Two-stage hydrocracking process for increasing yield of heavy naphtha

Abstract

The invention discloses a two-stage hydrocracking process for increasing the yield of heavy naphtha, which comprises the following steps: (1) in the presence of hydrogen, raw oil enters a hydrofining reaction zone, and reaction products are separated to obtain light fractions and heavy fractions; (2) in the presence of hydrogen, the heavy fraction obtained in the step (1) enters a first-stage hydrocracking reaction zone, a reaction product and the light fraction obtained in the step (1) enter a separation system, and a gas product, light naphtha, heavy naphtha and tail oil are obtained after separation; and (3) tail oil obtained in the step (2) enters a second-stage hydrocracking reaction zone, and reaction products enter the separation system in the step (2) for separation. According to the invention, the loading mode of the catalyst is adjusted to be matched with the material flow distribution condition in the reactor, so that the heavy naphtha selectivity and the liquid product yield in the diesel oil hydrocracking two-stage process are greatly increased.

Description

Technical Field

[0001] This invention belongs to the field of petroleum refining technology and relates to a hydrogenation process, particularly a two-stage hydrocracking process. Background Technology

[0002] With the adjustment of the global energy structure, the growth rate of demand for fuel oil products is gradually slowing down, while the demand for chemical products is accelerating. Integrated refining and chemical production has become an important development strategy for the petrochemical industry to improve the utilization efficiency of petroleum resources, reduce investment and production costs, and adapt to changes in the demand for oil and petrochemical products. Against this backdrop, diesel two-stage hydrocracking technology, which increases the production of heavy naphtha, has emerged to meet the needs of refineries in adjusting their product structure.

[0003] Two-stage hydrocracking technology for diesel fuel is a process in which the hydrocracking process is carried out in separate reactors. The technology first removes impurities such as sulfur and nitrogen from the feedstock in the first-stage reactor, improving the feedstock's purity while simultaneously performing a certain degree of hydrocracking. Then, in the second-stage reactor, the unconverted feedstock from the first-stage cracking undergoes a hydrocracking reaction, converting large hydrocarbon molecules into smaller molecules, particularly increasing the yield of heavy naphtha.

[0004] In the industrial application of diesel two-stage hydrocracking technology, further improving the yield of heavy naphtha has become a bottleneck restricting its further promotion and use. While the yield of heavy naphtha from two-stage hydrocracking using wax oil as feedstock can reach over 70%, the yield from diesel-based two-stage hydrocracking is difficult to break through the 70% mark. In some units, the yield has remained around 63% for a long time, seriously affecting the economic benefits and widespread application of this technology. Currently, there is a consensus in the field that one of the reasons for this problem is that the unconverted oil processed in the two-stage hydrocracking reaction is prone to excessive cracking during the reaction, resulting in more light components and a lower heavy naphtha yield. Summary of the Invention

[0005] During the research process, the applicant discovered that in the two-stage hydrocracking process for producing heavy naphtha from diesel, the material distribution within the second-stage reactor exhibits a clear liquid-phase extrapolation trend. Specifically, the concentration of liquid reactants is higher closer to the reactor wall, while the concentration of gaseous reactants is higher closer to the reactor center. This distribution characteristic becomes increasingly pronounced with the expansion of the reactor size. The technical solution of this invention is based on these findings. Given this reactor material distribution pattern (significantly uneven gas-liquid distribution), if the existing catalyst loading method is still used—that is, the same catalyst is loaded onto the same cross-section of the reactor—and the reaction conditions (temperature, hydrogen partial pressure) are also essentially the same, if process parameters are adjusted to maximize heavy naphtha production near the reactor center (where the gaseous reactant concentration is high), the reactor wall area (where the liquid reactant concentration is high) will not be able to produce maximum heavy naphtha production due to insufficient conversion depth. If the reactor sidewalls (where the liquid-phase reactant concentration is high) are positioned at the maximum heavy naphtha production level through process parameter adjustments, the reactor center (where the gas-phase reactant concentration is high) will experience an excessive conversion depth, leading to an increased yield of light naphtha. This invention adjusts the catalyst loading method to match the material distribution within the reactor, significantly increasing the selectivity of heavy naphtha and the yield of liquid products in the two-stage diesel hydrocracking process. Simultaneously, it reduces catalyst volume, providing technical support for enterprises to improve economic efficiency and increase heavy naphtha production. This solves the current problem of low heavy naphtha selectivity and the resulting large amounts of light products when increasing conversion rates in the two-stage diesel hydrocracking process.

[0006] To achieve the above-mentioned objective, the present invention first provides a two-stage hydrocracking process for increasing the production of heavy naphtha, comprising the following steps:

[0007] (1) In the presence of hydrogen, the feedstock enters the hydrorefining reaction zone, and the reaction products are separated to obtain light and heavy fractions;

[0008] (2) In the presence of hydrogen, the heavy fraction obtained in step (1) enters a hydrocracking reaction zone, and the reaction products and the light fraction obtained in step (1) enter the separation system. After separation, gaseous products, light naphtha, heavy naphtha and tail oil are obtained.

[0009] (3) The tail oil obtained in step (2) enters the second-stage hydrocracking reaction zone, and the reaction products enter the separation system in step (2) for separation.

[0010] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the hydrorefining reaction zone in step (1) is equipped with at least one hydrorefining reactor. The hydrorefining reaction zone is filled with a hydrorefining catalyst, which can be a commercially available product or prepared in-house using methods disclosed in the art. For example, hydrorefining catalysts such as FF-66, FF-56, FF-76, FHUDS-6, and FHUDS-8 developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd. can be selected. Even further, the hydrorefining reaction zone generally has one or more catalyst beds, preferably three catalyst beds.

[0011] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the hydrocracking reaction zone in step (2) is filled with a hydrocracking catalyst. This catalyst can be a commercially available product or prepared in-house using methods already disclosed in the art. For example, it can be one of the hydrocracking catalysts developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd., such as FC-52, FC-46, FC-76, and FC-86. Even further, the hydrocracking reaction zone generally has two or more catalyst beds, preferably three.

[0012] Furthermore, in the above-mentioned two-stage hydrocracking process for increasing heavy naphtha production, the two-stage hydrocracking reaction zone in step (3) is provided with a first reaction zone, a second reaction zone, and a third reaction zone according to the direction of liquid phase material flow. The volume of the first reaction zone is 2% to 20% of the total volume of the two-stage hydrocracking reaction zone; preferably 10% to 15%. The volume of the second reaction zone is 65% to 93% of the total volume of the two-stage hydrocracking reaction zone; preferably 70% to 80%. The remaining space is the volume of the third reaction zone.

[0013] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the first reaction zone is further filled with a catalyst having hydrorefining function and a catalyst having hydrocracking function. The catalysts for hydrorefining and hydrocracking are graded and filled according to the following principle: Following a radial principle, with the center of the reactor cross-section as the center point, the reactor is sequentially arranged with a central zone and a boundary zone from the center outwards; wherein, the central zone is circular, and the radius of the circle is 15%–25% of the reactor radius, preferably 18%–20%; the boundary zone is annular, and the radius of the outer ring is the reactor radius. Furthermore, the central zone is filled with a catalyst having hydrocracking function, which is the first hydrocracking catalyst, and the boundary zone is filled with a catalyst having hydrorefining function, which is also the first hydrorefining catalyst.

[0014] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the second reaction zone is further filled with a catalyst having hydrorefining function and a catalyst having hydrocracking function. The catalysts for hydrorefining and hydrocracking are graded and filled according to the following principle: Following a radial principle, with the center of the reactor cross-section as the center point, the reactor is sequentially arranged with a central zone, a transition zone, and a boundary zone from the center outwards; wherein, the central zone is circular, with a radius of 15%–25% of the reactor radius, preferably 18%–20%; the transition zone is annular, with an outer ring radius of 50%–90% of the reactor radius, preferably 60%–80%; the boundary zone is annular, with an outer ring radius equal to the reactor radius. Furthermore, the central zone is filled with a catalyst with hydrorefining function, and the boundary zone of the first reaction zone is filled with the same catalyst with hydrorefining function, namely, the first hydrorefining catalyst; the transition zone is filled with a catalyst with hydrocracking function, namely, the second hydrocracking catalyst; and the boundary zone is filled with a catalyst with hydrocracking function, namely, the third hydrocracking catalyst.

[0015] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the third reaction zone is further filled with a catalyst having hydrorefining function. Preferably, the catalyst with hydrorefining function is graded and filled according to the following principle: Following a radial principle, with the center of the reactor cross-section as the center point, the reactor is sequentially arranged with a central zone and a boundary zone from the center outwards; wherein, the central zone is circular, and the radius of the circle is 20%–50% of the reactor radius, preferably 25%–35%; the boundary zone is annular, and the radius of the outer ring is the reactor radius. Furthermore, the central zone is filled with a catalyst with hydrorefining function, which is a second hydrorefining catalyst; the boundary zone is filled with a catalyst with hydrorefining function, and this catalyst is the same as the catalyst filled in the boundary zone of the first reaction zone and the central zone of the second reaction zone, i.e., it is also filled with the first hydrorefining catalyst.

[0016] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the catalyst with hydrorefining function includes a support and a hydrorefining active metal component. The hydrorefining active metal component is supported on the support, and the hydrorefining active metal can be selected from at least one metal element from Group VIB, Group VIIB, and Group VIII. More preferably, the hydrorefining active metal is two or more elements selected from Co, Mo, Ni, and W. The support is generally at least one element selected from alumina, silica-containing alumina, and silicon oxide, preferably alumina. Preferably, the content of the hydrorefining active metal in the first and second hydrorefining catalysts decreases sequentially by 0.5 wt% to 10 wt%, preferably by 2 wt% to 9 wt%. Even more preferably, the content of the hydrorefining active metal in the first hydrorefining catalyst is 28 wt% to 32 wt%, preferably 28.5 wt% to 31.5 wt%.

[0017] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the catalyst with hydrorefining function can be selected from commercially available hydrorefining catalysts such as FF-12, FF-22, FF-34A, FF-56, FF-66, FF-76, and FHUDS-8 developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd., or it can be prepared according to common knowledge in the field as needed. More specifically, the first hydrorefining catalyst can be selected from at least one of FF-56, FF-66, FF-76, FHUDS-8, and FF-36 hydrorefining catalysts; the second hydrorefining catalyst can be selected from at least one of FF-33, FF-24, FF-12, FF-22, and FF-34A hydrorefining catalysts.

[0018] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the catalyst with hydrocracking function includes a support and a hydrocracking active metal component. The hydrocracking active metal component is loaded on the support, and the hydrocracking active metal can be selected from at least one metal element of Group VIB, Group VIIB, and Group VIII. More preferably, the hydrocracking active metal is two or more of Co, Mo, Ni, and W. The support includes a molecular sieve, and the molecular sieve can be at least one of Y molecular sieve, β molecular sieve, ZSM-5 molecular sieve, etc. More specifically, the molecular sieve content in the first, second, and third hydrocracking catalysts increases sequentially by 1 wt% to 10 wt%, preferably by 3 wt% to 7 wt%. Furthermore, the molecular sieve content in the first hydrocracking catalyst is 2 wt% to 6 wt%, preferably 3 wt% to 5 wt%; the molecular sieve content in the second hydrocracking catalyst is 6 wt% to 15 wt%, preferably 8 wt% to 10 wt%; and the molecular sieve content in the third hydrocracking catalyst is 15 wt% to 25 wt%, preferably 13 wt% to 15 wt%.

[0019] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the catalyst with hydrocracking function can be selected from commercially available hydrocracking catalysts such as FC-76, FC-52, FC-28, FC-14, FC-60, FC-50, FC-80, FC-75, FC-86, FC-46, and FC-82 developed by Sinopec (Dalian) Petrochemical Research Institute Co., Ltd., or it can be prepared according to common knowledge in the field as needed. More specifically, the first hydrocracking catalyst can be selected from at least one of FC-14, FC-28, FC-16, FC-50, FC-60, and FC-80; the second hydrocracking catalyst can be selected from at least one of FC-76, FC-75, FC-86, and FC-32; and the third hydrocracking catalyst can be selected from at least one of FC-52, FC-46, and FC-82.

[0020] Furthermore, in the above-mentioned two-stage hydrocracking process for increasing heavy naphtha production, the cutting temperature of the light and heavy fractions in step (1) is 130-260°C, preferably 160-200°C.

[0021] Furthermore, in the aforementioned two-stage hydrocracking process for increasing heavy naphtha production, the initial boiling point of the feedstock in step (1) is generally 120–200°C, and the final boiling point is generally 320–400°C, with no particular restrictions on sulfur and nitrogen content. Even further, the feedstock is diesel feedstock, specifically selected from one or more of straight-run diesel, coking diesel, and hydrotreated diesel.

[0022] Furthermore, in the above-mentioned two-stage hydrocracking process for increasing heavy naphtha production, the operating conditions of the hydrorefining reaction zone in step (1) are generally as follows: reaction temperature is 310–430℃, preferably 330–400℃; reaction pressure is 6.0–18.0 MPa, preferably 8.0–16.0 MPa; volume hourly space velocity is 0.2–10.0 h⁻¹. -1 Preferably, it is 0.5 to 2.5 hours. -1 The hydrogen-to-oil volume ratio is 500–2500, preferably 800–1600.

[0023] Furthermore, in the above-mentioned two-stage hydrocracking process for increasing heavy naphtha production, the operating conditions of the first-stage hydrocracking reaction zone in step (2) are generally as follows: reaction temperature is 310–430℃, preferably 350–410℃; reaction pressure is 6.0–18.0 MPa, preferably 8.0–16.0 MPa; volume hourly space velocity is 0.2–10.0 h⁻¹. -1 Preferably, it is 0.3 to 2.0 h. -1 The hydrogen-to-oil volume ratio is 500–2500, preferably 800–1600.

[0024] Furthermore, in the above-mentioned two-stage hydrocracking process for increasing heavy naphtha production, the operating conditions of the second-stage hydrocracking reaction zone in step (3) are generally as follows: reaction temperature is 290–430℃, preferably 300–390℃; reaction pressure is 6.0–18.0 MPa, preferably 8.0–16.0 MPa; volume hourly space velocity is 0.2–10.0 h⁻¹. -1 Preferably, it is 1.0 to 3.5 hours. -1 The hydrogen-to-oil volume ratio is 500–2500, preferably 500–1200.

[0025] Compared with existing technologies, the two-stage hydrocracking process for increasing heavy naphtha production provided by this invention has the following advantages:

[0026] 1. This invention provides a process method that matches the material distribution characteristics within a large-scale hydrocracking reactor, effectively improving the selectivity of heavy naphtha in a two-stage hydrocracking process using diesel as feedstock and enhancing the economic efficiency of the unit. The catalyst loading method in the two-stage hydrocracking reactor is specifically designed based on the flow trajectory of the reactants within the reactor (particularly suitable for large-scale hydrocracking reactors, with a reactor diameter generally greater than 4.6 meters). The "outward projection" effect on liquid materials inside the reactor is significantly increased. Based on the reactor cross-section, there is less liquid and more gaseous material near the center, and correspondingly, more liquid and less gaseous material near the edge, resulting in different processing difficulties and reaction behaviors. By changing the traditional catalyst loading method along the reactor's axial direction, a targeted radially graded catalyst loading mode is proposed, tailored to the reaction patterns of each stage of the two-stage hydrocracking process.

[0027] 2. In existing process schemes, the catalyst in the same cross-section of the reactor is the same, and the process conditions such as temperature and pressure are basically consistent. However, due to the different reactants in the same cross-section, if the process parameters are adjusted to make the area near the reactor center (high concentration of gaseous reactants) the maximum heavy naphtha production mode, the area near the reactor sidewall (high concentration of liquid reactants) will not be able to produce the maximum amount of heavy naphtha due to insufficient conversion depth. If the process parameters are adjusted to make the area near the reactor sidewall (high concentration of liquid reactants) the maximum heavy naphtha production mode, the reactor center (high concentration of gaseous reactants) will have an excessive conversion depth, leading to an increase in light naphtha yield. When the edge area is adjusted to the maximum heavy naphtha reaction zone by increasing the temperature, it will cause over-reaction in the central area, resulting in an increase in the yield of gaseous products and light naphtha. This phenomenon is more obvious in the two-stage hydrocracking reactor, which is the reason why there is an upper limit to the heavy naphtha yield in the current diesel two-stage hydrocracking process. Based on the hydrocracking reaction law and the reactor stream distribution law, this invention adjusts the catalyst loading method so that raw materials with different properties in different regions of the same cross section are contacted with catalysts of different activities. This ensures that the entire cross section is within the reaction operation domain for maximizing the production of heavy naphtha, maximizing the retention of heavy naphtha produced in the first and second stage reactions, avoiding excessive cracking of heavy naphtha into lighter components, significantly increasing the selectivity of heavy naphtha, and at the same time, minimizing the increase in hydrogen consumption.

[0028] 3. This invention provides more space within the reactor, allowing all catalysts to fully exert their catalytic activity. This avoids the bottleneck of some catalysts not being able to fully exert their activity in conventional modes, thus reducing the required catalyst loading compared to conventional processes. This reduces both the manufacturing cost of the reactor and the procurement cost of the catalyst, saving costs for the company. Attached Figure Description

[0029] Figure 1 This invention provides a schematic diagram of a two-stage hydrocracking process for increasing the production of heavy naphtha; wherein:

[0030] 1-Feedstock oil; 2-Hydrorefining reaction zone; 3-Hydrorefining reaction products; 4-First-stage hydrocracking reaction zone; 5-Gas-liquid separator; 6-Liquid phase product of gas-liquid separator; 7-Fracturing tower; 8-Gas product; 9-Light naphtha; 10-Heavy naphtha; 11-Gas phase product of gas-liquid separator; 12-Tail oil; 13-Second-stage hydrocracking reaction zone; 14-Second-stage hydrocracking reaction products; 15-Recycle hydrogen compressor; 16-First-stage hydrocracking reaction products; 17-Recycle hydrogen; 18-New hydrogen; 19-Primary separator; 20-Heavy fraction; 21-Light fraction. Detailed Implementation

[0031] The technical solution and technical effects of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0032] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0033] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0034] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0035] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0036] In the context of this specification, all numeric values ​​of parameters (e.g., quantities or conditions) should be understood to be modified by the term “about” in all cases, regardless of whether “about” actually appears before the numeric value.

[0037] In the context of this specification, the term "substantially" means that deviations that are acceptable or reasonable to a person skilled in the art are permitted, such as deviations within ±5%, ±2%, ±1%, ±0.5%, or ±0.1%.

[0038] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this instruction manual are based on weight, and the pressure is gauge pressure.

[0039] In the context of this specification, any two or more embodiments or aspects of the present invention may be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0040] The two-stage hydrocracking process for increasing heavy naphtha production provided by this invention is as follows: Figure 1As shown, in the presence of hydrogen (including new hydrogen 18 and recycled hydrogen 17), feedstock oil 1 enters the hydrorefining reaction zone 2 and reacts with the catalyst packed in the reactor. The hydrorefining reaction product 3 obtained from the reaction enters the primary separator 19 for separation to obtain light fraction 21 and heavy fraction 20. The heavy fraction 20 obtained enters the first-stage hydrocracking reaction zone 4. The first-stage hydrocracking reaction product 16 and the light fraction 21 obtained from the primary separator enter the gas-liquid separator 5 for separation. The gas phase product 11 obtained after separation is processed by the recycled hydrogen compressor 15 and used as recycled hydrogen 17, which can be recycled to the hydrorefining reaction zone and / or the second-stage hydrocracking reaction zone. The liquid product 6 obtained after separation from the gas-liquid separator enters the fractionation tower 7 for fractionation treatment, and the separated products are gaseous product 8, light naphtha 9, heavy naphtha 10 and tail oil 12. The tail oil 12 enters the second-stage hydrocracking reaction zone 13, and the reaction product 14 enters the gas-liquid separator 5 for separation.

[0041] In the context of this specification, the hydrorefining reaction zone is equipped with one hydrorefining reactor, the first-stage hydrocracking reaction zone is equipped with one hydrocracking reactor (hereinafter referred to as the first-stage hydrocracking reactor), and the second-stage hydrocracking reaction zone is equipped with one hydrocracking reactor (hereinafter referred to as the second-stage hydrocracking reactor).

[0042] Example 1

[0043] according to Figure 1 The process flow shown has the following characteristics: the initial separator has a cutting temperature of 175℃; the hydrorefining reactor has three catalyst beds, and the hydrorefining catalyst used is FF-66; the first-stage hydrocracking reactor has three catalyst beds, and the catalyst used is FC-76 hydrocracking catalyst.

[0044] The two-stage hydrocracking reactor is configured with a first reaction zone, a second reaction zone, and a third reaction zone according to the direction of liquid phase material flow. The volume of the first reaction zone is 15% of the total volume of the two-stage hydrocracking reactor, the volume of the second reaction zone is 75% of the total volume, and the volume of the third reaction zone is 10% of the total volume. The first reaction zone is packed radially, with the center of the reactor cross-section as the center point. From the center outwards, the reactor is sequentially arranged with a central zone and a boundary zone. The central zone is circular, with a radius of 20% of the reactor radius. The boundary zone is annular. The central zone is filled with HC1-1 hydrocracking catalyst (FC-14 hydrocracking catalyst), and the boundary zone is filled with HR1-1 hydrorefining catalyst (FF-66 hydrorefining catalyst). The second reaction zone, following a radial principle, is centered on the center of the reactor's cross-section, with a central zone, a transition zone, and a boundary zone arranged sequentially outwards. The central zone is circular, with a radius equal to 20% of the reactor's radius; the transition zone is annular, with an outer ring radius equal to 80% of the reactor's radius; and the boundary zone is annular, with an outer ring radius equal to the reactor's radius. The central zone is filled with HR1-1 hydrorefining catalyst (FF-66 hydrorefining catalyst), the transition zone with HC1-2 hydrocracking catalyst (FC-76 hydrocracking catalyst), and the boundary zone with HC1-3 hydrocracking catalyst (FC-52 hydrocracking catalyst). The third reaction zone, also following a radial principle, is centered on the center of the reactor's cross-section, with a central zone and a boundary zone arranged sequentially outwards. The central zone is circular, with a radius equal to 35% of the reactor's radius; and the boundary zone is annular, with an outer ring radius equal to the reactor's radius. The central zone is filled with HR1-2 hydrorefining catalyst (FF-33 hydrorefining catalyst), and the boundary zone is filled with HR1-1 hydrorefining catalyst (FF-66 hydrorefining catalyst). The active metal content of the hydrorefining catalyst is shown in Table 2, and the molecular sieve content of the hydrocracking catalyst is shown in Table 3.

[0045] The properties of the feedstock are shown in Table 1. The reaction pressure is 10.0 MPa, and the space velocity of the hydrorefining reactor is 0.8 h⁻¹. -1 The space velocity of the first-stage hydrocracking reactor is 1.0 h⁻¹. -1 The space velocity of the two-stage hydrocracking reactor is 2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio in the first-stage hydrocracking reactor was 1600, and the hydrogen-to-oil volume ratio in the second-stage hydrocracking reactor was 1200. The temperature of the hydrorefining reactor was controlled according to the nitrogen content of the refined oil being 10 mg / kg. The conversion depth of the first-stage hydrocracking reactor was 65%, and the conversion depth of the second-stage hydrocracking reactor was 60%. The reaction results are shown in Table 4.

[0046] Example 2

[0047] according to Figure 1 The process flow shown has the following characteristics: the initial separator has a cutting temperature of 160℃; the hydrorefining reactor has three catalyst beds, and the hydrorefining catalyst used is FF-56; the first-stage hydrocracking reactor has three catalyst beds, and the catalyst used is FC-86 hydrocracking catalyst.

[0048] The two-stage hydrocracking reactor is configured with a first reaction zone, a second reaction zone, and a third reaction zone according to the direction of liquid phase material flow. The volume of the first reaction zone is 12% of the total volume of the two-stage hydrocracking reactor, the volume of the second reaction zone is 80% of the total volume, and the volume of the third reaction zone is 8% of the total volume. The first reaction zone is packed radially, with the center of the reactor cross-section as the center point. From the center outwards, the reactor is sequentially divided into a central zone and a boundary zone. The central zone is circular, with a radius of 19% of the reactor radius. The boundary zone is annular. The central zone is filled with HC2-1 hydrocracking catalyst (FC-28 catalyst), and the boundary zone is filled with HR2-1 hydrorefining catalyst (FF-36 catalyst). The second reaction zone, following a radial principle, is centered on the center of the reactor's cross-section, with a central zone, a transition zone, and a boundary zone arranged sequentially outwards. The central zone is circular, with a radius equal to 18% of the reactor's radius; the transition zone is annular, with an outer ring radius equal to 60% of the reactor's radius; and the boundary zone is annular, with an outer ring radius equal to the reactor's radius. The central zone is filled with HR2-1 hydrorefining catalyst (FF-36 catalyst), the transition zone with HC2-2 hydrocracking catalyst (FC-32 catalyst), and the boundary zone with HC2-3 hydrocracking catalyst (FC-82 catalyst). The third reaction zone, also following a radial principle, is centered on the center of the reactor's cross-section, with a central zone and a boundary zone arranged sequentially outwards. The central zone is circular, with a radius equal to 30% of the reactor's radius; and the boundary zone is annular, with an outer ring radius equal to the reactor's radius. The central zone is filled with HR2-2 hydrorefining catalyst (FF-24 catalyst), and the boundary zone is filled with HR2-1 hydrorefining catalyst (FF-36 catalyst). The active metal content of the hydrorefining catalyst is shown in Table 2, and the molecular sieve content of the hydrocracking catalyst is shown in Table 3.

[0049] The properties of the feedstock are shown in Table 1. The reaction pressure is 12.0 MPa, and the space velocity of the hydrorefining reactor is 1.2 h⁻¹. -1 The space velocity of the first-stage hydrocracking reactor is 1.5 h⁻¹. -1 The space velocity of the two-stage hydrocracking reactor is 1.5 h⁻¹. -1The hydrogen-to-oil volume ratio in the first-stage hydrocracking reactor was 1200, and the hydrogen-to-oil volume ratio in the second-stage hydrocracking reactor was 1000. The temperature of the hydrorefining reactor was controlled according to the nitrogen content of the refined oil being 8 mg / kg. The conversion depth of the first-stage hydrocracking reactor was 63%, and the conversion depth of the second-stage hydrocracking reactor was 63%. The reaction results are shown in Table 4.

[0050] Example 3

[0051] according to Figure 1 The process flow shown has the following characteristics: the initial separator has a cutting temperature of 160℃; the hydrorefining reactor has four catalyst beds filled with FF-76 hydrorefining catalyst; and the first-stage hydrocracking reactor has three catalyst beds filled with FC-52 hydrocracking catalyst.

[0052] The two-stage hydrocracking reactor has three bed layers, arranged according to the direction of liquid phase material flow: a first reaction zone, a second reaction zone, and a third reaction zone. The volume of the first reaction zone is 10% of the total volume of the two-stage hydrocracking reactor, the volume of the second reaction zone is 70% of the total volume, and the volume of the third reaction zone is 20% of the total volume. The first reaction zone is packed radially, with the center of the reactor cross-section as the center point. From the center outwards, the reactor is arranged with a central zone and a boundary zone. The central zone is circular, with a radius of 18% of the reactor radius. The boundary zone is annular. The central zone is filled with HC3-1 hydrocracking catalyst (FC-16 catalyst), and the boundary zone is filled with HR3-1 hydrorefining catalyst (FF-76 catalyst). The second reaction zone, following a radial principle, is centered on the center of the reactor's cross-section, with a central zone, a transition zone, and a boundary zone arranged sequentially outwards. The central zone is circular, with a radius equal to 19% of the reactor's radius; the transition zone is annular, with an outer ring radius equal to 70% of the reactor's radius; and the boundary zone is annular, with an outer ring radius equal to the reactor's radius. The central zone is filled with HR3-1 hydrorefining catalyst (FF-76 catalyst), the transition zone with HC3-2 hydrocracking catalyst (FC-86 catalyst), and the boundary zone with HC3-3 hydrocracking catalyst (FC-46 catalyst). The third reaction zone, also following a radial principle, is centered on the center of the reactor's cross-section, with a central zone and a boundary zone arranged sequentially outwards. The central zone is circular, with a radius equal to 25% of the reactor's radius; and the boundary zone is annular, with an outer ring radius equal to the reactor's radius. The central zone is filled with HR3-2 hydrorefining catalyst (FF-12 catalyst), and the boundary zone is filled with HR3-1 hydrorefining catalyst (FF-76 catalyst). The active metal content of the hydrorefining catalyst is shown in Table 2, and the molecular sieve content of the hydrocracking catalyst is shown in Table 3.

[0053] The properties of the feedstock are shown in Table 1. The reaction pressure is 13.5 MPa, and the space velocity of the hydrorefining reactor is 1.5 h⁻¹. -1 The space velocity of the first-stage hydrocracking reactor is 1.8 h⁻¹. -1 The space velocity of the two-stage hydrocracking reactor is 1.1 h⁻¹. -1 The hydrogen-to-oil volume ratio in the first-stage hydrocracking reactor was 1000, and the hydrogen-to-oil volume ratio in the second-stage hydrocracking reactor was 800. The temperature of the hydrorefining reactor was controlled according to the nitrogen content of the refined oil being 12 mg / kg. The conversion depth of the first-stage hydrocracking reactor was 57%, and the conversion depth of the second-stage hydrocracking reactor was 63%. The reaction results are shown in Table 4.

[0054] Example 4

[0055] The example is basically the same as Example 1, except that in Example 4, the third reaction zone is only filled with HR1-1 hydrorefining catalyst (FF-66 catalyst).

[0056] The properties of the feedstock are shown in Table 1. The reaction pressure is 10.0 MPa, and the space velocity of the hydrorefining reactor is 0.8 h⁻¹. -1 The space velocity of the first-stage hydrocracking reactor is 1.0 h⁻¹. -1 The space velocity of the two-stage hydrocracking reactor is 2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio in the first-stage hydrocracking reactor was 1600, and the hydrogen-to-oil volume ratio in the second-stage hydrocracking reactor was 1200. The temperature of the hydrorefining reactor was controlled according to the nitrogen content of the refined oil being 10 mg / kg. The conversion depth of the first-stage hydrocracking reactor was 65%, and the conversion depth of the second-stage hydrocracking reactor was 60%. The reaction results are shown in Table 4.

[0057] Comparative Example 1

[0058] The properties of the feedstock are shown in Table 1. The hydrorefining reactor and the first-stage hydrocracking reactor were consistent with those in Example 1. The second-stage hydrocracking reactor used a conventional catalyst loading method, with HCl-3 (FC-52 catalyst), HCl-2 (FC-76 catalyst), HCl-1 (FC-14 catalyst), HR1-1 (FF-66 catalyst), and HR1-2 (FF-33 catalyst) loaded from top to bottom. The loading amount of each catalyst was consistent with that in Example 1. The reaction pressure was 10.0 MPa, and the space velocity of the hydrorefining reactor was 0.8 h⁻¹. -1 The space velocity of the first-stage hydrocracking reactor is 1.0 h⁻¹. -1 The space velocity of the two-stage hydrocracking reactor is 2.0 h⁻¹. -1 The hydrogen-to-oil volume ratio was 1600. The temperature of the hydrorefining reactor was controlled according to the nitrogen content of the refined oil being 10 mg / kg. The conversion depth of the first-stage hydrocracking reactor was 65%, and the conversion depth of the second-stage hydrocracking reactor was 60%. The reaction results are shown in Table 4.

[0059] Comparative Example 2

[0060] The properties of the feedstock are shown in Table 1. The hydrorefining reactor and the first-stage hydrocracking reactor are consistent with those in Example 2. The second-stage hydrocracking reactor uses a conventional catalyst loading method, with HC2-1 (FC-28 catalyst), HC2-2 (FC-32 catalyst), HC2-3 (FC-82 catalyst), HR2-2 (FC-24 catalyst), and HR2-1 (FF-36 catalyst) loaded from top to bottom. The loading amount of each catalyst is consistent with that in Example 2. The reaction pressure is 12.0 MPa, and the space velocity in the refining section is 1.2 h⁻¹. -1 The space velocity in the first cracking section is 1.5 h⁻¹. -1The space velocity in the second-stage cracking section is 1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio was 1200 in the first stage and 1000 in the second stage. The temperature in the refining stage was controlled to achieve a nitrogen content of 8 mg / kg in the refined oil. The conversion depth in both stages was 63%. The temperature in the cracking stage was controlled to maximize the production of heavy naphtha. The reaction results are shown in Table 4.

[0061] Table 1 Properties of Crude Oil

[0062]

[0063]

[0064] Table 2 Metal Content of Hydrorefining Catalysts

[0065] HR1-1 HR1-2 HR2-1 HR2-2 HR3-1 HR3-2 hydrogenation metal content, wt% 28.5 25.5 29.5 21.5 31 25.2

[0066] Table 3 Molecular sieve content in hydrocracking catalysts

[0067]

[0068] Table 4 Reaction Results

[0069]

[0070]

[0071] Analysis of the reaction results in Table 4 shows that the hydrocracking process provided by this invention can significantly improve the reaction efficiency. Through understanding the distribution of reactants and studying regional reaction patterns within the diesel hydrocracking unit, the invention overcomes the limitations on heavy naphtha yield in existing hydrocracking processes, ensuring that the reactions within the reactor are all in the optimal reaction zone, with an increase of approximately 5%. Simultaneously, the required liquid product yield is significantly increased, bringing substantial economic benefits to the enterprise.

Claims

1. A two-stage hydrocracking process for increasing the production of heavy naphtha, comprising the following steps: (1) In the presence of hydrogen, the feedstock enters the hydrorefining reaction zone, and the reaction products are separated to obtain light and heavy fractions; (2) In the presence of hydrogen, the heavy fraction obtained in step (1) enters a hydrocracking reaction zone, and the reaction products and the light fraction obtained in step (1) enter the separation system. After separation, gaseous products, light naphtha, heavy naphtha and tail oil are obtained. (3) The tail oil obtained in step (2) enters the two-stage hydrocracking reaction zone, and the reaction products enter the separation system in step (2) for separation. The two-stage hydrocracking reaction zone is set up with a first reaction zone, a second reaction zone and a third reaction zone according to the direction of liquid phase material flow. The first reaction zone is filled with a catalyst with hydrorefining function and a catalyst with hydrocracking function. The catalyst with hydrorefining function and the catalyst with hydrocracking function are graded and filled. According to the radial principle, with the center of the reactor cross-section as the center point, the reactor is set up with a central area and a boundary area from the center outward. The central area is filled with a catalyst with hydrocracking function. The catalyst with hydrocracking function is the first hydrocracking catalyst. The boundary area is filled with a catalyst with hydrorefining function. The catalyst with hydrorefining function is the first hydrorefining catalyst.

2. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The hydrorefining reaction zone in step (1) is filled with a hydrorefining catalyst, and the hydrorefining reaction zone is provided with one or more catalyst beds.

3. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, In step (2), a hydrocracking reaction zone is filled with hydrocracking catalyst, and the hydrocracking reaction zone has more than two catalyst beds.

4. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The volume of the first reaction zone is 2% to 20% of the total volume of the two-stage hydrocracking reaction zone; preferably 10% to 15%, and the volume of the second reaction zone is 65% to 93% of the total volume of the two-stage hydrocracking reaction zone; preferably 70% to 80%.

5. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The central area of ​​the first reaction zone is circular, with a radius of 15% to 25% of the reactor radius, preferably 18% to 20%; the boundary area of ​​the first reaction zone is annular, with the outer ring radius of the annulus being the reactor radius.

6. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The second reaction zone is filled with a catalyst with hydrorefining function and a catalyst with hydrocracking function. The catalysts with hydrorefining function and the catalysts with hydrocracking function are graded and filled in a radial manner. With the center of the reactor cross-section as the center point, the reactor is arranged in a central zone, a transition zone and a boundary zone from the center outward. The central zone is filled with a catalyst with hydrorefining function. The catalyst with hydrorefining function and the boundary zone of the first reaction zone are filled with the same catalyst with hydrorefining function, that is, the first hydrorefining catalyst. The transition zone is filled with a catalyst with hydrocracking function, which is a second hydrocracking catalyst; the boundary zone is filled with a catalyst with hydrocracking function, which is a third hydrocracking catalyst.

7. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 6, wherein, The central area of ​​the second reaction zone is circular, with a radius of 15% to 25% of the reactor radius, preferably 18% to 20%; the transition zone of the second reaction zone is annular, with an outer ring radius of 50% to 90% of the reactor radius, preferably 60% to 80%; the boundary zone of the second reaction zone is annular, with an outer ring radius equal to the reactor radius.

8. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The third reaction zone is filled with a catalyst with hydrorefining function. The catalyst with hydrorefining function is graded and filled according to the radial principle. With the center of the reactor cross-section as the center point, the reactor is arranged with a central zone and a boundary zone from the center outward. The central zone is filled with a catalyst with hydrorefining function, which is the second hydrorefining catalyst. The boundary zone is filled with a catalyst with hydrorefining function. The catalyst with hydrorefining function is the same as the catalyst with hydrorefining function filled in the boundary zone of the first reaction zone and the central zone of the second reaction zone, that is, it is filled with the first hydrorefining catalyst.

9. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 8, wherein, The central area of ​​the third reaction zone is circular, with a radius of 20% to 50% of the reactor radius, preferably 25% to 35%; the boundary area of ​​the third reaction zone is annular, with the outer ring radius being the reactor radius.

10. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The hydrogenation active metal content in the first hydrogenation refining catalyst is 28wt% to 32wt%, preferably 28.5wt% to 31.5wt%.

11. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 8, wherein, The content of hydrogenation active metal in the first and second hydrogenation refining catalysts decreases sequentially by 0.5 wt% to 10 wt%, preferably by 2 wt% to 9 wt%.

12. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 6, wherein, The molecular sieve content in the first, second, and third hydrocracking catalysts increases sequentially by 1 wt% to 10 wt%, preferably by 3 wt% to 7 wt%.

13. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 6, wherein, The molecular sieve content in the first hydrocracking catalyst is 2wt% to 6wt%, preferably 3wt% to 5wt%; the molecular sieve content in the second hydrocracking catalyst is 6wt% to 15wt%, preferably 8wt% to 10wt%; and the molecular sieve content in the third hydrocracking catalyst is 15wt% to 25wt%, preferably 13wt% to 15wt%.

14. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The cutting temperature of the light and heavy fractions in step (1) is 130-260°C, preferably 160-200°C.

15. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The feedstock oil in step (1) is diesel oil, selected from one or more of straight-run diesel oil, coking diesel oil, and hydrotreated diesel oil.

16. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The operating conditions of the hydrorefining reaction zone in step (1) are as follows: reaction temperature is 310–430℃, preferably 330–400℃; reaction pressure is 6.0–18.0 MPa, preferably 8.0–16.0 MPa; volume hourly space velocity is 0.2–10.0 h⁻¹. -1 Preferably, it is 0.5 to 2.5 hours. -1 The hydrogen-to-oil volume ratio is 500–2500, preferably 800–1600.

17. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The operating conditions of the hydrocracking reaction zone in step (2) are as follows: reaction temperature is 310–430℃, preferably 350–410℃; reaction pressure is 6.0–18.0 MPa, preferably 8.0–16.0 MPa; volume hourly space velocity is 0.2–10.0 h⁻¹. -1 Preferably, it is 0.3 to 2.0 h. -1 The hydrogen-to-oil volume ratio is 500–2500, preferably 800–1600.

18. The two-stage hydrocracking process for increasing heavy naphtha production according to claim 1, wherein, The operating conditions of the two-stage hydrocracking reaction zone in step (3) are as follows: reaction temperature is 290–430℃, preferably 300–390℃; reaction pressure is 6.0–18.0 MPa, preferably 8.0–16.0 MPa; volume hourly space velocity is 0.2–10.0 h⁻¹. -1 Preferably, it is 1.0 to 3.5 hours. -1 The hydrogen-to-oil volume ratio is 500–2500, preferably 500–1200.

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