Preparation method of catalytic cracking catalyst and preparation method of ZSM-5 molecular sieve

Abstract

The invention provides a preparation method of a catalytic cracking catalyst and a preparation method of a ZSM-5 molecular sieve, and the preparation method of the ZSM-5 molecular sieve comprises the following steps: step 1, mixing molecular sieve crystallization mother liquor with an aluminum salt solution, adjusting the pH value to be alkaline, and removing liquid to obtain silica-alumina gel; 2, mixing and heating a silicon source, a seed crystal and water to obtain a pretreatment solution; step 3, mixing the silica-alumina gel with the pretreatment liquid, and performing hydrothermal crystallization to obtain a ZSM-5 molecular sieve; wherein the silicon source comprises a liquid silicon source and a solid silicon source. The seed crystal is pretreated and then mixed with the silica-alumina gel, so that a large number of crystal nucleuses can be formed in a mixed system. More importantly, the solid silicon source and the liquid silicon source are adopted at the same time, and the silicon sources are subjected to pre-depolymerization treatment, so that not only can the yield of the ZSM-5 molecular sieve be improved, but also the dispersity of the obtained ZSM-5 molecular sieve can be improved.

Description

Technical Field

[0001] This invention relates to the fields of molecular sieve synthesis and catalytic cracking, specifically to a method for preparing a catalytic cracking catalyst and a method for preparing ZSM-5 molecular sieve. Background Technology

[0002] As the world's primary energy source, petroleum not only provides humanity with various fuels such as gasoline, diesel, and jet fuel, but also basic organic chemical raw materials such as olefins and aromatics. In recent years, to meet the ever-increasing demand for fuel, refining capacity has expanded rapidly, making it imperative to improve energy efficiency and develop clean, low-carbon energy technologies. To further expand the development space of the refining industry, my country's refining and chemical industry urgently needs structural transformation and upgrading, shifting from primarily producing fuels to primarily producing fuels / chemical raw materials. For refineries, this means implementing energy conservation, consumption reduction, and efficiency improvement measures on existing facilities to maximize the production of chemical raw materials.

[0003] Catalytic cracking, by producing more low-carbon olefins and aromatics, can not only significantly utilize excess refining capacity and achieve a balanced development between refining and downstream high-end petrochemical production, further enhancing corporate efficiency and market competitiveness, but also substantially increase the self-sufficiency rate of low-carbon olefins, alleviating the contradiction between supply and demand for petrochemical raw materials, thus playing a significant supporting role in the development of the national economy. The carbocation reaction in heavy oil catalytic cracking requires the catalysis of an acidic catalyst. Therefore, the development of high-performance solid acid catalysts has become the core of catalytic cracking technology research and innovation. ZSM-5 zeolite molecular sieves are among the most studied catalyst materials in catalytic cracking.

[0004] Patent CN101468805A discloses a method for synthesizing ZSM-5 molecular sieves. The method involves mixing a silicon source, an aluminum source, an alkali, and water to obtain a reaction mixture, which is then hydrothermally crystallized. The silicon source, alkali, and water are partially or entirely derived from the mother liquor generated during the preparation of titanium-silicon molecular sieves. This method effectively utilizes the mother liquor generated during the preparation of titanium-silicon molecular sieves, reducing environmental pollution caused by mother liquor discharge and lowering the synthesis cost of ZSM-5 molecular sieves. However, this technology uses a template agent, resulting in high synthesis costs.

[0005] The silicon source for synthesizing ZSM-5 molecular sieves is generally water glass or silica sol, as shown in CN1072654A, CN1082510A, USP5240892, and USP4061724. However, in conventional hydrothermal synthesis methods using water glass or silica sol as the silicon source, the initial feed has a high silica content, resulting in low single-reactor yields. Later, solid silica gel or aluminosilicate gel were used as raw materials, as shown in CN1194942A and CN1235875A, which use solid silica gel as the silicon source. However, these methods suffer from problems such as poor dispersibility of the synthesized ZSM-5 molecular sieves.

[0006] Therefore, further research is still needed in this field on the synthesis of ZSM-5 molecular sieves. Summary of the Invention

[0007] The main objective of this invention is to provide a method for preparing a catalytic cracking catalyst and a method for preparing ZSM-5 molecular sieves, so as to overcome the defects of low yield and poor dispersibility of ZSM-5 molecular sieves prepared in the prior art.

[0008] To achieve the above objectives, the present invention provides a method for preparing ZSM-5 molecular sieve, comprising the following steps:

[0009] Step 1: Mix the NaY molecular sieve crystallization mother liquor with the aluminum salt solution, adjust the pH to alkaline, remove the liquid, and obtain silica-alumina gel;

[0010] Step 2: Mix and heat the silicon source, seed crystal, and water to obtain a pretreatment solution;

[0011] Step 3: Mix the silica-alumina gel with the pretreatment solution and perform hydrothermal crystallization to obtain ZSM-5 molecular sieve;

[0012] The silicon source includes liquid silicon sources and solid silicon sources.

[0013] The method for preparing ZSM-5 molecular sieve according to the present invention further includes step 4, in which the ZSM-5 molecular sieve is exchanged with an ammonium salt solution, and then dried and calcined to obtain hydrogenated ZSM-5 molecular sieve.

[0014] The method for preparing ZSM-5 molecular sieve according to the present invention, wherein the NaY molecular sieve crystallization mother liquor and the aluminum salt solution are mixed by parallel dropwise addition, and the aluminum salt solution is at least one of aluminum sulfate solution, aluminum nitrate solution, and aluminum chloride solution.

[0015] The method for preparing ZSM-5 molecular sieve according to the present invention includes step 1 adjusting the pH value to 7-9.5, and the mass content of molecular sieve in the dry silica-alumina gel obtained in step 1 being 1-10%.

[0016] The method for preparing ZSM-5 molecular sieve according to the present invention includes the following: the liquid silicon source is water glass; the solid silicon source is one or more of silicon powder, sodium silicate, and silica; the seed crystal is one or more of octahedral molecular sieve, type A molecular sieve, β molecular sieve, and ZSM-5 molecular sieve; in step 2, the solid silicon source is SiO2, and the weight ratio of seed crystal to solid silicon source is 0.02-0.10:1.

[0017] In the preparation method of ZSM-5 molecular sieve of the present invention, the heating temperature in step 2 is 80-120℃, and stirring is performed during the heating process.

[0018] The method for preparing ZSM-5 molecular sieve according to the present invention, wherein in step 3, the molar ratio of each substance in the hydrothermal crystallization system is Na2O:SiO2:Al2O3:H2O=(0.08~0.16):1:(0.0125~0.05):(8~30); the hydrothermal crystallization temperature is 140~220℃, and the hydrothermal crystallization time is 12~32h.

[0019] The method for preparing ZSM-5 molecular sieve according to the present invention includes a calcination temperature of 500℃-600℃ and a calcination time of 1-24h.

[0020] To achieve the above objectives, the present invention also provides a method for preparing a catalytic cracking catalyst, comprising:

[0021] The ZSM-5 molecular sieve, REUSY molecular sieve, matrix material, and binder prepared by the above method are mixed to obtain a catalytic cracking catalyst.

[0022] The beneficial effects of this invention are:

[0023] This invention pre-treats the seed crystals before mixing them with silica-alumina gel, which allows for the formation of numerous crystal nuclei in the mixed system, resulting in smaller molecular sieve crystals with greater mesopore volume. More importantly, the silicon source in this invention includes both solid and liquid silicon sources, and the solid silicon source undergoes pre-depolymerization treatment. This not only improves the yield of ZSM-5 molecular sieves but also enhances their dispersibility, thereby increasing the propylene yield of the catalyst. Attached Figure Description

[0024] Figure 1 The image shows the XRD pattern of the H-ZSM-5-1 molecular sieve prepared in Example 1 of this invention.

[0025] Figure 2 This is a scanning electron microscope image of the H-ZSM-5-1 molecular sieve prepared in Example 1 of the present invention.

[0026] Figure 3 This is a scanning electron microscope image of the H-ZSM-5-9 molecular sieve prepared in Comparative Example 3 of this invention. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below. The following embodiments are implemented under the premise of the technical solution of the present invention and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following embodiments. Structures or experimental methods that do not specify specific conditions in the following embodiments are generally performed under conventional conditions.

[0028] This invention provides a method for preparing ZSM-5 molecular sieve, comprising the following steps:

[0029] Step 1: Mix the NaY molecular sieve crystallization mother liquor with the aluminum salt solution, adjust the pH to alkaline, remove the liquid, and obtain silica-alumina gel;

[0030] Step 2: Mix and heat the silicon source, seed crystal, and water to obtain a pretreatment solution;

[0031] Step 3: Mix the silica-alumina gel with the pretreatment solution and perform hydrothermal crystallization to obtain ZSM-5 molecular sieve;

[0032] The silicon source includes a liquid silicon source and a solid silicon source.

[0033] This invention pre-treats the seed crystals before mixing them with aluminosilicate gel, thus forming a large number of crystal nuclei in the mixed system. More importantly, the silicon source in this invention includes both a solid silicon source and a liquid silicon source, and the solid silicon source undergoes pre-depolymerization treatment, which not only improves the yield of ZSM-5 molecular sieves but also enhances the dispersibility of the resulting ZSM-5 molecular sieves. The liquid silicon source primarily provides alkalinity, avoiding the need for additional alkaline substances. The solid silicon source fulfills its function as a silicon source.

[0034] In this invention, the molecular sieve crystallization mother liquor includes not only the liquid remaining after the molecular sieve is separated from the crystallization system during the molecular sieve preparation process, but also the filtrate obtained from washing the molecular sieve.

[0035] In one embodiment, the aluminum salt solution is a mixture of aluminum salt and water. The aluminum salt is, for example, a soluble aluminum salt, and the aluminum salt solution is, for example, at least one of aluminum sulfate solution, aluminum nitrate solution, and aluminum chloride solution. In another embodiment, the molecular sieve crystallization mother liquor and the aluminum salt solution are mixed by co-current dropwise addition, for example, by simultaneously adding the molecular sieve crystallization mother liquor and the aluminum salt solution to the same container. This keeps the pH value of the formed silica-alumina gel constant, overcoming the problems of slow filtration speed, low yield, and low production efficiency of silica-alumina gel. In yet another embodiment, step 1 adjusts the pH value to 7-9.5 to precipitate silicon and aluminum species in the form of silica-alumina gel, and then the liquid is removed. The present invention does not particularly limit the specific method of liquid removal; centrifugation, filtration, etc., can be used to obtain silica-alumina gel. The mass content of molecular sieve in the dry silica-alumina gel is 1%-10%, for example, 5%-7%.

[0036] In one embodiment, the liquid silicon source of the present invention is water glass, and the solid silicon source is one or more of silicon powder, sodium silicate, and silica. The seed crystal is one or more of octahedral molecular sieve, type A molecular sieve, β molecular sieve, and ZSM-5 molecular sieve. In another embodiment, in step 2, the silicon source is SiO2, and the weight ratio of the seed crystal to the silicon source is 0.02-0.10:1.

[0037] Step 2 of this invention involves pretreating the seed crystals and silicon source. The heating temperature is, for example, 80-120°C, specifically 80-100°C or 100-120°C. Stirring can be performed during the heating process, and the treatment time is, for example, 1-24 hours. Pretreating the seed crystals allows the crystallization system to have more crystal nuclei; pretreating the solid silicon source not only improves the yield of ZSM-5 molecular sieves but also increases their dispersion.

[0038] Step 3 involves mixing the silica-alumina gel with the pretreatment solution and hydrothermally crystallizing it to transform the molecular sieve in the silica-alumina gel into crystals, thereby obtaining ZSM-5 molecular sieve.

[0039] In one embodiment, in the hydrothermal crystallization system of step 3, the molar ratio of each substance is Na2O:SiO2:Al2O3:H2O = (0.08~0.16):1:(0.0125~0.05):(8~30), and the preferred molar ratio of each component is Na2O:SiO2:Al2O3:H2O = (0.10~0.13):1:(0.02~0.04):(10~20); the hydrothermal crystallization temperature is 140~220℃, and the hydrothermal crystallization time is 12~32h.

[0040] The ZSM-5 molecular sieve obtained in step 3 is a Na-type ZSM-5 molecular sieve. In one embodiment, the present invention further includes step 4, in which the ZSM-5 molecular sieve obtained in step 3 is exchanged with an ammonium salt solution, and then dried and calcined to obtain a hydrogenated ZSM-5 molecular sieve.

[0041] This invention does not particularly limit the ammonium salt solution. In one embodiment, the ammonium salt solution is, for example, an ammonium chloride solution, specifically, the concentration of the ammonium salt solution is, for example, 0.5 mol / L-2 mol / L, preferably 1 mol / L. In another embodiment, the calcination temperature is 500℃-600℃, and the calcination time is 1-24 h. In yet another embodiment, the exchange conditions are as follows: the Na-type ZSM-5 molecular sieve and the ammonium salt solution are exchanged three times at 90℃ with a solid-liquid ratio of 1:5. After filtration, washing, and drying, the mixture is calcined in a muffle furnace at 550℃ for 5 h to obtain hydrogenated ZSM-5 molecular sieve.

[0042] This invention also provides a method for preparing a catalytic cracking catalyst, comprising:

[0043] The ZSM-5 molecular sieve, REUSY molecular sieve, matrix material, and binder prepared by the above method are mixed to obtain a catalytic cracking catalyst.

[0044] This invention does not impose any particular limitation on the preparation process of the catalytic cracking catalyst; conventional methods in the art are sufficient. In one embodiment, the mass ratio of matrix material: binder: ZSM-5 molecular sieve: REUSY molecular sieve is (20-50):(10-30):(2-10):(20-50). In another embodiment, the matrix material is one or more of kaolin, malachite, etc.

[0045] This invention first prepares a silica-alumina gel by neutralizing the crystallization mother liquor of NaY molecular sieve, and then prepares ZSM-5 molecular sieve. This not only allows for the low-cost conversion and crystallization synthesis of highly dispersed ZSM-5 molecular sieve using silica-alumina gel containing a small amount of NaY molecular sieve as a partial silica-alumina source, avoiding the environmental pollution caused by the discharge of NaY molecular sieve crystallization mother liquor, but also results in a catalytic cracking catalyst with a high propylene yield.

[0046] The technical solution of the present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents are commercially available. Unless otherwise specified, "%" below refers to mass percentage.

[0047] (1) Specifications of main raw materials:

[0048] Kaolin: Suzhou Kaolin, produced by China Kaolin Company, with a kaolinite content of 84%.

[0049] Binder: Al2O3 20.15%, produced by Lanzhou Petrochemical Company.

[0050] Water glass: SiO2 250g / L, Na2O 88g / L, produced by Lanzhou Petrochemical Company.

[0051] Aluminum sulfate: Al2O3 91g / L, produced by Lanzhou Petrochemical Company.

[0052] Silicon powder: SiO2 content greater than 98%, produced by Qingdao Xinfengda Chemical Co., Ltd., Shandong Province.

[0053] Ammonium chloride: chemically pure, produced by Tianjin Kemeo Chemical Reagent Co., Ltd.

[0054] ZSM-5 molecular sieve seed crystals: relative crystallinity greater than 96%, Nankai University Catalyst Factory.

[0055] Type A molecular sieve seed crystals: Nankai University Catalyst Factory.

[0056] β-zeolite seed crystals: relative crystallinity greater than 96%, produced by Nankai University Catalyst Factory.

[0057] (2) Analytical methods

[0058] Table 1. Main analytical methods involved in this invention.

[0059]

[0060] (3) Catalyst evaluation: The reaction performance was evaluated using a small fixed fluidized bed reactor. The feedstock was Xinjiang vacuum wide-fraction wax oil and Xinjiang vacuum residue oil, with a residue blending ratio of 30%. The reaction temperature was 500℃ and the space velocity was 12h. -1 The agent-to-oil ratio is 5, and the properties of the raw oil are shown in Table 2.

[0061] Table 2 Properties of feedstock used for catalyst selectivity assessment

[0062]

[0063]

[0064] Example 1:

[0065] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0066] Preparation of ZSM-5 molecular sieve: 97.92g of water glass was added to 191g of water, followed by 33.33g of silica powder and 4g of ZSM-5 molecular sieve seed crystals. The mixture was stirred at 100℃ for 24h to obtain pretreated solution B. After treatment, 74.36g of silica-alumina gel A was added and stirred evenly. The resulting gel was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 14h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7, yielding Na-type ZSM-5-1 molecular sieve. The prepared Na-ZSM-5-1 molecular sieve was exchanged three times with 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, the solution was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-1 molecular sieve.

[0067] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-1 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried to obtain catalytic cracking catalyst CAT-1.

[0068] Example 2:

[0069] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0070] Preparation of ZSM-5 molecular sieve: 97.92g of water glass was added to 191g of water, followed by 33.33g of silica powder and 4g of type A molecular sieve seed crystals. The mixture was stirred at 100℃ for 24h to obtain pretreated solution B. After treatment, 74.36g of silica-alumina gel A was added and stirred evenly. The resulting gel was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 14h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7, yielding Na-type ZSM-5-2 molecular sieve. The prepared Na-ZSM-5-2 molecular sieve was exchanged three times with a 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, the solution was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-2 molecular sieve.

[0071] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-2 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried after uniform mixing to obtain catalytic cracking catalyst CAT-2.

[0072] Example 3:

[0073] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0074] Preparation of ZSM-5 molecular sieve: 97.92g of water glass was added to 191g of water, followed by 33.33g of silica powder and 4g of β-molecular sieve seed crystals. The mixture was stirred at 100℃ for 24h to obtain pretreated solution B. After treatment, 74.36g of silica-alumina gel A was added and stirred evenly. The resulting gel was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 14h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7, yielding Na-type ZSM-5-3 molecular sieve. The prepared Na-ZSM-5-3 molecular sieve was exchanged three times with 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, the solution was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-3 molecular sieve.

[0075] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-3 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried to obtain catalytic cracking catalyst CAT-3.

[0076] Example 4:

[0077] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0078] Preparation of ZSM-5 molecular sieve: 97.92g of water glass was added to 191g of water, followed by 33.33g of silica powder and 4g of Y molecular sieve seed crystals. The mixture was stirred at 100℃ for 24h to obtain pretreated solution B. After treatment, 74.36g of silica-alumina gel A was added and stirred evenly. The resulting gel was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 14h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7, yielding Na-type ZSM-5-4 molecular sieve. The prepared Na-ZSM-5-4 molecular sieve was exchanged three times with a 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, the solution was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-4 molecular sieve.

[0079] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-4 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried to obtain catalytic cracking catalyst CAT-4.

[0080] Example 5:

[0081] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0082] Preparation of ZSM-5 molecular sieve: 104.74 g of water glass was added to 193 g of water, followed by 33.19 g of silica powder and 4 g of ZSM-5 molecular sieve seed crystals. The mixture was stirred at 100 °C for 24 h to obtain pretreated solution B. After pretreatment, 65.81 g of silica-alumina gel A was added and stirred until homogeneous. The resulting gel was transferred to a 500 ml high-pressure reactor and crystallized at 180 °C for 14 h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7 to obtain Na-type ZSM-5-5 molecular sieve. The prepared Na-ZSM-5-5 molecular sieve was exchanged three times with 1 mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90 °C. After filtration, washing, and drying, the solution was calcined in a muffle furnace at 550 °C for 5 h to obtain H-ZSM-5-5 molecular sieve.

[0083] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-5 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried to obtain catalytic cracking catalyst CAT-5.

[0084] Example 6:

[0085] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0086] Preparation of ZSM-5 molecular sieve: 105.32g of water glass was added to 202g of water, followed by 34.81g of silica powder and 4g of ZSM-5 molecular sieve seed crystals. The mixture was stirred at 100℃ for 24h to obtain pretreated solution B. After treatment, 54.85g of silica-alumina gel A was added and stirred evenly. The resulting gel was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 14h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7, yielding Na-type ZSM-5-6 molecular sieve. The prepared Na-ZSM-5-6 molecular sieve was exchanged three times with a 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, the solution was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-6 molecular sieve.

[0087] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-6 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried to obtain catalytic cracking catalyst CAT-6.

[0088] Comparative Example 1: Direct synthesis of ZSM-5 without the use of silica-alumina gel

[0089] Preparation of ZSM-5 molecular sieve: 159.15g of water glass was added to 178g of water, followed by 33.33g of silica powder, 32.64g of aluminum sulfate, and 4g of ZSM-5 molecular sieve seed crystals. After stirring evenly, the resulting mixture was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 24h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7, yielding Na-type ZSM-5-7 molecular sieve. The prepared Na-ZSM-5-7 molecular sieve was exchanged three times with a 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, it was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-7 molecular sieve.

[0090] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-7 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried to obtain catalytic cracking catalyst CAT-7.

[0091] Comparative Example 2: No seed crystals added

[0092] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0093] Preparation of ZSM-5 molecular sieve: 97.92g of water glass was added to 191g of water, followed by 33.33g of silica powder. The mixture was stirred at 100℃ for 24h to obtain pretreated solution B. After treatment, 74.36g of silica-alumina gel A was added and stirred until homogeneous. The resulting gel was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 24h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7, yielding Na-type ZSM-5-8 molecular sieve. The prepared Na-ZSM-5-8 molecular sieve was exchanged three times with 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, the solution was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-8 molecular sieve.

[0094] Comparative Example 3: No seed crystal pretreatment performed

[0095] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0096] Preparation of ZSM-5 molecular sieve: 97.92g of water glass was added to 191g of water, followed by 33.33g of silica powder. The mixture was stirred at 100℃ for 24h to obtain pretreated solution B. After pretreatment, 74.36g of silica-alumina gel A and 4g of ZSM-5 molecular sieve seed crystals were added. After stirring evenly, the resulting mixture was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 24h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7, yielding Na-type ZSM-5-9 molecular sieve. The prepared Na-ZSM-5-9 molecular sieve was exchanged three times with 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, the solution was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-9 molecular sieve.

[0097] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-9 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried to obtain catalytic cracking catalyst CAT-9.

[0098] Comparative Example 4: No silicon source pretreatment performed

[0099] Preparation of aluminosilicate gel: NaY molecular sieve crystallization mother liquor and aluminum sulfate solution were added dropwise in parallel streams, and the pH value was adjusted to 9.0 to precipitate the silicon and aluminum species in the form of aluminosilicate gel. After filtration and pulping, aluminosilicate gel A was obtained. Analysis showed that its SiO2 content was 14.3 wt%, Al2O3 content was 3.1 wt%, Na2O content was 0.36 wt%, density was 1.212 g / ml, and NaY molecular sieve accounted for about 5 wt% of the dry weight of the aluminosilicate gel.

[0100] Preparation of ZSM-5 molecular sieve: 4g of ZSM-5 molecular sieve seed crystals were stirred in 191g of water at 100℃ for 24h to obtain pretreatment solution B. 97.92g of water glass was added, followed by 33.33g of silica powder, and finally 74.36g of silica-alumina gel A. After stirring evenly, the resulting mixture was transferred to a 500ml high-pressure reactor and crystallized at 180℃ for 28h. After crystallization, the molecular sieve was filtered and washed with water until the pH value reached 7 to obtain Na-type ZSM-5-10 molecular sieve. The prepared Na-ZSM-5-10 molecular sieve was exchanged three times with 1mol / L ammonium chloride solution at a solid-liquid ratio of 1:5 at 90℃. After filtration, washing, and drying, it was calcined in a muffle furnace at 550℃ for 5h to obtain H-ZSM-5-10 molecular sieve.

[0101] Preparation of catalytic cracking catalyst: 126g (dry basis) of kaolin, 69g (dry basis) of binder, 9g (dry basis) of H-ZSM-5-10 molecular sieve, 96g (dry basis) of REUSY and 500g of water were mixed and pulped, and then spray-dried to obtain catalytic cracking catalyst CAT-10.

[0102] The physicochemical properties of the ZSM-5 molecular sieves prepared in Examples 1-6 and Comparative Examples 1-4 are shown in Table 3.

[0103] Table 3. Physicochemical properties of ZSM-5 molecular sieves prepared in the examples and comparative examples.

[0104]

[0105]

[0106] As can be seen from Table 3 and the attached figures, the molecular sieve with lower external specific surface area and pore volume is obtained without seed pretreatment. Without silicon source pretreatment, the total specific surface area of ​​the molecular sieve will be 10% lower. Using seed pretreatment in conjunction with silicon source pretreatment and using silica-alumina gel as part of the silica-alumina source can greatly shorten the crystallization time and the synthesized molecular sieve has better dispersibility and superior physicochemical properties.

[0107] The reaction performance of catalysts CAT-1 to CAT-6 prepared in Examples 1 to 6 and catalysts CAT-7, CAT-9, and CAT-10 prepared in Comparative Examples 1, 3, and 4 was evaluated, and the results are listed in Table 4.

[0108] Table 4 Evaluation of the reaction performance of different catalysts

[0109]

[0110]

[0111] *Aging at 800℃ for 10 hours with 100% moisture.

[0112] As shown in Table 4, compared with the comparative example, the catalyst prepared in the embodiments of the present invention has a higher propylene yield when used for feedstock catalytic cracking.

[0113] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing ZSM-5 molecular sieve, characterized in that, Includes the following steps: Step 1: Mix the NaY molecular sieve crystallization mother liquor with the aluminum salt solution, adjust the pH to alkaline, remove the liquid, and obtain silica-alumina gel; Step 2: Mix and heat the silicon source, seed crystal, and water to obtain a pretreatment solution; Step 3: Mix the silica-alumina gel with the pretreatment solution and perform hydrothermal crystallization to obtain ZSM-5 molecular sieve; The silicon source includes a liquid silicon source and a solid silicon source.

2. The method for preparing ZSM-5 molecular sieve according to claim 1, characterized in that, The process also includes step 4, in which the ZSM-5 molecular sieve is exchanged with an ammonium salt solution, and then dried and calcined to obtain hydrogenated ZSM-5 molecular sieve.

3. The method for preparing ZSM-5 molecular sieve according to claim 1, characterized in that, In step 2, the silicon source is SiO2, and the weight ratio of seed crystal to silicon source is 0.02-0.10:

1.

4. The method for preparing ZSM-5 molecular sieve according to claim 1, characterized in that, The NaY molecular sieve crystallization mother liquor and the aluminum salt solution are mixed by parallel dropwise addition, and the aluminum salt solution is at least one of aluminum sulfate solution, aluminum nitrate solution, and aluminum chloride solution.

5. The method for preparing ZSM-5 molecular sieve according to claim 1, characterized in that, Step 1: Adjust the pH value to 7-9.

5. The mass content of molecular sieve in the dry silica-alumina gel obtained in Step 1 is 1-10%.

6. The method for preparing ZSM-5 molecular sieve according to claim 1, characterized in that, The liquid silicon source is water glass, and the solid silicon source is one or more of silicon powder, sodium silicate, and fumed silica; the seed crystal is one or more of octahedral molecular sieve, type A molecular sieve, β molecular sieve, and ZSM-5 molecular sieve.

7. The method for preparing ZSM-5 molecular sieve according to claim 1, characterized in that, Step 2 involves heating at a temperature of 80-120℃, with stirring performed during the heating process.

8. The method for preparing ZSM-5 molecular sieve according to claim 1, characterized in that, In step 3, the molar ratio of each substance in the hydrothermal crystallization system is Na2O:SiO2:Al2O3:H2O = (0.08~0.16):1:(0.0125~0.05):(8~30); the hydrothermal crystallization temperature is 140~220℃, and the hydrothermal crystallization time is 12~32h.

9. The method for preparing ZSM-5 molecular sieve according to claim 2, characterized in that, The roasting temperature is 500℃-600℃, and the roasting time is 1-24h.

10. A method for preparing a catalytic cracking catalyst, characterized in that, include: The ZSM-5 molecular sieve, REUSY molecular sieve, matrix material, and binder prepared by the preparation method according to any one of claims 1-9 are mixed to obtain a catalytic cracking catalyst.

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