A method for producing middle distillates

Abstract

The present invention discloses a method for producing middle distillates. The method comprises the following steps: After being subjected to desulfurization and denitrification treatment, a heavy feedstock oil enters a hydrocracking reaction zone, and a hydrocracking catalyst and an isomerization catalyst are successively loaded in the hydrocracking reaction zone along the direction of the material flow. The volume ratio of the hydrocracking catalyst to the isomerization catalyst is 20:1 - 5:2. The hydrocracking catalyst contains Y zeolite, and the properties of the Y zeolite are as follows: 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 0.3 - 0.6 mL / g; the particle size is 500 - 1000 nm, and the isomerization catalyst uses ZSM-23 as the acidic component. When the method processes a heavy feedstock oil with high sulfur and nitrogen contents, it not only has a relatively high middle oil selectivity, but also has advantages such as a low freezing point of jet fuel and a low pour point of diesel fuel.

Description

Technical Field

[0001] The present invention relates to a method for producing middle distillates, and particularly to a method for hydrocracking heavy feedstock oil to produce middle distillates. Background Art

[0002] With the increasingly strict environmental protection requirements and the continuous upgrading of diesel quality standards, people in alpine regions or those living in winter 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, a large amount of low-freezing-point diesel is needed in the cold northern regions, and the low-temperature fluidity (pour point, cold filter plugging point, etc.) indicators of diesel become more important.

[0003] 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 around the world are constantly innovating in their production processes or detection standards. They are working on technological innovation and standard improvement to closely follow the market pulse and increase the production of jet fuel products with high market demand. The hydrocracking technology is the main process technology for producing high-quality middle distillates (jet fuel + diesel) from heavy feedstock oil.

[0004] Currently, the main process technology for producing high-quality middle distillates (jet fuel + diesel) from heavy feedstock oil mainly adopts a series process of hydrofining and hydrocracking. The cracking section catalyst uses a hydrocracking catalyst with traditional modified Y zeolite and other molecular sieves as the acidic component.

[0005] Hydrocracking catalysts containing Y-type molecular sieves such as CN104826646A, CN103100403A, CN101380588A, CN101450319A, and CN102786064A have the advantages of good activity, high ring-opening performance, and high selectivity cracking performance for heavy components rich in cyclic hydrocarbons. However, the freezing point of jet fuel is low, and the pour point of diesel is 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 meet the standard of 3# jet fuel. Summary of the Invention

[0006] Aiming at the deficiencies in the prior art, the present invention provides a method for hydrocracking heavy feedstock oil to produce middle distillates. When processing heavy feedstock oil with high sulfur and nitrogen contents, it not only has high middle oil selectivity but also has the advantages of low freezing point of jet fuel and low pour point of diesel.

[0007] A method for producing middle distillates, the method comprising the following: the heavy feedstock oil is subjected to desulfurization and denitrification treatment and then enters the hydrocracking reaction zone. The hydrocracking reaction zone is filled with a hydrocracking catalyst and an isomerization catalyst in sequence along the direction of the material flow. The volume ratio of the hydrocracking catalyst to the isomerization catalyst is 20:1 - 5:2. The hydrocracking catalyst contains Y zeolite, and the properties of the Y zeolite are as follows: 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 0.3 - 0.6 mL / g; the particle size is 500 - 1000 nm. The isomerization catalyst uses ZSM-23 as the acidic component.

[0008] In the method of the present invention, the feedstock 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 initial boiling point of the feedstock oil is 260 - 300°C, the final boiling point is 500 - 600°C, the nitrogen mass content is generally 1000 - 2500 ppm, and the aromatics are 40 - 50 wt%.

[0009] In the method of the present invention, the feedstock oil is subjected to desulfurization and denitrification under a hydrotreating catalyst. The hydrotreating catalyst is a conventional hydrofining catalyst, generally using an alumina carrier. The hydrogenation active metal components are preferably Group VIB metals molybdenum and / or tungsten (the content in terms of oxides is 15.0% - 25.0 wt% of the catalyst) and Group VIII metals cobalt and / or nickel (the content in terms of oxides is 4.0% - 7.0 wt% of the catalyst).

[0010] In the method of the present invention, the feedstock oil is subjected to desulfurization and denitrification under a hydrotreating catalyst. The hydrotreating reaction conditions are as follows: the reaction temperature is 350 - 400°C, preferably 360 - 390°C; the reaction pressure is 10 - 18 MPa, preferably 12 - 16 MPa; the hydrogen-oil volume ratio is 500 - 2000:1, preferably 800 - 1200:1; the liquid hourly space velocity is 0.5 - 2.0 h -1 , preferably 0.8 - 1.5 h -1 。 。

[0011] In the method of the present invention, based on the weight of the hydrocracking catalyst, the content of Y zeolite is 10 - 30 wt%, the content of amorphous silica-alumina is 30 - 60 wt%, the content of the binder is 10 - 30 wt%, the content of Group VIB metals in terms of oxides is 10 wt% - 30 wt%, and the content of Group VIII metals in terms of oxides is 3 wt% - 10 wt%. In the method of the present invention, the Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel.

[0012] In the method 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.

[0013] In the method of the present invention, the reaction conditions of the hydrocracking catalyst bed in the hydrocracking reaction zone are as follows: the reaction temperature is 350 to 420 °C, preferably 360 to 390 °C; the reaction pressure is 10 to 20 MPa, preferably 13 to 16 MPa; the hydrogen-oil volume ratio is 500 to 2000:1, preferably 800 to 1500:1; the liquid hourly space velocity is 0.5 to 1.8 h -1 -, preferably 0.8 to 1.5 h -1 .

[0014] In the method of the present invention, the content of HZSM-23 molecular sieve in the isomerization catalyst is 10 to 60 wt%, the content of macroporous alumina is 10 to 40 wt%, the content of the binder is 10 to 20 wt%, the content of Group VIB metal in terms of oxide is 10 wt% to 25 wt% and the content of Group VIII metal in terms of oxide is 4 wt% to 10 wt%. The Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel.

[0015] In the method of the present invention, the specific surface area of the isomerization catalyst is 250 to 500 m 2 / g, and the pore volume is 0.30 to 0.70 cm 3 / g; the specific surface area is preferably 300 to 450 m 2 / g, and the pore volume is preferably 0.37 to 0.60 cm 3 / g. The content of weak acid in the catalyst accounts for 75 - 90 of the total acid amount. Optionally, the content of weak acid accounts for 80 - 90% of the total acid amount.

[0016] In the method of the present invention, the properties of the HZSM-23 molecular sieve are as follows: the total acid amount is 0.1 to 0.25 mmol / g, and the content of strong acid is 10 to 25%; the relative crystallinity is 95 to 120%, and the relative crystallinity after steam hydrothermal treatment is 93 to 115%; preferably, the total acid amount is 0.15 to 0.25 mmol / g, and the content of strong acid

[0017] is 10 to 20%; the relative crystallinity is 98 to 116%, and the relative crystallinity after steam hydrothermal treatment is 95 to 114%.

[0018] In the method of the present invention, the HZSM-23 molecular sieve has a crystal size of 300-600 nm, a SiO2 / Al2O3 molar ratio of 80-130, a specific surface area of 300-400 m 2 / g, and a pore volume of 0.30-0.45 cm 3 / g.

[0019] In the method of the present invention, the macroporous alumina has a pore volume of 0.7-1.5 mL / g and a specific surface area of 400-600 m 2 / g.

[0020] In the method of the present invention, the binder can be a commonly used binder in the art, preferably small-pore alumina. The small-pore alumina used has a pore volume of 0.3-0.5 mL / g and a specific surface area of 200-400m 2 / g.

[0021] In the method provided by the present invention, the cracking section is composed of a graded loading of hydrocracking and isomerization catalysts. Macromolecules such as polycyclic naphthenes and aromatics in the raw material first undergo ring-opening and cracking reactions on the Y molecular sieve with a large number of strong acid and medium strong acid sites for primary cracking. Then, the long-chain alkanes undergo hydroisomerization reactions in the isomerization catalyst of the HZSM-23 molecular sieve rich in weak acid sites without cracking, improving the selectivity of middle distillates, reducing the freezing point of the kerosene fraction and the pour point of diesel, and increasing the smoke point of kerosene and the cetane number of diesel.

[0022] The hydrocracking catalyst of the present invention is suitable for heavy oil hydrocracking reactions, preferably applied to the production of middle distillates from heavy oil hydrocracking in a one-stage tandem hydrocracking process, and is particularly suitable for the flexible production of kerosene or diesel by refineries according to market demand. Detailed Embodiments

[0023] The preparation method of the isomerization catalyst of the present invention includes the preparation of a support and the loading of a hydrogenation active metal. The preparation method of the isomerization catalyst includes: mixing, shaping, drying, and calcining HZSM-23 molecular sieve, amorphous silica-alumina, and a binder to form a catalyst support. The preparation of the ZSM-23 molecular sieve refers to the preparation method of CN202210011767.9

[0024] The HZSM-23 molecular sieve in the isomerization catalyst of the present invention includes the following preparation steps:

[0025] (1) Prepare a mixed solution containing a structure-directing agent, amorphous silica-alumina, or an amorphous silica-alumina precursor;

[0026] (2) Add a supplementary silicon source to the material in step (1);

[0027] (3) The materials in step (2) are crystallized, filtered, washed, dried, and calcined to obtain ZSM-23 molecular sieve.

[0028] (4) The molecular sieve obtained in (3) is subjected to ammonium exchange to obtain HZSM-23 molecular sieve.

[0029] In step (1) of the above method, the structure-directing agent is one or more of isopropylamine, pyrrolidine, N,N-dimethylformamide, and dimethylamine.

[0030] In step (1) of the above method, the molar ratio of silicon (calculated as silicon dioxide) to aluminum (calculated as aluminum oxide) in the mixed solution is 1:(0.10 - 0.85), preferably 1:(0.20 - 0.79), and more preferably 1:(0.24 - 0.78); the molar ratio of aluminum (calculated as aluminum oxide) to the structure-directing agent is 1:(10 - 100), preferably 1:(15 - 85), and more preferably 1:(20 - 65).

[0031] In step (1) of the above method, an amorphous silica-alumina precursor mixture is prepared by the carbonization method, and then a structure-directing agent is added to the amorphous silica-alumina precursor mixture.

[0032] In the present invention, a non-limiting preparation process of the amorphous silica-alumina precursor mixture is specifically as follows: an aluminum source (preferably sodium aluminate) solution and a silicon-containing compound solution are respectively prepared; the sodium aluminate solution is mixed with a part of the silicon-containing compound solution, and CO2 gas is introduced for gelation. When the volume of the introduced CO2 gas accounts for 50 - 100% of the total introduced volume, preferably 70 - 90%, the remaining part of the silicon-containing compound solution is added, and then the remaining CO2 gas is introduced. Optionally, after aging, an amorphous silica-alumina precursor mixture is obtained.

[0033] In the above preparation process of the amorphous silica-alumina precursor mixture, the remaining part of the silicon-containing compound solution accounts for 20 - 90 wt% of the total silicon-containing compound solution added in terms of silicon dioxide, preferably 30 - 80 wt%.

[0034] In the above preparation process of the amorphous silica-alumina precursor mixture, the reaction temperature for gelation is 10 - 40 °C, preferably 15 - 35 °C, and the pH value after the end of gelation is controlled to be 9 - 12.

[0035] In the above preparation process of the amorphous silica-alumina precursor mixture, the silicon-containing compound solution is water glass and / or sodium silicate solution.

[0036] During the preparation of the above amorphous silica-alumina precursor mixture solution, based on the mass of Al2O3, the concentration of the aluminum source solution is 15 - 60 g Al2O3 / L, based on the mass of SiO2, the concentration of the silicon-containing compound solution is 40 - 260 g SiO2 / L, and the concentration of the CO2 gas is 30 - 60 v%.

[0037] During the preparation of the above amorphous silica-alumina precursor mixture solution, the aging time is 5 - 60 minutes, preferably 10 - 30 minutes; the aging temperature is 10 - 40 °C, preferably 15 - 35 °C.

[0038] In step (1) of the above method, the mixed solution is stirred at 10 - 35 °C for 0.2 - 1.5 hours, preferably stirred at 10 - 25 °C for 0.5 - 1 hour.

[0039] In step (2) of the above method, based on the aluminum (calculated as alumina) in the mixed solution of step (1), according to the total feeding molar ratio of SiO2:Al2O3:H2O = 1:(0.005 - 0.0125):(30 - 60) and SDA (structure-directing agent) / SiO2 = 0.10 - 1.8, a supplementary silicon source is added to the material in step (1).

[0040] In step (2) of the above method, the silicon source is one or more of fumed silica, silica sol, and water glass.

[0041] In step (3) of the above method, the crystallization conditions are: crystallization at 160 - 180 °C for 10 - 48 hours; drying temperature is 80 - 120 °C, time is 4 - 8 hours; calcination temperature is 500 - 600 °C, time is 2 - 8 hours.

[0042] In step (4) of the above method, the ammonium exchange is carried out by a conventional method, such as one or more times of ammonium exchange, and the Na2O content in the HZSM-23 molecular sieve after ammonium exchange is less than 0.1%; then washing, drying, and calcination can be carried out, where the drying temperature is 60 - 130 °C, time is 2 - 12 hours, preferably drying at 80 - 120 °C for 4 - 8 hours; the calcination temperature is 500 - 600 °C, time is 2 - 8 hours, preferably calcining at 530 - 570 °C for 3 - 6 hours.

[0043] In the preparation method of the HZSM-23 molecular sieve of the present invention, all the aluminum sources required for synthesis are added during the preparation of the amorphous silica-alumina precursor, which promotes the formation of the primary structural units of the molecular sieve; and when a structure-directing agent is added to the amorphous silica-alumina precursor, the structure-directing agent will preferentially chelate with Al species and then adsorb on the surface of the formed primary structural units to achieve the pre-assembly of the molecular sieve structure and generate a large number of crystal nuclei; at the same time, it can better control the binding sites of Al atoms, which helps to obtain ZSM-23 with more weak acid sites during the later crystallization. When a silicon source is added to form the final gel and then subjected to static crystallization, a large number of crystal nuclei can rapidly grow into ZSM-23 molecular sieves with high crystallinity and small crystal grain size.

[0044] The catalyst of the present invention can be formed according to actual needs, and the shape can be cylindrical bars, three-leaf clovers, etc. During the catalyst forming process, forming aids such as peptizing acid and extrusion aids can also be added. The catalyst support of the present invention is dried and calcined by conventional methods as follows: drying at a temperature of 80-150°C for 3-10 hours and calcining at 400-800°C for 3-12 hours.

[0045] 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, the catalyst support is impregnated with a solution containing the required active components, and 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 to obtain the final catalyst.

[0046] To better illustrate the present invention, the following further illustrates 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.

[0047] In the present invention, the specific surface area and pore volume are measured by the low-temperature liquid nitrogen physical adsorption method using a Micromeritics ASAP 2405 type physical adsorption instrument in the United States.

[0048] The silicon-aluminum molar ratio is measured by chemical analysis.

[0049] The XRD pattern of the sample is collected using a Dmax2500 type X-ray diffractometer produced by Rigaku Corporation in Japan. The relative crystallinity of the molecular sieve is measured by X-ray powder diffraction (XRD). Specifically, the sum of the diffraction peak heights at about 2θ of 11.3, 19.5 - 23° in the XRD pattern of the conventional ZSM-23 molecular sieve is taken as 100% of the crystallinity. The crystallinity of H-DZSM-23-1 prepared in Example 6 of the present invention is 100, and the relative crystallinity of other samples is obtained by comparison with it.

[0050] The crystal grain size is obtained by a JSM-7500F field emission scanning electron microscope of JEOL Company in Japan.

[0051] The acid distribution (including total acid amount and strong acid content) was measured by NH3 temperature-programmed desorption (NH3-TPD), and the acid amount corresponding to the desorption temperature above 350 °C was taken as the strong acid amount. Total acid content is The acid amount corresponding to the adsorption temperature of 150 °C 。

[0052] In the present invention, wt% is the mass fraction and v% is the volume fraction.

[0053] Example 1

[0054] (1) Preparation of amorphous silica-alumina precursor

[0055] Prepare a sodium aluminate working solution with a concentration of 40 g Al2O3 / L, take a sodium silicate solution containing 28 wt% SiO2, and then dilute it into a sodium silicate working solution with a concentration of 100 g SiO2 / L. Take 150 mL of the sodium aluminate working solution and place it in a gel-forming tank, then add 60 mL of the sodium silicate working solution, control the reaction temperature at 20 °C, and introduce CO2 gas with a concentration of 50 v%. Stop introducing CO2 when the pH value reaches 10.0, then add 80 mL of the sodium silicate working solution, and then introduce the remaining CO2 gas to stabilize. After aging at 25 °C for 30 minutes, an amorphous silica-alumina precursor is obtained. Based on the total weight of silica and alumina, the content of the amorphous silica-alumina precursor in terms of silica is 70 wt%.

[0056] (2) Preparation of gel

[0057] According to the total feeding molar ratio of SiO2:Al2O3:IPA:H2O = 1:0.01:0.04:0.7:45 (IPA is the structure-directing agent isopropylamine), add isopropylamine to the amorphous silica-alumina precursor obtained in step (1), and stir at 15 °C for 0.8 hours; then, add a mixture composed of silica sol and water to it and stir evenly to obtain a silica-alumina gel.

[0058] (3) Crystallization

[0059] Pour the gel obtained in step (2) into a stainless steel autoclave and crystallize statically at 160 °C for 20 hours. After the crystallization is completed, filter, wash until neutral, dry at 120 °C, and calcine in air at 550 °C for 3 hours to obtain the molecular sieve raw powder NaZSM-23-1.

[0060] (4) Ammonium exchange

[0061] Weigh a certain amount of NaZSM-23-1 molecular sieve, place it in an ammonium nitrate solution with a concentration of 2 mol / L, with a liquid-solid ratio of 10. Stir continuously in a water bath at 80 - 90 °C for 1 hour, then filter and wash. Repeat the above operation process twice, and then place the sample in an oven at 80 - 100 °C for 8 hours of drying and calcine it in an air atmosphere at 550 °C for 3 hours to obtain HZSM-23-1. Its relative crystallinity is measured by XRD; after HZSM-23-1 is hydrothermally treated with water vapor at 600 °C for 2 hours, its relative crystallinity after hydrothermal treatment is measured, and the specific properties are shown in Table 1.

[0062] (5) Catalyst preparation

[0063] Mix 18% by weight of HZSM-23-1 molecular sieve, 38% grams of macroporous alumina (pore volume 0.8 mL / g, specific surface area 450 m 2 / g), and 22% of small-pore alumina (pore volume 0.30 mL / g, specific surface area 300 m 2 / g) with a binder composed of 10% by weight concentration of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.28), 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 them at 550 °C for 4 hours to obtain the carrier TC-1.

[0064] 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 a programmed temperature of 500 °C for 4 hours to obtain the catalyst C-1. The corresponding catalyst properties are shown in Table 2.

[0065] Example 2

[0066] (1) Preparation of amorphous silica-alumina precursor

[0067] Prepare a sodium aluminate working solution with a concentration of 40 g Al2O3 / L, take a sodium silicate solution containing 28 wt% SiO2, and then dilute it into a sodium silicate working solution with a concentration of 120 g SiO2 / L. Take 200 mL of the sodium aluminate working solution and place it in a gelling tank, then add 40 mL of the sodium silicate working solution, control the reaction temperature at 25 °C, and introduce CO2 gas with a concentration of 50 v%. Stop introducing CO2 when the pH value reaches 10.5, then add 60 mL of the sodium silicate working solution, and then introduce the remaining CO2 gas to stabilize. After aging at 20 °C for 20 minutes, an amorphous silica-alumina precursor is obtained. Based on the total weight of silicon dioxide and alumina, the content of silicon dioxide is 40 wt%.

[0068] (2) Preparation of gel

[0069] According to the total feeding molar ratio of SiO2 : Al2O3 : IPA : H2O = 1 : 0.01 : 0.04 : 0.15 : 60, isopropylamine was added to the amorphous silica-alumina precursor obtained in step (1), and stirred at 20 °C for 1 hour; then, a mixture composed of silica sol and water was added thereto and stirred evenly to obtain a silica-alumina gel.

[0070] (3)Crystallization

[0071] The gel obtained in step (2) was poured into a stainless steel autoclave and crystallized statically at 180 °C for 22 hours. After the crystallization was completed, it was filtered, washed until neutral, dried at 120 °C, and calcined in air at 550 °C for 3 hours to obtain the molecular sieve raw powder NaZSM-23-2.

[0072] (4)Ammonium exchange

[0073] The preparation process of HZSM-23-2 was the same as that in Example 1 (4), except that the NaZSM-23-1 molecular sieve was replaced by HZSM-23-2, and the specific properties are shown in Table 1.

[0074] (5) Catalyst preparation

[0075] 31% by weight of HZSM-23-2 molecular sieve, 25% of macroporous alumina (pore volume 0.9 mL / g, specific surface area 480 m 2 / g,), and 17 grams of small-pore alumina (pore volume 0.30 mL / g, specific surface area 300 m 2 / g) and an adhesive composed of 10% by weight concentration of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.28) 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.

[0076] 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 rise for 4 hours to obtain the catalyst C-2, and the corresponding catalyst properties are shown in Table 2.

[0077] Example 3

[0078] (1)Preparation of amorphous silica-alumina precursor

[0079] Prepare a sodium aluminate working solution with a concentration of 35 g Al2O3 / L. Take a sodium silicate solution containing 22 wt% SiO2 and dilute it to a sodium silicate working solution with a concentration of 65 g SiO2 / L. Take 100 mL of the sodium aluminate working solution and place it in a gelling tank, then add 40 mL of the sodium silicate working solution. Control the reaction temperature at 30 °C and introduce CO2 gas with a concentration of 50 v%. Stop introducing CO2 when the pH value reaches 11.0, then add another 60 mL of the sodium silicate working solution, and then introduce the remaining CO2 gas to stabilize. After aging at 20 °C for 30 minutes, an amorphous silica-alumina precursor is obtained. Based on the total weight of silicon dioxide and alumina, the content of silicon dioxide in the amorphous silica-alumina precursor is 35 wt%.

[0080] (2) Preparation of gel

[0081] According to the total molar ratio of SiO2 : Al2O3 : IPA : H2O = 1 : 0.008 : 0.3 : 45, add isopropylamine to the amorphous silica-alumina precursor obtained in step (1) and stir at 15 °C for 1 hour; then, add a mixture composed of silica sol and water thereto and stir evenly to obtain a silica-alumina gel.

[0082] (3) Crystallization

[0083] Pour the gel obtained in step (2) into a stainless steel autoclave and crystallize statically at 160 °C for 25 hours. After the crystallization is completed, filter and wash until neutral, then dry at 120 °C and calcine in air at 550 °C for 3 hours to obtain the molecular sieve raw powder NaZSM-23-3.

[0084] (4) Ammonium exchange and removal of template agent

[0085] The preparation process of HZSM-‐23-3 is the same as that in Example 1(4), except that the NaZSM-23-1 molecular sieve is replaced by HZSM-23-3, and the specific properties are shown in Table 1.

[0086] (5) Catalyst preparation

[0087] Mix 38% by weight of HZSM-23-3 molecular sieve, 20% of macroporous alumina (pore volume 1.1 mL / g, specific surface area 530 m 2 / g), and 16% of small-pore alumina (pore volume 0.30 mL / g, specific surface area 300 m 2 / g) with a binder composed of 10% by weight dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.28) 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-3.

[0088] 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-3. The corresponding catalyst properties are shown in Table 2.

[0089] Example 4

[0090] (1) Preparation of amorphous silica-alumina precursor

[0091] A sodium aluminate working solution with a concentration of 40 g Al2O3 / L was prepared. A sodium silicate solution containing 28 wt% SiO2 was taken and diluted to a sodium silicate working solution with a concentration of 60 g SiO2 / L. 150 mL of the sodium aluminate working solution was placed in a gelling tank, and then 500 mL of the sodium silicate working solution was added. The reaction temperature was controlled at 20 °C, and CO2 gas with a concentration of 50 v% was introduced. When the pH value reached 10.0, the introduction of CO2 was stopped. Then, 50 mL of the sodium silicate working solution was added, and the remaining CO2 gas was introduced for stabilization. After aging at 25 ºC for 20 minutes, an amorphous silica-alumina precursor was obtained. Based on the total weight of silicon dioxide and alumina, the content of silicon dioxide in the amorphous silica-alumina precursor was 50 wt%.

[0092] (2) Preparation of gel

[0093] According to the total feed molar ratio of Al2O3 : SiO2 : IPA : H2O = 1 : 0.01 : 0.4 : 45, isopropylamine was added to the amorphous silica-alumina precursor obtained in step (1), and the mixture was stirred at 15 °C for 1 hour; then, a mixture composed of fumed silica and water was added thereto and stirred evenly to obtain a silica-alumina gel.

[0094] (3) Crystallization

[0095] The gel obtained in step (2) was poured into a stainless-steel autoclave and crystallized statically at 180 °C for 24 hours. After the crystallization was completed, it was filtered, washed until neutral, dried at 120 °C, and calcined in air at 550 °C for 3 hours to obtain the molecular sieve raw powder NaZSM-23-4.

[0096] (4) Ammonium exchange

[0097] The preparation process of HZSM-23-4 was the same as that in Example 1(4), except that the NaZSM-23-1 molecular sieve was replaced with HZSM-23-4. The specific properties are shown in Table 1.

[0098] (5) Catalyst preparation

[0099] 48% by weight of HZSM-23-4 molecular sieve and 15% of macroporous alumina (pore volume 1.2 mL / g, specific surface area 550 m 2 / g), and 12% small pore alumina (pore volume 0.30 mL / g, specific surface area 300 m 2 / g) and 10% by weight concentration dilute nitric acid as binder (molar ratio of HNO3 / small pore Al2O3 0.28), put into a rolling machine for mixing and rolling, add water, roll into a paste, extrude into strips, the extruded strips are dried at 110 °C for 4 hours, and then calcined at 550 °C for 4 hours to obtain carrier TC-4.

[0100] 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 programmed temperature rise for 4 hours to obtain catalyst C-4. The corresponding catalyst properties are shown in Table 2.

[0101] Example 5

[0102] 25% by weight of Y zeolite (particle size 800 nm, Na2O content 0.25 wt%, specific surface area 790 m 2 / g, pore volume 0.58 mL / g, SiO2 / Al2O3 molar ratio 45), 32% amorphous silica-alumina (pore volume 0.97 mL / g, specific surface area 370 m 2 / g, silica weight content 30%), and 12% small pore alumina (pore volume 0.30 mL / g, specific surface area 300 m 2 / g) and 10% by weight concentration dilute nitric acid as binder (molar ratio of HNO3 / small pore Al2O3 0.21), put into a rolling machine for mixing and rolling, add water, roll into a paste, extrude into strips, the extruded strips are dried at 110 °C for 4 hours, and then calcined at 550 °C for 4 hours to obtain carrier TA.

[0103] 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 programmed temperature rise for 4 hours to obtain catalyst A. The corresponding catalyst properties are shown in Table 2.

[0104] Example 6 (refer to CN101214971A)

[0105] Prepare materials according to the molar ratio of Al2O3 in the aluminum source:SiO2 in the silicon source:NaOH in the base source:isopropylamine:H2O = 0.01:1:0.06:0.8:12. The aluminum source is sodium aluminate, the silicon source is silica sol, and the base source is sodium hydroxide to prepare a reaction mixture. First, add the aluminum source to the sodium hydroxide aqueous solution, stir evenly; add the silicon source, stir evenly; then add isopropylamine, stir evenly to obtain a reaction mixture. Transfer the prepared reaction mixture to a high-pressure reaction kettle and hydrothermally crystallize at 170 °C for 3 days. Then filter, wash until neutral, and dry at 120 °C to obtain NaDZSM-23-1 zeolite.

[0106] (2) Ammonium exchange

[0107] The preparation process of H-DZSM-23-1 is the same as that of Example 1(4), except that the NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-1, and the specific properties are shown in Table 1.

[0108] (3) Catalyst preparation

[0109] The preparation method of CC-1 catalyst is the same as that of Example 1(5), except that the H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-1, and the specific properties are shown in Table 2.

[0110] Example 7 (referring to CN102992346A)

[0111] Mix 8.12 g of H2O and 0.092 g of aluminum sulfate uniformly, then add 0.38 g of NaOH thereto, and then add 3.32 g of silica sol with a silica content of 30.5 wt% under stirring. Continue stirring until the solution becomes uniform, and then add 10 wt% ZSM-23 molecular sieve as seed crystals (the amount of seed crystals is calculated as the mass percentage of the input SiO2). Add the reaction raw materials into a polytetrafluoroethylene stainless steel autoclave, and after dynamic crystallization at 160 °C for 10 hours, filter the product by suction and dry it to obtain the NaDZSM-23-2 molecular sieve product. The reaction raw material ratio is SiO2: 0.0083Al2O3: 0.27Na2O: 35H2O.

[0112] (2) Ammonium exchange

[0113] The preparation process of H-DZSM-23-2 is the same as that of Example 1(4), except that the NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-2, and the specific properties are shown in Table 1.

[0114] (3) Catalyst preparation

[0115] The preparation method of CC-2 catalyst is the same as that of Comparative Example 1(5), except that the H-DZSM-23-1 molecular sieve is replaced by H-DZSM-23-2, and the specific properties are shown in Table 2.

[0116] Example 8

[0117] (1) Preparation of amorphous silica-alumina precursor

[0118] Prepare a sodium aluminate working solution with a concentration of 50 g Al2O3 / L. Take a sodium silicate solution containing 22 wt% SiO2 and dilute it to a sodium silicate working solution with a concentration of 100 g SiO2 / L. Take 200 mL of the sodium aluminate working solution and place it in a gel-forming tank. Then add 60 mL of the sodium silicate working solution. Control the reaction temperature at 30 °C and introduce CO2 gas with a concentration of 50 v%. Stop introducing CO2 when the pH value reaches 10.0. Then add another 40 mL of the sodium silicate working solution. Then ventilate to stabilize the remaining CO2 gas. After aging for 30 minutes at 25 °C, an amorphous silica-alumina precursor is obtained. Based on the total weight of silica and alumina, the content of the amorphous silica-alumina precursor in terms of silica is 50 wt%.

[0119] (2)Preparation of gel

[0120] According to the total molar ratio of SiO2:Al2O3:IPA:H2O = 1:0.01:0.4:30, add a mixture composed of silica sol, isopropylamine, and water to the amorphous silica-alumina precursor obtained in step (1), and stir evenly to obtain a silica-alumina gel.

[0121] (3)Crystallization

[0122] Pour the gel obtained in step (2) into a stainless steel autoclave and perform static crystallization at 160 °C for 24 hours. After the crystallization is completed, filter and wash until neutral, and then dry at 120 °C to obtain the molecular sieve raw powder. After drying, the NaDZSM-23-2 molecular sieve product is obtained. The reaction raw material ratio is SiO2: 0.0083Al2O3: 0.27Na2O: 35H2O.

[0123] (4) Ammonium exchange

[0124] The preparation process of H-DZSM-23-2 is the same as that in Example 1 (4), except that the NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-2, and the specific properties are shown in Table 1.

[0125] (5) Catalyst preparation

[0126] The preparation method of the CC-3 catalyst is the same as that in Comparative Example 1 (5), except that the H-DZSM-23-1 molecular sieve is replaced by H-DZSM-23-3, and the specific properties are shown in Table 2.

[0127] Table 1 Properties of molecular sieves

[0128]

[0129] Table 2 Physicochemical properties of catalysts

[0130]

[0131] The catalytic performance evaluation tests were carried out on the above-mentioned catalyst of the present invention and the comparative catalyst. The tests were carried out on a 200 mL small-scale hydrogenation unit, adopting a one-stage series hydrocracking process. The properties of the feedstock oil used are shown in Table 3. In the refining catalyst, the mass content of molybdenum oxide is 22%, the mass content of nickel oxide is 5%, and the balance is alumina. The operating conditions of the refining catalyst are as follows: reaction pressure 15.7 MPa, hydrogen-oil volume ratio 1000:1, liquid hourly space velocity 1.0 h -1 , reaction temperature 380 °C. The operating conditions of the cracking section and the isomerization section are as follows: reaction pressure 15.7 MPa, hydrogen-oil volume ratio 1500:1, liquid hourly space velocity 1.5 h -1 , and the catalyst evaluation results after running for 300 hours are shown in Table 4.

[0132] Table 3 Properties of Feedstock Oil

[0133]

[0134] Table 4 Catalyst Reaction Evaluation Results

[0135]

[0136] It can be seen from the evaluation results of the catalyst in Table 4 that the method of the present invention processes vacuum VGO feedstock oil, has a high selectivity for middle distillates, and the freezing point of jet fuel and the pour point of diesel are low.

Claims

1. A method for producing middle distillates, characterized in that: The method includes the following steps: The heavy raw material oil enters the hydrocracking reaction zone after desulfurization and denitrification treatment. The hydrocracking reaction zone is filled with a hydrocracking catalyst and an isomerization catalyst in sequence along the direction of the material flow. The volume ratio of the hydrocracking catalyst to the isomerization catalyst is 20:1 - 5:

2. The hydrocracking catalyst contains Y zeolite, and the properties of the Y zeolite are as follows: 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 0.3 - 0.6 mL / g; the particle size is 500 - 1000 nm, The isomerization catalyst uses HZSM-23 as the acidic component; the content of weak acid in the isomerization catalyst accounts for 75% - 90% of the total acid amount; the properties of the HZSM-23 molecular sieve are as follows: the total acid amount is 0.1 - 0.25 mmol / g, and the content of strong acid is 10% - 25%; the relative crystallinity is 95% - 120%, and the relative crystallinity after steam hydrothermal treatment is 93% - 115%. The acid distribution including the total acid amount and the strong acid amount is measured by NH3 temperature-programmed desorption, where the acid amount corresponding to the desorption temperature above 350 °C is taken as the strong acid amount.

2. The method according to claim 1, wherein: The heavy feedstock oil includes one or more of vacuum gas oil, deasphalted oil, thermal cracked gas oil, and catalytic cracked gas oil.

3. The method according to claim 1, characterized in that: The heavy feedstock oil includes coker gas oil.

4. The method according to claim 1, wherein: The heavy feedstock oil has an initial boiling point of 260 - 300 °C, a final boiling point of 500 - 600 °C, a nitrogen mass content of 1000 - 2500 ppm, and an aromatic hydrocarbon content of 40 wt% - 50 wt%.

5. The method according to claim 1, wherein: The heavy feedstock oil is desulfurized and denitrified under a hydrotreating catalyst.

6. The method according to claim 5, wherein: The reaction conditions for desulfurization and denitrification are as follows: reaction temperature 350 - 400 °C; reaction pressure 10 - 18 MPa; hydrogen-oil volume ratio 500 - 2000:1; liquid hourly space velocity 0.5 - 2.0 h -1 .

7. The method according to claim 6, wherein: The reaction conditions for desulfurization and denitrification are as follows: the reaction temperature is 360 - 390 °C; the reaction pressure is 12 - 16 MPa; the hydrogen-oil volume ratio is 800 - 1200:1; the liquid hourly space velocity is 0.8 - 1.5 h -1 .

8. The method according to claim 1, characterized in that: Based on its weight, the hydrocracking catalyst contains 10 wt% - 30 wt% of Y zeolite, 30 wt% - 60 wt% of amorphous silica-alumina, 10 wt% - 30 wt% of binder, 10 wt% - 30 wt% of Group VIB metal calculated as the oxide, and 3 wt% - 10 wt% of Group VIII metal calculated as the oxide. The Group VIB metal is molybdenum and / or tungsten, and the Group VIII metal is cobalt and / or nickel.

9. The method according to claim 8, 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.

10. The method according to claim 8, characterized in that: The weight content of SiO2 in the amorphous silica-alumina described 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.

11. The method according to claim 1, characterized in that: The reaction conditions of the hydrocracking catalyst bed in the hydrocracking reaction zone are as follows: reaction temperature 350 - 420 °C; reaction pressure 10 - 20 MPa; hydrogen-oil volume ratio 500 - 2000:1; liquid hourly space velocity 0.5 - 1.8 h -1 .

12. The method according to claim 1, characterized in that: The reaction conditions of the hydrocracking catalyst bed in the hydrocracking reaction zone are as follows: reaction temperature 360 - 390 °C; reaction pressure 13 - 16 MPa; hydrogen-oil volume ratio 800 - 1500:1; liquid hourly space velocity 0.8 - 1.5 h -1 .

13. The method according to claim 1, characterized in that: Based on its weight, the isomerization catalyst contains 10 wt% - 60 wt% of HZSM-23 molecular sieve, 10 wt% - 40 wt% of macroporous alumina, 10 wt% - 20 wt% of binder, 10 wt% - 25 wt% of Group VIB metal calculated as the oxide, and 4 wt% - 10 wt% of Group VIII metal calculated as the oxide.

14. The method according to claim 13, wherein: In the isomerization catalyst, the Group VIB metal is molybdenum and / or tungsten, and the Group VIII metal is cobalt and / or nickel.

15. The method according to claim 1, wherein: The specific surface area of the isomerization catalyst is 250-500 m 2 / g, and the pore volume is 0.30-0.70 cm 3 / g; the content of weak acid in the catalyst accounts for 80%-90% of the total acid content.

16. The method according to claim 1, wherein: The specific surface area of the isomerization catalyst is 300 to 450 m 2 / g, and the pore volume is preferably 0.37 to 0.60 cm 3 / g.

17. The method according to claim 1, wherein: The properties of the HZSM-23 molecular sieve are as follows: the total acid amount is 0.15 - 0.25 mmol / g, and the content of strong acid is 10% - 20%; the relative crystallinity is 98% - 116%, and the relative crystallinity after steam hydrothermal treatment is 95% - 114%.

18. The method according to claim 15, wherein: The HZSM-23 molecular sieve has a crystal grain size of 300 to 600 nm, a SiO2 / Al2O3 molar ratio of 80 to 130, a specific surface area of 300 to 400 m 2 / g, and a pore volume of 0.30 to 0.45 cm 3 / g.

19. The method according to claim 13, wherein: The pore volume of the macroporous alumina is 0.7 to 1.5 mL / g, and the specific surface area is 400 to 600 m 2 / g.

20. The method according to claim 13, wherein: The binder used is small-pore alumina, and the pore volume of the small-pore alumina used is 0.3 to 0.5 mL / g, and the specific surface area is 200 to 400 m 2 / g.

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