A method for preparing potassium fluoride and co-producing white carbon black by using potassium fluosilicate

Abstract

The application discloses a method for preparing potassium fluoride and co-producing white carbon black by using potassium fluosilicate, which comprises the following steps: adding potassium fluosilicate into water to stir to obtain a suspension; adding urea into the suspension to obtain a raw material solution; preparing a potassium hydroxide solution, then adding the potassium hydroxide solution into the raw material solution to react under stirring to obtain a reaction solution; aging the reaction solution, and filtering to obtain a filtrate and a filter cake; after the filtrate is concentrated, spray drying is performed, and potassium fluoride is obtained; the filter cake is washed with warm water, and then dried to obtain white carbon black. The method has the advantages of simple operation steps, no need of adding equipment, low cost and simple process, and the obtained white carbon black has the characteristics of high purity and large specific surface area, and has an oil absorption value of 2.70-2.90 ml / g, a specific surface area of 108.63-112.74 m 2 / g and an average pore size of 49.09-55.85 nm.

Description

Technical Field

[0001] This invention belongs to the field of chemical production technology, specifically relating to a method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate. Background Technology

[0002] Silica is a white, non-toxic, amorphous, finely powdered inorganic silicon compound with excellent properties such as porosity, high dispersibility, light weight, good chemical stability, high temperature resistance, non-flammability, and good electrical insulation. Approximately 70% of it is used as a reinforcing material for rubber, and it is also applied in industries such as paint, ink, feed, pesticides, fire extinguishing agents, and papermaking.

[0003] Potassium fluoride can be prepared from potassium fluorosilicate, yielding silica as a byproduct. However, manufacturers using this method to produce potassium fluoride generally face the technical challenge of recovering high-quality silica. Alkaline hydrolysis of potassium fluorosilicate with potassium hydroxide can produce high-purity potassium fluoride, but the strong alkalinity of potassium hydroxide makes the reaction difficult to control, easily dissolving the silica formed during the hydrolysis process, leading to unstable silica quality. Patent CN106430223A discloses alkaline hydrolysis of potassium fluorosilicate using ammonia, which can obtain relatively good quality silica, but it easily causes a strong odor in the production environment, hindering actual production and polluting the environment. Patent CN104326475A discloses the co-production of silica from potassium fluorosilicate and potassium carbonate using potassium fluorosilicate and potassium carbonate, adding silica seed crystals to the reaction system, resulting in silica with a specific surface area of ​​200 m². 2 / g, but the cost is relatively high. Patent CN110436485A discloses the preparation of potassium fluorosilicate using potassium chloride and fluorosilicic acid, followed by the addition of dispersant TF-505 to react the potassium fluorosilicate with potassium hydroxide to prepare high-purity potassium fluoride and silica. However, it does not mention the properties of silica, such as specific surface area and oil absorption value. Patent CN117446812A discloses the addition of potassium carbonate near the endpoint of the reaction between potassium fluorosilicate and potassium hydroxide, which can avoid the quality degradation of silica due to excessive addition of strong alkali; however, the residual carbonate affects the quality of potassium fluoride.

[0004] In summary, the production of potassium fluoride and co-production of silica from potassium fluorosilicate still faces problems such as low silica performance, high cost of improving silica performance, and impact on potassium fluoride quality. Low-quality silica has no economic value and can only be discarded as solid waste, resulting in a waste of resources. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate. This method is simple and convenient to operate, low in cost, and can improve the performance of silica without affecting the quality of potassium fluoride.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate, comprising the following steps:

[0007] S1. Add potassium fluorosilicate to water and stir to obtain a suspension;

[0008] S2. Add urea to the suspension prepared in step S1 to obtain the raw material solution;

[0009] S3. Prepare a potassium hydroxide solution, and then add the potassium hydroxide solution to the raw material solution prepared in step S2 under stirring to react and obtain a reaction solution;

[0010] S4. The reaction solution obtained in step S3 is kept at a certain temperature and aged, and then filtered to obtain filtrate and filter cake.

[0011] S5. The filtrate obtained in step S4 is concentrated and then spray-dried to obtain potassium fluoride; the filter cake obtained in step S4 is washed with warm water and then dried to obtain silica.

[0012] Preferably, in step S1, 3.80 to 4.44 mL of water is added to each gram of potassium fluorosilicate; the mixture is stirred at 75-80°C to obtain a suspension.

[0013] Preferably, in step S2, the concentration of urea in the raw material solution is 22-27 g / L.

[0014] Preferably, in step S3, the reaction temperature is 75-80℃, the stirring speed is 80-100rpm, the concentration of potassium hydroxide solution is 48% w / w, and the final pH value of the reaction is 8.5-9.0.

[0015] Preferably, in step S3, the potassium hydroxide solution is added at a rate of 3% of the total volume of potassium hydroxide solution per minute in the early stage of the reaction, and 90% of the total volume of potassium hydroxide solution is added; the remaining 10% volume fraction of potassium hydroxide solution is added at a rate of 0.3% of the total volume of potassium hydroxide solution per minute.

[0016] Preferably, in step S4, the temperature is maintained at 75-80℃ for 1-3 hours.

[0017] Preferably, in step S5, the amount of warm water used is 2-3 times the volume of the filtrate; the drying temperature is 80-120℃.

[0018] Preferably, in step S5, the spray drying temperature is 150-160℃.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention utilizes potassium fluorosilicate to prepare high-performance silica. Urea is added before potassium hydroxide to alter the aqueous solution environment. In addition, urea plays the following roles in this invention: (1) as a buffer solution to prevent silica dissolution due to excessive alkalinity; (2) at 75°C, urea hydrolyzes into carbon dioxide and ammonia (reaction formula: NH2CONH2+H2O=CO2+2NH3), slowly releasing microbubbles, which is beneficial for silica to form a porous structure; (3) as a surfactant to reduce the surface tension of water, which is beneficial for forming smaller silica particles. Therefore, urea can be used as a pore expander to adjust the pore size of silica; (4) urea decomposes after high-temperature heating without affecting the quality of silica and potassium fluoride, and the resulting silica and potassium fluoride have very high purity.

[0021] In summary, the method of this invention has simple operation steps, requires no additional equipment, and uses inexpensive and readily available urea, thus possessing the advantages of low cost and simple process. The prepared silica has an oil absorption value of 2.70–2.90 ml / g and a specific surface area of ​​108.63–112.74 m². 2 The average pore size is 49.09–55.85 nm, and it has the characteristics of high purity and large specific surface area. Attached Figure Description

[0022] Figure 1 XRD patterns of silica prepared under different experimental conditions;

[0023] Figure 2 The adsorption-desorption curves and pore size distribution diagrams of the silica prepared in Examples 1(A), 2(B), 1(C), and 2(D) are shown. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0025] All raw materials and reagents in the embodiments of this application were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0026] Example 1

[0027] A method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate includes the following steps:

[0028] S1. Add 18.35g of potassium fluorosilicate to 81.5mL of water and stir at 75℃ for 10min to obtain a suspension;

[0029] S2. Add 2g of urea to the suspension prepared in step S1 to obtain the raw material solution. The concentration of urea in the raw material solution is 24.5g / L.

[0030] S3. Prepare 38.96 g of a 48% w / w potassium hydroxide solution, and then add the potassium hydroxide solution to the raw material solution prepared in step S2 under stirring (stirring speed 100 rpm) to react (reaction temperature 75℃) to obtain a reaction solution; the potassium hydroxide solution is added at a rate of 1 ml / min in the early stage of the reaction, and 90% of the total volume of potassium hydroxide solution is added; the remaining potassium hydroxide solution is added at a rate of 0.1 ml / min, the reaction time is 2 h, and the final pH value of the reaction is 8.5-9.0; the reaction formula is K2SiF6 + 4KOH = 6KF + SiO2 + 2H2O;

[0031] S4. The reaction solution obtained in step S3 is kept at 75°C for 3 hours and filtered while hot to obtain filtrate and filter cake.

[0032] S5. The filtrate obtained in step S4 is concentrated and spray-dried at 160°C to obtain potassium fluoride with a purity of 99.96%. The filter cake obtained in step S4 is washed with 330 ml of warm water, and then dried at 105°C to obtain 4.75 g of silica with a purity of 97.8%, a recovery rate of 95%, an oil absorption value of 2.90 ml / g, and a specific surface area of ​​112.74 m². 2 / g, average pore size 55.85nm.

[0033] Example 2

[0034] A method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate includes the following steps:

[0035] S1. Add 632.2 kg of potassium fluorosilicate to 2400 L of water and stir at 75 °C for 10 min to obtain a suspension;

[0036] S2. Add 60 kg of urea to the suspension prepared in step S1 to obtain the raw material solution. The concentration of urea in the raw material solution is 25 g / L.

[0037] S3. Prepare a 48% w / w potassium hydroxide solution (643.7 kg KOH, 697.3 kg H2O). Then, add the potassium hydroxide solution to the raw material solution prepared in step S2 under stirring (stirring speed 100 rpm) to react (reaction temperature 75℃) to obtain the reaction solution. The potassium hydroxide solution is added at a rate of 35 L / min in the early stage of the reaction, up to 90% of the total volume of potassium hydroxide solution added. The remaining potassium hydroxide solution is added at a rate of 3.5 L / min, the reaction time is 2 h, and the final pH value is 8.5-9.0. The reaction formula is K2SiF6 + 4KOH = 6KF + SiO2 + 2H2O.

[0038] S4. The reaction solution obtained in step S3 is kept at 75°C for 3 hours and filtered while hot to obtain filtrate and filter cake.

[0039] S5. The filtrate obtained in step S4 is concentrated and spray-dried at 160°C to obtain potassium fluoride with a purity of 98.12%. The filter cake obtained in step S4 is washed with 9 tons of warm water, and then dried at 105°C to obtain 163.6 kg of silica with a purity of 96.3%, a recovery rate of 95%, an oil absorption value of 2.70 ml / g, and a specific surface area of ​​108.63 m². 2 / g, average pore size 49.09nm.

[0040] This silica meets the standard for ordinary industrial grade (specific surface area 100-160 μm²). 2 The price of silica (g, purity ≥90%) is approximately 4000 yuan / ton. Assuming an annual silica production of 250 tons, the total value is 1 million yuan. It consumes 91.7 tons of urea, with a urea price of 1800 yuan / ton, resulting in a urea cost of 165,000 yuan. After deducting the urea cost, the annual net profit is 835,000 yuan.

[0041] Compare with Example 1

[0042] Unlike Example 1, this comparative example did not include urea, i.e., step S2 was omitted; all other steps remained the same as in Example 1. This comparative example yielded 4.75 g of silica, with a recovery rate of 95%, a purity of 94.2%, an oil absorption value of 2.54 ml / g, and a specific surface area of ​​37.85 m². 2 / g, has no economic value. From Figure 1 It can be seen that the silica contains potassium fluorosilicate impurities, while potassium fluorosilicate was not detected in the examples.

[0043] Compare with Example 2

[0044] Unlike Example 1, this comparative example does not add urea, i.e., step S2 is missing, and in step S3, potassium carbonate is used to replace part of the potassium hydroxide. All other steps remain the same as in Example 1. The specific steps are as follows:

[0045] S1. Take 18.35g of potassium fluorosilicate and add it to 81.5mL of water. Stir at 75℃ for 10min to obtain a suspension.

[0046] S3. Prepare 35g of KOH solution with a concentration of 48% w / w, and add it to the suspension obtained in step S1. Stir at 160 rpm, react at 75℃, add KOH solution at a rate of 1 ml / min, and react for 2 hours. Then add 4.6g of K2CO3 and stir for 0.5 hours to obtain the reaction solution.

[0047] S4. The reaction solution obtained in step S3 is kept at 75°C for 3 hours and filtered while hot to obtain filtrate and filter cake.

[0048] S5. Wash the filter cake with 330ml of warm water, then dry the filter cake at 105℃ to obtain 4.6g of silica, with a recovery rate of 92%, a purity of 98.5%, an oil absorption value of 2.67ml / g, and a specific surface area of ​​38.77m². 2 / g, which has no economic value. Although potassium fluorosilicate impurities were not detected in this silica sample, compared with the examples, the average pore size was smaller (29.396nm) and the porosity was less ( Figure 2 ).

Claims

1. A method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate, characterized in that, Includes the following steps: S1. Add potassium fluorosilicate to water and stir to obtain a suspension; S2. Add urea to the suspension prepared in step S1 to obtain the raw material solution; S3. Prepare a potassium hydroxide solution, and then add the potassium hydroxide solution to the raw material solution prepared in step S2 under stirring to react and obtain a reaction solution; The potassium hydroxide solution was added at a rate of 3% of its total volume per minute during the initial stage of the reaction, and then at a rate of 90% of its total volume per minute for the remaining 10% volume fraction. S4. The reaction solution obtained in step S3 is kept at 75-80℃ for 1-3 hours and then filtered to obtain filtrate and filter cake. S5. The filtrate obtained in step S4 is concentrated and then spray-dried to obtain potassium fluoride; the filter cake obtained in step S4 is washed with warm water and then dried to obtain silica.

2. The method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate according to claim 1, characterized in that, In step S1, 3.80~4.44 mL of water is added to each gram of potassium fluorosilicate; the mixture is stirred at 75-80℃ to obtain a suspension.

3. A method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate according to claim 1 or 2, characterized in that, In step S2, the concentration of urea in the raw material solution is 22-27 g / L.

4. A method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate according to claim 1 or 2, characterized in that, In step S3, the reaction temperature is 75-80℃, the stirring speed is 80-100 rpm, the concentration of potassium hydroxide solution is 48% w / w, and the final pH value of the reaction is 8.5-9.

0.

5. A method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate according to claim 1 or 2, characterized in that, In step S5, the amount of warm water used is 2-3 times the volume of the filtrate; the drying temperature is 80-120℃.

6. A method for preparing potassium fluoride and co-producing silica using potassium fluorosilicate according to claim 1 or 2, characterized in that, In step S5, the spray drying temperature is 150-160℃.

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