A monolithic catalyst for propane combustion and a method for preparing the same

Abstract

The application provides a monolithic catalyst for propane combustion, which comprises a square cordierite honeycomb ceramic carrier and a double-layer coating coated on the carrier, the square cordierite honeycomb ceramic has controllable pore size; the coating comprises active components Pt and Pd, the active components are loaded on modified composite alumina, the modified composite alumina has a composition of MO x -Al2O3; the mass ratio of the noble metals Pt and Pd is 1:(0.2-2); the weight proportion of the noble metals in the coating material is 1-5%. Through detection, the catalyst obtained by the technical scheme has a significantly improved purification efficiency for propane, and the purification efficiency after 8000h can reach or exceed 96%, and the catalyst has a high propane purification efficiency; after the catalyst is hydrothermally aged for 100h at 850 DEG C with 10% H2O, the purification efficiency for propane at 550 DEG C can still reach or exceed 97%, and the catalyst shows good high-temperature hydrothermal stability.

Description

Technical Field

[0001] This invention relates to the field of monolithic catalyst preparation, and more specifically to a monolithic catalyst for propane combustion and its preparation method. Background Technology

[0002] In today's industrial production, the emission of volatile organic compounds (VOCs) has attracted widespread attention. These VOCs, including low-carbon alkanes such as propane, not only cause serious environmental pollution but also have a profound impact on human living environments. Propane, in particular, requires high oxidation temperatures for effective purification due to its high chemical stability, making the treatment of this type of pollutant more difficult.

[0003] Catalytic oxidation, as an effective method for treating VOCs, has been widely used in industrial production. However, most industrial catalysts for propane currently contain a high proportion of precious metals (greater than 2.5 g / L). Although these catalysts can improve the oxidation efficiency of propane to some extent, their high cost and short service life significantly reduce the economic benefits of this treatment method.

[0004] Therefore, developing a catalyst with a low content of precious metals and good high-temperature hydrothermal stability is of great significance for solving the propane pollution problem. Summary of the Invention

[0005] To address the shortcomings of existing technologies, a monolithic catalyst for propane combustion and its preparation method are provided. This catalyst effectively reduces the cost of propane treatment, and its excellent stability ensures long-term use at high temperatures, thereby improving propane treatment efficiency and contributing to environmental improvement. The specific solution is as follows:

[0006] An integral catalyst for propane combustion, comprising a square cordierite honeycomb ceramic support and a double-layer coating applied to the support, wherein the pore size of the square cordierite honeycomb ceramic is controllable; the coating comprises active components Pt and Pd, wherein the active components are supported on a composite alumina, and the modified composite alumina is composed of MO. x -Al2O3; the mass ratio of noble metals Pt and Pd is 1:(0.2~2); the weight of noble metals accounts for 1~5% of the coating material.

[0007] Furthermore, the preparation method of square cordierite honeycomb ceramics with controllable pore size includes the following steps:

[0008] S1: Select polystyrene microspheres with a diameter of 200-500 nm as templates;

[0009] S2: Disperse polystyrene microspheres in a sodium silicate solution with a concentration of 0.1-0.5 mol / L while stirring at a speed of 500-1000 r / min for 1-2 h.

[0010] S3: Load the mixed solution into a high-pressure reactor, react at 150-200℃ for 12-24 hours;

[0011] S4. Calcination: The calcination temperature is 400-500℃, and the time is 2-4 hours;

[0012] S5: Characterize the pore structure and pore size distribution using scanning electron microscopy and nitrogen adsorption-desorption methods; optimize the pore structure and pore size by adjusting the aforementioned parameters according to actual needs.

[0013] Furthermore, modified composite alumina MO x In Al₂O₃, M is one or more combined oxides of La, Si, Y, and Zr; MO x The weight content is 0.5%-5% of Al2O3.

[0014] A method for preparing a monolithic catalyst for propane combustion includes the following steps:

[0015] S1. Pretreatment of modified composite alumina: The modified composite alumina powder is reduced at high temperature in a hydrogen atmosphere;

[0016] S2. Preparation of a double-layer coating:

[0017] S201. Preparation of the base coating: The Ce-containing precursor solution is impregnated onto the composite alumina powder, dried at 100°C, and calcined at 500°C; the composite alumina powder is made into a slurry, and the Pt precursor solution is uniformly added, followed by the gradual addition of a certain amount of precipitant, binder and thickener.

[0018] S202. Preparation of outer layer slurry: Impregnate the composite alumina powder with a La precursor solution, dry at 100°C, and calcine at 500°C; make a slurry from the composite alumina powder, uniformly add a Pd precursor solution, and then gradually add a certain amount of precipitant, binder and thickener.

[0019] S3: First, the bottom layer slurry is uniformly coated onto the cordierite honeycomb ceramic carrier and dried at 100℃ and calcined at 500℃; then the outer layer slurry is uniformly coated onto the cordierite honeycomb ceramic carrier, dried at 100℃ and calcined at 500℃ to obtain the final catalyst product.

[0020] Furthermore, the modified composite alumina powder in S1 is reduced at a temperature of 450–550 °C in a hydrogen atmosphere for a reduction time of 0.5–1.5 h.

[0021] Furthermore, the Pt precursor is one or a combination of several of nitrates, hydrochlorides, acetates, and acetylacetone salts, and the Pd precursor is one or a combination of several of nitrates, hydrochlorides, acetates, and acetylacetone salts.

[0022] Furthermore, the Ce-containing precursor is a composition of one or more of cerium nitrate, cerium chloride, cerium acetate, cerium ammonium nitrate, and cerium acetylacetonate, and the La-containing precursor is a composition of one or more of lanthanum nitrate, lanthanum acetate, and lanthanum acetylacetonate.

[0023] Furthermore, the precipitant is a cerium-alumina composite oxide or a molecular sieve; the binder is an aluminum sol; and the ratio of the precipitant, binder, and modified composite alumina is 1:(0.3-0.5).

[0024] (3.2~3.7).

[0025] Furthermore, when preparing the base coating and outer coating slurries, the pH of the slurry is controlled to be 4-6, the temperature of the slurry is controlled to be 40-60℃, and the solid content of the coating slurry is 20-40%.

[0026] Furthermore, the coating amount of the bottom layer slurry is 40-80 g / L, and the coating amount of the outer layer slurry is 40-80 g / L.

[0027] Beneficial effects:

[0028] This invention provides a monolithic catalyst for propane combustion and its preparation method, which has the following advantages:

[0029] (1) Compared with traditional catalysts with high noble metal content, the weight of noble metal in the catalyst in this technical solution accounts for only 1 to 5% of the coating material, which greatly reduces the cost of the catalyst.

[0030] (2) After testing, the catalyst obtained by this technical solution has significantly improved the purification efficiency of propane. After 8000h, the purification efficiency can reach or exceed 96%, which has a high propane purification efficiency. After hydrothermal aging of the catalyst at 850℃ and 10% H2O for 100h, the purification efficiency of propane at 550℃ can still reach or exceed 97%, which shows good high-temperature hydrothermal stability.

[0031] (3) The pore size can be optimized through specific preparation methods, thereby improving the activity and stability of the catalyst.

[0032] (4) The catalyst coating adopts a double-layer design, and the mass ratio of active components Pt and Pd in ​​the coating can be adjusted, so that the catalyst has better activity and selectivity. Attached Figure Description

[0033] Figure 1 This is a distribution diagram of the purification efficiency of the catalyst prepared in Example 3 for propane.

[0034] Figure 2 This is a distribution diagram showing the variation in catalytic capacity across different embodiments. Detailed Implementation

[0035] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0036] Example 1: (one)

[0038] Step 1: Select polystyrene microspheres with a diameter of 200 nm as templates.

[0039] Step 2: Disperse the polystyrene microspheres in a 0.1 mol / L sodium silicate solution and stir at a speed of 800 r / min for 1.5 hours.

[0040] Step 3: Pour the mixed solution into a high-pressure reactor, and react at 175°C for 18 hours.

[0041] Step 4: The roasting temperature is 450℃ and the time is 3 hours.

[0042] Step 5: Characterize the pore structure and pore size distribution using scanning electron microscopy and nitrogen adsorption-desorption methods. (two)

[0044] Modified composite alumina MO x- In Al2O3, M is a combined oxide of Y and Zr; the weight content of MOx is 2% of that in Al2O3. (three)

[0046] Step 1: Pretreatment of modified composite alumina: The modified composite alumina powder is reduced in a hydrogen atmosphere at a temperature of 500℃ for 1 hour.

[0047] Step 2: Preparation of the double-layer coating: Step 2.1: Preparation of the bottom coating:

[0048] The Ce precursor solution (cerium nitrate) was impregnated onto the composite alumina powder, dried at 100°C, and calcined at 500°C. The composite alumina powder was made into a slurry, and a Pt precursor solution (palladium nitrate) was uniformly added. Subsequently, a certain amount of precipitant (cerium-cadmium composite oxide), binder (aluminum sol) and thickener were gradually added.

[0049] Step 2.2: Preparation of outer layer slurry: Impregnate the composite alumina powder with a La precursor solution (lanthanum nitrate), dry at 100°C, and calcine at 500°C; make a slurry from the composite alumina powder, uniformly add a Pd precursor solution (palladium nitrate), and then gradually add a certain amount of precipitant (cerium-hexane composite oxide), binder (aluminum sol) and thickener.

[0050] Step 3: First, the bottom layer slurry is evenly coated onto the cordierite honeycomb ceramic carrier and dried at 100℃ and calcined at 500℃; then the outer layer slurry is evenly coated onto the cordierite honeycomb ceramic carrier, dried at 100℃ and calcined at 500℃ to obtain the final catalyst product.

[0051] Example 2: (one)

[0053] Step 1: Select polystyrene microspheres with a diameter of 400 nm as templates.

[0054] Step 2: Disperse the polystyrene microspheres in a 0.3 mol / L sodium silicate solution and stir at a speed of 800 r / min for 1.5 hours.

[0055] Step 3: Pour the mixed solution into a high-pressure reactor, and react at 175°C for 18 hours.

[0056] Step 4: The roasting temperature is 450℃ and the time is 3 hours.

[0057] Step 5: Characterize the pore structure and pore size distribution using scanning electron microscopy and nitrogen adsorption-desorption methods. (two)

[0059] Modified composite alumina MO x- In Al2O3, M is a combined oxide of La and Zr; the weight content of MOx is 2% of that in Al2O3. (three)

[0061] Step 1: Pretreatment of modified composite alumina: The modified composite alumina powder is reduced in a hydrogen atmosphere at a temperature of 500℃ for 1 hour.

[0062] Step 2: Preparation of the double-layer coating: Step 2.1: Preparation of the bottom coating:

[0063] The Ce precursor solution (cerium nitrate) was impregnated onto the composite alumina powder, dried at 100°C, and calcined at 500°C. The composite alumina powder was made into a slurry, and a Pt precursor solution (palladium nitrate) was uniformly added. Subsequently, a certain amount of precipitant (cerium-cadmium composite oxide), binder (aluminum sol) and thickener were gradually added.

[0064] Step 2.2: Preparation of outer layer slurry: Impregnate the composite alumina powder with a La precursor solution (a combination of lanthanum nitrate and lanthanum acetate), dry at 100°C, and calcine at 500°C; make a slurry from the composite alumina powder, uniformly add a Pd precursor solution (palladium nitrate), and then gradually add a certain amount of precipitant (cerium-hodoxurium composite oxide), binder (aluminum sol) and thickener.

[0065] Step 3: First, the bottom layer slurry is evenly coated onto the cordierite honeycomb ceramic carrier and dried at 100℃ and calcined at 500℃; then the outer layer slurry is evenly coated onto the cordierite honeycomb ceramic carrier, dried at 100℃ and calcined at 500℃ to obtain the final catalyst product.

[0066] Example 3: (one)

[0068] Step 1: Select polystyrene microspheres with a diameter of 500 nm as templates.

[0069] Step 2: Disperse polystyrene microspheres in a 0.5 mol / L sodium silicate solution and stir at a speed of 800 r / min for 1.5 hours.

[0070] Step 3: Pour the mixed solution into a high-pressure reactor, and react at 175°C for 18 hours.

[0071] Step 4: The roasting temperature is 450℃ and the time is 3 hours.

[0072] Step 5: Characterize the pore structure and pore size distribution using scanning electron microscopy and nitrogen adsorption-desorption methods. (two)

[0074] Modified composite alumina MO x- In Al2O3, M is a combination oxide of La, Si, Y, and Zr; the weight content of MOx is 2% of that in Al2O3. (three)

[0076] Step 1: Pretreatment of modified composite alumina: The modified composite alumina powder is reduced in a hydrogen atmosphere at a temperature of 500℃ for 1 hour.

[0077] Step 2: Preparation of the double-layer coating: Step 2.1: Preparation of the bottom coating:

[0078] The Ce precursor solution (cerium nitrate) was impregnated onto the composite alumina powder, dried at 100°C, and calcined at 500°C. The composite alumina powder was made into a slurry, and a Pt precursor solution (palladium nitrate) was uniformly added. Subsequently, a certain amount of precipitant (cerium-cadmium composite oxide), binder (aluminum sol) and thickener were gradually added.

[0079] Step 2.2: Preparation of outer layer slurry: Impregnate the composite alumina powder with a La precursor solution (a combination of lanthanum nitrate and lanthanum acetylacetonate), dry at 100°C, and calcine at 500°C; the composite alumina powder is made into a slurry, and a Pd precursor solution (palladium nitrate) is uniformly added, followed by the gradual addition of a certain amount of precipitant (cerium-hexane composite oxide), binder (aluminum sol) and thickener.

[0080] Step 3: First, the bottom layer slurry is evenly coated onto the cordierite honeycomb ceramic carrier and dried at 100℃ and calcined at 500℃; then the outer layer slurry is evenly coated onto the cordierite honeycomb ceramic carrier, dried at 100℃ and calcined at 500℃ to obtain the final catalyst product.

[0081] pass Figure 1-2 It can be seen that the catalyst obtained by this technical solution has significantly improved the purification efficiency of propane. After 8000h, the purification efficiency of the catalyst can reach ≥96%. After hydrothermal aging of the catalyst at 850℃ and 10% H2O for 100h, the purification efficiency of hydrocarbon compounds at 550℃ can reach ≥97%.

[0082] As a further improvement, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for the preparation of a monolithic catalyst for the combustion of propane, characterized in that, The method comprises the following steps: S1, pretreatment of the modified composite alumina: reducing the modified composite alumina powder at high temperature in a hydrogen atmosphere; S2, preparation of a double-layer coating: S201, preparation of a bottom layer coating: dipping a Ce-containing precursor solution into the composite alumina powder, drying at 100 DEG C, and calcining at 500 DEG C; preparing a slurry of the composite alumina powder, uniformly adding a Pt precursor solution, and then gradually adding a certain amount of a precipitant, a binder, and a thickening agent; S202, preparation of an outer layer slurry: dipping a La-containing precursor solution into the composite alumina powder, drying at 100 DEG C, and calcining at 500 DEG C; preparing a slurry of the composite alumina powder, uniformly adding a Pd precursor solution, and then gradually adding a certain amount of a precipitant, a binder, and a thickening agent; S3: uniformly coating the bottom layer slurry on the cordierite honeycomb ceramic carrier, drying at 100 DEG C, and calcining at 500 DEG C; then uniformly coating the outer layer slurry on the cordierite honeycomb ceramic carrier, drying at 100 DEG C, and calcining at 500 DEG C, to obtain a final catalyst product; The whole catalyst comprises a square cordierite honeycomb ceramic carrier and a double-layer coating coated on the carrier, the square cordierite honeycomb ceramic has controllable pore size; the coating comprises active components Pt and Pd, the active components are loaded on modified composite alumina, the composition of the modified composite alumina is MO x -Al2O3; the mass ratio of the noble metals Pt and Pd is 1: (0.2-2); the proportion of the noble metals in the coating material is 1-5%. Modified composite alumina MO x M is a combination oxide of one or more of La, Si, Y, Zr in AI2O3; MO x The weight content of MO is 0.5-5% in AI2O3.

2. The method for preparing a monolithic catalyst for propane combustion according to claim 1, characterized by, The method for preparing the square cordierite honeycomb ceramic with controllable pore size comprises the following steps: S1: selecting polystyrene microspheres with a diameter of 200-500 nm as templates; S2: dispersing the polystyrene microspheres in a sodium silicate solution with a concentration of 0.1-0.5 mol / L, while stirring at a speed of 500-1000 r / min for 1-2 h; S3: loading the mixed solution into a high-pressure reaction kettle, and reacting at a temperature of 150-200 DEG C for 12-24 h; S4, calcining: calcining at a temperature of 400-500 DEG C for 2-4 h; S5: characterizing the pore structure and pore size distribution by scanning electron microscopy and nitrogen adsorption-desorption; and adjusting the parameters to optimize the pore structure and pore size according to actual requirements.

3. A method of making a monolithic catalyst for propane combustion according to claim 1, wherein, The temperature for reducing the modified composite alumina powder in the hydrogen atmosphere in S1 is 450-550 DEG C, and the reduction time is 0.5-1.5 h.

4. The method of claim 1, wherein the monolithic catalyst for propane combustion is prepared by the steps of: The Pt precursor is one or a combination of nitrate, hydrochloride, acetate, and acetylacetone salt, and the Pd precursor is one or a combination of nitrate, hydrochloride, acetate, and acetyacetone salt.

5. The method of claim 1, wherein the monolithic catalyst for propane combustion is prepared by the steps of: The Ce-containing precursor is one or a combination of cerium nitrate, cerium chloride, cerium acetate, cerium ammonium nitrate, and cerium acetylacetone, and the La-containing precursor is one or a combination of lanthanum nitrate, lanthanum acetate, and lanthanum acetylacetone.

6. The method of claim 1, wherein the monolithic catalyst for propane combustion is prepared by the steps of: The precipitant is cerium-gallium composite oxide or a molecular sieve; the binder is aluminum sol; and the ratio between the precipitant, the binder, and the modified composite alumina is 1:(0.3-0.5):(3.2-3.7).

7. The method of claim 1, wherein the monolithic catalyst for propane combustion is prepared by the steps of: When preparing the bottom layer coating and the outer layer coating slurry, the PH of the slurry is controlled to be 4-6, and the temperature of the slurry is controlled to be 40-60 DEG C, and the solid content of the coating slurry is 20-40%.

8. The method of claim 1, wherein the monolithic catalyst for propane combustion is prepared by the steps of: The coating amount of the bottom layer coating slurry is 40-80 g / L, and the coating amount of the outer layer slurry is 40-80 g / L.

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