A gallium modified catalytic cracking catalyst, its preparation method and application

Abstract

The present application relates to a kind of gallium modified catalytic cracking catalyst and its preparation method and application, and the catalytic cracking catalyst contains modified hollow ZSM-5 hierarchical pore molecular sieve and carrier, the content of gallium in the modified hollow ZSM-5 hierarchical pore molecular sieve is 0.1-10% by weight as Ga2O3;Its preparation method includes: the step of synthesizing closed hollow ZSM-5 hierarchical pore molecular sieve, introducing gallium element modification, with carrier to form slurry, the step of spray drying.The gallium modified catalytic cracking catalyst of the present application can improve the yield of low carbon olefin and aromatic hydrocarbon in the process of hydrogenation LCO catalytic cracking in downflow bed reactor process.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a gallium-modified catalytic cracking catalyst, its preparation method, and its application. Background Technology

[0002] Ethylene, propylene, and other low-carbon olefins and aromatics are crucial chemical feedstocks. Currently, the world primarily uses naphtha steam cracking to produce ethylene as a main product and propylene as a byproduct, while aromatics are produced through naphtha reforming. Steam cracking suffers from several drawbacks, including high reaction temperatures and high energy consumption. Furthermore, naphtha production is limited. To overcome these shortcomings, technologies have been developed to produce low-carbon olefins or aromatics using heavier hydrocarbon oils, such as DCC technology, which utilizes heavy oil conversion to increase propylene production.

[0003] Catalytic conversion is crucial for producing low-carbon olefins from hydrocarbon oils. Currently, ZSM-5 molecular sieves are commonly used in catalysts for this process. ZSM-5 molecular sieves possess a unique pore structure, tunable acidity, and high thermal / hydrothermal stability. With changing market demand for fuel oil, there is a trend of oversupply in catalytic cracking of LCO. However, LCO has a relatively high polycyclic aromatic hydrocarbon content, making it difficult to increase the yield of light products such as low-carbon olefins and gasoline through direct cracking. While the coke yield is high, obtaining light aromatics is challenging. Therefore, some studies have explored hydrogenating LCO before conversion. However, hydrogenated LCO is rich in cycloalkanes, which are easily dehydrogenated and converted back into heavy aromatics, and its conversion efficiency still needs further improvement. Higher reaction temperatures, larger catalyst-to-oil ratios, and shorter residence times are beneficial for the catalytic cracking of hydrogenated LCO to produce aromatics and low-carbon olefins. Compared to traditional riser reactors, downflow bed reactors, due to the gravitational flow of reactant oil and gas and catalyst within the reactor, significantly reduce gas-solid backmixing, enabling ultra-short contact reactions. This is more conducive to the catalytic conversion of hydrogenated LCO into light aromatics and olefins. Under the ultra-short contact time conditions of downflow bed reactors, effectively achieving the rational conversion of polycyclic alkanes and polycyclic aromatics, controlling hydrogen transfer reactions, and promoting their efficient ring-opening cracking to convert more of them into high-value-added, light petrochemical products needed by the market is the key to technological innovation. Therefore, it is necessary to develop dedicated downflow bed catalysts that can promote the cracking of hydrogenated LCO feedstock to produce high-value-added low-carbon olefins and aromatics under short contact times.

[0004] CN110841696A provides a catalyst for the catalytic cracking of hydrotreated LCO. This catalyst comprises a modified Y-type molecular sieve. The modified Y-type molecular sieve has a rare earth content of 5-12 wt% (based on rare earth oxides), a sodium content of no more than 0.7 wt% (based on sodium oxide), and a zinc content of 0.5-5 wt% (based on zinc oxide). Using the modified Y-type molecular sieve as a new active component can improve the conversion efficiency of hydrotreated LCO and achieve a higher gasoline yield. This catalyst primarily produces gasoline via fluidized bed catalytic cracking and does not increase the production of low-carbon olefins.

[0005] CN114425419A discloses a catalytic cracking catalyst for the hydrogenation LCO conversion to produce more olefins and aromatics, its preparation method, and its application. The catalyst comprises a support and a gallium-containing core-shell molecular sieve. The gallium content in the gallium-containing core-shell molecular sieve, calculated as Ga₂O₃, is 0.1–10% by weight. The core phase of the gallium-containing core-shell molecular sieve is a ZSM-5 molecular sieve, and the shell is a β-molecular sieve. The ratio of the peak height at 2θ = 22.4° to the peak height at 2θ = 23.1° in the X-ray diffraction pattern is 0.1–10:1. The preparation method includes: synthesizing the core-shell molecular sieve, introducing gallium element for modification, forming a slurry with the support, and spray drying. This catalytic cracking catalyst exhibits higher yields of low-carbon olefins and aromatics in the catalytic cracking of hydrogenated LCO. However, the preparation process of the core-shell molecular sieve in this application is relatively complex, and the catalyst does not perform well in further increasing the yield of low-carbon olefins. Summary of the Invention

[0006] This invention addresses the aforementioned problems in the prior art by providing a gallium-modified catalytic cracking catalyst, which significantly improves the yield of low-carbon olefins and C10- and below methyl aromatics during the hydrogenation LCO catalytic cracking process. This invention further provides methods for preparing and applying the catalyst.

[0007] To achieve the above objectives, the present invention provides a gallium-modified catalytic cracking catalyst, which comprises a modified hollow ZSM-5 hierarchical porous molecular sieve and a support. Based on the dry weight of the catalytic cracking catalyst, the content of the modified hollow hierarchical porous ZSM-5 molecular sieve is 20-70% by weight, and the content of the support is 30-80% by weight; wherein...

[0008] The modified hollow ZSM-5 multi-level porous molecular sieve contains phosphorus and gallium, with a phosphorus-aluminum molar ratio of 0.1-1.5, a gallium content of 0.1-10% by weight (Ga2O3), an average grain size of 0.2-3.0 μm, and a bulk silicon-aluminum molar ratio to a surface silicon-aluminum molar ratio of 1.0-1.5. It has a closed hollow structure.

[0009] The preferred phosphorus-aluminum molar ratio of the modified hollow ZSM-5 multi-level porous molecular sieve is 0.2-1.3.

[0010] The gallium content of the modified hollow ZSM-5 multi-level porous molecular sieve, calculated as Ga2O3, can be 0.1-8% by weight, for example, 0.2-8% by weight, and the gallium content, calculated as Ga2O3, is preferably 0.1-5% by weight.

[0011] The average grain size of the modified hollow ZSM-5 hierarchical porous molecular sieve is 0.4-2.5 μm, for example, 0.5-2.0 micrometers.

[0012] The ratio of the bulk silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio of the modified hollow ZSM-5 hierarchical porous molecular sieve crystals is preferably 1.1-1.4.

[0013] The relative crystallinity of the modified hollow ZSM-5 hierarchical porous molecular sieve crystals is preferably 75-90%.

[0014] The total specific surface area of ​​the modified hollow ZSM-5 multi-level porous molecular sieve is preferably 250-350 m². 2 / g, for example, the total specific surface area of ​​the modified hollow ZSM-5 hierarchical porous molecular sieve is 280-380m². 2 / g.

[0015] The modified hollow ZSM-5 hierarchical porous molecular sieve has a mesoporous specific surface area of ​​20-100 m². 2 / g, for example, 30-80m 2 / g.

[0016] The mesoporous specific surface area of ​​the modified hollow ZSM-5 multi-level porous molecular sieve accounts for 15-40% of the total specific surface area, for example, 18-35%.

[0017] The N2 adsorption-desorption curve of the modified hollow ZSM-5 multi-level porous molecular sieve exhibits an H4-type hysteresis loop.

[0018] The modified hollow ZSM-5 multi-level porous molecular sieve has a strong Benzyl acid content of 55-70% of the total Benzyl acid content, for example, a strong Benzyl acid content of 55-65% of the total Benzyl acid content.

[0019] The modified hollow ZSM-5 multi-level porous molecular sieve has a strong L acid content of 50-70% of the total L acid content, for example, the strong L acid content accounts for 60-70% of the total L acid content.

[0020] Preferably, based on the dry weight of the catalytic cracking catalyst, the modified hollow hierarchical ZSM-5 molecular sieve comprises 25-65% by weight on a dry basis, and the support comprises 35-75% by weight on a dry basis.

[0021] The carrier can be selected from one or more of natural clay, alumina carrier, silica carrier, aluminum phosphate carrier, and aluminosilicate carrier. The silica carrier is, for example, one or more of neutral silica sol, acidic silica sol, or alkaline silica sol. The alumina carrier is, for example, one or more of alumina sol, acidified boehmite, hydrated alumina, and activated alumina. The aluminum phosphate carrier is, for example, aluminum phosphate gel. The aluminosilicate carrier can be selected from one or more of solid aluminosilicate materials, aluminosilicate sol, and aluminosilicate gel.

[0022] In one embodiment, the support comprises a silica support; the silica support, on a dry basis, comprises 1-20% by weight. In another embodiment, the catalytic cracking catalyst, on a dry basis, contains 20-50% by weight, for example, 25-45% by weight, of modified hollow ZSM-5 hierarchical porous molecular sieve, 20-50% by weight of clay, 10-30% by weight of acidified pseudoboehmite, 3-20% by weight of alumina sol, and 2-15% by weight of silica sol.

[0023] In one embodiment, the carrier is composed of boehmite, alumina sol, and clay.

[0024] A method for preparing the gallium-modified catalytic cracking catalyst, the method comprising: introducing phosphorus and gallium into a hollow ZSM-5 hierarchical porous molecular sieve having a closed hollow structure to form a modified hollow ZSM-5 hierarchical porous molecular sieve, forming a slurry with a support, the modified hollow ZSM-5 hierarchical porous molecular sieve and water, and spray drying.

[0025] The hollow ZSM-5 hierarchical porous molecular sieve with a closed hollow structure can be prepared by a method including the following steps:

[0026] (1) Mix and stir the first organosilicon source and the first solvent at 30-50°C for 0.5-5 hours, then heat to 70-100°C and mix and stir for 2-10 hours. Mix the resulting mixed liquid with the first template agent at 20-30°C for 0.5-3.0 hours to obtain the first mixed product.

[0027] (2) Mix the first alkali metal hydroxide (calculated as alkali metal oxide), the second solvent, and the first aluminum source (calculated as Al2O3) in a molar ratio of (1.5-5):(60-350):1 at 20-80°C for 0.5-2.0 hours to obtain the second mixed product;

[0028] (3) The first mixed product and the second mixed product are mixed and then dynamically crystallized. The resulting solid is taken out and subjected to a first calcination to obtain the first solid product.

[0029] (4) The first solid product is mixed with the first alkaline solution, and the temperature is raised to the reaction temperature at a rate of 1-5℃ / min. The reaction is carried out at the reaction temperature for 10-90 min to obtain the second solid product. The reaction temperature is 60-90℃, and the alkaline content in the first alkaline solution is 0.45-2 mol / L.

[0030] (5) The second solid product is subjected to first ammonium exchange and optionally calcined to obtain hollow ZSM-5 multi-level porous molecular sieve.

[0031] Alternatively, the hollow ZSM-5 hierarchical porous molecular sieve with a closed hollow structure can be prepared by a method including the following steps:

[0032] S1. The second template agent, the second inorganic silicon source, and the third solvent are mixed at 30-50°C for 0.5-3.0 hours. The resulting third mixed product is subjected to a first hydrothermal treatment and a second hydrothermal treatment in sequence to obtain a fourth mixed product. The conditions for the first hydrothermal treatment are: temperature 80-150°C and time 1-6 hours. The conditions for the second hydrothermal treatment are: temperature 160-180°C and time 12-260 hours.

[0033] S2. Mix the second alkali metal hydroxide (calculated as alkali metal oxide), the fourth solvent, and the second aluminum source (calculated as Al2O3) in a molar ratio of (1.5-5):(60-350):1 at 20-80°C for 0.5-2.0 hours to obtain the fifth mixed product.

[0034] S3. Mix the fourth mixed product and the fifth mixed product, subject the resulting mixture to a third hydrothermal treatment, remove the resulting solid and subject it to a second calcination to obtain a third solid product;

[0035] S4. The third solid product is mixed with the second alkaline solution, and the temperature is increased to the reaction temperature at a rate of 1-5℃ / min. The mixture is then reacted at the reaction temperature for 10-90 min to obtain the fourth solid product. The reaction temperature is 60-90℃, and the alkaline content in the second alkaline solution is 0.45-2 mol / L.

[0036] S5. The fourth solid product is subjected to a second ammonium exchange and optionally calcined to obtain a hollow ZSM-5 multi-level porous molecular sieve.

[0037] The first organosilicon source may be selected from one or more of methyl orthosilicate and ethyl orthosilicate.

[0038] The second inorganic silicon source can be selected from one or more of silica sol, water glass, and solid silica gel.

[0039] The first template agent and the second template agent may each be independently selected from one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine and hexamethylenediamine.

[0040] The first aluminum source and the second aluminum source can each be independently selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum isopropoxide, and aluminum sol.

[0041] The first alkali metal hydroxide and the second alkali metal hydroxide can each be independently selected from one or more of lithium hydroxide, sodium hydroxide, and potassium hydroxide.

[0042] The first alkaline solution and the second alkaline solution can each be independently selected from one or more of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide and barium hydroxide.

[0043] The total amount of the first template agent, the first solvent and the second solvent, the molar ratio of the first alkali metal hydroxide and the first organosilicon source is (0.06-0.55):(10-100):(0.02-1.5):1, and the molar ratio of the first organosilicon source to the first aluminum source is (20-500):1; wherein, the first organosilicon source is SiO2, the first alkali metal hydroxide is alkali metal oxide, and the first aluminum source is Al2O3.

[0044] Preferably, in step (2), the molar ratio of the first alkali metal hydroxide (calculated as alkali metal oxide), the second solvent, and the first aluminum source (calculated as Al2O3) is (2-4.5):(80-350):1;

[0045] Preferably, in step (4), the weight ratio of the first solid product to the first alkaline solution is 1:(2-10); the ratio of the bulk silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio of the first solid product is 1.2-5.0.

[0046] The molar ratio of the second template agent, the third solvent, the second alkali metal hydroxide, and the second inorganic silicon source is (0.06-0.55):(10-100):(0.02-1.5):1, and the molar ratio of the second inorganic silicon source to the second aluminum source is (20-500):1; wherein the second inorganic silicon source is calculated as SiO2, the second alkali metal hydroxide is calculated as alkali metal oxide, and the second aluminum source is calculated as Al2O3.

[0047] Preferably, in step S2, the molar ratio of the second alkali metal hydroxide (calculated as alkali metal oxide), the fourth solvent, and the second aluminum source (calculated as Al2O3) is (2-4.5):(80-350):1.

[0048] Preferably, in step S4, the weight ratio of the third solid product to the second alkali-containing solution is 1:(2-10), and the ratio of the bulk silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio of the third solid product is 1.2-5.0.

[0049] The conditions for dynamic crystallization include a temperature of 160-180℃ and a time of 12-60 hours.

[0050] The conditions for the third hydrothermal treatment include: a temperature of 160-180℃ and a time of 12-60 hours.

[0051] The conditions for the first and second calcinations each independently include: a temperature of 400-600℃ and a time of 2-6 hours;

[0052] In one embodiment, step (5), the first ammonium exchange of the second solid product includes: mixing the second solid product, the first ammonium source, and the fifth solvent in a weight ratio of 1:(0.5-1.0):(8-10), and reacting the resulting mixture at 70-90°C for 0.5-5 hours; optionally, calcining is performed after the ammonium exchange at a temperature of 400-600°C for 2-6 hours. The ammonium exchange can be performed once or multiple times, and calcination may or may not be performed after each ammonium exchange, preferably calcining after the last ammonium exchange.

[0053] In one embodiment, step S5, the second ammonium exchange of the fourth solid product includes: mixing the fourth solid product, the second ammonium source, and the sixth solvent in a weight ratio of 1:(0.5-1.0):(8-10), and reacting the resulting mixture at 70-90°C for 0.5-2 hours. Optional calcination is performed after the ammonium exchange at a temperature of 400-600°C for 2-6 hours. The ammonium exchange can be performed once or multiple times, and calcination may or may not be performed after each ammonium exchange; preferably, calcination is performed after the last ammonium exchange.

[0054] The first ammonium source and the second ammonium source are each independently selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.

[0055] One embodiment of introducing phosphorus and gallium into hollow ZSM-5 hierarchical porous molecular sieve includes the following steps:

[0056] (A1) The hollow ZSM-5 multi-level porous molecular sieve after ammonium exchange described in step (5) or step S5 is calcined to obtain an H-type molecular sieve (or denoted as hydrogen-type molecular sieve), wherein the Na2O content is preferably less than 0.15% by weight.

[0057] (A2) The H-type molecular sieve is contacted with phosphorus-containing compounds and gallium-containing compounds, for example, the H-type molecular sieve is impregnated with phosphorus-containing compounds and gallium-containing compounds or undergoes ion exchange with phosphorus-containing compounds and gallium-containing compounds, optionally filtered, optionally dried; then calcined at 350-600℃ for 0.5-5h; to obtain a hollow ZSM-5 multi-level porous molecular sieve containing phosphorus and gallium; the impregnation can be carried out by equal volume impregnation method, excess impregnation method, or multiple impregnation method; the phosphorus source is selected from at least one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate, and the gallium compound can be selected from one or more of gallium nitrate, chloride, and sulfate.

[0058] Alternatively, the method includes:

[0059] (A2') The H-type molecular sieve is impregnated with a phosphorus-containing compound or subjected to ion exchange with a phosphorus-containing compound, optionally filtered, and optionally dried; then calcined at 350–600℃ for 0.5–5 h to obtain a phosphorus-containing hollow ZSM-5 multi-level porous molecular sieve, which is then subjected to hydrothermal treatment; the phosphorus-containing hollow ZSM-5 multi-level porous molecular sieve is impregnated with a gallium-containing compound and subjected to ion exchange, optionally filtered, and optionally dried; then calcined at 350–600℃ for 0.5–5 h to obtain a phosphorus and gallium-containing hollow ZSM-5 multi-level porous molecular sieve.

[0060] The impregnation can be performed using an equal-volume impregnation method, an excessive impregnation method, or a multiple impregnation method; the phosphorus source is selected from at least one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate; and the gallium compound can be selected from one or more of gallium nitrates, chlorides, and sulfates.

[0061] According to the method for preparing gallium-containing catalytic cracking catalyst provided by the present invention, the method may further include: mixing catalyst particles obtained by spray drying, ammonium salt and water in a weight ratio of 1:(0.1-1):(5-15) for a third ammonium exchange, and optionally washing; the conditions for the third ammonium exchange include: a temperature of 50-100°C and a time of 0.5-2 hours; the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.

[0062] In one specific embodiment of the present invention, the method for preparing the catalytic cracking catalyst provided by the present invention may further include: mixing the particles obtained by spray drying or the particles obtained by calcination of the spray-dried particles, ammonium salt, and water in a weight ratio of 1:(0.1-1):(5-15) and performing a third ammonium exchange, and optionally washing; the conditions for the third ammonium exchange include: a temperature of 50-100°C and a time of 0.5-2 hours; the solution containing ammonium salt is calculated as ammonium salt, and the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate. The ammonium exchange may be performed once or multiple times. The calcination temperature is, for example, 400-600°C, and the calcination time is, for example, 1-6 hours or 2-5 hours.

[0063] The gallium-modified catalytic cracking catalyst is used for catalytic cracking of hydrogenated LCO as feedstock to produce low-carbon olefins and aromatics. Preferably, the catalytic cracking reaction is carried out in a descending bed reactor. Reaction conditions: reaction temperature is 600–700°C, and the catalyst-to-oil ratio (by weight) is 10–40.

[0064] The gallium-modified catalytic cracking catalyst provided by this invention can achieve high yields of low-carbon olefins and methylbenzene below C10, especially significantly higher propylene yield and selectivity, and a high concentration of methylbenzene below C10 in gasoline. Compared with existing ZSM-5 molecular sieve catalysts, the gallium-modified catalytic cracking catalyst provided by this invention can achieve higher yields of low-carbon olefins and methylbenzene below C10 in the hydrogenation LCO conversion. The gallium-modified catalytic cracking catalyst provided by this invention has a lower preparation cost than ZSM-5 / β core-shell molecular sieve catalysts, can react at higher temperatures, has good reaction performance, and achieves higher yields of low-carbon olefins and a higher concentration of methylbenzene below C10 in gasoline. This gallium-modified catalytic cracking catalyst can be applied to the field of increasing the production of low-carbon olefins and aromatics. Methylbenzene below C10 refers to toluene, xylene, trimethylbenzene, and tetramethylbenzene.

[0065] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0066] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof. In the drawings:

[0067] Figure 1 This is a TEM image of the modified closed hollow ZSM-5 hierarchical porous molecular sieve prepared in Example 1 of this invention.

[0068] Figure 2 This is a TEM image of the modified closed hollow ZSM-5 hierarchical porous molecular sieve prepared in Example 2 of this invention.

[0069] Figure 3 This is a schematic diagram of the structure of a distributor for a descending bed reactor, wherein 1-distributor shell, 2-first gas distribution plate, 3-sealing plate, 4-second gas distribution plate, 5-conical funnel, 6-descending bed reactor, 7-overflow pipe, 8-fluidizing gas inlet, 9-raw material oil and gas inlet, and 10-catalyst particles. Detailed Implementation

[0070] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0071] The gallium-modified catalytic cracking catalyst provided by this invention comprises a modified hollow ZSM-5 hierarchical porous molecular sieve and a support. Based on the dry weight of the catalytic cracking catalyst, the content of the modified hollow hierarchical porous ZSM-5 molecular sieve is 20-70% by weight, and the content of the support is 30-80% by weight. The modified hollow ZSM-5 hierarchical porous molecular sieve has a closed hollow structure, an average grain size of 0.2-3.0 μm, and a bulk silicon-aluminum molar ratio to surface silicon-aluminum molar ratio of 1.0-1.5. The modifying elements of the modified hollow ZSM-5 hierarchical porous molecular sieve are phosphorus and gallium, with a phosphorus-aluminum molar ratio of 0.1-1.5. The gallium content in the modified hollow ZSM-5 hierarchical porous molecular sieve, calculated as Ga2O3, is 0.1-10% by weight. The total specific surface area of ​​the modified hollow ZSM-5 hierarchical porous molecular sieve is 250-350 m². 2 / g, mesoporous specific surface area is 20-100m² 2 / g, the mesoporous specific surface area of ​​the modified hollow ZSM-5 multi-level porous molecular sieve accounts for 15-40% of the total specific surface area, the strong Brønsted acid content accounts for 65-80% of the total Brønsted acid content, and the strong Lewis acid content accounts for 50-75% of the total Lewis acid content.

[0072] The gallium-modified catalytic cracking catalyst of this invention contains a modified hollow ZSM-5 hierarchical porous molecular sieve. This modified hollow ZSM-5 hierarchical porous molecular sieve has a closed hollow structure, which refers to a structure with a completely closed shell and a hollow internal cavity. Using it in the hydrogenation LCO catalytic cracking process can effectively improve the yield of low-carbon olefins and aromatics. The closed hollow structure also gives the molecular sieve higher hydrothermal stability.

[0073] The modified hollow ZSM-5 hierarchical porous molecular sieve has a phosphorus-aluminum molar ratio of 0.2-1.3, and a content of 0.1-10% by weight as Ga2O3. In this invention, the phosphorus-aluminum molar ratio of the modified hollow ZSM-5 hierarchical porous molecular sieve is determined by XRF fluorescence method, and the content of Ga2O3 component is determined by XRF fluorescence method.

[0074] In one specific embodiment of the present invention, the average grain size of the modified hollow ZSM-5 hierarchical porous molecular sieve crystals is 0.4-2.5 μm, the ratio of the bulk silicon-aluminum molar ratio (based on SiO2 / Al2O3) to the surface silicon-aluminum molar ratio (based on SiO2 / Al2O3) is 1.1-1.4, and the relative crystallinity is 75-90%. In this invention, grain size refers to the size of the widest part of the grain, which can be obtained by measuring the size of the widest part of the grain projection plane in the SEM or TEM image of the sample. The average grain size is obtained by selecting any 10 molecular sieves from the SEM or TEM image and calculating their average value. The bulk silicon-aluminum molar ratio refers to the overall silicon-aluminum molar ratio of the ZSM-5 nanocrystalline material, which is determined by the XRF method, and the surface silicon-aluminum molar ratio is determined by the XPS method. The specific testing methods are well known to those skilled in the art and will not be described in detail here. The bulk silicon-aluminum molar ratio is 15-200. In this invention, the relative crystallinity of the molecular sieve is based on the XRD standard ZSM-5 molecular sieve standard from Sinopec Petrochemical Research Institute Co., Ltd., and the crystallinity of the standard is considered to be 100%.

[0075] In one specific embodiment of the present invention, the total specific surface area of ​​the modified hollow ZSM-5 hierarchical porous molecular sieve is 250-350 m². 2 / g, mesoporous specific surface area is 20-100m² 2 / g, wherein the mesoporous specific surface area accounts for 15-40% of the total specific surface area. The BET specific surface area is calculated using the BET formula, the micropore area is calculated using t-plot, and the pore size distribution is calculated using BJH. The N2 adsorption-desorption (adsorption-desorption) curve of the modified mesoporous ZSM-5 hierarchical molecular sieve exhibits an H4-type hysteresis loop.

[0076] In one specific embodiment of the present invention, the proportion of strong Benzyl acid in the modified hollow ZSM-5 hierarchical porous molecular sieve to the total Benzyl acid content is 70-80%, and the proportion of strong Lewis acid to the total Lewis acid content is 55-70%. The strong Benzyl acid content and the total Benzyl acid content are prepared using a pyridine infrared acidic method, and the strong Lewis acid content and the total Lewis acid content are also prepared using a pyridine infrared acidic method.

[0077] In one specific embodiment of the present invention, based on the dry weight of the catalytic cracking catalyst, the sodium oxide content in the catalytic cracking catalyst is preferably less than 0.15% by weight.

[0078] This invention provides a method for preparing a gallium-modified catalytic cracking catalyst. The method includes: introducing phosphorus and gallium into a closed, hollow ZSM-5 hierarchical porous molecular sieve to obtain a modified hollow ZSM-5 hierarchical porous molecular sieve, forming a slurry containing a support, the modified hollow ZSM-5 hierarchical porous molecular sieve, and an aqueous slurry, followed by spray drying. Spray drying is a commonly used method by those skilled in the art, capable of drying the material while simultaneously shaping the catalyst. Spray drying is well-known to those skilled in the art, and specific methods will not be described in detail here. The support can be selected from one or more of natural clay, alumina support, silica support, aluminum phosphate support, and aluminosilicate support. In one embodiment, the silica support is one or more of neutral silica sol, acidic silica sol, or alkaline silica sol; the alumina support is one or more of alumina sol, acidified boehmite, hydrated alumina, and activated alumina; the aluminum phosphate support is aluminum phosphate gel; and the aluminosilicate support is selected from one or more of solid aluminosilicate materials, aluminosilicate sol, and aluminosilicate gel.

[0079] This invention provides a method for preparing gallium-modified catalytic cracking catalysts. Preferably, the weight ratio of the modified hollow hierarchical ZSM-5 molecular sieve to the support is 25-65:35-75 on a dry basis.

[0080] In one specific embodiment of the present invention, the support comprises a silica support. The ratio of the silica support to the catalyst by dry weight, based on SiO2, is 1-20:100.

[0081] In one specific embodiment of the present invention, the weight ratio of modified hollow ZSM-5 hierarchical porous molecular sieve to clay on a dry basis is 20-50:20-50, the weight ratio of modified hollow ZSM-5 hierarchical porous molecular sieve to pseudoboehmite on a dry basis is 20-50:10-30, the weight ratio of modified hollow ZSM-5 hierarchical porous molecular sieve to alumina sol on a dry basis is 20-50:3-20, and the weight ratio of modified hollow ZSM-5 hierarchical porous molecular sieve to silica sol on a dry basis is 20-50:0-15, for example, 20-50:2-15.

[0082] In one specific embodiment of the present invention, the modified hollow ZSM-5 hierarchical porous molecular sieve is prepared by a method comprising the following steps:

[0083] (1) Mix and stir the first organosilicon source and the first solvent at 30-50°C for 0.5-5 hours, then heat to 70-100°C and mix and stir for 2-10 hours. Mix the resulting mixed liquid with the first template agent at 20-30°C for 0.5-3.0 hours to obtain the first mixed product; (2) Mix the first alkali metal hydroxide (calculated as alkali metal oxide), the second solvent, and the first aluminum source (calculated as Al2O3) in a molar ratio of (1.5-5):(60-350):1 at 20-80°C for 0.5-2.0 hours to obtain the second mixed product; (3) Mix the first mixed product with the second mixed product and then perform... Dynamic crystallization, the obtained solid is taken out and subjected to a first calcination to obtain a first solid product; (4) the first solid product is mixed with a first solution containing alkali, and the temperature is raised to the reaction temperature at a heating rate of 1-5℃ / min, and reacted at the reaction temperature for 10-90min to obtain a second solid product; wherein the reaction temperature is 60-90℃, and the alkali content in the first solution containing alkali is 0.45-2mol / L; (5) the second solid product is subjected to a first ammonium exchange, and after calcination, a third solid product is obtained, which is a ZSM-5 nanocrystalline material with hollow multi-level pores; (6) phosphorus and gallium are introduced into the third solid product for modification.

[0084] In a preferred embodiment of the present invention, in step (1), the first organosilicon source and the first solvent are mixed and stirred at 30-50°C for 0.5-5 hours, and then heated to 70-100°C and mixed and stirred for 2-10 hours. During this process, the evaporated first solvent is intermittently added to the system.

[0085] According to the present invention, the total amount of the first template agent, the first solvent, and the second solvent, and the molar ratio of the first alkali metal hydroxide to the first organosilicon source can vary within a wide range, for example, it can be (0.06-0.55):(10-100):(0.02-1.5):1, preferably (0.1-0.50):(15-85):(0.03-1.2):1, and the molar ratio of the first organosilicon source to the first aluminum source can be (20-500):1; wherein, the first organosilicon source is calculated as SiO2, the first alkali metal hydroxide is calculated as an alkali metal oxide (for example, when the first alkali metal hydroxide is NaOH, it is calculated as Na2O), and the first aluminum source is calculated as Al2O3. In one embodiment, the first template agent and the first alkali metal hydroxide contain OH. - The ratio of the total molar amount to the molar amount of the first organosilicon source, calculated as SiO2, is (0.01-1.5):1, preferably (0.02-1.2):1.

[0086] In this invention, in step (1), mixing the first template agent, the first organosilicon source and the first solvent at 30-50°C for 0.5-3.0 hours means mixing the first template agent, the first organosilicon source and the first solvent together and then stirring them at 30-50°C for 0.5-3.0 hours.

[0087] According to the present invention, in step (2), the molar ratio of the first alkali metal hydroxide (calculated as alkali metal oxide), the second solvent, and the first aluminum source (calculated as Al2O3) can vary within a large range, for example, it can be (2-4.5):(80-350):1.

[0088] According to the present invention, in step (3), dynamic crystallization is well known to those skilled in the art, and the conditions for dynamic crystallization may include: a temperature of 80-200°C and a time of 4-80 hours; preferably, a temperature of 160-180°C and a time of 12-60 hours.

[0089] According to the present invention, in step (4), the weight ratio of the first solid product to the amount of the first alkali-containing solution can be 1:(2-10), preferably 1:(8-10); the ratio of the bulk silicon-aluminum molar ratio and the surface silicon-aluminum molar ratio of the first solid product can be 1.2-5.0.

[0090] According to the present invention, in step (5), the first ammonium exchange of the second solid product includes: mixing the second solid product, the first ammonium source, and the fifth solvent in a weight ratio of 1:(0.5-1.0):(8-10), and then reacting the resulting mixture at 70-90°C for 0.5-5 hours. The first ammonium source is selected from one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate.

[0091] In one embodiment, the ZSM-5 nanocrystalline material with hollow hierarchical pores, before modification, has a mesoporous specific surface area increased by 100-500%, a mesoporous volume increased by 150-600%, and a total acid content increased by 50-250% compared with the first solid product.

[0092] According to the present invention, in step (6), the introduction of phosphorus and gallium into the third solid product can be achieved by contacting a solution containing a phosphorus source and a gallium source with the third solid product, wherein the weight ratio of the solution containing the phosphorus source and the gallium source to the third solid product is 1:(0.5-2.0). The contact can be performed once or multiple times, and each contact can introduce phosphorus and / or gallium. The phosphorus source can be a phosphorus compound, such as one or more of phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate; the gallium source can be a soluble salt of gallium, such as one or more of gallium sulfate, nitrate, chloride, and organic acid salts.

[0093] In another specific embodiment, the preparation method of the phosphorus and gallium-containing modified mesoporous ZSM-5 hierarchical molecular sieve includes: S1, mixing a second template agent, a second inorganic silicon source, and a third solvent at 30-50°C for 0.5-3.0 hours, and subjecting the resulting third mixed product to a first hydrothermal treatment and a second hydrothermal treatment sequentially to obtain a fourth mixed product; wherein, the conditions for the first hydrothermal treatment include: a temperature of 80-150°C and a time of 1-6 hours; the conditions for the second hydrothermal treatment include: a temperature of 160-180°C and a time of 12-60 hours; S2, mixing a second alkali metal hydroxide (calculated as alkali metal oxide), a fourth solvent, and a second aluminum source (calculated as Al2O3) in a molar ratio of (1.5-5):(60-350):1 at 20-80°C for 0.5-2.0 hours. S3. The fourth and fifth mixed products are mixed, and the resulting mixture is subjected to a third hydrothermal treatment. The resulting solid is taken out and subjected to a second calcination to obtain a fourth solid product. S4. The fourth solid product is mixed with a second alkaline solution, and the temperature is raised to the reaction temperature at a heating rate of 1-5℃ / min. The reaction is carried out at the reaction temperature for 10-90 min to obtain a fifth solid product. The reaction temperature is 60-90℃, and the alkaline content in the second alkaline solution is 0.45-2 mol / L. S5. The fifth solid product is subjected to a second ammonium exchange and calcined to obtain a sixth solid product, namely a hollow multi-level porous ZSM-5 molecular sieve, which is a ZSM-5 nanocrystalline material with hollow multi-level pores. S6. Phosphorus and gallium are introduced into the sixth solid product.

[0094] According to the present invention, the molar ratio of the total amount of the second template agent, the third solvent, and the fourth solvent, and the amount of the second alkali metal hydroxide and the second inorganic silicon source is (0.06-0.55):(10-100):(0.02-1.5):1, preferably (0.10-0.50):(15-85):(0.03-1.2):1, and the molar ratio of the second inorganic silicon source to the second aluminum source is (20-500):1; wherein the second inorganic silicon source is calculated as SiO2, the second alkali metal hydroxide is calculated as an alkali metal oxide (for example, when the second alkali metal hydroxide is NaOH, the second alkali metal hydroxide is calculated as Na2O), and the second aluminum source is calculated as Al2O3. In one embodiment, the second template agent and the second alkali metal hydroxide contain OH. - The ratio of the total molar amount to the molar amount of the second inorganic silicon source in terms of SiO2 (abbreviated as OH / SiO2) is (0.01-1.5):1, preferably (0.02-1.2):1.

[0095] According to the present invention, hydrothermal treatment is well known to those skilled in the art, and can be carried out, for example, in a heat-resistant, sealed container. The present invention does not limit the conditions of hydrothermal treatment; it can be carried out under the autogenous pressure of the reaction system or under applied pressure, preferably under autogenous pressure.

[0096] According to the present invention, in step S2, the molar ratio of the second alkali metal hydroxide (calculated as alkali metal oxide), the fourth solvent, and the second aluminum source (calculated as Al2O3) is (2-4.5):(80-350):1.

[0097] In one embodiment, in step S3, the conditions for the third hydrothermal treatment include: 160-180°C for 12-60 hours.

[0098] According to the present invention, in step S4, the weight ratio of the fourth solid product to the second alkali-containing solution is 1:(2-10), preferably 1:(8-10), and the ratio of the bulk silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio of the fourth solid product is 1.2-5.0.

[0099] According to the present invention, in step S5, the second ammonium exchange of the fifth solid product comprises: mixing the fifth solid product, the second ammonium source, and the sixth solvent in a weight ratio of 1:(0.5-1.0):(8-10), and reacting the resulting mixture at 70-90°C for 0.5-2 hours. The second ammonium source is selected from one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate. The above ammonium exchange can be performed once or multiple times.

[0100] According to one embodiment of the present invention, the ZSM-5 nanocrystalline material with hollow hierarchical pores, before modification, has a mesoporous specific surface area increased by 100-500%, a mesoporous volume increased by 150-600%, and a total acid content increased by 50-250% compared with the fourth solid product.

[0101] According to the present invention, in step S6, the introduction of phosphorus and gallium into the sixth solid product can be achieved by contacting a solution containing a phosphorus source and a gallium source with the sixth solid product, wherein the weight ratio of the solution containing the phosphorus source and the gallium source to the sixth solid product is 1:(0.5-2.0). The contact can be performed once or multiple times, and each contact can introduce phosphorus and / or gallium. The phosphorus source can be a phosphorus compound, such as one or more of phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate; the gallium source can be a soluble salt of gallium, such as one or more of gallium sulfate, nitrate, chloride, and organic acid salts.

[0102] According to the present invention, calcination is a technical means conventionally employed by those skilled in the art. For example, calcination can be carried out in a muffle furnace, a tube furnace, etc., at a temperature of 400-600°C and for a time of 2-6 hours. Preferably, the calcination temperature is 450-580°C and the calcination time is 2.5-4.5 hours. For example, in one embodiment, the conditions for the first calcination and the second calcination each independently include: a temperature of 400-600°C and a time of 2-6 hours, preferably a temperature of 450-580°C and a time of 3-5 hours.

[0103] According to the present invention, drying is a conventional technique used by those skilled in the art and can be carried out in a constant temperature drying oven. Typically, the drying temperature is 90-120°C, and the drying time depends on the drying method, as long as the molecular sieve is dried. In one embodiment, an oven-drying method is used, with a drying time of 2-24 hours.

[0104] According to the present invention, the first organosilicon source is selected from one or more of methyl orthosilicate and tetraethyl orthosilicate; the second inorganic silicon source is selected from one or more of silica sol, water glass and solid silica gel; the first template agent and the second template agent are each independently selected from one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine and hexamethylenediamine; the first aluminum source and the second aluminum source are each independently selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum isopropoxide and aluminum sol; the first alkali metal hydroxide and the second alkali metal hydroxide are each independently selected from one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide; the first alkaline solution and the second alkaline solution are each independently selected from one or more of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide and barium hydroxide.

[0105] According to the present invention, the solvent is water, that is, the first solvent, the second solvent, the third solvent, the fourth solvent, the fifth solvent and the sixth solvent are each water.

[0106] This invention provides an application of a gallium-modified catalytic cracking catalyst in a descending bed reactor process.

[0107] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0108] In the examples and comparative examples, the crystal size of the molecular sieve was measured by SEM. Ten crystal sizes were randomly measured, and the average value was taken to obtain the average crystal size of the molecular sieve sample.

[0109] The bulk silica-alumina ratio and phosphorus-aluminum molar ratio of the samples were determined by XRF method using a ZSX Primus II (Rigaku) ​​X-ray fluorescence spectrometer; test conditions: excitation voltage 50 kV, excitation current 50 mA, rhodium and palladium. The intensity of each elemental peak was determined using a scintillation counter and a proportional counter to perform elemental composition analysis of the molecular sieve.

[0110] The surface silicon-to-aluminum molar ratio of the samples was determined by XPS using a Thermo Fisher ESCALab 250 X-ray photoelectron spectrometer. The testing conditions were: monochromatic Al Kα X-rays as the excitation source, excitation energy 1496.6 eV, and power 150 W. The electron binding energy was corrected using the C1s peak (284.8 eV) of the contaminating carbon.

[0111] The total specific surface area and mesoporous specific surface area of ​​the samples were determined using the BET adsorption total analysis method. Instrument: Micromeritics ASAP 2420 adsorption analyzer (USA). Test conditions: The samples were degassed under vacuum at 100℃ and 300℃ for 0.5h and 6h, respectively, and then N2 adsorption-desorption tests were conducted at 77.4K. The adsorption and desorption amounts of nitrogen in the purified samples under different specific pressures were measured, and N2 adsorption-desorption isotherms were obtained. The BET specific surface area was calculated using the BET formula, the micropore area was calculated using t-plot, and the pore size distribution was calculated using the BJH method.

[0112] The relative crystallinity of the samples was determined by X-ray diffraction. Instrument: Empyrean. Test conditions: tube voltage 40kV, tube current 40mA, Cu target Kα radiation, 2θ scan range 5°-35°, scan rate 2 (°) / min.

[0113] The amounts of strong Brønsted acid (BBA) and total Brønsted acid in the samples were determined using pyridine infrared adsorption (IR) method. The amounts of strong Lewis acid (LBA) and total LBA were also determined using the same method. Instrument: NICOLET 6700 Fourier transform infrared spectrometer (BIQ-RAD, USA). Test method: The sample was compressed into a pellet and sealed in the in-situ cell of the infrared spectrometer. Adsorption and desorption were performed according to the following method. The amount of pyridine adsorbed acid was calculated based on the peak area. Test method: The sample was compressed into a pellet and sealed in the in-situ cell of the infrared spectrometer. A vacuum was then applied at 350℃ to 10... -3 The sample was heated to 10⁻³ Pa and held for 1 hour to allow gas molecules to desorb completely from the sample surface. It was then cooled to 50°C. Pyridine vapor was introduced into the in-situ cell, and after equilibration for 30 minutes, the temperature was raised to 200°C. A vacuum of 10⁻³ Pa was then applied again, held for 30 minutes, and cooled to 50°C. The infrared absorption spectrum of pyridine adsorption at 200°C was recorded within the wavenumber range of 1300 cm⁻¹ to 3900 cm⁻¹. The temperature was then raised to 350°C, and a vacuum of 10⁻³ Pa was applied again. -3Pa, maintain for 30 min, cool to room temperature, and record the infrared spectrum of pyridine adsorption at 350 °C. The amount of acid adsorbed by pyridine is calculated as peak area.

[0114] Examples 1-3 are examples of preparing modified hollow ZSM-5 hierarchical porous molecular sieves.

[0115] Example 1

[0116] (1) Weigh 91.2 g of tetraethyl orthosilicate, add 639.14 g of deionized water, stir and heat in a water bath at 40°C for 2 h, then raise the water bath temperature to 70°C and stir and heat for 4 h to remove the ethanol produced by the hydrolysis of the silicon source. During this process, water that evaporates at the same time as the ethanol is intermittently added to the system. The resulting mixed liquid is mixed and stirred with 111.65 g of tetrapropylammonium hydroxide aqueous solution (mass fraction of 25.0%) at 25°C for 1 h to obtain the first mixed product.

[0117] (2) Weigh 3.44 g of sodium hydroxide particles, add 60.8 g of deionized water to completely dissolve the sodium hydroxide, then add 8.16 g of aluminum nitrate nonahydrate, stir at room temperature for 1.0 h to obtain the second mixed product (i.e. aluminum source solution);

[0118] (3) The second mixed product was slowly added to the first mixed product and mixed evenly. The mixture was stirred at room temperature for 4.0 h. The resulting precursor liquid was transferred to a synthesis vessel and dynamically crystallized at 170 °C for 48 h. After crystallization, the product was centrifuged, filtered, washed, dried, and calcined at 550 °C for 4 h to obtain the first solid product I-M1.

[0119] (4) Mix the first solid product and a sodium hydroxide solution with a concentration of 0.65 mol / L evenly. The mass ratio of the first solid product to the alkaline solution is 1:10. Heat the solution to 80°C at a heating rate of 2°C / min, stir at this temperature for 30 min, filter, wash and dry to obtain the second solid product.

[0120] (5) Mix the second solid product: ammonium chloride: deionized water at a mass ratio of 1:1:10, stir and heat in an 80°C water bath for 30 min, filter, wash and dry, then mix the dried solid: ammonium chloride: deionized water at a mass ratio of 1:0.5:10, perform a second ammonium exchange, filter, wash and dry, and calcine at 550°C for 2 h to obtain hydrogen-type hollow hierarchical porous ZSM-5 nanocrystalline material, which is called the third solid product, denoted as I-S1-H;

[0121] (6) Dissolve 2.69 g of H3PO4 solution (concentration 85% by weight) and 2.75 g of gallium nitrate in 46.25 g of deionized water, stir until fully dissolved, to obtain a mixed salt solution containing phosphorus and gallium; spread 50 g of the third solid product in a petri dish, slowly add the mixed salt solution containing phosphorus and gallium dropwise, mix thoroughly until the molecular sieve is in a "viscous paste" state, dry in air at 115 °C for 4 h, and then calcine at 550 °C for 2 h to obtain the modified hollow ZSM-5 hierarchical porous molecular sieve of the present invention, denoted as SS-1, and its TEM image is shown below. Figure 1 As shown.

[0122] Example 2

[0123] (1) Weigh 60.0 g of methyl orthosilicate, add 425.0 g of deionized water, stir and heat in a water bath at 30°C for 5 h, then raise the water bath temperature to 70°C and stir for 4 h to remove the ethanol produced by the hydrolysis of the silicon source. During this process, water that evaporates at the same time as the ethanol is intermittently added to the system. The resulting mixed liquid is mixed and stirred with 34.5 g of tetrapropylammonium bromide aqueous solution (mass fraction of 25.0%) at 20°C for 0.5 h to obtain the first mixed product;

[0124] (2) Weigh 1.30 g of sodium hydroxide granules, add 31.0 g of deionized water to completely dissolve the sodium hydroxide, then add 0.85 g of sodium aluminate (alumina content is 62.0%), stir at room temperature for 2.0 h to obtain the second mixed product (i.e. aluminum source solution);

[0125] (3) The second mixed product was slowly added to the first mixed product and mixed evenly. The mixture was stirred at room temperature for 4.0 h. The resulting precursor liquid was transferred to a synthesis vessel and dynamically crystallized at 180 °C for 24 h. After crystallization, the product was centrifuged, filtered, washed, dried, and calcined at 550 °C for 4 h to obtain the first solid product I-M2.

[0126] (4) Mix the first solid product and a sodium hydroxide solution with a concentration of 0.6 mol / L evenly. The mass ratio of the first solid product to the alkaline solution is 1:10. Heat the solution to 80°C at a heating rate of 4°C / min, stir at this temperature for 30 min, filter, wash and dry to obtain the second solid product.

[0127] (5) Mix the second solid product: ammonium chloride: deionized water at a mass ratio of 1:1:10, stir and heat in an 80°C water bath for 30 min, filter, wash and dry, then mix the dried solid: ammonium chloride: deionized water at a mass ratio of 1:0.5:10, perform a second ammonium exchange, filter, wash and dry, and calcine at 550°C for 2 h to obtain hydrogen-type hollow hierarchical porous ZSM-5 nanocrystalline material, denoted as I-S2-H, i.e., the third solid product;

[0128] (6) Dissolve 2.68 g of ammonium dihydrogen phosphate and 2.75 g of gallium nitrate in 44.21 g of deionized water, stir until fully dissolved, and obtain a solution containing phosphorus and gallium; spread 50 g of the third solid product in a petri dish, slowly add the prepared solution containing phosphorus and gallium, mix thoroughly until the molecular sieve is in a "viscous paste" state; dry in air at 110 °C for 4 h, and calcine at 550 °C for 2 h to obtain the modified hollow ZSM-5 hierarchical porous molecular sieve of the present invention, designated as SS-2, and its TEM image is shown below. Figure 2 As shown.

[0129] Example 3

[0130] (1) Weigh 65.13 g of tetrapropylammonium hydroxide aqueous solution (mass fraction of 25.0%), add 476.62 g of deionized water, stir at room temperature for 10 min, then add 165.20 g of silica sol (SiO2 content of 25%), stir at 50℃ water bath for 1.0 h to obtain the third mixed product; transfer the third mixed product into a reaction vessel, crystallize at 80℃ for 2 h, then raise the temperature to 170℃ and crystallize for 12 h to obtain the fourth mixed product;

[0131] (2) Weigh 1.39 g of sodium hydroxide particles, add 27.2 g of deionized water to completely dissolve the sodium hydroxide, then add 4.76 g of aluminum nitrate nonahydrate, stir at room temperature for 1.0 h to obtain the fifth mixed product (i.e. aluminum source solution);

[0132] (3) Add the fifth mixed product from step 2 to the fourth mixed product, stir evenly, and continue to crystallize at 170℃ for 36h; after crystallization, centrifuge and filter, wash, dry, and calcine at 550℃ for 4h to obtain the third solid product I-M3.

[0133] (4) Mix the third solid product with a sodium hydroxide alkaline solution with a concentration of 1.0 mol / L. The mass ratio of molecular sieve to alkaline solution is 1:10. Heat the solution to 80°C at a heating rate of 5°C / min and stir at this temperature for 30 min. Filter, wash and dry to obtain the fourth solid product.

[0134] (5) Mix the fourth solid product: ammonium chloride: deionized water at a mass ratio of 1:1:10, stir and heat in an 80°C water bath for 30 min, filter, wash and dry, then mix the dried solid: ammonium chloride: deionized water at a mass ratio of 1:0.5:10, perform a second ammonium exchange, filter, wash and dry, and calcine at 550°C for 2 h to obtain hydrogen-type hollow multi-level porous ZSM-5 nanocrystalline material, denoted as I-S3-H, which is called the third solid product;

[0135] (6) Dissolve 1.71g of H3PO4 solution (concentration 85% by weight) and 1.60g of gallium nitrate in 42.49g of deionized water, stir until fully dissolved, to obtain a mixed solution containing phosphorus and gallium; spread 50g of the sixth solid product in a petri dish, slowly add the prepared mixed solution containing phosphorus and gallium, mix thoroughly until the molecular sieve is in the form of a "viscous paste"; dry in air at 115℃ for 4h, and then calcine at 550℃ for 2h to obtain the modified hollow ZSM-5 multi-level porous molecular sieve of the present invention, denoted as SS-3.

[0136] Comparative Example 1

[0137] The comparative example was a conventional ZSM-5 molecular sieve, DB1', purchased from Sinopec Catalyst Company Qilu Branch, with a silicon-aluminum molar ratio (SiO2 / Al2O3) of 25. 2.69 g of H3PO4 solution (85% by weight) and 2.75 g of gallium nitrate were dissolved in 46.25 g of deionized water and stirred until fully dissolved to obtain a mixed salt solution containing phosphorus and gallium. 50 g of DB1 was spread evenly in a petri dish, and the phosphorus-containing solution was slowly added dropwise, mixing thoroughly until the molecular sieve reached a "viscous paste" consistency. It was dried in air at 115°C for 4 hours and then calcined at 550°C for 2 hours to obtain the comparative molecular sieve, denoted as DB1.

[0138] Comparative Example 2

[0139] Similar to the steps in Example 1, step 6 only uses gallium nitrate modification, without phosphorus modification. This is denoted as DB2.

[0140] Comparative Example 3

[0141] Similar to the steps in Example 1, step 6 only uses phosphorus modification, not gallium modification. This is denoted as DB3.

[0142] Table 1 Sample Parameters

[0143]

[0144]

[0145] In Table 1, R represents the template agent, and the ratio of bulk to surface silicon-aluminum molar ratio represents the ratio of bulk silicon-aluminum molar ratio to surface silicon-aluminum molar ratio.

[0146] Examples 4-6 and Comparative Examples 4-6 illustrate the preparation of catalytic cracking catalysts. Unless otherwise specified, all raw materials used were commercially available. Kaolin was an industrial product of China Kaolin Corporation with a solid content of 75% by weight; boehmite was produced by Shandong Aluminum Plant with an alumina content of 65% by weight; alumina sol was produced by Qilu Branch of Sinopec Catalyst Co., Ltd. with an alumina content of 20% by weight; silica sol was produced by Qingdao Junqiang New Materials Co., Ltd. with a silica content of 25% by weight (alkaline silica sol, pH 9.5); and concentrated hydrochloric acid was chemically pure and produced by Beijing Innocare.

[0147] Examples 4-6

[0148] Catalysts were prepared using modified hollow ZSM-5 hierarchical porous molecular sieves prepared according to the methods in Examples 1-3, and the catalyst numbers were A1, A2, and A3 respectively. The preparation method of the catalytic cracking catalyst included: (1) mixing boehmite (abbreviated as boehmite) and water evenly, adding concentrated hydrochloric acid with a concentration of 36% by weight under stirring, and the acid-aluminum molar ratio was 0.2 (the weight ratio of HCl to boehmite calculated as Al2O3); aging the resulting mixture at 70°C for 1.5 hours to obtain an aged boehmite slurry. The alumina content of the aged pseudoboehmite slurry is 12% by weight; (2) The modified hollow ZSM-5 multi-level porous molecular sieve, alumina sol, silica sol, kaolin, the aged pseudoboehmite slurry and deionized water prepared above are mixed evenly to form a slurry with a solid content of 30% by weight, and spray-dried to obtain catalyst microspheres; (3) The catalyst microspheres are calcined at 550℃ for 4h; (4) The calcined catalyst microspheres are exchanged at 80℃ for 1h according to the weight ratio of catalyst microspheres:ammonium salt:H2O = 1:1:10, filtered, and the above exchange and filtration process is repeated once to make the sodium oxide content in the obtained catalytic cracking catalyst less than 0.15% by weight, and dried, wherein the ammonium salt is ammonium chloride. The composition of the prepared catalyst is shown in Table 2.

[0149] Comparative Example 4

[0150] Comparative Example 4 illustrates the preparation of a catalytic cracking catalyst using the molecular sieve DB1 provided in Comparative Example 1. Following the catalyst preparation method of Example 4, molecular sieve DB1 was mixed with boehmite, silica sol, kaolin, water, and alumina sol, and then spray-dried to prepare microsphere catalyst DB3.

[0151] Comparative Example 5

[0152] Comparative Example 5 illustrates the preparation of a catalytic cracking catalyst using the molecular sieve DB2 provided in Comparative Example 2. Following the catalyst preparation method of Example 4, molecular sieve DB2 was mixed with boehmite, silica sol, kaolin, water, and alumina sol, and then spray-dried to prepare microsphere catalyst DB4.

[0153] Comparative Example 6

[0154] Comparative Example 6 illustrates the preparation of a catalytic cracking catalyst using the molecular sieve DB3 provided in Comparative Example 3. Following the catalyst preparation method of Example 4, molecular sieve DB3 was mixed with boehmite, silica sol, kaolin, water, and alumina sol, and then spray-dried to prepare microsphere catalyst DB5.

[0155] Table 2 Catalyst Composition

[0156]

[0157] Performance testing

[0158] The catalytic cracking catalysts prepared in the examples and comparative examples were aged at 800°C and 100% (v / v) water vapor for 4 hours. Their catalytic cracking performance was then evaluated in a descending bed reactor. Before the reaction began, an appropriate amount of catalyst was added to the catalyst storage tank, and an appropriate amount of feed oil was added to the feed tank. The system was then heated. Once the predetermined temperature was reached, the catalyst flow control valve and feed pump were turned on, and nitrogen was used as a dilution gas. The catalyst and feed reacted in the descending bed reactor. The resulting oil-catalyst mixture was separated in a catalyst collection tank. The reaction products were separated into gas and liquid phases after two-stage condensation. The liquid product was collected and subjected to simulated distillation and PONA analysis, while the gaseous product was analyzed using chromatography. The reaction tube was 1.5 m long and 10 mm in inner diameter. The catalyst and hydrogenated LCO oil entered from the top of the reaction tube. The continuous entry time for the catalyst and feed was 1 min. The feed oil was 4.0 g, and the catalyst was 120 g, with a catalyst-to-oil ratio of 30 by weight. The reaction temperature was 650°C. The properties of the hydrogenated LCO are shown in Table 3, and the reaction results are shown in Table 4.

[0159] Table 3 Properties of hydrogenated LCO

[0160] Properties of hydrogenated LCO Sulfur content, mg / L 5.20 Nitrogen content, mg / L 0.30 <![CDATA[Density at 20 °C, kg / m 3 > 879.2 Hydrogen content, % 12.01 Carbon content, % 85.46 <![CDATA[Viscosity (20 °C), mm 2 / s]]> 2.748 Freezing point, ℃ ＜-50 Alkanes, w% 12.4 Total cycloalkanes, w% 31.9 Total monocyclic aromatic hydrocarbons, w% 44.5 Total bicyclic aromatic hydrocarbons, w% 6.2 Tricyclic aromatic hydrocarbons, w% 0.4

[0161] Table 4. Catalytic performance evaluation results

[0162]

[0163] As shown in Table 4, compared with the prior art, the gallium-modified catalytic cracking catalyst provided by this invention has higher hydrogenation LCO cracking capacity, higher yield of low-carbon olefins and C10 and below methylbenzene, and a significantly higher concentration of C10 and below methylbenzene in gasoline. Compared with the DB6 catalyst without gallium introduction, it has higher propylene yield and propylene selectivity, and a higher concentration of C10 and below methylbenzene in gasoline.

Claims

1. A gallium-modified catalytic cracking catalyst, comprising 20-70 wt% modified hollow ZSM-5 hierarchical porous molecular sieve and 30-80 wt% support, wherein, The modified hollow ZSM-5 hierarchical porous molecular sieve contains phosphorus and gallium, with a phosphorus-aluminum molar ratio of 0.2-1.

3. The gallium content in the modified hollow ZSM-5 hierarchical porous molecular sieve, calculated as Ga2O3, is 0.1-5% by weight. The average grain size of the modified hollow ZSM-5 hierarchical porous molecular sieve is 0.4-2.5 μm, and the ratio of bulk silicon-aluminum molar ratio to surface silicon-aluminum molar ratio is 1.1-1.

4. It has a closed hollow structure and a relative crystallinity of 75-90%. The total specific surface area of ​​the modified hollow ZSM-5 hierarchical porous molecular sieve is 250-350 m². 2 / g, mesoporous specific surface area is 20-100m² 2 / g, the mesoporous specific surface area accounts for 15-40% of the total specific surface area; the N2 adsorption-desorption curve of the modified hollow ZSM-5 hierarchical porous molecular sieve exhibits an H4-type hysteresis loop; in the modified hollow ZSM-5 hierarchical porous molecular sieve, the proportion of strong Brønsted acid to total Brønsted acid is 55-70%, and the proportion of strong Lewis acid to total Lewis acid is 50-70%.

2. The gallium-modified catalytic cracking catalyst according to claim 1, wherein, The modified hollow ZSM-5 multi-level porous molecular sieve has a total specific surface area of ​​280-350 m². 2 / g, mesoporous specific surface area is 30-80m² 2 / g, wherein the mesoporous specific surface area accounts for 18-35% of the total specific surface area.

3. The gallium-modified catalytic cracking catalyst according to claim 1, wherein, The modified hollow ZSM-5 multi-level porous molecular sieve has a strong Brønsted acid content of 55-65% of the total Brønsted acid content and a strong Lewis acid content of 60-70% of the total Lewis acid content.

4. The gallium-modified catalytic cracking catalyst according to claim 1, wherein, The carrier is one or more of the following: natural clay, alumina carrier, silica carrier, aluminum phosphate carrier, and silica-alumina oxide carrier.

5. The gallium-modified catalytic cracking catalyst according to claim 4, wherein, The silica carrier is one or more of neutral silica sol, acidic silica sol, or alkaline silica sol; the alumina carrier is one or more of alumina sol, acidified boehmite, hydrated alumina, and activated alumina; the aluminum phosphate carrier is aluminum phosphate gel; and the aluminosilicate carrier is one or more of solid aluminosilicate materials, aluminosilicate sol, and aluminosilicate gel.

6. The gallium-modified catalytic cracking catalyst according to claim 4, wherein, The support includes a silica support; the silica support content is 1-20% by weight based on the dry weight of the catalyst.

7. The gallium-modified catalytic cracking catalyst according to claim 1, wherein, Based on the dry weight of the catalyst, the gallium-modified catalytic cracking catalyst contains 20-50% by weight of the modified hollow ZSM-5 hierarchical porous molecular sieve, 20-50% by weight of clay, 10-30% by weight of acidified pseudoboehmite, 3-20% by weight of aluminum sol and 2-15% by weight of silica sol.

8. A method for preparing the gallium-modified catalytic cracking catalyst according to any one of claims 1-7, the method comprising: Phosphorus and gallium are introduced into a hollow ZSM-5 hierarchical porous molecular sieve with a closed hollow structure to form a modified hollow ZSM-5 hierarchical porous molecular sieve. A slurry is formed by a support, the modified hollow ZSM-5 hierarchical porous molecular sieve and water, and spray-dried. The particles obtained by spray drying, ammonium salt and water are mixed in a weight ratio of 1:(0.1-1):(5-15) for a third ammonium exchange. The hollow ZSM-5 hierarchical porous molecular sieve is prepared by a method including the following steps: (1) Mix and stir the first organosilicon source and the first solvent at 30-50°C for 0.5-5 hours, then heat to 70-100°C and mix and stir for 2-10 hours. Mix the resulting mixed liquid with the first template agent at 20-30°C for 0.5-3.0 hours to obtain the first mixed product. (2) Mix the first alkali metal hydroxide (calculated as alkali metal oxide), the second solvent, and the first aluminum source (calculated as Al2O3) in a molar ratio of (1.5-5):(60-350):1 at 20-80°C for 0.5-2.0 hours to obtain the second mixed product; (3) The first mixed product and the second mixed product are mixed and then subjected to dynamic crystallization. The resulting solid is taken out and subjected to a first calcination to obtain the first solid product. (4) The first solid product is mixed with the first alkaline solution, and the temperature is raised to the reaction temperature at a rate of 1-5℃ / min. The reaction is carried out at the reaction temperature for 10-90 min to obtain the second solid product. The reaction temperature is 60-90℃, and the alkaline content in the first alkaline solution is 0.45-2 mol / L. (5) The second solid product is subjected to first ammonium exchange and calcined to obtain hollow ZSM-5 hierarchical porous molecular sieve; Alternatively, the hollow ZSM-5 hierarchical porous molecular sieve can be prepared using a method comprising the following steps: S1. The second template agent, the second inorganic silicon source, and the third solvent are mixed at 30-50°C for 0.5-3.0 hours. The resulting third mixed product is subjected to a first hydrothermal treatment and a second hydrothermal treatment in sequence to obtain a fourth mixed product. The conditions for the first hydrothermal treatment are: temperature 80-150°C and time 1-6 hours. The conditions for the second hydrothermal treatment are: temperature 160-180°C and time 12-260 hours. S2. Mix the second alkali metal hydroxide (calculated as alkali metal oxide), the fourth solvent, and the second aluminum source (calculated as Al2O3) in a molar ratio of (1.5-5):(60-350):1 at 20-80°C for 0.5-2.0 hours to obtain the fifth mixed product. S3. Mix the fourth mixed product and the fifth mixed product, subject the resulting mixture to a third hydrothermal treatment, remove the resulting solid and subject it to a second calcination to obtain a third solid product; S4. The third solid product is mixed with the second alkaline solution, and the temperature is increased to the reaction temperature at a rate of 1-5℃ / min. The mixture is then reacted at the reaction temperature for 10-90 min to obtain the fourth solid product. The reaction temperature is 60-90℃, and the alkaline content in the second alkaline solution is 0.45-2 mol / L. S5. The fourth solid product is subjected to a second ammonium exchange and optionally calcined to obtain a hollow ZSM-5 hierarchical porous molecular sieve; The process of introducing phosphorus and gallium into a hollow ZSM-5 hierarchical porous molecular sieve with a closed hollow structure includes the following steps: (B1) Hollow ZSM-5 multi-level porous molecular sieve after ammonium exchange, with Na2O content less than 0.15% by weight, is calcined to obtain H-type molecular sieve; (B2) The H-type molecular sieve is impregnated with phosphorus-containing compounds and gallium-containing compounds or subjected to ion exchange with phosphorus-containing compounds and gallium-containing compounds, filtered, and dried; then calcined at 350~600 ℃ for 0.5~5 h; to obtain a modified hollow ZSM-5 hierarchical porous molecular sieve containing phosphorus and gallium; or (B2') The H-type molecular sieve is impregnated with phosphorus-containing compounds or subjected to ion exchange with phosphorus-containing compounds, filtered, and dried; then calcined at 350~600 ℃ for 0.5~5 h; to obtain a phosphorus-containing hollow ZSM-5 hierarchical porous molecular sieve, which is then subjected to hydrothermal treatment; the phosphorus-containing hollow ZSM-5 hierarchical porous molecular sieve is impregnated with gallium-containing compounds, subjected to ion exchange, filtered, and dried; then calcined at 350~600 ℃ for 0.5~5 h; to obtain a modified hollow ZSM-5 hierarchical porous molecular sieve containing phosphorus and gallium.

9. The method according to claim 8, wherein, The first organosilicon source is selected from one or both of methyl orthosilicate and tetraethyl orthosilicate; The second inorganic silicon source is selected from one or more of silica sol, water glass, and solid silica gel; The first template agent and the second template agent are each independently selected from one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine and hexamethylenediamine; The first aluminum source and the second aluminum source are each independently selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum isopropoxide and aluminum sol; The first alkali metal hydroxide and the second alkali metal hydroxide are each independently selected from one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide; The first alkaline solution and the second alkaline solution are each independently selected from one or more of sodium hydroxide solution, potassium hydroxide solution, lithium hydroxide and barium hydroxide.

10. The method according to claim 8, wherein, The total amount of the first template agent, the first solvent, and the second solvent, and the molar ratio of the first alkali metal hydroxide to the first organosilicon source are (0.06-0.55):(10-100):(0.02-1.5):1, and the molar ratio of the first organosilicon source to the first aluminum source is (20-500):1; wherein the first organosilicon source is calculated as SiO2, the first alkali metal hydroxide is calculated as alkali metal oxide, and the first aluminum source is calculated as Al2O3; In step (2), the molar ratio of the first alkali metal hydroxide (calculated as alkali metal oxide), the second solvent, and the first aluminum source (calculated as Al2O3) is (2-4.5):(80-350):1; In step (4), the weight ratio of the first solid product to the first alkaline solution is 1:(2-10); the ratio of the bulk silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio of the first solid product is 1.2-5.

0. The molar ratio of the second template agent, the third solvent, the second alkali metal hydroxide, and the second inorganic silicon source is (0.06-0.55):(10-100):(0.02-1.5):1, and the molar ratio of the second inorganic silicon source to the second aluminum source is (20-500):1; wherein the second inorganic silicon source is calculated as SiO2, the second alkali metal hydroxide is calculated as alkali metal oxide, and the second aluminum source is calculated as Al2O3; In step S2, the molar ratio of the second alkali metal hydroxide (calculated as alkali metal oxide), the fourth solvent, and the second aluminum source (calculated as Al2O3) is (2-4.5):(80-350):

1. In step S4, the weight ratio of the third solid product to the second alkali-containing solution is 1:(2-10), and the ratio of the bulk silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio of the third solid product is 1.2-5.

0.

11. The method according to claim 8, wherein, The conditions for dynamic crystallization include: a temperature of 160-180℃ and a time of 12-60 hours; The conditions for the third hydrothermal treatment include: a temperature of 160-180℃ and a time of 12-60 hours; The conditions for the first and second calcinations each independently include: a temperature of 400-600℃ and a time of 2-6 hours; In step (5), the first ammonium exchange of the second solid product includes: mixing the second solid product, the first ammonium source and the fifth solvent in a weight ratio of 1:(0.5-1.0):(8-10), and reacting the resulting mixture at 70-90°C for 0.5-5 hours. In step S5, the second ammonium exchange of the fourth solid product includes: mixing the fourth solid product, the second ammonium source and the sixth solvent in a weight ratio of 1:(0.5-1.0):(8-10), and then reacting the resulting mixture at 70-90°C for 0.5-2 hours. The first ammonium source and the second ammonium source are each independently selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.

12. The method according to claim 8, wherein, The impregnation in step (B2) is performed using an equal-volume impregnation method or an excess impregnation method; the phosphorus-containing compound is selected from at least one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate; and the gallium-containing compound is selected from one or more of gallium nitrates, chlorides, and sulfates. The impregnation in step (B2') is performed using an equal-volume impregnation method or an excess impregnation method; the phosphorus-containing compound is selected from at least one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate, and the gallium-containing compound is selected from one or more of gallium nitrates, chlorides, and sulfates.

13. The method according to claim 8, wherein, The method further includes: washing the third ammonium exchange product; the conditions for the third ammonium exchange include: a temperature of 50-100℃ and a time of 0.5-2 hours; the ammonium salt for the third ammonium exchange is selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate, and the particles obtained by spray drying are either roasted or not roasted.

14. The gallium-modified catalytic cracking catalyst according to any one of claims 1-7 is used for the catalytic cracking of hydrogenated LCO as feedstock to increase the production of low-carbon olefins and aromatics, wherein the reaction is carried out in a descending bed reactor.

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