Composite modified ZSM-5 molecular sieve and preparation method thereof

Abstract

The invention discloses a composite modified ZSM-5 molecular sieve and a preparation method thereof. The composite modified ZSM-5 molecular sieve comprises a phosphorus oxide, manganese oxide and a B-Al-ZSM-5 molecular sieve, and the absolute value of the difference between the crystal bulk phase silica-alumina ratio measured by XRF and the crystal surface silica-alumina ratio measured by EDS of the composite modified ZSM-5 molecular sieve is less than or equal to 1. The preparation method of the composite modified ZSM-5 molecular sieve comprises the following steps: impregnating a B-Al-ZSM-5 molecular sieve with a phosphorus-containing compound, and impregnating with a manganese-containing compound to obtain the composite modified ZSM-5 molecular sieve. The B, P and Mn three-element composite modified molecular sieve is prepared in the absence of a template agent and an organic additive, can be used in catalytic cracking, catalytic cracking and other reactions, and has the characteristics of high conversion rate, good low-carbon olefin selectivity and the like.

Description

Technical Field

[0001] This invention relates to a composite modified ZSM-5 molecular sieve and its preparation method, belonging to the field of catalytic materials 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 about one-third of the production from catalytic cracking units, making increasing propylene production a key objective in adjusting the product distribution of these units. Applying propylene-producing catalytic cracking co-catalysts is the main method to improve the propylene yield of catalytic cracking units.

[0003] ZSM-5 molecular sieves, due to their unique pore structure, abundant acidic centers, and good thermal and hydrothermal stability, have excellent applications in catalytic cracking for propylene production. With the increasing demand for propylene from refineries, the reactivity of ZSM-5, a key active component for increasing propylene production, needs further improvement. Modifying ZSM-5 molecular sieves is an important way to further enhance their reactivity.

[0004] Introducing heteroatoms during the synthesis of ZSM-5 molecular sieves, as well as modifying them with phosphorus and metals, are important ways to improve the propylene selectivity of ZSM-5 molecular sieves. Phosphorus modification is a crucial method for modifying ZSM-5, effectively improving its stability, modulating its acidity, and thus improving its propylene yield. Metal ion modification, such as Zn-modified ZSM-5 molecular sieves, is also an important way to improve the reactivity of ZSM-5 molecular sieves. Studies show that ZSM-5 molecular sieves modified with a combination of phosphorus and metals can further optimize their reactivity.

[0005] CN1298425C reports an aromatization catalyst, its preparation method, and its application. The catalyst utilizes modified ZSM-5 molecular sieve, with zinc, phosphorus, and rare earth metals as the modifying elements. The modification method involves mixing and stirring the ZSM-5 molecular sieve with zinc and rare earth compounds, followed by exchange, filtration, drying, and calcination. The calcined product is then contacted with a phosphorus-containing solution, dried, and calcined again to obtain the modified ZSM-5 molecular sieve. The catalyst prepared by this method exhibits high aromatization activity, strength, stability, and flowability.

[0006] CN101440302B discloses a method for reducing the benzene content in gasoline and its catalyst, wherein the active component of the catalyst contains modified ZSM-5 molecular sieve. The modifying elements of the ZSM-5 molecular sieve are phosphorus and one or more metals selected from zinc and rare earth metals. The modification method involves preparing a solution of phosphorus, zinc, and / or rare earth compounds, then impregnating it with ZSM-5 molecular sieve, followed by drying and calcination to obtain the modified ZSM-5 molecular sieve. This catalyst, when applied to catalytic cracking, can reduce the benzene content in gasoline and effectively increase propylene yield.

[0007] CN103816936B reports a modified aluminum phosphate molecular sieve and its preparation method. The modification method involves mixing ZSM-5 molecular sieve with water, then adding a phosphorus-containing compound and a zinc-containing compound. After stirring until homogeneous, the mixture is heated to 120-150℃ and stirred under a certain pressure for 120-150 min. The mixture is then filtered, dried, and calcined to obtain the modified aluminum phosphate molecular sieve. This molecular sieve exhibits strong Brønsted acid centers, good thermal and hydrothermal stability, and excellent adsorption and decomposition properties.

[0008] CN107737607A reports an SP-5 molecular sieve catalyst for increasing propylene production and its preparation method. The molecular sieve preparation steps are as follows: HZSM-5 is soaked in water; a solution containing diammonium hydrogen phosphate is slowly sprayed into HZSM-5 to obtain a wet PZSM-5 molecular sieve product; the wet product is then dried and calcined; a zinc nitrate and ferric chloride solution is added to the calcined PZSM-5 molecular sieve for impregnation, followed by drying and calcination to obtain the SP-5 molecular sieve product. This molecular sieve exhibits good thermal and hydrothermal stability, as well as excellent adsorption and pyrolysis performance.

[0009] In phosphorus- and metal-modified bifunctional molecular sieves, it is generally believed that phosphorus modification of ZSM-5 molecular sieves can improve their thermal and hydrothermal stability, while also optimizing their acidity distribution, thereby reducing secondary reactions in catalytic cracking and promoting propylene selectivity. Metal elements, such as zinc, have a certain dehydrogenation effect as modifying elements, which can promote alkane conversion in catalytic cracking. Currently, in phosphorus- and metal-modified bifunctional molecular sieves, the metal elements are mainly rare earth elements, zinc, and iron, with other types of metal elements rarely used for bifunctional modification. From the above reports, it can also be seen that existing phosphorus- and metal bifunctional modifications are mainly aimed at conventional ZSM-5 molecular sieves. There are few reports on the composite modification of heteroatom-containing ZSM-5 molecular sieves using phosphorus and metal elements. Introducing heteroatoms into the ZSM-5 molecular sieve synthesis process can effectively modulate the acidity distribution of ZSM-5 molecular sieves and is one of the widely studied modification methods.

[0010] Currently, numerous heteroatom-modified ZSM-5 molecular sieves, such as those substituted with Ga, B, Mg, Zn, Fe, and Ti, have been successfully synthesized. The introduction of boron can effectively modulate the acidity of ZSM-5 molecular sieves, enabling the catalysts to exhibit higher reaction selectivity in reactions such as methanol-to-olefins (MTO) and methanol-to-propylene (MTP). ZSM-5 molecular sieves with a boron-only framework (B-ZSM-5) suffer from extremely low MTO conversion rates due to their weak acidity. ZSM-5 molecular sieves with both aluminum and boron in their framework (B-Al-ZSM-5) exhibit moderate to strong acidity and have attracted considerable attention from researchers.

[0011] 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.

[0012] 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.

[0013] CN104098110B 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 synthesis, 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] In summary, existing 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. Summary of the Invention

[0019] To address at least one of the aforementioned technical problems, the present invention aims to provide a composite modified ZSM-5 molecular sieve and its preparation method. The composite modified ZSM-5 molecular sieve of the present invention has advantages such as uniform aluminum distribution inside and outside the crystals.

[0020] To achieve the above objectives, the first aspect of the present invention provides a composite modified ZSM-5 molecular sieve, comprising: phosphorus oxides, manganese oxides, and B-Al-ZSM-5 molecular sieve; based on the total weight of the B-Al-ZSM-5 molecular sieve as 100%, the content of phosphorus oxides in the composite modified ZSM-5 molecular sieve, calculated as phosphorus pentoxide, is 2%-8%, and the content of manganese oxide in the composite modified ZSM-5 molecular sieve is 0.1%-2%; wherein, the absolute value of the difference between the bulk silicon-aluminum ratio (i.e., SiO2 / Al2O3 molar ratio) of the composite modified ZSM-5 molecular sieve measured by XRF (X-ray fluorescence spectrometry) and the surface silicon-aluminum ratio measured by EDS (energy dispersive X-ray spectroscopy) is ≤1.

[0021] It should be noted that the phosphorus oxides in the composite modified ZSM-5 molecular sieve of the present invention are combined with the B-Al-ZSM-5 molecular sieve. Therefore, the form of the phosphorus oxides is not necessarily phosphorus pentoxide, but its content is calculated as phosphorus pentoxide.

[0022] According to a specific embodiment of the present invention, preferably, the silicon-to-aluminum ratio of the bulk crystal phase of the composite modified ZSM-5 molecular sieve is 16-50, and the silicon-to-aluminum ratio on the crystal surface is 15-51.

[0023] According to a specific embodiment of the present invention, preferably, the boron-to-aluminum ratio (i.e., the B2O3 / Al2O3 molar ratio) of the composite modified ZSM-5 molecular sieve is 0.2-0.6. This boron-to-silicon ratio can be determined using inductively coupled plasma atomic emission spectrometry (ICP).

[0024] According to a specific embodiment of the present invention, preferably, the crystallinity of the composite modified ZSM-5 molecular sieve is 80-90%. The composite modified ZSM-5 molecular sieve of the present invention has the characteristic of high crystallinity.

[0025] According to a specific embodiment of the present invention, preferably, the total acid content of the composite modified ZSM-5 molecular sieve, measured by pyridine-IR desorption at 150℃, is 80-170 μmol / g, and the strong acid content, measured by pyridine-IR desorption at 350℃, is 15-40 μmol / g. The composite modified ZSM-5 molecular sieve of the present invention has the characteristic of low strong acid content.

[0026] According to a specific embodiment of the present invention, preferably, the crystallinity reduction rate of the composite modified ZSM-5 molecular sieve after hydrothermal aging at 800℃ for 2 hours is 6-13%. The composite modified ZSM-5 molecular sieve of the present invention has the characteristic of good hydrothermal stability. The formula for calculating the crystallinity reduction rate is: (Crystallinity of the composite modified ZSM-5 molecular sieve - Crystallinity of the composite modified ZSM-5 molecular sieve after hydrothermal aging at 800℃ for 2 hours) ÷ Crystallinity of the composite modified ZSM-5 molecular sieve × 100%.

[0027] A second aspect of the present invention provides a method for preparing the above-mentioned composite modified ZSM-5 molecular sieve, comprising the following steps:

[0028] S1: The B-Al-ZSM-5 molecular sieve is impregnated with a phosphorus-containing compound and then calcined to obtain a P-modified molecular sieve.

[0029] S2: The P-modified molecular sieve is impregnated with a manganese-containing compound and then calcined to obtain the composite modified ZSM-5 molecular sieve.

[0030] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieves, preferably, the preparation steps of the B-Al-ZSM-5 molecules include:

[0031] (1) After mixing and pretreating the boron source, the first silicon source, the seed crystal and water, a first mixed system is obtained;

[0032] (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;

[0033] (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;

[0034] 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.

[0035] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step (1) of the preparation of B-Al-ZSM-5 molecular sieve, the boron source includes one or a combination of boric acid, sodium borate and boron oxide.

[0036] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step (1) of the preparation of B-Al-ZSM-5 molecular sieve, the first silicon source includes water glass, etc.

[0037] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step (1) of the preparation of 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 seed crystal to the total amount of SiO2 in the first silicon source and the second silicon source is (0.01-0.10):1.

[0038] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step (1) of the preparation of 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.

[0039] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step (2) of the preparation of 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.

[0040] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step (2) of the preparation of 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.

[0041] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step (2) of the preparation of 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.

[0042] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step (2) of the preparation of 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.

[0043] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in the preparation steps (1) and (2) 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.

[0044] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, 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).

[0045] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, 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 can be further added so that the molar ratio of each substance in the second mixed system meets the above-mentioned range.

[0046] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, 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.

[0047] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, in step (3) of the preparation of 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 of ion exchange.

[0048] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step S1, the phosphorus-containing compound includes one or a combination of several of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

[0049] In the above-described method for preparing composite modified ZSM-5 molecular sieve, preferably, in step S1, the amount of the phosphorus-containing compound is 2%-8% of the weight of the B-Al-ZSM-5 molecular sieve, based on phosphorus pentoxide.

[0050] In the above-described method for preparing composite modified ZSM-5 molecular sieve, in step S1, the specific method of impregnating the B-Al-ZSM-5 molecular sieve with a phosphorus-containing compound can be a conventional method in the art, and the present invention does not impose any special restrictions on the impregnation conditions.

[0051] In the above-mentioned method for preparing composite modified ZSM-5 molecular sieve, preferably, in step S2, the manganese-containing compound includes one or a combination of manganese nitrate, manganese chloride, manganese acetate and manganese sulfate.

[0052] In the above-described method for preparing composite modified ZSM-5 molecular sieve, preferably, in step S2, the amount of the manganese-containing compound, calculated as manganese oxide, is 0.1%-2% of the weight of the B-Al-ZSM-5 molecular sieve.

[0053] In the above-described method for preparing composite modified ZSM-5 molecular sieve, in step S2, the specific method of impregnating the P-modified molecular sieve with a manganese-containing compound can be a conventional method in the art, and the present invention does not impose any special restrictions on the impregnation conditions.

[0054] In the above-described method for preparing composite modified ZSM-5 molecular sieve, the calcination temperature and time in steps S1 and S2 can be conventionally adjusted by those skilled in the art, and the present invention does not impose any special restrictions on them.

[0055] The technical solution of the present invention has at least the following advantages and beneficial effects:

[0056] This invention achieves high-quality synthesis of B-Al-ZSM-5 molecular sieves through pretreatment with alkaline silicon and boron sources, the use of two silicon sources, the introduction of inorganic additives, and a two-stage crystallization process involving low temperature followed by high temperature, without the presence of template agents or organic additives. 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 crystals. The composite-modified ZSM-5 molecular sieve of this invention utilizes this B-Al-ZSM-5 molecular sieve and further optimizes its acidity and stability by modifying it with P and Mn elements. This invention prepares a B, P, and Mn three-element composite-modified molecular sieve without template agents or organic additives, exhibiting advantages such as high crystallinity, low strong acid content, good hydrothermal stability, and uniform aluminum distribution throughout the crystals. The composite-modified ZSM-5 molecular sieve of this invention can be used in catalytic cracking and catalytic pyrolysis reactions, exhibiting high conversion rates and good selectivity for low-carbon olefins. Attached Figure Description

[0057] Figure 1 The XRD patterns of molecular sieves ZBP-3 and DZ-2 prepared in Example 3 and Comparative Example 2 are shown.

[0058] Figure 2 The XRD patterns of molecular sieves ZBP-3 and DZ-2 prepared in Example 3 and Comparative Example 2 after hydrothermal aging at 800℃ for 2 hours are shown. Detailed Implementation

[0059] 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.

[0060] Analytical methods

[0061] The sample phases were characterized using a D / Max-3C X-ray diffractometer (XRD) manufactured by Rigaku Corporation of Japan, with a phase range of 22.5-25 μm. 0 The peak area of ​​the five-finger peak determines the crystallinity of the sample. Test conditions include: X-ray CuK... α The voltage was set to 40kV, the current to 20mA, and the scanning speed to 2° / min.

[0062] The bulk silicon-to-aluminum ratio of the sample was determined using a ZSX Primus X-ray fluorescence spectrometer 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.

[0063] 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.

[0064] 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.

[0065] 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). -3After 2 hours of cooling to room temperature to adsorb pyridine, the temperature was then programmed to the measurement temperature (fixed points of 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.

[0066] raw material

[0067] 1. Industrial ZSM-5 molecular sieve, SiO2 / Al2O3 = 33, catalyst plant of Lanzhou Petrochemical Company, China National Petroleum Corporation;

[0068] 2. NaOH, boron oxide, boric acid, sodium borate, aluminum chloride, aluminum nitrate, concentrated sulfuric acid (18.4 mol / L), reagents from China National Pharmaceutical Group.

[0069] 3. 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;

[0070] 4. Silica sol (SiO2 content 40%), Shandong Baite New Materials Co., Ltd.

[0071] 5. Silica (reduced by 13.04%), Zhuzhou Xinglong New Materials Co., Ltd.;

[0072] 6. Manganese chloride, manganese nitrate, manganese acetate, manganese sulfate, phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium sulfate, ammonium chloride, ammonium nitrate, China National Pharmaceutical Group Reagents;

[0073] 7. Kaolin, China Kaolin Co., Ltd.;

[0074] 8. Aluminum sol, silica gel (reduced by 11.86%), MASY molecular sieve (belonging to REUSY molecular sieve), Catalyst Division, Lanzhou Petrochemical Company, China National Petroleum Corporation.

[0075] Catalytic performance evaluation

[0076] The catalytic performance of the molecular sieves provided in the examples and comparative examples was evaluated using a fixed fluidized bed reactor. The feedstock oil 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 molecular sieves provided in the examples and comparative examples were prepared into catalysts for performance evaluation using the following method: The molecular sieve to be evaluated, along with kaolin, alumina sol, and MASY molecular sieve, were mixed with deionized water at a weight ratio of molecular sieve to be evaluated: kaolin: alumina sol: MASY molecular sieve = 3:52:15:30 to prepare a slurry. This slurry was then spray-dried into microspheres, which were then calcined at 480°C for 70 minutes. Subsequently, deionized water and ammonium chloride were added at 5.5 times and 0.45 times the mass of the microspheres, respectively. The mixture was heated to 89°C and stirred at a constant temperature for 38 minutes. After filtration and washing, the catalyst was obtained. The catalyst was aged at 800°C with 100% steam for 10 hours before evaluation. The evaluation temperature was 500°C, and the catalyst-to-oil ratio was 4.0.

[0077] Table 1 Properties of Crude Oil

[0078]

[0079]

[0080] Examples and Comparative Examples

[0081] 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.

[0082] Example 1

[0083] 8.034 g of boric acid was dissolved in 434.27 g of deionized water. After the boric acid was fully dissolved, 555.13 g of water glass and 11.92 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 70 °C and pretreated with stirring for 2.4 h. Subsequently, 121.45 g of silica gel was added and stirred for 36 min. Then, 155.93 g of aluminum sulfate and 10.83 g of ammonium phosphate were slowly added and stirred for 1.1 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O. =0.08:1:0.03:0.018:15; The resulting system was then transferred to a reactor and heated to 132℃ for crystallization for 3.9 h, followed by further heating to 150℃ for crystallization for 36 h; 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: deionized water: NH4Cl = 1:5.5:0.45, heated to 92℃, stirred at a constant temperature for 37 min, and then filtered, washed, and dried to obtain B-Al-ZSM-5-1.

[0084] Weigh 100g of B-Al-ZSM-5-1; then, based on the mass of P2O5, weigh ammonium phosphate at 2.0% of the mass of B-Al-ZSM-5-1, and dissolve the ammonium phosphate in 100g of deionized water to prepare solution A; after the ammonium phosphate is completely dissolved, mix solution A with B-Al-ZSM-5-1, mix thoroughly, and place in an oven at 103℃ for 10 hours to dry. After drying, calcine in a muffle furnace at 500℃ for 2.9 hours. BZSM-P-1 was obtained; then, manganese chloride was weighed according to the mass of MnO, and the amount of MnO was 0.7% of the mass of B-Al-ZSM-5-1. The manganese chloride was dissolved in 102g of deionized water to prepare solution B; after the manganese chloride was completely dissolved, solution B was mixed with BZSM-P-1. After mixing evenly, the mixture was placed in an oven at 108℃ and dried for 20h. After drying, it was placed in a muffle furnace at 595℃ and calcined for 2.1h to obtain ZBP-1.

[0085] Example 2

[0086] 6.433 g of boron oxide was dissolved in 3256.62 g of deionized water. After the boron oxide was fully dissolved, 1175.57 g of water glass and 4.62 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 40 °C and pretreated with stirring for 3.2 h. Then, 263.79 g of silica was added and stirred for 55 min. After that, 42.6 g of aluminum nitrate and 9.23 g of ammonium nitrate were slowly added and stirred for 0.8 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2. O = 0.13:1:0.013:0.006:30; the resulting system was then transferred to a reactor, heated to 110℃ for 6 hours of crystallization, and then further heated to 190℃ for 12 hours of 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: deionized water: NH4NO3 = 1:6.4:0.35, heated to 84℃, stirred at a constant temperature for 66 minutes, and then filtered, washed and dried to obtain B-Al-ZSM-5-2.

[0087] Weigh 100g of B-Al-ZSM-5-2; then, based on the mass of P2O5, weigh ammonium dihydrogen phosphate at 6.8% of the mass of B-Al-ZSM-5-2. Dissolve the ammonium dihydrogen phosphate in 105g of deionized water to prepare solution A. After the ammonium dihydrogen phosphate is completely dissolved, mix solution A with B-Al-ZSM-5-2. After mixing evenly, place the mixture in a 110℃ oven for 12 hours to dry. After drying, place the mixture in a 520℃ muffle furnace. After calcining for 2.5 h, BZSM-P-2 was obtained. Subsequently, manganese nitrate was weighed according to the mass of MnO, and the amount of MnO was 1.3% of the mass of B-Al-ZSM-5-2. The manganese nitrate was dissolved in 98 g of deionized water to prepare solution B. After the manganese nitrate was completely dissolved, solution B was mixed with BZSM-P-2. After mixing evenly, the mixture was placed in an oven at 102 °C and dried for 18 h. After drying, it was calcined in a muffle furnace at 510 °C for 2.5 h to obtain ZBP-2.

[0088] Example 3

[0089] 11.74 g of sodium borate was dissolved in 1023.05 g of deionized water. After the sodium borate was fully dissolved, 670.68 g of water glass and 8.5 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 53 °C and pretreated with stirring for 1 h. Then, 133.38 g of silica gel was added and stirred for 42 min. After that, 155.93 g of aluminum sulfate and 20.75 g of diammonium hydrogen phosphate were slowly added and stirred for 1.3 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O = The ratio of 0.10:1:0.026:0.028:22 was then transferred to a reactor, heated to 140℃ for 2 hours of crystallization, and then further heated to 170℃ for 22 hours of crystallization. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed in a weight ratio of molecular sieve dry basis: deionized water: (NH4)2SO4 = 1:9.2:0.27, heated to 68℃, stirred at a constant temperature for 49 minutes, and then filtered, washed, and dried to obtain B-Al-ZSM-5-3.

[0090] Weigh 100g of B-Al-ZSM-5-3; then, based on the mass of P2O5, weigh diammonium hydrogen phosphate at 6.8% of the mass of B-Al-ZSM-5-3. Dissolve the diammonium hydrogen phosphate in 96g of deionized water to prepare solution A. After the diammonium hydrogen phosphate is completely dissolved, mix solution A with B-Al-ZSM-5-3. After mixing evenly, place the mixture in an oven at 115℃ for 14 hours to dry. After drying, place the mixture in a muffle furnace at 550℃. Calcination was carried out for 2.0 h to obtain BZSM-P-3; then, manganese sulfate was weighed according to the mass of MnO, and the amount of MnO was 0.1% of the mass of B-Al-ZSM-5-3. The manganese sulfate was dissolved in 108 g of deionized water to prepare solution B; after the manganese sulfate was completely dissolved, solution B was mixed with BZSM-P-3. After mixing evenly, the mixture was placed in an oven at 116 ℃ and dried for 16 h. After drying, it was calcined in a muffle furnace at 545 ℃ for 2.3 h to obtain ZBP-3.

[0091] Example 4

[0092] 6.70 g of boron oxide was dissolved in 1908.68 g of deionized water. After the boron oxide was fully dissolved, 940.32 g of water glass and 33.52 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 62 °C and stirred for 2.6 h for pretreatment. Then, 824.85 g of silica sol was added and stirred for 82 min. Then, 36.67 g of aluminum chloride and 22.17 g of ammonium chloride were slowly added and stirred for 1.3 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O = 0.073:1:0.016:0.0112:20. The resulting system was then transferred to a reactor and heated to 123 °C for crystallization for 4.3 h. The temperature was then further increased to 163 °C for crystallization for 26 h. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed in a weight ratio of molecular sieve dry basis: deionized water: NH4Cl = 1:7.3:0.63, heated to 78℃, stirred at a constant temperature for 58 min, and then filtered, washed and dried to obtain B-Al-ZSM-5-4.

[0093] Weigh 100g of B-Al-ZSM-5-4; then, based on the mass of P2O5, weigh phosphoric acid at 6.8% of the mass of B-Al-ZSM-5-4, and dissolve the phosphoric acid in 93g of deionized water to prepare solution A; after the phosphoric acid is completely dissolved, mix solution A with B-Al-ZSM-5-4, mix thoroughly, and place in an oven at 123℃ for 10 hours to dry. After drying, calcine in a muffle furnace at 600℃ for 1.8 hours. BZSM-P-4 was obtained. Subsequently, manganese acetate was weighed according to the mass of MnO, and the amount of MnO was 1.1% of the mass of B-Al-ZSM-5-4. The manganese acetate was dissolved in 105g of deionized water to prepare solution B. After the manganese acetate was completely dissolved, solution B was mixed with BZSM-P-4. After mixing evenly, the mixture was placed in an oven at 120℃ and dried for 13h. After drying, it was calcined in a muffle furnace at 563℃ for 1.9h to obtain ZBP-4.

[0094] Example 5

[0095] 8.84 g of boric acid was dissolved in 1368.16 g of deionized water. After the boric acid was fully dissolved, 986.90 g of water glass, 30.95 g of industrial ZSM-5 molecular sieve, and 10.8 ml of concentrated sulfuric acid were added with stirring. The mixture was heated to 58 °C and pretreated with stirring for 4 h. Then, 131.83 g of silica was added and stirred for 108 min. After that, 155.93 g of aluminum sulfate and 30.95 g of ammonium sulfate 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:B2O3:H 2O = 0.11:1:0.021:0.0139:24; the resulting system was then transferred to a reactor, heated to 129℃ for 3.2 h of crystallization, and then further heated to 174℃ for 20 h of 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: deionized water = 1:8.4, heated to 96℃, hydrochloric acid solution was added, pH = 2.6 was adjusted, and the mixture was stirred at a constant temperature for 81 min, and then filtered, washed and dried to obtain B-Al-ZSM-5-5.

[0096] Weigh 100g of B-Al-ZSM-5-5; then, based on the mass of P2O5, weigh diammonium hydrogen phosphate at 8.0% of the mass of B-Al-ZSM-5-5. Dissolve the diammonium hydrogen phosphate in 109g of deionized water to prepare solution A. After the diammonium hydrogen phosphate is completely dissolved, mix solution A with B-Al-ZSM-5-5. After mixing evenly, place the mixture in a 109℃ oven for 16 hours to dry. After drying, place the mixture in a 580℃ muffle furnace. After calcining for 2.7 h, BZSM-P-5 was obtained. Subsequently, manganese chloride was weighed according to the mass of MnO, and the amount of MnO was 2.0% of the mass of B-Al-ZSM-5-5. The manganese chloride was dissolved in 94 g of deionized water to prepare solution B. After the manganese chloride was completely dissolved, solution B was mixed with BZSM-P-5. After mixing evenly, the mixture was placed in an oven at 124 ℃ and dried for 10 h. After drying, it was calcined in a muffle furnace at 528 ℃ for 1.8 h to obtain ZBP-5.

[0097] Comparative Example 1

[0098] 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. Al-ZSM-5 molecular sieve is prepared and then modified with P and Mn.

[0099] Weigh 1023.05g of deionized water, add 670.68g of water glass and 8.5g of industrial ZSM-5 molecular sieve while stirring, heat to 53℃, and stir for 1h pretreatment; then add 133.38g of silica gel, stir for 42min, then slowly add 155.93g of aluminum sulfate and 20.75g of diammonium hydrogen phosphate, and stir for 1.3h to homogenize the system. The molar ratio of each substance in the system is Na2O:SiO2:Al2O3:H2O = 0.10:1 The ratio of 0.026:22 was then transferred to a reactor, heated to 140℃ for 2 hours of crystallization, and then further heated to 170℃ for 22 hours of crystallization. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed in a weight ratio of molecular sieve dry basis: deionized water: (NH4)2SO4 = 1:9.2:0.27, heated to 68℃, stirred at a constant temperature for 49 minutes, and then filtered, washed, and dried to obtain DZM-1.

[0100] Weigh 100g of DZM-1; then, based on the mass of P2O5, weigh diammonium hydrogen phosphate at 6.8% of the mass of DZM-1, and dissolve the diammonium hydrogen phosphate in 96g of deionized water to prepare solution A; after the diammonium hydrogen phosphate is completely dissolved, mix solution A with DZM-1, and after mixing evenly, place it in an oven at 115℃ for 14h to dry. After drying, place it in a muffle furnace at 550℃ for 2.0h to obtain DZM-P-1; then, based on the mass of MnO, weigh manganese sulfate at 0.1% of the mass of DZM-1, and dissolve the manganese sulfate in 108g of deionized water to prepare solution B; after the manganese sulfate is completely dissolved, mix solution B with DZM-P-1, and after mixing evenly, place it in an oven at 116℃ for 16h to dry. After drying, place it in a muffle furnace at 545℃ for 2.3h to obtain DZ-1.

[0101] Comparative Example 2

[0102] The B-Al-ZSM-5 molecular sieve used in this comparative example had the same silicon-to-aluminum ratio as in Example 3. The preparation method was carried out according to the contents described in Journal of Solid State Chemistry 179(2006)855-865, and then it was modified with P and Mn.

[0103] 11.74 g of sodium borate was dissolved in 586.10 g of water. After the sodium borate was fully dissolved, 155.93 g of aluminum sulfate and 35.78 ml of concentrated sulfuric acid were added. Then, 1266.00 g of water glass was added dropwise. After stirring evenly, 8.5 g of industrial ZSM-5 molecular sieve was added to obtain a mixed system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O = 0.10:1:0.026:0.028:22. The resulting system was then transferred to a reaction vessel and heated to 170 °C for crystallization for 22 h. 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:deionized water:(NH4)2SO4 = 1:9.2:0.27. The mixture was heated to 68 °C and stirred at a constant temperature for 49 min. After filtration, washing, and drying, DZM-2 was obtained.

[0104] Weigh 100g of DZM-2; then, based on the mass of P2O5, weigh diammonium hydrogen phosphate at 6.8% of the mass of DZM-2, and dissolve the diammonium hydrogen phosphate in 96g of deionized water to prepare solution A; after the diammonium hydrogen phosphate is completely dissolved, mix solution A with DZM-2, and after mixing evenly, place it in an oven at 115℃ for 14h to dry. After drying, place it in a muffle furnace at 550℃ for 2.0h to obtain DZM-P-2; then, based on the mass of MnO, weigh manganese sulfate at 0.1% of the mass of DZM-2, and dissolve the manganese sulfate in 108g of deionized water to prepare solution B; after the manganese sulfate is completely dissolved, mix solution B with DZM-P-2, and after mixing evenly, place it in an oven at 116℃ for 16h to dry. After drying, place it in a muffle furnace at 545℃ for 2.3h to obtain DZ-2.

[0105] Comparative Example 3

[0106] 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 and further modification with P and Mn.

[0107] 11.74 g of sodium borate was dissolved in 1023.05 g of deionized water. After the sodium borate was fully dissolved, 670.68 g of water glass and 8.5 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 53 °C and stirred for 1 h for pretreatment. Then, 133.38 g of silica gel was added and stirred for 42 min. Finally, 155.93 g of aluminum sulfate was slowly added and stirred for 1.3 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O=0. The ratio of 10:1:0.026:0.028:22 was then transferred to a reactor, heated to 140℃ for 2 hours of crystallization, and then further heated to 170℃ for 22 hours of crystallization. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed in a weight ratio of molecular sieve dry basis: deionized water: (NH4)2SO4 = 1:9.2:0.27, heated to 68℃, stirred at a constant temperature for 49 minutes, and then filtered, washed, and dried to obtain DZM-3.

[0108] Weigh 100g of DZM-3; then, based on the mass of P2O5, weigh diammonium hydrogen phosphate at 6.8% of the mass of DZM-3, and dissolve the diammonium hydrogen phosphate in 96g of deionized water to prepare solution A; after the diammonium hydrogen phosphate is completely dissolved, mix solution A with DZM-3, and after mixing evenly, place it in an oven at 115℃ for 14h to dry. After drying, place it in a muffle furnace at 550℃ for 2.0h to obtain DZM-P-3; then, based on the mass of MnO, weigh manganese sulfate at 0.1% of the mass of DZM-3, and dissolve the manganese sulfate in 108g of deionized water to prepare solution B; after the manganese sulfate is completely dissolved, mix solution B with DZM-P-3, and after mixing evenly, place it in an oven at 116℃ for 16h to dry. After drying, place it in a muffle furnace at 545℃ for 2.3h to obtain DZ-3.

[0109] Comparative Example 4

[0110] The comparative example uses the same B-Al-ZSM-5 molecular sieve with the same silicon-to-aluminum ratio as Example 3. The difference is that only the first silicon source—water glass—is added, and the second silicon source—silica gel—is not added. Then, it is modified with P and Mn.

[0111] 11.74 g of sodium borate was dissolved in 601.92 g of deionized water. After the sodium borate was fully dissolved, 1266.0 g of water glass, 35.78 ml of concentrated sulfuric acid, and 8.5 g of industrial ZSM-5 molecular sieve were added with stirring. The mixture was heated to 53 °C and stirred for 1 h for pretreatment. Then, 155.93 g of aluminum sulfate and 20.75 g of diammonium hydrogen phosphate were slowly added, and the mixture was stirred for 1.3 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3:H2O=0. The ratio of 10:1:0.026:0.028:22 was then transferred to a reactor, heated to 140℃ for 2 hours of crystallization, and then further heated to 170℃ for 22 hours of crystallization. After crystallization, the crystallization product was filtered and washed. The prepared molecular sieve was then mixed in a weight ratio of molecular sieve dry basis: deionized water: (NH4)2SO4 = 1:9.2:0.27, heated to 68℃, stirred at a constant temperature for 49 minutes, and then filtered, washed, and dried to obtain DZM-4.

[0112] Weigh 100g of DZM-4; then, based on the mass of P2O5, weigh diammonium hydrogen phosphate at 6.8% of the mass of DZM-4, and dissolve the diammonium hydrogen phosphate in 96g of deionized water to prepare solution A; after the diammonium hydrogen phosphate is completely dissolved, mix solution A with DZM-4, and after mixing evenly, place it in an oven at 115℃ for 14h to dry. After drying, place it in a muffle furnace at 550℃ for 2.0h to obtain DZM-P-4; then, based on the mass of MnO, weigh manganese sulfate at 0.1% of the mass of DZM-4, and dissolve the manganese sulfate in 108g of deionized water to prepare solution B; after the manganese sulfate is completely dissolved, mix solution B with DZM-P-4, and after mixing evenly, place it in an oven at 116℃ for 16h to dry. After drying, place it in a muffle furnace at 545℃ for 2.3h to obtain DZ-4.

[0113] Comparative Example 5

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

[0115] 11.74 g of sodium borate was dissolved in 1497.48 g of deionized water. After the sodium borate was fully dissolved, 8.5 g of industrial ZSM-5 molecular sieve was added with stirring. The mixture was heated to 53 °C and pretreated with stirring for 1 h. Then, 283.64 g of silica gel and 59.33 g of sodium hydroxide were added. After stirring for 42 min, 155.93 g of aluminum sulfate and 20.75 g of diammonium hydrogen phosphate were slowly added. The mixture was then stirred for 1.3 h to homogenize the system. The molar ratio of each substance in the system was Na2O:SiO2:Al2O3:B2O3: H2O = 0.10:1:0.026:0.028:22; the resulting system was then transferred to a reactor, heated to 140℃ for 2 hours of crystallization, and then further heated to 170℃ for 22 hours of 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: deionized water: (NH4)2SO4 = 1:9.2:0.27, heated to 68℃, stirred at a constant temperature for 49 minutes, and then filtered, washed and dried to obtain DZM-5.

[0116] Weigh 100g of DZM-5; then, based on the mass of P2O5, weigh diammonium hydrogen phosphate at 6.8% of the mass of DZM-5, and dissolve the diammonium hydrogen phosphate in 96g of deionized water to prepare solution A; after the diammonium hydrogen phosphate is completely dissolved, mix solution A with DZM-5, and after mixing evenly, place it in an oven at 115℃ for 14h to dry. After drying, place it in a muffle furnace at 550℃ for 2.0h to obtain DZM-P-5; then, based on the mass of MnO, weigh manganese sulfate at 0.1% of the mass of DZM-5, and dissolve the manganese sulfate in 108g of deionized water to prepare solution B; after the manganese sulfate is completely dissolved, mix solution B with DZM-P-5, and after mixing evenly, place it in an oven at 116℃ for 16h to dry. After drying, place it in a muffle furnace at 545℃ for 2.3h to obtain DZ-5.

[0117] Comparative Example 6

[0118] 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 pretreatment step and without P and Mn modification.

[0119] 11.74 g of sodium borate was dissolved in 1023.05 g of deionized water. After the sodium borate was fully dissolved, 670.68 g of water glass and 8.5 g of industrial ZSM-5 molecular sieve were added with stirring, followed by 133.38 g of silica gel. After stirring for 42 min, 155.93 g of aluminum sulfate and 20.75 g of diammonium hydrogen phosphate were slowly added. The mixture was then stirred for 1.3 h to homogenize the system. The molar ratio of the substances in the system was Na2O:SiO2:Al2O3:B2O3:H2O = 0.10. The ratio of molecular sieve dry basis to deionized water to (NH4)2SO4 was 1:9.2:0.27. The mixture was heated to 170℃ and crystallized for 2 hours, then further heated to 170℃ and crystallized for 22 hours. After crystallization, the crystallized product was filtered and washed. The prepared molecular sieve was then mixed with deionized water at a weight ratio of 1:9.2:0.27. The mixture was heated to 68℃ and stirred at a constant temperature for 49 minutes. After filtration, washing and drying, DZM-6 was obtained.

[0120] Weigh 100g of DZM-6; then, based on the mass of P2O5, weigh diammonium hydrogen phosphate at 6.8% of the mass of DZM-6, and dissolve the diammonium hydrogen phosphate in 96g of deionized water to prepare solution A; after the diammonium hydrogen phosphate is completely dissolved, mix solution A with DZM-6, and after mixing evenly, place it in an oven at 115℃ for 14h to dry. After drying, place it in a muffle furnace at 550℃ for 2.0h to obtain DZM-P-6; then, based on the mass of MnO, weigh manganese sulfate at 0.1% of the mass of DZM-P-6, and dissolve the manganese sulfate in 108g of deionized water to prepare solution B; after the manganese sulfate is completely dissolved, mix solution B with DZM-P-6, and after mixing evenly, place it in an oven at 116℃ for 16h to dry. After drying, place it in a muffle furnace at 545℃ for 2.3h to obtain DZ-6.

[0121] The analysis and evaluation results of the above embodiments and comparative examples are as follows.

[0122] Figure 1 XRD patterns of molecular sieves ZBP-3 and DZ-2 prepared in Example 3 and Comparative Example 2 are shown. Figure 1 As can be seen, the ZBP-3 prepared in the embodiments of the present invention has a higher diffraction peak intensity compared with DZ-2. Calculations show that the crystallinity of ZBP-3 and DZ-2 is 83% and 62%, respectively, indicating that the method of the present invention is more advantageous for obtaining phosphorus and manganese modified B-Al-ZSM-5 molecular sieves with higher crystallinity under template-free conditions.

[0123] Figure 2 XRD patterns of molecular sieves ZBP-3 and DZ-2 prepared in Example 3 and Comparative Example 2 after hydrothermal aging at 800℃ for 2 hours are presented. Figure 2 As can be seen, the ZBP-3 prepared in the embodiments of the present invention exhibits higher diffraction peak intensity after hydrothermal aging compared to DZ-2. Calculations show that the crystallinity of ZBP-3 and DZ-2 after hydrothermal aging is 76% and 48%, respectively. The molecular sieves in the embodiments have a lower crystallinity decay rate, indicating that the phosphorus and manganese modified B-Al-ZSM-5 molecular sieves in the embodiments of the present invention have higher hydrothermal stability.

[0124] Table 2 shows the crystallinity of the phosphorus and manganese modified molecular sieves in each example and comparative example, the crystallinity after hydrothermal aging at 800℃ for 2 hours, and the crystallinity decay rate.

[0125] Table 2

[0126]

[0127]

[0128] The results of measuring the bulk silicon-to-aluminum ratio (using XRF) and surface silicon-to-aluminum ratio (using EDS) of the phosphorus and manganese modified molecular sieves prepared in the above examples and comparative examples, as well as the boron-to-aluminum ratio of the modified molecular sieves, are shown in Table 3.

[0129] Table 3

[0130]

[0131] As shown in Table 3, the silicon-to-aluminum ratio (S / A ratio) of the molecular sieves prepared in Comparative Examples 1-6 was 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 EDS and the S / A ratio measured by XRF for the composite modified ZSM-5 molecular sieves in each embodiment of this invention are all less than 1, indicating that the crystals of the composite modified ZSM-5 molecular sieves in each embodiment of this invention exhibit uniform aluminum distribution.

[0132] The pyridine-infrared (Py-IR) acid content of the phosphorus and manganese modified molecular sieves prepared in the above examples and comparative examples was determined, and the results are shown in Table 4.

[0133] Table 4

[0134]

[0135]

[0136] Table 4 presents the pyridine-infrared acid content data of the phosphorus and manganese modified 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 composite modified ZSM-5 molecular sieves of each embodiment of the present invention have a lower strong acid content.

[0137] The reaction performance evaluation results of the catalysts prepared by the phosphorus and manganese modified molecular sieves provided in the above examples and comparative examples are shown in Table 5.

[0138] Table 5

[0139]

[0140] As can be seen from the fixed-bed evaluation results in Table 5, when used in catalytic cracking reactions, the catalyst containing the composite modified ZSM-5 molecular sieve prepared in the embodiments of the present invention has significantly improved the liquefied gas yield and propylene yield compared with the catalyst containing the phosphorus and manganese modified molecular sieve prepared in the comparative example, showing excellent high propylene production performance and significantly improved propylene selectivity.

[0141] 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 composite modified ZSM-5 molecular sieve, comprising: Phosphorus oxides, manganese oxides, and B-Al-ZSM-5 molecular sieve; based on the total weight of the B-Al-ZSM-5 molecular sieve as 100%, the content of phosphorus oxides in the composite modified ZSM-5 molecular sieve, calculated as phosphorus pentoxide, is 2%-8%, and the content of manganese oxide in the composite modified ZSM-5 molecular sieve is 0.1%-2%. The absolute value of the difference between the silicon-aluminum ratio of the bulk phase of the composite modified ZSM-5 molecular sieve measured by XRF and the silicon-aluminum ratio of the crystal surface measured by EDS is ≤1.

2. The composite modified ZSM-5 molecular sieve according to claim 1, wherein, The composite modified 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 composite modified ZSM-5 molecular sieve according to claim 1, wherein, The boron-aluminum ratio of the composite modified ZSM-5 molecular sieve is 0.2-0.

6.

4. The composite modified ZSM-5 molecular sieve according to claim 1, wherein, The crystallinity of the composite modified ZSM-5 molecular sieve is 80-90%.

5. The composite modified ZSM-5 molecular sieve according to claim 1, wherein, The total acid content of the composite modified ZSM-5 molecular sieve, measured by pyridine-infrared desorption at 150℃, was 80-170 μmol / g, and the strong acid content, measured by pyridine-infrared desorption at 350℃, was 15-40 μmol / g.

6. The composite modified ZSM-5 molecular sieve according to claim 4, wherein, The crystallinity of the composite modified ZSM-5 molecular sieve decreased by 6-13% after hydrothermal aging at 800℃ for 2 hours.

7. A method for preparing the composite modified ZSM-5 molecular sieve according to any one of claims 1-6, comprising the following steps: S1: The B-Al-ZSM-5 molecular sieve is impregnated with a phosphorus-containing compound and then calcined to obtain a P-modified molecular sieve. S2: The P-modified molecular sieve is impregnated with a manganese-containing compound and then calcined to obtain the composite modified ZSM-5 molecular sieve.

8. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 7, wherein, The preparation steps of B-Al-ZSM-5 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.

9. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

10. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, wherein, In step (1) of the preparation of the B-Al-ZSM-5 molecular sieve, the first silicon source includes water glass.

11. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

12. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

13. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

14. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

15. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

16. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

17. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

18. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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).

19. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 8, 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.

20. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 7, wherein, In step S1, the phosphorus-containing compound includes one or a combination of several of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

21. The method for preparing the composite modified ZSM-5 molecular sieve according to claim 7, wherein, In step S2, the manganese-containing compound includes one or a combination of manganese nitrate, manganese chloride, manganese acetate, and manganese sulfate.

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