A method for preparing a heavy oil hydrodesulfurization catalyst

Abstract

The present invention aims to provide a method for preparing a heavy oil hydrodesulfurization catalyst, belonging to the field of catalyst preparation technology. The preparation method includes the following steps: preparing a phosphorus-containing aluminum sol; uniformly mixing the phosphorus-containing aluminum sol with spherical carbon particles, and forming the mixture by drop pelleting in an oil-ammonia column forming device; drying and calcining the formed product to obtain a phosphorus-modified alumina support precursor; immersing the phosphorus-modified alumina support precursor in an organic ammonium solution for hydrothermal treatment; drying the treated product to obtain a mixed-phase support of γ-Al₂O₃ and AlOOH; impregnating the mixed-phase support with an active component impregnation solution; and drying and calcining the impregnated support to obtain the hydrodesulfurization catalyst. The prepared catalyst exhibits suitable interaction between the active metal component and the support, possessing high hydrodesulfurization and demetallization activity while also exhibiting high activity stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, and specifically relates to a method for preparing a heavy oil hydrodesulfurization catalyst. Background Technology

[0002] With increasingly stringent environmental regulations and the growing trend towards heavier crude oil, efficient conversion of heavy oil has become a significant trend in refining technology development. Fixed-bed residue hydrotreating technology is an effective means to achieve efficient conversion of heavy oil. Residue oil has high viscosity, high impurity content, and complex molecular composition, making hydrotreating reactions challenging. It requires the effective removal of impurities such as metals, sulfur, nitrogen, and residual carbon from the residue oil through catalytic reactions. A single catalyst is insufficient; therefore, a matched packing system using catalysts with different functions, shapes, and sizes is necessary to achieve high activity and long-term industrial operation. Residue oil hydrotreating catalysts typically include protective catalysts, demetallizing catalysts, desulfurization catalysts, and denitrification catalysts, each with additional functions.

[0003] Currently, the preparation of residue hydrotreating catalysts generally involves using alumina or alumina containing a small amount of additives as a support. The support is impregnated with an aqueous solution containing active metal compounds, followed by post-treatment processes such as drying and baking. During the operation of the residue hydrotreating unit, due to the poor properties of the residue, a large number of aromatic polycyclic aromatic compounds easily deposit on the catalyst, forming carbon-rich organic deposits that clog the pores, cover the active sites of the catalyst, and deactivate it. This leads to a gradual increase in the pressure drop across the catalyst bed, thereby shortening the operating cycle of the industrial unit.

[0004] CN104646009B discloses a low-quality heavy oil hydrodesulfurization catalyst and its preparation method. The catalyst uses alumina as a support and Group VIII and VIB elements, particularly Ni-Mo, as the active components. The catalyst pore volume is 0.45–0.60 cm³. 3 / g, with a specific surface area of ​​205–260m² 2 The catalyst has an average pore size of 7.0–12.0 nm, with the average pore diameter gradually increasing radially from the center to the outer surface of the catalyst particles. The catalyst is prepared by treating the shaped and calcined support particles with an acid solution of continuously increasing concentration. However, the catalyst prepared by this method has a relatively small surface pore size, making it prone to clogging and causing catalyst deactivation.

[0005] CN111822011A discloses a support, catalyst, and preparation method thereof for hydrodesulfurization. The preparation method of the support is as follows: a solution containing phosphorus and / or boron additives is adsorbed onto a physical pore-expanding agent, then mixed with boehmite, kneaded, dried, and calcined to obtain a support intermediate; this intermediate is then immersed in an ammonium bicarbonate solution, sealed, heat-treated, and dried; the outer surface of the impregnated material is sprayed with a solution containing titanium additives, dried, and calcined to obtain an alumina support. This method regulates the pores of the alumina support and catalyst through rod-shaped alumina in the support, but the rod-shaped particles on the surface of the alumina support prepared by this method are prone to detachment.

[0006] Furthermore, in the preparation of heavy oil hydrodesulfurization catalysts using existing technologies, γ-alumina is generally used as the support, and metals such as Mo, W, Ni, and Co are used as active components. During catalyst calcination, the active metal components tend to interact strongly with the alumina support, thereby reducing the catalyst's activity. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing a hydrodesulfurization catalyst. During catalyst preparation, a mixed phase of γ-Al₂O₃ and AlOOH is selected as the support. The prepared catalyst exhibits suitable interaction between the active metal component and the support, resulting in high hydrodesulfurization and demetallization activity while also possessing high activity stability.

[0008] The present invention adopts the following technical solution:

[0009] A method for preparing a heavy oil hydrodesulfurization catalyst includes the following steps:

[0010] The first step is to prepare a phosphorus-containing aluminum sol;

[0011] The second step involves uniformly mixing phosphorus-containing aluminum sol with spherical carbon particles, then forming the mixture by drop in an oil-ammonia column forming device. The formed product is then dried and calcined to obtain a phosphorus-modified alumina carrier precursor.

[0012] The third step involves immersing the phosphorus-modified alumina carrier precursor in an organic ammonium solution for hydrothermal treatment. After treatment, the product is dried to obtain a mixed phase carrier of γ-Al2O3 and AlOOH.

[0013] The hydrothermal treatment is a closed-loop hydrothermal treatment carried out in a sealed container, and is divided into two stages: In the first stage, the organic ammonium solution has a mass concentration of 0.8%-2.0%, the solution volume is sufficient to completely submerge the solid material, the hydrothermal treatment temperature is 80-120℃, and the treatment time is 1-4 hours; In the second stage, the organic ammonium solution has a mass concentration of 3.5%-12.5%, the solution volume is sufficient to completely submerge the solid material, the hydrothermal treatment temperature is 140-180℃, and the treatment time is 4-10 hours; The type of organic ammonium used in the first and second stages of hydrothermal treatment may be the same or different, preferably the same;

[0014] The fourth step involves impregnating the mixed-phase support with an active component impregnation solution, followed by drying and calcination of the impregnated support to obtain the hydrodesulfurization catalyst.

[0015] Further, the preparation method of the phosphorus-containing aluminum sol in the first step is as follows: First, boehmite is mixed evenly with a certain volume of distilled water. Then, a certain amount of acid solution is added under stirring to acidify and obtain aluminum sol. Finally, a certain amount of phosphorus-containing compound is added to the aluminum sol to obtain phosphorus-containing aluminum sol. The boehmite is preferably boehmite with a pore size greater than 12.5 nm, more preferably prepared by the aluminum sulfate-sodium aluminate method. The phosphorus-containing compound includes one or a mixture of phosphoric acid, ammonium phosphate, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate, preferably ammonium phosphate. The mass ratio of the phosphorus-containing compound to the boehmite, calculated as elemental phosphorus (P), is 0.5:100-1:100. The acid solution includes one or a mixture of nitric acid, acetic acid, formic acid, and oxalic acid solutions, preferably nitric acid solution. The solid content in the sol is 15%-35%.

[0016] Furthermore, the spherical carbon particles mentioned in the second step can be commercially available or prepared by existing methods, and the particle size of the spherical carbon particles is 1-8 μm, preferably 1-5 μm.

[0017] Furthermore, the mass ratio of the spherical carbon particles to the aluminum sol in the second step is 0.2%-0.6%.

[0018] Furthermore, in the second step, the drying temperature is 120-180℃, and the drying time is 1-8 hours; the calcination temperature is 450-600℃, and the calcination time is 4-8 hours, with the calcination carried out in an oxygen atmosphere.

[0019] Furthermore, the organic ammonium solution mentioned in the third step includes one of tetramethylammonium hydroxide and tetrapropylammonium hydroxide, preferably tetraethylammonium hydroxide.

[0020] Furthermore, the drying temperature in the third step is 100-160℃, and the drying time is 2-8 hours.

[0021] Furthermore, the active component impregnation solution described in step four is a solution containing Group VIB and Group VIII metals. Group VIB metals include one or more of W and Mo, and Group VIII metals include one or more of Co and Ni. The content of Group VIB metals in the impregnation solution, calculated as metal oxides, is 7.5-18.5 g / 100 mL, and the content of Group VIII metals, calculated as metal oxides, is 2.5-5.5 g / 100 mL.

[0022] Furthermore, in the fourth step, the drying temperature is 100-160℃ and the drying time is 2-8 hours, and the calcination temperature is 450-550℃ and the calcination time is 4-6 hours.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. In the preparation of aluminum sol, modified elemental phosphorus is added. On the one hand, the elemental phosphorus reacts with the aluminum sol to improve the pore structure of the final alumina support and increase the macropore content. On the other hand, the modified elemental phosphorus is embedded or intercalated into the aluminum sol particles to improve the surface chemical properties of the final alumina, moderately increase the content of L acid and the concentration of surface hydroxyl groups on the alumina support surface, and improve the hydrodesulfurization activity of the final catalyst.

[0025] 2. When the phosphorus-modified alumina support precursor is immersed in an organic ammonium solution for sealed hydrothermal treatment, the alumina particles on the surface of the alumina support and in the micron-sized spherical pores of the bulk phase rehydrate and merge to form hexagonal flaky pseudoboehmite. This support material is a mixed phase of γ-Al₂O₃ and AlOOH. When the active component is impregnated with this mixed phase and calcined, the active component, along with AlOOH, transforms into γ-Al₂O₃, reducing the strong interaction between the active component and the alumina support. This increases the content of octahedral Mo species in the catalyst, thereby improving the hydrodesulfurization activity of the catalyst.

[0026] 3. The phosphorus-containing alumina support precursor undergoes two hydrothermal treatments, which cover or fill the micron-sized pores on the support surface and inside with hexagonal alumina particles, effectively increasing the macropore content on the support surface and in the bulk phase. This enhances the catalyst surface's anti-clogging ability and impurity tolerance. Attached Figure Description

[0027] Figure 1 shows the XRD pattern of the carrier prepared in Example 1.

[0028] Figure 2 This is a SEM image of the catalyst surface prepared in Example 1.

[0029] Figure 3 This is a cross-sectional SEM image of the catalyst prepared in Example 1.

[0030] Figure 4 The image shows a cross-sectional SEM image of the catalyst prepared in Comparative Example 1. Detailed Implementation

[0031] The technical solutions 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.

[0032] The microstructure of the sample was characterized using scanning electron microscopy. The specific operation was as follows: accelerating voltage 8KV, accelerating current 10µA, working distance 8mm.

[0033] The preparation method of the carbon particles used in this invention is referenced in the literature: Preparation of starch-based porous carbon materials and their methylene blue adsorption properties [J]. Journal of Dalian University of Technology, 2020, 39(6): 434-438. The carbon particles prepared are spherical with a particle size of 1-5 μm.

[0034] Example 1

[0035] (1) Weigh 100g of pseudoboehmite (prepared by aluminum sulfate-sodium aluminate method, with a pore size of 13.0nm), add 275g of distilled water, stir evenly, add 17.5ml of concentrated nitric acid to acidify into a sol, add 3.5g of ammonium phosphate to the above sol and continue stirring for 40 minutes to obtain phosphorus-modified aluminum sol.

[0036] (2) Weigh 100g of the above phosphorus-modified aluminum sol, add 0.45g of the above spherical carbon particles, and stir the material evenly; drip the mixture into the oil-ammonia column device to form droplets, age the formed material for 3 hours, then dry it at 150℃ for 4 hours, and calcine it at 500℃ in an oxygen atmosphere for 6 hours to obtain the phosphorus-modified alumina carrier precursor.

[0037] (3) Weigh an appropriate amount of the phosphorus-modified alumina carrier precursor from step (2) and add it to the polytetrafluoroethylene liner of the autoclave. Add a 1.6 wt% tetraethylammonium hydroxide solution to completely submerge the alumina carrier precursor. After sealing the autoclave, perform the first hydrothermal treatment at 95°C for 3 hours. After treatment, immerse the material again in a 6.5 wt% tetraethylammonium hydroxide solution. After sealing the autoclave, perform the second hydrothermal treatment at 165°C for 6.5 hours. After treatment, dry the material at 140°C for 4 hours to obtain a γ-Al2O3 / AlOOH mixed-phase carrier. The XRD pattern of the carrier is shown in [reference needed]. Figure 1 .

[0038] (4) Weigh 50 g of the mixed phase support from step (3), and impregnate the support with an equal volume of active component impregnation solution containing molybdenum oxide at a concentration of 15.6 g / 100 mL and nickel oxide at a concentration of 3.8 g / 100 mL. Dry the impregnated material at 140 °C for 4 hours and calcine at 450 °C for 5 hours to obtain hydrodesulfurization catalyst A-1. The particle morphology on the catalyst surface is hexagonal, with a particle coverage (the percentage of the surface area occupied by the plate-like particles to the outer surface area of ​​the alumina support) of 95%. The diameter of the pores formed by the accumulation of plate-like particles is 120-580 nm. The particle morphology in the micron-sized spherical pores is hexagonal, with a particle filling degree (the percentage of the volume filled by hexagonal plate-like particles to the volume of the micron-sized spherical pores) of 85%. The scanning electron microscope image of the support surface is shown below. Figure 2 The scanning electron microscope image of the cross-section is shown below. Figure 3 .

[0039] Example 2

[0040] Same as Example 1, except that in step (1) the amount of ammonium phosphate added is 4 grams; in step (2) the amount of spherical carbon particles added is 0.35 grams; in step (3), the concentration of tetraethylammonium hydroxide in the first hydrothermal treatment is 1.3 wt%, the hydrothermal treatment temperature is 105℃, and the treatment time is 2.5 hours; in the second hydrothermal treatment, the concentration of tetraethylammonium hydroxide is 9 wt%, the hydrothermal treatment temperature is 155℃, and the treatment time is 8.5 hours, thus obtaining hydrodesulfurization catalyst A-2. The particle morphology on the catalyst surface is hexagonal, the coverage of the plate particles (the percentage of the surface area occupied by the plate particles to the external surface area of ​​the alumina carrier) is 96%, and the diameter of the pores formed by the accumulation of plate particles is 110-590 nm. The particle morphology in the micron-sized spherical pores is hexagonal, and the filling degree of the plate particles in the micron-sized spherical pores (the percentage of the volume filled by the hexagonal plate particles in the micron-sized spherical pores to the volume of the micron-sized spherical pores) is 87%.

[0041] Example 3

[0042] Same as Example 1, except that in step (1) the amount of ammonium phosphate added is 4.5 g; in step (2) the amount of spherical carbon particles added is 0.25 g; in step (3), the concentration of tetraethylammonium hydroxide in the first hydrothermal treatment is 0.9 wt%, the hydrothermal treatment temperature is 115℃, and the treatment time is 1.5 hours; in the second hydrothermal treatment, the concentration of tetraethylammonium hydroxide is 4 wt%, the hydrothermal treatment temperature is 175℃, and the treatment time is 4.5 hours, thus obtaining hydrodesulfurization catalyst A-3. The particle morphology on the catalyst surface is hexagonal, the coverage of the plate particles (the percentage of the surface area occupied by the plate particles to the external surface area of ​​the alumina carrier) is 93%, the diameter of the pores formed by the accumulation of plate particles is 130-580 nm, the particle morphology in the micron-sized spherical pores is hexagonal, and the filling degree of the plate particles in the micron-sized spherical pores (the percentage of the volume filled by the hexagonal plate particles in the micron-sized spherical pores to the volume of the micron-sized spherical pores) is 82%.

[0043] Example 4

[0044] Same as Example 1, except that in step (1) the amount of ammonium phosphate added is 3 grams; in step (2) the amount of spherical carbon particles added is 0.55 grams; in step (3), the concentration of tetraethylammonium hydroxide in the first hydrothermal treatment is 1.9 wt%, the hydrothermal treatment temperature is 85℃, and the treatment time is 4 hours; in the second hydrothermal treatment, the concentration of tetraethylammonium hydroxide is 11.5 wt%, the hydrothermal treatment temperature is 145℃, and the treatment time is 10 hours, thus obtaining hydrodesulfurization catalyst A-4. The particle morphology on the catalyst surface is hexagonal, the coverage of the plate particles (the percentage of the surface area occupied by the plate particles to the outer surface area of ​​the alumina carrier) is 96%, the diameter of the pores formed by the accumulation of plate particles is 110-570 nm, the particle morphology in the micron-sized spherical pores is hexagonal, and the filling degree of the plate particles in the micron-sized spherical pores (the percentage of the volume filled by the hexagonal plate particles in the micron-sized spherical pores to the volume of the micron-sized spherical pores) is 83%.

[0045] Comparative Example 1

[0046] Same as Example 1, except that tetraethylammonium hydroxide in step (3) was replaced with an aqueous ammonia solution of a certain concentration, to prepare comparative hydrodesulfurization catalyst A-5. No hexagonal flaky particles were observed on the catalyst surface; the surface particles were granular. The diameter of the pores formed by the accumulation of granular particles was 10-30 nm. The surface particles of the micron-sized spherical pores were granular, and the spherical pores were not filled. The scanning electron microscope image of the catalyst cross-section is shown in [reference needed]. Figure 4 .

[0047] Comparative Example 2

[0048] Same as Example 1, except that tetraethylammonium hydroxide in step (3) was replaced with an aqueous solution of sodium hydroxide of a certain concentration, and comparative hydrodesulfurization catalyst A-6 was prepared. No hexagonal plate-shaped particles were observed on the catalyst surface, and the surface particles were granular. The diameter of the pores formed by the accumulation of granular particles was 10-30 nm. The surface particles of the micron-sized spherical pores were granular, and the spherical pores were not filled.

[0049] Example 5

[0050] The catalysts prepared in the above examples and comparative examples were respectively loaded into fixed-bed hydrogenation reactors. The feedstock contained 4.2% S and 138.6 µg / g (Ni+V). The reaction conditions were as follows: reaction temperature 375°C, hydrogen-to-oil volume ratio 850, and liquid hourly space velocity 0.8 h⁻¹. -1 The hydrogen partial pressure was 14.5 MPa, and the impurity removal properties were obtained after 2500 hours of continuous operation. See Table 1 for the properties of the impurity removal.

[0051] Table 1 Evaluation results of the catalyst

[0052]

[0053] As can be seen from the results in Table 1, the catalyst prepared by the method of the present invention has high hydrodemetallization activity and hydrodesulfurization activity.

Claims

1. A process for the preparation of a heavy oil hydrodesulfurization catalyst characterized by: Includes the following steps: The first step is to prepare a phosphorus-containing aluminum sol; The second step involves uniformly mixing phosphorus-containing aluminum sol with spherical carbon particles, then forming the mixture by drop in an oil-ammonia column forming device. The formed product is then dried and calcined to obtain a phosphorus-modified alumina carrier precursor. The third step involves immersing the phosphorus-modified alumina carrier precursor in an organic ammonium solution for hydrothermal treatment. After treatment, the product is dried to obtain a mixed phase carrier of γ-Al2O3 and AlOOH. The hydrothermal treatment is a closed-loop hydrothermal treatment carried out in a sealed container, and is divided into two stages: In the first stage, the organic ammonium solution has a mass concentration of 0.8%-2.0%, the solution volume is sufficient to completely submerge the solid material, the hydrothermal treatment temperature is 80-120℃, and the treatment time is 1-4 hours; In the second stage, the organic ammonium solution has a mass concentration of 3.5%-12.5%, the solution volume is sufficient to completely submerge the solid material, the hydrothermal treatment temperature is 140-180℃, and the treatment time is 4-10 hours; The type of organic ammonium used in the first and second stages of hydrothermal treatment may be the same or different. The fourth step involves impregnating the mixed-phase support with an active component impregnation solution, followed by drying and calcination of the impregnated support to obtain the hydrodesulfurization catalyst.

2. The process for preparing a heavy oil hydrodesulfurization catalyst according to claim 1, characterized by: The preparation method of the phosphorus-containing aluminum sol in the first step is as follows: First, boehmite is mixed evenly with distilled water, then an acid solution is added under stirring to acidify and obtain an aluminum sol. Finally, a phosphorus-containing compound is added to the aluminum sol to obtain a phosphorus-containing aluminum sol. The boehmite may have a pore size greater than 12.5 nm. The phosphorus-containing compound includes one or more of phosphoric acid, ammonium phosphate, ammonium monohydrogen phosphate, and ammonium dihydrogen phosphate. The mass ratio of the phosphorus-containing compound to the boehmite, calculated as elemental phosphorus (P), is 0.5:100-1:

100. The acid solution includes one or more of nitric acid, acetic acid, formic acid, and oxalic acid solutions. The solid content in the sol is 15%-35%.

3. The method for preparing a heavy oil hydrodesulfurization catalyst according to claim 1, characterized in that: The spherical carbon particles mentioned in the second step have a particle size of 1-8 μm.

4. The method for preparing a heavy oil hydrodesulfurization catalyst according to claim 1, characterized in that: The mass ratio of spherical carbon particles to alumina sol in the second step is 0.2%-0.6%.

5. The process for preparing a heavy oil hydrodesulfurization catalyst according to claim 1, characterized by: The drying temperature in the second step is 120-180℃, and the drying time is 1-8 hours; the calcination temperature is 450-600℃, and the calcination time is 4-8 hours, and the calcination is carried out in an oxygen atmosphere.

6. The process for preparing a heavy oil hydrodesulfurization catalyst according to claim 1, characterized by: The organic ammonium solution mentioned in the third step includes one of tetramethylammonium hydroxide and tetrapropylammonium hydroxide.

7. The method for preparing a heavy oil hydrodesulfurization catalyst according to claim 1, characterized in that: The drying temperature in the third step is 100-160℃, and the drying time is 2-8 hours.

8. The process for preparing a heavy oil hydrodesulfurization catalyst according to claim 1, characterized by: The active component impregnation solution mentioned in step four is a solution containing Group VIB and Group VIII metals. Group VIB metals include one or more of W and Mo, and Group VIII metals include one or more of Co and Ni. The content of Group VIB metals in the impregnation solution, calculated as metal oxides, is 7.5-18.5 g / 100 mL, and the content of Group VIII metals, calculated as metal oxides, is 2.5-5.5 g / 100 mL.

9. The process for preparing a heavy oil hydrodesulfurization catalyst according to claim 1, characterized by: The drying temperature in step four is 100-160℃, and the drying time is 2-8 hours. The calcination temperature is 450-550℃, and the calcination time is 4-6 hours.

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