A method for preparing, producing, and applying a metal-doped ZIFs-derived Co-based catalyst.

Abstract

This invention discloses a method for preparing a metal-doped ZIFs-derived Co-based catalyst, its product, and its application, relating to the field of carbon dioxide hydrogenation to methane catalyst technology. The aim is to improve the catalytic performance of ZIFs-derived Co-based catalysts. The invention includes high-temperature calcination of a ZIF-67 precursor to obtain a ZIF-67 precursor, followed by dispersion of a doped metal precursor salt in ultrapure water to achieve the desired doping amount. After complete dissolution, the doped metal precursor salt aqueous solution is added dropwise to the ZIF-67 precursor catalyst. After drying, the catalyst is calcined at high temperature to obtain the metal-doped ZIFs-derived Co-based catalyst, which can be applied to the thermocatalytic carbon dioxide methanation reaction. The preparation method of this invention is simple, and the resulting catalyst can more efficiently and selectively generate methane, reduce the formation of byproducts, and improve the purity of the product.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology for the hydrogenation of carbon dioxide to methane, specifically to a method for preparing a metal-doped ZIFs-derived Co-based catalyst, its product, and its application. Background Technology

[0002] The urgent need to reduce carbon dioxide emissions and achieve carbon neutrality has driven extensive research into carbon dioxide utilization technologies, particularly catalytic hydrogenation of carbon dioxide to methane (CO2 + 4H2 → CH4 + 2H2O). This reaction not only reduces greenhouse gas levels of carbon dioxide but also stores renewable energy in the chemically stable form of methane, a cornerstone of a circular carbon economy.

[0003] However, the practical implementation of carbon dioxide methanation depends on catalyst development, with catalyst activity, selectivity, and stability at moderate temperatures being particularly important. While traditional nickel-based catalysts are cost-effective, they often operate at temperatures above 300°C. o Catalysts above C are prone to sintering and carbon deposition; while noble metal catalysts (such as Ru and Rh) face scalability limitations due to their scarcity and high cost. Transition metal oxides (such as cobalt-based and iron-based catalysts) have become promising alternatives, but their performance is limited by insufficient active sites and poor CO2 activation kinetics.

[0004] Recent studies have shown that metal-oxide interfaces and surface defects, such as oxygen vacancies and hydroxyl groups, can synergistically enhance CO2 adsorption and modulate reaction pathways. For example, cobalt-based catalysts derived from zeolite imidazole salt frameworks (ZIFs) possess layered porosity and tunable electronic structures, but their methanation activity remains insufficient due to limited surface reactivity. Therefore, improving the catalytic performance of ZIFs-derived Co-based catalysts is one of the important research directions in the field of CO2 hydrogenation to methane. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing, a product of, and an application of a metal-doped ZIFs-derived Co-based catalyst, so as to improve the catalytic performance of the ZIFs-derived Co-based catalyst.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing a metal-doped ZIFs-derived Co-based catalyst, comprising the following steps:

[0007] Metal-organic framework-derived Co3O4 catalyst was obtained by high-temperature calcination of the metal-organic framework ZIF-67 precursor.

[0008] According to the required doping amount, the doped metal precursor salt is dispersed in ultrapure water. After it is fully dissolved, the doped metal precursor salt aqueous solution is added dropwise to the metal-organic framework-derived Co3O4 catalyst. After drying, it is calcined at high temperature to obtain the metal-doped ZIFs-derived Co-based catalyst.

[0009] Preferably, in the metal-doped ZIFs-derived Co-based catalyst, the mass ratio of the doped metal to the metal-organic framework-derived Co3O4 catalyst is (0.01–0.3):1.

[0010] Preferably, in the metal-doped ZIFs-derived Co-based catalyst, the mass ratio of the doped metal to the metal-organic framework-derived Co3O4 catalyst is (0.03-0.1):1.

[0011] Preferably, the calcination temperature of the metal-organic framework ZIF-67 precursor is 300–600°C, and the calcination time is 2–6 h; after the addition of the doped metal precursor salt aqueous solution, the calcination temperature is 300–800°C, and the calcination time is 2–6 h.

[0012] Preferably, the doping metal is Cr, Mn, Ni or La, and the doping metal precursor salt is selected from at least one of nitrate, acetate, carbonate, sulfate or chloride.

[0013] Preferably, the preparation steps of the metal-organic framework ZIF-67 precursor include: dissolving cobalt precursor salt and hexadecyltrimethylammonium bromide in deionized water to obtain solution A; dissolving 2-methylimidazole in deionized water to form solution B; slowly pouring B into A; stirring in a water bath at a constant temperature; drying; and calcining in air to obtain the metal-organic framework ZIF-67 precursor.

[0014] Preferably, the cobalt precursor salt is selected from at least one of cobalt nitrate, cobalt acetate, cobalt carbonate, cobalt sulfate, or cobalt chloride. The constant temperature stirring temperature is 30–80°C, the stirring time is 0.5–4 h, the drying temperature is 70–90°C, and the drying time is 12–24 h.

[0015] Another technical solution provided by the present invention: a metal-doped ZIFs-derived Co-based catalyst prepared by the above preparation method.

[0016] Preferably, the doped metal precursor salt is chromium nitrate.

[0017] Another technical solution provided by the present invention is the application of the above-mentioned metal-doped ZIFs-derived Co-based catalyst in the thermocatalytic carbon dioxide methanation reaction.

[0018] Preferably, the doped metal is chromium, and when the mass ratio of chromium to the metal-organic framework-derived Co3O4 catalyst is 0.05:1, the CO2 conversion rate can reach more than 50% at a reaction temperature of 300℃, while the methane selectivity is greater than 95% and the methane space-time yield is more than 2.5 times that of the metal-organic framework-derived Co3O4 catalyst.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] This paper describes the preparation method, products, and applications of metal-doped ZIFs-derived Co-based catalysts. The method involves calcining a metal-organic framework to obtain the derived Co-based catalyst. Different amounts of metal precursor (M) are introduced by adding a doped metal precursor salt solution, resulting in an MCoO bimetallic oxide catalyst. The interaction between M and Co can regulate the surface hydroxyl density, oxygen vacancy concentration, and intermediate stability, maintaining high catalytic activity and giving the catalyst greater economic value. The preparation method is simple, and the resulting catalyst, compared to traditional catalysts, can more efficiently and selectively generate methane, reducing byproduct formation and improving product purity. Attached Figure Description

[0021] Figure 1 The X-ray diffraction (XRD) patterns are shown for the catalyst prepared in Example 1 and the CrCoO-5 catalyst prepared in Example 2.

[0022] Figure 2 The image shows a SEM image of the CrCoO-5 catalyst prepared in Example 2.

[0023] Figure 3 The figures show the CO2 conversion rate versus reaction temperature for the catalysts prepared in Example 1 and Example 2 in a hydrogen-rich gas.

[0024] Figure 4 The curves show the changes in CO2 conversion and methane selectivity of the CrCoO-5 catalyst prepared in Example 2 with reaction temperature in a hydrogen-rich gas. Detailed Implementation

[0025] A method for preparing a metal-doped ZIFs-derived Co-based catalyst includes the following steps:

[0026] The metal-organic framework ZIF-67 precursor was calcined at high temperature to obtain a metal-organic framework-derived Co3O4 catalyst. For reference, the calcination temperature can be further selected as 300-600℃ and the calcination time can be further selected as 2-6h.

[0027] According to the required doping amount, the doped metal precursor salt is dispersed in ultrapure water. After it is fully dissolved, the aqueous solution of the doped metal precursor salt is added dropwise to the metal-organic framework-derived Co3O4 catalyst. After drying, it is calcined at high temperature to obtain the metal-doped ZIFs-derived Co-based catalyst. For reference, the calcination temperature can be further selected as 300-800℃, and the calcination time can be further selected as 2-6h.

[0028] In a preferred embodiment, the mass ratio of the doped metal to the metal-organic framework-derived Co3O4 catalyst in the metal-doped ZIFs-derived Co-based catalyst is (0.01–0.3):1. More preferably, when applied in the thermocatalytic carbon dioxide methanation reaction, the carbon dioxide conversion rate and methane selectivity are both high within the range of (0.03–0.1):1.

[0029] The doping metal may be further preferably Cr, Mn, Ni or La. For reference, the doping metal precursor salt may be selected from at least one of nitrate, acetate, carbonate, sulfate or chloride.

[0030] The preparation steps of the above-mentioned metal-organic framework ZIF-67 precursor include: dissolving cobalt precursor salt and hexadecyltrimethylammonium bromide in deionized water to obtain solution A; dissolving 2-methylimidazole in deionized water to form solution B; slowly pouring B into A; stirring in a water bath at a constant temperature; drying; and calcining in air to obtain the metal-organic framework ZIF-67 precursor.

[0031] For reference, the precursor salt of cobalt can be selected from at least one of cobalt nitrate, cobalt acetate, cobalt carbonate, cobalt sulfate, or cobalt chloride; the constant temperature stirring temperature can be controlled at 30-80℃, the stirring time can be controlled at 0.5h-4h, the drying temperature can be controlled at 70-90℃, and the drying time can be controlled at 12-24h.

[0032] In addition, the metal-organic framework ZIF-67 precursor is also available on the market.

[0033] In a preferred embodiment, the doping metal is chromium, and when the mass ratio of chromium to the metal-organic framework-derived Co3O4 catalyst is 0.05:1, the CO2 conversion rate can reach more than 50% at a reaction temperature of 300°C, while the methane selectivity is greater than 95% and the methane space-time yield is more than 2.5 times that of the metal-organic framework-derived Co3O4 catalyst.

[0034] The following examples further illustrate the content of the present invention. These examples are only some of the embodiments of the present invention and not all of them, and should not be regarded as an absolute limitation on the content of the present invention.

[0035] Example 1

[0036] (1) Preparation of Co3O4 catalyst: 291 mg of cobalt nitrate hexahydrate and 2 mg of hexadecyltrimethylammonium bromide were ultrasonically dissolved in 10 mL of deionized water to form solution A. 4.54 g of 2-methylimidazole was dissolved in 70 mL of deionized water to form solution B.

[0037] (2) Solution A was rapidly added to solution B, and the mixture was continuously stirred in a constant temperature water bath for 30 minutes to successfully form ZIF-67 cubes. The purple precipitate was collected by centrifugation and washed three times with water and ethanol. The ZIF-67 cubes were then dried in a vacuum oven at 60°C. Finally, the dried ZIF-67 cubes were transferred to a muffle furnace and heated at 5°C for 1 minute. -1 The heating rate was set at 350℃ for 2 hours to obtain the metal-organic framework derivative Co3O4 catalyst.

[0038] (3) The metal-organic framework derivative Co3O4 catalyst obtained after calcination was dried at 80°C for 24 hours, ground, then pressed into tablets and crushed, and sieved out 20-40 mesh particles for performance testing.

[0039] Example 2

[0040] (1) Preparation of Cr-doped Co3O4 catalyst: 0.231 g, 0.385 g, 0.770 g and 1.539 g of Cr(NO3)3·9H2O were dissolved in 1 g of deionized water, and after being fully dissolved, they were slowly added dropwise to 1.0 g of the particulate metal-organic framework derivative Co3O4 catalyst prepared in Example 1.

[0041] (2) After drying at 80℃ for 12 hours, transfer to a muffle furnace and heat at 5℃ for 1 minute. -1 The temperature was increased to 550℃ and held for 2 hours to prepare four Cr-doped Co3O4 catalysts with different ratios of Cr:1, 0.05:1, 0.1:1 and 0.2:1, respectively, denoted as CrCoO-X, where X represents the doping amount.

[0042] (3) Grind the four CrCoO-X catalysts, then press and crush them into tablets, and sieve out particles of 20-40 mesh for performance testing.

[0043] Example 3

[0044] (1) Preparation of other alternative Cr-doped MCoO-X catalysts: A certain amount of M nitrate was dissolved in 1g of deionized water, where M is Mn, Ni or La, and X represents the doping amount. After being fully dissolved, the solution was slowly added dropwise to 1.0g of the particulate metal-organic framework derivative Co3O4 catalyst prepared in Example 1.

[0045] (2) After drying at 80℃ for 12 hours, transfer to a muffle furnace and heat at 5℃ for 1 minute. -1 The heating rate is increased to 550℃ and maintained for 2 hours to obtain the MCoO-X catalyst.

[0046] (3) The MCoO-5 catalyst with 5wt% doping of three metals was ground, then pressed into tablets and crushed, and sieved out 20-40 mesh particles for performance testing.

[0047] Catalyst performance tests in the examples:

[0048] The catalyst was tested in a continuous flow fixed-bed tubular microreactor. 0.1 g of fresh catalyst was fixed with silica wool and diluted with 1 g of silica sand. The catalyst was tested at 400 °C with pure hydrogen (40 mL / min). -1 The reduction pretreatment was carried out for 1 hour. The mass hourly space velocity (WHSV) was 48,000 mL / g. cat -1 h -1 The feed gas was stoichiometrically supplied at a ratio of H2 / CO2 (3 / 1), containing 24% CO2, 72% H2, and 4% Ar. All experiments were conducted under non-equilibrium limiting conditions. Effluent samples were collected every 20 minutes via an automated gas sampling valve and analyzed using an online gas chromatograph equipped with a TCD. After reaching steady-state conditions (approximately 8 hours of operation), the carbon dioxide conversion (%) and methanol selectivity (%) were calculated based on the carbon mass balance using the average of three independent analyses.

[0049] Figure 1 The X-ray diffraction patterns are those of the catalysts prepared in Example 1 and Example 2. The X-ray diffraction peaks of both the metal-organic framework-derived Co3O4 catalyst and the CrCoO-5 catalyst formed by calcination of ZIF-67 can be indexed to the standard PDF card of the spinel Co3O4 phase. Furthermore, no diffraction peaks related to Cr2O3 were observed in the CrCoO-5 catalyst sample, indicating that the doping of Cr did not alter the structure of the metal-organic framework-derived Co-based catalyst, and Cr is highly dispersed in this catalyst.

[0050] Figure 3 The figures show the CO2 conversion rate as a function of reaction temperature for the catalysts prepared in Example 1 and Example 2 (CrCoO-5 catalyst). As the temperature increases, the CO2 conversion rate for the hydrogenation of CO2 to methanation gradually increases. The methanation performance of the Cr-doped metal-organic framework-derived Co-based catalyst is significantly better than that of the metal-organic framework-derived Co3O4 catalyst.

[0051] Figure 4The figures show the CO2 conversion and methane selectivity of the CrCoO-5 catalyst prepared in Example 2 as a function of reaction temperature in a hydrogen-rich gas environment. Experimental results of the CO2 methanation reaction indicate that both the CO2 conversion and CH4 selectivity of the catalyst for catalyzing CO2 hydrogenation to methane increase with increasing temperature. At 300°C, the CO2 conversion is higher than 50%, and the methane selectivity is greater than 95%.

[0052] CO2 hydrogenation performance test:

[0053] At 300℃, normal pressure, and 48000 mL gcat -1 h -1 The catalytic performance of metal-doped organic framework Co-based catalysts was tested under the following conditions. The methane synthesis from carbon dioxide hydrogenation to methane was carried out in a continuous fixed-bed reactor, and the performance data are shown in Table 1. Compared with the metal-organic framework-derived Co3O4 catalyst, the methanation performance of the M-doped metal-organic framework-derived Co-based catalysts was significantly improved. Among them, the CrCoO-5 catalyst showed the highest methane space-time yield (STY) of 263.1 mmol g. cat. -1 h -1 .

[0054] Table 1 Catalyst performance tests in Examples 1 to 3

[0055]

[0056] As shown in the table above, the catalyst of the present invention exhibits significantly higher performance than the metal-organic framework derivative Co3O4 catalyst when applied to the thermocatalytic carbon dioxide methanation reaction. With the increase of the doping ratio, the carbon dioxide conversion rate, methane selectivity, and methane space-time yield all show a trend of first increasing and then decreasing, reaching a peak when the mass ratio of the doped metal to the metal-organic framework derivative Co3O4 catalyst is 0.05:1. At the same doping ratio, Cr has a significantly greater advantage than Mn, Ni, and La, but these three doped metals can also significantly improve the carbon dioxide conversion rate, methane selectivity, and methane space-time yield.

[0057] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

[0058] Any aspects of this invention not described in detail are well-known to those skilled in the art.

Claims

1. The application of a metal-doped ZIFs-derived Co-based catalyst in the thermocatalytic carbon dioxide methanation reaction, characterized in that: Metal-organic framework-derived Co3O4 catalyst was obtained by high-temperature calcination of the metal-organic framework ZIF-67 precursor. According to the required doping amount, the doped metal precursor salt is dispersed in ultrapure water. After it is fully dissolved, the doped metal precursor salt aqueous solution is added dropwise to the metal-organic framework-derived Co3O4 catalyst. After drying, it is calcined at high temperature to obtain the metal-doped ZIFs-derived Co-based catalyst. When chromium is used as the dopant metal and its mass ratio with the metal-organic framework-derived Co3O4 catalyst is 0.05:1, the CO2 conversion rate can reach more than 50% at a reaction temperature of 300℃, while the methane selectivity is greater than 95% and the methane space-time yield is more than 2.5 times that of the metal-organic framework-derived Co3O4 catalyst.

2. The application of the metal-doped ZIFs-derived Co-based catalyst according to claim 1 in the thermocatalytic carbon dioxide methanation reaction, characterized in that: The calcination temperature of the metal-organic framework ZIF-67 precursor is 300–600℃, and the calcination time is 2–6h; after the addition of the doped metal precursor salt aqueous solution, the calcination temperature is 300–800℃, and the calcination time is 2–6h.

3. The application of the metal-doped ZIFs-derived Co-based catalyst according to claim 1 in the thermocatalytic carbon dioxide methanation reaction, characterized in that: The doped metal precursor salt is selected from at least one of nitrates, acetates, carbonates, sulfates, and chlorides.

4. The application of the metal-doped ZIFs-derived Co-based catalyst according to claim 1 in the thermocatalytic carbon dioxide methanation reaction, characterized in that, The preparation steps of the metal-organic framework ZIF-67 precursor include: dissolving cobalt precursor salt and hexadecyltrimethylammonium bromide in deionized water to obtain solution A; dissolving 2-methylimidazole in deionized water to form solution B; slowly pouring B into A; stirring in a water bath at a constant temperature; drying; and calcining in air to obtain the metal-organic framework ZIF-67 precursor.

5. The application of the metal-doped ZIFs-derived Co-based catalyst according to claim 4 in the thermocatalytic carbon dioxide methanation reaction, characterized in that: The cobalt precursor salt is selected from at least one of cobalt nitrate, cobalt acetate, cobalt carbonate, cobalt sulfate, or cobalt chloride. The constant temperature stirring temperature is 30–80°C, the stirring time is 0.5–4 h, the drying temperature is 70–90°C, and the drying time is 12–24 h.

6. The application of the metal-doped ZIFs-derived Co-based catalyst according to claim 3 in the thermocatalytic carbon dioxide methanation reaction, characterized in that: Chromium nitrate was used as the precursor salt for the doped metal.

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