Porous carbon with double effects of adsorption and catalysis, preparation method of porous carbon and application of porous carbon in waste gas treatment

Abstract

The invention discloses porous carbon with adsorption-catalysis double effects and a preparation method and application thereof in waste gas treatment, agricultural wastes and organic electronic wastes are used as raw materials, and the raw materials are respectively cleaned, dried and crushed to obtain raw material particles with a certain mesh number; respectively carrying out hydrothermal carbonization and tubular furnace carbonization on the agricultural wastes and the organic electronic wastes to obtain carbon with a small amount of pores; mixing the two kinds of carbon, ball-milling and mixing the two kinds of carbon with an alkaline activator, co-activating in a tubular furnace, and chemically modifying the surface of the agricultural waste by high-activity metal components in the organic electronic waste-based carbon in the co-activating process; and carrying out acid pickling, water washing and drying on the porous carbon obtained in the previous step to finally obtain the adsorption-catalysis dual-effect porous carbon. According to the method, the solid waste is used as the raw material, the preparation process is simple, the cost is low, large-scale industrial production and application are easy, and the high-value utilization approach of the solid waste is widened.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of adsorption-catalysis porous carbon, in particular to porous carbon with adsorption-catalysis dual functions, a preparation method thereof and application in waste gas treatment. Background Art

[0002] The emission of volatile organic compounds into the atmosphere has multiple environmental effects. It can induce the formation of ozone and photochemical smog. It can also irritate the human eyes, lungs, heart, nervous system, etc., causing a variety of human diseases, and causing serious harm to the environment and human health. Adsorption and catalytic oxidation have become key methods for controlling volatile organic compound emissions due to their simple operation and high efficiency, and have been widely used in industrial practice. In actual operation, due to the low concentration of volatile organic compounds in industrial waste gas, two process units, namely adsorption followed by catalytic oxidation, are often used to purify volatile organic compounds, which greatly increases equipment investment and the complexity of the process. The development of adsorption-catalysis integrated removal materials will shorten the waste gas purification process, reduce equipment operating costs, and improve purification efficiency.

[0003] Porous materials with highly active metal components on their surfaces have adsorption and catalytic effects on volatile organic compounds. Compared with other porous materials, carbon-based materials have a wide range of raw materials, low cost, and adjustable chemical properties, making them the preferred materials for controlling volatile organic compound emissions. Research on carbon-based adsorption-catalytic materials has been reported, but most of them use precious metals or commercial transition metals as metal sources and are prepared by redox precipitation, impregnation calcination, etc. The process is cumbersome and the cost of active metals is high, which limits large-scale industrial production applications. Summary of the invention

[0004] The first objective of the present invention is to address the deficiencies in the prior art and to provide a porous carbon having dual adsorption and catalytic effects on volatile organic compounds and a method for preparing the same, which can be applied to the adsorption and catalytic removal of volatile organic compounds in a variety of exhaust gases, and to provide new materials and methods for solving the problems of high preparation cost of dual-effect adsorption and catalytic materials and low removal efficiency of volatile organic pollutants.

[0005] The technical solution adopted by the present invention is as follows: A method for preparing porous carbon with dual functions of adsorption and catalysis comprises the following steps: Step (1), pre-treating agricultural waste and organic electronic waste; Step (2), carbonizing the pretreated agricultural waste and the pretreated organic electronic waste respectively to obtain agricultural waste-based carbon and organic electronic waste-based carbon; Step (3), mixing agricultural waste-based carbon and organic electronic waste-based carbon, adding an alkaline activator and performing high-temperature co-activation, and then sequentially acid-washing, water-washing and drying to obtain porous carbon.

[0006] Its further technical solution is: In the step (1), the agricultural waste includes straw and fruit shell waste, and the organic electronic waste includes plastic casings and circuit boards of household appliances and electronic equipment, and contains metal components such as Cu, Ni, Mn and Co.

[0007] In the step (1), the pretreatment specifically comprises: washing, drying, crushing and sieving the agricultural waste and the organic electronic waste respectively; wherein the agricultural waste is crushed by ball milling, and the organic electronic waste is crushed by ball milling after liquid nitrogen cooling, and 30-80 mesh granular raw materials are obtained after sieving.

[0008] In the step (2), the agricultural waste is carbonized in a hydrothermal reactor, and the organic electronic waste is carbonized in an inert atmosphere in a tubular furnace.

[0009] In the step (2), in the hydrothermal carbonization reaction, the mass ratio of agricultural waste to water is 1:5 to 1:15, the carbonization time is 120 to 480 min, and the temperature is 150 to 220 °C.

[0010] In the step (2), the carbonization reaction is carried out in a tubular furnace, the carbonization temperature of the organic electronic waste is 350-400°C, the heating rate is 5-10°C / min, the carbonization time is 60-120 min, and the inert atmosphere is nitrogen (N2) with a N2 flow rate of 100-300 mL / min.

[0011] In the step (3), the agricultural waste-based carbon and the organic electronic waste-based carbon are physically mixed at a mixing mass ratio of 0.5:1 to 1:3, and the mass percentage of each metal element in the mixed carbon is: Cu: 0.5-3%, Mn: 0.5-3%, Co: 0.1-1.5%, Ni: 0.1-1.5%.

[0012] In the step (3), the alkaline activator is KOH, KHCO3 or NaCO3, and the mass ratio of the mixed carbon to the activator is 1:1 to 1:3.

[0013] In the step (3), the mixed carbon activation temperature is 650-800°C, the heating rate is 5-10°C / min, and the activation time is 60-90 min; The pickling is carried out with hydrochloric acid, the concentration of which is 0.2 to 0.8 mol / L, and ultrapure water is used for washing until it becomes neutral. The drying temperature is 105 to 120 °C, and the drying time is 12 to 24 h. The second object of the present invention is to provide a porous carbon having dual functions of adsorption and catalysis, which is prepared by the above preparation method.

[0014] The third object of the present invention is to provide the application of the above-mentioned porous carbon with dual functions of adsorption and catalysis in the treatment of organic waste gas.

[0015] The beneficial effects of the present invention are as follows: The preparation method of the present invention selects organic components from agricultural waste with huge annual output and electronic waste with the fastest growth rate as basic raw materials, which are low in price; the porous carbon preparation method is simple and does not require additional expensive metal chemicals and equipment, which is conducive to large-scale production and is suitable for large-scale organic waste gas treatment.

[0016] The present invention makes full use of the metal source characteristics in organic electronic waste, converts the contained high-activity Cu, Ni, Mn, and Co metal components into catalytic sites on the surface of agricultural waste-based carbon, saving expensive metal costs. The metal active components exist in the raw materials themselves, avoiding the problems of pore structure blockage and reduced specific surface area caused by metal site loading methods such as impregnation calcination and redox precipitation. At the same time, some metal groups in organic electronic waste can also promote pore growth during carbonization and activation. There are many types of high-activity metal components in organic electronic waste, which can form multi-metal oxides and solid solution catalytic sites on the carbon surface, have stronger adaptability and catalytic performance to different volatile organic compounds, and increase the matching of adsorption-catalysis porous carbon materials with actual waste gas.

[0017] In summary, the present invention makes full use of the organic components and highly active metals in organic electronic waste, and uses low-cost agricultural waste as raw materials to prepare adsorption-catalytic porous carbon by co-activation, coupling adsorption and catalysis into one, and using integrated materials to achieve efficient purification of volatile organic pollutants in waste gas, simplifying the adsorption and catalytic tandem process, and reducing equipment investment and operating costs. Adsorption-catalytic porous carbon uses agricultural waste and organic electronic waste as raw materials, broadens the high-value utilization of solid waste, and promotes the development of my country's circular economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 N2 adsorption / desorption curve and pore size distribution diagram of the porous carbon prepared in the embodiment of the present invention.

[0019] Figure 2 This is a pore size distribution diagram of the porous carbon prepared in an embodiment of the present invention.

[0020] Figure 3 This is a comparison chart of the saturated adsorption capacity of volatile organic compounds on different carbon materials.

[0021] Figure 4 This is a diagram showing the catalytic oxidation efficiency of volatile organic compounds by the adsorption-catalytic porous carbon prepared in an embodiment of the present invention.

[0022] Figure 5This is a diagram showing the catalytic oxidation efficiency of volatile organic compounds by the waste circuit board-based porous carbon prepared in an embodiment of the present invention.

[0023] Figure 6 The present invention is a flow chart of the preparation method. DETAILED DESCRIPTION

[0024] Specific embodiments of the present invention are described below.

[0025] The porous carbon with dual functions of adsorption and catalysis for volatile organic compounds and the preparation method thereof of the present embodiment uses agricultural waste and organic electronic waste as raw materials, such as Figure 6 As shown, it includes the following processes: Step (1), raw material selection and processing: agricultural waste and organic electronic waste are selected as raw materials, and they are cleaned, dried, and crushed to obtain dry raw material particles with a certain mesh size; Step (2), carbonization treatment: subjecting the agricultural waste and organic electronic waste to hydrothermal carbonization and tubular furnace carbonization, respectively, and further cooling and grinding to obtain agricultural waste-based carbon and organic electronic waste-based carbon; wherein the mass ratio of agricultural waste to water is 1:5 to 1:15, the carbonization time is 120 to 480 min, and the temperature is 150 to 220 °C; the carbonization temperature of organic electronic waste is 350 to 400 °C, the heating rate is 5 to 10 °C / min, the carbonization time is 60 to 120 min, and the N2 flow rate is 100 to 300 mL / min; Step (3), activation treatment: the agricultural waste-based carbon and the organic electronic waste-based carbon described in step (2) are mixed, and the mixed carbon is further mixed with an alkaline activator by ball milling. The mixed carbon is placed in a tubular furnace for high-temperature activation and cooling to obtain porous carbon; wherein the mixing mass ratio of the agricultural waste-based carbon to the organic electronic waste-based carbon is 0.5:1 to 1:3; the mixed carbon activation temperature is 650 to 800 °C, the heating rate is 5 to 10 °C / min, and the activation time is 60 to 90 min; the mass ratio of the mixed carbon to the activator is 1:1 to 1:3.

[0026] Step 4: Cleaning: The porous carbon obtained in step (3) is sequentially acid-washed, water-washed, and dried to obtain the final adsorption-catalytic porous carbon; wherein the acid-washing uses a hydrochloric acid solution with a concentration of 0.2 to 0.8 mol / L, and the water uses ultrapure water, and the carbon is washed sequentially until it becomes neutral, the drying temperature is 105 to 120 °C, and the drying time is 12 to 24 h.

[0027] In the above embodiment, the agricultural waste includes straw and fruit shell waste; the organic electronic waste contains Cu, Ni, Mn, Co metal components, the alkaline activator is KOH, KHCO3 or NaCO3, and the metal component content characteristics of the mixed carbon before activation are as follows: Cu: 0.5-3%, Mn: 0.5~3%, Co: 0.1~1.5%, Ni: 0.1~1.5%; The porous carbon prepared by the preparation method of the above embodiment has its surface modified by highly active metal components in organic electronic waste, forming metal active sites with adsorption and catalytic effects. At different temperatures, the metal sites interact with the electrons of volatile organic compounds, promoting the adsorption and catalysis of volatile organic compounds and enhancing the removal efficiency.

[0028] As a specific implementation method, a method for preparing porous carbon having dual functions of adsorption and catalysis for volatile organic compounds comprises the following steps: S1: Select an agricultural waste rice straw, wash it with deionized water, dry it at 105 ℃ for 12 h, ball mill it and sieve it to obtain rice straw particles with a size of 30-80 mesh; select waste computer circuit boards containing metal components such as Cu, Ni, Mn and Co, wash them with deionized water, dry them at 105 ℃ for 12 h, cool them with liquid nitrogen and then ball mill them to obtain circuit board particles with a size of 30-80 mesh.

[0029] S2: Weigh 10 g of the rice straw particles prepared in step S1, put them into a 300 mL reactor, add 100 g of water, put the reactor into a drying oven, and react at 180 °C for 300 min.

[0030] S3: 25 g of the circuit board particles prepared in step S1 were placed in a tubular furnace for carbonization at a carbonization temperature of 380 °C, a heating rate of 5 °C / min, a carbonization time of 60 min, and a nitrogen flow rate of 200 mL / min.

[0031] S4: The rice straw-based carbon and the circuit board-based carbon obtained in steps S2 and S3 are mixed in a mass ratio of 1:1, and the mixed carbon is mixed with KHCO3 in a mass ratio of 1:2 by ball milling to obtain a mixed carbon loaded with an activator, wherein the content of the metal components in the mixed carbon is as follows: Cu: 2.91%, Mn: 1.31 %, Co: 0.86%, Ni: 0.730%; S5: The mixed carbon obtained in step S4 is placed in a tubular furnace for activation, with an activation temperature of 700 °C, a heating rate of 10 °C / min, an activation time of 90 min, and a N2 flow rate of 200 mL / min. After activation, it is cooled to room temperature under a N2 atmosphere.

[0032] S6: The porous carbon obtained in step S5 is washed with a 0.5 mol / L hydrochloric acid solution. When the washing solution is close to neutral, it is washed with ultrapure water until the washing solution is neutral. The filtered porous carbon is dried at 110 °C for 24 h and cooled to room temperature to obtain the final adsorption-catalytic porous carbon.

[0033] The N2 adsorption-desorption isotherms, pore size distribution and pore structure characteristic parameters of the prepared porous carbon are shown in Figure 1 , Figure 2 and as shown in Table 1. In order to better obtain the physical and chemical properties of each carbon, the carbons obtained in steps S2 and S3 were activated respectively using the same steps to obtain rice straw-based porous carbon and waste circuit board-based porous carbon, and their pore structure parameters are shown in Table 2. It can be found that the prepared adsorption-catalytic porous carbon has micro-mesoporous hierarchical channels, has a rich pore structure at a lower activation temperature and activator ratio, and has a large specific surface area. During the co-activation of the two carbons, the pore structure of the mixed carbon develops more than that of the single component carbon, and the metal ions have no adverse effect on the formation of the pore structure.

[0034] Table 1 Pore structure parameters of adsorption-catalysis porous carbon <![CDATA[BET specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (cm 3 / g)]]> <![CDATA[Micropore volume (cm 3 / g)]]> <![CDATA[Mesopore volume (cm 3 / g)]]> Average pore size (nm) Microporosity (%) 1634.2 0.9152 0.6873 0.2279 2.1 75.1 Table 2 Pore structure parameters of rice straw-based porous carbon and waste circuit board-based porous carbon project <![CDATA[BET specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (cm 3 / g)]]> <![CDATA[Micropore volume (cm 3 / g)]]> <![CDATA[Mesopore volume (cm 3 / g)]]> Average pore size (nm) Microporosity (%) Rice straw-based porous carbon 1620.2 0.9052 0.6637 0.2415 2.1 73.3 Circuit board based porous carbon 1521.1 0.8467 0.5136 0.3331 2.2 60.7 Performance test: The porous carbon prepared in the above embodiment was tested for volatile organic matter adsorption and catalytic performance. Toluene, ethyl acetate and acetone, which are common in organic waste gas, were selected as target substances.

[0035] (1) Volatile organic compound adsorption and catalytic performance evaluation were carried out in a fixed bed reactor with an inner diameter of 10 mm and a length of 400 mm. N2 was used as the balance gas. Adsorption conditions are as follows: Volatile organic matter concentration: 150 mg / m 3 , adsorption temperature: 120 ℃, total gas volume: 1 L / min, porous carbon usage: 50 mg. The adsorption breakthrough curve was tested using a portable volatile organic compound detection device.

[0036] The catalytic reaction conditions are as follows: Concentration of organic pollutants: 800 mg / m 3, catalytic temperature: 200 ℃, 240 ℃, total gas volume: 1 L / min, O2 content 20%, porous carbon usage: 50 mg. The outlet concentration of the fixed bed reactor was tested using a portable volatile organic compound detection device.

[0037] (2) The adsorption breakthrough curves were integrated to obtain the saturated adsorption amounts of the three volatile organic compounds on the porous carbon. The catalytic reaction efficiency was calculated based on the changes in the inlet and outlet concentrations.

[0038] (3) To demonstrate the excellent adsorption and catalytic performance of porous carbon on volatile organic compounds, rice straw-based porous carbon, circuit board-based porous carbon and a conventional commercial activated carbon were selected as comparisons, and the removal characteristics of three volatile organic compounds were tested under the same adsorption and catalytic conditions. The pore structure parameters of commercial activated carbon are shown in Table 3. The saturated adsorption capacities of the four carbon materials are shown in Table 3. Figure 3 The catalytic performance of adsorption-catalytic porous carbon is shown in Figure 4 As shown in the figure, the catalytic oxidation efficiency of volatile organic compounds by circuit board-based porous carbon is shown in the figure Figure 5 shown.

[0039] As can be seen from the above charts, the adsorption performance of the three prepared porous carbons is significantly better than that of commercial activated carbon, and the adsorption-catalytic porous carbon has an ethyl acetate adsorption capacity of 110.1 mg / g under the adsorption conditions of 120 ℃, which is 3.8 times that of commercial activated carbon, and the adsorption capacity is higher than that of rice straw-based porous carbon and circuit board-based porous carbon. At 200 ℃ and 240 ℃, the adsorption-catalytic porous carbon has extremely high removal efficiency for volatile organic compounds. At 240 ℃, the removal efficiency of the three volatile organic compounds is greater than 95%, maintaining a catalytic oxidation efficiency similar to that of circuit board-based porous carbon, while commercial activated carbon and rice straw-based porous carbon have almost no catalytic performance.

[0040] Table 3 Pore structure parameters of commercial activated carbon <![CDATA[BET specific surface area (m 2 / g)]]> <![CDATA[Total pore volume (cm 3 / g)]]> <![CDATA[Micropore volume (cm 3 / g)]]> <![CDATA[Mesopore volume (cm 3 / g)]]> Average pore size (nm) Microporosity (%) 925.4 0.4689 0.3859 0.083 1.85 82.3 The above test data show that the adsorption-catalytic porous carbon prepared by the present invention not only maintains the adsorption performance of rice straw-based porous carbon, but also embodies the catalytic oxidation properties of circuit board-based porous carbon.

[0041] It is to be understood that the above embodiments are exemplary and are not to be construed as limiting the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing porous carbon with dual functions of adsorption and catalysis, characterized in that: The preparation method comprises the following steps: Step (1), pre-treating agricultural waste and organic electronic waste; Step (2), carbonizing the pretreated agricultural waste and the pretreated organic electronic waste respectively to obtain agricultural waste-based carbon and organic electronic waste-based carbon; Step (3), mixing agricultural waste-based carbon and organic electronic waste-based carbon to obtain mixed carbon, adding an alkaline activator and performing high-temperature co-activation, and then sequentially acid-washing, water-washing and drying to obtain porous carbon.

2. The preparation method according to claim 1, characterized in that: In step (1), the agricultural waste includes straw and fruit shell waste; the organic electronic waste includes plastic casings and circuit boards of household appliances and electronic equipment, and contains metal components such as Cu, Ni, Mn and Co.

3. The preparation method according to claim 1, characterized in that: In step (2), agricultural waste is carbonized in a hydrothermal reactor, and organic electronic waste is carbonized in an inert atmosphere in a tubular furnace.

4. The preparation method according to claim 3, characterized in that: When carbonizing in a hydrothermal reactor, the mass ratio of agricultural waste to water is 1:5-1:15, the carbonization time is 120-480 min, and the temperature is 150-220 °C.

5. The preparation method according to claim 3, characterized in that: When carbonization is carried out in an inert atmosphere in a tubular furnace, the carbonization temperature is 350-400 °C, the heating rate is 5-10 °C / min, the carbonization time is 60-120 min, and the inert gas flow rate is 100-300 mL / min.

6. The preparation method according to claim 1, characterized in that: In step (3), the mass ratio of agricultural waste-based carbon to organic electronic waste-based carbon is 0.5:1-1:3, and the mass percentage of each metal element in the mixed carbon is: Cu: 0.5-3%, Mn: 0.5-3%, Co: 0.1-1.5%, Ni: 0.1-1.5%.

7. The preparation method according to claim 1, characterized in that: In step (3), the alkaline activator is KOH, KHCO3 or NaCO3, and the mass ratio of the mixed carbon to the alkaline activator is 1:1 to 3.

8. The preparation method according to claim 1, characterized in that: In step (3), the temperature of high-temperature co-activation is 650-800°C, the heating rate is 5-10°C / min, and the activation time is 60-90 min.

9. A porous carbon having dual functions of adsorption and catalysis, characterized in that: The method is prepared by any one of claims 1 to 8.

10. Use of the porous carbon with dual adsorption and catalytic effects as claimed in claim 9 in the treatment of organic waste gas.

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