A heterogeneous cracking catalyst, its preparation method and use

Abstract

The application discloses an isomerization and cracking catalyst, which comprises ZSM-48 molecular sieve, amorphous silicon aluminum, alumina and hydrogenation active metal; the application also relates to a preparation method of the catalyst, which comprises the following steps: compounding ZSM-48 molecular sieve, amorphous silicon aluminum and alumina to obtain a carrier, and then impregnating the carrier with hydrogenation active metal. The catalyst can effectively control product distribution, improve the selectivity and yield of target products and reduce the pour point of products in the isomerization and cracking of Fischer-Tropsch synthesis wax.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to an isomerization cracking catalyst, its preparation method, and its application, particularly for the isomerization cracking of Fischer-Tropsch synthetic waxes. Background Technology

[0002] For a Fischer-Tropsch synthetic oil unit with a current production capacity of 4 million tons per year, after the refined tail oil undergoes cracking and atmospheric and vacuum distillation, the fractions before the first cracking step can be used to produce naphtha, gasoline, and diesel. However, the fractions from the second and third cracking steps have too high a pour point and need to be returned to the cracking unit to produce naphtha, gasoline, and diesel, resulting in a decrease in capacity and yield.

[0003] CN105727981A discloses a Fischer-Tropsch synthesis wax hydrocracking catalyst, its preparation method, and its applications. The catalyst contains columnar saponite, alumina, and a hydrocracking active metal component; the hydrocracking active metal component is at least one metal element selected from Group VIII of the periodic table, and selectively contains at least one metal element selected from Group VIB of the periodic table. Using this catalyst for Fischer-Tropsch synthesis wax hydrocracking achieves high mid-oil yield while maintaining cracking activity.

[0004] CN101767024A discloses a cracking catalyst and its preparation and application. The catalyst preparation method includes mixing water, inorganic acid, clay, molecular sieve, boehmite, and a phosphorus-containing compound, slurrying to prepare a catalyst slurry, and drying. The inorganic acid is added in two stages: the first stage is added before all other materials except water, and the second stage is added after any other materials are added. The weight ratio of the first and second added inorganic acid is 1:2-3:1. The boehmite is added in two stages: the first stage is added before the molecular sieve, and the second stage is added after the molecular sieve. The weight ratio of the first and second added boehmite (based on alumina) is 1:2-3:1. The catalyst slurry obtained by this method has low viscosity. The prepared catalyst, when used in heavy oil catalytic cracking, exhibits high propylene yield, low coke yield, and low olefin content and high isoalkanes and aromatics content in gasoline.

[0005] CN101117592A discloses a cracking catalyst composition comprising catalyst M and catalyst L. Catalyst M consists of 10-50 wt% shape-selective molecular sieve, 2-30 wt% macroporous molecular sieve, 5-30 wt% binder, and 20-60 wt% filler, with an average particle size of 50-90 μm. Catalyst L consists of 2-30% shape-selective molecular sieve, 10-50% macroporous molecular sieve, 5-30% binder, and 20-60% filler, with an average particle size 1.05-2.0 times that of catalyst M. The weight ratio of catalyst M to L is between 0.6 and 5.0.

[0006] However, the existing technologies mentioned above have not solved the problems of low selectivity of products such as diesel after cracking of Fischer-Tropsch synthesis wax and high pour point of the products after reaction. In particular, the pour points of cracked secondary cracked oil, cracked tertiary cracked oil and cracked tail oil are too high, requiring them to be recycled back to the reactor for re-cracking.

[0007] To address these issues, the relevant cracking catalysts need to be redesigned. On the one hand, this ensures that Fischer-Tropsch synthesis wax can be cracked into the target product. On the other hand, it requires that the pour points of the second-stage cracked oil, the third-stage cracked oil, and the cracked tail oil be lowered to at least meet the pour point requirements of heavy diesel oil and industrial white oil, so that they can be sold as industrial products without having to be returned to the cracking reactor for re-cracking. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention provides an isomer cracking catalyst and its preparation method, which solves the problems of low selectivity and yield of products such as diesel oil after Fischer-Tropsch synthesis wax cracking and high pour point of the product after reaction in the prior art.

[0009] To achieve its purpose, the present invention adopts the following technical solution:

[0010] In one aspect of the invention, an isomerization cracking catalyst is provided, comprising ZSM-48 molecular sieve, amorphous aluminum silicate (ASA), alumina, and a hydrogenation-active metal. In a preferred embodiment, the ZSM-48 molecular sieve is H-ZSM-48 molecular sieve.

[0011] In a preferred embodiment, based on the total weight of the ZSM-48 molecular sieve, amorphous silica and alumina, the content of the ZSM-48 molecular sieve is 0.5-20 wt%, for example, 5 wt%, 10 wt%, 15 wt%, etc.; the content of the amorphous silica and alumina is 55-75 wt%, for example, 60 wt%, 65 wt%, 70 wt%, etc.; and the content of the alumina is 15-40 wt%, for example, 20 wt%, 25 wt%, 30%, etc.

[0012] In a specific embodiment of the present invention, the silicon-to-aluminum ratio of the ZSM-48 molecular sieve is 150-300, for example, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, etc., based on the molar ratio of SiO2 to Al2O3.

[0013] In a specific embodiment of the present invention, the silicon-to-aluminum ratio of the amorphous silicon-aluminum is 10-50, for example, 15, 20, 25, 30, 35, 40, 45, etc., based on the molar ratio of SiO2 to Al2O3.

[0014] In a specific embodiment of the present invention, the hydrogenation active metal comprises nickel and tungsten; preferably, based on the total weight of the ZSM-48 molecular sieve, amorphous silica-alumina, and alumina, the nickel content is 0.5-20 wt%, for example, 5 wt%, 10 wt%, 15 wt%, etc.; the tungsten content is 1-30 wt%, for example, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, etc.; or, the hydrogenation active metal comprises platinum and / or palladium, preferably, based on the total weight of the ZSM-48 molecular sieve, amorphous silica-alumina, and alumina, the platinum content is 0.1-2 wt%, for example, 0.5 wt%, 1.0 wt%, 1.5 wt%, etc.; the palladium content is 0.1-2 wt%, for example, 0.5 wt%, 1.0 wt%, 1.5 wt%, etc. In a preferred embodiment, the hydrogenation active metal is nickel and tungsten, optionally containing platinum and / or palladium. In another preferred embodiment, the hydrogenation active metal is platinum and / or palladium.

[0015] In a specific embodiment of the present invention, the alumina is selected from one or more of alumina sol, boehmite, or SB powder.

[0016] In another aspect of the invention, a method for preparing the above-described catalyst is provided, the method comprising the following steps:

[0017] (1) Mix ZSM-48 molecular sieve, amorphous silica-alumina and alumina evenly to obtain a mixture;

[0018] (2) Add dilute acid to the mixture obtained in step (1) and extrude it to obtain strips;

[0019] (3) The strips obtained in step (2) are aged, dried, roasted and optionally crushed to obtain a carrier;

[0020] (4) The salt of the hydrogenated active metal is impregnated onto the support obtained in step (3), and the catalyst is obtained by drying and calcining.

[0021] In a specific embodiment of the present invention, the dilute acid in step (2) is dilute nitric acid, and the amount of dilute acid added accounts for 1-3 wt% of the dry base mixture, such as 1.5 wt%, 2 wt%, 2.5 wt%, etc.; the water accounts for 40-90 wt% of the dry base mixture, such as 50 wt%, 60 wt%, 70 wt%, 80 wt%, etc.

[0022] In a specific embodiment of the present invention, the aging in step (3) is carried out at room temperature for 3-6 hours, for example 4 hours or 5 hours; the drying temperature is 100-150°C, for example 120°C, 130°C, or 140°C; the drying time is 3-12 hours, for example 5 hours, 7 hours or 9 hours; the calcination temperature is 500-600°C, for example 550°C; and the calcination time is 3-6 hours, for example 4 hours or 5 hours.

[0023] In a specific embodiment of the present invention, in step (4), the salt of the hydrogenated active metal is a nitrate; the impregnation temperature is 20-50℃, for example 30℃, 40℃, etc.; the time is 1-5h, for example 2h, 3h, 4h, etc.; the drying temperature is 30-120℃, for example 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃, etc.; the drying time is 2-12h, for example 4h, 6h, 8h, 10h, etc.; the calcination temperature is 450-550℃, for example 500℃, etc.; the calcination time is 3-6h, for example 4h, 5h, etc.

[0024] In a specific embodiment of the present invention, the preparation method further includes the preparation of ZSM-48 molecular sieve, which comprises the following steps:

[0025] (1) Mix and dissolve an alkali source, an aluminum source, a template agent, water and optional seed crystals to form a primary solution, and then add a silicon source to obtain a crystallization stock solution; preferably, the alkali source is sodium hydroxide, the aluminum source is aluminum sulfate or sodium aluminate, the template agent is ethylenediamine or hexamethylammonium bromide, and the silicon source is silica sol;

[0026] (2) The initial gel obtained in step (1) is subjected to hydrothermal crystallization, filtered and dried; preferably, the hydrothermal crystallization is carried out at 120-200℃ (e.g. 150℃, 180℃, etc.) for 24-48h (e.g. 36h, etc.); the drying temperature is 100-140℃ (e.g. 120℃, etc.);

[0027] (3) The product obtained in step (2) is subjected to alkali treatment, then filtered and washed to obtain a product with a hierarchical porous structure; preferably, the alkali treatment reagent is a sodium hydroxide solution of 0.1-1.0 mol / L (e.g., 0.2 mol / L, 0.5 mol / L, 0.7 mol / L, etc.), the temperature is 60-100℃ (e.g., 70℃, 80℃, 90℃, etc.), and the time is 0.5-2h (e.g., 1h, 1.5h, etc.);

[0028] (4) The product obtained in step (3) is subjected to ammonium cross-exchange, and then dried and calcined to obtain the ZSM-48 molecular sieve; preferably, ammonium cross-exchange is performed at least twice with 0.5-2 mol / L (e.g., 1 mol / L, 1.5 mol / L, etc.) ammonium chloride solution at 60-100℃ (e.g., 70℃, 80℃, 90℃, etc.), each time for 0.5-2 h (e.g., 1 h, 1.5 h, etc.); the drying temperature is 60-120℃ (e.g., 70℃, 80℃, 90℃, 100℃, 110℃, etc.), the drying time is 4-12 h (e.g., 4 h, 6 h, 8 h, 10 h, etc.), the calcination temperature is 500-600℃ (e.g., 550℃, etc.), and the calcination time is 3-6 h (e.g., 4 h, 5 h).

[0029] In a specific embodiment of the present invention, the preparation method further includes the preparation of amorphous silicon-aluminum, which comprises the following steps:

[0030] (1) Mix the alkali source, aluminum source, template agent, silicon source and water to obtain an initial gel; preferably, the alkali source is sodium hydroxide, the aluminum source is aluminum sulfate, the template agent is a quaternary ammonium salt (e.g., benzyltriethylammonium bromide), and the silicon source is silica sol;

[0031] (2) The initial gel obtained in step (1) is subjected to hydrothermal crystallization, filtered and dried; preferably, the hydrothermal crystallization is carried out at 100-300℃ (e.g. 120℃, 180℃, 220℃, 240℃, 260℃, etc.) for 24-48h (e.g. 36h, etc.); the drying temperature is 100-140℃ (e.g. 120℃, etc.);

[0032] (3) The product obtained in step (2) is calcined and ammonium-crosslinked, then dried and calcined to obtain the amorphous silica-alumina; preferably, the calcination temperature before ammonium-crosslinking is 500-600℃ (e.g., 550℃, etc.), and the calcination time is 4-8h (e.g., 5h, 6h, 7h, etc.); an ammonium chloride solution of 0.5-2mol / L (e.g., 1mol / L, 1.5mol / L, etc.) is used at 60-100℃ (e.g., 70℃, 80℃, etc.). Ammonium ion exchange should be performed at least twice at ℃, 90℃, etc., each time for 0.5-2 hours (e.g., 1 hour, 1.5 hours, etc.); after ammonium ion exchange, the drying temperature should be 60-120℃ (e.g., 70℃, 80℃, 90℃, 100℃, 110℃, etc.), and the drying time should be 4-12 hours (e.g., 6 hours, 8 hours, 10 hours, etc.); after ammonium ion exchange, the roasting temperature should be 500-600℃ (e.g., 550℃, etc.), and the roasting time should be 3-6 hours (e.g., 4 hours, 5 hours, etc.).

[0033] In another aspect of the invention, the use of the above-described catalyst or the catalyst prepared according to the above-described method in the isomerization cracking of Fischer-Tropsch synthetic waxes is involved. In specific embodiments of the invention, the catalyst of the present invention can be used not only for the isomerization cracking catalysis of Fischer-Tropsch synthetic waxes, but also for the isomerization cracking catalysis of tail waxes obtained from the refining of Fischer-Tropsch synthetic waxes.

[0034] The inventors of this application have discovered that, in order to ensure the pour point of the cracked naphtha, cracked naphtha tertiary oil, and cracked tail oil produced from Fischer-Tropsch synthetic wax cracking meets the requirements, the catalyst needs to fulfill two functions: cracking and isomerization. However, neither a single cracking catalyst nor a single isomerization catalyst can meet these requirements. Typical Fischer-Tropsch synthetic wax cracking reaction conditions include a temperature of 350°C and a pressure of 7.0 MPa. Under these conditions, metal / amorphous silica-alumina can catalyze the cracking reaction to produce products such as diesel. However, under these reaction conditions, metal / ZSM-5, ZSM-22, and ZSM-23 molecular sieves result in a significant amount of Fischer-Tropsch synthetic wax being over-cracked into light naphtha. Furthermore, combinations of amorphous silica-alumina with these molecular sieves cannot meet the aforementioned requirements.

[0035] To ensure that both cracking and isomerization functions are well utilized, the isomerization cracking catalyst of this invention achieves acid strength matching by controlling the silicon-to-aluminum ratio of the isomerization molecular sieve and the silicon-to-aluminum ratio of the amorphous silicon-aluminum. The two work synergistically to achieve both cracking and isomerization effects under the same conditions.

[0036] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

[0037] 1) Under the usual Fischer-Tropsch synthesis wax cracking reaction conditions, and with the use of a single catalyst, the isomerization cracking catalyst of the present invention can simultaneously satisfy both cracking and isomerization functions.

[0038] 2) The isomerization cracking catalyst of the present invention can effectively control product distribution and improve the yield and selectivity of target products such as diesel.

[0039] 3) After isomerization cracking of Fischer-Tropsch synthetic wax, the pour point of the cracked reduced-second, reduced-third and cracked tail oils can be reduced, so that the relevant products can be directly converted into industrial products without returning to the cracking reactor for secondary processing. Detailed Implementation

[0040] The method provided by the present invention will be described in further detail below, but the present invention is not limited thereto.

[0041] raw material

[0042] In the examples, the feedstock used for isomerization catalytic cracking was the tailings wax of Fischer-Tropsch synthesis after refining, and its main physical properties are shown in Table 1 below:

[0043] Table 1

[0044] project Tail wax Pour point, ℃ 90 <![CDATA[Density (20 °C), g / cm 3 > 0.8323 Aromatics, m% <0.02 Sulfur, μg / g <0.1 Nitrogen, μg / g <0.1 Alkali metals, μg / g <3 Fe, μg / g <4.5 Total metals, μg / g <10 Distillation range, °C (D2887) Initial distillate 367 2％ 390 5％ 411 10％ 430 30％ 480 50％ 516 70％ 563 90％ 631 95％ 655 98％ 675

[0045] Unless otherwise specified, all other ingredients mentioned in this article are commercially available.

[0046] Test methods and instruments

[0047] X-ray fluorescence analysis (XRF): Elemental analysis was performed using a Rigaku ZSX Primus II X-ray fluorescence spectrometer (Japan), which can determine the mass percentage of elements in the bulk phase. The phase structure of the samples was characterized using a Bruker D8 ADVANCE X-ray diffractometer (Germany), with a Cu Kα ray source, λ = 1.546 nm, a graphite monochromator, an operating voltage of 40 kV, an operating current of 30 mA, and a scan rate of 2°·min. -1 The scanning angle is 10° to 90°.

[0048] The crude product after the reaction was subjected to true boiling point cutting using an I-Ficher oil distillation instrument to obtain naphtha, light white oil, and diesel oil, etc. The pour point and cloud point of the product were measured using a German Herzog fully automatic pour point and cloud point analyzer, and the viscosity and density of the product were measured using a Mettler fully automatic viscometer.

[0049] Example

[0050] I. Catalyst Preparation

[0051] Example 1

[0052] 1) Synthesis of ZSM-48 molecular sieve

[0053] Sodium aluminate, sodium hydroxide, hexamethylammonium bromide, seed crystals, and water were mixed and dissolved to form a primary solution. After thorough mixing, silica sol was added and stirred until homogeneous, yielding a crystallization stock solution with the following composition: hexamethylammonium bromide:Al₂O₃:Na₂O:H₂O:SiO₂ = 0.025:0.005:0.11:15:1 (molar ratio). The seed crystal content was 5 wt% silicon dioxide. Crystallization was carried out at 170℃ for 48 hours, followed by filtration and drying at 120℃. 10 g of ZSM-48 molecular sieve was mixed with 300 mL of 0.5 mol / L sodium hydroxide solution and treated with alkali in an 80℃ water bath for 1 hour. The mixture was then filtered and washed with water to obtain the modified ZSM-48 molecular sieve. The resulting powder was then exchanged with 1 mol / L ammonium chloride solution at 80℃ for 1 hour, followed by filtration. This process was repeated twice to complete the ammonium exchange process. The exchange product was dried at 80℃ for 6 hours and calcined at 550℃ for 4 hours to obtain H-ZSM-48 molecular sieve.

[0054] 2) Synthesis of amorphous aluminum silica (ASA)

[0055] Sodium hydroxide, aluminum sulfate, quaternary ammonium salt (benzyltriethylammonium bromide), silica sol, and water were mixed to obtain an initial gel with the composition of quaternary ammonium salt:Al₂O₃:Na₂O:H₂O:SiO₂ = 0.010:0.05:0.12:20:1. The gel was crystallized at 120°C for 48 hours, filtered, dried at 120°C, and calcined at 550°C for 6 hours. The resulting powder was then exchanged with a 1 mol / L ammonium chloride solution at 80°C for 1 hour, followed by filtration. This process was repeated twice to complete the ammonium exchange process. The exchange product was dried at 80°C for 6 hours and calcined at 550°C for 4 hours to obtain ASA.

[0056] 3) Catalyst preparation

[0057] H-ZSM-48 and ASA were mixed with alumina (aluminum sol) at a dry basis ratio of m(H-ZSM-48):m(ASA):m(Al2O3) = 0.5:74.5:25. Dilute nitric acid was added as a binder, and then the mixture was extruded into strips. The amount of dilute nitric acid added was 2 wt% of the powder (dry basis) mass, and the amount of water was 70 wt% of the powder (dry basis) mass. The extruded support was aged at room temperature for 4 h, dried at 120 °C for 5 h, and calcined at 550 °C for 4 h to obtain support strips. Then, nickel nitrate and tungsten nitrate were prepared into a homogeneous solution and impregnated onto the support strips in equal volumes at 30 °C for 2 h. The nickel content was 5 wt% of the dry basis support, and the tungsten content was 20 wt% of the dry basis support. After impregnation, the strips were dried at 40 °C for 4 h, dried at 120 °C for 4 h, and calcined at 500 °C for 4 h to obtain the catalyst.

[0058] Example 2

[0059] 1) Synthesis of ZSM-48 molecular sieve

[0060] The preparation of ZSM-48 molecular sieve is the same as in Example 1.

[0061] 2) Synthesis of ASA

[0062] The preparation of ASA is the same as in Example 1.

[0063] 3) Catalyst preparation

[0064] The catalyst was prepared in the same manner as in Example 1, except that H-ZSM-48 and ASA were mixed with alumina at a dry basis ratio of m(H-ZSM-48):m(ASA):m(Al2O3) = 5:70:25.

[0065] Example 3

[0066] 1) Synthesis of ZSM-48 molecular sieve

[0067] The preparation of ZSM-48 molecular sieve is the same as in Example 1.

[0068] 2) Synthesis of ASA

[0069] The preparation of ASA is the same as in Example 1.

[0070] 3) Catalyst preparation

[0071] The catalyst was prepared in the same manner as in Example 1, except that H-ZSM-48 and ASA were mixed with alumina at a dry basis ratio of m(H-ZSM-48):m(ASA):m(Al2O3) = 20:55:25.

[0072] Comparative Example 1

[0073] Similar to Example 2, except that ZSM-48 molecular sieve is not used, and ASA is mixed with alumina at a dry basis ratio of m(ASA):m(Al2O3) = 75:25.

[0074] Comparative Example 2

[0075] Similar to Example 2, except that ASA is not used, and H-ZSM-48 is mixed with alumina at a dry basis ratio of m(H-ZSM-48):m(Al2O3) = 75:25.

[0076] Comparative Example 3

[0077] 1) Synthesis of ZSM-48 molecular sieve

[0078] The preparation of ZSM-48 molecular sieve is the same as in Example 1, except that the molar ratio of hexamethylammonium bromide:Al2O3:Na2O:H2O:SiO2 is 0.025:0.013:0.11:15:1.

[0079] 2) Synthesis of ASA

[0080] The preparation of ASA is the same as in Example 1.

[0081] 3) Catalyst preparation

[0082] The catalyst was prepared in the same manner as in Example 2.

[0083] Comparative Example 4

[0084] 1) Synthesis of ZSM-48 molecular sieve

[0085] The preparation of ZSM-48 molecular sieve is the same as in Example 1, except that the molar ratio of hexamethylammonium bromide:Al2O3:Na2O:H2O:SiO2 is 0.025:0.003:0.11:15:1.

[0086] 2) Synthesis of ASA

[0087] The preparation of ASA is the same as in Example 1.

[0088] 3) Catalyst preparation

[0089] The catalyst was prepared in the same manner as in Example 2.

[0090] Comparative Example 5

[0091] 1) Synthesis of ZSM-48 molecular sieve

[0092] ZSM-48 was prepared in the same manner as in Example 1.

[0093] 2) Synthesis of ASA

[0094] The preparation of ASA was the same as in Example 1, except that the molar ratio of quaternary ammonium salt:Al2O3:Na2O:H2O:SiO2 was 0.010:0.2:0.12:20:1.

[0095] 3) Catalyst preparation

[0096] The catalyst was prepared in the same manner as in Example 2.

[0097] Comparative Example 6

[0098] 1) Synthesis of ZSM-48 molecular sieve

[0099] ZSM-48 was prepared in the same manner as in Example 1.

[0100] 2) Synthesis of ASA

[0101] The preparation of ASA was the same as in Example 1, except that the molar ratio of quaternary ammonium salt:Al2O3:Na2O:H2O:SiO2 was 0.010:0.013:0.12:20:1.

[0102] 3) Catalyst preparation

[0103] The catalyst was prepared in the same manner as in Example 2.

[0104] II. Catalyst Performance Evaluation

[0105] The isomerization catalytic cracking of the tail wax after refining Fischer-Tropsch synthesis wax was carried out using the raw materials described above and the catalysts prepared in the examples and comparative examples. The main components of each catalyst and the results of catalytic cracking are shown in Table 2 below. The evaluation conditions were: pressure 6.5 MPa, hydrogen-to-oil ratio 800, and space velocity 1.5 h⁻¹. -1 .

[0106] Table 2

[0107]

[0108] Although the invention has been described in detail above for illustrative purposes, it should be understood that such detailed description is merely for illustration, and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention, which is defined only by the claims.

Claims

1. An isomerization cracking catalyst comprising ZSM-48 molecular sieve, amorphous silica-alumina, alumina, and a hydrogenation-active metal; in, Based on the molar ratio of SiO2 to Al2O3, the silicon-aluminum ratio of the ZSM-48 molecular sieve is 150-300. The silicon-to-aluminum ratio of the amorphous silicon-aluminum is 10-50, based on the molar ratio of SiO2 to Al2O3. The hydrogenation active metal includes nickel and tungsten; or, the hydrogenation active metal includes platinum and / or palladium.

2. The catalyst according to claim 1, wherein, Based on the total weight of the ZSM-48 molecular sieve, amorphous silica and alumina, the content of the ZSM-48 molecular sieve is 0.5-20 wt%, the content of the amorphous silica and alumina is 55-75 wt%, and the content of the alumina is 15-40 wt%.

3. The catalyst according to claim 1 or 2, wherein the nickel content is 0.5-20 wt% and the tungsten content is 1-30 wt% based on the total weight of the ZSM-48 molecular sieve, amorphous silica and alumina, and alumina; or, the platinum content is 0.1-2 wt% and the palladium content is 0.1-2 wt% based on the total weight of the ZSM-48 molecular sieve, amorphous silica and alumina, and alumina, respectively.

4. The catalyst according to claim 1 or 2, wherein, The alumina is aluminum sol and / or pseudoboehmite.

5. The catalyst according to claim 4, wherein, The pseudoboehmite is SB powder.

6. A method for preparing the isomeric cracking catalyst according to any one of claims 1-5, the method comprising the following steps: (1) Mix ZSM-48 molecular sieve, amorphous silica and alumina evenly to obtain a mixture; (2) Add dilute acid to the mixture obtained in step (1) and extrude it to obtain strips; (3) The strips obtained in step (2) are aged, dried and calcined to obtain a carrier; (4) The salt of the hydrogenated active metal is impregnated onto the support obtained in step (3), and the catalyst is obtained by drying and calcining.

7. The preparation method according to claim 6, wherein, In step (3), the material strips are crushed after roasting to obtain a carrier.

8. The preparation method according to claim 6, wherein, The dilute acid in step (2) is dilute nitric acid, and the amount of dilute acid added accounts for 1-3 wt% of the dry basis mixture, while water accounts for 40-90 wt% of the dry basis mixture. The aging in step (3) is carried out at room temperature for 3-6 hours; the drying temperature is 100-150℃ and the drying time is 3-12 hours; the calcination temperature is 500-600℃ and the calcination time is 3-6 hours. In step (4), the salt of the hydrogenated active metal is nitrate; the impregnation temperature is 20-50℃ and the time is 1-5h; the drying temperature is 30-120℃ and the drying time is 2-12h; the calcination temperature is 450-550℃ and the calcination time is 3-6h.

9. The preparation method according to any one of claims 6-8, wherein, The preparation method also includes the preparation of ZSM-48 molecular sieve, which includes the following steps: (1) Mix and dissolve the alkali source, aluminum source, template agent and water to form a primary solution, and then add the silicon source to obtain the crystallization stock solution; (2) Perform hydrothermal crystallization on the initial gel obtained in step (1), filter and dry; (3) The product obtained in step (2) is subjected to alkali treatment, then filtered and washed to obtain a product with a hierarchical porous structure; (4) The product obtained in step (3) is subjected to ammonium cross-exchange, and then dried and calcined to obtain the ZSM-48 molecular sieve.

10. The preparation method according to claim 9, wherein, In step (1), the primary solution further includes seed crystals; the alkali source is sodium hydroxide, the aluminum source is aluminum sulfate or sodium aluminate, the template agent is ethylenediamine or hexamethylammonium bromide, and the silicon source is silica sol; In step (2), the hydrothermal crystallization is carried out at 120-200℃ for 24-48 hours; the drying temperature is 100-140℃. In step (3), the alkali treatment reagent is a 0.1-1.0 mol / L sodium hydroxide solution, the temperature is 60-100℃, and the time is 0.5-2h; In step (4), ammonium chloride solution of 0.5-2 mol / L is used for ammonium ion exchange at least twice at 60-100℃, each time for 0.5-2h; the drying temperature is 60-120℃, the drying time is 4-12h, the calcination temperature is 500-600℃, and the calcination time is 3-6h.

11. The preparation method according to any one of claims 6-8, wherein, The preparation method further includes the preparation of amorphous silicon-aluminum, which comprises the following steps: (1) Mix the alkali source, aluminum source, template agent, silicon source and water to obtain the initial gel; (2) Perform hydrothermal crystallization on the initial gel obtained in step (1), filter and dry; (3) The product obtained in step (2) is roasted and ammonium-crosslinked, then dried and roasted to obtain the amorphous silicon-aluminum.

12. The preparation method according to claim 11, wherein, In step (1), the alkali source is sodium hydroxide, the aluminum source is aluminum sulfate, the template agent is a quaternary ammonium salt, and the silicon source is silica sol; In step (2), the hydrothermal crystallization is carried out at 100-300℃ for 24-48 hours; the drying temperature is 100-140℃. In step (3), the pre-ammonia calcination temperature is 500-600℃ and the calcination time is 4-8h; ammonia calcination is carried out at least twice at 60-100℃ using a 0.5-2mol / L ammonium chloride solution, each time for 0.5-2h; after ammonium calcination, the drying temperature is 60-120℃ and the drying time is 4-12h; after ammonium calcination, the calcination temperature is 500-600℃ and the calcination time is 3-6h.

13. Use of the isomerization cracking catalyst according to any one of claims 1-5 or the isomerization cracking catalyst obtained by the preparation method according to any one of claims 6-12 in the isomerization cracking of waxes in Fischer-Tropsch synthesis.

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