Porous calcium silicate and preparation method thereof

Abstract

The invention provides porous calcium silicate and a preparation method thereof. The preparation method comprises the following steps: providing a high-modulus water glass solution as a silicon source, providing lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and citric acid betaine to obtain a mixed solution, heating the mixed solution, and carrying out a synthetic reaction with lime to obtain calcium silicate slurry; carrying out pressure filtration on the calcium silicate slurry to obtain a crude calcium silicate filter cake; adding water and pulping to obtain slurry, heating the slurry, adding a dealkalizing agent, keeping the temperature at 90-95 DEG C, and carrying out dealkalization reaction to generate dealkalized calcium silicate slurry; and carrying out solid-liquid separation on the alkali-treated calcium silicate slurry to obtain a calcium silicate filter cake, drying and scattering to obtain the finished product porous calcium silicate. The specific surface area of the porous calcium silicate is obviously increased.

Description

Technical Field

[0001] The present application relates to the technical field of calcium silicate manufacturing, and in particular to porous calcium silicate and a preparation method thereof. Background Art

[0002] Porous calcium silicate has a honeycomb porous structure, a porous structure, a high specific surface area, and a high pore density. It is a good adsorption material. It has the characteristics of small particle size, low density, high oil absorption value, and large specific surface area, so it has strong adsorption characteristics. Its unique structural characteristics enable it to purify formaldehyde, benzene, and nitrogen oxides in the air and reduce the TVOC content of plastic products; it has the advantage of good removal effect when applied to the adsorption of heavy metal ions and nitrogen and phosphorus in wastewater. Porous calcium silicate has great potential in the application of papermaking, rubber, plastics, inks and coatings. Compared with traditional fillers such as white carbon black and carbon black, it has a lower cost, and as an alternative filler, it can also achieve the expected effect, which is conducive to the recycling of resources. Taking advantage of the advantages of calcium silicate's honeycomb porous structure, high adsorption capacity, high chemical stability, and excellent damping and thermal insulation properties, it has a wide range of application prospects as an adsorption material or filler.

[0003] The porous calcium silicate prepared by the traditional method is mainly a mixture of siliceous materials such as fly ash, silica ash, diatomaceous earth and calcium-rich materials in a certain proportion, and crystallized under specific reaction conditions. The hydrothermal synthesis method for preparing calcium silicate materials generally places the siliceous raw materials and calcium raw materials in a hydrothermal kettle and synthesizes them in an aqueous solution or water vapor at a certain temperature and pressure. The calcium silicate produced in this process mostly exists in the form of tobermorite and xonotlite. Increasing the temperature and pressure can increase the crystallinity of the calcium silicate product. The hydrothermal synthesis method can not only better promote the reaction, but also regulate the crystal shape. The products prepared by other synthesis methods have higher plasticity, but there is still the problem of small specific surface area of ​​porous calcium silicate, resulting in its low adsorption performance. Summary of the invention

[0004] The present application provides a porous calcium silicate and a preparation method thereof, so as to solve the above-mentioned problems mentioned in the background technology.

[0005] In a first aspect, the present application provides a method for preparing porous calcium silicate, the preparation method comprising the following steps: (1) providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and betaine citrate to the high modulus water glass solution under stirring to obtain a mixed solution, heating the mixed solution to 75-80° C., and then reacting the mixed solution with lime milk under stirring to obtain a calcium silicate slurry; (2) filtering the calcium silicate slurry by hydraulic pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake; (3) adding water to the crude calcium silicate filter cake to obtain a slurry, and heating the slurry to 90-95° C. to obtain a heated slurry; (4) adding a dealkalizing agent to the heated slurry, maintaining the temperature at 90-95°C and stirring at 200-600 r / min, and carrying out a dealkalizing reaction for 20-30 min to generate a dealkalized calcium silicate slurry; (5) After dealkalization, the calcium silicate slurry is subjected to solid-liquid separation to obtain a calcium silicate filter cake, which is then dried and broken up to obtain a finished porous calcium silicate.

[0006] Optionally, the preparation process of the high modulus water glass solution includes: mixing quartz sand with water and sodium hydroxide solution, heating to 150-200°C under stirring conditions, pressurizing to 0.5-0.8MPa, reacting for 1.5-4 hours, sending to a water glass transfer tank, cooling to 60-75°C, filtering, and obtaining a high modulus water glass solution.

[0007] Optionally, in the preparation process of the high modulus water glass solution, the weight ratio of quartz sand, water and sodium hydroxide solution is 3:2-5:1, and the mass concentration of the sodium hydroxide solution is 18%.

[0008] Optionally, the high modulus water glass solution has a modulus of 1.6-2.5.

[0009] Optionally, the preparation process of lime milk includes: adding water 5-8 times the weight of quicklime to quicklime, stirring, and digesting for 0.5-1h to obtain lime milk.

[0010] Optionally, in the preparation process of calcium silicate slurry: the weight ratio of high modulus water glass solution to lime milk is 1:2.5-3, and the weight ratio of dodecyltrimethylammonium chloride, betaine citric acid to high modulus water glass solution is 0.15-0.2:0.2-0.3:1.

[0011] Optionally, during slurrying, water is added to the crude calcium silicate filter cake, and the mixture is dispersed and slurried for 1-2 hours at a stirring speed of 400-600 r / min to obtain a slurry, wherein the weight ratio of the crude calcium silicate filter cake to water is 1:1-2.

[0012] Optionally, in the dealkalization reaction, the dealkalizing agent is aluminum sulfate, and the weight ratio of the slurry to the dealkalizing agent after heating is 1:0.15-0.2.

[0013] Optionally, before the dealkalized calcium silicate slurry is subjected to solid-liquid separation, the process further includes: stirring and mixing the dealkalized calcium silicate slurry with an acid solution, standing for 20-40 minutes to obtain an activated slurry, centrifuging the activated slurry, washing the obtained solid phase with water to a pH value of 8.5-11, dispersing the washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid in N,N-dimethylformamide, reacting at 100-120° C. for 4-10 hours, performing solid-liquid separation, washing, drying, and breaking up to obtain porous calcium silicate.

[0014] Optionally, the weight ratio of the solid phase after water washing, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid is 1:0.04-0.15:0.05-0.1, and the weight volume ratio of the solid phase after water washing and N,N-dimethylformamide is 1:50-60 g / mL.

[0015] In a second aspect, the present application provides a porous calcium silicate, which is obtained by the above-mentioned preparation method.

[0016] The porous calcium silicate preparation method provided in the present application realizes the preparation of porous calcium silicate and has the following beneficial effects compared with the prior art: (1) Calcium silicate is generated by using high modulus water glass solution as a silicon source and providing lime milk as a calcium source. During the reaction, by adding dodecyl trimethyl ammonium chloride and citric acid betaine, dodecyl trimethyl ammonium chloride can not only improve the reaction stability, but also help improve the reaction efficiency. In addition, a large number of positively charged groups are distributed on the outside of the micelles of the dodecyl trimethyl ammonium chloride surfactant, so that part of the dodecyl trimethyl ammonium chloride is grafted on the outside of the calcium silicate, thereby increasing the specific surface area of ​​the porous calcium silicate. At the same time, the outside of the citric acid betaine contains hydroxyl and carboxyl groups, which can repel each other with the calcium silicate, further improving the uniformity and stability of the calcium silicate reaction system, and forming a certain steric hindrance in the solution to avoid agglomeration of the reactants, and can avoid excessive adsorption of dodecyl trimethyl ammonium chloride, thereby increasing the specific surface area of ​​the subsequent porous calcium silicate, and helping the porous calcium silicate to have a good porosity. When used as an adsorbent material, the porous calcium silicate has significant adsorption properties.

[0017] (2) By controlling the addition amount of dodecyltrimethylammonium chloride and betaine citric acid, the dispersion stability of the reaction system and the grafting of dodecyltrimethylammonium chloride are balanced. It is avoided that the addition amount of surfactant is too small to achieve the purpose of uniform dispersion of the system, and the dodecyltrimethylammonium chloride grafted on the surface of calcium silicate is too small, which is not effective in improving the porosity and specific surface area of ​​porous calcium silicate. Excessive addition will lead to excessive dodecyltrimethylammonium chloride, which is not conducive to improving the porosity and specific surface area of ​​calcium silicate.

[0018] (3) By adding the dealkalizing agent aluminum sulfate, the residual alkali solution in the slurry after heating can be converted into soluble neutral salts, and then these soluble salts are washed and removed in the form of ions, thereby improving the stability of the porous structure in the porous calcium silicate and thus increasing the specific surface area of ​​the porous calcium silicate. As a result, the porous calcium silicate has significant adsorption performance when used as an adsorption material, and when used as a papermaking filler, it increases the bulk of the paper.

[0019] (4) Activating the dealkalized calcium silicate slurry with an acid solution and centrifuging it. The obtained solid phase is washed with water to a pH value of 8.5-11. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid are dispersed in N,N-dimethylformamide and reacted at 100-120° C. for 4-10 hours. N,N-dimethylformamide is used as a solvent and 2-aminobenzenesulfonic acid is used as a promoter, so that the carboxyl groups in 2,5-furandicarboxylic acid react with the active groups on the surface of the dealkalized calcium silicate, thereby further improving the porosity and specific surface area of ​​the porous calcium silicate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 This is the SEM morphology of the porous calcium silicate provided in Example 3 of the present application. Figure 1 (a) is a 1000-fold magnified morphology image. Figure 1 (b) is a 5000-fold magnified morphology image.

[0022] Figure 2 This is the SEM morphology of the porous calcium silicate provided in Example 7 of the present application. Figure 2 (a) is a 1000-fold magnified morphology image. Figure 2 (b) is a 5000-fold magnified morphology image. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application is clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work also fall within the scope of protection of the present application.

[0024] In a first aspect, the present application provides a method for preparing porous calcium silicate, the preparation method comprising the following steps: (1) providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and betaine citrate to the high modulus water glass solution under stirring to obtain a mixed solution, heating the mixed solution to 75-80° C., and then reacting the mixed solution with lime milk under stirring to obtain a calcium silicate slurry; (2) filtering the calcium silicate slurry by hydraulic pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake; (3) adding water to the crude calcium silicate filter cake to obtain a slurry, and heating the slurry to 90-95° C. to obtain a heated slurry; (4) adding a dealkalizing agent to the heated slurry, maintaining the temperature at 90-95°C and stirring at 200-600 r / min, and carrying out a dealkalizing reaction for 20-30 min to generate a dealkalized calcium silicate slurry; (5) After dealkalization, the calcium silicate slurry is subjected to solid-liquid separation to obtain a calcium silicate filter cake, which is then dried and broken up to obtain a finished porous calcium silicate.

[0025] Specifically, a high modulus water glass solution is used as a silicon source, and lime milk is provided as a calcium source. The water glass solution is an aqueous solution of sodium silicate. The silicate (SiO3 2- ) and calcium ions (Ca 2+ ) to form insoluble calcium silicate. Water glass exhibits colloidal solution characteristics at high modulus (SiO2 / Na2O molar ratio), and silicate exists in the form of colloid particles. After adding lime milk, Ca 2+ As a high-valent cation, it compresses the double layer of the colloid particles, causing the silicate colloid to destabilize and aggregate, forming silica gel (Si(OH)4) or further reacting with Ca 2+ Combined into a more complex calcium silicate structure. In the reaction process, dodecyl trimethyl ammonium chloride and betaine citric acid are first added to the high modulus water glass solution to obtain a mixed solution, and the mixed solution is heated to 75-80°C and then reacted with lime milk under stirring to obtain calcium silicate slurry.

[0026] Among them, dodecyl trimethyl ammonium chloride and betaine citric acid are surfactants, which can not only provide higher surface energy, but also improve the dispersion stability of water glass and lime milk, improve the uniformity of the reaction system, and then improve the stability of the reaction system, which is conducive to the efficient reaction. And a large number of positively charged groups are distributed outside the micelles of the dodecyl trimethyl ammonium chloride surfactant, which can attract silicate ions, so that part of dodecyl trimethyl ammonium chloride is grafted on the outside of calcium silicate, and the specific surface area of ​​porous calcium silicate is increased. At the same time, under stirring, betaine citric acid is evenly distributed in the reaction system, and the outside of betaine citric acid contains hydroxyl and carboxyl groups, which can repel each other with calcium silicate, further improving the uniformity and stability of the calcium silicate reaction system, and at the same time forming a certain steric hindrance in the solution, avoiding the agglomeration of reactants, and avoiding excessive adsorption of dodecyl trimethyl ammonium chloride, improving the subsequent specific surface area of ​​porous calcium silicate, and helping porous calcium silicate to have a good porosity.

[0027] The obtained calcium silicate slurry is filtered, the filter cake is taken and washed with water to obtain a crude calcium silicate filter cake, and water is added to wash away impurities in the filter cake. At the same time, the amount of washing water added is 2-3 times the weight of the filter cake, and the filter cake is washed with washing water at least 3 times. The crude calcium silicate filter cake is beaten with water to obtain a slurry, and the slurry is heated to 90-95°C to obtain a heated slurry. A dealkalizing agent is added to the heated slurry for dealkalization reaction. The pH value of the dealkalized calcium silicate slurry is 9.75-11, and the residual sodium is removed. Excessive residual sodium leads to excessive alkalinity of calcium silicate, which affects the structure and stability of calcium silicate. The CSH-type hydrated calcium silicate generated after dealkalization improves the stability of the loose porous structure, thereby increasing the specific surface area of ​​the porous calcium silicate. When used as an adsorption material, the porous calcium silicate has significant adsorption performance.

[0028] After dealkalization, the calcium silicate slurry is subjected to solid-liquid separation, such as centrifugation or filtration, to obtain a calcium silicate filter cake, which is dried at 200°C-300°C to constant weight and broken up to obtain a finished porous calcium silicate.

[0029] The present application realizes the preparation of porous calcium silicate through the above scheme. Calcium silicate is generated by using a high modulus water glass solution as a silicon source and providing lime milk as a calcium source. During the reaction, dodecyl trimethyl ammonium chloride and betaine citrate are added to the high modulus water glass solution. Dodecyl trimethyl ammonium chloride can not only improve the dispersion stability of water glass and lime milk, but also improve the uniformity of the reaction system, thereby improving the stability of the reaction system and facilitating the efficient reaction. In addition, a large number of positively charged groups are distributed on the outside of the micelles of the dodecyl trimethyl ammonium chloride surfactant, which can attract silicate ions, so that part of the dodecyl trimethyl ammonium chloride is grafted on the outside of the calcium silicate, thereby increasing the specific surface area of ​​the porous calcium silicate. At the same time, under stirring, betaine citric acid is evenly distributed in the reaction system, and the exterior of betaine citric acid contains hydroxyl and carboxyl groups, which can repel each other with calcium silicate, further improving the uniformity and stability of the calcium silicate reaction system, while forming a certain steric hindrance in the solution to avoid agglomeration of reactants, and can avoid excessive adsorption of dodecyltrimethylammonium chloride, thereby increasing the specific surface area of ​​subsequent porous calcium silicate, and helping the porous calcium silicate to have a good porosity. By adding a dealkalizer to remove residual sodium, the stability of the loose porous structure of the CSH-type hydrated calcium silicate generated after dealkalization is further improved, thereby increasing the specific surface area of ​​the porous calcium silicate, and when used as an adsorption material, the porous calcium silicate has significant adsorption performance.

[0030] Optionally, the preparation process of the high modulus water glass solution includes: mixing quartz sand with water and sodium hydroxide solution, heating to 150-200°C under stirring conditions, pressurizing to 0.5-0.8MPa, reacting for 1.5-4 hours, sending to a water glass transfer tank, cooling to 60-75°C, filtering, and obtaining a high modulus water glass solution. Under high temperature and high pressure conditions, sodium hydroxide reacts with quartz sand through a hydrothermal method to generate sodium silicate (Na2SiO3).

[0031] Among them, the particle size of quartz sand is 600-800 mesh.

[0032] Optionally, in the preparation process of high modulus water glass solution, the weight ratio of quartz sand, water and sodium hydroxide solution is 3:2-5:1, and the mass concentration of sodium hydroxide solution is 18%. This can ensure the full reaction of quartz sand and sodium hydroxide solution and avoid the waste of quartz sand and sodium hydroxide.

[0033] Optionally, the high modulus water glass solution has a modulus of 1.6-2.5.

[0034] Optionally, the preparation process of lime milk includes: adding water 5-8 times the weight of quicklime to quicklime, stirring, and digesting for 0.5-1h to obtain lime milk.

[0035] Optionally, in the preparation process of calcium silicate slurry: the weight ratio of high modulus water glass solution to lime milk is 1:2.5-3, and the weight ratio of dodecyltrimethylammonium chloride, betaine citric acid to high modulus water glass solution is 0.15-0.2:0.2-0.3:1.

[0036] Specifically, the addition amount of dodecyl trimethyl ammonium chloride and betaine citric acid is controlled so that the dispersion stability of the reaction system and the grafting of dodecyl trimethyl ammonium chloride are balanced. It is avoided that too little surfactant addition can not achieve the purpose of uniform dispersion of the system, and too little dodecyl trimethyl ammonium chloride grafted on the surface of calcium silicate is caused, which is not significant enough to improve the porosity and specific surface area of ​​porous calcium silicate. Too much addition will lead to too much dodecyl trimethyl ammonium chloride, which is not conducive to improving the porosity and specific surface area of ​​calcium silicate.

[0037] Optionally, during slurrying, water is added to the crude calcium silicate filter cake, and the mixture is dispersed and slurried for 1-2 hours at a stirring speed of 400-600 r / min to obtain a slurry, wherein the weight ratio of the crude calcium silicate filter cake to water is 1:1-2.

[0038] Optionally, in the dealkalization reaction, the dealkalizing agent is aluminum sulfate, and the weight ratio of the slurry to the dealkalizing agent after heating is 1:0.15-0.2.

[0039] Specifically, the dealkalizing agent aluminum sulfate can convert the residual alkali solution in the slurry after heating into soluble neutral salts, and then wash and remove these soluble salts in the form of ions, thereby improving the stability of the porous structure in the porous calcium silicate and thus increasing the specific surface area of ​​the porous calcium silicate, so that the porous calcium silicate has significant adsorption performance when used as an adsorption material, and improves the bulk of the paper when used as a papermaking filler.

[0040] Optionally, before the dealkalized calcium silicate slurry is subjected to solid-liquid separation, the process further includes: stirring and mixing the dealkalized calcium silicate slurry with an acid solution, standing for 20-40 minutes to obtain an activated slurry, centrifuging the activated slurry, washing the obtained solid phase with water to a pH value of 8.5-11, dispersing the washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid in N,N-dimethylformamide, reacting at 100-120° C. for 4-10 hours, performing solid-liquid separation, washing, drying, and breaking up to obtain porous calcium silicate.

[0041] Specifically, the dealkalized calcium silicate slurry is stirred and mixed with an acid solution, the dealkalized calcium silicate is activated, the activated slurry is centrifuged, the obtained solid phase is washed with water to a pH value of 8.5-11, the washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid are dispersed in N,N-dimethylformamide, and reacted at 100-120° C. for 4-10 hours, N,N-dimethylformamide is used as a solvent, and 2-aminobenzenesulfonic acid is used as a promoter, so that the carboxyl group in 2,5-furandicarboxylic acid reacts with the active group on the surface of the dealkalized calcium silicate, thereby further improving the porosity and specific surface area of ​​the porous calcium silicate.

[0042] The acid solution includes nitric acid or hydrochloric acid with a molar concentration of 5 moL / L, and the mass ratio of the calcium silicate slurry to the acid solution after dealkalization is 1:1-1.2.

[0043] Optionally, the weight ratio of the solid phase after water washing, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid is 1:0.04-0.15:0.05-0.1, and the weight volume ratio of the solid phase after water washing and N,N-dimethylformamide is 1:50-60 g / mL.

[0044] In a second aspect, the present application provides a porous calcium silicate, which is obtained by the above-mentioned preparation method.

[0045] The technical solution of the present application is described in detail below with reference to specific embodiments.

[0046] Example 1 A method for preparing porous calcium silicate, the preparation method comprising the following steps: (1) Preparation of high modulus water glass solution: Mix quartz sand with water and sodium hydroxide solution, raise the temperature to 150°C and pressurize to 0.5 MPa under stirring conditions, react for 1.5 hours, send to the water glass transfer tank, cool to 60°C, filter, and obtain a high modulus water glass solution. The weight ratio of quartz sand, water and sodium hydroxide solution is 3:2:1, and the mass concentration of sodium hydroxide solution is 18%. The modulus of the high modulus water glass solution is 1.6.

[0047] (2) Preparation of lime milk: Add 5 times the weight of water to quicklime and stir. Digest for 0.5 h to obtain lime milk.

[0048] (3) Preparation of calcium silicate slurry: providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and betaine citrate to the high modulus water glass solution under stirring to obtain a mixed solution, heating the mixed solution to 75°C, and reacting the mixed solution with lime milk under stirring to obtain a calcium silicate slurry; the weight ratio of the high modulus water glass solution to the lime milk is 1:2.5, and the weight ratio of dodecyl trimethyl ammonium chloride, betaine citrate to the high modulus water glass solution is 0.15:0.2:1.

[0049] (4) filtering the calcium silicate slurry by hydraulic pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake; (5) Add water to the crude calcium silicate filter cake and slurry it. Disperse and slurry it at a stirring speed of 400 r / min for 1 hour to obtain a slurry. Heat the slurry to 90° C. to obtain a heated slurry. The weight ratio of the crude calcium silicate filter cake to water is 1:1.

[0050] (4) adding a dealkalizing agent, aluminum sulfate, to the heated slurry, maintaining the temperature at 90°C and stirring at 200 r / min, and carrying out a dealkalizing reaction for 20 minutes to generate a dealkalized calcium silicate slurry having a pH value of 9.8; and the weight ratio of the heated slurry to the dealkalizing agent was 1:0.15.

[0051] (5) After dealkalization, the calcium silicate slurry is subjected to solid-liquid separation to obtain a calcium silicate filter cake, which is dried at 200°C to a constant temperature and broken up to obtain a finished porous calcium silicate.

[0052] Example 2 A method for preparing porous calcium silicate, the preparation method comprising the following steps: (1) Preparation of high modulus water glass solution: Mix quartz sand with water and sodium hydroxide solution, raise the temperature to 180°C and pressurize to 0.6 MPa under stirring conditions, react for 2.5 hours, send to the water glass transfer tank, cool to 70°C, filter, and obtain a high modulus water glass solution. The weight ratio of quartz sand, water and sodium hydroxide solution is 3:3.5:1, and the mass concentration of sodium hydroxide solution is 18%. The modulus of the high modulus water glass solution is 1.81.

[0053] (2) Preparation of lime milk: Add 7 times the weight of water to quicklime and stir. Digest for 45 minutes to obtain lime milk.

[0054] (3) Preparation of calcium silicate slurry: providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and betaine citrate to the high modulus water glass solution under stirring to obtain a mixed solution, heating the mixed solution to 78°C, and reacting the mixed solution with lime milk under stirring to obtain a calcium silicate slurry; the weight ratio of the high modulus water glass solution to the lime milk is 1:2.7, and the weight ratio of dodecyl trimethyl ammonium chloride, betaine citrate to the high modulus water glass solution is 0.18:0.25:1.

[0055] (4) filtering the calcium silicate slurry by hydraulic pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake; (5) Add water to the crude calcium silicate filter cake and slurry it. Disperse and slurry it at a stirring speed of 500 r / min for 1.5 hours to obtain a slurry. Heat the slurry to 92° C. to obtain a heated slurry. The weight ratio of the crude calcium silicate filter cake to water is 1:1.5.

[0056] (4) adding a dealkalizing agent, aluminum sulfate, to the heated slurry, maintaining the temperature at 92° C. and stirring at 400 r / min, and carrying out a dealkalizing reaction for 25 min to generate a dealkalized calcium silicate slurry having a pH value of 9.9; and the weight ratio of the heated slurry to the dealkalizing agent was 1:0.17.

[0057] (5) After dealkalization, the calcium silicate slurry is subjected to solid-liquid separation to obtain a calcium silicate filter cake, which is dried at 200°C to a constant temperature and broken up to obtain a finished porous calcium silicate.

[0058] Example 3 A method for preparing porous calcium silicate, the preparation method comprising the following steps: (1) Preparation of high modulus water glass solution: Mix quartz sand with water and sodium hydroxide solution, raise the temperature to 200°C, pressurize to 0.8 MPa, react for 4 hours, send to the water glass transfer tank, cool to 75°C, filter, and obtain high modulus water glass solution. The weight ratio of quartz sand, water and sodium hydroxide solution is 3:5:1, and the mass concentration of sodium hydroxide solution is 18%. The modulus of the high modulus water glass solution is 2.

[0059] (2) Preparation of lime milk: Add 8 times the weight of water to quicklime and stir. Digest for 1 hour to obtain lime milk.

[0060] (3) Preparation of calcium silicate slurry: providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and betaine citrate to the high modulus water glass solution under stirring to obtain a mixed solution, heating the mixed solution to 80°C, and reacting the mixed solution with lime milk under stirring to obtain a calcium silicate slurry; the weight ratio of the high modulus water glass solution to the lime milk is 1:3, and the weight ratio of dodecyl trimethyl ammonium chloride, betaine citrate to the high modulus water glass solution is 0.2:0.3:1.

[0061] (4) filtering the calcium silicate slurry by hydraulic pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake; (5) Add water to the crude calcium silicate filter cake and slurry it, disperse and slurry it at a stirring speed of 600 r / min for 2 hours to obtain a slurry, heat the slurry to 95° C., and obtain a heated slurry; the weight ratio of the crude calcium silicate filter cake to water is 1:2.

[0062] (4) adding a dealkalizing agent, aluminum sulfate, to the heated slurry, maintaining the temperature at 95°C and stirring at 600 r / min, and carrying out a dealkalizing reaction for 30 minutes to generate a dealkalized calcium silicate slurry having a pH value of 9.93; and the weight ratio of the heated slurry to the dealkalizing agent was 1:0.2.

[0063] (5) After dealkalization, the calcium silicate slurry is subjected to solid-liquid separation to obtain a calcium silicate filter cake, which is dried at 200°C to a constant temperature and broken up to obtain a finished porous calcium silicate.

[0064] Example 4 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 3 is that: (1) During the preparation process of the high modulus water glass solution, the modulus of the obtained high modulus water glass solution is 2.14.

[0065] (4) The pH value of calcium silicate slurry after dealkalization is 10.34.

[0066] Example 5 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 3 is that: (1) During the preparation of the high modulus water glass solution, the modulus of the obtained high modulus water glass solution is 2.5.

[0067] (4) The pH value of the calcium silicate slurry after dealkalization is 11.

[0068] Comparative Example 1 The difference from Example 3 is that: (1) During the preparation process of the high modulus water glass solution, the modulus of the obtained high modulus water glass solution is 1.21.

[0069] (4) The pH value of the calcium silicate slurry after dealkalization is 9.98.

[0070] Comparative Example 2 The difference from Example 3 is that: (1) During the preparation process of the high modulus water glass solution, the modulus of the obtained high modulus water glass solution is 1.59.

[0071] (4) The pH value of the calcium silicate slurry after dealkalization is 9.85.

[0072] Experimental Example 1 The porous calcium silicate provided in Example 3 was tested by scanning electron microscopy (SEM) to obtain the following morphology: Figure 1 The SEM morphology of porous calcium silicate shown.

[0073] observe Figure 1 It can be seen that the porous calcium silicate product provided in Example 3 presents a highly polymerized three-dimensional cage-type network structure with a dense internal structure. This honeycomb porous structure can provide more adsorption sites for the material itself.

[0074] Experimental Example 2 The specific surface area and conductivity of the porous calcium silicate obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were detected using a specific surface area analyzer and a conductivity meter. At least three parallel tests were performed for each test, and the average value was taken. The results are shown in Table 1.

[0075] Table 1 Water glass modulus <![CDATA[Specific surface area / m 2 / g]]> pH Conductivity Example 1 1.6 273 9.8 5.5 Example 2 1.81 297 9.8 4.49 Example 3 2 366 9.93 3.76 Example 4 2.14 350 10.34 3.2 Example 5 2.5 376 11 2.08 Comparative Example 1 1.21 246 9.98 5.72 Comparative Example 2 1.59 256 9.85 7.02 As can be seen from Table 1, the porous calcium silicate provided by the present application has a higher specific surface area than that of Comparative Examples 1 and 2. At the same time, when the modulus of the raw material water glass increases, the specific surface area increases accordingly, which helps to increase the adsorption sites of the porous calcium silicate and improve the adsorption efficiency. In addition, Examples 1 to 5 have good electrical conductivity. Generally, the lower the material conductivity, the higher the porosity.

[0076] Comparative Example 3 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 3 is that (3) Preparation of calcium silicate slurry: providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride to the high modulus water glass solution under stirring to obtain a mixed solution, heating the mixed solution to 80°C, and reacting the mixed solution with lime milk under stirring to obtain a calcium silicate slurry; the weight ratio of the high modulus water glass solution to the lime milk is 1:3, and the weight ratio of dodecyl trimethyl ammonium chloride to the high modulus water glass solution is 0.2:1.

[0077] Comparative Example 4 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 3 is that (3) Preparation of calcium silicate slurry: providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and betaine citrate to the high modulus water glass solution under stirring to obtain a mixed solution, heating the mixed solution to 80°C, and reacting the mixed solution with lime milk under stirring to obtain a calcium silicate slurry; the weight ratio of the high modulus water glass solution to the lime milk is 1:3, and the weight ratio of dodecyl trimethyl ammonium chloride, betaine citrate to the high modulus water glass solution is 0.15:0.28:1.

[0078] Comparative Example 5 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 3 is that (3) Preparation of calcium silicate slurry: providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and betaine citrate to the high modulus water glass solution under stirring to obtain a mixed solution, heating the mixed solution to 80°C, and reacting the mixed solution with lime milk under stirring to obtain a calcium silicate slurry; the weight ratio of the high modulus water glass solution to the lime milk is 1:3, and the weight ratio of dodecyl trimethyl ammonium chloride, betaine citrate to the high modulus water glass solution is 0.3:0.4:1.

[0079] Experimental Example 3 The specific surface area of ​​the porous calcium silicate provided in Example 3 and Comparative Examples 3 to 5 was tested using a specific surface area analyzer; According to GB / T26900-2011 "Bamboo Charcoal for Air Purification", the adsorption performance of the porous calcium silicate provided in Example 3 and Comparative Examples 3 to 5 was tested. At least 3 parallel tests were performed for each test, and the average value was taken. The results are shown in Table 2.

[0080] Table 2 <![CDATA[Specific surface area / m 2 / g]]> Formaldehyde adsorption rate / % TVOC adsorption rate / % Example 3 366 16.23 37.01 Comparative Example 3 126 7.23 8.56 Comparative Example 4 155 7.86 8.96 Comparative Example 5 168 8.02 8.26 Note: TVOC is a mixture of benzene, toluene, xylene and ethyl acetate.

[0081] As shown in Table 2, during the reaction, dodecyl trimethyl ammonium chloride and citric acid betaine are added, which is not only conducive to the efficient reaction, but also a large number of positively charged groups are distributed outside the micelle of the dodecyl trimethyl ammonium chloride surfactant, which can attract silicate ions, so that part of dodecyl trimethyl ammonium chloride is grafted outside the calcium silicate, and the specific surface area of ​​porous calcium silicate is improved. At the same time, the outside of citric acid betaine contains hydroxyl and carboxyl groups, which can repel each other with calcium silicate, further improve the uniformity and stability of the calcium silicate reaction system, and form a certain steric hindrance in the solution at the same time, avoid reactant agglomeration, and can improve the subsequent porous calcium silicate specific surface area, which helps porous calcium silicate to have a good porosity. When used as an adsorbent, porous calcium silicate is made to have significant adsorption properties.

[0082] Example 6 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 3 is that: (5) The dealkalized calcium silicate slurry is stirred and mixed with an acid solution and allowed to stand for 20 minutes to activate the dealkalized calcium silicate. The activated slurry is centrifuged and the obtained solid phase is washed with water until the pH value is 8.5. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid are dispersed in N,N-dimethylformamide and reacted at 100° C. for 4 hours. The solid-liquid separation is performed, washed, dried and dispersed to obtain porous calcium silicate.

[0083] The acid solution is hydrochloric acid with a molar concentration of 5 mol / L, and the mass ratio of the calcium silicate slurry to the acid solution after dealkalization is 1: 1. The weight ratio of the solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid after water washing is 1: 0.04: 0.05, and the weight volume ratio of the solid phase after water washing to N, N-dimethylformamide is 1: 50 g / mL.

[0084] Example 7 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 3 is that: (5) The dealkalized calcium silicate slurry is stirred and mixed with an acid solution and allowed to stand for 30 minutes to activate the dealkalized calcium silicate. The activated slurry is centrifuged and the obtained solid phase is washed with water until the pH value is 10. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid are dispersed in N,N-dimethylformamide and reacted at 110° C. for 7 hours. The solid-liquid separation is performed, washed, dried and dispersed to obtain porous calcium silicate.

[0085] The acid solution is hydrochloric acid with a molar concentration of 5 mol / L, and the mass ratio of calcium silicate slurry to the acid solution after dealkalization is 1:1.1. The weight ratio of the solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid after water washing is 1:0.1:0.075, and the weight volume ratio of the solid phase after water washing to N,N-dimethylformamide is 1:55 g / mL.

[0086] Example 8 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 3 is that: (5) The dealkalized calcium silicate slurry is stirred and mixed with an acid solution and allowed to stand for 40 minutes to activate the dealkalized calcium silicate. The activated slurry is centrifuged and the obtained solid phase is washed with water until the pH value is 11. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid are dispersed in N,N-dimethylformamide and reacted at 120° C. for 10 hours. The solid-liquid separation is performed, washed, dried and dispersed to obtain porous calcium silicate.

[0087] The acid solution is hydrochloric acid with a molar concentration of 5 mol / L, and the mass ratio of the calcium silicate slurry to the acid solution after dealkalization is 1:1.2. The weight ratio of the solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid after water washing is 1:0.15:0.1, and the weight volume ratio of the solid phase after water washing to N,N-dimethylformamide is 1:60 g / mL.

[0088] Comparative Example 6 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 7 is that (5) The dealkalized calcium silicate slurry is stirred and mixed with an acid solution and allowed to stand for 30 minutes to activate the dealkalized calcium silicate. The activated slurry is centrifuged and the obtained solid phase is washed with water until the pH value is 10. The washed solid phase and 2,5-furandicarboxylic acid are dispersed in N,N-dimethylformamide and reacted at 110° C. for 7 hours. The solid-liquid separation is performed, washed, dried, and dispersed to obtain porous calcium silicate.

[0089] The acid solution is hydrochloric acid with a molar concentration of 5 mol / L, and the mass ratio of the calcium silicate slurry to the acid solution after dealkalization is 1:1.1. The weight ratio of the solid phase after water washing to 2,5-furandicarboxylic acid is 1:0.1, and the weight volume ratio of the solid phase after water washing to N,N-dimethylformamide is 1:55 g / mL.

[0090] Comparative Example 7 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 7 is that (5) The dealkalized calcium silicate slurry is stirred and mixed with an acid solution and allowed to stand for 30 minutes to activate the dealkalized calcium silicate. The activated slurry is centrifuged and the obtained solid phase is washed with water until the pH value is 10. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid are dispersed in N,N-dimethylformamide and reacted at 110° C. for 7 hours. The solid-liquid separation is performed, washed, dried and dispersed to obtain porous calcium silicate.

[0091] The acid solution is hydrochloric acid with a molar concentration of 5 mol / L, and the mass ratio of calcium silicate slurry to the acid solution after dealkalization is 1:1.1. The weight ratio of the solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid after water washing is 1:0.16:0.075, and the weight volume ratio of the solid phase after water washing to N,N-dimethylformamide is 1:55 g / mL.

[0092] Comparative Example 8 A method for preparing porous calcium silicate, the preparation method comprising the following steps: The difference from Example 7 is that (5) The dealkalized calcium silicate slurry is stirred and mixed with an acid solution and allowed to stand for 30 minutes to activate the dealkalized calcium silicate. The activated slurry is centrifuged and the obtained solid phase is washed with water until the pH value is 10. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid are dispersed in N,N-dimethylformamide and reacted at 110° C. for 7 hours. The solid-liquid separation is performed, washed, dried and dispersed to obtain porous calcium silicate.

[0093] The acid solution is hydrochloric acid with a molar concentration of 5 mol / L, and the mass ratio of the calcium silicate slurry to the acid solution after dealkalization is 1:1.1. The weight ratio of the solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid after water washing is 1:0.03:0.075, and the weight volume ratio of the solid phase after water washing to N,N-dimethylformamide is 1:55 g / mL.

[0094] Experimental Example 4 The porous calcium silicate provided in Example 7 was tested by scanning electron microscopy (SEM) to obtain the following morphology: Figure 2 The morphology of porous calcium silicate is shown.

[0095] observe Figure 2 It can be seen that the porous calcium silicate product provided in Example 7 presents a highly polymerized three-dimensional cage-type network structure, with a dense internal structure, stronger encapsulation, and more fluffy particles. This honeycomb porous structure further improves the adsorption performance of the porous calcium silicate.

[0096] Experimental Example 5 The specific surface area of ​​the porous calcium silicate provided in Example 6 to Example 8 and Comparative Example 6 to Comparative Example 8 was tested using a specific surface area analyzer; According to GB / T26900-2011 "Bamboo Charcoal for Air Purification", the adsorption performance of the porous calcium silicate provided in Example 6-Example 8 and Comparative Example 6-Comparative Example 8 was tested. At least 3 parallel tests were performed for each test, and the average value was taken. The results are shown in Table 3.

[0097] Table 3 <![CDATA[Specific surface area / m 2 / g]]> Formaldehyde adsorption rate / % TVOC adsorption rate / % Example 6 705 26.5 46.3 Example 7 678 30.34 45.82 Example 8 689 33.28 43.68 Comparative Example 6 402 11.56 12.3 Comparative Example 7 425 12.89 10.56 Comparative Example 8 436 10.96 11.07 After the dealkalized calcium silicate is activated, N,N-dimethylformamide is used as a solvent and 2-aminobenzenesulfonic acid is used as a promoter to react, so that the carboxyl group in 2,5-furandicarboxylic acid reacts with the active group on the surface of the dealkalized calcium silicate, so that the pore structure is further enriched, and the porosity and specific surface area of ​​the porous calcium silicate are further improved.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, ordinary technicians in the field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing porous calcium silicate, characterized in that: The steps include: (1) providing a high modulus water glass solution as a silicon source and lime milk as a calcium source, adding dodecyl trimethyl ammonium chloride and betaine citrate to the high modulus water glass solution to obtain a mixed solution, heating the mixed solution to 75-80° C., and then performing a synthetic reaction with the lime milk under stirring to obtain a calcium silicate slurry; (2) filtering the calcium silicate slurry by hydraulic pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake; (3) adding water to the crude calcium silicate filter cake to obtain a slurry, and heating the slurry to 90-95° C. to obtain a heated slurry; (4) adding a dealkalizing agent to the heated slurry, maintaining the temperature at 90-95° C., and reacting for 20-30 minutes to generate a dealkalized calcium silicate slurry; (5) The de-alkali calcium silicate slurry is subjected to solid-liquid separation to obtain a calcium silicate filter cake, which is then dried and broken up to obtain a finished porous calcium silicate.

2. The method for preparing porous calcium silicate according to claim 1, characterized in that: The preparation process of the high modulus water glass solution comprises: mixing quartz sand with water and sodium hydroxide solution, heating to 150-200° C. and pressurizing to 0.5-0.8 MPa under stirring conditions, reacting for 1.5-4 hours, sending to a water glass transfer tank, cooling to 60-75° C., filtering, and obtaining the high modulus water glass solution.

3. The method for preparing porous calcium silicate according to claim 2, characterized in that: During the preparation of the high modulus water glass solution, the weight ratio of the quartz sand, the water and the sodium hydroxide solution is 3:2-5:1, and the mass concentration of the sodium hydroxide solution is 18%.

4. The method for preparing porous calcium silicate according to claim 1, characterized in that: The modulus of the high modulus water glass solution is 1.6-2.

5.

5. The method for preparing porous calcium silicate according to claim 1, characterized in that: The preparation process of the lime milk comprises: adding water 5-8 times the weight of the quicklime into quicklime, stirring, and digesting for 0.5-1h to obtain the lime milk.

6. The method for preparing porous calcium silicate according to claim 1, characterized in that: During the preparation of the calcium silicate slurry, the weight ratio of the high modulus water glass solution to the lime milk is 1:2.5-3, and the weight ratio of the dodecyltrimethylammonium chloride, the citrate betaine and the high modulus water glass solution is 0.15-0.2:0.2-0.3:

1.

7. The method for preparing porous calcium silicate according to claim 1, characterized in that: In the dealkalization reaction, the dealkalizing agent is aluminum sulfate, and the weight ratio of the slurry to the dealkalizing agent after the heating is 1:0.15-0.

2.

8. The method for preparing porous calcium silicate according to claim 1, characterized in that: Before the dealkalized calcium silicate slurry is subjected to solid-liquid separation, the method further comprises: stirring and mixing the dealkalized calcium silicate slurry with an acid solution, standing for 20-40 minutes to obtain an activated slurry, centrifuging the activated slurry, washing the obtained solid phase with water until the pH value is 8.5-11, dispersing the washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid in N,N-dimethylformamide, reacting at 100-120° C. for 4-10 hours, performing solid-liquid separation, washing, drying and breaking up to obtain the porous calcium silicate.

9. The method for preparing porous calcium silicate according to claim 8, characterized in that: The weight ratio of the water-washed solid phase, the 2,5-furandicarboxylic acid and the 2-aminobenzenesulfonic acid is 1:0.04-0.15:0.05-0.1, and the weight-volume ratio of the water-washed solid phase to the N,N-dimethylformamide is 1:50-60 g / mL.

10. A porous calcium silicate, characterized in that: Obtained according to the preparation method according to claim 9.

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