Chemical-looping methane dry reforming catalyst as well as preparation method and application thereof

Abstract

The invention discloses a chemical-looping methane dry reforming catalyst as well as a preparation method and application thereof, and belongs to the technical field of energy catalytic materials and chemical-looping reactions. The catalyst is composed of cerium dioxide and platinum, and the molar percentage content of platinum is 1.00%-4.00%. The preparation method of the catalyst comprises the following steps: (1) dissolving cerous nitrate and chloroplatinic acid in water to obtain a precursor solution; (2) under the condition of intense stirring, heating, adding a precipitant, carrying out a co-precipitation reaction, continuously stirring, and aging; and (3) washing, drying, and calcining at high temperature. The catalyst can effectively promote the catalytic conversion of CO2 and CH4, inhibit the generation of side reactions, improve the yield and selectivity of synthesis gas, and maintain good catalytic activity, thermal stability, carbon deposition resistance and inactivation resistance in long-time cycle operation, and has good application prospects. The method is of great significance in promoting engineering application and sustainable development of a chemical-looping methane dry reforming technology.

Description

Technical Field

[0001] The present invention relates to the technical field of energy catalytic materials and chemical chain reactions, and more particularly to a chemical chain methane dry reforming catalyst and a preparation method and application thereof. Background Art

[0002] As global climate change intensifies, large amounts of carbon dioxide (CO2) are released into the atmosphere, significantly enhancing the greenhouse effect. Global warming has become a major environmental and energy challenge facing human society. Carbon capture, utilization, and storage (CCUS) technology is considered an effective path to achieving carbon emission reduction, with the potential to simultaneously reduce CO2 emissions and convert it into high-value-added chemicals or fuels. However, the large-scale industrial application of this technology still faces many obstacles due to high energy consumption, high costs, and potential secondary environmental impacts.

[0003] Methane (CH4) and carbon dioxide (CO2) are two major greenhouse gases, and their synergistic conversion and efficient utilization have attracted widespread attention. Among them, the dry reforming of methane (DRM) reaction is a feasible technical route for converting CH4 and CO2 into synthesis gas (CO and H2). Synthesis gas is a key intermediate in various chemical processes and is widely used in fields such as Fischer-Tropsch synthesis, methanol synthesis, and other chemical production. However, the DRM reaction is a highly endothermic process and usually requires high temperature conditions. During this process, side reactions such as CH4 cracking and CO disproportionation are prone to occur, resulting in carbon deposition and catalyst deactivation. In addition, CO2 may also undergo a reverse water-gas shift reaction (RWGS) with the generated H2 to produce CO and H2O, thereby reducing the selectivity of the target product.

[0004] To overcome these issues, chemical-looping dry reforming of methane (CL-DRM) technology was proposed. This technology breaks down the traditional DRM reaction into two separate steps: first, in the fuel reactor, oxygen carriers (OCs) react with CH4, being reduced to produce syngas; then, in the air reactor, the reduced OCs react with CO2 to achieve regeneration. Through this step-by-step operation, CL-DRM effectively suppresses the occurrence of the RWGS reaction, alleviating thermodynamic limitations. It also consumes carbon deposits during the cycle and improves catalyst stability.

[0005] In CL-DRM technology, the selection and performance optimization of oxygen carriers play a decisive role. Currently, oxygen carriers mainly fall into two categories: metal oxides and composites. Metal oxide oxygen carriers primarily include nickel-, iron-, copper-, and manganese-based systems. Nickel-based oxygen carriers offer advantages such as low cost and mature preparation processes, but they are prone to sintering at high temperatures and carbon deposition, which affects long-term operational stability. Iron-based materials exhibit good thermal stability and low cost, but generally have low reactivity, requiring higher temperatures to achieve ideal conversion rates, and may experience structural degradation over long-term use. Copper-based oxygen carriers have good CO2 activation capabilities at lower temperatures, but are prone to volatilization or melting at high temperatures, resulting in oxygen carrier inactivation. Manganese-based oxygen carriers have high oxygen storage capacity and a certain degree of thermal stability, but their reaction rate is relatively slow, and their overall stability still needs to be improved. Composite oxygen carriers primarily include perovskite-, hexaaluminate-, and cerium-based oxygen carriers. Among them, perovskite-type oxygen carriers have excellent structural stability and high oxygen storage capacity, but they have problems of insufficient long-term stability and high cost under specific working conditions. Hexaaluminate-type oxygen carriers have good thermal stability and high oxygen storage capacity, but their preparation process is complex and the production cost is high. CeO2 has shown good performance in multiple catalytic systems due to its rich crystal defect structure and excellent oxygen storage / release capacity, especially in promoting by-product conversion and inhibiting carbon deposition, which is better than transition metal oxides such as Fe, Mn and Ni. In addition, CeO2 can also improve the mechanical strength and catalytic activity of the catalyst. However, pure CeO2 is prone to grain sintering in high-temperature environments, resulting in a decrease in its oxygen storage capacity, thereby affecting the catalytic performance.

[0006] Therefore, how to modify and design CeO2 oxygen carriers to further improve their thermal stability and catalytic activity is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0007] In view of this, an object of the present invention is to provide a chemical chain methane dry reforming catalyst and a preparation method and application thereof, so as to address the deficiencies in the prior art.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A chemical chain methane dry reforming catalyst is composed of a main component of cerium dioxide (CeO2) and a doping component of platinum (Pt), wherein the molar percentage of platinum is 1.00%-4.00%, preferably 4.00%.

[0010] In the present invention, Pt is highly dispersed within the CeO2 lattice or on its surface, with some Pt incorporating into the CeO2 lattice to form a solid solution structure and others distributed on the CeO2 surface as active sites. Pt-doping CeO2 achieves an optimal balance between oxygen transport, catalytic activity, and structural stability, significantly improving the catalyst's ability to activate CH4 and CO2.

[0011] A method for preparing the above-mentioned chemical linking methane dry reforming catalyst specifically comprises the following steps:

[0012] (1) Dissolving cerium nitrate (Ce(NO3)3·6H2O) and chloroplatinic acid (H2PtCl6·6H2O) in water to obtain a precursor solution;

[0013] (2) Under strong stirring conditions, the precursor solution is heated and then a precipitant is added to perform a co-precipitation reaction, and the mixture is continuously stirred and aged to obtain a precursor precipitate;

[0014] (3) The precursor precipitate is washed, dried, and calcined at high temperature to obtain a chemical chain methane dry reforming catalyst.

[0015] Furthermore, in the above step (1), the total concentration of cerium ions and platinum ions in the precursor solution is 0.10-0.50 mol / L, wherein the molar percentage of platinum ions is 1.00%-4.00%, preferably 4.00%.

[0016] Furthermore, in the above step (2), the temperature is raised to 80°C.

[0017] Furthermore, in the above step (2), the precipitant is sodium hydroxide, and the pH is adjusted to 10.00.

[0018] Furthermore, in the above step (2), the stirring time is 2 hours; and the aging time is 2 hours.

[0019] A further beneficial effect of the above method is that, through continuous stirring and aging, the metal ions are completely precipitated to form a uniform precursor precipitate.

[0020] Furthermore, in the above step (3), the washing reagent is deionized water, and the washing is repeated until there is no sodium ion.

[0021] Furthermore, in the above step (3), the drying equipment is an oven, the temperature is 110° C., and the drying time is 12-24 hours.

[0022] A further beneficial effect of the above method is that, through drying, moisture is fully removed to avoid decomposition of the precursor.

[0023] Furthermore, in the above step (4), the high-temperature calcination equipment is a muffle furnace, the atmosphere is air, the temperature is 500° C., and the time is 2 h.

[0024] A further beneficial effect of the above method is that, through high temperature calcination, organic residues are removed and the lattice reconstruction of Pt and Ce is completed, thereby forming a stable Pt-Ce composite oxide structure.

[0025] The present invention also seeks to protect the use of the chemical chaining methane dry reforming catalyst or the chemical chaining methane dry reforming catalyst prepared by the above preparation method in a chemical chaining methane dry reforming reaction.

[0026] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. Improve oxygen migration capacity and catalytic activity: The introduction of Pt effectively regulates the crystal structure of CeO2, increases the surface oxygen vacancy density, improves the oxygen carrier's ability to reduce CH4 in the fuel reactor, and improves its ability to oxidize CO2 during the regeneration process, thereby significantly improving the CH4 conversion rate and syngas selectivity.

[0028] 2. Enhance high-temperature structural stability: Pt element has the effect of inhibiting CeO2 grain growth, which can effectively reduce the sintering rate during high-temperature calcination and cyclic reaction, and improve the cycle life of the oxygen carrier.

[0029] 3. Improved anti-carbon deposition performance: The Pt-doped CeO2 system exhibits excellent inhibition of CH4 cracking side reactions, significantly reducing carbon deposition during the CL-DRM reaction and avoiding catalyst deactivation due to carbon deposition.

[0030] 4. The preparation process is simple, highly controllable, and suitable for large-scale production. The co-precipitation method used is simple in preparation process, has a wide range of raw materials, is easy to achieve large-scale production, and has good engineering application prospects.

[0031] 5. In response to the key technical bottlenecks of oxygen carrier materials in existing chemical chain methane dry reforming (CL-DRM) technology, such as poor thermal stability, easy sintering or phase change, rapid activity decline during recycling, severe carbon deposition and weak anti-deactivation ability under high-temperature reaction conditions, the present invention provides a modified cerium-based oxygen carrier material with excellent thermal stability and high catalytic activity and a controllable preparation method thereof. By introducing a suitable active additive, the crystal structure and surface oxygen vacancy distribution of the oxygen carrier are optimized, thereby significantly enhancing its structural stability and oxygen migration ability under high-temperature environment, thereby effectively improving its catalytic performance and cycle stability in the CL-DRM reaction.

[0032] 6. The present invention overcomes the problems of oxygen carrier materials (such as NiO, Fe2O3, Mn2O3, pure CeO2, etc.) in the prior art in the chemical chain methane dry reforming (CL-DRM) reaction, such as structural instability at high temperatures, easy grain sintering, decreased oxygen storage / release capacity, poor anti-carbon deposition performance, and insufficient catalytic activity. It provides a CeO2 oxygen carrier material based on Pt element doping modification and a controllable preparation method thereof. By introducing an appropriate amount of precious metal Pt, the material significantly improves its thermal stability, oxygen migration ability and surface catalytic activity, and optimizes its reaction kinetics in the CH4 reduction and CO2 oxidation regeneration process, thereby realizing efficient and stable conversion of CH4 and CO2 into highly selective synthesis gas (CO+H2).

[0033] 7. The present invention solves the problems of traditional oxygen carriers such as nickel-based materials that are prone to carbon deposition and deactivation, iron-based materials that have low reactivity, copper-based materials that have severe high-temperature volatilization, and manganese-based materials that are insufficiently stable. It overcomes the unfavorable factors of existing composite oxygen carriers such as perovskites and hexaaluminates, such as unstable cyclic performance. It develops a high-performance oxygen carrier material suitable for the CL-DRM reaction system with good industrial application prospects. This material can effectively promote the catalytic conversion of CO2 and CH4, inhibit the occurrence of side reactions, improve the yield and selectivity of synthesis gas, and maintain good catalytic activity, thermal stability, resistance to carbon deposition, and resistance to deactivation during long-term cyclic operation. It is of great significance for promoting the engineering application and sustainable development of chemical chain methane dry reforming technology.

[0034] 8. The preparation method of the present invention has a simple process, strong repeatability, and is suitable for large-scale production. It facilitates the large-scale preparation of oxygen carriers and their practical engineering application, providing key material support and technical foundation for promoting the industrialization of CL-DRM technology in the fields of low-carbon energy conversion and CO2 resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The CH4 conversion, CO selectivity and H2 / CO ratio of the chemical looping methane dry reforming catalyst in Example 1 are obtained after 5 cycles.

[0036] Figure 2 The concentration variation curve of CH4, CO2, CO and H2 over time in the second cycle of the chemical looping methane dry reforming catalyst in Example 1;

[0037] Figure 3 The CH4 conversion rate, CO selectivity and H2 / CO ratio of the chemical chaining methane dry reforming catalyst in Example 1 during 100 long cycles are shown. DETAILED DESCRIPTION

[0038] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0039] Example 1

[0040] A chemical chain methane dry reforming catalyst composed of cerium dioxide and platinum, wherein the molar percentage of platinum is 4.00%;

[0041] The preparation method of the chemical chaining methane dry reforming catalyst specifically comprises the following steps:

[0042] (1) dissolving cerium nitrate and chloroplatinic acid in deionized water to obtain a precursor solution having a total concentration of cerium ions and platinum ions of 0.50 mol / L, wherein the molar percentage of platinum ions is 4.00%;

[0043] (2) Under strong stirring conditions, the precursor solution was heated to 80°C, and sodium hydroxide was slowly added dropwise to adjust the pH to 10.00 for coprecipitation reaction. The mixture was stirred for 2 h and aged for 2 h to obtain a precursor precipitate.

[0044] (3) The precursor precipitate was repeatedly washed with deionized water until there was no sodium ion, then dried in an oven at 110°C for 24 hours, and finally placed in a muffle furnace at 500°C in an air atmosphere and calcined for 2 hours to obtain a chemical chain methane dry reforming catalyst.

[0045] Performance Testing

[0046] 1. Chemical looping methane dry reforming (CL-DRM) reaction 5 cycles

[0047] Sample pretreatment: The chemical chain methane dry reforming catalyst prepared in Example 1 was placed in a fixed bed reactor, and the temperature was raised to 800° C. and maintained for 30 min under a N 2 atmosphere to remove physically adsorbed water.

[0048] Fuel reaction stage: 5% CH4 gas (41 mL / min) was introduced, the reaction temperature was maintained at 800°C, the reaction time was 5 min, and the conversion rate of CH4 in the tail gas and the composition of the generated gas (mainly H2 and CO) were recorded.

[0049] Nitrogen purge stage: Close the CH4 gas line and switch to pure N2 gas (70 mL / min) for 10 min to remove residual gas in the pipeline and reactor, avoid cross contamination between different gases, and ensure that each stage can be carried out in the most optimized manner.

[0050] Regeneration reaction stage: close the N2 gas line and switch to 5% CO2 gas (37mL / min), and regenerate the oxygen carrier at the same temperature for 20min, so that the reduced oxygen carrier is reoxidized to restore its initial state for the next cycle.

[0051] Cyclic operation: Repeat the above fuel reaction and regeneration reaction steps for a total of 5 cycles, and analyze the changes in gas composition after each cycle. Figure 1-2 shown.

[0052] 2. Chemical looping methane dry reforming (CL-DRM) reaction 100 cycles

[0053] Sample pretreatment: The chemical chain methane dry reforming catalyst prepared in Example 1 was placed in a fixed bed reactor, and the temperature was raised to 800° C. and maintained for 30 min under a N 2 atmosphere to remove physically adsorbed water.

[0054] Fuel reaction stage: 5% CH4 gas (41 mL / min) was introduced, the reaction temperature was maintained at 800°C, the reaction time was 5 min, and the CH4 conversion rate in the tail gas and the composition of the generated gas (mainly H2 and CO) were recorded.

[0055] Nitrogen purge stage: Close the CH4 gas line and switch to pure N2 gas (70 mL / min) for 10 min to remove residual gas in the pipeline and reactor, avoid cross contamination between different gases, and ensure that each stage can be carried out in the most optimized manner.

[0056] Regeneration reaction stage: close the N2 gas line and switch to 5% CO2 gas (37mL / min), and regenerate the oxygen carrier at the same temperature for 20min, so that the reduced oxygen carrier is reoxidized to restore its initial state for the next cycle.

[0057] Cyclic operation: Repeat the above fuel reaction and regeneration reaction steps for 100 cycles, and analyze the changes in gas composition after each cycle. Figure 3 shown.

[0058] Depend on Figure 1-3It can be seen that the chemical chain methane dry reforming catalyst prepared in Example 1 of the present invention exhibits excellent catalytic reaction performance in the chemical chain methane dry reforming (CL-DRM) reaction. At a reaction temperature of 800°C, after 5 oxidation-reduction cycles, the CH4 conversion rate is stable at more than 97%, showing good reaction activity. The CO selectivity in the reaction products is higher than 96%, indicating that the oxygen carrier can efficiently promote the target reaction and effectively suppress side reactions. During long-term cyclic operation, the oxygen carrier did not show obvious deactivation, and still maintained a high conversion efficiency and product selectivity, reflecting excellent cyclic stability. It is particularly noteworthy that the H2 / CO ratio was lower than 2 throughout the experiment, indicating that no carbon deposits were generated, reflecting the excellent anti-carbon deposition performance of the oxygen carrier material. In addition, after continuous operation under high temperature conditions, its catalytic activity did not decrease significantly, indicating that the material has excellent thermal stability and is suitable for the harsh working conditions required for oxygen carriers in the CL-DRM reaction system.

[0059] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A chemical chain methane dry reforming catalyst, characterized in that: The invention consists of cerium dioxide and platinum, wherein the molar percentage of the platinum is 1.00%-4.00%.

2. The method for preparing a chemical linking methane dry reforming catalyst according to claim 1, characterized in that: The specific steps include: (1) dissolving cerium nitrate and chloroplatinic acid in water to obtain a precursor solution; (2) Under strong stirring conditions, the precursor solution is heated and then a precipitant is added to perform a co-precipitation reaction, and the mixture is continuously stirred and aged to obtain a precursor precipitate; (3) The precursor precipitate is washed, dried, and calcined at high temperature to obtain the chemical chain methane dry reforming catalyst.

3. The method for preparing a chemical linking methane dry reforming catalyst according to claim 1, characterized in that: In step (1), the total concentration of cerium ions and platinum ions in the precursor solution is 0.10-0.50 mol / L, wherein the molar percentage of platinum ions is 1.00%-4.00%.

4. The method for preparing a chemical linking methane dry reforming catalyst according to claim 1, characterized in that: In step (2), the temperature is raised to 80°C.

5. The method for preparing a chemical linking methane dry reforming catalyst according to claim 1, characterized in that: In step (2), the precipitant is sodium hydroxide, and the pH is adjusted to 10.

00.

6. The method for preparing a chemical linking methane dry reforming catalyst according to claim 1, characterized in that: In step (2), the continuous stirring time is 2 hours; the aging time is 2 hours.

7. The method for preparing a chemical linking methane dry reforming catalyst according to claim 1, characterized in that: In step (3), the washing reagent is deionized water.

8. The method for preparing a chemical linking methane dry reforming catalyst according to claim 1, characterized in that: In step (3), the drying equipment is an oven, the temperature is 110° C., and the drying time is 12-24 hours.

9. The method for preparing a chemical linking methane dry reforming catalyst according to claim 1, characterized in that: In step (4), the high-temperature calcination equipment is a muffle furnace, the atmosphere is air, the temperature is 500° C., and the time is 2 hours.

10. Use of the chemical linking methane dry reforming catalyst according to claim 1 or the chemical linking methane dry reforming catalyst prepared by the preparation method according to any one of claims 2 to 9 in a chemical linking methane dry reforming reaction.

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