Method for preparing silicon dioxide by supergravity continuous carbonization

Abstract

The application discloses a method for preparing silica by supergravity continuous carbonization, which comprises the following steps: 1) dissolving industrial-grade sodium silicate with a modulus of 2-5 in water to prepare a sodium silicate solution with a SiO2 mass fraction of 10-30%, and the initial pH of the solution is 11-14; 2) pumping the sodium silicate solution into a supergravity reactor to circulate, and after the solution temperature is kept constant at 40-80 DEG C, CO2 gas is introduced to perform carbonization reaction, and after the solution pH is reduced to below 8.5, the carbonization reaction is stopped, and the gel product is collected; 3) filtering, washing and drying the gel, and then placing the gel in a muffle furnace to calcine, and grinding to obtain silica powder. The reaction time of the method is shortened by 3-6 times compared with conventional preparation methods, the synthesis efficiency is high, the process operation is simple, the safety performance is good, any additive is not needed to assist, the secondary particle size of the prepared silica is less than <1 um, the distribution range is narrow, and the oil absorption value of the powder is greater than 180 cc / 100g.

Description

Technical Field

[0001] This invention relates to the field of silicon dioxide preparation technology, and specifically to a method for preparing silicon dioxide by continuous carbonization under supergravity. Background Technology

[0002] Silica is an environmentally friendly inorganic non-metallic material widely used in the chemical industry. Common silica is an agglomerate with a primary particle size of nanometers. It has excellent small size effect and macroscopic quantum tunneling effect, large specific surface area, low bulk density and easy dispersion. It is widely used in plastics, rubber, ceramics, pesticides and papermaking industries. It is also used in optoelectronic industries such as optical fiber communication, solar cells and integrated circuits due to its excellent photoelectric properties and thermodynamic stability.

[0003] There are several methods for preparing silica, including gas-phase methods, precipitation methods, sol-gel methods, and microemulsion methods. Among these, precipitation methods have become the best choice for industrial-scale silica preparation due to their advantages such as low raw material requirements, simple and easy operation, and considerable yield. Traditional precipitation methods commonly use silicates such as sodium silicate as raw materials and hydrochloric acid, sulfuric acid, nitric acid, and CO2 as precipitants. However, precipitation methods cannot precisely control crystal growth and formation, and have high requirements for the proportion of raw materials, impurity composition, pH judgment, and temperature in the reaction system. This leads to many significant problems in industrial production, such as a wide silica particle size distribution range, low yield, long reaction time to reach the final pH, and high energy consumption. These factors bring many disadvantages to the preparation of high-quality silica micropowder. Therefore, developing an efficient industrial-scale preparation technology for silica micropowder is currently a research focus.

[0004] In recent years, the preparation technology of silicon dioxide has been advancing, resulting in a series of patented inventions.

[0005] For example, Chinese patent application CN102753137A discloses a "continuous silica production process and silica products prepared by the process". This technology discloses a cyclic process for preparing silica using alkali metal silicates and acid precipitants to obtain silica particles with a median particle size of about 3-10 μm.

[0006] For example, Chinese patent application CN111847461A discloses a "new process for preparing silica by precipitation". This technology discloses that sodium silicate is used as the silicon source, dilute sulfuric acid is used as the precipitant, a chelating agent is added before acidification to remove metal impurities, the acidification reaction time is 1.5-3h, and the aging treatment time is 4.5-6h to obtain silica product.

[0007] For example, Chinese patent application CN108975341A discloses a "method for preparing silicon dioxide by precipitation and the silicon dioxide obtained therefrom". This technology discloses that an acid solution containing sodium dodecylbenzenesulfonate is added to a water glass solution containing sodium sulfate to carry out an acidification precipitation reaction to obtain a silicon dioxide product.

[0008] For example, Chinese patent application CN109319794A discloses "a continuous method for preparing precipitated silica". This technology discloses that a funnel-shaped acid-base high-efficiency mixer is used instead of a traditional kettle stirrer. The silica precipitate is prepared by mixing sodium silicate aqueous solution and sulfuric acid aqueous solution through three steps: seed preparation, precursor synthesis and precipitated silica synthesis.

[0009] For example, Chinese patent application CN120817609A discloses "a method for preparing amorphous silica by carbonization with controllable structure and morphology". This technology discloses that a dilute water glass solution is used as the silicon source. First, NaHCO3 solution is added and CO2 gas is introduced to obtain silica crystal nuclei. Then, the crystal nuclei are mixed into the water glass solution and heated and stirred. The gas-liquid flow field inside the reactor is controlled by a self-aspirating gas redistributor. Silica precipitate is obtained by carbonization at 80-150°C.

[0010] In summary, existing technologies for preparing silica have the following shortcomings: 1) The median particle size of the product in patent application CN102753137A is 3-10 μm, which is unsuitable for the high-end chemical industry; 2) The acidification reaction precipitation time and heat preservation aging time in patent application CN111847461A are both several hours, which is not conducive to continuous and efficient production in industrial scale-up; 3) The preparation technology in patent application CN108975341A requires the assistance of surfactant sodium dodecylbenzenesulfonate and dispersant sodium sulfate to obtain the target product, which increases the preparation cost, the difficulty of product washing, and the cost of wastewater treatment; 4) Patent application CN109319794A requires the prior preparation of seed crystals and precursor solutions, which results in poor batch-to-batch product stability and insufficient production continuity in industrial production; 5) Patent application CN120817609A is synthesized under high temperature and high pressure conditions, which poses certain safety hazards in industrial production. Summary of the Invention

[0011] The technical problem to be solved by this invention is to provide a method for preparing silica by continuous carbonization under supergravity. This method shortens the reaction time by 3-6 times compared to conventional methods, has high synthesis efficiency (e.g., in Example 1 of this invention, the reaction time is shortened by 3.9 times compared to Comparative Example 1), is simple to operate, has good safety performance, requires no additives, and produces silica with secondary particle sizes D90=1.01µm, D50=0.71µm, and D10=0.32µm, a narrow distribution range, good powder dispersibility, and an oil absorption value greater than 180cc / 100g, which meets the requirements for ordinary rubber products.

[0012] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for preparing silicon dioxide by continuous carbonization under supergravity includes the following steps: 1) Raw material preparation: Dissolve industrial grade sodium silicate with a modulus of 2-5 in water to prepare a sodium silicate solution with a SiO2 mass fraction of 10-30% and an initial pH of 11-14. 2) Hypergravity carbonization: The sodium silicate solution is pumped into the hypergravity reactor for circulation. After the solution temperature is constant at 40-80℃, CO2 gas is introduced to carry out the carbonization reaction. When the solution pH drops below 8.5, the carbonization reaction is stopped and the gel product is collected. 3) Post-gel treatment: After filtering, washing and drying the gel, place it in a muffle furnace and calcine it at 400-600℃ for 4-8 hours. Grind it to obtain white silica powder.

[0013] Preferably, in step 2), the gas-liquid ratio of the feed to the supergravity reactor is 2-5.

[0014] Preferably, in step 2), the flow rate of the sodium silicate solution pumped into the hypergravity reaction is 1-3 L / min.

[0015] Preferably, in step 2), the CO2 gas flow rate is 2-15 L / min.

[0016] Preferably, in step 2), the rotor speed of the hypergravity reactor is 900-1500 rpm.

[0017] Preferably, in step 3), the washing involves first washing with tap water 1-3 times, and then washing with ethanol 1-3 times.

[0018] Preferably, in step 3), the drying temperature is 70-100℃ and the drying time is 12-24h.

[0019] Preferably, in step 3), the grinding is carried out using a planetary agate ball mill with grinding balls of 1-4 mm in size and a ball-to-material mass ratio of 6:1-8:1, using ethanol wet grinding.

[0020] Preferably, in step 3), the grinding time is <40 min and the grinding speed is 250-400 rpm.

[0021] Any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0022] Unless otherwise specified, all raw materials used in this invention can be obtained commercially, and the equipment used in this invention can be conventional equipment in the relevant field or refer to existing technology in the relevant field.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) This invention is the first to propose the use of a supergravity reactor for carbonization to prepare silicon dioxide, which shortens the reaction time by 3-6 times and the volume of the synthesis equipment is only 1 / 10 of that of a batch reactor.

[0025] 2) This invention does not require any additives to control crystal particle size, nor does it require seed crystals or precursor preparation steps, making the process simple; it obtains silica gel in one step with a product particle size D50 < 1 μm, a narrow distribution range, and good powder dispersibility; the powder oil absorption value is > 180 cc / 100 g, which meets the HG / T 3061-2020 standard for oil absorption value of silica for rubber.

[0026] 3) This invention is carried out under normal pressure, which avoids the high-pressure operation hazards of traditional autoclave equipment, reduces energy consumption, and is conducive to industrial-scale production. Attached Figure Description

[0027] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Figure 1 This is a process flow diagram of the preparation of silicon dioxide using supergravity carbonization according to the present invention; Figure 2 SEM image of silica prepared in Example 1; Figure 3 SEM image of silica prepared in Example 2; Figure 4 SEM image of silica prepared in Example 3; Figure 5 Here is a SEM image of the silica prepared in Comparative Example 1; Figure 6 Here is a SEM image of the silica prepared in Comparative Example 2; Figure 7 Here is a SEM image of the silica prepared in Comparative Example 3; Figure 8 The image shows a SEM image of the silica prepared in Comparative Example 4. Detailed Implementation

[0028] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0029] As one aspect of the present invention, a method for preparing silicon dioxide by continuous carbonization under supergravity includes the following steps: 1) Raw material preparation: Dissolve industrial grade sodium silicate with a modulus of 2-5 in water to prepare a sodium silicate solution with a SiO2 mass fraction of 10-30% and an initial pH of 11-14. 2) Hypergravity carbonization: The sodium silicate solution is pumped into the hypergravity reactor for circulation. After the solution temperature is constant at 40-80℃, CO2 gas is introduced to carry out the carbonization reaction. When the solution pH drops below 8.5, the carbonization reaction is stopped and the gel product is collected. 3) Post-gel treatment: After filtering, washing and drying the gel, place it in a muffle furnace and calcine it at 400-600℃ for 4-8 hours. Grind it to obtain white silica powder.

[0030] According to certain embodiments of the present invention, in step 2), the feed gas-liquid ratio of the supergravity reactor is 2-5.

[0031] According to certain embodiments of the present invention, in step 2), the flow rate of the sodium silicate solution pumped into the hypergravity reaction is 1-3 L / min.

[0032] According to certain embodiments of the present invention, in step 2), the CO2 gas flow rate is 2-15 L / min.

[0033] According to certain embodiments of the present invention, in step 2), the rotor speed of the hypergravity reactor is 900-1500 rpm.

[0034] According to some embodiments of the present invention, in step 3), the washing is first washing with tap water 1-3 times, and then washing with ethanol 1-3 times.

[0035] According to certain embodiments of the present invention, in step 3), the drying temperature is 70-100°C and the drying time is 12-24 hours.

[0036] According to certain embodiments of the present invention, in step 3), the grinding is carried out using a planetary agate ball mill with grinding balls of 1-4 mm in size and a ball-to-material mass ratio of 6:1-8:1, using ethanol wet grinding.

[0037] According to certain embodiments of the present invention, in step 3), the grinding time is <40 min and the grinding speed is 250-400 rpm.

[0038] Example 1 A method for preparing silicon dioxide by continuous carbonization under supergravity includes the following steps: 1) Raw material preparation: Slowly add liquid sodium silicate with a modulus of 3 to water at 55°C under vigorous stirring to prepare a sodium silicate solution with a SiO2 mass fraction of 25% and an initial pH of 12.8. 2) Hypergravity carbonization: Weigh 4L of the sodium silicate solution prepared in step 1) and pump it into the hypergravity reactor for circulation. After the solution temperature is constant at 55℃, CO2 gas is introduced to carry out the carbonization reaction. The hypergravity rotation speed is 1500rpm. At this time, the liquid flow rate is 1L / min and the gas flow rate is 4L / min. When the solution pH drops below 8.5, the carbonization reaction is stopped. The reaction time is 14min. Collect the gel product. 3) Post-gel treatment: After filtering the gel, wash it twice with water and twice with ethanol, then dry it at 100℃ for 20h. Place the dried product in a muffle furnace and calcine it at 540℃ for 4h. Grind it in a ball mill to obtain white silica powder. The secondary particle size D50 was measured to be 0.71um, and the oil absorption value was 203cc / 100g.

[0039] Figure 2 This is a SEM image of the silica prepared in Example 1.

[0040] Example 2 A method for preparing silicon dioxide by continuous carbonization under supergravity includes the following steps: 1) Raw material preparation: Slowly add liquid sodium silicate with a modulus of 3 to water at 55°C under vigorous stirring to prepare a sodium silicate solution with a SiO2 mass fraction of 25% and an initial pH of 12.8. 2) Hypergravity carbonization: Weigh 4L of the sodium silicate solution prepared in step 1) and pump it into the hypergravity reactor for circulation. After the solution temperature is constant at 55℃, CO2 gas is introduced to carry out the carbonization reaction. The hypergravity rotation speed is 1500rpm. At this time, the liquid flow rate is 1L / min and the gas flow rate is 2L / min. When the solution pH drops below 8.5, the carbonization reaction is stopped. The reaction time is 18min. Collect the gel product. 3) Post-gel treatment: After filtering the gel, wash it twice with water and twice with ethanol, then dry it at 100℃ for 20h. Place the dried product in a muffle furnace and calcine it at 540℃ for 4h. Grind it in a ball mill to obtain white silica powder. The secondary particle size D50 was measured to be 0.92um and the oil absorption value was 187cc / 100g.

[0041] Figure 3 This is a SEM image of the silica prepared in Example 2.

[0042] Example 3 A method for preparing silicon dioxide by continuous carbonization under supergravity includes the following steps: 1) Raw material preparation: Slowly add liquid sodium silicate with a modulus of 3 to water at 55°C under vigorous stirring to prepare a sodium silicate solution with a SiO2 mass fraction of 25% and an initial pH of 12.8. 2) Hypergravity carbonization: Weigh 4L of the sodium silicate solution prepared in step 1) and pump it into the hypergravity reactor for circulation. After the solution temperature is constant at 65℃, CO2 gas is introduced to carry out the carbonization reaction. The hypergravity rotation speed is 1500rpm. At this time, the liquid flow rate is 1L / min and the gas flow rate is 4L / min. When the solution pH drops below 8.5, the carbonization reaction is stopped. The reaction time is 13.5min. Collect the gel product. 3) Post-gel treatment: After filtering the gel, wash it twice with water and twice with ethanol, then dry it at 100℃ for 20h. Place the dried product in a muffle furnace and calcine it at 540℃ for 4h. Grind it in a ball mill to obtain white silica powder. The secondary particle size D50 was measured to be 0.88um and the oil absorption value was 191cc / 100g.

[0043] Figure 4 This is a SEM image of the silica prepared in Example 3.

[0044] Comparative Example 1 Example 1 was repeated, except that in step 2), a traditional batch reactor was used to prepare silica by bubbling, with a carbonization temperature of 55°C, a stirring speed of 500 rpm, a CO2 gas flow rate of 2 L / min, and a reaction time of 55 min. The resulting silica micropowder had a secondary particle size D50 of 7.9 μm, an oil absorption value of 94 cc / 100 g, a wide particle size distribution, and an uneven morphology.

[0045] Figure 5 This is a SEM image of the silica prepared in Comparative Example 1.

[0046] Comparative Example 2

[0047] Repeat Example 1, except that in step 2), the liquid feed rate is 5L / min and the gas flow rate is 30L / min. During the carbonization process, the material overflows due to gravity and cannot react normally. A small amount of silica powder is collected, with a secondary particle size D50 of 5.4um and an oil absorption value of 117cc / 100g.

[0048] Figure 6 This is a SEM image of the silica prepared in Comparative Example 2.

[0049] Comparative Example 3 Repeat Example 1, except that in step 2), the supergravity liquid feed rate is 0.5L / min, the gas flow rate is 0.5L / min, the carbonization reaction time is 22.5min, and the secondary particle size D50 of the obtained silica micro powder is 3.5um, and the oil absorption value is 139cc / 100g.

[0050] Figure 7 This is a SEM image of the silica prepared in Comparative Example 3.

[0051] Comparative Example 4 Example 1 was repeated, except that in step 2), the rotation speed of the supergravity rotor was 500 rpm, the carbonization reaction time was 24 min, and the secondary particle size D50 of the silica micro powder was 6.7 μm with an oil absorption value of 104 cc / 100g.

[0052] Figure 8 This is a SEM image of the silica prepared in Comparative Example 4.

[0053] Table 1 below shows the comparative data of each embodiment and comparative example in the preparation of silica by supergravity carbonization: Table 1

[0054] Therefore, it can be seen that: 1) In Comparative Example 1, the use of traditional autoclave equipment for carbonization resulted in adverse consequences such as silica D50 > 7um and oil absorption value decreasing to 94cc / 100g.

[0055] 2) In Comparative Example 2, due to the rapid increase in gas-liquid feed rate and gas-liquid ratio, the supergravity feed could not react normally and the secondary particle size of silica D50 increased to 5.4 μm, resulting in an adverse consequence of the oil absorption value decreasing to 117 cc / 100g.

[0056] 3) In Comparative Example 3, due to the decrease in gas-liquid feed flow rate and gas-liquid ratio, the carbonization reaction time was extended to 22.5 min, resulting in the adverse consequences that the secondary particle size D50 of the obtained silica micro powder increased to 3.5 μm and the oil absorption value decreased to 139 cc / 100 g.

[0057] 4) In Comparative Example 4, due to the decrease in rotation speed under hypergravity to 500 rpm, the carbonization reaction time was extended to 24 min, resulting in the adverse consequences of the secondary particle size D50 of silica micropowder increasing to 6.7 μm and the oil absorption value decreasing to 104 cc / 100 g.

[0058] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for producing silicon dioxide by supergravity continuous carbonization, characterized by, Includes the following steps: 1) Raw material preparation: Dissolve industrial grade sodium silicate with a modulus of 2-5 in water to prepare a sodium silicate solution with a SiO2 mass fraction of 10-30% and an initial pH of 11-14. 2) Hypergravity carbonization: The sodium silicate solution is pumped into the hypergravity reactor for circulation. After the solution temperature is constant at 40-80℃, CO2 gas is introduced to carry out the carbonization reaction. When the solution pH drops below 8.5, the carbonization reaction is stopped and the gel product is collected. 3) Post-gel treatment: After filtering, washing and drying the gel, place it in a muffle furnace and calcine it at 400-600℃ for 4-8 hours. Grind it to obtain white silica powder.

2. The method of claim 1, wherein the method is a continuous process. In step 2), the gas-liquid ratio of the feed to the supergravity reactor is 2-5.

3. The method for preparing silicon dioxide by continuous carbonization under supergravity according to claim 1, characterized in that: In step 2), the flow rate of the sodium silicate solution pumped into the hypergravity reaction is 1-3 L / min.

4. The method for preparing silicon dioxide by continuous carbonization under supergravity according to claim 1, characterized in that: In step 2), the CO2 gas flow rate is 2-15 L / min.

5. The method for preparing silicon dioxide by continuous carbonization under supergravity according to claim 1, characterized in that: In step 2), the rotor speed of the hypergravity reactor is 900-1500 rpm.

6. The method for preparing silicon dioxide by continuous carbonization under supergravity according to claim 1, characterized in that: In step 3), the washing process involves first washing with tap water 1-3 times, and then washing with ethanol 1-3 times.

7. The method for preparing silicon dioxide by continuous carbonization under supergravity according to claim 1, characterized in that: In step 3), the drying temperature is 70-100℃ and the drying time is 12-24h.

8. The method for preparing silicon dioxide by continuous carbonization under supergravity according to claim 1, characterized in that: In step 3), the grinding is carried out using a planetary agate ball mill with grinding balls of 1-4 mm in size and a ball-to-material mass ratio of 6:1-8:1, using ethanol wet grinding.

9. The method for preparing silicon dioxide by continuous carbonization under supergravity according to claim 1, characterized in that: In step 3), the grinding time is less than 40 minutes and the grinding speed is 250-400 rpm.

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