Magnesium-modified ZSM-5 molecular sieve, catalytic cracking additive for increasing yield of propylene and co-producing ethylene, and preparation methods therefor

Abstract

Provided in the present invention are a magnesium-modified ZSM-5 molecular sieve, a catalytic cracking additive for increasing the yield of propylene and co-producing ethylene, and preparation methods therefor. The preparation method for a magnesium-modified ZSM-5 molecular sieve comprises: mixing and slurrying a ZSM-5 molecular sieve with water, adding a channel-occupying blocking agent, and stirring same; then adding magnesium hydroxide colloids prepared in advance, and stirring same; and calcining same, so as to obtain a magnesium-modified ZSM-5 molecular sieve. In the present invention, the outer surface of the ZSM-5 molecular sieve is loaded with magnesium hydroxide colloids, thereby significantly improving the selectivity and yield of propylene and ethylene in the process of catalytic cracking, and also reducing the occurrence of side reactions.

Description

Magnesium-modified ZSM-5 molecular sieve, catalytic cracking additive for increasing propylene and ethylene production, and preparation methods of both.

[0001] Cross-reference information

[0002] This application claims priority to Chinese Patent Application No. 202411433330.X, filed on October 14, 2024, entitled "Magnesium-modified ZSM-5 molecular sieve, catalytic cracking propylene and ethylene production booster and preparation method thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention belongs to the field of petroleum catalytic cracking and catalytic pyrolysis materials, specifically involving a magnesium-modified ZSM-5 molecular sieve, a catalytic cracking agent for increasing propylene and ethylene production, and methods for preparing both. Background Technology

[0004] Significant progress has been made in the field of catalytic cracking (FCC), particularly in research aimed at increasing propylene production, in recent years. Propylene, as a key chemical feedstock, plays a vital role in numerous industrial applications; therefore, improving its yield and selectivity in FCC processes is a key research focus. Traditional FCC catalysts, such as acid-based ZSM-5 molecular sieves, have been modified to improve propylene yield by adjusting pore structure and acidity strength or introducing metal elements such as iron and nickel. In addition to the modification of single catalysts, the development of novel composite auxiliaries is also underway. These auxiliaries combine different catalytic properties, such as combining acidic ZSM-5 with basic substances, to achieve even higher propylene yields and selectivity.

[0005] Research on catalytic cracking additives for increasing propylene and ethylene production is constantly developing, primarily because propylene, as an important chemical feedstock, plays a crucial role in many industrial processes. Propylene is mainly used to produce various plastics, solvents, polymers, and other chemicals. With increasing global demand for these products, improving propylene production efficiency and yield has become an important research topic. Catalytic cracking is one of the main industrial methods for producing propylene. This process involves breaking down heavy oil molecules into a mixture of smaller molecules, including propylene, under the action of a catalyst. However, the yield of propylene in traditional catalytic cracking processes is relatively low, so researchers have been searching for methods to optimize this process.

[0006] In recent years, researchers have developed various additives to enhance propylene yield in catalytic cracking. These additives are typically special chemicals added to the catalyst to alter its properties, thereby improving propylene selectivity and yield. For example, some additives can increase the number of acidic sites on the catalyst, which helps promote the cracking reaction and increase propylene production. Besides chemical modification, the physical structure of the catalyst is also an important research area. By changing the pore size and pore structure of the catalyst, propylene yield can be further improved. For example, developing catalysts with larger pore sizes can promote the cracking of larger molecules, thus increasing propylene production. Furthermore, researchers are exploring the use of novel catalysts, such as molecular sieves, metal oxides, and acidic ion exchange resins. These novel catalysts may exhibit higher selectivity and stability, enabling efficient propylene production over longer periods. Overall, research on additives for enhancing propylene and producing ethylene in catalytic cracking is progressing rapidly, encompassing not only the chemical and physical modification of catalysts but also the development of entirely new catalytic systems. This research is of great significance for improving propylene production efficiency and meeting global market demand. With continuous technological advancements and innovation, we can expect even more breakthroughs and applications in the future.

[0007] Furthermore, surface modification of catalysts, such as the introduction of chemical groups like phosphorus or boron, has been shown to effectively regulate the acidity and basicity of catalysts, thereby optimizing propylene production. In catalyst design and preparation, researchers are also exploring more environmentally friendly methods, such as using biomass feedstocks or developing recyclable and regenerable catalysts to reduce environmental impact. Besides improvements to the catalyst itself, optimizing reaction conditions, such as temperature, pressure, and feedstock feed rate, has also proven crucial for increasing propylene yield. These research advances indicate that through continuous optimization of catalyst design and reaction conditions, catalytic cracking technologies for increasing propylene production are developing towards higher efficiency, higher selectivity, and greater environmental friendliness. With the discovery of new materials and the application of new technologies, more innovative catalytic cracking additives and processes are expected to emerge in the future to better meet the needs of industrial production, further promoting the development of the petroleum refining and chemical industries.

[0008] ZSM-5 molecular sieves have wide applications in the petrochemical and fine chemical industries. The unique characteristic of ZSM-5 lies in its highly ordered microporous structure and specific surface area. Its main applications include catalytic cracking, alkylation, and aromatics synthesis. Modification of ZSM-5 molecular sieves aims to improve their catalytic performance and adaptability. Modification methods include acid washing, metal doping, and surface modification. For example, by introducing metals such as iron, copper, and cobalt into ZSM-5, its acidity and catalytic activity can be altered, making it more suitable for specific chemical reactions. In the petrochemical industry, modified ZSM-5 is used to improve the efficiency and selectivity of petroleum cracking processes, thereby improving fuel quality and reducing harmful emissions. In the fine chemical industry, modification of ZSM-5 enables it to catalyze a wider range of reactions, such as the synthesis of fine chemicals and pharmaceutical intermediates. Environmental modification of ZSM-5 is also significant. For example, modification can enhance the application of ZSM-5 in pollutant control, such as reducing nitrogen oxide emissions from vehicle exhaust.

[0009] With increasing environmental awareness and advancements in chemical processes, the research and application of ZSM-5 modification are receiving growing attention. Continuous optimization of modification methods can further enhance the performance of ZSM-5 molecular sieves and broaden their application range in the chemical industry. Traditional catalytic cracking technologies primarily rely on acidic molecular sieves, such as ZSM-5, which are widely used due to their unique pore structure and acidic properties. ZSM-5 molecular sieves, with their unique pore structure and high acidity, are considered ideal catalysts for improving olefin selectivity. However, these traditional catalysts face numerous challenges when processing heavy feedstocks, such as coke deposition, rapid deactivation of active sites, and limitations in olefin yield.

[0010] To improve the yield and selectivity of ethylene and propylene, researchers have attempted to optimize the catalytic performance of ZSM-5 molecular sieves by modifying them. These modification methods include controlling the pore structure, adjusting the acidity, and introducing new active components. In recent years, introducing basic components, such as magnesium hydroxide, onto the outer surface of ZSM-5 molecular sieves has become a promising approach. This method aims to create an alkaline environment on the outer surface of the molecular sieve, thereby providing dual catalytic action: acid catalysis in the internal pores and basic catalysis on the outer surface. However, the development of this novel catalyst faces several challenges. First, an effective method must be found to uniformly and stably load magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieves. Second, the loaded magnesium hydroxide colloid should not interfere with the acidic properties of the internal pores of the molecular sieve. Furthermore, to achieve optimal catalytic performance, the loading amount of magnesium hydroxide colloid and the processing conditions of the molecular sieve need to be optimized. Summary of the Invention

[0011] To address the aforementioned technical problems, the present invention aims to provide a magnesium-modified ZSM-5 molecular sieve, a catalytic cracking agent for increasing propylene and ethylene production, and a method for preparing both, thereby improving the yield and selectivity of low-carbon olefins during catalytic cracking.

[0012] To achieve the above objectives, the present invention provides a method for preparing magnesium-modified ZSM-5 molecular sieve, comprising the following steps:

[0013] 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.

[0014] The molecular sieve with the loaded colloid is 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; wherein the mass content of magnesium in the magnesium-modified ZSM-5 molecular sieve, calculated as oxide (based on the mass of magnesium-modified ZSM-5 molecular sieve), is 3-10%.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] This invention proposes a novel method for combining magnesium hydroxide colloid with ZSM-5 molecular sieve. By selectively loading magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieve without entering 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 the molecular sieve pores to maintain highly efficient acid catalysis, thereby enabling simultaneous acid-catalyzed and alkaline-catalyzed reactions in the same catalytic system.

[0020] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, the mass fraction of magnesium salt in magnesium hydroxide colloid, calculated as magnesium oxide, is 3-10%, more preferably 5-7%.

[0021] In the above method for preparing magnesium-modified ZSM-5 molecular sieves, preferably, the magnesium hydroxide colloid is prepared by the following method:

[0022] A surfactant is added to a magnesium salt solution, and an alkaline solution is 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 is 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% of the magnesium salt by mass (calculated as magnesium oxide).

[0023] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, during the preparation of magnesium hydroxide colloid, the stirring temperature is 20-60℃, the stirring speed is 300-600rpm, and the stirring time is 1-4h.

[0024] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, in the process of preparing magnesium hydroxide colloid, the magnesium salt includes one or more of magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0025] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, during the preparation of magnesium hydroxide colloid, the surfactant includes one or a combination of two or more of sodium dodecyl sulfate, polyvinylpyrrolidone, and sodium dodecylbenzenesulfonate.

[0026] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, in the process of 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.

[0027] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, 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, or a modified ZSM-5 molecular sieve or its derivative.

[0028] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, the particle size of the pore blocking agent is <2nm.

[0029] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, the calcination time is 1-4 hours; the calcination heating process adopts a programmed temperature rise method.

[0030] In the above-mentioned method for preparing magnesium-modified ZSM-5 molecular sieve, preferably, the molecular sieve loaded with colloid is pre-dried at 60-100℃ before calcination.

[0031] According to a specific embodiment of the present invention, preferably, the preparation method of the above-mentioned magnesium-modified ZSM-5 molecular sieve includes the following steps:

[0032] (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;

[0033] (2) Molecular sieve pretreatment: ZSM-5 molecular sieve is mixed with deionized water and pulped; then an appropriate amount of pore blocker is added to the mixture and stirred thoroughly to ensure that the blocker is evenly distributed in the molecular sieve pores and effectively penetrates.

[0034] (3) The pre-prepared magnesium hydroxide colloid is slowly added to the pretreated ZSM-5 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. The mass content of magnesium hydroxide in ZSM-5 molecular sieve is 1-10% based on magnesium oxide.

[0035] (4) The ZSM-5 molecular sieve with the loaded colloid was filtered and dried at 60-100℃ to remove excess moisture. Then, the dried molecular sieve was calcined at 400-600℃. The temperature was raised to the calcination temperature within 2-10 hours using the gradual heating method to fix magnesium hydroxide on the surface of the ZSM-5 molecular sieve, ensuring its stability and catalytic activity, and finally magnesium-modified ZSM-5 molecular sieve was obtained.

[0036] The present invention also provides a magnesium-modified ZSM-5 molecular sieve, which is obtained by the above-described method for preparing magnesium-modified ZSM-5 molecular sieve.

[0037] The present invention also provides an additive for increasing propylene and ethylene production in catalytic cracking, wherein the raw materials, by mass percentage, include: 20-30% magnesium-modified ZSM-5 molecular sieve on a dry basis, 10-30% phosphorus-modified ZSM-5 molecular sieve on a dry basis, 10-20% boehmite on a dry basis, 20-40% clay on a dry basis, 1-3% magnesium oxide or magnesium salt on a magnesium oxide basis, and 8-15% alkaline silica sol binder on a silica basis.

[0038] The magnesium-modified ZSM-5 molecular sieve is the magnesium-modified ZSM-5 molecular sieve described above.

[0039] In the above-mentioned catalytic cracking additives for increasing propylene and ethylene production, preferably, the mass content of phosphorus element in the phosphorus-modified ZSM-5 molecular sieve, calculated as phosphorus pentoxide (based on phosphorus-modified ZSM-5 molecular sieve), is 1-10%.

[0040] In the above-mentioned catalytic cracking additives for increasing propylene and ethylene production, preferably, the phosphorus-modified ZSM-5 molecular sieve is prepared by the following method:

[0041] ZSM-5 molecular sieve is mixed with water and slurryed. Phosphorus compound is added and the mixture is brought into full contact with ZSM-5 molecular sieve at 10-100℃ for 0.5-4h. The ZSM-5 molecular sieve is then removed and calcined at 300-800℃ for 0.5-4h to obtain the phosphorus-modified ZSM-5 molecular sieve.

[0042] In the above-mentioned catalytic cracking additives for increasing propylene and ethylene production, preferably, in the preparation of phosphorus-modified ZSM-5 molecular sieves, the phosphorus compound includes organic phosphorus compounds and / or inorganic phosphorus compounds. More preferably, in the preparation of phosphorus-modified ZSM-5 molecular sieves, the phosphorus compound includes one or more of the following: trimethyl phosphate, triphenylphosphine, trimethyl phosphite, tetrabutylphosphine bromide, tetrabutylphosphine chloride, tetrabutylphosphine hydroxide, triphenylethylphosphine bromide, triphenylbutylphosphine bromide, triphenylbenzylphosphine bromide, hexamethylphosphoric acid triamine, dibenzyldiethylphosphine, 1,3-xylenebistriethylphosphine, phosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, and boron phosphate.

[0043] In the above-mentioned catalytic cracking additives for increasing propylene and ethylene production, preferably, in the preparation of phosphorus-modified ZSM-5 molecular sieves, the calcination treatment is performed under atmospheric pressure or hydrothermal atmosphere under external pressure.

[0044] In the above-mentioned catalytic cracking additives for increasing propylene and ethylene production, preferably, the clay includes one or more of kaolin, halloysite, montmorillonite, sepiolite, hydrotalcite, and rettoite.

[0045] The present invention also provides a method for preparing the above-mentioned catalytic cracking additive for increasing propylene and ethylene production, which includes the following steps:

[0046] Boehmite, clay and water are mixed, acid is added and the mixture is gelled, then magnesium salt is added and mixed to obtain a colloid;

[0047] An alkaline silica sol binder, magnesium-modified ZSM-5 molecular sieve, and phosphorus-modified ZSM-5 molecular sieve are added to the colloid and mixed to obtain a slurry.

[0048] The slurry is spray-dried into particles and calcined to obtain the catalytic cracking additive that increases propylene and ethylene production.

[0049] In this invention, the role of magnesium salts includes two aspects: on the one hand, magnesium salts can modify the matrix, improve the catalyst's resistance to metal contamination, and optimize the acidity distribution, thereby improving the selectivity of the catalyst; on the other hand, magnesium salts can adjust the pH value of the colloid during the catalyst preparation process, preventing magnesium in the magnesium-modified ZSM-5 molecular sieve from being dissociated in the acidic system.

[0050] In the above-mentioned method for preparing the catalytic cracking additive for increasing propylene and ethylene production, preferably, the sol-gel treatment temperature is 30-60℃ and the sol-gel treatment time is 1-2h.

[0051] In the above-mentioned method for preparing the catalytic cracking additive for increasing propylene and ethylene production, preferably, 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 gelation without damaging the pore structure of the matrix. Generally, too little acid will result in insufficient gelation, while too much acid will damage the pore structure of the matrix. More preferably, the mass ratio of the acid to boehmite (calculated as alumina) is 0.1-0.4.

[0052] In the above-mentioned method for preparing the catalytic cracking additive for increasing propylene and ethylene production, preferably, the pH value of the colloid is not less than 6.5.

[0053] In the above-mentioned method for preparing the catalytic cracking additive for increasing propylene and ethylene production, preferably, rare earth additives can be added before adding acid to boehmite and clay.

[0054] In the above-mentioned method for preparing the catalytic cracking additive for increasing propylene and ethylene production, preferably, the calcination temperature of the particles is 300-600℃ and the calcination time is 0.5-2h.

[0055] According to a specific embodiment of the present invention, preferably, the preparation method of the above-mentioned catalytic cracking additive for increasing propylene and ethylene production specifically includes the following steps:

[0056] (1) Add deionized water and optional clay according to the mass percentage of 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.

[0057] (2) Add boehmite to the gelation reaction and mix thoroughly. Add acid according to the mass percentage of the catalyst, perform gelation treatment, and then add magnesium salt to obtain colloid.

[0058] (3) After the colloid obtained in step (2) is gelled, add alkaline silica sol binder, magnesium-modified ZSM-5 molecular sieve and phosphorus-modified ZSM-5 molecular sieve, mix and stir for 30-60 minutes to make a slurry;

[0059] (4) The formed colloid is dried by spray drying, wherein the conditions for spray drying are conventional conditions in the art;

[0060] (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 an additive for increasing propylene and ethylene production in catalytic cracking.

[0061] The present invention also provides a combined catalyst for catalytic cracking to increase propylene and ethylene production, which is composed of a main catalyst and an auxiliary agent in a mass ratio of 1:0.05-0.2, wherein the auxiliary agent is the above-mentioned auxiliary agent for catalytic cracking to increase propylene and ethylene production; and the main catalyst is a catalytic cracking catalyst.

[0062] The present invention also provides a catalytic cracking method, which includes: bringing the above-mentioned combined catalyst for catalytic cracking to produce propylene and ethylene into full contact with feedstock oil to carry out a catalytic cracking reaction.

[0063] In the above-mentioned catalytic cracking method, preferably, the reaction temperature is 450-550℃ and the catalyst-to-oil ratio is 4-8.

[0064] The technical solution provided by this invention has the following beneficial effects:

[0065] 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 designed in this invention significantly improves the selectivity and yield of propylene and ethylene during catalytic cracking, while reducing side reactions, coke formation, and the deactivation rate of the molecular sieve. This provides a more efficient and economical catalytic cracking solution for the petroleum refining and chemical industries. Attached Figure Description

[0066] Figure 1 shows the BET nitrogen adsorption-desorption curves of the magnesium-modified ZSM-5 molecular sieves prepared in Example 2 and Comparative Example 1.

[0067] Figure 2 shows an aberration-corrected transmission electron microscope (AC-STEM) image of the magnesium-modified ZSM-5 molecular sieve in Example 2. Detailed Implementation

[0068] 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.

[0069] In the following examples and comparative examples, the elemental content in the samples was determined by X-ray fluorescence analysis.

[0070] The origin and specifications of the raw materials used in the embodiments and comparative examples of this invention.

[0071] Magnesium chloride, magnesium nitrate, magnesium nitrate, starch, polyethylene glycol, activated carbon, sodium hydroxide, ammonia, polyacrylic acid, phosphoric acid (85%), diammonium hydrogen phosphate, trimethyl phosphate, etc. are commercially available reagents of analytical grade.

[0072] ZSM-5 molecular sieves are products of Tianjin Nanhua Catalyst Co., Ltd., with silicon-to-aluminum ratios of 30, 50, and 100.

[0073] The nano-silica sol is a product of Guangdong Huierte Nanotechnology Co., Ltd., and the alkaline silica sol binder is a product of Qingdao Haiyang Chemical Co., Ltd. The nano-silica sol has an average particle size of less than 2nm and a silica content of 30%; the alkaline silica sol has an average particle size of 20nm and a silica content of 30%.

[0074] Kaolin, halloysite, boehmite, silica sol, and alumina sol are all industrial products, supplied by the Catalyst Division of Lanzhou Petrochemical.

[0075] Example 1

[0076] This embodiment provides a catalyst for increasing propylene and ethylene production through catalytic cracking, and its preparation method is as follows:

[0077] (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;

[0078] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 968g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 30, add 714g of deionized water, add 167g of nano-silica sol under continuous stirring, and continue stirring for 1h; then add the prepared magnesium hydroxide colloidal solution, 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 3%;

[0079] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 1011g of ZSM-5 molecular sieve, add 925g of deionized water, and stir evenly; add 65g of phosphoric acid, and stir continuously at 40℃ for 2h; then dry and calcine at 300℃ for 4h to obtain phosphorus-modified ZSM-5 molecular sieve; the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 4%;

[0080] (4) Preparation of additives: Take 635g of boehmite, 1038g of kaolin, add 711g of deionized water, add 60g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 80℃ and keep for 40min, then add 101g of magnesium chloride, stir evenly to form a colloid.

[0081] Then, 533g of alkaline silica sol binder, 421g of modified ZSM-5 molecular sieve, and 211g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 300℃ for 2 hours to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as S1.

[0082] Example 2

[0083] This embodiment provides a catalyst for increasing propylene and ethylene production through catalytic cracking, and its preparation method is as follows:

[0084] (1) Preparation of magnesium hydroxide colloid: Weigh 252g of magnesium chloride hexahydrate, add 748g 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 0.75g 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;

[0085] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: 926g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 40 was taken, 588g of deionized water was added, and 233g of nano-silica sol was added under continuous stirring for 2h. Then, the prepared magnesium hydroxide colloidal solution was added, stirred for 2h, filtered, dried, and heated to 500℃ from room temperature in 5h using a programmed temperature rise method (heating rate ≤4℃ / min). Then, it was cured and calcined at 500℃ for 4h to obtain magnesium-modified ZSM-5 molecular sieve. The mass content of magnesium oxide in the magnesium-modified ZSM-5 molecular sieve was 5%.

[0086] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 1000g of ZSM-5 molecular sieve, add 919g of deionized water, and stir evenly; add 81g of phosphoric acid, and stir continuously at 50℃ for 1h; then dry and calcine at 450℃ for 3h to obtain phosphorus-modified ZSM-5 molecular sieve; the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 5%;

[0087] (4) Preparation of additives: Take 540g of boehmite, 810g of kaolin, add 1622g of deionized water, add 50g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 70℃ and keep for 60min, then add 101g of magnesium chloride, stir evenly to form a colloid.

[0088] Then, 667g of alkaline silica sol binder, 421g of modified ZSM-5 molecular sieve, and 421g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 400℃ for 2 hours to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as S2.

[0089] Example 3

[0090] This embodiment provides a catalyst for increasing propylene and ethylene production through catalytic cracking, and its preparation method is as follows:

[0091] (1) Preparation of magnesium hydroxide colloid: Weigh 302g of magnesium chloride hexahydrate, add 555g of deionized water, maintain a constant stirring speed of 400rpm, control the reaction temperature at 50℃, 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 10.0-10.5, and continue stirring for 4h to obtain a magnesium hydroxide colloidal solution for later use;

[0092] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: 884g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 60 was taken, 480g of deionized water was added, and 333g of nano-silica sol was added under continuous stirring for 2h. Then, the prepared magnesium hydroxide colloidal solution was added, stirred for 2h, filtered, dried, and the temperature was raised from room temperature to 500℃ in 8h using a programmed temperature rise method (heating rate ≤4℃ / min). Then, it was cured and calcined at 500℃ for 2h to obtain magnesium-modified ZSM-5 molecular sieve. The magnesium oxide content in the magnesium-modified ZSM-5 molecular sieve was 6%.

[0093] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 989g of ZSM-5 molecular sieve, add 913g of deionized water, and stir evenly; add 97g of phosphoric acid, and stir continuously at 70℃ for 2h; then dry and calcine at 450℃ for 3h to obtain phosphorus-modified ZSM-5 molecular sieve; the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 6%;

[0094] (4) Preparation of additives: Take 381g of boehmite, 684g of kaolin, add 1539g of deionized water, add 60g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 60℃ and keep for 60min, then add 20g of magnesium oxide, stir evenly to form a colloid.

[0095] Then, 1000g of alkaline silica sol binder, 526g of modified ZSM-5 molecular sieve, and 421g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 450℃ for 2 hours to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as S3.

[0096] Example 4

[0097] This embodiment provides a catalyst for increasing propylene and ethylene production through catalytic cracking, and its preparation method is as follows:

[0098] (1) Preparation of magnesium hydroxide colloid: Weigh 403g of magnesium chloride hexahydrate, add 597g of deionized water, maintain a constant stirring speed of 500rpm, control the reaction temperature at 60℃, and allow the magnesium chloride to dissolve completely; then add 2.4g of sodium dodecylbenzenesulfonate, slowly add ammonia water, maintain the pH value of the solution at 10.0-11.0, and continue stirring for 4h to obtain a magnesium hydroxide colloidal solution for later use;

[0099] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: 863g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 80 was taken, 401g of deionized water was added, and 333g of nano-silica sol was added under continuous stirring for 2h. Then, the prepared magnesium hydroxide colloidal solution was added and stirred for 2h. After filtration and drying, the temperature was raised from room temperature to 500℃ in 7h using a programmed temperature rise method (heating rate ≤4℃ / min). Then, it was cured and calcined at 500℃ for 2h to obtain magnesium-modified ZSM-5 molecular sieve. The magnesium oxide content in the magnesium-modified ZSM-5 molecular sieve was 8%.

[0100] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 979g of ZSM-5 molecular sieve, add 907g of deionized water, and stir evenly; add 114g of phosphoric acid, and stir continuously at 80℃ for 3h; then dry and calcine at 500℃ for 2h to obtain phosphorus-modified ZSM-5 molecular sieve; the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 7%;

[0101] (4) Preparation of additives: Take 476g of boehmite, 603g of halloysite, add 1526g of deionized water, add 60g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 60℃ and keep for 90min, then add 24g of magnesium oxide, stir evenly to form a colloid.

[0102] Then, 667g of alkaline silica sol binder, 632g of modified ZSM-5 molecular sieve, and 421g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 450℃ for 2 hours to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as S4.

[0103] Example 5

[0104] This embodiment provides a catalyst for increasing propylene and ethylene production through catalytic cracking, and its preparation method is as follows:

[0105] (1) Preparation of magnesium hydroxide colloid: Weigh 509g of magnesium nitrate hexahydrate, add 824g of deionized water, maintain a constant stirring speed of 500rpm, control the reaction temperature at 60℃, and allow magnesium chloride to dissolve completely; then add 4g 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 magnesium hydroxide colloidal solution for later use;

[0106] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: 842g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 80 was taken, 355g of deionized water was added, and 400g of nano-silica sol was added under continuous stirring for 2h. Then, the prepared magnesium hydroxide colloidal solution was added, stirred for 2h, filtered, dried, and heated to 600℃ from room temperature in 4h using a programmed temperature rise method (heating rate ≤4℃ / min). Then, it was cured and calcined at 600℃ for 1h to obtain magnesium-modified ZSM-5 molecular sieve. The magnesium oxide content in the magnesium-modified ZSM-5 molecular sieve was 8%.

[0107] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 968g of ZSM-5 molecular sieve, add 920g of deionized water, and stir evenly; add 112g of trimethyl phosphate, and stir continuously at 50℃ for 2h; then dry and calcine at 500℃ for 3h to obtain phosphorus-modified ZSM-5 molecular sieve; the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 8%;

[0108] (4) Preparation of additives: Take 444g of boehmite, 549g of kaolin, add 1400g of deionized water, add 60g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 60℃ and keep for 60min, then add 131g of magnesium chloride, stir evenly to form a colloid.

[0109] Then, 867g of silica sol, 632g of modified ZSM-5 molecular sieve, and 421g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 450℃ for 2 hours to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as S5.

[0110] Example 6

[0111] This embodiment provides a catalyst for increasing propylene and ethylene production through catalytic cracking, and its preparation method is as follows:

[0112] (1) Preparation of magnesium hydroxide colloid: Weigh 636g of magnesium nitrate hexahydrate, add 614g of deionized water, maintain a constant stirring speed of 600rpm, control the reaction temperature at 60℃, and allow magnesium chloride to dissolve completely; then add 4g 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 magnesium hydroxide colloidal solution for later use;

[0113] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 821g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 40, add 275g of deionized water, add 400g of nano-silica sol under continuous stirring, and continue stirring for 2h; then add the prepared magnesium hydroxide colloidal solution, stir for 2h, filter, dry, and use a programmed temperature rise method to raise the temperature from room temperature to 550℃ in 10h (heating rate ≤4℃ / min), and then solidify and calcine at 550℃ 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 10%;

[0114] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 958g of ZSM-5 molecular sieve, add 908g of deionized water, and stir evenly; add 167g of diammonium hydrogen phosphate, and stir continuously at 70℃ for 2h; then dry and calcine at 450℃ for 3h to obtain phosphorus-modified ZSM-5 molecular sieve; the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 9%;

[0115] (4) Preparation of additives: Take 571g of boehmite, 380g of halloysite, add 1054g of deionized water, add 80g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 60℃ and keep for 60min, then add 201g of magnesium chloride, stir evenly to form a colloid.

[0116] Then, 667g of alkaline silica sol binder, 526g of modified ZSM-5 molecular sieve, and 632g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 550℃ for 1 hour to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as S6.

[0117] Example 7

[0118] This embodiment provides a catalyst for increasing propylene and ethylene production through catalytic cracking, and its preparation method is as follows:

[0119] (1) Preparation of magnesium hydroxide colloid: Weigh 445g of magnesium nitrate hexahydrate, add 255g of deionized water, maintain a constant stirring speed of 600rpm, control the reaction temperature at 50℃, and allow magnesium chloride to dissolve completely; then add 2.8g 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;

[0120] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 895g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 25, add 480g of deionized water, add 267g of nano-silica sol under continuous stirring, and continue stirring for 3h; then add the prepared magnesium hydroxide colloidal solution, stir for 2h, filter, dry, and use a programmed temperature rise method to raise the temperature from room temperature to 600℃ in 10h (heating rate ≤4℃ / min), and then solidify and calcine at 600℃ 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 7%;

[0121] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 947g of ZSM-5 molecular sieve, add 868g of deionized water, and stir evenly; add 149g of boron phosphate, and stir continuously at 80℃ for 2h; then dry and calcine at 550℃ for 2h to obtain phosphorus-modified ZSM-5 molecular sieve; the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 10%;

[0122] (4) Preparation of additives: Take 476g of boehmite, 241g of kaolin, add 1215g of deionized water, add 60g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 60℃ and keep for 60min, then add 30g of magnesium oxide, stir evenly to form a colloid.

[0123] Then, 933g of alkaline silica sol binder, 632g of modified ZSM-5 molecular sieve, and 632g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 550℃ for 1.5h to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as S7.

[0124] Comparative Example 1

[0125] This comparative example provides a catalytic cracking aid, the preparation method of which is as follows:

[0126] (1) Preparation of magnesium solution: Weigh 252g of magnesium chloride hexahydrate, add 748g of deionized water, stir continuously to fully dissolve the magnesium chloride, and obtain magnesium chloride solution for later use;

[0127] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 926g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 40, add 588g of deionized water, stir evenly, then add the magnesium chloride solution prepared in step (1), stir for 2h, dry, use the programmed temperature rise method, raise the room temperature to 500℃ in 5h (heating rate ≤4℃ / min), and then solidify and calcine at 500℃ for 4h to obtain magnesium-modified ZSM-5 molecular sieve;

[0128] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 1000g of ZSM-5 molecular sieve, add 919g of deionized water, and stir evenly; add 81g of phosphoric acid, and stir continuously at 50℃ for 1h; then dry and calcine at 450℃ for 3h to obtain phosphorus-modified ZSM-5 molecular sieve.

[0129] (4) Preparation of catalyst: Take 540g of boehmite, 810g of kaolin, add 1622g of deionized water, add 102g of hydrochloric acid with a concentration of 36%-38% under continuous stirring, heat to 70℃ and keep for 60min, then add 101g of magnesium chloride, stir evenly to form a colloid.

[0130] Then, 667g of alkaline silica sol binder, 421g of modified ZSM-5 molecular sieve, and 421g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 400℃ for 2 hours to obtain the catalytic cracking aid. The sample was designated as D1.

[0131] This comparative example is similar to Example 2, except that magnesium chloride solution is used instead of magnesium hydroxide colloid.

[0132] Comparative Example 2

[0133] This comparative example is similar to Example 4, except that no pore-blocking agent was used. This comparative example provides a catalytic cracking aid, the preparation method of which is as follows:

[0134] (1) Preparation of magnesium hydroxide colloid: Weigh 403g of magnesium chloride hexahydrate, add 597g of deionized water, maintain a constant stirring speed of 500rpm, control the reaction temperature at 60℃, and allow the magnesium chloride to dissolve completely; then add 2.4g of sodium dodecyl sulfate, slowly add ammonia water, maintain the pH value of the solution at 10.0-11.0, and continue stirring for 4h to obtain a magnesium hydroxide colloidal solution for later use;

[0135] (2) Preparation of modified ZSM-5 molecular sieve: Take 863g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 80, add 401g of deionized water, and stir evenly; then add the prepared magnesium hydroxide colloidal solution, stir for 2h, filter, dry, and use the programmed temperature rise method to raise the temperature from room temperature to 500℃ in 7h (heating rate ≤4℃ / min), and then solidify and calcine at 500℃ for 2h to obtain magnesium modified ZSM-5 molecular sieve;

[0136] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 979g of ZSM-5 molecular sieve, add 907g of deionized water, and stir evenly; add 114g of phosphoric acid, and stir continuously at 80℃ for 3h; then dry and calcine at 500℃ for 2h to obtain phosphorus-modified ZSM-5 molecular sieve.

[0137] (4) Preparation of catalyst: Take 476g of boehmite, 603g of kaolin, add 1526g of deionized water, add 60g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 60℃ and keep for 90min, then add 24g of magnesium oxide, stir evenly to form a colloid.

[0138] Then, 667g of alkaline silica sol binder, 632g of modified ZSM-5 molecular sieve, and 421g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 450℃ for 2 hours to obtain the catalytic cracking aid. The sample was designated as D2.

[0139] This comparative example is similar to Example 4, except that no pore blocker is added in this comparative example.

[0140] Comparative Example 3

[0141] This comparative example provides a catalyst for increasing propylene and ethylene production in catalytic cracking, and its preparation method is as follows:

[0142] 1) Preparation of magnesium hydroxide colloid: Weigh 636g of magnesium nitrate hexahydrate, add 614g of deionized water, maintain a constant stirring speed of 600rpm, control the reaction temperature at 60℃, and allow magnesium chloride to dissolve completely; then add 4g 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;

[0143] (2) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 821g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 40, add 275g of deionized water, add 400g of nano-silica sol under continuous stirring, and continue stirring for 2h; then add the prepared magnesium hydroxide colloidal solution, stir for 2h, filter, dry, directly raise the temperature from room temperature to 550℃, and then solidify and calcine at 550℃ for 2h to obtain magnesium-modified ZSM-5 molecular sieve;

[0144] (3) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 958g of ZSM-5 molecular sieve, add 908g of deionized water, and stir evenly; add 167g of diammonium hydrogen phosphate and stir continuously at 70℃ for 2h; then dry and calcine at 450℃ for 3h to obtain phosphorus-modified ZSM-5 molecular sieve.

[0145] (4) Preparation of additives: Take 571g of boehmite, 380g of halloysite, add 1054g of deionized water, add 80g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 60℃ and keep for 60min, then add 201g of magnesium chloride, stir evenly to form a colloid.

[0146] Then, 667g of alkaline silica sol binder, 526g of modified ZSM-5 molecular sieve, and 632g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 550℃ for 1 hour to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as D3.

[0147] This comparative example is similar to Example 6, except that this comparative example did not use programmed temperature rise when preparing magnesium-modified ZSM-5 molecular sieve.

[0148] Comparative Example 4

[0149] This embodiment provides a catalyst for increasing propylene and ethylene production through catalytic cracking, and its preparation method is as follows:

[0150] (1) Preparation of magnesium-modified ZSM-5 molecular sieve: Take 895g of ZSM-5 molecular sieve with a silicon-to-aluminum ratio of 25, add 480g of deionized water, add 635g of anhydrous ethanol under continuous stirring, continue stirring and keep for 6h; then add 255g of deionized water and 445g of magnesium nitrate hexahydrate, stir for 2h, filter, dry, quickly raise from room temperature to 600℃, and then solidify and calcine at 600℃ for 2h to obtain magnesium-modified ZSM-5 molecular sieve;

[0151] (2) Preparation of phosphorus-modified ZSM-5 molecular sieve: Take 947g of ZSM-5 molecular sieve, add 868g of deionized water, and stir evenly; add 149g of boron phosphate, and stir continuously at 80℃ for 2h; then dry and calcine at 550℃ for 2h to obtain phosphorus-modified ZSM-5 molecular sieve; the mass content of phosphorus pentoxide in the phosphorus-modified ZSM-5 molecular sieve is 10%;

[0152] (3) Preparation of additives: Take 476g of boehmite, 241g of kaolin, add 1215g of deionized water, add 60g of hydrochloric acid with a concentration of 36-38% under continuous stirring, heat to 60℃ and keep for 60min, then add 30g of magnesium oxide, stir evenly to form a colloid.

[0153] Then, 933g of alkaline silica sol binder, 632g of modified ZSM-5 molecular sieve, and 632g of phosphorus-modified ZSM-5 molecular sieve were added to the colloid, mixed and stirred evenly, spray-dried, and cured and calcined at 550℃ for 1.5h to obtain the catalytic cracking propylene and ethylene production enhancement agent. The sample was designated as D4.

[0154] 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, an alcohol was used as the pore blocker, and a programmed temperature rise was not used.

[0155] Figure 1 shows the BET nitrogen adsorption-desorption curves of the magnesium-modified ZSM-5 molecular sieves prepared in Example 2 and Comparative Example 1. The pore structure data of the two modified molecular sieves are shown in Table 1.

[0156] Table 1. Pore structure properties of magnesium-modified ZSM-5 molecular sieves

[0157] Analysis of the pore structure properties shows that the magnesium-modified ZSM-5 molecular sieve prepared by the method of this invention exhibits significantly higher specific surface area and pore volume, superior to the comparative sample. This indicates that during the magnesium modification process, magnesium species are uniformly distributed on the surface of the molecular sieve without significantly blocking the pores. Conversely, in the molecular sieve prepared in the comparative example, the non-uniform accumulation of magnesium species within the pores leads to a significant decrease in specific surface area and pore volume. This result further demonstrates the effectiveness of the method of this invention in maintaining the openness of the molecular sieve pores.

[0158] Figure 2 shows an AC-STEM image of the magnesium-modified ZSM-5 molecular sieve in Example 2. As can be seen from the figure, the pores of the molecular sieve are relatively unobstructed, with no obvious blockage. Furthermore, the magnesium element is evenly distributed on the outer surface of the molecular sieve, and no large particle aggregation was observed. In addition, the crystal structure of the molecular sieve remains intact, with no obvious lattice distortion.

[0159] The pore volume and wear index of the additives in the above examples and comparative examples were tested, and the results are shown in Table 2. The catalyst pore volume was determined by the water droplet method, standard number NB / SH / T 0955; the wear index was determined by an MS-C / 6 wear index analyzer manufactured by Shenyang Kehui Instrument Manufacturing Co., Ltd., standard number NB / SH / T 0964.

[0160] Table 2 Pore volume and strength of catalysts

[0161] Table 2 shows the pore volume and wear index data for different additives, and in particular, by comparing with comparative samples, demonstrates the superiority of the additives of the present invention in these two key indicators. The pore volume of the additives in Table 2 ranges from 0.32 to 0.35 cm³. 3 / g, with an attrition index ranging from 0.9% to 2.4%. In contrast, the comparative samples (D1 to D4) showed significantly higher attrition indices, reaching a maximum of 15.8%. These data indicate that the additives of this invention exhibit better stability and durability during use, with more uniform pore volume, which is beneficial for improving catalytic efficacy.

[0162] Table 2 shows the performance advantages of the additive of the present invention in terms of pore volume and strength, highlighting its excellent performance in catalytic cracking. Pore volume and strength have a significant impact on the final catalytic effect of the additive. A larger pore volume provides more active sites and enhances reaction activity, while a lower wear index ensures the mechanical strength and durability of the additive in practical applications. The data in Table 1 show that the additive of the present invention has been optimized in terms of pore volume and strength, resulting in superior catalytic cracking performance.

[0163] Experimental Example 1

[0164] This experimental example is used to evaluate the reaction performance of the above-mentioned catalytic cracking aid.

[0165] The performance evaluation of the additives was conducted in a fixed fluidized bed reactor. LIP-300 catalyst (physicochemical properties shown in Table 3) and the aforementioned additives were mixed at a mass ratio of 9:1 to form a catalyst assemblies. The feedstock was the catalytic feedstock from the Lanzhou Petrochemical 3.0 Mt / a unit (feedstock properties shown in Table 4). The reaction temperature was 490℃, and the catalyst-to-oil ratio was 4. Before evaluation, the catalyst assemblies were treated with 100% steam at 800℃ for 10 hours.

[0166] Table 3 Physicochemical properties of LIP-300 catalyst

[0167] Table 4 Properties of Crude Oil

[0168] The evaluation results of this experiment are shown in Table 5.

[0169] The dry gas consists of C2 components, methane, H2, H2S, etc., including ethylene;

[0170] The components of liquefied petroleum gas (LPG) include C3 and C4 components, including propylene.

[0171] Table 5 Results of catalytic reaction

[0172] Based on the test results shown in Table 5, it can be seen that all embodiments (S1 to S7) of the present invention significantly improved the selectivity and yield of propylene and ethylene, and reduced the occurrence of side reactions. Specifically, the additives in the embodiments were superior to the comparative examples (D1 to D4) in terms of propylene yield, ethylene yield, and liquefied gas yield. For example, the propylene yield in embodiment S7 reached 10.53%, significantly higher than the 5.69% in comparative example D1. In addition, the dry gas yield of the additives in each embodiment was lower than that in the comparative example, indicating that the occurrence of side reactions was suppressed.

[0173] Based on comparative analysis, this invention provides a unique acid-base bifunctional catalytic environment by loading magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieve. This key approach significantly improves the selectivity of propylene and ethylene, and effectively reduces coke formation and the deactivation rate of additives. Compared to the comparative examples, the significant advantages of the examples in improving propylene and ethylene yields further verify the important role of loading magnesium hydroxide colloid onto the outer surface of ZSM-5 molecular sieve. This indicates that by optimizing the surface structure of the molecular sieve, this invention improves catalytic cracking efficiency.

Claims

1. A method for preparing magnesium-modified ZSM-5 molecular sieve, comprising the following steps: 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. wherein The magnesium content in magnesium-modified ZSM-5 molecular sieve, calculated as oxides, is 3-10% by mass.

2. The method of making a magnesium modified ZSM-5 molecular sieve of 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 method of making a magnesium modified ZSM-5 molecular sieve of 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 method of making a magnesium modified ZSM-5 molecular sieve of claim 2, wherein, The magnesium salt includes one or more of magnesium chloride, magnesium sulfate, and magnesium nitrate.

5. The method of making a magnesium modified ZSM-5 molecular sieve of claim 2, wherein, The surfactant includes one or a combination of two or more of sodium dodecyl sulfate, polyvinylpyrrolidone, and sodium dodecylbenzenesulfonate.

6. The method of making a magnesium modified ZSM-5 molecular sieve of claim 2, wherein, The alkaline solution includes one or a combination of two or more of sodium hydroxide solution, potassium hydroxide solution, and ammonia water.

7. The method of making a magnesium modified ZSM-5 molecular sieve of claim 1, wherein, The silicon-aluminum ratio of the ZSM-5 molecular sieve is 25-100.

8. The method of making a magnesium modified ZSM-5 molecular sieve of claim 1, wherein, The particle size of the pore blocking agent is <2nm.

9. The method of making a magnesium modified ZSM-5 molecular sieve of claim 1, wherein, The roasting time is 1-4 hours; the roasting temperature rise process adopts the programmed temperature rise method.

10. A magnesium-modified ZSM-5 molecular sieve, obtained by the preparation method of the magnesium-modified ZSM-5 molecular sieve according to any one of claims 1-9.

11. A catalyst for catalytically cracking a feedstock to increase the production of propylene and ethylene, the feedstock comprising, in mass percent: 20-30% magnesium-modified ZSM-5 molecular sieve on a dry basis, 10-30% phosphorus-modified ZSM-5 molecular sieve on a dry basis, 10-20% boehmite on a dry basis, 20-40% clay on a dry basis, 1-3% magnesium oxide or magnesium salt on a magnesium oxide basis, and 8-15% alkaline silica sol binder on a silica basis. The magnesium-modified ZSM-5 molecular sieve is the magnesium-modified ZSM-5 molecular sieve as described in claim 10.

12. The catalytic cracking propylene and ethylene co-producing promoter according to claim 11, wherein, The phosphorus content (calculated as phosphorus pentoxide) in the phosphorus-modified ZSM-5 molecular sieve is 1-10%.

13. The catalytic cracking propylene and ethylene co-producing promoter according to claim 11, wherein, The phosphorus-modified ZSM-5 molecular sieve was prepared by the following method: ZSM-5 molecular sieve is mixed with water and slurryed. Phosphorus compound is added and the mixture is brought into full contact with ZSM-5 molecular sieve at 10-100℃ for 0.5-4h. The ZSM-5 molecular sieve is then removed and calcined at 300-800℃ for 0.5-4h to obtain the phosphorus-modified ZSM-5 molecular sieve.

14. The FCC propylene and ethylene co-product enhancer of claim 13, wherein, The phosphorus compound includes one or more of the following: trimethyl phosphate, triphenylphosphine, trimethyl phosphite, tetrabutylphosphine bromide, tetrabutylphosphine chloride, tetrabutylphosphine hydroxide, triphenylethylphosphine bromide, triphenylbutylphosphine bromide, triphenylbenzylphosphine bromide, hexamethylphosphoric acid triamine, dibenzyldiethylphosphine, 1,3-xylenebistriethylphosphine, phosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, and boron phosphate.

15. The catalytic cracking propylene and ethylene co-producing promoter according to claim 11, wherein, The clay includes one or more of the following: kaolin, halloysite, montmorillonite, sepiolite, hydrotalcite, and rettoite.

16. A method for preparing an additive for increasing propylene and ethylene production through catalytic cracking as described in any one of claims 11-15, comprising the following steps: Boehmite, clay and water are mixed, acid is added and the mixture is gelled, then magnesium salt is added and mixed to obtain a colloid; An alkaline silica sol binder, magnesium-modified ZSM-5 molecular sieve, and phosphorus-modified ZSM-5 molecular sieve are added to the colloid and mixed to obtain a slurry. The slurry is spray-dried into particles and calcined to obtain the catalytic cracking additive for increasing propylene and ethylene production.

17. The process for the preparation of a catalyst for catalytic cracking for the production of propylene and co-production of ethylene according to claim 16, wherein, The sol-gel treatment temperature is 30-60℃, and the sol-gel treatment time is 1-2 hours.

18. The process for the preparation of a catalyst for catalytic cracking for the production of propylene and co-production of ethylene according to claim 16, wherein, The calcination temperature of the particles is 300-600℃, and the calcination time is 0.5-2h.

19. A combined catalyst for catalytic cracking to increase propylene and ethylene production, comprising a main catalyst and an additive in a mass ratio of 1:0.05-0.2, wherein the additive is the catalytic cracking additive for increasing propylene and ethylene production according to any one of claims 11-15; and the main catalyst is a catalytic cracking catalyst.

20. A catalytic cracking process comprising: The combined catalyst for catalytic cracking to increase propylene and ethylene production as described in claim 19 is brought into full contact with the feedstock oil to carry out the catalytic cracking reaction.

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