Composite metal oxide catalyst, preparation method and application thereof, and method for synergistically purifying carbon monoxide and volatile organic compounds

Abstract

The invention relates to the field of waste gas purification, and discloses a composite metal oxide catalyst, a preparation method and application thereof, and a method for synergistically purifying carbon monoxide and volatile organic compounds. The invention relates to a composite metal oxide catalyst, the catalyst comprises manganese oxide and M metal oxide, the M metal is selected from at least one of Fe, Co, Ni, Cu, Zn, Ag, Zr and Mo; wherein in the catalyst, the defect oxygen accounts for not less than 15% of the oxygen species in the catalyst. The composite metal oxide catalyst provided by the invention is applied to synergistic purification of carbon monoxide and volatile organic compounds, and has the advantage of good removal effect of carbon monoxide and volatile organic compounds.

Description

Composite metal oxide catalysts, their preparation methods and applications, and methods for synergistic purification of carbon monoxide and volatile organic compounds. Technical Field

[0001] This invention relates to the field of waste gas purification, specifically to a composite metal oxide catalyst, its preparation method and application, and a method for synergistic purification of carbon monoxide and volatile organic compounds. Background Technology

[0002] Volatile organic compounds (VOCs) are a class of volatile organic compounds with boiling points between 50-260℃. They are highly toxic and cause severe pollution. Many VOCs can cause human diseases and even cancer; under sunlight, VOCs generate photochemical smog, and some halogenated hydrocarbons can lead to ozone layer depletion. Given the catastrophic harm that VOC pollution brings to the Earth's environment and human health, countries around the world have successively formulated a series of regulations requiring the reduction of VOC emissions. Therefore, seeking effective treatment technologies has become the only way to solve VOC pollution. Emissions from industries such as steel sintering and waste incineration, as well as vehicle exhaust, seriously harm my country's air quality. These emissions contain large amounts of pollutants such as particulate matter, SO2, NOx, and acidic gases like VOCs. For example, in the steel industry, the "Emission Standard of Air Pollutants for Iron and Steel Sintering and Pelletizing Industry" (GB28662-2012) stipulates that the main pollutants produced by sintering equipment shall be subject to particulate matter concentrations of 50 mg / m³. 3 SO2 200mg / m 3 NOx 300mg / m 3 CO 5000mg / m³ 3 The emission limits are set at [specific standards]. CO is a reducing gas widely found in steel sintering, waste incineration flue gas, and vehicle exhaust. The interaction between NOx, sulfur oxides, and VOCs in the atmosphere causes primary particulate matter to transform into secondary particulate pollutants, leading to smog. Therefore, controlling VOCs and CO emissions is crucial for improving air quality in my country. There is an urgent need to develop a catalyst capable of simultaneously and efficiently removing VOCs and CO, converting them into non-toxic compounds; this would be a promising new technology.

[0003] CN107519871A discloses a method for preparing AuAg@SiO2 nanocatalysts for catalytic oxidation of CO. The specific steps of the method are as follows: (1) Mix 10mM HAuCl4 solution and 10mM AgNO3 solution, add 0.1g / ml surfactant solution, stir at room temperature for 20-30min, add 0.1M sodium borohydride solution, stir for 3h to obtain AuAg alloy sol; the 10mM The volume ratio of HAuCl4 solution, 10mM MgNO3 solution, 0.1g / ml surfactant and 0.1M sodium borohydride is 1:0.25-4:0.5-10:1-10; (2) Take the AuAg alloy sol obtained in step (1) and add it to the solvent. Add tetraethyl orthosilicate (TEOS) while stirring. After mixing evenly, add 28w.t% ammonia water dropwise and continue stirring for 2-5 hours. The solvent is a mixture of water and alcohol, and the volume ratio of water to alcohol is 1:1.25-5. The volume ratio of AuAg alloy sol, tetraethyl orthosilicate and 28w.t% ammonia water is 1:0.05-0.3:0.1-1. The above scheme has the problem that the preparation method of the catalyst is complicated and the preparation cost is high. CN103263917A discloses a method for preparing a Pt-BaTiO3 nanocatalyst for CO catalytic oxidation. This method employs a wet chemical reaction, using tetragonal perovskite BaTiO3 nanoparticles synthesized via a hydrothermal method, H2PtCl6·6H2O, NaBH4, and deionized water as reactants. Utilizing the reducing properties of NaBH4, Pt is reduced to the surface of the BaTiO3 nanoparticles, forming unstable Pt nanoparticles. These nanoparticles then undergo complete crystallization on the surface of the BaTiO3 ferroelectric nanoparticles during subsequent drying, thus obtaining the Pt-BaTiO3 nanocatalyst for CO catalytic oxidation. However, the CO purification catalysts provided by the above patent are not suitable for large-scale use due to the poor economic viability of using the precious metal Pt, the complex preparation method, and the harsh reaction conditions.

[0004] In the field of air pollution control, although the aforementioned catalysts can improve the purification capacity of CO and VOCs to some extent, there is still room for further improvement. Moreover, previous patents and literature have not studied the synergistic purification of VOCs and CO by catalysts. Therefore, developing a catalytic oxidation catalyst capable of simultaneously removing CO and VOCs from the air is of great practical significance. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a composite metal oxide catalyst, its preparation method, and its application, as well as a method for synergistically purifying carbon monoxide and volatile organic compounds. Applying the composite metal oxide catalyst provided by this invention to the synergistic purification of carbon monoxide and volatile organic compounds has the advantage of good removal efficiency for both.

[0006] To achieve the above objectives, the present invention provides a composite metal oxide catalyst, wherein the catalyst comprises manganese oxide and M metal oxide, wherein M metal is selected from at least one of Fe, Co, Ni, Cu, Zn, Ag, Zr and Mo;

[0007] In the catalyst, the proportion of defect oxygen sites to oxygen species in the catalyst is not less than 15%.

[0008] A second aspect of this invention provides a method for preparing a composite metal oxide catalyst, the method comprising the following steps:

[0009] (1) In the presence of a solvent, manganese salt, M salt and precipitant are subjected to a precipitation reaction to obtain a solid product; wherein, M metal is selected from at least one of Fe, Co, Ni, Cu, Zn, Ag, Zr and Mo;

[0010] (2) The solid product is calcined to obtain a catalyst precursor;

[0011] (3) The catalyst precursor is activated in a mixed gas with a hydrogen content of not more than 2 mol% at a temperature not higher than 300°C.

[0012] The third aspect of this invention provides the application of the composite metal oxide catalyst described in the first aspect or the composite metal oxide catalyst prepared by the preparation method described in the second aspect in waste gas treatment.

[0013] A fourth aspect of the present invention provides a method for synergistically purifying carbon monoxide and volatile organic compounds, the method comprising: contacting waste gas containing carbon monoxide and volatile organic compounds with a catalyst;

[0014] The catalyst is either the composite metal oxide catalyst described in the first aspect or the composite metal oxide catalyst prepared by the preparation method described in the second aspect.

[0015] The beneficial effects of the present invention through the above technical solution include:

[0016] The composite metal oxide catalyst provided by this invention has a high proportion of defect oxygen sites, which is beneficial for improving the oxidation capacity of pollutants. Applying this composite metal oxide catalyst to the synergistic purification of carbon monoxide and volatile organic compounds (VOCs) can efficiently and stably remove carbon monoxide and VOCs, meeting atmospheric requirements for their concentrations.

[0017] The composite metal oxide catalyst provided by this invention has a simple preparation process, low cost, and high decarbonization accuracy, which is conducive to industrial promotion. Attached Figure Description

[0018] Figure 1 is an XPS diagram of the composite metal oxide catalysts prepared in Examples 1 and 4 of this invention;

[0019] Figure 2 is a process flow diagram of the test example of the present invention. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] The first aspect of the present invention provides a composite metal oxide catalyst, the catalyst comprising manganese oxide and M metal oxide, wherein M metal is selected from at least one of Fe, Co, Ni, Cu, Zn, Ag, Zr and Mo;

[0022] In the catalyst, the proportion of defect oxygen sites to oxygen species in the catalyst is not less than 15%.

[0023] According to the present invention, in the catalyst, the proportion of defective oxygen sites to oxygen species in the catalyst is not less than 15%, specifically 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, and any two of these values, preferably 15-30%. This preferred embodiment provides more active sites, promotes oxygen adsorption, activation, and desorption, enhances the catalyst's ability to store and release oxygen, increases the overall activity of the catalyst, and thus improves the efficiency of the catalytic reaction.

[0024] In this invention, the proportion of defective oxygen in the catalyst is determined by XPS, specifically including: obtaining an O1s spectrum by XPS, followed by peak separation to distinguish oxygen species in different chemical environments, which may include:

[0025] Lattice oxygen (O_lattice): typically between 528-530 eV;

[0026] Ovary vacancy: typically between 531-532 eV;

[0027] Oxygen adsorbate (O_adsorbate): typically between 533-534 eV;

[0028] The proportion of defect oxygen in the catalyst is obtained by calculating the ratio of the peak area of ​​defect oxygen to the total peak area of ​​oxygen species.

[0029] According to the present invention, preferably, in the catalyst, the molar ratio of manganese oxide to M metal oxide is 1-15:1, more preferably 2-10:1. This preferred embodiment helps to ensure that the active metal manganese and the M metal are in their optimal valence states, which is beneficial for the rapid and efficient conversion of CO and VOCs.

[0030] In this invention, the molar ratio of manganese oxide to M metal oxide is determined by X-ray fluorescence spectroscopy.

[0031] According to the present invention, preferably, the M metal is selected from at least one of Cu, Fe, Ni, and Ag. This preferred embodiment is more conducive to improving the conversion efficiency of CO and VOCs.

[0032] In oxidation reactions, the valence state of metallic manganese has a significant impact on catalytic performance. Different oxidation states of manganese (such as Mn) 2+ Mn 3+ Mn 4+ Mn has a significant impact on the performance of catalytic reactions. Typically, Mn... 3+ and Mn 4+ It is relatively active in catalytic reactions. Mn 3+ It can be converted into an oxygen source in reactions and has strong oxidizing properties. It readily reacts with oxygen to form manganese oxides with higher oxidation states; Mn 4+ Manganese typically exhibits high stability in catalysis, effectively supporting oxygen desorption and resorption, thereby maintaining the catalyst's oxidation capacity. In general, the different oxidation states of manganese in the catalyst have a significant impact on its oxidation reaction performance. Preferably, the average valence of Mn in the catalyst is 3.2-3.8. This preferred embodiment is more conducive to improving the catalyst's performance.

[0033] The average oxidation state (AOS) of manganese described in this invention is calculated using the following formula:

[0034] AOS = 8.956 - 1.126 × ΔE, where ΔE is the difference between the high binding energy and low binding energy of manganese as measured by XPS Mn3S.

[0035] According to the present invention, preferably, the catalyst has a specific surface area of ​​45-90 cm². 2 / g, pore volume 0.35-0.65cm³ 3 / g.

[0036] In this invention, the specific surface area and pore volume of the catalyst are measured by the BET method.

[0037] According to the present invention, preferably, the catalyst further contains an alkali metal oxide.

[0038] The present invention has a wide range of choices for the types of alkali metals. Preferably, the alkali metal is potassium and / or sodium, and more preferably sodium.

[0039] According to the present invention, preferably, the molar ratio of alkali metal oxide to manganese oxide is 0.02-0.5:1, based on metal elements.

[0040] In this invention, the molar ratio of alkali metal oxide to manganese oxide is determined by X-ray fluorescence spectroscopy.

[0041] This invention does not impose any particular limitation on the preparation method of the composite metal oxide catalyst, as long as a composite metal oxide catalyst with the above-mentioned characteristic parameters can be obtained. To further improve the performance of the composite metal oxide catalyst, and also to better illustrate the preparation method of the composite metal oxide catalyst of this invention, this invention also provides a method for preparing the composite metal oxide catalyst.

[0042] A second aspect of this invention provides a method for preparing a composite metal oxide catalyst, the method comprising the following steps:

[0043] (1) In the presence of a solvent, manganese salt, M salt and precipitant are subjected to a precipitation reaction to obtain a solid product; wherein, M metal is selected from at least one of Cu, Fe, Ni, Zn, Zr, Ag, La and Mo;

[0044] (2) The solid product is calcined to obtain a catalyst precursor;

[0045] (3) The catalyst precursor is activated in a mixed gas with a hydrogen content of not more than 2 mol% at a temperature not higher than 300°C.

[0046] The present invention does not impose any particular limitation on the selection of the precipitation reaction conditions in step (1), and can refer to conventional methods in the art. Preferably, the precipitation reaction conditions in step (1) include: a temperature of 30-80℃ and a time of 0.1-6h.

[0047] According to the present invention, preferably, the precipitation reaction in step (1) is carried out under conditions of pH 7-14, preferably 8-10.

[0048] According to the present invention, preferably, the molar ratio of manganese salt to M salt, based on metal elements, is 1-15:1, more preferably 2-10:1.

[0049] Preferably, the M metal is selected from at least one of Cu, Fe, Ni and Ag.

[0050] The present invention does not impose any particular limitation on the order of adding the manganese salt, M salt, and precipitant in step (1). They can be added together or separately, depending on the specific circumstances. In the embodiments of the present invention, it is preferred to mix the manganese salt and M salt first, and then add the precipitant.

[0051] According to the present invention, preferably, the manganese salt is selected from at least one of potassium permanganate, potassium manganate, and sodium permanganate. During the synthesis process, some of the alkali metals potassium and sodium in the manganese salt can participate in crystal growth, embedding themselves in the crystal structure by balancing charges or maintaining the stability of the crystal structure. They play a role in charge balance or supporting structural stability in the crystal, ensuring the normal formation and stable existence of the crystal.

[0052] According to the present invention, preferably, the manganese salt is provided in the form of an aqueous solution of manganese salt, the concentration of which is 60-180 g / L.

[0053] According to the present invention, preferably, the M salt is selected from at least one of the sulfate, nitrate and acetate of metal M.

[0054] According to the present invention, preferably, the M salt is provided in the form of an aqueous solution of the M salt, the concentration of which is 50-200 g / L.

[0055] The precipitant described in this invention can be any conventional choice in the art. Preferably, the precipitant is selected from at least one of sodium carbonate, potassium carbonate, and sodium hydroxide.

[0056] According to the present invention, preferably, the precipitant is provided in the form of an aqueous precipitant solution, the concentration of which is 3-15 g / L.

[0057] The amount of precipitant used in this invention is such that the reaction pH is within the range described above.

[0058] The present invention allows for a wide range of solvent choices, which can be conventional choices in the field. Water is preferably used as the solvent in this invention.

[0059] Preferably, the method further includes: performing solid-liquid separation and washing on the precipitation reaction product described in step (1) to obtain a solid product.

[0060] The present invention does not particularly limit the specific method of solid-liquid separation, and conventional technical means in the field can be used.

[0061] The present invention does not have any particular limitation on the washing method, and it can be carried out with reference to conventional methods in the art.

[0062] According to the present invention, preferably, the calcination conditions in step (2) include: a temperature of 200-500℃, specifically 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, and any two of these values ​​forming a range, preferably 300-400℃; and a time of 1-10h, specifically 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, and any two of these values ​​forming a range, preferably 2-6h. Calcination at the aforementioned lower temperatures has the following advantages: ① Maintaining the catalyst structure: Low-temperature calcination can reduce catalyst grain growth and structural changes, thereby maintaining its original morphology and activity. ② Preventing the loss of active sites: High-temperature calcination may lead to the loss of active sites on the catalyst surface, while lower calcination temperatures help maintain the integrity of these sites. ③ Effective removal of impurities: Low-temperature calcination can effectively remove residual impurities in the catalyst during the synthesis process without causing excessive phase changes or structural damage. ④ Optimization of catalytic performance: Appropriate calcination temperature can promote the uniform distribution of promoter elements in the catalyst, thereby optimizing catalytic performance.

[0063] Preferably, before calcining the solid product obtained in step (1), ammonium exchange, solid-liquid separation and drying are performed in sequence.

[0064] The present invention does not particularly limit the ammonium exchange process, and can refer to conventional methods in the art to exchange alkali metal ions in the precipitant.

[0065] It should be noted that some alkali metal ions in manganese salts cannot be exchanged out because of their crystal structure.

[0066] The present invention does not particularly limit the specific method of solid-liquid separation, and conventional technical means in the field can be used.

[0067] The present invention does not have any particular limitation on the drying process, and it can be carried out with reference to conventional methods in the art.

[0068] The activation treatment of the catalyst precursor in step (3) of the present invention in a hydrogen-poor atmosphere and at low temperature is beneficial to increasing oxygen defect sites, which is beneficial to adsorbing oxygen in the oxidation reaction, reducing the activation energy of oxygen dissociation, and further improving the oxidation performance of the catalyst.

[0069] According to the present invention, preferably, the mixed gas comprises hydrogen and an inert gas. The inert gas described in this invention can be a conventional choice in the art. Preferably, the inert gas is selected from at least one of nitrogen, argon, neon, and helium.

[0070] According to the present invention, preferably, the hydrogen content in the mixed gas is 0.05-2 mol%, specifically 0.05 mol%, 0.1 mol%, 0.15 mol%, 0.2 mol%, 0.25 mol%, 0.3 mol%, 0.35 mol%, 0.4 mol%, 0.45 mol%, 0.5 mol%, 0.55 mol%, 0.6 mol%, 0.65 mol%, 0.7 mol%, 0.75 mol%, 0.8 mol%, 0.85 mol%, 0.9 mol%, 1 mol%, 1.1 mol%, 1.2 mol%, 1.3 mol%, 1.4 mol%, 1.5 mol%, 1.6 mol%, 1.7 mol%, 1.8 mol%, 1.9 mol%, 2 mol%, and the range of any two of these values, preferably 0.1-0.5 mol%.

[0071] According to the present invention, preferably, the activation treatment conditions in step (3) include: a temperature of 80-250℃, specifically 80℃, 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, and a range of any two of these values, preferably 100-180℃; and a time of 0.1-3 hours. The values ​​are 0.1h, 0.2h, 0.3h, 0.4h, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, 1h, 1.1h, 1.2h, 1.3h, 1.4h, 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, 3h, and the range of any two points among these values, preferably 0.2-2h.

[0072] The third aspect of this invention provides the application of the composite metal oxide catalyst described in the first aspect or the composite metal oxide catalyst prepared by the preparation method described in the second aspect in waste gas treatment, preferably in the synergistic purification of carbon monoxide and volatile organic compounds.

[0073] The catalyst described in this invention is suitable for waste gas treatment, especially for waste gas containing carbon monoxide and volatile organic compounds.

[0074] A fourth aspect of the present invention provides a method for synergistically purifying carbon monoxide and volatile organic compounds, the method comprising: contacting waste gas containing carbon monoxide and volatile organic compounds with a catalyst;

[0075] The catalyst is either the composite metal oxide catalyst described in the first aspect or the composite metal oxide catalyst prepared by the preparation method described in the second aspect.

[0076] According to the present invention, preferably, the contact conditions include: a temperature of 20-500°C, more preferably 100-400°C; and a volume hourly space velocity of 500-100000 h⁻¹. -1 Preferably 2000-20000h -1 .

[0077] The catalyst described in this invention is suitable for treating waste gases containing carbon monoxide and volatile organic compounds of different compositions. Preferably, the carbon monoxide content in the waste gas is 500-10000 ppm.

[0078] Preferably, the content of volatile organic compounds in the exhaust gas is 100-1000 ppm.

[0079] The present invention does not particularly limit the source of the waste gas, which can be waste gas containing carbon monoxide and volatile organic compounds obtained by various means, such as from refineries, boiler plants, kilns, steel plants, etc.

[0080] The present invention will be described in detail below through embodiments.

[0081] In the following examples, the concentrations of carbon monoxide, sulfur dioxide, and volatile organic compounds in the exhaust gas were measured by gas chromatography.

[0082] Example 1

[0083] 32.3 g of sodium permanganate was dissolved in 200 g of deionized water and heated and stirred to form a manganese salt solution. 5.5 g of sodium carbonate was dissolved in 1000 g of deionized water and stirred until homogeneous. 8.79 g of copper nitrate was dissolved in 50 g of deionized water and stirred until homogeneous. The above sodium permanganate and copper nitrate aqueous solutions were mixed, with n(Mn):n(Cu) = 4.2:1. Sodium carbonate aqueous solution was added dropwise to adjust the pH to 9.5, and then the reaction was carried out at 80 °C for 24 h. The reaction product was filtered and washed with deionized water until the pH of the washing liquid reached 7, yielding a filter cake. The filter cake was redispersed in deionized water, heated to 50 °C, and ion-exchanged with 2 mol / L ammonium carbonate aqueous solution for 6 h, and the solid material was filtered out. The solid material was dried at 120 °C overnight, calcined at 350 °C for 2 h, and then activated at 150 °C for 0.5 h under a 0.2 mol% H2-N2 atmosphere to obtain the catalyst. Its composition and characteristic parameters are shown in Table 1.

[0084] An exemplary XPS plot of the composite metal oxide catalyst prepared in Example 1 is shown in Figure 1. As can be seen from Figure 1, the characteristic peak value of the defect oxygen is located at approximately 531.5 eV, and the proportion of defect oxygen in the catalyst is 24.6%.

[0085] Example 2

[0086] 32.3 g of sodium permanganate was dissolved in 200 g of deionized water and heated and stirred to form a manganese salt solution. 5.5 g of sodium carbonate was dissolved in 1000 g of deionized water and stirred until homogeneous. 8.79 g of copper nitrate was dissolved in 50 g of deionized water and stirred until homogeneous. The above sodium permanganate and copper nitrate aqueous solutions were mixed, with n(Mn):n(Cu) = 2.4:1. Sodium carbonate aqueous solution was added dropwise to adjust the pH to 9.5, and then the reaction was carried out at 80 °C for 24 h. The reaction product was filtered and washed with deionized water until the pH of the washing liquid reached 7, yielding a filter cake. The filter cake was redispersed in deionized water, heated to 50 °C, and ion-exchanged with 2 mol / L ammonium carbonate aqueous solution for 6 h, and the solid material was filtered out. The solid material was dried at 120 °C overnight, calcined at 350 °C for 2 h, and then activated at 150 °C for 0.3 h under a 0.4 mol% H2-N2 atmosphere to obtain the catalyst. Its composition and characteristic parameters are shown in Table 1.

[0087] Example 3

[0088] 32.3 g of sodium permanganate was dissolved in 200 g of deionized water and heated and stirred to form a manganese salt solution. 5.5 g of sodium carbonate was dissolved in 1000 g of deionized water and stirred until homogeneous. 8.79 g of copper nitrate was dissolved in 50 g of deionized water and stirred until homogeneous. The above sodium permanganate and copper nitrate aqueous solutions were mixed, with n(Mn):n(Cu) = 9.7:1. Sodium carbonate aqueous solution was added dropwise to adjust the pH to 9.5, and the reaction was carried out at 80 °C for 24 h. The reaction product was filtered and washed with deionized water until the pH of the washing liquid reached 7, yielding a filter cake. The filter cake was redispersed in deionized water, heated to 50 °C, and ion-exchanged with 2 mol / L ammonium carbonate aqueous solution for 6 h, and the solid material was filtered out. The solid material was dried at 120 °C overnight, calcined at 350 °C for 2 h, and then activated at 100 °C for 0.8 h under a 0.2 mol% H2-N2 atmosphere to obtain the catalyst. Its composition and characteristic parameters are shown in Table 1.

[0089] Example 4

[0090] 32.3 g of sodium permanganate was dissolved in 200 g of deionized water and heated and stirred to form a manganese salt solution. 5.5 g of sodium carbonate was dissolved in 1000 g of deionized water and stirred until homogeneous. 8.79 g of ferric nitrate was dissolved in 50 g of deionized water and stirred until homogeneous. The above sodium permanganate and ferric nitrate solutions were mixed, with n(Mn):n(Fe) = 3.3:1. Sodium carbonate solution was added dropwise to adjust the pH to 9.5, and the reaction was carried out at 80 °C for 24 h. The reaction product was filtered and washed with deionized water until the pH of the washing liquid reached 7, yielding a filter cake. The filter cake was redispersed in deionized water, heated to 50 °C, and ion-exchanged with 2 mol / L ammonium carbonate solution for 6 h, and the solid material was filtered out. The solid material was dried at 120 °C overnight, calcined at 350 °C for 2 h, and then activated at 150 °C for 0.5 h under a 0.2 mol% H2-N2 atmosphere to obtain the catalyst. Its composition and characteristic parameters are shown in Table 1.

[0091] An exemplary XPS plot of the composite metal oxide catalyst prepared in Example 4 is shown in Figure 1. As can be seen from Figure 1, the characteristic peak value of the defect oxygen is located at approximately 531.5 eV, and the proportion of defect oxygen in the catalyst is 21.4%.

[0092] Example 5

[0093] 32.3 g of sodium permanganate was dissolved in 200 g of deionized water and heated and stirred to form a manganese salt solution. 5.5 g of sodium carbonate was dissolved in 1000 g of deionized water and stirred until homogeneous. 8.79 g of nickel nitrate was dissolved in 50 g of deionized water and stirred until homogeneous. The above sodium permanganate and nickel nitrate aqueous solutions were mixed, with n(Mn):n(Ni) = 3.3:1. Sodium carbonate aqueous solution was added dropwise to adjust the pH to 9.5, and then the reaction was carried out at 80 °C for 24 h. The reaction product was filtered and washed with deionized water until the pH of the washing liquid reached 7, yielding a filter cake. The filter cake was redispersed in deionized water, heated to 50 °C, and ion-exchanged with 2 mol / L ammonium carbonate aqueous solution for 6 h, and the solid material was filtered out. The solid material was dried at 120 °C overnight, calcined at 300 °C for 2 h, and then activated at 150 °C for 0.5 h under a 0.2 mol% H2-N2 atmosphere to obtain the catalyst. Its composition and characteristic parameters are shown in Table 1.

[0094] Example 6

[0095] 32.3 g of sodium permanganate was dissolved in 200 g of deionized water and heated and stirred to form a manganese salt solution. 5.5 g of sodium carbonate was dissolved in 1000 g of deionized water and stirred until homogeneous. 8.79 g of silver nitrate was dissolved in 50 g of deionized water and stirred until homogeneous. The above sodium permanganate and silver nitrate aqueous solutions were mixed, with n(Mn):n(Ag) = 3.3:1. Sodium carbonate aqueous solution was added dropwise to adjust the pH to 9.5, and then the reaction was carried out at 80 °C for 24 h. The reaction product was filtered and washed with deionized water until the pH of the washing liquid reached 7, yielding a filter cake. The filter cake was redispersed in deionized water, heated to 50 °C, and ion-exchanged with 2 mol / L ammonium carbonate aqueous solution for 6 h, and the solid material was filtered out. The solid material was dried at 120 °C overnight, calcined at 350 °C for 2 h, and then activated at 150 °C for 0.4 h under a 0.3 mol% H2-N2 atmosphere to obtain the catalyst. Its composition and characteristic parameters are shown in Table 1.

[0096] Comparative Example 1

[0097] 10wt% MnO2-10wt% CuO / Al2O3 was prepared by impregnation method

[0098] An alumina support was impregnated with an aqueous solution of manganese nitrate (50 wt%), copper nitrate (30 wt%), and manganese nitrate, followed by drying and calcination at 350 °C for 4 h to obtain the catalyst. Its composition and characteristic parameters are shown in Table 1.

[0099] Comparative Example 2

[0100] The procedure was carried out according to Example 1, except that copper nitrate was not added, resulting in a catalyst. Its composition and characteristic parameters are shown in Table 1.

[0101] Comparative Example 3

[0102] The process was carried out according to Example 1, except that n(Mn):n(Cu) = 20:1, resulting in a catalyst. Its composition and characteristic parameters are shown in Table 1.

[0103] Comparative Example 4

[0104] The procedure was carried out according to Example 1, except that no activation treatment was performed; the catalyst was obtained after calcination. Its composition and characteristic parameters are shown in Table 1.

[0105] Table 1

[0106]

[0107] Test Example 1

[0108] Figure 2 is a process flow diagram of the test example of the present invention. As shown in Figure 2, 2 mL of the catalysts prepared in the examples and comparative examples were weighed and placed in a fixed-bed reactor. Then, air containing CO and toluene (CO concentration of 6000 ppm and toluene concentration of 500 ppm) was introduced into the fixed-bed reactor through a mass flow meter. The reaction was carried out at 300°C and atmospheric pressure, with a volume hourly space velocity of 10000 h⁻¹. -1 One hour after the reaction stabilized, samples were taken for analysis, and the concentrations of CO and toluene were recorded. The results are shown in Table 2. The mixed gas after the reaction was introduced into the tail gas absorption tank. After testing and confirming that it met environmental protection requirements, it could be further treated or vented.

[0109] Table 2

[0110] Example Number | CO Concentration in Tail Gas (ppm) | Toluene Concentration in Tail Gas (ppm) | Example 1 | 0.05 | 0.33 | Example 2 | 0.08 | 2.45 | Example 3 | 0.06 | 1.01 | Example 4 | 0.09 | 0.79 | Example 5 | 0.06 | 1.55 | Example 6 | 0.10 | 1.15 | Comparative Example 1 | 379 | 108 | Comparative Example 2 | 15.6 | 14.9 | Comparative Example 3 | 10.1 | 10.8 | Comparative Example 4 | 6.8 | 6.1 surface

[0111] As can be seen from the results in Table 2, the composite metal oxide catalyst of the present invention exhibits better removal effects for both carbon monoxide and toluene. This demonstrates that the composite metal oxide catalyst of the present invention possesses significantly better oxidation performance.

[0112] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite metal oxide catalyst, characterized in that, The catalyst comprises manganese oxide and M metal oxide, wherein M metal is selected from at least one of Fe, Co, Ni, Cu, Zn, Ag, Zr and Mo; wherein, in the catalyst, the proportion of defect oxygen sites to oxygen species in the catalyst is not less than 15%.

2. The catalyst according to claim 1, wherein, In the catalyst, defect oxygen accounts for 15-30% of the oxygen species in the catalyst; preferably, the specific surface area of ​​the catalyst is 45-90 cm². 2 / g, pore volume 0.35-0.65cm³ 3 / g.

3. The catalyst according to claim 1 or 2, wherein, In the catalyst, the molar ratio of manganese oxide to M metal oxide is 1-15:1, preferably 2-10:1, based on metal elements; preferably, the M metal is selected from at least one of Cu, Fe, Ni and Ag; preferably, the average valence of Mn in the catalyst is 3.2-3.

8.

4. The catalyst according to any one of claims 1-3, wherein, The catalyst further contains an alkali metal oxide; preferably, the alkali metal is potassium and / or sodium, more preferably sodium; preferably, the molar ratio of the alkali metal oxide to the manganese oxide is 0.02-0.5:1 based on the metal element.

5. A method for preparing a composite metal oxide catalyst, the method comprising the following steps: (1) In the presence of a solvent, manganese salt, M salt and precipitant are subjected to precipitation reaction to obtain a solid product; wherein, M metal is selected from at least one of Cu, Fe, Ni, Zn, Zr, Ag, La and Mo; (2) The solid product is calcined to obtain a catalyst precursor; (3) The catalyst precursor is activated in a mixed gas with a hydrogen content of not more than 2 mol% at a temperature not higher than 300°C.

6. The method according to claim 5, wherein, The precipitation reaction conditions in step (1) include: a temperature of 30-80℃ and a time of 0.1-6h; preferably, the precipitation reaction in step (1) is carried out under the condition of pH 7-14, preferably 8-10; preferably, the molar ratio of manganese salt to M salt is 1-15:1, preferably 2-10:1, based on metal elements; preferably, the M metal is selected from at least one of Cu, Fe, Ni and Ag.

7. The method according to claim 5 or 6, wherein, The manganese salt is selected from at least one of potassium permanganate, potassium manganate, and sodium permanganate; preferably, the manganese salt is provided in the form of an aqueous solution of manganese salt with a concentration of 60-180 g / L; preferably, the M salt is selected from at least one of sulfate, nitrate, and acetate of metal M; preferably, the M salt is provided in the form of an aqueous solution of M salt with a concentration of 50-200 g / L; preferably, the precipitant is selected from at least one of sodium carbonate, potassium carbonate, and sodium hydroxide; preferably, the precipitant is provided in the form of an aqueous solution of precipitant with a concentration of 3-15 g / L.

8. The method according to any one of claims 5-7, wherein, The roasting conditions in step (2) include: a temperature of 200-500℃, preferably 300-400℃; and a time of 1-10h, preferably 2-6h.

9. The method according to any one of claims 5-8, wherein, The mixed gas includes hydrogen and an inert gas, wherein the inert gas is preferably selected from at least one of nitrogen, argon, neon and helium; preferably, the hydrogen content in the mixed gas is 0.05-2 mol%, preferably 0.1-0.5 mol%; preferably, the activation treatment conditions in step (3) include: a temperature of 80-250℃, preferably 100-180℃; and a time of 0.1-3h, preferably 0.2-2h.

10. The application of a composite metal oxide catalyst according to any one of claims 1-4 or a composite metal oxide catalyst prepared by any one of claims 5-9 in waste gas treatment, preferably in the synergistic purification of carbon monoxide and volatile organic compounds.

11. A method for synergistically purifying carbon monoxide and volatile organic compounds, the method comprising: Waste gas containing carbon monoxide and volatile organic compounds is contacted with a catalyst; wherein the catalyst is a composite metal oxide catalyst according to any one of claims 1-4 or a composite metal oxide catalyst prepared by any one of claims 5-9; preferably, the contact conditions include: a temperature of 20-500℃, preferably 100-400℃; and a volume hourly space velocity of 500-100000 h⁻¹. -1 Preferably 2000-20000h -1 Preferably, the carbon monoxide content in the exhaust gas is 500-10000 ppm; preferably, the volatile organic compound content in the exhaust gas is 100-1000 ppm.

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