A process for efficient separation and aromatic enrichment of oil slurry based on supercritical extraction

Abstract

The application discloses a supercritical extraction-based efficient separation and aromatic hydrocarbon enrichment process of oil slurry, and relates to the technical field of hydrocarbon oil refining in petroleum refining. The process is characterized in that: first, solid impurities are removed from the oil slurry, and then components are cut step by step through a staged supercritical countercurrent extraction under a staged pressure; modified adsorption fillers are filled in a high-pressure enrichment tower, and the modified adsorption fillers are obtained by anchoring aluminum salt-modified attapulgite particles on a honeycomb ceramic base. The four-stage staged extraction process is realized through solid-removing pretreatment, medium-pressure deasphalting, vacuum dealkylation, high-pressure three-ring and four-ring aromatic hydrocarbon enrichment, and the modified adsorption fillers are filled in the extraction tower, so that active sites on surfaces of the fillers can synchronously capture metal complexes, sulfur-nitrogen heterocycles and heavy resins in a dissolved state in the countercurrent extraction process, and the content of metal impurities, sulfur-containing and nitrogen-containing heterocycles in the three-ring and four-ring aromatic hydrocarbons is reduced.

Description

Technical Field

[0001] This application relates to the field of hydrocarbon refining technology in petroleum refining, and in particular to a process for efficient separation of oil slurry and enrichment of aromatics based on supercritical extraction. Background Technology

[0002] Oil slurry is rich in polycyclic aromatic hydrocarbon components, making it a high-quality raw material for preparing high-value-added carbon materials such as oil-based needle coke, COPNA resin, impregnated pitch, and high-end carbon black. However, oil slurry also contains impurities such as catalyst solid particles, asphaltenes, heavy gums, metal complexes, and sulfur-nitrogen heterocyclic compounds. Direct application of oil slurry will seriously degrade the structure and performance of downstream carbon materials. Therefore, it must be refined and separated before it can be used as a raw material for high-end carbon materials.

[0003] Currently, the mainstream industrial processes for oil slurry pretreatment and refining include solvent refining, vacuum distillation, electrostatic removal, and sedimentation filtration. Among these, the traditional furfural solvent refining process is the most widely used. However, this process suffers from inherent drawbacks such as a long process flow, high equipment investment, and high energy consumption. Furthermore, furfural is toxic, resulting in high costs for waste treatment and significant environmental pressure. Additionally, this process can only achieve coarse separation of aromatics and saturated hydrocarbons, failing to precisely cut aromatics according to ring number, making it difficult to balance aromatic yield and product purity, and thus unable to meet the stringent requirements of high-end needle coke and other products for raw material composition. Vacuum distillation, on the other hand, suffers from high separation temperatures, easy thermal condensation and coking of heavy components, poor precision in narrow fraction cutting, and ineffective removal of ash and metallic impurities.

[0004] Supercritical fluid extraction technology, with its significant advantages such as continuously adjustable solvent solubility, high mass transfer efficiency, easy solvent recovery and separation, and environmental friendliness, is gradually becoming the mainstream development direction for oil slurry refining and separation technology. Existing publicly available supercritical extraction oil slurry preparation processes use isopentane as the main extraction solvent. Through a three-stage extraction tower, the solvent solubility is controlled by progressively increasing the temperature within a single pressure range, sequentially achieving asphaltenes removal, mixed aromatics precipitation, and alkane separation. This yields a mixed aromatics product with low ash and asphaltenes content, meeting the feedstock requirements of ordinary oil-based needle coke and significantly improving the utilization value of the oil slurry.

[0005] However, existing supercritical extraction processes lack sufficient precision in aromatic hydrocarbon separation, making it difficult to selectively enrich tri- to tetracyclic aromatic hydrocarbons. This limits the potential for increasing product added value and fails to meet the raw material quality requirements of high-end carbon materials. Furthermore, when used to prepare needle coke materials, the product purification level is insufficient. The removal of trace metal complexes, sulfur and nitrogen heterocyclic compounds, heavy colloids, and other polar impurities dissolved and dispersed in the aromatic hydrocarbon phase is limited, resulting in high metal, sulfur, and nitrogen content in the aromatic hydrocarbon products. Subsequent hydrogenation refining processes are usually required to meet the specifications, increasing the process length and production operating costs.

[0006] Therefore, it is necessary to develop a supercritical oil extraction process that can achieve enrichment and deep deimpurification of tri- to tetra-cyclic aromatics to meet the requirements of high-end carbon material industries such as needle coke for aromatic feedstocks. Summary of the Invention

[0007] In order to solve at least one of the above-mentioned technical problems, and to develop an oil slurry supercritical extraction process that can achieve enrichment and deep deimpurification of tri- to tetra-ring aromatics, this application provides an oil slurry high-efficiency separation and aromatic enrichment process based on supercritical extraction.

[0008] On the one hand, the high-efficiency oil slurry separation and aromatic hydrocarbon enrichment process based on supercritical extraction provided in this application includes the following steps:

[0009] S1. Remove solid impurities from the oil slurry to obtain a clear oil slurry after solidification.

[0010] S2. The clarified oil slurry is subjected to countercurrent extraction with the first extractant to obtain a first extract containing alkanes, monocyclic to pentacyclic aromatics and the first extractant; at the same time, a first raffinate containing asphaltenes, heavy gums and residual ash is obtained.

[0011] S3. After reducing the pressure of the first extract, near-critical countercurrent extraction is performed using the second extractant to obtain a second extract containing alkanes, light aromatics with tricyclic rings or less, and the second extractant. At the same time, a second raffinate containing medium and heavy aromatics with tricyclic rings or more is obtained.

[0012] S4. After pressurizing the second raffinate, high-pressure supercritical countercurrent extraction is carried out in an extraction tower packed with modified adsorption packing through a third extractant to obtain a medium aromatic hydrocarbon enrichment solution containing three to four rings; at the same time, a third extract containing the third extractant and a third raffinate containing heavy aromatic hydrocarbons containing five rings or more are obtained.

[0013] The modified adsorption filler in S4 uses honeycomb ceramic as the matrix, and is obtained by anchoring aluminum salt modified attapulgite particles on the matrix through aluminum sol.

[0014] The above technical solution sets up an independent physical desolidification unit before the extraction and separation process to remove catalyst solid particles and mechanical impurities from the oil slurry in advance, reduce the interference of impurities on the subsequent extraction, separation and adsorption depurification processes, and avoid solid particles clogging the packing pores and coating the adsorption active sites.

[0015] Based on the core characteristic of supercritical fluids, whose solubility is continuously adjustable with density, the dissolution boundary of each extraction stage is adjusted by controlling the extraction pressure and temperature, achieving precise step-by-step extraction of components and targeted enrichment of tri- and tetra-cyclic aromatic hydrocarbons. By filling modified adsorption packing material, a large number of aluminum hydroxyl active sites are formed on the surface of the aluminum salt-modified attapulgite. Through acid-base interactions and coordination, these sites can target and capture polar metal complexes, sulfur- and nitrogen heterocyclic compounds, and heavy colloids dissolved in the oil phase, reducing the impurity content in the enriched tri- and tetra-cyclic aromatic hydrocarbons and improving purity. The resulting indicators are directly compatible with the raw material requirements of high-end carbon materials such as needle coke.

[0016] Optionally, the modified adsorption filler is prepared by: washing the honeycomb ceramic with alkali to remove oil, washing with acid to remove impurities, rinsing until neutral, and then drying and calcining to obtain the matrix;

[0017] After removing impurities from the attapulgite, it is crushed and sieved, then water is added to form a suspension and stirred to disperse it. An aluminum nitrate solution is prepared and added to the suspension, the pH is adjusted to 4.0~5.0, and the mixture is stirred in a water bath at a constant temperature to obtain an aluminum salt modified attapulgite suspension.

[0018] Aluminum salt modified attapulgite suspension was added to aluminum sol and polyethylene glycol, stirred and defoamed to obtain a coating slurry. The matrix was immersed in the coating slurry, fully wetted and dried, then heated and calcined to solidify. After cooling, the modified adsorbent filler was obtained.

[0019] Aluminum salt modification introduces a large number of Lewis acid active sites on the attapulgite surface through chemical bonding of aluminum hydroxide with silanol groups at pH 4.0-5.0. This allows for the directional adsorption of polar sulfur-nitrogen heterocycles and metal-colloidal complexes via acid-base interactions, reducing the impurity content in tri- and tetra-cyclic aromatic hydrocarbons. Using homologous aluminum sol as a binder, after calcination, it forms a continuous alumina binder phase with the modified attapulgite, ensuring the bonding strength between the active particles and the honeycomb ceramic matrix, preventing powder shedding and product contamination under supercritical fluid scouring, and avoiding clogging of adsorption channels. Polyethylene glycol, after pore formation and subsequent calcination and evaporation, forms mesoporous channels, enhancing the mass transfer and diffusion of supercritical fluids.

[0020] Optionally, in the preparation method of the modified adsorption filler, cobalt nitrate solution is added along with aluminum nitrate solution.

[0021] By simultaneously introducing cobalt nitrate during aluminum salt modification, a cobalt-aluminum composite modified attapulgite adsorption layer is formed. Cobalt can coordinate with sulfur atoms in macromolecular sulfides such as benzothiophene and dibenzothiophene, compensating for the insufficient selectivity of aluminum modification for macromolecular fused-ring sulfides. It also forms a synergistic adsorption effect with aluminum sites, broadening the adsorption coverage for sulfur and nitrogen impurities with different structures. This further enhances the removal capacity of macromolecular sulfur and nitrogen impurities, meeting the sulfur content requirements of high-end needle coke feedstocks, and further reducing the load and cost of subsequent hydrorefining.

[0022] Optionally, in S2, the first extractant is isopentane, the extraction temperature is 175~210℃, and the extraction pressure is 4.5~6MPa;

[0023] In S3, the second extractant is isopentane, the extraction temperature is 170~205℃, and the extraction pressure is 3.5~4.5MPa;

[0024] In S4, the third extractant is a mixture of isopentane and methylcyclopentane, wherein the mass percentage of methylcyclopentane is 10-12%, the extraction temperature is 220-255℃, and the extraction pressure is 15-18MPa.

[0025] By adopting the above technical solution, the pressure and temperature parameters of each tower are matched with the dissolution windows of the corresponding components. The medium pressure range of S2 ensures that alkanes and five-ring and smaller aromatic hydrocarbons are fully dissolved and asphaltenes are precipitated. The reduced pressure of S3 decreases the solvent's dissolution capacity, allowing three-ring and larger aromatic hydrocarbons to be accurately precipitated, while alkanes and light aromatic hydrocarbons remain dissolved. The high pressure of S4 significantly increases the solvent density. Methylcyclopentane, as a weakly polar cycloalkane, can enhance the solvent's selectivity for dissolving polycyclic aromatic hydrocarbons through π-π interactions, inhibit the co-dissolution of heavy aromatic hydrocarbons, and the compounded solvent selectively dissolves three- and four-ring aromatic hydrocarbons, achieving a clear separation from five-ring heavy aromatic hydrocarbons.

[0026] Optionally, in S1, solid impurities are removed from the oil slurry to obtain a clarified oil slurry after solidification, including:

[0027] The oil slurry is preheated, and then mixed with alkane-rich oil to reduce viscosity. The slurry after viscosity reduction is first subjected to primary coarse separation by a hydrocyclone separator to remove large particles of catalyst and impurities, and then obtained primary desoldered oil.

[0028] The primary desolidified oil is subjected to secondary separation using a high-speed horizontal screw centrifuge to remove medium-sized particulate catalyst, yielding secondary desolidified oil.

[0029] The secondary desolidified oil is subjected to tertiary fine filtration through a two-stage series cross-flow ceramic membrane system to remove ultrafine catalyst particles and obtain a clarified oil slurry.

[0030] By using self-produced alkane-rich oil to reduce viscosity, the catalyst agglomerates encapsulated in colloids can be broken down, releasing the encapsulated ultrafine particles and preventing particles from being trapped in the agglomerates. The particles are then removed in stages from large to small: large particles are removed by cyclone, medium particles by centrifuge, and ultrafine particles by ceramic membrane. This solves the problems of incomplete removal of ultrafine particles, easy blockage of extraction tower and packing, and poor stability during long-term operation in existing solidification processes.

[0031] Optionally, it also includes: after pressurizing the first raffinate, supercritical countercurrent extraction is performed to recover it through a fourth extractant to obtain a fourth extract containing pentacyclic or higher heavy aromatic hydrocarbons and the fourth extractant, while simultaneously obtaining a fourth raffinate containing highly concentrated asphaltenes and ash.

[0032] The fourth extractant is isopentane, the extraction temperature is 190~220℃, and the extraction pressure is 22~25MPa.

[0033] By extracting and recovering pentacyclic and higher heavy aromatic hydrocarbons from deoiled asphalt, the density of isopentane solvent is greatly increased under ultra-high pressure conditions of 22~25MPa, and the dissolving capacity breaks through the limit of conventional extraction. Soluble pentacyclic and higher heavy aromatic hydrocarbon components in the asphalt phase can be fully dissolved and separated from insoluble asphaltenes and ash, thereby improving the resource utilization rate of high-value-added heavy aromatic hydrocarbon components.

[0034] Secondly, this application provides a high-efficiency oil slurry separation and aromatic hydrocarbon enrichment system based on supercritical extraction, including an oil slurry desolidification unit, a primary deasphalting extraction tower, a dealkane extraction tower, and a medium aromatic hydrocarbon enrichment extraction tower.

[0035] The clarified slurry obtained from the slurry desolidification unit enters the first-stage deasphalting extraction tower from the top outlet through the top inlet of the first-stage deasphalting extraction tower.

[0036] The first extract obtained from the primary deasphalting extraction tower enters the dealkane extraction tower from the top outlet of the tower through the top inlet of the dealkane extraction tower.

[0037] The second raffinate obtained from the dealkane extraction tower enters the medium aromatic hydrocarbon enrichment extraction tower from the bottom outlet of the tower through the top inlet of the medium aromatic hydrocarbon enrichment extraction tower.

[0038] The lower section of the medium aromatic hydrocarbon enrichment and extraction tower is filled with modified adsorption packing, and the medium aromatic hydrocarbon enrichment liquid with three to four rings is extracted from the side outlet in the middle of the tower.

[0039] Optionally, it also includes a heavy aromatics recovery and extraction tower; the first raffinate obtained from the primary deasphalting extraction tower enters the heavy aromatics recovery and extraction tower from the bottom outlet of the tower through the top inlet of the heavy aromatics recovery and extraction tower.

[0040] The third raffinate obtained from the medium aromatics enrichment and extraction tower enters the heavy aromatics recovery and extraction tower from the bottom outlet of the tower through the top inlet of the heavy aromatics recovery and extraction tower.

[0041] Optionally, it also includes a solvent recovery unit; the second extract obtained from the dealkane extraction tower enters the solvent recovery unit from the top outlet of the tower through the inlet of the solvent recovery unit;

[0042] The fourth extract obtained from the heavy aromatic hydrocarbon recovery extraction tower enters the solvent recovery unit from the top outlet of the tower through the inlet of the solvent recovery unit;

[0043] The extractant recovered by the solvent recovery unit is recycled back into the tower from the solvent outlet through the bottom inlet of the primary deasphalting extraction tower and / or the dealkane extraction tower and / or the medium aromatics enrichment extraction tower.

[0044] Optionally, the third extract obtained from the aromatic hydrocarbon enrichment extraction tower is returned from the top outlet of the tower to the top inlet of the dealkane extraction tower for internal circulation and separation.

[0045] In summary, this invention employs a four-stage extraction process involving pretreatment for desolidification, medium-pressure deasphalting, reduced-pressure dealkane removal, and high-pressure enrichment of tri- and tetra-cyclic aromatic hydrocarbons. Furthermore, by packing modified adsorption packing material into the extraction tower, the active sites on the packing surface are utilized to simultaneously capture dissolved metal complexes, sulfur- and nitrogen-containing heterocycles, and heavy colloids during the countercurrent extraction process, thereby reducing the content of metal impurities and sulfur- and nitrogen-containing heterocycles in tri- and tetra-cyclic aromatic hydrocarbons. Detailed Implementation

[0046] The present application will be further described in detail below with reference to the embodiments.

[0047] Unless otherwise specified, all major components involved in the following embodiments of this application are purchased from commercially available products.

[0048] The basic properties of the oil slurry used in this application are shown in Table 1.

[0049] Table 1

[0050]

[0051] Isopentane: Purity ≥ 99.0%.

[0052] Methylcyclopentane: purity ≥ 98.0%.

[0053] Attapulgite clay: mineral purity approximately 85%, produced in Xuyi, Jiangsu Province.

[0054] Aluminum sol: Al2O3 mass fraction 20%.

[0055] Polyethylene glycol: PEG-400, analytical grade.

[0056] Cellular ceramic substrate: cordierite, 150 cpsi, wall thickness 0.4 mm.

[0057] Preparation Example 1

[0058] This preparation example is used to prepare the modified adsorption packing material of this application, as detailed below.

[0059] Cordierite honeycomb ceramic was cut into regular blocks of 100mm×100mm×150mm, immersed in a 5wt% sodium hydroxide solution, and soaked at a constant temperature of 80℃ for 2 hours to remove oil. It was then taken out and rinsed with deionized water until neutral, and then immersed in a 5wt% hydrochloric acid solution at 60℃ for 1 hour to dissolve the free metal on the surface. After rinsing again until neutral, it was dried at 120℃ for 4 hours, calcined at 500℃ for 2 hours, and naturally cooled to obtain the pretreated matrix.

[0060] The attapulgite soil was crushed and passed through a 200-mesh sieve. Deionized water was added to prepare a 6wt% suspension. After high-speed stirring for 30 minutes, the suspension was allowed to settle for 2 hours, and the lower coarse residue was discarded. The upper suspension was centrifuged at 3000 rpm for 10 minutes, and the lower fine impurities were discarded to obtain a purified attapulgite concentrate with a solid content of 10.5wt%. The concentrate was diluted to a solid content of 8wt%, and 1.0mol / L aluminum nitrate solution was added according to the final Al2O3 loading of 10wt%. The pH was slowly adjusted to 4.5 with dilute ammonia water, and the suspension was stirred at a constant temperature of 70℃ for 2.5 hours to obtain an aluminum salt modified attapulgite suspension.

[0061] Aluminum sol was added to the modified attapulgite suspension, and the Al2O3 content in the aluminum sol was controlled to be 15 wt% of the total solids in the slurry. Then, 0.8 wt% of PEG-400 relative to the total solids was added, and the mixture was homogenized at high speed for 30 min and ultrasonically defoamed for 10 min to obtain a coating slurry with a solid content of 25 wt%. The pretreated matrix was completely immersed in the slurry and allowed to stand for 8 min. It was then pulled out at a uniform speed of 3 cm / min, and the residual slurry in the pores was blown away with low-pressure air. After air drying at room temperature for 2 h, it was dried at 120℃ for 4 h and the coating was repeated twice. The temperature was increased to 400℃ at 2℃ / min and held for 3 h. The modified adsorbent filler was obtained by furnace cooling.

[0062] Preparation Example 2

[0063] This preparation example is used to prepare the modified adsorbent packing material of this application. The difference between this preparation example and preparation example 1 is that 2.5 wt% cobalt nitrate is added in this preparation example, as detailed below.

[0064] Cordierite honeycomb ceramic was cut into regular blocks of 100mm×100mm×150mm, immersed in a 5wt% sodium hydroxide solution, and soaked at a constant temperature of 80℃ for 2 hours to remove oil. It was then taken out and rinsed with deionized water until neutral, and then immersed in a 5wt% hydrochloric acid solution at 60℃ for 1 hour to dissolve the free metal on the surface. After rinsing again until neutral, it was dried at 120℃ for 4 hours, calcined at 500℃ for 2 hours, and naturally cooled to obtain the pretreated matrix.

[0065] The attapulgite soil was crushed and passed through a 200-mesh sieve. Deionized water was added to prepare a 6wt% suspension. After high-speed stirring for 30 min, the mixture was allowed to settle for 2 h, and the lower coarse residue was discarded. The upper suspension was centrifuged at 3000 rpm for 10 min, and the lower fine impurities were discarded to obtain a purified attapulgite concentrate with a solid content of 10.5wt%. The concentrate was diluted to a solid content of 8wt%. 1.0 mol / L aluminum nitrate solution was added according to the final Al2O3 loading of 10wt%, and 0.5 mol / L aluminum nitrate solution was added according to the final CoO loading of 2.5wt%. The pH was slowly adjusted to 4.5 with dilute ammonia water, and the mixture was stirred at a constant temperature of 70℃ for 2.5 h to obtain a cobalt-aluminum salt modified attapulgite suspension.

[0066] Aluminum sol was added to the modified attapulgite suspension, and the Al2O3 content in the aluminum sol was controlled to be 15 wt% of the total solids in the slurry. Then, 0.8 wt% of PEG-400 relative to the total solids was added, and the mixture was homogenized at high speed for 30 min and ultrasonically defoamed for 10 min to obtain a coating slurry with a solid content of 25 wt%. The pretreated matrix was completely immersed in the slurry and allowed to stand for 8 min. It was then pulled out at a uniform speed of 3 cm / min, and the residual slurry in the pores was blown away with low-pressure air. After air drying at room temperature for 2 h, it was dried at 120℃ for 4 h and the coating was repeated twice. The temperature was increased to 400℃ at 2℃ / min and held for 3 h. The modified adsorbent filler was obtained by furnace cooling. Specific Implementation

[0068] Example 1

[0069] This embodiment provides a process for efficient separation of oil slurry and enrichment of aromatics based on supercritical extraction, as detailed below.

[0070] The oil slurry was preheated to 100°C and mixed with the alkane-rich oil produced by the unit at a volume ratio of 8:1 to reduce viscosity. After mixing, the kinematic viscosity of the oil slurry was reduced to 76 mmHg. 2 / s; The viscosity-reduced oil slurry is first fed into a hydrocyclone separator for primary coarse separation at an operating pressure of 0.3 MPa to remove large catalyst particles larger than 20 μm, yielding primary desoldered oil; the primary desoldered oil is then fed into a high-speed horizontal screw centrifuge at 4000 rpm to remove medium particles of 5~20 μm, yielding secondary desoldered oil; the secondary desoldered oil is then fed into a two-stage series cross-flow ceramic membrane system, where it is sequentially filtered through ceramic membranes with pore sizes of 0.2 μm and 0.05 μm at an operating temperature of 140℃, yielding a clarified oil slurry with an ash content of 12 ppm on the permeate side.

[0071] The clarified oil slurry is heated to 180°C and fed from the top of the primary deasphalting extraction tower; the first extractant, isopentane, is fed from the bottom of the tower at a mass ratio of 5:1; the temperature inside the tower is controlled at 190°C and the pressure at 5.0 MPa, and countercurrent contact extraction is performed; the top of the tower yields the first extract containing alkanes, monocyclic to pentacyclic aromatics and isopentane, and the bottom of the tower yields the first raffinate containing asphaltenes, heavy gums and residual ash.

[0072] The first extract was depressurized to 4.0 MPa, heated to 185 °C, and fed from the top of the dealkane extraction column; the second extractant, isopentane, was fed from the bottom of the column at a mass ratio of 4:1; the temperature inside the column was controlled at 190 °C and the pressure at 4.0 MPa, and near-critical countercurrent extraction was performed; the top of the column yielded a second extract containing alkanes, light aromatics of bicyclic and smaller rings, and isopentane, and the bottom of the column yielded a second raffinate containing medium and heavy aromatics of tricyclic and larger rings.

[0073] The second raffinate phase was pressurized to 15 MPa and heated to 230 °C before being fed from the top of the aromatic hydrocarbon enrichment extraction tower. The third extractant was an isopentane-methylcyclopentane compound solvent, with methylcyclopentane accounting for 10% by mass, which was fed from the bottom of the tower at a solvent-to-oil mass ratio of 6:1. The temperature inside the tower was controlled at 235 °C and the pressure at 15 MPa, and high-pressure supercritical countercurrent extraction was performed.

[0074] The column is filled from bottom to top with the modified adsorption packing layer prepared in Preparation Example 1 and the 316L stainless steel Pall ring packing layer, wherein the height of the modified adsorption packing layer accounts for 1 / 3 of the total height of the packing layer; during the countercurrent process, the modified packing simultaneously adsorbs and removes dissolved metal complexes, sulfur and nitrogen heterocycles and heavy colloids; the side stream in the middle of the column is used to collect the enriched liquid of three and four ring aromatics, the top of the column is used to obtain the third extract containing light aromatics and compound solvent, and the bottom of the column is used to obtain the third raffinate containing five rings and above heavy aromatics; the third extract at the top of the column is returned to the feed end of the dealkane tower for recycling and separation.

[0075] Example 2

[0076] This embodiment provides a process for efficient separation of oil slurry and enrichment of aromatics based on supercritical extraction. The difference from Example 1 is that this embodiment uses the modified adsorption packing material prepared in Preparation Example 2. Otherwise, it is the same as Example 1, as detailed below.

[0077] The oil slurry was preheated to 100°C and mixed with the alkane-rich oil produced by the unit at a volume ratio of 8:1 to reduce viscosity. After mixing, the kinematic viscosity of the oil slurry was reduced to 76 mmHg. 2 / s; The viscosity-reduced oil slurry is first fed into a hydrocyclone separator for primary coarse separation at an operating pressure of 0.3 MPa to remove large catalyst particles larger than 20 μm, yielding primary desoldered oil; the primary desoldered oil is then fed into a high-speed horizontal screw centrifuge at 4000 rpm to remove medium particles of 5~20 μm, yielding secondary desoldered oil; the secondary desoldered oil is then fed into a two-stage series cross-flow ceramic membrane system, where it is sequentially filtered through ceramic membranes with pore sizes of 0.2 μm and 0.05 μm at an operating temperature of 140℃, yielding a clarified oil slurry with an ash content of 12 ppm on the permeate side.

[0078] The clarified oil slurry is heated to 180°C and fed from the top of the primary deasphalting extraction tower; the first extractant, isopentane, is fed from the bottom of the tower at a mass ratio of 5:1; the temperature inside the tower is controlled at 190°C and the pressure at 5.0 MPa, and countercurrent contact extraction is performed; the top of the tower yields the first extract containing alkanes, monocyclic to pentacyclic aromatics and isopentane, and the bottom of the tower yields the first raffinate containing asphaltenes, heavy gums and residual ash.

[0079] The first extract was depressurized to 4.0 MPa, heated to 185 °C, and fed from the top of the dealkane extraction column; the second extractant, isopentane, was fed from the bottom of the column at a mass ratio of 4:1; the temperature inside the column was controlled at 190 °C and the pressure at 4.0 MPa, and near-critical countercurrent extraction was performed; the top of the column yielded a second extract containing alkanes, light aromatics of bicyclic and smaller rings, and isopentane, and the bottom of the column yielded a second raffinate containing medium and heavy aromatics of tricyclic and larger rings.

[0080] The second raffinate phase was pressurized to 15 MPa and heated to 230 °C before being fed from the top of the aromatic hydrocarbon enrichment extraction tower. The third extractant was an isopentane-methylcyclopentane compound solvent, with methylcyclopentane accounting for 10% by mass, which was fed from the bottom of the tower at a solvent-to-oil mass ratio of 6:1. The temperature inside the tower was controlled at 235 °C and the pressure at 15 MPa, and high-pressure supercritical countercurrent extraction was performed.

[0081] The column is filled from bottom to top with the modified adsorption packing layer prepared in Preparation Example 2 and the 316L stainless steel Pall ring packing layer, wherein the height of the modified adsorption packing layer accounts for 1 / 3 of the total height of the packing layer; during the countercurrent process, the modified packing simultaneously adsorbs and removes dissolved metal complexes, sulfur and nitrogen heterocycles and heavy colloids; the side stream in the middle of the column is used to collect the enriched liquid of three and four ring aromatics, the top of the column is used to obtain the third extract containing light aromatics and compound solvent, and the bottom of the column is used to obtain the third raffinate containing five rings and above heavy aromatics; the third extract at the top of the column is returned to the feed end of the dealkane tower for recycling and separation.

[0082] Example 3

[0083] This embodiment provides a high-efficiency oil slurry separation and aromatic hydrocarbon enrichment process based on supercritical extraction. The difference from Embodiment 1 is that the extraction temperature of the first-stage deasphalting extraction tower is 210℃ and the extraction pressure is 6.0 MPa; the extraction temperature of the dealkane extraction tower is 205℃ and the extraction pressure is 4.5 MPa; the extraction temperature of the medium aromatic hydrocarbon enrichment extraction tower is 255℃ and the extraction pressure is 18 MPa; and the methylcyclopentane content in the third extractant is 12%. Details are as follows.

[0084] The oil slurry was preheated to 100°C and mixed with the alkane-rich oil produced by the unit at a volume ratio of 8:1 to reduce viscosity. After mixing, the kinematic viscosity of the oil slurry was reduced to 76 mmHg. 2 / s; The viscosity-reduced oil slurry is first fed into a hydrocyclone separator for primary coarse separation at an operating pressure of 0.3 MPa to remove large catalyst particles larger than 20 μm, yielding primary desoldered oil; the primary desoldered oil is then fed into a high-speed horizontal screw centrifuge at 4000 rpm to remove medium particles of 5~20 μm, yielding secondary desoldered oil; the secondary desoldered oil is then fed into a two-stage series cross-flow ceramic membrane system, where it is sequentially filtered through ceramic membranes with pore sizes of 0.2 μm and 0.05 μm at an operating temperature of 140℃, yielding a clarified oil slurry with an ash content of 12 ppm on the permeate side.

[0085] The clarified oil slurry is heated to 200°C and fed from the top of the primary deasphalting extraction tower; the first extractant, isopentane, is fed from the bottom of the tower at a mass ratio of 5:1; the temperature inside the tower is controlled at 210°C and the pressure at 6.0 MPa, and countercurrent contact extraction is performed; the top of the tower yields the first extract containing alkanes, monocyclic to pentacyclic aromatics and isopentane, and the bottom of the tower yields the first raffinate containing asphaltenes, heavy gums and residual ash.

[0086] The first extract was depressurized to 4.5 MPa, heated to 200 °C, and fed from the top of the dealkane extraction column; the second extractant, isopentane, was fed from the bottom of the column at a mass ratio of 4:1; the temperature inside the column was controlled at 205 °C and the pressure at 4.5 MPa, and near-critical countercurrent extraction was performed; the top of the column yielded a second extract containing alkanes, light aromatics of bicyclic and smaller, and isopentane, and the bottom of the column yielded a second raffinate containing medium and heavy aromatics of tricyclic and larger.

[0087] The second raffinate phase was pressurized to 18 MPa and heated to 250 °C before being fed from the top of the aromatic hydrocarbon enrichment extraction tower. The third extractant was an isopentane-methylcyclopentane complex solvent, with methylcyclopentane accounting for 12% by mass, which was fed from the bottom of the tower at a solvent-to-oil mass ratio of 6:1. The temperature inside the tower was controlled at 255 °C and the pressure at 18 MPa, and high-pressure supercritical countercurrent extraction was performed.

[0088] The column is filled from bottom to top with the aforementioned modified adsorption packing layer and the 316L stainless steel Pall ring packing layer, with the height of the modified adsorption packing layer accounting for 1 / 3 of the total height of the packing layer. During the countercurrent process, the modified packing simultaneously adsorbs and removes dissolved metal complexes, sulfur and nitrogen heterocycles, and heavy colloids. The side stream in the middle of the column produces a concentrated liquid of three- and four-ring aromatics, the top of the column yields a third extract containing light aromatics and a compound solvent, and the bottom of the column yields a third raffinate containing five-ring and above heavy aromatics. The third extract at the top of the column is returned to the feed end of the dealkane tower for recycling and separation.

[0089] Comparative Example 1

[0090] The same batch of catalytic slurry as in Example 1 was heated to 100°C and mixed evenly with the diluent isopentane at a volume ratio of 8:1. The mixture was then heated to 150°C and fed from the top of the asphalt extraction tower. The main solvent, isopentane, was fed from the bottom of the tower, with a volume ratio of 7:1 between the main solvent and the diluent. The temperature inside the tower was controlled at 160°C and the pressure at 4.5 MPa, and the two phases were subjected to countercurrent contact extraction. An extract containing aromatics and alkanes was obtained at the top of the tower, and the asphalt flowing out from the bottom of the tower was discharged into an asphalt collection tank.

[0091] The extract obtained at the top of the column is fed into the top of the aromatic oil extraction column. The temperature inside the column is controlled at 200℃ and the pressure at 4.5MPa, and countercurrent extraction continues. The top of the column yields an extract containing alkane oil, and the bottom of the column yields a mixed aromatic oil product.

[0092] The extract obtained from the top of the column is fed into the top of the supercritical light deoiling column. The temperature inside the column is controlled at 230℃ and the pressure at 4.5MPa for supercritical extraction and separation. The alkane oil product is obtained at the bottom of the column, and the solvent is recovered from the top of the column and recycled.

[0093] Comparative Example 2

[0094] The difference between this comparative example and Example 1 is that the entire aromatic hydrocarbon enrichment and extraction tower is filled with 316L stainless steel Pall rings, and no modified adsorption packing is used, as detailed below.

[0095] The oil slurry was preheated to 100°C and mixed with the alkane-rich oil produced by the unit at a volume ratio of 8:1 to reduce viscosity. After mixing, the kinematic viscosity of the oil slurry was reduced to 76 mmHg. 2 / s; The viscosity-reduced oil slurry is first fed into a hydrocyclone separator for primary coarse separation at an operating pressure of 0.3 MPa to remove large catalyst particles larger than 20 μm, yielding primary desoldered oil; the primary desoldered oil is then fed into a high-speed horizontal screw centrifuge at 4000 rpm to remove medium particles of 5~20 μm, yielding secondary desoldered oil; the secondary desoldered oil is then fed into a two-stage series cross-flow ceramic membrane system, where it is sequentially filtered through ceramic membranes with pore sizes of 0.2 μm and 0.05 μm at an operating temperature of 140℃, yielding a clarified oil slurry with an ash content of 12 ppm on the permeate side.

[0096] The clarified oil slurry is heated to 180°C and fed from the top of the primary deasphalting extraction tower; the first extractant, isopentane, is fed from the bottom of the tower at a mass ratio of 5:1; the temperature inside the tower is controlled at 190°C and the pressure at 5.0 MPa, and countercurrent contact extraction is performed; the top of the tower yields the first extract containing alkanes, monocyclic to pentacyclic aromatics and isopentane, and the bottom of the tower yields the first raffinate containing asphaltenes, heavy gums and residual ash.

[0097] The first extract was depressurized to 4.0 MPa, heated to 185 °C, and fed from the top of the dealkane extraction column; the second extractant, isopentane, was fed from the bottom of the column at a mass ratio of 4:1; the temperature inside the column was controlled at 190 °C and the pressure at 4.0 MPa, and near-critical countercurrent extraction was performed; the top of the column yielded a second extract containing alkanes, light aromatics of bicyclic and smaller rings, and isopentane, and the bottom of the column yielded a second raffinate containing medium and heavy aromatics of tricyclic and larger rings.

[0098] The second raffinate phase was pressurized to 15 MPa and heated to 230 °C before being fed from the top of the aromatic hydrocarbon enrichment extraction tower. The third extractant was an isopentane-methylcyclopentane compound solvent, with methylcyclopentane accounting for 10% by mass, which was fed from the bottom of the tower at a solvent-to-oil mass ratio of 6:1. The temperature inside the tower was controlled at 235 °C and the pressure at 15 MPa, and high-pressure supercritical countercurrent extraction was performed.

[0099] The tower is packed with 316L stainless steel Pall ring packing; a side stream from the middle of the tower extracts a concentrated liquid of three- and four-ring aromatics, a third extract containing light aromatics and a compound solvent is obtained at the top of the tower, and a third raffinate containing five-ring and above heavy aromatics is obtained at the bottom of the tower; the third extract at the top of the tower is returned to the feed end of the dealkane tower for recycling and separation.

[0100] The detection results of the tri- and tetra-cyclic aromatic hydrocarbon enriched solutions prepared in Examples 1-3 and Comparative Examples 1-2 are shown in Table 2.

[0101] Table 2

[0102]

[0103] Comparing Example 1 and Comparative Example 1, it can be seen that this application employs a four-stage extraction process involving pretreatment, medium-pressure deasphalting, reduced-pressure dealkane removal, and high-pressure enrichment of tri- and tetra-cyclic aromatics. By packing modified adsorption packing material into the extraction tower, the active sites on the packing surface are utilized to simultaneously capture dissolved metal complexes, sulfur- and nitrogen-containing heterocycles, and heavy colloids during countercurrent extraction, thereby reducing the content of metal impurities and sulfur- and nitrogen-containing heterocycles in tri- and tetra-cyclic aromatics. The proportion of tri- and tetra-cyclic aromatics in the main product is increased from 42.97% to over 78%, and the total purity of aromatics is increased from 73.28% to over 92%. The component uniformity is significantly improved, making it suitable as a raw material for high-end oil-based needle coke and COPNA resin, thus increasing the added value of the product.

[0104] Comparing Example 1 and Comparative Example 2, it can be seen that after adding modified adsorption packing material to the medium aromatic hydrocarbon enrichment extraction tower, the total Ni+V content in the main product decreased from 5.7 μg / g to 2.1 μg / g, with a removal rate of 63%; the sulfur content decreased from 0.29 wt% to 0.18 wt%, with a removal rate of 38%; and the nitrogen content decreased from 760 μg / g to 420 μg / g, with a removal rate of 45%. Comparing Example 1 and Example 2, it can be seen that after using cobalt-aluminum salt to modify attapulgite, the sulfur and nitrogen removal effect is further improved, which can omit or significantly simplify the subsequent hydrogenation refining process, shorten the process, and reduce costs.

[0105] Example 4

[0106] This embodiment provides a high-efficiency oil slurry separation and aromatic hydrocarbon enrichment process based on supercritical extraction. It adds a heavy aromatic hydrocarbon recovery step to the process described in Example 1, as follows:

[0107] The first and third raffinate phases are mixed and pressurized to 23 MPa, heated to 205 °C, and fed from the top of the heavy aromatics recovery extraction tower. The fourth extractant, isopentane, is fed from the bottom of the tower at a mass ratio of 7:1. The temperature inside the tower is controlled at 205 °C and the pressure at 23 MPa, and ultra-high pressure supercritical countercurrent extraction is performed. The top of the tower yields a fourth extract containing pentacyclic and higher heavy aromatics and isopentane, while the bottom yields highly concentrated asphaltenes and ash residue. The fourth extract is sent to the solvent recovery unit to recover the solvent, and then the heavy aromatics product is obtained.

[0108] This embodiment adds an ultra-high pressure heavy aromatic hydrocarbon recovery step, which can further recover high-value-added heavy aromatic hydrocarbon components from asphalt residue, reduce the amount of residue discharged, and improve the overall economic benefits of the process.

[0109] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A process for efficient separation and aromatic enrichment of oil slurry based on supercritical fluid extraction, characterized in that, Includes the following steps: S1. Remove solid impurities from the oil slurry to obtain a clear oil slurry after solidification. S2. The clarified oil slurry is subjected to countercurrent extraction with the first extractant to obtain a first extract containing alkanes, monocyclic to pentacyclic aromatics and the first extractant; at the same time, a first raffinate containing asphaltenes, heavy gums and residual ash is obtained; the first extractant is isopentane, the extractant-to-oil mass ratio is 5:1, the extraction temperature is 175~210℃, and the extraction pressure is 4.5~6MPa. S3. After reducing the pressure of the first extract, near-critical countercurrent extraction is performed using a second extractant to obtain a second extract containing alkanes, light aromatics with tricyclic rings or less, and the second extractant. At the same time, a second raffinate containing medium and heavy aromatics with tricyclic rings or more is obtained. The second extractant is isopentane, with an extractant-to-oil mass ratio of 4:1, an extraction temperature of 170~205℃, and an extraction pressure of 3.5~4.5MPa. S4. After pressurizing the second raffinate, high-pressure supercritical countercurrent extraction is performed in an extraction tower packed with modified adsorption packing using a third extractant to obtain a medium-aromatic hydrocarbon enrichment solution containing three to four rings; simultaneously, a third extract containing the third extractant and a third raffinate containing heavy aromatic hydrocarbons containing five rings or more are obtained; the third extractant is a mixture of isopentane and methylcyclopentane, wherein the mass percentage of methylcyclopentane is 10-12%, the extractant-to-oil mass ratio is 6:1, the extraction temperature is 220-255℃, and the extraction pressure is 15-18MPa; The modified adsorption filler in S4 uses honeycomb ceramic as the matrix, and is obtained by anchoring aluminum salt modified attapulgite particles on the matrix through aluminum sol.

2. The process for efficient oil slurry separation and aromatic hydrocarbon enrichment based on supercritical extraction according to claim 1, characterized in that, The modified adsorption filler is prepared by: The honeycomb ceramic is degreased by alkaline washing, impurities removed by acid washing, rinsed until neutral, dried and calcined to obtain the matrix; After removing impurities from the attapulgite, it is crushed and sieved, then water is added to form a suspension and stirred to disperse it. An aluminum nitrate solution is prepared and added to the suspension according to the final Al2O3 loading on the calcined filler of 10wt%. The pH is adjusted to 4.0~5.0, and the mixture is stirred in a water bath at a constant temperature to obtain an aluminum salt modified attapulgite suspension. Aluminum salt-modified attapulgite suspension was added to alumina sol and polyethylene glycol, stirred, and defoamed to obtain a coating slurry. Based on the total solids of the coating slurry, the alumina sol contained 15 wt% Al2O3 and 0.8 wt% PEG-400. The matrix is ​​immersed in the coating slurry, fully wetted, dried, then heated and calcined to solidify, and cooled to obtain the modified adsorbent filler.

3. The process for efficient oil slurry separation and aromatic hydrocarbon enrichment based on supercritical extraction according to claim 2, characterized in that, In the preparation method of the modified adsorption packing, while adding aluminum nitrate solution, cobalt nitrate solution is also added at a final CoO loading of 2.5 wt% on the packing after calcination.

4. The process for efficient oil slurry separation and aromatic hydrocarbon enrichment based on supercritical extraction according to claim 1, characterized in that, In S1, solid impurities are removed from the oil slurry to obtain a clarified oil slurry after solidification, including: The oil slurry is preheated, and then mixed with alkane-rich oil to reduce viscosity. The slurry after viscosity reduction is first subjected to primary coarse separation by a hydrocyclone separator to remove large particles of catalyst and impurities, and then obtained primary desoldered oil. The primary desolidified oil is subjected to secondary separation using a high-speed horizontal screw centrifuge to remove medium-sized particulate catalyst, yielding secondary desolidified oil. The secondary desolidified oil is subjected to tertiary fine filtration through a two-stage series cross-flow ceramic membrane system to remove ultrafine catalyst particles and obtain a clarified oil slurry.

5. The process for efficient oil slurry separation and aromatic hydrocarbon enrichment based on supercritical extraction according to claim 1, characterized in that, Also includes: After pressurizing the first raffinate, it is recovered by supercritical countercurrent extraction using the fourth extractant to obtain a fourth extract containing pentacyclic and above heavy aromatic hydrocarbons and the fourth extractant, while also obtaining a fourth raffinate containing highly concentrated asphaltenes and ash. The fourth extractant is isopentane, the extraction temperature is 190~220℃, and the extraction pressure is 22~25MPa.

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