Slurry-based molecular sieve loaded alpha-MnO2 catalyst based on acid treatment-metal impregnation dual regulation and control

Abstract

The invention relates to a slurry-based molecular sieve loaded alpha-MnO2 catalyst based on acid treatment-metal impregnation dual regulation and control. According to the method, activated slurry is taken as a raw material, a Na-type ZSM-5 molecular sieve is synthesized through hydrothermal crystallization, and then the H-type molecular sieve is prepared through ion exchange. Then alpha-MnO2 is loaded, the acidity of a framework is adjusted through weak acid treatment, the pore environment is optimized, the dispersity and the active site exposure degree of the alpha-MnO2 are improved, the content of Mn < 4 + > is increased, generation of surface lattice oxygen is promoted, and the redox cycle driving force is enhanced. And furthermore, through doping of metal ions such as Cu < 2 + >, Fe < 3 + > and Ce < 3 + >, the oxygen migration capability and the catalytic oxidation capability are improved. The catalyst shows excellent low-temperature activity, poisoning resistance and structural stability in low-temperature catalytic oxidation of VOCs in an oil field. The method disclosed by the invention is mild in process condition, green and environment-friendly, and wide in raw material source, has a good industrial application prospect, and is particularly suitable for waste recycling and VOCs pollution treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalysis and solid waste resource utilization. Specifically, it relates to a supported catalyst using H-type ZSM-5 molecular sieve synthesized from oilfield mud as a carrier, loaded with α-MnO2, and then modified with acid and metal impregnation, and its preparation method. The catalyst is primarily used for the efficient, low-temperature catalytic oxidation of VOCs in oilfields, and is particularly suitable for the treatment of typical volatile organic compounds (VOCs), such as associated gas or light hydrocarbon waste gas. This technology combines pollutant emission reduction with the resource reuse of oilfield waste, and has excellent engineering promotion value. Technical Background

[0002] With the continuous increase in the intensity of oil and gas field development, the large amount of volatile organic compounds (VOCs) produced during oil field production has become a major source of air pollution that needs to be controlled. In particular, saturated hydrocarbons represented by light hydrocarbons such as propane, butane, and pentane in oil field VOCs not only have low reaction starting temperatures and high toxicity, but also easily react with NO under sunlight. x Photochemical reactions occur to form ozone and PM 2.5 Secondary pollutants such as VOCs seriously threaten human health and ecological safety. Therefore, the development of efficient catalysts suitable for special VOCs in oil fields has become an urgent problem to be solved.

[0003] Low-temperature catalytic oxidation is a VOCs treatment technology with high efficiency, wide applicability, and minimal secondary pollution. Catalyst performance plays a decisive role in reaction activity and stability. ZSM-5 molecular sieve, due to its regular pore structure, excellent thermal stability, and tunability, shows great potential for VOCs catalytic oxidation. However, the high cost of commercially available ZSM-5 raw materials and the complex preparation process limit its widespread application in large-scale industrial waste gas treatment.

[0004] The large amount of solid waste mud generated during oilfield drilling, production, storage, and transportation is rich in silicon and aluminum components and is a potential precursor for molecular sieve synthesis. Reusing this mud for the green production of ZSM-5 molecular sieve not only significantly reduces catalyst material costs but also helps achieve harmless and resourceful treatment of solid waste, in line with the concept of green and low-carbon development.

[0005] In order to further improve the catalytic performance, the present invention adopts a multi-step regulation strategy. First, α-MnO2 is loaded on the surface of the slurry-based ZSM-5 molecular sieve through an improved hydrothermal-calcination method to construct catalytic active oxygen species sites; then, the framework acidity is adjusted by acid treatment, the pore environment is optimized, the dispersion and active site exposure of α-MnO2 are improved, and the Mn content in α-MnO2 is increased. 4+ The content of Mn 4+ With Mn3+ The redox cycle driving force between them; then, transition metals such as Cu, Fe, and Ce are introduced through the metal salt impregnation method to enhance the oxygen migration ability, promote the generation of active oxygen free radicals, and significantly improve the low-temperature activity and anti-poisoning performance of the catalyst.

[0006] The catalyst preparation process is controllable, the raw materials are cheap, and the resulting material has a stable structure. It exhibits excellent low-temperature catalytic oxidation ability of light hydrocarbon VOCs, strong resistance to carbon deposition and resistance to sulfur poisoning. It is particularly suitable for complex working conditions such as high humidity and high carbon load in oilfield VOCs treatment, and has good application prospects and promotion value. Summary of the Invention

[0007] The preparation method of the catalyst of the present invention mainly comprises the following steps: the present invention provides an H-type ZSM-5 molecular sieve synthesized from mud resources as a carrier, firstly loads α-MnO2, then adjusts the acidic environment through acid treatment, and finally introduces Cu by metal salt impregnation method. 2+ 、Fe 3+ or Ce 3+ The present invention relates to a molecular sieve supported catalyst containing transition metal ions and a preparation method thereof. The method improves the dispersibility and active site exposure of α-MnO2 by acid treatment, thereby increasing the Mn content in α-MnO2. 4+ The content of Mn 4+ With Mn 3+ The driving force of the redox cycle between them. Water-soluble metal salts are selected for the metal impregnation part, and the distribution density of the active centers is controlled by an appropriate concentration gradient. Finally, the structure is stabilized by hydrothermal reaction and calcination to achieve synergistic enhancement of the active components. The catalyst of the present invention exhibits excellent low-temperature catalytic oxidation performance of propane, good anti-poisoning ability and high-temperature stability, and is particularly suitable for continuous catalytic oxidation treatment processes under high load and humid conditions in the treatment of oilfield VOCs (mainly light hydrocarbon components). The preparation method of the catalyst of the present invention mainly comprises the following steps:

[0008] Synthesis of S1 and ZSM-5 molecular sieves

[0009] Dried, calcined, and activated oilfield drilling mud is used as the silicon and aluminum source. A silicon source, an organic amine template, seed crystals, and deionized water are added to form a precursor colloid system. After uniform stirring, the system is transferred to a hydrothermal reactor and crystallized at a controlled temperature for a specified time to obtain a crude product. The organic template is removed through solid-liquid separation, neutralization and washing, drying, and high-temperature calcination to produce the Na-type ZSM-5 molecular sieve.

[0010] Preparation of S2 and H type molecular sieves

[0011] Disperse the Na-type ZSM-5 molecular sieve in ammonium chloride or ammonium nitrate solution, stir in a water bath and perform multiple ion exchange reactions to make the Na + Exchanged to NH4 + After sufficient washing, freeze-drying and high-temperature calcination for deamination, H-type ZSM-5 molecular sieve is obtained.

[0012] S3, α-MnO2 loading

[0013] Potassium permanganate and ammonium oxalate are dissolved in water separately to form a redox system, which reacts in a warm water bath to generate nano-scale MnO2 precipitate. H-type ZSM-5 molecular sieve is then added to the reaction system, stirred and mixed evenly, and then transferred to a hydrothermal reaction kettle to uniformly load α-MnO2 into the molecular sieve carrier. The product is centrifuged, washed with water, freeze-dried, and moderately calcined to obtain a loaded material.

[0014] S4. Acid modification treatment

[0015] The supported material prepared in S3 is immersed in dilute acid solutions of varying concentrations. After stirring or ultrasonic treatment for a specified period of time, it is thoroughly washed to neutrality and then dried. This process adjusts the acidity distribution of the molecular sieve, removes weak acid sites and some exchangeable metals, and improves the synergistic dispersion of the active components.

[0016] S5. Metal salt impregnation modification

[0017] The acid-modified supported catalyst is placed in a metal salt solution with a certain concentration, immersed for a period of time, separated by centrifugation or filtration, washed, dried and calcined to obtain the final slurry-based molecular sieve-supported α-MnO2 catalyst with dual control of acid treatment and metal impregnation.

[0018] Optional parameter settings:

[0019] Optionally, the crystallization temperature during the molecular sieve synthesis process is 150-200°C and the time is 36-60h;

[0020] Optionally, the calcination temperature for removing the template is 500-600° C. and the time is 3-6 hours;

[0021] Optionally, the ion exchange liquid is 1 mol / L NH4Cl or NH4NO3, the exchange temperature is 60-90°C, each time is 1-2 hours, and repeated 2-4 times;

[0022] Optionally, the water bath reaction temperature during the preparation of the supported catalyst is 50-70°C, the hydrothermal reaction temperature is 140-180°C, the time is 8-16h, the calcination temperature is set to 0-400°C, the heating rate is 3-10°C / min, and the holding time is 1-3h;

[0023] Optionally, the acid modification solution may be hydrochloric acid, sulfuric acid, acetic acid, etc., with a concentration of 0.01-0.5 mol / L, a liquid-solid ratio of 3:500-10:500, and a modification time of 3-12 h;

[0024] Optionally, the metal salt is selected from nitrate or sulfate, the solution concentration is 0.01-0.1 mol / L, the immersion time is 3-12 hours, the roasting temperature is set to 200-400°C, the heating rate is 3-10°C / min, and the holding time is 1-3 hours. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of the preparation method provided for an example of the present invention;

[0026] Figure 2 This is a scanning electron microscope image of a slurry-based molecular sieve-loaded α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation provided in Example 4 of the present invention;

[0027] Figure 3 A transmission electron micrograph of a slurry-based molecular sieve-supported α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation provided in Example 4 of the present invention;

[0028] Figure 4 XPS graph of Mn 2p orbitals of the slurry-based molecular sieve-supported α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation provided in Examples 2 and 3 of the present invention;

[0029] Figure 5 N2 adsorption-desorption isotherms and pore size distribution diagrams of the slurry-based molecular sieve-supported α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation provided in Examples 2, 3, and 4 of the present invention;

[0030] Figure 6 This is a diagram showing the degradation efficiency of propane at different temperatures for the prepared slurry-based molecular sieve-loaded α-MnO2 catalyst with dual control of acid treatment and metal impregnation. DETAILED DESCRIPTION

[0031] Example 1: A slurry-based molecular sieve-loaded α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation and its preparation method

[0032] 5g of a slurry (containing 41.89% SiO2, 13.62% Al2O3, 4.27% Fe2O3, and 2.85% MgO) was physically mixed with 1g of NaOH for 15 minutes in a zirconia ark. The mixture was then heated to 900°C at a rate of 5°C / min and calcined in air for 120 minutes. The activated slurry precursor was then mixed with 6.7g of a silicon source (silica gel), 4.03g of n-butylamine, 0.378g of seed crystals, and 70ml of deionized water. The mixture was stirred at room temperature for 3 hours. The gel was then transferred to a Teflon-lined stainless steel crystallization kettle and hydrothermally crystallized in a 170°C oven for 48 hours. After crystallization, the mixture was cooled, the mother liquor was filtered to remove, and the solid product was washed by suction until neutral, freeze-dried, and calcined in a muffle furnace at 550°C for 4 hours to remove the template, yielding the Na-type ZSM-5 molecular sieve. At 80 ° C, the Na type molecular sieve was ion exchanged three times with 1 mol / L NH4Cl solution (liquid to solid ratio is 10 ml / g), each time for 1.5 hours, and then freeze-dried and calcined at 550 ° C for 4 hours to obtain the H type ZSM-5 molecular sieve.

[0033] Dissolve 498 mg of potassium permanganate in 25 mL of deionized water, and 227 mg of ammonium oxalate monohydrate in 40 mL of deionized water. Stir each mixture for 30 minutes, marking them as Solution A and Solution B, respectively. Next, place Solution A in a 60°C water bath. Slowly add Solution B to Solution A and continue stirring with a magnetic stirrer for 30 minutes. After stirring, add molecular sieves and continue stirring until evaporated to dryness. After evaporation, dry at 90°C. Finally, calcine the dried product in a muffle furnace at 300°C to obtain the supported catalyst.

[0034] Example 2: A slurry-based molecular sieve-loaded α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation and its preparation method

[0035] The difference between this embodiment and embodiment 1 is that a different loading method is adopted.

[0036] 5g of a slurry (containing 41.89% SiO2, 13.62% Al2O3, 4.27% Fe2O3, and 2.85% MgO) was physically mixed with 1g of NaOH for 15 minutes in a zirconia ark. The mixture was then heated to 900°C at a rate of 5°C / min and calcined in air for 120 minutes. The activated slurry precursor was then mixed with 6.7g of a silicon source (silica gel), 4.03g of n-butylamine, 0.378g of seed crystals, and 70ml of deionized water. The mixture was stirred at room temperature for 3 hours. The gel was then transferred to a Teflon-lined stainless steel crystallization kettle and hydrothermally crystallized in a 170°C oven for 48 hours. After crystallization, the mixture was cooled, the mother liquor was filtered to remove, and the solid product was washed by suction until neutral, freeze-dried, and calcined in a muffle furnace at 550°C for 4 hours to remove the template, yielding the Na-type ZSM-5 molecular sieve. At 80 ° C, the Na type molecular sieve was ion exchanged three times with 1 mol / L NH4Cl solution (liquid to solid ratio is 10 ml / g), each time for 1.5 hours, and then freeze-dried and calcined at 550 ° C for 4 hours to obtain the H type ZSM-5 molecular sieve.

[0037] Dissolve 498 mg of potassium permanganate in 25 mL of deionized water, and 227 mg of ammonium oxalate monohydrate in 40 mL of deionized water. Stir each mixture for 30 minutes, each designated as solution A and solution B. Next, place solution A in a 60°C constant-temperature water bath, slowly add solution B to solution A, and continue stirring with a magnetic stirrer for 30 minutes. After stirring, add molecular sieves and stir at room temperature for 40 minutes. The resulting mixture is then transferred to a 100 mL hydrothermal reactor and reacted at 160°C for 12 hours. After the reaction is complete, the product is washed several times by centrifugation with deionized water and then freeze-dried. Finally, the dried product is calcined in a muffle furnace at 300°C to obtain a supported catalyst.

[0038] After performance testing, it was found that the catalytic performance of the supported catalyst prepared by the hydrothermal method (Example 2) was much better than that of the supported catalyst prepared by the calcination method (Example 1). 90 From 350℃ to 320℃)

[0039] Example 3: A slurry-based molecular sieve-loaded α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation and its preparation method

[0040] The difference between this embodiment and embodiment 2 is that acid modification is performed.

[0041] 5g of a slurry (containing 41.89% SiO2, 13.62% Al2O3, 4.27% Fe2O3, and 2.85% MgO) was physically mixed with 1g of NaOH for 15 minutes in a zirconia ark. The mixture was then heated to 900°C at a rate of 5°C / min and calcined in air for 120 minutes. The activated slurry precursor was then mixed with 6.7g of a silicon source (silica gel), 4.03g of n-butylamine, 0.378g of seed crystals, and 70ml of deionized water. The mixture was stirred at room temperature for 3 hours. The gel was then transferred to a Teflon-lined stainless steel crystallization kettle and hydrothermally crystallized in a 170°C oven for 48 hours. After crystallization, the mixture was cooled, the mother liquor was filtered to remove, and the solid product was washed by suction until neutral, freeze-dried, and calcined in a muffle furnace at 550°C for 4 hours to remove the template, yielding the Na-type ZSM-5 molecular sieve. At 80 ° C, the Na type molecular sieve was ion exchanged three times with 1 mol / L NH4Cl solution (liquid to solid ratio is 10 ml / g), each time for 1.5 hours, and then freeze-dried and calcined at 550 ° C for 4 hours to obtain the H type ZSM-5 molecular sieve.

[0042] Dissolve 498 mg of potassium permanganate in 25 mL of deionized water, and 227 mg of ammonium oxalate monohydrate in 40 mL of deionized water. Stir each mixture for 30 minutes, each designated as solution A and solution B. Next, place solution A in a 60°C constant-temperature water bath, slowly add solution B to solution A, and continue stirring with a magnetic stirrer for 30 minutes. After stirring, add molecular sieves and stir at room temperature for 40 minutes. The resulting mixture is then transferred to a 100 mL hydrothermal reactor and reacted at 160°C for 12 hours. After the reaction is complete, the product is washed several times by centrifugation with deionized water and then freeze-dried. Finally, the dried product is calcined in a muffle furnace at 300°C to obtain a supported catalyst.

[0043] 0.3 g of the supported catalyst was weighed and dissolved in 50 ml of a 0.3 mol / L dilute hydrochloric acid solution. After ultrasonic stirring for 20 min, the solution was placed on a magnetic stirrer and stirred continuously at room temperature for 6 h. The solution was then centrifuged and washed with distilled water until neutral, and freeze-dried to obtain the acidified supported catalyst.

[0044] The performance test showed that the performance of the acid-modified catalyst was improved compared with that of the unmodified catalyst. 90 From 320℃ to 276℃. BET test showed that acid modification opened some of the original micropores and increased the gas adsorption capacity of the catalyst. XPS test showed that the (Mn 3+ ) / Mn 4+ The ratio decreases, which indicates that acid modification can greatly increase the Mn content in manganese-based catalysts. 4+content, and the catalyst has more oxygen vacancies, active oxygen, and higher redox activity.

[0045] Example 4: A slurry-based molecular sieve-loaded α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation and its preparation method

[0046] The difference between this embodiment and embodiment 3 is that metal modification is performed.

[0047] 5g of a slurry (containing 41.89% SiO2, 13.62% Al2O3, 4.27% Fe2O3, and 2.85% MgO) was physically mixed with 1g of NaOH for 15 minutes in a zirconia ark. The mixture was then heated to 900°C at a rate of 5°C / min and calcined in air for 120 minutes. The activated slurry precursor was then mixed with 6.7g of a silicon source (silica gel), 4.03g of n-butylamine, 0.378g of seed crystals, and 70ml of deionized water. The mixture was stirred at room temperature for 3 hours. The gel was then transferred to a Teflon-lined stainless steel crystallization kettle and hydrothermally crystallized in a 170°C oven for 48 hours. After crystallization, the mixture was cooled, the mother liquor was filtered to remove, and the solid product was washed by suction until neutral, freeze-dried, and calcined in a muffle furnace at 550°C for 4 hours to remove the template, yielding the Na-type ZSM-5 molecular sieve. At 80 ° C, the Na type molecular sieve was ion exchanged three times with 1 mol / L NH4Cl solution (liquid to solid ratio is 10 ml / g), each time for 1.5 hours, and then freeze-dried and calcined at 550 ° C for 4 hours to obtain the H type ZSM-5 molecular sieve.

[0048] Dissolve 498 mg of potassium permanganate in 25 mL of deionized water, and 227 mg of ammonium oxalate monohydrate in 40 mL of deionized water. Stir each mixture for 30 minutes, each designated as solution A and solution B. Next, place solution A in a 60°C constant-temperature water bath, slowly add solution B to solution A, and continue stirring with a magnetic stirrer for 30 minutes. After stirring, add molecular sieves and stir at room temperature for 40 minutes. The resulting mixture is then transferred to a 100 mL hydrothermal reactor and reacted at 160°C for 12 hours. After the reaction is complete, the product is washed several times by centrifugation with deionized water and then freeze-dried. Finally, the dried product is calcined in a muffle furnace at 300°C to obtain a supported catalyst.

[0049] 0.3 g of the supported catalyst was weighed and dissolved in 50 ml of a 0.3 mol / L dilute hydrochloric acid solution. After ultrasonic stirring for 20 min, the solution was placed on a magnetic stirrer and stirred continuously at room temperature for 6 h. The solution was then centrifuged and washed with distilled water until neutral, and freeze-dried to obtain the acidified supported catalyst.

[0050] 0.3 g of the acidified supported catalyst was weighed and dissolved in 50 ml of 0.05 mol / L copper nitrate solution, and stirred continuously at room temperature for 8 h. The solution was then centrifuged and washed four times with distilled water, freeze-dried, and calcined at 300° C. for 2 h to obtain a composite modified supported catalyst.

[0051] Example 5: A slurry-based molecular sieve-loaded α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation and its preparation method

[0052] The difference between this embodiment and embodiment 4 is the type of metal salt and the immersion time.

[0053] 5g of a slurry (containing 41.89% SiO2, 13.62% Al2O3, 4.27% Fe2O3, and 2.85% MgO) was physically mixed with 1g of NaOH for 15 minutes in a zirconia ark. The mixture was then heated to 900°C at a rate of 5°C / min and calcined in air for 120 minutes. The activated slurry precursor was then mixed with 6.7g of a silicon source (silica gel), 4.03g of n-butylamine, 0.378g of seed crystals, and 70ml of deionized water. The mixture was stirred at room temperature for 3 hours. The gel was then transferred to a Teflon-lined stainless steel crystallization kettle and hydrothermally crystallized in a 170°C oven for 48 hours. After crystallization, the mixture was cooled, the mother liquor was filtered to remove, and the solid product was washed by suction until neutral, freeze-dried, and calcined in a muffle furnace at 550°C for 4 hours to remove the template, yielding the Na-type ZSM-5 molecular sieve. At 80 ° C, the Na type molecular sieve was ion exchanged three times with 1 mol / L NH4Cl solution (liquid to solid ratio is 10 ml / g), each time for 1.5 hours, and then freeze-dried and calcined at 550 ° C for 4 hours to obtain the H type ZSM-5 molecular sieve.

[0054] Dissolve 498 mg of potassium permanganate in 25 mL of deionized water, and 227 mg of ammonium oxalate monohydrate in 40 mL of deionized water. Stir each mixture for 30 minutes, each designated as solution A and solution B. Next, place solution A in a 60°C constant-temperature water bath, slowly add solution B to solution A, and continue stirring with a magnetic stirrer for 30 minutes. After stirring, add molecular sieves and stir at room temperature for 40 minutes. The resulting mixture is then transferred to a 100 mL hydrothermal reactor and reacted at 160°C for 12 hours. After the reaction is complete, the product is washed several times by centrifugation with deionized water and then freeze-dried. Finally, the dried product is calcined in a muffle furnace at 300°C to obtain a supported catalyst.

[0055] 0.3 g of the supported catalyst was weighed and dissolved in 50 ml of a 0.3 mol / L dilute hydrochloric acid solution. After ultrasonic stirring for 20 min, the solution was placed on a magnetic stirrer and stirred continuously at room temperature for 6 h. The solution was then centrifuged and washed with distilled water until neutral, and freeze-dried to obtain the acidified supported catalyst.

[0056] 0.3 g of the acidified supported catalyst was weighed and dissolved in 50 ml of 0.1 mol / L cerium nitrate solution, and stirred continuously at room temperature for 4 h. The solution was then centrifuged and washed four times with distilled water, freeze-dried, and calcined at 300° C. for 2 h to obtain a composite modified supported catalyst.

[0057] Example 6: A slurry-based molecular sieve-loaded α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation and its preparation method

[0058] The difference between this embodiment and embodiment 5 is the type of metal salt.

[0059] 5g of a slurry (containing 41.89% SiO2, 13.62% Al2O3, 4.27% Fe2O3, and 2.85% MgO) was physically mixed with 1g of NaOH for 15 minutes in a zirconia ark. The mixture was then heated to 900°C at a rate of 5°C / min and calcined in air for 120 minutes. The activated slurry precursor was then mixed with 6.7g of a silicon source (silica gel), 4.03g of n-butylamine, 0.378g of seed crystals, and 70ml of deionized water. The mixture was stirred at room temperature for 3 hours. The gel was then transferred to a Teflon-lined stainless steel crystallization kettle and hydrothermally crystallized in a 170°C oven for 48 hours. After crystallization, the mixture was cooled, the mother liquor was filtered to remove, and the solid product was washed by suction until neutral, freeze-dried, and calcined in a muffle furnace at 550°C for 4 hours to remove the template, yielding the Na-type ZSM-5 molecular sieve. At 80 ° C, the Na type molecular sieve was ion exchanged three times with 1 mol / L NH4Cl solution (liquid to solid ratio is 10 ml / g), each time for 1.5 hours, and then freeze-dried and calcined at 550 ° C for 4 hours to obtain the H type ZSM-5 molecular sieve.

[0060] Dissolve 498 mg of potassium permanganate in 25 mL of deionized water, and 227 mg of ammonium oxalate monohydrate in 40 mL of deionized water. Stir each mixture for 30 minutes, each designated as solution A and solution B. Next, place solution A in a 60°C constant-temperature water bath, slowly add solution B to solution A, and continue stirring with a magnetic stirrer for 30 minutes. After stirring, add molecular sieves and stir at room temperature for 40 minutes. The resulting mixture is then transferred to a 100 mL hydrothermal reactor and reacted at 160°C for 12 hours. After the reaction is complete, the product is washed several times by centrifugation with deionized water and then freeze-dried. Finally, the dried product is calcined in a muffle furnace at 300°C to obtain a supported catalyst.

[0061] 0.3 g of the supported catalyst was weighed and dissolved in 50 ml of a 0.3 mol / L dilute hydrochloric acid solution. After ultrasonic stirring for 20 min, the solution was placed on a magnetic stirrer and stirred continuously at room temperature for 6 h. The solution was then centrifuged and washed with distilled water until neutral, and freeze-dried to obtain the acidified supported catalyst.

[0062] 0.3 g of the acidified supported catalyst was weighed and dissolved in 50 ml of 0.1 mol / L ferric nitrate solution, and stirred continuously at room temperature for 4 h. The solution was then centrifuged and washed four times with distilled water, freeze-dried, and calcined at 300° C. for 2 h to obtain a composite modified supported catalyst.

[0063] Experimental Example 1

[0064] Experiment on low-temperature catalytic oxidation degradation of propane using a slurry-based molecular sieve-supported catalyst in Example 1-6:

[0065] 0.2 g of the slurry-based molecular sieve supported catalysts in Examples 1-6 were weighed and loaded into a U-shaped reactor. The U-shaped reactor was loaded into a low-temperature catalytic oxidation test device, and the initial propane concentration was set to 1080 mg·m -3 , and control the mass space velocity to 15000 mL·g -1 ·h -1 The catalyst was first subjected to room temperature adsorption without heating, and then heated after reaching adsorption equilibrium. Gas chromatography was used to test the degradation rate of propane at different temperatures.

[0066] Depend on Figure 4 It can be seen that the catalysts prepared in Examples 1-6 have different low-temperature catalytic oxidation activities, among which the catalyst prepared in Example 1 has higher low-temperature catalytic oxidation activity for propane than the catalysts prepared in Examples 2, 3, and 4. The degradation rate of propane in Example 4 at 266°C reaches 90%.

[0067] The applicant declares that the above embodiments are intended to illustrate the detailed operations and process flows of the present invention, but are not intended to be limiting of the present invention. Persons skilled in the relevant art should understand that any equivalent structures or equivalent process modifications made using the present description, or any direct or indirect application in other related technical fields, fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a slurry-based molecular sieve-supported α-MnO2 catalyst based on dual regulation of acid treatment and metal impregnation, comprising the following steps: S1. Activation treatment of mud precursor: The slurry is dried and then mixed evenly with an alkali source, and then calcined at a certain heating rate in an air atmosphere to achieve activation, thereby obtaining an activated slurry precursor; Synthesis of S2 and Na type ZSM-5 molecular sieves: The activated slurry is mixed with a silicon source, an organic template, a seed crystal and deionized water in a certain proportion and stirred evenly to form a gel system with a suitable molar ratio, and then transferred to a stainless steel crystallization kettle with a polytetrafluoroethylene lining. The crystallization reaction is carried out at a certain temperature and for a certain time to obtain an initial product. After cooling, filtering, washing to neutrality, drying and calcining to remove the template, the Na-type ZSM-5 molecular sieve is obtained; Synthesis of S3 and H type molecular sieves: The obtained Na-type ZSM-5 molecular sieve is subjected to multiple ion exchange treatments with ammonium salt solution under certain temperature conditions, and then dried and calcined to obtain H-type ZSM-5 molecular sieve; S4, loaded α-MnO2: A certain proportion of potassium permanganate and a reducing agent such as ammonium oxalate are dissolved in deionized water to form two solutions, which are mixed and reacted in a water bath to generate an α-MnO2 precursor solution. The H-type ZSM-5 molecular sieve obtained in step S3 is added to the precursor solution, and the mixture is stirred for a period of time before being transferred to a hydrothermal reactor for reaction. The product is washed, freeze-dried, and calcined to obtain an α-MnO2-loaded catalyst. S5, acid modification: The catalyst loaded with α-MnO2 is placed in a dilute acid solution for impregnation treatment, the acid concentration is adjustable, the impregnation time is appropriate, and then centrifuged, washed to neutrality and freeze-dried to obtain an acid-modified catalyst; S6, Metal Impregnation Modification: The acid-modified catalyst is placed in a metal salt solution for impregnation treatment. The metal salt is preferably a nitrate or sulfate of copper, iron or cerium. The molar ratio of the metal to manganese is within an appropriate range. After the impregnation is completed, the catalyst is washed, freeze-dried and calcined to obtain a metal-modified catalyst.

2. The method according to claim 1, wherein: The mass ratio of the slurry to NaOH is controlled within a certain range, the roasting temperature is 800-950° C., and the time is not less than 1 hour.

3. The method according to claim 1, wherein: The synthesis molar ratio of the ZSM-5 molecular sieve is SiO2:Al2O3:template:H2O=1:(0.02-0.06):(0.2-0.5):(20-30), the crystallization temperature is 150-200°C, the crystallization time is 36-60h, the calcination temperature is 500-600°C, and the calcination time is 3-6 hours.

4. The method according to claim 1, wherein: The concentration of the ammonium salt solution in the ion exchange step is 0.5-2 mol / L, the exchange temperature is 60-90° C., the time is 1-2 hours, and the number of exchanges is 2-4 times.

5. The method according to claim 1, wherein: The hydrothermal temperature of the loaded α-MnO2 is 140-180°C, the reaction time is 8-16h, and the final calcination temperature is 0-400°C.

6. The method according to claim 1, wherein: Acid modification uses dilute hydrochloric acid, dilute nitric acid or acetic acid with a concentration range of 0.01-0.5 mol / L and an immersion time of 3-12 hours.

7. The method according to claim 1, wherein: The concentration of the metal salt solution is controlled at 0.01-0.1 mol / L, the impregnation time is 3-12 hours, and the roasting temperature is 200-400°C.

Images