A method for preparing a step pore desulfurization catalyst

Abstract

The invention discloses a preparation method of a hierarchical pore desulfurization catalyst, comprising the following contents: (1) preparing a first pseudo-boehmite having the following properties: 1.0 < P1 ≤ 1.3, 1.1 < P2 ≤ 1.5, P1=D(120) / D(031), P2=D(120) / D(020), wherein D represents the grain size of the crystal plane corresponding to the characteristic peak in the XRD pattern of pseudo-boehmite grains; (2) impregnating the first pseudo-boehmite with a first active component impregnation solution, and drying to obtain modified pseudo-boehmite; (3) kneading and molding the modified pseudo-boehmite and a second pseudo-boehmite, and drying and roasting the molded product to obtain a modified alumina carrier; (4) impregnating the modified alumina carrier with a second active component impregnation solution, drying and roasting to obtain the hierarchical pore desulfurization catalyst. The catalyst of the invention has a macropore-mesopore hierarchical pore structure, the hydrogenation reaction activity at macropores is high, the high hydrogenation reaction active sites are well matched with the pore channels of the catalyst, and the catalyst has broad application prospects in the field of heterogeneous catalysis.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation, and specifically relates to a method for preparing a cascade pore desulfurization catalyst. Background Technology

[0002] In recent years, with the increasing weight of crude oil resources, the growing demand for fuel oil, and increasingly stringent environmental regulations, the use of hydrogenation technology to convert residue oil into high-quality light fuel oil and chemical products helps to improve crude oil processing depth, reduce environmental pollution, increase light oil yield, and improve product quality. Residue oil is enriched with most of the heteroatoms in crude oil, such as sulfur, nitrogen, and metals (mainly Ni and V). The metals in residue oil are mainly found in macromolecular compounds such as gums and asphaltenes. These compounds have complex structures, large molecular sizes, and are difficult to diffuse. Traditional alumina supports have small pores, which is not conducive to the diffusion of large molecular reactants in residue oil; therefore, it is necessary to develop alumina supports with larger pores.

[0003] CN201510191156.7 discloses a heavy oil hydrogenation catalyst and its preparation method. The catalyst comprises an alumina support composed of sheet-like polycrystalline γ-alumina and a hydrogenation active metal. The preparation method of the catalyst is as follows: sheet-like γ-polycrystalline alumina powder is added to a binder and an extrusion aid, kneaded, shaped, dried and calcined to obtain an alumina support, and an active metal is loaded onto the obtained alumina support using conventional methods. The preparation method of sheet-like γ-polycrystalline alumina includes the following steps: (1) inorganic aluminum salt, low-carbon alcohol and / or water, and low-carbon epoxy alkane are mixed evenly to form a gel, and then the gel is aged; (2) the gel obtained in step (1) is soaked in low-carbon alcohol, and then dried and calcined; (3) the material obtained in step (2) is immersed in ammonia water for closed hydrothermal treatment, solid-liquid separation, and drying to obtain sheet-like γ-polycrystalline alumina powder. This invention adjusts the pore structure of an alumina support by adding lamellar polycrystalline γ-alumina to the alumina support. However, the preparation process of lamellar polycrystalline γ-alumina is relatively complex. On the other hand, the matching degree between the active metal component and the catalyst pores needs to be further improved.

[0004] CN201910265729.4 discloses a preparation method of a hydrodemetallization catalyst. The preparation method of the hydrodemetallization catalyst of the present invention comprises: (1) preparing rod-shaped alumina clusters; (2) impregnating the rod-shaped alumina clusters of step (1) with an impregnation solution containing hydrogenation active component I and drying to obtain modified rod-shaped alumina clusters, kneading, molding, drying and calcining the modified rod-shaped alumina clusters and pseudo-boehmite to obtain support I; (3) mixing the support I obtained in step (2) with ammonium bicarbonate and water, then performing sealed heat treatment, drying and calcining the treated material to obtain support II; (4) impregnating the support II of step (3) with an impregnation solution containing hydrogenation active component II, and drying and calcining the support to obtain the hydrodemetallization catalyst. This method adjusts the pore structure and active metal distribution of the catalyst by using rod-shaped alumina clusters modified with active components, thereby improving the activity of the catalyst. However, the pores formed by the accumulation of rod-shaped particles in the rod-shaped alumina clusters are relatively large, which is not conducive to the full exertion of the hydrogenation activity of the catalyst. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the present invention provides a preparation method of a hierarchical pore desulfurization catalyst. The catalyst of the present invention has a hierarchical pore structure of macropores-mesopores, the hydrogenation reaction activity at the macropores is high, and the high hydrogenation reaction active sites are well matched with the pores of the catalyst. The catalyst has high hydrodemetallization and desulfurization activities during the heavy oil hydrogenation reaction process.

[0006] The preparation method of the hierarchical pore desulfurization catalyst of the present invention comprises the following contents: (1) Preparing first pseudo-boehmite with the following properties: 1.0 < P1 ≤ 1.3, 1.1 < P2 ≤ 1.5, P1 = D(120) / D(031), P2 = D(120) / D(020), wherein D represents the grain size of the crystal plane corresponding to the characteristic peak in the XRD pattern of pseudo-boehmite grains; (2) Impregnating the first pseudo-boehmite with a first active component impregnation solution, and drying the impregnated material to obtain modified pseudo-boehmite; (3) Kneading and molding the modified pseudo-boehmite and the second pseudo-boehmite, drying and calcining the molded product to prepare a modified alumina support; (4) Impregnating the modified alumina support with a second active component impregnation solution, drying and calcining the impregnated material to obtain the hierarchical pore desulfurization catalyst.

[0007] In the method of this invention, in the first pseudoboehmite prepared in step (1), D(120) represents the grain size of the crystal plane corresponding to the peak (120) in the XRD pattern of the pseudoboehmite grains, and D(120) is 75-105 Å; D(031) represents the grain size of the crystal plane corresponding to the peak (031) in the XRD pattern of the pseudoboehmite grains, and D(031) is 70-90 Å; D(020) represents the grain size of the crystal plane corresponding to the peak (020) in the XRD pattern of the pseudoboehmite grains. The grain size, D(020), is 60-70 Å; the 120 peak refers to the characteristic peak with 2θ of 25.5-29.9º in the XRD spectrum; the 031 peak refers to the characteristic peak with 2θ of 36.3-40.5º in the XRD spectrum; the 020 peak refers to the characteristic peak with 2θ of 12.0-16.2º in the XRD spectrum; D=Kλ / (Bcosθ), where K is the Scherrer constant, λ is the diffraction wavelength of the target material, B is the half-width at half-maximum of the diffraction peak, and θ is the diffraction angle; The preparation method of the first pseudoboehmite in the method of the present invention is as follows: calcined nitric acid is crushed and sieved to obtain powdered material, the powdered material is immersed in propylene oxide solution and sealed for heat treatment, and the treated material is dried to obtain the first pseudoboehmite; the first pseudoboehmite has a platy structure.

[0008] In the above-mentioned method for preparing the first pseudoboehmite, the calcination temperature is 450-650℃, and the calcination time is 4-8 hours. The particle size of the powdered material is greater than 100 mesh, preferably greater than 200 mesh. The mass concentration of the propylene oxide solution is 2.5%-12%, preferably 4%-8%, and the mass ratio of the propylene oxide solution to the aluminum oxide is 3:1-10:1, preferably 4:1-8:1. The hydrothermal treatment is carried out in a closed container, preferably an autoclave, at a temperature of 110-180℃, preferably 120-160℃, for 4-8 hours, and the pressure inside the sealed container during hydrothermal treatment is autogenous pressure. The drying temperature is 100-160℃, and the drying time is 2-8 hours.

[0009] In the method of the present invention, the first active component impregnation solution in step (2) is a W-Ni-P solution containing WO3 and NiO, wherein the WO3 content in the solution is 1-5g / 100mL and the NiO content is 0.2-1g / 100mL, the amount of impregnation solution used is to completely submerge the material, the impregnation time is 1-4 hours, the drying temperature is 100-160℃, and the drying time is 2-8 hours.

[0010] In the method of the present invention, the second boehmite in step (3) can be boehmite prepared by any method, such as acid precipitation, alkali precipitation, aluminum alkoxide hydrolysis, etc., preferably boehmite with a pore size of 10-20 nm, more preferably boehmite with a pore content of 10-20 nm accounting for more than 40% of the total pore volume.

[0011] In the method of the present invention, the mass ratio of the modified flaky boehmite to the second boehmite in step (3) is 1:4-2:3.

[0012] In the method of this invention, the kneading and molding in step (3) is carried out using conventional methods in the art. During the molding process, conventional molding aids, such as adhesives, extrusion aids, etc., can be added as needed. The adhesive is one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, oxalic acid, etc., with a mass concentration of 0.5%-2%, and the amount of adhesive depends on the molding effect. The extrusion aid is guar gum powder, and the amount added is 1%-3% of the final alumina carrier weight. The drying temperature is 100-160℃, and the drying time is 6-10 hours. The calcination temperature is 550-750℃, and the calcination time is 4-6 hours. The calcination is carried out in an oxygen-containing atmosphere, preferably in an air atmosphere.

[0013] In the method of the present invention, the second active component impregnation solution in step (4) is a solution containing MoO3 and NiO. The concentration of MoO3 in the solution is 8.5g / 100mL-15.5g / 100mL, and the concentration of NiO is 2.0g / 100mL-3.8g / 100mL. Equal volume impregnation is used during impregnation. After impregnation, the material is dried at 80-120℃ for 4-8 hours, and calcined at 400-550℃ for 4-8 hours.

[0014] The stepwise porous desulfurization catalyst prepared by the method of this invention is suitable for hydrodesulfurization and demetallization reactions of residual oil.

[0015] Compared with the prior art, the present invention has the following advantages: (1) The present invention first prepares a first pseudoboehmite, which has high crystallinity, uniform plate-like particle structure and interwoven stacking to form a large number of 50-150nm pores. The plate-like grains support each other, which can ensure that the pores formed by stacking are not easily destroyed during carrier molding. Therefore, when using this plate-like pseudoboehmite as raw material to prepare alumina carrier, the macropore content of the carrier can be effectively increased.

[0016] (2) In this invention, the first active metal impregnation solution is used to pre-impregnate the flaky boehmite, thereby ensuring that the content of active metal components in the macropores formed by the accumulation of the flaky particles of the prepared catalyst is high and consists of multiple components of Mo, W and Ni, which increases the number of active sites for hydrogenation reaction during the hydrogenation reaction. At the same time, the pores formed by the accumulation of flaky particles are uniform, which allows the catalyst to exert high hydrogenation reaction activity while effectively avoiding catalyst deactivation caused by metal deposition and carbon buildup at the active sites, ensuring long-term operation of the catalyst. Attached Figure Description

[0017] Figure 1 is a SEM image of the platy pseudoboehmite P1-1 prepared in Example 1.

[0018] Figure 2 shows the XRD pattern of the platy boehmite P1-1 prepared in Example 1.

[0019] Figure 3 SEM images of materials P1-6 prepared in Comparative Example 3. Implementation

[0020] The technical solution and effects of the present invention will be further illustrated below with reference to the embodiments, but the invention is not limited to the following embodiments. In the present invention, wt% represents mass fraction.

[0021] BET Method: The pore structure of the carriers in the examples and comparative examples was characterized using N2 physical adsorption-desorption. The specific procedure was as follows: The pore structure of the samples was characterized using an ASAP-2420 N2 physical adsorption-desorption instrument. A small amount of sample was vacuum-treated at 300℃ for 3-4 hours, and finally, the product was placed under liquid nitrogen cryogenic conditions (-200℃) for nitrogen adsorption-desorption testing. The specific surface area was obtained according to the BET equation, and the pore volume and pore diameter distribution below 30nm were obtained according to the BJH model.

[0022] The microstructure of the alumina support was characterized using scanning electron microscopy. The specific operation was as follows: The microstructure of the support was characterized using a JSM-7500F scanning electron microscope with an accelerating voltage of 5KV, an accelerating current of 20µA, and a working distance of 8mm.

[0023] Mercury porosimetry: The pore diameter distribution of the carriers in the examples and comparative cases was characterized using a mercury porosimetry instrument. The specific procedure was as follows: The pore distribution of the samples was characterized using a Micron AutoPore 9500 fully automated mercury porosimetry instrument. After drying, the samples were weighed and placed into a dilatometer. The sample was then degassed for 30 minutes under the vacuum conditions specified by the instrument before mercury was added. The dilatometer was then placed in an autoclave, and the pressure was evacuated. Pressure increase and decrease tests were then performed. The mercury contact angle was 130°, and the mercury interfacial tension was 0.485 N / cm. -1 The distribution rate of pores with a diameter of 100 nm or more was measured by mercury porosimetry.

[0024] Most probable pore size determination: The differential distribution curve of pore size is obtained by plotting the material pore size on the x-axis and the rate of change of pore volume with pore size on the y-axis. The peak value in the curve is the most probable pore size.

[0025] The Ni and V content in oil products was determined using the standard method of GB / T 34099-2017.

[0026] V+Ni removal rate % = (V+Ni content in feedstock oil - V+Ni content in product oil) / V+Ni content in feedstock oil × 100%.

[0027] Relative demetallization rate: The demetallization rate of a catalyst is measured, and its relative demetallization rate is defined as 100%. The relative impurity removal rate is calculated as the ratio of the impurity removal rate of other catalysts to the defined impurity removal rate of the catalyst × 100%.

[0028] Preparation of active metal-modified flaky pseudoboehmite material HP: Example 1

[0029] Weigh an appropriate amount of aluminum nitrate and place it in a crucible. Roast at 500°C for 6.5 hours. The roasted material is then pulverized. The sample was crushed and sieved to obtain particles larger than 200 mesh. 100 grams of the sieved particles were weighed and added to 500 grams of a 6.5% propylene oxide aqueous solution. The mixture was magnetically stirred for 30 minutes. The mixture was then transferred to an autoclave, sealed, and heated at 145°C for 5.5 hours. After cooling, the solid material was filtered, washed, and dried at 140°C for 5 hours to obtain platy boehmite P1-1. Scanning electron microscopy (SEM) revealed that the sample's microstructure consisted of platy crystal aggregates. (SEM image shown below). Figure 1 XRD pattern can be found Figure 2 P1=1.12, P2=1.29, D(120) is 84Å, D(031) is 75Å, D(020) is 65Å.

[0030] (2) Weigh an appropriate amount of the flaky pseudoboehmite from step (1), and impregnate it for 2 hours with the first active component impregnation solution with a WO3 concentration of 3.0 g / 100 mL and a NiO concentration of 0.7 g / 100 mL. After impregnation, dry the material at 140 °C for 5 hours to obtain active metal modified flaky pseudoboehmite HP1-1.

[0031] (3) Weigh 100g of active metal modified flake pseudoboehmite HP1-1 from step (2), 233g of pseudoboehmite P2 (self-made by aluminum sulfate-sodium aluminate method, with 10-20nm pores accounting for 55% of the total pore volume), and 3.5g of guar gum powder. Mix the above materials evenly, then add an appropriate amount of acetic acid solution with a mass concentration of 1%, knead evenly, and then extrude into strips. Dry the formed product at 130℃ for 8 hours and calcine at 600℃ for 5 hours to obtain the active metal modified alumina carrier of the present invention.

[0032] (4) Weigh 50 g of the active metal modified alumina support from step (3), and spray the active metal modified alumina support with the second active component impregnation solution with a MoO3 concentration of 13.1 g / 100 mL and a NiO concentration of 3.5 g / 100 mL in a saturated impregnation manner. The impregnated material is dried at 140 °C for 5 hours and calcined at 450 °C for 5 hours to obtain the stepped pore hydrogenation catalyst Cat-1 of the present invention. The properties of the catalyst are shown in Table 1. Example 2

[0033] Same as Example 1, except that in step (1), the calcination temperature of aluminum nitrate was 550℃, the calcination time was 5.5 hours, the concentration of propylene oxide was 5.4%, the solution volume was 630 g, the hydrothermal treatment temperature was 135℃, and the treatment time was 6.5 hours. The resulting flaky boehmite had P1=1.13, P2=1.31, D(120) was 93 Å, D(031) was 82 Å, and D(020) was 71 Å. In step (2), the concentration of WO3 in the first active component impregnation solution was 3.5 g / 100 mL, and the concentration of NiO was 0.8 g / 100 mL. In step (3), the amount of boehmite P2 added was 185 g. In step (4), the concentration of MoO3 in the second active component impregnation is 12.0 g / 100 mL and the concentration of NiO is 3.1 g / 100 mL, thus preparing the ladder-pore hydrogenation catalyst Cat-2 of the present invention. The properties of the catalyst are shown in Table 1. Example 3

[0034] Same as Example 1, except that in step (1), the calcination temperature of aluminum nitrate was 450℃, the calcination time was 7.5 hours, the concentration of propylene oxide was 4.3%, the solution volume was 720 g, the hydrothermal treatment temperature was 155℃, and the treatment time was 4.5 hours. The resulting platy boehmite crystals had P1=1.07, P2=1.33, D(120) was 89 Å, D(031) was 83 Å, and D(020) was 67 Å. In step (2), the concentration of WO3 in the first active component impregnation solution was 2.5 g / 100 mL, and the concentration of NiO was 0.6 g / 100 mL. In step (3), the amount of boehmite P2 added was 150 g. In step (4), the concentration of MoO3 in the second active component impregnation is 11.3 g / 100 mL and the concentration of NiO is 2.7 g / 100 mL, thus obtaining the ladder-pore hydrogenation catalyst Cat-3 of the present invention. The properties of the catalyst are shown in Table 1. Example 4

[0035] Same as Example 1, except that in step (1), the calcination temperature of aluminum nitrate was 600℃, the calcination time was 4.5 hours, the concentration of propylene oxide was 7.5%, the solution volume was 430 g, the hydrothermal treatment temperature was 125℃, and the treatment time was 7.5 hours. The resulting platy boehmite grain sizes were P1=1.17, P2=1.28, D(120) was 96 Å, D(031) was 82 Å, and D(020) was 75 Å. In step (2), the concentration of WO3 in the first active component impregnation solution was 4.0 g / 100 mL, and the concentration of NiO was 1.0 g / 100 mL. In step (3), the amount of boehmite P2 added was 300 g. In step (4), the concentration of MoO3 in the second active component impregnation is 13.5 g / 100 mL and the concentration of NiO is 4.2 g / 100 mL, thus obtaining the ladder-pore hydrogenation catalyst Cat-4 of the present invention. The properties of the catalyst are shown in Table 1.

[0036] Comparative Example 1 Same as Example 1, except that in step (1) propylene oxide was replaced with the same amount of ethylene oxide. After hydrothermal treatment, no plate-like crystals were observed to form in the microstructure of material P1-5, and the comparative catalyst Cat-5 was obtained. The properties of the catalyst are shown in Table 1.

[0037] Comparative Example 2 Same as Example 1, except that aluminum nitrate is replaced with aluminum sulfate in step (1). After hydrothermal treatment, the solid material particles dissolve and are not separated to obtain the product.

[0038] Comparative Example 3 Same as Example 1, except that aluminum nitrate in step (1) is replaced with aluminum chloride. After hydrothermal treatment, no lamellar grains were observed in the microstructure of material P1-6. P1=1.09, P2=1.46, D(120) is 76 Å, D(031) is 70 Å, and D(020) is 52 Å. The scanning electron microscope image is shown below. Figure 3 The comparative catalyst Cat-6 was prepared, and its properties are shown in Table 1.

[0039] Comparative Example 4 Same as Example 1, except that the impregnation process in step (2) is missing. Instead, a one-step impregnation method is used to prepare the comparative catalyst Cat-7 with the same active metal loading. The catalyst properties are shown in Table 1.

[0040] Table 1 Catalyst Properties catalyst Cat-1 Cat-2 Cat-3 Cat-4 Cat-5 Cat-6 Cat-7 <![CDATA[Specific surface area, m 2 / g]]> 213 193 181 232 168 151 198 Pore ​​volume, mL / g 0.93 0.91 0.95 0.94 0.81 0.76 0.92 <![CDATA[Content of MoO₃, wt%]]> 12.9 11.7 11.5 13.2 13.1 13.3 12.8 NiO content, wt% 3.8 3.5 2.9 4.3 3.9 4.1 3.8 <![CDATA[WO3 content, wt%]]> 1.3 1.7 1.4 1.4 1.2 1.4 1.3 10-30nm pore content, v% 59.3 57.6 55.1 61.1 62.5 61.2 58.1 50-100nm pore content, v% 17.3 18.9 22.6 15.4 3.5 1.7 17.9

[0041] The catalytic performance of the stepwise porous desulfurization catalysts (Cat-1-Cat-7) prepared in the above examples and comparative examples was evaluated using the following methods: Using a certain residual oil as feedstock, the feedstock oil contained 113 μg / g of metals (Ni+V) and 0.26 wt% sulfur. The catalytic performance of the stepwise porous hydrogenation catalyst Cat-1-Cat-6 was evaluated using a 200 mL small-scale evaluation apparatus under the following conditions: reaction temperature 385℃, pressure 14.0 MPa, and liquid hourly space velocity (LISH) 0.70 h⁻¹. -1 The hydrogen-to-oil volume ratio was 800. After 3000 hours of reaction, the content of each impurity in the generated oil was measured, the impurity removal rate was calculated, and the evaluation results are shown in Table 2.

[0042] Table 2 Comparison of catalyst hydrogenation performance Relative demetallization (V+Ni) rate, % 126 135 138 123 100 93 116 Relative desulfurization rate, % 129 126 128 133 100 95 120 As can be seen from the data in Table 2, compared with the comparative catalyst, the catalyst prepared by the method of the present invention has higher hydrodemetallization activity and hydrodesulfurization activity.

Claims

1. A method for preparing a stepped porous desulfurization catalyst, characterized in that... Comprising the following steps: (1) preparing first pseudo-boehmite having the following properties: 1.0 < P1 ≤ 1.3, 1.1 < P2 ≤ 1.5, P1 = D120 / D031, P2 = D120 / D020, wherein D represents the grain size of the crystal plane corresponding to the characteristic peak in the XRD pattern of pseudo-boehmite grains; (2) impregnating the first pseudo-boehmite with a first active component impregnation solution, and drying the impregnated material to obtain modified pseudo-boehmite; (3) kneading and molding the modified pseudo-boehmite and second pseudo-boehmite, drying and calcining the molded product to prepare a modified alumina support; (4) impregnating the modified alumina support with a second active component impregnation solution, drying and calcining the impregnated material to obtain a stepped pore hydrogenation catalyst; in the first pseudo-boehmite prepared in step (1), said D120 represents the grain size of the crystal plane corresponding to the 120 peak in the XRD pattern of pseudo-boehmite grains, and D120 is 75-105Å; D031 represents the grain size of the crystal plane corresponding to the 031 peak in the XRD pattern of pseudo-boehmite grains, and D031 is 70-90Å; D020 represents the grain size of the crystal plane corresponding to the 020 peak in the XRD pattern of pseudo-boehmite grains, and D020 is 60-70Å; said 120 peak refers to a characteristic peak with 2θ of 25.5-29.9º in the XRD pattern; said 031 peak refers to a characteristic peak with 2θ of 36.3-40.5º in the XRD pattern; said 020 peak refers to a characteristic peak with 2θ of 12.0-16.2º in the XRD pattern, D=Kλ / (Bcosθ), K is the Scherrer constant, λ is the diffraction wavelength of the target material, B is the half-peak width of the diffraction peak, and θ is the diffraction angle; said first pseudo-boehmite has a sheet-like structure; said first active component impregnation solution in step (2) is a W-Ni-P solution containing WO3 and NiO; said second active component impregnation solution in step (4) is a solution containing MoO3 and NiO.

2. The method according to claim 1, characterized in that: The preparation method of said first pseudo-boehmite is as follows: crushing and sieving calcined aluminum nitrate to obtain a powdery material, immersing the powdery material in a propylene oxide solution for sealed heat treatment, and drying the treated material to obtain the first pseudo-boehmite.

3. The method according to claim 2, characterized in that: In the preparation method of the first pseudo-boehmite, the calcination temperature is 450-650°C, and the calcination time is 4-8 hours; the particle size of the powdery material is greater than 100 mesh.

4. The method according to claim 2, characterized in that: In the preparation method of the first pseudo-boehmite, the mass concentration of said propylene oxide solution is 2.5%-12%, and the mass ratio of the propylene oxide solution to the aluminum-containing oxide is 3:1-10:1; said sealed heat treatment is carried out in a closed container, the sealed heat treatment temperature is 110-180°C, the sealed heat treatment time is 4-8 hours, and the pressure in the closed container during sealed heat treatment is autogenous pressure.

5. The method according to claim 1, characterized in that: In step (2), the WO3 content in the first active component impregnation solution is 1-5g / 100mL, the NiO content is 0.2-1g / 100mL, the amount of impregnation solution used is to completely submerge the material, the impregnation time is 1-4 hours, the drying temperature is 100-160℃, and the drying time is 2-8 hours.

6. The method according to claim 1, characterized in that: The second pseudoboehmite described in step (3) has a pore size of 10-20 nm.

7. The method according to claim 1, characterized in that: The mass ratio of the modified boehmite to the second boehmite in step (3) is 1:4-2:

3.

8. The method according to claim 1, characterized in that: In step (4), the concentration of MoO3 in the second active component impregnation solution is 8.5g / 100mL-15.5g / 100mL, and the concentration of NiO is 2.0g / 100mL-3.8g / 100mL. Equal volume impregnation is used during impregnation. After impregnation, the material is dried at 80-120℃ for 4-8 hours and calcined at 400-550℃ for 4-8 hours.

9. The application of a stepped-pore desulfurization catalyst prepared by the method according to any one of claims 1 to 8 in the process of hydrodesulfurization and demetallization of residual oil.

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