A hydrocracking catalyst for producing middle distillates, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a hydrocracking catalyst for producing middle distillates, a preparation method thereof and an application thereof. The method includes the preparation of a support and the loading of a hydrogenation active metal. The preparation method of the support includes: mixing ZSM-23 molecular sieve, Y molecular sieve, amorphous silica-alumina and a binder, forming, then drying and calcining to prepare a catalyst support. The Y molecular sieve has the following properties: the weight content of Na2O is less than 0.3%; the silica-alumina molar ratio SiO2 / Al2O3 is 35-50; the specific surface area is 600-900 m 2 / g; the pore volume is 0.4-0.7 mL / g; the ZSM-23 molecular sieve has the following properties: the specific surface area is 300-430 m 2 / g, the pore volume is 0.31-0.5 cm 3 / g, the micropore specific surface area is 50-170 m 2 / g, the mesopore specific surface area is 150-310 m 2 / g; preferably, the specific surface area is 320-405 m 2 / g, the pore volume is 0.34-0.45 cm 3 / g, the micropore specific surface area is 80-140 m 2 / g, the mesopore specific surface area is 261-295 m 2 / g. The catalyst prepared by the method has high middle oil selectivity for the hydrocracking reaction of heavy feedstock oil, and at the same time has the characteristics of low freezing point of jet fuel and low pour point of diesel oil.

Description

Technical Field

[0001] The present invention relates to a hydrocracking catalyst for producing middle distillates, a preparation method thereof, and an application thereof. The hydrocracking catalyst has high selectivity for middle distillates, and at the same time, the freezing point of jet fuel and the pour point of diesel are low. Background Art

[0002] With the continuous exploitation of petroleum resources, the quality of crude oil is becoming increasingly heavy. Improving the deep processing technology for the lightening of crude oil is an important measure to solve the energy crisis and improve the utilization rate of petroleum resources, and it has important significance. With the increasing demand for middle distillates in the international oil product market, it is necessary to obtain more middle distillates from heavy oil, and the hydrocracking process is one of the important means for the lightening of heavy oil.

[0003] With the increasingly strict environmental protection requirements and the continuous upgrading of diesel quality standards, especially the Euro IV and Euro V standards for emission standards have put forward more stringent requirements for indicators such as sulfur and aromatic hydrocarbon content, cetane number, density, and T95 in diesel. In addition, people in alpine regions or in winter life pay more attention to the low-temperature flow performance of diesel products. Only diesel products with low pour points can meet the actual use requirements. In winter, large amounts of low-freezing diesel are needed in the cold northern regions, and the low-temperature flow performance (pour point, cold filter plugging point, pour point, etc.) indicators of diesel are more important.

[0004] Due to the special strategic value of jet fuel and the high growth rate of the international market demand rate, jet fuel producers and technology patent holders in various countries are constantly innovating in their production processes or detection standards, and are working on the technological innovation and standard improvement to closely follow the market pulse and increase the production of jet fuel products with large market demand. The core of the hydrocracking technology is the hydrocracking catalyst, and the progress of the technology depends on the improvement of the catalyst level. As the main acidic component of the hydrocracking catalyst, molecular sieve plays a decisive role in the activity, selectivity, and product quality of the catalyst.

[0005] Currently, the industrialized molecular sieve type hydrocracking catalysts usually use modified Y-type molecular sieves as the main component. Hydrocracking catalysts containing Y-type molecular sieves such as CN104826646A, CN103100403A, CN101380588A, CN101450319A, and CN102786064A have advantages such as good activity, high ring-opening performance, and high selectivity cracking performance for heavy components rich in cyclic hydrocarbons, but the freezing point of jet fuel and the pour point of diesel are low. Especially when the refinery broadens the distillation range according to market demand to produce wide-cut jet fuel, the freezing point of jet fuel will be <47 °C, and the index cannot reach the standard of No. 3 jet fuel. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a hydrocracking catalyst for producing middle distillates, a preparation method thereof, and an application thereof. When the catalyst is used for the hydrocracking reaction of heavy feedstock oil, it has a relatively high middle oil selectivity, and at the same time, has the characteristics of low freezing point of jet fuel and low pour point of diesel fuel.

[0007] A preparation method of a hydrocracking catalyst for producing middle distillates, the method comprising the preparation of a support and the loading of a hydrogenation active metal, wherein the preparation method of the support comprises: mixing ZSM-23 molecular sieve, Y molecular sieve, amorphous silica-alumina and a binder, forming, and then drying and calcining to prepare a catalyst support. The Y molecular sieve has the following properties: the weight content of Na2O is less than 0.3%; the silica-alumina molar ratio SiO2 / Al2O3 is 35-50; the specific surface area is 600-900m 2 / g; the pore volume is 0.4-0.7mL / g; the ZSM-23 molecular sieve has the following properties: the specific surface area is 300-430m 2 / g, the pore volume is 0.31-0.5cm 3 / g, the microporous specific surface area is 50-170m 2 / g, the mesoporous specific surface area is 150-310m 2 / g; preferably, the specific surface area is 320-405m 2 / g, the pore volume is 0.34-0.45cm 3 / g, the microporous specific surface area is 80-140m 2 / g, the mesoporous specific surface area is 261-295m 2 / g.

[0008] In the method of the present invention, the mesoporous pore volume of 3-6nm of the ZSM-23 molecular sieve accounts for 45-90% of the total pore volume of the molecular sieve, preferably 50-85%, and more preferably 55-81%; the relative crystallinity of the molecular sieve is 95-120%, and the relative crystallinity retention of the molecular sieve after hydrothermal treatment with water vapor at 600°C for 2 hours is 95-100%.

[0009] In the method of the present invention, in the hydrocracking catalyst of the present invention, the weight content of SiO2 in the amorphous silica-alumina is 20%-50%, preferably 25%-40%. The amorphous silica-alumina has the following properties: the pore volume is 0.7-1.2mL / g, preferably 0.8-1.0 mL / g, and the specific surface area is 300-500 m 2 / g, preferably 350-500 m 2 / g.

[0010] In the method of the present invention, the binder used may be a commonly used binder in the art, and preferably small-pore alumina is used. The small-pore alumina used has a pore volume of 0.3 to 0.5 mL / g and a specific surface area of 200 to 400 m 2 / g.

[0011] In the method of the present invention, the hydrogenation active metal is a metal of Group VIB and / or Group VIII. The metal of Group VIB is preferably molybdenum and / or tungsten, and the metal of Group VIII is preferably cobalt and / or nickel.

[0012] In the method of the present invention, the catalyst can be formed according to actual needs, and the shape can be cylindrical bars, clovers, etc. During the catalyst forming process, forming aids such as peptizing acid and extrusion aids can also be added. The catalyst carrier of the present invention is dried and calcined by conventional methods, specifically as follows: drying at a temperature of 80 to 150 °C for 3 to 10 hours and calcining at 400 to 800 °C for 3 to 12 hours.

[0013] In the method of the present invention, the loading of the hydrogenation active metal can be carried out by a conventional loading method in the prior art, preferably the impregnation method, which can be saturated impregnation, excess impregnation or complex impregnation, that is, the catalyst carrier is impregnated with a solution containing the required active components. The impregnated carrier is dried at 100 °C to 150 °C for 4 to 12 hours and then calcined at 400 °C to 750 °C for 3 to 8 hours to obtain the final catalyst.

[0014] A hydrocracking catalyst prepared by the above method, the catalyst comprising a carrier and a hydrogenation active component, the carrier comprising ZSM-23 zeolite, Y zeolite, amorphous silica-alumina and a binder. Based on the weight of the carrier, the content of ZSM-23 zeolite is 2 to 20 wt%, the content of Y zeolite is 10 to 30 wt%, the content of amorphous silica-alumina is 20 to 60 wt%, and the content of the binder is 15 to 35 wt%. Based on the weight of the catalyst, the content of the Group VIB metal (calculated as the oxide) is 10 wt% to 25 wt% and the content of the Group VIII metal (calculated as the oxide) is 4 wt% to 15 wt%, and the content of the carrier is 60.0% to 90.0%.

[0015] The properties of the hydrocracking catalyst of the present invention are as follows: the specific surface area is 280 to 600 m 2 / g, the pore volume is 0.3 to 0.7 mL / g. In the catalyst of the present invention, the mesopores with a pore diameter of 3 - 6 nm in the catalyst account for 35 to 60% of the total pore volume, and the mesopores with a pore diameter of 6 - 15 nm (excluding 6 nm) account for 30 to 55% of the total pore volume; preferably, the mesopores with a pore diameter of 3 - 6 nm account for 40 to 55% of the total pore volume, and the mesopores with a pore diameter of 6 - 15 nm account for 35 to 50% of the total pore volume.

[0016] A hydrocracking method for producing middle distillates, where the heavy oil includes one or more of various hydrocarbon oils such as vacuum gas oil, coker gas oil, deasphalted oil, thermal cracking gas oil, fluid catalytic cracking gas oil, and fluid catalytic cracking recycle oil. The heavy oil usually contains hydrocarbons with a boiling range of 300 - 600 °C, and the nitrogen mass content is generally 500 - 2500 ppm.

[0017] According to the method of the present invention, the reaction conditions are as follows: the reaction temperature is 350 - 420 °C, preferably 360 - 390 °C; the reaction pressure is 6 - 20 MPa, preferably 9 - 16 MPa; the hydrogen - to - oil volume ratio is 500 - 2000:1, preferably 800 - 1500:1; the liquid hourly space velocity is 0.5 - 1.8 h -1 preferably 0.8 - 1.5 h -1 .

[0018] In the catalyst of the present invention, ZSM - 23 zeolite and Y zeolite are used together as cracking centers. This not only fully utilizes their respective performance characteristics but also enables the synergistic catalytic effect of the two zeolites. The high - silica - to - alumina ratio Y zeolite reduces the occurrence probability of over - cracking and secondary cracking. Due to the good ring - opening characteristics of the Y zeolite, the catalyst can have good activity, middle - oil selectivity, and excellent product properties. The 3 - 6 nm highly concentrated pore distribution characteristics of the ZSM - 23 zeolite in the hydrocracking catalyst of the present invention can well adsorb and isomerize long side chains on paraffins or aromatics. While avoiding the secondary cracking of product molecules, it further reduces the freezing point of jet fuel, the pour point of diesel, and improves the middle - oil selectivity of the catalyst. The hydrocracking catalyst of the present invention is applicable to the heavy - oil hydrocracking reaction, preferably applied to the heavy - oil hydrocracking for producing middle distillates in a one - stage series hydrocracking process, and is especially suitable for the refinery to flexibly produce jet fuel or diesel according to market demand. Detailed implementation mode

[0019] The preparation of ZSM - 23 zeolite in the hydrocracking catalyst of the present invention refers to the preparation method of CN202210011767.9

[0020] The ZSM - 23 zeolite mentioned above includes the following preparation steps:

[0021] (1) Prepare or select amorphous silica;

[0022] (2) Perform alkali treatment on the amorphous silica;

[0023] (3) Use the alkali - treated amorphous silica as the silicon source to prepare ZSM - 23 zeolite.

[0024] In the above method step (1), the amorphous silica has a specific surface area of 600 - 1300 m 2 / g, preferably 700 - 1200 m 2 / g; the pore volume is 0.6 - 1.3 cm 3 / g, preferably 0.7 - 1.2 cm 3 / g; the pore diameter is 1 - 15 nm, preferably 2 - 10 nm.

[0025] In the above method step (1), the preparation process of the amorphous silica is as follows: Add the silicon source to deionized water and disperse evenly, then add a surfactant and stir; After adjusting the pH of the solution to 1 - 5, preferably 1.5 - 4, perform a water bath heating treatment for a period of time; After filtration, washing, drying, and calcination, amorphous mesoporous silica is obtained.

[0026] In the above method, during the preparation process of the amorphous silica, the silicon source is an inorganic silicon source, preferably one or more of water glass, silica sol, or white carbon black.

[0027] In the above method, during the preparation process of the amorphous silica, the surfactant is one or more of cetyltrimethylammonium bromide / chloride, octadecyltrimethylammonium chloride / bromide.

[0028] In the above method, during the preparation process of the amorphous silica, the molar ratio of the silicon source calculated as SiO2 to the surfactant is 1 : (0.02 - 0.3), preferably 1 : (0.05 - 0.2).

[0029] In the above method, during the preparation process of the amorphous silica, the molar ratio of the silicon source calculated as SiO2 to deionized water is 1 : (30 - 300), preferably 1 : (50 - 220);

[0030] In the above method, during the preparation process of the amorphous silica, the heating temperature is 30 - 80 °C, and the heating time is 0.5 - 8 h; Preferably, the heating temperature is 40 - 70 °C, and the heating time is 3 - 6 h.

[0031] In the above method step (2), the alkali treatment is to add the amorphous silica prepared in step (1) to an alkaline solution and perform heating and stirring.

[0032] In the above method, the alkali treatment uses an inorganic alkali treatment, and the inorganic alkali is one or more of sodium hydroxide, potassium hydroxide, or ammonia water.

[0033] In the above method, the heating and stirring time of the alkali treatment is 0.5 - 12 h, preferably 2 - 8 h; The heating temperature is 25 - 60 °C, preferably 30 - 50 °C.

[0034] In the above method, the molar ratio of amorphous silica (calculated as SiO₂) to inorganic base is 0.04 - 0.15, preferably 0.05 - 0.13.

[0035] In step (3) of the above method, using the amorphous silica after alkali treatment as the silicon source, mixing the silicon source with an aluminum source, an alkali source (MOH), a template agent (R), and water to form a gel, and then obtaining the ZSM-23 molecular sieve through crystallization, filtration, washing, drying, and calcination.

[0036] Preferably, the molar ratio of the silicon source (calculated as SiO₂): aluminum source (calculated as Al₂O₃): alkali source (calculated as hydroxide): template agent: H₂O in the gel system is 1: (0.003 - 0.03): (0.03 - 0.3): (0.05 - 2): (10 - 90); more preferably, the molar ratio of the silicon source (calculated as SiO₂): aluminum source (calculated as Al₂O₃): alkali source (calculated as hydroxide): template agent: H₂O in the gel system is 1: (0.005 - 0.02): (0.03 - 0.15): (0.08 - 1.6): (20 - 70);

[0037] Preferably, the gel is crystallized at 150 - 200 °C for 24 - 96 h, preferably the crystallization temperature is 170 - 180 °C and the crystallization time is 36 - 72 h, and then the ZSM-23 molecular sieve is obtained through filtration, washing, drying, and calcination.

[0038] In step (3) of the above method, the drying temperature is 80 - 120 °C, the drying time is 4 - 12 h, the calcination temperature is 500 - 600 °C, and the calcination time is 2 - 6 h.

[0039] In the preparation process of the ZSM-23 molecular sieve of the present invention, mesoporous amorphous silica was prepared with the assistance of a surfactant in the initial stage and used as the silicon source for the subsequent synthesis of the ZSM-23 molecular sieve. The amorphous silica generated in this process has both a mesoporous structure and is not highly crystallized into a stable crystal form. After being treated in a low-concentration alkaline solution for a period of time, some —Si—O— bonds are opened, which helps the formation of —Si—O—Al— bonds in the subsequent molecular sieve structure, but most of the mesoporous structure is retained. Under the action of a microporous template agent in the later stage, in a suitable ZSM-23 molecular sieve synthesis system, a microporous structure is generated, and at the same time, the mesoporous structure is further crystallized and stabilized, thus obtaining a micro-mesoporous composite ZSM-23 molecular sieve. The ZSM-23 molecular sieve synthesized by the method of the present invention has both the acid properties with adjustable microporous structure and the macropore characteristics of the mesoporous structure, with a high specific surface area and pore volume, as well as high crystallinity, strong thermal stability, and hydrothermal stability.

[0040] To better illustrate the present invention, the following examples and comparative examples are used to further explain the present invention. However, the scope of the present invention is not limited to the scope of these examples. The analysis methods of the present invention: the specific surface area and pore volume are measured by the ASAP2405 low-temperature liquid nitrogen physical adsorption method, and the relative crystallinity of the molecular sieve is determined by the X-ray powder diffraction method (XRD). Among them, the sum of the diffraction peak heights at 2θ of ~11.3 and 19.5 - 23° in the XRD pattern of the microporous ZSM-23 molecular sieve is taken as 100% crystallinity. The crystallinity of NaDZSM-23-1 prepared in Comparative Example 1 of the present invention is 100, and the relative crystallinity of other samples is obtained by comparison with it. The silicon-aluminum molar ratio is determined by a chemical method. In the present invention, wt% is the mass fraction and v% is the volume fraction.

[0041] To better illustrate the present invention, the following examples and comparative examples are used to further explain. However, the scope of the present invention is not limited to the scope of these examples.

[0042] Example 1

[0043] (1) Preparation of mesoporous silicon source

[0044] Add 50 g of water glass (mass fraction of SiO2 is 27%) to 250 g of deionized water, stir and disperse evenly, and then add octadecyltrimethylammonium chloride (C 18 TMACl) and stir for 0.5 hours, where the molar ratio of SiO2 to C 18 TMACl is 1:0.07; after adjusting the pH of the solution to 2 with hydrochloric acid, place it in a water bath at 50 °C and heat for 4 hours; after completion, filter, wash, dry, and calcine at 550 °C for 3 hours to obtain amorphous silica;

[0045] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0046] a) Dissolve 0.35 g of NaOH in 35 mL of deionized water, add 3.7 g of the mesoporous silicon source prepared in (1), and stir in a water bath at 45 °C for 3 hours;

[0047] b) Dissolve aluminum sulfate and isopropylamine (IPA) in the remaining water in turn, and then add the silicon source dispersion obtained in a) to obtain a gel with a total molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: NaOH: IPA: H2O = 1:0.01:0.08:1.0:50. After crystallization at 180 °C for 48 hours, filter, wash, dry, and calcine to obtain the product NaZSM-23-1. Measure its relative crystallinity, specific surface area, pore volume, and pore size distribution. After hydrothermal treatment with steam at 600 °C for 2 hours, measure its hydrothermal stability. The specific properties are shown in Table 1.

[0048] (3) Ammonium exchange

[0049] Weigh a certain amount of NaZSM-23-1 molecular sieve sample, place it in a 2 mol / L ammonium nitrate solution with a liquid-solid ratio of 10, continuously stir in a water bath at 80-90 °C for 1 hour, then filter and wash. After repeating the above operation process twice, place the sample in an oven at 80-100 °C for 8 hours and calcine in an air atmosphere at 550 °C for 3 hours to obtain HZSM-23-1.

[0050] (4) Catalyst preparation

[0051] 11% by weight of HZSM-23-1 molecular sieve, 14% of Y molecular sieve (specific surface area 765 m 2 / g, pore volume 0.54 mL / g, SiO2 / Al2O3 molar ratio 42), 55% of amorphous silica-alumina (pore volume 1.0 mL / g, specific surface area 360 m 2 / g, silica weight content 32%), and 20% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) and an adhesive composed of 10% by weight concentration of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.25) are put into a rolling mill for mixing and rolling, adding water, rolling into a paste, extruding into strips, drying the extruded strips at 110 °C for 4 hours, and then calcining at 550 °C for 4 hours to obtain the carrier TC-1.

[0052] The carrier is impregnated with an impregnating solution containing tungsten and nickel at room temperature for 2 hours, dried at 120 °C for 4 hours, and calcined at 500 °C with a programmed temperature rise for 4 hours to obtain the catalyst C-1. The corresponding catalyst properties are shown in Table 2.

[0053] Example 2

[0054] (1) Preparation of mesoporous silicon source

[0055] Add 50 g of water glass (SiO2 mass fraction is 27%) to 250 g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMACl) and stir for 0.5 hour, where the molar ratio of SiO2 to C 18 TMACl is 1:0.07; adjust the pH of the solution to 2 with hydrochloric acid, then place it in a water bath at 50 °C and heat for 4 hours; after completion, filter, wash, dry, and calcine at 550 °C for 3 hours to obtain amorphous silica;

[0056] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0057] a) Dissolve 0.42 g of NaOH in 40 mL of deionized water, add 3.7 g of the mesoporous silicon source prepared in (1), and place it in a water bath at 35 °C and stir for 6 hours;

[0058] b) Dissolve aluminum sulfate and isopropylamine (IPA) in the remaining water in sequence, then add the silicon source dispersion obtained in a) to it to prepare a gel with a molar ratio of SiO2 in the silicon source : Al2O3 in the aluminum source : NaOH : IPA : H2O = 1 : 0.01 : 0.10 : 1.0 : 50. After crystallization at 180 °C for 48 hours, it is filtered, washed, dried, and calcined, and named NaZSM-23-2. Its relative crystallinity, specific surface area, pore volume, and pore size distribution are measured. After hydrothermal treatment with steam at 600 °C for 2 hours, its hydrothermal stability is measured. The specific properties are shown in Table 1.

[0059] (3) Ammonium exchange

[0060] The preparation process of HZSM-23-2 is the same as that in Example 1 (3), except that the NaZSM-23-1 molecular sieve is replaced by HZSM-23-2.

[0061] (4) Catalyst preparation

[0062] Mix 9% by weight of HZSM-23-2 molecular sieve, 16% of Y molecular sieve (specific surface area 765 m 2 / g, pore volume 0.54 mL / g, SiO2 / Al2O3 molar ratio 42), 55% of amorphous silica-alumina (pore volume 1.0 mL / g, specific surface area 360 m 2 / g, silica weight content 32%), and 20% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) with a binder composed of 10% by weight concentration of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.25) in a rolling mill, add water, roll into a paste, extrude into strips, dry the extruded strips at 110 °C for 4 hours, and then calcine at 550 °C for 4 hours to obtain the carrier TC-2.

[0063] The carrier is impregnated with an impregnating solution containing tungsten and nickel at room temperature for 2 hours, dried at 120 °C for 4 hours, and calcined at 500 °C with a programmed temperature increase for 4 hours to obtain the catalyst C-2. The corresponding catalyst properties are shown in Table 2.

[0064] Example 3

[0065] (1) Preparation of mesoporous silicon source

[0066] Add 50 g of water glass (SiO2 mass fraction is 27%) to 1200 g of deionized water, stir and disperse evenly, and then add octadecyltrimethylammonium chloride (C18 Stirred with TMACl for 2 hours, where the molar ratio of SiO2 to C 18 is 1:0.2; after adjusting the pH of the solution to 3 with hydrochloric acid, it was placed in a water bath at 50 °C and heated for 4 hours; after completion, it was filtered, washed, dried, and calcined at 550 °C for 3 hours to obtain amorphous silica;

[0067] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0068] a) Dissolve 0.2 g of NaOH in 35 mL of deionized water, add 3.7 g of the mesoporous silicon source prepared in (1), and stir in a water bath at 45 °C for 3 hours;

[0069] b) After dissolving aluminum sulfate, isopropylamine (IPA), and sodium hydroxide in the remaining water in sequence, add the silicon source dispersion obtained in a) to obtain a gel with a molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: NaOH: IPA: H2O = 1:0.01: 0.08: 1.0: 50. After crystallization at 180 °C for 48 hours, it was filtered, washed, dried, and calcined, and named NaZSM-23-3. Its relative crystallinity, specific surface area, pore volume, and pore size distribution were measured. After hydrothermal treatment with steam at 600 °C for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0070] (3) Ammonium exchange

[0071] The preparation process of HZSM-23-3 is the same as that in Example 1 (3), except that the NaZSM-23-1 molecular sieve is replaced by HZSM-23-3.

[0072] (4) Catalyst preparation

[0073] 7.5% by weight of HZSM-23-3 molecular sieve, 17.5% of Y molecular sieve (specific surface area 765m 2 / g, pore volume 0.54 mL / g, SiO2 / Al2O3 molar ratio 42), 55% of amorphous silica-alumina (pore volume 1.0 mL / g, specific surface area 360m 2 / g, silica weight content 32%), and 20% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) and an adhesive composed of 10% by weight concentration of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.25) were put into a rolling mill and mixed and rolled, water was added, rolled into a paste, extruded into strips, the extruded strips were dried at 110 °C for 4 hours, and then calcined at 550 °C for 4 hours to obtain the carrier TC-2.

[0074] The carrier was impregnated with a tungsten- and nickel-containing impregnating solution at room temperature for 2 hours, dried at 120 °C for 4 hours, and calcined at a programmed temperature of 500 °C for 4 hours to obtain catalyst C-2. The corresponding catalyst properties are shown in Table 2.

[0075] Example 4

[0076] (1) Preparation of mesoporous silicon source

[0077] To 800 g of deionized water, 50 g of water glass (mass fraction of SiO2 is 27%) was added, stirred and dispersed evenly, and then octadecyltrimethylammonium chloride (C 18 TMACl) was added and stirred for 2 hours, where the molar ratio of SiO2 to C 18 TMACl is 1:0.2; after adjusting the pH of the solution to 4 with hydrochloric acid, it was placed in a water bath at 50 °C and heated for 4 hours; after completion, it was filtered, washed, dried, and calcined at 550 °C for 3 hours to obtain amorphous silica;

[0078] (2) Preparation of micro-mesoporous ZSM-23 molecular sieve:

[0079] a) 0.42 g of NaOH was dissolved in 40 mL of deionized water, 3.7 g of the mesoporous silicon source prepared in (1) was added, and it was stirred in a water bath at 40 °C for 3 hours;

[0080] b) After dissolving aluminum sulfate and isopropylamine (IPA) in the remaining water in turn, the silicon source dispersion obtained from a) was added thereto to prepare a gel with a molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: NaOH: IPA: H2O = 1: 0.005: 0.10: 1.0: 50. After crystallization at 180 °C for 48 hours, it was filtered, washed, dried, and calcined, and named NaZSM-23-4. Its relative crystallinity, specific surface area, pore volume, and pore size distribution were measured. After hydrothermal treatment with steam at 600 °C for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0081] (3) Ammonium exchange

[0082] The preparation process of HZSM-23-4 is the same as that in Example 1 (3), except that the NaZSM-23-1 molecular sieve is replaced by HZSM-23-4.

[0083] (4) Catalyst preparation

[0084] 6% by weight of the carrier of HZSM-23-1 molecular sieve, 19% of Y molecular sieve (specific surface area 765 m 2 / g, pore volume 0.54 mL / g, SiO2 / Al2O3 molar ratio 42), 55% of amorphous silica-alumina (pore volume 1.0 mL / g, specific surface area 360 m2 / g, with a silica weight content of 32%), and 20% by weight of small-pore alumina (pore volume of 0.35 mL / g and specific surface area of 330 m 2 / g) and 10% by weight of dilute nitric acid to form a binder (molar ratio of HNO3 / small-pore Al2O3 is 0.25). Put it into a rolling mill for mixing and rolling, add water, roll it into a paste, extrude it into strips, dry the extruded strips at 110 °C for 4 hours, and then calcine at 550 °C for 4 hours to obtain the support TC-4.

[0085] The support was impregnated with an impregnating solution containing tungsten and nickel at room temperature for 2 hours, dried at 120 °C for 4 hours, and calcined at 500 °C with a programmed temperature increase for 4 hours to obtain the catalyst C-4. The corresponding catalyst properties are shown in Table 2.

[0086] Comparative Example 1 (refer to CN105540607A)

[0087] (1) Molecular sieve preparation

[0088] Under stirring at 35 °C, 0.51 g of pseudo-boehmite and 0.3 g of sodium hydroxide were added to 26 mL of deionized water. After the solution was homogenized, 0.3 g of isopropylamine was added, and then 21 g of white carbon black was added. The mixture was homogenized and mixed again for 1 hour. 24.5 g of cereal starch was added, and the mixture was heated to 90 °C and stirred and aged for 6 hours. Finally, the obtained mixture was transferred to a hydrothermal reaction kettle with a polytetrafluoroethylene inner lining, crystallized statically at 160 °C for 144 hours, taken out, cooled, filtered, and dried at 80 °C to obtain the molecular sieve raw powder. It was calcined at 500 °C in an air atmosphere for 12 hours to obtain the micro-mesoporous composite NaDZSM-23-1 molecular sieve. Its relative crystallinity, specific surface area, pore volume, and pore size distribution were measured. After hydrothermal treatment with water vapor at 600 °C for 2 hours, its hydrothermal stability was measured. The specific properties are shown in Table 1.

[0089] (2) Ammonium exchange

[0090] The preparation process of H-DZSM-23-1 is the same as that of Example 1(3), except that the NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-1.

[0091] (3) Catalyst preparation

[0092] The preparation method of CC-1 catalyst is the same as that of Example 4(4), except that the H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-1. The specific properties are shown in Table 2.

[0093] Comparative Example 2

[0094] (1) Preparation of mesoporous silicon source

[0095] Add 50 g of water glass (mass fraction of SiO2 is 27%) to 1200 g of deionized water, stir and disperse evenly, then add octadecyltrimethylammonium chloride (C 18 TMACl) and stir for 2 hours, where the molar ratio of SiO2 to C 18 TMACl is 1:0.2; after adjusting the pH of the solution to 3 with hydrochloric acid, place it in a water bath at 50 °C and heat for 4 hours; after completion, filter, wash, dry, and calcine at 550 °C to obtain amorphous silica;

[0096] (2) a) Dissolve 0.70 g of NaOH in 40 mL of deionized water, add 3.7 g of the mesoporous silica source prepared in (1), and place it in a water bath at 45 °C and stir for 3 hours;

[0097] b) Dissolve aluminum sulfate and isopropylamine (IPA) in the remaining water in turn, then add the silica source dispersion obtained in a) to obtain a gel with a molar ratio of SiO2 in the silica source: Al2O3 in the aluminum source: NaOH: IPA: H2O = 1:0.01:0.16:1.0:50. After crystallization at 180 °C for 48 hours, filter, wash, dry, and calcine to obtain the sample NaDZSM-23-2. Measure its relative crystallinity, specific surface area, pore volume, and pore size distribution. After hydrothermal treatment with steam at 600 °C for 2 hours, measure its hydrothermal stability. The specific properties are shown in Table 1.

[0098] (3) Ammonium exchange

[0099] The preparation process of H-DZSM-23-2 is the same as that in Example 1 (3), except that the NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-2.

[0100] (4) Catalyst preparation

[0101] The preparation method of the CC-2 catalyst is the same as that in Example 4 (4), except that the H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-2. The specific properties are shown in Table 2.

[0102] Comparative Example 3

[0103] (1) Preparation of molecular sieve samples

[0104] Mix sodium silicate, aluminum sulfate, isopropylamine (IPA), sodium hydroxide and water to prepare a gel with a total molar ratio of SiO2 in the silicon source : Al2O3 in the aluminum source : NaOH : IPA : H2O = 1 : 0.01 : 0.08 : 1.0 : 50. After heating at 180 °C for 72 hours, filter, wash, dry and calcine to obtain a product named NaDZSM-23-3. Measure its relative crystallinity, specific surface area, pore volume and pore size distribution. After hydrothermal treatment with steam at 600 °C for 2 hours, measure its hydrothermal stability. The specific properties are shown in Table 1.

[0105] (2) Ammonium exchange

[0106] The preparation process of H-DZSM-23-3 is the same as that of Example 1(3), except that the NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-3.

[0107] (3) Catalyst preparation

[0108] The preparation method of CC-3 catalyst is the same as that of Example 4(4), except that the H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-3. The specific properties are shown in Table 2.

[0109] Comparative Example 4

[0110] Mix 25% by weight of Y molecular sieve (specific surface area 765 m 2 / g, pore volume 0.54 mL / g, SiO2 / Al2O3 molar ratio 42), 55% of amorphous silica-alumina (pore volume 1.0 mL / g, specific surface area 360 m 2 / g, silica weight content 32%) and 20% of small pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) with a binder composed of 10% by weight concentration of dilute nitric acid (molar ratio of HNO3 / small pore Al2O3 is 0.25), put it into a roller mill for mixing and rolling, add water, roll it into a paste, extrude it into strips, dry the extruded strips at 110 °C for 4 hours, and then calcine at 550 °C for 4 hours to obtain the carrier TC-4.

[0111] The carrier is impregnated with an impregnating solution containing tungsten and nickel at room temperature for 2 hours, dried at 120 °C for 4 hours, and calcined at 500 °C with a programmed temperature rise for 4 hours to obtain the catalyst CC-4. The corresponding catalyst properties are shown in Table 2.

[0112] Table 1 Properties of molecular sieves

[0113]

[0114] a The product generated under this condition is mainly other molecular sieves, so this property cannot be analyzed;

[0115] Degree of relative crystallinity retention = Crystallinity after hydrothermal treatment / Relative crystallinity. Due to the existence of measurement errors, the results greater than 100% are recorded as 100%.

[0116] Table 2 Physicochemical properties of the catalyst

[0117]

[0118] The above-mentioned catalysts of the present invention and the comparative catalysts were subjected to a catalytic performance evaluation test. The test was carried out on a 200 mL small-scale hydrogenation unit, using a single-stage series hydrocracking process. The properties of the feedstock oil used are shown in Table 3. The operating conditions are as follows: reaction pressure 15.7 MPa, hydrogen-oil volume ratio 1200:1, liquid hourly space velocity 1.0 h -1 , controlling the nitrogen content of the refined oil at 10 ppm. The catalyst evaluation results after running for 300 hours are shown in Table 4.

[0119] Table 3 Properties of the feedstock oil

[0120]

[0121] Table 4 Catalyst reaction evaluation results

[0122]

[0123] It can be seen from the evaluation results of the catalysts in Table 4 that the catalysts of the present invention have high middle oil selectivity, and the freezing point of jet fuel and the pour point of diesel are low.

Claims

1. A preparation method of a hydrocracking catalyst for producing middle distillates, characterized in that: The method includes the preparation of a support and the loading of a hydrogenation active metal. The method for preparing the support includes: mixing ZSM-23 zeolite, Y zeolite, amorphous silica-alumina, and a binder, shaping them, and then drying and calcining to obtain a catalyst support. The described Y zeolite has the following properties: the weight content of Na2O is less than 0.3%; the molar ratio of silicon to aluminum SiO2 / Al2O3 is 35 to 50; the specific surface area is 600 to 900 m 2 / g; the pore volume is 0.4 to 0.7 mL / g; The properties of the ZSM-23 molecular sieve are as follows: the specific surface area is 300 - 430 m 2 / g, the pore volume is 0.31 - 0.5 cm 3 / g, the micropore specific surface area is 50 - 140 m 2 / g, the mesopore specific surface area is 261 - 310 m 2 / g; the mesopore volume of 3 - 6 nm of the ZSM-23 molecular sieve accounts for 45 - 90% of the total pore volume of the molecular sieve, and the relative crystallinity is 95 - 120%. The relative crystallinity retention of the ZSM-23 molecular sieve after hydrothermal treatment with steam at 600 °C for 2 hours is 95 - 100%; In the catalyst, the mesopores with a pore diameter of 3 - 6 nm account for 35 - 60% of the total pore volume, and the mesopores with a pore diameter greater than 6 nm and less than or equal to 15 nm account for 30 - 55% of the total pore volume.

2. The method according to claim 1, wherein: The properties of the ZSM-23 molecular sieve are as follows: the specific surface area is 320-405 m 2 / g, the pore volume is 0.34-0.45 cm 3 / g, the micropore specific surface area is 80-140 m 2 / g, and the mesopore specific surface area is 261-295 m 2 / g.

3. The method according to claim 1, characterized in that: The mesopore volume of the ZSM-23 zeolite with a pore diameter of 3 - 6 nm accounts for 50 - 85% of the total pore volume of the zeolite.

4. The method according to claim 1, characterized in that: The mesopore volume of the ZSM-23 zeolite with a pore diameter of 3 - 6 nm accounts for 55 - 81% of the total pore volume of the zeolite.

5. The method according to claim 1, wherein: The weight content of SiO2 in the amorphous silica-alumina described is 20% to 50%, and the properties of the amorphous silica-alumina are as follows: the pore volume is 0.7 to 1.2 mL / g, and the specific surface area is 300 to 500 m 2 / g.

6. The method according to claim 5, characterized in that: The weight content of SiO2 in the amorphous silica-alumina described above is 25% to 40%, and the properties of the amorphous silica-alumina are as follows: the pore volume is 0.8 to 1.0 mL / g, and the specific surface area is 350 to 500 m 2 / g.

7. The method according to claim 1, characterized in that: The hydrogenation active metal is a metal of Group VIB and / or Group VIII.

8. The method according to claim 7, wherein: The metal of Group VIB is molybdenum and / or tungsten, and the metal of Group VIII is cobalt and / or nickel.

9. The method according to claim 1, wherein: The shape of the support after shaping is a cylindrical bar or a clover.

10. The method according to claim 9, wherein: A shaping aid is added during the shaping process.

11. The method according to claim 1, characterized in that: The support is dried at a temperature of 80 - 150 °C for 3 - 10 hours and calcined at 400 - 800 °C for 3 - 12 hours.

12. The method according to claim 1, wherein: The loading of the hydrogenation active metal is carried out by an impregnation method, that is, the catalyst support is impregnated with a solution containing the required active components. The impregnated support is dried at 100 °C - 150 °C for 4 - 12 hours and then calcined at 400 °C - 750 °C for 3 - 8 hours.

13. A hydrocracking catalyst prepared by any of the methods of claims 1 to 12, characterized in that: The catalyst includes a support and a hydrogenation active component. The support includes ZSM-23 zeolite, Y zeolite, amorphous silica-alumina, and a binder. Based on the weight of the support, the content of ZSM-23 zeolite is 2 - 20 wt%, the content of Y zeolite is 10 - 30 wt%, the content of amorphous silica-alumina is 20 - 60 wt%, and the content of the binder is 15 - 35 wt%. Based on the weight of the catalyst, the content of the metal of Group VIB in terms of oxide is 10 wt% - 25 wt% and the content of the metal of Group VIII in terms of oxide is 4 wt% - 15 wt%. The content of the support is 60.0% - 90.0%, and the sum of the contents of each component is 100%.

14. A hydrocracking process for producing middle distillates, characterized in that: The catalyst prepared by the method according to any one of claims 1-12 has the following hydrocracking reaction conditions: the reaction temperature is 350-420 °C, the reaction pressure is 6-20 MPa, the hydrogen-oil volume ratio is 500-2000:1, and the liquid hourly space velocity is 0.5-1.8 h -1 .

15. The method according to claim 14, characterized in that: The hydrocracking reaction conditions are as follows: the reaction temperature is 360 - 390 °C, the reaction pressure is 9 - 16 MPa, the hydrogen-oil volume ratio is 800 - 1500:1, and the liquid hourly space velocity is 0.8 - 1.5 h -1 .

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