Nickel-cobalt composite oxide catalyst for photo-thermal catalytic oxidation of CO and preparation method thereof

Abstract

The invention discloses a nickel-cobalt composite oxide catalyst for photo-thermal catalytic oxidation of CO and a preparation method thereof, and belongs to the field of catalytic purification of industrial flue gas. According to the catalyst, a nickel-cobalt composite oxide serves as a main active substance, zirconium serves as an auxiliary agent, and the shape of the catalyst is a three-dimensional flower-shaped microsphere with a high specific surface area and an open pore channel structure. The preparation method of the catalyst comprises the following steps: dissolving Ni (NO3) 2.6 H2O and urea in a mixed solvent, adding Co (NO3) 2.6 H2O, fully stirring and uniformly mixing, and then adding Zr (NO3) 4.5 H2O for hydrothermal synthesis reaction; after the reaction is completed, cooling to room temperature, and carrying out solid-liquid separation, washing, drying and calcining on the mixture to obtain the catalyst. According to the preparation method, the NiCo composite oxide with good oxidation-reduction property and excellent conductivity is prepared, Zr with the characteristics of electronic structure regulation and selective sulfur resistance is used as an auxiliary agent for doping, the novel Zr-NiCo composite catalyst is prepared and constructed, the photo-thermal synergistic effect is fully utilized, and the performance of the catalyst is improved. The bottleneck of insufficient CO oxidation low-temperature activity, sulfur resistance, water resistance and operation stability is broken through synchronously, and an advanced catalytic material suitable for actual industrial flue gas is developed.

Description

Technical Field

[0001] This invention relates to the field of industrial flue gas catalytic purification, and in particular to a zirconium-doped nickel-cobalt composite oxide photothermal catalytic oxidation catalyst for CO and its preparation method. Background Technology

[0002] CO emitted with flue gas from non-electric industries such as coke ovens and sintering plants is an important greenhouse gas that can cause photochemical smog, harming human health and ecosystems. It is one of the most important air pollutants in my country.

[0003] In recent years, with the implementation of national requirements for the treatment of coal-fired flue gas and ultra-low emissions, pollutant emissions from coal-fired flue gas have been largely controlled. However, the environmental impact of pollutants emitted from non-power industrial flue gas is becoming increasingly prominent. Currently, the national "Ambient Air Quality Standard" (GB3095-2012) has set higher requirements for CO content in the air, requiring a 24-hour average CO concentration limit of only 4 mg / L. Therefore, controlling CO emissions from non-power industrial flue gas such as coke ovens and sintering plants is imperative.

[0004] In CO emission control technologies, adsorption, direct combustion, and catalytic oxidation are the main methods. Direct combustion, due to the high ignition temperature of CO (approximately 650 ºC), suffers from high energy consumption and operating costs. Adsorption typically uses adsorbents such as activated carbon and molecular sieves to capture CO, but it has drawbacks such as limited adsorption capacity and the need for frequent regeneration or adsorbent replacement. In contrast, catalytic oxidation, under the action of a catalyst, utilizes the existing O2 in the flue gas to efficiently oxidize CO into harmless CO2 at relatively low temperatures (usually much lower than the direct combustion temperature). The process is simple, has low operating costs, and can be widely applied in industrial waste gas treatment.

[0005] Currently, research on CO catalytic oxidation catalysts mainly falls into two categories: noble metals and transition metal oxides. Noble metal catalysts (such as Pt, Pd, and Au) have attracted much attention due to their excellent catalytic activity. For example, invention patent (CN202510899423.X) discloses a catalyst with different oxides supported on the noble metal Pt. Test results show that the CO oxidation rate can reach 90% under optimal conditions of 378 ºC, but higher temperatures are still required. Patent (CN105312064A) discloses a Pd-Ag / CeO2-ZrO2-Y2O3 catalyst, which achieves a CO removal rate of 95% at 140 ºC, but its activity is limited to low CO concentration environments (200 ppm). Ruth K et al. (Applied Catalysis B: Environmental, 2000, 24: 133-145.) studied the noble metal catalyst Au / TiO2. Although it exhibits high activity at low temperatures, it is extremely sensitive to SO2: after introducing 0.05% SO2, it completely deactivated after 2.5 hours, and the activity was irreversible. Transition metal oxide catalysts (such as Cu, Mn, and Ce-based catalysts) have become alternatives to noble metal catalysts due to their low cost, abundant reserves, and easy availability. For example, Mobini S. et al. (Chemical Engineering Science, 2019, 197: 37-51.) studied the CO oxidation performance of MnO2 supported on different supports. The results showed that the 20% Mn / CeO2 catalyst had the best activity, achieving a conversion rate of 100% at 200 ºC. However, this catalyst had significantly insufficient resistance to water vapor, decreasing from 100% to 50% in the presence of 5 vol% H2O within 5 hours. Szanyi J. et al. (Catalysis Letters, 2018, 148: 1445–1450.) introduced CuO-supported CeO2-ZrO 2， Although it shows potential in low-temperature CO oxidation, trace amounts of SO2 (1 ppm) in flue gas can cause irreversible deactivation of the catalyst. Studies by Shen Z. et al. (Journal of the Energy Institute, 2023, 110, 101339.) show that CuO / γ-Fe2O3 can achieve a CO conversion rate of 98.5% at 180 °C. However, this catalyst is prone to carbonate species accumulation, which covers active sites, thus affecting its stability and resistance to poisoning during long-term operation or in complex atmospheres.

[0006] The temperature of flue gas from non-electric industrial processes such as coke ovens and sintering plants is generally below 240 °C, and the flue gas contains a large amount of SO2 and water vapor. Noble metal catalysts have strong sulfur resistance, but their low-temperature activity is not high, and carbon deposition easily forms on the catalyst surface under low-temperature conditions (<280 °C), and their high cost limits their large-scale industrial application. Transition metal oxide catalysts have relatively high low-temperature activity, achieving complete CO oxidation at 150–180 °C, but their stability and resistance to poisoning in complex industrial flue gas environments (especially those containing sulfur and water) remain insufficient. Therefore, developing a catalyst with high low-temperature activity suitable for the catalytic oxidation of CO in coke oven and sintering flue gas is of great significance.

[0007] Photothermal catalytic oxidation of CO utilizes light energy to excite the catalyst to generate electron-hole pairs, and leverages the localized heating caused by the photothermal effect to synergistically promote the oxidation reaction. It exhibits high CO catalytic oxidation activity even at low temperatures and can be placed after desulfurization processes, representing an effective approach for efficient and low-cost catalytic CO oxidation. For example, Novello et al. (ACS Catal. 2019, 9, 578–586) reported that for Au / MgO catalysts prone to deactivation due to surface carbonate accumulation, reasonable utilization of light energy and metal doping could potentially solve the problems of catalyst activity, stability, and anti-poisoning. Zhou Y. et al. (ACS Catal. 2018, 8, 11398) also pointed out that light irradiation induces the adsorption and activation of oxygen at active sites on the surface of Pt / TiO2 catalysts. However, current photothermal catalytic CO oxidation systems still face the following challenges: firstly, high-performance catalysts often rely on precious metals (such as Au and Pt), resulting in high costs and hindering practical application; secondly, existing photothermal catalyst preparation methods are often complex and difficult to meet the needs of large-scale applications. Therefore, developing a photothermal catalyst based on non-precious metals that has a simple preparation process and is highly efficient and stable is of great practical significance.

[0008] NiCo composite oxides are frequently used in electrochemistry due to their high conductivity, abundant oxygen vacancies, good stability, and low cost (Pan Y X. et al., Nanoscale, 2023, 15, 14068–14080., Liu BB et al., J. Mater. Chem. A, 2019, 7, 16222). Based on these advantages, their application in photothermal catalytic CO systems can be further optimized through structural tuning. Metal doping is an effective strategy for improving the performance of non-noble metal catalysts. For example, Zhao F et al. (RSC Adv. 2019, 9, 2343–2352) found that Mn doping not only enhanced CO adsorption capacity but also significantly increased oxygen adsorption on the catalyst surface, promoting the reaction. Wang M et al. (iScience, 2022, 25, 104103) showed that Sn doping can significantly improve the SO2 resistance of Co / CeO2 catalysts because it can act as a sacrificial site to protect the active center. Ryou Y S. et al. (Catal. Today 2015, 258, 518-524.) prepared a Pd / (Ce-Zr)O2 catalyst to change the form of sulfur species, thereby effectively reducing sulfur poisoning. Summary of the Invention

[0009] 1. The technical problem that the invention aims to solve

[0010] The purpose of this invention is to improve the efficiency of CO oxidation to CO2 under low-temperature conditions, and to place CO oxidation after the desulfurization process to solve the shortcomings of existing catalysts with poor sulfur resistance under low-temperature conditions. This invention provides a zirconium-doped nickel-cobalt composite oxide photothermal catalytic oxidation catalyst for CO and its preparation method. The zirconium-doped nickel-cobalt composite oxide catalyst prepared by the technical solution of this invention is expected to efficiently oxidize CO to CO2 through photothermal reaction under low-temperature conditions. CO oxidation can be placed after the desulfurization system to achieve long-term stable operation of CO oxidation.

[0011] 2. Technical Solution

[0012] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0013] This invention provides a nickel-cobalt composite oxide catalyst for photothermal catalytic oxidation of CO. The catalyst uses nickel-cobalt composite oxide as the main active material and zirconium as an auxiliary agent. The catalyst has the morphology of three-dimensional flower-like microspheres with high specific surface area and open pore structure.

[0014] Furthermore, the molar ratio of nickel to cobalt in the catalyst is 1~3:1, and the molar ratio of Zr to Ni is 0.03~0.07:1.

[0015] Furthermore, the molar ratio of nickel to cobalt in the catalyst is 3:1, and the molar ratio of Zr to Ni is 0.05:1.

[0016] This invention also provides a method for preparing the above-mentioned nickel-cobalt composite oxide catalyst for photothermal catalytic oxidation of CO, specifically including the following steps:

[0017] Step 1: Preparation of precursors

[0018] (1) Dissolve Ni(NO3)2·6H2O and urea in a mixed solvent of deionized water and ethylene glycol and stir thoroughly;

[0019] (2) Slowly add Co(NO3)2·6H2O to the mixture in step (1) in proportion, and stir until evenly mixed;

[0020] (3) Add Zr(NO3)4·5H2O to the mixture in step (2) in proportion and stir until well mixed;

[0021] (4) Place the mixture from step (3) in a high-pressure reactor for hydrothermal reaction;

[0022] Step 2: Preparation of Zr-NiCoO catalyst

[0023] After cooling the mixture in step one to room temperature, solid-liquid separation was achieved by centrifugation to obtain the reacted solid. The solid was then washed alternately with deionized water and anhydrous ethanol to remove nitrate and nitrite ions from the surface. Finally, the solid was dried and calcined to obtain the Zr-NiCoO catalyst.

[0024] Furthermore, in step one (1), the volume ratio of deionized water to ethylene glycol is 1:2; in steps one (2) and (3), the stirring and mixing temperature is 40 ºC; in step one (4), the hydrothermal reaction temperature is 100~120 ºC and the hydrothermal reaction time is 14~18 h.

[0025] Furthermore, in step two, the solid drying temperature is 80 ºC and the drying time is 12 h; the catalyst calcination temperature is 250~350 ºC and the calcination time is 3 h.

[0026] The aforementioned nickel-cobalt composite oxide catalyst can be applied in photothermal catalytic oxidation of CO.

[0027] The innovative aspects of this invention are as follows:

[0028] The scientific principle behind the improved CO catalytic oxidation performance of the zirconium-doped nickel-cobalt composite oxide catalyst of this invention is mainly based on the synergistic optimization of catalyst surface properties and reaction mechanism by zirconium doping. Zirconium doping introduces high-valence Zr... 4+The presence of ions effectively modulates the electronic structure of the NiCoO catalyst. To maintain charge balance, a large number of oxygen vacancies are generated inside the catalyst, significantly enhancing its adsorption and activation capacity for oxygen molecules. The catalytic reaction follows the Mars-van Krevelen (MvK) mechanism, where CO molecules react with lattice oxygen on the catalyst surface to generate CO2, while the resulting oxygen vacancies are replenished and regenerated by oxygen molecules in the gas phase. The abundant oxygen vacancies induced by zirconium doping greatly promote this redox cycle, thus achieving excellent CO oxidation activity at low temperatures.

[0029] Regarding sulfur resistance, SO2 in flue gas typically competes with reactants for active sites on the catalyst surface, forming stable sulfate species that lead to permanent catalyst deactivation. In this invention, zirconium-doped sites preferentially and selectively adsorb SO2, forming localized sulfate species. This "selective adsorption-protection" mechanism effectively blocks the poisoning of SO2 on the nickel-cobalt main active center, enabling the catalyst to maintain high catalytic efficiency even in sulfur-containing atmospheres.

[0030] Regarding water resistance, water vapor molecules reversibly compete for adsorption onto the active sites on the catalyst surface. Zirconium doping induces catalyst morphology reconstruction, forming three-dimensional flower-like microspheres with high specific surface area and open pore structure (see appendix). Figure 1 This not only exposes more active sites but also optimizes the mass transfer process between reactants and products. Therefore, even in the presence of water vapor, the catalyst can retain sufficient effective active sites, exhibiting good stability and water vapor tolerance.

[0031] In summary, zirconium doping, by optimizing oxygen vacancy concentration, introducing selective sulfur resistance mechanisms, and constructing a multi-level pore structure, synergistically enhances the low-temperature activity, sulfur resistance, water resistance, and long-term operational stability of NiCoO catalysts, laying a scientific foundation for their application in complex flue gas environments.

[0032] Compared with the prior art, the present invention achieves the following technical effects:

[0033] 1. This invention prepares a NiCo composite oxide with good redox properties and excellent electrical conductivity. Zr, characterized by its electronic structure regulation and selective sulfur resistance, is used as a promoter for doping to construct a novel Zr-NiCo composite catalyst. By fully utilizing the photothermal synergistic effect, it simultaneously overcomes the bottlenecks of insufficient low-temperature activity, sulfur and water resistance, and operational stability in CO oxidation, developing an advanced catalytic material suitable for actual industrial flue gas. Currently, the activity temperature window of thermocatalytic nickel-cobalt composite oxide catalysts is generally between 150 and 400 °C. Their low-temperature activity is inferior to that of precious metals, their thermal stability is limited, and their sulfur and water resistance is weak. They are prone to activity decay due to sulfate poisoning from SO2 or high humidity covering active sites. Optimal activity is only achieved above 150 °C (conversion rate is less than 70% below 120 °C), and above 450 °C, they are prone to sintering, agglomeration, and loss of active components, resulting in a short long-term service life. The zirconium-doped nickel-cobalt composite oxide catalyst described in this invention has a lower temperature window, achieving a CO removal efficiency of 95% at 80 °C. Furthermore, after reacting at 100℃ for 20 h, the catalyst activity still reaches 100%. Even under conditions where the flue gas contains sulfur and moisture, it still exhibits good CO conversion. Simultaneously, the catalyst prepared by the method provided in this invention has its active components uniformly distributed amorphously on the catalyst surface.

[0034] 2. The preparation method of this invention is simple, the raw materials are widely available, and the cost is low. This invention optimizes the exposed crystal facets through doping modification, improving surface activity and enhancing the catalyst's CO removal activity and long-term stability at low temperatures. Simultaneously, it ensures the catalyst retains a certain degree of catalytic activity in the presence of SO2 and H2O, providing an important technical foundation for promoting the engineering application of low-temperature CO removal technology.

[0035] Instruction manual illustrations

[0036] Figure 1 The image shows the microstructure of the nickel-cobalt oxide composite catalyst prepared in Example 3 of this invention.

[0037] As shown in the figure, zirconium doping induces morphological reconstruction of the nickel-cobalt oxide catalyst, resulting in a catalyst with a high specific surface area.

[0038] Three-dimensional flower-shaped microspheres with an accumulation and open pore structure. Detailed Implementation

[0039] The technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] A method for preparing a zirconium-doped nickel-cobalt oxide composite catalyst employs a two-step hydrothermal-calcination process. The nickel-cobalt oxide is the active component, prepared as follows: First, Ni(NO3)2·6H2O and an appropriate amount of urea are dissolved in a mixed solvent of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, Co(NO3)2·6H2O is slowly added, and the mixture is magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O is slowly added according to the molar ratio of zirconium to nickel, and the mixture is stirred for 6 h. The resulting solution is transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor for hydrothermal reaction. After cooling the reaction system to room temperature, the precipitate is collected by centrifugation (8000 rpm, 3 min). The product is then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash until nitrate (NO3) is detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined and ground at a programmed heating rate of 5 °C / min to obtain zirconium-doped nickel-cobalt oxide composite catalyst powder.

[0041] Example 1

[0042] (1) Preparation of precursors

[0043] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.00, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 16 h to obtain the precursor solution.

[0044] (2) Preparation of catalyst

[0045] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0046] Example 2

[0047] (1) Preparation of precursors

[0048] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.03, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 16 h to obtain the precursor solution.

[0049] (2) Preparation of catalyst

[0050] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0051] Example 3

[0052] (1) Preparation of precursors

[0053] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 16 h to obtain the precursor solution.

[0054] (2) Preparation of catalyst

[0055] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected.3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0056] Example 4

[0057] (1) Preparation of precursors

[0058] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.07, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 16 h to obtain the precursor solution.

[0059] (2) Preparation of catalyst

[0060] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0061] Example 5

[0062] (1) Preparation of precursors

[0063] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 16 h to obtain the precursor solution.

[0064] (2) Preparation of catalyst

[0065] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 250 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0066] Example 6

[0067] (1) Preparation of precursors

[0068] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 16 h to obtain the precursor solution.

[0069] (2) Preparation of catalyst

[0070] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 350 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0071] Example 7

[0072] (1) Preparation of precursors

[0073] First, 6 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 16 h to obtain the precursor solution.

[0074] (2) Preparation of catalyst

[0075] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0076] Example 8

[0077] (1) Preparation of precursors

[0078] First, 18 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 16 h to obtain the precursor solution.

[0079] (2) Preparation of catalyst

[0080] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2-Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0081] Example 9

[0082] (1) Preparation of precursors

[0083] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 14 h to obtain the precursor solution.

[0084] (2) Preparation of catalyst

[0085] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0086] Example 10

[0087] (1) Preparation of precursors

[0088] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 110 °C for 18 h to obtain the precursor solution.

[0089] (2) Preparation of catalyst

[0090] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0091] Example 11

[0092] (1) Preparation of precursors

[0093] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 100 °C for 16 h to obtain the precursor solution.

[0094] (2) Preparation of catalyst

[0095] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0096] Example 12

[0097] (1) Preparation of precursors

[0098] First, 12 mmol Ni(NO3)2·6H2O and an appropriate amount of urea were dissolved in a mixed solvent consisting of 40 mL deionized water and 80 mL ethylene glycol. After thorough stirring, 6 mmol Co(NO3)2·6H2O was slowly added, and the mixture was magnetically stirred for 6 h to form a homogeneous precursor solution. Then, Zr(NO3)4·5H2O was added at a Zr to Ni molar ratio of 0.05, and the mixture was stirred for another 6 h. The resulting solution was transferred to a 250 mL polytetrafluoroethylene-lined high-pressure reactor and subjected to a hydrothermal reaction at 120 °C for 16 h to obtain the precursor solution.

[0099] (2) Preparation of catalyst

[0100] After the reaction system was cooled to room temperature, the precipitate was collected by centrifugation (8000 rpm, 3 min). The product was then washed alternately with deionized water and anhydrous ethanol, with the solid and liquid phases separated under the same centrifugation conditions after each wash, until nitrate (NO) ions were detected. 3- ) and nitrite (NO 2- Ions were completely removed. After obtaining the precursor powder by vacuum drying at 80 °C for 12 h, it was placed in a muffle furnace and calcined at 300 °C for 3 h with a heating rate of 5 °C / min. The calcined catalyst was then ground to obtain zirconium-doped nickel-cobalt composite oxide catalyst powder.

[0101] Catalyst performance testing

[0102] 1. Performance Test 1

[0103] 0.4 g of catalyst with a particle size of approximately 0.3–0.5 mm (40–60 mesh) prepared in Examples 1–12 was weighed and loaded into a quartz reactor to test its CO removal activity. The catalyst sample was irradiated from the top surface of the quartz using a xenon lamp (a 300 W Xe lamp equipped with a cutoff filter (<400 nm)). The reactor was covered with aluminum foil to protect it from light during the dark reaction. The CO concentration after 1 h of reaction was taken as the average value. Subsequently, visible light was introduced for 1 h under the same conditions. The test conditions were as follows: N2 as the equilibrium gas, total feed flow rate controlled at 100 mL / min, inlet CO concentration controlled at 5000 ppm, O2 volume concentration controlled at 8%, and test temperature range of 60℃–100℃. The results are shown in Table 1.

[0104] Table 1. CO removal activity of catalysts in Examples 1-12 of catalyst preparation

[0105]

[0106] As can be seen from the CO removal activity test of the catalyst in Table 1, when there is no SO2 and H2O in the flue gas, Examples 1-12 showed good CO removal activity at 90 °C under light conditions. Example 3 was the catalyst under the best preparation conditions under light conditions, and its CO removal activity reached 95% at 80 °C and remained at 100% in the temperature range of 90 °C to 100 °C.

[0107] 2. Performance Test Two

[0108] 0.4 g of catalyst with a particle size of approximately 0.3–0.5 mm (40–60 mesh) prepared in Examples 1–6 were weighed and loaded into a quartz reactor to test its CO removal activity. The catalyst sample was irradiated from the top surface of the quartz using a xenon lamp (a 300 W Xe lamp equipped with a cutoff filter (<400 nm)). The reactor was covered with aluminum foil to protect it from light during the dark reaction. The CO concentration after 1 hour of reaction was taken as the average value. Subsequently, visible light was introduced for 1 hour under the same conditions. The test conditions were as follows: N2 as the equilibrium gas, total feed flow rate controlled at 100 mL / min, inlet CO concentration controlled at 5000 ppm, O2 volume concentration at 8%, SO2 concentration at 50 ppm, H2O concentration at 5 vol%, and test temperature at 100 ℃. The results are shown in Table 2.

[0109] Table 2. Test of the catalyst's resistance to sulfur water

[0110]

[0111] Table 2 shows the catalyst's resistance to sulfur and water. Under 50 ppm SO2 illumination, the catalyst activity gradually decreased with increasing reaction time. Under 5 vol% H2O illumination, the catalyst activity also gradually decreased with increasing reaction time. Example 3 exhibited excellent sulfur and water resistance; after 5 h of 50 ppm SO2 illumination, the catalyst activity was 100%, and after 9 h of reaction with 5 vol% H2O, the catalyst's CO removal activity was 97%.

[0112] 3. Performance Test Three

[0113] 0.4 g of catalyst with a particle size of approximately 0.3–0.5 mm (40–60 mesh) prepared in Examples 1–6 were weighed and loaded into a quartz reactor to test its CO removal activity. The catalyst sample was irradiated from the top surface of the quartz using a xenon lamp (a 300 W Xe lamp equipped with a cutoff filter (<400 nm)). The reactor was covered with aluminum foil to protect it from light during the dark reaction. The CO concentration after 1 hour of reaction was taken as the average value. Subsequently, visible light was introduced for 1 hour under the same conditions. The test conditions were as follows: N2 as the equilibrium gas, total feed flow rate controlled at 100 mL / min, inlet CO concentration controlled at 5000 ppm, O2 volume concentration controlled at 8%, test time from 1 to 20 hours, and test temperature at 100 °C. The results are shown in Table 3.

[0114] Table 3. Stability tests of catalysts in Examples 1 and 3 of catalyst preparation.

[0115]

[0116] As can be seen from Table 3, both Example 1 and Example 3 exhibit excellent stability. The catalyst in Example 3, under optimal preparation conditions, showed 100% activity after 20 hours of reaction.

Claims

1. A nickel-cobalt composite oxide catalyst for photothermal catalytic oxidation of CO, characterized in that: The catalyst uses nickel-cobalt composite oxide as the main active material and zirconium as an auxiliary agent. The catalyst has the morphology of three-dimensional flower-like microspheres with high specific surface area and open pore structure.

2. The nickel-cobalt composite oxide catalyst for photothermal catalytic oxidation of CO as described in claim 1, characterized in that, The molar ratio of nickel to cobalt in this catalyst is 1~3:1, and the molar ratio of Zr to Ni is 0.03~0.07:

1.

3. The nickel-cobalt composite oxide catalyst for photothermal catalytic oxidation of CO as described in claim 2, characterized in that, The catalyst has a nickel to cobalt molar ratio of 3:1 and a Zr to Ni molar ratio of 0.05:

1.

4. A method for preparing a nickel-cobalt composite oxide catalyst for photothermal catalytic oxidation of CO as described in any one of claims 1-3, characterized in that... Includes the following steps: Step 1: Preparation of precursors (1) Dissolve Ni(NO3)2·6H2O and urea in a mixed solvent of deionized water and ethylene glycol and stir thoroughly; (2) Slowly add Co(NO3)2·6H2O to the mixture in step (1) in proportion, and stir until evenly mixed; (3) Add Zr(NO3)4·5H2O to the mixture in step (2) in proportion and stir until well mixed; (4) Place the mixture from step (3) in a high-pressure reactor for hydrothermal reaction; Step 2: Preparation of Zr-NiCoO catalyst After cooling the mixture in step one to room temperature, solid-liquid separation was achieved by centrifugation to obtain the reacted solid. The solid was then washed alternately with deionized water and anhydrous ethanol to remove nitrate and nitrite ions from the surface. Finally, the solid was dried and calcined to obtain the Zr-NiCoO catalyst.

5. The preparation method of the nickel-cobalt composite oxide catalyst for photothermal catalytic oxidation of CO as described in claim 4, characterized in that, In step one (1), the volume ratio of deionized water to ethylene glycol is 1:2; in steps one (2) and (3), the stirring and mixing temperature is 40 ºC and the stirring and mixing time is 6h; in step one (4), the hydrothermal reaction temperature is 100~120 ºC and the hydrothermal reaction time is 14~18h.

6. The method for preparing the nickel-cobalt composite oxide catalyst for photothermal catalytic oxidation of CO as described in claim 4, characterized in that, In step two, the solid drying temperature is 80 ºC and the drying time is 12 h; the solid calcination temperature is 250~350 ºC and the calcination time is 3 h.

7. The application of the nickel-cobalt composite oxide catalyst as described in claim 1 in photothermal catalytic oxidation of CO.

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