Metal-containing zsm-5 molecular sieve, method for preparing the same, and use thereof

Abstract

The present disclosure relates to a metal-containing ZSM-5 molecular sieve and a preparation method and application thereof, the method comprising: S1, mixing a silicon source, an aluminum source, an alkali source, seeds and water to obtain a first mixture; S2, mixing an active metal source, a peroxide, water and the first mixture and then performing a hydrothermal reaction; wherein the peroxide is selected from one or more of sodium persulfate, hydrogen peroxide and Fenton reagent; and the metal in the active metal source is one or more of nickel, copper, zinc, manganese, lanthanum and cerium. The method of the present disclosure uses a peroxide to synthesize a molecular sieve without using a template containing amine nitrogen, thereby avoiding amine nitrogen wastewater discharge, achieving clean production of the metal-containing ZSM-5 molecular sieve, and enabling preparation of a ZSM-5 molecular sieve having an active metal component distributed in the molecular sieve channel, which, when used in a diesel catalytic cracking reaction, has a relatively optimal yield of low-carbon olefins.

Description

Technical Field

[0001] This application relates to a metal-containing ZSM-5 molecular sieve, its preparation method, and its application. Background Technology

[0002] Catalytic cracking refers to the process of converting hydrocarbons into low-carbon olefins such as ethylene, propylene, and butene under the action of a catalyst, while simultaneously producing light aromatics. The heavy oil catalytic cracking process for producing low-carbon olefins has long held a significant market share due to its advantages of strong feedstock adaptability and lower production costs. Since the mid-1980s, the Research Institute of Petroleum Processing (RIPP) of China Petroleum & Chemical Corporation (Sinopec) has been continuously researching this technology. In 1994, RIPP developed a catalytic cracking (DCC) process for producing low-carbon olefins from heavy oil (vacuum distillate, coking wax oil, and residue oil, etc.). After the successful industrialization of DCC technology, RIPP further developed a catalytic thermal cracking (CPP) process for directly producing ethylene and propylene from heavy oil, offering multiple production options including maximum ethylene production, maximum propylene production, and the simultaneous production of ethylene and propylene. Compared to steam cracking, the CPP process broadens the sources of ethylene feedstock, reduces ethylene feedstock costs, and, due to its lower reaction temperature compared to steam cracking, significantly reduces energy consumption. Light oil catalytic cracking mainly refers to the process of producing ethylene and propylene from light gasoline or naphtha in the presence of a catalyst. This process enables the conversion of petroleum resources into basic chemical feedstocks and will play an important role in future chemical refineries.

[0003] ZSM-5 molecular sieve is a silica-alumina type MFI molecular sieve with a specific three-dimensional ten-membered ring channel structure and suitable acid properties, exhibiting good propylene selectivity. It also possesses excellent hydrothermal stability and a suppressive effect on coke precursors, making it one of the most promising active components for catalytic cracking catalysts. The acid properties of molecular sieves include acid type, acid quantity, acid strength, and acid center distribution. Elemental modification is a simple and effective method to modulate the acidity of molecular sieves. Studies have shown that modifying ZSM-5 molecular sieves with alkaline earth metals such as Mg, Ca, Ba, and Sr promotes the conversion of some strong acid sites into weak acid sites. When n-butane is used as a reactant, the introduction of Ba yielded the highest ethylene and propylene yields, while the aromatic yield decreased significantly, possibly due to the inhibition of hydrogen transfer reactions. However, in high-temperature reactions, metal particles often aggregate or become deactivated due to metal leaching.

[0004] Existing technologies include methods for encapsulating metals within all-silica or high-silica MFI molecular sieves, but research on encapsulating metals within silica-alumina MFI molecular sieves remains relatively limited. This is because directly introducing metals into the synthesis system can lead to difficulties in synthesis or low activity due to the tendency of metals to form hydroxide precipitates in alkaline environments and their susceptibility to phosphorus interactions. Furthermore, while nickel, as a dehydrogenation component, possesses some dehydrogenation activity, its application is significantly limited because it is also a poison in catalytic cracking. Summary of the Invention

[0005] The purpose of this disclosure is to provide a metal-containing ZSM-5 molecular sieve, its preparation method, and its application. This method does not use amine nitrogen organic compounds or amine nitrogen ligands, has no amine nitrogen wastewater discharge, is clean and pollution-free, and the prepared molecular sieve has a uniform distribution of active metals. When used in the catalytic cracking reaction of diesel, it has a better yield of low-carbon olefins.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a method for preparing metal-containing ZSM-5 molecular sieves, the method comprising:

[0007] S1. Mix the silicon source, aluminum source, alkali source, seed crystal and water to obtain the first mixture;

[0008] S2. The active metal source, peroxide, water and the first mixture are mixed and then subjected to a hydrothermal reaction.

[0009] The peroxide is selected from one or more of sodium persulfate, hydrogen peroxide, and Fenton's reagent; the metal in the active metal source is one or more of nickel, copper, zinc, manganese, lanthanum, and cerium.

[0010] Optionally, step S2 includes:

[0011] SS1. The active metal source, peroxide, and water are mixed to obtain a second mixture; the molar ratio of the active metal source, peroxide, and water, based on the metal oxide, is 1:(0.2-3.5):(300-1400), preferably 1:(0.3-2.7):(500-1200).

[0012] SS2. The first mixture and the second mixture are mixed and then subjected to the hydrothermal reaction; the molar ratio of the first mixture (calculated as Al2O3) to the second mixture (calculated as the metal oxide) is 1:(0.1-2.0), preferably 1:(0.3-1.5).

[0013] Optionally, in step S1, the molar ratio of the silicon source (calculated as SiO2), the aluminum source (calculated as Al2O3), the alkali source (calculated as alkali metal oxide), and the water is (30-100):1:(2-15):(300-1500), preferably (35-70):1:(2-10):(350-1000).

[0014] Based on SiO2, the amount of the seed crystal is 1-15% by weight, preferably 8-10% by weight, relative to the total weight of the silicon source.

[0015] Optionally, in step S2, the conditions for the hydrothermal reaction include: a temperature of 150-220℃ and a time of 8-32h.

[0016] Optionally, the method further includes: subjecting the solid product obtained by hydrothermal treatment to ammonium exchange and calcination; the calcination conditions include: a temperature of 400-800℃, a time of 0.5-8h, and an atmosphere of air or water vapor.

[0017] Optionally, the silicon source includes one or more of silica gel, silicon dioxide, silica fume, and silicates;

[0018] The aluminum source includes one or more of sodium aluminate, SB powder, aluminum alkoxide, aluminum oxide, aluminum hydroxide, and aluminum sulfate;

[0019] The alkaline source includes sodium hydroxide and / or potassium hydroxide;

[0020] The seed crystals include one or more ZSM-5 molecular sieves with a silicon-to-aluminum ratio of 20-50, and the average particle size of the ZSM-5 molecular sieve is 0.5-2 μm.

[0021] The active metal source includes one or more of nickel nitrate, nickel sulfate, nickel hydroxide, copper nitrate, copper sulfate, zinc nitrate, zinc sulfate, manganese nitrate, manganese sulfate, lanthanum nitrate, lanthanum sulfate, cerium nitrate, and cerium sulfate.

[0022] The second aspect of this disclosure provides a metal-containing ZSM-5 molecular sieve prepared by the method provided in the first aspect of this disclosure.

[0023] Optionally, the metal-containing ZSM-5 molecular sieve has a structure in which an active metal component is internally encapsulated within the ZSM-5 molecular sieve; the active metal component is distributed within the pores of the ZSM-5 molecular sieve.

[0024] Optionally, the specific surface area of ​​the metal-containing ZSM-5 molecular sieve is 200-550 m². 2 / g, total pore volume is 0.150-0.22cm³ 3 ·g -1The micropore volume is 0.130-0.180 cm³. 3 ·g -1 The mesopore volume is 0.010-0.100 cm³. 3 ·g -1 The relative crystallinity is 80-100%;

[0025] In the metal-containing ZSM-5 molecular sieve, the molar ratio of SiO2 to Al2O3 is 20-100;

[0026] The content of the active metal component, calculated as metal oxide, is 1-3% by weight relative to the total weight of the metal-containing ZSM-5 molecular sieve.

[0027] The third aspect of this disclosure provides an application of the metal-containing ZSM-5 molecular sieve provided in the second aspect of this disclosure in diesel catalytic cracking reactions.

[0028] Optionally, the conditions for the catalytic cracking reaction include: a temperature of 530-720°C and a reaction mass hourly space velocity of 20-40 h⁻¹. -1 The reaction pressure is 0.8-1.2 MPa, and the agent-to-oil weight ratio is 1-2.

[0029] Through the above technical solution, the method disclosed herein does not use amine nitrogen organic compounds or amine nitrogen ligands, has no amine nitrogen wastewater discharge, is clean and pollution-free, and the molecular sieve prepared has a uniform distribution of active metals. When used in the catalytic cracking reaction of diesel, it has a better yield of low-carbon olefins.

[0030] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0031] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0032] Figure 1 This is the X-ray diffraction pattern of the copper-containing ZSM-5 molecular sieve A prepared in Example 1 of this disclosure.

[0033] Figure 2 This is a scanning electron microscope image of the copper-containing ZSM-5 molecular sieve A prepared in Example 1 of this disclosure.

[0034] Figure 3 This is a transmission electron microscope (TEM) image of the copper-containing ZSM-5 molecular sieve A prepared in Example 1 of this disclosure.

[0035] Figure 4 This is a mapping image of the copper-containing ZSM-5 molecular sieve A prepared in Example 1 of this disclosure.

[0036] Figure 5 This is the X-ray diffraction pattern of the lanthanum-containing ZSM-5 molecular sieve B prepared in Example 2 of this disclosure.

[0037] Figure 6 This is a scanning electron microscope image of the lanthanum-containing ZSM-5 molecular sieve B prepared in Example 2 of this disclosure.

[0038] Figure 7 This is a mapping image of the lanthanum-containing ZSM-5 molecular sieve B prepared in Example 2 of this disclosure.

[0039] Figure 8 This is the X-ray diffraction pattern of the nickel-containing ZSM-5 molecular sieve F prepared in Example 6 of this disclosure.

[0040] Figure 9 This is a scanning electron microscope image of the nickel-containing ZSM-5 molecular sieve F prepared in Example 6 of this disclosure.

[0041] Figure 10 This is a transmission electron microscope (TEM) image of the nickel-containing ZSM-5 molecular sieve F prepared in Example 6 of this disclosure.

[0042] Figure 11 This is a mapping image of the nickel-containing ZSM-5 molecular sieve F prepared in Example 6 of this disclosure.

[0043] Figure 12 This is the X-ray diffraction pattern of the nickel-containing ZSM-5 molecular sieve G prepared in Example 7 of this disclosure.

[0044] Figure 13 This is a transmission electron microscope (TEM) image of the nickel-containing ZSM-5 molecular sieve G prepared in Example 7 of this disclosure.

[0045] Figure 14 This is a mapping image of the nickel-containing ZSM-5 molecular sieve G prepared in Example 7 of this disclosure.

[0046] Figure 15 This is the X-ray diffraction pattern of the nickel-containing ZSM-5 molecular sieve H prepared in Example 8 of this disclosure. Detailed Implementation

[0047] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0048] The first aspect of this disclosure provides a method for preparing metal-containing ZSM-5 molecular sieves, the method comprising: S1, mixing a silicon source, an aluminum source, an alkali source, seed crystals and water to obtain a first mixture; S2, mixing an active metal source, a peroxide, water and the first mixture and then carrying out a hydrothermal reaction; wherein the peroxide is selected from one or more of sodium persulfate, hydrogen peroxide and Fenton's reagent; and the metal in the active metal source is one or more of nickel, copper, zinc, manganese, lanthanum and cerium.

[0049] The method disclosed herein uses peroxides to synthesize molecular sieves without using template agents containing amine nitrogen, thus avoiding the discharge of amine nitrogen wastewater and achieving clean production of metal-containing ZSM-5 molecular sieves.

[0050] In a preferred embodiment of this disclosure, the peroxide is sodium persulfate or hydrogen peroxide, more preferably sodium persulfate. The aforementioned peroxide can simultaneously interact with both the metal and the molecular sieve precursor, promoting molecular sieve nucleation around the metal and encapsulating the metal within the molecular sieve.

[0051] In one specific embodiment of this disclosure, step S2 includes: SS1, mixing the active metal source, peroxide, and water to obtain a second mixture; the molar ratio of the active metal source, peroxide, and water, based on the metal oxide, is 1:(0.2-3.5):(200-1400), preferably 1:(0.3-2.7):(250-1200), more preferably 1:(0.35-0.8):(500-1000); SS2, mixing the first mixture and the second mixture and then performing the hydrothermal reaction; the molar ratio of the first mixture, based on Al2O3, to the second mixture, based on the metal oxide, is 1:(0.1-2.0), preferably 1:(0.15-1.5). Within the above range of proportions, the second mixture can be free of free metal ions, avoiding the presence of aggregated active metal components in the prepared molecular sieve, thereby further improving its catalytic performance.

[0052] In one specific embodiment of this disclosure, in step S1, the molar ratio of the silicon source (calculated as SiO2), the aluminum source (calculated as Al2O3), the alkali source (calculated as alkali metal oxide), and the water is (30-100):1:(2-15):(300-1500), preferably (35-70):1:(2-10):(350-1000), more preferably (40-60):1:(4-6):(350-1000); the amount of the seed crystal (calculated as SiO2) relative to the total weight of the silicon source is 1-15% by weight, preferably 8-10% by weight.

[0053] According to this disclosure, hydrothermal treatment is well known to those skilled in the art and can be carried out in equipment familiar to those skilled in the art, such as a closed, heat-resistant, and pressure-resistant reactor. In one specific embodiment of this disclosure, in step S2, the conditions for the hydrothermal reaction include: a temperature of 150-220°C and a time of 8-32 hours; preferably, a temperature of 150-180°C and a time of 8-20 hours. This disclosure does not impose specific limitations on the pressure of the hydrothermal reaction; for example, it can be carried out under the autogenous pressure of the reaction system or under an applied pressure, preferably under the autogenous pressure of the reaction system.

[0054] In one specific embodiment of this disclosure, the method further includes: subjecting the solid product obtained from the hydrothermal treatment to ammonium exchange and calcination; the calcination conditions include: a temperature of 400-800°C, a time of 0.5-8 hours, and an atmosphere of air or water vapor; preferably, the temperature is 500-600°C, and the time is 2-4 hours. Calcination is well known to those skilled in the art and can be performed, for example, in a muffle furnace, a tube furnace, etc. In a preferred embodiment, the solid product is washed until neutral before ammonium exchange; the washing liquid can be any type of liquid that does not react with the solid product, such as deionized water. In another preferred embodiment, the solid obtained from ammonium exchange is dried before calcination; the drying conditions may include: a temperature of 100-150°C, and a time of 5-20 hours.

[0055] In one specific embodiment of this disclosure, the solid product obtained from hydrothermal treatment can be removed by methods such as centrifugation and precipitation.

[0056] According to this disclosure, the silicon source, aluminum source, and alkali source are well known to those skilled in the art. In one specific embodiment of this disclosure, the silicon source includes one or more of silica gel, silicon dioxide, silica fume, and silicates; the aluminum source includes one or more of sodium aluminate, SB powder, aluminum alkoxide, aluminum oxide, aluminum hydroxide, and aluminum sulfate; and the alkali source includes sodium hydroxide and / or potassium hydroxide.

[0057] According to this disclosure, the active metal source can be a water-soluble metal salt, preferably a nitrate metal salt and / or a sulfate metal salt of an active metal. In a preferred embodiment, the active metal source includes one or more of nickel nitrate, nickel sulfate, nickel hydroxide, copper nitrate, copper sulfate, zinc nitrate, zinc sulfate, manganese nitrate, manganese sulfate, lanthanum nitrate, lanthanum sulfate, cerium nitrate, and cerium sulfate.

[0058] In one specific embodiment of this disclosure, the seed crystals include one or more ZSM-5 molecular sieves with a silicon-to-aluminum ratio of 20-50, such as, but not limited to, ZPR molecular sieves and ZSP molecular sieves; the average particle size of the ZSM-5 molecular sieve is 0.5-2 μm, preferably 1-2 μm. In this disclosure, the average particle size of the ZSM-5 molecular sieve refers to the average particle size estimated by performing SEM analysis on the molecular sieve and measuring the particle size of 50 randomly selected particles from its SEM image, using a HITACHI S-4800 SEM instrument.

[0059] The second aspect of this disclosure provides a metal-containing ZSM-5 molecular sieve prepared by the method provided in the first aspect of this disclosure.

[0060] In one specific embodiment of this disclosure, the metal-containing ZSM-5 molecular sieve has a structure in which an active metal component is internally encapsulated within the ZSM-5 molecular sieve; the active metal component is distributed within the pores of the ZSM-5 molecular sieve.

[0061] After aging, the metal active components of the molecular sieve disclosed herein are more evenly distributed inside the sieve, which is more conducive to the selective dehydrogenation of alkanes into olefins within the sieve channels, rather than dehydrogenation on the outer surface of the sieve, i.e., confined dehydrogenation. The introduction of metal elements can modulate the acid properties of the ZSM-5 molecular sieve, improve its catalytic function for cracking and dehydrogenation, and introduce the metal active components into the interior of the molecular sieve in an encapsulated manner, further reducing the severity of the diesel catalytic cracking reaction and improving the conversion rate of saturated hydrocarbons and the selectivity of low-carbon olefins.

[0062] In one specific embodiment of this disclosure, the specific surface area of ​​the metal-containing ZSM-5 molecular sieve is 200-500 m². 2 / g, preferably 300-400m 2 / g, total pore volume is 0.150-0.22cm³ 3 ·g -1 The preferred size is 0.160-0.22cm. 3 ·g -1 The micropore volume is 0.130-0.180 cm³. 3 ·g -1 The preferred size is 0.140-0.180cm. 3 ·g -1 The mesopore volume is 0.010-0.100 cm³. 3 ·g -1 The preferred value is 0.010-0.080cm. 3 ·g -1 The relative crystallinity is 80-100%, preferably 85-95%;

[0063] In the metal-containing ZSM-5 molecular sieve, the molar ratio of SiO2 to Al2O3 is 20-100; the content of the active metal component, calculated as metal oxide, is 1-3% by weight relative to the total weight of the metal-containing ZSM-5 molecular sieve. The molar ratio of SiO2 to Al2O3 can be obtained by X-ray fluorescence spectroscopy. The relative crystallinity is determined using a Siemens D5005 X-ray diffractometer, based on the ZSM-5 molecular sieve standard sample from the Research Institute of Petroleum Processing (i.e., the relative crystallinity of the ZSM-5 molecular sieve standard sample from the Research Institute of Petroleum Processing, China Petroleum & Chemical Corporation is 100%). The specific surface area and pore volume parameters can be determined using a specific surface area analyzer according to the N2 adsorption principle and the BET calculation method (see Petrochemical Analytical Methods (RIPP Test Methods), RIPP 151-90, Science Press, 1990). The content of the iron active component, calculated as Fe2O3, is obtained by X-ray fluorescence spectroscopy.

[0064] The third aspect of this disclosure provides an application of the metal-containing ZSM-5 molecular sieve provided in the second aspect of this disclosure in diesel catalytic cracking reactions.

[0065] In one specific embodiment of this disclosure, the conditions for the catalytic cracking reaction include: a temperature of 530-720°C and a reaction mass hourly space velocity of 20-40 h⁻¹. -1 The reaction pressure is 0.8-1.2 MPa, and the agent-to-oil weight ratio is 1-2; preferably, the temperature is 580-660℃, and the reaction mass hourly space velocity is 20-40 h⁻¹. -1 The reaction pressure is 0.8-1.2 MPa, and the agent-to-oil weight ratio is 1.2-1.9.

[0066] The present disclosure will be further illustrated by the following examples, but the present disclosure is not limited thereto.

[0067] The silicon-aluminum molar ratio is the molar ratio of SiO2 to Al2O3, which is detected by X-ray fluorescence spectroscopy. The instrument is a Rigaku Electric Co., Ltd. 3013 X-ray fluorescence spectrometer. The test conditions are: tungsten target, excitation voltage 40kV, and excitation current 50mA.

[0068] Relative crystallinity: Based on the ZSM-5 molecular sieve standard sample from the Research Institute of Petroleum Processing (i.e., the relative crystallinity of the ZSM-5 molecular sieve standard sample from the Research Institute of Petroleum Processing of China Petroleum & Chemical Corporation is 100%), the crystallinity was measured using a Siemens D5005 X-ray diffractometer.

[0069] Specific surface area: determined using a specific surface area analyzer based on the N2 adsorption principle and the BET calculation method (see Petrochemical Analysis Methods (RIPP Test Methods), RIPP151-90, Science Press, 1990).

[0070] Method for testing pore volume: The sample is evacuated to a vacuum of 1.33 × 10⁻⁶ at 350°C. -2 The pressure was maintained at a constant temperature and pressure for 15 hours. Tests were conducted at liquid nitrogen temperature -196℃ to measure the adsorption and desorption of N2 by the sample under different relative pressures (p / p0). Desorption branching data were calculated using the BJH (Barrett-Joyner-Halenda) method to obtain the pore size distribution data of the sample.

[0071] The transmission electron microscope was a JEM-2100 (200kV) transmission electron microscope manufactured by Nippon Electron Ltd.; the test conditions were: accelerating voltage of 200kV, sample preparation, and observation of the crystal morphology and size of the molecular sieve samples at magnifications of 5000-30000.

[0072] STEM-Mapping test method and instrument: JEM-2100 (200kV) transmission electron microscope, NEC Corporation. The accelerating voltage of the electron microscope was 200kV. The sample was dispersed in anhydrous ethanol and then dropped onto a sample grid with a diameter of 3mm for observation and testing.

[0073] Test method for the content of active metal components in terms of metal oxides: Semi-quantitative analysis of metal elements is performed by measuring the intensity of characteristic spectral lines of each element by XRF.

[0074] Example 1

[0075] This embodiment uses the following steps to prepare copper-containing ZSM-5 molecular sieve A:

[0076] (1) Add 0.99g sodium hydroxide, 40.8g deionized water, 20g silica gel, 6.78g low-alkali sodium aluminate (Na2O: 153.5g / L, Al2O3: 102.5g / L) and 1.97g ZSM-5 seed crystals in sequence under stirring, and stir thoroughly to obtain the first mixture;

[0077] The molar ratio of silicon source (SiO2), aluminum source (Al2O3), alkali source (alkali metal oxide), and water is 55:1:4.68:589; the amount of ZSM-5 seed crystals is 10% by weight relative to the total weight of silicon source (SiO2); the silicon-aluminum ratio of ZSM-5 seed crystals is 27, and the average particle size is 1-2 μm.

[0078] (2) Dissolve 0.36g of copper nitrate trihydrate in 10g of deionized water, add 0.14g of sodium persulfate, and stir thoroughly until clear and transparent to obtain the second mixture;

[0079] The molar ratio of the metal source (calculated as CuO), sodium persulfate, and water added in step (2) is 1:0.31:293, and the molar ratio of the aluminum source (calculated as Al2O3) to the metal source (calculated as CuO) is 1:0.285.

[0080] (3) Add the second mixture to the first mixture, mix thoroughly and evenly, then transfer to a stainless steel autoclave and perform hydrothermal treatment at 170°C for 12 hours;

[0081] (4) The product obtained from the hydrothermal treatment in step (3) was filtered, washed until pH = 7-8, and then subjected to ammonium exchange. It was dried at 120℃ for 12h and then calcined at 550℃ for 2h in air to obtain copper-containing ZSM-5 molecular sieve, denoted as A. Its structural parameters are listed in Table 1, its X-ray diffraction pattern is shown in Figure 1, and its scanning electron microscope image is shown in Figure 2. Figure 2 Transmission electron microscope images can be found Figure 3 See the mapping photos. Figure 3 .

[0082] Example 2

[0083] Copper-containing ZSM-5 molecular sieve B was prepared using the same method as in Example 1, except that in step (2), 0.72 g of copper nitrate trihydrate was dissolved in 10 g of deionized water, and 0.14 g of sodium persulfate was added. The mixture was stirred thoroughly until it became clear and transparent, resulting in a second mixture. The molar ratio of the metal source (calculated as CuO), sodium persulfate, and water added in step (2) was 1:0.16:293, and the molar ratio of the aluminum source (calculated as Al2O3) to the metal source (calculated as CuO) was 1:0.570. The copper-containing ZSM-5 molecular sieve, denoted as B, was prepared, and its structural parameters are listed in Table 1.

[0084] Example 3

[0085] Lanthanum-containing ZSM-5 molecular sieve C was prepared using the same method as in Example 1, except that in step (2), 0.31 g of lanthanum chloride was dissolved in 10 g of deionized water, and 0.14 g of sodium persulfate was added. The mixture was stirred thoroughly until it became clear and transparent, resulting in a second mixture. The molar ratio of the metal source (based on La2O3), sodium persulfate, and water added in step (2) was 1:0.46:434, and the molar ratio of the aluminum source (based on Al2O3) to the metal source (based on La2O3) was 1:0.19. The resulting lanthanum-containing ZSM-5 molecular sieve, denoted as C, has structural parameters listed in Table 1.

[0086] Example 4

[0087] Lanthanum-containing ZSM-5 molecular sieve D was prepared using the same method as in Example 1, except that in step (2), 0.62 g of lanthanum chloride was dissolved in 10 g of deionized water, and 0.14 g of sodium persulfate was added. The mixture was stirred thoroughly until clear and transparent to obtain a second mixture. The molar ratio of the metal source (based on La2O3), sodium persulfate, and water added in step (2) was 1:0.23:434, and the molar ratio of the aluminum source (based on Al2O3) to the metal source (based on La2O3) was 1:0.38. The resulting lanthanum-containing ZSM-5 molecular sieve, denoted as D, has structural parameters listed in Table 1.

[0088] Example 5

[0089] The manganese-containing ZSM-5 molecular sieve E was prepared using the same method as in Example 1, except that in step (2), 0.31 g of lanthanum chloride was dissolved in 10 g of deionized water, and 0.28 g of sodium persulfate was added. The mixture was stirred thoroughly until it became clear and transparent, resulting in a second mixture. The molar ratio of the metal source (based on La2O3), sodium persulfate, and water added in step (2) was 1:0.91:428, and the molar ratio of the aluminum source (based on Al2O3) to the metal source (based on La2O3) was 1:0.195. The lanthanum-containing ZSM-5 molecular sieve, denoted as E, was obtained, and its structural parameters are listed in Table 1.

[0090] Example 6

[0091] Nickel-containing ZSM-5 molecular sieve F was prepared using the same method as in Example 1, except that in step (2), 0.2 g of nickel sulfate was dissolved in 10 g of deionized water, and 0.14 g of sodium persulfate was added. The mixture was stirred thoroughly until it became clear and transparent, resulting in a second mixture. The molar ratio of nickel source (based on NiO), sodium persulfate, and water added in step (2) was 1:0.78:731, and the molar ratio of aluminum source (based on Al2O3) to nickel source (based on NiO) was 1:0.114. The resulting nickel-containing ZSM-5 molecular sieve, denoted as F, has the structural parameters listed in Table 1. Its X-ray diffraction pattern is shown in Figure 8, and its scanning electron microscope image is shown in Figure 9. Figure 9 Transmission electron microscope images can be found Figure 10 See the mapping photos. Figure 11 .

[0092] Example 7

[0093] Nickel-containing ZSM-5 molecular sieve G was prepared using the same method as in Example 1, except that in step (2), 0.5 g of nickel sulfate was dissolved in 10 g of deionized water, and 0.14 g of sodium persulfate was added. The mixture was stirred thoroughly until it became clear and transparent, resulting in a second mixture. The molar ratio of nickel source (based on NiO), sodium persulfate, and water added in step (2) was 1:0.31:293, and the molar ratio of aluminum source (based on Al2O3) to nickel source (based on NiO) was 1:0.285. The resulting nickel-containing ZSM-5 molecular sieve, denoted as G, has the structural parameters listed in Table 1. Its X-ray diffraction pattern is shown in Table 12, and its transmission electron microscope image is shown in Table 13. Figure 13 See the mapping photos. Figure 14 .

[0094] Example 8

[0095] Nickel-containing ZSM-5 molecular sieve H was prepared using the same method as in Example 1, except that in step (2), 0.8 g of nickel sulfate was dissolved in 10 g of deionized water, and 0.14 g of sodium persulfate was added. The mixture was stirred thoroughly until it became clear and transparent, resulting in a second mixture. The molar ratio of nickel source (based on NiO), sodium persulfate, and water added in step (2) was 1:0.2:185, and the molar ratio of aluminum source (based on Al2O3) to nickel source (based on NiO) was 1:0.45. The encapsulated nickel ZSM-5 molecular sieve, denoted as H, was obtained. Its structural parameters are listed in Table 1, and its X-ray diffraction pattern is shown in [Table 1]. Figure 15 .

[0096] Example 9

[0097] Nickel-containing ZSM-5 molecular sieve I was prepared using the same method as in Example 1, except that in step (1), 0.45 g of sodium hydroxide, 38.2 g of deionized water, 20 g of silica gel, 10.08 g of low-alkali sodium aluminate (Na2O: 153.5 g / L, Al2O3: 102.5 g / L), and 1.97 g of ZSM-5 seed crystals were added sequentially under stirring and stirred thoroughly to obtain the first mixture; wherein, the molar ratio of silicon source (based on SiO2), aluminum source (based on Al2O3), alkali source (based on alkali metal oxide), and water was 37:1:3.15:396; the amount of ZSM-5 seed crystals was 10% by weight relative to the total weight of silicon source; the silicon-aluminum ratio of ZSM-5 seed crystals was 27, and the average particle size was 1-2 μm;

[0098] In step (2), 0.8 g of nickel sulfate was dissolved in 10 g of deionized water, and 0.14 g of sodium persulfate was added. The mixture was stirred thoroughly until it became clear and transparent, resulting in a second mixture. The molar ratio of nickel source (calculated as NiO), sodium persulfate, and water added in step (2) was 1:0.2:185, and the molar ratio of aluminum source (calculated as Al2O3) to nickel source (calculated as NiO) was 1:0.45. Encapsulated nickel ZSM-5 molecular sieve was obtained, denoted as I, and its structural parameters are listed in Table 1.

[0099] Example 10

[0100] Copper-containing ZSM-5 molecular sieve J was prepared using the same method as in Example 1, except that in step (1), 2.92g of sodium hydroxide, 71.3g of deionized water, 20g of silica gel, 4.64g of low-alkali sodium aluminate (Na2O: 153.5g / L, Al2O3: 102.5g / L), and 1.28g of ZSM-5 seed crystals were added sequentially under stirring and stirred thoroughly to obtain the first mixture;

[0101] The molar ratio of silicon source (SiO2), aluminum source (Al2O3), alkali source (alkali metal oxide), and water was 80:1:12:1280. The amount of ZSM-5 seed crystals was 10% by weight relative to the total weight of the silicon source (SiO2). The silicon-to-aluminum ratio of the ZSM-5 seed crystals was 27, and the average particle size was 1-2 μm. Encapsulated copper ZSM-5 molecular sieve, denoted as J, was obtained, and its structural parameters are listed in Table 1.

[0102] Comparative Example 1

[0103] This comparative example illustrates the differences between the metal-free parent ZSM-5 molecular sieve.

[0104] (1) Add 0.99g sodium hydroxide, 50.8g deionized water, 20g silica gel, 6.78g low-alkali sodium aluminate (Na2O: 153.5g / L, Al2O3: 102.5g / L) and 1.97g ZSM-5 seed crystals in sequence under stirring, and stir thoroughly to obtain the first mixture; after thorough mixing, transfer to a stainless steel kettle and hydrothermally treat at 170℃ for 12h;

[0105] The molar ratio of silicon source (SiO2), aluminum source (Al2O3), alkali source (alkali metal oxide), and water is 55:1:4.68:589; the amount of ZSM-5 seed crystals is 10% by weight relative to the total weight of silicon source (SiO2); the silicon-aluminum ratio of ZSM-5 seed crystals is 27, and the average particle size is 1-2 μm.

[0106] (2) The product obtained by hydrothermal treatment in step (1) was filtered, washed until pH=7-8, and then ammonium exchanged. It was dried at 120℃ for 12h and then calcined at 550℃ for 2h in air atmosphere to obtain the parent ZSM-5 molecular sieve, denoted as D1. The structural parameters are listed in Table 1.

[0107] Comparative Example 2

[0108] Nickel-containing ZSM-5 molecular sieve D2 was prepared using the same method as in Example 6, except that sodium persulfate was not added. Its structural parameters are listed in Table 1.

[0109] Test case

[0110] The metal-containing ZSM-5 molecular sieves prepared in the examples and comparative examples were subjected to aging treatment. The specific aging treatment method is as follows: the aging furnace was a self-made hydrothermal aging device from the Institute of Petroleum Research, and the state after aging at 800℃ for 17 hours was used to simulate the balancing agent during industrial operation.

[0111] The ZSM-5 molecular sieves prepared in the examples and comparative examples were used as catalysts in the catalytic cracking reaction of diesel fuel. The specific method is as follows: the reaction was carried out in a fixed-bed reactor, the feedstock was diesel fuel, the carrier gas was nitrogen at a flow rate of 30 mL / min, the reaction temperature was 600 °C, the regeneration temperature was 600 °C, the reaction pressure was 0.1 MPa, and the weight hourly space velocity was 20 hr. -1 The molecular sieve tablets were sieved into 20-40 mesh particles, with a loading of 2.0 g and an oil-to-reactive agent ratio of 1.28. The reaction time was 70 s, followed by purging for 900 s. Samples were then taken for analysis, and material balance calculations were performed. The product distribution is shown in Table 1.

[0112] The micro-reaction conversion rate X of the raw material and the yield S of the product are calculated using the following formulas. i :

[0113]

[0114]

[0115]

[0116]

[0117] Table 1

[0118]

[0119]

[0120]

[0121] As shown in Table 1, the metal-containing ZSM-5 molecular sieve prepared by the method of introducing free radical initiators in this disclosure has a relatively high crystallinity of 80-93%. Transmission electron microscopy (TEM) images of the metal-containing ZSM-5 molecular sieves prepared in Examples 1 and 6 show that the grain size of the metal-containing ZSM-5 molecular sieves prepared by the method of this disclosure is 1-2 μm. STEM-Mapping images of the metal-containing ZSM-5 molecular sieves prepared in Examples 1 and 6 show that the active metal components such as Ni, Cu, and La are uniformly distributed in the metal-containing ZSM-5 molecular sieves prepared by the method of this disclosure.

[0122] Furthermore, according to the data in Table 1, when the metal-containing ZSM-5 molecular sieve prepared by the method of this disclosure is used in the catalytic cracking reaction of diesel, it can obtain a higher micro-reaction conversion rate and a better low-carbon olefin yield compared with the metal-free parent molecular sieve. Preferably, when the molar ratio of active metal source, peroxide and water (calculated as metal oxide) is 1:(0.3-2.7):(250-1200), a higher micro-reaction conversion rate and propylene yield can be obtained. Preferably, when the molar ratio of silicon source (calculated as SiO2), aluminum source (calculated as Al2O3), alkali source (calculated as alkali metal oxide) and water is (35-70):1:(2-10):(350-1000).

[0123] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0124] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0125] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing metal-containing ZSM-5 molecular sieves, the method comprising: S1. A silicon source, an aluminum source, an alkali source, a seed crystal, and water are mixed to obtain a first mixture; wherein the molar ratio of the silicon source (based on SiO2), the aluminum source (based on Al2O3), the alkali source (based on alkali metal oxide), and the water is (30-100):1:(2-15):(300-1500); and the amount of the seed crystal relative to the total weight of the silicon source is 1-15% by weight (based on SiO2). S2. Mix the active metal source, peroxide, and water to obtain a second mixture; the molar ratio of the active metal source, peroxide, and water, based on the metal oxide, is 1:(0.2-3.5):(200-1400). The first mixture and the second mixture are mixed and subjected to a hydrothermal reaction. The solid product obtained from the hydrothermal reaction is subjected to ammonium exchange and calcination. The calcination conditions include: a temperature of 400-800℃, a time of 0.5-8h, and an atmosphere of air or water vapor. The molar ratio of the first mixture (calculated as Al2O3) to the second mixture (calculated as the metal oxide) is 1:(0.1-2.0). The peroxide is selected from one or more of sodium persulfate, hydrogen peroxide, and Fenton's reagent; the metal in the active metal source is one or more of nickel, copper, zinc, manganese, lanthanum, and cerium.

2. The method according to claim 1, wherein, Step S2 includes: SS1. The active metal source, peroxide, and water are mixed to obtain a second mixture; the molar ratio of the active metal source, peroxide, and water, based on the metal oxide, is 1:(0.3-2.7):(250-1200). SS2. The first mixture and the second mixture are mixed and then subjected to the hydrothermal reaction; the molar ratio of the first mixture (calculated as Al2O3) to the second mixture (calculated as the metal oxide) is 1:(0.15-1.5).

3. The method according to claim 1, wherein, In step S1, the molar ratio of the silicon source (calculated as SiO2), the aluminum source (calculated as Al2O3), the alkali source (calculated as alkali metal oxide), and the water is (35-70):1:(2-10):(350-1000). Based on SiO2, the amount of seed crystals used is 8-10% by weight relative to the total weight of the silicon source.

4. The method according to claim 1, wherein, In step S2, the conditions for the hydrothermal reaction include: a temperature of 150-220℃ and a time of 8-32h.

5. The method according to claim 1, wherein, The silicon source includes silicon dioxide and / or silicates; The aluminum source includes one or more of sodium aluminate, SB powder, aluminum alkoxide, aluminum oxide, aluminum hydroxide, and aluminum sulfate; The alkaline source includes sodium hydroxide and / or potassium hydroxide; The seed crystals include one or more ZSM-5 molecular sieves with a silicon-to-aluminum ratio of 20-50, and the average particle size of the ZSM-5 molecular sieve is 0.5-2 μm. The active metal source includes one or more of nickel nitrate, nickel sulfate, nickel hydroxide, copper nitrate, copper sulfate, zinc nitrate, zinc sulfate, manganese nitrate, manganese sulfate, lanthanum nitrate, lanthanum sulfate, cerium nitrate, and cerium sulfate.

6. The method according to claim 1, wherein, The silicon source includes silica gel and / or silica.

7. The metal-containing ZSM-5 molecular sieve prepared by the method according to any one of claims 1-6.

8. The metal-containing ZSM-5 molecular sieve according to claim 7, wherein, The metal-containing ZSM-5 molecular sieve has a structure in which an active metal component is internally encapsulated within the ZSM-5 molecular sieve; the active metal component is distributed within the pores of the ZSM-5 molecular sieve.

9. The metal-containing ZSM-5 molecular sieve according to claim 7, wherein, The specific surface area of ​​the metal-containing ZSM-5 molecular sieve is 200-500 m². 2 / g, total pore volume is 0.150-0.22cm³ 3 ·g -1 The micropore volume is 0.130-0.180 cm³. 3 ·g -1 The mesopore volume is 0.010-0.100 cm³. 3 ·g -1 The relative crystallinity is 80-100%; In the metal-containing ZSM-5 molecular sieve, the molar ratio of SiO2 to Al2O3 is 20-100; The content of active metal components, calculated as metal oxides, is 1-3% by weight relative to the total weight of the metal-containing ZSM-5 molecular sieve.

10. The application of the metal-containing ZSM-5 molecular sieve according to any one of claims 7-9 in the catalytic cracking reaction of diesel fuel.

11. The application according to claim 10, wherein, The conditions for the catalytic cracking reaction include: a temperature of 530-720℃ and a reaction mass hourly space velocity of 20-40 h⁻¹. -1 The reaction pressure is 0.8-1.2 MPa, and the agent-to-oil weight ratio is 1-2.

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