Porous carbon with adsorption-catalysis dual functions, preparation method thereof and application thereof in exhaust gas treatment

Abstract

The application discloses porous carbon with adsorption-catalysis dual functions, a preparation method thereof and application of the porous carbon in waste gas treatment, and is characterized in that agricultural waste and organic electronic garbage are used as raw materials, the raw materials are cleaned, dried and crushed to obtain raw material particles with a certain mesh number, the agricultural waste and the organic electronic garbage are subjected to hydrothermal carbonization and pipe furnace carbonization respectively to obtain carbon with a small amount of pores, the two kinds of carbon are mixed and simultaneously mixed with an alkaline activator by ball milling, and co-activation is carried out in a pipe furnace, in the co-activation process, high-activity metal components in the organic electronic garbage-based carbon perform chemical modification on the surface of the agricultural waste, and the porous carbon obtained through the above steps is subjected to acid pickling, water washing and drying to finally obtain the porous carbon with adsorption-catalysis dual functions. The method uses solid waste as the raw material, has simple preparation process and low cost, is easy to be applied to large-scale industrial production, and widens a high-value utilization way of the solid waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorption-catalytic porous carbon preparation, and particularly relates to a porous carbon with adsorption-catalytic dual functions, a preparation method thereof and application thereof in waste gas treatment. BACKGROUND

[0002] The emission of volatile organic compounds into the atmospheric environment has multiple environmental effects, can induce the formation of ozone and photochemical smog, and can also stimulate the eyes, lungs, heart, nervous system and other parts of the human body, causing various human diseases and bringing great harm to the environment and human health. Adsorption and catalytic oxidation are key methods for the control of volatile organic compound emissions due to their simple operation and high efficiency, and are widely used in industrial practice. In actual operation, due to the low concentration of volatile organic compounds in industrial waste gas, two process units of adsorption followed by catalytic oxidation are often used to purify volatile organic compounds, greatly increasing equipment investment and process complexity. The development of adsorption-catalytic integrated removal materials will shorten the waste gas purification process, reduce equipment operation costs and improve purification efficiency.

[0003] Porous materials containing high-activity metal components on the surface have adsorption and catalytic effects on volatile organic compounds. Compared with other porous materials, carbon-based materials have wide raw material sources, low cost and adjustable chemical properties, and thus become the preferred material for the control of volatile organic compound emissions. There have been reports on carbon-based adsorption-catalytic materials, but most of them use noble metals or commercial transition metals as metal sources, and are prepared by oxidation-reduction precipitation, impregnation and calcination, which is a complicated process and the cost of active metals is high, limiting large-scale industrial production and application. SUMMARY

[0004] The first object of the present application is to provide a porous carbon with adsorption-catalytic dual functions and a preparation method thereof to solve the problems of high preparation cost of adsorption-catalytic dual function materials and low removal efficiency of volatile organic pollutants, and to provide new materials and methods for the adsorption and catalytic removal of volatile organic compounds in various waste gases.

[0005] The technical scheme adopted by the present application is as follows:

[0006] A preparation method of a porous carbon with adsorption-catalytic dual functions, comprising the following steps:

[0007] Step (1), pretreating agricultural waste and organic electronic waste;

[0008] 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;

[0009] Step (3), mixing the agricultural waste-based carbon and the organic electronic waste-based carbon, adding an alkaline activator, and then performing high-temperature co-activation, and then sequentially performing acid washing, water washing, and drying to obtain the porous carbon.

[0010] Further technical solutions thereof are as follows:

[0011] In the step (1), the agricultural waste comprises straw and shell waste, and the organic electronic waste comprises plastic housings and circuit boards of household appliances and electronic equipment, and contains Cu, Ni, Mn, and Co metal components.

[0012] In the step (1), the pretreatment specifically comprises: cleaning, drying, crushing, and sieving the agricultural waste and the organic electronic waste respectively; the agricultural waste is crushed by ball milling, the organic electronic waste is crushed by ball milling after being cooled by liquid nitrogen, and the sieved agricultural waste and the sieved organic electronic waste are obtained as 30-80 mesh granular raw materials.

[0013] In the step (2), the agricultural waste is carbonized in a hydrothermal reaction kettle, and the organic electronic waste is carbonized in a tube furnace in an inert atmosphere.

[0014] In the step (2), in the hydrothermal carbonization reaction, the mass ratio of the agricultural waste to water is 1:5-1:15, the carbonization time is 120-480 min, and the temperature is 150-220 ℃.

[0015] In the step (2), in the tube furnace carbonization reaction, the carbonization temperature of the organic electronic waste is 350-400 ℃, the heating rate is 5-10 ℃ / min, the carbonization time is 60-120 min, the inert atmosphere is nitrogen (N2), and the N2 flow rate is 100-300 mL / min.

[0016] In the step (3), the agricultural waste-based carbon and the organic electronic waste-based carbon are physically mixed, the mass ratio of the mixed carbon is 0.5:1-1:3, and the mass percentages of the metal elements in the mixed carbon are as follows: Cu: 0.5-3%, Mn: 0.5-3%, Co: 0.1-1.5%, and Ni: 0.1-1.5%.

[0017] In the step (3), the alkaline activator is KOH, KHCO3, or NaCO3, and the mass ratio of the mixed carbon to the activator is 1:1-1:3.

[0018] In the step (3), the activation temperature of the mixed carbon is 650-800 ℃, the heating rate is 5-10 ℃ / min, and the activation time is 60-90 min.

[0019] In the step (3), the acid washing adopts hydrochloric acid, the concentration of the hydrochloric acid solution is 0.2-0.8 mol / L, the water is ultrapure water, the sequential washing is performed until neutral, the drying temperature is 105-120 ℃, and the drying time is 12-24 h.

[0020] A second object of the present application is to provide a porous carbon with adsorption-catalysis dual functions, prepared by the above preparation method.

[0021] A third object of the present application is to provide the application of the above porous carbon with adsorption-catalysis dual functions in organic waste gas treatment.

[0022] The beneficial effects of the present application are as follows:

[0023] The present application selects organic components in agricultural wastes with huge annual output and electronic wastes with the fastest growth rate as basic raw materials, which are low in price; the porous carbon preparation method is simple, does not require additional expensive metal chemical agents and equipment, is conducive to large-scale production, and is suitable for large-scale organic waste gas treatment.

[0024] The present application fully utilizes the metal source characteristics in organic electronic wastes, converts the high-activity Cu, Ni, Mn and Co metal components into catalytic sites on the carbon surface of agricultural waste, saves the cost of expensive metals, and avoids the problems of pore structure blockage and reduced specific surface area caused by impregnation, calcination, oxidation and reduction precipitation and other metal site loading methods. In addition, some metal components in organic electronic wastes can also promote pore growth during carbonization and activation. The high-activity metal components in organic electronic wastes are of various types, which can form multi-metal oxide and solid solution catalytic sites on the carbon surface, have stronger adaptability and catalytic performance for different volatile organic compounds, and increase the matching of the adsorption-catalysis porous carbon material and actual waste gas.

[0025] In summary, the present application fully utilizes the organic components and high-activity metals in organic electronic wastes, and uses low-cost agricultural wastes as raw materials to prepare adsorption-catalysis porous carbon by co-activation, which couples adsorption and catalysis in one, uses integrated materials to achieve efficient purification of volatile organic pollutants in waste gas, simplifies the adsorption and catalysis series process, and reduces equipment investment and operating cost. The adsorption-catalysis porous carbon uses agricultural wastes and organic electronic wastes as raw materials, which widens the high-value utilization way of solid waste, and helps the development of China's circular economy. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 N2 adsorption / desorption curve and pore size distribution graph of the porous carbon prepared in the embodiment of the present application.

[0027] Figure 2 Pore size distribution graph of the porous carbon prepared in the embodiment of the present application.

[0028] Figure 3 Comparison graph of the saturated adsorption amount of volatile organic compounds on different carbon materials.

[0029] Figure 4 The catalytic oxidation efficiency of the porous carbon prepared in the embodiment of the present application on volatile organic compounds is shown in the figure.

[0030] Figure 5 The catalytic oxidation efficiency of the porous carbon prepared in the embodiment of the present application on volatile organic compounds is shown in the figure.

[0031] Figure 6 The flow chart of the preparation method of the present application is shown in the figure. DETAILED DESCRIPTION

[0032] The detailed description of the present application is described as follows.

[0033] The porous carbon with adsorption-catalysis dual functions on volatile organic compounds and the preparation method thereof in the embodiment are selected from agricultural wastes and organic electronic wastes as raw materials, such as Figure 6 The preparation method comprises the following steps as shown in the figure:

[0034] Step (1), raw material selection and processing: agricultural wastes and organic electronic wastes are selected as raw materials, which are cleaned, dried and crushed to obtain dried raw material particles with a certain mesh size;

[0035] Step (2), carbonization treatment: the agricultural wastes and organic electronic wastes are respectively subjected to hydrothermal carbonization and tube furnace carbonization, and then further cooled and ground to obtain agricultural waste-based carbon and organic electronic waste-based carbon; wherein the mass ratio of agricultural wastes to water is 1:5-1:15, the carbonization time is 120-480 min, and the temperature is 150-220 ℃; the carbonization temperature of organic electronic wastes is 350-400 ℃, the heating rate is 5-10 ℃ / min, the carbonization time is 60-120 min, and the N2 flow rate is 100-300 mL / min;

[0036] Step (3), activation treatment: the agricultural waste-based carbon and the organic electronic waste-based carbon in step (2) are mixed, and the mixed carbon is further mixed with an alkaline activator by ball milling, and then the mixed carbon is placed in a tube furnace for high-temperature activation and cooling to obtain porous carbon; wherein the mass ratio of the agricultural waste-based carbon to the organic electronic waste-based carbon is 0.5:1-1:3; the activation temperature of the mixed carbon is 650-800 ℃, the heating rate is 5-10 ℃ / min, the activation time is 60-90 min, and the mass ratio of the mixed carbon to the activator is 1:1-1:3.

[0037] Step four, cleaning treatment: the porous carbon obtained in step (3) is sequentially subjected to acid washing, water washing, and drying to obtain the final adsorption-catalysis porous carbon; wherein the acid washing uses a hydrochloric acid solution, the concentration of the hydrochloric acid solution is 0.2-0.8 mol / L, the water uses ultrapure water, and the sequential washing is until neutral, the drying temperature is 105-120 ℃, and the drying time is 12-24 h.

[0038] In the above embodiment, the agricultural waste includes straw and shell waste; the organic electronic waste contains Cu, Ni, Mn, and Co metal components; the alkaline activator is KOH, KHCO3, or NaCO3; and the metal component content characteristics before mixing carbon activation are as follows:

[0039] Cu: 0.5-3%,

[0040] Mn: 0.5-3%,

[0041] Co: 0.1-1.5%,

[0042] Ni: 0.1-1.5%;

[0043] The porous carbon prepared by the preparation method of the above embodiment is modified by the high-activity metal components in the organic electronic waste, forming metal active sites with adsorption and catalysis 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.

[0044] As a specific embodiment, a preparation method of porous carbon with adsorption-catalysis dual functions for volatile organic compounds is as follows:

[0045] S1: Select a kind of agricultural waste rice straw, wash with deionized water, dry at 105 ℃ for 12 h, ball mill and sieve to obtain 30-80 mesh rice straw particles; select waste computer circuit boards containing Cu, Ni, Mn, and Co metal components, wash with deionized water, dry at 105 ℃ for 12 h, cool with liquid nitrogen, and then ball mill and crush to obtain 30-80 mesh circuit board particles.

[0046] S2: Weigh 10 g of the rice straw particles prepared in step S1, put them into a 300 mL reaction kettle, add 100 g of water, and put the reaction kettle into a drying oven, and react at 180 ℃ for 300 min.

[0047] S3: Put 25 g of the circuit board particles prepared in step S1 into a tube furnace for carbonization, the carbonization temperature is 380 ℃, the heating rate is 5 ℃ / min, the carbonization time is 60 min, and the nitrogen flow rate is 200 mL / min.

[0048] S4: The rice straw-based carbon and the circuit board-based carbon obtained in steps S2 and S3 were mixed in a mass ratio of 1:1, and the mixed carbon was ball-milled with KHCO3 in a mass ratio of 1:2 to obtain mixed carbon loaded with an activating agent, and the content of the metal component in the mixed carbon was as follows:

[0049] Cu: 2.91 %,

[0050] Mn: 1.31 %,

[0051] Co: 0.86%,

[0052] Ni: 0.730%;

[0053] S5: The mixed carbon obtained in step S4 was placed in a tube furnace for activation, the activation temperature was 700 ℃, the heating rate was 10 ℃ / min, the activation time was 90 min, and the N2 flow rate was 200 mL / min. After activation, the mixed carbon was cooled to room temperature under N2 atmosphere.

[0054] S6: The porous carbon obtained in step S5 was washed with a 0.5 mol / L hydrochloric acid solution, and when the washing liquid was close to neutral, the porous carbon was washed with ultrapure water until the washing liquid was neutral. The filtered porous carbon was dried at 110 ℃ for 24 h, and the final adsorption-catalytic porous carbon was obtained after cooling to room temperature.

[0055] The N2 adsorption-desorption isotherm, pore size distribution and pore structure characteristic parameters of the prepared porous carbon are shown in Figure 1 , Figure 2 and Table 1. In order to better obtain the physicochemical properties of each carbon, the carbon obtained in steps S2 and S3 was activated by the same steps to obtain rice straw-based porous carbon and waste circuit board-based porous carbon, and the pore structure parameters are shown in Table 2. It can be found that the prepared adsorption-catalytic porous carbon has micro-mesoporous hierarchical pores, has rich pore structure at a lower activation temperature and activating agent ratio, has a large specific surface area, and in the co-activation process of the two carbons, the pore structure of the mixed carbon is more developed than that of the single-component carbon, and the metal ions do not have an adverse effect on the pore structure formation.

[0056] Table 1 Pore structure parameters of adsorption-catalytic porous carbon

[0057] BET specific surface area (m 2 / g) Total pore volume (cm 3 / g) Micropore volume (cm3 / g) 3 / g) Mesopore volume (cm 3 / g)]]> Average pore diameter (nm) Microporosity (%) 1634.2 0.9152 0.6873 0.2279 2.1 75.1

[0058] Table 2 Pore structure parameters of rice straw-based porous carbon and waste circuit board-based porous carbon

[0059] Item BET specific surface area (m 2 / g)]]> Total pore volume (cm 3 / g) Micropore volume (cm3 / g) 3 / g)]]> Mesopore volume (cm 3 / g)]]> Average pore diameter (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

[0060] Performance test: The volatile organic compound adsorption and catalytic performance test was carried out on the porous carbon prepared in the above embodiments. Toluene, ethyl acetate and acetone commonly found in organic waste gas were selected as target substances.

[0061] (1) The adsorption of volatile organic compounds and the catalytic performance evaluation were carried out on a fixed bed reactor. The fixed bed reactor has an inner diameter of 10 mm and a length of 400 mm. N2 was used as the balance gas.

[0062] The adsorption conditions were as follows: the concentration of volatile organic compounds was 150 mg / m3, the adsorption temperature was 120 °C, the total gas flow was 1 L / min, and the amount of porous carbon used was 50 mg. The adsorption breakthrough curve was tested using a portable volatile organic compound detection device. 3

[0063] The catalytic reaction conditions were as follows: the concentration of organic pollutants was 800 mg / m3, the catalytic temperature was 200 °C or 240 °C, the total gas flow was 1 L / min, the O2 content was 20%, and the amount of porous carbon used was 50 mg. The outlet concentration of the fixed bed reactor was tested using a portable volatile organic compound detection device. 3

[0064] (2) The saturated adsorption capacity of the three volatile organic compounds on the porous carbon was obtained by integrating the adsorption breakthrough curve. The catalytic reaction efficiency was calculated based on the change in the inlet and outlet concentrations.

[0065] (3) To demonstrate the excellent adsorption and catalytic performance of the porous carbon for volatile organic compounds, rice straw-based porous carbon, circuit board-based porous carbon, and a conventional commercial activated carbon were selected as the comparison. The removal characteristics of the three volatile organic compounds were tested under the same adsorption and catalytic conditions. The pore structure parameters of the commercial activated carbon are shown in Table 3, the saturated adsorption capacities of the four carbon materials are shown in Table 4, the catalytic performance results of the adsorption-catalytic porous carbon are shown in Table 5, and the catalytic oxidation efficiency of the circuit board-based porous carbon for volatile organic compounds is shown in Figure 4. Figure 3 Figure 4 Figure 5

[0066] As can be seen from the above tables and figures, the adsorption performance of the three prepared porous carbons is significantly better than that of the commercial activated carbon. Under the adsorption conditions at 120 °C, the adsorption capacity of the adsorption-catalytic porous carbon for ethyl acetate is 110.1 mg / g, which is 3.8 times that of the commercial activated carbon, and the adsorption capacity is higher than that of the rice straw-based porous carbon and the circuit board-based porous carbon. The adsorption-catalytic porous carbon has a very high removal efficiency for volatile organic compounds at 200 °C and 240 °C. At an environment of 240 °C, the removal efficiency of the three volatile organic compounds is greater than 95%, maintaining a similar catalytic oxidation efficiency to the circuit board-based porous carbon, while the commercial activated carbon and the rice straw-based porous carbon have almost no catalytic performance.

[0067] Table 3 Pore structure parameters of commercial activated carbon

[0068] BET specific surface area (m 2 / g) Total pore volume (cm 3 / g) Micropore volume (cm3 / g) 3 / g) Mesopore volume (cm 3 / g)]]> Average pore diameter (nm) Microporosity (%) 925.4 0.4689 0.3859 0.083 1.85 82.3

[0069] ​​​​​The above test data show that the prepared adsorption-catalysis porous carbon maintains the adsorption performance of the rice stem-based porous carbon and embodies the catalytic oxidation characteristics of the circuit board-based porous carbon.

[0070] It can be understood that the above examples are exemplary and cannot be understood as limiting the application, and those skilled in the art can change, modify, replace and modify the above examples within the scope of the application.

Claims

1. A method for preparing porous carbon with dual adsorption and catalytic properties, characterized in that: The preparation method comprises the following steps: Step (1), pre-treating agricultural waste and organic electronic waste; wherein the organic electronic waste includes plastic housings and circuit boards of household appliances and electronic equipment, and contains metal components such as Cu, Ni, Mn, and Co; 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): agricultural waste-based carbon and organic electronic waste-based carbon are mixed to obtain mixed carbon, an alkaline activator is added and co-activated at high temperature, and then acid-washed, water-washed and dried in sequence 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.

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 to 1:15, the carbonization time is 120 to 480 min, and the temperature is 150 to 220 °C.

5. The preparation method according to claim 3, characterized in that When carbonization is carried out in an inert atmosphere in a tube 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 to 1:3, and the mass percentage of each metal element in the mixed carbon is: Cu: 0.5 to 3%, Mn: 0.5 to 3%, Co: 0.1 to 1.5%, Ni: 0.1 to 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 with dual adsorption and catalytic properties, characterized in that: The method according to any one of claims 1 to 8 is used to prepare the present invention.

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

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