Heavy oil catalytic cracking catalyst and preparation method thereof

Abstract

The invention provides a heavy oil catalytic cracking catalyst and a preparation method thereof, and the catalyst comprises the following raw materials by mass: 30-50% of a magnesium modified ZSM-5 molecular sieve on a dry basis, 5-20% of a Y-type molecular sieve on a dry basis, 0.5-4% of a rare earth compound on an oxide basis, 20-30% of an inorganic oxide binder on an oxide basis, and the balance of a solvent. On a dry basis, the acid modified clay accounts for 10-35%, and the magnesium salt accounts for 1-3%. The catalyst provided by the invention significantly improves the catalytic cracking efficiency of heavy oil, improves the selectivity of propylene and ethylene, reduces the occurrence of side reactions, and provides a new solution for heterogeneous catalysis.

Description

Technical Field

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

[0002] With the rapid growth in demand for low-carbon olefins such as ethylene, propylene, and aromatics, the oil refining industry is undergoing a crucial transformation towards chemical production. Utilizing various oil products to increase chemical production through catalytic reactions has become a research hotspot in the refining field. Among these technologies, catalytic cracking of oil products, as a novel process for producing low-carbon olefins, lowers the reaction temperature and improves oil utilization compared to traditional steam cracking by introducing catalysts. This increases the yield of ethylene and propylene and effectively reduces CO2 emissions, demonstrating its potential as a major source of low-carbon olefins.

[0003] The growth of the chemical and petroleum industries has driven the increasing demand for propylene and ethylene. These two compounds are key raw materials for numerous chemicals and plastics, making the improvement of their production efficiency and yield a crucial goal for research and industry. While traditional catalytic cracking processes can produce these compounds, their yields are limited by catalyst characteristics and reaction conditions. Therefore, developing catalysts that can simultaneously increase the yield of propylene and ethylene has become an important research topic. Researchers have begun exploring catalysts combining acidic and basic catalytic properties, with basic catalysts exhibiting excellent performance in certain chemical reactions involving oxygen-containing compounds. Introducing basic properties into traditional acidic catalytic cracking processes holds promise for improving the selectivity of the cracking reaction, particularly in increasing the production of propylene and ethylene.

[0004] The basic principle of catalytic cracking is to use a catalyst to promote the breakdown of hydrocarbons at lower temperatures, converting large molecules into smaller ones and generating free radicals that further promote chain reactions. Compared to thermal cracking (catalyst-free cracking), catalytic cracking occurs at lower temperatures and under milder conditions, making it more economical and efficient. The key to catalytic cracking lies in the selection and design of the catalyst. Traditional catalysts are mainly acidic, such as zeolite molecular sieves, which are widely used due to their unique pore structure and acidic properties. These catalysts not only improve reaction selectivity but also control the composition of the final product. For example, ZSM-5 molecular sieves, due to their unique pore structure and strong acidity, perform excellently in the preparation of high-quality fuels.

[0005] With technological advancements and increasing environmental demands, catalytic cracking technology is constantly evolving and improving. Researchers are dedicated to developing more efficient and environmentally friendly catalysts, optimizing cracking processes, and reducing energy consumption and pollutant emissions. Simultaneously, with changing demands for olefins (especially propylene and ethylene), catalyst and process improvements are also geared towards increasing the yield and quality of these products. Currently, catalysts used in catalytic cracking processes are primarily based on zeolite molecular sieves, especially the ZSM-5 type. These catalysts are renowned for their unique pore structure, high specific surface area, and excellent thermal stability, enabling efficient conversion of heavy oils into light, high-value hydrocarbons. However, despite their importance in the petroleum refining industry, they have limitations. First, traditional zeolite molecular sieve catalysts are primarily strongly acidic, resulting in low selectivity for specific compounds during catalytic cracking. While these acidic catalysts effectively promote hydrocarbon cracking, their effectiveness in increasing the yield of specific products such as light olefins is limited. These light olefins are highly valuable in the manufacture of plastics, rubber, and chemicals, making yield improvement a key research focus. Second, catalyst deactivation is a major challenge. High temperatures and carbon deposition lead to gradual catalyst deactivation; although activity can be restored through regeneration, this increases operational complexity and cost. Frequent regeneration cycles also affect the long-term stability and efficiency of catalysts. Furthermore, environmental issues are a significant consideration for catalytic cracking catalysts. With increasingly stringent environmental standards, reducing pollutants generated during catalytic cracking has become a crucial factor in catalyst design and selection. Existing catalysts require improvement in this regard. Therefore, developing novel catalysts that improve selectivity for specific products while reducing environmental impact, and enhancing catalyst stability and lifespan, has become a major research direction in the field of catalytic cracking technology. This includes exploring new materials such as modified zeolite molecular sieves and metal-organic frameworks (MOFs), as well as developing more efficient catalyst regeneration technologies. Through these studies, catalytic cracking processes can be further optimized, improving petroleum refining efficiency and environmental sustainability.

[0006] Currently, catalytic cracking processes suffer from limitations in selectivity and efficiency, particularly in simultaneously increasing the production of propylene and ethylene. Existing catalysts typically optimize only one type of reaction—either acidic or basic catalysis—and cannot effectively promote both types of reactions simultaneously. Summary of the Invention

[0007] To address the aforementioned technical problems, the present invention aims to provide a heavy oil catalytic cracking catalyst and its preparation method, thereby improving the heavy oil cracking efficiency.

[0008] To achieve the above objectives, the present invention provides a heavy oil catalytic cracking catalyst, the raw materials of which, by mass percentage, include: 30-50% magnesium-modified ZSM-5 molecular sieve on a dry basis, 5-20% Y-type molecular sieve on a dry basis, 0.5-4% rare earth compounds on an oxide basis, 20-30% inorganic oxide binder on an oxide basis, 10-35% acid-modified clay on a dry basis, and 1-3% magnesium salt on a magnesium oxide basis;

[0009] The magnesium oxide content in the magnesium-modified ZSM-5 molecular sieve is 1-5% by mass.

[0010] The magnesium-modified ZSM-5 molecular sieve was prepared by the following method:

[0011] Mix ZSM-5 molecular sieve with water to form a slurry, add 5-15% of a pore-blocking agent by mass of ZSM-5 molecular sieve, and stir to block the pores of the molecular sieve. The pore-blocking agent includes one or more of nano-silica sol, polyacrylic acid nanoparticles, and polyvinyl alcohol nanoparticles. Then add pre-prepared magnesium hydroxide colloid and stir to load the magnesium hydroxide colloid onto the outer surface of the ZSM-5 molecular sieve.

[0012] The molecular sieve with the loaded colloid was removed, heated to 400-600℃ at a rate not exceeding 4℃ / min, and calcined at this temperature to obtain magnesium-modified ZSM-5 molecular sieve.

[0013] Existing catalytic materials typically possess only single-acid or single-base catalytic properties, which limits their application range and efficiency in complex chemical reactions. Especially in reactions requiring simultaneous acid-base catalysis, traditional catalysts often fail to meet the requirements of high efficiency and high selectivity.

[0014] This invention proposes a novel method for combining magnesium hydroxide colloid with ZSM-5 molecular sieves. By selectively loading magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieves without penetrating the internal pores, an effective alkaline catalytic environment is provided on the outer surface of the molecular sieve without interfering with the internal pore structure and acidic properties. This allows for efficient acid catalysis within the molecular sieve pores, enabling simultaneous acid and alkaline catalytic reactions in the same catalytic system. Consequently, the catalytic cracking efficiency of the catalyst is improved, leading to increased production of propylene and ethylene.

[0015] Conventional methods for modifying magnesium in molecular sieves use magnesium ions, which can cause reverse exchange with the blockage agents that fill the sieve channels, thus re-entering the channels and interfering with the acidic properties of the molecular sieve. This invention uses magnesium hydroxide colloid loaded onto the molecular sieve, which prevents the magnesium component from migrating into the sieve channels.

[0016] This invention uses nano-silica sol, polyacrylic acid nanoparticles, and other substances as pore-blocking agents. These materials effectively seal the pores of the molecular sieve, providing a stable outer surface for subsequent loading of magnesium hydroxide colloid. This sealing method differs from existing organic sealing methods and offers better control, ensuring that the acidic properties within the pores remain unaffected.

[0017] This invention controls the heating rate and calcination temperature after loading magnesium hydroxide colloid to prevent magnesium components from migrating into the molecular sieve framework or channels through solid phase under high-temperature calcination conditions. This allows the magnesium-modified ZSM-5 molecular sieve to simultaneously possess acid catalytic and base catalytic properties, significantly improving the selectivity and yield of propylene and ethylene during catalytic cracking.

[0018] According to a specific embodiment of the present invention, preferably, in the method for preparing magnesium-modified ZSM-5 molecular sieve, the mass fraction of magnesium salt in magnesium hydroxide colloid, calculated as magnesium oxide, is 3-10%, more preferably 5-7%.

[0019] According to a specific embodiment of the present invention, preferably, in the method for preparing magnesium-modified ZSM-5 molecular sieve, the magnesium hydroxide colloid is prepared by the following method:

[0020] A surfactant was added to a magnesium salt solution, and an alkaline solution was slowly and continuously added under constant temperature and constant speed stirring conditions to maintain the pH value of the solution between 9 and 11. The mixture was stirred continuously to obtain magnesium hydroxide colloid.

[0021] The magnesium salt solution contains 3-10% magnesium salt by mass (calculated as magnesium oxide), and the amount of surfactant added is 1-5% by mass (calculated as magnesium oxide) of the magnesium salt.

[0022] According to a specific embodiment of the present invention, preferably, in the method for preparing the magnesium hydroxide colloid, the stirring temperature is 20-60℃, the stirring speed is 300-600rpm, and the stirring time is 1-4h.

[0023] According to a specific embodiment of the present invention, preferably, in the method for preparing the magnesium hydroxide colloid, the magnesium salt includes one or a combination of two or more of magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0024] According to a specific embodiment of the present invention, preferably, in the method for preparing the magnesium hydroxide colloid, the surfactant includes one or a combination of two or more of sodium dodecyl sulfate, polyvinylpyrrolidone, and sodium dodecylbenzenesulfonate.

[0025] According to a specific embodiment of the present invention, preferably, in the method for preparing magnesium hydroxide colloid, the alkaline solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water; more preferably, the pH value of the alkaline solution does not exceed 12.

[0026] According to a specific embodiment of the present invention, preferably, in the preparation method of magnesium-modified ZSM-5 molecular sieve, the particle size of the pore blocking agent is <2nm.

[0027] According to a specific embodiment of the present invention, preferably, in the preparation method of the magnesium-modified ZSM-5 molecular sieve or magnesium-modified Y-type molecular sieve, the calcination time is 1-4 hours; the calcination heating process adopts a programmed temperature rise method.

[0028] According to a specific embodiment of the present invention, preferably, in the preparation method of the magnesium-modified ZSM-5 molecular sieve, the silica-alumina ratio of the ZSM-5 molecular sieve is 25-100. More preferably, the ZSM-5 molecular sieve is selected from ordinary low-silica shape-selective ZSM-5 molecular sieve, modified ZSM-5 molecular sieve, or derivative thereof.

[0029] According to a specific embodiment of the present invention, preferably, the Y-type molecular sieve includes one or more combinations of HY molecular sieve, USY molecular sieve, REUSY molecular sieve, REY molecular sieve, and their modified or derivative products. More preferably, the mass content of Na2O in the Y-type molecular sieve is not greater than 0.5%.

[0030] According to a specific embodiment of the present invention, preferably, the preparation method of the magnesium-modified ZSM-5 molecular sieve or the magnesium-modified Y-type molecular sieve includes the following steps:

[0031] (1) Preparation of magnesium hydroxide colloid: Dissolve a predetermined amount of magnesium source salt in a suitable solvent (such as deionized water), ensuring that enough water is used to completely dissolve the magnesium salt to form a magnesium salt solution; then add a surfactant and stir evenly; subsequently, slowly add alkali solution to the solution containing magnesium salt using a titrator, while monitoring the pH value of the solution in real time using a pH meter, and controlling the pH value between 9 and 11; throughout the alkali addition process, keep the solution continuously stirred, maintain constant stirring and temperature conditions to promote uniform nucleation and growth of magnesium hydroxide particles, while avoiding excessive particle growth or aggregation; after a reaction of 1-4 hours, a stable magnesium hydroxide colloid is formed;

[0032] (2) Molecular sieve pretreatment: ZSM-5 molecular sieve / Y-type molecular sieve is mixed with deionized water and pulped; then an appropriate amount of pore blocker is added to the slurry, and the blocker is thoroughly stirred to ensure that it is evenly distributed in the molecular sieve pores and effectively penetrates.

[0033] (3) The pre-prepared magnesium hydroxide colloid is slowly added to the pretreated ZSM-5 molecular sieve / Y-type molecular sieve and stirred under a certain constant temperature condition to ensure the uniform distribution and effective loading of magnesium hydroxide colloid on the outer surface of ZSM-5 molecular sieve / Y-type molecular sieve. The mass content of magnesium hydroxide in ZSM-5 molecular sieve / Y-type molecular sieve is 1-10% based on magnesium oxide.

[0034] (4) The ZSM-5 molecular sieve / Y-type molecular sieve loaded with colloid is filtered and dried at 60-100℃ to remove excess moisture. Then, the dried molecular sieve is calcined at 400-600℃. The temperature is raised to the calcination temperature within 2-10 hours using a programmed temperature rise method to fix magnesium hydroxide on the outer surface of the ZSM-5 molecular sieve / Y-type molecular sieve, ensuring its stability and catalytic activity, and finally magnesium-modified ZSM-5 molecular sieve / magnesium-modified Y-type molecular sieve is obtained.

[0035] According to a specific embodiment of the present invention, preferably, the inorganic oxide binder includes one or more of aluminum sol, silica sol, boehmite, and aluminosilicate sol.

[0036] According to a specific embodiment of the present invention, preferably, the rare earth compound is a water-soluble rare earth compound; the rare earth elements in the rare earth compound include one or more combinations of lanthanum, cerium, praseodymium, neodymium, and yttrium.

[0037] According to a specific embodiment of the present invention, preferably, the pH value of the acid-modified clay is 0-2; the clay used in the acid-modified clay includes one or more combinations of kaolin, halloysite, montmorillonite, sepiolite, hydrotalcite, and rettoite.

[0038] In the heavy oil catalytic cracking catalyst of the present invention, the modified clay is acid-modified clay. The method of modifying clay with acid is not specifically limited, and conventional methods in the industry can be used. For example, after the clay is slurried with deionized water, it is stirred evenly at 60-70°C, acidic substances are added and the pH value of the system is maintained between 0 and 2. The mixture is stirred continuously for not less than 1 hour to obtain acid-modified clay.

[0039] The present invention also provides a method for preparing the above-mentioned heavy oil catalytic cracking catalyst, which includes the following steps:

[0040] S1. Inorganic oxide binder, acid-modified clay, rare earth compound and water are mixed, acid is added and gel treatment is performed, then magnesium salt is added and mixed to obtain colloid;

[0041] S2. Add magnesium-modified ZSM-5 molecular sieve and Y-type molecular sieve to the colloid and mix them to obtain a slurry;

[0042] S3. The slurry is spray-dried into particles and calcined to obtain the heavy oil catalytic cracking catalyst.

[0043] In the preparation of heavy oil catalytic cracking catalysts, magnesium salts play two roles: firstly, magnesium salts can modify the matrix, improve the catalyst's resistance to metal contamination, and optimize the acidity distribution, thereby improving the catalyst's selectivity; secondly, magnesium salts can adjust the pH value of the colloid obtained in S1 during catalyst preparation, preventing magnesium in the magnesium-modified ZSM-5 molecular sieve from being dissociated in the acidic system.

[0044] In the above-mentioned method for preparing heavy oil catalytic cracking catalyst, preferably, the pH value of the colloid is 6.5-9, more preferably 8-9.

[0045] In the above-mentioned method for preparing a catalyst for increasing propylene and ethylene production through catalytic cracking, preferably, in step S1, the sol-gel treatment temperature is 40-80℃ and the sol-gel treatment time is 1-2h.

[0046] In the above-mentioned method for preparing the heavy oil catalytic cracking catalyst, preferably, in step S1, the acid includes one or a combination of two or more of hydrochloric acid, nitric acid, formic acid, and acetic acid. The amount of acid used should be sufficient to ensure adequate colloidation without damaging the pore structure of the matrix. Generally, too little acid will result in insufficient colloidation, while too much acid will damage the pore structure of the matrix. More preferably, when the inorganic oxide binder is boehmite, the mass ratio of the acid to the boehmite (calculated as alumina) does not exceed 0.1.

[0047] In the above-mentioned method for preparing heavy oil catalytic cracking catalyst, preferably, the calcination temperature of the particles is 300-600℃ and the calcination time is 0.5-2h.

[0048] According to a specific embodiment of the present invention, the preferred method for preparing the above-mentioned heavy oil catalytic cracking catalyst specifically includes the following steps:

[0049] (1) Add deionized water, optional clay, and rare earth compounds according to the mass percentage of the catalyst to the gelation reactor and mix thoroughly. Add acidic substances, slurry and mix evenly, and react at 60-70℃ for no less than 1 hour.

[0050] (2) Add boehmite to the gelation reactor and mix thoroughly. Add acid according to the mass percentage of the catalyst for gelation treatment. After forming a colloid, add magnesium salt and mix evenly to obtain a colloid.

[0051] (3) After the colloid obtained in step (2) is gelled, magnesium-modified ZSM-5 molecular sieve and Y-type molecular sieve are added, and the mixture is stirred for 30-60 minutes to make a slurry.

[0052] (4) The formed colloid is dried by spray drying, wherein the conditions for spray drying are conventional conditions in the art;

[0053] (5) After the particles are dried and shaped in step (4), they are calcined and cured at 300-600℃ for 0.5-2h to obtain calcined particles;

[0054] (6) The calcined particles obtained in step (5) are washed with an aqueous solution of ammonium chloride to obtain a heavy oil catalytic cracking catalyst.

[0055] The present invention also provides a method for catalytic cracking of heavy oil, which includes: bringing the above-mentioned heavy oil catalytic cracking catalyst into full contact with heavy oil to carry out a cracking reaction.

[0056] In the above-mentioned heavy oil catalytic cracking method, preferably, the reaction temperature is 550-600℃ and the catalyst-to-oil ratio is 7-10; more preferably, the reaction temperature is 590℃ and the catalyst-to-oil ratio is 9.0.

[0057] The technical solution provided by this invention has the following beneficial effects:

[0058] This invention, by loading magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieves, not only provides an effective alkaline catalytic environment on its outer surface but also does not interfere with the internal pore structure and acidic properties of the molecular sieve. This maintains highly efficient acid catalysis within the molecular sieve's pores, thereby enabling simultaneous acid and alkaline catalytic reactions in the same catalytic system. The catalyst provided by this invention significantly improves the catalytic cracking efficiency of heavy oil and enhances the selectivity for propylene and ethylene, while reducing the occurrence of side reactions, offering a new solution for heterogeneous catalysis.

[0059] The development of this heavy oil catalytic cracking catalyst is based on a deep understanding of the catalytic cracking process and an awareness of the limitations of existing catalysts. Combining acidic and basic catalytic properties, this invention not only overcomes the limitations of existing technologies in increasing the yield of specific products but also demonstrates new ideas for catalyst design. This is of great significance for increasing propylene and ethylene production and will have a profound impact on the development of catalyst science and petroleum refining technology. Attached Figure Description

[0060] Figure 1 BET nitrogen adsorption-desorption curves of the magnesium-modified ZSM-5 molecular sieves prepared in Example 4 and Comparative Example 2. Detailed Implementation

[0061] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0062] In the following examples and comparative examples, the elemental content in the samples was determined by X-ray fluorescence analysis.

[0063] The origin and specifications of the raw materials used in the embodiments and comparative examples of this invention.

[0064] ZSM-5 molecular sieves are products of Tianjin Nanhua Catalyst Co., Ltd., with silicon-to-aluminum ratios of 30, 50, and 100.

[0065] The nano silica sol is a product of 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%.

[0066] Kaolin, halloysite, boehmite, silica sol, alumina sol, Y-type molecular sieve, etc. are all industrial products, provided by Lanzhou Petrochemical Catalyst Division.

[0067] Example 1

[0068] This embodiment provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0069] (1) Preparation of magnesium hydroxide colloid: Weigh 151g of magnesium chloride hexahydrate, add 849g of deionized water, maintain a constant stirring speed of 300rpm, control the reaction temperature at 20℃, and allow the magnesium chloride to dissolve completely; then add 0.3g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 9.0-9.5, and continue stirring for 3h to obtain a magnesium hydroxide colloidal solution for later use;

[0070] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 989g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30, add 793g of deionized water, add 167g of nano-silica sol under continuous stirring, and continue stirring for 1h; then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter, dry, and use a programmed temperature rise method to raise the temperature from room temperature to 400℃ within 2h (heating rate ≤4℃ / min), and then solidify and calcine at 400℃ for 4h to obtain magnesium-modified ZSM-5 molecular sieve; the mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve is 1%;

[0071] (3) Preparation of heavy oil catalytic cracking catalyst: Take 595g of kaolin, add 771g of deionized water and 90g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 70℃ and stir continuously for 60min to obtain acid-modified clay; add 952g of aluminum sol, 476g of boehmite and 22g of lanthanum chloride to the acid-modified clay, add 20g of concentrated hydrochloric acid while stirring continuously, keep at 70℃ and stir continuously for 60min, add 101g of magnesium chloride, stir thoroughly to obtain colloid, at which time the pH of the system is 8.2;

[0072] Add 632g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 506g of REUSY molecular sieve, and 2195g of deionized water to the colloid, mix and stir evenly to obtain a slurry. Spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 120℃, and then cure and calcine at 400℃ for 2 hours to obtain calcined microspheres. Then wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30 minutes, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as S1.

[0073] Example 2

[0074] This embodiment provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0075] (1) Preparation of magnesium hydroxide colloid: Weigh 101g of magnesium chloride hexahydrate, add 109g of deionized water, maintain a constant stirring speed of 400rpm, control the reaction temperature at 30℃, and allow the magnesium chloride to dissolve completely; then add 0.24g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 9.0-9.5, and continue stirring for 3h to obtain a magnesium hydroxide colloidal solution for later use;

[0076] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 968g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 50, add 731g of deionized water, add 200g of nano-silica sol under continuous stirring, and continue stirring for 1h; then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter and dry; use the programmed temperature rise method to raise the temperature from room temperature to 450℃ within 4h (heating rate ≤4℃ / min), and then solidify and calcine at 450℃ for 2h to obtain magnesium-modified ZSM-5 molecular sieve; the mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve is 2%;

[0077] (3) Preparation of heavy oil catalytic cracking catalyst: Take 554g of kaolin, add 679g of deionized water and 100g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 80℃ and stir continuously for 60min to obtain acid-modified clay; add 952g of aluminum sol, 476g of boehmite and 43g of lanthanum chloride to the acid-modified clay, add 10g of concentrated hydrochloric acid while stirring continuously, keep at 60℃ and stir continuously for 60min, add 212g of magnesium chloride, stir thoroughly to obtain colloid, at this time the pH of the system is 8.7;

[0078] Add 737g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 380g of REUSY molecular sieve, and 2217g of deionized water to the colloid, mix and stir evenly to obtain a slurry. Spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃, and then cure and calcine at 450℃ for 1h to obtain calcined microspheres. Then wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as S2.

[0079] Example 3

[0080] This embodiment provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0081] (1) Preparation of magnesium hydroxide colloid: Weigh 151g of magnesium chloride hexahydrate, add 314g of deionized water, maintain a constant stirring speed of 500rpm, control the reaction temperature at 50℃, and allow the magnesium chloride to dissolve completely; then add 0.6g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 10.0-10.5, and continue stirring for 2h to obtain a magnesium hydroxide colloidal solution for later use;

[0082] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 947g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 100, add 668g of deionized water, add 233g of nano-silica sol under continuous stirring, and continue stirring for 1h; then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter and dry; use the programmed temperature rise method to raise the temperature from room temperature to 500℃ within 6h (heating rate ≤4℃ / min), and then solidify and calcine at 500℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve; the mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve is 3%;

[0083] (3) Preparation of heavy oil catalytic cracking catalyst: Take 795g of kaolin, add 1020g of deionized water and 70g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 90℃ and stir continuously for 90min to obtain acid-modified clay; add 1048g of aluminum sol, 444g of boehmite and 65g of lanthanum chloride to the acid-modified clay, add 20g of concentrated hydrochloric acid while stirring continuously, keep at 70℃ and stir continuously for 60min, add 212g of magnesium chloride, stir thoroughly to obtain colloid, at which point the pH of the system is 8.7;

[0084] Add 632g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 253g of REUSY molecular sieve, and 1782g of deionized water to the colloid, mix and stir evenly to obtain a slurry. Spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃, and then cure and calcine at 550℃ for 1h to obtain calcined microspheres. Then wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as S3.

[0085] Example 4

[0086] This embodiment provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0087] (1) Preparation of magnesium hydroxide colloid: Weigh 201g of magnesium chloride hexahydrate, add 299g of deionized water, maintain a constant stirring speed of 600rpm, control the reaction temperature at 60℃, and allow the magnesium chloride to dissolve completely; then add 1.2g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 10.5-11.0, and continue stirring for 2h to obtain a magnesium hydroxide colloidal solution for later use;

[0088] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 916g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 25, add 583g of deionized water, add 300g of nano-silica sol under continuous stirring, and continue stirring for 2h; then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter and dry; use the programmed temperature rise method to raise the temperature from room temperature to 600℃ within 10h (heating rate ≤4℃ / min), and then solidify and calcine at 600℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve; the mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve is 4%;

[0089] (3) Preparation of heavy oil catalytic cracking catalyst: Take 552g of kaolin, add 701g of deionized water and 100g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 80℃ and stir continuously for 90min to obtain acid-modified clay; add 1048g of aluminum sol, 508g of boehmite and 87g of lanthanum chloride to the acid-modified clay, add 20g of concentrated hydrochloric acid while stirring continuously, keep at 60℃ and stir continuously for 60min, add 222g of magnesium chloride, stir thoroughly to obtain colloid, at which point the pH of the system is 8.4;

[0090] Add 842g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 177g of REUSY molecular sieve, and 2114g of deionized water to the colloid, mix and stir evenly, and spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃. Then, cure and calcine at 450℃ for 0.5h to obtain calcined microspheres. Then, wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as S4.

[0091] Example 5

[0092] This embodiment provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0093] (1) Preparation of magnesium hydroxide colloid: Weigh 254g of magnesium nitrate hexahydrate, add 366g of deionized water, maintain a constant stirring speed of 600rpm, control the reaction temperature at 40℃, and allow magnesium chloride to dissolve completely; then add 1.6g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 10.5-11.0, and continue stirring for 4h to obtain a magnesium hydroxide colloidal solution for later use;

[0094] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 874g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 25, add 474g of deionized water, add 400g of nano-silica sol under continuous stirring, and continue stirring for 2h; then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter and dry; use the programmed temperature rise method to raise the temperature from room temperature to 550℃ within 8h (heating rate ≤4℃ / min), and then solidify and calcine at 550℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve; the mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve is 5%;

[0095] (3) Preparation of heavy oil catalytic cracking catalyst: Take 418g of kaolin, add 466g of deionized water and 70g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 70℃ and stir continuously for 90min to obtain acid-modified clay; add 1143g of aluminum sol, 508g of boehmite and 130g of lanthanum chloride to the acid-modified clay, add 10g of concentrated hydrochloric acid while stirring continuously, keep at 60℃ and stir continuously for 60min, add 50g of magnesium oxide, stir thoroughly to obtain colloid, at which time the pH of the system is 8.4;

[0096] Add 947g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 127g of REUSY molecular sieve, and 2259g of deionized water to the colloid, mix and stir evenly, and spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃. Then, cure and calcine at 450℃ for 0.5h to obtain calcined microspheres. Then, wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as S5.

[0097] Example 6

[0098] This embodiment provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0099] (1) Preparation of magnesium hydroxide colloid: Weigh 254g of magnesium nitrate hexahydrate, add 413g of deionized water, maintain a constant stirring speed of 500rpm, control the reaction temperature at 40℃, and allow magnesium chloride to dissolve completely; then add 2g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 10.5-11.0, and continue stirring for 4h to obtain a magnesium hydroxide colloidal solution for later use;

[0100] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 863g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30, add 469g of deionized water, add 467g of nano-silica sol under continuous stirring, and continue stirring for 2h; then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter and dry; use the programmed temperature rise method to raise the temperature from room temperature to 500℃ within 6h (heating rate ≤4℃ / min), and then solidify and calcine at 500℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve; the mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve is 4%;

[0101] (3) Preparation of heavy oil catalytic cracking catalyst: Take 284g of kaolin, add 583g of deionized water and 70g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 60℃ and stir continuously for 90min to obtain acid-modified clay; add 1143g of aluminum sol, 571g of boehmite and 87g of lanthanum chloride to the acid-modified clay, add 15g of concentrated hydrochloric acid while stirring continuously, keep at 50℃ and stir continuously for 60min, add 282g of magnesium chloride, stir thoroughly to obtain colloid, at which time the pH of the system is 8.7;

[0102] Add 1011g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 152g of REUSY molecular sieve, and 2048g of deionized water to the colloid, mix and stir evenly, and spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃, then cure and calcine at 450℃ for 0.5h to obtain calcined microspheres; then wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as S5.

[0103] Example 7

[0104] This embodiment provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0105] (1) Preparation of magnesium hydroxide colloid: Weigh 159g of magnesium nitrate hexahydrate, add 198g of deionized water, maintain a constant stirring speed of 400rpm, control the reaction temperature at 40℃, and allow magnesium chloride to dissolve completely; then add 0.75g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 10.0-10.5, and continue stirring for 4h to obtain a magnesium hydroxide colloidal solution for later use;

[0106] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 932g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30, add 642g of deionized water, add 300g of nano-silica sol under continuous stirring, and continue stirring for 2h; then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter and dry; use the programmed temperature rise method to raise the temperature from room temperature to 450℃ within 4h (heating rate ≤4℃ / min), and then solidify and calcine at 450℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve; the mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve is 2.5%;

[0107] (3) Preparation of heavy oil catalytic cracking catalyst: Take 392g of kaolin, add 1018g of deionized water and 85g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 70℃ and stir continuously for 90min to obtain acid-modified clay; add 1143g of aluminum sol, 571g of boehmite and 174g of lanthanum chloride to the acid-modified clay, add 5g of concentrated hydrochloric acid while stirring continuously, keep at 60℃ and stir continuously for 60min, add 50g of magnesium oxide, stir thoroughly to obtain colloid, at this time the pH of the system is 8.6;

[0108] Add 737g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 329g of REUSY molecular sieve, and 1634g of deionized water to the colloid, mix and stir evenly to obtain a slurry. Spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃, and then cure and calcine at 500℃ for 0.5h to obtain calcined microspheres. Then wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as S7.

[0109] Comparative Example 1

[0110] This comparative example provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0111] (1) Preparation of magnesium hydroxide colloid: Weigh 101g of magnesium chloride hexahydrate, add 109g of deionized water, maintain a constant stirring speed of 400rpm, control the reaction temperature at 30℃, and allow the magnesium chloride to dissolve completely; then add 0.24g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 9.0-9.5, and continue stirring for 3h to obtain a magnesium hydroxide colloidal solution for later use;

[0112] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 968g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 50, add 731g of deionized water, then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter and dry; use the programmed temperature rise method to raise the temperature from room temperature to 450℃ within 4h, and then solidify and calcine at 450℃ for 2h to obtain magnesium-modified ZSM-5 molecular sieve;

[0113] (3) Take 554g of kaolin, add 679g of deionized water and 100g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 80℃ and stir continuously for 60min to obtain acid-modified clay; add 952g of aluminum sol, 476g of boehmite and 43g of lanthanum chloride to the acid-modified clay, add 10g of concentrated hydrochloric acid while stirring continuously, keep at 60℃ and stir continuously for 60min, add 212g of magnesium chloride, stir thoroughly to obtain colloid, at this time the pH of the system is 8.7;

[0114] Then, 737g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 380g of REUSY molecular sieve, and 2217g of deionized water were added to the colloid and mixed evenly. The resulting slurry was spray-dried at an inlet temperature of 350℃ and an outlet temperature of 140℃, and then cured and calcined at 450℃ for 1h to obtain calcined microspheres. The microspheres were then washed with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filtered, and dried to obtain the heavy oil catalytic cracking catalyst. The sample was designated as D1.

[0115] Compared to Example 2, this comparative example does not contain any pore blockage agent.

[0116] Comparative Example 2

[0117] This comparative example provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0118] (1) Preparation of magnesium chloride solution: Weigh 201g of magnesium chloride hexahydrate, add 299g of deionized water, maintain a constant stirring speed of 600rpm, control the reaction temperature at 60℃, so that the magnesium chloride is fully dissolved to obtain magnesium chloride solution for later use.

[0119] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 916g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 25, add 583g of deionized water, add 300g of nano-silica sol under continuous stirring, and continue stirring for 2h; then add the magnesium chloride solution prepared in step (1), stir for 2h, filter and dry; use the programmed temperature rise method to raise the temperature from room temperature to 600℃ within 10h, and then solidify and calcine at 600℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve;

[0120] (3) Preparation of heavy oil catalytic cracking catalyst: Take 552g of kaolin, add 701g of deionized water, 1048g of aluminum sol and 87g of lanthanum chloride, add 80g of concentrated hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 50℃ and stir continuously for 90min, add 222g of magnesium chloride, stir thoroughly to obtain colloid, at which time the pH of the system is 8.4;

[0121] Add 842g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 177g of REUSY molecular sieve, and 2114g of deionized water to the colloid, mix and stir evenly, and spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃. Then, cure and calcine at 450℃ for 0.5h to obtain calcined microspheres. Then, wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as D2.

[0122] This comparative example is similar to Example 4, except that magnesium chloride solution is used instead of magnesium hydroxide colloid in this comparative example.

[0123] Comparative Example 3

[0124] This comparative example provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0125] (1) Preparation of magnesium hydroxide colloid: Weigh 254g of magnesium nitrate hexahydrate, add 413g of deionized water, maintain a constant stirring speed of 500rpm, control the reaction temperature at 40℃, and allow magnesium chloride to dissolve completely; then add 2g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 10.5-11.0, and continue stirring for 4h to obtain a magnesium hydroxide colloidal solution for later use;

[0126] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 863g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30, add 469g of deionized water, add 467g of nano-silica sol under continuous stirring, and continue stirring for 2h; then add the magnesium hydroxide colloidal solution prepared in step (1), stir for 2h, filter and dry; then solidify and calcine at 500℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve; the mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve is 4%;

[0127] (3) Preparation of heavy oil catalytic cracking catalyst: Take 284g of kaolin, add 583g of deionized water and 70g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 60℃ and stir continuously for 90min to obtain acid-modified clay; add 1143g of aluminum sol, 571g of boehmite and 87g of lanthanum chloride to the acid-modified clay, add 15g of concentrated hydrochloric acid while stirring continuously, keep at 50℃ and stir continuously for 60min, add 282g of magnesium chloride, stir thoroughly to obtain colloid, at which time the pH of the system is 8.7;

[0128] Add 1011g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 152g of REUSY molecular sieve, and 2048g of deionized water to the colloid, mix and stir evenly, and spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃. Then, cure and calcine at 450℃ for 0.5h to obtain calcined microspheres. Then, wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as D3.

[0129] This comparative example is similar to Example 6, except that the temperature programmed method is not used in the calcination process of preparing the modified ZSM-5 molecular sieve.

[0130] Comparative Example 4

[0131] This embodiment provides a heavy oil catalytic cracking catalyst, the preparation method of which is as follows:

[0132] (1) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 932g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30, add 1200g of deionized water, add 265g of sucrose under continuous stirring, continue stirring and keep for 5h; then add 159g of magnesium nitrate hexahydrate, stir for 2h, filter and dry; then solidify and calcine at 450℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve;

[0133] (3) Preparation of heavy oil catalytic cracking catalyst: Take 392g of kaolin, add 1018g of deionized water and 85g of concentrated hydrochloric acid with a concentration of 36-38%, heat to 70℃ and stir continuously for 90min to obtain acid-modified clay; add 1143g of aluminum sol, 571g of boehmite and 174g of lanthanum chloride to the acid-modified clay, add 5g of concentrated hydrochloric acid while stirring continuously, keep at 60℃ and stir continuously for 60min, add 50g of magnesium oxide, stir thoroughly to obtain colloid, at this time the pH of the system is 8.6;

[0134] Add 737g of the magnesium-modified ZSM-5 molecular sieve prepared in step (2), 329g of REUSY molecular sieve, and 1634g of deionized water to the colloid, mix and stir evenly, and spray dry the slurry at an inlet temperature of 350℃ and an outlet temperature of 140℃. Then, cure and calcine at 500℃ for 0.5h to obtain calcined microspheres. Then, wash the microspheres with ammonium chloride solution (water:ammonium chloride mass ratio 100:1) at 60℃ for 30min, filter and dry to obtain the heavy oil catalytic cracking catalyst. The sample is designated as D4.

[0135] This comparative example is similar to Example 7, except that magnesium hydroxide colloid was not used in the preparation of the modified ZSM-5 molecular sieve, a sugar substance was used as the pore blocker, and a programmed temperature rise was not used.

[0136] Figure 1 The BET nitrogen adsorption-desorption curves of the magnesium-modified ZSM-5 molecular sieves prepared in Example 4 and Comparative Example 2 are shown in Table 1. The pore structure data of the two modified molecular sieves are shown in Table 1.

[0137] Table 1 Elemental composition and properties of the samples

[0138] Magnesium-modified ZSM-5 molecular sieve Specific surface area / (m 2 ·g -1 )]]> Pore volume / (mL.g -1 )]]> Comparative Example 2 228.4 0.064 Example 4 321.1 0.125

[0139] The data on pore structure properties show that, compared to modification using magnesium salt solutions, the magnesium-modified ZSM-5 molecular sieve prepared using the method provided in this invention has significantly higher specific surface area and pore volume. This indicates that during the magnesium modification process, magnesium species did not clog the pores of the molecular sieve in large quantities, but were instead uniformly distributed on the surface of the molecular sieve. Conversely, the molecular sieve prepared in Comparative Example 2 exhibited a significant decrease in specific surface area and pore volume due to the distribution and accumulation of magnesium species within the pores.

[0140] Catalyst evaluation:

[0141] The elemental content in the above-mentioned heavy oil catalytic cracking catalyst was determined by X-ray fluorescence analysis. The test standard was Q / SY LS1050, and the results are shown in Table 2.

[0142] Table 2. MgO and Na2O content in heavy oil catalytic cracking catalysts

[0143] catalyst S1 S2 S3 S4 S5 S6 S7 D1 D2 D3 D4 MgO mass % 1.25 2.41 2.63 3.48 4.12 4.21 2.98 1.75 2.74 3.54 1.84 Na2O mass % 0.10 0.11 0.10 0.12 0.11 0.09 0.11 0.11 0.13 0.12 0.11

[0144] The reaction performance of the catalysts prepared in the above examples and comparative examples was evaluated using an ACE evaluation test apparatus. The catalyst samples were placed in reactors for the ACE experiment. The reactants were feedstock from the Lanzhou Petrochemical 3 million tons / year catalytic cracking unit; the properties of the feedstock are shown in Table 3. The reaction temperature was 590℃, the regeneration temperature was 685℃, the feed rate was 1.80 g, the cold trap temperature was -13.5℃, and the catalyst-to-oil ratio was 9.0. The product distribution and conversion rate after the reaction were analyzed and calculated.

[0145] The evaluation results are shown in Table 4.

[0146] Wherein, conversion rate = (100 - diesel balance percentage - heavy oil balance percentage) × 100%;

[0147] The components of dry gas include: C2 components, methane, H2, H2S, etc., which contain ethylene;

[0148] The components of liquefied petroleum gas (LPG) include C3 and C4 components, including propylene.

[0149] Table 3. Properties of Feedstock for Lanzhou Petrochemical's 3 Million Tons / Year Catalytic Cracking Unit

[0150]

[0151] Table 4. ACE Evaluation Results of Heavy Oil Catalytic Cracking Catalysts

[0152]

[0153]

[0154] According to the ACE evaluation results in Table 2, the embodiments of the present invention exhibit excellent technical performance in terms of cracking efficiency and selectivity. The conversion rates of all embodiments are higher than 83.76%, reaching a maximum of 85.79% (S6), which is significantly higher than the conversion rates of comparative examples D1, D2, D3, and D4 (81.18%, 80.31%, 74.31%, and 75.89%, respectively). Furthermore, the catalyst of the present invention shows significant advantages in ethylene and propylene selectivity. The highest ethylene yield is 4.69% in S6, far exceeding the 2.55%, 2.44%, 1.58%, and 2.15% of the comparative examples; the highest propylene yield is 18.91% in S7, far exceeding the 12.21%, 11.12%, 9.41%, and 9.76% of the comparative examples. Simultaneously, coke production is also effectively controlled.

[0155] These results demonstrate that by loading magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieve, this invention enhances the acid-base synergistic catalytic activity of the catalyst, retaining the acidic properties within the molecular sieve while providing an alkaline catalytic environment externally, thus significantly improving cracking efficiency and propylene selectivity. Overall, the heavy oil catalytic cracking catalyst of this invention significantly outperforms the comparative example in terms of cracking efficiency and propylene and ethylene selectivity, showcasing promising prospects for industrial application.

Claims

1. A heavy oil catalytic cracking catalyst, wherein the feedstock comprises, by weight percentage: Magnesium-modified ZSM-5 molecular sieve 30-50% on a dry basis, Y-type molecular sieve 5-20% on a dry basis, rare earth compounds 0.5-4% on an oxide basis, inorganic oxide binder 20-30% on an oxide basis, acid-modified clay 10-35% on a dry basis, and magnesium salts 1-3% on an oxide basis. The magnesium oxide content in the magnesium-modified ZSM-5 molecular sieve is 1-5% by mass. The magnesium-modified ZSM-5 molecular sieve was prepared by the following method: Mix ZSM-5 molecular sieve with water to form a slurry, add 5-15% of a pore-blocking agent by mass of ZSM-5 molecular sieve, and stir to block the pores of the molecular sieve. The pore-blocking agent includes one or more of nano-silica sol, polyacrylic acid nanoparticles, and polyvinyl alcohol nanoparticles. Then add pre-prepared magnesium hydroxide colloid and stir to load the magnesium hydroxide colloid onto the outer surface of the ZSM-5 molecular sieve. The molecular sieve with the loaded colloid was removed, heated to 400-600℃ at a rate not exceeding 4℃ / min, and calcined at this temperature to obtain magnesium-modified ZSM-5 molecular sieve.

2. The heavy oil catalytic cracking catalyst according to claim 1, wherein, The magnesium hydroxide colloid was prepared by the following method: A surfactant was added to a magnesium salt solution, and an alkaline solution was slowly and continuously added under constant temperature and constant speed stirring conditions to maintain the pH value of the solution between 9 and 11. The mixture was stirred continuously to obtain magnesium hydroxide colloid. The magnesium salt solution contains 3-10% magnesium salt by mass (calculated as magnesium oxide), and the amount of surfactant added is 1-5% by mass (calculated as magnesium oxide) of the magnesium salt.

3. The heavy oil catalytic cracking catalyst according to claim 2, wherein, The stirring temperature is 20-60℃, the stirring speed is 300-600 rpm, and the stirring time is 1-4 hours.

4. The heavy oil catalytic cracking catalyst according to claim 2, wherein, The magnesium salt includes one or more of magnesium chloride, magnesium sulfate, and magnesium nitrate. The surfactant includes one or more of sodium dodecyl sulfate, polyvinylpyrrolidone, and sodium dodecylbenzene sulfonate; The alkaline solution includes one or a combination of two or more of the following: sodium hydroxide solution, potassium hydroxide solution, and ammonia water.

5. The heavy oil catalytic cracking catalyst according to claim 1, wherein, The particle size of the pore blocking agent is <2nm.

6. The heavy oil catalytic cracking catalyst according to claim 1, wherein, The roasting time is 1-4 hours; the roasting temperature rise process adopts the programmed temperature rise method.

7. The heavy oil catalytic cracking catalyst according to claim 1, wherein, The silicon-aluminum ratio of the ZSM-5 molecular sieve is 25-100.

8. The heavy oil catalytic cracking catalyst according to claim 1, wherein, The Y-type molecular sieve includes one or more combinations of HY molecular sieve, USY molecular sieve, REUSY molecular sieve, REY molecular sieve, and their modified or derivative products.

9. The heavy oil catalytic cracking catalyst according to claim 1, wherein, The inorganic oxide binder includes one or more of aluminum sol, silica sol, pseudoboehmite, and silica-alumina sol.

10. The heavy oil catalytic cracking catalyst according to claim 1, wherein, The rare earth compound is a water-soluble rare earth compound; the rare earth elements in the rare earth compound include one or more of lanthanum, cerium, praseodymium, neodymium, and yttrium.

11. The heavy oil catalytic cracking catalyst according to claim 1, wherein, The pH value of the acid-modified clay is 0-2; the clay used in the acid-modified clay includes one or more of the following: kaolin, halloysite, montmorillonite, sepiolite, hydrotalcite, and rettoite.

12. A method for preparing a heavy oil catalytic cracking catalyst according to any one of claims 1-11, comprising the following steps: S1. Inorganic oxide binder, acid-modified clay, rare earth compound and water are mixed, acid is added and gel treatment is performed, then magnesium salt is added and mixed to obtain colloid; S2. Add magnesium-modified ZSM-5 molecular sieve and Y-type molecular sieve to the colloid and mix them to obtain a slurry; S3. The slurry is spray-dried into particles and calcined to obtain the heavy oil catalytic cracking catalyst.

13. The method for preparing the heavy oil catalytic cracking catalyst according to claim 12, wherein, The pH value of the colloid is 6.5-9.

14. The method for preparing the heavy oil catalytic cracking catalyst according to claim 12, wherein, The sol-gel treatment temperature is 40-80℃, and the sol-gel treatment time is 1-2h; the calcination temperature of the particles is 300-600℃, and the calcination time is 0.5-2h.

15. A method for catalytic cracking of heavy oil, comprising: The heavy oil catalytic cracking catalyst according to any one of claims 1-12 is brought into full contact with heavy oil to carry out the cracking reaction.

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