A high-entropy catalyst for synergistically degrading vocs at low temperature and a preparation method thereof

Abstract

The application discloses a high-entropy catalyst for synergistically degrading VOCs through light and heat at low temperature and a preparation method thereof. The catalyst uses a cheap metal composite oxide as a thermal catalyst carrier, and loads a Bi-based photocatalyst to form a light-heat synergistic catalyst. The cheap metal composite oxide is 3-5 kinds of Mn, Cu, Fe, Co, Ni, Cr, Zn, Ba, Ca, Mg, Al, the Bi-based photocatalytic material is BiOX (X is halogen), and the loaded Bi-based photocatalytic material accounts for 5-15% of the total mass of the catalyst. The application ingeniously uses the adsorption of the cheap metal composite oxide to halogen anions, realizes zero discharge of anion "waste liquid" in the process of green catalyst construction, and has the advantages of green and environment-friendly preparation process, rich raw material sources and low cost. The prepared catalyst has high catalytic activity, high VOCs conversion rate, low required temperature and long service period.

Description

Technical Field

[0001] This invention relates to a high-entropy catalyst for the photothermal synergistic degradation of VOCs at low temperatures and its preparation method, belonging to the fields of new materials and environmental protection. Background Technology

[0002] Volatile organic compounds (VOCs) are organic compounds with a saturated vapor pressure greater than 70.91 Pa at room temperature and a boiling point less than 260℃ at normal pressure. Most VOCs have an unpleasant odor and are toxic, irritating, teratogenic, and carcinogenic. Benzene, toluene, and formaldehyde, in particular, can cause significant harm to human health. As research into VOCs deepens, it has become increasingly clear that they not only pose immeasurable risks to human health and environmental quality but also damage the atmospheric ecosystem. Therefore, it is essential to focus on the prevention and control of VOCs.

[0003] To control VOCs, researchers both domestically and internationally have conducted extensive research and developed various VOCs control technologies, including adsorption, absorption, membrane separation, low-temperature plasma, combustion, biodegradation, photocatalytic oxidation, and thermocatalytic oxidation. However, each of these technologies has its own shortcomings in the VOCs control process, such as limited adsorption capacity, difficulty in post-treatment of absorbents, high membrane costs, high energy consumption in condensation methods, and the tendency of low-temperature plasma methods to generate harmful byproducts (O3, NO). x VOCs are generated at high temperatures (≥800℃) during combustion, and biodegradation is selective, photocatalytic degradation efficiency is low, and thermocatalytic oxidation temperature is too high. Therefore, a single technology is still insufficient to effectively control VOCs, so the development of inexpensive and highly efficient photocatalytic catalysts is an urgent problem to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of low photocatalytic efficiency and high thermal catalytic energy consumption, and to provide a high-entropy catalyst for low-temperature photothermal synergistic degradation of VOCs and its preparation method.

[0005] To address the aforementioned technical problems, this invention provides a high-entropy catalyst for the photothermal synergistic degradation of VOCs at low temperatures. This catalyst uses a thermal catalyst formed from an inexpensive metal composite oxide as a support, and loads a Bi-based photocatalyst to form a photothermal synergistic high-entropy catalyst. The inexpensive metal is selected from 3 to 5 of Mn, Cu, Fe, Co, Ni, Cr, Zn, Ba, Ca, Mg, and Al. The Bi-based photocatalyst is selected from 1 to 2 of BiOF, BiOCl, BiOBr, and BiOI, wherein the loaded Bi-based photocatalyst accounts for 5 to 15% of the total mass of the catalyst.

[0006] The present invention also provides a method for preparing the high-entropy catalyst for photothermal synergistic degradation of VOCs at low temperature, comprising the following steps:

[0007] (1) prepare a mixed colloidal aqueous solution of transition metal hydroxide, alkaline earth metal oxide and aluminum oxide, control the molar ratio of divalent metal ions to trivalent metal ions at 2.0-5.0:1, control the total concentration of metal ions at 2.0-5.0 mol / L, control the pH value at 9-11 by using amino lye, put into an autoclave after stirring at room temperature for 1-10 hours, fill in 0-5.0 Mpa carbon dioxide, hydrothermal treatment at 80-120 DEG C for 12-48 hours, cool to room temperature, filter the obtained colloid, wash, dry at 60-100 DEG C, put into a muffle furnace and calcine at 300-600 DEG C for 4-8 hours to obtain a solid powder;

[0008] (2) add a certain amount of Bi salt ethanol solution to the solid powder obtained in (1), stir at 20-60 DEG C for 1-3 hours, continue to control the pH value at 9-11 by using amino lye, continue hydrothermal treatment at 80-120 DEG C for 6-12 hours, then filter or centrifugal dehydrate the obtained colloid, wash with water until neutral, dry at 60-100 DEG C, put into a muffle furnace and calcine at 300-500 DEG C for 4-8 hours to prepare a corresponding high-entropy metal composite oxide loaded Bi-based material, a new type of photo-thermal synergistic high-entropy catalyst.

[0009] Further, in step (1), the transition metal hydroxide is 3-5 kinds of Mn(OH)2, Cu(OH)2, Fe(OH)3, Co(OH)2, Ni(OH)2, Cr(OH)3 and Zn(OH)2.

[0010] Further, in step (1), the alkaline earth metal oxide is 1-2 kinds of BaO, CaO and MgO.

[0011] Further, in steps (1) and (2), the amino lye is 1-2 kinds of NH4OH, CO(NH2)2, H2NCH2CH2NH2 and CH3NH2.

[0012] Further, in step (2), the Bi salt is 1-2 kinds of BiF3, BiCl3, BiBr3 and BiI3.

[0013] Further, in step (2), the loaded Bi-based photocatalytic material accounts for 5-15% of the total mass of the catalyst.

[0014] The application uses high-entropy metal oxide as a carrier, assembles a single layer of BiOX on the carrier, and then precisely constructs a BiOX / M x O y photo-thermal synergistic catalytic system and applies it to the degradation of VOCs. The application will, on one hand, provide a BiOX / M x Oy The cheap catalytic system provides a green production process, strives to realize zero discharge of anion waste liquid, thereby improving atomic economy, realizing energy saving and emission reduction; on the other hand, an environmentally friendly, efficient and industrialized process route is explored for the degradation of VOCs at low temperature; and a key new technology is developed for the coordinated governance of air environmental pollution reduction and carbon reduction.

[0015] The present application has the following beneficial effects:

[0016] (1) The prepared high-entropy photo-thermal synergistic catalyst shows high activity in the degradation of VOCs at low temperature, the degradation efficiency of VOCs can reach 95% at low temperature, the catalyst requires low temperature, the catalyst is a pure inorganic material, has a long service life, and has high temperature stability without deactivation for 700-1000 hours; the new catalyst shows a new use of efficiently degrading VOCs at low temperature.

[0017] (2) The present application ingeniously utilizes the adsorption of cheap metal composite oxides on halide anions, realizes zero discharge of anion 'waste liquid' in the green construction of catalyst process, and has the advantages of green and environmentally friendly catalyst preparation process, rich raw material sources, low cost, and no anion 'waste liquid'.

[0018] (3) The catalyst obtained by the present application overcomes the disadvantages of low efficiency of photocatalysts and high energy consumption of thermal catalysts. DETAILED DESCRIPTION

[0019] The present application will be further described below. The following examples are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0020] Reaction and detection conditions: The catalytic oxidation performance test of the catalyst on VOCs (ethyl acetate, toluene, benzene, dimethylbenzene, chlorobenzene, propane, etc.) adopts a tubular furnace with a program-controlled temperature rising function to control the temperature of the catalytic bed, and the concentration of toluene selected in the experiment is 4000mg·m -3 -1 -1 (GHSV = 30000mL·(gh -1 ) 100mL·min The catalyst filling amount is 0.2g (40-60 mesh), and quartz sand is added in the catalyst to eliminate the thermal effect. In order to prevent the adsorption phenomenon of the catalyst in the initial stage from causing the decrease of the outlet VOCs concentration, VOCs pre-adsorption treatment is carried out before the catalytic oxidation experiment, and then the temperature is programmed after the outlet VOCs concentration is stable. The VOCs concentration at the outlet of the reactor is analyzed online by a gas chromatograph (Shanghai Qiyang GC-9680-5C), and the CO2 concentration is detected by a hydrogen flame ionization detector of a nickel conversion furnace. The VOCs degradation efficiency is (inlet concentration-outlet concentration)*100% / inlet concentration.

[0021] Example 1

[0022] 10 mol Mn(OH)2, 10 mol Cu(OH)2, 10 mol Fe(OH)3, 60 mol BaO and 30 mol Al2O3 were prepared into 50 L colloids with deionized water; and NH4OH was added to control the pH value of the mixed solution to 9.0; 1.0 hour of intense stirring at room temperature, moved into an autoclave, hydrothermal treatment at 80℃ for 12 hours, then cooled to room temperature, the obtained colloids were filtered, washed, dried at 60℃, and then put into a muffle furnace for calcination at 300℃ for 4 hours, then 0.15 mol / L bismuth trichloride ethanol solution 50 L was added, stirred for 1 hour at 20℃, and NH4OH was added to control the pH value of the mixed solution to 9.0, and then moved into an autoclave for hydrothermal treatment at 80℃ for 6 hours. Then the obtained colloids were filtered and dehydrated, washed with water until neutral, dried at 60℃, and then put into a muffle furnace for calcination at 300℃ for 4 hours, to prepare a corresponding high-entropy metal composite oxide supported Bi-based material, a photo-thermal synergistic high-entropy catalyst. The degradation efficiency of toluene was tested in a tubular furnace with a program-controlled temperature rise function to control the catalytic bed, and the degradation efficiency of toluene could reach 95% at 120℃ under normal pressure, and the catalyst was not deactivated after 700 hours of use.

[0023] Example 2

[0024] 20 mol Co(OH)2, 30 mol Ni(OH)2, 10 mol Cr(OH)3, 20 mol Zn(OH)2, 20 mol Fe(OH)3, 30 mol BaO, 30 mol MgO and 30 mol Al2O3 were prepared into 36 L colloids with deionized water; and CH3NH2 was added to control the pH value of the mixed solution to 11.0; 10.0 hours of intense stirring at room temperature, moved into an autoclave, filled with 5.0 Mpa carbon dioxide, hydrothermal treatment at 120℃ for 48 hours, then cooled to room temperature, the obtained colloids were filtered, washed, dried at 100℃, and then put into a muffle furnace for calcination at 600℃ for 8 hours, then 0.8 mol / L bismuth trifluoride ethanol solution 50 L was added, stirred for 3 hours at 60℃, and CH3NH2 was added to control the pH value of the mixed solution to 11.0, and then moved into an autoclave for hydrothermal treatment at 120℃ for 12 hours. Then the obtained colloids were filtered and dehydrated, washed with water until neutral, dried at 100℃, and then put into a muffle furnace for calcination at 500℃ for 8 hours, to prepare a corresponding high-entropy metal composite oxide supported Bi-based material, a photo-thermal synergistic high-entropy catalyst. The degradation efficiency of toluene was tested in a tubular furnace with a program-controlled temperature rise function to control the catalytic bed, and the degradation efficiency of toluene could reach 95% at 115℃ under normal pressure, and the catalyst was not deactivated after 800 hours of use.

[0025] Example 3

[0026] 15 mol of Mn(OH)2, 15 mol of Cu(OH)2, 15 mol of Co(OH)2, 15 mol of Ni(OH)2, 15 mol of BaO, 15 mol of MgO and 30 mol of Al2O3 were prepared into 50 L colloids with deionized water; and CO(NH2)2was added to control the pH value of the mixed solution to 10.0; the mixture was stirred vigorously at room temperature for 8.0 hours, then was moved into an autoclave, 4 Mpa carbon dioxide was filled, and the mixture was hydrothermally treated at 100°C for 24 hours, then was cooled to room temperature, the obtained colloids were filtered, washed, dried at 100°C, and then were put into a muffle furnace to be calcined at 450°C for 4 hours, then 0.4 mol / L bismuth tribromide ethanol solution 50 L was added, the mixture was stirred at 25°C for 2 hours, and CO(NH2)2was added to control the pH value of the mixed solution to 10.0, then the mixture was continuously moved into an autoclave for hydrothermal treatment at 100°C for 8 hours. Then the obtained colloids were filtered, dehydrated, washed with water until neutral, dried at 80°C, and then were put into a muffle furnace to be calcined at 450°C for 4 hours, thereby a Bi-based material loaded with high-entropy metal composite oxides, i.e. a light-heat synergistic high-entropy catalyst was prepared. The degradation efficiency of ethyl acetate was tested in a tube furnace with a temperature-programmed heating function, and the degradation efficiency of ethyl acetate could reach 95% at 80°C under normal pressure, and the catalyst was not deactivated after 1000 hours of use.

[0027] Example 4

[0028] 15 mol Mn(OH)2, 15 mol Cu(OH)2, 15 mol Co(OH)2, 15 mol Fe(OH)3, 15 mol Ni(OH)2, 15 mol BaO, 15 mol MgO and 15 mol Al2O3 were prepared into 50 L colloids with deionized water; and H2NCH2CH2NH2 and CH3NH2 were added to control the pH value of the mixed solution to 10.0; the solution was stirred vigorously at room temperature for 8.0 hours, moved into an autoclave, filled with 3 MPa carbon dioxide, and hydrothermally treated at 100°C for 24 hours, then cooled to room temperature, the obtained colloids were filtered, washed, dried at 100°C, put into a muffle furnace and calcined at 450°C for 4 hours, then 0.2 mol / L bismuth tribromide and 0.2 mol / L bismuth trifluoride ethanol solution 50 L were added, stirred at 25°C for 2 hours, and the pH value of the mixed solution was controlled to 10.0 with H2NCH2CH2NH2 and CH3NH2, then the solution was moved into an autoclave and hydrothermally treated at 100°C for 8 hours. Then the obtained colloids were filtered, dehydrated, washed with water until neutral, dried at 80°C, put into a muffle furnace and calcined at 450°C for 4 hours, to prepare a corresponding high-entropy metal composite oxide supported Bi-based material, a light-heat synergistic high-entropy catalyst. The degradation efficiency of xylene was tested in a tube furnace with a temperature programming function in a catalytic bed, and the degradation efficiency of xylene could reach 95% at 90°C under normal pressure, and the catalyst was not deactivated after 800 hours of use.

[0029] Example 5

[0030] 15 mol Mn(OH)2, 30 mol Cu(OH)2, 15 mol Cr(OH)3, 15 mol Zn(OH)2, 15 mol CaO, 15 mol MgO and 15 mol Al2O3 were prepared into 50 L colloids with deionized water; and NH4OH was added to control the pH value of the mixed solution to 10.0; the solution was stirred vigorously at room temperature for 6.0 hours, moved into an autoclave, filled with 4 Mpa carbon dioxide, and hydrothermally treated at 80°C for 12 hours, then cooled to room temperature, the obtained colloids were filtered, washed, dried at 100°C, put into a muffle furnace and calcined at 450°C for 4 hours, then 0.3 mol / L bismuth triiodide and 0.3 mol / L bismuth trifluoride ethanol solution 50 L was added, stirred at 25°C for 2 hours, and NH4OH was used to control the pH value of the mixed solution to 10.0, then the solution was moved into an autoclave and hydrothermally treated at 100°C for 8 hours. Then the obtained colloids were filtered, dehydrated, washed with water until neutral, dried at 80°C, put into a muffle furnace and calcined at 450°C for 4 hours, to prepare the corresponding high-entropy metal composite oxide supported Bi-based material, a photo-thermal synergistic high-entropy catalyst. The degradation efficiency of chlorobenzene was tested in a tube furnace with a temperature programming function, and the chlorobenzene degradation efficiency could reach 95% at 85°C under normal pressure, and the catalyst was not deactivated after 700 hours of use.

[0031] Example 6

[0032] 15 mol Mn(OH)2, 15 mol Cu(OH)2, 15 mol Ni(OH)2, 15 mol Cr(OH)3, 15 mol Zn(OH)2, 15 mol CaO, 15 mol BaO and 15 mol Al2O3 are prepared into 50 L colloids with deionized water; and NH4OH and CO(NH2)2 are added to control the pH value of the mixed solution to be 10.0; the solution is stirred vigorously at room temperature for 6.0 hours, is moved into an autoclave, is filled with 4 Mpa carbon dioxide, is hydrothermally treated at 80°C for 12 hours, is cooled to room temperature, is filtered, is washed, is dried at 100°C, is placed into a muffle furnace, is calcined at 450°C for 4 hours, then 50 L of 0.3 mol / L bismuth trichloride ethanol solution is added, the solution is stirred at 25°C for 2 hours, and NH4OH and CO(NH2)2 are used to control the pH value of the mixed solution to be 10.0, and the solution is continuously moved into an autoclave for hydrothermal treatment at 100°C for 8 hours. Then the obtained colloids are filtered, dehydrated, washed with water until neutral, dried at 80°C, and placed into a muffle furnace for calcination at 450°C for 4 hours, thereby a corresponding high-entropy metal composite oxide loaded Bi-based material, i.e. a light-heat synergistic high-entropy catalyst, is prepared. A mixture of propane and ethyl acetate is used as a representative probe molecule, and the degradation efficiency of the mixture of propane and ethyl acetate is tested in a tube furnace with a temperature programming function to control the catalytic bed, and the degradation efficiency of ethyl acetate can reach 93% and the degradation efficiency of propane can reach 95% at 65°C under normal pressure, and the catalyst is not deactivated after 1000 hours of use.

[0033] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and modifications without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a high-entropy catalyst for synergistically degrading VOCs at low temperatures, characterized by, It comprises the following steps: (1) preparing a mixed colloidal aqueous solution of transition metal hydroxide, alkaline earth metal oxide and aluminum oxide, controlling the molar ratio of divalent metal ions to trivalent metal ions at 2.0-5.0:1, controlling the total concentration of metal ions at 2.0-5.0 mol / L, controlling the pH value with amino base solution at 9-11, stirring at room temperature for 1-10 hours, then putting into an autoclave, filling with 0-5.0 Mpa carbon dioxide, hydrothermal treatment at 80-120 ℃ for 12-48 hours, cooling to room temperature, filtering the obtained colloid, washing, drying at 60-100 ℃, putting into a muffle furnace and calcining at 300-600 ℃ for 4-8 hours to obtain a solid powder; (2) adding a certain amount of Bi salt ethanol solution to the solid powder obtained in (1), stirring at 20-60 ℃ for 1-3 hours, continuing to control the pH value with amino base solution at 9-11, continuing hydrothermal treatment at 80-120 ℃ for 6-12 hours; then filtering or centrifuging the obtained colloid, washing with water to neutral, drying at 60-100 ℃, putting into a muffle furnace and calcining at 300-500 ℃ for 4-8 hours to prepare a corresponding high-entropy metal composite oxide loaded Bi-based material, i.e. a high-entropy catalyst for synergistic degradation of VOCs at low temperature; the Bi-based material is 1-2 of BiOF, BiOCl, BiOBr and BiOI; in step (1), the transition metal hydroxide is 3-5 of Mn(OH)2, Cu(OH)2, Fe(OH)3, Co(OH)2, Ni(OH)2, Cr(OH)3 and Zn(OH)2.

2. The method for preparing a high-entropy catalyst for synergistically degrading VOCs at low temperatures according to claim 1, characterized in that, In step (1), the alkaline earth metal oxide is 1-2 of BaO, CaO and MgO.

3. The method of claim 1, wherein the high-entropy catalyst is prepared by the following steps: (1) preparing a precursor solution by mixing a metal salt and a solvent; (2) preparing a high-entropy catalyst by mixing the precursor solution with a reducing agent; and (3) washing and drying the high-entropy catalyst. In steps (1) and (2), the amino base solution is 1-2 of NH4OH, CO(NH2)2, H2NCH2CH2NH2 and CH3NH2.

4. The method of claim 1, wherein the high-entropy catalyst is prepared by the following steps: (1) preparing a precursor solution by mixing a metal salt and a solvent; (2) preparing a high-entropy catalyst by mixing the precursor solution with a reducing agent; and (3) washing and drying the high-entropy catalyst. In step (2), the Bi salt is 1-2 of BiF3, BiCl3, BiBr3 and BiI3.

5. The method for preparing a high-entropy catalyst for low-temperature photothermal synergistic degradation of VOCs according to claim 1, characterized in that, The Bi-based material loaded in step (2) accounts for 5-15% of the total mass of the catalyst.