Process for increasing production of high-aromatics potential naphthas from carbon dioxide coupled straight-run diesel hydroconversion

Abstract

The application discloses a method for increasing high-aromatic potential naphtha by coupling carbon dioxide and straight-run diesel hydrogen conversion, and the method comprises the following steps: mixing straight-run diesel raw material, CO2 and cycle oil, and then entering a CO2 coupling reaction zone to generate a CO2 and alkane coupling reaction; mixing the obtained liquid phase stream after gas-liquid separation with hydrogen, and then entering a hydrogen refining reaction zone and a hydrogen cracking reaction zone in sequence; and separating and fractionating the obtained hydrogen cracking reaction zone effluent to obtain dry gas, liquefied gas, light naphtha, heavy naphtha and diesel, wherein the diesel is cycle oil. The method can effectively utilize the alkane components of the straight-run diesel, and realizes the purpose of effectively increasing high-aromatic potential heavy naphtha.

Description

Technical Field

[0001] This invention belongs to the field of oil refining technology, and specifically relates to a method for hydrogenating straight-run diesel. Background Technology

[0002] With the dramatic changes in the motor vehicle consumer market and the continuous decline in diesel and gasoline prices, hydrogenation technology to increase gasoline production has been widely researched and applied. Hydrocracking of heavy naphtha results in high levels of cycloalkanes and aromatics. After catalytic reforming, it can produce high-value-added chemical feedstocks such as benzene, toluene, and xylene, and can also serve as a high-quality gasoline blending component. The aromatics in heavy naphtha are mainly monocyclic aromatics; increasing the content of monocyclic aromatics in heavy naphtha can significantly improve its aromatic potential and octane number. Producing high-aromatic-potential heavy naphtha through diesel hydrocracking can effectively reduce the diesel-to-gasoline ratio and address the diesel surplus problem. Straight-run diesel, as a significant component of crude oil processing, currently has a relatively low value in the refining product structure adjustment due to changes in market demand. How to utilize technologies such as hydrocracking to process straight-run diesel and maximize the production of high-quality gasoline or chemical feedstocks has become a key focus.

[0003] CN116948695A discloses a method for producing heavy naphtha via hydrocracking. Diesel feedstock containing straight-run diesel is fed from the top of the hydropre-refining reaction zone, while aromatic diesel feedstock is fed from the lower middle part of the hydropre-refining reaction zone. The effluent is fractionated after hydrocracking to obtain dry gas, liquefied petroleum gas (LPG), light naphtha, heavy naphtha, and recycled oil. The recycled oil is recycled back to the hydrorefining zone, and a portion of the LPG and light naphtha are recycled back to the hydrocracking reaction zone, thereby increasing the production of heavy naphtha. CN116042270A discloses a hydrocracking method for producing heavy naphtha and jet fuel. The feedstock oil, after hydrorefining, enters a partitioned hydrocracking reactor. The tail oil and a small amount of refined effluent enter the upper part of the partitioned reactor for reaction. The upper effluent and the remaining refined oil enter the lower part for reaction, followed by separation and fractionation. This method can efficiently convert feedstock oil into heavy naphtha or jet fuel in a large proportion. CN113122321B discloses a hydrocracking method for improving the aromatic potential of heavy naphtha. The method involves separating the product oil from the high-nitrogen feedstock through hydrorefining into light and heavy fractions. An upstream hydrorefining bed and a downstream hydrocracking bed are set up in the hydrocracking reactor. The light fraction enters directly downstream, while the heavy fraction enters from the upstream. The effluent is separated and fractionated, thereby increasing the aromatic potential content of the obtained heavy naphtha components.

[0004] In fact, straight-run diesel fractions, when subjected to conventional hydrocracking, exhibit low aromatic potential in heavy naphtha due to their high alkane content and low aromatic content, making it difficult to effectively produce high-aromatic-potential heavy naphtha from straight-run diesel fractions. To achieve the goal of producing high-aromatic-potential heavy naphtha, it is necessary to modify the properties and composition of straight-run diesel to enrich it with aromatics, transforming it into a suitable feedstock for high-aromatic-potential heavy naphtha production. This is of great significance for the efficient utilization of straight-run diesel. Among methods for converting alkanes to aromatics, coupling carbon dioxide to aromatics is a promising technical route. CN116120139A discloses a method for producing aromatics by coupling light alkanes and carbon dioxide. By adjusting the partial pressure of carbon dioxide, the H / C ratio of C2-C6 alkane products is controlled, thereby achieving high selectivity for aromatics production. CN115851309A discloses a method for the coupled conversion of naphtha and carbon dioxide to aromatics on a zeolite molecular sieve catalyst, achieving an aromatics selectivity exceeding 72%. The above methods are only applicable to light feedstocks with a carbon number of less than 12, and are not suitable for diesel fractions with a higher carbon number or more complex structures. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for increasing the production of high-aromatic-potential heavy naphtha through the hydroconversion of straight-run diesel coupled with carbon dioxide. This method effectively utilizes the alkane components of straight-run diesel, thereby achieving the goal of effectively increasing the production of high-aromatic-potential heavy naphtha.

[0006] This invention provides a method for increasing the production of high-aromatic heavy naphtha by hydroconversion of straight-run diesel fuel coupled with carbon dioxide. The method includes: mixing straight-run diesel feedstock, CO2, and recycled oil and then entering a CO2 coupling reaction zone, where a CO2-alkane coupling reaction occurs. The resulting stream is separated into liquid and mixed with hydrogen, and then sequentially enters a hydrorefining reaction zone and a hydrocracking reaction zone. The effluent from the hydrocracking reaction zone is separated and fractionated to obtain dry gas, liquefied petroleum gas, light naphtha, heavy naphtha, and diesel fuel, wherein the diesel fuel is the recycled oil.

[0007] In the above method, straight-run diesel feedstock, CO2, and recycled oil are mixed and then reacted in a CO2 coupling reaction zone to produce the first stream. The liquid stream obtained after gas-liquid separation of the first stream is mixed with hydrogen and then reacted in a hydrorefining reaction zone to produce the second stream. The second stream is then mixed with hydrogen and then reacted in a hydrocracking reaction zone to produce the third stream. The liquid stream obtained after gas-liquid separation of the first stream is a diesel stream rich in aromatics, while the gaseous stream consists of CO2, CO, and other gaseous components.

[0008] In the above method, the initial boiling point of the straight-run diesel oil is generally 220–300℃; the final boiling point is generally 330–380℃; the nitrogen content is generally below 100 μg / g; and the sulfur content is above 2000 μg / g, more preferably 2000–10000 μg / g. The alkane content of the straight-run diesel oil is generally 30%–60%, preferably 35%–55%. The aromatic content of the straight-run diesel oil is generally 10%–35%, preferably 15%–30%.

[0009] The straight-run diesel fuel described above can be any fraction of crude oil with a distillation range of 220℃ to 380℃ obtained by passing it through a conventional atmospheric distillation column.

[0010] The above method, specifically the CO2-alkane coupling reaction, involves the straight-run diesel feedstock (and circulating oil) entering the CO2 coupling reaction zone and reacting under a CO2 atmosphere. This causes the high-content alkane components in the straight-run diesel to undergo a coupling reaction with CO2 to generate aromatics, resulting in an aromatic-rich stream.

[0011] In the above method, the CO2-alkane coupling reaction occurs in a fixed-bed reactor, and the shaped catalyst used includes a modified molecular sieve. The modified molecular sieve is a molecular sieve obtained through metal ion exchange. The molecular sieve is at least one of the following configurations: MFI, BEA, TON, MOR, MEL, and MWW, preferably MFI, and more preferably ZSM-5. The molecular sieve has a particle size of 400–600 nm, with mesopores of 2–8 nm accounting for more than 50% of the total pore volume, preferably 55%–80%, and a Si / Al molar ratio of 5–100, preferably 5–50. The molecular sieve can be prepared according to conventional methods in the art, such as the method described in CN102464336B. The metal used for metal ion exchange is preferably selected from at least one of La, Zn, Ga, Fe, Mo, and Cr, more preferably Zn. The modified molecular sieve obtained by metal ion exchange has a metal content of 3%–15% by mass. The modified molecular sieve content in the catalyst is 50%–90%, preferably 60%–80%. The catalyst may also contain binders and other components. This invention uses the aforementioned modified molecular sieve as a catalyst, which allows for the regulation of both the pore structure and the acidity of the outer surface of the catalyst. This not only effectively improves the activity and selectivity of converting alkane molecules into aromatics, but also facilitates the diffusion of hydrocarbon molecules, ensuring the retention of the generated aromatics as much as possible and slowing down the catalyst deactivation rate. The carbon dioxide coupling conversion catalyst can be prepared according to the above description and common knowledge in the art, such as by kneading and extrusion molding.

[0012] The operating conditions for the CO2-alkane coupling reaction described above are: inlet oil volume hourly space velocity (HHSV) of 0.5–5 h⁻¹. -1 Preferably 1 to 3 hours -1 The partial pressure of carbon dioxide is 4.0–13.0 MPa, preferably 8–12 MPa, and the inlet carbon dioxide mass hourly space velocity is 0.5–5 h⁻¹. -1 Preferably 1 to 3 hours -1 The reaction temperature is 300–500℃, preferably 350–450℃.

[0013] In the above method, the hydrorefining reaction zone carries out the hydrorefining reaction. Specifically, the hydrorefining reaction is as follows: after the straight-run diesel fuel is converted by CO2, the resulting liquid stream is separated into gas and liquid phases and then contacted with the hydrorefining catalyst under hydrogen conditions to undergo desulfurization and denitrification reactions. Preferably, the polycyclic aromatic hydrocarbons in the stream are simultaneously hydrogenated to obtain cycloalkyl monocyclic aromatic hydrocarbons, while the monocyclic aromatic hydrocarbons are retained.

[0014] The above method uses a hydrorefining catalyst comprising a support and a supported hydrogenating metal. The hydrogenating metal typically includes Group VIB and Group VIII metals from the periodic table, with Group VIB metals preferably being tungsten and / or molybdenum, and Group VIII metals preferably being nickel and / or cobalt. Based on the weight of the catalyst, the content of the Group VIB metal component, calculated as oxides, is 10%–35%; the content of the Group VIII metal, calculated as oxides, is 1%–7%. The support can be an inorganic refractory oxide, generally selected from at least one of alumina, silica, amorphous silica-alumina, and titanium oxide. The hydrorefining catalyst can be selected from various existing commercial catalysts, or it can be prepared according to common knowledge in the art as needed.

[0015] In the above method, the hydrocracking reaction zone carries out a hydrocracking reaction. Specifically, the hydrocracking reaction involves contacting the hydrorefined stream with a hydrocracking catalyst under hydrogen-bearing conditions. On the hydrocracking catalyst, side-chain scission reactions of cycloalkyl monocyclic aromatics and alkane chains occur to obtain the target heavy naphtha component. The hydrocracking catalyst needs to possess suitable hydrogenation activity and acidity to reduce multiple cracking processes, decrease gas and light naphtha production, and simultaneously reduce hydrogen consumption. The hydrocracking catalyst should also have an appropriate pore size, allowing reactant molecules to easily diffuse to the active centers on the catalyst's inner surface, while simultaneously allowing product molecules to quickly leave the catalyst's inner surface, thereby avoiding multiple cracking processes and reducing coke buildup.

[0016] The hydrocracking catalyst described above can be any type of hydrocracking catalyst already available in the prior art, as long as it can achieve the purpose of breaking the side chains of cycloalkyl monocyclic aromatic hydrocarbons and alkanes. Various existing commercial catalysts can be selected, such as the FC series catalysts developed by the Dalian Petrochemical Research Institute of Sinopec (e.g., FC-50, FC-26, etc.), or it can be prepared according to common knowledge in the art as needed. The hydrocracking catalyst includes a hydrocracking active metal, a molecular sieve component, and alumina. The hydrocracking active metal typically includes Group VIB and Group VIII metals from the periodic table, wherein the Group VIB metals are preferably tungsten and / or molybdenum, and the Group VIII metals are preferably nickel and / or cobalt. Based on the mass of the catalyst, the content of Group VIB metals as oxides is 10%–30%, the content of Group VIII metals as oxides is 3%–10%, the molecular sieve content is 2%–40%, and the alumina content is 10%–80%. The molecular sieve can be an acidic molecular sieve, such as a Y-type molecular sieve.

[0017] The above method, wherein the operating conditions for the hydrogenation purification reaction are: liquid hourly space velocity (LHSV) is generally 0.3–4 h⁻¹. -1 The pressure is generally 3.0 to 12.0 MPa, the inlet hydrogen-to-oil volume ratio is generally 300:1 to 3000:1, and the reaction temperature is generally 250 to 430℃.

[0018] The above method uses hydrocracking reaction under the following operating conditions: liquid hourly space velocity (LHSV) is generally 0.5–5 h⁻¹. -1 The pressure is generally 6.0 to 12.0 MPa, the inlet hydrogen-to-oil volume ratio is generally 500:1 to 1200:1, and the reaction temperature is generally 330 to 440℃.

[0019] In the above method, the effluent from the hydrocracking reaction zone, i.e., the third stream, undergoes gas-liquid separation to separate hydrogen, which is then recycled back to the hydrorefining reaction zone and the hydrocracking reaction zone. The liquid phase is fractionated to obtain dry gas, liquefied petroleum gas (LPG), light naphtha, heavy naphtha, and diesel. The fractionation is a conventional separation method in the art, as long as it can achieve the purpose of separating dry gas, LPG, light naphtha, heavy naphtha, and diesel.

[0020] The distillation range of the light naphtha obtained by the above method is 30℃~70℃; the distillation range of the heavy naphtha is 70℃~160℃; and the distillation range of the diesel is 160℃~380℃.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] (1) Studies have shown that straight-run diesel fractions have a high alkane content. When produced by conventional hydrocracking, the resulting heavy naphtha fraction also has a high alkane content, but low cycloalkanes and aromatics content, making it an undesirable high-aromatic-potential heavy naphtha product. This invention couples hydroconversion and carbon dioxide conversion to process straight-run diesel, transforming it from an unsuitable feedstock for producing high-aromatic-potential heavy naphtha into a suitable feedstock. In the conversion stage of the carbon dioxide coupling reaction zone, the high-content alkane in the straight-run diesel can be efficiently converted into aromatics through the control of catalysts and reaction conditions, thereby effectively reducing the alkane content in the straight-run diesel. In the subsequent hydroconversion stage of the reaction zone, the composition-modified straight-run diesel undergoes reactions such as aromatic saturation, side-chain breaking, and alkane chain breaking, significantly increasing the aromatic potential and aromatic content of the heavy naphtha. Overall, the entire process effectively utilizes the alkane components of straight-run diesel, altering its composition and transforming it into a feedstock suitable for producing high-aromatic-potential heavy naphtha.

[0023] (2) The method provided by the present invention deeply couples the hydroconversion of straight-run diesel and the conversion of carbon dioxide and alkanes in the process flow. Based on targeted treatment of raw materials and improved product selectivity, it achieves ideal processing effect. In addition, carbon dioxide as raw material can be widely obtained from factory exhaust gas or direct air capture. While increasing the production of high aromatic potential heavy naphtha, carbon dioxide is effectively utilized, which can effectively alleviate a series of problems caused by excessive carbon dioxide content in the atmosphere. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating the method of the present invention. Detailed Implementation

[0025] The method of the present invention will now be described in detail with reference to the accompanying drawings. Figure 1 This is only a schematic diagram of the process flow; some necessary equipment and containers have been omitted from the diagram.

[0026] like Figure 1 As shown, the method for increasing the production of high-aromatic heavy naphtha by hydroconversion of straight-run diesel fuel coupled with carbon dioxide provided by the present invention includes: straight-run diesel feedstock 1 and fractionated recycled diesel stream 13 entering CO2 coupled conversion reaction zone 2 for reaction to obtain first stream 3; the liquid stream obtained by gas-liquid separation of this stream enters hydrorefining reaction zone 4 for reaction to obtain second stream 5; this stream enters hydrocracking reaction zone 6 for reaction to obtain third stream 7; this stream enters separation and fractionation system 8 for separation to obtain dry gas 9, liquefied petroleum gas 10, light naphtha 11, heavy naphtha product 12, and diesel stream 13. Diesel stream 13 is recycled to CO2 coupled conversion reaction zone 2 for reaction again.

[0027] Specifically, the separation and fractionation system 8 includes a gas-liquid separator and a fractionation device connected in sequence (not shown in the figures).

[0028] Examples 1-5

[0029] Examples 1-5 all employ the process of this invention, such as... Figure 1 As shown, straight-run diesel fuel, after being heated in a furnace, is mixed with carbon dioxide and enters the carbon dioxide coupling conversion zone for a coupled reaction. The aromatic-rich product oil obtained after gas-liquid separation is mixed with recycled hydrogen and enters the hydrorefining reaction zone for hydrodesulfurization, denitrification, and polycyclic aromatic hydrocarbon hydrogenation saturation. The resulting product oil is then mixed with recycled hydrogen and enters the hydrocracking reaction zone, where selective ring-opening of cycloalkyl monocyclic aromatics, side-chain breaking, and alkane chain breaking reactions occur on the hydrocracking catalyst. The resulting product oil is then separated and fractionated to obtain dry gas, liquefied petroleum gas, light naphtha, heavy naphtha, and diesel fuel. The diesel fuel components are recycled back to the carbon dioxide coupling conversion zone.

[0030] The catalyst used in the carbon dioxide coupling conversion zone of this embodiment is the modified molecular sieve catalyst A of this invention. The mesoporous molecular sieve is prepared according to the method described in CN102464336B, wherein the modified molecular sieve is a metal ion exchange molecular sieve. Catalyst A is prepared by conventional kneading and extrusion molding method, and the binder is small-pore alumina. The catalyst used in the hydrorefining reaction zone is the commercially available FF-36 hydrotreatment catalyst. The catalyst used in the hydrocracking reaction zone is the commercially available FC-50 hydrocracking catalyst. The properties of the raw materials are shown in Table 1, the properties of the catalyst are shown in Table 2, and the operating conditions and properties of the main products are shown in Table 3.

[0031] Comparative Example 1

[0032] Comparative Example 1 used the same process and straight-run diesel as the feedstock as the Example. The catalyst used in the carbon dioxide co-conversion zone was a conventional naphtha-carbon dioxide co-conversion catalyst, specifically modified molecular sieve catalyst B, using a metal ion exchange molecular sieve. Catalyst B was prepared using a conventional kneading and extrusion molding method, with small-pore alumina as the binder. The catalyst used in the hydrorefining reaction zone was the commercially available FF-36 hydrotreatment catalyst. The catalyst used in the hydrocracking reaction zone was the commercially available FC-50 hydrocracking catalyst. Feedstock properties are shown in Table 1, catalyst properties in Table 2, and operating conditions and main product properties in Table 3.

[0033] Comparative Example 2

[0034] Comparative Example 2 used the same straight-run diesel as the example for production. The process differed from the example; the straight-run diesel did not enter the carbon dioxide coupled reactor but instead went directly into the hydrorefining reactor. The catalyst used in the hydrorefining reaction zone of Comparative Example 2 was the commercially available FF-36 hydrotreatment catalyst; the catalyst used in the hydrocracking reaction zone was the commercially available FC-50 hydrocracking catalyst. The properties of the feedstock are shown in Table 1, and the operating conditions and properties of the main products are shown in Table 3.

[0035] Table 1 Properties of Raw Materials

[0036] raw material Straight-run diesel Straight-run diesel percentage, % 100 Density, g / cm 3 ]] 0.8459 Distillation range, ℃ 230～369 Sulfur, μg / g 5500 Nitrogen, μg / g 95 Aromatic content, wt% 23.6 Alkane content, wt% 48.5

[0037] Table 2 Properties of carbon dioxide coupled conversion catalysts

[0038]

[0039] Table 3 Operating conditions and product properties

[0040]

[0041] The embodiments described above are merely detailed descriptions of the technical solutions of the present invention, but the present invention is not limited to the above embodiments, that is, the present invention does not depend on the steps described in the above embodiments to be implemented. In summary, any improvements made to the present invention by those skilled in the art, including the substitution of the raw materials and additives described in the present invention, the selection of specific implementation methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for increasing the production of high-aromatic, potentially heavy naphtha through hydrogenation conversion of straight-run diesel coupled with carbon dioxide, comprising: Straight-run diesel feedstock, CO2, and recycled oil are mixed and then enter the CO2 coupling reaction zone, where CO2 and alkanes undergo a coupling reaction. The resulting stream is separated into liquid and mixed with hydrogen, and then enters the hydrorefining reaction zone and the hydrocracking reaction zone. The effluent from the hydrocracking reaction zone is separated and fractionated to obtain dry gas, liquefied petroleum gas, light naphtha, heavy naphtha, and diesel, wherein the diesel is the recycled oil.

2. The method according to claim 1, characterized in that, The straight-run diesel oil has an initial boiling point of 220–300℃, a final boiling point of 330–380℃, a nitrogen content of less than 100 μg / g, and a sulfur content of more than 2000 μg / g. Preferably, the straight-run diesel oil has an alkane content of 30% to 60%, more preferably 35% to 55%, and an aromatic content of 10% to 35%, more preferably 15% to 30%.

3. The method according to claim 1, characterized in that, The CO2-alkane coupling reaction is specifically as follows: straight-run diesel feedstock enters the CO2 coupling reaction zone and reacts under a CO2 atmosphere, causing the high-content alkane components in the straight-run diesel to couple with CO2 to generate aromatics, resulting in an aromatic-rich stream.

4. The method according to claim 1 or 3, characterized in that, The CO2-alkane coupling reaction occurs in a fixed-bed reactor, and the shaped catalyst used includes modified molecular sieves. The molecular sieve is at least one of the molecular sieves with MFI, BEA, TON, MOR, MEL, and MWW configurations, preferably an MFI molecular sieve, and more preferably a ZSM-5 molecular sieve; preferably, the content of the modified molecular sieve in the catalyst is 50% to 90%, more preferably 60% to 80%.

5. The method according to claim 4, characterized in that, The molecular sieve has a particle size of 400–600 nm, and mesopores with a pore size of 2–8 nm account for more than 50% of the total pore volume, preferably 55%–80%. The Si / Al molar ratio of the molecular sieve is 5–100, preferably 5–50. Alternatively, the modified molecular sieve is a modified molecular sieve obtained by metal ion exchange. Alternatively, the metal used in the metal ion exchange is preferably selected from at least one of La, Zn, Ga, Fe, Mo, and Cr, more preferably Zn. Alternatively, the modified molecular sieve obtained by metal ion exchange has a metal content of 3%–15% by mass, calculated as an element.

6. The method according to claim 1 or 3, characterized in that, The operating conditions for the CO2-alkane coupling reaction are: inlet oil volume hourly space velocity (VHSV) of 0.5–5 h⁻¹. -1 Preferably 1 to 3 hours -1 The partial pressure of carbon dioxide is 4.0–13.0 MPa, preferably 8–12 MPa, and the inlet carbon dioxide mass hourly space velocity is 0.5–5 h⁻¹. -1 Preferably 1 to 3 hours -1 The reaction temperature is 300–500℃, preferably 350–450℃.

7. The method according to claim 1, characterized in that, The hydrorefining reaction specifically involves the following steps: after the straight-run diesel fuel is converted by CO2, the resulting liquid stream is separated into gas and liquid phases. The liquid stream is then contacted with a hydrorefining catalyst under hydrogen conditions to undergo desulfurization and denitrification reactions. Preferably, the polycyclic aromatic hydrocarbons in the stream are simultaneously hydrogenated to obtain cycloalkyl monocyclic aromatic hydrocarbons, while the monocyclic aromatic hydrocarbons are retained.

8. The method according to claim 7, characterized in that, The hydrogenation refining catalyst comprises a support and a hydrogenation metal supported thereon; the hydrogenation metal comprises Group VIB and Group VIII metals of the periodic table, wherein the Group VIB metal is preferably tungsten and / or molybdenum, and the Group VIII metal is preferably nickel and / or cobalt; preferably, based on the weight of the catalyst, the content of the Group VIB metal component, calculated as oxides, is 10% to 35%; and the content of the Group VIII metal, calculated as oxides, is 1% to 7%.

9. The method according to claim 1, characterized in that, The operating conditions for the hydrogenation refining reaction are: liquid hourly space velocity (LISH) of 0.3–4 h⁻¹. -1 The pressure is 3.0–12.0 MPa, the inlet hydrogen-to-oil volume ratio is 300:1–3000:1, and the reaction temperature is 250–430℃.

10. The method according to claim 1, characterized in that, The hydrocracking reaction specifically involves contacting the hydrorefined stream with a hydrocracking catalyst under hydrogen conditions, where cycloalkyl monocyclic aromatic hydrocarbon side chain scission and alkane chain scission reactions occur on the hydrocracking catalyst to obtain heavy naphtha.

11. The method according to claim 10, characterized in that, The hydrocracking catalyst comprises a hydrocracking active metal, a molecular sieve component, and alumina; the hydrocracking active metal comprises Group VIB and Group VIII metals of the periodic table, wherein the Group VIB metal is preferably tungsten and / or molybdenum, and the Group VIII metal is preferably nickel and / or cobalt; preferably, based on the mass of the catalyst, the content of the Group VIB metal as oxide is 10% to 30%, the content of the Group VIII metal as oxide is 3% to 10%, the content of the molecular sieve is 2% to 40%, and the content of alumina is 10% to 80%.

12. The method according to claim 1, characterized in that, The operating conditions for the hydrocracking reaction are: liquid hourly space velocity (LHSV) of 0.5–5 h⁻¹. -1 The pressure is 6.0–12.0 MPa, the inlet hydrogen-to-oil volume ratio is 500:1–1200:1, and the reaction temperature is 330–440℃.

13. The method according to claim 1, characterized in that, The distillation range of light naphtha is 30℃~70℃; the distillation range of heavy naphtha is 70℃~160℃; and the distillation range of diesel oil is 160℃~380℃.

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