An activated carbon fiber composite type manganese-based catalyst for VOCs catalytic combustion, and a preparation method and application thereof

Abstract

The application discloses an activated carbon fiber composite manganese-based catalyst for VOCs catalytic combustion and a preparation method and application thereof, and belongs to the technical field of catalyst preparation. The method comprises the following steps: firstly, adding a precipitant to a metal salt solution for precipitation; then, sequentially performing aging, filtration, washing and drying to obtain a metal hydroxide precursor; adding the metal hydroxide precursor, a solid forming agent, an extruding agent and activated carbon fibers into a ball mill for grinding and uniform mixing; after the uniform mixing, adding acid to bond the raw materials into a group and performing second aging; extruding the material after the second aging again and performing third aging; drying the material after the third aging, and calcining after the drying, so that the composite manganese-based catalyst is obtained. The prepared activated carbon fiber composite manganese-based catalyst is simple in preparation, large in specific surface area, high in efficient capture-catalytic activity for low-concentration VOCs waste gas, and suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst preparation, and particularly relates to an activated carbon fiber composite manganese-based catalyst for VOCs catalytic combustion, a preparation method and application thereof. BACKGROUND

[0002] Currently, the VOCs treatment technologies generally used at home and abroad include adsorption / absorption method, condensation method, membrane separation method, photocatalysis method, direct combustion method and catalytic combustion method. Among them, the catalytic combustion method is an economical VOCs treatment method. It is a new type of treatment method with low energy consumption, low emission, green environmental protection and no secondary pollution. Common catalysts are generally divided into two categories: noble metal supported catalysts and transition metal oxide catalysts. The noble metal catalysts mainly use Pt, Pd, Rh, Au, Ru, etc. as active components, and active carbon, molecular sieve, rare earth composite oxide, non-active high specific surface area oxide, etc. as carriers, so as to improve the dispersity and anti-poisoning ability, and generally have excellent low-temperature catalytic performance, but the cost is high, the raw materials are scarce and easy to sinter. The transition metal oxide catalysts mainly use Mn, Fe, Co, Cu, Ni, Ce, etc. transition metal oxides as active components, and directly use or load on active carbon, Al2O3, TiO2, etc. large specific surface area carriers, utilize the multiple valence of transition metal, and the synergistic effect of metal oxides after mutual doping, effectively improve the catalytic activity, and also can take different doping combinations for different types of VOCs.

[0003] In the related art, the preparation methods of VOCs treatment catalysts mainly include co-precipitation method, template method, citric acid complexation method, etc., and also include some preparation methods of supported and monolithic catalysts. A Mn-Ce catalyst for catalytic combustion of VOCs waste gas is disclosed in the patent application 202310157637.0. The patent uses manganese metal salt as a precursor and other metal salts as modifiers, citric acid as a complex, and obtains the catalyst by pyrolysis of the metal salt. When the molar ratio of Mn to Ce is 4:1, the catalyst can degrade 90% of toluene or ethyl acetate below 200℃. A catalyst preparation method for VOC catalytic combustion is disclosed in the patent application 202210404645.6. The steps are as follows: after the metal oxide is dissolved, centrifuged, washed, dried and calcined, the metal oxide is obtained as a carrier. Then, the noble metal solution is mixed with the metal oxide carrier, and after washing, drying and calcining, a rare earth metal oxide-metal oxide supported noble metal catalyst is obtained. This catalyst can effectively degrade benzene at 200-260℃. Although the catalysts prepared by these preparation methods have excellent performance, the preparation cost is high, the utilization rate of active components is low, and the degradation effect of some low-concentration VOCs is poor. Therefore, how to prepare a catalyst suitable for low-concentration VOCs degradation and industrial production is a problem to be solved at present. SUMMARY

[0004] To solve the above problems, the present application provides a preparation method of an activated carbon fiber composite manganese-based catalyst for VOCs catalytic combustion. This method uses ball milling, mixing and extrusion molding technology to prepare a catalyst with a certain fixed form, effectively increasing the utilization rate of active components. The addition of activated carbon fiber can effectively enhance the capture of VOCs by the catalyst, and the VOCs catalytic oxidation catalyst is suitable for use under industrial conditions.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] A preparation method of an activated carbon fiber composite manganese-based catalyst for VOCs catalytic combustion, comprising the following steps:

[0007] (1) A precipitant is added to a metal salt solution for precipitation, and after aging, filtering, washing and drying, a metal hydroxide precursor is obtained;

[0008] (2) The metal hydroxide precursor, solid forming agent, extrusion agent and activated carbon fiber are added to a ball mill for grinding and mixing uniformly. After mixing, acid is added to bond the raw materials into a lump and age;

[0009] (3) The aged material of step (2) is extruded and aged again;

[0010] (4) drying the material after aging in step (3), and calcining after drying, to obtain the composite manganese-based catalyst.

[0011] In the above preparation method: in step (1), the metal composition in the metal salt is copper-manganese with a molar ratio of 1-3:1-3, or iron-manganese with a molar ratio of 1-3:1-3, or cerium-manganese with a molar ratio of 1-3:1-3.

[0012] In the above preparation method: in step (1), the precipitant is one of sodium hydroxide solution or potassium hydroxide solution, the concentration of the precipitant is 1-4 mol / L, and the precipitation condition is pH value of 10-12.

[0013] In the above preparation method: in step (1), the drying temperature is 60-120℃, and the drying time is 12-24 hours.

[0014] In the above preparation method: in step (2), the solid forming agent is one of pseudo-boehmite or alumina, and the extruding agent is one of sesbania gum or talc.

[0015] In the above preparation method: in step (2), the mass ratio of the solid forming agent to the metal hydroxide precursor is 3-7:3-10, the added mass of the extruding agent is 2-5% of the total mass of the solid forming agent and the metal hydroxide precursor, and the added amount of the active carbon fiber is 1-5% of the total mass of the solid forming agent and the metal hydroxide precursor.

[0016] In the above preparation method: in step (2), the added acid is nitric acid solution with a volume fraction of 2.5-15%, and the volume ratio of the raw material to the acid after ball milling is 1:1-1.7:1.

[0017] In the above preparation method: in steps (1) - (3), the aging temperature is room temperature, and the aging time is 24-48 hours.

[0018] Preferably: in step (4), the drying temperature is 100-140℃, the drying time is 20-24 hours, the calcining temperature is 450-550℃, and the calcining time is 3-6 hours.

[0019] An active carbon fiber composite manganese-based catalyst for catalytic combustion of VOCs is prepared by the above method.

[0020] In the technical scheme of the present application, the catalyst prepared by the above method is applied to catalytic combustion of VOCs.

[0021] The concept of the present application is as follows:

[0022] The application is in view of the problems of large industrial production waste gas, strong volatility, difficult post-processing, lack of effective treatment for some low concentration VOCs, and many catalyst preparation methods not suitable for industrial large-scale production, etc. The application creatively provides a preparation method of activated carbon fiber composite manganese-based catalyst for VOCs catalytic combustion. The method adopts ball milling, mixing and extrusion molding technology to prepare a catalyst with a certain fixed form. The extrusion molding technology can effectively increase the utilization rate of active components, and at the same time, the catalyst ratio can be changed to cope with different catalytic scenes. The addition of activated carbon fiber can effectively enhance the capture of VOCs by the catalyst, and the adsorption-catalysis technology is combined, which is suitable for effective capture and adsorption of some volatile and low concentration VOCs under industrial conditions, and further catalytic degradation of VOCs, reducing the harm of VOCs to the environment and human body.

[0023] The application has the following beneficial effects:

[0024] 1. The preparation method of the application can effectively reduce the cost of raw materials, and is suitable for industrial large-scale use,

[0025] 2. A certain amount of activated carbon fiber is added in the preparation method of the application to enhance the adsorption effect, which can effectively improve the capture ability of low concentration VOCs in the environment, and realize complete catalytic combustion of VOCs at a lower temperature. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 For the effect of degrading different VOCs in Example 1; the space velocity condition is 6000h -1 ; the VOCs concentration is 1000ppm.

[0027] Figure 2 For the effect of catalyst catalytic degradation of ethyl acetate before and after adding 5% activated carbon fiber; the space velocity condition is 15000h -1 ; the ethyl acetate concentration is 1000ppm.

[0028] Figure 3 For the effect of catalyst catalytic degradation of ethyl acetate before and after adding 5% activated carbon fiber; the space velocity condition is 15000h -1 ; the ethyl acetate concentration is 1000ppm. DETAILED DESCRIPTION

[0029] The application will be further described below in combination with examples, but the protection scope of the application is not limited thereto:

[0030] Example 1:

[0031] (1) Dissolve two kinds of metal salts Ce(N03)3 and Mn(N03)2 in water according to the molar ratio of metal elements as 1:2, add 1 mol / L NaOH solution as a precipitant in the solution, stir the solution until pH = 12; stand for 24 hours at room temperature, filter, wash, and dry at 100°C for 12 hours to obtain CuMn metal hydroxide precursor.

[0032] (2) Add CuMn metal oxide precursor and pseudoboehmite into a ball mill according to the mass ratio of 5:5, and add 2% wt sesbania gum (the amount is relative to the total mass of CuMn metal oxide precursor and pseudoboehmite) and 5% wt activated carbon fiber (the amount is relative to the total mass of CuMn metal oxide precursor and pseudoboehmite) at the same time, and mix uniformly. (The activated carbon fiber is purchased from Jiangsu Xingjulong Environmental Protection Technology Co., Ltd.; model: XJF-100; website: www.ahxj- acf.com

[0033] (3) When the raw materials are stirred uniformly, add 10% concentration (volume fraction) of dilute nitric acid solution, and stick together according to the raw material and dilute nitric acid water powder ratio of 1.4:1, and stand for 24 hours at room temperature.

[0034] (4) Extrude the raw materials into a mold using a mold, and stand for 24 hours at room temperature again.

[0035] (5) Put the shaped catalyst into an oven, dry at 100°C for 24 hours.

[0036] (6) Put the dried catalyst into a muffle furnace, calcine at 500°C for 3 hours to obtain a composite manganese-based catalyst.

[0037] Example 2:

[0038] (1) Dissolve two kinds of metal salts Ce(N03)3 and Mn(N03)2 in water according to the molar ratio of metal elements as 1:3, add 2 mol / L NaOH solution as a precipitant in the solution, stir the solution until pH = 12; stand for 24 hours, filter, wash, and dry at 100°C for 24 hours to obtain CeMn metal hydroxide precursor.

[0039] (2) Add CeMn metal oxide precursor and pseudoboehmite into a ball mill according to the mass ratio of 7:3, and add 3% wt talc powder (the amount is relative to the total mass of CeMn metal oxide precursor and pseudoboehmite) and 5% wt activated carbon fiber (the amount is relative to the total mass of CeMn metal oxide precursor and pseudoboehmite) at the same time, and mix uniformly.

[0040] ​(3) After the raw materials are stirred evenly, 10% by volume of dilute nitric acid solution is added, and the raw materials are bonded into a lump at a raw material:dilute nitric acid water powder ratio of 1.2:1, and are aged at room temperature for 24 hours.

[0041] (4) The raw materials are extruded into a shape using a mold, and are aged at room temperature again for 24 hours.

[0042] (5) The shaped catalyst is placed into an oven, dried at 120°C for 24 hours.

[0043] (6) The dried catalyst is placed into a muffle furnace, calcined at a high temperature of 500°C for 4 hours, and a composite manganese-based catalyst is obtained.

[0044] Example 3:

[0045] (1) Cu(NO3)2 and Mn(NO3)2 two kinds of metal salts are dissolved in water at a metal element molar ratio of 1:3, 3 mol / L KOH solution is added as a precipitating agent in the solution, and the solution is stirred until pH=12; after 24 hours of standing and aging, filtration, washing, and drying at 100°C for 24 hours, a CuMn metal hydroxide precursor is obtained.

[0046] (2) The CuMn metal oxide precursor and pseudoboehmite are added to a ball mill at a mass ratio of 7:3, and 2% wt of sesbania gum (the amount added is relative to the total mass of the CuMn metal oxide precursor and the pseudoboehmite) and 1% wt of activated carbon fiber (the amount added is relative to the total mass of the CuMn metal oxide precursor and the pseudoboehmite) are simultaneously added, and are mixed evenly.

[0047] (3) After the raw materials are stirred evenly, 2.5% by volume of dilute nitric acid solution is added, and the raw materials are bonded into a lump at a raw material:dilute nitric acid water powder ratio of 1.3:1, and are aged at room temperature for 24 hours.

[0048] (4) The raw materials are extruded into a shape using a mold, and are aged at room temperature again for 24 hours.

[0049] (5) The shaped catalyst is placed into an oven, dried at 100°C for 24 hours.

[0050] (6) The dried catalyst is placed into a muffle furnace, calcined at a high temperature of 450°C for 3 hours, and a composite manganese-based catalyst is obtained.

[0051] Example 4:

[0052] (1) Dissolve Fe(NO3)3 and Mn(NO3)2 two kinds of metal salts in water according to the molar ratio of metal elements 1:3, add 4 mol / L NaOH solution as precipitant in the solution, stir the solution to pH=10; after 24 hours of standing and aging, filter, wash, and dry at 120°C for 16 hours to obtain FeMn metal hydroxide precursor.

[0053] (2) Add FeMn metal oxide precursor and pseudoboehmite to the ball mill according to the mass ratio of 9:1, and add 5%wt talc (the amount added is 5%wt relative to the total mass of FeMn metal oxide precursor and pseudoboehmite) and 5%wt activated carbon fiber (the amount added is 5%wt relative to the total mass of FeMn metal oxide precursor and pseudoboehmite) at the same time, and mix uniformly.

[0054] (3) After the raw materials are stirred uniformly, add 15% volume fraction of dilute nitric acid solution, and stick together according to the raw material and dilute nitric acid powder ratio of 1.1:1, and age at room temperature for 24 hours.

[0055] (4) Use a mold to extrude the raw materials into a shape, and age again at room temperature for 48 hours.

[0056] (5) Put the shaped catalyst into an oven and dry at 120°C for 24 hours.

[0057] (6) Put the dried catalyst into a muffle furnace and calcine at 550°C for 6 hours to obtain a composite manganese-based catalyst.

[0058] Comparative Example 1

[0059] (1) Preparation of the catalyst

[0060] Except that no activated carbon fiber is added in the catalyst preparation process, the rest of the conditions are the same as in Example 2.

[0061] (2) Test of catalytic performance

[0062] Taking the degradation of ethyl acetate as an example, the degradation rate of the catalyst with activated carbon fiber at each temperature is significantly higher than that of the catalyst without activated carbon fiber.

[0063] Comparative Example 2

[0064] (1) Preparation of the catalyst

[0065] According to Example 2, after step (1), the catalyst is directly calcined in a muffle furnace at 500°C for 4 hours to obtain a coprecipitated CeMn catalyst.

[0066] (2) Test of catalytic performance

[0067] Take the degradation of ethyl acetate as an example, the catalyst prepared by the method of the present patent has better performance in degrading ethyl acetate than the catalyst prepared by the common coprecipitation method.

[0068] Figure 1 For the effect comparison of degrading different VOCs in Example 1, the space velocity of the reaction was 6000h -1 -1, and the concentration of VOCs was 1000ppm. The temperature at which the degradation rate of toluene, xylene, ethyl acetate and butyl acetate reached 98% was about 180℃, 240℃, 100℃ and 180℃, respectively.

[0069] Figure 2 For the effect comparison of Comparative Example 1 and Example 2, the effect of the catalyst on the degradation of ethyl acetate before and after adding 5% mass fraction of activated carbon fiber; the space velocity was 15000h -1 -1, and the concentration of ethyl acetate was 1000ppm. After adding the activated carbon fiber, the degradation rate of ethyl acetate at each temperature point was improved. The addition of the activated carbon fiber is beneficial to the capture of low-concentration ethyl acetate in the air by the catalyst and improves the catalytic activity.

[0070] Figure 3 For the effect comparison of Comparative Example 2 and Example 2, the effect comparison of the catalyst prepared by the common coprecipitation method and the catalyst prepared by the method of Example 2 on the degradation of ethyl acetate; the space velocity was 15000h -1 -1, and the concentration of ethyl acetate was 1000ppm. The catalyst prepared by the method of the present patent can effectively improve the degradation capacity of the catalyst for ethyl acetate at low temperature.

Claims

1. A method for preparing an activated carbon fiber composite type manganese-based catalyst for catalytic combustion of VOCs, characterized by: It comprises the following steps: (1) adding a precipitant to a metal salt solution to precipitate, and then aging, filtering, washing and drying to obtain a metal hydroxide precursor; In step (1), the metal composition in the metal salt is copper-manganese with a molar ratio of 1:1-3, iron-manganese with a molar ratio of 1:1-3, or cerium-manganese with a molar ratio of 1:1-3; the concentration of the precipitant is 1-4 mol / L, and the precipitation condition is a pH value of 10-12; (2) adding the metal hydroxide precursor, a solid forming agent, an extruding agent and activated carbon fiber into a ball mill to grind and mix uniformly; after mixing, adding an acid to make the raw materials stick together and age; In step (2), the mass ratio of the solid forming agent to the metal hydroxide precursor is 3-7:3-10; the added amount of the extruding agent is 2-5% of the total mass of the solid forming agent and the metal hydroxide precursor; and the added amount of the activated carbon fiber is 1%-5% of the total mass of the solid forming agent and the metal hydroxide precursor; In step (2), the added acid is a nitric acid solution with a volume fraction of 2.5-15%; and the volume ratio of the raw materials to the acid after ball milling is 1:1-1.7:1; (3) extruding and shaping the aged material of step (2) again and aging; (4) drying the aged material of step (3), and calcining after drying to obtain a composite manganese-based catalyst; In step (4), the drying temperature is 100-140℃, the drying time is 20-24 h; the calcining temperature is 450-550℃, and the calcining time is 3-6 hours.

2. The preparation method of the activated carbon fiber composite type manganese-based catalyst according to claim 1, characterized by: In step (1), the precipitant is one of a sodium hydroxide solution or a potassium hydroxide solution.

3. The preparation method of the activated carbon fiber composite type manganese-based catalyst according to claim 1, characterized by: In step (1), the drying temperature is 60-120℃, and the drying time is 12-24 hours.

4. The preparation method of the activated carbon fiber composite type manganese-based catalyst according to claim 1, characterized by: In step (2), the solid forming agent is one of pseudo-boehmite or alumina, and the extruding agent is one of sesbania gum or talc powder.

5. The preparation method of the activated carbon fiber composite type manganese-based catalyst according to claim 1, characterized by: In steps (1)-(3), the aging temperature is room temperature, and the aging time is 24-48 hours.

6. An activated carbon fiber composite type manganese-based catalyst for catalytic combustion of VOCs, characterized by: The catalyst is prepared by the method of any one of claims 1-5.

7. The use of the catalyst prepared by the method of claim 1 in catalyzing the combustion of VOCs.

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