A biochar with carbon fixation-carbon capture-in-situ conversion function and a preparation method and application thereof

Abstract

The application discloses a kind of biochar with carbon fixation-carbon capture-in situ conversion function and its preparation method and application, the preparation method includes the following steps: after being washed with waste biomass water filtration, drying, with nitrogen source mixing grinding, be placed in tube furnace, in inert atmosphere sequentially pyrolysis carbonization and physical activation, after cooling nitrogen-doped biochar is obtained;Nitrogen-doped biochar is added to zinc nitrate solution, after stirring and mixing, drying is obtained with carbon fixation-carbon capture-in situ conversion function biochar.The carbon yield of biochar of the application is high, can effectively capture and fix source low concentration CO2, and in tetrabutylammonium bromide and oxidation styrene mixed solution, CO2 captured can be in situ converted into styrene cyclic carbonate, and significant carbon sequestration benefit and excellent carbon capture-in situ conversion effect are shown.

Description

Technical Field

[0001] This invention belongs to the field of biochar preparation technology, specifically relating to a biochar with carbon fixation-carbon capture-in-situ conversion functions, its preparation method, and its application. Background Technology

[0002] In recent years, the problem of climate change caused by global warming has become increasingly prominent. Frequent extreme weather events have had a huge impact on humanity and nature, one of the main reasons being the large-scale emission of CO2. CO2 is the most significant greenhouse gas, primarily originating from the development and use of fossil fuels. Although my country is actively deploying clean energy to reduce the proportion of coal in its energy mix, CO2 emissions continue to show a year-on-year upward trend, making carbon emission reduction an increasingly urgent issue.

[0003] Biological carbon sequestration is an environmentally friendly carbon reduction technology. Biomass can convert CO2 into carbohydrates through photosynthesis, which are then fixed in the plant as organic carbon. my country is rich in biomass resources, and converting agricultural and forestry organic waste, industrial organic waste, and other waste biomass into stable biochar through pyrolysis carbonization is a feasible negative emission technology.

[0004] Carbon capture, utilization, and storage (CCUS) technology is also a practical CO2 emission reduction technology, widely used in industrial and biomass / coal-fired power plants and other low-concentration CO2 stationary emission sources. The captured CO2 can be subsequently converted into high-value chemical products, realizing the resource utilization of CO2. Amine solution absorption and solid adsorption are two of the most widely used CO2 capture technologies. Amine solution absorption inevitably leads to amine escape and corrosion problems, while solid adsorption has the characteristics of simple operation and low regeneration energy consumption, showing good application prospects. Among these, the adsorbent is the key to efficient CO2 capture and conversion. Biochar has abundant pore structure, easily controllable surface chemical properties, and low cost advantages; using it for CO2 capture can simultaneously achieve carbon fixation and carbon capture functions. However, biochar prepared by direct pyrolysis lacks specific functional groups, resulting in a low CO2 adsorption capacity. Furthermore, after adsorbing CO2, biochar usually undergoes desorption and compression processes to obtain high-purity CO2 for subsequent resource utilization. Styrene cyclic carbonates are important "green chemicals" that can be produced from CO2 and ethylene oxide under mild conditions. However, styrene cyclic carbonates primarily use high-purity CO2 (>99%) as a raw material, making it difficult to perform in-situ conversion of low-concentration CO2 from stationary sources. Biochar, with its abundant porous structure, can serve as both an adsorbent and a catalyst support, holding promise for integrating low-concentration CO2 capture and in-situ conversion. Developing a biochar that integrates carbon fixation, carbon capture, and in-situ conversion functions is of great significance for realizing the resource utilization of low-concentration CO2 from stationary sources. Summary of the Invention

[0005] Technical problem to be solved: In view of the problems of poor CO2 adsorption performance of existing biochar and difficulty in in-situ conversion of low-concentration CO2 into high-value chemical products, the first objective of this invention is to provide a method for preparing biochar with carbon fixation-carbon capture-in-situ conversion function. This method uses waste biomass and nitrogen source for co-pyrolysis to prepare nitrogen-doped biochar, and then impregnates it with zinc nitrate solution to enable it to have adsorption-in-situ conversion function. This method has a wide range of raw material sources, low cost, simple process and is easy to industrial production.

[0006] The second objective of this invention is to provide a biochar with carbon fixation-carbon capture-in-situ conversion function and its application. Based on the preparation method of the biochar with carbon fixation-carbon capture-in-situ conversion function provided by this invention, the biochar is rich in nitrogen, which can improve the adsorption performance of CO2. At the same time, it is loaded with zinc nitrate, which has catalytic active sites, and can convert the captured CO2 in-situ into styrene cyclic carbonates under mild conditions, showing excellent carbon fixation-capture-in-situ conversion effect.

[0007] Technical solution: A method for preparing biochar with carbon fixation, carbon capture, and in-situ conversion functions, comprising the following steps:

[0008] S1. After washing, filtering and drying the waste biomass, it is mixed and ground with a nitrogen source and placed in a tube furnace. In an inert atmosphere, it is pyrolyzed, carbonized and physically activated in sequence. After cooling, nitrogen-doped biochar is obtained.

[0009] S2. Nitrogen-doped biochar was added to a zinc nitrate solution, stirred and mixed, and then dried to obtain biochar with carbon fixation-carbon capture-in-situ conversion functions.

[0010] Preferably, the waste biomass is selected from one or more of the following: fruit shells, waste wood chips, straw, coffee grounds, and biogas residue.

[0011] Preferably, the nitrogen source is urea, melamine, or graphitic carbon nitride.

[0012] Preferably, the mass ratio of waste biomass to nitrogen source in S1 is 1:(0.5-2).

[0013] Preferably, step S1 specifically involves: washing and filtering the waste biomass with water, drying it in an oven at 80°C, mixing it with a nitrogen source and grinding it to 10-100 mesh, placing it in a tube furnace, and carbonizing it at 400-600°C for 1-2 hours under an inert atmosphere at a heating rate of 3-5°C / min, followed by physical activation at 700-900°C for 0.2-1 hours.

[0014] Preferably, the inert atmosphere in S1 is nitrogen, argon, or helium.

[0015] Preferably, the atmosphere for physical activation in S1 is CO2, water vapor, or a mixture thereof.

[0016] Preferably, the solute in the zinc nitrate solution in S2 is Zn(NO3)2·6H2O, with a mass fraction of 10% to 20%, and the mass ratio of nitrogen-doped biochar to Zn(NO3)2·6H2O is (1 to 4):1.

[0017] Preferably, the stirring time in step S2 is 24 hours, and the drying temperature is 80-100°C.

[0018] Biochar with carbon fixation, carbon capture, and in-situ conversion functions was prepared by the above method.

[0019] The application of the above-mentioned biochar in carbon fixation, carbon capture and in-situ conversion is as follows: the biochar is saturated with adsorption in a CO2 gas stream with a volume fraction of 15% at 40-60°C, and then placed in a mixed solution of tetrabutylammonium bromide and styrene oxide with a molar ratio of 1:100. The mixture is stirred at 60-80°C for 24 hours and then centrifuged to obtain styrene cyclic carbonate.

[0020] Beneficial effects: This invention uses environmentally friendly waste biomass as a carbon source to obtain a biochar with carbon fixation-carbon capture-in-situ conversion function, which is conducive to promoting pollution reduction and carbon reduction. At the same time, the preparation method is simple and convenient for industrial production.

[0021] The biochar prepared by this invention has carbon fixation-carbon capture-in-situ conversion functions, which enhances the nitrogen active sites of the biochar and improves the CO2 capture performance of the biochar. Compared with ordinary biochar, the adsorption capacity can be increased by about 5 times. At the same time, it overcomes the difficulty of existing biochar having a single function and being unable to achieve low-concentration CO2 capture and in-situ conversion. It can capture low-concentration CO2 and convert it into styrene cyclic carbonates under mild conditions, showing excellent carbon fixation efficiency and carbon capture-in-situ conversion effect. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the preparation process and application of biochar with carbon fixation, carbon capture, and in-situ conversion functions in this invention.

[0023] Figure 2 This is a schematic diagram of the CO2 conversion principle of biochar with carbon fixation-carbon capture-in-situ conversion function in an embodiment of the present invention.

[0024] Figure 3 This is a SEM image of the biochar with carbon fixation-carbon capture-in-situ conversion function prepared in the embodiments of the present invention.

[0025] Figure 4The CO2 dynamic adsorption breakthrough curve of biochar with carbon fixation-carbon capture-in-situ conversion function prepared in an embodiment of the present invention is shown. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0027] The method for preparing biochar with carbon fixation-carbon capture-in-situ conversion function of the present invention includes the following steps:

[0028] (1) After washing, filtering and drying the waste biomass, it is mixed and ground with a nitrogen source and placed in a tube furnace for low-temperature pyrolysis and carbonization in an inert atmosphere. Then, it is physically activated at high temperature and cooled to obtain nitrogen-doped biochar.

[0029] (2) Nitrogen-doped biochar was added to zinc nitrate solution, stirred and mixed evenly, and then dried in an oven to obtain biochar with carbon fixation-carbon capture-in-situ conversion function.

[0030] Among them, waste biomass includes any one of fruit shells, waste wood chips, straw, coffee grounds, biogas residue, etc., or a mixture thereof.

[0031] The nitrogen source can be any one of urea, melamine, or graphitic carbon nitride.

[0032] In step (1), the mass ratio of waste biomass to nitrogen source is 1:(0.5-2).

[0033] In step (1), the waste biomass is washed and filtered, dried in an oven at 80°C, mixed with a nitrogen source and ground to 10-100 mesh, placed in a tube furnace, and heated at a rate of 3-5°C / min under an inert atmosphere until it is carbonized at 400-600°C for 1-2 hours, and then physically activated at 700-900°C for 0.2-1 hours.

[0034] In step (1), the inert atmosphere is any one of nitrogen, argon, or helium.

[0035] In step (1), the physical activation atmosphere is CO2, water vapor, or a mixture thereof; the volume ratio of CO2 to water vapor in the mixed gas is (2-4):1. In step (2), the solute of the zinc nitrate solution is Zn(NO3)2·6H2O, with a mass fraction of 10%-20%, and the mass ratio of the nitrogen-doped biochar to Zn(NO3)2·6H2O is (1-4):1.

[0036] In step (2), nitrogen-doped biochar is mixed with zinc nitrate solution and stirred at room temperature for 24 hours, and then dried in an oven at 80-100°C.

[0037] The above-mentioned process flow for the preparation and application of biochar with carbon fixation, carbon capture, and in-situ conversion functions is as follows: Figure 1 As shown, nitrogen atoms are doped onto the surface of biochar by co-pyrolysis of waste biomass and a nitrogen source, while simultaneously impregnating it with zinc nitrate, giving it the functions of carbon fixation, carbon capture, and in-situ conversion.

[0038] In this invention, the carbon fixation effect is evaluated using carbon yield (X), which is calculated using the following formula:

[0039]

[0040] M1 and M2 are the masses of biomass and biochar, respectively, in g; C2 and C1 are the mass fractions of carbon in biomass and biochar, respectively, in %.

[0041] The CO2 capture-in-situ conversion process in this invention is as follows: Biochar is saturated with 15% CO2 by adsorption at 60°C, then placed in a mixed solution of tetrabutylammonium bromide and styrene oxide at a molar ratio of 1:100. The solution is stirred at 60–80°C for 24 hours, followed by centrifugation to obtain styrene cyclic carbonates. The conversion principle is as follows: Figure 2 As shown.

[0042] The carbon capture effect was evaluated using dynamic adsorption capacity. The specific process was as follows: 1g of biochar with carbon fixation-carbon capture-in-situ conversion function was placed in a fixed-bed reactor with a diameter of 1cm. The reaction temperature was 60℃. First, nitrogen gas was introduced for 2 hours, followed by the introduction of 15% CO2 gas at a flow rate of 500mL / min. The outlet CO2 concentration was measured using an infrared carbon dioxide analyzer, and the dynamic adsorption breakthrough curve was obtained. The CO2 adsorption capacity (Q) was calculated using the following equation:

[0043]

[0044] Q (mmol / g) is the adsorption capacity; F (mL / min) is the gas flow rate; m (g) is the adsorbate loading; t (min) is the adsorption time; C0 and C i (%) represents the initial CO2 and outlet CO2 concentrations, respectively.

[0045] CO2 conversion rate (Y) is calculated using the following equation:

[0046]

[0047] The biochar prepared above, which has carbon fixation, carbon capture, and in-situ conversion functions, is shown in the SEM image as follows: Figure 3As shown, the biochar has a rich pore structure, is loaded with nitrogen on the surface, and has a high CO2 capture capacity. The loaded zinc nitrate has a catalytic conversion function. When the biochar after capturing CO2 is added to a 1:100 mixed solution of tetrabutylammonium bromide and styrene oxide, the captured CO2 can be converted into styrene cyclic carbonate in situ under mild conditions, with excellent conversion effect.

[0048] The present invention will be further described below with reference to specific embodiments.

[0049] Example 1

[0050] After washing, filtering, and drying the fruit shells, 10g was weighed and mixed with 10g of urea, then ground to 60 mesh. The mixture was placed in a tube furnace and carbonized at 400℃ for 1h in a nitrogen atmosphere at a heating rate of 3℃ / min. Then, it was physically activated at 700℃ in a CO2 atmosphere for 30min. After cooling, nitrogen-doped biochar was obtained. 2g of Zn(NO3)2·6H2O was dissolved in 18mL of aqueous solution, and 2g of nitrogen-doped biochar was added. The mixture was stirred at room temperature for 24h and then dried in an oven at 80℃ to obtain biochar BC1 with carbon fixation, carbon capture, and in-situ conversion functions. The mass and carbon content of the fruit shells and BC1 biochar were tested respectively, and the carbon yield was calculated.

[0051] 1 g of the prepared BC1 biochar was placed in a fixed-bed reactor with a diameter of 1 cm. The reaction temperature was 60 °C. First, nitrogen gas was introduced for 2 h, and then 15% CO2 gas was introduced. The flow rate of each gas was 500 mL / min. The outlet CO2 concentration was measured using an infrared carbon dioxide analyzer to obtain the dynamic adsorption breakthrough curve and calculate its adsorption capacity. The adsorption-saturated BC1 was placed in a mixed solution of tetrabutylammonium bromide and styrene oxide with a molar ratio of 1:100. The mixture was stirred at 60 °C for 24 h and centrifuged to obtain styrene cyclic carbonate. The mass of styrene cyclic carbonate was weighed and its molar number was calculated. The CO2 conversion rate was further calculated.

[0052] Example 2

[0053] Coffee grounds were washed, filtered, and dried. 10g of the mixture was weighed, mixed with 5g of melamine, and ground to 80 mesh. The mixture was placed in a tube furnace and carbonized at 500℃ for 1 hour in a nitrogen atmosphere at a heating rate of 5℃ / min. Then, it was physically activated at 800℃ in a steam atmosphere for 20 minutes. After cooling, nitrogen-doped biochar was obtained. 2g of Zn(NO3)2·6H2O was dissolved in 18mL of aqueous solution, and 4g of nitrogen-doped biochar was added. The mixture was stirred at room temperature for 24 hours and then dried in an oven at 100℃ to obtain biochar BC2 with carbon fixation, carbon capture, and in-situ conversion functions. The mass and carbon content of the coffee grounds and BC2 biochar were tested, and the carbon yield was calculated.

[0054] 1 g of the prepared BC2 biochar was placed in a fixed-bed reactor with a diameter of 1 cm. The reaction temperature was 60 °C. First, nitrogen gas was introduced for 2 h, and then 15% CO2 gas was introduced. The flow rate of each gas was 500 mL / min. The outlet CO2 concentration was measured using an infrared carbon dioxide analyzer to obtain the dynamic adsorption breakthrough curve and calculate its adsorption capacity. The adsorption-saturated BC2 was placed in a mixed solution of tetrabutylammonium bromide and styrene oxide with a molar ratio of 1:100. The mixture was stirred at 70 °C for 24 h and centrifuged to obtain styrene cyclic carbonate. The mass of styrene cyclic carbonate was weighed and its molar number was calculated. The CO2 conversion rate was further calculated.

[0055] Example 3

[0056] After washing, filtering, and drying the straw, 10g of the straw was weighed and mixed with 20g of graphitic carbon nitride, then ground to 100 mesh. The mixture was placed in a tube furnace and carbonized at 600℃ for 2 hours in a helium atmosphere at a heating rate of 4℃ / min. Then, it was physically activated at 800℃ in a mixed atmosphere of CO2 and water vapor for 15 minutes with a mixed gas volume ratio of 4:1. After cooling, nitrogen-doped biochar was obtained. 2g of Zn(NO3)2·6H2O was dissolved in 18mL of aqueous solution, and 6g of nitrogen-doped biochar was added. The mixture was stirred at room temperature for 24 hours and then dried in an oven at 100℃ to obtain biochar BC3 with carbon fixation, carbon capture, and in-situ conversion functions. The mass and carbon content of the straw and BC3 biochar were tested respectively, and the carbon yield was calculated.

[0057] 1 g of the prepared BC3 biochar was placed in a fixed-bed reactor with a diameter of 1 cm. The reaction temperature was 60 °C. First, nitrogen gas was introduced for 2 h, and then 15% CO2 gas was introduced. The flow rate of each gas was 500 mL / min. The outlet CO2 concentration was measured using an infrared carbon dioxide analyzer to obtain the dynamic adsorption breakthrough curve and calculate its adsorption capacity. The adsorption-saturated BC3 was placed in a mixed solution of tetrabutylammonium bromide and styrene oxide with a molar ratio of 1:100. The mixture was stirred at 80 °C for 24 h and centrifuged to obtain styrene cyclic carbonate. The mass of styrene cyclic carbonate was weighed and its molar number was calculated. The CO2 conversion rate was then calculated.

[0058] Comparative Example 1

[0059] This comparative example is exactly the same as the preparation method and application of biochar with carbon fixation-carbon capture-in-situ conversion function in Example 1, except that urea is not added.

[0060] Comparative Example 2

[0061] This comparative example is exactly the same as the preparation method and application of biochar with carbon fixation-carbon capture-in-situ conversion function in Example 1, except that high-temperature physical activation is not performed.

[0062] Comparative Example 3

[0063] This comparative example is exactly the same as the preparation method and application of biochar with carbon fixation-carbon capture-in-situ conversion function in Example 2, except that Zn(NO3)2·6H2O is not added.

[0064] Comparative Example 4

[0065] This comparative example is exactly the same as the preparation method and application of biochar with carbon fixation-carbon capture-in-situ conversion function in Example 3. The difference is that graphitic carbon nitride and Zn(NO3)2·6H2O are not added.

[0066] The CO2 dynamic adsorption breakthrough curves of various embodiments and comparative examples of the present invention are as follows: Figure 4 As shown.

[0067] Table 1 shows the test results of carbon yield, CO2 adsorption capacity, and CO2 conversion rate for each embodiment and comparative example of the present invention.

[0068]

[0069] As can be seen from Table 1, the biochar prepared by this invention has a good carbon yield; the introduction of nitrogen source is beneficial to improving CO2 adsorption capacity, and the loading of zinc nitrate has an important influence on the conversion of CO2 into styrene cyclic carbonates; at the same time, the addition of N source also helps CO2 conversion, because N in the biochar framework can activate CO2 and can form catalytic active sites with zinc nitrate, promoting CO2 conversion, so that the biochar prepared by this invention maintains excellent carbon fixation-carbon capture-in-situ conversion effect.

Claims

1. A method for preparing biochar with carbon fixation-carbon capture-in-situ conversion functions, characterized in that, Includes the following steps: S1. After washing, filtering, and drying the waste biomass, mix and grind it with a nitrogen source, place it in a tube furnace, and perform pyrolysis carbonization in an inert atmosphere: the heating rate is 3~5 ℃ / min, carbonization is carried out at 400~600 ℃ for 1~2 h, and then physical activation is carried out at 700~900 ℃ for 0.2~1 h. After cooling, nitrogen-doped biochar is obtained; wherein, the nitrogen source is urea, melamine or graphitic carbon nitride; the mass ratio of waste biomass to nitrogen source is 1:(0.5~2). S2. Nitrogen-doped biochar is added to zinc nitrate solution, stirred and mixed, and then dried to obtain biochar with carbon fixation-carbon capture-in-situ conversion function; wherein the solute of zinc nitrate solution is Zn(NO3)2·6H2O, and its mass fraction is 10%~20%, and the mass ratio of nitrogen-doped biochar to Zn(NO3)2·6H2O is (1~4):

1.

2. The method for preparing biochar with carbon fixation-carbon capture-in-situ conversion function according to claim 1, characterized in that, The waste biomass is selected from one or more of the following: fruit shells, waste wood chips, straw, coffee grounds, and biogas residue.

3. The method for preparing biochar with carbon fixation-carbon capture-in-situ conversion function according to claim 1, characterized in that, In step S1: the waste biomass is washed and filtered, dried in an oven at 80 ℃, and then mixed with a nitrogen source and ground to 10~100 mesh.

4. The method for preparing biochar with carbon fixation-carbon capture-in-situ conversion function according to claim 1, characterized in that, The inert atmosphere in S1 is nitrogen, argon, or helium.

5. The method for preparing biochar with carbon fixation-carbon capture-in-situ conversion function according to claim 1, characterized in that, The atmosphere for physical activation in S1 is CO2, water vapor, or a mixture thereof.

6. The method for preparing biochar with carbon fixation-carbon capture-in-situ conversion function according to claim 1, characterized in that, The stirring time in S2 is 24 hours, and the drying temperature is 80~100℃.

7. Biochar with carbon fixation-carbon capture-in-situ conversion function prepared by the method according to any one of claims 1 to 6.

8. The application of the biochar according to claim 7 in carbon fixation, carbon capture and in-situ conversion, characterized in that, The specific application is as follows: the biochar is saturated with CO2 gas at 40-60 °C in a 15% (v / v) CO2 gas stream, then placed in a mixed solution of tetrabutylammonium bromide and styrene oxide at a molar ratio of 1:100, stirred at 60-80 °C for 24 h, and centrifuged to obtain styrene cyclic carbonate.

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