Hydrocracking process for increasing the yield of heavy naphtha

Abstract

The application discloses a method for increasing production of heavy naphtha by hydrocracking. The method adopts a two-stage hydrocracking process, wherein a first reaction zone and a second reaction zone are arranged, the first reaction zone comprises a first hydrocracking reaction zone, and the second reaction zone comprises a second hydrocracking reaction zone. The method comprises the following steps: (1) after a hydrocracking raw material is mixed with hydrogen, the mixture is introduced into the first hydrocracking reaction zone to perform a first hydrocracking reaction; (2) after the first hydrocracking reaction effluent of step (1) is separated and fractionated, gaseous light hydrocarbon, liquid light hydrocarbon, light naphtha, heavy naphtha and tail oil I are obtained; (3) in the presence of hydrogen, the tail oil I of step (2) is introduced into the second hydrocracking reaction zone to perform a second hydrocracking reaction; and (4) after the second hydrocracking reaction effluent of step (3) is introduced into a separation and fractionation system, gaseous light hydrocarbon, liquid light hydrocarbon, light naphtha, heavy naphtha and tail oil II are obtained. The method can process conventional raw materials of a hydrocracking device, and the purpose of increasing production of heavy naphtha can be achieved in the two-stage hydrocracking process.

Description

Technical Field

[0001] This invention relates to a two-stage hydrocracking process, specifically a two-stage full-cycle hydrocracking method for increasing the production of heavy naphtha. Background Technology

[0002] Currently, clean and low-carbon development has become one of the key paths for the petrochemical industry, and "reducing oil and increasing chemicals" has become an important direction for adjusting the structure of refining products. Therefore, "oil-to-chemicals" technologies, which directly produce chemical feedstocks from crude oil, such as light chemical oils, light hydrocarbon feedstocks, ethylene-rich and ethane-rich gases, and "oil-to-chemicals" technologies, which directly produce chemicals from crude oil, such as benzenes, olefins, ethers, styrene, and ethylbenzene, will face enormous development potential. The core development direction is to increase the production of ethylene and aromatic feedstocks, especially aromatic feedstocks.

[0003] Aromatic hydrocarbons are the most basic raw materials in the organic chemical industry. Benzene, toluene, and xylene, in particular, are important basic raw materials in the petrochemical industry, with a market size second only to ethylene and propylene. Aromatic hydrocarbon products are widely used in industries such as synthetic resins, synthetic fibers, synthetic rubber, detergents, plasticizers, dyes, pharmaceuticals, fragrances, and pesticides, playing a vital role in economic development and improving people's lives.

[0004] Catalytic reforming is one of the core technologies for producing aromatics. Tracing back from product to feedstock, increasing aromatics production necessitates expanding the reforming scale. This requires more heavy naphtha to fill the feedstock gap. Correspondingly, hydrocracking technology needs to improve product selectivity to produce heavy naphtha and also expand its processing scale. Among the various hydrocracking processes, the two-stage full-cycle technology, compared to the conventional single-stage full-cycle technology, has one of the biggest advantages: it can expand the feedstock processing scale. Under conditions of concentrated capacity, it can maximize the production of the target product. Therefore, the development space and market demand for two-stage full-cycle hydrocracking technology, which produces more heavy naphtha, are still very broad in the future.

[0005] CN201711119101.0 discloses a hydrocracking method for improving the yield of heavy naphtha. The method includes: mixing feedstock oil with hydrogen and then feeding it into a hydrorefining reactor, where it contacts a hydrorefining catalyst to undergo refining reactions such as hydrodesulfurization, hydrodenitrogenation, and aromatic saturation; mixing the resulting product oil with hydrocracking tail oil and feeding it into a hydrocracking reactor for hydrocracking, mixing with circulating oil between different bed layers, and continuing the reaction; the resulting product oil entering a separation system to obtain hydrogen for recycling, and the resulting distillate oil entering a fractionation system to obtain gas, light naphtha, heavy naphtha, middle distillate oil, and hydrocracking tail oil; the hydrocracking tail oil being recycled to the inlet of the hydrocracking reactor, and the middle distillate oil being returned to the catalyst bed layer of the hydrocracking reactor.

[0006] CN201310523162.9 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 then 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, reducing the yield of low-value-added products such as dry gas, liquefied petroleum gas, and light naphtha, and improving the selectivity of heavy naphtha.

[0007] CN202110725139.2 discloses a petroleum hydrocracking system for increasing heavy naphtha production, comprising a primary process unit, an HPNA removal unit, and a secondary process unit. The primary process unit includes a primary refining reactor, a primary cracking reactor, a high-pressure separator, a low-pressure separator, and a fractionation tower. The HPNA removal unit includes an HPNA adsorption tank and a post-adsorption filter connected to each other. The secondary process unit includes a secondary cracking reactor. The fractionation tower is equipped with a feed inlet, a heavy naphtha outlet, and a tail oil outlet. The tail oil outlet is connected to both the HPNA adsorption tank and the secondary cracking reactor, and the outlet of the secondary cracking reactor is connected to the high-pressure separator. The addition of the HPNA removal unit in this system allows a portion of the circulating oil to pass through the HPNA removal unit before entering the secondary cracking reactor, effectively reducing the HPNA accumulation rate, thereby reducing the amount of tail oil spilled and increasing the yield of heavy naphtha. This method improves the yield of heavy naphtha through process optimization.

[0008] In existing technologies, some methods increase the production of heavy naphtha by returning the circulating oil to different locations, some by optimizing process parameters, and some by improving the process flow. However, none of these methods take into account the impact of the difference between the first and second stages of the reaction process on the production increase process. Therefore, much more research is needed on how to improve the yield of heavy naphtha. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a hydrocracking method for increasing the production of heavy naphtha. This method can process conventional feedstocks for hydrocracking units and achieves the goal of increasing heavy naphtha production in a two-stage hydrocracking process.

[0010] This invention provides a hydrocracking method for increasing the production of heavy naphtha. The method employs a two-stage hydrocracking process, comprising a first-stage reaction zone and a second-stage reaction zone. The first-stage reaction zone includes a first hydrocracking reaction zone, and the second-stage reaction zone includes a second hydrocracking reaction zone. The method includes:

[0011] (1) The hydrocracking feedstock is mixed with hydrogen and then enters the first hydrocracking reaction zone to carry out the first hydrocracking reaction;

[0012] (2) After separation and fractionation, the effluent from the first hydrocracking reaction in step (1) yields gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil I.

[0013] (3) In the presence of hydrogen, the tail oil I from step (2) enters the second hydrocracking reaction zone for the second hydrocracking reaction;

[0014] (4) The second hydrocracking effluent obtained in step (3) enters the separation and fractionation system to obtain gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha and tail oil II;

[0015] Preferably, in step (3), the second hydrocracking reaction zone is provided with multiple hydrocracking catalyst beds, preferably more than two; the feedstock of the second hydrocracking reaction zone is at the top of each hydrocracking catalyst bed, and the feedstock is fed from top to bottom; along the flow direction, the feedstock feed rate decreases sequentially, and the mass ratio of feedstock feed rate between adjacent catalyst beds is 1.7:1 to 3.0:1, preferably 1.7:1 to 2.7:1.

[0016] According to the present invention, in step (1), the hydrocracking feedstock can be a conventional hydrocracking feedstock, referring to feedstock suitable for hydrocracking processing, generally in principle wax oil and / or diesel fraction, preferably wax oil fraction. The final boiling point of the wax oil fraction is generally 460-560℃, preferably 480-550℃, and the initial boiling point is 250-350℃, preferably 280-320℃; the density at 20℃ is generally 0.94 g / cm³. 3 The preferred value is 0.92 g / cm³. 3 The nitrogen content is generally below 0.2 wt%, preferably below 0.18 wt%, more preferably 0.02 wt% to 0.18 wt%; the sulfur content is generally below 4 wt%, preferably below 3 wt%, more preferably 0.03 wt% to 3 wt%. The wax oil fraction can be one or more of various vacuum gas oils (VGOs) obtained from processing Middle Eastern crude oil, such as Iranian VGO, Saudi VGO, etc., or one or more of various vacuum gas oils (VGOs) obtained from processing Daqing crude oil or Liaohe crude oil, or wax oil fractions obtained after secondary processing units, such as coking wax oil, deasphalted oil, etc. Any liquid-phase wax oil product suitable as feedstock for a hydrocracking unit is within the applicable range.

[0017] According to the present invention, in step (1), a hydropretreatment reaction zone is set up before the first hydrocracking reaction zone in a reaction zone; the purpose of the hydropretreatment reaction zone is to desulfurize, denitrify, and saturate aromatics in the hydrocracking feedstock. The nitrogen content in the reaction effluent from the hydropretreatment reaction zone is no more than 15 mg / kg, preferably no more than 10 mg / kg. At this point, it can be considered that the removal of other corresponding impurities has been achieved simultaneously, and this stream can enter the hydrocracking reaction zone for subsequent reactions.

[0018] According to the present invention, in step (1), the hydrogenation pretreatment reaction zone may be provided with multiple hydrogenation pretreatment catalyst beds, preferably two or more, and more preferably two to four. Each hydrogenation pretreatment catalyst bed is separated by facilities such as a cold hydrogen tank.

[0019] According to the present invention, in step (1), the hydrogenation pretreatment reaction zone is filled with a hydrogenation pretreatment catalyst. The catalyst includes a support and an active metal component; the active metal includes Group VIB metals and / or Group VIII metals, and the support is an inorganic refractory oxide material, selected from one or more of alumina, amorphous aluminum silicate, silica, titanium dioxide, etc. The Group VIB metals are preferably W and / or Mo, and the Group VIII metals are preferably Ni and / or Co. Based on the weight of the catalyst, the content of the Group VIB metals as oxides is 12%–37%, preferably 15%–32%, and the content of the Group VIII metals as oxides is 0.3%–7.5%, preferably 0.5%–7%. Hydrotreating catalysts can be various conventional commercial catalysts currently in use, such as FF-36, FF-46, FF-56, and FF-66 hydrocracking pretreatment catalysts developed by the Dalian Petrochemical Research Institute; hydrotreating catalysts can also be prepared according to conventional methods in this field as needed.

[0020] According to the present invention, in step (1), the process conditions of the hydrotreating reaction zone are as follows: average reaction temperature of 305℃~445℃, inlet hydrogen-to-oil volume ratio of 400:1~1100:1, reaction pressure of 7.0MPa~17.0MPa, and liquid hourly space velocity of 0.3h. -1 ~5.0h -1 The preferred process conditions are: an average reaction temperature of 310℃~440℃, an inlet hydrogen-to-oil volume ratio of 500:1~1000:1, a reaction pressure of 8.5MPa~16.5MPa, and a liquid hourly space velocity of 0.4h. -1 ~4.5h -1 .

[0021] According to the present invention, in step (1), the pretreated product is cracked in the first hydrocracking reaction zone to obtain various hydrocarbon components, the purpose of which is to complete the generation process of each hydrocracking product. The present invention takes into account the matching relationship between the first and second reaction zones, and since the core target product is a light component, the conversion rate of the first stage can be controlled to be slightly higher. It is necessary to control the conversion rate of the feedstock oil in the first hydrocracking reaction zone to be 50%–90%, preferably 60%–80%, by mass. The temperature cut-off point corresponding to this conversion rate is the initial boiling point of tail oil I.

[0022] According to the present invention, in step (1), the first hydrocracking reaction zone is conventionally equipped with multiple (preferably more than 3, more preferably 3 to 5) first hydrocracking catalyst beds, which are arranged at approximately the same height in a conventional proportion. The catalyst beds can be separated by facilities such as a cold hydrogen tank.

[0023] According to the present invention, in step (1), the first hydrocracking reaction zone is filled with a first hydrocracking catalyst. The first hydrocracking catalyst can be a conventional hydrocracking catalyst suitable for the production of heavy naphtha, generally a light oil-type hydrocracking catalyst. The first hydrocracking catalyst includes a cracking component, a hydrogenation component, and a binder. The cracking component contains amorphous silica-alumina and / or molecular sieves, wherein the molecular sieves include, but are not limited to, Y-type molecular sieves (such as at least one of USY-type molecular sieves and ASSY-type molecular sieves), and the binder is alumina and / or silica. The hydrogenation component is generally selected from one or more of Group VI, Group VII, and Group VIII metals, metal oxides, or sulfides, preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, nickel, or their sulfides or oxides. Based on the weight of the catalyst, the hydrogenation component, calculated as oxides, has a content of 12wt% to 40wt%, preferably 15wt% to 35wt%, and the molecular sieve content has a content of 45wt% to 70wt%, preferably 50wt% to 65wt%. The first hydrocracking catalyst can be selected from existing industrial hydrocracking catalysts, such as HC-185 developed by UOP and FC-52 and FC-82 developed by Dalian Petrochemical Research Institute, or a specific hydrocracking catalyst that meets the requirements can be prepared as needed.

[0024] According to the present invention, in step (1), the process conditions of the first hydrocracking reaction zone are as follows: average reaction temperature of 315℃~450℃, inlet hydrogen-to-oil volume ratio of 600:1~1500:1, reaction pressure of 7.0MPa~17.0MPa, and liquid hourly space velocity of 0.2h. -1 ~4.5h -1Preferably, the average reaction temperature is 320℃~440℃, the inlet hydrogen-to-oil volume ratio is 700:1~1400:1, the reaction pressure is 8.5MPa~16.5MPa, and the liquid hourly space velocity is 0.5h⁻¹. -1 ~4.0h -1 .

[0025] According to the present invention, in step (2), the separation and fractionation process is well known in the art. Generally, the separation process is set up with several tanks, and the gas phase and liquid phase are flashed out as required. Hydrogen is separated from the final gas phase and returned as recycled hydrogen to the first and second reaction zones of the hydrogenation. The final liquid phase enters the fractionation system and obtains various streams through a step-by-step gas-liquid exchange process, which are the fractionation products mentioned in step (2). All kinds of products are arranged according to conventional destinations, and need not be elaborated here.

[0026] According to the present invention, in the hydrocracking method, the hydropretreatment reaction zone and the first hydrocracking reaction zone may use protective agents and / or post-treatment agents in practical applications, depending on the characteristics of the feedstock.

[0027] According to the present invention, in steps (2) and (4), the heavy naphtha is the heaviest component among all discharged products, with an initial boiling point of 63°C to 67°C and a final boiling point of 170°C to 175°C. The tail oil I and tail oil II are tail oils heavier than heavy naphtha, with an initial boiling point of 170°C to 175°C.

[0028] According to the present invention, in step (3), the second hydrocracking reaction zone is provided with multiple hydrocracking catalyst beds, preferably two or more; more preferably three to four. The hydrocracking catalyst beds are arranged at approximately the same height. The beds can be separated by facilities such as a cold hydrogen tank.

[0029] According to the present invention, in step (3), the second hydrocracking reaction zone is filled with a second hydrocracking catalyst. The second hydrocracking catalyst comprises a cracking component, a hydrogenation component, and a binder. The cracking component contains amorphous silica-alumina and / or molecular sieves, wherein the molecular sieves should include, but are not limited to, Y-type molecular sieves, such as USY-type molecular sieves and ASSY-type molecular sieves, and the binder is alumina and / or silica. The hydrogenation component is generally selected from one or more metals, metal oxides, or sulfides of Group VI, Group VII, and Group VIII, preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, nickel, or their sulfides or oxides. Based on the weight of the catalyst, the hydrogenation component, calculated as oxides, has a content of 13wt% to 41wt%, preferably 16wt% to 36wt%, and the molecular sieve content is 35wt% to 60wt%, preferably 40wt% to 55wt%. The second hydrocracking catalyst can be selected from existing industrial hydrocracking catalysts, such as HC-680 developed by UOP and FC-46 developed by Dalian Petrochemical Research Institute, or a specific hydrocracking catalyst that meets the requirements can be prepared as needed.

[0030] According to the present invention, in step (3), the process conditions of the second hydrocracking reaction zone are: average reaction temperature 285℃~420℃, hydrogen-to-oil volume ratio 600:1~1500:1, reaction pressure 7.0MPa~17.0MPa, and liquid hourly space velocity 0.5h. -1 ~6.0h -1 Preferably, the average reaction temperature is 290℃~410℃, the hydrogen-to-oil volume ratio is 700:1~1400:1, the reaction pressure is 8.5MPa~16.5MPa, and the liquid hourly space velocity is 0.6h. -1 ~5.0h -1 .

[0031] According to the present invention, in step (3), hydrogen gas is introduced into the second hydrocracking reaction zone in the same direction as the feedstock oil.

[0032] According to the present invention, in the hydrocracking method, considering the differences in feedstocks processed in the first and second stages and the differences in reaction atmospheres, in order to further improve the yield of heavy naphtha and reduce the probability of multiple cracking, a control method is adopted that adjusts the difference in feedstock reaction difficulty and catalyst activity in the same direction. The molecular sieve content in the second hydrocracking catalyst should be at least 10 percentage points lower than that in the first hydrocracking catalyst, preferably at least 12 percentage points, and more preferably 12 to 22 percentage points, by mass.

[0033] According to the present invention, the separation and fractionation system of the second hydrocracking reaction effluent in step (4) can share a system with the separation and fractionation system of the first hydrocracking reaction effluent in step (2).

[0034] According to the present invention, preferably, the tail oil II in step (4) is mixed with the tail oil I in step (2) as circulating oil and used together as feedstock for the second hydrocracking reaction zone. The total amount of tail oil I accounts for 60wt% to 80wt% of the total feedstock mass of the second hydrocracking reaction zone.

[0035] According to the present invention, in the hydrocracking method, the second hydrocracking reaction zone may use a protective agent and / or a post-treatment agent in practical applications, depending on the characteristics of the feedstock.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) In current hydrocracking processes, when using a two-stage process to produce heavy naphtha, most processes employ a two-stage full-cycle hydrocracking technology. The inventors of this invention have discovered that, when producing more heavy naphtha in a two-stage hydrocracking process, fractions with a distillation range greater than that of heavy naphtha can be circulated in a segmented, directional manner to the inlet positions of different beds in the second hydrocracking reaction zone for graded injection. This improves the molecular structure layout within the reaction system, effectively creating a graded transition atmosphere, improving the reactant concentration in key parts of the catalyst bed, increasing the adsorption efficiency of heavy components, suppressing unintended excessive cracking in the hydrocracking process, and maximizing heavy naphtha production, thereby achieving the ultimate objective of this invention.

[0038] Preferably, in hydrocracking processes that maximize heavy naphtha production, especially in two-stage full-cycle processes, the cracking agents used in the first and second stages generally have high cracking activity. While cracking the target product, multiple side reactions also occur, resulting in an increase in non-target products such as light hydrocarbons and gases. This invention addresses this by considering the characteristics of the catalyst and the differences between the reactants in the first and second stages. In the first stage, during the processing of hydrocracking feedstock, a highly active cracking agent is selected based on the characteristics of the reaction process, and an appropriate conversion depth is controlled to maximize heavy naphtha production from a technical perspective. In the second stage, during the processing of hydrocracking tail oil, a cracking agent with moderately reduced cracking activity is selected based on the characteristics of the reaction process, and heavy cycle components are introduced in stages. This achieves differentiation of reactants in different stages, reduces the excessive cracking of the target component, minimizes the occurrence of non-target reactions, and ultimately improves the yield of heavy naphtha.

[0039] (2) This invention injects circulating oil into different parts of the cracking process in the two-stage reaction zone. Through optimized design, the amount of cold hydrogen used in the current traditional bed-cooled hydrogen cooling mode can be reduced. By adopting a mixed cooling mode of cold oil and cold hydrogen, the total energy consumption of the circulating hydrogen compressor can be reduced, saving power costs. In addition, the circulating oil is not fractionated according to the weight of the fractions; it only needs to be pumped as a whole and distributed proportionally using valve positions. The overall energy consumption of the unit will be reduced, which is in line with the development trend of energy conservation and consumption reduction.

[0040] (3) In the implementation of the hydrocracking method of the present invention, the power source of the second-stage reaction zone can be reused by the existing circulating oil pump of the existing device with minor modifications. At the same time, the bed cooling method needs to be optimized. The overall workload is very small. The maximum production of heavy naphtha can be achieved without any additional investment. The method itself has the advantages of small modifications, low investment and quick results. Its practical value for application and promotion is quite significant. Attached Figure Description

[0041] Figure 1 The above are process flow diagrams for embodiments 1 to 4 of the present invention.

[0042] Explanation of key figure labels:

[0043] 1-Feedstock oil, 2-Hydrotreating pretreatment reaction zone, 3-Pretreatment reaction effluent, 4-First hydrocracking reaction zone, 5-First hydrocracking reaction effluent, 6-Separation system, 7-Separated hydrogen, 8-Recycled hydrogen compressor, 9-Make-up hydrogen, 10-Recycled hydrogen, 11-Liquid phase stream, 12-Fracturing system, 13-Gaseous light hydrocarbons, 14-Liquid light hydrocarbons, 15-Light naphtha, 16-Heavy naphtha, 17-Tail oil (Tail oil I + Tail oil II), 18-Second hydrocracking reaction zone, 19-Second hydrocracking reaction effluent. Detailed Implementation

[0044] The following is combined Figure 1 The process is described in detail in this invention. Some conventional parts that do not affect this invention are not all mentioned in detail, such as protective agents, post-treatment catalysts, cold hydrogen injection systems, etc. Some necessary units that are also conventional are reasonably integrated in the figure, only utilizing their functions, such as separation systems and fractionation systems.

[0045] like Figure 1 As shown, the process flow of the present invention is described as follows:

[0046] After the feedstock oil 1 is mixed with circulating hydrogen 10, it enters the hydrotreating pretreatment reaction zone 2 in the first-stage reaction zone as a reactant for feedstock pretreatment. The pretreatment effluent 3 enters the first hydrocracking reaction zone 4 in the first-stage reaction zone for the first hydrocracking reaction. The first hydrocracking reaction effluent 5 enters the subsequent separation system 6 for separation. The separated hydrogen 7 obtained from the top passes through the circulating hydrogen compressor 8 and is combined with the supplementary hydrogen 9 to become circulating hydrogen 10. The liquid phase stream 11 discharged from the bottom of the separation system enters the subsequent fractionation system 12 for product fractionation and recycling. In the fractionation system 12, from top to bottom, light hydrocarbons (gaseous light hydrocarbons 13, liquid light hydrocarbons 14), light naphtha 15, heavy naphtha 16, and tail oil tail oil I are obtained sequentially. Tail oil I (which will be combined with tail oil II later) enters the second hydrocracking reaction zone 18 in the second-stage reaction zone according to the above requirements for the second hydrocracking reaction. Then, its second hydrocracking reaction effluent 19 enters the separation 6 fractionation system 12 ( Figure 1 In this process, the separation and fractionation system for the effluent from the second hydrocracking reaction and the separation and fractionation system for the effluent from the first hydrocracking reaction share a single system to obtain the corresponding products (including tail oil II). Tail oil II is mixed with tail oil I, i.e., tail oil 17, and used as feedstock for the second hydrocracking reaction zone.

[0047] The detailed features of the method of the present invention will be described in more detail below through specific embodiments and comparative examples. Unless otherwise specified, all percentages in the description of the embodiments and comparative examples refer to mass percentages.

[0048] In this invention, the conversion rate of the feedstock oil in the first hydrocracking reaction zone corresponds to a temperature cutoff point of 175°C.

[0049] In this invention, each embodiment employs the following... Figure 1 The process flow is shown below.

[0050] In this invention, the properties of the feedstock oils for each hydrocracking example are shown in Table 1, the main physicochemical properties of the catalyst are shown in Table 2, and the implementation effects of the examples and comparative examples are shown in Table 3. In Table 3, the heavy naphtha yield is the total yield after 2000 h of reaction, by mass.

[0051] In this invention, the hydrogenation pretreatment reaction zone in each embodiment is filled with industrial catalyst FF-66. The first hydrocracking reaction zone is filled with industrial catalyst FC-52. The second hydrocracking reaction zone is filled with industrial catalyst FC-46. All of these are hydrogenation catalysts developed by the Dalian Research Institute of Petroleum and Chemical Industry.

[0052] Example 1

[0053] (1) After the hydrocracking feedstock is mixed with hydrogen, it enters the hydrocracking pretreatment reaction zone for hydrocracking pretreatment. Then, the hydrocracking pretreatment reaction effluent enters the first hydrocracking reaction zone for the first hydrocracking reaction.

[0054] The hydrotreating pretreatment reaction zone has a liquid hourly space velocity (LHSV) of 1.0 h⁻¹, based on fresh feedstock. -1 The reaction pressure was 15.0 MPa, the average reaction temperature was 366℃, the inlet hydrogen-to-oil volume ratio was 750, and the nitrogen content of the oil generated by the hydrogenation pretreatment was controlled to be 5 mg / kg.

[0055] First hydrocracking reaction zone: Liquid hourly space velocity (LHSV) 1.5 h⁻¹ -1 The reaction pressure was 14.7 MPa, the average reaction temperature was 370℃, the inlet hydrogen-to-oil volume ratio was 1100, and the feedstock conversion rate in the first hydrocracking reaction zone was 65% by mass. The first hydrocracking reaction zone had four catalyst beds.

[0056] (2) After separation and fractionation, the effluent from the first hydrocracking reaction in step (1) yields gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil I.

[0057] (3) In the presence of hydrogen, the tail oil I from step (2) enters the second hydrocracking reaction zone for the second hydrocracking reaction; in the second hydrocracking reaction zone, hydrogen is introduced in the same direction as the feed oil.

[0058] (4) The second hydrocracking effluent obtained in step (3) enters the separation and fractionation system to obtain gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil II. Tail oil II is used as circulating oil and mixed with tail oil I obtained from the separation and fractionation of the first hydrocracking effluent in step (2) as feedstock for the second hydrocracking reaction zone. The total amount of tail oil I accounts for 70 wt% of the total feedstock mass of the second hydrocracking reaction zone.

[0059] The second hydrocracking reaction zone has a liquid hourly space velocity (LHSV) of 2.5 h⁻¹ based on the total feed. -1 The average reaction temperature was 355℃, the reaction pressure was 14.5MPa, and the hydrogen-to-oil volume ratio was 1200.

[0060] The second hydrocracking reaction zone has three hydrocracking catalyst beds arranged at equal heights. The feedstock in the second hydrocracking reaction zone is fed from the top of each hydrocracking catalyst bed. The feedstock is fed from top to bottom; the feed rate decreases sequentially along the flow direction. In this example, the mass ratio of the feedstock from top to bottom is 60:27:13.

[0061] In this example, the final boiling point of the heavy naphtha is 175°C, and the initial boiling point is 65°C. The initial boiling points of tail oil I and tail oil II are both 175°C.

[0062] Example 2

[0063] (1) After the hydrocracking feedstock is mixed with hydrogen, it enters the hydrocracking pretreatment reaction zone for hydrocracking pretreatment, and then the hydrocracking pretreatment effluent enters the first hydrocracking reaction zone for the first hydrocracking reaction.

[0064] The hydrotreating pretreatment reaction zone has a liquid hourly space velocity (LHSV) of 1.1 h⁻¹, based on fresh feedstock. -1 The reaction pressure was 15.5 MPa, the average reaction temperature was 364℃, the inlet hydrogen-to-oil volume ratio was 850, and the nitrogen content of the oil generated by the hydrogenation pretreatment was controlled to be 10 mg / kg.

[0065] First hydrocracking reaction zone: Liquid hourly space velocity (LHSV) 1.6 h⁻¹ -1 The reaction pressure was 15.2 MPa, the average reaction temperature was 373℃, the inlet hydrogen-to-oil volume ratio was 1200, and the feedstock conversion rate in the first hydrocracking reaction zone was 66% by mass. The first hydrocracking reaction zone had four catalyst beds.

[0066] (2) After separation and fractionation, the effluent from the first hydrocracking reaction in step (1) yields gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil I.

[0067] (3) In the presence of hydrogen, the tail oil I from step (2) enters the second hydrocracking reaction zone for the second hydrocracking reaction; in the second hydrocracking reaction zone, hydrogen is introduced in the same direction as the feed oil.

[0068] (4) The second hydrocracking effluent obtained in step (3) enters the separation and fractionation system to obtain gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil II. Tail oil II is used as circulating oil and mixed with tail oil I obtained from the separation and fractionation of the first hydrocracking effluent in step (2) as feedstock for the second hydrocracking reaction zone. The total amount of tail oil I accounts for 68 wt% of the total feedstock mass of the second hydrocracking reaction zone.

[0069] The second hydrocracking reaction zone has a liquid hourly space velocity (LHSV) of 2.5 h⁻¹ based on the total feed. -1 The average reaction temperature was 354℃, the reaction pressure was 14.5MPa, and the hydrogen-to-oil volume ratio was 1200.

[0070] The second hydrocracking reaction zone has three hydrocracking catalyst beds arranged at equal heights. The feedstock in the second hydrocracking reaction zone is fed from the top of each hydrocracking catalyst bed. The feedstock is fed from top to bottom; the feed rate decreases sequentially along the flow direction. In this example, the mass ratio of the feedstock from top to bottom is 59:27:14.

[0071] In this example, the final boiling point of the heavy naphtha is 175°C, and the initial boiling point is 65°C. The initial boiling points of tail oil I and tail oil II are both 175°C.

[0072] Example 3

[0073] (1) After the hydrocracking feedstock is mixed with hydrogen, it enters the hydrocracking pretreatment reaction zone for hydrocracking pretreatment, and then the hydrocracking pretreatment effluent enters the first hydrocracking reaction zone for the first hydrocracking reaction.

[0074] The hydrotreating pretreatment reaction zone has a liquid hourly space velocity (LHSV) of 1.0 h⁻¹, based on fresh feedstock. -1 The reaction pressure was 15.0 MPa, the average reaction temperature was 366℃, the inlet hydrogen-to-oil volume ratio was 750, and the nitrogen content of the oil generated by the hydrogenation pretreatment was controlled to be 5 mg / kg.

[0075] First hydrocracking reaction zone: Liquid hourly space velocity (LHSV) 1.5 h⁻¹ -1 The reaction pressure was 14.7 MPa, the average reaction temperature was 370℃, the inlet hydrogen-to-oil volume ratio was 1100, and the feedstock conversion rate in the first hydrocracking reaction zone was 65% by mass. The first hydrocracking reaction zone had four catalyst beds.

[0076] (2) After separation and fractionation, the effluent from the first hydrocracking reaction in step (1) yields gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil I.

[0077] (3) In the presence of hydrogen, the tail oil I from step (2) enters the second hydrocracking reaction zone for the second hydrocracking reaction; in the second hydrocracking reaction zone, hydrogen is introduced in the same direction as the feed oil.

[0078] (4) The second hydrocracking effluent obtained in step (3) enters the separation and fractionation system to obtain gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil II. Tail oil II is used as circulating oil and mixed with tail oil I obtained from the separation and fractionation of the first hydrocracking effluent in step (2) as feedstock for the second hydrocracking reaction zone. The total amount of tail oil I accounts for 65 wt% of the total feedstock mass of the second hydrocracking reaction zone.

[0079] The second hydrocracking reaction zone has a liquid hourly space velocity (LHSV) of 2.5 h⁻¹ based on the total feed.-1 The average reaction temperature was 352℃, the reaction pressure was 14.5MPa, and the hydrogen-to-oil volume ratio was 1200.

[0080] The second hydrocracking reaction zone is equipped with four hydrocracking catalyst beds, arranged at equal heights. The feedstock in the second hydrocracking reaction zone is fed from the top of each hydrocracking catalyst bed. The feedstock is fed from top to bottom; the feed rate decreases sequentially along the flow direction. In this example, the mass ratio of the feedstock from top to bottom is 56:26:13:5.

[0081] In this example, the final boiling point of the heavy naphtha is 175°C, and the initial boiling point is 65°C. The initial boiling points of tail oil I and tail oil II are both 175°C.

[0082] Example 4

[0083] (1) After the hydrocracking feedstock is mixed with hydrogen, it enters the hydrocracking pretreatment reaction zone for hydrocracking pretreatment, and then the hydrocracking pretreatment effluent enters the first hydrocracking reaction zone for the first hydrocracking reaction.

[0084] The hydrotreating pretreatment reaction zone has a liquid hourly space velocity (LHSV) of 1.0 h⁻¹, based on fresh feedstock. -1 The reaction pressure was 15.0 MPa, the average reaction temperature was 366℃, the inlet hydrogen-to-oil volume ratio was 750, and the nitrogen content of the oil generated by the hydrogenation pretreatment was controlled to be 5 mg / kg.

[0085] First hydrocracking reaction zone: Liquid hourly space velocity (LHSV) 1.5 h⁻¹ -1 The reaction pressure was 14.7 MPa, the average reaction temperature was 376 °C, the inlet hydrogen-to-oil volume ratio was 1100, and the feedstock conversion rate in the first hydrocracking reaction zone was 75% by mass. The first hydrocracking reaction zone had four catalyst beds.

[0086] (2) After separation and fractionation, the effluent from the first hydrocracking reaction in step (1) yields gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil I.

[0087] (3) In the presence of hydrogen, the tail oil I from step (2) enters the second hydrocracking reaction zone for the second hydrocracking reaction; in the second hydrocracking reaction zone, hydrogen is introduced in the same direction as the feed oil.

[0088] (4) The second hydrocracking effluent obtained in step (3) enters the separation and fractionation system to obtain gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil II. Tail oil II is used as circulating oil and mixed with tail oil I obtained from the separation and fractionation of the first hydrocracking effluent in step (2) as feedstock for the second hydrocracking reaction zone. The total amount of tail oil I accounts for 70 wt% of the total feedstock mass of the second hydrocracking reaction zone.

[0089] The second hydrocracking reaction zone has a liquid hourly space velocity (LHSV) of 2.1 h⁻¹ based on the total feed. -1 The average reaction temperature was 348℃, the reaction pressure was 14.5MPa, and the hydrogen-to-oil volume ratio was 1200.

[0090] The second hydrocracking reaction zone has three hydrocracking catalyst beds arranged at equal heights. The feedstock in the second hydrocracking reaction zone is fed from the top of each hydrocracking catalyst bed. The feedstock is fed from top to bottom; the feed rate decreases sequentially along the flow direction. In this example, the mass ratio of the feedstock from top to bottom is 60:27:13.

[0091] In this example, the final boiling point of the heavy naphtha is 175°C, and the initial boiling point is 65°C. The initial boiling points of tail oil I and tail oil II are both 175°C.

[0092] Comparative Example 1

[0093] The feedstock oils in Table 1 are processed using a conventional two-stage full-cycle process. This example process is similar to... Figure 1 The only difference is that, Figure 1 The tail oil 17 obtained in the process was all fed from the top inlet of the second hydrocracking reaction zone 18. Other steps and parameters were the same as in Example 1.

[0094] Comparative Example 2

[0095] The feedstock oils listed in Table 1 are used. The process in this example is similar to that in Example 1. The process in this example is... Figure 1 The only difference is that Figure 1 The tail oil 17 obtained is fed into the top of the three catalyst beds in the second hydrocracking reaction zone, divided into three sections according to the weight of the fractions, along the flow direction. The three catalyst beds are designated as bed one, bed two, and bed three, from top to bottom, along the flow direction. In this example, tail oil 17 is divided into three sections: first tail oil (>320℃), second tail oil (250–320℃), and third tail oil (175–250℃). The first tail oil returns to the top inlet of bed one, the second tail oil returns to the top inlet of bed two, and the third tail oil returns to the top inlet of bed three.

[0096] The other steps and parameters are the same as in Example 1.

[0097] Comparative Example 3

[0098] The feedstock oils listed in Table 1 are used. The process in this example is similar to that in Example 1. The only difference is that the feedstock oil in the second hydrocracking reaction zone is fed from the top of each hydrocracking catalyst bed, and the feedstock oil is fed from top to bottom; the feedstock oil feed rate is equal along the flow direction. That is, the mass ratio of the feedstock oil feed rate from top to bottom in this example is 1:1:1. Other steps and parameters are the same as in Example 1.

[0099] Table 1. Properties of Crude Oil

[0100] Source of raw materials Stress-relieving wax oil <![CDATA[Density (20°C) / g·cm -3 > 0.9102 Distillation range / ℃ 312～543 <![CDATA[Sulfur / mg·kg -1 > 16100 <![CDATA[Nitrogen / mg·kg -1 > 1010

[0101] Table 2 Main physicochemical properties of the catalyst

[0102]

[0103]

[0104] Table 3 Comparison of Results for Each Example

[0105]

[0106] The specific embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combining the various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A hydrocracking method for increasing the production of heavy naphtha, employing a two-stage hydrocracking process, wherein, The method comprises setting up a primary reaction zone and a secondary reaction zone, wherein the primary reaction zone includes a first hydrocracking reaction zone and the secondary reaction zone includes a second hydrocracking reaction zone; the method includes: (1) The hydrocracking feedstock is mixed with hydrogen and then enters the first hydrocracking reaction zone to carry out the first hydrocracking reaction; (2) After separation and fractionation, the effluent from the first hydrocracking reaction in step (1) yields gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha, and tail oil I. (3) In the presence of hydrogen, the tail oil I from step (2) enters the second hydrocracking reaction zone for the second hydrocracking reaction; (4) The second hydrocracking effluent obtained in step (3) enters the separation and fractionation system to obtain gaseous light hydrocarbons, liquid light hydrocarbons, light naphtha, heavy naphtha and tail oil II; Preferably, in step (3), the second hydrocracking reaction zone is provided with multiple hydrocracking catalyst beds, preferably more than two; the feedstock of the second hydrocracking reaction zone is at the top of each hydrocracking catalyst bed; the feedstock is fed from top to bottom; along the flow direction, the feedstock feed rate decreases sequentially, and the mass ratio of feedstock feed rate between adjacent catalyst beds is 1.7:1 to 3.0:1, preferably 1.7:1 to 2.7:

1.

2. The method according to claim 1, characterized in that, In step (1), a hydrogenation pretreatment reaction zone is set up before the first hydrocracking reaction zone in a reaction zone; wherein, the nitrogen content in the reaction effluent of the hydrogenation pretreatment reaction zone is not greater than 15 mg / kg, preferably not greater than 10 mg / kg.

3. The method according to claim 1, characterized in that, In step (1), the process conditions in the hydrotreating reaction zone are as follows: average reaction temperature of 305℃~445℃, inlet hydrogen-to-oil volume ratio of 400:1~1100:1, reaction pressure of 7.0MPa~17.0MPa, and liquid hourly space velocity of 0.3h⁻¹. -1 ~5.0h -1 ; The preferred process conditions are: an average reaction temperature of 310℃~440℃, an inlet hydrogen-to-oil volume ratio of 500:1~1000:1, a reaction pressure of 8.5MPa~16.5MPa, and a liquid hourly space velocity of 0.4h. -1 ~4.5h -1 .

4. The method according to claim 1, characterized in that, In step (1), the conversion rate of feedstock oil in the first hydrocracking reaction zone is controlled to be 50% to 90%, preferably 60% to 80%, by mass.

5. The method according to claim 1, characterized in that, In step (1), the process conditions of the first hydrocracking reaction zone are as follows: average reaction temperature of 315℃~450℃, inlet hydrogen-to-oil volume ratio of 600:1~1500:1, reaction pressure of 7.0MPa~17.0MPa, and liquid hourly space velocity of 0.2h. -1 ~4.5h -1 Preferably, the average reaction temperature is 320℃~440℃, the inlet hydrogen-to-oil volume ratio is 700:1~1400:1, the reaction pressure is 8.5MPa~16.5MPa, and the liquid hourly space velocity is 0.5h⁻¹. -1 ~4.0h -1 .

6. The method according to claim 1, characterized in that, In step (1), the first hydrocracking reaction zone is filled with a first hydrocracking catalyst; the first hydrocracking catalyst includes a cracking component, a hydrogenation component, and a binder; the cracking component contains amorphous silica-alumina and / or molecular sieves, the molecular sieves include Y-type molecular sieves, and the binder is alumina and / or silica; the hydrogenation component is selected from one or more of metals, metal oxides, or sulfides of Group VI, Group VII, and Group VIII, preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, nickel, or their sulfides or oxides; based on the weight of the catalyst, the hydrogenation component, calculated as oxides, has a content of 12wt% to 40wt%, preferably 15wt% to 35wt%, and the molecular sieve content is 45wt% to 70wt%, preferably 50wt% to 65wt%.

7. The method according to claim 1, characterized in that, In steps (2) and (4), the initial boiling point of the heavy naphtha is 63℃~67℃, and the final boiling point is 170~175℃. And / or, the tail oil I and tail oil II are tail oils heavier than heavy naphtha, with an initial boiling point of 170–175°C.

8. The method according to claim 1, characterized in that, In step (3), the second hydrocracking reaction zone is provided with multiple hydrocracking catalyst beds, preferably more than two; further, three to four.

9. The method according to claim 1, characterized in that, In step (3), the process conditions of the second hydrocracking reaction zone are as follows: average reaction temperature of 285℃~420℃, hydrogen-to-oil volume ratio of 600:1~1500:1, reaction pressure of 7.0MPa~17.0MPa, and liquid hourly space velocity of 0.5h⁻¹. -1 ~6.0h -1 Preferably, the average reaction temperature is 290℃~410℃, the hydrogen-to-oil volume ratio is 700:1~1400:1, the reaction pressure is 8.5MPa~16.5MPa, and the liquid hourly space velocity is 0.6h⁻¹. -1 ~5.0h -1 .

10. The method according to claim 1, characterized in that, In step (3), the second hydrocracking reaction zone is filled with a second hydrocracking catalyst; the second hydrocracking catalyst includes a cracking component, a hydrogenation component and a binder; the cracking component contains amorphous silica-alumina and / or molecular sieves, the molecular sieves including Y-type molecular sieves; the hydrogenation component is selected from one or more of metals, metal oxides or sulfides of Group VI, Group VII, and Group VIII, preferably one or more of iron, chromium, molybdenum, tungsten, cobalt, nickel, or their sulfides or oxides; Based on the weight of the catalyst, the hydrogenation component, calculated as oxide, has a content of 13 wt% to 41 wt%, preferably 16 wt% to 36 wt%, and the molecular sieve content has a content of 35 wt% to 60 wt%, preferably 40 wt% to 55 wt%.

11. The method according to claim 1, characterized in that, The separation and fractionation system of the second hydrocracking reaction effluent in step (4) and the separation and fractionation system of the first hydrocracking reaction effluent in step (2) share the same system.

12. The method according to claim 1, characterized in that, The tail oil II mentioned in step (4) is mixed with the tail oil I mentioned in step (2) as circulating oil and used together as feed oil for the second hydrocracking reaction zone; the total amount of tail oil I accounts for 60wt% to 80wt% of the total feed oil mass of the second hydrocracking reaction zone.

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