CN114425421B

CN114425421B - Catalytic cracking catalyst and preparation method and application thereof

Info

Publication number: CN114425421B
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: 2023-07-11
Anticipated expiration: 2040-09-22
Also published as: CN114425421A

Abstract

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

Description

Catalytic cracking catalyst and 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 naphthene ring.

Background

The method mainly adopts naphtha steam cracking to produce the low-carbon olefin, and has the defects of high reaction temperature, high energy consumption and the like. In order to overcome the problems, a great deal of catalytic cracking technology research is 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 on one hand, improve the yield of the low-carbon olefin on the other hand and flexibly regulate the product distribution on the other hand.

However, catalytic cracking is performed using different feedstocks, different cracking catalysts, different reaction conditions, and often different products are obtained, and refineries often also require different product distributions for different purposes. Vacuum distillate (VGO) is a product of vacuum distillation of crude oil, which often contains a large amount of aromatic hydrocarbons, and these aromatic hydrocarbons are often not converted into light oil products in the catalytic cracking process, and for this purpose, it is studied to hydrogenate VGO, saturate or partially saturate aromatic hydrocarbons therein to obtain hydrogenated VGO, and then perform catalytic cracking conversion. However, the hydrogenated VGO is converted in a plurality of directions, for example, it can be dehydrogenated to form aromatic hydrocarbon, or can be ring-opened cracked to form hydrocarbon products such as low-carbon olefin, gasoline and diesel oil, and it is hoped to produce liquefied gas and heavy oil products as much as possible, and reduce gasoline and diesel oil light oil products. 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 VGO conversion and has higher low-carbon olefin yield.

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

The catalytic cracking catalyst according to any of the above embodiments, wherein the core-shell molecular sieve (abbreviated as core-shell molecular sieve) is a ZSM-5/β core-shell molecular sieve, and the ratio of the peak height (D1) at 2θ=22.4° to the peak height (D2) at 2θ=23.1° is 0.1-10:1, preferably 0.1-8:1, for example 0.1-5:1 or 0.12-4:1 or 0.8-8:1.

The peak at 2θ=22.4° is a peak in the X-ray diffraction pattern in the range of 2θ angle 22.4°±0.1°, and the peak at 2θ=23.1° is a peak in the X-ray diffraction pattern in the range of 2θ angle 23.1°±0.1°.

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

The catalyst according to any one of the above aspects, 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 420m ² For example, 420m ² /g-650m ² Preferably, the total specific surface area of the core-shell molecular sieve is more than 450m ² For example 450m ² /g-620m ² /g or 480m ² /g-600m ² /g or 490m ² /g-580m ² /g or 500m ² /g-560m ² /g。

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

The catalytic cracking catalyst according to any of the above embodiments, wherein the total pore volume of the core-shell molecular sieve is from 0.28mL/g to 0.42mL/g, e.g., from 0.3mL/g to 0.4mL/g or from 0.32mL/g to 0.38mL/g.

The catalytic cracking catalyst according to any of the above embodiments, wherein the total pore volume of the core-shell molecular sieve is 40% -90%, such as 40% -88% or 50% -85% or 60% -85% or 70% -82%, of the pore volume of pores having a pore diameter of 0.3nm to 0.6nm in the core-shell molecular sieve.

The catalytic cracking catalyst according to any of the above embodiments, wherein the core-shell molecular sieve has a pore volume of 3% -20%, such as 3% -15% or 3% -9%, of pores with a pore diameter of 0.7nm to 1.5nm, based on the total pore volume of the core-shell molecular sieve.

The catalytic cracking catalyst according to any of the above embodiments, wherein the core-shell molecular sieve has a pore volume of pores with a pore diameter of 2nm to 4nm of 4% to 50%, such as 4% to 40% or 4% to 20% or 4% to 10%, based on the total pore volume of the core-shell molecular sieve.

The catalytic cracking catalyst according to any of the above embodiments, wherein the core-shell molecular sieve has a pore volume of pores with a pore diameter of 20nm to 80nm of 5% to 40%, such as 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 molecular sieve.

According to any one of the above embodiments, in one embodiment, the core-shell molecular sieve has a pore volume of pores with a pore diameter of 2nm to 80nm of 10% to 30%, for example 11% to 25%, of the total pore volume.

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

The total pore volume and pore size distribution can be measured by a low-temperature nitrogen adsorption capacity method, and the pore size distribution can be calculated by using a BJH calculation method, and reference can be made to the Ripp-151-90 method (petrochemical analysis method, RIPP test method, scientific Press, 1990).

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

The catalytic cracking catalyst according to any of the above embodiments, wherein the shell molecular sieve of the core-shell molecular sieve has an average crystal grain size of 10nm to 500nm, for example, 50nm to 500nm.

The catalytic cracking catalyst according to any one of the above technical schemes, wherein the silicon-aluminum ratio of the core-shell molecular sieve and the shell molecular sieve is SiO ₂ /Al ₂ O ₃ The molar ratio of silicon to aluminum is 10 to 500, preferably 10 to 300, for example 30 to 200 or 25 to 200.

The catalytic cracking catalyst according to any one of the above technical solutions, wherein the silica-alumina ratio of the core-phase molecular sieve of the core-shell molecular sieve is SiO ₂ /Al ₂ O ₃ The calculated silicon-aluminum mole ratio is 10-infinity, for example 20- ≡or 50- ++or 30-300 or 30-200 or 25-70 or 20-80 or 30-60.

The catalytic cracking catalyst according to any one of the above-mentioned aspects, wherein the average crystal grain size of the core-phase molecular sieve of the core-shell molecular sieve is 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 according to any of the above embodiments, wherein the core-shell molecular sieve, the average particle size of the core phase molecular sieve is 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 one of the above technical solutions, wherein the core-phase molecular sieve particles of the core-shell 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 embodiments, wherein the core-shell molecular sieve has a shell coverage of 50% -100%, for example 80-100%.

The catalytic cracking catalyst according to any one of the above technical solutions, wherein 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 RE ₂ O ₃ Preferably 5 to 17% by weight. In one embodiment, the framework silicon-aluminum ratio of the Y-type molecular sieve is SiO ₂ /Al ₂ O ₃ The molar ratio is 4.9-14.

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

The catalytic cracking catalyst according to any of the above embodiments, wherein the carrier may be a carrier of a cracking catalyst, for example, one or more of an alumina sol carrier, a zirconia 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, and the third molecular sieve, the 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 preparation method of the core-shell molecular weight comprises the following steps:

(1) Contacting ZSM-5 molecular sieve with surfactant solution to obtain 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 solution III, and crystallizing; recovering to obtain the sodium type core-shell molecular sieve;

(5) Sodium core-shell molecular sieves are ammonium exchanged, preferably, by allowingNa in core-shell molecular sieve ₂ An O content of less than 0.15 wt.%;

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

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

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

According to any one of the above technical schemes for preparing catalytic cracking catalysts, in one embodiment, the weight ratio of the surfactant solution in the step (1) to the ZSM-5 molecular sieve based on dry basis is 10-200:1.

According to the method for preparing a catalytic cracking catalyst of any one of the above embodiments, in the method for synthesizing a core-shell molecular sieve, the surfactant solution may further contain a salt, wherein the salt is a salt having an electrolyte property such as one or more of alkali metal salt and ammonium salt which can be dissolved in water, preferably one or more of alkali metal chloride salt, ammonium chloride salt, alkali metal nitrate and ammonium nitrate, and the salt is one or more of ammonium chloride, sodium chloride, potassium chloride and ammonium nitrate; the concentration of salt in the surfactant solution is preferably from 0.05 wt% to 10.0 wt%, for example from 0.2 wt% to 2 wt%. The addition of the salt facilitates adsorption of the surfactant.

According to any one of the above methods for preparing a catalytic cracking catalyst, the surfactant may be at least one selected from polymethyl methacrylate, polydiallyl dimethyl ammonium chloride, tetraethylammonium bromide, dipicolinate, n-butylamine, tetraethylammonium hydroxide, ammonia, ethylamine, tetrapropylammonium hydroxide, tetrapropylammonium bromide, and tetrabutylammonium hydroxide.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, the silicon-aluminum molar ratio of the ZSM-5 molecular sieve (raw material) in the step (1) is equal to SiO ₂ /Al ₂ O ₃ The meter (namely the silicon-aluminum ratio) is 10-infinity; for example, the ZSM-5 molecular sieve (raw material) in the molar ratio of silicon to aluminum in the step (1) is prepared by using SiO ₂ /Al ₂ O ₃ The meter can be 20- ++or 50- ++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 according to any one of the above technical schemes, which is a synthesis method of a core-shell molecular sieve, wherein the ZSM-5 molecular sieve (raw material) in the step (1) has an average grain size of 0.05 μm to 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. Mu.m.

The method for producing a catalytic cracking catalyst according to any one of the above-mentioned aspects, wherein the ZSM-5 molecular sieve (starting material) has an average particle size of preferably 0.1 μm to 30. Mu.m, for example, 0.5 μm to 25. Mu.m, or 1 μm to 5. Mu.m, or 1 μm to 20. Mu.m, or 2 μm to 4. Mu.m.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, the ZSM-5 molecular sieve (raw material) in the step (1) is 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 ZSM-5 molecular sieve (such as Na-type ZSM-5 molecular sieve) with ions other than alkali metal, such as transition metal ion, ammonium ion, alkaline earth metal ion, group IIIA metal ion, group IVA metal ion and group VA metal ion.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, in the step (1), the drying is not particularly required, and may be, for example, drying, flash drying, and air drying. In one embodiment, the drying temperature 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 4h.

According to the method for preparing a catalytic cracking catalyst in any one of the above embodiments, in the method for synthesizing a core-shell molecular sieve, the contacting in the step (2) includes the steps of mixing a ZSM-5 molecular sieve I with a slurry containing beta zeolite (beta zeolite is also referred to as beta molecular sieve), filtering, and drying. One embodiment includes: adding ZSM-5 molecular sieve I into slurry containing beta zeolite, stirring at 20-60 ℃ for more than 0.5 hours, such as 1-24 hours, filtering, and drying to obtain ZSM-5 molecular sieve II.

The method for preparing a catalytic cracking catalyst according to any one of the above embodiments, wherein in the method for synthesizing a core-shell 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%.

According to the method for preparing a catalytic cracking catalyst in any of the above embodiments, in the method for synthesizing a core-shell molecular sieve, 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, 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.

The method for preparing a catalytic cracking catalyst according to any one of the above embodiments, wherein in the step (2) of the slurry containing zeolite beta, the average crystal grain size of zeolite beta is 10nm to 500nm, for example, 50nm to 400nm or 10nm to 300nm or 100nm to 300nm or 200 to 500nm. 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 average crystallite size of the beta zeolite in the beta zeolite-containing slurry is 10nm to 500nm smaller than the average crystallite size of the ZSM-5 molecular sieve feedstock. For example, the ZSM-5 molecular sieve has an average crystallite size that is 1.5 times or more, e.g., 2 to 50 or 5 to 20 times the average crystallite size of the zeolite beta.

The process for producing a catalytic cracking catalyst according to any one of the above-mentioned aspects, wherein in the process for synthesizing a core-shell molecular sieve, the average particle size of the zeolite beta in the slurry containing zeolite beta in the 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-crystal particles.

The method for preparing a catalytic cracking catalyst according to any one of the above embodiments, wherein in the method for synthesizing a core-shell molecular sieve, the molar ratio of silicon to aluminum of the beta zeolite in the slurry containing the beta zeolite in the step (2) is represented by SiO ₂ /Al ₂ O ₃ The meter (i.e. the silicon to aluminum ratio) is 10 to 500, for example 30 to 200 or 25 to 200. In one embodiment, the silica to alumina ratio of the beta zeolite in the slurry containing beta zeolite of step (2) differs from the silica to alumina ratio of the shell molecular sieve by no more than ± 10%, e.g., the beta zeolite has the same silica to alumina ratio as the shell molecular sieve of the synthesized core-shell molecular sieve.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, in the step (3), the molar ratio of the silicon source, the aluminum source, the template agent (represented by R) and water is: R/SiO ₂ =0.1-10, e.g. 0.1-3 or 0.2-2.2, h ₂ O/SiO ₂ =2-150, e.g. 10-120, sio ₂ /Al ₂ O ₃ =10-800, e.g. 20-800, na ₂ O/SiO ₂ =0-2, e.g. 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 synthesizing a core-shell molecular sieve, in the step (3), the silicon source may be at least one selected from ethyl orthosilicate, water glass, coarse pore silica gel, silica sol, white carbon black and activated clay; the aluminum source can be at least one selected from aluminum sulfate, aluminum isopropoxide, aluminum nitrate, aluminum sol, sodium metaaluminate or gamma-aluminum oxide; the template agent (R) is, for example, one or more of tetraethylammonium fluoride, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, polyvinyl alcohol, triethanolamine or sodium carboxymethyl cellulose, and preferably, the template agent includes at least one of tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide.

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

According to any one of the above technical solutions, in the method for synthesizing a core-shell molecular sieve, the crystallization in step (3) is the first crystallization, so that the crystallization state of the obtained synthesis liquid III is a state that the crystal grains will not appear yet, and is near the end of the crystallization induction period, i.e., is about to enter the crystal nucleus rapid growth stage. XRD analysis was performed on the resultant synthetic solution III, with a spectral peak present at 2θ=22.4°, and no spectral peak present at 2θ=21.2°. Preferably, the XRD pattern of the said synthetic liquid iii has an infinite ratio of peak intensity at 2θ=22.4° to peak intensity at 2θ=21.2°. The XRD analysis method of the synthetic solution III can be carried out according to the following method: and (3) filtering, washing, drying and roasting the synthetic solution III at 550 ℃ for 4 hours, and then performing XRD analysis. The washing may be with deionized water. The 2θ=22.4° is within the range of 2θ=22.4° ±0.1°, and the 2θ=21.2° is within the range of 2θ=21.2° ±0.1°.

According to the method for preparing a catalytic cracking catalyst in any of the above embodiments, in the method for synthesizing a core-shell molecular sieve, in the step (4), the ZSM-5 molecular sieve II is mixed with the synthesis solution III, for example, the ZSM-5 molecular sieve II is added to 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 ZSM-5 molecular sieve on a dry basis to the synthesis liquid III on a dry basis is greater than 0.2:1, for example 0.3-20:1 or 1-15:1 or 0.5-10:1 or 0.5-5:1 or 0.8-2:1 or 0.9-1.7:1.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, the crystallization in the step (4) is called a second crystallization, the crystallization temperature of the second crystallization is 50-300 ℃, and the crystallization time is 10-400 h.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, in the step (4), after the ZSM-5 molecular sieve II is mixed with the synthesis solution III, crystallization is carried out for 30-350h at 100-250 ℃ for second crystallization. The crystallization temperature of the second crystallization is, for example, 100-200 ℃, and the crystallization time is, for example, 50-120 h.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, in the step (4), the sodium-type core-shell molecular sieve is recovered after crystallization, and the recovery may include a step of filtering, and optionally may further include one or more steps of washing, drying and roasting. 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 in 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, for example, the washing can be carried out once or more times until the pH value of the washed water is 8-9. The roasting temperature can be 350-600 ℃, and the roasting time can be 1-6 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 obtained core-shell molecular sieve is a ZSM-5 molecular sieve, a shell layer is a beta molecular sieve, and the silicon-aluminum molar ratio of the shell layer is SiO ₂ /Al ₂ O ₃ And is calculated to be 10-500, e.g., 25-200.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, the ammonium exchange in the step (5) is performed according to the sodium type core-shell molecular sieve: ammonium salt: h ₂ O=1: (0.1-1): (5-15) exchange and filtration at 50-100deg.C, wherein the exchange and filtration process can be carried out one or more timesSecondary times; the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.

According to any one of the above technical schemes, in the synthesis method of the core-shell molecular sieve, in the step (6), the core-shell molecular sieve obtained in the step (5) is dried and then baked, and the template agent is removed, so that the core-shell molecular sieve is obtained. In one embodiment, the firing is performed at 350-600 ℃ for 2-6 hours.

According to any one 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 DASY molecular sieve, DASY molecular sieve containing rare earth, HRY molecular sieve containing rare earth, DOSY molecular sieve, USY molecular sieve containing rare earth, REY molecular sieve, HY molecular sieve, and 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 RE ₂ O ₃ Preferably 5 to 17% by weight. The silicon-aluminum ratio of the Y-type molecular sieve is preferably 4.9-14.0.

According to any one of the above technical schemes, the third molecular sieve is a molecular sieve with pore opening diameter of 0.65-0.70 nm. The molecular sieve with the pore canal opening diameter of 0.65-0.70 nanometers 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 structures; preferably at least one of Beta, SAPO-5, SAPO-40, SSZ-13, CIT-1, ITQ-7, ZSM-18, mordenite and gmelinite. The third molecular sieve is more preferably a beta molecular sieve, for example, a hydrogen form beta molecular sieve (hβ molecular sieve).

The process for preparing a catalytic cracking catalyst according to any one of the above-mentioned aspects, wherein the carrier is preferably one or more of clay, alumina carrier and silica carrier.

The preparation method of the catalytic cracking catalyst according to any one of the technical schemes, wherein the silica carrier is one or more of neutral silica sol, acidic silica sol or alkaline silica solThe method comprises the steps of carrying out a first treatment on the surface of the Preferably, the silica sol content of the catalyst is SiO ₂ 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, noboehmite, amorphous aluminum hydroxide. Such as one or more of non-gamma-alumina, eta-alumina, chi-alumina, delta-alumina, theta-alumina, 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, for example, as kaolin, montmorillonite, diatomaceous earth, halloysite, quasi-halloysite, saponite, rectorite, sepiolite, attapulgite, hydrotalcite, and bentonite.

According to any one of the above technical schemes, the preparation method of the catalytic cracking catalyst comprises the steps of ₂ The O content is preferably not more than 0.15% by weight.

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

According to the preparation method of the catalytic cracking catalyst in any technical scheme, the spray drying condition is a drying condition commonly used in the preparation process of the catalytic cracking catalyst. Generally, 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 subjected to exchange washing, and can be subjected to exchange washing by using ammonium salt solution. In one embodiment, the exchange wash is performed as a catalyst: ammonium salt: h ₂ O=1: (0.01-1): (5-15) exchange and filtration at 50-100 ℃, wherein the exchange and filtration processes can be carried out one or more times; the ammonium salt may be selected from one or more of ammonium chloride, ammonium sulfate, ammonium nitrate. PreferablyThe exchange washing is to make Na in the obtained catalytic cracking catalyst ₂ The O content is less than 0.15% by weight. The washed catalyst was exchanged and dried. The method of preparing a catalytic cracking catalyst may further comprise a calcination process, which may be performed before and/or after the exchange wash. The calcination may be carried out by conventional calcination methods, for example, at a calcination temperature of 350 to 650℃for 1 to 10 hours, and in one embodiment, at 400 to 600℃for 2 to 6 hours.

A catalytic cracking method for heavy oil 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 the low-carbon olefin by the heavy oil catalytic cracking can adopt the conventional reaction conditions of the heavy oil catalytic cracking, for example, the reaction temperature is 480-600 ℃, for example, 500-600 ℃, preferably 500-550 ℃, and the weight hourly space velocity is 5-30 hours ^-1 Preferably 8-20 hours ^-1 The ratio of the agent to the oil is 1-15, preferably 2-12. The catalyst to oil ratio refers to the weight ratio of catalyst to raw oil. The heavy oil is preferably hydrogenated VGO.

The catalytic cracking catalyst provided by the invention has rich pore canal structure, excellent heavy oil cracking capability and higher low-carbon olefin selectivity. The catalyst can be used for VGO conversion, and has higher liquefied gas yield and low-carbon olefin yield, higher propylene yield, preferably higher ethylene yield and higher butene yield.

The heavy oil catalytic cracking method provided by the invention can have 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 based on the weight of the catalyst.

In one embodiment, the core-shell molecular sieve is a ZSM-5/beta core-shell molecular sieve, and the ratio of the peak height of the peak at 2θ=22.4° to the peak height of the peak at 2θ=23.1° in the X-ray diffraction pattern is 0.1-10:1, for example, 0.1-5:1 or 0.12-4:1 or 0.8-8:1, and the total specific surface area is greater than 420m ² For example 450m ² /g-620m ² /g or 480m ² /g-600m ² /g or 490m ² /g-580m ² /g or 500m ² /g-560m ² The proportion of the mesopore surface area per g to the total specific surface area is preferably from 10% to 40%, for example from 12% to 35%, the average grain size of the shell molecular sieve is from 10nm to 500nm, for example from 50 to 500nm, the shell thickness of the shell molecular sieve is from 10nm to 2000nm, for example from 50nm to 2000nm, the average grain size of the core molecular sieve is from 0.05 μm to 15. Mu.m, preferably from 0.1 μm to 10. Mu.m, for example from 0.1 μm to 5 μm or from 0.1 μm to 1.2. Mu.m, the average grain size of the core molecular sieve is preferably from 0.1 μm to 30. Mu.m, for example from 0.2 μm to 25 μm or from 0.5 μm to 10 μm or from 1 μm to 5 μm or from 2 μm to 4. Mu.m, the core molecular sieve is an agglomerate of a plurality of grains, and the silica-alumina molar ratio of the shell molecular sieve is SiO ₂ /Al ₂ O ₃ A molar ratio of silicon to aluminum of from 10 to 500, preferably from 10 to 300, for example from 30 to 200 or from 25 to 200, based on SiO ₂ /Al ₂ O ₃ The ratio of the core to the shell of the core-shell molecular sieve is preferably 0.2-20:1, such as 1-15:1, and the pore volume of pores with a pore diameter of 20-80nm accounts for 50% -70% of the pore volume of pores with a pore diameter of 2-80nm, in terms of 10- +.. In one embodiment, the ZSM-5/beta core-shell molecular sieve pores have a pore volume of 40% -88% of the total pore volume, pores with a pore diameter of 0.7-1.5nm have a pore volume of 3-20% of the total pore volume, pores with a pore diameter of 2-4nm have a pore volume of 4-50% of the total pore volume, and pores with a pore diameter of 20-80nm have a pore volume of 5-40% of the total pore volume.

In one embodiment, the core-shell molecular sieve can be prepared by the following method:

(1) Adding ZSM-5 molecular sieve into surfactant solution with weight percentage concentration of 0.05% -50%, stirring for 0.5-48h, and treating, wherein surfactant and ZSM-5 are separatedThe weight ratio of the sub-sieves is preferably 0.02-0.5:1, filtering and drying to obtain ZSM-5 molecular sieve I, wherein the mole ratio SiO of silicon to aluminum of the ZSM-5 molecular sieve is ₂ /Al ₂ O ₃ Preferably 20- ≡ for example 50- ≡;

(2) Adding ZSM-5 molecular sieve I to a slurry containing beta zeolite, wherein the content of beta zeolite in the slurry containing beta zeolite is 0.2-8 wt%, and the weight ratio of beta zeolite to ZSM-5 molecular sieve I is preferably 0.03-0.30 in terms of dry basis: 1, stirring for at least 0.5 hours, for example 0.5h-24h, then filtering and 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, stirring the mixed solution for 4 to 100 hours at 50 to 300 ℃, and preferably stirring the mixed solution for 10 to 80 hours at 75 to 250 ℃ to obtain a synthetic solution III; wherein R/SiO ₂ ＝0.1-10:1，H ₂ O/SiO ₂ ＝2-150:1，SiO ₂ /Al ₂ O ₃ ＝10-800:1，Na ₂ O/SiO ₂ =0-2:1, the above ratios are molar ratios. The silicon source is at least one selected from tetraethoxysilane, water glass, coarse pore 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 agent is selected from one or more of tetraethylammonium fluoride, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, triethanolamine or sodium carboxymethyl cellulose;

(4) Adding ZSM-5 molecular sieve II into the synthetic solution III, crystallizing for 10-400 h at 50-300 ℃. Preferably, ZSM-5 molecular sieve II is added into the synthetic solution III and crystallized for 30 to 350 hours at the temperature of between 100 and 250 ℃. Filtering, washing and drying after crystallization to obtain the ZSM-5/beta core-shell molecular sieve material. Preferably, the silicon source and the aluminum source are used in such an amount that the silicon-aluminum molar ratio of the obtained shell beta molecular sieve is calculated as SiO ₂ /Al ₂ O ₃ 25-200;

(5) Ammonium exchange to make Na in core-shell molecular sieve ₂ The O content is less than 0.15 wt%;

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

The preparation method of the catalyst provided by the invention, one implementation mode, comprises the following steps:

(A) Sodium type core-shell molecular sieve is subjected to ammonium exchange to lead Na in the molecular sieve ₂ An O content of less than 0.15 wt.%;

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

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

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

or the catalyst microsphere obtained in the step (C) is subjected to ammonium exchange washing and then roasting. Preferably, the exchange wash causes Na in the catalyst ₂ The O content is less than 0.15% by weight.

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 employed instrumentation and test conditions: instrument: empyrean. Test conditions: tube voltage 40kV, tube current 40mA, cu target K alpha radiation, 2 theta scanning range 5-35 DEG, scanning speed 2 (°)/min. The ratio of the core layer to the shell layer is calculated by analyzing the spectrum peak through X-ray diffraction, and the fitting calculation is carried out 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 a molecular sieve sample; the particle size of 10 particles was randomly measured and averaged to give an average particle size of the molecular sieve sample.

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

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

The mesoporous surface area (mesoporous specific surface area), specific surface area, pore volume (total pore volume) and pore size distribution are measured by adopting a low-temperature nitrogen adsorption capacity method, a micro-medium company ASAP2420 adsorption instrument is used, samples are subjected to vacuum degassing at 100 ℃ and 300 ℃ for 0.5h and 6h respectively, N2 adsorption and desorption tests are carried out at 77.4K, and the adsorption capacity and the desorption capacity of the test samples on nitrogen under different specific pressure conditions are used to obtain an N2 adsorption-desorption isothermal curve. BET specific surface area (total specific surface area) was calculated using the BET formula, and the micropore area was calculated by t-plot.

The silicon-aluminum ratio of the shell molecular sieve is measured by using a TEM-EDS method.

XRD analysis of the synthesis solution III was carried out as follows: the resultant solution III was filtered, washed with 8 times the weight of deionized water, dried at 120℃for 4 hours, calcined at 550℃for 4 hours, and cooled, and then XRD measured (the apparatus and analytical method used for XRD measurement are as described above).

Example 1

(1) 500g of H-type ZSM-5 molecular sieve (silica alumina ratio 30, average crystal grain size of 1.2 μm, ZSM-5 molecular sieve average particle size of 15 μm, crystallinity of 93.0%) as a core phase was added to 5000g of an aqueous solution of methyl methacrylate and sodium chloride (wherein the concentration of methyl methacrylate is 0.2% by mass and the concentration of sodium chloride is 5.0%) at room temperature (25 ℃ C.) and stirred for 1 hour, filtered, and dried under an air atmosphere at 50 ℃ C.) to give ZSM-5 molecular sieve I;

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

(3) 100.0g of aluminum isopropoxide is dissolved in 1500g of deionized water, 65g of NaOH particles are added, and 1000g of silica sol (SiO ₂ 25.0 wt% of tetraethylammonium hydroxide solution (the mass fraction of tetraethylammonium hydroxide in the tetraethylammonium hydroxide solution is 25 wt%) and 2000g of tetraethylammonium hydroxide solution, after being stirred uniformly, the mixture is transferred into a polytetrafluoroethylene-lined reaction kettle for crystallization, and the mixture is crystallized for 48 hours at 80 ℃ to obtain a synthetic solution III; after the synthetic solution III is filtered, washed, dried and roasted, peaks exist at 2 theta=22.4 degrees and no peaks exist at 2 theta=21.2 degrees in an XRD spectrum;

(4) Adding ZSM-5 molecular sieve II into synthetic solution III (the weight ratio of ZSM-5 molecular sieve II to synthetic solution III is 1:10 based on dry basis), crystallizing at 120 ℃ for 60 hours, filtering, washing, drying and roasting after crystallization is finished 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 sieve ₄ Exchange washing of Cl solution to Na ₂ The O content is less than 0.15 wt%, filtered, dried and calcined at 550 ℃ for 2 hours. Obtaining the core-shell molecular sieve SZ-1.

Example 2

(1) 500.0g of H-type ZSM-5 molecular sieve (silica-alumina ratio 60, average grain size 0.5 μm, average grain size 10 μm, crystallinity 90.0%) was added to 5000g of an aqueous solution of polydiallyl dimethyl ammonium chloride and sodium chloride (in which the polydiallyl dimethyl ammonium chloride is 0.2% by mass and the sodium chloride is 0.2% by mass) at room temperature (25 ℃) and stirred for 2 hours, and the mixture was filtered, and the filter cake was dried under an air atmosphere at 50℃to give ZSM-5 molecular sieve I;

(2) Adding ZSM-5 molecular sieve I into H-type beta molecular sieve suspension (the weight percentage concentration of beta molecular sieve in the beta molecular sieve suspension is 2.5 percent by weight, the average grain size of the beta molecular sieve is 0.1 mu m, the silicon-aluminum ratio is 30.0, and the crystallinity is 92.0 percent); 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 aluminum sol (Al ₂ O ₃ Is 25 weight percentThe mole ratio of aluminum to chlorine is 1.1; ) Dissolving in 500g deionized water, adding 30g NaOH particles, and sequentially adding 4500mL water glass (SiO) ₂ 251g/L, modulus 2.5) and 1600g tetraethylammonium hydroxide solution (mass fraction of tetraethylammonium hydroxide solution is 25%), after fully and uniformly stirring, transferring into a polytetrafluoroethylene lining reaction kettle for crystallization, and crystallizing for 10 hours at 150 ℃ to obtain a synthetic solution III; after the synthetic solution III is filtered, washed, dried and roasted, peaks exist at 2 theta=22.4 degrees and no peaks exist at 2 theta=21.2 degrees in an XRD spectrum;

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

(5) NH is used for Na-type ZSM-5/beta core-shell molecular sieve ₄ Exchange washing of Cl solution to Na ₂ The O content is less than 0.15 weight percent, filtered, dried and baked for 2 hours at 550 ℃; obtaining the core-shell molecular sieve SZ-2.

Example 3

(1) Adding H-type ZSM-5 molecular sieve (silicon-aluminum ratio 100, average grain size 100nm, average grain size 5.0 microns, crystallinity 91.0%, amount 500 g) serving as a core phase into 5000g of n-butylamine and aqueous solution of sodium chloride (mass percent of n-butylamine is 5.0%, mass percent of sodium chloride is 2%), stirring for 24H, filtering, and drying in an air atmosphere at 70 ℃ to obtain ZSM-5 molecular sieve I;

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

(3) 100g of sodium metaaluminate is dissolved in 1800g of deionized water, 60g of NaOH particles are added, and 1000g of coarse pore silica gel (SiO ₂ Content 98.0 wt%) and 1800g of tetraethylammonium bromide solution (tetraethylammonium bromide solution)After being stirred uniformly, the mixture is transferred into a polytetrafluoroethylene lining reaction kettle for crystallization, and the mixture is crystallized for 30 hours at 130 ℃ to obtain a synthetic solution III; after the synthetic solution III is filtered, washed, dried and roasted, peaks exist at 2 theta=22.4 degrees and no peaks exist at 2 theta=21.2 degrees in an XRD spectrum;

(4) Adding ZSM-5 molecular sieve II into synthetic solution III (the weight ratio of the ZSM-5 molecular sieve II to the synthetic solution III is 1:4 based on dry basis), crystallizing at 80 ℃ for 100h, filtering, washing, drying and roasting to obtain Na-type ZSM-5/beta core-shell molecular sieve;

(5) NH is used for Na-type ZSM-5/beta core-shell molecular sieve ₄ Exchange washing of Cl solution to Na ₂ The O content is less than 0.15 weight percent, and the mixture is filtered, dried and roasted at 550 ℃ for 2 hours; obtaining the core-shell molecular sieve SZ-3.

Comparative example 1

(1) Taking water glass, aluminum sulfate and ethylamine aqueous solution as raw materials, and taking the molar ratio SiO ₂ ：A1 ₂ O ₃ ：C ₂ H ₅ NH ₂ ：H ₂ 0=40: 1:10:1792 gelling, crystallizing at 140deg.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 with 0.5 weight percent of sodium chloride salt solution of methyl methacrylate (NaCl concentration is 5 weight percent) for 30min, filtering, drying, adding into 0.5 weight percent of beta molecular sieve suspension (nano beta molecular sieve, the mass ratio of ZSM-5 molecular sieve to beta molecular sieve suspension is 1:10) 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 sources, sodium aluminate and TEAOH are used as raw materials, and the raw materials are mixed according to the ratio of TEAOH to SiO ₂ :A1 ₂ O ₃ :H ₂ Feeding O=13:30:1:1500, adding the nuclear phase molecular sieve obtained in the step (2), and then filling the nuclear phase molecular sieve into a stainless steel kettle with a tetrafluoroethylene lining for crystallization at 140 ℃ for 54 hours;

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

(5) NH for Na-type molecular sieve ₄ Cl solution exchange washingTo Na (Na) ₂ The O content is less than 0.15 weight percent, and the mixture is filtered, dried and roasted at 550 ℃ for 2 hours; obtaining the core-shell molecular sieve DZ1.

Comparative example 2

According to the proportion of the example 1, except that the crystallization temperature is 30 ℃ and the crystallization time is 3 hours in the step 3, the crystallization product is filtered, washed, dried and roasted, and no peak exists at 2θ=22.4 degrees and no peak exists at 2θ=21.2 degrees in an XRD spectrum. Molecular sieve DZ2 is obtained.

Comparative example 3

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

The synthesis conditions of examples 1-3 and comparative examples 1-2 are listed in Table 1.

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

TABLE 1

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Table 1 (follow) (D1/D2 in the table indicates the ratio of peak height (D1) at 2θ=22.4° to peak height (D2) at 2θ=23.1° in the XRD spectrum)

Note that: *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 chinese kaolin company having a solids content of 75 wt%;

the pseudo-boehmite used was obtained from Shandong aluminum company and had an alumina content of 65% by weight;

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

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

Y-type molecular sieve, brand: HSY-12, rare earth content of 12 wt%, si/Al ratio of 6.09, crystallinity of 53.0%, qilu division of China petrochemical catalyst Co.

Beta molecular sieve, hbeta, silicon-aluminum ratio 25.0, crystallinity 91.4%, qilu division of China petrochemical catalyst Co.

Examples 4 to 7

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

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

(1) Mixing pseudo-boehmite (aluminum stone for short) and water uniformly, adding 36 wt% concentrated hydrochloric acid (chemical pure, produced by Beijing chemical plant) with an acid-aluminum ratio (36 wt% hydrochloric acid to pseudo-boehmite calculated as aluminum oxide) of 0.2 under stirring, and aging the obtained mixture at 70deg.C for 1.5 hours to obtain aged pseudo-boehmite. The alumina content of the bauxite slurry was 12% by weight;

(2) Mixing a core-shell molecular sieve, a Y-type molecular sieve, a beta molecular sieve, an alumina sol, a modified silica sol, kaolin, the aged pseudo-boehmite 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: h ₂ The weight ratio of O=1:1:10 is exchanged for 1h at 80 ℃, filtered, and the exchanging and filtering processes are repeated for one time, and dried.

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

Table 3 shows the compositions of catalysts A1 to A3 of the examples, in weight percent on a dry basis. The contents of the modified core-shell 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 sieves prepared in comparative examples 1 to 3, the Y-type molecular sieves, the beta-type molecular sieves, the aged pseudo-boehmite, the silica sol, the alumina sol, the kaolin and water were mixed, spray-dried to prepare catalyst microspheres, and exchanged, filtered and dried, respectively, according to the catalyst preparation method of example 4. The catalyst numbers are as follows: DB1, DB2, and DB3.

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

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

TABLE 2

TABLE 3 Table 3

TABLE 4 Table 4

Hydrogenated VGO Properties
		Density at 20 ℃, g/cm3	0.8974
Refractive index at 70 DEG C	1.4794
		Viscosity at 80 ℃ and mm2/s	15.87
Carbon residue, m%	0.3
		Four components, m%
Saturated hydrocarbons	78.8
		Aromatic hydrocarbons	19.6
Colloid	1.6
		Asphaltenes	＜0.1
Hydrocarbon composition, m%
		Paraffin hydrocarbons	30.5
Total cycloalkane	48.3

TABLE 5

Wherein the yield is calculated based on the raw material feed.

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

Claims

1. The catalytic cracking catalyst for producing low-carbon olefin by means of VGO catalytic cracking contains 30-79 wt% of carrier, 5-15 wt% of core-shell molecular sieve, 15-45 wt% of Y-type molecular sieve and 1-10 wt% of molecular sieve with pore opening diameter of 0.65-0.70 nm; wherein the core phase of the core-shell molecular sieve is ZSM-5 molecular sieve, the shell layer is beta molecular sieve, the ratio of 2 theta=22.4 DEG peak height to 2 theta=23.1 DEG peak height in an X-ray diffraction spectrogram is 0.1-10:1, and the total specific surface area is more than 420 m ² And/g, wherein the average grain size of the shell molecular sieve of the core-shell molecular sieve is 10nm-500nm, and the average grain size of the core-phase molecular sieve of the core-shell molecular sieve is 0.05 mu m-15 mu m; the carrier is one or more of aluminum sol, zirconium sol, pseudo-boehmite, silica sol and clay.

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

3. The catalyst of claim 2, wherein the core-shell molecular sieve has a core-to-shell ratio of 1-15:1.

4. The catalyst of claim 1, wherein the total specific surface area of the core-shell molecular sieve is greater than 420m ² The ratio of the surface area of the mesopores to the total surface area is 10-40%.

5. The catalyst of claim 4, wherein the total specific surface area of the core-shell molecular sieve is 490m ² /g-580m ² /g。

6. The catalyst of claim 1, wherein the shell molecular sieve of the core shell molecular sieve has an average crystallite size of 50-500nm.

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

8. The catalyst of claim 1, wherein the core-shell molecular sieve has a molar ratio of silicon to aluminum of SiO ₂ /Al ₂ O ₃ And is 10-500.

9. The catalyst of claim 1, wherein the core-shell molecular sieve has a molar ratio of silicon to aluminum of the core-phase molecular sieve of SiO ₂ /Al ₂ O ₃ Counting as 10- ≡.

10. The catalyst of claim 1, wherein the silica to alumina molar ratio of the core-shell molecular sieve is based on SiO ₂ /Al ₂ O ₃ 25-200, wherein the silicon-aluminum molar ratio of the nuclear phase molecular sieve of the nuclear shell molecular sieve is calculated by SiO ₂ /Al ₂ O ₃ And is calculated as 30-200.

11. The catalyst of claim 1, wherein the average crystallite size of the core-phase molecular sieve of the core-shell molecular sieve is 0.1 μιη to 5 μιη.

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

13. The catalyst of any one of claims 1-12, wherein the core-shell molecular sieve shell coverage is 50% -100% and the sodium oxide content in the core-shell molecular sieve is no more than 0.15% by weight.

14. The catalyst of any one of claims 1-12, wherein the core-shell molecular sieve has a pore volume of from 20-80nm pores with a pore diameter of from 50% -70% of the pore volume of from 2-80nm pores.

15. The catalyst of claim 1, wherein the Y-type molecular sieve is a rare earth-containing Y-type molecular sieve, and the rare earth content of the rare earth-containing Y-type molecular sieve is RE ₂ O ₃ 5 to 17% by weight.

16. The catalyst of claim 1 or 15, wherein the molecular sieve having pore opening diameters of 0.65-0.70 nm is a beta molecular sieve.

17. The catalyst of claim 16 wherein the beta molecular sieve is a hydrogen form beta molecular sieve.

18. A method of preparing the catalytic cracking catalyst of claim 1, comprising: forming a slurry comprising the first molecular sieve, the second molecular sieve, and the third molecular sieve, the 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, the third molecular sieve is a molecular sieve with pore opening diameters of 0.65-0.70 nanometers, and the carrier is one or more of clay, an alumina carrier and a silica carrier.

19. The method of claim 18, wherein the synthesis method of the core-shell molecular sieve comprises the steps of:

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

(5) Sodium core-shell molecular sieve ammonium exchange to make Na in core-shell molecular sieve ₂ The O content is less than 0.15 wt%;

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

20. The method of claim 19, wherein the contacting in step (1) is by: and adding the ZSM-5 molecular sieve into a surfactant solution with the weight percentage concentration of 0.05-50% to contact for at least 0.5h, filtering and drying to obtain the ZSM-5 molecular sieve I.

21. The process of claim 19, wherein the contacting in step (1) is for a period of 1h to 36h and a contacting temperature of 20 ℃ to 70 ℃.

22. The method of claim 19, wherein the surfactant is selected from at least one of polymethyl methacrylate, polydiallyl dimethyl ammonium chloride, ammonia, n-butylamine, tetraethylammonium hydroxide, dipicolinate, ethylamine, tetrapropylammonium hydroxide, tetrapropylammonium bromide, tetraethylammonium bromide, tetrabutylammonium hydroxide.

23. The process of claim 19, wherein the ZSM-5 molecular sieve of step (1) is silica to alumina molar ratio in SiO ₂ /Al ₂ O ₃ Counting as 10- ++the ZSM-5 molecular sieve has an average grain size of 0.05 μm to 20 μm.

24. The method of claim 19, wherein the contacting in step (2) comprises: adding ZSM-5 molecular sieve I into slurry containing beta zeolite, stirring at 20-60 ℃ for at least 0.5 hour, filtering, and drying to obtain 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 0.1-10 wt%.

25. The method of claim 24, wherein the concentration of beta zeolite in the beta zeolite-containing slurry in step (2) is 0.3 wt% to 8 wt%.

26. The method of claim 19, wherein in step (3), the silicon source, the aluminum source, and the template agent are represented by R, and the molar ratio of water is: R/SiO ₂ =0.1-10:1，SiO ₂ /Al ₂ O ₃ =10-800:1，H ₂ O/SiO ₂ =2-150:1， Na ₂ O/SiO ₂ =0-2:1。

27. The method of claim 26, wherein the R/SiO ₂ =0.1-3:1, said H ₂ O/SiO ₂ =10-120:1, the Na ₂ O/SiO ₂ = 0.01-1.7:1。

28. The method of claim 19, wherein in step (3), the silicon source is selected from at least one of ethyl orthosilicate, silica sol, water glass, coarse pore 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-aluminum oxide; the template agent is one or more of tetraethylammonium fluoride, polyvinyl alcohol, tetraethylammonium hydroxide, tetraethylammonium chloride, tetraethylammonium bromide, triethanolamine or sodium carboxymethyl cellulose.

29. The method of claim 19, wherein in step (3), the silicon source, the aluminum source, the template agent and deionized water are mixed to form a synthetic solution, and then crystallized at 75-250 ℃ for 10-80 hours to obtain synthetic solution III.

30. The method of claim 29, wherein the crystallizing in step (3): the crystallization temperature is 80-180 ℃ and the crystallization time is 18-50 hours.

31. A method according to claim 19, 29 or 30, wherein the resultant liquid III of step (3) is subjected to XRD analysis with a spectral peak present at 2θ=22.4° and no spectral peak present at 2θ=21.2°.

32. The method of claim 19, wherein the crystallizing in step (4): the crystallization temperature is 100-250 ℃ and the crystallization time is 30-350h.

33. The method of claim 32, wherein the crystallizing in step (4): the crystallization temperature is 100-200 ℃ and the crystallization time is 50-120 h.

34. The method of claim 19, wherein the ammonium exchange of step (5) is performed according to a core-shell molecular sieve: ammonium salt: h ₂ O=1: (0.1-1): (5-15) exchanging and filtering at 50-100 ℃ by weight ratio, wherein the process is carried out one or more times; the ammonium salt is selected from one or more of ammonium chloride, ammonium sulfate and ammonium nitrate.

35. The method of claim 19, wherein the firing in step (6) is performed at a firing temperature of 350-600 ℃ for a firing time of 2-6 h to remove the templating agent.

36. The method of claim 19, wherein the rare earth content of the Y-type molecular sieve is RE ₂ O ₃ 5-17 wt% of the third molecular sieve is beta molecular sieve.

37. The method of claim 18, wherein the silica support is one or more of a neutral silica sol, an acidic silica sol, or an alkaline silica sol; the silica sol content in the catalyst is SiO ₂ 1-15 wt%.

38. A catalytic cracking catalyst obtainable by the process of any one of claims 19 to 37.

39. A method for catalytic cracking of heavy oil, comprising the step of contacting the heavy oil with the catalytic cracking catalyst of any one of claims 1 to 17 or claim 38.

40. A method of catalytic cracking of hydrogenated VGO comprising the step of contacting hydrogenated VGO with the catalyst of any of claims 1 to 17 or claim 38.