阅读说明：本技术 一种催化裂化催化剂及其制备和应用 (Catalytic cracking catalyst, preparation and application thereof ) 是由 袁帅 田辉平 陈振宇 周灵萍 张蔚琳 沙昊 于 2018-06-29 设计创作，主要内容包括：一种催化裂化催化剂及其制备和应用,该催化剂含有改性Y型分子筛、氧化铝粘结剂和粘土；所述的改性Y型分子筛的氧化镁含量为0.5重量％～4.5重量％,氧化钠含量为0.1重量％～0.5重量％,总孔体积为0.33mL/g～0.39mL/g,该改性Y型分子筛的孔径为2nm～100nm的二级孔的孔体积占总孔体积的百分比为10％～25％,晶胞常数为2.440nm～2.455nm,该改性Y型分子筛中非骨架铝含量占总铝含量的百分比不高于20％,晶格崩塌温度不低于1040℃,并且,用吡啶吸附红外法在200℃时测定的该改性Y型分子筛的总酸量中B酸量与L酸量的比值不低于2.30；该分子筛进行紫外可见光分析时,紫外可见吸收光谱285nm～295nm处没有吸收。该催化裂化催化剂用于重油催化裂化,具有较低的焦炭选择性,具有更高的汽油收率、液化气收率,且汽油中具有更高的异构烃含量。(A catalytic cracking catalyst, its preparation and application, the catalyst contains modified Y-type molecular sieve, alumina binder and clay; the modified Y-type molecular sieve has the magnesium oxide content of 0.5-4.5 wt%, the sodium oxide content of 0.1-0.5 wt%, the total pore volume of 0.33-0.39 mL/g, the pore volume of secondary pores with the pore diameter of 2-100 nm accounting for 10-25% of the total pore volume, the unit cell constant of 2.440-2.455 nm, the non-framework aluminum content of the modified Y-type molecular sieve accounting for not more than 20% of the total aluminum content, the lattice collapse temperature of not less than 1040 ℃, and the ratio of the B acid amount to the L acid amount of the total acid amount of the modified Y-type molecular sieve determined by a pyridine adsorption infrared method at 200 ℃ of not less than 2.30; when the molecular sieve is used for ultraviolet and visible light analysis, no absorption exists at the position of 285 nm-295 nm of an ultraviolet and visible absorption spectrum. The catalytic cracking catalyst is used for heavy oil catalytic cracking, has lower coke selectivity, higher gasoline yield and liquefied gas yield, and has higher content of isomeric hydrocarbon in gasoline.)

1. A catalytic cracking catalyst comprises 10-50 wt% of modified Y-type molecular sieve calculated by dry basis, 10-40 wt% of alumina binder calculated by alumina and 10-80 wt% of clay calculated by dry basis; the modified Y-type molecular sieve has the magnesium oxide content of 0.5-4.5 wt%, the sodium oxide content of 0.1-0.5 wt%, the total pore volume of 0.33-0.39 mL/g, the pore volume of secondary pores with the pore diameter of 2-100 nm accounting for 10-25% of the total pore volume, the unit cell constant of 2.440-2.455 nm, the non-framework aluminum content of the modified Y-type molecular sieve accounting for not more than 20% of the total aluminum content, the lattice collapse temperature of not less than 1040 ℃, and the ratio of the B acid amount to the L acid amount of the total acid amount of the modified Y-type molecular sieve determined by a pyridine adsorption infrared method at 200 ℃ of not less than 2.30; when the molecular sieve is used for ultraviolet and visible light analysis, no absorption peak exists at the position of 285 nm-295 nm of an ultraviolet and visible absorption spectrum.

2. The catalytic cracking catalyst of claim 1, wherein the modified Y-type molecular sieve has secondary pores with a pore diameter of 2-100 nm, the pore volume of which accounts for 15-21% of the total pore volume, the non-framework aluminum content of which accounts for 13-19% of the total aluminum content, and the framework silicon-aluminum ratio which is SiO₂/Al₂O₃The molar ratio is 7.3-14, and the molecular sieve lattice collapsesThe temperature is 1045-1080 ℃, and the ratio of the B acid amount to the L acid amount in the total acid amount of the modified Y-type molecular sieve measured by a pyridine adsorption infrared method at 200 ℃ is 2.4-4.2.

3. The catalytic cracking catalyst according to claim 1, wherein the modified Y-type molecular sieve has a relative crystal retention of 33% or more, for example, 33 to 45%, after severe aging at 800 ℃ under normal pressure in a 100% steam atmosphere for 17 hours.

4. The catalytic cracking catalyst of claim 1, wherein the modified Y-type molecular sieve has a relative crystallinity of 58 to 70%.

5. The catalytic cracking catalyst according to any one of claims 1 to 4, wherein the modified Y-type molecular sieve has a magnesium oxide content of 0.6 to 4.3 wt%, a sodium oxide content of 0.2 to 0.5 wt%, a unit cell constant of 2.442 to 2.450nm, and a framework silica-alumina ratio of 8.4 to 12.6.

6. A preparation method of a catalytic cracking catalyst comprises the steps of preparing a modified Y-type molecular sieve, forming slurry comprising the modified Y-type molecular sieve, an alumina binder, clay and water, and spray drying, wherein the preparation method of the modified Y-type molecular sieve comprises the following steps:

(1) contacting the NaY molecular sieve with a soluble magnesium salt solution to perform an ion exchange reaction, filtering, washing, and optionally drying to obtain a Y-type molecular sieve with a conventional unit cell size and reduced sodium oxide content and containing magnesium;

(2) roasting the Y-type molecular sieve with the reduced sodium oxide content and the conventional unit cell size containing magnesium at the temperature of 350-480 ℃ for 4.5-7 hours in the atmosphere of 30-90 vol% of water vapor, and optionally drying to obtain the Y-type molecular sieve with the reduced unit cell constant;

(3) according to SiCl₄: the Y-type molecular sieve with reduced unit cell constant is 0.1-0.7: 1 weight ratio of the Y-type molecular sieve with reduced unit cell constant to silicon tetrachloride gasAnd (3) controlling the reaction temperature to be 200-650 ℃, controlling the reaction time to be 10 minutes-5 hours, washing and filtering to obtain the modified Y-type molecular sieve.

7. The process of claim 6, wherein said reduced sodium oxide content magnesium-containing conventional unit cell size Y-type molecular sieve of step (1) has a unit cell constant of 2.465 to 2.472nm and a sodium oxide content of no more than 8.8 wt%; the unit cell constant of the Y-type molecular sieve with the reduced unit cell constant obtained in the step (2) is 2.450 nm-2.462 nm, and the water content in the Y-type molecular sieve with the reduced unit cell constant is not more than 1 weight percent.

8. The process of claim 7, wherein in step (1), the magnesium-containing conventional unit cell size Y-type molecular sieve having a reduced sodium oxide content has a magnesium content of 0.6 to 5.5 wt.% as MgO, a sodium oxide content of 4 to 8.8 wt.%, such as 5.5 to 8.5 wt.%, and a unit cell constant of 2.465nm to 2.472 nm.

9. The method of claim 6, wherein the step (1) of contacting the NaY molecular sieve with the solution of soluble magnesium salt is carried out by ion exchange reaction according to the following formula: soluble magnesium salt: h₂O is 1: 0.005-0.19: 5-15, mixing NaY molecular sieve, soluble magnesium salt and water, and stirring.

10. The method of claim 6 or 9, wherein the step (1) of contacting the NaY molecular sieve with a solution of soluble magnesium salt for an ion exchange reaction comprises: mixing NaY molecular sieve with water, adding soluble magnesium salt and/or soluble magnesium salt solution under stirring to perform ion exchange reaction, filtering and washing; the conditions of the ion exchange reaction are as follows: the exchange temperature is 15-95 ℃, and the exchange time is 30-120 minutes; the soluble magnesium salt is preferably magnesium chloride and/or magnesium nitrate.

11. The method of claim 6, wherein the roasting temperature in the step (2) is 380-460 ℃, the roasting atmosphere is 40-80% of water vapor atmosphere, and the roasting time is 5-6 hours.

12. The method of claim 6, wherein the washing method in step (3) is washing with water under the washing conditions that the molecular sieve: h₂O is 1: 6-15, the pH value is 2.5-5.0, and the washing temperature is 30-60 ℃.

13. A catalytic cracking method comprises the step of carrying out contact reaction on heavy oil and a catalytic cracking catalyst under FCC conditions, wherein the catalytic cracking catalyst is the catalytic cracking catalyst according to any one of claims 1 to 5; the FCC conditions are, for example: the reaction temperature is 480-530 ℃, the reaction time is 1-10 seconds, and the ratio of the solvent to the oil is 3-20: 1 weight ratio.

Technical Field

The invention relates to a heavy oil catalytic cracking catalyst, a preparation method and application thereof.

Background

At present, the hydrothermal method is mainly adopted for industrially preparing the high-silicon Y-type zeolite. The rare earth-containing high-silicon Y-type zeolite can be prepared by carrying out multiple rare earth ion exchange and multiple high-temperature roasting on NaY zeolite, which is the most conventional method for preparing the high-silicon Y-type zeolite, but the rare earth high-silicon Y-type zeolite prepared by a hydrothermal method has the following defects: because the structure of the zeolite can be damaged by too harsh hydrothermal treatment conditions, the Y-type zeolite with high silica-alumina ratio can not be obtained; while the production of extra-framework aluminum is beneficial for improving the stability of the zeolite and forming new acid centers, the excess extra-framework aluminum reduces the selectivity of the zeolite; in addition, many dealumination cavities in the zeolite cannot be timely supplemented by silicon migrated from the framework, so that lattice defects of the zeolite are often caused, and the crystallization retention of the zeolite is low. And because the conventional Y molecular sieve only contains rare earth, silicon, aluminum and other elements, the adjustment of the structure and the performance of the conventional Y molecular sieve is limited in a certain range, and the composition of a product is often stabilized in a certain range. Therefore, the thermal and hydrothermal stability of the rare earth-containing high-silicon Y-type zeolite prepared by the hydrothermal method is poor, which is shown in that the lattice collapse temperature is low, the crystallinity retention rate and the specific surface area retention rate are low after hydrothermal aging, and the selectivity is poor. Moreover, the content of the isomeric hydrocarbon in the gasoline produced by the catalyst prepared in the conventional Y molecular sieve is stable in a certain range and is difficult to increase. This limits the improvement of the quality of the catalytically cracked gasoline and reduces the competitiveness of the catalytically cracked gasoline product.

In U.S. Pat. Nos. 4,849,287 and 4,4429053, NaY zeolite is exchanged with rare earth ions and then treated with water vapor, in the method, the aluminum removal of zeolite is difficult in the water vapor treatment process due to the shielding effect and support of the rare earth ions, the unit cell parameters of zeolite before the water vapor treatment are increased to 2.465-2.475 nm, the unit cell parameters after the treatment are 2.420-2.464 nm, and the temperature required for reducing the unit cell parameters is high (593-733 ℃).

In the methods provided by US5340957 and US5206194, the originalSiO of NaY zeolite₂/Al₂O₃The ratio is 6.0, and the method is to perform rare earth exchange of NaY and then perform hydrothermal treatment, and has the disadvantages of the aforementioned U.S. Pat. Nos. 4,849,287 and 4429053.

Gas phase chemical processes are another important process for preparing high silica zeolites first reported by Beyer and Mankui in 1980. The gas phase chemical method generally adopts SiCl under the protection of nitrogen₄Reacting with anhydrous NaY zeolite at a certain temperature. Fully utilizes SiCl in the whole reaction process₄The supplied foreign Si source completes dealuminization and silicon supplement reaction at one time through isomorphous substitution. U.S. Pat. Nos. 4,42737,178, U.S. Pat. No. 4,4438178, Chinese patent Nos. CN1382525A, CN1194941A and CN1683244A disclose the use of SiCl₄A process for preparing ultra-stable Y-type zeolite by gas-phase chemical dealumination. The gas phase ultrastable molecular sieve has almost no secondary pores.

Zhuhuayuan (Petroleum institute, 2001, 17(6):6-10) et al proposed the effect of magnesium-containing modified molecular sieve on the performance of FCC catalyst. Researches find that the FCC catalyst containing the Mg and Ca molecular sieves has strong heavy oil conversion capability, high hydrogen transfer reaction activity and higher isobutane product content. However, the Y molecular sieve prepared by the method has poor thermal and hydrothermal stability and unsatisfactory reaction activity and selectivity, and can only increase the content of isobutane but not effectively increase the content of isomeric hydrocarbon in gasoline under certain conditions.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a catalytic cracking catalyst with higher content of isomeric hydrocarbon in hot gasoline, wherein the catalyst contains a Y-type molecular sieve. The invention also aims to provide a preparation method and an application method of the catalytic cracking catalyst.

The invention provides a catalytic cracking catalyst, which contains 10 wt.% on a dry basis, on a dry basis50 wt% of modified Y-type molecular sieve, 10-40 wt% of alumina binder calculated by alumina and 10-80 wt% of clay calculated by dry basis; the modified molecular sieve has the advantages that the content of magnesium oxide is 0.5-4.5 wt%, the content of sodium oxide is 0.1-0.5 wt%, the total pore volume is 0.33-0.39 mL/g, the percentage of the pore volume of secondary pores with the pore diameter of 2-100 nm in the total pore volume of the modified Y-type molecular sieve is 10-25%, the unit cell constant is 2.440-2.455 nm, and the framework silicon-aluminum ratio (SiO)₂/Al₂O₃Molar ratio) is: 7.3-14.0, the percentage of non-framework aluminum content in the molecular sieve to the total aluminum content is not higher than 20%, the lattice collapse temperature is not lower than 1040 ℃, and the ratio of the B acid amount to the L acid amount in the total acid amount of the modified Y-type molecular sieve measured by a pyridine adsorption infrared method at 200 ℃ is not lower than 2.30.

In the catalytic cracking catalyst provided by the invention, the lattice collapse temperature (structure collapse temperature) of the modified Y-type molecular sieve is not lower than 1040 ℃, preferably 1045-1080 ℃, for example 1047-1058 ℃, 1057-1075 ℃ or 1047-1065 ℃.

In the catalytic cracking catalyst provided by the invention, the modified Y-type molecular sieve,

the ratio of the amount of B acid to the amount of L acid in the total acid amount of the modified Y-type molecular sieve measured at 200 ℃ by a pyridine adsorption infrared method is preferably 2.4 to 4.2, for example, 2.4 to 3.5.

The unit cell constant of the modified Y-type molecular sieve provided by the invention is 2.440-2.455 nm, such as 2.442-2.452 nm.

In the catalytic cracking catalyst provided by the invention, the unit cell constant of the modified Y-type molecular sieve is 2.440-2.455 nm, such as 2.442-2.452 nm.

In the catalytic cracking catalyst provided by the invention, the modified Y-type molecular sieve is a high-silicon Y-type molecular sieve, and the framework silicon-aluminum ratio (SiO) of the modified Y-type molecular sieve₂/Al₂O₃Molar ratio) of 7.3 to 14.0, for example: 8.4-12.6.

In the catalytic cracking catalyst provided by the invention, the non-framework aluminum content of the modified Y-type molecular sieve accounts for not more than 20% of the total aluminum content, for example, 13-19 wt%.

In the catalytic cracking catalyst provided by the invention, the modified Y-type molecular sieve has a crystal retention of 33% or more, such as 33-48%, 33-45%, 36-40% or 39-45%, after aging for 17 hours at 800 ℃ under normal pressure and in a 100 volume% steam atmosphere. The normal pressure is 1 atm.

In the catalytic cracking catalyst provided by the invention, the relative crystallinity of the modified Y-type molecular sieve is not less than 58%, preferably, the relative crystallinity of the modified Y-type molecular sieve provided by the invention is 58-70%, for example, 59-68% or 59-64%.

In the catalytic cracking catalyst provided by the invention, according to an implementation mode, the specific surface area of the modified Y-shaped molecular sieve is 620-670 m²The/g is, for example, 630 to 660m²/g。

In the catalytic cracking catalyst provided by the invention, preferably, the total pore volume of the modified Y-type molecular sieve is 0.35-0.39 mL/g, for example, 0.355-0.375 mL/g.

In the catalytic cracking catalyst provided by the invention, the pore volume of the modified Y-type molecular sieve with the secondary pore with the pore diameter (diameter) of 2.0-100 nm accounts for 10-25% of the total pore volume, and the preferred percentage is 15-21%.

In one embodiment, the modified Y-type molecular sieve has a micropore volume of 0.25-0.35 mL/g, such as 0.26-0.32 mL/g.

In the catalytic cracking catalyst provided by the invention, the modified Y-shaped molecular sieve contains magnesium element, and the magnesium content of the modified Y-shaped molecular sieve calculated by MgO can be 0.8-4.5 wt%, preferably 1-4.5 wt%, for example 1.2-4.3 wt%.

In the catalytic cracking catalyst provided by the invention, the content of the modified Y-type molecular sieve sodium oxide is not more than 0.5%, and can be 0.15-0.5 wt%, for example, 0.30-0.5 wt% or 0.35-0.48 wt%.

In the catalytic cracking catalyst provided by the invention, the ultraviolet visible light absorption spectrum of the modified Y-type molecular sieve has no absorption peak at the wavelength of 285 nm-295 nm.

The catalyst provided by the invention can also contain other molecular sieves except the modified Y-type molecular sieve, and the content of the other molecular sieves is, for example, 0-40 wt%, for example, 0-30 wt% or 1-20 wt% in terms of dry basis based on the weight of the catalyst. The other molecular sieve is selected from one or more of molecular sieves used in catalytic cracking catalysts, such as zeolite with MFI structure, zeolite Beta, other Y-type zeolite, and non-zeolite molecular sieves. Preferably, the content of the other Y-type molecular sieve is not more than 40 wt% on a dry basis, for example, 1 to 40 wt% or 0 to 20 wt%. Such as one or more of REY, REHY, DASY, SOY, PSRY, MFI structure zeolites such as one or more of HZSM-5, ZRP, ZSP, beta zeolites such as H β, non-zeolitic molecular sieves such as one or more of aluminum phosphate molecular sieves (AlPO molecular sieves), silicoaluminophosphate molecular sieves (SAPO molecular sieves).

In the catalytic cracking catalyst provided by the invention, the content of the modified Y-type molecular sieve is 10-50 wt% on a dry basis, preferably 15-45 wt%, for example 25-40 wt%.

In the catalytic cracking catalyst provided by the invention, the clay is selected from one or more of clays used as a cracking catalyst component, such as one or more of kaolin, halloysite, montmorillonite, diatomite, halloysite, saponite, rectorite, sepiolite, attapulgite, hydrotalcite and bentonite. These clays are well known to those of ordinary skill in the art. Preferably, the content of the clay in the catalytic cracking catalyst provided by the invention is 20-55 wt% or 30-50 wt% on a dry basis.

In the catalytic cracking catalyst provided by the invention, the content of the alumina binder is 10-40 wt%, for example 20-35 wt%. The alumina binder of the present invention is one or more selected from various forms of alumina, hydrated alumina and alumina sol generally used in cracking catalysts. For example, one or more selected from gamma-alumina, eta-alumina, theta-alumina, chi-alumina, pseudo-Boehmite (Pseudobioemite), diaspore (Boehmite), Gibbsite (Gibbsite), Bayer stone (Bayerite) and alumina sol, preferably pseudo-Boehmite and alumina sol, for example, the catalytic cracking catalyst contains 2-15 wt% of alumina sol, preferably 3-10 wt% of alumina sol, and 10-30 wt% of alumina sol, preferably 15-25 wt% of pseudo-Boehmite.

The catalyst of the present invention can be prepared by the methods disclosed in patents CN1098130A and CN 1362472A. Typically comprising the steps of forming a slurry comprising the modified Y-type molecular sieve, a binder, clay and water, spray drying, optionally washing and drying. Spray drying, washing and drying are the prior art, and the invention has no special requirements.

The preparation method of the catalytic cracking catalyst comprises the steps of preparing a modified Y-shaped molecular sieve, forming slurry comprising the modified Y-shaped molecular sieve, an alumina binder, clay and water, and spray drying, wherein the preparation method of the modified Y-shaped molecular sieve comprises the following steps:

(1) contacting the NaY molecular sieve with a soluble magnesium salt solution to perform an ion exchange reaction, filtering and washing to obtain a Y-type molecular sieve with a conventional unit cell size containing magnesium and with reduced sodium oxide content; wherein the soluble magnesium salt solution is also called magnesium salt solution;

(2) modifying the Y-type molecular sieve with the reduced sodium oxide content and the conventional magnesium-containing unit cell size, and optionally drying to obtain the Y-type molecular sieve with the reduced unit cell constant, wherein the modifying treatment is to roast the Y-type molecular sieve with the reduced sodium oxide content and the conventional magnesium-containing unit cell size at the temperature of 350-480 ℃ in an atmosphere containing 30-90 vol% of water vapor (also called 30-90 vol% of water vapor atmosphere or 30-90 vol% of water vapor) for 4.5-7 hours;

(3) mixing the Y-type molecular sieve sample with SiCl, wherein the unit cell constant is reduced₄Gas is contacted and reacted at the temperature of 200-650 ℃, wherein SiCl is contained₄: the weight ratio of the Y-type molecular sieve with reduced unit cell constant obtained in the step (2) on a dry basis is 0.1-0.7: 1, reaction time is 10 minutes to 5 hours, thenAnd washing and filtering to obtain the modified Y-type molecular sieve. Wherein the water content of the Y-type molecular sieve sample with reduced unit cell constant is preferably not more than 1 wt%; if the water content in the Y-type molecular sieve sample obtained by modification treatment in the step (2) (in the Y-type molecular sieve sample obtained by roasting) is not more than 1 wt%, the Y-type molecular sieve sample can be directly used for contacting silicon tetrachloride to carry out the reaction, and if the water content in the Y-type molecular sieve sample obtained by roasting in the step (2) exceeds 1 wt%, the Y-type molecular sieve sample with the reduced unit cell constant obtained by roasting in the step (2) is dried to enable the water content to be lower than 1 wt%.

The invention also provides a catalytic cracking method, which comprises the step of carrying out contact reaction on heavy oil and the catalytic cracking catalyst provided by the invention under the condition of heavy oil FCC. The heavy oil such as one or more of vacuum wax oil, atmospheric residue oil, vacuum residue oil and heavy deasphalted oil, the FCC condition is a reaction condition of fluidized catalytic cracking of the heavy oil, and generally, the reaction temperature of the reaction is 480-530 ℃, the reaction time is 1-10 seconds, and the agent-oil ratio is 3-20: 1 weight ratio.

The catalytic cracking catalyst provided by the invention contains the modified Y-shaped molecular sieve with high thermal and hydrothermal stability, has higher hydrothermal stability, is used for heavy oil catalytic cracking, has lower coke selectivity and higher gasoline yield and liquefied gas yield compared with the existing catalytic cracking catalyst containing the Y-shaped molecular sieve, and has higher content of isomeric hydrocarbon in gasoline. For example, the catalytic cracking catalyst SC3 containing 30.0 wt% of modified Y molecular sieve SZ3, 42 wt% of kaolin, 25 wt% of pseudo-boehmite, and 3 wt% of alumina sol prepared by the method of the present invention was evaluated with heavy oil on a fixed fluidized bed ACE evaluation apparatus, and the heavy oil conversion rate of the SC3 catalyst was 73.93 wt%, the liquefied gas yield was 16.04 wt%, the gasoline yield was 52.18 wt%, the content of iso-hydrocarbons in gasoline was 39.25 wt%, the light oil yield was 69.3 wt%, the total liquid yield was 85.34 wt%, the coke selectivity was 5.95%, whereas the catalyst DC3 having the same content of high-silica molecular sieve components prepared by the conventional method had a liquefied gas conversion rate of 73.92 wt%, a yield of 15.48 wt%, a gasoline yield of 50.69 wt%, a content of iso-hydrocarbons in gasoline was 36.57 wt%, and a light oil yield was 68.34 wt%, total liquor yield 83.82 wt%, coke selectivity 8.70%; therefore, the catalyst has higher heavy oil conversion capacity, higher liquefied gas yield and gasoline yield, higher content of isomeric hydrocarbon in the gasoline and better coke selectivity. The light oil micro-reverse evaluation result shows that the catalytic cracking catalyst prepared by the invention has higher activity and hydrothermal stability.

In the present invention, the isoparaffin refers to a chain isoparaffin and a chain isoolefin. The term "bis-methyl isomeric hydrocarbons" means that the carbon chain contains two methyl branches, and the term "mono-methyl isomeric hydrocarbons" means that the carbon chain contains one methyl branch.

Detailed Description

The catalytic cracking catalyst provided by the invention contains 10-50 wt% of modified Y-type molecular sieve, 10-40 wt% of alumina binder and 10-80 wt% of clay on a dry basis, wherein the weight of the catalyst is taken as a reference. Preferably, the catalytic cracking catalyst contains 25 to 40 wt% of the modified Y-type molecular sieve on a dry basis, 20 to 35 wt% of an alumina binder on an alumina basis, and 30 to 50 wt% of clay on a dry basis.

The catalytic cracking catalyst provided by the invention contains a modified Y-type molecular sieve, and in one embodiment, the modified Y-type molecular sieve has a magnesium oxide content of 0.5-4.5 wt%, preferably 0.8-4.3 wt%, a sodium oxide content of 0.1-0.5 wt%, for example 0.2-0.48 wt%, a total pore volume of 0.33-0.39 mL/g, a pore volume percentage of secondary pores with a pore diameter of 2-100 nm in the total pore volume of 10-25%, preferably 15-21%, a unit cell constant of 2.440-2.455 nm, and a framework silica-alumina ratio (SiO 2/Al)₂/Al₂O₃Molar ratio) is: 7.3 to 14.0, for example, 8.5 to 12.6, the non-framework aluminum content in the molecular sieve is not more than 20%, preferably 13 to 19%, the relative crystallinity is not less than 60%, and the lattice collapse temperature is 1040 to 1080 ℃, for example1045-1060 ℃, and the ratio of the B acid amount to the L acid amount in the total acid amount of the modified Y-type molecular sieve measured by a pyridine absorption infrared method at 200 ℃ is not lower than 2.30, preferably 2.4-4.2.

In the catalytic cracking catalyst provided by the invention, the preparation process of the modified Y-type molecular sieve comprises the step of contacting the Y-type molecular sieve with silicon tetrachloride to carry out dealuminization and silicon supplementation reaction.

In the preparation method of the modified Y-type molecular sieve, the NaY molecular sieve and a soluble magnesium salt solution are subjected to ion exchange reaction in the step (1) to obtain the Y-type molecular sieve with the conventional unit cell size of magnesium and with the reduced sodium oxide content. The NaY molecular sieve can be purchased commercially or prepared according to the existing method, and in one embodiment, the unit cell constant of the NaY molecular sieve is 2.465-2.472 nm, and the framework silicon-aluminum ratio (SiO)₂/Al₂O₃Molar ratio) of 4.5 to 5.2, a relative crystallinity of 85% or more, for example, 85 to 95%, and a sodium oxide content of 13.0 to 13.8% by weight. The NaY molecular sieve and the soluble magnesium salt solution are subjected to ion exchange reaction, the exchange temperature is preferably 15-95 ℃, for example 65-95 ℃, and the exchange time is preferably 30-120 minutes, for example 45-90 minutes. NaY molecular sieve (dry basis), soluble magnesium salt (MgO basis), H₂The weight ratio of O to O is 1:0.005 to 0.19:5 to 15, for example, 1: 0.01-0.15: 6-12 weight ratio or 1: 0.05-0.12: 6 to 12 weight ratio. In one embodiment, the ion exchange reaction of the NaY molecular sieve and the soluble magnesium salt solution comprises the following steps of₂Forming a mixture of NaY molecular sieve (also called NaY zeolite), soluble magnesium salt and water in a weight ratio of 1: 0.005-0.19: 5-15, and stirring at 15-95 ℃, for example, 65-95 ℃, preferably for 30-120 minutes to exchange magnesium ions and sodium ions, wherein the water is decationized water, deionized water or a mixture thereof. Mixing NaY molecular sieve, soluble magnesium salt and water to form a mixture, forming slurry by the NaY molecular sieve and the water, and then adding soluble magnesium salt and/or soluble magnesium salt aqueous solution into the slurry, wherein the soluble magnesium salt solution is soluble magnesium salt aqueous solution, and the soluble magnesium is soluble magnesiumThe salt may be one or more of magnesium chloride, magnesium nitrate, magnesium sulphate, preferably magnesium chloride and/or magnesium nitrate. The washing in step (1) is intended to wash out exchanged sodium ions, and for example, deionized water or decationized water may be used for washing. Preferably, the magnesium content of the magnesium-containing Y-type molecular sieve with conventional unit cell size and reduced sodium oxide content obtained in step (1) is 0.5-4.5 wt% such as 0.7-4.5 wt% or 0.55-4.5 wt% calculated on MgO, the sodium oxide content is not more than 9 wt% such as 5.5-8.5 wt% or 5.5-7.5 wt%, and the unit cell constant is 2.465 nm-2.472 nm.

In the preparation method of the catalytic cracking catalyst provided by the invention, in the preparation method of the modified Y-shaped molecular sieve,

and (2) roasting the Y-type molecular sieve containing magnesium and having the conventional unit cell size at the temperature of 350-480 ℃ for 4.5-7 hours in the atmosphere of 30-90 vol% of water vapor, preferably, the roasting temperature in the step (2) is 380-460 ℃, the roasting atmosphere is 40-80 vol% of water vapor, and the roasting time is 5-6 hours. The water vapor atmosphere contains 30-90% by volume, preferably 40-80% by volume of water vapor, and also contains other gases, such as one or more of air, helium or nitrogen. The Y-type molecular sieve with the reduced unit cell constant in the step (2) has the unit cell constant of 2.450 nm-2.462 nm. Preferably, the calcined molecular sieve is also dried in step (2) so that the water content in the Y-type molecular sieve having a reduced unit cell constant is preferably not more than 1 wt%.

In the preparation method of the catalytic cracking catalyst, the SiCl is added in the step (3)₄: the weight ratio of the Y-type zeolite (on a dry basis) is preferably 0.3-0.6: 1, the reaction temperature is preferably 350-500 ℃, and the washing method in the step (3) can adopt a conventional washing method, and can be washed by water, such as decationized water or deionized water, so as to remove Na remained in the zeolite⁺，Cl^-And Al³⁺Etc. soluble by-products, for example the washing conditions may be: the weight ratio of the washing water to the molecular sieve can be 5-20: 1, typically molecular sieve: h₂1: 6-15 by weight of O, PThe H value is preferably 2.5-5.0, and the washing temperature is 30-60 ℃. Preferably, the washing is performed such that no free Na is detected in the washing solution after washing⁺，Cl^-And Al³⁺Plasma, Na in the washing liquid after washing in general⁺，Cl^-And Al³⁺The respective contents of ions do not exceed 0.05 wt.%.

In the preparation method of the catalytic cracking catalyst provided by the invention, one embodiment of the preparation method of the modified Y-type molecular sieve comprises the following steps:

(1) carrying out ion exchange reaction on a NaY molecular sieve (also called NaY zeolite) and a soluble magnesium salt solution, filtering and washing to obtain a Y-type molecular sieve with reduced sodium oxide content and containing magnesium and with a conventional unit cell size; the ion exchange is carried out for 30-120 minutes under the conditions of stirring and the temperature of 15-95 ℃, preferably 65-95 ℃;

(2) roasting the rare earth-containing Y-type molecular sieve with the normal unit cell size and the reduced sodium oxide content for 4.5-7 hours at the temperature of 350-480 ℃ in the atmosphere containing 30-90 vol% of water vapor, and drying to obtain the Y-type molecular sieve with the reduced unit cell constant and the water content of less than 1 wt%; the unit cell constant of the Y-type molecular sieve with the reduced unit cell constant is 2.450 nm-2.462 nm;

(3) mixing the Y-type molecular sieve with water content lower than 1 wt% and SiCl vaporized by heating₄Gas contact of SiCl₄: the weight ratio of the Y-type molecular sieve with the water content lower than 1 wt% and the reduced unit cell constant (calculated by dry basis) is 0.1-0.7: 1, carrying out contact reaction for 10 minutes to 5 hours at the temperature of 200-650 ℃, and washing and filtering to obtain the modified Y-type molecular sieve.

The following examples further illustrate the invention but are not intended to limit the invention thereto.