A coal tar pitch-based nickel catalyst, its preparation method and application

Abstract

This invention provides a coal tar pitch-based nickel catalyst, its preparation method, and its application, belonging to the field of solid waste resource recycling and synthetic carbon materials technology. This invention uses a mixed roasting method to prepare a coal tar pitch-based nickel catalyst with micropores and mesopores from the residual coal tar pitch after coal tar extraction. The synergistic effect of active nickel as an active site and the functional groups on the support surface significantly improves its catalytic liquefaction performance, exhibiting the advantages of "low cost, high temperature resistance, and strong adaptability." The preparation method provided by this invention not only offers an effective way for the high-value recycling of coal tar pitch but also provides a low-cost material for green conversion, environmental governance, catalysis, and other fields. It represents a green resource utilization strategy with significant economic and environmental benefits and broad commercial prospects.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource recycling and synthetic carbon materials technology, and in particular to a coal tar pitch-based nickel catalyst, its preparation method, and its application. Background Technology

[0002] With the overexploitation of energy and escalating environmental pollution, the search for clean and sustainable energy sources has become a major focus. Biomass refers to organic matter derived from living organisms, encompassing plant resources, agricultural waste, kitchen waste, organic matter from animal and microbial sources, and municipal solid waste. Among these, agricultural waste, rich in lignocellulose, has become a key area of ​​research in biomass conversion technology due to its abundant resources and high renewability. Through efficient conversion technologies, agricultural waste can not only effectively alleviate environmental pollution problems caused by traditional disposal methods but also be transformed into green energy with broad application prospects.

[0003] Currently, mainstream biomass conversion pathways include direct combustion, gasification, liquefaction, fermentation, and pyrolysis, which can convert biomass into energy forms suitable for various residential and industrial uses. Among these technologies, hydrothermal liquefaction (HTL) has attracted much attention because it uses water as the reaction medium and directly converts wet biomass into liquid fuel under mild temperature (250~350℃) and pressure (5~25MPa) conditions, avoiding the energy-intensive drying pretreatment stage in traditional processes and significantly reducing process costs.

[0004] However, the HTL process using water as the solvent alone still suffers from limited conversion efficiency, high content of heteroatoms such as nitrogen and sulfur in the resulting bio-crude oil, and significant oxygen content, which restricts its quality and application potential as a fossil fuel substitute. To overcome these bottlenecks, the introduction of catalysts is widely regarded as a key strategy to improve the efficiency and product quality of the HTL process.

[0005] Coal tar pitch, or CTP for short, is the residue remaining after coal tar undergoes distillation to extract chemical fractions such as light oil, naphthalene oil, wash oil, phenolic oil, and anthracene oil. Its yield accounts for approximately 50-55% of the total mass of coal tar. From the perspective of high-value resource utilization, CTP possesses significant advantages, including abundant reserves, low market prices, and high content of carbonization products (such as fixed carbon). Transforming low-value-added CTP into functional carbon materials such as porous carbon (PCs), carbon fibers, carbon foam, graphite, and electrodes can not only significantly improve the overall economic benefits of the coal chemical industry chain but also promote the recycling of energy resources, providing crucial support for achieving sustainable development goals in the energy sector.

[0006] However, coal tar pitch contains a large number of impurities, resulting in a low proportion of effective catalytic components in catalysts prepared from coal tar pitch, leading to poor catalytic effects. At the same time, the effective catalytic components in the catalyst also have fewer catalytic active sites, causing the catalytic effect of catalysts prepared from coal tar pitch to fail to meet technical requirements.

[0007] Therefore, how to prepare catalysts with good catalytic effects from coal tar pitch, so as to realize the high-value utilization of coal tar pitch, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a coal tar pitch-based nickel catalyst, its preparation method, and its application. The preparation method provided by this invention can prepare a highly efficient nickel-supported catalyst constructed from 1,8-dimethylaminonaphthyl carboxylate-like functional structural units and active sites, solving the environmental protection problem of harmless treatment of waste coal tar pitch and providing a new path for the resource utilization of solid waste and the low-cost preparation of high-end functional materials.

[0009] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a coal tar pitch-based nickel catalyst, comprising the following steps: (1) Coal tar pitch and extractant are mixed and then extracted to obtain extracted coal tar pitch; (2) The extracted coal tar obtained in step (1) is mixed with nickel nitrate hexahydrate and then carbonized to obtain a coal tar-based nickel catalyst.

[0010] Preferably, the elemental composition of the coal tar pitch in step (1) by mass percentage includes: 75-85% carbon, 0.5-1.5% nitrogen, 2-5% hydrogen, 0.5-1.5% sulfur and 10-20% oxygen.

[0011] Preferably, the extractant in step (1) is any one or more of n-heptane, n-hexane, and n-octane; the extraction method is extraction in a Soxhlet extractor.

[0012] Preferably, the mass ratio of coal tar pitch to extractant in step (1) is 1:(5~10).

[0013] Preferably, the extraction temperature in step (1) is 80~130℃.

[0014] Preferably, the particle size of the coal tar pitch after extraction in step (1) is 50~200 mesh.

[0015] Preferably, in step (2), the mass of nickel nitrate hexahydrate is 5-20% of the mass of the extracted coal tar pitch.

[0016] Preferably, the carbonization holding temperature in step (2) is 550~900℃; the carbonization holding time is 1~4h; and the carbonization atmosphere is nitrogen.

[0017] This invention provides a coal tar pitch-based nickel catalyst prepared by the preparation method described in the above technical solution.

[0018] This invention provides the application of the coal tar pitch-based nickel catalyst described above in the catalytic hydrothermal liquefaction reaction of biomass.

[0019] This invention provides a method for preparing a coal tar pitch-based nickel catalyst, comprising the following steps: (1) mixing coal tar pitch and an extractant and then extracting to obtain extracted coal tar pitch; (2) mixing the extracted coal tar pitch obtained in step (1) with nickel nitrate hexahydrate and then carbonizing to obtain a coal tar pitch-based nickel catalyst. This invention uses a mixed roasting method to prepare a coal tar pitch-based nickel catalyst with micropores and mesopores from the residual coal tar pitch after coal tar extraction. The synergistic effect of active metallic nickel as an active site and the functional groups on the support surface can greatly improve its catalytic liquefaction performance, exhibiting the performance advantages of "low cost, high temperature resistance, and strong adaptability." The preparation method provided by this invention not only provides an effective way for the high-value recycling of coal tar pitch, but also provides low-cost materials for green conversion, environmental governance, catalysis, and other fields. It is a green resource utilization strategy with significant economic and environmental benefits and broad commercial prospects. This invention transforms the residual coal tar residue after coal tar extraction into a high-performance coal tar-based nickel catalyst. Compared to catalysts prepared by traditional impregnation methods, this catalyst has a higher specific surface area, higher active metal loading, and contains microporous carbon materials. It can be used to catalyze the hydrothermal liquefaction of biomass, exhibiting high selectivity and easily tunable and optimizable performance. It is an ideal low-cost, high-performance catalytic material for developing new clean and renewable energy sources using coal tar. The results of the embodiments show that the preparation method provided by this invention has a significant regulatory effect on the catalyst structure, allowing for precise control of pore structure parameters to adapt to different application scenarios. Simultaneously, the coal tar-based catalyst exhibits superior catalytic performance in the hydrothermal liquefaction reaction of biomass, with a solid waste conversion rate increased to a maximum of 68.15%, indicating that the catalyst prepared by this invention has great potential in catalyzing the hydrothermal liquefaction of biomass. Attached Figure Description

[0020] Figure 1 Here is a SEM image of the coal tar pitch-based nickel catalyst obtained in Example 4; Figure 2 The XRD patterns of the coal tar pitch-based nickel catalysts obtained in Examples 1-5 are shown below. Figure 3 The solid waste conversion rate of biomass hydrothermal liquefaction catalyzed by the coal tar pitch-based nickel catalysts obtained in Examples 1-5 and Comparative Example 1 is shown. Detailed Implementation

[0021] This invention provides a method for preparing a coal tar pitch-based nickel catalyst, comprising the following steps: (1) Coal tar pitch and extractant are mixed and then extracted to obtain extracted coal tar pitch; (2) The extracted coal tar obtained in step (1) is mixed with nickel nitrate hexahydrate and then carbonized to obtain a coal tar-based nickel catalyst.

[0022] This invention involves mixing coal tar pitch and an extractant, followed by extraction to obtain extracted coal tar pitch.

[0023] This invention does not specifically limit the source of the coal tar pitch; any coal tar pitch well known to those skilled in the art can be used. As one embodiment of this invention, the elemental composition of the coal tar pitch, by mass percentage, may include: 75-85% carbon, 0.5-1.5% nitrogen, 2-5% hydrogen, 0.5-1.5% sulfur, and 10-20% oxygen; or it may include: 79.35% carbon, 1.01% nitrogen, 3.36% hydrogen, 0.93% sulfur, and 15.35% oxygen.

[0024] In this invention, the coal tar pitch is preferably pretreated before mixing; the pretreatment is preferably pulverization. This invention does not impose any specific limitations on the pulverization operation; based on the technical knowledge of those skilled in the art, any operation that results in a larger specific surface area for the coal tar pitch is acceptable. By pulverizing the coal tar pitch, this invention allows it to have a larger contact area after mixing with the extractant, thereby improving extraction efficiency.

[0025] In this invention, the extractant is preferably one or more of n-heptane, n-hexane, and n-octane, more preferably n-heptane; the extraction method is preferably extraction in a Soxhlet extractor. This invention does not impose any special limitation on the specific amounts of coal tar pitch and extractant, which can be determined based on the technical knowledge of those skilled in the art, until the extractant in the Soxhlet extractor no longer changes color. As one embodiment of this invention, the mass ratio of coal tar pitch to extractant can be 1:(5~10), or it can be 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10.

[0026] In this invention, the extraction temperature is preferably 80-130℃. As one embodiment of this invention, the extraction temperature can be 80℃, 85℃, 90℃, 95℃, 100℃, 101℃, 102℃, 105℃, 108℃, 110℃, 112℃, 115℃, 118℃, 120℃, 125℃, or 130℃. This invention does not have a specific limitation on the extraction time; it is sufficient to continue extraction until the extractant in the Soxhlet extractor no longer changes color. This invention removes impurities such as colloids, aromatic hydrocarbons, and saturated hydrocarbons from coal tar pitch through extraction, thereby improving the performance of coal tar pitch-based nickel catalysts.

[0027] The present invention preferably further includes drying and pulverizing the extracted product; the drying temperature is preferably 70~90℃, more preferably 75~85℃, and even more preferably 80℃; the drying is preferably carried out in a forced-air drying oven; the pulverization method is preferably grinding.

[0028] In this invention, the particle size of the extracted coal tar pitch is preferably 50-200 mesh. As one embodiment of this invention, the particle size of the extracted coal tar pitch can be 50 mesh, 60 mesh, 80 mesh, 100 mesh, 120 mesh, 140 mesh, 150 mesh, 160 mesh, 180 mesh, or 200 mesh.

[0029] This invention removes colloids, aromatic hydrocarbons and saturated hydrocarbons from coal tar pitch by extraction. After extraction, the nitrogen content of coal tar pitch decreases by 20%, the sulfur content decreases by 53%, and the thermal stability increases by 18.6%.

[0030] After obtaining the extracted coal tar pitch, the present invention mixes the extracted coal tar pitch with nickel nitrate hexahydrate and then carbonizes it to obtain a coal tar pitch-based nickel catalyst.

[0031] In this invention, the mass of the nickel nitrate hexahydrate is preferably 5-20% of the mass of the extracted coal tar pitch. As one embodiment of this invention, the mass of the nickel nitrate hexahydrate can be 5%, 6%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, or 20% of the mass of the extracted coal tar pitch.

[0032] In this invention, the carbonization holding temperature is preferably 550~900℃; the carbonization holding time is preferably 1~4h; the heating rate to the carbonization holding temperature is preferably 3~15℃ / min; and the carbonization atmosphere is preferably nitrogen. As one embodiment of this invention, the carbonization holding temperature can be 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, or 900℃; the carbonization holding time can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, or 4h; and the heating rate to the carbonization holding temperature can be 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, or 15℃ / min.

[0033] This invention limits the carbonization heating temperature to 550~900℃. This is because when the temperature exceeds 900℃, the carbon skeleton undergoes high-temperature rearrangement, transforming disordered amorphous carbon into ordered graphitized carbon. The originally loose porous structure collapses due to the orderly stacking of aromatic rings, resulting in a sharp reduction in the number of micropores and mesopores, a dramatic decrease in the specific surface area of ​​the catalyst, and even the formation of dense, non-porous carbon blocks, completely losing the ability to anchor the nickel component and the mass transfer ability of the reactants. Simultaneously, when the temperature exceeds 900℃, small-diameter nickel particles undergo Ostwald ripening due to atomic migration, dissolving and depositing onto the surface of larger particles, eventually agglomerating to form larger nickel particles. This agglomeration of nickel particles directly leads to a significant decrease in the specific surface area of ​​active sites, reducing the effective contact area for the catalytic reaction and significantly reducing catalyst activity. Furthermore, with the graphitization of the carbon support, some nickel particles are completely encapsulated by the rearranged graphitized carbon layer, forming a "core-shell" structure. The encapsulated nickel particles cannot contact reactant molecules, completely losing their catalytic activity.

[0034] This invention limits the carbonization holding time to 1-4 hours. This is because when the holding time is less than 1 hour, the carbonization reaction, ligand synthesis, and nickel loading processes of coal tar pitch are incomplete, damaging catalyst performance from three core dimensions: carbon support structure, active component state, and coordination complex formation. The essence of the carbonization process is the thermal cracking, condensation, and aromatization of coal tar pitch, requiring sufficient time for the escape of small molecule gases and the construction of the carbon skeleton. Too short a time will result in a sparse pore structure with poor connectivity and low mechanical strength and stability of the carbon support. When the holding time exceeds 4 hours, it will cause negative effects on the carbon support structure, the state of the nickel active component, and the stability of the coordination complex, leading to catalyst performance degradation. Therefore, the optimal time for coal tar pitch carbonization is the balance point of "sufficient escape of small molecule gases and cross-linking and formation of the carbon skeleton." If the carbonization time is too long, the carbon skeleton will undergo excessive condensation: the originally loose mesoporous-microporous structure will gradually collapse due to the continuous stacking of aromatic rings, and the connected channels will become closed or dead pores; the specific surface area of ​​the catalyst will decrease; excessively long holding time will accelerate the transformation of amorphous carbon into graphitized carbon, and the active functional groups on the surface of the carbon support will completely disappear due to continuous high-temperature pyrolysis. At the same time, graphitized carbon has strong chemical inertness, and its interaction with the active components of nickel weakens from chemical coordination and bonding to physical adsorption, which cannot effectively anchor nickel particles. Excessive carbonization time will cause some nickel particles to undergo high-temperature sintering, reducing the particle surface energy and stabilizing the crystal form, but significantly reducing the number of catalytic active sites. In addition, an inert oxide layer (such as NiO) is easily formed on the surface of the sintered nickel particles, further reducing their catalytic activity.

[0035] This invention employs a carbon support mixed with active metals to prepare a catalyst through calcination. The active metal loading is reinforced while the support is pyrolyzed, and coal tar pitch forms a porous carbon material at high temperature. This process is not a one-step synthesis but rather involves a complex pathway of "decomposition-reconstruction-coordination-carbonization / graphitization," as detailed below: I. In the carbonization process of this invention, the weight loss of the extracted coal tar pitch in the 0~200℃ stage is mainly due to the removal of adsorbed water in the extracted coal tar pitch and the volatilization of a small amount of low-boiling-point impurities; in the 200~550℃ stage, the macromolecular structure in the coal tar pitch begins to break, the side chains and some aromatic ring structures decompose, and a large amount of small molecule gases are released; in the 550~900℃ stage, the process becomes relatively slow, mainly due to some difficult-to-decompose aromatic condensation structures continuing to undergo slow carbonization reactions to form amorphous carbon, which provides a carbon support for the preparation of the catalyst.

[0036] II. Under high-temperature carbonization conditions, coal tar pitch does not merely function as an inert carbon precursor. Instead, it comprises a nitrogen-containing fused-ring aromatic backbone (naphthalene, phenanthrene, and anthracene, etc.) and oxygen-containing heteroatom structures (quinoline-type N, pyridine-type N, carboxyl groups, and phenolic hydroxyl groups). This process involves a series of complex aromatization and structural rearrangement processes, gradually forming a carbonaceous matrix dominated by fused-ring aromatic structures and rich in nitrogen and oxygen heteroatom sites. The original naphthalene-based aromatic units in coal tar pitch exhibit high structural stability during heat treatment, with some being retained and serving as the backbone structure for subsequent coordination reactions. Simultaneously, the high-temperature environment promotes the exposure, migration, and rearrangement of nitrogen-containing functional groups, leading to the gradual enrichment of amine or quaternary ammonium-type nitrogen-containing structures at the ortho positions of the aromatic backbone. Weak oxidation or functional group transformation at the carbon backbone edges favors the formation of oxygen-containing sites in carboxylates. These processes collectively contribute to the formation of ligand units that simultaneously possess an aromatic backbone, ortho-nitrogen groups, and carboxylate functional sites in their local structures. Their configurations are highly similar to those of 1,8-dimethylaminonaphthylcarbamate in terms of spatial and coordination characteristics.

[0037] III. Nickel nitrate hexahydrate undergoes dehydration and nitrate decomposition under high temperature conditions to generate Ni with high coordination activity. 2+ The reaction formula for this species, under high temperature conditions, is as follows: Ni(NO3)2·6H2O→NiO+2NO2↑+O2↑+6H2O↑. This Ni... 2+ The species tends to undergo multidentate chelate coordination with electron-rich N and O functional groups in the coal tar pitch-derived carbon matrix, forming stable coordination structures characterized by Ni-N and Ni-O bonds. Simultaneously, the synergistic effect of the ortho-amine group and the carboxylate group contributes to Ni... 2+ It provides a favorable chelation environment, which helps to construct coordination units of the 1,8-dimethylaminonaphthylcarbamate type, thereby significantly enhancing the metal-support interaction.

[0038] IV. Under the synergistic stabilizing effect of the spatial confinement effect of the carbonaceous framework and the π-conjugated system, the above-mentioned coordination structure effectively inhibits the migration and aggregation of Ni species at high temperatures, enabling nickel to be anchored on the carbon matrix surface in a highly dispersed and coordinateably stable form. These Ni coordination centers not only maintain good structural stability, but their electronic structure is also regulated by surrounding nitrogen- and oxygen-containing ligands, thus providing favorable conditions for the adsorption, activation, and transformation of reactant molecules in subsequent catalytic reactions. In summary, the coal tar pitch-derived 1,8-dimethylaminonaphthyl carboxylate-like functional structural units play a crucial role in the stable anchoring of Ni species and the construction of active sites, and are an important structural basis for the formation of highly efficient nickel-supported catalysts.

[0039] This invention utilizes a mixed roasting method to prepare a microporous and mesoporous coal tar-based nickel catalyst from the residual coal tar residue after coal tar extraction. The synergistic effect of active nickel as the active site and the functional groups on the support surface significantly improves its catalytic liquefaction performance, exhibiting advantages of "low cost, high temperature resistance, and strong adaptability." The preparation method provided by this invention not only offers an effective approach for the high-value recycling of coal tar but also provides a low-cost material for green conversion, environmental remediation, and catalysis, representing a green resource utilization strategy with significant economic and environmental benefits and broad commercial prospects.

[0040] This invention transforms the residual coal tar residue after coal tar extraction into a high-performance coal tar-based nickel catalyst. Compared with catalysts prepared by the traditional impregnation method, it has a higher specific surface area, higher active metal loading, and contains porous carbon materials with micropores. It can be used to catalyze the hydrothermal liquefaction of biomass, exhibiting high selectivity and easy-to-control and optimize performance. It is an ideal low-cost, high-performance catalytic material for the development of new clean and renewable energy using coal tar.

[0041] The present invention also provides a coal tar pitch-based nickel catalyst prepared by the preparation method described in the above technical solution.

[0042] The coal tar-based nickel catalyst provided by this invention has a 1,8-dimethylaminonaphthyl carbamate-like functional structural unit, which plays a key role in the stable anchoring of Ni species and the construction of active sites, and is an important structural basis for the formation of highly efficient nickel-supported catalysts.

[0043] The coal tar pitch-based nickel catalyst provided by this invention can solve the environmental problem of harmless treatment of waste coal tar pitch, and provide a new path for the resource utilization of solid waste and the low-cost preparation of high-end functional materials.

[0044] The present invention also provides the application of the coal tar pitch-based nickel catalyst described in the above technical solution in the catalytic hydrothermal liquefaction reaction of biomass.

[0045] The present invention does not impose any special limitations on the specific operation of the application, which can be determined based on the technical common sense of those skilled in the art.

[0046] In one embodiment of the present invention, the application can be carried out by: mixing coal tar pitch-based nickel catalyst, biomass, and water evenly, then conducting a hydrothermal liquefaction reaction in a nitrogen atmosphere, and finally filtering. In the present invention, the biomass can be cotton stalks; the mass ratio of the coal tar pitch-based nickel catalyst to biomass can be (0.005~0.05):1, or (0.01~0.02):1; the mass ratio of water to biomass can be (5~15):1, or 10:1; the holding temperature of the hydrothermal liquefaction reaction can be 240~280℃, or 260℃; the holding time of the hydrothermal liquefaction reaction can be 10~30min, or 20min; the heating rate to the holding temperature of the hydrothermal liquefaction reaction can be 2~5℃ / min, or 3~4℃ / min.

[0047] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0048] Example 1 A coal tar pitch-based nickel catalyst comprises the following steps: (1) After pulverizing the coal tar pitch, extract it with the extractant in a Soxhlet extractor until the extractant in the extraction tube of the Soxhlet extractor no longer changes color. After taking it out, dry it in a forced-air drying oven at 80°C, and finally grind it to obtain extracted coal tar pitch with a particle size of 100 mesh. The elemental composition of the coal tar pitch by mass percentage is: carbon 79.35%, nitrogen 1.01%, hydrogen 3.36%, sulfur 0.93% and oxygen 15.35%. The extractant is n-heptane. The mass ratio of the coal tar pitch to the extractant is 1:10. The extraction temperature is 101°C. (2) The extracted coal tar pitch and nickel nitrate hexahydrate obtained in step (1) are mixed and placed in a ceramic boat. The ceramic boat is placed in a tube furnace and carbonized under a nitrogen atmosphere to obtain a coal tar pitch-based nickel catalyst. The mass of the nickel nitrate hexahydrate is 7% of the mass of the extracted coal tar pitch. The carbonization holding temperature is 600℃ and the holding time is 3h. The heating rate to the carbonization holding temperature is 5℃ / min.

[0049] Example 2 In step (2), the mass of nickel nitrate hexahydrate is 8% of the mass of the extracted coal tar pitch, and other conditions are the same as in Example 1.

[0050] Example 3 In step (2), the mass of nickel nitrate hexahydrate is 9% of the mass of the extracted coal tar pitch, and other conditions are the same as in Example 1.

[0051] Example 4 In step (2), the mass of nickel nitrate hexahydrate is 10% of the mass of the extracted coal tar pitch, and other conditions are the same as in Example 1.

[0052] Example 5 In step (2), the mass of nickel nitrate hexahydrate is 11% of the mass of the extracted coal tar pitch, and other conditions are the same as in Example 1.

[0053] Comparative Example 1 A coal tar pitch-based nickel catalyst comprises the following steps: (1) After pulverizing the coal tar pitch, extract it with the extractant in a Soxhlet extractor until the extractant in the extraction tube of the Soxhlet extractor no longer changes color. After taking it out, dry it in a forced-air drying oven at 80°C, and finally grind it to obtain extracted coal tar pitch with a particle size of 100 mesh. The elemental composition of the coal tar pitch by mass percentage is: carbon 79.35%, nitrogen 1.01%, hydrogen 3.36%, sulfur 0.93% and oxygen 15.35%. The extractant is n-heptane. The mass ratio of the coal tar pitch to the extractant is 1:10. The extraction temperature is 101°C. (2) The extracted coal tar obtained in step (1) is placed in a ceramic boat, and the ceramic boat is placed in a tube furnace and carbonized under a nitrogen atmosphere to obtain a coal tar-based nickel catalyst; the carbonization holding temperature is 600℃ and the holding time is 3h; the heating rate to the carbonization holding temperature is 5℃ / min.

[0054] The coal tar-based nickel catalyst obtained in Example 4 was observed using a scanning electron microscope (SEM), and the resulting SEM images are shown below. Figure 1 As shown.

[0055] The coal tar pitch-based nickel catalysts obtained in Examples 1-5 were observed using X-ray diffraction, and the obtained XRD patterns are shown below. Figure 2 As shown.

[0056] Depend on Figure 1 and Figure 2 It can be seen that the structural performance of the coal tar pitch-based nickel catalysts obtained in Examples 1-5 is ranked as follows: Example 4 > Example 5 > Example 3 > Example 2 > Example 1, which directly confirms that the dosage of nickel nitrate hexahydrate has a significant regulatory effect on the catalyst structure.

[0057] The structural characteristics of the coal tar pitch-based nickel catalyst obtained in Example 4 are shown in Table 1: Table 1. Structural characteristics of the coal tar pitch-based nickel catalyst prepared in Example 4

[0058] In Table 1, S BET V is the specific surface area. P Let D be the volume of the pore. P The average pore size shows that the microporous structure of the coal tar-based nickel catalyst is highly developed and the pore size distribution is concentrated. This indicates that by optimizing the preparation process of the coal tar-based nickel catalyst, the pore structure parameters can be precisely controlled, thereby adapting it to different application scenarios.

[0059] The performance of the coal tar pitch-based nickel catalysts prepared in Examples 1-5 and Comparative Example 1 in catalytic liquefaction of biomass was tested, and the test steps are as follows: The hydrothermal liquefaction of catalytic biomass was tested using a high-pressure reactor (MSG100-P7-T5-SS1-SV-R) from Kemei Instruments. Coal tar pitch, nickel catalyst, biomass, and water were added to the reactor and mixed thoroughly. The biomass was cotton stalks. The mass ratio of coal tar pitch, nickel catalyst, and biomass was 0.01:1, and the mass ratio of water to biomass was 10:1. The reactor was then purged with nitrogen. The temperature was then increased to 260℃ at a rate of 3℃ / min for 20 minutes for hydrothermal liquefaction. After the reaction, the solid waste was filtered out and dried in an oven at 80℃ for 24 hours. The solid waste conversion rate was calculated, and the results are shown below. Figure 3 As shown, Figure 3 The blank group in the figure is the control group that does not add coal pitch or nickel catalyst for hydrothermal liquefaction reaction.

[0060] Depend on Figure 3 It can be seen that, compared with Examples 1, 2, 3 and 5, the coal tar pitch-based catalyst prepared in Example 4 exhibits superior catalytic performance in the hydrothermal liquefaction of biomass, with its solid waste conversion rate increasing to 68.15%. Meanwhile, the coal tar pitch-based catalysts prepared in Examples 1 to 5 all show significantly higher catalytic performance in the hydrothermal liquefaction of biomass than Comparative Example 1, indicating that the coal tar pitch-based catalyst prepared in this invention has great potential in the hydrothermal liquefaction of biomass.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a coal tar pitch-based nickel catalyst, comprising the following steps: (1) Coal tar pitch and extractant are mixed and then extracted to obtain extracted coal tar pitch; (2) The extracted coal tar obtained in step (1) is mixed with nickel nitrate hexahydrate and then carbonized to obtain a coal tar-based nickel catalyst.

2. The preparation method according to claim 1, characterized in that, The elemental composition of the coal tar pitch in step (1) by mass percentage includes: 75-85% carbon, 0.5-1.5% nitrogen, 2-5% hydrogen, 0.5-1.5% sulfur and 10-20% oxygen.

3. The preparation method according to claim 1, characterized in that, In step (1), the extractant is any one or more of n-heptane, n-hexane, and n-octane; the extraction method is extraction in a Soxhlet extractor.

4. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of coal tar pitch to extractant is 1:(5~10).

5. The preparation method according to claim 1, characterized in that, The extraction temperature in step (1) is 80~130℃.

6. The preparation method according to claim 1, characterized in that, In step (1), the particle size of the coal tar pitch after extraction is 50~200 mesh.

7. The preparation method according to claim 1, characterized in that, In step (2), the mass of nickel nitrate hexahydrate is 5-20% of the mass of the extracted coal tar pitch.

8. The preparation method according to claim 1, characterized in that, The carbonization holding temperature in step (2) is 550~900℃; the carbonization holding time is 1~4h; and the carbonization atmosphere is nitrogen.

9. The coal tar pitch-based nickel catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the coal tar pitch-based nickel catalyst of claim 9 in the catalytic hydrothermal liquefaction reaction of biomass.

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