NiPt-CaO / MgO bifunctional material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of CO2 capture and conversion utilization materials, and provides a NiPt-CaO / MgO bifunctional material as well as a preparation method and application thereof. According to the material, the loading capacity of Ni is 5-15 wt.%, the loading capacity of Pt is 0.1-1 wt.%, and the mass ratio of CaO to MgO is (4-19): 1. A reduction method of the material in CO2 capture-conversion comprises the following steps: loading the NiPt-CaO / MgO bifunctional material into a fixed bed reactor, introducing N2 to replace and remove CO2, O2 and water vapor in the system, introducing a reducing gas CO until the concentration is kept stable, and heating to a reduction temperature for reduction. According to the NiPt-CaO / MgO bifunctional material, in the CO2 capture-methane dry reforming process, through the mild reduction process, Ni particle sintering is effectively inhibited, the active site dispersity is improved, and then the conversion efficiency and long-term cycle stability of the NiPt-CaO / MgO bifunctional material are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of CO2 capture and conversion utilization materials, and particularly relates to a NiPt-CaO / MgO bifunctional material and a preparation method and application thereof. BACKGROUND

[0002] Since the industrial revolution, human activities have led to a continuous increase in the concentration of greenhouse gases in the atmosphere, among which the greenhouse effect caused by CO2 and CH4 is particularly significant. Among various CO2 emission reduction technologies, the integrated CO2 capture-methane dry reforming technology (ICCC-DRM) simultaneously converts two greenhouse gases, CO2 and CH4, into syngas (CO+H2). This technology reduces operating costs and energy consumption through system integration, while achieving the resource utilization of greenhouse gases. The obtained syngas is the basic raw material for important chemical processes such as ammonia synthesis, methanol synthesis, and Fischer-Tropsch synthesis, and the market demand is continuously growing. Therefore, the ICCC-DRM technology not only helps to reduce carbon emissions, but also provides raw material support for the synthesis of downstream high-value-added products.

[0003] In the ICCC-DRM system, H2 is commonly used to reduce and activate Ni-CaO-based bifunctional materials (DFMs), but the reduction process of H2 is intense, which easily leads to significant sintering of Ni particles during the reduction stage, thereby affecting the dispersion and stability of active sites and reducing the overall performance of the material. Han et al. (Han R, Xing S, Wang Y, et al. Two birds with one stone: MgO promoted Ni-CaO as stable and coke-resistant bifunctional materials for integrated CO2 capture and conversion[J]. Separation and Purification Technology, 2023, 307, 122808.) prepared Ni-CaO / MgO DFMs by a sol-gel method and obtained them by reduction with H2. However, the reduction process of H2 is intense, which easily leads to significant sintering of Ni particles during the reduction stage, thereby affecting the dispersion and stability of active sites and reducing the overall performance of the material. 10Mg, the average time and space yield of CO and H2 in the 10th cycle reached 1.01 and 0.94 mmol / (g·min), respectively. Hu et al. (Hu J, Hongmanorom P, Chirawatkul P, et al. Efficient Integration of CO2 Capture and Conversion over a Ni Supported CeO2-modified CaO Microsphere at Moderate Temperature[J]. Chemical Engineering Journal, 2021, 426, 130864.) prepared Ni / Ca 85 Ce 15 The average time and space yield of CO and H2 in the 9th cycle reached 0.98 and 0.71 mmol / (g·min), respectively. Existing studies have focused on the performance degradation caused by carbon deposition and high-temperature sintering during the reaction process, but have paid insufficient attention to the metal sintering that has already occurred during the reduction stage and its impact on the subsequent cycle stability. Therefore, it is of great significance to develop a milder and controllable reduction method to effectively inhibit Ni particle sintering at the initial stage of material activation, in order to improve the long-term cycle stability and overall process efficiency of DFMs. SUMMARY

[0004] In view of the problem that the existing H2 reduction method is prone to cause Ni particle sintering and affect the conversion performance of the bifunctional material, the present application provides a NiPt-CaO / MgO bifunctional material and a preparation method and application thereof. The NiPt-CaO / MgO bifunctional material of the present application effectively inhibits Ni particle sintering through a mild reduction process, improves the dispersion of active sites, and thus improves its conversion efficiency and long-term cycle stability in the CO2 capture-methane dry reforming process.

[0005] The present application provides a NiPt-CaO / MgO bifunctional material, characterized in that the Ni loading is 5-15wt.%, the Pt loading is 0.1-1wt.%, and the mass ratio of CaO to MgO is (4-19):1.

[0006] Loading (%) = mass of active component / (mass of active component + mass of carrier) x 100% The present application also provides a preparation method of the above-mentioned NiPt-CaO / MgO bifunctional material, comprising the following steps: S1, a certain amount of calcium nitrate tetrahydrate, magnesium nitrate hexahydrate and nickel nitrate hexahydrate are dissolved in water, a certain amount of chloroplatinic acid solution is added, and anhydrous citric acid is added as a chelating agent; wherein the molar ratio of total metal cations, anhydrous citric acid and deionized water is 1:1.2:60; S2, the solution prepared in step S1 is placed in a water bath and stirred vigorously to form a gel, then the gel is dried and placed in a muffle furnace for calcination to obtain a bifunctional material NiPt-CaO / MgO, the Ni loading is 5-15wt.%, the Pt loading is 0.1-1wt.%, and the mass ratio of CaO to MgO is (4-19):1.

[0007] Preferably, the water bath temperature in step S2 is 70-95℃, and the stirring time is 4-8h.

[0008] Preferably, the drying temperature of the gel in step S2 is 100-140℃, and the drying time is 6-12h.

[0009] Preferably, the calcination in step S2 is: heating at a rate of 3-10℃ / min to 700-900℃ for calcination, and the calcination time is 1-4h.

[0010] The application also provides the use of the above-mentioned NiPt-CaO / MgO bifunctional material for CO2 capture-conversion, which can be applied to the capture and conversion of flue gas CO2 in large-scale industrial processes.

[0011] The application also provides a reduction method for the above-mentioned NiPt-CaO / MgO bifunctional material in CO2 capture-conversion, the NiPt-CaO / MgO bifunctional material is loaded into a fixed bed reactor, N2 is introduced to displace and remove CO2, O2 and water vapor in the system, reduction gas CO is introduced until its concentration remains stable, and the temperature is raised to the reduction temperature for reduction.

[0012] Preferably, the Ni loading in the NiPt-CaO / MgO bifunctional material is 5-15wt.%, the Pt loading is 0.1-1wt.%, and the mass ratio of CaO to MgO is (4-19):1.

[0013] Preferably, the concentration of the reduction gas CO is 5-20%, and the balance gas of the reduction gas CO is N2.

[0014] Preferably, the temperature is raised at a rate of 5-10℃ / min from room temperature to 700-900℃, and the reduction time is 1-4h.

[0015] Compared with the prior art, the application has the following advantages: 1. The NiPt-CaO / MgO bifunctional material of this invention uses CaO / MgO as a support to load bimetallic NiPt active sites. Its porous structure facilitates rapid CO2 adsorption and prevents CaO agglomeration. Furthermore, the doping of metal and metal oxides into the CaO particles effectively segments the CaO, preventing high-temperature sintering and maintaining stable cyclic CO2 adsorption performance. The incorporation of trace amounts of Pt improves the interaction between Ni and the support, and the NiPt alloy formed with Ni reduces the size of the active sites and improves the dispersion, solving the problem of rapid deactivation due to carbon deposition and sintering in Ni-based catalysts.

[0016] 2. This invention uses a solution-gel method to synthesize bifunctional materials in one step. The preparation process is simple, the raw material cost is low, and it is suitable for large-scale preparation.

[0017] 3. In the reduction method for CO2 capture-conversion of NiPt-CaO / MgO bifunctional materials of this invention, CO is used as a reducing agent, which can effectively inhibit the sintering of Ni particles in the early stage of activation. Simultaneously, in-situ reduction occurs during the reaction, resulting in a gentler reduction process. This method first gently reduces the Ni active sites on the material surface through CO. In the subsequent conversion stage, the surface reconstruction that occurs during the carbonization of CaO to CaCO3 gradually migrates the unreduced NiO from the interior to the surface, achieving in-situ reduction. This in-situ reduction process is under mild conditions, further inhibiting the agglomeration of Ni particles, thereby improving the dispersibility and stability of the active sites. Using this method, the space-time yield gradually increases with the number of cycles, effectively solving the problem of severe sintering caused by H2 reduction, improving the conversion performance and cycle stability of DFMs, and enhancing the overall process efficiency and economy. This technology possesses high-efficiency carbon emission reduction capabilities while producing high-value-added products. Furthermore, by utilizing high-temperature flue gas carbon capture and in-situ conversion, it achieves efficient energy utilization, making it suitable for large-scale industrial applications and possessing significant economic and social benefits. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the NiPt-CaO / MgO bifunctional material in Example 1 of the present invention; Figure 2 This is a scanning electron microscope image of the NiPt-CaO / MgO bifunctional material in Example 2 of the present invention; Figure 3 This is a scanning electron microscope image of the NiPt-CaO / MgO bifunctional material in Example 3 of the present invention; Figure 4 This is a transmission electron microscope (TEM) image of the reduced NiPt-CaO / MgO bifunctional material in Example 5 of this invention. Figure 5This is a transmission electron microscope image of the reduced NiPt-CaO / MgO bifunctional material in Comparative Example 1 of this invention; Figure 6 The CH4 conversion rate of the NiPt-CaO / MgO bifunctional material in Example 5 and Comparative Examples 1-2 of this invention during 20 cycles; Figure 7 The CO2 conversion rate of the NiPt-CaO / MgO bifunctional material in Example 5 and Comparative Examples 1-2 of this invention is shown in the figure for 20 cycles. Figure 8 The average space-time yield of H2 in 20 cycles for the NiPt-CaO / MgO bifunctional materials in Example 5 and Comparative Examples 1-2 of this invention; Figure 9 The average space-time yield of CO in 20 cycles is given by the NiPt-CaO / MgO bifunctional material in Example 5 and Comparative Examples 1-2 of this invention. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only, and the present invention is not limited thereto.

[0020] Example 1:

[0021] A NiPt-CaO / MgO bifunctional material is characterized by a Ni loading of 5 wt.%, a Pt loading of 1 wt.%, and a CaO to MgO mass ratio of 80:20.

[0022] The preparation method of the above-mentioned NiPt-CaO / MgO bifunctional material includes the following steps: S1. Weigh out a certain amount of 3.1665g of calcium nitrate tetrahydrate, 1.1962g of magnesium nitrate hexahydrate and 0.2477g of nickel nitrate hexahydrate, dissolve them in water, add 12.833mL of 2.106g / L chloroplatinic acid solution (Pt content is 37wt.%), and add anhydrous citric acid as a chelating agent; wherein, the molar ratio of total metal cations, anhydrous citric acid and deionized water is set to 1:1.2:60; S2. The solution was vigorously stirred in a water bath at 95°C for 4 hours. The resulting gel was then dried in an oven at 100°C for 12 hours. It was then placed in a muffle furnace and calcined at 700°C at a heating rate of 3°C / min for 4 hours to obtain the bifunctional material NiPt-CaO / MgO with a Ni loading of 5 wt.%, a Pt loading of 1 wt.%, and a CaO to MgO mass ratio of 80:20.

[0023] Reduction method for CO2 capture-conversion of NiPt-CaO / MgO bifunctional material obtained in Example 1: 0.1g of NiPt-CaO / MgO bifunctional material obtained in Example 1 was loaded into a fixed-bed reactor. The sample was fixed with quartz wool, and the bed height was 15mm. Then, 100mL / min of N2 was introduced to replace and remove CO2, O2 and water vapor in the system. CO was introduced as a reducing gas at 8mL / min and the N2 flow rate was set to 92mL / min. The temperature was increased to 750℃ at 7℃ / min and maintained for 3.5h. Then, the CO gas was turned off and the temperature was lowered to 650℃ for performance evaluation.

[0024] Example 2:

[0025] A NiPt-CaO / MgO bifunctional material is characterized by a Ni loading of 15 wt.%, a Pt loading of 0.1 wt.%, and a CaO to MgO mass ratio of 95:5.

[0026] The preparation method of the above-mentioned NiPt-CaO / MgO bifunctional material includes the following steps: S1. Weigh out a certain amount of 3.3962g of calcium nitrate tetrahydrate, 0.2701g of magnesium nitrate hexahydrate and 0.7432g of nickel nitrate hexahydrate, dissolve them in water, add 1.283mL of 2.106g / L chloroplatinic acid solution (Pt content is 37wt.%), and add anhydrous citric acid as a chelating agent; wherein, the molar ratio of total metal cations, anhydrous citric acid and deionized water is set to 1:1.2:60; S2. The solution was vigorously stirred in a water bath at 70°C for 8 hours. The resulting gel was then dried in an oven at 140°C for 6 hours. It was then placed in a muffle furnace and calcined at 900°C at a heating rate of 10°C / min for 1 hour to obtain the bifunctional material NiPt-CaO / MgO with a Ni loading of 15 wt.%, a Pt loading of 0.1 wt.%, and a CaO to MgO mass ratio of 95:5.

[0027] Reduction method for CO2 capture-conversion of NiPt-CaO / MgO bifunctional material obtained in Example 2: 0.1g of NiPt-CaO / MgO bifunctional material obtained in Example 2 was loaded into a fixed-bed reactor. The sample was fixed with quartz wool, and the bed height was 15mm. Then, 100mL / min of N2 was introduced to replace and remove CO2, O2 and water vapor in the system. CO was introduced as a reducing gas at 12mL / min and the N2 flow rate was set to 88mL / min. The temperature was increased to 850℃ at 9℃ / min and maintained for 2.5h. Then, the CO gas was turned off and the temperature was lowered to 650℃ for performance evaluation.

[0028] Example 3:

[0029] A NiPt-CaO / MgO bifunctional material is characterized by a Ni loading of 10 wt.%, a Pt loading of 0.5 wt.%, and a CaO to MgO mass ratio of 85:15.

[0030] The preparation method of the above-mentioned NiPt-CaO / MgO bifunctional material includes the following steps: S1. Weigh out a certain amount of 3.2033g of calcium nitrate tetrahydrate, 0.8542g of magnesium nitrate hexahydrate and 0.4955g of nickel nitrate hexahydrate, dissolve them in water, add 6.417mL of 2.106g / L chloroplatinic acid solution (Pt content is 37wt.%), and add anhydrous citric acid as a chelating agent; wherein, the molar ratio of total metal cations, anhydrous citric acid and deionized water is set to 1:1.2:60; S2. The solution was vigorously stirred in a water bath at 80°C for 6 hours. The resulting gel was then dried in an oven at 120°C for 8 hours. It was then placed in a muffle furnace and calcined at 800°C at a heating rate of 5°C / min for 2 hours to obtain the bifunctional material NiPt-CaO / MgO with a Ni loading of 10 wt.%, a Pt loading of 0.5 wt.%, and a CaO to MgO mass ratio of 85:15.

[0031] Reduction method for CO2 capture-conversion of NiPt-CaO / MgO bifunctional material obtained in Example 3: 0.1g of NiPt-CaO / MgO bifunctional material obtained in Example 3 was loaded into a fixed-bed reactor. The sample was fixed with quartz wool and the bed height was 15mm. Then, 100mL / min of N2 was introduced to replace and remove CO2, O2 and water vapor in the system. CO was introduced as a reducing gas at 5mL / min and the N2 flow rate was set to 95mL / min. The temperature was increased to 700℃ at 5℃ / min and maintained for 4h. Then, the CO gas was turned off and the temperature was lowered to 650℃ for performance evaluation.

[0032] Example 4:

[0033] 0.1g of the NiPt-CaO / MgO bifunctional material obtained in Example 3 was loaded into a fixed-bed reactor. The sample was fixed with quartz wool, and the bed height was 15mm. Then, 100mL / min of N2 was introduced to replace and remove CO2, O2 and water vapor in the system. CO was introduced as a reducing gas at 15mL / min, and the N2 flow rate was set to 85mL / min. The temperature was increased to 800℃ at 6℃ / min and maintained for 3h. Then, the CO gas was turned off and the temperature was lowered to 650℃ for performance evaluation.

[0034] Example 5:

[0035] 0.1g of the NiPt-CaO / MgO bifunctional material obtained in Example 3 was loaded into a fixed-bed reactor. The sample was fixed with quartz wool, and the bed height was 15mm. Then, 100mL / min of N2 was introduced to replace and remove CO2, O2 and water vapor in the system. Then, 10mL / min of CO was introduced as a reducing gas and the N2 flow rate was set to 90mL / min. The temperature was increased to 750℃ at 10℃ / min and maintained for 2h. Then, the CO gas was turned off and the temperature was lowered to 650℃ for performance evaluation.

[0036] Example 6:

[0037] 0.1g of the NiPt-CaO / MgO bifunctional material obtained in Example 3 was loaded into a fixed-bed reactor. The sample was fixed with quartz wool, and the bed height was 15mm. Then, 100mL / min of N2 was introduced to replace and remove CO2, O2 and water vapor in the system. 20mL / min of CO was introduced as a reducing gas, and the N2 flow rate was set to 80mL / min. The temperature was increased to 900℃ at 8℃ / min and maintained for 1h. Then, the CO gas was turned off and the temperature was lowered to 650℃ for performance evaluation.

[0038] Comparative Example 1: In Example 5, the reducing gas CO was replaced with H2, while everything else remained the same.

[0039] Comparative Example 2: 0.1g of the NiPt-CaO / MgO bifunctional material obtained in Example 3 was loaded into a fixed-bed reactor. The sample was fixed with quartz wool and the bed height was 15mm. Then, 100mL / min of N2 was introduced to replace and remove CO2, O2 and water vapor in the system. The temperature was then directly increased to 750℃ at 10℃ / min and held for 2h. Subsequently, the temperature was cooled to 650℃ for performance evaluation.

[0040] Results and Analysis: Scanning electron microscope (SEM) images of the NiPt-CaO / MgO bifunctional materials of Examples 1-3 of this invention are attached. Figures 1-3 As shown in the figure, the NiPt-CaO / MgO bifunctional materials of Examples 1-3 of the present invention all have porous structures. The NiPt-CaO / MgO bifunctional material of Example 3 has both macroporous and mesoporous structures, and has better conversion and trapping effects.

[0041] Transmission electron microscope (TEM) images of the bifunctional materials after reduction in Example 5 and Comparative Example 1 of this invention are shown below. Figure 4 , Figure 5As shown in the figure, CO reduction yields Ni particles with an average particle size of 4.3 ± 0.3 nm, while H2 reduction yields Ni particles with an average particle size of 10.1 ± 0.3 nm. Smaller active sites have higher activity, and CO reduction can give DFMs better conversion performance.

[0042] DFMs performance evaluation testing methods: This invention evaluates conversion performance and cycle stability in a fixed-bed reactor. The operation process is as follows: (1) Collection stage: 15% CO2 / N2 gas (i.e., CO2 at 15 mL / min and N2 at 85 mL / min) is introduced at a flow rate of 100 mL / min and maintained for 15 min; (2) Purging stage: Switch the gas to 100% N2 at a flow rate of 100 mL / min and purge for 3 min; (3) Conversion stage: Switch the gas to 3% CH4 / N2 gas at 100 mL / min (i.e., CH4 at 3 mL / min and N2 at 97 mL / min) and maintain it for 10 min; (4) Purging stage: Switch the gas to 100% N2 at 100 mL / min and purge for 3 min.

[0043] The above operation process was repeated 20 times. The contents of CH4, CO2, CO, and H2 in the exhaust gas were analyzed using a non-spectral infrared detector. The CH4 conversion rate, CO2 conversion rate, and average space-time yields of H2 and CO were calculated, defined as follows:

[0044]

[0045]

[0046]

[0047] Among these technical indicators, the average space-time yield of H2 and CO is more meaningful than the CH4 conversion rate and CO2 conversion rate, and better reflects the economic and social benefits of this technology for industrial production.

[0048] The performance test results of Examples 1-6 and Comparative Examples 1-2 are as follows: Table 1 Performance test results of the examples and comparative examples

[0049] Performance test results of Example 1: The bifunctional material NiPt-CaO / MgO (Ni loading 5 wt.%, Pt loading 1 wt.%, CaO to MgO mass ratio 80:20) underwent 20 cycles of reduction at 750℃ with 8% CO, and the results are shown in Table 1. Initially, the conversion performance was low, but it gradually improved with each cycle. By the 5th cycle, the CH4 and CO2 conversion rates had increased to 62.45% and 68.33%, respectively, with average space-time yields of H2 and CO reaching 1.02 and 1.21 mmol / (g·min), respectively. By the 20th cycle, the CH4 conversion rate had increased to 70.11%, the CO2 conversion rate to 74.56%, and the average space-time yields of H2 and CO reaching 1.28 and 1.45 mmol / (g·min), respectively, demonstrating good activation performance and stable cycling performance.

[0050] Performance test results of Example 2: The bifunctional material NiPt-CaO / MgO (Ni loading 15 wt.%, Pt loading 0.1 wt.%, CaO to MgO mass ratio 95:5) underwent 20 cycles of reduction at 850 °C with 12% CO, and the results are shown in Table 1. The initial conversion performance was slightly better than in Example 1, with a CH4 conversion of 48.67% and a CO2 conversion of 52.89% in the first cycle. With continued cycling, the performance continued to improve, reaching 65.78% CH4 conversion and 71.45% CO2 conversion in the fifth cycle, with average space-time yields of 1.13 and 1.32 mmol / (g·min), respectively. By the 20th cycle, the CH4 conversion increased to 72.34%, the CO2 conversion to 75.67%, and the average space-time yields of 1.35 and 1.51 mmol / (g·min), respectively, demonstrating good activation performance and stability.

[0051] Performance test results of Example 3: The bifunctional material NiPt-CaO / MgO (Ni loading 10 wt.%, Pt loading 0.5 wt.%, CaO to MgO mass ratio 85:15) underwent 20 cycles of reduction at 700℃ with 5% CO, as shown in Table 1. Although the material's conversion performance was relatively poor, it gradually improved during cycling, exhibiting a clear activation period. Even up to the 20th cycle, the performance continued to slowly increase, reaching CH4 conversion of 74.31% and CO2 conversion of 76.21% in the 20th cycle, demonstrating excellent stability. The average space-time yields of H2 and CO continuously increased over the 20 cycles, with the average H2 space-time yield increasing from an initial 0.94 to 1.29 mmol / (g·min) and the average CO space-time yield increasing from an initial 1.14 to 1.52 mmol / (g·min), demonstrating good activation performance and stable cycling performance.

[0052] Performance test results of Example 4: The experimental results of the bifunctional material NiPt-CaO / MgO (Ni loading of 10 wt.%, Pt loading of 0.5 wt.%, CaO to MgO mass ratio of 85:15) after 20 cycles of reduction at 800℃ and 15% CO are shown in Table 1. The activation period of performance was mainly in the first 5 cycles, with CH4 conversion increasing from 40.33% to 75.26%, CO2 conversion from 47.69% to 75.90%, H2 average space-time yield increasing from 0.52 to 1.48 mmol / (g·min), and CO average space-time yield increasing from 0.69 to 1.69 mmol / (g·min). The average space-time yields of H2 and CO increased by 186.6% and 159%, respectively, in the first 5 cycles. After the 5th cycle, the conversion performance was basically stable. By the 20th cycle, CH4 conversion was 76.49%, CO2 conversion was 78.17%, H2 average space-time yield was 1.53 mmol / (g·min), and CO average space-time yield was 1.71 mmol / (g·min), demonstrating good activation performance and stable cycling performance.

[0053] Performance test results of Example 5: The experimental results of the bifunctional material NiPt-CaO / MgO (Ni loading of 10 wt.%, Pt loading of 0.5 wt.%, CaO to MgO mass ratio of 85:15) after 20 cycles of reduction at 750℃ and 10% CO are shown in Appendix Table 1. The activation period of performance mainly occurred in the first 5 cycles, with CH4 conversion increasing from 52.16% to 78.31%, CO2 conversion from 54.31% to 75.59%, average H2 space-time yield increasing from 0.83 to 1.58 mmol / (g·min), and average CO space-time yield increasing from 0.93 to 1.71 mmol / (g·min), showing a significant improvement in the average space-time yield of the products. After the 5th cycle, the performance was very stable. By the 20th cycle, the average H2 space-time yield was 1.56 mmol / (g·min), the average CO space-time yield was 1.71 mmol / (g·min), and the average product space-time yield remained at a high level, demonstrating good activation performance and stable cycling performance.

[0054] Performance test results of Example 6: The experimental results of the bifunctional material NiPt-CaO / MgO (Ni loading of 10 wt.%, Pt loading of 0.5 wt.%, CaO to MgO mass ratio of 85:15) after 20 cycles of reduction at 900℃ and 20% CO are shown in Table 1. In the first 5 cycles, the CH4 conversion increased from 39.58% to 72.24%, the CO2 conversion increased from 44.83% to 75.26%, the average H2 space-time yield increased from 0.46 to 1.39 mmol / (g·min), and the average CO space-time yield increased from 0.63 to 1.58 mmol / (g·min). After the 5th cycle, the conversion and average product space-time yield showed a slow increase. By the 20th cycle, the CH4 conversion was 74.23%, the CO2 conversion was 77.26%, the average H2 space-time yield was 1.46 mmol / (g·min), and the average CO space-time yield was 1.64 mmol / (g·min), demonstrating good activation performance and stable cycling performance.

[0055] Performance test results for Comparative Example 1: The experimental results of the bifunctional material NiPt-CaO / MgO (Ni loading 10 wt.%, Pt loading 0.5 wt.%, CaO to MgO mass ratio 85:15) after 20 cycles of reduction at 750℃ and 10% H2 are shown in Table 1. Figures 6-9It can be seen that although the initial conversion performance was relatively high, the conversion performance showed a significant decline in the first 4 cycles. The CH4 conversion rate decreased from 82.86% to 64.06%, the average space-time yield of H2 decreased from 1.49 to 1.09 mmol / (g·min), and the average space-time yield of CO decreased from 1.47 to 1.29 mmol / (g·min). After the 4th cycle, the conversion rate and the average space-time yield of the products showed a slow increase and reached a stable level. By the 20th cycle, the CH4 conversion rate was 67.21%, the CO2 conversion rate was 77.37%, the average space-time yield of H2 was 1.19 mmol / (g·min), and the average space-time yield of CO was 1.40 mmol / (g·min).

[0056] Performance test results for Comparative Example 2: The experimental results of the bifunctional material NiPt-CaO / MgO (Ni loading 10 wt.%, Pt loading 0.5 wt.%, CaO to MgO mass ratio 85:15) after 20 cycles at 750℃ and 100% N2 purging are shown in Table 1. Figures 6-9 It can be seen that the ICCC-DRM process can still proceed smoothly before the cycle without pre-reduction. This is because during the conversion stage, the introduced CH4 can reduce NiO in situ, and the DRM reaction and NiO reduction occur simultaneously. Due to the presence of in-situ reduction, the performance fluctuations in the first 5 cycles are small. The average space-time yields of H2 and CO can remain stable after the second cycle. By the 20th cycle, the CH4 conversion rate is 66.67%, the CO2 conversion rate is 77.43%, the average space-time yield of H2 is 1.17 mmol / (g·min), and the average space-time yield of CO is 1.34 mmol / (g·min).

[0057] Table 2 Performance Comparison of Different DFMs

[0058] Analysis of the impact of reducing gas on the performance of DFMs: As shown in Table 2, Example 5 of this invention achieved average space-time yields of 1.71 mmol / (g·min) for CO and 1.56 mmol / (g·min) for H2 over 20 cycles, demonstrating superior conversion performance and stability compared to the aforementioned results. Compared to H2 reduction (Comparative Example 1) and non-reduced N2 purging (Comparative Example 2), CO reduction at 750°C (Example 5) continuously activated the material in the first 5 cycles, resulting in higher average space-time yields of H2 and CO, as well as CH4 conversion. In the subsequent 15 cycles, all performance indicators remained stable and were significantly superior to H2 reduction and non-reduced N2 purging. This higher conversion performance is attributed to the characteristic of CO reduction being a mild, self-limiting surface reduction. CO only reduces the surface NiO, preventing further reduction of the internal NiO, which reduces the size of Ni particles and improves the dispersion of active sites (e.g., ...). Figure 4 , Figure 5 As shown in the figure, during the capture process, the volume change of Ca species can release NiO from the inside to the surface. During the conversion process, the NiO that has migrated to the surface can be reduced in situ, thereby realizing the gradual activation of conversion performance. Analysis of the effect of reduction temperature on the performance of DFMs: The performance test results from Examples 1-6 show that the reduction temperature affects both the reduction degree of NiO and the sintering degree of Ni particles. Reduction at 750℃ balances these two effects, achieving higher conversion performance and stability. Below 750℃, the reduction degree of NiO weakens; above 750℃, the sintering degree of Ni particles increases, affecting the reduction of NiO.

[0059] The CO-reduced NiPt-CaO / MgO bifunctional material proposed in this invention has the characteristics of small Ni particle size, high conversion activity, and simple process. Although there is an activation period in the early stage of the cycle, this stage coincides with the start-up stage of actual industrial operation and does not affect its excellent long-term operating stability. Therefore, it has significant prospects for industrial application.

Claims

1. A NiPt-CaO / MgO bifunctional material, characterized in that, The Ni loading is 5-15 wt.%, the Pt loading is 0.1-1 wt.%, and the mass ratio of CaO to MgO is (4-19):

1.

2. The preparation method of the NiPt-CaO / MgO bifunctional material according to claim 1, comprising the following steps: S1. Weigh out a certain amount of calcium nitrate tetrahydrate, magnesium nitrate hexahydrate and nickel nitrate hexahydrate and dissolve them in water. Add a certain amount of chloroplatinic acid solution and anhydrous citric acid as a chelating agent. The molar ratio of total metal cations, anhydrous citric acid and deionized water is 1:1.2:

60. S2. Place the solution prepared in step S1 in a water bath and stir vigorously until it becomes a gel. Then dry the gel and calcine it in a muffle furnace to obtain the bifunctional material NiPt-CaO / MgO, with Ni loading of 5-15 wt.%, Pt loading of 0.1-1 wt.%, and CaO to MgO mass ratio of (4-19):

1.

3. The method for preparing NiPt-CaO / MgO bifunctional materials according to claim 2, characterized in that, In step S2, the water bath temperature is 70-95℃ and the stirring time is 4-8h.

4. The method for preparing NiPt-CaO / MgO bifunctional materials according to claim 2, characterized in that, In step S2, the drying temperature of the gel is 100-140℃, and the drying time is 6-12h.

5. The method for preparing NiPt-CaO / MgO bifunctional materials according to claim 2, characterized in that, In step S2, calcination is carried out by heating the temperature to 700-900℃ at a heating rate of 3-10℃ / min for 1-4 hours.

6. The application of the NiPt-CaO / MgO bifunctional material according to claim 1, characterized in that, It was applied to CO2 capture-conversion.

7. The reduction method for CO2 capture-conversion of NiPt-CaO / MgO bifunctional material according to claim 1, wherein the NiPt-CaO / MgO bifunctional material is loaded into a fixed-bed reactor, N2 is introduced to replace and remove CO2, O2 and water vapor in the system, reducing gas CO is introduced until its concentration remains stable, and the temperature is raised to the reduction temperature for reduction.

8. The reduction method for CO2 capture-conversion using NiPt-CaO / MgO bifunctional materials according to claim 7, characterized in that, The NiPt-CaO / MgO bifunctional material has a Ni loading of 5-15 wt.%, a Pt loading of 0.1-1 wt.%, and a CaO to MgO mass ratio of (4-19):

1.

9. The reduction method for CO2 capture-conversion using NiPt-CaO / MgO bifunctional materials according to claim 7, characterized in that, The concentration of the reducing gas CO is 5-20%, and the equilibrium gas for reducing gas CO is N2.

10. The reduction method for CO2 capture-conversion using NiPt-CaO / MgO bifunctional materials according to claim 7, characterized in that, The temperature is increased from room temperature to 700-900℃ at a rate of 5-10℃ / min, and the reduction time is 1-4h.

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