Mesoporous silicon-based material prepared based on coal gasification slag and phase change material

Abstract

The application discloses a kind of mesoporous silicon-based materials and phase change materials based on coal gasification slag preparation, the mesoporous silicon-based material based on coal gasification slag preparation has spatial three-dimensional network structure, pore size is 5-30nm, specific surface area is 550-900m 2 / g, pore volume is 0.45-0.80cm 3 / g.The mesoporous silicon-based material of the application is obtained by modifying treatment with industrial solid waste coal gasification slag as raw material, which can be applied in industry, has large specific surface area and high structural strength, can be compounded with paraffin to obtain mesoporous silicon-based phase change composite material, the prepared mesoporous silicon-based phase change composite material has high structural strength, light weight and high thermal conductivity, and has excellent strength and thermal conductivity when applied in cement-based material, which not only solves the problem of easy outflow of phase change material paraffin in heat storage system, but also improves the problem of low heat storage cycle efficiency of phase change material, so it has large-scale application prospect.

Description

Technical Field

[0001] This invention belongs to the field of materials technology that undergo physical state changes during use, specifically relating to a mesoporous silicon-based material and phase change material prepared from coal gasification slag. Background Technology

[0002] Thermal energy is one of the most common forms of energy in people's production and daily life. However, the use of thermal energy is time-sensitive, which leads to a large amount of thermal energy being directly emitted without being effectively utilized, resulting in energy waste.

[0003] Thermal energy storage technology not only solves the problem of time-sensitive thermal energy supply but also reduces the operating costs of energy systems. Phase change thermal energy storage, one such technology, utilizes the property of phase change materials (PCAs) to absorb or release heat during a phase transition while maintaining a constant temperature. The selection criteria for PCAs are high latent heat, minimal or no supercooling, non-toxicity, low cost, abundant availability, and stable properties. Paraffin-based PCAs possess these properties, with a latent heat of 150-230 J / g. Being a mixture of various alkanes, its phase transition temperature and latent heat are related to the carbon chain length and structure. Therefore, by altering the carbon chain length and structure of paraffin, a PCA with the desired phase transition temperature can be obtained, greatly expanding the applicability of this type of material. Despite these advantages, paraffin, being a solid-liquid PCA material, melts into a liquid during the phase transition, threatening the safety of the thermal storage system and reducing its recycling efficiency. Therefore, modification is necessary to obtain solid-solid PCA materials.

[0004] my country consumes a huge amount of coal every year, generating a large amount of solid waste from coal gasification slag during processing and conversion. However, landfilling is the primary method of disposal, and the harmful substances in this slag cause serious pollution to the atmosphere, soil, and groundwater. Therefore, it is urgent to find ways to utilize coal gasification slag with high added value.

[0005] This invention utilizes solid waste material, coal gasification slag, to prepare mesoporous silica-based materials. These materials are then used to encapsulate paraffin wax, restricting the flow of the melted wax. This not only enhances the safety of the thermal storage system but also improves its recycling rate. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the shortcomings of the existing technology by providing a mesoporous silicon-based material and phase change material prepared from coal gasification slag. The mesoporous silicon-based material has a high specific surface area and large pore volume, and its spatial network structure has high strength. After being coated with paraffin, it is made into a phase change material and has the advantages of low density, high strength and good thermal conductivity when applied in cement-based materials such as thermal insulation mortar or thermal insulation board.

[0007] This invention provides a mesoporous silicon-based material prepared from coal gasification slag, which has a three-dimensional network structure with a pore size of 5-30 nm and a specific surface area of ​​550-900 m². 2 / g, pore volume is 0.45-0.80cm³ 3 / g.

[0008] The present invention also provides a method for preparing the above-mentioned mesoporous silica-based material based on coal gasification slag: the coal gasification slag is dried and ground, activated at high temperature and then acid-leached to remove impurities to obtain coal gasification acid-leached slag, the obtained coal gasification acid-leached slag is mixed with NaOH and Na2SiO3, reacted at high temperature and water-leached to obtain an alkali-fused product, the obtained alkali-fused product is modified with a cationic surfactant to obtain a coal gasification slag reinforcing precursor, the obtained coal gasification slag reinforcing precursor is subjected to a polycondensation reaction with silane to obtain a coal gasification slag wet gel, the obtained coal gasification slag wet gel is then subjected to surface reinforcement treatment, aging, solvent replacement and surface modification, and finally cleaned and dried to obtain a mesoporous silica-based material.

[0009] According to the above scheme, the SiO2 content in the coal gasification slag is not less than 40%, and the loss on ignition is not more than 15%.

[0010] According to the above scheme, the cationic surfactant is hexadecyltrimethylammonium bromide.

[0011] According to the above scheme, the silane is methyltrimethoxysilane and methyltriethoxysilane.

[0012] The specific steps of the above-mentioned method for preparing mesoporous silica-based materials based on coal gasification slag are as follows:

[0013] Step 1: Dry the coal gasification slag to constant weight, then grind it using a planetary ball mill to ensure a specific surface area of ​​not less than 350 m². 2 / g, then the finely ground coal gasification slag is activated at high temperature and ground to obtain activated coal gasification slag. The obtained activated coal gasification slag is mixed with a mixture of hydrochloric acid and acetic acid for acid leaching reaction. After the reaction is completed, the solid and liquid are separated, and the obtained filter residue is washed and dried to obtain coal gasification acid leaching residue.

[0014] Step 2: Mix the coal gasification acid leaching residue obtained in Step 1 with NaOH and Na2SiO3, heat and react. After the reaction is completed, remove it and place it in cold water for rapid cooling. Separate the solid and liquid to obtain a precipitate. Wash and dry the precipitate to obtain the alkali fusion product.

[0015] Step 3: Dissolve the alkali fusion product obtained in Step 2 in water to obtain an alkali fusion solution. Add a cationic surfactant and an ammonia solution (0.1-0.5 mol / L). Stir for 0.5-3 h. Then, add acetic acid solution (0.5-1 mol / L) dropwise to the resulting mixed solution to adjust the pH value of the system to 8-12. Continue stirring for 8-24 h to obtain the coal gasification slag enhanced precursor.

[0016] Step 4: Mix the enhanced precursor of coal gasification slag obtained in Step 3 with a silane mixed solution, add a catalyst, and finally add an ammonia solution (0.1-0.5 mol / L) to adjust the pH of the system to 10-12, and carry out a gelation reaction to obtain wet gel of coal gasification slag.

[0017] Step 5: Add sodium dodecylbenzenesulfonate to the wet gel obtained in Step 4 to strengthen the wet gel and obtain a reinforced wet gel. Place the obtained reinforced wet gel in anhydrous ethanol for aging treatment. After the aging treatment, obtain an aged gel. Then, replace the aqueous phase solution in the pores of the aged gel with anhydrous ethanol multiple times. Then, place the replaced gel in a silane solution for surface modification. After the modification is completed, clean it with n-hexane and dry it under normal pressure to obtain a mesoporous silica-based material.

[0018] According to the above scheme, the conditions for the high-temperature activation process in step one are: heating at 600-950℃ for 0.5-2 hours. High-temperature activation decomposes the residual carbon and other salt components in the coal gasification slag, leaving behind high-temperature activated silicon dioxide.

[0019] According to the above scheme, in step one, the concentration of hydrochloric acid in the mixed acid of hydrochloric acid and acetic acid is 0.1-0.5 mol / L, and the concentration of acetic acid is 0.5-1 mol / L. The solid-liquid ratio of the coal gasification slag to the mixed acid of hydrochloric acid and acetic acid is 0.14-0.30 g / L. The acid leaching reaction conditions are: reaction at 80-120℃ for 1-4 hours. The purpose of acid leaching is twofold: first, to remove impurities by dissolving oxides such as iron, aluminum, and magnesium in the coal gasification slag, leaving silica residue; second, hydrochloric acid and acetic acid have a certain activating effect. Hydrochloric acid is beneficial for activating calcium aluminum silicates and hematite in the coal gasification slag, and acetic acid can react with the Ca phase in the coal gasification slag to generate hydrated aluminum hydroxide acetate ((CH3COO)2Al(OH)) and calcium carbonate (CaAl2(CO3)2(OH)4·3H2O).

[0020] According to the above scheme, the mass ratio of the coal gasification acid leaching residue to NaOH and Na2SiO3 in step two is 1:1-2:0.5-1.5. Preferably, it is 1:1-1.5:0.5-1.0. The main component of the coal gasification acid leaching residue is SiO2. NaOH can react with SiO2 to produce active sodium silicate, while the Na2SiO3 added to the system can provide a certain alkaline environment and soluble Si during the reaction. Na2SiO3 hydrolyzes to generate silicic acid colloid Si(OH)4 and produces a large amount of OH. - Ions, silicic acid colloid Si(OH)4 has adsorption properties similar to [OSi(OH)3] and [OSi(OH)3] generated from coal gasification slag in an alkaline environment. 2- Hydrated monomers and dimers, among other network-like gels, adsorb to each other, forming a dense, interconnected spatial network structure that optimizes the pore structure and improves strength.

[0021] According to the above scheme, the heating reaction conditions for step two are: reacting at 550-800℃ for 1-4 hours.

[0022] According to the above scheme, the concentration of the alkali fusion solution in step three is 20-60 wt%.

[0023] According to the above scheme, the mass ratio of the alkali fusion product in step three to the cationic surfactant and the ammonia in the ammonia solution is 1:0.1-0.8:2-8. Preferably, it is 1:0.1-0.4:4-7.

[0024] According to the above scheme, the silane mixed solution is obtained by mixing methyltrimethoxysilane, methyltriethoxysilane, anhydrous ethanol, and isopropanol in a mass ratio of 1:2:50:30.

[0025] According to the above scheme, the catalyst is obtained by mixing ammonia fluoride and dimethylformamide at a mass ratio of 1:5.

[0026] According to the above scheme, the mass ratio of the coal gasification slag enhanced precursor, silane mixed solution and catalyst in step four is 1-5:5-10:0.1-0.5. Preferably, it is 1-3:5-8:0.1-0.3.

[0027] According to the above scheme, the gelation reaction conditions for step four are: reaction at 40-75℃ for 4-12 hours.

[0028] According to the above scheme, the mass ratio of the coal gasification slag wet gel to sodium dodecylbenzenesulfonate in step five is 1:0.1-0.5. Preferably, it is 1:0.1-0.3.

[0029] According to the above scheme, the enhancement treatment time in step five is 8-16 hours, preferably 8-12 hours. This enhancement treatment can regulate the chemical composition of the gel and improve the uniformity and strength of the gel precursor skeleton structure.

[0030] According to the above scheme, the aging treatment temperature in step five is 45-55℃, and the time is 8-20 hours. Preferably, it is 12-20 hours.

[0031] According to the above scheme, the silane solution in step five is obtained by mixing trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, and polyethylene glycol in a volume ratio of 1-5:1-8:6-12:2-6. Preferably, the ratio is 1-3:1-5:6-10:2-5.

[0032] According to the above scheme, the mass ratio of the replaced gel to the silane solution in step five is 1:2-4.

[0033] According to the above scheme, the surface modification time in step five is 12-48 hours, preferably 12-36 hours.

[0034] The present invention also includes a mesoporous silicon-based phase change composite material prepared according to the above-mentioned mesoporous silicon-based material.

[0035] The preparation method of the above-mentioned mesoporous silica-based phase change composite material is as follows: the mesoporous silica-based material and paraffin are mixed at a mass ratio of 1:0.2-0.8, and the paraffin is dispersed in the internal pores of the mesoporous silica-based material by ultrasonic vibration at 70-120℃ (preferably 85-110℃) to obtain the mesoporous silica-based phase change composite material.

[0036] Preferably, the mass ratio of the mesoporous silica-based material to paraffin is 1:0.3-0.6.

[0037] According to the above scheme, the ultrasonic oscillation time is 0.2-2h (preferably 0.5-2h).

[0038] The present invention also includes a thermal insulation board prepared based on the above-mentioned mesoporous silicon-based phase change composite material.

[0039] The specific preparation method of the above-mentioned insulation board is as follows: First, 40 parts of PO 42.5 cement, 8 parts of pulp fiber, 30 parts of 0.6-2.26mm ceramic sand, 20 parts of water, and 2 parts of the above-prepared mesoporous silica-based phase change composite material are mixed evenly using a mortar mixer. Then, the mixture is poured into a 150mm×150mm mold and then pressurized to 5MPa using a press at a force of 0.1MPa / s and held for 3 minutes to obtain a 150mm×150mm×5mm insulation board blank. Finally, the insulation board blank is cured for 7-14 days to obtain the insulation board.

[0040] Although coal gasification slag contains a certain amount of aluminosilicate materials, the high impurity content makes it difficult to effectively utilize the silicon element to prepare mesoporous silicon with a certain structural strength to meet practical application requirements. This invention first removes impurities through calcination and acid leaching, then reacts with alkali followed by calcination and rapid cooling in cold water to obtain an alkali-fused product. Subsequently, a wet gel is prepared using hexadecyltrimethylammonium bromide and sodium dodecylbenzenesulfonate as surface reinforcing agents. This two-stage reinforcement allows sol particles and small clusters to attach and grow in the solution, forming clusters that expand the gel network and further promote cross-linking of the gel's condensation reaction. Through cross-linking, the gel can further... To further enhance or reinforce the network structure, a stable, high-porosity, and low-density wet gel is ultimately obtained. The gel surface is then modified with a silane solution obtained from a mixture of trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, and polyethylene glycol. This alkylation of the silanol groups on the gel surface allows for the grafting of hydrophobic groups onto the pore surface, reducing capillary pressure and preventing excessive shrinkage and structural collapse during drying. This enhances the strength of the mesoporous silica-based material and helps maintain its spatial network structure. The resulting mesoporous silica-based material exhibits a large specific surface area and pore volume, as well as high spatial structural strength. Phase change materials prepared by coating paraffin with this mesoporous silica-based material can be applied to cement-based materials, such as insulation boards, exhibiting excellent strength and thermal conductivity, while also being lightweight, low-density, and highly safe.

[0041] The beneficial effects of this invention are as follows: 1. This invention uses industrial solid waste coal gasification slag as raw material and obtains mesoporous silica-based materials that can be applied in industry through modification treatment. It has a large specific surface area and high structural strength. It can be combined with paraffin to obtain mesoporous silica-based phase change composite materials. The prepared mesoporous silica-based phase change composite materials have high structural strength, light weight and high thermal conductivity. When applied to cement-based materials, it has both excellent strength and thermal conductivity. It can not only solve the problem of easy paraffin leakage in phase change materials in thermal storage systems, but also improve the problem of low thermal storage cycle efficiency of phase change materials. Therefore, it has the prospect of large-scale application.

[0042] 2. The preparation method provided by this invention has relatively simple steps, low requirements for process conditions, good repeatability, and less environmental pollution. It can improve the utilization rate and added value of solid waste materials and has high environmental and economic benefits. Attached Figure Description

[0043] Figure 1 This is a SEM image of the mesoporous silicon-based material prepared in Example 3 of the present invention. Detailed Implementation

[0044] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of this application will be clearly and completely described below.

[0045] There are no particular restrictions on the specific dispersion and mixing methods used in this application, as long as the purpose of dispersion and mixing is achieved.

[0046] The raw materials used in the examples and comparative examples are described below: the SiO2 content in the coal gasification slag used was 43.9%, and the loss on ignition was 12.2%. The hexadecyltrimethylammonium bromide, methyltrimethoxysilane, methyltriethoxysilane, anhydrous ethanol, and isopropanol used were purchased from Aladdin Reagent Company; ammonia fluoride, dimethylformamide, sodium dodecylbenzenesulfonate, trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, polyethylene glycol (PEG-400), and anhydrous ethanol were purchased from Sinopharm Group Reagent Company; hydrochloric acid, acetic acid, ammonia, sodium silicate, sodium hydroxide, and other raw materials were all commercially available raw materials unless otherwise specified.

[0047] Example 1

[0048] A method for preparing mesoporous silica-based materials based on coal gasification slag includes the following steps:

[0049] Step 1: Dry the coal gasification slag in an oven at 105℃ until constant weight, then ball mill the dried coal gasification slag using a planetary ball mill for 0.5 hours. The specific surface area of ​​the ball-milled product is 350 m². 2 / g, then the finely ground coal gasification slag is placed in a muffle furnace and calcined at 950℃ for 0.5h. Then, it is ground with a glass mortar and pestle until it all passes through a 75-micron square hole sieve to obtain activated coal gasification slag. 100g of activated coal gasification slag is weighed and placed in a 500mL three-necked flask. Hydrochloric acid (0.5mol / L) and acetic acid (1mol / L) are mixed at a volume ratio of 1:1 to form a mixed acid. Then, the mixed acid is added to the three-necked flask at a solid-liquid ratio of 0.2g / L. The mixture is stirred for 3h under oil bath heating at 95℃ and a stirring rate of 500rpm. After the reaction is completed, the solid and liquid are separated by suction filtration to obtain acid leaching solution and acid leaching residue. The acid leaching residue is washed with a large amount of deionized water until the washing filtrate does not show white precipitate or turbidity when titrated with AgNO3 solution. The washed acid leaching residue is placed in an oven at 105℃ and dried for 24h to obtain coal gasification acid leaching residue.

[0050] Step 2: Mix the coal gasification acid leaching residue obtained in Step 1 with NaOH and Na2SiO3 at a mass ratio of 1:1.2:1.0, heat in a muffle furnace at 550℃ for 1 hour, remove and cool in cold water, and separate the solid and liquid by vacuum filtration. Wash the precipitate with distilled water 10 times and then place it in a vacuum drying oven at room temperature for 48 hours to obtain the alkali fusion product.

[0051] Step 3: Dissolve the alkali fusion product obtained in Step 2 in water to obtain an alkali fusion solution with a concentration of 40 wt%, and mix it with hexadecyltrimethylammonium bromide and ammonia water in an ammonia solution (0.2 mol / L) at a mass ratio of 1:0.2:5. After stirring for 1 h, add acetic acid solution (0.6 mol / L) dropwise to the system to adjust the pH value of the system to 10, and continue stirring for 12 h to obtain the coal gasification slag enhanced precursor.

[0052] Step 4: Mix the enhanced precursor of coal gasification slag obtained in Step 3 with a silane mixed solution (methyltrimethoxysilane, methyltriethoxysilane, anhydrous ethanol, and isopropanol mixed in a mass ratio of 1:2:50:30), then add the catalysts ammonium fluoride and dimethylformamide (ammonium fluoride to dimethylformamide mass ratio of 1:5), and finally add an ammonia solution (0.2 mol / L) to adjust the pH of the system to 11. The mass ratio of the above precursor:silane mixed solution:catalyst is 1.5:6:0.1. Adjust the temperature to 60℃ and react for 8 hours to obtain coal gasification slag wet gel.

[0053] Step 5: Add sodium dodecylbenzenesulfonate to the wet gel obtained in Step 4 to enhance the wet gel. The mass ratio of wet gel to sodium dodecylbenzenesulfonate is 1:0.15, and the reaction time is 8 hours to obtain an enhanced wet gel. Immerse the enhanced wet gel in anhydrous ethanol for aging treatment at 50°C for 16 hours. After aging treatment, an aged gel is obtained. Then, the aqueous phase solution in the pores of the aged gel is replaced multiple times with anhydrous ethanol. The replaced gel is then placed in a silane solution for solvent replacement and surface modification to alkylate the silanol groups on the gel surface. The silane solution is obtained by mixing trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, and polyethylene glycol in a volume ratio of 1:2:6:3. The mass ratio of the replaced gel to the silane solution is 1:3. After modification for 12 hours, wash with n-hexane and finally dry under normal pressure to obtain a mesoporous silica-based material.

[0054] The mesoporous silica-based phase change composite material prepared in this embodiment is prepared by the following method: the mesoporous silica-based material and paraffin are mixed at a mass ratio of 1:0.3. At 90°C, the paraffin is dispersed in the pores of the mesoporous silica-based material by ultrasonic vibration for 1 hour to obtain the mesoporous silica-based phase change composite material.

[0055] Example 2

[0056] A method for preparing mesoporous silica-based materials based on coal gasification slag includes the following steps:

[0057] Step 1: Dry the coal gasification slag in an oven at 105℃ until constant weight. Then, ball mill the dried coal gasification slag using a planetary ball mill for 0.5 hours. The specific surface area of ​​the ball-milled product should be no less than 350 m². 2 / g, then the finely ground coal gasification slag is placed in a muffle furnace and calcined at 950℃ for 0.5h. Then, it is ground with a glass mortar and pestle until it all passes through a 75-micron square hole sieve to obtain activated coal gasification slag. 100g of activated coal gasification slag is weighed and placed in a 500mL three-necked flask. Hydrochloric acid (0.5mol / L) and acetic acid (1mol / L) are mixed at a volume ratio of 1:1 to form a mixed acid. Then, the mixed acid is added to the three-necked flask at a solid-liquid ratio of 0.2g / L. The mixture is stirred for 3h under oil bath heating at 95℃ and a stirring rate of 500rpm. After the reaction is completed, the solid and liquid are separated by suction filtration to obtain acid leaching solution and acid leaching residue. The acid leaching residue is washed with a large amount of deionized water until the washing filtrate does not show white precipitate or turbidity when titrated with AgNO3 solution. The washed acid leaching residue is placed in an oven at 105℃ and dried for 24h to obtain coal gasification acid leaching residue.

[0058] Step 2: Mix the coal gasification acid leaching residue obtained in Step 1 with NaOH and Na2SiO3 at a mass ratio of 1:1.2:1.0, heat in a muffle furnace at 550℃ for 1 hour, remove and cool in cold water, and separate the solid and liquid by vacuum filtration. Wash the precipitate with distilled water 10 times and then place it in a vacuum drying oven at room temperature for 48 hours to obtain the alkali fusion product.

[0059] Step 3: Dissolve the alkali fusion product obtained in Step 2 in water to obtain an alkali fusion solution with a concentration of 40 wt%, and mix it with hexadecyltrimethylammonium bromide and ammonia water in an ammonia solution (0.2 mol / L) at a mass ratio of 1:0.3:6. After stirring for 1 h, add acetic acid solution (0.6 mol / L) dropwise to the system to adjust the pH value of the system to 10, and continue stirring for 12 h to obtain the coal gasification slag enhanced precursor.

[0060] Step 4: Mix the enhanced precursor of coal gasification slag obtained in Step 3 with a silane mixed solution (methyltrimethoxysilane, methyltriethoxysilane, anhydrous ethanol, and isopropanol mixed in a mass ratio of 1:2:50:30), then add the catalysts ammonium fluoride and dimethylformamide (ammonium fluoride to dimethylformamide mass ratio of 1:5), and finally add an ammonia solution (0.2 mol / L) to adjust the pH of the system to 11. The mass ratio of the above precursor:silane mixed solution:catalyst is 2:7:0.2. Adjust the temperature to 60℃ and react for 10 h to obtain coal gasification slag wet gel.

[0061] Step 5: Add sodium dodecylbenzenesulfonate to the wet gel obtained in Step 4 to enhance the wet gel. The mass ratio of the wet gel to sodium dodecylbenzenesulfonate is 1:0.2, and the reaction time is 10 h to obtain the enhanced wet gel. Immerse the enhanced wet gel in anhydrous ethanol for aging treatment at 50°C for 20 h. After the aging treatment, the aged gel is obtained. Then, the aqueous phase solution in the pores of the aged gel is replaced multiple times with anhydrous ethanol. The replaced gel is then placed in a silane solution for solvent replacement and surface modification to alkylate the silanol groups on the gel surface. The silane solution is obtained by mixing trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, and polyethylene glycol in a volume ratio of 2:3:7:4. The mass ratio of the replaced gel to the silane solution is 1:3. After modification for 16 h, wash with n-hexane and finally dry under normal pressure to obtain the mesoporous silica-based material.

[0062] The mesoporous silica-based phase change composite material prepared in this embodiment is prepared by the following method: the mesoporous silica-based material and paraffin are mixed at a mass ratio of 1:0.3. At 90°C, the paraffin is dispersed in the pores of the mesoporous silica-based material by ultrasonic vibration for 1 hour to obtain the mesoporous silica-based phase change composite material.

[0063] Example 3

[0064] A method for preparing mesoporous silica-based materials based on coal gasification slag includes the following steps:

[0065] Step 1: Dry the coal gasification slag in an oven at 105℃ until constant weight. Then, ball mill the dried coal gasification slag using a planetary ball mill for 0.5 hours. The specific surface area of ​​the ball-milled product should be no less than 350 m². 2 / g, then the finely ground coal gasification slag is placed in a muffle furnace and calcined at 950℃ for 0.5h. Then, it is ground with a glass mortar and pestle until it all passes through a 75-micron square hole sieve to obtain activated coal gasification slag. 100g of activated coal gasification slag is weighed and placed in a 500mL three-necked flask. Hydrochloric acid (0.5mol / L) and acetic acid (1mol / L) are mixed at a volume ratio of 1:1 to form a mixed acid. Then, the mixed acid is added to the three-necked flask at a solid-liquid ratio of 0.2g / L. The mixture is stirred for 3h under oil bath heating at 95℃ and a stirring rate of 500rpm. After the reaction is completed, the solid and liquid are separated by suction filtration to obtain acid leaching solution and acid leaching residue. The acid leaching residue is washed with a large amount of deionized water until the washing filtrate does not show white precipitate or turbidity when titrated with AgNO3 solution. The washed acid leaching residue is placed in an oven at 105℃ and dried for 24h to obtain coal gasification acid leaching residue.

[0066] Step 2: Mix the coal gasification acid leaching residue obtained in Step 1 with NaOH and Na2SiO3 at a mass ratio of 1:1.2:1.0, heat in a muffle furnace at 550℃ for 1 hour, remove and cool in cold water, and separate the solid and liquid by vacuum filtration. Wash the precipitate with distilled water 10 times and then place it in a vacuum drying oven at room temperature for 48 hours to obtain the alkali fusion product.

[0067] Step 3: Dissolve the alkali fusion product obtained in Step 2 in water to obtain an alkali fusion solution with a concentration of 40 wt%, and mix it with hexadecyltrimethylammonium bromide and ammonia water in an ammonia solution (0.2 mol / L) at a mass ratio of 1:0.4:7. After stirring for 1 h, add acetic acid solution (0.6 mol / L) dropwise to the system to adjust the pH value of the system to 10, and continue stirring for 12 h to obtain the coal gasification slag enhanced precursor.

[0068] Step 4: Mix the enhanced precursor of coal gasification slag obtained in Step 3 with a silane mixed solution (methyltrimethoxysilane, methyltriethoxysilane, anhydrous ethanol, and isopropanol mixed in a mass ratio of 1:2:50:30), then add the catalysts ammonium fluoride and dimethylformamide (ammonium fluoride to dimethylformamide in a mass ratio of 1:5), and finally add an ammonia solution (0.2 mol / L) to adjust the pH of the system to 11. The mass ratio of the above precursor:silane mixed solution:catalyst is 3:8:0.3. Adjust the temperature to 60℃ and react for 10 h to obtain coal gasification slag wet gel.

[0069] Step 5: Add sodium dodecylbenzenesulfonate to the wet gel obtained in Step 4 to enhance the wet gel. The mass ratio of the wet gel to sodium dodecylbenzenesulfonate is 1:0.3, and the reaction time is 10 h to obtain the enhanced wet gel. Immerse the enhanced wet gel in anhydrous ethanol for aging treatment at 50°C for 20 h. After the aging treatment, the aged gel is obtained. Then, the aqueous phase solution in the pores of the aged gel is replaced multiple times with anhydrous ethanol. The replaced gel is then placed in a silane solution for solvent replacement and surface modification to alkylate the silanol groups on the gel surface. The silane solution is obtained by mixing trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, and polyethylene glycol in a volume ratio of 3:4:8:3. The mass ratio of the replaced gel to the silane solution is 1:3. After 20 h of modification, wash with n-hexane and finally dry under normal pressure to obtain the mesoporous silica-based material.

[0070] Figure 1 The image shows a SEM image of the mesoporous silicon-based material prepared in this embodiment. As can be seen from the image, the mesoporous silicon-based material has a three-dimensional network structure with a pore size of 10-30 nm.

[0071] The mesoporous silica-based phase change composite material prepared in this embodiment is prepared by the following method: the mesoporous silica-based material and paraffin are mixed at a mass ratio of 1:0.4. At 95°C, the paraffin is dispersed in the pores of the mesoporous silica-based material by ultrasonic vibration for 1.5 hours to obtain the mesoporous silica-based phase change composite material.

[0072] Example 4

[0073] A method for preparing mesoporous silica-based materials based on coal gasification slag includes the following steps:

[0074] Step 1: Dry the coal gasification slag in an oven at 105℃ until constant weight. Then, ball mill the dried coal gasification slag using a planetary ball mill for 0.5 hours. The specific surface area of ​​the ball-milled product should be no less than 350 m². 2 / g, then the finely ground coal gasification slag is placed in a muffle furnace and calcined at 950℃ for 0.5h. Then, it is ground with a glass mortar and pestle until it all passes through a 75-micron square hole sieve to obtain activated coal gasification slag. 100g of activated coal gasification slag is weighed and placed in a 500mL three-necked flask. Hydrochloric acid (0.5mol / L) and acetic acid (1mol / L) are mixed at a volume ratio of 1:1 to form a mixed acid. Then, the mixed acid is added to the three-necked flask at a solid-liquid ratio of 0.2g / L. The mixture is stirred for 3h under oil bath heating at 95℃ and a stirring rate of 500rpm. After the reaction is completed, the solid and liquid are separated by suction filtration to obtain acid leaching solution and acid leaching residue. The acid leaching residue is washed with a large amount of deionized water until the washing filtrate does not show white precipitate or turbidity when titrated with AgNO3 solution. The washed acid leaching residue is placed in an oven at 105℃ and dried for 24h to obtain coal gasification acid leaching residue.

[0075] Step 2: Mix the coal gasification acid leaching residue obtained in Step 1 with NaOH and Na2SiO3 at a mass ratio of 1:1.2:1.0, heat in a muffle furnace at 550℃ for 1 hour, remove and cool in cold water, and separate the solid and liquid by vacuum filtration. Wash the precipitate with distilled water 10 times and then place it in a vacuum drying oven at room temperature for 48 hours to obtain the alkali fusion product.

[0076] Step 3: Dissolve the alkali fusion product obtained in Step 2 in water to obtain an alkali fusion solution with a concentration of 40 wt%, and mix it with hexadecyltrimethylammonium bromide and ammonia water in an ammonia solution (0.2 mol / L) at a mass ratio of 1:0.4:7. After stirring for 1 h, add acetic acid solution (0.6 mol / L) dropwise to the system to adjust the pH value of the system to 10, and continue stirring for 12 h to obtain the coal gasification slag enhanced precursor.

[0077] Step 4: Mix the enhanced precursor of coal gasification slag obtained in Step 3 with a silane mixed solution (methyltrimethoxysilane, methyltriethoxysilane, anhydrous ethanol, and isopropanol mixed in a mass ratio of 1:2:50:30), then add the catalysts ammonium fluoride and dimethylformamide (ammonium fluoride to dimethylformamide in a mass ratio of 1:5), and finally add an ammonia solution (0.2 mol / L) to adjust the pH of the system to 11. The mass ratio of the above precursor:silane mixed solution:catalyst is 3:8:0.3. Adjust the temperature to 60℃ and react for 12 h to obtain a wet gel of coal gasification slag.

[0078] Step 5: Add sodium dodecylbenzenesulfonate to the wet gel obtained in Step 4 to enhance the wet gel. The mass ratio of the wet gel to sodium dodecylbenzenesulfonate is 1:0.3, and the reaction time is 12h to obtain the enhanced wet gel. Immerse the enhanced wet gel in anhydrous ethanol for aging treatment at 50℃ for 20h. After the aging treatment, the aged gel is obtained. Then, the aqueous phase solution in the pores of the aged gel is replaced multiple times with anhydrous ethanol. The replaced gel is then placed in a silane solution for solvent replacement and surface modification to alkylate the silanol groups on the gel surface. The silane solution is obtained by mixing trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, and polyethylene glycol in a volume ratio of 3:5:9:4. The mass ratio of the replaced gel to the silane solution is 1:3. After 24h of modification, wash with n-hexane and finally dry under normal pressure to obtain the mesoporous silica-based material.

[0079] The mesoporous silica-based phase change composite material prepared in this embodiment is prepared by the following method: the mesoporous silica-based material and paraffin are mixed at a mass ratio of 1:0.5. At 105°C, the paraffin is dispersed in the pores of the mesoporous silica-based material by ultrasonic vibration for 1 hour to obtain the mesoporous silica-based phase change composite material.

[0080] Comparative Example 1

[0081] In Comparative Example 1, except that no hexadecyltrimethylammonium bromide was added for enhancement treatment in step three, the other methods were the same as in Example 1.

[0082] Comparative Example 2

[0083] In Comparative Example 2, except that sodium dodecylbenzenesulfonate was not added for enhancement treatment in step four, the other methods were the same as in Example 1.

[0084] Comparative Example 3

[0085] In Comparative Example 3, except that in step four, a mixed solution of trimethylchlorosilane, hexamethyldisiloxane, diethanol monoisopropanolamine, and polyethylene glycol was not added for solvent replacement and surface modification, the other methods were the same as in Example 1.

[0086] The aforementioned phase change materials were made into mortar lightweight insulation boards and mortar test blocks, and their density, strength, and thermal conductivity were tested.

[0087] Preparation method of mortar lightweight insulation board: First, mix 40 parts of PO 42.5 cement, 8 parts of pulp fiber, 30 parts of 0.6-2.26mm ceramic sand, 20 parts of water, and 2 parts of the above-prepared mesoporous silica-based phase change composite material evenly using a mortar mixer. Then, pour the mixture into a 150mm×150mm mold and pressurize it to 5MPa using a press at a force of 0.1MPa / s, holding the pressure for 3 minutes to obtain a 150mm×150mm×5mm insulation board blank. Finally, cure the insulation board blank for 7 days to obtain the mesoporous silica-based phase change composite material insulation board.

[0088] Mortar specimen preparation method: First, mix 40 parts of PO 42.5 cement, 8 parts of pulp fiber, 30 parts of 0.6-2.26mm ceramic sand, 20 parts of water, and 2 parts of the above-prepared mesoporous silica-based phase change composite material evenly using a mortar mixer. Then, use a cement mortar vibrating table to form mortar specimens of 160 mm × 40 mm × 40 mm. After demolding, standard cure for 28 days.

[0089] The test results are shown in Table 1 below: Alkali fusion

[0090] Table 1

[0091]

[0092] The test results of Examples 1-4 and Comparative Examples 1-3 show that the mesoporous silica-based materials prepared by reinforcing the wet gel with hexadecyltrimethylammonium bromide or sodium dodecylbenzenesulfonate, and by using a mixed solution of trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, and polyethylene glycol as solvent replacement and surface modification treatment, have a larger specific surface area and pore volume. When applied to lightweight thermal insulation mortar and insulation board, the mortar has higher flexural and compressive strength and a higher thermal conductivity, indicating that the mesoporous silica-based materials prepared in Examples 1-4 of this invention have a certain structural strength.

[0093] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing mesoporous silica-based materials based on coal gasification slag, characterized in that, The specific steps are as follows: Step 1: Dry the coal gasification slag to constant weight, then grind it using a planetary ball mill to ensure a specific surface area of ​​not less than 350 m². 2 / g, and then the finely ground coal gasification slag is activated at high temperature and ground to obtain activated coal gasification slag. The high temperature activation process conditions are: heating at 600-950℃ for 0.5-2h, mixing the obtained activated coal gasification slag with a mixture of hydrochloric acid and acetic acid for acid leaching reaction, and separating solid and liquid after the reaction. The obtained filter residue is washed and dried to obtain coal gasification acid leaching residue. Step 2: Mix the coal gasification acid leaching residue obtained in Step 1 with NaOH and Na2SiO3, heat and react. After the reaction is completed, remove it and place it in cold water for rapid cooling. Separate the solid and liquid to obtain a precipitate. Wash and dry the precipitate to obtain the alkali fusion product. Step 3: Dissolve the alkaline fusion product obtained in Step 2 in water to obtain an alkaline fusion solution, add a cationic surfactant and an ammonia solution, wherein the cationic surfactant is hexadecyltrimethylammonium bromide, stir for 0.5-3 hours, add acetic acid solution dropwise to the obtained mixed solution to adjust the pH value of the system to 8-12, and continue stirring for 8-24 hours to obtain a coal gasification slag enhanced precursor; Step 4: Mix the enhanced precursor of coal gasification slag obtained in Step 3 with a silane mixed solution. The silane mixed solution is obtained by mixing methyltrimethoxysilane, methyltriethoxysilane, anhydrous ethanol and isopropanol in a mass ratio of 1:2:50:

30. Then add a catalyst and finally add an ammonia solution to adjust the pH of the system to 10-12. Perform a gelation reaction to obtain wet gel of coal gasification slag. Step 5: Add sodium dodecylbenzenesulfonate to the wet gel obtained in Step 4 to enhance the wet gel, resulting in an enhanced wet gel. The mass ratio of the wet gel to sodium dodecylbenzenesulfonate is 1:0.1-0.

5. Place the enhanced wet gel in anhydrous ethanol for aging treatment. After the aging treatment, an aged gel is obtained. Then, the aqueous phase solution in the pores of the aged gel is replaced multiple times with anhydrous ethanol. The replaced gel is then placed in a silane solution for surface modification. The silane solution is obtained by mixing trimethylchlorosilane, hexamethyldisiloxane, diethanolmonoisopropanolamine, and polyethylene glycol in a volume ratio of 1-5:1-8:6-12:2-6. After the modification is completed, the gel is washed with n-hexane and then dried under normal pressure to obtain a mesoporous silica-based material.

2. The method for preparing mesoporous silica-based materials based on coal gasification slag according to claim 1, characterized in that, The SiO2 content in the coal gasification slag is not less than 40%, and the loss on ignition is not more than 15%.

3. The method for preparing mesoporous silica-based materials based on coal gasification slag according to claim 1, characterized in that, In step one, the concentration of hydrochloric acid in the mixed acid of hydrochloric acid and acetic acid is 0.1-0.5 mol / L, and the concentration of acetic acid is 0.5-1 mol / L. The solid-liquid ratio of the coal gasification slag to the mixed acid of hydrochloric acid and acetic acid is 0.14-0.30 g / L. The acid leaching reaction conditions are: reaction at 80-120℃ for 1-4 hours.

4. The method for preparing mesoporous silica-based materials based on coal gasification slag according to claim 1, characterized in that, The mass ratio of the coal gasification acid leaching residue to NaOH and Na2SiO3 in step two is 1:1-2:0.5-1.5; the heating reaction conditions in step two are: 550-800℃ for 1-4 hours.

5. The method for preparing mesoporous silica-based materials based on coal gasification slag according to claim 1, characterized in that, The concentration of the alkali fusion solution in step three is 20-60 wt%; the mass ratio of the alkali fusion product in step three to the cationic surfactant and the ammonia in the ammonia solution is 1:0.1-0.8:2-8.

6. The method for preparing mesoporous silica-based materials based on coal gasification slag according to claim 1, characterized in that, The catalyst described in step four is obtained by mixing ammonium fluoride and dimethylformamide at a mass ratio of 1:5; the mass ratio of the coal gasification slag enhanced precursor, silane mixed solution and catalyst described in step four is 1-5:5-10:0.1-0.5; the gelation reaction conditions in step four are: reaction at 40-75℃ for 4-12h.

7. The method for preparing mesoporous silica-based materials based on coal gasification slag according to claim 1, characterized in that, The enhancement treatment in step five takes 8-16 hours; the aging treatment in step five takes 8-20 hours at a temperature of 45-55°C; the mass ratio of the replaced gel to the silane solution in step five is 1:2-4; and the surface modification in step five takes 12-48 hours.

8. A mesoporous silica-based material prepared from coal gasification slag according to any one of claims 1-7, characterized in that, It has a three-dimensional network structure with a pore size of 5-30 nm and a specific surface area of ​​550-900 m². 2 / g, pore volume is 0.45-0.80cm³ 3 / g.

9. The mesoporous silicon-based phase change composite material and insulation board prepared from the mesoporous silicon-based material according to claim 8.

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