Rh-Ni bimetallic catalyst and preparation method and application thereof

Abstract

The invention provides an Rh-Ni bimetallic catalyst as well as a preparation method and application thereof, and relates to the technical field of catalyst preparation. The confinement effect is utilized, a small amount of precious metal rhodium is introduced into the nickel-based catalyst, the catalytic activity of the catalyst is enhanced through the synergistic effect of rhodium and nickel, high performance of the catalyst is guaranteed while addition of precious metal is reduced, and the Rh-Ni bimetallic catalyst with excellent catalytic activity and carbon deposition resistance is prepared. According to the method, migration and aggregation of metal particles can be effectively inhibited, generation of carbon deposition is reduced, and the service life of the catalyst is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and in particular to a Rh-Ni bimetallic catalyst and a preparation method and application thereof. Background Art

[0002] Driven by the global economic expansion and population growth, the surge in energy demand, especially the reliance on traditional fossil fuels, has triggered the dual crises of resource depletion and environmental degradation. In particular, the emissions of carbon dioxide and methane have increased dramatically. As the main force of greenhouse gases, they bear an unshirkable responsibility for global warming. Faced with this grim situation, the international community is working together to explore new ways to reduce greenhouse gas emissions and seek clean and sustainable energy alternatives.

[0003] The rise of methane dry reforming technology (DRM) has opened up a new perspective for addressing the above challenges. This technology innovatively uses chemical reactions to convert methane and carbon dioxide, two greenhouse gases, into synthesis gas (rich in carbon monoxide and hydrogen), which can not only directly reduce greenhouse gas emissions, but also convert them into high-value-added chemicals and liquid fuels, such as fuels made by the Fischer-Tropsch synthesis process, realizing a green transformation from "waste" to "treasure".

[0004] However, the widespread application of DRM technology still faces many difficulties. The core challenge lies in improving the stability of the catalyst and its ability to resist carbon deposition. Currently, nickel-based catalysts are favored for their economy and catalytic activity, but they are easily troubled by metal sintering and carbon deposition in actual operation, which leads to rapid failure of the catalyst and hinders its industrialization process. Metal sintering is particularly significant under high temperature conditions. It reduces the specific surface area of ​​the catalyst, causing the active sites to aggregate, thereby weakening the catalytic efficiency. The carbon deposition problem originates from the methane cracking and carbon monoxide disproportionation reactions. The generated carbon layer covers the surface of the catalyst, blocking the contact between the reactants and the active sites and accelerating the degradation of the catalyst.

[0005] In contrast, precious metal catalysts (such as platinum, palladium, and rhodium) show excellent catalytic activity and resistance to carbon deposition, but their high cost and scarcity have become bottlenecks restricting their large-scale application. Therefore, it is urgent to develop an innovative strategy that can not only retain the economy of nickel-based catalysts, but also significantly improve their stability and resistance to carbon deposition, or find more economical and efficient precious metal catalyst alternatives to break through the existing limitations of DRM technology and promote its widespread application in global low-carbon development. Summary of the invention

[0006] The present invention aims to provide a Rh-Ni bimetallic catalyst and a preparation method and application thereof. The catalyst confines active metal rhodium and nickel in a specific carrier through the confinement effect, and simultaneously utilizes the synergistic effect of rhodium and nickel to enhance the catalytic activity of the catalyst, thereby significantly improving the stability and anti-carbon deposition ability of the catalyst.

[0007] In a first aspect, the present invention provides a Rh-Ni bimetallic catalyst, comprising a carrier and an active component supported on the carrier, wherein the carrier is MgAl, and the active component comprises alloy particles of rhodium and nickel.

[0008] The Rh-Ni bimetallic catalyst provided by the present invention can effectively inhibit the migration and aggregation of metal particles, reduce the generation of carbon deposits, and thus extend the service life of the catalyst.

[0009] Optionally, the MgAl carrier is magnesium aluminum spinel with a specific surface area of ​​80m 2 / g-120m 2 / g, pore volume 0.3cm 3 / g-0.5cm 3 / g.

[0010] Optionally, the rhodium accounts for 0.1wt%-1.0wt% of the mass of the catalyst.

[0011] Optionally, the nickel accounts for 1.0wt%-2.0wt% of the mass of the catalyst.

[0012] Optionally, the introduction of rhodium can improve the dispersion of nickel and promote Ni 2+ reduction, increasing the number of active sites.

[0013] Optionally, the alloy particles have an average particle size of 2 nm-10 nm, so that they can be highly dispersed on the MgAl carrier, reducing sintering and carbon deposition of metal particles.

[0014] In a second aspect, the present invention provides a method for preparing the above catalyst, comprising the following steps:

[0015] In a solvent environment, aluminum salt, magnesium salt, rhodium salt and nickel salt are crystallized to obtain a precursor;

[0016] The precursor is calcined to obtain a RhNi-MgAl catalyst.

[0017] The catalyst preparation method provided by the present invention introduces a small amount of precious metal rhodium into the nickel-based catalyst, further confines the active metal nickel and rhodium on the surface space, significantly improves the dispersion of nickel, and simultaneously utilizes the synergistic effect of rhodium and nickel to enhance the catalytic activity of the catalyst. The method can effectively inhibit the migration and aggregation of metal particles, reduce the generation of carbon deposits, and increase the service life of the catalyst.

[0018] Optionally, the solvent environment includes at least one of methanol and ethanol.

[0019] Optionally, the pH of the solvent environment is 8-11.

[0020] Optionally, the aluminum salt includes any one of aluminum isopropoxide, aluminum nitrate and aluminum chloride.

[0021] Optionally, the magnesium salt includes any one of magnesium nitrate, magnesium sulfate and magnesium chloride.

[0022] Optionally, the rhodium salt includes any one of rhodium trichloride and rhodium nitrate.

[0023] Optionally, the nickel salt includes any one of nickel sulfate, nickel nitrate and nickel chloride.

[0024] Optionally, the molar ratio of the aluminum salt, magnesium salt, rhodium salt and nickel salt is (2-3):(0.8-1):(0.1-0.3):(0.4-1.2).

[0025] Optionally, the crystallization of the aluminum salt, magnesium salt, rhodium salt and nickel salt comprises: crystallization in a high pressure reactor at 150° C.-170° C. for 10 h-12 h.

[0026] Optionally, the prepared precursor needs to be cooled, filtered and dried.

[0027] Optionally, the calcination of the precursor includes: calcination at 700° C.-900° C. for 4 h-6 h in an air atmosphere.

[0028] Optionally, the calcination time and temperature of the precursor depend on the crystallinity and specific surface area required for the catalyst. Specifically, the calcination time and temperature are positively correlated with the crystallinity of the catalyst, and negatively correlated with the specific surface area of ​​the catalyst.

[0029] In a third aspect, the present invention provides an application of a catalyst prepared by any of the above optional preparation methods in a methane dry gas reforming reaction.

[0030] When the catalyst provided by the present invention is used for a methane dry gas reforming reaction, it has excellent stability and anti-carbon deposition performance compared to other catalysts.

[0031] Optionally, at 550°C-700°C, methane and carbon dioxide are reacted with a catalyst to generate carbon monoxide and hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly introduce the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments.

[0033] Figure 1The UV-visible spectra of the carrier and catalyst prepared in Example 1 of the present invention and the catalysts prepared in Comparative Examples 1 and 2;

[0034] Figure 2 The methane conversion rate of the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention in the methane dry gas reforming reaction at 600° C. for 0 h to 20 h;

[0035] Figure 3 Thermogravimetric analysis results of the catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention after undergoing methane dry gas reforming reaction at 100° C. to 800° C. for 20 hours. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described through the following embodiments in conjunction with the accompanying drawings. However, the following embodiments are illustrative and are only used to specifically describe the present invention rather than to limit the present invention.

[0037] The invention provides a Rh-Ni bimetallic catalyst, which comprises a carrier and an active component loaded on the carrier, wherein the carrier is MgAl, and the active component comprises alloy particles of rhodium and nickel.

[0038] In some embodiments, the MgAl carrier is a magnesium aluminum spinel with a specific surface area of ​​80 m 2 / g-120m 2 / g, pore volume 0.3cm 3 / g-0.5cm 3 / g.

[0039] In some embodiments, the rhodium accounts for 0.1 wt% to 1.0 wt% of the catalyst.

[0040] In some embodiments, the nickel accounts for 1.0 wt% to 2.0 wt% of the catalyst mass.

[0041] In some embodiments, the average particle size of the alloy particles is 2 nm-10 nm.

[0042] The present invention also provides a method for preparing the above catalyst, comprising the following steps:

[0043] S1. In a solvent environment, aluminum salt, magnesium salt, rhodium salt and nickel salt are crystallized to obtain a precursor;

[0044] S2. calcining the precursor to obtain a RhNi-MgAl catalyst.

[0045] In some embodiments, when executing step S1, the solvent environment includes at least one of methanol and ethanol.

[0046] In some embodiments, when performing step S1, the pH of the solvent environment is 8-11.

[0047] In some embodiments, when performing step S1, the aluminum salt includes any one of aluminum isopropoxide, aluminum nitrate and aluminum chloride.

[0048] In some embodiments, when performing step S1, the magnesium salt includes any one of magnesium nitrate, magnesium sulfate and magnesium chloride.

[0049] In some embodiments, when performing step S1, the rhodium salt includes any one of rhodium trichloride and rhodium nitrate.

[0050] In some embodiments, when performing step S1, the nickel salt includes any one of nickel sulfate, nickel nitrate and nickel chloride.

[0051] In some embodiments, when performing step S1, the molar ratio of the aluminum salt, magnesium salt, rhodium salt and nickel salt is (2-3):(0.8-1):(0.1-0.3):(0.4-1.2).

[0052] In fact, when executing step S1, the following sub-steps are included:

[0053] S1.1, in a high pressure reactor, in a solvent environment, aluminum salt and magnesium salt react to obtain a MgAl carrier;

[0054] S1.2, adding rhodium salt and nickel salt to the MgAl carrier for crystallization to obtain a precursor.

[0055] In some embodiments, when performing step S1.2, the crystallization of the MgAl carrier, rhodium salt and nickel salt includes: crystallization at 150°C-170°C for 10h-12h.

[0056] In some embodiments, when executing step S1.2, the prepared precursor needs to be cooled, filtered, and dried.

[0057] In some embodiments, when performing step S2, the calcination of the precursor includes: calcination at 700° C.-900° C. for 4 h-6 h in an air atmosphere.

[0058] The present invention also provides an application of the catalyst in a methane dry gas reforming reaction, comprising:

[0059] At 550℃-700℃, methane and carbon dioxide generate carbon monoxide and hydrogen under the action of catalyst.

[0060] Example 1

[0061] Embodiment 1 of the present invention provides a method for preparing a Rh-Ni bimetallic catalyst, comprising the following steps:

[0062] S1.1, in a 100 mL autoclave, dissolve 10 g aluminum isopropoxide and 3 g magnesium nitrate hexahydrate in 45 mL ethanol and stir vigorously to prepare a MgAl carrier;

[0063] S1.2, add 1g rhodium trichloride and 3g nickel nitrate hexahydrate into the inner container of the autoclave, and crystallize in an oil bath at 160°C for 10h to obtain a precursor;

[0064] S2. After the precursor is crystallized in an oil bath, it is allowed to stand and cool, and then filtered to obtain a solid. The solid is washed with deionized water, dried in an oven at 80°C for 8 h, and then ground into powder. The powder is calcined at 800°C for 5 h in an air atmosphere to obtain a Rh-Ni bimetallic catalyst.

[0065] In a fixed bed reactor, RhNi-MgAl catalyst was prepared by in-situ reduction at 75°C for 2h with a 10% H2-Ar mixed gas at a flow rate of 30mL / min, which can be used for methane dry gas reforming reaction.

[0066] Comparative Example 1

[0067] Comparative Example 1 of the present invention provides a method for preparing a Rh-based catalyst, which is different from Example 1 in that: 1.72 g of rhodium trichloride is added in step S1; nickel nitrate hexahydrate is not added in step S1, and finally a Rh-MgAl catalyst is prepared.

[0068] Comparative Example 2

[0069] Comparative Example 2 of the present invention provides a method for preparing a Ni-based catalyst, which is different from Example 1 in that: no rhodium trichloride is added in step S1, and a Ni-MgAl catalyst is finally prepared.

[0070] UV-vis spectroscopy analysis

[0071] UV-vis spectroscopy analysis was performed on the MgAl carrier and RhNi-MgAl catalyst prepared in Example 1, the Rh-MgAl catalyst prepared in Comparative Example 1, and the Ni-MgAl catalyst prepared in Comparative Example 2. Figure 1As shown in the figure, the results show that absorption peaks are detected at 380nm and 720nm for Ni-MgAl catalyst and RhNi-MgAl catalyst, proving the existence of octahedral spinel NiO in these two catalysts. At the same time, absorption peaks are detected at 590nm and 650nm, proving the existence of tetrahedral spinel NiAl in these two catalysts. In summary, Ni in Ni-MgAl catalyst and RhNi-MgAl catalyst exists in the form of NiO and NiAl. In addition, Rh is detected at about 410nm for Rh-MgAl catalyst and RhNi-MgAl catalyst. 3+ characteristic peaks.

[0072] Stability test

[0073] The catalysts prepared in Example 1, Comparative Example 1 and Comparative Example 2 were respectively used for methane dry gas reforming reaction:

[0074] First, RhNi-MgAl catalyst powder, Rh-MgAl catalyst powder and Ni-MgAl catalyst powder were sieved through a press sheet to 60 mesh to prepare a granular catalyst. 50 mg of the catalyst was respectively loaded into a quartz tube with an inner diameter of 6 mm and blocked at both ends with quartz wool. The catalyst was heated from room temperature to 750°C in a 10% H2 / Ar atmosphere with a space velocity of 30 mL / min and maintained for 2 h. After the reduction was completed, the reaction gas (CH4:CO2=1:1, WHSV=18,000 mL g cat -1 h -1 , p = 1atm), and tested the methane conversion rate and carbon dioxide conversion rate of the three catalysts for methane dry gas reforming reaction at 600℃ from 0h to 20h. The results are as follows Figure 2 shown.

[0075] The results showed that under the action of Rh-MgAl catalyst and RhNi-MgAl catalyst, with the increase of reaction time, the methane conversion rate remained stable and did not decrease significantly, indicating that the two catalysts were not deactivated and had a certain stability. Under the action of Ni-MgAl catalyst, with the increase of reaction time, the methane conversion rate decreased from 43% to 35%, proving that the activity of Ni-MgAl catalyst decreased and the stability was poor.

[0076] The TGA analysis process of the catalyst can be divided into two temperature ranges: the weight loss below 220°C is mainly attributed to the evaporation of water adsorbed inside the catalyst; while within 220°C to 700°C, the weight loss of the catalyst is directly related to the gasification of carbon on the catalyst surface. The three catalysts were subjected to methane dry gas reforming reaction at 600°C for 20 hours, and their different thermogravimetric behaviors were analyzed by TGA. The results are as follows Figure 3 shown.

[0077] TGA analysis shows that the Ni-MgAl catalyst exhibits a significant exothermic peak at 616 °C, accompanied by a weight loss step of up to 21%, indicating a large amount of carbon deposition on its surface, with a specific carbon generation amount reaching 266 mg / g. cat ; In contrast, the Rh-MgAl catalyst only shows a weak exothermic signal of carbon combustion near 302 °C, with a weight loss step of only 2%, and the carbon generation amount is significantly reduced to 15 mg / g. cat , showing certain anti-carbon deposition characteristics. Notably, the RhNi-MgAl catalyst does not show a weight loss step within the entire test range, directly proving that no carbon deposition occurs after continuous reaction at 600 °C for 20 h, demonstrating excellent anti-carbon deposition ability.

[0078] In summary, the anti-carbon deposition performance of the three catalysts is ranked as: Ni-MgAl < Rh-MgAl < RhNi-MgAl. Therefore, adding a small amount of noble metal rhodium to the nickel-based catalyst not only effectively inhibits the formation of carbon deposition, but also significantly enhances the anti-carbon deposition property and low-temperature operation stability of the catalyst. It should be noted that compared with the pure noble metal rhodium-based catalyst, the nickel-based catalyst containing a small amount of rhodium can maintain a catalytic efficiency similar to that of the pure noble metal catalyst while reducing the noble metal usage by 72.7%. This not only greatly reduces the preparation cost of the catalyst, but also shows higher economic efficiency and practicality.

[0079] Although the embodiments of the present invention have been described in detail above, it is obvious to those skilled in the art that various modifications and changes can be made to these embodiments. However, it should be understood that such modifications and changes are all within the scope and spirit of the present invention described in the claims. Moreover, the present invention described herein may have other embodiments and can be implemented or realized in various ways.

Claims

1. A Rh-Ni bimetallic catalyst, characterized in that: The catalyst comprises a carrier and an active component supported on the carrier, wherein the carrier is MgAl, and the active component comprises alloy particles of rhodium and nickel.

2. The catalyst according to claim 1, characterized in that The MgAl carrier is magnesium aluminum spinel with a specific surface area of ​​80m 2 / g-120m 2 / g, pore volume 0.3cm 3 / g-0.5cm 3 / g.

3. The catalyst according to claim 1, characterized in that The rhodium accounts for 0.1wt%-1.0wt% of the mass of the catalyst; the nickel accounts for 1.0wt%-2.0wt% of the mass of the catalyst; and the average particle size of the alloy particles is 2nm-10nm.

4. A method for preparing the catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: In a solvent environment, aluminum salt, magnesium salt, rhodium salt and nickel salt are crystallized to obtain a precursor; The precursor is calcined to obtain a RhNi-MgAl catalyst.

5. The preparation method according to claim 4, characterized in that: The solvent environment includes at least one of methanol and ethanol; the pH of the solvent environment is 8-11.

6. The preparation method according to claim 4, characterized in that: The aluminum salt includes any one of aluminum isopropoxide, aluminum nitrate and aluminum chloride; the magnesium salt includes any one of magnesium nitrate, magnesium sulfate and magnesium chloride; the rhodium salt includes any one of rhodium trichloride and rhodium nitrate; the nickel salt includes any one of nickel sulfate, nickel nitrate and nickel chloride; the molar ratio of the aluminum salt, magnesium salt, rhodium salt and nickel salt is (2-3):(0.8-1):(0.1-0.3):(0.4-1.2).

7. The preparation method according to claim 4, characterized in that: The crystallization of the aluminum salt, magnesium salt, rhodium salt and nickel salt comprises: crystallizing at 150° C.-170° C. for 10 h-12 h in a high-pressure reactor.

8. The preparation method according to claim 4, characterized in that: The calcination of the precursor includes: calcination at 700° C.-900° C. for 4 h-6 h in an air atmosphere.

9. A catalyst according to any one of claims 1 to 2, or a catalyst prepared by the preparation method according to any one of claims 3 to 8, characterized in that: Application in methane dry gas reforming reaction.

10. The use according to claim 9, characterized in that: At 550℃-700℃, methane and carbon dioxide generate carbon monoxide and hydrogen under the action of catalyst.

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