A method for preparing a catalytic reforming catalyst and a catalytic reforming catalyst
By encapsulating platinum group metals in ZSM-5 molecular sieve precursors and preparing catalysts using steam-assisted crystallization, the problems of chlorine loss and metal sintering in traditional catalysts were solved, the stability and aromatic selectivity of the catalysts were improved, and highly efficient catalytic reforming reaction effects were achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2022-03-18
- Publication Date
- 2026-06-02
AI Technical Summary
Traditional catalytic reforming catalysts suffer from significant chlorine loss during use, leading to equipment corrosion and product contamination. Additionally, the active metal components are prone to sintering and agglomeration, resulting in insufficient catalyst stability and aromatic selectivity.
ZSM-5 molecular sieve catalysts loaded with platinum group metals were prepared by steam-assisted crystallization. By encapsulating the platinum group metals in the molecular sieve precursor and controlling the molecular sieve particle size, the thermal stability and diffusion performance of the catalyst were improved.
This catalyst exhibits excellent aromatic selectivity, aromatic yield, and resistance to carbon deposition, ensuring that the active metal component is not easily sintered at high temperatures.
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Figure CN116786156B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of industrial catalysis, and relates to a method for preparing a catalytic reforming catalyst and the catalytic reforming catalyst itself. Background Technology
[0002] Catalytic reforming is a secondary crude oil processing method that primarily uses gasoline as a feedstock to produce high-octane gasoline and light aromatics. Catalytically reformed gasoline has a high aromatic content and low olefin and sulfur content, with an octane number above 90, making it a high-quality gasoline blending component. With increasingly stringent environmental regulations and the growing global demand for aromatics, catalytic reforming is playing an increasingly important role in the petrochemical industry.
[0003] Catalytic reforming catalysts are crucial to catalytic reforming technology. A catalytic reforming catalyst is a bifunctional catalyst, with the metal active component providing hydrogenation and the support providing acidification. Traditional catalytic reforming catalysts typically use platinum group metals as the active metal and alumina as the support. These catalysts exhibit good isomerization and aromatization performance for cycloalkanes, but their selectivity for aromatization of alkanes is poor. Furthermore, traditional catalytic reforming catalysts experience continuous chlorine loss during operation, requiring continuous chlorine injection to maintain water-chlorine balance. Chlorine injection increases process complexity, and free chloride ions accelerate equipment corrosion and contaminate the reformed product.
[0004] Compared to traditional catalytic reforming catalysts, catalytic reforming catalysts supported by molecular sieves have advantages such as lower chlorine loss during use and higher reactivity and selectivity for alkane aromatization. However, during high-temperature calcination, the active metal components of catalytic reforming catalysts supported by molecular sieves are prone to sintering and agglomeration, resulting in low catalyst stability. Consequently, the selectivity, yield, and resistance to carbon deposition in catalytic reforming reactions remain unsatisfactory. Summary of the Invention
[0005] This invention provides a method for preparing a catalytic reforming catalyst. The ZSM-5 molecular sieve catalyst supported on platinum group metals prepared by this method has the advantages of high thermal stability, small molecular sieve particle size, and excellent diffusion performance. It exhibits excellent aromatic selectivity, aromatic yield, and anti-carbon deposition performance in catalytic reforming reactions.
[0006] The present invention also provides a catalytic reforming catalyst prepared by the above preparation method. The catalyst has excellent aromatic selectivity, aromatic yield and anti-carbon deposition properties.
[0007] The first aspect of this invention provides a method for preparing a catalytic reforming catalyst, comprising the following steps:
[0008] 1) Add platinum group metal precursors to a system containing a first silicon source and an aluminum source and mix, then add a second silicon source to obtain a silicon-aluminum precursor coated with platinum group metals;
[0009] The first silicon source includes a silane compound containing aminopropyl groups;
[0010] 2) The silicon-aluminum precursor containing platinum group metals is subjected to steam-assisted crystallization treatment to obtain the catalytic reforming catalyst.
[0011] In the preparation method described above, the first silicon source is a mixture of a first silane compound and a second silane compound, wherein the first silane compound is selected from at least one of aminopropyltriethoxysilane and aminopropyltrimethoxysilane, and the second silane compound is selected from at least one of methyl orthosilicate, tetraethyl orthosilicate, silica sol, and sodium silicate; and / or,
[0012] The second silicon source is selected from at least one of methyl orthosilicate, ethyl orthosilicate, silica sol, and sodium silicate.
[0013] In the preparation method described above, in step 1), the mass ratio of the first silicon source to the second silicon source is (0.2~2):1.
[0014] In the preparation method described above, in step 1), the mixing is carried out at 30–80°C.
[0015] In the preparation method described above, in step 2), the temperature of the steam-assisted crystallization treatment is 130–200°C, and the time is 12–100 h.
[0016] In the preparation method described above, step 1) further includes a first structure-directing agent in the system, wherein the first structure-directing agent is selected from cationic surfactants.
[0017] In the preparation method described above, in step 2), the steam-assisted crystallization treatment is carried out under aqueous vapor containing a second structure directing agent;
[0018] The second structure directing agent is selected from at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and tetrapropylammonium chloride.
[0019] In the preparation method described above, the mass concentration of the second structure directing agent in the aqueous solution containing the second structure directing agent is 5-40%.
[0020] The second aspect of the present invention provides a catalytic reforming catalyst, which is prepared using the preparation method provided in the first aspect of the present invention.
[0021] The catalytic reforming catalyst described above, wherein the support for the catalytic reforming catalyst is a nano-sized hydrogen-type ZSM-5 molecular sieve;
[0022] The silicon-aluminum molar ratio of the molecular sieve is (20-50):1;
[0023] The average particle size of the molecular sieve is 50–500 nm.
[0024] The active component loading of the catalytic reforming catalyst is 0.05–5 wt%.
[0025] The preparation method of the catalytic reforming catalyst of the present invention, by at least partially encapsulating a platinum group metal precursor within a molecular sieve precursor, prevents the active metal components from sintering and agglomerating during high-temperature calcination, thereby giving the catalyst good thermal stability. Furthermore, steam-assisted crystallization treatment allows for a smaller particle size in the molecular sieve support, improving the catalyst's diffusion performance. These two factors enhance the catalyst's aromatic selectivity, aromatic yield, and resistance to carbon deposition in catalytic reforming reactions.
[0026] The catalytic reforming catalyst of the present invention, prepared by the above-described method, exhibits excellent aromatic selectivity, aromatic yield, and anti-carbon deposition properties in catalytic reforming reactions. Attached Figure Description
[0027] Figure 1 XRD comparison charts for Cat.1 to Cat.4;
[0028] Figure 2 SEM image for Cat.1;
[0029] Figure 3 SEM image of Cat.2;
[0030] Figure 4 SEM image for Cat.3;
[0031] Figure 5 This is a SEM image for Cat.4. Detailed Implementation
[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0033] The first aspect of this invention provides a method for preparing a catalytic reforming catalyst, comprising the following steps:
[0034] 1) Add platinum group metal precursors to a system containing a first silicon source and an aluminum source and mix, then add a second silicon source to obtain a silicon-aluminum precursor coated with platinum group metals;
[0035] The first silicon source includes a silane compound containing aminopropyl groups;
[0036] 2) The silicon-aluminum precursor containing platinum group metals is subjected to steam-assisted crystallization treatment to obtain a catalytic reforming catalyst.
[0037] The catalytic reforming catalyst prepared by the above method is a hydrogen-form ZSM-5 molecular sieve catalyst supported on platinum group metals.
[0038] In step 1), the first silicon source, aluminum source and the second silicon source are all raw materials for preparing ZSM-5 molecular sieve. The platinum group metal precursor refers to the form of platinum group metals before they react with ZSM-5 molecular sieve, usually the chlorate of platinum group metals, such as platinate.
[0039] Platinum group metal precursors are added to a system containing a first silicon source and an aluminum source. Since the first silicon source includes a silane compound containing an aminopropyl group, there is a good adsorption relationship between the aminopropyl group and the platinum group metal precursor, which allows the platinum group metal precursor to attach to the surface of the molecular sieve precursor formed by the first silicon source and the aluminum source. Then, a second silicon source is added to the system, and the second silicon source continues to attach to the surface of the platinum group metal precursor, thereby making the platinum group metal precursor tightly wrapped in the molecular sieve precursor. This makes the metal active components of the catalyst less prone to sintering and agglomeration during high-temperature calcination, and gives it good thermal stability.
[0040] After adding a second silicon source and mixing, the mixed system is further filtered, dried and calcined to obtain a silicon-aluminum precursor coated with platinum group metals.
[0041] Compared to traditional hydrothermal crystallization, steam-assisted crystallization separates the liquid medium from the solid raw material to be crystallized. Under suitable temperature conditions, the precisely proportioned liquid vaporizes into steam, which then interacts with the solid raw material. After a certain period of crystallization, the corresponding molecular sieve product is finally formed. In step 2), steam-assisted crystallization of the catalyst precursor allows the ZSM-5 molecular sieve precursor to complete the transformation from amorphous to MFI crystalline form. Steam-assisted crystallization is more conducive to the formation of molecular sieve crystals with smaller sizes, thereby giving the catalyst excellent diffusion performance.
[0042] After steam-assisted crystallization, the crystallized system is washed, dried, and calcined to obtain the catalytic reforming catalyst.
[0043] The method for preparing the catalytic reforming catalyst provided by this invention involves encapsulating a platinum group metal precursor within a ZSM-5 molecular sieve precursor. This prevents the platinum group metal active components from sintering and agglomerating during calcination, resulting in excellent thermal stability of the catalyst. Furthermore, steam-assisted crystallization treatment yields nanoscale molecular sieve crystals, enhancing the catalyst's diffusion performance. Through the combined effect of these two factors, the selectivity, yield, and resistance to carbon deposition of the catalyst in catalytic reforming reactions are improved.
[0044] The present invention does not impose any special limitation on the aluminum source used in the preparation process, and any aluminum source commonly used in the art can be used, including but not limited to aluminum isopropoxide, aluminum nitrate, aluminum chloride and at least one of boehmite.
[0045] Furthermore, the first silicon source of the present invention is a mixture of a first silane compound and a second silane compound, wherein the first silane compound is selected from at least one of aminopropyltriethoxysilane and aminopropyltrimethoxysilane, and the second silane compound is selected from at least one of methyl orthosilicate, tetraethyl orthosilicate, silica sol, and sodium silicate; and / or,
[0046] The second silicon source is selected from at least one of methyl orthosilicate, ethyl orthosilicate, silica sol, and sodium silicate.
[0047] The selection of both the first and second silicon sources can enable the molecular sieve crystals to have good nucleation and growth rates, thereby giving the support good morphological characteristics, which is conducive to the catalyst exerting stable catalytic activity.
[0048] Furthermore, in step 1), the mass ratio of the first silicon source to the second silicon source is (0.2 to 2):1.
[0049] Furthermore, the mixing in step 1) can be carried out at 30–80°C.
[0050] The system in step 1) also includes a first structure-directing agent, which is a cationic surfactant. Further, the cationic surfactant is selected from long-chain alkane quaternary ammonium salt type cationic surfactants, specifically at least one selected from dodecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, or octadecyltrimethylammonium bromide. While acting as a structure-directing agent, the cationic surfactant also limits the charge density of the molecular sieve framework, thus facilitating a high silicon-to-aluminum ratio in the catalyst.
[0051] In one specific embodiment, the system containing the first silicon source and the aluminum source also includes an alkaline medium, which is selected from concentrated ammonia or sodium hydroxide solution. The pH value of the system is usually controlled by the alkaline medium to provide suitable alkaline conditions for the synthesis of the catalyst.
[0052] In one specific embodiment, step 1) includes adding a first silicon source and an aluminum source to an alkaline system containing a first structure directing agent, stirring at 30–80°C for 0.1–0.5 h, adding a platinum group metal precursor and stirring for another 0.1–0.5 h, then adding a second silicon source and stirring for another 0.5–3.0 h, and then filtering, drying and calcining to obtain a silicon-aluminum precursor with a mesoporous structure encapsulating platinum group metals.
[0053] Among them, the mesoporous structure can provide a suitable pore structure for catalytic reforming reactions, which is beneficial to the aromatization of alkane.
[0054] The temperature and time of steam-assisted crystallization treatment also significantly affect the performance of molecular sieves. Too short a crystallization time or too low a crystallization temperature will prevent the gel layer in the molecular sieve precursor from completely transforming into molecular sieve crystals. The presence of the gel layer will cause cracks on the molecular sieve surface, affecting the stability of the catalyst. Too long a crystallization time or too high a crystallization temperature will affect the catalytic activity of the metal active component. Studies have shown that when the temperature of the steam-assisted crystallization treatment in step 2) is 130–200℃ and the time is 12–100 h, the catalyst exhibits excellent stability and catalytic activity.
[0055] As mentioned earlier, steam-assisted crystallization is a process in which a liquid medium and a solid raw material to be crystallized are placed separately, and under suitable temperature conditions, the liquid is vaporized into steam, which then interacts with the solid raw material to be crystallized to achieve crystallization. In this invention, the solid raw material to be crystallized is the silicon-aluminum precursor coated with platinum group metals obtained in step 1), and the liquid medium is an aqueous solution containing a second structure directing agent. The second structure directing agent is selected from at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and tetrapropylammonium chloride.
[0056] To ensure that the aqueous solution containing the second structure directing agent has both good structure directing and vaporization properties, the mass concentration of the second structure directing agent in the aqueous solution can be controlled to be 5-40%.
[0057] In one specific embodiment, step 2) includes placing the catalyst precursor in the upper part of a stainless steel high-pressure reactor with an inner liner support, adding an aqueous solution containing a second structure directing agent to the lower part of the stainless steel high-pressure reactor, crystallizing at a temperature of 130-200°C for 12-100 hours, then cooling the reactor to room temperature, and obtaining the solid product by washing with water, drying, and calcining to obtain the catalytic reforming catalyst of the present invention.
[0058] The second aspect of the present invention provides a catalytic reforming catalyst, which is obtained by the preparation method provided in the first aspect of the present invention. The metal active component in the catalyst is not easy to agglomerate and sinter during high-temperature calcination, and has good stability. Furthermore, the molecular sieve support in the catalyst has the characteristics of small particle size and excellent diffusion performance, thereby exhibiting excellent aromatic selectivity, aromatic yield and anti-carbon deposition properties in the catalytic reforming reaction.
[0059] Furthermore, the support for the catalytic reforming catalyst of the present invention is a nano-sized hydrogen-type ZSM-5 molecular sieve, with a silicon-to-aluminum molar ratio of (20-50):1, an average molecular sieve particle size of 50-500 nm, and a catalyst active component loading of 0.05-5 wt%. When the silicon-to-aluminum molar ratio, molecular sieve particle size, and active component loading of the catalytic reforming catalyst are within the above ranges, the catalyst exhibits superior aromatic selectivity, aromatic yield, and resistance to carbon deposition. Specifically, the above parameters can be controlled by adjusting the content of each component, mixing temperature, crystallization temperature, and crystallization time during the preparation of the catalytic reforming catalyst.
[0060] The present invention also provides a catalytic reforming reaction of naphtha, wherein the reaction is carried out by catalytic reforming catalyst obtained by the preparation method provided in the first aspect of the present invention or catalytic reforming catalyst provided in the second aspect of the present invention.
[0061] Furthermore, when the above-mentioned catalytic reforming reaction is carried out at a temperature of 490℃, a pressure of 0.7MPa, and a naphtha mass hourly space velocity of 2.0h... -1 When the hydrogen-to-oil molecular ratio is 3:1, better aromatic selectivity, aromatic yield and resistance to carbon buildup can be obtained.
[0062] The preparation method of the catalytic reforming catalyst provided by the present invention will be further described in detail below with reference to specific embodiments.
[0063] It should be noted that, unless otherwise specified, the raw materials used in the following embodiments can be obtained by commercial purchase or conventional methods, and the experimental methods without specific conditions are all conventional methods and conditions well known in the art.
[0064] Example 1
[0065] The preparation method of the catalytic reforming catalyst in this embodiment includes the following steps:
[0066] 1. Add 0.20 g of hexadecyltrimethylammonium bromide to a 60 mL mixture of deionized water and ethanol (volume ratio of deionized water to ethanol is 1:1), stir and dissolve at 50 °C. Then add ammonia to the mixture to adjust the pH to 9. Next, add 1.0 g of tetraethyl orthosilicate and 0.2 g of aminopropyltriethoxysilane. Calculate the amount of aluminum isopropoxide to be added based on a silicon-to-aluminum ratio of 20:1 to be 0.6 g. Add aluminum isopropoxide to the mixture and continue stirring for 0.1 h to obtain the ZSM-5 molecular sieve precursor solution.
[0067] 2. Add 0.1% of the ZSM-5 molecular sieve precursor to a 0.2 mg / mL chloroplatinic acid solution, and continue stirring at 50°C for 0.1 h. Then add 0.5 g of tetraethyl orthosilicate to the mixture and continue stirring for 0.5 h. After filtration, washing with water, drying at 80°C for 10 h, and calcining at 550°C for 6 h, a silicon-aluminum precursor with a mesoporous structure and encapsulated platinum group metals is obtained.
[0068] 3. A 5% (w / w) aqueous solution of tetrapropylammonium hydroxide was placed in the lower part of a stainless steel high-pressure reactor with an inner support. The silicon-aluminum precursor coated with platinum group metals obtained in step 2 was placed on the support. After crystallization at 130°C for 100 h, the reactor was cooled to room temperature. The resulting solid product was washed with water and dried in a drying oven at 100°C. Then it was placed in a muffle furnace and calcined at 500°C for 4 h in air atmosphere to obtain the catalytic reforming catalyst Cat.1.
[0069] Among them, Cat.1 has a silicon-to-aluminum molar ratio of 20:1, an average molecular sieve particle size of 130 nm, and a Pt loading of 0.1 wt%.
[0070] Example 2
[0071] The preparation method of the catalytic reforming catalyst in this embodiment includes the following steps:
[0072] 1. Add 0.20 g of hexadecyltrimethylammonium bromide to a 60 mL mixture of deionized water and ethanol (volume ratio of deionized water to ethanol is 1:1), stir and dissolve at 50 °C. Then add ammonia to the mixture to adjust the pH to 10. Next, add 1.0 g of tetraethyl orthosilicate and 0.1 g of aminopropyltriethoxysilane. Calculate the amount of aluminum isopropoxide to be added based on a silicon-to-aluminum ratio of 30:1. Add aluminum isopropoxide to the mixture and continue stirring for 0.1 h to obtain the ZSM-5 precursor solution.
[0073] 2. Add 1% of the ZSM-5 molecular sieve precursor to a 0.2 mg / mL chloroplatinic acid solution, stir at 50 °C for 0.1 h, then add 1 g of tetraethyl orthosilicate to the mixture and stir for another 1.0 h. Filter the mixture, wash it with water, dry it at 80 °C for 10 h, and calcine it at 550 °C for 6 h to obtain a silicon-aluminum precursor with a mesoporous structure encapsulating platinum group metals.
[0074] 3. A 20% (w / w) aqueous solution of tetrapropylammonium hydroxide was placed in the lower part of a stainless steel high-pressure reactor with an inner support. The silicon-aluminum precursor coated with platinum group metals obtained in step 2 was placed on the support. After crystallization at 150°C for 72 hours, the reactor was cooled to room temperature. The resulting solid product was washed with water and dried in a drying oven at 100°C. Then it was placed in a muffle furnace and calcined at 500°C for 4 hours in air atmosphere to obtain the catalytic reforming catalyst Cat.2.
[0075] Among them, Cat.2 has a silicon-to-aluminum molar ratio of 30:1, an average molecular sieve particle size of 300 nm, and a Pt loading of 0.1 wt%.
[0076] Example 3
[0077] The preparation method of the catalytic reforming catalyst in this embodiment includes the following steps:
[0078] 1. Add 0.40g of octadecyltrimethylammonium bromide to a 60mL mixture of deionized water and ethanol (volume ratio of deionized water to ethanol is 1:1), stir and dissolve at 50℃. Then add ammonia to the mixture to adjust the pH to 11. Add 1.0g of tetraethyl orthosilicate and 0.05g of aminopropyltriethoxysilane. Calculate the amount of aluminum isopropoxide to be added based on a silicon-to-aluminum ratio of 40:1. Add aluminum isopropoxide to the mixture and continue stirring for 0.1h to obtain ZSM-5 molecular sieve.
[0079] 2. Add 5% of the ZSM-5 molecular sieve precursor to a 0.2 mg / mL chloroplatinic acid solution, stir at 50 °C for 0.1 h, then add 5 g of tetraethyl orthosilicate to the mixture and stir for another 1.0 h. After filtration, washing with water, drying at 80 °C for 10 h, and calcining at 550 °C for 4 h, a silicon-aluminum precursor with a mesoporous structure encapsulating platinum group metals is obtained.
[0080] 3. A 40% (w / w) aqueous solution of tetrapropylammonium hydroxide was placed in the lower part of a stainless steel high-pressure reactor with an inner support. The silicon-aluminum precursor coated with platinum group metals obtained in step 2 was placed on the support. After crystallization at 200°C for 12 hours, the reactor was cooled to room temperature. The resulting solid product was washed with water and dried in a drying oven at 100°C. Then it was placed in a muffle furnace and calcined at 500°C for 4 hours in air atmosphere to obtain the catalytic reforming catalyst Cat.3.
[0081] Among them, Cat.3 has a silicon-to-aluminum molar ratio of 40:1, an average molecular sieve particle size of 200 nm, and a Pt loading of 0.5%.
[0082] Example 4
[0083] The preparation method of the catalytic reforming catalyst in this embodiment includes the following steps:
[0084] 1. Add 0.40 g of octadecyltrimethylammonium bromide to a 60 mL mixture of deionized water and ethanol (volume ratio of deionized water to ethanol is 1:1), stir and dissolve at 50 °C. Then add ammonia to the mixture to adjust the pH to 12. Next, add 1.0 g of tetraethyl orthosilicate and 0.05 g of aminopropyltriethoxysilane. Calculate the amount of aluminum isopropoxide to be added based on a silicon-to-aluminum ratio of 50:1 to be 0.24 g. Add aluminum isopropoxide to the mixture and continue stirring for 0.1 h to obtain the ZSM-5 molecular sieve precursor solution.
[0085] 2. Add 10% of the ZSM-5 molecular sieve precursor to a 0.2 mg / mL chloroplatinic acid solution, and continue stirring at 50°C for 0.1 h. Then add 5 g of tetraethyl orthosilicate to the mixture and continue stirring for 1.0 h. After filtering and washing with water, dry at 80°C for 10 h and calcine at 550°C for 4 h to remove the template agent, a silicon-aluminum precursor with a mesoporous structure encapsulating platinum group metals is obtained.
[0086] 3. A 40% (w / w) aqueous solution of tetrapropylammonium hydroxide was placed in the lower part of a stainless steel high-pressure reactor with an inner support. The catalyst precursor obtained in step 2 was placed on the support. After crystallization at 200°C for 12 hours, the reactor was cooled to room temperature. The resulting solid product was washed with water and dried in a drying oven at 100°C. Then it was placed in a muffle furnace and calcined at 500°C for 4 hours in air atmosphere to obtain the catalytic reforming catalyst Cat.4.
[0087] Among them, Cat.4 has a silicon-to-aluminum molar ratio of 50:1, an average molecular sieve particle size of 95 nm, and a Pt loading of 1.0%.
[0088] Comparative Example 1
[0089] The preparation method of the catalytic reforming catalyst in this comparative example includes the following steps:
[0090] 1. Add 0.40 g of octadecyltrimethylammonium bromide to a 60 mL mixture of deionized water and ethanol (volume ratio of deionized water to ethanol is 1:1), stir and dissolve at 50 °C. Then add ammonia to the mixture to adjust the pH to 12, and add 1.0 g of tetraethyl orthosilicate. Calculate the amount of aluminum isopropoxide to be added based on a silicon-to-aluminum ratio of 50:1. Add aluminum isopropoxide to the mixture and continue stirring for 0.1 h to obtain the ZSM-5 molecular sieve precursor solution.
[0091] 2. Add 10% of the ZSM-5 molecular sieve precursor to a 0.2 mg / mL chloroplatinic acid solution, and continue stirring at 50°C for 0.1 h. Then add 5 g of tetraethyl orthosilicate to the mixture and continue stirring for 1.0 h. After filtering and washing with water, dry at 80°C for 10 h and calcine at 550°C for 4 h to remove the template agent, a mesoporous silicon-aluminum precursor encapsulating platinum group metals is obtained.
[0092] 3. A 40% (w / w) aqueous solution of tetrapropylammonium hydroxide was placed in the lower part of a stainless steel high-pressure reactor with an inner support. The silicon-aluminum precursor coated with platinum group metals obtained in step 2 was placed on the support. After crystallization at 200°C for 12 hours, the reactor was cooled to room temperature. The resulting solid product was washed with water and dried in a drying oven at 100°C. Then it was placed in a muffle furnace and calcined at 500°C for 4 hours in air atmosphere to obtain the catalytic reforming catalyst Cat.5.
[0093] Among them, Cat.5 has a silicon-to-aluminum molar ratio of 50:1, an average molecular sieve particle size of 100 nm, and a Pt loading of 1.0%.
[0094] Comparative Example 2
[0095] The preparation method of the catalytic reforming catalyst in this comparative example includes the following steps:
[0096] 1. ZSM-5 molecular sieve was synthesized using a traditional hydrothermal method. First, 12 g of tetrapropylammonium hydroxide was added to deionized water at room temperature and stirred to dissolve. Then, 8 g of tetraethyl orthosilicate, 15 g of water, and 4 g of sodium hydroxide were added, and stirring was continued at room temperature for 24 h. Next, 1.0 g of aluminum isopropoxide was added, and stirring was continued for 4 h. Finally, the gel was transferred to a stainless steel synthesis vessel and crystallized at 170 °C for 72 h. The resulting solid product was centrifuged, washed, and then dried overnight at 110 °C. Finally, it was calcined at 550 °C for 6 h to remove the template agent, yielding a sodium-form ZSM-5 molecular sieve precursor. The sodium-form molecular sieve precursor was then subjected to three ion exchanges in a 1 mol / L NH4NO3 solution at 80 °C, each lasting 2 h, followed by drying and calcination to obtain the hydrogen-form ZSM-5 molecular sieve precursor.
[0097] 2. Add 10% of the mass of the ZSM-5 molecular sieve precursor obtained in step 1 to a 0.2 mg / mL chloroplatinic acid solution, and continue stirring at 50 °C for 0.1 h. Then add 5 g of tetraethyl orthosilicate to the mixture and continue stirring for 1.0 h. After filtering, washing with water, drying at 80 °C for 10 h, and calcining at 550 °C for 4 h, the template agent is removed to obtain the catalytic reforming catalyst Cat.6.
[0098] Among them, Cat.6 has a silicon-to-aluminum molar ratio of 50:1, an average molecular sieve particle size of 1.5 μm, and a Pt loading of 1.0%.
[0099] Test case
[0100] 1. The catalytic reforming catalysts prepared in Examples 1 to 4 were characterized by XRD and SEM.
[0101] Figure 1 These are XRD comparison charts for Cat.1 to Cat.4. Figure 1 As can be seen, the XRD patterns of Cat.1 to Cat.4 are consistent with the characteristic patterns of the standard MFI topology, with high diffraction peak intensities and good crystallization. No obvious diffraction peaks of platinum metal oxides are observed in the patterns, indicating that the active metal platinum is uniformly dispersed in the molecular sieve support.
[0102] Figure 2 This is a SEM image for Cat.1. Figure 3 This is a SEM image of Cat.2. Figure 4 This is a SEM image for Cat.3. Figure 5 This is a SEM image for Cat.4. From... Figures 2-5 It can be seen that the grain size of Cat.1 to Cat.4 is relatively small, and they are all nanoscale molecular sieves.
[0103] 2. The catalyst performance of the catalytic reforming catalysts prepared in the above examples and comparative examples was evaluated. The evaluation method was as follows: the catalyst was pressed into tablets, granulated and sieved, and 1.0 g of catalyst with a particle size of 20-40 mesh was weighed and loaded into a fixed bed reactor to carry out the catalytic reforming reaction of naphtha.
[0104] The catalytic reforming reaction conditions were as follows: the catalyst was activated by reduction under a hydrogen atmosphere, with a hydrogen flow rate of 50 mL / min, a reduction temperature of 400℃, a reduction time of 2.0 h, and a pressure of atmospheric pressure. The activated catalyst was then subjected to a reaction at a temperature of 490℃, a reaction pressure of 0.7 MPa, and a naphtha mass hourly space velocity of 2.0 h⁻¹. -1 Catalytic reforming was carried out under the condition of a hydrogen-to-oil molecular ratio of 3:1. The aromatic selectivity, aromatic yield, and carbon deposition were calculated at the initial stage and after 48 hours of reaction.
[0105] The aromatic selectivity is calculated as follows: mass of aromatics in the product / total mass of the product; the aromatic yield is calculated as: mass of aromatics in the product / mass of naphtha; the coking amount is calculated as follows: coking amount is calculated based on the mass of fresh catalyst (fresh catalyst refers to the mass of catalyst before catalytic reaction), coking amount = W 48h -W 新鲜 Among them, W 48h and W 新鲜 The values represent the mass of the catalyst after 48 hours of reaction and the mass of the fresh catalyst, respectively.
[0106] The calculation results are shown in Table 1.
[0107] Table 1
[0108]
[0109] A comparison of Examples 1-4 with Comparative Examples 1 and 2 shows that the catalytic reforming catalyst prepared by the method of this application exhibits excellent aromatic selectivity and aromatic yield, as well as low carbon deposition, in the catalytic reforming reaction of naphtha.
[0110] As can be seen from the data in Table 1, the aromatic yield of the catalyst in Comparative Example 1 was only 10.5% after 0.5 h of reaction and only 8.6% after 48 h of reaction. This may be because no aminopropyl silane compound was added to the first silicon source, and the platinum group metal precursor was not encapsulated in the molecular sieve precursor. During the catalyst synthesis process, a large amount of active metal was lost, resulting in poor catalytic effect. The catalyst prepared by the conventional hydrothermal synthesis method in Comparative Example 2 had a large average particle size of molecular sieve, resulting in poor diffusion performance of the catalyst. Therefore, the aromatic selectivity and aromatic yield of the catalyst in Comparative Example 2 were also worse than those in Examples 1-4, and the amount of carbon deposited was also higher.
[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a catalytic reforming catalyst, comprising the following steps: 1) Add platinum group metal precursors to the molecular sieve precursor system containing the first silicon source and aluminum source, mix, then add the second silicon source, and filter, dry and calcine the mixed system. A silicon-aluminum precursor coated with platinum group metals is obtained; the second silicon source is selected from at least one of methyl orthosilicate, ethyl orthosilicate, silica sol, and sodium silicate. The first silicon source is a mixture of a first silane compound and a second silane compound; The first silane compound is selected from at least one of aminopropyltriethoxysilane and aminopropyltrimethoxysilane, and the second silane compound is selected from at least one of methyl orthosilicate, tetraethyl orthosilicate, silica sol, and sodium silicate. 2) The silicon-aluminum precursor containing platinum group metals is subjected to steam-assisted crystallization treatment, and the crystallized system is washed, dried, and calcined to obtain the catalytic reforming catalyst; the temperature of the steam-assisted crystallization treatment is 130~200℃, and the time is 12~100h; the support of the catalytic reforming catalyst is nano-sized hydrogen-type ZSM-5 molecular sieve; the loading of the active component of the catalytic reforming catalyst is 0.05~5wt%.
2. The preparation method according to claim 1, characterized in that, In step 1), the mass ratio of the first silicon source to the second silicon source is (0.2~2):
1.
3. The preparation method according to claim 1, characterized in that, In step 1), the mixing is carried out at 30~80°C.
4. The preparation method according to any one of claims 1-3, characterized in that, In step 1), the system further includes a first structure directing agent, which is selected from cationic surfactants.
5. The preparation method according to any one of claims 1-3, characterized in that, In step 2), the steam-assisted crystallization treatment is carried out under aqueous vapor containing a second structure directing agent; The second structure directing agent is selected from at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and tetrapropylammonium chloride.
6. The preparation method according to claim 5, characterized in that, The mass concentration of the second structure directing agent in the aqueous solution containing the second structure directing agent is 5-40%.
7. A catalytic reforming catalyst, characterized in that, It is prepared according to any one of claims 1-6.
8. The catalytic reforming catalyst according to claim 7, characterized in that, The catalyst for catalytic reforming is supported by nanoscale hydrogen-type ZSM-5 molecular sieve. The silicon-aluminum molar ratio of the molecular sieve is (20~50):1; The average particle size of the molecular sieve is 50~500nm; The active component loading of the catalytic reforming catalyst is 0.05~5wt%.