CN116062770A - ZSM-5 molecular sieve with aluminum-enriched surface, and preparation method and application thereof - Google Patents

ZSM-5 molecular sieve with aluminum-enriched surface, and preparation method and application thereof Download PDF

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CN116062770A
CN116062770A CN202111302199.XA CN202111302199A CN116062770A CN 116062770 A CN116062770 A CN 116062770A CN 202111302199 A CN202111302199 A CN 202111302199A CN 116062770 A CN116062770 A CN 116062770A
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aluminum
molecular sieve
zsm
alkali metal
hours
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韩蕾
王鹏
宋海涛
王若瑜
周翔
王丽霞
彭博
赵留周
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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Sinopec Research Institute of Petroleum Processing
China Petroleum and Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • C01B39/36—Pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
    • C01B39/38—Type ZSM-5
    • C01B39/40—Type ZSM-5 using at least one organic template directing agent
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/60—Compounds characterised by their crystallite size
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • 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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  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
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  • General Life Sciences & Earth Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Inorganic Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Silicates, Zeolites, And Molecular Sieves (AREA)

Abstract

The invention relates to a ZSM-5 molecular sieve with aluminum-enriched surface, a preparation method and application thereof, wherein the ZSM-5 molecular sieve is a flat-like cylinder, the average grain size of the ZSM-5 molecular sieve is 0.2-3.0 mu m, the ratio of the bulk phase silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio is 1.2-5.0, and the relative crystallinity is 80-110%. The ZSM-5 molecular sieve of the invention has the advantages of rich aluminum on the outer surface and better catalytic activity.

Description

ZSM-5 molecular sieve with aluminum-enriched surface, and preparation method and application thereof
Technical Field
The invention relates to a ZSM-5 molecular sieve with an aluminum-rich surface, and a preparation method and application thereof.
Background
The ZSM-5 molecular sieve has crystal structure of orthorhombic crystal system, two-dimensional ten-membered ring channel formed by connecting silicon (aluminum) oxygen tetrahedron through oxygen bridge bond, and its basic structural unit is composed of eight five-membered rings. The pore structure is composed of elliptic straight pore (pore size of 0.54nm×0.56 nm) and approximately circular Z-shaped pore (pore size of 0.52nm×0.58 nm). Its channels, i.e. its cavities, do not have a cage similar to the type a, type X and type Y zeolites. The ZSM-5 molecular sieve has a stable framework structure, adjustable aperture, higher specific surface, better shape selectivity and good water and heat stability, so that the ZSM-5 molecular sieve has wide application value in the fields of adsorption, separation, shape selective catalysis and the like. In the synthesis process, the Al distribution, morphology and pore canal structure can be regulated and controlled to effectively improve the catalytic performance, wherein the Al distribution is an important factor influencing the catalytic activity of the molecular sieve. ZSM-5 molecular sieve pore structure belongs to microporous structure, and for larger reactant molecules, diffusion limitation exists, so that accessibility of active center is reduced.
Disclosure of Invention
The invention aims to provide a ZSM-5 molecular sieve with aluminum-enriched surface, a preparation method and application thereof, and the ZSM-5 molecular sieve has aluminum-enriched surface, and can improve the conversion rate and the target product yield when being used for hydrocarbon catalytic cracking reaction.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a surface aluminum-enriched ZSM-5 molecular sieve, the ZSM-5 molecular sieve being a flat-like cylinder, the ZSM-5 molecular sieve having an average crystal grain size of 0.2 to 3.0 μm, a ratio of a bulk phase silicon to aluminum molar ratio to a surface silicon to aluminum molar ratio of 1.2 to 5.0, and a relative crystallinity of 80 to 110%.
Optionally, the ratio of the bulk to surface silica to alumina mole ratio of the ZSM-5 molecular sieve is 1.2 to 4.0.
Alternatively, the ZSM-5 molecular sieve has a relative crystallinity of from 85 to 100% and an average crystallite size of from 0.4 to 2. Mu.m.
Optionally, the ZSM-5 molecular sieve has an average height of 0.2 to 1.0 μm and an average aspect ratio of 1: (2-10).
In a second aspect, the present invention provides a process for preparing the surface aluminum enriched ZSM-5 molecular sieve as provided in the first aspect of the present invention, the process comprising:
(1) Mixing the first template agent, the first silicon source and the first solvent for 0.5-3.0 hours at the temperature of 30-50 ℃ to obtain a first mixed product;
(2) Mixing the first alkali metal hydroxide, the first aluminum source and the second solvent for 0.5-2.0 hours at 20-80 ℃ to obtain a second mixed product;
(3) Mixing the first mixed product and the second mixed product, then carrying out dynamic crystallization, taking out the obtained solid, and carrying out first roasting; or alternatively, the process may be performed,
the method comprises the following steps:
s1, mixing a second template agent, a second silicon source and a third solvent for 0.5-3.0 hours at the temperature of 30-50 ℃, and performing first hydrothermal treatment and second hydrothermal treatment on the obtained third mixed product in sequence to obtain a fourth mixed product; wherein the conditions of the first hydrothermal treatment include: the temperature is 80-120 ℃ and the time is 1-6 hours; the conditions of the second hydrothermal treatment include: the temperature is 160-180 ℃ and the time is 12-60 hours;
s2, mixing the second alkali metal hydroxide, the second aluminum source and the fourth solvent for 0.5-2.0 hours at 20-80 ℃ to obtain a fifth mixed product;
and S3, mixing the fourth mixed product and the fifth mixed product, performing third hydrothermal treatment on the obtained mixture, taking out the obtained solid, and performing second roasting.
Optionally, the first silicon source is selected from one or more of methyl orthosilicate and ethyl orthosilicate;
the second silicon source is selected from one or more of silica sol, water glass and solid silica gel;
the first template agent and the second template agent are respectively and independently selected from one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine and hexamethylenediamine;
the first aluminum source and the second aluminum source are respectively and independently selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum isopropoxide and aluminum sol;
the first alkali metal hydroxide and the second alkali metal hydroxide are respectively and independently selected from one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide.
Optionally, the molar ratio of the total amount of the first template, the first solvent, and the second solvent, the amount of the first alkali metal hydroxide, and the amount of the first silicon source is (0.06-0.55): (10-110): (0.02-1.5): 1, a step of; the molar ratio of the first silicon source to the first aluminum source is (20-500): 1, a step of; wherein the first silicon source is SiO 2 The first alkali metal hydroxide is calculated as alkali metal oxide, and the first aluminum source is calculated as Al 2 O 3 Counting;
the molar ratio of the total amount of the second template, the third solvent and the fourth solvent, the amount of the second alkali metal hydroxide and the amount of the second silicon source is (0.06-0.55): (10-100): (0.02-1.5): 1, a step of; the molar ratio of the second silicon source to the second aluminum source is (20-500): 1, a step of; wherein the second silicon source is SiO 2 The second alkali metal hydroxide is calculated as alkali metal oxide, and the second aluminum source is calculated as Al 2 O 3 And (5) counting.
Optionally, in step (2), the first alkali metal hydroxide, the second solvent and the first aluminum source are used in a molar ratio of (1.5-5): (60-500): 1, a step of;
in step S2, the molar ratio of the amounts of the second alkali metal hydroxide, the fourth solvent and the second aluminum source is (1.5-5): (60-500): 1.
optionally, the conditions of the dynamic crystallization include: the temperature is 160-180 ℃ and the time is 12-60 hours;
the conditions of the third hydrothermal treatment include: 160-180 ℃ for 12-60 hours;
the conditions of the first firing and the second firing each independently include: the temperature is 400-600 ℃ and the time is 2-6 hours.
The third aspect of the invention provides an application of the ZSM-5 molecular sieve with the aluminum-enriched surface provided by the first aspect of the invention in petrochemical industry and/or fine chemical industry.
The ZSM-5 molecular sieve has the characteristic of rich aluminum on the outer surface, aluminum is mainly distributed on the outer surface of the molecular sieve, accessibility of active sites of the molecular sieve can be improved, catalytic conversion of macromolecular reactants is promoted, conversion rate and target product yield are improved, modification efficiency of a subsequent metal or nonmetal modification process of the molecular sieve is improved, and the molecular sieve can be applied to the fields of petrochemical industry, fine chemical industry and the like, and has good industrial application value especially for hydrocarbon catalytic cracking reaction.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate the invention and together with the description serve to explain, without limitation, the invention. In the drawings:
FIG. 1 is an SEM photograph of ZSM-5 molecular sieve prepared in example 1 of the invention;
FIG. 2 is an SEM photograph of ZSM-5 molecular sieve prepared in example 2 of the invention;
FIG. 3 is an SEM photograph of ZSM-5 molecular sieve prepared according to example 3 of the invention;
FIG. 4 is an SEM photograph of ZSM-5 molecular sieve prepared according to example 4 of the invention.
Detailed Description
The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The ZSM-5 molecular sieve with the aluminum-enriched surface is a flat-like cylinder, the average grain size of the ZSM-5 molecular sieve is 0.2-3.0 mu m, the ratio of the bulk phase silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio is 1.2-5.0, and the relative crystallinity is 80-110%.
The ZSM-5 molecular sieve of the invention contains aluminum which is mainly distributed on the outer surface of the molecular sieve, improves the accessibility of active sites of the molecular sieve, and increases the collision probability of reactant molecules and active centers of a molecular sieve catalyst, thereby effectively improving the catalytic performance of the molecular sieve, being beneficial to improving the modification efficiency of the subsequent metal or nonmetal modification process of the molecular sieve, being applicable to the fields of petrochemical industry, fine chemical industry and the like, and having good industrial application value. In the invention, the oblate-like cylinder is a cylinder with a smaller height and diameter, is similar to a moon cake shape, and the radial section of the oblate-like cylinder can be circular, elliptic and the like.
In one embodiment of the present invention, the ratio of the bulk to surface silica to alumina mole ratio of the ZSM-5 molecular sieve may vary over a wide range, preferably from 1.2 to 4, more preferably from 1.2 to 2. Wherein the bulk silicon to aluminum ratio is determined by the XRF method and the surface silicon to aluminum ratio is determined by the XPS method, the specific test methods are well known to those skilled in the art and will not be described in detail herein.
In one embodiment of the invention, the ZSM-5 molecular sieve has a relative crystallinity of from 85 to 100% and an average crystallite size of from 0.4 to 2. Mu.m, preferably from 0.6 to 2.0. Mu.m. In the invention, the crystallinity of the molecular sieve sample is detected by adopting an X-ray diffraction method. The relative crystallinity of the molecular sieve is based on XRD standard sample ZSM-5 molecular sieve standard sample of China institute of petrochemical industry, and the crystallinity of the standard sample is regarded as 100%. The grain size refers to the dimension of the widest part of the grain, and can be obtained by measuring the dimension of the widest part of the projection surface of the grain in an SEM or TEM image of a sample, and the average grain size is obtained by selecting any 10 molecular sieve grains in the SEM or TEM image and calculating the average value thereof.
In one embodiment of the present invention, the ZSM-5 molecular sieve may have an average height of from 0.2 to 1.0. Mu.m, or from 0.1 to 1. Mu.m, preferably from 0.2 to 0.8. Mu.m, and the average aspect ratio may vary over a wide range, for example, may be 1: (2-10), preferably 1: (4-8). The aspect ratio in the invention refers to the ratio of the height of the molecular sieve to the maximum diameter of the top surface or the bottom surface of the molecular sieve, and the average aspect ratio can be obtained by selecting any 10 molecular sieves in SEM or TEM images, respectively calculating the aspect ratio and then taking the average value.
In a second aspect, the present invention provides a process for preparing the surface aluminum enriched ZSM-5 molecular sieve provided in the first aspect of the invention.
In one embodiment, a method of preparing a surface aluminum enriched ZSM-5 molecular sieve provided in the first aspect of the present invention includes: (1) Mixing the first template agent, the first silicon source and the first solvent for 0.5-3.0 hours at the temperature of 30-50 ℃ to obtain a first mixed product; (2) Mixing the first alkali metal hydroxide, the first aluminum source and the second solvent for 0.5-2.0 hours at 20-80 ℃ to obtain a second mixed product; (3) And mixing the first mixed product and the second mixed product, then carrying out dynamic crystallization, taking out the obtained solid, and carrying out first roasting.
According to the present invention, the molar ratio of the total amount of the first template, the first solvent and the second solvent, the amount of the first alkali metal hydroxide and the first silicon source may vary within a wide range, and may be, for example, (0.06-0.55): (10-110): (0.02-1.5): 1, preferably (0.10-0.50): (15-85): (0.03-1.2): 1, a step of; the molar ratio of the first silicon source to the first aluminum source may also vary within a wide range, for example (20-500): 1, preferably (25-200): 1, a step of; wherein the first silicon source is SiO 2 The first alkali metal hydroxide is calculated as alkali metal oxide (e.g., when the first alkali metal hydroxide is NaOH, the first alkali metal hydroxide is Na 2 O meter), the first aluminum source is Al 2 O 3 And (5) counting. In one embodiment, the first template and the first alkali metal hydroxide comprise OH - Total molar mass of (2) and SiO 2 Molar ratio of the first silicon source(abbreviated as OH/SiO) 2 ) Is (0.01-1.5): 1, preferably (0.02-1.2): 1.
according to the invention, in step (2), the first alkali metal hydroxide, the second solvent and the first aluminum source are used in a molar ratio of (1.5-5): (60-500): 1, preferably (2.0-4.5): (80-450): 1.
according to the present invention, in step (3), dynamic crystallization is well known to those skilled in the art, and the conditions of the dynamic crystallization may include: the temperature is 80-200deg.C for 4-80 hr, preferably 160-180deg.C for 12-60 hr.
According to the invention, step (3) further comprises taking out the obtained solid, sequentially performing a first washing and a first drying, and then performing a first roasting. The solution used for washing is not particularly limited, for example, deionized water can be used, drying is a technical means conventionally adopted by those skilled in the art, drying can be performed in a constant-temperature drying oven or natural air drying, and the conditions of the first drying can include: the temperature is 90-120 ℃ and the time is 2-24 hours.
In another embodiment, a method of preparing a surface aluminum enriched ZSM-5 molecular sieve provided in the first aspect of the present invention includes: s1, mixing a second template agent, a second silicon source and a third solvent for 0.5-3.0 hours at the temperature of 30-50 ℃, and performing first hydrothermal treatment and second hydrothermal treatment on the obtained third mixed product in sequence to obtain a fourth mixed product; wherein the conditions of the first hydrothermal treatment include: the temperature is 80-150 ℃ and the time is 1-6 hours; the conditions of the second hydrothermal treatment include: the temperature is 160-180 ℃ and the time is 2-24 hours; s2, mixing the second alkali metal hydroxide, the second aluminum source and the fourth solvent for 0.5-2.0 hours at 20-80 ℃ to obtain a fifth mixed product; and S3, mixing the fourth mixed product and the fifth mixed product, performing third hydrothermal treatment on the obtained mixture, taking out the obtained solid, and performing second roasting. According to the present invention, the molar ratio of the total amount of the second template, the third solvent and the fourth solvent, the amount of the second alkali metal hydroxide and the second silicon source may vary within a wide range,for example, (0.06-0.55): (10-110): (0.02-1.5): 1, preferably (0.10-0.50): (15-85): (0.03-1.2): 1, a step of; the molar ratio of the second silicon source to the amount of the second aluminum source may also vary within a wide range, and may be, for example, (20-500): 1, preferably (25-200): 1, a step of; wherein the second silicon source is SiO 2 The second alkali metal hydroxide is calculated as alkali metal oxide, and the second aluminum source is calculated as Al 2 O 3 And (5) counting. In one embodiment, the second template and the second alkali metal hydroxide comprise OH - Total molar mass of (2) and SiO 2 The ratio of the molar amounts of the second silicon source (abbreviated as OH/SiO 2 ) Is (0.01-1.5): 1, preferably (0.02-1.2): 1.
according to the present invention, in step S1, the conditions of the first hydrothermal treatment include: the temperature is 80-150 ℃ and the time is 1-6 hours; the conditions of the second hydrothermal treatment include: the temperature is 160-180 ℃ and the time is 12-60 hours.
According to the invention, in step S2, the second alkali metal hydroxide, the fourth solvent and the second aluminum source are used in a molar ratio of (1.5-5): (60-500): 1, preferably (2-4.5): (80-450): 1.
according to the invention, the hydrothermal treatment is well known to the person skilled in the art and can be carried out, for example, in a heat-resistant closed vessel. In one embodiment, in step S3, the conditions of the third hydrothermal treatment include: 160-180 ℃ for 12-60 hours. The conditions of the hydrothermal treatment are not limited in the present invention, and the hydrothermal treatment may be carried out under autogenous pressure of the reaction system or under an applied pressure, preferably under autogenous pressure.
According to the present invention, the firing may be performed in a muffle furnace, a tube furnace, or the like by technical means conventionally employed by those skilled in the art. In one embodiment, the conditions of the first firing and the second firing each independently include: the temperature is 400-600 ℃ for 2-6 hours, preferably 450-600 ℃ for 3-6 hours.
According to the invention, step S3 further comprises taking out the obtained solid, sequentially performing a second washing and a second drying, and then performing a second roasting. The solution used for washing is not particularly limited, for example, deionized water can be used, drying is a technical means conventionally adopted by those skilled in the art, drying can be performed in a constant-temperature drying oven, natural air drying can be also used, and the conditions of the second drying can include: the temperature is 90-120 ℃ and the time is 2-24 hours.
According to the invention, the first silicon source is selected from one or more of methyl orthosilicate and ethyl orthosilicate; the second silicon source is selected from one or more of silica sol, water glass and solid silica gel; the first template agent and the second template agent are respectively and independently selected from one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine and hexamethylenediamine; the first aluminum source and the second aluminum source are respectively and independently selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum isopropoxide and aluminum sol; the first alkali metal hydroxide and the second alkali metal hydroxide are respectively and independently selected from one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide.
According to the present invention, the method for removing the solid is not limited, and for example, filtration, centrifugal separation, and the like can be used.
The third aspect of the invention provides an application of the ZSM-5 molecular sieve with the aluminum-enriched surface provided by the first aspect of the invention in petrochemical industry and/or fine chemical industry.
In a preferred embodiment of the present invention, the present invention provides the use of a surface aluminum-rich ZSM-5 molecular sieve in a hydrocarbon catalytic cracking reaction.
The invention is further illustrated by the following examples, which are not intended to be limiting in any way.
The raw materials used in the following examples and comparative examples are commercially available without particular description.
In the following examples and comparative examples, the morphology of molecular sieve samples was observed by taking SEM photographs of the samples. The average height of the molecular sieve is obtained by randomly selecting the average value of the calculated heights of 10 particles in an SEM photo, and the average height-diameter ratio is obtained by calculating the height-diameter ratio of 10 particles respectively and then averaging.
The grain size of the molecular sieve is measured by SEM, 10 grain sizes are randomly measured, and the average value is taken to obtain the average grain size of the molecular sieve sample.
The crystallinity of the sample is detected by an X-ray diffraction method, and the instrument: empyrean. Test conditions: tube voltage 40kV, tube current 40mA, cu target K alpha radiation, 2 theta scanning range 5-35 DEG, scanning speed 2 (°)/min.
The bulk silica-alumina ratio of the sample was determined by XRF method, the instrument was a ZSX Primus II (Rigaku) X-ray fluorescence spectrometer; test conditions: excitation voltage is 50kV, excitation current is 50mA, rhodium and palladium are adopted. And measuring the peak intensity of each element spectrum by using a scintillation counter and a proportional counter, and analyzing the element composition of the molecular sieve.
The surface silicon-aluminum ratio of the sample is determined by XPS method, and the instrument is ESCALab250 type X-ray photoelectron spectrometer of thermo Fisher company, test condition: the excitation source is monochromized AlK alpha X-ray, the excitation energy is 1496.6eV, and the power is 150W. The electron binding energy was corrected for the C1s peak of the contaminating carbon (284.8 eV).
Example 1
(1) 111.65 g of tetrapropylammonium hydroxide aqueous solution (mass fraction is 25.0%) is weighed, 623.14 g of deionized water is added, stirring is carried out at room temperature for 10min, 91.2 g of tetraethoxysilane is then added, and stirring is carried out for 2.0h under the water bath condition of 40 ℃ to obtain a first mixed product;
(2) Weighing 3.44 g of sodium hydroxide particles, adding 76.80 g of deionized water to dissolve sodium hydroxide completely, adding 8.16 g of aluminum nitrate, and stirring at room temperature (25 ℃ and the same below) for 1.0h to obtain a second mixed product (namely an aluminum source solution);
(3) Slowly adding the second mixed product into the first mixed product, uniformly mixing, and stirring for 4.0h at room temperature; transferring the obtained precursor liquid into a synthesis kettle, and dynamically crystallizing at 170 ℃ for 48 hours; after crystallization, centrifugal filtration, washing and drying are carried out, and roasting is carried out for 4 hours at 550 ℃ to obtain ZSM-5 molecular sieve A, and SEM pictures of the ZSM-5 molecular sieve A are shown in figure 1.
Example 2
(1) 34.5 g of tetrapropylammonium bromide aqueous solution (mass fraction is 25.0%) is weighed, 425.0 g of deionized water is added, stirring is carried out for 10min at room temperature, then 60.0 g of methyl orthosilicate is added, and stirring is carried out for 5.0h under the water bath condition of 30 ℃ to obtain a first mixed product;
(2) Weighing 1.30 g of sodium hydroxide particles, adding 31.0 g of deionized water to dissolve sodium hydroxide completely, adding 0.85 g of sodium aluminate, and stirring at room temperature for 2.0h to obtain a second mixed product (namely an aluminum source solution);
(3) Slowly adding the second mixed product into the first mixed product, uniformly mixing, and stirring for 4.0h at room temperature; transferring the obtained precursor liquid into a synthesis kettle, and dynamically crystallizing for 24 hours at 180 ℃; after crystallization, centrifugal filtration, washing, drying and roasting at 500 ℃ for 6 hours to obtain ZSM-5 molecular sieve B, wherein SEM photograph is shown in figure 2.
Example 3
(1) 65.13 g of tetrapropylammonium hydroxide aqueous solution (mass fraction: 25.0%) was weighed, 462.62 g of deionized water was added, stirred at room temperature for 10min, and then 165.20 g of silica Sol (SiO) 2 25% of content), stirring for 1.0h under the water bath condition of 50 ℃, transferring the obtained third mixed product into a reaction kettle, performing hydrothermal treatment at 80 ℃ for 2 hours, and then heating to 170 ℃ for 12 hours to obtain a fourth mixed product;
(2) Weighing 1.39 g of sodium hydroxide particles, adding 39.7 g of deionized water to dissolve sodium hydroxide completely, adding 4.76 g of aluminum nitrate nonahydrate, and stirring at room temperature for 1.0h to obtain a fifth mixed product (namely an aluminum source solution);
(3) Adding the fifth mixed product into the fourth mixed product, uniformly stirring, and continuously performing third hydrothermal treatment on the obtained precursor liquid at 170 ℃ for 36 hours; after the hydrothermal treatment, centrifugal filtration, washing and drying are carried out, and roasting is carried out for 4 hours at 550 ℃ to obtain the ZSM-5 molecular sieve C, and SEM pictures of the ZSM-5 molecular sieve C are shown in figure 3.
Example 4
(1) 65.13 g of tetrapropylammonium hydroxide aqueous solution (mass fraction is 25.0%) is weighed, 823.60 g of deionized water is added, stirring is carried out at room temperature for 10min, then 134.4 g of tetraethoxysilane is added, and stirring is carried out for 1.0h under the water bath condition of 50 ℃ to obtain a first mixed product;
(2) Weighing 2.0 g of sodium hydroxide particles, adding 36.0 g of deionized water to dissolve sodium hydroxide completely, adding 4.76 g of aluminum nitrate nonahydrate, and stirring at room temperature for 1.0h to obtain a second mixed product (namely an aluminum source solution);
(3) Slowly adding the second mixed product into the first mixed product, uniformly mixing, and stirring for 4.0h at room temperature; transferring the precursor liquid into a synthesis kettle, and dynamically crystallizing at 160 ℃ for 60 hours; (5) After crystallization, centrifugal filtration, washing and drying are carried out, and roasting is carried out for 4 hours at 550 ℃ to obtain the ZSM-5 molecular sieve D, and SEM pictures of the ZSM-5 molecular sieve D are shown in figure 4.
Example 5
ZSM-5 molecular sieve E was prepared in the same manner as in example 3 except that the amount of water in the solution of the second step was lower.
(1) 65.13 g of tetrapropylammonium hydroxide aqueous solution (mass fraction: 25.0%) was weighed, 482.32 g of deionized water was added, stirred at room temperature for 10min, and then 165.20 g of silica Sol (SiO) 2 25% of content), stirring for 1.0h under the water bath condition of 50 ℃, transferring the obtained third mixed product into a reaction kettle, performing hydrothermal treatment at 80 ℃ for 2 hours, and then heating to 170 ℃ for 12 hours to obtain a fourth mixed product;
(2) Weighing 1.39 g of sodium hydroxide particles, adding 20.0 g of deionized water to dissolve sodium hydroxide completely, adding 4.76 g of aluminum nitrate nonahydrate, and stirring at room temperature for 1.0h to obtain a fifth mixed product (namely an aluminum source solution);
(3) Adding the fifth mixed product into the fourth mixed product, uniformly stirring, and continuously performing third hydrothermal treatment on the obtained precursor liquid at 170 ℃ for 36 hours; after the hydrothermal treatment is finished, centrifugally filtering, washing, drying and roasting for 4 hours at 550 ℃ to obtain the ZSM-5 molecular sieve E.
Comparative example 1
Molecular sieve a was prepared in the same manner as in example 1, except that the third mixed product was subjected to a hydrothermal treatment in step (1) at 160℃for 8 hours.
Comparative example 2
Conventional-grained ZSM-5 molecular sieve b purchased from Qilu division, a petrochemical catalyst company, si/Al molar ratio (SiO 2 /Al 2 O 3 ) 50.
TABLE 1
Figure BDA0003338851030000131
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Figure BDA0003338851030000132
Figure BDA0003338851030000141
In Table 1, R represents the template agent, and the ratio of the surface Si/Al molar ratio represents the ratio of the bulk Si/Al molar ratio to the surface Si/Al molar ratio.
Evaluation of reaction
The molecular sieves prepared in the examples and comparative examples were subjected to ammonium exchange to give a sodium oxide content of less than 0.1 wt% to give an H-type molecular sieve, and the ammonium exchange conditions were: molecular sieve: ammonium chloride: h 2 O=1:0.5:10, ammonium exchange temperature 85 ℃, ammonium exchange time 1h. After ammonium exchange, filtering, washing and drying, and roasting for 2 hours at 550 ℃. The H-type molecular sieve sample obtained above is evaluated on a fixed bed micro-reaction device FB, raw oil is model compound decalin, and the evaluation conditions are as follows: the reaction temperature was 600℃and the catalyst to oil ratio (by weight) was 0.15, and the results are shown in Table 2.
TABLE 2
Figure BDA0003338851030000142
Figure BDA0003338851030000151
As can be seen from Table 2, the ZSM-5 molecular sieve with the aluminum-enriched surface has better catalytic performance, and has higher conversion rate and lower olefin yield when being used for catalytic cracking reaction.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.
In addition, the specific features described in the above embodiments may be combined in any suitable manner, and in order to avoid unnecessary repetition, various possible combinations are not described further.
Moreover, any combination of the various embodiments of the invention can be made without departing from the spirit of the invention, which should also be considered as disclosed herein.

Claims (10)

1. A ZSM-5 molecular sieve with aluminum-enriched surface is a flat-like cylinder, the average grain size of the ZSM-5 molecular sieve is 0.2-3.0 mu m, the ratio of the bulk phase silicon-aluminum molar ratio to the surface silicon-aluminum molar ratio is 1.2-5.0, and the relative crystallinity is 80-110%.
2. The ZSM-5 molecular sieve of claim 1, wherein the molar ratio of the bulk to surface silica to alumina ratio of the ZSM-5 molecular sieve is 1.2-4.0.
3. The ZSM-5 molecular sieve of claim 1, wherein the ZSM-5 molecular sieve has a relative crystallinity of 85-100% and an average grain size of 0.4-2 μm.
4. The ZSM-5 molecular sieve of claim 1, wherein the ZSM-5 molecular sieve has an average height of 0.2-1.0 μm and an average aspect ratio of 1: (2-10).
5. A process for preparing the surface aluminum enriched ZSM-5 molecular sieve as in any of claims 1-4, the process comprising:
(1) Mixing the first template agent, the first silicon source and the first solvent for 0.5-3.0 hours at the temperature of 30-50 ℃ to obtain a first mixed product;
(2) Mixing the first alkali metal hydroxide, the first aluminum source and the second solvent for 0.5-2.0 hours at 20-80 ℃ to obtain a second mixed product;
(3) Mixing the first mixed product and the second mixed product, then carrying out dynamic crystallization, taking out the obtained solid, and carrying out first roasting; or alternatively, the process may be performed,
the method comprises the following steps:
s1, mixing a second template agent, a second silicon source and a third solvent for 0.5-3.0 hours at the temperature of 30-50 ℃, and performing first hydrothermal treatment and second hydrothermal treatment on the obtained third mixed product in sequence to obtain a fourth mixed product; wherein the conditions of the first hydrothermal treatment include: the temperature is 80-150 ℃ and the time is 1-6 hours; the conditions of the second hydrothermal treatment include: the temperature is 160-180 ℃ and the time is 12-60 hours;
s2, mixing the second alkali metal hydroxide, the second aluminum source and the fourth solvent for 0.5-2.0 hours at 20-80 ℃ to obtain a fifth mixed product;
and S3, mixing the fourth mixed product and the fifth mixed product, performing third hydrothermal treatment on the obtained mixture, taking out the obtained solid, and performing second roasting.
6. The method of claim 5, wherein the first silicon source is selected from one or more of methyl orthosilicate and ethyl orthosilicate;
the second silicon source is selected from one or more of silica sol, water glass and solid silica gel;
the first template agent and the second template agent are respectively and independently selected from one or more of tetrapropylammonium bromide, tetrapropylammonium hydroxide, n-butylamine and hexamethylenediamine;
the first aluminum source and the second aluminum source are respectively and independently selected from one or more of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum isopropoxide and aluminum sol;
the first alkali metal hydroxide and the second alkali metal hydroxide are respectively and independently selected from one or more of lithium hydroxide, sodium hydroxide and potassium hydroxide.
7. The method of claim 5, wherein the molar ratio of the total amount of the first template, the first solvent, and the second solvent, the amount of the first alkali metal hydroxide, and the amount of the first silicon source is (0.06-0.55): (10-110): (0.02-1.5): 1, a step of; the molar ratio of the first silicon source to the first aluminum source is (20-500): 1, a step of; wherein the first silicon source is SiO 2 The first alkali metal hydroxide is calculated as alkali metal oxide, and the first aluminum source is calculated as Al 2 O 3 Counting;
the molar ratio of the total amount of the second template, the third solvent and the fourth solvent, the amount of the second alkali metal hydroxide and the amount of the second silicon source is (0.06-0.55): (10-100): (0.02-1.5): 1, a step of; the molar ratio of the second silicon source to the second aluminum source is (20-500): 1, a step of; wherein the second silicon source is SiO 2 The second alkali metal hydroxide is calculated as alkali metal oxide, and the second aluminum source is calculated as Al 2 O 3 And (5) counting.
8. The method of claim 5, wherein in step (2), the first alkali metal hydroxide, the second solvent, and the first aluminum source are used in a molar ratio of (1.5-5): (60-500): 1, a step of;
in step S2, the molar ratio of the amounts of the second alkali metal hydroxide, the fourth solvent and the second aluminum source is (1.5-5): (60-500): 1.
9. the method of claim 5, wherein the conditions of dynamic crystallization comprise: the temperature is 160-180 ℃ and the time is 12-60 hours;
the conditions of the third hydrothermal treatment include: 160-180 ℃ for 12-60 hours;
the conditions of the first firing and the second firing each independently include: the temperature is 400-600 ℃ and the time is 2-6 hours.
10. Use of the surface-enriched ZSM-5 molecular sieve as claimed in any of claims 1-4 in petrochemical and/or fine chemical industry.
CN202111302199.XA 2021-11-04 2021-11-04 ZSM-5 molecular sieve with aluminum-enriched surface, and preparation method and application thereof Pending CN116062770A (en)

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