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CN116371457B - Low-carbon alkane aromatization catalyst and preparation method thereof - Google Patents

Low-carbon alkane aromatization catalyst and preparation method thereof Download PDF

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CN116371457B
CN116371457B CN202310644226.4A CN202310644226A CN116371457B CN 116371457 B CN116371457 B CN 116371457B CN 202310644226 A CN202310644226 A CN 202310644226A CN 116371457 B CN116371457 B CN 116371457B
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clay
crystallization
acid
catalyst
roasting
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CN116371457A (en
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刘从华
赵晓争
许维农
郭玉生
丁兆易
荆惠子
李中付
李蛟
杜庆洋
孙海滨
龚丽华
高兆俊
闫涛
赵楷文
王群斐
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Zibo Baogang Lingzhi Rare Earth High Tech Co ltd
Weifang Zhengxuan Rare Earth Catalytic Materials Co ltd
Shandong University of Technology
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Zibo Baogang Lingzhi Rare Earth High Tech Co ltd
Weifang Zhengxuan Rare Earth Catalytic Materials Co ltd
Shandong University of Technology
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    • 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
    • B01J29/405—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 containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • 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
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
    • B01J35/51—Spheres
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
    • B01J37/0018—Addition of a binding agent or of material, later completely removed among others as result of heat treatment, leaching or washing,(e.g. forming of pores; protective layer, desintegrating by heat)
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
    • 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
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/16—After treatment, characterised by the effect to be obtained to increase the Si/Al ratio; Dealumination
    • 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
    • B01J2229/10—After treatment, characterised by the effect to be obtained
    • B01J2229/20—After treatment, characterised by the effect to be obtained to introduce other elements in the catalyst composition comprising the molecular sieve, but not specially in or on the molecular sieve itself
    • 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

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Catalysts (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

The invention belongs to the technical field of coal chemical industry catalysts, and particularly relates to a low-carbon alkane aromatization catalyst and a preparation method thereof. The invention provides a preparation method of a low-carbon alkane aromatization catalyst, acid-pumped clay and pre-crystallization liquid are added into preparation raw materials, and the catalyst is prepared by an in-situ crystallization molecular sieve technology, so that the prepared low-carbon alkane aromatization catalyst has high content of nano zeolite ZSM-5, and ZSM-5 nano crystal grains have synergistic effect with gallium, thereby greatly improving the conversion rate of alkane and the selectivity of aromatic hydrocarbon and improving the activity stability of the catalyst.

Description

Low-carbon alkane aromatization catalyst and preparation method thereof
Technical Field
The invention belongs to the technical field of coal chemical industry catalysts, and particularly relates to a low-carbon alkane aromatization catalyst and a preparation method thereof.
Background
ZSM-5 zeolite is widely used as a catalyst and an auxiliary agent in petrochemical process due to its unique three-dimensional pore structure and excellent shape selective catalytic function. ZSM-5 zeolite shows excellent activity and selectivity in aromatic synthesis, aromatic isomerization, alkylation, dealkylation, and hydrocarbon catalytic cracking reactions.
Aromatic hydrocarbons are an indispensable basic raw material for the chemical industry, and the conversion of inexpensive low-carbon alkanes into high-added-value benzene, toluene and xylene (BTX) is a long-lasting industrial and research hotspot for decades. The catalyst commonly used for aromatization of low-carbon hydrocarbon can be divided into a metal supported catalyst and a molecular sieve catalyst, wherein the preparation of the functionalized ZSM-5 molecular sieve and the metal modification are important points for the development of the aromatization catalyst.
Chinese patent CN1938245A discloses a Pt/Ga-ZSM-5 molecular sieve catalyst which is suitable for aromatization reaction of C2-C6 alkane, and the aromatization selectivity of propane is only 30-40%; US4175057a discloses a Zn, ga and Cu loaded ZSM-5 zeolite catalyst suitable for aromatization reactions of propane and butane with aromatics selectivity not exceeding 40%.
In the existing catalyst technology of ZSM-5 zeolite molecular sieve applied to arene reaction, two methods are generally adopted to introduce zeolite components into the catalyst, one method is a semisynthesis technology, namely, separately synthesized ZSM-5 zeolite is mixed with a matrix and a binder to prepare slurry, and the slurry is subjected to spray drying or other molding methods, roasting and other steps to prepare the catalyst; another method is an in-situ crystallization technique, in which clay is pulped, sprayed into microspheres or other shapes, and then calcined and hydrothermally crystallized to prepare the ZSM-5 zeolite catalyst.
The development of high-performance aromatization catalyst needs to increase the content of ZSM-5 zeolite, and the consumption of binder needs to be increased in order to ensure the antiwear strength of the catalyst, however, too much binder tends to block the pore channels of the molecular sieve, so that the performance of catalytic reaction is limited. It has been found that the use of nano-sized shape selective molecular sieves can improve the cracking performance of the catalyst. However, in the semisynthesis technology, aggregation phenomenon occurs in the process of post-treatment exchange sodium reduction and roasting of the nano molecular sieve, so that the reaction performance of the nano molecular sieve cannot be fully exerted.
Chinese patent CN1586721a discloses a method for preparing a low-carbon hydrocarbon aromatization catalyst, which uses nano ZSM-5 molecular sieve as a catalyst matrix, and maintains the diffusion smoothness of micropores of the molecular sieve by modification. The aromatization catalyst prepared based on the method has super strong carbon deposition deactivation resistance under the reaction conditions of hydrogen and non-hydrogen, but the aromatic hydrocarbon selectivity needs to be improved; chinese patent CN109622023a discloses a nano HZSM-5 aromatization catalyst containing ZnFePt, and for aromatization reaction of propane, pure modified molecular sieve is used as catalyst, and its aromatic selectivity is only 55.3%; CN103831127a discloses a catalyst for hydroaromatization of four carbon atoms and a preparation method, which is prepared by mixing five-membered ring high silicon zeolite raw powder smaller than 500nm with alumina and ferric trichloride to form, then sequentially carrying out roasting and demoulding, ammonium exchange, roasting, water vapor aging, acid solution washing and roasting treatment, wherein the prepared catalyst has good coking resistance in the mixed low-temperature hydroaromatization reaction of four carbon atoms, has obvious isobutane conversion capability, has a carbon tetraolefin conversion rate of 99.6% under the conditions of 380 ℃ and 3MPa, contains more than five carbon atoms in the product as 54.2%, has an arene content of 59.7% in gasoline, and has weaker aromatization capability on alkane; chinese patent CN101462741a discloses a method for preparing ZSM-5 molecular sieve by in situ crystallization, which adds silicon-rich clay with silicon-aluminum molar ratio greater than 2 into kaolin slurry, thereby reducing the roasting temperature of clay microsphere, improving the ZSM-5 content of crystallized product, but the crystal grain of the in situ crystallized molecular sieve is larger, in addition, in order to improve the silicon-aluminum ratio of roasted clay microsphere, the invention preferably performs acid extraction treatment, thus the extracted active aluminum is wasted due to filtration, resulting in poor wear resistance of crystallized microsphere, and being difficult to meet the requirement of industrial catalytic device high-speed fluidization process on microsphere catalyst strength; CN101332995a discloses a method for in-situ crystallization of ZSM-5 molecular sieve with modified kaolin microspheres. The method is technically characterized in that kaolin and a modified component are mixed, spray-formed, kaolin microspheres are mixed with an external silicon-aluminum source, a template agent, seed crystals and water after being roasted at high temperature, and the kaolin-based ZSM-5 molecular sieve is synthesized through hydrothermal crystallization, wherein the relative crystallinity is 30-80%.
As can be seen from the above document data, the research and development of the low-carbon alkane aromatization catalyst is focused on modifying various functionalized ZSM-5 molecular sieves with metals such as Ga, zn, pt and the like, and mainly adopts the steps of synthesizing and modifying micro-or nano-ZSM-5 molecular sieves, and then mixing the synthesized micro-or nano-ZSM-5 molecular sieves with a matrix, a binder and the like to prepare the catalyst. The problems of low aromatic hydrocarbon selectivity and poor thermal stability are commonly caused by the negative effects of molecular sieve particle agglomeration and blocking of pore channels by binders caused by post-treatment.
Disclosure of Invention
In view of the above, the present invention aims to provide a low-carbon alkane aromatization catalyst and a preparation method thereof. The low-carbon alkane aromatization catalyst prepared by the preparation method has high content of nano ZSM-5 zeolite, and ZSM-5 nano grains and gallium have synergistic effect, so that the conversion rate of alkane and the selectivity of aromatic hydrocarbon can be greatly improved, and the activity stability of the catalyst is improved.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a low-carbon alkane aromatization 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, an alkali-containing aqueous solution and a first template agent for hydrothermal crystallization to obtain an in-situ crystallization product;
and mixing the in-situ crystallization product with a gallium compound, and then performing third roasting to obtain the low-carbon alkane aromatization 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 second template agent, an aluminum source, a silicon source and an alkaline substance, 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 And the molar ratio of the second template agent to the aluminum source to the silicon source to the alkaline substance is 2-20:1:20-100:1-20.
Preferably, the first and second templates independently comprise 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 25-65%.
The invention also provides a low-carbon alkane aromatization catalyst obtained by the preparation method, which comprises the following components in percentage by mass in terms of dry basis: 45-95% of nano ZSM-5 zeolite and 0.1-3% of Ga 2 O 3 And the balance amorphous silica alumina.
Compared with the prior art, the invention has the following beneficial effects:
the invention provides a preparation method of a low-carbon alkane aromatization catalyst (Ga/ZSM-5 catalyst), which is characterized in that acid-pumped clay and pre-crystallization liquid are added into a preparation raw material, and the catalyst is prepared 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; in the process of acid extraction of clay, the residual silicon oxide is activated in advance, which is favorable for subsequent in-situ growth of molecular sieve, and the prepared nano Ga/ZSM-5 catalyst has high ZSM-5 zeolite contentDeveloped mesopores and synergistic effect of in-situ crystallization nano ZSM-5 and gallium, and greatly improves the conversion rate of alkane and the selectivity of aromatic hydrocarbon. Meanwhile, since the molecular sieve ZSM-5 and the carrier (comprising Ga 2 O 3 And amorphous silica alumina) are tightly combined with similar chemical bonds, thus enhancing the activity stability and the service life of the catalyst.
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 the low-carbon alkane aromatization catalyst prepared by the preparation method, which has high crystallinity up to 80%; the grain size is fine, and the molecular sieve grain size is 100-200 nm. The catalyst of the invention is used for aromatization reaction of propane, can fully exert the reaction performance of the catalyst, has the remarkable characteristics of high alkane conversion rate and high aromatic hydrocarbon selectivity, and the example data show that the propane conversion rate reaches 70.3 percent and the aromatic hydrocarbon selectivity reaches 80.2 percent.
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 prepared in example 3.
FIGS. 2 and 3 are SEM pictures of the CY-1 prepared in example 3 at different magnifications.
Detailed Description
The invention provides a preparation method of a low-carbon alkane aromatization 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, an alkali-containing aqueous solution and a first template agent for hydrothermal crystallization to obtain an in-situ crystallization product;
And mixing the in-situ crystallization product with a gallium compound, and then performing third roasting to obtain the low-carbon alkane aromatization 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 further comprises adding ammonia water to adjust the pH value of the acid-pumped clay solution obtained by mixing, wherein the pH value of the acid-pumped clay solution is preferably 2-6; 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 ℃.
In the present invention, the slurry obtained after mixing with the acidic solution preferably has an average particle diameter of 0.3 to 25 μm, more preferably 0.5 to 20 μm.
The invention performs acid extraction treatment on clay raw materials, and can extract alumina and impurities from the clay framework, thereby improving the SiO framework 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 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 a method comprising the steps of:
mixing a second template agent, an aluminum source, a silicon source and an alkaline substance, 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 second template agent to the aluminum source to the silicon source to the alkaline substance is preferably 2-20:1:20-100:1-20.
In the invention, the second 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 and TPAOH in the mixture of TPABr and TPAOH is preferably 80-170:25-100.
In the present invention, the alkaline substance preferably includes sodium hydroxide or n-butylamine.
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.
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 65%, 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, an alkali-containing aqueous solution and a first template agent 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 to 8 hours, more preferably 1 to 6 hours, and the effect of the second roasting is to ensure 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 invention, the alkali-containing aqueous solution preferably comprises 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, the alkali-containing aqueous solution and the first template agent 2 With OH - The molar ratio of (2) is preferably 1:0.05-0.4, and proper alkalinity of the crystallization system is ensured.
In the present invention, the types included in the first template are preferably the same as the types included in the second template, and will not be described herein.
In the invention, the active SiO in the mixed solution obtained by mixing the calcined microsphere, the aqueous solution containing alkali and the first template agent 2 The molar ratio of the first template agent to the first template agent is preferably 1:0.005-1.0.
In the invention, the temperature of the hydrothermal crystallization is preferably 100-250 ℃, more preferably 120-220 ℃, and the temperature of the hydrothermal crystallization is suitable for molecular sieve growth; the time is preferably 5 to 40 hours, more preferably 8 to 35 hours. 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 and the gallium compound are mixed and then subjected to third roasting, so that the low-carbon alkane aromatization catalyst is obtained.
In the present invention, the gallium compound preferably includes one or more of gallium nitrate, gallium chloride and gallium sulfate.
In the present invention, the in-situ crystallization product, the gallium compound, and the method preferably further comprise the following steps before mixing: and after uniformly mixing the in-situ crystallization product, ammonium salt and water, stirring, filtering and washing sequentially, wherein the stirring temperature is preferably 65-85 ℃, 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.
In the present invention, the ammonium salt functions to exchange and reduce sodium oxide.
In the invention, the mass ratio of the ammonium salt to the in-situ crystallization product is preferably 0.05-0.30 in terms of dry basis: 1.
In the present invention, the mixing of the in-situ crystallized product and the gallium compound preferably further comprises adding water to uniformly mix the components, and the drying is preferably further included before the third firing.
In the present invention, the gallium compound is Ga in dry basis 2 O 3 The weight ratio of the in-situ crystallization product to the gallium compound is preferably 1:0.001 to 0.04.
In the invention, the temperature of the third roasting is preferably 500-1200 ℃, more preferably 550-1100 ℃, and the time is preferably 0.5-8 h, more preferably 1-6 h, and the effect of the third roasting is to activate the modified metal element.
The invention also provides a low-carbon alkane aromatization catalyst obtained by the preparation method, which comprises the following components in percentage by mass in terms of dry basis: 45-95% of nano ZSM-5 zeolite and 0.1-3% of Ga 2 O 3 And the balance amorphous silica alumina.
In the invention, the mass fraction of the nano ZSM-5 zeolite in the low-carbon alkane aromatization catalyst is preferably 70-90% based on dry basis, and the nano ZSM-5 zeolite in the low-carbon alkane aromatization catalyst has high content and good wear resistance.
In the present invention, ga in the lower alkane aromatization catalyst is calculated on a dry basis 2 O 3 The mass fraction of (2) is preferably 0.15-0.25%.
In the invention, the crystallinity of the low-carbon alkane aromatization catalyst is preferably 50-95%.
In the invention, the grain size of the low-carbon alkane aromatization catalyst is preferably 100-400 nm.
The low-carbon alkane aromatization catalyst has high crystallinity and fine crystal grains, can fully exert the reaction performance of the catalyst when being applied to low-carbon alkane aromatization reaction, and has the remarkable characteristics of high alkane conversion rate and high arene selectivity.
In the present invention, the lower alkane aromatization reaction is preferably an aromatization reaction of propane.
In the invention, the aromatization reaction of the light alkane is preferably carried out on a fixed fluidized bed device, the reaction temperature is preferably 530 ℃ and the normal pressure, and the feeding mass space velocity (WHSV) is preferably 0.8h -1 The product is preferably subjected to gas-liquid separation by a condenser and then subjected to gas phase detection.
For further explanation of the present invention, the low carbon alkane aromatization catalyst of the present invention and the process for preparing the same are described in detail below with reference to the accompanying drawings and examples, which 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%; SB powder, solid content 75%; aluminum nitrate, chemically pure; sodium hydroxide, solids; sodium bicarbonate, solid; potassium hydroxide, solid.
6) Ammonium chloride; ammonium sulfate; ammonium nitrate; ammonium phosphate; ammonium dihydrogen phosphate.
7) Gallium nitrate (Ga (NO) 3 ) 3 ) Gallium chloride (GaCl) 3 ) Are all chemically pure.
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 #: 2000 g of kaolin is roasted in a muffle furnace at 650 ℃ for 5 hours, the mass content of the active alumina is measured to be 12.5%, the active alumina is cooled and then placed in a stainless steel reaction kettle, 3M hydrochloric acid is added for 6L, the mixture is stirred uniformly, the temperature is raised to 80 ℃, the mixture is stirred at constant temperature for 1 hour, the mixture is cooled to be lower than 50 ℃, and then concentrated ammonia water is added for 0.4L, so that the 1# acid extraction clay (pH value is 2) is obtained.
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 to obtain active alumina with the mass content of 18.7%, cooling, placing in a stainless steel reaction kettle, adding 4.5L of 4M nitric acid, uniformly stirring, heating to 70 ℃, stirring at constant temperature for 2 hours, cooling to below 50 ℃, adding 0.6L of concentrated ammonia water, and stirring for 0.5 hour to obtain 2# acid suction clay (pH value is 3).
3# acid extraction clay: and (3) roasting 1000 g of kaolin and 1000 g of halloysite in a muffle furnace at 850 ℃ for 1.5 hours, wherein the mass content of the measured active alumina is 25.5%, cooling, placing in a stainless steel reaction kettle, adding 4L of 2M sulfuric acid, uniformly stirring, heating to 60 ℃, and stirring at constant temperature for 3 hours to obtain the 3# acid extraction clay (the pH value is smaller than 1).
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, stirring is continued vigorously for 2 hours, the mixture is transferred into a high-pressure crystallization kettle, the temperature is raised to 160 ℃ for 15 hours, and the 2# pre-crystallization liquid is obtained after crystallization.
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 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 3-9 and comparative examples 1-2.
。
Example 3
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of clay, kaolin, diatomite, silica sol, 1# pre-crystallization liquid and a proper amount of deionized water are added into a gel forming tank to be mixed and homogenized, so that the solid content of the slurry is 45%, and the slurry is spray-dried to obtain clay microspheres with 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 mass content of (2) was 65%. 1000g of calcined microsphere, 3000g of deionized water, 80g of sodium hydroxide and 100g of tetrapropylammonium bromide are taken and stirred for 0.5 hour. Transferring the mixture into a stainless steel reaction kettle with polytetrafluoroethylene lining, heating to 180 ℃ for 2 hours, crystallizing at constant temperature for 24 hours, filtering, washing with water, and drying to obtain crystallized products.
3. Post-treatment of crystallization products: mixing 500g of crystallization product, 52g of ammonium chloride and 5000g of water uniformly, stirring at 80 ℃ for 1 hour, filtering, washing, adding a mixture consisting of 7 g of gallium nitrate and 50 g of water into a filter cake, stirring uniformly, drying, roasting at 550 ℃ for 3 hours to obtain a CY-1 catalyst product, and measuring that the ZSM-5 zeolite mass content in the product is 81 percent, ga 2 O 3 The content was 0.51wt% and the microreactor was 50.
Example 4
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of clay, diatomaceous earth, montmorillonite, silica sol, 2# pre-crystallization liquid and a proper amount of deionized water were added to a colloid forming tank and mixed and homogenized so that the solid content of the slurry was 40%, and the slurry was spray-dried to obtain clay microspheres with 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 mass content of (2) was 61%. 1000g of calcined microsphere, 2500g of deionized water, 700g of sodium metaaluminate solution and 60g of tetrapropylammonium bromide are taken and stirred for 1 hour. Transferring the mixture into polytetrafluoroethylene-lined stainless steel And heating to 170 ℃ in the reaction kettle, crystallizing for 28 hours at constant temperature, filtering, washing with water, and drying to obtain a crystallized product.
3. Post-treatment of crystallization products: mixing 500g of crystallization product, 41g of ammonium nitrate and 6000g of water uniformly, stirring at 75 ℃ for 1.5 hours, filtering, washing, adding a mixture consisting of 4 g of gallium nitrate and 40 g of water into a filter cake, stirring uniformly, drying, roasting at 550 ℃ for 3 hours to obtain a CY-2 catalyst product, wherein the ZSM-5 zeolite content in the product is 79% and Ga is measured 2 O 3 The content was 0.29wt% and the microreactor was 47.
Example 5
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of clay, kaolin, diatomite, silica sol, no. 1 pre-crystallization liquid and a proper amount of deionized water are added into a gel forming tank to be mixed and homogenized, so that the solid content of the slurry is 42%, and the slurry is spray-dried to obtain clay microspheres with an average particle diameter of 66 μm. 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 mass content of (2) was 68%. 1000g of calcined microsphere, 3200g of deionized water, 85g of sodium hydroxide and 150g of triethylamine 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.
3. Post-treatment of crystallization products: mixing 500g of crystallization product, 42g of ammonium chloride and 7000g of water uniformly, stirring for 1.5 hours at 65 ℃, filtering, washing, adding a mixture of 6.4 g of gallium chloride and 50g of water into a filter cake, stirring uniformly, drying, roasting at 550 ℃ for 3 hours to obtain a CY-3 catalyst product, wherein the ZSM-5 zeolite content in the product is 83% by mass, ga 2 O 3 The content was 0.68wt% and the microreactor was 48.
Example 6
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of clay, diatomaceous earth, montmorillonite, silica sol, 2# pre-crystallization liquid and a proper amount of deionized water were added to a colloid forming tank and mixed and homogenized so that the solid content of the slurry was 46%, and the slurry was spray-dried to obtain clay microspheres with 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 990 ℃ for 2 hours to obtain the active SiO in the roasted microsphere 2 The mass content of (2) was 63%. 1000g of calcined microsphere, 2300g of deionized water, 850g of sodium metaaluminate solution, 80g of triethylamine and stirring 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.
3. Post-treatment of crystallization products: mixing 500g crystallization product, 59g ammonium chloride and 4500g water uniformly, stirring at 65 ℃ for 1.2 hours, filtering, washing, adding a mixture of 5 g gallium chloride and 40 g water into a filter cake, drying, roasting at 550 ℃ for 3 hours to obtain CY-4 catalyst product, wherein the ZSM-5 zeolite content is 79% by mass, ga 2 O 3 The content was 0.53wt% and the microreactor was 49.
Example 7
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of clay, diatomaceous earth, water glass, silica sol, no. 1 pre-crystallization liquid and a proper amount of deionized water were added to a gel forming tank and mixed and homogenized so that the solid content of the slurry was 48%, and the slurry was spray-dried to obtain clay microspheres with an average particle diameter of 60. 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 1020 ℃ for 1.5 hours to obtain the active SiO in the roasted microsphere 2 The mass content of (2) was 69%. 1000g of calcined microsphere, 3100g of deionized water, 69g of sodium hydroxide, 150g of tetrapropylammonium hydroxide and stirring for 1.2 hours. Transferring the mixture into polytetrafluoroethylene-lined stainless steel And heating to 175 ℃ in the reaction kettle, crystallizing for 20 hours at constant temperature, filtering, washing with water, and drying to obtain a crystallized product.
3. Post-treatment of crystallization products: mixing 500g of crystallized product, 55 ammonium phosphate and 5500g of water uniformly, stirring at 85 ℃ for 1 hour, filtering, washing, adding a mixture consisting of 20 g of gallium nitrate and 60 g of water into a filter cake, stirring uniformly, drying, roasting at 550 ℃ for 3 hours to obtain a CY-5 catalyst product, and measuring that the ZSM-5 zeolite content in the product is 84% and Ga 2 O 3 The content was 1.5wt% and the microreactor was 51.
Example 8
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of clay, diatomaceous earth, montmorillonite, silica sol, 3# pre-crystallization liquid and a proper amount of deionized water were added to a colloid forming tank and mixed and homogenized so that the solid content of the slurry was 43%, and the slurry was spray-dried to obtain clay microspheres with an average particle diameter of 58. 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 930 ℃ for 3 hours to obtain the active SiO in the roasted microsphere 2 The mass content of (2) was 61%. 1000g of calcined microsphere, 2800g of deionized water, 750g of sodium metaaluminate solution, 100g of tetrapropylammonium 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.
3. Post-treatment of crystallization products: mixing 500g of crystallization product, 54g of ammonium nitrate and 5500g of water uniformly, stirring at 70 ℃ for 0.8 hour, filtering, washing, adding a mixture consisting of 4g of gallium chloride and 40 g of water into a filter cake, stirring uniformly, drying, roasting at 550 ℃ for 3 hours to obtain a CY-6 catalyst product, wherein the ZSM-5 zeolite content in the product is 78% by mass, ga 2 O 3 The content was 0.42wt% and the microreactor was 47.
Example 9
1. Preparation of microspheres: according to the composition shown in Table 1, 2000g of clay, halloysite, diatomite, silica sol, 1# pre-crystallization liquid and a proper amount of deionized water are added into a gel forming tank to be mixed and homogenized, so that the solid content of the slurry is 41%, and the slurry is spray-dried 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 mass content of (2) was 67%. 1000g of calcined microsphere, 2500g of deionized water, 950g of sodium metaaluminate solution, 60g of tetrapropylammonium 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.
3. Post-treatment of crystallization products: mixing 500g of crystallization product, 61g of ammonium nitrate and 6000g of water uniformly, stirring at 70 ℃ for 1.5 hours, filtering, washing, adding a mixture consisting of 5 g of gallium nitrate and 50 g of water into a filter cake, stirring uniformly, drying, roasting at 550 ℃ for 3 hours to obtain a CY-7 catalyst product, wherein the ZSM-5 zeolite content in the product is 77% by mass, ga 2 O 3 The content was 0.37wt% and the microreactor was 46.
Comparative example 1
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 gel forming tank for mixing and homogenizing, so that the solid content of the slurry is 46%, 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 mass content of (2) was 41.5%, and the mass content of activated alumina was 5.1%. Adding 1000g of calcined microsphere and 4370g of deionized water into a reactor, uniformly mixing, stirring for 5 minutes at 90 ℃, then adding 3700g of water glass, stirring for 20 hours, then adding 4370g of deionized water, stirring for 10 minutes, and slowly adding 1200g of 3M sulfuric acid solution into the system The system alkalinity is regulated by the liquid, 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 roasting crystallization product with 2500g of 0.5mol/L ammonium chloride solution uniformly, stirring for 1 hour at 90 ℃, and repeating exchange twice. After filtration, a mixture of 6g of gallium nitrate and 50 g of water was added to the filter cake, stirred uniformly, dried at 120℃and calcined at 540℃for 4 hours to obtain a DB-1 catalyst sample. The mass content of ZSM-5 zeolite in the sample was found to be 41% and Ga 2 O 3 The content was 0.44wt% and the microreactor was 37.
Comparative example 2
(1) Weighing 0.3279g of sodium metaaluminate, placing the sodium metaaluminate into a beaker, adding 38.75g of deionized water, 20.336 g of tetrapropylammonium hydroxide aqueous solution with mass fraction of 25% and 0.1g of sodium hydroxide, stirring until the solution is clear, slowly dripping 20.833g of tetraethyl orthosilicate, stirring for 12 hours, transferring the solution into a hydrothermal reaction kettle, crystallizing at 170 ℃ for 4 days, centrifuging to remove mother liquor, washing the mother liquor with deionized water until the solution becomes neutral, drying overnight at 100 ℃, and roasting at 600 ℃ for 10 hours to obtain a ZSM-5 molecular sieve matrix;
(2) Grinding the prepared ZSM-5 molecular sieve matrix into powder, weighing 1g of ZSM-5 molecular sieve matrix (0.4 g containing silicon is measured), 0.01g of sodium hydroxide and 0.002g of sodium metaaluminate, dispersing in 5mL of water and 3mL of 1mol/L tetrapropylammonium hydroxide solution, stirring for 10 minutes, transferring into a hydrothermal reaction kettle, carrying out hydrothermal treatment at 170 ℃ for 1 day, centrifuging to remove mother liquor, washing the mother liquor with deionized water to be neutral, drying overnight at 100 ℃, and roasting at 600 ℃ for 6 hours to obtain the ZSM-5 molecular sieve with a macroporous and microporous structure;
(3) Treating the ZSM-5 molecular sieve with the macroporous and microporous structures with 0.005-0.5 mol/L sodium carbonate solution at 60-65 ℃ for 6 hours, centrifuging to remove mother liquor, washing with deionized water to neutrality, and drying overnight at 100 ℃ to obtain the ZSM-5 molecular sieve with multistage holes;
(4) Ion-exchanging with 1mol/L ammonium nitrate solution at 80 ℃ for two times, each time for 4 hours, centrifuging to remove mother liquor, washing with deionized water for 3 times, drying overnight at 100 ℃, and roasting at 550 ℃ for 6 hours to obtain a modified ZSM-5 molecular sieve;
(5) Exchanging the obtained modified ZSM-5 molecular sieve with a gallium nitrate solution, wherein gallium accounts for 0.5% of the mass of the modified ZSM-5 molecular sieve, drying overnight at 100 ℃, and roasting at 550 ℃ for 4 hours to obtain the modified Ga/ZSM-5 molecular sieve;
(6) 14g of the modified Ga/ZSM-5 molecular sieve is mixed with 6gSB powder, and the mixture is molded, dried and roasted for 6 hours at 550 ℃ in sequence to obtain the aromatization catalyst DB-2.
FIG. 1 is an XRD spectrum of CY-1 obtained in example 3, with CY-1 having a relative crystallinity of 81%.
FIGS. 2 and 3 are SEM photographs of the CY-1 prepared in example 3 at different magnifications, and it can be seen that the molecular sieve grains are 100-200 nm.
The relative crystallinity of DB-1 obtained in comparative example 1 was tested and found to be 41%.
The molecular sieve grains of DB-1 prepared in comparative example 1 were tested, resulting in 300-800 nm.
Compared with the in-situ crystallization product of the comparative example, the SEM of the sample of the invention has smooth appearance, presents nano-cluster particles, has high XRD diffraction intensity and complete crystallization; the in-situ crystallized ZSM-5 product of the invention has obvious difference from the comparative sample.
Example 10
The catalysts CY-1-7 and the catalysts DB-1 and DB-2 of the comparative examples are used for aromatization reaction of propane, and the reaction temperature is 530 ℃ and the normal pressure are carried out on a fixed fluidized bed device, and the feeding mass space velocity (WHSV) is 0.8h -1 The product was subjected to gas-liquid separation by a condenser and analyzed on a Shimadzu gas chromatograph, and the experimental data obtained are shown in Table 2.
Table 2 aromatization reaction data for propane.
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As shown in Table 2, compared with the contrast agents DB-1 and DB-2, the low-carbon alkane aromatization catalyst provided by the invention grows high-zeolite nanometer ZSM-5 in situ, and the synergistic effect of ZSM-5 nanometer grains and Ga modification greatly improves the aromatization capability of the low-carbon alkane and the selectivity of aromatic hydrocarbon products. Thus, the catalyst of the present invention shows higher propane conversion and aromatics selectivity.
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 (7)

1. The preparation method of the low-carbon alkane aromatization 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;
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;
the pre-crystallization liquid is prepared by a method comprising the following steps:
mixing a second template agent, an aluminum source, a silicon source and an alkaline substance, 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 second template agent to the aluminum source to the silicon source to the alkaline substance is as follows2~20:1:20~100:1~20；
The mixed slurry comprises the following components in percentage by mass 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 25-65%;
performing second roasting on the microspheres, and mixing the obtained roasted microspheres, an alkali-containing aqueous solution and a first template agent for hydrothermal crystallization to obtain an in-situ crystallization product;
and mixing the in-situ crystallization product with a gallium compound, and then performing third roasting to obtain the low-carbon alkane aromatization catalyst.
2. 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.
3. 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.
4. The method of preparing according to claim 1, wherein the first and second templates independently comprise one or more of tetraethylammonium hydroxide, tetrapropylammonium bromide, triethylamine, diethylamine, and aqueous ammonia.
5. The method of claim 1, wherein the aluminum source comprises one or more of pseudoboehmite, boehmite, sodium metaaluminate, aluminum sulfate, aluminum nitrate, and aluminum chloride.
6. The method of claim 1, 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.
7. The low-carbon alkane aromatization catalyst obtained by the preparation method of any one of claims 1 to 6, which is characterized by comprising the following components in percentage by mass on a dry basis: 45-95% of nano ZSM-5 zeolite and 0.1-3% of Ga 2 O 3 And the balance amorphous silica alumina.
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CN101618337A (en) * 2009-08-03 2010-01-06 大连理工大学 Method for improving catalytic property of methane aromatization catalyst
CN106215973A (en) * 2016-08-12 2016-12-14 清华大学 A kind of modified ZSM-5 5 molecular sieve catalyst method of preparation and use
CN115805099A (en) * 2023-02-17 2023-03-17 河北鑫鹏新材料科技有限公司 Auxiliary agent for maximizing propylene octane number and preparation method thereof
CN115872415A (en) * 2023-02-17 2023-03-31 河北鑫鹏新材料科技有限公司 Nano ZSM-5 molecular sieve and preparation method thereof

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JPH01103916A (en) * 1987-07-15 1989-04-21 Res Assoc Util Of Light Oil Production of crystalline galloaluminosilicate and production of aromatic hydrocarbon
US5202513A (en) * 1987-07-15 1993-04-13 Research Association For Utilization Of Light Oil Process for producing aromatic hydrocarbons
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CN115805099A (en) * 2023-02-17 2023-03-17 河北鑫鹏新材料科技有限公司 Auxiliary agent for maximizing propylene octane number and preparation method thereof
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