A hydro-dehydrating catalyst and a method for preparing the same

Abstract

The application provides a hydro-dehydration catalyst and a preparation method thereof, which are used for preparing C16 and C18 normal alkanes from animal and vegetable oils and fats, and the hydro-dehydration catalyst comprises a carrier and an active component, the carrier comprises magnesium-aluminum spinel, the active component comprises molybdenum and nickel, and the molar ratio of molybdenum to nickel is 85-100:1. The catalyst of the application takes the magnesium-aluminum spinel as the carrier, takes the molybdenum-nickel as the active component, and controls the molar ratio of molybdenum to nickel within the range of 85-100:1, so that the catalyst of the application has higher conversion rate and higher selectivity of C18 normal alkanes when used for preparing normal alkanes from animal and vegetable oils and fats.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials and relates to a hydrogenation dehydration catalyst made from animal and vegetable oils and its preparation method. Background Technology

[0002] Magnesium aluminum spinel is a novel catalytic hydrogenation and deoxygenation material, notably possessing characteristics not only of two metal oxides but also novel properties beyond those of two metal compounds. Magnesium aluminum spinel has a large specific surface area and high pore volume, making it suitable as a catalyst support. Its catalytic performance primarily depends on its specific surface area and pore volume. Furthermore, magnesium aluminum spinel exhibits high thermal stability, high mechanical strength and hardness, and good resistance to erosion, corrosion, and exfoliation, as well as good thermal shock resistance. Therefore, magnesium aluminum spinel is widely used as a catalyst and catalyst support in chemical reactions.

[0003] C15–C18 n-alkanes are mainly used in phase change materials, pharmaceutical cold chain logistics, phase change energy storage buildings, phase change microcapsules for textiles, and temperature control for electronic components. C18 n-alkanes are also used as solvents for separating and analyzing lower hydrocarbons, as dewaxing solvents, in machining oils, as base oils for special rust-preventive oils, as base oils for metalworking, as metal cleaning agents, and as reference materials and stationary phases in gas chromatography. They can also be used for gas storage functions such as hydrogen and nitrogen storage. Among them, n-hexadecane is also used as a standard substance for determining the combustion quality of diesel fuel.

[0004] Currently, most technologies for preparing monomeric n-alkanes through hydrodeoxygenation produce mixed alkanes that are components of second-generation biodiesel. These technologies suffer from problems such as low conversion rates and selectivity of animal and vegetable oils into alkanes, side reactions such as decarbonylation and decarboxylation, and the presence of C15 and C17 byproducts in the products.

[0005] CN201210322774 discloses a method for preparing alkanes by hydrodeoxygenation of non-edible animal and vegetable oils. Using a molybdenum-nickel catalyst, it produces mixed alkanes with C15 to C18 as the main components. The alkane yield is about 82%, and the yield of C15 to C18 mixed alkanes is about 80%. In the prepared mixed aromatics, decarbonylation and decarboxylation reactions occur, generating C15 and C17 alkanes, but the selectivity is not high.

[0006] CN201711055764 discloses a method for preparing a mesoporous bulk Mo-Ni hydrodeoxygenation catalyst. The method involves dissolving soluble nickel salt, soluble molybdenum salt, and organic acid in an aqueous ethanol solution, mixing the solutions thoroughly, and adjusting the pH of the mixed solution to 1-5. A hard template agent is added to the mixed solution, and the mixture is stirred to obtain a suspension. The suspension is then stirred until a sol is formed, followed by ultrasonic oscillation, aging at room temperature, and drying to obtain a mixture of dry gel and hard template agent. The resulting mixture is calcined under a nitrogen atmosphere to obtain Mo-Ni composite oxide powder. The obtained Mo-Ni composite oxide powder, binder, hard template agent, and guar gum powder are mixed thoroughly, and then dilute nitric acid is added dropwise for extrusion molding, followed by calcination to obtain the catalyst. A continuous flow fixed-bed reactor using a n-octane solution containing 20% ​​jatropha oil as raw material was employed, achieving a 100% deoxygenation rate for the jatropha oil.

[0007] CN202110942495 discloses a water-resistant core-shell catalyst for the hydrodeoxygenation of vegetable oil, which assembles Ni-Al-Mo7O on the surface of alumina. 24 6- LDHs with a shell structure yielded a Ni-Mo / γ-Al₂O₃ core-shell catalyst, which significantly improved water stability and provided mild reaction conditions in the hydrodeoxygenation reaction of methyl palmitate, a model compound from vegetable oil. However, in this hydrodeoxygenation reaction, the selectivity for n-hexadecane was only 55% when the deoxygenation conversion reached 86%, producing a large amount of n-pentadecane; and the deoxygenation conversion was only 15% when the n-hexadecane selectivity reached 92%.

[0008] CN201910743836 discloses the synthesis of a porous silica-alumina-phosphorus material and its catalyst preparation, as well as its application in the hydrogenation of palm oil and other oils to produce biofuels. The synthesis of the porous silica-alumina-phosphorus support does not involve the addition of amine template agents. By adjusting the silicon and alkali sources and finding suitable hydrothermal synthesis conditions, a template-free porous silica-alumina-phosphorus support can be obtained. Furthermore, the resulting support does not require calcination; sodium ions are removed from the crystals through ion exchange, making it suitable as a catalyst for the hydrodeoxygenation, hydroisomerization, and hydrocracking of palm oil and other vegetable oils to produce biofuels. Using methylated palm oil as raw material, the highest conversion rate of 99% was achieved, with a maximum C17-C18 selectivity of 66.7%, and a large amount of C5-C16 alkanes were produced as byproducts.

[0009] Therefore, further research is needed in this field on hydrogenation dehydration catalysts for animal and vegetable oils. Summary of the Invention

[0010] The main objective of this invention is to provide a hydrogenation dehydration catalyst and its preparation method, so as to overcome the problems of low conversion rate, low selectivity, and easy occurrence of side reactions such as decarbonylation and decarboxylation when the catalysts in the prior art are used to prepare n-alkanes from animal and vegetable oils.

[0011] To achieve the above objectives, the present invention provides a hydrodehydration catalyst for the preparation of C16 and C18 n-alkanes from animal and vegetable oils. The hydrodehydration catalyst includes a support and an active component. The support includes magnesium aluminum spinel, and the active component includes molybdenum and nickel, wherein the molar ratio of molybdenum to nickel is 85 to 100:1.

[0012] The hydrodehydration catalyst of the present invention further includes a modifying agent, wherein the modifying agent is at least one of iron, cobalt, and cerium.

[0013] The hydrodehydration catalyst of the present invention, wherein the active component, calculated as molybdenum oxide and nickel oxide, accounts for 10-30% of the mass of the support.

[0014] In the hydrodehydration catalyst of the present invention, the modified auxiliary agent, calculated as a metal oxide, accounts for 0.3 to 0.7% of the mass of the support.

[0015] To achieve the above objectives, the present invention also provides a method for preparing the above-mentioned hydrodehydration catalyst, characterized by comprising the following steps:

[0016] Step 1: Prepare magnesium aluminum spinel;

[0017] Step 2: The magnesium aluminum spinel, aluminum hydroxide dry glue, and guar gum powder are mixed, inorganic acid is added, extruded into strips, and calcined to obtain a carrier;

[0018] Step 3: Impregnate the support with a solution containing molybdenum precursor and nickel precursor to obtain the catalyst.

[0019] The method for preparing the hydrodehydration catalyst of the present invention further includes a step of impregnating the support with an organosilicon solution before impregnating the support with the active component; and / or the organosilicon is an alkoxysilane.

[0020] The preparation method of the hydrodehydration catalyst of the present invention further includes the steps of impregnating the catalyst obtained in step 3 with a solution containing a modified auxiliary agent precursor, and then drying and calcining it.

[0021] The method for preparing the hydrogenation dehydration catalyst of the present invention, wherein the preparation of magnesium aluminum spinel is: mixing magnesium source, aluminum source, complexing agent and citric acid, and calcining to obtain magnesium aluminum spinel.

[0022] The preparation method of the hydrogenation dehydration catalyst of the present invention, wherein the molybdenum precursor is a molybdenum-containing inorganic salt, the nickel precursor is a nickel-containing inorganic salt, and the mass ratio of magnesium aluminum spinel, aluminum hydroxide dry gel, and guar gum powder is, for example, 5-7:1.2-2.0:0.2-0.4.

[0023] The method for preparing the hydrodehydration catalyst of the present invention, wherein the modified auxiliary precursor is at least one of iron salt, cobalt salt, and cerium salt.

[0024] The beneficial effects of this invention are:

[0025] The catalyst of this invention uses magnesium aluminum spinel as a support and molybdenum nickel as the active component, and controls the molar ratio of molybdenum to nickel within the range of 85 to 100:1. As a result, the catalyst of this invention has a high conversion rate and high selectivity for C18 n-alkanes when used to prepare n-alkanes from animal and vegetable oils. Detailed Implementation

[0026] The technical solution of the present invention will be described in detail below. The following embodiments are implemented under the premise of the technical solution of the present invention and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following embodiments. Structures or experimental methods that do not specify specific conditions in the following embodiments are generally performed under conventional conditions.

[0027] This invention provides a hydrodehydration catalyst for the preparation of C16 and C18 n-alkanes from animal and vegetable oils. The hydrodehydration catalyst includes a support and an active component. The support includes magnesium aluminum spinel, and the active component includes molybdenum and nickel, with a molar ratio of molybdenum to nickel of 85 to 100:1.

[0028] The catalyst of this invention uses magnesium aluminum spinel as a support and molybdenum-nickel as the active component, and controls the molar ratio of molybdenum to nickel within the range of 85 to 100:1. This allows the catalyst to cause the animal and vegetable oils to undergo mainly hydrogenation and dehydration reactions when used to prepare n-alkanes, avoiding the occurrence of hydrogenation decarbonylation or decarboxylation side reactions, thereby improving the selectivity of C16 and C18 n-alkanes.

[0029] In detail, the hydrodeoxygenation of animal and vegetable oils involves two pathways: hydrodehydration and hydrodecarbonyl / carboxylation. During hydrodehydration, the oxygen in the fatty acid ester is converted to water, the fatty acid carbon chain does not break, and n-hexadecane and n-octadecane are produced, with higher yields of n-hexadecane and n-octadecane. During hydrodecarbonyl / carboxylation, the oxygen in the fatty acid ester is converted to CO or CO2, the fatty acid carbon chain breaks at the terminal position, and n-pentadecane and n-heptadecane are produced, with higher yields of n-pentadecane and n-heptadecane. This invention, through catalyst improvement, ensures that animal and vegetable oils primarily undergo hydrodehydration.

[0030] This invention does not impose any particular limitation on magnesium aluminum spinel, and any commercially available product can be used. In one embodiment, the magnesium aluminum spinel of this invention is prepared by the following method:

[0031] Magnesium source, aluminum source, complexing agent, and citric acid are mixed and calcined to obtain magnesium aluminum spinel.

[0032] This invention does not particularly limit the magnesium source or aluminum source. For example, the magnesium source may be magnesium nitrate, and the aluminum source may be aluminum nitrate. The complexing agent may be, for example, dodecyltrimethylammonium bromide, and this invention does not particularly limit it. In one embodiment, water is also added during the mixing process. The molar ratio of the magnesium source, aluminum source, complexing agent, citric acid, and water is 1:1–3:4–8:0.01–0.05:60–75, preferably 1:2:6:0.01:70.

[0033] In one embodiment, the present invention involves mixing a magnesium source, an aluminum source, a complexing agent, and citric acid, stirring at 60-90°C for 2-3 hours until the solution becomes a gel, then allowing it to stand at room temperature for a period of time, aging it in an oven, and finally calcining it at 600-800°C to obtain magnesium aluminum spinel. In another embodiment, the calcination temperature is 680-720°C, the heating rate is 2-3°C / min, and the calcination time is 6-10 hours.

[0034] In one embodiment, the catalyst support of the present invention further includes alumina. The preparation method of the support includes: mixing magnesium aluminum spinel, aluminum hydroxide dry glue and guar gum powder evenly, then adding inorganic acid extrusion strips and calcining to obtain the catalyst support.

[0035] The mass ratio of magnesium aluminum spinel, aluminum hydroxide dry adhesive, and guar gum powder is, for example, 5-7:1.2-2.0:0.2-0.4, preferably 6:1.5:0.3. The inorganic acid is, for example, dilute nitric acid, with a mass concentration of, for example, 2%. The ratio of dilute nitric acid to the mixture of magnesium aluminum spinel, aluminum hydroxide dry adhesive, and guar gum powder is, for example, 1.0 mL / g.

[0036] The present invention does not impose a particular limitation on the calcination temperature during the preparation of the catalyst support, for example, 680-720℃.

[0037] In one embodiment, the carrier of the present invention further includes, before loading the active component, impregnating the carrier with an organosilicon solution.

[0038] The organosilicon is, for example, an alkoxysilane, and more particularly, a tetraethoxysilane. The concentration of the organosilicon solution is, for example, 0.005–0.05 g / ml, preferably 0.01–0.02 g / ml. The impregnation method is, for example, equal-volume impregnation; the impregnation temperature is, for example, 20–30°C; the impregnation time is, for example, 20–30 min; and after impregnation, drying is performed; the drying temperature is, for example, 110–150°C; and the drying time is, for example, 3–7 h.

[0039] In the catalyst of the present invention, the active component is supported on a support, and the active component includes molybdenum and nickel, with a molar ratio of molybdenum to nickel of 85 to 100:1.

[0040] The present invention does not specifically limit the way the active component is loaded onto the carrier. For example, an impregnation method can be used, such as equal volume impregnation or excessive impregnation.

[0041] In one embodiment, the method for loading active components onto a carrier according to the present invention includes:

[0042] Molybdenum and nickel precursors were dissolved in water to prepare an impregnation solution. The support was then mixed with the impregnation solution, stirred, dried, and calcined to obtain the catalyst.

[0043] This invention does not particularly limit the molybdenum precursor or the nickel precursor. In one embodiment, the molybdenum precursor is ammonium molybdate, and the nickel precursor is nickel nitrate. The mass ratio of the impregnation solution to the carrier is 0.5-0.8:1.0. In this invention, stirring can be performed at intervals, for example, every 10-30 minutes. The drying temperature is, for example, 110-150°C, and the drying time is, for example, 4-12 hours. The calcination temperature is, for example, 480-650°C, preferably 550-600°C, and the calcination time is, for example, 3-5 hours.

[0044] In one embodiment, the catalyst of the present invention further includes a modifying agent, wherein the modifying agent is at least one of iron, cobalt, and cerium; in another embodiment, the modifying agent of the present invention is at least two of iron, cobalt, and cerium.

[0045] In one embodiment, the carrier of the present invention is loaded with a modifying agent after loading the active component. The following is an exemplary description of a method for loading a modifying agent onto a carrier after loading the active component: after impregnating the carrier with an active component impregnation solution, it is dried (without calcination), then impregnated with a modifying agent solution, dried, and calcined.

[0046] The modified additive solution is an aqueous solution of the modified additive precursor, wherein the concentration of the modified additive is, for example, 0.50–1.5 mol / L. The precursor of iron is an iron salt, such as ferric nitrate; the precursor of cobalt is a cobalt salt, such as cobalt nitrate; and the precursor of cerium is a cerium salt, such as cerium nitrate. The mass ratio of the modified additive solution to the support is, for example, 0.5–0.8:1.0. After impregnation, the solution is allowed to stand at room temperature for 8–12 h, dried at 105–120 °C for 3–5 h, and calcined at 480–650 °C, preferably 550–600 °C, for 3–5 h to obtain the catalyst.

[0047] In the catalyst of this invention, the active components, calculated as molybdenum oxide and nickel oxide, account for 10-30% of the support mass, preferably 20-25%, and the molybdenum:nickel molar ratio is 85-100:1, for example 87:1, 88:1, 89:1, 90:1, 92:1, 94:1, 95:1. In one embodiment, the support is modified with organosilicon, and the mass of the support in this case is, for example, the mass of the support after organosilicon modification.

[0048] In one embodiment, the catalyst of the present invention has the modified additive, calculated as a metal oxide, comprising 0.3 to 0.7% of the catalyst mass.

[0049] The catalyst of this invention is used to catalyze the hydrogenation and dehydration reaction of animal and vegetable oils to obtain C18 n-alkanes. In one embodiment, the animal and vegetable oils are non-edible vegetable oils and / or waste animal and vegetable oils, which can be purchased directly or obtained by refining oils as raw materials. The purpose of refining animal and vegetable oils is to remove impurities such as phosphorus and chlorine metals from the animal and vegetable oils.

[0050] In one embodiment, the hydrodehydration reaction is carried out in a fixed-bed reactor at a reaction temperature of 320–400°C, preferably 350–380°C, a reaction pressure of 1–4 MPa, preferably 1.5–2.5 MPa, and a mass hourly space velocity of 0.5–2 h⁻¹. -1 Preferably 0.8–1.5 h -1 The hydrogen-to-oil volume ratio is 100–400:1, preferably 150–300:1.

[0051] In another embodiment, a solvent is also added to the hydrodehydration reaction, and the solvent accounts for 70-95% of the volume of the reaction mixture, preferably 75-90%. The reaction mixture here includes the reactants and the solvent. The present invention does not particularly limit the solvent, for example, it may be n-octadecane or n-hexadecane, or the hydrodeoxygenation product in this embodiment.

[0052] The mixture after the hydrogenation and dehydration reaction of this invention can be first separated into oil and water, and then distilled to obtain C18 n-alkanes.

[0053] The catalyst of this invention is used to catalyze the reaction of animal and vegetable oils, which can avoid the occurrence of decarbonylation and decarboxylation side reactions during the reaction process, improve the selectivity of n-octadecane, and produce more n-octadecane. The selectivity of n-octadecane can be above 96%.

[0054] The technical solution of the present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the reagents and materials mentioned are commercially available.

[0055] Nickel nitrate: Nickel nitrate hexahydrate, Aladdin reagent, AR, 98%

[0056] Molybdenum nitrate: Shanghai Yihe Biotechnology, AR, 99.95%

[0057] Magnesium nitrate: Magnesium nitrate hexahydrate, Tianjin Fuchen, 98%

[0058] Aluminum nitrate: Tianjin Fuchen, 99%

[0059] Citric acid: Jinan Century Tongda, 95%

[0060] Dodecyltrimethylammonium bromide: Aladdin reagent, AR, 98%

[0061] Ferric nitrate: Tianjin Fuchen, 98.5%

[0062] Cobalt nitrate: Guangzhou Deli Chemical Co., Ltd., 98%

[0063] Cerium nitrate: Aladdin's reagent, 99.5%

[0064] Tetraethoxysilane: Merrill, 98%

[0065] Jatropha curcas refined oil: Yunnan Shenyu

[0066] Comparative Example 1

[0067] (1) Weigh out a certain amount of NiSO4·6H2O, H2MoO4·H2O, and glycolic acid according to the proportions, with a Mo:Ni molar ratio of 1.0 and a (Mo+Ni):glycolic acid molar ratio of 0.5. Dissolve them separately in a certain amount of 70wt% ethanol aqueous solution. After mixing, make the total amount of ethanol aqueous solution 500ml / (Mo+Ni)mol. Mix the solution evenly and adjust the pH of the solution to 1 with 27wt% ammonia. Then add the hard template agent polystyrene microspheres to the above solution according to the ratio of 40g hard template agent / (Mo+Ni)mol. Stir mechanically to obtain a suspension. Place the suspension in a 90℃ water bath and stir magnetically until a sol is formed. Ultrasonically vibrate for 30min, age at room temperature for 3h, and dry at 105℃ to obtain a dry gel and polystyrene microsphere mixture. Calcine the obtained mixture at 180℃ for 4h in a tube furnace under a nitrogen atmosphere, and then calcine at 700℃ for 2h in an air atmosphere in a muffle furnace to obtain Mo-Ni composite oxide powder. Mo-Ni powder, pseudoboehmite and polystyrene microspheres (psequential to polystyrene microsphere mass ratio of 3:1), and guar gum powder were mixed evenly at a mass ratio of 7:4:0.3. 2 wt% dilute nitric acid (1.5 ml / (Mo-Ni) g) was added dropwise, and the mixture was extruded into strips with a diameter of 2 mm. The strips were then calcined in an air atmosphere in a muffle furnace at 550 °C for 4 h to obtain a bulk Mo-Ni hydrodeoxygenation catalyst.

[0068] (2) Using a n-octane solution containing 20% ​​jacaranda oil by volume as raw material, a continuous flow fixed bed was used at a reaction temperature of 305℃, a reaction pressure of 2.0 MPa, and a reaction space velocity of 2.0 h⁻¹. -1 Hydrodeoxygenation was carried out under a hydrogen-to-oil volume ratio of 200:1, and the hydrodeoxygenation product was subjected to water separation. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenated product is shown in Table 3.

[0069] Comparative Example 2

[0070] (1) First, dissolve citric acid in water, then add magnesium nitrate, aluminum nitrate, and dodecyltrimethylammonium bromide in sequence. The molar ratio of magnesium nitrate, aluminum nitrate, dodecyltrimethylammonium bromide, citric acid, and water is 1:2:6:0.01:70. Stir at 80℃ for 2-3 hours until the solution becomes a gel. Let stand at room temperature for 1 hour, then age in an oven. Calcinate in a muffle furnace at 700℃ with a heating rate of 2-3℃ / min for 6-10 hours to obtain magnesium aluminum spinel.

[0071] Magnesium aluminum spinel powder, aluminum hydroxide dry adhesive, and guar gum powder were mixed evenly in a mass ratio of 8:2:0.3. Dilute nitric acid with a mass concentration of 4% was added dropwise according to the ratio of 0.8 mL / g MgAl2O4 powder. The mixture was then extruded into strips and calcined in a muffle furnace at 400℃ for 6 hours to obtain the catalyst support.

[0072] (2) Weigh out a certain amount of C4H6O4Ni·4H2O, Mo(NO3)3·5H2O and malic acid according to the proportion. The amount of active component (Mo+Ni) added is 20% of the mass of the support, based on the mass of MoO3+NiO. The molar ratio of Mo:Ni is 5 and the molar ratio of (Mo+Ni):malic acid is 1.5:1. Dissolve in deionized water. The mass ratio of deionized water to support is 0.7:1. Load the active component using the equal volume impregnation method. Let stand at 30℃ for 10h. Dry in a muffle furnace at 110℃ for 4h and calcine at 600℃ for 3.5h to obtain the desired catalyst.

[0073] (3) Catalyst Evaluation

[0074] Using a n-octane solution containing 20% ​​jatropha oil by volume as feedstock, a continuous fixed bed reactor was used at a temperature of 370℃, a pressure of 2 MPa, and a space velocity of 1.0 h⁻¹. -1 Under the condition of a hydrogen-to-oil volume ratio of 200:1, a hydrodeoxygenation reaction was carried out. The hydrodeoxygenation product was separated into water. The properties of the raw material jatropha oil are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrotreated product is shown in Table 3.

[0075] Example 1

[0076] (1) Preparation of the carrier

[0077] First, citric acid is dissolved in water. Then, magnesium nitrate, aluminum nitrate, and dodecyltrimethylammonium bromide are added sequentially, with a molar ratio of 1:2:6:0.01:70. The mixture is stirred at 80°C for 2–3 hours until it becomes a gel. After standing at room temperature for 1 hour, it is aged in an oven. Finally, it is calcined in a muffle furnace at 700°C with a heating rate of 2–3°C / min for 6–10 hours to obtain magnesium aluminum spinel.

[0078] Magnesium aluminum spinel powder, aluminum hydroxide dry adhesive, and guar gum powder were mixed evenly in a mass ratio of 6:1.2:0.2. Dilute nitric acid with a mass concentration of 2% was added at a liquid-to-solid ratio of 1.0 mL / g. The mixture was then extruded into strips and calcined in a muffle furnace at 700℃ for 2 hours to obtain the catalyst support.

[0079] (2) Carrier modification

[0080] Tetraethoxysilane was added to water at a concentration of 0.005 g / ml. The solution was then impregnated onto the catalyst support using an equal-volume impregnation method. After impregnation for 30 min, the catalyst was dried in an oven at 115 °C for 12 h.

[0081] (3) Active ingredient loading

[0082] First, molybdenum nitrate and nickel nitrate were dissolved in water to prepare an impregnation solution. The active component, calculated as MoO3 + NiO, accounted for 20% of the carrier mass, and the molar ratio of molybdenum to nickel was 95. The mass ratio of the impregnation solution to the carrier was 0.7:1. After impregnation, the solution was allowed to stand at room temperature for 12 hours and then dried in an oven at 115°C for 12 hours.

[0083] (4) Additive loading

[0084] A mixed solution of ferric nitrate and cobalt nitrate was prepared by liquid impregnation. The concentration of ferric nitrate was 0.5 mol / L and the concentration of cobalt nitrate was 0.6 mol / L. The solution was impregnated onto a catalyst support with a mass ratio of solution to support of 0.5:1. After impregnation, the solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0085] (5) Catalyst Evaluation

[0086] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of the aforementioned catalyst. The reaction temperature was 360℃, the reaction pressure was 1.0 MPa, and the reaction mass hourly space velocity was 1.8 h⁻¹. -1 The hydrogen-to-oil volume ratio was 130:1, the solvent accounted for 80% of the reaction mixture volume, and the hydrogenation dehydration product was subjected to water separation. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenation product is shown in Table 3.

[0087] Example 2

[0088] (1) The carrier was prepared according to Example 1.

[0089] (2) Carrier modification

[0090] Tetraethoxysilane was added to water at a concentration of 0.04 g / ml. The solution was then impregnated onto the support using an equal-volume impregnation method. After impregnation for 30 min, the support was dried at 120 °C for 5 h to obtain the final support.

[0091] (3) Active ingredient loading

[0092] First, molybdenum nitrate and nickel nitrate were dissolved in water to prepare an impregnation solution. The active component, calculated as MoO3 + NiO, accounted for 20% of the carrier mass, and the molar ratio of molybdenum to nickel was 95. The mass ratio of the impregnation solution to the carrier was 0.7:1. After impregnation, the solution was allowed to stand at room temperature for 12 hours and then dried in an oven at 115°C for 12 hours.

[0093] (4) Additive loading

[0094] A cerium nitrate solution with a concentration of 0.5 mol / L was prepared and impregnated onto a catalyst support at a mass ratio of 0.5:1. After impregnation, the solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0095] (5) Catalyst Evaluation

[0096] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of a hydrodeoxygenation catalyst. The reaction temperature was 370℃, the reaction pressure was 4.0 MPa, and the reaction mass hourly space velocity was 1.2 h⁻¹. -1 The hydrogen-to-oil volume ratio was 400:1, the solvent volume accounted for 70% of the reaction mixture, and the hydrogenation dehydration product was subjected to water separation. The properties of the raw material jatropha oil are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenation product is shown in Table 3.

[0097] Example 3

[0098] (1) The carrier was prepared according to Example 1.

[0099] (2) Carrier modification

[0100] Tetraethoxysilane was added to water at a concentration of 0.05 g / ml. The solution was then impregnated onto the support using an equal-volume impregnation method. After impregnation for 30 min, the support was dried at 120 °C for 5 h to obtain the final support.

[0101] (3) Active ingredient loading

[0102] First, nickel nitrate and molybdenum nitrate were used to prepare an impregnation solution. The active component, calculated as MoO3 + NiO, accounted for 20% of the carrier mass, and the molar ratio of molybdenum to nickel was 100. The mass ratio of the impregnation solution to the carrier was 0.7:1. After impregnation, the solution was allowed to stand at room temperature for 12 hours and then dried in an oven at 115℃ for 12 hours.

[0103] (4) Additive loading

[0104] A mixed solution of ferric nitrate and cobalt nitrate was prepared, with a concentration of 0.7 mol / L for ferric nitrate and 0.8 mol / L for cobalt nitrate. The solution was impregnated onto a catalyst support at a mass ratio of 0.5:1. After impregnation, the solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0105] (5) Catalyst Evaluation

[0106] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of a hydrodeoxygenation catalyst. The reaction temperature was 390℃, the reaction pressure was 3MPa, and the reaction mass hourly space velocity was 2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 100:1, and the solvent volume accounted for 90%. The hydrogenation dehydration product was subjected to water separation. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenated product is shown in Table 3.

[0107] Example 4

[0108] (1) The carrier was prepared according to Example 1.

[0109] (2) Carrier modification

[0110] Tetraethoxysilane was added to water at a concentration of 0.01 g / ml. The solution was then impregnated onto the support using an equal-volume impregnation method. After impregnation for 30 min, the support was dried at 120 °C for 5 h to obtain the final support.

[0111] (3) Active ingredient loading

[0112] First, molybdenum nitrate and nickel nitrate were dissolved in water to prepare an impregnation solution. The active component, calculated as MoO3 + NiO, accounted for 20% of the carrier mass, and the molar ratio of molybdenum to nickel was 85. The mass ratio of the impregnation solution to the carrier was 0.7:1. After impregnation, the solution was allowed to stand at room temperature for 12 hours and then dried in an oven at 115°C for 12 hours.

[0113] (4) Additive loading

[0114] A mixed solution of ferric nitrate and cerium nitrate was prepared, with a concentration of ferric nitrate of 0.8 mol / L and a concentration of cerium nitrate of 0.5 mol / L. The solution was impregnated onto a catalyst support at a mass ratio of 0.5:1. After impregnation, the solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0115] (5) Catalyst Evaluation

[0116] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of a hydrodeoxygenation catalyst. The reaction temperature was 360℃, the reaction pressure was 1.5 MPa, and the reaction mass hourly space velocity was 0.9 h⁻¹. -1 The hydrogen-to-oil volume ratio was 170:1, and the solvent volume accounted for 75% of the reaction mixture. The hydrogenation dehydration product was subjected to water separation. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenation product is shown in Table 3.

[0117] Example 5

[0118] (1) Carrier preparation and carrier modification were carried out in accordance with Example 4.

[0119] (2) Active ingredient loading

[0120] First, molybdenum nitrate and nickel nitrate were dissolved in water to prepare an impregnation solution. The active component, calculated as MoO3 + NiO, accounted for 20% of the carrier mass, and the molar ratio of molybdenum to nickel was 90. The mass ratio of the impregnation solution to the carrier was 0.7:1. After impregnation, the solution was allowed to stand at room temperature for 12 hours and then dried in an oven at 115°C for 12 hours.

[0121] (3) Additive loading

[0122] A mixed solution of ferric nitrate and cerium nitrate was prepared, with a concentration of 1.0 mol / L for ferric nitrate and a concentration of 0.5 mol / L for cerium nitrate. The solution was impregnated onto a catalyst support at a mass ratio of 0.5:1 to the support. After impregnation, the solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0123] (4) Catalyst Evaluation

[0124] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of a hydrodeoxygenation catalyst. The reaction temperature was 370℃, the reaction pressure was 2.0 MPa, and the reaction mass hourly space velocity was 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 200:1, the solvent volume accounted for 80% of the reaction mixture, and the hydrogenation dehydration product was subjected to water separation. The properties of the raw material jatropha oil are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenation product is shown in Table 3.

[0125] Example 6

[0126] (1) The carrier was prepared according to Example 1.

[0127] (2) Carrier modification

[0128] Tetraethoxysilane was added to water at a concentration of 0.02 g / ml. The solution was then impregnated onto the support using an equal-volume impregnation method. After impregnation for 30 min, the support was dried at 120 °C for 5 h to obtain the final support.

[0129] (3) Active ingredient loading

[0130] First, molybdenum nitrate and nickel nitrate were dissolved in water to prepare an impregnation solution. The active component, calculated as MoO3 + NiO, accounted for 20% of the carrier mass. The molar ratio of molybdenum to nickel was 85, and the mass ratio of the impregnation solution to the carrier was 0.7:1. After impregnation, the solution was allowed to stand at room temperature for 12 hours and then dried in an oven at 115°C for 12 hours.

[0131] (4) Additive loading

[0132] A mixed solution of ferric nitrate and cerium nitrate was prepared, with a concentration of 0.6 mol / L for both ferric nitrate and cerium nitrate. The solution was impregnated onto a catalyst support at a mass ratio of 0.5:1. After impregnation, the solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0133] (5) Catalyst Evaluation

[0134] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of a hydrodeoxygenation catalyst. The reaction temperature was 355℃, the reaction pressure was 2.0 MPa, and the reaction mass hourly space velocity was 1.1 h⁻¹. -1 The hydrogen-to-oil volume ratio was 180:1, the solvent volume accounted for 90% of the reaction mixture, and the hydrogenation dehydration product was subjected to water separation. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenation product is shown in Table 3.

[0135] Example 7

[0136] (1) The carrier was prepared and modified according to Example 6.

[0137] (2) Active ingredient loading

[0138] First, molybdenum nitrate and nickel nitrate were dissolved in water to prepare an impregnation solution. The active component, calculated as MoO3 + NiO, accounted for 20% of the carrier mass. The molar ratio of molybdenum to nickel was 90, and the mass ratio of the impregnation solution to the carrier was 0.7:1. After impregnation, the solution was allowed to stand at room temperature for 12 hours and then dried in an oven at 115°C for 12 hours.

[0139] (3) Additive loading

[0140] A mixed solution of ferric nitrate and cerium nitrate was prepared, with a concentration of ferric nitrate of 0.9 mol / L and a concentration of cerium nitrate of 0.6 mol / L. The solution was impregnated onto a catalyst support at a mass ratio of 0.5:1. The solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0141] (4) Catalyst Evaluation

[0142] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of a hydrodeoxygenation catalyst. The reaction temperature was 365℃, the reaction pressure was 2.5 MPa, and the reaction mass hourly space velocity was 1.3 h⁻¹. -1 The hydrogen-to-oil volume ratio was 210:1, the solvent volume accounted for 80% of the reaction mixture, the hydrodeoxygenation product was separated by water, the properties of the raw material jatropha oil are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenated product is shown in Table 3.

[0143] Example 8

[0144] (1) The carrier was prepared according to Example 1.

[0145] (2) Carrier modification

[0146] Tetraethoxysilane was added to water at a concentration of 0.01 g / ml. The solution was then impregnated onto the support using an equal-volume impregnation method. After impregnation for 30 min, the support was dried at 120 °C for 5 h to obtain the final support.

[0147] (3) Active component loading

[0148] First, molybdenum nitrate and nickel nitrate were dissolved in water to prepare an impregnation solution. The active component, calculated as MoO3 + NiO, accounted for 20% of the carrier mass. The molar ratio of molybdenum to nickel was 90, and the mass ratio of the impregnation solution to the carrier was 0.7:1. After impregnation, the solution was allowed to stand at room temperature for 12 hours and then dried in an oven at 115°C for 12 hours.

[0149] (4) Additive loading

[0150] A mixed solution of ferric nitrate and cerium nitrate was prepared, with a concentration of ferric nitrate of 0.5 mol / L and a concentration of cerium nitrate of 0.8 mol / L. The solution was impregnated onto a catalyst support at a mass ratio of 0.5:1. The solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0151] (5) Catalyst Evaluation

[0152] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of a hydrodeoxygenation catalyst. The reaction temperature was 360℃, the reaction pressure was 2.5 MPa, and the reaction mass hourly space velocity was 0.9 h⁻¹. -1 The hydrogen-to-oil volume ratio was 250:1, and the solvent volume accounted for 75% of the reaction mixture. The hydrogenation dehydration product was subjected to water separation. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenation product is shown in Table 3.

[0153] Example 9

[0154] (1) According to Example 8, a carrier was prepared, the carrier was modified, and molybdenum-nickel metal components were loaded.

[0155] (2) Additive loading

[0156] A mixed solution of ferric nitrate and cerium nitrate was prepared, with a concentration of ferric nitrate of 0.4 mol / L and a concentration of cerium nitrate of 1.0 mol / L. The solution was impregnated onto a catalyst support at a mass ratio of 0.5:1. After impregnation, the solution was allowed to stand at room temperature for 10 h, dried in a muffle furnace at 110 °C for 4 h, and calcined at 600 °C for 4 h to obtain the desired catalyst.

[0157] (3) Catalyst Evaluation

[0158] Jatropha curcas refined oil was mixed with a solvent and subjected to a hydrodehydration reaction in a fixed-bed reactor under the action of a hydrodeoxygenation catalyst. The reaction temperature was 380℃, the reaction pressure was 2.0 MPa, and the reaction mass hourly space velocity was 1.4 h⁻¹. -1 The hydrogen-to-oil volume ratio was 180:1, the solvent volume accounted for 85% of the reaction mixture, and the hydrogenation dehydration product was subjected to water separation. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenation product is shown in Table 3.

[0159] Example 10

[0160] (1) First, dissolve citric acid in water, then add magnesium nitrate, aluminum nitrate, and dodecyltrimethylammonium bromide in sequence. The molar ratio of magnesium nitrate, aluminum nitrate, dodecyltrimethylammonium bromide, citric acid, and water is 1:2:6:0.01:70. Stir at 80℃ for 2-3 hours until the solution becomes a gel. Let stand at room temperature for 1 hour, then age in an oven. Calcinate in a muffle furnace at 700℃ with a heating rate of 2-3℃ / min for 6-10 hours to obtain magnesium aluminum spinel.

[0161] Magnesium aluminum spinel powder, aluminum hydroxide dry adhesive, and guar gum powder were mixed evenly in a mass ratio of 8:2:0.3. Dilute nitric acid with a mass concentration of 2% was added dropwise according to the ratio of 1.2 mL / g MgAl2O4 powder. The mixture was then extruded into strips and calcined in a muffle furnace at 800℃ for 2 hours to obtain the catalyst support.

[0162] (2) Weigh out a certain amount of NiSO4·6H2O and (NH4)6Mo7O according to the proportion. 24 • 4H₂O and glycolic acid were added. The amount of the active component (Mo+Ni) added was 20% of the support mass based on the mass of MoO₃+NiO, with a Mo:Ni molar ratio of 90 and a (Mo+Ni):glycolic acid molar ratio of 0.3:1. The solution was dissolved in deionized water, with a deionized water-to-support mass ratio of 0.7:1. The active component was loaded using an equal-volume impregnation method, allowed to stand at 20°C for 12 hours, and then dried in an oven at 110°C for 12 hours. Finally, it was calcined at 480°C for 5 hours to prepare the desired catalyst.

[0163] (3) Evaluation of catalysts

[0164] The evaluation raw materials and conditions were the same as those in Comparative Example 2. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenated product is shown in Table 3.

[0165] Example 11

[0166] (1) First, dissolve citric acid in water, then add magnesium nitrate, aluminum nitrate, and dodecyltrimethylammonium bromide in sequence. The molar ratio of magnesium nitrate, aluminum nitrate, dodecyltrimethylammonium bromide, citric acid, and water is 1:2:6:0.01:70. Stir at 80℃ for 2-3 hours until the solution becomes a gel. Let stand at room temperature for 1 hour, then age in an oven. Calcinate in a muffle furnace at 700℃ with a heating rate of 2-3℃ / min for 6-10 hours to obtain magnesium aluminum spinel.

[0167] Magnesium aluminum spinel powder, aluminum hydroxide dry adhesive, and guar gum powder were mixed evenly in a mass ratio of 8:2:0.3. Dilute nitric acid with a mass concentration of 2% was added dropwise according to the ratio of 1.2 mL / g MgAl2O4 powder. The mixture was then extruded into strips and calcined in a muffle furnace at 800℃ for 2 hours to obtain the catalyst support.

[0168] (2) Weigh out a certain amount of NiSO4·6H2O and (NH4)6Mo7O according to the proportion. 24• 4H₂O and glycolic acid were added. The amount of the active component (Mo+Ni) added was 20% of the support mass based on the mass of MoO₃+NiO, with a Mo:Ni molar ratio of 90 and a (Mo+Ni):glycolic acid molar ratio of 0.3:1. The solution was dissolved in deionized water at a deionized water to support mass ratio of 0.7:1. The active component was loaded using an equal-volume impregnation method, allowed to stand at 20°C for 12 hours, and then dried in an oven at 110°C for 12 hours. A 1.5 mol / L ferric nitrate solution was impregnated onto the support loaded with the active component at a solution to support mass ratio of 0.5:1. The solution was allowed to stand at 15°C for 10 hours, dried in a muffle furnace at 120°C for 3 hours, and calcined at 480°C for 5 hours to prepare the desired catalyst.

[0169] (3) Evaluation of catalysts

[0170] The evaluation raw materials and conditions were the same as those in Comparative Example 2. The properties of the raw material, jatropha oil, are shown in Table 1, the evaluation results are shown in Table 2, and the composition of the hydrogenated product is shown in Table 3.

[0171] The calculation method for the hydrodehydration rate in Table 2:

[0172] Given that the total amount of C18 esters in jatropha oil is approximately 83.15 ω% and the total amount of C17 esters is approximately 0.02 ω%, the C17 esters are assumed to be zero when calculating the hydrodehydration rate. The generation of C17 n-alkanes from the hydrodehydration of C17 esters is also assumed to be zero. All C17 n-alkanes in the products are generated from the decarbonylation and decarboxylation of C18 esters, i.e.:

[0173]

[0174] Table 1. Composition of Refined Tamarix Oil

[0175]

[0176] Note: Lauric acid (C12:0) indicates lauric acid without carbon-carbon double bonds, and linolenic acid (C18:3) indicates linolenic acid with three carbon-carbon double bonds.

[0177]

[0178]

[0179] A higher hydrodehydration rate indicates a lower probability of hydrogenation decarbonylation and decarboxylation side reactions, meaning less carbon chain terminal breakage to generate CO2 and CO in the product, and a higher proportion of C16 and C18 n-alkanes in the product. The objective of this invention is to increase the hydrodehydration rate and thus the yield of the target C16 and C18 n-alkanes. As shown in Tables 2 and 3, in Comparative Example 1, the molybdenum / nickel molar ratio was 1, and the active component, calculated as MoO3 + NiO, accounted for approximately 70% of the catalyst mass (excessive active component content leads to excessive cost). No silicon modification or additive modification was performed, and the hydrodehydration rate was 89.5%. In Comparative Example 2, the molybdenum / nickel molar ratio was 5, and no silicon or additive modification was performed, resulting in a hydrodehydration rate of only 18.9%, exhibiting the worst dehydration selectivity. In Example 10, the molybdenum / nickel molar ratio was 90, and no silicon or additive modification was performed, yet the hydrodehydration rate improvement was only 59.7%. In Example 11, the molybdenum / nickel molar ratio was 90, and only iron additive modification was performed, resulting in a hydrodehydration rate of 91.8%, a significant improvement. This indicates that additives and the molybdenum / nickel molar ratio can, to some extent, improve the hydrodehydration rate. Therefore, in the examples, adjustments were made to the molybdenum / nickel molar ratio, the type of additives (silicon, iron, cerium, cobalt), and the additive concentration, resulting in a significant improvement in the hydrodehydration rate. Ultimately, in Example 5, with a molybdenum / nickel molar ratio of 90, after silicon modification and iron-cerium additive modification, the hydrodehydration rate reached 97.2%, and the product contained 80.41% C18 n-alkanes and 14.04% C16 n-alkanes.

[0180] This invention controls the occurrence of side reactions and improves the selectivity of the target product by adjusting the molybdenum-nickel ratio in the catalyst and adding modifying agents. The resulting C18 n-alkanes have high purity and extremely low content of impurities such as sulfur, nitrogen, and aromatics, which avoids the problems of complex production process and harsh process conditions in the traditional fossil raw material production of n-alkanes.

[0181] Therefore, the catalyst of this invention uses magnesium aluminum spinel as a support and molybdenum-nickel as the active component, controlling the molar ratio of molybdenum to nickel within the range of 85–100:1. The catalyst of this invention achieves 100% conversion in the hydrogenation and dehydration of animal and vegetable oils to n-alkanes and can improve the selectivity of C18 n-alkanes. Furthermore, by modifying the support and catalyst with silicon, iron, cobalt, and cerium additives, the selectivity of the target product C18 n-alkanes can be further improved, decarbonylation and decarboxylation reactions can be reduced, byproduct formation can be decreased, and the content of the target product in the final product increases, thus reducing the pressure on subsequent separation.

[0182] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A hydrodehydration catalyst, characterized in that, This hydrogenation dehydration catalyst is used to prepare C16 and C18 n-alkanes from animal and vegetable oils. It includes a support, an active component, and a modifying agent. The support includes magnesium aluminum spinel, which is modified with organosilicon. The active component includes molybdenum and nickel, with a molar ratio of molybdenum to nickel of 85 to 100:

1. The modifying agent is at least one of iron, cobalt, and cerium.

2. The hydrodehydration catalyst according to claim 1, characterized in that, In the hydrodehydration catalyst, the active component, calculated as molybdenum oxide and nickel oxide, accounts for 10-30% of the mass of the support.

3. The hydrodehydration catalyst according to claim 1, characterized in that, The modified additive, calculated as a metal oxide, accounts for 0.3 to 0.7% of the mass of the catalyst.

4. The method for preparing the hydrodehydration catalyst according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Prepare magnesium aluminum spinel; Step 2: The magnesium aluminum spinel, aluminum hydroxide dry glue, and guar gum powder are mixed, an inorganic acid is added, and the mixture is extruded and calcined to obtain a carrier; the carrier is then impregnated with an organosilicon solution. Step 3: Impregnate the carrier obtained in Step 2 with a solution containing molybdenum precursor and nickel precursor, and then dry it; Then, the solution containing the modified precursor is impregnated, dried, and calcined.

5. The method for preparing the hydrodehydration catalyst according to claim 4, characterized in that, The organosilicon is an alkoxysilane.

6. The method for preparing the hydrodehydration catalyst according to claim 4, characterized in that, The preparation of magnesium aluminum spinel involves mixing a magnesium source, an aluminum source, a complexing agent, and citric acid, followed by calcination to obtain magnesium aluminum spinel.

7. The method for preparing the hydrodehydration catalyst according to claim 4, characterized in that, The molybdenum precursor is a molybdenum-containing inorganic salt, and the nickel precursor is a nickel-containing inorganic salt; the mass ratio of magnesium aluminum spinel, aluminum hydroxide dry glue, and guar gum powder is 5~7:1.2~2.0:0.2~0.

4.

8. The method for preparing the hydrodehydration catalyst according to claim 4, characterized in that, The modified additive precursor is at least one of iron salt, cobalt salt, and cerium salt.

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