C4 olefin catalytic cracking catalyst and preparation method thereof

Abstract

The invention provides a C4 olefin catalytic cracking catalyst which comprises the following components in percentage by weight: 40-90% of modified ZSM-5 molecular sieve in terms of dry basis, 10-30% of alkaline binder in terms of oxide and 0-40% of clay in terms of dry basis, wherein the total weight of the C4 olefin catalytic cracking catalyst is 100%; the preparation method of the modified ZSM-5 molecular sieve comprises the following steps: in a stirring state, adding a pore channel blocking agent with the particle size of less than 2nm into mixed slurry of a ZSM-5 molecular sieve and deionized water, then adding magnesium hydroxide colloid, drying, heating to 400-600 DEG C within 2-10 hours, and roasting to decompose the pore channel blocking agent, so as to obtain the modified ZSM-5 molecular sieve. The C4 olefin catalytic cracking catalyst provided by the invention can effectively integrate acidic and alkaline catalytic characteristics while maintaining high stability, thereby improving the yield and selectivity of ethylene and propylene.

Description

Technical Field

[0001] This invention belongs to the field of petroleum catalytic cracking, specifically relating to a C4 olefin catalytic cracking catalyst and its preparation method. Background Technology

[0002] Ethylene and propylene, as some of the most critical basic raw materials in the chemical industry, play an indispensable role in both the chemical industry and daily life. Ethylene, as the simplest olefin compound, constitutes the basic manufacturing unit of many chemicals, including polyethylene, ethylene glycol, acetic acid, and vinyl chlorides. As one of the highest-volume plastics, polyethylene is widely used in packaging materials, containers, pipes, and insulation materials. Ethylene glycol is a key raw material for manufacturing polyester fibers, resins, antifreeze, and lubricants. Furthermore, vinyl chlorides play a major role in the manufacture of PVC plastics, which are widely used in pipes, wire insulation, and various consumer products. Meanwhile, propylene, another important olefin, is also a fundamental raw material for many chemicals and plastics. Its main derivatives include polypropylene, acrylic acid and its esters, acrylonitrile, and acrylamide. Polypropylene is widely used in automotive parts, textiles, and packaging materials due to its lightweight, heat resistance, and chemical resistance. Acrylic acid and its esters are key raw materials for manufacturing coatings, adhesives, and sealants, while acrylonitrile is a major component of synthetic fibers, plastics, and rubber.

[0003] Meanwhile, technological advancements and the development of new applications have also impacted the demand for these chemicals. For example, in the automotive, aerospace, and construction industries, the use of ethylene and propylene is increasing with the development of new high-performance plastics and composite materials. However, the environmental impact of ethylene and propylene production processes has also attracted widespread attention. Ethylene and propylene production typically involves high energy consumption and greenhouse gas emissions, especially when using traditional petrochemical processes. Therefore, researching and developing more environmentally friendly and efficient production methods has become a key research direction in this field, such as through catalytic cracking and the conversion of bio-based feedstocks.

[0004] C4 olefins (butadiene), including isobutylene, butene, and butane, are byproducts of petroleum refining. As an important chemical feedstock containing four carbon atoms and a double bond, the conversion of C4 olefins is crucial for optimizing the economic efficiency of refineries. In the modern petrochemical industry, C4 olefins are generally converted into smaller olefin molecules such as ethylene and propylene, basic chemical feedstocks, under high temperature and catalysis. Traditionally, this process relies on energy-intensive and poorly selective thermal cracking methods, which not only increase energy consumption but also cause severe wear and tear on equipment. Therefore, developing highly efficient catalysts that can improve cracking efficiency and selectivity has become a research hotspot in this field.

[0005] Acidic molecular sieves, such as ZSM-5, have attracted widespread attention due to their unique microporous structure and highly acidic site distribution. Acidic molecular sieve catalysts can promote the cracking of C4 olefins at lower temperatures and improve the yields of ethylene and propylene. However, acidic catalysts are prone to coke deposition, which can clog pores and reduce catalyst activity and lifetime. To maintain sufficient activity, they often need to operate at high temperatures, increasing energy consumption and operating costs. To address this issue, researchers have begun exploring new methods combining basic components with traditional acidic molecular sieves. For example, Chinese patent document CN101176849A discloses a catalyst and preparation method for highly selective propylene production. This method modifies the active component, ZSM-5 molecular sieve catalyst, by using rare earth elements to stabilize the molecular sieve structure, using basic substances to change surface acidity, and modifying the pores through online silanization. The resulting catalyst, used in fluidized bed reactions, is prepared by spray drying and exhibits high selectivity for propylene production. Chinese patent document CN106140262A discloses a supported catalyst and its preparation method. The supported catalyst is composed of zinc oxide, zinc bromide, auxiliary oxide, and magnesium-modified hydrogen-form ZSM-5 molecular sieve support. The preparation method includes the following steps: (1) treating hydrogen-form ZSM-5 molecular sieve with magnesium salt solution to obtain magnesium-modified ZSM-5 molecular sieve support; (2) introducing zinc oxide into magnesium-modified hydrogen-form ZSM-5 molecular sieve support; (3) brominated the support after introducing zinc oxide; (4) preparing auxiliary oxide; (5) introducing auxiliary oxide into the brominated material in step (3). This catalyst can selectively convert bromomethane into isobutylene. Chinese patent document CN112691695A discloses a ZSM-5 molecular sieve catalyst, which includes at least ZSM-5 molecular sieve, SiO2, P element, and alkaline earth metal element and / or rare earth metal element; wherein, the ZSM-5 molecular sieve has an outer surface covered with acidic sites.

[0006] Although the aforementioned catalysts all use basic components to modify ZSM-5 molecular sieves, theoretically, this multifunctional, basic-modified catalyst can operate at lower temperatures, reduce coke formation, and improve overall cracking efficiency. However, when used for the catalytic cracking of C4 olefins, it generally suffers from low ethylene and propylene yields and poor stability. The reason for this is that the basic components are not uniformly loaded onto the ZSM-5 molecular sieve. Only by precisely controlling the loading process and ensuring uniform loading of the basic components onto the molecular sieve can the pores be prevented from being blocked, while maintaining sufficient acidic active sites. Furthermore, catalyst stability (especially under long-term operation and high-temperature conditions) is also a critical issue.

[0007] Therefore, the main technical challenges currently faced in the catalytic cracking of C4 olefins include improving the yield and selectivity of ethylene and propylene, achieving an effective combination of acidic and basic catalytic functions, and maintaining catalyst stability and longevity. Existing catalysts on the market typically only optimize one catalytic environment (acidic or basic), making it difficult to achieve efficient acidic and basic catalysis simultaneously in a single catalyst. Furthermore, catalyst stability and lifetime are also crucial for improving efficiency in industrial applications. Therefore, designing a catalyst that effectively integrates acidic and basic catalytic properties to improve the yield and selectivity of ethylene and propylene in the catalytic cracking of C4 olefins is of great significance. Summary of the Invention

[0008] In view of this, the present invention provides a novel C4 olefin catalytic cracking catalyst and its preparation method. By effectively loading magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieve, a highly efficient acid catalytic environment is provided within the pores of the molecular sieve, while an effective alkaline catalytic environment is created on its outer surface. This achieves the integration of alkaline and acidic catalytic functions in the same catalyst. Components such as alkaline binders and clay not only enhance the stability and resistance to metal contamination of the catalyst, improving its stability and long-term effectiveness, but also increase the yield and selectivity of ethylene and propylene obtained from the catalytic cracking of C4 olefins. This has significant economic and technological implications for the petrochemical industry.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A C4 olefin catalytic cracking catalyst, based on 100% of the total weight of the C4 olefin catalytic cracking catalyst, comprises 40% to 90% of modified ZSM-5 molecular sieve on a dry basis, 10% to 30% of alkaline binder on an oxide basis, and 0% to 40% of clay on a dry basis.

[0011] The preparation method of the modified ZSM-5 molecular sieve includes the following steps:

[0012] Under stirring, a pore-blocking agent with a particle size of less than 2 nm is added to a mixture of ZSM-5 molecular sieve and deionized water. Then, magnesium hydroxide colloid is added. After drying, the mixture is heated to 400-600℃ for 1-3 hours within 2-10 hours to decompose the pore-blocking agent, thereby obtaining modified ZSM-5 molecular sieve.

[0013] In one alternative embodiment, the content of magnesium oxide is 1% to 5% based on 100% by mass of the modified ZSM-5 molecular sieve.

[0014] In one alternative embodiment, the pore-blocking agent is selected from nano-silica sol or polymer nanoparticles; preferably, the polymer nanoparticles are selected from polyacrylic acid and / or polyvinyl alcohol.

[0015] In one optional embodiment, the amount of the nano-silica sol added is 5% to 15% of the mass of the ZSM-5 molecular sieve, based on silica.

[0016] The amount of polymer nanoparticles added is 3% to 8% of the mass of the ZSM-5 molecular sieve.

[0017] In one optional embodiment, the ZSM-5 molecular sieve is selected from low-silica shape-selective ZSM-5 molecular sieve, phosphorus-modified ZSM-5 molecular sieve, or phosphorus and metal-modified ZSM-5 molecular sieve; the metal is selected from iron, zinc, etc.; preferably, the silicon-to-aluminum ratio of the ZSM-5 molecular sieve is 25 to 100.

[0018] In one optional embodiment, the preparation method of the modified ZSM-5 molecular sieve includes the following steps:

[0019] ZSM-5 molecular sieve was mixed with deionized water to obtain a mixed slurry;

[0020] Under stirring, a pore-blocking agent with a particle size of less than 2 nm is added to the mixed slurry. Thorough stirring ensures that the blocker is uniformly distributed and effectively penetrates the molecular sieve pores. Then, magnesium hydroxide colloid is slowly added to ensure uniform distribution and effective loading on the outer surface of the ZSM-5 molecular sieve. Afterward, the mixture is dried to remove excess moisture. Subsequently, the dried mixture is calcined at a constant temperature of 400–600 °C over 2–10 hours using a temperature-increasing method to fix magnesium hydroxide on the surface of the ZSM-5 molecular sieve, ensuring its stability and catalytic activity.

[0021] In one optional embodiment, the method for preparing the magnesium hydroxide colloid includes the following steps:

[0022] Under stirring conditions, a surfactant was added to the magnesium salt solution, followed by the addition of an alkaline substance and the pH of the system was controlled at 9–11 to carry out the reaction, resulting in a stable magnesium hydroxide colloid.

[0023] Preferably, the magnesium salt, calculated as magnesium oxide, has a magnesium oxide content of 3% to 10% by mass in the magnesium salt solution, more preferably 5% to 10%;

[0024] The amount of surfactant added is 0.1% to 5% of the mass of magnesium oxide in the magnesium salt solution.

[0025] In one optional embodiment, during the preparation of magnesium hydroxide colloid, the stirring rate is 300–600 rpm; the reaction temperature is 20–60°C; and the reaction time is 1–4 h.

[0026] In one optional embodiment, during the preparation of magnesium hydroxide colloid, the magnesium salt is a soluble magnesium salt, preferably at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0027] The surfactant is selected from at least one of sodium dodecyl sulfate, polyvinylpyrrolidone, and sodium dodecylbenzene sulfonate;

[0028] The alkaline substance is selected from ammonia water; preferably, the pH of the ammonia water is ≤12.

[0029] In one optional embodiment, the method for preparing the magnesium hydroxide colloid includes the following steps:

[0030] A predetermined amount of magnesium salt is dissolved in a suitable solvent (such as deionized water) to form a magnesium salt solution. A surfactant is then added and stirred until homogeneous. An alkaline substance is slowly added to the system containing the magnesium salt and surfactant using a titrator. During the addition of the alkaline substance, the pH value of the system is monitored and controlled in real time using a pH meter, maintaining it between 9 and 11. Simultaneously, continuous and constant stirring and temperature are maintained throughout the entire process of adding the alkaline substance to promote uniform nucleation and growth of magnesium hydroxide particles, while preventing excessive particle growth or aggregation. After a reaction of 2–4 hours, a stable magnesium hydroxide colloid is formed.

[0031] In one optional embodiment, the alkaline binder is an alkaline silica sol, preferably, the silica content in the alkaline silica sol is 20% to 50%.

[0032] The clay is selected from at least one of kaolin, halloysite, montmorillonite, sepiolite, hydrotalcite, and rettoite.

[0033] The present invention also provides a method for preparing the above-mentioned C4 olefin catalytic cracking catalyst, comprising the following steps:

[0034] S1: Add plasticizer, extrusion aid, pore-forming agent and deionized water to the mixture of modified ZSM-5 molecular sieve and alkaline binder, mix well and then form to obtain a plastic body;

[0035] S2: The plastic body is extruded to obtain a wet catalyst, which is then dried and calcined to obtain the C4 olefin catalytic cracking catalyst;

[0036] Preferably, based on the total mass of the C4 olefin catalytic cracking catalyst as 100%, the amount of plasticizer added is 0.5% to 5%, the amount of extrusion aid added is 0.5% to 5%, and the amount of pore-forming agent added is 0.5% to 5%.

[0037] In an optional embodiment, step S1 further includes adding clay to the mixture of the modified ZSM-5 molecular sieve and the alkaline binder, that is, adding clay, plasticizer, extrusion aid, pore-forming agent and deionized water to the mixture of the modified ZSM-5 molecular sieve and the alkaline binder, mixing it evenly and then molding it to obtain a plastic body.

[0038] In one optional embodiment, the plasticizer is at least one of phthalate compounds;

[0039] The extrusion aid is selected from guar gum powder and / or starch;

[0040] The pore-forming agent is selected from at least one of polyethylene glycol, activated carbon, methylcellulose, and polyacrylamide.

[0041] In one optional embodiment, the parameters for drying the wet catalyst are not specifically limited, as long as the moisture in the wet catalyst is removed. The present invention recommends a drying temperature of 60–150°C, a calcination temperature of 400–600°C, and a calcination time of 1–4 hours.

[0042] The beneficial effects of this invention are as follows:

[0043] Existing C4 olefin catalytic cracking catalysts typically possess only single acid or base catalytic properties, limiting their application range and efficiency in complex chemical reactions. Especially in reactions requiring simultaneous acid-base catalysis, traditional catalysts often fail to meet the demands for high efficiency and selectivity. The C4 olefin catalytic cracking catalyst provided by this invention solves this technical challenge by first occupying the internal pores of a ZSM-5 molecular sieve with a pore blocker, then loading magnesium hydroxide colloid onto the outer surface of the ZSM-5 molecular sieve, and finally decomposing the pore blocker to release the internal pores of the ZSM-5 molecular sieve. This composite catalyst not only provides an effective base catalytic environment on its outer surface but also enables highly efficient acid catalysis within the pores of the molecular sieve, thus achieving simultaneous acid-base catalytic reactions in the same catalytic system. This design significantly improves the efficiency and selectivity of the catalytic reaction while reducing the occurrence of side reactions, providing a new solution for heterogeneous catalysis. The C4 olefin catalytic cracking catalyst provided by this invention can effectively integrate acidic and base catalytic properties while maintaining high stability, thereby improving the yield and selectivity of ethylene and propylene. Attached Figure Description

[0044] Figure 1 The N2 adsorption-desorption curves of the modified ZSM-5 molecular sieves prepared in Example 1 and Comparative Example 4 are shown.

[0045] Figure 2 The N2 adsorption-desorption curves are for the modified ZSM-5 molecular sieves prepared in Example 4 and Comparative Example 3. Detailed Implementation

[0046] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0047] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0048] Analysis and testing methods:

[0049] The pore structure of the samples was determined using a Micromeritics ASAP3000 automated physical adsorption analyzer.

[0050] raw material:

[0051] Polyethylene glycol (molecular weight 1000), polyvinyl alcohol, Sinopharm reagent.

[0052] Activated carbon, black powder, purchased from Tianjin Yongda Chemical Reagent Co., Ltd.

[0053] ZSM-5 molecular sieves were purchased from Tianjin Nanhua Catalyst Co., Ltd., with silicon-to-aluminum ratios of 30, 50, and 100, respectively. Phosphorus-modified ZSM-5 molecular sieves (with a P2O5 content of 4.4% by mass), phosphorus-zinc-modified ZSM-5 molecular sieves (with a P2O5 content of 4.6% by mass and a Zn content of 1.4% by mass), and phosphorus-iron-modified ZSM-5 molecular sieves (with a P2O5 content of 4.2% by mass and an Fe content of 1.5% by mass) were purchased from Beijing Bowen Kefeng Trading Co., Ltd., all with a silicon-to-aluminum ratio of 25.

[0054] The nano-silica sol was purchased from Guangdong Huierte Nanotechnology Co., Ltd. The average particle size of the nano-silica sol is less than 2 nanometers, and the silica content is 30%.

[0055] The alkaline silica sol binder was purchased from Qingdao Ocean Chemical Co., Ltd., and its silica content was 30%.

[0056] Kaolin and halloysite are both industrial products, supplied by the Catalyst Division of Lanzhou Petrochemical.

[0057] The raw materials and their sources listed above are not intended to limit the present invention. The present invention will be further illustrated below by way of examples, but it is not believed that the present invention is limited to these examples.

[0058] Example 1

[0059] This embodiment provides a C4 olefin catalytic cracking catalyst, the preparation method of which includes the following steps:

[0060] (1) Preparation of modified ZSM-5 molecular sieve:

[0061] 151 g of magnesium chloride hexahydrate was dissolved in 440 g of deionized water at a constant stirring speed of 300 rpm at 20 °C. Then, 0.3 g of sodium dodecyl sulfate was added and stirred until homogeneous. Ammonia water was slowly added dropwise, and the pH value of the system was monitored and controlled in real time using a pH meter to maintain it at 9.0-9.5. After stirring continuously for 1 hour, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0062] 968 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30 was mixed with 265 g of deionized water to obtain a mixed slurry. 167 g of nano-silica sol was added to the mixed slurry under continuous stirring for 1 hour. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2 hours. After filtration and drying at 80°C to remove moisture, the temperature was increased from room temperature to 400°C in 2 hours and then cured and calcined at 400°C for 2 hours to obtain the modified ZSM-5 molecular sieve.

[0063] The modified ZSM-5 molecular sieve contains 3% magnesium oxide by mass.

[0064] (2) Catalyst preparation: 421 g of the modified ZSM-5 molecular sieve was mixed with 667 g of alkaline silica sol, then 663 g of kaolin was added, followed by 5 g of dioctyl phthalate, 5 g of starch, 5 g of polyethylene glycol, and 279 g of deionized water. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was then extruded in an extruder to obtain a wet catalyst. The catalyst was dried at 80 °C to remove moisture and calcined at 400 °C for 2 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as S1, and the reaction performance is shown in Table 1.

[0065] In the catalyst of this embodiment, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis):m(clay, on a dry basis) = 40%:20%:40%.

[0066] Example 2

[0067] This embodiment provides a C4 olefin catalytic cracking catalyst, the preparation method of which includes the following steps:

[0068] (1) Preparation of modified ZSM-5 molecular sieve:

[0069] 252 g of magnesium chloride hexahydrate and 248 g of deionized water were dissolved in a constant stirring speed of 400 rpm at 40 °C. Then, 0.25 g of sodium dodecyl sulfate was added and stirred until homogeneous. Ammonia water was then slowly added dropwise, and the pH of the system was monitored and controlled in real time using a pH meter to maintain it at 9.0-10.0. After stirring continuously for 3 hours, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0070] 905 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 50 was mixed with 279 g of deionized water to obtain a mixed slurry. 300 g of nano-silica sol was added to the mixed slurry under continuous stirring for 1 hour. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2 hours. After filtration and drying at 90°C to remove moisture, the temperature was increased from room temperature to 600°C in 10 hours and then cured and calcined at 600°C for 2 hours to obtain the modified ZSM-5 molecular sieve.

[0071] The modified ZSM-5 molecular sieve contains 5% magnesium oxide by mass.

[0072] (2) Catalyst preparation: 526 g of the modified ZSM-5 molecular sieve was mixed with 667 g of alkaline silica sol, then 380 g of halloysite was added, followed by 10 g of dioctyl phthalate, 10 g of starch, 15 g of polyethylene glycol, and 94 g of deionized water. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was then extruded in an extruder to obtain a wet catalyst. The catalyst was dried at 90 °C to remove moisture and calcined at 400 °C for 2 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as S2, and its reaction performance is shown in Table 1.

[0073] In the catalyst of this embodiment, m(modified molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis):m(clay, on a dry basis) = 50%:20%:30%.

[0074] Example 3

[0075] This embodiment provides a C4 olefin catalytic cracking catalyst, the preparation method of which includes the following steps:

[0076] (1) Preparation of modified ZSM-5 molecular sieve:

[0077] 254 g of magnesium nitrate hexahydrate and 264 g of deionized water were dissolved in a constant stirring speed of 400 rpm at 50 °C. Then, 0.36 g of polyvinylpyrrolidone was added and stirred until homogeneous. Ammonia was then slowly added dropwise, and the pH of the system was monitored and controlled in real time using a pH meter to maintain it at 9.5-10.0. After stirring continuously for 2 hours, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0078] 884 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 100 was mixed with 216 g of deionized water to obtain a mixed slurry. 400 g of nano-silica sol was added to the mixed slurry under continuous stirring for 2 hours. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2 hours. After filtration and drying at 100°C to remove moisture, the temperature was increased from room temperature to 500°C in 5 hours and then cured and calcined at 500°C for 2 hours to obtain the modified ZSM-5 molecular sieve.

[0079] The modified ZSM-5 molecular sieve contains 4% magnesium oxide by mass.

[0080] (2) Catalyst preparation: 737 g of the modified ZSM-5 molecular sieve was mixed with 1000 g of alkaline silica sol, and then 40 g of diallyl phthalate, 30 g of guar gum powder, and 30 g of polyethylene glycol were added. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was placed in an extruder and extruded to obtain a wet catalyst. The catalyst was dried at 100 °C to remove moisture and calcined at 400 °C for 2 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as S3, and the reaction performance is shown in Table 1.

[0081] In the catalyst of this embodiment, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis) = 70%:30%.

[0082] Example 4

[0083] This embodiment provides a C4 olefin catalytic cracking catalyst, the preparation method of which includes the following steps:

[0084] (1) Preparation of modified ZSM-5 molecular sieve:

[0085] 191 g of magnesium nitrate hexahydrate and 809 g of deionized water were dissolved in a constant stirring speed of 500 rpm at 60 °C. Then, 0.6 g of polyvinylpyrrolidone was added and stirred until homogeneous. Ammonia was then slowly added dropwise, and the pH of the system was monitored and controlled in real time using a pH meter to maintain it between 9.5 and 11.0. After stirring continuously for 3 hours, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0086] 989 g of phosphorus-modified ZSM-5 molecular sieve was mixed with 410 g of deionized water to obtain a mixed slurry. 30 g of polyvinyl alcohol was added to the mixed slurry under continuous stirring for 2 hours. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2 hours. After filtration and drying at 110°C to remove moisture, the temperature was increased from room temperature to 400°C in 4 hours and then cured and calcined at 400°C for 2 hours to obtain the modified ZSM-5 molecular sieve.

[0087] The modified ZSM-5 molecular sieve contains 3% magnesium oxide by mass.

[0088] (2) Catalyst preparation: 737 g of the modified ZSM-5 molecular sieve and 833 g of alkaline silica sol were mixed, then 63 g of kaolin was added, followed by 30 g of dioctyl phthalate, 20 g of starch, 30 g of activated carbon, and 137 g of deionized water. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was then extruded in an extruder to obtain a wet catalyst. The catalyst was dried at 110 °C to remove moisture and calcined at 600 °C for 4 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as S4, and its reaction performance is shown in Table 1.

[0089] In the catalyst of this embodiment, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis):m(clay, on a dry basis) = 70%:25%:5%.

[0090] Example 5

[0091] This embodiment provides a C4 olefin catalytic cracking catalyst, the preparation method of which includes the following steps:

[0092] (1) Preparation of modified ZSM-5 molecular sieve:

[0093] 159 g of magnesium nitrate hexahydrate and 258 g of deionized water were dissolved in a constant stirring speed of 500 rpm at 50 °C. Then, 0.5 g of polyvinylpyrrolidone was added and stirred until homogeneous. Ammonia was then slowly added dropwise, and the pH of the system was monitored and controlled in real time using a pH meter to maintain it between 9.5 and 11.0. After stirring continuously for 3 hours, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0094] 974 g of phosphorus-zinc modified ZSM-5 molecular sieve was mixed with 701 g of deionized water to obtain a mixed slurry. 50 g of polyvinyl alcohol was added to the mixed slurry under continuous stirring for 2 hours. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2 hours. After filtration and drying at 120°C to remove moisture, the temperature was increased from room temperature to 400°C in 6 hours and then cured and calcined at 400°C for 3 hours to obtain the modified ZSM-5 molecular sieve.

[0095] The modified ZSM-5 molecular sieve contains 2.5% magnesium oxide by mass.

[0096] (2) Catalyst preparation: 842 g of the modified ZSM-5 molecular sieve was mixed with 667 g of alkaline silica sol, then 38 g of kaolin was added, followed by 30 g of diallyl phthalate, 20 g of starch, 30 g of polyethylene glycol, and 220 g of deionized water. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was then extruded in an extruder to obtain a wet catalyst. The catalyst was dried at 120 °C to remove moisture and calcined at 600 °C for 1 hour to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as S5, and its reaction performance is shown in Table 1.

[0097] In the catalyst of this embodiment, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis):m(clay, on a dry basis) = 80%:17%:3%.

[0098] Example 6

[0099] This embodiment provides a C4 olefin catalytic cracking catalyst, the preparation method of which includes the following steps:

[0100] (1) Preparation of modified ZSM-5 molecular sieve:

[0101] 50 g of magnesium chloride hexahydrate and 79 g of deionized water were dissolved in a constant stirring speed of 600 rpm at 40 °C. Then, 0.4 g of sodium polydodecylbenzenesulfonate was added and stirred until homogeneous. Ammonia water was then slowly added dropwise, and the pH of the system was monitored and controlled in real time using a pH meter to maintain it at 10.0-11.0. After stirring continuously for 4 hours, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0102] 968 g of phosphorus-iron modified ZSM-5 molecular sieve was mixed with 673 g of deionized water to obtain a mixed slurry. 70 g of polyvinyl alcohol was added to the mixed slurry under continuous stirring for 2 hours. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2 hours. After filtration and drying at 150°C to remove moisture, the temperature was increased from room temperature to 500°C in 8 hours and then cured and calcined at 500°C for 2 hours to obtain the modified ZSM-5 molecular sieve.

[0103] The modified ZSM-5 molecular sieve contains 1% magnesium oxide by mass.

[0104] (2) Catalyst preparation: 947 g of the modified ZSM-5 molecular sieve was mixed with 333 g of alkaline silica sol, then 50 g of dioctyl phthalate, 50 g of starch, 20 g of polyethylene glycol, and 386 g of deionized water were added. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was placed in an extruder and extruded to obtain a wet catalyst. The catalyst was dried at 150 °C to remove moisture and calcined at 500 °C for 3 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as S4, and the reaction performance is shown in Table 1.

[0105] In the catalyst of this embodiment, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis) = 90%:10%.

[0106] Example 7

[0107] This embodiment provides a C4 olefin catalytic cracking catalyst, the preparation method of which includes the following steps:

[0108] (1) Preparation of modified ZSM-5 molecular sieve:

[0109] 101 g of magnesium chloride hexahydrate and 149 g of deionized water were dissolved in a constant stirring speed of 500 rpm at 40 °C. Then, 0.6 g of sodium dodecylbenzenesulfonate was added and stirred until homogeneous. Ammonia water was then slowly added dropwise, and the pH of the system was monitored and controlled in real time using a pH meter to maintain it between 9.5 and 10.5. After stirring continuously for 2 hours, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0110] 958 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30 was mixed with 559 g of deionized water to obtain a mixed slurry. 233 g of nano-silica sol was added to the mixed slurry under continuous stirring for 2 hours. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2 hours. After filtration and drying at 90°C to remove moisture, the temperature was increased from room temperature to 500°C in 6 hours and then cured and calcined at 500°C for 1.5 hours to obtain the modified ZSM-5 molecular sieve.

[0111] The modified ZSM-5 molecular sieve contains 2% magnesium oxide by mass.

[0112] (2) Catalyst preparation: 789 g of the modified ZSM-5 molecular sieve was mixed with 500 g of alkaline silica sol, then 141 g of halloysite was added, followed by 40 g of dioctyl phthalate, 20 g of guar gum powder, 50 g of polyethylene glycol, and 251 g of deionized water. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was then extruded in an extruder to obtain a wet catalyst. The catalyst was dried at 100 °C to remove moisture and calcined at 600 °C for 2 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as S7, and its reaction performance is shown in Table 1.

[0113] In the catalyst of this embodiment, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis):m(clay, on a dry basis) = 75%:15%:10%.

[0114] Comparative Example 1

[0115] The C4 olefin catalytic cracking catalyst provided in this comparative example is similar to that in Example 7, except that magnesium hydroxide colloid is not formed in this comparative example. The preparation method of the C4 olefin catalytic cracking catalyst provided in this comparative example includes the following steps:

[0116] (1) Preparation of modified ZSM-5 molecular sieve:

[0117] Weigh 101 g of magnesium chloride hexahydrate and 149 g of deionized water and dissolve the magnesium chloride completely at a constant stirring speed of 500 rpm at 40°C to obtain a magnesium chloride solution for later use.

[0118] 958 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30 was mixed with 559 g of deionized water to obtain a mixed slurry. 233 g of nano-silica sol was added to the mixed slurry under continuous stirring for 2 hours. Then, the prepared magnesium chloride solution was added and stirred for 2 hours. After filtration and drying at 90°C to remove moisture, the temperature was increased from room temperature to 500°C in 6 hours and then cured and calcined at 500°C for 1.5 hours to obtain the modified ZSM-5 molecular sieve.

[0119] The modified ZSM-5 molecular sieve contains 2% magnesium oxide by mass.

[0120] (2) Catalyst preparation: 789 g of the modified ZSM-5 molecular sieve was mixed with 500 g of alkaline silica sol, then 141 g of halloysite was added, followed by 40 g of dioctyl phthalate, 20 g of starch, 50 g of polyethylene glycol, and 251 g of deionized water. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was then extruded in an extruder to obtain a wet catalyst. The catalyst was dried at 100 °C to remove moisture and calcined at 600 °C for 2 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as D-1, and its reaction performance is shown in Table 1.

[0121] In the catalyst of this comparative example, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis):m(clay, on a dry basis) = 75%:15%:10%.

[0122] Comparative Example 2

[0123] The C4 olefin catalytic cracking catalyst provided in this comparative example is similar to that in Example 3, except that a pore blocker is not used. The preparation method of the C4 olefin catalytic cracking catalyst provided in this comparative example includes the following steps:

[0124] (1) Preparation of modified ZSM-5 molecular sieve:

[0125] 254 g of magnesium nitrate hexahydrate and 264 g of deionized water were dissolved in a constant stirring speed of 400 rpm at 50 °C. Then, 0.36 g of polyvinylpyrrolidone was added and stirred until homogeneous. Ammonia was then slowly added dropwise, and the pH of the system was monitored and controlled in real time using a pH meter to maintain it at 9.5-10.0. After stirring continuously for 2 hours, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0126] 884 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 100 was mixed with 216 g of deionized water to obtain a mixed slurry. The prepared magnesium hydroxide colloidal solution was added to the mixed slurry under continuous stirring and stirred for 2 hours. The mixture was then filtered and dried at 100°C to remove moisture. The temperature was then increased from room temperature to 500°C over 5 hours and cured and calcined at 500°C for 2 hours to obtain the modified ZSM-5 molecular sieve.

[0127] The modified ZSM-5 molecular sieve contains 4% magnesium oxide by mass.

[0128] (2) Catalyst preparation: 737 g of the modified ZSM-5 molecular sieve was mixed with 1000 g of alkaline silica sol, and then 40 g of diallyl phthalate, 30 g of guar gum powder, and 30 g of polyethylene glycol were added. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was placed in an extruder and extruded to obtain a wet catalyst. The catalyst was dried at 100 °C to remove moisture and calcined at 400 °C for 2 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as D-2, and the reaction performance is shown in Table 1.

[0129] In the catalyst of this comparative example, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis) = 70%:30%.

[0130] Comparative Example 3

[0131] The C4 olefin catalytic cracking catalyst provided in this comparative example is similar to that in Example 4, except that it does not form magnesium hydroxide colloid and does not use a blocker. The preparation method of the C4 olefin catalytic cracking catalyst provided in this comparative example includes the following steps:

[0132] (1) Preparation of modified ZSM-5 molecular sieve:

[0133] 191 g of magnesium nitrate hexahydrate was dissolved in 809 g of deionized water at a constant stirring speed of 500 rpm at 60 °C to obtain a magnesium nitrate solution for later use.

[0134] 989 g of phosphorus-modified ZSM-5 molecular sieve was mixed with 410 g of deionized water to obtain a mixed slurry. The prepared magnesium nitrate solution was added to the mixed slurry under continuous stirring and stirred for 2 hours. The mixture was then filtered and dried at 110°C to remove moisture. The temperature was then increased from room temperature to 400°C in 4 hours and solidified and calcined at 400°C for 2 hours to obtain the modified ZSM-5 molecular sieve.

[0135] The modified ZSM-5 molecular sieve contains 3% magnesium oxide by mass.

[0136] (2) Catalyst preparation: 737 g of the modified ZSM-5 molecular sieve and 833 g of alkaline silica sol were mixed, 63 g of kaolin was added, followed by 30 g of dioctyl phthalate, 20 g of starch, 30 g of activated carbon, and 137 g of deionized water. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was then extruded in an extruder to obtain a wet catalyst. The catalyst was dried at 110 °C to remove moisture and calcined at 600 °C for 4 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as D-3, and its reaction performance is shown in Table 1.

[0137] In the catalyst used in this comparison, m(modified ZSM-5 molecular sieve, on a dry basis): m(silica sol binder, on an oxide basis): m(clay, on a dry basis) = 70%: 25%: 5%.

[0138] Comparative Example 4

[0139] The C4 olefin catalytic cracking catalyst provided in this comparative example is similar to that in Example 1, except that the particle size of the pore blocker is different and that a temperature program is not used. The preparation method of the C4 olefin catalytic cracking catalyst provided in this comparative example includes the following steps:

[0140] (1) Preparation of modified ZSM-5 molecular sieve:

[0141] 151 g of magnesium chloride hexahydrate was dissolved in 440 g of deionized water at a constant stirring speed of 300 rpm at 20 °C. Then, 0.3 g of sodium dodecyl sulfate was added and stirred until homogeneous. Ammonia water was slowly added dropwise, and the pH of the system was monitored and controlled in real time using a pH meter to maintain it at 9.0-9.5. After stirring continuously for 3 hours, a stable colloidal solution of magnesium hydroxide was obtained and ready for use.

[0142] 968 g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30 was mixed with 265 g of deionized water to obtain a mixed slurry. 167 g of silica sol (average particle size of 60 nm, from Guangdong Huierte Nanotechnology Co., Ltd.) was added to the mixed slurry under continuous stirring, and the mixture was stirred continuously for 1 hour. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2 hours. The mixture was then filtered, dried at 80 °C to remove moisture, and cured and calcined at 400 °C for 2 hours to obtain the modified ZSM-5 molecular sieve.

[0143] The modified ZSM-5 molecular sieve contains 3% magnesium oxide by mass.

[0144] (2) Catalyst preparation: 421 g of the modified ZSM-5 molecular sieve was mixed with 667 g of alkaline silica sol, then 663 g of kaolin was added, followed by 5 g of dioctyl phthalate, 5 g of starch, 5 g of polyethylene glycol, and 279 g of deionized water. After mixing evenly, the mixture was kneaded to form a plastic body. The kneaded plastic body was then extruded in an extruder to obtain a wet catalyst. The catalyst was dried at 80 °C to remove moisture and calcined at 400 °C for 2 hours to obtain the C4 olefin catalytic cracking catalyst. The sample was designated as S1, and the reaction performance is shown in Table 1.

[0145] In the catalyst of this embodiment, m(modified ZSM-5 molecular sieve, on a dry basis):m(silica sol binder, on an oxide basis):m(clay, on a dry basis) = 40%:20%:40%.

[0146] The modified ZSM-5 molecular sieves prepared in each embodiment and comparative example, as well as the unmodified ZSM-5 molecular sieves, were subjected to pore structure testing. The results showed that the modified ZSM-5 molecular sieves prepared in each embodiment had high specific surface area and pore volume, indicating that the plugging agent completely decomposed and released the internal pores of the molecular sieve, and that the silica generated after the thermal decomposition of the nano-silica sol did not block the internal pores of the molecular sieve. Simultaneously, magnesium oxide did not block the external pores of the molecular sieve. Conversely, the modified ZSM-5 molecular sieves prepared in each comparative example showed significantly reduced specific surface area and pore volume. The following examples, using Example 1 and Comparative Example 4, and Example 4 and Comparative Example 3, provide specific examples for illustration. Figure 1 and Figure 2 The N2 adsorption-desorption curves for Example 1 and Comparative Example 4, and Example 4 and Comparative Example 3 are shown in the figure. Figure 1 and Figure 2 And the data in the table below.

[0147] Table 1

[0148]

[0149] Depend on Figure 1 and Figure 2As can be seen from the pore structure data in Table 1, compared with the unmodified molecular sieve, the modified ZSM-5 molecular sieve provided by this invention shows smaller changes in specific surface area and pore volume. This indicates that during the modification process, magnesium species did not clog the pores of the molecular sieve in large quantities, but were uniformly distributed on the surface of the molecular sieve; the plugging agent after calcination and decomposition also did not clog the internal pores of the molecular sieve. Conversely, the modified molecular sieve prepared in the comparative example showed a significant reduction in specific surface area and pore volume due to the distribution and accumulation of magnesium species in the pores of the molecular sieve.

[0150] Evaluation of catalyst performance:

[0151] The catalyst evaluation was conducted in a small fixed-bed catalytic cracking reactor. To assess the catalyst's stability and long-term effectiveness, it was subjected to high-temperature hydrothermal treatment at 780℃ and 100% steam for 48 hours prior to evaluation. This simulated the harsh conditions of industrial operation, examining changes in the catalyst's reactivity under high temperature and high steam conditions. This pretreatment allowed for the detection of the catalyst's hydrothermal stability and potential deactivation mechanisms in practical applications, ensuring good catalytic cracking selectivity during long-term use and ultimately improving the catalyst's lifespan and reactivity. The reaction conditions were: feedstock 1-butene, catalyst loading 30g, reaction temperature 550℃, atmospheric pressure, and volume hourly space velocity (VHSV) 1500 h⁻¹. -1 The obtained data is shown in Table 2.

[0152] Table 2 Catalytic cracking performance

[0153]

[0154]

[0155] As shown in the table above, the C4 olefin catalytic cracking catalyst provided by this invention effectively loads magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieve, pre-fills the pores inside the molecular sieve with a pore blocker, and releases it upon subsequent heating. This provides a highly efficient acid catalytic environment within the pores of the molecular sieve, while simultaneously creating an effective alkaline catalytic environment on its outer surface. This achieves the integration of alkaline and acidic catalytic functions in the same catalyst. Combined with alkaline binders and clay components, this not only enhances the stability and longevity of the catalyst but also increases the yield and selectivity of ethylene and propylene obtained from the catalytic cracking of C4 olefins.

[0156] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A C4 olefin catalytic cracking catalyst, characterized in that, The total weight of the C4 olefin catalytic cracking catalyst is 100%, including 40% to 90% modified ZSM-5 molecular sieve on a dry basis, 10% to 30% alkaline binder on an oxide basis, and 0% to 40% clay on a dry basis. The preparation method of the modified ZSM-5 molecular sieve includes the following steps: Under stirring, a pore-blocking agent with a particle size of less than 2 nm is added to a mixture of ZSM-5 molecular sieve and deionized water. Then, magnesium hydroxide colloid is added. After drying, the mixture is calcined at 400-600℃ for 2-10 hours to decompose the pore-blocking agent, thereby obtaining modified ZSM-5 molecular sieve.

2. The C4 olefin catalytic cracking catalyst according to claim 1, characterized in that, Based on the mass of the modified ZSM-5 molecular sieve as 100%, the content of magnesium oxide is 1% to 5%.

3. The C4 olefin catalytic cracking catalyst according to claim 1, characterized in that, The pore blocking agent is selected from nano-silica sol or polymer nanoparticles; preferably, the polymer nanoparticles are selected from polyacrylic acid and / or polyvinyl alcohol.

4. The C4 olefin catalytic cracking catalyst according to claim 1, characterized in that, The amount of the nano-silica sol added is 5% to 15% of the mass of the ZSM-5 molecular sieve, based on silica. The amount of polymer nanoparticles added is 3% to 8% of the mass of the ZSM-5 molecular sieve.

5. The C4 olefin catalytic cracking catalyst according to claim 1, characterized in that, The ZSM-5 molecular sieve is selected from low-silica shape-selective ZSM-5 molecular sieve, phosphorus-modified ZSM-5 molecular sieve, or phosphorus and metal-modified ZSM-5 molecular sieve; preferably, the silicon-to-aluminum ratio of the ZSM-5 molecular sieve is 25~100.

6. The C4 olefin catalytic cracking catalyst according to any one of claims 1-5, characterized in that, The preparation method of the magnesium hydroxide colloid includes the following steps: Under stirring conditions, a surfactant was added to the magnesium salt solution, followed by the addition of an alkaline substance and the pH of the system was controlled at 9-11 to carry out the reaction, resulting in a stable magnesium hydroxide colloid. Preferably, the magnesium salt solution contains 3% to 10% magnesium oxide by mass. The amount of surfactant added is 0.1% to 5% of the mass of magnesium oxide in the magnesium salt solution.

7. The C4 olefin catalytic cracking catalyst according to claim 1, characterized in that, The alkaline binder is an alkaline silica sol; and / or The clay is selected from at least one of kaolin, halloysite, montmorillonite, sepiolite, hydrotalcite, and rettoite.

8. A method for preparing a C4 olefin catalytic cracking catalyst according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Add plasticizer, extrusion aid, pore-forming agent and deionized water to the mixture of modified ZSM-5 molecular sieve and alkaline binder, mix well and then form to obtain a plastic body; S2: The plastic body is extruded to obtain a wet catalyst, which is then dried and calcined to obtain the C4 olefin catalytic cracking catalyst; Preferably, based on the total mass of the C4 olefin catalytic cracking catalyst as 100%, the amount of plasticizer added is 0.5% to 5%, the amount of extrusion aid added is 0.5% to 5%, and the amount of pore-forming agent added is 0.5% to 5%.

9. The preparation method according to claim 8, characterized in that, It also includes the step of adding clay to the mixture of the modified ZSM-5 molecular sieve and the alkaline binder.

10. The preparation method according to claim 8 or 9, characterized in that, The plasticizer is at least one of phthalate compounds; The extrusion aid is selected from guar gum powder and / or starch; The pore-forming agent is selected from at least one of polyethylene glycol, activated carbon, methylcellulose, and polyacrylamide.

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