CN114130426B

CN114130426B - Catalytic cracking catalyst for high-yield low-carbon olefin by hydrogenating LCO (liquid Crystal on silicon), and preparation method and application thereof

Info

Publication number: CN114130426B
Application number: CN202010915532.3A
Authority: CN
Inventors: 韩蕾; 林伟; 王鹏; 宋海涛; 王振波; 王丽霞; 周翔
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: 2020-09-03
Filing date: 2020-09-03
Publication date: 2023-08-08
Anticipated expiration: 2040-09-03
Also published as: CN114130426A

Abstract

The invention belongs to the technical field of catalyst preparation, and relates to a catalytic cracking catalyst for high-yield low-carbon olefin by hydrogenating LCO (liquid crystal on silicon), and a preparation method and application thereof, wherein the catalyst comprises a carrier, a core-shell molecular sieve and a molecular sieve with pore canal opening diameter of 0.65-0.70 nanometers; the core-shell molecular sieve is a ZSM-5 molecular sieve, the shell layer is a beta molecular sieve, and the ratio of the peak height of 2θ=22.4 degrees to the peak height of 2θ=23.1 degrees in an X-ray diffraction spectrogram is 0.1-10:1. The preparation method comprises the steps of forming slurry by a carrier, a core-shell molecular sieve and a molecular sieve with pore canal opening diameter of 0.65-0.70 nanometers, and spray drying. The catalyst is used for the catalytic pyrolysis of hydrogenated LCO, and has higher conversion rate and higher low-carbon olefin yield.

Description

Catalytic cracking catalyst for high-yield low-carbon olefin by hydrogenating LCO (liquid Crystal on silicon), and preparation method and application thereof

Technical Field

The invention relates to a catalytic cracking catalyst, in particular to a catalytic cracking catalyst for hydrogenating LCO to produce more low-carbon olefin.

Background

Ethylene and propylene are very important chemical raw materials, and naphtha steam cracking is mainly adopted to produce low-carbon olefin in the world at present. However, the yield of naphtha is limited, and the world demand for low-carbon olefins is increasing, so that the development and utilization of other raw materials for producing low-carbon olefins are of great significance.

With the change in the world fuel oil market, LCO has a superfluous trend. LCO contains more polycyclic aromatic hydrocarbon, and the polycyclic aromatic hydrocarbon does not generate cracking reaction under the condition of catalytic cracking, so that coke is easier to form. The aromatic hydrocarbon in the LCO can be converted into small-molecular hydrocarbon by hydrogenating the LCO to saturate or partially saturate the polycyclic aromatic hydrocarbon and then converting the polycyclic aromatic hydrocarbon. The naphthene ring in the hydrogenated LCO can be subjected to ring opening cracking reaction to generate small-molecule hydrocarbon under the condition of catalytic cracking, and can also be subjected to dehydrogenation reaction to generate aromatic hydrocarbon. In order to produce more low-carbon olefins, the hydrogenated LCO catalytic cracking catalyst is expected to have better ring-opening cracking activity and low-carbon olefin selectivity.

In a catalytic cracking catalyst for producing light olefins from heavy oil, a ZSM-5 molecular sieve having an MFI topology and a beta molecular sieve having a BEA topology are generally used. ZSM-5 molecular sieve has unique pore structure, belongs to orthorhombic system and has unit cell parameters ofThe number of Al atoms in the unit cell can be changed from 0 to 27, and the silicon-aluminum ratio can be changed in a wide range; the ZSM-5 skeleton contains two 10-membered ring channel systems which are mutually intersected, wherein one channel is S-shaped bent, and the aperture is +.>The pore canal is in a straight line shape, and the pore diameter is +. >However, although ZSM-5 molecular sieve has shape selective function, it has smaller pore diameter, which is unfavorable for the diffusion and adsorption of macromolecular reactant, especially cyclic hydrocarbon, while beta molecular sieve has larger pore size, which is a macroporous three-dimensional structure high-silicon zeolite with cross-deca-binary ring channel system, the pore size of the twelve-membered ring three-dimensional cross-channel system is->And->Larger molecular reactants may enter, increasing active center accessibility.

However, the existing heavy oil catalytic cracking catalyst containing ZSM-5 molecular sieve and beta molecular sieve is used for the catalytic cracking of hydrogenated LCO, and the effect of increasing the yield of low-carbon olefin is poor.

Disclosure of Invention

In the present invention, the grain size means: the dimension at the widest of the grains can be obtained by measuring the dimension at the widest of the grain projection plane in an SEM or TEM image of the sample. The average grain size of the plurality of grains is the average grain size of the sample.

Particle size: particle widest dimension the average particle size of a plurality of particles can be determined by measuring the particle size at the widest point of the projection surface of the particles in an SEM or TEM image of the sample, the average particle size of the plurality of particles being the average particle size of the sample. It can also be measured by a laser particle sizer. One or more grains may be included in one particle.

The core-shell molecular sieve (called core-shell molecular sieve for short) has a shell coverage of more than 50%.

The dry basis of the invention is as follows: the material was calcined in air at 850 ℃ for 1 hour to give a solid product.

The invention aims to solve the technical problem of providing a hydrogenation LCO catalytic cracking catalyst which is used for hydrogenation LCO conversion and has higher low-carbon olefin yield.

The invention provides a catalytic cracking catalyst for producing low-carbon olefin by hydrogenating LCO (liquid Crystal on silicon), which comprises 60-85 wt% of carrier, 10-35 wt% of core-shell molecular sieve, and 5-15 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 of the core-shell molecular sieve is 0.1-10:1, and the total specific surface area is more than 420m ² And/g. In the invention, the core-shell molecular sieve is called a first molecular sieve, and the molecular sieve with pore opening diameters of 0.65-0.70 nanometers is called a second molecular sieve.

The carrier in the catalytic cracking catalyst can be a carrier used for the catalytic cracking catalyst in the prior art, for example, the carrier can comprise one or more of clay, an alumina carrier, a silica-alumina carrier and an aluminum phosphate carrier; optionally, the support comprises additives such as phosphorus oxides, alkaline earth metal oxides. Preferably, the support is a clay and alumina support, or a clay, alumina support and silica support. Preferably, the support comprises a silica support. The silica support, for example, a solid silica gel support and/or a silica sol support, is more preferably a silica sol support. The content of the silicon oxide carrier in the catalytic cracking catalyst is SiO ₂ For example, 0 to 15 wt.%, for example 1 to 15 wt.%, or 10 to 15 wt.%, or 5 to 15 wt.%.

In one embodiment, the catalytic cracking catalyst comprises, on a dry basis, 15 to 40 weight percent core-shell molecular sieve, 35 to 50 weight percent clay, 10 to 30 weight percent acidified pseudoboehmite (pseudoboehmite), 5 to 15 weight percent alumina sol, and 0 to 15 weight percent silica sol, for example 5 to 15 weight percent silica sol.

According to the catalytic cracking catalyst for producing the low-carbon olefin by hydrogenating LCO provided by the invention, in the core-shell molecular sieve, the ratio of the peak height (D1) at 2 theta=22.4 degrees to the peak height (D2) at 2 theta=23.1 degrees is 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 for producing the low-carbon olefin by the hydrogenated LCO provided by the invention has the advantages that the ratio of the core layer to the shell layer of the core-shell molecular sieve is 0.2-20:1, for example, 1-15:1, and the ratio of the core layer to the shell layer can be calculated by adopting the peak area of an X-ray diffraction spectrum.

The invention provides a catalytic cracking catalyst for producing low-carbon olefin by hydrogenating LCO, wherein the catalyst comprises The specific surface area (also called total specific surface area) of the core-shell molecular sieve is more than 420m ² For example 450m ² /g-620m ² /g or 490m ² /g-580m ² /g or 500m ² /g-560m ² /g。

The catalytic cracking catalyst for producing the low-carbon olefin by the hydrogenated LCO provided by the invention, wherein the proportion of the mesoporous surface area of the core-shell molecular sieve to the total surface area (or the mesoporous specific surface area to the total specific surface area) is 10% -40%, such as 12% -35%. Wherein, the mesopores are pores with the pore diameter of 2nm-50 nm.

The catalytic cracking catalyst for producing the low-carbon olefin by the hydrogenated LCO provided by the invention, wherein the average grain size of the shell molecular sieve of the core-shell molecular sieve can be 10nm-500nm, such as 50-500nm.

The invention provides a catalytic cracking catalyst for producing low-carbon olefin by hydrogenating LCO, wherein the silicon-aluminum ratio of a shell molecular sieve of a core-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 thickness of the shell molecular sieve of the core-shell molecular sieve can be 10nm-2000nm, for example, 50nm-2000nm.

The catalytic cracking catalyst for producing the low-carbon olefin by hydrogenating LCO provided by the invention, wherein the average grain size of the core phase molecular sieve of the core-shell molecular sieve is 0.05-15 mu m, preferably 0.1-10 mu m, such as 0.1-5 mu m or 0.1-1.2 mu m.

The catalytic cracking catalyst for producing low-carbon olefin by hydrogenating LCO provided by the invention, wherein the average particle size of the core phase molecular sieve of the core-shell molecular sieve is preferably 0.1-30 μm, such as 0.2-25 μm or 0.5-10 μm or 1-5 μm or 2-4 μm.

According to the catalytic cracking catalyst for producing the low-carbon olefin by the hydrogenated LCO provided by the invention, preferably, the number of crystal grains in single particles of the nuclear phase molecular sieve is not less than 2.

Hydrogenated LCO production provided in accordance with the present inventionThe low-carbon olefin catalytic cracking catalyst, wherein the silicon-aluminum molar ratio of the nuclear phase molecular sieve of the nuclear shell molecular sieve is SiO ₂ /Al ₂ O ₃ For example, 10- ++e.g. 20- ++or 50- ++or 30-300 or 30-200 or 20-80 or 25-70 or 30-60.

The catalytic cracking catalyst for producing the low-carbon olefin by the hydrogenated LCO provided by the invention has the shell coverage of 50-100%, such as 80-100%.

According to the catalytic cracking catalyst for producing low-carbon olefin by hydrogenated LCO provided by the invention, in one embodiment, the pore volume of the pores with the pore diameter of 20nm-80nm in the core-shell molecular sieve accounts for 50% -70%, such as 55% -65% or 58% -64%, of the pore volume of the pores with the pore diameter of 2nm-80 nm.

The invention provides a catalyst for catalyzing and cracking low-carbon olefin by hydrogenating LCO (liquid crystal on silicon), wherein the total pore volume of a core-shell molecular sieve is taken as a reference, and the pore volume of pores with the pore diameter of 0.3-0.6 nm in the core-shell molecular sieve accounts for 40-90%, such as 40-88%, or 50-85%, or 60-85%, or 70-82%.

The invention provides a catalyst for catalyzing and cracking low-carbon olefin production by hydrogenated LCO, wherein the total pore volume of a core-shell molecular sieve is taken as a reference, and the pore volume of pores with the pore diameter of 0.7nm-1.5nm in the core-shell molecular sieve accounts for 3% -20%, such as 3% -15% or 3% -9%.

The invention provides a catalyst for catalyzing and cracking low-carbon olefin by hydrogenating LCO, wherein the total pore volume of the core-shell molecular sieve is taken as a reference, and the pore volume of pores with the pore diameter of 2nm-4nm in the core-shell molecular sieve accounts for 4% -50%, such as 4% -40% or 4% -20% or 4% -10%.

The invention provides a catalyst for catalyzing and cracking low-carbon olefin by hydrogenating LCO (liquid crystal on silicon), wherein the total pore volume of a core-shell molecular sieve is taken as a reference, and the pore volume of pores with the pore diameter of 20nm-80nm in the core-shell molecular sieve accounts for 5% -40%, such as 5% -30% or 6% -20% or 7% -18% or 8% -16%.

According to the catalytic cracking catalyst for producing low-carbon olefin by hydrogenating LCO provided by the invention, in one embodiment, the pore volume of the pores with the pore diameter of 2nm-80nm in the core-shell molecular sieve accounts for 10% -30%, such as 11% -25%, of the total pore volume.

The total pore volume of the core-shell molecular sieve is 0.28mL/g-0.42mL/g, such as 0.3mL/g-0.4mL/g or 0.32mL/g-0.38mL/g.

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 publication).

The invention provides a preparation method of a catalytic cracking catalyst, which comprises the following steps:

forming slurry comprising a core-shell molecular sieve, a second molecular sieve, a carrier and water, and spray drying; the second molecular sieve is a molecular sieve with pore canal opening diameter of 0.65-0.70 nanometers.

The invention provides a catalytic cracking catalyst for producing low-carbon olefin by hydrogenating LCO, wherein the preparation method of a core-shell molecular sieve 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 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; (4) Mixing ZSM-5 molecular sieve II with synthetic solution III, and crystallizing; (5) recovering the core-shell molecular sieve.

According to the preparation method of the catalytic cracking catalyst provided by the invention, the contact method in the step (1) can be 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 the preparation method of the catalytic cracking catalyst provided by the invention, the contact time (or treatment time) in the step (1) can be more than 0.5h, for example, 0.5-48h or 1-36 h, and the contact temperature (or treatment temperature) is 20-70 ℃.

According to the preparation method of the catalytic cracking catalyst provided by the invention, the weight ratio of the surfactant solution in the step (1) to the ZSM-5 molecular sieve in dry basis can be 10-200:1. The surfactant solution may further contain a salt which has an electrolyte property for separating or dispersing the surfactant, for example, one or more of alkali metal salt and ammonium salt which are soluble in water, preferably one or more of alkali metal chloride salt, alkali metal nitrate, ammonium chloride salt and ammonium nitrate, for example, one or more of sodium chloride, potassium chloride, ammonium 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. The surfactant may be at least one selected from polymethyl methacrylate, polydiallyl dimethyl ammonium chloride, dipicolinic acid, ammonia water, ethylamine, n-butylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium hydroxide.

The preparation method of the catalytic cracking catalyst provided by the invention comprises the following steps of (1) preparing the ZSM-5 molecular sieve (raw material) by silicon-aluminum molar ratio of 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 40-70 or 20-80 or 25-70 or 30-60.

The preparation method of the catalytic cracking catalyst provided by the invention is characterized in that the average grain size of the ZSM-5 molecular sieve (raw material) in the step (1) is preferably 0.05-20 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.

According to the method for preparing the catalytic cracking catalyst provided by the invention, 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 20 μm or 1 μm to 5 μm or 2 μm to 4 μm.

According to the preparation method of the catalytic cracking catalyst provided by the invention, the ZSM-5 molecular sieve (raw material) in the step (1) can be 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 the preparation method of the catalytic cracking catalyst provided by the invention, in the step (1), the drying is not particularly required, and can be, for example, drying, flash drying and air flow 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 preparation method of the catalytic cracking catalyst provided by the invention, the contact in the step (2) comprises the steps of mixing ZSM-5 molecular sieve I with slurry containing beta zeolite (beta zeolite is also called 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 preparation method of the catalytic cracking catalyst provided by the invention comprises the step (2), wherein the concentration of beta zeolite in the slurry containing the beta zeolite is 0.1-10 wt%, such as 0.3-8 wt% or 0.2-1 wt%.

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

According to the preparation method of the catalytic cracking catalyst provided by the invention, in the slurry containing the beta zeolite in the step (2), the average grain size of the beta zeolite is 10nm-500nm, such as 50nm-400nm or 100nm-300nm or 10nm-300nm or 200-500nm. 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.

According to the method for producing a catalytic cracking catalyst provided by the present invention, wherein 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 invention provides a preparation method of a catalytic cracking catalyst, wherein the silicon-aluminum molar ratio of beta zeolite in the slurry containing beta zeolite in the step (2) is equal to SiO ₂ /Al ₂ O ₃ The meter (i.e., the silicon to aluminum ratio) is preferably 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 the preparation method of the catalytic cracking catalyst provided by the invention, in the step (3), the molar ratio of a silicon source, an aluminum source, a template agent (expressed by R) and water is as follows: R/SiO ₂ =0.1 to 10, e.g. 0.1 to 3 or 0.2 to 2.2, na ₂ O/SiO ₂ =0-2, e.g. 0.01-1.7 or 0.05-1.3 or 0.1-1.1, sio ₂ /Al ₂ O ₃ =10-800, e.g. 20-800, h ₂ O/SiO ₂ =2-150, e.g. 10-120.

According to the preparation method of the catalytic cracking catalyst provided by the invention, in the step (3), the template agent (R) is one or more of tetraethylammonium fluoride, tetraethylammonium hydroxide, tetraethylammonium bromide, triethanolamine, tetraethylammonium chloride, polyvinyl alcohol or sodium carboxymethyl cellulose, preferably, the template agent comprises at least one of tetraethylammonium hydroxide, tetraethylammonium bromide and tetraethylammonium chloride; the silicon source can be at least one of tetraethoxysilane, coarse pore silica gel, water glass, white carbon black, silica sol or activated clay; the aluminum source may be selected from at least one of aluminum sulfate, aluminum nitrate, aluminum isopropoxide, sodium metaaluminate, aluminum sol, or gamma-alumina.

According to the preparation method of the catalytic cracking catalyst provided by the invention, in the step (3), a silicon source, an aluminum source, a template agent and deionized water are mixed to form a synthetic liquid, and then the synthetic liquid III is obtained by crystallization for 10-80 hours at 75-250 ℃, and the crystallization process is called first crystallization (or 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 the preparation method of the catalytic cracking catalyst provided by the invention, the crystallization in the step (3) is the first crystallization, so that the crystallization state of the obtained synthetic liquid III is the state that the crystal grains are not yet appeared, and the crystal grains are close to the end of the crystallization induction period and 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 preparation method of the catalytic cracking catalyst provided by the invention, in the step (4), the ZSM-5 molecular sieve II is mixed with the synthesis liquid III, for example, the ZSM-5 molecular sieve II is added into the synthesis liquid III, wherein the weight ratio of the synthesis liquid 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 the preparation method of the catalytic cracking catalyst provided by the invention, the crystallization in the step (4) is called 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 the step (4), ZSM-5 molecular sieve II and synthetic solution III are mixed and crystallized 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 the preparation method of the catalytic cracking catalyst provided by the invention, the crystallization product containing the core-shell molecular sieve is obtained after the crystallization in the step (4) is finished. And (5) recovering the core-shell molecular sieve in the crystallized product to obtain the core-shell molecular sieve, wherein the core-shell molecular sieve is ZSM-5/beta core-shell molecular sieve. The recovery generally includes: one or more of the steps of filtering, washing, drying, calcining, e.g., the crystallized product is filtered, then washed and dried, optionally calcined. Drying methods such as air drying, oven drying, air drying, flash drying, in one embodiment, drying conditions such as: the temperature is 50-150 ℃ and the time is 0.5-4 h. The washing can be performed by water, for example, the water can be one or more of deionized water, distilled water and decationized water, the ratio of the core-shell molecular sieve to the water is 1:5-20, for example, the washing can be performed one or more times until the pH value of the washed water is 8-9. The roasting conditions are, for example, a roasting temperature of 400-600 ℃ and a roasting time of 2-10h.

The invention provides a preparation method of a catalytic cracking catalyst, wherein the core-shell molecular sieve obtained in the step (5) is a ZSM-5/beta core-shell molecular sieve with a core phase of ZSM-5 molecular sieve and a shell layer of beta molecular sieve, and the silicon-aluminum molar ratio of the shell layer is SiO ₂ /Al ₂ O ₃ Preferably 10 to 500, more preferably 25 to 200.

According to the preparation method of the catalytic cracking catalyst provided by the invention, the molecular sieve recovered in the step (5) can be directly used for preparing the catalyst or used for preparing the catalyst after exchange.

According to the preparation method of the catalytic cracking catalyst provided by the invention, the core-shell molecular sieve obtained in the step (5) can be subjected to ammonium exchange, and then pulped with a second molecular sieve, a carrier and water, and preferably, the preparation method comprises the following steps:

(S1) contacting the recovered core-shell molecular sieve with ammonium salt for ion exchange to obtain an ammonium exchanged core-shell molecular sieve, wherein the sodium oxide content of the ammonium exchanged core-shell molecular sieve is less than 0.15 wt%;

(S2) roasting the ammonium exchanged core-shell molecular sieve to remove the template agent and obtain a hydrogen type core-shell molecular sieve; the firing, for example: roasting at 400-600 deg.c for 2-10 hr;

(S3) pulping the hydrogen type core-shell molecular sieve, the molecular sieve with the pore canal opening diameter of 0.65-0.70 nanometers, the carrier and water, and spray drying.

In one embodiment, the ammonium exchange method of step (S1) comprises: according to the core-shell molecular sieve: ammonium salt: h ₂ O=1: (0.1-1): (5-15) making the core-shell molecular sieve and ammonium salt solution contact at 50-100 deg.C to make exchange and filtration, and making said ammonium exchange process be implemented once or more than twice; the ammonium salt is selected from one or a mixture of more of ammonium chloride, ammonium sulfate and ammonium nitrate.

According to the preparation method of the catalytic cracking catalyst, the carrier can be a carrier commonly used in the catalytic cracking catalyst. Preferably, the support comprises one or more of clay, alumina support, silica support, aluminum phosphate support, silica alumina support. The clay is one or more of kaolin, montmorillonite, diatomite, halloysite, quasi halloysite, saponite, rectorite, sepiolite, attapulgite, hydrotalcite, bentonite and the like. 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 silica support is one or more of silica sol, silica gel, and solid silica gel. The silicon-aluminum oxide carrier is one or more of silicon-aluminum materials, silicon-aluminum sol and silicon-aluminum gel. The silica sol is one or more of neutral silica sol, acidic silica sol or alkaline silica sol. In the slurry comprising the gallium-containing core-shell molecular sieve and the carrier, the weight ratio of the gallium-containing core-shell molecular sieve dry basis to the carrier dry basis is 15-50:50-85, for example 25-45:55-75. The slurry of the core shell molecular sieve and the carrier typically has a solids content of from 10 to 50 wt%, preferably from 15 to 30 wt%.

According to the method for preparing the catalytic cracking catalyst of the present invention, preferably, the carrier comprises clay and a carrier having a binding function. The carrier having a binding function is called a binder, and the binder is one or more of a silica binder, an alumina binder, and a phosphoalumina gel, wherein the silica binder is silica sol, and the alumina binder is alumina sol and/or acidified pseudo-boehmite. Preferably, the carrier comprises one or more of acidified pseudo-boehmite, an alumina sol and a silica sol. In one embodiment, the binder comprises an alumina sol and/or an acidified pseudo-boehmite. In one embodiment, the binder comprises a silica sol, optionally further comprising an alumina sol and/or acidified pseudo-boehmite; the silica sol is added in such an amount that the silica content (in terms of SiO ₂ From 1 to 15% by weight.

According to the preparation method of the catalytic cracking catalyst, preferably, in the slurry comprising the core-shell molecular sieve, the second molecular sieve and the carrier, on a dry basis, the core-shell molecular sieve is as follows: second molecular sieve: clay: aluminum sol: acidifying pseudo-boehmite: the weight ratio of the silica sol is (15-40): (5-15): (35-50): (5-15): (10-30): (0-15). The support may also contain an inorganic oxide matrix such as one or more of a silica alumina material, activated alumina, silica gel.

The second molecular sieve is a molecular sieve with pore opening diameter of 0.65-0.70 nanometers and is selected from at least one 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 second molecular sieve is preferably a beta molecular sieve, preferably a hβ molecular sieve, having a silica to alumina ratio (SiO ₂ /Al ₂ O ₃ Molar ratio) is preferably from 10 to 500.

The preparation method of the catalytic cracking catalyst according to any one of the above technical schemes, wherein the slurry comprising the core-shell molecular sieve, the second molecular sieve, the carrier and water can also contain additives. The additive can be added into part of the carrier, can be added into all the carriers, and can also be added into slurry formed by the core-shell molecular sieve, the second molecular sieve and the carrier and water slurry. Such as phosphorus oxide additives, metal oxide additives; such as alkaline earth metal oxides or one or more of their precursors.

The preparation method of the catalytic cracking catalyst provided by the invention comprises the following steps: mixing and pulping the core-shell molecular sieve, the second molecular sieve, clay, silica binder and/or alumina binder, optionally inorganic oxide matrix and water to form a slurry, wherein the solid content of the slurry formed by pulping is generally 10-50 wt%, preferably 15-30 wt%; and then spray drying and optionally roasting to obtain the catalytic cracking catalyst. The spray drying conditions are commonly used in the preparation process of the catalytic cracking catalyst. In general, the spray drying temperature may be from 100 to 350℃and preferably from 150 to 300℃such as from 200 to 300 ℃. When the carrier contains additives, the additives may be added to the slurry before drying or introduced after drying, for example by impregnation. The roasting conditions are as follows: the calcination temperature is, for example, 550℃and the calcination time is, for example, 6 hours.

According to the present inventionThe preparation method of the catalytic cracking catalyst provided by the invention can also comprise the step of exchanging after spray drying. Preferably, the exchange results in a catalytic cracking catalyst having a sodium oxide content of no more than 0.15 wt.%. The exchange may employ an ammonium salt solution. In one embodiment, the ammonium exchange is performed as a catalyst: ammonium salt: h ₂ O=1: (0.1-1): (5-15) contacting the catalyst with an ammonium salt solution at a weight ratio of 50-100 ℃, filtering, which may be carried out one or more times, e.g. at least twice; the ammonium salt can be one or a mixture of more of ammonium chloride, ammonium sulfate and ammonium nitrate. Optionally, a washing step is also included to wash away sodium ions exchanged from the catalyst, which may be washed with water, for example, decationized water, distilled water or deionized water.

According to the preparation method of the catalytic cracking catalyst, after spray drying, the preparation method can further comprise the step of roasting, wherein the roasting can be carried out before or after the exchange. The roasting method can adopt the roasting method in the prior art, and in one implementation mode, the roasting temperature is 400-600 ℃ and the roasting time is 2-6 hours.

The invention also provides a hydrogenation LCO catalytic cracking method, which comprises the step of carrying out contact reaction on the hydrogenation LCO and the catalytic cracking catalyst provided by the invention. The reaction conditions of the hydrogenated LCO conversion method provided by the invention comprise: the reaction temperature is 550-620 ℃, preferably 560-600 ℃, 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 catalytic cracking catalyst provided by the invention has excellent hydrogenation LCO cracking capacity and higher low-carbon olefin yield, is used for hydrogenation LCO conversion, and can have higher conversion rate and higher low-carbon olefin yield.

Detailed Description

The catalytic cracking catalyst provided by the invention comprises the following components in percentage by weight on a dry basis: 60-85 wt%, e.g., 60-85 wt%, of a carrier on a dry basis, 10-35 wt%, preferably 10-25 wt%, of a core-shell molecular sieve on a dry basis, and 5-15 wt%, e.g., 8-12 wt%, of a second molecular sieve on a dry basis; the second molecular sieve is a molecular sieve with pore canal opening diameter of 0.65-0.70 nanometers.

In one embodiment, 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, and the total specific surface area is greater than 420m ² The ratio of the mesoporous surface area to the total specific surface area is preferably 10-40%, the average grain size of the shell molecular sieve is 10-500 nm, the shell thickness of the shell molecular sieve is 10-2000 nm, the average grain size of the core phase molecular sieve is 0.05-15 mu m, the average grain size of the core phase molecular sieve is preferably 0.1-30 mu m, the core phase molecular sieve is an aggregate of a plurality of grains, and the silicon-aluminum mole ratio of the shell molecular sieve is expressed by SiO ₂ /Al ₂ O ₃ The weight ratio (i.e. silicon-aluminum ratio) is 10-500, and the silicon-aluminum mole ratio of the nuclear phase molecular sieve is calculated by SiO ₂ /Al ₂ O ₃ The ratio of the core-shell molecular sieve core to the shell is preferably 0.2-20:1, e.g., 1-15:1, the pore volume of the pores with the pore diameter of 0.3-0.6nm is 40% -88% of the total pore volume, the pore volume of the pores with the pore diameter of 0.7-1.5nm is 3-20% of the total pore volume, the pore volume of the pores with the pore diameter of 2-4nm is 4-50% of the total pore volume, and the pore volume of the pores with the pore diameter of 20-80nm is 5-40% of the total pore volume. The sodium oxide content in the core-shell molecular sieve is preferably not more than 0.15 wt.%.

In one embodiment, the preparation method of the core-shell molecular sieve comprises the following steps:

(1) Adding ZSM-5 molecular sieve into surfactant solution with weight percentage concentration of 0.05% -50%, stirring for 0.5-48h, wherein the weight ratio of surfactant to ZSM-5 molecular sieve 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, e.g. 0.01-1:1, 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 ℃;

(5) Filtering, washing and drying to obtain the sodium type core-shell molecular sieve; preferably, the silicon source and the aluminum source are used in an amount such that the silicon-aluminum molar ratio of the shell molecular sieve in the obtained core-shell molecular sieve is equal to that of SiO ₂ /Al ₂ O ₃ And is calculated as 25-200.

(6) The sodium type core-shell molecular sieve is contacted with ammonium salt for ion exchange,

(7) Roasting to remove the template agent, wherein the roasting temperature is 400-600 ℃ and the roasting time is 2-10.

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

(1) The Na in the core-shell molecular sieve is made by the sodium core-shell molecular sieve through ammonium exchange ₂ The O content is less than 0.15 wt%;

(2) Drying the molecular sieve obtained in the step (1), and roasting at 400-600 ℃ for 2-10 hours to remove the template agent;

(3) Mixing and pulping the obtained core-shell molecular sieve obtained in the step (2), the second molecular sieve and the carrier, and spray drying;

(4) Roasting the catalyst obtained in the step (3) at 400-600 ℃ for 1-6h; obtaining a roasted catalyst; and

optionally (5) ammonium exchanging the roasted catalyst, washing to make Na in the catalyst ₂ The O content is less than 0.15 wt.%, and drying.

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 grain size is the size of the widest part of the grain, and is obtained by measuring the diameter size of the projection maximum circumcircle of the grain. The particle size is the size at the widest point of the particle, and is obtained by measuring the diameter size of the largest circumscribed circle of the projection of the particle.

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) 100g of aluminum isopropoxide are dissolved in 1500g of deionized water, 65g of NaOH particles are added, and 1000g of silica sol (SiO ₂ 25.0 wt.% of sodium oxide, pH 10.0, and 0.10 wt.% of sodium oxide) and 2000g of tetraethylammonium hydroxide solution (the mass fraction of tetraethylammonium hydroxide in the tetraethylammonium hydroxide solution is 25 wt.%After being stirred uniformly, the mixture is transferred into a polytetrafluoroethylene lining 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 the ZSM-5 molecular sieve II to the 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 a sodium type core-shell molecular sieve;

(5) NH for sodium type core-shell molecular sieve obtained in step (4) ₄ Exchange washing of Cl solution to make Na in core-shell molecular sieve ₂ The O content is lower than 0.15 weight percent, and the molecular sieve is filtered, dried and roasted for 2 hours at 550 ℃ to obtain the SZ-1 molecular sieve.

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 5000.0g of an aqueous solution of polydiallyl dimethyl ammonium chloride and sodium chloride (in which the mass percentage of polydiallyl dimethyl ammonium chloride is 0.2% and the mass percentage of sodium chloride is 0.2%) 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 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 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 The concentration of (2) was 25% by weight and the aluminum-chlorine molar ratio was 1.1; ) Dissolving in 500.0g deionized water, adding 30g NaOH particles, and sequentially adding 4500.0mL water glass (SiO ₂ Concentration 251g/L, modulus 2.5) and 1600g tetraethylammonium hydroxide solution (mass fraction of tetraethylammonium hydroxide solution 25%), after being fully and evenly stirred, transferred into polytetrafluoroethylene liningCrystallizing in the reaction kettle at 150 ℃ for 10 hours 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 a sodium type core-shell molecular sieve;

(5) NH for the obtained sodium type core-shell molecular sieve ₄ Exchange washing of Cl solution to make Na in core-shell molecular sieve ₂ The O content was less than 0.15 wt%, filtered, dried, and calcined at 550℃for 2 hours, the resulting molecular sieve was designated 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 5000.0g of n-butylamine and sodium chloride aqueous solution (the mass percentage of n-butylamine is 5.0%, the mass percentage of sodium chloride is 2%) at room temperature of 25 ℃, stirring for 24 hours, filtering, and drying under 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 98.0 wt%) and 1800g of tetraethylammonium bromide solution (mass fraction of tetraethylammonium bromide solution is 25%), stirring uniformly, transferring into a polytetrafluoroethylene lining reaction kettle for crystallization, crystallizing for 30h at 130 ℃ to obtain 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 1:4 based on dry basis), crystallizing at 80 ℃ for 100h, filtering, washing, drying, roasting and obtaining Na-type ZSM-5/beta core-shell molecular sieve;

(5) NH is used for the Na-type ZSM-5/beta core-shell molecular sieve ₄ Exchange Cl solution, wash, make Na ₂ The O content was less than 0.15 wt%, filtered, dried, and calcined at 550℃for 2 hours, the resulting molecular sieve was designated 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 the core-shell molecular sieve obtained in the step (4) ₄ Exchange washing with Cl solution to make 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; the resulting molecular sieve was designated 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. The resulting molecular sieve was designated DZ2.

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. The resulting molecular sieve mixture was designated DZ3.

The conditions for the preparation of examples 1-3 and comparative examples 1-2 are shown in Table 1, and the properties of the molecular sieves obtained in step (4) of examples 1-3 and comparative examples 1-2 are shown in Table 1 (the continuation). The properties of the mixed molecular sieve of comparative example 3 are shown in Table 1 (below).

TABLE 1

Table 1 (subsequent)

d1/D2 in table 1 (section) represents the ratio of the peak height (D1) at 2θ=22.4° to the peak height (D2) at 2θ=23.1°; *1 represents 1, N represents a plurality of

The following examples illustrate the preparation of the catalytic cracking catalyst provided by the present invention, wherein the kaolin used in the examples is a commercial product of China Kaolin corporation having a solids content of 75% by weight; the pseudo-boehmite used was obtained from Shandong aluminum company and had an alumina content of 65% by weight; the alumina sol is produced by Qilu division of petrochemical catalyst in China, and the alumina content is 21 weight percent. Silica sol was produced by Beijing chemical plant, and had a silica content of 25% by weight and a pH of 3.0. The second molecular sieve is beta molecular sieve, H-type, silicon-aluminum ratio is 35, sodium oxide content is 0.1 wt%, crystallinity is 91.3%, and China petrochemical catalyst Qilu division company is produced.

Examples 4 to 6

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, stirring, adding 36 wt% concentrated hydrochloric acid (chemical pure, beijing chemical plant product) under stirring, and mixing with aluminum acid at 0.2 (36 wt% concentrated hydrochloric acid and Al ₂ O ₃ Calculated pseudo-boehmite mass ratio), the obtained mixture is heated to 70 ℃ and aged for 1.5 hours, and the aged pseudo-boehmite slurry is obtained. The alumina content in the aged pseudo-boehmite slurry was 12% by weight;

(2) Uniformly mixing a first molecular sieve, a second molecular sieve, alumina sol, silica sol, kaolin, the aged pseudo-boehmite slurry and deionized water to obtain slurry with the solid content of 28 weight percent, and spray-drying; the first molecular sieves used in examples 4-6 were core-shell molecular sieves SZ-1, SZ-2, SZ-3, respectively;

(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 exchange and filtering processes are repeated for 1 time, and dried.

Example 7

A catalyst was prepared according to the procedure of example 4, except that no silica sol was used and an equivalent amount of alumina sol was used instead to give catalyst A4.

Table 2 shows the numbers and amounts of the core-shell molecular sieves (first molecular sieve representation), the second molecular sieve type and amount, the alumina sol, silica sol and kaolin used in examples 4-7. Based on 1Kg of catalytic cracking catalyst, based on dry weight.

The dry weight percent compositions of catalysts A1-A4 of examples 4-7 are given in Table 3. The contents of the first molecular sieve, the second molecular sieve, the binder and the kaolin in the catalyst composition are calculated.

Comparative examples 4 to 6

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

The first molecular sieve (molecular sieves DZ1, DZ2 and DZ3 prepared in comparative examples 1-3, respectively) and the second molecular sieve, pseudo-boehmite, kaolin, silica sol, alumina sol and water were mixed and slurried, respectively, and spray-dried to prepare the microsphere catalyst according to the catalyst preparation method of example 4. The catalyst numbers are as follows: DB1, DB2, and DB3.

Table 2 shows the type and amount of the first molecular sieve, the second molecular sieve, the alumina sol, the silica sol and the kaolin used for the catalysts of comparative examples 4-6, based on 1Kg of catalyst prepared, on a dry basis.

The dry weight percentage composition of the catalysts DB1-DB3 is given in Table 3.

The catalytic cracking catalysts A1 to A4 and DB1 to DB3 prepared in examples 4 to 7 and comparative examples 4 to 6 were aged with 100% by volume of steam at 800℃for 4 hours, respectively, and then the catalytic cracking reaction performance was evaluated on a small-sized fixed fluidized bed reactor under the conditions of a reaction temperature of 580℃and a weight space velocity of 4.0 hours ^-1 The oil ratio was 12 weight ratio. The properties of the hydrogenated LCO are shown in Table 4, and the reaction results are shown in Table 5.

TABLE 2

In Table 2, the amounts of the first molecular sieve, the second molecular sieve, the alumina sol, the silica sol, and the kaolin clay were based on 1kg of the catalyst prepared.

TABLE 3 Table 3

TABLE 4 Table 4

w% represents the weight percentage.

TABLE 5

Catalyst	A1	A2	A3	A4	DB1	DB2	DB3
								Reaction conditions
Reaction temperature/. Degree.C	580	580	580	580	580	580	580
								Weight space velocity/h ^-1	4	4	4	4	4	4	4
Ratio of agent to oil	12	12	12	12	12	12	12
								Distribution of the product, wt%
Dry gas	9.48	9.14	8.78	10.01	6.89	7.64	7.14
								Liquefied gas	36.83	35.0	34.21	33.04	21.75	23.35	22.84
Gasoline	30.51	29.78	28.61	30.15	37.06	37.74	37.51
								Diesel oil	18.04	19.21	21.87	20.63	26.47	24.84	25.83
Heavy oil	2.98	4.47	4.25	3.33	4.97	4.84	4.75
								Coke	2.16	2.40	2.25	2.84	2.86	1.59	1.93
Low-carbon olefin, wt%	30.96	28.45	27.45	26.82	20.74	22.48	21.42

The product distribution described in Table 5 was calculated on the basis of the raw material feed. The low-carbon olefin refers to C2-C4 olefin.

As can be seen from the results shown in Table 5, the catalytic cracking catalyst provided by the invention can be used for hydrogenating LCO conversion, and has higher cracking capacity and lower olefin yield, and can have higher liquefied gas yield.

Claims

1. A catalytic cracking catalyst for producing low-carbon olefin by hydrogenating LCO, which comprises 60-85 wt% of carrier, 10-35 wt% of core-shell molecular sieve and 5-15 wt% of second molecular sieve based on dry weight; the core-shell molecular sieve core phase is ZSM-5 molecular sieve, and 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 the X-ray diffraction spectrogram of the core-shell molecular sieve is 0.1-10:1, 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 second molecular sieve is a molecular sieve with pore opening diameter of 0.65-0.70 nanometers, and the molecular sieve with pore 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; the carrier comprises one or more of clay, a silicon oxide carrier, an aluminum oxide carrier and a phosphor-aluminum glue.

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

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

4. The catalytic cracking 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 catalytic cracking catalyst of claim 4, wherein the total specific surface area of the core-shell molecular sieve is 450m ² /g-620 m ² /g，The proportion of the surface area of the mesopores to the total surface area is 12% -35%.

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

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

8. The catalytic cracking catalyst of claim 7, wherein the shell molecular sieve of the shell-to-core shell molecular sieve has a molar ratio of silicon to aluminum of SiO ₂ /Al ₂ O ₃ And is calculated as 25-200.

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

10. The catalytic cracking catalyst of claim 9, 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 And is calculated as 30-200.

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

12. The catalytic cracking catalyst of claim 1, wherein the shell molecular sieve of the core-shell molecular sieve has a thickness of 10nm to 2000nm.

13. The catalytic cracking catalyst of claim 12, wherein the shell molecular sieve of the core-shell molecular sieve has a thickness of 50nm to 2000nm.

14. The catalytic cracking 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 10 μιη.

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

16. The catalytic cracking catalyst of claim 1, wherein the core-shell molecular sieve shell coverage is 50% -100%.

17. The catalytic cracking catalyst of any one of claims 1-16, wherein the core-shell molecular sieve has pore volume of pores with a pore diameter of 20nm to 80nm that is 50% -70% of the pore volume of pores with a pore diameter of 2nm to 80 nm.

18. The catalytic cracking catalyst of claim 1, wherein the molecular sieve having pore opening diameters of 0.65-0.70 nanometers is at least one of Beta, SAPO-5, SAPO-40, SSZ-13, CIT-1, ITQ-7, ZSM-18, mordenite, and gmelinite.

19. The catalytic cracking catalyst of claim 1, wherein the support contains an additive.

20. The catalytic cracking catalyst of claim 19, wherein the additive is a phosphorus oxide or an alkaline earth metal oxide.

21. The catalytic cracking catalyst of claim 1, wherein the sodium oxide content of the core-shell molecular sieve is no more than 0.15 wt%.

22. A method of preparing the catalytic cracking catalyst of claim 1, comprising the steps of:

23. The method of claim 22, wherein the method of synthesizing the core-shell molecular sieve comprises the steps of:

(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 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;

(4) Mixing ZSM-5 molecular sieve II with synthetic solution III, and crystallizing;

(5) And (5) recovering the core-shell molecular sieve.

24. The method of claim 23, wherein the contacting in step (1) is by: adding ZSM-5 molecular sieve into surfactant solution with weight percentage concentration of 0.05% -50% to contact for at least 0.5h, filtering, drying to obtain ZSM-5 molecular sieve I, wherein the contact time is 1h-36h, and the contact temperature is 20-70 ℃.

25. The method of claim 23, wherein the surfactant is selected from at least one of polymethyl methacrylate, polydiallyl dimethyl ammonium chloride, dipicolinate, ammonia, ethylamine, n-butylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium hydroxide.

26. The method of claim 23, wherein the ZSM-5 molecular sieve in step (1) is silica to alumina molar ratio of 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.

27. The method of claim 23, wherein the contacting in step (2) comprises: adding the 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 the ZSM-5 molecular sieve II, wherein the concentration of beta zeolite in the slurry containing beta zeolite is 0.1-10 wt%, and the weight ratio of the slurry containing beta zeolite to the ZSM-5 molecular sieve I on a dry basis is 10-50:1.

28. The method of claim 27, wherein the concentration of beta zeolite in the beta zeolite-containing slurry is between 0.3 wt% and 8 wt%.

29. The method of claim 23, 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，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。

30. The method of claim 29, 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 = 0.1-3:1，H ₂ O/SiO ₂ = 10-120:1， Na ₂ O/SiO ₂ = 0.01-1.7:1。

31. The method of claim 23, wherein in step (3), the silicon source is selected from at least one of ethyl orthosilicate, water glass, coarse silica gel, silica sol, 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, tetraethylammonium hydroxide, tetraethylammonium bromide, tetraethylammonium chloride, polyvinyl alcohol, triethanolamine or sodium carboxymethyl cellulose.

32. The method of claim 23, 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 ℃ to 250 ℃ for 10 hours to 80 hours to obtain synthetic solution III.

33. The method according to claim 23, wherein the crystallization in step (3): the crystallization temperature is 80-180 ℃ and the crystallization time is 18-50 hours.

34. The method according to claim 23, 32 or 33, wherein the synthetic solution III obtained in 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 °.

35. The method according to claim 23, wherein the crystallization in step (4): the crystallization temperature is 100-250 ℃ and the crystallization time is 30-350h.

36. The method of claim 23, wherein the crystallization in step (4): the crystallization temperature is 100-200 ℃ and the crystallization time is 50-120 h.

37. The method according to any one of claims 23-36, comprising the steps of:

(S1) contacting the recovered core-shell molecular sieve with ammonium salt for ion exchange to obtain an ammonium exchanged core-shell molecular sieve, wherein the sodium oxide content in the ammonium exchanged core-shell molecular sieve is less than 0.15 wt%;

(S2) roasting the ammonium-exchanged core-shell molecular sieve to obtain a hydrogen-type core-shell molecular sieve;

38. The method according to claim 37, wherein the step (S1) is performed byThe ammonium exchange method comprises the following steps: according to the core-shell molecular sieve: ammonium salt: h ₂ O=1: (0.1-1): (5-15) making the core-shell molecular sieve and ammonium salt solution contact at 50-100 deg.C to make exchange and filtration, and making said ammonium exchange process be implemented once or more than twice; the ammonium salt is selected from one or a mixture of more of ammonium chloride, ammonium sulfate and ammonium nitrate; and (2) roasting, wherein the roasting temperature is 400-600 ℃, and the roasting time is 2-10 h.

39. The method according to claim 22 or 23, further comprising the step of ammonium exchange and/or calcination after spray drying; the ammonium exchange results in a catalytic cracking catalyst having a sodium oxide content of less than 0.15 wt.%.

40. The method of claim 39 wherein the support is a clay and alumina support or a clay, silica support and optionally an alumina support.

41. The method of claim 40, wherein the support comprises a silica support in the form of SiO ₂ The content of the silica carrier is 1-15 wt%, and the silica carrier is one or more of neutral silica sol, acidic silica sol or alkaline silica sol.

42. A catalytic cracking catalyst obtainable by the process of any one of claims 22 to 41.

43. A method of catalytic cracking of hydrogenated LCO, comprising the step of contacting the hydrogenated LCO with a catalytic cracking catalyst according to any one of claims 1 to 21 or claim 42.