A propylene yield increasing catalytic cracking aid, its preparation method and application

Abstract

The application provides a propylene yield increasing catalytic cracking additive and a preparation method and application thereof, and the main active component of the propylene yield increasing catalytic cracking additive is ZSM-5 molecular sieve; the pore volume of the propylene yield increasing catalytic cracking additive is greater than 0.2 cm 3 / g; the pore size is in a multimodal distribution, and at least one most probable pore size is between 3-10 nm. The preparation method of the propylene yield increasing catalytic cracking additive is a multi-stage pore treatment on a catalytic cracking additive matrix. The propylene yield increasing catalytic cracking additive is mesoporous, the preparation method is simple, the diffusion resistance to diesel is small, the cracking capacity is strong, and the propylene yield increasing catalytic cracking additive can increase the yield of low carbon olefins, especially the yield of propylene, when used in a process for preparing low carbon olefins from catalytic cracking of petroleum products containing diesel and / or gasoline.

Description

Technical Field

[0001] This invention belongs to the field of petrochemicals, specifically a catalytic cracking additive for increasing propylene production, its preparation method, and its application. Background Technology

[0002] With the continuous development of the oil refining and petrochemical industries, the demand structure for petrochemical products has undergone significant changes. Gasoline and diesel are in surplus, while the demand for low-carbon olefins, primarily ethylene and propylene, and high-quality gasoline is increasing daily. Propylene is one of the important chemical raw materials, traditionally obtained through steam cracking. However, with the robust market demand, catalytic cracking technology for producing more propylene has become an important development direction and has experienced rapid growth in recent years.

[0003] In addition to cracking catalysts, catalytic cracking processes also employ various auxiliary catalytic cracking promoters. These promoters, when added to the cracking catalyst, can improve the octane number of gasoline, increase the yield of liquefied petroleum gas (LPG) and its propylene concentration, promote the conversion of CO to CO2, passivate the toxicity of heavy metal impurities in the feedstock to the catalyst activity, or reduce SO2 levels in the regenerated flue gas. x The content and other functions of propylene are discussed. Among these, increasing propylene production by adding catalytic cracking additives during catalytic cracking is widely used due to its advantages of simple operation, flexible reaction, and minimal impact on the overall process. Currently, using catalysts or additives containing zeolites with MFI structures is an effective method for increasing propylene production. A typical example of an MFI-structured zeolite is ZSM-5 zeolite. The basic reaction mechanism of MFI-structured zeolites is the selective cracking of C6-C12 alkanes and olefins in gasoline fractions to generate C3-C5 olefins, thereby increasing the yield of low-carbon olefins and simultaneously increasing the octane number of gasoline.

[0004] Generally speaking, catalytic cracking additives with high activity have a strong ability to increase propylene production; the higher the concentration of the additive in the catalyst, the higher the propylene yield. However, when the additive concentration reaches a certain level, the propylene yield will actually decrease. To improve the activity of catalytic cracking additives, those skilled in the art have proposed many effective methods through research. For example, patent application CN114453008A discloses a catalytic cracking additive for increasing the propylene concentration in liquefied petroleum gas and its application. It uses a modified sol prepared from Al2O3, IVB metal oxides, and P2O5 to modify ZSM-5 zeolite, resulting in a ZSM-5 zeolite-containing additive. This gives ZSM-5 zeolite higher activity and heavy oil cracking capability, exhibiting excellent propylene yield and propylene selectivity.

[0005] However, ZSM-5 molecular sieves have narrow pores (around 0.5 nm). Due to this pore size limitation, larger reactant molecules have difficulty entering the pores for reaction, resulting in low utilization of the catalytic cracking additive. Current catalytic cracking additives can only crack a portion of gasoline or liquefied petroleum gas into propylene, while the diesel components produced during catalytic cracking are too large to enter the additive, preventing diesel from being cracked. Furthermore, because of the narrow pores, some product molecules cannot diffuse out, easily leading to deep dehydrogenation and coking, which accelerates molecular sieve deactivation, resulting in a short lifespan and rapid activity reduction. Recent research on catalytic cracking additives has also disclosed methods to enrich the mesoporous and macroporous structures within the additives.

[0006] For example, patent application CN112387302A discloses a catalytic cracking additive, its preparation method and application, and a method for catalytic cracking of hydrocarbon oils. A certain amount of one-dimensional through-pore mesoporous silica material is mixed with and modified with high-silica ZSM-5 hydrogen-type zeolite molecular sieve. It is used as the main component of the catalytic cracking additive in the catalytic cracking reaction, which can effectively increase the propylene concentration in the cracking product liquefied gas and increase the octane number of gasoline products.

[0007] For example, patent application CN111939971A discloses a method for preparing a propylene-enhancing catalytic cracking additive. This method involves exchanging ZSM-5 molecular sieve with hydrochloric acid, and then calcining the exchange product at 550–650°C with steam to obtain HZSM-5 molecular sieve. The HZSM-5 molecular sieve is then modified with a mixture of two or more elements from rare earth, phosphorus, magnesium, and zinc to obtain the propylene-enhancing catalytic cracking additive. This patent uses mixed components as the main raw material in the preparation process. The added additives interact with the mixed components, effectively regulating the pore structure of the additive and enriching its internal mesoporous and macroporous structure, especially the proportion of macropores, which prevents pore accumulation.

[0008] However, the above modifications to catalytic cracking additives to achieve hierarchical porosity all involve first modifying ZSM-5 molecular sieves to achieve hierarchical porosity, and then mixing the molecular sieve with a matrix and binder to form the catalytic cracking additive, or adding modifiers during the additive forming process to achieve hierarchical porosity. In other words, the modification of the molecular sieve channels is performed before the additive is formed. During the forming process, the matrix and binder can block some of the original channels, resulting in poor channel connectivity in the obtained catalytic cracking additive, failing to reduce the diffusion resistance of macromolecules. Furthermore, existing catalytic cracking additives that achieve high propylene production enhancement are costly and complex to prepare. Moreover, during catalytic cracking, they primarily enhance propylene production by promoting the conversion of gasoline to propylene, offering little to no cracking promotion effect for diesel and heavy oil. Diesel consumption peaked in 2016, yet there is still no effective method to solve the difficulty of converting diesel to propylene. Therefore, there is an urgent need for further research and development of novel catalytic cracking additives that can promote the conversion and utilization of diesel. Summary of the Invention

[0009] In view of the shortcomings of the prior art, the purpose of this invention is to provide a propylene-enhancing catalytic cracking additive, its preparation method and application. This propylene-enhancing catalytic cracking additive has many mesopores and a simple preparation method. It has low diffusion resistance to diesel and strong cracking ability. When used for catalytic cracking of petroleum products containing diesel and / or gasoline, it can increase the yield of low-carbon olefins, especially the yield of propylene.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] In a first aspect, the present invention provides a propylene-enhancing catalytic cracking additive, wherein the main active ingredient of the propylene-enhancing catalytic cracking additive is ZSM-5 molecular sieve.

[0012] According to the propylene-enhancing catalytic cracking additive of the present invention, the pore volume of the propylene-enhancing catalytic cracking additive has a pore size of 3-20 nm and is greater than 0.2 cm³. 3 / g; the pore size has a multi-peak distribution and has at least one most probable pore size between 3-10nm, preferably at least one most probable pore size between 4-10nm, more preferably a first most probable pore size between 4-6nm, and a second most probable pore size between 6-9nm.

[0013] In some embodiments of the present invention, the pore volume of the propylene-enhancing catalytic cracking additive has a pore size of 3-20 nm and a pore volume ranging from 0.2-0.4 cm³. 3 Between / g; preferably, the pore volume is greater than 0.25cm³ with a pore size of 4-6nm. 3 / g; more preferably, the pore volume of a pore size of 4-8 nm is greater than 0.25 cm³.3 / g.

[0014] According to the propylene-enhancing catalytic cracking additive of the present invention, the propylene-enhancing catalytic cracking additive is obtained by modifying the catalytic cracking additive matrix by desilication, dealuminization, or dealuminization-silicon replenishment to make it multi-level porous.

[0015] According to the propylene catalytic cracking additive provided by the present invention, the modifier used in the desilication method is selected from one or more of sodium hydroxide, potassium hydroxide and calcium hydroxide.

[0016] According to the propylene catalytic cracking additive provided by the present invention, the modifier used in the dealumination process is selected from one or more of citric acid, hydrochloric acid and nitric acid.

[0017] According to the propylene catalytic cracking additive provided by the present invention, the modifier used in the dealumination and silicon replenishment method is ammonium hexafluorosilicate.

[0018] The modification involves impregnating the catalytic cracking aid matrix with a modifier solution, followed by filtration, drying, and calcination.

[0019] In some embodiments of the present invention, the concentration of the modifier solution is 0.1-1 mol / L; more preferably, the concentration of the modifier is 0.1-0.8 mol / L, for example 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, or 0.8 mol / L.

[0020] In some embodiments of the present invention, the impregnation conditions are: a solid-liquid ratio of 1:5-1:10 (mass ratio), an impregnation temperature of 50-100°C, and an impregnation time of 3-12 hours. More preferably, the impregnation conditions are: a solid-liquid ratio of 1:6-1:8, an impregnation temperature of 60-80°C, and an impregnation time of 6-10 hours.

[0021] In some embodiments of the present invention, the drying temperature is 100-140℃, for example 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃; the drying time is 10-14h, for example 10h, 11h, 12h, 13h, 14h; preferably, the drying temperature is 120℃ and the drying time is 12h.

[0022] In some embodiments of the present invention, the calcination temperature is 450-550℃, for example 450℃, 480℃, 500℃, 520℃, 550℃; the calcination time is 4-8h, for example 4h, 5h, 6h, 7h, 8h; preferably, the calcination temperature is 500℃ and the calcination time is 6h.

[0023] Secondly, the present invention provides a method for preparing a propylene-enhancing catalytic cracking additive, which involves multi-level pore treatment of the catalytic cracking additive matrix.

[0024] The multi-level pore treatment involves impregnating the catalytic cracking aid matrix in a modifier solution for modification, followed by filtration, drying, and calcination to obtain a multi-level pore propylene-enhancing catalytic cracking aid.

[0025] In some embodiments of the present invention, the concentration of the modifier solution is 0.1-1 mol / L; more preferably, the concentration of the modifier is 0.1-0.8 mol / L, for example 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, or 0.8 mol / L.

[0026] In some embodiments of the present invention, the impregnation conditions are: a solid-liquid ratio of 1:5 to 1:10, an impregnation temperature of 50 to 100°C, and an impregnation time of 3 to 12 hours. More preferably, the impregnation conditions are: a solid-liquid ratio of 1:6 to 1:8, an impregnation temperature of 60 to 80°C, and an impregnation time of 6 to 10 hours.

[0027] In some embodiments of the present invention, the drying temperature is 100-140℃, for example 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃; the drying time is 10-14h, for example 10h, 11h, 12h, 13h, 14h; preferably, the drying temperature is 120℃ and the drying time is 12h.

[0028] In some embodiments of the present invention, the calcination temperature is 450-550℃, for example 450℃, 480℃, 500℃, 520℃, 550℃; the calcination time is 4-8h, for example 4h, 5h, 6h, 7h, 8h; preferably, the calcination temperature is 500℃ and the calcination time is 6h.

[0029] According to the preparation method of the propylene-enhancing catalytic cracking additive provided by the present invention, the multi-stage pore treatment method is selected from any one of the desilication method, the dealumination method, or the dealumination-silication replenishment method.

[0030] The modifier used in the desilication method is selected from one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0031] The modifier for the dealumination process is selected from one or more of citric acid, hydrochloric acid, and nitric acid.

[0032] The modifier for the dealumination and silicon replenishment method is ammonium hexafluorosilicate.

[0033] The catalytic cracking additive matrix mentioned above is a commercially available catalytic cracking additive with propylene production enhancement effect or a catalytic cracking additive prepared by existing publicly disclosed catalytic cracking additive preparation methods, such as catalytic cracking additives prepared by any of the methods described in CN 103254925 B, CN102049284 B, CN 104549445 B, CN 102794194 B, etc.

[0034] Thirdly, the present invention provides the application of the propylene-enhancing catalytic cracking additive of the first aspect or the propylene-enhancing catalytic cracking additive prepared by the preparation method of the second aspect in the catalytic cracking of petroleum products containing diesel and / or gasoline.

[0035] The application involves adding a propylene-enhancing catalytic cracking aid from the first aspect or a propylene-enhancing catalytic cracking aid prepared by the second aspect method to the catalytic cracking catalyst at an addition amount of 3-12 wt% during the process of producing low-carbon olefins from diesel and / or gasoline; preferably, the low-carbon olefin is propylene.

[0036] The beneficial effects of this invention are as follows:

[0037] This invention provides a propylene-enhancing catalytic cracking additive with ZSM-5 molecular sieve as the main active ingredient. This propylene-enhancing catalytic cracking additive has many mesopores, low diffusion resistance to diesel fuel, and strong cracking ability. When used in the catalytic cracking of petroleum products containing diesel fuel and / or gasoline to prepare low-carbon olefins, it can increase the yield of low-carbon olefins, especially the yield of propylene.

[0038] This invention utilizes desilication, dealumination, or dealumination-silicon replenishment methods to modify the catalytic cracking additive matrix, resulting in multi-level porosification and thus a propylene-enhancing catalytic cracking additive. The preparation method is simple and flexible, allowing for the rapid production of propylene-enhancing catalytic cracking additives with specific pore size distributions and pore volume ranges, leading to better social and economic benefits. Compared to existing technologies that modify molecular sieves for multi-level pore formation before additive molding, this effectively avoids the problem of reduced macromolecular diffusion resistance caused by blockage or damage to existing pores during molding. Moreover, the method of this invention can be used to post-modify catalytic cracking additives containing matrix, molecular sieve and binder components after molding. The modifier acts not only on the molecular sieve in the catalytic cracking additive but also on the matrix and binder parts of the catalytic cracking additive, making the distribution of intermediate pores in the modified catalytic cracking additive more uniform and enabling the newly formed pores to communicate with the original pores. This results in better pore connectivity in the entire structural system. The multi-level pore system formed by the post-modification method of this invention reduces the diffusion resistance of diesel components in the additive pores, thereby increasing the diesel cracking capacity and increasing the yield of low-carbon olefins while reducing diesel production. Attached Figure Description

[0039] Figure 1 The results show the pore size analysis of the catalytic cracking additive matrix and the propylene-enhancing catalytic cracking additive of this invention. Detailed Implementation

[0040] The following examples further illustrate the technology of the present invention. These examples are illustrative and exemplary of the present invention and do not limit the scope of the invention in any way.

[0041] Example 1

[0042] I. Preparation of Catalytic Cracking Additive Matrix

[0043] (1) Mix 4.39 kg of pseudoboehmite (containing 3 kg of Al2O3) with 5.4 kg of decationized water for 30 min. Add 10.3 kg of 85% concentrated phosphoric acid to the slurry while stirring, then add 5.28 kg of 68% concentrated nitric acid and continue stirring for 45 min to obtain colorless and transparent aluminum phosphate sol.

[0044] (2) Add 1.18 kg of water to 1.05 kg (dry basis) ZSM-5 (SiO2 / Al2O3=50) molecular sieve, homogenize with a shearing machine, then add 65.5 mL of La(NO3)3 solution (La2O3 is 103.13 g / L), stir for 2 h to prepare molecular sieve slurry.

[0045] (3) Under stirring, 1775g of kaolin and 2170mL of water were mixed and slurried for 30min. 1.5kg of aluminum phosphate sol was added to the kaolin slurry, and stirring was continued for 1h. Then, ZSM-5 molecular sieve slurry was added, and stirring was continued for 2h. The solid content of the resulting slurry was 38wt%. After homogenization, the slurry was spray-molded to obtain a catalytic cracking propylene additive containing 35wt% ZSM-5 molecular sieve.

[0046] II. Preparation of Propylene Catalytic Cracking Additives (Desilication Method)

[0047] (1) The catalytic cracking additive matrix obtained above was impregnated and modified in a sodium hydroxide solution with a concentration of 0.1 mol / L. The impregnation conditions were: solid-liquid ratio of 1:5, impregnation temperature of 50℃, and impregnation time of 3h.

[0048] (2) After impregnation, solid-liquid separation is carried out, and the solid part is dried and calcined. The drying temperature is 120℃ and the drying time is 12h. The calcination temperature is 500℃ and the calcination time is 6h.

[0049] Example 2

[0050] I. Preparation of Catalytic Cracking Additive Matrix

[0051] (1) Mix 4.39 kg of pseudoboehmite (containing 3 kg of Al2O3) with 5.4 kg of decationized water for 30 min. Add 10.3 kg of 85% concentrated phosphoric acid to the slurry while stirring, then add 5.28 kg of 68% concentrated nitric acid and continue stirring for 45 min to obtain colorless and transparent aluminum phosphate sol.

[0052] (2) Add 1.18 kg of water to 1.05 kg (dry basis) ZSM-5 (SiO2 / Al2O3=50) molecular sieve, homogenize with a shearing machine, then add 65.5 mL of La(NO3)3 solution (La2O3 is 103.13 g / L), stir for 2 h to prepare molecular sieve slurry.

[0053] (3) Under stirring, 1775g of kaolin and 2170mL of water were mixed and slurried for 30min. 1.5kg of aluminum phosphate sol was added to the kaolin slurry, and stirring was continued for 1h. Then, ZSM-5 molecular sieve slurry was added, and stirring was continued for 2h. The solid content of the resulting slurry was 38wt%. After homogenization, the slurry was spray-molded to obtain a catalytic cracking propylene additive containing 35wt% ZSM-5 molecular sieve.

[0054] II. Preparation of Propylene Catalytic Cracking Additives (Desilication Method)

[0055] (1) The catalytic cracking additive matrix obtained above was impregnated and modified in a sodium hydroxide solution with a concentration of 0.1 mol / L. The impregnation conditions were: solid-liquid ratio of 1:5, impregnation temperature of 50℃, and impregnation time of 3h.

[0056] (2) After impregnation, solid-liquid separation is carried out, and the solid part is dried and calcined. The drying temperature is 120℃ and the drying time is 12h. The calcination temperature is 500℃ and the calcination time is 6h.

[0057] Example 3

[0058] I. Preparation of Catalytic Cracking Additive Matrix

[0059] (1) Mix 4.39 kg of pseudoboehmite (containing 3 kg of Al2O3) with 5.4 kg of decationized water for 30 min. Add 10.3 kg of 85% concentrated phosphoric acid to the slurry while stirring, then add 5.28 kg of 68% concentrated nitric acid and continue stirring for 45 min to obtain colorless and transparent aluminum phosphate sol.

[0060] (2) Add 1.18 kg of water to 1.05 kg (dry basis) ZSM-5 (SiO2 / Al2O3=50) molecular sieve, homogenize with a shearing machine, then add 65.5 mL of La(NO3)3 solution (La2O3 is 103.13 g / L), stir for 2 h to prepare molecular sieve slurry.

[0061] (3) Under stirring, 1775g of kaolin and 2170mL of water were mixed and slurried for 30min. 1.5kg of aluminum phosphate sol was added to the kaolin slurry, and stirring was continued for 1h. Then, ZSM-5 molecular sieve slurry was added, and stirring was continued for 2h. The solid content of the resulting slurry was 38wt%. After homogenization, the slurry was spray-molded to obtain a catalytic cracking propylene additive containing 35wt% ZSM-5 molecular sieve.

[0062] II. Preparation of Propylene Catalytic Cracking Additives (Dealuminate Method)

[0063] (1) The catalytic cracking additive matrix obtained above was impregnated and modified in a citric acid solution with a concentration of 0.5 mol / L. The impregnation conditions were: solid-liquid ratio of 1:10, impregnation temperature of 100℃, and impregnation time of 10h.

[0064] (2) After impregnation, solid-liquid separation is carried out, and the solid part is dried and calcined. The drying temperature is 120℃ and the drying time is 12h. The calcination temperature is 500℃ and the calcination time is 6h.

[0065] Example 4

[0066] I. Preparation of Catalytic Cracking Additive Matrix

[0067] (1) Mix 4.39 kg of pseudoboehmite (containing 3 kg of Al2O3) with 5.4 kg of decationized water for 30 min. Add 10.3 kg of 85% concentrated phosphoric acid to the slurry while stirring, then add 5.28 kg of 68% concentrated nitric acid and continue stirring for 45 min to obtain colorless and transparent aluminum phosphate sol.

[0068] (2) Add 1.18 kg of water to 1.05 kg (dry basis) ZSM-5 (SiO2 / Al2O3=50) molecular sieve, homogenize with a shearing machine, then add 65.5 mL of La(NO3)3 solution (La2O3 is 103.13 g / L), stir for 2 h to prepare molecular sieve slurry.

[0069] (3) Under stirring, 1775g of kaolin and 2170mL of water were mixed and slurried for 30min. 1.5kg of aluminum phosphate sol was added to the kaolin slurry, and stirring was continued for 1h. Then, ZSM-5 molecular sieve slurry was added, and stirring was continued for 2h. The solid content of the resulting slurry was 38wt%. After homogenization, the slurry was spray-molded to obtain a catalytic cracking propylene additive containing 35wt% ZSM-5 molecular sieve.

[0070] II. Preparation of Propylene Catalytic Cracking Additives (Dealuminization and Silicon Supplementation Method)

[0071] (1) The catalytic cracking additive matrix obtained above was impregnated and modified in a 0.3 mol / L ammonium hexafluorosilicate solution. The impregnation conditions were: solid-liquid ratio of 1:8, impregnation temperature of 80℃, and impregnation time of 6h.

[0072] (2) After impregnation, solid-liquid separation is carried out, and the solid part is dried and calcined. The drying temperature is 120℃ and the drying time is 12h. The calcination temperature is 500℃ and the calcination time is 6h.

[0073] Application Examples

[0074] I. Physical Performance Analysis

[0075] The average specific surface area and average pore size of the catalytic cracking additive matrix prepared in Example 4 and the propylene-enhancing catalytic cracking additives prepared in Examples 1-4 are shown in Table 1 below:

[0076] Table 1

[0077]

[0078] Pore ​​size analysis was performed on the catalytic cracking additive matrix and the propylene production enhancement catalytic cracking additive prepared in Example 4 to obtain... Figure 1 .from Figure 1 It can be seen that after modification of the catalytic cracking additive matrix by the dealumination and silicon replenishment method, the resulting propylene-enhancing catalytic cracking additive matrix has significantly more mesopores than the untreated matrix, with pore volumes greater than 0.2 cm³ for particles with diameters of 3-20 nm. 3 / g, with two most probable pore sizes between 4-10nm, a first most probable pore size at 5.2nm, and a second most probable pore size at 7.6nm.

[0079] II. Catalytic Performance Analysis

[0080] The catalytic cracking additive matrix prepared in Example 4 and the propylene-enhancing catalytic cracking additives prepared in Examples 1-4 were added to the catalytic cracking catalyst at a dosage of 3%. Catalytic performance was analyzed using a riser catalytic cracking reaction evaluation device. The riser outlet temperature was 520°C, the catalyst-to-oil ratio was 1:6, and the reaction pressure was 25 kPa. The results are shown in Table 2 below. Table 2 shows that the propylene-enhancing catalytic cracking additive of this invention can promote the conversion of diesel fuel into propylene and liquefied petroleum gas.

[0081] Table 2

[0082]

[0083] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The embodiments describe the present invention, and it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention.

Claims

1. A propylene-enhancing catalytic cracking additive, characterized in that, The main active ingredient of the propylene-enhancing catalytic cracking additive is ZSM-5 molecular sieve; the pore size of the propylene-enhancing catalytic cracking additive is 3-20 nm, and the pore volume ranges from 0.2-0.4 cm. 3 The pore size is between / g; the pore size has a multi-peak distribution, with a first most probable pore size between 4-6nm and a second most probable pore size between 6-9nm; The propylene-enhancing catalytic cracking additive is obtained by modifying the catalytic cracking additive matrix using a dealumination method to make it multi-level porous. The catalytic cracking aid matrix is ​​prepared as follows: (1) Mix 4.39 kg of boehmite with 5.4 kg of decationized water for 30 min, add 10.3 kg of 85% concentrated phosphoric acid to the slurry while stirring, then add 5.28 kg of 68% concentrated nitric acid, and continue stirring for 45 min to obtain a colorless and transparent aluminum phosphate sol; wherein, 4.39 kg of boehmite contains 3 kg of Al2O3; (2) Add 1.18 kg of water to 1.05 kg of ZSM-5 molecular sieve, homogenize with a shearing machine, then add 65.5 mL of La(NO3)3 solution and stir for 2 h to prepare ZSM-5 molecular sieve slurry; wherein, the SiO2 / Al2O3 ratio of ZSM-5 molecular sieve is 50; and the concentration of La(NO3)3 in the La(NO3)3 solution is 103.13 g / L; (3) Under stirring, 1775g of kaolin and 2170mL of water were mixed and slurried for 30min. 1.5kg of the phosphorus aluminum sol prepared in step (1) was added to the kaolin slurry and stirred for 1h. Then the ZSM-5 molecular sieve slurry prepared in step (2) was added and stirred for 2h to obtain a slurry with a solid content of 38wt%. After homogenization, the slurry was spray-molded to obtain a catalytic cracking aid matrix containing 35wt% ZSM-5 molecular sieve. The propylene-enhancing catalytic cracking additive is used for the catalytic cracking of petroleum products containing diesel and / or gasoline.

2. The propylene-enhancing catalytic cracking additive according to claim 1, characterized in that, The modifier used in the dealumination method is selected from one or more of citric acid, hydrochloric acid, and nitric acid.

3. A method for preparing the propylene-enhancing catalytic cracking additive as described in claim 1 or 2, characterized in that, The preparation method involves subjecting the catalytic cracking aid matrix to a multi-level pore treatment. The multi-level pore treatment involves impregnating the catalytic cracking aid matrix in a modifier solution for modification, followed by filtration, drying, and calcination to obtain a multi-level porous propylene-enhancing catalytic cracking aid. The impregnation conditions are as follows: solid-liquid ratio of 1:5-1:10, impregnation temperature of 50-100℃, and impregnation time of 3-12h; wherein, the solid-liquid ratio is in mass ratio. The multi-stage porosimetry method is selected from the dealumination method.

4. The preparation method according to claim 3, characterized in that, The concentration of the modifier solution is 0.1-1 mol / L; and / or The drying temperature is 100-140℃, and the drying time is 10-14 hours; and / or The roasting temperature is 450-550℃, and the roasting time is 4-8h.

5. The preparation method according to claim 3, characterized in that, The impregnation conditions are as follows: solid-liquid ratio of 1:6-1:8, impregnation temperature of 60-80℃, and impregnation time of 6-10h.

6. The application of a propylene-enhancing catalytic cracking additive prepared by the method of any one of claims 1 or 2, or any one of claims 3-5, in the production of low-carbon olefins from petroleum products containing diesel and / or gasoline through catalytic cracking, wherein the low-carbon olefins include propylene.

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