A method for producing low-freezing diesel oil

Abstract

The present invention discloses a method for producing low-freezing diesel oil. The method comprises the following steps: the feedstock oil successively passes through a hydrofining reaction zone and a hydrocracking reaction zone. In the hydrocracking reaction zone, a hydrocracking catalyst and an isomerization catalyst are successively loaded along the material flow direction. The loading volume ratio of the hydrocracking catalyst to the isomerization catalyst is 20:1 - 2:1, preferably 18:1 - 3:1, and more preferably 15:1 - 5:1. The method can maximize the production of diesel oil when processing heavy feedstock oil with a high nitrogen content, and at the same time has a good pour point reduction effect.

Description

Technical Field

[0001] The present invention relates to a method for producing low-freezing diesel oil, and more specifically to a method for maximizing the production of low-freezing diesel oil through hydrocracking. Background Art

[0002] With the increasingly active social and economic activities in winter, 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 freezing points can meet the actual use requirements. In winter, large amounts of low-freezing diesel are needed in cold northern regions, and the low-temperature fluidity (freezing point, cold filter plugging point, pour point, etc.) indicators of diesel become more important. The hydrocracking technology is the main process technology for producing high-quality diesel from heavy feedstocks.

[0003] When using the hydrocracking catalysts containing Y-type molecular sieves in CN104826646A and CN103100403A to produce diesel, the freezing point of diesel is low, especially when deep-drawing diesel or producing wide-cut diesel, this problem is more prominent. The catalysts disclosed in CN101578353A and CN106140280A can be used to produce more low-freezing-point diesel fractions, and the molecular sieve component of the used catalyst is selected as β molecular sieve. When producing diesel by these methods, a tandem process of hydrofining and hydrocracking is adopted, and the selectivity of diesel is not high and the freezing point of diesel is high. CN109988644A discloses a method for producing gasoline and low-freezing diesel by a catalyst assembly technology.

[0004] The cracking section catalyst adopts an extreme matching system, and the molecular sieves of the catalyst are respectively Y-type molecular sieve and β-type molecular

[0005] sieve, which is used to process inferior feedstocks such as vacuum gas oil to produce gasoline and diesel. The selectivity of diesel is low and the

[0006] freezing point of diesel needs to be further improved. Summary of the Invention

[0007] Aiming at the deficiencies in the prior art, the present invention provides a method for producing low-freezing diesel. When processing heavy feedstocks with high nitrogen content, the production of diesel is maximized, and at the same time, it has a good pour point reduction effect.

[0008] A method for producing low-freezing diesel, the method includes the following steps: the feedstock sequentially passes through a hydrofining reaction zone and a hydrocracking reaction zone. In the hydrocracking reaction zone, a hydrocracking catalyst and an isomerization catalyst are sequentially loaded along the material flow direction. The loading volume ratio of the hydrocracking catalyst to the isomerization catalyst is 20:1 - 2:1, preferably 18:1~3:1, and further preferably 15:1~5:1.

[0009] In the above method, the properties of the feedstock oil are as follows: heavy VGO with a distillation range of 300 - 600 °C, and the nitrogen mass content is generally 800 - 2500 ppm.

[0010] In the above method, the hydrofining catalyst loaded in the hydrofining reaction zone is a conventional hydrofining catalyst. Generally, an alumina support is used, and metals of Group VIB and Group VIII are used as the hydrohydrogenation active metal components. 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 metal of Group VIB (calculated as the oxide) is 13.0% - 25.0%, and the content of the metal of Group VIII (calculated as the oxide) is 4.0% - 7.0%. In the above method, the operating conditions of the hydrofining reaction zone are as follows: the reaction temperature is 350 - 400 °C, preferably 360 - 390 °C; the reaction pressure is 10 - 20 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 above method, based on the weight of the hydrocracking catalyst, the content of β-zeolite is 10 - 30 wt%, the content of amorphous silica-alumina is 20 - 60 wt%, the content of the binder is 10 - 40 wt%, the content of the metal of Group VIB (calculated as the oxide) is 10 wt% - 25 wt% and the content of the metal of Group VIII (calculated as the oxide) is 4 wt% - 15 wt%. The metal of Group VIB is preferably molybdenum and / or tungsten, and the metal of Group VIII is preferably cobalt and / or nickel. The weight content of SiO2 in the amorphous silica-alumina is 20% - 50%, preferably 25% - 40%. The properties of the amorphous silica-alumina are as follows: the pore volume is 0.7 - 1.2 mL / 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. For the β-zeolite, its properties are as follows: the weight content of Na2O is less than 0.3%; the silica-alumina molar ratio SiO2 / Al2O3 is 60 - 90; the specific surface area is 400 - 700 m 2 / g; the pore volume is 0.3 - 0.6 mL / g; the particle size is 500 - 1000 nm. The β-type zeolite can be prepared by the prior art.

[0012] In the above method, based on the weight of the isomerization catalyst, the content of HZSM-23 molecular sieve is 20-60 wt%, the content of macroporous alumina is 15-40 wt%, the content of binder is 10-25 wt%, the content of Group VIB metal (calculated as oxide) is 10 wt% - 25 wt% and the content of Group VIII metal (calculated as oxide) is 4 wt% - 15 wt%. The Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel. The isomerization catalyst can be prepared by the prior art or by the specific method of the present invention, and the latter is preferred.

[0013] The isomerization catalyst prepared by the specific method of the present invention has a specific surface area of 250-500 m 2 / g and a pore volume of 0.30-0.70 cm 3 / g; the specific surface area is preferably 300-450 m 2 / g and the pore volume is preferably 0.37-0.60 cm 3 / g; the content of weak acid in the catalyst accounts for 75-90% of the total acid amount; preferably, the content of weak acid accounts for 80-90% of the total acid amount. For the isomerization catalyst prepared by the method of the present invention, the high content of weak acid in the catalyst is beneficial to the isomerization reaction of the material after hydrocracking and reduces the cracking reaction.

[0014] In the above method, the operating conditions of the hydrocracking catalyst bed in the hydrocracking reaction zone are as follows: reaction temperature 360-420 °C, preferably 370-390 °C; reaction pressure 10-20 MPa, preferably 12-16 MPa; hydrogen-oil volume ratio 500-2000:1, preferably 800-1200:1; liquid hourly space velocity 0.5-2.0 h -1 -1, preferably 0.8-1.5 h -1 .

[0015] In the above method, the operating conditions of the isomerization catalyst bed in the hydrocracking reaction zone are as follows: reaction temperature 360-400 °C, preferably 370-390 °C; reaction pressure 10-20 MPa, preferably 12-16 MPa; hydrogen-oil volume ratio 500-2000:1, preferably 800-1200:1; liquid hourly space velocity 0.5-2.0 h -1 -1, preferably 1.0-1.5 h -1 .

[0016] In the method for producing low-freezing diesel provided by the present invention, a hydrocracking catalyst and an isomerization catalyst are successively loaded in the hydrocracking reaction zone. After refining, the material undergoes ring-opening and cracking reactions, i.e., primary cracking, on the β zeolite with a large number of strong acid sites, and the long-chain alkanes undergo isomerization reactions on the β zeolite with a small number of weak acid sites, which improves the selectivity of the catalyst for the diesel fraction and reduces the freezing point of the diesel. After cracking, the material enters the HZSM-23 zeolite for hydroisomerization reaction, which improves the selectivity of the wide-cut diesel while increasing the cetane number of the product and reducing the freezing point of the diesel. The method of the present invention can produce the maximum amount of low-freezing-point diesel. Detailed implementation mode

[0017] In the method of the present invention, the preparation method of the isomerization catalyst includes the following steps: Mix ZSM-23 zeolite, macroporous alumina, and a binder, form them, and then dry and calcine to make a carrier; then load a hydrogenation active metal. 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, impregnate the catalyst carrier 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 isomerization catalyst.

[0018] In the preparation method of the isomerization catalyst of the present invention, 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.

[0019] In the preparation method of the isomerization catalyst of the present invention, the binder can adopt the commonly used binders in the art, preferably small-pore alumina. The pore volume of the used small-pore alumina is 0.3 to 0.5 mL / g, and the specific surface area is 200 to 400 m 2 / g.

[0020] In the preparation method of the isomerization catalyst of the present invention, the preparation of ZSM-23 zeolite refers to the preparation method of HZSM-23 zeolite described in CN202210011752.2. The preparation steps of the HZSM-23 zeolite are as follows:

[0021] (1) Prepare a mixed solution containing a structure-directing agent, amorphous silica-alumina, or an amorphous silica-alumina precursor;

[0022] (2) Add a supplementary silicon source to the material in step (1);

[0023] (3) The material in step (2) is crystallized, filtered, washed, dried, and calcined to obtain ZSM-23 zeolite.

[0024] (4) Perform ammonium exchange on the zeolite obtained in (3) to obtain HZSM-23 zeolite.

[0025] In the above method step (1), the structure directing agent is one or more of isopropylamine, pyrrolidine, N,N-dimethylformamide, and dimethylamine.

[0026] In the above method step (1), the molar ratio of silicon (calculated as silicon dioxide):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):structure directing agent is 1:(10 - 100), preferably 1:(15 - 85), and more preferably 1:(20 - 65).

[0027] In the above method step (1), an amorphous silica-alumina precursor mixture is prepared by a carbonization method, and then a structure directing agent is added to the amorphous silica-alumina precursor mixture.

[0028] A non-limiting preparation process of the amorphous silica-alumina precursor mixture in the embodiments of the present invention 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.

[0029] In the above preparation process of the amorphous silica-alumina precursor mixture, the remaining part of the silicon-containing compound solution accounts for 30 - 90 wt% of the total silicon-containing compound solution added in terms of silicon dioxide, preferably 40 - 80 wt%.

[0030] 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.

[0031] 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.

[0032] In the above preparation process of the amorphous silica-alumina precursor mixture, based on the mass of A12O3, 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%.

[0033] During the preparation of the above amorphous silica-alumina precursor mixture, the aging time is 5 to 60 minutes, preferably 10 to 30 minutes; the aging temperature is 10 to 40 °C, preferably 15 to 35 °C.

[0034] In step (1) of the above method, the mixed solution is stirred at 10 to 35 °C for 0.2 to 1.5 hours, preferably stirred at 10 to 25 °C for 0.5 to 1 hour.

[0035] 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 to 0.0125):(30 to 60) and SDA (structure directing agent) / SiO2 = 0.10 to 1.8, a supplementary silicon source is added to the material of step (1).

[0036] In step (2) of the above method, the silicon source is one or more of fumed silica, silica sol and water glass.

[0037] In step (3) of the above method, the crystallization conditions are: crystallization at 160 to 180 °C for 10 to 48 hours; drying temperature is 80 to 120 °C, time is 4 to 8 hours; calcination temperature is 500 to 600 °C, time is 2 to 8 hours.

[0038] In step (4) of the above method, ammonium exchange is carried out by a conventional method, such as single or multiple ammonium exchanges. 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. Among them, the drying temperature is 60 to 130 °C, time is 2 to 12 hours, preferably drying at 80 to 120 °C for 4 to 8 hours; the calcination temperature is 500 to 600 °C, time is 2 to 8 hours, preferably calcination at 530 to 570 °C for 3 to 6 hours.

[0039] The properties of the HZSM-23 molecular sieve are as follows: the crystal grain size is 300 to 600 nm, the SiO2 / Al2O3 molar ratio is 80 to 130, the specific surface area is 300 to 400 m 2 / g, the pore volume is 0.30 to 0.45 cm 3 / g. The total acid amount is 0.1 to 0.25 mmol / g, the strong acid content 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, the strong acid content is 10 to 20%; the relative crystallinity is 98 to 116%, and the relative crystallinity after steam hydrothermal treatment is 95 to 114%.

[0040] The catalyst of the present invention 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 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.

[0041] In the preparation method of HZSM-23 molecular sieve of the present invention, all the aluminum sources required for synthesis are added when preparing 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 is helpful for the later crystallization to obtain ZSM-23 with more weak acid sites. When the 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.

[0042] To better illustrate the present invention, the following examples and comparative examples are used to further illustrate the present invention. However, the scope of the present invention is not limited to the scope of these examples.

[0043] 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.

[0044] The silicon-aluminum molar ratio is measured by chemical analysis.

[0045] The XRD pattern of the sample is collected by 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 = 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.

[0046] The crystal grain size is obtained by a JSM-7500F field emission scanning electron microscope of JEOL Company in Japan.

[0047] The acid distribution (including total acid amount and strong acid content) is measured by NH3 temperature-programmed desorption (NH3-TPD). Among them, the acid amount corresponding to the desorption temperature above 350 °C is used as the strong acid amount. Less than 350 °C is weak acid, The total acid content is The acid amount corresponding to the adsorption temperature of 150 °C 。

[0048] In the present invention, wt% represents mass fraction and v% represents volume fraction.

[0049] Example 1

[0050] (1) Preparation of amorphous silica-alumina precursor

[0051] Prepare a sodium aluminate working solution with a concentration of 40 g Al2O3 / L. Take a sodium silicate solution containing 28 wt% SiO2 and dilute it to 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 gelation 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 silicon dioxide and alumina, the content of silicon dioxide in the amorphous silica-alumina precursor is 70 wt%.

[0052] (2) Preparation of gel

[0053] 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 thereto and stir evenly to obtain a silica-alumina gel.

[0054] (3) Crystallization

[0055] Pour the gel obtained in step (2) into a stainless steel autoclave and carry out static crystallization at 160 °C for 20 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-23-1.

[0056] (4) Ammonium exchange

[0057] Weigh a certain amount of NaZSM-23-1 molecular sieve, place it in a ammonium nitrate solution with a concentration of 2 mol / L, 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 to dry for 8 hours and calcine in an air atmosphere at 550 °C for 3 hours to obtain HZSM-23-1, and measure its relative crystallinity by XRD; after HZSM-23-1 is hydrothermally treated with water vapor at 600 °C for 2 hours, measure its relative crystallinity after hydrothermal treatment, and the specific properties are shown in Table 1.

[0058] (5) Catalyst preparation

[0059] HZSM-23-1 molecular sieve accounting for 22% of the catalyst weight, 40% of macroporous alumina (pore volume 0.9 mL / g, specific surface area 450 m 2 / g), and 17% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) and an adhesive composed of 10% weight concentration dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.26) are put into a rolling mill for mixing and rolling, water is added, 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-1.

[0060] 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 for 4 hours with a programmed temperature rise to obtain the catalyst C-1. The corresponding catalyst properties are shown in Table 2.

[0061] Example 2

[0062] (1) Preparation of amorphous silica-alumina precursor

[0063] Prepare a sodium aluminate working solution with a concentration of 40 g Al2O3 / L, take a sodium silicate solution containing 28 wt% SiO2, and 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 gel-forming tank, then add 40 mL of the sodium silicate working solution, control the reaction temperature at 25 °C, 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%.

[0064] (2) Preparation of gel

[0065] According to the total feeding molar ratio of SiO2 : Al2O3 : IPA : H2O = 1 : 0.01 : 0.04 : 0.15 : 60, isopropylamine is 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 is added thereto and stirred evenly to obtain a silica-alumina gel.

[0066] (3) Crystallization

[0067] Pour the gel obtained in step (2) into a stainless-steel autoclave and perform static crystallization at 180 °C for 22 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 zeolite powder NaZSM-23-2.

[0068] (4)Ammonium exchange

[0069] The preparation process of HZSM-23-2 is the same as that in Example 1 (4), except that the NaZSM-23-1 zeolite is replaced by HZSM-23-2, and the specific properties are shown in Table 1.

[0070] (5)Catalyst preparation

[0071] Mix 30% by weight of HZSM-23-2 zeolite, 32% of macroporous alumina (pore volume 1.0 mL / g, specific surface area 470 m 2 / g), and 15% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) with a binder composed of 12% by weight of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.26) 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.

[0072] 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.

[0073] Example 3

[0074] (1)Preparation of amorphous silica-alumina precursor

[0075] Prepare a sodium aluminate working solution with a concentration of 35 g Al2O3 / L, take a sodium silicate solution containing 28 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 gel-forming 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 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 is 35 wt%.

[0076] (2)Preparation of gel

[0077] According to the total molar ratio of SiO2 : Al2O3 : IPA : H2O = 1 : 0.008 : 0.3 : 45, isopropylamine was added to the amorphous silica-alumina precursor obtained in step (1), and stirred at 15 °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.

[0078] (3)Crystallization

[0079] The gel obtained in step (2) was poured into a stainless steel autoclave and crystallized statically at 160 °C for 25 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 powder NaZSM-23-3.

[0080] (4)Ammonium exchange

[0081] The preparation process of HZSM-23-3 was the same as that in Example 1(4), except that the NaZSM-23-1 molecular sieve was replaced by HZSM-23-3, and the specific properties are shown in Table 1.

[0082] (5)Catalyst preparation

[0083] 40% by weight of HZSM-23-3 molecular sieve, 23% of macroporous alumina (pore volume 1.1 mL / g, specific surface area 500 m 2 / g), and 12% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) and an adhesive composed of 10% weight concentration dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.26) were put into a rolling mill for mixing and rolling, 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-3.

[0084] 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-3, and the corresponding catalyst properties are shown in Table 2.

[0085] Example 4

[0086] (1)Preparation of amorphous silica-alumina precursor

[0087] Prepare a sodium aluminate working solution with a concentration of 40 g Al2O3 / L. Take a sodium silicate solution containing 28 wt% SiO2 and dilute it to a sodium silicate working solution with a concentration of 60 g SiO2 / L. Take 150 mL of the sodium aluminate working solution and place it in a gelling tank, then add 500 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 another 50 mL of the sodium silicate working solution, and then introduce the remaining CO2 gas to stabilize. After aging for 20 minutes at 25 °C, an amorphous silica-alumina precursor is obtained. The content of the amorphous silica-alumina precursor based on the total weight of silica and alumina is 50 wt% in terms of silica.

[0088] (2)Preparation of gel

[0089] According to the total feeding molar ratio of Al2O3 : SiO2 : IPA : H2O = 1 : 0.01 : 0.4 : 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 fumed silica and water thereto and stir evenly to obtain a silica-alumina gel.

[0090] (3)Crystallization

[0091] Pour the gel obtained in step (2) into a stainless steel autoclave and crystallize statically at 180 °C for 24 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-23-4.

[0092] (4)Ammonium exchange

[0093] The preparation process of HZSM-23-4 is the same as that in Example 1 (4), except that the NaZSM-23-1 molecular sieve is replaced by HZSM-23-4, and the specific properties are shown in Table 1.

[0094] (5)Catalyst preparation

[0095] Mix 45% by weight of HZSM-23-4 molecular sieve, 21% of macroporous alumina (pore volume 1.2 mL / g, specific surface area 560 m 2 / g), and 11% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) with an adhesive composed of 17% by weight of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 is 0.26) 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 support TC-4.

[0096] 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 500 °C for 4 hours with a programmed temperature increase to obtain catalyst C-4. The corresponding catalyst properties are shown in Table 2.

[0097] Example 5

[0098] 20% by weight of β zeolite (particle size 800 nm, Na2O content 0.25 wt%, specific surface area 620 m 2 / g, pore volume 0.57 mL / g, SiO2 / Al2O3 molar ratio 80), 35% of amorphous silica-alumina (pore volume 0.9 mL / g, specific surface area 390 m 2 / g, silica weight content 30%), and 18% of small-pore alumina (pore volume 0.35 mL / g, specific surface area 330 m 2 / g) and a binder composed of 10% by weight concentration of dilute nitric acid (molar ratio of HNO3 / small-pore Al2O3 0.30) were put into a rolling mill, mixed and rolled, water was added, 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 carrier TA.

[0099] 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 500 °C for 4 hours with a programmed temperature increase to obtain catalyst A.

[0100] Example 6 (refer to CN101214971A)

[0101] Prepare materials according to the molar ratio of Al2O3 in the aluminum source:SiO2 in the silicon source:NaOH in the alkali 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 alkali 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 and wash until neutral, and dry at 120 °C to obtain NaDZSM-23-1 zeolite.

[0102] (2) Ammonium exchange

[0103] The preparation process of H-DZSM-23-1 is the same as that of Example 1(4), except that NaZSM-23-1 zeolite is replaced by NaDZSM-23-1. The specific properties are shown in Table 1.

[0104] (3) Catalyst preparation

[0105] The preparation method of the 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.

[0106] Example 7 (referring to CN102992346A)

[0107] 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 seeds (the amount of seeds 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 obtain the NaDZSM-23-2 molecular sieve product after drying. The reaction raw material ratio is SiO2: 0.0083Al2O3: 0.27Na2O: 35H2O.

[0108] (2) Ammonium exchange

[0109] 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.

[0110] (3)Catalyst preparation

[0111] The preparation method of the CC-2 catalyst is the same as that of Example 1(5), except that the H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-2, and the specific properties are shown in Table 2.

[0112] Example 8

[0113] (1)Preparation of amorphous silica-alumina precursor

[0114] Prepare a sodium aluminate working solution with a concentration of 50 g Al2O3 / L, take a sodium silicate solution containing 28 wt% SiO2, and dilute it into 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 40 mL of the sodium silicate working solution, and then ventilate the remaining CO2 gas to stabilize. After aging at 25 ºC for 30 minutes, obtain an amorphous silica-alumina precursor. The amorphous silica-alumina precursor is based on the total weight of silica and alumina, and the content calculated as silica is 50 wt%.

[0115] (2)Preparation of gel

[0116] According to the total molar ratio of SiO2 : Al2O3 : IPA : H2O = 1 : 0.01 : 0.4 : 30, add the mixture composed of silica sol, isopropylamine, and water to the amorphous silica-alumina precursor obtained in step (1), stir evenly to obtain a silica-alumina gel.

[0117] (3) Crystallization

[0118] 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.

[0119] (4) Ammonium exchange

[0120] 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.

[0121] (5) Catalyst preparation

[0122] The preparation method of the CC-3 catalyst is the same as that in Example 1 (5), except that the H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-3, and the specific properties are shown in Table 2.

[0123] Table 1 Properties of molecular sieves

[0124]

[0125] Table 2 Physicochemical properties of the catalyst

[0126]

[0127] Perform a catalytic performance evaluation test on the catalyst of the present invention and the comparative catalyst above. The test is carried out on a 200 mL small-scale hydrogenation unit, adopting a one-stage series hydrocracking process, and the properties of the feedstock oil used are shown in Table 3. The mass composition of the refining catalyst: the content of molybdenum oxide is 18%, and the content of nickel oxide is 6%. The operating conditions of the refining catalyst are as follows: reaction pressure 13.8 MPa, hydrogen-oil volume ratio 1000:1, liquid hourly space velocity 1.0 h -1 , reaction temperature 375 °C. The operating conditions of the cracking section and the isomerization section are as follows: reaction pressure 13.8 MPa, hydrogen-oil volume ratio 1000:1, liquid hourly space velocity 1.5 h -1 , and the catalyst evaluation results after running for 300 hours are shown in Table 4.

[0128] Table 3 Properties of feedstock oil

[0129]

[0130] Table 4 Catalyst reaction evaluation results

[0131]

[0132] 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 high diesel selectivity, good product properties, especially low diesel pour point.

Claims

1. A method for producing low-freezing diesel oil, characterized in that: The method includes the following: the feedstock oil passes through a hydrofining reaction zone and a hydrocracking reaction zone in sequence. In the hydrocracking reaction zone, a hydrocracking catalyst and an isomerization catalyst are loaded in sequence along the material flow direction. The loading volume ratio of the hydrocracking catalyst to the isomerization catalyst is 20:1 - 2:1; The hydrocracking catalyst comprises beta zeolite; the beta 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; the particle size is 500 to 1000 nm; The isomerization catalyst includes HZSM-23 molecular sieve; the properties of the HZSM-23 molecular sieve are as follows: the crystal grain size is 300-600 nm, the SiO2 / Al2O3 molar ratio is 80-130, the specific surface area is 300-400 m 2 / g, the pore volume is 0.30-0.45 cm 3 / g; the total acid amount is 0.1-0.25 mmol / g, the strong acid content is 10-25%; the relative crystallinity is 95-120%, and the relative crystallinity after steam hydrothermal treatment is 93-115%; The content of weak acid in the isomerization catalyst accounts for 75% - 90% of the total acid content; The acid distribution including the total acid content and the strong acid content is measured by NH3 temperature-programmed desorption. Among them, the acid amount corresponding to the desorption temperature above 350 °C is used as the strong acid amount, and the acid amount less than 350 °C is the weak acid.

2. The method according to claim 1, wherein: The loading volume ratio of the hydrocracking catalyst to the isomerization catalyst is 18:1 - 3:

1.

3. The method according to claim 1, wherein: The loading volume ratio of the hydrocracking catalyst to the isomerization catalyst is 15:1 - 5:

1.

4. The method according to claim 1, characterized in that: The properties of the feedstock oil are as follows: heavy VGO with a distillation range of 300 - 600 °C, and the nitrogen mass content is 800 - 2500 ppm.

5. The method according to claim 1, characterized in that: The hydrofining catalyst loaded in the hydrofining reaction zone uses alumina as the carrier and metals of Group VIB and Group VIII as the hydrohydrogenation active metal components.

6. The method according to claim 1, wherein: The operating conditions of the hydrofining reaction zone are as follows: reaction temperature 350 - 400 °C; reaction pressure 10 - 20 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, characterized in that: The operating conditions of the hydrofining reaction zone 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, wherein: Based on its weight, the content of β zeolite in the hydrocracking catalyst is 10 - 30 wt%, the content of amorphous silica-alumina is 20 - 60 wt%, the content of the binder is 10 - 40 wt%, 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%.

9. The method according to claim 8, wherein: The weight content of SiO2 in the amorphous silica-alumina 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: Based on its weight, the content of HZSM-23 zeolite in the isomerization catalyst is 20 - 60 wt%, the content of macroporous alumina is 15 - 40 wt%, the content of the binder is 10 - 25 wt%, 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%.

12. The method according to claim 11, characterized in that: The isomerization catalyst has a specific surface area of 250 to 500 m 2 / g and a pore volume of 0.30 to 0.70 cm 3 / g; the content of weak acid in the catalyst accounts for 80% to 90% of the total acid content.

13. The method according to claim 11, characterized in that: The isomerization catalyst has a specific surface area of 300 to 450 m 2 / g and a pore volume of 0.37 to 0.60 cm 3 / g.

14. The method according to claim 1, wherein: The operating conditions of the hydrocracking catalyst bed in the hydrocracking reaction zone are as follows: reaction temperature 360 - 420 °C; reaction pressure 10 - 20 MPa; hydrogen-oil volume ratio 500 - 2000:1; liquid hourly space velocity 0.5 - 2.0 h -1 .

15. The method according to claim 1, characterized in that: The operating conditions of the hydrocracking catalyst bed in the hydrocracking reaction zone are as follows: reaction temperature 370 - 390 °C; reaction pressure 12 - 16 MPa; hydrogen-oil volume ratio 800 - 1200:1; liquid hourly space velocity 0.8 - 1.5 h -1 .

16. The method according to claim 1, characterized in that: The operating conditions of the isomerization catalyst bed in the hydrocracking reaction zone are as follows: reaction temperature 360 - 400 °C; reaction pressure 10 - 20 MPa; hydrogen-oil volume ratio 500 - 2000:1; liquid hourly space velocity 0.5 - 2.0 h -1 .

17. The method according to claim 1, characterized in that: The operating conditions of the isomerization catalyst bed in the hydrocracking reaction zone are as follows: reaction temperature 370 - 390 °C; reaction pressure 12 - 16 MPa; hydrogen-oil volume ratio 800 - 1200:1; liquid hourly space velocity 1.0 - 1.5 h -1 .

Images