A method for maximizing the production of aviation kerosene through hydroconversion of straight-run diesel

Abstract

The present invention discloses a method for maximizing the production of jet fuel by hydroconversion of straight-run diesel. The method comprises loading a hydroisomerization catalyst into a hydrocracking reaction zone to isomerize the hydrocracking product. The isomerization catalyst contains an HZSM-23 molecular sieve having a grain size of 300 to 600 nm, a SiO2 / Al2O3 molar ratio of 80 to 130, and a specific surface area of 300 to 400 m2. 2 / g, pore volume 0.30~0.45 cm 3 / g, a total acid content of 0.1-0.25 mmol / g, a strong acid content of 10-25%, a relative crystallinity of 95-120%, and a relative crystallinity of 93-115% after steam hydrothermal treatment. The method is suitable for hydrocracking straight-run diesel to produce more jet fuel, and has the characteristics of high jet fuel yield and good product quality, especially a low freezing point.

Description

Technical Field

[0001] The present invention relates to a method for maximizing the production of aviation kerosene by hydrogenating straight-run diesel, and in particular to a method for maximizing the production of high-quality aviation kerosene by hydrogenating straight-run diesel. Background Art

[0002] Given the special strategic value of jet fuel and its rapidly growing market demand, diesel demand in bulk commodity road transportation and major industrial sectors will be saturated or shrink. In order to maximize efficiency and seek to adjust its product structure and solve the imbalance between diesel and jet fuel supply and demand, Chinese refineries will inevitably need to convert some of their excess diesel fractions into jet fuel products. While reducing diesel production, they will also produce some jet fuel products with strong market demand, thereby optimizing the integrated refining and chemical development of their enterprises.

[0003] Refining companies can utilize existing medium-pressure diesel hydrotreating units or higher-grade medium-pressure hydrotreating units, and after adaptive modification, use straight-run diesel as the main raw material to hydrocracking to increase the production of high-quality jet fuel products.

[0004] Hydrocracking technology is the primary process for hydroconverting straight-run diesel into high-quality jet fuel. It primarily utilizes a tandem hydrorefining and hydrocracking process. The cracking centers in the cracking catalyst are provided by molecular sieves, and the key cracking components in these catalysts are typically Y and β molecular sieves. Because the smoke point of 3# jet fuel is greater than 25, the insufficient aromatic saturation capacity of β molecular sieves results in a relatively low smoke point. Currently, this type of hydrocracking catalyst is typically based on modified Y molecular sieves.

[0005] CN201610289569.3 discloses a hydrocracking method. This method involves contacting a straight-run diesel feedstock with a hydrocracking catalyst to carry out a hydrocracking reaction. The resulting hydrocracking products are separated to produce heavy naphtha, diesel, jet fuel, and hydrotreated tail oil. The hydrocracking catalyst uses a modified Y-type molecular sieve, amorphous silica-alumina, and alumina as supports. The method exhibits high catalytic activity, high jet fuel yield, and improved product quality.

[0006] When the above catalyst is used in the hydrocracking process of straight-run diesel to produce more aviation kerosene, when the aviation kerosene distillation range is widened, there are generally problems of low jet kerosene product yield and poor quality to varying degrees, especially when the freezing point is >47°C, and 3# aviation kerosene (jet fuel) cannot be directly produced.

[0007] The hydrocarbon molecules in straight-run diesel have relatively large carbon numbers, with paraffins having a high freezing point and cyclic hydrocarbons having a low smoke point. This requires hydrocracking catalysts with excellent cracking and isomerization properties, capable of converting the higher-freezing-point components in the feedstock into lower-freezing-point products while maintaining a high jet fuel yield. Furthermore, hydrocracking catalysts must possess strong aromatic hydrogenation and ring-opening capabilities to ensure that the smoke point and naphthylene content of the jet fuel product meet jet fuel quality standards. Therefore, the selection of a hydrocracking catalyst system is crucial. Summary of the Invention

[0008] To address the problems in the prior art, the present invention provides a method for maximizing the production of jet fuel by hydrocracking straight-run diesel. The method is suitable for hydrocracking straight-run diesel to produce more jet fuel, and has high jet fuel yield and good product quality, particularly a low freezing point.

[0009] A method for maximizing the production of jet fuel by hydroconversion of straight-run diesel, comprising loading a hydroisomerization catalyst (referred to as catalyst 2, hereinafter referred to as the same) into a hydrocracking reaction zone to subject the hydrocracking product to an isomerization reaction, wherein the isomerization catalyst comprises an HZSM-23 molecular sieve having a grain size of 300 to 600 nm, a SiO2 / Al2O3 molar ratio of 80 to 130, and a specific surface area of 300 to 400 m2. 2 / g, pore volume 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 water vapor hydrothermal treatment is 93~115%; preferably, the total acid amount is 0.15~0.25 mmol / g, the strong acid content is 10~20%; the relative crystallinity is 98~116%, and the relative crystallinity after water vapor hydrothermal treatment is 95~114%.

[0010] According to the method of the present invention, the density of the straight-run diesel is 0.84-0.87 g / cm 3 , dry point is 350~380℃, S content is 10000~30000µg / g, N content is 200-1000µg / g.

[0011] According to the method of the present invention, the isomerization catalyst, based on the weight of the catalyst, has an HZSM-23 molecular sieve content of 30 to 60 wt%, a macroporous alumina content of 10 to 40 wt%, a binder content of 10 to 30 wt%, a Group VIB metal content of 10 wt% to 25 wt% in terms of oxide, and a Group VIII metal content of 4 wt% to 10 wt% (in terms of oxide). The Group VIB metal is preferably molybdenum and / or tungsten, and the Group VIII metal is preferably cobalt and / or nickel.

[0012] According to the method of the present invention, the specific surface area of the isomerization catalyst is 250-500 m 2 / g, 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 weak acid content in the catalyst accounts for 75-90% of the total acid content; preferably, the weak acid content accounts for 80-90% of the total acid content.

[0013] According to the method of the present invention, straight-run diesel enters the hydrocracking reaction zone after hydrotreatment, and the operating conditions of the hydrotreatment are as follows: reaction temperature 340-380°C, total reaction pressure 6-10 MPa, liquid hourly volume space velocity 0.5-3h -1 The hydrogen-to-oil volume ratio is 500:1 to 1500:1. The properties of the hydroprocessing catalyst are as follows: an alumina support is generally used, and the hydrogenation-active metal components are Group VIB and Group VIII metals. The Group VIB metal (preferably molybdenum and / or tungsten) oxide content is 13.0% to 25.0%, and the Group VIII metal (preferably cobalt and / or nickel) oxide content is 4.0% to 7.0%, based on the weight of the catalyst.

[0014] According to the method of the present invention, the hydrocracking catalyst (i.e., catalyst 1, the same below) loaded in the hydrocracking reaction zone has, based on its weight, a Y molecular sieve content of 10-30 wt%, amorphous silica-alumina content of 30-60 wt%, a binder content of 10-30 wt%; a VIB group metal content (calculated as oxide) of 10 wt% to 30 wt% and a Group VIII metal content (calculated as oxide) of 4 wt% to 10 wt%, wherein the Y molecular sieve has the following properties: a Na2O weight content of less than 0.3%; a silicon-aluminum molar ratio SiO2 / Al2O3 of 20-35; a specific surface area of 600-900 m 2 / g; pore volume is 0.3~0.6mL / g; particle size is 500~1000nm, the VIB group metal is preferably molybdenum and / or tungsten, and the group VIII metal is preferably cobalt and / or nickel.

[0015] According to the method of the present invention, the volume ratio of the hydrocracking catalyst to the isomerization catalyst loaded in the hydrocracking reaction zone is 20:1-5:2.

[0016] According to the method of the present invention, the operating conditions of the cracking stage are as follows: reaction pressure 5-15 MPa, hydrogen-oil volume ratio 500-1000:1, liquid hourly volume space velocity 0.5-1.2h -1 .

[0017] The cracking stage catalyst of the method provided by the present invention is composed of a catalyst 1 and a catalyst 2 loaded in layers. The catalysts 1 and 2 are loaded from top to bottom in a cracking reactor. The loading of the catalysts 1 and 2 allows the feedstock oil entering the reactor to contact the catalysts 1 and 2 in sequence. Macromolecules such as polycyclic cycloalkanes and aromatic hydrocarbons in the feedstock first pass through the catalyst 1 above the cracking bed layer, and then undergo ring opening and cracking reactions on the Y molecular sieve having a large amount of strong acid and medium-strong acid sites for primary cracking. This reduces the probability of over-cracking and secondary cracking, and improves the yield of the jet fuel distillate oil of the catalyst. Due to the strong aromatic hydrogenation saturation and ring opening capabilities of the Y molecular sieve, the smoke point and naphthalene hydrocarbon content of the jet fuel product can meet the jet fuel quality index requirements.

[0018] Some of the long-chain alkanes then undergo hydroisomerization in the HZSM-23 molecular sieve, rich in weak acid sites, on catalyst 2 below the cracking bed, without cracking. This further lowers the freezing point of the jet fuel and increases the catalyst's jet fuel yield. The present method, used for producing jet fuel from straight-run diesel hydrocracking, broadens the jet fuel distillation range, and offers high jet fuel yields and excellent product quality, particularly a low freezing point. DETAILED DESCRIPTION

[0019] The preparation method of the hydrogenation catalyst 1 of the present invention includes the preparation of a carrier and the loading of a hydrogenation active metal, wherein the preparation method of the catalyst 1 carrier includes: mixing and shaping Y molecular sieve, amorphous silica-alumina and a binder, and then drying and calcining to prepare the catalyst carrier.

[0020] In the carrier of the hydrogenation catalyst 1 of the present invention, the weight content of SiO2 in the amorphous silica-alumina is 20% to 50%, preferably 25% to 40%, and the properties of the amorphous silica-alumina are as follows: pore volume is 0.7 to 1.2 mL / g, preferably 0.8 to 1.0 mL / g, specific surface area is 300 to 500 m 2 / g, preferably 350 to 500 m 2 / g.

[0021] In the carrier of the hydrogenation catalyst 1 of the present invention, the Y-type molecular sieve can be prepared using existing technology.

[0022] The preparation method of the hydrogenation catalyst 2 of the present invention includes the preparation of a carrier and the loading of a hydrogenation active metal, wherein the preparation method of the catalyst 2 carrier includes: mixing and shaping HZSM-23 molecular sieve, macroporous alumina and a binder, and then drying and calcining to prepare a catalyst carrier.

[0023] In the catalyst 2 carrier of the present invention, the pore volume of the macroporous alumina is 0.7-1.5 mL / g, and the specific surface area is 400-600 m 2 / g.

[0024] In the catalyst carrier of the present invention, the binder can be a commonly used binder in the art, preferably a small-pore alumina. 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.

[0025] The preparation of the HZSM-23 molecular sieve described in Catalyst 2 of the present invention refers to the preparation method of CN202210011752.2, including the following preparation steps:

[0026] (1) preparing a mixed solution containing a structure directing agent, amorphous silicon aluminum or an amorphous silicon aluminum precursor;

[0027] (2) adding a supplementary silicon source to the material of step (1);

[0028] (3) The material of step (2) is crystallized, filtered, washed, dried and calcined to obtain ZSM-23 molecular sieve.

[0029] (4) The molecular sieve obtained in (3) is subjected to ammonium exchange to obtain HZSM-23 molecular sieve.

[0030] In step (1) of the above method, the structure directing agent is one or more of isopropylamine, pyrrolidine, N,N-dimethylformamide, and dimethylamine.

[0031] In step (1) of the above method, the molar ratio of silicon (calculated as silicon oxide) 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 structure directing agent is 1: (10-100), preferably 1: (15-85), and more preferably 1: (20-65).

[0032] In step (1) of the above method, a carbonization method is used to prepare an amorphous silicon-aluminum precursor mixture, and then a structure directing agent is added to the amorphous silicon-aluminum precursor mixture.

[0033] A non-limiting process for preparing an amorphous silicon-aluminum precursor mixture in an embodiment of the present invention is as follows: prepare an aluminum source (preferably sodium aluminate) solution and a silicon-containing compound solution separately; mix the sodium aluminate solution with part of the silicon-containing compound solution, and introduce CO2 gas to form a gel; when the volume of the introduced CO2 gas accounts for 50~100% of the total volume introduced, preferably 70~90%, add the remaining part of the silicon-containing compound solution, and then introduce the remaining CO2 gas, and optionally age it to obtain an amorphous silicon-aluminum precursor mixture.

[0034] During the preparation of the amorphous silicon-aluminum precursor mixed solution, the remaining portion of the silicon-containing compound solution, calculated as silicon dioxide, accounts for 20-90 wt %, preferably 30-80 wt %, of the total amount of the added silicon-containing compound solution, calculated as silicon dioxide.

[0035] During the preparation of the amorphous silicon-aluminum precursor mixture, the reaction temperature for gelation is 10-40° C., preferably 15-35° C., and the pH value after gelation is controlled to be 9-12.

[0036] During the preparation of the amorphous silicon-aluminum precursor mixed solution, the silicon-containing compound solution is water glass and / or sodium silicate solution.

[0037] During the preparation of the above-mentioned amorphous silicon-aluminum precursor mixture, the concentration of the aluminum source solution is 15~60 g Al2O3 / L based on the mass of Al2O3, the concentration of the silicon-containing compound solution is 40~260 g SiO2 / L based on the mass of SiO2, and the concentration of the CO2 gas is 30~60 v%.

[0038] During the preparation of the amorphous silicon-aluminum precursor mixture, the aging time is 5 to 60 minutes, preferably 10 to 30 minutes; and the aging temperature is 10 to 40°C, preferably 15 to 35°C.

[0039] In step (1) of the above method, the mixed solution is stirred at 10-35°C for 0.2-1.5 hours, preferably at 10-25°C for 0.5-1 hour.

[0040] In step (2) of the above method, based on the aluminum (calculated as alumina) in the mixed solution of step (1), a supplementary silicon source is added to the material of step (1) at a total feed molar ratio of SiO2:Al2O3:H2O=1:(0.005~0.0125):(30~60) and SDA (structure directing agent) / SiO2=0.10~1.8.

[0041] In step (2) of the above method, the silicon source is one or more of fumed silica, silica sol and water glass.

[0042] In step (3) of the above method, the crystallization conditions are: crystallization at 160-180°C for 10-48 hours; drying temperature at 80-120°C for 4-8 hours; and calcination temperature at 500-600°C for 2-8 hours.

[0043] In step (4) of the above method, ammonium exchange is carried out by conventional methods, such as one or more ammonium exchanges, and the Na2O content in the HZSM-23 molecular sieve after ammonium exchange is less than 0.1%; washing, drying and calcination can then be carried out, wherein the drying temperature is 60~130℃ and the time is 2~12 hours, preferably drying at 80~120℃ for 4~8 hours; the calcination temperature is 500~600℃ and the time is 2~8 hours, preferably calcining at 530~570℃ for 3~6 hours.

[0044] In the preparation process of the ZSM-23 molecular sieve of the present invention, mesoporous amorphous silica is prepared in the early stage with the assistance of a surfactant, and is used as a silicon source for the later synthesis of the ZSM-23 molecular sieve. The amorphous silica generated in this process has a mesoporous structure and is not highly crystallized into a stable crystalline form. After being treated in a further low-concentration alkaline solution for a period of time, some of the -Si-O- bonds are opened, which helps to form -Si-O-Al- bonds in the molecular sieve structure. However, most of the mesoporous structure is retained. Under the action of a microporous template agent in the later stage, a microporous structure is generated in a suitable ZSM-23 molecular sieve synthesis system, and the mesoporous structure is further crystallized and stabilized, thereby preparing a micro-mesoporous composite ZSM-23 molecular sieve. The ZSM-23 molecular sieve synthesized by the method of the present invention has both the acidic properties of the microporous structure being adjustable and the large pore characteristics of the mesoporous structure, high specific surface area and pore volume, high crystallinity, and strong thermal stability and hydrothermal stability.

[0045] The catalyst of the present invention can be shaped as needed, such as cylindrical bars or clover leaves. During the catalyst shaping process, shaping aids such as peptizing acid and extrusion aids may also be added. The catalyst carrier of the present invention is dried and calcined using conventional methods, specifically by drying at 80-150°C for 3-10 hours and calcining at 400-800°C for 3-12 hours.

[0046] According to the present invention, in the preparation method of a straight-run diesel hydrocracking catalyst, the active metal loading method can be conventional loading methods, preferably impregnation, which can be saturation impregnation, excess impregnation, or complex impregnation. Furthermore, the impregnation method comprises impregnating the support with a solution containing the active metal, drying, and calcining the support. The drying step is performed at 100°C to 120°C for 1 to 12 hours. The calcination step is performed at 400°C to 600°C for 3 to 10 hours.

[0047] In order to better illustrate the present invention, the present invention is further illustrated below in conjunction with Examples and Comparative Examples. However, the scope of the present invention is not limited to the scope of these Examples.

[0048] In the present invention, the specific surface area and pore volume are measured by using a low-temperature liquid nitrogen physical adsorption method using an ASAP 2405 physical adsorption instrument produced by Micromeritics Corporation of the United States.

[0049] The silicon to aluminum molar ratio was determined by chemical analysis.

[0050] XRD patterns of the samples were collected using a Dmax2500 X-ray diffractometer manufactured by Rigaku Corporation. The relative crystallinity of the molecular sieves was determined by X-ray powder diffraction (XRD). Specifically, the sum of the heights of the diffraction peaks at 2θ of approximately 11.3 and 19.5-23° in the XRD spectrum of a conventional ZSM-23 molecular sieve was taken as 100% crystallinity. The crystallinity of the H-DZSM-23-1 prepared according to the present invention was set to 100, and the relative crystallinity of the other samples was determined by comparison with this ratio.

[0051] The grain size was obtained by a JSM-7500F field emission scanning electron microscope from JEOL, Japan.

[0052] Acid distribution (including total acid content and strong acid content) was measured by NH3 temperature-programmed desorption (NH3-TPD), where the acid content corresponding to a desorption temperature above 350°C was defined as the strong acid content. The total acid content was defined as the acid content corresponding to an adsorption temperature of 150°C.

[0053] In the present invention, wt% refers to mass fraction and v% refers to volume fraction.

[0054] Example 1

[0055] (1) Preparation of amorphous silicon aluminum precursor

[0056] 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. Place 150 mL of the sodium aluminate working solution in a gelling tank, then add 60 mL of the sodium silicate working solution. Maintain the reaction temperature at 20°C and introduce 50 vol% CO₂ gas. When the pH reaches 10.0, stop the CO₂ flow and add 80 mL of the sodium silicate working solution. Continue bubbling with the remaining CO₂ gas to stabilize the mixture. After aging at 25°C for 30 minutes, an amorphous silicon-alumina precursor is obtained. The amorphous silicon-alumina precursor contains 70 wt% silicon dioxide, based on the total weight of silicon dioxide and aluminum oxide.

[0057] (2) Preparation of gel

[0058] According to the total feed molar ratio of SiO2: Al2O3: IPA: H2O = 1: 0.01: 0.04: 0.7: 45 (IPA is the structure-directing agent isopropylamine), isopropylamine is added to the amorphous silica-alumina precursor obtained in step (1), and stirred at 15 ° C for 0.8 hours; then, a mixture consisting of silica sol and water is added thereto and stirred evenly to obtain silica-alumina gel.

[0059] (3) Crystallization

[0060] The gel obtained in step (2) was poured into a stainless steel reactor and statically crystallized at 160°C for 20 hours. After the crystallization, it was filtered, washed to neutrality, dried at 120°C, and calcined in air at 550°C for 3 hours to obtain the molecular sieve raw powder NaZSM-23-1.

[0061] (4) Ammonium exchange

[0062] A certain amount of NaZSM-23-1 molecular sieve 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. The relative crystallinity of the HZSM-23-1 was determined by XRD. The relative crystallinity of the HZSM-23-1 was also measured after hydrothermal treatment with steam at 600°C for 2 hours. Specific properties are shown in Table 1.

[0063] (5) Catalyst preparation

[0064] The catalyst weight was 35% HZSM-23-1 molecular sieve, 25% macroporous alumina (pore volume 0.8 mL / g, specific surface area 420 m 2 / g), and 12% microporous alumina (pore volume 0.30 mL / g, specific surface area 320 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), placed in a roller compactor, mixed and ground, water was added, and the mixture was rolled into a paste, which was 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 carrier TC-1.

[0065] 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.

[0066] Example 2

[0067] 1) Preparation of amorphous silicon aluminum precursor

[0068] A sodium aluminate working solution with a concentration of 40 g Al2O3 / L was prepared. A sodium silicate solution containing 28 wt% SiO2 was diluted to a sodium silicate working solution with a concentration of 120 g SiO2 / L. 200 mL of the sodium aluminate working solution was placed in a gelling tank, followed by the addition of 40 mL of the sodium silicate working solution. The reaction temperature was controlled at 25°C, and 50% CO2 gas was introduced. When the pH reached 10.5, the CO2 flow was stopped, and 60 mL of the sodium silicate working solution was added. The remaining CO2 gas was then introduced for stabilization. After aging at 20°C for 20 minutes, an amorphous silicon-alumina precursor was obtained. The amorphous silicon-alumina precursor contained 40 wt% silicon dioxide, based on the total weight of silicon dioxide and aluminum oxide.

[0069] (2) Preparation of gel

[0070] Isopropylamine was added to the amorphous silica-alumina precursor obtained in step (1) at a total feed molar ratio of SiO2: Al2O3: IPA: H2O = 1: 0.01: 0.04: 0.15: 60, and the mixture was stirred at 20°C for 1 hour; thereafter, a mixture consisting of silica sol and water was added thereto and stirred uniformly to obtain silica-alumina gel.

[0071] (3) Crystallization

[0072] The gel obtained in step (2) was poured into a stainless steel reactor and statically crystallized at 180°C for 22 hours. After the crystallization, the gel was filtered, washed to neutrality, dried at 120°C, and calcined in air at 550°C for 3 hours to obtain the molecular sieve raw powder NaZSM-23-2.

[0073] (4) Ammonium exchange

[0074] The preparation process of HZSM-23-2 is the same as that of Example 1 (4), except that NaZSM-23-1 molecular sieve is replaced by HZSM-23-2. The specific properties are shown in Table 1.

[0075] (5) Catalyst preparation

[0076] The catalyst weight was 40% HZSM-23-2 molecular sieve, 20% macroporous alumina (pore volume 0.9 mL / g, specific surface area 480 m 2 / g), and 15% small pore alumina (pore volume 0.30 mL / g, specific surface area 320 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), placed in a roller compactor, mixed and ground, water was added, and the mixture was rolled into a paste, which was 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 carrier TC-2.

[0077] 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-2. The corresponding catalyst properties are shown in Table 2.

[0078] Example 3

[0079] (1) Preparation of amorphous silicon aluminum precursor

[0080] 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. Place 100 mL of the sodium aluminate working solution in a gelling tank, then add 40 mL of the sodium silicate working solution. Control the reaction temperature at 30°C and introduce 50 vol% CO₂ gas. Stop the CO₂ flow when the pH reaches 11.0, then add 60 mL of the sodium silicate working solution. Continue bubbling with the remaining CO₂ gas to stabilize the mixture. After aging at 20°C for 30 minutes, an amorphous silicon-alumina precursor is obtained. The amorphous silicon-alumina precursor contains 35 wt% silicon dioxide, based on the total weight of silicon dioxide and aluminum oxide.

[0081] (2) Preparation of gel

[0082] Isopropylamine was added to the amorphous silica-alumina precursor obtained in step (1) at a total feed molar ratio of SiO2: Al2O3: IPA: H2O = 1: 0.008: 0.3: 45, and the mixture was stirred at 15°C for 1 hour; thereafter, a mixture consisting of silica sol and water was added thereto and stirred uniformly to obtain silica-alumina gel.

[0083] (3) Crystallization

[0084] The gel obtained in step (2) was poured into a stainless steel reactor and statically crystallized at 160°C for 25 hours. After the crystallization, the gel was filtered, washed to neutrality, dried at 120°C, and calcined in air at 550°C for 3 hours to obtain the molecular sieve raw powder NaZSM-23-3.

[0085] (4) Ammonium exchange and template removal agent

[0086] The preparation process of HZSM-23-3 is the same as that of Example 1 (4), except that NaZSM-23-1 molecular sieve is replaced by HZSM-23-3. The specific properties are shown in Table 1.

[0087] (5) Catalyst preparation

[0088] The catalyst weight was 45% HZSM-23-3 molecular sieve, 17% macroporous alumina (pore volume 1.0 mL / g, specific surface area 520 m 2 / g), and 14% small pore alumina (pore volume 0.30 mL / g, specific surface area 320 m 2 The mixture was mixed and ground in a roller compactor. Water was added and the mixture was compacted into a paste. The paste was extruded into strips. The strips were dried at 110°C for 4 hours and then calcined at 550°C for 4 hours to obtain the carrier TC-3.

[0089] 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-3. The corresponding catalyst properties are shown in Table 2.

[0090] Example 4

[0091] (1) Preparation of amorphous silicon aluminum precursor

[0092] 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. Place 150 mL of the sodium aluminate working solution in a gelling tank, then add 500 mL of the sodium silicate working solution. Control the reaction temperature at 20°C and introduce 50% CO₂ gas. When the pH reaches 10.0, stop the CO₂ flow and add another 50 mL of the sodium silicate working solution. Continue bubbling with the remaining CO₂ gas to stabilize the mixture. After aging at 25°C for 20 minutes, an amorphous silicon-alumina precursor is obtained. The amorphous silicon-alumina precursor contains 50 wt% silicon dioxide, based on the total weight of silicon dioxide and aluminum oxide.

[0093] (2) Preparation of gel

[0094] Isopropylamine was added to the amorphous alumina-silica precursor obtained in step (1) at a total feed molar ratio of Al2O3: SiO2: IPA: H2O = 1: 0.01: 0.4: 45, and the mixture was stirred at 15°C for 1 hour; thereafter, a mixture of fumed silica and water was added thereto, and the mixture was stirred evenly to obtain alumina-silica gel.

[0095] (3) Crystallization

[0096] The gel obtained in step (2) was poured into a stainless steel reactor and statically crystallized at 180°C for 24 hours. After the crystallization, it was filtered, washed to neutrality, dried at 120°C, and calcined in air at 550°C for 3 hours to obtain the molecular sieve raw powder NaZSM-23-4.

[0097] (4) Ammonium exchange

[0098] The preparation process of HZSM-23-4 is the same as that of Example 1 (4), except that NaZSM-23-1 molecular sieve is replaced by HZSM-23-4. The specific properties are shown in Table 1.

[0099] (5) Catalyst preparation

[0100] The catalyst weight was 50% HZSM-23-1 molecular sieve, 13% macroporous alumina (pore volume 1.0 mL / g, specific surface area 420 m 2 / g), and 11% small pore alumina (pore volume 0.30 mL / g, specific surface area 320 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), placed in a roller compactor, mixed and ground, water was added, and the mixture was rolled into a paste, which was 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-4.

[0101] 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-4. The corresponding catalyst properties are shown in Table 2.

[0102] Example 5

[0103] The carrier weight was 18% of Y molecular sieve (particle size 800nm, Na2O content 0.23wt%, specific surface area 750m 2 / g, pore volume 0.50mL / g, SiO2 / Al2O3 molar ratio 28), 32% amorphous silica-alumina (pore volume 0.8mL / g, specific surface area 300m 2 / g, silica weight content 29%), and 22% microporous alumina (pore volume 0.30 mL / g, specific surface area 320 m 2 / g) and a binder consisting of 10% by weight diluted nitric acid (the molar ratio of HNO3 / small pore Al2O3 is 0.23), water is added, and the mixture is rolled into a paste, extruded into strips, and the extruded strips are dried at 110°C for 4 hours and then calcined at 550°C for 4 hours to obtain the carrier TA.

[0104] 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 A. The corresponding catalyst properties are shown in Table 2.

[0105] Comparative Example 1 (Refer to CN101214971A)

[0106] A reaction mixture was prepared using a molar ratio of Al2O3 from the aluminum source: SiO2 from the silicon source: NaOH from the alkali source: isopropylamine: H2O of 0.01:1:0.06:0.8:12. The aluminum source was sodium metaaluminate, the silicon source was silica sol, and the alkali source was sodium hydroxide. The aluminum source was first added to an aqueous sodium hydroxide solution and stirred uniformly. The silicon source was then added and stirred uniformly. Finally, isopropylamine was added and stirred uniformly to obtain a reaction mixture. The resulting reaction mixture was transferred to an autoclave and hydrothermally crystallized at 170°C for 3 days. The mixture was then filtered, washed until neutral, and dried at 120°C to obtain NaDZSM-23-1 molecular sieve.

[0107] (2) Ammonium exchange

[0108] The preparation process of H-DZSM-23-1 is the same as that of Example 1 (4), except that NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-1. The specific properties are shown in Table 1.

[0109] (3) Catalyst preparation

[0110] The preparation method of CC-1 catalyst is the same as that of Example 1 (5), except that H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-1. The specific properties are shown in Table 2.

[0111] Comparative Example 2 (refer to CN102992346A)

[0112] 8.12 g of H₂O and 0.092 g of aluminum sulfate were mixed uniformly, followed by the addition of 0.38 g of NaOH. Then, 3.32 g of silica sol with a silica content of 30.5 wt% was added with stirring. Stirring was continued until the solution became homogeneous, and 10 wt% ZSM-23 molecular sieve was added as seed crystals (the seed amount was calculated as a percentage of the mass of the SiO₂ input). The raw materials were added to a Teflon-coated stainless steel reactor and subjected to dynamic crystallization at 160°C for 10 hours. The product was then filtered and dried to obtain NaDZSM-23-2 molecular sieve. The raw material ratio was SiO₂: 0.0083% Al₂O₃: 0.27% Na₂O: 35% H₂O.

[0113] (2) Ammonium exchange

[0114] The preparation process of H-DZSM-23-2 is the same as that of Example 1 (4), except that NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-2. The specific properties are shown in Table 1.

[0115] (3) Catalyst preparation

[0116] The preparation method of CC-2 catalyst is the same as that of Example 1 (5), except that H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-2. The specific properties are shown in Table 2.

[0117] Comparative Example 3

[0118] (1) Preparation of amorphous silicon aluminum precursor

[0119] 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 to a sodium silicate working solution with a concentration of 100 g SiO2 / L. Place 200 mL of the sodium aluminate working solution in a gelling tank, then add 60 mL of the sodium silicate working solution. Control the reaction temperature at 30°C and introduce 50% CO2 gas. When the pH reaches 10.0, stop the CO2 flow and add 40 mL of the sodium silicate working solution. Aerate the mixture until the remaining CO2 gas is stable. After aging at 25°C for 30 minutes, an amorphous silicon-alumina precursor is obtained. The amorphous silicon-alumina precursor contains 50 wt% silicon dioxide, based on the total weight of silicon dioxide and aluminum oxide.

[0120] (2) Preparation of gel

[0121] A mixture of silica sol, isopropylamine and water was added to the amorphous silica-alumina precursor obtained in step (1) at a total feed molar ratio of SiO2: Al2O3: IPA: H2O = 1: 0.01: 0.4: 30, and the mixture was stirred evenly to obtain silica-alumina gel.

[0122] (3) Crystallization

[0123] The gel obtained in step (2) was poured into a stainless steel reactor and statically crystallized at 160°C for 24 hours. After crystallization, the mixture was filtered, washed to neutrality, and dried at 120°C to obtain the molecular sieve raw powder. After drying, the NaDZSM-23-2 molecular sieve product was obtained. The reaction raw material ratio was SiO2: 0.0083Al2O3: 0.27Na2O: 35H2O.

[0124] (4) Ammonium exchange

[0125] The preparation process of H-DZSM-23-2 is the same as that of Example 1 (4), except that NaZSM-23-1 molecular sieve is replaced by NaDZSM-23-2. The specific properties are shown in Table 1.

[0126] (5) Catalyst preparation

[0127] The preparation method of CC-3 catalyst is the same as that of Example 1 (5), except that H-ZSM-23-1 molecular sieve is replaced by H-DZSM-23-3. The specific properties are shown in Table 2.

[0128] Table 1 Properties of molecular sieves

[0129]

[0130] Table 2 Physicochemical properties of catalysts

[0131]

[0132] The above catalysts were subjected to activity evaluation tests. The tests were conducted on a small 200mL hydrogenation unit using a one-stage cascade hydrogenation reforming process. The properties of the feedstock oil used are shown in Table 4. The refined catalyst composition is as follows: based on the weight of the catalyst, the content of molybdenum oxide is 15.0%, the content of nickel oxide is 5%, and the balance is aluminum oxide. The refined catalyst operating conditions are as follows: reaction pressure 8.0MPa, hydrogen to oil volume ratio 1000:1, liquid hourly volume space velocity 1.0h -1 , reaction temperature 360℃. The operating conditions of the cracking stage are as follows: reaction pressure 8.0MPa, hydrogen to oil volume ratio 800:1, liquid hourly volume space velocity 0.8h -1 , <260℃ conversion rate ~75wt%. The catalyst activity test results are shown in Table 4.

[0133] Table 3 Properties of crude oil

[0134]

[0135] Table 4 Catalyst activity evaluation results

[0136]

[0137] It can be seen from the evaluation results of the catalyst in Table 4 that, compared with the comparative example, the method of the present invention has a higher jet fuel yield and a lower jet fuel freezing point, and can produce high-quality 3 # Jet fuel.

Claims

1. A method for maximizing the production of jet fuel by hydroconversion of straight-run diesel, characterized by: The method comprises the steps of loading an isomerization catalyst in a hydrocracking reaction zone to carry out an isomerization reaction on a hydrocracking product, wherein the isomerization catalyst contains an HZSM-23 molecular sieve having a grain size of 300 to 600 nm, a SiO2 / Al2O3 molar ratio of 80 to 130, and a specific surface area of 300 to 400 m 2 / g, pore volume of 0.30~0.45 cm 3 / g; The properties of the HZSM-23 molecular sieve are as follows: total acid content of 0.1-0.25 mmol / g, strong acid content of 10-25%, relative crystallinity of 95-120%, and relative crystallinity of 93-115% after steam hydrothermal treatment; The acid distribution was measured by temperature-programmed desorption of NH3, where the acid amount corresponding to a desorption temperature above 350°C was considered as the strong acid amount; The isomerization catalyst comprises, based on the weight of the catalyst, 30-60 wt% of HZSM-23 molecular sieve, 10-40 wt% of macroporous alumina, 10-30 wt% of binder, 10-25 wt% of Group VIB metal oxide, and 4-10 wt% of Group VIII metal oxide; wherein the Group VIB metal is molybdenum and / or tungsten, and the Group VIII metal is cobalt and / or nickel; The hydrocracking catalyst loaded in the hydrocracking reaction zone contains Y molecular sieve; the properties of the Y molecular sieve are as follows: Na2O weight content is less than 0.3%; silicon aluminum molar ratio SiO2 / Al2O3 is 20-35; specific surface area is 600-900m 2 / g; pore volume is 0.3~0.6mL / g; particle size is 500~1000nm.

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

3. The method according to claim 1, wherein: The density of the straight-run diesel is 0.84-0.87 g / cm 3 , dry point is 350~380℃, S content is 10000~30000µg / g, N content is 200-1000µg / g.

4. The method according to claim 1, wherein: After being hydrotreated, straight-run diesel enters the hydrocracking reaction zone.

5. The method according to claim 4, characterized in that: The operating conditions of the hydrotreatment are as follows: reaction temperature 340-380°C, total reaction pressure 6-10 MPa, liquid hourly volume space velocity 0.5-3 h -1 , hydrogen-oil volume ratio 500:1~1500:

1.

6. The method according to claim 4, characterized in that: The properties of the catalyst used in the hydroprocessing are as follows: an alumina carrier, and the hydrogenation active metal components are Group VIB and Group VIII metals.

7. The method according to claim 1, wherein: The hydrocracking catalyst loaded in the hydrocracking reaction zone has, based on its weight, a Y molecular sieve content of 10 to 30 wt%, amorphous silica-alumina content of 30 to 60 wt%, a binder content of 10 to 30 wt%; a Group VIB metal content of 10 to 30 wt% and a Group VIII metal content of 4 to 10 wt% in terms of oxide.

8. The method according to claim 1, wherein: The volume ratio of the hydrocracking catalyst and the isomerization catalyst loaded in the hydrocracking reaction zone is 20:1-5:

2.

9. The method according to claim 1, wherein: The operating conditions of the hydrocracking reaction zone are as follows: reaction pressure 5-15 MPa, hydrogen to oil volume ratio 500-1000:1, liquid hourly volume space velocity 0.5-1.2h -1 .

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