Co-fe bimetallic active site synergistic catalyst, preparation method thereof and application of the catalyst in carbonation coupled with ethane oxidative dehydrogenation

Abstract

The application discloses a cobalt-iron double active site synergistic catalyst, a preparation method thereof and application of the catalyst in carbonated salt pyrolysis CO2 coupling ethane oxidation dehydrogenation, and adopts a soluble metal salt mixed solution and an alkaline solution to obtain the cobalt-iron double active site synergistic catalyst through nucleation stirring, crystallization and high-temperature calcination. The catalyst prepared by the application has excellent catalytic activity, selectivity and thermal stability, realizes efficient preparation of C2H4 and CO, simultaneously realizes full utilization of waste heat in the carbonated salt pyrolysis process and resource conversion of CO2, and contributes to the development of an environment-friendly society and a circular economy.

Description

Technical Field

[0001] This invention belongs to the field of catalyst preparation technology, specifically relating to a cobalt-iron dual-active-site synergistic catalyst, its preparation method, and its application in carbonate pyrolysis CO2 coupled with ethane oxidative dehydrogenation. Background Technology

[0002] Metal oxides produced by the pyrolysis of carbonates are important raw materials in process industries such as cement, steel, and refractory materials. However, while carbonates decompose at high temperatures to generate metal oxides, they also produce and release large amounts of CO2. Statistics show that over 50% of industrial carbon emissions nationwide originate from the high-temperature pyrolysis of carbonates. Therefore, significantly reducing CO2 emissions while simultaneously ensuring the effective utilization of carbonate resources is crucial.

[0003] CO2-ODHE is an effective method for converting the greenhouse gas CO2 and C2H6 into C2H4 and CO. C2H4 is a basic organic feedstock for the production of chemicals such as styrene, ethylene oxide, and vinyl chloride, and is a core component of the petrochemical industry. Using CO in downstream reactions allows for the synthesis of a series of platform chemicals through existing mature processes such as Fischer-Tropsch synthesis and methanol synthesis. However, the industrial application of CO2-ODHE technology is limited by factors such as catalyst deactivation due to carbon buildup at high temperatures and low CO2 conversion rates.

[0004] To date, research on CO2-ODHE has been extensive, with noble metal catalysts exhibiting high activity, but their high cost limits their large-scale application. In contrast, non-noble metal catalysts, especially cobalt-based catalysts, are widely used in the dehydrogenation reactions of low-carbon alkanes due to their low cost and selective disruption of CH bonds. However, the conversion rate for the CO2-ODHE reaction is low, and adjusting the catalytic performance and controllable product selectivity of cobalt catalysts remains a challenge. Summary of the Invention

[0005] This invention is proposed to overcome the shortcomings of the prior art, and its purpose is to provide a cobalt-iron dual-active-site synergistic catalyst, its preparation method, and its application in carbonate pyrolysis CO2 coupled with ethane oxidative dehydrogenation.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a cobalt-iron dual-active-site synergistic catalyst includes the following steps:

[0008] (i) Prepare a soluble metal salt mixed solution;

[0009] (ii) Prepare an alkaline solution;

[0010] (iii) Add the soluble metal salt mixture and alkaline solution to the nucleation reactor, and stir to obtain the initial product;

[0011] (iv) The initial product was placed in a reaction vessel for crystallization. After crystallization, the product was washed, dried, and ground to obtain the cobalt-iron dual-active-site synergistic catalyst precursor (Co). x Mg3Al2Fe y -LDHs);

[0012] (v) The cobalt-iron dual-active-site synergistic catalyst precursor is calcined at high temperature to obtain the cobalt-iron dual-active-site synergistic catalyst (Co). x Mg3Al2Fe y -MMO).

[0013] In the above technical solution, the solutes of the soluble metal salt mixed solution include soluble cobalt salt, soluble magnesium salt, soluble iron salt and soluble aluminum salt; the solvent of the soluble metal salt mixed solution is deionized water.

[0014] In the above technical solution, both the soluble metal salt mixed solution and the alkaline solution are prepared by ultrasonic dispersion for 5 min to 30 min.

[0015] In the above technical solution, the soluble cobalt salt is cobalt nitrate or cobalt chloride; the soluble magnesium salt is magnesium nitrate or magnesium chloride; the soluble iron salt is ferric nitrate or ferric chloride; and the soluble aluminum salt is aluminum nitrate or aluminum chloride.

[0016] In the above technical solution, the molar ratio of the soluble cobalt salt, soluble magnesium salt, soluble aluminum salt and soluble iron salt is (0.5~2):3:2:(0.1~0.5).

[0017] In the above technical solution, the solute of the alkaline solution includes sodium hydroxide and sodium carbonate, and the solvent of the alkaline solution is deionized water.

[0018] In the above technical solution, the molar amount of sodium carbonate is twice the total molar amount of trivalent cations in the soluble metal salt mixed solution; the molar amount of sodium hydroxide is 1.6 times the total molar amount of cations in the soluble metal salt mixed solution.

[0019] In the above technical solution, the stirring speed of nucleation in step (iii) is 3000 rpm and the stirring time is 5 min; the crystallization conditions in step (iv) are crystallization at 120℃ for 24 h; and the high-temperature calcination conditions in step (v) are calcination at 800℃ for 4 h in an air atmosphere.

[0020] A cobalt-iron dual-active-site synergistic catalyst, wherein the catalyst is Co1Mg3Al2-MMO, Co1Mg3Al2Fe 0.1 -MMO,Co1Mg3Al2Fe 0.2 -MMO or Co1Mg3Al2Fe 0.5-MMO.

[0021] The application of a cobalt-iron dual-active-site synergistic catalyst in the CO2-coupled ethane oxidative dehydrogenation of carbonate pyrolysis, wherein the reaction conditions for the CO2-coupled ethane oxidative dehydrogenation of carbonate pyrolysis are as follows: under atmospheric pressure, a continuous fixed-bed reactor is filled with a cobalt-iron dual-active-site synergistic catalyst, and a mixture of ethane and carbon dioxide is introduced for the reaction. The reaction gas composition is 5% CO2 + 5% C2H6 + Ar. The reaction temperature is 600℃~700℃, and the space velocity is 9000 ml·g. -1 ·h -1 .

[0022] The beneficial effects of this invention are:

[0023] This invention provides a cobalt-iron dual-active-site synergistic catalyst, its preparation method, and its application in the coupled ethane oxidative dehydrogenation of carbonate pyrolysis (CO2). The cobalt-iron dual-active-site synergistic catalyst prepared according to this invention achieves synergistic catalysis by controlling the Co and Fe content on a MgAl2O4 spinel support. Co selectively breaks the CH bond, serving as the main active site promoting ethane dehydrogenation, while Fe sites are responsible for carbon dioxide dissociation, supplementing lattice oxygen to enhance ethane oxidative dehydrogenation. Based on this, its application in the CO2-ODHE reaction exhibits excellent catalytic performance. At 675℃, the ethane conversion rate can reach 18.2%, and the ethylene selectivity exceeds 90%, with good catalyst stability during the reaction. Compared with existing catalysts, the CO2-ODHE catalyst provided by this invention has strong high-temperature stability and advantages such as simple preparation method and low production cost. Coupling the carbonate pyrolysis CO2 and ethane dehydrogenation reactions in the same catalytic system reduces energy consumption and production costs. This invention enables full utilization of the high-temperature waste heat generated by carbonate pyrolysis, while promoting the secondary utilization of carbon sources in carbonates, effectively reducing CO2 emissions, promoting the efficient production of ethylene and CO, and opening up new avenues for carbon cycling and sustainable resource utilization, with significant environmental and economic benefits. Attached Figure Description

[0024] Figure 1 This is a scanning electron microscope image of the cobalt-iron dual-active-site synergistic catalyst prepared in Example 1 of this invention;

[0025] Figure 2 This is a transmission electron microscope image of the cobalt-iron dual-active-site synergistic catalyst prepared in Example 1 of this invention;

[0026] Figure 3 This is a stability diagram of the cobalt-iron dual-active-site synergistic catalyst prepared in Example 1 of this invention.

[0027] Figure 4This is a comparison chart of the application performance of the catalyst prepared in Example 1 of this invention with other catalysts.

[0028] Figure 5 This is a performance comparison chart of the catalysts prepared in Examples 1-4 of this invention.

[0029] For those skilled in the art, other related figures can be obtained from the above figures without any creative effort. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] Example 1

[0032] A cobalt-iron dual-active-site synergistic catalyst (Co1Mg3Al2Fe) 0.2 The preparation method of -MMO is as follows:

[0033] First, a mixed solution of 0.01 mol / L cobalt nitrate, 0.01 mol / L magnesium nitrate, 0.01 mol / L ferric nitrate, and 0.01 mol / L aluminum nitrate was prepared using deionized water. A mixed solution of sodium hydroxide (1.6 times the total molar amount of cations) and sodium carbonate (2 times the molar amount of trivalent cations) was prepared using deionized water. Both mixed solutions were transferred to a nucleation reactor and stirred for 5 min. The mixture was then placed in a reaction vessel and crystallized at 120 °C for 24 h to obtain Co1Mg3Al2Fe. 0.2 -LDH catalyst precursor; the obtained product was washed, dried, and ground, then heated to 800℃ in a muffle furnace at 5℃ / min, calcined for 4 h, and then cooled to room temperature at 10℃ / min. 0.1 g of catalyst was used for the carbon dioxide oxidation and ethane dehydrogenation reaction.

[0034] The Co1Mg3Al2Fe obtained in this embodiment 0.2 The SEM image of the MMO catalyst is attached. Figure 1 ,from Figure 1 The stable existence of the hydrotalcite nanosheet morphology can be observed; Figure 2 The Co1Mg3Al2Fe obtained in this embodiment 0.2 HRTEM image of -MMO catalyst Figure 3 This indicates that Co1Mg3Al2Fe 0.2 -MMO catalyst at a space velocity of 9000 ml·g -1 ·h -1 Under these conditions, it exhibits good catalytic activity and stability; Figure 4 This indicates that the Co1Mg3Al2Fe obtained in this embodiment is... 0.2-MMO catalysts exhibit higher ethane conversion and ethylene selectivity compared to other catalysts.

[0035] Example 2

[0036] A method for preparing a cobalt-iron dual-active-site synergistic catalyst (Co1Mg3Al2-MMO) includes the following specific steps:

[0037] First, a mixed solution of 0.01 mol / L cobalt nitrate, 0.01 mol / L magnesium nitrate, and 0.01 mol / L aluminum nitrate was prepared using deionized water. A mixed solution of sodium hydroxide with 1.6 times the total molar amount of cations and sodium carbonate with 2 times the molar amount of trivalent cations was prepared using deionized water. Both mixed solutions were transferred to a nucleation reactor and stirred for 5 minutes. The mixed solutions were then loaded into a reaction vessel and crystallized at 120 °C for 24 hours to obtain the Co1Mg3Al2-LDH catalyst precursor. The obtained product was washed, dried, and ground, then calcined in a muffle furnace at 5 °C / min to 800 °C for 4 hours, followed by cooling to room temperature at 10 °C / min. 0.1 g of the catalyst was weighed for the carbon dioxide oxidation and ethane dehydrogenation reaction.

[0038] Example 3

[0039] A cobalt-iron dual-active-site synergistic catalyst (Co1Mg3Al2Fe) 0.1 The preparation method of -MMO is as follows:

[0040] First, a mixed solution of 0.01 mol / L cobalt nitrate, 0.01 mol / L magnesium nitrate, 0.01 mol / L ferric nitrate, and 0.01 mol / L aluminum nitrate was prepared using deionized water. A mixed solution of sodium hydroxide (1.6 times the total molar amount of cations) and sodium carbonate (2 times the molar amount of trivalent cations) was prepared using deionized water. Both mixed solutions were transferred to a nucleation reactor and stirred for 5 minutes. The mixture was then placed in a reaction vessel and crystallized at 120°C for 24 hours to obtain Co1Mg3Al2Fe. 0.1 -LDH catalyst precursor; the obtained product was washed, dried, and ground, then heated to 800℃ in a muffle furnace at 5℃ / min, calcined for 4 h, and then cooled to room temperature at 10℃ / min. 0.1 g of catalyst was used for the carbon dioxide oxidation and ethane dehydrogenation reaction.

[0041] Example 4

[0042] A cobalt-iron dual-active-site synergistic catalyst (Co1Mg3Al2Fe) 0.5 The preparation method of -MMO is as follows:

[0043] First, a mixed solution of 0.01 mol / L cobalt nitrate, 0.01 mol / L magnesium nitrate, 0.01 mol / L ferric nitrate, and 0.01 mol / L aluminum nitrate was prepared using deionized water. A mixed solution of sodium hydroxide (1.6 times the total molar amount of cations) and sodium carbonate (2 times the molar amount of trivalent cations) was prepared using deionized water. Both mixed solutions were transferred to a nucleation reactor and stirred for 5 minutes. The mixture was then placed in a reaction vessel and crystallized at 120°C for 24 hours to obtain Co1Mg3Al2Fe. 0.5 -LDH catalyst precursor; the obtained product was washed, dried, and ground, then heated to 800℃ in a muffle furnace at 5℃ / min, calcined for 4 h, and then cooled to room temperature at 10℃ / min. 0.1 g of catalyst was used for the carbon dioxide oxidation and ethane dehydrogenation reaction.

[0044] Figure 5 This is a performance comparison chart of the catalysts obtained in Examples 1-4 of this invention. It can be seen that: Co1Mg3Al2-MMO, Co1Mg3Al2Fe 0.1 -MMO,Co1Mg3Al2Fe 0.2 -MMO,Co1Mg3Al2Fe 0.5 -MMO catalysts exhibit good catalytic performance, Co1Mg3Al2Fe 0.2 -MMO catalysts exhibit the best catalytic activity.

[0045] The principle of this invention:

[0046] This invention achieves high selectivity and high stability in the carbon dioxide oxidative ethane dehydrogenation reaction (CO2-ODHE); it combines the carbonate pyrolysis process with the ethane dehydrogenation reaction, making full use of the high-calorific-value CO2 in the industrial tail gas of carbonate pyrolysis; using cobalt nitrate hexahydrate, magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and ferric nitrate nonahydrate as raw materials, a Co with an adjustable cobalt-iron ratio is prepared by a nucleation crystallization isolation method. x Mg3Al2Fe y -LDHs, as catalyst precursors, were further calcined to obtain a series of catalysts. Studies have shown that Co selectively breaks the CH bond, which is the main active site promoting ethane dehydrogenation, while Fe sites are responsible for carbon dioxide dissociation, supplementing lattice oxygen to enhance the oxidative dehydrogenation of ethane. Under the synergistic catalysis of cobalt and iron dual active sites, good catalytic activity and stability were exhibited, thus effectively solving the problem of low product selectivity in the reaction process. This provides a new method for the efficient conversion of carbon dioxide, opens up new avenues for carbon cycling and sustainable resource utilization, and provides ideas for the design of innovative dehydrogenation catalysts.

[0047] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0048] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. Application of a cobalt-iron dual active site synergistic catalyst in the carbonation of ethane oxidation dehydrogenation coupled with CO2 pyrolysis, characterized by: The catalyst is Co1Mg3Al2Fe 0.1 - MMO, Co1Mg3Al2Fe 0.2 - MMO or Co1Mg3Al2Fe 0.5 - MMO; The preparation method of the catalyst comprises the following steps: (i) preparing a mixed solution of soluble metal salts; (ii) preparing an alkaline solution; (iii) adding the mixed solution of soluble metal salts and the alkaline solution into a nucleation reactor, and stirring to obtain an initial product; (iv) loading the initial product into a reactor for crystallization, and then washing, drying and grinding the product after crystallization to obtain a cobalt-iron dual active site synergistic catalyst precursor; (v) high-temperature calcining the cobalt-iron dual active site synergistic catalyst precursor to obtain the cobalt-iron dual active site synergistic catalyst.

2. The cobalt-iron dual active site synergistic catalyst for use in the pyrolysis of carbonates to couple CO2 with ethane oxidative dehydrogenation according to claim 1, characterized in that: The solutes of the mixed solution of soluble metal salts include soluble cobalt salts, soluble magnesium salts, soluble iron salts and soluble aluminum salts; and the solvent of the mixed solution of soluble metal salts is deionized water.

3. The cobalt-iron dual active site synergistic catalyst for use in the pyrolysis of carbonates to couple CO2 with ethane oxidative dehydrogenation according to claim 1, characterized in that: The mixed solution of soluble metal salts and the alkaline solution are both dispersed by ultrasonic for 5-30 minutes.

4. The cobalt-iron dual active site synergistic catalyst for use in the pyrolysis of carbonates to couple CO2 with ethane oxidative dehydrogenation according to claim 2, characterized in that: The soluble cobalt salt is cobalt nitrate or cobalt chloride; the soluble magnesium salt is magnesium nitrate or magnesium chloride; the soluble iron salt is iron nitrate or iron chloride; and the soluble aluminum salt is aluminum nitrate or aluminum chloride.

5. The cobalt-iron dual active site synergistic catalyst for use in the pyrolysis of carbonates to couple CO2 with ethane oxidative dehydrogenation according to claim 2, characterized in that: The concentration of the soluble cobalt salt is 0.01-0.05 mol / L.

6. The cobalt-iron dual active site synergistic catalyst according to claim 1 for use in the carbonate pyrolysis CO2 coupling ethane oxidative dehydrogenation, characterized in that: The solutes of the alkaline solution include sodium hydroxide and sodium carbonate, and the solvent of the alkaline solution is deionized water.

7. The cobalt-iron dual active site synergistic catalyst for use in the thermal decomposition of carbonates coupled with the oxidative dehydrogenation of ethane according to claim 6, characterized in that: The molar amount of sodium carbonate is 2 times the total molar amount of trivalent cations in the mixed solution of soluble metal salts; and the molar amount of sodium hydroxide is 1.6 times the total molar amount of cations in the mixed solution of soluble metal salts.

8. The cobalt-iron dual active site synergistic catalyst according to claim 1 for use in the carbonate pyrolysis CO2 coupling ethane oxidative dehydrogenation, characterized in that: The stirring speed of the step (iii) is 3000 rpm, and the stirring time is 5 minutes; the crystallization condition of the step (iv) is crystallization at 120℃ for 24 hours; and the high-temperature calcining condition of the step (v) is calcining at 800℃ for 4 hours in an air atmosphere.

9. The cobalt-iron dual active site synergistic catalyst according to claim 1 for use in the carbonate pyrolysis CO2 coupling ethane oxidative dehydrogenation, characterized in that: The reaction conditions of the carbonic acid salt pyrolysis CO2 coupling ethane oxidation dehydrogenation are as follows: under normal pressure, a continuous fixed bed reactor is filled with a cobalt-iron dual active site synergistic catalyst, reaction gas is introduced for reaction, the reaction gas is composed of CO2, C2H6 and Ar, CO2 accounts for 5% of the total volume of the reaction gas, C2H6 accounts for 5% of the total volume of the reaction gas; the reaction temperature is 600 DEG C ~ 700 DEG C, the space velocity is 9000 ml·g -1 ·h -1 .

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