Single crystal hollow ZSM-5 molecular sieve, catalyst comprising molecular sieve, and preparation method therefor and use thereof

Abstract

The present invention relates to a single crystal hollow ZSM-5 molecular sieve. Particles of the single crystal hollow ZSM-5 molecular sieve have a single crystal structure, a hexagonal morphology and a double-layer cavity structure, in which an inner cavity is sheathed in an outer one, wherein the inner-layer cavity is at least partially enclosed by a first molecular sieve wall layer, and the outer-layer cavity is completely enclosed by a second molecular sieve wall layer; and the ratio of the length of a molecular sieve crystal grain to the length of the outer-layer cavity is 1.1-2.0, and the ratio of the width of the molecular sieve crystal grain to the width of the outer-layer cavity is 1.05-1.5. The present invention further relates to a preparation method for and the use of the single crystal hollow ZSM-5 molecular sieve.

Description

A single crystal hollow ZSM-5 molecular sieve, a catalyst containing the molecular sieve, and its preparation method and use Technical Field

[0001] The present invention belongs to the technical field of catalytic materials, and relates to a single crystal hollow ZSM-5 molecular sieve, a preparation method and use thereof, and also relates to a catalytic cracking catalyst comprising the single crystal hollow ZSM-5 molecular sieve, a preparation method and use thereof. Background Art

[0002] Petroleum is an important source of automotive fuel and organic raw materials. Petroleum is a mixture of hydrocarbons that is often fractionated during processing, leaving a large portion of the product as heavy oil. However, heavy oil is difficult to use directly and requires further processing and conversion. Refineries often catalytically crack heavy oil into different products and adjust the ratio of these products based on market demand. For example, some refineries primarily produce automotive fuels such as gasoline and diesel, others focus on gasoline and light olefins, and still others focus on producing chemical raw materials, aiming to minimize gasoline and diesel production. A key factor in the catalytic cracking of heavy oil into different products is the catalytic cracking catalyst.

[0003] Catalytic cracking catalysts are the technical core of the petrochemical industry and the source of technological progress in the petrochemical industry. Catalytic cracking to produce light olefins is a typical high-temperature acid-catalyzed reaction, and its core is the development and design of catalytic cracking catalysts. Catalytic cracking often adjusts the target product according to market demand. ZSM-5 molecular sieve has a unique pore structure, adjustable acidity and high thermal / hydrothermal stability, making it the first choice for hydrocarbon catalytic cracking catalysts. However, although its regular and orderly microporous structure enhances the selectivity of specific products, it also limits the diffusion of large molecular hydrocarbon reactants and products, and also promotes the formation of carbon deposits, further covering active sites and causing catalyst deactivation. The existing technology has proposed cavity ZSM-5 molecular sieves, but these cavity ZSM-5 molecular sieves have a single morphology and are mostly synthesized using a large amount of organic templates.

[0004] Light olefins (ethylene, propylene, etc.) are important basic raw materials for the petrochemical industry. With the rapid development of the global economy, the petrochemical industry is in a period of rapid growth, and the demand for light olefins has increased dramatically. In particular, ethylene is an important basic raw material supporting the national economy and social development and is known as the "mother of petrochemicals." The scale, output, and technological level of its industrial production have become important indicators for measuring the level of a country's chemical industry. The catalytic cracking of hydrocarbons is an important means of obtaining small-molecule hydrocarbons such as ethylene and propylene from large-molecule hydrocarbons. During the cracking process, hydrocarbons undergo a large number of parallel and serial reactions. In addition to cracking to form small-molecule hydrocarbons, they may also aromatize to form aromatic hydrocarbons. The side-chain aromatic hydrocarbons formed may continue to crack or dealkylate to form BTX light aromatic hydrocarbons, or they may form heavy aromatic hydrocarbons through hydrogen transfer.

[0005] The main technical routes for ethylene production include naphtha cracking, coal / methanol to olefins, heavy oil catalytic cracking / catalytic cracking, and light hydrocarbon cracking. Catalytic cracking uses heavy oil, naphtha and light olefins as main raw materials. It can produce ethylene at a relatively low reaction temperature under the action of a catalyst. It has the advantages of flexible and adjustable product distribution, lower energy consumption level and relatively more friendly to the ecological environment. Heavy oil catalytic cracking is based on catalytic cracking and uses a catalyst that can produce more light olefins and appropriately adjusts the reaction conditions, such as increasing the reaction temperature, to convert heavy oil under more harsh conditions. Catalytic cracking catalysts are key factors affecting the catalytic cracking of heavy oil. The co-production of BTX during the catalytic cracking reaction can provide space for subsequent product adjustments. Aromatic hydrocarbons generated by hydrocarbon cracking are by-products of light olefin production. However, the existing technology does not disclose how to have a higher BTX yield while having a higher ethylene yield.

[0006] CN103157507A discloses a catalytic cracking catalyst comprising 2-50% by weight of an ultrastable rare earth Y-type molecular sieve, 0.5-30% by weight of one or more other molecular sieves, 0.5-70% by weight of clay, 1.0-65% by weight of a high-temperature-resistant inorganic oxide, and 0.01-12.5% ​​by weight of a rare earth oxide. The catalyst has strong heavy oil conversion capabilities and a high light oil yield. This catalyst is primarily used to increase gasoline yield, but has limited contribution to increasing light olefin yields.

[0007] CN112138712A discloses a catalytic cracking catalyst, a preparation method thereof, and a method for catalytic cracking of hydrocarbon oil. The catalyst contains 1-30 wt% of a Y-type molecular sieve on a dry basis, 5-55 wt% of a mesoporous, phosphorus- and metal-rich MFI-structured molecular sieve on a dry basis, 1-60 wt% of an inorganic binder on a dry basis, and optionally 0-60 wt% of a second clay on a dry basis. The inorganic binder includes a phosphorus-aluminum inorganic binder and / or other inorganic binders. The catalyst has better ethylene selectivity in the catalytic cracking reaction of petroleum hydrocarbons and can simultaneously produce more propylene and BTX.

[0008] In recent years, the raw materials have become heavier and inferior in quality. The existing technology does not involve catalysts that can further improve the conversion of heavy oil and take into account the yield of gasoline and light olefins under different working conditions.

[0009] Summary of the Invention

[0010] The present invention provides a novel molecular sieve and catalyst useful in the petrochemical and / or fine chemical industries, as well as a method for preparing and using the same. The molecular sieve can be used to prepare catalysts used in the petrochemical and / or fine chemical industries, particularly catalysts for catalytic cracking of heavy oils to increase the production of gasoline and light olefins.

[0011] The inventors of the present invention have discovered through research that by adjusting the pore structure and acid center distribution of the molecular sieve, the formation of aromatic hydrocarbons can be partially inhibited or promoted. This adjustable property makes it possible to adjust the distribution of catalytic cracking products, thereby enabling the production of light olefins through catalytic cracking and providing a reasonable product distribution for subsequent utilization of the products. However, to date, those skilled in the art do not know how to perform such adjustments.

[0012] According to a first aspect of the present invention, the present invention provides a single crystal hollow ZSM-5 molecular sieve, wherein the particles of the single crystal hollow ZSM-5 molecular sieve have a single crystal structure, a hexagonal morphology, and a double-layer cavity structure with an inner and outer layer, wherein the inner cavity is at least partially enclosed by a first molecular sieve wall layer, and the outer cavity is completely enclosed by a second molecular sieve wall layer, and wherein the ratio of the length of the molecular sieve grain (represented by Dt) to the length of the outer cavity (represented by Dj) is 1.1-2.0, and the ratio of the width of the molecular sieve grain to the width of the outer cavity is 1.1-2.0. The ratio is 1.05-1.5, wherein the length and width of the molecular sieve grains are obtained by randomly measuring the size of the maximum dimension in the projection surface and the size of the dimension perpendicular to the maximum dimension of 10 grains in the SEM or TEM image of the molecular sieve sample, and then calculating their average values, and the length and width of the outer cavity are obtained by randomly measuring the size of the maximum dimension in the projection surface of 10 grains and the size of the dimension perpendicular to the maximum dimension of the bright white part in the SEM or TEM image of the molecular sieve sample, and then calculating their average values.

[0013] According to a second aspect of the present invention, the present invention provides a method for preparing a single-crystal hollow ZSM-5 molecular sieve, wherein the particles of the single-crystal hollow ZSM-5 molecular sieve have a single crystal structure, a hexagonal morphology, and a double-layer cavity structure with an inner and outer cavity, wherein the inner cavity is at least partially enclosed by a first molecular sieve wall layer, and the outer cavity is completely enclosed by a second molecular sieve wall layer, and wherein the ratio of the length Dt of the molecular sieve grain to the length Dj of the outer cavity is 1.1-2.0, and the ratio of the width of the molecular sieve grain to the width of the outer cavity is 1.05-1.5, characterized in that the method comprises:

[0014] Step A, preparing a seed solution, comprises the following sub-steps:

[0015] (A1) mixing a first silicon source, a template, and water to obtain a first mixed solution;

[0016] (A2) subjecting the first mixed solution obtained in sub-step (1) to hydrothermal dynamic crystallization to obtain a seed solution;

[0017] Step B, preparing a single crystal hollow ZSM-5 molecular sieve, comprises the following sub-steps:

[0018] (B1) adding the alkaline source solution, the second silicon source dispersion, and the aluminum source dispersion sequentially into water under stirring to obtain a second mixed solution;

[0019] (B2) adding a certain amount of the seed solution to the second mixed solution under stirring to obtain a third mixed solution;

[0020] (B3) subjecting the third mixed solution to hydrothermal dynamic crystallization; filtering the obtained product, optionally washing, drying, and calcining to obtain a parent molecular sieve;

[0021] (B4) mixing the obtained parent molecular sieve with an alkali solution to obtain a solid product; and optionally

[0022] (B5) treating the obtained solid product to obtain an H-type single crystal hollow ZSM-5 molecular sieve, and optionally

[0023] (B6) Introducing phosphorus into the H-type single crystal hollow ZSM-5 molecular sieve obtained in sub-step (B5).

[0024] More specifically, the method for preparing a single crystal hollow ZSM-5 molecular sieve comprises:

[0025] A. Preparation of seed molecular sieve, comprising the following sub-steps:

[0026] (A1) dissolving a first silicon source and a template in water under stirring, and stirring at 30-60° C. for more than 1 hour, preferably 2-6 hours, to obtain a first mixed solution, wherein the molar ratio of the template R / SiO2 is preferably 0.05-0.50, and the molar ratio of H2O / SiO2 is 10-80;

[0027] (A2) subjecting the first mixed solution of substep (A1) to hydrothermal dynamic crystallization at a temperature of 140-180° C. for more than 1 hour, for example, 8-24 hours, preferably 10-18 hours, for example, transferring the mixed solution to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting the mixture to hydrothermal crystallization under stirring to obtain a solution containing a crystallized product, referred to as a seed solution. Preferably, the seed crystals in the seed solution have a grain size of 200-800 nm;

[0028] B. Preparation of single crystal hollow ZSM-5 molecular sieve, comprising the following sub-steps:

[0029] (B1-1) dissolving an alkali source in water and stirring uniformly to obtain an alkali source solution;

[0030] (B1-2) dissolving an aluminum source in water and stirring uniformly to obtain an aluminum source solution;

[0031] (B1-3) mixing the second silicon source with the alkali source solution obtained in sub-step (B1-1) under stirring, preferably at room temperature for more than 5 minutes, preferably more than 10 minutes;

[0032] (B1-4) the product obtained in sub-step (B1-3) is optionally mixed with water for dilution, and then mixed with the aluminum source solution obtained in sub-step (B1-2) under stirring, preferably at room temperature for more than 1 minute, preferably for 30-60 minutes, to obtain a mixed solution, referred to as a second mixed solution, wherein the mixed solution has the following molar ratio: n(SiO2) / n(Al2O3)=20-200, n(MB2O) / n(SiO2)=0.10-0.20, n(H2O) / n(SiO2)=20-60, wherein MB represents an alkali metal; preferably, MB represents one or more of K, Rb, and Cs;

[0033] (B2) adding a certain amount of the seed solution obtained in sub-step A(2) to the second mixed solution obtained in sub-step (B1-4) under stirring, preferably stirring at room temperature for more than 10 minutes, for example, stirring for 1-6 hours, to obtain a mixed solution, referred to as a third mixed solution;

[0034] (B3) subjecting the third mixed solution of substep (B2) to hydrothermal dynamic crystallization at a temperature above 100° C., for example, for more than 1 hour, preferably at a temperature of 140-180° C., preferably 150-170° C., for 6-48 hours, preferably 10-40 hours; filtering the obtained product, optionally washing, drying, and calcining to obtain a parent molecular sieve;

[0035] (B4) mixing the parent molecular sieve obtained in sub-step (B3) with an alkali-containing solution under stirring, for example, at a temperature of 60-90° C. for, for example, 20-60 minutes, wherein, preferably, the alkali content in the alkali-containing solution is 0.4-1.0 mol / L, to obtain a solid product; and optionally

[0036] (B5) exchanging the solid product obtained in sub-step (B4) to obtain an H-type single crystal hollow ZSM-5 molecular sieve; and optionally

[0037] (B6) Introducing phosphorus into the H-type single crystal hollow ZSM-5 molecular sieve obtained in sub-step (B5).

[0038] In the present specification, the room temperature is 20-35° C. As an illustration, in this specification, the grain size of the seed crystal is obtained by randomly selecting 10 seed crystals, measuring the size of their largest dimension, and then taking the average value.

[0039] According to the third aspect of the present invention, the present invention also relates to the use of a single crystal hollow ZSM-5 molecular sieve according to the first aspect of the present invention or a single crystal hollow ZSM-5 molecular sieve obtained by the method of the second aspect of the present invention in the field of petrochemical industry and / or fine chemical industry.

[0040] According to the fourth aspect of the present invention, the present invention also relates to a catalyst, especially a catalytic cracking catalyst, containing a single crystal hollow ZSM-5 molecular sieve obtained by the first aspect of the present invention or a single crystal hollow ZSM-5 molecular sieve obtained by the method of the second aspect of the present invention.

[0041] According to a fifth aspect of the present invention, the present invention also relates to a method for preparing the catalyst according to the fourth aspect.

[0042] According to a sixth aspect of the present invention, the present invention also relates to the use of the catalytic cracking catalyst according to the fourth aspect in catalytic cracking of heavy oil to produce light olefins (ethylene, propylene, etc.) and gasoline.

[0043] According to a seventh aspect of the present invention, a catalytic cracking method is provided, comprising contacting and reacting hydrocarbon oil with the single crystal hollow ZSM-5 molecular sieve according to the first aspect of the present invention or the catalyst according to the fourth aspect of the present invention.

[0044] The particles of the single crystal hollow ZSM-5 molecular sieve according to the present invention or the single crystal hollow ZSM-5 molecular sieve obtained according to the method of the present invention have a single crystal structure, a hexagonal morphology, and a double-layer cavity structure with inner and outer layers nested, wherein the inner cavity is at least partially enclosed by the first molecular sieve wall layer, and the outer cavity is completely enclosed by the second molecular sieve wall layer, and wherein the ratio of the length Dt of the molecular sieve grain to the length Dj of the outer cavity is 1.1-2.0, and the ratio of the width of the molecular sieve grain to the width of the outer cavity is 1.05-1.5.

[0045] The preparation method of the single crystal hollow ZSM-5 molecular sieve provided by the present invention is simple, does not require the use of a large amount of organic templates, has good technical and economic efficiency, and can prepare the single crystal hollow ZSM-5 molecular sieve provided by the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are used to illustrate the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention.

[0047] FIG1 shows a transmission electron microscope image of the hydrogen-type single-crystalline hollow ZSM-5 molecular sieve obtained in Example 1.

[0048] FIG2 shows the Fourier transform diffraction spectrum of the hydrogen-type single crystal hollow ZSM-5 molecular sieve prepared in Example 1.

[0049] FIG3 shows a simple schematic diagram of a single-crystal hollow ZSM-5 molecular sieve crystal of the present invention. DETAILED DESCRIPTION

[0050] The following specific embodiments describe the specific embodiments of the present invention in detail. It should be understood that the specific embodiments described herein are only used to illustrate preferred embodiments of the present invention and are not intended to limit the scope of the present invention.

[0051] Any specific numerical value disclosed in the present specification (including the endpoints of a numerical range) is not limited to the exact value of the numerical value, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Moreover, for a disclosed numerical range, the values ​​between the endpoints of the range, between the endpoints and the specific points in the range, and between the specific points can be arbitrarily combined to form one or more new numerical ranges, and these new numerical ranges should also be considered to be specifically disclosed herein.

[0052] Unless otherwise specified, the terms used in the specification of the present invention have the same meanings as commonly understood by those skilled in the art. If a term is defined herein and its definition is different from the commonly understood meaning in the art, the definition in this article shall prevail.

[0053] In the description of the present invention, except for the contents explicitly described, any matters or issues not mentioned are directly applicable to those known in the art without any changes. Moreover, any embodiment described herein can be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas formed thereby are considered part of the original disclosure or original description of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

[0054] All patent and non-patent literature, including but not limited to textbooks and journal articles, mentioned in the specification of the present invention are incorporated herein by reference in their entirety.

[0055] In the present description, the term "comprising" is synonymous with "including" and "containing", and is inclusive or open, without excluding other elements not specified. It should be understood that the term "comprising" includes the exclusive and closed term "consisting of . . . "Based on" is synonymous with "comprising at least 80% by weight". In the absence of explicit instructions, the percentages given are weight %. In addition, in this description, the term "substantially" or "essentially" corresponds to an approximation of ±5%, preferably ±1%, very preferably ±0.5%, for example ±0.1%. For example, an effluent that substantially comprises compound A or is substantially composed of compound A corresponds to an effluent that comprises at least 95% by weight of compound A.

[0056] The measurement of the performance parameters disclosed in the description of the present invention, unless otherwise specified, is carried out by the most conventional methods in the art.

[0057] As described above, according to the first aspect of the present invention, the present invention provides a single crystal hollow ZSM-5 molecular sieve, wherein the particles of the single crystal hollow ZSM-5 molecular sieve have a single crystal structure, a hexagonal morphology, and a double-layer cavity structure with inner and outer layers nested, wherein the inner cavity is at least partially enclosed by the first molecular sieve wall layer, and the outer cavity is completely enclosed by the second molecular sieve wall layer, and wherein the length of the molecular sieve grain (expressed by D t Indicated by) and the length of the outer cavity (denoted by D j The ratio of the width of the molecular sieve crystal to the width of the outer cavity is 1.1-2.0, and the ratio of the width of the molecular sieve crystal to the width of the outer cavity is 1.05-1.5.

[0058] In this specification, the expression "the length of the molecular sieve grains" is equivalent to the expression "the average grain size of the molecular sieve", which refers to the size of the largest dimension of the grains, which can be obtained by measuring the size of the largest dimension of the grain projection surface in the SEM or TEM image of the molecular sieve sample. In order to avoid contingency, 10 molecular sieve grains are generally randomly selected to measure the length and then take the average value. As an illustration, the length of the grains, the width of the grains, the length of the cavity, the width of the cavity, and the thickness of the molecular sieve wall of the molecular sieve sample of the present invention are obtained by randomly selecting 10 molecular sieve grains in the SEM or TEM image of the molecular sieve sample, measuring the length of the grains, the width of the grains, the length of the cavity, the width of the cavity, and the thickness of the molecular sieve wall, and then calculating their arithmetic average.

[0059] As shown in FIG3 , the molecular sieve crystal comprises an inner cavity 1, a first molecular sieve wall layer 2, an outer cavity 3 and a second molecular sieve wall layer 4, wherein the length of the molecular sieve crystal is represented by D t Indicates that the length of the grain D t Usually refers to the length along the ac axis; the length of the outer cavity is Dj It refers to the maximum dimension of the cavity. Usually, the maximum dimension of the cavity has the same direction as the maximum dimension of the grain. It can be obtained by randomly measuring the maximum dimension of the bright white part in the projection surface of 10 grains in the SEM or TEM image of the molecular sieve sample and then calculating their average value. The inner cavity length is expressed as D i It refers to the maximum dimension of the inner cavity structure projection in the SEM or TEM image of the molecular sieve sample, which is also obtained by calculating the average value; the inner cavity width is expressed as D o It refers to the dimension perpendicular to the length direction of the inner cavity, where D i >D o . The “width of the molecular sieve crystal grain” refers to the dimension perpendicular to the length direction of the molecular sieve crystal grain, and the width of the outer cavity refers to the dimension perpendicular to the length direction of the outer cavity, which can also be obtained by measuring the SEM or TEM image of the molecular sieve sample. The thickness of the first molecular sieve wall layer (i.e., the distance between the outer wall surface of the inner cavity and the inner wall surface of the outer cavity) is the distance obtained by randomly measuring and calculating the average value between the outer wall surface of the inner cavity and the inner wall surface of the outer cavity; the thickness of the second molecular sieve wall layer is the distance obtained by randomly measuring and calculating the average value between the inner wall of the outer cavity and the outer wall of the molecular sieve crystal.

[0060] The inventors surprisingly discovered through research that the molecular sieve according to the present invention has a specific hexagonal crystal shape and size, a double-layer cavity structure, a pore structure and an acid center distribution, which makes the molecular sieve have improved selectivity in catalytic cracking. It can not only produce light olefins through catalytic cracking, but also obtain gasoline components with higher yields in the cracking products, providing a reasonable product distribution for the subsequent utilization of the products.

[0061] According to a preferred embodiment, the length D of the single crystal hollow ZSM-5 molecular sieve grains according to the present invention is t The length D of the outer cavity j The ratio of the width of the molecular sieve crystal to the width of the outer cavity is 1.1-2.0, preferably 1.3-1.8, such as 1.4, 1.5, 1.6 or 1.7, and the ratio of the width of the molecular sieve crystal to the width of the outer cavity is 1.05-1.5, preferably 1.1-1.4, such as 1.2 or 1.3. The above ratio allows the second molecular sieve wall layer to have a smaller thickness, which simultaneously provides the molecular sieve with sufficient mechanical strength and a shorter diffusion path, thereby improving the accessibility of the active center and the catalytic selectivity, and providing a sufficient mass transfer rate, allowing hydrocarbon molecules to quickly approach the active center.

[0062] For the single crystal hollow ZSM-5 molecular sieve according to the present invention, as shown in Figure 1, the expression "double-layer" is intended to indicate that the single crystal hollow ZSM-5 molecular sieve crystal includes two molecular sieve wall layers and two cavity layers that are alternately surrounded, that is, the first molecular sieve wall layer at least partially encloses the inner cavity, and outside the first molecular sieve wall layer is the outer cavity layer; the second molecular sieve wall layer completely encloses the outer cavity; the expression "single crystal" is intended to indicate that the ZSM-5 molecular sieve particles have a single crystal structure; the expression "hollow" and the expression "cavity" in this specification can be used equivalently, and are intended to indicate that there is a space in the ZSM-5 molecular sieve grains that does not contain ZSM-5 molecular sieve, and the space is at least partially enclosed by a ZSM-5 molecular sieve wall layer having a certain thickness.

[0063] According to an embodiment of the first aspect of the present invention, the particles of the single-crystalline hollow ZSM-5 molecular sieve have a single-crystalline structure, and the average grain size thereof is 1.0-3.0 μm, for example, 1.5-2.9 μm.

[0064] According to an embodiment of the first aspect of the present invention, the single crystal hollow ZSM-5 molecular sieve single grain grows along the ac axis direction (along the 010 plane), and the growth orientation of the entire particle is consistent, that is, it grows along the ac axis direction. The entire particle of the single crystal hollow ZSM-5 molecular sieve has a single crystal structure. The crystal structure and growth orientation of the single crystal hollow ZSM-5 molecular sieve can be observed by a high-power spherical aberration electron microscope.

[0065] According to one embodiment of the first aspect of the present invention, the single crystal hollow ZSM-5 molecular sieve has a regular hexagonal morphology.

[0066] According to an embodiment of the first aspect of the present invention, the length of the single crystal hollow ZSM-5 molecular sieve grain is 1.0-3.0 μm, for example 1.2-2.9 μm, the width of the grain is 0.5-2.5 μm, preferably 0.5-2.0 μm, for example 0.8-1.8 μm, the length of the inner cavity is 100-800 nm, for example 200-700 nm, the length of the inner cavity is greater than the width of the inner cavity, and their ratio is 1.01-1.2, the thickness of the first molecular sieve wall is less than 400 nm, for example 100-250 nm. The thickness of the second molecular sieve wall layer (i.e., the distance between the outer wall of the outer cavity and the outer wall of the molecular sieve crystal) is generally less than 700 nm, for example 100-500 nm, preferably 150-400 nm.

[0067] The single crystal hollow ZSM-5 molecular sieve according to the present invention has excellent hydrothermal stability, high crystal retention and excellent catalytic performance due to its special single crystal structure and pore distribution.

[0068] The relative crystallinity of the molecular sieve according to the present invention is calculated based on the XRD standard ZSM-5 molecular sieve standard sample of Sinopec Research Institute of Petroleum Processing Co., Ltd., and the crystallinity of the standard sample is regarded as 100%.

[0069] According to one embodiment of the first aspect of the present invention, the single crystal hollow ZSM-5 molecular sieve contains phosphorus or does not contain phosphorus. Preferably, the phosphorus / aluminum molar ratio in the single crystal hollow ZSM-5 molecular sieve is 0.5-1.5, and under the condition of hydrothermal treatment at 800°C for 17 hours, the crystallization retention is greater than or equal to 90%, for example, 91-92%, and the acidity retention is greater than or equal to 30%; or, after the single crystal hollow ZSM-5 molecular sieve is modified at a phosphorus / aluminum molar ratio of 1, under the condition of hydrothermal treatment at 800°C for 17 hours, the crystallization retention is greater than or equal to 90%, for example, 91-92%, and the acidity retention is greater than or equal to 30%, for example, 30-40% or 30.5-35%; this indicates that the molecular sieve has good hydrothermal stability after phosphorus modification. The crystallinity retention refers to the ratio of the relative crystallinity of the product obtained after the molecular sieve is modified at a phosphorus / aluminum molar ratio of 1 and then hydrothermally treated at 800°C for 17 hours (referred to as the relative crystallinity after hydrothermal treatment) to the relative crystallinity of the product obtained after the molecular sieve is modified at a phosphorus / aluminum molar ratio of 1 (referred to as the relative crystallinity before hydrothermal treatment); the acidity retention refers to the ratio of the acidity of the product obtained after the molecular sieve is modified at a phosphorus / aluminum molar ratio of 1 and then hydrothermally treated at 800°C for 17 hours (referred to as the acidity after hydrothermal treatment) to the acidity of the product obtained after the molecular sieve is modified at a phosphorus / aluminum molar ratio of 1 (referred to as the acidity before hydrothermal treatment). The hydrothermal treatment is carried out in an atmosphere of 100% by volume water vapor.

[0070] The acidity of the molecular sieve according to the present invention is obtained using the NH3-TPD method. The acidity of the molecular sieve is determined using an Autochem II 2920 temperature-programmed desorber from Mack, USA. Specific testing method: 0.2 g of a 20-40 mesh molecular sieve is weighed in a sample tube and placed in a heating furnace. Using He as the carrier gas at a flow rate of 25 ml / min, the temperature is raised to 600°C at 20°C / min and purged for 90 minutes to remove impurities adsorbed on the surface of the molecular sieve. The temperature is then lowered to 150°C and held constant for 5 minutes. NH3-He gas (10% by mass NH3 and 90% by mass He) is introduced into the system for 60 minutes of adsorption, followed by a He purge for 120 minutes until the baseline is stable to desorb physically adsorbed ammonia. The temperature is then programmed to 600°C at a temperature ramp rate of 10°C / min for desorption, held for 60 minutes, and desorption is completed. A TCD is used to detect changes in gas composition, and the instrument automatically integrates to obtain the total acidity.

[0071] The modification of the single crystal hollow ZSM-5 molecular sieve under the condition of a phosphorus / aluminum molar ratio of about 1 can be implemented using an equal volume impregnation method, which is as follows: the molecular sieve sample is evenly spread on a watch glass or a crucible, and the phosphorus-containing solution is slowly poured onto the molecular sieve sample so that the molecular sieve sample finally presents a "slurry state", and after stirring evenly, it is dried in an oven; then it is ground evenly and calcined at 550°C for 4 hours. Usually, the mass ratio of the phosphorus-containing solution to the molecular sieve is 1-3. The phosphorus-containing solution is, for example, a phosphoric acid solution or an ammonium dihydrogen phosphate solution or a diammonium hydrogen phosphate solution. In the present invention, the phosphorus / aluminum molar ratio of the single crystal hollow ZSM-5 molecular sieve can be obtained by XRF fluorescence detection.

[0072] According to an embodiment of the first aspect of the present invention, the mesoporous specific surface area of ​​the single crystal hollow ZSM-5 molecular sieve accounts for 5-15% of the total specific surface area, such as 8-14%.

[0073] According to an embodiment of the first aspect of the present invention, the mesopore volume of the single crystal hollow ZSM-5 molecular sieve accounts for 30-50% of the total pore volume, for example, 32-41%.

[0074] The total specific surface area, mesopore specific surface area, micropore specific surface area and pore volume of the single crystal hollow ZSM-5 molecular sieve of the present invention are measured by low-temperature nitrogen adsorption method, wherein the instrument used in the low-temperature nitrogen adsorption analysis is ASAP2420 physical adsorption instrument (from American Mac Instrument Company), and the experimental method is as follows: the first step is to pretreat the sample: weigh a certain amount of sample and put it into a sample tube that has been measured with a blank, put it into a degassing treatment unit, and degas for 6 hours at a furnace temperature of 300°C and a vacuum degree of less than 1.33 Pa. The second step is to measure the sample: put the pretreated sample tube into the measurement unit, fill the Dewar flask with liquid nitrogen, input the analysis file and start the measurement. The measurement process is to use the static capacity method to measure the adsorption isotherm, calculate the total pore volume according to the adsorption amount of P / P0=0.98, calculate the pore size distribution according to the BJH method, obtain the mesopore volume, and calculate the specific surface area using the BET formula. Test conditions: Samples were vacuum degassed at 100°C and 300°C for 0.5 h and 6 h, respectively. N2 adsorption-desorption tests were then conducted at 77.4 K. The adsorption and desorption of nitrogen from the purified samples were measured under different pressure ratios, and N2 adsorption-desorption isotherms were obtained. The BET surface area was calculated using the BET formula, the micropore area was calculated using a t-plot, and the pore size distribution was calculated using the BJH method.

[0075] The single crystal hollow ZSM-5 molecular sieve provided by the present invention has an inner and outer double-layer cavity structure that is at least partially enclosed by two molecular sieve layers, and the molecular sieve pores are mainly microporous structures, while being rich in mesopores and macroporous structures between the molecular sieve layers, which can further provide multi-directional diffusion paths, expand the confined space, improve the accessibility of the active center, and have improved catalytic macromolecular hydrocarbon conversion, such as cracking. Because the single crystal hollow ZSM-5 molecular sieve of the present invention has a relatively regular hexagonal morphology, its grain surface is regular and smooth without attachments, and the average grain size is 1.0-3.0 μm, so that all single crystal hollow ZSM-5 molecular sieve particles have very similar structural parameters to each other, including but not limited to pore size and pore length. The inventors were surprised to find that the molecular sieve with this structure is particularly suitable for catalytic cracking of macromolecules to produce gasoline and light olefins.

[0076] The single crystal hollow ZSM-5 molecular sieve according to the present invention can be an H-type single crystal hollow ZSM-5 molecular sieve or a phosphorus-containing single crystal hollow ZSM-5 molecular sieve. The phosphorus content of the phosphorus-containing single crystal hollow ZSM-5 molecular sieve can be greater than 0 to 15% by weight, for example, 0.5-10% by weight, calculated as P2O5.

[0077] According to a second aspect of the present invention, the present invention provides a method for preparing a single-crystal hollow ZSM-5 molecular sieve, wherein the particles of the single-crystal hollow ZSM-5 molecular sieve are single-crystal structures, have a hexagonal morphology, and have a double-layer cavity structure with inner and outer layers nested, wherein the inner cavity is at least partially enclosed by a first molecular sieve wall layer, and the outer cavity is completely enclosed by a second molecular sieve wall layer, and wherein the ratio of the length Dt of the molecular sieve grain to the length Dj of the outer cavity is 1.1-2.0, and the ratio of the width of the molecular sieve grain to the width of the outer cavity is 1.05-1.5, characterized in that the method comprises:

[0078] Step A, preparing a seed solution, comprises the following sub-steps:

[0079] (A1) mixing a first silicon source, a template, and water to obtain a first mixed solution;

[0080] (A2) subjecting the first mixed solution obtained in sub-step (1) to hydrothermal dynamic crystallization to obtain a seed solution;

[0081] Step B, preparing a single crystal hollow ZSM-5 molecular sieve, comprises the following sub-steps:

[0082] (B1) adding the alkaline source solution, the second silicon source dispersion, and the aluminum source dispersion sequentially into water under stirring to obtain a second mixed solution;

[0083] (B2) adding a certain amount of the seed solution to the second mixed solution under stirring to obtain a third mixed solution;

[0084] (B3) subjecting the third mixed solution to hydrothermal dynamic crystallization; filtering the obtained product, optionally washing, drying, and calcining to obtain a parent molecular sieve;

[0085] (B4) mixing the obtained parent molecular sieve with an alkali solution to obtain a solid product; and optionally

[0086] (B5) treating the obtained solid product to obtain an H-type single crystal hollow ZSM-5 molecular sieve, and optionally

[0087] (B6) Introducing phosphorus into the H-type single crystal hollow ZSM-5 molecular sieve obtained in sub-step (B5).

[0088] According to one embodiment of the above preparation method, the method includes:

[0089] A. Preparation of seed molecular sieve, comprising the following sub-steps:

[0090] (A1) dissolving a first silicon source and a template in water under stirring, and stirring at 30-60° C. for more than 1 hour, preferably 2-6 hours, to obtain a first mixed solution, wherein the molar ratio of the template R / SiO2 is preferably 0.05-0.50, and the molar ratio of H2O / SiO2 is 10-80;

[0091] (A2) subjecting the first mixed solution of substep (A1) to hydrothermal dynamic crystallization at a temperature of 140-180° C. for more than 1 hour, for example, 8-24 hours, preferably 10-18 hours, for example, transferring the mixed solution to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting the mixture to hydrothermal crystallization under stirring to obtain a solution containing a crystallized product, referred to as a seed solution. Preferably, the seed crystals in the seed solution have a grain size of 200-800 nm;

[0092] B. Preparation of single crystal hollow ZSM-5 molecular sieve, comprising the following sub-steps:

[0093] (B1-1) dissolving an alkali source in water and stirring uniformly to obtain an alkali source solution;

[0094] (B1-2) dissolving an aluminum source in water and stirring uniformly to obtain an aluminum source solution;

[0095] (B1-3) mixing the second silicon source with the alkali source solution obtained in sub-step (B1-1) under stirring, preferably at room temperature for more than 5 minutes, preferably more than 10 minutes;

[0096] (B1-4) the product obtained in sub-step (B1-3) is optionally mixed with water for dilution, and then mixed with the aluminum source solution obtained in sub-step (B1-2) under stirring, preferably at room temperature for more than 1 minute, preferably for 30-60 minutes, to obtain a mixed solution, referred to as a second mixed solution, wherein the mixed solution has the following molar ratio: n(SiO2) / n(Al2O3)=20-200, n(MB2O) / n(SiO2)=0.10-0.20, n(H2O) / n(SiO2)=20-60, wherein MB represents an alkali metal; preferably, MB represents one or more of K, Rb, and Cs;

[0097] (B2) adding a certain amount of the seed solution obtained in sub-step A(2) to the second mixed solution obtained in sub-step (B1-4) under stirring, preferably stirring at room temperature for more than 10 minutes, for example, stirring for 1-6 hours, to obtain a mixed solution, referred to as a third mixed solution;

[0098] (B3) subjecting the third mixed solution of substep (B2) to hydrothermal dynamic crystallization at a temperature above 100° C., for example, for more than 1 hour, preferably at a temperature of 140-180° C., preferably 150-170° C., for 6-48 hours, preferably 10-40 hours; filtering the obtained product, optionally washing, drying, and calcining to obtain a parent molecular sieve;

[0099] (B4) mixing the parent molecular sieve obtained in sub-step (B3) with an alkali-containing solution under stirring, for example, at a temperature of 60-90° C. for, for example, 20-60 minutes, wherein, preferably, the alkali content in the alkali-containing solution is 0.4-1.0 mol / L, to obtain a solid product; and optionally

[0100] (B5) exchanging the solid product obtained in sub-step (B4) to obtain an H-type single crystal hollow ZSM-5 molecular sieve; and optionally

[0101] (B6) Introducing phosphorus into the H-type single crystal hollow ZSM-5 molecular sieve obtained in sub-step (B5).

[0102] For the purposes of the present invention, room temperature refers to a temperature of 20-35°C.

[0103] According to one embodiment of the above preparation method, in sub-step (A1), the first silicon source is selected from one or more of methyl orthosilicate or ethyl orthosilicate, and / or the template is selected from one or more of tetrapropylammonium hydroxide or tetrapropylammonium bromide.

[0104] According to one embodiment of the above preparation method, in sub-step (A1), the molar ratio of template R / SiO2 is 0.05-0.50, for example, 0.1-0.4, and / or the molar ratio of H2O / SiO2 is 10–80, for example, 30-55.

[0105] According to a preferred embodiment of the above preparation method, in sub-step (B1-1), the mass concentration of the alkali source solution is 10-30%, for example, 15-25% by weight, and preferably, the alkali source is selected from one or more of potassium hydroxide, rubidium hydroxide or cesium hydroxide;

[0106] According to a preferred embodiment of the above preparation method, in sub-step (B1-2), the mass concentration of the aluminum source solution is 5-20%, for example, 8-12% by weight. Preferably, the aluminum source is selected from one or more of aluminum sulfate, aluminum nitrate, aluminum isopropoxide, sodium aluminate or aluminum chloride.

[0107] According to a preferred embodiment of the above preparation method, in sub-step (B1-3), the second silicon source is silica sol, preferably, the silica sol is selected from ammonium silica sol, sodium silica sol or a mixture thereof; the SiO2 content in the silica sol is 10-45% by weight, for example, the SiO2 mass content of the silica sol is 15%, 25%, 30%, 45% or a range formed by any two of these data values ​​as endpoints.

[0108] According to a preferred embodiment of the above preparation method, the second mixed liquid has the following molar ratio: n(SiO2) / n(Al2O3)=20-200, for example, 30-100, preferably 40-80, more preferably 45-65; n(MB2O) / n(SiO2)=0.10-0.20, preferably 0.12-0.16; n(H2O) / n(SiO2)=20-60, preferably 40-60; wherein MB represents an alkali metal; preferably, MB represents one or more of K, Rb, and Cs.

[0109] According to a preferred embodiment of the above preparation method, in sub-step (B2), the mass ratio of SiO2 in the seed solution to SiO2 in the second silicon source in sub-step (B1-3) is 5-20:100 or 6-10:100.

[0110] According to a preferred embodiment of the above preparation method, in sub-step A(2), the grain size of the seed crystals in the seed solution (or seed solution) is 200-800 nm, preferably 300-700 nm, for example 400 nm, 500 nm or 600 nm.

[0111] According to a preferred embodiment of the above preparation method, in sub-step (B3), the third mixed solution of sub-step (B2) is subjected to hydrothermal dynamic crystallization at a temperature above 100°C, for example, for more than 1 hour, preferably at a temperature of 140-180°C, preferably 150-170°C, for 6-48 hours, preferably 10-40 hours. For example, the mixed solution obtained in step (B3) can be transferred to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner, and then subjected to hydrothermal dynamic crystallization. The dynamic crystallization is to perform the crystallization reaction of the mixed solution in a moving state, such as under stirring.

[0112] According to a preferred embodiment of the above preparation method, in sub-step (B3), the obtained product is filtered to separate the crystallized molecular sieve from the mother liquor, and then washed with water to remove the mother liquor attached to the molecular sieve, for example, using deionized water, and then dried and calcined. The drying is carried out at a temperature above 40°C, for example, at a temperature of 50-150°C, for more than 1 minute, preferably 1-10 minutes; the calcination can be carried out at a calcination temperature of 450-600°C, for example, 500-600°C, for more than 0.5 hour, for example, the calcination time is 2-12 hours, for example, 3-6 hours.

[0113] In sub-step (B3), the parent molecular sieve is obtained, which mainly exists in the form of solid crystals, the central part of the solid crystals is rich in silicon and the peripheral part is rich in aluminum.

[0114] According to the preparation method of the single crystal hollow ZSM-5 molecular sieve provided by the present invention, in sub-step (B4), the parent molecular sieve is mixed with an alkaline solution for more than 5 minutes under agitation, for example, stirred at a temperature of 60-90 ° C for 20-60 minutes, and the molecular sieve crystal is treated to form a hollow structure. The solid obtained is then recovered and filtered, and optionally washed, for example, with deionized water to wash away the residual alkali solution in the treated parent molecular sieve, and then dried to obtain a molecular sieve solid. The alkaline solution is, for example, an alkaline solution containing one or more of sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. The content of alkali in the alkaline solution is 0.4-2.0 mol / L in terms of metal molar amount, for example, 0.4-1 mol / L.

[0115] According to a preferred embodiment of the above-mentioned method for preparing molecular sieves, in sub-step (B5), the solid product obtained in sub-step (B4) is treated to obtain an H-type single crystal hollow ZSM-5 molecular sieve. According to one embodiment, the treatment includes subjecting the solid product obtained in sub-step (B4) to ion exchange, such as ammonium exchange, filtering, optionally washing, and then drying and calcining. The operation methods of the ammonium exchange, drying and calcining are well known to those skilled in the art. For example, drying can be carried out at a temperature above 40°C for more than 1 minute, and calcination can be carried out at a temperature above 400°C, preferably 500-600°C, for more than 0.5 hours, preferably 1-5 hours. According to a preferred embodiment, the ammonium exchange is referred to as the first ammonium exchange, wherein the temperature of the first ammonium exchange can be 50-95°C, the exchange time can be 0.5-2 hours, wherein the mass ratio of ZSM-5 molecular sieve, ammonium salt and water can be 1: (0.1-1): (5-15); the ammonium salt can be selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate. The first ammonium exchange can be carried out once or multiple times.

[0116] According to a preferred embodiment of the above-mentioned method for preparing molecular sieves, step (B6) introduces phosphorus into the H-type single crystal hollow ZSM-5 molecular sieve to obtain a phosphorus-containing single crystal hollow ZSM-5 molecular sieve. The method of introducing phosphorus can be carried out according to existing methods, for example, phosphorus can be introduced into the H-type single crystal hollow ZSM-5 molecular sieve by impregnation, which generally includes the steps of contacting the H-type single crystal hollow ZSM-5 molecular sieve with an impregnation solution, drying, and calcining. The impregnation solution can be a phosphoric acid solution, an ammonium phosphate solution, a diammonium hydrogen phosphate solution, an ammonium dihydrogen phosphate solution, or a mixture of these solutions.

[0117] The drying and calcining methods can be carried out according to existing methods, such as oven drying, air flow drying, and rotary drying; and the calcination can be carried out at a temperature of 450-600° C. for 1-6 hours.

[0118] The single crystal hollow ZSM-5 molecular sieve obtained by the preparation method of the present invention has an inner and outer double-layer cavity structure at least partially enclosed by two molecular sieve layers and a regular hexagonal morphology. Its grain surface is regular, smooth and free of attachments, and the average grain size is 1.0-3.0 μm.

[0119] According to the third aspect of the present invention, the present invention also relates to the use of a single crystal hollow ZSM-5 molecular sieve according to the first aspect of the present invention or a single crystal hollow ZSM-5 molecular sieve obtained by the method of the second aspect of the present invention in the field of petrochemical industry and / or fine chemical industry.

[0120] The single crystal hollow ZSM-5 molecular sieve preparation method according to the second aspect of the present invention can obtain the single crystal hollow ZSM-5 molecular sieve of the present invention. In addition, in the single crystal hollow ZSM-5 molecular sieve synthesis method according to the present invention, there is no need to use a large amount of organic template agent, making the synthesis method environmentally friendly.

[0121] According to an embodiment of the third aspect, the single crystal hollow ZSM-5 molecular sieve according to the present invention can be applied to the adsorption separation or catalytic cracking / cracking of hydrocarbon compounds. When the single crystal hollow ZSM-5 molecular sieve is used in the catalytic cracking reaction of hydrocarbon compounds, a higher gasoline yield and light olefin (ethylene and propylene) yield can be obtained. Therefore, the single crystal hollow ZSM-5 molecular sieve according to the present invention has good industrial application value.

[0122] According to an embodiment of the third aspect, the single crystal hollow ZSM-5 molecular sieve is used for the catalytic cracking of hydrocarbon oil, which includes contacting the hydrocarbon oil with the single crystal hollow ZSM-5 molecular sieve and performing a catalytic cracking reaction step. According to a preferred embodiment, the single crystal hollow ZSM-5 molecular sieve is a hydrogen-type molecular sieve. According to a preferred embodiment, the single crystal hollow ZSM-5 molecular sieve contains phosphorus, which is called a phosphorus-containing single crystal hollow ZSM-5 molecular sieve, wherein the phosphorus content can be, for example, 0.5-10% by weight, such as 6% by weight, 7% by weight, 8% by weight or 9% by weight, relative to the weight of the molecular sieve.

[0123] Since the single crystal hollow ZSM-5 molecular sieve according to the present invention has a double-layer cavity structure and a regular hexagonal morphology, its grain surface is regular, smooth and free of attachments, and has a rich pore structure, including a microporous structure, a mesoporous structure and a macroporous structure, the single crystal hollow ZSM-5 molecular sieve according to the present invention can provide a multi-directional diffusion path for macromolecular reactants, thereby improving the accessibility of the active center of the molecular sieve. Since the single crystal hollow ZSM-5 molecular sieve has an improved accessibility of the active site of the molecular sieve, it has excellent catalytic performance, especially selectivity, for the cracking of macromolecular hydrocarbon compounds. For example, when it is used in the catalytic cracking reaction of macromolecular hydrocarbon compounds, it can significantly increase the production of gasoline and light olefins.

[0124] According to the fourth aspect of the present invention, the present invention also relates to a catalyst containing a single crystal hollow ZSM-5 molecular sieve according to the first aspect of the present invention or a single crystal hollow ZSM-5 molecular sieve obtained by the method according to the second aspect of the present invention, especially a catalytic cracking catalyst.

[0125] According to one embodiment of the fourth aspect of the present invention, the catalytic cracking catalyst contains the single crystal hollow ZSM-5 molecular sieve, the Y-type molecular sieve and the carrier according to the above-mentioned first aspect. Preferably, in the catalyst, the content of the single crystal hollow ZSM-5 molecular sieve is 10-40% by weight, the content of the Y-type molecular sieve is 10-30% by weight, and the content of the carrier is 30-80% by weight.

[0126] Preferably, the single-crystal hollow ZSM-5 molecular sieve has a double-layer closed hollow structure and a regular hexagonal morphology, an average grain size of 1.0-3.0 μm, and the entire particle is a single-crystal structure.

[0127] Preferably, the single crystal hollow ZSM-5 molecular sieve grows along the ac axis, and the growth orientation of the entire particle is consistent.

[0128] Preferably, the single crystal hollow ZSM-5 molecular sieve may contain phosphorus or not, and the phosphorus content of the single crystal hollow ZSM-5 molecular sieve is 0-15% by weight, for example, 0.5-10% by weight, calculated as P2O5. The single crystal hollow ZSM-5 molecular sieve has a phosphorus / aluminum molar ratio of 0.5-1.5, preferably 0.8-1.2.

[0129] Preferably, the single crystal hollow ZSM-5 molecular sieve contains no phosphorus, or has a phosphorus / aluminum molar ratio of less than 1. It exhibits the following properties: after modification at a phosphorus / aluminum molar ratio of 1, i.e., introducing phosphorus into the single crystal hollow ZSM-5 molecular sieve to achieve a phosphorus / aluminum molar ratio of 1, the crystal retention is greater than or equal to 90%, and / or the acid retention is greater than or equal to 30%, after hydrothermal treatment at 800°C for 17 hours. The modification can be performed by introducing phosphorus into the single crystal hollow ZSM-5 molecular sieve at a phosphorus / aluminum molar ratio of 1 using an isovolumetric impregnation method. The method is as follows: evenly spread the molecular sieve sample on a watch glass or crucible, slowly pour a phosphorus-containing solution onto the molecular sieve sample until it forms a slurry, stir evenly, and dry in an oven; then, grind evenly and calcine at 550°C for 4 hours. Typically, the mass ratio of phosphorus-containing solution to molecular sieve is 1-3. The phosphorus-containing solution can be, for example, a phosphoric acid solution.

[0130] Preferably, the single crystal hollow ZSM-5 molecular sieve contains phosphorus, and its phosphorus / aluminum molar ratio is 0.5-1.5 or above 1.5, for example, 1. The single crystal hollow ZSM-5 molecular sieve has a crystallization retention rate greater than or equal to 90% and / or an acid retention rate greater than or equal to 30% under hydrothermal treatment at 800°C for 17 hours.

[0131] The atmosphere of the hydrothermal treatment is a 100% by volume water vapor atmosphere. The crystallization retention is the ratio of the relative crystallinity of the single crystal hollow ZSM-5 molecular sieve obtained by modifying the single crystal hollow ZSM-5 molecular sieve at a phosphorus / aluminum molar ratio of 1 or the single crystal hollow ZSM-5 molecular sieve having a phosphorus / aluminum molar ratio of 0.5 or 1 to the relative crystallinity before the hydrothermal treatment. The acid retention is the ratio of the acid content of the single crystal hollow ZSM-5 molecular sieve obtained by modifying the single crystal hollow ZSM-5 molecular sieve at a phosphorus / aluminum molar ratio of 1 or the single crystal hollow ZSM-5 molecular sieve having a phosphorus / aluminum molar ratio of 0.5 or more, such as 1 or more, after the hydrothermal treatment to the acid content before the hydrothermal treatment.

[0132] Preferably, the mesoporous specific surface area of ​​the single crystal hollow ZSM-5 molecular sieve accounts for 5-15% of the total specific surface area, for example, 8-14%.

[0133] Preferably, the mesopore volume of the single crystal hollow ZSM-5 molecular sieve accounts for 30-50% of the total pore volume, for example, 30-45% or 32-41%.

[0134] Preferably, the relative crystallinity of the single crystal hollow ZSM-5 molecular sieve is 80-100%.

[0135] Preferably, the silicon / aluminum molar ratio of the single crystal hollow molecular sieve is 20-100 in terms of SiO2 / Al2O3.

[0136] In the present invention, the phosphorus / aluminum molar ratio of the single crystal hollow ZSM-5 molecular sieve can be obtained by XRF fluorescence detection, and the content of the rare earth component can also be obtained by XRF fluorescence detection.

[0137] The rare earth content in the Y-type molecular sieve is 2-25 wt %, calculated as RE 2 O 3 , for example, 2-12 wt % or 8-15 wt %.

[0138] The Y-type molecular sieve contains rare earth and may or may not contain phosphorus. The phosphorus content in the Y-type molecular sieve may be 0-10% by weight as calculated as P2O5.

[0139] The rare earth element is preferably one or both of lanthanum and cerium.

[0140] According to the present invention, the silicon-aluminum ratio of the Y-type molecular sieve is preferably 4.0-8.0, for example, 5-8, in terms of SiO2 / Al2O3 molar ratio.

[0141] According to the present invention, the Y-type molecular sieve can be one or more of a Y-type molecular sieve that has been subjected to hydrothermal ultrastability and / or gas-phase ultrastability or a rare earth-containing Y-type molecular sieve. The Y-type molecular sieve is preferably an ultrastable Y-type molecular sieve. The ultrastable Y-type molecular sieve can be one or more of a Y-type molecular sieve that has been subjected to only hydrothermal ultrastability, a Y-type molecular sieve that has been subjected to only gas-phase ultrastability, and a Y-type molecular sieve that has been subjected to both hydrothermal ultrastability and gas-phase ultrastability.

[0142] The "hydrothermal ultra-stabilization" refers to treating the Y molecular sieve in the presence of water vapor to dealuminate the molecular sieve so as to increase the silicon-to-aluminum ratio of the Y molecular sieve. The "gas-phase ultra-stabilization" refers to treating the Y molecular sieve in the presence of silicon tetrachloride to dealuminate and siliconize the molecular sieve so as to increase the silicon-to-aluminum ratio of the molecular sieve. According to one embodiment, a Y molecular sieve that has undergone hydrothermal ultra-stabilization and gas-phase ultra-stabilization is obtained as follows: the Y molecular sieve is usually first subjected to a certain degree of hydrothermal ultra-stabilization treatment, and then subjected to gas-phase ultra-stabilization treatment. Since the gas-phase ultra-stabilization method and the hydrothermal ultra-stabilization method are well known to those skilled in the art, they will not be repeated here.

[0143] The gas-phase ultrastable molecular sieve is selected from one or more of HSY-4, HSY-12, SCY-4, and SCY-12. The hydrothermal ultrastable molecular sieve is selected from one or more of DASY-2.0, DSCY-2, RSCY-12, SOY-2, RSCY, SOY-8, and SOY-12. The RSCY molecular sieve typically has a rare earth content (calculated as RE2O3) of 16% to 18% by weight. The rare earth Y molecular sieve can be selected from one or more of REY and HRY.

[0144] Preferably, the support is selected from one or more of natural clay, alumina support, silica support, aluminum phosphate support and silica-alumina support;

[0145] Preferably, the silica carrier is one or more of neutral silica sol, acidic silica sol or alkaline silica sol; the alumina carrier is one or more of aluminum sol, acidified pseudo-boehmite, hydrated alumina and activated alumina; the aluminum phosphate carrier is phosphate aluminum gel; the silica aluminum oxide carrier is one or more of solid silica aluminum material, silica aluminum sol and silica aluminum gel.

[0146] Preferably, the carrier comprises a silicon oxide carrier; preferably, the content of the silicon oxide carrier in terms of SiO2 is 1-20 wt% based on the dry mass of the catalyst.

[0147] According to one embodiment, in the catalytic cracking catalyst, based on the dry weight of the catalyst, the content of the single crystal hollow ZSM-5 molecular sieve is 10-40 wt%, the content of the Y-type molecular sieve is 10-30 wt%, and the content of the carrier is 30-70 wt%. According to one embodiment, the catalytic cracking catalyst comprises single-crystal mesoporous ZSM-5 molecular sieve, Y-type molecular sieve, pseudo-boehmite, aluminum sol, silica sol, and clay. Based on the dry weight of the catalytic cracking catalyst, the content of the single-crystal hollow ZSM-5 molecular sieve is 10-40% by weight, preferably 20-30% by weight, the content of the Y-type molecular sieve is 10-30% by weight, preferably 15-25% by weight, the content of the pseudo-boehmite is 5-30% by weight, preferably 10-20% by weight, calculated as alumina, the content of the aluminum sol is 5-20% by weight, preferably 10-15% by weight, calculated as alumina, the content of the silica sol is 2-15% by weight, preferably 5-12% by weight, calculated as silicon oxide, and the content of the clay is 10-50% by weight, preferably 20-40% by weight, calculated as a dry weight. The pseudo-boehmite is preferably acidified pseudo-boehmite, and the acidification method is well known to those skilled in the art.

[0148] According to the fifth aspect of the present invention, the present invention also provides a method for preparing a catalyst according to the fourth aspect above, the method comprising: spray drying and calcining a slurry containing a carrier, a single crystal hollow ZSM-5 molecular sieve according to the present invention, a Y-type molecular sieve and water to form catalyst particles.

[0149] The spray drying is a technique commonly used by those skilled in the art, which can simultaneously dry the material and shape the catalyst. Spray drying is well known to those skilled in the art, and the specific method will not be described in detail here.

[0150] According to one embodiment of the fifth aspect above, the present invention provides a method for preparing a catalytic cracking catalyst, further comprising: mixing the catalyst particles obtained by spray drying and calcining, an ammonium salt, and a solvent in a weight ratio of 1: (0.1-1): (5-15) and then performing ammonium exchange, referred to as a second ammonium exchange, and optionally washing. One condition for the second ammonium exchange includes: a temperature of 50-100°C and a time of 0.5-2 hours; the solution containing the ammonium salt is calculated as an ammonium salt, and the ammonium salt can be selected from one or more of ammonium chloride, ammonium sulfate, and ammonium nitrate, and the solvent is, for example, water. The second ammonium exchange can be performed once or multiple times.

[0151] According to an embodiment of the fifth aspect, the slurry formed containing the carrier, the single crystal hollow ZSM-5 molecular sieve according to the present invention, the Y-type molecular sieve and water is spray dried and calcined. Spray drying can form the catalyst while drying the material. Spray drying and calcination can be carried out by spray drying and calcination methods conventionally used by those skilled in the art. According to a preferred embodiment, the calcination temperature can be, for example, 450-600° C., and the calcination time can be, for example, 1-5 hours.

[0152] According to one embodiment of the fifth aspect, in the method for preparing a catalytic cracking catalyst, the catalyst particles obtained by spray drying may be subjected to ammonium exchange to reduce the sodium oxide content in the catalyst. The ammonium exchange may be performed before or after calcination.

[0153] According to an embodiment of the fifth aspect, based on the dry weight of the catalytic cracking catalyst, the content of sodium oxide in the catalytic cracking catalyst is preferably 0.15 wt% or less.

[0154] According to a sixth aspect of the present invention, the present invention also relates to the use of the catalytic cracking catalyst according to the fourth aspect in catalytic cracking of heavy oil to produce light olefins (ethylene, propylene, etc.) and gasoline.

[0155] According to the seventh aspect of the present invention, the present invention also provides a catalytic cracking method, comprising contacting and reacting hydrocarbon oil with the single crystal hollow ZSM-5 molecular sieve according to the first aspect of the present invention or the catalyst according to the fourth aspect of the present invention.

[0156] According to one embodiment of the seventh aspect, the catalytic cracking method is carried out in a fluidized bed reactor. Preferably, the reaction temperature of the catalytic cracking is 550-650°C, preferably 580-620°C, the catalyst-oil ratio by weight is 5-30, preferably 8-20, and the weight hourly space velocity is 5-30h - 1 , for example 8-20h -1 .

[0157] According to one embodiment of the seventh aspect, the single crystal hollow ZSM-5 molecular sieve is an H-type and / or phosphorus-containing single crystal hollow ZSM-5 molecular sieve, wherein the phosphorus content can be 0.5-10% by weight as P2O5.

[0158] The present invention is further illustrated below by way of examples, but the present invention is not limited thereto.

[0159] Unless otherwise specified, the raw materials used in the following examples and comparative examples were commercially available.

[0160] The acid content of the molecular sieve can be determined using an Autochem II 2920 programmed temperature desorption instrument from Micromeritics, USA.

[0161] Low-temperature nitrogen adsorption analysis was performed using an ASAP2420 physical adsorption analyzer (Micromeritics Instruments, Inc., USA). The experimental method involved sample pretreatment: a certain amount of sample was weighed and placed into a blank-tested sample tube. The tube was then placed in a degassing unit and degassed for 6 hours at a furnace temperature of 300°C and a vacuum of less than 1.33 Pa. The second step involved sample measurement: the pretreated sample tube was placed into the measurement unit, the Dewar flask was filled with liquid nitrogen, and the analysis file was entered to begin the measurement. The measurement process involved determining the adsorption isotherm using the static volumetric method, calculating the pore size distribution using the BJH method, and calculating the specific surface area using the BET formula.

[0162] Fourier transform diffraction spectrum, the measuring electron microscope model is JEM-ARM200F, and the electron diffraction mode of the electron microscope is directly photographed.

[0163] The room temperature of the following examples and comparative examples was 26°C.

[0164] Example 1

[0165] Prepare seed solution:

[0166] (A1) 60.0 g of ethyl orthosilicate, 34.0 g of tetrapropylammonium hydroxide, and 140.5 g of deionized water were mixed and heated with stirring at 40° C. for 4 hours;

[0167] (A2) transferring the solution from substep (A1) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to dynamic crystallization at 170° C. for 12 hours;

[0168] (A3) After the crystallization is completed, the crystallized product is taken out from the reactor and recorded as seed solution 1.

[0169] Preparation of single crystal hollow ZSM-5 molecular sieve:

[0170] (B1-1) Add 2.65 g of potassium hydroxide to 7.95 g of deionized water and stir to obtain an alkaline source solution;

[0171] (B1-2) Add 2.10 g of aluminum sulfate 18hydrate to 18.9 g of deionized water and stir to obtain an aluminum source solution;

[0172] (B1-3) Slowly adding 29.70 g of silica sol (silicon oxide content: 30%, pH: 9.2, sodium-type silica sol, sodium oxide content: 0.22 wt %, the same below) to the alkaline source solution of substep (B1-1), and stirring at room temperature for 30 minutes to obtain a first mixed solution;

[0173] (B1-4) adding 85.45 g of deionized water to the product obtained in sub-step (B1-3), then adding the aluminum source solution in sub-step (B1-2) with stirring, and stirring at room temperature for 30 minutes to obtain a second mixed solution;

[0174] (B2) adding 6.24 g of the seed solution 1 obtained in sub-step (A3) to the mixed solution of sub-step (B1-4), and stirring at room temperature for 4 hours to obtain a third mixed solution;

[0175] (B3) transferring the third mixed solution in sub-step (B2) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to hydrothermal dynamic crystallization at 170° C. for 48 hours; filtering, washing, drying, and calcining the obtained product (calcination temperature: 550° C., calcination time: 2 hours, the same below) to obtain molecular sieve N-1;

[0176] (B4) mixing molecular sieve N-1 and a 0.6 mol / L sodium hydroxide solution in a mass ratio of 1:10, heating the mixture to 80°C at a heating rate of 4°C / min, stirring the mixture at the same temperature for 30 minutes, filtering, washing, and drying to obtain molecular sieve N-1-J;

[0177] (B5) Molecular sieve N-1-J, ammonium chloride, and deionized water are mixed in a mass ratio of 1:1:10 for molecular sieve N-1-J: ammonium chloride: deionized water, stirred and heated in an 80°C water bath for 30 minutes, filtered, washed, and dried, and then the dried solid, ammonium chloride, and deionized water are mixed in a mass ratio of 1:0.5:10, subjected to a second ammonium exchange, filtered, washed, dried, and calcined at 550°C for 2 hours to obtain a hydrogen-type single crystal hollow ZSM-5 molecular sieve, designated N-1-JH. Figure 1 is a transmission electron microscope image of the molecular sieve, showing a regular hexagonal morphology, and Figure 2 is its Fourier transform diffraction spectrum. According to Figure 2, it can be seen that the single crystal hollow ZSM-5 molecular sieve has a single crystal structure.

[0178] Example 2

[0179] Prepare seed solution:

[0180] (A1) 54.0 g of ethyl orthosilicate, 48.0 g of tetrapropylammonium hydroxide, and 180.7 g of deionized water were mixed and heated with stirring at 40° C. for 4 hours;

[0181] (A2) transferring the solution from step (A1) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to dynamic crystallization at 170° C. for 12 hours;

[0182] (A3) is taken out after the crystallization is completed and recorded as seed solution 2.

[0183] Preparation of single crystal hollow ZSM-5 molecular sieve:

[0184] (B1-1) Add 2.56 g of potassium hydroxide to 11.66 g of deionized water and stir to obtain an alkaline source solution;

[0185] (B1-2) Add 1.35 g of aluminum isopropoxide to 15.53 g of deionized water and stir to obtain an aluminum source solution;

[0186] (B1-3) Slowly adding 30.60 g of silica sol (silicon oxide content 30%) to the alkali source solution of step (B1-1), stirring at room temperature for 30 minutes to obtain a first mixed solution;

[0187] (B1-4) adding 115.81 g of deionized water to the first mixed solution obtained in step (B1-3), then adding the aluminum source solution in step (B2) with stirring, and stirring at room temperature for 30 minutes to obtain a second mixed solution;

[0188] (B2) adding 9.18 g of the seed solution 2 from step (A3) to the second mixed solution from step (B1-4), and stirring at room temperature for 4 hours to obtain a third mixed solution;

[0189] (B3) transferring the third mixed solution of step (B2) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to hydrothermal dynamic crystallization at 170° C. for 48 hours; filtering, washing, drying, and calcining the obtained product to obtain molecular sieve N-2;

[0190] (B4) molecular sieve N-2 and a 1.0 mol / L sodium hydroxide solution were mixed uniformly, with the mass ratio of molecular sieve N-2 to sodium hydroxide solution being 1:10, and the mixture was heated to 80° C. at a heating rate of 4° C. / min, stirred at the same temperature for 30 minutes, filtered, washed, and dried to obtain molecular sieve N-2-J;

[0191] (B5) Molecular sieve N-2-J: ammonium chloride: deionized water were mixed in a mass ratio of 1:1:10, stirred and heated in a water bath at 80°C for 30 minutes, filtered, washed, and dried, and then the dried solid: ammonium chloride: deionized water were mixed in a mass ratio of 1:0.5:10, subjected to a second ammonium exchange, filtered, washed, dried, and calcined at 550°C for 2 hours to obtain a hydrogen-type single crystal hollow ZSM-5 molecular sieve with a regular hexagonal morphology, denoted as N-2-JH.

[0192] Example 3

[0193] Prepare seed solution:

[0194] (A1) 45.4 g of ethyl orthosilicate, 65.3 g of tetrapropylammonium hydroxide, and 150.2 g of deionized water were mixed and heated with stirring at 40° C. for 4 hours;

[0195] (A2) transferring the solution from step (A1) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to dynamic crystallization at 170° C. for 12 hours;

[0196] After the crystallization is completed, (A3) is taken out and recorded as seed solution 3.

[0197] Preparation of single crystal hollow ZSM-5 molecular sieve:

[0198] (B1-1) Add 6.80 g of rubidium hydroxide to 27.2 g of deionized water and stir to obtain an alkaline source solution;

[0199] (B1-2) Add 1.08 g of sodium aluminate to 9.72 g of deionized water and stir to obtain an aluminum source solution;

[0200] (B1-3) Slowly adding 62.3 g of silica sol (silicon oxide content 30%) to the alkaline source solution of step (B1-1), stirring at room temperature for 30 minutes to obtain a first mixed solution;

[0201] (B1-4) adding 163.58 g of deionized water to the product obtained in step (B1-3), then adding the aluminum source solution in step (B1-2) with stirring, and stirring at room temperature for 30 minutes to obtain a second mixed solution;

[0202] (B2) adding 22.43 g of the seed solution 3 from step (A3) to the second mixed solution from step (B1-4), and stirring at room temperature for 4 hours to obtain a third mixed solution;

[0203] (B3) transferring the third mixed solution of step (B2) to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting it to hydrothermal dynamic crystallization at 170° C. for 48 hours; filtering, washing, drying, and calcining the obtained product to obtain molecular sieve N-3;

[0204] (B4) molecular sieve N-3 and a 0.6 mol / L sodium hydroxide solution were mixed uniformly, with the mass ratio of molecular sieve N-3 to sodium hydroxide solution being 1:10, and the mixture was heated to 80°C at a rate of 4°C / min, stirred at the same temperature for 30 minutes, filtered, washed, and dried to obtain molecular sieve N-3-J;

[0205] (B5) Molecular sieve N-3-J: ammonium chloride: deionized water are mixed in a mass ratio of 1:1:10, stirred and heated in a water bath at 80°C for 30 minutes, filtered, washed, and dried, and then the dried solid: ammonium chloride: deionized water are mixed in a mass ratio of 1:0.5:10, subjected to a second ammonium exchange, filtered, washed, dried, and calcined at 550°C for 2 hours to obtain a hydrogen-type single crystal hollow ZSM-5 molecular sieve with a regular hexagonal morphology, which is recorded as N-3-JH.

[0206] Comparative Example 1

[0207] Conventional ZSM-5 molecular sieve was purchased from Sinopec Catalyst Company Qilu Branch, with a silicon-aluminum molar ratio (SiO2 / Al2O3 of 25), and was denoted as DB1-H.

[0208] Comparative Example 2

[0209] (1) Mix conventional ZSM-5 molecular sieve and 0.2 mol / L sodium hydroxide solution, with the mass ratio of ZSM-5 molecular sieve to alkaline solution being 1:10, heat and stir at 80°C for 30 minutes, filter, wash, and dry;

[0210] (2) The conventional ZSM-molecular sieve after alkali treatment: ammonium chloride: deionized water are mixed in a mass ratio of 1:1:10, stirred and heated in a water bath at 80°C for 30 minutes, filtered, washed, and dried, and then the dried solid: ammonium chloride: deionized water are mixed in a mass ratio of 1:0.5:10, subjected to a second ammonium exchange, filtered, washed, dried, and calcined at 550°C for 2 hours to obtain a hydrogen-type molecular sieve DB2-H, which is not a hollow molecular sieve.

[0211] Comparative Example 3

[0212] Conventional ZSM-5 molecular sieve was purchased from Sinopec Catalyst Company Qilu Branch, with a silicon-aluminum molar ratio (SiO2 / Al2O3) of 25.

[0213] (1) Mix conventional ZSM-5 molecular sieve and 1.0 mol / L sodium hydroxide solution, with the mass ratio of ZSM-5 molecular sieve to alkaline solution being 1:10, heat and stir at 80°C for 30 minutes, filter, wash, and dry;

[0214] (2) The purchased ZSM-5 molecular sieve after alkali treatment: ammonium chloride: deionized water are mixed in a mass ratio of 1:1:10, stirred and heated in a water bath at 80°C for 30 minutes, filtered, washed, and dried, and then the dried solid: ammonium chloride: deionized water are mixed in a mass ratio of 1:0.5:10, subjected to a second ammonium exchange, filtered, washed, dried, and calcined at 550°C for 2 hours to obtain a hydrogen-type molecular sieve DB3-H, which is not a hollow molecular sieve.

[0215] Comparative Example 4

[0216] The molecular sieve of this comparative example was prepared according to the method of Example 1, except that in substep (B1-2), 3.20 g of aluminum sulfate 18-hydrate was added to 10.9 g of deionized water and stirred uniformly to obtain an aluminum source solution; and in substep (B1-3), 18.80 g of silica sol (silicon oxide content 30%, pH 9.2, sodium silicate, sodium oxide content 0.22% by weight, the same below) was slowly added to the alkali source solution of substep (B1-1), stirred at room temperature for 30 minutes, to obtain a first mixed solution. The other preparation steps were the same. The resulting hydrogen-type single-crystalline hollow ZSM-5 molecular sieve had a regular hexagonal morphology and was designated DB4-H.

[0217] Table 1

[0218] The molecular sieve synthesis ratio in Table 1 is the ratio of the product of step (B1-4). The seed size is the average size of the seed crystals, and the grain size is the average grain size of the final product.

[0219] Molecular sieve evaluation

[0220] According to the molecular sieves of the embodiments and comparative examples, after modification and calcination under a phosphorus / aluminum molar ratio of 1:1 (the method is as follows: the molecular sieve sample is evenly spread on a watch glass or crucible, and the phosphorus-containing solution is slowly poured onto the molecular sieve sample so that the molecular sieve sample finally presents a "slurry state", and after stirring evenly, it is dried in an oven; then it is evenly ground and calcined at 550°C for 4 hours), it is aged and deactivated at 800°C and 100% water vapor for 17 hours, and 40-60 mesh particles are sieved out of the tablets. The evaluation is carried out on a fixed bed microreactor FB, using n-hexadecane as the model compound, and the evaluation conditions are: reaction temperature 620°C, and agent-oil ratio (weight) of 0.75. The results are listed in Table 2.

[0221] Table 2

[0222] As shown in Table 2, the single-crystal hollow ZSM-5 molecular sieve provided by the present invention has a higher diene (ethylene and propylene) yield and a higher propylene / ethylene ratio compared to the comparative example. Furthermore, the molecular sieve provided by the present invention has excellent mechanical strength, and no damage to the molecular sieve particles was observed after the above-mentioned catalytic performance test experiments.

[0223] Examples 4-6 and Comparative Examples 2-3 illustrate the preparation of catalytic cracking catalysts.

[0224] Examples 4-6

[0225] Examples 4, 5, and 6, respectively, used single-crystal hollow ZSM-5 molecular sieves prepared according to the methods of Examples 1, 2, and 3 to prepare catalytic cracking catalysts according to the present invention. The catalysts are numbered A1, A2, and A3. The single-crystal hollow ZSM-5 molecular sieves prepared according to Examples 1-3 were phosphorus-modified with a phosphorus compound at a phosphorus / aluminum molar ratio of 1:1 using an equal volume impregnation method. After drying and calcination, the phosphorus compound used was diammonium hydrogen phosphate. The molecular sieve obtained after phosphorus modification of N-1-JH was designated N-1-J-HP, the phosphorus-modified N-2-JH was designated N-2-J-HP, and the phosphorus-modified N-3-JH was designated N-3-J-HP.

[0226] The preparation method of the catalytic cracking catalyst comprises: (1) uniformly mixing pseudo-boehmite (abbreviated as diaspore) and water, adding concentrated hydrochloric acid with a concentration of 36 weight % under stirring, and the acid / aluminum weight ratio is 0.2 (the weight ratio of the hydrochloric acid with a concentration of 36 weight % to the pseudo-boehmite with Al2O3); aging the obtained mixture at a temperature of 70°C for 1.5 hours to obtain an aged pseudo-boehmite slurry. The aged pseudo-boehmite slurry has an alumina content of 12 wt%; (2) the above-prepared single crystal hollow ZSM-5 molecular sieve, Y-type molecular sieve, aluminum sol, silica sol, kaolin and the above-mentioned aged pseudo-boehmite slurry and deionized water are uniformly mixed to form a slurry with a solid content of 30 wt%, and spray-dried to obtain catalyst microspheres; (3) the catalyst microspheres are calcined at 550°C for 4 hours; (4) the calcined catalyst microspheres are exchanged at 80°C for 1 hour according to a weight ratio of catalyst microspheres: ammonium salt: H2O = 1:1:10, filtered, and the above exchange and filtration process is repeated once, and the catalyst is dried, wherein the ammonium salt is ammonium chloride, and the sodium oxide content in the obtained catalytic cracking catalyst is less than 0.15 wt%.

[0227] Comparative Example 5

[0228] Comparative Example 5 illustrates the preparation of a catalytic cracking catalyst using the molecular sieve DB1-H provided in Comparative Example 1. Following the catalyst preparation method of Example 4, molecular sieve DB1-H was modified with phosphorus (denoted as DB1-HP) and then mixed with Y-type molecular sieve, pseudo-boehmite, silica sol, kaolin, water, and aluminum sol. The mixture was spray-dried, calcined, and ammonium-exchanged to prepare microspherical catalyst DB2.

[0229] Comparative Example 6

[0230] A catalyst was prepared according to the method of Example 4, except that the content of the Y-type molecular sieve in the catalyst was 35% by weight and the content of the ZSM-5 molecular sieve was 10% by weight. The composition of the prepared catalyst is shown in Table 3.

[0231] Table 3 Catalyst composition

[0232] Catalyst performance testing

[0233] The catalytic cracking catalysts prepared in the examples and comparative examples were aged at 800°C and 100% by volume steam for 17 hours, and then their catalytic cracking reaction performance was evaluated in a small fixed fluidized bed reactor. The evaluation conditions were reaction temperature of 540°C and 570°C, catalyst-to-oil ratio of 8.0 (weight ratio), and weight hourly space velocity of 10h. -1 The properties of heavy oil are shown in Table 4, and the reaction results are shown in Tables 5 and 6.

[0234] Table 4 Heavy oil properties

[0235] Table 5 Catalytic performance evaluation results 1

[0236] Table 6 Catalytic performance evaluation results 2

[0237] As shown in Tables 5 and 6, the catalytic cracking catalyst provided by the present invention has a higher heavy oil conversion capacity under both low reaction severity and high reaction severity conditions, and has higher gasoline and light olefin yields (ethylene and propylene). In addition, it can also have a lower coke yield and a higher liquefied gas yield. In addition, the catalytic cracking catalyst provided by the present invention has excellent mechanical strength, and after the above-mentioned catalyst performance test experiment, no damage to the catalyst particles was found.

Claims

1. A single-crystal hollow ZSM-5 molecular sieve, wherein the particles of the single-crystal hollow ZSM-5 molecular sieve have a single-crystal structure, a hexagonal morphology, and a double-layer cavity structure with inner and outer layers nested, wherein the inner cavity is at least partially enclosed and surrounded by a first molecular sieve wall layer, and the outer cavity is completely enclosed and surrounded by a second molecular sieve wall layer, and wherein the ratio of the length of the molecular sieve grain to the length of the outer cavity is 1.1-2.0, and the ratio of the width of the molecular sieve grain to the width of the outer cavity is 1.05-1.5, wherein the length and width of the molecular sieve grain are obtained by randomly measuring the maximum dimension and the dimension perpendicular to the maximum dimension of 10 grains in the projection surface of the molecular sieve sample in the SEM or TEM image, and then calculating their average values ​​respectively, and the length and width of the outer cavity are obtained by randomly measuring the maximum dimension and the dimension perpendicular to the maximum dimension of the bright white part in the projection surface of 10 grains in the SEM or TEM image of the molecular sieve sample, and then calculating their average values ​​respectively.

2. The single crystal hollow ZSM-5 molecular sieve according to claim 1 is characterized in that the particles of the single crystal hollow ZSM-5 molecular sieve have a regular hexagonal morphology, the ZSM-5 molecular sieve grows along the ac axis direction, the growth orientation of the entire particle is consistent, and has an average grain size of 1.0-3.0 μm.

3. The single crystal hollow ZSM-5 molecular sieve according to claim 1 or 2, characterized in that the single crystal hollow ZSM-5 molecular sieve contains phosphorus or does not contain phosphorus, and / or the silicon-aluminum ratio of the single crystal hollow ZSM-5 molecular sieve is 20-100 in terms of SiO2 / Al2O3; preferably, the phosphorus / aluminum molar ratio in the single crystal hollow ZSM-5 molecular sieve is 0.5-1.5, or, after the single crystal hollow ZSM-5 molecular sieve is modified under the condition of a phosphorus / aluminum molar ratio of 1, after hydrothermal treatment at 800°C for 17 hours, its crystal retention is greater than or equal to 90%, and the acid retention is greater than or equal to 30%.

4. The single crystal hollow ZSM-5 molecular sieve according to any one of claims 1 to 3, characterized in that the mesoporous specific surface area of ​​the single crystal hollow ZSM-5 molecular sieve accounts for 5-15% of the total specific surface area, preferably 8-14%, and / or the mesopore volume accounts for 30-50% of the total pore volume, preferably 30-45%.

5. The single crystal hollow ZSM-5 molecular sieve according to claim 1 is characterized in that the length of the single crystal hollow ZSM-5 molecular sieve grain is 1.0-3.0 μm, the width of the grain is 0.5-2.5 μm, the length of the inner cavity is 100-800 nm, the ratio of the length of the inner cavity to the width of the inner cavity is 1.01-1.2, and the thickness of the first molecular sieve wall is less than 300 nm.

6. A method for preparing a single-crystal hollow ZSM-5 molecular sieve, wherein the particles of the single-crystal hollow ZSM-5 molecular sieve have a single crystal structure, a hexagonal morphology, and a double-layer cavity structure with inner and outer layers nested, wherein the inner cavity is at least partially enclosed by a first molecular sieve wall layer, and the outer cavity is completely enclosed by a second molecular sieve wall layer, and wherein the ratio of the length of the molecular sieve grain to the length of the outer cavity is 1.1-2.0, and the ratio of the width of the molecular sieve grain to the width of the outer cavity is 1.05-1.5, characterized in that the method comprises: Step A, preparing a seed solution, comprises the following sub-steps: (A1) mixing a first silicon source, a template and water to obtain a first mixed solution; (A2) subjecting the first mixed solution obtained in sub-step (1) to hydrothermal dynamic crystallization to obtain a seed solution; Step B, preparing a single crystal hollow ZSM-5 molecular sieve, comprises the following sub-steps: (B1) adding the alkali source solution, the second silicon source dispersion and the aluminum source dispersion into water in sequence under stirring to obtain a second mixed solution; (B2) adding a certain amount of the seed solution to the second mixed solution under stirring to obtain a third mixed solution; (B3) subjecting the third mixed solution to hydrothermal dynamic crystallization; The obtained product is filtered, optionally washed, dried, and calcined to obtain a parent molecular sieve; (B4) mixing the obtained parent molecular sieve with an alkali solution to obtain a solid product; and optionally (B5) treating the obtained solid product to obtain an H-type single crystal hollow ZSM-5 molecular sieve, and optionally (B6) Introducing phosphorus into the H-type single crystal hollow ZSM-5 molecular sieve obtained in sub-step (B5).

7. The method according to any one of claims 5 to 6, characterized in that the method comprises: A. Preparation of seed molecular sieve, comprising the following sub-steps: (A1) dissolving a first silicon source and a template in water under stirring, stirring at 30-60° C. for more than 1 hour, preferably 2-6 hours, to obtain a first mixed solution, preferably, the molar ratio of the template R / SiO2 is 0.05-0.50, and the molar ratio of H2O / SiO2 is 10-80; (A2) subjecting the first mixed solution of substep (A1) to hydrothermal dynamic crystallization at a temperature of 140-180° C. for more than 1 hour, for example, 8-24 hours, preferably 10-18 hours, for example, transferring the mixed solution to a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner and subjecting the mixture to hydrothermal crystallization under stirring to obtain a solution containing a crystallized product, which is referred to as a seed solution. Preferably, the crystal grain size of the seed crystals in the seed solution is 200-800 nm; B. Preparation of single crystal hollow ZSM-5 molecular sieve, comprising the following sub-steps: (B1-1) dissolving an alkali source in water and stirring to obtain an alkali source solution; (B1-2) dissolving an aluminum source in water and stirring the water to obtain an aluminum source solution; (B1-3) mixing the second silicon source with the alkali source solution obtained in sub-step (B1-1) under stirring, preferably stirring at room temperature for more than 5 minutes, preferably stirring for more than 10 minutes; (B1-4) the product obtained in sub-step (B1-3) is optionally mixed with water for dilution, and then mixed with the aluminum source solution obtained in sub-step (B1-2) under stirring, preferably stirred at room temperature for more than 1 minute, preferably stirred for 30-60 minutes, to obtain a mixed solution, referred to as a second mixed solution, wherein the mixed solution has the following molar ratio: n(SiO2) / n(Al2O3)=20-200, n(MB2O) / n(SiO2)=0.10-0.20, n(H2O) / n(SiO2)=20-60, wherein MB represents an alkali metal; preferably, MB is one or more of K, Rb, and Cs; (B2) adding a certain amount of the seed solution obtained in sub-step A(2) to the second mixed solution obtained in sub-step (B1-4) under stirring, preferably stirring at room temperature for more than 10 minutes, for example, stirring for 1-6 hours, to obtain a mixed solution, referred to as a third mixed solution; (B3) subjecting the third mixed solution of substep (B2) to hydrothermal dynamic crystallization at a temperature higher than 100° C., for example, for more than 1 hour, preferably at a temperature of 140-180° C., preferably 150-170° C., for 6-48 hours, preferably 10-40 hours; filtering the obtained product, and optionally washing, drying, and calcining to obtain a parent molecular sieve; (B4) mixing the parent molecular sieve obtained in sub-step (B3) with an alkali-containing solution under stirring, for example, at a temperature of 60-90° C. for, for example, 20-60 minutes, wherein, preferably, the alkali content in the alkali-containing solution is 0.4-1.0 mol / L, to obtain a solid product; and optionally (B5) subjecting the solid product obtained in sub-step (B4) to an exchange treatment to obtain an H-type single crystal hollow ZSM-5 molecular sieve; and optionally (B6) Introducing phosphorus into the H-type single crystal hollow ZSM-5 molecular sieve obtained in sub-step (B5).

8. The method according to claim 7, characterized in that, in sub-step (A1), the first silicon source is one or more of methyl orthosilicate or ethyl orthosilicate, and / or, the template is one or more of tetrapropylammonium hydroxide or tetrapropylammonium bromide, preferably, in sub-step (A1), the template R / SiO2 molar ratio is 0.1-0.4, and / or, the H2O / SiO2 molar ratio is 30-55; and / or, in sub-step (B1), the mass concentration of the alkali source solution is 10-30%, And the alkali source is selected from one or more of potassium hydroxide, rubidium hydroxide or cesium hydroxide; and / or, in sub-step (B2), the mass concentration of the aluminum source solution is 5-20%, and the aluminum source is selected from one or more of aluminum sulfate, aluminum nitrate, aluminum isopropoxide, sodium aluminate or aluminum chloride, and / or, in sub-step (B3), the second silicon source is silica sol, preferably, the silica sol is selected from ammonium type silica sol, sodium type silica sol or a mixture thereof; the SiO2 content in the silica sol is 10-45% by weight.

9. The method according to any one of claims 7-8 is characterized in that the second mixed solution has the following molar ratio: n(SiO2) / n(Al2O3)=45-65, n(K2O) / n(SiO2)=0.12-0.16, n(H2O) / n(SiO2)=40-60; and / or, in sub-step (B2), the mass ratio of SiO2 in the seed solution to SiO2 in the second silicon source in sub-step (B1-3) is 5-20:100 or 5-10:

100.

10. Use of the single crystal hollow ZSM-5 molecular sieve according to any one of claims 1 to 5 or the single crystal hollow ZSM-5 molecular sieve obtained by the method according to any one of claims 6 to 12, for catalyzing catalytic cracking reactions of hydrocarbons.

11. A catalyst, characterized in that the catalyst contains the single crystal hollow ZSM-5 molecular sieve according to any one of claims 1 to 5 or the single crystal hollow ZSM-5 molecular sieve obtained by the method according to any one of claims 6 to 9.

12. The catalyst according to claim 11 is characterized in that the catalyst is a catalytic cracking catalyst, which also comprises a Y-type molecular sieve and a carrier. Preferably, based on the dry weight of the catalyst, the catalytic cracking catalyst contains 10-40 wt% of single crystal hollow ZSM-5 molecular sieve, 10-30 wt% of Y-type molecular sieve and 30-80 wt% of the carrier.

13. The catalyst according to claim 12 is characterized in that the silicon-aluminum ratio of the Y-type molecular sieve is 4-8 in terms of SiO2 / Al2O3 molar ratio; preferably, the Y-type molecular sieve is selected from ultra-stable Y-type molecular sieve and / or rare earth-containing Y-type molecular sieve, wherein the ultra-stable Y-type molecular sieve is a hydrothermally ultra-stable Y-type molecular sieve and / or a gas-phase ultra-stable Y-type molecular sieve, preferably, the rare earth content of the Y-type molecular sieve is 2-25% by weight, preferably 2-12% by weight, calculated as RE2O3 oxide, preferably, the rare earth element can be preferably one or both of lanthanum and cerium.

14. The catalyst according to any one of claims 12 to 13, wherein The carrier is selected from one or more of natural clay, alumina carrier, silica carrier, aluminum phosphate carrier and silica-alumina oxide carrier; preferably, the silica carrier is selected from one or more of neutral silica sol, acidic silica sol or alkaline silica sol; the alumina carrier is preferably selected from one or more of aluminum sol, acidified pseudo-boehmite, hydrated alumina and activated alumina; the aluminum phosphate carrier is selected from phosphate aluminum gel; the silica-alumina oxide carrier is selected from one or more of solid silica-alumina material, silica-alumina sol and silica-alumina gel.

15. The catalyst according to any one of claims 12 to 14, characterized in that, based on the dry weight of the catalyst, the catalyst contains: 10-40 wt% of the single crystal hollow ZSM-5 molecular sieve on a dry basis, 10-30 wt% of the Y-type molecular sieve on a dry basis, 5-30 wt% of pseudo-boehmite on alumina basis, 5-20 wt% of aluminum sol on alumina basis, 2-15 wt% of silica sol on silicon oxide basis, and 10-50 wt% of clay on a dry basis; preferably, the pseudo-boehmite is acidified pseudo-boehmite.

16. A method for preparing the catalyst according to any one of claims 11 to 15, the method comprising: The slurry containing the carrier, the single crystal hollow ZSM-5 molecular sieve, the Y-type molecular sieve and water is spray dried.

17. The method according to claim 16, wherein: The method further comprises: mixing the catalyst particles obtained by the spray drying, an ammonium salt and a solvent in a weight ratio of 1:(0.1-1):(5-15) to perform ammonium exchange, and optionally washing; preferably, the conditions of the ammonium exchange include: a temperature of 50-100°C and a time of 0.5-2 hours; preferably, the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate, and preferably, the solvent is selected from water.

18. Use of the catalyst according to any one of claims 11 to 15, for catalytic cracking reaction of heavy oil to increase the production of gasoline and light olefins.

19. A method for catalytic cracking of hydrocarbon oil, comprising contacting the hydrocarbon oil with the single crystal hollow ZSM-5 molecular sieve according to any one of claims 1 to 4 or the catalyst according to any one of claims 11 to 16 for reaction.

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