CN116351460A - Small-grain ZSM-5 catalytic cracking catalyst and preparation method thereof - Google Patents

Small-grain ZSM-5 catalytic cracking catalyst and preparation method thereof Download PDF

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Publication number
CN116351460A
CN116351460A CN202310644238.7A CN202310644238A CN116351460A CN 116351460 A CN116351460 A CN 116351460A CN 202310644238 A CN202310644238 A CN 202310644238A CN 116351460 A CN116351460 A CN 116351460A
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clay
crystallization
zsm
acid
catalytic cracking
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Inventor
刘从华
许维农
赵晓争
王秉军
郭玉生
俞小源
胡森
王伟
***
邵明迪
高杰
姚方艳
温宗曦
段成林
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Weifang Zhengxuan Rare Earth Catalytic Materials Co ltd
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Weifang Zhengxuan Rare Earth Catalytic Materials Co ltd
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Priority to CN202310644238.7A priority Critical patent/CN116351460A/en
Publication of CN116351460A publication Critical patent/CN116351460A/en
Priority to CN202311035028.4A priority patent/CN117065788A/en
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    • C—CHEMISTRY; METALLURGY
    • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
    • C10G11/02—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils characterised by the catalyst used
    • C10G11/04—Oxides
    • C10G11/05—Crystalline alumino-silicates, e.g. molecular sieves
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
    • B01J2229/30—After treatment, characterised by the means used
    • B01J2229/42—Addition of matrix or binder particles
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a small-grain ZSM-5 catalytic cracking catalyst and a preparation method thereof. The invention extracts part of Al from clay raw material by acid 2 O 3 And impurities are extracted from the framework of the first clay to improve the framework SiO 2 /Al 2 O 3 The ratio improves the pore structure and can also lead the residual SiO to be 2 The method is activated in advance, which is beneficial to the subsequent in-situ growth of ZSM-5; extracted active Al 2 O 3 Is fully utilized, avoids the loss and waste of active aluminum, and improves the wear resistance of the small-grain ZSM-5 catalytic cracking catalyst. In addition, the small-grain ZSM-5 prepared by the invention is catalytically crackedThe catalyst has high ZSM-5 zeolite content, developed mesopores, fine grains and high MAT micro-reaction activity, is used for petroleum hydrocarbon catalytic cracking reaction, and can greatly improve the yield of low-carbon olefin (ethylene and propylene) and liquefied gas.

Description

Small-grain ZSM-5 catalytic cracking catalyst and preparation method thereof
Technical Field
The invention belongs to the technical field of petrochemical catalysts, and particularly relates to a small-grain ZSM-5 catalytic cracking catalyst and a preparation method thereof.
Background
With the rapid development of petrochemical industry, the demand of ethylene and propylene is continuously increased, and the supply and demand gap is large. Naphtha steam cracking is a main mode for preparing ethylene and propylene, and although the steam cracking process is mature, the method has the defects of high construction cost, high energy consumption of the device (the reaction temperature is higher than 800 ℃), high carbon emission and the like.
In order to cope with the increasingly serious energy consumption and environmental pollution problems worldwide, hydrocarbon catalytic cracking process technology (Park Yong-Ki, lee Chul Wee, kang Na Young, et al Catalytic cracking of lower-valued hydrocarbons for producing light olefins [ J ]. Cat Surv Asia, 2010, 14 (2): 75-84) which converts long-chain hydrocarbons into lower olefins with high added values such as ethylene, propylene and the like at a higher reaction temperature (600-700 ℃) is developed. The cleavage reaction path of hydrocarbons can be divided into a carbonium mechanism, which generates mainly propylene and butene characteristic products by the action of solid acids, and a free radical mechanism, which generates ethylene characteristic products under thermally initiated conditions. In the microsphere catalytic cracking catalyst, a shape selective cracking molecular sieve with small and medium pore diameters and auxiliary metal elements are generally adopted as main cracking components, and the aim of increasing the yield of propylene and ethylene is achieved by coordinating carbon ion and free radical reactions.
The preparation process of the existing microsphere catalytic cracking catalyst mostly adopts a semisynthesis preparation method: the catalyst is prepared by mixing active components of a shape selective cracking molecular sieve (such as ZSM-5) with a matrix and a binder to prepare slurry, and performing spray drying, roasting and other steps. The development of high-performance catalytic cracking catalyst needs to increase the content of the shape-selective molecular sieve, and the consumption of the binder needs to be increased in order to ensure the wear resistance of the catalyst, however, excessive binder often blocks the pore channels of the molecular sieve, and the catalytic cracking performance is limited.
Chinese patent CN101332995A discloses a method for in-situ crystallization of ZSM-5 molecular sieve by using modified kaolin microspheres, which comprises the steps of mixing kaolin with modified components, spray forming, mixing the kaolin microspheres with an external silicon-aluminum source, a template agent, a seed crystal and water after high-temperature roasting, and synthesizing the kaolin-based ZSM-5 molecular sieve by hydrothermal crystallization, wherein the relative crystallinity is 30-80%.
The patent US005145659A synthesizes a ZSM-5 molecular sieve by adopting a clay matrix microsphere and an organic amine template agent method, and the method involves mixing kaolin, solid silica gel and ZSM-5 seed crystal to form, roasting for 3 hours at 982 ℃, mixing with water and NaOH, reacting for 16 hours at 100 ℃, and crystallizing for 4 days at a high temperature of 149 ℃, wherein the mass content of ZSM-5 in the obtained product is 40%. However, the product contained a significant amount of ex situ crystallized ZSM-5.
The patent EP0156595A3 is prepared by mixing clay, a silicon-aluminum source and a high-silicon molecular sieve seed crystal, forming, roasting at high temperature, mixing with an alkali solution, and performing low-temperature aging and high-temperature crystallization to obtain an in-situ crystallized ZSM-5 product with the mass content of 60%, wherein the high-temperature crystallization time is up to 4 days.
Chinese patent CN103253684a discloses a method for preparing ZSM-5 by direct in-situ crystallization without using template agent, which comprises pretreating high-temperature calcined kaolin microspheres containing five-membered ring feature structural units with water glass, adding acid to prepare reaction mixture, and obtaining in-situ crystallized ZSM-5 molecular sieve product by hydrothermal crystallization, wherein the crystallinity can reach 65%, and the grain size is 0.1-3 μm. However, since the method requires water glass pretreatment of the calcined kaolin microspheres, a large amount of ex-situ crystallization products are generated, and the in-situ crystallization molecular sieve cannot be uniformly distributed in the microspheres, thereby limiting the practical application thereof.
Chinese patent CN104743573a discloses a method for preparing ZSM-5 molecular sieve without template agent, comprising crushing, roasting and acid treatment of silicon-aluminum minerals, mixing with self-made ZSM-5 molecular sieve seed crystal and alkaline aqueous solution through separation and impurity removal, then carrying out sufficient grinding treatment, and carrying out hydrothermal crystallization at 170-190 ℃ for 6-12 hours to synthesize submicron-sized ZSM-5 molecular sieve. The method needs to be fully ground, and has the problems of loss of the extracted alumina raw material and the like.
In the above documents, the ZSM-5 microsphere catalyst synthesized by in-situ crystallization by the template method has the problem of larger crystal grains of the molecular sieve, while the non-template method can lead to the generation of a large amount of ex-situ crystallization products. The existing catalyst is applied to hydrocarbon catalytic cracking reaction, and has the problem of low yield of diene (ethylene and propylene).
Disclosure of Invention
In view of the above, the present invention aims to provide a small-grain ZSM-5 catalytic cracking catalyst and a preparation method thereof. The small-grain ZSM-5 catalytic cracking catalyst prepared by the preparation method has high content of nano ZSM-5 zeolite, fine grains and high MAT micro-reaction activity, is used for petroleum hydrocarbon catalytic cracking reaction, and can greatly improve the yield of low-carbon olefin.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a small-grain ZSM-5 catalytic cracking catalyst, which comprises the following steps: drying the mixed slurry to obtain microspheres, wherein the mixed slurry contains unmodified clay, acid-pumped clay, an additional silicon source, pre-crystallization liquid and water; the acid extraction clay is prepared by a method comprising the following steps: mixing clay raw materials with an acidic solution after first roasting to obtain the acid-pumped clay; performing second roasting on the microspheres, and mixing the obtained roasted microspheres with an alkali-containing aqueous solution for hydrothermal crystallization to obtain an in-situ crystallization product; and carrying out third roasting on the in-situ crystallized product to obtain the small-grain ZSM-5 catalytic cracking catalyst.
Preferably, the acidic solution comprises one or more of hydrochloric acid, sulfuric acid, nitric acid and orthophosphoric acid; the concentration of the acid solution is 0.5-12 mol/L; the weight ratio of the acidic solution to the clay raw material dry basis is 1.5-10:1.
Preferably, the temperature of the first roasting is 500-950 ℃ and the time is 0.1-8 h.
Preferably, the unmodified clay and clay raw material independently comprise one or more of kaolin, halloysite, diatomaceous earth, bentonite, montmorillonite, attapulgite, pyrophyllite and perlite.
Preferably, the pre-crystallization liquid is prepared by a method comprising the following steps:
mixing a template agent, an aluminum source and a silicon source, and then performing pre-crystallization to obtain the pre-crystallization liquid;
the temperature of the pre-crystallization is 80-250 ℃ and the time is 2-48 h;
the aluminum source is Al 2 O 3 The silicon source is represented by SiO 2 The molar ratio of the template agent to the aluminum source to the silicon source is preferably 2-20: 1: 20-100.
Preferably, the template comprises one or more of tetraethylammonium hydroxide, tetrapropylammonium bromide, triethylamine, diethylamine and aqueous ammonia.
Preferably, the aluminum source comprises one or more of pseudoboehmite, boehmite, sodium metaaluminate, aluminum sulfate, aluminum nitrate, and aluminum chloride.
Preferably, the additional silicon source and the silicon source independently comprise one or more of white carbon black, silicone grease, silicone gel, silica sol and water glass.
Preferably, the mixed slurry comprises the following components in mass fraction on a dry basis: 5-80% of acid-pumped clay, 5-70% of unmodified clay, 5-50% of additional silicon source and 0.5-20% of pre-crystallized liquid; the solid content of the mixed slurry is 25-65wt%.
The invention also provides a small-grain ZSM-5 catalytic cracking catalyst obtained by the preparation method, which comprises the following components in percentage by mass based on dry basis: 25-85% of ZSM-5 molecular sieve and the balance of amorphous silica-alumina.
The beneficial effects are that: the invention provides a preparation method of a small-grain ZSM-5 catalytic cracking catalyst, which comprises the steps of adding acid-pumped clay and pre-crystallization liquid into a preparation raw material, and preparing the catalyst by an in-situ crystallization molecular sieve technology. In the acid extraction process of clay, alumina and impurities are extracted from the clay framework, so that the framework SiO is improved 2 /Al 2 O 3 Ratio, and improve pore structure; moreover, the extracted active Al 2 O 3 The alumina is kept in the clay slurry to be fully utilized, so that the loss and waste of active aluminum are avoided, and the extracted alumina exists in the form of aluminum ions and has certain bonding performance. Meanwhile, the residual silicon oxide in the clay acid extraction process is activated in advance, so that the subsequent in-situ growth of the molecular sieve is facilitated, the prepared catalyst has high ZSM-5 zeolite content, developed mesopores, fine grains and high MAT micro-reaction activity, can fully play the high-efficiency reaction effect of the nano molecular sieve, is used for the catalytic cracking reaction of petroleum hydrocarbon, and can greatly improve the yield of low-carbon olefin (ethylene+propylene) and liquefied gas. Meanwhile, because the molecular sieve ZSM-5 is tightly combined with the amorphous silica-alumina component of the carrier in a similar chemical bond, the activity stability and the service life of the catalyst are enhanced And (5) a life.
Furthermore, the pre-crystallization liquid is completely crystallized nano molecular sieve pre-crystallization liquid, and is fully mixed with various silicon sources of a system, thereby being beneficial to the rapid growth of small-grain molecular sieves in the subsequent crystallization process.
The invention also provides a small-grain ZSM-5 catalytic cracking catalyst prepared by the preparation method, which has high crystallinity and fine grains, and the catalyst provided by the invention is used for petrochemical catalytic cracking reaction, has high conversion rate, greatly increases the yield of liquefied gas and the yield of diene (ethylene and propylene), and shows excellent catalytic cracking reaction performance.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is an XRD spectrum of CY-1 catalyst prepared in example 3.
FIGS. 2 and 3 are SEM pictures of the CY-1 catalyst prepared in example 3 at different magnifications, wherein the scale of FIG. 2 is 10 μm and the scale of FIG. 3 is 1. Mu.m.
FIG. 4 is an XRD spectrum of the DB-1 catalyst prepared in comparative example 1.
FIGS. 5 and 6 are SEM pictures of the DB-1 catalyst prepared in comparative example 1 at different magnifications, in which the scale of FIG. 5 is 20 μm and the scale of FIG. 6 is 1. Mu.m.
FIG. 7 is an XRD spectrum of DB-2 catalyst prepared in comparative example 2.
FIGS. 8 and 9 are SEM pictures of different magnifications of the DB-2 catalyst prepared in comparative example 2, in which FIG. 8 is 20 μm and FIG. 9 is 1. Mu.m.
Detailed Description
The invention provides a preparation method of a small-grain ZSM-5 catalytic cracking catalyst, which comprises the following steps: drying the mixed slurry to obtain microspheres, wherein the mixed slurry contains unmodified clay, acid-pumped clay, an additional silicon source, pre-crystallization liquid and water; the acid extraction clay is prepared by a method comprising the following steps: mixing clay raw materials with an acidic solution after first roasting to obtain the acid-pumped clay; performing second roasting on the microspheres, and mixing the obtained roasted microspheres with an alkali-containing aqueous solution for hydrothermal crystallization to obtain an in-situ crystallization product; and carrying out third roasting on the in-situ crystallized product to obtain the small-grain ZSM-5 catalytic cracking catalyst.
In the present invention, materials and equipment used are commercially available in the art unless otherwise specified.
The invention dries the mixed slurry to obtain microspheres, wherein the mixed slurry contains unmodified clay, acid-pumped clay, an additional silicon source, pre-crystallization liquid and water; the acid extraction clay is prepared by a method comprising the following steps: and mixing the clay raw material with an acidic solution after the first roasting to obtain the acid-pumped clay.
In the present invention, the unmodified clay and clay raw material preferably independently include one or more of kaolin, halloysite, diatomaceous earth, bentonite, montmorillonite, attapulgite, pyrophyllite, and perlite.
In the invention, the clay raw material is preferably kaolin, a mixture of kaolin and montmorillonite or a mixture of kaolin and halloysite, wherein the mass ratio of the kaolin to the montmorillonite in the mixture of the kaolin and the montmorillonite is preferably 3:1, and the mass ratio of the kaolin to the halloysite in the mixture of the kaolin and the halloysite is preferably 1:1.
In the invention, the temperature of the first roasting is preferably 500-950 ℃, more preferably 550-900 ℃; the time is preferably 0.1 to 8 hours, more preferably 0.3 to 7 hours; in a specific embodiment of the present invention, the conditions of the first firing preferably include: roasting at 650 ℃ for 5 hours, at 750 ℃ for 3.5 hours or at 850 ℃ for 1.5 hours.
In the invention, the mass content of the activated alumina in the calcined clay obtained after the first calcination is preferably 12.5-25.5%.
In the present invention, the acidic solution preferably includes one or more of hydrochloric acid, sulfuric acid, nitric acid, and orthophosphoric acid. In the invention, the concentration of the acid solution is preferably 0.5-12 mol/L, more preferably 1-10 mol/L, and most preferably 2-4 mol/L; the weight ratio of the acidic solution to the clay raw material dry basis is preferably 1.5-10:1, more preferably 2-8:1.
In the invention, the mixing mode of the calcined clay obtained after the first calcination and the acid solution is preferably constant-temperature stirring, and the temperature of constant-temperature stirring is preferably 40-150 ℃, more preferably 60-80 ℃; the time is preferably 0.3-8 hours, more preferably 1-3 hours; the mixing step preferably comprises the step of adding ammonia water for adjusting the pH value of the acid-pumped clay slurry obtained by mixing; the pH value of the acid-pumped clay slurry is preferably less than 1, and the pH value of the acid-pumped clay slurry is preferably 2-6, more preferably 2-3 after ammonia water is added for adjustment; the ammonia water is preferably strong ammonia water, and the mass concentration of the strong ammonia water is preferably 27%; preferably, cooling is further included before adding the ammonia water, and the temperature after cooling is preferably lower than 50 ℃.
The invention performs acid extraction treatment on clay, and can extract alumina and impurities from the clay skeleton, thereby improving the SiO skeleton 2 /Al 2 O 3 Ratio, and improve pore structure. The acid extraction treatment enables the residual silicon oxide of the clay to be activated in advance, which is beneficial to the subsequent in-situ growth of the molecular sieve.
In the present invention, the acid-extracted clay is preferably used in the form of an acid-extracted clay slurry obtained by mixing calcined clay obtained after the first calcination with an acid solution. The acid extraction clay slurry is directly used, the clay is extracted to obtain the active alumina through acid extraction treatment, and the active alumina is completely utilized in the process of preparing the microsphere by the mixed slurry, so that the resource can be saved. In the present invention, the average particle diameter of the acid-pumped clay slurry is preferably 0.3 to 25. Mu.m, more preferably 0.5 to 20. Mu.m.
In the present invention, the additional silicon source preferably includes one or more of white carbon black, silicone grease, silicone gel, silica sol and water glass.
In the present invention, the pre-crystallization liquid is preferably prepared by the steps ofIs prepared by the method of: mixing a template agent, an aluminum source and a silicon source, and then performing pre-crystallization to obtain the pre-crystallization liquid; the temperature of the pre-crystallization is preferably 80-250 ℃, more preferably 160-200 ℃; the time is preferably 2-48 hours, more preferably 15-30 hours; the aluminum source is Al 2 O 3 The silicon source is represented by SiO 2 The molar ratio of the template agent to the aluminum source to the silicon source is preferably 2-20: 1: 20-100.
In the invention, the template agent preferably comprises one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide (TPAOH), tetrapropylammonium bromide (TPABr), triethylamine, diethylamine, n-butylamine and ammonia water, more preferably a mixture of TPABr and TPAOH, and the mass ratio of TPABr to TPAOH in the mixture of TPABr and TPAOH is preferably 80-170:25-100.
In the present invention, the aluminum source preferably includes one or more of pseudo-boehmite, sodium metaaluminate, aluminum sulfate, aluminum nitrate, and aluminum chloride.
In the present invention, the silicon source preferably includes one or more of white carbon black, silicone grease, silicone gel, silica sol and water glass.
In the present invention, the preparation raw material of the pre-crystallization liquid preferably further comprises a base, the base preferably comprises NaOH, and the aluminum source is prepared by using Al 2 O 3 The molar ratio of the aluminum source to the base is preferably 1:1 to 20, more preferably 1: 5-10.
The pre-crystallization liquid is completely crystallized nano molecular sieve pre-crystallization liquid, and is fully mixed with various silicon sources of a system after being added, thereby being beneficial to the rapid growth of small-grain molecular sieves in the subsequent crystallization process.
In the present invention, the mixed slurry preferably comprises the following components in mass fraction on a dry basis: 5-80% of acid-pumped clay, 5-70% of unmodified clay, 5-50% of additional silicon source and 0.5-20% of pre-crystallized liquid. In the invention, the mass fraction of the acid-pumped clay in the mixed slurry is preferably 10-70% on a dry basis.
In the invention, the mass fraction of the unmodified clay in the mixed slurry is preferably 10-70% on a dry basis; the unmodified clay comprises kaolin and other clay except for the kaolin, the mass fraction of the kaolin in the mixed slurry is preferably 5-40%, and the mass fraction of the other clay except for the kaolin in the mixed slurry is preferably 10-60%.
In the invention, the mass fraction of the additional silicon source in the mixed slurry is preferably 7-45% on a dry basis.
In the invention, the mass fraction of the pre-crystallization liquid in the mixed slurry is preferably 1-18% on a dry basis.
In the present invention, the mixed slurry more preferably comprises the following components in mass fraction on a dry basis: 10-70% of acid-pumped clay, 5-40% of kaolin, 10-60% of clay except kaolin, 7-45% of additional silicon source and 1-18% of pre-crystallization liquid.
In the present invention, the solid content of the mixed slurry is preferably 25 to 65wt%, more preferably 30 to 60%.
In the present invention, the manner of drying the mixed slurry is preferably spray drying, and the conditions of the spray drying preferably include: the spraying pressure is 8-12 MPa, the tower inlet temperature is 600-650 ℃, and the tail gas temperature is 120-300 ℃.
In the present invention, the drying preferably further comprises washing, filtering and re-drying the obtained solid material in sequence; the washing reagent is preferably acidic deionized water, the temperature of the acidic deionized water is preferably 50 ℃, the pH value of the acidic deionized water is preferably 2-3, and the weight ratio of the solid material to the acidic deionized water is preferably 1:8 during washing; the temperature of the re-drying is preferably 50-200 ℃, and the time is preferably 1-5 h.
In the present invention, the particle diameter of the microspheres is preferably 50 to 70. Mu.m, more preferably 58 to 66. Mu.m.
After the microspheres are obtained, the microspheres are subjected to second roasting, and the obtained roasted microspheres and an aqueous solution containing alkali are mixed for hydrothermal crystallization to obtain an in-situ crystallization product.
In the invention, the temperature of the second roasting is preferably 500-1200 ℃, more preferably 600-1100 ℃; the time is preferably 0.5-8 hours, more preferably 1-6 hours; the second firing can increase the strength of the microspheres. In a specific embodiment of the present invention, the conditions of the second firing preferably include: 980 c for 3h, 950 c for 4h, 1000 c for 1.5h, 990 c for 2h, 1020 c for 1.5h, 930 c for 3h or 1030 c for 1.2h.
In the present invention, the active SiO in the calcined microsphere 2 The mass content of (2) is preferably 60-70%, more preferably 61-69%; the active SiO 2 SiO which is in an amorphous state for the microspheres in the second roasting process 2 Can be converted into ZSM-5 zeolite in the subsequent hydrothermal crystallization process.
In the present invention, the alkali-containing aqueous solution preferably includes one or more of sodium hydroxide solution, sodium metaaluminate solution, water glass and ammonia water, and the active SiO in the mixed solution obtained by mixing the calcined microsphere and the alkali-containing aqueous solution 2 With OH - The molar ratio of (2) is preferably 1:0.05-0.4; the active SiO 2 With OH - The molar ratio of (2) can provide a suitable basicity for the crystallization system.
In the invention, the temperature of the hydrothermal crystallization is preferably 100-250 ℃, more preferably 120-220 ℃; the time is preferably 5-40 hours, more preferably 8-35 hours; the temperature of the hydrothermal crystallization is more suitable for molecular sieve growth. The hydrothermal crystallization can be performed by various methods known to those skilled in the art, such as constant temperature crystallization or multi-stage variable temperature crystallization, and static crystallization, dynamic crystallization or intermittent dynamic crystallization can be superimposed. In a specific embodiment of the present invention, the hydrothermal crystallization conditions preferably include: the temperature is kept constant for 24 hours at 180 ℃, 28 hours at 170 ℃, 30 hours at 165 ℃, 25 hours at 185 ℃, 20 hours at 175 ℃, 21 hours at 190 ℃ or 24 hours at 185 ℃.
In the invention, the hydrothermal crystallization preferably further comprises the steps of sequentially filtering, washing and drying to obtain the in-situ crystallization product. The specific modes of filtration, washing with water and drying are not particularly limited in the present invention, and may be any modes known to those skilled in the art.
After the in-situ crystallization product is obtained, the in-situ crystallization product is subjected to third roasting to obtain the small-grain ZSM-5 catalytic cracking catalyst.
In the present invention, the third firing preferably further includes the steps of: mixing the in-situ crystallization product, ammonium salt and water uniformly, and then sequentially stirring, filtering, washing and drying, wherein the stirring temperature is preferably 65-85 ℃ and the stirring time is preferably 0.8-1.5 h, and the ammonium salt preferably comprises one or more of ammonium chloride, ammonium phosphate and ammonium nitrate; the mass ratio of the ammonium salt to the in-situ crystallization product is preferably 0.05-0.3 in terms of dry basis: 1, more preferably 0.1 to 0.2:1, a step of; the addition of the ammonium salt can reduce sodium oxide in the crystallized product.
In the invention, the temperature of the third roasting is preferably 400-750 ℃, more preferably 450-700 ℃, and more preferably 550 ℃; the time is preferably 0.5-8 hours, more preferably 1-3 hours; the third firing is capable of activating the modified metal element.
The invention also provides a small-grain ZSM-5 catalytic cracking catalyst obtained by the preparation method, which comprises the following components in percentage by mass based on dry basis: 25-85% of ZSM-5 molecular sieve and the balance of amorphous silica-alumina.
In the invention, the mass fraction of the ZSM-5 molecular sieve in the small-grain ZSM-5 catalytic cracking catalyst is preferably 28-80%, more preferably 57-65% based on dry basis, and the ZSM-5 molecular sieve in the small-grain ZSM-5 catalytic cracking catalyst has high content and good wear resistance.
In the invention, the crystallinity of the small-grain ZSM-5 catalytic cracking catalyst is preferably 59-70%.
In the invention, the grain size of the small-grain ZSM-5 catalytic cracking catalyst is preferably 300-500 nm.
In a specific embodiment of the present invention, the catalytic cracking reaction preferably includes the steps of: the catalyst is treated for 17 hours under the condition of 800 ℃ and 100% water vapor, and the raw oil is subjected to catalytic cracking reaction on a fixed fluidized bed device, wherein the catalytic cracking reaction temperature is 650 ℃, the catalyst-to-oil ratio (i.e. the mass ratio of the catalyst to the raw oil) is 15, and the catalyst loading is 60g.
For further explanation of the present invention, the small-grained ZSM-5 catalytic cracking catalyst of the present invention and its preparation method are described in detail below with reference to the accompanying drawings and examples, but they should not be construed as limiting the scope of the present invention.
The analysis and test method used in the embodiment of the invention comprises the following steps:
1) ZSM-5 content determination: x-ray diffraction method for measuring XRD patterns 2 theta of sample and standard sample at 22.5-25 respectively o The sum of peak areas of five characteristic diffraction peaks is the content of ZSM-5; the standard sample is selected from high-quality ZSM-5 molecular sieve produced by Nanka, and the crystallinity is determined to be 95%.
2) Clay activity SiO 2 And (3) measuring: in the high-temperature roasting process of the microsphere, part of SiO is contained 2 Remains in an amorphous state and can be converted into zeolite during the hydrothermal crystallization process, and the SiO part 2 Called active SiO 2 . The measuring method comprises the following steps: weighing 5g of sample, placing into a conical flask, adding 25mL of 15% sodium hydroxide solution, extracting at constant temperature in a water bath at 80 ℃ for 1h, intermittently shaking, filtering, flushing solid product with 0.5mol/L sodium hydroxide solution, transferring filtrate into a 250mL volumetric flask, adding 0.5mol/L sodium hydroxide solution to dilute to scale, and re-titrating SiO thereof 2 The weight percentage of the clay is active SiO 2 Is contained in the composition.
3) Clay active Al 2 O 3 And (3) measuring: weighing 5g of sample, placing into a 250mL conical flask, adding 36.8mL of 6mol/L hydrochloric acid solution, extracting in a constant-temperature water bath at 80 ℃ for 80min, filtering, washing with 150mL of 0.5mol/L hydrochloric acid solution at 60 ℃ for three times, collecting filtrate into a 250mL volumetric flask, determining volume, and titrating to analyze Al 2 O 3 The content of the active Al is the percentage of the clay weight 2 O 3 The content is as follows.
4) Kaolinite and halloysite: an X-ray diffraction method; elemental composition and silicon to aluminum ratio: XRF fluorescence.
5) Solid content: burning, 800 ℃/1 hour; wear index: the straight tube method of the abrasion instrument.
6) Average particle size: laser particle size analyzer method; and (3) crystal grains: SEM electron microscopy analysis.
7) Microreaction Activity (MA): the raw oil is light diesel oil in hong Kong, the catalyst loading is 5.0 g, the catalyst-oil ratio is 3.2, the reaction temperature is 460 ℃, the reaction time is 70 seconds, MA= (gasoline+gas+coke) in the product is lower than 200 ℃, and the total amount of oil inlet is multiplied by 100%.
Raw material specifications (weight percent, unless specified as industrial product) used in the examples of the present invention:
1) Tetrapropylammonium hydroxide (TPAOH), wakame@national pharmaceutical chemicals limited, 25%; tetrapropylammonium bromide (TPABr), an Anhui Jinao chemical Co., ltd., solid; triethylamine, liquid.
2) Kaolin, kaolinite content 87%, solid content 85.4%, average particle size 2.0 μm, quartz content 0.5%; halloysite, halloysite content 76%, solids content 85.4% and average particle size 4.1 μm.
3) Montmorillonite, siO 2 51.2% MgO, 4.1% MgO, 84.6% solid, and an average particle size of 7.8 μm; diatomite, siO 2 Content 93.5%, fe 2 O 3 Content 1.2%, average particle size 18 μm, solid content 83.8%.
4) Water glass, siO 2 Content of 250g/L, na 2 O content is 88g/L; silica sol, siO 2 The content is 30 percent; white carbon black, siO 2 The content is 99 percent.
5) Sodium metaaluminate, al 2 O 3 Content of 50g/L, na 2 O content is 100g/L; aluminum sulfate, al 2 O 3 The content is 145g/L; pseudo-boehmite, al 2 O 3 98.5% of solid content and 66%; sodium hydroxide, solid.
6) Manganese nitrate (Mn (NO) 3 ) 2 ·4H 2 O), cerous nitrate (Ce (NO) 3 ) 3 .6H 2 O, silver nitrate (AgNO) 3 ) Are all chemically pure.
7) Ammonium chloride; ammonium sulfate; ammonium nitrate; ammonium phosphate; ammonium dihydrogen phosphate.
8) 36% of hydrochloric acid; phosphoric acid 85%; 98% of sulfuric acid; and 27% of concentrated ammonia water.
EXAMPLE 1 preparation of acid-extracted clay
Acid clay 1 #: and (3) roasting 2000 g of kaolin in a muffle furnace at 650 ℃ for 5 hours, measuring that the mass content of active alumina is 12.5%, cooling, placing in a stainless steel reaction kettle, adding 4L of 6M hydrochloric acid, uniformly stirring, heating to 80 ℃, stirring at constant temperature for 1 hour, cooling to below 50 ℃, and then adding 0.6L of concentrated ammonia water to obtain the 1# acid extraction clay.
Acid clay of 2# extraction: roasting 1500 g of kaolin and 500 g of montmorillonite in a muffle furnace at 750 ℃ for 3.5 hours, measuring that the mass content of active alumina is 18.7%, cooling, placing in a stainless steel reaction kettle, adding 6L of 4M nitric acid, uniformly stirring, heating to 70 ℃, stirring at constant temperature for 2 hours, cooling to below 50 ℃, adding 1L of concentrated ammonia water, and stirring for 0.5 hour to obtain the No. 2 acid-pumped clay.
3# acid extraction clay: and (3) roasting 1000 g of kaolin and 1000 g of halloysite in a muffle furnace for 1.5 hours at 850 ℃, wherein the mass content of the measured active alumina is 25.5%, cooling, placing in a stainless steel reaction kettle, adding 7.2L of 3M sulfuric acid, uniformly stirring, heating to 60 ℃, and stirring at constant temperature for 3 hours to obtain the 3# acid extraction clay.
EXAMPLE 2 preparation of Pre-crystallization liquid
1# pre-crystallization liquid: adding 950g of deionized water, 170g of TPABr and 100g of TPAOH (mass content of 25%) solution into a reaction kettle, adding 14g (dry basis) of boehmite and 62g of NaOH, stirring for 5 minutes, slowly adding 380g (dry basis) of white carbon black and 60g of water glass, keeping the colloid flowing all the time, continuing to stir vigorously for 1.5 hours, transferring into a high-pressure crystallization kettle, heating to 180 ℃ for crystallization for 20 hours, and obtaining the No. 1 pre-crystallization liquid.
2# pre-crystallization liquid: 600g of TPAOH (mass content 25%) solution, 130g of n-butylamine and 25 g of concentrated ammonia water are added into a reaction kettle, 17g (dry basis) of pseudo-boehmite is added, after stirring for 5 minutes, 1100g of silica sol is slowly added, the mixture is continuously stirred vigorously for 2 hours, the mixture is transferred into a high-pressure crystallization kettle, the temperature is raised to 160 ℃ for 1.5 hours, and the mixture is crystallized for 15 hours, so that the No. 2 pre-crystallization liquid is obtained.
3# pre-crystallization liquid: 400g of TPAOH (25% by mass) solution and 80g of TPABr, 20g of n-butylamine, 19g (based on dry basis) of pseudo-boehmite are added into a reaction kettle, after stirring for 5 minutes, 1200g of silica sol and 120g of water glass are slowly added, the mixture is continuously and vigorously stirred for 1 hour, the mixture is transferred into a high-pressure crystallization kettle, the temperature is raised to 200 ℃ for 2.5 hours, and the mixture is crystallized for 30 hours, so that 3# pre-crystallization liquid is obtained.
Table 1 microsphere feedstock compositions for the catalysts of examples 3-10 and comparative examples 1-2.
Figure SMS_1
。
Example 3
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of the clay microspheres were prepared by mixing and homogenizing a slurry of 2000g of a dry basis of 1# acid-extracted kaolin, diatomaceous earth, silica sol, 1# pre-crystallized liquid and a proper amount of deionized water in a gel forming tank, and spray-drying the slurry to obtain clay microspheres having an average particle diameter of 65. Mu.m. According to the microsphere: water=1:8 by weight, the microspheres were washed with deionized water at 50 ℃ at pH 2.5, then filtered and dried.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 980 ℃ for 3 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 65% by weight. 1000g of calcined microsphere, 3000g of deionized water and 81g of sodium hydroxide are taken and stirred for 0.5 hour. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 180 ℃, crystallizing at constant temperature for 24 hours, filtering, washing with water, and drying to obtain crystallized products. The crystallized product was calcined at 550℃for 2 hours.
3. Post-treatment of crystallization products: mixing 500g of roasting crystallization product with 52g of ammonium chloride and 5000g of water uniformly, stirring for 1 hour at 80 ℃, and then filtering, washing and drying to obtain a CY-1 catalyst product. The ZSM-5 zeolite content of this product was found to be 64% and the micro-reaction activity was found to be 44%.
Example 4
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of the clay microspheres were prepared by mixing and homogenizing a 1# acid-extracted kaolin, diatomaceous earth, montmorillonite, silica sol, 2# pre-crystallized liquid and a proper amount of deionized water in a gel forming tank to obtain a slurry having a solid content of 40% by weight, and spray-drying the slurry to obtain clay microspheres having an average particle diameter of 63. Mu.m. According to the microsphere: water=1:8 by weight, the microspheres were washed with deionized water at 50 ℃ at pH 2.5, then filtered and dried.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 950 ℃ for 4 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 61% by weight. 1000g of calcined microsphere, 2500g of deionized water and 75g of sodium hydroxide are taken and stirred for 1 hour. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 170 ℃, crystallizing at constant temperature for 28 hours, filtering, washing with water, and drying to obtain crystallized products. The crystallized product was calcined at 550℃for 3 hours.
3. Post-treatment of crystallization products: mixing 500g of calcined crystallization product with 42 g of ammonium nitrate and 6000g of water uniformly, stirring at 75 ℃ for 1.5 hours, filtering, washing and drying to obtain a CY-2 catalyst product. The ZSM-5 zeolite content of this product was found to be 67% and the microreflection activity was found to be 46%.
Example 5
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of the clay microspheres were prepared by mixing and homogenizing a slurry of 2000g of a dry basis, comprising 2# acid-extracted kaolin, diatomaceous earth, silica sol, 1# pre-crystallized liquid and a proper amount of deionized water in a gel tank, and spray-drying the slurry to obtain clay microspheres having an average particle diameter of 66. Mu.m. According to the microsphere: water=1:8 by weight, the microspheres were washed with deionized water at 50 ℃ at pH 2.5, then filtered and dried.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 1000 deg.c for 1.5 hr to obtain active SiO 2 The content of (2) was 68% by weight. 1000g of calcined microsphere, 3200g of deionized water and 85g of sodium hydroxide are taken and stirred for 0.3 hour. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 165 ℃, crystallizing for 30 hours at constant temperature, filtering, washing with water, and drying to obtain crystallized products. The crystallized product was calcined at 550℃for 3 hours.
3. Post-treatment of crystallization products: mixing 500g of calcined crystallization product with 43g of ammonium chloride and 7000g of water uniformly, stirring for 1.5 hours at 65 ℃, and then filtering, washing and drying to obtain a CY-3 catalyst product. The ZSM-5 zeolite content of this product was found to be 65% and the microreflection activity was found to be 44.
Example 6
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of the clay microspheres were prepared by mixing and homogenizing a slurry having a solid content of 46% by weight, obtained by spray-drying the slurry, with a dry basis of 2000g of a clay microsphere having an average particle diameter of 66. Mu.m, and adding a 2# acid-extracted kaolin, diatomaceous earth, montmorillonite, silica sol, a 2# pre-crystallized liquid and a proper amount of deionized water to a gel-forming tank. According to the microsphere: water=1:8 by weight, the microspheres were washed with deionized water at 50 ℃ at pH 2.5, then filtered and dried.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 990 ℃ for 2 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 63% by weight. 1000g of calcined microsphere, 2300g of deionized water and 77g of sodium hydroxide are taken and stirred for 0.6 hour. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 185 ℃, crystallizing at constant temperature for 25 hours, filtering, washing with water, and drying to obtain crystallized products. The crystallized product was calcined at 550℃for 2.5 hours.
3. Post-treatment of crystallization products: mixing 500g of roasting crystallization product with 61g of ammonium sulfate and 4500g of water uniformly, stirring for 1.2 hours at 65 ℃, filtering, washing and drying to obtain CY-4 catalyst product. The ZSM-5 zeolite content of the product was found to be 70% and the micro-reaction activity was found to be 49%.
Example 7
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of the clay microspheres were charged on a dry basis, and the clay microspheres having an average particle diameter of 60 μm were obtained by mixing and homogenizing a slurry having a solids content of 48% by weight, obtained by adding a 3# acid-drawn kaolin, diatomaceous earth, water glass, silica sol, 1# pre-crystallized liquid and a proper amount of deionized water to a gel tank. According to the microsphere: water=1:8 by weight, the microspheres were washed with deionized water at 50 ℃ at pH 2.5, then filtered and dried.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 1020 ℃ for 1.5 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 69% by weight. 1000g of calcined microsphere, 3100g of deionized water and 70.2g of sodium hydroxide are taken and stirred for 1.2 hours. Transferring the mixture into a container withAnd (3) heating the mixture to 175 ℃ in a stainless steel reaction kettle with a polytetrafluoroethylene lining, crystallizing the mixture for 20 hours at constant temperature, filtering, washing the mixture with water, and drying the mixture to obtain a crystallized product. The crystallized product was calcined at 550℃for 3.5 hours.
3. Post-treatment of crystallization products: mixing 500g of calcined and crystallized product with 55g of ammonium phosphate and 5500g of water uniformly, stirring for 1 hour at 85 ℃, and then filtering, washing and drying to obtain a CY-5 catalyst product. The ZSM-5 zeolite content of this product was found to be 67% and the micro-reaction activity was found to be 47%.
Example 8
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of the clay microspheres were prepared by mixing and homogenizing a slurry having a solids content of 43% by weight, obtained by spray-drying the slurry, wherein the slurry had an average particle diameter of 58. Mu.m, by adding 2000g of a dry matter of kaolin, diatomaceous earth, montmorillonite, silica sol, 3# pre-crystallized liquid and a proper amount of deionized water to a gel-forming tank. According to the microsphere: water=1:8 by weight, the microspheres were washed with deionized water at 50 ℃ at pH 2.5, then filtered and dried.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 930 ℃ for 3 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 61% by weight. 1000g of calcined microsphere, 3500g of deionized water and 79g of sodium hydroxide are taken and stirred for 1.5 hours. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 190 ℃, crystallizing at constant temperature for 21 hours, filtering, washing with water, and drying to obtain crystallized products. The crystallized product was calcined at 550℃for 3.5 hours.
3. Post-treatment of crystallization products: mixing 500g of calcined and crystallized product with 57g of ammonium nitrate and 5500g of water uniformly, stirring for 0.8 hours at 70 ℃, and then filtering, washing and drying to obtain a CY-6 catalyst product. The ZSM-5 zeolite content of the product was found to be 59% and the micro-reflection activity was found to be 40%.
Example 9
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of the clay microspheres were prepared by mixing and homogenizing a slurry of 2000g of a dry basis of 2# acid-extracted kaolin, halloysite, diatomaceous earth, silica sol, 1# pre-crystallized liquid and a proper amount of deionized water in a gel tank, and spray-drying the slurry to obtain clay microspheres with an average particle diameter of 62. Mu.m. According to the microsphere: water=1:8 by weight, the microspheres were washed with deionized water at 50 ℃ at pH 2.5, then filtered and dried.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 1030 ℃ for 1.2 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 67% by weight. 1000g of calcined microsphere, 3600g of deionized water, 82g of sodium hydroxide and stirring for 0.8 hour. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 185 ℃, crystallizing at constant temperature for 24 hours, filtering, washing with water, and drying to obtain crystallized products. The crystallized product was calcined at 550℃for 4 hours.
3. Post-treatment of crystallization products: mixing 500g of roasting crystallization product with 61g of ammonium sulfate and 6000g of water uniformly, stirring at 70 ℃ for 1.5 hours, and then filtering, washing and drying to obtain a CY-7 catalyst product. The ZSM-5 zeolite content of the product was found to be 62% and the micro-reflection activity was found to be 42%.
Example 10
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of the clay microspheres were charged on a dry basis, and 3# acid-pumped kaolin, montmorillonite, water glass, silica sol, 3# pre-crystallized liquid and a proper amount of deionized water were added to a colloid forming tank, mixed and homogenized so that the slurry had a solid content of 38% by weight, and the slurry was spray-dried to obtain clay microspheres having an average particle diameter of 67. Mu.m. According to the microsphere: water=1:8 by weight, the microspheres were washed with deionized water at 50 ℃ at pH 2.5, then filtered and dried.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 995 ℃ for 1.2 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 64% by weight. 1000g of calcined microsphere, 3500g of deionized water, 77g of sodium hydroxide and stirring for 1.2 hours. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 185 ℃, crystallizing at constant temperature for 18 hours, filtering, washing with water, and drying to obtain crystallized products. The crystallized product was calcined at 550℃for 3 hours.
3. Post-treatment of crystallization products: mixing 500g of roasting crystallization product with 48g of ammonium chloride and 5200g of water uniformly, stirring for 0.8 hours at 77 ℃, and then filtering, washing and drying to obtain a CY-8 catalyst product. The ZSM-5 zeolite content of the product was found to be 66% and the micro-reaction activity was found to be 46%.
Comparative example 1
An in situ crystallized ZSM-5 product DB-1 was prepared with reference to example 6 in CN 101462741A.
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of kaolin, diatomaceous earth and a proper amount of deionized water were fed in a gel tank, mixed and homogenized to give a slurry having a solid content of 30% by weight, and the slurry was spray-dried to give clay microspheres having an average particle diameter of 51. Mu.m. According to the microsphere: water = 1:10 weight ratio, the microspheres were washed twice with deionized water at pH 2.5.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 980 ℃ for 2 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 38.8% by weight. 1000g of calcined microsphere, 3600g of deionized water, 94g of sodium hydroxide and 165g of n-butylamine are taken and stirred uniformly. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 150 ℃, dynamically crystallizing for 16 hours at constant temperature, filtering, washing with water, and drying to obtain crystallized products. The crystallized product was calcined at 550℃for 2 hours.
3. Post-treatment of crystallization products: mixing 500g of roasting crystallization product with 15g of ammonium sulfate and 5000g of water uniformly, stirring at 80 ℃ for 0.5 hour, and repeating for three times to remove sodium ions. Then filtering and drying at 120 ℃ to obtain a DB-1 catalyst sample. The ZSM-5 zeolite content of this sample was found to be 38% and the microreaction activity was found to be 35%.
Comparative example 2
An in situ crystallized ZSM-5 product DB-2 was prepared with reference to example 1 of CN 103253684A.
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of kaolin, water glass and a proper amount of deionized water are added into a colloid forming tank for mixing and homogenizing, so that the solid content of the slurry is 46% by weight, and the slurry is spray-dried to obtain clay microspheres with the particle size of 12-205 mu m.
2. Roasting and crystallizing the microspheres: roasting the microsphere at 950 ℃ for 2 hours to obtain the active SiO in the roasted microsphere 2 The content of (2) was 41.5% by weight and the content of activated alumina was 5.1% by weight. Adding roasting micro-particles into a reactorThe balls 1000g and 4370g of deionized water are evenly mixed, stirred for 5 minutes at 90 ℃, then 3700g of water glass is added, stirred for 20 hours, then 4370g of deionized water is added, stirred for 10 minutes, 1200g of 3mol/L sulfuric acid solution is slowly added into the system to adjust the alkalinity of the system, and stirring is continued for 1 hour. Transferring the uniform mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 180 ℃, carrying out static crystallization for 24 hours at constant temperature, filtering, washing with water, and drying to obtain an in-situ crystallization product.
3. Post-treatment of crystallization products: mixing 500g of the calcined and crystallized product with 2500g of 0.5mol/L ammonium chloride solution uniformly, stirring for 1 hour at 90 ℃, and repeating exchange twice. The catalyst was filtered, dried at 120℃and calcined at 540℃for 4 hours to give a sample of DB-2 catalyst. The ZSM-5 zeolite content of this sample was found to be 41% and the microreflection activity was found to be 37%.
FIG. 1 is an XRD spectrum of CY-1 catalyst prepared in example 3, with CY-1 having a relative crystallinity of 63%.
FIGS. 2 and 3 are SEM photographs of the CY-1 catalyst prepared in example 3 at different magnifications, wherein the scale of FIG. 2 is 10 μm and the scale of FIG. 3 is 1. Mu.m, and it can be seen that the molecular sieve has a grain size of 300-500 nm.
FIG. 4 is an XRD spectrum of the DB-1 catalyst prepared in comparative example 1, with DB-1 having a relative crystallinity of 38%.
FIGS. 5 and 6 are SEM pictures of the DB-1 catalyst prepared in comparative example 1 at different magnifications, wherein the scale of FIG. 5 is 20 μm and the scale of FIG. 6 is 1. Mu.m, and it can be seen that the molecular sieve grains have a size of 200-400 nm.
FIG. 7 is an XRD spectrum of DB-2 catalyst obtained in comparative example 2, DB-2 having a relative crystallinity of 41%.
FIGS. 8 and 9 are SEM pictures of the DB-2 catalyst prepared in comparative example 2 at different magnifications, wherein the scale of FIG. 8 is 20 μm and the scale of FIG. 9 is 1. Mu.m, and it can be seen that the molecular sieve grains have a size of 300-800 nm.
As can be seen from fig. 1 to 9, the catalyst prepared by the invention has smooth SEM morphology, presents small-grain regular particles, has high XRD diffraction intensity and is completely crystallized. The surfaces of DB-1 and DB-2 are rough, different crystal phase particles appear, the XRD diffraction intensity is low, and obvious miscellaneous crystal diffraction peaks appear, which indicates that the crystallization is incomplete. Thus, the catalyst product prepared according to the present invention is significantly different from the catalyst prepared according to the comparative example.
Example 11
Taking a fixed fluidized bed reaction as an example, the catalysts of examples 3 to 10 and comparative examples 1 to 2 were subjected to steam treatment and catalytic cracking reaction: the catalyst was treated at 800℃for 17 hours with 100% steam. The catalytic cracking reaction is carried out on the raw oil on a fixed fluidized bed device, the reaction temperature is 650 ℃, the catalyst-to-oil ratio is 15, and the catalyst loading is 60 g. Table 2 shows the results of the performance parameters of the raw oil, and Table 3 shows the catalytic cracking effect of the catalyst.
Table 2 performance parameters of the feedstock.
Figure SMS_2
。
Table 3 catalytic cracking effect of the catalyst.
Figure SMS_3
。
As shown in Table 3, compared with DB-1 and DB-2, the small-grain ZSM-5 catalytic cracking catalyst prepared by the invention has lower attrition index, and has high catalytic cracking conversion rate, greatly improved liquefied gas yield and diene (ethylene+propylene) yield, and excellent catalytic cracking reaction performance due to higher ZSM-5 molecular sieve content, small grain, high MAT micro-reaction activity and good hydrothermal activity stability.
While the foregoing embodiments have been described in some, but not all embodiments of the invention, other embodiments of the invention can be made and still fall within the scope of the invention without undue effort.

Claims (10)

1. The preparation method of the small-grain ZSM-5 catalytic cracking catalyst is characterized by comprising the following steps of:
drying the mixed slurry to obtain microspheres, wherein the mixed slurry contains unmodified clay, acid-pumped clay, an additional silicon source, pre-crystallization liquid and water; the acid extraction clay is prepared by a method comprising the following steps: mixing clay raw materials with an acidic solution after first roasting to obtain the acid-pumped clay;
performing second roasting on the microspheres, and mixing the obtained roasted microspheres with an alkali-containing aqueous solution for hydrothermal crystallization to obtain an in-situ crystallization product;
and carrying out third roasting on the in-situ crystallized product to obtain the small-grain ZSM-5 catalytic cracking catalyst.
2. The method of claim 1, wherein the acidic solution comprises one or more of hydrochloric acid, sulfuric acid, nitric acid, and orthophosphoric acid; the concentration of the acid solution is 0.5-12 mol/L; the weight ratio of the acidic solution to the clay raw material dry basis is 1.5-10:1.
3. The method according to claim 1, wherein the first firing is performed at a temperature of 500 to 950 ℃ for a time of 0.1 to 8 hours.
4. The method of claim 1, wherein the unmodified clay and clay raw materials independently comprise one or more of kaolin, halloysite, diatomaceous earth, bentonite, montmorillonite, attapulgite, pyrophyllite, and perlite.
5. The preparation method according to claim 1, wherein the pre-crystallization liquid is prepared by a method comprising the steps of:
mixing a template agent, an aluminum source and a silicon source, and then performing pre-crystallization to obtain the pre-crystallization liquid;
the temperature of the pre-crystallization is 80-250 ℃ and the time is 2-48 h;
the aluminum source is Al 2 O 3 The silicon source is represented by SiO 2 The molar ratio of the template agent to the aluminum source to the silicon source is 2-20: 1: 20-100.
6. The method of claim 5, wherein the template comprises one or more of tetraethylammonium hydroxide, tetrapropylammonium bromide, triethylamine, diethylamine, and aqueous ammonia.
7. The method of claim 5, wherein the aluminum source comprises one or more of pseudoboehmite, boehmite, sodium metaaluminate, aluminum sulfate, aluminum nitrate, and aluminum chloride.
8. The method of claim 5, wherein the additional silicon source and the silicon source independently comprise one or more of white carbon black, silicone grease, silicone gel, silica sol, and water glass.
9. The preparation method according to claim 1, wherein the mixed slurry comprises the following components in mass fraction on a dry basis: 5-80% of acid-pumped clay, 5-70% of unmodified clay, 5-50% of additional silicon source and 0.5-20% of pre-crystallized liquid; the solid content of the mixed slurry is 25-65wt%.
10. The small-grain ZSM-5 catalytic cracking catalyst obtained by the preparation method of any one of claims 1 to 9, characterized in that the small-grain ZSM-5 catalytic cracking catalyst comprises the following components in mass fraction on a dry basis: 25-85% of ZSM-5 molecular sieve and the balance of amorphous silica-alumina.
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