A pyrolytic carbon black and its preparation method

Abstract

A method for preparing pyrolytic carbon black, especially for preparing pyrolytic carbon black with low ash content and high specific surface area, the method comprising: (1) providing a pyrolytic carbon black particle; (2) preparing a saturated solution of an alkali metal carbonate and immersing the carbon black of step (1) into the above-mentioned saturated solution; removing water from the saturated solution to obtain carbon black deposited with an alkali metal carbonate; (3) immersing the carbon black deposited with an alkali metal carbonate into an acid solution and performing ultrasonic treatment; (4) then filtering, washing and drying to obtain carbon black particles. A large amount of carbon dioxide generated by the reaction of the alkali metal carbonate deposited on the carbon black with the acid, in combination with ultrasonic treatment, greatly reduces the ash content and increases the specific surface area.

Description

Technical Field

[0001] The present invention relates to a pyrolytic carbon black and a preparation method thereof, in particular to a pyrolytic carbon black with low ash content and high specific surface area and a preparation method thereof. Technical Background

[0002] Since its birth, the tire has played an important role in the field of science and technology, especially in the transportation field. At present, the global quantity of waste tires is huge, with an annual output of up to 1.5 billion, and it is still growing continuously. Tires are mainly composed of rubber, carbon black, skeleton materials, and additives. By subjecting waste tires to high-temperature pyrolysis, substances such as pyrolysis oil, pyrolytic carbon black, and pyrolysis gas can be decomposed. Among them, pyrolysis oil and pyrolysis gas can be effectively utilized. For example, pyrolysis oil has a relatively high calorific value and can be used as a substitute for traditional liquid fuels; pyrolysis gas (such as hydrogen) can be directly burned to provide energy for industrial production; while pyrolytic carbon black is more difficult to handle. The main chemical components of waste tire pyrolytic carbon black are carbon, oxygen, copper, zinc, silicon, etc., and its ash content is relatively high. In addition, pyrolytic carbon black also deposits some tar generated during the pyrolysis process. Compared with ordinary carbon black, due to impurities such as ash and tar, the pyrolytic carbon black has obvious differences in chemical properties and has a poor reinforcing effect on rubber, unable to meet the application requirements.

[0003] Some prior art has disclosed technical means for removing impurities such as ash. CN110964350A records a pyrolytic carbon black deashing process, including the following steps: mixing pyrolytic carbon black, an acid solution, a dispersant, and a complexing agent, reacting, performing solid-liquid separation to obtain a filter residue and a filtrate, washing and granulating the filter residue to obtain a carbon black product; reducing the ash content of the carbon black from 18.1 wt% to about 5 wt%. CN102504619A records a purification process for waste tire pyrolytic carbon black, including subjecting the carbon black that has undergone acid washing and alkali washing to an acid washing process again; the ash content of the obtained carbon black is about 2.6 wt%. However, such impurity removal effects are still insufficient, and the ash content is still relatively high, and it cannot be used alone as a reinforcing carbon black for rubber materials.

[0004] Therefore, there is still a need in the prior art to further reduce impurities such as ash in waste tire pyrolytic carbon black to obtain pyrolytic carbon black with low ash content and high specific surface area. Summary of the Invention

[0005] The technical problem solved by this application is: to provide a pyrolytic carbon black with low ash content and high specific surface area, whose performance is close to that of commercial carbon black.

[0006] The present invention provides a preparation method of pyrolytic carbon black, including the following steps:

[0007] (1) Provide a pyrolytic carbon black particle;

[0008] (2) Prepare a saturated solution of alkali metal carbonate, and immerse the carbon black obtained in step (1) into the above-mentioned saturated solution; remove the moisture in the saturated solution to obtain carbon black deposited with alkali metal carbonate;

[0009] (3) Treat the carbon black deposited with alkali metal carbonate with an acid under ultrasonic waves;

[0010] (4) Subsequently, filter, wash, and dry to obtain carbon black particles.

[0011] Among them, the pyrolytic carbon black particles are prepared by pyrolyzing waste tires, then pulverized, and iron filings are removed using a magnetic device. The pyrolysis method used can be: direct pyrolysis, molten salt pyrolysis, co-pyrolysis, plasma pyrolysis, etc. For example, waste tires without steel wires and fibers are broken into small pieces, washed, dried, and then put into a pyrolysis furnace for pyrolysis. The final pyrolysis temperature is 350 - 700 °C, such as 400 °C, 450 °C, 500 °C, 550 °C, 600 °C, 650 °C, etc., and the heating rate is 5 - 30 °C / min, such as 5 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, 25 °C / min, 30 °C / min, etc. The holding time at the final temperature is 10 - 120 min. Subsequently, the obtained carbon black is ground evenly, and iron filings are removed using a magnetic device to obtain pyrolytic carbon black.

[0012] Among them, the alkali metal carbonate in step (2) is one or more of sodium bicarbonate, sodium carbonate, potassium bicarbonate, and potassium carbonate. Preferably, it is a combination of sodium bicarbonate and potassium carbonate. When preparing a mixed solution of sodium bicarbonate and potassium carbonate, saturated solutions of sodium bicarbonate and potassium carbonate are prepared separately first, and then mixed according to a certain volume ratio. The ratio between the two can be any ratio, preferably 1:5 - 5:1, such as 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, etc.; the temperature for preparing the saturated solution of alkali metal carbonate is 20 - 90 °C, preferably 50 - 80 °C. The solid-liquid ratio of the carbon black particles in step (1) and the saturated solution of alkali metal carbonate is 1:0.1 - 4 (g / mL), preferably 1:0.5 - 2.5 (g / mL), so that the carbon black particles are partially or completely immersed in the saturated solution of alkali metal carbonate. At this time, the surface of the carbon black can be fully wetted with the saturated solution of alkali metal carbonate by means of stirring, turning, vibrating, etc. The soaking time is 2 - 48 hours, preferably 12 - 36 hours, such as 12 hours, 16 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, etc.

[0013] Among them, the acid solution described in step (3) is a common inorganic acid in the art, such as one or more of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid; in step (3), the concentration of the acid is 1-30 mol / L, the time of ultrasonic treatment is 0.5-50 hours, preferably 4-24 hours, and the treatment temperature is: 50-90 °C. The molar ratio of the alkali metal carbonate to the acid is 1:4-40, preferably 1:8-20.

[0014] Preferably, step (5) is carried out after step (4). Step (5) is to add the carbon black particles obtained in step (4) into the acid solution and carry out ultrasonic treatment; then filtration, washing, and drying treatments are carried out. The acid solution described in step (5) is a common inorganic acid in the art, such as one or more of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid. In step (5), the concentration of the acid is 1-30 mol / L, the solid-liquid ratio of the carbon black particles to the acid is 1:5-30 (g / mL), the time of ultrasonic treatment is 0.5-50 hours, preferably 4-24 hours, and the treatment temperature is: 50-90 °C.

[0015] Preferably, sulfuric acid or hydrochloric acid is used for treatment in step (3), and hydrofluoric acid is used for treatment in step (5).

[0016] Optionally, a method for preparing carbon black obtained by pyrolyzing waste tires according to the present invention further includes a step of treating the carbon black particles with a strong base. The strong base can be sodium hydroxide, potassium hydroxide, etc.

[0017] The present invention discloses a method for preparing carbon black obtained by pyrolyzing waste tires. By this method, the ash content is significantly reduced and the specific surface area is increased. This method first deposits an alkali metal carbonate on the outer surface and the surface of the inner pores of the carbon black. Subsequently, it is immersed in an acid solution, and the alkali metal carbonate reacts with the acid to generate a large amount of carbon dioxide gas, and with the cooperation of ultrasonic action, the ash on the carbon black, including the ash in the inner pores, can be separated from the surface of the carbon black and fully react with the acid to be converted into a soluble salt. During this process, organic substances such as tar deposited on the carbon black will also be partially separated. In addition, the subsequent second acid treatment and optional alkali treatment can further reduce the contents of ash and organic substances. Specific Embodiments

[0018] The following describes the present invention in combination with embodiments, aiming to help readers better understand the technical solution of the present invention, and does not constitute any limitation to the implementation scope of the technical solution of the present invention.

[0019] Preparation Examples

[0020] The waste tires without steel wires and fibers are crushed into small pieces with a diameter of 1.5 cm, washed, dried, and then put into a pyrolysis furnace for pyrolysis. The pyrolysis conditions are as follows: nitrogen atmosphere, initial temperature of 80 °C, final pyrolysis temperature of 500 °C, heating rate of 10 °C / min, and holding time at the final pyrolysis temperature of 50 min. Subsequently, the obtained carbon black is ground evenly, and iron filings are removed by a magnetic device. Finally, pyrolytic carbon black A is prepared.

[0021] Example 1

[0022] Weigh 100 g of pyrolytic carbon black A obtained in the preparation example; prepare a saturated sodium carbonate solution at 80 °C, and soak pyrolytic carbon black A in the saturated sodium carbonate solution at 80 °C for 24 hours. The solid-liquid ratio of pyrolytic carbon black A to the saturated sodium carbonate solution is 1:1.5 (g / mL); heat to remove the water in the saturated solution to obtain carbon black deposited with sodium carbonate; put the carbon black deposited with sodium carbonate into 5 mol / L sulfuric acid and perform ultrasonic treatment for 5 hours. The molar ratio of alkali metal carbonate to acid is 1:16; then filter, wash 3 times with water at 50 °C, and vacuum dry to obtain carbon black particles.

[0023] Example 2

[0024] Referring to the preparation method of Example 1, the difference from Example 1 is that: a saturated sodium bicarbonate solution is used to replace the saturated sodium carbonate solution.

[0025] Example 3

[0026] Referring to the preparation method of Example 1, the difference from Example 1 is that: a saturated potassium bicarbonate solution is used to replace the saturated sodium carbonate solution.

[0027] Example 4

[0028] Referring to the preparation method of Example 1, the difference from Example 1 is that: a saturated potassium carbonate solution is used to replace the saturated sodium carbonate solution.

[0029] Example 5

[0030] Referring to the preparation method of Example 1, the difference from Example 1 is that: saturated sodium bicarbonate and potassium carbonate solutions are prepared at 80 °C respectively, and two solutions with a volume ratio of 1:1 are mixed to form a saturated alkali metal carbonate solution to replace the saturated sodium carbonate solution.

[0031] Example 6

[0032] Referring to the preparation method of Example 1, the difference from Example 1 is that: saturated sodium bicarbonate and potassium carbonate solutions are prepared at 80 °C respectively, and two solutions with a volume ratio of 2:1 are mixed to form a saturated alkali metal carbonate solution to replace the saturated sodium carbonate solution.

[0033] Example 7

[0034] Referring to the preparation method of Example 1, the difference from Example 1 is that saturated solutions of sodium bicarbonate and potassium carbonate are prepared at 80 °C respectively, and two solutions with a volume ratio of 1:2 are mixed to form a saturated solution of alkali metal carbonate, replacing the saturated solution of sodium carbonate.

[0035] Example 8

[0036] Referring to the preparation method of Example 7, the difference from Example 7 is that 7 mol / L hydrochloric acid is used to replace sulfuric acid.

[0037] Example 9

[0038] Referring to the preparation method of Example 7, the difference from Example 7 is that 7 mol / L nitric acid is used to replace sulfuric acid.

[0039] Example 10

[0040] Referring to the preparation method of Example 7, the difference from Example 7 is that 5 mol / L hydrofluoric acid is used to replace sulfuric acid.

[0041] Example 11

[0042] Referring to the preparation method of Example 7, the difference from Example 7 is that after the first acid treatment, filtration, washing and drying, a second acid treatment is carried out using 5 mol / L hydrofluoric acid, and the solid-liquid ratio of carbon black particles to acid is 1:10 (g / mL). Specifically, the dried carbon black is added to hydrofluoric acid, ultrasonicated for 5 hours, then filtered, washed 3 times with water at 50 °C and vacuum dried to obtain carbon black particles.

[0043] Example 12

[0044] Referring to the preparation method of Example 8, the difference from Example 8 is that after the first pickling, filtration, washing and drying, a second acid treatment is carried out using 5 mol / L hydrofluoric acid, and the solid-liquid ratio of carbon black particles to acid is 1:10 (g / mL). Specifically, the dried carbon black is added to hydrofluoric acid, ultrasonicated for 5 hours, then filtered, washed 3 times with water at 50 °C and vacuum dried to obtain carbon black particles.

[0045] Comparative Example 1

[0046] Weigh 100 g of the pyrolytic carbon black A obtained in the preparation example; prepare a saturated sodium carbonate solution at 80 °C, soak the pyrolytic carbon black A in the saturated sodium carbonate solution at 80 °C and ultrasonically treat it for 5 hours. The solid-liquid ratio of the pyrolytic carbon black A to the saturated sodium carbonate solution is 1:5 (g / mL); then filter, wash it 3 times with water at 50 °C, and vacuum dry it; put the obtained carbon black into 5 mol / L sulfuric acid and ultrasonically treat it for 5 hours; then filter, wash it 3 times with water at 50 °C, and vacuum dry it to obtain carbon black particles.

[0047] Comparative Example 2

[0048] Weigh 100 g of the pyrolytic carbon black A obtained in the preparation example; prepare a 10 mol / L sodium hydroxide solution at 80 °C, soak the pyrolytic carbon black A in the saturated sodium hydroxide solution at 80 °C and ultrasonically treat it for 5 hours. The solid-liquid ratio of the pyrolytic carbon black A to the saturated sodium hydroxide solution is 1:5 (g / mL); then filter, wash it 3 times with water at 50 °C, and vacuum dry it; put the obtained carbon black into 5 mol / L sulfuric acid and ultrasonically treat it for 5 hours; then filter, wash it 3 times with water at 50 °C, and vacuum dry it to obtain carbon black particles.

[0049] Comparative Example 3

[0050] Weigh 100 g of the pyrolytic carbon black A obtained in the preparation example; put the obtained carbon black into 5 mol / L sulfuric acid and ultrasonically treat it for 5 hours; then filter, wash it 3 times with water at 50 °C, and vacuum dry it; prepare a saturated sodium hydroxide solution at 80 °C, soak the pyrolytic carbon black A in the 10 mol / L sodium hydroxide solution at 80 °C and ultrasonically treat it for 5 hours. The solid-liquid ratio of the pyrolytic carbon black A to the saturated sodium hydroxide solution is 1:5 (g / mL); then filter, wash it 3 times with water at 50 °C, and vacuum dry it to obtain carbon black particles.

[0051] Measure the ash content and specific surface area of the carbon black particles prepared in the preparation example, Examples 1-12, and Comparative Examples 1-3 according to the national standard:

[0052] 1) Ash content: Detect according to the operation steps of GB / T 3780.10-2017;

[0053] 2) Specific surface area: Detect according to the operation steps of GB / T 3780.5-2017.

[0054] The specific measurement results are listed in Table 1.

[0055] Table 1

[0056]

[0057] Examples 1-12 adopted the preparation method of the present application. Among them, Examples 1-4 adopted a single alkali metal carbonate, Examples 5-10 adopted a combination of sodium bicarbonate and potassium carbonate, and Examples 11 and 12 additionally used a second acid treatment. The main difference between Comparative Example 1 and Example 1 is that the saturated solution of carbon black alkali metal carbonate was ultrasonically treated, followed by filtration, washing, and drying; rather than depositing the alkali metal carbonate on the carbon black. The main difference between Comparative Example 2 and Example 1 is that instead of ultrasonically treating the carbon black with an alkali metal carbonate solution, the carbon black was alkali-washed with sodium hydroxide commonly used in the prior art. Comparative Example 3 changed the order of the acid treatment and the alkali treatment on the basis of Comparative Example 2. From the data in Table 1, it can be seen that for Examples 1-12 prepared by the preparation method of the present application, especially Examples 5-10, and more especially Examples 11-12, the ash content and specific surface area of the prepared carbon black are significantly better than those of Comparative Examples 1-3 and the Preparation Example. In Comparative Example 1, the alkali metal carbonate was not deposited on the surface of the carbon black and then reacted with the acid, and its effect was poor, even worse than that of Comparative Examples 2 and 3 using sodium hydroxide. It can be seen that depositing the alkali metal carbonate on the surface of the carbon black and then reacting with the acid is very crucial. In addition, according to Examples 1-7, it can be seen that the effects of different alkali metal carbonates are different, and the combination of sodium bicarbonate and potassium carbonate has a better effect. Further, using a secondary acid treatment can further reduce the ash content and increase the specific surface area.

Claims

1. A method for preparing pyrolytic carbon black, comprising the following steps: (1) Provide a pyrolytic carbon black particle; (2) Prepare a saturated solution of an alkali metal carbonate, and immerse the carbon black in step (1) into the above saturated solution; the immersion time is 2 - 48 hours; remove the moisture in the saturated solution to obtain carbon black deposited with the alkali metal carbonate; (3) Immerse the carbon black deposited with the alkali metal carbonate in an acid solution and perform ultrasonic treatment; (4) Subsequently, filter, wash, and dry to obtain carbon black particles.

2. The preparation method of pyrolytic carbon black according to claim 1, characterized in that: In step (2), the temperature for preparing the saturated solution of the alkali metal carbonate is 20 - 90 °C.

3. The preparation method of thermal cracking carbon black according to claim 1, characterized in that: In step (2), the alkali metal carbonate is one or more of sodium bicarbonate, sodium carbonate, potassium bicarbonate, and potassium carbonate.

4. The preparation method of pyrolytic carbon black according to claim 1, characterized in that: In step (2), the alkali metal carbonate is a combination of sodium bicarbonate and potassium carbonate.

5. The preparation method of thermal cracking carbon black according to claim 1, characterized in that: In step (3), the acid solution is one or more of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid.

6. The preparation method of pyrolytic carbon black according to claim 1, characterized in that: In step (3), the time for ultrasonic treatment is 0.5 - 50 hours.

7. The preparation method of thermal cracking carbon black according to claim 1, characterized in that: After step (4), step (5) is also carried out, specifically: add the carbon black particles to the acid solution again and perform ultrasonic treatment; subsequently, perform filtration, washing, and drying treatments.

8. A method for preparing pyrolytic carbon black according to claim 7, characterized in that: In step (5), the acid solution is one or more of hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid.

9. The preparation method of thermal cracking carbon black according to claim 7, characterized in that: The acid solution in step (3) is sulfuric acid or hydrochloric acid, and the acid solution in step (5) is hydrofluoric acid.

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