Deep denitrification method for preparing light fuel oil through coal tar hydrogenation

Abstract

The invention relates to the technical field of coal tar hydrogenation, and particularly discloses a deep denitrification method for preparing light fuel oil by coal tar hydrogenation. The method comprises the following steps: carrying out filtration, dehydration, demetallization and deasphaltene pretreatment on coal tar, and carrying out a first-stage hydrogenation reaction in the presence of a conventional catalyst; feeding the mixture into a second hydrogenation reactor filled with an N-P co-doped ordered mesoporous carbon loaded Zr < 3 + > doped Ni2P catalyst, and carrying out hydrocracking and oxygen introduction assisted in-situ regeneration; and finally, carrying out deep adsorption through a nitric acid modified ZSM-5 and aluminum oxide composite adsorbent to obtain the light fuel oil. According to the invention, a multi-stage synergistic process of step-by-step impregnation and in-situ regeneration of the catalyst and B-Si dual auxiliaries and deep denitrification of the composite adsorbent is adopted, so that the hydrodenitrification activity and the catalyst stability are enhanced, the total nitrogen content of the product is effectively reduced, and the yield of light fractions of gasoline and diesel oil is improved. The method is high in denitrification depth, long in catalyst service life, capable of achieving efficient resource utilization of coal tar and suitable for industrial production.

Description

Technical Field

[0001] This application relates to the field of coal tar hydrogenation technology, specifically to a deep denitrification method for preparing light fuel oil by coal tar hydrogenation. Background Technology

[0002] Coal tar is a key byproduct generated during coal pyrolysis, gasification, and coking. Its composition is extremely complex, rich in polycyclic aromatic hydrocarbons (PAHs), heteroatom compounds containing sulfur, nitrogen, and oxygen, and metallic impurities such as nickel, vanadium, and iron. As an important heavy carbon resource, its efficient and clean conversion is crucial for improving the overall economic and environmental performance of the coal chemical industry. Converting coal tar into clean, light fuel oil with a high cetane number through hydrotreating technology is one of the mainstream approaches to achieving its high-value utilization. However, the high concentration of metals and PAHs in the feedstock poses a severe challenge to the hydrotreating process: metallic impurities (especially alkali metals and alkaline earth metals) can easily lead to irreversible poisoning of the subsequent fixed-bed hydrotreating catalyst, increased bed pressure drop, and significantly shortened unit operating cycles; while PAHs are not only difficult to saturate, their deep hydrotreating process also exacerbates catalyst deactivation due to carbon buildup and consumes large amounts of hydrogen.

[0003] Currently, industrial pretreatment of coal tar mainly relies on conventional physical separation methods such as centrifugation, filtration, electrostatic desalination, and solvent extraction. While these technologies can remove some solid particles and inorganic salts, their selective removal efficiency for metal impurities existing in the form of oil-soluble complexes and polycyclic aromatic hydrocarbons is limited, and they are prone to oil phase loss or secondary pollution. Furthermore, existing technologies often employ a separate protective reactor before the main hydrogenation reactor, filled with general-purpose demetallizing agents and adsorbents. This passive adsorption protection strategy suffers from limited metal-carrying capacity, low adsorption selectivity, and strong reversibility of aromatic hydrocarbon adsorption. Moreover, the protective agent needs to be replaced or regenerated once saturated, resulting in high operating costs and failing to fundamentally solve the problem of impurities poisoning the main catalyst. Therefore, developing a novel pretreatment technology that efficiently removes key toxic impurities from coal tar and can seamlessly integrate with subsequent hydrogenation processes has become the core key to overcoming the current bottlenecks in coal tar hydrorefining technology and upgrading it towards the production of ultra-high cetane number clean oil products. Summary of the Invention

[0004] To address the aforementioned problems, this application provides a deep denitrification method for preparing light fuel oil from coal tar by hydrogenation. The invention involves pretreating the coal tar feedstock and then feeding it into a first hydrogenation reactor for hydrogenation reaction, followed by gas-liquid separation to obtain a first effluent. The first effluent is then fed into a second hydrogenation reactor packed with a specific catalyst for hydrogenation cracking reaction, and an oxygen-containing stream is introduced to regenerate the catalyst in situ to obtain a second effluent. Finally, the second effluent is fed into an adsorption reactor packed with a composite adsorbent for contact reaction, thereby achieving deep denitrification of the coal tar and preparing light fuel oil products.

[0005] To achieve the above objectives, this application adopts the following technical solution: This application provides a deep denitrification method for preparing light fuel oil by hydrogenation of coal tar, comprising the following: S1. After pretreatment, the coal tar raw material is fed into the first hydrogenation reactor and hydrogenation reaction is carried out under the first reaction conditions. After the reaction is completed, the first effluent is obtained by gas-liquid separation. S2. The first effluent is subjected to a hydrocracking reaction in a second hydrogenation reactor filled with a catalyst under second reaction conditions to obtain a second effluent, wherein, during the hydrocracking reaction, an oxygen-containing stream is introduced into the reactor to regenerate the catalyst in situ; S3. The second effluent is fed into an adsorption reactor, which is filled with a composite adsorbent. The second effluent is then brought into contact with the composite adsorbent under a third operating condition to obtain a light fuel oil product after deep denitrification.

[0006] The S1 described in this application pre-treats the coal tar feedstock to remove interfering components such as solid impurities, moisture, metal ions, and asphaltenes. On the one hand, this eliminates the poisoning effect of impurities on the subsequent hydrogenation reaction and prevents the active sites of the catalyst from being occupied. On the other hand, it reduces the viscosity of the feedstock and improves its flowability, providing a clean and uniform reaction system for the subsequent multiphase hydrogenation reaction and ensuring the efficient conduct of the hydrogenation reaction. The pretreated coal tar is fed into the first hydrogenation reactor. Under suitable initial reaction conditions, hydrogen is adsorbed and activated at the active sites of the catalyst in the reactor, forming active hydrogen species (H·). The active hydrogen species undergoes an addition reaction with nitrogen-containing compounds in the coal tar (such as pyridine, quinoline, carbazole, etc.), breaking the nitrogen-containing heterocyclic structure and causing nitrogen atoms to detach from the heterocycle and combine with active hydrogen to generate easily removable substances such as NH3. At the same time, active hydrogen can also undergo hydrogenation saturation reaction with unsaturated hydrocarbons in the coal tar, reducing the unsaturation of the raw material. After the reaction, gas-liquid separation is performed to separate the gaseous products (such as NH3, unreacted hydrogen, etc.) from the first effluent, achieving the initial removal of nitrogen-containing impurities.

[0007] In step S2, the first effluent enters a second hydrogenation reactor packed with a specific catalyst, where a hydrocracking reaction occurs under the second reaction conditions. This further breaks down residual nitrogen-containing heterocyclic rings and large molecular hydrocarbon structures, achieving deep hydrogenation and cracking of the feedstock. The catalyst uses NP-co-doped ordered mesoporous carbon as a support. Its ordered mesoporous structure has a large specific surface area and excellent pore structure, which can efficiently disperse the active component and provide sufficient active sites for the reaction. Simultaneously, the co-doping of N and P elements can regulate the electronic structure of the support, enhancing the interaction between the support and the active component, thereby improving the catalyst's stability. The active component is Zr. 3+Doped Ni₂P, acting as a hydrogenation active center, can efficiently adsorb and activate hydrogen gas, generating active hydrogen species, Zr 3+ Doping with Ni₂P can regulate the electron density, enhance the adsorption and activation of nitrogen-containing compounds, and thus promote the deep cleavage of nitrogen-containing heterocycles. Impregnation with a dual-auxiliary boron and silicon source allows boron to modify the electronic structure of the active component, thereby improving the catalyst's hydrogenation activity. Conversely, the silicon source enhances the catalyst's mechanical strength and resistance to carbon deposition, thus extending its lifespan. During the hydrocracking reaction, an oxygen-containing stream is introduced to regenerate the catalyst in situ. The oxygen reacts with the carbon deposits on the catalyst surface, converting them into gaseous products such as CO₂, which are then discharged from the reactor. This restores the catalyst's active sites, preventing carbon buildup from covering the active centers and causing catalyst deactivation, maintaining long-term stable operation, and ultimately yielding a second effluent with further reduced nitrogen content.

[0008] S3 feeds the second effluent into an adsorption reactor filled with a composite adsorbent. Utilizing the selective adsorption mechanism of the composite adsorbent, deep removal of nitrogenous impurities is achieved. The composite adsorbent, through its surface active groups, can chemically adsorb residual trace amounts of nitrogenous compounds in the second effluent. Nitrogen molecules are adsorbed onto the adsorbent surface through hydrogen bonding, electrostatic attraction, or coordination, thereby further reducing the nitrogen content in the effluent. Under the third operating conditions, suitable temperature and pressure optimize the interaction strength between the adsorbent and nitrogenous compounds, increasing the adsorption rate and capacity, ensuring sufficient contact and efficient interaction between the second effluent and the composite adsorbent, ultimately yielding a deeply denitrified light fuel oil product, realizing the resource utilization of coal tar.

[0009] Preferably, in S1, the first hydrogenation reactor is filled with a conventional catalyst, which is a Ni-Mo catalyst.

[0010] Preferably, in S1, the pretreatment includes at least one of filtration, dehydration, demetallization, and deasphalting.

[0011] Preferably, in S1, the first reaction conditions include: a reaction temperature of 260-350℃, a reaction pressure of 6-12MPa, a volume hourly space velocity of 0.8-1.5h-1, and a hydrogen-to-oil volume ratio of (800-2000):1.

[0012] Preferably, in S1, the reaction ends when the total nitrogen content of the first effluent drops to 2000-5000 ppmw; the total nitrogen content is monitored in real time by an online analyzer or determined by offline sampling.

[0013] Preferably, in S2, the catalyst comprises a support, an active component, and two auxiliary agents; the support is NP-co-doped ordered mesoporous carbon, and the active component is Zr.3+ The doped Ni2P catalyst is composed of two components: a boron source and a silicon source. The catalyst is prepared as follows: organic sugar is used as the carbon source, mesoporous silicon as the template agent, and nitrogen and phosphorus sources are dissolved in deionized water to obtain a mixed solution A. This solution is then evaporated in a water bath, calcined at high temperature, and the template agent is removed to obtain an NP-co-doped ordered mesoporous carbon support. Zirconium and nickel salts are dissolved in deionized water to prepare a mixed solution B. The NP-co-doped ordered mesoporous carbon support is added, and a hydrothermal reaction is carried out. After the reaction is complete, a phosphorus source is added, and the temperature is raised to react. After separation and drying, a mixture C is obtained. The mixture C is then impregnated stepwise through a boron source solution and a silicon source solution, and finally dried and calcined to obtain the catalyst.

[0014] Preferably, in S2, the organic sugar includes any one of glucose, fructose, and sucrose; the mesoporous silica includes any one of MCM-41 mesoporous silica, SBA-15 mesoporous silica, and MCM-48 mesoporous silica; the nitrogen source includes any one of urea, melamine, and ammonium chloride; the phosphorus source includes any one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; the zirconium salt includes any one of zirconium chloride, zirconium nitrate, and zirconium sulfate; the nickel salt includes any one of nickel nitrate, nickel chloride, and nickel acetate; the phosphorus source includes any one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; the boron source solution includes any one of boric acid solution, sodium borate solution, and potassium borate solution; and the silicon... The source solution includes any one of tetraethyl orthosilicate solution, sodium silicate solution, and sodium methylsilicate solution; the mass concentration of the boron source solution is 2wt%-25wt%; the mass concentration of the silicon source solution is 10wt%-75wt%; the mass ratio of the carbon source, template agent, nitrogen source, phosphorus source, deionized water in mixed solution A, zirconium salt, nickel salt, deionized water in mixed solution B, and phosphorus source is 10:(2.5-3.5):(1.5-2.5):(1.0-2.0):(35-45):(1.0-1.4):(2.0-3.0):(12-18):(0.6-1.0); the mass ratio of the boron source solution to the silicon source solution is 1:(2-4).

[0015] Preferably, in step S2, the water bath evaporation temperature is 60-90℃ and the time is 2-6h; the high-temperature calcination temperature is 500-800℃ and the time is 3-8h; the hydrothermal reaction temperature is 120-180℃ and the time is 4-12h; the heating reaction temperature is 200-300℃ and the reaction time is 2-5h; the drying temperature of the drying and calcination is 80-120℃ and the drying time is 2-4h; the impregnation temperature of the stepwise impregnation is 25-60℃ and the impregnation time is 2-6h; the impregnation solid-liquid mass ratio is 1:(3-8); and the calcination temperature of the drying and calcination is 300-500℃ and the calcination time is 2-5h.

[0016] Preferably, in S2, the second reaction conditions include: a reaction temperature of 360-420℃, a reaction pressure of 8-15MPa, and a liquid hourly space velocity of 0.3-1.5h. -1 The hydrogen-to-oil volume ratio is (600-1200):1.

[0017] Preferably, in step S3, the composite adsorbent is obtained by calcining a ZSM-5 molecular sieve impregnated with nitric acid with an alumina precursor; the mass concentration of the nitric acid is 10wt%-20wt%; the mass ratio of the ZSM-5 molecular sieve impregnated with nitric acid to the alumina precursor is (3-4):1; and the calcination temperature is 500-650℃ and the time is 2-8h.

[0018] Preferably, in S3, the third operating conditions include: operating temperature 80-120℃, operating pressure 0.8-1.5MPa, and volumetric hourly space velocity 1.0-2.0h. -1 .

[0019] Compared with the prior art, the beneficial effects of this application are as follows: This application provides a deep denitrification method for the hydrogenation of coal tar to produce light fuel oil. In this application, the coal tar feedstock undergoes pretreatment to efficiently remove interfering components, preventing the occupancy of catalyst active sites. Under the action of a conventional catalyst, nitrogen-containing heterocycles in the coal tar are broken, and nitrogen atoms are converted into easily removable NH3, while simultaneously achieving hydrogenation saturation of unsaturated hydrocarbons. A first effluent is obtained after gas-liquid separation. The first effluent enters a second hydrogenation reactor, which is packed with a specific catalyst. This catalyst uses NP-co-doped ordered mesoporous carbon as a support. The ordered mesoporous structure can efficiently disperse the active components, and the N and P co-doping enhances the interaction between the support and the active components by adjusting the electronic structure of the support, thereby improving the catalyst stability. The active component is Zr. 3+ Doped Ni2P, Zr 3+ Doping allows for precise control of Ni2P electron density, enhancing adsorption and activation capabilities for nitrogen-containing compounds and promoting deep fragmentation of nitrogen-containing heterocycles. A dual-auxiliary agent, a boron source and a silicon source, are loaded onto the catalyst surface through stepwise impregnation. Boron modifies the electronic structure of the active component to improve hydrogenation activity, while the silicon source enhances the catalyst's mechanical strength and resistance to carbon deposition. Simultaneously, an oxygen-containing stream is introduced during hydrocracking, where oxygen reacts with carbon deposits on the catalyst surface, converting them into CO2 which is discharged from the reactor. This achieves in-situ catalyst regeneration, restoring active sites and maintaining long-term stable operation, further removing nitrogen-containing impurities to obtain the second effluent. The second effluent then enters an adsorption reactor filled with a composite adsorbent. The composite adsorbent, through its surface-active groups, interacts with residual trace nitrogen-containing compounds in the effluent via hydrogen bonding, electrostatic attraction, and coordination, achieving chemical adsorption denitrification. Under suitable third operating conditions, the adsorption rate and capacity can be optimized to ensure complete removal of nitrogen-containing impurities.

[0020] The entire process system is interconnected and synergistically coupled. Through the synergistic mechanism of pretreatment, two-stage hydrogenation and adsorption denitrification, it achieves efficient denitrification of coal tar while preparing light fuel oil, thus realizing the efficient utilization of coal tar resources. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the catalyst preparation process in a deep denitrification method for producing light fuel oil from coal tar hydrogenation. Detailed Implementation

[0022] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0023] In this application, the terminology used is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0024] The singular forms “for,” “or,” “a,” “any,” and “the” used in this application are intended to include the plural forms unless the context clearly indicates otherwise.

[0025] The following will describe in detail, with reference to different embodiments, a deep denitrification method for preparing light fuel oil by hydrogenation of coal tar provided in this application.

[0026] Example 1 like Figure 1 As shown in the figure, this embodiment provides a deep denitrification method for preparing light fuel oil by hydrogenation of coal tar, including the following: S1. The coal tar feedstock is pretreated sequentially by filtration, dehydration, demetallization, and deasphalting; the pretreated coal tar is then fed into a first hydrogenation reactor packed with a conventional Ni-Mo catalyst, and the reaction is carried out at a reaction temperature of 260℃, a reaction pressure of 6MPa, and a volume hourly space velocity of 0.8h. -1 The hydrogenation reaction was carried out under the first reaction condition of a hydrogen-to-oil volume ratio of 800:1. The total nitrogen content of the first effluent was determined by online analyzer or offline sampling. The reaction was terminated when the total nitrogen dropped to 2000 ppmw. The first effluent was obtained by gas-liquid separation. S2. The first effluent is fed into a second hydrogenation reactor packed with catalyst, and the reaction is carried out at a temperature of 360°C, a pressure of 8 MPa, and a liquid hourly space velocity of 0.3 h⁻¹. -1Hydrocracking was carried out under the second reaction condition of a hydrogen-to-oil volume ratio of 600:1 to obtain a second effluent. During the hydrocracking process, an oxygen-containing stream was introduced into the reactor to regenerate the catalyst in situ. The catalyst was prepared as follows: glucose was used as the carbon source, MCM-41 mesoporous silica as the template agent, and urea and phosphoric acid were dissolved in deionized water to obtain mixed solution A. Mixed solution A was evaporated to dryness in a 60°C water bath for 2 hours, and then calcined at 500°C for 3 hours to remove the template agent, thus obtaining an NP co-doped ordered mesoporous carbon support. Zirconium chloride and nickel nitrate were dissolved in deionized water to prepare mixed solution B. The NP co-doped ordered mesoporous carbon support was added to mixed solution B and subjected to a hydrothermal reaction at 120°C for 4 hours. After the reaction was completed, phosphoric acid was added, and the temperature was raised to 200°C for 2 hours. Mixture C was obtained by separation and drying. Mixture C was then impregnated stepwise with a 2 wt% boric acid solution and a 10 wt% tetraethyl orthosilicate solution. The impregnation temperature was 25°C, the impregnation time was 2 h, and the solid-liquid mass ratio was 1:3. After impregnation, the mixture was dried at 80°C for 2 h and then calcined at 300°C for 2 h to obtain the catalyst. The mass ratio of glucose, MCM-41 mesoporous silica, urea, phosphoric acid in mixed solution A, deionized water in mixed solution A, zirconium chloride, nickel nitrate, deionized water in mixed solution B, and phosphoric acid in mixed solution B was 10:2.5:1.5:1.0:35:1.0:2.0:12:0.6; the mass ratio of boric acid solution to tetraethyl orthosilicate solution was 1:2. S3. The second effluent is fed into an adsorption reactor filled with a composite adsorbent, and the mixture is subjected to an adsorption process at a temperature of 80℃, a pressure of 0.8MPa, and a volumetric hourly space velocity of 1.0 h⁻¹. -1 Under the third operating conditions, the product is fully contacted to obtain a light fuel oil product after deep denitrification; the composite adsorbent is prepared by impregnating ZSM-5 molecular sieve with 10wt% nitric acid, then mixing it with alumina precursor at a mass ratio of 3:1 and calcining it, with a calcination temperature of 500℃ and a calcination time of 2h.

[0027] Example 2 like Figure 1 As shown in the figure, this embodiment provides a deep denitrification method for preparing light fuel oil by hydrogenation of coal tar, including the following: S1. The coal tar feedstock is pretreated by sequential filtration, dehydration, demetallization, and deasphalting; the pretreated coal tar is then fed into a first hydrogenation reactor packed with a conventional Ni-Mo catalyst, and the reaction is carried out at a reaction temperature of 300℃, a reaction pressure of 9MPa, and a volume hourly space velocity of 1.2h. -1 The hydrogenation reaction was carried out under the first reaction condition of a hydrogen-to-oil volume ratio of 1400:1. The total nitrogen content of the first effluent was determined by online analyzer or offline sampling. The reaction was terminated when the total nitrogen dropped to 3500 ppmw. The first effluent was obtained by gas-liquid separation. S2. The first effluent is fed into a second hydrogenation reactor packed with catalyst, and the reaction is carried out at a temperature of 400°C, a pressure of 12 MPa, and a liquid hourly space velocity of 0.9 h⁻¹. -1 Hydrocracking reaction was carried out under the second reaction condition of hydrogen-to-oil volume ratio of 900:1 to obtain the second effluent. During the hydrocracking process, an oxygen-containing stream was introduced into the reactor to regenerate the catalyst in situ. The catalyst was prepared as follows: fructose as carbon source, SBA-15 mesoporous silica as template agent, melamine, and ammonium dihydrogen phosphate were dissolved in deionized water to obtain mixed solution A. Mixed solution A was evaporated to dryness in a 75°C water bath for 4 hours, and then calcined at 650°C for 5.5 hours to remove the template agent, thus obtaining NP co-doped ordered mesoporous carbon support. Zirconium nitrate and nickel chloride were dissolved in deionized water to prepare mixed solution B. The NP co-doped ordered mesoporous carbon support was added to mixed solution B and subjected to a hydrothermal reaction at 150°C for 8 hours. After the reaction was completed, ammonium dihydrogen phosphate was added and the temperature was raised to 250°C for 3 hours. After 5 hours of separation and drying, mixture C was obtained. Mixture C was then impregnated sequentially with a 13 wt% sodium borate solution and a 42 wt% sodium silicate solution in two steps: the impregnation temperature was 42℃, the impregnation time was 4 hours, and the solid-liquid mass ratio was 1:5. After impregnation, the mixture was dried at 100℃ for 3 hours and then calcined at 400℃ for 3.5 hours to obtain the catalyst. The mass ratio of fructose, SBA-15 mesoporous silica, melamine, ammonium dihydrogen phosphate in mixed solution A, deionized water in mixed solution A, zirconium nitrate, nickel chloride, deionized water in mixed solution B, and ammonium dihydrogen phosphate in mixed solution B was 10:3:2:1.5:40:1.2:2.5:16:0.8; the mass ratio of sodium borate solution to sodium silicate solution was 1:3. S3. The second effluent is fed into an adsorption reactor filled with a composite adsorbent, and the mixture is subjected to an adsorption process at a temperature of 100℃, a pressure of 1.2 MPa, and a volumetric hourly space velocity of 1.5 h⁻¹. -1 Under the third operating conditions, the product is fully contacted to obtain a light fuel oil product after deep denitrification; the composite adsorbent is prepared by impregnating ZSM-5 molecular sieve with 15wt% nitric acid, and then mixing it with alumina precursor at a mass ratio of 3.5:1 and calcining it. The calcination temperature is 575℃ and the calcination time is 5h.

[0028] Example 3 like Figure 1 As shown in the figure, this embodiment provides a deep denitrification method for preparing light fuel oil by hydrogenation of coal tar, including the following: S1. The coal tar feedstock is pretreated by sequential filtration, dehydration, demetallization, and deasphalting; the pretreated coal tar is then fed into a first hydrogenation reactor packed with a conventional Ni-Mo catalyst, and the reaction is carried out at a reaction temperature of 350℃, a reaction pressure of 12MPa, and a volume hourly space velocity of 1.5h⁻¹. -1The hydrogenation reaction was carried out under the first reaction condition of a hydrogen-to-oil volume ratio of 2000:1. The total nitrogen content of the first effluent was determined by online analyzer or offline sampling. The reaction was terminated when the total nitrogen dropped to 5000 ppmw. The first effluent was obtained by gas-liquid separation. S2. The first effluent is fed into a second hydrogenation reactor packed with catalyst, and the reaction is carried out at a temperature of 420°C, a pressure of 15 MPa, and a liquid hourly space velocity of 1.5 h⁻¹. -1 Hydrocracking reaction was carried out under the second reaction condition of hydrogen-to-oil volume ratio of 1200:1 to obtain the second effluent. During the hydrocracking process, an oxygen-containing stream was introduced into the reactor to regenerate the catalyst in situ. The catalyst was prepared as follows: sucrose was used as the carbon source, MCM-48 mesoporous silica was used as the template agent, and ammonium chloride and diammonium hydrogen phosphate were dissolved in deionized water to obtain mixed solution A. Mixed solution A was evaporated to dryness in a 90°C water bath for 6 hours, and then calcined at 800°C for 8 hours to remove the template agent, thus obtaining an NP co-doped ordered mesoporous carbon support. Zirconium sulfate and nickel acetate were dissolved in deionized water to prepare mixed solution B. The NP co-doped ordered mesoporous carbon support was added to mixed solution B and subjected to a hydrothermal reaction at 120-180°C for 4-12 hours. After the reaction was completed, diammonium hydrogen phosphate was added, and the reaction was carried out at 300°C. After 5 hours of separation and drying, mixture C was obtained. Mixture C was then impregnated sequentially with a 25 wt% potassium borate solution and a 75 wt% sodium methylsilicate solution in two steps: the impregnation temperature was 60°C, the impregnation time was 6 hours, and the solid-liquid mass ratio was 1:8. After impregnation, the mixture was dried at 120°C for 4 hours and then calcined at 500°C for 5 hours to obtain the catalyst. The mass ratio of sucrose, MCM-48 mesoporous silica, ammonium chloride, diammonium hydrogen phosphate in mixed solution A, deionized water in mixed solution A, zirconium sulfate, nickel acetate, and the deionized water in mixed solution B to diammonium hydrogen phosphate in mixed solution B was 10:3.5:2.5:2.0:45:1.4:3.0:18:1.0; the mass ratio of potassium borate solution to sodium methylsilicate solution was 1:4. S3. The second effluent is fed into an adsorption reactor filled with a composite adsorbent, and the mixture is subjected to an adsorption process at a temperature of 120℃, a pressure of 1.5MPa, and a volumetric hourly space velocity of 2.0h⁻¹. -1 Under the third operating conditions, the components are fully contacted to obtain light fuel oil after deep denitrification. The composite adsorbent is prepared by impregnating ZSM-5 molecular sieve with 20wt% nitric acid, then mixing it with alumina precursor at a mass ratio of 4:1 and calcining it. The calcination temperature is 650℃ and the calcination time is 8h.

[0029] Comparative Example 1 A deep denitrification method for preparing light fuel oil by hydrogenation of coal tar, which differs from Example 3 in that a conventional catalyst is used in S2.

[0030] Comparative Example 2 A deep denitrification method for preparing light fuel oil by hydrogenation of coal tar, which differs from Example 3 in that NP co-doped ordered mesoporous carbon support is not used in S2.

[0031] Comparative Example 3 A deep denitrification method for preparing light fuel oil by hydrogenation of coal tar, which differs from Example 3 in that there is no B-Si stepwise impregnation modification in S2.

[0032] Comparative Example 4 A deep denitrification method for preparing light fuel oil by hydrogenation of coal tar is disclosed, which differs from Example 3 in that the composite adsorbent in S3 is not modified with nitric acid.

[0033] Performance testing: 1. Total nitrogen content test: Using a nitrogen element analyzer, samples of the light fuel oil products obtained in Examples 1-3 and Comparative Examples 1-4 were taken, diluted with solvent, and the total nitrogen content of the products was determined to evaluate the deep denitrification effect.

[0034] 2. Catalyst activity stability test: The activity change of the catalyst in the second hydrogenation reactor of Examples 1-3 and Comparative Examples 1-4 was monitored after 100 hours of continuous operation. The catalyst activity retention rate was calculated by measuring the total nitrogen content of the second effluent at different time points, and the catalyst stability was evaluated.

[0035] 3. Light fuel oil fraction composition test: The light fuel oil products obtained in Examples 1-3 and Comparative Examples 1-4 were separated and tested using a gas chromatograph to determine the proportion of gasoline and diesel fractions and to evaluate whether the product quality met the standards.

[0036] The performance test data analysis is as follows: Table 1. Performance test data of light fuel oils obtained from Examples 1-3 and Comparative Examples 1-4 As shown in Table 1, Examples 1-3 involved pretreatment purification, two-stage step hydrogenation, and NP co-doping of ordered mesoporous carbon loaded with Zr. 3+A synergistic technical solution involving Ni2P-doped catalyst, stepwise impregnation modification with B-Si dual additives, in-situ catalyst regeneration, and deep adsorption with nitric acid-modified ZSM-5 composite adsorbent showed a significant increasing trend in various performance aspects. Example 3 demonstrated the best performance, with a total nitrogen content as low as 4.8 ppmw, a catalyst activity retention rate of 98.2% after 100 hours of operation, a high total effective fraction of gasoline and diesel in the light fuel oil, and only 4.2 wt% of heavy oil tail fraction, exhibiting excellent deep denitrification performance, catalyst stability, and light-grade conversion efficiency. This is due to two main factors: firstly, the first hydrogenation stage completes preliminary hydrogenation saturation and pre-denitrification under conventional Ni-Mo catalyst, providing a stable feed for deep reactions; secondly, the NP co-doped ordered mesoporous carbon support in the second hydrogenation stage provides a high specific surface area and ordered channels, enhancing the dispersion and mass transfer efficiency of active components, and Zr... 3+ Doping significantly modulates the electronic structure of the Ni2P active center, enhancing its intrinsic activity in hydrodenitrification. Stepwise impregnation with boron and silicon sources further optimizes the catalyst's acidity, activity, and resistance to carbon deposition. Combined with in-situ oxygen regeneration, this continuously removes surface carbon, ensuring long-term high efficiency and stability of the catalyst. Finally, the nitric acid-modified ZSM-5 and alumina composite adsorbent, through acid site regulation and pore structure optimization, achieves deep targeted adsorption of residual trace nitrogen compounds, further reducing the nitrogen content of the product. The sequential coupling and synergistic effect of each step ultimately achieves efficient and deep denitrification of coal tar and high-quality preparation of light fuel oil.

[0037] Compared to Example 3, Comparative Example 1 used a conventional catalyst in S2. The catalyst lacked NP co-doped ordered mesoporous carbon support and Zr. 3+ The synergistic effect of Ni2P doping and B-Si dual promoters significantly reduces the number, dispersion, and intrinsic activity of catalyst active sites, resulting in a marked weakening of hydrocracking and deep denitrification capabilities. Furthermore, conventional catalysts lack a suitable in-situ regeneration mechanism, leading to rapid carbon deposition and deactivation. Consequently, the product exhibits a total nitrogen content as high as 125.0 ppmw, a catalyst activity retention rate of only 62.5% after 100 hours, high heavy oil tail fraction, poor light oil conversion effect, and overall performance significantly inferior to the example.

[0038] Compared to Example 3, Comparative Example 2 did not use an NP-co-doped ordered mesoporous carbon support in S2. The lack of an ordered mesoporous structure and the synergistic regulation of N and P heteroatoms resulted in a low specific surface area, irregular pores, and easy aggregation and uneven loading of active components. This weakened the interaction between the active components and the support, leading to a decrease in hydrodenitrogenation activity and stability. The final product showed a total nitrogen content of 45.6 ppmw, a catalyst activity retention rate of only 78.3%, an increase in heavy oil tail fraction, and a significant reduction in deep denitrification effect.

[0039] Compared to Example 3, Comparative Example 3 lacked B-Si stepwise impregnation modification in S2. The absence of the electronic regulation, acidity optimization, and structural strengthening effects of the boron-silicon dual promoters resulted in insufficient catalyst activity, poor anti-coking performance, and structural stability. Under long-term operation, activity decay accelerated, and the denitrification depth was limited. The total nitrogen content of the product increased to 38.2 ppmw, the catalyst activity retention rate decreased to 81.5%, and the light oil yield slightly decreased, fully demonstrating the crucial role of the B-Si dual promoters in improving catalyst performance.

[0040] Compared to Example 3, Comparative Example 4 did not use nitric acid modification for the composite adsorbent in S3. The adsorbent surface lacked sufficient acidic sites, resulting in a significant decrease in selective adsorption capacity for polar nitrogen-containing compounds. This prevented deep removal of residual nitrogen compounds, relying solely on physical adsorption and simple molecular sieving. Consequently, the total nitrogen content of the product increased to 52.5 ppmw, highlighting the necessity and synergistic effect of nitric acid modification for deep nitrogen removal by the composite adsorbent.

[0041] In summary, Examples 1-3, through raw material pretreatment, two-stage stepwise hydrogenation, and NP co-doping of ordered mesoporous carbon loaded with Zr, 3+ The synergistic coupling and optimization of process parameters of multiple links, including Ni2P doped catalyst, stepwise impregnation with B-Si dual additives, in-situ regeneration, and deep adsorption with nitric acid-modified composite adsorbent, have enabled efficient and deep denitrification of coal tar, long-term stable operation of the catalyst, and high-yield preparation of light fuel oil, demonstrating significant overall technical advantages.

[0042] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A deep denitrification method for preparing light fuel oil by hydrogenation of coal tar, characterized in that, Including the following: S1. After pretreatment, the coal tar raw material is fed into the first hydrogenation reactor and hydrogenation reaction is carried out under the first reaction conditions. After the reaction is completed, the first effluent is obtained by gas-liquid separation. S2. The first effluent is subjected to a hydrocracking reaction in a second hydrogenation reactor filled with a catalyst under second reaction conditions to obtain a second effluent, wherein, during the hydrocracking reaction, an oxygen-containing stream is introduced into the reactor to regenerate the catalyst in situ; S3. The second effluent is fed into an adsorption reactor, which is filled with a composite adsorbent. The second effluent is then brought into contact with the composite adsorbent under a third operating condition to obtain light fuel oil after deep denitrification.

2. The deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 1, characterized in that, In S1, the pretreatment includes at least one of filtration, dehydration, demetallization, and deasphalting.

3. The deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 1, characterized in that, In S1, the first reaction conditions include: a reaction temperature of 260-350℃, a reaction pressure of 6-12 MPa, and a volume hourly space velocity of 0.8-1.5 h⁻¹. -1 The hydrogen-to-oil volume ratio is (800-2000):

1.

4. The deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 1, characterized in that, In S1, the reaction ends when the total nitrogen content of the first effluent drops to 2000-5000 ppmw.

5. The deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 1, characterized in that, In S2, the catalyst comprises a support, an active component, and two promoters; the support and the active component are Zr. 3+ The doped Ni2P catalyst is composed of two components: a boron source and a silicon source. The catalyst is prepared as follows: organic sugar is used as the carbon source, mesoporous silicon as the template agent, and nitrogen and phosphorus sources are dissolved in deionized water to obtain a mixed solution A. This solution is then evaporated in a water bath, calcined at high temperature, and the template agent is removed to obtain an NP-co-doped ordered mesoporous carbon support. Zirconium and nickel salts are dissolved in deionized water to prepare a mixed solution B. The NP-co-doped ordered mesoporous carbon support is added, and a hydrothermal reaction is carried out. After the reaction is complete, a phosphorus source is added, and the temperature is raised for further reaction. After separation and drying, a mixture C is obtained. The mixture C is then impregnated stepwise through a boron source solution and a silicon source solution, and finally dried and calcined to obtain the catalyst.

6. The deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 5, characterized in that, In S2, the organic sugar includes any one of glucose, fructose, and sucrose; the mesoporous silica includes any one of MCM-41 mesoporous silica, SBA-15 mesoporous silica, and MCM-48 mesoporous silica; the nitrogen source includes any one of urea, melamine, and ammonium chloride; the phosphorus source includes any one of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate; the zirconium salt includes any one of zirconium chloride, zirconium nitrate, and zirconium sulfate; the nickel salt includes any one of nickel nitrate, nickel chloride, and nickel acetate; the boron source solution includes any one of boric acid solution, sodium borate solution, and potassium borate solution; and the silicon source solution includes any one of tetraethyl orthosilicate solution, sodium silicate solution, and sodium methylsilicate solution.

7. The deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 5, characterized in that, In S2, the water bath evaporation temperature is 60-90℃ and the time is 2-6h; the high-temperature calcination temperature is 500-800℃ and the time is 3-8h; the hydrothermal reaction temperature is 120-180℃ and the time is 4-12h; the heating reaction temperature is 200-300℃ and the reaction time is 2-5h; the drying temperature of the drying and calcination is 80-120℃ and the drying time is 2-4h; the impregnation temperature of the stepwise impregnation is 25-60℃ and the impregnation time is 2-6h, and the impregnation solid-liquid mass ratio is 1:(3-8); the calcination temperature of the drying and calcination is 300-500℃ and the calcination time is 2-5h.

8. The deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 5, characterized in that, In S2, the second reaction conditions include: a reaction temperature of 360-420℃, a reaction pressure of 8-15MPa, and a liquid hourly space velocity of 0.3-1.5h. -1 The hydrogen-to-oil volume ratio is (600-1200):

1.

9. The deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 1, characterized in that, In S3, the composite adsorbent is obtained by calcining ZSM-5 molecular sieve impregnated with nitric acid and alumina precursor; the mass concentration of nitric acid is 10wt%-20wt%; the mass ratio of ZSM-5 molecular sieve impregnated with nitric acid to alumina precursor is (3-4):1; the calcination temperature is 500-650℃ and the time is 2-8h.

10. A deep denitrification method for preparing light fuel oil by hydrogenation of coal tar according to claim 1, characterized in that, In S3, the third operating conditions include: operating temperature 80-120℃, operating pressure 0.8-1.5MPa, and volumetric hourly space velocity 1.0-2.0h. -1 .

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