A hydrocracking catalyst, a preparation method thereof, and an application thereof

Abstract

The present invention discloses a hydrocracking catalyst, a preparation method thereof and an application. In the hydrocracking 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 of 6 - 15 nm account for 30 - 55% of the total pore volume. The preparation method of the hydrocracking catalyst 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, β molecular sieve, amorphous silica-alumina and a binder, shaping, then drying and calcining to make a catalyst support. The hydrocracking catalyst is used for maximizing the production of low-freezing diesel and has the characteristics of high diesel selectivity and low diesel freezing point.

Description

Technical Field

[0001] The present invention relates to a hydrocracking catalyst, a preparation method thereof and an application thereof, and particularly to a hydrocracking catalyst for maximizing the production of low-freezing diesel oil, a preparation method thereof and an application thereof. Background Art

[0002] Hydrocracking technology is an effective technical measure to reduce environmental pollution, improve the quality of petroleum products and increase the market response ability, and has become the most important process unit in modern refineries. 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 put forward more stringent requirements for indicators such as sulfur and aromatic hydrocarbon content, cetane number, density, T95, etc. in diesel. In addition, people living in alpine regions or in winter pay more attention to the low-temperature flow performance of diesel products. Only low-freezing point diesel products can meet the actual use requirements. A large amount of low-freezing diesel is needed in the cold northern regions in winter, and the low-temperature flow performance (freezing point, cold filter plugging point, pour point, etc.) indicators of diesel are more important.

[0003] As a component providing cracking activity and isomerization activity in a hydrocracking catalyst, the performance of molecular sieve is crucial to the performance of the hydrocracking catalyst. Using a modified molecular sieve with excellent performance is beneficial to further improving the catalytic performance of the hydrocracking catalyst.

[0004] Currently, the industrialized molecular sieve type hydrocracking catalysts usually mainly use modified Y-type molecular sieves. The hydrocracking catalysts containing Y-type molecular sieves such as CN104826646A and CN103100403A have advantages such as good activity, high ring-opening performance, and high selectivity cracking performance for heavy components rich in cyclic hydrocarbons, but the diesel freezing point is low, especially when diesel deep distillation or wide-cut diesel production is carried out, this problem is more prominent. Compared with Y-type molecular sieve, the main pore diameter of β molecular sieve is 0.56 - 0.75 nm. The pore characteristics of β molecular sieve make it have a good effect on the selective cleavage of chain hydrocarbons in the cracking reaction and have strong isomerization performance. For example, CN101578353A, CN106140280A, etc. can be used as cracking components to produce more low-freezing point middle oil fractions. CN107344111A, CN106669799A, CN106140282A, CN107344117A, US5,350,501, US5,447,623, US5,279,726 and US5,536,687, etc. introduce a high-middle oil selective hydrocracking catalyst containing β molecular sieve and Y-type molecular sieve. For these above catalysts, the selectivity of diesel fraction oil is not high and the diesel freezing point still needs to be further improved. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a hydrocracking catalyst, a preparation method thereof, and an application thereof. The hydrocracking catalyst of the present invention can produce low-freezing diesel oil in the largest amount, and has the characteristics of high diesel selectivity and low diesel freezing point.

[0006] The hydrocracking catalyst of the present invention comprises a carrier and a hydrogenation active component. The carrier comprises ZSM-23 molecular sieve, β molecular sieve, amorphous silica-alumina and a binder. Based on the weight of the carrier, the content of ZSM-23 molecular sieve is 2-20 wt%, the content of β molecular sieve is 10-30 wt%, the content of amorphous silica-alumina is 20-60 wt%, and the content of the binder is 15-40 wt%. Preferably, the content of ZSM-23 molecular sieve is 5-15 wt%, the content of β molecular sieve is 15-25 wt%, the content of amorphous silica-alumina is 25-50 wt%, and the content of the binder is 20-35 wt%. 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 of 6-15 nm account for 30-55% of the total pore volume; preferably, the mesopores with a pore diameter of 3-6 nm account for 40-55% of the total pore volume, and the mesopores with a pore diameter of 6-15 nm (excluding 6 nm) account for 35-50% of the total pore volume.

[0007] In the hydrocracking catalyst of the present invention, the properties of the hydrocracking catalyst are as follows: the specific surface area is 280-600 m 2 / g, and the pore volume is 0.3-0.7 mL / g.

[0008] In the hydrocracking catalyst of the present invention, the properties of the ZSM-23 molecular sieve are as follows: the mesopore volume with a pore diameter of 3-6 nm 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 after the molecular sieve is hydrothermally treated with steam at 600 °C for 2 hours is 95-100%.

[0009] In the hydrocracking catalyst of the present invention, 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 specific surface area of micropores is 50-170 m 2 / g, and the specific surface area of mesopores 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 specific surface area of micropores is 80-140 m 2 / g, and the specific surface area of mesopores is 261-295 m 2 / g.

[0010] In the hydrocracking catalyst of the present invention, the weight content of SiO2 in the amorphous silica-alumina is 20% to 50%, preferably 25% to 40%. The properties of the amorphous silica-alumina are as follows: the pore volume is 0.7 to 1.2 mL / g, preferably 0.8 to 1.0 mL / g, and the specific surface area is 300 to 500 m 2 / g, preferably 350 to 500 m 2 / g.

[0011] In the hydrocracking catalyst of the present invention, the β zeolite has the following properties: the weight content of Na2O is less than 0.3%; the silica-alumina molar ratio SiO2 / Al2O3 is 60 to 90; the specific surface area is 400 to 700 m 2 / g; the pore volume is 0.3 to 0.6 mL / g.

[0012] In the hydrocracking catalyst of the present invention, the binder can 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.

[0013] In the hydrocracking catalyst of the present invention, the hydroactive 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. 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%.

[0014] The preparation method of the hydrocracking catalyst of the present invention includes the preparation of the carrier and the loading of the hydroactive metal. The preparation method of the carrier includes: mixing ZSM-23 zeolite, β zeolite, amorphous silica-alumina and a binder, shaping, and then drying and calcining to make the catalyst carrier. The preparation of ZSM-23 zeolite refers to the preparation method of CN202210011767.9.

[0015] In the hydrocracking catalyst of the present invention, the ZSM-23 zeolite includes the following preparation steps:

[0016] (1) Prepare or select amorphous silica;

[0017] (2) Perform alkali treatment on the amorphous silica;

[0018] (3) Prepare ZSM-23 zeolite using the alkali-treated amorphous silica as the silicon source.

[0019] In the above method step (1), the specific surface area of the amorphous silica is 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.

[0020] 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 the surfactant and stir; adjust the pH of the solution to 1 - 5, preferably 1.5 - 4, and then perform water bath heating treatment for a period of time; filter, wash, dry, and calcine to obtain amorphous mesoporous silica.

[0021] 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.

[0022] In the above method, during the preparation process of the amorphous silica, the surfactant is one or more of cetyltrimethyl bromide / ammonium chloride and octadecyltrimethyl chloride / bromide.

[0023] 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).

[0024] 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);

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In the above method, the molar ratio of amorphous silica to inorganic base calculated as SiO2 is 0.04 to 0.15, preferably 0.05 to 0.13.

[0030] 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 after crystallization, filtration, washing, drying, and calcination.

[0031] 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 to 0.03): (0.03 to 0.3): (0.05 to 2): (10 to 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 to 0.02): (0.03 to 0.15): (0.08 to 1.6): (20 to 70);

[0032] Preferably, the gel is crystallized at 150 to 200 °C for 24 to 96 h, preferably the crystallization temperature is 170 to 180 °C, and the crystallization time is 36 to 72 h, and then the ZSM-23 molecular sieve is obtained after filtration, washing, drying, and calcination.

[0033] In step (3) of the above method, the drying temperature is 80 to 120 °C, the drying time is 4 to 12 h, the calcination temperature is 500 to 600 °C, and the calcination time is 2 to 6 h.

[0034] The catalyst of the present invention can be shaped according to actual needs, and the shape can be cylindrical bars, clovers, etc. During the catalyst shaping process, shaping 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 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.

[0035] In the preparation method of the hydrocracking catalyst of the present invention, the loading of the hydrogenation active metal can adopt the conventional loading methods in the prior art, preferably the impregnation method, which can be saturated impregnation, excess impregnation or complex impregnation, that is, impregnating the catalyst carrier with a solution containing the required active component, and 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.

[0036] The application of the above hydrocracking catalyst in the production of low-freezing diesel from heavy oil by hydrocracking, 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, and catalytic cracking gas 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.

[0037] According to the present invention, the conditions of the reaction 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 .

[0038] 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 molecular sieve structure later, 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 acid properties with adjustable microporous structures and the characteristics of large pores in the mesoporous structure, with a high specific surface area and pore volume, and at the same time has a high crystallinity, strong thermal stability and hydrothermal stability.

[0039] The ZSM-23 molecular sieve and the β molecular sieve used in the catalyst of the present invention act as cracking centers together, not only giving full play to their respective performance characteristics, but also enabling the two molecular sieves to produce a synergistic catalytic effect. The high-silica-alumina ratio β molecular sieve improves the selectivity of the catalyst for wide-cut diesel, has a good isomerization effect on long side chains on paraffins or aromatics, can effectively reduce the pour point of the product, and synergistically with the 3 - 6 nm highly concentrated pore distribution characteristics of the ZSM-23 molecular sieve of the present invention, has a good adsorption and isomerization effect on long side chains on paraffins or aromatics, avoids the secondary cracking of product molecules, and further reduces the pour point of the product and improves the diesel selectivity and cetane number of the catalyst. The hydrocracking catalyst of the present invention can produce low-freezing-point diesel in the largest amount. In the present invention, the catalyst is suitable for heavy oil hydrocracking reactions, and is preferably applied to the heavy oil hydrocracking for the production of middle distillates in a one-stage series hydrocracking process. Detailed implementation manners

[0040] To better illustrate the present invention, the following will further explain the present invention in combination with examples and comparative examples. However, the scope of the present invention is not limited to the scope of these examples. The analysis method of the present invention: 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 X-ray powder diffraction method (XRD). Among them, the sum of the peak heights at 2θ of ~11.3 and 19.5 - 23° in the XRD spectrum of microporous ZSM-23 molecular sieve is taken as 100% of the 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 comparing with it. The silicon-aluminum molar ratio is measured by 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 will further explain in combination with examples and comparative examples. 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) Aluminum sulfate and isopropylamine (IPA) were sequentially dissolved in the remaining water, and the silicon source dispersion obtained in a) was added thereto to prepare a gel having 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, the product, NaZSM-23-1, was obtained after filtration, washing, drying, and calcination. The relative crystallinity, specific surface area, pore volume, and pore size distribution of the product were measured. After hydrothermal treatment with water vapor at 600°C for 2 hours, the hydrothermal stability of the product was measured. Specific properties are shown in Table 1.

[0048] (3) Ammonium exchange

[0049] A certain amount of NaZSM-23-1 molecular sieve sample was weighed and placed in a 2 mol / L ammonium nitrate solution with a liquid-to-solid ratio of 10. After continuous stirring in an 80-90°C water bath for 1 hour, the solution was filtered and washed. This process was repeated twice. The sample was then dried in an oven at 80-100°C for 8 hours and calcined in air at 550°C for 3 hours to obtain HZSM-23-1.

[0050] (4) Catalyst preparation

[0051] The carrier weight is 6% HZSM-23-1 molecular sieve, 21% β molecular sieve (specific surface area 685m 2 / g, pore volume 0.55mL / g, SiO2 / Al2O3 molar ratio 72), 54% amorphous silica-alumina (pore volume 1.0mL / g, specific surface area 380m 2 / g, silica weight content 31%), and 19% g of small pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) and a binder consisting of 10% by weight of dilute nitric acid (the molar ratio of HNO3 / small-pore Al2O3 is 0.27) were extruded into strips, which were dried at 110°C for 4 hours and then calcined at 550°C for 4 hours to obtain carrier TC-1.

[0052] The support was impregnated with an impregnation solution containing tungsten and nickel at room temperature for 2 hours, dried at 120°C for 4 hours, and calcined at 500°C for 4 hours to obtain 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 18Stir with TMACl for 0.5 h, where the molar ratio of SiO2 to C 18 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 h; after completion, filter, wash, dry, and calcine at 550 °C for 3 h 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 stir in a water bath at 35 °C for 6 h;

[0058] b) After dissolving aluminum sulfate and isopropylamine (IPA) in the remaining water in turn, 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 = 1:0.01:0.10:1.0:50. After crystallization at 180 °C for 48 h, filter, wash, dry, and calcine, and name it NaZSM-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 h, measure its hydrothermal stability. 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 with HZSM-23-2.

[0061] (4) Catalyst preparation

[0062] Mix 8% by weight of HZSM-23-2 molecular sieve, 19% of β molecular sieve (specific surface area 685 m 2 / g, pore volume 0.55 mL / g, SiO2 / Al2O3 molar ratio 72), 54% of amorphous silica-alumina (pore volume 1.0 mL / g, specific surface area 380 m 2 / g, silica weight content 31%), and 19% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) with an adhesive composed of 10% by weight concentration of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.27), 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 h, and then calcine at 550 °C for 4 h to obtain the carrier TC-2.

[0063] The carrier was impregnated with a tungsten- and nickel-containing impregnation solution 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 catalyst C-2. The corresponding catalyst properties are shown in Table 2.

[0064] Example 3

[0065] (1) Preparation of mesoporous silicon source

[0066] 50 g of water glass (mass fraction of SiO2 is 27%) was added to 1200 g of deionized water, stirred and dispersed evenly, and then cetyltrimethylammonium 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 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) 0.20 g of NaOH was dissolved in 35 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 45 °C for 3 hours;

[0069] b) After dissolving aluminum sulfate, isopropylamine (IPA), and sodium hydroxide 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 = 1:0.01:0.08:1.0:50. 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 was replaced with HZSM-23-3.

[0072] (4) Catalyst preparation

[0073] 10% by weight of the carrier of HZSM-23-3 molecular sieve, 17% of β molecular sieve (specific surface area 685m 2 [[ID=2 / g, with a silica weight content of 31%), and 19% 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 0.27). It is put into a rolling machine for mixing and kneading, water is added, and it is kneaded into a paste, extruded into strips. The extruded strips are dried at 110 °C for 4 hours and then calcined at 550 °C for 4 hours to obtain the support TC-2.

[0074] The support 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 a programmed temperature of 500 °C for 4 hours to obtain the catalyst C-2. The corresponding catalyst properties are shown in Table 2.

[0075] Example 4

[0076] (1) Preparation of mesoporous silicon source

[0077] 50 g of water glass (SiO2 mass fraction is 27%) is added to 800 g of deionized water, stirred and dispersed evenly, and then cetyltrimethylammonium chloride (C 18 TMACl) is 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 is placed in a water bath at 50 °C and heated for 4 hours; after completion, it is 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 is dissolved in 40 mL of deionized water, and 3.7 g of the mesoporous silicon source prepared in (1) is added, and it is 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) is added to it to prepare a gel with a molar ratio of SiO2 in the silicon source: Al2O3 in the aluminum source: NaOH: IPA: H2O = 1:0.005:0.10:1.0:50. After crystallization at 180 °C for 48 hours, it is filtered, washed, dried, and calcined, and named NaZSM-23-4. 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.

[0081] (3) Ammonium exchange

[0082] The preparation process of HZSM-23-4 is the same as that of 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 HZSM-23-4 molecular sieve, 21% of β molecular sieve (specific surface area 685 m 2 / g, pore volume 0.55 mL / g, SiO2 / Al2O3 molar ratio 72), 54% of amorphous silica-alumina (pore volume 1.0 mL / g, specific surface area 380 m 2 / g, silica weight content 31%), and 19% 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 0.27) are put into a rolling mill for mixing and rolling, water is added, and it is rolled into a paste, extruded into strips, the extruded strips are dried at 110 °C for 4 hours, and then calcined at 550 °C for 4 hours to obtain the support TC-4.

[0085] The support 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-4. The corresponding catalyst properties are shown in Table 2.

[0086] Comparative Example 1 (referring to CN105540607A)

[0087] (1) Molecular sieve preparation

[0088] Under stirring at 35 °C, 0.51 g of pseudoboehmite and 0.3 g of sodium hydroxide are added to 26 mL of deionized water. After the solution is homogenized, 0.3 g of isopropylamine is added, and then 21 g of white carbon black is added, and it is homogenized and mixed again for 1 hour. 24.5 g of cereal starch is added, the mixture is heated to 90 °C, and stirred and aged for 6 hours. Finally, the obtained mixture is transferred to a hydrothermal reaction kettle with a polytetrafluoroethylene inner lining, statically crystallized at 160 °C for 144 hours, taken out, cooled, filtered, and dried at 80 °C to obtain the molecular sieve raw powder. It is calcined in an air atmosphere at 500 °C 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 are measured. After hydrothermal treatment with water vapor at 600 °C for 2 hours, its hydrothermal stability is measured. The specific properties are shown in Table 1. <x

[0089] (2) Ammonium exchange [[ID=Y]]<x

[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 H-ZSM-23-4 molecular sieve is replaced by H-DZSM-23-1, and 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, and 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 silicon 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, and then 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 = 1:0.01:0.16:1.0:50. 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, and the specific properties are shown in Table 1. (3) Ammonium exchange

[0098] The preparation process of H-DZSM-23-2 is the same as that of Example 1(3), except that NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-2.

[0099] (3) Catalyst preparation

[0100] The preparation method of CC-2 catalyst is the same as that of Example 4(4), except that H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-2, and the specific properties are shown in Table 2.

[0101] Comparative Example 3

[0102] (1) Preparation of molecular sieve sample

[0103] Sodium silicate, aluminum sulfate, isopropylamine (IPA), sodium hydroxide and water were mixed 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, it was filtered, washed, dried and calcined, and the product was named Na-DZSM-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.

[0104] (2) Ammonium exchange

[0105] The preparation process of H-DZSM-23-3 was the same as that of Example 1(3), except that the NaZSM-23-1 molecular sieve was replaced with NaDZSM-23-3.

[0106] (3) Catalyst preparation

[0107] The preparation method of the CC-3 catalyst was the same as that of Example 4(4), except that the H-ZSM-23-1 molecular sieve was replaced with H-DZSM-23-3. The specific properties are shown in Table 2.

[0108] Comparative Example 4

[0109] 27% by weight of the carrier β molecular sieve (specific surface area 685 m 2 / g, pore volume 0.55 mL / g, SiO2 / Al2O3 molar ratio 72), 54% amorphous silica-alumina (pore volume 1.0 mL / g, specific surface area 380 m 2 / g, silica weight content 31%), and 19% 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 0.27) were put into a rolling mill and mixed and rolled, water was added, and it was rolled into a paste, extruded into strips, and 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-4.

[0110] The carrier 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 CC-4. The corresponding catalyst properties are shown in Table 2.

[0111] Table 1 Properties of molecular sieves *

[0112]

[0113] a The product generated under this condition was mainly other molecular sieves, so this property could not be analyzed;

[0114] dRelative crystallinity retention = crystallinity after hydrothermal treatment / relative crystallinity. Due to measurement error, results greater than 100% are considered 100%.

[0115] From the data in Table 1, it can be seen that the preparation method of the embodiment of the present invention can prepare a ZSM-23 molecular sieve with a micro-mesoporous composite structure through a simple synthesis process, which has high crystallinity, large specific surface area and pore volume, high mesopore content, relatively concentrated size distribution, and good thermal stability and hydrothermal stability.

[0116] Table 2 Physicochemical properties of catalysts

[0117]

[0118] The catalysts of the present invention and comparative catalysts were tested for catalytic performance. The tests were conducted on a 200 mL small-scale hydrogenation unit using a single-stage cascade hydrocracking process. The feedstock properties are shown in Table 3. The operating conditions were as follows: reaction pressure 15.7 MPa, hydrogen-to-oil volume ratio 1200:1, liquid hourly space velocity 1.0 h-1 / h-2. -1 The nitrogen content of the refined oil was controlled at 10 ppm. The evaluation results of the catalyst after 300 hours of operation are shown in Table 4.

[0119] Table 3 Properties of crude 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 good diesel selectivity on the basis of high activity, good product properties, especially low diesel pour point.

Claims

1. A hydrocracking catalyst, characterized in that: The catalyst comprises a carrier and a hydrogenation active metal, wherein the carrier comprises ZSM-23 molecular sieve, β molecular sieve, amorphous silica-alumina and a binder. Based on the weight of the carrier, the content of ZSM-23 molecular sieve is 2-20wt%, the content of β molecular sieve is 10-30wt%, the content of amorphous silica-alumina is 20-60wt%, and the content of the binder is 15-40wt%. In the catalyst, mesopores with a pore size of 3-6 nm account for 35-60% of the total pore volume, and mesopores with a pore size greater than 6 nm and less than or equal to 15 nm account for 30-55% of the total pore volume. The properties of the ZSM-23 molecular sieve are as follows: the mesopore volume with a pore size of 3 to 6 nm accounts for 45 to 90% of the total pore volume of the molecular sieve, the relative crystallinity is 95 to 120%, and the relative crystallinity retention of the ZSM-23 molecular sieve after hydrothermal treatment with steam at 600°C for 2 hours is 95 to 100%; The properties of the beta molecular sieve are as follows: Na2O weight content is less than 0.3%; silicon aluminum molar ratio SiO2 / Al2O3 is 60-90; specific surface area is 400-700m 2 / g; pore volume is 0.3~0.6mL / g.

2. The catalyst according to claim 1, characterized in that: Based on the weight of the carrier, the content of ZSM-23 molecular sieve is 5-15wt%, the content of beta molecular sieve is 15-25wt%, the content of amorphous silica alumina is 25-50wt%, and the content of binder is 20-35wt%.

3. The catalyst according to claim 1, characterized in that: In the catalyst, mesopores with a pore diameter of 3-6 nm account for 40-55% of the total pore volume, and mesopores with a pore diameter greater than 6 nm and less than or equal to 15 nm account for 35-50% of the total pore volume.

4. The catalyst according to claim 1, characterized in that: The properties of the hydrocracking catalyst are as follows: the specific surface area is 280-600 m 2 / g, and the pore volume is 0.3~0.7 mL / g.

5. The catalyst according to claim 1, characterized in that: The properties of the ZSM-23 molecular sieve are as follows: the mesopore volume with a pore diameter of 3 to 6 nm accounts for 50-85% of the total pore volume of the molecular sieve.

6. The catalyst according to claim 1, characterized in that: The properties of the ZSM-23 molecular sieve are as follows: the mesopore volume with a pore diameter of 3 to 6 nm accounts for 55 to 81% of the total pore volume of the molecular sieve.

7. The catalyst according to claim 1, characterized in that: The weight content of SiO2 in the amorphous silicon-aluminum is 20% to 50%. The properties of the amorphous silicon-aluminum are as follows: pore volume is 0.7 to 1.2 mL / g, specific surface area is 300 to 500 m 2 / g.

8. The catalyst according to claim 7, characterized in that: The weight content of SiO2 in the amorphous silicon-aluminum is 25% to 40%. The properties of the amorphous silicon-aluminum are as follows: pore volume is 0.8 to 1.0 mL / g, specific surface area is 350 to 500 m 2 / g.

9. The catalyst according to claim 1, characterized in that: The hydrogenation active metal is a metal of Group VIB and / or Group VIII. Based on the weight of the catalyst, the content of the Group VIB metal as oxide is 10wt% to 25wt%, the content of the Group VIII metal as oxide is 4wt% to 15wt%, the content of the carrier is 60.0% to 90.0%, and the sum of the contents of each component is 100%.

10. The catalyst according to claim 9, characterized in that: The metals of Group VIB are molybdenum and / or tungsten, and the metals of Group VIII are cobalt and / or nickel.

11. The method for preparing the catalyst according to any one of claims 1 to 10, characterized in that: The method includes the preparation of a carrier and the loading of hydrogenation active metals, wherein the preparation method of the carrier includes: mixing and shaping ZSM-23 molecular sieve, beta molecular sieve, amorphous silicon aluminum and a binder, and then drying and calcining to prepare a catalyst carrier.

12. The method according to claim 11, wherein: The ZSM-23 molecular sieve comprises the following preparation steps: (1) preparing or selecting amorphous silicon dioxide; (2) alkaline treatment of amorphous silica; (3) ZSM-23 molecular sieve was prepared using alkali-treated amorphous silica as the silicon source.

13. Use of the hydrocracking catalyst according to any one of claims 1 to 10 in the production of low-freezing point diesel by hydrocracking of heavy oil, characterized in that: The heavy oil includes one or more of vacuum gas oil, deasphalted oil, thermal cracking gas oil, and catalytic cracking gas oil.

14. The use according to claim 13, characterized in that: The thermal cracking gas oil is coking gas oil.

15. The use according to claim 13, characterized in that: The conditions for the hydrocracking reaction are: reaction temperature of 350-420°C, reaction pressure of 6-20 MPa, hydrogen-to-oil volume ratio of 500-2000:1, liquid hourly space velocity of 0.5-1.8 h -1 .

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

Images