Catalytic cracking catalyst and use thereof

Abstract

The application provides a catalytic cracking catalyst and application thereof. The catalytic cracking catalyst comprises a carrier and a first molecular sieve, the mass ratio of the carrier to the first molecular sieve is 25-80:20-60, and the first molecular sieve comprises a modified ZSM-5 molecular sieve. The preparation method of the modified ZSM-5 molecular sieve comprises the following steps: mixing seeds and a seed assembly agent to obtain a seed mixture; mixing the seed mixture with an alkali source, a first aluminum source and a first silicon source to obtain a crystallization gel; performing first crystallization and first calcination on the crystallization gel to obtain the ZSM-5 molecular sieve; and sequentially performing ammonium exchange and phosphorus exchange on the ZSM-5 molecular sieve to obtain the modified ZSM-5 molecular sieve. The application also provides application of the catalytic cracking catalyst in a catalytic cracking process. The catalytic cracking catalyst has high catalytic performance, can produce low-carbon olefins, and has high catalytic activity and low-carbon olefin selectivity.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalytic cracking, and particularly relates to a catalytic cracking catalyst and application thereof. BACKGROUND

[0002] In modern times, with the improvement of productivity and the acceleration of industrialization, petroleum has become one of the important energy sources. However, the use value of light alkanes generated in the petroleum processing process is relatively low. Therefore, the catalytic cracking technology for light oil is particularly important. Catalytic cracking reaction refers to the process of pyrolysis and cracking of oil products by using a catalyst to convert them into more useful chemicals. In the catalytic cracking process, heavy alkanes in petroleum are successively broken to form light alkanes and olefins, such as ethylene, propylene, propane, isobutane, butene, etc. In this process, ZSM-5 molecular sieve as a commonly used catalyst has been widely studied and applied.

[0003] ZSM-5 molecular sieve as a porous material has been focused on in the fields of catalysis, adsorption and the like due to its flexible adjustable acidity, excellent thermal stability and a series of characteristics. ZSM-5 molecular sieve has two kinds of intersecting channel structures, namely, a ten-membered ring straight channel in the b-axis direction and a sinusoidal ten-membered ring channel along the a-axis direction: the two kinds of channel structures are 0.51 nm x 0.55 nm (

[100] direction) and 0.53 nm x 0.56 nm (

[010] direction), respectively. ZSM-5 molecular sieve has the characteristics of high stability, high catalytic activity and flexible adjustable acidity, and is considered to be one of the most suitable molecular sieve materials for developing catalytic cracking catalysts.

[0004] The ZSM-5 molecular sieve currently used is still mainly based on the traditional ZSM-5 molecular sieve derived from the traditional ZSM-5 molecular sieve. The traditional ZSM-5 molecular sieve has a morphology that is thinner in the b-axis than in the a-axis and c-axis. Most of the synthesized special morphology molecular sieves, such as thin-layer ZSM-5 molecular sieves, also highlight the characteristics of strengthening the short b-axis, and do not essentially change the structural characteristics of ZSM-5 molecular sieve, so its performance has no breakthrough. The research on the catalytic cracking characteristics of ZSM-5 molecular sieve with the characteristics of short straight channel and short sinusoidal channel has not been reported.

[0005] In addition, the commonly used template for synthesizing the flaky molecular sieve at present is a long-chain monoammonium or long-chain diammonium surfactant and a double quaternary ammonium salt template with a special structure. Among them, the double quaternary ammonium salt template with a special structure has a complex preparation process and a high synthesis cost; the long-chain monoammonium or long-chain diammonium surfactant has the following disadvantages: 1. The commonly used reaction solvent is water, and a large amount of foam is easily generated under the dynamic condition after the surfactant is dissolved in water, which affects the uniformity of the product; 2. The crystallization process of the molecular sieve is difficult to control when the double ammonium or monoamine surfactant is used as the template; 3. The cost of the double ammonium or monoamine surfactant template is high, recycling is difficult, and it often needs to be prepared by oneself, which seriously affects the practicability of the method and reduces the practical value of the product.

[0006] Therefore, in order to improve the catalytic cracking characteristics of the molecular sieve, it is important to develop a low-cost ZSM-5 molecular sieve with the characteristics of short straight channels and short sinusoidal zigzag channels. SUMMARY

[0007] In order to overcome the above problems, the purpose of the present application is to provide a catalytic cracking catalyst and its application. The catalytic cracking catalyst has high catalytic performance, can produce low-carbon olefins, and has high catalytic activity and low-carbon olefin selectivity.

[0008] In order to achieve the above purpose, the present application provides a catalytic cracking catalyst, which comprises a carrier and a first molecular sieve.

[0009] The mass ratio of the carrier to the first molecular sieve is 25-80:20-60.

[0010] The first molecular sieve comprises a modified ZSM-5 molecular sieve, and the preparation method of the modified ZSM-5 molecular sieve comprises the following steps:

[0011] S1. Mixing seeds and seed assembly agents to obtain a seed mixture;

[0012] S2. Mixing the seed mixture with an alkali source, a first aluminum source and a first silicon source to obtain a crystallization gel;

[0013] S3. Making the crystallization gel undergo first crystallization and first calcination to obtain a ZSM-5 molecular sieve;

[0014] S4. sequentially performing ammonium exchange and phosphorus exchange on the ZSM-5 molecular sieve to obtain the modified ZSM-5 molecular sieve.

[0015] According to a specific embodiment of the present application, compared with conventional ZSM-5 molecular sieve, the ZSM-5 molecular sieve without ion exchange (S3 is prepared, hereinafter referred to as "unmodified ZSM-5 molecular sieve") and the modified ZSM-5 molecular sieve in the present application both have a trend of orientation change of shortening a axis and lengthening b axis. Specifically, in the above unmodified ZSM-5 molecular sieve and the modified ZSM-5 molecular sieve prepared in the present application, the characteristic peak intensity of (051) crystal face and (151) crystal face is enhanced relative to the characteristic peak intensity of (051) crystal face and (151) crystal face in conventional ZSM-5 molecular sieve.

[0016] According to a specific embodiment of the present application, the above unmodified ZSM-5 molecular sieve and the modified ZSM-5 molecular sieve of the present application have a diffraction peak intensity of (051) crystal face stronger than that of (501) crystal face, and a diffraction peak intensity of (151) crystal face stronger than that of (303) crystal face. In the X-ray diffraction spectrum of the ZSM-5 molecular sieve prepared by S3, the crystal face corresponding to 2θ = 23.18±0.5° is (501) crystal face, and the diffraction peak intensity of this 2θ angle is a;

[0017] The crystal face corresponding to 2θ = 23.32±0.5° is (051) crystal face, and the diffraction peak intensity of this 2θ angle is b;

[0018] The crystal face corresponding to 2θ = 23.74±0.5° is (151) crystal face, and the diffraction peak intensity of this 2θ angle is c;

[0019] The crystal face corresponding to 2θ = 23.99±0.5° is (303) crystal face, and the diffraction peak intensity of this 2θ angle is d;

[0020] b≥a, c≥d.

[0021] The above diffraction peak characteristics indicate that the modified ZSM-5 molecular sieve of the present application has a long b axis and a short a axis, and has a long straight channel and a short zigzag channel structure. The crystal grains with long b axis and short a axis are arranged in parallel in the molecular sieve, and the exposed crystal faces and acid sites are different from those of conventional ZSM-5 molecular sieve, so that the morphology and catalytic activity (such as the catalytic activity for producing more ethylene in the catalytic cracking process) of the modified ZSM-5 molecular sieve of the present application are different from those of existing ZSM-5 molecular sieve.

[0022] According to specific embodiments of the present application, the unmodified and modified ZSM-5 molecular sieves can be in a platelet structure, further can be in a winglet structure formed by ordered agglomeration. The platelet and winglet morphology makes the external surface of the unmodified and modified ZSM-5 molecular sieves abundant, and the diffusion distance in the sinusoidal channel short. The "winglet" structure refers to the thin platelet crystals form loose structure (not dense combination) in parallel (mainly) or vertical intersection (small amount). Compared with the conventional secondary agglomeration of molecular sieve particles to form disordered structure, the winglet structure formed by ordered agglomeration of molecular sieve particles in the present application makes the molecular sieve structure more stable. In some specific embodiments, the above ordered agglomeration structure can be achieved by ordered pre-assembly of seeds in the preparation process.

[0023] According to specific embodiments of the present application, the winglet morphology of the unmodified ZSM-5 molecular sieve (S3 prepared ZSM-5 molecular sieve) is formed by ordered stacking of several platelets. The thickness of a single platelet in the unmodified ZSM-5 molecular sieve is 20 nm-200 nm, and can be specifically 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, and the like, and a range with any two of the above specific values as endpoints.

[0024] According to specific embodiments of the present application, the particle size of the unmodified ZSM-5 molecular sieve is 300 nm-3 μm. The above particle size is the overall particle size of the molecular sieve, and for the winglet molecular sieve, the above particle size is the overall particle size of the molecular sieve after ordered stacking of the platelets. In some specific embodiments, the particle size of the unmodified ZSM-5 molecular sieve can be specifically 300 nm, 400 nm, 500 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, and the like, and a range with any two of the above specific values as endpoints.

[0025] According to specific embodiments of the present application, the winglet morphology of the modified ZSM-5 molecular sieve is formed by ordered stacking of several platelets. The thickness of a single platelet in the modified ZSM-5 molecular sieve is 20 nm-200 nm, and can be specifically 20 nm, 50 nm, 100 nm, 150 nm, 200 nm, and the like, and a range with any two of the above specific values as endpoints.

[0026] According to specific embodiments of the present application, the modified ZSM-5 molecular sieve has a particle size of 300 nm-3 μm. The above-mentioned particle size is the overall particle size of the molecular sieve, and for the flake-shaped molecular sieve, the above-mentioned particle size is the overall particle size of the molecular sieve after the ordered stacking of the flake layers. In some specific embodiments, the particle size of the modified ZSM-5 molecular sieve can be specifically 300 nm, 400 nm, 500 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, and the like, and ranges with any two of the above-mentioned specific values as the end points.

[0027] According to specific embodiments of the present application, the unmodified and modified ZSM-5 molecular sieve has a developed external specific surface area, which is beneficial to improve the selectivity of the catalyst. In some specific embodiments, the total specific surface area of the ZSM-5 molecular sieve prepared by S3 is 300 m 2 / g-500 m 2 / g, for example, 360 m 2 / g-440 m 2 / g. The external specific surface area of the ZSM-5 molecular sieve prepared by S3 is 80 m 2 / g-220 m 2 / g, for example, 120 m 2 / g-210 m 2 / g.

[0028] The present application researches and finds that by first mixing the seed crystals with the diamine seed assembly agent, relying on the interaction between the nitrogen atoms of the amine groups and the silicon hydroxyl groups on the surface of the seed crystals, the seed crystals can be orderly pre-assembled to obtain secondary seed crystals. After mixing the secondary seed crystals with the silicon source, the aluminum source and the alkali source, and then performing a hydrothermal crystallization reaction, since the secondary seed crystals have been orderly assembled, the secondary seed crystals can promote the ordered agglomeration of the molecular sieve during the crystallization process, and then the modified ZSM-5 molecular sieve with a flake-shaped morphology is obtained. The reaction raw materials used in the method are all cheap industrial products, and the diamine seed assembly agent has a stable structure and can be recycled after the crystallization reaction is completed, thereby reducing the emission of pollutants in the product post-processing process. Compared with the existing synthesis method using ammonium surfactant template agents or double-quaternary ammonium salt template agents with special structures, the above-mentioned modified ZSM-5 preparation method of the present application is green and simple, and can effectively reduce the product production cost and environmental protection cost, and has strong practical application significance.

[0029] According to specific embodiments of the present application, the seed assembly agent can include an organic compound having two amine groups (i.e. a diamine type seed assembly agent). In some specific embodiments, the seed assembly agent can include one or a combination of two or more of p-phenylenediamine, m-phenylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, piperazine, homopiperazine, 1,4-diazabicyclo[2.2.2]octane, 1,5-naphthalenediamine, 2,6-naphthalenediamine.

[0030] According to specific embodiments of the present application, the seed includes a molecular sieve having an MFI crystal structure.

[0031] According to specific embodiments of the present application, the seed has a silica-to-alumina ratio (molar ratio of SiO2 to Al2O3) generally equal to or greater than 30, for example, can be 30-400, 30-150, and the silica-to-alumina ratio of the seed can be as high as pure silica.

[0032] According to specific embodiments of the present application, the seed has a grain size of 10-200 nm. The grain size of the seed can be specifically 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, and the like specific values and ranges with any two of the above specific values as end points.

[0033] According to specific embodiments of the present application, the seed can be a commercially available molecular sieve having an MFI structure, or can be a seed obtained by the preparation method described below. Compared with the commercially available molecular sieve, the seed prepared by the present application has a smaller crystal size, and the preparation of ZSM-5 molecular sieve is better. Specifically, the preparation method of the seed can include: mixing a second silicon source, an organic template agent, and water to obtain a seed precursor, and subjecting the seed precursor to a second crystallization to obtain the seed.

[0034] wherein the second silicon source is calculated as SiO2, the organic template agent is calculated as organic cation R + , and the chemical composition of the seed precursor satisfies the following molar ratio ranges: R + / SiO2 = 0.15-0.4, and H2O / SiO2 = 15-50.

[0035] In some specific embodiments, the molar ratio of R + / SiO2 can be 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, and the like specific values and ranges with any two of the above specific values as end points. The molar ratio of H2O / SiO2 can be 15, 20, 25, 30, 35, 40, 45, 50, and the like specific values and ranges with any two of the above specific values as end points.

[0036] In the method for preparing the seed crystal, the seed crystal precursor further comprises a second aluminum source, the second silicon source in terms of SiO2 and the second aluminum source in terms of Al2O3, and the chemical composition of the seed crystal precursor further satisfies the following molar ratio range: SiO2 / Al2O3≥25. The molar ratio of SiO2 / Al2O3 can be specifically 25, 30, 35, 40, 45, 50, 60, 70, 80, and the like, and a range with any two of the above specific values as the end points.

[0037] In the method for preparing the seed crystal, the temperature of the second crystallization can be controlled to be 80-110°C, and can be specifically 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, and the like, and a range with any two of the above specific values as the end points. The time of the second crystallization can be controlled to be 16-24h, and can be specifically 16h, 18h, 20h, 22h, 24h, and the like, and a range with any two of the above specific values as the end points.

[0038] In the method for preparing the seed crystal, the second silicon source can include tetraethyl orthosilicate and / or fumed silica, and the like.

[0039] In the method for preparing the seed crystal, the organic template agent can include tetrapropylammonium hydroxide and / or n-butylamine, and the like.

[0040] In the method for preparing the seed crystal, the second aluminum source can include aluminum isopropoxide and / or sodium aluminate, and the like.

[0041] According to a specific embodiment of the present application, in S1, the seed crystal and the seed assembly agent can be mixed to occur ordered pre-assembly, and a secondary seed crystal is obtained. The temperature of the mixing can be 20-80°C, for example, 60-80°C; and the temperature of the mixing can be specifically 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, and the like, and a range with any two of the above specific values as the end points.

[0042] According to a specific embodiment of the present application, in S1, the time of the mixing can be 0.5h-24h, for example, 2h-12h. In some specific embodiments, the time of the mixing can be 0.5h, 1h, 2h, 6h, 12h, 24h, and the like, and a range with any two of the above specific values as the end points.

[0043] According to a specific embodiment of the present application, in S2, the first silicon source in terms of SiO2, the first aluminum source in terms of Al2O3, and the seed crystal in terms of contained SiO2, the chemical composition of the crystallization gel satisfies the following molar ratio range:

[0044] Si02(from the first silicon source) / Al203= 25-400, seed / Si02(from the first silicon source) = 0.002-0.25, MO / Si02= 0.05-0.50, H20 / Si02(from the first silicon source) = 15-120, seed assembly agent / Si02(from the first silicon source) = 0.03-0.20; wherein M is an alkali metal and / or an alkaline earth metal.

[0045] The above M at least includes metal cations in the alkali source, and further includes alkali metals, alkaline earth metals, etc. in other sources (such as aluminum sources) in the raw materials. It can be understood that MO represents the oxide of metal cations in the alkali source, and is not limited to the case where the molar ratio of M to O is 1:1, and also includes the case where M:O is less than 1, for example, MO can be Na20, K20, etc.

[0046] Further, in S2, the first silicon source is in terms of Si02, and the seed is in terms of Si02 contained, and the chemical composition of the crystallization gel can further satisfy the following molar ratio range: seed / Si02= 0.005-0.15. That is, Si02 / Al203= 25-400, seed / Si02= 0.05-0.15, MO / Si02= 0.05-0.50, H20 / Si02= 15-120, seed assembly agent / Si02= 0.03-0.20; wherein M is an alkali metal. In some specific embodiments, the molar ratio of seed / Si02(from the first silicon source) can be 0.002, 0.005, 0.010, 0.015, 0.020, 0.050, 0.070, 0.080, 0.10, 0.15, 0.20, 0.25, etc. specific values and ranges with any two of the above specific values as endpoints.

[0047] According to specific embodiments of the present application, in the crystallization gel of S2, the molar ratio of Si02 / Al203may be 25-400, and specifically can be 25, 30, 50, 100, 150, 200, 250, 300, 350, 400, etc. specific values and ranges with any two of the above specific values as endpoints.

[0048] According to specific embodiments of the present application, in the crystallization gel of S2, the molar ratio of MO / Si02(from the first silicon source) can be 0.05-0.50, and specifically can be 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, 0.50, etc. specific values and ranges with any two of the above specific values as endpoints.

[0049] According to specific embodiments of the present application, in the crystallization gel of S2, the molar ratio of H2O / SiO2 (from the first silicon source) can be 15-120, specifically can be 15, 20, 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, and the like, and ranges using any two of the foregoing as endpoints.

[0050] According to specific embodiments of the present application, in the crystallization gel of S2, the molar ratio of seed assembly agent / SiO2 (from the first silicon source) is 0.03-0.20, specifically can be 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.13, 0.15, 0.17, 0.19, 0.20, and the like, and ranges using any two of the foregoing as endpoints.

[0051] According to specific embodiments of the present application, in S2, the first silicon source can include one or a combination of two or more of silica gel, silica sol, and fumed silica. In some specific embodiments, the silica gel can be coarse-pore silica gel.

[0052] According to specific embodiments of the present application, in S2, the first aluminum source can include one or a combination of two or more of pseudoboehmite, aluminum isopropoxide, sodium metaaluminate, and aluminum sulfate.

[0053] According to specific embodiments of the present application, in S2, the base source can include sodium hydroxide and / or potassium hydroxide.

[0054] According to specific embodiments of the present application, in S3, the temperature of the first crystallization is 120°C-190°C, for example, 140-180°C, 140°C-175°C. The temperature of the first crystallization can be specifically 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, and the like, and ranges using any two of the foregoing as endpoints.

[0055] According to specific embodiments of the present application, in S3, the time of the first crystallization is 12h-120h, for example, 12h-96h. The time of the first crystallization can be specifically 12h, 24h, 36h, 48h, 60h, 72h, 84h, 96h, 108h, 120h, and the like, and ranges using any two of the foregoing as endpoints.

[0056] According to specific embodiments of the present application, in S3, the first crystallization can be a dynamic crystallization process.

[0057] According to a specific embodiment of the present application, in S3, the first calcination can be performed at a temperature of 500-600°C for 2-24 hours.

[0058] S3 of the preparation method can further include a post-treatment of the first crystallized product before the first calcination. The post-treatment can include filtration, washing, drying, etc.

[0059] According to a specific embodiment of the present application, the ZSM-5 molecular sieve obtained in S3 can be a wing-shaped ZSM-5 molecular sieve. The molecular sieve has a short b-axis and a short a-axis.

[0060] According to a specific embodiment of the present application, the mass content of phosphorus in the modified ZSM-5 molecular sieve prepared in S4 is 0.1%-10% by mass of P2O5.

[0061] According to a specific embodiment of the present application, in S4, the phosphorus exchange process includes mixing the ammonium-exchanged product of the ZSM-5 molecular sieve with a phosphorus source and then performing calcination and hydrothermal aging treatment.

[0062] According to a specific embodiment of the present application, the phosphorus source includes phosphoric acid and / or a phosphorus salt. The phosphorus salt can include one or a combination of two or more of ammonium phosphate, di-ammonium hydrogen phosphate, and ammonium di-hydrogen phosphate.

[0063] According to a specific embodiment of the present application, S4 can specifically include: ammonium-exchanging the ZSM-5 molecular sieve, performing second calcination; mixing the product of the second calcination with a phosphorus source, performing third calcination and hydrothermal aging treatment, to obtain the modified ZSM-5 molecular sieve. In some specific embodiments, the product of the second calcination can be a wing-shaped ZSM-5 molecular sieve in hydrogen form. The second calcination can be performed at a temperature of 500-600°C for 2-24 hours. The second calcination can also use other conventional calcination conditions in the art.

[0064] According to a specific embodiment of the present application, in S4, the second calcination, the third calcination, and the hydrothermal aging process are conventional calcination and aging means in the art, and the present application does not specially limit the operation method and conditions of the above processes.

[0065] According to a specific embodiment of the present application, the third calcination is performed at a temperature of 500-600°C for 2-24 hours. The third calcination can also use other conventional calcination conditions in the art.

[0066] According to specific embodiments of the present application, the hydrothermal aging treatment process can improve the activity stability of the molecular sieve in industrial applications, prolong the life of the molecular sieve and improve the catalytic activity. The conditions of the hydrothermal aging treatment can be: the treatment temperature is 550-800°C, for example, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, and the like, and ranges with any two of the above specific values as endpoints;

[0067] the treatment time is 1h-24h, for example, 1h, 2h, 3h, 6h, 8h, 10h, 12h, 24h, and the like, and ranges with any two of the above specific values as endpoints;

[0068] the water vapor content is 5%-80%, for example, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the like, and ranges with any two of the above specific values as endpoints.

[0069] According to specific embodiments of the present application, the carrier can include one or a combination of two or more of natural minerals, amorphous silica-alumina, alumina, and silica. In some specific embodiments, the natural minerals include one or a combination of two or more of kaolin, montmorillonite, diatomite, bentonite, and rectorite. The alumina can include pseudoboehmite and the like.

[0070] According to specific embodiments of the present application, the catalytic cracking catalyst can further include a second molecular sieve, the mass of the carrier is 25%-80%, the mass of the first molecular sieve is 20%-60%, and the mass of the second molecular sieve is 0-30%, based on the total mass of 100% of the catalytic cracking catalyst dry basis.

[0071] According to specific embodiments of the present application, the second molecular sieve includes one or a combination of two or more of molecular sieves having BEA structure, FAU structure, MFI structure, and MWW structure. For example, the second molecular sieve includes one or a combination of two or more of β molecular sieve, Y molecular sieve, ZSM-5 molecular sieve, and MCM-49 molecular sieve. Alternatively, the second molecular sieve can further include the modified ZSM-5 molecular sieve of the present application. The above-mentioned second molecular sieve can be a molecular sieve of the corresponding structure without treatment or with treatment.

[0072] According to specific embodiments of the present application, the silica-to-alumina molar ratio (silicon-to-aluminum ratio) of the second molecular sieve can be 5-150, for example, 6-50. Specifically, the silica-to-alumina molar ratio of the second molecular sieve can be 5, 6, 10, 50, 100, 150, and the like, and ranges with any two of the above specific values as endpoints.

[0073] According to a specific embodiment of the present application, the second molecular sieve is a molecular sieve subjected to one or a combination of more than two of the following treatments: ultrastabilization treatment, metal modification treatment, acid-base modification treatment. The ultrastabilization treatment includes hydrothermal ultrastabilization treatment and / or gas phase ultrastabilization treatment.

[0074] In some specific embodiments, the second molecular sieve can include one or a combination of more than two of the following: ultrastabilized beta molecular sieve, ultrastabilized Y molecular sieve, ultrastabilized ZSM-5 molecular sieve, ultrastabilized MCM-49 molecular sieve.

[0075] The present application also provides a preparation method of the catalytic cracking catalyst described above, which includes: mixing the carrier, the first molecular sieve and the binder to obtain a slurry, drying to obtain solid particles, and performing a fourth calcination on the solid particles to obtain the catalyst.

[0076] In the preparation method described above, when the catalytic cracking catalyst further includes the second molecular sieve, the second molecular sieve is added together with the carrier, the first molecular sieve and the binder.

[0077] In the preparation method described above, the drying method can include spray drying.

[0078] In the preparation method described above, the diameter of the solid particles can be 30-120 μm.

[0079] In the preparation method described above, the temperature of the fourth calcination can be 500-600°C, for example 550°C; and the time of the fourth calcination can be 2-24 h, for example 4 h.

[0080] According to a specific embodiment of the present application, the binder can include one or a combination of more than two of the following: aluminum sol, silicon sol, phosphorus-containing aluminum sol. The mass of the binder remaining in the catalyst after the fourth calcination is equal to the mass of the carrier.

[0081] The present application also provides the use of the catalytic cracking catalyst described above in a catalytic cracking process. The modified ZSM-5 molecular sieve in the catalytic cracking catalyst has the structural characteristics of short a-axis and b-axis, and has a developed external specific surface area. When applied in a catalytic cracking process (especially a light hydrocarbon catalytic cracking process), the catalytic cracking catalyst has higher catalytic activity and product selectivity, and has outstanding pore advantages.

[0082] In some specific embodiments, the catalytic cracking process parameters described above can include: reaction temperature 550°C, mass space velocity 2.0 h -1 , nitrogen carrier gas flow rate 300 mL / h.

[0083] The present application has the following beneficial effects:

[0084] The present application can improve the catalytic activity of the catalytic cracking catalyst prepared by using the modified ZSM-5 molecular sieve as a raw material, which has the structural characteristics of developed external specific surface area and long straight pore and short tortuous pore, and has a wide application prospect due to the high selectivity of the catalytic cracking catalyst to low-carbon olefins such as ethylene. BRIEF DESCRIPTION OF DRAWINGS

[0085] Figure 1 XRD pattern of seed 1.

[0086] Figure 2 SEM image of seed 1.

[0087] Figure 3 XRD pattern of seed 2.

[0088] Figure 4 SEM image of seed 2.

[0089] Figure 5 XRD pattern of ZSM-5 molecular sieve prepared in step 1 of Example 1.

[0090] Figure 6 SEM image of ZSM-5 molecular sieve prepared in step 1 of Example 1.

[0091] Figure 7 XRD pattern of ZSM-5 molecular sieve prepared in step 1 of Example 2.

[0092] Figure 8 SEM image of ZSM-5 molecular sieve prepared in step 1 of Example 2.

[0093] Figure 9 XRD pattern of ZSM-5 molecular sieve prepared in step 1 of Example 3.

[0094] Figure 10 SEM image of ZSM-5 molecular sieve prepared in step 1 of Example 3.

[0095] Figure 11 XRD pattern of ZSM-5 molecular sieve prepared in step 1 of Example 4.

[0096] Figure 12 SEM image of ZSM-5 molecular sieve prepared in step 1 of Example 4.

[0097] Figure 13 XRD pattern of ZSM-5 molecular sieve prepared in step 1 of Comparative Example 1.

[0098] Figure 14SEM image of the ZSM-5 zeolite prepared in Step 1 of Comparative Example 1.

[0099] Figure 15 XRD pattern of the ZSM-5 zeolite used in Comparative Example 2.

[0100] Figure 16 SEM image of the ZSM-5 zeolite used in Comparative Example 2.

[0101] Figure 17 、 Figure 18 XRD pattern of the ZSM-5 zeolite used in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0102] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present application, the technical solutions of the present application will be described in detail below, but it should not be understood as limiting the scope of the present application.

[0103] The raw materials used in the examples are as follows:

[0104] Silicon source: coarse-pored silica gel (purity 99%), silica sol (30% aqueous solution), white carbon black (purity 99%)

[0105] Aluminum source: pseudo-boehmite (alumina content 65%), aluminum isopropoxide (purity 99%), sodium metaaluminate (alumina content 41wt%, Na2O content 25wt%), aluminum sulfate (purity 99%).

[0106] Seed assembly agent: p-phenylenediamine (purity 99%), m-phenylenediamine (purity 99%), 1,3-propanediamine (purity 99%), 1,4-butanediamine (purity 99%), 1,5-pentanediamine (purity 99%), 1,6-hexanediamine (purity 99%), piperazine (purity 99%), homopiperazine (purity 99%), 1,4-diazabicyclo[2.2.2]octane (CAS: 280-57-9, molecular weight 112, purity 99%), 1,5-naphthalenediamine (purity 99%), 2,6-naphthalenediamine (purity 99%).

[0107] Alkali source: sodium hydroxide (purity 99%), potassium hydroxide (purity 99%).

[0108] Support: kaolin (solid content 70%), pseudo-boehmite (alumina content 65%), montmorillonite (solid content 70%), aluminum sol (alumina content 22%), silica sol (silica content 30%), phosphorus-containing aluminum sol (phosphorus content 12%, aluminum content 6%).

[0109] Phosphorus-containing compound: ammonium dihydrogen phosphate (99%), diammonium hydrogen phosphate (99%), phosphoric acid (85%)

[0110] Second molecular sieve: Y molecular sieve (silicon aluminum ratio 7.6, solid content 90%), beta molecular sieve (silicon aluminum ratio 23.5, solid content 90%), ZSM-5 molecular sieve (silicon aluminum ratio 22.7, solid content 90%).

[0111] Others: deionized water.

[0112] Preparation example

[0113] The experiment provides two preparation methods of the seed crystal liquid, which specifically include:

[0114] The tetraethyl orthosilicate, tetrapropylammonium hydroxide (template agent) and deionized water are fully mixed, and the molar ratio of the mixed materials (the silicon source is calculated according to the SiO2 effective component contained, and the template agent is calculated according to the organic cation R + ) is: R + / SiO2=0.25, H2O / SiO2=30, and a crystallization reaction is performed under hydrothermal conditions, the crystallization reaction condition is: 90 DEG C, time 24 h. 2 times mass of deionized water is added to the above reaction product and mixed uniformly, that is, the effective seed solubility in the reaction product is diluted to one third of the original solubility, which is marked as seed crystal liquid 1, and the average crystal size is 200 nm. The SiO2 mass content in the seed crystal liquid 1 is 2.48%.

[0115] The tetraethyl orthosilicate, aluminum isopropylate, tetrapropylammonium hydroxide and deionized water are fully mixed, and the molar ratio of the mixed materials (the silicon source is calculated according to the SiO2 effective component contained, and the template agent is calculated according to the organic cation R + ) is: SiO2 / Al2O3=30, R + / SiO2=0.25, H2O / SiO2=30, and a crystallization reaction is performed under hydrothermal conditions, the crystallization reaction condition is: 90 DEG C, time 16 h, 2 times mass of deionized water is added to the above reaction product and mixed uniformly, that is, the effective seed solubility in the reaction product is diluted to one third of the original solubility, which is marked as seed crystal liquid 2, and the average crystal size is 100 nm. The SiO2 mass content in the seed crystal liquid 2 is 2.43%. The silicon aluminum ratio of the seed crystal liquid 2 is 30.

[0116] Figure 1 , Figure 2 The XRD spectrum and the SEM photo of the seed crystal liquid 1 are shown in Figs. 1 and 2 respectively. Figure 3 , Figure 4 The XRD spectrum and the SEM photo of the seed crystal liquid 2 are shown in Figs. 3 and 4 respectively. As can be seen from the figures, the seed crystals in the seed crystal liquid 1 and the seed crystal liquid 2 both have MFI crystal structure.

[0117] It should be noted that the raw materials, the ratio, the reaction conditions and the dilution ratio used in the preparation of the seed crystal liquid of the present application are not limited to the above process, and the seed crystal liquid can also be prepared by using the purchased molecular sieve product.

[0118] Example 1

[0119] The present example provides a catalytic cracking catalyst, and a preparation method thereof, which comprises:

[0120] 1. Under the condition of 60℃ water bath, 1.83g of seed liquid 1 was dispersed in 20g of deionized water, and 1.0g of p-phenylenediamine was slowly added under continuous stirring. After stirring for 3h, no obvious stratification was observed in the liquid to obtain a seed mixture. 0.28g of sodium hydroxide and 0.82g of sodium metaaluminate were dissolved in 25g of deionized water, and 20.0g of silica sol was slowly added under continuous stirring. Then, the seed mixture was slowly added, and the mixture was continuously stirred for 3h to obtain a crystallization gel. The crystallization gel was transferred to a high-pressure reaction kettle, and crystallization was carried out at 150℃ for 72h. After washing, filtering, drying and calcining, the molecular sieve product was obtained.

[0121] 2. The molecular sieve was stirred in a 1mol / L ammonium ion solution at 80℃ for 2h for ammonium exchange. After several times of exchange, the Na2O content of the molecular sieve was less than 0.1% (mass ratio). The ammonium-exchanged molecular sieve solid, 3% of ammonium dihydrogen phosphate based on the dry mass of the molecular sieve, and an appropriate amount of deionized water were thoroughly mixed, dried, calcined at 550℃ for 4h, and then subjected to hydrothermal aging treatment under the following conditions: 650℃, 10h, and water vapor content of 20% to obtain a modified ZSM-5 molecular sieve. The structure parameters of the modified ZSM-5 molecular sieve are shown in Table 1.

[0122] 3. Kaolin, aluminum sol, modified ZSM-5 molecular sieve, Y molecular sieve and deionized water were mixed according to a certain proportion to make a slurry, and the obtained slurry was spray dried into particles with a diameter of 30-120μm. The particles were calcined at 550℃ for 4h to obtain a catalyst C1. The composition of the catalyst is shown in Table 2.

[0123] The XRD spectrum of the molecular sieve product prepared in step 1 is shown in Figure 5 , and the product has typical MFI structure characteristic peaks. The SEM image of the molecular sieve product is shown in Figure 6 , and the product has a wing shape. The total specific surface area of the molecular sieve obtained in step 1 was 413.5m 2 / g, of which the external specific surface area was 201.1m 2 / g.

[0124] Example 2

[0125] The present example provides a catalytic cracking catalyst, and a preparation method thereof, which comprises:

[0126] 1. Under the condition of 60℃ water bath, 1.83g seed crystal solution 1 was dispersed in 20g deionized water, 0.69g 1,3-propanediamine was slowly added under continuous stirring, and the mixture was stirred for 3h until no obvious stratification was observed to obtain a seed crystal mixture. 0.28g sodium hydroxide and 0.82g sodium metaaluminate were dissolved in 25g deionized water, 20.0g silica sol was slowly added under continuous stirring, and the seed crystal mixture was slowly added. After the mixing was completed, the mixture was continuously stirred for 3h to obtain a crystallization gel. The crystallization gel was transferred to a high-pressure reaction kettle, and crystallization was carried out at 150℃ for 72h. After washing, filtering, drying and calcining, the molecular sieve product was obtained.

[0127] 2. The molecular sieve was stirred in 1mol / L ammonium ion solution at 80℃ for 2h for ammonium exchange. After several exchanges, the Na2O content of the molecular sieve was less than 0.1% (mass ratio). The molecular sieve solid, 1% ammonium dihydrogen phosphate based on the dry mass of the molecular sieve, and an appropriate amount of deionized water were thoroughly mixed, dried, calcined at 550℃ for 4h, and then subjected to hydrothermal aging treatment under the following conditions: 650℃, 6h, and water vapor content of 15% to obtain a modified ZSM-5 molecular sieve. The structure parameters of the modified ZSM-5 molecular sieve are shown in Table 1.

[0128] 3. Kaolin, aluminum sol, modified ZSM-5 molecular sieve, Y molecular sieve, and deionized water were mixed according to a certain proportion to make a slurry, the obtained slurry was spray dried into particles with a diameter of 30-120μm, and then calcined at 550℃ for 4h to obtain a catalyst C2. The catalyst composition is shown in Table 2.

[0129] The XRD spectrum of the molecular sieve product prepared in step 1 is shown in Figure 7 , and the product has typical MFI structure characteristic peaks. The SEM image is shown in Figure 8 , and the product is in the form of fins. The total specific surface area of the molecular sieve obtained in step 1 was analyzed, and the total specific surface area was 436.3m 2 / g, of which the external specific surface area was 197.2m 2 / g.

[0130] Example 3

[0131] The present embodiment provides a catalytic cracking catalyst, and a preparation method of the catalyst comprises:

[0132] 1. Under the condition of 70℃ water bath, 3.66g seed crystal liquid 1 was dispersed in 40g deionized water, 2.0g 1,6-hexanediamine was slowly added under continuous stirring, and the liquid was stirred for 2h until no obvious stratification was observed to prepare a seed crystal mixture. 0.35g sodium hydroxide and 0.45g pseudoboehmite were dissolved in 50g deionized water, 20.0g silica sol was slowly added under continuous stirring, and the seed crystal mixture was slowly added. After the mixing was completed, the mixture was continuously stirred for 3h to prepare a crystallization gel. The crystallization gel was transferred to a high-pressure reaction kettle, and was crystallized at 160℃ for 96h. After the product was washed, filtered, dried and calcined, a molecular sieve product was obtained.

[0133] 2. The molecular sieve was stirred in 1mol / L ammonium ion solution at 80℃ for 2h for ammonium exchange. After several exchanges, the Na2O content of the molecular sieve was less than 0.1% (mass ratio). The molecular sieve solid, diammonium hydrogen phosphate with P2O5 content of 5% of the dry basis mass of the molecular sieve, and appropriate amount of deionized water were thoroughly mixed, dried, calcined at 550℃ for 4h, and then subjected to hydrothermal aging treatment under the following conditions: 700℃, 3h, and water vapor content of 50% to prepare a modified ZSM-5 molecular sieve. The structure parameters of the modified ZSM-5 molecular sieve are shown in Table 1.

[0134] 3. Pseudoboehmite, phosphorus-containing aluminum sol, modified ZSM-5 molecular sieve, β molecular sieve and deionized water were mixed according to a certain proportion to prepare a slurry, the slurry was spray dried into particles with a diameter of 30-120μm, and the particles were calcined at 550℃ for 4h to obtain a catalyst C3. The catalyst composition is shown in Table 2.

[0135] The XRD spectrum of the molecular sieve product prepared in step 1 is shown in Figure 9 , and the product has typical MFI structure characteristic peaks. The SEM image is shown in Figure 10 , and the product has a wing shape. The total specific surface area of the molecular sieve obtained in step 1 was analyzed, and the total specific surface area was 383.5m 2 / g, wherein the external specific surface area was 125.7m 2 / g.

[0136] Example 4

[0137] The present embodiment provides a catalytic cracking catalyst, and a preparation method of the catalyst comprises:

[0138] 1. Under the condition of 80℃ water bath, 3.66g seed liquid 2 was dispersed in 25g deionized water, 2.0g 1,4-diazabicyclo[2.2.2]octane was slowly added under continuous stirring, and the liquid was stirred for 3h until no obvious layering was observed to prepare a seed mixture. 0.38g potassium hydroxide and 0.27g sodium metaaluminate were dissolved in 25g deionized water, 20.0g silica sol was slowly added under continuous stirring, and the seed mixture was slowly added. After the mixing was completed, the mixture was continuously stirred for 3h to prepare a crystallization gel. The crystallization gel was transferred to a high-pressure reaction kettle, and crystallization was carried out at 170℃ for 48h. After the product was washed, filtered, dried, and calcined, a molecular sieve product was obtained.

[0139] 2. The molecular sieve was stirred in a 1mol / L ammonium ion solution at 80℃ for 2h for ammonium exchange. After several exchanges, the Na2O content of the molecular sieve was less than 0.1% (mass ratio). The molecular sieve solid, diammonium hydrogen phosphate with a P2O5 content of 8% of the dry basis mass of the molecular sieve, and an appropriate amount of deionized water were thoroughly mixed, dried, calcined at 550℃ for 4h, and then subjected to hydrothermal aging treatment under the following conditions: 550℃, 2h, and a water vapor content of 60% to prepare a modified ZSM-5 molecular sieve. The structure parameters of the modified ZSM-5 molecular sieve are shown in Table 1.

[0140] 3. Pseudo-boehmite, phosphorus-containing aluminum sol, modified ZSM-5 molecular sieve, β molecular sieve, and deionized water were mixed and slurried in a certain proportion, the obtained slurry was spray dried into particles with a diameter of 30-120μm, and the particles were calcined at 550℃ for 4h to obtain a catalyst C3. The catalyst composition is shown in Table 2.

[0141] The XRD spectrum of the molecular sieve product prepared in step 1 is shown in Figure 11 , and the product has typical MFI structure characteristic peaks. The SEM image is shown in Figure 12 , and the product has a wing shape. The total specific surface area of the molecular sieve obtained in step 1 was analyzed, and the total specific surface area was 375.9m 2 / g, of which the external specific surface area was 164.8m 2 / g.

[0142] Example 5

[0143] The present embodiment provides a catalytic cracking catalyst, and a preparation method of the catalyst comprises:

[0144] 1. Under the condition of 80℃ water bath, 1.83g of seed liquid 2 was dispersed in 60g of deionized water, 2.8g of 2,6-naphthalenediamine was slowly added under continuous stirring, and the mixture was stirred for 12h until no obvious stratification was observed to prepare a seed mixture. 0.45g of sodium hydroxide and 0.15g of sodium metaaluminate were dissolved in 60g of deionized water, 6.0g of crude silica gel was slowly added under continuous stirring, and the seed mixture was slowly added, and the mixture was continuously stirred for 3h after completion of mixing to prepare a crystallization gel. The crystallization gel was transferred to a high-pressure reaction kettle, and crystallization was carried out at 170℃ for 72h. After washing, filtering, drying and calcining, a molecular sieve product was obtained.

[0145] 2. The molecular sieve was stirred in a 1mol / L ammonium ion solution at 80℃ for 2h for ammonium exchange. After several exchanges, the Na2O content of the molecular sieve was less than 0.1% (mass ratio). The molecular sieve solid was mixed with 0.5% of phosphoric acid based on the dry mass of the molecular sieve, and a proper amount of deionized water, and then dried and calcined at 550℃ for 4h. Then, the modified ZSM-5 molecular sieve was prepared by hydrothermal aging treatment under the following conditions: 600℃, 6h, and 20% water vapor content. The structure parameters of the modified ZSM-5 molecular sieve are shown in Table 1.

[0146] 3. Montmorillonite, silica sol, modified ZSM-5 molecular sieve, ZSM-5 molecular sieve and deionized water were mixed according to a certain proportion to prepare a slurry, and the slurry was spray dried into particles with a diameter of 30-120μm. The particles were calcined at 550℃ for 4h to obtain a catalyst C5. The catalyst composition is shown in Table 2.

[0147] The molecular sieve product prepared in step 1 has an MFI structure and is a wing-shaped ZSM-5 molecular sieve. The total specific surface area of the molecular sieve obtained in step 1 was 365.5m2 / g, wherein the external specific surface area was 121.3m2 / g. 2 2 / g.

[0148] Example 6

[0149] The present embodiment provides a catalytic cracking catalyst, and a preparation method of the catalyst comprises the following steps:

[0150] 1. Under the condition of 80℃ water bath, 1.83g of seed liquid 2 was dispersed in 60g of deionized water, 2.8g of 2,6-naphthalenediamine was slowly added under continuous stirring, and the mixture was stirred for 12h until no obvious stratification was observed to prepare a seed mixture. 0.45g of sodium hydroxide and 0.15g of sodium metaaluminate were dissolved in 60g of deionized water, 6.0g of crude silica gel was slowly added under continuous stirring, and the seed mixture was slowly added, and the mixture was continuously stirred for 3h after completion of mixing to prepare a crystallization gel. The crystallization gel was transferred to a high-pressure reaction kettle, and crystallization was carried out at 170℃ for 72h. After washing, filtering, drying and calcining, a molecular sieve product was obtained.​

[0151] 2. Stir the molecular sieve in 1 mol / L ammonium ion solution at 80°C for 2 h for ammonium exchange. Exchange several times until the Na2O content of the molecular sieve is less than 0.1% (mass ratio). Mix the molecular sieve solid, 10% diammonium hydrogen phosphate based on the dry mass of the molecular sieve, and a proper amount of deionized water, and then dry and calcine at 550°C for 4 h. Then perform hydrothermal aging treatment at 800°C for 12 h with a water vapor content of 15% to obtain the modified ZSM-5 molecular sieve. The structure parameters of the modified ZSM-5 molecular sieve are shown in Table 1.

[0152] 3. Mix the montmorillonite, silica sol, modified ZSM-5 molecular sieve, and deionized water according to a certain proportion to make a slurry, spray dry the slurry to obtain particles with a diameter of 30-120 μm, and then calcine at 550°C for 4 h to obtain the catalyst C6. The catalyst composition is shown in Table 2.

[0153] The molecular sieve product prepared in Step 1 has an MFI crystal structure and is a wing-shaped ZSM-5 molecular sieve. The total specific surface area of the molecular sieve obtained in Step 1 is 425.5 m 2 / g, wherein the external specific surface area is 197.6 m 2 / g.

[0154] Example 7

[0155] The present example provides a ZSM-5 molecular sieve, and a preparation method thereof, which comprises:

[0156] Under the condition of a 40°C water bath, 1.83 g of the seed crystal liquid 1 was dispersed in 20 g of deionized water, and 1.0 g of p-phenylenediamine was slowly added under continuous stirring. After stirring for 18 h until there was no obvious stratification in the liquid, a seed crystal mixture was prepared. 0.28 g of sodium hydroxide and 0.82 g of sodium metaaluminate were dissolved in 25 g of deionized water, and 20.0 g of silica sol was slowly added under continuous stirring. The seed crystal mixture was slowly added, and after the mixing was completed, the mixture was continuously stirred for 3 h to prepare a crystallization gel. The crystallization gel was transferred to a high-pressure reaction kettle, and crystallization was performed at 120°C for 120 h. After the product was washed, filtered, dried, and calcined, a molecular sieve product was obtained.

[0157] The XRD spectrum of the molecular sieve product is shown in Figure 13 , the product has typical MFI structure characteristic peaks, the SEM image is shown in Figure 14 , and the product is a wing-shaped structure formed by the ordered stacking of sheet molecular sieves. The total specific surface area of the molecular sieve is 363.1 m 2 / g, wherein the external specific surface area is 131.8 m 2 / g.

[0158] Example 8

[0159] The present embodiment provides a ZSM-5 molecular sieve, and a preparation method thereof, which comprises the following steps:

[0160] Under the condition of 20℃ water bath, 2.0g of 1,4-diazabicyclo[2.2.2]octane was slowly added into 3.66g of seed liquid 2 under continuous stirring, and the seed mixture was prepared after stirring for 24h until there was no obvious stratification in the liquid. 0.38g of potassium hydroxide and 0.27g of sodium metaaluminate were dissolved in 25g of deionized water, 20.0g of silica sol was slowly added under continuous stirring, and the seed mixture was slowly added. After the mixing was completed, the crystallization gel was prepared after stirring for 3h. The crystallization gel was transferred to a high-pressure reaction kettle, and crystallization was carried out at 180℃ for 12h. After the product was washed, filtered, dried and calcined, the molecular sieve product was obtained.

[0161] The XRD spectrum of the molecular sieve product is shown in Figure 15 , the product has typical MFI structure characteristic peaks, and the SEM image is shown in Figure 16 , the product is a fin-shaped structure formed by ordered stacking of sheet molecular sieves. The total specific surface area of the molecular sieve was analyzed, and the total specific surface area was 368.2m 2 / g, wherein the external specific surface area was 141.3m 2 / g.

[0162] Comparative Example 1

[0163] The present comparative example provides a catalytic cracking catalyst, and a preparation method thereof, which comprises the following steps:

[0164] 1. 0.28g of sodium hydroxide, 0.82g of sodium metaaluminate and 1.0g of p-phenylenediamine were dissolved in 45g of deionized water, 20.0g of silica sol was slowly added under continuous stirring, and 1.83g of seed liquid 1 was slowly added. After the mixing was completed, the crystallization gel was prepared after stirring for 3h. The crystallization gel was transferred to a high-pressure reaction kettle, and crystallization was carried out at 150℃ for 72h. After the product was washed, filtered, dried and calcined, the molecular sieve product was obtained.

[0165] 2. The molecular sieve was stirred in a 1mol / L ammonium ion solution at 80℃ for 2h for ammonium exchange. After several times of exchange, the Na2O content of the molecular sieve was less than 0.1% (mass ratio). The molecular sieve solid, 3% of ammonium dihydrogen phosphate based on the dry mass of the molecular sieve, and an appropriate amount of deionized water were thoroughly mixed, dried, calcined at 550℃ for 4h, and then subjected to hydrothermal aging treatment under the following conditions: 800℃, 6h, water vapor content 10%, to obtain a modified ZSM-5 molecular sieve. The structure parameters of the modified ZSM-5 molecular sieve are shown in Table 1.

[0166] 3. The kaolin, aluminum sol, modified ZSM-5 molecular sieve, Y molecular sieve and deionized water were mixed according to a certain proportion to make a slurry, the slurry was spray dried into particles with a diameter of 30-120 μm, and the particles were calcined at 550 ℃ for 4 h to obtain a catalyst D1. The catalyst composition is shown in Table 2.

[0167] The XRD spectrum of the molecular sieve product prepared in step 1 is shown in Figure 13 , the product has typical MFI structure characteristic peaks, and the SEM image is shown in Figure 14 , the product has a microcrystalline stacking morphology, and the XRD comparison spectrum of the molecular sieve prepared in step 1 of Example 1 is shown in Figure 17 、 Figure 18 The total specific surface area of the molecular sieve prepared in step 1 was analyzed, and the total specific surface area was 365.7 m 2 / g, wherein the external specific surface area was 103.2 m 2 / g.

[0168] As can be seen from Figure 17 、 Figure 18 , the diffraction peak intensity of the (051) crystal plane of the unmodified ZSM-5 molecular sieve prepared in Example 1 is stronger than that of the (501) crystal plane, and the diffraction peak intensity of the (151) crystal plane is stronger than that of the (303) crystal plane; and the diffraction peak intensity of the (151) crystal plane of the unmodified ZSM-5 molecular sieve prepared in Comparative Example 1 is weaker than that of the (303) crystal plane. It can be seen that the molecular sieve prepared in Comparative Example 1 has the structural characteristics of a short b-axis, which is the typical structure of conventional ZSM-5 molecular sieve; and the unmodified ZSM-5 molecular sieve prepared in Example 1 has the structural characteristics of a long b-axis and a short a-axis, and the exposed acid sites are different from those of conventional ZSM-5 molecular sieve, which can exhibit catalytic performance different from that of conventional molecular sieve.

[0169] By comparing the present comparative example with Example 1, it can be seen that the separate mixing of the seed crystals and the seed assembly agent can pre-assemble the seed crystals, which is beneficial to obtaining the fin-shaped ZSM-5 molecular sieve and promoting the formation of the molecular sieve with a long b-axis and a short a-axis. If the seed assembly agent is added during the preparation of the crystallization gel, it cannot effectively pre-assemble the seed crystals, and cannot effectively change the morphology and structure of the molecular sieve.

[0170] Comparative Example 2

[0171] A commercially available sodium-type ZSM-5 molecular sieve with a silicon-aluminum ratio of 25 was purchased for comparative test, and the XRD spectrum of the molecular sieve is shown in Figure 15 , the product has typical MFI structure characteristic peaks, and the SEM image is shown in Figure 16 , the product has a blocky morphology.

[0172] The sodium type molecular sieve is stirred in 1 mol / L ammonium ion solution at 80°C for 2 hours for ammonium exchange. After several exchanges, the Na2O content of the molecular sieve is less than 0.1% (mass ratio). The molecular sieve solid, 3% (molecular sieve dry basis) ammonium dihydrogen phosphate, and a proper amount of deionized water are thoroughly mixed, dried, calcined at 550°C for 4 hours, and then subjected to hydrothermal aging treatment under the following conditions: 800°C, 6 hours, and 10% water vapor content. The modified ZSM-5 molecular sieve is prepared. The structure parameters of the modified ZSM-5 molecular sieve are shown in Table 1.

[0173] The kaolin, aluminum sol, modified ZSM-5 molecular sieve, Y molecular sieve, and deionized water are mixed according to a certain proportion, and the obtained slurry is spray dried into particles with a diameter of 30-120 μm and calcined at 550°C for 4 hours to obtain catalyst D2. The catalyst composition is shown in Table 2.

[0174] Table 1 shows the average value of the overall particle size and the average value of the thickness of the individual sheet layer of the modified ZSM-5 molecular sieves prepared in the above examples and comparative examples.

[0175] Table 1

[0176] Average sheet thickness (nm) Particle size (nm) Example 1 30 1200 Example 2 20 1500 Example 3 40 1000 Example 4 80 500 Example 5 100 800 Example 6 150 1000

[0177] Table 2 shows the specific composition of the catalysts prepared in the above examples and comparative examples. In Table 2, the mass fraction of the carrier, the mass fraction of the modified ZSM-5 molecular sieve, and the mass fraction of the second molecular sieve refer to the mass fraction of the above three components in the catalyst. The phosphorus content refers to the mass content of phosphorus in the modified ZSM-5 molecular sieve.

[0178] Table 2

[0179]

[0180] Table 3 shows the raw material ratio and morphology of the molecular sieve products prepared in step 1 of the above examples and comparative example 1.

[0181] Table 3

[0182]

[0183] The catalysts obtained in Examples 1 to 6 and Comparative Examples 1 to 2 are applied to the catalytic cracking reaction of n-heptane to evaluate the performance. The reaction conditions are as follows: 550°C, mass space velocity 2.0 h-1, nitrogen carrier gas flow rate 300 mL / h, and the evaluation results are shown in Table 4. In Table 4, BTX refers to light aromatic hydrocarbons including benzene, toluene, and xylene. Triene refers to ethylene, propylene, and butylene. -1

[0184] Table 4

[0185] ​

[0186] From the comparison result can know, the catalyst of the application is applied to the light hydrocarbon catalytic cracking reaction, can improve the conversion rate of n-heptane, the conversion rate can reach above 99%; the catalyst can also improve the selectivity of low carbon olefin, especially the selectivity of propylene, ethylene, light aromatic hydrocarbon.

[0187] Of course, the present application can also have other various embodiments, without departing from the spirit and essence of the present application, those skilled in the art can make various corresponding changes and modifications according to the present application, but these corresponding changes and modifications should all belong to the protection scope of the present application.

Claims

1. A catalytic cracking catalyst, the catalytic cracking catalyst comprising a support and a first molecular sieve; in, The mass ratio of the carrier to the first molecular sieve is 25-80:20-60; The first molecular sieve includes a modified ZSM-5 molecular sieve, and the preparation method of the modified ZSM-5 molecular sieve includes: S1. Mix the seed crystals with the seed crystal assembly agent to obtain a seed crystal mixture; S2. Mix the seed crystal mixture with the alkali source, the first aluminum source, and the first silicon source to obtain a crystallized gel; S3. Perform a first crystallization and a first calcination on the crystallized gel to obtain ZSM-5 molecular sieve; S4. The ZSM-5 molecular sieve is subjected to ammonium exchange and phosphorus exchange in sequence to obtain the modified ZSM-5 molecular sieve; In the X-ray diffraction pattern of the ZSM-5 molecular sieve prepared by S3, the crystal plane corresponding to 2θ=23.18±0.5° is the (501) crystal plane, and the diffraction peak intensity of this 2θ angle is a; The crystal plane corresponding to 2θ = 23.32 ± 0.5° is the (051) crystal plane, and the diffraction peak intensity of this 2θ angle is b; The crystal plane corresponding to 2θ = 23.74 ± 0.5° is the (151) crystal plane, and the diffraction peak intensity of this 2θ angle is c; The crystal plane corresponding to 2θ = 23.99 ± 0.5° is the (303) crystal plane, and the intensity of the diffraction peak at this 2θ angle is d; b≥a, c≥d; The seed assembling agent comprises an organic compound having two amine groups.

2. The catalytic cracking catalyst according to claim 1, wherein, The total specific surface area of ​​the ZSM-5 molecular sieve prepared by S3 is 300 m². 2 / g-500m 2 / g; The ZSM-5 molecular sieve prepared by S3 has an external specific surface area of ​​80 m². 2 / g-220m 2 / g.

3. The catalytic cracking catalyst according to claim 1, wherein, The thickness of a single layer in the modified ZSM-5 molecular sieve is 20nm-200nm, and the particle size of the modified ZSM-5 molecular sieve is 300nm-3μm.

4. The catalytic cracking catalyst according to claim 1, wherein, The seed assembly agent includes one or more of the following: p-phenylenediamine, m-phenylenediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, piperazine, high piperazine, 1,4-diazabicyclo[2.2.2]octane, 1,5-naphthyldiamine, and 2,6-naphthyldiamine.

5. The catalytic cracking catalyst according to claim 1, wherein, The seed crystals include molecular sieves with an MFI crystal structure.

6. The catalytic cracking catalyst according to claim 5, wherein, The grain size of the seed crystal is 10nm-200nm.

7. The catalytic cracking catalyst according to claim 1, wherein, The method for preparing the seed crystals includes: A second silicon source, an organic template agent and water are mixed to obtain a seed precursor, and the seed precursor is subjected to a second crystallization to obtain the seed crystal. Among them, the second silicon source is calculated as SiO2, and the organic template agent is an organic cationic R + The chemical composition of the seed precursor satisfies the following molar ratio range: R + / SiO2 =0.15-0.4, H2O / SiO2 =15-50.

8. The catalytic cracking catalyst according to claim 7, wherein, The second crystallization temperature is 80℃-110℃, and the second crystallization time is 16h-24h.

9. The catalytic cracking catalyst according to claim 7, wherein, The seed precursor further includes a second aluminum source, the second silicon source is calculated as SiO2, and the second aluminum source is calculated as Al2O3. The chemical composition of the seed precursor further satisfies the following molar ratio range: SiO2 / Al2O3≥25.

10. The catalytic cracking catalyst according to claim 1, wherein, In S1, the mixing temperature is 20℃-80℃, and the mixing time is 0.5h-24h.

11. The catalytic cracking catalyst according to claim 10, wherein, In S1, the mixing temperature is 60℃-80℃, and the mixing time is 2h-12h.

12. The catalytic cracking catalyst according to claim 1, wherein, The first silicon source is calculated as SiO2, the first aluminum source as Al2O3, and the seed crystal as the SiO2 it contains. The chemical composition of the crystallized gel satisfies the following molar ratio range: SiO2 / Al2O3 = 25-400, seed crystal / SiO2 = 0.002-0.25, MO / SiO2 = 0.05-0.50, H2O / SiO2 = 15-120, seed crystal assembler / SiO2 = 0.03-0.20; where M is an alkali metal and / or alkaline earth metal.

13. The catalytic cracking catalyst according to claim 12, wherein, The first silicon source is calculated as SiO2, and the seed crystal is calculated as the SiO2 it contains. The chemical composition of the crystallized gel satisfies the following molar ratio range: seed crystal / SiO2 = 0.005-0.

15.

14. The catalytic cracking catalyst according to claim 1, wherein, The first crystallization temperature is 120℃-190℃, and the first crystallization time is 12h-120h.

15. The catalytic cracking catalyst according to claim 14, wherein, The first crystallization temperature is 140-180℃, and the first crystallization time is 12h-96h.

16. The catalytic cracking catalyst according to claim 1, wherein, The mass of phosphorus is expressed as P2O5, and the mass content of phosphorus in the modified ZSM-5 molecular sieve is 0.1%-10%.

17. The catalytic cracking catalyst according to claim 1, wherein, The phosphorus exchange process includes mixing the ammonium exchange product of ZSM-5 molecular sieve with a phosphorus source, followed by calcination and hydrothermal aging treatment.

18. The catalytic cracking catalyst according to claim 17, wherein, The hydrothermal aging treatment is performed at a temperature of 550-800℃ for 1-24 hours, with a water vapor content of 5%-80%.

19. The catalytic cracking catalyst according to any one of claims 1-18, wherein, The catalytic cracking catalyst further includes a second molecular sieve. Based on the total dry mass of the catalytic cracking catalyst as 100%, the mass of the support is 25%-80%, the mass of the first molecular sieve is 20%-60%, and the mass of the second molecular sieve is 0-30%.

20. The catalytic cracking catalyst according to claim 19, wherein, The second molecular sieve includes one or more combinations of molecular sieves having BEA structure, FAU structure, MFI structure, and MWW structure.

21. The catalytic cracking catalyst according to claim 20, wherein, The second molecular sieve includes one or more of β molecular sieve, Y molecular sieve, ZSM-5 molecular sieve, and MCM-49 molecular sieve.

22. The catalytic cracking catalyst according to claim 20, wherein, The molar ratio of silicon dioxide to aluminum oxide in the second molecular sieve is 5-150.

23. The catalytic cracking catalyst according to claim 22, wherein, The molar ratio of silicon dioxide to aluminum oxide in the second molecular sieve is 6-50.

24. The application of the catalytic cracking catalyst according to any one of claims 1-23 in a catalytic cracking process.

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