Catalyst for hydrodesulfurization of catalytically cracked gasoline as well as preparation method and application of catalyst

Abstract

The invention belongs to the technical field of catalysts, and particularly relates to a catalyst for hydrodesulfurization of catalytically cracked gasoline as well as a preparation method and application of the catalyst. The preparation method comprises the following steps: (1) mixing aluminum oxide with water, carrying out hydrothermal treatment to obtain a solid-liquid mixture, filtering, and taking a solid substance to obtain hydrothermal modified aluminum oxide; (2) mixing an acidified molybdenum salt aqueous solution with a quaternary ammonium salt aqueous solution to obtain a turbid liquid, then mixing the turbid liquid with the hydrothermal modified aluminum oxide prepared in the step (1), heating, filtering to obtain a solid, and roasting to obtain molybdenum-loaded aluminum oxide; and (3) dipping the molybdenum-loaded alumina prepared in the step (2) in a cobalt salt solution, then taking out the molybdenum-loaded alumina, and roasting to obtain the catalyst. The catalyst provided by the invention has high selectivity on hydrogen desulfurization of simulated catalytic cracking gasoline.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a catalyst for catalytic cracking gasoline hydrodesulfurization, and a preparation method and application thereof. Background Art

[0002] The National VI(B) gasoline standard, which came into effect nationwide on January 1, 2023, requires a sulfur content of no more than 10 mg / kg and an olefin content of no more than 15% for motor gasoline. High-sulfur, high-olefin fuel cell (FCC) gasoline accounts for approximately 70% to 80% of the finished gasoline pool. Currently, hydrodesulfurization (HDS) technology remains the most important approach for reducing the sulfur content of FCC gasoline and producing clean gasoline. While selective deep hydrodesulfurization of FCC gasoline is crucial for avoiding olefin saturation, a key technical challenge in producing high-octane gasoline remains.

[0003] The active phase composition and microstructure of supported CoMo catalysts have a significant impact on their hydrodesulfurization selectivity. Compared with MoS2, the formation of CoMoS active phase is beneficial to improving the hydrodesulfurization performance of the catalyst while inhibiting the olefin saturation reaction (see references: S.He, X.Wang, C.Wen, Y.Fan, Fuel. 366 (2024) 131387; W.Bao, C.Feng, C.Zhang, S.Ma, C.Wang, T.Huang, H.Guo, Y.Pan, Y.Liu, C.Liu, D.Sun, Y.Lu, J.Catal. 426 (2023) 71-85). For supported CoMoS catalysts, in the brim-edge model (see references: H. In a CoMo-based catalyst, the brim sites (the top and bottom layers of the MoS2 platelet) exhibit both HDS and olefin saturation activity, while the edge sites catalyze only HDS (see Xu Jingdong, Li Wentao, Li Huisheng, Ai Zilong, Wang Tinghai, and Xu Renwei, Journal of Fuel Chemistry and Technology, 53 (2024), 1-8). The number of MoS2 platelets stacked affects the ratio of brim to edge sites, while smaller MoS2 platelet size increases the number of active sites, thereby improving catalytic performance. Therefore, optimizing the active phase composition and structure of CoMo-based catalysts is a key approach to improving FCC gasoline HDS selectivity.

[0004] Currently, this type of work mainly focuses on using alumina supports with different crystal phases, modifying the elements of the alumina supports, or introducing additives (including organic acids, organic acid ammonium, organic alcohols, etc.).

[0005] Chinese patent CN116983977A discloses a hydrodesulfurization catalyst, its preparation method, and its application. Modified alumina is obtained by multi-step processing of raw alumina, including mixing with distilled water and drying, mixing with an alcohol, drying, and high-temperature treatment, mixing with an aluminum nitrate solution and filtering, and then filtering, washing, and heat-treating the modified alumina. This method effectively reduces the amount of basic sites on the alumina surface, resulting in a Mo-supported catalyst with improved thiophene hydrodesulfurization performance. The present invention does not provide information on the olefin saturation performance of the catalyst.

[0006] Chinese patent CN101195763A discloses a method for selective hydrodesulfurization of gasoline. The catalyst used contains a catalyst carrier containing α-Al2O3. The catalyst contains 0.5-35% by weight of a Group VIB metal, 0.1-10% by weight of a Group VIII metal, and 55-99.4% by weight of a carrier. Evaluation results indicate that the surface catalyst exhibits high hydrodesulfurization selectivity. However, the present invention does not provide data on the composition and microstructure of the catalyst's active phase.

[0007] Chinese patent CN113797938A discloses a gasoline selective hydrodesulfurization catalyst supported by graphene oxide-coated alumina. During the sulfurization process, the catalyst's active sites adopt an eggshell-like structure, concentrated on the catalyst's outer surface, improving hydrodesulfurization selectivity. The catalyst's CoMoS platelets range in length from 3.0 to 8.0 nm, with a layer count of 2.0 to 4.0.

[0008] Chinese patents CN112742431A and CN112742404A use metal oxides with specific molybdenum equilibrium adsorption capacity, specific surface area and pore volume as carriers (including but not limited to alumina), and then impregnate them with (ammonia) aqueous solutions containing active metals (Co, Mo) and additives such as phosphoric acid, citric acid or ammonium citrate, and then dry them to obtain catalysts.

[0009] Chinese patent CN107638882A discloses a catalyst using a hydrothermal treatment of γ-Al2O3 at a certain temperature, followed by drying and calcination to dehydrate the catalyst. The catalyst, impregnated with the active components Mo and Co, exhibits high gasoline hydrodesulfurization selectivity. The hydrothermal treatment weakens the interaction between the support and the metal, resulting in larger MoS2 particles (approximately 4.4 nm) and improved hydrodesulfurization selectivity. However, detailed data on the active phase composition, lamellae length, and layer number distribution are not provided.

[0010] It can be seen from the above reports that current researchers mainly improve the HDS selectivity of catalysts by improving the carrier or introducing additives during the impregnation process, and there is little research on how to effectively regulate the composition and microstructure of the active phase of the catalyst to improve its selectivity. Summary of the Invention

[0011] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, the present invention provides a catalyst for hydrodesulfurization of catalytically cracked gasoline, its preparation method, and its application. The preparation method effectively modulates the composition and structure of the active centers of the cobalt-molybdenum catalyst, enhancing its gasoline hydrodesulfurization activity while suppressing its olefin saturation activity, ultimately improving the catalyst's hydrodesulfurization selectivity for simulated catalytically cracked gasoline.

[0012] A first aspect of the present invention provides a method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline.

[0013] A method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline comprises the following steps:

[0014] (1) mixing alumina with water, performing hydrothermal treatment to obtain a solid-liquid mixture, filtering, and collecting a solid to obtain hydrothermally modified alumina;

[0015] (2) mixing an acidified molybdenum salt aqueous solution with a quaternary ammonium salt aqueous solution to obtain a suspension, then mixing the suspension with the hydrothermally modified alumina prepared in step (1), heating, filtering, obtaining a solid, and calcining to obtain a molybdenum-loaded alumina;

[0016] (3) Immersing the molybdenum-loaded alumina prepared in step (2) in a cobalt salt solution, then taking out the molybdenum-loaded alumina and calcining it to obtain the catalyst.

[0017] Preferably, in step (1), the alumina is porous γ-alumina.

[0018] Preferably, the alumina has a particle size of 1 to 8 mm and a specific surface area of ​​100 to 450 m 2 / g, pore volume is 0.10-0.98mL / g; further preferably, the particle size of the alumina is 1-5mm, and the specific surface area is 100-350m 2 / g, and the pore volume is 0.15-0.95mL / g.

[0019] Preferably, the mass ratio of the γ-Al2O3 to deionized water in step (1) is 1:1 to 1:8.

[0020] Preferably, in step (1), the hot water treatment is carried out in a sealed reactor, which is placed in an oven and treated at 80-180° C. for 10-35 hours.

[0021] Preferably, in step (1), the obtained solid-liquid mixture is filtered, the solid is taken, washed, and then dried at 90 to 150° C. for 1 to 10 hours to obtain hydrothermally modified alumina Al 2 O 3 -HT.

[0022] Preferably, in step (2), the acidification is carried out using an inorganic acid selected from at least one of hydrochloric acid, sulfuric acid or nitric acid; further preferably, the inorganic acid is hydrochloric acid with a concentration of 2.3-2.5 mol / L.

[0023] Preferably, in step (2), the molybdenum salt in the molybdenum salt aqueous solution is selected from at least one of ammonium molybdate, sodium molybdate, and potassium molybdate; further preferably, the molybdenum salt is sodium molybdate.

[0024] Preferably, in step (2), the quaternary ammonium salt in the quaternary ammonium salt aqueous solution is at least one of alkyltrimethylammonium bromide or alkyltrimethylammonium chloride (the carbon number of the alkyl group is 2 to 16), tetraalkylammonium bromide or ammonium chloride (the carbon number of the alkyl group is 1 to 8); preferably, the quaternary ammonium salt in the quaternary ammonium salt aqueous solution is tetraethylammonium bromide.

[0025] Preferably, in step (2), the pH of the acidified molybdenum salt aqueous solution is 2.0-6.5.

[0026] Preferably, in step (2), the concentration of molybdenum salt in the acidified molybdenum salt aqueous solution is 0.15 to 2.50 mol / L.

[0027] Preferably, in step (2), the concentration of the quaternary ammonium salt aqueous solution is 0.10 to 1.50 mol / L.

[0028] Preferably, in step (2), the mixing can be performed by stirring or ultrasonication; preferably, the stirring time is 2-180 min.

[0029] Preferably, in step (2), the suspension is acidified and then mixed with the hydrothermally modified alumina, and the pH of the acidified suspension is 2.0-5.5.

[0030] Preferably, in step (2), the heating temperature is 50-180° C., and the heating time is 12-40 hours. The stirring at 50-180° C. for 12-40 hours is carried out in a rotary oven.

[0031] Preferably, in step (2), the heating is carried out in a reactor, and the reactor is a high-pressure reactor that can withstand a pressure of 108 Pa.

[0032] Preferably, in step (2), the solid is dried before calcination, and the drying is performed at 90-150° C. for 1-10 hours.

[0033] Preferably, in step (2), the calcination is carried out at 300-550° C. for 2-10 h.

[0034] The filtration and water washing in the above steps (1) and (2) are conventional operating steps in the field. Those skilled in the art can select appropriate means to filter and wash the solid-liquid mixture or suspension according to the needs of on-site operations.

[0035] Preferably, in step (3), the cobalt salt in the cobalt salt solution is selected from at least one of cobalt nitrate and cobalt acetate. Preferably, the cobalt salt in the cobalt salt solution is cobalt acetate.

[0036] Preferably, in step (3), the cobalt salt concentration in the cobalt salt solution is 0.30 to 2.50 mol / L.

[0037] Preferably, in step (3), the molybdenum-loaded alumina is impregnated in a cobalt salt solution in equal volumes and allowed to stand at room temperature for 10 to 35 hours.

[0038] Preferably, in step (3), the molybdenum-loaded alumina is impregnated in a cobalt salt solution in equal volumes, and then allowed to stand, dried at 90-150° C. for 2-10 h, and calcined at 350-550° C. for 2-8 h to obtain the catalyst.

[0039] Preferably, the molar ratio of cobalt to molybdenum in catalyst D is 0.20 to 0.85: 1. Experiments have shown that the catalyst prepared when the molar ratio of cobalt to molybdenum is 0.40 to 0.50: 1 has a high desulfurization selectivity.

[0040] Preferably, in step (3), the impregnation method is a conventional technical means in the art, and those skilled in the art can select a suitable impregnation method according to the needs of on-site operations; for example, an equal volume impregnation method or an excessive volume impregnation method.

[0041] A method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline comprises the following steps:

[0042] (1) adding deionized water to a hydrothermal reactor containing γ-alumina, performing hydrothermal treatment on the sealed reactor, and filtering, washing, and drying the resulting solid-liquid mixture to obtain hydrothermally modified alumina Al2O3-HT;

[0043] (2) Molybdenum is loaded onto the surface of Al2O3-HT by a hydrothermal deposition method. First, a molybdenum salt aqueous solution A acidified with an inorganic acid is prepared. The molybdenum salt aqueous solution A is mixed with a quaternary ammonium salt aqueous solution and stirred to obtain a suspension. After acidification, the suspension is transferred to a reactor containing hydrothermally modified alumina Al2O3-HT. The reactor is sealed, stirred, and heated for a period of time, and then filtered and washed to obtain a solid B. B is dried and calcined to obtain a solid C.

[0044] (3) Solid C is impregnated with an equal volume of cobalt salt solution, and then allowed to stand, dried, and calcined to obtain catalyst D.

[0045] A second aspect of the present invention provides a catalyst for hydrodesulfurization of catalytic cracking gasoline.

[0046] A catalyst for catalytic cracking gasoline hydrodesulfurization is prepared by the above preparation method.

[0047] Preferably, the catalyst comprises molybdenum oxide, cobalt oxide and aluminum oxide, and the molybdenum oxide and cobalt oxide are supported on the aluminum oxide.

[0048] Preferably, the catalyst comprises 6.0-40.0 wt% of molybdenum oxide, 1.5-12 wt% of cobalt oxide, and the balance is aluminum oxide.

[0049] The third aspect of the present invention provides an application of a method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline.

[0050] The catalyst prepared by the above preparation method is used in gasoline hydrodesulfurization.

[0051] Preferably, the catalyst prepared by the above preparation method is used in the hydrodesulfurization of model gasoline.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) The preparation method of the present invention increases the number of hydroxyl groups on the surface of alumina through hydrothermal modification, thereby achieving a suitable interaction between the metal and the support. Quaternary ammonium salt cations are combined with polyoxomolybdate anions to obtain organic-inorganic hybrid nanoparticles; the organic-inorganic hybrid nanoparticles are then deposited onto the surface of the hydrothermally modified alumina using a hydrothermal deposition technique, and then subjected to subsequent treatment to obtain a hydrothermally modified alumina-loaded molybdenum substance. Using molybdenum-based organic-inorganic hybrid nanoparticles as a molybdenum precursor ensures that molybdenum is highly dispersed on the support surface, while the weaker molybdenum-support interaction improves the reduction and sulfurization properties of molybdenum in the catalyst.

[0054] (2) The present invention achieves the regulation of the gasoline hydrodesulfurization selectivity of the catalyst by regulating the active phase composition and microstructure of the catalyst.

[0055] (3) The advantages of the method for regulating and preparing the gasoline hydrodesulfurization catalyst of the present invention lie in the comprehensive application of the following three methods: 1. Hydrothermal modification of γ-Al2O3 to achieve a suitable interaction between the molybdenum and the carrier; 2. Preparation of a MoO3 / Al2O3 catalyst with highly dispersed molybdenum species using molybdenum-based organic-inorganic hybrid nanoparticles as a molybdenum precursor; and 3. Adjustment of the catalyst solid content to achieve effective regulation of the active phase composition and microstructure of the cobalt-molybdenum catalyst. Compared with cobalt-molybdenum catalysts prepared by traditional impregnation methods, the catalyst prepared by the present invention has a higher proportion of CoMoS in the active phase obtained after sulfurization, a higher degree of dispersion of the active phase, and a larger number of lamellae, ultimately resulting in a higher gasoline hydrodesulfurization selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 X-ray diffraction spectra of the catalysts prepared in Examples 1-4 and Comparative Examples 1-3;

[0057] Figure 2 The hydrogen-temperature-programmed reduction (H2-TPR) spectra of the catalysts prepared in Example 2 and Comparative Examples 1-3 are shown;

[0058] Figure 3 The figure shows the distribution of MoS2 platelet length and stacking layer number of the catalysts prepared in Examples 1-4 and Comparative Examples 1-3 after sulfurization. DETAILED DESCRIPTION

[0059] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0060] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0061] Example 1

[0062] A method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline comprises the following steps:

[0063] (1) Weigh 5.00 g of Al2O3 support with a diameter of 1-3 mm (pore volume of 0.5 mL / g, specific surface area of ​​200 m 2 / g) was placed in the lining of a reactor, 43.8 mL of distilled water was added, and the mixture was placed in a rotary drying oven and hydrothermally treated at 100°C for 24 h. After the hydrothermal treatment, the solid-liquid mixture was filtered and washed with water, and the obtained solid was transferred to an evaporating dish and dried at a constant temperature of 120°C for 4 h to obtain hydrothermally modified alumina Al2O3-HT;

[0064] (2) preparing 43.3 mL of a 0.17 mol / L sodium molybdate aqueous solution, and adding 5.0 mL of 2.4 mol / L hydrochloric acid dropwise to the sodium molybdate aqueous solution with stirring to obtain solution A;

[0065] (3) Then, 20 mL of a 0.13 mol / L tetraethylammonium bromide (TEAB) aqueous solution was prepared and added dropwise to solution A at a constant rate under stirring to form a suspension. The suspension was stirred for 5 min, and 2.4 mol / L hydrochloric acid was added dropwise to the suspension until the pH of the suspension reached 2.5.

[0066] (4) The suspension was transferred to a reactor pre-filled with 5.09 g of hydrothermally modified alumina Al2O3-HT, and the sealed reactor was placed in an electric blast rotary drying oven to allow the particles in the suspension to diffuse and settle at 125°C for 15 h. The suspension was then filtered and washed with water to obtain solid B. B was dried at 120°C for 4 h and then calcined at 450°C for 4 h to obtain solid C.

[0067] (5) Finally, 7.3 mL of a 0.36 mol / L aqueous solution of cobalt acetate was prepared, and 6.1 mL was added dropwise to 5.7 g of solid C to soak it. The solid was allowed to stand at room temperature for 24 h, then dried at 120 °C for 4 h, and then calcined at 450 °C for 4 h to obtain a supported bimetallic gasoline hydrodesulfurization catalyst, which was designated as S1.

[0068] During the preparation of catalyst S1, the molar ratio of TEAB, cobalt salt, and molybdenum salt was 0.37:0.29:1; the contents of Co and Mo oxides in catalyst S1 are shown in Table 1.

[0069] Example 2

[0070] A method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline comprises the following steps:

[0071] (1) Weigh 5.00 g of Al2O3 support with a diameter of 1-3 mm (pore volume of 0.5 mL / g, specific surface area of ​​200 m 2 / g) was placed in the lining of a reactor, 43.8 mL of distilled water was added, and the mixture was placed in a rotary drying oven and hydrothermally treated at 100°C for 24 h. After the hydrothermal treatment, the solid-liquid mixture was filtered and washed with water, and the obtained solid was transferred to an evaporating dish and dried at a constant temperature of 120°C for 4 h to obtain hydrothermally modified alumina Al2O3-HT;

[0072] (2) preparing 43.3 mL of a 0.17 mol / L sodium molybdate aqueous solution, and adding 5.0 mL of 2.4 mol / L hydrochloric acid dropwise to the sodium molybdate aqueous solution with stirring to obtain solution A;

[0073] (3) Then, 20 mL of a 0.13 mol / L tetraethylammonium bromide (TEAB) aqueous solution was prepared and added dropwise to solution A at a constant rate under stirring to form a suspension. The suspension was stirred for 5 min, and 2.4 mol / L hydrochloric acid was added dropwise to the suspension until the pH of the suspension reached 2.5.

[0074] (4) The suspension was transferred to a reactor pre-filled with 5.09 g of hydrothermally modified alumina Al2O3-HT, and the sealed reactor was placed in an electric blast rotary drying oven to allow the particles in the suspension to diffuse and settle at 125°C for 15 h. The suspension was then filtered and washed with water to obtain solid B. B was dried at 120°C for 4 h and then calcined at 450°C for 4 h to obtain solid C.

[0075] (5) Finally, 7.3 mL of a 0.56 mol / L aqueous solution of cobalt acetate was prepared, and 6.1 mL was added dropwise to 5.7 g of solid C to soak it. The solid was allowed to stand at room temperature for 24 h, then dried at 120 °C for 4 h, and then calcined at 450 °C for 4 h to obtain a supported bimetallic gasoline hydrodesulfurization catalyst, which was designated as S2.

[0076] During the preparation of catalyst S2, the molar ratio of TEAB, cobalt salt, and molybdenum salt was 0.37:0.45:1; the contents of Co and Mo oxides in catalyst S2 are shown in Table 1.

[0077] Example 3

[0078] A method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline comprises the following steps:

[0079] (1) Weigh 5.00 g of Al2O3 support with a diameter of 1-3 mm (pore volume of 0.5 mL / g, specific surface area of ​​200 m 2 / g) was placed in the lining of a reactor, 43.8 mL of distilled water was added, and the mixture was placed in a rotary drying oven and hydrothermally treated at 100°C for 24 h. After the hydrothermal treatment, the solid-liquid mixture was filtered and washed with water, and the obtained solid was transferred to an evaporating dish and dried at a constant temperature of 120°C for 4 h to obtain hydrothermally modified alumina Al2O3-HT;

[0080] (2) preparing 43.3 mL of a 0.17 mol / L sodium molybdate aqueous solution, and adding 5.0 mL of 2.4 mol / L hydrochloric acid dropwise to the sodium molybdate aqueous solution with stirring to obtain solution A;

[0081] (3) Then, 20 mL of a 0.13 mol / L tetraethylammonium bromide (TEAB) aqueous solution was prepared and added dropwise to solution A at a constant rate under stirring to form a suspension. The suspension was stirred for 5 min, and 2.4 mol / L hydrochloric acid was added dropwise to the suspension until the pH of the suspension reached 2.5.

[0082] (4) The suspension was transferred to a reactor pre-filled with 5.09 g of hydrothermally modified alumina Al2O3-HT, and the sealed reactor was placed in an electric blast rotary drying oven to allow the particles in the suspension to diffuse and settle at 125°C for 15 h. The suspension was then filtered and washed with water to obtain solid B. B was dried at 120°C for 4 h and then calcined at 450°C for 4 h to obtain solid C.

[0083] (5) Finally, 7.3 mL of a 0.77 mol / L aqueous solution of cobalt acetate was prepared, and 6.1 mL was added dropwise to 5.7 g of solid C to soak it. The solid was allowed to stand at room temperature for 24 h, then dried at 120 °C for 4 h, and then calcined at 450 °C for 4 h to obtain a supported bimetallic gasoline hydrodesulfurization catalyst, which was designated as S3.

[0084] During the preparation of catalyst S3, the molar ratio of TEAB, cobalt salt, and molybdenum salt was 0.37:0.61:1; the contents of Co and Mo oxides in catalyst S3 are shown in Table 1.

[0085] Example 4

[0086] A method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline comprises the following steps:

[0087] (1) Weigh 5.00 g of Al2O3 support with a diameter of 1-3 mm (pore volume of 0.5 mL / g, specific surface area of ​​200 m 2 / g) was placed in the lining of a reactor, 43.8 mL of distilled water was added, and the mixture was placed in a rotary drying oven and hydrothermally treated at 100°C for 24 h. After the hydrothermal treatment, the solid-liquid mixture was filtered and washed with water, and the obtained solid was transferred to an evaporating dish and dried at a constant temperature of 120°C for 4 h to obtain hydrothermally modified alumina Al2O3-HT;

[0088] (2) preparing 43.3 mL of a 0.17 mol / L sodium molybdate aqueous solution, and adding 5.0 mL of 2.4 mol / L hydrochloric acid dropwise to the sodium molybdate aqueous solution with stirring to obtain solution A;

[0089] (3) Then, 20 mL of a 0.13 mol / L tetraethylammonium bromide (TEAB) aqueous solution was prepared and added dropwise to solution A at a constant rate under stirring to form a suspension. The suspension was stirred for 5 min, and 2.4 mol / L hydrochloric acid was added dropwise to the suspension until the pH of the suspension reached 2.5.

[0090] (4) The suspension was transferred to a reactor pre-filled with 5.09 g of hydrothermally modified alumina Al2O3-HT, and the sealed reactor was placed in an electric blast rotary drying oven to allow the particles in the suspension to diffuse and settle at 125°C for 15 h. The suspension was then filtered and washed with water to obtain solid B. B was dried at 120°C for 4 h and then calcined at 450°C for 4 h to obtain solid C.

[0091] (5) Finally, 7.3 mL of a 0.99 mol / L aqueous solution of cobalt acetate was prepared, and 6.1 mL was added dropwise to 5.7 g of solid C to soak it. The solid was allowed to stand at room temperature for 24 h, then dried at 120 °C for 4 h, and then calcined at 450 °C for 4 h to obtain a supported bimetallic gasoline hydrodesulfurization catalyst, which was designated as S4.

[0092] During the preparation of catalyst S4, the molar ratio of TEAB, cobalt salt, and molybdenum salt was 0.37:0.77:1; the contents of Co and Mo oxides in catalyst S4 are shown in Table 1.

[0093] Comparative Example 1

[0094] The CoMo / Al2O3 catalyst was prepared by conventional isovolumetric impregnation method. The specific steps are as follows:

[0095] (1) Prepare 14.9 ml of 0.18 mol / L ammonium molybdate solution as the impregnation solution, take 12.8 ml of it and gradually add it dropwise to 10.0 g of γ-Al2O3 support with a diameter of 1-3 mm. Let it stand at room temperature for 24 h. The resulting solid is dried at 120°C for 4 h and calcined at 450°C for 4 h to obtain Mo / Al2O3;

[0096] (2) 14.5 ml of a 0.56 mol / L aqueous solution of cobalt acetate was prepared, and 11.8 ml of the aqueous solution was added dropwise to 11.5 g of Mo / Al2O3. The mixture was allowed to stand at room temperature for 24 h. The resulting solid was dried at 120°C for 4 h and calcined at 450°C for 4 h to obtain a supported bimetallic CoMo / Al2O3 catalyst, designated as D1. The contents of Co and Mo oxides in catalyst D1 are shown in Table 1.

[0097] Comparative Example 2

[0098] The CoMo / Al2O3-HT catalyst was prepared by conventional isovolumetric impregnation method. The specific steps are as follows:

[0099] (1) Weigh 5.00 g of Al2O3 support with a diameter of 1-3 mm (pore volume of 0.5 mL / g, specific surface area of ​​200 m 2 / g) was placed in the lining of a reactor, 43.8 mL of distilled water was added, and the mixture was placed in a rotary drying oven and hydrothermally treated at 100°C for 24 h. After the hydrothermal treatment, the solid-liquid mixture was filtered and washed with water, and the obtained solid was transferred to an evaporating dish and dried at a constant temperature of 120°C for 4 h to obtain hydrothermally modified alumina Al2O3-HT;

[0100] (2) Prepare 14.8 ml of 0.15 mol / L ammonium molybdate solution as the impregnation solution, take 12.7 ml of it and gradually add it dropwise to 10.2 g of Al2O3-HT. Let it stand at room temperature for 24 h. The resulting solid is dried at 120°C for 4 h and calcined at 450°C for 4 h to obtain Mo / Al2O3-HT.

[0101] (3) 15.0 ml of a 0.56 mol / L aqueous solution of cobalt acetate was prepared, and 12.9 ml was added dropwise to 12.2 g of Mo / Al2O3-HT. The mixture was allowed to stand at room temperature for 24 h. The resulting solid was dried at 120°C for 4 h and calcined at 450°C for 4 h to obtain a supported bimetallic CoMo / Al2O3-HT catalyst, designated as D2. The contents of Co and Mo oxides in catalyst D2 are shown in Table 1.

[0102] Comparative Example 3

[0103] This comparative example is similar to Example 2 except that the alumina support is not hydrothermally modified. The specific steps are as follows:

[0104] (1) Prepare 43.3 mL of a 0.17 mol / L sodium molybdate aqueous solution, and add 5.0 mL of 2.4 mol / L hydrochloric acid dropwise to the sodium molybdate aqueous solution with stirring to obtain solution A;

[0105] (2) Prepare 20 mL of a 0.13 mol / L tetraethylammonium bromide (TEAB) aqueous solution, add the TEAB aqueous solution dropwise to solution A at a constant rate while stirring to form a suspension, stir for 5 min, and then add 2.4 mol / L hydrochloric acid dropwise to the suspension until the pH of the suspension reaches 2.5;

[0106] (3) The suspension was transferred to a reactor pre-filled with 5.0 g of Al2O3. The sealed reactor was then placed in an electric blast rotary drying oven to allow the particles in the suspension to diffuse and settle at 125°C for 15 h. The suspension was then filtered and washed with water to obtain solid B. B was dried at 120°C for 4 h and calcined at 450°C for 4 h to obtain solid C.

[0107] (4) Finally, 7.3 mL of a 0.56 mol / L aqueous solution of cobalt acetate was prepared, and 6.1 mL of the aqueous solution was added dropwise to 5.7 g of solid C to soak it. The solid was allowed to stand at room temperature for 24 h, then dried at 120 °C for 4 h and calcined at 450 °C for 4 h to obtain a supported bimetallic gasoline hydrodesulfurization catalyst, which was designated as D3.

[0108] During the preparation of catalyst D3, the molar ratio of TEAB, cobalt salt, and molybdenum salt was 0.37:0.45:1; the contents of Co and Mo oxides in catalyst D3 are shown in Table 1.

[0109] Product effect testing

[0110] The compositions of the catalysts prepared in the above examples and comparative examples are shown in Table 1.

[0111] Table 1

[0112] serial number <![CDATA[MoO3 / wt%]]> CoO / wt% Example 1 S1 17 2.6 Example 2 S2 17 4.0 Example 3 S3 17 5.4 Example 4 S4 17 6.8 Comparative Example 1 D1 17 4.0 Comparative Example 2 D2 17 4.0 Comparative Example 3 D3 17 4.0

[0113] The catalysts obtained in Examples 1-4 and Comparative Examples 1-3 were subjected to X-ray diffraction (XRD) analysis. The XRD spectra were as follows: Figure 1 shown.

[0114] From Table 1 and Figure 1 It can be seen that the catalyst S2 prepared by the method provided by the present invention has the same CoO and MoO3 content as the catalyst D2 prepared by the impregnation method. The characteristic diffraction peak of MoO3 does not appear in the XRD spectrum of catalysts S1 to S4, while the characteristic diffraction peak of MoO3 exists in the XRD spectrum of D2, indicating that the method provided by the present invention is conducive to the dispersion of Mo on the surface of hydrothermally modified Al2O3.

[0115] The H2-TPR spectra of the catalysts obtained in Example 2 and Comparative Examples 1 to 3 are as follows: Figure 2 shown.

[0116] Figure 2The reduction peak in the low-temperature region of 473.5-488.2°C is attributed to the reduction of octahedral Mo species from +6 to +4, while the reduction peak in the high-temperature region of 804.3-807.2°C is partially attributed to the reduction of octahedral Mo species from +4 to 0 and partially to the reduction of tetrahedral Mo species from 6 to 0. Compared to the low-temperature reduction peak temperature of 488.2°C for Catalyst D1, that of 481.7°C for Catalyst D2 and 486.4°C for Catalyst D3 is lower, indicating that hydrothermal modification of Al2O3 and Mo loading via hydrothermal deposition effectively weaken the interaction between Mo and Al2O3, forming a highly reducible Mo species. Compared with the reduction peak temperature of catalysts D2 and D3 in the low temperature zone, that of catalyst S2 is lower at 473.3℃, ​​indicating that the hydrothermal modification of the Al2O3 support and the loading of Mo by hydrothermal deposition can weaken the interaction between Mo and Al2O3, which is beneficial to the sulfurization of Mo on the catalyst surface. After sulfurization, a MoS2 active phase with a higher number of stacking layers can be formed.

[0117] The X-ray photoelectron spectroscopy (XPS) method was used to measure the proportion of Mo in different valence states on the surface of the catalysts obtained in Examples 1-4 and Comparative Examples 1-3 after sulfurization (where Mo 4+ The proportion is the Mo sulfidation and the proportion of different forms of Co species. The results are shown in Table 2.

[0118] Table 2 shows the sulfidation degree and CoMoS ratio. Compared to Catalyst D1 (30.2%), Catalysts D2 and D3 have higher sulfidation degrees, at 31.1% and 41.5%, respectively. Catalyst S2 has a higher sulfidation degree of 45.9%, compared to 31.1% and 41.5% for Catalysts D2 and D3, respectively. This is attributed to the hydrothermal modification of Al2O3 and the effective weakening of the interaction between Mo and Al2O3 by Mo loading via hydrothermal deposition. For Catalysts S1–S4, the sulfidation degree first increases and then decreases with increasing CoO content, indicating that a suitable CoO content facilitates the sulfidation of the primary metallic Mo on the catalyst surface. Regarding the ratio of different Co species, Catalysts D2 and D3 have higher CoMoS ratios than Catalyst D1. This is because the higher sulfidation of Mo on the surfaces of Catalysts D2 and D3 facilitates the promoter effect of Co, forming more CoMoS active centers. For catalysts S1 to S4, as the CoO content increases, the CoMoS ratio first increases and then decreases. When the CoO content is 4.0 wt%, catalyst S2 has a higher CoMoS ratio, which indicates that the appropriate Co content can optimize the CoMoS ratio and increase the number of active centers on the catalyst surface.

[0119] Table 2

[0120] sample D1 D2 D3 S1 S2 S3 S4 <![CDATA[Mo 4+ (%)]]> 30.2 31.1 41.5 42.6 45.9 44.9 43.7 <![CDATA[Mo 5+ (%)]]> 58.8 55.7 47.5 44.8 35.3 33.6 23.0 <![CDATA[Mo 6+ (%)]]> 11.0 13.2 10.9 12.4 18.8 21.5 33.3 CoMoS 17.0 25.2 29.7 29.9 34.2 31.9 30.3 <![CDATA[Co9S8]]> 18.3 30.2 27.3 15.0 13.2 11.9 11.1 CoO 64.7 44.5 42.9 55.1 52.5 56.1 58.5

[0121] The catalysts obtained in Examples 1-4 and Comparative Examples 1-3 were characterized by high-resolution transmission electron microscopy (HRTEM). The length and stacking number of MoS2 platelets on the surface of the catalysts after sulfurization were statistically analyzed to obtain the distribution of the length and stacking number of MoS2 platelets. The results are as follows: Figure 3 shown.

[0122] The average length of MoS2 flakes can be calculated by Equation 1 and Equation 2 and the number of stacking layers As shown in Table 3

[0123]

[0124] Where M i is the length of the lamella or the number of stacking layers, x i It is the number of lamellae with a certain lamella length or number of stacking layers.

[0125] Table 3

[0126]

[0127] Note: a and b are the average MoS2 platelet length and stacking layer number, respectively; c is the ratio of the number of Mo atoms at the edge of the MoS2 platelet to the total number of Mo atoms, i.e., the dispersion of MoS2.

[0128] From Table 3 and Figure 3 It can be seen that compared with catalyst D1 prepared by the impregnation method, catalyst D2 has a slightly smaller average platelet length and a slightly larger average platelet layer number and MoS2 dispersion.

[0129] Figure 1 Compared with catalyst D1, the MoO3 diffraction peak intensity of catalyst D2 is weaker, and there are fewer crystalline MoO3 species on its surface. Figure 2Compared to Catalyst D1, Catalyst D2 exhibits a lower-temperature reduction peak, indicating weaker interaction between the surface Mo species and alumina. This suggests that, for CoMo / Al2O3 prepared by the isovolumetric impregnation method, hydrothermal modification of alumina facilitates the dispersion of Mo species on the support surface and weakens the interaction between Mo and the support. Compared to Catalyst D1, Catalyst D3 exhibits a smaller average lamellae length, a larger average number of lamellae layers, and a higher MoS2 dispersion, indicating that the use of Mo-based organic-inorganic hybrid nanoparticles as a Mo precursor facilitates the dispersion of Mo species on the support surface and weakens the interaction between Mo and the support. Catalyst S2, prepared by combining hydrothermal modification of alumina with the use of Mo-based organic-inorganic hybrid nanoparticles as a Mo precursor, exhibits a smaller average lamellae length, a larger average number of lamellae layers, and a higher MoS2 dispersion than Catalysts D2 and D3. This suggests that combining these two methods can further modulate the microstructure of the active phase lamellae on the CoMoS / Al2O3 surface. For catalysts S1 to S4, despite differences in Co content, the average MoS2 lamellae length first decreases and then increases, while the average number of lamellae layers and MoS2 dispersion first increase and then decrease with increasing CoO content. At 4.0 wt% CoO, the average lamellae length is smaller, while the average number of lamellae layers and MoS2 dispersion are larger. Combined with XPS results, it is clear that for hydrothermally modified Al2O3-supported CoMo catalysts, adjusting the CoO content effectively modulates the composition and microstructure of the active phase lamellae on the CoMoS / Al2O3 surface.

[0130] Application Examples

[0131] The model gasoline hydrodesulfurization performance of catalysts S1-S4 prepared by the method of the present invention and catalysts D1-D3 prepared by the comparative example was evaluated in a micro high-pressure catalytic hydrogenation reaction device.

[0132] The model gasoline is a n-heptane solution (density 0.69 g / mL) containing thiophene (sulfur content of 100 μg / g) and 1-octene (mass fraction of 30 wt%), and the catalyst loading is 4.39 g. Before the reaction, the catalyst is pre-sulfurized with a 3% (mass fraction) n-heptane solution as the sulfurized oil. The pre-sulfurization conditions are: temperature 350°C, pressure 1.1 MPa, H2 / model gasoline (V / V) 100, and time 4 hours. After the sulfurization is completed, the sulfurized oil is switched to model gasoline. The reaction conditions are: temperature 230°C, pressure 1.1 MPa, H2 / model gasoline (V / V) 100, and volume space velocity 5.5 h -1 .

[0133] The desulfurization rate, olefin saturation rate and HDS selectivity factor are used as the evaluation indicators of model gasoline hydrodesulfurization performance. The calculation method is as follows:

[0134] Desulfurization rate (%) = (Sf -S p ) / S f (3)

[0135] Olefin saturation rate (%) = (O f -O p ) / O f (4)

[0136] Selectivity factor = ln(S f / S p ) / ln(O f / O p ) (5)

[0137] In the above formula, S f 、S p are the sulfur contents of the model gasoline feedstock and the reaction products (μg / g), O f , O p are the olefin contents (v%) of the model gasoline feedstock and the reaction products, respectively.

[0138] The evaluation results of the selective hydrodesulfurization performance of catalysts S1-S4 and catalysts D1-D3 on model gasoline are shown in Table 4.

[0139] Table 4

[0140] catalyst Desulfurization rate / % Olefin saturation rate / % Selectivity Factor S1 82.1 76.8 1.18 S2 91.5 66.2 2.27 S3 86.4 71.5 1.59 S4 83.6 75.2 1.30 D1 63.8 82.6 0.58 D2 76 80.1 0.88 D3 81.5 77.2 1.14

[0141] Table 5 shows that compared to catalyst D1, catalysts D2 and D3 have higher desulfurization rates and lower olefin saturation rates, resulting in higher selectivity factors. Meanwhile, for catalysts S1 to S4, as the CoO content increases, the desulfurization rate first increases and then decreases, while the olefin saturation rate first decreases and then increases. Catalyst S2 has a higher desulfurization rate, a lower olefin saturation rate, and a higher selectivity factor.

[0142] These results demonstrate that hydrothermal modification of Al2O3 effectively weakens the interaction between Mo and Al2O3. Using Mo-based organic-inorganic hybrid nanocrystals as Mo precursors ensures a high dispersion of Mo species on the Al2O3 surface. The combination of these two factors results in catalyst S2 exhibiting higher MoS2 platelet dispersion, a higher average stacking number, and a greater number of CoMoS active sites compared to catalysts D1-D3, leading to higher desulfurization rates and lower olefin saturation rates. For catalysts S1-S4, as the CoO content increases from 2.6wt% to 6.8wt%, the degree of Mo sulfidation on the catalyst surface first increases and then decreases, the average stacking number and dispersion of MoS2 first increase and then decrease, and the average platelet length first decreases and then increases. When the CoO content is 4.0wt%, the catalyst exhibits a higher degree of Mo sulfidation, a smaller average length, a larger average stacking number of MoS2 platelets, and a higher CoMoS fraction, ultimately resulting in a higher hydrodesulfurization selectivity factor. Therefore, Al2O3 is hydrothermally modified, and molybdenum-based organic-inorganic hybrid nanocrystals are used as molybdenum precursors. By adjusting the CoO content, the surface active phase composition and microstructure of CoMo / Al2O3 can be effectively regulated, thereby achieving the regulation of its hydrodesulfurization selectivity.

Claims

1. A method for preparing a catalyst for hydrodesulfurization of catalytic cracking gasoline, characterized in that: The following steps are involved: (1) mixing alumina with water, performing hydrothermal treatment to obtain a solid-liquid mixture, filtering, and collecting a solid to obtain hydrothermally modified alumina; (2) mixing an acidified molybdenum salt aqueous solution with a quaternary ammonium salt aqueous solution to obtain a suspension, then mixing the suspension with the hydrothermally modified alumina prepared in step (1), heating, filtering, obtaining a solid, and calcining to obtain a molybdenum-loaded alumina; (3) Immersing the molybdenum-loaded alumina prepared in step (2) in a cobalt salt solution, then taking out the molybdenum-loaded alumina and calcining it to obtain the catalyst.

2. The preparation method according to claim 1, characterized in that In step (1), the alumina is porous γ-alumina; and / or the alumina has a particle size of 1 to 8 mm and a specific surface area of ​​100 to 450 m 2 / g, and the pore volume is 0.10-0.98mL / g.

3. The preparation method according to claim 1, characterized in that In step (1), the hot water treatment is carried out in a sealed reactor, which is placed in an oven and treated at 80-180° C. for 10-35 hours.

4. The preparation method according to claim 1, characterized in that In step (2), the acidification is carried out using an inorganic acid selected from at least one of hydrochloric acid, sulfuric acid or nitric acid; and / or, in step (2), the molybdenum salt in the molybdenum salt aqueous solution is selected from at least one of ammonium molybdate, sodium molybdate and potassium molybdate.

5. The preparation method according to claim 1, characterized in that In step (2), the quaternary ammonium salt in the quaternary ammonium salt aqueous solution is at least one of alkyltrimethylammonium bromide or alkyltrimethylammonium chloride, tetraalkylammonium bromide or ammonium chloride; and / or, in step (2), the pH of the acidified molybdenum salt aqueous solution is 2.0-6.

5.

6. The preparation method according to claim 1, characterized in that In step (2), the concentration of molybdenum salt in the acidified molybdenum salt aqueous solution is 0.15 to 2.50 mol / L; and / or, in step (2), the concentration of the quaternary ammonium salt aqueous solution is 0.10 to 1.50 mol / L.

7. The preparation method according to any one of claims 1 to 6, characterized in that In step (2), the heating temperature is 50-180° C. and the heating time is 12-40 hours; and / or, in step (2), the calcination is performed at 300-550° C. for 2-10 hours; and / or, in step (3), the cobalt salt in the cobalt salt solution is selected from at least one of cobalt nitrate and cobalt acetate.

8. A catalyst for hydrodesulfurization of catalytic cracking gasoline, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. The catalyst according to claim 8, characterized in that The catalyst includes molybdenum oxide, cobalt oxide and aluminum oxide, and the molybdenum oxide and cobalt oxide are supported on the aluminum oxide.

10. Use of the catalyst prepared by the preparation method according to any one of claims 1 to 7 or the catalyst according to claim 8 or 9 in gasoline hydrodesulfurization.

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