Catalytic cracking cocatalyst for increasing propylene yield and preparation method of catalytic cracking cocatalyst

Abstract

The invention discloses a catalytic cracking cocatalyst for increasing propylene yield and a preparation method thereof. The cocatalyst contains a B-Al-ZSM-5 molecular sieve, and the absolute value of the difference between the crystal bulk phase silica-alumina ratio of the B-Al-ZSM-5 molecular sieve measured by XRF and the crystal surface silica-alumina ratio measured by EDS is less than or equal to 1. The preparation method of the cocatalyst comprises the following steps: pulping the B-Al-ZSM-5 molecular sieve, the clay, the binder, the Fe component source and the P component source with water, forming and roasting to obtain the cocatalyst. The cocatalyst adopts the B-Al-ZSM-5 molecular sieve with uniformly distributed aluminum inside and outside the crystal as an active component, and has the characteristics of high liquefied gas yield and good propylene selectivity.

Description

Technical Field

[0001] This invention relates to a catalytic cracking co-catalyst that produces a high yield of propylene and its preparation method, belonging to the field of catalytic cracking technology. Background Technology

[0002] Due to the supply-demand imbalance of refined oil products and the rapid development of new energy vehicles, refining enterprises are facing overcapacity, making the transformation and upgrading of refining and chemical industries a significant challenge. Propylene, as an important chemical feedstock, accounts for approximately one-third of the production from catalytic cracking units, making increasing propylene production a crucial objective for adjusting the product distribution of these units. Applying propylene-producing catalytic cracking co-catalysts is a primary means of improving propylene yield in catalytic cracking units. ZSM-5 molecular sieves, with their unique pore structure, abundant acidic centers, and excellent thermal and hydrothermal stability, have proven effective in catalytic cracking and pyrolysis for high propylene production.

[0003] CN112387302A discloses a catalytic cracking additive, its preparation method, its application, and a method for catalytic cracking of hydrocarbon oils. The catalytic cracking additive comprises high-silica zeolite, mesoporous silica, a binder, and a modifier; wherein the high-silica zeolite is a hydrogen-form zeolite with an MFI framework structure and a silica-to-alumina molar ratio (SiO2 / Al2O3) of not less than 100; the mesoporous silica is a one-dimensional, through-pore mesoporous silica material; and the modifier is selected from at least one of alkaline earth metal oxides, rare earth metal oxides, and non-metallic oxides. When used in the catalytic cracking process of hydrocarbon oils, this catalytic cracking additive can increase the propylene concentration in the liquefied petroleum gas (LPG) while ensuring the yield of LPG, and further increase the octane number of the catalytic cracked gasoline.

[0004] CN114425405A discloses a catalytic cracking additive for increasing propylene concentration, its preparation method, and its application. Based on the total weight of the catalytic cracking additive, it contains 10–50 wt% ZSM-5 zeolite, 5–40 wt% modified sol, 2–30 wt% modified slag, and 20–70 wt% clay; based on the total weight of the modified slag, it contains 0–2.0 wt% Na₂O, 10–40 wt% Al₂O₃, 20–70 wt% SiO₂, and 1–15 wt% RE₂O₃, and the specific surface area of ​​the modified slag is 180–350 m². 2 / g, pore volume is 0.6~1.0mL / g, and average pore size is 10~50nm.

[0005] CN115591573A discloses a propylene yield-enhancing additive and its preparation method. The additive comprises 35-55 wt% of a cracking active component, 1-5 wt% of Fe₂O₃, 6-23 wt% of clay, and 30-40 wt% of a binder. The binder includes aluminum phosphate sol, the particles of which have an outer layer structure and an internal structure within the outer layer. Based on the weight of the additive, the content of the aluminum phosphate sol, on a dry basis, is 10-40 wt%. The preparation method of the additive includes forming a slurry comprising the binder, clay, active component, iron compound, and water, followed by spray drying. This propylene yield-enhancing additive, used in catalytic cracking processes, can achieve a high distribution of high-value-added products while ensuring catalyst strength, effectively increasing the yield of propylene and butene, and improving the propylene concentration in catalytic cracking liquefied petroleum gas.

[0006] CN113546668A discloses a catalytic cracking aid containing a small-particle-size porous mesoporous composite material, its preparation method, and its application. This catalytic cracking aid comprises ZSM-5 molecular sieve, a small-particle-size porous mesoporous composite material, and an oxide. The composite material has an average particle size of 25-35 μm and a specific surface area of ​​100-650 m². 2 The pore volume is 0.5-1.8 mL / g, and the pore size exhibits a multi-peak distribution, with the first most probable pore size being 3-10 nm, the second most probable pore size being 20-30 nm, and the third most probable pore size being 40-50 nm. This additive, used in catalytic cracking processes, can significantly increase the propylene concentration in LPG without increasing the yield of catalytic cracked LPG, while also improving the octane number of catalytic cracked gasoline.

[0007] CN116920923A discloses an additive for increasing propylene production, its preparation method, catalyst and application, and a method for catalytic conversion of hydrocarbon oils. Based on the total dry weight of the additive, it comprises: 24-35 wt% P (based on P2O5), 15-60 wt% MFI structured molecular sieve (based on dry weight), and 1-8 wt% M (based on oxides); wherein P includes P1 and P2; M includes M1, which is selected from at least one group VIII metal; P1 and M1 react with the MFI structured molecular sieve to form an active component; P2 exists in the form of a phosphorus-aluminum inorganic binder; and the ratio of the resonance signal peak area with a chemical shift of 40±2 ppm to the resonance signal peak area with a chemical shift of 55±2 ppm, as determined by (27)Al nuclear magnetic resonance spectroscopy, is 1-20. When applied to catalytic cracking reactions, this additive can effectively increase the concentration of ethylene and propylene in catalytic cracking liquefied petroleum gas, thus improving its heavy oil conversion capacity.

[0008] CN116920936A discloses a catalytic cracking additive for increasing the production of propylene and butene, and its preparation method. Based on the dry weight of the additive, the additive comprises 10-75 wt% molecular sieve, 1-20 wt% zirconium sol, and 3.0-35 wt% phosphorus additive. Using this catalytic cracking additive can improve the yield and selectivity of propylene and butene, while reducing the ethylene concentration in the dry gas.

[0009] CN114453008A discloses a catalytic cracking aid for increasing the propylene concentration in liquefied petroleum gas (LPG) and its application. Based on a dry weight basis, the catalytic cracking aid contains 20–50 wt% ZSM-5 zeolite, 15–75 wt% clay, and 5–35 wt% modified sol. The modified sol contains 28–60 wt% Al₂O₃, 1–15 wt% IVB metal oxide, and 40–70 wt% P₂O₅, with a P to Al molar ratio of 0.9–2.1, an IVB metal to Al molar ratio of 0.02–0.2, and a pH value of 1.7–3.0. When applied to the catalytic cracking process, this catalytic cracking aid can significantly increase the propylene concentration in LPG.

[0010] CN115869988A discloses a catalyst for the catalytic cracking of naphtha to produce low-carbon olefins and its preparation method. The catalyst comprises an HZSM-5 molecular sieve, a first promoter, and a second promoter, which are sequentially modified and supported on the HZSM-5 molecular sieve. The preparation method is simple. The preferential loading of the metal oxide of the first promoter reduces the damage to the framework structure of the HZSM-5 by the second promoter, P2O5, and prevents dealumination. This technology has the advantages of low reaction temperature and low energy consumption, and achieves high yields of ethylene and propylene, as well as high conversion rates of naphtha. Furthermore, the reaction exhibits good stability and can be applied to industrial applications of naphtha catalytic cracking to produce low-carbon olefins such as ethylene, propylene, and butene.

[0011] As can be seen from the above, ZSM-5 molecular sieve is the main active component of catalytic cracking and pyrolysis catalysts. Numerous publicly available technologies show that by optimizing the performance of ZSM-5 molecular sieve, the reaction selectivity of cracking and pyrolysis catalysts can be effectively improved.

[0012] CN116174024A discloses a catalytic cracking catalyst, its preparation method, and its application. This catalytic cracking catalyst contains a support and a phosphorus-containing hollow ZSM-5 hierarchical porous molecular sieve. Based on the dry weight of the catalyst, the support content is 50-85% by weight, and the phosphorus-containing hollow hierarchical porous ZSM-5 molecular sieve content is 15-50% by weight. This catalytic cracking catalyst exhibits superior molecular diffusion properties, resulting in higher yields of low-carbon olefins when used in the catalytic cracking of naphtha.

[0013] CN115999623A discloses a method for preparing a catalyst to increase the propylene concentration in liquefied petroleum gas (LPG), a product of catalytic cracking. First, an alkaline solution of gallium is prepared. Then, sodium aluminate and silica sol are added to the gallium alkaline solution to form a mixed gel. ZSM-5 seed crystals are then added to the mixed gel, and the mixture is crystallized in a reactor to obtain a ZSM-5 molecular sieve. After ammonium nitrate exchange, filtration, washing, drying, and calcination, an HZSM-5 molecular sieve is obtained. This sieve is then combined with clay, filler, and binder, shaped, and calcined to obtain a microspherical catalyst for catalytic cracking. This catalyst, using gallium as the active component, not only adjusts the pore structure of the molecular sieve and improves the diffusion performance of the reactants and products, but also effectively reduces the acid strength of the catalyst, minimizing the occurrence of side reactions such as hydrogen transfer. It can effectively improve the yield and selectivity of the propylene product, and the preparation method is simple, resulting in high economic benefits when applied to catalytic cracking units.

[0014] CN115990508A discloses a ZSM-5 molecular sieve catalyst, its preparation method, and its applications. The catalyst exhibits the following properties: the ratio of framework aluminum content at the intersection of straight and sinusoidal channels to the framework aluminum content within the straight and sinusoidal channels is 1.4:1 to 10:1; and the micropore volume accounts for 70% to 92% of the total pore volume. When used in the catalytic cracking of olefins to produce propylene and ethylene, this catalyst exhibits a low hydrogen transfer index, high stability, high conversion rate of the feedstock olefins, and high selectivity for the products propylene and ethylene.

[0015] As can be seen from the above, optimizing the physicochemical properties of ZSM-5 molecular sieves can significantly improve the reaction performance of catalytic cracking catalysts. With the increasing demand for propylene from oil refineries, the reaction performance of ZSM-5, a key active component for increasing propylene production, needs further improvement. Currently, a large number of heteroatom-substituted ZSM-5 molecular sieves, such as those with Ga, B, Mg, Zn, Fe, and Ti heteroatoms, have been successfully synthesized. Among them, the boron-containing framework B-Al-ZSM-5 has attracted considerable attention from researchers.

[0016] CN103708497A discloses a nanoparticle-stacking B-Al-ZSM-5 zeolite catalyst for methanol-to-olefins (MTP) and its preparation method and application. By introducing a boron source and MFI-type zeolite seeds into the ZSM-5 zeolite synthesis system (silicon source, aluminum source, alkali source, template agent, and water), the synthesized nanoparticle-stacking B-Al-ZSM-5 zeolite exhibits high crystallinity and controllable crystal size. When used in the MTP reaction, it can improve the diffusion rate, enhance resistance to carbon deposition, and improve the acid properties of the ZSM-5 molecular sieve, which is beneficial for enhancing propylene selectivity and extending catalyst lifetime.

[0017] CN103301880A discloses a method for preparing ZSM-5 molecular sieves containing heteroatoms and their application in the dehydrogenation of methanol to formaldehyde. Tetrapropylammonium bromide is dissolved in water, followed by the sequential addition of 1,6-hexanediamine, NaOH, and boric acid. The mixture is stirred until dissolved, and then silica is added while stirring. The reaction solution is poured into a crystallization vessel. After crystallization, the product is filtered and washed with deionized water until neutral. After drying, ZSM-5 raw powder containing heteroatoms is obtained. The raw powder is calcined at 550°C with air for 2 hours to remove the template agent, yielding the molecular sieve. This technique produces ZSM-5 molecular sieves containing heteroatoms containing boron with high crystallinity and good reproducibility using mixed template agents. Furthermore, boron-containing ZSM-5 molecular sieves with a silicon-to-boron ratio of 5.5–10 exhibit high catalytic activity and formaldehyde selectivity.

[0018] CN104098110A discloses a method for preparing B-A1-ZSM-5 zeolite with controllable particle size and its application. The method uses boron, aluminum, silicon, alkali, inorganic salts, and a template agent as raw materials. Seed crystals are added to the reaction system, followed by crystallization in a crystallization reactor, filtration, washing, drying, and calcination to obtain B-A1-ZSM-5 zeolite with a particle size of 100 nm-15 μm. This technology has a simple synthesis process and allows for the recycling of waste liquid during the synthesis process, thereby reducing wastewater discharge, raw material consumption, and production costs. By adding one of ZSM-5, BZSM-5, or Silicalite-1 nano-zeolite seed crystals to the reaction system, the particle size of B-A1-ZSM-5 zeolite can be effectively adjusted. When this B-A1-ZSM-5 zeolite is used to catalyze the synthesis of propylene from methanol, it exhibits high propylene selectivity, methanol conversion rate, and catalyst lifetime.

[0019] The synthesis of B-A1-ZSM-5 still requires the introduction of a template agent, but the introduction of a template agent often increases the synthesis cost. Furthermore, the introduction of a template agent leads to the discharge of wastewater containing organic matter, and the high-temperature calcination removal of the template agent results in high energy consumption and air pollution. Therefore, template-free methods for preparing B-A1-ZSM-5 still need further development.

[0020] CN114751426A discloses a method for preparing B-Al-ZSM-5 molecular sieves and their applications. This method, without adding organic ammonium, directly introduces a high-concentration system of boron source, MFI-type molecular sieve seed crystal aid, and solid silicon-aluminum source into an alkaline solution. Following hydrothermal crystallization, filtration, washing, and drying, it efficiently synthesizes B-Al-ZSM-5 molecular sieves with a high silicon-to-aluminum ratio. The advantages of this technology are high raw material utilization, high single-reactor yield, low cost, and no nitrogen oxide emissions. However, this technology still introduces alcohol compounds and polymers as additives, and the introduction of organic additives can still cause environmental pollution.

[0021] The introduction of boron often affects the synthesis of ZSM-5 molecular sieves. Therefore, the synthesis of B-Al-ZSM-5 usually requires the introduction of template agents or organic additives.

[0022] Wei Zhou et al. compared the synthesis of B-Al-ZSM-5 without a template agent with the synthesis using a seed crystal method (Journal of Solid State Chemistry 179(2006)855-865), and found that the seed crystal method for synthesizing B-Al-ZSM-5 easily produces impure phases. The study also pointed out that the template-free synthesized B-Al-ZSM-5 has more defect sites, resulting in poor hydrothermal stability and a tendency for structural collapse during high-temperature hydrothermal treatment.

[0023] In summary, existing organic template-free synthesis systems for B-Al-ZSM-5 molecular sieves still suffer from problems such as narrow synthesis phase regions, easy generation of impure phases, and poor hydrothermal stability. Furthermore, traditional organic template-free synthesis of ZSM-5 molecular sieves often results in silicon-rich interiors and aluminum-rich surfaces, with uneven aluminum distribution throughout the crystal. The aluminum-rich surface also makes the ZSM-5 molecular sieve surface more susceptible to secondary reactions, leading to poorer reaction selectivity. Therefore, it is necessary to develop new methods for synthesizing B-Al-ZSM-5 molecular sieves with uniform aluminum distribution throughout the crystal and to use these as active components to further optimize the reaction performance of catalytic cracking catalysts. Summary of the Invention

[0024] To address at least one of the aforementioned technical problems, the present invention aims to provide a catalytic cracking co-catalyst with high propylene yield and its preparation method. This catalytic cracking co-catalyst uses a B-Al-ZSM-5 molecular sieve with uniform aluminum distribution throughout the crystal as the active component, and exhibits high liquefied petroleum gas (LPG) yield and good propylene selectivity.

[0025] To achieve the above objectives, the first aspect of the present invention provides a catalytic cracking co-catalyst for high propylene production, comprising, by 100% dry weight: 30-55% B-Al-ZSM-5 molecular sieve, 15-51% clay, 2-10% binder, 2-10% Fe component (calculated as Fe2O3), and 12-18% P component (calculated as P2O5).

[0026] The absolute value of the difference between the bulk silicon-aluminum ratio of the B-Al-ZSM-5 molecular sieve measured by XRF (X-ray fluorescence spectrometer) and the surface silicon-aluminum ratio (i.e., SiO2 / Al2O3 molar ratio) measured by EDS (X-ray energy dispersive spectroscopy) is ≤1.

[0027] In the above-mentioned catalytic cracking co-catalyst for high propylene production, preferably, the bulk silica-alumina ratio of the B-Al-ZSM-5 molecular sieve is 16-50, and the surface silica-alumina ratio is 15-51.

[0028] In the aforementioned catalytic cracking co-catalyst for high propylene production, preferably, the boron-aluminum ratio (i.e., B2O3 / Al2O3 molar ratio) of the boron-containing ZSM-5 molecular sieve is 0.2-0.6. This boron-silicon ratio can be determined using inductively coupled plasma atomic emission spectrometry (ICP).

[0029] In the aforementioned catalytic cracking co-catalyst for high propylene production, preferably, the crystallinity of the B-Al-ZSM-5 molecular sieve is 85-100%. The B-Al-ZSM-5 molecular sieve of the present invention has the characteristic of high crystallinity.

[0030] In the aforementioned catalytic cracking co-catalyst for high propylene production, preferably, the total acid content of the B-Al-ZSM-5 molecular sieve, measured by pyridine-IR desorption at 150℃, is 120-220 μmol / g, and the strong acid content, measured by pyridine-IR desorption at 350℃, is 30-55 μmol / g. The B-Al-ZSM-5 molecular sieve of the present invention has the characteristic of low strong acid content.

[0031] In the aforementioned catalytic cracking co-catalyst for high propylene production, preferably, the crystallinity reduction rate of the B-Al-ZSM-5 molecular sieve after hydrothermal aging at 800℃ for 2 hours is 10-20%. The B-Al-ZSM-5 molecular sieve of the present invention exhibits good hydrothermal stability. The formula for calculating the crystallinity reduction rate is: (Crystallinity of B-Al-ZSM-5 molecular sieve - Crystallinity of B-Al-ZSM-5 molecular sieve after hydrothermal aging at 800℃ for 2 hours) ÷ Crystallinity of B-Al-ZSM-5 molecular sieve × 100%.

[0032] In the aforementioned propylene-producing catalytic cracking co-catalysts, preferably, the binder comprises one or a combination of several of the following: alumina sol, acidified boehmite, silica sol, and phosphoalumina sol. In this invention, the binder, on a dry weight basis, is a binder based on Al2O3 and / or SiO2.

[0033] In the above-mentioned catalytic cracking co-catalyst for high propylene production, preferably, the clay includes one or a combination of several of the following: kaolin, halloysite, porous stone, diatomite, and sepiolite.

[0034] A second aspect of the present invention provides a method for preparing the above-mentioned propylene-producing catalytic cracking co-catalyst, comprising the following steps:

[0035] B-Al-ZSM-5 molecular sieve, clay, binder, Fe component source and P component source are mixed with water to obtain a slurry; the slurry is then subjected to at least molding and calcination to obtain the propylene-producing catalytic cracking co-catalyst.

[0036] In the above-described method for preparing the co-catalyst, preferably, the preparation steps of the B-Al-ZSM-5 molecular sieve include:

[0037] (1) After mixing and pretreating the boron source, the first silicon source, the seed crystal and water, a first mixed system is obtained;

[0038] (2) After the first mixture system, the second silicon source, the aluminum source and the inorganic additive are mixed evenly, the second mixture system is obtained;

[0039] (3) After crystallizing the second mixed system, it is then subjected to at least solid-liquid separation, washing, ion exchange and drying to obtain the B-Al-ZSM-5 molecular sieve;

[0040] The first silicon source is an alkaline silicon source, the second silicon source is one or a combination of alkaline silicon sources, neutral silicon sources and acidic silicon sources, and the inorganic additive is an inorganic ammonium salt.

[0041] In the above-mentioned method for preparing the co-catalyst, preferably, in step (1) of preparing the B-Al-ZSM-5 molecular sieve, the boron source includes one or a combination of boric acid, sodium borate and boron oxide.

[0042] In the above-mentioned method for preparing the co-catalyst, preferably, in step (1) of preparing the B-Al-ZSM-5 molecular sieve, the first silicon source includes water glass, etc.

[0043] In the above-mentioned method for preparing the co-catalyst, preferably, in step (1) of preparing the B-Al-ZSM-5 molecular sieve, the seed crystal is a molecular sieve with an MFI crystal structure, and the weight ratio of the amount of the seed crystal to the total amount of SiO2 in the first silicon source and the second silicon source is (0.01-0.10):1.

[0044] In the above-mentioned method for preparing the co-catalyst, preferably, in step (1) of the preparation of the B-Al-ZSM-5 molecular sieve, the pretreatment is carried out under stirring conditions, the temperature of the pretreatment is 40-70℃, and the time is 1-4h.

[0045] In the above-mentioned method for preparing the co-catalyst, preferably, in step (2) of preparing the B-Al-ZSM-5 molecular sieve, the second silicon source includes one or a combination of several of water glass, silica gel, silica sol and fumed silica.

[0046] In the above-mentioned method for preparing the co-catalyst, preferably, in step (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the aluminum source includes one or a combination of several of sodium aluminate, aluminum sulfate, aluminum chloride and aluminum nitrate.

[0047] In the above-mentioned method for preparing the co-catalyst, preferably, in step (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the inorganic additive includes one or a combination of several of the following: ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

[0048] In the above-mentioned method for preparing the co-catalyst, preferably, in step (2) of preparing the B-Al-ZSM-5 molecular sieve, the weight ratio of the amount of the inorganic additive to the total amount of SiO2 in the first silicon source and the second silicon source is (0.02-0.10):1.

[0049] In the above-mentioned method for preparing the co-catalyst, preferably, in steps (1) and (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the weight ratio of SiO2 in the first silicon source to SiO2 in the second silicon source is (0.5-1.7):1.

[0050] In the above-mentioned method for preparing the co-catalyst, preferably, in step (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the molar ratio of each substance in the second mixed system satisfies Na2O:SiO2:Al2O3:B2O3:H2O=(0.07-0.14):1:(0.013-0.042):(0.006-0.03):(14-30).

[0051] In the above-mentioned method for preparing the co-catalyst, preferably, in the preparation steps (1) and / or (2) of the B-Al-ZSM-5 molecular sieve, an alkaline source such as sodium hydroxide or an acid such as concentrated sulfuric acid may be further added so that the molar ratio of each substance in the second mixed system meets the above-mentioned range.

[0052] In the above-mentioned method for preparing the co-catalyst, preferably, in step (3) of preparing the B-Al-ZSM-5 molecular sieve, the crystallization is a two-stage crystallization; the temperature of the first stage crystallization is 110-140℃ and the time of the first stage crystallization is 2-6h; the temperature of the second stage crystallization is 150-190℃ and the time of the second stage crystallization is 12-36h.

[0053] In the above-mentioned method for preparing the co-catalyst, in step (3) of preparing the B-Al-ZSM-5 molecular sieve, the ion exchange can be carried out using conventional techniques in the field, such as acid exchange or ammonium salt exchange. The present invention does not impose any special restrictions on the conditions for ion exchange.

[0054] In the above-described method for preparing the co-catalyst, preferably, the Fe component source includes one or a combination of several of ferric chloride, ferric nitrate, ferric sulfate, and ferric oxide.

[0055] In the above-described method for preparing the co-catalyst, preferably, the P component source includes one or a combination of several of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate, more preferably phosphoric acid.

[0056] In the above-described method for preparing the co-catalyst, preferably, the molding process is spray molding.

[0057] In the above-mentioned method for preparing the co-catalyst, preferably, the calcination temperature is 400-600℃ and the time is 0.3-3.0h.

[0058] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0059] ZSM-5 molecular sieve is the main active component of a propylene-producing catalytic cracking co-catalyst. This invention achieves high-quality synthesis of B-Al-ZSM-5 molecular sieve without template agents or organic additives by employing pretreatment with alkaline silicon and boron sources, utilizing two silicon sources, introducing inorganic additives, and designing a two-stage crystallization process involving both low-temperature and high-temperature steps. The B-Al-ZSM-5 molecular sieve of this invention features low cost, high crystallinity, low strong acid content, good hydrothermal stability, and uniform aluminum distribution throughout the crystal. Due to the advantages of the aluminum distribution and acidity characteristics of the B-Al-ZSM-5 molecular sieve, the catalytic cracking co-catalyst prepared using this B-Al-ZSM-5 molecular sieve exhibits high liquefied petroleum gas (LPG) yield and good propylene selectivity. Attached Figure Description

[0060] Figure 1 The XRD patterns of molecular sieves B-Al-ZSM-5-3 and DZM-2 prepared in Example 3 and Comparative Example 2 are shown.

[0061] Figure 2 The XRD patterns of molecular sieves B-Al-ZSM-5-3 and DZM-2 prepared in Example 3 and Comparative Example 2 after hydrothermal aging at 800℃ for 2 hours are shown. Detailed Implementation

[0062] To provide a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the present invention will now be described in detail below, but this should not be construed as limiting the scope of the invention.

[0063] Analytical methods

[0064] The phase composition of the sample was characterized using a D / Max-3C X-ray diffractometer (XRD) manufactured by Rigaku Corporation of Japan. The crystallinity of the sample was determined by the peak area of ​​the five-finger peak between 22.5° and 25°. Test conditions included: X-ray CuK... α The voltage was set to 40kV, the current to 20mA, and the scanning speed to 2° / min.

[0065] The bulk silicon-to-aluminum ratio of the sample was determined using a ZSXPrimus X-ray fluorescence spectrometer (XRF) manufactured by Rigaku Corporation of Japan. The EZ mode was used for scanning, which means that the instrument automatically adjusts the test conditions according to different elements to obtain the spectral peaks of each element in the sample, including the spectral peak information of all elements after fluorine in the periodic table (including fluorine elements). The accompanying software automatically normalizes and calculates all the scanned spectral peak data to obtain the content of each element.

[0066] The surface silicon-to-aluminum ratio of the samples was determined using an X-ray energy dispersive spectrometer (EDAXXM2 60S) attached to a Zeiss Ultra-Plus field emission scanning electron microscope (SEM) from Germany.

[0067] The boron-to-aluminum ratio of the sample was determined using an Agilent 5110 inductively coupled plasma optical emission spectrometer (ICP). Before testing, 50 mg of the sample was stirred overnight in a mixture of 1 mL aqua regia and 100 μL hydrofluoric acid. The hydrofluoric acid was then removed from the mixture in an 80°C oil bath. The hydrofluoric acid-free mixture was then diluted, filtered through an aqueous filter, and brought to a final volume of 10 mL to obtain the test solution.

[0068] The pyridine-infrared (Py-IR) acidity of the sample was determined using a Bruker TENS0R27 Fourier transform infrared spectrometer from Germany. The specific method included: pressing approximately 10 mg of the powder sample into a thin sheet, fixing it in the infrared cell, and first purifying it under vacuum (350℃, 1×10⁻⁶). -3 After 2 hours of cooling to room temperature to adsorb pyridine, the temperature was then programmed to the determination temperature (fixed points were 150℃ and 350℃) for vacuum desorption (1×10⁻⁶). -3 (pa) 60 minutes, record 1700-1400cm -1 Infrared spectra of the region. The total acid content (L and Brønsted acid) of the sample was measured after desorption at 150℃, and the strong acid content (L and Brønsted acid) was measured after desorption at 350℃. In the infrared spectra at each desorption temperature, the concentration at 1540 cm⁻¹... -1 The peak at 1450 cm⁻¹ represents the Brønsted acid site. -1 The peak at the L acid site is used to calculate the amount of B acid and L acid by measuring the peak area. The sum of the two is the amount of acid measured at that desorption temperature.

[0069] raw material

[0070] 1. Industrial ZSM-5 molecular sieve, SiO2 / Al2O3 = 33, catalyst plant of Lanzhou Petrochemical Company, China National Petroleum Corporation;

[0071] 2. NaOH, boron oxide, boric acid, sodium borate, aluminum chloride, aluminum nitrate, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, ammonium sulfate, ammonium chloride, ammonium nitrate, reagents from China National Pharmaceutical Group.

[0072] 3. Ferric sulfate, ferric nitrate, ferric chloride, ferric oxide, concentrated sulfuric acid (18.4 mol / L), reagents from China National Pharmaceutical Group;

[0073] 4. Water glass (density 1.266 g / ml, SiO2 content 250 g / l, Na2O content 88 g / l), aluminum sulfate (Al2O3, 90 g / l), catalyst plant of Lanzhou Petrochemical Company, China National Petroleum Corporation;

[0074] 5. Silica sol (SiO2 content 40%), Shandong Baite New Materials Co., Ltd.

[0075] 6. Silica (reduced by 13.04%), Zhuzhou Xinglong New Materials Co., Ltd.;

[0076] 7. Kaolin, Halloysite, China Kaolin Co., Ltd.;

[0077] 8. Aluminum sol and silica gel (reduced by 11.86%), Catalyst Division, Lanzhou Petrochemical Company, China National Petroleum Corporation.

[0078] 9. LZR-20 catalyst, Catalyst Division, Lanzhou Petrochemical Company, China National Petroleum Corporation.

[0079] Catalyst performance evaluation

[0080] The performance of the co-catalyst was evaluated using an ACE evaluation device. The feedstock used was from the 3 million tons / year heavy oil catalytic cracking unit of Lanzhou Petrochemical, and its properties are shown in Table 1. The LZR-20 catalyst (as the main catalyst) and co-catalyst were aged at 800℃ and 100% steam for 10 hours before evaluation. Subsequently, the LZR-20 catalyst and co-catalyst were blended at a weight ratio of 95:5 before evaluation. The evaluation temperature was 530℃, and the catalyst-to-oil ratio was 5.0.

[0081] Table 1 Properties of Crude Oil

[0082]

[0083]

[0084] Examples and Comparative Examples

[0085] The present invention is illustrated below by way of examples and comparative examples, but the present invention is not limited to these examples. Of course, various modifications can be made within the scope of the present invention.

[0086] Example 1

[0087] 6.09 g of boron oxide was dissolved in 1496.75 g of water. After the boron oxide was fully dissolved, 813.86 g of water glass and 12.0 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 41 °C and pretreated with stirring for 2.7 h. Then, 158.03 g of silica gel was added and stirred for 42 min. After that, 179.92 g of aluminum sulfate and 28.9 g of ammonium dihydrogen phosphate were slowly added and stirred for 0.7 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2. O = 0.11:1:0.025:0.021:25; the resulting system was then transferred to a reactor, heated to 133℃ for crystallization for 3.4 h, and then further heated to 188℃ for crystallization for 12 h; after crystallization, the crystallization product was filtered and washed; then the prepared molecular sieve was mixed according to the weight ratio of molecular sieve dry basis: water: NH4Cl = 1:6.3:0.28, heated to 79℃, stirred at a constant temperature for 46 min, and then filtered, washed and dried to obtain B-Al-ZSM-5-1.

[0088] The prepared B-Al-ZSM-5-1 was mixed with water to form a slurry with a solid content of 39%, based on the dry weight ratio of B-Al-ZSM-5-1:FeCl3 (calculated as Fe2O3) silica sol (calculated as SiO2):kaolin (calculated as P2O5) = 32:2:2:51:13. The slurry was then spray-molded and calcined at 489℃ for 2.2 h to obtain the co-catalyst CAT-1.

[0089] Example 2

[0090] 12.12 g of sodium borate was dissolved in 321.29 g of water. After the sodium borate was fully dissolved, 626.31 g of water glass, 5.89 g of industrial ZSM-5 molecular sieve, and 1.88 ml of concentrated sulfuric acid were added with stirring. The mixture was heated to 63 °C and pretreated with stirring for 1.3 h. Subsequently, 181.88 g of silica sol was added, and after stirring for 58 min, 36.67 g of aluminum chloride and 4.32 g of ammonium sulfate were slowly added. The mixture was then stirred for 1.1 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O 3:H2O=0.08:1:0.042:0.029:15; the resulting system was then transferred to a reactor, heated to 112℃ for crystallization for 5.6h, and then further heated to 153℃ for crystallization for 36h; after crystallization, the crystallization product was filtered and washed; then the prepared molecular sieve was mixed according to the weight ratio of molecular sieve dry basis: water: NH4NO3=1:5.3:0.38, heated to 86℃, stirred at a constant temperature for 58min, filtered, washed, and dried to obtain B-Al-ZSM-5-2.

[0091] The prepared B-Al-ZSM-5-2 was mixed with water in the following proportions (by dry weight): B-Al-ZSM-5-2: Fe(NO3)3 (based on Fe2O3): silica sol (based on SiO2): kaolin (based on dry weight): phosphoric acid (based on P2O5): diammonium hydrogen phosphate (based on P2O5) = 53:4:10:15:14:4, to form a slurry with a solid content of 43%. The slurry was then spray-molded and calcined at 540℃ for 1.1 h to obtain the co-catalyst CAT-2.

[0092] Example 3

[0093] 4.35 g of boron oxide was dissolved in 3267.73 g of water. After the boron oxide was fully dissolved, 1358.02 g of water glass and 31.69 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 57 °C and pretreated with stirring for 3.9 h. Then, 294.98 g of silica gel was added and stirred for 62 min. After that, 179.92 g of aluminum sulfate and 28.52 g of diammonium hydrogen phosphate were slowly added and stirred for 0.9 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2. O = 0.13:1:0.014:0.007:28; the resulting system was then transferred to a reactor, heated to 139℃ for 2.3 h for crystallization, and then further heated to 162℃ for 24 h for crystallization; after crystallization, the crystallization product was filtered and washed; then the prepared molecular sieve was mixed according to the weight ratio of molecular sieve dry basis: water: (NH4)2SO4 = 1:8.5:0.58, heated to 93℃, stirred at a constant temperature for 66 min, filtered, washed, and dried to obtain B-Al-ZSM-5-3.

[0094] The prepared B-Al-ZSM-5-3 was mixed with water in the following proportions (by dry weight): B-Al-ZSM-5-3:Fe2(SO4)3 (Fe2O3):aluminum sol (Al2O3):kaolin (by dry weight):phosphoric acid (P2O5) = 42:10:6:27:15 to form a slurry with a solid content of 41%. The slurry was then spray-molded and calcined at 522℃ for 1.5 h to obtain the co-catalyst CAT-3.

[0095] Example 4

[0096] 8.45 g of boron oxide was dissolved in 1071.11 g of water. After the boron oxide was fully dissolved, 437.07 g of water glass, 25.89 g of industrial ZSM-5 molecular sieve, and 3.18 g of sodium hydroxide were added with stirring. The mixture was heated to 68 °C and pretreated with stirring for 3.3 h. Then, 198.50 g of silica was added and stirred for 82 min. After that, 173.92 g of aluminum sulfate and 17.09 g of ammonium chloride were slowly added and stirred for 1.6 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B The ratio of 2O3:H2O was 0.07:1:0.028:0.028:20. The resulting system was then transferred to a reactor and heated to 126℃ for crystallization for 2.9 h, followed by further heating to 172℃ for crystallization for 18 h. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed with water and NH4Cl at a weight ratio of 1:9.5:0.72 (dry basis of molecular sieve): 82℃ and stirred at a constant temperature for 92 min. The mixture was then filtered, washed, and dried to obtain B-Al-ZSM-5-4.

[0097] The prepared B-Al-ZSM-5-4 was mixed with water to form a slurry with a solid content of 35%, based on the dry weight ratio of B-Al-ZSM-5-4:Fe2O3:aluminum sol (calculated as Al2O3):kaolin (calculated as P2O5) = 38:6:5:37:14. The slurry was then spray-molded and calcined at 571℃ for 1.7h to obtain the co-catalyst CAT-4.

[0098] Example 5

[0099] 9.02 g of boric acid was dissolved in 2452.17 g of water. After the boric acid was fully dissolved, 982.94 g of water glass and 3.55 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 52 °C and stirred for 1.9 h for pretreatment. Then, 182.58 g of silica gel was added and stirred for 118 min. 42.6 g of aluminum nitrate and 15.27 g of ammonium nitrate were slowly added and stirred for 1.4 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O=0. The ratio of 13:1:0.017:0.012:30 was then used to transfer the resulting system into a reactor. The mixture was heated to 122℃ and crystallized for 4.7 h, followed by further heating to 176℃ and crystallizing for 28 h. After crystallization, the crystallization product was filtered and washed. Subsequently, the prepared molecular sieve was mixed with water at a weight ratio of 1:7.6 (dry basis of molecular sieve): 73℃, and hydrochloric acid solution was added to adjust the pH to 2.5. The mixture was stirred at a constant temperature for 86 min, filtered, washed, and dried to obtain B-Al-ZSM-5-5.

[0100] The prepared B-Al-ZSM-5-5 was mixed with water in the following proportions (by dry weight): B-Al-ZSM-5-5: FeCl3 (Fe2O3): silica sol (SiO2): alumina sol (Al2O3): halloysite: phosphoric acid (P2O5) = 47:7:2:5:23:16, to form a slurry with a solid content of 45%. The slurry was then spray-formed and calcined at 586℃ for 0.8 h to obtain the co-catalyst CAT-5.

[0101] Comparative Example 1

[0102] The molecular sieve prepared in this comparative example has the same silicon-to-aluminum ratio as in Example 3, except that no boron source is added, resulting in the preparation of Al-ZSM-5 molecular sieve.

[0103] Weigh 3267.73g of water, add 1358.02g of water glass and 31.69g of industrial ZSM-5 molecular sieve while stirring, heat to 57℃, and stir for 3.9h pretreatment. Then add 294.98g of silica gel, stir for 62min, and slowly add 179.92g of aluminum sulfate and 28.52g of diammonium hydrogen phosphate. Stir for 0.9h to homogenize the system. The molar ratio of each substance in the system is Na2O:SiO2:Al2O3:H2O = 0.13. The resulting system was then transferred to a reactor and heated to 139°C for 2.3 hours to crystallize, followed by further heating to 162°C for 24 hours to crystallize. After crystallization, the crystallization product was filtered and washed. Subsequently, the prepared molecular sieve was mixed with water at a weight ratio of 1:8.5:0.58 (dry basis of molecular sieve: (NH4)2SO4), heated to 93°C, stirred at a constant temperature for 66 minutes, filtered, washed, and dried to obtain DZM-1.

[0104] The prepared DZM-1 was mixed with water in a ratio of 42:10:6:27:15 (dry weight) to form a slurry with a solid content of 41%. The slurry was then spray-molded and calcined at 522℃ for 1.5 h to obtain the co-catalyst DC-1.

[0105] Comparative Example 2

[0106] The B-Al-ZSM-5 molecular sieve used in this comparative example had the same silicon-to-aluminum ratio as in Example 3, and its preparation method was carried out according to the contents described in Journal of Solid State Chemistry 179(2006)855-865.

[0107] 4.35g of boron oxide was dissolved in 3267.73g of water. After the boron oxide was fully dissolved, 179.92g of aluminum sulfate and 76.5ml of concentrated sulfuric acid were added, followed by the dropwise addition of 1358.02g of water glass. After stirring evenly, 31.69g of industrial ZSM-5 molecular sieve was added to obtain a mixed system. The molar ratio of the substances in this system was Na2O:SiO2:Al2O3:B2O3:H2O = 0.13:1:0.014:0.007:28. The resulting system was then transferred to a reaction vessel and heated to 162℃ for crystallization for 24h. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed according to the weight ratio of molecular sieve dry basis:water:(NH4)2SO4 = 1:8.5:0.58, heated to 93℃, stirred at a constant temperature for 66min, filtered, washed, and dried to obtain DZM-2.

[0108] The prepared DZM-2 was mixed with water in a ratio of 42:10:6:27:15 (dry weight) to form a slurry with a solid content of 41%. The slurry was then spray-molded and calcined at 522℃ for 1.5 h to obtain the co-catalyst DC-2.

[0109] Comparative Example 3

[0110] The comparative example uses the same B-Al-ZSM-5 molecular sieve with the same silicon-to-aluminum ratio as Example 3, but without the addition of inorganic additives.

[0111] 4.35 g of boron oxide was dissolved in 3267.73 g of water. After the boron oxide was fully dissolved, 1358.02 g of water glass and 31.69 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 57 °C and pretreated with stirring for 3.9 h. Then, 294.98 g of silica gel was added and stirred for 62 min. Finally, 179.92 g of aluminum sulfate was slowly added and stirred for 0.9 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O = The mixture was prepared with a molecular sieve ratio of 0.13:1:0.014:0.007:28. The resulting system was then transferred to a reactor and heated to 139°C for 2.3 hours to crystallize. The temperature was then further increased to 162°C for 24 hours to crystallize. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed with water at a weight ratio of 1:8.5:0.58 (dry molecular sieve: water:(NH4)2SO4). The mixture was heated to 93°C and stirred at a constant temperature for 66 minutes. The mixture was then filtered, washed, and dried to obtain DZM-3.

[0112] The prepared DZM-3 was mixed with water in a ratio of 42:10:6:27:15 (dry weight) to form a slurry with a solid content of 41%. The slurry was then spray-molded and calcined at 522℃ for 1.5 h to obtain the co-catalyst DC-3.

[0113] Comparative Example 4

[0114] The comparative example uses the same B-Al-ZSM-5 molecular sieve with the same silicon-to-aluminum ratio as Example 3, except that only the first silicon source—water glass—is added, and the second silicon source—silica gel—is not added.

[0115] 4.35 g of boron oxide was dissolved in 2301.36 g of water. After the boron oxide was fully dissolved, 2674.66 g of water glass, 79.13 ml of concentrated sulfuric acid, and 31.69 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 57 °C and pretreated with stirring for 3.9 h. Then, 179.92 g of aluminum sulfate and 28.52 g of diammonium hydrogen phosphate were slowly added, and the mixture was stirred for 0.9 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O. =0.13:1:0.014:0.007:28; The resulting system was then transferred to a reactor, heated to 139℃ for 2.3 h of crystallization, and then further heated to 162℃ for 24 h of crystallization; After crystallization, the crystallization product was filtered and washed; The prepared molecular sieve was then mixed according to the weight ratio of molecular sieve dry basis: water: (NH4)2SO4 = 1:8.5:0.58, heated to 93℃, stirred at a constant temperature for 66 min, filtered, washed, and dried to obtain DZM-4.

[0116] The prepared DZM-4 was mixed with water in the following proportions: DZM-4:Fe2(SO4)3 (Fe2O3):aluminum sol (Al2O3):kaolin (P2O5) (dry weight) = 42:10:6:27:15, to form a slurry with a solid content of 41%. The slurry was then spray-formed and calcined at 522℃ for 1.5 h to obtain the co-catalyst DC-4.

[0117] Comparative Example 5

[0118] The comparative example uses the same B-Al-ZSM-5 molecular sieve with the same silicon-to-aluminum ratio as Example 3, except that only the second silicon source—silica gel—is added, and the first silicon source—water glass—is not added.

[0119] 4.35 g of boron oxide was dissolved in 4201.36 g of water. After the boron oxide was fully dissolved, 31.69 g of industrial ZSM-5 molecular sieve and 120.14 g of sodium hydroxide were added with stirring. The mixture was heated to 57 °C and pretreated with stirring for 3.9 h. Then, 599.23 g of silica gel was added and stirred for 62 min. After that, 179.92 g of aluminum sulfate and 28.52 g of diammonium hydrogen phosphate were slowly added and stirred for 0.9 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O 3:H2O=0.13:1:0.014:0.007:28; The resulting system was then transferred to a reactor, heated to 139℃ for crystallization for 2.3h, and then further heated to 162℃ for crystallization for 24h; After crystallization, the crystallization product was filtered and washed; The prepared molecular sieve was then mixed according to the weight ratio of molecular sieve dry basis: water: (NH4)2SO4=1:8.5:0.58, heated to 93℃, stirred at a constant temperature for 66min, filtered, washed, and dried to obtain DZM-5.

[0120] The prepared DZM-5 was mixed with water in a ratio of 42:10:6:27:15 (dry weight) to form a slurry with a solid content of 41%. The slurry was then spray-molded and calcined at 522℃ for 1.5 h to obtain the co-catalyst DC-5.

[0121] Comparative Example 6

[0122] The comparative example uses the same B-Al-ZSM-5 molecular sieve with the same silicon-to-aluminum ratio as Example 3, except that no pretreatment step is performed.

[0123] 4.35 g of boron oxide was dissolved in 3267.73 g of water. After the boron oxide was fully dissolved, 1358.02 g of water glass and 31.69 g of industrial ZSM-5 molecular sieve were added with stirring, followed by 294.98 g of silica gel. After stirring for 62 min, 179.92 g of aluminum sulfate and 28.52 g of diammonium hydrogen phosphate were slowly added, and the mixture was stirred for 0.9 h to homogenize the system. The molar ratio of the substances in the system was Na2O:SiO2:Al2O3:B2O3:H2O = 0.1. The ratio of molecular sieve to water was 3:1:0.014:0.007:28. The resulting system was then transferred to a reactor and heated to 139°C for 2.3 hours to crystallize. The temperature was then further increased to 162°C for 24 hours to crystallize. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed with water at a weight ratio of 1:8.5:0.58 (dry molecular sieve: water:(NH4)2SO4). The mixture was heated to 93°C and stirred at a constant temperature for 66 minutes. After filtration, washing, and drying, DZM-6 was obtained.

[0124] The prepared DZM-6 was mixed with water in the following proportions: DZM-6:Fe2(SO4)3 (Fe2O3):aluminum sol (Al2O3):kaolin (P2O5) (dry weight) = 42:10:6:27:15, to form a slurry with a solid content of 41%. The slurry was then spray-molded and calcined at 522℃ for 1.5 h to obtain the co-catalyst DC-6.

[0125] The analysis and evaluation results of the above embodiments and comparative examples are as follows.

[0126] Figure 1 XRD patterns of the molecular sieves B-Al-ZSM-5-3 and DZM-2 prepared in Example 3 and Comparative Example 2 are shown. Figure 1 As can be seen, the B-Al-ZSM-5-3 prepared in the embodiments of the present invention has a higher diffraction peak intensity compared with DZM-2. Calculations show that the crystallinity of B-Al-ZSM-5-3 and DZM-2 are 91% and 69%, respectively, indicating that the method of the present invention is more advantageous for obtaining B-Al-ZSM-5 molecular sieves with higher crystallinity under template-free conditions.

[0127] Figure 2 XRD patterns of molecular sieves B-Al-ZSM-5-3 and DZM-2 prepared in Example 3 and Comparative Example 2 after hydrothermal aging at 800℃ for 2 hours are presented. Figure 2As can be seen, the B-Al-ZSM-5-3 prepared in this embodiment of the invention exhibits higher diffraction peak intensity after hydrothermal aging compared to DZM-2. Calculations show that the crystallinity of B-Al-ZSM-5-3 and DZM-2 after hydrothermal aging are 78% and 44%, respectively. The molecular sieve of this embodiment has a lower crystallinity decay rate, indicating that the B-Al-ZSM-5 molecular sieve of this embodiment has higher hydrothermal stability.

[0128] Table 2 shows the crystallinity of the molecular sieves in each embodiment and comparative example, the crystallinity after hydrothermal aging at 800℃ for 2 hours, and the crystallinity decay rate.

[0129] Table 2

[0130]

[0131] The results of measuring the bulk silicon-to-aluminum ratio (using XRF) and surface silicon-to-aluminum ratio (using EDS) of the molecular sieves prepared in the above examples and comparative examples, as well as the boron-to-aluminum ratio of the molecular sieves, are shown in Table 3.

[0132] Table 3

[0133]

[0134] As shown in Table 3, the silicon-to-aluminum ratio (S / A ratio) of the molecular sieves prepared in Comparative Examples 1-6 is significantly higher than that measured by EDS than by XRF. EDS primarily measures the elemental distribution on the crystal surface, indicating that the molecular sieves prepared in Comparative Examples 1-6 are characterized by high silicon content within the crystals and high aluminum content on the surface. In contrast, the absolute values ​​of the differences between the S / A ratio measured by XRF and the S / A ratio measured by EDS for the B-Al-ZSM-5 molecular sieves in each embodiment of this invention are all less than 1, indicating that the B-Al-ZSM-5 molecular sieve crystals in each embodiment of this invention have a uniform aluminum distribution.

[0135] The pyridine-infrared (Py-IR) acidity of the molecular sieves prepared in the above examples and comparative examples was determined, and the results are shown in Table 4.

[0136] Table 4

[0137]

[0138] Table 4 presents the pyridine-infrared acid content data of the molecular sieves prepared in the above embodiments and comparative examples, where the acid content at 150℃ and 350℃ represents the total acid content and the strong acid content, respectively. As can be seen from Table 4, the B-Al-ZSM-5 molecular sieves of each embodiment of the present invention have a lower strong acid content.

[0139] The reaction performance evaluation results of the cocatalysts prepared in the above examples and comparative examples are shown in Table 5.

[0140] Table 5

[0141]

[0142]

[0143] As can be seen from the ACE evaluation results in Table 5, when used in catalytic cracking reactions, the co-catalyst of the present invention significantly improves the liquefied gas yield and propylene yield compared with the co-catalyst of the comparative example, demonstrating excellent propylene production performance and significantly improved propylene selectivity.

[0144] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A catalytic cracking co-catalyst for high propylene production, comprising, by 100% dry weight of the co-catalyst: 30-55% B-Al-ZSM-5 molecular sieve on a dry basis, 15-51% clay on a dry basis, 2-10% binder on a dry basis, 2-10% Fe component on a Fe2O3 basis, and 12-18% P component on a P2O5 basis. The absolute value of the difference between the bulk silicon-aluminum ratio of the B-Al-ZSM-5 molecular sieve measured by XRF and the surface silicon-aluminum ratio measured by EDS is ≤1.

2. The catalytic cracking co-catalyst for producing more propylene according to claim 1, wherein, The B-Al-ZSM-5 molecular sieve has a bulk silicon-to-aluminum ratio of 16-50 and a surface silicon-to-aluminum ratio of 15-51.

3. The catalytic cracking co-catalyst for producing more propylene according to claim 1, wherein, The boron-aluminum ratio of the B-Al-ZSM-5 molecular sieve is 0.2-0.

6.

4. The catalytic cracking co-catalyst for producing more propylene according to claim 1, wherein, The crystallinity of the B-Al-ZSM-5 molecular sieve is 85-100%.

5. The catalytic cracking co-catalyst for producing more propylene according to claim 1, wherein, The total acid content of the B-Al-ZSM-5 molecular sieve, measured by pyridine-IR desorption at 150℃, was 120-220 μmol / g, and the strong acid content, measured by pyridine-IR desorption at 350℃, was 30-55 μmol / g.

6. The catalytic cracking co-catalyst for producing more propylene according to claim 4, wherein, The crystallinity of the B-Al-ZSM-5 molecular sieve decreased by 10-20% after hydrothermal aging at 800℃ for 2 hours.

7. The catalytic cracking co-catalyst for producing more propylene according to claim 1, wherein, The binder includes one or a combination of several of the following: aluminum sol, acidified boehmite, silica sol, and phosphoaluminate sol.

8. The catalytic cracking co-catalyst for producing more propylene according to claim 1, wherein, The clay includes one or a combination of several of the following: kaolin, halloysite, porous stone, diatomite, and zeolite.

9. A method for preparing a catalytic cracking co-catalyst for producing more propylene according to any one of claims 1-8, comprising the following steps: B-Al-ZSM-5 molecular sieve, clay, binder, Fe component source and P component source are mixed with water to obtain a slurry; The slurry is subjected to at least molding and calcination to obtain the propylene-producing catalytic cracking co-catalyst.

10. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 9, wherein, The preparation steps of the B-Al-ZSM-5 molecular sieve include: (1) After mixing and pretreating the boron source, the first silicon source, the seed crystal and water, a first mixed system is obtained; (2) After the first mixture system, the second silicon source, the aluminum source and the inorganic additive are mixed evenly, the second mixture system is obtained; (3) After crystallizing the second mixed system, it is then subjected to at least solid-liquid separation, washing, ion exchange and drying to obtain the B-Al-ZSM-5 molecular sieve; The first silicon source is an alkaline silicon source, the second silicon source is one or a combination of alkaline silicon sources, neutral silicon sources and acidic silicon sources, and the inorganic additive is an inorganic ammonium salt.

11. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (1) of the preparation of the B-Al-ZSM-5 molecular sieve, the boron source includes one or a combination of boric acid, sodium borate and boron oxide.

12. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (1) of the preparation of the B-Al-ZSM-5 molecular sieve, the first silicon source includes water glass.

13. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (1) of the preparation of the B-Al-ZSM-5 molecular sieve, the seed crystal is a molecular sieve with an MFI crystal structure, and the weight ratio of the amount of the seed crystal to the total amount of SiO2 in the first silicon source and the second silicon source is (0.01-0.10):

1.

14. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (1) of the preparation of the B-Al-ZSM-5 molecular sieve, the pretreatment is carried out under stirring conditions, the temperature of the pretreatment is 40-70℃, and the time is 1-4h.

15. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the second silicon source includes one or a combination of several of water glass, silica gel, silica sol and fumed silica.

16. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the aluminum source includes one or a combination of sodium aluminate, aluminum sulfate, aluminum chloride and aluminum nitrate.

17. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the inorganic additives include one or a combination of several of the following: ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate.

18. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the weight ratio of the amount of inorganic additive to the total amount of SiO2 in the first silicon source and the second silicon source is (0.02-0.10):

1.

19. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In steps (1) and (2) of the preparation of the B-Al-ZSM-5 molecular sieve, the weight ratio of SiO2 in the first silicon source to SiO2 in the second silicon source is (0.5-1.7):

1.

20. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (2) of the preparation of B-Al-ZSM-5 molecular sieve, the molar ratio of each substance in the second mixed system satisfies Na2O:SiO2:Al2O3:B2O3:H2O=(0.07-0.14):1:(0.013-0.042):(0.006-0.03):(14-30).

21. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 10, wherein, In step (3) of the preparation of B-Al-ZSM-5 molecular sieve, the crystallization is a two-stage crystallization; the temperature of the first stage crystallization is 110-140℃ and the time of the first stage crystallization is 2-6h; the temperature of the second stage crystallization is 150-190℃ and the time of the second stage crystallization is 12-36h.

22. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 9, wherein, The Fe component source includes one or a combination of several of ferric chloride, ferric nitrate, ferric sulfate, and ferric oxide.

23. The method for preparing the propylene-producing catalytic cracking co-catalyst according to claim 9, wherein, The P component source includes one or a combination of several of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate.

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