Ethylene tar refining catalyst system and use thereof

Abstract

The application provides an ethylene tar refining catalyst system and application thereof, the catalyst system comprises a carrier and a modified element; the carrier is Al2O3, Al2O3-TiO2-SiO2 and Al2O3-SiO2 multi-element composite carrier, and the modified element is selected from Ni, Mo, La, W, K, P and Co. The catalyst system provided by the application can better solve the problem of the contradiction between high conversion of naphthalene and high selectivity of tetrahydronaphthalene of the ethylene tar refining catalyst in the prior art under mild process conditions, and can be used in industrial production of ethylene tar upgrading and efficiency improvement.

Description

Technical Field

[0001] This invention relates to the field of ethylene tar processing technology, and more specifically to an ethylene tar refining catalyst system and its application. Background Technology

[0002] Ethylene tar, also known as cracked tar, is a high-boiling-point liquid product of the steam cracking process for producing ethylene. It belongs to the diesel fraction (205-360℃) and mainly originates from the bottom of quench oil towers and heavy fuel oil stripping towers. Ethylene tar is a heavy distillate oil rich in aromatics, primarily containing monocyclic heavy aromatics, polycyclic or fused-ring aromatics. It has a complex composition, is prone to polymerization, and has high levels of gum, heavy metals, and ash, making it unsuitable for direct use. The yield of ethylene tar varies depending on the cracking feedstock, generally accounting for about 1 / 5 of the ethylene production. With the increasing use of heavier feedstocks in ethylene production, its yield shows an increasing trend.

[0003] Ethylene tar has a high yield (approximately 70%) in the fractions between 205℃ and 300℃, followed by gum and asphaltenes. Ethylene tar also has a high sulfur content, high polycyclic aromatic hydrocarbon content, high density, and short side chains in its aromatic compounds. The main components of the fraction from the initial boiling point to 205℃ are indene and its homologues; the fraction from 205℃ to 225℃ is naphthalene; the fraction from 225℃ to 245℃ is mainly methylnaphthalene; the fraction from 245℃ to 300℃ is mainly dimethylnaphthalene; the fraction from 300℃ to 360℃ contains large amounts of anthracene, acenaphthene, and phenanthrene; and the substances above 360℃ are mainly gums and asphaltenes with a high carbon-to-hydrogen ratio. Therefore, all fractions of ethylene tar are important raw materials for chemical organic synthesis, from which many valuable chemical products can be extracted, demonstrating significant utilization value.

[0004] The main uses of ethylene tar include its application as fuel, production of carbon black, extraction of naphthalene and methylnaphthalene, and production of aromatic solvent oils. Hydrogenation of ethylene tar can produce high-value-added BTX aromatics, significantly improving the utilization rate of ethylene tar and contributing to the value-added utilization of ethylene byproducts, thus possessing promising market prospects. Foreign companies have already begun using cracked fuel oil to produce aromatic solvent oils, with major producers including ExxonMobil (USA), Shell (Netherlands), and Maruzen Petroleum (Japan). Overall, ethylene tar is primarily used for low-value fuel applications. Being untreated, rich in sulfur and nitrogen, and highly unsaturated, its fuel utilization will become increasingly limited, and its future prospects remain uncertain.

[0005] Research on catalysts for the hydrotreating of heavy distillate oils has long been one of the most active areas of research. Alumina-supported Co(Ni)Mo(W) / Al₂O₃ catalysts were first applied in industrial hydrotreating reactions as early as 1943 and remain commonly used catalysts in many hydrorefining processes. Currently, the most common combination of active components in typical hydrotreating catalysts is Co-Mo, Ni-Mo, and Ni-W, which typically contain 1-4 wt% Co(Ni)O, 8-16 wt% MoO₃, or 12-25 wt% WO₃.

[0006] US5300212 discloses a process for hydrotreating inferior heavy oil. This method involves the conversion of heavy oil feedstock, hydrogen, and catalyst in two reactors. Specifically, the feedstock and a dispersed catalyst with molybdenum phosphate as a precursor first enter a first slurry-bed hydrotreating reactor, where a conversion reaction occurs at 343–482°C and 0.345–34.5 MPa. The reaction products, after separation, enter a second fluidized bed hydrotreating reactor, where conversion occurs at 343–399°C and 5.5–27.6 MPa under the action of a supported catalyst. The reaction products then enter a distillation column, yielding a <524°C fraction and a >524°C fraction. The <524°C fraction is taken as the product, while the >524°C heavy fraction is recycled back to the second reactor. This process can upgrade inferior heavy oil. However, because the first reactor uses a dispersed catalyst and the second reactor uses a supported catalyst, catalyst particles carried out from the first reactor can easily clog the pores of the heavily supported catalyst in the second reactor or cover the active sites of the catalyst, causing catalyst deactivation and affecting the overall operating cycle.

[0007] The gasoline hydrotreating catalyst disclosed in CN85104438 uses high-purity alumina as a support, tungsten and nickel as active components, and fluorine as an auxiliary agent. The fluorine in this catalyst is easily lost during industrial operation, and it corrodes equipment and pollutes the environment.

[0008] CN1872959A discloses a hydrogenation catalyst using alumina as a support, nickel, molybdenum, and tungsten as active components, and fluorine as an auxiliary agent. Compared with traditional bimetallic hydrogenation catalysts, the trimetallic catalyst provided by this catalyst exhibits improved activity. However, due to limitations in support performance and other factors, the improvement is limited, and the activity remains relatively low. Furthermore, this catalyst also faces challenges such as fluorine loss during industrial operation, fluorine corrosion of equipment, and environmental pollution.

[0009] CN1040610A discloses a hydrorefining catalyst supported on γ-Al₂O₃ containing TiO₂. The supported catalyst γ-Al₂O₃ contains 5-30% titanium oxide, with W, Mo, and Ni as active components. The performance of the hydrorefining catalyst supported on TiO₂-modified Al₂O₃ is improved to some extent. However, the support has a lower acidity, especially fewer moderately strong acid centers, which is unfavorable for the ring-opening and breaking of nitrogen heterocycles, resulting in a less significant denitrification effect.

[0010] The petroleum hydrocarbon hydrotreating method proposed in USP4880524 employs a highly active hydrogenation catalyst. This catalyst is of the Ni-Mo / Al₂O₃ type with a specific surface area greater than 300 m². 2 / g, with pore sizes smaller than 7nm exceeding 70%. This catalyst exhibits good initial hydrorefining activity for light distillate oils, but it is prone to pore blockage and deactivation when processing distillate oils containing naphthalene and naphthalene derivatives. Summary of the Invention

[0011] In view of the technical problem of the contradiction between high naphthalene conversion and high selectivity of tetrahydronaphthalene in ethylene tar refining catalysts in the prior art, one of the objectives of this invention is to provide an ethylene tar refining catalyst system: the upper bed support is Al2O3, which has low acid content of strong acids, large pore size, strong carbon capacity, and relatively low reaction temperature, enabling the hydrogenation of a partially removed diene to a monoolefin, avoiding the formation of polymers at high temperatures; the middle bed support is Al2O3-TiO2-SiO2, which has high acid content of strong acids, large specific surface area, and high hydrogenation activity of TiO2, but poor thermal stability. Its combination with Al2O3-SiO2 significantly improves thermal stability while maintaining strong hydrogenation activity, achieving a high naphthalene conversion rate; the lower bed support is Al2O3-SiO2, with lower acid content of strong acids than the middle bed, and loaded with active metals, enabling deep desulfurization and denitrification. The catalyst system of this invention can also vary the packing volume of the upper, middle, and lower catalysts according to different raw material compositions. Using different supports in the upper, middle, and lower beds of this invention, catalysts modified with several of the elements Ni, Mo, La, W, P, and Co were applied to the hydrorefining of ethylene tar under relatively mild reaction conditions (inlet temperature 240°C, reaction pressure 2.5 MPa, H2 / Oil molar ratio 1000, and feed liquid hourly space velocity 0.8 h⁻¹). -1 With a naphthalene conversion rate of over 97%, a bromine value of less than 0.5 g Br2 / 100 g oil in hydrogenated products, a tetrahydronaphthalene selectivity of 99%, and sulfur and nitrogen content of less than 2 ppm, it can be used as a high-quality raw material for the production of BTX, realizing the upgrading of oil products to chemical products and greatly enhancing the added value of the products.

[0012] The second objective of this invention is to provide a catalyst system corresponding to the first objective in the refining of ethylene tar.

[0013] To achieve one of the above objectives, the technical solution adopted by the present invention is as follows:

[0014] An ethylene tar refining catalyst system includes: a first catalyst, a second catalyst, and a third catalyst, wherein,

[0015] The first catalyst comprises a first support and a first modifying element. The first support is Al2O3, preferably γ-Al2O3. The first modifying element is selected from at least three of Ni, Mo, La, W, P, and Co, preferably from at least four of Ni, Mo, La, W, P, and Co, more preferably from at least five of Ni, Mo, La, W, P, and Co, and even more preferably including Ni, Mo, La, W, P, and Co.

[0016] The second catalyst comprises a second support and a second modifying element. The second support is an Al2O3-TiO2-SiO2 multi-element composite support. The second modifying element is selected from at least three of Ni, Mo, La, W, P, and Co, preferably from at least four of Ni, Mo, La, W, P, and Co, more preferably from at least five of Ni, Mo, La, W, P, and Co, and even more preferably from Ni, Mo, La, W, P, and Co.

[0017] The third catalyst includes a third support and a third modifying element. The third support is an Al2O3-SiO2 multi-element composite support. The third modifying element is selected from at least three of Ni, Mo, La, W, P and Co, preferably from at least four of Ni, Mo, La, W, P and Co.

[0018] In some preferred embodiments of the present invention, the volume ratio of the first catalyst, the second catalyst and the third catalyst is (1-5):(2-8):(1-3), preferably (1-4):(4-8):(1-2), and more preferably (1-3):(5-8):(1-2).

[0019] In some preferred embodiments of the present invention, the volume ratio of the first catalyst, the second catalyst, and the third catalyst is (2-4):(4-6):(1-3), preferably (2.5-3.5):(4.5-7.5):(1.5-2.5).

[0020] In some preferred embodiments of the present invention, the third modifying element includes Mo, La, P and Co.

[0021] In some preferred embodiments of the present invention, the first catalyst and the second catalyst have the same type of first modifying element and the same proportion of each in the catalyst.

[0022] In some preferred embodiments of the present invention, in the Al2O3-TiO2-SiO2 multi-element composite carrier, based on the total weight of the Al2O3-TiO2-SiO2 multi-element composite carrier, the mass percentage of Al2O3 is 80% to 98%, the mass percentage of TiO2 is 1% to 10%, and the mass percentage of SiO2 is 1% to 10%.

[0023] In some preferred embodiments of the present invention, in the Al2O3-TiO2-SiO2 multi-element composite carrier, based on the total weight of the Al2O3-TiO2-SiO2 multi-element composite carrier, the mass percentage of Al2O3 is 80% to 90%, the mass percentage of TiO2 is 2% to 7%, and the mass percentage of SiO2 is 8% to 13%.

[0024] In some preferred embodiments of the present invention, the Al2O3-SiO2 multi-component composite carrier has an Al2O3 mass percentage content of 90% to 99% and a SiO2 mass percentage content of 1% to 10%, based on the total weight of the Al2O3-SiO2 multi-component composite carrier.

[0025] In some preferred embodiments of the present invention, the Al2O3-SiO2 multi-component composite carrier has an Al2O3 mass percentage content of 85% to 96% and a SiO2 mass percentage content of 5% to 15%, based on the total weight of the Al2O3-SiO2 multi-component composite carrier.

[0026] In some preferred embodiments of the present invention, the specific surface area of ​​the first carrier is 180 m². 2 / g~320m 2 / g; average pore size 7–14 nm; pore volume 0.6–0.88 cm³ 3 / g; preferably, the specific surface area of ​​the first carrier component is 190m². 2 / g~250m 2 / g, with an average pore size of 8–13 nm and a pore volume of 0.7–0.85 cm³. 3 / g.

[0027] In some preferred embodiments of the present invention, the specific surface area of ​​the second carrier is 200 m². 2 / g~360m 2 / g; average pore size 8–13 nm; pore volume 0.50–0.85 cm³ 3 / g; preferably, the specific surface area of ​​the second carrier is 220m². 2 / g~350m2 / g, with an average pore size of 8–12 nm and a pore volume of 0.65–0.82 cm³. 3 / g.

[0028] In some preferred embodiments of the present invention, the specific surface area of ​​the third carrier is 200 m². 2 / g~360m 2 / g; average pore size 8–12 nm; pore volume 0.6–0.85 cm³ 3 / g; preferably, the specific surface area of ​​the second carrier is 220m². 2 / g~300m 2 / g, with an average pore size of 8–11 nm and a pore volume of 0.65–0.83 cm³. 3 / g.

[0029] In some preferred embodiments of the present invention, the average pore size of the first carrier is greater than the average pore size of the second carrier and the average pore size of the third carrier.

[0030] In some preferred embodiments of the present invention, the amount of medium-strong acid in the first carrier is 100-150 μmol / g; the total acid amount is 170-230 μmol / g.

[0031] In some preferred embodiments of the present invention, the amount of the medium-strong acid in the second carrier is 180-380 μmol / g; the total acid amount is 400-600 μmol / g.

[0032] In some preferred embodiments of the present invention, the amount of the medium-strong acid in the third carrier is 150-250 μmol / g; the total acid amount is 200-350 μmol / g.

[0033] In some preferred embodiments of the present invention, the amount of medium-strong acid in the second carrier is greater than that in the third carrier, which is greater than that in the first carrier.

[0034] In some preferred embodiments of the present invention, the first catalyst, based on the total weight of the first catalyst, has a mass percentage content of 50% to 80%, preferably 70% to 80%, and a mass percentage content of the first modifying element, calculated as oxides, is 20% to 50%, preferably 20% to 30%.

[0035] In some preferred embodiments of the present invention, the first catalyst, based on the total weight of the first catalyst, comprises, by mass percentage (calculated as NiO), 3% to 10%; Mo, 15% to 25%; La, 0% to 3% (calculated as La2O5), preferably 0.1% to 1%; W, 0% to 15% (calculated as WO3), preferably 8% to 15%; P, 0% to 5% (calculated as P2O5), preferably 0.5% to 2%; and Co, 0% to 10% (calculated as CoO), preferably 2% to 6%.

[0036] In some preferred embodiments of the present invention, the second catalyst, based on the total weight of the second catalyst, has a mass percentage content of 50% to 80%, preferably 55% to 70%, and a mass percentage content of the second modifying element, calculated as oxides, is 20% to 50%, preferably 20% to 30%.

[0037] In some preferred embodiments of the present invention, the second catalyst, based on the total weight of the second catalyst, comprises: Ni (calculated as NiO) of 3% to 10% by mass; Mo (calculated as MoO3) of 15% to 25% by mass; La (calculated as La2O5) of 0% to 3%, preferably 0.1% to 1% by mass; W (calculated as WO3) of 0% to 15%, preferably 8% to 15% by mass; P (calculated as P2O5) of 0% to 5%, preferably 0.5% to 2% by mass; and Co (calculated as CoO) of 0% to 10%, preferably 2% to 6% by mass.

[0038] In some preferred embodiments of the present invention, the third catalyst, based on the total weight of the third catalyst, has a mass percentage content of 70% to 95%, preferably 80% to 90%, and the third modifying element, calculated as an oxide, has a mass percentage content of 5% to 30%, preferably 10% to 20%.

[0039] In some preferred embodiments of the present invention, the third catalyst, based on the total weight of the third catalyst, comprises: Ni (calculated as NiO) of 0% to 3% by mass; Mo (calculated as MoO3) of 5% to 15%, preferably 8% to 12% by mass; La (calculated as La2O5) of 0% to 3%, preferably 0.1% to 1% by mass; W (calculated as WO3) of 0% to 3% by mass; P (calculated as P2O5) of 0% to 5%, preferably 0.1% to 1% by mass; and Co (calculated as CoO) of 0% to 10%, preferably 1% to 5% by mass.

[0040] In some preferred embodiments of the present invention, the first catalyst, the second catalyst, and the third catalyst constitute a catalyst bed, wherein the first catalyst is located in the upper layer of the catalyst bed, the second catalyst is located in the middle layer of the catalyst bed, and the third catalyst is located in the lower layer of the catalyst bed.

[0041] In some preferred embodiments of the present invention, the first catalyst, the second catalyst, and the third catalyst are in direct contact.

[0042] In some preferred embodiments of the present invention, the preparation method of the first carrier includes the following steps:

[0043] S11. The raw material system containing the first Al2O3 powder, the first additive and the first adhesive solvent is subjected to molding treatment to obtain the first carrier precursor;

[0044] S12. The first carrier precursor is dried and calcined sequentially to obtain the first carrier.

[0045] In some preferred embodiments of the present invention, in step S11, the first Al2O3 powder is γ-Al2O3; and / or the average particle size of the first Al2O3 powder is 0.1 micrometer to 2 micrometer.

[0046] In some preferred embodiments of the present invention, in step S11, the first auxiliary agent is selected from at least one of guar gum powder, starch and hydroxymethyl cellulose; the first adhesive solvent is selected from an aqueous solution containing nitric acid and / or citric acid, preferably, the mass percentage content of nitric acid is 1% to 5% and the mass percentage content of citric acid is 0.1% to 3%.

[0047] In some preferred embodiments of the present invention, in step S11, the mass ratio of the first Al2O3 powder, the first additive and the first adhesive solvent is 100:(1-10):(80-150).

[0048] According to the present invention, the molding process in step S11 is not limited and can adopt the molding methods commonly used in the art, such as, but not limited to, kneading the raw material system into a plastic body in a kneader and then molding it in an extruder.

[0049] According to the present invention, in step S11, the shape of the first carrier precursor formed is not particularly limited, and can be elongated, cylindrical or clover-shaped.

[0050] In some preferred embodiments of the present invention, in step S12, the calcination conditions include: a temperature of 450°C to 650°C, preferably 500°C to 600°C; and a time of 1 hour to 12 hours, preferably 2 hours to 5 hours.

[0051] According to the present invention, in step S12, the first carrier precursor can be dried first, and then calcined. Drying is a conventional operation in the art, and the present invention does not intend to impose too many limitations on it. Exemplarily, it can be first air-dried at room temperature for a period of time, and then treated in an oven at 100°C to 150°C for 1 to 12 hours.

[0052] According to the present invention, in the context of the present invention, room temperature can be any temperature value within the temperature range of 25°C to 35°C.

[0053] In some preferred embodiments of the present invention, the method for preparing the second carrier includes the following steps:

[0054] S21. Provide a first solution containing a titanium source, a second solution containing a silicon source, and a third solution containing ethanol, water, and nitric acid with a pH value of 3 to 5;

[0055] S22. Mix the first solution, the second solution, and the third solution to obtain a fourth solution;

[0056] S23. Mix the fourth solution with the second Al2O3 powder to obtain a first mixture;

[0057] S24. The mixture is dried and calcined sequentially to obtain Al2O3-TiO2-SiO2 powder;

[0058] S25. Mix the Al2O3-TiO2-SiO2 powder, the second additive, and the second adhesive solvent to obtain a second mixture.

[0059] S26. The second mixture is subjected to molding treatment to obtain a second carrier precursor;

[0060] S27. The second carrier precursor is dried and calcined sequentially to obtain the second carrier.

[0061] In some preferred embodiments of the present invention, in step S21, the first solution containing the titanium source includes the titanium source and anhydrous ethanol.

[0062] According to the present invention, the amount of anhydrous ethanol in the first solution containing the titanium source is not particularly limited, as long as it is sufficient to dissolve the titanium source.

[0063] In some preferred embodiments of the present invention, in step S21, the second solution containing the silicon source includes the silicon source and anhydrous ethanol.

[0064] According to the present invention, the amount of anhydrous ethanol in the second solution containing the silicon source is not particularly limited, as long as it is sufficient to dissolve the silicon source.

[0065] In some preferred embodiments of the present invention, in step S21, the mass ratio of ethanol to water in the third solution is (3-6):1; preferably, the water is distilled water, more preferably double-distilled water; and / or the pH value is adjusted to 3-5 by nitric acid.

[0066] In some preferred embodiments of the present invention, in step S21, the titanium source is selected from at least one of titanate compounds, preferably at least one of tetrabutyl titanate and tetrahexyl titanate; and / or the silicon source is selected from at least one of tetraethyl orthosilicate, silica sol and fumed silica.

[0067] According to the present invention, both commercially available silica sol and fumed silica can be applied to this application and achieve the same technical effects.

[0068] In some preferred embodiments of the present invention, in step S22, the volume ratio of the first solution, the second solution and the third solution is (2-5):(2-5):10;

[0069] In some preferred embodiments of the present invention, in step S22, the mixing may be carried out by slowly adding the first solution and the second solution to the third solution dropwise under vigorous stirring (e.g., at a speed of about 100 rpm to 600 rpm), and continuing to stir at a speed of 100 rpm to 600 rpm for 2 hours after the addition is completed.

[0070] In some preferred embodiments of the present invention, in step S23, the second Al2O3 powder is γ-Al2O3; and / or the average particle size of the second Al2O3 powder is 0.1 micrometer to 2 micrometer.

[0071] In some preferred embodiments of the present invention, in step S23, the mixing may be performed by adding the fourth solution dropwise to the second Al2O3 powder. Preferably, the second Al2O3 powder is dried. More preferably, after the addition is complete, the resulting system is kept at room temperature for 8 to 12 hours to obtain the first mixture.

[0072] In some preferred embodiments of the present invention, in step S24, the drying conditions include: a temperature of 80°C to 120°C and a time of 1 hour to 12 hours.

[0073] In some preferred embodiments of the present invention, in step S24, the calcination conditions include: a temperature of 400°C to 550°C and a time of 1 hour to 12 hours.

[0074] In some preferred embodiments of the present invention, in step S25, the second auxiliary agent is selected from at least one of guar gum powder, starch and hydroxymethyl cellulose; the second adhesive solvent is selected from an aqueous solution containing nitric acid and / or phosphoric acid and / or glacial acetic acid, preferably, the mass percentage of nitric acid is 0.5% to 5%, the mass percentage of phosphoric acid is 0.1% to 3%, and the mass percentage of glacial acetic acid is 0.1% to 3%.

[0075] In some preferred embodiments of the present invention, in step S25, the mass ratio of Al2O3-TiO2-SiO2 powder, the second additive, and the second adhesive solvent is 100:(1-10):(0.1-5):(80-150).

[0076] According to the present invention, in step S26, the molding process is not limited and can adopt the molding methods commonly used in the art, such as, but not limited to, kneading the raw material system into a plastic body in a kneader and then molding it in an extruder.

[0077] According to the present invention, in step S26, the shape of the formed second carrier precursor is not particularly limited, and can be elongated, cylindrical or clover-shaped.

[0078] In some preferred embodiments of the present invention, in step S27, the drying conditions include: a temperature of 80°C to 120°C and a time of 1 hour to 12 hours.

[0079] In some preferred embodiments of the present invention, in step S27, the calcination conditions include: a temperature of 450°C to 650°C, preferably 500°C to 600°C; and a time of 1 hour to 12 hours, preferably 2 hours to 5 hours.

[0080] In some preferred embodiments of the present invention, the method for preparing the third carrier includes the following steps:

[0081] S31. A raw material system containing third Al2O3 powder, third additive, silica sol and third adhesive solvent is subjected to molding treatment to obtain a third carrier precursor;

[0082] S32. The third carrier precursor is dried and calcined sequentially to obtain the third carrier.

[0083] In some preferred embodiments of the present invention, in step S31, the third Al2O3 powder is γ-Al2O3; and / or the average particle size of the third Al2O3 powder is 0.1 micrometer to 2 micrometers.

[0084] In some preferred embodiments of the present invention, in step S31, the silicon content in the silica sol is 20wt% to 40wt% based on silicon dioxide.

[0085] In some preferred embodiments of the present invention, in step S31, the third auxiliary agent is selected from at least one of guar gum powder, starch and hydroxymethyl cellulose; the third adhesive solvent is selected from an aqueous solution containing nitric acid, preferably, the mass percentage of nitric acid is 1% to 5%.

[0086] In some preferred embodiments of the present invention, in step S31, the mass ratio of the third Al2O3 powder, the third additive, the silica sol, and the third adhesive solvent is 100:(1-10):(2.5-20):(60-100).

[0087] According to the present invention, in step S31, the molding process is not limited and can adopt the molding methods commonly used in the art, such as, but not limited to, kneading the raw material system into a plastic body in a kneader and then molding it in an extruder.

[0088] According to the present invention, in step S31, the shape of the formed third carrier precursor is not particularly limited, and can be elongated, cylindrical or clover-shaped.

[0089] In some preferred embodiments of the present invention, in step S32, the calcination conditions include: a temperature of 450°C to 650°C, preferably 500°C to 600°C; and a time of 1 hour to 12 hours, preferably 2 hours to 5 hours.

[0090] According to the present invention, in step S32, the third carrier precursor can be dried first, and then calcined. Drying is a conventional operation in the art, and the present invention does not intend to impose too many limitations on it. Exemplarily, it can be air-dried at room temperature for a period of time first, and then treated in an oven at 100°C to 150°C for 1 to 12 hours.

[0091] According to the present invention, the preparation methods of the first catalyst, the second catalyst, and the third catalyst are not particularly limited, and all can be prepared according to the conventional impregnation method in the art. Exemplarily, the first support, the second support, and the third support can be mixed with solutions of compounds containing different modifying elements, dried, and calcined respectively. The drying temperature is preferably 60–150°C, more preferably 80–120°C. The drying time is preferably 2–24 hours, more preferably 3–8 hours. The calcination temperature is preferably 250–750°C, more preferably 350–550°C. The calcination time is preferably 2–12 hours, more preferably 3–8 hours. There are no particular requirements for the calcination atmosphere; both oxidizing and inert atmospheres are acceptable and can yield comparable technical effects. Oxidizing atmospheres include, but are not limited to, oxygen-containing atmospheres, with air atmospheres preferred from an economic perspective. Inert atmospheres include, but are not limited to, at least one of nitrogen or inert gas atmospheres, where the inert gas can be nitrogen, helium, argon, etc. From an economic perspective, nitrogen is often chosen as the inert atmosphere. For comparability, air atmosphere is used in all embodiments of the present invention.

[0092] According to the present invention, compounds of Ni are not particularly limited, such as, but not limited to, nickel nitrate, nickel acetate, nickel oxalate, etc. Compounds of Mo are not particularly limited, such as, but not limited to, ammonium molybdate, ammonium heptamolybdate, etc. Compounds of La are not particularly limited, such as, but not limited to, lanthanum nitrate, lanthanum chloride, lanthanum acetate, etc. Compounds of W are not particularly limited, such as, but not limited to, ammonium tungstate, ammonium metatungstate, tungstic acid, etc. Compounds of P are not particularly limited, such as, but not limited to, phosphoric acid, phosphorous acid, etc. Compounds of Co are not particularly limited, such as, but not limited to, cobalt acetate, cobalt nitrate, cobalt carbonate, etc.

[0093] To achieve the second objective mentioned above, the technical solution adopted by the present invention is as follows:

[0094] The application of the catalyst system described in any one of the above embodiments in the refining of ethylene tar includes:

[0095] S41. The crude ethylene tar is subjected to deweighting treatment and a first-stage hydrogenation treatment in sequence to produce refined raw material;

[0096] S42. The refined raw material is passed into a reactor containing the catalyst system for a refining reaction to obtain the refined product.

[0097] In step S41, the ethylene tar refining feedstock contains, by mass percentage, 2%–5% dienes, 30%–38% naphthalene compounds, and 25–50 mg / 100g oil gum; and / or in step S42, the refining reaction conditions include: an inlet temperature of 200℃–270℃, a reaction pressure of 2.3–6.0 MPa, a hydrogen-to-oil volume ratio of 400–1500, and a liquid hourly space velocity of 0.2–1.8 h⁻¹. -1 .

[0098] According to the present invention, in step S42, the refined raw material enters from the top and exits from the bottom.

[0099] According to the present invention, unless otherwise specified, the pressure described herein refers to a gauge manometer.

[0100] According to the present invention, the catalyst system can be pre-sulfurized before the contact is performed. Pre-sulfurization is a conventional operation in the art, and the present invention does not intend to impose excessive limitations on it. Exemplarily, pre-sulfurization is performed using the following steps: cyclohexane containing 100–10000 ppm CS2 is used as the sulfiding oil, and the mixture is subjected to a space velocity of 0.2–8 h⁻¹. -1 The hydrogen-to-oil volume ratio is 100–2500:1, and the catalyst is pre-sulfurized at an operating pressure of 1.0–10.0 MPa.

[0101] In the above pre-sulfurization, the concentration of CS2 in the sulfurized oil is preferably 500 to 5000 ppm, such as, but not limited to, 500 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm, 5000 ppm, etc. More preferably, it is 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm.

[0102] However, for comparison, the catalyst in the specific embodiment of the present invention is sulfided using the following steps: Under a system pressure of 0.5 MPa, N2 is introduced at a rate of 30°C / h to raise the temperature to 170°C, with an N2 flow rate of 850 ml / min. N2 is then stopped, and H2 and sulfided oil (containing 2500 ppm CS2) are introduced. The system pressure is raised to 2.5 MPa, the hydrogen-to-oil volume ratio is 300, and the sulfided oil volume hourly space velocity is 4.0 h⁻¹. -1 Simultaneously, the temperature is increased to 230℃ at a rate of 20℃ / h for 3 hours, held at this temperature for 4 hours, then increased to 320℃ at a rate of 20℃ / h for 4.5 hours, and held at this temperature for 24 hours, at which point the catalyst sulfidation is complete. With sulfiding oil flowing through, the bed inlet temperature is lowered to the required reaction temperature.

[0103] According to the present invention, both the degravation treatment and the first-stage hydrogenation treatment are conventional operations in the art, and the present invention does not intend to impose any special limitations on them. As long as the refined raw materials with the desired composition can be obtained, they can be applied to the present invention.

[0104] The beneficial effects of this invention are at least as follows: using the catalyst system provided by this invention, the bromine value of the refined ethylene tar product obtained is less than 0.5gBr2 / 100g oil, the selectivity of tetrahydronaphthalene is 99%, and the sulfur and nitrogen content is less than 2ppm. It can be used as a high-quality raw material for the production of BTX, realizing the upgrading of oil products to chemical products, greatly improving the added value of the product, and achieving good technical results. Attached Figure Description

[0105] Figure 1 This is a schematic diagram showing the changes in naphthalene conversion rate and bromine value over time in Example 6. Detailed Implementation

[0106] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0107] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0108] In the following embodiments, NH3-TPD was measured using an Altamira AMI-3300 chemisorption analyzer from Micrometrics Corporation, USA; the pore structure parameters of the carrier were measured using a Tristar3000 surface area analyzer from Micrometrics Corporation, at a test temperature of -196°C. Before the test, the sample was vacuum activated at 300°C for 6 hours.

[0109] In the following embodiments, unless otherwise specified, "%" refers to the percentage content by mass.

[0110] In the following embodiments, unless otherwise specified, the Al2O3 powder used is γ-Al2O3 with an average particle size of 0.8 micrometers.

[0111]

Example 1

[0112] 1. Preparation of the carrier

[0113] First carrier: 400g of Al2O3 powder, 16g of guar gum powder, and 2.4g of hydroxymethyl cellulose were thoroughly mixed, and 400g of an aqueous solution containing 2.5% nitric acid and 1% citric acid was added. The mixture was kneaded in a kneader to form a plastic body, and then shaped in an extruder to obtain a clover-shaped carrier with a diameter of 1.5mm and a length of 3.0mm. The carrier was dried at room temperature for 24 hours, dried in an oven at 120℃ for 6 hours, and calcined in a muffle furnace at 550℃ for 3 hours to obtain the upper Al2O3 carrier.

[0114] Second carrier: 85.08 g of tetrabutyl titanate was dissolved in 60 g of anhydrous ethanol and stirred until homogeneous to obtain solution 1. 138.88 g of tetraethyl orthosilicate and an appropriate amount of 90 g of anhydrous ethanol solution were mixed and stirred until homogeneous to obtain solution 2. 115 g of anhydrous ethanol and 60 g of deionized water were mixed until homogeneous, and the pH was adjusted to 4 with nitric acid to obtain solution 3. Solutions 1 and 2 were slowly added dropwise under vigorous stirring. After the addition was completed, stirring was continued for 2 hours to obtain solution 4. Finally, solution 4 was slowly added to 340 g of dried Al2O3 powder and impregnated for 12 hours. After drying at 110℃ for 4 hours, it was calcined in a muffle furnace at 500℃ for 4 hours and cooled to room temperature to prepare a middle-layer Al2O3-TiO2-SiO2 powder. 400g of Al2O3-TiO2-SiO2 powder, 16g of guar gum powder, and 2.4g of hydroxymethyl cellulose were thoroughly mixed, and 360g of an aqueous solution containing 1.5% nitric acid, 1% phosphoric acid, and 1% glacial acetic acid was added. The mixture was kneaded in a kneader to form a plastic body, then shaped in an extruder, cured, dried, and calcined at high temperature to obtain the middle-bed Al2O3-TiO2-SiO2 support. The mass ratio of Al2O3, TiO2, and SiO2 was 85:5:10.

[0115] The third carrier: 364 g of Al2O3 powder, 90 g of 40% silica sol, 16 g of guar gum powder, and 2.4 g of hydroxymethyl cellulose were thoroughly mixed, and 400 g of an aqueous solution containing 2.5% nitric acid was added. The mixture was kneaded in a kneader to form a plastic body, and then shaped in an extruder to obtain a clover-shaped carrier with a diameter of 1.5 mm and a length of 3.0 mm. The carrier was dried at room temperature for 24 hours, dried in an oven at 120°C for 6 hours, and calcined in a muffle furnace at 550°C for 3 hours to obtain the lower bed carrier. The mass ratio of Al2O3 to SiO2 was 91:9.

[0116] The amount of medium-strong acid and total acid content of each carrier are shown in Table 1; the pore structure parameters are shown in Table 2.

[0117] 2. Catalyst Preparation

[0118] Take 1L of the first support Al2O3, the second support Al2O3-TiO2-SiO2 and the third support Al2O3-SiO2 respectively, mix them with 0.75L of a mixed solution of nickel acetate, lanthanum nitrate and ammonium molybdate (containing 80g NiO, 5g La2O3 and 195g MoO3), dry at 110℃ for 6 hours and calcine at 450℃ for 4 hours.

[0119] The catalyst contains 80 g / L NiO, 5 g / L La2O3, and 195 g / L MoO3.

[0120] 3. Catalyst loading

[0121] The first catalyst, the second catalyst, and the third catalyst are loaded into the adiabatic bed reactor in a volume ratio of 3:5:2, with the reactants flowing from top to bottom.

[0122] 4. Catalyst sulfidation

[0123] At a system pressure of 0.5 MPa, N2 was introduced at a rate of 30 °C / h to raise the temperature to 170 °C. The N2 flow rate was 850 ml / min. Then, N2 was stopped, and H2 and sulfurized oil (containing 2500 ppm CS2) were introduced. The system pressure rose to 2.5 MPa, the hydrogen-to-oil volume ratio was 300, and the sulfurized oil volume hourly space velocity was 4.0 h⁻¹. -1 Simultaneously, the temperature is increased to 230℃ at a rate of 20℃ / h for 3 hours, held at this temperature for 4 hours, then increased to 320℃ at a rate of 20℃ / h for 4.5 hours, and held at this temperature for 24 hours, at which point the catalyst sulfidation is complete. With sulfiding oil flowing through, the bed inlet temperature is lowered to the required reaction temperature.

[0124] 5. Catalyst Evaluation

[0125] Catalyst evaluation feedstock: Crude ethylene tar is deweighted and subjected to a first-stage hydrogenation reaction to produce corresponding monoolefins and alkyl aromatics as refining feedstock. Feedstock requirements: bromine value ≤ 40gBr2 / 100g oil, diene ≤ 2gI2 / 100g oil, gum ≤ 50mg / 100g oil.

[0126] Catalyst evaluation conditions: inlet temperature 240℃, reaction pressure 3.0MPa, H2 / Oil molar ratio 1000, and feed liquid hourly space velocity 0.8h. -1 Catalyst evaluation was conducted.

[0127] For ease of comparison, the types and contents of the modified elements, as well as the evaluation results of the catalysts, are listed in Table 3.

[0128]

Example 2

[0129] 1. Preparation of the carrier

[0130] First carrier: Same as in Example 1.

[0131] Second carrier: Same as in Example 1.

[0132] The third carrier is the same as in Example 1.

[0133] 2. Catalyst Preparation

[0134] Take 1L of the first support Al2O3, the second support Al2O3-TiO2-SiO2 and the third support Al2O3-SiO2 respectively, and mix them with 0.75L of a mixed solution of nickel acetate, ammonium metatungstate and ammonium molybdate (containing 55g NiO, 80g MoO3 and 145g WO3). Dry at 110℃ for 6 hours and calcine at 450℃ for 4 hours.

[0135] The catalyst contains 55 g / L NiO, 145 g / L WO3, and 80 g / L MoO3.

[0136] 3. Catalyst loading

[0137] The first catalyst, the second catalyst, and the third catalyst are loaded into the adiabatic bed reactor in a volume ratio of 3:5:2, with the reactants flowing from top to bottom.

[0138] 4. Catalyst sulfidation

[0139] Same as Example 1.

[0140] 5. Catalyst Evaluation

[0141] Same as Example 1.

[0142]

Example 3

[0143] 1. Preparation of the carrier

[0144] First carrier: Same as in Example 1.

[0145] Second carrier: Same as in Example 1.

[0146] Second carrier: Same as in Example 1.

[0147] 2. Catalyst Preparation

[0148] Take 1 L of the first support Al2O3, the second support Al2O3-TiO2-SiO2 and the third support Al2O3-SiO2 respectively, and mix them with 0.75 L of a mixed solution of nickel acetate, ammonium metatungstate, lanthanum nitrate and ammonium molybdate (containing 50 g NiO, 80 g MoO3, 5 g La2O3 and 145 g WO3). Dry at 110 °C for 6 hours and calcine at 450 °C for 4 hours.

[0149] The catalyst contains 50 g / L NiO, 80 g / L MoO3, 5 g / L La2O3, and 145 g / L WO3.

[0150] 3. Catalyst loading

[0151] The first catalyst, the second catalyst, and the third catalyst are loaded into the adiabatic bed reactor in a volume ratio of 3:5:2, with the reactants flowing from top to bottom.

[0152] 4. Catalyst sulfidation

[0153] Same as Example 1.

[0154] 5. Catalyst Evaluation

[0155] Same as Example 1.

[0156]

Example 4

[0157] 1. Preparation of the carrier

[0158] First carrier: Same as in Example 1.

[0159] Second carrier: Same as in Example 1.

[0160] The third carrier is the same as in Example 1.

[0161] 2. Catalyst Preparation

[0162] Take 1 L of the first support Al2O3, the second support Al2O3-TiO2-SiO2 and the third support Al2O3-SiO2 respectively, and mix them with 0.75 L of a mixed solution of nickel acetate, ammonium metatungstate, lanthanum nitrate, ammonium molybdate and phosphoric acid (containing 40 g NiO, 80 g MoO3, 5 g La2O3, 145 g WO3 and 10 g P2O5). Dry at 110 °C for 6 hours and calcine at 450 °C for 4 hours.

[0163] The catalyst contains 40 g / L NiO, 80 g / L MoO3, 5 g / L La2O3, 145 g / L WO3, and 10 g / L P2O5.

[0164] 3. Catalyst loading

[0165] The first catalyst, the second catalyst, and the third catalyst are loaded into the adiabatic bed reactor in a volume ratio of 3:5:2, with the reactants flowing from top to bottom.

[0166] 4. Catalyst sulfidation

[0167] Same as Example 1.

[0168] 5. Catalyst Evaluation

[0169] Same as Example 1.

[0170]

Example 5

[0171] 1. Preparation of the carrier

[0172] First carrier: Same as in Example 1.

[0173] Second carrier: Same as in Example 1.

[0174] The third carrier is the same as in Example 1.

[0175] 2. Catalyst Preparation

[0176] Take 1 L of the first support Al2O3, the second support Al2O3-TiO2-SiO2 and the third support Al2O3-SiO2 respectively, and mix them with 0.75 L of a mixed solution of nickel acetate, ammonium metatungstate, lanthanum nitrate, ammonium molybdate, cobalt nitrate, cobalt acetate and phosphoric acid (containing 40 g NiO, 60 g MoO3, 5 g La2O3, 120 g WO3, 45 g CoO and 10 g P2O5). Dry at 110 °C for 6 hours and calcine at 450 °C for 4 hours.

[0177] The catalyst contains 40 g / L NiO, 60 g / L MoO3, 5 g / L La2O3, 120 g / L WO3, 45 g / L CoO, and 10 g / L P2O5.

[0178] 3. Catalyst loading

[0179] The first catalyst, the second catalyst, and the third catalyst are loaded into the adiabatic bed reactor in a volume ratio of 3:5:2, with the reactants flowing from top to bottom.

[0180] 4. Catalyst sulfidation

[0181] Same as Example 1.

[0182] 5. Catalyst Evaluation

[0183] Same as Example 1.

[0184]

Example 6

[0185] 1. Preparation of the carrier

[0186] First carrier: Same as in Example 1.

[0187] Second carrier: Same as in Example 1.

[0188] Second carrier: Same as in Example 1.

[0189] 2. Catalyst Preparation

[0190] Take 1 L of the first support Al2O3 and the second support Al2O3-TiO2-SiO2, respectively, and mix them with 0.75 L of a mixed solution of nickel acetate, ammonium metatungstate, lanthanum nitrate, ammonium molybdate, cobalt nitrate, cobalt acetate and phosphoric acid (containing 40 g NiO, 60 g MoO3, 5 g La2O3, 165 g WO3 and 10 g P2O5). Dry at 110 °C for 6 hours and calcine at 450 °C for 4 hours.

[0191] The first and second catalysts contain 40 g / L NiO, 60 g / L MoO3, 5 g / L La2O3, 165 g / L WO3, and 10 g / L P2O5.

[0192] Take 1 L of the third carrier Al2O3-SiO2 and mix it with 0.75 L of a mixed solution of ammonium molybdate, cobalt nitrate, cobalt acetate and phosphoric acid (containing 96 g of MoO3, 25 g of CoO, 5 g of La2O3 and 5 g of P2O5). Dry at 110 °C for 6 hours and calcine at 450 °C for 4 hours.

[0193] The third catalyst contains 96 g / L MoO3, 5 g / L La2O3, 25 g / L CoO, and 5 g / L P2O5.

[0194] 3. Catalyst loading

[0195] The first catalyst, the second catalyst, and the third catalyst are loaded into the adiabatic bed reactor in a volume ratio of 3:5:2, with the reactants flowing from top to bottom.

[0196] 4. Catalyst sulfidation

[0197] Same as Example 1.

[0198] 5. Catalyst Evaluation

[0199] Same as in Example 1, the results are listed in Table 4.

[0200]

Example 7

[0201] 1. Preparation of the carrier

[0202] First carrier: Same as in Example 1.

[0203] Second carrier: Same as in Example 1.

[0204] The third carrier is the same as in Example 1.

[0205] 2. Catalyst Preparation

[0206] Same as Example 6.

[0207] 3. Catalyst loading

[0208] The first catalyst, the second catalyst, and the third catalyst are loaded into the adiabatic bed reactor in a volume ratio of 1:8:1, with the reactants flowing from top to bottom.

[0209] 4. Catalyst sulfidation

[0210] Same as Example 6.

[0211] 5. Catalyst Evaluation

[0212] Same as Example 6.

[0213]

Example 8

[0214] 1. Preparation of the carrier

[0215] First carrier: Same as in Example 1.

[0216] Second carrier: Same as in Example 1.

[0217] The third carrier is the same as in Example 1.

[0218] 2. Catalyst Preparation

[0219] Same as Example 6.

[0220] 3. Catalyst loading

[0221] The first catalyst, the second catalyst, and the third catalyst, in a volume ratio of 33:34:33, are sequentially loaded into the adiabatic bed reactor, with the reactants flowing from top to bottom.

[0222] 4. Catalyst sulfidation

[0223] Same as Example 6.

[0224] 5. Catalyst Evaluation

[0225] Same as Example 6.

[0226]

Example 9

[0227] 1. Preparation of the carrier

[0228] First carrier: Same as in Example 1.

[0229] Second carrier: Same as in Example 1.

[0230] The third carrier is the same as in Example 1.

[0231] 2. Catalyst Preparation

[0232] Same as Example 1.

[0233] 3. Catalyst loading

[0234] The first catalyst, the second catalyst, and the third catalyst are loaded into the adiabatic bed reactor in a volume ratio of 3:5:2, with the reactants flowing from top to bottom.

[0235] 4. Catalyst sulfidation

[0236] Same as Example 6.

[0237] 5. Catalyst Evaluation

[0238] Same as Example 6.

[0239] Comparative Example 1

[0240] 1. Preparation of Al2O3 support

[0241] The preparation method is the same as that of the first carrier in Example 1.

[0242] 2. Catalyst Preparation

[0243] Take 1L of the molded Al2O3 support and mix it with 0.75L of a mixed solution of nickel acetate, ammonium metatungstate, lanthanum nitrate, ammonium molybdate, cobalt nitrate, cobalt acetate and phosphoric acid (containing 40g NiO, 60g MoO3, 5g La2O3, 120g WO3, 45g CoO and 10g P2O5). Dry at 110℃ for 6 hours and calcine at 450℃ for 4 hours.

[0244] The catalyst contains 40 g / L NiO, 60 g / L MoO3, 5 g / L La2O3, 120 g / L WO3, 45 g / L CoO, and 10 g / L P2O5.

[0245] 3. Catalyst loading

[0246] Take a catalyst equal to the total amount of catalyst in Example 1 and load it into a simulated adiabatic bed reactor, with the reactants flowing in from the top and out from the bottom.

[0247] 4. Catalyst sulfidation

[0248] Catalyst sulfidation

[0249] Same as Example 1.

[0250] 5. Catalyst Evaluation

[0251] Same as Example 1.

[0252] Comparative Example 2

[0253] 1. Preparation of the carrier

[0254] First carrier: The preparation method is the same as that of the first carrier in Example 1.

[0255] Second carrier: The preparation method is the same as that of the second carrier in Example 1.

[0256] The third carrier was prepared using the same method as the third carrier in Example 1.

[0257] 2. Catalyst Preparation

[0258] Same as Example 5.

[0259] 3. Catalyst loading

[0260] The first catalyst, the second catalyst, and the third catalyst, in a volume ratio of 16:3:1, are sequentially loaded into the adiabatic bed reactor, with the reactants flowing from top to bottom.

[0261] 4. Catalyst sulfidation

[0262] Same as Example 1.

[0263] 5. Catalyst Evaluation

[0264] Same as Example 1.

[0265] Table 1

[0266] First carrier Second carrier Third carrier Medium-strong acid content (μmol / g) 130 368 205 Total acid content (μmol / g) 198 486 319

[0267] Table 2

[0268]

[0269] Table 3

[0270]

[0271] Table 4

[0272]

[0273] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. An ethylene tar refining catalyst system comprising: a first catalyst, a second catalyst and a third catalyst, wherein the first catalyst comprises a first carrier and a first modified element, the first carrier is Al2O3, and the first modified element is selected from at least three of Ni, Mo, La, W, P and Co, the second catalyst comprises a second carrier and a second modified element, the second carrier is an Al2O3-TiO2-SiO2 multi-component carrier, and the second modified element is selected from at least three of Ni, Mo, La, W, P and Co, the third catalyst comprises a third carrier and a third modified element, the third carrier is an Al2O3-SiO2 multi-component carrier, and the third modified element is selected from at least three of Ni, Mo, La, W, P and Co; in the Al2O3-TiO2-SiO2 multi-component carrier, the mass percentage of Al2O3 is 80% to 98%, the mass percentage of TiO2 is 1% to 10%, and the mass percentage of SiO2 is 1% to 10%, based on the total weight of the Al2O3-TiO2-SiO2 multi-component carrier; in the Al2O3-SiO2 multi-component carrier, the mass percentage of Al2O3 is 90% to 99%, and the mass percentage of SiO2 is 1% to 10%, based on the total weight of the Al2O3-SiO2 multi-component carrier; the first catalyst, the second catalyst and the third catalyst form a catalyst bed, the first catalyst is located in the upper layer of the catalyst bed, the second catalyst is located in the middle layer of the catalyst bed, and the third catalyst is located in the lower layer of the catalyst bed.

2. The catalyst system of claim 1, wherein, the volume ratio of the first catalyst, the second catalyst and the third catalyst is (1-5):(2-8):(1-3); and / or the first carrier is γ-Al2O3; and / or the first modified element is selected from at least four of Ni, Mo, La, W, P and Co; and / or the second modified element is selected from at least four of Ni, Mo, La, W, P and Co; and / or the third modified element is selected from at least four of Ni, Mo, La, W, P and Co.

3. The catalyst system of claim 2, wherein, the volume ratio of the first catalyst, the second catalyst and the third catalyst is (1-4):(4-8):(1-2); and / or the first modified element is selected from at least five of Ni, Mo, La, W, P and Co; and / or the second modified element is selected from at least five of Ni, Mo, La, W, P and Co.

4. The catalyst system of claim 3, wherein, the volume ratio of the first catalyst, the second catalyst and the third catalyst is (1-3):(5-8):(1-2); and / or the first modified element comprises Ni, Mo, La, W, P and Co; and / or the second modified element comprises Ni, Mo, La, W, P and Co.

5. The catalyst system according to any one of claims 1 to 4, characterized in that, The specific surface area of the first carrier is 180 m 2 / g ~ 320 m 2 / g; the average pore diameter is 7 ~ 14 nm; the pore volume is 0.6 ~ 0.88 cm 3 / g; and / or The specific surface area of the second carrier is 200 m 2 / g to 360 m 2 / g; the average pore diameter is 8 to 13 nm; the pore volume is 0.50 to 0.85 cm 3 / g; and / or The specific surface area of the third carrier is 200 m 2 / g to 360 m 2 / g; the average pore diameter is 8 to 12 nm; the pore volume is 0.6 to 0.85 cm 3 / g.

6. The catalyst system of claim 5, wherein, The specific surface area of the first carrier is 190 m 2 / g ~ 250 m 2 / g, the average pore diameter is 8 ~ 13 nm, and the pore volume is 0.7 ~ 0.85 cm 3 / g; and / or The specific surface area of the second carrier is 220 m 2 / g ~ 350 m 2 / g, the average pore diameter is 8 ~ 12 nm, and the pore volume is 0.65 ~ 0.82 cm 3 / g; and / or The specific surface area of the third carrier is 220 m 2 / g ~ 300 m 2 / g, the average pore diameter is 8 ~ 11 nm, and the pore volume is 0.65 ~ 0.83 cm 3 / g; and / or the average pore size of the first carrier > the average pore size of the second carrier > the average pore size of the third carrier.

7. The catalyst system according to any one of claims 1 to 4, characterized in that, the first carrier has a medium-strong acid amount of 100-150 μmol / g; a total acid amount of 170-230 μmol / g; and / or the second carrier has a medium-strong acid amount of 180-380 μmol / g; a total acid amount of 400-600 μmol / g; and / or the third carrier has a medium-strong acid amount of 150-250 μmol / g; a total acid amount of 200-350 μmol / g.

8. The catalyst system of claim 7, wherein, the medium-strong acid amount of the second carrier > the medium-strong acid amount of the third carrier > the medium-strong acid amount of the first carrier.

9. The catalyst system according to any one of claims 1 to 4, characterized in that, in the first catalyst, the mass percentage content of the first carrier is 50-80% and the mass percentage content of the first modifying element is 20-50% in terms of oxides, based on the total weight of the first catalyst; and / or in the first catalyst, the mass percentage content of Ni is 3-10% in terms of NiO, the mass percentage content of Mo is 15-25% in terms of MoO3, the mass percentage content of La is 0-3% in terms of La2O5, the mass percentage content of W is 0-15% in terms of WO3, the mass percentage content of P is 0-5% in terms of P2O5, and the mass percentage content of Co is 0-10% in terms of CoO, based on the total weight of the first catalyst; and / or in the second catalyst, the mass percentage content of the second carrier is 50-80% and the mass percentage content of the second modifying element is 20-50% in terms of oxides, based on the total weight of the second catalyst; and / or in the second catalyst, the mass percentage content of Ni is 3-10% in terms of NiO, the mass percentage content of Mo is 15-25% in terms of MoO3, the mass percentage content of La is 0-3% in terms of La2O5, the mass percentage content of W is 0-15% in terms of WO3, the mass percentage content of P is 0-5% in terms of P2O5, and the mass percentage content of Co is 0-10% in terms of CoO, based on the total weight of the second catalyst; and / or in the third catalyst, the mass percentage content of the third carrier is 70-95% and the mass percentage content of the third modifying element is 5-30% in terms of oxides, based on the total weight of the third catalyst; and / or in the third catalyst, the mass percentage content of Ni is 0-3% in terms of NiO, the mass percentage content of Mo is 5-15% in terms of MoO3, the mass percentage content of La is 0-3% in terms of La2O5, the mass percentage content of W is 0-3% in terms of WO3, the mass percentage content of P is 0-5% in terms of P2O5, and the mass percentage content of Co is 0-10% in terms of CoO, based on the total weight of the third catalyst.

10. The catalyst system of claim 9, wherein, in the first catalyst, the mass percentage content of the first carrier is 70-80% and the mass percentage content of the first modifying element is 20-30% in terms of oxides, based on the total weight of the first catalyst; and / or The mass percentage of La in the first catalyst is 0.1% to 1% as La2O5, and / or the mass percentage of W is 8% to 15% as WO3, and / or the mass percentage of P is 0.5% to 2% as P2O5, and / or the mass percentage of Co is 2% to 6% as CoO, based on the total weight of the first catalyst; and / or The mass percentage of the second carrier in the second catalyst is 55% to 70%, and the mass percentage of the second modified element is 20% to 30% as an oxide, based on the total weight of the second catalyst; and / or The mass percentage of La in the second catalyst is 0.1% to 1% as La2O5, and / or the mass percentage of W is 8% to 15% as WO3, and / or the mass percentage of P is 0.5% to 2% as P2O5, and / or the mass percentage of Co is 2% to 6% as CoO, based on the total weight of the second catalyst; and / or The mass percentage of the third carrier in the third catalyst is 80% to 90%, and the mass percentage of the third modified element is 10% to 20% as an oxide, based on the total weight of the third catalyst; and / or The mass percentage of Mo in the third catalyst is 8% to 12% as MoO3, and / or the mass percentage of La is 0.1% to 1% as La2O5, and / or the mass percentage of P is 0.1% to 1% as P2O5, and / or the mass percentage of Co is 1% to 5% as CoO, based on the total weight of the third catalyst.

11. The catalyst system according to any one of claims 1 to 4, characterized in that, The preparation method of the first carrier comprises the following steps: S11. A raw material system comprising a first Al2O3 powder, a first auxiliary agent, and a first peptizing agent is subjected to a shaping treatment to obtain a first carrier precursor; S12. The first carrier precursor is sequentially subjected to drying and calcination to obtain the first carrier.

12. The catalyst system of claim 11, wherein, In step S11, the first Al2O3 powder is γ-Al2O3; and / or the average particle size of the first Al2O3 powder is 0.1 microns to 2 microns; and / or In step S12, the calcination is performed at a temperature of 450°C to 650°C for 1 hour to 12 hours.

13. The catalyst system of claim 12, wherein, In step S12, the calcination is performed at a temperature of 500°C to 600°C for 2 hours to 5 hours.

14. The catalyst system of any one of claims 1-4, wherein, The preparation method of the second carrier comprises the following steps: S21. A first solution containing a titanium source, a second solution containing a silicon source, and a third solution containing ethanol, water, and nitric acid and having a pH value of 3 to 5 are provided; S22. The first solution, the second solution, and the third solution are mixed to obtain a fourth solution; S23. The fourth solution is mixed with a second Al2O3 powder to obtain a first mixture; S24. The mixture is sequentially subjected to drying and calcination to obtain an Al2O3-TiO2-SiO2 powder; S25. mixing the Al2O3-TiO2-SiO2 powder, the second additive and the second peptizing agent to obtain a second mixture; S26. performing a shaping treatment on the second mixture to obtain a second carrier precursor; S27. sequentially performing drying and calcination on the second carrier precursor to obtain a second carrier.

15. The catalyst system of claim 14, wherein, In step S21, the titanium source is at least one selected from the group consisting of titanium ester compounds; and / or the silicon source is at least one selected from the group consisting of tetraethyl orthosilicate, silica sol and fumed silica; and / or In step S23, the second Al2O3 powder is γ-Al2O3; and / or the average particle size of the second Al2O3 powder is 0.1-2 microns; and / or In step S24, the calcination is performed at a temperature of 400-550°C for 1-12 hours; and / or In step S27, the calcination is performed at a temperature of 450-650°C for 1-12 hours.

16. The catalyst system of claim 15, wherein, In step S21, the titanium source is at least one selected from the group consisting of tetra-n-butyl titanate and tetrahexyl titanate; and / or In step S27, the calcination is performed at a temperature of 500-600°C for 2-5 hours.

17. The catalyst system of any one of claims 1-4, wherein, The preparation method of the third carrier comprises the following steps: S31. performing a shaping treatment on a raw material system comprising a third Al2O3 powder, a third additive, silica sol and a third peptizing agent to obtain a third carrier precursor; S32. sequentially performing drying and calcination on the third carrier precursor to obtain a third carrier.

18. The catalyst system of claim 17, wherein, In step S31, the third Al2O3 powder is γ-Al2O3; and / or the average particle size of the third Al2O3 powder is 0.1-2 microns; and / or In step S32, the calcination is performed at a temperature of 450-650°C for 1-12 hours.

19. The catalyst system of claim 18, wherein, In step S32, the calcination is performed at a temperature of 500-600°C for 2-5 hours.

20. Use of the catalyst system according to any one of claims 1-19 in refining of ethylene tar, comprising: S41. sequentially performing heavy component removal treatment and first-stage hydroprocessing on crude ethylene tar to obtain a refined raw material; S42. passing the refined raw material into a reactor containing the catalyst system to perform a refining reaction, thereby obtaining a refined product, In step S41, the ethylene tar refining raw material contains 2% to 5% di-olefins, 30% to 38% naphthalene series and 25 to 50 mg / 100 g oil of gum in terms of mass percentage; and / or in step S42, the reaction conditions of the refining reaction include: an inlet temperature of 200 to 270 DEG C, a reaction pressure of 2.3 to 6.0 MPa, a hydrogen / oil volume ratio of 400 to 1500, and a liquid phase volume space velocity of 0.2 to 1.8 hours -1 .

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