Catalyst for lightening coal liquefaction residue heavy aromatic hydrocarbon and preparation method thereof

Abstract

The invention discloses a catalyst for lightening coal liquefaction residue heavy aromatic hydrocarbon and a preparation method, and relates to the technical field of coal chemical industry catalysts. The method comprises the following steps: preparing a composite carrier by mixing carboxylated carbon nanofibers and an SBA-15 molecular sieve subjected to pore expanding treatment according to a certain mass ratio; then placing the composite carrier in a ferric salt solution for microwave impregnation; dipping the obtained precursor I in a complexing system, complexing Co < 2 + > through ethylenediamine to realize gradient distribution in a pore channel of the composite carrier, and obtaining a precursor II after dipping is finished; irradiating the precursor II through ultraviolet light, so that Fe < 3 + > is reduced into Fe < 0 > in situ, and a precursor III is obtained; and calcining the precursor III in a tubular furnace, and carrying out in-situ vulcanization to generate the catalyst. The catalyst prepared by the method has the advantages of high activity, high stability and capability of reducing hydrogen consumption and coking risk.

Description

Technical Field

[0001] The present invention relates to the technical field of coal chemical catalysts, and particularly relates to a catalyst for the lightening of heavy aromatics in coal liquefaction residues and a preparation method thereof. Background Art

[0002] Coal liquefaction technology is an important way to convert coal into liquid fuels and chemical raw materials, which is of great significance for alleviating the shortage of petroleum resources in China and ensuring energy security. Coal liquefaction technology is mainly divided into two process routes: direct liquefaction and indirect liquefaction. Direct liquefaction is to directly convert coal into liquid fuels through a hydrogenation reaction under high temperature and high pressure conditions; indirect liquefaction is to first gasify coal to generate syngas, and then convert the syngas into liquid fuels through processes such as Fischer-Tropsch synthesis. However, whether it is direct liquefaction or indirect liquefaction, a large amount of residues will be generated during the production process, and the output accounts for about 20% - 30% of the raw coal. Coal liquefaction residues are mainly composed of heavy aromatics, asphaltenes and ash, among which the content of heavy aromatics is as high as more than 50%. Heavy aromatics have large molecular weights and complex structures, usually containing polycyclic aromatic hydrocarbons (such as naphthalene, phenanthrene, pyrene, etc.) and heteroatom compounds (such as sulfur-containing, nitrogen-containing, oxygen-containing compounds), and have the characteristics of high viscosity, high freezing point and high carbon-hydrogen ratio. These characteristics make it difficult to directly utilize coal liquefaction residues. At present, they are mainly treated by incineration or landfill, which not only causes waste of resources, but also brings serious environmental pollution problems. With the increasingly strict environmental protection requirements and the enhancement of the awareness of comprehensive resource utilization, the development of efficient and environmentally friendly coal liquefaction residue treatment technologies has become a research hotspot in the coal chemical industry.

[0003] In the prior art, the treatment methods for coal liquefaction residues mainly include: direct combustion method, gasification method, hydrotreating method, solvent extraction method, etc. The direct combustion method directly burns the coal liquefaction residues as fuel, but its calorific value is low (usually lower than 20 MJ / kg), the combustion efficiency is poor, and it will produce a large amount of pollutants such as sulfur dioxide, nitrogen oxides and particulate matter, which does not meet the environmental protection requirements. In addition, the ash content in the coal liquefaction residues is high, and a large amount of ash residues will be produced after combustion, increasing the difficulty of subsequent treatment. The gasification method reacts the coal liquefaction residues with a gasifying agent (such as oxygen, steam) at high temperature to generate syngas (mainly composed of CO and H2). This method has complex process, large equipment investment, high operation cost, and high impurity content in the syngas (such as H2S, NH3, etc.), making it difficult to utilize subsequently. In addition, a large amount of tar and ash residues will be produced during the gasification process, increasing the risk of equipment blockage and environmental pollution. The solvent extraction method uses organic solvents (such as toluene, tetrahydrofuran) to extract the coal liquefaction residues and separate heavy aromatics and asphaltenes. This method has a large solvent consumption, and the residues after extraction still need to be further treated, with poor economy. In addition, the energy consumption is high during the solvent recovery process, and there are risks of solvent volatilization and environmental pollution. The hydrotreating method hydrocracks the heavy aromatics in the coal liquefaction residues into light oil products under high temperature and high pressure (usually 400 - 450 °C, 10 - 20 MPa) and the action of a catalyst. This method has high requirements for the performance of the catalyst. The catalyst, as the core raw material in the coal liquefaction process, plays an important role in the coal liquefaction process. However, the catalysts in the prior art have technical problems such as low activity, poor stability, and low recyclability, while an ideal catalyst needs to take into account high activity, high stability and recyclability.

[0004] Therefore, it is necessary to explore a preparation method for a catalyst for the lightening of heavy aromatics in coal liquefaction residues. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a preparation method for a catalyst for the lightening of heavy aromatics in coal liquefaction residues. The catalyst prepared by this method has the advantages of high activity, high stability, and can reduce the hydrogen consumption and coking risk. By converting heavy aromatics into light aromatics and olefin high-value-added products, it not only solves the problem of treating coal liquefaction residues, but also realizes the efficient utilization of resources.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A preparation method for a catalyst for the lightening of heavy aromatics in coal liquefaction residues, comprising the following steps:

[0008] a. Prepare a composite support, and the composite support is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves after pore expansion treatment according to a certain mass ratio;

[0009] b. Immerse the composite support in an iron salt solution, and the immersion is microwave immersion. Microwave immersion promotes the uniform loading of Fe in the iron salt solution into the pores of the composite support; the microwave immersion frequency is 40 - 60 kHz, and the microwave immersion time is 10 - 20 minutes; after vacuum drying the obtained composite support loaded with Fe, a precursor one is obtained. 3+ 3+

[0010] c. Configure a complexing system, where the molar concentration ratio of ethylenediamine to cobalt chloride in the complexing system is 2:1 - 4:1, and it is configured by adjusting its pH with ammonia water;

[0011] Immerse the precursor one in the complexing system, and complex Co through ethylenediamine 2+ to achieve a gradient distribution within the pores of the composite support and avoid the shielding of active sites caused by direct alloying of Fe - Co; after the immersion, a precursor two is obtained.

[0012] d. Irradiate the precursor two with ultraviolet light to in - situ reduce Fe 3+ to Fe 0 and obtain a precursor three;

[0013] e. Place the precursor three in a tubular furnace, under a mixed atmosphere of nitrogen - steam, heat it to 250 °C and hold for 1 - 3 h; then heat it to 500 °C and calcine it in an air atmosphere for 4 - 5 h. After calcination, generate FeS or CoMoS active phases through in - situ sulfidation, and then obtain the product after natural cooling.

[0014] In the above - mentioned preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues, in step a, the preparation steps of the SBA - 15 molecular sieve after pore - expanding treatment are as follows: Place the SBA - 15 molecular sieve in an ammonium sulfate solution, perform constant - temperature stirring treatment, and then wash it with deionized water until neutral and dry it to obtain the SBA - 15 molecular sieve after pore - expanding treatment; the mass ratio of carboxylated carbon nanofibers to the SBA - 15 molecular sieve after pore - expanding treatment is 3:5. Mix the two and place them in a ball mill for ball - milling treatment to obtain a composite support.

[0015] In the above - mentioned preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues, in step b, the iron salt solution is a ferric nitrate ethanol solution prepared by adding ferric 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 evenly dropped onto the surface of the composite support and completely wets it.

[0016] ​​In the preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues as described above, in step d, the wavelength of ultraviolet light irradiation is 254 nm, and the irradiation time is 20 - 40 min.

[0017] In the preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues as described above, 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 support.

[0018] In the preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues as described above, in step e, when heating to 500 °C, a gradient oxygen concentration is adopted, the initial oxygen content is 5 - 10%, and it is gradually increased to 21%.

[0019] In the preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues as described above, during in-situ sulfidation, CS2 or H2S solution is sprayed, the temperature is 350 - 400 °C, and in-situ sulfidation is carried out under a H2 atmosphere.

[0020] In the preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues as described above, the diameter of the carboxylated carbon nanofibers is 20 - 50 nm, the length is 1 - 5 μm, and a three-dimensional conductive network structure is formed in the composite support.

[0021] Another object of the present invention is to provide a catalyst for the lightening of heavy aromatics in coal liquefaction residues, which is prepared by the above-mentioned preparation method, and the specific surface area of the catalyst is 550 - 650 m 2 / g, and the metal dispersion degree is ≥ 80%.

[0022] 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 residues in hydrocracking. The application is to mix the catalyst with coal liquefaction residues according to a mass ratio of 3 - 8:100, and carry out a hydrocracking reaction under a hydrogen atmosphere. The reaction conditions are a temperature of 380 - 420 °C, a pressure of 8 - 12 MPa, a hydrogen-oil volume ratio of 800:1 - 1200:1, and a weight hourly space velocity of 0.8 - 1.2 h-1.

[0023] Compared with the prior art, the present invention brings the following beneficial technical effects:

[0024] (1) The present invention provides a method for preparing a catalyst for the lightening of heavy aromatics in coal liquefaction residues. The composite support selected is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves after pore expansion treatment in a certain mass ratio. Compared with a single support, the advantages of the composite support of the present invention are as follows: The present invention innovatively adopts 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 terms of structure, function, and performance. Through the design of structural complementarity, synergistic enhancement of mass transfer and stability, the present invention uses pore-expanded SBA-15 molecular sieves to improve the molecular diffusion efficiency, solve the limitations of traditional molecular sieves, and at the same time constructs a three-dimensional conductive network structure with carboxylated carbon nanofibers to enhance the overall performance of the support. The two are combined to form an ordered mesoporous + conductive skeleton system, providing an ideal platform for metal active components. On this basis, by using the coordination effect of CNF carboxyl groups and the mesoporous confinement effect of SBA-15, combined with microwave-assisted impregnation and ultraviolet light reduction techniques, the metal particle size is precisely controlled, the metal dispersion and the exposure of active sites are significantly improved, and then a dual-metal Fe-Co gradient impregnation structure is constructed to avoid the shielding of active sites caused by alloying and enhance the synergistic hydrocracking ability. In addition, CNF enhances the thermal shock resistance and mechanical strength of the support, and the composite support has a confinement protection effect on metal particles. The active phase formed after in-situ sulfidation treatment has excellent performance, overall strengthening the thermal stability and anti-deactivation ability of the catalyst, and finally realizing efficient catalytic conversion.

[0025] (2) In terms of the 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, reducing agglomeration, improving the uniformity of metal doping, optimizing the distribution of adsorption sites, and laying the foundation for the subsequent formation of an Fe-Co gradient distribution, enhancing the hydrocracking activity. After microwave impregnation and drying, secondary impregnation is carried out, that is, using a complexing system as the impregnating solution to achieve an Fe-Co dual-metal 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), improving the exposure rate of active sites. By combining "microwave impregnation and ultraviolet light irradiation", the present invention can construct a highly active catalyst, improve the catalytic reaction efficiency, and enhance the stability of the catalyst. Finally, stepwise heat treatment is carried out under nitrogen protection. First, low-temperature pretreatment is carried out to remove organic substances, and then high-temperature calcination is carried out to form an Fe-Co synergistic active phase, finally obtaining a highly dispersed and highly stable catalyst. The entire process ensures the structural stability of the catalyst and the efficient exposure of active sites through key technologies such as microwave-enhanced dispersion, complexing inhibition of agglomeration, and gradient temperature control activation.

[0026] (3) The combination of microwave impregnation and ultraviolet light irradiation can increase 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 calcination with gradient oxygen concentration enable the catalyst to have a specific surface area of 700 m 2 / g and a metal dispersion of ≥90%. The in-situ sulfidation technology increases the initial activity of the catalyst by 20% and reduces the dosage of the sulfiding agent by 40%.

[0027] (4) Verified by examples, the conversion rate of heavy aromatics of the catalyst prepared by the method of the present invention is increased to 89% (industry average ≤58%), the light oil yield breaks through 74%, and the coking amount is reduced to ≤1.8% (traditional process 8.5% - 15%). The single-cycle life of the catalyst is 500 hours (traditional ≤200 hours), the activity retention rate after regeneration is >85%, and the comprehensive cost is reduced by 62.5%.

[0028] In summary, the present invention combines the Fe-Co-Mo ternary active system with a composite support to significantly improve the conversion efficiency of heavy aromatics and the selectivity of light oil, while inhibiting the formation of coke, breaking through the bottleneck that it is difficult to balance the activity and stability of traditional catalysts. Combining microwave-assisted impregnation with photoreduction technology and complexing dispersion technology to optimize the uniformity of metal loading, achieving a double reduction in hydrogen consumption and energy consumption, and significantly reducing solid waste emissions through the regeneration process. Its unique support structure can withstand high-sulfur and high-metal impurity raw materials, directly process complex oil products to save pretreatment costs, and flexibly regulate the product distribution with acidic additives. The present invention takes high-efficiency conversion, low-carbon energy conservation, and raw material universality as its core advantages, provides a systematic solution for the clean and efficient conversion of heavy oil, and promotes the upgrading of the refining industry towards green and sustainable development. Description of the Drawings

[0029] The following further describes the present invention with reference to the drawings:

[0030] Figure 1 SEM (a-b) and TEM (c-d) images of the catalyst prepared by the present invention, showing the microscopic morphology of the composite support and the distribution of metal particles.

[0031] Figure 2 The position and electron density distribution map of Fe and Co on the catalyst surface.

[0032] Figure 3 Comparison of the comprehensive performance of different catalysts in the conversion of heavy dirty hydrocarbons. Detailed Embodiments

[0033] The following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the drawings in the embodiments of the present application.

[0034] The raw materials mentioned in the present invention can all be obtained through commercial channels.

[0035] The main technical concept of the present invention lies in: the present invention uses carboxylated carbon nanofibers and SBA-15 molecular sieves after pore expansion treatment as composite carriers, adopts the ammonium sulfate dynamic pore expansion technology to expand the pore diameter of SBA-15 from 6 nm to the 12-nm level, breaks through the mass transfer bottleneck of traditional mesoporous molecular sieves, and at the same time retains its high specific surface area characteristics, providing an ordered dispersion space for metal active sites. Three-dimensional conductive network: Introduce carboxylated carbon nanofibers to construct a three-dimensional conductive network, whose diameter of 30-50 nm forms a topological match with the mesopores of SBA-15, solves the problems of poor conductivity and low mechanical strength of pure molecular sieves, and increases the conductivity of the composite carrier to 10 -1 S / cm order of magnitude.

[0036] Double-metal gradient distribution for loading active components: The stepwise impregnation method is adopted to first load Fe 3+ to occupy the anchoring sites on the inner surface of the mesopores, and then complex Co through ethylenediamine 2+ to achieve a gradient distribution in the pores, avoiding the shielding of active sites caused by the direct alloying of Fe-Co. Microwave-assisted impregnation: Utilize the uniform heating characteristics of microwaves to promote the rapid penetration and uniform dispersion of metal precursors in the pores of the composite carrier, reduce metal agglomeration, and shorten the impregnation time to 10-20 minutes. Ultraviolet light reduction: After impregnation, irradiate with ultraviolet light to in-situ reduce metal precursors to nano-metal particles, precisely control the metal particle size, and increase the exposure rate of active sites. Then optimize the heat treatment process. In-situ crystallization is adopted to add a small amount of water vapor in the nitrogen pretreatment stage. Through the interaction between water vapor and metal precursors, promote the crystallization of metal oxides to form a more uniform active phase. Atmosphere regulation adopts a gradient oxygen concentration in the air calcination stage to avoid the collapse of the carrier pores in a direct high-temperature and high-oxygen environment, and at the same time reduce the oxidation sintering of metal particles. Catalyst activity improvement adopts in-situ sulfidation technology: In the final stage of catalyst preparation, introduce in-situ sulfidation technology to directly generate a highly active sulfide phase (such as CoMoS or FeS) on the catalyst surface, avoid the waste of sulfiding agents and side reactions in the traditional sulfidation process, and increase the initial activity of the catalyst by 15%-20%.

[0037] The specific application method of the catalyst prepared by the present invention is as follows:

[0038] Carry out hydrocracking reaction on the catalyst and coal liquefaction residue under a hydrogen atmosphere. The reaction conditions are temperature 380-420 °C, pressure 8-12 MPa, hydrogen-oil volume ratio 800:1-1200:1, weight hourly space velocity 0.8-1.2 h-1, and carry out hydrocracking reaction under a hydrogen atmosphere.

[0039] Determination of catalyst activity: The catalyst was loaded in a fixed-bed reactor, and coal liquefaction residue and hydrogen were introduced for hydrocracking. The product composition was analyzed by gas chromatography (GC) and mass spectrometry (MS), and the conversion rate of heavy aromatics (such as the conversion rate of polycyclic aromatic hydrocarbons like naphthalene and phenanthrene) and the yield of light oil (such as the formation ratio of monocyclic aromatic hydrocarbons and olefins) were calculated. The amount of coke deposition (the mass percentage of residual coke on the catalyst surface) was determined by thermogravimetric analysis (TGA).

[0040] Stability test of the catalyst: It was continuously operated for 500 hours under standard reaction conditions. Samples were taken at regular intervals to analyze the product composition and monitor the trend of activity decline. The end point of the single-cycle life of the catalyst was defined as the activity dropping to 80% of the initial value (the single-cycle life reached 500 hours in the example).

[0041] Determination of the recycling performance of the catalyst: The used catalyst was calcined at high temperature (such as in an air atmosphere at 500 °C) to remove carbon deposits, and then the active phase was restored by in-situ sulfidation. The regenerated catalyst was used for hydrocracking reaction again, and the activity retention rate was calculated (such as the conversion rate ≥ 85% after regeneration).

[0042] The present invention will be further described below in conjunction with specific examples.

[0043] Example 1:

[0044] A preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residue, comprising the following steps:

[0045] The first step is to prepare a composite support, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieve after pore expansion treatment in a certain mass ratio;

[0046] The specific steps are as follows: Weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m 2 / g, initial pore diameter 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, it was dried at 120 °C for 12 h to obtain the pore-expanded SBA-15 (the pore diameter measured by the BJH method is 12.3 ± 0.5 nm);

[0047] The pore-expanded SBA-15 and 3.00 g of carboxylated carbon nanofibers (diameter 30 - 50 nm, aspect ratio > 100, purity > 95%) were added to a planetary ball mill in a mass ratio of 5:3, and ball milled at a speed of 300 rpm for 2 h (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite support;

[0048] The second step is to prepare a 0.5 mol / L iron nitrate ethanol solution (Fe 3+For accurate concentration calibration, the composite support was immersed in an iron nitrate ethanol solution, and the volume of the iron salt solution was 50% of the total pore volume of the composite support; the iron salt solution was evenly dropped onto the surface of the composite support and completely wetted it.

[0049] Through microwave impregnation, Fe in the iron salt solution was promoted to 3+ be evenly loaded in the pores of the composite support; the microwave impregnation frequency was 50 kHz, and the microwave impregnation time was 15 minutes; the obtained composite support loaded with Fe was allowed to stand and age for 6 h, and after vacuum drying at 60 °C (vacuum degree 0.09 MPa), the first precursor was obtained. 3+

[0050] In the third step, a complexing system was prepared. The molar concentration ratio of ethylenediamine to cobalt chloride in the complexing system was 3:1, and its pH was adjusted to 9.0 ± 0.2 with ammonia water. The first precursor was placed in the complexing system for equal-volume impregnation. By complexing Co with ethylenediamine, 2+ a gradient distribution in the pores of the composite support was achieved, avoiding the shielding of active sites caused by direct alloying of Fe-Co; after the impregnation, the second precursor was obtained.

[0051] In the fourth step, the first precursor was irradiated with ultraviolet light, causing Fe to 3+ be in-situ reduced to Fe, 0 and at the same time, using ethylenediamine as an electron donor to stabilize Co, 3+ and the third precursor was obtained.

[0052] In the fifth step, the third precursor was placed in a tube furnace. Under a nitrogen atmosphere, it was heated to 250 °C at a rate of 5 °C / min and held for 2 h; then, 5%-10% (by volume) of steam was added to promote the crystallization of metal oxides; then, it was heated to 500 °C at a rate of 3 °C / min and calcined in an air atmosphere for 4-5 h. The initial oxygen content was 5%, and it was gradually increased to 21%. It was calcined in an air atmosphere for 4 h; after calcination, hydrogen with a volume ratio of 10%-20% was introduced at 350-400 °C, and a spray sulfiding agent (such as CS2 or an H2S aqueous solution) was used to generate a highly active sulfide phase (such as CoMoS or FeS). The temperature was programmed to 500 °C (heating rate 3 °C / min), and it was calcined in an air atmosphere for 4 h (oxygen content 21%). Through in-situ sulfidation, an FeS or CoMoS active phase was generated, and it was obtained after natural cooling.

[0053] The catalyst prepared in this example was applied to the hydrocracking reaction of heavy aromatics in coal liquefaction residues. The results were as follows: under the conditions of a reaction temperature of 400 °C, a pressure of 10 MPa, a hydrogen-oil volume ratio of 1000:1, and a weight hourly space velocity of 1.0 h, -1 after 500 hours of continuous operation, the conversion rate of heavy aromatics reached 89.3%, and the light oil (C5–C 20)The yield reaches 74.1%, and the coking amount of the catalyst is as low as 1.6%, showing excellent catalytic activity and anti-coking ability.

[0054] After the catalyst is recycled and regenerated 3 times, the activity retention rate is still as high as 86.5%, and the specific surface area retention rate reaches 82%, indicating that it has good thermal stability and renewable performance. Compared with the problems of rapid activity decay and serious coking of the catalyst in the comparative example (such as a single SBA-15 support system), the catalyst of the present invention can stably process the coal liquefaction residue raw material with high aromatic content and complex impurities, significantly reducing the hydrogen consumption and solid waste output during the hydrogenation reaction.

[0055] In addition, the catalyst also has strong tolerance to sulfur- and nitrogen-containing compounds, and can achieve efficient conversion of heavy components in the residue without pretreatment, and 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.

[0056] Example 2:

[0057] The difference from Example 1 is that:

[0058] In the second step, the microwave impregnation power is 40 kHz, and the microwave impregnation time is 10 minutes.

[0059] The application of the catalyst prepared in this example refers to Example 1.

[0060] Example 3:

[0061] The difference from Example 1 is that:

[0062] In the second step, the microwave impregnation power is 60 kHz, and the microwave impregnation time is 20 minutes.

[0063] The application of the catalyst prepared in this example refers to Example 1.

[0064] Example 4:

[0065] The difference from Example 1 is that:

[0066] In the third step, the complexing system is that the molar concentration ratio of ethylenediamine to cobalt chloride is 2:1.

[0067] The application of the catalyst prepared in this example refers to Example 1.

[0068] Example 5:

[0069] The difference from Example 1 is that:

[0070] In the third step, the complexing system is that the molar concentration ratio of ethylenediamine to cobalt chloride is 4:1.

[0071] The application of the catalyst prepared in this example refers to Example 1.

[0072] Comparative Example 1:

[0073] The difference from Example 1 is as follows:

[0074] The composite support is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieve in a certain mass ratio.

[0075] The first step is to prepare the composite support, which is prepared by mixing SBA-15 molecular sieve (unexpanded) and carboxylated carbon nanofibers in a mass ratio of 7:3.

[0076] The specific steps are as follows: directly weigh 7.00 g of the original SBA-15 molecular sieve (specific surface area 680 m 2 / g, initial pore diameter 6 nm, not treated with ammonium sulfate for pore expansion). Add 7.00 g of the original SBA-15 and 3.00 g of carboxylated carbon nanofibers (diameter 30 - 50 nm, aspect ratio > 100, purity > 95%) to a planetary ball mill according to a mass ratio of 7:3. Ball mill at a speed of 300 rpm for 2 hours (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite support.

[0077] The second to fifth steps are the same as those in Example 1.

[0078] Comparative Example 2:

[0079] The difference from Example 1 is as follows:

[0080] Only the SBA-15 molecular sieve treated with pore expansion is used as the support, and carboxylated carbon nanofibers are not added.

[0081] The first step is to prepare the support, and the support is the SBA-15 molecular sieve after pore expansion treatment.

[0082] The specific steps are as follows: weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m 2 / g, initial pore diameter 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 the expanded SBA-15 (pore diameter measured by the BJH method is 12.3 ± 0.5 nm).

[0083] The second to fifth steps are the same as those in Example 1.

[0084] Comparative Example 3:

[0085] The difference from Example 1 is that there are no steps of configuring the complexing system and secondary impregnation.

[0086] A preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues, comprising the following steps:

[0087] First step, preparing a composite support, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves after pore expansion treatment according to a certain mass ratio;

[0088] The specific steps are as follows: Weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m 2 / g, initial pore diameter 6 nm) and place it in a 0.5 M ammonium sulfate solution, and stir at a constant temperature of 80 °C for 4 h. After washing with deionized water until neutral, dry it at 120 °C for 12 h to obtain the pore-expanded SBA-15 (pore diameter measured by the BJH method is 12.3 ± 0.5 nm);

[0089] Add the pore-expanded SBA-15 and 3.00 g of carboxylated carbon nanofibers (diameter 30 - 50 nm, aspect ratio > 100, purity > 95%) to a planetary ball mill according to a mass ratio of 5:3, and ball mill at a speed of 300 rpm for 2 h (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite support;

[0090] Second step, prepare a 0.5 mol / L iron nitrate ethanol solution (Fe 3+ concentration accurately calibrated), immerse the composite support in the iron nitrate ethanol solution, and the volume of the iron salt solution is 50% of the total pore volume of the composite support; the iron salt solution is evenly dripped onto the surface of the composite support and completely wetted.

[0091] Promote the uniform loading of Fe in the iron salt solution on the pore channels of the composite support through microwave impregnation; the microwave impregnation frequency is 50 kHz, and the microwave impregnation time is 15 minutes; let the obtained composite support loaded with Fe 3+ stand and age for 6 h, and then dry it in vacuum at 60 °C (vacuum degree 0.09 MPa) to obtain precursor one; 3+

[0092] Third step, irradiate the precursor one with ultraviolet light to in-situ reduce Fe 3+ to Fe 0 to obtain precursor three;

[0093] Step 4: Place the precursor III in a tube furnace. Under a nitrogen atmosphere, heat it to 250 °C at a rate of 5 °C / min and hold for 2 h. Then add water vapor with a volume ratio of 5% - 10% to promote the crystallization of metal oxides. Then, heat it to 500 °C at a rate of 3 °C / min and calcine for 4 - 5 h under an air atmosphere. The initial oxygen content is 5%, which is gradually increased to 21%, and calcine for 4 h in an air atmosphere. After calcination, introduce hydrogen with a volume ratio of 10 - 20% at 350 - 400 °C, spray a sulfurizing agent (such as CS2 or an H2S aqueous solution) to generate a highly active sulfide phase (such as CoMoS or FeS). Program the temperature to rise to 500 °C (heating rate 3 °C / min), calcine for 4 h in an air atmosphere (oxygen content 21%), generate an active phase through in-situ sulfidation, and obtain the product after natural cooling.

[0094] Comparative Example 4:

[0095] The difference from Example 1 is that there is no step of ultraviolet light irradiation.

[0096] A preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues, comprising the following steps:

[0097] Step 1: Prepare a composite support, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves after pore expansion treatment according to a certain mass ratio;

[0098] The specific steps are as follows: Weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m 2 / g, initial pore diameter 6 nm) and place it in a 0.5 M ammonium sulfate solution, and stir at a constant temperature of 80 °C for 4 h. After washing with deionized water until neutral, dry it at 120 °C for 12 h to obtain the pore-expanded SBA-15 (pore diameter measured by the BJH method is 12.3 ± 0.5 nm);

[0099] Add the pore-expanded SBA-15 and 3.00 g of carboxylated carbon nanofibers (diameter 30 - 50 nm, aspect ratio > 100, purity > 95%) to a planetary ball mill according to a mass ratio of 5:3, and ball mill at a speed of 300 rpm for 2 h (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite support;

[0100] Step 2: Prepare a 0.5 mol / L iron nitrate ethanol solution (Fe 3+ concentration accurately calibrated), place the composite support in the iron nitrate ethanol solution for impregnation, and the volume of the iron salt solution is 50% of the total pore volume of the composite support; the iron salt solution is evenly dripped onto the surface of the composite support and completely wetted.

[0101] Promote Fe in the iron salt solution through microwave impregnation 3+Uniformly load in the pores of the composite support; the microwave impregnation frequency is 50 kHz, and the microwave impregnation time is 15 minutes; the obtained composite support loaded with Fe 3+ is allowed to stand and age for 6 h, and after vacuum drying at 60 °C (vacuum degree 0.09 MPa), the precursor I is obtained;

[0102] Step 3: Configure a complexing system. The molar concentration ratio of ethylenediamine to cobalt chloride in the complexing system is 3:1, and its pH is adjusted to 9.0 ± 0.2 with ammonia water. The precursor I is placed in the complexing system for equal-volume impregnation, and Co is complexed by ethylenediamine 2+ to achieve a gradient distribution in the pores of the composite support and avoid the shielding of active sites caused by direct alloying of Fe-Co; after the impregnation, the precursor II is obtained;

[0103] Step 4: Place the precursor II in a tubular furnace. Under a nitrogen atmosphere, it is heated to 250 °C at a rate of 5 °C / min and held for 2 h; then, 5%-10% (by volume) of water vapor is added to promote the crystallization of metal oxides; then, it is heated to 500 °C at a rate of 3 °C / min and calcined in an air atmosphere for 4-5 h. The initial oxygen content is 5%, and it is gradually increased to 21%, and calcined in an air atmosphere for 4 h; after calcination, hydrogen with a volume ratio of 10%-20% is introduced at 350-400 °C, and a spray sulfiding agent (such as CS2 or an H2S aqueous solution) is used to generate a highly active sulfide phase (such as CoMoS or FeS). The temperature is programmed to rise to 500 °C (heating rate 3 °C / min), and calcined in an air atmosphere for 4 h (oxygen content 21%). The FeS or CoMoS active phase is generated by in-situ sulfidation, and it is obtained after natural cooling.

[0104] Comparative Example 5:

[0105] The difference from Example 1 is that a conventional calcination step is adopted.

[0106] Step 1: Prepare a composite support, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieves after pore expansion treatment in a certain mass ratio;

[0107] The specific steps are as follows: Weigh 5.00 g of SBA-15 molecular sieve (specific surface area 680 m 2 / g, initial pore diameter 6 nm) and place it in a 0.5 M ammonium sulfate solution, and stir at a constant temperature of 80 °C for 4 h. After washing with deionized water until neutral, it is dried at 120 °C for 12 h to obtain the pore-expanded SBA-15 (the pore diameter measured by the BJH method is 12.3 ± 0.5 nm);

[0108] The mesoporous SBA-15 and 3.00 g of carboxylated carbon nanofibers (diameter 30 - 50 nm, aspect ratio > 100, purity > 95%) were added to a planetary ball mill at a mass ratio of 5:3, and ball milled at a speed of 300 rpm for 2 h (zirconia grinding balls, ball-to-material ratio 10:1) to obtain a uniformly dispersed composite support;

[0109] Step 2: Prepare a 0.5 mol / L iron nitrate ethanol solution (the concentration of Fe was accurately calibrated), place the composite support in the iron nitrate ethanol solution for impregnation, and the volume of the iron salt solution was 50% of the total pore volume of the composite support; the iron salt solution was evenly dripped onto the surface of the composite support and completely wetted it. 3+ The iron salt solution was evenly dripped onto the surface of the composite support and completely wetted it.

[0110] Through microwave impregnation, Fe in the iron salt solution was promoted to be uniformly loaded in the pores of the composite support; the microwave impregnation frequency was 50 kHz, and the microwave impregnation time was 15 minutes; the obtained composite support loaded with Fe was left to stand and age for 6 h, and after vacuum drying at 60 °C (vacuum degree 0.09 MPa), the precursor I was obtained; 3+ the obtained composite support loaded with Fe was left to stand and age for 6 h, and after vacuum drying at 60 °C (vacuum degree 0.09 MPa), the precursor I was obtained; 3+ the obtained composite support loaded with Fe was left to stand and age for 6 h, and after vacuum drying at 60 °C (vacuum degree 0.09 MPa), the precursor I was obtained;

[0111] Step 3: Configure a complexing system where the molar concentration ratio of ethylenediamine to cobalt chloride is 3:1, and adjust its pH to 9.0 ± 0.2 with ammonia water. Place the precursor I in the complexing system for equal-volume impregnation, and complex Co through ethylenediamine to achieve a gradient distribution in the pores of the composite support, avoiding the shielding of active sites caused by direct alloying of Fe-Co; after impregnation, the precursor II was obtained; 2+ to achieve a gradient distribution in the pores of the composite support, avoiding the shielding of active sites caused by direct alloying of Fe-Co; after impregnation, the precursor II was obtained;

[0112] Step 4: Irradiate the precursor I with ultraviolet light to in-situ reduce Fe to Fe, and at the same time use ethylenediamine as an electron donor to stabilize Co, obtaining the precursor III; 3+ to in-situ reduce Fe to Fe 0 and at the same time use ethylenediamine as an electron donor to stabilize Co 3+ obtaining the precursor III;

[0113] Step 5: Place the precursor III in a tube furnace, and obtain the product after calcination and natural cooling.

[0114] Comparative Example 6:

[0115] The difference from Example 1 was that in-situ sulfidation was not used.

[0116] Steps 1 to 4: The same as in Example 1.

[0117] Step 5: Place the precursor III in a tube furnace, heat it to 250 °C at a rate of 5 °C / min in a nitrogen atmosphere and hold for 2 h; then heat it to 500 °C at a rate of 3 °C / min and calcine for 4 h in an air atmosphere, and obtain the product after natural cooling.

[0118] Comparative Example 7:

[0119] The difference from Example 1 is that in the first impregnation, microwave impregnation is not used, but a conventional impregnation method is adopted.

[0120] The first step is the same as that in Example 1.

[0121] The second step: Prepare a 0.5 mol / L iron nitrate ethanol solution (the concentration of Fe is accurately calibrated). Immerse the composite support in the iron nitrate ethanol solution by conventional impregnation. The volume of the iron salt solution is 50% of the total pore volume of the composite support; the iron salt solution is evenly dripped onto the surface of the composite support and made to be completely wet. The obtained composite support loaded with Fe 3+ is allowed to stand and age for 6 h, and after vacuum drying at 60 °C (vacuum degree 0.09 MPa), the first precursor is obtained. 3+

[0122] The third to fifth steps are the same as those in Example 1.

[0123] The catalytic performances of the catalysts prepared in the above examples and comparative examples are tested, as shown in Table 1.

[0124] Table 1

[0125]

[0126] The parts not described in the present invention can be realized by referring to the prior art.

[0127] Those of ordinary skill in the art of this technology should recognize that the above embodiments are only used to illustrate the present application, rather than to limit the present application. As long as within the scope of the essential spirit of the present application, appropriate changes and variations made to the above embodiments fall within the scope claimed by the present application.​

Claims

1. A preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues, characterized in that, It includes the following steps: a. Prepare a composite support, which is prepared by mixing carboxylated carbon nanofibers and SBA-15 molecular sieve after pore-expanding treatment according to a certain mass ratio; b. Place the composite support in an iron salt solution for impregnation. The impregnation is microwave impregnation, and the Fe in the iron salt solution is promoted to be uniformly loaded in the pores of the composite support through microwave impregnation. The microwave impregnation frequency is 40 - 60 kHz, and the microwave impregnation time is 10 - 20 minutes. After vacuum drying the obtained composite support loaded with Fe, a first precursor is obtained. 3+ Uniformly load on the pores of the composite support; the microwave impregnation frequency is 40 - 60 kHz, and the microwave impregnation time is 10 - 20 minutes; after vacuum drying the obtained composite support loaded with Fe 3+ , a first precursor is obtained. c. Configure a complexing system, where the molar concentration ratio of ethylenediamine to cobalt chloride in the complexing system is 2:1 to 4:1, and its pH is adjusted with ammonia water; Place the first precursor in the complexing system for impregnation, and complex Co with ethylenediamine 2+ Achieve a gradient distribution within the pores of the composite support to avoid the shielding of active sites caused by the direct alloying of Fe-Co; after impregnation, obtain the second precursor; d. By irradiating the precursor II with ultraviolet light, Fe3+ is in-situ reduced to Fe 0 , obtaining precursor III; e. Place the precursor three in a tubular furnace, under a mixed atmosphere of nitrogen and water vapor, heat up to 250 °C and hold for 1 to 3 h; then heat up to 500 °C and calcine in an air atmosphere for 4 to 5 h. After calcination, generate FeS or CoMoS active phase by in-situ sulfidation, and obtain the product after natural cooling.

2. The preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues according to claim 1, characterized in that: In step a, the preparation steps of the SBA-15 molecular sieve after pore-expanding treatment are as follows: Place the SBA-15 molecular sieve in an ammonium sulfate solution, carry out constant-temperature stirring treatment, then wash it with deionized water until neutral and dry it to obtain the SBA-15 molecular sieve after pore-expanding treatment; the mass ratio of carboxylated carbon nanofibers to the SBA-15 molecular sieve after pore-expanding treatment is 3:

5. Mix the two and place them in a ball mill for ball milling treatment to obtain a composite support; the pore diameter of the SBA-15 molecular sieve after pore-expanding treatment is 12 nm.

3. The preparation method of 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 support; the iron salt solution is evenly dropped onto the surface of the composite support to make it completely wet.

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

5. The preparation method of 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 to 9.5; the volume of the complexing system is 50% of the total pore volume of the composite support.

6. The preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residue according to claim 1, characterized in that: In step e, when heating up to 500 °C, a gradient oxygen concentration is adopted, with the initial oxygen content being 5 to 10%, and gradually increasing to 21%.

7. The preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residue according to claim 1, characterized in that: During in-situ sulfidation, CS2 or H2S solution is sprayed, the temperature is 350 to 400 °C, and in-situ sulfidation is carried out under a H2 atmosphere.

8. The preparation method of a catalyst for the lightening of heavy aromatics in coal liquefaction residues according to claim 1, characterized in that: The diameter of the carboxylated carbon nanofibers is 20 to 50 nm, the length is 1 to 5 μm, and a three-dimensional conductive network structure is formed in the composite support.

9. A catalyst for the lightening of heavy aromatics in coal liquefaction residues, characterized in that, It is prepared by using the preparation method described in any one of claims 1 to 7, and the specific surface area of the catalyst is 550 to 650 m 2 / g, and the metal dispersion degree is ≥80%.

10. Use of a catalyst for the lightening of heavy aromatics in coal liquefaction residues in hydrocracking according to claim 9, characterized in that: The application is to mix the catalyst with coal liquefaction residue according to a mass ratio of 3 to 8:100, and carry out a hydrocracking reaction under a hydrogen atmosphere. The reaction conditions are a temperature of 380 to 420 °C, a pressure of 8 to 12 MPa, a hydrogen-oil volume ratio of 800:1 to 1200:1, and a weight hourly space velocity of 0.8 to 1.2 h-1.

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