Manganese-based catalyst as well as preparation method and application thereof

Abstract

The invention provides a manganese-based catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: a) mixing manganese salt and mixed metal salt in water to obtain a solution A; the mixed metal salt comprises aluminum salt; b) dropwise adding a sodium bicarbonate solution into the solution A and continuously stirring to obtain a solution B; c) standing the solution B to obtain a solid C; d) sequentially filtering, washing and drying the solid C to obtain a solid D; and e) roasting the solid D in an ozone atmosphere to obtain the manganese-based catalyst. The method can solve the problem that sulfur-containing VOCs are difficult to remove in the prior art, and is suitable for the field of catalyst synthesis.

Description

Technical Field

[0001] The present invention relates to the field of catalyst synthesis, and in particular to a manganese-based catalyst and a preparation method and application thereof. Background Art

[0002] Biofermentation processes are a crucial component of the industrialization of biotechnology. The biofermentation industry combines fermentation technology with modern biotechnology, using starch and other agricultural byproducts as raw materials. Using the biocatalytic functions of biological cells or enzymes, it conducts large-scale material processing and conversion to produce high-value-added products. Fermentation processes have attracted widespread attention due to their numerous steps, complex fermentation gas composition, and odor. The process emits significant amounts of volatile organic compounds (VOCs), such as those containing carbon or sulfur. Implementing effective waste gas purification and odor control technologies to minimize the environmental impact of fermentation gases is a key concern for biofermentation companies.

[0003] Catalytic oxidation can efficiently oxidize carbon-containing VOCs into pollution-free products such as CO2 and H2O at relatively low temperatures (250-500°C), achieving VOC removal. However, VOCs produced in the fermentation industry, in addition to carbon-containing VOCs, often also include sulfur-containing VOCs. When sulfur-containing VOCs are catalytically oxidized and removed using existing catalysts, the resulting sulfur-containing gas products are prone to secondary pollution to the environment. Therefore, there is a lack of effective and environmentally friendly methods for removing these sulfur-containing VOCs. Summary of the Invention

[0004] The main purpose of the present invention is to provide a manganese-based catalyst and its preparation method and application, so as to solve the problem that it is difficult to remove sulfur-containing VOCs in the prior art.

[0005] To achieve the above objectives, according to a first aspect of the present invention, a method for preparing a manganese-based catalyst is provided, comprising: a) mixing a manganese salt and a mixed metal salt in water to obtain a solution A; the mixed metal salt includes an aluminum salt; b) dripping a sodium bicarbonate solution into solution A while continuously stirring to obtain a solution B; c) treating solution B under heating and pressurizing conditions to obtain a solid C; d) filtering, washing, and drying solid C in sequence to obtain a solid D; and e) calcining solid D in an ozone atmosphere to obtain a manganese-based catalyst.

[0006] Furthermore, a) comprises mixing a manganese salt with a mixed metal salt, and stirring in deionized water to obtain solution A; preferably, the manganese salt comprises one or more of manganese nitrate, manganese chloride or manganese sulfate; preferably, the aluminum salt in the mixed metal comprises one or more of aluminum chloride, aluminum nitrate or aluminum acetate.

[0007] Furthermore, the mass ratio of the manganese salt to the mixed metal salt is 0.3 to 1:1; preferably, the mixed metal salt also includes chlorides and / or nitrates of auxiliary metal elements; the auxiliary metal elements include one or more of iron, cerium, zinc or copper; preferably, the molar ratio of the aluminum element in the mixed metal salt to the auxiliary metal element in the mixed metal salt is 10 to 20:1; preferably, the total mass fraction of the manganese salt and the mixed metal salt in solution A is 3 to 12%.

[0008] Furthermore, b) comprises adding sodium bicarbonate solution dropwise into solution A while stirring until the pH of the solution reaches 7.5 to 9.5, and then stopping stirring to obtain solution B; preferably, the molar concentration of sodium bicarbonate is 0.05 to 0.2 mol / L.

[0009] Furthermore, in c), the standing still comprises: the heating and pressurizing conditions include: a pressure of 0.1 to 0.3 MPa and a temperature of 105 to 110° C.; preferably, the treatment time is 18 to 24 hours.

[0010] Furthermore, in d), washing includes washing with alcohol; preferably, the temperature of the drying treatment is 40 to 60° C.; preferably, the alcohol includes anhydrous ethanol, propanol or isopropanol.

[0011] Furthermore, in e), the ozone atmosphere further comprises anhydrous air, nitrogen or carbon dioxide; preferably, in the ozone atmosphere, the volume concentration of ozone is 1 to 10%; preferably, the calcination temperature is 250 to 400° C.; preferably, the calcination time is 30 to 150 minutes.

[0012] In order to achieve the above-mentioned purpose, according to the second aspect of the present invention, a manganese-based catalyst is provided, which comprises manganese trioxide, aluminum trioxide and a first metal oxide; the first metal oxide comprises one or more of iron trioxide, cerium trioxide, zinc oxide or copper oxide; and the surface of the manganese-based catalyst contains oxygen-containing functional groups and oxygen defect vacancies.

[0013] Furthermore, the mass ratio of manganese tetraoxide, aluminum oxide and the first metal oxide is 0.25-0.95:1:0.06-0.12; preferably, the manganese-based catalyst includes a manganese-based catalyst prepared by any of the above-mentioned methods for preparing manganese-based catalysts; preferably, the specific surface area of ​​the manganese-based catalyst is ≥500m 2 / g.

[0014] To achieve the above objectives, according to a third aspect of the present invention, a method for preparing any one of the above-mentioned manganese-based catalysts or the use of any one of the above-mentioned manganese-based catalysts in the removal of sulfur-containing volatile organic compounds is provided; the use comprises: mixing the manganese-based catalyst with sulfur-containing volatile organic compounds and heating them to achieve the removal of the sulfur-containing volatile organic compounds; the heating temperature is 300-500°C.

[0015] By applying the technical solution of the present invention and utilizing the above-mentioned preparation method, a manganese salt and a mixed metal salt containing an aluminum salt are mixed in water to obtain a solution A, and then a sodium bicarbonate solution is dripped into the solution A to obtain a mixed solution B of a highly soluble manganese salt and other metal salts. The solid C generated after standing is filtered, washed, and dried in sequence to obtain a solid D. Finally, the solid D is placed in an ozone atmosphere for calcination, so that the upper surface of the manganese-based catalyst contains oxygen-containing functional groups and oxygen defect vacancies. The oxygen defect vacancies can combine with sulfur elemental substances to avoid the generation of secondary gaseous sulfur-containing pollutants, thereby achieving effective removal of sulfur-containing VOCs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0017] Figure 1 A schematic diagram showing the results of the catalytic removal efficiency of VOCs by the manganese-based catalyst according to Example 1 of the present invention is shown.

[0018] Figure 2 A schematic diagram showing the results of the catalytic removal efficiency of VOCs by the manganese-based catalyst according to Example 2 of the present invention is shown.

[0019] Figure 3 A schematic diagram showing the results of the catalytic removal efficiency of VOCs by the manganese-based catalyst according to Example 3 of the present invention is shown. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0021] As mentioned in the background, when using existing technologies to remove VOCs in the fermentation industry, sulfur-containing VOCs are difficult to remove using existing catalysts, which can easily lead to secondary pollution. In this application, the inventors have attempted to develop a manganese-based catalyst, its preparation method, and its application, resulting in a manganese-based catalyst that can effectively remove sulfur-containing VOCs. Consequently, a series of protection schemes are proposed in this application.

[0022] In a first typical embodiment of the present application, a method for preparing a manganese-based catalyst is provided, which comprises: a) mixing a manganese salt and a mixed metal salt in water to obtain a solution A; the mixed metal salt includes an aluminum salt; b) dripping a sodium bicarbonate solution into the solution A and continuously stirring until a solution B is obtained; c) treating the solution B under heating and pressurizing conditions to obtain a solid C; d) filtering, washing and drying the solid C in sequence to obtain a solid D; and d) calcining the solid D in an ozone atmosphere to obtain a manganese-based catalyst.

[0023] Manganese-based catalysts are commonly used VOC catalysts due to their low cost, excellent stability, and oxygen storage and release properties. However, existing catalysts of this type are not very active at low temperatures (250-500°C). Conventional manganese-based mixed metal oxide catalysts suffer from low specific surface area and poor dispersibility, making them unsuitable for the catalytic oxidation of VOCs, particularly for the removal of carbon- and sulfur-containing VOCs in the fermentation industry.

[0024] In the preparation method of the present application, a manganese-based catalyst is prepared by using a mixed metal salt containing an aluminum salt and a manganese salt. After the solid D containing manganese and aluminum elements is calcined with ozone, a manganese-based catalyst with a main skeleton of O-Al-O (oxygen-aluminum-oxygen) structure is prepared. This skeleton structure is conducive to the continuous grafting of other metal elements (including but not limited to manganese, iron, cerium, zinc or copper) on its surface to form a MO structure (M represents a metal element).

[0025] In the above step b), sodium bicarbonate is mixed with solution A. Sodium bicarbonate dissolves in water to form bicarbonate ions and sodium ions. In addition to adjusting the pH, the bicarbonate ions react with the mixed metal salt to form a soluble bicarbonate, simplifying the subsequent purification process. Furthermore, since the subsequent high-temperature and high-pressure static reaction requires sufficient dispersion of the metal ions in the solution, the sodium ions in the sodium bicarbonate solution can also prevent aggregation of the various mixed metal ions in the solution generated during the preparation process.

[0026] In the above-mentioned e) "ozone atmosphere" refers to an atmosphere containing ozone, including an atmosphere consisting of pure ozone or a gas mixture formed by mixing ozone with other gases. Calcination in an ozone-containing atmosphere can oxidize the metal oxide on the surface of solid D into a high-valent, stable metal oxide. Due to the change in the valence of the metal in the metal oxide, lattice oxygen defects, i.e., oxygen vacancies, are generated on the surface of the manganese-based catalyst.

[0027] Different from the oxygen vacancies on the catalyst surface obtained by calcining with oxygen-containing gas in the prior art, the oxygen vacancies on the catalyst surface obtained by the prior art method cannot generate peroxy functional groups after adsorbing oxygen molecules, thereby failing to achieve the advantages of ozone calcination in the present invention. The oxygen vacancies in the present application can capture oxygen in the gas phase and convert it into peroxy functional groups (O2 - ), rather than the free oxygen functional groups (O 2- ), can promote and continuously and rapidly oxidize VOCs, and can also capture and absorb the S element produced after the oxidation of sulfur-containing VOCs, to prevent the S element from being further oxidized to SO2 and re-entering the fermentation exhaust gas.

[0028] The manganese-based catalysts prepared by the existing technology are difficult to completely remove sulfur-containing VOCs, or they will release secondary sulfur-containing gaseous pollutants SO2 during the removal process, which can easily cause secondary pollution. In the present application, a manganese salt and a mixed metal salt solution undergo a hydrothermal crystallization reaction under alkaline conditions, and then undergo filtering, washing and drying, and finally undergo an ozone roasting process to obtain a hydrotalcite-like material with a surface rich in peroxy functional groups, namely the above-mentioned manganese-based catalyst. The surface of the manganese-based catalyst prepared by the technical solution of the present application contains rich peroxy functional groups and oxygen defect vacancies, which can effectively and deeply purify VOCs in the fermentation industry under low temperature (250-500°C). The preparation method of the present application has low raw material cost and convenient preparation operation. The VOCs in the exhaust gas have no secondary pollution after purification, the product is clean, and it is easy to achieve industrial application.

[0029] The specific surface area of ​​the manganese-based catalyst prepared by the above method is >500m 2 / g.

[0030] In a preferred embodiment, a) comprises mixing a manganese salt with a mixed metal salt, and stirring the mixture in deionized water to obtain solution A; preferably, the manganese salt comprises one or more of manganese nitrate, manganese chloride or manganese sulfate; preferably, the aluminum salt in the mixed metal comprises one or more of aluminum chloride, aluminum nitrate or aluminum acetate.

[0031] The mass fraction of the above-mentioned solution A includes but is not limited to 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11% or 12%.

[0032] In a preferred embodiment, the mass ratio of the manganese salt to the first mixed metal salt is 0.3 to 1:1; preferably, the above-mentioned mixed metal salt also includes chlorides and / or nitrates of auxiliary metal elements, and the auxiliary metal elements include one or more of iron, cerium, zinc or copper; preferably, the molar ratio of the aluminum element in the mixed metal salt to the chlorides and / or nitrates of the auxiliary metal elements in the mixed metal salt is 10 to 20:1; preferably, the total mass fraction of the manganese salt and the mixed metal salt in solution A is 3 to 12%.

[0033] Fe, Ce, Zn, and Cu have good oxygen capture capabilities in the catalytic oxidation of VOCs and can effectively reduce the temperature required for the catalytic reaction.

[0034] The mass ratio of the manganese salt to the first mixed metal salt includes, but is not limited to, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1. The molar ratio of the aluminum element in the first mixed metal salt to the metal element in the second mixed metal salt includes, but is not limited to, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, or 20:1.

[0035] In a preferred embodiment, b) comprises adding sodium bicarbonate solution dropwise into solution A while stirring until the pH of the solution reaches 7.5 to 9.5, and then stopping stirring to obtain solution B; preferably, the molar concentration of sodium bicarbonate is 0.05 to 0.2 mol / L.

[0036] The pH value of the solution B includes, but is not limited to, 7.5, 7.6, 7.8, 7.9, 8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.7, 8.9, 9.0, 9.1, 9.2, 9.3, 9.4, or 9.5. The molar concentration of the sodium bicarbonate includes, but is not limited to, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or 0.2 mol / L.

[0037] In a preferred embodiment, in c), the heating and pressurizing conditions include: a pressure of 0.1 to 0.3 MPa and a temperature of 105 to 110° C.; preferably, the treatment time is 18 to 24 hours.

[0038] The above-mentioned pressure includes but is not limited to 0.1, 0.2 or 0.3 MPa. The above-mentioned temperature includes but is not limited to 105, 106, 107, 108, 109 or 110°C. The above-mentioned time includes but is not limited to 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 23.5 or 24h. The present application places solution B in a high-temperature and high-pressure reactor, and produces solid C by self-crystallization under heating and pressurization conditions. In a preferred embodiment, in d), washing includes alcohol washing; the temperature of the drying treatment is 40 to 60°C; preferably, the alcohol washing includes alcohol washing with alcohol; preferably, the alcohol solution includes anhydrous ethanol, propanol or isopropanol.

[0039] The drying temperature includes but is not limited to 40°C, 50°C or 60°C.

[0040] In a preferred embodiment, in e), the ozone atmosphere further comprises anhydrous air, nitrogen or carbon dioxide; preferably, in the ozone atmosphere, the volume concentration of ozone is 1 to 10%; preferably, the calcination temperature is 250 to 400° C.; preferably, the calcination time is 30 to 150 minutes.

[0041] The volume concentration of the ozone includes, but is not limited to, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%. The calcination temperature includes, but is not limited to, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C or 400°C.

[0042] During the preparation process of the present application, a mixed atmosphere containing ozone is used to calcine the solid obtained after filtration, washing, and drying. Therefore, the manganese-based catalyst prepared in the present application has a rich surface containing oxygen-containing functional groups and oxygen vacancies, which can effectively and deeply purify VOCs in the fermentation industry under low temperature conditions. In a second typical embodiment of the present application, a manganese-based catalyst prepared by any of the above-mentioned methods for preparing a manganese-based catalyst is provided.

[0043] In a second typical embodiment of the present application, a manganese-based catalyst is provided, which includes manganese trioxide, aluminum trioxide and a first metal oxide; the first metal oxide includes one or more of iron trioxide, cerium trioxide, zinc oxide or copper oxide; the surface of the manganese-based catalyst contains oxygen-containing functional groups and oxygen defect vacancies.

[0044] In a preferred embodiment, the mass ratio of manganese tetraoxide, aluminum oxide and the first metal oxide is 0.25-0.95:1:0.06-0.12; preferably, the manganese-based catalyst is prepared by any of the above-mentioned methods for preparing manganese-based catalysts; preferably, the specific surface area of ​​the manganese-based catalyst is ≥500m 2 / g.

[0045] The specific surface area of ​​a catalyst refers to the effective surface area per unit volume of the catalyst, which is usually used to indirectly reflect the activity and reaction efficiency of the catalyst. The larger the specific surface area of ​​the catalyst, the larger its effective area, thus providing more active sites for the reaction to occur. Due to the limitations of the preparation method, the specific surface area of ​​the manganese-based catalyst in the existing technology is generally only 50 to 280 m 2 / g, and the manganese-based catalyst prepared by the preparation method of the present application has an O-Al-O structural main skeleton and oxygen defect vacancies, resulting in more surface active sites, so the specific surface area is larger than that of the manganese-based catalyst prepared in the prior art (>500m 2 / g), which can effectively promote the catalytic reaction.

[0046] In a third typical embodiment of the present application, a method for preparing any one of the above-mentioned manganese-based catalysts or the use of the above-mentioned manganese-based catalysts in the removal of sulfur-containing volatile organic compounds is provided; the application comprises: mixing the manganese-based catalyst with the sulfur-containing volatile organic compounds and heating them to achieve the removal of the sulfur-containing volatile organic compounds; the heating temperature is 300-500°C, including but not limited to 300, 350, 400, 425, 450 or 500°C.

[0047] The manganese-based catalyst prepared by the present application can catalytically oxidize carbon-containing VOCs into CO2 and H2O under aerobic conditions, and can also catalytically oxidize sulfur-containing VOCs into elemental S, CO2 and H2O without generating secondary sulfur-containing gaseous pollutants, and the removal efficiency is higher than 95%.

[0048] The beneficial effects of the present application will be further explained in detail below with reference to specific embodiments.

[0049] Example 1

[0050] 1. Manganese nitrate and mixed metal salt (aluminum chloride and cerium nitrate in a molar ratio of 10:1) were mixed at a ratio of 0.5:1, dissolved in deionized water, and stirred at room temperature and pressure to form a solution A with a mass fraction of 7%.

[0051] 2. Add 0.05 mol / L NaHCO3 solution dropwise into solution A and stir at room temperature and pressure until the pH of the solution reaches 8.0 to obtain solution B.

[0052] 3. Place solution B in an adjustable pressure autoclave and let it stand at 105°C and 0.3 MPa pressure for 24 hours.

[0053] 4. The mixed liquid in the high-pressure reactor was taken out and filtered to obtain solid C particles. The solid particles were washed once with anhydrous ethanol and then dried in a vacuum drying oven at 50°C for 6 hours to obtain solid D.

[0054] 5. Solid D was placed in a tube furnace and calcined at 250° C. for 90 min in a mixed atmosphere containing ozone (mixed anhydrous air containing 10% by volume of ozone) to obtain a manganese-based catalyst.

[0055] 6. The obtained manganese-based catalyst was tested for activity. The activity of the manganese-based catalyst can be expressed by the removal rate of ethanol, acetaldehyde and diethyl sulfide. The activity test was carried out in a fixed-bed quartz reactor under the following reaction conditions: ethanol concentration of 1200ppm, acetaldehyde concentration of 400ppm, diethyl sulfide concentration of 400ppm, and space velocity of 20000h -1 .

[0056] 7. The specific surface area of ​​the obtained manganese-based catalyst was tested by nitrogen adsorption and desorption test. The specific surface area of ​​the manganese-based catalyst prepared in this example was 642 m 2 / g.

[0057] The schematic diagram of the catalytic removal rate of VOCs is as follows Figure 1 As shown. Figure 1 It can be seen that the manganese-based catalyst prepared by this embodiment can achieve a 100% ethanol removal rate at 500°C, a 100% acetaldehyde removal rate at 425°C, and a 100% diethyl sulfide removal rate at 450°C, and does not produce SO2 gas, which shows that the manganese-based catalyst prepared by this embodiment has a significant effect on the removal of VOCs and will not cause secondary pollution.

[0058] Example 2

[0059] 1. Manganese chloride and mixed metal salt (aluminum nitrate and ferric nitrate in a molar ratio of 20:1) were mixed at a ratio of 0.3:1, dissolved in deionized water, and stirred at room temperature and pressure to form a solution A with a mass fraction of 12%.

[0060] 2. Add 0.15 mol / L NaHCO3 solution dropwise into solution A and stir at room temperature and pressure until the pH of the solution reaches 9.5 to obtain solution B.

[0061] 3. Place solution B in an adjustable pressure autoclave and let it stand at 108°C and 0.2 MPa pressure for 20 hours.

[0062] 4. The mixed liquid in the high-pressure reactor was taken out and filtered to obtain solid C particles. The solid particles were washed three times with propanol and then dried in a vacuum drying oven at 60°C for 6 hours to obtain solid D.

[0063] 5. Solid D was placed in a tube furnace and calcined at 330° C. for 150 min in a mixed atmosphere containing ozone (mixed nitrogen containing 5% by volume of ozone) to obtain a manganese-based catalyst.

[0064] 6. The activity of the obtained manganese-based catalyst was tested in a fixed-bed quartz reactor. The reaction conditions were: ethanol concentration 1200 ppm, acetaldehyde concentration 400 ppm, diethyl sulfide concentration 400 ppm, space velocity 20000 h -1 .

[0065] The specific surface area of ​​the manganese-based catalyst prepared in this embodiment is 587m 2 / g; the results of catalytic removal rate of VOCs are shown in the figure below. Figure 2 As shown, from Figure 2 It can be seen that the manganese-based catalyst prepared by this embodiment can achieve a 100% ethanol removal rate at 400°C, a 100% acetaldehyde removal rate at 300°C, and a 100% diethyl sulfide removal rate at 400°C, and no SO2 gas is generated. This shows that the manganese-based catalyst prepared by this embodiment has a significant effect on the removal of VOCs and will not cause secondary pollution.

[0066] Example 3

[0067] 1. Manganese salt (manganese sulfate and manganese chloride in a molar ratio of 3:1) and mixed metal salt (aluminum acetate, zinc chloride and copper nitrate in a molar ratio of 15:0.5:0.5) were mixed in a ratio of 1:1, dissolved in deionized water and stirred at room temperature and pressure to form a solution A with a mass fraction of 3%.

[0068] 2. Add 0.2 mol / L NaHCO3 solution dropwise into solution A and stir at room temperature and pressure until the pH of the solution reaches 7.5 to obtain solution B.

[0069] 3. Place solution B in an adjustable pressure autoclave and let it stand at 110°C and 0.1 MPa pressure for 18 hours.

[0070] 4. The mixed liquid in the autoclave was taken out after standing and filtered to obtain solid C particles. The solid particles were washed twice with isopropyl alcohol and then dried in a vacuum drying oven at 40°C for 6 hours to obtain solid D.

[0071] 5. Solid D was placed in a tube furnace and calcined at 400° C. for 30 min in a mixed atmosphere containing ozone (mixed carbon dioxide containing 1% by volume of ozone) to obtain a manganese-based catalyst.

[0072] 6. The activity of the obtained manganese-based catalyst was tested in a fixed-bed quartz reactor. The reaction conditions were: ethanol concentration 1200 ppm, acetaldehyde concentration 400 ppm, diethyl sulfide concentration 400 ppm, space velocity 20000 h -1 .

[0073] The specific surface area of ​​the manganese-based catalyst prepared in this embodiment is 549m 2 / g; the results of catalytic removal rate of VOCs are shown in the figure below. Figure 3 As shown, from Figure 3 It can be seen that the manganese-based catalyst prepared by this embodiment can achieve a 100% ethanol removal rate at 450°C, a 100% acetaldehyde removal rate at 350°C, and a 100% diethyl sulfide removal rate at 425°C, and does not produce SO2 gas, which shows that the manganese-based catalyst prepared by this embodiment has a significant effect on the removal of VOCs and will not cause secondary pollution.

[0074] Example 4

[0075] 1. Manganese chloride and mixed metal salt (aluminum nitrate and cerium nitrate in a molar ratio of 25:1) were mixed at a ratio of 1.2:1, dissolved in deionized water, and stirred at room temperature and pressure to form a solution A with a mass fraction of 15%.

[0076] 2. Add 0.25 mol / L NaHCO3 solution dropwise into solution A and stir at room temperature and pressure until the pH of the solution reaches 11.0 to obtain solution B.

[0077] 3. Place solution B in an adjustable pressure autoclave and let it stand at 115°C and 0.33 MPa for 28 hours.

[0078] 4. The mixed liquid in the high-pressure reactor was taken out and filtered to obtain solid C particles. The solid particles were washed three times with anhydrous ethanol and then dried in a vacuum drying oven at 70°C for 12 hours to obtain solid D.

[0079] 5. Solid D was placed in a tube furnace and calcined at 500° C. for 210 min in a mixed atmosphere containing ozone (mixed nitrogen containing 12% by volume of ozone) to obtain a manganese-based catalyst.

[0080] 6. The activity of the obtained manganese-based catalyst was tested in a fixed-bed quartz reactor. The reaction conditions were: ethanol concentration 1200 ppm, acetaldehyde concentration 400 ppm, diethyl sulfide concentration 400 ppm, space velocity 20000 h -1 .

[0081] The specific surface area of ​​the manganese-based catalyst prepared in this embodiment is 508m 2 / g.

[0082] For the removal of ethanol and acetaldehyde: 95% ethanol removal rate can be achieved at 500℃, and 97% acetaldehyde removal rate can be achieved at 475℃.

[0083] For the removal of diethyl sulfide: at 450°C, a removal rate of 99% of diethyl sulfide can be achieved, and SO2 gas is not detected in the outlet gas.

[0084] The VOCs removal effect of the manganese-based catalyst prepared in this example is slightly worse than that of the manganese-based catalyst prepared in Examples 1-3.

[0085] Example 5

[0086] 1. Manganese nitrate and mixed metal salt (aluminum acetate and copper nitrate in a molar ratio of 7:1) were mixed at a ratio of 0.2:1, dissolved in deionized water, and stirred at room temperature and pressure to form a solution A with a mass fraction of 2%.

[0087] 2. Add 0.03 mol / L NaHCO3 solution dropwise into solution A and stir at room temperature and pressure until the pH of the solution reaches 7.2 to obtain solution B.

[0088] 3. Place solution B in an adjustable pressure autoclave and let it stand at 100°C and 0.05 MPa for 15 hours.

[0089] 4. The mixed liquid in the high-pressure reactor was taken out and filtered to obtain solid C particles. The solid particles were washed three times with anhydrous ethanol and then dried in a vacuum drying oven at 35°C for 4 hours to obtain solid D.

[0090] 5. Solid D was placed in a tube furnace and calcined at 225° C. for 24 min in a mixed atmosphere containing ozone (a mixed nitrogen gas containing 0.5% by volume of ozone) to obtain a manganese-based catalyst.

[0091] 6. The activity of the obtained manganese-based catalyst was tested in a fixed-bed quartz reactor. The reaction conditions were: ethanol concentration 1200 ppm, acetaldehyde concentration 400 ppm, diethyl sulfide concentration 400 ppm, space velocity 20000 h -1 .

[0092] The specific surface area of ​​the manganese-based catalyst prepared in this embodiment is 527m 2 / g.

[0093] For the removal of ethanol and acetaldehyde: 96% ethanol removal rate can be achieved at 475℃, and 95% acetaldehyde removal rate can be achieved at 500℃.

[0094] For the removal of diethyl sulfide: at 475°C, a removal rate of 97% of diethyl sulfide can be achieved, and SO2 gas is not detected in the outlet gas.

[0095] The VOCs removal effect of the manganese-based catalyst prepared in this example is slightly worse than that of the manganese-based catalyst prepared in Examples 1-3.

[0096] Comparative Example 1

[0097] The difference from Example 1 is that the mixed atmosphere during the calcination of solid D in this comparative example does not contain ozone but contains oxygen, and the remaining steps are the same as in Example 1. The specific surface area of ​​the manganese-based catalyst in this comparative example is 376 m 2 / g.

[0098] For the removal of ethanol and acetaldehyde: 89% ethanol removal rate can be achieved at 450℃, and 94% acetaldehyde removal rate can be achieved at 425℃.

[0099] Regarding the removal of diethyl sulfide: a removal rate of 92% of diethyl sulfide can be achieved at 500° C. When the manganese-based catalyst prepared in this comparative example removes diethyl sulfide, SO 2 gas is generated, causing secondary pollution.

[0100] Comparative Example 2

[0101] The catalyst activity test of Example 1 of this application was carried out using a manganese-based catalyst commonly used in the prior art. The preparation method is described in patent application 202110497948.2. The specific surface area of ​​the manganese-based catalyst in this comparative example is 215m 2 / g. The removal of ethanol and acetaldehyde by this manganese-based compound: 93% ethanol removal rate can be achieved at 425°C, and 91% acetaldehyde removal rate can be achieved at 500°C.

[0102] Regarding the removal of diethyl sulfide: at 500°C, a removal rate of 46% of diethyl sulfide can be achieved, generating SO2 gas, causing secondary pollution.

[0103] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects: the present invention obtains a manganese-based catalyst, which is prepared by a hydrothermal crystallization reaction of a manganese salt and a mixed metal salt solution under alkaline conditions, and then washed with alcohol and calcined with ozone to obtain a manganese-based catalyst, the surface of which contains rich oxygen-containing functional groups and oxygen defect vacancies. The manganese-based catalyst prepared by the present application can be used to catalyze the oxidation and removal of VOCs produced in the fermentation industry. The preparation method is simple, and the removal efficiency of carbon-containing and sulfur-containing VOCs is higher than 95%. Moreover, when removing sulfur-containing VOCs, no sulfur-containing gas that pollutes the atmosphere is generated. It can achieve efficient removal of VOCs while not causing secondary pollution.

[0104] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a manganese-based catalyst, characterized in that: The preparation method comprises: a) mixing a manganese salt and a mixed metal salt in water to obtain a solution A; b) adding a sodium bicarbonate solution dropwise to the solution A while continuously stirring to obtain a solution B; c) treating the solution B under heating and pressure conditions to obtain solid C; d) filtering, washing, and drying the solid C in sequence to obtain a solid D; e) calcining the solid D in an ozone atmosphere to obtain the manganese-based catalyst; Wherein, the mixed metal salt includes aluminum salt.

2. The preparation method according to claim 1, characterized in that The a) step comprises mixing the manganese salt and the mixed metal salt in deionized water and stirring to obtain the solution A; Preferably, the manganese salt comprises one or more of manganese nitrate, manganese chloride or manganese sulfate; Preferably, the aluminum salt in the mixed metal comprises one or more of aluminum chloride, aluminum nitrate or aluminum acetate.

3. The preparation method according to claim 1 or 2, characterized in that The mass ratio of the manganese salt to the mixed metal salt is 0.3 to 1:1; Preferably, the mixed metal salt further comprises chlorides and / or nitrates of auxiliary metal elements; the auxiliary metal elements comprise one or more of iron, cerium, zinc or copper; Preferably, the molar ratio of the aluminum element in the mixed metal salt to the auxiliary metal element in the mixed metal salt is 10 to 20:1; Preferably, the total mass fraction of the manganese salt and the mixed metal salt in the solution A is 3-12%.

4. The preparation method according to claim 1, characterized in that b) includes adding the sodium bicarbonate solution dropwise into the solution A while stirring until the pH of the solution reaches 7.5 to 9.5, and then stopping stirring to obtain the solution B; Preferably, the concentration of the sodium bicarbonate is 0.05-0.2 mol / L.

5. The preparation method according to claim 1, characterized in that In c), the heating and pressurizing conditions include: a pressure of 0.1 to 0.3 MPa and a temperature of 105 to 110°C; Preferably, the treatment time is 18 to 24 hours.

6. The preparation method according to claim 1, characterized in that In said d), said washing comprises washing with alcohol; Preferably, the drying temperature is 40-60°C; Preferably, the alcohol comprises anhydrous ethanol, propanol or isopropanol.

7. The preparation method according to claim 1, characterized in that In said e), the ozone atmosphere further comprises anhydrous air, nitrogen or carbon dioxide; Preferably, in the ozone atmosphere, the volume concentration of ozone is 1 to 10%; Preferably, the calcination temperature is 250-400°C; Preferably, the calcination time is 30 to 150 minutes.

8. A manganese-based catalyst, characterized in that The manganese-based catalyst comprises manganese trioxide, aluminum trioxide and a first metal oxide; The first metal oxide includes one or more of ferric oxide, cerium oxide, zinc oxide or copper oxide; The surface of the manganese-based catalyst contains oxygen-containing functional groups and oxygen defect vacancies.

9. The manganese-based catalyst according to claim 8, characterized in that The mass ratio of the manganese manganese oxide, the aluminum oxide and the first metal oxide is 0.25-0.95:1:0.06-0.12; Preferably, the manganese-based catalyst comprises a manganese-based catalyst prepared by the method for preparing a manganese-based catalyst according to any one of claims 1 to 7; Preferably, the specific surface area of ​​the manganese-based catalyst is ≥500m 2 / g.

10. The method for preparing the manganese-based catalyst according to any one of claims 1 to 7 or the use of the manganese-based catalyst according to any one of claims 8 to 9 in removing sulfur-containing volatile organic compounds; The applications include: Mixing the manganese-based catalyst with the sulfur-containing volatile organic compound and heating them to remove the sulfur-containing volatile organic compound; The heating temperature is 300-500°C.

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