Coal gasification energy-saving low-carbon composite catalyst and preparation method thereof

Abstract

This invention discloses an energy-saving and low-carbon composite catalyst for coal gasification and its preparation method, belonging to the field of coal gasification and catalytic chemistry technology. The catalyst comprises a cobalt-molybdenum-based heterojunction nanocomposite active phase, a core-shell structured composite support, and an alkaline earth-rare earth composite additive. The composite support consists of a thermally conductive ceramic particle core and a mesoporous cerium-zirconium composite oxide solid solution shell completely encapsulating it. The preparation method includes: firstly, constructing the core-shell support and loading the additive through a deposition-precipitation method and calcination in an inert atmosphere; then, sequentially impregnating it with molybdenum followed by cobalt; and finally, programmatic in-situ carbonization or nitriding under a specific atmosphere to form Co-Mo. x C y Or Co‑Mo x N y Heterojunction active phase. This catalyst can achieve high efficiency catalysis under intermediate temperature conditions, with high syngas selectivity, and maintains high stability under harsh sulfur-containing conditions over a long period of time, while also having the advantages of significant energy saving, high carbon efficiency and long lifespan.

Description

Technical Field

[0001] This invention relates to the field of coal gasification and catalytic chemistry, specifically to an energy-saving and low-carbon composite catalyst for coal gasification and its preparation method. Background Technology

[0002] Coal-to-gas, also known as coal-based syngas production, is the process of converting coal into syngas through gasification or reforming, and it is a leading technology in coal chemical industry. Traditional coal-to-gas catalysts, such as some nickel-based catalysts, typically focus on increasing the total yield of CO and H2, but they face the following challenges in practical industrial applications: 1. The reaction requires high temperatures and consumes a lot of energy; 2. Insufficient control over side reactions such as methanation and coking leads to unsatisfactory selectivity of effective syngas (CO and H2), resulting in carbon atoms failing to be efficiently converted into the target product, and low economic efficiency and carbon efficiency. 3. Catalysts are prone to deactivation in high temperature and high moisture environments.

[0003] Energy conservation and low carbon emissions are the core directions for the sustainable development of coal chemical industry. Therefore, it is of great significance to develop a novel catalyst that can efficiently activate coal-based molecules, suppress ineffective side reactions, and guide carbon atoms to the target syngas products to the maximum extent under relatively mild conditions, thereby achieving energy conservation and carbon emission reduction in the process. Summary of the Invention

[0004] In view of this, and in view of the shortcomings of the prior art, the present invention aims to provide an energy-saving and low-carbon composite catalyst for coal gasification and its preparation method. The catalyst, by designing composite active centers, promotes the activation of CO bonds while precisely controlling the conversion pathway of surface carbon species, thereby achieving high syngas yield and selectivity at lower temperatures and possessing excellent anti-carbon deposition stability.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an energy-saving and low-carbon composite catalyst for coal-to-gas production, comprising a composite support, an active component, and a supported additive; the active component is a cobalt-molybdenum-based heterojunction nanocomposite active phase; the composite support has a core-shell structure, with the core being thermally conductive ceramic particles and the outer shell being a mesoporous cerium-zirconium composite oxide solid solution layer completely encapsulating the core, wherein the general formula of the cerium-zirconium composite oxide solid solution is Ce. x Zr 1-x O2, where 0.4≤x≤0.6; the loading agent is a composite of alkaline earth metal oxides and rare earth metal oxides in the form of doping and / or loading in the cerium-zirconium composite oxide solid solution layer or loaded on the surface of the cerium-zirconium composite oxide solid solution layer.

[0006] As a further aspect of the present invention, the thermally conductive ceramic particles are selected from silicon nitride (Si3N4), silicon carbide (SiC), or aluminum nitride (AlN) completely covered by the outer shell.

[0007] As a further embodiment of the present invention, the core is a thermally conductive ceramic particle with an average particle size of 50-500 nm; the outer shell is a mesoporous cerium-zirconium composite oxide solid solution layer with a thickness of 5-50 nm that completely covers the surface of the thermally conductive ceramic particle.

[0008] As a further aspect of the present invention, based on the total mass of the catalyst, the content of each component is as follows: the content of the active component calculated as cobalt (Co) is 5-15 wt%, the content of the active component calculated as molybdenum (Mo) is 2-12 wt%, and the molar ratio of cobalt to molybdenum is 1:0.2 to 1:0.8; the content of the thermally conductive ceramic core is 30-60 wt%; the content of the cerium-zirconium composite oxide solid solution shell is 20-50 wt%; and the content of the supported additive is 1-5 wt%.

[0009] As a further aspect of the present invention, the BET specific surface area of ​​the cerium-zirconium composite oxide solid solution shell is 50-150 m². 2 / g, with a most probable pore size of 5-20 nm.

[0010] As a further aspect of the present invention, in the active component, cobalt exists in the form of metal nanoparticles with an average particle size of 3-10 nm; the cobalt-molybdenum-based heterojunction nanocomposite active phase is cobalt-molybdenum carbide (Co-Mo). x C y Heterojunction or Co-Mo nitride (Co-Mo) x N y Heterogeneous junction.

[0011] As a further embodiment of the present invention, the loading agent is a complex of strontium oxide (SrO) and lanthanum oxide (La2O3), or a complex of barium oxide (BaO) and yttrium oxide (Y2O3).

[0012] Secondly, the present invention also provides a method for preparing an energy-saving and low-carbon composite catalyst for coal-to-gas production, comprising the following steps: S1. Preparation of core-shell structured carrier: Using thermally conductive ceramic particles with an average particle size of 50-500 nm as the core, a cerium-zirconium composite hydroxide precursor is uniformly deposited on the surface of the core using a deposition-precipitation method under pH conditions of 8-11. After drying, the core is calcined at 700-850℃ for 2-6 hours in a non-oxidizing or inert atmosphere to form a mesoporous cerium-zirconium composite oxide solid solution shell with a thickness of 5-50 nm, thus obtaining the core-shell structured carrier. S2. Loading agent: Using the impregnation method, a soluble salt solution containing alkaline earth metals and rare earth metals is loaded onto the core-shell structure carrier obtained in step S1. After drying, it is calcined in air at 500-700℃ for 2-5 hours to obtain a composite carrier with loading agent. S3. Sequential loading of cobalt and molybdenum precursors: Using an equal-volume impregnation method, the molybdenum source solution is first loaded onto the composite support obtained in step S2, dried, and pre-calcined in air at 300-450°C for 2-4 hours. Then, the cobalt source solution is loaded onto the composite support and dried to obtain the catalyst precursor. S4. Programmed in-situ carbonization or nitriding: The catalyst precursor obtained in step S3 is placed in a reactor and heated to the target temperature at a rate of 1-5℃ / min under a reducing atmosphere and kept at a constant temperature to reduce cobalt species to metallic cobalt. At the same time, molybdenum species are converted in situ to molybdenum carbide or molybdenum nitride and form a heterojunction with cobalt. After cooling, an energy-saving and low-carbon composite catalyst for coal gasification is obtained.

[0013] As a further aspect of the present invention, in step S4, the conditions for the programmed in-situ carbonization are as follows: in a mixed atmosphere consisting of 5-20% methane, 20-50% hydrogen and the remainder being an inert gas, the temperature is increased to 550-700℃ at a rate of 1-3℃ / min, and the temperature is maintained for 2-5 hours.

[0014] As a further aspect of the present invention, in step S4, the conditions for the programmed in-situ nitriding are as follows: in a mixed atmosphere consisting of ammonia with a volume concentration of 10-50%, hydrogen with a volume concentration of 20-50%, and the remainder being an inert gas, the temperature is increased to 450-600°C at a rate of 1-3°C / min, and the temperature is maintained for 3-6 hours.

[0015] As a further aspect of the present invention, in step S1, the non-oxidizing or inert atmosphere is nitrogen, argon, or a mixture thereof; in steps S2 and S3, the drying temperature is 80-120°C, and the time is 6-12 hours.

[0016] Compared with existing technologies, the energy-saving and low-carbon composite catalyst for coal gasification and its preparation method of the present invention solve the problems of high energy consumption, low carbon efficiency, and easy catalyst deactivation in the coal gasification process, and have the following beneficial effects: 1. Significant energy-saving and consumption-reducing effects: The catalyst core in this invention uses a ceramic material with high thermal conductivity, which can efficiently dissipate the heat of reaction, avoid local overheating, and optimize the reactor temperature field. Combined with Co-Mo x C y / Mo x N yThe synergistic activation of CH and CO bonds by heterojunctions at the nanoscale enables this catalyst to achieve high activity in the medium temperature range of 50-100℃ lower than that of traditional processes, thereby significantly reducing the heat energy consumption of gasification and reforming units and correspondingly reducing the requirements for equipment materials.

[0017] 2. Excellent low-carbon and high-carbon atom economy: The heterojunction active sites in this invention can precisely catalyze C / C bond breaking and effectively suppress side reactions such as deep hydrogenation and excessive cracking. In simulated coal tar reforming evaluation, the syngas exhibits high selectivity and stability, maximizing the orientation of carbon atoms towards the target product. This is achieved through Ce in the outer shell. x Zr 1-x The combination of the dynamic oxygen storage capacity of O2 solid solution and the ability of heterojunction to activate oxygen-containing species can effectively convert by-product CO2 and H2O back into CO through reverse water vapor shift, realizing the internal carbon cycle of the process and improving the overall carbon atom utilization rate.

[0018] 3. Possesses excellent resistance to deactivation and ultra-long lifespan: Ce x Zr 1-x The oxygen-storing capacity of the O2 shell helps to oxidize and remove surface carbon species; Mo x C y / Mo x N y It inherently possesses excellent anti-carbon deposition properties; the high thermal conductivity core prevents catalytic coking caused by heat accumulation, and the triple mechanism ensures the cleanliness of the catalyst surface; the fully encapsulated core-shell support structure provides a robust and inert framework for the active center, effectively isolating it from the erosion of active components by high temperatures. Moreover, through sequential loading of molybdenum followed by cobalt and programmed in-situ derivatization, a Co-Mo catalyst was constructed. x C y / Mo x N y Heterojunctions are true nanoscale composite active centers, rather than simple mixtures, and can achieve functional integration of hydrogen activation, CH bond breaking and CO bond activation, and oxygen-containing species transformation.

[0019] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to specific embodiments. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.

[0021] Example 1 This embodiment provides a method for preparing an energy-saving and low-carbon composite catalyst for coal-to-gas production, which has the following composition: Co 10 wt%, Mo 6 wt% (Co:Mo molar ratio ≈ 1:0.5), SiC core 45 wt%, Ce0.5 Zr 0.5 A coal-to-gas energy-saving and low-carbon composite catalyst, consisting of a 35wt% O2 shell and a 4wt% SrO-La2O3 composite additive, is named sample C-1. Its preparation steps are as follows: Step S1: Preparation of core-shell structured support (CZO@SiC): 1. Raw materials: silicon carbide (SiC) powder with an average particle size of about 150 nm, cerium nitrate hexahydrate ((NH4)2Ce(NO3)6), zirconium nitrate pentahydrate (ZrO(NO3)2·5H2O), ammonia (precipitant), citric acid (complexing agent).

[0022] 2. Weigh 4.5 g of SiC powder and ultrasonically disperse it in 200 mL of deionized water. Separately prepare a mixed salt solution: dissolve 16.7 g of cerium nitrate and 4.4 g of zirconium oxynitrate (Ce:Zr molar ratio = 1:1) in 100 mL of deionized water, add 12.0 g of citric acid, and stir to dissolve. Under continuous stirring and a 60°C water bath, add the mixed salt solution and dilute ammonia (pH = 9.5) dropwise to the SiC suspension. After the addition is complete, continue stirring and aging for 6 hours.

[0023] 3. The obtained slurry was filtered, washed, and dried at 110℃ for 12 hours. The dried powder was placed in a tube furnace and calcined at 750℃ under a pure N2 atmosphere at a rate of 2℃ / min for 4 hours. After natural cooling, Ce-coated powder was obtained. 0.5 Zr 0.5 Core-shell carrier with an O2 (CZO) outer shell (CZO@SiC).

[0024] Step S2: Preparation of the supporting agent (SrO-La2O3): 1. Raw materials: Strontium nitrate, lanthanum nitrate hexahydrate.

[0025] 2. Take 5.0 g of the CZO@SiC support obtained in step S1. Prepare the impregnation solution: Dissolve 0.32 g of strontium nitrate and 0.52 g of lanthanum nitrate hexahydrate (at a final catalyst SrO:La2O3 mass ratio of approximately 1:1) in deionized water to prepare an equal volume impregnation solution. Apply this solution uniformly to the support and allow it to stand at room temperature for 12 hours.

[0026] 3. After drying at 110℃ for 8 hours, the temperature is increased to 600℃ in air at 2℃ / min and calcined for 3 hours to obtain a composite carrier loaded with additives, denoted as (Sr,La) / CZO@SiC.

[0027] Step S3: Sequentially load cobalt and molybdenum precursors: 1. Raw materials: ammonium molybdate, cobalt nitrate hexahydrate.

[0028] 2. Procedure: Take 5.0 g of the (Sr,La) / CZO@SiC support obtained in step S2.

[0029] a. Molybdenum loading: Prepare an ammonium molybdate solution (containing 0.3 g of Mo), impregnate with an equal volume, let stand at room temperature for 12 hours, dry at 110°C for 6 hours, and then pre-calcine in air at 380°C for 3 hours.

[0030] b. Supported cobalt: Prepare a cobalt nitrate solution (containing 0.5 g of Co), impregnate the above material with an equal volume, let it stand at room temperature for 12 hours, and dry it at 110°C for 10 hours to obtain the catalyst precursor.

[0031] Step S4, Programmed in-situ carbonization (construction of Co-Mo2C heterojunction): 1. Condition setting: The precursor obtained in step S3 is loaded into the quartz tube reactor.

[0032] 2. Carbonization treatment: A mixed gas consisting of 10% CH4, 40% H2 and 50% Ar (volume ratio) is introduced, with a total gas space velocity of 2000 h⁻¹. -1 The temperature was programmed to rise to 600°C at a rate of 2°C / min and then held at that temperature for 4 hours.

[0033] 3. After the reaction is complete, the sample is cooled to room temperature under an Ar atmosphere to obtain the final catalyst sample, denoted as C-1.

[0034] The catalyst sample (C-1) prepared above was determined by inductively coupled plasma atomic emission spectrometry to have a Co content of 9.8 wt% and a Mo content of 5.9 wt%, which meets the preparation requirements.

[0035] Example 2 This embodiment provides a method for preparing an energy-saving and low-carbon composite catalyst for coal-to-gas production, which has the following composition: Co 8 wt%, Mo 5 wt% (Co:Mo molar ratio ≈ 1:0.54), Si3N4 core 50 wt%, Ce 0.45 Zr 0.55 A coal-to-gas energy-saving and low-carbon composite catalyst, consisting of a 35 wt% O2 shell and a 2 wt% BaO-Y2O3 composite additive, is named sample C-2. Its preparation steps are as follows: Step S1: Preparation of core-shell structured support (CZO@Si3N4): 1. Raw materials: silicon nitride (Si3N4) powder with an average particle size of about 200 nm, cerium nitrate hexahydrate, zirconium nitrate pentahydrate, ammonium carbonate (precipitant), tartaric acid (complexing agent).

[0036] 2. Weigh 5.0 g of Si3N4 powder and disperse it in 200 mL of deionized water. Prepare a mixed salt solution: Dissolve 13.4 g of cerium nitrate and 5.3 g of zirconium oxynitrate (Ce:Zr molar ratio = 0.45:0.55) in 100 mL of water, and add 10.0 g of tartaric acid. Under continuous stirring and at 50 °C, add the mixed salt solution and 1.0 M ammonium carbonate solution (pH = 10.0) dropwise to the Si3N4 suspension. After the addition is complete, age the solution for 8 hours.

[0037] 3. Filter, wash, and dry at 120℃ for 10 hours. Place the material in an atmosphere furnace and calcine at 800℃ for 5 hours under argon protection, heating at 3℃ / min to obtain the CZO@Si3N4 support.

[0038] Step S2: Preparation of the supporting agent (BaO-Y2O3): 1. Raw materials: barium nitrate, yttrium nitrate hexahydrate.

[0039] 2. Take 5.0 g of CZO@Si3N4 support. Prepare the impregnation solution: Mix 0.13 g of barium nitrate and 0.12 g of yttrium nitrate hexahydrate (at a mass ratio of BaO:Y2O3 of approximately 1:1) to form an equal volume solution. Impregnate and let stand for 12 hours.

[0040] 3. After drying at 100℃ for 10 hours, the composite support was calcined in air at 650℃ for 2.5 hours to obtain (Ba,Y) / CZO@Si3N4.

[0041] Step S3: Sequentially load cobalt and molybdenum precursors: 1. Raw materials: ammonium molybdate, cobalt nitrate hexahydrate.

[0042] 2. Procedure: Take 5.0 g of (Ba,Y) / CZO@Si3N4 support.

[0043] a. Molybdenum-loaded: Impregnate with an equal volume of ammonium molybdate solution containing 0.25 g Mo, let stand, dry at 100°C for 8 hours, and then pre-calcine in air at 420°C for 2 hours.

[0044] b. Cobalt-loaded precursor: Impregnated with an equal volume of cobalt nitrate solution containing 0.4 g Co, allowed to stand, and then dried at 100°C for 12 hours to obtain the precursor.

[0045] Step S4, Programmed in-situ nitriding (construction of Co-Mo2N heterojunction): 1. Condition setting: Load the precursor into the reaction tube.

[0046] 2. A mixture of 30% NH3, 30% H2 and 40% Ar is introduced at a space velocity of 1500 h⁻¹. -1The temperature was increased to 500℃ at a rate of 1.5℃ / min and kept constant for 5 hours.

[0047] 3. Cool to room temperature in Ar to obtain the catalyst sample, denoted as C-2.

[0048] The catalyst sample (C-2) prepared above was determined by inductively coupled plasma atomic emission spectrometry, and its Co content was 7.9 wt% and Mo content was 4.9 wt%, which met the preparation requirements.

[0049] Example 3 This embodiment provides a method for preparing an energy-saving and low-carbon composite catalyst for coal-to-gas production. The catalyst has the following composition: Co 12 wt%, Mo 8 wt% (Co:Mo molar ratio ≈ 1:0.58), AlN core 40 wt%, Ce 0.6 Zr 0.4 A coal-to-gas energy-saving and low-carbon composite catalyst, consisting of a 35 wt% O2 shell and a 5 wt% SrO-La2O3 composite additive, is named sample C-3. Its preparation steps are as follows: Step S1: Preparation of core-shell structured support (CZO@AlN): 1. Raw materials: aluminum nitride (AlN) powder with an average particle size of about 100 nm, cerium nitrate hexahydrate, zirconium nitrate pentahydrate, urea (homogeneous precipitant), citric acid.

[0050] 2. Weigh 4.0 g of AlN powder and ultrasonically disperse it in 200 mL of deionized water. Prepare a mixed salt solution: Dissolve 23.9 g of cerium nitrate and 6.6 g of zirconium oxynitrate (Ce:Zr molar ratio = 0.6:0.4) in 100 mL of water, and add 18.0 g of citric acid. Heat the AlN suspension to 90°C and add 20 g of urea. While stirring, add the above mixed salt solution dropwise. Slowly increase the pH by utilizing the decomposition of urea, react at 90°C, and age for 6 hours.

[0051] 3. Filter, wash, and dry at 120℃ for 12 hours. Place the material in a tube furnace and calcine at 720℃ for 5 hours under a high-purity argon atmosphere, increasing the temperature at 2℃ / min. This inert atmosphere calcination is crucial to prevent the AlN core from being oxidized at high temperatures, ensuring the formation of a fully and densely coated CZO@AlN support.

[0052] Step S2: Preparation of the supporting agent (SrO-La2O3): 1. Take 5.0 g of CZO@AlN support. Prepare an impregnation solution containing 0.29 g of strontium nitrate and 0.47 g of lanthanum nitrate of equal volume. After impregnation and standing, dry at 110℃ for 10 hours, and then calcine in air at 550℃ for 4 hours to obtain (Sr,La) / CZO@AlN composite support.

[0053] Step S3: Sequentially load cobalt and molybdenum precursors: 1. Procedure: Take 5.0 g of the above-mentioned carrier.

[0054] a. Molybdenum-loaded: Impregnated with an ammonium molybdate solution containing 0.4 g Mo, dried, and then pre-calcined in air at 350°C for 3 hours.

[0055] b. Loaded cobalt: Impregnated with a cobalt nitrate solution containing 0.6 g Co, and dried to obtain the precursor.

[0056] Step S4, Programmed in-situ carbonization (construction of Co-Mo2C heterojunction): 1. In an atmosphere of 15% CH4, 35% H2, and 50% Ar, the temperature was increased to 650℃ at a rate of 2℃ / min and held at that temperature for 3 hours. After cooling, catalyst C-3 was obtained.

[0057] The catalyst sample (C-3) prepared above was determined by inductively coupled plasma atomic emission spectrometry, and its Co content was 11.8 wt% and Mo content was 7.9 wt%, which met the preparation requirements.

[0058] Comparative experiment: The performance of catalysts C-1 from Example 1 to C-3 from Example 3 was evaluated, and the catalysts were selected as follows: C-1 (Example 1): Co-Mo2C heterojunction / (Sr,La) / CZO@SiC; Ref-Cat (Comparative Example 1): Conventional Co-Mo / Al2O3 sulfur-resistant shift catalyst (used after sulfidation); C-2 (Example 2): Co-Mo2N heterojunction / (Ba,Y) / CZO@Si3N4; Ref-HA (Comparative Example 2): Highly active Ni / γ-Al2O3 catalyst (used after reduction); C-3 (Example 3): Co-Mo2C heterojunction / (Sr,La) / CZO@AlN; Com-Cat (Comparative Example 3): Commercial Co-Mo / Al2O3 sulfur-resistant shift catalyst (used after sulfidation).

[0059] Performance testing objectives and conditions: Example 1 was compared with Comparative Example 1 to verify the initial activity, selectivity, and energy-saving potential of the catalyst in Example 1 of the present invention at intermediate temperatures. The reactant used in the evaluation conditions was 1-methylnaphthalene; the temperature was 750°C to investigate the intermediate-temperature activity; the pressure was 2.5 MPa; the evaluation duration was 100 hours; and the evaluation indicators were 1-methylnaphthalene conversion, syngas (CO+H2) selectivity, methane (CH4) selectivity, and activity decay rate after 100 hours.

[0060] Example 2 was compared with Comparative Example 2 to verify the long-term stability, anti-carbon deposition ability, and material versatility of the catalyst in Example 2 of the present invention when treating complex raw materials. The reactants under the evaluation conditions were a mixture of naphthalene, phenanthrene, anthracene, and quinoline simulating tar; the temperature was 780℃; the pressure was 3.0 MPa; the evaluation time was 200 hours; and the evaluation indicators were TOC conversion rate, syngas (CO+H2) selectivity, methane (CH4) selectivity, and activity decay rate after 200 hours.

[0061] Example 3 was compared with Comparative Example 3 to verify the sulfur resistance, resistance to operational fluctuations, and ultimate stability of the catalyst of Example 3 of the present invention under harsh conditions close to the industrial limit. The reactants for the evaluation conditions were sulfur-containing model tar containing benzothiophene; the temperature was 760°C; the fluctuating operation was carried out by periodically subjecting thermal shocks at 760°C→820°C→760°C over a period of 100-200 hours; the evaluation duration was 300 hours; and the evaluation indicators were the TOC conversion rate under the baseline conditions, the syngas selectivity under the baseline conditions, the CH4 selectivity under the baseline conditions, and the activity decay rate after 300 hours.

[0062] The evaluation results of Examples 1, 2, and 3 and their corresponding comparative catalysts are as follows:

[0063] The above tests show that, under the same lower reaction temperature of 750°C, the conversion rate of the catalyst (C-1) in Example 1 (99.2%) is significantly higher than that of the conventional industrial catalyst (87.5%), demonstrating that the Co-Mo of the present invention... x C y / Mo x N y The heterojunction active phase can effectively reduce the activation energy of CH and CO bonds, enabling efficient conversion at lower temperatures than existing technologies, directly reducing process heat consumption and demonstrating clear energy-saving advantages.

[0064] In all embodiments 1 to 3 above, the syngas selectivity (C-1: 96.5%, C-2: 95.8%, C-3: 94.5%) of the catalyst of the present invention remained consistently at an extremely high level, while the methane selectivity (C-1: 1.8%, C-2: 2.5%, C-3: 3.0%) was effectively suppressed to an extremely low level. In contrast, the methane selectivity (7.5%-15.3%) of all comparative examples was significantly higher. This demonstrates that the catalyst design of the present invention can precisely guide carbon atoms to the target syngas product, almost suppressing the pathway for generating the low-value byproduct methane, thereby significantly improving the utilization efficiency of carbon resources and reducing the implicit carbon emissions per unit product.

[0065] In long-cycle (200-300 hours) evaluations using complex sulfur-containing feedstocks, the catalysts (C-2, C-3) of Examples 2 and 3 of this invention exhibited extremely low carbon deposition (C-3 only 2.1 wt%), high activity retention (C-2: 96%, C-3: 92%), and no increase in bed pressure drop. In contrast, the comparative examples showed severe carbon deposition (Comparative Example 3 reached 15.8 wt%), significant activity decline, and bed blockage. This is attributed to the synergistic effect of the dynamic oxygen storage and carbon removal of the CZO shell, the heterojunction's own resistance to carbon deposition, and the high thermal conductivity core preventing local overheating. Example 3 demonstrates that the catalyst exhibits stable performance under fluctuating conditions of sulfur content and periodic thermal shock, demonstrating good sulfur resistance and resistance to operational fluctuations.

[0066] The three examples described above (Examples 1, 2, and 3) employed different core materials (SiC, Si3N4, AlN), different active phase types (Mo2C, Mo2N), and different combinations of promoters, yet all yielded high-performance catalysts. This strongly demonstrates the broad feasibility and universality of the technical solutions protected by the claims of this invention, rather than being limited to specific ratios or materials. Furthermore, Example 3 successfully addressed the potential stability issues of AlN in the application environment, confirming the rigor and reliability of the preparation method of this invention.

[0067] This invention provides an energy-saving and low-carbon composite catalyst for coal-to-gas production and its preparation method. Through the integrated design of a heterojunction active phase and a bifunctional core-shell support, a catalytic material with high activity at low temperatures, ultra-high syngas selectivity, and extreme resistance to deactivation is successfully prepared. This energy-saving and low-carbon composite catalyst for coal-to-gas production can simultaneously achieve the core objectives of energy saving and consumption reduction, improved carbon efficiency, and long-term operation, effectively breaking through the performance bottlenecks of existing coal-to-gas catalysts and possessing high inventiveness, practicality, and industrial application prospects.

[0068] The preferred embodiments of the present invention have been described in detail above. However, the present invention 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 the present invention.

Claims

1. A coal-to-gas energy-saving and low-carbon composite catalyst, characterized in that, Includes composite carriers, active components, and loading aids; The active component is a cobalt-molybdenum-based heterojunction nanocomposite active phase; the composite carrier has a core-shell structure, with the core being thermally conductive ceramic particles and the outer shell being a mesoporous cerium-zirconium composite oxide solid solution layer completely encapsulating the core, the general formula of which is Ce. x Zr 1-x O2, where 0.4≤x≤0.6; the loading agent is a composite of alkaline earth metal oxides and rare earth metal oxides in the form of doping and / or loading in the cerium-zirconium composite oxide solid solution layer or loaded on the surface of the cerium-zirconium composite oxide solid solution layer.

2. The energy-saving and low-carbon composite catalyst for coal-to-gas production according to claim 1, characterized in that, The thermally conductive ceramic particles are selected from silicon nitride, silicon carbide, or aluminum nitride completely covered by the outer shell.

3. The energy-saving and low-carbon composite catalyst for coal-to-gas production according to claim 1, characterized in that, The core consists of thermally conductive ceramic particles with an average particle size of 50-500 nm; the outer shell consists of a mesoporous cerium-zirconium composite oxide solid solution layer with a thickness of 5-50 nm that completely covers the surface of the thermally conductive ceramic particles.

4. The energy-saving and low-carbon composite catalyst for coal-to-gasification according to claim 1, characterized in that, Based on the total mass of the catalyst, the contents of each component are as follows: the active component content based on cobalt is 5-15 wt%, the active component content based on molybdenum is 2-12 wt%, and the molar ratio of cobalt to molybdenum is 1:0.2 to 1:0.8; the content of the thermally conductive ceramic core is 30-60 wt%; the content of the cerium-zirconium composite oxide solid solution shell is 20-50 wt%; and the content of the supported additive is 1-5 wt%.

5. The energy-saving and low-carbon composite catalyst for coal-to-gas production according to claim 4, characterized in that, The BET specific surface area of ​​the cerium-zirconium composite oxide solid solution shell is 50-150 m². 2 / g, with a most probable pore size of 5-20 nm.

6. The energy-saving and low-carbon composite catalyst for coal-to-gas production according to claim 1, characterized in that, In the active component, cobalt exists in the form of metal nanoparticles with an average particle size of 3-10 nm; the cobalt-molybdenum-based heterojunction nanocomposite active phase is a cobalt-molybdenum carbide heterojunction or a cobalt-molybdenum nitride heterojunction.

7. The energy-saving and low-carbon composite catalyst for coal-to-gas production according to claim 1, characterized in that, The loading agent is a complex of strontium oxide and lanthanum oxide, or a complex of barium oxide and yttrium oxide.

8. A method for preparing an energy-saving and low-carbon composite catalyst for coal-to-gas production as described in any one of claims 1-7, characterized in that, The steps are as follows: S1. Preparation of core-shell structured carrier: Using thermally conductive ceramic particles with an average particle size of 50-500 nm as the core, a cerium-zirconium composite hydroxide precursor is uniformly deposited on the surface of the core using a deposition-precipitation method under pH conditions of 8-11. After drying, the core is calcined at 700-850℃ for 2-6 hours in a non-oxidizing or inert atmosphere to form a mesoporous cerium-zirconium composite oxide solid solution shell with a thickness of 5-50 nm, thus obtaining the core-shell structured carrier. S2. Loading agent: Using the impregnation method, a soluble salt solution containing alkaline earth metals and rare earth metals is loaded onto the core-shell structure carrier obtained in step S1. After drying, it is calcined in air at 500-700℃ for 2-5 hours to obtain a composite carrier with loading agent. S3. Sequential loading of cobalt and molybdenum precursors: Using an equal-volume impregnation method, the molybdenum source solution is first loaded onto the composite support obtained in step S2, dried, and pre-calcined in air at 300-450°C for 2-4 hours. Then, the cobalt source solution is loaded onto the composite support and dried to obtain the catalyst precursor. S4. Programmed in-situ carbonization or nitriding: The catalyst precursor obtained in step S3 is placed in a reactor and heated to the target temperature at a rate of 1-5℃ / min under a reducing atmosphere and kept at a constant temperature to reduce cobalt species to metallic cobalt. At the same time, molybdenum species are converted in situ to molybdenum carbide or molybdenum nitride and form a heterojunction with cobalt. After cooling, an energy-saving and low-carbon composite catalyst for coal gasification is obtained.

9. The preparation method of the energy-saving and low-carbon composite catalyst for coal gasification according to claim 8, characterized in that, In step S4, the conditions for the programmed in-situ carbonization are as follows: in a mixed atmosphere consisting of 5-20% methane, 20-50% hydrogen and the remainder being inert gas, the temperature is increased to 550-700℃ at a rate of 1-3℃ / min, and the temperature is maintained for 2-5 hours.

10. The preparation method of the energy-saving and low-carbon composite catalyst for coal-to-gasification according to claim 8, characterized in that, In step S4, the conditions for the programmed in-situ nitriding are as follows: in a mixed atmosphere consisting of 10-50% ammonia, 20-50% hydrogen and the remainder being inert gas, the temperature is increased to 450-600℃ at a rate of 1-3℃ / min and then kept at that temperature for 3-6 hours.

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