Process for the preparation of a hydrocracking catalyst

Abstract

The application discloses a preparation method of a hydrocracking catalyst, and comprises the following steps: (1) a mixed solution and an alkaline precipitant are dropwise added into a solution containing a Ni component in parallel flow to perform a coprecipitation reaction, and slurry M is obtained; wherein the mixed solution is a mixed solution of sodium tungstate, sodium molybdate and sodium metaaluminate; (2) the slurry M is divided into two parts, i.e., slurry M-1 and slurry M-2, and the two parts are separately subjected to aging, and the two aging products are mixed to obtain slurry N; (3) the slurry N is subjected to vacuum filtration, and the obtained filter cake is subjected to two times of health maintenance; (4) the filter cake is subjected to drying treatment, and then is mixed and kneaded with a molecular sieve and a molding aid, and then is subjected to extrusion and molding to obtain a molded product, and the molded product is subjected to calcination treatment to obtain the hydrocracking catalyst. The hydrocracking catalyst with a bimodal pore structure is obtained through aging and gelation by means of pH value swing in batches, the problem that small molecule aromatic hydrocarbons are at a disadvantage in competitive adsorption and reaction processes is solved, the aromatic hydrocarbon removal efficiency is improved, and the hydrocracking catalyst is suitable for a hydrocracking process for producing industrial 5# white oil.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of catalyst preparation, and particularly relates to a preparation method of a hydrocracking catalyst with high activity, high-efficiency conversion of small-molecule aromatic hydrocarbons, and production of 5# industrial white oil in a hydrocracking process. BACKGROUND

[0002] The hydrocracking process can be flexibly adjusted according to market changes to produce various high-quality fuels and chemical raw materials, such as naphtha, diesel, aviation kerosene, lubricating oil base oil, and special oil. The current demand for finished oil products continues to decline. In addition to the consensus that producing more basic chemical raw materials has become one of the industry's transformation and upgrading, the production of high-value-added special oil by the hydrocracking process has also become a popular choice. Among special oil white oil products, 5# industrial white oil has high added value, and the distillation range of diesel and 5# industrial white oil is close. If diesel can be converted to 5# industrial white oil through production optimization, the economic efficiency of enterprises can be improved, and the purpose of reducing diesel production can be achieved. Compared with conventional hydrocracking products such as finished oil products and chemical raw materials, special oil has significantly different quality indicators. Special oil has strict requirements for low-temperature fluidity indicators, especially for aromatic hydrocarbon content, which is extremely strictly limited. For example, the aromatic hydrocarbon content of 5# industrial white oil is required to be no more than 5%, so the hydrocracking catalyst needs to have high aromatic hydrocarbon conversion capacity. At present, domestic hydrocracking technology mainly focuses on producing clean oil products and chemical raw materials, emphasizing the ring-opening conversion capacity of heavy oil raw materials to improve the quality of tail oil, and the aromatic hydrocarbon content of diesel fraction products is relatively high, which is difficult to meet the aromatic hydrocarbon indicators of such special oil products.

[0003] To solve this problem, breaking through the metal loading limit in the preparation method of the existing hydrocracking catalyst, strengthening the hydrogenation performance of the catalyst, and increasing the aromatic hydrocarbon saturation depth in the hydrocracking process are key methods to reduce the aromatic hydrocarbon content of diesel fraction special oil products. The most effective solution to break through the metal loading limit of the hydrocracking catalyst is to develop a bulk-phase hydrocracking catalyst. The coprecipitation method is the most advantageous method for preparing bulk-phase hydrocracking catalysts. It not only uniformly mixes various components, but also can use relatively low-priced sodium-containing raw materials to replace some high-priced or "ammonia-nitrogen" containing raw materials, greatly reducing the cost of catalyst raw materials and the cost of nitrogen-containing wastewater treatment. However, the introduction of a large amount of sodium ions makes it difficult to completely remove sodium ions from the bulk-phase catalyst. A large amount of impurity sodium is present in the coprecipitated material, which leads to poor adhesion of the material and makes it difficult to form or the catalyst has poor strength after forming. At the same time, the unremoved impurity sodium is also not conducive to the formation of the pore structure of the catalyst, resulting in small pore volume and pore size of the catalyst, affecting the diffusion efficiency in the catalytic reaction process. The bulk-phase catalyst with too high sodium content also leads to the aggregation of active metals or affects the activity of the molecular sieve in the hydrocracking catalyst, reducing the hydrogenation activity of the catalyst.

[0004] In addition, during the hydrocracking reaction process, the proportion of small molecule aromatic hydrocarbons (1-2 rings) in the diesel fraction of the raw material is smaller than that of the condensed ring aromatic molecules in the heavy fraction, and in the process of participating in competitive adsorption and reaction, the steric hindrance effect of the side chain of the small molecule aromatic hydrocarbons is more significant than that of the condensed ring aromatic molecules, which affects the contact of the small molecule aromatic hydrocarbons with the active sites and reduces the reaction efficiency, making it difficult to remove the small molecule aromatic hydrocarbons and unable to meet the requirement of the content of aromatic hydrocarbons in the special oil.

[0005] CN109722292B discloses a hydrocracking method for producing crude white oil, which realizes a method for producing crude white oil through two kinds of hydrocracking catalyst grading technology, but the method cannot realize direct production of industrial white oil and only provides a raw material source for producing white oil.

[0006] CN101722007A discloses a preparation method of a hydrocracking catalyst composition, which adopts a mixed alkaline solution of sodium metaaluminate and sodium tungstate as a precipitant, and sodium hydroxide is used for pH adjustment in the process, and the final product contains a certain amount of impurity sodium, and the sodium remaining in the catalyst can cause the material to be difficult to form and have small mechanical strength, and the remaining sodium ions also reduce the pore volume and specific surface area of the catalyst.

[0007] CN114471688A and CN114471689A both disclose a preparation method of a hydrocracking catalyst. The method partially uses sodium-containing raw materials such as sodium tungstate, sodium hydroxide, sodium carbonate and sodium bicarbonate, adopts a coprecipitation method for preparation, and is subjected to sodium salt removal treatment. The method selects sodium salt removal after catalyst extrusion molding, but in actual catalyst preparation process, when the sodium salt content is too high, the catalyst cannot be formed or has small strength after formation, so the method has certain requirements for the sodium content of the catalyst preparation raw material; at the same time, since a large amount of sodium ions exist in the coprecipitation reaction product, part of the sodium chloride crystals will be precipitated and attached to the internal pores during the drying process of the coprecipitation reaction product, which also has an adverse effect on the formation of the pore structure of the catalyst. In addition, the sodium salt removal after catalyst extrusion molding increases the adsorption degree of sodium ions on the catalyst, which is more difficult to remove. SUMMARY

[0008] In view of the deficiencies of the prior art, the present application provides a preparation method of a hydrocracking catalyst. The present application obtains a bimodal pore structure hydrocracking catalyst through aging and pH value swing in batches to form glue, solves the problem that small molecule aromatic hydrocarbons are at a disadvantage in the process of competitive adsorption and reaction, improves the aromatic hydrocarbon removal efficiency, and is suitable for a hydrocracking process for producing industrial 5# white oil.

[0009] The preparation method of the hydrocracking catalyst of the present application comprises the following contents:

[0010] (1) the mixed solution and the alkaline precipitant are dropped into the solution containing the Ni component to carry out a coprecipitation reaction, to obtain slurry M; wherein the mixed solution is a mixed solution of sodium tungstate, sodium molybdate and sodium metaaluminate;

[0011] (2) the slurry M is divided into two parts, slurry M-1 and slurry M-2, to carry out aging respectively, and the two aging products are mixed to obtain slurry N;

[0012] wherein the aging process of the slurry M-1 is: (a) first, a sodium metaaluminate solution is added, then a sodium hydroxide solution is used to control the pH value to 11.0-12.5, and the aging time is 0.2-1.0 hours; then the aging pH value is adjusted to 8.8-9.6, and the aging time is 0.2-1.0 hours; then the aging pH value is adjusted to 6.5-7.5, and the aging time is 0.2-0.8 hours; (b) step (a) is repeated 2-6 times to complete the aging, to obtain an aging product A;

[0013] the aging process of the slurry M-2 is: (c) first, a sodium metaaluminate solution is added, then a sodium carbonate solution is used to control the pH value to 12.5-13.5, and the aging time is 0.2-0.6 hours; then the aging pH value is adjusted to 10.8-11.8, and the aging time is 0.2-0.6 hours; then the aging pH value is adjusted to 7.5-8.5, and the aging time is 0.2-0.6 hours; (d) step (c) is repeated 2-6 times to complete the aging, then the pH value is adjusted to be the same as that of the aging product A, to obtain an aging product B;

[0014] (3) the slurry N is vacuum filtered to obtain a filter cake, which is subjected to a first aging; after the first aging, a certain proportion P of deionized water is added to the top of the filter cake, and vacuum filtration is carried out; the filter cake is subjected to a second aging, a certain proportion S of deionized water is added to the top of the filter cake, and vacuum filtration is carried out to obtain a filter cake;

[0015] (4) the filter cake is dried, then kneaded with molecular sieves and a shaping aid, and then extruded into a strip to obtain a shaped product, which is subjected to a calcination treatment to obtain a hydrocracking catalyst.

[0016] In the method of the present application, in the mixed solution of step (1), the molar concentration of sodium tungstate is 0.1-1.2 mol / L, preferably 0.3-0.7 mol / L, the molar concentration of sodium molybdate is 0.15-0.8 mol / L, preferably 0.3-0.6 mol / L, and the molar concentration of sodium metaaluminate, calculated as Al2O3, is 0.05-1.0 mol / L, preferably 0.1-0.5 mol / L.

[0017] In the method, the alkaline precipitant in step (1) is one or more of sodium hydroxide, ammonia, sodium carbonate and sodium bicarbonate, and the alkaline precipitant is prepared to have a pH value of no less than 12.5, preferably a pH value of 12.8-13.5.

[0018] In the method, the soluble nickel salt in the reaction bottom water in step (1) is, for example, nickel acetate, nickel chloride, nickel sulfate or nickel nitrate, and the molar concentration of Ni (calculated as NiO) is 0.2-1.4 mol / L, preferably 0.5-0.9 mol / L.

[0019] In the method, the coprecipitation reaction conditions in step (1) are as follows: the reaction time is 25-200 minutes, preferably 45-85 minutes; the reaction temperature is 40-95℃, preferably 50-80℃; the pH value of the reaction solution is measured on line, and the pH value of the reaction system is kept in the range of 6.0-7.8, preferably 6.5-7.5.

[0020] In the method, the molar concentration of Al (calculated as Al2O3) in the sodium aluminate solution in step (2) is 0.1-0.5 mol / L, preferably 0.2-0.4 mol / L; the sodium aluminate solution added in the aging process of M-1 is divided into 2-6 portions, and the sodium aluminate solution added in the aging process of M-2 is divided into 2-6 portions.

[0021] In the method, the mass ratio of the slurry M-1 to the slurry M-2 in step (2) is 0.3-4:1, preferably 0.3-3:1; and the mass ratio of the sodium aluminate solution added in the aging process of M-1 to the mass ratio of M-2 is the mass ratio of M-1 to M-2.

[0022] In the method, the mass fraction of Al (calculated as Al2O3) added in the aging process in step (2) accounts for 10%-60% of the mass of the prepared catalyst Al2O3 (not including Al2O3 in the molecular sieve), preferably 15%-50%.

[0023] In the method, the aging temperature of the slurry M-1 in step (2) is in the range of 35-45℃, preferably 38-40℃; and the aging temperature of the slurry M-2 is in the range of 60-90℃, preferably 70-80℃.

[0024] In the method, the acid used for adjusting the pH value in the aging process in step (2) is hydrochloric acid or acetic acid, and the base is sodium hydroxide, and the concentration and amount are adjusted according to the actual needs.

[0025] In the method, the humidity of the filter cake in step (3) is greater than 83% during the first incubation; the temperature of the first incubation is 33-48 DEG C, preferably 36-42 DEG C; and the incubation time is 0.3-2 hours, preferably 0.5-1.0 hour. The second incubation process is repeated once the first incubation process.

[0026] The incubation process can be carried out in any environment meeting the above conditions, preferably directly in a vacuum filtration device without moving the filter cake, thereby simplifying the process.

[0027] In the method, the deionized water in step (3) has a mass ratio of deionized water to catalyst preparation of P>3.0, preferably 4-5:1, and a temperature of 36-42 DEG C, preferably consistent with the temperature of the first incubation; and the deionized water has a mass ratio of deionized water to catalyst preparation of n>0.4, preferably 0.6-2:1, and a temperature of 36-42 DEG C, preferably consistent with the temperature of the first incubation.

[0028] In the method, the deionized water is added to the top of the filter cake during the filtration process in step (3), and the filter cake is not stirred.

[0029] In the method, the drying and shaping in step (4) can be carried out by conventional methods in the art. The drying conditions are as follows: drying at 70-150 DEG C for 1-24 hours, preferably 80-120 DEG C for 3-10 hours. The shaped catalyst can be prepared in various shapes as needed, such as clover, four-leaf clover, sheet, sphere, cylindrical strip, etc., preferably clover or four-leaf clover.

[0030] In the method, the molecular sieve in step (4) is Y-type molecular sieve and / or beta molecular sieve, and the content of the molecular sieve is generally 10-45 wt% based on the weight of the hydrocracking catalyst.

[0031] In the method, the calcination temperature in step (4) is 380-540 DEG C, preferably 440-520 DEG C; and the calcination time is 4-12 hours, preferably 6-8 hours.

[0032] The present application also provides a hydrocracking catalyst with a bimodal pore structure, and the pore distribution is as follows: the pore volume of pores with a pore diameter of less than 3 nm accounts for 0.1-1% of the total pore volume; the pore volume of pores with a pore diameter of 3-8 nm accounts for 35-48% of the total pore volume; the pore volume of pores with a pore diameter of 8-15 nm accounts for 8-15% of the total pore volume; the pore volume of pores with a pore diameter of 15-60 nm accounts for 30-48% of the total pore volume; and the pore volume of pores with a pore diameter of more than 60 nm accounts for 5-10% of the total pore volume.

[0033] Preferably, the catalyst pore distribution is as follows: the pore volume of the pores with a pore diameter of 3 nm or less accounts for 0.1% to 0.5% of the total pore volume, the pore volume of the pores with a pore diameter of 3 to 8 nm accounts for 38% to 48% of the total pore volume, the pore volume of the pores with a pore diameter of 8 to 15 nm accounts for 8% to 12% of the total pore volume, the pore volume of the pores with a pore diameter of 15 to 60 nm accounts for 35% to 48% of the total pore volume, and the pore volume of the pores with a pore diameter of 60 nm or more accounts for 5% to 8% of the total pore volume.

[0034] The specific surface area of the hydrocracking catalyst is 200 to 400 m 2 / g, the pore volume is 0.32 to 0.52 mL / g, and the catalyst strength is not less than 15.5 N·mm -1 .

[0035] The hydrocracking catalyst comprises oxides of tungsten, molybdenum, nickel and aluminum and molecular sieves; the content of the oxides of tungsten, molybdenum and nickel is 40 wt% to 80 wt%, preferably 58 wt% to 75 wt%; the content of the molecular sieves is 10 wt% to 45 wt%, preferably 12 wt% to 25 wt%; the content of the aluminum oxide is 10 wt% to 50 wt%; the sodium content is ≯0.1%; the molar ratio of W / Mo of the hydrocracking catalyst is 0.5 to 10:1, preferably 1 to 5:1, and the molar ratio of (Mo+W) / Ni is 1 to 9:1, preferably 3 to 6:1.

[0036] Compared with the prior art, the present application has the following advantages:

[0037] The method of the present application performs aging treatment on the co-precipitation slurry by a specific method, and the aluminum-containing solution is added in batches during the pH value swing of the slurry in the aging process. The amorphous oxide in the oxide particles formed by co-precipitation is dissolved by the pH value swing, and the size of the oxide particles is modified again by the addition of the aluminum-containing solution. After n times of pH value swing, the growth of the oxide particles is controlled, so that the oxide particles are more uniform and have a suitable size, and excessive aggregation of the particles does not occur, and the dispersion of the active metal of the bulk catalyst is improved.

[0038] The present application respectively ages slurry M-1 and M-2, wherein M-2 is different from M-1 in the pH swing gelation process, sodium metaaluminate is added, and then sodium carbonate is used to adjust the pH value to the highest point, and CO2 gas is continuously released in the subsequent pH swing process, and appropriate CO2 exists in the aged slurry in the form of small molecules, which impacts the inside of the modified oxide particle pores, plays a hole expanding role, and promotes the movement of the product of the aged slurry M-2 to large pores. At the same time, the slurry M-2 increases the aging temperature in the pH swing process and the pH value in the oxide modification process, which is also conducive to the movement of the product of the slurry M-2 to large pores. The co-precipitation product after the above-mentioned respective aging treatment will form a bimodal pore structure, which can make the small molecule aromatic hydrocarbons in the raw material be selectively hydrogenated and saturated in the smaller pores of the bimodal structure, and the condensed ring aromatic hydrocarbons in the raw material are hydrogenated and saturated in the larger pores of the bimodal structure, which overcomes the problem that small molecule aromatic hydrocarbons are at a disadvantage in the process of competitive adsorption and reaction, improves the aromatic hydrocarbon removal efficiency, and is especially suitable for the hydrocracking process for producing industrial 5# white oil.

[0039] The present application removes impurity sodium from the product in a short time after the aging treatment, and sodium ions are less adsorbed on the material, are more easily removed, and have high impurity removal efficiency; compared with the traditional beating and washing, the two times of incubation and vacuum filtration and washing in the present application can remove a large amount of impurity sodium in the filter cake with a small amount of water, meet the requirement that the sodium content in the filter cake is ≯0.1%, reduce the washing times, and simplify the process and greatly reduce the amount of water used in preparation. The present application removes impurity sodium, solves the problem that the bulk catalyst is not easy to be formed or has small mechanical strength when the sodium content is too high, and eliminates the influence of sodium elements on the activity of the molecular sieve in the hydrocracking catalyst.

[0040] In the present application, the sodium ions in the filter cake are precipitated from the material in the first incubation and the second incubation process, so that the special bimodal pore structure formed in the pH swing gelation process is retained, and the change of the special pore structure of the material caused by the occupation of impurity sodium is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The pore size distribution graphs of examples 1 to 4.

[0042] Figure 2 The pore size distribution graphs of examples 1 and comparative examples. DETAILED DESCRIPTION

[0043] The technical solutions of the present application will be clearly and completely described below in combination with specific embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. In the catalyst testing and characterization method, an Agilent inductively coupled plasma mass spectrometer (7700 ICP-MS) is used for element analysis; an ASAP-2405 type BET nitrogen adsorption instrument in the United States is used to measure the specific surface area and pore size distribution of the carrier; a particle strength tester is used to measure the crushing strength of the catalyst; and a Nicolet 6700 type Fourier transform infrared spectrometer is used to measure the acidity of the molecular sieve. Tables 1 and 2 are the properties of the molecular sieves used in the examples and comparative examples. Example 1

[0044] A mixed solution is prepared: the molar concentration of sodium tungstate is 0.80 mol / L, the molar concentration of sodium molybdate is 0.40 mol / L. The molar concentration of sodium metaaluminate (calculated as Al2O3) is 0.10 mol / L; a sodium hydroxide solution with a pH value of 13.0 is prepared as an alkaline precipitant; a nickel chloride solution is prepared, and the molar concentration of nickel (calculated as NiO) is 0.70 mol / L.

[0045] Under high-speed stirring, the mixed solution and the alkaline precipitant are dropped into the nickel chloride solution in a concurrent flow to perform a coprecipitation reaction, the reaction temperature is 68℃, the reaction pH value is controlled at 6.8-6.9, and the slurry M is obtained after 70 min.

[0046] A sodium metaaluminate solution is prepared, and the molar concentration of aluminum (calculated as Al2O3) is 0.20 mol / L, which is divided into 8 equal parts. The slurry is divided into two parts with a mass ratio of M-1:M-2=1:1, and each part is subjected to aging treatment.

[0047] M-1 aging: the aging temperature is 40℃; first, one part of the sodium metaaluminate solution is added, then an 8wt% sodium hydroxide solution is used to adjust the pH value to 11.5-11.6, and the aging time is 0.5 h; then the pH value is adjusted to 9.0-9.1, and the aging time is 0.5 h; then the pH value is adjusted to 7.0-7.1, and the aging time is 0.4 h; the above is the complete addition process of one part of the sodium metaaluminate solution, and the above process is repeated 4 times to complete the aging of M-1.

[0048] M-2 aging: the aging temperature is 75℃; first, one part of the sodium metaaluminate solution is added, then a 10wt% sodium carbonate solution is used to adjust the pH value to 13.2-13.3, and the aging time is 0.5 h; then the pH value is adjusted to 11.3-11.4, and the aging time is 0.4 h; then the pH value is adjusted to 7.8-7.9, and the aging time is 0.3 h; the above is the complete addition process of one part of the sodium metaaluminate solution, and the above process is repeated 4 times to complete the aging of M-2.

[0049] M-2 was adjusted to pH 7.0-7.1 and mixed with M-1, and the addition amount of Al in the aging process was 50.0% of the Al2O3 component in the final catalyst.

[0050] Vacuum filtration was performed to obtain a filter cake, which was subjected to a first aging process. The aging was directly performed on the vacuum filter, and the aging environment had a humidity of 88% and a temperature of 40℃. The aging time was 1.2 h. Deionized water was added to the upper layer of the filter cake at a mass ratio of 4.5:1 to the catalyst preparation, and the temperature of the deionized water was 40℃. Vacuum filtration was performed until no filter liquid dropped from the filter cake. The filter cake was subjected to a second aging process, which repeated the first aging process. Then, deionized water was added to the upper layer of the filter cake at a mass ratio of 1.2:1 to the catalyst preparation, and the temperature of the deionized water was 40℃. Vacuum filtration was performed until no filter liquid dropped from the filter cake.

[0051] The filter cake was dried at 80℃ for 8 h. Y-type molecular sieves (25 wt% of the catalyst) were added and kneaded, and then the mixture was extruded into clover-shaped strips. The strips were calcined at a temperature of 500℃ for 6 h to obtain the final catalyst ①. The main properties of the catalyst are shown in Table 3. Figure 1 . Example 2

[0052] A mixed solution was prepared, in which the molar concentration of sodium tungstate was 0.40 mol / L, the molar concentration of sodium molybdate was 0.50 mol / L, and the molar concentration of sodium metaaluminate (Al2O3) was 0.15 mol / L. A mixed solution of sodium hydroxide and sodium bicarbonate with a pH value of 13.5 was prepared as an alkaline precipitant. A nickel chloride solution was prepared, in which the molar concentration of nickel (NiO) was 0.40 mol / L.

[0053] Under high-speed stirring, the mixed solution and the alkaline precipitant were simultaneously dropped into the nickel chloride solution to perform a co-precipitation reaction. The reaction temperature was 58℃, and the reaction pH value was controlled at 7.2-7.3. After 80 min, slurry M was obtained.

[0054] A sodium metaaluminate solution was prepared, in which the molar concentration of Al (Al2O3) was 0.10 mol / L. The solution was divided into two parts with a mass ratio of 3:1, denoted as a and b. Sodium metaaluminate a was divided into 6 equal parts, and sodium metaaluminate b was divided into 3 equal parts. The slurry was divided into two parts with a mass ratio of M-1:M-2=3:1, and each part was subjected to aging treatment.

[0055] M-1 aging: The aging temperature was 38℃. First, one part of the sodium metaaluminate a solution was added, and then a 10 wt% sodium hydroxide solution was used to adjust the pH value to 12.0-12.1, and the aging time was 0.7 h. Then, the pH value was adjusted to 9.4-9.5, and the aging time was 0.3 h. Next, the pH value was adjusted to 6.8-6.9, and the aging time was 0.5 h. The above process was repeated 6 times to complete the aging of M-1.

[0056] M-2 aging: aging temperature 70℃; first add a portion of sodium metaaluminate b solution, then adjust the pH value to 12.9~13.0 using 8wt% sodium carbonate solution, aging for 0.6 hours; then adjust the pH value to 10.9~11.0, aging for 0.6 hours; then adjust the pH value to 8.1~8.2, aging for 0.4 hours; the above is the complete addition process of one portion of sodium metaaluminate solution, repeat the above process 3 times to complete the M-2 aging.

[0057] After adjusting the pH value of M-2 to 6.8~6.9, mix with M-1, the addition amount of Al in the aging process accounts for 25.0% of the Al2O3 component of the final catalyst.

[0058] Vacuum filtration to obtain filter cake for one-time curing, the curing is directly carried out in the vacuum filter, the curing environment humidity is 85%, the curing temperature is 36℃, and the time is 1h; add deionized water with a mass ratio of 4:1 to the upper layer of the filter cake, the temperature of the deionized water is 38℃, and vacuum filtration is carried out until the filter cake is completely free of filter liquid drops. Continue to carry out secondary curing of the filter cake, repeat the one-time curing process; then add deionized water with a mass ratio of 1.5:1 to the upper layer of the filter cake, the temperature of the deionized water is 38℃, and vacuum filtration is carried out until the filter cake is completely free of filter liquid drops.

[0059] Drying treatment of the filter cake, drying at 90℃ for 6h; add Y-type molecular sieve (accounting for 20wt% of the mass of the catalyst) and knead, then extrude into cylindrical shape, and the formed strip is calcined, the calcination temperature is 490℃, and the calcination time is 8h, to obtain the final catalyst ②, the main properties are shown in Table 3, Figure 1 . Example 3

[0060] Prepare a mixed solution: the molar concentration of sodium tungstate is 0.90mol / L, the molar concentration of sodium molybdate is 0.30mol / L. The molar concentration of sodium metaaluminate is 0.2mol / L (calculated as Al2O3); prepare a mixed solution of sodium hydroxide and sodium carbonate with pH value = 13.2 as the alkaline precipitant; prepare a nickel chloride solution, the molar concentration of nickel is 0.90mol / L (calculated as NiO).

[0061] Under high-speed stirring, the mixed solution and the alkaline precipitant are dropped into the nickel chloride solution for co-precipitation reaction, the reaction temperature is 80℃, the reaction pH value is controlled at 6.4~6.5, and the slurry M is obtained after 50min.

[0062] Prepare a sodium metaaluminate solution, the molar concentration of Al is 0.30mol / L (calculated as Al2O3), divide it into two parts with a mass ratio of 1:2, marked as a and b, divide the sodium metaaluminate a into two equal parts, and divide the sodium metaaluminate b into five equal parts. Divide the slurry into two parts with a mass ratio of M-1:M-2=1:2, and age them respectively.

[0063] M-1 aging: aging temperature 45℃; first add a portion of sodium metaaluminate a solution, then adjust the pH value to 12.3~12.4 using 12wt% sodium hydroxide solution, aging 0.3 hours; then adjust the pH value to 8.9~9.0, aging 0.6 hours; then adjust the pH value to 7.3~7.4, aging 0.7 hours; the above is the complete addition process of one portion of sodium metaaluminate solution, repeat the above process twice to complete M-1 aging.

[0064] M-2 aging: aging temperature 80℃; first add a portion of sodium metaaluminate b solution, then adjust the pH value to 12.7~12.8 using 12wt% sodium carbonate solution, aging 0.4 hours; then adjust the pH value to 11.6~11.7, aging 0.5 hours; then adjust the pH value to 7.6~7.7, aging 0.5 hours; the above is the complete addition process of one portion of sodium metaaluminate solution, repeat the above process five times to complete M-2 aging.

[0065] After adjusting the pH value of M-2 to 7.3~7.4, mix with M-1, the addition amount of Al in the aging process accounts for 33.3% of the Al2O3 component of the final catalyst.

[0066] Vacuum filtration to obtain filter cake for one-time curing, the curing is directly carried out in the vacuum filter, the curing environment humidity is 90%, the curing temperature is 45℃, and the time is 0.4h; add deionized water with a mass ratio of 3.2:1 to the upper layer of the filter cake, the deionized water temperature is 42℃, and vacuum filtration is carried out until the filter cake is completely free of filter liquid drops. Continue to carry out secondary curing of the filter cake, repeat the process once; then add deionized water with a mass ratio of 0.5:1 to the upper layer of the filter cake, the deionized water temperature is 40℃, and vacuum filtration is carried out until the filter cake is completely free of filter liquid drops.

[0067] Drying treatment of the filter cake, drying at 120℃ for 3h; add Y-type molecular sieve (accounting for 10wt% of the mass of the catalyst) and β molecular sieve (accounting for 5wt% of the mass of the catalyst) and knead, then extrude into clover-shaped strips, and the formed strips are calcined, the calcination temperature is 510℃, and the calcination time is 5h, to obtain the final catalyst ③, the main properties are shown in Table 3, Figure 1 . Example 4

[0068] Prepare a mixed solution: the molar concentration of sodium tungstate is 0.60mol / L, the molar concentration of sodium molybdate is 0.60mol / L. The molar concentration of sodium metaaluminate is 0.24mol / L in terms of Al2O3; prepare an ammonia solution with pH value=12.9 as the alkaline precipitant; prepare a nickel chloride solution, the molar concentration of nickel in terms of NiO is 0.50mol / L.

[0069] The mixed solution and the alkaline precipitant were dropped into the nickel chloride solution in a co-current manner under high-speed stirring to carry out a co-precipitation reaction, the reaction temperature was 48℃, the pH value was controlled at 7.5-7.6, and the slurry M was obtained after 100 minutes.

[0070] A sodium meta-aluminate solution was prepared, the molar concentration of Al (calculated as Al2O3) was 0.40 mol / L, and the solution was divided into two parts with a mass ratio of 2:1, and was marked as a and b. The sodium meta-aluminate solution a was divided into 5 parts, and the sodium meta-aluminate solution b was divided into 4 parts. The slurry was divided into two parts with a mass ratio of M-1:M-2=2:1, and was aged respectively.

[0071] M-1 aging: the aging temperature was 36℃; first, one part of the sodium meta-aluminate solution a was added, then a 10wt% sodium hydroxide solution was used to adjust the pH value to 11.3-11.4, and the aging time was 0.6 hours; then the pH value was adjusted to 9.2-9.3, and the aging time was 0.4 hours; then the pH value was adjusted to 6.6-6.7, and the aging time was 0.6 hours; the above was the complete adding process of one part of the sodium meta-aluminate solution, and the above process was repeated 5 times to complete the aging of M-1.

[0072] M-2 aging: the aging temperature was 66℃; first, one part of the sodium meta-aluminate solution b was added, then an 8wt% sodium carbonate solution was used to adjust the pH value to 13.4-13.5, and the aging time was 0.3 hours; then the pH value was adjusted to 11.5-11.6, and the aging time was 0.3 hours; then the pH value was adjusted to 8.3-8.4, and the aging time was 0.6 hours; the above was the complete adding process of one part of the sodium meta-aluminate solution, and the above process was repeated 4 times to complete the aging of M-2.

[0073] After the pH value of M-2 was adjusted to 6.6-6.7, M-2 was mixed with M-1, and the adding amount of Al (calculated as Al2O3) in the aging process accounted for 40% of the Al2O3 component of the final catalyst.

[0074] The filter cake was obtained by vacuum filtration and was aged once. The aging process was carried out in an incubator, the humidity was 93%, the temperature was 33℃, and the time was 0.8 hours. The filter cake was placed on the filter cloth of the vacuum filter without any gap, and deionized water with a mass ratio of 6:1 to the catalyst was added to the upper layer of the filter cake, the temperature of the deionized water was 45℃, and the vacuum filtration was carried out until no filter liquid dropped from the filter cake. The filter cake was aged twice, and the process was repeated once. Then deionized water with a mass ratio of 1.8:1 to the catalyst was added to the upper layer of the filter cake, the temperature of the deionized water was 45℃, and the vacuum filtration was carried out until no filter liquid dropped from the filter cake.

[0075] The filter cake was dried at 140℃ for 2 hours, β molecular sieve (accounting for 35wt% of the mass of the catalyst) was added and kneaded, and then the mixture was extruded into clover-shaped strips. The strips were calcined at a temperature of 440℃ for 10 hours to obtain the final catalyst ④, and the main properties are shown in Table 3,Figure 1 .

[0076] Comparative Example 1

[0077] The other steps of the present comparative example are consistent with Example 1, except that the aging treatment of the present comparative example is different from step (2), the aging process: aging treatment is carried out on the slurry M, the aging temperature is 80℃, the aging pH value is 7.0-7.1, and the aging time is 2 hours, to obtain the aged slurry.

[0078] Finally, catalyst ⑤ is obtained, and the main properties are shown in Table 3, Figure 2 .

[0079] Comparative Example 2

[0080] The other steps of the present comparative example are consistent with Example 1, except that the aging treatment of the present comparative example is different from step (2), the aging process: a sodium meta-aluminate solution is prepared, the molar concentration of Al (calculated as Al2O3) is 0.20 mol / L, and it is evenly divided into 8 parts. Aging treatment is carried out on the slurry M: the aging temperature is 40℃; first, one part of the sodium meta-aluminate solution is added, then the pH value is adjusted to 11.5-11.6 using an 8wt% sodium hydroxide solution, and the aging time is 0.5 hours; then the pH value is adjusted to 9.0-9.1, and the aging time is 0.5 hours; then the pH value is adjusted to 7.0-7.1, and the aging time is 0.4 hours; the above is the complete addition process of one part of the sodium meta-aluminate solution, and the above process is repeated 8 times to complete the aging process. The addition amount of Al (calculated as Al2O3) in the aging process accounts for 50.0% of the Al2O3 component of the final catalyst.

[0081] Finally, catalyst ⑥ is obtained, and the main properties are shown in Table 3, Figure 2 .

[0082] Comparative Example 3

[0083] The other steps of the present comparative example are consistent with Example 1, except that the present comparative example does not carry out the impurity removal process of step (3) after the aging treatment.

[0084] Finally, catalyst ⑦ is obtained, and the main properties are shown in Table 3, Figure 2 .

[0085] Comparative Example 4

[0086] The other steps of the present comparative example are consistent with Example 1, except that the present comparative example does not carry out the impurity removal process of step (3) after the aging treatment.

[0087] Finally, catalyst ⑧ is obtained, and the main properties are shown in Table 3, Figure 2 .

[0088] Comparative Example 5

[0089] The other steps of the present comparative example are consistent with example 1, except that the impurity removal process in step (3) is carried out according to the method disclosed in CN114471689A to remove impurities sodium:

[0090] After the aging process in step (2) is completed, the filter cake obtained by vacuum filtration is dried at 80°C for 8h. After kneading with Y-type molecular sieves (accounting for 25wt% of the mass of the catalyst), the mixture is extruded into clover-shaped strips. The formed strips are incubated at a temperature of 75°C for 48 hours; the temperature is reduced to 19°C and incubation is continued for 34 hours; the strips are washed with deionized water for 3 times, and the wet strips after washing are dried at 80°C for 10 hours. Then calcination is carried out at a calcination temperature of 500°C for 6h to obtain the final catalyst ⑨, and the main properties are shown in Table 3, Figure 2 . Example 5

[0091] This example is an activity evaluation experiment of the catalyst of the present application, and is compared with comparative example catalysts. The catalysts ① and ② of the present application and the comparative example catalysts ⑤, ⑥, ⑧ and ⑨ are used to carry out comparative evaluation experiments in a small hydrogenation device.

[0092] The evaluation process conditions are: reaction pressure 14.7MPa, hydrogen / oil volume ratio 1200:1, volume space velocity 1.8h -1 , reaction temperature 370°C, and the main properties of the evaluation raw materials are shown in Table 4, and the evaluation results of the catalysts of different examples and comparative examples are shown in Tables 5 and 6.

[0093] As shown in Table 5, the hydrogenation cracking catalysts ① and ② prepared by the present application have good hydrogenation cracking activity, and the cracking activity of the comparative example catalysts ⑤, ⑥, ⑧ and ⑨ which have similar composition with catalyst ① is slightly lower than that of catalyst ①, but the difference is not large.

[0094] From Table 6, it can be seen that the hydrogen cracking catalysts used for evaluation all have white oil fraction in the product reaching the requirement of ≯10 μg / g of sulfur content of 5# industrial white oil, but the aromatic hydrocarbon contents are different. The aromatic hydrocarbon contents of the catalysts prepared in Examples ① and ② are 3.5 wt% and 3.0 wt% respectively, reaching the requirement of less than 5 wt% of aromatic hydrocarbon content of 5# industrial white oil, while the aromatic hydrocarbon contents of the catalysts prepared in Comparative Examples ⑤, ⑥, ⑧ and ⑨ all exceed 5 wt%, indicating that the bimodal pore structure characteristics of the hydrogen cracking catalysts prepared by the method of the present application can make the small molecule aromatic hydrocarbons in the raw material be highly selectively hydrogenated and saturated in the smaller pore channels of the bimodal pore structure, and the condensed ring aromatic hydrocarbons in the raw material be hydrogenated and saturated in the larger pore channels of the bimodal pore structure, overcoming the problem that the small molecule aromatic hydrocarbons are at a disadvantage in the competitive adsorption and reaction process, and improving the aromatic hydrocarbon removal efficiency; at the same time, the pH swing gelation in the aging process and the special method for removing impurity sodium in the present application improve the dispersion of active metals of the hydrogen cracking catalyst, and maintain the bimodal pore structure of the catalyst, thereby promoting the hydrogenation activity of the hydrogen cracking catalyst prepared by the method of the present application.

[0095] Table 1 Properties of β molecular sieves in Examples

[0096] Molecular sieve properties Beta molecular sieve Silica to alumina molar ratio 70.4 Specific surface area, m 2 / g]] 587 Pore volume, mL / g 0.45 Infrared total acid, mmol / g 0.35 Na2O, wt% 0.080

[0097] Table 2 Properties of Y molecular sieves in Examples and Comparative Examples

[0098] Molecular sieve properties Y-type molecular sieve Relative crystallinity, % 116 Unit cell parameter, nm 2.430 molar ratio of SiO2 / Al2O3 80.5 Specific surface area, m 2 / g]] 864 Pore volume, mL / g 0.488 Infrared total acid, mmol / g 0.241 B acid / L acid 11.27 Na2O, wt% <0.01

[0099] Table 3 Catalyst composition and properties prepared in Examples and Comparative Examples

[0100] Catalyst number ① ② ③ ④ ⑤ ⑥ ⑦ ⑧ ⑨ Catalyst composition MoO3, wt% 15 25 13 19.5 15 15 15 15 15 WO3, wt% 30 20 39 19.5 30 30 30 30 30 NiO, wt% 15 25 20 13 15 15 15 15 15 Molecular sieve 25 20 15 35 25 25 25 25 25 Na, ppm 319 453 841 269 365 285 79442 2113 2482 Specific surface area, m 2 / g]] 281 331 258 346 243 274 87 278 264 Pore volume, mL / g 0.408 0.376 0.445 0.362 0.340 0.359 0.092 0.403 0.386 Mechanical strength, N / mm 18.9 18.7 17.2 20.4 18.3 20.1 4.1 18.5 12.3

[0101] Table 4 Properties of raw oil

[0102] Feed oil Middle East vacuum gas oil Density (20°C) / g-cm -3 ]] 0.9026 Distillation range / °C IBP / 10% 321 / 370 30% / 50% 395 / 415 70% / 90% 432 / 481 95% / EBP 507 / 526 S, pg / g 18925 N, pg / g 1124 Mass spectrum composition, % Paraffins 28.7 Naphthenes 32.6 Aromatics 38.7

[0103] Table 5 Catalyst evaluation results

[0104] Catalyst number ① ② ⑤ ⑥ ⑧ ⑨ Product distribution, wt% Light naphtha (less than 82°C) 2.7 2.4 2.6 2.5 2.4 2.6 Heavy naphtha (82-134°C) 7.9 7.6 7.6 7.8 7.8 7.5 Marine gas oil (134-260°C) 32.0 31.2 31.7 31.9 32.0 31.8 White oil (260-371°C) 28.1 27.6 27.9 27.9 27.7 27.6 Tail oil (>371°C) 28.0 30.3 29.0 28.5 28.9 29.2 [C5 + Yield, wt%]] 98.7 99.1 98.8 98.6 98.8 98.7 Conversion, % 71.6 69.4 70.6 71.1 70.7 70.4

[0105] Table 6 Analysis results of white oil fraction product (260~371℃)

[0106] Catalyst ① ② ⑤ ⑥ ⑧ ⑨ Density (20°C), g / cm 3 ]] 0.8163 0.8145 0.8212 0.8196 0.8177 0.8179 Sulfur, pg / g 3.1 2.6 7.9 7.2 4.6 5.3 Nitrogen, pg / g 1.0 1.0 1.0 1.0 1.0 1.0 Flash point, °C 134 136 123 127 132 132 Aromatic content, wt% 3.5 3.0 9.4 8.6 5.1 5.8

Claims

1. A method for preparing a hydrocracking catalyst, characterized in that... Includes the following: (1) The mixed solution and the alkaline precipitant are added dropwise in parallel to a Ni-containing component solution to carry out a co-precipitation reaction to obtain slurry M; wherein the mixed solution is a mixed solution of sodium tungstate, sodium molybdate and sodium aluminate; (2) Slurry M is divided into two parts, slurry M-1 and slurry M-2, which are aged separately. The two aged products are then mixed to form slurry N. The aging process of the slurry M-1 is as follows: (a) First, add one part of sodium aluminate solution, then use sodium hydroxide solution to control the pH value to 11.0~12.5, and the aging time is 0.2~1.0 hours; then adjust the aging pH value to 8.8~9.6, and the aging time is 0.2~1.0 hours; then adjust the aging pH value to 6.5~7.5, and the aging time is 0.2~0.8 hours; (b) Repeat step (a) 2~6 times to complete the aging and obtain the aging product A; The aging process of the slurry M-2 is as follows: (c) First, add one part of sodium aluminate solution, then use sodium carbonate solution to control the pH value to 12.5~13.5, and the aging time is 0.2~0.6 hours; then adjust the aging pH value to 10.8~11.8, and the aging time is 0.2~0.6 hours; then adjust the aging pH value to 7.5~8.5, and the aging time is 0.2~0.6 hours; (d) Repeat step (c) 2~6 times to complete the aging, and then adjust the pH value to be the same as that of aging product A to obtain aging product B; (3) Vacuum filter the slurry N, and the obtained filter cake is cured once; after curing, add a certain proportion of P deionized water to the top of the filter cake and vacuum filter; perform a second curing on the filter cake, add a certain proportion of S deionized water to the top of the filter cake, and vacuum filter to obtain the filter cake. (4) The filter cake is dried, then mixed with molecular sieve and molding aid, and extruded into strips to obtain the molded product. The product is then calcined to obtain the hydrocracking catalyst. In step (3), the humidity of the filter cake during the first curing process is greater than 83%; the temperature during the first curing process is 33℃~48℃, and the curing time is 0.3~2 hours; the second curing process repeats the first curing process.

2. The method according to claim 1, characterized in that: In the mixed solution described in step (1), the molar concentration of sodium tungstate is 0.1~1.2 mol / L, the molar concentration of sodium molybdate is 0.15~0.8 mol / L, and the molar concentration of sodium aluminate, calculated as Al2O3, is 0.05~1.0 mol / L.

3. The method according to claim 1, characterized in that: The alkaline precipitant in step (1) is one or more of sodium hydroxide, ammonia, sodium carbonate, and sodium bicarbonate aqueous solution, and the pH value of the alkaline precipitant is not less than 12.

5.

4. The method according to claim 1, characterized in that: The Ni-containing component in step (1) is a soluble nickel salt; the molar concentration of Ni, calculated as NiO, is 0.2~1.4 mol / L.

5. The method according to claim 1, characterized in that: The coprecipitation reaction conditions in step (1) are: reaction time 25~200 minutes, reaction temperature 40~95℃; online measurement of the pH value of the reaction solution, and the pH value of the reaction system is maintained between 6.0 and 7.

8.

6. The method according to claim 1, characterized in that: In step (2), the sodium aluminate solution contains Al as Al2O3 with a molar concentration of 0.1~0.5 mol / L. The sodium aluminate solution added during the M-1 aging process is divided into 2~6 portions, and the sodium aluminate solution added during the M-2 aging process is divided into 2~6 portions.

7. The method according to claim 1, characterized in that: In step (2), the mass ratio of slurry M-1 to slurry M-2 is 0.3~4:1; the mass ratio of sodium aluminate solution added during the aging of slurry M-1 and slurry M-2 is the same as the mass ratio of slurry M-1 to slurry M-2.

8. The method according to claim 1, characterized in that: The Al added in step (2) during the aging process accounts for 10% to 60% of the mass fraction of Al2O3 in the prepared catalyst, while the Al2O3 in the molecular sieve is not included.

9. The method according to claim 1, characterized in that: The aging temperature range of slurry M-1 in step (2) is 35~45℃; the aging temperature range of slurry M-2 is 60~90℃.

10. The method according to claim 1, characterized in that: In step (3), the temperature for each health-preserving session is 36℃~42℃, and the duration of the health-preserving session is 0.5~1.0 hours.

11. The method according to claim 1, characterized in that: In step (3), after adding deionized water above the filter cake, it should not be stirred with the filter cake, but should be directly filtered.

12. The method according to claim 1, characterized in that: The drying conditions for step (4) are as follows: dry at 70~150℃ for 1~24 hours.

13. The method according to claim 1, characterized in that: The molecular sieve in step (4) is a Y-type molecular sieve and / or a β-type molecular sieve, and the content of the molecular sieve is 10wt%~45wt% based on the weight of the hydrocracking catalyst.

14. The method according to claim 1, characterized in that: The roasting temperature in step (4) is 380~540℃ and the roasting time is 4~12 hours.

15. A hydrocracking catalyst prepared by the method according to any one of claims 1 to 14, characterized in that: It exhibits a bimodal pore structure, with the following pore distribution: pores with a diameter of less than 3 nm account for 0.1% to 1% of the total pore volume; pores with a diameter of 3 to 8 nm account for 35% to 48% of the total pore volume; pores with a diameter of 8 to 15 nm account for 8% to 15% of the total pore volume; pores with a diameter of 15 to 60 nm account for 30% to 48% of the total pore volume; and pores with a diameter of more than 60 nm account for 5% to 10% of the total pore volume.

16. The catalyst according to claim 15, characterized in that: The catalyst pore distribution is as follows: pores with a diameter of less than 3 nm account for 0.1% to 0.5% of the total pore volume; pores with a diameter of 3 to 8 nm account for 38% to 48% of the total pore volume; pores with a diameter of 8 to 15 nm account for 8% to 12% of the total pore volume; pores with a diameter of 15 to 60 nm account for 35% to 48% of the total pore volume; and pores with a diameter of more than 60 nm account for 5% to 8% of the total pore volume.

17. The catalyst according to claim 15, characterized in that: The hydrocracking catalyst has a specific surface area of ​​200-400 m². 2 / g, pore volume 0.32~0.52mL / g, catalyst strength not less than 15.5N·mm -1 .

18. The catalyst according to claim 15, characterized in that: The hydrocracking catalyst comprises oxides of tungsten, molybdenum, nickel, and aluminum, and molecular sieves; wherein the proportion of tungsten, molybdenum, and nickel oxides is 40wt%~80wt%, the proportion of molecular sieves is 10wt%~45wt%, and the proportion of alumina is 10wt%~50wt%; the sodium content is ≤0.1%; the molar ratio of W / Mo in the hydrocracking catalyst is 0.5~10:1, and the molar ratio of (Mo+W) / Ni is 1~9:1.

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