Porous calcium silicate and preparation method thereof

Abstract

The present application provides a porous calcium silicate and a preparation method thereof, comprising the steps of: providing a high modulus water glass solution as a silicon source, providing lime milk as a calcium source, adding dodecyl trimethylammonium chloride and betaine citric acid, obtaining a mixed solution, heating the mixed solution, reacting with lime synthesis to obtain a calcium silicate slurry; filtering the calcium silicate slurry to obtain a crude calcium silicate filter cake; adding water to pulp to obtain a slurry, heating the slurry, adding a dealkalizing agent, maintaining the temperature at 90-95°C, dealkalizing reaction, generating a dealkalized calcium silicate slurry; solid-liquid separation of the alkali-containing calcium silicate slurry to obtain a calcium silicate filter cake, drying, breaking up, and obtaining a finished porous calcium silicate. The present application significantly improves the specific surface area of ​​porous calcium silicate.

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 exhibits a honeycomb-like porous structure, high specific surface area, and high pore density, making it an excellent adsorption material. Its small particle size, low density, high oil absorption, and large specific surface area contribute to its strong adsorption properties. Its unique structural characteristics enable it to purify formaldehyde, benzene series, and nitrogen oxides from the air and reduce TVOC levels in plastic products. It also effectively removes heavy metal ions and nitrogen and phosphorus from wastewater. Porous calcium silicate has great potential for application in papermaking, rubber, plastics, and inks and coatings. Compared to traditional fillers such as silica and carbon black, it offers lower costs and can achieve the desired results as an alternative filler, facilitating resource recycling. Leveraging its advantages, such as its honeycomb porous structure, high adsorption capacity, high chemical stability, and excellent damping and thermal insulation properties, calcium silicate has broad application prospects as an adsorption material or filler.

[0003] The porous calcium silicate prepared by traditional methods is mainly a mixture of siliceous materials such as fly ash, silica fume, and diatomaceous earth with 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 can 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, which leads to its low adsorption performance. Summary of the Invention

[0004] The present application provides a porous calcium silicate and a preparation method thereof, 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:

[0006] (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;

[0007] (2) Filtering the calcium silicate slurry by pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake;

[0008] (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;

[0009] (4) adding a dealkalizing agent to the heated slurry, maintaining the temperature at 90-95°C and stirring at a speed of 200-600 r / min, and carrying out a dealkalizing reaction for 20-30 minutes to generate a dealkalized calcium silicate slurry;

[0010] (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.

[0011] 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 0.5-0.8 MPa, 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.

[0012] 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%.

[0013] Optionally, the high modulus water glass solution has a modulus of 1.6-2.5.

[0014] Optionally, the preparation process of lime milk includes: adding water 5-8 times the weight of the quicklime to quicklime, stirring, and digesting for 0.5-1 hour to obtain lime milk.

[0015] Optionally, during the preparation 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.

[0016] Optionally, during beating, water is added to the crude calcium silicate filter cake, and the mixture is dispersed and beated at a stirring speed of 400-600 r / min for 1-2 hours to obtain a slurry, wherein the weight ratio of the crude calcium silicate filter cake to water is 1:1-2.

[0017] 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.

[0018] 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, allowing the mixture to stand 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.

[0019] Optionally, the weight ratio of the washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid is 1:0.04-0.15:0.05-0.1, and the weight-to-volume ratio of the washed solid phase to N,N-dimethylformamide is 1:50-60 g / mL.

[0020] In a second aspect, the present application provides a porous calcium silicate, which is obtained by the above-mentioned preparation method.

[0021] The method for preparing porous calcium silicate provided in this application realizes the preparation of porous calcium silicate and has the following beneficial effects compared with the existing technology:

[0022] (1) Calcium silicate is generated by using high modulus water glass solution as a silicon source and 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. At the same time, a certain amount of steric hindrance is formed in the solution to avoid agglomeration of the reactants and to 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 adsorption material, the porous calcium silicate has significant adsorption properties.

[0023] (2) By controlling the addition amount of dodecyltrimethylammonium chloride and betaine citric acid, a balance is achieved between the dispersion stability of the reaction system and the grafting of dodecyltrimethylammonium chloride. It is important to avoid adding too little surfactant, which will not achieve the purpose of uniform dispersion of the system and will result in too little dodecyltrimethylammonium chloride grafted on the surface of calcium silicate, which will not significantly improve the porosity and specific surface area of ​​porous calcium silicate. Adding too much surfactant will result in too much dodecyltrimethylammonium chloride, which is not conducive to improving the porosity and specific surface area of ​​calcium silicate.

[0024] (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 away 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.

[0025] (4) The dealkalized calcium silicate slurry is activated by an acid solution and centrifuged. The resulting solid phase is washed with water to a pH 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

[0026] 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 any creative work.

[0027] 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.

[0028] 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

[0029] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts also fall within the scope of protection of this application.

[0030] In a first aspect, the present application provides a method for preparing porous calcium silicate, the preparation method comprising the following steps:

[0031] (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;

[0032] (2) Filtering the calcium silicate slurry by pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake;

[0033] (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;

[0034] (4) adding a dealkalizing agent to the heated slurry, maintaining the temperature at 90-95°C and stirring at a speed of 200-600 r / min, and carrying out a dealkalizing reaction for 20-30 minutes to generate a dealkalized calcium silicate slurry;

[0035] (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.

[0036] Specifically, high modulus water glass solution is used as silicon source, lime milk is provided as calcium source, water glass solution is an aqueous solution of sodium silicate, silicate (SiO3 2- ) and calcium ions in lime milk (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 colloidal particles. After adding lime milk, Ca 2+ As high-valent cations compress the double layer of the colloid particles, it causes 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. During the reaction process, dodecyl trimethyl ammonium chloride and betaine citrate are first added to a high modulus water glass solution to obtain a mixed solution. After the mixed solution is heated to 75-80°C, it is reacted with lime milk under stirring to obtain a calcium silicate slurry.

[0037] Among them, dodecyl trimethyl ammonium chloride and citric acid betaine 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 the outside of the micelle of the dodecyl trimethyl ammonium chloride surfactant is distributed with a large number of positively charged groups, which can attract silicate ions, so that part of dodecyl trimethyl ammonium chloride is grafted on the outside of calcium silicate, thereby increasing the specific surface area of ​​porous calcium silicate. At the same time, under stirring, citric acid betaine is evenly distributed in the reaction system, and the outside of citric acid betaine 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, avoiding reactant agglomeration, and avoiding excessive adsorption of dodecyl trimethyl ammonium chloride, thereby increasing the specific surface area of ​​subsequent porous calcium silicate, and helping porous calcium silicate to have a good porosity.

[0038] The obtained calcium silicate slurry is hydraulically filtered, and the filter cake is taken and washed with water to obtain a crude calcium silicate filter cake. 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 washing water is washed with the filter cake at least three 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 to carry out a dealkalization reaction. The pH value of the dealkalized calcium silicate slurry is 9.75-11 to remove residual sodium. Excessive residual sodium leads to excessive alkalinity of the calcium silicate, which affects the structure and stability of the 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 properties.

[0039] 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 then dried at 200°C-300°C to a constant weight and broken up to obtain a finished porous calcium silicate.

[0040] 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 process, dodecyltrimethylammonium chloride and betaine citric acid are added to the high modulus water glass solution. Dodecyltrimethylammonium 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 dodecyltrimethylammonium chloride surfactant, which can attract silicate ions, so that part of the dodecyltrimethylammonium 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 external hydroxyl and carboxyl groups of betaine citric acid can repel each other with calcium silicate, further improving the uniformity and stability of the calcium silicate reaction system. At the same time, a certain steric hindrance is formed in the solution to avoid agglomeration of the reactants, and excessive adsorption of dodecyltrimethylammonium chloride can be avoided, thereby increasing the specific surface area of ​​the subsequent porous calcium silicate and helping the porous calcium silicate to have a good porosity. By adding a dealkalizing agent 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. When used as an adsorption material, the porous calcium silicate has significant adsorption performance.

[0041] Alternatively, a high-modulus water glass solution can be prepared by mixing quartz sand with water and sodium hydroxide solution, heating the mixture to 150-200°C and pressurizing it to 0.5-0.8 MPa while stirring. The mixture reacts for 1.5-4 hours before transferring the mixture to a water glass transfer tank, cooling the mixture to 60-75°C, and filtering the mixture to obtain a high-modulus water glass solution. Under high temperature and pressure, sodium hydroxide reacts with the quartz sand hydrothermally to form sodium silicate (Na2SiO3).

[0042] Among them, the particle size of quartz sand is 600-800 mesh.

[0043] Optionally, during the preparation 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%. This ensures sufficient reaction between the quartz sand and the sodium hydroxide solution, avoiding waste of quartz sand and sodium hydroxide.

[0044] Optionally, the high modulus water glass solution has a modulus of 1.6-2.5.

[0045] Optionally, the preparation process of lime milk includes: adding water 5-8 times the weight of the quicklime to quicklime, stirring, and digesting for 0.5-1 hour to obtain lime milk.

[0046] Optionally, during the preparation 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.

[0047] Specifically, the addition amounts of dodecyltrimethylammonium chloride and betaine citric acid are controlled to achieve a balance between the dispersion stability of the reaction system and the grafting of dodecyltrimethylammonium chloride. It is also avoided that too little surfactant addition will fail to achieve the purpose of uniform dispersion of the system, and too little dodecyltrimethylammonium chloride will be grafted onto the surface of the calcium silicate, which will not significantly improve the porosity and specific surface area of ​​the porous calcium silicate. Excessive addition will lead to excessive dodecyltrimethylammonium chloride, which is not conducive to improving the porosity and specific surface area of ​​the calcium silicate.

[0048] Optionally, during beating, water is added to the crude calcium silicate filter cake, and the mixture is dispersed and beated at a stirring speed of 400-600 r / min for 1-2 hours to obtain a slurry, wherein the weight ratio of the crude calcium silicate filter cake to water is 1:1-2.

[0049] 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.

[0050] 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. 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.

[0051] 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, allowing the mixture to stand 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.

[0052] 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 the reaction is carried out at 100-120° C. for 4-10 hours, with N,N-dimethylformamide as a solvent and 2-aminobenzenesulfonic acid 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.

[0053] The acid solution includes nitric acid or hydrochloric acid with a molar concentration of 5moL / L, and the mass ratio of the dealkalized calcium silicate slurry to the acid solution is 1:1-1.2.

[0054] Optionally, the weight ratio of the washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid is 1:0.04-0.15:0.05-0.1, and the weight-to-volume ratio of the washed solid phase to N,N-dimethylformamide is 1:50-60 g / mL.

[0055] In a second aspect, the present application provides a porous calcium silicate, which is obtained by the above-mentioned preparation method.

[0056] The technical solution of this application is described in detail below with reference to specific embodiments.

[0057] Example 1

[0058] A method for preparing porous calcium silicate, comprising the following steps:

[0059] (1) Preparation of high modulus water glass solution: Mix quartz sand with water and sodium hydroxide solution, raise the temperature to 150°C, pressurize to 0.5 MPa, and react for 1.5 hours. Then transfer the mixture to a water glass transfer tank, cool it to 60°C, and filter it to 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 the sodium hydroxide solution is 18%. The modulus of the high modulus water glass solution is 1.6.

[0060] (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.

[0061] (3) Preparation of calcium silicate slurry: provide a high modulus water glass solution as a silicon source and provide lime milk as a calcium source. Add dodecyltrimethylammonium chloride and betaine citric acid to the high modulus water glass solution under stirring to obtain a mixed solution. After heating the mixed solution to 75°C, carry out a synthesis reaction with lime milk under stirring to obtain 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 dodecyltrimethylammonium chloride, betaine citric acid to the high modulus water glass solution is 0.15:0.2:1.

[0062] (4) Filtering the calcium silicate slurry by pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake;

[0063] (5) The crude calcium silicate filter cake was slurried with water, and the mixture was dispersed and slurried at a stirring speed of 400 r / min for 1 h to obtain a slurry, and the slurry was heated to 90° C. to obtain a heated slurry; the weight ratio of the crude calcium silicate filter cake to water was 1:1.

[0064] (4) A dealkalizing agent, aluminum sulfate, was added to the heated slurry. The dealkalizing reaction was carried out for 20 minutes while maintaining the temperature at 90°C and the stirring speed at 200 r / min to generate a dealkalized calcium silicate slurry. The pH value of the dealkalized calcium silicate slurry was 9.8. The weight ratio of the heated slurry to the dealkalizing agent was 1:0.15.

[0065] (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.

[0066] Example 2

[0067] A method for preparing porous calcium silicate, comprising the following steps:

[0068] (1) Preparation of high modulus water glass solution: Quartz sand was mixed with water and sodium hydroxide solution. Under stirring conditions, the temperature was raised to 180°C and the pressure was increased to 0.6 MPa. The mixture was allowed to react for 2.5 hours. The mixture was then transferred to a water glass transfer tank, cooled to 70°C, and filtered to obtain a high modulus water glass solution. The weight ratio of quartz sand, water, and sodium hydroxide solution was 3:3.5:1, and the mass concentration of the sodium hydroxide solution was 18%. The modulus of the high modulus water glass solution was 1.81.

[0069] (2) Preparation of lime milk: Add 7 times the weight of water to quicklime and stir. Digest for 45 minutes to obtain lime milk.

[0070] (3) Preparation of calcium silicate slurry: provide a high modulus water glass solution as a silicon source and provide lime milk as a calcium source. Add dodecyltrimethylammonium chloride and betaine citric acid to the high modulus water glass solution under stirring to obtain a mixed solution. After heating the mixed solution to 78°C, carry out a synthesis reaction with lime milk under stirring to obtain 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 dodecyltrimethylammonium chloride, betaine citric acid to the high modulus water glass solution is 0.18:0.25:1.

[0071] (4) Filtering the calcium silicate slurry by pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake;

[0072] (5) The crude calcium silicate filter cake was slurried with water, and the mixture was dispersed and slurried at a stirring speed of 500 r / min for 1.5 h to obtain a slurry, and the slurry was heated to 92° C. to obtain a heated slurry; the weight ratio of the crude calcium silicate filter cake to water was 1:1.5.

[0073] (4) A dealkalizing agent, aluminum sulfate, was added to the heated slurry. The dealkalizing reaction was carried out for 25 minutes while maintaining the temperature at 92°C and the stirring speed at 400 r / min to generate a dealkalized calcium silicate slurry. The pH value of the dealkalized calcium silicate slurry was 9.9. The weight ratio of the heated slurry to the dealkalizing agent was 1:0.17.

[0074] (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.

[0075] Example 3

[0076] A method for preparing porous calcium silicate, comprising the following steps:

[0077] (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, and react for 4 hours. Then transfer the mixture to a water glass transfer tank, cool it to 75°C, and filter it to obtain a 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 the sodium hydroxide solution is 18%. The modulus of the high modulus water glass solution is 2.

[0078] (2) Preparation of lime milk: Add 8 times the weight of water to quicklime and stir. Digest for 1 hour to obtain lime milk.

[0079] (3) Preparation of calcium silicate slurry: provide a high modulus water glass solution as a silicon source and provide lime milk as a calcium source. Add dodecyltrimethylammonium chloride and betaine citric acid to the high modulus water glass solution under stirring to obtain a mixed solution. After heating the mixed solution to 80°C, carry out a synthesis reaction with lime milk under stirring to obtain 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 dodecyltrimethylammonium chloride, betaine citric acid to the high modulus water glass solution is 0.2:0.3:1.

[0080] (4) Filtering the calcium silicate slurry by pressure, taking the filter cake and washing it with water to obtain a crude calcium silicate filter cake;

[0081] (5) The crude calcium silicate filter cake was slurried with water, and the mixture was dispersed and slurried at a stirring speed of 600 r / min for 2 h to obtain a slurry, and the slurry was heated to 95° C. to obtain a heated slurry; the weight ratio of the crude calcium silicate filter cake to water was 1:2.

[0082] (4) A dealkalizing agent, aluminum sulfate, was added to the heated slurry. The dealkalizing reaction was carried out for 30 minutes while maintaining the temperature at 95°C and the stirring speed at 600 r / min to generate a dealkalized calcium silicate slurry. The pH value of the dealkalized calcium silicate slurry was 9.93. The weight ratio of the heated slurry to the dealkalizing agent was 1:0.2.

[0083] (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.

[0084] Example 4

[0085] A method for preparing porous calcium silicate, comprising the following steps:

[0086] The difference from Example 3 is that:

[0087] (1) During the preparation of the high modulus water glass solution, the modulus of the obtained high modulus water glass solution was 2.14.

[0088] (4) The pH value of the calcium silicate slurry after dealkalization is 10.34.

[0089] Example 5

[0090] A method for preparing porous calcium silicate, comprising the following steps:

[0091] The difference from Example 3 is that:

[0092] (1) During the preparation of the high modulus water glass solution, the modulus of the obtained high modulus water glass solution is 2.5.

[0093] (4) The pH value of the calcium silicate slurry after dealkalization is 11.

[0094] Comparative Example 1

[0095] The difference from Example 3 is that:

[0096] (1) During the preparation of the high modulus water glass solution, the modulus of the obtained high modulus water glass solution was 1.21.

[0097] (4) The pH value of the calcium silicate slurry after dealkalization is 9.98.

[0098] Comparative Example 2

[0099] The difference from Example 3 is that:

[0100] (1) During the preparation of the high modulus water glass solution, the modulus of the obtained high modulus water glass solution was 1.59.

[0101] (4) The pH value of the calcium silicate slurry after dealkalization is 9.85.

[0102] Experimental Example 1

[0103] 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 is shown.

[0104] 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.

[0105] Experimental Example 2

[0106] The specific surface area and conductivity of the porous calcium silicate obtained in Examples 1 to 5 and Comparative Examples 1 and 2 were tested 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.

[0107] Table 1

[0108] 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

[0109] As shown in Table 1, the porous calcium silicate provided in this application has a higher specific surface area than Comparative Examples 1 and 2. Furthermore, as the modulus of the raw material water glass increases, the specific surface area also increases, which helps increase the adsorption sites of the porous calcium silicate and improves adsorption efficiency. Furthermore, Examples 1-5 have good electrical conductivity. Generally, the lower the material's electrical conductivity, the higher the porosity.

[0110] Comparative Example 3

[0111] A method for preparing porous calcium silicate, comprising the following steps:

[0112] The difference from Example 3 is that

[0113] (3) Preparation of calcium silicate slurry: provide a high modulus water glass solution as a silicon source and lime milk as a calcium source, add dodecyltrimethylammonium chloride to the high modulus water glass solution under stirring to obtain a mixed solution, heat the mixed solution to 80°C, and then react with lime milk under stirring to obtain 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 dodecyltrimethylammonium chloride to the high modulus water glass solution is 0.2:1.

[0114] Comparative Example 4

[0115] A method for preparing porous calcium silicate, comprising the following steps:

[0116] The difference from Example 3 is that

[0117] (3) Preparation of calcium silicate slurry: provide a high modulus water glass solution as a silicon source and provide lime milk as a calcium source. Add dodecyltrimethylammonium chloride and betaine citric acid to the high modulus water glass solution under stirring to obtain a mixed solution. After heating the mixed solution to 80°C, carry out a synthesis reaction with lime milk under stirring to obtain 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 dodecyltrimethylammonium chloride, betaine citric acid to the high modulus water glass solution is 0.15:0.28:1.

[0118] Comparative Example 5

[0119] A method for preparing porous calcium silicate, comprising the following steps:

[0120] The difference from Example 3 is that

[0121] (3) Preparation of calcium silicate slurry: provide a high modulus water glass solution as a silicon source and provide lime milk as a calcium source. Add dodecyltrimethylammonium chloride and betaine citric acid to the high modulus water glass solution under stirring to obtain a mixed solution. After heating the mixed solution to 80°C, carry out a synthesis reaction with lime milk under stirring to obtain 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 dodecyltrimethylammonium chloride, betaine citric acid to the high modulus water glass solution is 0.3:0.4:1.

[0122] Experimental Example 3

[0123] 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;

[0124] The adsorption performance of the porous calcium silicate provided in Example 3 and Comparative Examples 3 to 5 was tested in accordance with GB / T26900-2011 "Bamboo Charcoal for Air Purification". At least three parallel tests were performed for each test, and the average value was taken. The results are shown in Table 2.

[0125] Table 2

[0126] <![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

[0127] Note: TVOC is a mixture of benzene, toluene, xylene and ethyl acetate.

[0128] As shown in Table 2, during the reaction, the addition of dodecyl trimethyl ammonium chloride and citric acid betaine not only facilitates the efficient reaction, but also results in a large amount of positively charged groups being distributed outside the micelle of the dodecyl trimethyl ammonium chloride surfactant, which can attract silicate ions and cause some dodecyl trimethyl ammonium chloride to be grafted outside the calcium silicate, thereby improving the specific surface area of ​​porous calcium silicate. Simultaneously, the outside of citric acid betaine 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, thus avoiding reactant agglomeration, and being able to improve subsequent porous calcium silicate specific surface area, thus contributing to porous calcium silicate having a good porosity. As an adsorbent, porous calcium silicate is provided with significant adsorption properties.

[0129] Example 6

[0130] A method for preparing porous calcium silicate, comprising the following steps:

[0131] The difference from Example 3 is that:

[0132] (5) The dealkalized calcium silicate slurry was stirred and mixed with the acid solution and allowed to stand for 20 minutes. The dealkalized calcium silicate was activated and the activated slurry was centrifuged. The obtained solid phase was washed with water until the pH value was 8.5. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid were dispersed in N,N-dimethylformamide and reacted at 100°C for 4 hours. The solid and liquid were separated, washed, dried and dispersed to obtain porous calcium silicate.

[0133] The acid solution was hydrochloric acid with a molar concentration of 5 mol / L, and the mass ratio of the dealkalized calcium silicate slurry to the acid solution was 1:1. The weight ratio of the washed solid phase, 2,5-furandicarboxylic acid, and 2-aminobenzenesulfonic acid was 1:0.04:0.05, and the weight-to-volume ratio of the washed solid phase to N,N-dimethylformamide was 1:50 g / mL.

[0134] Example 7

[0135] A method for preparing porous calcium silicate, comprising the following steps:

[0136] The difference from Example 3 is that:

[0137] (5) The dealkalized calcium silicate slurry was stirred and mixed with the acid solution and allowed to stand for 30 minutes. The dealkalized calcium silicate was activated and the activated slurry was centrifuged. The obtained solid phase was washed with water until the pH value was 10. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid were dispersed in N,N-dimethylformamide and reacted at 110°C for 7 hours. The solid and liquid were separated, washed, dried and dispersed to obtain porous calcium silicate.

[0138] The acid solution was hydrochloric acid with a molar concentration of 5 mol / L. The mass ratio of the dealkalized calcium silicate slurry to the acid solution was 1:1.1. The weight ratio of the washed solid phase, 2,5-furandicarboxylic acid, and 2-aminobenzenesulfonic acid was 1:0.1:0.075, and the weight-to-volume ratio of the washed solid phase to N,N-dimethylformamide was 1:55 g / mL.

[0139] Example 8

[0140] A method for preparing porous calcium silicate, comprising the following steps:

[0141] The difference from Example 3 is that:

[0142] (5) The dealkalized calcium silicate slurry was stirred and mixed with the acid solution and allowed to stand for 40 minutes. The dealkalized calcium silicate was activated and the activated slurry was centrifuged. The obtained solid phase was washed with water until the pH value was 11. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid were dispersed in N,N-dimethylformamide and reacted at 120°C for 10 hours. The solid and liquid were separated, washed, dried and dispersed to obtain porous calcium silicate.

[0143] The acid solution was hydrochloric acid with a molar concentration of 5 mol / L. The mass ratio of the dealkalized calcium silicate slurry to the acid solution was 1:1.2. The weight ratio of the washed solid phase, 2,5-furandicarboxylic acid, and 2-aminobenzenesulfonic acid was 1:0.15:0.1, and the weight-to-volume ratio of the washed solid phase to N,N-dimethylformamide was 1:60 g / mL.

[0144] Comparative Example 6

[0145] A method for preparing porous calcium silicate, comprising the following steps:

[0146] The difference from Example 7 is that

[0147] (5) The dealkalized calcium silicate slurry was stirred and mixed with the acid solution and allowed to stand for 30 minutes to activate the dealkalized calcium silicate. The activated slurry was centrifuged and the obtained solid phase was washed with water until the pH value was 10. The washed solid phase and 2,5-furandicarboxylic acid were dispersed in N,N-dimethylformamide and reacted at 110°C for 7 hours. The solid and liquid were separated, washed, dried, and dispersed to obtain porous calcium silicate.

[0148] The acid solution was hydrochloric acid with a molar concentration of 5 mol / L, and the mass ratio of the dealkalized calcium silicate slurry to the acid solution was 1:1.1. The weight ratio of the washed solid phase to 2,5-furandicarboxylic acid was 1:0.1, and the weight-to-volume ratio of the washed solid phase to N,N-dimethylformamide was 1:55 g / mL.

[0149] Comparative Example 7

[0150] A method for preparing porous calcium silicate, comprising the following steps:

[0151] The difference from Example 7 is that

[0152] (5) The dealkalized calcium silicate slurry was stirred and mixed with the acid solution and allowed to stand for 30 minutes. The dealkalized calcium silicate was activated and the activated slurry was centrifuged. The obtained solid phase was washed with water until the pH value was 10. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid were dispersed in N,N-dimethylformamide and reacted at 110°C for 7 hours. The solid and liquid were separated, washed, dried and dispersed to obtain porous calcium silicate.

[0153] The acid solution was hydrochloric acid with a molar concentration of 5 mol / L. The mass ratio of the dealkalized calcium silicate slurry to the acid solution was 1:1.1. The weight ratio of the washed solid phase, 2,5-furandicarboxylic acid, and 2-aminobenzenesulfonic acid was 1:0.16:0.075, and the weight-to-volume ratio of the washed solid phase to N,N-dimethylformamide was 1:55 g / mL.

[0154] Comparative Example 8

[0155] A method for preparing porous calcium silicate, comprising the following steps:

[0156] The difference from Example 7 is that

[0157] (5) The dealkalized calcium silicate slurry was stirred and mixed with the acid solution and allowed to stand for 30 minutes. The dealkalized calcium silicate was activated and the activated slurry was centrifuged. The obtained solid phase was washed with water until the pH value was 10. The washed solid phase, 2,5-furandicarboxylic acid and 2-aminobenzenesulfonic acid were dispersed in N,N-dimethylformamide and reacted at 110°C for 7 hours. The solid and liquid were separated, washed, dried and dispersed to obtain porous calcium silicate.

[0158] The acid solution was hydrochloric acid with a molar concentration of 5 mol / L. The mass ratio of the dealkalized calcium silicate slurry to the acid solution was 1:1.1. The weight ratio of the washed solid phase, 2,5-furandicarboxylic acid, and 2-aminobenzenesulfonic acid was 1:0.03:0.075, and the weight-to-volume ratio of the washed solid phase to N,N-dimethylformamide was 1:55 g / mL.

[0159] Experimental Example 4

[0160] 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.

[0161] 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.

[0162] Experimental Example 5

[0163] The specific surface area of ​​the porous calcium silicate provided in Examples 6 to 8 and Comparative Examples 6 to 8 was tested using a specific surface area analyzer;

[0164] The adsorption performance of the porous calcium silicate provided in Examples 6 to 8 and Comparative Examples 6 to 8 was tested in accordance with GB / T 26900-2011 "Bamboo Charcoal for Air Purification". At least three parallel tests were performed for each test, and the average value was taken. The results are shown in Table 3.

[0165] Table 3

[0166] <![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

[0167] 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 groups in 2,5-furandicarboxylic acid react with the active groups on the surface of the dealkalized calcium silicate, thereby further enriching the pore structure and further improving the porosity and specific surface area of ​​the porous calcium silicate.

[0168] 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 them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions 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 dodecyltrimethylammonium 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) hydraulically filtering the calcium silicate slurry, 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 carrying out a dealkalizing reaction for 20-30 minutes to generate a dealkalized calcium silicate slurry; (5) The dealkalized 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 product.

2. The method for preparing porous calcium silicate according to claim 1, wherein: 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. and pressurizing to 0.5-0.8 MPa under stirring conditions, reacting for 1.5-4 hours, transferring to a water glass transfer tank, cooling to 60-75° C., and filtering to obtain the high modulus water glass solution.

3. The method for preparing porous calcium silicate according to claim 2, wherein: 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, wherein: 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, wherein: The preparation process of the lime milk comprises: adding water 5-8 times the weight of the quicklime to quicklime, stirring, and digesting for 0.5-1 hour to obtain the lime milk.

6. The method for preparing porous calcium silicate according to claim 1, wherein: 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 citric acid 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, wherein: 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.

8. The method for preparing porous calcium silicate according to claim 1, wherein: Before the dealkalized calcium silicate slurry is subjected to solid-liquid separation, the process further comprises: stirring and mixing the dealkalized calcium silicate slurry with an acid solution, allowing the mixture to stand 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 the mixture to obtain the porous calcium silicate.

9. The method for preparing porous calcium silicate according to claim 8, wherein: The weight ratio of the 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-to-volume ratio of the 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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