A hydrocracking method for improving the quality of heavy naphtha

Abstract

The application discloses a hydrocracking method for improving the quality of heavy naphtha. The method comprises the following steps: (1) feeding a wax oil raw material and hydrogen into a hydrofining reactor, and reacting with a hydrofining catalyst to obtain a hydrofining stream; (2) feeding the hydrofining stream into a hydrocracking reactor, and separating and fractionating the obtained product to obtain heavy naphtha and the like; wherein a hydrocracking catalyst bed is arranged at the upstream of the hydrocracking reactor, and a post-hydrofining catalyst bed is arranged at the downstream of the hydrocracking reactor; a material P is introduced between the hydrocracking catalyst bed and the post-hydrofining catalyst bed, the material P is one or more of C7-C11 olefin alcohol, olefin aldehyde, acetylene alcohol and acetylene aldehyde; and an air cooling device is arranged before fractionation of the obtained product, wherein the air cooling device is water injected so that the material P in the product is taken out of the reaction system by the water phase. The method can improve the bromine index of the heavy naphtha without changing the distribution and yield of the hydrocracking product.

Description

Technical Field

[0001] This invention relates to the field of hydrocracking technology, and more specifically to a hydrocracking method for improving the quality of heavy naphtha. Background Technology

[0002] In recent years, stringent environmental regulations and economic development have led to a rapid increase in demand for chemical feedstocks in the oil market. Hydrocracking processes can convert heavy, low-quality feedstocks into lighter products. Heavy naphtha is a crucial feedstock for aromatics production, while tail oil and hydrocracking diesel are important feedstocks for ethylene production. Currently, recycling diesel and tail oil fractions to the hydrocracking reactor is an effective way to maximize heavy naphtha production. However, increasing the conversion depth can lead to over-cracking of hydrocarbons and an increase in the yield of light hydrocarbons. Therefore, developing hydrocracking technology that can simultaneously meet market demand and maximize the production of chemical feedstocks is of significant practical importance.

[0003] CN101210195A discloses a hydrocracking method for producing more light chemical oil from low-quality heavy feedstock. This method uses a preferred hydrorefining catalyst and a hydrocracking catalyst to process high-sulfur, high-nitrogen low-quality heavy feedstock in a single-stage, one-pass process, achieving a naphtha yield of approximately 35%. However, this one-pass process also produces some middle distillate and tail oil, thus limiting the naphtha yield.

[0004] CN104560169B discloses a hydrocracking method for producing heavy naphtha from high-nitrogen feedstock. The method includes: mixing high-nitrogen feedstock oil with hydrogen-rich gas, heating the mixture, and then introducing it into a first reaction zone for hydrorefining and hydrocracking reactions. The reaction stream is cooled, separated from the gas, and fractionated to obtain light naphtha, heavy naphtha, and tail oil fractions. The tail oil fraction is pressurized and mixed with recycled hydrogen before entering a second reaction zone for hydrocracking. In this method, the second reaction zone can convert all the difficult-to-convert tail oil fractions into naphtha fractions under high space velocity and low harshness conditions. However, it does not fully consider the enhanced conversion of hydrocarbon zones, and the yields of low-value-added products such as dry gas, liquefied petroleum gas, and light naphtha remain relatively high.

[0005] CN113122322B discloses a hydrocracking method for reducing the bromine index of heavy naphtha. The method includes: (1) mixing hydrocracking feedstock with hydrogen and then introducing it into a hydrocracking pretreatment reactor for hydrorefining; (2) introducing the hydrorefining effluent into a hydrocracking reactor, contacting it with a highly active hydrocracking catalyst, and conducting a hydrocracking reaction under high scorching conditions; (3) introducing the effluent from step (2) into the bottom of the hydrocracking reactor, contacting it with a weakly active hydrocracking catalyst for reaction; and (4) separating and fractionating the hydrocracking product obtained in step (3) to obtain a heavy naphtha product with a reduced bromine index. This method can improve the quality of the obtained heavy naphtha product while maintaining the yield of the light fraction.

[0006] However, the weakly hydrocracking catalyst in the method disclosed in CN113122322B still possesses cracking activity, which will have a certain cracking effect on the products. This means that products such as heavy naphtha, jet fuel, and diesel still carry the risk of over-cracking, which is detrimental to product yield. Furthermore, this method is only applicable to high-activity hydrocracking catalysts and high reaction temperatures, resulting in low flexibility. When adjusting the operating conditions to lower the reaction temperature in a unit using a high-activity hydrocracking catalyst, this method is not ideal. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a hydrocracking method for improving the quality of heavy naphtha. This method can specifically improve the bromine index of heavy naphtha without altering the distribution and yield of the hydrocracking products.

[0008] The hydrocracking method for improving the quality of heavy naphtha provided by this invention includes the following steps:

[0009] (1) Wax oil raw material and hydrogen enter the hydrorefining reactor, and come into contact with the hydrorefining catalyst to carry out the hydrorefining reaction, and obtain the hydrorefined stream.

[0010] (2) The hydrorefined stream enters the hydrocracking reactor, and the resulting products are separated and fractionated to obtain light naphtha, heavy naphtha, jet fuel, diesel oil and tail oil fractions; wherein a hydrocracking catalyst bed is set up upstream of the hydrocracking reactor and a post-hydrorefining catalyst bed is set up downstream; material P is introduced between the hydrocracking catalyst bed and the post-hydrorefining catalyst bed, wherein material P is one or more of C7-C11 olefin alcohols, olefin aldehydes, alkyne alcohols and alkyne aldehydes; an air cooling device is set up before the fractionation of the resulting products, wherein the air cooling device is injected with water so that material P in the products is carried out of the reaction system by the aqueous phase.

[0011] In the method of this invention, both the hydrorefining reactor and the hydrocracking reactor are fixed-bed reactors.

[0012] In the method of this invention, the hydrorefining reactor adopts a conventional top-feed, bottom-discharge method. In the hydrocracking reactor, the hydrorefined stream and hydrogen gas adopt a top-feed, bottom-discharge method.

[0013] In the method of this invention, the initial boiling point of the wax oil feedstock is generally 200℃~350℃, and the dry point is generally 500℃~600℃, preferably 530℃~590℃; the nitrogen content is below 2500μg / g, generally 500μg / g~2000μg / g; the sulfur content is not strictly limited, and the content of other impurities only needs to meet conventional requirements. The wax oil feedstock can be at least one of various straight-run or secondary-processed wax oils obtained from processing naphthenic crude oil, intermediate-based crude oil, or paraffinic crude oil, preferably straight-run wax oil components or deasphalted oils from primary-processed paraffinic crude oil, which can be selected from at least one of various vacuum gas oils (VGO) and deasphalted oils (DAO) obtained from processing paraffinic crude oil, such as Daqing VGO, DAO, Changqing VGO, DAO, Shengli VGO, DAO, or several of them. The hydrogen gas is a feedstock with a commonly used industrial impurity content that meets the requirements.

[0014] In the method of this invention, the operating conditions of the hydrorefining reactor in step (1) are as follows: the reaction temperature is 300℃~420℃, preferably 310℃~390℃; the reactor inlet pressure is 6MPa~20MPa, preferably 8MPa~18MPa; and the volume hourly space velocity is 0.5h. -1 ~3.0h -1 0.6h is preferred -1 ~2.5h -1 The hydrogen-to-oil volume ratio at the reactor inlet is 400–1200, preferably 500–1100.

[0015] In the method of this invention, the hydrorefining catalyst and the post-hydrorefining catalyst can be hydrocracking pretreatment catalysts, comprising a support and a hydrogenation metal. Based on the weight of the catalyst, it typically includes a Group VIB metal component from the periodic table, such as tungsten and / or molybdenum, with a mass content of 10%–35% (based on oxides), preferably 15%–30%, and a Group VIII metal, such as nickel and / or cobalt, with a mass content of 1%–7% (based on oxides), preferably 1.5%–6%. The support is an inorganic refractory oxide, generally selected from at least one of alumina, amorphous aluminum silicate, silica, titanium dioxide, etc. The hydrorefining catalyst preferably has a Mo-Ni metal combination with a specific surface area ≥160 m². 2 / g, pore volume ≥0.3mL / g. The preferred metal catalyst for post-hydrogenation refining is a Mo-Co combination with a specific surface area ≥160m². 2 / g, pore volume ≥0.3mL / g. The conventional hydrocracking pretreatment catalyst can be any of the existing commercial catalysts, such as the 3936, 3996, FF-12, FF-16, FF-26, FF-36, FF-46, and FF-66 catalysts developed by the Fushun Petrochemical Research Institute (FRIPP); alternatively, the required catalyst can be prepared according to common knowledge in the field. The refining reaction is a process of removing impurities such as desulfurization, denitrification, and aromatic saturation. The hydrorefining catalyst and the post-hydrorefining catalyst can be the same or different.

[0016] In the method of this invention, the operating conditions of the hydrocracking catalyst bed in the hydrocracking reactor in step (2) are as follows: the reaction temperature is 350℃~435℃, preferably 360℃~430℃; the reactor inlet pressure is 6MPa~20MPa, preferably 8MPa~18MPa; and the volume hourly space velocity is 0.5h. -1 ~5.0h -1 0.6h is preferred -1 ~3.0h -1 The hydrogen-to-oil volume ratio at the reactor inlet is 400–2000, preferably 500–1100. Generally, during the later stages of operation, the hydrocracking reaction temperature is 380℃–430℃.

[0017] In the method of this invention, the operating conditions of the hydrorefining catalyst bed after the hydrocracking reactor in step (2) are as follows: the reaction temperature is 360℃~435℃, preferably 375℃~430℃; the volume hourly space velocity of the hydrocracking bed products is 10h. -1 ~25h -1 12h preferred -1 ~20h -1 The hydrogen-to-oil volume ratio is 400–2000, preferably 500–1100, and the reactor inlet pressure is 6 MPa–20 MPa, preferably 8 MPa–18 MPa. Generally, the reaction temperature of the post-hydrogenation refining catalyst bed is 390℃–430℃ during the later stages of operation.

[0018] In the method of this invention, the hydrocracking catalyst comprises a cracking component and a hydrogenation component, and may also include a binder. The cracking component typically comprises at least one amorphous silica-alumina and / or molecular sieve, such as Y-type, β-type, or USY molecular sieves, and the binder is typically alumina and / or silica. The hydrogenation component is selected from at least one metal, metal oxide, or metal sulfide from Group VIB, Group VIIB, or Group VIII, with the hydrogenation metal more preferably being one or more of iron, chromium, molybdenum, tungsten, cobalt, and nickel. Based on the weight of the catalyst, the hydrogenation component, calculated as oxides, comprises 5% to 35%, preferably 10% to 35%, the molecular sieve content is 35% or more, preferably 35% to 70%, and the remainder is amorphous silica-alumina and / or binder components. Conventional hydrocracking catalysts can be selected from various existing commercial catalysts, such as FC-46, FC-52, and FC-82 catalysts developed by FRIPP. Specific hydrocracking catalysts can also be prepared as needed according to common knowledge in the art.

[0019] In the method of the present invention, the material P is selected from one or more of C7-C11 olefin alcohols, olefin aldehydes, alkyne alcohols, and alkyne aldehydes, and is further selected from one or more of octynol, 3-nonenol, 2-decenal, and 2-undecenal.

[0020] In the method of the present invention, preferably, relative to the post-hydrorefining catalyst, the volume hourly space velocity of the material P accounts for 28% to 72% of the total volume hourly space velocity of the hydrocracking bed products and the material P, more preferably 30% to 60%, for example, but not limited to 30%, 32%, 35%, 40%, 50%, 55%, 60%, etc., and any value within the range formed by any two of these values.

[0021] In the method of this invention, preferably, after the hydrocracking bed product stream passes through the post-hydrorefining catalyst, the C8-C10 alkanes retention rate is above 85 wt%, more preferably 90 wt% to 95 wt%. Wherein, the C8-C10 alkanes retention rate = (C8-C10 alkanes concentration in the post-refined product / C8-C10 alkanes concentration in the hydrocracking bed product stream) * 100%.

[0022] The inventors discovered that the high bromine index of heavy naphtha is mainly due to the alkane component. Effectively retaining the alkane component would be highly beneficial for the operation of the reforming unit. Further research revealed that material P will be present at lower space velocities (1.5–2.5 h⁻¹). -1 The hydrodeoxygenation reaction is carried out at relatively low temperatures (300–330 °C), but post-hydrogenation purification at high space velocities (2.8–18.0 h⁻¹) is necessary. -1Deoxygenation reactions are difficult to occur in reaction environments with high temperatures (360℃~435℃). Therefore, introducing material P before post-hydrogenation refining in the hydrocracking reactor can inhibit the dehydrogenation reaction of alkanes in the material during post-refining, which helps to retain alkanes efficiently. At the same time, material P is highly soluble in water, so material P can be effectively removed before product fractionation. Thus, it will not only not affect the product composition and distribution of heavy naphtha, but also ensure that the bromine index of heavy naphtha does not increase, making it a high-quality feed for reforming units.

[0023] Hydrocracking units typically involve a separation process (generally including hot high-performance fraction, hot low-performance fraction, cold high-performance fraction, and cold low-performance fraction) before fractionation of the hydrocracking products. This process separates the gaseous components from the products, improving the efficiency of the fractionation process and reducing energy consumption. Specifically, a water injection process occurs after the hot high-performance fraction and before air cooling. This is to prevent the precipitation of ammonium salts during the cooling process, which could clog pipelines and equipment. Since the material P in the method of this invention is highly soluble in water, it can be carried out of the reaction system by the aqueous phase.

[0024] In the method of the present invention, an air cooling device is set up before the fractionation of the obtained product. The air cooling device is injected with water so that the material P in the product is carried out of the reaction system by the aqueous phase. The amount of water injected is 2 to 30 times the mass flow rate of material P, preferably 3 to 8 times the mass flow rate of material P.

[0025] In the method of this invention, the subsequent product separation, fractionation process and various qualified products are all conventional technical contents familiar to those skilled in the art, and will not be described in detail here.

[0026] In the method of this invention, the final boiling point of light naphtha is 50–68°C, preferably 55–62°C; the initial boiling point of heavy naphtha is 55–75°C, preferably 60–68°C, and the final boiling point is 150–190°C, preferably 167–180°C; the initial boiling point of jet fuel is 160–200°C, preferably 170–185°C, and the final boiling point is 220–250°C, preferably 225–240°C; the initial boiling point of diesel fuel is 230–270°C, preferably 230–265°C, and the final boiling point is 330–380°C, preferably 340–375°C; and the initial boiling point of tail oil is 350–390°C, preferably 365–375°C.

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

[0028] (1) The catalysts used in the hydrocracking unit in the method of the present invention are all conventional catalysts, and there is no need to develop new catalysts;

[0029] (2) In the method of the present invention, the problem of bromine index of heavy naphtha is specifically improved by introducing material P, without causing changes in product distribution and other product properties;

[0030] (3) In the method of the present invention, material P is soluble in water and can be discharged from the system with the demineralized water during the separation of hydrocracking products. It will not enter the fractionation system, so that the heavy naphtha components will not have any impurities. The process is energy-saving and efficient.

[0031] (4) The method of the present invention has strong applicability and can improve the bromine index of heavy naphtha for any hydrocracking catalyst and process conditions. The adjustment method is flexible. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the process of the present invention;

[0033] The annotations in the attached figures are explained as follows:

[0034] 1-Feedstock oil and hydrogen, 2-Hydrorefining reactor, 3-Hydrorefining product, 4-Hydrocracking reactor, 5-Hydrocracking catalyst bed, 6-Post-hydrorefining catalyst bed, 7-Feed P, 8-Hydrocracking product, 9-Hot high-efficiency fractionator, 10-Hot high-efficiency fractionator gas phase component, 11-Water, 12-Air cooler, 13-Cooled feedstock, 14-Cold high-efficiency fractionator, 15-Cold high-efficiency fractionator gas phase component, 16-Acidic water, 17-Cold high-efficiency fractionator oil phase component, 18-Cold low-efficiency fractionator, 19-Cold low-efficiency fractionator gas phase component, 20-Cold low-efficiency fractionator oil phase component, 21-Hot high-efficiency fractionator oil phase component, 22-Hot low-efficiency fractionator, 23-Hot low-efficiency fractionator gas phase component, 24-Hot low-efficiency fractionator oil phase component, 25-Fractioning system. Detailed Implementation

[0035] The method of the present invention will be described in more detail below with reference to specific embodiments and comparative examples.

[0036] The hydrocracking method for improving the quality of heavy naphtha provided by this invention, such as... Figure 1 As shown, it includes:

[0037] Feedstock oil and hydrogen 1 are sequentially passed through hydrorefining reactor 2 and hydrocracking reactor 4 (equipped with hydrocracking catalyst bed 5 and post-hydrorefining catalyst bed 6). Material P7 is introduced between the hydrocracking catalyst bed 5 and the post-hydrorefining catalyst bed 6. The product from the hydrocracking bed and material P7 are passed together through the post-hydrorefining catalyst bed 6 to obtain hydrocracking product 8. Hydrocracking product 8 passes through hot high-efficiency separator 9. The hot high-efficiency gas phase component 10 is mixed with water 11 and then enters air cooler 12 for cooling. The cooled material 13 enters cold high-efficiency separator 14 for separation to obtain cold high-efficiency gas phase component 15, cold high-efficiency oil phase component 17, and acidic water 16. The acidic water 16 contains material P7 dissolved in water. Hot high-grade oil phase component 21 enters hot low-grade separator 22 for separation to obtain hot low-grade gas phase component 23 and hot low-grade oil phase component 24. Cold high-grade oil phase component 17 and hot low-grade gas phase component 23 enter cold low-grade separator 18 for separation to obtain cold low-grade gas phase component 19 and cold low-grade oil phase component 20. Cold low-grade oil phase component 20 and hot low-grade oil phase component 24 enter fractionation system 25 for separation.

[0038] In the embodiments and comparative examples of the present invention, the distillation range of light naphtha is the fraction below 62°C, the distillation range of heavy naphtha is 62-178°C, the distillation range of jet fuel is 178-230°C, the distillation range of diesel is 230-370°C, and the tail oil is the fraction above 370°C.

[0039] The properties of the feedstock used in the following examples and comparative examples are shown in Table 1, and the main properties of the catalysts used in the examples and comparative examples are shown in Table 2.

[0040] Table 1 Main Properties of Crude Oil

[0041] project crude oil type Straight-run wax oil <![CDATA[Density, g / cm 3 > 0.9032 Distillation range, °C 305～535 S, wt% 1.37 N, μg / g 1098

[0042] Table 2 Main properties of the catalyst

[0043]

[0044] Example 1

[0045] Adopting such Figure 1 This is a series process flow. Hydrorefining catalyst A is used, hydrocracking catalyst B is used, and post-hydrorefining catalyst A is used again. Feed material P is 2-undecenal, and the heavy naphtha yield is controlled at approximately 35%. The bromine index of the heavy naphtha is sampled and analyzed.

[0046] Example 2

[0047] Adopting such Figure 1This is a series process flow. Hydrorefining catalyst A is used, hydrocracking catalyst B is used, and post-hydrorefining catalyst A is used again. Feed material P uses 3-nonenol and 2-decenal (mass ratio 1:1). The heavy naphtha yield is controlled at approximately 40%, and the bromine index of the heavy naphtha is sampled and analyzed.

[0048] Example 3

[0049] Adopting such Figure 1 This is a series process flow. Hydrorefining catalyst A is used, hydrocracking catalyst B is used, and post-hydrorefining catalyst C is used. Feedstock P consists of octyryne alcohol, 2-decenal, and 2-undecenal (mass ratio 2:1:1). The heavy naphtha yield is controlled at approximately 40%, and the bromine index of the heavy naphtha is analyzed by sampling.

[0050] Comparative Example 1

[0051] Compared with Example 1, the only difference is that material P is not introduced and water is injected into the air-cooled room in a conventional manner.

[0052] A conventional single-stage series process was adopted. Catalyst A was used for hydrorefining, catalyst B for hydrocracking, and catalyst A was used for post-hydrorefining. The heavy naphtha yield was controlled at approximately 35%, and the bromine index of the heavy naphtha was sampled and analyzed.

[0053] Comparative Example 2

[0054] Compared with Example 3, the only difference is that material P is not introduced and water is injected into the air-cooled room in a conventional manner.

[0055] A conventional single-stage series process was adopted. Catalyst A was used for hydrorefining, catalyst B for hydrocracking, and catalyst C for post-hydrorefining. The heavy naphtha yield was controlled at approximately 40%, and the bromine index of the heavy naphtha was analyzed by sampling.

[0056] Comparative Example 3

[0057] The difference compared to Example 3 is that the material P is different.

[0058] Adopting such Figure 1 This is a series process flow. Hydrorefining catalyst A is used, hydrocracking catalyst B is used, and post-hydrorefining catalyst C is used. Feedstock P consists of propynyl aldehyde, pentylenal, 3-buten-1-ol, and 5-hexyn-1-ol (mass ratio 1:1.3:2.5:1.4). The heavy naphtha yield is controlled at approximately 40%, and the bromine index of the heavy naphtha is analyzed by sampling.

[0059] The effects of the above embodiments and comparative examples are compared in Table 3.

[0060] Table 3. Reaction conditions and results for each embodiment and comparative example.

[0061]

Claims

1. A hydrocracking method for improving the quality of heavy naphtha, comprising the following steps: (1) Wax oil raw material and hydrogen enter the hydrorefining reactor, and come into contact with the hydrorefining catalyst to carry out the hydrorefining reaction, and obtain the hydrorefined stream. (2) The hydrorefined stream enters the hydrocracking reactor, and the resulting products are separated and fractionated to obtain light naphtha, heavy naphtha, jet fuel, diesel oil and tail oil fractions; wherein a hydrocracking catalyst bed is set up upstream of the hydrocracking reactor and a post-hydrorefining catalyst bed is set up downstream; material P is introduced between the hydrocracking catalyst bed and the post-hydrorefining catalyst bed, wherein material P is one or more of C7-C11 olefin alcohols, olefin aldehydes, alkyne alcohols and alkyne aldehydes; an air cooling device is set up before the fractionation of the resulting products, wherein the air cooling device is injected with water so that material P in the products is carried out of the reaction system by the aqueous phase.

2. The method according to claim 1, characterized in that, The initial boiling point of the wax oil raw material is 200℃~350℃, and the dry point is 500℃~600℃, preferably 530℃~590℃; the nitrogen content is below 2500μg / g, and more preferably 500μg / g~2000μg / g.

3. The method according to claim 1, characterized in that, The operating conditions of the hydrorefining reactor in step (1) are as follows: reaction temperature is 300℃~420℃, preferably 310℃~390℃; reactor inlet pressure is 6MPa~20MPa, preferably 8MPa~18MPa; volume hourly space velocity is 0.5h. -1 ~3.0h -1 0.6h is preferred -1 ~2.5h -1 The hydrogen-to-oil volume ratio at the reactor inlet is 400–1200, preferably 500–1100.

4. The method according to claim 1, characterized in that, The aforementioned hydrorefining catalyst and post-hydrorefining catalyst are hydrocracking pretreatment catalysts, comprising a support and a hydrogenating metal. Based on the weight of the catalyst, the mass content of Group VIB metal components, calculated as oxides, is 10%–35%, preferably 15%–30%, and the mass content of Group VIII metals, calculated as oxides, is 1%–7%, preferably 1.5%–6%. Preferably, the hydrogenating metal in the hydrorefining catalyst is Mo-Ni, with a specific surface area ≥160 m². 2 / g, pore volume ≥0.3mL / g; preferably, the hydrogenating metal in the post-hydrogenation refining catalyst is Mo-Co, with a specific surface area ≥160m². 2 / g, pore volume ≥0.3mL / g.

5. The method according to claim 1, characterized in that, The operating conditions of the hydrocracking catalyst bed in the hydrocracking reactor in step (2) are as follows: reaction temperature is 350℃~435℃, preferably 360℃~430℃; reactor inlet pressure is 6MPa~20MPa, preferably 8MPa~18MPa; volume hourly space velocity is 0.5h. -1 ~5.0h -1 0.6h is preferred -1 ~3.0h -1 The hydrogen-to-oil volume ratio at the reactor inlet is 400–2000, preferably 500–1100.

6. The method according to claim 1, characterized in that, The operating conditions for the hydrorefining catalyst bed after the hydrocracking reactor in step (2) are as follows: reaction temperature is 360℃~435℃; volume hourly space velocity of the hydrocracking bed products is 10h. -1 ~25h -1 The hydrogen-to-oil volume ratio is 400–2000; the reactor inlet pressure is 6 MPa–20 MPa; preferably, the reaction temperature is 375°C–430°C; and the volume hourly space velocity (VHSV) of the hydrocracking bed products is 12 h⁻¹. -1 ~20h -1 The hydrogen-to-oil volume ratio is 500–1100; the reactor inlet pressure is 8 MPa–18 MPa.

7. The method according to claim 1, characterized in that, The hydrocracking catalyst comprises a cracking component and a hydrogenation component. The cracking component comprises amorphous silica-alumina and / or molecular sieves (the molecular sieves are selected from at least one of Y-type, β-type, or USY molecular sieves). The hydrogenation component is selected from at least one of Group VIB, Group VIIB, or Group VIII. The hydrogenation metal is more preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, and nickel. Preferably, based on the weight of the catalyst, the content of the hydrogenation component as oxides is 5% to 35%, more preferably 10% to 35%, and the content of molecular sieves is 35% or more, more preferably 35% to 70%.

8. The method according to claim 1, characterized in that, The material P is selected from one or more of octynol, 3-nonenol, 2-decenal, and 2-undecenal.

9. The method according to claim 1, characterized in that, Compared to the post-hydrocracking catalyst, the volume hourly space velocity of the material P accounts for 28% to 72% of the total volume hourly space velocity of the hydrocracking bed products and the material P, and is more preferably 30% to 60%.

10. The method according to claim 1, characterized in that, The water injection volume of the air-cooling device is 2 to 30 times the mass flow rate of material P, preferably 3 to 8 times the mass flow rate of material P.

11. The method according to claim 1, characterized in that, After the hydrocracking bed product flows through the post-hydrorefining catalyst, the C8-C10 alkanes retain more than 85 wt%, and more preferably 90 wt% to 95 wt%.

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