Ternary mixed metal oxide catalyst as well as preparation method and application thereof

Abstract

The invention relates to preparation of a transition metal element doped modified cobalt-based metal oxide catalyst and application of the transition metal element doped modified cobalt-based metal oxide catalyst in CO preferential oxidation (CO-PROX) reaction. The ternary mixed metal oxide catalyst is formed by doping two transition metal elements with a modified cobalt-based metal oxide, the cobalt element accounts for 50-99%, and the transition metal elements account for 1-50%. The preparation method comprises the following steps: dissolving cobalt salt, M salt containing two transition metal elements, ammonium fluoride and urea in deionized water to form a mixed solution, stirring at room temperature, carrying out hydrothermal treatment, centrifugally washing and drying a product, and calcining to obtain the catalyst. Wherein transition metal elements in the M salt are selected from manganese, iron and the like; the concentration of ammonium fluoride is 0.2 to 0.5 mol / L, and the concentration of urea is 0.7 to 1.2 mol / L. The catalyst is applied to CO-PROX reaction, has excellent low-temperature catalytic activity and high CO selectivity under the conditions of normal pressure,-50 to 110 DEG C, reaction space velocity of 6000 to 72000 mL. (gcat.h) <-1 > and specific reaction gas composition, can reduce the cost, widens the application temperature window, and also has certain H2O and CO2 resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, specifically to a method for preparing a transition metal-doped cobalt-based metal oxide catalyst and its application in the CO preferential oxidation (CO-PROX) reaction. By introducing specific transition metal elements into the cobalt-based metal oxide for doping and modification, the present invention aims to produce a ternary mixed metal oxide catalyst with high catalytic activity and selectivity, thereby meeting the demand for efficient removal of trace CO from hydrogen-rich gas streams in applications such as proton exchange membrane fuel cells (PEMFCs). Background Art

[0002] CO (carbon monoxide) is a colorless, odorless, toxic gas primarily derived from motor vehicle exhaust and the incomplete combustion of carbon-based compounds. Atmospheric CO emissions not only pose a serious threat to the environment but, when CO levels exceed 0.1%, pose a threat to human health, causing poisoning and even death. Therefore, controlling and reducing CO emissions is extremely important.

[0003] As a highly efficient and clean energy conversion device, proton exchange membrane fuel cells (PEMFCs) have shown broad application prospects in the automotive, power generation, and aerospace industries due to their low operating temperature, high power density, and energy conversion efficiency. However, PEMFCs require extremely high fuel gas purity, particularly CO content, which must be kept to extremely low levels (typically below 10 ppm). This is because even small amounts of CO can severely poison the platinum-based catalysts in PEMFCs, significantly reducing the performance and lifespan of the fuel cell.

[0004] Common methods for removing trace CO from hydrogen-rich gas streams include physical adsorption, chemical absorption, and catalytic oxidation. Among these, CO preferential oxidation (CO-PROX) technology is considered one of the most direct and effective methods for removing CO from hydrogen-rich gas streams due to its high efficiency, cost-effectiveness, and ease of operation. CO-PROX catalysts can preferentially oxidize CO in hydrogen-rich environments without consuming significant amounts of hydrogen, thereby improving the purity of the hydrogen-rich gas stream.

[0005] CO-PROX catalysts can be categorized into precious metal catalysts, primarily based on Pt, Pd, and Au, and non-precious metal catalysts, primarily based on transition metals, depending on the active components involved in the reaction. While precious metal catalysts exhibit excellent catalytic activity at low temperatures, their high cost, limited reserves, and poor thermal stability limit their large-scale application in CO-PROX reactions. Therefore, developing non-precious metal catalysts with excellent low-temperature catalytic activity and high selectivity for CO over a wide temperature window has become a research hotspot.

[0006] As a unique transition metal oxide with a spinel structure, Co3O4 has attracted widespread attention in the field of catalysis due to its low cost, good stability and wide availability. However, the catalytic performance of pure Co3O4 catalyst in the CO-PROX reaction still needs to be improved. In order to further improve its catalytic performance, researchers began to explore methods of doping and modifying Co3O4 by introducing other transition metal elements. This doping modification can not only regulate the surface structure and electronic properties of the catalyst, but also enhance its catalytic activity and selectivity. Based on this, this patent proposes a method for preparing a transition metal element doped and modified cobalt-based metal oxide catalyst, aiming to prepare a ternary mixed metal oxide catalyst with high catalytic activity and high selectivity to meet the needs of the CO-PROX reaction. Summary of the Invention

[0007] This invention aims to provide a method for preparing a highly efficient transition metal-doped cobalt-based metal oxide catalyst and explore its application in the CO preferential oxidation (CO-PROX) reaction. By introducing specific transition metal elements into the cobalt-based metal oxide, the goal is to prepare a ternary mixed metal oxide catalyst with high catalytic activity and selectivity, thereby reducing the catalyst cost and broadening its application temperature window in the CO-PROX reaction.

[0008] One of the technical problems to be solved by the present invention is to provide a method for preparing a transition metal element-doped modified cobalt-based metal oxide catalyst. The method should be able to simply and efficiently prepare a ternary mixed metal oxide catalyst with excellent catalytic performance.

[0009] The second technical problem addressed by the present invention is the application of the ternary mixed metal oxide catalyst prepared above in the CO preferential oxidation (CO-PROX) reaction. This catalyst should exhibit good catalytic activity over a wide temperature window and high CO selectivity, meeting the demand for efficient removal of trace CO from hydrogen-rich streams in applications such as proton exchange membrane fuel cells (PEMFCs).

[0010] In order to solve one of the above technical problems, the technical solution adopted by the present invention is as follows:

[0011] A method for preparing a ternary mixed metal oxide catalyst, wherein the ternary mixed metal oxide is composed of a cobalt-based metal oxide doped with two transition metal elements. The method comprises the following steps:

[0012] S01. A certain amount of cobalt salt, M salt, ammonium fluoride and urea were dissolved in deionized water to form a mixed solution;

[0013] S02. The mixed solution obtained in step S01 is stirred at room temperature for not less than 1 hour, stirred thoroughly, and after mixing evenly, transferred to a polytetrafluoroethylene reactor and subjected to hydrothermal treatment at 100-200 ° C (preferably 120 ° C);

[0014] S03. The product obtained in step S02 is centrifuged, washed several times, and dried at 60-120°C;

[0015] S04. Place the dried solid powder in a muffle furnace and calcine it at 250-800°C.

[0016] The M salt is a salt precursor containing two transition metal elements, and the transition metal elements are selected from manganese, iron, copper, nickel, cerium, zirconium and lanthanum.

[0017] The present invention combines the synergistic effect of ammonium fluoride (NH4F) and urea (CO(NH2)2) through a hydrothermal method to regulate the morphology of the cobalt-based metal oxide precursor, and ultimately achieves high performance of the ternary mixed metal oxide catalyst. The fluoride ion (F - ) can react with cobalt ions (such as Co 3+ ) to form stable complexes (such as [CoF6] 3- ), slowing down the precipitation rate of metal ions and regulating the nucleation process of the precursor, F - The precursor may be induced to form a specific morphology (such as layered or nanosheet structure) through electrostatic interaction or steric hindrance effect, and the presence of fluoride can reduce the surface energy of metal hydroxide, promote uniform nucleation, and inhibit particle agglomeration.

[0018] Urea decomposes into NH3 and CO2 under high temperature hydrothermal conditions. The generated NH3 provides OH - , slowly adjust the solution pH to alkaline (about 8-10) to avoid the violent precipitation caused by traditional strong bases (such as NaOH). - The CO2 bubbles generated by urea decomposition may act as a soft template to induce the precursor to form a porous or layered structure.

[0019] In addition, ammonium fluoride delays nucleation and urea provides continuous OH - , achieving the temporal and spatial separation of nucleation and growth, and promoting the directional growth of the precursor. The two can synergistically control the precursor to layered hydroxides (LDHs), nanosheet assemblies or hierarchical porous structures.

[0020] Furthermore, the concentration of the ammonium fluoride is 0.2 to 0.5 mol / L, the concentration of the urea is 0.7 to 1.2 mol / L, and the cobalt element is derived from one of cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt chloride, cobalt bromide, and cobalt carbonate.

[0021] To solve the second of the above technical problems, the technical solution adopted by the present invention is as follows:

[0022] The ternary mixed metal oxide catalyst prepared by the above preparation method was applied to the CO preferential oxidation (CO-PROX) reaction. The reaction conditions were: normal pressure, reaction temperature of -50 to 110°C, reaction space velocity of 6000 to 72000 mL·(g cat h) -1 The reaction gas composition is 1.5 vol.% CO, 1.5 vol.% O2, 50 vol.% H2 and 47 vol.% N2.

[0023] The test conditions for evaluating the ternary mixed metal oxide catalyst's resistance to H2O and CO2 reactions were: atmospheric pressure, reaction temperature of 70°C, reaction space velocity of 18000 mL·(g cat h) -1 The reaction gas composition is 1.5 vol.% CO, 1.5 vol.% O2, 50 vol.% H2, 5 vol.% H2O, 5 vol.% CO2 and 37 vol.% N2.

[0024] This invention uses a hydrothermal method to prepare layered metal hydroxides doped with different transition metal elements, which are then calcined at high temperature to form a mixed metal oxide catalyst. The cobalt content is 50-99%, and the other transition metal elements account for 1-50%. This catalyst reduces the cost of the CO preferential oxidation (CO-PROX) reaction and exhibits superior catalytic activity and higher CO selectivity over a wider temperature window than comparable bimetallic oxide catalysts. It also exhibits reasonable resistance to both H2O and CO2.

[0025] Specifically, the ternary mixed metal oxide catalyst prepared by the preparation method of the present invention exhibits the following significant technical effects in the CO preferential oxidation (CO-PROX) reaction:

[0026] 1. Excellent low-temperature catalytic activity: The catalyst can exhibit good catalytic activity under low-temperature conditions (such as -50 to 110°C), effectively removing trace CO in hydrogen-rich gas streams and reducing reaction energy consumption.

[0027] 2. High CO selectivity: The catalyst has high selectivity for CO and can preferentially oxidize CO without consuming a large amount of hydrogen, thereby improving the purity of the hydrogen-rich gas stream and meeting the high purity requirements of fuel gas in fields such as PEMFC.

[0028] 3. Reduced cost: Compared with noble metal catalysts, the catalyst of the present invention has lower cost, is conducive to large-scale application, and reduces the catalyst application cost in the CO-PROX reaction.

[0029] 4. Wide application temperature window: The catalyst can exhibit good catalytic performance within a wide temperature window, broadening its application range.

[0030] 5. Resistance to H2O and CO2: Even in the presence of H2O and CO2, the catalyst can still maintain good catalytic activity and stability, demonstrating its application potential in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the XRD pattern of the catalyst prepared in Example 1 of the present invention.

[0032] Figure 2 The N2 adsorption-desorption isotherm and pore size distribution diagram of the catalyst prepared in Example 1 of the present invention.

[0033] Figure 3 This is the SEM image of the catalyst prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to specific examples, but the present invention is not limited to the following examples. The methods described are conventional methods unless otherwise specified, and the raw materials described can be obtained from public commercial channels unless otherwise specified.

[0035] Doping and modifying cobalt-based metal oxides with transition metal elements is an effective material modification method aimed at improving the electrochemical performance, structural stability, and other related properties of the materials. The main purpose of doping modification is to modify the unit cell defects in cobalt-based metal oxides by introducing other transition metal elements, thereby increasing the lattice energy of the material and stabilizing its structure. During the doping modification process, transition metal elements with similar chemical properties or the ability to form stable compounds are generally selected as dopants. These elements may include manganese, iron, nickel, copper, cerium, zirconium, lanthanum, etc. These elements are selected based on their reactivity, relative cheapness, and their potential to form new compounds with cobalt and oxygen. Currently, the most common method of modifying cobalt-based metal oxides by doping with transition metal elements is to form binary mixed oxides. For example, the introduction of manganese can form cobalt-manganese binary oxides, such as MnCo2O4.

[0036] When studying doped and modified cobalt-based metal oxides, a variety of characterization techniques are typically used to analyze the material's structure, composition, and properties. These techniques may include X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). These characterization techniques help reveal the effects of doping elements on the structure of cobalt-based metal oxides and the mechanisms underlying the enhanced electrochemical performance of doped and modified cobalt-based metal oxides.

[0037] The M salt is derived from a salt precursor containing manganese, iron, copper, nickel, cerium, zirconium, and lanthanum. The precursor is a form of existence before obtaining the target product, mostly in the form of an organic-inorganic complex or a mixture solid, and some in the form of a sol. However, for salt precursors containing manganese, iron, copper, nickel, cerium, zirconium, and lanthanum, their preparation methods and specific forms of existence may vary depending on the target product. In addition, due to the large differences in chemical properties between these elements, it is necessary to strictly control the reaction conditions and process parameters during the preparation process to ensure the quality and stability of the precursor.

[0038] As for single salt precursors containing all the mentioned elements (manganese, iron, copper, nickel, cerium, zirconium, and lanthanum), in practice, they may not exist or be difficult to prepare. This is mainly because these elements have significant differences in chemical properties, ionic radius, and coordination ability, making it difficult to form a stable single salt precursor through simple chemical reactions.

[0039] 1. Method for preparing ternary mixed metal oxide catalyst:

[0040] A method for preparing a ternary mixed metal oxide catalyst, wherein the ternary mixed metal oxide is composed of a cobalt-based metal oxide doped with two transition metal elements and modified, wherein the cobalt element accounts for 50-99% and the two transition metal elements account for 1-50%. The method comprises the following steps:

[0041] S01: Dissolve a certain amount of cobalt salt, M salt, ammonium fluoride and urea in deionized water to form a mixed solution.

[0042] S02: Stir the mixed solution obtained in step S01 at room temperature for not less than 1 hour. After mixing evenly, transfer the mixed solution to a polytetrafluoroethylene reactor and perform hydrothermal treatment at 100-200° C. (preferably 120° C.).

[0043] S03: The product obtained in step S02 is centrifuged, washed several times, and dried at 60-120°C.

[0044] S04: Place the dried solid powder in a muffle furnace and calcine it at 250-800°C.

[0045] Wherein, the M salt is a salt precursor containing two transition metal elements, and the transition metal elements are selected from manganese, iron, copper, nickel, cerium, zirconium and lanthanum;

[0046] The ternary mixed metal oxide catalyst prepared in the above steps has the performance of widening the temperature of CO preferential oxidation (CO-PROX) reaction to -50 to 110°C.

[0047] 2. Other features of the catalyst preparation method:

[0048] Step S02: The stirring time is not less than 1 hour, and the temperature of the hydrothermal treatment is 100-200°C, preferably 120°C.

[0049] Step S03: Drying temperature is 60-120°C.

[0050] Step S04: calcination temperature is 250-800°C.

[0051] Ammonium fluoride concentration: 0.2~0.5mol / L.

[0052] Urea concentration: 0.7~1.2mol / L.

[0053] Source of cobalt element: one of cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt chloride, cobalt bromide and cobalt carbonate.

[0054] 3. Ternary mixed metal oxide catalyst

[0055] A ternary mixed metal oxide catalyst prepared by any of the above catalyst preparation methods.

[0056] 4. Application of catalysts in CO preferential oxidation (CO-PROX) reaction

[0057] The ternary mixed metal oxide catalyst is applied to the CO preferential oxidation (CO-PROX) reaction, and the specific reaction conditions are as follows:

[0058] Reaction conditions: normal pressure, reaction temperature -50 to 110°C, reaction space velocity 6000 to 72000 mL·(g cat h) -1 The reaction gas composition is 1.5 vol.% CO, 1.5 vol.% O2, 50 vol.% H2 and 47 vol.% N2.

[0059] Evaluation of the reaction conditions for H2O and CO2: atmospheric pressure, reaction temperature of 70°C, reaction space velocity of 18000 mL·(g cath) -1 The reaction gas composition is 1.5 vol.% CO, 1.5 vol.% O2, 50 vol.% H2, 5 vol.% H2O, 5 vol.% CO2 and 37 vol.% N2.

[0060] Example 1

[0061] (1) Weigh 1.9402 g Co(NO3)2·6H2O, 1.1918 g 50 wt.% Mn(NO3)2 solution, 1.4456 g Ce(NO3)3·6H2O, 1 g NH4F, and 4 g CO(NH2)2 into a beaker, add 93 ml deionized water to dissolve, and mix well.

[0062] (2) The dissolved mixed solution was stirred at room temperature for 1 h to mix uniformly, and then transferred to a 200 ml polytetrafluoroethylene reactor and hydrothermally treated at 120 ° C for 24 h;

[0063] (3) After the reactor is cooled, the resulting precipitate is centrifuged and washed several times with ethanol and water until the pH is neutral;

[0064] (4) The centrifuged sample was dried in an oven at 60°C for 12 hours, and then calcined in a muffle furnace at 350°C for 4 hours at a heating rate of 5°C / min. CoMnCeO x -N catalyst.

[0065] Figure 1 This is the XRD pattern of the catalyst prepared in Example 1 of the present invention.

[0066] Figure 2 The N2 adsorption-desorption isotherm and pore size distribution diagram of the catalyst prepared in Example 1 of the present invention.

[0067] Figure 3 This is the SEM image of the catalyst prepared in Example 1 of the present invention.

[0068] Figure 3 The typical electron micrograph of layered metal oxides shows the formation of an ordered layered structure. The layered structure of the precursor provides a high specific surface area and exposed active sites, which is conducive to the formation of metal oxide nanosheets during the subsequent calcination process. - It promotes the growth of metal hydroxide along the c-axis to form two-dimensional nanosheets; the complexation effect of ammonium fluoride may induce the nanosheets to stack into a three-dimensional flower-like structure. Figure 2 The N2 adsorption-desorption curves show the distribution of mesopores and macropores (BET specific surface area can reach 100-200m 2 / g), which is attributed to the template effect of CO2 bubbles produced by urea decomposition.

[0069] The layered structure and high specific surface area increase the density of active sites and shorten the CO / O2 diffusion path. Ternary doping (such as Co-Mn-Ce) synergistically optimizes the electronic structure, enhancing CO adsorption and O2 activation. The porous structure alleviates the competitive adsorption of H2O and CO2, maintaining the stability of the active sites.

[0070] The addition of rare earth element Ce promotes the formation of oxygen vacancies and enhances the catalyst's resistance to poisoning. The precursor morphology control combined with the calcination process enables the catalyst to maintain high activity within the -50 to 110°C range. In this example, the CO conversion rate reached 46.2% at -50°C.

[0071] Example 2

[0072] Weigh 1.9402g Co(NO3)2·6H2O, 0.8021g Cu(NO3)2·3H2O, 1.4456g Ce(NO3)3·6H2O, 1g NH4F and 4g CO(NH2)2 in a beaker, add 93ml deionized water to dissolve, and mix well;

[0073] The preparation method described in this embodiment differs from that in Example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 160°C for 12 hours, dried at 80°C for 12 hours, and then calcined in a muffle furnace at 550°C for 4 hours at a heating rate of 5°C / min. CoCuCeO x -N catalyst.

[0074] Example 3

[0075] Weigh 1.9402g Co(NO3)2·6H2O, 1.3413g Fe(NO3)3·9H2O, 0.9654g Ni(NO3)2·6H2O, 1g NH4F and 4g CO(NH2)2 into a beaker, add 93ml deionized water to dissolve and mix well.

[0076] The preparation method described in this embodiment differs from that in embodiment 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 200°C for 8 hours, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 250°C for 4 hours with a heating rate of 5°C / min. CoFeNiO is obtained. x -N catalyst.

[0077] Example 4

[0078] Weigh 1.9402g Co(NO3)2·6H2O, 1.4253g Zr(NO3)4·5H2O, 1.4376g La(NO3)3·6H2O, 1g NH4F and 4g CO(NH2)2 into a beaker, add 93ml deionized water to dissolve and mix well.

[0079] The preparation method described in this embodiment differs from that in Example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 100°C for 24 hours, dried at 60°C for 12 hours, and then calcined in a muffle furnace at 350°C for 4 hours at a heating rate of 5°C / min. CoZrLaO is obtained. x -N catalyst.

[0080] Example 5

[0081] Weigh 1.9402g Co(NO3)2·6H2O, 1.3413g Fe(NO3)3·9H2O, 1.4456g Ce(NO3)3·6H2O, 1g NH4F and 4g CO(NH2)2 into a beaker, add 93ml deionized water to dissolve and mix well.

[0082] The preparation method described in this embodiment differs from that in Example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 140°C for 16 hours, dried at 60°C for 12 hours, and then calcined in a muffle furnace at 350°C for 4 hours at a heating rate of 5°C / min. CoFeCeO x -N catalyst.

[0083] Example 6

[0084] Weigh 1.9402g Co(NO3)2·6H2O, 0.8021g Cu(NO3)2·3H2O, 1.3413g Fe(NO3)3·9H2O, 1g NH4F and 4g CO(NH2)2 into a beaker, add 93ml deionized water to dissolve and mix well.

[0085] The preparation method described in this embodiment differs from that in Example 1 only in that the type of M salt added in step (1) is different, the product is hydrothermally treated at 140°C for 16 hours, dried at 60°C for 12 hours, and then calcined in a muffle furnace at 350°C for 4 hours with a heating rate of 5°C / min. CoCuFeO is obtained. x -N catalyst.

[0086] Comparative Example 1

[0087] (1) Weigh 1.9402 g Co(NO3)2·6H2O, 1.1918 g 50 wt.% Mn(NO3)2 solution, 1 g NH4F, and 4 g CO(NH2)2 into a beaker, add 93 ml deionized water to dissolve, and mix well.

[0088] (2) The dissolved mixed solution was stirred at room temperature for 1 h, then transferred to a 200 ml polytetrafluoroethylene reactor and hydrothermally treated at 120 °C for 24 h;

[0089] (3) After the reactor is cooled, the resulting precipitate is centrifuged and washed several times with ethanol and water until the pH is neutral;

[0090] (4) The centrifuged sample was placed in an oven and dried at 60°C for 12 hours, and then calcined in a muffle furnace at 350°C for 4 hours at a heating rate of 5°C / min. CoMnO x -N catalyst.

[0091] Comparative Example 2

[0092] (1) Weigh 1.9402 g Co(NO3)2·6H2O, 1.4456 g Ce(NO3)3·6H2O, 1 g NH4F, and 4 g CO(NH2)2 into a beaker, add 93 ml deionized water to dissolve, and mix well;

[0093] The preparation method described in this comparative example differs from that in comparative example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 120°C for 24 hours, dried at 60°C for 12 hours, and then calcined in a muffle furnace at 350°C for 4 hours at a heating rate of 5°C / min. CoCeO x -N catalyst.

[0094] Comparative Example 3

[0095] (1) Weigh 1.9402 g Co(NO3)2·6H2O, 0.8021 g Cu(NO3)2·3H2O solution, 1 g NH4F, and 4 g CO(NH2)2 into a beaker, add 93 ml deionized water to dissolve, and mix well.

[0096] The preparation method described in this comparative example differs from that in comparative example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 160°C for 12 hours, dried at 80°C for 12 hours, and then calcined at 550°C in a muffle furnace for 4 hours at a heating rate of 5°C / min. CoCuO is obtained. x -N catalyst.

[0097] Comparative Example 4

[0098] (1) Weigh 1.9402 g Co(NO3)2·6H2O, 1.3413 g Fe(NO3)3·9H2O solution, 1 g NH4F, and 4 g CO(NH2)2 into a beaker, add 93 ml deionized water to dissolve, and mix well;

[0099] The preparation method described in this comparative example differs from that in comparative example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 200°C for 8 hours, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 250°C for 4 hours with a heating rate of 5°C / min. CoFeO is obtained. x -N catalyst.

[0100] Comparative Example 5

[0101] (1) Weigh 1.9402 g Co(NO3)2·6H2O, 0.9654 g Ni(NO3)2·6H2O solution, 1 g NH4F, and 4 g CO(NH2)2 into a beaker, add 93 ml deionized water to dissolve, and mix well.

[0102] The preparation method described in this comparative example differs from that in comparative example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 200°C for 8 hours, dried at 120°C for 12 hours, and then calcined in a muffle furnace at 250°C for 4 hours at a heating rate of 5°C / min. CoNiO is obtained. x -N catalyst.

[0103] Comparative Example 6

[0104] (1) Weigh 1.9402 g Co(NO3)2·6H2O, 1.4253 g Zr(NO3)4·5H2O solution, 1 g NH4F, and 4 g CO(NH2)2 into a beaker, add 93 ml deionized water to dissolve, and mix well.

[0105] The preparation method described in this comparative example differs from that in comparative example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 100°C for 24 hours, dried at 60°C for 12 hours, and then calcined in a muffle furnace at 350°C for 4 hours at a heating rate of 5°C / min. CoZrO is obtained. x -N catalyst.

[0106] Comparative Example 7

[0107] (1) Weigh 1.9402 g Co(NO3)2·6H2O, 1.4376 g La(NO3)3·6H2O solution, 1 g NH4F, and 4 g CO(NH2)2 into a beaker, add 93 ml deionized water to dissolve, and mix well.

[0108] The preparation method described in this comparative example differs from that in comparative example 1 only in that the type of M salt added in step (1) is different. The product is hydrothermally treated at 100°C for 24 hours, dried at 60°C for 12 hours, and then calcined in a muffle furnace at 350°C for 4 hours at a heating rate of 5°C / min. CoLaO is obtained. x -N catalyst.

[0109] Example 7-36

[0110] According to the parameters designed in Table 1, other parameters and steps in the implementation scheme are the same except for the designed parameters.

[0111] Table 1: Design parameters of Examples 7-36

[0112]

[0113]

[0114] The catalysts prepared in Examples 1-36 and Comparative Examples 1-7 were used for CO preferential oxidation (CO-PROX) under the following conditions: atmospheric pressure, reaction temperature of -50 to 110°C, reaction space velocity of 6000 to 72000 mL·(g cat h) -1 The reaction gas composition was 1.5 vol.% CO, 1.5 vol.% O2, 50 vol.% H2, and 47 vol.% N2. The analysis results are shown in Table 2.

[0115] Table 2: Catalyst activity test analysis results

[0116]

[0117]

[0118]

[0119]

[0120] The catalytic performance of Examples 1-6 and Comparative Examples 1-7 was tested in a feed gas containing H2O and CO2 under the following conditions: atmospheric pressure, reaction temperature of 70°C, reaction space velocity of 18000 mL·(g cat h) -1The reaction gas composition is 1.5vol.% CO, 1.5vol.% O2, 50vol.% H2, 5vol.% H2O, 5vol.% CO2 37vol.% N2.

[0121] Table 3: Catalyst activity test analysis results

[0122]

[0123]

[0124] As shown in Tables 2 and 3, the inventors discovered that using two transition metal elements rather than just one resulted in a transition metal-doped modified cobalt-based metal oxide catalyst with improved performance. Compared to the comparative binary mixed oxide catalyst, the ternary mixed oxide catalyst prepared in this invention exhibited excellent low-temperature catalytic activity and CO selectivity over a wider temperature window. Furthermore, it exhibited good catalytic activity and stability in the presence of both H₂O and CO₂.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to preferred embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present application can still be modified or some technical features can be replaced by equivalents, which should all be included in the scope of the technical solutions requested for protection in this application.

Claims

1. A method for preparing a ternary mixed metal oxide catalyst, wherein the ternary mixed metal oxide is composed of a cobalt-based metal oxide doped with two transition metal elements, wherein the cobalt element accounts for 50-99% and the two transition metal elements account for 1-50%; the method is characterized in that: The method comprises the following steps: S01. A certain amount of cobalt salt, M salt, ammonium fluoride and urea were dissolved in deionized water to form a mixed solution; S02. The mixed solution obtained in step S01 was stirred at room temperature, mixed evenly, and then transferred to a polytetrafluoroethylene reactor for hydrothermal treatment; S03. The product obtained in step S02 is centrifuged, washed several times, and dried; S04. The dried solid powder was placed in a muffle furnace and calcined; Wherein, the M salt is a salt precursor containing two transition metal elements, and the transition metal elements are selected from manganese, iron, copper, nickel, cerium, zirconium and lanthanum; The ternary mixed metal oxide catalyst has the performance of widening the temperature of CO preferential oxidation (CO-PROX) reaction to -50 to 110°C.

2. The method for preparing a catalyst according to claim 1, wherein: In step S02, the stirring time is not less than 1 hour, and the temperature of the hydrothermal treatment is 100-200°C, preferably 120°C.

3. The method for preparing a catalyst according to claim 1, wherein: In step S03, the drying temperature is 60-120°C.

4. The method for preparing a catalyst according to claim 1, wherein: In step S04, the calcination temperature is 250-800°C.

5. The method for preparing a catalyst according to claim 1, wherein: The concentration of the ammonium fluoride is 0.2-0.5 mol / L, and the concentration of the urea is 0.7-1.2 mol / L.

6. The method for preparing a catalyst according to claim 1, wherein: The cobalt element is derived from one of cobalt nitrate, cobalt sulfate, cobalt acetate, cobalt chloride, cobalt bromide and cobalt carbonate.

7. A ternary mixed metal oxide catalyst, characterized in that: The catalyst is prepared by the catalyst preparation method according to any one of claims 1 to 6.

8. Use of the ternary mixed metal oxide catalyst according to claim 7 as a catalyst in a CO preferential oxidation (CO-PROX) reaction.

9. The use according to claim 8, characterized in that The CO preferential oxidation (CO-PROX) reaction conditions are: Normal pressure, reaction temperature is -50~110℃, reaction space velocity is 6000~72000mL·(g cat h) -1 The reaction gas composition is 1.5 vol.% CO, 1.5 vol.% O2, 50 vol.% H2 and 47 vol.% N2.

10. The use according to claim 8, characterized in that The test conditions for evaluating the resistance to H2O and CO2 reactions are: At normal pressure, the reaction temperature was 70°C, and the reaction space velocity was 18000 mL·(g cat h) -1 The reaction gas composition is 1.5 vol.% CO, 1.5 vol.% O2, 50 vol.% H2, 5 vol.% H2O, 5 vol.% CO2 and 37 vol.% N2.

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