Process for upgrading a hydrocarbon feedstock

Abstract

A process for upgrading a hydrocarbon feedstock can include introducing the hydrocarbon feedstock to a hydrocracking unit to obtain a hydrocracked product, introducing the hydrocracked product to a fractionation unit to obtain distillate oil and unconverted oil, the unconverted oil having a boiling point higher than 375°C, introducing the unconverted oil and supercritical water to a supercritical water unit to obtain a treated product, wherein the supercritical water has a pressure greater than 21 MPa and a temperature higher than 374°C, and separating the treated product to obtain a purified product and a concentrated product, wherein the concentrated product comprises heavy polynuclear aromatic hydrocarbons (HPNA).

Description

Cross-references to related applications

[0001] This application claims the benefit of U.S. Patent Application No. 18 / 439,417, filed February 12, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The implementation schemes described in this article generally relate to methods for upgrading hydrocarbon feedstocks. Background Technology

[0003] Hydrocracking uses catalysts and hydrogen to break down large hydrocarbon molecules into smaller ones, producing products that can be used as fuels and chemical feedstocks.

[0004] Hydrocracking catalysts often coke, thus shortening catalyst lifetime. Coke precursors present in the feed or formed in the reactor undergo coupling, condensation, cyclization, aromatization, and dehydrogenation reactions to form coke on the catalyst. Coke is formed from strongly adsorbed aromatic compounds on the catalyst surface and subsequent condensation reactions. To compensate for the reduced catalyst activity caused by coking, the severity of process conditions may be increased. However, higher process severity accelerates coke formation, ultimately leading to catalyst deactivation.

[0005] Generally, typical hydrocarbon feedstocks used in hydrocracking, such as vacuum gas oil (VGO), contain polynuclear aromatics with 2 to 6 rings. The ring number can be increased through coupling or condensation reactions occurring under the high-temperature conditions typically used in hydrocracking, thus forming heavy polynuclear aromatics. Heavy polynuclear aromatics contain 7 or more (7+) aromatic rings, are uncharged, nonpolar, and have a planar structure, making them highly efficient coke precursors. During the hydrocracking reaction, heavy polynuclear aromatics are formed by the coupling or condensation of smaller polynuclear aromatics and monocyclic aromatics. Under conventional hydrocracking conditions, heavy polynuclear aromatics are inert and therefore are usually not decomposed or hydrogenated. Therefore, improved methods for upgrading hydrocarbon feedstocks are needed to address the catalyst deactivation problem caused by heavy polynuclear aromatics. Summary of the Invention

[0006] The embodiments of this disclosure address this and other requirements by utilizing supercritical water treatment to reduce heavy polynuclear aromatic hydrocarbons (HPNAs) in upgraded hydrocarbons. The method may include introducing a hydrocarbon feedstock into a hydrocracking unit to obtain hydrocracking products, introducing the hydrocracking products into a fractionation unit to obtain distillate oil and unconverted oil, the unconverted oil having a boiling point above 375°C, introducing the unconverted oil and supercritical water into a supercritical water (SCW) unit to obtain treated products, wherein the supercritical water has a pressure greater than 21 MPa and a temperature above 374°C, and separating the treated products to obtain purified products and concentrated products, wherein the concentrated products contain heavy polynuclear aromatic hydrocarbons (HPNAs).

[0007] It should be understood that the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. Other features and advantages of the embodiments will be set forth in the detailed description and, in part, will be readily understood by those skilled in the art based on the description (including the appended drawings and claims) or will be recognized through practice of the described embodiments. The included drawings are intended to provide a further understanding of the embodiments and, together with the detailed description, serve to explain the principles and operation of the claimed subject matter. However, the embodiments depicted in the drawings are illustrative and exemplary in nature and are not intended to limit the claimed subject matter. Attached Figure Description

[0008] The following detailed explanation will be better understood by referring to the accompanying diagrams, in which: Figure 1 A schematic diagram of an example system for upgrading hydrocarbon feedstocks is shown, which can be applied to a method for upgrading hydrocarbon feedstocks.

[0009] Figure 2 A schematic diagram of an example setup for an SCW unit is shown.

[0010] Figure 3 A schematic diagram of a comparative method for upgrading hydrocarbon feedstock is shown. Detailed Implementation

[0011] This disclosure generally relates to a method for upgrading hydrocarbon feedstocks. The method typically includes introducing the hydrocarbon feedstock into a hydrocracking unit to obtain hydrocracking products, introducing the hydrocracking products into a fractionation unit to obtain distillate oil and unconverted oil, the unconverted oil having a boiling point above 375°C, introducing the unconverted oil and supercritical water into a supercritical water unit to obtain treated products, wherein the supercritical water has a pressure greater than 21 MPa and a temperature above 374°C, and separating the treated products to obtain purified products and heavy polynuclear aromatics.

[0012] As used in this disclosure, "catalyst" means any inorganic substance other than water that increases the rate of a particular chemical reaction.

[0013] As used in this disclosure, "cracking" generally refers to a chemical reaction in which a molecule having carbon-carbon bonds is broken into more than one molecule by breaking one or more carbon-carbon bonds; a compound containing a cyclic moiety (such as an aromatic hydrocarbon) is converted into a compound not containing a cyclic moiety; or a molecule having a carbon-carbon double bond is reduced to a carbon-carbon single bond. Some catalysts may exhibit multiple forms of catalytic activity, and naming a catalyst after a particular function does not mean that the catalyst cannot be catalytically active for other functions.

[0014] As used throughout this disclosure, “crude oil” means full-range crude oil, distilled crude oil, residue oil, top-extracted crude oil, refinery product streams, steam cracking product streams, liquefied coal, liquid products recovered from oil sands or tar sands, bitumen, oil shale, asphaltenes, biomass hydrocarbons, liquid products from gas-to-liquid (GTL) processes, liquid products from chemically recovered waste plastics / municipal waste, and other similar petroleum-based oils.

[0015] As used in this disclosure, "hydrocracking" refers to cracking that occurs in the presence of hydrogen (such as hydrogen gas or hydrogen in the form of a hydrogen donor).

[0016] As used throughout this disclosure, “Standard Ambient Temperature and Pressure” or “SATP” means conditions of 25°C and 100 kPa.

[0017] As used throughout this disclosure, “supercritical” refers to a substance that exists at pressures and temperatures above its critical pressures and temperatures, such that there are no distinguishable phases and the substance exhibits gaseous diffusivity while also dissolving like a liquid.

[0018] As used throughout this disclosure, “supercritical water” or “SCW” means water with a temperature above the critical temperature of water and a pressure above the critical pressure of water.

[0019] As used throughout this disclosure, “unconverted oil” or “UCO” refers to the fraction of hydrocracking products with a boiling point above 375°C.

[0020] As used throughout this disclosure, the terms "upgrade," "upgraded," or "upgrading" refer to a process that at least partially converts at least some lower-value petroleum-based materials into at least some higher-value chemical products and intermediates. As a non-limiting example, at least some crude oil may be upgraded to produce at least some ethylene, propylene, and butene.

[0021] See now Figure 1An exemplary system 100 is schematically depicted, which can be used in the methods disclosed and described herein for upgrading hydrocarbon feedstocks. The method generally includes introducing hydrocarbon feedstock 150 into a hydrocracking unit 200 to obtain hydrocracking product 250; introducing the hydrocracking product 250 into a fractionation unit 300 to obtain distillate oil 330 and unconverted oil 350, the unconverted oil 350 having a boiling point above 375°C; introducing the unconverted oil 350 and supercritical water 450 into a supercritical water unit 400 to obtain a treated product 440, wherein the supercritical water 450 has a pressure greater than 21 MPa and a temperature above 374°C; and separating the treated product 440 to obtain a purified product 575 and a concentrated product 550. The concentrated product 550 contains heavy polynuclear aromatic hydrocarbons (HPNAs).

[0022] In some embodiments, the hydrocarbon feedstock 150 may include raw hydrocarbon material (such as crude oil) that has not been pretreated, separated, or otherwise refined. In some embodiments, the hydrocarbon feedstock 150 may include hydrocarbon material that has undergone some degree of processing (such as treatment, separation, reaction, purification, or other operations). In various embodiments, the hydrocarbon feedstock 150 may include full-range crude oil, or crude oil fractions such as atmospheric residue, vacuum gas oil, and vacuum residue, and combinations thereof. In one or more embodiments, the hydrocarbon feedstock 150 may include vacuum gas oil with a boiling range of 300°C to 600°C. In one or more embodiments, the hydrocarbon feedstock 150 may include cracked fuel oil from a steam cracking unit. In one or more embodiments, the hydrocarbon feedstock 150 may include liquid hydrocarbons from plastics liquefaction, biomass liquefaction, coal liquefaction, or combinations thereof. In one or more embodiments, the hydrocarbon feedstock 150 may include deasphalted oil.

[0023] In some implementations, the concentration of heavy polynuclear aromatic hydrocarbons in hydrocarbon feedstock 150 can be from 0 to 800 parts per million by weight (ppmw). In some embodiments, the concentration of heavy polynuclear aromatics in the hydrocarbon feedstock 150 may be 0 to 800 ppmw, 0 to 775 ppmw, 0 to 750 ppmw, 0 to 725 ppmw, 0 to 700 ppmw, 0 to 650 ppmw, 0 to 600 ppmw, 0 to 500 ppmw, 0 to 250 ppmw, 0 to 100 ppmw, 100 to 800 ppmw, 100 to 775 ppmw, 100 to 750 ppmw, 100 to 725 ppmw, 100 to 700 ppmw, 100 to 650 ppmw, 100 to 600 ppmw, 100 to 500 ppmw, 100 to 250 ppmw, 250 to 800 ppmw, 250 to 775 ppmw, 250 to 750 ppmw, 250 to 725 ppmw. ppmw, 250 to 700 ppmw, 250 to 650 ppmw, 250 to 600 ppmw, 250 to 500 ppmw, 500 to 800 ppmw, 500 to 775 ppmw, 500 to 750 ppmw, 500 to 725 ppmw, 500 to 700 ppmw, 500 to 650 ppmw, or 500 to 600 ppmw.

[0024] In some implementations, the concentration of heavy polynuclear aromatics in the hydrocarbon feedstock 150 can reach as high as 800 ppmw. Such a high concentration of heavy polynuclear aromatics is unacceptable for conventional hydrocracking processes because of the demanding process conditions required for high conversion (hydrogen pressure of 6 MPa to 25 MPa, temperature of 350°C to 450°C, and space velocities as low as 0.05 hr in the hydrocracking unit). - ¹ to 1 hr - ¹) This can lead to severe catalyst coking. However, this method allows for the use of milder process conditions and achieves a considerable overall conversion rate because supercritical water treatment also contributes to the conversion products.

[0025] In various embodiments, the hydrocracking unit 200 may include a fixed-bed reactor, a moving-bed reactor, a fluidized-bed reactor, or a slurry-bed reactor. In some embodiments, the hydrocracking unit 200 may include a single-stage reactor or a multi-stage reactor. In one or more embodiments, the hydrocracking unit 200 may operate at temperatures of 300°C to 500°C, 300°C to 475°C, 300°C to 450°C, 315°C to 500°C, 315°C to 475°C, or 315°C to 450°C. In one or more embodiments, the hydrocracking unit 200 may operate at pressures from 5 MPa to 25 MPa, for example at pressures from 5.5 MPa to 25 MPa, 6 MPa to 25 MPa, 5 MPa to 24 MPa, 5.5 MPa to 24 MPa, 6 MPa to 24 MPa, 5 MPa to 23 MPa, 5.5 MPa to 23 MPa, 6 MPa to 23 MPa, 5 MPa to 22 MPa, 5.5 MPa to 22 MPa, 6 MPa to 22 MPa, 5 MPa to 21 MPa, 5.5 MPa to 21 MPa, 6 MPa to 21 MPa, 5 MPa to 20 MPa, 5.5 MPa to 20 MPa, or 6 MPa to 20 MPa.

[0026] In one or more embodiments, the liquid hourly space velocity (LHSV) of the hydrocarbon feedstock 150 in the hydrocracking unit 200 can be from 0.05 to 3 hr. -1 ), for example 0.1 hr -1 up to 3 hours -1 0.5 hr -1 up to 3 hours -1 1 hr -1 up to 3 hours -1 2 hr -1 up to 3 hours -1 The liquid hourly space velocity (LHSV) of hydrocarbon feedstock 150 in hydrocracking unit 200 can be 0.05 to 2 hr. -1 ), for example 0.1hr -1 up to 2 hours -1 0.5 hr -1 up to 2 hours -1 1 hr -1 up to 2 hours -1 The liquid hourly space velocity (LHSV) of hydrocarbon feedstock 150 in hydrocracking unit 200 can be 0.05 to 1 hr. -1 ), for example 0.1 hr -1 up to 1 hr -1 0.5 hr -1 up to 1 hr -1 0.05 hr-1 up to 0.5hr -1 0.1 hr -1 up to 0.5 hr -1 or 0.05 hr -1 up to 0.1 hr -1 .

[0027] In various embodiments, the hydrocracking unit 200 may include a catalyst. In some embodiments, the catalyst may include an active metal compound supported on an acidic support. In one or more embodiments, the active metal may be a nickel (Ni), cobalt (Co), molybdenum (Mo), or tungsten (W) sulfide. In one or more embodiments, the acidic support may be zeolite, amorphous silica-alumina, alumina, or a complex thereof. In some embodiments, the catalyst may include a co-catalyst, such as a transition metal, rare earth metal, alkali metal, alkaline earth metal, or a combination thereof.

[0028] Hydrogen feed 110 can be introduced into the hydrocracking unit 200 at a pressure of 5 MPa to 25 MPa, for example at pressures of 5.5 MPa to 25 MPa, 6 MPa to 25 MPa, 5 MPa to 24 MPa, 5.5 MPa to 24 MPa, 6 MPa to 24 MPa, 5 MPa to 23 MPa, 5.5 MPa to 23 MPa, 6 MPa to 23 MPa, 5 MPa to 22 MPa, 5.5 MPa to 22 MPa, 6 MPa to 22 MPa, 5 MPa to 21 MPa, 5.5 MPa to 21 MPa, 6 MPa to 21 MPa, 5 MPa to 20 MPa, 5.5 MPa to 20 MPa, or 6 MPa to 20 MPa. In some embodiments, the hydrogen feed flow rate can be 300 to 3000 cubic meters (m³) per cubic meter of hydrocarbon feedstock. 3 For example, 350 m³ of hydrocarbon feedstock per cubic meter 3 up to 3000 m 3 400 m 3 up to 3000 m 3 450 m 3 up to 3000 m 3 500 m 3 up to 3000 m 3 300 m 3 up to 2500 m 3 350 m 3 up to 2500 m 3 400 m 3 up to 2500 m 3 450 m 3 up to 2500 m 3500 m 3 up to 2500 m 3 300 m 3 up to 2000 m 3 350 m 3 up to 2000 m 3 400 m 3 up to 2000 m 3 450 m 3 up to 2000 m 3 500 m 3 up to 2000 m 3 350 m 3 Up to 1500 m 3 400 m 3 Up to 1500 m 3 450 m 3 Up to 1500 m 3 500 m 3 Up to 1500 m 3 .

[0029] In various implementation schemes, the hydrocracking unit 200 can be operated to achieve a conversion rate of at least 50%, for example, 50% to 100%, wherein the conversion rate is determined according to equation (1).

[0030]

[0031] In some embodiments, the hydrocracking product 250 may contain less than or equal to 50 weight percent (wt%) of unconverted oil, for example, 0 to 50 weight percent of unconverted oil.

[0032] As described above, the method includes introducing hydrocracking products 250 into a fractionation unit 300 to obtain distillate oil 330 and unconverted oil 350. In some embodiments, the fractionation unit 300 may be a single-stage or multi-stage gas-liquid separator and distillation column. In one or more embodiments, the fractionation unit 300 may separate the distillate oil into liquefied petroleum gas, naphtha, and gas oil.

[0033] In various embodiments, the UCO may have a sulfur content of less than 100 ppmw, for example, 0 to 100 ppmw, 0 to 75 ppmw, 0 to 50 ppmw, or 0 to 25 ppmw. In some embodiments, the UCO may have a nitrogen content of less than 10 ppmw, for example, 0 to 10 ppmw, 0 to 8 ppmw, 0 to 5 ppmw, or 0 to 2 ppmw. In various embodiments, the UCO may have a metal content of less than 10 ppmw, for example, 0 to 10 ppmw, 0 to 8 ppmw, 0 to 5 ppmw, or 0 to 2 ppmw.

[0034] In some embodiments, the supercritical water 450 may be demineralized water. In one or more embodiments, the supercritical water 450 may have a salinity defined by a conductivity of less than 1 microsiemens (μS) / cm. In one or more embodiments, the supercritical water 450 may have a salinity of less than 1 μS / cm, less than 0.75 μS / cm, less than 0.5 μS / cm, less than 0.25 μS / cm, less than 0.1 μS / cm, less than 0.075 μS / cm, less than 0.065 μS / cm, less than 0.060 μS / cm, less than 0.0575 μS / cm, or less than 0.055 μS / cm, or less than 0.050 μS / cm. In one or more embodiments, the feed water may contain less than or equal to 5 micrograms per liter (μg / L) of sodium. In one or more embodiments, the feed water may contain sodium at a concentration of 5 μg / L, 4 μg / L, 3 μg / L, 2 μg / L, or 1 μg / L. In one or more embodiments, the feed water may contain chloride at a concentration of 5 μg / L. In one or more embodiments, the feed water may contain chloride at a concentration of 5 μg / L, 4 μg / L, 3 μg / L, 2 μg / L, or 1 μg / L. In one or more embodiments, the feed water may contain silica at a concentration of 3 μg / L. In one or more embodiments, the feed water may contain silica at a concentration of 3 μg / L, 2 μg / L, 1 μg / L, 0.5 μg / L, or 0.25 μg / L.

[0035] For reference Figure 2 In various embodiments, unconverted oil 350 and supercritical water 450 are delivered to supercritical water unit 400 via separate pumps. In one or more embodiments, the pump may be a metering pump, a plunger pump, or a combination thereof.

[0036] In one or more embodiments, the supercritical water 450 has a pressure exceeding 21 MPa and a temperature greater than or equal to 374°C. In one or more embodiments, the water feed 405 can be pressurized by a pump 422 and heated by one or more heaters 426 to generate the supercritical water 450. In one or more embodiments, the heater can be a flame furnace, an electric heater, a heat exchanger, other similar heaters, or a combination thereof. In one or more embodiments, the pump can compress the water feed 405 to a pressure reaching 21 MPa to 35 MPa, 22 MPa to 35 MPa, 23 MPa to 35 MPa, 25 MPa to 35 MPa, 30 MPa to 35 MPa, 21 MPa to 30 MPa, 22 MPa to 30 MPa, 23 MPa to 30 MPa, 25 MPa to 30 MPa, 21 MPa to 25 MPa, 22 MPa to 25 MPa, or 23 MPa to 25 MPa. In one or more embodiments, the water feed 405 can be heated to 374°C to 700°C, 400°C to 700°C, 425°C to 600°C, 450°C to 700°C, 500°C to 700°C, 550°C to 700°C, 374°C to 600°C, 400°C to 600°C, 425°C to 600°C, 450°C to 600°C, 500°C to 600°C, 550°C to 600°C, 374°C to 7 ...50°C to 600°C, 500°C to 600°C, 550°C to 600°C, 374°C to 700°C, 400 Temperatures of 550°C, 400°C to 550°C, 425°C to 550°C, 450°C to 550°C, 500°C to 550°C, 374°C to 500°C, 400°C to 500°C, 425°C to 500°C, 450°C to 500°C, 374°C to 450°C, 400°C to 450°C, 425°C to 450°C, 374°C to 425°C, 400°C to 425°C, or 374°C to 400°C.

[0037] In one or more embodiments, the unconverted oil 350 may be pressurized to a pressure exceeding 21 MPa. In one or more embodiments, the unconverted oil 350 may be pressurized by a pump 322. In one or more embodiments, the pump may compress the unconverted oil 350 to pressures of 21 MPa to 35 MPa, 22 MPa to 35 MPa, 23 MPa to 35 MPa, 25 MPa to 35 MPa, 30 MPa to 35 MPa, 21 MPa to 30 MPa, 22 MPa to 30 MPa, 23 MPa to 30 MPa, 25 MPa to 30 MPa, 21 MPa to 25 MPa, 22 MPa to 25 MPa, or 23 MPa to 25 MPa.

[0038] In some embodiments, the unconverted oil 350 may be heated to a temperature greater than or equal to 50°C and less than or equal to 350°C. In one or more embodiments, the unconverted oil 350 may be heated by one or more heaters 326. In one or more embodiments, the heater may be a flame furnace, an electric heater, a heat exchanger, other similar heaters, or a combination thereof. In one or more embodiments, the unconverted oil may be heated to 50°C to 350°C, 75°C to 350°C, 100°C to 350°C, 150°C to 350°C, 200°C to 350°C, 250°C to 350°C, 300°C to 350°C, 50°C to 300°C, 75°C to 300°C, 100°C to 300°C, 150°C to 300°C, 200°C to 300°C, 250°C to 300°C. Temperatures ranging from 50°C to 250°C, 75°C to 250°C, 100°C to 250°C, 150°C to 250°C, 200°C to 250°C, 50°C to 200°C, 75°C to 200°C, 100°C to 200°C, 150°C to 200°C, 50°C to 150°C, 75°C to 150°C, 100°C to 150°C, 50°C to 100°C, 75°C to 100°C, 50°C to 75°C, or combinations thereof.

[0039] In one or more embodiments, the supercritical water 450 and the unconverted oil 350 may have a flow rate defined by a flow ratio of 20:1 to 1:1 at standard ambient temperature and pressure (SATP). In one or more embodiments, the supercritical water 450 and unconverted oil 350 may have ratios of 20:1 to 1:1, 20:1 to 2:1, 20:1 to 3:1, 20:1 to 4:1, 20:1 to 5:1, 20:1 to 6:1, 20:1 to 7:1, 20:1 to 8:1, 20:1 to 9:1, 20:1 to 10:1, 10:1 to 1:1, 10:1 to 2:1, 10:1 to 3:1, 10:1 to 4:1, 10:1 to 5:1, 10:1 to 6:1, 10:1 to 7:1, 10:1 to 8:1, 10:1 to 9:1, 9:1 to 1:1, 9:1 to 2:1, 9:1 to 3:1, 9:1 to 4:1, 9:1 to 5:1 under SATP conditions. :1 to 6:1, 9:1 to 7:1, 9:1 to 8:1, 8:1 to 1:1, 8:1 to 2:1, 8:1 to 3:1, 8:1 to 4:1, 8:1 to 5:1, 8:1 to 6:1, 8:1 to 7:1, 7:1 to 1:1, 7:1 to 2:1, 7:1 to 3:1, 7:1 to 4:1, 7:1 to 5:1, 7:1 to 6: 1. Flow rates of 6:1 to 1:1, 6:1 to 2:1, 6:1 to 3:1, 6:1 to 4:1, 6:1 to 5:1, 5:1 to 1:1, 5:1 to 2:1, 5:1 to 3:1, 5:1 to 4:1, 4:1 to 1:1, 4:1 to 2:1, 4:1 to 3:1, 3:1 to 1:1, 3:1 to 2:1, or 2:1 to 1:1.

[0040] In various embodiments, supercritical water 450 and heated unconverted oil 350 may be combined via mixer 425 before being introduced into supercritical water unit 400. Mixer 425 may be an inline mixer, tee, static mixer, stirred mixer, or other similar mixer. In some embodiments, supercritical water unit 400 may be a tubular reactor, a pipeline reactor, a continuous stirred tank reactor (CSTR), or a combined reactor.

[0041] Unbound by theory, supercritical water is assumed to dissolve organic compounds due to its low dielectric constant. However, the solubility of organic compounds depends on their structure and molecular weight. Generally, larger molecules are less likely to dissolve rapidly in supercritical water. Polynuclear aromatic hydrocarbons (PAHs), including HPNAs, tend to aggregate in supercritical water (SCW) environments due to strong interactions between them caused by van der Waals forces. Larger HPNAs are more likely to aggregate in SCWs than smaller PAHs. Molecules other than PAHs can influence the size of the formed HPNA aggregates. Small aromatic compounds such as toluene can increase the solubility of PAHs, thereby ultimately reducing the size of the aggregates. In contrast, alkane molecules decrease the solubility of PAHs in SCWs. Under SCW conditions, PAHs and HPNAs do not decompose, but they may vaporize if the SCW has a temperature above or equal to 800°C.

[0042] In SCW, large alkane molecules can cleave to form smaller paraffins and alkenes. These paraffins and alkenes can then form aromatic compounds through cyclization, aromatization, and dehydrogenation. However, the formation of aromatic compounds under SCW conditions is considered a secondary reaction. Due to the short residence time of UCO in the SCW unit (60 minutes or less), significant aromatic formation is not expected. Therefore, it can be inferred that the SCW reactor contains paraffins and alkenes, as well as small amounts of aromatics and HPNA.

[0043] UCO is considered a highly saturated substance (>95% by weight saturated compound), meaning that most of its molecules are alkanes. The alkanes in UCO are readily soluble in SCW and cleave to form alkanes and alkenes. The original alkanes and the newly formed alkane / alkene prevent the dissolution of HPNA and induce phase segregation of HPNA. The separated phase has a significantly higher concentration of HPNA and a lower concentration of SCW. Therefore, HPNA undergoes a radical-induced condensation reaction to generate larger HPNA molecules.

[0044] In one or more embodiments, the residence time of the combined supercritical water 450 and unconverted oil 350 in the supercritical water unit 400 may be greater than or equal to 10 seconds and less than or equal to 60 minutes. In one or more embodiments, the residence time of the combined supercritical water 450 and unconverted oil 350 in the supercritical water unit 400 can be 10 seconds to 60 minutes, 30 seconds to 60 minutes, 1 minute to 60 minutes, 5 minutes to 60 minutes, 10 minutes to 60 minutes, 15 minutes to 60 minutes, 20 minutes to 60 minutes, 30 minutes to 60 minutes, 10 seconds to 45 minutes, 30 seconds to 45 minutes, 1 minute to 45 minutes, 5 minutes to 45 minutes, 10 minutes to 45 minutes, 15 minutes to 45 minutes, 20 minutes to 45 minutes, 30 minutes to 45 minutes, 10 seconds to 30 minutes, 30 seconds to 30 minutes, 1 minute to 30 minutes, 5 minutes to 30 minutes, 10 minutes to 30 minutes, 15 minutes to 30 minutes, or 20 minutes to 30 minutes. The residence time can be calculated by assuming that the density of the fluid in the reactor has the density of water under the reaction conditions.

[0045] In one or more embodiments, the combined supercritical water 450 and unconverted oil 350 may be in a turbulent state with a Reynolds number greater than or equal to 3000. For example, the combined supercritical water 450 and unconverted oil 350 may be in a turbulent state with a Reynolds number greater than or equal to 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000, 20,000, 25,000, 50,000, 75,000, or 100,000. The Reynolds number can be calculated by assuming that the density of the fluid in the reactor has the density of water under the reaction conditions.

[0046] In one or more embodiments, the volume of the supercritical water unit 400 can be selected by determining the desired residence time of the combined supercritical water 450 and unconverted oil 350 in the supercritical water unit 400 (assuming the internal fluid is 100% water). In one or more embodiments, the supercritical water unit 400 can be configured as horizontal, vertical, inclined, downward-sloping, or a combination thereof.

[0047] In one or more embodiments, the supercritical water unit 400 can operate at a temperature greater than or equal to 374°C. In one or more embodiments, the supercritical water unit 400 can operate at temperatures ranging from 374°C to 600°C, 380°C to 600°C, 390°C to 600°C, 400°C to 600°C, 425°C to 600°C, 450°C to 600°C, 460°C to 600°C, 475°C to 600°C, 500°C to 600°C, 550°C to 600°C, 374°C to 550°C, 380°C to 550°C, 3... 90℃ to 550℃, 400℃ to 550℃, 425℃ to 550℃, 450℃ to 550℃, 460℃ to 550℃, 475℃ to 550℃, 500℃ to 550℃, 374℃ to 500℃, 380℃ to 500℃, 390℃ to 500℃, 400℃ to 500℃, 425℃ to 500℃, 450℃ to 500℃, 460℃ to 500℃, 475℃ to 5 00℃, 374℃ to 475℃, 380℃ to 475℃, 390℃ to 475℃, 400℃ to 475℃, 425℃ to 475℃, 450℃ to 475℃, 460℃ to 475℃, 374℃ to 460℃, 380℃ to 460℃, 390℃ to 460℃, 400℃ to 460℃, 425℃ to 460℃, 450℃ to 460℃, 374℃ to 450℃, 3 Operate at temperatures ranging from 80°C to 450°C, 390°C to 450°C, 400°C to 450°C, 425°C to 450°C, 374°C to 425°C, 380°C to 425°C, 390°C to 425°C, 400°C to 425°C, 374°C to 400°C, 380°C to 400°C, 390°C to 400°C, 374°C to 390°C, 380°C to 390°C, or 374°C to 380°C.

[0048] In one or more embodiments, the supercritical water unit 400 can operate at a pressure greater than or equal to 21 MPa. In one or more embodiments, the supercritical water unit 400 can operate at pressures of 21 MPa to 35 MPa, 22 MPa to 35 MPa, 23 MPa to 35 MPa, 25 MPa to 35 MPa, 30 MPa to 35 MPa, 21 MPa to 30 MPa, 22 MPa to 30 MPa, 23 MPa to 30 MPa, 25 MPa to 30 MPa, 21 MPa to 25 MPa, 22 MPa to 25 MPa, or 23 MPa to 25 MPa.

[0049] In one or more embodiments, cracking, dealkylation, isomerization, alkylation, condensation, ring-opening, cyclization, dehydrogenation, hydrogenation and dimerization reactions may occur in the supercritical water unit 400.

[0050] In various embodiments, the processed product 440 may pass through a cooler 432. In one or more embodiments, the cooler 432 may cool the processed product 440 to a temperature greater than or equal to 50°C and less than or equal to 350°C. In one or more embodiments, the cooler 432 can cool the processed product 440 to a temperature between 50°C and 350°C, 100°C and 350°C, 150°C and 350°C, 200°C and 350°C, 250°C and 350°C, 300°C and 350°C, 50°C and 300°C, 100°C and 300°C, 150°C and 300°C, 200°C and 300°C, 250°C and 300°C, 50°C and 250°C, 100°C and 250°C, 150°C and 250°C, 200°C and 250°C, 50°C and 200°C, 100°C and 200°C, 150°C and 200°C, 50°C and 150°C, 100°C and 150°C, or 50°C and 100°C.

[0051] In one or more embodiments, the processed product 440 may pass through a pressure reducer 448. In some embodiments, the pressure reducer 448 may be a pressure reducing valve, a back pressure regulator, a pressure control valve, a series of capillary tubes, other similar devices, or combinations thereof. In one or more embodiments, the pressure reducer 448 may reduce the pressure of the processed product 440 to a pressure greater than or equal to 0.1 MPa and less than or equal to 1 MPa. In one or more embodiments, the pressure reducer 448 may reduce the pressure of the first upgraded output to a pressure between 0.1 MPa and 1 MPa, 0.2 MPa and 1 MPa, 0.5 MPa and 1 MPa, or any combination thereof. In one or more embodiments, the processed product 440 may pass through both a cooler 432 and a pressure reducer 448.

[0052] As described above, the treated product 440 can be separated to obtain a purified product 575 and a concentrated product 550. In some embodiments, separating the treated product 440 may include feeding the treated product 440 to a separation unit 500. In one or more embodiments, the separation unit 500 may be an extraction unit, a fractionation unit, or a filtration unit to obtain the purified product 575 and the concentrated product 550. In some embodiments, at least a portion of the purified product may be recycled back to the hydrocracking unit 200. In some embodiments, all the purified product may be recycled back to the hydrocracking unit 200.

[0053] Unbound by theory, it is believed that heavy polynuclear aromatic hydrocarbons form sheet-like materials due to their planar structure. The strong van der Waals interactions between the heavy polynuclear aromatic hydrocarbon sheets can form suspended or precipitated particles in the treated product 440, which can be separated by filtration, fractionation, or extraction.

[0054] In various embodiments, filtration may include the use of a filtration apparatus comprising a single filter element or multiple filter elements. In some embodiments, extraction may include the use of an extraction solvent. The extraction solvent may be selected from C3 to C8 alkanes, such as n-pentane and n-heptane. Heavy polynuclear aromatic hydrocarbons have low solubility in C3 to C8 alkanes, and therefore can be separated from other components in the treated product.

[0055] In some embodiments, separating the treated product 440 to obtain a purified product 575 and a concentrated product 550 may include separating the treated product in a gas-liquid separator to obtain a gaseous product and a liquid product. In various embodiments, the method may further include separating the liquid product in an oil-water separator to obtain an aqueous product and an oil product. In one or more embodiments, the oil-water separator may be a gravity-assisted oil-water separator, a condensation-assisted oil-water separator, a centrifugal oil-water separator, or other similar oil-water separator. In one or more embodiments, the method further includes conveying the oil product to an extraction unit, a fractionation unit, or a filtration unit to separate the oil product, thereby obtaining a purified product and a concentrated product.

[0056] In various embodiments, the gaseous product may comprise H2, H2O, CO, CO2, H2S, NH3, C1 hydrocarbons, C2 hydrocarbons, C3 hydrocarbons, C4 hydrocarbons, C5 hydrocarbons, C6 hydrocarbons, or combinations thereof. In one or more embodiments, the gaseous product may comprise 0 to 5% H2, 0 to 10% H2O, 0 to 5% CO, 0 to 5% CO2, 0 to 25% H2S, 0 to 25% NH3, 0 to 25% C1 hydrocarbons, 0 to 50% C2 hydrocarbons, 0 to 50% C3 hydrocarbons, 0 to 60% C4 hydrocarbons, 0 to 25% C5 hydrocarbons, and 0 to 5% C6 hydrocarbons.

[0057] In some embodiments, the purified product 575 may contain less than 300 ppmw, less than 250 ppmw, less than 200 ppmw, less than 150 ppmw, less than 100 ppmw, less than 75 ppmw, less than 50 ppmw, or less than 35 ppmw of heavy polynuclear aromatic hydrocarbons, such as 0 to 300 ppmw, 0 to 250 ppmw, 0 to 200 ppmw, 0 to 150 ppmw, 0 to 100 ppmw, 0 to 75 ppmw, 0 to 50 ppmw, or 0 to 35 ppmw of heavy polynuclear aromatic hydrocarbons.

[0058] In some embodiments, the method may further include using heavy polynuclear aromatics to form bitumen. In one or more embodiments, the bitumen is isotropic bitumen. In one or more embodiments, the bitumen is mesophase bitumen. Bitumen is typically prepared by polymerizing tar from wood, coal, and / or petroleum-based heavy residues (e.g., petroleum residue oils, such as vacuum distillation bottoms, FCC decant oil, and cracked fuel oil from steam cracking processes). Under ambient conditions, bitumen is in solid form. Petroleum-based bitumen is produced by heat treatment and distillation of high aromatic and heavy fractions from crude oil, refinery streams, and steam cracking unit products (such as cracked fuel oil). Bitumen is a complex mixture dominated by aromatic compounds and alkylated aromatic compounds.

[0059] Bituminous asphalt can be classified into two categories based on its optical and crystallographic properties: isotropic bituminous asphalt and mesophase bituminous asphalt. Unless further processed, petroleum-based bituminous asphalt is typically in isotropic form, which can be used to produce final carbon products with relatively low crystallinity (such as carbon fibers). Mesophase bituminous asphalt is formed by heat-treating it at temperatures between 300°C and 500°C, resulting in optically anisotropic bituminous asphalt. Mesophase bituminous asphalt exhibits liquid crystal properties and short-range orientational ordering of aromatic lamellae. It is a precursor to activated carbon fibers and other high-end carbon materials with high crystallinity.

[0060] The primary reaction necessary for the formation of mesophase pitch is the dehydrogenation polymerization and cleavage of aliphatic substituents on the aromatic nucleus. When heavy polynuclear aromatics are processed in a supercritical water unit, treatment with supercritical water can cleave the side chains of any alkylated aromatics, thereby yielding heavy polynuclear aromatics that may require less processing to form mesophase pitch. Furthermore, pitch with a high carbon / hydrogen ratio and minimal heteroatom content is preferred. Treatment in a supercritical water unit can facilitate the removal of heteroatoms such as sulfur, nitrogen, and metals.

[0061] In some implementations, the bitumen is prepared in accordance with J. Mater. Sci, 21(20), 1986, 424-428, the entire contents of which are incorporated herein by reference.

[0062] Example Various implementations of methods and systems for upgrading crude oil will be further illustrated by the following examples. These examples are illustrative in nature and should not be construed as limiting the subject matter of this disclosure.

[0063] Comparative Example Computer simulations were performed using Aspen-HYSYS, and the following results were obtained.

[0064] like Figure 3As shown, a hydrocracking unit, a fractionation unit, and a vacuum distillation unit were set up. Fresh vacuum gas oil was used, and its characteristics are shown in Table 1.

[0065] Table 1 Characteristics of vacuum gas oil

[0066] For reference Figure 3 Fresh vacuum gas oil (150) used as hydrocarbon feedstock is introduced into hydrocracking unit 200 at a rate of 5246 metric tons / day (MTD) and 35365 barrels / day (BPD), recycled vacuum gas oil (855) at a rate of 1404 MTD and 9630 BPD, and hydrogen (110) at a rate of 213 MTD. Hydrocracking unit 200 operates at a 68% volume conversion, where vol% conversion is defined as the product distillate oil volume divided by the total hydrocracker feed (the amount of fresh vacuum gas oil 150 plus the amount of unconverted vacuum gas oil 855). The amount of unconverted oil (350) in the fractionation products is approximately 30% volume. After hydrocracking, hydrocracking product 250 is introduced into fractionation unit 300 to obtain distillate oil (330) and unconverted oil (350). Distillate oil 330 comprises 570 MTD of gas, 1744 MTD and 15483 BPD of naphtha, 627 MTD and 4891 BPD of kerosene, and 1784 MTD and 13630 BPD of diesel. Unconverted oil 350 is produced at a rate of 2138 MTD and 14353 BPD. Unconverted oil 350 is fed to vacuum distillation unit 800 to obtain circulating depressurized gas oil 855 and discharge stream 955.

[0067] To maintain the HPNA content in all hydrocarbon inputs entering hydrocracking unit 200 (i.e., fresh vacuum gas oil 150 and recycled vacuum gas oil 855), the major portion (34 wt%) of unconverted oil 350 is disposed of as effluent 955. The recycled vacuum gas oil 855 has an HPNA content of 210 ppmw, resulting in an HPNA content of 44 ppmw for all hydrocarbon inputs entering hydrocracking unit 200. Effluent 955 has an HPNA content of approximately 7000 ppmw, with the HPNA concentrated in the bottoms / vacuum residue fraction. Effluent 955 is discharged at rates of 735 MTD and 4502 BPD. A summary of the products and their production rates is shown in Table 2.

[0068] Table 2: Products and their production rates

[0069] Invention Embodiments like Figure 1As shown, a hydrocracking unit, a fractionation unit, a supercritical water unit, and a separation unit were set up. Fresh vacuum gas oil with the characteristics of the fresh vacuum gas oil in the comparative example was also used.

[0070] For reference Figure 1 Fresh vacuum gas oil (used as hydrocarbon feedstock 150) is introduced into hydrocracking unit 200 at a rate of 6505 MTD and 43847 BPD, recycled vacuum gas oil (575) at a rate of 677 MTD and 4490 BPD, and hydrogen (110) at a rate of 230 MTD. After hydrocracking, hydrocracking product 250 is introduced into fractionation unit 300 to obtain distillate oil 330 and unconverted oil 350. Distillate oil 330 comprises 521 MTD of gas, 1544 MTD and 13707 BPD of naphtha, 468 MTD and 3655 BPD of kerosene, and 1804 MTD and 13789 BPD of diesel oil. Unconverted oil 350 is produced at a rate of 3075 MTD and 20639 BPD. Unconverted oil 350 is fed to SCW unit 400 to obtain processed products. The processed products are then conveyed to separation unit 500, which is the second fractionation unit. The separation unit separates the processed products into 92 MTD of gas, 791 MTD and 6581 BPD of naphtha, 379 MTD and 2788 BPD of kerosene, 1039 MTD and 7467 BPD of diesel, 677 MTD and 4490 BPD of vacuum gas oil, and 97 MTD and 576 BPD of vacuum residue, which contains HPNA. The HPNA content in the circulating vacuum gas oil 575 is 170 ppmw. Because the SCW concentrates HPNA into the vacuum residue fraction, its concentration is lower than the comparative example. The HPNA content in all hydrocarbon inputs entering hydrocracking unit 200 is 16 ppmw. No vacuum gas oil is discharged. The HPNA concentration in the vacuum residue is 8.6% by weight, indicating that vacuum residue is a good precursor for asphalt production. HPNA is concentrated in the vacuum residue fraction, while the recycled vacuum gas oil 575 has a lower HPNA concentration due to the condensation reaction occurring in SCW unit 400. A summary of the products and their production rates is shown in Table 3.

[0071] Table 3: Products and their production rates

[0072] The vacuum residue was processed according to the mesophase bitumen preparation procedure in J. Mater. Sci, 21(20), 1986, 424-428, the entire contents of which are incorporated herein by reference. The yield of bitumen products was approximately 72% by weight. The mesophase fraction of the resulting bitumen was approximately 82% by weight.

[0073] The combined conversion of unconverted vacuum gas oil 575 by the hydrocracking unit 200 and SCW unit 400 is approximately 109% vol. conversion, where vol. conversion is defined as the product distillate oil content divided by the amount of fresh vacuum gas oil 150. However, similar to the comparative example, the amount of unconverted oil 350 in the fractionation products is approximately 40% vol. Since the SCW unit 400 is able to upgrade UCO 350 and ultimately produce distillate oil, the UCO 350 fraction can be maintained at a higher level than in the comparative example (30% vol).

[0074] The higher level of unconverted oil production allows the hydrocracking unit 200 to have higher throughput (meaning that a higher LHSV in the hydrocracking unit 200 is acceptable to achieve the target distillate oil production). In this embodiment, the hydrocracking unit 200 has a throughput of 48,337 BPD, which is 7.4% higher than the comparative example. Because the SCW unit 400 converts a large amount of UCO to distillate oil, the amount of vacuum gas oil circulating is much lower than in the comparative example (4,490 BPD vs. 9,630 BPD), resulting in a higher throughput of fresh vacuum gas oil (43,847 BPD vs. 35,365 BPD, a 24% increase). This increase in the capacity of the hydrocracking unit 200 brings significant economic benefits. In addition, the lower HPNA content in the hydrocarbon feedstock (16 ppmw vs. 44 ppmw) extends the catalyst lifetime.

[0075] Having described the subject matter of this disclosure in detail and with reference to specific embodiments, it should be noted that the various details described herein should not be construed as implying that such details pertain to essential components of the various embodiments described herein, even where a particular element is shown in the accompanying drawings. Rather, the appended claims should be considered the sole expression of the breadth of this disclosure and the corresponding scope of the various embodiments described herein. Furthermore, it will be apparent to those skilled in the art that various modifications and variations can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter. Therefore, this specification is intended to cover modifications and variations of the various described embodiments, provided that such modifications and variations fall within the scope of the appended claims and their equivalents.

[0076] It should be noted that one or more of the following claims use the term "wherein" as a transitional phrase. In defining this technology, it should be noted that this term is introduced in the claims as an open-ended transitional phrase to introduce a set of features defining the structure, and should be interpreted in the same way as the more commonly used open-ended prepositional term "comprising".

[0077] The transitional phrases “composed of” and “substantially composed of” can be interpreted as a subset of open-ended transitional phrases (such as “comprising” and “including”), thus any limitation using an open-ended phrase to introduce a series of elements, components, materials, or steps should be interpreted as also disclosing the use of the closed terms “composed of” and “substantially composed of” to limit that series of elements, components, materials, or steps. For example, the limitation of a composition “comprising” components A, B, and C should be interpreted as also disclosing compositions “composed of” components A, B, and C, as well as compositions “substantially composed of” components A, B, and C.

[0078] Any quantitative values ​​expressed in this application may be regarded as including both open-ended embodiments consistent with the transitional phrases “comprising” or “including”, and closed or semi-closed embodiments consistent with the transitional phrases “consisting of” and “substantially consisting of”.

[0079] This disclosure includes several aspects, as described below, referred to as aspects 1 to 20.

[0080] Aspect 1. A method for upgrading hydrocarbon feedstock, the method comprising: introducing the hydrocarbon feedstock into a hydrocracking unit to obtain hydrocracking products; introducing the hydrocracking products into a fractionation unit to obtain distillate oil and unconverted oil, the unconverted oil having a boiling point above 375°C; introducing the unconverted oil and supercritical water into a supercritical water unit to obtain a treated product, wherein the supercritical water has a pressure greater than 21 MPa and a temperature above 374°C; and separating the treated product to obtain a purified product and a concentrated product, the concentrated product comprising heavy polynuclear aromatic hydrocarbons (HPNAs).

[0081] Aspect 2. The method according to aspect 1, wherein the residence time of the unconverted oil in the supercritical water unit, in the supercritical reactor, is from 10 seconds to 60 minutes.

[0082] Aspect 3. The method according to aspect 1 or aspect 2 further includes recycling at least a portion of the purified product to a hydrocracking unit.

[0083] Aspect 4. The method according to any one of aspects 1 to 3 further includes mixing the unconverted oil and supercritical water before introducing the unconverted oil and supercritical water into the supercritical water unit.

[0084] Aspect 5. The method according to any one of aspects 1 to 4, wherein the raw material is vacuum gas oil.

[0085] Aspect 6. The method according to any one of Aspects 1 to 5, wherein the feedstock comprises less than or equal to 800 ppmw of heavy polynuclear aromatic hydrocarbons.

[0086] Aspect 7. The method according to any one of Aspects 1 to 6, wherein when unconverted oil and supercritical water are introduced into the supercritical water unit, the ratio of the flow rate of supercritical water to the flow rate of unconverted oil is 20:1 to 1:1.

[0087] Aspect 8. The method according to any one of Aspects 1 to 7, wherein the supercritical water is demineralized water comprising: conductivity less than 1 μS / cm; sodium content less than 5 μg / L; chloride content less than 5 μg / L; and silica content less than 3 μg / L.

[0088] Aspect 9. The method according to any one of Aspects 1 to 8, wherein at least one of the following is true: the supercritical water unit operates at a pressure greater than 21 MPa and a temperature of 374°C to 600°C; the supercritical water has a pressure greater than 21 MPa and a temperature of 400°C to 700°C before being introduced into the supercritical water unit; the unconverted oil has a pressure greater than 21 MPa and a temperature of 50°C to 350°C before being introduced into the supercritical water unit; and the fluid in the supercritical water unit is in a turbulent state with a Reynolds number greater than 3,000.

[0089] Aspect 10. The method according to any one of Aspects 1 to 9, wherein the hydrocracking unit operates at a pressure of 5 MPa to 25 MPa, a temperature of 300°C to 600°C, and a liquid hourly space velocity of the feedstock of 0.05 hr. -1 up to 3 hours -1 .

[0090] Aspect 11. The method according to any one of Aspects 1 to 10, wherein the hydrocarbon feedstock is vacuum gas oil (VGO).

[0091] Aspect 12. The method according to any one of aspects 1 to 11, wherein the hydrocracking product comprises 0 to 50% by weight of unconverted oil.

[0092] Aspect 13. The method according to any one of Aspects 1 to 12, wherein separating the treated product to obtain a purified product and a concentrated product comprises: conveying the treated product to an extraction apparatus, a fractionation apparatus, or a filtration apparatus to obtain a purified product and a concentrated product; and optionally, separating the treated product in a gas-liquid separator to obtain a gaseous product and a liquid product; separating the liquid product in an oil-water separator to obtain an aqueous product and an oil product; and conveying the oil product to an extraction apparatus, a fractionation apparatus, or a filtration apparatus to separate the oil product, thereby obtaining a purified product and a concentrated product.

[0093] Aspect 14. The method according to any one of aspects 1 to 13, wherein the purified product comprises 0 to 35 ppmw of heavy polynuclear aromatic hydrocarbons.

[0094] Aspect 15. The method according to any one of aspects 1 to 14 further includes using heavy polynuclear aromatic hydrocarbons to form bitumen, wherein the bitumen is mesophase bitumen.

Claims

1. A method for upgrading hydrocarbon feedstock, the method comprising: Hydrocarbon feedstock is introduced into a hydrocracking unit to obtain hydrocracking products; The hydrocracking products are introduced into a fractionation unit to obtain distillate oil and unconverted oil, the unconverted oil having a boiling point above 375°C; The unconverted oil and supercritical water are introduced into a supercritical water unit to obtain a treated product, wherein the supercritical water has a pressure greater than 21 MPa and a temperature greater than 374°C; and The processed product is separated to obtain a purified product and a concentrated product, wherein the concentrated product contains heavy polynuclear aromatic hydrocarbons (HPNA).

2. The method according to claim 1, wherein the residence time of the unconverted oil in the supercritical water unit, in the supercritical reactor, is from 10 seconds to 60 minutes.

3. The method according to claims 1 to 2, further comprising recycling at least a portion of the purified product to the hydrocracking unit.

4. The method according to claims 1 to 3, further comprising mixing the unconverted oil and the supercritical water before introducing the unconverted oil and the supercritical water into the supercritical water unit.

5. The method according to claims 1 to 4, wherein the raw material is vacuum gas oil.

6. The method according to claims 1 to 5, wherein the raw material comprises less than or equal to 800 ppmw of heavy polynuclear aromatic hydrocarbons.

7. The method according to claims 1 to 6, wherein, When the unconverted oil and the supercritical water are introduced into the supercritical water unit, the ratio of the flow rate of the supercritical water to the flow rate of the unconverted oil is 20:1 to 1:

1.

8. The method according to claims 1 to 7, wherein the supercritical water is desalinated water, comprising: a conductivity of less than 1 μS / cm; Sodium content is less than 5 μg / L; Chloride content less than 5 μg / L; and The silica content is less than 3 μg / L.

9. The method according to claims 1 to 8, wherein at least one of the following: The supercritical water unit operates at pressures greater than 21 MPa and temperatures ranging from 374°C to 600°C. Before the supercritical water is introduced into the supercritical water unit, the supercritical water has a pressure greater than 21 MPa and a temperature of 400°C to 700°C. Before the supercritical water is introduced into the supercritical water unit, the unconverted oil has a pressure greater than 21 MPa and a temperature of 50°C to 350°C; and The fluid in the supercritical water unit is in a turbulent state with a Reynolds number greater than 3000.

10. The method according to claims 1 to 9, wherein the hydrocracking unit operates at a pressure of 5 MPa to 25 MPa and a temperature of 300°C to 600°C, and the liquid hourly space velocity of the feedstock is 0.05 hr. -1 up to 3 hours -1 .

11. The method according to claims 1 to 10, wherein the hydrocarbon feedstock is vacuum gas oil (VGO).

12. The method according to claims 1 to 11, wherein the hydrocracking product comprises 0 to 50% by weight of unconverted oil.

13. The method according to claims 1 to 12, wherein, Separating the processed product to obtain the purified product and the concentrated product includes: The treated product is fed to an extraction unit, a fractionation unit, or a filtration unit to obtain the purified product and the concentrated product; and optionally, The processed products are separated in a gas-liquid separator to obtain gaseous and liquid products; The liquid product is separated in an oil-water separator to obtain an aqueous product and an oil product; and The oil product is fed to an extraction device, a fractionation device, or a filtration device to separate the oil product, thereby obtaining the purified product and the concentrated product.

14. The method according to claims 1 to 13, wherein the purified product comprises 0 to 35 ppmw of heavy polynuclear aromatic hydrocarbons.

15. The method according to claims 1 to 14, further comprising using the heavy polynuclear aromatic hydrocarbon to form bitumen, wherein the bitumen is mesophase bitumen.

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