A hydrocracking process for producing heavy naphtha

Abstract

The application discloses a hydrocracking method for producing heavy naphtha. The method comprises the following steps: after a hydrocracking raw material is mixed with hydrogen, the mixture is sequentially introduced into a first hydrocracking reaction zone and a second hydrocracking reaction zone to perform a hydrocracking reaction; second hydrocracking reaction effluent is separated and fractionated to obtain dry gas, liquefied gas, light naphtha, heavy naphtha, aviation fuel, diesel oil and tail oil; the first hydrocracking reaction zone is filled with a first hydrocracking catalyst; a cracking component in the first hydrocracking catalyst comprises amorphous silicon aluminum and a molecular sieve; the content of the amorphous silicon aluminum is associated with the content of alkanes in the hydrocracking raw material; and the content of the molecular sieve is associated with the content of nitrogen in the hydrocracking raw material. The method solves the problem of damage of "poison" to the cracking catalyst when processing naphthenic raw materials to produce heavy naphtha, and can ensure long-period stable operation of the device and improve liquid yield.

Description

Technical Field

[0001] This invention belongs to the field of hydrocracking, specifically relating to a hydrocracking method for producing heavy naphtha. Background Technology

[0002] Fossil petroleum is a complex mixture of multiple elements, and it can be classified in several ways according to different classification standards. If classified according to chemical composition, it is generally divided into paraffinic crude oil, cycloalkyl crude oil, and intermediate-based crude oil. Paraffinic crude oil typically contains a high proportion of alkanes, has a high pour point, and a low sulfur content; cycloalkyl crude oil has a high proportion of cyclic hydrocarbons, a higher specific gravity, and a lower pour point; while intermediate-based crude oil's properties fall between those of paraffinic and cycloalkyl crude oils. Generally speaking, Liaohe crude oil, Karamay crude oil, and marine crude oil belong to the cycloalkyl crude oil category. Due to the numerous production sites, their processing scope and intensity in refining enterprises are very broad, and their corresponding components are also feedstocks for other secondary processing units.

[0003] For hydrocracking units processing naphthenic feedstocks, when the primary objective is to produce heavy naphtha, a current industrial phenomenon has emerged where, when the nitrogen content of the refined oil is controlled at a low level and the hydrocracking section temperature is controlled according to conventional methods, the temperature rise of the first-bed catalyst is extremely low. The only solution is to increase the reaction temperature for optimization, but this negatively impacts product distribution and long-term stable operation. Furthermore, this problem gradually migrates to the bottom, accelerating catalyst deactivation and resulting in a top-down gradual deactivation of the hydrocracking catalyst. Preliminary analysis suggests that a certain compound (or a cumulative effect) in the feedstock is inhibiting catalyst activity. To address this issue in hydrocracking units producing heavy naphtha and achieve the goals of "safe, stable, long-term, full-capacity, high-quality, and comfortable" operation, an effective solution is urgently needed to eliminate abnormal catalyst operation and ensure stable heavy naphtha production.

[0004] CN201610389886.2 discloses a method for increasing jet fuel production through hydrocracking. The method includes: mixing hydrocracking feedstock, cyclic hydrocarbon feedstock, and selectively added nitrogen-containing compounds to obtain a mixed feedstock oil; mixing the mixed feedstock oil with hydrogen and then sequentially contacting it with a hydrorefining catalyst I and a hydrocracking catalyst for reaction; cooling, separating, and fractionating the reaction effluent to obtain jet fuel fractions with a distillation range of 130℃ to 290℃; and the mixed feedstock oil containing 20% ​​to 50% by weight of dicyclic hydrocarbon molecules. This method can increase the jet fuel fraction yield in a single-pass hydrocracking unit. Compared with existing technologies, the jet fuel fraction has higher selectivity, better quality, and lower hydrogen consumption. While the invention optimizes the structure and composition of the feedstock and utilizes the inhibitory effect of nitrogen-containing compounds to produce the target component, it does not address the problems encountered in processing high-nitrogen cycloalkyl feedstocks, nor does it propose solutions.

[0005] CN202011115361.2 discloses a hydrocracking method for producing ethylene feedstock. The method includes the following steps: Feedstock oil or feedstock oil pretreated with hydrotreating is mixed with hydrogen and then fed into a hydrorefining reaction zone for reaction. The reaction effluent enters a first hydrocracking reaction zone for hydrocracking and deep hydrodenitrification. The reaction effluent is then separated into gas and liquid phases by a separator to obtain hydrogen-rich gas, which is used as recycled hydrogen. The liquid phase is mixed with hydrogen and then fed into a second hydrocracking reaction zone. The reaction effluent from this second zone is separated into gas and liquid phases by a separator to obtain hydrogen-rich gas, which is also used as recycled hydrogen. The liquid phase enters a fractionation tower for fractionation to obtain gas, light naphtha, heavy naphtha, jet fuel, and tail oil. This method can directly process high-nitrogen, high-drying-point feedstock oils, enabling long-cycle operation to produce low-pour-point diesel and ethylene feedstock. However, this method essentially separates the gas phase of the front-end reaction using a separator. In addition to being complex in process, it also separates the beneficial substances in the gas phase, without addressing the corresponding issues of catalyst performance and impurity removal in the raw materials.

[0006] The methods described above either utilize new flash tanks to process naphthenic feedstocks or leverage the characteristics of naphthenic feedstocks to produce corresponding components. However, none of these methods effectively address the problems encountered during the processing of naphthenic wax oils into heavy naphtha, let alone discuss how to solve them. Summary of the Invention

[0007] To address the problem in existing technologies where hydrocracking catalysts are easily deactivated from top to bottom during the production of heavy naphtha using naphthenic feedstocks, leading to shortened production cycles and reduced heavy naphtha yield, this invention provides a hydrocracking method for producing heavy naphtha. This method solves the problem of "poisoning" damage to the cracking catalyst during the production of heavy naphtha from naphthenic feedstocks, ensures long-term stable operation of the unit, and improves liquid yield.

[0008] This invention provides a hydrocracking method for producing heavy naphtha. The method includes:

[0009] After being mixed with hydrogen, the hydrocracking feedstock is sequentially fed into the first hydrocracking reaction zone and the second hydrocracking reaction zone for hydrogenation reaction. The effluent from the second hydrocracking reaction is separated and fractionated to obtain dry gas, liquefied petroleum gas, light naphtha, heavy naphtha, jet fuel, diesel oil and tail oil.

[0010] The first hydrocracking reaction zone is filled with a first hydrocracking catalyst; the cracking components in the first hydrocracking catalyst include amorphous silica-alumina and molecular sieves;

[0011] Preferably, based on the mass of the first hydrocracking catalyst, the mass content of amorphous silicon and aluminum in the first hydrocracking catalyst is not less than (0.65-A)*100%, and the mass content of amorphous silicon and aluminum does not exceed 62%, where A is the mass content of alkanes in the hydrocracking feedstock.

[0012] Preferably, based on the mass of the first hydrocracking catalyst, the mass content of molecular sieve in the first hydrocracking catalyst is (0.180-30.0B)*(1±0.15)*100%, where B is the mass content of nitrogen in the hydrocracking feedstock.

[0013] According to the present invention, the components and products can be discharged from the hydrocracking unit according to the flow path.

[0014] According to the present invention, the hydrocracking feedstock is a cycloalkane-based feedstock oil. That is, the hydrocracking feedstock refers to crude oil with cycloalkane-based properties, preferably a wax oil fraction, including one or more of the following: vacuum gas oil (VGO) obtained through atmospheric and vacuum distillation or deasphalted oil (DAO) and coking oil (CGO) obtained through other secondary processing. The final boiling point of the hydrocracking feedstock is generally 450–570°C, preferably 460–560°C; the initial boiling point is 220–350°C, preferably 250–345°C. The density at 20°C is generally 0.90 g / cm³. 3 ~0.95g / cm 3 0.91g / cm 3 ~0.94g / cm 3The nitrogen content is generally above 1000 mg / kg, preferably 1000–3000 mg / kg. There are no special requirements for sulfur content. By mass, the total proportion of cycloalkanes and aromatics in the hydrocracking feedstock is not less than 80 wt%, preferably 80%–95%; the alkanes content is not more than 20 wt%, preferably 5.0 wt%–20 wt%; more preferably, the cycloalkanes content is not less than 40 wt%, generally 40 wt%–80 wt%. The wax oil feedstock can be derived from suitable fractions obtained by processing land-based crude oils such as Liaohe crude oil and Karamay crude oil, or various marine crude oils. Any liquid-phase wax oil component that meets the above-mentioned requirements and is suitable as feedstock for a hydrocracking unit is within the scope of this invention. The feedstock can also be formulated according to the above requirements.

[0015] According to the present invention, based on the mass of the first hydrocracking catalyst, the mass content of amorphous silicon-aluminum in the first hydrocracking catalyst is not less than (0.65-A)*100%, and the mass content of amorphous silicon-aluminum does not exceed 62%, wherein A is the mass content of alkanes in the hydrocracking feedstock. Preferably, the value of A has at least two significant decimal places. Preferably, by mass, the alkanes content in the hydrocracking feedstock is not higher than 20 wt%, preferably 5.0 wt% to 20 wt%. For example, when the alkanes content in the hydrocracking feedstock is 20 wt%, the value of A is 0.20, then the mass content of amorphous silicon-aluminum in the first hydrocracking catalyst is 45% to 62%.

[0016] According to the present invention, based on the mass of the first hydrocracking catalyst, the mass content of molecular sieve in the first hydrocracking catalyst is (0.180-30.0B)*(1±0.15)*100%, where B is the mass content of nitrogen in the hydrocracking feedstock. Preferably, the value of B has at least four significant decimal places. Preferably, the nitrogen content in the hydrocracking feedstock is above 1000 mg / kg, more preferably 1000-3000 mg / kg. For example, when the nitrogen content in the hydrocracking feedstock is 2000 mg / kg, the value of B is 0.002000, then the mass content of molecular sieve in the first hydrocracking catalyst is 10.2%-13.8%.

[0017] According to the present invention, a hydropretreatment reaction zone is provided before the first hydrocracking reaction zone along the feed direction. The function of the hydropretreatment reaction zone is to remove impurities, that is, to pretreat the feedstock through a hydrotreating reaction, mainly involving desulfurization, denitrification, and aromatic saturation reactions, with the aim of providing suitable feedstock for the subsequent hydrocracking reaction process. The nitrogen content in the reaction effluent from the hydropretreatment reaction zone is below 10 mg / kg, preferably below 5 mg / kg. At this point, the removal of other corresponding impurities can be considered achieved simultaneously, and this feedstock can then proceed to the subsequent hydrocracking reaction.

[0018] According to the present invention, the hydrotreating reaction zone is provided with multiple hydrotreating catalyst beds, preferably two or more, and more preferably two to four. The hydrotreating catalyst beds are separated by facilities such as a hydrogen cooling tank.

[0019] According to the present invention, the hydrogenation pretreatment reaction zone is filled with a hydrogenation pretreatment catalyst. The hydrogenation pretreatment catalyst comprises a support and an active metal component. The support is typically an inorganic refractory oxide, selected from one or more of alumina, amorphous aluminum silicate, silica, titanium dioxide, etc. The active metal component is derived from Group VIB metals and / or Group VIII metals. 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 hydrogenation pretreatment catalyst, the content of the Group VIB metals as oxides is 10 wt% to 38 wt%, preferably 11 wt% to 37 wt%, and the content of the Group VIII metals as oxides is 0.2 wt% to 8.5 wt%, preferably 0.5 wt% to 8 wt%. The hydrogenation pretreatment catalyst can be developed and prepared according to actual needs and common knowledge in the art. Alternatively, existing industrialized conventional commercial catalysts can be used, such as the hydrocracking pretreatment catalysts FF-30, FF-36, FF-46, FF-56, FF-66, and FF-76 developed by Sinopec (Dalian) Petrochemical Research Institute.

[0020] According to the present invention, the process conditions of the hydrotreating reaction zone are as follows: average reaction temperature of 320℃~450℃, inlet hydrogen-to-oil volume ratio of 550:1~1000:1, reaction pressure of 8.5MPa~18.5MPa, and liquid hourly space velocity of 0.2h. -1 ~3.5h -1 The preferred process conditions are: an average reaction temperature of 330℃~440℃, an inlet hydrogen-to-oil volume ratio of 600:1~950:1, a reaction pressure of 9.0MPa~18.0MPa, and a liquid hourly space velocity of 0.3h⁻¹. -1 ~3.0h -1 .

[0021] According to the present invention, the function of the first hydrocracking reaction zone is to convert impurity hydrocarbons in the feedstock, preferably removing polycyclic hydrocarbons. The first hydrocracking reaction zone, taking into account the characteristics of the feedstock, improves catalyst properties and optimizes process conditions through correlation, thereby reducing influencing factors (such as ammonia adsorption) and achieving the removal of polycyclic hydrocarbons most prone to coking from the feedstock. Operating according to the method of the present invention can reduce their content to meet the feedstock requirements of subsequent functional zones, laying the foundation for further production of heavy naphtha.

[0022] According to the present invention, the first hydrocracking reaction zone is provided with at least one first hydrocracking catalyst bed, preferably one or two. The first hydrocracking catalyst beds are separated by facilities such as a cold hydrogen tank.

[0023] According to the present invention, the first hydrocracking reaction zone is packed with a first hydrocracking catalyst. The first hydrocracking catalyst comprises a cracking component, a hydrogenation component, and a binder component. The cracking component comprises amorphous silica-alumina and molecular sieves. The binder may be alumina and / or silica. The hydrogenation component may be selected from one or more metals of Group VIB and Group VIII, preferably one or more of iron, chromium, tungsten, molybdenum, cobalt, and nickel. Based on the mass of the first hydrocracking catalyst, the content of the hydrogenation component, calculated as oxides, is 15 wt% to 45 wt%, preferably 16 wt% to 44 wt%, preferably 2 wt% to 7 wt%, preferably 2.5 wt% to 6.5 wt%, of Group VIII metals; and the content of Group VIB metals, calculated as oxides, is 13 wt% to 38 wt%, preferably 13.5 wt% to 37.5 wt%.

[0024] According to the present invention, the amorphous silica-alumina in the first hydrocracking catalyst has the following properties: a specific surface area of ​​200 m². 2 / g~400m 2 / g, and / or, pore volume of 0.5ml / g to 0.8ml / g, and / or, acidity of 0.4mmol / g to 0.6mmol / g. In the amorphous silica-alumina, the mass percentage of SiO2 is 20% to 70%, and the mass percentage of Al2O3 is 30% to 80%. The molecular sieve includes, but is not limited to, Y-type molecular sieves, such as USY-type molecular sieves. The specific surface area of ​​the molecular sieve is 500m². 2 / g~800m 2 / g, and / or, pore volume of 0.3ml / g to 0.5ml / g, and / or, acidity of 0.5mmol / g to 0.8mmol / g. In the molecular sieve, the mass percentage of SiO2 is 70% to 95%, and the mass percentage of Al2O3 is 5% to 30%.

[0025] According to the present invention, the first hydrocracking catalyst is prepared in accordance with common knowledge in the art, thereby achieving the ultimate objective of the present invention.

[0026] According to the present invention, the process conditions of the first hydrocracking reaction zone are as follows: average reaction temperature of 390℃~410℃, inlet hydrogen-to-oil volume ratio of 850:1~1700:1, reaction pressure of 8.3MPa~18.3MPa, and liquid hourly space velocity of 1.5h⁻¹. -1 ~15.0h -1Preferably, the average reaction temperature is 390℃~410℃, the inlet hydrogen-to-oil volume ratio is 900:1~1650:1, the reaction pressure is 8.8MPa~17.8MPa, and the liquid hourly space velocity is 2.0h. -1 ~14.0h -1 .

[0027] According to the present invention, more preferably, the limitation on the average reaction temperature of the first hydrocracking reaction zone should also be related to the nitrogen content in the feedstock, taking into account the main characteristics of the first hydrocracking reaction zone and the optimized matching of upstream and downstream processes. Preferably, a four-stage control method is set according to the different nitrogen contents in the hydrocracking feedstock. Specifically: when the nitrogen content in the hydrocracking feedstock is less than 1500 mg / kg, the average reaction temperature of the first hydrocracking reaction zone is greater than or equal to 390℃ and less than 395℃; when the nitrogen content in the hydrocracking feedstock is greater than or equal to 1500 mg / kg and less than 2000 mg / kg, the average reaction temperature of the first hydrocracking reaction zone is greater than or equal to 395℃ and less than 400℃; when the nitrogen content in the hydrocracking feedstock is greater than or equal to 2000 mg / kg and less than 2500 mg / kg, the average reaction temperature of the first hydrocracking reaction zone is greater than or equal to 400℃ and less than 405℃; when the nitrogen content in the hydrocracking feedstock is greater than or equal to 2500 mg / kg (preferably, the nitrogen content is not higher than 3000 mg / kg), the average reaction temperature of the first hydrocracking reaction zone is greater than or equal to 405℃ and less than 410℃.

[0028] According to the present invention, the function of the second hydrocracking reaction zone is to further convert the qualified and high-quality feedstock from the first hydrocracking functional zone, which has undergone hydropretreatment and is now ready for processing, into various gaseous and liquid products, with heavy naphtha as the primary product, through the second hydrocracking reaction. In the overall hydrocracking reaction process, the depth of the reaction is defined by the conversion rate. According to the present invention, the total conversion rate of the first and second hydrocracking reaction zones is controlled to be 70% or more, preferably 70% to 95% by mass; the temperature cut-off point corresponding to this conversion rate is the initial boiling point of the tail oil.

[0029] According to the present invention, a plurality of second hydrocracking catalyst beds are provided in the second hydrocracking reaction zone. The number of catalyst beds in the second hydrocracking reaction zone is at least two, preferably two to four. The second hydrocracking catalyst beds are separated from each other by facilities such as a cold hydrogen tank.

[0030] According to the present invention, the second hydrocracking reaction zone is filled with a second hydrocracking catalyst. The second hydrocracking catalyst is a hydrocracking catalyst primarily used for the production of heavy naphtha, and generally belongs to the light oil type hydrocracking catalyst. Preferably, the second hydrocracking catalyst includes a cracking component, a hydrogenation component, and may also contain a binder component. The cracking component includes a molecular sieve, and may also include amorphous silica-alumina, wherein the molecular sieve includes, but is not limited to, Y-type molecular sieves, such as USY molecular sieves, ASSY-type molecular sieves, etc. The binder may be alumina and / or silica. The hydrogenation component is selected from one or more metals of Group VIB and Group VIII, preferably one or more of iron, chromium, tungsten, molybdenum, cobalt, and nickel. Based on the mass of the second hydrocracking catalyst, the content of the hydrogenation component, calculated as oxides, is 8 wt% to 38 wt%, preferably 10 wt% to 35 wt%. More preferably, the content of Group VIII metals, calculated as oxides, is 1 wt% to 6 wt%, preferably 1.5 wt% to 5.6 wt%; the content of Group VIB metals, calculated as oxides, is 7 wt% to 32 wt%, preferably 8.5 wt% to 29.5 wt%; and the content of molecular sieves is 35 wt% to 65 wt%, preferably 40 wt% to 60 wt%. The second hydrocracking catalyst can be developed and prepared according to actual needs and common knowledge in the field, or existing industrialized conventional commercial catalysts can be selected. Examples include HC-185 and HC-680 developed by UOP and FC-52 and FC-82 hydrocracking catalysts developed by Sinopec (Dalian) Petrochemical Research Institute.

[0031] According to the present invention, the process conditions of the second hydrocracking reaction zone are as follows: average reaction temperature of 315℃~445℃, inlet hydrogen-to-oil volume ratio of 950:1~2000:1, reaction pressure of 8.2MPa~18.2MPa, and liquid hourly space velocity of 0.5h⁻¹. -1 ~10.0h -1 Preferably, the average reaction temperature is 320℃~440℃, the inlet hydrogen-to-oil volume ratio is 1000:1~1950:1, the reaction pressure is 8.7MPa~17.7MPa, and the liquid hourly space velocity is 0.8h. -1 ~9.0h -1 .

[0032] According to the present invention, the separation and fractionation processes in the hydrocracking method are well known in the art and have no special requirements. Generally, the separation system performs flash separation, flashing off gas and liquid phases as required; hydrogen is separated from the gas phase and returned as recycled hydrogen to the pretreatment hydrocracking reaction zone, the first hydrocracking reaction zone, and the second hydrocracking reaction zone for continued use; the liquid phase enters the fractionation system, and through a step-by-step gas-liquid exchange process, various streams are obtained, namely the fractionation products mentioned in the above steps: dry gas, liquefied petroleum gas, light naphtha, heavy naphtha, jet fuel, diesel, and tail oil. All products are disposed of according to conventional routes and need not be elaborated here.

[0033] According to the present invention, the initial boiling point of the heavy naphtha is 63°C to 67°C, and the final boiling point is 170°C to 175°C. The initial boiling point of the tail oil is 315°C to 325°C.

[0034] According to the present invention, in the hydrocracking method, the hydropretreatment reaction zone, the first hydrocracking reaction zone, and the second hydrocracking reaction zone may use hydroprotective agents and / or hydroposttreatment agents in actual application, depending on the properties of the feedstock and the characteristics of the reaction. Cold hydrogen may also be injected to control the bed temperature. Although these are all necessary components in the process, they do not affect the implementation of the invention, so they will not be described in detail here.

[0035] Compared with the prior art, the main advantages of the present invention include:

[0036] (1) In response to the problems encountered in the current industrial processing of naphthenic wax oils, the inventors have discovered that the influencing factors are mainly twofold: the increase in cyclic structure and the strong inhibition by ammonia partial pressure. The synergistic effect and combined influence of these two factors cause the hydrocracking catalyst to gradually deactivate from top to bottom. This invention organically combines process technology with catalysts. First, by optimizing the process, the inhibition of the reaction process by ammonia partial pressure is reduced. Second, by adjusting the catalyst composition, the influence of ammonia partial pressure on catalyst performance is further weakened. At the same time, its ring-opening ability for polycyclic hydrocarbons is enhanced, reducing its ability to over-react and produce coking precursors (poisons). Furthermore, for the first time, the content of poisons and impurities in the feedstock is correlated with the composition of the catalyst. The method of this invention solves the problem of damage to the cracking catalyst by "poisons" in the production of heavy naphthenic oil from naphthenic feedstocks, ensuring long-term stable operation of the unit, thereby achieving the objective of this invention.

[0037] Considering the challenges of ammonia inhibition in processing cycloalkyl feedstocks and the difficulty of cracking polycyclic structures, coupled with the mutual inhibition between these factors leading to shorter production cycles, this invention addresses these issues by utilizing the characteristics of "poisonous" substances in the feedstock and adjusting the properties of the hydrocracking catalyst at higher reaction temperatures. Specifically, a new hydrocracking functional zone (i.e., the first hydrocracking reaction zone) is added between the existing hydropretreatment and hydrocracking functional zones (i.e., the second hydrocracking reaction zone), using a defined first hydrocracking catalyst. The content of amorphous silica and aluminum in this first hydrocracking catalyst is directly related to the alkane content in the hydrocracking feedstock, and the molecular sieve content is related to the nitrogen content in the hydrocracking feedstock. Simultaneously, the reaction temperature in the first hydrocracking reaction zone is also related to the nitrogen content in the hydrocracking feedstock. For the first time, the characteristics of the raw materials being processed are linked to the catalyst. This solution solves the problem that the catalyst bed is inhibited by ammonia when producing heavy naphtha in the current industrial process, making it difficult to process polycyclic hydrocarbons in the raw materials. This can reduce the cracking pressure on the lower catalyst and avoid the formation of coking precursors that cause rapid catalyst deactivation and shorten the production cycle.

[0038] (2) The raw materials processed by this invention have a high proportion of cyclic hydrocarbons and high oil viscosity, making diffusion reaction difficult. Therefore, the increase in the reaction temperature of the first hydrocracking functional zone reduces the oil viscosity, which is beneficial to diffusion reaction and improves reaction efficiency.

[0039] (3) The method of this invention enables the processing of wax oil feedstock with low-chain alkanes, high nitrogen, and high cyclic hydrocarbon content, solving the problems of rapid catalyst deactivation and abnormal temperature rise in the first bed of the cracking section of conventional hydrocracking units. By linking the feedstock composition with the amorphous silica-alumina content in the catalyst, the influence of coking precursors on the catalyst can be minimized. By linking the ammonia adsorption inhibition effect with the molecular sieve content in the catalyst, the catalyst reactivity can be maximized. The combination of the two can remove "poisons" in the feedstock, inhibiting their gradual conversion and poisoning of the catalyst, thus preventing the drawbacks of excessively rapid temperature rise and shortened cycle time. In essence, it is somewhat similar to the role of a hydrocracking process protectant, but the implementation method is different. The interconnected factors that affect each other under conventional process conditions are suppressed and decomposed through catalyst properties (composition adjustment and correlation with hydrocracking feedstock properties) and process optimization (temperature increase to reduce ammonia adsorption on hydrocracking catalyst), treated separately, and removed in a targeted manner to achieve the purpose of protecting the lower hydrocracking catalyst. Ultimately, this improved the liquid yield of the unit, stabilized the production of heavy naphtha (at least 25%), and extended the operating cycle. Detailed Implementation

[0040] The technical solution and effects of the method of the present invention will be described in detail below with reference to specific embodiments and comparative examples. In the description of the examples, only the main controlled process conditions are given; other factors that do not affect the effect of the invention, such as the separation system, fractionation system, cold hydrogen, protective agent, and post-treatment agent, are not described in detail. The examples listed below do not constitute a limitation on the method of the invention.

[0041] In this invention, unless otherwise specified, all percentages refer to mass percentages.

[0042] In this invention, the preparation methods of Agent 1, Agent 2, Agent 3, Agent 1A, Agent 1B, Agent 1C, and Agent 1D in Table 2 are consistent with the preparation methods of conventional hydrocracking catalysts, and there are no specific requirements. It is only necessary to conform to the catalyst composition limitations proposed in this invention. The impregnation method is used in this invention.

[0043] In this invention, the acid content of amorphous silica-alumina and the acid content of molecular sieves were measured using NH3-TPD. The instrument used was an Auto-Chem II 2920 chemisorption analyzer from Micron Instruments. Ammonia was used as the adsorption / desorption medium, and helium was used as the carrier gas. The total acid content was obtained using temperature-programmed desorption and chromatographic analysis, with the ammonia desorption temperature corresponding to the total acid content ranging from 150℃ to 450℃.

[0044] In this invention, the contents of cycloalkanes, aromatics and alkanes in the hydrocracking feedstock are determined by mass spectrometry (SHT0659).

[0045] In this invention, the nitrogen content in the hydrocracking feedstock is determined using the heavy oil nitrogen analysis method (NBSHT0704).

[0046] In this invention, the properties of the amorphous silicon-aluminum described in Table 2 are as follows: specific surface area of ​​290 m². 2 The amorphous silica-alumina has a pore volume of 0.7 ml / g and an acidity (measured by NH3-TPD) of 0.55 mmol / g. The amorphous silica-alumina comprises 40% SiO2 and 60% Al2O3 by mass.

[0047] In this invention, the properties of the molecular sieve in Table 2 are as follows: specific surface area is 550 m². 2 The molecular sieve has a pore volume of 0.41 ml / g and an acid content (measured by NH3-TPD) of 0.72 mmol / g. The molecular sieve contains 83% SiO2 and 17% Al2O3 by mass.

[0048] In this invention, the heavy naphtha is the primary product. The heavy naphtha has a final boiling point of 175°C and an initial boiling point of 65°C. The tail oil has an initial boiling point of 320°C.

[0049] Examples 1-5

[0050] After being mixed with hydrogen, the hydrocracking feedstock enters the hydropretreatment reaction zone, the first hydrocracking reaction zone, and the second hydrocracking reaction zone in sequence for hydrocracking reaction. The effluent from the second hydrocracking reaction is separated and fractionated to obtain dry gas, liquefied petroleum gas, light naphtha, heavy naphtha, jet fuel, diesel oil, and tail oil.

[0051] The properties of the hydrocracking feedstock wax oil used in each example are shown in Table 1, the main physicochemical properties of the catalyst used are shown in Table 2, the process conditions used in each example are shown in Table 3, and the application test results of each example after 6 months of stable operation are shown in Table 4.

[0052] Comparative Example 1

[0053] The difference between this example and Example 1 is that the average reaction temperature of the first hydrocracking reaction zone is different.

[0054] The process flow in this example is the same as in Example 1. The properties of the hydrocracking feedstock wax oil used in this example are shown in Table 1, the main physicochemical properties of the catalyst used are shown in Table 2, the process conditions used are shown in Table 3, and the total conversion rate at >320℃ in the first and second hydrocracking reaction zones of Example 1 is controlled to maintain the same conversion depth as in Example 1. The application test results after 6 months of stable operation are shown in Table 4.

[0055] Comparative Example 2

[0056] The difference between this example and Example 1 is that this example uses a conventional catalyst and controls the total conversion rate at >320°C in the first and second hydrocracking reaction zones of Example 1 to maintain the same conversion depth.

[0057] The process flow in this example is the same as in Example 1. The properties of the hydrocracking feedstock wax oil used in this example are shown in Table 1, the main physicochemical properties of the catalyst used are shown in Table 2, the process conditions used are shown in Table 3, and the application test results after 6 months of stable operation are shown in Table 4.

[0058] Comparative Examples 3-5

[0059] The difference between Comparative Examples 3-5 and Example 1 lies in the different first hydrocracking catalysts. In Comparative Example 3, the amorphous silicon-aluminum content in the first hydrocracking catalyst is outside the range defined by this invention. Similarly, in Comparative Examples 4 and 5, the molecular sieve content in the first hydrocracking catalyst is outside the range defined by this invention.

[0060] Comparative Examples 3-5 follow the same process flow as Example 1. The properties of the hydrocracking feedstock wax oil are shown in Table 1, the main physicochemical properties of the catalyst are shown in Table 2, and the process conditions are shown in Table 3. The total conversion rate at >320℃ in the first and second hydrocracking reaction zones of Example 1 is controlled to maintain the same conversion depth as in Example 1. The application test results after 6 months of stable operation are shown in Table 4.

[0061] Table 1 Properties of Crude Oil

[0062] Raw material oil 1 Raw material oil 2 3 raw material oils Raw material type (number) Naphthenic wax oil (I) Naphthenic wax oils (II) Naphthenic wax oils (III) <![CDATA[Density (20°C) / g·cm -3 > 0.9215 0.9177 0.9309 Distillation range / ℃ 336～498 345～505 344～507 <![CDATA[Sulfur / mg·kg -1 > 2200 4500 3500 <![CDATA[Nitrogen / mg·kg -1 > 1970 1400 2200 Composition, wt% Alkanes 12.1 17.6 5.9 Cycloalkanes 53.1 49.1 56.5 Aromatics 34.8 33.3 37.6

[0063] Table 2 Main physicochemical properties of the catalyst

[0064]

[0065]

[0066] Table 3 Main Operating Conditions for Each Example

[0067]

[0068]

[0069] Table 4 Comparison of Results for Each Example

[0070] *Deactivation rate, °C / month, catalyst temperature rise rate after six months of operation.

Claims

1. A hydrocracking method for producing heavy naphtha, comprising: After being mixed with hydrogen, the hydrocracking feedstock is sequentially fed into the first hydrocracking reaction zone and the second hydrocracking reaction zone for hydrogenation reaction. After separation and fractionation, the effluent from the second hydrocracking reaction yields dry gas, liquefied petroleum gas, light naphtha, heavy naphtha, jet fuel, diesel oil, and tail oil. The first hydrocracking reaction zone is filled with a first hydrocracking catalyst; the cracking components in the first hydrocracking catalyst include amorphous silica-alumina and molecular sieves; Preferably, based on the mass of the first hydrocracking catalyst, the mass content of amorphous silicon and aluminum in the first hydrocracking catalyst is not less than (0.65-A)*100%, and the mass content of amorphous silicon and aluminum does not exceed 62%, where A is the mass content of alkanes in the hydrocracking feedstock. Preferably, based on the mass of the first hydrocracking catalyst, the mass content of molecular sieve in the first hydrocracking catalyst is (0.180-30B)*(1±0.15)*100%, where B is the mass content of nitrogen in the hydrocracking feedstock.

2. The method according to claim 1, characterized in that, The hydrocracking feedstock is a cycloalkane-based feedstock oil, which refers to the wax oil fraction in crude oil with cycloalkane-based properties; the final boiling point of the hydrocracking feedstock is 450-570℃, preferably 460-560℃; the initial boiling point is 220-350℃, preferably 250-345℃. Furthermore, the nitrogen content of the hydrocracking feedstock is above 1000 mg / kg, preferably 1000–3000 mg / kg; Furthermore, in the hydrocracking feedstock, the total proportion of cycloalkanes and aromatics is not less than 80 wt%, preferably 80 wt% to 95 wt%; Furthermore, the alkanes in the hydrocracking feedstock are not higher than 20 wt%, preferably 5.0 wt% to 20 wt%; Further preferably, the hydrocracking feedstock contains cycloalkanes of not less than 40 wt%, preferably 40 wt% to 80 wt%.

3. The method according to claim 1, characterized in that, Along the flow direction, a hydropretreatment reaction zone is set up before the first hydrocracking reaction zone; the nitrogen content in the reaction effluent from the hydropretreatment reaction zone is less than 10 mg / kg, preferably less than 5 mg / kg; And / or, the process conditions in the hydrotreating reaction zone are: an average reaction temperature of 320℃~450℃, an inlet hydrogen-to-oil volume ratio of 550:1~1000:1, a reaction pressure of 8.5MPa~18.5MPa, and a liquid hourly space velocity of 0.2h⁻¹. -1 ~3.5h -1 The preferred process conditions are: an average reaction temperature of 330℃~440℃, an inlet hydrogen-to-oil volume ratio of 600:1~950:1, a reaction pressure of 9.0MPa~18.0MPa, and a liquid hourly space velocity of 0.3h⁻¹. -1 ~3.0h -1 .

4. The method according to claim 1, characterized in that, The function of the first hydrocracking reaction zone is to convert impurity hydrocarbons in the feedstock, preferably to remove polycyclic hydrocarbons; The first hydrocracking catalyst comprises a cracking component, a hydrogenation component, and a binder component; the hydrogenation component is selected from one or more metals of Group VIB and Group VIII, preferably one or more of iron, chromium, tungsten, molybdenum, cobalt, and nickel; based on the weight of the first hydrocracking catalyst, the content of the hydrogenation component, calculated as oxides, is 15wt% to 45wt%, preferably 16wt% to 44wt%, preferably, the content of Group VIII metals, calculated as oxides, is 2wt% to 7wt%, preferably 2.5wt% to 6.5wt%; the content of Group VIB metals, calculated as oxides, is 13wt% to 38wt%, preferably 13.5wt% to 37.5wt%.

5. The method according to claim 1, characterized in that, In the first hydrocracking catalyst, the amorphous silicon-aluminum has the following properties: a specific surface area of ​​200 m². 2 / g~400m 2 / g, and / or, pore volume of 0.5ml / g to 0.8ml / g, and / or, acidity of 0.4mmol / g to 0.6mmol / g; in the amorphous silica-alumina, the mass percentage of SiO2 is 20% to 70%, and the mass percentage of Al2O3 is 30% to 80%; the molecular sieve includes a Y-type molecular sieve; the specific surface area of ​​the molecular sieve is 500m². 2 / g~800m 2 / g, and / or, pore volume of 0.3ml / g to 0.5ml / g, and / or, acidity of 0.5mmol / g to 0.8mmol / g; in the molecular sieve, the mass percentage of SiO2 is 70% to 95%, and the mass percentage of Al2O3 is 5% to 30%.

6. The method according to claim 1, characterized in that, The process conditions of the first hydrocracking reaction zone are as follows: average reaction temperature of 390℃~410℃, inlet hydrogen-to-oil volume ratio of 850:1~1700:1, reaction pressure of 8.3MPa~18.3MPa, and liquid hourly space velocity of 1.5h⁻¹. -1 ~15.0h -1 Preferably, the average reaction temperature is 390℃~410℃, the inlet hydrogen-to-oil volume ratio is 900:1~1650:1, the reaction pressure is 8.8MPa~17.8MPa, and the liquid hourly space velocity is 2.0h. -1 ~14.0h -1 .

7. The method according to claim 1, 2, or 6, characterized in that, The average reaction temperature in the first hydrocracking reaction zone is correlated with the nitrogen content in the hydrocracking feedstock; Preferably, a four-stage control method is adopted based on the different nitrogen contents in the hydrocracking feedstock, specifically: When the nitrogen content in the hydrocracking feedstock is less than 1500 mg / kg, the average reaction temperature in the first hydrocracking reaction zone is greater than or equal to 390℃ and less than 395℃. When the nitrogen content in the hydrocracking feedstock is greater than or equal to 1500 mg / kg and less than 2000 mg / kg, the average reaction temperature in the first hydrocracking reaction zone is greater than or equal to 395℃ and less than 400℃. When the nitrogen content in the hydrocracking feedstock is greater than or equal to 2000 mg / kg and less than 2500 mg / kg, the average reaction temperature in the first hydrocracking reaction zone is greater than or equal to 400℃ and less than 405℃. When the nitrogen content in the hydrocracking feedstock is greater than or equal to 2500 mg / kg (preferably, the nitrogen content is not higher than 3000 mg / kg), the average reaction temperature of the first hydrocracking reaction zone is greater than or equal to 405℃ and less than 410℃.

8. The method according to claim 1, characterized in that, The total conversion rate of the first hydrocracking reaction zone and the second hydrocracking reaction zone is controlled to be above 70%, preferably 70% to 95%, by mass.

9. The method according to claim 1, characterized in that, The second hydrocracking reaction zone is filled with a second hydrocracking catalyst; Preferably, the second hydrocracking catalyst includes a cracking component and a hydrogenation component; the cracking component includes a molecular sieve; the molecular sieve includes a Y-type molecular sieve; the hydrogenation component is selected from one or more metals of Group VIB and Group VIII, preferably one or more of iron, chromium, tungsten, molybdenum, cobalt, and nickel; Preferably, based on the mass of the second hydrocracking catalyst, the content of the hydrogenation component, calculated as oxides, is 8 wt% to 38 wt%, more preferably 10 wt% to 35 wt%; preferably, the content of Group VIII metals, calculated as oxides, is 1 wt% to 6 wt%, more preferably 1.5 wt% to 5.6 wt%; the content of Group VIB metals, calculated as oxides, is 7 wt% to 32 wt%, more preferably 8.5 wt% to 29.5 wt%; and the content of molecular sieves is 35 wt% to 65 wt%, more preferably 40 wt% to 60 wt%.

10. The method according to claim 1, characterized in that, The process conditions for the second hydrocracking reaction zone are as follows: average reaction temperature of 315℃~445℃, inlet hydrogen-to-oil volume ratio of 950:1~2000:1, reaction pressure of 8.2MPa~18.2MPa, and liquid hourly space velocity of 0.5h⁻¹. -1 ~10.0h -1 Preferably, the average reaction temperature is 320℃~440℃, the inlet hydrogen-to-oil volume ratio is 1000:1~1950:1, the reaction pressure is 8.7MPa~17.7MPa, and the liquid hourly space velocity is 0.8h. -1 ~9.0h -1 .

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