Hydrogenation stepped conversion method and system of heavy hydrocarbon raw material

Abstract

The invention relates to the technical field of petroleum processing, in particular to a hydroprocessing stepped conversion method and system for a heavy hydrocarbon raw material, and the method adopts a two-stage reaction integration and material circulation design: firstly, a wax oil raw material is subjected to first-stage high-pressure hydrocracking, and a high-quality ethylene cracking material and a catalytic reforming material are synchronously produced at a high conversion rate; then, the generated middle distillate oil is subjected to hydroisomerization pour point depressing and deep hydrofining in the second-stage reaction to be directionally converted into class II light white oil and transformer oil base oil with high additional values, and non-target fractions obtained through precise fractionation are returned to the first stage to participate in the reaction; the method realizes the integrated and high-yield conversion of heavy wax oil to high-end chemical raw materials and special oil products, has the advantages of high product value, strong raw material adaptability and high material utilization rate, and solves the problem that in the heavy wax oil hydro-conversion technology, due to the lack of a chemical raw material and special oil product co-production connection process, the production cost is low. And the maximization of the product value cannot be realized.

Description

Technical Field

[0001] This invention relates to the field of petroleum processing and chemical technology, specifically to a method and system for the hydrogen-dependent step conversion of heavy hydrocarbon feedstocks. Background Technology

[0002] With the rapid increase in car ownership, the demand for gasoline and diesel has continued to climb, becoming a significant driving force for the development of the refining and chemical industry. However, in recent years, on the one hand, continuous technological advancements in the automotive industry and improved engine efficiency have reduced fuel consumption per unit mileage; on the other hand, the rapid development of the new energy vehicle industry, with electric vehicles, hybrid vehicles, and other new modes of transportation gradually expanding their market share, has created a significant substitution effect on the demand for traditional gasoline and diesel. These factors combined have led to a significant slowdown in the growth of demand for traditional vehicle fuels, and even a structural surplus.

[0003] In stark contrast, the demand for basic chemical raw materials, represented by low-carbon olefins such as ethylene and propylene, as well as aromatics, is showing a robust and sustained growth trend. These basic chemical raw materials are core ingredients in the production of many chemical products and are widely used in plastics, rubber, fibers, coatings, and many other fields. With the upgrading of manufacturing and the rise of emerging industries, the demand for various chemical products is constantly increasing, which in turn drives the rapid growth in demand for basic chemical raw materials. Against this market backdrop, "reducing oil and increasing chemicals" or "transforming oil refining into chemical processing" has become an inevitable choice for refining and chemical enterprises to enhance their core competitiveness and achieve sustainable development.

[0004] Among these technologies, hydrocracking stands out due to its unique advantages, including strong feedstock adaptability and flexible product formulations. Hydrocracking technology has a wide range of feedstock sources and can process various feedstock oils with different properties, including straight-run wax oil and coking wax oil. In terms of product formulations, hydrocracking technology can produce a variety of different types of products. Heavy naphtha is a high-quality feedstock for catalytic reforming to produce aromatics. Aromatics are important basic chemical raw materials, widely used in chemical, pharmaceutical, and pesticide industries. Through catalytic reforming, heavy naphtha can be converted into aromatic products such as benzene, toluene, and xylene, providing crucial feedstock support for downstream chemical industries. Tailings oil is an excellent feedstock for steam cracking to produce olefins. Low-carbon olefins such as ethylene and propylene are fundamental raw materials for synthetic plastics, synthetic rubber, and other polymer materials, playing a crucial role in chemical production. Through steam cracking, tailings oil can be converted into low-carbon olefins such as ethylene and propylene, meeting the strong market demand for basic chemical raw materials.

[0005] To maximize feedstock yield, two-stage hydrocracking processes are increasingly favored by refining companies due to their greater operational flexibility and overall feedstock yield. By rationally setting reaction stages and optimizing process conditions, two-stage hydrocracking processes can more precisely control the reaction process, improving the yield and quality of target products. In the first stage, the feedstock is hydrorefined under relatively mild conditions to remove impurities such as sulfur, nitrogen, oxygen, and metallic impurities, while partially saturating aromatics to improve the feedstock's properties. The products from the first stage then enter the second stage, where hydrocracking occurs under more stringent conditions, further breaking down heavy fractions into lighter fractions, thus increasing the feedstock yield. For example, Chinese invention patent CN101089141A discloses a two-stage hydrocracking method. This method employs a bulk catalyst bed containing three metal components: Mo, W, and Ni. Before sulfidation, W and Ni exist as composite oxides, while Mo exists as an oxide. The composite oxide precursor is generated through co-precipitation and mixed with MoO3 to form Ni. x W y O z Composite oxide and MoO3 compositions are used in the hydrotreating pretreatment and hydrocracking reaction zones to reduce the harshness of pretreatment and extend catalyst life, but their primary goal remains the production of clean fuels. Chinese invention patent CN1952067A also discloses a two-stage hydrocracking method. The first stage uses an organic nitrogen-resistant hydrocracking catalyst, with the feedstock directly contacting the hydrorefining catalyst and the single-stage hydrocracking catalyst. The resulting tail oil is used as feed for the second stage hydrocracking, where it is further cracked by a non-organic nitrogen-resistant hydrocracking catalyst. This fully utilizes the catalyst's cracking performance, aiming to improve the yield of middle distillate oil and reduce the cost of hydrocracking catalysts. It is evident that current optimization of hydrocracking technology, oriented towards increasing the production of chemical feedstocks, mainly focuses on process adjustment and catalyst improvement. The product solutions essentially remain within the traditional framework of "fuel + conventional chemical feedstocks." In these technologies, middle distillate oil is still treated as a "target product" or "important product" for production and optimization. However, given the current shrinking demand in the diesel market, this product strategy has failed to maximize the value of this product segment.

[0006] Meanwhile, market demand for specialty oils, especially high-end Group II light white oil and transformer oil, is strong, and the added value of these specialty oils is far higher than that of ordinary diesel. Traditionally, these specialty oils rely on crude oils of specific bases or independent, complex "hydrocracking-isomerization dewaxing-supplementary refining" specialized units for production, which suffers from problems such as limited raw materials, long process flow, and high investment and energy consumption. If the middle distillate oil produced by hydrocracking units, whose properties have been initially improved, could be directly and directionally converted into these high-value specialty oils in its subsequent processes, thereby achieving an integrated process of co-production of chemical feedstocks and specialty oils in the same system, it would be of great significance for realizing the integration of "oil, chemical, and specialty" industries. Summary of the Invention

[0007] To address the problem that existing heavy wax oil hydroconversion technologies cannot maximize product value due to the lack of a process for the co-production of chemical raw materials and specialty oils, this invention provides a hydrogen-dependent stepwise conversion method for heavy hydrocarbon feedstocks.

[0008] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for the hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstocks, comprising: The wax oil feedstock is subjected to a hydrocracking reaction to obtain the first stage reaction effluent; The effluent from the first stage reaction is separated into gas and liquid phases to obtain hydrogen-rich gas and liquid phase material. The separated hydrogen-rich gas is then treated with desulfurization and deammoniation and used as recycled hydrogen for hydrocracking reaction. The separated liquid phase material is fractionated to obtain a light naphtha fraction with a final boiling point not higher than 60℃, a heavy naphtha fraction with a boiling range of (60℃, 175℃), an intermediate distillate with a boiling range of (175℃, 375℃), and a tail oil fraction with an initial boiling point not lower than 375℃. The light naphtha fraction and the tail oil fraction are used as feedstock for ethylene cracking to prepare olefins, and the heavy naphtha fraction is used as feedstock for catalytic reforming to prepare aromatics. The middle distillate oil was subjected to hydroisomerization dewaxing catalytic reaction and deep hydrorefining catalytic reaction in sequence to obtain the second stage reaction effluent after upgrading; The effluent from the second stage reaction is separated and finely fractionated to obtain light white oil fraction, transformer oil base oil fraction, and light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction. The light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction are then used for hydrocracking reaction to achieve the hydrocracking stepwise conversion of heavy hydrocarbon feedstock.

[0009] Optionally, the wax oil feedstock includes straight-run wax oil and / or coking wax oil; the sulfur content of the wax oil feedstock is 1.5wt% to 3.5wt%, the nitrogen content is 500 to 1500 μg / g, and the density at 20°C is 0.90 to 0.94 g / cm³. 3 The BMCI value is 45-60, the initial boiling point is 200℃-260℃, and the 95% distillation temperature is 480℃-550℃.

[0010] Optionally, the conditions for the hydrocracking reaction are: a total pressure of 14.0–16.0 MPa and a total volume hourly space velocity of 0.5–2.0 h⁻¹. -1 The hydrogen to oil volume ratio is (800:1) to (1500:1), the reaction temperature is 360℃ to 400℃, and the single-pass conversion rate of the wax oil raw material is 80% to 90%.

[0011] Optionally, the catalyst used in the hydrocracking reaction is a hydrocracking catalyst, which includes a support and a hydrocracking active metal component supported on the support; the support includes alumina and Y-type molecular sieve, wherein, based on the mass of the support of the hydrocracking catalyst, the content of Y-type molecular sieve is 50wt% to 70wt%; the hydrocracking active metal component includes tungsten and nickel, wherein, based on tungsten trioxide, the tungsten content is 22wt% to 30wt%, and based on nickel oxide, the nickel content is 4wt% to 7wt%.

[0012] Optionally, the catalyst used in the hydroisomerization-depressing catalytic reaction comprises, in sequence, a pretreated catalyst, a pre-purified catalyst, and a hydroisomerization-depressing main catalyst; wherein the pretreated catalyst accounts for 1% to 10% of the total volume of all catalysts; the pre-purified catalyst accounts for 15% to 35% of the total volume of all catalysts; and the hydroisomerization-depressing main catalyst accounts for 55% to 80% of the total volume of all catalysts. The pretreatment catalyst comprises an alumina and / or silica-alumina support, on which a pretreatment active metal component is loaded. The pretreatment active metal component is selected from non-noble metal elements of Group VIB and Group VIII. Based on the total weight of the pretreatment catalyst, the total content of the pretreatment active metal element in the pretreatment catalyst, calculated as oxides, is 3wt% to 30wt%. The pre-purified catalyst comprises an alumina and / or silica-alumina support, on which a pre-purified active metal component is loaded. The pre-purified active metal component is selected from non-noble metal elements of Group VIB and Group VIII. Based on the total weight of the pre-purified catalyst, the total content of the pre-purified active metal element in the pre-purified catalyst, calculated as oxide, is 3wt% to 30wt%. The hydroisomerization depressant main catalyst comprises alumina and an acidic molecular sieve support, on which a hydroisomerization depressant active metal component is loaded. The acidic molecular sieve includes one or more of SAPO-11 molecular sieve, ZSM-22 molecular sieve, and TON structured molecular sieve. Based on the total weight of the support for the hydroisomerization depressant main catalyst, the content of the acidic molecular sieve is 30wt% to 55wt%. The hydroisomerization depressant active metal component is platinum and / or palladium. Based on the total weight of the hydroisomerization depressant main catalyst, the total content of the hydroisomerization depressant active metal component, calculated as elemental metal, is 0.3wt% to 1.2wt%.

[0013] Optionally, the hydroisomerization dewaxing catalytic reaction conditions are as follows: reaction pressure of 14.0–16.0 MPa, reaction temperature of 320°C–340°C, and volume hourly space velocity of 0.8–1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is (700:1) to (1000:1).

[0014] Optionally, the catalyst used in the deep hydrorefining catalytic reaction is a deep hydrorefining catalyst, which includes an alumina or silica-containing alumina support, on which a deep hydrorefining active metal component is loaded. The deep hydrorefining active metal component is platinum and / or palladium, and the total content of the deep hydrorefining active metal component, calculated as elemental metal, is 0.15wt% to 0.8wt% based on the total weight of the deep hydrorefining catalyst; and the loading volume ratio of the deep hydrorefining catalyst is 30% to 60% based on the total loading volume of the catalyst used in the hydroisomerization dewaxing catalytic reaction and the deep hydrorefining catalytic reaction.

[0015] Optionally, the conditions for the deep hydrorefining catalytic reaction are: a reaction pressure of 14.0–16.0 MPa, a reaction temperature of 200°C–220°C, and a volume hourly space velocity of 0.3–0.8 h⁻¹. -1 The hydrogen-to-oil volume ratio is (400:1) to (600:1).

[0016] A hydrocrack conversion system for heavy hydrocarbon feedstocks is provided to realize the above-mentioned hydrocrack conversion method. The system includes a first-stage hydrocracking reaction unit, a separation and fractionation unit, a second-stage directional reforming reaction unit, and a precision separation unit connected in sequence. The system comprises a first-stage hydrocracking reaction unit, a separation and fractionation unit, a second-stage directional reforming reaction unit, and a precision separation unit connected in sequence. The first stage hydrocracking reaction unit is used to perform a hydrocracking reaction on the wax oil feedstock to obtain the first stage reaction effluent; The separation and fractionation unit is used to fractionate the separated liquid phase material to obtain a light naphtha fraction with a final boiling point not higher than 60°C, a heavy naphtha fraction with a boiling range of (60°C, 175°C), an intermediate distillate oil with a boiling range of (175°C, 375°C), and a tail oil fraction with an initial boiling point not lower than 375°C. The light naphtha fraction and the tail oil fraction are used as feedstock for ethylene cracking to prepare olefins, and the heavy naphtha fraction is used as feedstock for catalytic reforming to prepare aromatics. The second stage of directional reforming reaction unit is used to sequentially perform hydroisomerization dewaxing catalytic reaction and deep hydrorefining catalytic reaction on the middle distillate oil to obtain the reformed second stage reaction effluent; The precision separation unit is used to separate and precisely fractionate the effluent from the second stage reaction to obtain light white oil fraction, transformer oil base oil fraction, and light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction. The light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction are then used for hydrocracking reaction to achieve the hydrocracking stepwise conversion of heavy hydrocarbon feedstock.

[0017] Optionally, the first hydrocracking reaction unit includes at least a hydrorefining reactor and a hydrocracking reactor; The separation and fractionation unit includes at least a hot high-pressure separator, a cold high-pressure separator, an alkaline washing tower, a hot low-pressure separator, a cold low-pressure separator, a first atmospheric pressure tower, and a first vacuum tower. The second stage of the directional reforming reaction unit includes at least a hydroisomerization dewaxing reactor and a supplementary refining reactor; The precision separation unit includes at least a high-pressure separator, a low-pressure separator, a second atmospheric pressure tower, and a second vacuum tower; The wax oil feedstock undergoes hydrocracking in a hydrorefining reactor and a hydrocracking reactor, and then sequentially enters a hot high-pressure separator and a cold high-pressure separator for gas-liquid separation to obtain hydrogen-rich gas and liquid phase material. The hydrogen-rich gas is desulfurized and deammonened in an alkaline scrubbing tower and then returned to the hydrocracking reactor as recycled hydrogen to participate in the reaction. The liquid phase material is sequentially separated in a hot low-pressure separator and a cold low-pressure separator, and then enters a first atmospheric pressure tower for fractionation to obtain light naphtha fraction, heavy naphtha fraction, and residual liquid phase material. The residual liquid phase material enters a first vacuum tower for fractionation to obtain middle distillate oil and tail oil fraction. The middle distillate oil is sequentially subjected to hydroisomerization dewaxing reactor and supplementary refining reactor for hydroisomerization pour point depressant catalytic reaction and deep hydrorefining catalytic reaction to obtain the upgraded second-stage reaction effluent; the second-stage reaction effluent is sequentially separated by high-pressure separator and low-pressure separator, and then enters the second atmospheric distillation tower for fractionation to obtain light white oil fraction and residual material; the residual material enters the second vacuum distillation tower for fractionation to obtain transformer oil base oil fraction as well as light components and heavy components not included in the range of the light white oil fraction and transformer oil base oil fraction; The light and heavy components are returned to the inlet of the hydrocracking reactor to continue participating in the reaction.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a hydrocrack conversion method for heavy hydrocarbon feedstocks. The method employs a two-stage integrated hydrocrack conversion process. The first stage involves hydrocracking the heavy hydrocarbon feedstock followed by separation and fractionation to obtain light naphtha fraction, heavy naphtha fraction, middle distillate, and tail oil fraction. The light naphtha fraction, heavy naphtha fraction, and tail oil fraction can be used to prepare olefins and aromatics. This not only achieves high conversion rates to maximize the total yield of chemical feedstocks but also allows for precise control of the reaction depth, ensuring that the unconverted tail oil has an extremely low BMCI value, making it a top-quality ethylene cracking feedstock. The second stage further involves hydroisomerization and dewaxing catalytic reactions, as well as deep hydrorefining catalytic reactions and fractionation of the middle distillate, to obtain high-quality light white oil fraction and transformer oil base oil fraction, among other specialty oil products. This effectively increases the added value of the products while overcoming the drawbacks of traditional specialty oil production, such as limited feedstock, long process cycles, and high costs and energy consumption. It significantly improves the utilization value of the feedstock, eliminates low-value byproducts, and increases economic benefits. Furthermore, the materials generated at each stage of the conversion process were fully and rationally utilized. The hydrogen-rich gas separated from the first-stage reaction effluent was treated and recycled for hydrocracking, achieving hydrogen recycling and reducing hydrogen consumption costs. Light and heavy components not included in the light white oil and transformer oil base oil fractions were also reused in hydrocracking, further improving feedstock conversion rates, reducing waste emissions, and maximizing resource utilization, truly achieving the "complete utilization" of heavy wax oil feedstock. The entire process flow is rationally designed, with close connections between each step, forming an organic whole. Starting from hydrocracking, through gas-liquid separation, fractionation, catalytic reactions, and other stages, heavy hydrocarbon feedstock is gradually converted into various target products. Each stage works in concert, fully leveraging the advantages of different reaction and separation technologies, improving the overall process efficiency and stability. The process is simple, with low modification costs, and represents a new technological path for the simultaneous, efficient, and flexible production of high-quality chemical feedstocks and high-end specialty oils, providing core technological support for refining enterprises to achieve integrated "oil, chemical, and specialty" development.

[0019] Utilizing a high-performance hydrorefining catalyst and a specially designed hydrocracking catalyst, and conducting the reaction under high pressure, suitable space velocity, and a high hydrogen-to-oil ratio, this process achieves efficient desulfurization and denitrification of the feedstock while simultaneously realizing deep saturation of aromatics and selective cracking of alkanes and cycloalkanes. This not only ensures a single-pass conversion rate of over 80%, maximizing the yield of chemical feedstocks, but more importantly, by controlling the cracking depth and hydrogen saturation level, it is possible to directionally shape the molecular structure of the unconverted tail oil, giving it an extremely low BMCI value. This makes it a top-tier feedstock for ethylene cracking, significantly enhancing the value of the tail oil as a chemical feedstock.

[0020] This innovative approach transforms middle distillate oil from a conventional diesel product into a "high-quality feedstock" for producing high-value-added specialty oils. Employing a stepped catalyst loading strategy—pretreatment, pre-refining, isomerization and pour point depletion, and deep refining—along optimized process conditions, it sequentially removes residual impurities, depletes long-chain n-alkane isomerization, and achieves ultimate aromatic saturation while protecting the activity of the precious metal catalyst. This integrated design successfully enables the co-production of Group II light white oil conforming to NB / SH / T 0913 standard and transformer oil conforming to GB2536 standard on mainstream heavy oil processing units, opening up a new path for the high-value utilization of middle distillate oil.

[0021] This invention also provides a hydrocracking step conversion system for heavy hydrocarbon feedstocks. This system achieves integrated production of high-quality chemical feedstocks and high-end specialty oils through the high integration of a separation and fractionation unit, a second-stage directional reforming reaction unit, and a precision separation unit. The system achieves "one-stage high-pressure cracking for directional production of high-quality chemical feedstocks" through the first-stage hydrocracking reaction unit and the separation and fractionation unit; and achieves "two-stage high-pressure reforming for directional production of specialty oils" through the second-stage directional reforming reaction unit and the precision separation unit. The integration of these units achieves the integration of two-stage process configurations, synergistically addressing the problems of low product value and fragmented processes in existing technologies. Simultaneously, this invention achieves closed-loop processing and near 100% directional conversion of materials throughout the entire process by recycling non-target light and heavy components generated from the second-stage precision fractionation back to the first-stage hydrocracking reaction unit for reprocessing. This effectively avoids the generation of low-value byproducts and further improves the overall economic efficiency of the process. Attached Figure Description

[0022] Figure 1 This is a schematic flowchart of a method for the hydrogen-dependent step conversion of heavy hydrocarbon feedstock according to the present invention.

[0023] Figure 2 This is a structural diagram of a hydrogenation-based step conversion system for heavy hydrocarbon feedstock according to the present invention.

[0024] 1- Hydrogenation refining reactor; 2- Hydrogenation cracking reactor; 3- Hot high-pressure separator; 4- Cold high-pressure separator; 5- Alkali washing tower; 6- Hot low-pressure separator; 7- Cold low-pressure separator; 8- First atmospheric pressure tower; 9- First vacuum tower; 10- Hydrogenation isomerization dewaxing reactor; 11- Supplementary refining reactor; 12- High-pressure separator; 13- Low-pressure separator; 14- Second atmospheric pressure tower; 15- Second vacuum tower. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0027] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0028] See Figure 1 This invention discloses a method for the hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstocks, comprising: S1: The wax oil feedstock is subjected to a hydrocracking reaction to obtain the first-stage reaction effluent. Specifically, the wax oil feedstock is subjected to a hydrocracking reaction under the following conditions: total pressure of 14.0–16.0 MPa, preferably 14.5–15.5 MPa, and total volume hourly space velocity of 0.5–2.0 h⁻¹. -1 Preferably, it is 1.0 to 3.0 h. -1The hydrogen-to-oil volume ratio is (800:1) to (1500:1), preferably (1000:1) to (1300:1). Under these optimized conditions of high pressure, suitable space velocity, and high hydrogen-to-oil ratio, the efficient conversion of heavy aromatics and nitrogen-containing compounds can be guaranteed, while sufficient hydrogen partial pressure can be provided to suppress catalyst carbonization and maintain long-term stable operation of the system. The reaction temperature is 360℃ to 400℃, and the single-pass conversion rate of the wax oil feedstock is 80% to 90%. This allows the wax oil feedstock to undergo deep hydrodesulfurization and denitrogenation, aromatic saturation, and selective cracking reactions to obtain the first-stage reaction effluent. By controlling the single-pass conversion rate within this range, the yield of light products (naphtha) can be maximized while avoiding excessive cracking that would lead to a significant increase in the yield of undesirable light hydrocarbon gases and an increase in hydrogen consumption. This also helps to maintain the thermal balance and operational stability of the reaction system. In this process, after hydrocracking, the single-pass conversion rate of wax oil based on the fraction above 375°C is greater than 80%, and the BMCI value of the resulting tail oil fraction is ensured to be less than or equal to 10, preferably 5-10, and more preferably 8. Controlling the BMCI value of the tail oil fraction within this low range ensures excellent ethylene yield and a longer cracking furnace operating cycle when used as a steam cracking feedstock, thereby maximizing its value as a chemical feedstock. The "single-pass conversion rate of wax oil based on the fraction above 375°C" is calculated using the following formula: Conversion rate = [(mass of the >375℃ fraction in the feedstock wax oil) – (mass of the tail oil fraction)] / (mass of the >375℃ fraction in the feedstock wax oil) × 100% The BMCI value (aromatics correlation index) of the tail oil fraction is calculated according to the industry-standard method, and its value represents the potential ethylene yield of the oil as a steam cracking feedstock. Preferably, the wax oil feedstock is selected from straight-run wax oil and / or coking wax oil, wherein the sulfur content of the wax oil feedstock is 1.5wt% to 3.5wt%, the nitrogen content is 500 to 1500 μg / g, and the density at 20°C is 0.90 to 0.94 g / cm³. 3 The BMCI value is 45-60, the initial boiling point is 200℃-260℃, and the 95% distillation temperature is 480℃-550℃. The catalyst used in the hydrocracking reaction is a hydrocracking catalyst, which includes a support and a hydrocracking active metal component supported on the support. The support includes alumina and Y-type molecular sieves, wherein the content of Y-type molecular sieves is 50wt%–70wt% based on the mass of the support of the hydrocracking catalyst. The hydrocracking active metal component includes tungsten and nickel, wherein the tungsten content is 22wt%–30wt% based on tungsten trioxide, and the nickel content is 4wt%–7wt% based on nickel oxide. The hydrocracking catalyst needs to be pre-sulfurized before use to form active sulfides. In a preferred online pre-sulfurization method, the following steps are taken: In the presence of hydrogen, using light gas oil with a distillation range of 200℃–380℃ and containing sulfiding agents such as dimethyl disulfide (DMDS) or carbon disulfide as the sulfiding oil, the pre-sulfurization is performed sequentially at low temperatures of 200℃–260℃, followed by high-temperature isothermal pre-sulfurization at 290℃–330℃. During the pre-sulfurization process, the system pressure is maintained at 8.0–20.0 MPa, and the H2S concentration in the circulating hydrogen is controlled. This liquid-phase pre-sulfurization method allows for more thorough contact between the sulfiding agent and the catalyst, resulting in a smooth and complete sulfidation process, which is beneficial for the formation of highly active sulfide-state metal centers. Preferably, the hydrocracking catalyst has a clover-shaped extrusion diameter of 1.0–1.5 mm, a lateral crushing strength of not less than 18 N / mm, and a specific surface area of ​​350–450 m². 2 / g, total pore volume is 0.55~0.75cm³ 3 / g.

[0029] S2: The effluent from the first stage reaction is subjected to gas-liquid separation to obtain hydrogen-rich gas and liquid phase material. The separated hydrogen-rich gas is then treated with desulfurization and deammoniation and used as circulating hydrogen for hydrocracking reaction. The separated hydrogen-rich gas is used to maintain the purity of circulating hydrogen in the system at not less than 95% after desulfurization and deammoniation treatment. S3: The separated liquid phase material is fractionated to obtain a light naphtha fraction with a final boiling point not higher than 60℃, a heavy naphtha fraction with a boiling range of (60℃, 175℃), a middle distillate with a boiling range of (175℃, 375℃), and a tail oil fraction with an initial boiling point not lower than 375℃. The light naphtha fraction and the tail oil fraction are used as feedstock for ethylene cracking to prepare olefins, and the heavy naphtha fraction is used as feedstock for catalytic reforming to prepare aromatics. Preferably, the cut point is controlled during the fractionation process. This design ensures that the final boiling point of the light naphtha fraction is 50℃~60℃, the boiling range of the heavy naphtha fraction is 65℃~170℃, the boiling range of the middle distillate is 180℃~370℃, and the initial boiling point of the tail oil fraction is 375℃~380℃. This separation scheme effectively separates the target fractions with concentrated properties, providing qualified feedstock for downstream processing units; producing high-quality chemical raw materials, with light naphtha and tail oil serving as high-quality ethylene cracking feedstock; and heavy naphtha serving as high-aromatic-potential reforming feedstock.

[0030] S4: The middle distillate oil is subjected to a hydroisomerization and pour point depressant catalytic reaction followed by a deep hydrorefining catalytic reaction to obtain the upgraded second-stage reaction effluent, specifically: The middle distillate oil was reacted at a pressure of 14.0–16.0 MPa, a temperature of 320–340℃, and a volume hourly space velocity of 0.8–1.5 h⁻¹. -1 Hydroisomerization dewaxing catalytic reaction is carried out under the condition of hydrogen-to-oil volume ratio of ~; wherein, the catalyst used in the hydroisomerization dewaxing catalytic reaction includes, in sequence, a pretreatment catalyst, a pre-purification catalyst and a hydroisomerization dewaxing main catalyst; The pretreated catalyst accounts for 1% to 10% of the total volume of all catalysts; the pre-purified catalyst accounts for 15% to 35% of the total volume of all catalysts; and the hydroisomerization dewaxing main catalyst accounts for 55% to 80% of the total volume of all catalysts. The pretreatment catalyst comprises an alumina and / or silica-alumina support, on which a pretreatment active metal component is loaded. The pretreatment active metal component is selected from non-noble metal elements of Group VIB and Group VIII, preferably containing a Mo-Ni or W-Ni combination. Based on the total weight of the pretreatment catalyst, the total content of the pretreatment active metal element in the pretreatment catalyst, calculated as oxides, is 3wt% to 30wt%. The pre-purified catalyst comprises an alumina and / or silica-alumina support, on which a pre-purified active metal component is loaded. The pre-purified active metal component is selected from non-noble metal elements of Group VIB and Group VIII, preferably containing a Mo-Ni or W-Ni combination. Based on the total weight of the pre-purified catalyst, the total content of the pre-purified active metal element in the pre-purified catalyst, calculated as oxide, is 3wt% to 30wt%, preferably 5wt% to 25wt%. The hydroisomerization dewaxing main catalyst comprises alumina and an acidic molecular sieve support, on which a hydroisomerization dewaxing active metal component is loaded. The acidic molecular sieve includes one or more of SAPO-11, ZSM-22, and TON structured molecular sieves. Based on the total weight of the support for the hydroisomerization dewaxing main catalyst, the content of the acidic molecular sieve is 30wt%–55wt%, preferably 35wt%–50wt%. The hydroisomerization dewaxing active metal component is platinum and / or palladium. Based on the total weight of the hydroisomerization dewaxing main catalyst, the total content of the hydroisomerization dewaxing active metal component (calculated as elemental metal) is... The content is 0.3wt% to 1.2wt%, preferably 0.5wt% to 1.0wt%. This composition and content can provide sufficient cracking activity to adjust product viscosity while ensuring high isomerization selectivity, which is the key to producing high viscosity index specialty oil base materials. Specifically, the ratio of pretreatment agent, pre-refining agent, and isomerization catalyst by volume is (0.05–0.15):(0.25–0.35):1, which can gradient-remove residual sulfur and nitrogen impurities in the feed and saturate some aromatics, providing a clean and moderately reactive feed for the downstream precious metal catalyst. This is a core measure to ensure the long-term stable operation of the precious metal catalyst. Preferably, the hydroisomerization pour point depressant catalyst is a cloverleaf extruder with an equivalent diameter of 1.4–1.8 mm, a side crushing strength of not less than 10 N / mm, and a specific surface area of ​​200 m². 2 / g~250 m 2 / g, total pore volume is 0.35 cm³ 3 / g~0.50 cm 3 / g.

[0031] The middle distillate oil after hydroisomerization and pour point depressing catalytic reaction was subjected to a reaction pressure of 14.0–16.0 MPa, a reaction temperature of 200–220 °C, and a volume hourly space velocity of 0.3–0.8 h⁻¹. -1 Under conditions where the hydrogen-to-oil volume ratio is ~, a deep hydrorefining catalytic reaction is carried out to obtain the modified second-stage reaction effluent; The catalyst used in the deep hydrorefining catalytic reaction is a deep hydrorefining catalyst, comprising an alumina or silica-containing alumina support, on which a deep hydrorefining active metal component is loaded. The deep hydrorefining active metal component is platinum and / or palladium, and the total content of the deep hydrorefining active metal component, calculated as elemental metal, is 0.15 wt% to 0.8 wt% based on the total weight of the deep hydrorefining catalyst. Based on the total loading volume of the catalyst used in the hydroisomerization dewaxing catalytic reaction and the deep hydrorefining catalytic reaction, the loading volume ratio of the deep hydrorefining catalyst is 30% to 60%. Preferably, the deep hydrorefining catalyst is a cloverleaf extruder with an equivalent diameter of 1.4 to 1.8 mm, a lateral crushing strength of not less than 12 N / mm, and a specific surface area of ​​300 to 350 m². 2 / g, total pore volume is 0.55~0.70 cm³ 3 / g.

[0032] Both the hydroisomerization dewaxing catalyst and the deep hydrorefining catalyst are reduced noble metal catalysts, which need to be activated online before use. A preferred reduction procedure is carried out in a hydrogen atmosphere at a system pressure of 10.0–18.0 MPa, and includes the following temperature program: increasing the temperature from room temperature to 150–170°C at a rate of 20°C / h–50°C / h and holding it at that temperature for 2–4 hours to remove physical water and some water of crystallization; then increasing the temperature to 190–210°C at a rate of 15°C / h–30°C / h and holding it at that temperature for 1–3 hours for preliminary reduction; and finally slowly increasing the temperature to 320°C–360°C at a rate of 10°C / h–20°C / h and holding it at that temperature for 3–5 hours to completely reduce the noble metal oxide to a metallic state with high hydrogenation activity. After the reduction is complete, the system needs to be slowly cooled to the target reaction temperature in a hydrogen atmosphere. This segmented heating reduction strategy can effectively control the reduction rate and prevent the noble metal grains from sintering and growing due to excessive heat of reduction, thereby obtaining metal centers with higher dispersion and more stable activity.

[0033] S5: The effluent from the second-stage reaction is separated and finely fractionated to obtain light white oil fraction, transformer oil base oil fraction, and light and heavy components not included in the light white oil fraction and transformer oil base oil fraction ranges. The light and heavy components not included in the light white oil fraction and transformer oil base oil fraction ranges are used for hydrocracking to achieve the hydrocracking stepwise conversion of heavy hydrocarbon feedstocks. During the separation and fine fractionation process, light white oil product fraction and transformer oil product fraction conforming to commercial standards are precisely cut according to the target product specifications. The light white oil product refers to a product that meets the technical requirements of Class 2 light white oil in the NB / SH / T 0913-2015 standard, which is at least one of the following grades: W2-60, W2-70, W2-80, W2-90, W2-100, or W2-110. The transformer oil base oil products refer to oils with a distillation range of 280℃ to 360℃ and whose properties meet the requirements of GB 2536-2011 standard.

[0034] This method, through the above-mentioned raw material adaptation, two-stage reaction division, precise matching and synergy of key catalyst systems, and closed-loop design of recycling by-product oils from the refining of specialty oils, can efficiently convert heavy wax oil raw materials into high-quality ethylene cracking feedstock, reforming feedstock, and high-value-added light white oil and transformer oil, thus realizing a path to maximize the value from raw materials to high-end products.

[0035] See Figure 2 The present invention also provides a hydrogenation step conversion system for heavy hydrocarbon feedstock, characterized in that it includes a first stage hydrocracking reaction unit, a separation and fractionation unit, a second stage directional reforming reaction unit, and a precision separation unit; The first stage hydrocracking reaction unit is used to perform hydrocracking reaction on wax oil feedstock to obtain the first stage reaction effluent, including hydrorefining reactor 1 and hydrocracking reactor 2; The separation and fractionation unit is connected to the first stage hydrocracking reaction unit and is used to separate the gas and liquid phases of the first stage reaction effluent to obtain hydrogen-rich gas and liquid phase material. The separated hydrogen-rich gas is treated with desulfurization and deammoniation and then used as recycled hydrogen for hydrocracking reaction. The unit includes a hot high-pressure separator 3, a cold high-pressure separator 4, an alkaline washing tower 5, a hot low-pressure separator 6, a cold low-pressure separator 7, a first atmospheric pressure tower 8, and a first vacuum tower 9. The second stage of directional reforming reaction unit is connected to the middle distillate oil output end of the separation and fractionation unit, and is used to sequentially perform hydroisomerization dewaxing catalytic reaction and deep hydrorefining catalytic reaction on the middle distillate oil to obtain the reformed second stage reaction effluent, including hydroisomerization dewaxing reactor 10 and supplementary refining reactor 11. The precision separation unit is connected to the output end of the second stage reaction effluent of the second stage directional reforming reaction unit. It is used to separate and precisely fractionate the second stage reaction effluent to obtain light white oil fraction, transformer oil base oil fraction, and light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction. The light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction are used for hydrocracking reaction to realize the hydrogen-dependent step conversion of heavy hydrocarbon feedstock. The unit includes a high-pressure separator 12, a low-pressure separator 13, a second atmospheric pressure tower 14, and a second vacuum tower 15.

[0036] The system's workflow is as follows: The wax oil raw material is subjected to hydrocracking reaction in hydrorefining reactor 1 and hydrocracking reactor 2, and then separated in sequence by hot high-pressure separator 3 and cold high-pressure separator 4 to output hydrogen-rich gas and liquid phase material. The hydrogen-rich gas, after being desulfurized and deammonened in the alkaline scrubbing tower 5, is returned to the hydrocracking reactor 2 as recycled hydrogen. The liquid material is flashed and separated in hot low-pressure separator 6 and cold low-pressure separator 7, and then sent to the first atmospheric pressure tower 8 for fractionation to obtain light naphtha fraction and heavy naphtha fraction; the bottom oil of the first atmospheric pressure tower 8 is sent to the first vacuum tower 9 for fractionation to obtain middle distillate oil and tail oil fraction. The middle distillate oil is sequentially subjected to hydroisomerization dewaxing reactor 10 and supplementary refining reactor 11 for hydroisomerization dewaxing catalytic reaction and deep hydrorefining catalytic reaction, and then the modified second stage reaction effluent is output. The effluent from the second stage reaction is separated sequentially by a high-pressure separator 12 and a low-pressure separator 13. The liquid phase is then fed into a second atmospheric distillation tower 14 for precision fractionation to obtain qualified light white oil fraction. The bottom oil of the second atmospheric distillation tower 14 is fed into a second vacuum distillation tower 15 for fractionation to obtain transformer oil base oil fraction, as well as light and heavy components that do not fall within the range of the light white oil fraction and transformer oil base oil fraction. The light and heavy components that do not enter the light white oil fraction and transformer oil base oil fraction range are returned to the inlet of hydrocracking reactor 2 for further processing.

[0037] To further illustrate the technical solution of the present invention, the following detailed description is provided in conjunction with specific embodiments. The properties of the raw materials and catalysts used in the embodiments are as follows: all catalysts are prepared using conventional impregnation, calcination, and molding processes in the art.

[0038] Properties of the wax oil raw materials used in the examples: The raw material is a mixture of straight-run wax oil and coking wax oil, and its main properties are: sulfur content 2.35 wt%, nitrogen content 850 μg / g, and density at 20℃ 0.9210 g / cm³. 3BMCI value 51.2, initial boiling point 232℃, 50% distillation temperature 433℃, 95% distillation temperature 495℃, final boiling point 539℃.

[0039] The yield of the light naphtha fraction is defined as the percentage of the mass of the separated light naphtha fraction (final boiling point ≤ 60℃) to the mass of the wax oil feedstock, i.e.: Light naphtha yield = (mass of light naphtha fraction / mass of wax oil feedstock) × 100%.

[0040] The yield of the heavy naphtha fraction is defined as the percentage of the mass of the separated heavy naphtha fraction (distillation range 60℃~175℃) to the mass of the wax oil feedstock, i.e.: Heavy naphtha yield = (mass of heavy naphtha fraction / mass of wax oil feedstock) × 100%.

[0041] The yield of the middle distillate oil is defined as the percentage of the mass of the separated middle distillate oil (distillation range 175℃~375℃) to the mass of the wax oil feedstock, i.e.: Middle distillate oil yield = (middle distillate oil mass / wax oil feedstock mass) × 100%.

[0042] The yield of the tail oil fraction is defined as the percentage of the mass of the separated tail oil fraction (initial boiling point ≥ 375℃) to the mass of the wax oil feedstock, i.e.: Tail oil yield = (tail oil fraction mass / wax oil feedstock mass) × 100%.

[0043] The yield of the special oil products (light white oil, transformer oil) is calculated as a percentage of the mass of the qualified product fraction to the mass of the wax oil raw material.

[0044] The hydrocracking catalyst used is HCAT-1: This catalyst comprises an alumina and Y-type molecular sieve support, with the Y-type molecular sieve content being 58 wt% based on the total weight of the support. Based on the total weight of the hydrocracking catalyst, the tungsten content (calculated as WO3) is 25.0 wt%, and the nickel content (calculated as NiO) is 5.5 wt%. This catalyst is a cloverleaf extruder with a diameter of 1.3 mm, a lateral crushing strength of 21 N / mm, and a specific surface area of ​​390 m². 2 / g, total pore volume is 0.64 cm³ 3 / g.

[0045] In the processes of hydroisomerization dewaxing catalysis and deep hydrorefining catalysis: The hydroisomerization dewaxing catalyst uses PCAT-1 as a pretreated catalyst: the pretreated catalyst uses alumina as a support, and based on the total weight of the pretreated catalyst, the support is loaded with MoO3 and NiO, and the total content of MoO3 and NiO based on the oxides of the pretreated catalyst is 12 wt%.

[0046] The pre-purified catalyst, PCAT-2, is supported on silica-alumina and contains WO3 and NiO by weight of the total pre-purified catalyst, with a total active metal content of 20 wt% based on oxides.

[0047] The hydroisomerization dewaxing catalyst is ICAT-1, which comprises an alumina and SAPO-11 molecular sieve support. Based on the total weight of the support, the SAPO-11 molecular sieve content is 45 wt%. Based on the total weight of the catalyst, the platinum (Pt) content is 0.65 wt%, and the palladium (Pd) content is 0.20 wt%. This catalyst is a cloverleaf extruder with an equivalent diameter of 1.6 mm, a lateral crushing strength of 11 N / mm, and a specific surface area of ​​225 m². 2 / g, total pore volume is 0.42cm³ 3 / g.

[0048] The deep hydrorefining catalyst is FCAT-1: This deep hydrorefining catalyst uses alumina as a support, and based on the total weight of the catalyst, the supported platinum (Pt) content is 0.25 wt% and the palladium (Pd) content is 0.30 wt%. This deep hydrorefining catalyst is a cloverleaf extruder with an equivalent diameter of 1.6 mm, a lateral crushing strength of 13 N / mm, and a specific surface area of ​​325 m². 2 / g, total pore volume is 0.66 cm³ 3 / g.

[0049] Example 1 According to the method of this invention, the wax oil feedstock is introduced into a first-stage reaction system consisting of a hydrorefining reactor 1 and a hydrocracking reactor 2 connected in series for reaction. The reaction effluent undergoes gas-liquid separation via a hot high-pressure separator 3 and a cold high-pressure separator 4. The hydrogen-rich gas is desulfurized by an alkaline scrubbing tower 5 and returned to the hydrocracking reactor 2 as circulating hydrogen. The liquid phase is fractionated via a cold low-pressure separator 6, a first atmospheric pressure tower 7, and a first vacuum tower 8 to obtain light naphtha fraction, heavy naphtha fraction, middle distillate oil, and tail oil fraction. The obtained middle distillate oil is introduced into a second-stage reaction system and sequentially passed through a hydroisomerization dewaxing reactor 9 in a hydroisomerization dewaxing reaction zone and a deep hydrorefining reaction zone, and a supplementary refining reactor 10 for upgrading. The upgraded oil is then separated and precisely fractionated via a high-pressure separator 11, a low-pressure separator 12, a second atmospheric pressure tower 13, and a second vacuum tower 14 to obtain qualified light white oil and transformer oil products. The light and heavy components that did not enter the target product from the precision fractionation are returned to the inlet of the first-stage hydrocracking reactor 2. Specific process parameters and catalyst loading ratios are shown in Table 1, and the yields and properties of the main products are shown in Table 2.

[0050] Example 2 This embodiment follows the same process flow and catalyst system as Example 1, except that the severity of some process operations was adjusted (e.g., reducing the reaction temperature and increasing the space velocity) and the catalyst loading ratio in the second-stage reaction system were also adjusted. Specific process parameters and catalyst loading ratios are shown in Table 1, and the main product yields and properties are shown in Table 2.

[0051] Example 3 This embodiment follows the same process flow and catalyst system as Example 1. The difference lies in the use of more stringent operating conditions, such as higher reaction pressure and temperature, and lower space velocity. The catalyst loading ratio in the second-stage reaction system was also adjusted to match the requirements for deep conversion. Specific process parameters and catalyst loading ratios are shown in Table 1, and the yields and properties of the main products are shown in Table 2.

[0052] Example 4 This embodiment follows the same process flow and catalyst system as Example 1. The main differences are the use of a higher volumetric space velocity, a suitable temperature and hydrogen-to-oil ratio, and a corresponding catalyst loading ratio to examine the operational performance under high throughput conditions. Specific process parameters and catalyst loading ratios are shown in Table 1, and the main product yields and properties are shown in Table 2.

[0053] Table 1 Reaction conditions for each example

[0054] Table 2 Product Properties and Yields of Examples

[0055] Comparative Example 1 This comparative example is used to illustrate the value and advantages of the integrated process of the present invention compared to the traditional fuel-based route.

[0056] Using the exact same wax oil feedstock, catalyst system (including all catalysts packed in the first-stage hydrocracking and second-stage reaction systems) and reaction operating conditions as in Example 1, the only change to the process is as follows: the hydroisomerization dewaxing and deep hydrorefining reactions in the second-stage reaction system are not initiated. Instead, the middle distillate oil (boiling range 175-375°C) produced in the first stage is directly separated into kerosene fraction (approximately 175-280°C) and diesel fraction (approximately 280-375°C), which are then discharged as fuel products. Accordingly, the material recycling step is eliminated. The yields and properties of the main products are shown in the table below:

[0057] As can be seen from the comparison between the examples and the comparative examples, the method of the present invention can create significantly higher economic value compared with the traditional fuel-based processing route under the same raw material and energy input, providing a practical and feasible technical path for refining and chemical enterprises to achieve transformation and upgrading of "reducing oil and increasing chemical production, improving quality and efficiency".

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for the hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstock, characterized in that, include: The wax oil feedstock is subjected to a hydrocracking reaction to obtain the first stage reaction effluent; The effluent from the first stage reaction is separated into gas and liquid phases to obtain hydrogen-rich gas and liquid phase material. The separated hydrogen-rich gas is then treated with desulfurization and deammoniation and used as recycled hydrogen for hydrocracking reaction. The separated liquid phase material is fractionated to obtain a light naphtha fraction with a final boiling point not higher than 60℃, a heavy naphtha fraction with a boiling range of (60℃, 175℃), an intermediate distillate with a boiling range of (175℃, 375℃), and a tail oil fraction with an initial boiling point not lower than 375℃. The light naphtha fraction and the tail oil fraction are used as feedstock for ethylene cracking to prepare olefins, and the heavy naphtha fraction is used as feedstock for catalytic reforming to prepare aromatics. The middle distillate oil was subjected to hydroisomerization dewaxing catalytic reaction and deep hydrorefining catalytic reaction in sequence to obtain the second stage reaction effluent after upgrading; The effluent from the second stage reaction is separated and finely fractionated to obtain light white oil fraction, transformer oil base oil fraction, and light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction. The light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction are then used for hydrocracking reaction to achieve the hydrocracking stepwise conversion of heavy hydrocarbon feedstock.

2. The method for hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstock according to claim 1, characterized in that, The wax oil feedstock includes straight-run wax oil and / or coking wax oil; the sulfur content of the wax oil feedstock is 1.5wt% to 3.5wt%, the nitrogen content is 500 to 1500 μg / g, and the density at 20℃ is 0.90 to 0.94 g / cm³. 3 The BMCI value is 45-60, the initial boiling point is 200℃-260℃, and the 95% distillation temperature is 480℃-550℃.

3. The method for hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstock according to claim 1, characterized in that, The conditions for the hydrocracking reaction are: total pressure of 14.0–16.0 MPa and total volume hourly space velocity of 0.5–2.0 h⁻¹. -1 The hydrogen to oil volume ratio is (800:1) to (1500:1), the reaction temperature is 360℃ to 400℃, and the single-pass conversion rate of the wax oil raw material is 80% to 90%.

4. The method for hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstock according to claim 1, characterized in that, The catalyst used in the hydrocracking reaction is a hydrocracking catalyst, which includes a support and a hydrocracking active metal component supported on the support; the support includes alumina and Y-type molecular sieve, wherein, based on the mass of the support of the hydrocracking catalyst, the content of Y-type molecular sieve is 50wt% to 70wt%; the hydrocracking active metal component includes tungsten and nickel, wherein, based on tungsten trioxide, the tungsten content is 22wt% to 30wt%, and based on nickel oxide, the nickel content is 4wt% to 7wt%.

5. The method for hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstock according to claim 1, characterized in that, The catalyst used in the hydroisomerization dewaxing catalytic reaction comprises, in sequence, a pretreated catalyst, a pre-purified catalyst, and a hydroisomerization dewaxing main catalyst; wherein the pretreated catalyst accounts for 1% to 10% of the total volume of all catalysts; the pre-purified catalyst accounts for 15% to 35% of the total volume of all catalysts; and the hydroisomerization dewaxing main catalyst accounts for 55% to 80% of the total volume of all catalysts. The pretreatment catalyst comprises an alumina and / or silica-alumina support, on which a pretreatment active metal component is loaded. The pretreatment active metal component is selected from non-noble metal elements of Group VIB and Group VIII. Based on the total weight of the pretreatment catalyst, the total content of the pretreatment active metal element in the pretreatment catalyst, calculated as oxides, is 3wt% to 30wt%. The pre-purified catalyst comprises an alumina and / or silica-alumina support, on which a pre-purified active metal component is loaded. The pre-purified active metal component is selected from non-noble metal elements of Group VIB and Group VIII. Based on the total weight of the pre-purified catalyst, the total content of the pre-purified active metal element in the pre-purified catalyst, calculated as oxide, is 3wt% to 30wt%. The hydroisomerization depressant main catalyst comprises alumina and an acidic molecular sieve support, on which a hydroisomerization depressant active metal component is loaded. The acidic molecular sieve includes one or more of SAPO-11 molecular sieve, ZSM-22 molecular sieve, and TON structured molecular sieve. Based on the total weight of the support for the hydroisomerization depressant main catalyst, the content of the acidic molecular sieve is 30wt% to 55wt%. The hydroisomerization depressant active metal component is platinum and / or palladium. Based on the total weight of the hydroisomerization depressant main catalyst, the total content of the hydroisomerization depressant active metal component, calculated as elemental metal, is 0.3wt% to 1.2wt%.

6. The method for hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstock according to claim 1, characterized in that, The conditions for the hydroisomerization dewaxing catalytic reaction are as follows: reaction pressure 14.0–16.0 MPa, reaction temperature 320℃–340℃, and volume hourly space velocity 0.8–1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is (700:1) to (1000:1).

7. The method for hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstock according to claim 1, characterized in that, The catalyst used in the deep hydrorefining catalytic reaction is a deep hydrorefining catalyst, which includes an alumina or silica-containing alumina support, on which a deep hydrorefining active metal component is loaded. The deep hydrorefining active metal component is platinum and / or palladium, and the total content of the deep hydrorefining active metal component, calculated as elemental metal, is 0.15 wt% to 0.8 wt% based on the total weight of the deep hydrorefining catalyst. Based on the total packing volume of the catalyst used in the hydroisomerization dewaxing catalytic reaction and the deep hydrorefining catalytic reaction, the packing volume of the deep hydrorefining catalyst accounts for 30% to 60%.

8. The method for hydrogen-dependent stepwise conversion of heavy hydrocarbon feedstock according to claim 1, characterized in that, The conditions for the deep hydrorefining catalytic reaction are: reaction pressure of 14.0–16.0 MPa, reaction temperature of 200–220 °C, and volume hourly space velocity of 0.3–0.8 h⁻¹. -1 The hydrogen-to-oil volume ratio is (400:1) to (600:1).

9. A hydrocrack conversion system for heavy hydrocarbon feedstocks, used to implement the hydrocrack conversion method according to any one of claims 1-8, characterized in that, The system comprises a first-stage hydrocracking reaction unit, a separation and fractionation unit, a second-stage directional reforming reaction unit, and a precision separation unit connected in sequence. The first stage hydrocracking reaction unit is used to perform a hydrocracking reaction on the wax oil feedstock to obtain the first stage reaction effluent; The separation and fractionation unit is used to fractionate the separated liquid phase material to obtain a light naphtha fraction with a final boiling point not higher than 60°C, a heavy naphtha fraction with a boiling range of (60°C, 175°C), an intermediate distillate oil with a boiling range of (175°C, 375°C), and a tail oil fraction with an initial boiling point not lower than 375°C. The light naphtha fraction and the tail oil fraction are used as feedstock for ethylene cracking to prepare olefins, and the heavy naphtha fraction is used as feedstock for catalytic reforming to prepare aromatics. The second stage of directional reforming reaction unit is used to sequentially perform hydroisomerization dewaxing catalytic reaction and deep hydrorefining catalytic reaction on the middle distillate oil to obtain the reformed second stage reaction effluent; The precision separation unit is used to separate and precisely fractionate the effluent from the second stage reaction to obtain light white oil fraction, transformer oil base oil fraction, and light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction. The light and heavy components that do not fall within the range of light white oil fraction and transformer oil base oil fraction are then used for hydrocracking reaction to achieve the hydrocracking stepwise conversion of heavy hydrocarbon feedstock.

10. The hydrogenation-step conversion system for heavy hydrocarbon feedstock according to claim 9, characterized in that, The first stage hydrocracking reaction unit includes at least a hydrorefining reactor and a hydrocracking reactor; The separation and fractionation unit includes at least a hot high-pressure separator, a cold high-pressure separator, an alkaline washing tower, a hot low-pressure separator, a cold low-pressure separator, a first atmospheric pressure tower, and a first vacuum tower. The second stage of the directional reforming reaction unit includes at least a hydroisomerization dewaxing reactor and a supplementary refining reactor; The precision separation unit includes at least a high-pressure separator, a low-pressure separator, a second atmospheric pressure tower, and a second vacuum tower; The wax oil feedstock undergoes hydrocracking in a hydrorefining reactor and a hydrocracking reactor, and then sequentially enters a hot high-pressure separator and a cold high-pressure separator for gas-liquid separation to obtain hydrogen-rich gas and liquid phase material. The hydrogen-rich gas is desulfurized and deammonened in an alkaline scrubbing tower and then returned to the hydrocracking reactor as recycled hydrogen to participate in the reaction. The liquid phase material is sequentially separated in a hot low-pressure separator and a cold low-pressure separator, and then enters a first atmospheric pressure tower for fractionation to obtain light naphtha fraction, heavy naphtha fraction, and residual liquid phase material. The residual liquid phase material enters a first vacuum tower for fractionation to obtain middle distillate oil and tail oil fraction. The middle distillate oil is sequentially subjected to hydroisomerization dewaxing reactor and supplementary refining reactor for hydroisomerization pour point depressant catalytic reaction and deep hydrorefining catalytic reaction to obtain the upgraded second-stage reaction effluent; the second-stage reaction effluent is sequentially separated by high-pressure separator and low-pressure separator, and then enters the second atmospheric distillation tower for fractionation to obtain light white oil fraction and residual material; the residual material enters the second vacuum distillation tower for fractionation to obtain transformer oil base oil fraction as well as light components and heavy components not included in the range of the light white oil fraction and transformer oil base oil fraction; The light and heavy components are returned to the inlet of the hydrocracking reactor to continue participating in the reaction.

Images