Process and system for the hydrogenation of ethylene tar to light aromatics

Abstract

The present application provides a method and system for hydrogenation of ethylene tar to produce light aromatic hydrocarbons, comprising: a) pretreating and separating the ethylene tar raw material to remove gum; b) removing the gum from the ethylene tar raw material to obtain a first liquid-phase hydrogenation stream; c) after gas-liquid separation of the first liquid-phase hydrogenation stream, performing second gas-phase hydrogenation on the liquid-phase stream to make the unsaturated hydrocarbon components in the liquid-phase stream undergo second gas-phase hydrogenation, thereby obtaining a second gas-phase hydrogenation stream; d) after gas-liquid separation of the second gas-phase hydrogenation stream, obtaining a liquid-phase hydrogenation product, performing third gas-phase hydrogenation, e) performing gas-liquid separation on the third gas-phase hydrogenation product, and performing rectification separation on the liquid-phase product to obtain light hydrocarbon products and BTX products. The present application can be used to treat refinery device by-products, such as ethylene tar containing C9+, C10+, to increase the production of high-value light aromatic hydrocarbons.

Description

Technical Field

[0001] This invention relates to a method and system for hydrogenating ethylene tar to produce light aromatics. Background Technology

[0002] Ethylene tar is a byproduct of ethylene production from hydrocarbon cracking. Its main components are aromatic compounds, with a distillation range of 205–360℃, falling within the diesel fraction. It primarily originates from the bottom of quench oil towers and heavy fuel oil stripping towers. Ethylene tar is a heavy distillate oil rich in aromatics, mainly containing monocyclic heavy aromatics and polycyclic aromatic hydrocarbons.

[0003] In recent years, my country has gradually increased the number of ethylene cracking units, leading to a continuous increase in ethylene tar production capacity. Ethylene tar production typically accounts for 15%-20% of ethylene production. Ethylene tar is generally used as fuel oil, which is not economically efficient and pollutes the environment. Currently, the comprehensive utilization of ethylene tar in my country is still in its early stages. A small portion is used to extract naphthalene and methylnaphthalene, or to prepare pitch and needle coke, but overall processing and utilization are difficult and the utilization rate is low.

[0004] Currently, there are few methods for hydrogenating and lightening ethylene tar.

[0005] CN110540865B discloses a method for hydrorefining cracked tar, using tar and hydrogen as raw materials to produce fuel oil through a reaction in the presence of a catalyst. CN101724448B discloses a hydrocracking method for blending ethylene tar, in which light fractions of ethylene tar are blended into conventional hydrocracking feedstock for hydrocracking. In the presence of hydrogen, the mixture is sequentially contacted with a hydroprotection catalyst, a hydrorefining catalyst, a hydrodecarbonization catalyst, and a hydrocracking catalyst. The hydrocracking effluent is then separated to obtain light fuel oil.

[0006] CN101148596A discloses a start-up method for a coal tar hydrotreating process. In the initial startup phase, after sulfidation, one or more of the following are selected as diluents: coking diesel, coking wax oil, catalytic diesel, catalytic reclaimed oil, deasphalted oil, coal liquefaction diesel fraction, coal liquefaction wax oil fraction, and wax oil and diesel fraction obtained from coal tar hydrotreating. Then, polar substances such as alcohols, phenols, and esters are selected and added to the diluent in a specific ratio. The prepared diluent containing the polar substances is directly added to the reactor, and finally, the coal tar feedstock is switched. In this method, the initial sulfidation still uses the traditional sulfidation method of a residue hydrotreating unit. After sulfidation, additional distillate oils and polar substances need to be selected, and diluents need to be prepared in a specific ratio, making the start-up process relatively cumbersome. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies for the light processing of ethylene tar, such as low product conversion rate and low utilization rate, by providing a process for the hydrogenation of ethylene tar to produce light aromatics. This method can effectively convert ethylene tar into chemical products, producing high-conversion-rate BTX and light aromatics, and has the advantages of high conversion activity, high product yield, and high product added value.

[0008] To achieve the aforementioned objective, according to a first aspect of the present invention, the present invention provides a method for the hydrogenation and lightening of ethylene tar, the method comprising:

[0009] a) Pre-treat the ethylene tar feedstock to separate and remove gum;

[0010] b) The ethylene tar feedstock, after the gum has been removed, is subjected to first-phase hydrogenation to remove easily polymerizable components at temperatures above 300°C, resulting in a first-phase hydrogenated stream.

[0011] c) After the first liquid phase hydrogenation stream is separated into gas and liquid, the liquid phase stream undergoes a second gas phase hydrogenation to allow the unsaturated hydrocarbon components in the liquid phase stream to undergo a second gas phase hydrogenation, thus obtaining a second gas phase hydrogenation stream.

[0012] d) After gas-liquid separation, the second gas-phase hydrogenation stream yields a liquid-phase hydrogenation product, which is then subjected to third gas-phase hydrogenation.

[0013] e) After the third gas-phase hydrogenation stream is separated into gas and liquid phases, the liquid phase mixture is separated to obtain BTX product and light hydrocarbon product.

[0014] According to a second aspect of the present invention, the present invention provides a hydrotreating system for ethylene tar, the system comprising:

[0015] The pretreatment unit is used to pretreat and separate colloids from ethylene tar feedstock.

[0016] The first liquid phase hydrogenation unit is used to remove easily polymerizable components at high temperatures above 300°C from the ethylene tar feedstock after degumming to obtain the first liquid phase hydrogenated stream.

[0017] The first separation unit is used for gas-liquid separation of the first liquid-phase hydrogenated stream;

[0018] The second gas phase hydrogenation unit is used to perform second gas phase hydrogenation on the liquid stream obtained from the first separation unit, so that monoolefins and / or naphthalene aromatics in the liquid stream are subjected to second gas phase hydrogenation to obtain a second gas phase hydrogenated stream.

[0019] The second separation unit is used for gas-liquid separation of the second gas-phase hydrogenated stream;

[0020] The third gas phase hydrogenation unit is used to perform third gas phase hydrogenation on the liquid stream obtained from the second separation unit, so that the tetrahydronaphthalene series and polycyclic components in the liquid stream are hydrogenated in the third gas phase to obtain the third gas phase hydrogenated stream.

[0021] The third separation unit is used for gas-liquid separation of the third gas-phase hydrogenated stream;

[0022] The fourth separation unit is used to separate the liquid mixture obtained from the third separation unit to obtain the distillation range BTX product and the light hydrocarbon product (light hydrocarbon product).

[0023] The system of this invention mainly includes two process production units: a hydrogenation reaction unit and a separation unit. The hydrogenation reaction unit includes a first-stage liquid-phase hydrogenation, a second-stage gas-phase hydrogenation, and a third-stage gas-phase hydrogenation. The system also includes auxiliary units as needed: a hydrogen circulation unit required for the reaction, a water system, and a vacuum system required for the separation unit.

[0024] The device of the present invention can recover and separate products such as BTX and light hydrocarbons.

[0025] This invention targets ethylene tar components, employing a three-stage gas-phase hydrogenation reaction followed by a first-stage low-temperature liquid-phase hydrogenation process to obtain light fractions. This method can be used to process C9+ and C10+ ethylene tar, a byproduct of refinery operations, to increase the production of high-value-added light aromatics or light hydrocarbon components.

[0026] The present invention contains C9 + C10 + The method for hydrogenating ethylene tar to lighten the product involves removing gum from the feedstock and then passing it through a three-stage hydrogenation reaction system. The reaction products are then stripped in one step to separate light hydrocarbon products. The bottom product is then distilled to separate crude BTX aromatics, and the heavy fraction is collected from the bottom of the tower.

[0027] The products obtained by the method of this invention are all highly economical and high-value-added chemical products, which have obvious economic advantages. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the method of the present invention. Detailed Implementation

[0029] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0030] According to the present invention, the gum refers to the components in ethylene tar with a boiling point higher than 350°C.

[0031] In this invention, the ethylene tar feedstock is a byproduct obtained from the production of ethylene by cracking hydrocarbons; according to this invention, the ethylene tar feedstock refers to the high-boiling-point byproduct of the separation of ethylene and propylene after ethylene steam cracking.

[0032] This invention provides a method for the hydrogenation and lightening of ethylene tar, the method comprising:

[0033] a) Pre-treat the ethylene tar feedstock to separate and remove gum;

[0034] b) The ethylene tar feedstock, after the gum has been removed, is subjected to first-phase hydrogenation to remove easily polymerizable components at temperatures above 300°C, resulting in a first-phase hydrogenated stream.

[0035] c) After the first liquid phase hydrogenation stream is separated into gas and liquid, the liquid phase stream undergoes a second gas phase hydrogenation to allow the unsaturated hydrocarbon components in the liquid phase stream to undergo a second gas phase hydrogenation, thus obtaining a second gas phase hydrogenation stream.

[0036] d) After the second gas-phase hydrogenated stream is separated into gas and liquid phases, the liquid phase mixture is separated to obtain the second liquid-phase hydrogenated stream. After being mixed with hydrogen, the third gas-phase hydrogenated stream is obtained.

[0037] e) After the third gas-phase hydrogenation stream is separated into gas and liquid, the reaction products of the liquid phase mixture are stripped to separate light hydrocarbon products, and the bottom material is further separated into crude BTX aromatics by distillation, with heavy fractions collected from the bottom of the tower.

[0038] In this invention, the heavy fraction refers to C10+ aromatics, alkanes, and naphthalene compounds.

[0039] According to a preferred embodiment of the present invention, the method includes:

[0040] a) The ethylene tar feedstock is first separated by a pretreatment unit. The bottom of the pretreatment unit removes the gum from the feedstock, and the top of the unit yields a fraction with a final boiling point of no more than 300°C.

[0041] b) The fraction with a final boiling point not exceeding 300°C enters a first-stage hydrogenation reactor for first-phase liquid-phase hydrogenation, converting easily polymerizable substances including dienes and alkenyl aromatics into monoolefins and alkyl aromatics, and converting indene into indene; thus obtaining the first-phase hydrogenated stream.

[0042] c) After gas-liquid separation of the first liquid phase hydrogenation stream, the liquid phase stream enters the second-stage hydrogenation reactor for second gas phase hydrogenation, to hydrogenate monoolefins and / or naphthalene aromatics, to obtain the second gas phase hydrogenation stream.

[0043] d) After gas-liquid separation, the liquid mixture of the second gas-phase hydrogenated stream enters the three-stage hydrogenation reactor for third gas-phase hydrogenation, where tetrahydronaphthalene and polycyclic aromatic hydrocarbons are hydrogenated to obtain the third gas-phase hydrogenated stream.

[0044] e) After the third gas-phase hydrogenation stream is separated into gas and liquid phases, the liquid phase mixture is separated to obtain BTX product and light fraction.

[0045] According to a preferred embodiment of the present invention, the ethylene tar feedstock contains one or more of the following: non-aromatic hydrocarbons, benzene series, naphthalene series, biphenyl, polycyclic and diene substances, and the distillation range of ethylene tar is generally 30-350°C.

[0046] According to a preferred embodiment of the present invention, the ethylene tar feedstock contains: 1-15 wt% non-aromatic hydrocarbons, 40-80 wt% benzene series, 10-40 wt% naphthalene series, 0.01-10 wt% biphenyl, and 0.01-15 wt% polycyclic aromatic hydrocarbons.

[0047] According to a preferred embodiment of the present invention, in step c), the liquid phase stream after gas-liquid separation of the first liquid phase hydrogenation stream comprises one or more of the following: benzene series, naphthalene series, biphenyl, polycyclic aromatic hydrocarbons, alkyl aromatic hydrocarbons and monoenes.

[0048] According to a preferred embodiment of the present invention, in step d), the second gas-phase hydrogenation mainly involves mono-olefin saturation and selective hydrogenation of polycyclic aromatic hydrocarbons to generate alkyl aromatic hydrocarbons and tetrahydronaphthalene compounds. According to the present invention, the liquid mixture following gas-liquid separation of the second gas-phase hydrogenation stream preferably comprises one or more of benzene compounds, tetrahydronaphthalene compounds, alkyl aromatic hydrocarbons, and polycyclic aromatic hydrocarbons.

[0049] According to a preferred embodiment of the present invention, in step e), the third gas-phase hydrogenation mainly involves hydrocracking of tetrahydronaphthalenes and polycyclic aromatic hydrocarbons to generate alkyl aromatics and light hydrocarbon compounds. According to the present invention, the liquid mixture following gas-liquid separation of the third gas-phase hydrogenation stream preferably comprises one or more of non-aromatic hydrocarbons, cycloalkanes, benzenes, and alkyl aromatics.

[0050] This invention does not have special requirements for the conditions of the first liquid-phase hydrogenation. Any conditions and catalysts that can achieve the requirements of this invention can be used. According to a preferred embodiment of this invention, the conditions for the first liquid-phase hydrogenation include: a pressure of 1–7 MPa, preferably 3.5–6.5 MPa; and / or a temperature of 40–280°C, preferably 90–150°C; and / or a feed liquid hourly space velocity of not more than 1.0 h⁻¹. -1 Preferably 0.8 to 1 hour -1 .

[0051] This invention does not have special requirements for the conditions of the second gas-phase hydrogenation. Any conditions and catalysts that can achieve the requirements of this invention can be used. According to a preferred embodiment of this invention, the conditions for the second gas-phase hydrogenation include: a pressure of 1–8 MPa, preferably 3.5–7.5 MPa; and / or a temperature of 150–500°C, preferably 200–450°C; and / or a feed gas hourly space velocity of 0.1–2 h⁻¹. -1 Preferably, it is 0.8 to 1.2 hours. -1 .

[0052] This invention does not have special requirements for the conditions of third gas-phase hydrogenation. Any conditions and catalysts that can achieve the requirements of this invention can be used. According to a preferred embodiment of this invention, the third gas-phase hydrogenation conditions include: a pressure of 1–10 MPa, preferably 3.5–8.5 MPa; and / or a temperature of 150–500°C, preferably 250–450°C; and / or a feed gas hourly space velocity of 0.1–2 h⁻¹. -1 Preferably, it is 0.7 to 1.2 hours. -1 .

[0053] In this invention, there are no special requirements for the catalyst for the first liquid-phase hydrogenation. Commonly used liquid-phase hydrogenation catalysts can be used in this invention. For example, a supported catalyst made of Group VIII noble metals Ni or / and Pd with a metal content of 0.1 to 10 wt% is used in this invention.

[0054] In this invention, there are no special requirements for the catalyst for the second gas-phase hydrogenation. Commonly used gas-phase hydrogenation catalysts can be used in this invention. For example, for this invention, a supported catalyst of one or more of the group VIII, group VIB and group VIIB non-noble metals with a metal content of 0.1 to 10 wt% is preferred.

[0055] In this invention, there are no special requirements for the catalyst for the third gas-phase hydrogenation. Commonly used gas-phase hydrogenation catalytic cracking agents can be used in this invention. For example, a molecular sieve hydrogenation catalyst supported on Ni-Mo metal can be used in this invention.

[0056] In this invention, there are no special requirements for the pretreatment separation steps and conditions. Any method that can achieve the purpose of this invention is applicable to this invention. According to a preferred embodiment of this invention, step a) the pretreatment separation operation is a low-pressure operation. The preferred pretreatment separation conditions include: pressure -0.0001 to -0.1 MPa; temperature 100 to 350°C, preferably 200 to 300°C.

[0057] According to a preferred embodiment of the present invention, step e) includes: after the third gas-phase hydrogenation reaction, the liquid phase product obtained by gas-liquid separation enters a gas stripping separation tower, light hydrocarbons (also known as light fractions, light hydrocarbon products) are obtained from the top of the gas stripping separation tower, and light aromatic hydrocarbons are obtained from the bottom of the tower. The light aromatic hydrocarbons enter a product separation tower for separation, BTX is obtained from the top of the product separation tower, and heavy fractions are collected from the bottom of the product separation tower.

[0058] According to a preferred embodiment of the present invention, the operating conditions of the stripping separator include: pressure 0.01-2.8 MPa, preferably 0.2-2.0 MPa; temperature 100-350℃, preferably 150-230℃.

[0059] According to a preferred embodiment of the present invention, the operating conditions of the product separation tower include: pressure 0.1-1.5 MPa, preferably 0.2-1.0 MPa; temperature 100-380°C, preferably 250-300°C.

[0060] According to a preferred embodiment of the present invention, the first liquid-phase hydrogenation, the second gas-phase hydrogenation, and the third gas-phase hydrogenation each include recycling the separated hydrogen as a hydrogen feedstock.

[0061] According to a preferred embodiment of the present invention, the second gas-phase hydrogenation is preferably carried out in the presence of H2S, and the H2S concentration is preferably 0.0001-5 wt%.

[0062] All the aforementioned hydrolighting methods capable of achieving the present invention can be used in the present invention, and there are no special requirements for the equipment or system used. According to a preferred embodiment of the present invention, the present invention provides a hydrolighting system for ethylene tar, the system comprising:

[0063] The pretreatment unit is used to pretreat and separate colloids from ethylene tar feedstock.

[0064] The first liquid phase hydrogenation unit is used to remove easily polymerizable components at high temperatures above 300°C from the ethylene tar feedstock after degumming to obtain the first liquid phase hydrogenated stream.

[0065] The first separation unit is used for gas-liquid separation of the first liquid-phase hydrogenated stream;

[0066] The second gas phase hydrogenation unit is used to perform second gas phase hydrogenation on the liquid stream obtained from the first separation unit, so that monoolefins and / or naphthalene aromatics in the liquid stream are subjected to second gas phase hydrogenation to obtain a second gas phase hydrogenated stream.

[0067] The second separation unit is used for gas-liquid separation of the second gas-phase hydrogenated stream;

[0068] The third gas phase hydrogenation unit is used to perform third gas phase hydrogenation on the liquid stream obtained from the second separation unit, so that the tetrahydronaphthalene series and polycyclic aromatic hydrocarbon components in the liquid stream are subjected to third gas phase hydrogenation cracking to obtain the third gas phase hydrogenated stream.

[0069] The third separation unit is used for gas-liquid separation of the third gas-phase hydrogenated stream.

[0070] The fourth separation unit is used to separate the liquid mixture obtained from the third separation unit to obtain the distillation range BTX product and light hydrocarbon product;

[0071] According to a preferred embodiment of the present invention, the pretreatment unit preferably includes a pretreatment separation tower 2.

[0072] According to a preferred embodiment of the present invention, the first liquid-phase hydrogenation unit preferably includes: a hydrogenation reactor 6.

[0073] According to a preferred embodiment of the present invention, the first separation unit preferably includes: a section separator 8.

[0074] According to a preferred embodiment of the present invention, the second gas-phase hydrogenation unit preferably includes a two-stage hydrogenation reactor 12; the second separation unit includes a two-stage separator 15.

[0075] According to a preferred embodiment of the present invention, the third gas-phase hydrogenation unit preferably includes a three-stage hydrogenation reactor 17; the third separation unit includes a three-stage separator 20.

[0076] According to a preferred embodiment of the present invention, the fourth separation unit preferably includes a stripping separator and a product separation separator.

[0077] According to a preferred embodiment of the present invention, preferably, the stripping separation tower is used for stripping the liquid mixture obtained from the third separation unit, with light hydrocarbon products obtained at the top of the tower and light aromatic hydrocarbons obtained at the bottom of the tower.

[0078] According to a preferred embodiment of the present invention, preferably, a product separation tower is used to separate the light aromatic hydrocarbons, with BTX product obtained at the top of the tower and heavy fraction obtained at the bottom of the tower.

[0079] According to a preferred embodiment of the present invention, the system includes: a pretreatment separation tower 2, a first-stage hydrogenation reactor 6, a first-stage separator 8, a second-stage hydrogenation reactor 12, a second-stage separator 15, a third-stage hydrogenation reactor 17, a third-stage separator 20, a stripping separation tower 23, and a product separation tower 26, which are connected in series along the material flow direction.

[0080] According to a preferred embodiment of the present invention, the system further includes an auxiliary unit, which mainly includes a hydrogen circulation unit, a water supply unit, a raw material supply unit, and a vacuum supply unit.

[0081] According to a preferred embodiment of the present invention, preferably, the gas phase outlet of a first-stage separator 8 is connected to the gas inlet of a first-stage hydrogenation reactor 6 to serve as a circulating hydrogen pipeline.

[0082] According to a preferred embodiment of the present invention, preferably, the gas phase outlet of the two-stage separator 15 is connected to the gas inlet of the two-stage hydrogenation reactor 12 to serve as a circulating hydrogen pipeline.

[0083] According to a preferred embodiment of the present invention, preferably, the gas phase outlet of the three-stage separator 20 is connected to the gas inlet of the two-stage hydrogenation reactor 17 to serve as a circulating hydrogen pipeline.

[0084] The embodiments of the present invention are described below with reference to the accompanying drawings.

[0085] like Figure 1 As shown, ethylene tar 1 enters pretreatment separation tower 2, obtaining gum 4 at the bottom and pretreated ethylene tar 3 at the top. Pretreated ethylene tar 3 is mixed with fresh hydrogen 5 and first-stage recycled hydrogen 9 and enters first-stage hydrogenation reactor 6 to obtain first-stage hydrogenation product 7. First-stage hydrogenation product 7 enters first-stage separator 8 to obtain first-stage recycled hydrogen 9 and first-stage hydrogenation separation product 10. First-stage hydrogenation separation product 10 is mixed with supplementary hydrogen 11 and second-stage recycled hydrogen 14 and enters second-stage hydrogenation reactor 12 to obtain second-stage hydrogenation product 13. Second-stage hydrogenation product 13 enters second-stage separator 15 to obtain second-stage recycled hydrogen 14 and second-stage hydrogenation separation product 16. Second-stage hydrogenation separation product 16 enters third-stage hydrogenation reactor 17 to obtain third-stage hydrogenation product 18. Third-stage hydrogenation product 18 enters third-stage separator 20 to obtain third-stage recycled hydrogen 19 and third-stage hydrogenation separation product 22. Stripping separator 23 separates emission hydrocarbons (light hydrocarbon product) 24 at the top and light aromatic hydrocarbons 25 at the bottom. The obtained light aromatic hydrocarbons 25 enter product separation tower 26, where BTX product 27 is obtained at the top and heavy fraction 28 is collected at the bottom. The following examples follow the procedure as follows... Figure 1 The process shown is as follows.

[0086] The present invention will be further illustrated below through examples.

[0087] Example 1

[0088] The ethylene tar feedstock, a byproduct of ethylene production from hydrocarbon cracking, is first pretreated and separated. The pretreatment separation tower operates under negative pressure, with separation conditions of -0.089 MPa and 250°C.

[0089] After pretreatment and removal of gums, the ethylene tar enters a first-stage hydrogenation reactor for cryogenic liquid-phase hydrogenation. This process converts readily polymerizable compounds such as dienes and alkenyl aromatics into monoolefins and alkyl aromatics, while indene is hydrogenated to indene compounds. The first-stage hydrogenation reaction conditions are: pressure 4 MPa, temperature 100 °C, Ni-based catalyst, and feed liquid space velocity (LHSV) of 0.8 h⁻¹. -1 .

[0090] After gas-liquid separation, the liquid stream from the first-stage hydrogenation reactor enters the second-stage hydrogenation reactor for gas-phase hydrogenation of monoolefins and naphthalene-based aromatics. The second-stage hydrogenation reaction is conducted at a pressure of 5.8 MPa, a temperature of 290 °C, a Ni-Co-Mo catalyst, and a feedstock volume hourly space velocity of 0.8 h⁻¹. -1 .

[0091] After two stages of hydrogenation, the liquid stream is separated into liquid and enters a three-stage hydrogenation reactor for gas-phase hydrogenation of tetrahydronaphthalenes and polycyclic aromatic hydrocarbons. The three-stage hydrogenation reaction is carried out at a pressure of 6.8 MPa, a temperature of 330 °C, a Ni-Mo molecular sieve catalyst, and a feed volume hourly space velocity of 0.85 h⁻¹. -1 .

[0092] After the three-stage hydrogenation process, the liquid phase stream enters a stripping tower to separate light hydrocarbon products. Light aromatic hydrocarbons are obtained at the bottom of the tower. The separation pressure conditions are: 0.5 MPa and 190°C.

[0093] The obtained light aromatics are fed into a product separation tower under the following conditions: pressure 0.7 MPa, temperature 290 °C. BTX is collected at the top of the tower, and the heavy fraction is collected at the bottom.

[0094] The composition of raw materials and reaction results are shown in Tables 1 and 2.

[0095] Table 1. Components of Ethylene Tar

[0096] Non-fragrant 9.54 Benzene series 53.2 Naphthalene series 24.83 Biphenyl 2.16 Multi-ring 10.27

[0097] Table 2 Results of Reaction Indicators

[0098] <![CDATA[C1-C3]]> 40.03 benzene 11.13 <![CDATA[C4H 10 ]]> 41.92 Toluene 32.68 <![CDATA[C5H 12 ]]> 14.17 C8 aromatics 36.93 other 3.88 other 19.26 sum 100 sum 100

[0099] As shown in Table 2, hydrogenation effectively utilizes the aromatics in the feedstock, increases the production of light hydrocarbons and BTX products, and enhances the added value of the products.

[0100] The products obtained by the method of this invention are all chemical products with high economic efficiency and high added value, which have greater economic advantages.

[0101] Example 2

[0102] The ethylene tar feedstock, a byproduct of ethylene production from hydrocarbon cracking, is first pretreated and separated. The pretreatment separation tower operates at low pressure, with separation conditions of -0.085 MPa and 255 °C.

[0103] The pretreated ethylene tar, after being degummed, enters a primary hydrogenation reactor for cryogenic liquid-phase hydrogenation. The primary hydrogenation reaction conditions are: pressure 3.8 MPa, temperature 90 °C, Ni-based catalyst, and feed liquid space velocity (LHSV) of 0.8 h⁻¹. -1 .

[0104] After gas-liquid separation, the liquid stream from the first-stage hydrogenation reactor enters the second-stage hydrogenation reactor for gas-phase hydrogenation. The second-stage hydrogenation reaction is conducted at a pressure of 6.3 MPa, a temperature of 296 °C, a Ni-Co-Mo catalyst, and a feedstock volume hourly space velocity of 0.85 h⁻¹. -1 After two stages of hydrogenation, the liquid stream is separated into liquid and enters a three-stage hydrogenation reactor for gas-phase hydrogenation of tetrahydronaphthalenes and polycyclic aromatic hydrocarbons. The three-stage hydrogenation reaction is conducted at a pressure of 7.0 MPa, a temperature of 320 °C, a Ni-Mo molecular sieve catalyst, and a feedstock volume hourly space velocity of 0.95 h⁻¹. -1 .

[0105] After the three-stage hydrogenation process, the liquid phase stream enters a stripping tower to separate light hydrocarbon products (light hydrocarbon products). Light aromatic hydrocarbons are obtained at the bottom of the tower. The separation pressure conditions are: pressure 0.52 MPa and temperature 200℃.

[0106] The resulting light aromatics enter a product separation column under the following conditions: pressure 0.6 MPa, temperature 275 °C. BTX is collected at the top of the column, and the heavy fraction is collected at the bottom.

[0107] The raw material composition and the results of lightening are shown in Tables 3 and 4.

[0108] Table 3 Ethylene Tar Components

[0109] Non-fragrant 7.28 Benzene series 54.29 Naphthalene series 24.6 Biphenyl 2.98 Multi-ring 10.85

[0110] Table 4 Results of Reaction Indicators

[0111] <![CDATA[C1-C3]]> 39.62 benzene 11.24 <![CDATA[C4H 10 ]]> 41.06 Toluene 33.01 <![CDATA[C5H 12 ]]> 13.73 C8 aromatics 37.31 other 5.59 other 18.44 sum 100 sum 100

[0112] As can be seen from the table above, hydrogenation effectively utilizes the aromatics in the raw materials, increases the production of light hydrocarbons and BTX products, and enhances the added value of the products.

[0113] The products obtained by the method of this invention are all chemical products with high economic efficiency and high added value, which have greater economic advantages.

[0114] Example 3

[0115] The ethylene tar feedstock, a byproduct of ethylene production from hydrocarbon cracking, is first pretreated and separated. The pretreatment separation tower operates under negative pressure, with separation conditions of -0.092 MPa and 241°C.

[0116] After pretreatment and removal of gums, the ethylene tar enters a first-stage hydrogenation reactor for cryogenic liquid-phase hydrogenation. The first-stage hydrogenation reaction conditions are: pressure 3.5 MPa, temperature 100 °C, Ni-based catalyst, and feed liquid space velocity of 1 h⁻¹. -1 .

[0117] After gas-liquid separation, the liquid stream from the first-stage hydrogenation reactor enters the second-stage hydrogenation reactor for gas-phase hydrogenation. The second-stage hydrogenation reaction is conducted at a pressure of 7.0 MPa, a temperature of 280 °C, a Ni-Co-Mo catalyst, and a feedstock volume hourly space velocity of 1.0 h⁻¹. -1 .

[0118] After two stages of hydrogenation, the liquid stream is separated into liquid and enters a three-stage hydrogenation reactor for gas-phase hydrogenation of tetrahydronaphthalenes and polycyclic aromatic hydrocarbons. The three-stage hydrogenation reaction is conducted at a pressure of 7.2 MPa, a temperature of 330 °C, a Ni-Mo molecular sieve catalyst, and a feed volume hourly space velocity of 0.75 h⁻¹. -1 .

[0119] After the three-stage hydrogenation process, the liquid phase stream enters the stripping tower to separate light hydrocarbon products (light hydrocarbon products). Light aromatic hydrocarbons are obtained at the bottom of the tower. The separation pressure conditions are: pressure 0.57 MPa and temperature 218℃.

[0120] The obtained light aromatics are fed into a product separation tower under the following conditions: pressure 0.7 MPa and temperature 285 °C. BTX is collected at the top of the tower, and the heavy fraction is collected at the bottom.

[0121] The raw material composition and the results of lightening are shown in Tables 5 and 6.

[0122] Table 5 Ethylene Tar Components

[0123] Non-fragrant 5.16 Benzene series 48.2 Naphthalene series 33.28 Biphenyl 2.08 Multi-ring 11.28

[0124] Table 6 Results of Reaction Indicators

[0125] <![CDATA[C1-C3]]> 40.27 benzene 10.95 <![CDATA[C4H 10 ]]> 42.18 Toluene 32.18 <![CDATA[C5H 12 ]]> 14.25 C8 aromatics 36.37 other 3.30 other 20.50 sum 100 sum 100

[0126] As can be seen from the above examples, this invention can process ethylene tar containing C9+ and C10+ as a byproduct of refinery operations, increasing the production of high-value-added light aromatics and light hydrocarbon product components. The products obtained by the method of this invention are all highly economical and high-value-added chemical products, thus possessing greater economic advantages.

[0127] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for hydrogenating and lightening ethylene tar, characterized in that, The method includes: a) The ethylene tar feedstock is first separated by a pretreatment unit. The bottom of the pretreatment unit removes the gum from the feedstock, and the top of the unit yields a fraction with a final boiling point of no more than 300°C. b) The fraction with a final boiling point not exceeding 300°C is subjected to first-phase hydrogenation to remove easily polymerizable components, resulting in a first-phase hydrogenated stream; the first-phase hydrogenation conditions include a pressure of 3.5–6.5 MPa; c) After gas-liquid separation of the first liquid-phase hydrogenated stream, the liquid-phase stream undergoes second gas-phase hydrogenation to allow the unsaturated hydrocarbon components in the liquid-phase stream to undergo second gas-phase hydrogenation, resulting in a second gas-phase hydrogenated stream; the second gas-phase hydrogenation conditions include a pressure of 3.5–7.5 MPa; d) After gas-liquid separation, the second gas-phase hydrogenation stream yields a liquid-phase hydrogenation product, which is then subjected to third gas-phase hydrogenation. The conditions for third gas-phase hydrogenation include a pressure of 3.5–8.5 MPa. e) After the third gas-phase hydrogenation stream is separated by gas-liquid separation, the liquid phase mixture is separated to obtain BTX product and light hydrocarbon product; The ethylene tar feedstock contains: 1-15 wt% non-aromatic hydrocarbons, 40-80 wt% benzene compounds, 10-40 wt% naphthalene compounds, 0.01-10 wt% biphenyl, and 0.01-15 wt% polycyclic aromatic hydrocarbons.

2. The method according to claim 1, wherein, The method includes: a) The ethylene tar feedstock is first separated by a pretreatment unit. The bottom of the pretreatment unit removes the gum from the feedstock, and the top of the unit yields a fraction with a final boiling point of no more than 300°C. b) The fraction with a final boiling point not exceeding 300°C enters a first-stage hydrogenation reactor for first-phase liquid-phase hydrogenation, converting easily polymerizable substances including dienes and alkenyl aromatics into monoolefins and alkyl aromatics, and converting indene into indene; thus obtaining the first-phase hydrogenated stream. c) After gas-liquid separation of the first liquid phase hydrogenation stream, the liquid phase stream enters the second-stage hydrogenation reactor for second gas phase hydrogenation, to hydrogenate monoolefins and / or naphthalene aromatics, to obtain the second gas phase hydrogenation stream. d) After gas-liquid separation, the second gas-phase hydrogenation stream is used to obtain the liquid-phase hydrogenation product, which is then subjected to third gas-phase hydrogenation to hydrogenate tetrahydronaphthalene and polycyclic aromatic hydrocarbons to obtain the third gas-phase hydrogenation stream. e) After the third gas-phase hydrogenation stream is separated into gas and liquid phases, the liquid phase mixture is separated to obtain light hydrocarbon products and BTX products.

3. The method according to claim 1, wherein, The ethylene tar feedstock is a byproduct obtained from the production of ethylene through hydrocarbon cracking; In step c), the liquid phase stream after gas-liquid separation of the first liquid phase hydrogenation stream comprises one or more of the following: benzene series, naphthalene series, biphenyl, polycyclic aromatic hydrocarbons, alkyl aromatic hydrocarbons, and monoenes. In step d), the liquid phase mixture after gas-liquid separation of the second gas-phase hydrogenation stream comprises one or more of the following: benzene series, tetrahydronaphthalene series, alkyl aromatics and polycyclic aromatics; In step e), the liquid phase mixture of the third gas-phase hydrogenation product after gas-liquid separation includes one or more of the following: non-aromatic hydrocarbons, benzene compounds, and alkyl aromatic hydrocarbons.

4. The method according to claim 1, wherein, The first liquid-phase hydrogenation conditions include: Temperature 40–280℃; and / or The time hourly space velocity of the feed liquid is not greater than 1.0 h⁻¹. -1 .

5. The method according to claim 4, wherein, The first liquid-phase hydrogenation conditions include: Temperature is 90–150℃; and / or The time space velocity of the feed liquid is 0.8–1 h. -1 .

6. The method according to claim 1, wherein, Temperature 150–500℃; and / or The raw material gas hourly space velocity is 0.1~2h. -1 .

7. The method according to claim 6, wherein, The second gas-phase hydrogenation conditions include: Temperatures of 200–450°C; and / or The raw material gas hourly space velocity is 0.8~1.2 h⁻¹. -1 .

8. The method according to claim 1, wherein, The third gas-phase hydrogenation conditions include: Temperature 150–500℃; and / or The raw material gas hourly space velocity is 0.1~2h. -1 .

9. The method according to claim 8, wherein, The third gas-phase hydrogenation conditions include: Temperatures of 250–450°C; and / or The raw material gas hourly space velocity is 0.7~1.2 h⁻¹. -1 .

10. The method according to claim 1, wherein, Step a) The pretreatment separation operation is a negative pressure operation; and / or Step e) includes: after the third gas-phase hydrogenation reaction, the liquid product obtained from gas-liquid separation enters a gas stripping separation tower, and a light hydrocarbon product is obtained from the top of the gas stripping separation tower; light aromatic hydrocarbons are obtained from the bottom of the tower, and the light aromatic hydrocarbons enter a product separation tower for separation, and BTX product is obtained from the top of the product separation tower. The operating conditions for the gas stripping separator include: pressure 0.01-2.8 MPa; temperature 100-350℃. The operating conditions for the product separation tower include: pressure 0.1-1.5 MPa; temperature 100-380℃.

11. The method according to claim 10, wherein, Step a) Pretreatment separation conditions include: pressure -0.0001~-0.1MPag; temperature 100~350℃; and / or In step e): The operating conditions for the gas stripping separator include: pressure of 0.2~2.0MPa; temperature of 150~230℃. The operating conditions for the product separation tower include: pressure 0.2~1.0MPa; temperature 250~320℃.

12. The method according to claim 11, wherein, Step a) Pretreatment separation conditions include: temperature of 200~300℃.

13. The method according to claim 1, wherein, The first liquid-phase hydrogenation, the second gas-phase hydrogenation, and the third gas-phase hydrogenation each involve recycling the separated hydrogen as a hydrogen feedstock.

14. The method according to any one of claims 1-13, wherein the method is carried out in a hydrolightening system for ethylene tar, the system comprising: The pretreatment unit is used to pretreat and separate colloids from ethylene tar feedstock. The first liquid phase hydrogenation unit is used to remove easily polymerizable components at high temperatures above 300°C from the ethylene tar feedstock after degumming to obtain the first liquid phase hydrogenated stream. The first separation unit is used for gas-liquid separation of the first liquid-phase hydrogenated stream; The second gas phase hydrogenation unit is used to perform second gas phase hydrogenation on the liquid stream obtained from the first separation unit, so that monoolefins and / or naphthalene aromatics in the liquid stream are subjected to second gas phase hydrogenation to obtain a second gas phase hydrogenated stream. The second separation unit is used for gas-liquid separation of the second gas-phase hydrogenated stream; The third gas phase hydrogenation unit is used to perform third gas phase hydrogenation on the liquid stream obtained from the second separation unit, so that the tetrahydronaphthalene system and polycyclic components in the liquid stream are subjected to gas phase hydrogenation cracking to obtain the third gas phase hydrogenated stream. The third separation unit is used for gas-liquid separation of the third gas-phase hydrogenated stream; The fourth separation unit is used to separate the liquid mixture obtained from the third separation unit to obtain the distillation range BTX product and light hydrocarbon product.

15. The method according to claim 14, wherein, The pretreatment unit includes: a pretreatment separation tower (2); the first liquid phase hydrogenation unit includes: a first-stage hydrogenation reactor (6); the first separation unit includes: a first-stage separator (8); the second gas phase hydrogenation unit includes: a second-stage hydrogenation reactor (12); the second separation unit includes: a second-stage separator (15); the third gas phase hydrogenation unit includes: a third-stage hydrogenation reactor (17); the third separation unit includes: a third-stage separator (20). The fourth separation unit includes a gas stripping separator and a product separation separator; The gas stripping separation tower is used for gas stripping separation of the liquid mixture obtained from the third separation unit, with light hydrocarbon products obtained at the top of the tower and light aromatic hydrocarbons obtained at the bottom of the tower. The product separation column is used to separate the light aromatics, with BTX product obtained at the top and heavy fraction obtained at the bottom.

16. The method of claim 14, wherein, The system includes: a pretreatment separation tower (2), a first-stage hydrogenation reactor (6), a first-stage separator (8), a second-stage hydrogenation reactor (12), a second-stage separator (15), a third-stage hydrogenation reactor (17), a third-stage separator (20), a gas stripping separation tower (23), and a product separation tower (26), all connected in series along the material flow direction; and / or The system also includes an auxiliary unit, which mainly includes a hydrogen circulation unit, a water supply unit, a raw material supply unit, and a vacuum supply unit.

17. The method according to claim 16, wherein, The gas phase outlet of a first-stage separator (8) is connected to the gas inlet of a first-stage hydrogenation reactor (6) to serve as a circulating hydrogen pipeline; The gas phase outlet of the second-stage separator (15) is connected to the gas inlet of the second-stage hydrogenation reactor (12) to serve as a circulating hydrogen pipeline. The gas phase outlet of the three-stage separator (20) is connected to the inlet of the three-stage hydrogenation reactor (17) to serve as a circulating hydrogen pipeline.

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