Start-up catalyst for increasing yield of gasoline and propylene as well as preparation method and application of start-up catalyst

Abstract

The invention relates to a startup catalyst for high yield of gasoline and propylene and a preparation method and application thereof.The catalyst contains a composition A, a composition B and a composition C. On the basis of the dry base weight of the catalyst, the content of the composition A is 20-90%, the content of the composition B is 5-65%, and the content of the composition C is 5-20%. Wherein the main active components of the composition B are a modified small-grain Y-type molecular sieve and a ZSM-5 molecular sieve material, the content of the composition C is 5-15%, and the metal oxide loading capacity of the composition C is 2-10%. The preparation method of the catalyst comprises the step of physically and uniformly mixing the composition A, the composition B and the composition C according to a certain proportion. The catalyst provided by the invention has excellent physical and chemical properties, is used in the start-up stage of an MIP catalytic cracking device, such as shutdown overhaul start-up, new device start-up, poising agent poisoning rapid replacement, and device abnormal running as a supplementary catalyst, and can realize rapid and stable operation of the device.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and relates to a start-up catalyst that produces more gasoline and propylene, its preparation method and application. Background Technology

[0002] Catalytic cracking is an important method for producing gasoline, and it also produces liquefied petroleum gas (LPG). Propylene in LPG is an important chemical feedstock. To maximize both propylene and gasoline production, refiners have developed technologies for producing cleaner gasoline, such as MIP (Mini-Injection Catalytic Cracking Process for Clean Gasoline and Propylene, Xu Youhao et al., *Petroleum Refining and Chemical Engineering*, Vol. 32, No. 8, pp. 1-5). Based on this, a series of MIP technologies have been developed, such as MIP-CGP (A MIP Process for Clean Gasoline and Propylene, developed by Sinopec Research Institute of Petroleum Processing Co., Ltd. based on catalytic cracking technology for producing isoalkanes, a process for producing gasoline that meets Euro III emission standards and increasing propylene production), MIP-LTG, and MIP-DCR (Development and Industrial Application of MIP-DCR Technology, Gong Jianhong et al., *Petroleum Refining and Chemical Engineering*, Vol. 44, No. 3, March 2013, pp. 9-14). Currently, there are approximately 70 MIP-CGP units in China, and several more FCC units will be converted to MIP units in the future. The start-up of new units often cannot use the catalytic cracking catalysts used during normal operation due to their excessively high activity, which can easily cause significant operational fluctuations and often prevent successful start-up. Therefore, existing catalytic cracking units typically start up using the balance agent from normal production. However, using the balance agent often results in insufficient quantities, and new units often lack their own generated balance agent. Using balance agents from other units leads to prolonged start-up times due to poor compatibility. Therefore, new units require start-up agents with high physicochemical compatibility to ensure stable and efficient start-up. Furthermore, during routine operation, if the feedstock suddenly becomes heavier, leading to catalyst poisoning, or if abnormal catalyst runoff occurs, excellent start-up agent resources are needed for rapid replacement or replenishment to ensure stable operation. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a start-up catalyst suitable for the start-up of a unit that produces both gasoline and propylene, and a method for preparing the same catalyst. This catalyst can achieve efficient and stable start-up of a catalytic cracking unit that produces both propylene and gasoline, such as a MIP catalytic cracking unit, during the start-up phase (including shutdown for maintenance, rapid replacement after balancer poisoning, or replenishment of catalyst due to unit malfunction).

[0004] The catalyst contains composition A, composition B, and composition C. Based on the dry weight of the catalyst, the content of composition A is 20-90% by weight, the content of composition B is 5-65% by weight, and the content of composition C is 5-15% by weight. The main active components of composition B include modified small-crystal Y-type molecular sieve and optional ZSM-5 molecular sieve material. The content (or loading) of metal oxide (or modified metal oxide) in composition C is 2-10% by weight.

[0005] The catalyst can be prepared by physically mixing composition A, composition B and composition C in a certain proportion.

[0006] Optionally, in the catalyst, wherein the composition A has a specific surface area ≥ 100 m² 2 / g for example 100-150m 2 / g; Nickel content ≤6000μg / g, for example 200~5500μg / g; Vanadium content ≤5000μg / g, for example 500~3500μg / g; Iron content ≤5000μg / g, for example 500~4700μg / g; Sodium content ≤3000μg / g, for example 200~2000μg / g; Calcium content ≤3000μg / g, for example 200~2000μg / g; Crystallinity of Y-type molecular sieve ≥20.0%, for example 20-30%; Crystallinity of ZSM-5 molecular sieve ≥2.0%, for example 2~10%. The crystallinity is measured according to the NB / SH / T6024-2021 method.

[0007] Optionally, in the catalyst, the composition A has a particle size of 0–20 μm ≤ 3.0 v%, a particle size of 0–40 μm ≤ 18.0 v%, a particle size of 0–149 μm ≥ 90.0 v%, and an average particle size of 60.0–80.0 μm. The particle size refers to the particle diameter.

[0008] For particle size distribution, please refer to NB / SH / T 0951-2017 Determination of Particle Size Distribution of Catalytic Cracking Catalysts by Laser Scattering. The 0–20 μm particle size refers to the cumulative volume fraction of particles with a diameter of 0–20 micrometers; particle sizes of 0–40 μm and 0–149 μm are similarly defined.

[0009] Optionally, the catalyst, wherein the cracking activity of the composition A is 55-65.

[0010] The method for measuring the cracking activity of this invention is in accordance with NB / SH / T 0952-2017, "Microreactor Activity of Catalytic Cracking Catalysts".

[0011] Composition A can be a catalytic cracking equilibrium agent.

[0012] Optionally, in the catalyst, the apparent loose density of composition B is 0.80–0.94 g / mL, and the attrition index is ≤2.0. For apparent loose density measurement, refer to standard: NB / SH / T 0954-2017 Method for Determination of Apparent Loose Density of Catalytic Cracking Catalysts; for attrition index measurement, refer to: NB / SH / T 0964-2017 Determination of Attrition Index of Catalytic Cracking Catalysts - Straight Tube Method.

[0013] Optionally, in the catalyst, the composition B has a particle size of 0–20 μm ≤ 2.0 v%, a particle size of 0–40 μm ≤ 18.0 v%, a particle size of 0–149 μm ≥ 90.0 v%, and an average particle size of 60.0–85.0 μm. v% refers to volume%.

[0014] Optionally, in the catalyst, the active component of composition B is a modified small-crystal Y-type molecular sieve and optionally a ZSM-5 molecular sieve, wherein the content of the active component on a dry basis is 5-15% by weight of composition B; the ZSM-5 molecular sieve is an existing ZSM-5 molecular sieve, for example, it can be one or more of conventional ZSM-5 molecular sieve, hierarchical ZSM-5 molecular sieve, metal-modified hierarchical ZSM-5 molecular sieve, or hollow mesoporous ZSM-5 molecular sieve. The conventional ZSM-5 molecular sieve refers to a conventionally produced ZSM-5 molecular sieve without mesoporous structures, which can be a hydrogen-form ZSM-5 molecular sieve or a phosphorus and / or modified metal-modified ZSM-5 molecular sieve.

[0015] In one embodiment, the modified small-crystal Y-type molecular sieve to ZSM-5 molecular sieve weight ratio, on a dry basis, is greater than 2, for example, 2-100:1 or 2-10:1.

[0016] The modified small-grained Y-type molecular sieve can be commercially available or prepared using existing methods, such as the method disclosed in Chinese Patent 202011180404.5 (CN114433215B), or the method disclosed in any one of claims 2-17 or any one of Examples 1-3. The average grain size of the modified small-grained Y-type molecular sieve is preferably 300-700 nm, calculated using the Scherrer equation via XRD. The modification refers to rare earth modification and gas-phase ultrastable and / or hydrothermal ultrastable modification.

[0017] The modified small-crystal Y-type molecular sieve has a rare earth element content of no more than 20% by weight, calculated as RE2O3, for example, 1-20% by weight or 2-18% by weight.

[0018] In one embodiment, the modified small-grained Y-type molecular sieve has a silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of, for example, 5.1 to 10.

[0019] Optionally, the catalyst, wherein the composition B further comprises a matrix support, the content of which is 85-95% by weight of the composition B, wherein the matrix support is selected from one or more of natural clay, alumina support and silica support; preferably, the alumina support is one or more of alumina sol, acidified boehmite, hydrated alumina and activated alumina; the silica support is one or more of neutral silica sol, acidic silica sol or alkaline silica sol.

[0020] In one embodiment, the composition B comprises 2-15 wt%, for example 2-10 wt%, of modified small-crystal Y-type molecular sieve, 0-5 wt%, for example 1-5 wt%, of ZSM-5 molecular sieve, 65-85 wt%, of clay such as kaolin, 3-10 wt%, of pseudoboehmite, 3-10 wt%, of alumina sol, and 3-10 wt%, of silica sol.

[0021] Optionally, in the catalyst, the content or loading of the metal oxide (referred to as modified metal oxide) in the composition C is 2-10% by weight. The metal oxide may be one or more of magnesium oxide, barium oxide, strontium oxide, and radium oxide.

[0022] Optionally, the catalyst, wherein the composition C can be obtained by modifying inert microspheres with modified metal elements, i.e., by loading metal elements, such as by impregnation with a metal salt solution, or by adding metal elements, such as metal salts, to a catalyst precursor and then spray drying. The modified metal element in the composition C is one or more of Mg, Ba, Sr, and Ra, preferably Mg and / or Ba.

[0023] In one embodiment, composition C comprises: 3-10 wt% boehmite, 3-10 wt% aluminum sol, 3-10 wt% silica sol, 2-10 wt% alkaline earth metal oxide, and 70-89 wt% clay, such as kaolin. The alkaline earth metal is one or more of Mg, Ba, Sr, and Ra, preferably Mg and / or Ba.

[0024] Optionally, according to the catalyst of the present invention, the metal salt used in the preparation of the composition C may be one or more of magnesium nitrate, barium nitrate, strontium nitrate, or radium nitrate.

[0025] Optionally, the apparent loose density of the catalyst is 0.90 to 0.94 g / mL.

[0026] Optionally, the catalyst has a wear index ≤ 2.0. The wear index is measured in %h. -1 .

[0027] Optionally, the catalyst has a specific surface area ≥110 m². 2 / g, for example, is 110-200m 2 / g.

[0028] Optionally, the catalyst has the following characteristics: nickel content ≤ 5000 μg / g, for example 500–4500 μg / g; vanadium content ≤ 4000 μg / g, for example 200–3500 μg / g; iron content ≤ 4000 μg / g, for example 500–4000 μg / g; sodium content ≤ 2000 μg / g, for example 100–1500 μg / g; calcium content ≤ 2000 μg / g, for example 50–1800 μg / g; particle size ≤ 2.0 v% for 0–20 μm; particle size ≤ 18.0 v% for 0–40 μm; particle size ≥ 90.0 v% for 0–149 μm; and average particle size of 65.0–85.0 μm.

[0029] Optionally, the catalyst has the following characteristics: cracking activity of 55-65, coke factor ≤0.125 (e.g., 0.05-0.12), gasoline factor ≥0.430 (e.g., 0.43-0.48), and propylene factor ≥0.420 (e.g., 0.42-0.47). The cracking activity of the catalyst is determined using the method specified in NB / SH / T 0952-2017.

[0030] Measurement methods for coke factor, gasoline factor, and propylene factor: at a reaction temperature of 520℃, a fuel-to-oil ratio of 10 by weight, and a gravity hourly space velocity of 10 h⁻¹. -1 Hydrogenated heavy oil feedstock is evaluated in a fixed fluidized bed unit. Conversion rate = dry gas yield + liquefied petroleum gas (LPG) yield + gasoline yield + coke yield. Coke factor = coke yield / conversion rate, gasoline factor = gasoline yield / conversion rate, propylene factor = propylene yield / LPG yield. Yields are weight yields.

[0031] Optionally, the catalyst, wherein the method of composition B includes: pulping a slurry of a matrix support and modified small-crystal Y-type molecular sieve, ZSM-5 molecular sieve and water, spray drying, and optionally calcining.

[0032] Optionally, the catalyst, wherein the preparation method of composition C is method 1, which includes: pulping and spray drying the matrix support, performing metal modification by impregnation, drying, and calcining.

[0033] Optionally, the catalyst, wherein the preparation method of composition C is method 2, which includes: mixing a matrix support and a metal salt solution evenly into a slurry, spray drying, and optionally calcining.

[0034] Optionally, the catalyst, wherein composition C is a mixture of the compositions obtained by methods 1 and 2 described above.

[0035] Optionally, the catalyst, wherein the preparation method of component B and / or composition C further includes: mixing catalyst particles obtained by spray drying, ammonium salt and water in a weight ratio of 1:(0.1-1):(5-15) for ammonium exchange, and optionally washing, so that the Na2O content in composition B and composition C is less than 0.15% by weight respectively; the ammonium exchange conditions 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.

[0036] Optionally, the catalyst is obtained by physically blending composition A, composition B and composition C in a certain proportion.

[0037] The catalyst is used in catalytic cracking units that produce propylene and gasoline, such as MIP series technology units, especially MIP-CGP catalytic cracking units. The application includes: unit modification and start-up, rapid replacement after balancer poisoning, or catalyst replenishment when the unit is experiencing abnormal catalyst loss. It can achieve efficient and stable start-up or rapid replacement of balancer and rapid replenishment of catalyst.

[0038] The catalyst of this invention can be used for the start-up of units producing large quantities of gasoline and propylene, such as in the start-up phase of MIP series technology units, especially MIP-CGP catalytic cracking units. This includes, but is not limited to, start-up after unit shutdown for maintenance, start-up of new units, rapid replacement after balancer poisoning, or replenishment of catalyst in case of abnormal catalyst runoff. It enables efficient and stable start-up of the unit, allowing it to operate quickly and smoothly. For example, existing MIP units, such as MIP-CGP catalytic cracking units, often require one month or longer to achieve stable operation and reach design goals during start-up using balancers. In contrast, the catalyst of this invention can achieve stable operation and reach design goals within one week.

[0039] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0040] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0041] The kaolin used in the examples and comparative examples was a product of Suzhou China Kaolin Co., Ltd., with a solid content of 76% by weight.

[0042] Aluminum sol, a product of Sinopec Catalyst Co., Ltd. Qilu Branch, with an Al2O3 content of 21.5% by weight.

[0043] The silica sol is a product of Qingdao Junqiang New Materials Co., Ltd., with a SiO2 content of 30% by weight and a pH value of 9.5.

[0044] Boehmite, a product of Shandong Aluminum Company, with an Al2O3 content of 62% by weight.

[0045] Modified small-crystal Y-type molecular sieve, with an average grain size of 500 nm, sourced from Qilu Branch of Sinopec Catalyst Co., Ltd., has a silicon-to-aluminum ratio (SiO2 / Al2O3 molar ratio) of 5.2, and is modified with lanthanum at a content of 12% by weight.

[0046] Example 1

[0047] (1) Composition A comes from the balance agent (or waste agent) of the catalytic cracking unit. The balance agent is subjected to physical fractionation to achieve a certain particle size requirement; and then subjected to chemical demetallization to achieve a certain metal content. The physical properties are shown in Table 1.

[0048] (2) Composition B:

[0049] Boehmite and water were mixed evenly, and concentrated hydrochloric acid with a concentration of 36 wt% was added under stirring. The acid-to-alumina ratio was 0.2 (the weight ratio of 36 wt% hydrochloric acid to boehmite calculated as Al2O3). The resulting mixture was aged at 70°C for 1.5 hours to obtain an aged boehmite slurry. The alumina content of this aged boehmite slurry was 12 wt%. Modified small-grained Y-type molecular sieves (average grain size 500 nm, source: Qilu Branch of Sinopec Catalyst Co., Ltd., SiO2 / Al2O3 molar ratio of 5.2, lanthanum as the modifying element, content of 12 wt%), ZRP-1 molecular sieves (P2O5 content 6.0 wt%, SiO2 / Al2O3 molar ratio of 25, Qilu Branch of Sinopec Catalyst Co., Ltd.), and alumina sol were used. The silica sol, kaolin, and the above-mentioned aged pseudoboehmite slurry, along with deionized water, are mixed evenly to form a slurry with a solid content of 30% by weight. The slurry is then spray-dried to obtain microspheres of composition B. The microspheres of composition B are calcined at 550°C for 4 hours. The calcined microspheres of composition B are then exchanged at 80°C for 1 hour according to the weight ratio of composition B: ammonium salt: H2O = 1:1:10. The mixture is then filtered, and the exchange and filtration process is repeated once. The microspheres are then dried. The ammonium salt is ammonium chloride, and the sodium oxide content in the obtained composition B is less than 0.15% by weight.

[0050] (3) Composition C:

[0051] Boehmite and water were mixed evenly, and concentrated hydrochloric acid with a concentration of 36% by weight was added under stirring. The acid-to-aluminum ratio was 0.2 (the weight ratio of 36% by weight concentrated hydrochloric acid to boehmite calculated as Al2O3). The resulting mixture was aged at 70°C for 1.5 hours to obtain an aged boehmite slurry. The alumina content of this aged boehmite slurry was 12% by weight. Aluminum sol, silica sol, kaolin, the above-mentioned aged boehmite slurry, and deionized water were mixed evenly to form a slurry with a solid content of 30% by weight. The mixture was spray-dried and calcined at 550°C for 4 hours.

[0052] A magnesium nitrate solution was prepared by dissolving 18.4 g of magnesium nitrate in 50 g of deionized water. Spray-dried microspheres were impregnated with the prepared magnesium nitrate solution at 50°C for 2 hours, followed by direct drying and calcination to obtain composition C.

[0053] (4) Mix composition A, composition B and composition C in a certain proportion to obtain the catalyst of Example 1.

[0054] Example 2

[0055] (1) Composition A is a balance agent from a catalytic cracking unit. After physical fractionation, it reaches a certain particle size requirement. After chemical demetallization, it reaches a certain metal content. The physical properties are shown in Table 1.

[0056] (2) Composition B:

[0057] Boehmite and water were mixed evenly, and concentrated hydrochloric acid with a concentration of 36 wt% was added under stirring. The acid-to-alumina ratio was 0.2 (the weight ratio of 36 wt% concentrated hydrochloric acid to boehmite calculated as Al2O3). The resulting mixture was aged at 70°C for 1.5 hours to obtain an aged boehmite slurry. The alumina content of this aged boehmite slurry was 12 wt%. Modified small-grained Y-type molecular sieves (average grain size 500 nm, source: Qilu Branch of Sinopec Catalyst Co., Ltd., SiO2 / Al2O3 molar ratio 5.2, lanthanum as the modifying element, content 12 wt%) and RMPZ molecular sieves (rare earth content 2.5 wt% calculated as RE2O3, P2O5 content 6.0 wt%, SiO2 / Al2O3 molar ratio 25, pore distribution at 10 nm with the highest concentration of rare earth elements) were used. The microspheres of the catalyst were mixed evenly with aluminum sol, silica sol, kaolin, and the aged pseudoboehmite slurry and deionized water to form a slurry with a solid content of 30% by weight. The mixture was spray-dried to obtain composition B. The microspheres of composition B were calcined at 550°C for 4 hours. The calcined catalyst microspheres were exchanged at 80°C for 1 hour according to the weight ratio of composition B: ammonium salt: H2O = 1:1:10. The mixture was filtered, and the exchange and filtration process was repeated once. The mixture was then dried. The ammonium salt was ammonium chloride. The sodium oxide content in the obtained composition B was less than 0.15% by weight.

[0058] (3) Composition C:

[0059] Boehmite and water were mixed evenly, and concentrated hydrochloric acid with a concentration of 36% by weight was added under stirring. The acid-to-alumina ratio was 0.2 (the weight ratio of hydrochloric acid (36% by weight) to boehmite calculated as Al2O3). The resulting mixture was aged at 70°C for 1.5 hours to obtain an aged boehmite slurry. The alumina content of this aged boehmite slurry was 12% by weight. Barium nitrate solution (10.2 g of barium nitrate dissolved in 50 g of deionized water), alumina sol, silica sol, kaolin, the above-mentioned aged boehmite slurry, and deionized water were mixed evenly to form a slurry with a solid content of 30% by weight. The mixture was spray-dried and calcined at 550°C for 4 hours to obtain composition C.

[0060] (4) Mix composition A, composition B and composition C in a certain proportion to obtain the catalyst of Example 2.

[0061] Example 3

[0062] In Example 1, composition B did not contain ZSM-5 molecular sieve, and its physical properties are shown in Table 1.

[0063] Comparative Example 1

[0064] Composition A in Comparative Example 1 was derived from the balance agent of a catalytic cracking unit, and its physical properties are shown in Table 1.

[0065] Table 1. Parameters for Examples and Comparative Examples

[0066]

[0067]

[0068] In compositions B and C, the contents of small-crystal Y-type molecular sieves are calculated on a dry basis, the contents of ZSM-5 molecular sieves are calculated on a dry basis, the contents of boehmite are calculated as Al2O3, the contents of alumina sol are calculated as Al2O3, the contents of silica sol are calculated as SiO2, the contents of kaolin are calculated on a dry basis, and the contents of alkaline earth metals are calculated as oxides.

[0069] Performance testing

[0070] The catalytic cracking catalysts prepared in the examples and comparative examples were evaluated for their cracking reaction performance in a fixed fluidized bed reactor. The evaluation conditions were: reaction temperature 520°C, catalyst-to-oil ratio 10, and space velocity 10 h⁻¹. -1 The feedstock was hydrotreated heavy oil, and the physical properties are shown in Table 2. The evaluation results are shown in Table 3.

[0071] Table 2 Properties of Heavy Oil

[0072]

[0073] Table 3. Catalytic performance evaluation results

[0074] Example 1 Example 2 Comparative Example 1 Example 3 Cracking activity 60.3 60.7 51.0 61.7 Reactivity Coke factor 0.114 0.118 0.147 0.117 gasoline factor 0.467 0.463 0.415 0.469 Propylene factor 0.450 0.446 0.398 0.442

[0075] The yield mentioned above is calculated based on the raw material feed.

[0076] Product yield = Product output (by weight) / Heavy oil feed rate (by weight) × 100%

[0077] Coke factor = Coke yield (by weight) / Conversion rate

[0078] Gasoline factor = Gasoline yield (by weight) / Conversion rate

[0079] Propylene factor = Propylene yield (by weight) / LPG yield

[0080] As shown in Table 3, the catalyst provided by this invention has higher gasoline and propylene factors, thus achieving the technical goal of producing more gasoline and propylene.

Claims

1. A catalyst comprising composition A, composition B, and composition C, wherein, based on the dry weight of the catalyst, the content of composition A is 20-90%, the content of composition B is 5-65%, and the content of composition C is 5-15%, wherein, The main active components of composition B include modified small-crystal Y-type molecular sieve and optional ZSM-5 molecular sieve. Composition C contains a support and a metal oxide, wherein the content of the metal oxide in composition C is 2-10% by weight.

2. The catalyst according to claim 1, wherein, The composition A is a catalytic cracking catalyst, and the specific surface area of ​​composition A is ≥100 m². 2 / g; Nickel content ≤6000μg / g, Vanadium content ≤5000μg / g, Iron content ≤5000μg / g, Sodium content ≤3000μg / g, Calcium content ≤3000μg / g, Y-type molecular sieve crystallinity ≥20.0%, ZSM-5 molecular sieve crystallinity ≥2.0%. The composition A has the following particle sizes: 0-20 μm particles ≤3.0 v, 0-40 μm particles ≤18.0 v, 0-149 μm particles ≥90.0 v, and average particle size 60.0-80.0 μm.

3. The catalyst according to claim 1 or 2, wherein, The cracking activity of composition A is 55-65; Preferably, the apparent bulk density of composition B is 0.8–0.94 g / mL, and the abrasion index is ≤2.0; The composition B has the following particle sizes: 0-20 μm particles ≤ 2.0 v, 0-40 μm particles ≤ 18.0 v, 0-149 μm particles ≥ 90.0 v, and average particle size 60.0-85.0 μm.

4. The catalyst according to claim 1, wherein, The composition B further includes a matrix carrier and an active component. Based on the dry weight of composition B, the matrix carrier comprises 85-95% by weight of composition B on a dry basis, and the active component comprises 5-15% by weight of composition B on a dry basis. The active component of composition B is a modified small-crystal Y-type molecular sieve and optionally a ZSM-5 molecular sieve. The ZSM-5 molecular sieve may be, for example, a conventional ZSM-5 molecular sieve, a hierarchical ZSM-5 molecular sieve, a metal-modified hierarchical ZSM-5 molecular sieve, or a hollow mesoporous ZSM-5 molecular sieve. Optionally, the weight ratio of Y molecular sieve to ZSM-5 molecular sieve is greater than 2; Optionally, the average grain size of the modified small-grained Y-type molecular sieve is 300-700 nm; the rare earth content of the modified small-grained Y-type molecular sieve can be 1-20% by weight; and the silicon-to-aluminum ratio, calculated as the SiO2 / Al2O3 molar ratio, is, for example, 5.1-10. The matrix carrier is selected from one or more of natural clay, alumina carrier, and silica carrier; preferably, The alumina carrier is one or more of alumina sol, acidified boehmite, hydrated alumina, and activated alumina; the silica carrier is one or more of neutral silica sol, acidic silica sol, or alkaline silica sol.

5. The catalyst according to claim 1, wherein, The metal oxide loading of composition C is 2-10% by weight, and the metal oxide of composition C can be one or more of magnesium oxide, barium oxide, strontium oxide, and radium oxide.

6. The catalyst according to claim 1, wherein, The composition C can be obtained by modifying inert microspheres with metal elements, or by adding metal elements to a catalyst precursor and then spray drying. For example, composition C is prepared by any one or more of the following methods: Method 1, which includes: pulping and spray drying the matrix carrier, impregnating it with a metal salt solution for metal modification, drying and calcining; Method 2, which includes: mixing a matrix carrier and a metal salt solution evenly into a slurry, spray drying, and optionally calcining, wherein the metal salt may be one or more of magnesium nitrate, barium nitrate, strontium nitrate, or radium nitrate.

7. The catalyst according to claim 1, wherein, The catalyst has an apparent bulk density of 0.90–0.94 g / mL and a wear index of ≤2.

0. The catalyst has the following characteristics: nickel content ≤ 5000 μg / g, vanadium content ≤ 4000 μg / g, iron content ≤ 4000 μg / g, sodium content ≤ 2000 μg / g, and calcium content ≤ 2000 μg / g. The particle size distribution of the catalyst is as follows: particles with a size of 0–20 μm ≤ 2.0 v, particles with a size of 0–40 μm ≤ 18.0 v, particles with a size of 0–149 μm ≥ 90.0 v, and an average particle size of 65.0–85.0 μm; Preferably, the catalyst has a cracking activity of 55-65, a coke factor ≤0.125 (e.g., 0.05-0.12), a gasoline factor ≥0.430 (e.g., 0.43-0.48), and a propylene factor ≥0.420 (e.g., 0.42-0.47).

8. The catalyst according to any one of claims 1 to 7, wherein, The preparation method of the composition B includes: pulping a slurry comprising a matrix support, a small-crystal Y-type molecular sieve and a ZSM-5 molecular sieve and water, spray drying, and optionally calcining; Optionally, the preparation method of composition B and / or composition C further includes: mixing ingredients in a weight ratio of 1:(0.1-1): (5-15) The catalyst particles obtained by spray drying, ammonium salt and water are mixed for ammonium exchange, and optionally washed, so that the Na2O content in composition B and composition C is less than 0.15% by weight respectively; the ammonium exchange conditions include: temperature of 50-100°C and time of 0.5-2 hours; the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.

9. The catalyst according to claim 1, wherein, The catalyst is prepared by physically mixing composition A, composition B and composition C in a certain proportion.

10. The use of the catalyst according to any one of claims 1 to 9 in a catalytic cracking unit for producing propylene and gasoline, said unit being, for example, a MIP catalytic cracking unit, said use comprising, for example: Catalyst replenishment is required when starting a new plant after renovation, when rapidly replacing the balancer after poisoning, or when the plant experiences abnormal catalyst runoff.

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