Preparation method of silicon dioxide with porous structure

Abstract

The invention discloses a preparation method of silicon dioxide with a porous structure, and belongs to the technical field of inorganic new materials. Solid sodium silicate is used as a silicon source, sulfuric acid is used as an acidifying agent, key parameters such as reaction pH, temperature and material dripping rate are strictly controlled through a process route of'one-step sol-gel + pore-foaming agent compounding regulation under acidic conditions', and post-treatment steps such as spray drying and high-temperature firing are combined, so that the high-performance silicon-based composite material is obtained. The prepared silicon dioxide powder is uniform in multi-level pore structure, high in specific surface area and uniform in particle size distribution. The method is simple and efficient in process, low in raw material cost and suitable for industrial mass production.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a method for preparing porous silica. Background Technology

[0002] Porous silica is the most common and widely studied porous material. It has the characteristics of large specific surface area, good adsorption, strong chemical activity, and good biocompatibility, and has broad application prospects in the fields of optics, thermal, acoustics, electricity and chemistry.

[0003] Currently, the main methods for preparing porous silica include physical and chemical methods. Physical methods include mechanical grinding, flame spheroidization, high-temperature melt spraying, and plasma methods; chemical methods mainly include gas-phase methods and liquid-phase methods (sol-gel method, precipitation method, microemulsion method), etc. Physical methods for preparing porous silica have widely available and inexpensive raw materials, but require high-quality quartz and demand specific equipment. Chemical methods, on the other hand, produce spherical silica powder with uniform particle size and higher purity. However, the preparation process requires a large amount of surfactant, which significantly increases production costs. Furthermore, the removal of organic impurities is difficult, leading to agglomeration, making industrial-scale production challenging.

[0004] Currently, over 90% of silica products in China are produced by precipitation, due to its relatively simple production process and significant price advantage. However, precipitation methods suffer from low purity and agglomeration. During production, it is crucial to carefully monitor the effects of factors such as the type of precipitant, silicate concentration, precipitation pH, and temperature on product purity, pore size, and pore size distribution. This results in stringent production conditions and makes it difficult to effectively control the pore size and distribution of silica.

[0005] Therefore, further research and exploration are needed on the industrial production process of porous silica. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for preparing porous silica, which solves the problem that the existing process cannot easily and efficiently control the pore size and distribution of silica.

[0007] To achieve the above objectives, the present invention provides a process for preparing porous silica, comprising the following steps:

[0008] 1) Preparation of dilute alkaline solution: Add solid sodium silicate and process water to a liquefaction tank, liquefy under high temperature and pressure, add process water, stir thoroughly to obtain a dilute alkaline solution with a concentration of 0.1-2.0 mol / L, and set aside for later use.

[0009] 2) Preparation of mother liquor: Dissolve the ionic salt in process water to obtain a mother liquor with a mass fraction of 0.3 to 20.0 wt%, which is then used for later use.

[0010] 3) Preparation of dilute sulfuric acid solution: Prepare a 0.1-5.0 mol / L dilute sulfuric acid solution for later use.

[0011] 4) Sol-gel reaction: Add the mother liquor prepared in step 2) to the reaction vessel, add a certain amount of the dilute sulfuric acid solution obtained in step 3), stir thoroughly at 30-100℃, and continue to add dilute alkali solution and dilute sulfuric acid solution dropwise at a certain flow rate using a liquid feed pump while stirring. After the dilute sulfuric acid solution is added, adjust the pH to 2.0, add the pore-forming agent, and continue stirring until the reaction system gels, then stop adding dilute alkali solution.

[0012] 5) Post-processing: The gel material obtained in step 4) is spray-dried, calcined at high temperature, centrifuged, washed, dried and crushed to obtain silica powder.

[0013] Preferably, the modulus of the solid sodium silicate in step 1) is 3.00 to 3.55;

[0014] Preferably, the ionic salt in step 2) is one or two of sodium sulfate, barium chloride, calcium chloride, strontium nitrate, potassium chloride, sodium fluoride, and potassium sulfate;

[0015] Preferably, the pore-forming agent in step 4) is one, two, or three of the following: nonionic surfactant, cationic surfactant, or water-soluble polymer.

[0016] More preferably, the nonionic surfactant is PEG-2000, PEG-4000, PEG-6000, dodecyl polyethylene glycol ether, dinonylphenol polyoxyethylene ether, coconut oil fatty acid diacetamide, polyoxyethylene (20) sorbitan monolaurate T-20, or glyceryl stearate.

[0017] More preferably, the cationic surfactant is hexadecyltrimethylammonium bromide (CTAB), octadecyltrimethylammonium chloride, N,N-dimethyldodecylamine, solomin A, methyl ditaurate ethyl-2-hydroxyethyl ammonium sulfate, or dodecyl dimethyl benzyl ammonium chloride;

[0018] More preferably, the water-soluble polymer is a low-polymer cellulose ether, starch, xylan, chitosan, galactan, xanthan gum, sorbitol, pectin, sodium alginate, or guar gum.

[0019] Preferably, the amount of mother liquor added in step 4) is 8-20 ml. 3 The amount of dilute sulfuric acid added in advance is 0.1–2.0 mg / L. 3 ;

[0020] Preferably, the weight of the dilute sulfuric acid solution added in step 4) is 4-12 mg / L. 3 The amount of dilute alkali added is 10-30 mg / L. 3 ;

[0021] Preferably, in step 4), the pH of the reaction system is controlled to be less than 2 throughout the entire process;

[0022] Preferably, in step 4), the dropping rate of the dilute alkali solution is 1.0–15.0 m³ / h, and the dropping rate of the dilute sulfuric acid solution is 0.5–7.5 m³ / h. 3 / h;

[0023] Preferably, the high-temperature burning temperature in step 5) is 600-1000℃ and the time is 2h.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] The process is simple and efficient, and can be mass-produced industrially: This invention adopts a one-step sol-gel method, which only involves inexpensive raw materials such as sodium silicate, sulfuric acid, ionic salts and pore-forming agents, and does not require complex equipment. It solves the problem that existing laboratory control methods are difficult to mass-produce, and is suitable for large-scale production.

[0026] The product boasts excellent and adjustable performance: by controlling the alkali concentration, reaction temperature and pH, mother liquor concentration, and the type and amount of pore-forming agent, the macroscopic performance indicators of the final product can be effectively regulated, meeting the needs of different application scenarios.

[0027] The product has high purity and a wide range of applications: the pore-forming agent is completely volatilized through high-temperature calcination, and the product is pure inorganic silica with excellent chemical inertness and biocompatibility. It can be safely used in fields with high purity requirements such as dentistry, food and pharmaceuticals, and medicine. It is also suitable for industrial fields such as catalyst carriers, environmental treatment, and silicone rubber reinforcement. Detailed Implementation

[0028] The following specific embodiments further illustrate the content of the present invention in detail. It should also be understood that the following embodiments are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the principles described in the present invention are within the scope of protection of the present invention.

[0029] The specific process parameters in the examples below are merely examples within a suitable range. Those skilled in the art can make appropriate selections based on the description herein, and are not intended to be limited to the specific data in the examples below. Unless otherwise specified, the raw materials, reagents, or apparatus used in the following examples and comparative examples are all available from conventional commercial sources or can be obtained by existing known methods.

[0030] Example 1

[0031] Preparation of porous silica

[0032] 1. Preparation of dilute alkaline solution: Solid sodium silicate with a modulus of 3.50 is liquefied at high temperature and then water is added to prepare a solution with a concentration of 0.8 mol / L. The solution is stirred for 30 minutes and then set aside.

[0033] 2. Preparation of mother liquor: Add a certain amount of sodium sulfate reagent to the process water to prepare 12.0 m3 of 1.0 wt% sodium sulfate solution, and stir for 30 minutes for later use.

[0034] 3. Preparation of dilute sulfuric acid solution: Concentrated sulfuric acid was slowly added to process water and stirred until homogeneous to prepare a 2.0 mol / L dilute sulfuric acid solution. (6.1 m) 3 .

[0035] 4. Sol-gel reaction: Add 12.0 m³ of mother liquor to the reactor, then add 0.4 m³ of dilute sulfuric acid solution beforehand. Start stirring to bring the pH to 0.8, while maintaining the temperature at 50°C. After thorough stirring, use a feed pump to dispense the solution at a rate of 6.0 m³ / min. 3 Dilute alkali solution is added dropwise at a flow rate of / h, while simultaneously adding it at a rate of 2.7m. 3 Dilute sulfuric acid solution was added dropwise at a flow rate of / h, maintaining the pH at 1.5. After adding the dilute acid solution, dilute alkali solution was continued to be added dropwise until the pH reached 2.0. Then, 7.71 kg (0.3 wt% silica) of a PEG2000-guar gum 1:1 (weight ratio) porogen was added, and stirring continued until the reaction system gelled. The addition of dilute alkali solution was then stopped. The total amount of dilute alkali solution added was 15.3 mg / L. 3 .

[0036] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 200℃, outlet air 90℃), calcined at 700℃ for 2 hours, centrifuged and washed until the conductivity was 180 μs / cm, dried at 110℃ for 5 hours, and then broken up by airflow to obtain porous silica powder.

[0037] Example 2

[0038] Preparation of porous silica

[0039] 1. Preparation of dilute alkaline solution: Solid sodium silicate with a modulus of 3.25 is liquefied at high temperature and then water is added to prepare a solution with a concentration of 1.25 mol / L. The solution is stirred for 30 minutes and then set aside.

[0040] 2. Preparation of mother liquor: Sodium fluoride and strontium nitrate (1:1) are added to process water to form 10 m3 of 8.0 wt% mother liquor solution. Stir for 30 minutes and set aside.

[0041] 3. Preparation of dilute sulfuric acid solution: 8.3 m3 of 3.0 mol / L dilute sulfuric acid solution.

[0042] 4. Sol-gel reaction: Add 10 m³ of mother liquor with a salt content of 8 wt% to the reaction vessel, then add 0.6 m³ of dilute sulfuric acid solution beforehand. Start stirring, keeping the pH below 1 and the temperature at 70℃. After thorough stirring, proceed according to 10.3 m³... 3 Dilute alkali solution is added dropwise at a flow rate of / h, while simultaneously at a rate of 4.3m. 3 Dilute sulfuric acid solution was added dropwise at a flow rate of / h, maintaining the pH at 1.2. After adding the dilute acid solution, dilute alkali solution was added dropwise until the pH reached 2.0. Then, 34.1 kg (0.7 wt% silica) of a chitosan-starch-xanthan gum mixture in a 1:1:2 weight ratio was added as a pore-forming agent. The mixture was stirred until the reaction system gelled, at which point the addition of dilute alkali solution was stopped. The total amount of dilute alkali solution added was 20 mg / h. 3 .

[0043] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 180℃, outlet air 80℃), calcined at 900℃ for 2 hours, centrifuged and washed until the conductivity was 150 μs / cm, dried at 105℃ for 6 hours, and crushed to obtain porous silica powder.

[0044] Example 3

[0045] Preparation of porous silica

[0046] 1. Preparation of dilute alkaline solution: Sodium silicate solution preparation: Solid sodium silicate with a modulus of 3.45 is liquefied at high temperature and then water is added to prepare a solution with a concentration of 1.5 mol / L. The solution is stirred for 30 minutes and ready for use.

[0047] 2. Preparation of mother liquor: Barium chloride and sodium sulfate (1:2) were added to process water and stirred for 30 minutes to obtain a 10.2 wt% mother liquor solution. 3 .

[0048] 3. Preparation of dilute sulfuric acid solution: Prepare 8.1 mL of 3.5 mol / L sulfuric acid solution. 3 spare.

[0049] 4. Sol-gel reaction: Add 8 m³ of mother liquor with a salt content of 10.2 wt% to the reaction vessel, then add 0.3 m³ of dilute sulfuric acid solution beforehand. Start stirring to maintain the pH below 1 and the temperature at 65°C. After thorough stirring, use a feed pump to dispense the solution at a rate of 12.6 m³ / min. 3 Dilute alkali solution is added dropwise at a flow rate of / h, while simultaneously adding it at a rate of 5.3m. 3Dilute sulfuric acid solution was added dropwise at a flow rate of / h, maintaining the pH at 1.8. After adding the dilute acid solution, dilute alkali solution was added dropwise until the pH reached 2.0. Then, 11.7 kg (0.02 wt% silica) of a porogen in a PEG-4000:sorbitol:sodium alginate ratio of 1:1:1 (by weight) was added. The mixture was stirred until the reaction system gelled, at which point the addition of dilute alkali solution was stopped. The total amount of dilute alkali solution added was 18.9 mg / L. 3 .

[0050] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 180℃, outlet air 80℃), calcined at 650℃ for 2 hours, centrifuged and washed until the conductivity was 188μs / cm, dried at 105℃ for 6 hours, and crushed to obtain porous silica powder.

[0051] Example 4

[0052] Preparation of porous silica

[0053] 1. Preparation of dilute alkaline solution: Solid sodium silicate with a modulus of 3.14 is liquefied at high temperature and then mixed with water to prepare a solution with a concentration of 1.00 mol / L. The solution is stirred for 30 minutes and ready for use.

[0054] 2. Preparation of mother liquor: Calcium chloride was added to process water and stirred for 30 minutes to obtain 11.5 ml of a 2.5 wt% mother liquor solution. 3 .

[0055] 3. Preparation of dilute sulfuric acid solution: Prepare 8.1 mL of 3.0 mol / L sulfuric acid solution. 3 spare.

[0056] 4. Sol-gel reaction: Add 11.5 m³ of mother liquor with a salt content of 2.5 wt% to the reactor, then add 0.4 m³ of dilute sulfuric acid solution beforehand. Start stirring to maintain the pH below 1 and the temperature at 70°C. After thorough stirring, use a feed pump to dispense the solution at a rate of 8.2 m³ / min. 3 Add dilute alkali solution dropwise at a flow rate of / h, while simultaneously adding it at a rate of 3.3m. 3 Dilute sulfuric acid solution was added dropwise at a flow rate of / h, maintaining the pH at 1.4. After adding the dilute acid solution, dilute alkali solution was continued to be added dropwise until the pH reached 2.0. Then, 23.3 kg (0.5 wt% silica) of a porogen composed of N,N-dimethyldodecylamine and hemigalactose in a 1:4 weight ratio was added. The mixture was stirred until the reaction system gelled, at which point the addition of dilute alkali solution was stopped. The total amount of dilute alkali solution added was 24.8 mg / h. 3 .

[0057] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 180℃, outlet air 80℃), calcined at 850℃ for 2 hours, centrifuged and washed until the conductivity was 190 μs / cm, dried at 105℃ for 6 hours, and crushed to obtain porous silica powder.

[0058] Example 5

[0059] Preparation of porous silica

[0060] 1. Preparation of dilute alkaline solution: Solid sodium silicate with a modulus of 3.41 is liquefied at high temperature and then water is added to prepare a solution with a concentration of 0.6 mol / L. The solution is stirred for 30 minutes and then set aside.

[0061] 2. Preparation of mother liquor: Sodium fluoride and potassium sulfate were added to process water in a 1:1 ratio and stirred for 30 minutes to obtain a 5.0 wt% mother liquor solution (6.4 m). 3 .

[0062] 3. Preparation of dilute sulfuric acid solution: Prepare 5.4 mL of 1.6 mol / L sulfuric acid solution. 3 spare.

[0063] 4. Sol-gel reaction: Add 6.0 mL of a solution with a salt content of 5.0 wt% to the reaction vessel. 3 Add 0.23 m³ of dilute sulfuric acid solution to the mother liquor, then start stirring to maintain the pH below 1 and the temperature at 95°C. After thorough stirring, use a feed pump to dispense the solution at a rate of 7.2 m³ / min. 3 Dilute alkali solution is added dropwise at a flow rate of / h, while simultaneously adding it at a rate of 2.8m. 3 Dilute sulfuric acid solution was added dropwise at a flow rate of / h, maintaining the pH at 0.9. After adding the dilute acid solution, dilute alkali solution was added dropwise until the pH reached 2.0. Then, 11.50 kg (0.65 wt% silica) of a PEG 4000:xylan mixture in a 2:3 weight ratio was added as a porogen. The mixture was stirred until the reaction system gelled, at which point the addition of dilute alkali solution was stopped. The total amount of dilute alkali solution added was 14.4 m³. 3 .

[0064] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 180℃, outlet air 80℃), calcined at 700℃ for 2 hours, centrifuged and washed until the conductivity was 190 μs / cm, dried at 105℃ for 6 hours, and crushed to obtain porous silica powder.

[0065] Example 6

[0066] Preparation of porous silica

[0067] 1. Preparation of dilute alkaline solution: Solid sodium silicate with a modulus of 3.06 is liquefied at high temperature and then water is added to prepare a solution with a concentration of 2.0 mol / L. The solution is stirred for 30 minutes and then set aside.

[0068] 2. Preparation of mother liquor: Potassium nitrate was added to process water and stirred for 30 minutes to obtain a 15.0 wt% mother liquor solution (18.4 m). 3 .

[0069] 3. Preparation of dilute sulfuric acid solution: Prepare 11.0 mL of 3.98 mol / L sulfuric acid solution. 3 spare.

[0070] 4. Sol-gel reaction: Add 18.4 m³ of mother liquor with a salt content of 15.0 wt% to the reactor, then add 1.2 m³ of dilute sulfuric acid solution beforehand. Start stirring to maintain the pH below 1 and the temperature at 40°C. After thorough stirring, use a feed pump to dispense the solution at a rate of 9.75 m³ / min. 3 Dilute alkali solution was added dropwise at a flow rate of / h, while simultaneously adding it at a rate of 4.93m. 3 Dilute sulfuric acid solution was added dropwise at a flow rate of / h, maintaining the pH at 1.8. After adding the dilute acid solution, dilute alkali solution was continued to be added dropwise until the pH reached 2.0. Then, 61.0 kg (0.78 wt% silica) of a PEG2000-xanthan gum mixture in a 1:2 (weight ratio) was added as a porogen. The mixture was stirred until the reaction system gelled, at which point the addition of dilute alkali solution was stopped. The total amount of dilute alkali solution added was 21.3 mg / L. 3 .

[0071] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 180℃, outlet air 80℃), calcined at 950℃ for 2 hours, centrifuged and washed until the conductivity was 170 μs / cm, dried at 105℃ for 6 hours, and crushed to obtain porous silica powder.

[0072] Comparative Example 1

[0073] Preparation of porous silica

[0074] 1. Preparation of dilute alkaline solution: Solid sodium silicate with a modulus of 3.33 is liquefied at high temperature and then water is added to prepare a solution with a concentration of 0.9 mol / L. The solution is stirred for 30 minutes and then set aside.

[0075] 2. Preparation of mother liquor: Sodium sulfate was added to process water and stirred for 30 minutes to obtain a 4.0 wt% mother liquor solution (7.5 ml). 3 .

[0076] 3. Preparation of dilute sulfuric acid solution: Prepare 4.2 mL of 2.7 mol / L sulfuric acid solution. 3 spare.

[0077] 4. Sol-gel reaction: Add 7.5 m³ of mother liquor with a salt content of 4.0 wt% to the reaction vessel, then add 0.25 m³ of dilute sulfuric acid solution beforehand. Start stirring to maintain the pH below 1 and the temperature at 85℃. After thorough stirring, use a feed pump to dispense the solution at a rate of 8.5 m³ / min. 3 Dilute alkali solution is added dropwise at a flow rate of / h, while simultaneously adding it at a rate of 3.0m. 3 Dilute sulfuric acid solution was added dropwise at a flow rate of / h, with the pH controlled at 1.4. After the addition of the dilute acid solution, dilute alkali solution was added dropwise, and stirring continued until the reaction system gelled. The addition of dilute alkali solution was then stopped. The total amount of dilute alkali solution added was 12.8 mg / h. 3 .

[0078] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 180℃, outlet air 80℃), calcined at 950℃ for 2 hours, centrifuged and washed until the conductivity was 170 μs / cm, dried at 105℃ for 6 hours, and crushed to obtain porous silica powder.

[0079] Comparative Example 2

[0080] Preparation of porous silica

[0081] 1. Preparation of dilute alkaline solution: Solid sodium silicate with a modulus of 3.31 is liquefied at high temperature and then water is added to prepare a solution with a concentration of 1.37 mol / L. The solution is stirred for 30 minutes and then set aside.

[0082] 2. Preparation of mother liquor: Sodium fluoride was added to process water and stirred for 30 minutes to obtain a 7.3 wt% mother liquor solution (7.89 mL). 3 .

[0083] 3. Preparation of dilute sulfuric acid solution: Prepare 6.5 mL of 3.71 mol / L sulfuric acid solution. 3 spare.

[0084] 4. Sol-gel reaction: Add 7.89 m³ of mother liquor with a salt content of 7.3 wt% to the reaction vessel, then add 0.41 m³ of dilute sulfuric acid solution beforehand. Start stirring to maintain the pH below 1 and the temperature at 65°C. After thorough stirring, use a feed pump to dispense the solution at a rate of 8.5 m³ / min. 3 Dilute alkali solution is added dropwise at a flow rate of / h, while simultaneously adding it at a rate of 3.2m. 3 Dilute sulfuric acid solution was added dropwise at a flow rate of / h, with the pH controlled at 1.7. After the addition of the dilute acid solution, dilute alkali solution was added dropwise, and stirring continued until the reaction system gelled. The addition of dilute alkali solution was then stopped. The total amount of dilute alkali solution added was 17.8 mg / h. 3 .

[0085] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 180℃, outlet air 80℃), calcined at 900℃ for 2 hours, centrifuged and washed until the conductivity was 180 μs / cm, dried at 105℃ for 6 hours, and crushed to obtain porous silica powder.

[0086] Comparative Example 3

[0087] Preparation of porous silica

[0088] 1. Preparation of dilute alkaline solution: Solid sodium silicate with a modulus of 3.01 is liquefied at high temperature and then water is added to prepare a solution with a concentration of 0.8 mol / L. The solution is stirred for 30 minutes and then set aside.

[0089] 2. Preparation of mother liquor: Strontium nitrate was added to process water and stirred for 30 minutes to obtain a 1.6 wt% mother liquor solution. (14 ml) 3 .

[0090] 3. Preparation of dilute sulfuric acid solution: Prepare 8.3 mL of 2.3 mol / L sulfuric acid solution. 3 spare.

[0091] 4. Sol-gel reaction: Add 14 m³ of mother liquor with a salt content of 1.6 wt% to the reaction vessel, while controlling the temperature at 70℃. After thorough stirring, use a feed pump to dispense the solution at a rate of 18.6 m³ / min. 3 Dilute alkali solution is added dropwise at a flow rate of / h, while simultaneously adding it at a rate of 6.5m. 3 Dilute sulfuric acid solution was added dropwise at a flow rate of / h, with the pH controlled at 8. After adding the dilute alkali solution, 10.3 kg (0.3 wt% silica) of a porogen composed of octadecyltrimethylammonium chloride and solomon's A in a weight ratio of 1:3 was added. Stirring was continued for 30 min until the reaction system gelled. The addition of the dilute alkali solution was then stopped. The total amount of dilute alkali solution added was 23.7 m³. 3 .

[0092] 5. Post-processing: The gel material obtained in step 4 was spray-dried (inlet air 180℃, outlet air 80℃), calcined at 650℃ for 2 hours, centrifuged and washed until the conductivity was 180 μs / cm, dried at 105℃ for 6 hours, and crushed to obtain porous silica powder.

[0093] Performance testing

[0094] The products of the above embodiments and comparative examples were subjected to performance tests, including the following indicators.

[0095] 1. Specific surface area (BET) and pore volume: tested using the static volumetric method.

[0096] 2. Oil Absorption Value (DOA): Tested according to standard ASTM-D281.

[0097] 3. Center aperture D50 Tested according to national standard GB / T 19077-2016.

[0098] 4. CTAB value: Tested according to standard ASTM D6845-18.

[0099] The test results are shown in Table 1.

[0100] Table 1 Performance test results of porous silica

[0101] project BET(㎡ / g) CTAB (m² / g) <![CDATA[D 50 (nm)]]> <![CDATA[Pore volume (cm 3 / g)]]> DOA (ml / 100g) Example 1 430.23 300.18 15.97 1.72 108 Example 2 699.00 655.2 14.57 2.55 80 Example 3 582.31 302.34 9.12 1.32 60 Example 4 532.98 434.23 15.93 2.12 102 Example 5 377.32 369.12 20.12 1.89 42 Example 6 783.12 699.29 14.53 2.84 123 Comparative Example 1 532.46 174.29 5.23 0.69 92 Comparative Example 2 473.09 157.20 4.23 0.50 70 Comparative Example 3 187.44 134.02 10.23 0.48 143

[0102] The test results from the above embodiments show that the present invention can effectively control the macroscopic performance indicators of the final product, such as specific surface area and oil absorption value, by controlling the concentration of dilute alkaline solution, reaction temperature, mother liquor concentration, and the type and amount of pore-forming agent. Compared with the comparative example, the analysis of the embodiments shows that by applying the technical route of the present invention, silica products with high specific surface area and high porosity can be obtained.

Claims

1. A preparation process of porous silica, comprising the following steps: 1) Preparation of dilute alkali solution: solid sodium silicate and process water are added into a liquefaction tank, and after high-temperature and high-pressure liquefaction, the process water is fully stirred to obtain a dilute alkali solution with a concentration of 0.1-2.0 mol / L, which is ready for use; 2) Preparation of mother liquor: an ionic salt is dissolved in process water to obtain a mother liquor with a mass fraction of 0.3-20.0 wt%, which is ready for use; 3) Preparation of dilute sulfuric acid solution: a dilute sulfuric acid solution with a concentration of 0.1-5.0 mol / L is prepared, which is ready for use; 4) Sol-gel reaction: the mother liquor prepared in step 2) is added into a reaction kettle, a certain amount of the dilute sulfuric acid solution prepared in step 3) is added in advance, and after fully stirring at 30-100℃, the dilute alkali solution and the dilute sulfuric acid solution are added dropwise at a certain flow rate under stirring, after the addition of the dilute sulfuric acid solution is completed, the pH is adjusted to 2.0, a pore-forming agent is added, and the stirring is continued until the reaction system is gelled, and the addition of the dilute alkali solution is stopped; 5) Post-treatment process: the gelled material obtained in step 4) is spray dried, high-temperature calcined, centrifugally washed, dried, and crushed to obtain a silica powder.

2. The preparation process of claim 1, wherein, In step 1), the modulus of the solid sodium silicate is 3.00-3.

55.

3. The preparation process of claim 1, wherein, In step 2), the ionic salt is one or two of sodium sulfate, barium chloride, calcium chloride, strontium nitrate, potassium chloride, sodium fluoride, and potassium sulfate.

4. The preparation process of claim 1, wherein, In step 4), the pore-forming agent is one, two, or three of a non-ionic surfactant, a cationic surfactant, or a water-soluble high-molecular polymer.

5. The preparation process according to claim 4, wherein the non-ionic surfactant is PEG-2000, PEG-4000, PEG-6000, dodecyl polyethylene glycol ether, dinonyl phenol polyoxyethylene ether, coconut fatty acid diacetamide, polyoxyethylene (20) sorbitan monolaurate T-20, glycerol stearate; the cationic surfactant is cetyltrimethylammonium bromide CTAB, octadecyltrimethylammonium chloride, N,N dimethyl dodecyl amine, soromin A, methyl di-tallowoyl ethyl-2-hydroxyethyl methyl ammonium sulfate, dodecyl dimethyl benzyl ammonium chloride; and the water-soluble high-molecular polymer is a low polymer cellulose ether, starch, xylan, chitosan, galactan, xanthan gum, sorbitol, pectin, sodium alginate, and guar gum. In step 4), the pH of the reaction system is controlled to be less than 2 throughout the process. In step 5), the high-temperature calcination temperature is 600-1000℃, and the time is 2 h. ​ 6. The preparation process of claim 1, wherein, The amount of mother liquor added in step 4) is 8-20 m 3 , and the amount of dilute sulfuric acid added in advance is 0.1-2.0 m 3 .

7. The preparation process of claim 1, wherein, The amount of the dilute sulfuric acid solution added in the step 4) is 4-12 m 3 ; and the amount of the dilute alkali solution added is 10-30 m 3 .

8. The preparation process of claim 1, wherein, ​ 9. The preparation process of claim 1, wherein, The dropping speed of the dilute alkali solution in the step 4) is 1.0-15.0 m 3 / h, and the dropping speed of the dilute sulfuric acid solution is 0.5-7.5 m 3 / h.

10. The preparation process of claim 1, wherein, ​