsorbing gas to maintain vacuum, and does not consider chemical adsorption of CO2 or stability in high-temperature tail gas environment. Therefore, the porous ceramic materials in the prior art have limitations in CO2 capture and cannot balance high porosity, good connectivity, high strength and the ability to actively adsorb CO2.

[0005] Therefore, there is an urgent need in the art to develop a porous ceramic material with high porosity, excellent connectivity, good mechanical properties and active carbon adsorption function, in order to solve the problems of low adsorption capacity, poor thermal stability and difficult regeneration of existing carbon capture materials, and the problems of high cost, complex process and difficulty in balancing high performance of traditional porous ceramic preparation methods. SUMMARY

[0006] The present application aims to solve the problems of low adsorption capacity, poor thermal stability, and difficult regeneration of existing carbon capture materials, as well as the problems of high cost, complex process, and difficulty in balancing high performance of traditional porous ceramic preparation methods, and provides a calcium oxide / water foaming type porous ceramic and a preparation method thereof. The porous ceramic has high porosity, a three-dimensional interconnected pore structure, good mechanical properties, and high CO2 adsorption capacity, and is suitable for industrial tail gas carbon capture and building thermal insulation fields.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: The present application uses calcium oxide (CaO) and water (H2O) as foaming agents, generates calcium hydroxide through hydration reaction and releases heat and gas to form a three-dimensional interconnected pore structure; the base material is a composite phase of silicon carbide (SiC) and aluminum oxide (Al2O3); and the built-in carbon absorption active layer is composed of residual CaO and loaded nanoscale magnesium oxide (MgO).

[0008] The present application aims to provide a calcium oxide / water foaming type carbon absorption porous ceramic for industrial tail gas carbon capture. The porous ceramic is a three-dimensional interconnected pore structure skeleton formed by silicon carbide (SiC) and aluminum oxide (Al2O3) as the base, wherein the mass ratio of SiC to Al2O3 is (1.5~1.2):1; and a carbon absorption active layer distributed on the pore wall of the skeleton; the carbon absorption active layer is composed of residual calcium oxide (CaO) and loaded nanoscale magnesium oxide (MgO).

[0009] Further limited, the CO2 adsorption capacity of the porous ceramic follows the following formula:

[0010] wherein, is the CO2 adsorption capacity, unit: mol / g; SBET is the specific surface area, unit: m 2 / g; P is the porosity, unit: %; T is the adsorption temperature, unit: K; k and a are material-related constants (k=0.12±0.03, a=0.005) Further limited, the three-dimensional interconnected pore structure is formed by foaming reaction of SiC powder, Al2O3 powder, CaO powder, PVA binder and deionized water (H2O), wherein the molar ratio of CaO to H2O is (1~0.8):1, the pore volume (Vp, unit: cm³ / g) and the CaO addition amount (wt%) and the sintering temperature (T, unit: ℃) satisfy the following relationship: .

[0011] ​​​Further limited, the pore size distribution of the porous ceramic is 10-200 mu m, the porosity is 70-85%, and the compressive strength is greater than or equal to 5 MPa.

[0012] Another object of the present application is to provide a preparation method of the above-mentioned calcium oxide / water foaming type carbon absorption porous ceramic applied to industrial tail gas carbon capture.

[0013] A preparation method of a calcium oxide / water foaming type carbon absorption porous ceramic applied to industrial tail gas carbon capture, comprising the following steps: Step 1, raw material mixing: mixing SiC powder, Al2O3 powder and CaO powder in proportion, and adding PVA binder to obtain a mixture; Step 2, foaming molding: adding deionized water to the mixture, initiating the CaO hydration foaming reaction by stirring, then pouring into a mold and standing for solidification to form a porous body; Step 3, pre-sintering: pre-sintering the obtained porous body in a protective atmosphere to remove organic matter; Step 4, high-temperature sintering: sintering the pre-sintered body at 1350-1450 DEG C to form a porous ceramic skeleton with a three-dimensional interconnected pore structure, and part of CaO remains on the pore wall; Step 5, surface modification: loading a nano-MgO coating on the pore wall of the porous ceramic skeleton by dipping and calcining to form the carbon absorption active layer.

[0014] Further limited, in the high-temperature sintering step, part of CaO reacts with Al2O3 to form CaAl2O4, and the conversion rate (eta) is determined by the holding time (t, unit: h) and the sintering temperature (T, unit: DEG C) together, and the calculation formula is:

[0015] Further limited, the surface modification step specifically includes: immersing the sintered porous ceramic in a 0.5 mol / L Mg(NO3)2 solution, and then calcining at 600 DEG C for 2 hours.

[0016] In addition, the use of the above-mentioned porous ceramic of the present application is also provided, and the porous ceramic is applied to the treatment of industrial flue gas at 200-400 DEG C as a carbon capture module.

[0017] The use of the above-mentioned porous ceramic material of the present application is also provided, and the porous ceramic material is used as a building thermal insulation material.

[0018] The present application provides a technical solution: a preparation method of a calcium oxide / water foaming type carbon absorption porous ceramic applied to industrial tail gas carbon capture, and the specific operation steps are as follows: Step 1, raw material mixing:​ Silicon carbide (SiC) powder, aluminum oxide (Al2O3) powder and calcium oxide (CaO) powder are mixed in proportion, wherein the mass ratio of SiC to Al2O3 is (1.5~1.2):1, the CaO addition amount is 16wt%~22 wt% of the total mass of the powder, an appropriate amount of PVA binder is added, and the mixture is uniformly mixed by a ball mill; Step 2, foaming molding: An appropriate amount of deionized water is added to the mixture, the molar ratio of CaO to H2O is (1~0.8):1, the CaO hydration foaming reaction is initiated by stirring, then the mold is injected and solidified to form a porous body with a three-dimensional interconnected pore structure; Step 3, pre-sintering: The porous body is pre-sintered under a protective atmosphere, heated to 600℃ at a rate of 5℃ / min, and held for 1 h to completely remove organic matter; Step 4, high-temperature sintering: The pre-sintered body is sintered at 1350℃~1450℃ for 3 h to form a porous ceramic skeleton with a three-dimensional interconnected pore structure, and part of the CaO remains on the pore wall; Step 5, surface modification: A nano-MgO coating is loaded on the pore wall of the porous ceramic skeleton by immersion and calcination to form a carbon absorption active layer. Specifically, the sintered porous ceramic is immersed in a 0.5 mol / L Mg(NO3)2 solution, then calcined at 600℃ for 2 hours to decompose the magnesium nitrate into nano-MgO.

[0019] The porous ceramic material prepared by the above method has a three-dimensional interconnected pore structure, a pore size distribution of 10~200 μm, a porosity of 70%~85%, a compressive strength of ≥5 MPa, a CO2 adsorption efficiency of ≥80%, and a thermal conductivity of ≤0.15 W / (m·K). The present application has the advantages of: The present application uses a CaO / H2O foaming system, which is simple and low in cost, forms a three-dimensional interconnected pore structure, and is beneficial to gas diffusion and adsorption, solving the problems of high cost and complex process of traditional foaming methods and poor pore structure connectivity; The present application enhances the strength of the skeleton by combining SiC and Al2O3, and further improves the mechanical properties by converting part of the CaO into CaAl2O4, solving the problems of low strength and insufficient thermal stability of porous ceramics; The present application introduces a composite carbon absorption layer composed of MgO nano-coating and residual CaO to realize physical and chemical synergistic adsorption, with a CO2 adsorption efficiency of ≥80%, solving the problems of low adsorption capacity and difficult regeneration of existing carbon capture materials; The porous ceramic has heat insulation performance (thermal conductivity is less than or equal to 0.15 W / (m*K)), can be used in the field of building energy saving, and can be recycled and reused, and solves the problems of single material function and narrow application range.

[0020] Compared with the prior art, the technical effects of the present application are embodied in the following aspects: 1. Precise pore structure regulation, high adsorption and mass transfer efficiency: through the controllable foaming reaction of calcium oxide and water, a multi-stage pore structure mainly with three-dimensional connectivity is formed in situ, the pore size distribution is concentrated in 10-200 mu m, and the porosity is as high as 70%-85%. Such open channels greatly reduce the gas diffusion resistance, enabling CO2 in industrial tail gas to quickly penetrate into the material interior and fully contact with active sites, thereby significantly improving the capture rate and adsorption capacity.

[0021] 2. Mechanical strength and thermal stability are significantly enhanced: a composite ceramic framework is constructed with silicon carbide and alumina, and a CaAl2O4 phase is generated by the reaction of part of the calcium oxide and alumina during high-temperature sintering, which effectively bridges and strengthens the particles. This structure enables the material to maintain high porosity while achieving a compressive strength of more than 5 MPa, and can operate stably in an industrial flue gas environment of 200-400 DEG C for a long time, solving the problem of strength degradation of traditional porous materials due to high porosity.

[0022] 3. Composite carbon adsorption active layer realizes synergistic high-efficiency adsorption: the carbon adsorption active layer is composed of residual CaO and loaded nano-MgO. Nano-MgO provides a large number of surface adsorption sites, while CaO can participate in carbonation under certain conditions. The synergistic effect of the two realizes the organic combination of physical adsorption and chemical adsorption, making the CO2 adsorption efficiency of the material stable at more than 80% in the temperature range of 200-400 DEG C, and the relationship between adsorption performance and key parameters is quantified by formula, providing clear guidance for material design and application.

[0023] 4. Simple preparation process, low cost and environmentally friendly: using CaO and water as foaming agents, the process is simple and does not require complex equipment, and the foaming process does not produce harmful substances. The entire preparation process is easy to scale up, effectively overcoming the shortcomings of complex process, high cost or organic residue of traditional template method, gel injection molding, etc.

[0024] 5. One material, multiple uses, wide application and recyclable: in addition to being used as an efficient carbon capture module, the material's inherent porous ceramic structure also gives it excellent thermal insulation performance (thermal conductivity is less than or equal to 0.15 W / (m . K), which can be directly used as a building insulation material. In addition, the material after adsorption saturation can restore most of the adsorption performance through thermal regeneration, realizing the recycling of resources and expanding the application scenarios and economy.

[0025] For a further understanding of the features and technical content of the present application, reference should be made to the detailed description and accompanying drawings. It should be noted that the accompanying drawings are provided for illustrative purposes only and are not intended to limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 SEM image of the porous ceramic prepared by the method described in Example 1; Figure 2 SEM image of the porous ceramic prepared by the method described in Example 2; Figure 3 SEM image of the porous ceramic prepared by the method described in Example 3. DETAILED DESCRIPTION

[0027] The present application will be described in detail below with reference to specific examples. These examples are helpful for those skilled in the art to further understand the present application, but should not be regarded as limiting the present application. It should be noted that, for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made. These all fall within the scope of the present application. EXAMPLE

[0028] SiC powder 150 g, Al2O3 powder 100 g (mass ratio 1.5:1), CaO powder 50 g (16.7 wt% of the total mass of the powder), 10 g PVA binder was added, mixed uniformly in a ball mill, the mixing time was 30 min, and the mixture was obtained.

[0029] Step 2, foaming molding: Deionized water 18 g (molar ratio of CaO to H2O is 1:1) was added to the mixture, and the stirring was initiated for 5 min to initiate the CaO hydration foaming reaction, then it was injected into a cylindrical mold (diameter 50 mm, height 20 mm), and it was left to solidify for 2 h to form a porous body.

[0030] Step 3, pre-sintering: The porous body was placed in a tube furnace and heated to 600 ℃ at a rate of 5 ℃ / min under a nitrogen protective atmosphere, and held for 1 h to completely remove the organic matter.

[0031] Step 4, high-temperature sintering: The pre-sintered body was sintered at 1350 ℃ for 3 h, and the furnace was cooled to form a porous ceramic skeleton with a three-dimensional interconnected pore structure. According to the formula, the pore volume was about 1.2 cm 3 / g.

[0032] Step 5, surface modification: The sintered porous ceramic was immersed in a 0.5 mol / L Mg(NO3)2 solution for 10 min, then dried at 100 ℃ for 1 h, and then calcined at 600 ℃ for 2 h to decompose magnesium nitrate into a nano-MgO coating, forming a carbon-absorbing active layer. Example

[0033] Step 1, Mixing raw materials: Weigh 120 g of SiC powder, 100 g of Al2O3 powder (mass ratio 1.2:1), and 60 g of CaO powder (accounting for 21.4 wt% of the total powder mass). Add 12 g of PVA binder and mix them evenly in a ball mill for 30 min to obtain a mixture.

[0034] Step 2, Foaming and Molding: Add 13.5 g of deionized water (the molar ratio of CaO to H2O is 0.8:1) to the mixture, stir for 5 min to initiate the reaction, pour into a mold and let stand to solidify for 2 h to form a porous preform.

[0035] Step 3, Pre-sintering: The porous preform was placed in a tube furnace and heated to 600 °C at a rate of 5 °C / min under a nitrogen protective atmosphere, and held for 1 hour to completely remove organic matter.

[0036] Step 4, High-temperature sintering: The pre-sintered green body was sintered at 1450 °C for 3 h and then cooled in the furnace. Based on the formula, the pore volume was calculated to be approximately 0.9 cm³. 3 / g.

[0037] Step 5, Surface modification: The sintered porous ceramic was immersed in a 0.5 mol / L Mg(NO3)2 solution for 10 min, then dried at 100 ℃ for 1 h, and then calcined at 600 ℃ for 2 h to decompose magnesium nitrate into a nano-MgO coating, forming a carbon-absorbing active layer. Example

[0038] Step 1, Mixing raw materials: Weigh 135 g of SiC powder, 100 g of Al2O3 powder (mass ratio 1.35:1), and 55 g of CaO powder (accounting for 18.6 wt% of the total powder mass). Add 11 g of PVA binder and mix them evenly in a ball mill for 30 min to obtain the mixture.

[0039] Step 2, Foaming and Molding: The mixture was added with 16 g of deionized water (molar ratio of CaO to H2O was 0.9:1), and the reaction was initiated by stirring for 5 min. The mixture was poured into a mold and left to solidify for 2 h to form a porous body.

[0040] Step 3, pre-sintering: The porous body was placed in a tube furnace and heated to 600 ℃ at a rate of 5 ℃ / min under a nitrogen atmosphere, and kept at this temperature for 1 h to completely remove the organic matter.

[0041] Step 4, high-temperature sintering: The pre-sintered body was sintered at 1400 ℃ for 3 h and cooled in the furnace. According to the formula, the pore volume was about 1.0 cm 3 / g.

[0042] Step 5, surface modification: The sintered porous ceramic was immersed in a 0.5 mol / L Mg(NO3)2 solution for 10 min, and then dried at 100 ℃ for 1 h. Subsequently, the sample was calcined at 600 ℃ for 2 h to decompose the magnesium nitrate into a nano-MgO coating, forming an active carbon absorption layer.

[0043] The porous ceramic materials prepared in Examples 1-3 were tested for performance, and the results are shown in Table 1. Table 1

[0044] Table 1 shows that the porous ceramic material prepared by the present application has excellent three-dimensional interconnected pore structure, high adsorption capacity, good mechanical properties and thermal insulation performance, and is suitable for industrial tail gas carbon capture and building insulation fields.

[0045] The above describes the specific embodiments of the present application in detail. It should be noted that the present application is not limited to the above specific embodiments. Those skilled in the art can make various modifications or changes without departing from the scope of the protection defined by the claims, and these modifications or changes all belong to the technical solution of the present application.

Claims

1. A calcium oxide / water-foamed porous ceramic, characterized by, The porous ceramic is a three-dimensional interconnected pore structure skeleton formed by silicon carbide (SiC) and aluminum oxide (Al2O3) as a matrix, wherein the mass ratio of SiC to Al2O3 is (1.5-1.2):1; and a carbon adsorption active layer distributed on the pore wall of the skeleton; the carbon adsorption active layer is composed of residual calcium oxide (CaO) and loaded nano-magnesium oxide (MgO).

2. The porous ceramic of claim 1, wherein, The CO2 adsorption capacity thereof follows the formula: wherein, SBET is the specific surface area in m2 / g; P is the porosity in %; T is the adsorption temperature in K; k and a are material dependent constants (k = 0.12 ± 0.03, a = 0.005). 2 SBET is the specific surface area in m2 / g; P is the porosity in %; T is the adsorption temperature in K; k and a are material dependent constants (k = 0.12 ± 0.03, a = 0.005).

3. The porous ceramic of claim 1, wherein, The three-dimensional interconnected pore structure is formed through a foaming reaction of SiC powder, Al2O3 powder, CaO powder, PVA binder, and deionized water (H2O), wherein the molar ratio of CaO to H2O is (1~0.8):1, and the pore volume ( (unit cm³ / g) and CaO addition amount ( (unit: wt%) and sintering temperature ( (unit: °C) satisfies the following relationship: 。 4. The porous ceramic of any one of claims 1-3, wherein, The pore size distribution of the porous ceramic is 10-200 μm, the porosity is 70%-85%, and the compressive strength is ≥5 MPa.

5. The method of producing porous ceramics according to any one of claims 1 to 4, wherein The method comprises the following steps: Step 1, raw material mixing: SiC powder, Al2O3 powder and CaO powder are mixed in proportion, and a PVA binder is added to obtain a mixture; Step 2, foaming molding: deionized water is added to the mixture, and after stirring to initiate the CaO hydration foaming reaction, the mixture is poured into a mold and left to solidify, forming a porous body; Step 3, pre-sintering: the obtained porous body is pre-sintered in a protective atmosphere to remove organic matter; Step 4, high-temperature sintering: the pre-sintered body is sintered at 1350-1450℃ to form a porous ceramic skeleton with a three-dimensional interconnected pore structure, and part of the CaO remains on the pore wall; Step 5, surface modification: by dipping and calcining, a nano-MgO coating is loaded on the pore wall of the porous ceramic skeleton to form the carbon adsorption active layer.

6. The method of claim 5, wherein, In the high-temperature sintering step, some CaO reacts with Al2O3 to form CaAl2O4, and its conversion rate (η) is determined by the holding time (t, in hours) and the sintering temperature (t). The unit (°C) is jointly determined, and the calculation formula is as follows: 。 7. The method of claim 5, wherein, The surface modification step specifically comprises: after sintering, the porous ceramic is immersed in a 0.5 mol / L Mg(NO3)2 solution, and then taken out and calcined at 600℃ for 2 hours.

8. Use of a porous ceramic material according to any one of claims 1 to 4, characterized in that The porous ceramic is applied to the treatment of industrial flue gas at 200-400℃ as a carbon capture module.

9. Use of a porous ceramic material according to any one of claims 1 to 4, characterized in that The porous ceramic material is used as a building thermal insulation material.

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