A propylene yield enhancing zsm-5 additive and methods of making and using the same

Abstract

The application belongs to the field of petroleum refining catalysis technology, and discloses a ZSM-5 additive for increasing propylene production and a preparation and use method thereof. In the method, waste filtrate prepared by using SAPO-34 molecular sieve is used to improve the stability of the molecular sieve under a high-temperature water-containing atmosphere, prevent the molecular sieve channels from being blocked by excessive phosphorus elements, reduce environmental pollution caused by the waste filtrate, improve the specific surface area of the ZSM-5 additive and the stability of the product, realize the dual effects of the stabilization of the molecular sieve by the phosphorus elements and the protection of the organic ammonium channels, complement the low-molecular-weight ammonium polyacrylate, white carbon black and phosphorus aluminum binder, construct a hierarchical pore structure (micropore-mesopore-macropore hierarchical pore), and then obtain the additive with a specific surface area of 150-170 m 2 / g, an addition amount of only 10 wt% can achieve a propylene production effect better than that of 20 wt% of a commercially available additive, the catalyst procurement cost of a refinery is greatly reduced, and the slurry oil yield is reduced and the heavy oil cracking capacity is improved.

Description

Technical Field

[0001] This invention belongs to the field of petroleum refining catalysis technology, specifically relating to a ZSM-5 propylene production enhancer and its preparation and application methods. Background Technology

[0002] Fluidized catalytic cracking (FCC) is a core process in the petroleum refining industry for converting heavy oil into light fuels and chemical feedstocks. With the continued rise in global demand for low-carbon olefins such as propylene, the development of highly efficient propylene-enhancing FCC additives has become a research hotspot in the industry. ZSM-5 molecular sieve, due to its unique three-dimensional microporous structure, suitable acidic site distribution, and excellent shape-selective catalytic performance, is currently the most widely used active component in industrial FCC propylene-enhancing additives. Its performance directly determines the propylene yield and the economic benefits of refineries.

[0003] In practical applications of ZSM-5 additives, specific surface area and hydrothermal stability are key indicators affecting their catalytic activity and service life. On the one hand, a higher specific surface area provides more exposed active sites, enhancing heavy oil cracking and low-carbon olefin formation reactions, while also promoting the diffusion and transport of reactants and products. On the other hand, the regeneration stage of the FCC process is conducted in a high-temperature, water-containing atmosphere, where ZSM-5 molecular sieves are prone to structural deterioration such as framework dealumination and pore blockage, leading to a decrease in catalytic activity. Therefore, continuous replenishment of fresh additives is necessary to maintain the increased production effect.

[0004] In existing technologies, the preparation of ZSM-5 additives often faces multiple bottlenecks: First, the traditional ZSM-5 molecular sieve has a simple pore structure, and particle agglomeration and pore blockage are prone to occur during the preparation process, making it difficult to increase its specific surface area. To achieve the expected increase in propylene production, 10% or more of ZSM-5 additives need to be added to the FCC catalyst, which significantly increases the refinery's catalyst procurement costs. Second, high additions of ZSM-5 additives will dilute the active matrix components in the FCC catalyst, reduce the heavy oil cracking capacity, and easily lead to an increase in slurry yield, affecting the overall processing efficiency of the unit. Third, in order to improve the hydrothermal stability of ZSM-5 molecular sieves, phosphorus is often used for modification, but excessive phosphorus can easily block the molecular sieve pores, thereby reducing its specific surface area and catalytic activity, making it difficult to balance stability and catalytic performance. Fourth, in industrial production, the preparation process of SAPO-34 molecular sieves generates a large amount of waste filtrate, which contains phosphorus, organic ammonium, and other components. Direct discharge can easily cause environmental pollution, and how to realize its resource utilization has become an urgent problem to be solved by the industry.

[0005] Furthermore, in the existing preparation process, problems such as unreasonable selection and ratio of binders and poor dispersion further exacerbate the defects of pore blockage and insufficient specific surface area of ​​ZSM-5 additives. Even with conventional post-processing methods, it is difficult to effectively overcome the bottleneck of specific surface area improvement and meet the industrial demand for increased propylene production with low cost, high activity and long life.

[0006] Therefore, developing a ZSM-5 additive preparation method that can significantly improve specific surface area and hydrothermal stability, reduce the amount added, and realize the resource utilization of waste can not only solve the pain points of existing technologies, but also reduce production costs and improve processing efficiency for refineries, and has important industrial application value and environmental benefits. Summary of the Invention

[0007] To address the above technical problems, the present invention aims to provide a method for preparing a propylene-enhancing ZSM-5 additive. This method involves steps such as preparing a phosphorus-aluminum binder, pretreating ZSM-5 molecular sieves with SAPO-34 waste filtrate, preparing and dispersing a slurry, spray drying, calcining, and washing and drying with citric acid. The waste filtrate from SAPO-34 molecular sieves is used to stabilize the ZSM-5 molecular sieve, improving its stability in high-temperature, water-containing atmospheres. Furthermore, the organic ammonium in the waste filtrate protects the pore structure of the molecular sieve, preventing clogging by excessive phosphorus. This reduces environmental pollution from the waste filtrate and increases the specific surface area and stability of the ZSM-5 additive, achieving a dual effect of phosphorus stabilization and organic ammonium pore protection. A hierarchical pore structure is constructed by combining low-molecular-weight ammonium polyacrylate dispersion with silica. After calcination, washing with citric acid further enhances the matrix specific surface area. The ZSM-5 additive prepared by this method has a specific surface area of ​​150-170 m². 2 / g, with an addition of only 10wt% in the FCC process, the propylene production increase effect can be achieved with 20wt% of commercially available additives, significantly reducing refinery catalyst procurement costs, while also reducing slurry oil yield, improving heavy oil cracking capacity, and realizing the resource utilization of SAPO-34 waste filtrate, thus possessing both industrial application value and environmental benefits. The additive prepared by this invention has excellent hydrothermal stability, is suitable for high-temperature, water-containing FCC regeneration processes, and can maintain catalytic activity for a long time.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a propylene-enhancing ZSM-5 additive includes the following steps: S1. Preparation of phosphorus aluminum binder: After selecting boehmite and deionized water and stirring to disperse them evenly, phosphoric acid is added and the temperature is raised to 70~90℃. The temperature is kept constant and stirred. Then citric acid is added to complete the gelation and obtain the aluminum phosphate binder. S2. Molecular sieve pretreatment: ZSM-5 molecular sieve raw powder was mixed and stirred with SAPO-34 waste filtrate, so that the phosphorus and organic ammonium in the waste filtrate were adsorbed on the surface of the molecular sieve. S3, Slurry preparation: Add the phosphorus aluminum binder, low molecular weight ammonium polyacrylate and silica to the S2 mixture system, add deionized water to adjust the total slurry solid content to 30~40wt%, and perform dispersion treatment to control the slurry particle size D90≤4.0μm; S4. Spray drying: The dispersed slurry in S3 was spray-dried to obtain microsphere precursors, wherein the inlet temperature of the drying device was controlled at 370~400℃ and the outlet temperature at 120~135℃. S5, roasting: The dried microsphere precursor was calcined at a constant temperature under a weak oxidizing atmosphere, and then cooled naturally after calcination was completed. S6. Post-pickling treatment: The calcined microspheres were washed and dried with citric acid solution to obtain the target ZSM-5 additive.

[0009] The aforementioned weak oxidizing atmosphere is a mixture of air and nitrogen with an oxygen volume fraction of 2-5%.

[0010] Preferably, in S1, based on 100 parts by weight of boehmite, the amount of deionized water added is 340-360 parts, the amount of phosphoric acid added is 270-295 parts, and the amount of citric acid added is 60-100 parts. The temperature is raised to 80°C; The constant temperature stirring time is 30~50 minutes.

[0011] Preferably, in step S2, based on 100 parts by weight of ZSM-5 molecular sieve raw powder, the amount of SAPO-34 waste filtrate added is 15 to 25 parts. The mixing and stirring time is 20-40 minutes.

[0012] Preferably, in S2, the SAPO-34 waste filtrate contains 2.5-3.0 wt% phosphorus, 1.5-2.0 wt% organic ammonium, 1-1.2 wt% alumina, 0.1-0.3 wt% silica, and the remainder is water and trace impurities.

[0013] Preferably, in step S3, based on 100 parts by weight of ZSM-5 molecular sieve raw powder, the amount of low molecular weight ammonium polyacrylate added is 0.2 to 0.6 parts, and the molecular weight is 1000 to 3000. The amount of silica added is 6 to 10 parts; The amount of the phosphorus aluminum binder added is 61-68 parts; Add deionized water to adjust the total slurry solids content to 36 wt%. The dispersion process is carried out using a combination of high-speed shearing and sand milling. The controlled slurry particle size D90 ≤ 3.5 μm.

[0014] Preferably, in S3, the ZSM-5 molecular sieve powder has a silica-to-alumina ratio of 29 and a specific surface area of ​​401 m². 2 / g, particle size D50≤3.9μm; The precipitated silica has a pore volume of 0.9 mL / g and a specific surface area of ​​345 m². 2 / g.

[0015] Preferably, in step S5, the calcination process involves raising the temperature to 540-560°C at a rate of 1.5-2.5°C / min and maintaining the temperature for 2-3 hours.

[0016] Preferably, in step S6, the molar concentration of the citric acid solution is 0.2~0.5 mol / L, the washing temperature is 45~50℃, and the washing time is 0.8~1.5h.

[0017] A ZSM-5 additive for increasing propylene production, wherein the ZSM-5 additive has a specific surface area of ​​150~170 m². 2 / g, abrasion index 1.8~2.5% / h.

[0018] A method for using ZSM-5 propylene-increasing additive, wherein the ZSM-5 additive is used after being aged at 800~850℃ and 100% steam for 20~25h, and then compounded with RFCC balancing agent at an addition amount of 10wt%, resulting in an increase in propylene yield of 9.0~9.4wt%.

[0019] Compared with the prior art, the present invention has at least the following technical effects: This invention provides a method for preparing an additive to increase propylene production ZSM-5, which includes steps such as preparing a phosphorus aluminum binder, pretreating ZSM-5 molecular sieve with SAPO-34 waste filtrate, preparing and dispersing a slurry, spray drying, calcining, and washing and drying with citric acid.

[0020] Among them, the waste filtrate prepared using SAPO-34 molecular sieve can be used to stabilize ZSM-5 molecular sieve with phosphorus, improving the stability of the molecular sieve in high-temperature and water-containing atmospheres. On the other hand, the organic ammonium in the waste filtrate can protect the pore structure of the molecular sieve and prevent the pores from being blocked by excessive phosphorus. In addition, it reduces environmental pollution caused by waste filtrate and improves the specific surface area and product stability of ZSM-5 additives. Thus, it achieves the dual effect of phosphorus stabilization of molecular sieve and organic ammonium pore protection. After dispersion with low molecular weight polyacrylate and reduction of interparticle agglomeration, silica and phosphorus aluminum binder are added to complement each other to construct a hierarchical pore structure (micropore-mesopore-macropore hierarchical pores), thereby increasing the total specific surface area and pore volume. After calcination, washing with citric acid further improves the matrix specific surface area of ​​the catalyst.

[0021] The ZSM-5 additive prepared by this method has a specific surface area of ​​150~170m². 2 / g, with an addition of only 10wt% in the FCC process, can achieve propylene production increase effect superior to that of commercially available additives of 20wt%, significantly reducing refinery catalyst procurement costs, while reducing slurry yield, improving heavy oil cracking capacity, and realizing resource utilization of SAPO-34 waste filtrate, thus combining industrial application value and environmental benefits.

[0022] The additive prepared by this method has excellent hydrothermal stability, is suitable for FCC regeneration processes with high temperature and water content, and can maintain catalytic activity for a long time. Detailed Implementation

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be briefly introduced below in conjunction with the description of the embodiments or the prior art. Obviously, the following description of the technical solutions is merely some embodiments of the present invention. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0024] One specific embodiment of the present invention is as follows: In each embodiment, the specific surface area of ​​the samples was determined by the BET low-temperature nitrogen adsorption method, the elemental composition of the samples was determined by X-ray fluorescence spectrometry, and the wear index of the samples was determined by a wear index analyzer. The catalytic cracking reaction in the embodiments and comparative examples was evaluated in a micro fluidized bed reactor (ACE) and its associated gas chromatograph. The research octane number (RON) was analyzed using an Agilent 7980A gas chromatograph. The additives in the comparative examples and embodiments were aged at 820°C with 100% steam for 24 hours, and then their catalytic cracking performance was evaluated using RFCC balancing agent + 10wt% additives. Other testing methods are detailed in the "National Standard for Testing Methods of Petroleum and Petroleum Products" (published by China Standards Press, 1989).

[0025] I. Raw Material Preparation 1. ZSM-5 molecular sieve raw powder: from Runhe Catalyst Co., Ltd., with a silicon-to-aluminum ratio of 29 and a specific surface area of ​​401 m². 2 / g, particle size D50≤3.9μm; 2. Boehmite: pore volume 0.45 mL / g, gel solubility 99%; 3. As modifiers: citric acid (industrial grade), phosphoric acid (industrial grade, containing 85% H3PO4); 4. SAPO-34 waste filtrate: phosphorus content 2.8wt%, organic ammonium (triethylamine) content 1.9wt%, Al2O3 content 1.2wt%, SiO2 content 0.2wt%, the remainder is water and trace impurities; 5. Dispersant and pore-forming components: Low molecular weight ammonium polyacrylate (molecular weight 1000~3000, analytical grade), silica (pore volume 0.9 mL / g, specific surface area 345 m²). 2 / g); 6. Comparative raw material: Industrial propylene ZSM-5 additive (commercially available, specific surface area 91 m²) 2 / g, P2O5 content is 17.2wt%, wear index is 2.3% / h), RFCC balancer (industrial grade, see Table 2 for specific properties); 7. Raw material oil: Properties are shown in Table 1.

[0026] Table 1 Properties of Crude Oil

[0027] 8. RFCC balancing agent: industrial grade, properties are shown in Table 2.

[0028] Table 2 Main Properties of RFCC Balancing Agent

[0029] II. Implementation Examples Example 1: A method for preparing a propylene-enhancing ZSM-5 additive includes the following steps: 1.1 Binder preparation (citric acid + phosphoric acid treatment of boehmite) Take 100 kg of boehmite, add 350 kg of deionized water, stir and disperse evenly, add 282 kg of phosphoric acid, heat to 80℃, stir at a constant temperature for 40 min, then add 88 kg of citric acid to complete the gelation and obtain the aluminum phosphate binder for later use.

[0030] 1.2 Preparation of ZSM-5 additive 1. Take 100 kg of ZSM-5 molecular sieve raw powder, add 20 kg of SAPO-34 waste filtrate, stir for 30 min, so that the phosphorus and organic ammonium in the waste filtrate are fully adsorbed on the surface of the molecular sieve, and complete the molecular sieve stabilization pretreatment. 2. Add 64 kg of the phosphorus aluminum binder prepared in step 1.1, 0.5 kg of low molecular weight ammonium polyacrylate, and 8 kg of silica to the above system, add deionized water to adjust the total slurry solid content to 36 wt%, and disperse using a combination of high-speed shearing and sand milling to control the slurry D90 ≤ 3.5 μm; 3. The uniformly dispersed slurry is spray-dried, with the inlet temperature controlled at 380℃ and the outlet temperature at 125℃, to obtain the microsphere precursor; 4. Calcination of microsphere precursor: Decompose template agent and organic matter at 550℃ for 2.5h and stabilize the phosphorus aluminum phase. The heating rate is 2℃ / min, and the process is carried out in a weak oxidizing atmosphere. After calcination, the temperature is naturally lowered. 5. The calcined microspheres were washed with 0.3 mol / L citric acid solution at 45°C for 1 hour. After washing, they were dried to obtain the target ZSM-5 additive.

[0031] 1.3 Performance Testing and ACE Evaluation The prepared ZSM-5 additive was subjected to physicochemical property testing. After aging at 820℃ and 100% steam for 24 hours, it was compounded with RFCC balancer (RFCC balancer + 10wt% additive) and evaluated for ACE catalytic cracking. The results are shown in Table 3.

[0032] Example 2: The only difference between this embodiment and Embodiment 1 is that: 1. In the preparation of the binder, add 270 kg of phosphoric acid and 100 kg of citric acid (other binder preparation parameters: 100 kg of boehmite, 350 kg of deionized water, temperature 80℃, constant temperature stirring for 40 min). 2. In the preparation of the additives, the amount of low molecular weight ammonium polyacrylate added is 0.2 kg, the amount of fumed silica added is 6 kg, and the amount of aluminum phosphate binder added is 68 kg; 3. After calcination, wash with 0.2 mol / L citric acid solution (washing temperature and time are the same as in Example 1).

[0033] The remaining preparation steps (slurry solid content 36wt%, dispersed particle size D90≤3.5μm, spray drying parameters, calcination process, etc.), detection and ACE evaluation methods are the same as in Example 1, and the results are shown in Table 3.

[0034] Example 3: The only difference between this embodiment and Embodiment 1 is that: 1. In the preparation of the binder, add 295 kg of phosphoric acid and 60 kg of citric acid (other binder preparation parameters: 100 kg of boehmite, 350 kg of deionized water, temperature 80℃, constant temperature stirring for 40 min). 2. In the preparation of the additives, the amount of low molecular weight ammonium polyacrylate added is 0.5 kg, the amount of fumed silica added is 10 kg, and the amount of aluminum phosphate binder added is 68 kg; 3. After calcination, wash with 0.5 mol / L citric acid solution (washing temperature and time are the same as in Example 1).

[0035] The remaining preparation steps (slurry solid content 36wt%, dispersed particle size D90≤3.5μm, spray drying parameters, calcination process, etc.), detection and ACE evaluation methods are the same as in Example 1, and the results are shown in Table 3.

[0036] Example 4: (Adjusting the amount of SAPO-34 waste filtrate) The only difference between this embodiment and Embodiment 1 is that: 1. In the preparation of the additive, the amount of SAPO-34 waste filtrate added is 15kg (other pretreatment parameters: stirring time 30min remains unchanged). 2. In the preparation of the binder, add 278 kg of phosphoric acid and 95 kg of citric acid (the other binder preparation parameters are: 100 kg of boehmite, 350 kg of deionized water, temperature 80℃, and constant temperature stirring for 40 min). 3. After calcination, wash with 0.3 mol / L citric acid solution for 1.5 h (washing temperature is the same as in Example 1).

[0037] The remaining preparation steps (slurry solid content 36wt%, dispersed particle size D90≤3.5μm, spray drying parameters, calcination process, etc.), detection and ACE evaluation methods are the same as in Example 1, and the results are shown in Table 3.

[0038] Example 5: (Adjusting the amount of phosphorus aluminum binder) The only difference between this embodiment and Embodiment 1 is that: 1. In the preparation of the additives, the amount of phosphorus aluminum binder added is 61 kg, and the amount of silica added is 6 kg (the other additive preparation parameters remain unchanged: 20 kg of SAPO-34 waste filtrate and 0.5 kg of low molecular weight ammonium polyacrylate). 2. In the preparation of the binder, add 288 kg of phosphoric acid and 85 kg of citric acid (other binder preparation parameters: 100 kg of boehmite, 350 kg of deionized water, temperature 80℃, constant temperature stirring for 40 min). 3. The spray drying inlet temperature is adjusted to 390℃ and the outlet temperature is adjusted to 130℃.

[0039] The remaining preparation steps (slurry solid content 36wt%, dispersed particle size D90≤3.5μm, calcination process, washing process, etc.), detection and ACE evaluation methods are the same as in Example 1, and the results are shown in Table 3.

[0040] Example 6: (Adjusting the washing process) The only difference between this embodiment and Embodiment 1 is that: 1. After calcination, the product was washed with a 0.4 mol / L citric acid solution at a temperature of 50°C (the washing time was the same as in Example 1, which was 1 hour). 2. In the preparation of the binder, add 280 kg of phosphoric acid and 90 kg of citric acid (the other binder preparation parameters are: 100 kg of boehmite, 350 kg of deionized water, temperature 80℃, and constant temperature stirring for 40 min). 3. The amount of low molecular weight ammonium polyacrylate added is 0.4 kg, and the amount of silica added is 7 kg.

[0041] The remaining preparation steps (slurry solid content 36wt%, dispersed particle size D90≤3.5μm, spray drying parameters, calcination process, etc.), detection and ACE evaluation methods are the same as in Example 1, and the results are shown in Table 3.

[0042] Example 7: (Adjusting the amount of dispersant) The only difference between this embodiment and Embodiment 1 is that: 1. In the preparation of the additives, the amount of low molecular weight ammonium polyacrylate added is 0.6 kg, and the amount of silica added is 8 kg (the other additive preparation parameters remain unchanged: 20 kg of SAPO-34 waste filtrate and 64 kg of phosphorus aluminum binder). 2. In the preparation of the binder, add 285 kg of phosphoric acid and 86 kg of citric acid (other binder preparation parameters: 100 kg of boehmite, 350 kg of deionized water, temperature 80℃, constant temperature stirring for 40 min). 3. After the slurry is dispersed, control D90 ≤ 3.2μm (other dispersion parameters: high-speed shear + sand milling combined dispersion remains unchanged).

[0043] The remaining preparation steps (slurry solid content 36wt%, spray drying parameters, calcination process, washing process, etc.), detection and ACE evaluation methods are the same as in Example 1, and the results are shown in Table 3.

[0044] Comparative Example 1: (Conventional ZSM-5 additive without the innovative features of this invention) 1.1 Preparation of Additives 1. Take 100 kg of ZSM-5 molecular sieve raw powder (same as in Example 1), add 64 kg of unmodified aluminum phosphate binder (not treated with citric acid, containing 34% P2O5), without adding SAPO-34 waste filtrate, low molecular weight ammonium polyacrylate and white carbon black, add deionized water to adjust the slurry solid content to 36 wt%, disperse and spray dry (parameters same as in Example 1). 2. The same calcination process as in Example 1 (550℃ constant temperature for 2.5h, heating rate of 2℃ / min, weak oxidizing atmosphere) was used for treatment without citric acid washing to obtain conventional ZSM-5 additive.

[0045] 1.2 Performance Testing and ACE Evaluation The physicochemical performance testing and ACE evaluation methods were the same as in Example 1, and the results are shown in Table 3.

[0046] Comparative Example 2: (10wt% industrial propylene ZSM-5 additive) Commercially available industrial propylene ZSM-5 additive (specific surface area 91 m²) was used. 2 / g, P2O5 content is 17.2wt%, wear index is 2.3% / h, conventional phosphorus aluminum binder system, no SAPO-34 waste filtrate utilization, no hierarchical pore construction), directly carried out physicochemical property testing, after aging at 820℃ and 100% water vapor for 24 hours, it was compounded with RFCC balancer (RFCC balancer + 10wt% additive), and evaluated according to the same ACE catalytic cracking evaluation conditions as in Example 1. The results are shown in Table 3.

[0047] Comparative Example 3: (20wt% industrial propylene ZSM-5 additive) The only difference from Comparative Example 2 is that the RFCC balancing agent is compounded (RFCC balancing agent + 20wt% additives).

[0048] III. Summary of Performance Testing and ACE Evaluation Results Table 3 Performance Testing and ACE Evaluation Results

[0049] Note: The data in the table are the ACE evaluation results of RFCC balancing agent + 10 wt% or 20 wt% additives after aging at 820℃ and 100% water vapor for 24 hours.

[0050] The results showed that the amount of additives added in Examples 1-7 was only 10 wt% to achieve a better propylene yield increase than that in Comparative Example 3 (20 wt%).

[0051] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a propylene-enhancing ZSM-5 additive, characterized in that, Includes the following steps: S1. Preparation of phosphorus aluminum binder: After selecting boehmite and deionized water and stirring to disperse them evenly, phosphoric acid is added and the temperature is raised to 70~90℃. The temperature is kept constant and stirred. Then citric acid is added to complete the gelation and obtain the aluminum phosphate binder. S2. Molecular sieve pretreatment: ZSM-5 molecular sieve raw powder was mixed and stirred with SAPO-34 waste filtrate, so that the phosphorus and organic ammonium in the waste filtrate were adsorbed on the surface of the molecular sieve. S3, Slurry preparation: Add the phosphorus aluminum binder, low molecular weight ammonium polyacrylate and silica to the S2 mixture system, add deionized water to adjust the total slurry solid content to 30~40wt%, and perform dispersion treatment to control the slurry particle size D90≤4.0μm; S4. Spray drying: The dispersed slurry in S3 was spray-dried to obtain microsphere precursors, wherein the inlet temperature of the drying device was controlled at 370~400℃ and the outlet temperature at 120~135℃. S5, roasting: The dried microsphere precursor was calcined at a constant temperature under a weak oxidizing atmosphere, and then cooled naturally after calcination was completed. S6. Post-pickling treatment: The calcined microspheres were washed and dried with citric acid solution to obtain the target ZSM-5 additive.

2. The preparation method according to claim 1, characterized in that, In S1, based on 100 parts by weight of boehmite, the amount of deionized water added is 340-360 parts, the amount of phosphoric acid added is 270-295 parts, and the amount of citric acid added is 60-100 parts. The temperature is raised to 80°C; The constant temperature stirring time is 30~50 minutes.

3. The preparation method according to claim 1, characterized in that, In S2, based on 100 parts by weight of ZSM-5 molecular sieve raw powder, the amount of SAPO-34 waste filtrate added is 15 to 25 parts. The mixing and stirring time is 20-40 minutes.

4. The preparation method according to claim 3, characterized in that, In S2, the SAPO-34 waste filtrate contains 2.5-3.0 wt% phosphorus, 1.5-2.0 wt% organic ammonium, 1-1.2 wt% alumina, 0.1-0.3 wt% silica, and the remainder is water and trace impurities.

5. The preparation method according to claim 1, characterized in that, In S3, based on 100 parts by weight of ZSM-5 molecular sieve raw powder, the amount of low molecular weight ammonium polyacrylate added is 0.2 to 0.6 parts, and the molecular weight is 1000 to 3000. The amount of silica added is 6 to 10 parts; The amount of the phosphorus aluminum binder added is 61-68 parts; Add deionized water to adjust the total slurry solids content to 36 wt%. The dispersion process is carried out using a combination of high-speed shearing and sand milling. The controlled slurry particle size D90 ≤ 3.5 μm.

6. The preparation method according to claim 5, characterized in that, In S3, the ZSM-5 molecular sieve powder has a silica-to-alumina ratio of 29 and a specific surface area of ​​401 m². 2 / g, particle size D50≤3.9μm; The precipitated silica has a pore volume of 0.9 mL / g and a specific surface area of ​​345 m². 2 / g.

7. The preparation method according to claim 1, characterized in that, In step S5, the calcination process involves raising the temperature to 540-560°C at a rate of 1.5-2.5°C / min and maintaining the temperature for 2-3 hours.

8. The preparation method according to claim 1, characterized in that, In step S6, the molar concentration of the citric acid solution is 0.2~0.5 mol / L, the washing temperature is 45~50℃, and the washing time is 0.8~1.5h.

9. A propylene-enhancing ZSM-5 adjuvant prepared by the method according to any one of claims 1 to 8, characterized in that, The specific surface area of ​​the ZSM-5 additive is 150~170m². 2 / g, abrasion index 1.8~2.5% / h.

10. A method of using the ZSM-5 propylene-enhancing adjuvant as described in claim 9, characterized in that, The ZSM-5 additive, after being aged at 800-850℃ and 100% steam for 20-25 hours, is used in combination with the RFCC balancing agent at an addition rate of 10 wt%, resulting in an increase in propylene yield of 9.0-9.4 wt%.

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