Method for preparing pyrolytic oil and activated carbon through lignin one-step pyrolysis

Abstract

The invention belongs to the field of lignin, and provides a method for preparing pyrolytic oil and activated carbon by utilizing lignin one-step pyrolysis, which comprises the following steps: in an oxygen-free environment, pyrolyzing lignin at 500-680 DEG C for 10-15 minutes, introducing inert gas in the pyrolysis process, obtaining pyrolytic carbon and volatile matter after the pyrolysis is completed, and condensing and washing the volatile matter to obtain pyrolytic oil; activating the pyrolytic carbon in a carbon dioxide atmosphere to obtain primary activated carbon; the primary activated carbon is subjected to acid pickling, and the activated carbon is obtained. Aiming at the problem that the value of a solid-phase product is low due to rapid pyrolysis of lignin, the method for preparing pyrolytic oil and activated carbon through one-step pyrolysis of lignin is realized by combining the characteristics of lignin and a preparation method of activated carbon on the basis of preparing pyrolytic oil through rapid pyrolysis of lignin.

Description

Technical Field

[0001] The invention belongs to the field of lignin and relates to a method for preparing pyrolysis oil and activated carbon by utilizing one-step pyrolysis of lignin. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] The global pulp and paper industry produces 50 million tons of lignin by-products each year, and most of the lignin is not utilized in a high-value way, resulting in serious waste.

[0004] Lignin pyrolysis offers the advantages of low raw material purity requirements, wide raw material adaptability, and high yields of liquid products, making it an effective strategy for large-scale lignin utilization. Pyrolysis typically involves heating lignin to a pyrolysis temperature. The resulting products include solid products (pyrolysis carbon), liquid products (pyrolysis oil), and gaseous products (pyrolysis gas). However, currently, lignin pyrolysis carbon is often directly burned as a solid fuel.

[0005] A study has disclosed a method for co-producing adsorbed activated carbon and bio-aviation fuel precursors using waste lignin. The composition and proportion of the lignin pyrolysis liquid product (bio-aviation fuel precursor) are regulated by catalysts, but the performance of the activated carbon still needs to be improved. Summary of the Invention

[0006] To address the above-mentioned issues, the present invention combines the characteristics of lignin pyrolysis to provide a method for preparing pyrolysis oil and activated carbon using lignin pyrolysis in a one-step process, thereby achieving energy conservation and emission reduction during the preparation of lignin pyrolysis oil and activated carbon. The present invention has discovered that under specific rapid pyrolysis conditions, while the lignin is in a molten state, volatile gases generated by the internal pyrolysis of the lignin form bubbles in the molten lignin. When the molten lignin further carbonizes, the bubbles remain in the molten state and become a void structure. This significantly increases the specific surface area of the subsequent activated carbon while ensuring a high yield of activated carbon and pyrolysis oil.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: The first aspect of the present invention provides a method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin, comprising: In an oxygen-free environment, lignin is pyrolyzed at 500-680°C for 10-15 minutes. Inert gas is introduced during the pyrolysis process. After the pyrolysis is completed, pyrolysis carbon and volatiles are obtained. The volatiles are condensed and washed to obtain pyrolysis oil. Activating the pyrolytic carbon in a carbon dioxide atmosphere to obtain primary activated carbon; The primary activated carbon is acid-washed to obtain the activated carbon.

[0008] The present invention discovered that under specific rapid heating conditions, lignin softens and moltens, while simultaneously releasing volatile gases from the pyrolysis process. These gases alter the physical form of the molten lignin, resulting in a pyrolytic carbon with a more porous structure. The carbon produced by rapid pyrolysis of lignin at specific temperatures and times exhibits a higher specific surface area than carbon produced by conventional slow pyrolysis, creating an inherent advantage for further activation of the pyrolytic carbon to produce activated carbon.

[0009] The second aspect of the present invention provides pyrolysis oil and activated carbon prepared by the above method.

[0010] The present invention addresses the problem of low value of solid products due to rapid pyrolysis of lignin. Combining the characteristics of lignin itself, on the basis of preparing pyrolysis oil by rapid pyrolysis of lignin, combined with the preparation method of activated carbon, a method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin is realized.

[0011] The third aspect of the present invention provides applications of the above-mentioned activated carbon in the fields of chemical industry, medicine and environment.

[0012] Beneficial effects of the present invention (1) The method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin proposed in the present invention realizes the continuous pyrolysis of lignin and activation of pyrolysis carbon, and simultaneously obtains lignin pyrolysis oil and activated carbon, thereby improving the utilization value of lignin and reducing energy consumption and environmental pollution.

[0013] (2) The specific advantages of the present invention are as follows: After the lignin pyrolysis is completed, it is directly used for activation after switching to the gas, which shortens the heating time and reduces energy consumption. The one-step preparation of activated carbon and lignin pyrolysis oil from lignin is realized, and the process is simple. At the same time, the characteristics of lignin itself that it melts and pyrolyzes at high temperatures to produce volatile gases are utilized to form a void structure in the pyrolytic carbon, providing a higher specific surface area for subsequent activation, reducing the time for preparing activated carbon and increasing the specific surface area of the activated carbon.

[0014] (3) The preparation method of the present invention is simple, practical, and easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0016] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0017] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0018] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in accordance with conventional methods in the art or according to product specifications. Similarly, unless otherwise specified, the test methods of the present invention are also tested in accordance with conventional methods in the art or the common methods or standards in the industry. In addition, any methods and materials similar to or equivalent to the described contents can be applied to the inventive method. The preferred embodiments and materials described herein are for demonstration purposes only.

[0019] The present invention provides a method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin, comprising: In an oxygen-free environment, lignin is pyrolyzed at 500-680°C for 10-15 minutes. Inert gas is introduced during the pyrolysis process. After the pyrolysis is completed, pyrolysis carbon and volatiles are obtained. The volatiles are condensed and washed to obtain pyrolysis oil. Activating the pyrolytic carbon in a carbon dioxide atmosphere to obtain primary activated carbon; The primary activated carbon is acid-washed to obtain the activated carbon.

[0020] In some embodiments, the inert gas is selected from one or more of nitrogen, argon, and carbon dioxide. The inert gas has two functions: first, it provides an inert atmosphere to prevent oxygen from reacting with the pyrolysis products. Second, it purges volatile gases generated by pyrolysis out of the reaction apparatus, preventing secondary reactions.

[0021] In some embodiments, the flow rate of the inert gas is 100-150 mL / min, so as to blow the volatile gases generated by pyrolysis away from the high-temperature area and prevent the volatile gases from undergoing secondary reactions, thereby reducing the yield of the liquid phase product.

[0022] The present invention has found that if a catalyst is added during the rapid pyrolysis stage, it will affect the specific surface area of the activated carbon prepared by subsequent activation with carbon dioxide. Therefore, no catalyst is added during the rapid pyrolysis stage of the present application. The present application does not impose any particular limitation on the washing solvent. In some embodiments, the washing solvent is at least one of ethyl acetate and dioxane to improve the washing effect.

[0023] In the present invention, rapid pyrolysis and activation are two distinct stages. After rapid pyrolysis, pyrolysis oil and pyrolytic carbon are obtained. The pyrolytic carbon is then activated with carbon dioxide to produce activated carbon. Rapid pyrolysis alone does not produce activated carbon; high-performance activated carbon requires a combination of rapid pyrolysis and carbon dioxide activation. Therefore, in some embodiments, the activation temperature is 650-900°C, and the activation time is 30-50 minutes. During the activated carbon activation process, carbon dioxide reacts with carbon on the surface of the pyrolytic carbon to produce CO, which increases the porosity of the activated carbon.

[0024] The activation heating rate affects the formation of the activated carbon pore structure and the reaction rate. Therefore, the present invention studies the activation heating rate. In some embodiments, the activation heating rate is 5-20°C / min to increase the porosity and reaction rate of the activated carbon.

[0025] The flow rate of carbon dioxide affects the pore size distribution and specific surface area of activated carbon. Therefore, the present invention studies the flow rate of carbon dioxide. In some embodiments, the flow rate of carbon dioxide is 100-150 mL / min to improve the performance of activated carbon.

[0026] The present invention does not impose any particular limitation on the pickling solution. In some embodiments, the pickling solution is hydrochloric acid with a concentration of 1.5-2 mol / L to improve the efficiency of pickling.

[0027] More specifically, they include: (1) Heat the reaction device to 500-680℃, add industrial lignin directly into the reaction device and keep it warm for 10-15 minutes while introducing protective gas.

[0028] (2) During the pyrolysis of lignin, volatile substances are generated. The volatile substances are purged out of the reaction device with protective gas and condensed. The uncondensed gas is washed with an organic solvent. After the pyrolysis is completed, the pipeline is washed with an organic solvent and mixed with the washing liquid and then rotary evaporated to obtain pyrolysis oil. Lignin pyrolysis oil and pyrolysis gas are obtained.

[0029] (3) After the pyrolysis reaction is completed, the protective gas is converted into carbon dioxide, the temperature is raised to 650-900℃ and kept warm for 30-50 minutes to obtain primary activated carbon.

[0030] (4) Wash the primary activated carbon with hydrochloric acid at a concentration of 1.5 mol / L, collect the washing liquid for later use, and dry the washed primary activated carbon to obtain high-quality activated carbon.

[0031] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0032] In the following examples, the testing method for the BET specific surface area of activated carbon is based on the standard number: GB / T 7702.20-2008.

[0033] The activated carbon yield and pyrolysis oil yield are calculated as the ratio of the mass of the final activated carbon or pyrolysis oil to the mass of the lignin used to produce the activated carbon or pyrolysis oil.

[0034] Example 1: 20 g of industrial lignin was weighed and added to a quartz tube. The air in the tube furnace was expelled with nitrogen. The temperature of the pyrolysis furnace was raised to 650 °C. Nitrogen was introduced at a flow rate of 100 mL / min. The quartz tube was placed in the tube furnace and kept pyrolyzed for 10 min. During the pyrolysis process, pyrolytic carbon (yield 40.3%, BET specific surface area 199.98 m) was obtained. 2 / g) and volatiles. The volatiles were condensed in a condenser and washed with ethyl acetate to obtain lignin pyrolysis oil. After the pyrolysis was completed, the gas was switched to carbon dioxide at a flow rate of 100 mL / min. The pyrolysis carbon was heated to 750°C in a carbon dioxide atmosphere at a rate of 5°C / min and activated at 750°C for 30 min. The primary activated carbon was washed with 1.5 mol / L hydrochloric acid, and the washing liquid was collected for later use. The washed primary activated carbon was dried to obtain high-quality activated carbon. The BET specific surface area of the activated carbon was measured to be 1004.8 m 2 / g, the activated carbon yield was 19.3% and the pyrolysis oil yield was 22.3%.

[0035] Example 2: 20 g of industrial lignin was weighed and added to a quartz tube. Nitrogen was used to remove air from the tube furnace. The pyrolysis furnace was heated to 650°C and nitrogen was introduced at a flow rate of 100 mL / min. The quartz tube was placed in the tube furnace and kept pyrolyzed for 10 minutes. Pyrolysis carbon and volatiles were obtained during the pyrolysis process. The volatiles were condensed in a condenser and washed with dioxane to obtain lignin pyrolysis oil. After the pyrolysis was completed, the gas was switched to carbon dioxide at a flow rate of 100 mL / min. The pyrolysis carbon was heated to 750°C in a carbon dioxide atmosphere at a heating rate of 10°C / min. It was activated at 750°C for 40 minutes and washed with 1.5 mol / L hydrochloric acid. The washing liquid was collected for later use. The washed primary activated carbon was dried to obtain high-quality activated carbon. The BET specific surface area of the activated carbon was measured to be 746.1 m 2 / g, the activated carbon yield was 18.4% and the pyrolysis oil yield was 22.3%.

[0036] Example 3: 20 g of industrial lignin was weighed and added to a quartz tube. Nitrogen was used to remove the air in the tube furnace. The pyrolysis furnace was heated to 550°C and nitrogen was introduced at a flow rate of 100 mL / min. The quartz tube was placed in the tube furnace and kept pyrolyzed for 10 minutes. Pyrolysis carbon and volatiles were obtained during the pyrolysis process. The volatiles were condensed in a condenser and washed with ethyl acetate to obtain lignin pyrolysis oil. After the pyrolysis was completed, the gas was switched to carbon dioxide at a flow rate of 100 mL / min. The pyrolysis carbon was heated to 750°C in a carbon dioxide atmosphere at a heating rate of 5°C / min. It was activated at 750°C for 30 minutes and washed with 1.5 mol / L hydrochloric acid. The washing liquid was collected for later use. The washed primary activated carbon was dried to obtain high-quality activated carbon. The BET specific surface area of the activated carbon was measured to be 988.7 m 2 / g, the activated carbon yield was 21.3% and the pyrolysis oil yield was 20.6%.

[0037] Comparative Example 1 The difference from Example 1 is that the pyrolytic carbon was activated at 750 °C for 60 min in a carbon dioxide atmosphere after rapid pyrolysis, and the BET specific surface area of the activated carbon was 626.60 m 2 / g, the activated carbon yield was 12.0%, and the pyrolysis oil yield was 22.3%.

[0038] Comparative Example 2 The difference from Example 1 is that the pyrolytic carbon was activated at 850 °C for 30 min in a carbon dioxide atmosphere after rapid pyrolysis, and the BET specific surface area of the activated carbon was determined to be 688.87 m 2 / g, the activated carbon yield was 13.70% and the pyrolysis oil yield was 22.3%.

[0039] Comparative Example 3 The difference from Example 1 is that after the pyrolytic carbon is rapidly pyrolyzed, it is taken out and mixed with KOH in a mass ratio of 1:2.5, and then heated to 800 degrees Celsius under a nitrogen environment and kept warm for 60 minutes for activation. The BET specific surface area of the activated carbon is measured to be 1004.8 m 2 / g, the activated carbon yield was 13.70% and the pyrolysis oil yield was 22.3%.

[0040] Comparative Example 4 20 g of industrial lignin was weighed and added to a quartz tube. Carbon dioxide was introduced at a flow rate of 100 mL / min. The quartz tube was placed in a tube furnace and heated from room temperature to 750°C at a rate of 5°C / min. The temperature was activated at 750°C for 30 min. The primary activated carbon was washed with 1.5 mol / L hydrochloric acid. The washing liquid was collected for later use. The washed primary activated carbon was dried to obtain activated carbon. The BET specific surface area of the activated carbon was measured to be 444.55 m 2 / g, and the activated carbon yield was 38.8%.

[0041] From the comparison between Example 1 and Comparative Examples 1 and 2, it can be seen that as the activation temperature increases, the specific surface area and yield of activated carbon decrease.

[0042] From the comparison between Example 1 and Comparative Example 3, it can be seen that compared with KOH, the yield of activated carbon obtained by CO2 activation is higher.

[0043] From the comparison between Example 1 and Comparative Example 4, it can be seen that the rapid pyrolysis treatment effectively increases the specific surface area of the activated carbon.

[0044] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin, characterized in that: include: In an oxygen-free environment, lignin is pyrolyzed at 500-680°C for 10-15 minutes. Inert gas is introduced during the pyrolysis process. After the pyrolysis is completed, pyrolysis carbon and volatiles are obtained. The volatiles are condensed and washed to obtain pyrolysis oil. Activating the pyrolytic carbon in a carbon dioxide atmosphere to obtain primary activated carbon; The primary activated carbon is acid-washed to obtain the activated carbon.

2. The method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin according to claim 1, characterized in that: The inert gas is selected from one or more of nitrogen, argon and carbon dioxide.

3. The method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin according to claim 1, characterized in that: The flow rate of the inert gas is 100-150 mL / min.

4. The method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin according to claim 1, characterized in that: The solvent used for the washing is at least one of ethyl acetate and dioxane.

5. The method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin according to claim 1, characterized in that: The activation temperature is 650-900° C., and the activation time is 30-50 min.

6. The method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin according to claim 1, wherein: The activation heating rate is 5-20°C / min.

7. The method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin according to claim 1, wherein: The flow rate of the carbon dioxide is 100-150 mL / min.

8. The method for preparing pyrolysis oil and activated carbon by one-step pyrolysis of lignin according to claim 1, characterized in that: The pickling solution is hydrochloric acid with a concentration of 1.5-2 mol / L.

9. Pyrolysis oil and activated carbon prepared by the method according to any one of claims 1 to 8.

10. Use of the activated carbon according to claim 9 in the fields of chemical industry, medicine and environment.

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