A method for producing white carbon black by carbonization

Abstract

This invention discloses a method for producing silica using a carbonization process. Industrial water glass is used as raw material, diluted with deionized water to a concentration of 5-15 wt%. 4-6 wt% sodium bicarbonate is added as an electrolyte, and 0.005-0.01 wt% sodium dodecylbenzenesulfonate is added as a dispersant. The carbonization reaction temperature is 50-80℃, and the reaction endpoint is determined by pH value. The carbonization reaction is carried out in three tandem bubble columns of identical size and structure. The first is the main carbonization column, and the second and third are carbonization-washing columns. The stirring speed is 300-350 r / min. After the reaction in the third column is completed, the silica product is obtained through filtration, aging, ethanol replacement, and drying. This invention solves the problems of difficult washing and low surface area of ​​silica caused by gel dissociation and agglomeration during traditional carbonization-based silica production. Testing shows that the silica produced by this invention stably meets the Class A standard requirements of HG / T-3061-2020 for hydrated silica in rubber compounding agents.

Description

Technical Field

[0001] This invention relates to the technology for preparing precipitated silica by water glass carbonization, which belongs to the field of fine inorganic chemicals. Background Technology

[0002] Silica is short for amorphous hydrated silica. It has excellent properties such as porosity, large specific surface area, high dispersibility, light weight, and good chemical stability. It is an important fine inorganic chemical product with wide applications in various fields such as rubber, plastics, pesticides, paints, inks, papermaking, pharmaceuticals, and daily chemicals.

[0003] Currently, industrialized methods for producing precipitated silica both domestically and internationally fall into two main categories: gas-phase methods and precipitation methods. Compared to gas-phase methods, precipitation methods offer advantages such as simpler production processes, lower investment, and lower costs, making them the mainstream process for precipitated silica production. Precipitation methods typically use water glass as raw material and strong acids such as sulfuric acid, hydrochloric acid, and nitric acid as precipitants. The reaction is a liquid-liquid reaction with a fast reaction rate, simple production process, and stable precipitated silica product quality. However, it also generates a large amount of low-concentration sodium salt wastewater, which has low value and high recovery costs, increasing the overall cost of precipitated silica production. This is the main problem with using strong acids as precipitants. In contrast, carbonation methods produce carbonates with high added value and have a significant carbon emission reduction effect. Furthermore, CO2 gas is mostly a byproduct with low cost, demonstrating the cost and carbon emission reduction advantages of carbonation methods. However, the following problems are the main reasons why carbonation methods have not yet replaced traditional strong acids as precipitants: 1. CO2 has weak acidity, making it difficult to adjust the pH of the carbonization solution to below 8, which directly affects the quality of silica products; 2. The carbonization process for producing silica involves a gas-liquid-solid three-phase reaction. The reaction rate is controlled by the solubility of CO2. The reaction rate is slow and the reaction time is long. Water glass dissociates and precipitates silica flocculent precipitates, forming polymerization centers and causing severe encapsulation, which affects the quality of silica. 3. Increasing the temperature is beneficial for sol dissociation and prevents gel aggregation, but it will affect CO2 solubility and thus reduce the carbonization reaction rate.

[0004] Based on this, ZL201510010298 proposed using a high-pressure spray tower to enhance the reaction process and control particle size, resulting in stable quality of the prepared silica product; CN202411392574.8 proposed enhancing the reaction process and controlling product particle size and structure by increasing the pressure of the reactor; CN202410988128.7 proposed carrying out the carbonization reaction in a double-circulation double-effect device, enhancing mixing through external circulation to increase the reaction rate, and installing several ultrasonic transducers and microwave radiators on the side inside the carbonization tank to control product particle size; ZL201310165170.0 proposed using low-modulus water glass as raw material and sodium sulfate as solvent to enhance sol dissociation and prepare silica by carbonization; CN202311127112.9 proposed a method for preparing highly dispersible silica by using industrial water glass as raw material, adding one or more combinations of surfactants, electrolytes, and ammonium salts, and employing multi-reactor series pressurized carbonization. CN202010037188.2 utilizes the high-speed characteristics of supersonic carbon dioxide to enhance the reaction between CO2 and water glass, reducing the pH of the reaction system to below 8.8. After solid-liquid separation, washing, and spray drying, spherical silica is obtained. The primary particle size of the silica is 40–62 nm, and the SiO2 purity of the silica product is not less than 97%. Meanwhile, many research papers have also prepared silica products with nanoscale particle sizes and normal distribution by controlling the CO2 throughput during the carbonization process, using sodium carbonate as an electrolyte, adding surfactants, and enhancing the carbonization reaction process, or by combining surface grafting modification to improve the physical properties of silica products.

[0005] This invention, based on existing research reports, addresses the advantages and disadvantages of current carbonization-based silica production methods. It proposes using sodium bicarbonate as the electrolyte and sodium dodecylbenzene sulfonate as the dispersant, coupling carbonization with carbonization-washing. This shortens the pH adjustment time, improves the washing effect, and avoids the impact of water glass dissociation and gel condensation on the finished silica product. This is of great significance for the industrialization of carbonization-based silica. Summary of the Invention

[0006] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution: A carbonization method for producing silica involves using industrial water glass as raw material, sodium bicarbonate as electrolyte, sodium dodecylbenzenesulfonate as dispersant, and industrial carbon dioxide as precipitant. Carbonization and washing are carried out in a bubbling tower, followed by aging, ethanol replacement, and drying to produce silica.

[0007] The bubble column consists of three columns connected in series, namely, the first bubble column (carbonization column 1), the second bubble column (carbonization column 2), and the third bubble column (carbonization column 3). The specific production method includes the following steps: First production: S1. Prepare a sodium silicate solution with a mass content of 5-15 wt% by adding industrial water glass and deionized water. Add the solution to the first bubble column. Add 4-6 wt% sodium bicarbonate and 0.005-0.01 wt% sodium dodecylbenzenesulfonate from the industrial water glass solution to the first bubble column. Control the stirring speed at 300-350 r / min and the carbonization temperature at 50-80℃. Introduce industrial carbon dioxide. When the pH of the reaction solution is 9.0±0.2, stop the aeration and heating and pump the reaction solution to the filter to obtain a primary filter cake and a primary filtrate. S2. The primary filter cake obtained in step S1 is adjusted with deionized water to form a slurry with a solid content of 10-15 wt%. At the same time, 0.005-0.01 wt% sodium dodecylbenzenesulfonate industrial water glass solution is added and transferred to the second bubble column. The stirring speed is controlled at 300-350 r / min, the carbonization temperature is 50-80℃, and industrial carbon dioxide is introduced. When the pH of the reaction solution is 8.2±0.2, the aeration and heating are stopped, and the reaction solution is pumped to the filter to obtain the secondary filter cake and secondary filtrate. S3. Add deionized water to the secondary filter cake obtained in step S2 to adjust it into a slurry with a solid content of 10-15 wt%. At the same time, add 0.005-0.01 wt% sodium dodecylbenzenesulfonate industrial water glass solution and transfer it to the third bubble column. Control the stirring speed at 300-350 r / min and the carbonization temperature at 50-80℃, and introduce industrial carbon dioxide. When the pH of the reaction solution is 7.6±0.2, end the carbonization operation. Send the obtained reaction solution to a filter for solid-liquid separation to obtain a third filter cake and a third filtrate. S4. Add deionized water to the obtained three-stage filter cake to make a slurry of 20-30wt%. After stirring thoroughly, let it stand and age at 80-90℃ for 20-24 hours, then filter. Soak the filter cake in anhydrous ethanol of 2-3 times the weight of the filter cake for 12-24 hours, then filter and dry to obtain the white carbon black product. Normal production: The sodium bicarbonate added in step S1 is a solution obtained by concentrating and crystallizing the primary filtrate. The deionized water in step S1 is replaced by the secondary filtrate obtained in step S2; The deionized water in step S2 is replaced by the three filtrates obtained in step S3; Sodium dodecylbenzenesulfonate is no longer added in steps S1 and S2.

[0008] The modulus of the water glass is 2.8-3.2.

[0009] The volume concentration of CO2 in the industrial carbon dioxide is ≥98.5%.

[0010] The prepared silica product meets the Class A standard quality requirements of HG-T-3061-2020 Rubber Compounding Agents Hydrated Silica.

[0011] The bubble column described in this invention has a diameter of 1m and a height of 5m. Five baffles, each 4.5m high and 0.1m long, are longitudinally arranged on the inner wall of the bubble column. Four sets of stirring blades, each 0.7m in diameter and 1.2m apart, are arranged from top to bottom inside the bubble column. The bottom stirring blade is the bottom blade. A gas distributor is also provided at the bottom of the bubble column, positioned below the bottom blade and 0.1m away from it. The bottom of the gas distributor is connected to a CO2 inlet pipe.

[0012] This invention relates to a method for producing precipitated silica using water glass as raw material via carbonization. The entire carbonization process consists of three bubble columns connected in series. The carbonization separation liquid is recycled, while the third bubble column contains deionized water. Industrial water glass with a modulus of 2.8-3.2 is used as raw material. During the initial production run, the water glass concentration is diluted to 5-15 wt% with deionized water. During normal production, carbonization concentrate is added to replenish the electrolyte. During the initial production run, 0.005-0.01 wt% sodium dodecylbenzenesulfonate solution is added to each column as a dispersant to prevent excessive aggregation and encapsulation of colloids. During normal production, the carbonization separation liquid is recycled, and the dispersant is only added to the third column. The carbonization reaction temperature is 50-80℃, with the first bubble column being the main carbonization column. The first and second bubbling towers primarily function as washing towers, with carbonization as a secondary process. Material transfer between towers is determined by pH. All three towers are identical in size, with a diameter of 1m and a height of 5m. Each tower contains five baffles measuring 4.5m x 0.1m. The stirring speed is 300-350 rpm, and the stirring blades are paddle-type with a diameter of 0.7m. The stirring blades consist of four sets, alternating between forward and reverse directions with a spacing of 1.2m. After the reaction in the third bubbling tower is completed, the product is obtained through filtration, aging, ethanol replacement, and drying.

[0013] The carbonization method for producing silica of the present invention has the following advantages compared with the traditional carbonization method: 1. The main equipment for the carbonization process is a bubble column, which has a simple structure and is easy to operate; 2. Carbonization and washing are both carried out in a bubble tower, which achieves step-by-step carbonization and washing of silica at the same time. This avoids the slow pH reduction, long carbonization time, gel dissociation and precipitation at high electrolysis concentrations in a single carbonization tower, and excessively large particles generated by condensation with precipitation as the core, thereby reducing oil absorption value and specific surface area. 3. This study is the first to propose using sodium bicarbonate as an electrolyte, taking advantage of sodium bicarbonate's low pH and HCO3- content. -The mild interaction between anions and hydroxyl groups on the surface of silica gel effectively promotes the breaking of silicon-oxygen bonds in silica gel, prevents excessive aggregation of gel, and shortens carbonization reaction time. 4. The sodium in the carbonation separation liquid is mainly sodium bicarbonate. After concentration, it can be returned to the carbonation tower as an electrolyte. A portion can be further concentrated and crystallized to produce sodium bicarbonate, which has high recovery value and avoids the problem of adding new electrolytes in traditional methods. Attached Figure Description

[0014] Figure 1 This is a process flow diagram of the present invention; Figure 2 This is a front view schematic diagram of the bubble column of the present invention; Figure 3 This is a top view of the bubble column of the present invention; In the diagram: 1-bubbling tower, 2-stirring blade, 3-baffle, 4-CO2 inlet pipe, 5-gas distributor, 6-bottom blade. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited by the embodiments. Example 1

[0016] Initial production: Industrial water glass with a modulus of 3.0 was mixed with deionized water to prepare a sodium silicate solution with a mass content of 10%. The total mass of 3500 kg was added to the first bubble column, along with 175 kg of sodium bicarbonate (5 wt% of the water glass solution) and 0.28 kg of sodium dodecylbenzenesulfonate (0.008%). Steam was introduced to heat the mixture at a stirring speed of 300 r / min and maintain the reaction temperature at 50°C. CO2 gas with a volume concentration of 98.5% was introduced. When the pH of the carbonized liquid reached 9.0, the gas supply and heating were stopped, and the reaction solution was pumped to a filter to obtain the first filter cake and the first filtrate.

[0017] The first filter cake was mixed with deionized water to form a slurry with a solid content of 12 wt%, and 0.175 kg of sodium dodecylbenzenesulfonate was added. The mixture was then transferred to the second bubble column. After being heated to 60°C with steam, CO2 gas with a volume concentration of 98.5% was introduced. When the pH of the carbonized liquid reached 8.2, the gas supply and heating were stopped, and the reaction liquid was pumped to the filter to obtain the second filter cake and the second filtrate.

[0018] The second filter cake was mixed with deionized water to form a slurry with a solid content of 12 wt%, and 0.35 kg of sodium dodecylbenzenesulfonate was added. The mixture was then transferred to the third bubble column. After being heated to 60°C with steam, CO2 gas with a volume concentration of 98.5% was introduced. When the pH of the carbonized liquid reached 7.5, the gas supply and heating were stopped, and the reaction liquid was pumped to the filter to obtain the third filter cake and the third filtrate.

[0019] The third filter cake was mixed with deionized water to form a 20wt% slurry. After thorough stirring, it was allowed to stand at 90℃ for 20 hours and then filtered. The filter cake was then soaked in anhydrous ethanol with twice its weight for 12 hours, filtered, and dried to obtain the silica product. The test results of relevant indicators of the prepared silica product are shown in Table 1.

[0020] Table 1. Test results of relevant indicators of the silica product prepared in Example 1

[0021] Example 2

[0022] Normal production: 500 kg of industrial water glass with a modulus of 3.2 and a sodium silicate content of 35%, 192 kg of concentrated crystals from the first filtrate obtained in the first production (solid content of 73 wt%), and 2808 kg of the second filtrate are mixed to prepare a 3500 kg mixture with a sodium bicarbonate content of 4 wt% and a sodium silicate content of 5 wt%. This mixture is added to the first bubble column, heated with steam at a stirring speed of 350 r / min, and the reaction temperature is maintained at 50°C. 98.5% CO2 gas is introduced. When the pH of the carbonized liquid reaches 8.8, the gas supply and heating are stopped, and the reaction solution is pumped to a filter to obtain the first filter cake and the first filtrate. The first filter cake is mixed with the third filtrate obtained in the first production and transferred to the second bubble column. The mixture is heated to 80°C with steam and then... CO2 gas with a volume concentration of 98.5% was introduced. When the pH of the carbonization solution reached 7.8, the gas flow and heating were stopped, and the reaction solution was pumped to a filter to obtain a second filter cake and a second filtrate. The second filter cake was mixed with deionized water to form a slurry with a solid content of 10 wt%, and 0.25 kg of sodium dodecylbenzenesulfonate was added. The mixture was then transferred to a third tower. After heating with steam to 80°C, CO2 gas with a volume concentration of 98.5% was introduced. When the pH of the carbonization solution reached 7.4, the gas flow and heating were stopped, and the reaction solution was pumped to a filter to obtain a third filter cake and a third filtrate. The third filter cake was mixed with deionized water to form a 30 wt% slurry. After thorough stirring, the mixture was allowed to stand at 80°C for 24 hours and then filtered. The filter cake was then soaked in anhydrous ethanol with a volume of 3 times its weight for 24 hours, filtered, and dried to obtain the precipitated silica product. The test results of the relevant indicators of the prepared precipitated silica product are shown in Table 2.

[0023] Table 2. Test results of relevant indicators of the silica product prepared in Example 2

[0024] Example 3

[0025] Normal production: 1442 kg of industrial water glass with a modulus of 2.8 and a sodium silicate content of 36.4% is mixed with 280 kg of concentrated crystals from the first filtrate (75 wt% solid content) and 1778 kg of the second filtrate from normal production to prepare a 3500 kg mixture with a sodium bicarbonate content of 6 wt% and a sodium silicate content of 15 wt%. This mixture is then added to the first bubble column. Steam is introduced at a stirring speed of 330 r / min to maintain the reaction temperature at 80°C. 99% CO2 gas is introduced. When the pH of the carbonized liquid reaches 9.2, the gas supply and heating are stopped, and the reaction solution is pumped to a filter to obtain the first filter cake and the first filtrate. The first filter cake is mixed with the third filtrate from normal production and transferred to the second bubble column. The mixture is then heated to 50°C with steam and then 3500 kg of concentrated CO2 gas is introduced. CO2 gas with a concentration of 99% was introduced. When the pH of the carbonization liquid reached 8.4, the gas flow and heating were stopped, and the reaction liquid was pumped to a filter to obtain a second filter cake and a second filtrate. The second filter cake was mixed with deionized water to form a slurry with a solid content of 15 wt%, and 0.35 kg of sodium dodecylbenzenesulfonate was added. The mixture was then transferred to a third bubble column. After heating with steam to 50°C, CO2 gas with a volume concentration of 99% was introduced. When the pH of the carbonization liquid reached 7.8, the gas flow and heating were stopped, and the reaction liquid was pumped to a filter to obtain a third filter cake and a third filtrate. The third filter cake was mixed with deionized water to form a slurry with a concentration of 25 wt%. After thorough stirring, the mixture was allowed to stand at 85°C for 16 hours and then filtered. The filter cake was then soaked in anhydrous ethanol with a mass of 2.5 times its weight for 16 hours, filtered, and dried to obtain the precipitated silica product. The test results of the relevant indicators of the prepared precipitated silica product are shown in Table 3.

[0026] Table 3. Test results of relevant indicators of the silica product prepared in Example 3 Example 4

[0027] Normal production: 838 kg of industrial water glass with a modulus of 3.1 and a sodium silicate content of 33.4% is mixed with 227 kg of crystallized solution (first filtrate) from the first carbonization tower (first filtrate) during normal production (solid content of 77 wt%) and 2435 kg of separation liquid (second filtrate) from the second carbonization tower to prepare a mixture of 5 wt% sodium bicarbonate and 8 wt% sodium silicate. This mixture is then added to the first bubble column. Steam is introduced at a stirring speed of 310 r / min to heat the mixture and maintain the reaction temperature at 70°C. CO2 gas with a volume concentration of 98.7% is introduced. When the pH of the carbonization liquid reaches 8.9, the gas supply and heating are stopped, and the reaction liquid is pumped to a filter to obtain the first filter cake and the first filtrate. The first filter cake is mixed with all the separation liquid (third filtrate) from the third bubble column during normal production and transferred to the second bubble column. After heating to 60°C with steam, CO2 gas with a volume concentration of 98.7% was introduced. When the pH of the carbonization liquid reached 8.2, the gas supply and heating were stopped, and the reaction solution was pumped to a filter to obtain a second filter cake and a second filtrate. The second filter cake was mixed with deionized water to form a slurry with a solid content of 13 wt%, and 0.25 kg of sodium dodecylbenzenesulfonate was added. The mixture was then transferred to a third bubble column. After heating to 60°C with steam, CO2 gas with a volume concentration of 98.7% was introduced. When the pH of the carbonization liquid reached 7.5, the gas supply and heating were stopped, and the reaction solution was pumped to a filter to obtain a third filter cake and a third filtrate. The third filter cake was mixed with deionized water to form a slurry with a volume concentration of 27 wt%. After thorough stirring, the mixture was allowed to stand at 80°C for 20 hours and then filtered. The filter cake was then soaked in anhydrous ethanol at a concentration of 2.0 times its weight for 12 hours, filtered, and dried to obtain the precipitated silica product. The test results of the relevant indicators of the prepared precipitated silica product are shown in Table 4.

[0028] Table 4. Test results of relevant indicators of the silica product prepared in Example 4

[0029]

[0030] As can be seen from Tables 1-4, the prepared silica products meet the Class A standard quality requirements of HG-T-3061-2020 Rubber Compounding Agents Hydrated Silica.

Claims

1. A method for producing silica via carbonization, characterized in that, Using industrial water glass as raw material, sodium bicarbonate as electrolyte, sodium dodecylbenzenesulfonate as dispersant, and industrial carbon dioxide as precipitant, carbonization and washing are completed in a bubble column, and then aging, ethanol replacement and drying are performed to produce white carbon black; the bubble column consists of three bubble columns arranged in series, namely the first bubble column, the second bubble column and the third bubble column. The specific production method includes the following steps: First production: S1. Prepare a sodium silicate solution with a mass content of 5-15 wt% by adding industrial water glass and deionized water. Add the solution to the first bubble column. Add 4-6 wt% sodium bicarbonate and 0.005-0.01 wt% sodium dodecylbenzenesulfonate from the industrial water glass solution to the first bubble column. Control the stirring speed at 300-350 r / min and the carbonization temperature at 50-80℃. Introduce industrial carbon dioxide. When the pH of the reaction solution is 9.0±0.2, stop the aeration and heating and pump the reaction solution to the filter to obtain a primary filter cake and a primary filtrate. S2. The primary filter cake obtained in step S1 is adjusted with deionized water to form a slurry with a solid content of 10-15 wt%. At the same time, 0.005-0.01 wt% sodium dodecylbenzenesulfonate industrial water glass solution is added and transferred to the second bubble column. The stirring speed is controlled at 300-350 r / min, the carbonization temperature is 50-80℃, and industrial carbon dioxide is introduced. When the pH of the reaction solution is 8.2±0.2, the aeration and heating are stopped, and the reaction solution is pumped to the filter to obtain the secondary filter cake and secondary filtrate. S3. Add deionized water to the secondary filter cake obtained in step S2 to adjust it into a slurry with a solid content of 10-15 wt%. At the same time, add 0.005-0.01 wt% sodium dodecylbenzenesulfonate industrial water glass solution and transfer it to the third bubble column. Control the stirring speed at 300-350 r / min and the carbonization temperature at 50-80℃, and introduce industrial carbon dioxide. When the pH of the reaction solution is 7.6±0.2, end the carbonization operation. Send the obtained reaction solution to a filter for solid-liquid separation to obtain a third filter cake and a third filtrate. S4. Add deionized water to the obtained three-stage filter cake to make a slurry of 20-30wt%. After stirring thoroughly, let it stand and age at 80-90℃ for 20-24 hours, then filter. Soak the filter cake in anhydrous ethanol of 2-3 times the weight of the filter cake for 12-24 hours, then filter and dry to obtain the white carbon black product. Normal production: The sodium bicarbonate added in step S1 is a solution obtained by concentrating and crystallizing the primary filtrate. The deionized water in step S1 is replaced by the secondary filtrate obtained in step S2; The deionized water in step S2 is replaced by the three filtrates obtained in step S3; Sodium dodecylbenzenesulfonate is no longer added in steps S1 and S2.

2. The method for producing silica by carbonization according to claim 1, characterized in that, The modulus of the water glass is 2.8-3.

2.

3. The method for producing silica by carbonization according to claim 1, characterized in that, The volume concentration of CO2 in the industrial carbon dioxide is ≥98.5%.

4. The method for producing silica by carbonization according to claim 1, characterized in that, The prepared silica product meets the Class A standard quality requirements of HG-T-3061-2020 Rubber Compounding Agents Hydrated Silica.

5. The method for producing silica by carbonization according to claim 1, characterized in that, The bubble column has a diameter of 1m and a height of 5m. Five baffles are arranged longitudinally on the inner wall of the bubble column, with a height of 4.5m and a length of 0.1m. Four sets of stirring blades are arranged from top to bottom inside the bubble column. The diameter of the stirring blades is 0.7m and the distance between two adjacent sets of stirring blades is 1.2m. The stirring blade at the bottom of the bubble column is the bottom blade.

6. The method for producing silica by carbonization according to claim 5, characterized in that, The bottom of the bubble tower is also equipped with a gas distributor, which is located below the bottom blades and the distance between the gas distributor and the bottom blades is 0.1m.

7. A method for producing silica by carbonization according to claim 6, characterized in that, The bottom of the gas distributor is connected to the CO2 inlet pipe.

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