Ru / MgO material as well as preparation method and application thereof

Abstract

The invention discloses a Ru / MgO material as well as a preparation method and application thereof. The preparation method of the Ru / MgO material comprises the following steps: S1, preparing a solid-liquid mixture containing a ruthenium source and a magnesium precursor; s2, placing the solid-liquid mixture in liquid nitrogen to obtain a solid containing a ruthenium source coated magnesium precursor; s3, carrying out vacuum freeze drying on the solid; s4, calcining for 4 to 6 hours at the temperature of 500 to 700 DEG C in an oxygen-containing atmosphere, so as to obtain Ru2O3 / MgO; and S5, heating and reducing the Ru2O3 / MgO in a reducing atmosphere to obtain the Ru / MgO. According to the invention, a ruthenium source and a magnesium precursor are used as raw materials, a solid containing the ruthenium source coated on the surface of the magnesium precursor is obtained through liquid nitrogen freezing synthesis, and the Ru / MgO material is obtained through calcination and reduction treatment. The Ru / MgO material can effectively solve the problem that the catalytic activity is reduced due to the fact that ruthenium nanoparticles are easily and gradually inactivated at a high temperature, and has good catalytic activity and relatively high stability.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and more particularly, to a Ru / MgO material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, the excessive consumption of traditional fossil fuels has led to a continuous increase in the concentrations of greenhouse gases such as CH4 and CO2 in the atmosphere, exacerbating the greenhouse effect and global warming. According to the prediction of the Intergovernmental Panel on Climate Change (IPCC), if the existing emission trajectory is maintained, the global temperature will rise by 3.2 °C by the end of this century, far exceeding the goal of the Paris Agreement to limit global warming to less than 1.5 °C; among them, CO2 contributes approximately 63% to the greenhouse effect, and the global warming potential of CH4 is 65 times that of CO2. Therefore, developing efficient catalytic conversion technologies to convert CH4 and CO2 into high-value-added chemicals is a promising solution to alleviate the greenhouse effect.

[0003] The methane dual reforming reaction (methane-carbon dioxide-water dual reforming), i.e., 3CH4 + CO2 + 2H2O = 4CO + 8H2, can simultaneously activate and convert two greenhouse gases, CH4 and CO2. It not only delays carbon deposition in the reforming reaction by adding water but also adjusts the H2 / CO ratio by introducing carbon dioxide, synthesizing n (H2) / n (CO) synthesis gas with a ratio of approximately 2, providing raw materials for synthesizing high-value-added chemicals such as green methanol and light olefins. At the same time, it effectively alleviates the pressure of greenhouse gas emission reduction and improves the efficient utilization rate of carbon resources. Therefore, using the methane dual reforming technology to produce synthesis gas is a C1 chemical process with great application prospects and is of great significance in the fields of environmental protection, energy transformation, and scientific research.

[0004] Non-precious metal nickel-based catalysts have been widely studied for catalytic methane reforming reactions due to their low price and abundant production. However, the low activation energy of nickel-based catalysts for methane cracking leads to deep cracking of methane on their surface. The excessively high cracking rate causes carbon species to rapidly nucleate and grow on the catalyst surface, covering the active sites and deactivating the catalyst. In addition, due to its low Tamman temperature (about 590 °C), it is extremely prone to sintering under high-temperature conditions.

[0005] However, compared with non-noble transition metals, noble metal-based catalysts (such as Ru) usually exhibit excellent activity and anti-coking performance. However, their high production cost greatly limits their industrial applications. In this regard, the prior art has developed catalysts with low Ru loading (<1 wt%), but there are the following problems: on the one hand, the conversion rate of the catalysts with low Ru loading in the methane dry reforming reaction is much lower than that of the catalysts with high Ru loading (>1 wt%); on the other hand, for the Ru catalysts prepared by the existing preparation methods, the dispersion degree of the active component Ru is not high under the condition of low loading, and it is easy to agglomerate at high temperature, resulting in a decrease in catalytic activity and a short service life. If the conversion rate of the catalytic reaction is to be maintained above a certain target, a new catalyst needs to be replaced. Since the catalytic conversion rate of the catalysts with low Ru loading is lower than that of the catalysts with high Ru loading, the replacement frequency of the catalysts with low Ru loading is higher than that of the catalysts with high Ru loading. Generally speaking, using the catalysts with low Ru loading does not have much cost advantage. Summary of the Invention

[0006] The object of the present invention is to provide a preparation method of Ru / MgO material. The Ru / MgO material prepared by the preparation method has good catalytic activity, high stability and a long service life.

[0007] Another object of the present invention is to provide the Ru / MgO material prepared by the above preparation method.

[0008] Still another object of the present invention is to provide the application of the above Ru / MgO material in the catalytic methane dry reforming reaction.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is as follows: In the first aspect, a preparation method of Ru / MgO material includes the following steps: S1. Prepare a solid-liquid mixture containing a ruthenium source and a magnesium precursor; S2. Place the solid-liquid mixture in liquid nitrogen to obtain a solid containing the ruthenium source-coated magnesium precursor; S3. Vacuum freeze-dry the solid; S4. Calcinate at 500-700 °C for 4-6 h in an oxygen-containing atmosphere to obtain Ru2O3 / MgO; S5. Heat and reduce the Ru2O3 / MgO in a reducing atmosphere to obtain Ru / MgO.

[0010] The present invention uses a ruthenium source and a magnesium precursor as raw materials, and obtains a solid with the ruthenium source coated on the surface of the magnesium precursor through synthesis using liquid nitrogen freezing. After calcination and reduction treatment, magnesium oxide with medium strong basicity and high specific surface area is formed, and Ru nanoparticles are anchored on the surface of MgO to obtain the Ru / MgO material. The Ru / MgO material can effectively solve the problem that ruthenium nanoparticles are prone to gradually deactivate at high temperatures and reduce catalytic activity. Therefore, the Ru / MgO material of the present invention has good catalytic activity and high stability.

[0011] The catalytic performance of Ru-based material catalysts depends on the physicochemical properties of the support (such as specific surface area, acidity and basicity, oxygen storage capacity, etc.) and the preparation method of the material. These factors jointly determine the dispersion degree of the active metal Ru and the adsorption and activation ability of reactants, thus significantly affecting the catalytic performance.

[0012] Through research, it is found that the strong acidity of the catalyst support usually easily accelerates carbon deposition, resulting in catalyst deactivation. Therefore, the Lewis acidity of ZrO2 and Al2O3 will cause the deep cracking of methane to form carbon species that are difficult to oxidize. In addition, when using inert SiO2 as the catalyst support, due to the weak metal-support interaction, the active metal Ru is extremely easy to sinter at high temperatures.

[0013] When using alkaline earth metal oxide MgO as the support, its strong Lewis basicity is beneficial to the adsorption and activation of CO2, promoting the elimination of carbon deposition precursors by the active O* species formed by the dissociation of CO2. When the catalyst uses MgO as the support, a longer service life can be obtained compared with using ZrO2, Al2O3, and SiO2 as the support. However, through research, it is found that the catalytic activity and stability of Ru / MgO obtained by using the existing preparation methods (such as wet impregnation method to prepare MgO-supported Ru) are still not high and need to be further improved. The present invention uses alkaline earth metal oxide MgO as the support and adopts the preparation method of the present invention to obtain MgO with a large specific surface area, and enables MgO to form a strong metal-support interaction with the active metal Ru, promoting the dispersion of the active metal Ru, improving the atomic utilization rate of the active metal Ru, and effectively inhibiting the sintering of active sites, thereby improving the stability.

[0014] Optionally, in step S1, the ruthenium source and the magnesium precursor are dispersed in water to prepare a solid-liquid mixture containing the ruthenium source and the magnesium precursor. As one implementation, weigh the target mass of the ruthenium source and the magnesium precursor, dissolve or disperse them in deionized water, and perform ultrasonic treatment on the obtained solid-liquid mixture.

[0015] Conventional water-soluble ruthenium sources in the art can all be used in the present invention. Optionally, the ruthenium source is one or more of ruthenium chloride, ruthenium acetate, ruthenium nitrosyl nitrate, or ruthenium acetylacetonate; or, the ruthenium source is a solution containing one or more of ruthenium chloride, ruthenium acetate, ruthenium nitrosyl nitrate, or ruthenium acetylacetonate. Preferably, the ruthenium source is ruthenium chloride.

[0016] Optionally, the magnesium source is one or more of magnesium chloride, magnesium nitrate, magnesium hydroxide, magnesium carbonate, or magnesium acetate. Preferably, the magnesium source is magnesium hydroxide.

[0017] In step S3 of the present invention, the solid is subjected to vacuum freeze-drying. Optionally, the temperature of the vacuum freeze-drying is -50 to -20 °C. The time of the vacuum freeze-drying is 1 to 3 days (d), preferably 2 to 3 d.

[0018] In step S4 of the present invention, it is calcined at 500 to 700 °C for 4 to 6 h in an oxygen-containing atmosphere to obtain Ru2O3 / MgO; as one of the embodiments, the calcination temperature is 700 °C and the calcination time is 4 h. Optionally, the heating rate of the calcination is set to 2 °C / min.

[0019] Optionally, the oxygen-containing atmosphere is one or more of static or flowing air, 5% O2 / N2 mixture gas.

[0020] In step S5 of the present invention, the temperature of the heating reduction is 450 to 650 °C, and the reduction time is 1 to 2 h. The heating rate of the heating reduction is 5 to 10 °C / min.

[0021] Optionally, the reducing atmosphere is one or more of H2, H2 / N2, or H2 / Ar mixture gas.

[0022] The preparation method of the present invention can be used to prepare low-loading Ru / MgO. The loading of Ru in the Ru / MgO is 0.1 to 0.5 wt%. The loading refers to the mass fraction of the catalytically active component Ru in the whole Ru / MgO.

[0023] In the second aspect, the present invention also provides a Ru / MgO material, and the Ru / MgO material is prepared by the preparation method described in the first aspect.

[0024] In the Ru / MgO material of the present invention, the carrier MgO prepared by the preparation method has a large specific surface area and strong Lewis basicity, which can promote the dispersion degree of the active metal Ru, so as to improve the anti-coking and anti-sintering abilities of the Ru / MgO material. Therefore, the Ru / MgO material has good catalytic activity and stability, and can effectively catalyze the methane dual reforming reaction to synthesize syngas, and is used for the synthesis of downstream high-value-added chemicals.

[0025] Therefore, the application of the Ru / MgO material of the present invention as a catalyst in catalytic reactions, especially in the methane dual reforming reaction, should also be within the protection scope of the present invention.

[0026] In a third aspect, the present invention provides the application of the Ru / MgO material in the methane dual reforming reaction.

[0027] The Ru / MgO material of the present invention has not significantly deactivated after operating at 800 °C for at least 100 h in the methane dual reforming reaction. The methane conversion rate is maintained at 82-84%, the carbon dioxide conversion rate is maintained at 75-79%, and synthesis gas with an n(H2) / n(CO) of about 2 is obtained, which is beneficial to the synthesis of downstream green methanol.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses a ruthenium source and a magnesium precursor as raw materials, and obtains a solid with a ruthenium source coated on the surface of the magnesium precursor through cryosynthesis using liquid nitrogen. After calcination and reduction treatment, medium-strength basic and high-specific-surface-area magnesium oxide is formed, and Ru nanoparticles are anchored on the surface of MgO to obtain the Ru / MgO material. The Ru / MgO material can effectively solve the problem that ruthenium nanoparticles are prone to gradual deactivation at high temperatures, thereby reducing catalytic activity. Therefore, the Ru / MgO material of the present invention has good catalytic activity and high stability. Description of the Drawings

[0029] Figure 1 N2 adsorption-desorption isotherm and pore size distribution curve of the catalyst in Example 3.

[0030] Figure 2 Test result diagram of the catalyst stability of the examples and comparative examples; among them, Figure 2 a is the test result diagram of Example 3; Figure 2 b is the test result diagram of Comparative Example 1; Figure 2 c is the test result diagram of Comparative Example 3; Figure 2 d is the test result diagram of Comparative Example 4.

[0031] Figure 3 Test result diagram of the catalyst in Example 3 participating in the catalytic reaction for 100 h. Detailed Embodiments

[0032] The present invention will be further described below in conjunction with embodiments. These embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. For the experimental methods without specific conditions indicated in the following embodiments, they are generally carried out according to the conventional conditions in the art or according to the conditions recommended by the manufacturer; the raw materials, reagents, etc. used, unless otherwise specified, are all raw materials and reagents that can be obtained from commercial channels such as conventional markets. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention fall within the scope of protection required by the present invention.

[0033] The sources of the raw materials used in the following examples and comparative examples are as follows: Anhydrous ruthenium trichloride, Macklin, molecular weight: 207.42, CAS No.: 10049-08-8.

[0034] Ruthenium acetate, Macklin, purity: 99%, molecular weight: 278.20, CAS No.: 72196-32-8.

[0035] Ruthenium nitrosyl nitrate, Macklin, molecular weight: 318.1, CAS No.: 34513-98-9.

[0036] Ruthenium acetylacetonate, Macklin, purity: 99.95%, molecular weight: 398.39, CAS No.: 14284-93-6.

[0037] Commercial MgO, Macklin, purity: 99.9%, molecular weight: 40.30, grade: M761792, CAS No.: 1309-48-4.

[0038] Magnesium hydroxide, Macklin, purity: ≥99.0%, molecular weight: 58.32, CAS No.: 1309-42-8.

[0039] Anhydrous magnesium chloride, Macklin, purity: 99.9%, molecular weight: 95.21, CAS No.: 7786-30-3.

[0040] Magnesium nitrate hexahydrate, Guangzhou Chemical Reagent Factory, molecular weight: 256.41, CAS No.: 13446-18-9.

[0041] Magnesium carbonate hydrate, Macklin, molecular weight: 84.31, CAS No.: 23389-33-5.

[0042] Magnesium acetate, Macklin, purity: 98%, molecular weight: 142.39, CAS No.: 142-72-3.

[0043] Examples 1 to 3 The purpose of Examples 1 to 3 is to prepare Ru / MgO materials with different Ru loadings (as shown in Table 1), and the specific preparation method is as follows: Accurately weigh the corresponding masses of ruthenium trichloride and magnesium hydroxide, dissolve or disperse them in 30 mL of deionized water, sonicate for 30 min, and stir for 2 h to form a homogeneous solid-liquid mixture. Pour the homogeneous solid-liquid mixture quickly into a polytetrafluoroethylene inner liner filled with liquid nitrogen to obtain a solid with the ruthenium source coated on the surface of the magnesium precursor. Then, vacuum freeze-dry the solid at -50 °C for 48 h (2 d) to obtain the precursor Ru 3+ / Mg(OH)2. Put the obtained Ru 3+ / Mg(OH)2 into a muffle furnace, heat it at a rate of 2 °C / min, and calcine it at 700 °C for 4 h in an air atmosphere to obtain Ru2O3 / MgO. Finally, in-situ reduce Ru2O3 / MgO at 650 °C for 2 h in a 10% H2 / N2 reducing atmosphere.

[0044] Table 1

[0045] Examples 4 - 7 The purpose of Examples 4 - 7 is to investigate the influence of different magnesium precursors (such as MgCl2, MgCO3, etc.) on the catalytic performance of Ru / MgO materials. The specific preparation method is as follows: Accurately weigh the corresponding masses of ruthenium trichloride and magnesium precursor (see Table 2 for details), dissolve or disperse them in 30 mL of deionized water, sonicate for 30 min, and stir for 2 h to form a homogeneous solid-liquid mixture. Pour the homogeneous solid-liquid mixture quickly into a polytetrafluoroethylene inner liner filled with liquid nitrogen to obtain a solid with the ruthenium source coated on the surface of the magnesium precursor. Then, vacuum freeze-dry the solid at -50 °C for 48 h to obtain a Ru 3+ / Mg precursor. Put the obtained Ru 3+ / Mg precursor into a muffle furnace, heat it at a rate of 2 °C / min, and calcine it at 700 °C for 4 h in an air atmosphere to obtain Ru2O3 / MgO. Finally, in-situ reduce Ru2O3 / MgO at 650 °C for 2 h in a 10% H2 / N2 reducing atmosphere.

[0046] Table 2

[0047] Examples 8 - 10 The purpose of Examples 8 - 10 is to investigate the influence of different ruthenium sources (see Table 3) on the catalytic performance of Ru / MgO materials. The specific preparation method is as follows: Accurately weigh the corresponding mass of ruthenium source and magnesium hydroxide, dissolve or disperse them in 30 mL of deionized water, sonicate for 30 min, and stir for 2 h to form a homogeneous solid-liquid mixture. Pour the homogeneous solid-liquid mixture quickly into a polytetrafluoroethylene inner lining filled with liquid nitrogen to obtain a solid with the ruthenium source coated on the surface of magnesium precursor. Then, freeze-dry the solid at -50 °C under vacuum for 48 h (2 d) to obtain the precursor Ru 3+ / Mg(OH)2. Put the obtained Ru 3+ / Mg(OH)2 into a muffle furnace, heat it at a rate of 2 °C / min, and calcine it at 700 °C for 4 h in an air atmosphere to obtain Ru2O3 / MgO. Finally, in-situ reduce Ru2O3 / MgO at 650 °C for 2 h in a 10% H2 / N2 reducing atmosphere.

[0048] Table 3

[0049] Examples 11 - 12 Examples 11 - 12 aim to investigate the influence of different conditions in the preparation method on the catalytic performance of Ru / MgO materials. Ru / MgO with a loading of 0.5 wt% is prepared, and the specific preparation method is as follows: Example 11: Different from the preparation method of Example 3, in the vacuum freeze-drying treatment of Example 11, the temperature of vacuum freeze-drying is -20 °C, and the time of vacuum freeze-drying is 1 d.

[0050] Example 12: Different from the preparation method of Example 3, in the calcination of the precursor Ru 3+ / Mg(OH)2 in an oxygen-containing atmosphere, the calcination temperature is 500 °C, and the calcination time is 6 h; when heating and reducing Ru2O3 / MgO, the heating and reduction temperature is 450 °C, and the reduction time is 1 h.

[0051] Comparative Example 1 This comparative example aims to investigate the influence of the traditional wet impregnation method on the catalytic performance of Ru / MgO materials. Ru / MgO with a loading of 0.5 wt% is prepared, and the specific preparation method is as follows: Accurately weigh the corresponding mass of ruthenium trichloride and magnesium hydroxide, dissolve or disperse them in 30 mL of deionized water, sonicate for 30 min, and stir for 2 h to form a homogeneous solid-liquid mixture. Then, place it in an oven at 100 °C and dry it overnight to completely remove the moisture to obtain the precursor Ru 3+ / Mg(OH)2. Put the obtained Ru 3+Ru2O3 / MgO was obtained by putting Ru2O3 / Mg(OH)2 into a muffle furnace, heating at a rate of 2 °C / min, and calcining in an air atmosphere at 700 °C for 4 h. Finally, Ru2O3 / MgO was in-situ reduced at 650 °C for 2 h in a 10% H2 / N2 reducing atmosphere.

[0052] Comparative Example 2 In this comparative example, commercial MgO was directly used as the support to load Ru, and Ru / MgO with a loading of 0.5 wt% was prepared by the traditional wet impregnation method. The specific preparation method is as follows: Weigh accurately the corresponding masses of ruthenium trichloride and MgO, dissolve or disperse them in 30 mL of deionized water, sonicate for 30 min, and stir for 2 h to form a homogeneous solid-liquid mixture. Then place it in an oven at 100 °C and dry overnight to fully remove the moisture, obtaining the precursor Ru 3+ / MgO. The obtained Ru 3+ / MgO was put into a muffle furnace, heated at a rate of 2 °C / min, and calcined in an air atmosphere at 700 °C for 4 h to obtain Ru2O3 / MgO. Finally, Ru2O3 / MgO was in-situ reduced at 650 °C for 2 h in a 10% H2 / N2 reducing atmosphere.

[0053] Comparative Example 3 In this comparative example, commercial MgO was directly used as the support to load Ru, and Ru / MgO with a loading of 0.5 wt% was prepared. The specific preparation method is as follows: Weigh accurately the corresponding masses of ruthenium trichloride and MgO, dissolve or disperse them in 30 mL of deionized water, sonicate for 30 min, and stir for 2 h to form a homogeneous solid-liquid mixture. Pour the homogeneous solid-liquid mixture quickly into a polytetrafluoroethylene inner liner filled with liquid nitrogen to obtain a solid containing the ruthenium source and MgO. Then vacuum freeze-dry the solid at -50 °C for 2 d to obtain Ru 3+ / MgO. The obtained Ru 3+ / MgO was put into a muffle furnace, heated at a rate of 2 °C / min, and calcined at 700 °C for 4 h in an air atmosphere to obtain Ru2O3 / MgO. Finally, Ru2O3 / MgO was in-situ reduced at 650 °C for 2 h in a 10% H2 / N2 reducing atmosphere.

[0054] Comparative Example 4 The purpose of this comparative example was to investigate the influence of the traditional wet impregnation method on the catalytic performance of Ru / MgO materials. Ru / MgO with a loading of 1 wt% was prepared. The specific preparation method is as follows: Accurately weigh the corresponding mass of ruthenium trichloride and magnesium hydroxide, dissolve or disperse them in 30 mL of deionized water, sonicate for 30 min, and stir for 2 h to form a homogeneous solid-liquid mixture. Subsequently, place it in an oven at 100 °C and dry overnight to fully remove the moisture, obtaining the precursor Ru 3+ / Mg(OH)2. Put the obtained Ru 3+ / Mg(OH)2 into a muffle furnace, with a heating rate of 2 °C / min, and calcine at 700 °C in an air atmosphere for 4 h to obtain Ru2O3 / MgO. Finally, in-situ reduce Ru2O3 / MgO in a 10% H2 / N2 reducing atmosphere at 650 °C for 2 h.

[0055] Characterization and Performance Testing 1. Characterization The catalysts prepared in the above examples and comparative examples were characterized by the following means.

[0056] 1) ICP-OES test: Using ICP-OES technology, the actual loading of the active metal Ru in the catalysts prepared in the above examples and comparative examples was tested. The results are shown in Table 4. After ICP-OES testing, the actual loading of the active metal Ru was basically the same as the theoretical loading.

[0057] Table 4

[0058] 2) N2 physical adsorption-desorption test: A gas adsorption analyzer (Micromeritics ASAP 2460) was used to evaluate the specific surface area and pore structure, and the Brunauer-Emmett-Teller (BET) method was used to calculate the specific surface area. Specifically, before N2 physical adsorption measurement, the sample was degassed under vacuum conditions at 300 °C. The N2 adsorption / desorption isotherm was collected at -196 °C. According to the linear part of the adsorption isotherm, the total specific surface area was determined using the Brunauer-Emmett-Teller (BET) equation. The Barrett-Joyner-Halenda (BJH) model was used to calculate the total pore volume and average pore diameter.

[0059] As Figure 1 shown, the catalyst prepared in Example 3 exhibited a characteristic Type IV isotherm, accompanied by an H3-type hysteresis loop, indicating the presence of a unique mesoporous structure. By calculation, the BET specific surface area of the catalyst prepared in Example 3 was 15.66 m 2 g −1 , and the total pore volume was 0.17 cm 3 g −1, the average pore size is 36.25 nm.

[0060] 2. Performance Test To evaluate the catalytic performance of the catalyst, the methane dry reforming reaction was carried out in a fixed-bed reactor with an inner diameter of 8 mm under atmospheric pressure. The basic test steps and conditions are as follows: A quartz tube filled with 200 mg of the catalyst (20 - 40 mesh) was vertically placed in a fixed-bed heating furnace, and pure CH4, CO2, and N2 raw material gases with flow rates of 36 mL / min, 12 mL / min, and 12 mL / min were introduced. Using N2 as an internal standard, liquid water (flow rate of 0.0193 mL / min) was introduced using a syringe pump. After vaporization in a preheating furnace, it was mixed with other raw material gases and then injected into the fixed-bed reactor. The stoichiometric ratio was fixed as CH4:CO2:N2:H2O = 3:1:1:2, and the weight hourly space velocity (WHSV) was approximately 25000 mL g-1 Cat h -1 , and a gas-liquid separator was used to separate the residual water. A gas chromatograph with a thermal conductivity detector (TCD) was used for measurement. The gas chromatograph used a molecular sieve 5A column to separate H2, N2, CH4, and CO, and a Porapak Q column to separate CO2.

[0061] The conversion rates of CH4 and CO2 (Con.CH4 and Con.CO2), n (H2) / n (CO) were calculated as follows:

[0062] In the formula, In and out refer to the peak areas of the gas chromatograph, F H2 and F CO refer to the correction factors of H2 and CO. V CH4 is the methane flow rate (2.16 L / h), and V m is the molar volume of the gas under the experimental conditions (22.4 L / mol).

[0063] 1) Catalytic Activity Based on the above basic test steps and conditions, the test temperature range was controlled to be 650 - 800 °C, the temperature interval was 50 °C, the heating rate was 10 °C / min, and each temperature point was maintained for 2 h. The test results of Examples 1 - 7 and Comparative Example 1 are shown in Table 5: Table 5

[0064] On the basis of the basic test steps and conditions, the test temperature was controlled at 800 °C, the heating rate was 10 °C / min. The test results of Examples 8-12 and Comparative Examples 2-4 after running for 1 h when the temperature reached 800 °C are shown in Table 6: Table 6

[0065] 2) Catalyst stability To evaluate the catalytic stability of the catalyst, on the basis of the basic test steps and conditions, the test temperature was controlled at 800 °C, the test time was 40 h, and the heating rate was 10 °C / min. The test results of Example 3, Comparative Examples 1, 3, and 4 are as Figure 2 shown.

[0066] By Figure 2 a compared with Figure 2 b, 2c, and 2d, it can be seen that the stability of the catalyst prepared in Example 3 is significantly higher than that of the catalysts prepared in Comparative Example 1, Comparative Example 3, and Comparative Example 4. Among them, by comparing Example 3 with Comparative Example 1, it can be seen that under the condition of the same or similar Ru loading, adopting the preparation method of the present invention can not only effectively improve the CH4 conversion rate and CO2 conversion rate of the catalyst, but also extend the service life.

[0067] By comparing Example 3 with Comparative Example 3, it can be seen that although Comparative Example 3 uses the same preparation method as the present invention, due to directly using commercial MgO as the carrier, its catalytic activity and long-term stability are significantly inferior to the carrier system derived from magnesium precursors such as magnesium hydroxide.

[0068] By comparing Example 3 with Comparative Example 4, it can be seen that although the Ru loading of the catalyst prepared in Example 3 is only half of that of Comparative Example 4, the CH4 conversion rate and CO2 conversion rate of Example 3 are slightly higher than those of Comparative Example 4, and the stability of Example 3 is significantly better than that of Comparative Example 4.

[0069] To evaluate the long-term catalytic stability of the catalyst in Example 3, on the basis of the basic test steps and conditions, the test temperature was controlled at 800 °C, the test time was 100 h, and the heating rate was 10 °C / min.

[0070] The test results are as Figure 3 shown. It can be seen that after the catalyst prepared in Example 3 continuously catalyzes the methane dual reforming reaction at 800 °C for 100 hours, its CH4 conversion rate and CO2 conversion rate still do not show a decreasing trend. It can be seen that the catalyst prepared in Example 3 has high stability.

[0071] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a Ru / MgO material, characterized in that: The following steps are involved: S1. Preparing a solid-liquid mixture comprising a ruthenium source and a magnesium precursor; S2. placing the solid-liquid mixture in liquid nitrogen to obtain a solid containing a ruthenium source coated magnesium precursor; S3. The solid is freeze-dried in vacuum; S4. Calcinate at 500-700 °C for 4-6 h in an oxygen-containing atmosphere to obtain Ru2O3 / MgO; S5. The Ru2O3 / MgO is heated and reduced in a reducing atmosphere to obtain Ru / MgO.

2. The method for preparing the Ru / MgO material according to claim 1, characterized in that: In step S1, a ruthenium source and a magnesium precursor are dispersed in water to prepare a solid-liquid mixture containing the ruthenium source and the magnesium precursor.

3. The method for preparing the Ru / MgO material according to claim 1 or 2, characterized in that: The ruthenium source is one or more of ruthenium chloride, ruthenium acetate, ruthenium nitrosyl nitrate or ruthenium acetylacetonate; or, the ruthenium source is a solution containing one or more of ruthenium chloride, ruthenium acetate, ruthenium nitrosyl nitrate or ruthenium acetylacetonate.

4. The method for preparing the Ru / MgO material according to claim 1 or 2, characterized in that: The magnesium source is one or more of magnesium chloride, magnesium nitrate, magnesium hydroxide, magnesium carbonate or magnesium acetate.

5. The method for preparing the Ru / MgO material according to claim 1, characterized in that: In step S3, the vacuum freeze-drying temperature is -50 to -20 °C.

6. The method for preparing the Ru / MgO material according to claim 1, characterized in that: In step S4, the oxygen-containing atmosphere is one or more of static or flowing air, 5% O2 / N2 mixed gas.

7. The method for preparing the Ru / MgO material according to claim 1, characterized in that: In step S5, the temperature of the heating reduction is 450-650°C, and the reduction time is 1-2 hours; the reducing atmosphere is one or more of H2, H2 / N2 or H2 / Ar mixed gas.

8. The method for preparing the Ru / MgO material according to claim 1, characterized in that: The loading amount of Ru in the Ru / MgO is 0.1-0.5 wt %.

9. A Ru / MgO material, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Ru / MgO material according to claim 9 in catalyzing the double reaction of methane.

Images