A method for increasing yield of hydrogenated straight-run diesel coupled with carbon dioxide

Abstract

The application discloses a method for increasing production of aviation kerosene by coupling carbon dioxide and straight-run diesel hydrogenation conversion. The method comprises the following steps: straight-run diesel enters a coupling reaction zone to contact with a catalyst under CO2 atmosphere to perform a CO2 and alkane coupling reaction, so as to obtain a first stream; the first stream is subjected to gas-liquid separation, and then a liquid phase stream obtained after the gas-liquid separation enters a hydrofining reaction zone to contact with a catalyst under a hydrogenation condition to perform a hydrofining reaction, so as to obtain a second stream; the second stream enters a hydrocracking reaction zone to contact with a catalyst under a hydrogenation condition to perform a hydrocracking reaction, so as to obtain a third stream; the third stream enters a separation and fractionation system to be separated, so as to obtain dry gas, naphtha, aviation kerosene products and tail oil; and the tail oil is recycled to the coupling reaction zone. The method can effectively convert high-content alkane components in the straight-run diesel into aromatic hydrocarbons, and then enriches the aromatic hydrocarbons in aviation kerosene components through hydrogenation conversion, so that the aviation kerosene is effectively increased.

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] Jet kerosene, as a power source for aircraft, is suitable for use as fuel in high-speed aircraft turbine engines and is a petroleum product with high added value. Currently, global demand for jet kerosene is increasing year by year, which has not only greatly boosted the global oil market's demand for high-quality jet kerosene but also promoted the rapid development of jet kerosene production technology in the refining industry. There are currently two main methods for producing jet kerosene: straight-run jet kerosene hydrorefining or hydrocracking. The former requires high-quality crude oil, specifically naphthenic or intermediate-aryl crude oil; the latter, due to the reaction characteristics of the hydrocracking process, often produces jet kerosene with insufficient aromatics to meet standards. Therefore, for the production of high-quality jet kerosene with aromatic requirements, the selection of raw materials and the rational utilization of hydrocracking units to produce high-quality jet kerosene are key indicators of technological advancement. With the stagnation of diesel demand growth, the technology of converting diesel into jet kerosene through hydrocracking has become one of the ideal ways to address diesel surplus.

[0003] CN111088072A discloses a hydrocracking method for improving the smoke point of jet fuel. The method involves mixing feedstock oil with hydrogen and then sequentially performing hydrorefining and hydrocracking reactions. The hydrocracking product oil passes through high- and low-pressure separators and enters a fractionation tower, where it is fractionated to obtain light and heavy jet fuel. Part or all of the light jet fuel is recycled back to the hydrocracking reactor. CN106520195A discloses a hydrocracking method for improving jet fuel quality. The method fractionates the liquid-phase products from the hydrocracking reaction zone, introduces the resulting kerosene fraction into a kerosene fractionation tower for further fractionation, and obtains light, medium, and heavy jet fuel fractions. At least a portion of the medium jet fuel fraction is extracted, and the light, heavy, and optionally remaining medium jet fuel fractions are discharged from the unit as jet fuel products. These technologies improve product quality through jet fuel fractionation but do not optimize the aromatics content in the jet fuel. CN1114679C discloses a medium-pressure hydrocracking process capable of producing qualified jet fuel. It adds a hydrosaturation reactor to the existing medium-pressure hydrocracking process to achieve deep hydrosaturation of the jet fuel fraction, enabling the medium-pressure hydrocracking process to produce qualified jet fuel under most conditions. This technology requires additional equipment and involves a large kerosene fraction circulation volume, making operation complex. CN114437783A discloses a hydrocracking method for producing jet fuel. It sets up 1-N (N>2) catalyst beds in the hydrocracking reaction zone, sequentially loading hydrocracking catalyst and hydrotreating catalyst along the feed direction. Aromatic materials are introduced between the Nth and N-1th catalyst beds, allowing them to concentrate and enrich in the jet fuel components after a brief hydrocracking process, thereby increasing the aromatic content of high-quality jet fuel. CN107177375A discloses a hydrocracking method for producing jet fuel from straight-run diesel. The straight-run diesel feedstock is mixed with hydrogen and directly subjected to hydrocracking reaction, and then enters the hydrorefining reaction zone. The refined full-fraction product is then fed into a separation and distillation system to obtain naphtha and jet fuel products. This method can produce jet fuel in the largest possible quantity from straight-run diesel. However, this technology does not achieve the optimization of aromatics in jet fuel.

[0004] Studies have shown that straight-run diesel fractions are characterized by high alkane content. Therefore, when straight-run diesel fractions undergo conventional hydrocracking, the yield of kerosene fraction products is low, making it difficult to effectively produce jet fuel from straight-run diesel fractions. Modifying the properties and composition of straight-run diesel to enrich it with aromatics, thus transforming it into a suitable feedstock for jet fuel production, is crucial for the efficient utilization of diesel. Among methods for converting alkanes to aromatics, coupling carbon dioxide to aromatics is a promising technical route. CN116120139A discloses a method for the coupled production of aromatics from 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%. However, the above methods are only applicable to light feedstocks with fewer than 12 carbon atoms and are not suitable for diesel fractions with higher carbon numbers or greater complexity. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for increasing jet fuel production through hydrogenation conversion of straight-run diesel coupled with carbon dioxide. This method effectively converts the high-content alkane components in straight-run diesel into aromatics, which are then enriched in jet fuel components through hydrogenation, thereby achieving a significant increase in jet fuel production.

[0006] This invention provides a method for increasing jet fuel production through the hydroconversion of straight-run diesel fuel coupled with carbon dioxide, comprising the following steps:

[0007] (1) Straight-run diesel feedstock enters the coupled reaction zone and undergoes a coupled reaction of CO2 and alkanes with the catalyst under a CO2 atmosphere to obtain the first feedstock;

[0008] (2) The liquid phase obtained after gas-liquid separation of the first stream obtained in step (1) enters the hydrorefining reaction zone and undergoes hydrorefining reaction with the catalyst under hydrogen conditions to obtain the second stream.

[0009] (3) The second stream obtained in step (2) enters the hydrocracking reaction zone and undergoes hydrocracking reaction with the catalyst under hydrogen conditions to obtain the third stream;

[0010] (4) The third stream obtained in step (3) enters the separation and fractionation system for separation to obtain dry gas, naphtha, aviation kerosene products and tail oil.

[0011] (5) The tail oil obtained in step (4) is recycled to the coupling reaction zone described in step (1).

[0012] In the above method, the liquid phase stream obtained after gas-liquid separation of the first stream in step (2) is a diesel stream rich in aromatics, and the gas phase stream is a gaseous stream containing CO2, CO and other gaseous components.

[0013] In the above method, the straight-run diesel feedstock described in step (1) generally has an initial boiling point of 220–300°C and a final boiling point of 330–380°C. Its nitrogen content is generally below 100 μg / g, and its sulfur content is above 2000 μg / g, more preferably 2000–10000 μg / g. The alkane content of the straight-run diesel feedstock is generally 30%–60%, preferably 35%–55%. The aromatic content of the straight-run diesel feedstock is generally 10%–35%, preferably 15%–30%.

[0014] In the above method, the straight-run diesel in step (1) can be any fraction of crude oil with a distillation range of 220℃ to 380℃ obtained by conventional atmospheric distillation.

[0015] The above method, in step (1), the coupling reaction of CO2 and alkanes is specifically as follows: straight-run diesel feedstock enters the coupling reaction zone and reacts under a CO2 atmosphere, so that the high-content alkane components in the straight-run diesel react with CO2 to generate aromatics, and the first stream rich in aromatics is obtained.

[0016] In the above method, the CO2-alkane coupling reaction in step (1) 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 by metal ion exchange. The molecular sieve is at least one of the molecular sieves with MFI, BEA, TON, MOR, MEL, and MWW configurations, preferably MFI molecular sieve, and more preferably ZSM-5 molecular sieve. The molecular sieve has a particle size of 400–600 nm, and the mesopore volume with a pore size of 2–8 nm accounts 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. 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 metal content in the modified molecular sieve obtained by metal ion exchange is 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.

[0017] In the above method, the operating conditions for the CO2-alkane coupling reaction in step (1) are: inlet oil volume hourly space velocity 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℃.

[0018] The above method, specifically the hydrorefining reaction in step (2) is as follows: the first stream obtained after the straight-run diesel is converted by CO2 coupling is separated into a liquid stream by gas-liquid separation and then contacted with the hydrorefining catalyst under hydrogen conditions to undergo desulfurization and denitrification reactions. Preferably, the aromatics in the first stream are simultaneously hydrogenated to obtain cycloalkanes.

[0019] The hydrogenation refining catalyst in step (2) of the above method comprises a support and a supported hydrogenation metal. The hydrogenation metal typically includes Group VIB and Group VIII metals from the periodic table, wherein Group VIB metals are preferably tungsten and / or molybdenum, and Group VIII metals are preferably 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 hydrogenation refining catalyst can be selected from various existing commercial catalysts, or it can be prepared according to common knowledge in the art as needed.

[0020] In the above method, the hydrocracking reaction in step (3) specifically involves the second stream obtained after hydrorefining contacting the hydrocracking catalyst under hydrogen-containing conditions. Cycloalkanes undergo ring-opening and chain-breaking reactions on the hydrocracking catalyst to obtain the target jet fuel component. The hydrocracking catalyst in step (3) needs to have high hydrogenation activity and suitable acidity to reduce secondary cracking and lower hydrogen consumption. Simultaneously, the catalyst should have an appropriate pore size so that reactant molecules can easily diffuse to the active centers on the inner surface of the catalyst, while product molecules can easily leave the inner surface of the catalyst, thereby avoiding secondary cracking and reducing coke buildup.

[0021] In the above method, the hydrocracking catalyst in step (3) can be any type of hydrocracking catalyst already available in the prior art, as long as it can achieve the purpose of cycloalkanes opening and chain scission in step (3). Various existing commercial catalysts can be selected, such as the FC series catalysts (e.g., FC-50A) developed by the Dalian Petrochemical Research Institute of Sinopec, or it can be prepared according to common knowledge in the field 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 Group VIB metals are preferably tungsten and / or molybdenum, and 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 wt%, the content of Group VIII metals as oxides is 4–10 wt%, the content of molecular sieves is 10–70 wt%, and the content of alumina is 10–50 wt%. The molecular sieve can be an acidic molecular sieve, such as a Y-type molecular sieve.

[0022] The operating conditions for the hydrogenation purification reaction in step (2) of the above method are: the liquid hourly space velocity is generally 0.3 to 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℃.

[0023] The operating conditions for the hydrocracking reaction in step (3) of the above method are: liquid hourly space velocity (LHSV) is generally 0.5–4 h⁻¹. -1 The pressure is generally 4.0 to 13.0 MPa, the inlet hydrogen-to-oil volume ratio is generally 300:1 to 1000:1, and the reaction temperature is generally 350 to 430℃.

[0024] In the above method, the separation in step (4) is gas-liquid separation. The third stream undergoes gas-liquid separation to separate hydrogen as circulating hydrogen and recycle it back to the hydrorefining and hydrocracking reaction zone. The liquid phase is fractionated to obtain dry gas, naphtha, jet fuel and tail oil. The fractionation is a conventional separation method in the field, as long as it can achieve the purpose of separating dry gas, naphtha, jet fuel and tail oil.

[0025] The naphtha obtained in step (4) of the above method has a distillation range of 30℃~160℃, the jet fuel has a distillation range of 160℃~290℃, and the tail oil has a distillation range of 290℃~380℃.

[0026] In the above method, the tail oil in step (5) is recycled to the coupling zone in step (1) and mixed with straight-run diesel feedstock to continue the reaction.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) The main characteristic of straight-run diesel fraction is its high alkanes content. Studies have shown that when alkanes in straight-run diesel fraction undergo conventional hydrocracking, most of the product is naphtha, while the yield of jet fuel fraction is low. Therefore, the route for producing jet fuel from straight-run diesel fraction is difficult to implement effectively. This invention couples hydroconversion and carbon dioxide conversion to process straight-run diesel, transforming it from an unsuitable feedstock for jet fuel production into one suitable for jet fuel production. In the carbon dioxide coupling conversion stage of the coupled reaction zone, the alkanes with high content in straight-run diesel can be efficiently converted into aromatics through the control of catalysts and reaction conditions, thereby effectively reducing the alkanes content in straight-run diesel. In the hydrorefining reaction zone and the hydrocracking reaction zone, the straight-run diesel with altered composition undergoes aromatic saturation and ring-opening and chain-breaking reactions, significantly improving the jet fuel component yield. Overall, the entire process effectively utilizes the alkanes in straight-run diesel, changing its composition and transforming it into a feedstock suitable for jet fuel production.

[0029] (2) The method provided by the present invention deeply couples the hydrogenation conversion 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 jet fuel, carbon dioxide is effectively utilized, which can effectively alleviate a series of problems caused by excessive carbon dioxide content in the atmosphere.

[0030] (3) The method of the present invention can significantly improve the yield of aviation kerosene and the content of aromatic hydrocarbons in aviation kerosene, and at the same time significantly reduce the freezing point of aviation kerosene. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the method of the present invention. Detailed Implementation

[0032] 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.

[0033] like Figure 1 As shown, the method for increasing jet fuel production through the hydroconversion of straight-run diesel fuel coupled with carbon dioxide provided by the present invention includes: straight-run diesel feedstock 1 enters a coupled reaction zone 2 for a CO2 coupled conversion reaction to obtain a first stream 3; the liquid stream obtained from this stream undergoes gas-liquid separation and enters a hydrorefining reaction zone 4 for a hydrorefining reaction to obtain a second stream 5; this stream enters a hydrocracking reaction zone 6 for a hydrocracking reaction to obtain a third stream 7; this stream enters a separation and fractionation system 8 to obtain dry gas 9, naphtha product 10, jet fuel product 11, and tail oil stream 12. The tail oil stream 12 is recycled back to the coupled reaction zone 2 and mixed with the straight-run diesel feedstock 1 for subsequent reactions.

[0034] Specifically, the separation and fractionation system 8 includes a gas-liquid separator and a fractionation device connected in sequence (not shown in the figures).

[0035] Examples 1-5

[0036] Examples 1-5 all employ the process of this invention, such as... Figure 1As 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 aromatic hydrogenation saturation. The resulting cycloalkane-rich product oil is mixed with recycled hydrogen and enters the hydrocracking reaction zone, where selective ring-opening cracking of cycloalkanes and chain scission of alkanes occur on the hydrocracking catalyst. The resulting product oil is fractionated to obtain dry gas, naphtha, jet fuel, and tail oil. The tail oil components are recycled back to the carbon dioxide coupling conversion zone.

[0037] 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-50A 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.

[0038] Comparative Example 1

[0039] 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-50A hydrocracking catalyst. Feedstock properties are shown in Table 1, catalyst properties in Table 2, and operating conditions and main product properties in Table 3.

[0040] Comparative Example 2

[0041] 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-50A 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.

[0042] Table 1 Properties of Raw Materials

[0043] raw material Straight-run diesel Straight-run diesel percentage, % 100 <![CDATA[Density, g / cm 3 > 0.8356 Distillation range, ℃ 228～355 Sulfur, μg / g 4500 Nitrogen, μg / g 35 Aromatic content, wt% 21.1 Alkane content, wt% 47.2

[0044] Table 2 Properties of carbon dioxide coupled conversion catalysts

[0045]

[0046]

[0047] Table 3 Operating conditions and product properties

[0048]

[0049]

[0050] 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 jet fuel production through hydrogenation conversion of straight-run diesel coupled with carbon dioxide, comprising the following steps: (1) Straight-run diesel feedstock enters the coupled reaction zone and undergoes a coupled reaction of CO2 and alkanes with the catalyst under a CO2 atmosphere to obtain the first feedstock; (2) The liquid phase obtained after gas-liquid separation of the first stream obtained in step (1) enters the hydrorefining reaction zone and undergoes hydrorefining reaction with the catalyst under hydrogen conditions to obtain the second stream. (3) The second stream obtained in step (2) enters the hydrocracking reaction zone and undergoes hydrocracking reaction with the catalyst under hydrogen conditions to obtain the third stream; (4) The third stream obtained in step (3) enters the separation and fractionation system for separation to obtain dry gas, naphtha, aviation kerosene products and tail oil. (5) The tail oil obtained in step (4) is recycled to the coupling reaction zone described in step (1).

2. The method according to claim 1, characterized in that, The initial boiling point of the straight-run diesel in step (1) is 220-300℃; the final boiling point is 330-380℃; the nitrogen content is below 100μg / g; and the sulfur content is above 2000μg / 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 in step (1) specifically involves the straight-run diesel feedstock entering the coupling reaction zone and reacting under a CO2 atmosphere, causing the high-content alkane components in the straight-run diesel to undergo a coupling reaction with CO2 to generate aromatics, thus obtaining a first stream rich in aromatics.

4. The method according to claim 1 or 3, characterized in that, The CO2-alkane coupling reaction described in step (1) 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 in step (1) are: inlet oil volume hourly space velocity 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 in step (2) specifically involves the following: the first stream obtained after the straight-run diesel is converted by CO2 coupling is separated into a liquid stream by gas-liquid separation and then contacted with a hydrorefining catalyst under hydrogen conditions to undergo desulfurization and denitrification reactions. Preferably, the aromatics in the first stream are simultaneously hydrogenated to obtain cycloalkanes.

8. The method according to claim 7, characterized in that, The hydrorefining catalyst in step (2) includes a support and a hydrogenation metal supported thereon; the hydrogenation metal includes Group VIB and Group VIII metals in 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 as oxide is 10% to 35%; and the content of the Group VIII metal as oxide is 1% to 7%.

9. The method according to claim 1, characterized in that, The operating conditions for the hydrogenation purification reaction in step (2) 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 in step (3) specifically involves the second stream obtained after hydrorefining being contacted with a hydrocracking catalyst under hydrogen conditions, where cycloalkanes undergo ring-opening and chain-breaking reactions to obtain jet fuel.

11. The method according to claim 10, characterized in that, The hydrocracking catalyst described in step (3) comprises a hydrocracking active metal, a molecular sieve component, and alumina; the hydrocracking active metal comprises Group VIB and Group VIII metals in 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 10-30 wt%, the content of the Group VIII metal as oxide is 4-10 wt%, the content of the molecular sieve is 10-70 wt%, and the content of alumina is 10-50 wt%.

12. The method according to claim 1, characterized in that, The operating conditions for the hydrocracking reaction in step (3) are: liquid hourly space velocity (LHSV) of 0.5–4 h⁻¹. -1 The pressure is 4.0–13.0 MPa, the inlet hydrogen-to-oil volume ratio is 300:1–1000:1, and the reaction temperature is 350–430℃.

13. The method according to claim 1, characterized in that, The naphtha obtained in step (4) has a distillation range of 30℃~160℃, the jet fuel has a distillation range of 160℃~290℃, and the tail oil has a distillation range of 290℃~380℃.

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