Coal tar cracking catalyst, its preparation method and application

Abstract

The application belongs to the technical field of coal chemical industry and energy catalytic material, and discloses a coal tar cracking catalyst, a preparation method and application thereof, a heterojunction composite carrier is constructed by two-dimensional graphite phase carbon nitride (g-C3N4) and graphene oxide (GO) to enhance electron migration and thermal stability; a nickel-cerium bimetallic oxide (NiO-CeO2) is uniformly loaded on the surface of the heterojunction to form a strong coupling interface and play a synergistic effect; through a controllable preparation method (such as hydrothermal synthesis combined with impregnation calcination), the microstructure can be adjusted and controlled to ensure that the catalyst has high activity, high selectivity and long service life in coal tar cracking.

Description

Technical Field

[0001] This application belongs to the field of coal chemical and energy catalytic materials technology, specifically relating to a coal tar cracking catalyst, its preparation method and application. Background Technology

[0002] Coal tar cracking is an important coal chemical technology, commonly used to convert coal tar into valuable petroleum products. Traditional coal tar cracking catalysts typically use porous materials (such as Al₂O₃, SiO₂, TiO₂, etc.) as supports, and load transition metals or their compounds (such as Ni, Mo, W, Co) as active metal centers. Existing catalysts are prone to catalyst poisoning, deactivation, and metal particle aggregation during operation.

[0003] The problems and disadvantages of traditional coal tar cracking catalysts are as follows:

[0004] 1. Insufficient catalyst activity and selectivity;

[0005] Traditional coal tar cracking catalysts (such as NiO / SiO2, MoO3 / Al2O3, etc.) have limited cracking efficiency for polycyclic aromatic hydrocarbons and high molecular weight components in coal tar, often resulting in incomplete cracking and the generation of many by-products.

[0006] Reasons: The single metal component has limited active centers, making it difficult to simultaneously achieve hydrogenation and aromatization; poor metal dispersibility leads to insufficient effective active sites.

[0007] 2. The catalyst deactivates quickly and has a short lifespan;

[0008] Traditional catalysts are prone to rapid deactivation during the cracking process due to carbon buildup or metal sintering, resulting in a shortened catalytic life.

[0009] Reasons: Coal tar contains a large amount of polycyclic aromatic hydrocarbons and heteroatom compounds (N, S, O), which are prone to condensation and coking at metal active sites; metal oxide particles are prone to agglomeration under high temperature conditions, reducing dispersion and thus reducing effective active sites.

[0010] 3. Low metal utilization and poor dispersibility;

[0011] In traditional catalysts, metal particles are unevenly distributed on the support surface, and some metals are in an agglomerated state, resulting in the waste of active components.

[0012] Reasons: Traditional catalysts (such as Al2O3 and SiO2) lack controllable interfacial interactions on their surfaces, making it difficult to suppress the migration and aggregation of metal particles; the weak interaction between the metal and the support makes it easy for metal particles to sinter at high temperatures.

[0013] 4. The catalyst has poor structural stability;

[0014] Coal tar cracking is a high-temperature, high-reduction environment where conventional metal oxides are prone to reduction, aggregation, and structural disintegration, which reduces catalyst stability.

[0015] Reasons: The pore structure of traditional carriers is prone to collapse, which leads to a decrease in specific surface area after long-term use; metal oxides undergo phase transformation or agglomeration at high temperatures, which destroys the microstructure of the catalyst.

[0016] 5. Environmental protection and recycling issues;

[0017] Traditional catalysts suffer from severe carbon buildup during use, and frequent regeneration not only increases energy consumption but can also lead to metal loss and performance degradation. Some catalysts also contain toxic or scarce elements (such as Mo, W, and Co), which are detrimental to green and sustainable applications.

[0018] Reasons: Traditional catalysts are insufficient in terms of structural regulation and anti-coking ability, resulting in low regeneration efficiency; the regeneration process (such as coking) can easily cause instability in the metal redox cycle, thereby reducing the catalyst life.

[0019] In summary, most catalysts used in current coal tar cracking processes suffer from several problems, such as insufficient catalytic activity, poor selectivity, short catalyst life, and poor metal dispersion. Therefore, developing a novel coal tar viscosity reducer has great market potential. Summary of the Invention

[0020] The purpose of this application is to address the problems of the prior art by providing a coal tar cracking catalyst, its preparation method, and its application.

[0021] To solve the technical problem, the technical solution of this application is: a method for preparing a coal tar cracking catalyst, comprising the following steps:

[0022] Step 1: Construction of heterojunction carrier;

[0023] Step 1-1: Prepare two-dimensional graphitic carbon nitride g-C3N4 by calcining urea or melamine;

[0024] Steps 1-2: Graphene oxide solution is ultrasonically dispersed and then mixed with two-dimensional graphitic carbon nitride g-C3N4. The concentration of graphene oxide solution is 2 mg / mL and the ratio of graphene oxide solution to two-dimensional graphitic carbon nitride g-C3N4 is 2:1. The heterojunction composite carrier is formed by sol-gel or hydrothermal method.

[0025] Step 2: Introduction of nickel-cerium bimetallic oxide; using co-precipitation or impregnation methods, nickel salt and cerium salt are uniformly loaded onto the surface of the heterojunction composite carrier. The molar ratio of nickel salt to cerium salt is x:y, and the range of x:y is 1:1 to 3:1. The amount ratio of nickel salt to heterojunction composite carrier is 3.5:1. After drying and high-temperature calcination, highly dispersed NiCe(x:y) / g-C3N4 / GO nanoparticles are formed.

[0026] Preferably, step 1-1 specifically involves: weighing urea or melamine and placing it in a covered alumina crucible, then placing it in a muffle furnace. In the muffle furnace, the temperature is increased from room temperature to 550°C at a rate of 5°C / min, and held at 550°C for 4-6 hours. After naturally cooling to room temperature, the resulting pale yellow block is removed and ground into powder to obtain bulk g-C3N4 powder.

[0027] Bulk g-C3N4 powder was dispersed in deionized water to obtain a dispersion. The ratio of bulk g-C3N4 powder to deionized water was 1 mg: 1~1.5 mL. The dispersion was sonicated for 8~10 hours at 500 W. The dispersion was then centrifuged at 8000~1000 rpm for 20~40 minutes. The upper milky white suspension was collected and freeze-dried to obtain two-dimensional graphitic carbon nitride g-C3N4 powder.

[0028] Preferably, steps 1-2 are as follows: two-dimensional graphitic carbon nitride (g-C3N4) powder is weighed and dispersed in deionized water at a ratio of 1 mg to 2-2.5 mL. The mixture is sonicated for 30-40 minutes to ensure full dispersion. Then, graphene oxide solution is added and sonicated for another 1-2 hours. The mixture is then transferred to a round-bottom flask and refluxed in an 80°C water bath with magnetic stirring at 300-400 rpm for 12-14 hours. After the reaction is complete, the mixture is filtered and washed three times with deionized water. The filter cake is dried in an 80°C oven for 12-14 hours and then ground to obtain the g-C3N4 / GO heterojunction composite carrier.

[0029] Preferably, step 2 specifically comprises:

[0030] Step 2-1: Prepare the metal salt solution; Weigh Ni(NO3)2·6H2O and Ce(NO3)3·6H2O, with the molar ratio of Ni to Ce in Ni(NO3)2·6H2O and Ce(NO3)3·6H2O being 1:1 to 3:1, and dissolve them together in deionized water. The ratio of Ni(NO3)2·6H2O and Ce(NO3)3·6H2O to deionized water is 0.025 to 0.055 g / mL. Stir magnetically for 30 to 40 minutes until completely dissolved to obtain the metal salt solution.

[0031] Step 2-2: Equal volume impregnation; Weigh M g of g-C3N4 / GO heterojunction composite carrier, calculate its pore volume as A mL / g, and the required volume of metal salt solution is A. M mL, using the equal-volume impregnation method, slowly and dropwise add A using a pipette. M mL of metal salt solution was added to the g-C3N4 / GO heterojunction composite carrier while stirring to ensure uniform adsorption of the solution, resulting in the impregnated wet material.

[0032] Steps 2-3: Drying and calcination: The impregnated wet material is aged at room temperature for 12-14 hours, then dried in an 80 °C forced-air drying oven for 6-8 hours. The dried precursor powder is placed in a ceramic boat and placed in a tube furnace. Under a nitrogen atmosphere, the temperature is increased to 400 °C at a flow rate of 100 mL / min and a rate of 2 °C / min. The material is then calcined at this temperature for 4-6 hours. After natural cooling, the final catalyst sample, NiCe(x:y) / g-C3N4 / GO nanoparticles, is obtained.

[0033] Preferably, a coal tar cracking catalyst is prepared by the method described above, wherein the catalyst is NiCe(x:y) / g-C3N4 / GO nanoparticles, and the x:y ratio ranges from 1:1 to 3:1.

[0034] Preferably, the catalyst is NiCe(x:y) / g-C3N4 / GO nanoparticles, with an x:y ratio of 2:1.

[0035] Preferably, the application of a coal tar cracking catalyst is carried out by the aforementioned method for preparing a coal tar cracking catalyst, and the application steps of the catalyst are as follows:

[0036] Step 1: The pretreated catalyst NiCe(x:y) / g-C3N4 / GO nanoparticles are uniformly packed into the reactor, with a catalyst mass of 10~12g;

[0037] Step 2: Start the reactor, set the reaction temperature to 500℃, and the coal tar feed rate to 5 mL / h;

[0038] Step 3: During the reaction, monitor the temperature and pressure in real time to maintain the stable operation of the system. After the reaction is completed, perform qualitative and quantitative analysis of the product by gas chromatography and liquid chromatography.

[0039] Compared with the prior art, the advantages of this application are:

[0040] (1) This application proposes a coal tar cracking catalyst, which uses two-dimensional graphitic carbon nitride (g-C3N4) and graphene oxide (GO) to construct a heterojunction composite support to enhance electron migration and thermal stability; nickel-cerium bimetallic oxide (NiO-CeO2) is uniformly loaded on the surface of the heterojunction to form a strong coupling interface and exert a synergistic effect; the microstructure can be controlled by a controllable preparation method (such as hydrothermal synthesis combined with impregnation and calcination) to ensure that the catalyst has high activity, high selectivity and long life in coal tar cracking;

[0041] (2) This application constructs a heterojunction composite support through the two-dimensional structure of g-C3N4 and GO, which effectively inhibits electron-hole recombination and enhances the number of active sites on the catalyst surface; the heterojunction composite support endows the catalyst with excellent electron transport performance and thermal stability, and improves the rate of free radical reaction in coal tar cracking;

[0042] (3) The nickel-cerium bimetallic oxide of this application has a synergistic effect. Nickel promotes C–C bond breaking and dehydrogenation reaction, and improves the yield of light oil fraction. The redox properties of cerium provide oxygen vacancies, enhance the resistance to poisoning and the catalyst regeneration ability, and the catalyst still maintains excellent performance in multiple cycles of use. Nickel and cerium form an interface synergistic effect, which improves the controllability of product distribution and reduces coke deposition.

[0043] (4) This application has high efficiency in coal tar conversion. Compared with traditional catalysts, the catalyst of this invention can achieve high conversion rate at a lower pyrolysis temperature; it can significantly reduce by-product coke and increase the yield of liquid fuels and combustible gases; it has excellent stability and reusability.

[0044] (5) The catalyst of this application has high activity and can achieve high pyrolysis conversion rate under medium and low temperature conditions; it has high selectivity, improves the yield of liquid fuel and gaseous fuel, and reduces coke generation; it has strong resistance to poisoning, and the nickel-cerium bimetallic oxide effectively resists the poisoning effect of nitrogen, sulfur and oxygen compounds; the synergistic effect of g-C3N4 / GO heterojunction composite support and NiO-CeO2 nanoparticles achieves the activity and stability that traditional catalysts cannot achieve simultaneously; the catalyst of this application can effectively improve the conversion rate and reduce coke generation in the coal tar pyrolysis process, and has good catalytic performance and long-term stability, making it suitable for industrial application. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the heterojunction composite support structure constructed from two-dimensional graphitic carbon nitride (g-C3N4) and graphene oxide (GO) in this application.

[0046] Figure 2 This is a schematic diagram of the nickel-cerium bimetallic oxide (NiO-CeO2) supported on a heterojunction composite carrier according to this application.

[0047] Figure 3 The graph shows the conversion rate of the catalyst in this application at different temperatures;

[0048] Figure 4 This is a distribution diagram of the cracking products of the catalyst in this application;

[0049] Figure 5 This is a graph showing the activity decay of the catalyst in this application;

[0050] Figure 6 This is a graph showing the metal dispersion of the catalyst in this application.

[0051] Explanation of reference numerals in the attached figures:

[0052] 1-Two-dimensional graphitic carbon nitride (g-C3N4);

[0053] 2-Graphene oxide (GO);

[0054] 3-Heterojunction interface (g-C3N4 / GO);

[0055] 4-NiO-CeO2 (NiO-CeO2);

[0056] 5-Heterogeneous composite carrier. Detailed Implementation

[0057] The present application is described in detail below with reference to the accompanying drawings and specific embodiments, but the present application is not limited to these embodiments. The present application covers any alternatives, modifications, equivalent methods, and solutions made within the spirit and scope of the present application. To provide the public with a thorough understanding of the present application, specific details are described in detail in the following embodiments, but those skilled in the art will fully understand the present application even without these detailed descriptions.

[0058] This application discloses a method for preparing a coal tar cracking catalyst, comprising the following steps:

[0059] Step 1: Construction of heterojunction carrier;

[0060] Step 1-1: Prepare two-dimensional graphitic carbon nitride g-C3N4 by calcining urea or melamine;

[0061] Steps 1-2: Graphene oxide solution is ultrasonically dispersed and then mixed with two-dimensional graphitic carbon nitride g-C3N4. The concentration of graphene oxide solution is 2 mg / mL and the ratio of graphene oxide solution to two-dimensional graphitic carbon nitride g-C3N4 is 2:1. The heterojunction composite carrier is formed by sol-gel or hydrothermal method.

[0062] Step 2: Introduction of nickel-cerium bimetallic oxide; using co-precipitation or impregnation methods, nickel salt and cerium salt are uniformly loaded onto the surface of the heterojunction composite carrier. The molar ratio of nickel salt to cerium salt is x:y, and the range of x:y is 1:1 to 3:1. The amount ratio of nickel salt to heterojunction composite carrier is 3.5:1. After drying and high-temperature calcination, highly dispersed NiCe(x:y) / g-C3N4 / GO nanoparticles are formed.

[0063] Preferably, step 1-1 specifically involves: weighing urea or melamine and placing it in a covered alumina crucible, then placing it in a muffle furnace. In the muffle furnace, the temperature is increased from room temperature to 550°C at a rate of 5°C / min, and held at 550°C for 4-6 hours. After naturally cooling to room temperature, the resulting pale yellow block is removed and ground into powder to obtain bulk g-C3N4 powder.

[0064] Bulk g-C3N4 powder was dispersed in deionized water to obtain a dispersion. The ratio of bulk g-C3N4 powder to deionized water was 1 mg: 1~1.5 mL. The dispersion was sonicated for 8~10 hours at 500 W. The dispersion was then centrifuged at 8000~1000 rpm for 20~40 minutes. The upper milky white suspension was collected and freeze-dried to obtain two-dimensional graphitic carbon nitride g-C3N4 powder.

[0065] Preferably, steps 1-2 are as follows: two-dimensional graphitic carbon nitride (g-C3N4) powder is weighed and dispersed in deionized water at a ratio of 1 mg to 2-2.5 mL. The mixture is sonicated for 30-40 minutes to ensure full dispersion. Then, graphene oxide solution is added and sonicated for another 1-2 hours. The mixture is then transferred to a round-bottom flask and refluxed in an 80°C water bath with magnetic stirring at 300-400 rpm for 12-14 hours. After the reaction is complete, the mixture is filtered and washed three times with deionized water. The filter cake is dried in an 80°C oven for 12-14 hours and then ground to obtain the g-C3N4 / GO heterojunction composite carrier.

[0066] Preferably, step 2 specifically comprises:

[0067] Step 2-1: Prepare the metal salt solution; Weigh Ni(NO3)2·6H2O and Ce(NO3)3·6H2O, with the molar ratio of Ni to Ce in Ni(NO3)2·6H2O and Ce(NO3)3·6H2O being 1:1 to 3:1, and dissolve them together in deionized water. The ratio of Ni(NO3)2·6H2O and Ce(NO3)3·6H2O to deionized water is 0.025 to 0.055 g / mL. Stir magnetically for 30 to 40 minutes until completely dissolved to obtain the metal salt solution.

[0068] Step 2-2: Equal volume impregnation; Weigh M g of g-C3N4 / GO heterojunction composite carrier, calculate its pore volume as A mL / g, and the required volume of metal salt solution is A. M mL, using the equal-volume impregnation method, slowly and dropwise add A using a pipette. M mL of metal salt solution was added to the g-C3N4 / GO heterojunction composite carrier while stirring to ensure uniform adsorption of the solution, resulting in the impregnated wet material.

[0069] Steps 2-3: Drying and calcination: The impregnated wet material is aged at room temperature for 12-14 hours, then dried in an 80 °C forced-air drying oven for 6-8 hours. The dried precursor powder is placed in a ceramic boat and placed in a tube furnace. Under a nitrogen atmosphere, the temperature is increased to 400 °C at a flow rate of 100 mL / min and a rate of 2 °C / min. The material is then calcined at this temperature for 4-6 hours. After natural cooling, the final catalyst sample, NiCe(x:y) / g-C3N4 / GO nanoparticles, is obtained.

[0070] Preferably, a coal tar cracking catalyst is prepared by the method described above, wherein the catalyst is NiCe(x:y) / g-C3N4 / GO nanoparticles, and the x:y ratio ranges from 1:1 to 3:1.

[0071] Preferably, the catalyst is NiCe(x:y) / g-C3N4 / GO nanoparticles, with an x:y ratio of 2:1.

[0072] Preferably, the application of a coal tar cracking catalyst is carried out by the aforementioned method for preparing a coal tar cracking catalyst, and the application steps of the catalyst are as follows:

[0073] Step 1: The pretreated catalyst NiCe(x:y) / g-C3N4 / GO nanoparticles are uniformly packed into the reactor, with a catalyst mass of 10~12g;

[0074] Step 2: Start the reactor, set the reaction temperature to 500℃, and the coal tar feed rate to 5 mL / h;

[0075] Step 3: During the reaction, monitor the temperature and pressure in real time to maintain the stable operation of the system. After the reaction is completed, perform qualitative and quantitative analysis of the product by gas chromatography and liquid chromatography.

[0076] Example 1

[0077] Preparation of g-C3N4 / GO heterojunction supported NiO-CeO2 catalyst (Ni / Ce molar ratio 2:1).

[0078] 1. Raw materials and equipment;

[0079] Main ingredients:

[0080] Urea (analytical grade, Sinopharm Group);

[0081] Graphene oxide (GO) dispersion (2 mg / mL, sheet diameter 0.5~5 μm, Nanjing Xianfeng Nanomaterials).

[0082] Nickel nitrate hexahydrate (Ni(NO3)2·6H2O, analytical grade, Aladdin);

[0083] Cerium nitrate hexahydrate (Ce(NO3)3·6H2O, analytical grade, Aladdin);

[0084] Deionized water;

[0085] Main equipment:

[0086] Muffle furnace (SX-G07123, Tianjin Zhonghuan Electric Furnace);

[0087] Forced-air drying oven (DHG-9070A, Shanghai Jinghong);

[0088] Ultrasonic cleaner (KQ-500DE, Kunshan Ultrasonic);

[0089] Heat-collecting constant temperature magnetic stirrer (DF-101S, Zhengzhou Kefeng);

[0090] Vacuum filtration device;

[0091] Tube furnace (OTF-1200X, Hefei Kejing);

[0092] 2. Preparation steps;

[0093] Step 1: Preparation of g-C3N4;

[0094] Weigh 30g of urea and place it in a covered alumina crucible, then place it in a muffle furnace. In the muffle furnace, heat the urea from room temperature to 550°C at a rate of 5°C / min, and hold at 550°C for 4 hours. After naturally cooling to room temperature, remove the resulting pale yellow block, grind it into powder, and obtain the bulk phase g-C3N4.

[0095] To further exfoliate into thinner nanosheets, 200 mg of the above bulk g-C3N4 powder was dispersed in 200 mL of deionized water and sonicated (500 W) for 8 hours. Subsequently, the dispersion was centrifuged at 8000 rpm for 20 minutes, and the upper milky white suspension was collected and freeze-dried to obtain two-dimensional g-C3N4 nanosheet powder.

[0096] Step 2: Construction of the g-C3N4 / GO heterojunction support;

[0097] Weigh 100 mg of the prepared g-C3N4 nanosheet powder and disperse it in 200 mL of deionized water. Sonicate for 30 minutes to ensure thorough dispersion. Then, add 100 mL of GO dispersion (containing 200 mg of GO) and continue sonicating for 1 hour. Transfer the mixture to a 500 mL round-bottom flask and reflux in an 80 °C water bath with magnetic stirring (300 rpm) for 12 hours. After the reaction, filter the mixture, wash three times with deionized water, and dry the filter cake in an 80 °C oven for 12 hours. Grind the dried cake to obtain the g-C3N4 / GO heterojunction composite support, as shown below. Figure 1 As shown, 1 is two-dimensional graphitic carbon nitride (g-C3N4), 2 is graphene oxide (GO), and 3 (-----) is a heterojunction interface (g-C3N4 / GO).

[0098] Step 3: Loading of NiO-CeO2 bimetallic oxide;

[0099] a. Preparation of metal salt solution: Accurately weigh 1.746 g Ni(NO3)2·6H2O (corresponding to 0.6 mmol of Ni element) and 0.868 g Ce(NO3)3·6H2O (corresponding to 0.3 mmol of Ce element), dissolve them together in 50 mL of deionized water, and stir magnetically for 30 minutes until completely dissolved to obtain a solution with a total metal concentration of 0.018 mol / L (Ni / Ce molar ratio of 2:1).

[0100] b. Equal-volume impregnation: Weigh 500 mg of the g-C3N4 / GO heterojunction composite carrier prepared in step two. Calculate its pore volume to be approximately 0.8 mL / g, therefore the required impregnation liquid volume is approximately 0.4 mL. Using the equal-volume impregnation method, slowly and dropwise add 0.4 mL of the above metal salt solution to the carrier powder with a pipette, stirring continuously to ensure uniform adsorption.

[0101] c. Drying and calcination: The impregnated wet material was aged at room temperature for 12 hours, and then dried in an 80 °C forced-air drying oven for 6 hours. The dried precursor powder was placed in a ceramic boat, placed in a tube furnace, and heated to 400 °C at a rate of 2 °C / min under a nitrogen atmosphere (flow rate 100 mL / min), and calcined at this temperature for 4 hours. After natural cooling, the final catalyst sample was obtained, denoted as NiCe(2:1) / g-C3N4 / GO.

[0102] Example 2

[0103] Step 1: Preparation of g-C3N4;

[0104] Weigh 30g of urea and place it in a covered alumina crucible, then place it in a muffle furnace. In the muffle furnace, heat the urea from room temperature to 550°C at a rate of 5°C / min, and hold at 550°C for 6 hours. After naturally cooling to room temperature, remove the resulting pale yellow block, grind it into powder, and obtain the bulk phase g-C3N4.

[0105] To further exfoliate into thinner nanosheets, 200 mg of the above bulk g-C3N4 powder was dispersed in 300 mL of deionized water and sonicated (500 W) for 10 hours. Subsequently, the dispersion was centrifuged at 9000 rpm for 25 minutes, and the upper milky white suspension was collected and freeze-dried to obtain two-dimensional g-C3N4 nanosheet powder.

[0106] Step 2: Construction of the g-C3N4 / GO heterojunction support;

[0107] Weigh 100 mg of the prepared g-C3N4 nanosheet powder and disperse it in 250 mL of deionized water. Sonicate for 40 minutes to ensure complete dispersion. Then, add 100 mL of GO dispersion (containing 200 mg of GO) and continue sonicating for 2 hours. Transfer the mixture to a 500 mL round-bottom flask and reflux in an 80 °C water bath with magnetic stirring (300 rpm) for 14 hours. After the reaction, filter the mixture, wash three times with deionized water, and dry the filter cake in an 80 °C oven for 14 hours. Grind the dried cake to obtain the g-C3N4 / GO heterojunction composite support.

[0108] Step 3: Loading of NiO-CeO2 bimetallic oxide;

[0109] a. Preparation of metal salt solution: Accurately weigh 0.873 g Ni(NO3)2·6H2O (corresponding to 0.3 mmol of Ni element) and 0.868 g Ce(NO3)3·6H2O (corresponding to 0.3 mmol of Ce element), dissolve them together in 50 mL of deionized water, and stir magnetically for 30 minutes until completely dissolved to obtain a solution with a total metal concentration of 0.018 mol / L (Ni / Ce molar ratio of 1:1).

[0110] b. Equal-volume impregnation: Weigh 500 mg of the g-C3N4 / GO heterojunction composite carrier prepared in step two. Calculate its pore volume to be approximately 0.8 mL / g, therefore the required impregnation liquid volume is approximately 0.4 mL. Using the equal-volume impregnation method, slowly and dropwise add 0.4 mL of the above metal salt solution to the carrier powder with a pipette, stirring continuously to ensure uniform adsorption.

[0111] c. Drying and calcination: The impregnated wet material was aged at room temperature for 12 hours, and then dried in an 80 °C forced-air drying oven for 6 hours. The dried precursor powder was placed in a ceramic boat and then placed in a tube furnace. Under a nitrogen atmosphere (flow rate 100 mL / min), the temperature was increased to 400 °C at a rate of 2 °C / min, and calcined at this temperature for 4 hours. After natural cooling, the final catalyst sample was obtained, denoted as NiCe(1:1) / g-C3N4 / GO.

[0112] like Figure 2 As shown, 4 is a nickel-cerium bimetallic oxide (NiO-CeO2), and 5 is a g-C3N4 / GO heterojunction composite support. The nickel-cerium bimetallic oxide is loaded on the surface of the heterojunction composite support.

[0113] Application Example 1

[0114] 1. Experimental setup:

[0115] This experiment uses a fixed-bed reactor, which is filled with an appropriate amount of catalyst and connected to an atmosphere control system and a temperature control system. Coal tar feedstock is introduced into the reactor through the feed inlet at the bottom, and pyrolysis products are collected through the exhaust outlet at the top. The temperature inside the reactor is controlled between 450 and 600°C, and the coal tar pyrolysis reaction is carried out under normal pressure.

[0116] 2. Experimental steps:

[0117] The pretreated catalyst (NiCe(2:1) / g-C3N4 / GO) was uniformly packed into the reactor, with a catalyst mass of 10 g.

[0118] Start the reactor, set the reaction temperature to 500℃, and the coal tar feed rate to 5 mL / h.

[0119] During the reaction, temperature and pressure are monitored in real time to maintain stable system operation.

[0120] After the reaction was completed, the products were qualitatively and quantitatively analyzed by gas chromatography and liquid chromatography.

[0121] 3. Experimental Results and Data:

[0122] a. Reaction conversion rate:

[0123] In the experiment, the conversion rate of coal tar was significantly improved compared with that of traditional catalysts.

[0124] like Figure 3 As shown, at 500℃, the coal tar conversion rate reached 85% when using the NiCe(2:1) / g-C3N4 / GO catalyst, compared to only 70% for conventional catalysts (such as single Ni or Ce catalysts).

[0125] Results analysis: The catalyst still exhibits high conversion efficiency at lower temperatures (e.g., 450℃), and the conversion rate reaches its maximum at 500℃, proving that the catalyst has high catalytic efficiency in the medium to high temperature range.

[0126] b. Product distribution:

[0127] Product analysis shows that, for example Figure 4 As shown: Light oil (C5-C) in the cracking products 12 Combustible gases (C1-C4) account for 60%, combustible gases (C1-C4) account for 25%, while coke production accounts for only 15%.

[0128] Compared to traditional catalysts, the amount of coke produced is reduced by about 30%, significantly reducing coke accumulation.

[0129] c. Catalyst stability and lifetime:

[0130] Catalyst activity decay: such as Figure 5 As shown, after five repeated uses, the catalyst's catalytic activity remained above 80% of its initial value, demonstrating that the catalyst possesses good regeneration capability and stability.

[0131] Metal dispersion analysis: such as Figure 6 As shown, analysis using high-resolution transmission electron microscopy (HRTEM) revealed that nickel and cerium in the catalyst exhibited good dispersion with no obvious agglomeration. The figure also showed that the nickel and cerium metal oxides were uniformly distributed, further demonstrating their excellent dispersibility.

[0132] 4. Data Analysis:

[0133] Relationship between temperature and conversion rate:

[0134] Within the reaction temperature range of 450℃ to 600℃, the conversion rate shows an increasing trend as the temperature rises.

[0135] The conversion rate reached its highest level of 85% at 500℃, but decreased slightly at 600℃, possibly due to side reactions caused by excessively high temperatures.

[0136] Relationship between coke formation and conversion rate:

[0137] When using this catalyst, the amount of coke produced is low, which is inversely related to the higher conversion rate. This indicates that the catalyst can effectively promote the cracking of coal tar without producing excessive solid byproducts.

[0138] This application proposes a coal tar cracking catalyst, which constructs a heterojunction composite support using two-dimensional graphitic carbon nitride (g-C3N4) and graphene oxide (GO) to enhance electron migration and thermal stability; uniformly loads nickel-cerium bimetallic oxide (NiO-CeO2) on the surface of the heterojunction to form a strong coupling interface and exert a synergistic effect; and achieves tunable microstructure through controllable preparation methods (such as hydrothermal synthesis combined with impregnation and calcination) to ensure that the catalyst has high activity, high selectivity and long lifespan in coal tar cracking.

[0139] This application constructs a heterojunction composite support through a two-dimensional structure of g-C3N4 and GO, which effectively suppresses electron-hole recombination and enhances the number of active sites on the catalyst surface. The heterojunction composite support endows the catalyst with excellent electron transport performance and thermal stability, thereby increasing the rate of free radical reaction in coal tar cracking.

[0140] The nickel-cerium bimetallic oxide of this application exhibits a synergistic effect. Nickel promotes C–C bond breaking and dehydrogenation reactions, thereby increasing the yield of light oil fractions. The redox properties of cerium provide oxygen vacancies, enhancing resistance to poisoning and catalyst regeneration capabilities, allowing the catalyst to maintain excellent performance even after multiple cycles of use. The synergistic effect of nickel and cerium at the interface improves the controllability of product distribution and reduces coke deposition.

[0141] This application demonstrates highly efficient coal tar conversion performance. Compared with traditional catalysts, the catalyst of this invention can achieve high conversion rates at lower pyrolysis temperatures; it can significantly reduce by-product coke and increase the yield of liquid fuels and combustible gases; and it possesses excellent stability and reusability.

[0142] The catalyst of this application exhibits high activity, achieving high pyrolysis conversion rates under medium and low temperature conditions; it also demonstrates high selectivity, improving the yield of liquid and gaseous fuels while reducing coke formation; it possesses strong resistance to poisoning, with the nickel-cerium bimetallic oxide effectively resisting the poisoning effects of nitrogen-, sulfur-, and oxygen-containing compounds; the synergistic effect of the g-C3N4 / GO heterojunction composite support and NiO-CeO2 nanoparticles achieves a balance between activity and stability that traditional catalysts cannot simultaneously achieve; the catalyst of this application can effectively improve the conversion rate and reduce coke formation during coal tar pyrolysis, and possesses good catalytic performance and long-term stability, making it suitable for industrial applications.

[0143] The preferred embodiments of this application have been described in detail above. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application.

[0144] Many other changes and modifications can be made without departing from the concept and scope of this application. It should be understood that this application is not limited to the specific embodiments, and the scope of this application is defined by the appended claims.

Claims

1. A method for preparing a coal tar cracking catalyst, characterized by, The method comprises the following steps: Step 1: Heterojunction carrier construction; Step 1-1: preparing two-dimensional graphite phase carbon nitride g-C3N4 by calcining urea or melamine; Step 1-2: dispersing by ultrasonic wave using graphene oxide solution, and mixing after dispersion, wherein the concentration of the graphene oxide solution is 2 mg / mL, and the use amount ratio of the graphene oxide solution to the two-dimensional graphite phase carbon nitride g-C3N4 is 2:1, to form a heterojunction composite carrier; The step 1-2 is specifically as follows: two-dimensional graphite phase carbon nitride g-C3N4 powder is weighed and dispersed in deionized water, the use amount ratio of the two-dimensional graphite phase carbon nitride g-C3N4 powder to the deionized water is 1 mg:2-2.5 mL, ultrasonic wave is applied for 30-40 minutes to fully disperse, then the graphene oxide solution is added, and ultrasonic wave is continuously applied for 1-2 hours, the mixture is transferred to a round bottom flask, and magnetic stirring is applied for reflux reaction at 80°C for 12-14 hours, the rotating speed is 300-400 rpm, after the reaction is completed, the mixture is subjected to suction filtration, washed with deionized water for three times, and the filter cake is dried in a 80°C air drying oven for 12-14 hours, and after grinding, the g-C3N4 / GO heterojunction composite carrier is obtained; Step 2: introducing nickel-cerium double metal oxide; the nickel salt and the cerium salt are uniformly loaded on the surface of the heterojunction composite carrier by a coprecipitation method or an impregnation method, the molar ratio of the nickel salt to the cerium salt is x:y, the range of x:y is 1:1-3:1, and the use amount ratio of the nickel salt to the heterojunction composite carrier is 3.5:1, and through drying and high-temperature calcination, the highly dispersed NiCe(x:y) / g-C3N4 / GO nanoparticles are formed.

2. The method for preparing a coal tar cracking catalyst according to claim 1, characterized in that: The step 1-1 is specifically as follows: urea or melamine is weighed and placed in an alumina crucible with a cover, the alumina crucible is placed in a muffle furnace, the temperature is raised from room temperature to 550°C at a rate of 5°C / min in the muffle furnace, and the temperature is kept at 550°C for 4-6 hours, after natural cooling to room temperature, the obtained light yellow block is taken out and ground into powder to obtain the bulk g-C3N4 powder; The bulk g-C3N4 powder is dispersed in deionized water to obtain a dispersion liquid, the use amount ratio of the bulk g-C3N4 powder to the deionized water is 1 mg:1-1.5 mL, ultrasonic treatment is applied for 8-10 hours at a power of 500 W, the dispersion liquid is centrifuged at a rotating speed of 8000-1000 rpm for 20-40 minutes, the upper layer of milky white suspension liquid is collected, and after freeze drying, the two-dimensional graphite phase carbon nitride g-C3N4 powder is obtained.

3. The method for preparing a coal tar cracking catalyst according to claim 1, characterized in that: The step 2 is specifically as follows: Step 2-1: preparing a metal salt solution; Ni(NO3)2·6H2O and Ce(NO3)3·6H2O are weighed, the molar ratio of Ni element to Ce element in the Ni(NO3)2·6H2O and the Ce(NO3)3·6H2O is 1:1-3:1, the Ni(NO3)2·6H2O and the Ce(NO3)3·6H2O are dissolved in deionized water, the use amount ratio of the Ni(NO3)2·6H2O and the Ce(NO3)3·6H2O to the deionized water is 0.025-0.055 g / mL, and the metal salt solution is obtained after magnetic stirring for 30-40 minutes until complete dissolution; Step 2-2: equal volume impregnation; weigh the g-C3N4 / GO heterojunction composite carrier of Mg, calculate its pore volume as A mL / g, and the volume of metal salt solution needed is A M mL, using equal volume impregnation method, slowly and drop by drop using a pipette to add A M mL of metal salt solution into the g-C3N4 / GO heterojunction composite carrier, stirring while adding to ensure uniform adsorption of the solution, obtaining the impregnated wet material; Step 2-3: Drying and calcination: The impregnated wet material is aged at room temperature for 12-14 hours, then dried in a 80 °C air drying oven for 6-8 hours. The dried precursor powder is placed in a porcelain boat and put into a tube furnace. The temperature is raised to 400 °C at a rate of 2 °C / min under nitrogen atmosphere with a flow rate of 100 mL / min, and calcined at this temperature for 4-6 hours. After natural cooling, the final catalyst sample, NiCe(x:y) / g-C3N4 / GO nanoparticles, is obtained.

4. A coal tar cracking catalyst characterized by, The catalyst is NiCe(x:y) / g-C3N4 / GO nanoparticles, and the ratio of x:y is 2:

1.

5. The coal tar cracking catalyst according to claim 4, characterized by, The catalyst is NiCe(x:y) / g-C3N4 / GO nanoparticles, and the ratio of x:y is 2:

1.

6. Use of a coal tar cracking catalyst, characterized in that, The catalyst is prepared by the preparation method of a coal tar cracking catalyst according to any one of claims 1-3, and the application steps of the catalyst are as follows: Step 1: The pretreated catalyst NiCe(x:y) / g-C3N4 / GO nanoparticles are uniformly filled into the reactor, and the mass of the catalyst is 10-12 g; Step 2: Start the reactor and set the reaction temperature to 500 °C, and the coal tar feeding rate to 5 mL / h; Step 3: During the reaction, the temperature and pressure are monitored in real time to maintain the stable operation of the system. After the reaction is completed, the products are qualitatively and quantitatively analyzed by gas chromatography and liquid chromatography.

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