Metal-modified zsm-5@asa micro-mesoporous composite catalyst and preparation and application thereof

Abstract

The present application relates to the technical field of petroleum chemical industry, in particular to a metal modified ZSM-5@ASA micro-mesoporous composite catalyst and its preparation and application. The metal modified ZSM-5@ASA micro-mesoporous composite catalyst provided by the present application has the micropore of ZSM-5 molecular sieve and the mesopore of amorphous silicon aluminum (ASA). The ZSM-5 molecular sieve core provides excellent shape selectivity and strong B acid sites, the ASA shell provides abundant mesopores and L acid sites, has better accessibility and anti-coking ability, and the metal modification further adjusts the acidity of the catalyst, so that the composite catalyst has suitable acid density, excellent diffusion performance and pore structure. The metal modified ZSM-5@ASA micro-mesoporous composite catalyst has higher selectivity and yield for the catalytic cracking reaction of hydrocarbons, and has potential application value in the field of petroleum chemical industry.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, specifically to a metal-modified ZSM-5@ASA microporous composite catalyst and its preparation and application. Background Technology

[0002] Olefins are among the most important chemicals and feedstocks in the petrochemical industry. Low-carbon olefins, such as ethylene, propylene, and butene, are the main petrochemical feedstocks for the production of various polymers and other value-added chemicals, and can be produced through the thermal and catalytic cracking of hydrocarbons. Compared with steam cracking technology, catalytic cracking has significant advantages such as lower reaction temperature, lower carbon dioxide emissions, and the ability to modify product distribution by adjusting catalyst properties, allowing for flexible adjustments to production plans based on market demand.

[0003] Microporous molecular sieves have been widely used in catalytic cracking as effective solid acid catalysts. Microporous ZSM-5 molecular sieves exhibit good catalytic cracking ability, high selectivity for low-carbon olefins, and low hydrogen transfer reaction activity and dehydrogenation condensation ability. However, the product molecules after the reaction are difficult to diffuse and escape rapidly, leading to secondary cracking and increased coking. Mesoporous catalysts, such as amorphous aluminosilicate (ASA), are composite materials formed from Al2O3 and SiO2. They possess large pore size, pore volume, and a certain acidity, enabling pre-cracking of feedstocks and improving the accessibility of reactive sites on the catalyst. This facilitates both reactant diffusion and adsorption at active sites and rapid product desorption and diffusion to the main reaction body, reducing the probability of secondary reactions and coking formation. However, their acidity is weak, resulting in poor cracking performance. Combining microporous ZSM-5 molecular sieves with amorphous aluminosilicate catalysts can overcome the shortcomings of both microporous zeolites and mesoporous catalysts, allowing them to complement each other's advantages.

[0004] To improve the selectivity and yield of low-carbon olefins, catalyst modification is necessary. Common modification methods include alkali metal and alkaline earth metal ion modification, transition metal ion or oxide modification, rare earth ion or oxide modification, and phosphorus modification. Metal modification can adjust the number of acidic sites and the ratio of acid types (B / L ratio) on the catalyst, thereby affecting the cracking pathway of hydrocarbons on the catalyst and improving the selectivity and yield of low-carbon olefins. Summary of the Invention

[0005] Therefore, the purpose of this invention is to provide a metal-modified ZSM-5@ASA microporous composite catalyst, its preparation, and its application. The catalyst provided by this invention exhibits high selectivity and high yield for low-carbon olefins when used to catalyze hydrocarbons.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a metal-modified ZSM-5@ASA microporous composite catalyst, comprising a metal oxide, a ZSM-5@ASA microporous composite material, and a metal oxide supported on the ZSM-5@ASA microporous composite material;

[0008] The ZSM-5@ASA micro-mesoporous composite material comprises ZSM-5 molecular sieve and amorphous silica-alumina mesoporous material coated on the surface of the ZSM-5 molecular sieve, wherein the mass content of ZSM-5 molecular sieve in the ZSM-5@ASA micro-mesoporous composite material is 20-85%.

[0009] The mass of the metal element in the metal oxide is 0.1-5% of the mass of the metal-modified ZSM-5@ASA microporous composite catalyst; the metal element includes at least one of magnesium, calcium, iron, copper, zinc, zirconium, lanthanum, cerium and yttrium.

[0010] Preferably, the specific surface area of ​​the metal-modified ZSM-5@ASA microporous composite catalyst is 300~480 m². 2 / g, pore volume 0.2~2.0cm³ 3 / g.

[0011] Preferably, the molar ratio of SiO2 / Al2O3 in the ZSM-5 molecular sieve is 25~150; the ZSM-5 molecular sieve includes H-type ZSM-5 molecular sieve, Na-type ZSM-5 molecular sieve and NH4-type ZSM-5 molecular sieve;

[0012] The specific surface area of ​​the ZSM-5@ASA microporous composite material is 320~500 m². 2 / g, pore volume 0.3~2.1cm³ 3 / g.

[0013] This invention also provides a method for preparing the metal-modified ZSM-5@ASA microporous composite catalyst described above, comprising the following steps:

[0014] The silicon source, ZSM-5 molecular sieve, aluminum source, lower alcohol and water were first mixed, and the pH value was adjusted to 7-10 to obtain ZSM-5@ASA precursor emulsion.

[0015] The ZSM-5@ASA precursor emulsion was aged and then calcined to obtain the ZSM-5@ASA microporous composite material.

[0016] The ZSM-5@ASA microporous composite material, metal salt, and water are mixed in a second process, followed by concentration, drying, and a second calcination to obtain a metal-modified ZSM-5@ASA microporous composite catalyst. The metal element in the metal salt includes at least one of magnesium, calcium, iron, copper, zinc, zirconium, lanthanum, cerium, and yttrium. The mass of the metal element in the metal salt is 0.1-5% of the mass of the metal-modified ZSM-5@ASA microporous composite catalyst.

[0017] Preferably, the silicon source includes at least one of sodium silicate, silica sol, fumed silica, and tetraethyl orthosilicate;

[0018] The aluminum source includes at least one of aluminum sulfate, aluminum nitrate, aluminum acetylacetone, boehmite, and aluminum hydroxide.

[0019] The molar ratio of the aluminum source to the silicon source is 1:0.01~16;

[0020] The mass ratio of SiO2 to ZSM-5 molecular sieve in the silicon source is 1:0.1~10;

[0021] The pH adjuster used to adjust the pH value includes acids and / or bases, wherein the acid includes at least one of acetic acid, hydrochloric acid, nitric acid and formic acid, and the base includes at least one of ammonia, NaOH, KOH and tetrapropylammonium hydroxide.

[0022] Preferably, the first mixture comprises:

[0023] The silicon source was dissolved in a lower alcohol, and the pH was adjusted to 3-5 to obtain gel A.

[0024] Gel A was mixed with ZSM-5 molecular sieve to obtain gel B;

[0025] An aluminum source was dissolved in water, and the pH was adjusted to 7-10 to obtain gel C.

[0026] Mix the gel B, gel C and lower alcohol.

[0027] Preferably, the aging temperature is 30~80℃ and the time is 6~24h;

[0028] The first roasting temperature is 450~650℃ and the time is 6~8h.

[0029] Preferably, the second calcination temperature is 400~600℃ and the time is 4~10h.

[0030] This invention also provides the application of the metal-modified ZSM-5@ASA microporous composite catalyst described in the above technical solution or the metal-modified ZSM-5@ASA microporous composite catalyst prepared by the preparation method described in the above technical solution in the field of catalytic cracking.

[0031] Preferably, the application includes at least one of the following: catalytic cracking of naphtha components, olefins, chain alkanes, and cycloalkanes.

[0032] The metal-modified ZSM-5@ASA microporous composite catalyst provided by this invention has a core-shell structure, possessing both the micropores of ZSM-5 molecular sieve and the mesoporous channels of amorphous aluminosilicate (ASA). The ZSM-5 molecular sieve core provides excellent shape selectivity and strong Brønsted acid sites, while the ASA shell provides abundant mesopores (2~20 nm) and Lewis acid sites, exhibiting superior accessibility and anti-coking ability. Metal modification further adjusts the catalyst's acidity, resulting in a composite catalyst with suitable acid density, excellent diffusion performance, and a suitable pore structure. The outer (ASA) mesopores, with larger pore size and weaker acidity, activate reactants, weakening the bond energies of CH and C-C bonds. The activated reactants then enter the inner microporous material (ZSM-5 molecular sieve) with smaller pore size and stronger acidity, where they undergo further cleavage at the acidic sites of the ZSM-5 molecular sieve. The metal-modified ZSM-5@ASA microporous composite catalyst of this invention exhibits higher selectivity and yield for low-carbon olefins (such as ethylene and propylene) obtained from the catalytic cracking reaction of hydrocarbons, and has potential application value in the petrochemical field.

[0033] The catalyst of this invention has a simpler synthesis procedure. First, ZSM-5 molecular sieve is prepared, then ASA is coated onto the ZSM-5 core using the sol-gel method, and finally, metal is loaded using the wet impregnation method. This allows for precise control of the silica-alumina ratio, acidity, and pore size of the ZSM-5 core and ASA shell in the composite catalyst, which is more conducive to improving the selectivity and yield of its catalytic cracking of naphtha to produce low-carbon olefins.

[0034] The method for preparing the metal-modified ZSM-5@ASA microporous composite catalyst provided by this invention involves coating ASA onto the surface of ZSM-5 molecular sieve using a sol-gel method, followed by loading metal using a post-modification method (wet impregnation). This method has minimal impact on the specific surface area and pore structure of the ZSM-5@ASA microporous composite material. Furthermore, it allows for precise control over the silica-alumina ratio, acidity, and pore size of the ZSM-5 molecular sieve (core) and ASA mesoporous material (shell) in the metal-modified ZSM-5@ASA microporous composite catalyst, which is more conducive to improving the selectivity and yield of its catalytic cracking of naphtha to produce low-carbon olefins. Moreover, the preparation method provided by this invention is simple, easy to operate, uses widely available raw materials, has low production costs, and is suitable for industrial production. Attached Figure Description

[0035] Figure 1 The XRD pattern of Fe / ZSM-5@ASA prepared in Example 3;

[0036] Figure 2 The pore size distribution diagram of Fe / ZSM-5@ASA prepared in Example 3;

[0037] Figure 3 SEM image of Fe / ZSM-5@ASA prepared in Example 3;

[0038] Figure 4 TEM image of Fe / ZSM-5@ASA prepared in Example 3;

[0039] Figure 5 The stability results of the catalytic cracking of n-heptane by ZSM-5@ASA prepared in Example 2 and La / ZSM-5@ASA prepared in Example 5 are shown in the figure. Detailed Implementation

[0040] This invention provides a metal-modified ZSM-5@ASA microporous composite catalyst, comprising a metal oxide, a ZSM-5@ASA microporous composite material, and a metal oxide supported on the ZSM-5@ASA microporous composite material;

[0041] The ZSM-5@ASA microporous composite material comprises ZSM-5 molecular sieve and amorphous aluminum silicate (ASA) mesoporous material coated on the surface of the ZSM-5 molecular sieve, wherein the mass content of ZSM-5 molecular sieve in the ZSM-5@ASA microporous composite material is 20-85%.

[0042] The mass of the metal element in the metal oxide is 0.1-5% of the mass of the metal-modified ZSM-5@ASA microporous composite catalyst; the metal element includes at least one of magnesium, calcium, iron, copper, zinc, zirconium, lanthanum, cerium and yttrium.

[0043] In this invention, the ZSM-5@ASA microporous composite material has a core-shell structure, comprising a ZSM-5 molecular sieve and an ASA mesoporous material coating the surface of the ZSM-5 molecular sieve. In this invention, the mass content of the ZSM-5 molecular sieve in the ZSM-5@ASA microporous composite material is 20-85%, and can also be 30-75%, or further 40-60%, specifically 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%. In this invention, the mass content of the amorphous silica-alumina mesoporous material in the ZSM-5@ASA microporous composite material is 15-80%, and can also be 25-70%, or further 40-60%, specifically 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%.

[0044] In this invention, the specific surface area of ​​the ZSM-5@ASA microporous composite material can be 320~500 m². 2 / g, and can also be 380~450m 2 / g, which can be further increased to 400~410m 2 / g; the pore volume of the ZSM-5@ASA microporous composite material can be 0.3~2.1cm³. 3 / g, and can also be 0.5~1.5cm 3 / g, which can be further reduced to 0.8~1cm 3 / g; the pore size of the ZSM-5@ASA micro-mesoporous composite material can be 4~30nm, or 10~20nm, or even 12.2~12.3nm.

[0045] The ZSM-5@ASA microporous composite catalyst used in this invention has moderate acidity and possesses both the micropores of ZSM-5 molecular sieve and the mesoporous channels of ASA catalyst. The mesoporous channel structure of ASA can effectively improve the accessibility of active sites and enhance the catalyst diffusion performance.

[0046] In this invention, the molar ratio of SiO2 / Al2O3 in the ZSM-5 molecular sieve can be 25~150, or 50~100, specifically 25, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150. In this invention, the ZSM-5 molecular sieve includes at least one of H-type ZSM-5 molecular sieve, Na-type ZSM-5 molecular sieve, and NH4-type ZSM-5 molecular sieve.

[0047] In this invention, the metal element in the metal oxide includes at least one selected from magnesium, calcium, iron, copper, zinc, zirconium, lanthanum, cerium, and yttrium. In this invention, the mass of the metal element in the metal oxide is 0.1% to 5% of the mass of the metal-modified ZSM-5@ASA microporous composite catalyst, specifically 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0048] In this invention, the specific surface area of ​​the metal-modified ZSM-5@ASA microporous composite catalyst can be 300~480 m². 2 / g, and can also be 350~450m 2 / g, which can be further increased to 390~400m 2 / g; the pore volume of the metal-modified ZSM-5@ASA microporous composite catalyst can be 0.2~2.0 cm³. 3 / g, and can also be 0.5~1.5cm 3 / g, which can be further reduced to 0.7~0.8cm 3 / g; the pore size of the metal-modified ZSM-5@ASA micro-mesoporous composite catalyst can be 4~30nm, or 10~20nm, or even 12~12.2nm.

[0049] This invention also provides a method for preparing the metal-modified ZSM-5@ASA microporous composite catalyst described above, comprising the following steps:

[0050] The silicon source, ZSM-5 molecular sieve, aluminum source, lower alcohol and water were first mixed, and the pH value was adjusted to 7-10 to obtain ZSM-5@ASA precursor emulsion.

[0051] The ZSM-5@ASA precursor emulsion was aged and then calcined to obtain the ZSM-5@ASA microporous composite material.

[0052] The ZSM-5@ASA microporous composite material, metal salt, and water are mixed in a second process, followed by concentration, drying, and a second calcination to obtain a metal-modified ZSM-5@ASA microporous composite catalyst. The metal element in the metal salt includes at least one of magnesium, calcium, iron, copper, zinc, zirconium, lanthanum, cerium, and yttrium. The mass of the metal element in the metal salt is 0.1-5% of the mass of the metal-modified ZSM-5@ASA microporous composite catalyst.

[0053] Unless otherwise specified, the materials and equipment used in this invention are all commercially available products in the field.

[0054] In this invention, a silicon source, ZSM-5 molecular sieve, aluminum source, lower alcohol and water are first mixed, and the pH value is adjusted to 7~10 to obtain ZSM-5@ASA precursor emulsion.

[0055] In this invention, the silicon source may include at least one of sodium silicate, silica sol, fumed silica, and tetraethyl orthosilicate.

[0056] In this invention, the aluminum source includes at least one of aluminum sulfate, aluminum nitrate, aluminum acetylacetone, boehmite, and aluminum hydroxide.

[0057] In this invention, the molar ratio of the aluminum source to the silicon source can be 1:0.01~16, or 1:0.5~5, specifically 1:0.01, 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, or 1:16.

[0058] In this invention, the mass ratio of SiO2 to ZSM-5 molecular sieve in the silicon source is 1:0.1~10, and can also be 1:1~5, specifically 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:1.5, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 or 1:10.

[0059] In this invention, the lower alcohol may include at least one of ethanol, isopropanol, and n-propanol.

[0060] In this invention, the first mixing may include stirring or ultrasonic mixing. In this invention, the first mixing may include:

[0061] A silicon source is dissolved in a lower alcohol, and the pH is adjusted to 3-5 to obtain gel A. The solid-liquid ratio of the silicon source to the lower alcohol can be 1g:10-200mL, or 1g:20-50mL, specifically 1g:10mL, 1g:20mL, 1g:32mL, 1g:40mL, 1g:50mL, 1g:80mL, 1g:100mL, 1g:120mL, 1g:150mL, 1g:180mL, or 1g:200mL. The pH value can be 3, 3.5, 4, 4.5, or 5.

[0062] Gel A is mixed with ZSM-5 molecular sieve to obtain gel B; the mixing temperature can be 20~60℃, or 30~50℃, specifically 20℃, 30℃, 35℃, 40℃, 45℃, 50℃ or 60℃; the mixing time can be 30~120min, or 40~80min, specifically 30min, 40min, 50min, 60min, 70min or 80min.

[0063] An aluminum source is dissolved in water, and the pH value is adjusted to 7-10. Mixing continues to obtain gel C. The mass ratio of the aluminum source to water can be 1:1-20, or 1:1-3, specifically 1:1, 1:1.5, 1:1.85, 1:2, 1:3, 1:4, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, or 1:20. The mixing temperature can be 30-80℃, or 40-70℃, or even 50-60℃. The mixing time can be 5-60 minutes, specifically 15 minutes. The pH value can be 7, 7.5, 8, 8.5, 9, 9.5, or 10.

[0064] Mix the gel B, gel C, and lower alcohol; the solid-liquid ratio of the silicon source and the lower alcohol (the lower alcohol added in this step) can be 1g:20~100mL, or 1g:30~50mL, specifically 1g:20mL, 1g:30mL, 1g:40mL, 1g:50mL, 1g:60mL, 1g:70mL, 1g:80mL, 1g:90mL, or 1g:100mL; the mixing temperature can be 50~80℃, or 60~70℃; the mixing time can be 0.5~2h, or 1~1.5h.

[0065] In this invention, the pH adjuster used to adjust the pH value includes acids and / or bases. In this invention, the acid may include at least one of acetic acid, hydrochloric acid, nitric acid, and formic acid; the concentration of the acid may be 0.05~5 mol / L, or 1~4 mol / L, specifically 0.05 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, or 5 mol / L. In this invention, the alkali may include at least one of ammonia, NaOH, KOH, and tetrapropylammonium hydroxide (TPAOH); the mass concentration of the ammonia may be 15-35%, or 20-30%, specifically 15%, 20%, 25%, 28%, 30%, or 35%; the tetrapropylammonium hydroxide is used in the form of an aqueous solution, and the mass concentration of the aqueous solution may be 10-50%, or 10-40%, specifically 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%.

[0066] In this invention, the pH value is adjusted to 7-10 after the first mixing, and the pH value can specifically be 7, 7.5, 8, 8.5, 9, 9.5 or 10.

[0067] This invention does not impose any particular limitation on the preparation method of the ZSM-5 molecular sieve; any preparation method well known to those skilled in the art can be used. In this invention, the ZSM-5 molecular sieve can be a calcined ZSM-5 molecular sieve or an uncalcined ZSM-5 molecular sieve.

[0068] In this invention, the preparation method of the uncalcined ZSM-5 molecular sieve may include the following steps:

[0069] The alkali source, aluminum source, and template agent are dissolved in water to obtain a mixture;

[0070] The silicon source was mixed with the mixture and aged to obtain a silica-alumina gel.

[0071] The silica-alumina gel was subjected to hydrothermal crystallization to obtain uncalcined ZSM-5 molecular sieve.

[0072] This invention dissolves an alkali source, an aluminum source, and a template agent in water to obtain a mixture. In this invention, the alkali source may include hydroxides, specifically sodium hydroxide and / or potassium hydroxide. In this invention, the aluminum source may include at least one of aluminum sulfate octadecahydrate, aluminum nitrate nonahydrate, aluminum acetylacetonate, boehmite, and aluminum hydroxide. In this invention, the template agent may include at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrapropylammonium bromide. In this invention, the water may be at least one of deionized water, ultrapure water, and distilled water. In this invention, the dissolution can be carried out under stirring conditions. The stirring temperature can be 20-60°C, or 30-50°C, specifically 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C. The stirring time can be 0.5-3 hours, or 1-2.5 hours, or even 1.5-2 hours.

[0073] After obtaining the mixture, the present invention mixes the silicon source with the mixture and ages it to obtain a silica-alumina gel. In the present invention, the silicon source may include at least one of sodium silicate, silica sol, fumed silica, and tetraethyl orthosilicate. In the present invention, the aging temperature may be 20-50°C, or 25-40°C, or even 25-30°C; the aging time may be 0.5-6 hours, or 1-5 hours, or even 2-3 hours; the aging can be carried out under stirring conditions.

[0074] In this invention, the molar ratio of the effective components SiO2: alkali source: template agent: Al2O3: H2O in the silica-alumina gel can be 0.1~0.5:0.1~2:0.001~0.05:6~40, or 1:0.12~0.3:0.12~1:0.005~0.03:10~30, or even 1:0.15~0.2:0.15~0.5:0.01~0.02:15~20, or specifically 1:0.16:0.15:0.01:15.

[0075] After obtaining the silica-alumina gel, the present invention performs hydrothermal crystallization on the silica-alumina gel to obtain uncalcined ZSM-5 molecular sieve. In the present invention, the hydrothermal crystallization temperature can be 120~200℃, or 150~190℃, or even 160~180℃; the hydrothermal crystallization time can be 1~5 days, or 2~4 days, or even 2~3 days.

[0076] In this invention, the hydrothermal crystallization process may further include: cooling the reaction solution obtained from the hydrothermal crystallization to room temperature, performing solid-liquid separation, washing the resulting solid until pH < 9, and drying to obtain uncalcined ZSM-5 molecular sieve. This invention does not impose any particular limitation on the solid-liquid separation; any solid-liquid separation method well-known to those skilled in the art can be used, such as centrifugation, filtration, or vacuum filtration. In this invention, centrifugation and washing until pH < 9 may also involve centrifugation and washing until neutral. In this invention, the drying temperature may be 60~120℃, or 80~100℃; the drying time may be 4~48h, or 10~20h.

[0077] In this invention, the preparation method of the ZSM-5 molecular sieve may further include: calcining the uncalcined ZSM-5 molecular sieve (referred to as the third calcination) to obtain calcined ZSM-5 molecular sieve. In this invention, the temperature of the third calcination may be 400~800℃, or 500~700℃, or even 550~600℃; the time of the third calcination may be 4~10h, or 5~8h, or even 6~7h.

[0078] After obtaining the calcined ZSM-5 molecular sieve, the present invention may further include: mixing the calcined ZSM-5 molecular sieve with an ammonium salt solution, performing an ion exchange reaction, and then drying to obtain an NH4-type ZSM-5 molecular sieve. In the present invention, the ammonium salt in the ammonium salt solution may include at least one of ammonium nitrate, ammonium chloride, and ammonium sulfate; the concentration of the ammonium salt solution may be 0.5~4 mol / L, or 1~3 mol / L, or even 1~2 mol / L. In the present invention, the mass ratio of the calcined ZSM-5 molecular sieve to the ammonium salt solution may be 1:20~200, or 1:50~150, or even 1:80~100. In this invention, the ion exchange temperature can be 50-95℃, or 55-80℃, or even 60-70℃; the number of ion exchanges can be 2-4 times, or even 3 times; the time for a single ion exchange can be 2-10 hours, or even 5-7 hours, specifically 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours. In this invention, after the first ion exchange reaction, the reaction system obtained from the ion exchange reaction may further include solid-liquid separation, washing the obtained solid component with water, and then performing the next ion exchange reaction. This invention does not have a special limitation on the solid-liquid separation; any solid-liquid separation method well known to those skilled in the art can be used, such as centrifugation, filtration, or vacuum filtration. In this invention, the drying temperature can be 60-120℃, or even 80-100℃; the drying time can be 6-24 hours, or even 10-15 hours.

[0079] After obtaining the NH4-type ZSM-5 molecular sieve, the present invention may further include: calcining the NH4-type ZSM-5 molecular sieve (referred to as the fourth calcination) to obtain the H-type ZSM-5 molecular sieve. In the present invention, the temperature of the fourth calcination can be 400~800℃, or 500~700℃, or even 550~600℃; the time of the fourth calcination can be 4~10h, or 5~8h, or even 6~7h.

[0080] After obtaining the ZSM-5@ASA precursor emulsion, the present invention ages the ZSM-5@ASA precursor emulsion and then performs a first calcination to obtain the ZSM-5@ASA microporous composite material.

[0081] In this invention, the aging temperature can be 30~80℃, or 40~70℃, or even 50~60℃; the aging time can be 6~24h, or 10~24h, specifically 6h, 10h, 12h, 15h, 18h, 20h, 22h or 24h; the aging can be carried out under normal pressure and static conditions.

[0082] After the aging process is completed, the present invention may further include solid-liquid separation of the aging system obtained by aging, washing the resulting solid components, and then drying them. The present invention does not have a particular limitation on the solid-liquid separation; any solid-liquid separation method well known to those skilled in the art can be used, such as centrifugation, filtration, or vacuum filtration. In the present invention, the washing solvent may include at least one of water, ethanol, and acetone, and the water may be deionized water. In the present invention, the drying temperature may be 60~120℃, or 70~110℃, or further 80~100℃; the drying time may be 10~24h, or 12~15h, specifically 10h, 12h, 15h, 18h, 20h, 22h, or 24h.

[0083] In this invention, the temperature of the first roasting can be 450~650℃, or 500~600℃, specifically 450℃, 480℃, 500℃, 520℃, 550℃, 580℃ or 600℃; the roasting time of the first roasting can be 6~8h, or 6~7h, specifically 6h, 6.5h, 7h, 7.5h or 8h.

[0084] After obtaining the ZSM-5@ASA microporous composite material, the present invention further mixes the ZSM-5@ASA microporous composite material, metal salt and water, and then concentrates, dries and calcines them in sequence to obtain the metal-modified ZSM-5@ASA microporous composite catalyst.

[0085] In this invention, the metal in the metal salt includes at least one selected from magnesium, calcium, iron, copper, zinc, zirconium, lanthanum, cerium, and yttrium; the metal salt may include at least one selected from nitrates, chlorides, and sulfates. In this invention, the mass of the metal element in the metal salt is 0.1-5% of the mass of the metal-modified ZSM-5@ASA microporous composite catalyst, specifically 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%.

[0086] In this invention, the mass ratio of the ZSM-5@ASA microporous composite material to water can be 1:10~50, or 1:10~20, specifically 1:10, 1:20, 1:30, 1:40 or 1:50.

[0087] In this invention, the second mixing can be: a third mixing of ZSM-5@ASA microporous composite material and water to obtain a dispersion; and a fourth mixing of the dispersion with a metal salt. In this invention, the temperature of the fourth mixing can be 40~80℃, or 40~60℃, or even 40~50℃; the time of the fourth mixing can be 2~24h, or 5~15h, specifically 2h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h, or 24h.

[0088] In this invention, the concentration may include rotary evaporation; the concentration temperature may be 60~100℃, or 70~90℃, or even 80℃; this invention does not have any special limitation on the concentration, as long as the concentration is carried out until the liquid level no longer drops.

[0089] In this invention, the drying temperature can be 80~100℃ or 80~90℃; the drying time can be 6~48h or 10~20h, specifically 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 25h, 30h, 35h, 40h, 45h or 48h.

[0090] In this invention, the second calcination temperature can be 400~600℃, or 450~550℃, specifically 400℃, 420℃, 450℃, 480℃, 500℃, 520℃, 550℃, 580℃ or 600℃; the second calcination time can be 4~10h, or 5~8h, specifically 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0091] This invention also provides the application of the metal-modified ZSM-5@ASA microporous composite catalyst described in the above technical solution or the metal-modified ZSM-5@ASA microporous composite catalyst prepared by the preparation method described in the above technical solution in the field of catalytic cracking.

[0092] In this invention, the application includes the catalytic cracking of naphtha components, olefins, chain alkanes, and cycloalkanes. In this invention, the number of carbon atoms in the olefins can be 5 to 12, specifically 5, 6, 7, 8, 9, 10, 11, or 12; the olefins can specifically include at least one of pentene, hexene, and heptene. In this invention, the number of carbon atoms in the chain alkanes can be 5 to 12, specifically 5, 6, 7, 8, 9, 10, 11, or 12; the chain alkanes can specifically include at least one of pentane, hexane, and heptane. In this invention, the number of carbon atoms in the cycloalkanes can be 5 to 12, specifically 5, 6, 7, 8, 9, 10, 11, or 12; the cycloalkanes can specifically include at least one of cyclohexane and methylcyclohexane.

[0093] The metal-modified ZSM-5@ASA microporous composite catalyst provided by this invention has suitable acid density and pore structure. When used to catalyze the cracking of naphtha components, heptane, heptene and other substances, this catalyst exhibits better product selectivity and yield.

[0094] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, of the metal-modified ZSM-5@ASA microporous composite catalyst, its preparation method, and its application, should not be construed as limiting the scope of protection of the present invention.

[0095] Example 1

[0096] Preparation of H-type ZSM-5 molecular sieve

[0097] Step 1): Dissolve NaOH, Al2(SO4)3·18H2O and TPAOH in water at 30℃ to obtain a mixed solution;

[0098] Step 2): Add silica sol to the mixture and stir and age at 30°C for 3 hours to obtain silica-alumina gel; wherein, the molar ratio of SiO2:NaOH:TPAOH:Al2(SO4)3:H2O is 1:0.16:0.15:0.01:15;

[0099] Step 3): The silica-alumina gel was placed in a crystallization vessel with a polytetrafluoroethylene liner, crystallized in an oven at 180°C for 2 days, cooled naturally to room temperature, centrifuged, and the resulting solid was washed with deionized water until neutral. It was dried at 100°C for 12 hours and calcined at 550°C for 6 hours to obtain Na-type ZSM-5 molecular sieve.

[0100] Step 4): Mix Na-type ZSM-5 molecular sieve with a 1 mol / L ammonium chloride aqueous solution at a mass ratio of 1:100, and perform ion exchange at 500 r / min and 60℃ for 6 h. Filter the mixture, wash the resulting solid component with water, and then perform ion exchange again. Perform ion exchange three times in total. After that, dry at 80℃ for 12 h and calcine at 550℃ for 6 h to obtain H-type ZSM-5 molecular sieve.

[0101] Example 2

[0102] Preparation of ZSM-5@ASA microporous composite material (abbreviated as ZSM-5@ASA)

[0103] Step 1): Dissolve 3.75g of tetraethyl orthosilicate in 120mL of anhydrous ethanol at 30℃ with stirring, and adjust the pH to 3.5 with 0.2mol / L acetic acid solution to obtain gel A;

[0104] Step 2): Add 2.8g of the H-type ZSM-5 molecular sieve prepared in Example 1 to gel A, and stir at 30°C for 60 min to obtain gel B;

[0105] Step 3): Dissolve 13.5g of aluminum nitrate nonahydrate in 25g of water at 30℃ with stirring. Adjust the pH to 9 with 28wt% ammonia. Stir at 60℃ for 15min to obtain gel C.

[0106] Step 4): Add gel B to gel C, add 150 mL of anhydrous ethanol, stir at 60 °C for 2 h, adjust the pH to 9 with 28 wt% ammonia water to obtain ZSM-5@ASA precursor emulsion.

[0107] Step 5): The ZSM-5@ASA precursor emulsion was aged at 30°C and atmospheric pressure for 24 hours under static conditions. After centrifugation, the resulting solid components were washed with deionized water, dried at 100°C for 12 hours, and calcined at 550°C for 6 hours to obtain the ZSM-5@ASA microporous composite material.

[0108] Example 3

[0109] Preparation of Fe / ZSM-5@ASA microporous composite catalyst (abbreviated as Fe / ZSM-5@ASA)

[0110] The ZSM-5@ASA microporous composite material prepared in Example 2 was dispersed in water to obtain a dispersion. The dispersion was then stirred with ferric nitrate nonahydrate at 40°C for 10 hours to obtain a mixture. This mixture was then rotary evaporated at 80°C until the liquid level no longer decreased. The resulting solid was dried in a vacuum oven at 80°C for 12 hours, ground, and then transferred to a muffle furnace for calcination at 550°C for 6 hours to obtain the Fe / ZSM-5@ASA microporous composite catalyst. The mass ratio of ferric nitrate nonahydrate, ZSM-5@ASA microporous composite material, and water was 0.01:1:10.

[0111] Example 4

[0112] Preparation of Mg / ZSM-5@ASA micro-mesoporous composite catalyst (abbreviated as Mg / ZSM-5@ASA)

[0113] The only difference from Example 3 is that ferric nitrate nonahydrate is replaced with magnesium nitrate hexahydrate.

[0114] Example 5

[0115] Preparation of La / ZSM-5@ASA microporous composite catalyst (abbreviated as La / ZSM-5@ASA)

[0116] The only difference from Example 3 is that ferric nitrate nonahydrate is replaced with lanthanum nitrate hexahydrate.

[0117] Example 6

[0118] Preparation of Ca / ZSM-5@ASA microporous composite catalyst (abbreviated as Ca / ZSM-5@ASA)

[0119] The only difference from Example 3 is that ferric nitrate nonahydrate is replaced with calcium nitrate tetrahydrate.

[0120] Example 7

[0121] Preparation of Cu / ZSM-5@ASA microporous composite catalyst (abbreviated as Cu / ZSM-5@ASA)

[0122] The only difference from Example 3 is that ferric nitrate nonahydrate is replaced with copper nitrate trihydrate.

[0123] Example 8

[0124] Preparation of Zn / ZSM-5@ASA microporous composite catalyst (abbreviated as Zn / ZSM-5@ASA)

[0125] The only difference from Example 3 is that ferric nitrate nonahydrate is replaced with zinc nitrate hexahydrate.

[0126] Example 9

[0127] Preparation of Ce / ZSM-5@ASA microporous composite catalyst (abbreviated as Ce / ZSM-5@ASA)

[0128] The only difference from Example 3 is that ferric nitrate nonahydrate is replaced with cerium nitrate hexahydrate.

[0129] Test Example 1

[0130] The metal-modified ZSM-5@ASA microporous composite catalysts prepared in Examples 3-9 were analyzed by XRD, N2- adsorption-desorption, scanning electron microscopy, and transmission electron microscopy.

[0131] Figure 1 XRD of Fe / ZSM-5@ASA Figure 1 As can be seen, Fe / ZSM-5@ASA has good crystallinity and exhibits typical MFI diffraction peaks, while no diffraction peaks of iron oxide or ferrous oxide are observed, indicating that the iron content is highly dispersed.

[0132] Figure 2 The pore size distribution of Fe / ZSM-5@ASA shows that the pore size is between 10 and 15 nm.

[0133] Figures 3-4 The images shown are SEM and TEM images of Fe / ZSM-5@ASA. It can be seen that Fe / ZSM-5@ASA has a core-shell structure, with ZSM-5 molecular sieve as the core and ASA mesoporous material as the shell material wrapped around the outer surface of ZSM-5 molecular sieve.

[0134] The specific surface area, pore size, and pore volume data of the ZSM-5@ASA composite material prepared in Example 2 and the metal-modified ZSM-5@ASA microporous composite catalysts prepared in Examples 3-9 are shown in Table 1.

[0135] Table 1. Characterization results of the pore structure of the catalyst

[0136]

[0137] As can be seen from Table 1, the metal-modified ZSM-5@ASA micro-mesoporous composite catalyst prepared in this invention has a slightly lower specific surface area, and the pore size and pore volume are also reduced compared with the unmodified ZSM-5@ASA micro-mesoporous composite catalyst.

[0138] Test Example 2

[0139] The ZSM-5@ASA micro-mesoporous composite catalysts prepared in Example 2 and those prepared in Examples 3-9 catalyze the cracking reaction of n-heptane.

[0140] The catalytic cracking of n-heptane was evaluated using a CEL-GPPCH fixed-bed reactor with an inner diameter of 1 cm and a length of 110 cm. The reaction conditions were as follows: reaction temperature range of 500–700 °C, catalyst loading of 0.2 g, carrier gas nitrogen flow rate of 20 mL / min, and WHSV of 5 h⁻¹. -1 At atmospheric pressure. Online analysis of the product composition was performed using a Shimadzu GC-2014 gas chromatograph (30m × 0.32mm × 0.5μm) with a capillary column and a flame ionization detector (FID) to determine the composition.

[0141] The catalyst stability evaluation reaction conditions were as follows: continuous reaction at 650℃ for 10 h, catalyst loading of 0.2 g, n-heptane injection flow rate of 0.025 mL / min, carrier gas nitrogen flow rate of 20 mL / min, and corresponding WHSV of 5 h. -1 The experimental results of the catalytic cracking reaction of n-heptane are shown in Table 2.

[0142] Table 2 Results of the catalyst-catalyzed cracking reaction of n-heptane

[0143]

[0144] Note: In Tables 2-3, BTX represents a mixture of benzene, toluene, and xylene, which is generally considered a precursor for coking.

[0145] As can be seen from Table 2, the metal-modified ZSM-5@ASA microporous composite catalyst prepared by n-heptane in this invention has low selectivity for BTX but high overall selectivity for ethylene and propylene, with La / ZSM-5@ASA exhibiting the best catalytic performance.

[0146] Figure 5 The results of the catalytic cracking stability of n-heptane by ZSM-5@ASA and La / ZSM-5@ASA prepared in Example 2 show that, at 650℃, the conversion rate of n-heptane decreased by 13.55% after 10 hours of continuous reaction with unmodified ZSM-5@ASA, while the conversion rate of La / ZSM-5@ASA decreased by only 5.4%. This indicates that the metal-modified ZSM-5@ASA microporous composite catalyst is more conducive to the catalytic cracking of n-heptane to generate olefins, and the yield of coke precursors such as BTX is lower, making coking less likely.

[0147] Test Example 3

[0148] The metal-modified ZSM-5@ASA microporous composite catalysts prepared in Examples 3-9 and the ZSM-5@ASA catalysts prepared in Example 2 for the 1-hepten pyrolysis reaction.

[0149] The catalytic cracking of 1-hepten was evaluated using a CEL-GPPCH type fixed-bed reactor with an inner diameter of 1 cm and a length of 110 cm. The reaction conditions were as follows: reaction temperature range of 500–700 °C, catalyst loading of 0.2 g, carrier gas nitrogen flow rate of 20 mL / min, and WHSV of 5 h⁻¹. -1 At atmospheric pressure. Online analysis of the product composition was performed using a Shimadzu GC-2014 gas chromatograph (30m × 0.32mm × 0.5μm capillary column) and a flame ionization detector (FID) to determine the composition. The experimental results are shown in Table 3.

[0150] Table 3 Results of the catalytic cracking reaction of 1-hepten.

[0151]

[0152] As shown in Table 3, the selectivity of 1-heptene for ethylene-propylene under La / ZSM-5@ASA catalysis is significantly higher than that under unmodified ZSM-5@ASA, and the BTX value is also lower. This indicates that the metal-modified ZSM-5@ASA microporous composite catalyst provided by this invention facilitates the catalytic cracking of 1-heptene to produce ethylene-propylene, and the yield of coke precursors such as BTX is lower, making coking less likely.

[0153] The embodiments of the present invention provide a metal-modified ZSM-5@ASA micro-mesoporous composite catalyst with higher selectivity and better stability for the catalytic cracking reaction of naphtha model compounds (n-heptane and 1-heptene) to produce ethylene and propylene, which has potential application value in the petrochemical field.

[0154] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A metal-modified ZSM-5@ASA micro-mesoporous composite catalyst for catalytic cracking of hydrocarbon substances to produce lower olefins, characterized in that, The metal oxide and the ZSM-5@ASA micro-mesoporous composite material and the metal oxide loaded on the ZSM-5@ASA micro-mesoporous composite material; The ZSM-5@ASA micro-mesoporous composite material comprises ZSM-5 molecular sieve and amorphous silicon-aluminum mesoporous material coated on the surface of the ZSM-5 molecular sieve, and the mass content of the ZSM-5 molecular sieve in the ZSM-5@ASA micro-mesoporous composite material is 20-85%; The mass of the metal element in the metal oxide is 0.1-5% of the mass of the metal-modified ZSM-5@ASA micro-mesoporous composite catalyst; the metal element comprises at least one of magnesium, calcium, iron, copper, zinc, zirconium, lanthanum, cerium and yttrium; The specific surface area of the metal-modified ZSM-5@ASA micro-mesoporous composite catalyst is 300-480 m 2 / g, and the pore volume is 0.2-2.0 cm 3 / g.

2. The metal-modified ZSM-5@ASA micro-mesoporous composite catalyst of claim 1, wherein, The molar ratio of SiO2 / Al2O3 in the ZSM-5 molecular sieve is 25-150; the ZSM-5 molecular sieve comprises H-type ZSM-5 molecular sieve, Na-type ZSM-5 molecular sieve and NH4-type ZSM-5 molecular sieve; The specific surface area of the ZSM-5@ASA micro-mesoporous composite material is 320-500 m 2 / g, and the pore volume is 0.3-2.1 cm 3 / g.

3. The method for preparing the metal-modified ZSM-5@ASA micro-mesoporous composite catalyst according to any one of claims 1-2, characterized in that, The method comprises the following steps: The silicon source, the ZSM-5 molecular sieve, the aluminum source, the lower alcohol and water are first mixed, and the pH value is adjusted to 7-10 to obtain a ZSM-5@ASA precursor emulsion; The first mixing comprises: dissolving the silicon source in the lower alcohol, and adjusting the pH value to 3-5 to obtain gel A; The gel A is mixed with the ZSM-5 molecular sieve to obtain gel B; the aluminum source is dissolved in water, and the pH value is adjusted to 7-10 to obtain gel C; and the gel B, the gel C and the lower alcohol are mixed; The molar ratio of the aluminum source to the silicon source is 1:0.01-16; The mass ratio of SiO2 in the silicon source to the ZSM-5 molecular sieve is 1:0.1-10; The ZSM-5@ASA micro-mesoporous composite material is obtained after the ZSM-5@ASA precursor emulsion is aged and first calcined; The ZSM-5@ASA micro-mesoporous composite material, a metal salt and water are second mixed, and are sequentially concentrated, dried and second calcined to obtain a metal-modified ZSM-5@ASA micro-mesoporous composite catalyst; the metal element in the metal salt comprises at least one of magnesium, calcium, iron, copper, zinc, zirconium, lanthanum, cerium and yttrium; and the mass of the metal element in the metal salt is 0.1-5% of the mass of the metal-modified ZSM-5@ASA micro-mesoporous composite catalyst.

4. The production method according to claim 3, characterized by, The silicon source comprises at least one of sodium silicate, silica sol, fumed silica and tetraethyl orthosilicate; The aluminum source comprises at least one of aluminum sulfate, aluminum nitrate, aluminum acetylacetonate, pseudo-boehmite and aluminum hydroxide; The pH adjusting agent used for adjusting the pH value comprises an acid and / or a base; the acid comprises at least one of acetic acid, hydrochloric acid, nitric acid and formic acid; and the base comprises at least one of ammonia, NaOH, KOH and tetrapropylammonium hydroxide.

5. The production method according to claim 3 or 4, characterized by, The temperature of the aging is 30-80°C, and the time is 6-24h; The temperature of the first calcination is 450-650°C, and the time is 6-8h.

6. The preparation method according to claim 3, characterized in that, The temperature of the second calcination is 400-600°C, and the time is 4-10h.

7. Use of the metal-modified ZSM-5@ASA micro-mesoporous composite catalyst of any one of claims 1-2 or the metal-modified ZSM-5@ASA micro-mesoporous composite catalyst prepared by the method of any one of claims 3-6 in catalytic cracking.

8. Use according to claim 7, characterized in that, The use includes catalytic cracking of at least one of naphtha components, olefins, chain alkanes, and cycloalkanes.

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