A catalyst for lightening heavy aromatics of coal liquefaction residue and a preparation method thereof

Abstract

The application discloses a catalyst for lightening heavy aromatic hydrocarbons of coal liquefaction residues and a preparation method, and relates to the technical field of coal chemical catalysts. The method comprises the following steps: preparing a composite carrier by mixing carboxylated nanometer carbon fibers and SBA-15 molecular sieves treated by hole expansion according to a certain mass ratio; then, the composite carrier is placed in an iron salt solution for microwave impregnation; then, a precursor I obtained is placed in a complexing system for impregnation, Co 2+ Gradient distribution in the pore channel of the composite carrier is realized, and a precursor II is obtained after the impregnation is completed; Fe 3+ is in-situ reduced to Fe 0 by irradiating the precursor II with ultraviolet light, so that a precursor III is obtained; the precursor III is placed in a tube furnace for calcination, and a catalyst is generated by in-situ sulfuration. The catalyst prepared by the method has the advantages of high activity, high stability, and the advantages of reducing hydrogen consumption and coking risk.

Description

Technical Field

[0001] This invention relates to the field of coal chemical catalyst technology, specifically to a catalyst and its preparation method for the lightening of heavy aromatic hydrocarbons in coal liquefaction residue. Background Technology

[0002] Coal liquefaction technology is an important way to convert coal into liquid fuels and chemical feedstocks, and it is of great significance for alleviating the shortage of petroleum resources and ensuring energy security. Coal liquefaction technology is mainly divided into two process routes: direct liquefaction and indirect liquefaction. Direct liquefaction directly converts coal into liquid fuel through a hydrogenation reaction under high temperature and high pressure conditions; indirect liquefaction first gasifies coal to generate syngas, and then converts the syngas into liquid fuel through processes such as Fischer-Tropsch synthesis. However, both direct and indirect liquefaction processes generate a large amount of residue, which accounts for about 20% to 30% of the raw coal output. Coal liquefaction residue mainly consists of heavy aromatics, asphaltenes, and ash, with heavy aromatics accounting for over 50%. Heavy aromatics have large molecular weights and complex structures, typically containing polycyclic aromatic hydrocarbons (such as naphthalene, phenanthrene, and pyrene) and heteroatom compounds (such as sulfur-, nitrogen-, and oxygen-containing compounds), and are characterized by high viscosity, high freezing point, and high carbon-to-hydrogen ratio. These characteristics make coal liquefaction residue difficult to utilize directly, and it is currently mainly disposed of through incineration or landfill, which not only wastes resources but also causes serious environmental pollution problems. With increasingly stringent environmental protection requirements and a growing awareness of comprehensive resource utilization, the development of efficient and environmentally friendly coal liquefaction residue treatment technologies has become a research hotspot in the field of coal chemical industry.

[0003] Existing technologies for treating coal liquefaction residue mainly include: direct combustion, gasification, hydrotreating, and solvent extraction. Direct combustion uses the residue as fuel, but it has a low calorific value (typically below 20 MJ / kg), poor combustion efficiency, and produces large amounts of pollutants such as sulfur dioxide, nitrogen oxides, and particulate matter, failing to meet environmental protection requirements. Furthermore, the high ash content of the residue results in a large amount of ash residue after combustion, increasing the difficulty of subsequent treatment. Gasification reacts the residue with a gasifying agent (such as oxygen or steam) at high temperatures to generate syngas (mainly composed of CO and H2). This method is complex, requires large equipment investment, has high operating costs, and the syngas contains high levels of impurities (such as H2S and NH3), making subsequent utilization difficult. Additionally, the gasification process generates large amounts of tar and ash residue, increasing the risk of equipment blockage and environmental pollution. Solvent extraction uses organic solvents (such as toluene or tetrahydrofuran) to extract the residue, separating heavy aromatics and asphaltenes. This method consumes a large amount of solvent, and the residue after extraction still requires further treatment, making it economically unsound. Furthermore, solvent recovery is energy-intensive and poses risks of solvent volatilization and environmental pollution. Hydrotreating involves hydrogenating and cracking heavy aromatics in coal liquefaction residue into light oil products under high temperature and pressure (typically 400-450℃, 10-20MPa) and the action of a catalyst. This method places high demands on catalyst performance. As a core raw material in the coal liquefaction process, the catalyst plays a crucial role. However, existing catalysts suffer from low activity, poor stability, and low recyclability. An ideal catalyst needs to balance high activity, high stability, and recyclability. Therefore, it is necessary to explore a method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue. Summary of the Invention

[0004] One of the objectives of this invention is to provide a method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue. The catalyst prepared by this method has the advantages of high activity, high stability, and reduced hydrogen consumption and coking risk. By converting heavy aromatics into light aromatics and olefins, high-value-added products, it not only solves the problem of coal liquefaction residue treatment, but also realizes the efficient utilization of resources.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue includes the following steps: a. Preparation of composite carrier, wherein the composite carrier is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves after pore expansion treatment in a certain mass ratio; b. The composite carrier is immersed in an iron salt solution for microwave immersion, wherein microwave immersion promotes the precipitation of Fe in the iron salt solution. 3+ The Fe is uniformly loaded into the pores of the composite carrier; the microwave impregnation frequency is 40-60 kHz, and the microwave impregnation time is 10-20 minutes; the resulting Fe-loaded composite carrier is then subjected to microwave impregnation. 3+ After vacuum drying, the composite carrier yields precursor one; c. Prepare a complexation system, wherein the complexation system is prepared by mixing ethylenediamine and cobalt chloride in a molar ratio of 2:1 to 4:1 and adjusting the pH with ammonia. The precursor was impregnated in the complexation system, and Co was complexed with ethylenediamine. 2+ A gradient distribution is achieved within the pores of the composite carrier to avoid the shielding of active sites caused by direct Fe-Co alloying; precursor II is obtained after impregnation. d. By irradiating the precursor II with ultraviolet light, Fe³⁺ is reduced in situ to Fe. 0 Thus, precursor three were obtained; e. Place the precursor three in a tube furnace and heat it to 250°C for 1-3 hours in a nitrogen-water vapor mixed atmosphere; then heat it to 500°C and calcine it in air for 4-5 hours. After calcination, FeS active phase is generated by in-situ sulfidation and then naturally cooled to obtain the product.

[0006] The preparation method of the catalyst for the lightening of heavy aromatic hydrocarbons in coal liquefaction residue, as described above, includes the following steps in step a: the preparation of the pore-expanded SBA-15 molecular sieve is as follows: the SBA-15 molecular sieve is placed in an ammonium sulfate solution and stirred at a constant temperature, then washed with deionized water until neutral and dried to obtain the pore-expanded SBA-15 molecular sieve; the mass ratio of carboxylated carbon nanofibers to the pore-expanded SBA-15 molecular sieve is 3:5, and the two are mixed and then ball-milled to obtain the composite support.

[0007] In the preparation method of the catalyst for the lightening of heavy aromatic hydrocarbons in coal liquefaction residue, step b, the iron salt solution is an iron nitrate ethanol solution prepared by adding iron nitrate to ethanol; the volume of the iron salt solution is 50% of the total pore volume of the composite support; the iron salt solution is uniformly dripped onto the surface of the composite support and completely wetted.

[0008] In the above-mentioned method for preparing a catalyst for the lightening of heavy aromatic hydrocarbons in coal liquefaction residue, in step d, the ultraviolet light irradiation wavelength is 254 nm and the irradiation time is 20~40 min.

[0009] In the preparation method of the catalyst for the lightening of heavy aromatics in coal liquefaction residue, in step c, the pH of the complexing system is 8.5 to 9.5; the volume of the complexing system is 50% of the total pore volume of the composite support.

[0010] In the above-mentioned method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue, in step e, when the temperature is raised to 500℃, a gradient oxygen concentration is used, with an initial oxygen content of 5-10% and gradually increasing to 21%.

[0011] The above-mentioned method for preparing a catalyst for the lightening of heavy aromatic hydrocarbons in coal liquefaction residue involves in-situ sulfidation using CS2 or H2S solution spray at a temperature of 350–400°C under an H2 atmosphere.

[0012] The above-mentioned method for preparing a catalyst for the lightening of heavy aromatic hydrocarbons in coal liquefaction residues, wherein the carboxylated carbon nanofibers have a diameter of 20-50 nm and a length of 1-5 μm, and form a three-dimensional conductive network structure in a composite support.

[0013] Another objective of this invention is to provide a catalyst for the lightening of heavy aromatic hydrocarbons in coal liquefaction residue, which is prepared by the above-described preparation method. The catalyst has a specific surface area of ​​550–650 m² / g and a metal dispersion of ≥80%.

[0014] Another object of the present invention is to provide the application of the above-mentioned catalyst for the lightening of heavy aromatics in coal liquefaction residue in hydrocracking. The application involves mixing the catalyst with coal liquefaction residue at a mass ratio of 3 to 8:100 and carrying out a hydrocracking reaction in a hydrogen atmosphere. The reaction conditions are: temperature 380 to 420°C, pressure 8 to 12 MPa, hydrogen-to-oil volume ratio 800:1 to 1200:1, and weight hourly space velocity 0.8 to 1.2 h⁻¹.

[0015] Compared with the prior art, the present invention brings the following beneficial technical effects: (1) This invention proposes a method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue. The composite support used is prepared by mixing carboxylated carbon nanofibers (CNF) and pore-expanded SBA-15 molecular sieves in a certain mass ratio. Compared with a single support, the advantages of the composite support of this invention are as follows: This invention innovatively uses a support system composed of carboxylated carbon nanofibers (CNF) and pore-expanded SBA-15 molecular sieves. Compared with traditional single supports (such as SBA-15 or CNF used alone), it shows significant advantages in three dimensions: structure, function, and performance. This invention uses a design of complementary structure and synergistic enhancement of mass transfer and stability. It utilizes pore-expanded SBA-15 molecular sieves to improve molecular diffusion efficiency and overcome the limitations of traditional molecular sieves. At the same time, it uses carboxylated carbon nanofibers to construct a three-dimensional conductive network structure to enhance the overall performance of the support. The two are combined to form an ordered mesoporous + conductive framework system, providing an ideal platform for metal active components. Building upon this foundation, the coordination effect of CNF carboxyl groups and the mesoporous confinement effect of SBA-15, combined with microwave-assisted impregnation and UV reduction techniques, precisely control the metal particle size, significantly improve metal dispersion and active site exposure, and thus construct a bimetallic Fe-Co gradient impregnation structure. This avoids active site shielding caused by alloying and enhances synergistic hydrogenation cracking capabilities. Furthermore, CNF enhances the thermal shock resistance and mechanical strength of the support, and the composite support provides confined-domain protection for the metal particles. The active phase formed after in-situ sulfidation treatment exhibits excellent performance, comprehensively strengthening the catalyst's thermal stability and resistance to deactivation, ultimately achieving highly efficient catalytic conversion.

[0016] (2) In terms of preparation method, the present invention first places the composite support in an iron salt solution for microwave impregnation. During the microwave impregnation process, the metal in the iron salt solution can quickly penetrate into the pores of the support, reduce agglomeration, improve the uniformity of metal doping, optimize the distribution of adsorption sites, and lay the groundwork for the formation of Fe-Co gradient distribution in the later stage, thereby enhancing the hydrogenation cracking activity. After microwave impregnation and drying, a second impregnation is performed, that is, the complex system is used as the impregnation liquid to realize the Fe-Co bimetallic gradient distribution. Then, ultraviolet light irradiation can enhance the specific surface area of ​​the carbon material of the composite support, optimize the pore size distribution, and precisely control the metal nanoparticles (3-5 nm), thereby improving the exposure rate of active sites. The present invention can construct a highly active catalyst by combining "microwave impregnation and ultraviolet light irradiation", improve the catalytic reaction efficiency, and improve the stability of the catalyst. Finally, a step-by-step heat treatment is performed under nitrogen protection. First, low-temperature pretreatment is used to remove organic matter, and then high-temperature calcination is used to form the Fe-Co synergistic active phase, ultimately obtaining a highly dispersed and highly stable catalyst. The entire process utilizes key technologies such as microwave-enhanced dispersion, complexation-induced agglomeration inhibition, and gradient temperature-controlled activation to ensure catalyst structural stability and efficient exposure of active sites.

[0017] (3) The combination of microwave impregnation and ultraviolet irradiation can improve the metal dispersion to ≥90%, shorten the impregnation time by 50%, and increase the conversion rate of light aromatics to 91%. In-situ crystallization and gradient oxygen concentration calcination can make the catalyst specific surface area reach 700 m² / g and the metal dispersion ≥90%. In-situ sulfidation technology can improve the initial activity of the catalyst by 20% and reduce the amount of sulfiding agent by 40%.

[0018] (4) Verification by examples shows that the catalyst prepared by the method of the present invention achieves a heavy aromatics conversion rate of 89% (industry average ≤58%), a light oil yield exceeding 74%, and a coking amount reduced to ≤1.8% (traditional process 8.5%~15%). The catalyst has a single-cycle life of 500 hours (traditional ≤200 hours), an activity retention rate of >85% after regeneration, and a comprehensive cost reduction of 62.5%.

[0019] In summary, this invention significantly improves the conversion efficiency of heavy aromatics and the selectivity of light oils by combining an Fe-Co bimetallic active system with a composite support, while simultaneously inhibiting coking formation, overcoming the bottleneck of traditional catalysts that struggle to balance activity and stability. By combining microwave-assisted impregnation and photoreduction technologies with complexation dispersion techniques to optimize metal loading uniformity, both hydrogen and energy consumption are reduced, and solid waste emissions are significantly reduced through regeneration processes. Its unique support structure can tolerate high-sulfur and high-metal-impurity feedstocks, directly processing complex oils and eliminating pretreatment costs. The addition of acidic additives allows for flexible control of product distribution. With its core advantages of high-efficiency conversion, low-carbon energy saving, and universal feedstock compatibility, this invention provides a systematic solution for the clean and efficient conversion of heavy oils, driving the refining industry towards a green and sustainable future. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings: Figure 1 The images show SEM (ab) and TEM (cd) images of the catalyst prepared in this invention, illustrating the microstructure of the composite support and the distribution of metal particles.

[0021] Figure 2 The locations of Fe and Co on the catalyst surface and the electron density distribution diagram.

[0022] Figure 3 Comparison of the overall performance of different catalysts in the conversion of heavy waste hydrocarbons. Detailed Implementation

[0023] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings.

[0024] All the raw materials mentioned in this invention can be purchased through commercial channels.

[0025] The main technical concept of this invention lies in the following: This invention uses carboxylated carbon nanofibers and SBA-15 molecular sieves that have undergone pore-expanding treatment as a composite carrier. Employing ammonium sulfate dynamic pore-expanding technology, the pore size of SBA-15 is expanded from 6 nm to the 12 nm level, breaking through the mass transfer bottleneck of traditional mesoporous molecular sieves while retaining its high specific surface area characteristics, providing an ordered dispersion space for metal active sites. Three-dimensional conductive network: A three-dimensional conductive network is constructed by introducing carboxylated carbon nanofibers. Their 30-50 nm diameter forms a topological match with the SBA-15 mesopores, solving the problems of poor conductivity and low mechanical strength of pure molecular sieves, thus increasing the conductivity of the composite carrier to 10. -1 The order of magnitude is in the S / cm range.

[0026] The active component loading employs a bimetallic gradient distribution: Fe is first loaded using a stepwise impregnation method. 3+ It occupies the anchoring point on the inner surface of the mesopore, and then complexes Co with ethylenediamine. 2+ A gradient distribution within the pores is achieved, avoiding the shielding of active sites caused by direct Fe-Co alloying. Microwave-assisted impregnation: Utilizing the uniform heating characteristics of microwaves, rapid penetration and uniform dispersion of the metal precursor within the composite carrier pores are promoted, reducing metal agglomeration and shortening the impregnation time to 10-20 minutes. Ultraviolet reduction: After impregnation, ultraviolet light irradiation is used to in-situ reduce the metal precursor into nano-sized metal particles, precisely controlling the metal particle size and improving the exposure rate of active sites. Further optimization of the heat treatment process involves in-situ crystallization using a small amount of water vapor added during the nitrogen pretreatment stage. The interaction between water vapor and the metal precursor promotes the crystallization of metal oxides, forming a more uniform active phase. Atmosphere control: A gradient oxygen concentration is used during the air calcination stage to avoid the collapse of the carrier pores under direct high-temperature, high-oxygen conditions, while also reducing the oxidation and sintering of metal particles. The catalyst activity is enhanced by in-situ sulfidation technology: In the final stage of catalyst preparation, in-situ sulfidation technology is introduced to directly generate highly active sulfide phases (such as FeS) on the catalyst surface, avoiding the waste of sulfiding agents and side reactions in the traditional sulfidation process, and improving the initial activity of the catalyst by 15%-20%.

[0027] The specific application methods of the catalyst prepared by this invention are as follows: The catalyst and coal liquefaction residue were subjected to hydrocracking reaction in a hydrogen atmosphere. The reaction conditions were: temperature 380-420℃, pressure 8-12MPa, hydrogen-to-oil volume ratio 800:1-1200:1, weight hourly space velocity 0.8-1.2 h⁻¹, and hydrocracking reaction was carried out in a hydrogen atmosphere.

[0028] Catalyst activity determination: The catalyst was loaded into a fixed-bed reactor, and coal liquefaction residue and hydrogen were introduced for hydrocracking. The product composition was analyzed using gas chromatography (GC) and mass spectrometry (MS), and the conversion rates of heavy aromatics (such as polycyclic aromatic hydrocarbons like naphthalene and phenanthrene) and light oil yields (such as the proportions of monocyclic aromatic hydrocarbons and olefins) were calculated. Thermogravimetric analysis (TGA) was used to determine the amount of coke (the percentage by mass of residual coke on the catalyst surface).

[0029] Catalyst stability testing: The catalyst was continuously run for 500 hours under standard reaction conditions, and samples were taken at regular intervals to analyze the product composition and monitor the trend of activity decline. The catalyst's single-cycle lifetime was defined as the activity decreasing to 80% of its initial value (in the examples, the single-cycle lifetime reached 500 hours).

[0030] Catalyst recycling performance testing: After use, the catalyst is calcined at high temperature (e.g., 500℃ in air atmosphere) to remove carbon deposits, and then in-situ sulfidation is performed to restore the active phase. The regenerated catalyst is then subjected to hydrocracking reaction again, and the activity retention rate is calculated (e.g., conversion rate ≥85% after regeneration).

[0031] The present invention will be further described below with reference to specific embodiments.

[0032] Example 1: A method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue includes the following steps: The first step is to prepare a composite carrier, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves that have undergone pore-expanding treatment in a certain mass ratio. The specific steps are as follows: Weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m² / g, initial pore size 6 nm) and place it in a 0.5 M ammonium sulfate solution, and stir at 80 °C for 4 h. After washing with deionized water until neutral, dry at 120 °C for 12 h to obtain expanded pore SBA-15 (pore size determined by BJH method: 12.3 ± 0.5 nm). Pore-expanded SBA-15 and 3.00g of carboxylated carbon nanofibers (diameter 30-50nm, aspect ratio >100, purity >95%) were added to a planetary ball mill at a mass ratio of 5:3 and ball milled at 300rpm for 2h (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite carrier. Step 2: Prepare a 0.5 mol / L ferric nitrate ethanol solution (Fe 3+ (Accurate concentration calibration) The composite carrier is immersed in ferric nitrate ethanol solution, and the volume of the ferric salt solution is 50% of the total pore volume of the composite carrier; the ferric salt solution is evenly added to the surface of the composite carrier and made to completely wet it.

[0033] Microwave impregnation promotes the Fe content in iron salt solutions3+ The Fe is uniformly loaded into the pores of the composite carrier; the microwave impregnation frequency is 50 kHz, and the microwave impregnation time is 15 minutes; the resulting Fe-loaded composite carrier is then subjected to microwave impregnation. 3+ The composite carrier was allowed to stand for aging for 6 hours, and then vacuum dried at 60℃ (vacuum degree 0.09MPa) to obtain precursor one; The third step involves preparing the complexation system. The complexation system consists of ethylenediamine and cobalt chloride in a molar ratio of 3:1, with the pH adjusted to 9.0 ± 0.2 using ammonia. Precursor I is then placed in the complexation system for equal-volume impregnation. The Co chloride is then complexed using ethylenediamine. 2+ A gradient distribution is achieved within the pores of the composite carrier to avoid the shielding of active sites caused by direct Fe-Co alloying; precursor II is obtained after impregnation. Step 4: The precursor 1 is irradiated with ultraviolet light to reduce Fe³⁺ to Fe in situ. 0 Simultaneously, ethylenediamine is used as an electron donor to stabilize Co. 3+ Thus, precursor three were obtained; Step 5: Place the precursor three in a tube furnace and heat it to 250℃ at a nitrogen atmosphere at a rate of 5℃ / min, holding for 2 hours. Then, add 5%-10% (v / v) water vapor to promote the crystallization of the metal oxide. Next, heat the precursor to 500℃ at a rate of 3℃ / min and calcine it in air for 4-5 hours, starting with an initial oxygen content of 5% and gradually increasing it to 21%, calcining for another 4 hours in air. After calcination, introduce 10-20% (v / v) hydrogen gas at 350-400℃ and spray a sulfiding agent (such as CS2 or H2S aqueous solution) to generate a highly active sulfide phase (such as FeS). Program the temperature to 500℃ (heating rate 3℃ / min) and calcine in air for 4 hours (oxygen content 21%) to generate the FeS active phase through in-situ sulfidation. After natural cooling, the product is obtained.

[0034] The catalyst prepared in this embodiment was applied to the hydrocracking reaction of heavy aromatics in coal liquefaction residue. The results were as follows: reaction temperature 400℃, pressure 10 MPa, hydrogen-to-oil volume ratio 1000:1, and weight hourly space velocity 1.0 h⁻¹. -1 Under these conditions, after 500 hours of continuous operation, the conversion rate of heavy aromatics reached 89.3%, and the conversion rate of light oil (C5–C60) was [missing information]. 20 The yield reached 74.1%, and the catalyst coking amount was as low as 1.6%, demonstrating excellent catalytic activity and anti-coking ability.

[0035] After three cycles of catalyst regeneration, the activity retention rate remained as high as 86.5%, and the specific surface area retention rate reached 82%, indicating that it has good thermal stability and regenerability. Compared with comparative catalysts (such as the single SBA-15 support system), which suffer from rapid activity decay and severe coking, the catalyst of this invention can stably process coal liquefaction residue feedstock with high aromatic content and complex impurities, significantly reducing hydrogen consumption and solid waste generation during the hydrogenation reaction.

[0036] In addition, the catalyst has strong tolerance to sulfur- and nitrogen-containing compounds and can achieve efficient conversion of heavy components in residues without pretreatment. It has broad application prospects in industrial scenarios such as deep utilization of heavy oil, upgrading of refinery residue hydrogenation units, and preparation of coal-based clean fuels.

[0037] Example 2: The difference from Example 1 is that: In the second step, the microwave immersion power is 40 kHz and the microwave immersion time is 10 minutes.

[0038] The application of the catalyst prepared in this embodiment is described in Example 1.

[0039] Example 3: The difference from Example 1 is that: In the second step, the microwave immersion power is 60 kHz and the microwave immersion time is 20 minutes.

[0040] The application of the catalyst prepared in this embodiment is described in Example 1.

[0041] Example 4: The difference from Example 1 is that: In the third step, the complexation system consists of ethylenediamine and cobalt chloride in a molar ratio of 2:1.

[0042] The application of the catalyst prepared in this embodiment is described in Example 1.

[0043] Example 5: The difference from Example 1 is that: In the third step, the complexation system consists of ethylenediamine and cobalt chloride in a molar ratio of 4:1.

[0044] The application of the catalyst prepared in this embodiment is described in Example 1.

[0045] Comparative Example 1: The difference from Example 1 is that: The composite carrier was prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves in a certain mass ratio.

[0046] The first step is to prepare a composite carrier, which is prepared by mixing SBA-15 molecular sieve (unexpanded) and carboxylated carbon nanofibers at a mass ratio of 7:3.

[0047] The specific steps are as follows: 7.00g of raw SBA-15 molecular sieve (specific surface area 680 m² / g, initial pore size 6nm, without ammonium sulfate pore-expansion treatment) was directly weighed. The raw SBA-15 and 3.00g of carboxylated carbon nanofibers (diameter 30-50nm, aspect ratio >100, purity >95%) were added to a planetary ball mill at a mass ratio of 7:3. The mixture was ball-milled at 300 rpm for 2 hours (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite carrier.

[0048] Steps two through five are the same as in Example 1.

[0049] Comparative Example 2: The difference from Example 1 is that: Only SBA-15 molecular sieves with expanded pores are used as the carrier, without adding carboxylated carbon nanofibers.

[0050] The first step is to prepare a support, which is an SBA-15 molecular sieve that has undergone pore-expanding treatment.

[0051] The specific steps are as follows: Weigh 5.00g of SBA-15 molecular sieve (specific surface area 680 m² / g, initial pore size 6nm) and place it in a 0.5M ammonium sulfate solution, and stir at 80℃ for 4h. After washing with deionized water until neutral, dry at 120℃ for 12h to obtain expanded pore SBA-15 (pore size determined by BJH method: 12.3±0.5nm).

[0052] Steps two through five are the same as in Example 1.

[0053] Comparative Example 3: The difference from Example 1 is that the complexation system and the secondary impregnation step are not included.

[0054] A method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue includes the following steps: The first step is to prepare a composite carrier, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves that have undergone pore-expanding treatment in a certain mass ratio. The specific steps are as follows: Weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m² / g, initial pore size 6 nm) and place it in a 0.5 M ammonium sulfate solution, and stir at 80 °C for 4 h. After washing with deionized water until neutral, dry at 120 °C for 12 h to obtain expanded pore SBA-15 (pore size determined by BJH method: 12.3 ± 0.5 nm). Pore-expanded SBA-15 and 3.00g of carboxylated carbon nanofibers (diameter 30-50nm, aspect ratio >100, purity >95%) were added to a planetary ball mill at a mass ratio of 5:3 and ball milled at 300rpm for 2h (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite carrier. Step 2: Prepare a 0.5 mol / L ferric nitrate ethanol solution (Fe 3+ (Accurate concentration calibration) The composite carrier is immersed in ferric nitrate ethanol solution, and the volume of the ferric salt solution is 50% of the total pore volume of the composite carrier; the ferric salt solution is evenly added to the surface of the composite carrier and made to completely wet it.

[0055] Microwave impregnation promotes the Fe content in iron salt solutions 3+ The Fe is uniformly loaded into the pores of the composite carrier; the microwave impregnation frequency is 50 kHz, and the microwave impregnation time is 15 minutes; the resulting Fe-loaded composite carrier is then subjected to microwave impregnation. 3+ The composite carrier was allowed to stand for aging for 6 hours, and then vacuum dried at 60℃ (vacuum degree 0.09MPa) to obtain precursor one; The third step involves irradiating the precursor with ultraviolet light to reduce Fe³⁺ to Fe in situ. 0 Thus, precursor three were obtained; Step 4: Place the precursor III in a tube furnace and heat it to 250℃ at a nitrogen atmosphere at a rate of 5℃ / min, holding for 2 hours. Then, add 5%-10% (v / v) water vapor to promote the crystallization of the metal oxide. Next, heat the precursor to 500℃ at a rate of 3℃ / min and calcine it in air for 4-5 hours, starting with an initial oxygen content of 5% and gradually increasing it to 21%, calcining for another 4 hours in air. After calcination, introduce 10-20% (v / v) hydrogen gas at 350-400℃ and spray a sulfiding agent (such as CS2 or H2S aqueous solution) to generate a highly active sulfide phase (such as FeS). Program the temperature to 500℃ (heating rate 3℃ / min) and calcine in air for 4 hours (oxygen content 21%) to generate the active phase through in-situ sulfidation. After natural cooling, the desired product is obtained.

[0056] Comparative Example 4: The difference from Example 1 is that there is no ultraviolet light irradiation step.

[0057] A method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue includes the following steps: The first step is to prepare a composite carrier, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves that have undergone pore-expanding treatment in a certain mass ratio. The specific steps are as follows: Weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m² / g, initial pore size 6 nm) and place it in a 0.5 M ammonium sulfate solution, and stir at 80 °C for 4 h. After washing with deionized water until neutral, dry at 120 °C for 12 h to obtain expanded pore SBA-15 (pore size determined by BJH method: 12.3 ± 0.5 nm). Pore-expanded SBA-15 and 3.00g of carboxylated carbon nanofibers (diameter 30-50nm, aspect ratio >100, purity >95%) were added to a planetary ball mill at a mass ratio of 5:3 and ball milled at 300rpm for 2h (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite carrier. Step 2: Prepare a 0.5 mol / L ferric nitrate ethanol solution (Fe 3+ (Accurate concentration calibration) The composite carrier is immersed in ferric nitrate ethanol solution, and the volume of the ferric salt solution is 50% of the total pore volume of the composite carrier; the ferric salt solution is evenly added to the surface of the composite carrier and made to completely wet it.

[0058] Microwave impregnation promotes the Fe content in iron salt solutions 3+ The Fe is uniformly loaded into the pores of the composite carrier; the microwave impregnation frequency is 50 kHz, and the microwave impregnation time is 15 minutes; the resulting Fe-loaded composite carrier is then subjected to microwave impregnation. 3+ The composite carrier was allowed to stand for aging for 6 hours, and then vacuum dried at 60℃ (vacuum degree 0.09MPa) to obtain precursor one; The third step involves preparing the complexation system. The complexation system consists of ethylenediamine and cobalt chloride in a molar ratio of 3:1, with the pH adjusted to 9.0 ± 0.2 using ammonia. Precursor I is then placed in the complexation system for equal-volume impregnation. The Co chloride is then complexed using ethylenediamine. 2+ A gradient distribution is achieved within the pores of the composite carrier to avoid the shielding of active sites caused by direct Fe-Co alloying; precursor II is obtained after impregnation. Step 4: Place precursor 2 in a tube furnace and heat to 250℃ at 5℃ / min under a nitrogen atmosphere, holding for 2 hours. Then add 5%-10% (v / v) water vapor to promote the crystallization of the metal oxide. Next, heat to 500℃ at a rate of 3℃ / min and calcine in air for 4-5 hours, with an initial oxygen content of 5%, gradually increasing to 21%, and calcine in air for 4 hours. After calcination, introduce 10-20% (v / v) hydrogen gas at 350-400℃ and spray a sulfiding agent (such as CS2 or H2S aqueous solution) to generate a highly active sulfide phase (such as FeS). Program the temperature to 500℃ (heating rate 3℃ / min) and calcine in air for 4 hours (oxygen content 21%) to generate the FeS active phase through in-situ sulfidation. After natural cooling, the desired product is obtained.

[0059] Comparative Example 5: The difference from Example 1 is that a conventional calcination process is used.

[0060] The first step is to prepare a composite carrier, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves that have undergone pore-expanding treatment in a certain mass ratio. The specific steps are as follows: Weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m² / g, initial pore size 6 nm) and place it in a 0.5 M ammonium sulfate solution, and stir at 80 °C for 4 h. After washing with deionized water until neutral, dry at 120 °C for 12 h to obtain expanded pore SBA-15 (pore size determined by BJH method: 12.3 ± 0.5 nm). Pore-expanded SBA-15 and 3.00g of carboxylated carbon nanofibers (diameter 30-50nm, aspect ratio >100, purity >95%) were added to a planetary ball mill at a mass ratio of 5:3 and ball milled at 300rpm for 2h (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite carrier. Step 2: Prepare a 0.5 mol / L ferric nitrate ethanol solution (Fe 3+ (Accurate concentration calibration) The composite carrier is immersed in ferric nitrate ethanol solution, and the volume of the ferric salt solution is 50% of the total pore volume of the composite carrier; the ferric salt solution is evenly added to the surface of the composite carrier and made to completely wet it.

[0061] Microwave impregnation promotes the Fe content in iron salt solutions 3+ The Fe is uniformly loaded into the pores of the composite carrier; the microwave impregnation frequency is 50 kHz, and the microwave impregnation time is 15 minutes; the resulting Fe-loaded composite carrier is then subjected to microwave impregnation. 3+ The composite carrier was allowed to stand for aging for 6 hours, and then vacuum dried at 60℃ (vacuum degree 0.09MPa) to obtain precursor one; The third step involves preparing the complexation system. The complexation system consists of ethylenediamine and cobalt chloride in a molar ratio of 3:1, with the pH adjusted to 9.0 ± 0.2 using ammonia. Precursor I is then placed in the complexation system for equal-volume impregnation. The Co chloride is then complexed using ethylenediamine. 2+ A gradient distribution is achieved within the pores of the composite carrier to avoid the shielding of active sites caused by direct Fe-Co alloying; precursor II is obtained after impregnation. Step 4: The precursor 1 is irradiated with ultraviolet light to reduce Fe³⁺ to Fe in situ. 0 Simultaneously, ethylenediamine is used as an electron donor to stabilize Co. 3+ Thus, precursor three were obtained; Step 5: Place the precursor three in a tube furnace, calcine and allow it to cool naturally to obtain the final product.

[0062] Comparative Example 6: The difference from Example 1 is that in-situ vulcanization is not used.

[0063] Steps one through four are the same as in Example 1.

[0064] Step 5: Place the precursor three in a tube furnace and heat it to 250°C at a rate of 5°C / min under a nitrogen atmosphere and hold for 2 hours; then heat it to 500°C at a rate of 3°C / min and calcine it in an air atmosphere for 4 hours, and then let it cool naturally to obtain the product.

[0065] Comparative Example 7: The difference from Example 1 is that the first impregnation does not use microwave impregnation, but uses a conventional impregnation method.

[0066] The first step is the same as in Example 1.

[0067] The second step involves preparing a 0.5 mol / L ferric nitrate ethanol solution (with precise Fe³⁺ concentration calibration). The composite support is then immersed in the ferric nitrate ethanol solution using standard procedures, with the volume of the iron salt solution being 50% of the total pore volume of the composite support. The iron salt solution is then uniformly added dropwise to the surface of the composite support, ensuring complete wetting. The resulting Fe³⁺-loaded composite support is allowed to age statically for 6 hours, followed by vacuum drying at 60°C (0.09 MPa) to obtain precursor one.

[0068] Steps three through five are the same as in Example 1.

[0069] The catalytic performance of the catalysts prepared in the above examples and comparative examples was tested, as shown in Table 1.

[0070] Table 1 Any parts not mentioned in this invention can be achieved by referring to existing technologies.

[0071] Those skilled in the art should recognize that the above embodiments are only used to illustrate this application and are not intended to limit this application. Any appropriate changes and variations made to the above embodiments within the essential spirit and scope of this application fall within the scope of protection claimed in this application.

Claims

1. A method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue, characterized in that, Includes the following steps: a. Preparation of composite carrier, wherein the composite carrier is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves after pore expansion treatment in a certain mass ratio; b. The composite carrier is immersed in an iron salt solution for microwave immersion, wherein microwave immersion promotes the precipitation of Fe in the iron salt solution. 3+ The Fe is uniformly loaded into the pores of the composite carrier; the microwave impregnation frequency is 40-60 kHz, and the microwave impregnation time is 10-20 minutes; the resulting Fe-loaded composite carrier is then subjected to microwave impregnation. 3+ After vacuum drying, the composite carrier yields precursor one; c. Prepare a complexation system, wherein the complexation system is prepared by mixing ethylenediamine and cobalt chloride at a molar concentration of 2:1 to 4:1 and adjusting its pH with ammonia water; The precursor was impregnated in the complexation system, and Co was complexed with ethylenediamine. 2+ A gradient distribution is achieved within the pores of the composite carrier to avoid the shielding of active sites caused by direct Fe-Co alloying; precursor II is obtained after impregnation. d. By irradiating the precursor II with ultraviolet light, Fe... 3+ In-situ reduction to Fe 0 Three precursors were obtained; e. Place the precursor three in a tube furnace and heat it to 250°C for 1-3 hours in a mixed atmosphere of nitrogen and water vapor; then heat it to 500°C and calcine it in an air atmosphere for 4-5 hours. After calcination, the active phase is generated by in-situ sulfidation and then naturally cooled to obtain the product. In step a, the preparation steps of the pore-expanding SBA-15 molecular sieve are as follows: the SBA-15 molecular sieve is placed in an ammonium sulfate solution and stirred at a constant temperature. Then it is washed with deionized water until neutral and dried to obtain the pore-expanding SBA-15 molecular sieve; the mass ratio of carboxylated carbon nanofibers to the pore-expanding SBA-15 molecular sieve is 3:

5. The two are mixed and then ball-milled to obtain a composite carrier; the pore size of the pore-expanding SBA-15 molecular sieve is 12 nm. In step e, during in-situ vulcanization, CS2 or H2S solution is sprayed at a temperature of 350–400°C, and in-situ vulcanization is carried out under an H2 atmosphere; when the temperature is raised to 500°C, a gradient oxygen concentration is used, with an initial oxygen content of 5–10%, which is gradually increased to 21%.

2. The method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue according to claim 1, characterized in that: In step b, the iron salt solution is an iron nitrate ethanol solution prepared by adding iron nitrate to ethanol; the volume of the iron salt solution is 50% of the total pore volume of the composite carrier; the iron salt solution is uniformly dripped onto the surface of the composite carrier and completely wetted.

3. The method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue according to claim 1, characterized in that: In step d, the ultraviolet light irradiation wavelength is 254 nm, and the irradiation time is 20~40 min.

4. The method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue according to claim 1, characterized in that: In step c, the pH of the complexing system is 8.5–9.5; the volume of the complexing system is 50% of the total pore volume of the composite carrier.

5. The method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residue according to claim 1, characterized in that: The carboxylated carbon nanofibers have a diameter of 20–50 nm and a length of 1–5 μm, and form a three-dimensional conductive network structure in the composite carrier.

6. A catalyst for the lightening of heavy aromatics in coal liquefaction residue, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 5, and the specific surface area of ​​the catalyst is 550 to 650 m². 2 / g, metal dispersion ≥80%.

7. The application of the catalyst for the lightening of heavy aromatics in coal liquefaction residue according to claim 6 in hydrocracking, characterized in that: The application involves mixing the catalyst with coal liquefaction residue at a mass ratio of 3–8:100, and then carrying out a hydrocracking reaction under a hydrogen atmosphere. The reaction conditions are: temperature 380–420℃, pressure 8–12 MPa, hydrogen-to-oil volume ratio 800:1–1200:1, and weight hourly space velocity 0.8–1.2 h⁻¹. -1 .

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