CN114425421A

CN114425421A - Catalytic cracking catalyst, preparation method and application thereof

Info

Publication number: CN114425421A
Application number: CN202010998863.8A
Authority: CN
Inventors: 王鹏; 宋海涛; 韩蕾; 周翔; 王振波; 王丽霞
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2020-09-22
Filing date: 2020-09-22
Publication date: 2022-05-03
Anticipated expiration: 2040-09-22
Also published as: CN114425421B

Abstract

A catalytic cracking catalyst, a preparation method and application thereof. The catalyst contains 30-79 wt% of carrier, 5-15 wt% of core-shell type molecular sieve, 15-45 wt% of Y type molecular sieve and 1-10 wt% of molecular sieve with pore canal opening diameter of 0.65-0.70 nm; wherein, the core phase of the core-shell type molecular sieve is ZSM-5 molecular sieve, the shell layer is beta molecular sieve, the ratio of the peak height of 22.4 degrees 2 theta to the peak height of 23.1 degrees 2 theta in an X-ray diffraction pattern is 0.1-10:1, and the total specific surface area is more than 420m²(ii) in terms of/g. The preparation method comprises the steps of forming slurry comprising a carrier, a core-shell type molecular sieve, a Y-type molecular sieve, a molecular sieve with a pore opening diameter of 0.65-0.70 nm and water, and spray drying. The catalyst has higher conversion rate and low-carbon olefin yield when being used for heavy oil.

Description

Catalytic cracking catalyst, preparation method and application thereof

Technical Field

The invention relates to a catalytic cracking catalyst and a preparation method thereof, in particular to a heavy oil conversion catalytic cracking catalyst containing naphthenic rings.

Background

The low-carbon olefins (ethylene, propylene and butylene) are very important chemical raw materials, naphtha steam cracking is mainly adopted to produce the low-carbon olefins in the world, and the method has the defects of high reaction temperature, large energy consumption and the like. In order to overcome the problems, a large number of catalytic cracking technical researches are carried out at home and abroad, and the introduction of catalytic action is expected to properly reduce the reaction temperature, reduce coking and energy consumption, improve the yield of low-carbon olefin and adjust the product distribution more flexibly.

However, catalytic cracking is carried out using different feedstocks, with different catalysts and different reaction conditions, often resulting in different products, and refineries often also need different product distributions for different purposes. Vacuum distillate oil (VGO) is a product of vacuum distillation of crude oil, and often contains a large amount of aromatic hydrocarbons, and the aromatic hydrocarbons are not converted into light oil products in the catalytic cracking process. However, hydrogenated VGO can be converted in multiple directions, for example, it can be dehydrogenated to form aromatic hydrocarbons, and can also be ring-opened cracked to form hydrocarbon products such as low-carbon olefins, gasoline and diesel oil, and it is also desirable to produce liquefied gas and heavy oil products as much as possible to reduce the light oil products of gasoline and diesel oil. An important factor in controlling the direction of product conversion is the catalyst used.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a catalytic cracking catalyst which is used for hydrogenation VGO conversion and has higher yield of low-carbon olefins.

The invention provides a catalytic cracking catalyst for producing low-carbon olefin by hydrogenation VGO catalytic cracking, which comprises 30-79 wt% of a carrier, 5-15 wt% of a core-shell type molecular sieve (called a first molecular sieve), 15-45 wt% of a Y-type molecular sieve (called a second molecular sieve) and 1-10 wt% of a molecular sieve (called a third molecular sieve) with the opening diameter of a pore channel of 0.65-0.70 nanometer, wherein the carrier is in dry weight; wherein, the core phase of the core-shell type molecular sieve is ZSM-5 molecular sieve, the shell layer is beta molecular sieve, the ratio of the peak height of 22.4 degrees 2 theta to the peak height of 23.1 degrees 2 theta in an X-ray diffraction pattern is 0.1-10:1, and the total specific surface area is more than 420m²/g。

In the catalytic cracking catalyst according to any of the above technical schemes, the core-shell type molecular sieve (abbreviated as core-shell molecular sieve) is a ZSM-5/β core-shell molecular sieve, wherein the ratio of the peak height at 22.4 ° (D1) to the peak height at 23.1 ° (D2) is 0.1-10:1, preferably 0.1-8:1, such as 0.1-5:1 or 0.12-4:1 or 0.8-8: 1.

The peak at 22.4 ° is a peak in the range of 22.4 ° ± 0.1 ° in the X-ray diffraction pattern, and the peak at 23.1 ° is a peak in the range of 23.1 ° ± 0.1 ° in the X-ray diffraction pattern.

The catalytic cracking catalyst according to any of the above technical schemes, wherein the ratio of the core phase to the shell layer of the core-shell type molecular sieve is 0.2-20:1, for example, 1-15:1, wherein the ratio of the core phase to the shell layer can be calculated by adopting the peak area of the X-ray diffraction spectrum.

The catalytic cracking catalyst according to any of the preceding claims, wherein the total specific surface area of the core-shell molecular sieve (also referred to as the specific surface area of the core-shell molecular sieve) is greater than 420m²G is, for example, 420m²/g-650m²The total specific surface area of the core-shell type molecular sieve is preferably more than 450m²G is, for example, 450m²/g-620m²(iv)/g or 480m²/g-600m²G or 490m²/g-580m²G or 500m²/g-560m²/g。

The catalytic cracking catalyst according to any of the preceding claims, wherein the ratio of the mesopore surface area to the total surface area (or the mesopore specific surface area to the total specific surface area) of the core-shell type molecular sieve is 10% to 40%, for example 12% to 35%. Wherein, the mesopores refer to pores with a pore diameter of 2nm to 50 nm.

In the catalytic cracking catalyst according to any of the above technical solutions, the total pore volume of the core-shell type molecular sieve is 0.28mL/g to 0.42mL/g, for example, 0.3mL/g to 0.4mL/g or 0.32mL/g to 0.38 mL/g.

The catalytic cracking catalyst according to any of the above technical solutions, wherein the total pore volume of the core-shell type molecular sieve is taken as a reference, and the pore volume of pores with a pore diameter of 0.3nm to 0.6nm in the core-shell type molecular sieve accounts for 40% to 90%, for example, 40% to 88%, or 50% to 85%, or 60% to 85%, or 70% to 82%.

The catalytic cracking catalyst according to any of the above technical solutions, wherein the pore volume of the pores with a pore diameter of 0.7nm to 1.5nm in the core-shell type molecular sieve accounts for 3% to 20%, for example, 3% to 15% or 3% to 9%, based on the total pore volume of the core-shell type molecular sieve.

The catalytic cracking catalyst according to any of the above technical solutions, wherein the pore volume of the pores with a pore diameter of 2nm to 4nm in the core-shell type molecular sieve is 4% to 50%, for example, 4% to 40%, or 4% to 20%, or 4% to 10%, based on the total pore volume of the core-shell type molecular sieve.

The catalytic cracking catalyst according to any of the above technical solutions, wherein the pore volume of the pores with a pore diameter of 20nm to 80nm in the core-shell type molecular sieve is 5% to 40%, for example, 5% to 30%, or 7% to 18%, or 6% to 20%, or 8% to 16%, based on the total pore volume of the core-shell type molecular sieve.

In one embodiment of the catalytic cracking catalyst according to any of the above technical schemes, the pore volume of pores with pore diameters of 2nm to 80nm in the core-shell molecular sieve accounts for 10% to 30%, for example 11% to 25%, of the total pore volume.

The catalytic cracking catalyst according to any of the above technical solutions, wherein in one embodiment, the pore volume of the pores with pore diameter of 20nm to 80nm in the core-shell type molecular sieve accounts for 50% to 70%, such as 55% to 65% or 58% to 64%, of the pore volume of the pores with pore diameter of 2nm to 80 nm.

The total pore volume and the pore size distribution can be measured by a low-temperature nitrogen adsorption volumetric method, and the pore size distribution can be calculated by a BJH calculation method, which can refer to a Ripp-151-90 method (a petrochemical analysis method, a RIPP test method, a scientific publishing company, 1990).

The catalytic cracking catalyst according to any of the preceding claims, wherein the shell molecular sieve of the core-shell molecular sieve has a thickness of 10nm to 2000nm, for example, 50nm to 2000 nm.

The catalytic cracking catalyst according to any of the above technical solutions, wherein the average grain size of the shell layer molecular sieve of the core-shell type molecular sieve is 10nm to 500nm, for example, 50nm to 500 nm.

The catalytic cracking catalyst according to any of the above technical schemes, wherein the silica-alumina ratio of the core-shell molecular sieve and the shell molecular sieve is SiO₂/Al₂O₃The molar ratio of silicon to aluminium is 10 to 500, preferably 10 to 300, for example 30 to 200 or 25 to 200.

The catalytic cracking catalyst according to any of the above technical solutions, wherein the silica-alumina ratio of the core-phase molecular sieve of the core-shell molecular sieve is SiO₂/Al₂O₃The molar ratio of Si to Al is 10-infinity, for example 20-infinity or 50-infinity or 30-300 or 30-200 or 25-70 or 20-80 or 30-60.

The catalytic cracking catalyst according to any of the preceding claims, wherein the core phase molecular sieve of the core-shell molecular sieve has an average crystallite size of 0.05 μm to 15 μm, preferably 0.1 μm to 10 μm, such as 0.1 μm to 5 μm or 0.1 μm to 1.2 μm.

The catalytic cracking catalyst of any of the preceding claims, wherein the core-shell molecular sieve, the core-phase molecular sieve have an average particle size of 0.1 μm to 30 μm, such as 0.2 μm to 25 μm, or 1 μm to 5 μm, or 0.5 μm to 10 μm, or 2 μm to 4 μm.

The catalytic cracking catalyst according to any of the above technical solutions, wherein the core phase molecular sieve particles of the core-shell type molecular sieve are agglomerates of a plurality of ZSM-5 grains, and the number of grains in a single particle of the core phase molecular sieve is not less than 2.

The catalytic cracking catalyst according to any of the above technical schemes, wherein the shell coverage of the core-shell molecular sieve is 50% -100%, for example 80-100%.

According to the catalytic cracking catalyst of any of the above technical schemes, the Y-type molecular sieve is preferably a rare earth-containing Y-type molecular sieve, and the rare earth content in the rare earth-containing Y-type molecular sieve is as RE₂O₃Preferably 5-17 wt%. In one embodiment, the framework Si/Al ratio of the Y-type molecular sieve is SiO₂/Al₂O₃The molar ratio is 4.9-14.

The catalytic cracking catalyst according to any of the above technical schemes, wherein the molecular sieve with pore opening diameter of 0.65-0.70 nm is a beta molecular sieve, and the beta molecular sieve can be a hydrogen type beta molecular sieve.

The catalytic cracking catalyst according to any of the above technical solutions, wherein the carrier may be a carrier of a cracking catalyst, and for example, may be one or more of an aluminum sol carrier, a zirconium sol carrier, a silica sol carrier, a pseudo-boehmite carrier, and a clay carrier.

The invention provides a preparation method of a catalytic cracking catalyst, which comprises the following steps: forming a slurry comprising the first molecular sieve, the second molecular sieve, the third molecular sieve, a carrier, and water, and spray drying. The first molecular sieve is a core-shell molecular sieve, the second molecular sieve is a Y-type molecular sieve, and the third molecular sieve is a molecular sieve with pore opening diameters of 0.65-0.70 nanometers.

In one embodiment, the method for preparing the core-shell molecular weight comprises the following steps:

(1) contacting the ZSM-5 molecular sieve with a surfactant solution to obtain a ZSM-5 molecular sieve I;

(2) contacting ZSM-5 molecular sieve I with slurry containing beta zeolite to obtain ZSM-5 molecular sieve II;

(3) crystallizing a synthetic solution containing a silicon source, an aluminum source, a template agent and water such as deionized water at 50-300 ℃ for 4-100h to obtain a synthetic solution III;

(4) mixing ZSM-5 molecular sieve II with synthetic liquid III, and crystallizing; recovering to obtain the sodium type core-shell molecular sieve;

(5) ammonium exchange of the sodium type core-shell molecular sieve, preferably, the ammonium exchange causes Na in the core-shell molecular sieve₂The O content is less than 0.15 wt%;

(6) and (3) drying the core-shell type molecular sieve obtained in the step (5), and roasting, for example, roasting at 350-600 ℃ for 2-6h to remove the template agent.

According to the preparation method of the catalytic cracking catalyst and the synthesis method of the core-shell type molecular sieve in the technical scheme, in one embodiment, the contacting method in the step (1) is as follows: adding the ZSM-5 molecular sieve (raw material) into a surfactant solution with the weight percentage concentration of 0.05% -50%, preferably 0.1% -30%, for example 0.1% -5%, to be treated, for example, stirred for more than 0.5h, for example 0.5h-48h, and filtering and drying to obtain the ZSM-5 molecular sieve I.

According to one embodiment of the method for preparing a catalytic cracking catalyst and the method for synthesizing a core-shell molecular sieve in any one of the above technical schemes, in the step (1), the contact time (or treatment time) is more than 0.5h, for example, 0.5-48h or 1h-36h, and the contact temperature (or treatment temperature) is 20 ℃ to 70 ℃.

According to the preparation method of the catalytic cracking catalyst, the core-shell molecular sieve synthesis method, in one embodiment, the weight ratio of the surfactant solution to the ZSM-5 molecular sieve in dry basis in step (1) is 10-200: 1.

In the method for preparing a catalytic cracking catalyst according to any one of the above embodiments, in the method for synthesizing a core-shell type molecular sieve, the surfactant solution may further contain a salt, which has an electrolyte property and acts as a separation or dispersion function on the surfactant, for example, one or more of alkali metal salt and ammonium salt that can be dissolved in water, preferably one or more of alkali metal chloride salt, ammonium chloride salt, alkali metal nitrate, and ammonium nitrate, such as one or more of ammonium chloride, sodium chloride, potassium chloride, and ammonium nitrate; the concentration of the salt in the surfactant solution is preferably 0.05 wt% to 10.0 wt%, for example 0.2 wt% to 2 wt%. The addition of the salt is beneficial to the adsorption of the surfactant.

In the method for preparing the catalytic cracking catalyst according to any of the above technical solutions, in the method for synthesizing the core-shell type molecular sieve, the surfactant may be at least one selected from the group consisting of polymethyl methacrylate, polydiallyldimethylammonium chloride, tetraethylammonium bromide, dipicolinic acid, n-butylamine, tetraethylammonium hydroxide, ammonia water, ethylamine, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and tetrabutylammonium hydroxide.

In the method for preparing a catalytic cracking catalyst according to any of the above technical solutions, in the synthesis method of the core-shell type molecular sieve, the silica-alumina molar ratio of the ZSM-5 molecular sieve (raw material) in step (1) is SiO₂/Al₂O₃The calculated (namely the silicon-aluminum ratio) is 10-infinity; for example, the ZSM-5 molecular sieve (raw material) in the step (1) has a Si/Al molar ratio of SiO₂/Al₂O₃It may be 20-infinity, or 50-infinity, or 30-300, or 30-200, or 20-80, or 40-70, or 25-70, or 30-60.

The preparation method of the catalytic cracking catalyst and the synthesis method of the core-shell type molecular sieve in any one of the above technical schemes, wherein the average grain size of the ZSM-5 molecular sieve (raw material) in the step (1) is 0.05 μm-20 μm; for example, the ZSM-5 molecular sieve (feedstock) described in step (1) has an average crystallite size of from 0.1 μm to 10 μm.

In the method for preparing a catalytic cracking catalyst according to any of the above technical schemes, in the method for synthesizing the core-shell type molecular sieve, the average particle size of the ZSM-5 molecular sieve (raw material) is preferably 0.1 μm to 30 μm, for example, 0.5 μm to 25 μm or 1 μm to 5 μm or 1 μm to 20 μm or 2 μm to 4 μm.

In the method for preparing a catalytic cracking catalyst according to any one of the above technical solutions, in the synthesis method of the core-shell type molecular sieve, the ZSM-5 molecular sieve (raw material) in step (1) is a Na-type, hydrogen-type or ion-exchanged ZSM-5 molecular sieve. The ion-exchanged ZSM-5 molecular sieve refers to an exchanged ZSM-5 molecular sieve obtained by exchanging a ZSM-5 molecular sieve (such as a Na-type ZSM-5 molecular sieve) with ions other than alkali metals, such as transition metal ions, ammonium ions, alkaline earth metal ions, IIIA group metal ions, IVA group metal ions and VA group metal ions.

According to the preparation method of the catalytic cracking catalyst in any of the above technical schemes, in the synthesis method of the core-shell type molecular sieve, in the step (1), the drying has no special requirement, and for example, the drying may be drying, flash drying, or pneumatic drying. In one embodiment, the temperature of drying is 50 ℃ to 150 ℃ and the drying time is not limited as long as the sample is dried, and may be, for example, 0.5h to 4 h.

In the method for preparing a catalytic cracking catalyst according to any of the above technical solutions, in the step (2), the contacting includes the steps of mixing, filtering and drying the ZSM-5 molecular sieve I and a slurry containing beta zeolite (beta zeolite is also referred to as beta molecular sieve). One embodiment includes: adding ZSM-5 molecular sieve I into slurry containing beta zeolite, stirring at 20-60 deg.C for more than 0.5 hr such as 1-24 hr, filtering, and drying to obtain ZSM-5 molecular sieve II.

In the method for preparing a catalytic cracking catalyst according to any of the above technical solutions, in the method for synthesizing a core-shell type molecular sieve, the concentration of the beta zeolite in the slurry containing the beta zeolite in the step (2) is 0.1 wt% to 10 wt%, for example, 0.3 wt% to 8 wt% or 0.2 wt% to 1 wt%.

In the method for preparing a catalytic cracking catalyst according to any of the above technical solutions, in the step (2), the weight ratio of the slurry containing beta zeolite to the ZSM-5 molecular sieve I on a dry basis is 10-50:1, and preferably, the weight ratio of the beta zeolite to the ZSM-5 molecular sieve I on a dry basis is 0.01-1:1, for example, 0.02-0.35: 1.

In the method for preparing a catalytic cracking catalyst according to any of the above technical solutions, in the slurry containing beta zeolite in step (2), the average crystallite size of the beta zeolite is 10nm to 500nm, for example, 50nm to 400nm, or 10nm to 300nm, or 100nm to 300nm, or 200 to 500 nm. Preferably, the average crystallite size of the beta zeolite is less than the average crystallite size of the ZSM-5 molecular sieve (feedstock). In one embodiment, the zeolite beta-containing slurry has an average crystallite size of from 10nm to 500nm less than an average crystallite size of a ZSM-5 molecular sieve feedstock. For example, the average crystallite size of the ZSM-5 molecular sieve is 1.5 times or more, for example, 2 to 50 or 5 to 20 times larger than the average crystallite size of the zeolite beta.

In the method for preparing a catalytic cracking catalyst according to any of the above technical solutions, in the method for synthesizing a core-shell type molecular sieve, the average particle size of the beta zeolite in the slurry containing the beta zeolite in step (2) is preferably 0.01 μm to 0.5 μm, for example, 0.05 μm to 0.5 μm. Typically, the particles of zeolite beta are single-grain particles.

In the method for preparing a catalytic cracking catalyst according to any of the above technical solutions, in the method for synthesizing the core-shell molecular sieve, the mole ratio of silicon to aluminum of the beta zeolite in the slurry containing the beta zeolite in the step (2) is SiO₂/Al₂O₃A gauge (i.e. silicon to aluminium ratio) of 10 to 500, for example 30 to 200 or 25 to 200. In one embodiment, the silica-alumina ratio of the beta zeolite in the slurry containing the beta zeolite of step (2) differs by no more than ± 10% from the silica-alumina ratio of the shell molecular sieve, e.g., the beta zeolite has the same silica-alumina ratio as the shell molecular sieve of the synthesized core-shell molecular sieve.

In the method for preparing a catalytic cracking catalyst according to any one of the above technical aspects, in the step (3), the molar ratio of the silicon source, the aluminum source, the template (represented by R), and the water is as follows: R/SiO₂0.1-10, e.g. 0.1-3 or 0.2-2.2, H₂O/SiO₂2-150 e.g. 10-120, SiO₂/Al₂O₃10-800 e.g. 20-800, Na₂O/SiO₂0-2, for example 0.01-1.7 or 0.05-1.3 or 0.1-1.1.

According to any one of the above technical solutions, in the method for preparing a catalytic cracking catalyst, in the step (3), the silicon source may be at least one selected from ethyl orthosilicate, water glass, coarse silica gel, silica sol, white carbon black, and activated clay; the aluminum source can be selected from at least one of aluminum sulfate, aluminum isopropoxide, aluminum nitrate, aluminum sol, sodium metaaluminate or gamma-alumina; the template (R) is, for example, one or more of tetraethylammonium fluoride, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, polyvinyl alcohol, triethanolamine or sodium carboxymethylcellulose, and preferably, the template comprises at least one of tetraethylammonium hydroxide, tetraethylammonium chloride and tetraethylammonium bromide.

According to the preparation method of the catalytic cracking catalyst in any one of the above technical schemes, in the synthesis method of the core-shell type molecular sieve, in the step (3), the silicon source, the aluminum source, the template agent R and the deionized water are mixed to form a synthetic liquid, and then the synthetic liquid is crystallized at 75-250 ℃ for 10-80 h to obtain a synthetic liquid III, wherein the crystallization process is called as first crystallization (or first crystallization reaction); preferably, the crystallization temperature of the first crystallization is 80 ℃ to 180 ℃, and the crystallization time of the first crystallization is 18 hours to 50 hours.

According to the preparation method of the catalytic cracking catalyst in any technical scheme, in the synthesis method of the core-shell molecular sieve, the crystallization in the step (3) is the first crystallization, so that the crystallization state of the obtained synthetic liquid III is a state that crystal grains are not appeared yet, and the crystallization state is close to the end of a crystallization induction period and is about to enter a rapid crystal nucleus growth stage. XRD analysis of the obtained synthetic liquid III showed the presence of a peak at 2 θ ═ 22.4 ° and the absence of a peak at 2 θ ═ 21.2 °. Preferably, the XRD pattern of the synthetic liquid iii has infinite peak intensity ratio between the peak at 22.4 ° and the peak at 21.2 ° in 2 θ. The XRD analysis method of the synthetic liquid III can be carried out according to the following method: and filtering, washing, drying and roasting the synthetic liquid III at 550 ℃ for 4 hours, and then carrying out XRD analysis. The washing may be with deionized water. The 2 θ -22.4 ° range means a2 θ -22.4 ° ± 0.1 ° range, and the 2 θ -21.2 ° range means a2 θ -21.2 ° ± 0.1 ° range.

In the method for preparing a catalytic cracking catalyst according to any of the above technical schemes, in the step (4), ZSM-5 molecular sieve II is mixed with the synthesis solution III, for example, the ZSM-5 molecular sieve II is added into the synthesis solution III, wherein the weight ratio of the synthesis solution III to the ZSM-5 molecular sieve II on a dry basis is 2-10:1, for example, 4-10: 1. Preferably, the weight ratio of the ZSM-5 molecular sieve on a dry basis to the synthesis solution III on a dry basis is greater than 0.2:1, for example 0.3 to 20:1 or 1 to 15:1 or 0.5 to 10:1 or 0.5 to 5:1 or 0.8 to 2:1 or 0.9 to 1.7: 1.

According to the preparation method of the catalytic cracking catalyst in any technical scheme, in the synthesis method of the core-shell type molecular sieve, the crystallization in the step (4) is called as second crystallization, the crystallization temperature of the second crystallization is 50-300 ℃, and the crystallization time is 10-400 h.

According to the preparation method of the catalytic cracking catalyst in any technical scheme, in the synthesis method of the core-shell type molecular sieve, in the step (4), the ZSM-5 molecular sieve II and the synthesis liquid III are mixed and then crystallized for 30-350h at 100-250 ℃ for second crystallization. The crystallization temperature of the second crystallization is, for example, 100 ℃ to 200 ℃, and the crystallization time is, for example, 50h to 120 h.

According to the preparation method of the catalytic cracking catalyst in any of the above technical solutions, in the synthesis method of the core-shell type molecular sieve, in the step (4), the sodium type core-shell type molecular sieve is recovered after crystallization is completed, and the recovery may include a filtering step, and optionally may further include one or more steps of washing, drying, and calcining. Drying methods such as air drying, oven drying, air flow drying, flash drying, drying conditions such as: the temperature is 50-150 ℃ and the time is 0.5-4 h. The washing method is the prior art, for example, water can be used for washing, the water can be deionized water, the ratio of the core-shell molecular sieve to the water is 1:5-20, and the washing can be carried out once or for multiple times until the pH value of the water after washing is 8-9. The roasting temperature may be 350-600 deg.c and the roasting time may be 1-6 hr.

The preparation method of the catalytic cracking catalyst according to any one of the above technical schemes, in the synthesis method of the core-shell type molecular sieveThe obtained core-shell molecular sieve has a ZSM-5 molecular sieve as a core phase and a beta molecular sieve as a shell layer, and the silica-alumina molar ratio of the shell layer is SiO₂/Al₂O₃In the range of 10-500, for example 25-200.

According to the preparation method of the catalytic cracking catalyst in any one of the above technical solutions, in the synthesis method of the core-shell type molecular sieve, the ammonium exchange in the step (5) is performed according to a sodium type core-shell type molecular sieve: ammonium salt: h₂O is 1: (0.1-1): (5-15) exchanging and filtering at 50-100 ℃ in a weight ratio, wherein the exchanging and filtering processes can be carried out once or more times; the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.

According to the catalytic cracking catalyst preparation method of any one of the technical methods, in the core-shell molecular sieve synthesis method, the core-shell molecular sieve obtained in the step (5) is dried and then calcined in the step (6), and the template agent is removed to obtain the core-shell molecular sieve. In one embodiment, the roasting is carried out at 350-600 ℃ for 2-6 h.

According to the preparation method of the catalytic cracking catalyst in any of the above technical schemes, the second molecular sieve is a Y-type molecular sieve, for example, the Y-type molecular sieve may be one or more of a DASY molecular sieve, a rare earth-containing DASY molecular sieve, an HRY molecular sieve, a rare earth-containing HRY molecular sieve, a DOSY molecular sieve, a USY molecular sieve, a rare earth-containing USY molecular sieve, a REY molecular sieve, an HY molecular sieve, and an REHY molecular sieve. The Y-type molecular sieve is preferably a rare earth-containing Y-type molecular sieve, and the rare earth content in the Y-type molecular sieve is RE₂O₃Preferably 5-17 wt%. The silicon-aluminum ratio of the Y-type molecular sieve is preferably 4.9-14.0.

According to the preparation method of the catalytic cracking catalyst in any one of the above technical schemes, the third molecular sieve is a molecular sieve with pore opening diameters of 0.65-0.70 nm. The molecular sieve with the pore opening diameter of 0.65-0.70 nm is one or more of molecular sieves with AET, AFR, AFS, AFI, BEA, BOG, CFI, CON, GME, IFR, ISV, LTL, MEI, MOR, OFF and SAO structure; preferably at least one of Beta, SAPO-5, SAPO-40, SSZ-13, CIT-1, ITQ-7, ZSM-18, mordenite and gmelinite. More preferably, the third molecular sieve is a beta molecular sieve, such as a hydrogen form beta molecular sieve (H beta molecular sieve).

The preparation method of the catalytic cracking catalyst according to any of the above technical schemes, wherein the carrier is preferably one or more of clay, alumina carrier and silica carrier.

According to the preparation method of the catalytic cracking catalyst of any one technical scheme, the silica carrier is one or more of neutral silica sol, acidic silica sol or alkaline silica sol; preferably, the content of the silica sol in the catalyst is SiO₂Calculated as 1-15 wt%. The alumina carrier is one or more of acidified pseudo-boehmite, alumina sol, hydrated alumina and activated alumina. Such as one or more of pseudoboehmite (not acidified), boehmite, gibbsite, bayerite, nordstrandite, amorphous aluminum hydroxide. Such as one or more of gamma alumina, eta alumina, chi alumina, delta alumina, theta alumina, and kappa alumina. The alumina carrier is preferably one or more of acidified pseudo-boehmite and alumina sol. Such as one or more of the clays described such as kaolin, montmorillonite, diatomaceous earth, halloysite, pseudohalloysite, saponite, rectorite, sepiolite, attapulgite, hydrotalcite and bentonite.

The preparation method of the catalytic cracking catalyst according to any one of the above technical schemes, wherein Na of the core-shell type molecular sieve₂The O content is preferably not more than 0.15% by weight.

According to the preparation method of the catalytic cracking catalyst in any one of the above technical schemes, the first molecular sieve, the second molecular sieve, the third molecular sieve, the carrier and water are mixed to form slurry, and the solid content of the slurry is generally 10-50 wt%, and preferably 15-30 wt%.

According to the preparation method of the catalytic cracking catalyst in any one of the technical schemes, the spray drying condition is a drying condition commonly used in the preparation process of the catalytic cracking catalyst. In general, the spray-drying temperature is from 100 to 350 ℃ and preferably from 200 to 300 ℃.

According to the preparation method of the catalytic cracking catalyst in any technical scheme, the catalyst obtained by spray drying can be exchanged and washed, and the exchange and washing can be carried out by using an ammonium salt solution. In one embodiment, the exchange wash is performed according to catalyst: ammonium salt: h₂O is 1: (0.01-1): (5-15) exchanging and filtering at 50-100 ℃ in a weight ratio, wherein the exchanging and filtering can be carried out for one or more times; the ammonium salt can be selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate. Preferably, the exchange washing is to make Na in the obtained catalytic cracking catalyst₂The O content is less than 0.15 wt%. The washed catalyst was exchanged and dried. The preparation method of the catalytic cracking catalyst can also comprise a roasting process, and the roasting process can be carried out before the exchange washing and/or after the exchange washing. The calcination may be carried out by conventional calcination methods, for example, at a calcination temperature of 350 to 650 deg.C for a calcination time of 1 to 10 hours, and in one embodiment, at 400 to 600 deg.C for 2 to 6 hours.

A heavy oil catalytic cracking method comprises the step of carrying out contact reaction on heavy oil and the catalytic cracking catalyst provided by the invention. The reaction conditions of the method for producing low-carbon olefins by catalytic cracking of heavy oil provided by the invention can adopt the conventional reaction conditions of catalytic cracking of heavy oil, such as the reaction temperature of 480-600 ℃, for example, 500-600 ℃, preferably 500-550 ℃, and the weight hourly space velocity of 5-30 hours^-1Preferably 8 to 20 hours^-1The ratio of agent to oil is 1-15, preferably 2-12. The catalyst-to-oil ratio refers to the weight ratio of the catalyst to the feedstock oil. The heavy oil is preferably hydrogenated VGO.

The catalytic cracking catalyst provided by the invention has rich pore channel structures, excellent heavy oil cracking capability and higher low-carbon olefin selectivity. The catalyst is used for hydrogenation VGO conversion, has higher liquefied gas yield and lower olefin yield, has higher propylene yield, and preferably has higher ethylene yield and higher butylene yield.

The heavy oil catalytic cracking method provided by the invention has higher heavy oil conversion rate.

The hydrogenation VGO catalytic cracking method provided by the invention has the advantages of high liquefied gas yield, high low-carbon olefin yield and high propylene yield.

Detailed Description

The catalytic cracking catalyst provided by the invention comprises 30-79 wt%, preferably 40-70 wt% of carrier, 5-15 wt%, preferably 8-12 wt% of core-shell type molecular sieve, 15-45 wt%, preferably 20-35 wt% of Y type molecular sieve and 1-15 wt%, preferably 4-10 wt% of molecular sieve with pore opening diameter of 0.65-0.70 nm based on the weight of the catalyst and calculated by dry weight.

In one embodiment, the core-shell molecular sieve is a ZSM-5/β core-shell molecular sieve having an X-ray diffraction pattern with a ratio of the peak height at 22.4 ° 2 θ to the peak height at 23.1 ° 2 θ of 0.1 to 10:1, e.g., 0.1 to 5:1 or 0.12 to 4:1 or 0.8 to 8:1, and a total specific surface area greater than 420m²G is, for example, 450m²/g-620m²(iv)/g or 480m²/g-600m²G or 490m²/g-580m²G or 500m²/g-560m²Per g, the ratio of the mesopore surface area to the total specific surface area is preferably 10% to 40%, for example 12% to 35%, the average grain size of the shell molecular sieve is 10nm to 500nm, for example 50 to 500nm, the shell thickness of the shell molecular sieve is 10nm to 2000nm, for example 50nm to 2000nm, the average grain size of the core phase molecular sieve is 0.05 μm to 15 μm, preferably 0.1 μm to 10 μm, for example 0.1 μm to 5 μm or 0.1 μm to 1.2 μm, the average grain size of the core phase molecular sieve is 0.1 μm to 30 μm, for example 0.2 μm to 25 μm or 0.5 μm to 10 μm or 1 μm to 5 μm or 2 μm to 4 μm, the core phase molecular sieve is an agglomerate of a plurality of grains, the molar ratio of silica to alumina of the shell molecular sieve is SiO₂/Al₂O₃In terms of silica to alumina ratio, of 10 to 500, preferably 10 to 300, for example 30 to 200 or 25 to 200, the silica to alumina molar ratio of the core phase molecular sieve being in SiO₂/Al₂O₃The ratio of the core phase to the shell layer of the core-shell molecular sieve is preferably 0.2 to 20:1, for example 1 to 15:1, and the pore volume of pores having a pore diameter of 20 to 80nm accounts for 50 to 70% of the pore volume of pores having a pore diameter of 2 to 80nm, in terms of 10 to infinity, for example 20 to infinity, or 50 to infinity, or 30 to 300, or 30 to 200, or 20 to 80, or 25 to 70, or 30 to 60. In one embodiment, the ZSM-5/beta core-shell molecular sieve has a pore size diameter of 0The pore volume of pores with the diameter of 3-0.6nm accounts for 40-88% of the total pore volume, the pore volume of pores with the diameter of 0.7-1.5nm accounts for 3-20% of the total pore volume, the pore volume of pores with the diameter of 2-4nm accounts for 4-50% of the total pore volume, and the pore volume of pores with the diameter of 20-80nm accounts for 5-40% of the total pore volume.

In one embodiment, the core-shell molecular sieve may be prepared by:

(1) adding the ZSM-5 molecular sieve into a surfactant solution with the weight percentage concentration of 0.05-50%, and stirring for 0.5-48h for treatment, wherein the weight ratio of the surfactant to the ZSM-5 molecular sieve is preferably 0.02-0.5: 1, filtering and drying to obtain a ZSM-5 molecular sieve I, wherein the ZSM-5 molecular sieve has a silica-alumina molar ratio SiO₂/Al₂O₃Preferably 20- ∞, for example 50- ∞;

(2) adding ZSM-5 molecular sieve I into slurry containing beta zeolite, wherein the content of the beta zeolite in the slurry containing the beta zeolite is 0.2-8 wt%, and the weight ratio of the weight of the beta zeolite to the weight of the ZSM-5 molecular sieve I on a dry basis is preferably 0.03-0.30: 1, stirring for at least 0.5h, such as 0.5h-24h, then filtering, drying to obtain ZSM-5 molecular sieve II,

(3) mixing a silicon source, an aluminum source, a template agent (represented by R) and water to form a mixed solution, and stirring the mixed solution at 50-300 ℃ for 4-100h, preferably at 75-250 ℃ for 10-80 h to obtain a synthetic solution III; wherein, R/SiO₂＝0.1-10:1，H₂O/SiO₂＝2-150:1，SiO₂/Al₂O₃＝10-800:1，Na₂O/SiO₂The above ratio is a molar ratio of 0-2: 1. The silicon source is selected from at least one of tetraethoxysilane, water glass, coarse silica gel, silica sol, white carbon black or activated clay; the aluminum source is selected from at least one of aluminum sulfate, aluminum isopropoxide, aluminum nitrate, aluminum sol, sodium metaaluminate or gamma-alumina, and the template is selected from one or more of tetraethylammonium fluoride, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, triethanolamine or sodium carboxymethylcellulose;

(4) adding ZSM-5 molecular sieve II into the synthetic liquid III, and crystallizing at 50-300 ℃ for 10-400 h. Preferably, ZSM-5The molecular sieve II is added into the synthetic liquid III and crystallized for 30 to 350 hours at the temperature of between 100 and 250 ℃. And filtering, washing and drying after crystallization to obtain the ZSM-5/beta core-shell type molecular sieve material. Preferably, the silicon source and the aluminum source are used in such amounts that the molar ratio of silicon to aluminum of the obtained shell beta molecular sieve is SiO₂/Al₂O₃25-200;

(5) ammonium exchange for Na in core-shell molecular sieve₂The O content is less than 0.15 wt%;

(6) drying and roasting, for example, at 350-600 ℃ for 2-6h to remove the template agent.

The preparation method of the catalyst provided by the invention comprises the following steps:

(A) subjecting the sodium type core-shell molecular sieve to ammonium exchange to make Na in the molecular sieve₂The O content is less than 0.15 wt%;

(B, drying the molecular sieve obtained in the step (A), and roasting at 350-600 ℃ for 2-6h to remove the template agent;

(C) mixing the core-shell type molecular sieve obtained in the step (B), the Y-type molecular sieve, the molecular sieve with the pore opening diameter of 0.65-0.70 nm, a carrier and water, pulping, and spray-drying; obtaining catalyst microspheres; the catalyst microsphere can be directly used as a catalytic cracking catalyst and can also be used as a catalyst for catalytic cracking

Roasting the catalyst microspheres obtained in the step (C) at 400-600 ℃ for 2-6h, and then carrying out exchange washing;

or the catalyst microspheres obtained in the step (C) are subjected to ammonium exchange washing and then are roasted. Preferably, the exchange washing is conducted to remove Na from the catalyst₂The O content is less than 0.15 wt%.

The invention will be further illustrated by the following examples, which are not to be construed as limiting the invention.

In the examples and comparative examples, XRD analysis was performed using the following instruments and test conditions: the instrument comprises the following steps: empyrean. And (3) testing conditions are as follows: tube voltage 40kV, tube current 40mA, Cu target Ka radiation, 2 theta scanning range 5-35 degrees, scanning speed 2(°)/min. And (3) calculating the proportion of the nuclear phase and the shell layer by analyzing the spectrum peak through X-ray diffraction, and performing fitting calculation by using a fitting function pseudo-voigt through JADE software.

Measuring the grain size and the particle size of the molecular sieve by SEM, randomly measuring 10 grain sizes, and taking the average value to obtain the average grain size of the molecular sieve sample; the particle sizes of 10 particles were randomly measured and averaged to obtain the average particle size of the molecular sieve sample.

The thickness of the shell layer molecular sieve is measured by adopting a TEM method, the thickness of a shell layer at a certain position of one core-shell molecular sieve particle is randomly measured, 10 particles are measured, and the average value is taken.

The coverage of the molecular sieve is measured by adopting an SEM method, the proportion of the outer surface area of a shell layer of one nuclear phase particle to the outer surface area of the nuclear phase particle is calculated, the coverage of the particle is taken as the coverage, 10 particles are randomly measured, and the average value is taken.

The mesopore surface area (mesopore specific surface area), the specific surface area, the pore volume (total pore volume) and the pore size distribution are measured by a low-temperature nitrogen adsorption capacity method, a sample is subjected to vacuum degassing for 0.5h and 6h at 100 ℃ and 300 ℃ respectively by using an ASAP2420 adsorption instrument of Micromeritics company in America, an N2 adsorption and desorption test is carried out at 77.4K, and the adsorption quantity and the desorption quantity of the sample to nitrogen under different specific pressures are tested to obtain an N2 adsorption-desorption isothermal curve. The BET specific surface area (total specific surface area) was calculated using the BET formula, and the micropore area was calculated using t-plot.

And measuring the silicon-aluminum ratio of the shell layer molecular sieve by adopting a TEM-EDS method.

XRD analysis of the synthetic liquid III is carried out by the following method: the synthesis solution III was filtered, washed with deionized water 8 times the weight of the solid, dried at 120 ℃ for 4 hours, calcined at 550 ℃ for 4 hours, and cooled before XRD measurement was performed (the XRD measurement was performed using the same instrument and analysis method as described above).

Example 1

(1) Adding 500g of H-type ZSM-5 molecular sieve (the silica-alumina ratio is 30, the average grain size is 1.2 mu m, the average particle size of the ZSM-5 molecular sieve is 15 mu m, and the crystallinity is 93.0%) serving as a nuclear phase into 5000g of aqueous solution of methyl methacrylate and sodium chloride (wherein the mass percentage concentration of the methyl methacrylate is 0.2%, and the mass concentration of the sodium chloride is 5.0%) at room temperature (25 ℃), stirring for 1H, filtering, and drying at 50 ℃ in an air atmosphere to obtain ZSM-5 molecular sieve I;

(2) putting a ZSM-5 molecular sieve I into a beta molecular sieve suspension (suspension formed by an H-type beta molecular sieve and water, wherein the weight percentage concentration of the beta molecular sieve in the beta molecular sieve suspension is 0.3 wt%, the average grain size of the beta molecular sieve is 0.2 micron, the silica-alumina ratio is 30, the crystallinity is 89%, and the beta molecular sieve particles are single grain particles), wherein the mass ratio of the ZSM-5 molecular sieve I to the beta molecular sieve suspension is 1:10, stirring for 1 hour at the temperature of 50 ℃, filtering, and drying a filter cake in an air atmosphere at the temperature of 90 ℃ to obtain a ZSM-5 molecular sieve II;

(3) 100.0g of aluminum isopropoxide was dissolved in 1500g of deionized water, 65g of NaOH pellets were added, and 1000g of silica Sol (SiO) was sequentially added₂25.0 weight percent of sodium oxide, 10.0 pH value and 0.10 weight percent of sodium oxide, 2000g of tetraethylammonium hydroxide solution (the weight percentage of tetraethylammonium hydroxide in the tetraethylammonium hydroxide solution is 25 weight percent), uniformly stirring, transferring into a reaction kettle with a polytetrafluoroethylene lining for crystallization, and crystallizing at 80 ℃ for 48 hours to obtain a synthetic liquid III; after the synthetic liquid III is filtered, washed, dried and roasted, a peak exists at a position with 2 theta being 22.4 degrees and no peak exists at a position with 2 theta being 21.2 degrees in an XRD spectrogram;

(4) adding a ZSM-5 molecular sieve II into the synthetic liquid III (the weight ratio of the ZSM-5 molecular sieve II to the synthetic liquid III is 1:10 in terms of dry basis), crystallizing for 60 hours at 120 ℃, and after crystallization, filtering, washing, drying and roasting to obtain the Na-type ZSM-5/beta core-shell molecular sieve.

(5) NH is used for Na-type ZSM-5/beta core-shell molecular sieve₄Cl solution exchange washing to Na₂O content is less than 0.15 wt%, filtered, dried and roasted at 550 deg.C for 2 hours. Obtaining the core-shell molecular sieve SZ-1.

Example 2

(1) Adding 500.0g of H-type ZSM-5 molecular sieve (the silica-alumina ratio is 60, the average grain size is 0.5 mu m, the average particle size is 10 mu m, and the crystallinity is 90.0%) into 5000g of aqueous solution of poly (diallyldimethylammonium chloride) and sodium chloride (the mass percent of the poly (diallyldimethylammonium chloride) in the solution is 0.2% and the mass percent of the sodium chloride is 0.2%) at room temperature (25 ℃), stirring for 2h, filtering, and drying a filter cake at 50 ℃ in an air atmosphere to obtain a ZSM-5 molecular sieve I;

(2) putting a ZSM-5 molecular sieve I into an H-type beta molecular sieve suspension (the weight percentage concentration of the beta molecular sieve in the beta molecular sieve suspension is 2.5 wt%, the average grain size of the beta molecular sieve is 0.1 mu m, the silica-alumina ratio is 30.0, and the crystallinity is 92.0%); the mass ratio of the ZSM-5 molecular sieve I to the beta molecular sieve suspension is 1:45, the mixture is stirred for 2 hours at 50 ℃, filtered and dried in the air atmosphere at 90 ℃ to obtain a ZSM-5 molecular sieve II;

(3) 200.0g of alumina sol (Al)₂O₃Is 25% by weight, the aluminium to chlorine molar ratio is 1.1; ) Dissolving in 500g deionized water, adding 30g NaOH granules, and adding 4500mL water glass (SiO)₂251g/L of concentration, 2.5 of modulus) and 1600g of tetraethylammonium hydroxide solution (the mass fraction of the tetraethylammonium hydroxide solution is 25 percent), stirring the solution fully and uniformly, transferring the solution into a reaction kettle with a polytetrafluoroethylene lining for crystallization, and crystallizing the solution for 10 hours at 150 ℃ to obtain synthetic liquid III; after the synthetic liquid III is filtered, washed, dried and roasted, a peak exists at a position with 2 theta being 22.4 degrees and no peak exists at a position with 2 theta being 21.2 degrees in an XRD spectrogram;

(4) adding a ZSM-5 molecular sieve II into the synthetic liquid III (the weight ratio of the ZSM-5 molecular sieve II to the synthetic liquid III is 1:10 in terms of dry basis), then crystallizing for 80 hours at 130 ℃, filtering, washing, drying and roasting to obtain a Na-type ZSM-5/beta core-shell molecular sieve;

(5) NH is used for Na-type ZSM-5/beta core-shell molecular sieve₄Cl solution exchange washing to Na₂O content is lower than 0.15 wt%, filtering, drying, and roasting at 550 deg.C for 2 hr; obtaining the core-shell molecular sieve SZ-2.

Example 3

(1) Adding an H-type ZSM-5 molecular sieve (the silica-alumina ratio is 100, the average grain size is 100nm, the average particle size is 5.0 microns, the crystallinity is 91.0 percent, and the dosage is 500g) used as a nuclear phase into 5000g of n-butylamine and sodium chloride aqueous solution (the mass percent of the n-butylamine is 5.0 percent, and the mass fraction of the sodium chloride is 2 percent) at room temperature of 25 ℃, stirring for 24 hours, filtering, and drying at 70 ℃ in an air atmosphere to obtain a ZSM-5 molecular sieve I;

(2) putting a ZSM-5 molecular sieve I into an H-type beta molecular sieve suspension (the weight percentage concentration of the beta molecular sieve in the beta molecular sieve suspension is 5.0 wt%, the average grain size of the beta molecular sieve is 50nm, the silica-alumina ratio is 30.0, and the crystallinity is 95.0%), wherein the mass ratio of the ZSM-5 molecular sieve I to the beta molecular sieve suspension is 1:20, stirring for 10 hours at the temperature of 50 ℃, filtering, and drying a filter cake in an air atmosphere at the temperature of 120 ℃ to obtain a ZSM-5 molecular sieve II;

(3) dissolving 100g sodium metaaluminate in 1800g deionized water, adding 60g NaOH particles, and sequentially adding 1000g coarse silica gel (SiO)₂Content 98.0 wt%) and 1800g tetraethylammonium bromide solution (mass fraction of the tetraethylammonium bromide solution is 25%), stirring uniformly, transferring into a reaction kettle with a polytetrafluoroethylene lining for crystallization, and crystallizing at 130 ℃ for 30h to obtain synthetic liquid III; after the synthetic liquid III is filtered, washed, dried and roasted, a peak exists at a position with 2 theta being 22.4 degrees and no peak exists at a position with 2 theta being 21.2 degrees in an XRD spectrogram;

(4) adding a ZSM-5 molecular sieve II into the synthetic liquid III (the weight ratio of the ZSM-5 molecular sieve II to the synthetic liquid III is 1:4 in terms of dry basis), crystallizing for 100 hours at 80 ℃, filtering, washing, drying and roasting to obtain a Na-type ZSM-5/beta core-shell molecular sieve;

(5) NH is used for Na-type ZSM-5/beta core-shell molecular sieve₄Cl solution exchange washing to Na₂O content is lower than 0.15 wt%, filtering, drying, roasting at 550 deg.C for 2 hr; obtaining the core-shell molecular sieve SZ-3.

Comparative example 1

(1) Using water glass, aluminum sulfate and ethylamine water solution as raw materials according to the mol ratio of SiO₂：A1₂O₃：C₂H₅NH₂：H₂0-40: 1: 10: 1792 gelatinizing, crystallizing at 140 deg.C for 3 days, and synthesizing large-grain cylindrical ZSM-5 molecular sieve (grain size 4.0 μm);

(2) pretreating the synthesized large-grain cylindrical ZSM-5 molecular sieve for 30min by using a sodium chloride salt solution (NaCl concentration is 5 wt%) of 0.5 wt% of methyl methacrylate, filtering, drying, adding into a beta molecular sieve suspension (a nano beta molecular sieve, the mass ratio of the ZSM-5 molecular sieve to the beta molecular sieve suspension is 1:10) which is dispersed by deionized water, adhering for 30min, filtering, drying, and roasting at 540 ℃ for 5h to obtain a nuclear phase molecular sieve;

(3) white carbon black and Tetraethoxysilane (TEOS) are used as silicon source, sodium aluminate and TEAOH are used as raw materials according to the proportion of TEAOH to SiO₂:A1₂O₃:H₂Feeding materials with the ratio of O to 13:30:1:1500, adding the nuclear phase molecular sieve obtained in the step (2), and then putting the nuclear phase molecular sieve into a stainless steel kettle with a tetrafluoroethylene lining for crystallization at 140 ℃ for 54 hours;

(4) and after crystallization, filtering, washing, drying and roasting.

(5) Adding NH into Na-type molecular sieve₄Cl solution exchange washing to Na₂O content is lower than 0.15 wt%, filtering, drying, roasting at 550 deg.C for 2 hr; obtaining the core-shell molecular sieve DZ 1.

Comparative example 2

According to the mixture ratio of the example 1, except that the crystallization temperature in the step 3 is 30 ℃, the crystallization time is 3 hours, and after filtering, washing, drying and roasting, the crystallized product has no peak at 22.4 degrees 2 theta and no peak at 21.2 degrees 2 theta in an XRD spectrogram. Molecular sieve DZ2 was obtained.

Comparative example 3

The ZSM-5 and beta sieves used in the prior art (ZSM-5 and beta sieves used in steps 1 and 2) were mechanically mixed according to the formulation of example 1 and then characterized. Molecular sieve DZ3 was obtained.

The synthesis conditions of examples 1 to 3 and comparative examples 1 to 2 are shown in Table 1.

The properties of the core-shell molecular sieve obtained in step (4) of examples 1 to 3 and the molecular sieve obtained in step (4) of comparative examples 1 to 2 and the molecular sieve mixture of comparative example 3 are shown in Table 1 (next).

TABLE 1

Table 1 (continent) (in table D1/D2 represents the ratio of the peak height at 22.4 ° (D1) to the peak height at 23.1 ° (D2) in XRD spectrum)

Note: 1 represents 1, N represents a plurality; comparative example 3 is a molecular sieve mixture.

In the following examples and comparative examples:

kaolin is an industrial product of China Kaolin company, and the solid content of the kaolin is 75 percent by weight;

the pseudoboehmite is produced by Shandong aluminum industry company, and the alumina content of the pseudoboehmite is 65 percent by weight;

the alumina sol is produced by Qilu division of China petrochemical catalyst, and the content of alumina is 21 percent by weight;

the silica sol was obtained from Beijing chemical plant, and had a silica content of 25% by weight and a pH of 3.1.

Y type molecular sieve, trade mark: HSY-12, 12 percent of rare earth, 6.09 percent of silicon-aluminum ratio, 53.0 percent of crystallinity and is produced by Qilu division of China petrochemical catalyst Limited company.

Beta molecular sieve, beta, Si/Al ratio of 25.0, crystallinity of 91.4%, produced by Qilu division of Chinese petrochemical catalyst, Inc.

Examples 4 to 7

Examples 4-6 illustrate the preparation of catalytic cracking catalysts provided by the present invention.

The core-shell type molecular sieves prepared in examples 1 to 3 were prepared as catalysts, and the catalysts were numbered in the order of: a1, A2 and A3. The preparation method of the catalyst comprises the following steps:

(1) pseudo-boehmite (referred to as alundum) and water are mixed uniformly, concentrated hydrochloric acid (chemical purity, product of Beijing chemical plant) with the concentration of 36 weight percent is added under stirring, the acid-aluminum ratio (the weight ratio of the hydrochloric acid with the concentration of 36 weight percent to the pseudo-boehmite calculated by alumina) is 0.2, the obtained mixture is heated to 70 ℃ and aged for 1.5 hours, and the aged pseudo-boehmite is obtained. The alumina content of the aluminum oxide slurry was 12 wt%;

(2) mixing a core-shell type molecular sieve, a Y-type molecular sieve, a beta molecular sieve, alumina sol, modified silica sol, kaolin, the aged pseudoboehmite and deionized water to obtain slurry with the solid content of 28 weight percent, stirring for 30 minutes, and spray drying;

(3) according to the catalyst: ammonium salt: h₂Exchanging at 80 deg.C for 1h with the weight ratio of 1:1:10, filtering, repeating the exchanging and filtering processes once, and oven drying.

Table 2 shows the type and amount of the core-shell type molecular sieve (first molecular sieve) used, and the amounts of the Y-type molecular sieve (second molecular sieve), the β -type molecular sieve (third molecular sieve), the alumina sol, the pseudo-boehmite, the silica sol, and the kaolin used, based on 1kg of the catalyst prepared, in terms of dry basis weight.

Table 3 shows the composition of catalysts A1-A3 for each example as a weight percent composition on a dry basis. The contents of the modified core-shell type molecular sieve, the Y-type molecular sieve, the beta molecular sieve, the binder (alumina sol, silica sol and pseudo-boehmite) and the kaolin in the catalyst composition are calculated.

Comparative examples 4 to 6

Comparative examples 4-6 illustrate heavy oil catalytic cracking catalysts prepared using the molecular sieves provided in comparative examples 1-3.

The molecular sieve and the Y-type molecular sieve prepared in comparative examples 1 to 3, the beta molecular sieve, the aged pseudo-boehmite, the silica sol, the alumina sol, the kaolin and water were mixed according to the catalyst preparation method of example 4, and the mixture was spray-dried to prepare catalyst microspheres, which were subjected to exchange, filtration and drying. The serial numbers of the catalysts are as follows: DB1, DB2, and DB 3.

Table 2 shows the type and amount of core-shell type molecular sieve used in the comparative catalyst, the amounts of Y-type molecular sieve, beta molecular sieve, alumina sol, silica sol and kaolin, in terms of dry weight to prepare 1Kg of catalyst. Table 3 shows the composition of catalyst DB1-DB3 (composition in weight percentages on a dry basis)

After catalysts A1-A3 and DB1-DB3 are aged for 17 hours by 100 percent of water vapor at 800 ℃, the catalytic cracking reaction performance of the catalysts is evaluated on a small fixed fluidized bed reactor under the conditions that the reaction temperature is 520 ℃, and the weight space velocity is 4.0 hours^-1The agent-oil ratio is 8 (weight ratio). The heavy oil properties are shown in Table 4, the reaction structureThe results are shown in Table 5.

TABLE 2

TABLE 3

TABLE 4

Hydrogenated VGO Properties
		Density at 20 ℃ g/cm3	0.8974
Refraction at 70 deg.C	1.4794
		Viscosity at 80 ℃ in mm2/s	15.87
Carbon residue, m%	0.3
		Four components, m%
Saturated hydrocarbons	78.8
		Aromatic hydrocarbons	19.6
Glue	1.6
		Asphaltenes	＜0.1
Composition of hydrocarbons, m%
		Alkane hydrocarbons	30.5
Total cycloalkanes	48.3

TABLE 5

Wherein the yield is calculated based on the feedstock.

As can be seen from the results listed in table 5, the catalytic cracking catalyst provided by the present invention has higher heavy oil conversion capability, higher low carbon olefin yield, higher liquefied gas yield, and higher propylene yield.

Claims

1. A catalytic cracking catalyst for producing low carbon olefin by hydrogenation VGO catalytic cracking comprises, by weight on a dry basis, 30-79% of a carrier, 5-15% of a core-shell type molecular sieve, 15-45% of a Y-type molecular sieve and 1-10% of a molecular sieve having a pore opening with a diameter of 0.65-0.70 nm; wherein the core phase of the core-shell type molecular sieve is ZSM-5 moleculesThe shell layer of the sieve is beta molecular sieve, the ratio of the peak height of 22.4 degrees 2 theta to the peak height of 23.1 degrees 2 theta in an X-ray diffraction pattern is 0.1-10:1, and the total specific surface area is more than 420m²/g。

2. The catalyst of claim 1, wherein the ratio of core phase to shell phase of the core-shell molecular sieve is 0.2-20:1 or 1-15: 1.

3. The catalyst of claim 1, wherein the total specific surface area of the core-shell molecular sieve is greater than 420m²G is, for example, 490m²/g-580m²The proportion of mesopore surface area to the total surface area is preferably from 10% to 40%.

4. The catalyst of claim 1, wherein the shell molecular sieve of the core-shell molecular sieve has an average crystallite size of from 10nm to 500nm, such as from 50 to 500 nm.

5. The catalyst of claim 1, wherein the shell molecular sieve of the core-shell molecular sieve has a thickness of 50nm to 2000 nm.

6. The catalyst of claim 1, wherein the core-shell molecular sieve has a silica to alumina molar ratio in SiO₂/Al₂O₃In the range of 10-500, for example 25-200.

7. The catalyst of claim 1, wherein the core phase molecular sieve of the core-shell molecular sieve has a silica to alumina molar ratio in SiO₂/Al₂O₃In the amount of 10- ∞, for example, 30-200.

8. The catalyst of claim 1, wherein the core phase molecular sieve of the core-shell molecular sieve has an average crystallite size of from 0.05 μ ι η to 15 μ ι η.

9. The catalyst of claim 1, wherein the number of crystal grains in the single particle of the nuclear phase molecular sieve is not less than 2, and the average particle size of the nuclear phase molecular sieve is preferably 0.1 μm to 30 μm.

10. The catalyst of any one of claims 1-10, wherein the shell coverage of the core-shell molecular sieve is 50% to 100%, and the sodium oxide content of the core-shell molecular sieve is preferably no more than 0.15 wt%.

11. The catalyst of any one of claims 1-10, wherein the pore volume of the core-shell molecular sieve shell pores having a diameter of 20-80nm comprises 50% -70% of the pore volume of the pores having a diameter of 2-80 nm.

12. The catalyst of claim 1, wherein the Y-type molecular sieve is a rare earth-containing Y-type molecular sieve, and the content of rare earth in the rare earth-containing Y-type molecular sieve is as RE₂O₃Calculated as 5-17 wt%.

13. The catalyst according to claim 1 or 12, wherein the molecular sieve having pore opening diameters of 0.65-0.70 nm is a beta molecular sieve, such as a hydrogen form beta molecular sieve.

14. The catalyst of claim 1, wherein the carrier is one or more of alumina sol, zirconium sol, pseudoboehmite, silica sol and clay.

15. A method of preparing a catalytic cracking catalyst comprising: forming a slurry comprising the first molecular sieve, the second molecular sieve, the third molecular sieve, a carrier and water, and spray drying; the first molecular sieve is a core-shell molecular sieve, the second molecular sieve is a Y-type molecular sieve, and the third molecular sieve is a molecular sieve with pore opening diameters of 0.65-0.70 nanometers.

16. The method of claim 15, wherein the method of synthesizing the core-shell molecular sieve comprises the steps of:

(3) crystallizing a synthetic solution containing a silicon source, an aluminum source, a template agent and water at 50-300 ℃ for 4-100h to obtain a synthetic solution III;

(5) ammonium exchange of sodium type core-shell molecular sieve for Na in core-shell molecular sieve₂The O content is less than 0.15 wt%;

(6) and (5) drying and roasting the core-shell type molecular sieve obtained in the step (5).

17. The method of claim 16, wherein the contacting in step (1) is performed by: adding the ZSM-5 molecular sieve into a surfactant solution with the weight percentage concentration of 0.05-50% for contacting for at least 0.5h, filtering and drying to obtain the ZSM-5 molecular sieve I, wherein the contact time is 1h-36h, and the contact temperature is preferably 20-70 ℃.

18. The method of claim 16, wherein the surfactant is selected from at least one of polymethylmethacrylate, polydiallyldimethylammonium chloride, ammonia, n-butylamine, tetraethylammonium hydroxide, dipicolinic acid, ethylamine, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium bromide, tetrabutylammonium hydroxide.

19. The process of claim 16, wherein the ZSM-5 molecular sieve in step (1) has a silica to alumina molar ratio of SiO₂/Al₂O₃The average grain size of the ZSM-5 molecular sieve is 0.05-20 mu m and is counted as 10- ∞.

20. The method of claim 16, wherein the contacting in step (2) comprises: adding the ZSM-5 molecular sieve I into slurry containing beta zeolite, stirring for at least 0.5 hour at the temperature of 20-60 ℃, then filtering and drying to obtain a ZSM-5 molecular sieve II; the weight ratio of the slurry containing the beta zeolite to the ZSM-5 molecular sieve I on a dry basis is 10-50:1, and the concentration of the beta zeolite in the slurry containing the beta zeolite is 0.1 wt% to 10 wt%, for example 0.3 wt% to 8 wt%.

21. The method as claimed in claim 16, wherein in the step (3), the molar ratio of the silicon source, the aluminum source, the template (represented by R) and the water is as follows: R/SiO₂0.1-10:1, e.g. 0.1-3:1, SiO₂/Al₂O₃＝10-800:1，H₂O/SiO₂2-150:1, e.g. 10-120:1, Na₂O/SiO₂0-2:1 is, for example, 0.01-1.7: 1.

22. The method according to claim 16, wherein in step (3), the silicon source is selected from at least one of tetraethoxysilane, silica sol, water glass, coarse silica gel, white carbon black or activated clay; the aluminum source is at least one selected from aluminum sulfate, aluminum isopropoxide, aluminum nitrate, aluminum sol, sodium metaaluminate or gamma-alumina; the template agent is one or more of tetraethylammonium fluoride, polyvinyl alcohol, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, triethanolamine or sodium carboxymethylcellulose.

23. The method as claimed in claim 16, wherein in the step (3), the silicon source, the aluminum source, the template agent and the deionized water are mixed to form a synthetic solution, and then the synthetic solution is crystallized at 75-250 ℃ for 10-80 h to obtain the synthetic solution III.

24. The method of claim 22, wherein the crystallizing in step (3): the crystallization temperature is 80-180 ℃, and the crystallization time is 18-50 hours.

25. A process according to claim 16 or 22 or 23, wherein the resultant synthesis III from step (3) is XRD analysed and a peak at 22.4 ° 2 θ and no peak at 21.2 ° 2 θ are present.

26. The method of claim 16, wherein the crystallizing in step (4): the crystallization temperature is 100-250 ℃, the crystallization time is 30-350h, for example, the crystallization in the step (4): the crystallization temperature is 100-200 ℃, and the crystallization time is 50-120 h.

27. The method of claim 16, wherein the ammonium exchange of step (5) is performed according to a core-shell molecular sieve: ammonium salt: h₂O is 1: (0.1-1): (5-15) exchanging and filtering at 50-100 ℃ in a weight ratio, wherein the process can be carried out once or more times; the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.

28. The method as claimed in claim 16, wherein the roasting in step (6) is carried out at 350-600 ℃ for 2-6h to remove the template agent.

29. The method of claim 15, wherein the Y-type molecular sieve has a rare earth content of RE₂O₃The third molecular sieve is preferably beta molecular sieve, accounting for 5-17 wt%.

30. The method of claim 15, wherein the support is one or more of a clay, an alumina support, and a silica support.

31. The method of claim 15, wherein the silica support is one or more of a neutral silica sol, an acidic silica sol, or a basic silica sol; preferably, the content of the silica sol in the catalyst is SiO₂Calculated as 1-15 wt%.

32. A catalytic cracking catalyst obtainable by the process of any of claims 16 to 31.

33. A process for catalytic cracking of heavy oil comprising the step of contacting heavy oil with the catalytic cracking catalyst of any one of claims 1 to 14 or 32.

34. A hydrogenated VGO catalytic cracking process comprising the step of contacting hydrogenated VGO with the catalyst of any one of claims 1 to 14 or claim 32.