Catalyst for catalytic oxidation of volatile organic compounds, preparation method and application thereof

Abstract

The present invention provides a catalyst for the catalytic oxidation of volatile organic compounds, a preparation method thereof, and an application thereof. The catalyst contains an alkaline earth metal-modified alumina carrier and an alkali metal and a noble metal loaded on the modified alumina carrier, wherein the alkaline earth metal-modified alumina carrier has a micro-mesoporous multi-level pore structure. The present invention utilizes the confinement effect of the micropores, and the active components are more stable in the micropores and surface vacancies, with a higher degree of dispersion; while the reactants and products are more conducive to diffusion and transmission in the mesopores. The catalyst prepared by the present invention has a micro-mesoporous multi-level pore structure, and the active component noble metal particles are more stable in the micropores and surface vacancies, with a higher degree of dispersion, more surface active oxygen species, and the mesoporous structure is conducive to the diffusion of volatile organic compounds in the catalyst bulk phase, thereby increasing the catalytic activity and stability.

Description

Technical Field

[0001] The invention relates to a catalyst for catalytic oxidation of volatile organic compounds, a preparation method and an application thereof. Background Art

[0002] Volatile organic compounds (VOCs) are a general term for organic compounds with melting points below room temperature and boiling points below 200-260°C at standard atmospheric pressure. These compounds primarily include alkanes, hydrocarbons, esters, alcohols, and benzene series. Anthropogenic sources of VOC emissions primarily include stationary combustion sources, road and mobile sources, industrial processes, and solvent use. They are a key precursor to photochemical smog and a recognized precursor to PM2.5. VOCs can irritate the skin, respiratory system, and blood system, affect the heart and nervous system, and can even cause cancer.

[0003] VOCs emission control technologies mainly include recovery technologies (absorption, condensation, membrane separation, etc.) and destruction technologies (combustion, plasma, photocatalysis, biodegradation, etc.). Catalytic combustion technology decomposes VOCs in exhaust gas into carbon dioxide and water through low-temperature combustion under the action of a catalyst.

[0004] Combustion methods are generally categorized as thermal combustion and catalytic combustion (catalytic oxidation). Thermal combustion requires higher operating temperatures and consumes a lot of energy. Catalytic combustion, on the other hand, uses a catalyst to oxidize volatile organic compounds (VOCs) into harmless carbon dioxide and water vapor at lower temperatures, offering advantages such as high efficiency, energy conservation, and ease of control.

[0005] The core of catalytic combustion technology lies in the design, preparation, and selection of high-performance catalysts. Precious metal catalysts (such as Pt, Pd, and Rh) are widely used due to their high catalytic activity and excellent thermal stability. Current development of precious metal catalysts focuses on improving the dispersion of precious metals to maximize their potential. Furthermore, they utilize carriers with specialized pore structures and selectively load the active metal within the pores, thereby preventing the migration of precious metal particles and increasing their stability.

[0006] Traditional γ-Al2O3 has a low specific surface area, large pore size, and wide pore distribution, making it inadequate for catalytic reactions requiring specific shape selectivity, stability, and contact area. However, structurally controllable mesoporous alumina materials, with pore sizes bridging the gap between micropores and mesopores, can be functionalized with active elements, demonstrating their unique advantages in the catalytic combustion of VOCs. Summary of the Invention

[0007] The purpose of the present invention is to provide a multi-level porous catalyst. By using a microporous-mesoporous multi-level porous modified alumina carrier and utilizing the confinement effect of micropores, the active components are more stable in the micropores and surface vacancies and have a higher dispersion; on the other hand, the mesopores are conducive to the diffusion and transmission of reactants and products, and can show good activity and stability against VOCs.

[0008] According to a first aspect of the present invention, the present invention provides a catalyst for the catalytic oxidation of volatile organic compounds, which catalyst contains an alkaline earth metal modified alumina carrier and an alkali metal and a precious metal loaded on the modified alumina carrier, wherein the alkaline earth metal modified alumina carrier has a micro-mesoporous multi-level pore structure.

[0009] According to a second aspect of the present invention, the present invention provides a method for preparing the catalyst of the present invention, the method comprising: 1) preparing an alkaline earth metal modified alumina carrier;

[0010] 2) The modified alumina carrier is loaded with alkali metal and noble metal by an impregnation method, and the impregnated alumina is dried and calcined to obtain a catalyst.

[0011] According to a third aspect of the present invention, the present invention provides use of the catalyst of the present invention in catalytic combustion.

[0012] The present invention utilizes the confinement effect of micropores, and the active components are more stable and have higher dispersion in the micropores and surface vacancies; while the reactants and products are more conducive to diffusion and transmission in the mesopores.

[0013] In a preferred embodiment, the alkaline earth metal added during the preparation of the micro-mesoporous alumina is modified, and after impregnation with the alkali metal and the active component, more active oxygen species are present on the surface, and the catalytic activity is higher.

[0014] The catalyst prepared by the present invention has a micro-mesoporous multi-level pore structure, the active component noble metal particles are more stable in the micropores and surface vacancies, have a higher dispersion, and have more surface active oxygen species. The mesoporous structure is conducive to the diffusion of volatile organic compounds in the catalyst bulk phase, thereby improving the catalytic activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a nitrogen adsorption-desorption isotherm diagram of the catalyst of Example 1 of the present invention;

[0016] Figure 2 TEM image of the catalyst of Example 1 of the present invention;

[0017] Figure 3 This is the O2-TPD diagram of the catalyst of Example 1 of the present invention;

[0018] Figure 4 This is the methane / ethylene catalytic combustion activity diagram of the catalyst in Example 1 of the present invention. DETAILED DESCRIPTION

[0019] The endpoints of the ranges and any values ​​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 endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0020] The present invention provides a catalyst for catalytic oxidation of volatile organic compounds. The catalyst contains an alkaline earth metal modified alumina carrier and an alkali metal and a noble metal loaded on the modified alumina carrier. The alkaline earth metal modified alumina carrier has a micro-mesoporous multi-level pore structure.

[0021] According to a preferred embodiment of the present invention, the micropores of the alkaline earth metal modified alumina carrier are distributed in the range of 1.2 to 2.0 nm, and the mesopores are distributed in the range of 2 to 5 nm.

[0022] According to a preferred embodiment of the present invention, the atomic ratio of the alkaline earth metal to the aluminum in the alumina is 1:(5-40).

[0023] According to a preferred embodiment of the present invention, preferably, the alkaline earth metal content is 0.2-1 wt % based on the total weight of the modified alumina carrier and calculated as a single substance.

[0024] According to a preferred embodiment of the present invention, preferably, the alkaline earth metal is one or more of magnesium, calcium, strontium and barium, preferably one or more of magnesium, strontium and barium.

[0025] According to a preferred embodiment of the present invention, preferably, the specific surface area of ​​the catalyst is 428-633m 2 / g.

[0026] According to a preferred embodiment of the present invention, preferably, the pore volume of the catalyst is 0.25-0.34 cm 3 / g.

[0027] According to a preferred embodiment of the present invention, preferably, the average pore diameter of the catalyst is 1.8-3 nm.

[0028] According to a preferred embodiment of the present invention, preferably, the particle size of the noble metal nanoparticles of the catalyst is 4-9 nm, preferably 5-8 nm.

[0029] According to a preferred embodiment of the present invention, the catalyst contains 85-99 wt% of an alumina carrier, 1-8 wt% of an alkali metal and 0.5-3 wt% of a noble metal, based on the total weight of the catalyst.

[0030] According to the present invention, the optional range of the types of the precious metal is relatively wide. Preferably, the precious metal is selected from one or more of Pt, Pd, Rh, Ru, Ag and Au, preferably selected from one or more of Pt, Pd and Ru, and more preferably selected from one or more of Pt and Pd.

[0031] According to the present invention, the alkali metal may be selected from a wide range of types. Preferably, the alkali metal is selected from K and / or Na.

[0032] The alkaline earth metal modified alumina having the aforementioned properties of the present invention can achieve the purpose of the present invention. For the present invention, the preparation method of the alkaline earth metal modified alumina preferably includes: uniformly mixing acid, alcohol, surfactant, silica gel, alkaline earth metal source and aluminum source, performing heat treatment to volatilize the solvent and roasting.

[0033] According to the present invention, the surfactant preferably includes surfactant A and surfactant B, wherein the surfactant A is fatty alcohol polyoxyethylene ether (AEO-7), and the surfactant B is a combination of one or more of P123, F127 and F68.

[0034] According to the present invention, the mass ratio of surfactant B to surfactant A is preferably 1:9-1:1.5.

[0035] According to the present invention, the acid is an organic acid and / or an inorganic acid. Preferably, the organic acid is selected from one or more of aqueous hydrochloric acid, citric acid, glacial acetic acid, malic acid, gluconic acid and lauric acid, preferably one or more of aqueous hydrochloric acid, citric acid, lauric acid and glacial acetic acid.

[0036] According to the present invention, preferably, the inorganic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid.

[0037] According to the present invention, the alcohol is preferably a low-carbon monohydric alcohol, preferably one or more of methanol, ethanol and propanol, preferably ethanol.

[0038] According to the present invention, the alkaline earth metal can be selected from a wide range of types. For example, the alkaline earth metal is one or more of magnesium, calcium, strontium and barium, preferably one or more of magnesium, strontium and barium.

[0039] According to the present invention, the alkaline earth metal source is preferably one or more of a magnesium compound, a calcium compound, a strontium compound and a barium compound, preferably one or more of a magnesium compound, a strontium compound and a barium compound.

[0040] According to the present invention, the range of aluminum source types to be selected is relatively wide. For the present invention, the aluminum source is preferably one or more of aluminum isopropoxide, aluminum sec-butoxide, sodium aluminate, aluminum nitrate, aluminum chloride and aluminum sulfate, preferably one or more of aluminum isopropoxide, aluminum n-butoxide and sodium aluminate.

[0041] According to a preferred embodiment of the present invention, the viscosity of the silicone gel is 500-3000 MPa·s. Preferably, the silicone gel is an addition-type silicone gel with a viscosity in the range of 1000-2000 MPa·s, a 1:1 mixture of the two components, a needle penetration of ≥150 mm, and an operability time of 10-15 hours at room temperature.

[0042] According to a preferred embodiment of the present invention, the acid contains an inorganic acid and an organic acid, based on 100% by weight, the amount of the surfactant is 10-18% by weight (for example, 10%, 11% .... 23%, 17%, 18%, and so on, the above ranges of data are applicable to the present invention): the amount of the aluminum source is 20-35% by weight: the amount of the organic acid is 6-25% by weight (for example, 6%, 7%, 8%, 9%, 10%, 11% .... 23%, 24%, 25%, and so on, and so on, the above ranges of data are applicable to the present invention); By analogy, the data in the above ranges are applicable to the present invention): the amount of inorganic acid is 30-40 weight % (for example, 30%, 35%, 40%, etc., the data in this range are applicable to the present invention); the amount of silica gel is 1-4 weight % (for example, 1%, 2%, 3%, 4%, and so on, the data in the above ranges are applicable to the present invention); the amount of alkaline earth metal source is 1-5 weight % (for example, 1%, 2%, 3%, 4%, 5%, and so on, the data in the above ranges are applicable to the present invention).

[0043] According to a preferred embodiment of the present invention, based on 100 weight%, the amount of surfactant is 12-17 weight%, the amount of aluminum source is 22-33 weight%, the amount of organic acid is 7-25 weight%, the amount of inorganic acid is 34-40 weight%, the amount of silica gel is 1.2-3.8 weight%, and the amount of alkaline earth metal source is 1.6-5 weight%.

[0044] According to the present invention, the heat treatment conditions may be common heat treatment conditions. According to a preferred embodiment of the present invention, the heat treatment conditions include: a temperature of 30-80°C, and a time that can be determined according to the temperature, preferably 48-72 hours.

[0045] According to the present invention, the roasting conditions can be commonly used roasting conditions. According to a preferred embodiment of the present invention, the roasting conditions include: heating to 300°C at a heating rate of 0.5-2°C / min and holding for 1-3 hours, and then heating to 400-800°C at a heating rate of 1-5°C / min and roasting for 3-10 hours.

[0046] According to a preferred embodiment of the present invention, the preparation method of the alkaline earth metal modified alumina carrier preferably includes: dissolving a surfactant in an 80-98 wt% ethanol aqueous solution, then adding an organic carboxylic acid, an inorganic acid, an alkaline earth metal salt and an aluminum source under stirring, maintaining the system temperature at 20-60°C, adding silica gel, and continuously stirring for 6-24 hours under sealed conditions, then introducing the reaction mixture into an evaporating dish to evaporate the alcohol and water at 30-80°C for 48-72 hours, and after drying, heating to 300°C at 0.5-2°C / min and holding for 1-3 hours, and finally heating to 400-800°C at 1-5°C / min and calcining for 5-10 hours.

[0047] The purpose of the present invention can be achieved by using the aforementioned catalysts of the present invention. There is no special requirement for the preparation method thereof. For the present invention, the preparation method of the catalyst of the present invention is preferred, which comprises:

[0048] 1) preparing an alkaline earth metal modified alumina support;

[0049] 2) The modified alumina carrier is loaded with alkali metal and noble metal by an impregnation method, and the impregnated alumina is dried and calcined to obtain a catalyst.

[0050] According to a preferred embodiment of the present invention, the impregnation method comprises:

[0051] The modified alumina carrier is impregnated with a mixed solution of alkali metal and noble metal, and then dried and calcined to obtain a catalyst; the preferred drying conditions include: rotary evaporation at 60-80°C, and then oven drying at 80-100°C for 8-12 hours.

[0052] According to a preferred embodiment of the present invention, the calcination conditions include: calcining at 400-600° C. for 4-6 hours to obtain the catalyst.

[0053] According to the present invention, the preparation method of the hierarchically porous alumina has been described in detail above and will not be repeated here. The catalyst prepared by the present invention has a micro-mesoporous hierarchical pore structure. The active component, noble metal particles, are more stable and dispersed in the micropores and surface vacancies, resulting in a higher number of surface active oxygen species. The mesoporous structure facilitates the diffusion of volatile organic compounds in the catalyst bulk, thereby enhancing catalytic activity and stability.

[0054] The present invention provides application of the catalyst of the present invention in catalytic combustion.

[0055] The present invention uses a fully automatic specific surface area and porosity analyzer (Tristar 3020) from Micromeritics Instrument of the United States to perform N2 adsorption-desorption isotherms at liquid nitrogen temperature (-196°C).

[0056] The present invention adopts Japanese JEOL JEM ARM200F to carry out high-resolution transmission electron microscopy (HRTEM) testing.

[0057] The present invention uses an AutoChem II 2920 chemical adsorption instrument from Micromeritics Instrument of the United States to obtain the O2-TPD graph.

[0058] Example 1

[0059] (1) Preparation of micro-mesoporous alumina support: 0.2 g of ethylene oxide triblock copolymer (P123) and 0.8 g of fatty alcohol polyoxyethylene ether (AEO-7) were mixed and dissolved in 20 ml of 95% ethanol aqueous solution. 1.5 ml of concentrated nitric acid (65 wt%), 0.7 g of citric acid, 0.0989 g of magnesium nitrate, and 2.04 g of aluminum isopropoxide (the atomic ratio of alkaline earth metal magnesium to aluminum was 1:15) were then added and stirred rapidly. 0.2 g of silica gel (viscosity 1000 MPa·s) was then added, the opening was sealed with plastic film, and the mixture was placed in a 30°C water bath with stirring for 6 h. The mixture was then poured into an evaporating dish and placed in a 60°C oven for solvent evaporation and self-assembly reaction for 48 h. The precursor formed after drying was placed in a muffle furnace and calcined at 300 °C at a rate of 1 °C / min for 2 h, and finally at 400 °C at a rate of 2 °C / min for 5 h to obtain a microporous-mesoporous alumina support with a specific surface area of ​​642 m 2 / g, pore volume 0.29cm 3 / g, the micro-mesopores are mainly distributed in the range of 1.2 to 4 nm, with an average pore diameter of 1.94 nm.

[0060] (2) Impregnation: 0.1767 g of K2CO3 and 0.1667 g of Pt(NO3)2 were weighed and dissolved in 50 ml of deionized water to obtain a solution. 5 g of the carrier prepared in step (1) was added to the above salt solution, and the solution was rotary evaporated at 60°C, dried at 80°C for 12 h, and then calcined at 550°C for 5 h to obtain a catalyst for catalytic combustion of volatile organic compounds (specific surface area of ​​633 m 2 / g, pore volume 0.34cm 3 / g, an average pore size of 1.87nm, and a particle size of the noble metal nanoparticles of 4.6nm), the catalyst contains 2wt% of alkali metal Na and 0.5wt% of Pt as a single substance.

[0061] Figure 1The catalyst in this example was analyzed for N adsorption-desorption isotherms at liquid nitrogen (-196°C) using a Micromeritics Instruments Tristar 3020 fully automated surface area and porosity analyzer. The initial portion resembled a Type I isotherm, indicating the presence of micropores. However, at relative partial pressures greater than 0.4, a significant hysteresis loop, caused by capillary condensation in the mesopores, began to appear.

[0062] Figure 2 This is a TEM image of the catalyst in this embodiment obtained by high-resolution transmission electron microscopy (HRTEM) using Japan JEOL JEM ARM200F. The Pt component particles are spherical or elliptical, with a particle size of only 4.6 nm, no obvious agglomeration phenomenon, and are evenly dispersed and high.

[0063] Figure 3 This is an O2-TPD plot of the catalyst of this example, obtained using a Micromeritics Instrument AutoChem II 2920 chemisorption instrument. The desorption peak between 50 and 150°C is attributed to physically adsorbed oxygen, the peak between 150 and 300°C is attributed to surface oxygen, and the peak above 300°C is attributed to lattice oxygen. The surface oxygen species of the catalyst of this invention are primarily lattice oxygen, which facilitates the catalytic reaction.

[0064] Figure 4 The catalyst of this embodiment is active for catalytic combustion of ethylene in a fixed bed reactor. The reaction conditions are: catalyst 40-60 mesh, VOCs concentration 700ppm, 10% O2, 5% H2O, reaction space velocity 25000h -1 The reaction temperature is 100-500℃, and the reaction is carried out in a fixed bed with continuous online monitoring. The temperature T corresponding to the VOCs conversion rate of 90% is the complete conversion temperature, which is recorded as T90. The smaller the T90, the lower the corresponding conversion temperature, indicating that the catalyst is more active. In this embodiment, when the temperature reaches 164℃ (T 90 ), ethylene can be fully converted.

[0065] Example 2

[0066] (1) Preparation of micro-mesoporous alumina support: 0.3 g (F127) and 0.7 g fatty alcohol polyoxyethylene ether (AEO-7) were mixed and dissolved in 20 ml of 95% ethanol aqueous solution. Then 2.1 ml of concentrated hydrochloric acid (37 wt%), 1.8 g of glacial acetic acid, 0.2614 g of barium nitrate and 1.64 g of sodium metaaluminate (the atomic ratio of alkaline earth metal barium to aluminum is 1:20) were added and stirred rapidly. Then 0.1 g of silica gel (viscosity 3000 MPa·s) was added, the mouth was sealed with plastic film and placed in a 60°C water bath and stirred for 6 hours, then poured into an evaporating dish and placed in an 80°C oven for solvent evaporation and self-assembly reaction for 48 hours. The precursor formed after drying was then placed in a muffle furnace, heated to 300°C at 1°C / min and calcined for 3 hours, and finally heated to 700°C at 2°C / min and calcined for 3 hours to obtain a micro-mesoporous alumina support with a specific surface area of ​​435 m 2 / g, pore volume 0.26cm 3 / g, the micro-mesopores are mainly distributed in the range of 1.5-4.5nm, with an average pore diameter of 2.75nm.

[0067] (2) Impregnation: 0.4610 g of Na2CO3 and 1.0 g of Pd(NO3)2 solution were weighed and dissolved in 50 ml of deionized water to obtain a solution. 5 g of the support prepared in step (1) was added to the above salt solution, and the solution was rotary evaporated at 80°C, dried at 100°C for 3 h, and then calcined at 550°C for 5 h to obtain a catalyst (specific surface area of ​​428 m 2 / g, pore volume 0.25cm 3 / g, an average pore size of 2.69nm, a particle size of the noble metal nanoparticles of 5.7nm), 4wt% of alkali metal Na and 3wt% of Pd in ​​terms of elemental content in the catalyst.

[0068] The catalyst was loaded into a fixed bed reactor with a CH4 concentration of 1000 ppm, 10% O2, and 5% H2O, and a reaction space velocity of 25000 h -1 The reaction temperature is 100-500℃, and continuous online monitoring is adopted. When the temperature reaches 349℃ (T 90 ), CH4 can be completely converted.

[0069] Example 3

[0070] (1) Preparation of micro-mesoporous alumina support: 0.1g (F68) and 0.9g fatty alcohol polyoxyethylene ether (AEO-7) were mixed and dissolved in 20ml 95wt% ethanol aqueous solution. Then 1.7ml concentrated sulfuric acid, 0.6g lauric acid, 0.4232g strontium nitrate and 2.46g aluminum n-butoxide (the atomic ratio of alkaline earth metal strontium to aluminum is 1:5) were added. Then 0.3g silica gel (viscosity 500MPa·s) was added, the mouth was sealed with plastic film and placed in a 30℃ water bath and stirred for 24h, then poured into an evaporating dish and placed in a 30℃ oven for solvent evaporation and self-assembly reaction for 72h. The precursor formed after drying was then placed in a muffle furnace, heated to 300℃ at 1℃ / min and calcined for 2h, and finally heated to 500℃ at 2℃ / min and calcined for 3h to obtain a micro-mesoporous alumina support with a specific surface area of ​​572m 2 / g, pore volume 0.31cm3 / g, micro-mesopores are mainly distributed in the range of 1.8 to 5nm, and the average pore diameter is 2.43nm.

[0071] (2) Impregnation: 0.9220 g of Na2CO3 and 0.1027 g of RuCl3 were weighed and dissolved in 50 ml of deionized water to obtain a solution. 5 g of the catalyst prepared in step (2) was added to the salt solution, and the solution was rotary evaporated at 70°C, dried at 90°C for 3 h, and then calcined at 600°C for 4 h to obtain a catalyst (specific surface area of ​​568 m 2 / g, pore volume 0.30cm 3 / g, an average pore size of 2.37nm, and a particle size of the noble metal nanoparticles of 5.5nm), the catalyst contains 8wt% of alkali metal Na and 1wt% of Ru as a single substance.

[0072] The catalyst was loaded into a fixed bed reactor with a C2H4 concentration of 700 ppm, 10% O2, and 5% H2O, and a reaction space velocity of 25,000 h -1 The reaction temperature is 100-500℃, and continuous online monitoring is adopted. When the temperature reaches 289℃ (T 90 ), C2H4 can achieve complete conversion.

[0073] Example 4

[0074] This embodiment adopts the preparation method similar to that of Example 1, except that in Example 4, only 1.0 g (AEO-7) is added during the preparation of the microporous-mesoporous multi-level porous alumina support, and the obtained support has a specific surface area of ​​653 m 2 / g, pore volume 0.25cm 3 / g, with an average pore size of 1.75nm. After impregnation with alkali metals and precious metals, the catalyst has a specific surface area of ​​649m 2 / g, pore volume 0.24cm 3 / g, micro-mesopores are mainly distributed in the range of 1.2 to 4 nm, with an average pore diameter of 1.72 nm, noble metal nanoparticles of 6.4 nm, and the catalyst contains 2 wt% of alkali metal Na and 0.5 wt% of Pt as a single substance.

[0075] The catalyst was loaded into a fixed bed reactor with a C2H4 concentration of 700 ppm, 10% O2, and 5% H2O, and a reaction space velocity of 25,000 h -1 The reaction temperature is 100-500℃, and continuous online monitoring is adopted. When the temperature reaches 215℃ (T 90 ), C2H4 can achieve complete conversion.

[0076] Example 5

[0077] This embodiment was prepared using a similar preparation method to Example 1, except that, in Example 5, 0.4 g of P123 and 0.6 g of fatty alcohol polyoxyethylene ether (AEO-7) were added to the microporous-mesoporous multi-level alumina support, mixed, and dissolved in 20 ml of 95 wt% ethanol aqueous solution. The resulting microporous-mesoporous multi-level alumina support was impregnated with alkali metals and noble metals, and the resulting catalyst was passed through a fixed-bed reactor with a C2H4 concentration of 700 ppm, 10% O2, and 5% H2O at a reaction space velocity of 25,000 h. -1 The reaction temperature is 100-500℃, and continuous online monitoring is adopted. When the temperature reaches 197℃ (T 90 ), C2H4 can achieve complete conversion.

[0078] Comparative Example 1

[0079] This embodiment adopts a preparation method similar to that of Example 1, except that, in Example 1, a commercial mesoporous alumina carrier modified with alkaline earth metal is used, and then alkali metal and precious metal are impregnated. Specifically, 0.9697g of magnesium nitrate is weighed and dissolved in 50ml of deionized water, and then 5.0g of commercial mesoporous alumina (the atomic ratio of alkaline earth metal magnesium to aluminum is 1:15) is added, heated and stirred, and the water is evaporated, and the modified carrier is obtained after drying and roasting. Then, 0.1767g of K2CO3 and 0.1667g of Pt(NO3)2 are weighed and dissolved in 50ml of deionized water to obtain a solution. 5g of the modified carrier is added to the above salt solution, and the catalyst obtained by rotary evaporation, drying and roasting has a specific surface area of ​​139m 2 / g, pore volume 0.67cm 3 / g, an average pore size of 19.36nm, and a particle size of the noble metal nanoparticles of 5.1nm). Through a fixed bed reaction, a C2H4 concentration of 700ppm, 10% O2, 5% H2O, and a reaction space velocity of 25000h -1The reaction temperature is 100-500℃, and continuous online monitoring is adopted. When the temperature reaches 262℃ (T 90 ), C2H4 can achieve complete conversion.

[0080] Comparative Example 2

[0081] This embodiment was prepared using a similar preparation method to Example 1, except that no silica gel was added during the preparation of the microporous-mesoporous multi-level alumina support in Comparative Example 2. Specifically, 0.2g (P123) and 0.8g (AEO-7) were mixed and dissolved in 20ml of 95% ethanol aqueous solution. 1.5ml of concentrated nitric acid (65wt%), 0.7g of citric acid, 0.0989g of magnesium nitrate, and 2.04g of aluminum isopropoxide (the atomic ratio of alkaline earth metal magnesium to aluminum was 1:15) were then added and rapidly stirred. The mixture was sealed with plastic film and placed in a 30°C waterbath with stirring for 6h. The mixture was then poured into an evaporating dish and placed in a 60°C oven for solvent evaporation and self-assembly reaction for 48h. The mixture was then dried and calcined in a muffle furnace to obtain the modified alumina support. Next, 0.1767 g of K2CO3 and 0.1667 g of Pt(NO3)2 were weighed and dissolved in 50 ml of deionized water to obtain a solution. 5 g of the modified support was added to the above salt solution. The catalyst obtained by rotary evaporation, drying and calcination was reacted in a fixed bed with a C2H4 concentration of 700 ppm, 10 vol% O2, and 5 vol% H2O at a reaction space velocity of 25000 h -1 The reaction temperature is 100-500℃, and continuous online monitoring is adopted. When the temperature reaches 175℃ (T 90 ), C2H4 can be completely converted. However, after the reaction, the catalyst was removed and found to be partially pulverized, while the sample with silica gel added did not have this phenomenon, indicating that silica gel can improve the mechanical strength of the catalyst.

[0082] Comparative Example 3

[0083] This embodiment was prepared using a similar preparation method to Example 1, except that in Comparative Example 3, no alkaline earth metal was added when preparing the microporous-mesoporous multi-level porous alumina support. Instead, alkaline earth metal, alkali metal, and precious metal were simultaneously added during the impregnation. Specifically, 0.2g (P123) and 0.8g (AEO-7) were mixed and dissolved in 20ml of 95% ethanol aqueous solution. 1.5ml of concentrated nitric acid (65wt%), 0.7g of citric acid, and 2.04g of aluminum isopropoxide were then added and stirred rapidly. The mixture was sealed with plastic film and placed in a 30°C water bath with stirring for 6h. The mixture was then poured into an evaporating dish and placed in a 60°C oven to allow the solvent to evaporate and self-assemble for 48h. The mixture was then dried and calcined in a muffle furnace to obtain the modified alumina support. Next, 0.9597g of magnesium nitrate, 0.1767g of K2CO3, and 0.1667g of Pt(NO3)2 were dissolved in 50ml of deionized water to obtain a solution. 5g of the modified support was added to the salt solution and the resulting catalyst was dried and calcined by rotary evaporation. In a fixed-bed reactor, the C2H4 concentration was 700ppm, the reaction temperature was 10% O2, and the reaction space velocity was 25000h. -1 The reaction temperature is 100-500℃, and continuous online monitoring is adopted. When the temperature reaches 222℃ (T 90 ), C2H4 can achieve complete conversion.

[0084] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A catalyst for catalytic oxidation of volatile organic compounds, characterized in that: The catalyst contains an alkaline earth metal modified alumina carrier and an alkali metal and a noble metal supported on the modified alumina carrier, wherein the alkaline earth metal modified alumina carrier has a micro-mesoporous multi-level pore structure; The alkaline earth metal modified alumina carrier has micropores distributed in the range of 1.2-2.0 nm and mesopores distributed in the range of 2-5 nm; The atomic ratio of alkaline earth metal to aluminum in alumina is 1:(5-40); The alkaline earth metal is one or more of magnesium, calcium, strontium and barium; The noble metal is selected from one or more of Pt, Pd, Rh, Ru, Ag and Au; The alkali metal is selected from K and / or Na; The specific surface area of ​​the catalyst is 428-633m 2 / g, pore volume of 0.25-0.34cm 3 / g, the average pore size is 1.8-3nm, and the particle size of the noble metal nanoparticles is 4-9nm; The catalyst contains 85-99 wt% of a modified alumina support, 1-8 wt% of an alkali metal in elemental form, and 0.5-3 wt% of a noble metal in elemental form, based on the total weight of the catalyst; The sum of the mass percentages of each component in the catalyst is equal to 100%.

2. The catalyst according to claim 1, wherein The alkaline earth metal is one or more of magnesium, strontium and barium; and / or The particle size of the noble metal nanoparticles is 5-8 nm.

3. The catalyst according to claim 1, wherein The noble metal is selected from one or more of Pt, Pd and Ru.

4. The catalyst according to claim 3, wherein The noble metal is selected from one or more of Pt and Pd.

5. The catalyst according to claim 1, wherein The preparation method of the alkaline earth metal modified alumina carrier comprises: uniformly mixing acid, alcohol, surfactant, silica gel, alkaline earth metal source and aluminum source, performing heat treatment to volatilize the solvent, and calcining. The catalyst according to claim 5, wherein The surfactant comprises surfactant A and surfactant B, wherein surfactant A is fatty alcohol polyoxyethylene ether, and surfactant B is a combination of one or more of P123, F127 and F68; and / or The acid is an organic acid and / or an inorganic acid, and the organic acid is one or more of citric acid, glacial acetic acid, malic acid, gluconic acid and lauric acid; The inorganic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; and / or The alcohol is a C1-C5 monohydric alcohol; and / or The aluminum source is one or more of aluminum isopropoxide, aluminum n-butoxide, sodium metaaluminate, aluminum nitrate, aluminum chloride and aluminum sulfate; and / or The viscosity of the silicone gel is 500-3000 MPa·s; and / or Based on 100% by weight, the amount of surfactant is 10-18% by weight: the amount of aluminum source is 20-35% by weight: the amount of organic acid is 6-25% by weight: the amount of inorganic acid is 30-40% by weight: the amount of silica gel is 1-4% by weight: the amount of alkaline earth metal source is 1-5% by weight; and / or Heat treatment conditions include: temperature of 30-80°C, time of 48-72 hours; and / or The calcination conditions include: heating to 300° C. at a heating rate of 0.5-2° C. / min and holding for 1-3 hours, then heating to 400-800° C. at a heating rate of 1-5° C. / min and calcining for 3-10 hours.

7. The catalyst according to claim 6, wherein The mass ratio of the surfactant B to the surfactant A is 1:9-1:1.5; and / or The organic acid is one or more of citric acid, lauric acid and glacial acetic acid; The acid contains an inorganic acid and an organic acid; and / or The alcohol is one or more of methanol, ethanol and propanol.

8. The catalyst according to claim 5 or 6, wherein The preparation method of the alkaline earth metal modified alumina carrier includes: dissolving a surfactant in an 80-98 weight percent ethanol aqueous solution, then adding an organic acid, an inorganic acid, an alkaline earth metal salt and an aluminum source under stirring, maintaining the system temperature at 20-60°C, adding silica gel, and continuously stirring for 6-24 hours under sealed conditions, then introducing the reaction mixture into an evaporating dish to evaporate the alcohol and water at 30-80°C for 48-72 hours, and after drying, heating to 300°C at a rate of 0.5-2°C / min and holding for 1-3 hours, and finally heating to 400-800°C at a rate of 1-5°C / min and calcining for 5-10 hours.

9. The method for preparing the catalyst according to any one of claims 1 to 8, characterized in that: The method includes: 1) Preparation of alkaline earth metal modified alumina support; 2) The modified alumina carrier is loaded with alkali metal and noble metal by an impregnation method, and the impregnated alumina is dried and calcined to obtain a catalyst.

10. The preparation method according to claim 9, wherein The impregnation method comprises: The modified alumina carrier is impregnated with a mixed solution of alkali metal and noble metal, and then dried and calcined to obtain a catalyst.

11. The preparation method according to claim 10, wherein The drying conditions include: rotary evaporation at 60-80 DEG C, and then drying in an oven at 80-100 DEG C for 8-12 hours; the calcination conditions include: calcining at 400-600 DEG C for 4-6 hours to obtain the catalyst.

12. The preparation method according to claim 9, wherein The preparation method of the alkaline earth metal modified alumina carrier comprises: uniformly mixing acid, alcohol, surfactant, silica gel, alkaline earth metal source and aluminum source, performing heat treatment to volatilize the solvent, and calcining.

13. The preparation method according to claim 12, wherein The surfactant comprises surfactant A and surfactant B, wherein surfactant A is fatty alcohol polyoxyethylene ether, and surfactant B is a combination of one or more of P123, F127 and F68; and / or The acid is an organic acid and / or an inorganic acid, and the organic acid is one or more of citric acid, acetic acid, malic acid, gluconic acid and lauric acid; and / or The inorganic acid is one or more of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid; and / or The alcohol is a C1-C5 monohydric alcohol; and / or The aluminum source is one or more of aluminum isopropoxide, aluminum sec-butoxide, sodium metaaluminate, aluminum nitrate, aluminum chloride and aluminum sulfate; and / or The viscosity of the silicone gel is 500-3000 MPa·s; and / or Heat treatment conditions include: temperature of 30-80°C, time of 48-72 hours; and / or The calcination conditions include: heating to 300° C. at a heating rate of 0.5-2° C. / min and holding for 1-3 hours, then heating to 400-800° C. at a heating rate of 1-5° C. / min and calcining for 3-10 hours.

14. The preparation method according to claim 13, wherein The mass ratio of surfactant B to surfactant A is 1:9-1:1.5; and / or The alcohol is one or more of methanol, ethanol and propanol; and / or The acid contains an inorganic acid and an organic acid, based on 100% by weight, the amount of the surfactant is 12-17% by weight, the amount of the aluminum source is 22-33% by weight, the amount of the organic acid is 7-25% by weight, the amount of the inorganic acid is 34-40% by weight, the amount of the silica gel is 1.2-3.8% by weight, and the amount of the alkaline earth metal source is 1.6-5% by weight; and / or The preparation method of the alkaline earth metal modified alumina carrier includes: dissolving a surfactant in an 80-98 weight percent ethanol aqueous solution, then adding an organic acid, an inorganic acid, an alkaline earth metal salt and an aluminum source under stirring, maintaining the system temperature at 20-60°C, adding silica gel, and continuously stirring for 6-24 hours under sealed conditions, then introducing the reaction mixture into an evaporating dish to evaporate the alcohol and water at 30-80°C for 48-72 hours, and after drying, heating to 300°C at a rate of 0.5-2°C / min and holding for 1-3 hours, and finally heating to 400-800°C at a rate of 1-5°C / min and calcining for 5-10 hours.

15. Use of the catalyst according to any one of claims 1 to 8 in the catalytic oxidation of volatile organic compounds.

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