A preparation method of thermal insulation precipitated silica

Abstract

The invention discloses a preparation method of thermal insulation precipitated silica, which comprises the following steps: S1, first selecting solid sodium silicate with a modulus of 3.0-3.5, preparing a certain volume of a sodium silicate solution with a concentration of 15-20wt%, preparing a certain volume of a sulfuric acid solution with a concentration of 10-20wt%, and selecting pyrrolidine as a reaction template; S2, adding the sulfuric acid solution prepared in step S1 into a reactor, maintaining the reaction temperature at 50-60°C, and stirring at a speed of 40-60r / min; S3, dropwise adding the sodium silicate solution prepared in step S1 into the sulfuric acid solution obtained in S2, maintaining the reaction temperature and stirring speed unchanged, increasing the stirring speed to 60-80r / min after the dropwise addition is completed, continuing to add the sulfuric acid solution, and stopping the dropwise addition of sulfuric acid when emulsification occurs, at which time the pH is controlled within the range of 9.0-11; the target product of the invention is used as a wall insulation material and has the characteristics of light weight, high porosity, stable chemical properties, low thermal conductivity, good fire resistance, and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon dioxide production, and particularly relates to a method for preparing thermally insulating precipitated silicon dioxide. Background Art

[0002] Exterior wall insulation systems are a major advancement in improving human living conditions. They not only provide thermal insulation for the main structure of a building, but also buffer changes in indoor temperature, avoid possible structural deformation, extend the service life of the building, and improve the durability of the main structure. Therefore, it is very important to develop and optimize new energy-saving wall insulation materials, especially considering that the area of the exterior walls of a building accounts for about 40% of the total building area. Improving the thermal insulation effect of walls is one of the effective measures for energy conservation. Therefore, it is particularly important to gradually develop and optimize new energy-saving wall insulation materials. Silica is a new type of wall insulation material that is currently widely used. It has low thermal conductivity and is an economical and environmentally friendly insulation material. Therefore, silica has high porosity and low thermal conductivity, which can effectively improve the thermal insulation effect of walls. Based on this, it is necessary to develop a preparation method for thermal insulating precipitated silica. Summary of the Invention

[0003] In order to overcome the deficiencies of the prior art, the present invention proposes a method for preparing thermally insulating precipitated silica to solve the above problems.

[0004] To achieve this object, the present invention adopts the following technical solutions:

[0005] S1 first selects solid sodium silicate with a modulus of 3.0-3.5, prepares a certain volume of sodium silicate solution with a concentration of 15-20wt%, prepares a certain volume of sulfuric acid solution with a concentration of 10-20wt%, and selects pyrrolidine as a reaction template;

[0006] S2: Add the sulfuric acid solution prepared in step S1 into the reactor, maintain the reaction temperature at 50-60°C, and stir at a speed of 40-60 r / min;

[0007] S3: adding the sodium silicate solution prepared in step S1 dropwise to the sulfuric acid solution obtained in step S2, maintaining the reaction temperature and stirring speed unchanged. After the addition is complete, the stirring speed is increased to 60-80 r / min, and the sulfuric acid solution is continued to be added. When emulsification occurs, the addition of sulfuric acid is stopped, and the pH is controlled within the range of 9.0-11.

[0008] S4: Add pyrrolidine to the reaction system of S3, raise the reaction temperature to 55-65°C, age for 40 minutes, and then continue to dropwise add sulfuric acid solution until the pH of the reaction system is in the range of 2.5-4.5. Stop dropping sulfuric acid solution, keep stirring at the same speed, and stir for 10-20 minutes to obtain the target product slurry, and the reaction is completed;

[0009] In S5, the slurry is subjected to filter pressing, washing, beating, drying and air flow milling steps to obtain the target product, silicon dioxide.

[0010] The present invention adds pyrrolidine as a reaction template agent, so that more gaps are generated during the growth process of silicon dioxide particles and a higher specific surface area is obtained.

[0011] Preferably, the amount of pyrrolidine added in step S4 is 1% of the mass of silicon dioxide.

[0012] Preferably, in step S5, the drying method is spray drying or freeze drying.

[0013] Preferably, in step S5, the drying method is spray drying.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The porosity of the target product of the present invention reaches 80-85%, and the thermal conductivity is lower than 0.025W / (m·k);

[0016] 2. The present invention uses pyrrolidine as a reaction template to generate more voids during the growth of silica particles and obtain a higher specific surface area;

[0017] 3. The target product of the present invention is used as a wall insulation material and has the characteristics of light weight, high porosity, stable chemical properties, low thermal conductivity, and good fire resistance. DETAILED DESCRIPTION

[0018] To better illustrate the present invention and facilitate understanding of the technical solution of the present invention, the present invention is further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0019] The following are typical but non-limiting examples of the present invention:

[0020] Example 1:

[0021] This embodiment provides a method for thermally precipitating silicon dioxide, the method comprising the following steps:

[0022] S1 first selects solid sodium silicate with a modulus of 3.0-3.5 and prepares a sodium silicate solution with a concentration of 15-20wt%; at the same time, prepares a sulfuric acid solution with a concentration of 10-20wt%, and selects pyrrolidine as a reaction template, and the addition amount is 1% of the mass of silica;

[0023] S2: adding the sulfuric acid solution prepared in step S1 into the reactor, maintaining the reaction temperature in the range of 50-60°C, and stirring at a speed of 40-60 r / min;

[0024] S3: Add the sodium silicate solution prepared in step S1 dropwise to the sulfuric acid solution obtained in step S2. Maintain the reaction temperature and stirring speed unchanged. After the addition is complete, increase the stirring speed to 60-80 rpm and continue adding sulfuric acid solution. Stop adding sulfuric acid when emulsification occurs. At this point, ensure that the pH value of the reaction system is controlled within the range of 9.0-11.

[0025] S4: adding pyrrolidine to the reaction system in S3, raising the reaction temperature to 55-65° C., and maintaining the reaction for 40 minutes for aging; thereafter, continuously adding sulfuric acid solution dropwise until the pH value of the reaction system is within the range of 2.5-4.5; after stopping the addition of sulfuric acid solution, maintaining the stirring rate constant, and continuing stirring for 10-20 minutes to obtain a slurry of the target product; at this point, the reaction is complete;

[0026] Finally, S5, the obtained slurry is processed by filter pressing, washing, beating and other steps; then spray drying is performed to spray the slurry into particles, and air flow pulverization is performed to obtain the final target product, i.e., silicon dioxide;

[0027] It was determined that the silica prepared in this embodiment had a BET of 250-300 m2 / g, a particle size D50 of 10-15 μm, a pore size of 20-50 nm, a porosity of 80-85%, a bulk density of 100-150 kg / m3, a pH of 5.0-8.0, and a thermal conductivity of ≤0.025 W / (m·k) (25°C).

[0028] Example 2:

[0029] This embodiment provides a method for thermally precipitating silica, comprising the following steps:

[0030] S1 first selects solid sodium silicate with a modulus of 3.0-3.5 and prepares a sodium silicate solution with a concentration of 15-20wt%; at the same time, prepares a sulfuric acid solution with a concentration of 10-20wt%, and selects pyrrolidine as a reaction template, and the addition amount is 1% of the mass of silica;

[0031] S2: adding the sulfuric acid solution prepared in step S1 into the reactor, maintaining the reaction temperature in the range of 40-50°C, and stirring at a speed of 40-60 r / min;

[0032] S3: Add the sodium silicate solution prepared in step S1 dropwise to the sulfuric acid solution obtained in step S2; maintain the reaction temperature and stirring speed unchanged. After the addition is complete, increase the stirring speed to 60-80 rpm and continue adding sulfuric acid solution; stop adding sulfuric acid when emulsification occurs. At this time, ensure that the pH value of the reaction system is controlled within the range of 7.0-9.

[0033] S4: Add pyrrolidine to the reaction system in S3, raise the reaction temperature to 45-55°C, and maintain the reaction for 40 minutes for aging. Then, continue to dropwise add sulfuric acid solution until the pH value of the reaction system is within the range of 0.5-2.5. After stopping the dropwise addition of sulfuric acid solution, maintain the stirring speed unchanged and continue stirring for 10-20 minutes to obtain a slurry of the target product. The reaction is now complete.

[0034] Finally, S5, the obtained slurry is processed by filter pressing, washing, beating and other steps; then spray drying is performed to spray the slurry into particles, and air flow pulverization is performed to obtain the final target product, i.e., silicon dioxide;

[0035] It was determined that the silica prepared in this embodiment had a BET of 200-250 m2 / g, a particle size D50 of 8-10 μm, a pore size of 10-20 nm, a porosity of 50-60%, a bulk density of 140-170 kg / m3, a pH of 3.0-5.0, and a thermal conductivity of ≤0.04 W / (m·k) (25°C).

[0036] Example 3

[0037] This embodiment provides a method for thermally precipitating silica, comprising the following steps:

[0038] S1 first selects solid sodium silicate with a modulus of 3.0-3.5 and prepares a sodium silicate solution with a concentration of 15-20wt%; at the same time, prepares a sulfuric acid solution with a concentration of 10-20wt%, and selects pyrrolidine as a reaction template, and the addition amount is 1% of the mass of silica;

[0039] S2: adding the sulfuric acid solution prepared in step S1 into the reactor, maintaining the reaction temperature in the range of 60-70°C, and stirring at a speed of 40-60 r / min;

[0040] S3: Add the sodium silicate solution prepared in step S1 dropwise to the sulfuric acid solution obtained in step S2; maintain the reaction temperature and stirring speed unchanged. After the addition is complete, increase the stirring speed to 60-80 r / min and continue adding sulfuric acid solution; stop adding sulfuric acid when emulsification occurs. At this time, ensure that the pH value of the reaction system is controlled within the range of 11.0-12;

[0041] S4: adding pyrrolidine to the reaction system in S3, raising the reaction temperature to 65-75°C, and maintaining the reaction for 40 minutes for aging; then, continuously adding sulfuric acid solution dropwise until the pH value of the reaction system is within the range of 4.5-6.5; after stopping the addition of sulfuric acid solution, maintaining the stirring rate constant, and continuing stirring for 10-20 minutes to obtain a slurry of the target product; at this point, the reaction is complete;

[0042] Finally, S5, the obtained slurry is processed through steps such as filter pressing, washing, and beating; then spray drying is performed to spray the slurry into particles, and air flow pulverization is performed to obtain the final target product, namely silicon dioxide.

[0043] It was determined that the silica prepared in this embodiment had a BET of 300-350 m2 / g, a particle size D50 of 15-20 μm, a pore size of 30-60 nm, a porosity of 60-75%, a bulk density of 130-180 kg / m3, a pH of 4.0-6.0, and a thermal conductivity of ≤0.03 W / (m·k) (25°C).

[0044] From the above examples, it can be seen that the present invention can obtain silica samples with different properties by precisely controlling the process parameters including pH and temperature and adding pyrrolidine as a reaction template to control the production process and structure of silica microparticles. The method is simple to operate, and the silica that can be prepared has the characteristics of light weight, high porosity, stable chemical properties, low thermal conductivity, and good fire resistance.

[0045] The applicant declares that the present invention is illustrated by the above-described embodiments, but the present invention is not limited to the above-described process. This does not mean that the present invention must rely on the above-described process in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of raw materials and operations, addition of auxiliary raw materials and operations, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing thermal insulation precipitated silica, characterized in that: The method comprises the following steps: S1 first selects solid sodium silicate with a modulus of 3.0-3.5, prepares a certain volume of sodium silicate solution with a concentration of 15-20wt%, prepares a certain volume of sulfuric acid solution with a concentration of 10-20wt%, and selects pyrrolidine as a reaction template; S2: Add the sulfuric acid solution prepared in step S1 into the reactor, maintain the reaction temperature at 50-60°C, and stir at a speed of 40-60 r / min; S3: adding the sodium silicate solution prepared in step S1 dropwise to the sulfuric acid solution obtained in step S2, maintaining the reaction temperature and stirring speed unchanged. After the addition is complete, the stirring speed is increased to 60-80 r / min, and the sulfuric acid solution is continued to be added. When emulsification occurs, the addition of sulfuric acid is stopped, and the pH is controlled within the range of 9.0-11. S4: Add pyrrolidine to the reaction system of S3, raise the reaction temperature to 55-65°C, age for 40 minutes, and then continue to dropwise add sulfuric acid solution until the pH of the reaction system is in the range of 2.5-4.

5. Stop dropping sulfuric acid solution, keep stirring at the same speed, and stir for 10-20 minutes to obtain the target product slurry, and the reaction is completed; In S5, the slurry is subjected to filter pressing, washing, beating, drying and air flow milling steps to obtain the target product, silicon dioxide.

2. The method for preparing thermal insulation precipitated silica according to claim 1, wherein: The amount of pyrrolidine added in step S4 is 1% of the mass of the silicon dioxide.

3. The method for preparing thermal insulation precipitated silica according to claim 1, wherein: The drying method in step S5 is spray drying or freeze drying.

4. The method for preparing thermal insulation precipitated silica according to claim 3, wherein: The drying method in step S5 is spray drying.