Full range ethylene tar hydroprocessing process

Abstract

This invention relates to the field of hydrogenation technology for inferior oil products, specifically to a hydrogenation process for full-fraction ethylene tar. The hydrogenation process includes the following steps: ethylene tar is mixed with a reaction improver and then hydrogenated under the action of a hydrogenation catalyst to obtain a hydrogenation reaction effluent; the hydrogenation reaction effluent enters a high-pressure separator, where it is separated to obtain high-fraction gas and high-pressure product oil; the high-pressure product oil enters a low-pressure separator, where it is processed to obtain low-fraction gas, low-pressure product oil, and side-stream extractable oil, wherein the side-stream extractable oil is extracted from the side-stream outlet, and the low-pressure product oil is discharged from the bottom outlet; the side-stream extractable oil is recycled back to the ethylene tar for blending. This invention features mild process conditions, high deasphalting rate, low coking rate and slow deactivation of the system pipelines and catalyst, simple process steps, low energy consumption cost, and high cleanliness of the hydrogenated product oil, achieving efficient conversion of full-fraction ethylene tar through hydrogenation.

Description

Technical Field

[0001] This invention relates to the field of hydrogenation technology for inferior oil products, specifically to a hydrogenation process for full-fraction ethylene tar. Background Technology

[0002] The efficient and clean conversion of high-asphalt content, low-quality oil products such as ethylene tar from petroleum refining processes is a crucial research topic urgently needing resolution in the industry. Ethylene tar has an initial boiling point of 170–260℃ and a final boiling point >600℃. It has a complex composition, high density and odor, high asphalt content, and is rich in polycyclic aromatic hydrocarbons (PAHs) and fused-ring aromatic hydrocarbons (FEHs). Its sulfur, nitrogen, heavy metal, and ash content are relatively low; some ethylene tar even contains visible, viscous condensate polymers adhering to the walls. Currently, ethylene tar is mainly used for fuel oil combustion, which has the disadvantage of severely polluting the environment. In the future, it will be treated as hazardous waste, seriously hindering the economic benefits of petrochemical enterprises.

[0003] Hydrogenation technology, as a means of upgrading and lightening heavy oil, still has significant advantages. Hydrogenation technology is divided into fixed-bed hydrogenation and fluidized-bed hydrogenation. The fluidized-bed heavy oil hydrogenation process, which has been industrially applied, can process low-quality heavy oil feedstocks with high asphaltenes content, efficiently converting asphaltenes into light oil products under high temperature and pressure. However, its disadvantages include increased reactor pressure drop due to the heavy composition, high viscosity, and poor fluidity of the feedstock oil; and the harsh process conditions, high investment, and high catalyst consumption costs. Fixed-bed hydrogenation technology is mature and requires less investment, but it can only process heavy feedstock oils with an asphaltenes content typically not exceeding 5%, and the process conditions are also very harsh, with temperatures usually exceeding 380℃, even reaching 400℃, and pressures above 10MPa.

[0004] Based on the existing understanding of hydrogenation technology for inferior heavy oil with high asphaltene content, in the fixed-bed hydrogenation process technology for producing fuel oil blending components from ethylene tar, the light fraction of ethylene tar is usually hydrogenated separately at a suitable cut point to produce gasoline and diesel fuel oil products, while the heavy fraction is generally treated with decarbonization processes such as coking and solvent deasphalting.

[0005] For example, patent CN102234539A discloses a processing method for ethylene tar, which involves fractionating ethylene tar into light and heavy fractions, then treating the heavy fraction with a solvent deasphalting method to obtain deasphalted oil and deoiled pitch. The deasphalted oil and the light fraction of ethylene tar are mixed with hot low-grade oil and hydrogenated to obtain hydrocracking product oil. Part of the product oil is recycled and mixed with the deasphalted oil and the light fraction of ethylene tar to go to the hydrogenation reaction zone. The remaining part is separated to obtain gasoline and diesel fractions. The deoiled pitch is used as a general-purpose carbon fiber pitch raw material.

[0006] Currently, there are no reports on fixed-bed hydrotreating of the entire fraction of ethylene tar to efficiently convert asphaltenes and produce clean fuel oil. Summary of the Invention

[0007] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a full-fraction ethylene tar hydrogenation process with mild process conditions, high deasphalting rate, low coking rate and slow deactivation of system pipelines and catalysts, simple process steps, low energy consumption cost, and high cleanliness of hydrogenated oil, thus achieving efficient conversion of full-fraction ethylene tar hydrogenation.

[0008] The whole-fraction ethylene tar hydrogenation process of the present invention includes the following steps:

[0009] (1) Hydrogenation reaction: Ethylene tar is mixed with reaction improver and then mixed with hydrogen and fed into hydrogenation reactor. Under the action of hydrogenation catalyst, hydrogenation treatment is carried out to obtain hydrogenation reaction effluent, which is oil-gas mixture.

[0010] (2) High-pressure separation: The hydrogenation reaction effluent enters the high-pressure separator, and after separation, high-precision gas and high-pressure product oil are obtained;

[0011] (3) Low-pressure separation: High-pressure generated oil enters the low-pressure separator. The low-pressure separator is equipped with a bottom outlet and a side line extraction outlet. After processing, low-pressure gas, low-pressure generated oil and side line extraction oil are obtained. The side line extraction oil is extracted from the side line extraction outlet, and the low-pressure generated oil is discharged from the bottom outlet.

[0012] (4) Circulating blending: The side-stream extracted oil is recycled back to the ethylene tar in step (1) for blending.

[0013] The ethylene tar is derived from the ethylene unit of a petrochemical enterprise, with an asphaltene content of 16-36 wt%, a sulfur content of less than 0.2 wt%, and a distillation range of 165-660℃, preferably 175-645℃.

[0014] The asphaltenes and viscous condensates contained in ethylene tar undergo free radical polymerization reactions during the hydrogenation reaction stage through free radical or metal catalytic mechanisms. Especially in high-temperature hydrogenation reactors, strong self-polymerization and association reactions cause the molecular weight of asphaltenes to increase, forming layered self-polymer particles similar to carbon structures, resulting in catalyst coking and deactivation.

[0015] In the hydrogenation reaction stage, this invention mixes a reaction improver with ethylene tar. The improver can break down the network structure formed by the aggregation of asphaltene and asphalt gum or other components, reduce the viscosity of the feedstock oil, enhance the compatibility of asphaltene components in the feedstock oil, slow down the coking deposition rate in the pipeline, improve the catalyst reaction activity, and improve and promote the hydrogenation conversion reaction of the feedstock oil in the reactor catalyst bed.

[0016] The reaction-improving agent is a nonionic surfactant, preferably sorbitan fatty acid ester, and more preferably sorbitan anhydride monooleate. It has good dispersing and solubilizing effects, can break down the aggregated structures between asphaltenes and asphalt gums in the feedstock, and reduce the viscosity of the viscous condensate in the ethylene tar feedstock.

[0017] The reaction-improving additive accounts for 100–600 μg·g of the ethylene tar mass fraction. -1 Preferably, the concentration is 150–550 μg·g. -1 .

[0018] The operating conditions for the hydrogenation reaction stage are: reaction temperature 220–390℃, reaction pressure 2.2–14.5 MPa, and volume hourly space velocity (VHSV) 0.1–2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 150–900; the preferred operating conditions are: reaction temperature 235–385℃, reaction pressure 3.0–13.0 MPa, and volume hourly space velocity 0.4–1.4 h⁻¹. -1 The hydrogen-to-oil volume ratio is 250–750.

[0019] The hydrogenation reactor used in the hydrogenation reaction stage is one of the following: isothermal fixed-bed reactor, fluidized bed reactor, or suspended bed reactor.

[0020] The hydrotreating catalyst can be any hydrotreating catalyst commonly used in residual oil or diesel hydrotreating reactors, or any catalyst with hydrotreating and depurifying functions.

[0021] During the high-pressure separation stage, the operating conditions of the high-pressure separator are: temperature of 180–280℃ and reaction pressure of 3.0–5.5 MPa.

[0022] During the low-pressure separation stage, the operating conditions of the low-pressure separator are: temperature of 100-180℃ and reaction pressure of 1.0-2.5MPa.

[0023] The mass ratio of the side-stream extracted oil to the low-pressure generated oil is (1-15):(85-100), preferably (2-10):(90-98).

[0024] The side-stream extracted oil contains more than 70% aromatic hydrocarbons, of which more than 20% are methyltetrahydronaphthalene, tetrahydronaphthalene and cycloalkane aromatic hydrocarbon components.

[0025] The low-pressure product oil is further stripped with hydrogen to obtain a hydrogenated product oil. The distillation range of the hydrogenated product oil is 70–600℃, preferably 75–580℃.

[0026] The high-score gas produced in the high-pressure separation stage and the low-score gas produced in the low-pressure separation stage are combined to obtain hydrogenation tail gas for discharge or sampling.

[0027] In the method of this invention, the inventors unexpectedly discovered that recycling a portion of the hydrogenated oil back into the ethylene feedstock for blending prevents catalyst coking, improves the hydrogenation reaction performance of the feedstock, and significantly increases the removal rate of asphaltenes. Because the hydrogenated ethylene feedstock has an increased hydrogen-to-carbon ratio and contains some hydrogen-donating components such as methyltetrahydronaphthalene, tetrahydronaphthalene, and aromatic components with cycloalkane aromatic structures, it can synergistically interact with reaction improvers in the feedstock, reducing the self-polymerization and association of viscous polymers and asphaltenes. This softens the asphaltenes, increases their solubility in the feedstock, and makes the feedstock gas more readily available for hydrogenation conversion. Furthermore, during the hydrogenation reactor reaction stage, the synergistic effect of the hydrogen-donating components, hydrogen, and the hydrogenation catalyst in the reactor provides more active hydrogen and reactive sites, improving the catalyst's reaction performance. This results in higher desulfurization and deasphalting conversion rates for ethylene tar under milder conditions.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The whole-fraction ethylene tar hydrotreating process of the present invention overcomes the limitation of the feedstock index on the existing ethylene tar fixed bed hydrotreating technology, and opens up a technical route for the whole-fraction ethylene tar fixed bed hydroconversion treatment. It has the advantages of simple process steps, mild process operating conditions and low investment.

[0030] (2) In the hydrogenation reaction stage, the present invention proposes to mix a reaction improvement agent with ethylene tar. The agent can break down the network structure formed by the aggregation of asphaltene and asphalt gum or other components, reduce the viscosity of the feed oil, enhance the compatibility of asphaltene components in the feed oil, slow down the coking deposition rate of the pipeline, improve the catalyst reaction activity, increase the hydrogenation conversion reaction performance of the feed oil, and greatly improve the deasphalting rate of the catalyst.

[0031] (3) In the recycling stage of this invention, the hydrogen-to-carbon ratio of the hydrogenated ethylene feedstock is increased, and it contains some hydrogen-donating components such as methyltetrahydronaphthalene, tetrahydronaphthalene and aromatic components with cycloalkane aromatic structures. These components can work synergistically with the reaction improvers in the feedstock, making the feedstock gas easier to undergo hydrogenation conversion reaction. Furthermore, in the hydrogenation reactor reaction stage, the hydrogen-donating components, hydrogen and the hydrogenation catalyst in the reactor further work synergistically, so that the feedstock and catalyst provide more active hydrogen and reactive sites. This combined process can prevent coking and deposition in pipelines and catalysts, improve the reaction performance of the catalyst, and enable ethylene tar to have a higher desulfurization and deasphalting conversion rate under milder conditions. Detailed Implementation

[0032] To make the content of this invention easier to understand, the invention will be described in further detail.

[0033] The feedstock oils used in the examples were all ethylene tar, a byproduct of an ethylene plant, which consisted of visibly viscous condensate adhering to the walls. The properties of the feedstock oils are shown in Table 1.

[0034] The catalyst used in the examples is FHUDS-6 developed by the Dalian Petrochemical Research Institute of China Petroleum & Chemical Corporation; the reaction improvement agent used is sorbitan monooleate.

[0035] Table 1. Analysis of the properties of ethylene tar feedstock

[0036] project Ethylene tar feedstock <![CDATA[Kinematic viscosity (50 °C) / mm 2 ·s -1 > 1578 <![CDATA[Density (15 °C) / kg·m -3 > 1.1013 Sulfur content / wt% 0.110 Asphalt / wt% 24.5 Distillation range / ℃ / Initial boiling point 182 10％ 348 30％ 471 50％ 512 90％ 559 Dry 638 Cleanliness 5

[0037] Example 1

[0038] The ethylene tar listed in Table 1 was used as a raw material and mixed with the reaction improver sorbitan monooleate. The amount of sorbitan monooleate added was 350 μg·g of the raw material oil. -1 The mixture is then introduced into a fixed-bed reactor for hydrogenation, where it undergoes hydrogenation treatment in the presence of a hydrogenation catalyst to obtain the hydrogenation effluent. The operating conditions for the hydrogenation reaction are: reaction temperature 330℃, reaction pressure 6 MPa, and volume hourly space velocity (VHSV) 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 400:1, and the catalyst used in the fixed-bed reactor was FHUDS-6, developed by the Dalian Research Institute of Petroleum & Chemical Industry, China Petroleum & Chemical Corporation. In the high-pressure separation stage, the hydrotreating effluent, i.e., the oil-gas mixture, entered the high-pressure separator, where high-grade gas and high-pressure product oil were obtained. The temperature of the high-pressure separator was 230℃, and the reaction pressure was 4.5 MPa. In the low-pressure separation stage, the high-pressure product oil entered the low-pressure separator, where low-grade gas, low-pressure product oil exiting from the bottom of the low-pressure separator, and side-stream extracted oil from the side-stream outlet of the low-pressure separator were obtained. The high-grade gas and low-grade gas were combined to form hydrotreating tail gas, which was discharged or sampled. The low-pressure product oil was extracted to obtain hydrotreated product oil. The temperature of the low-pressure separator was 150℃, and the reaction pressure was 2.2 MPa. In the recycling and blending stage, the side-stream extracted oil from the low-pressure separator was recycled back to the ethylene feedstock for blending. The ratio of low-pressure side-stream extracted oil to low-pressure product oil was 7:93. The reaction results are shown in Table 2.

[0039] Example 2

[0040] The ethylene tar from Table 1 was used as a raw material and mixed with the reaction improver sorbitan monooleate. The amount of the improver added was 150 μg·g of the raw material oil. -1The mixture is then introduced into a fixed-bed reactor for hydrogenation, where it undergoes hydrogenation treatment in the presence of a hydrogenation catalyst to obtain the hydrogenation effluent. The operating conditions for the hydrogenation reaction are: reaction temperature 320℃, reaction pressure 6 MPa, and volume hourly space velocity (VHSV) 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 400:1, and the catalyst used in the fixed-bed reactor was FHUDS-6, developed by the Dalian Research Institute of Petroleum & Chemical Industry, China Petroleum & Chemical Corporation. In the high-pressure separation stage, the hydrotreating effluent, i.e., the oil-gas mixture, entered the high-pressure separator, where high-grade gas and high-pressure product oil were obtained. The temperature of the high-pressure separator was 220℃, and the reaction pressure was 4.0 MPa. In the low-pressure separation stage, the high-pressure product oil entered the low-pressure separator, where low-grade gas, low-pressure product oil exiting from the bottom of the low-pressure separator, and side-stream extracted oil from the side-stream outlet of the low-pressure separator were obtained. The high-grade gas and low-grade gas were combined to form hydrotreating tail gas, which was discharged or sampled. The low-pressure product oil was extracted to obtain hydrotreated product oil. The temperature of the low-pressure separator was 180℃, and the reaction pressure was 2.5 MPa. In the recycling and blending stage, the side-stream extracted oil from the low-pressure separator was recycled back to the ethylene feedstock for blending. The ratio of low-pressure side-stream extracted oil to low-pressure product oil was 2:98. The reaction results are shown in Table 2.

[0041] Example 3

[0042] The ethylene tar from Table 1 was used as a raw material and mixed with the reaction improver sorbitan monooleate. The amount of the improver added was 550 μg·g of the raw material oil. -1 The mixture is then introduced into a fixed-bed reactor for hydrogenation, where it undergoes hydrogenation treatment in the presence of a hydrogenation catalyst to obtain the hydrogenation effluent. The operating conditions for the hydrogenation reaction are: reaction temperature 340℃, reaction pressure 6 MPa, and volume hourly space velocity (VHSV) 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 400:1, and the catalyst used in the fixed-bed reactor was FHUDS-6, developed by the Dalian Research Institute of Petroleum & Chemical Industry, China Petroleum & Chemical Corporation. In the high-pressure separation stage, the hydrotreating effluent, i.e., the oil-gas mixture, entered the high-pressure separator, where high-grade gas and high-pressure product oil were obtained. The temperature of the high-pressure separator was 250℃, and the reaction pressure was 5.0 MPa. In the low-pressure separation stage, the high-pressure product oil entered the low-pressure separator, where low-grade gas, low-pressure product oil exiting from the bottom of the low-pressure separator, and side-stream extracted oil from the side-stream outlet of the low-pressure separator were obtained. The high-grade gas and low-grade gas were combined to form hydrotreating tail gas, which was discharged or sampled. The low-pressure product oil was extracted to obtain hydrotreated product oil. The temperature of the low-pressure separator was 130℃, and the reaction pressure was 1.5 MPa. In the recycling and blending stage, the side-stream extracted oil from the low-pressure separator was recycled back to the ethylene feedstock for blending. The ratio of low-pressure side-stream extracted oil to low-pressure product oil was 5:95. The reaction results are shown in Table 2.

[0043] Example 4

[0044] The ethylene tar from Table 1 was used as a raw material and mixed with the reaction improver sorbitan monooleate. The amount of the improver added was 260 μg·g of the raw material oil. -1 The mixture is then introduced into a fixed-bed reactor for hydrogenation, where it undergoes hydrogenation treatment in the presence of a hydrogenation catalyst to obtain the hydrogenation effluent. The operating conditions for the hydrogenation reaction are: reaction temperature 350℃, reaction pressure 6 MPa, and volume hourly space velocity (VHSV) 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 400:1, and the catalyst used in the fixed-bed reactor was FHUDS-6, developed by the Dalian Research Institute of Petroleum & Chemical Industry, China Petroleum & Chemical Corporation. In the high-pressure separation stage, the hydrotreating effluent, i.e., the oil-gas mixture, entered the high-pressure separator, where high-grade gas and high-pressure product oil were obtained. The temperature of the high-pressure separator was 280℃, and the reaction pressure was 3.0 MPa. In the low-pressure separation stage, the high-pressure product oil entered the low-pressure separator, where low-grade gas, low-pressure product oil exiting from the bottom of the low-pressure separator, and side-stream extracted oil from the side-stream outlet of the low-pressure separator were obtained. The high-grade gas and low-grade gas were combined to form hydrotreating tail gas, which was discharged or sampled. The low-pressure product oil was extracted to obtain hydrotreated product oil. The temperature of the low-pressure separator was 170℃, and the reaction pressure was 2.0 MPa. In the recycling and blending stage, the side-stream extracted oil from the low-pressure separator was recycled back to the ethylene feedstock for blending. The ratio of low-pressure side-stream extracted oil to low-pressure product oil was 10:90. The reaction results are shown in Table 2.

[0045] Example 5

[0046] The ethylene tar from Table 1 was used as a raw material and mixed with the reaction improver sorbitan monooleate. The amount of the improver added was 460 μg·g of the raw material oil. -1 The mixture is then introduced into a fixed-bed reactor for hydrogenation, where it undergoes hydrogenation treatment in the presence of a hydrogenation catalyst to obtain the hydrogenation effluent. The operating conditions for the hydrogenation reaction are: reaction temperature 330℃, reaction pressure 6 MPa, and volume hourly space velocity (VHSV) 1.0 h⁻¹. -1The hydrogen-to-oil volume ratio was 400:1, and the catalyst used in the fixed-bed reactor was FHUDS-6, developed by the Dalian Research Institute of Petroleum & Chemical Industry, China Petroleum & Chemical Corporation. In the high-pressure separation stage, the hydrotreating effluent, i.e., the oil-gas mixture, entered the high-pressure separator, where high-grade gas and high-pressure product oil were obtained. The temperature of the high-pressure separator was 260℃, and the reaction pressure was 5.5 MPa. In the low-pressure separation stage, the high-pressure product oil entered the low-pressure separator, where low-grade gas, low-pressure product oil exiting from the bottom of the low-pressure separator, and side-stream extracted oil from the side-stream outlet of the low-pressure separator were obtained. The high-grade gas and low-grade gas were combined to form hydrotreating tail gas, which was discharged or sampled. The low-pressure product oil was extracted to obtain hydrotreated product oil. The temperature of the low-pressure separator was 100℃, and the reaction pressure was 1.0 MPa. In the recycling and blending stage, the side-stream extracted oil from the low-pressure separator was recycled back to the ethylene feedstock for blending. The ratio of low-pressure side-stream extracted oil to low-pressure product oil was 3:97. The reaction results are shown in Table 2.

[0047] Comparative Example 1

[0048] The ethylene tar from Table 1 was used as a raw material and mixed with the reaction improver sorbitan monooleate. The amount of the improver added was 350 μg·g of the raw material oil. -1 The mixture is then introduced into a fixed-bed reactor for hydrogenation, where it undergoes hydrogenation treatment in the presence of a hydrogenation catalyst to obtain the hydrogenation effluent. The operating conditions for the hydrogenation reaction are: reaction temperature 330℃, reaction pressure 6 MPa, and volume hourly space velocity (VHSV) 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 400:1, and the catalyst used in the fixed-bed reactor was FHUDS-6, developed by the Dalian Research Institute of Petroleum & Chemical Industry, China Petroleum & Chemical Corporation. In the high-pressure separation stage, the hydrotreating effluent, i.e., the oil-gas mixture, entered the high-pressure separator, where high-grade gas and high-pressure product oil were obtained. The temperature of the high-pressure separator was 230℃, and the reaction pressure was 4.5 MPa. In the low-pressure separation stage, the high-pressure product oil entered the low-pressure separator, where low-grade gas and low-pressure product oil were obtained. The high-grade gas and low-grade gas were combined to form the hydrotreating tail gas, which was discharged or sampled. The low-pressure product oil was extracted to obtain the hydrotreating product oil. The temperature of the low-pressure separator was 150℃, and the reaction pressure was 2.2 MPa. The reaction results are shown in Table 2.

[0049] Comparative Example 2

[0050] Using ethylene tar from Table 1 as feedstock, a mixture of hydrogen and feedstock was introduced into a fixed-bed hydrotreating reactor. Hydrotreating was performed in the presence of a hydrotreating catalyst to obtain the hydrotreating effluent. The operating conditions for the hydrotreating reaction were: reaction temperature 330℃, reaction pressure 6 MPa, and volume hourly space velocity (VHSV) 1.0 h⁻¹. -1The hydrogen-to-oil volume ratio was 400:1, and the catalyst used in the fixed-bed reactor was FHUDS-6, developed by the Dalian Research Institute of Petroleum & Chemical Industry, China Petroleum & Chemical Corporation. In the high-pressure separation stage, the hydrotreating effluent, i.e., the oil-gas mixture, entered the high-pressure separator, where high-grade gas and high-pressure product oil were obtained. The temperature of the high-pressure separator was 230℃, and the reaction pressure was 4.5 MPa. In the low-pressure separation stage, the high-pressure product oil entered the low-pressure separator, where low-grade gas, low-pressure product oil exiting from the bottom of the low-pressure separator, and side-stream extracted oil from the side-stream outlet of the low-pressure separator were obtained. The high-grade gas and low-grade gas were combined to form hydrotreating tail gas, which was discharged or sampled. The low-pressure product oil was extracted to obtain hydrotreated product oil. The temperature of the low-pressure separator was 150℃, and the reaction pressure was 2.2 MPa. In the recycling and blending stage, the side-stream extracted oil from the low-pressure separator was recycled back to the ethylene feedstock for blending. The ratio of low-pressure side-stream extracted oil to low-pressure product oil was 7:93. The reaction results are shown in Table 2.

[0051] Comparative Example 3

[0052] Using ethylene tar from Table 1 as feedstock, a mixture of hydrogen and feedstock was introduced into a fixed-bed hydrotreating reactor. Hydrotreating was performed in the presence of a hydrotreating catalyst to obtain the hydrotreating effluent. The operating conditions for the hydrotreating reaction were: reaction temperature 330℃, reaction pressure 6 MPa, and volume hourly space velocity (VHSV) 1.0 h⁻¹. -1 The hydrogen-to-oil volume ratio is 400:1, and the catalyst used in the fixed-bed reactor is FHUDS-6, developed by the Dalian Research Institute of Petroleum & Chemical Industry, China Petroleum & Chemical Corporation. In the high-pressure separation stage, the hydrotreating effluent, i.e., the oil-gas mixture, enters the high-pressure separator, where it is separated into high-grade gas and high-pressure product oil. The temperature of the high-pressure separator is 230℃, and the reaction pressure is 4.5 MPa. In the low-pressure separation stage, the high-pressure product oil enters the low-pressure separator, where it is separated into low-grade gas and low-pressure product oil. The high-grade gas and low-grade gas are combined to form the hydrotreating tail gas, which is then discharged or sampled. The low-pressure product oil is extracted to obtain the hydrotreated product oil. The temperature of the low-pressure separator is 150℃, and the reaction pressure is 2.2 MPa.

[0053] Table 2 Experimental operating conditions and properties of hydrogenated oil

[0054]

[0055]

[0056] As shown in Table 2, the deasphalting rate of ethylene tar in the full-fraction ethylene tar hydrotreating process of this invention increases from below 60 wt% to over 80 wt%; the desulfurization rate also shows the same trend. This indicates that after adding the reaction improvement additive, the additive can break down the network structure formed by the aggregation of asphaltenes and asphalt gum or other components, reduce the viscosity of the feedstock oil, enhance the compatibility of asphaltenes in the feedstock oil, reduce the flow resistance of the feedstock oil, reduce the pressure drop of the entire reaction system, slow down the coking deposition rate in the pipeline, and increase the hydroconversion reaction performance of the feedstock oil. The reduction in flow resistance and pressure drop of the reaction system can fully utilize the catalyst's reactivity and improve the deasphalting rate of the catalyst. Part of the hydrogenated ethylene feedstock is recycled back to the ethylene feedstock blending process. Due to the increased hydrogen-to-carbon ratio of the recycled oil, it contains hydrogen-donating components such as methyltetrahydronaphthalene, tetrahydronaphthalene, and aromatic components with cycloalkane aromatic structures. These components synergistically interact with the additives in the feedstock, making the feedstock gas more readily available for hydrogenation conversion. Furthermore, during the hydrogenation reactor reaction stage, the synergistic effect of the hydrogen-donating components, hydrogen gas, and the hydrogenation catalyst in the reactor provides more active hydrogen and reactive sites to the feedstock and catalyst. This combined process prevents catalyst coking, improves catalyst reactivity, and results in higher desulfurization and deasphalting conversion rates for ethylene tar under milder conditions, leading to a significant improvement in oil quality.

[0057] Simultaneously, the shutdown cycle for cleaning filters and pipeline valve blockages in each embodiment and comparative example was monitored, and catalyst carbonization was analyzed. The results are shown in Table 3.

[0058] Table 3. Experimental shutdown and decoking cycle and catalyst carbonization analysis results.

[0059]

[0060]

[0061] As shown in Table 3, the whole-fraction ethylene tar hydrogenation process of this invention has significant technical advantages over traditional hydrogenation methods in terms of the hydrogenation reaction process for the deep conversion of ethylene tar, whether considering the cleaning and clogging cycle of raw material filters and valve pipelines or the result of catalyst carbonization. It provides a good technical means to improve the overall value of inferior ethylene tar raw materials.

Claims

1. A process for hydrogenating full-fraction ethylene tar, characterized in that: Includes the following steps: (1) Hydrogenation reaction: Ethylene tar is mixed with reaction improver and then mixed with hydrogen and fed into the hydrogenation reactor. Under the action of hydrogenation catalyst, hydrogenation treatment is carried out to obtain hydrogenation reaction effluent, which is an oil-gas mixture; the reaction improver is a nonionic surfactant. (2) High-pressure separation: The hydrogenation reaction effluent enters the high-pressure separator, and after separation, high-precision gas and high-pressure product oil are obtained; (3) Low-pressure separation: High-pressure generated oil enters the low-pressure separator. The low-pressure separator is equipped with a bottom outlet and a side line extraction outlet. After processing, low-pressure gas, low-pressure generated oil and side line extraction oil are obtained. The side line extraction oil is extracted from the side line extraction outlet, and the low-pressure generated oil is discharged from the bottom outlet. (4) Circulating blending: The side-stream extracted oil is recycled back to the ethylene tar in step (1) for blending; The reaction-improving agent is sorbitan monooleate.

2. The whole-fraction ethylene tar hydrogenation process according to claim 1, characterized in that: Ethylene tar has an asphaltenes content of 16-36 wt%, a sulfur content of less than 0.2 wt%, and a distillation range of 165-660℃.

3. The whole-fraction ethylene tar hydrogenation process according to claim 1, characterized in that: The mass ratio of reaction improver to ethylene tar is 100~600 μg·g. -1 .

4. The whole-fraction ethylene tar hydrogenation process according to claim 1, characterized in that: The operating conditions for the hydrogenation reaction stage are: reaction temperature 220~390℃, reaction pressure 2.2~14.5MPa, and volume hourly space velocity 0.1~2.0h⁻¹. -1 The hydrogen-to-oil volume ratio is 150-900.

5. The whole-fraction ethylene tar hydrogenation process according to claim 1, characterized in that: During the high-pressure separation stage, the operating conditions of the high-pressure separator are: temperature of 180~280℃ and reaction pressure of 3.0~5.5MPa.

6. The whole-fraction ethylene tar hydrogenation process according to claim 1, characterized in that: During the low-pressure separation stage, the operating conditions of the low-pressure separator are: temperature of 100~180℃ and reaction pressure of 1.0~2.5MPa.

7. The whole-fraction ethylene tar hydrogenation process according to claim 1, characterized in that: During the low-pressure separation stage, the mass ratio of the side-stream extracted oil to the low-pressure generated oil is (1~15):(85~100).

8. The whole-fraction ethylene tar hydrogenation process according to claim 7, characterized in that: The side-stream extracted oil contains more than 70% aromatics, of which more than 20% are methyltetrahydronaphthalene, tetrahydronaphthalene and cycloalkane aromatic components.

9. The whole-fraction ethylene tar hydrogenation process according to claim 7, characterized in that: The low-pressure product oil is further stripped with hydrogen to obtain hydrotreated product oil, which has a distillation range of 70~600℃.

10. The whole-fraction ethylene tar hydrogenation process according to claim 7, characterized in that: The low-pressure product oil is further stripped with hydrogen to obtain hydrotreated product oil, which has a distillation range of 75~580℃.

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