A polycyclic aromatic hydrocarbon selective hydrogenation catalyst, a preparation method and application thereof

Abstract

The application provides a polycyclic aromatic hydrocarbon selective hydrogenation catalyst, and a preparation process thereof comprises the following steps: uniformly mixing a group VIB metal precursor, pseudo-boehmite, nitric acid and water, extruding, drying, calcining, and obtaining a catalyst precursor; mixing a group VIII metal salt and an organic ligand to form a solution, reacting, impregnating the catalyst precursor with the solution as an impregnation liquid, drying, and pyrolyzing under an inert atmosphere to obtain the catalyst. In the preparation process of the catalyst, amorphous carbon and nitrogen with a large specific surface area and a pore structure are generated in a metal organic framework pyrolysis process, the catalyst carrier is endowed with a large specific surface area and a rich carrier pore structure, the carbon layer covers the surface of the carrier, the carrier acidity is adjusted, and deep hydrogenation of reactant molecules on the catalyst is avoided, so that the polycyclic aromatic hydrocarbon selectivity of the catalyst is improved.

Description

Technical Field

[0001] This invention relates to a selective hydrogenation catalyst for polycyclic aromatic hydrocarbons, belonging to the field of catalytic hydrogenation technology. Background Technology

[0002] With the increasing deterioration of crude oil quality, the aromatic content in secondary processed oil products is rising. Excessive aromatic content and the high proportion of polycyclic aromatic hydrocarbons (PAHs) in these products severely impact their quality, leading to incomplete combustion, high combustion temperatures, and the generation of large amounts of PM2.5 in exhaust gases, thus posing a significant threat to the ecological environment. Furthermore, the trend of chemical transformation in petroleum refining is becoming increasingly evident. The selective hydrogenation of PAHs into partially saturated aromatics with higher added value is essential, which is of great significance for both environmental protection and chemical industry transformation.

[0003] CN111495400A discloses a method for preparing a non-precious metal aromatic hydrocarbon hydrogenation refining catalyst. This method involves adding nickel and tungsten salts to a support, followed by drying and calcination, to develop a low-cost, high-activity non-precious metal aromatic hydrocarbon hydrogenation refining catalyst. CN101099934A discloses a metal nitride catalyst for saturated aromatic hydrocarbon hydrogenation. A nickel-molybdenum bimetallic nitride is supported on alumina, and after impregnation, drying, tableting, and heating in argon at 650-680°C for 2 hours, followed by switching to hydrogen and continuing heating for another 2 hours, then cooling to room temperature and finally passivation, a metal nitride dearomatization catalyst is obtained. This catalyst exhibits high catalytic performance in the saturated hydrogenation reactions of monocyclic and bicyclic aromatic hydrocarbons. However, this catalyst is suitable for aromatic hydrocarbon saturation; both monocyclic and bicyclic aromatic hydrocarbons will become hydrogen-saturated, making it suitable for deep dearomatization processes. The catalysts mentioned in the above patent documents are all suitable for deep hydrogenation dearomatization reactions, but they cannot achieve selective hydrogenation of polycyclic aromatic hydrocarbons, thus failing to realize the high-value conversion of polycyclic aromatic hydrocarbons.

[0004] CN109395740A discloses a selective hydrogenation catalyst for polycyclic aromatic hydrocarbons (PAHs). The catalyst is prepared as follows: Co / Ni / Fe metal salts are supported on a carrier and calcined at 400–600 °C to obtain catalyst I with a core-phase structure. Subsequently, shell-phase metal salts such as Pt / Pd / Ir / Rh are impregnated onto catalyst I, and the catalyst is calcined at 400–600 °C to obtain the PAH selective hydrogenation catalyst. CN109395731A, CN109395726A, and CN109395727A all relate to the preparation of selective hydrogenation catalysts for PAHs, with processes similar to CN109395740A, mainly differing in the combination of shell-phase metals or the types of core-phase metals. The catalysts mentioned in the aforementioned patent documents have the advantages of high selective hydrogenation rate of polycyclic aromatic hydrocarbons and low loss of monocyclic aromatic hydrocarbons when used to process materials containing monocyclic aromatic hydrocarbons and fused-ring aromatic hydrocarbons. However, the catalysts use precious metals, resulting in high costs, strict requirements on raw materials, and a narrow range of applicable raw materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a selective hydrogenation catalyst for polycyclic aromatic hydrocarbons (PAHs). This catalyst is low in cost, simple to prepare, and adaptable to various raw materials. It enables the selective hydrogenation of PAHs, promotes the production of more chemical raw materials from oil processing, and achieves efficient utilization of oil products.

[0006] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows:

[0007] The first aspect of this invention provides a method for preparing a selective hydrogenation catalyst for polycyclic aromatic hydrocarbons, comprising the following:

[0008] (1) Mix the group VIB metal precursor, inorganic refractory oxide or its precursor, nitric acid and water evenly, extrude and mold, dry and calcine to obtain the catalyst precursor;

[0009] (2) Dissolve the group VIII metal salt in a solvent to obtain a metal salt solution, dissolve the organic ligand in a solvent and then mix it with the metal salt solution to obtain a group VIII metal-organic framework material M-MOF precursor solution;

[0010] (3) Impregnate the catalyst precursor of step (1) with M-MOF precursor solution, dry it, and pyrolyze it under an inert atmosphere to obtain the catalyst.

[0011] Furthermore, the group VIB metal precursor raw material mentioned in step (1) is an oxide of a group VIB metal or its ammonium salt.

[0012] Furthermore, the Group VIII metal is selected from at least one of Fe, Co, and Ni, preferably Co and / or Ni; the Group VIB metal is selected from at least one of Cr, Mo, and W, preferably Mo and / or W.

[0013] Furthermore, in the reaction, the amount of group VIB metal precursor and group VIII metal salt added is based on the total weight of the catalyst, such that the group VIII metal oxide accounts for 0.5-25.0%, preferably 1.2-9.0%; and the group VIB metal oxide accounts for 1.0-45%, preferably 8.0-32.0%.

[0014] Furthermore, in step (1), the amount of nitric acid added is 0.1wt%-10wt% of the oxide, preferably 0.5wt%-5.8wt%, based on the oxide in the inorganic refractory oxide or its precursor; the amount of water added is 50wt%-250wt% of the oxide, preferably 85wt%-200wt%.

[0015] Furthermore, the inorganic refractory oxide or its precursor is selected from one or more of boehmite, amorphous aluminum silicate, alumina, silica, zirconium oxide, titanium oxide and SBA-15, preferably at least one of boehmite, amorphous aluminum silicate and alumina.

[0016] Furthermore, the amount of organic ligand added in step (2) is such that the C of the carbonized organic ligand accounts for 0.1% to 15.0% of the total weight of the carrier, preferably 1.0% to 8.0%.

[0017] Furthermore, as a specific implementation, in step (2), based on oxides, the amount of organic ligand added is 0.16% to 65% of the dry basis of the oxide, preferably 1.5% to 35%.

[0018] Furthermore, the organic ligand is selected from one or more of terephthalic acid, imidazole, 2-methylimidazolium, 2-aminoterephthalic acid, trimesic acid, 1,4-bis(1-imidazolyl)benzene, 1,3,5-trimethyl-2,4,6-tris(3',5'-dicarboxyphenyl) and 2,5-dihydroxyterephthalic acid, preferably one or more of terephthalic acid, 2-methylimidazolium, trimesic acid and 2,5-dihydroxyterephthalic acid.

[0019] Furthermore, the drying conditions in step (1) are: drying temperature 60-200℃, drying time 1-8 hours.

[0020] Furthermore, the roasting conditions in step (1) are: roasting temperature 300-800℃, roasting time 2-8 hours.

[0021] Furthermore, the Group VIII metal salt mentioned in step (2) is selected as a soluble salt of at least one of nitrates, acetates, chlorides and sulfates, preferably nitrates or acetates.

[0022] Furthermore, the solvent in step (2) is selected from one or more of water, ethanol, methanol, isopropanol and N,N-dimethylformamide, preferably at least one of water, ethanol and N,N-dimethylformamide.

[0023] Furthermore, the impregnation in step (3) is either equal-volume impregnation or vacuum rotary evaporation impregnation;

[0024] Furthermore, the drying conditions in step (3) are: drying temperature 50-220℃, drying time 1-10 hours.

[0025] Furthermore, the inert atmosphere mentioned in step (3) is at least one of nitrogen or an inert gas.

[0026] Furthermore, the pyrolysis temperature in step (3) is 350~1000℃, preferably 400~650℃.

[0027] The technical objective of the second aspect of this invention is to provide a selective hydrogenation catalyst for polycyclic aromatic hydrocarbons prepared by the above method.

[0028] The selective hydrogenation catalyst for polycyclic aromatic hydrocarbons prepared by the above method includes a support and a hydrogenation active component. The support is an inorganic refractory oxide with a surface-modified carbon layer, and the hydrogenation active component is a Group VIII metal oxide and a Group VIB metal oxide. The surface carbon mainly comes from the pyrolysis of organic complexes. During the pyrolysis of metal-organic framework materials, amorphous carbon and nitrogen with large specific surface area and porous structure are generated, which endows the catalyst support with a large specific surface area and abundant pore structure. The carbon layer covering the surface of the support adjusts the acidity of the support and avoids deep hydrogenation of reactant molecules on the catalyst.

[0029] The technical objective of the third aspect of this invention is to provide a method for selective hydrogenation of oil products with high aromatic content, using the above-mentioned selective hydrogenation catalyst for polycyclic aromatic hydrocarbons as a catalyst.

[0030] Furthermore, the oil with high aromatic content is selected from catalytic diesel, coking diesel, etc. The catalyst of the present invention can achieve selective hydrogenation of polycyclic aromatic hydrocarbons in the oil while hydrogenating and refining to remove impurities (nitrogen and sulfur), thus producing more monocyclic aromatic hydrocarbons.

[0031] Furthermore, the hydrorefining catalyst is subjected to sulfidation treatment before catalytic hydrogenation reaction. The sulfidation is either dry sulfidation or wet sulfidation, preferably wet sulfidation. The sulfidation conditions are: sulfidation pressure of 3~7MPa, sulfidation temperature of 240~380℃, and sulfidation time of 5~20h. The sulfiding agent for dry sulfidation is hydrogen sulfide. The sulfiding agent for wet sulfidation is one or more of carbon disulfide, methyl sulfide, dimethyl disulfide, and n-butyl sulfide.

[0032] The technical solution of the present invention has the following technical effects:

[0033] Hydrorefining catalysts can achieve hydrorepurification of distillate oils, but while achieving desulfurization and denitrogenation, they often lead to deep saturation of aromatics, resulting in high hydrogen consumption and reduced product value. Selective hydrogenation of polycyclic aromatic hydrocarbons (PAHs) in distillate oils to produce more monocyclic aromatic hydrocarbons (MAHs) can improve the utilization value of the oil and make it a high-quality feedstock for the production of high-value chemicals. In this invention, amorphous carbon with a large specific surface area and porous structure is generated during the pyrolysis of metal-organic framework materials. This increases the specific surface area and enriches the pore structure of the support. Furthermore, the complexation of the active component with organic ligands reduces metal particle agglomeration during catalyst heating, resulting in better dispersion of active metals. Additionally, it can coat the support surface, adjust the acidity of the support, and prevent deep hydrogenation of reactant molecules on the catalyst, thereby improving the selectivity of PAHs in the catalyst. Detailed Implementation

[0034] The present invention will be described in detail below through embodiments, but the present invention is not limited to these embodiments. Example 1

[0035] Take 86.7g of boehmite (83% dry basis), 34.3g of ammonium molybdate, 3.6g of concentrated nitric acid and 72g of deionized water, mix them evenly, roll for 30 minutes, and extrude them into cylindrical strips using a cylindrical perforated plate with a diameter of 1.8cm. Then dry them at 150℃ for 4 hours and calcine them at 730℃ for 5 hours to obtain catalyst precursor I1.

[0036] 15.7 g of nickel nitrate was dissolved in 30 mL of ethanol to obtain a clear solution a. 10.1 g of 2-methylimidazole was added as an organic ligand to the 30 mL ethanol solution to obtain a clear solution b. Solutions a and b were mixed evenly and stirred for 30 minutes to obtain a nickel-2-methylimidazole metal inorganic complex solution c.

[0037] Solution c was impregnated onto precursor I1 by vacuum rotary evaporation, dried at 80°C for 6 hours, and calcined at 600°C for 5 hours under a nitrogen atmosphere to obtain hydrorefining catalyst A.

[0038] In hydrorefining catalyst A, the molybdenum oxide content is 25.75%, the nickel oxide content is 3.69%, and C accounts for approximately 5.05% of the support. Example 2

[0039] Take 86.7g of boehmite (83% dry basis), 34.3g of ammonium molybdate, 3.6g of concentrated nitric acid and 72g of deionized water, mix them evenly, roll for 30 minutes, and extrude them into cylindrical strips using a cylindrical perforated plate with a diameter of 1.8cm. Then dry them at 130℃ for 4 hours and calcine them at 750℃ for 3 hours to obtain catalyst precursor I2.

[0040] 15.4 g of nickel nitrate was dissolved in 30 mL of ethanol to obtain a clear solution a. 1.1 g of 2-methylimidazole was added as an organic ligand to 10 mL of ethanol solution to obtain a clear solution b. Solutions a and b were mixed evenly and stirred for 30 minutes to obtain a nickel-2-methylimidazole metal inorganic complex solution c.

[0041] Solution C was impregnated onto precursor I2 by vacuum rotary evaporation, dried at 80°C for 6 hours, and calcined at 600°C for 5 hours under a nitrogen atmosphere to obtain hydrogenation refining catalyst B.

[0042] In the hydrorefining catalyst B, the molybdenum oxide content is 26.85%, the nickel oxide content is 3.78%, and C accounts for approximately 0.5% of the support. Example 3

[0043] Take 93.5g of boehmite (77% dry basis), 34.3g of ammonium molybdate, 3.9g of concentrated nitric acid and 70g of deionized water, mix them evenly, roll for 30 minutes, and extrude them into cylindrical strips using a cylindrical perforated plate with a diameter of 1.8cm. Then dry them at 110℃ for 4 hours and calcine them at 700℃ for 3 hours to obtain catalyst precursor I3.

[0044] 15.4 g of nickel nitrate was dissolved in 20 mL of water to obtain a clear solution a. 5.0 g of 2-methylimidazole was added as an organic ligand to 20 mL of the aqueous solution to obtain a clear solution b. Solutions a and b were mixed evenly and stirred for 30 minutes to obtain a nickel-2-methylimidazole metal inorganic complex solution c.

[0045] Solution C was impregnated onto precursor I3 by vacuum rotary evaporation, dried at 120°C for 3 hours, and calcined at 650°C for 4 hours under a nitrogen atmosphere to obtain hydrorefining catalyst C.

[0046] In the hydrorefining catalyst C, the molybdenum oxide content is 26.36%, the nickel oxide content is 3.71%, and carbon accounts for approximately 3.4% of the support. Example 4

[0047] Take 91.1g of boehmite (79% dry basis), 34.3g of ammonium molybdate, 3.4g of concentrated nitric acid and 78g of deionized water, mix them evenly, roll for 30 minutes, and extrude them into cylindrical strips using a cylindrical perforated plate with a diameter of 1.8cm. Then dry them at 110℃ for 4 hours and calcine them at 700℃ for 3 hours to obtain catalyst precursor I4.

[0048] 15.4 g of nickel nitrate was dissolved in 20 mL of a mixture of ethanol and water (volume ratio 1:1) to obtain a clear solution a. 19.3 g of 2-methylimidazole was added as an organic ligand to 40 mL of a mixture of ethanol and water (volume ratio 1:1) to obtain a clear solution b. Solutions a and b were mixed evenly and stirred for 30 minutes to obtain a nickel-2-methylimidazole metal inorganic complex solution c.

[0049] Solution C was impregnated onto precursor I4 by vacuum rotary evaporation, dried at 110°C for 2 hours, and calcined at 680°C for 3 hours under a nitrogen atmosphere to obtain hydrogenation refining catalyst D.

[0050] In the hydrorefining catalyst D, the molybdenum oxide content is 24.72%, the nickel oxide content is 3.60%, and carbon accounts for approximately 11.8% of the support.

[0051] Comparative Example 1

[0052] Take 86.7g of boehmite (83% dry basis), 34.3g of ammonium molybdate, 3.6g of concentrated nitric acid and 72g of deionized water, mix them evenly, roll for 30 minutes, and extrude them into cylindrical strips using a cylindrical perforated plate with a diameter of 1.8cm. Then dry them at 110℃ for 6 hours and calcine them at 750℃ for 3 hours to obtain catalyst precursor I3.

[0053] 17.4 g of nickel nitrate was dissolved in 30 mL of methanol to obtain a clear solution a. 42 g of 2-methylimidazole was added as an organic ligand to 120 mL of methanol solution to obtain a clear solution b. Solutions a and b were mixed evenly and stirred for 30 minutes to obtain a nickel-2-methylimidazole metal inorganic complex solution c.

[0054] Solution C was impregnated onto precursor I3 by vacuum rotary evaporation, dried at 80°C for 6 hours, and calcined at 600°C for 5 hours under a nitrogen atmosphere to obtain hydrorefining catalyst C.

[0055] In the hydrorefining catalyst C, the molybdenum oxide content is 22.47%, the nickel oxide content is about 3.56%, and C accounts for about 22.6% of the support.

[0056] Comparative Example 2

[0057] Take 86.7g of boehmite (83% dry basis), 34.3g of ammonium molybdate, 3.6g of concentrated nitric acid and 72g of deionized water, mix them evenly, roll for 30 minutes, and extrude them into cylindrical strips using a cylindrical perforated plate with a diameter of 1.8cm. Then dry them at 120℃ for 5 hours and calcine them at 750℃ for 3 hours to obtain catalyst precursor I4.

[0058] 14.8 g of nickel nitrate was dissolved in 25 mL of methanol to obtain a clear solution a.

[0059] Solution a was impregnated onto precursor I4 by vacuum impregnation, and then dried at 80°C for 6 hours and calcined at 600°C for 5 hours to obtain hydrogenation refining catalyst D.

[0060] In the hydrorefining catalyst D, the molybdenum oxide content is 27.01%, the nickel oxide content is 3.66%, and there is no C layer in the support. Example 5

[0061] This example illustrates the performance of the catalyst provided by the present invention for the hydrogenation reaction of polycyclic aromatic hydrocarbons:

[0062] The catalyst was loaded into a laboratory fixed-bed reactor for reaction, with straight-run diesel oil as the feedstock. The catalyst was sulfided using an in-reactor sulfidation reaction.

[0063] Catalyst sulfidation conditions: 2 wt% CS2 jet fuel as sulfiding oil, volume hourly space velocity 1.0 h⁻¹ -1 The hydrogen-to-oil volume ratio was 40, and the catalyst was sulfided under a pressure of 6.0 MPa. The heating program was as follows: the temperature was increased to 120°C at a rate of 1°C / min, and the sulfiding oil was introduced and held at this temperature for 4 hours; then the temperature was increased to 230°C at a rate of 1°C / min and held at this temperature for 10 hours; then the temperature was increased to 310°C at a rate of 1°C / min and held at this temperature for 7 hours to complete the sulfidation process.

[0064] Reaction conditions: operating pressure 6.8 MPa, reaction temperature 345℃, hydrogen-to-oil volume ratio 600, and volume hourly space velocity 1.5 h⁻¹. -1 The evaluation results are shown in Table 2.

[0065] Table 2 Properties of Raw Materials and Products

[0066]

Claims

1. A method for preparing a selective hydrogenation catalyst for polycyclic aromatic hydrocarbons, comprising the following: (1) Mix the group VIB metal precursor, inorganic refractory oxide or its precursor, nitric acid and water evenly, extrude and mold, dry and calcine to obtain the catalyst precursor; (2) Dissolve the group VIII metal salt in a solvent to obtain a metal salt solution, dissolve the organic ligand in a solvent and then mix it with the metal salt solution to react. The amount of organic ligand added is such that the C after carbonization of the organic ligand accounts for 0.1% to 15.0% of the total weight of the carrier, to obtain a group VIII metal-organic framework material M-MOF precursor solution. (3) Impregnate the catalyst precursor of step (1) with M-MOF precursor solution, dry it, and pyrolyze it under an inert atmosphere at a temperature of 350~1000℃ to obtain the catalyst.

2. The preparation method according to claim 1, characterized in that, The group VIB metal precursor raw material mentioned in step (1) is an oxide of a group VIB metal or its ammonium salt.

3. The preparation method according to claim 1, characterized in that, The Group VIII metal is selected from at least one of Fe, Co and Ni, and the Group VIB metal is selected from at least one of Cr, Mo and W.

4. The preparation method according to claim 1, characterized in that, In the reaction, the amount of group VIB metal precursor and group VIII metal salt added is based on the total weight of the catalyst, such that group VIII metal oxide accounts for 0.5-25.0% and group VIB metal oxide accounts for 1.0-45%.

5. The preparation method according to claim 1, characterized in that, In step (1), the amount of nitric acid added is 0.1wt%-10wt% of the amount of the inorganic refractory oxide or its precursor, and the amount of water added is 50wt%-250wt% of the amount of the inorganic refractory oxide or its precursor.

6. The preparation method according to claim 1, characterized in that, In step (2), based on oxides, the amount of organic ligand added is 0.16% to 65% of the oxides.

7. The preparation method according to claim 1, characterized in that, The organic ligand is selected from one or more of terephthalic acid, imidazole, 2-methylimidazolium, 2-aminoterephthalic acid, pyromellitic acid, 1,4-bis(1-imidazolyl)benzene, 1,3,5-trimethyl-2,4,6-tris(3',5'-dicarboxyphenyl) and 2,5-dihydroxyterephthalic acid.

8. The preparation method according to claim 1, characterized in that, The Group VIII metal salt mentioned in step (2) is a soluble salt selected from at least one of nitrates, acetates, chlorides and sulfates.

9. The preparation method according to claim 1, characterized in that, The solvent mentioned in step (2) is selected from one or more of water, ethanol, methanol, isopropanol and N,N-dimethylformamide.

10. The preparation method according to claim 1, characterized in that, The drying conditions in step (3) are: drying temperature 50-220℃, drying time 1-10 hours.

11. The selective hydrogenation catalyst for polycyclic aromatic hydrocarbons prepared by the preparation method according to any one of claims 1-10.

12. A method for selective hydrogenation of oil with high aromatic content, wherein the polycyclic aromatic hydrocarbon selective hydrogenation catalyst of claim 11 is contacted with the oil with high aromatic content to carry out a catalytic reaction.

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