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

Abstract

The invention discloses a method for preparing potassium fluoride and co-producing white carbon black by using potassium fluosilicate. The method comprises the following steps: adding potassium fluosilicate into water, and stirring to obtain turbid liquid; adding urea into the turbid liquid to obtain a raw material solution; preparing a potassium hydroxide solution, and then adding the potassium hydroxide solution into the raw material solution under stirring for reaction to obtain a reaction solution; carrying out heat preservation and aging on the reaction liquid, and filtering to obtain filtrate and a filter cake; concentrating the filtrate, and performing spray drying to obtain potassium fluoride; and washing the filter cake with warm water, and then drying the filter cake to obtain the white carbon black. The method has the advantages that the operation steps are simple, equipment does not need to be added, the urea is low in price and easy to obtain, the cost is low, and the process is simple, the oil absorption value of the obtained white carbon black is 2.70-2.90 ml / g, the specific surface area is 108.63-112.74 m < 2 > / g, the average pore size is 49.09-55.85 nm, and the white carbon black has the characteristics of high purity and large specific surface area.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical production, and particularly relates to a method for preparing potassium fluoride and co-producing white carbon black by utilizing potassium fluorosilicate. Background Art

[0002] Silica gel is a white, non-toxic, amorphous fine powder inorganic silicon compound with excellent properties such as porosity, high dispersibility, light weight, good chemical stability, high temperature resistance, non-combustibility, and good electrical insulation. About 70% of it is used as a reinforcing material for rubber. It is also used in paints, inks, feed, pesticides, fire extinguishing agents, papermaking and other industries.

[0003] Potassium fluoride can be prepared from potassium fluorosilicate to obtain white carbon black as a byproduct. Manufacturers using this method to prepare potassium fluoride generally face the technical difficulty of recovering high-quality white carbon black. Potassium fluorosilicate can be hydrolyzed with potassium hydroxide to produce high-purity potassium fluoride, but because the alkalinity of potassium hydroxide is too strong, the reaction is difficult to control, and it is very easy to dissolve the silicon dioxide formed in the hydrolysis process, resulting in unstable quality of white carbon black. Patent No. CN106430223A discloses the use of ammonia water to hydrolyze potassium fluorosilicate to obtain white carbon black of better quality, but it is easy to cause the problem of strong odor in the production environment, which is not conducive to actual production and pollutes the environment. Patent No. CN104326475A discloses the use of potassium fluorosilicate and potassium carbonate to prepare potassium fluoride and co-produce white carbon black, and white carbon seeds are added to the reaction system. The obtained white carbon black has a specific surface area of 200m 2 / g, but the cost is high. Patent publication number CN110436485A discloses the use of potassium chloride and fluosilicic acid to prepare potassium fluosilicate, and then adding dispersant TF-505 to react potassium fluosilicate with potassium hydroxide to prepare high-purity potassium fluoride and white carbon black. However, the properties of white carbon black, such as specific surface area and oil absorption value, are not mentioned. Patent publication number CN117446812A discloses that the addition of potassium carbonate near the end of the reaction between potassium fluosilicate and potassium hydroxide can avoid the deterioration of white carbon black quality caused by excessive addition of strong base, but the residual carbonate affects the quality of potassium fluoride.

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

[0005] The present invention aims to provide a method for preparing potassium fluoride and co-producing white carbon black by utilizing potassium fluorosilicate. The method is simple and convenient to operate, has low cost, and can improve the performance of white carbon black without affecting the quality of potassium fluoride.

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

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

[0008] S2, adding urea to the suspension prepared in step S1 to obtain a raw material solution;

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

[0010] S4, the reaction solution obtained in step S3 is kept warm and aged, and filtered to obtain a filtrate and a 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 white carbon black.

[0012] Preferably, in step S1, 3.80-4.44 mL of water is added to each gram of potassium fluorosilicate; and 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° C., the stirring speed is 80-100 rpm, the concentration of the potassium hydroxide solution is 48% w / w; and the pH value at the reaction endpoint 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 the potassium hydroxide solution in the early stage of the reaction per minute, and 90% of the total volume of the potassium hydroxide solution is added; and the potassium hydroxide solution with a remaining volume fraction of 10% is added at a rate of 0.3% of the total volume of the potassium hydroxide solution per minute.

[0016] Preferably, in step S4, the mixture is kept at 75-80° C. for 1-3 hours.

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

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

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

[0020] The present invention utilizes potassium fluorosilicate to prepare high-performance silica. Urea is added before potassium hydroxide to modify the aqueous solution environment. Furthermore, urea has the following functions in the present invention: (1) as a buffer solution, it prevents silica from dissolving due to excessive alkali; (2) at 75°C, urea hydrolyzes into carbon dioxide and ammonia (the reaction formula is NH2CONH2+H2O=CO2+2NH3), slowly releasing microbubbles, which is conducive to the formation of a porous structure of silica; (3) as a surfactant, it reduces the surface tension of water, which is conducive to the formation of smaller silica particles. Therefore, urea can be used as a pore-enlarging agent to adjust the pore size of silica; and (4) urea decomposes after high-temperature heating without affecting the quality of silica and potassium fluoride. The resulting silica and potassium fluoride are both of high purity.

[0021] In summary, the method of the present invention has simple operation steps, does not require additional equipment, and urea is cheap and easily available, so it has the advantages of low cost and simple process. The prepared white carbon black has an oil absorption value of 2.70-2.90 ml / g and a specific surface area of 108.63-112.74 m 2 / g, with an average pore diameter of 49.09-55.85nm, and is characterized by high purity and large specific surface area. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0023] Figure 2 These are the adsorption-desorption curves and pore size distribution diagrams of the white carbon black prepared in Example 1 (A), Example 2 (B), Control Example 1 (C), and Control Example 2 (D), respectively. DETAILED DESCRIPTION

[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 examples of this application were purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0026] Example 1

[0027] A method for preparing potassium fluoride and co-producing white carbon black by using potassium fluorosilicate comprises the following steps:

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

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

[0030] S3, prepare 38.96g of potassium hydroxide solution with a concentration of 48% w / w, 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°C) to obtain a reaction solution; the potassium hydroxide solution is added at a rate of 1ml / min in the early stage of the reaction, and 90% of the total volume of the potassium hydroxide solution is added; the remaining potassium hydroxide solution is added at a rate of 0.1ml / min, the reaction time is 2h, and the reaction end point pH is 8.5-9.0; the reaction formula is K2SiF6+4KOH=6KF+SiO2+2H2O;

[0031] S4, the reaction solution obtained in step S3 was kept at 75° C. for 3 h, and filtered while hot to obtain a filtrate and a filter cake;

[0032] S5. The filtrate obtained in step S4 was concentrated and spray-dried at 160° C. to obtain potassium fluoride with a purity of 99.96%. The filter cake obtained in step S4 was washed with 330 ml of warm water and then dried at 105° C. to obtain 4.75 g of white carbon black 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 m 2 / g, average pore size 55.85nm.

[0033] Example 2

[0034] A method for preparing potassium fluoride and co-producing white carbon black by using potassium fluorosilicate comprises 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 a raw material solution, wherein the concentration of urea in the raw material solution is 25 g / L;

[0037] S3, prepare a potassium hydroxide solution (643.7kg KOH, 697.3kgH2O) with a concentration of 48% w / w, and then add the potassium hydroxide solution to the raw material solution prepared in step S2 under stirring (stirring speed 100rpm) to react (reaction temperature 75°C) to obtain a reaction solution; the potassium hydroxide solution is added at a rate of 35L / min in the early stage of the reaction, and 90% of the total volume of the potassium hydroxide solution is added; the remaining potassium hydroxide solution is added at a rate of 3.5L / min, the reaction time is 2h, and the reaction end point pH is 8.5-9.0; the reaction formula is K2SiF6+4KOH=6KF+SiO2+2H2O;

[0038] S4, the reaction solution obtained in step S3 was kept at 75° C. for 3 h, and filtered while hot to obtain a filtrate and a filter cake;

[0039] S5. The filtrate obtained in step S4 was concentrated and spray-dried at 160° C. to obtain potassium fluoride with a purity of 98.12%. The filter cake obtained in step S4 was washed with 9 tons of warm water and then dried at 105° C. to obtain 163.6 kg of white carbon black 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 m 2 / g, average pore size 49.09nm.

[0040] The white carbon black has reached the standard of ordinary industrial grade (specific surface area 100-160m 2 / g, purity ≥90%), priced at approximately 4,000 yuan / ton. Assuming annual silica production is 250 tons, with a total value of 1 million yuan, 91.7 tons of urea are consumed, priced at 1,800 yuan / ton, and the urea cost is 165,000 yuan. After deducting the urea cost, the annual net profit is 835,000 yuan.

[0041] Comparative Example 1

[0042] The difference from Example 1 is that urea is not added in this control example, that is, step S2 is missing, and the other steps are the same as those in Example 1. This control example obtains 4.75 g of white carbon black 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 m 2 / g, has no economic value. Figure 1 It can be seen that the white carbon black contains potassium fluorosilicate as an impurity, while potassium fluorosilicate is not detected in the examples.

[0043] Comparative Example 2

[0044] The difference from Example 1 is that urea is not added in this control example, that is, step S2 is missing, and potassium carbonate is used to replace part of potassium hydroxide in step S3. The other steps are the same as those in Example 1. The specific steps are as follows:

[0045] S1. Add 18.35 g of potassium fluorosilicate to 81.5 mL of water and stir at 75 °C for 10 min to obtain a suspension.

[0046] S3. Prepare 35 g of a 48% w / w KOH solution, then add it to the suspension obtained in step S1. Stir at 160 rpm, reaction temperature 75°C, KOH solution addition rate 1 ml / min, reaction time 2 h. Then add 4.6 g of K2CO3 and stir for 0.5 h to obtain a reaction solution.

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

[0048] S5. Wash the filter cake with 330 ml of warm water and then dry it at 105 ° C to obtain 4.6 g of white carbon black with a recovery rate of 92%, a purity of 98.5%, an oil absorption value of 2.67 ml / g, and a specific surface area of 38.77 m 2 / g, and has no economic value. Although potassium fluorosilicate impurities were not detected in the white carbon black sample, the average pore size was smaller (29.396nm) and the pores were less ( Figure 2 ).

Claims

1. A method for preparing potassium fluoride and co-producing white carbon black using potassium fluorosilicate, characterized in that: The following steps are involved: S1. Add potassium fluorosilicate to water and stir to obtain a suspension; S2, adding urea to the suspension prepared in step S1 to obtain a raw material solution; S3, preparing a potassium hydroxide solution, and then adding the potassium hydroxide solution to the raw material solution prepared in step S2 under stirring to react to obtain a reaction solution; S4, the reaction solution obtained in step S3 is kept warm and aged, and filtered to obtain a filtrate and a 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 white carbon black.

2. The method for preparing potassium fluoride and co-producing white carbon black by utilizing 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; and the mixture is stirred at 75-80° C. to obtain a suspension.

3. A method for preparing potassium fluoride and co-producing white carbon black by utilizing 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 white carbon black by utilizing potassium fluorosilicate according to claim 1 or 2, characterized in that: In step S3, the reaction temperature is 75-80° C., the stirring speed is 80-100 rpm, the concentration of the potassium hydroxide solution is 48% w / w; and the pH value at the reaction endpoint is 8.5-9.

0.

5. The method for preparing potassium fluoride and co-producing white carbon black by utilizing potassium fluorosilicate according to claim 1 or 2, characterized in that: In step S3, the potassium hydroxide solution is added at a rate of 3% of the total volume of the potassium hydroxide solution in the early stage of the reaction per minute, and 90% of the total volume of the potassium hydroxide solution is added; the potassium hydroxide solution with a remaining volume fraction of 10% is added at a rate of 0.3% of the total volume of the potassium hydroxide solution per minute.

6. A method for preparing potassium fluoride and co-producing white carbon black by utilizing potassium fluorosilicate according to claim 1 or 2, characterized in that: In step S4, the mixture is kept at 75-80° C. for 1-3 hours.

7. The method for preparing potassium fluoride and co-producing white carbon black by utilizing 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; and the drying temperature is 80-120°C.

8. The method for preparing potassium fluoride and co-producing white carbon black by utilizing potassium fluorosilicate according to claim 1 or 2, characterized in that: In step S5, the spray drying temperature is 150-160°C.

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