Cobalt-cerium composite oxide catalyst as well as preparation method and application thereof
By doping Ce into Co-based oxides to form a (Co-S-O)-Ce structure, the problem of cobalt-based catalyst inactivation at high temperatures and poisoning in sulfur-containing environments is solved, and a cobalt-cerium composite oxide catalyst with high SO2 tolerance and long-life is achieved, and the methane combustion performance is optimized.
Patent Information
- Application Number
- CN202510282622.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-11
- Publication Date
- 2025-05-13
AI Technical Summary
In the prior art, cobalt-based catalysts are prone to inactivate at high temperatures, have poor water resistance, and are prone to poisoning in sulfur-containing environments, resulting in a short service life of the catalyst and difficult to achieve high SO2 tolerance.
By doping Ce into Co-based oxides, a (Co-S-O)-Ce structure is formed, using the oxygen storage capacity of CeO2 and the surface oxygen vacancies, the active components are protected from toxicity by SO2, and the structure and performance of the catalyst are optimized through interface engineering.
The cobalt-cerium composite oxide catalyst has high activity and high resistance to heat and poisoning at low temperatures, improves the SO2 tolerance and service life of the catalyst, and optimizes methane combustion performance.
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Figure CN119972096A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of energy and environmental technology, and more specifically to a cobalt-cerium composite oxide catalyst and a preparation method and application thereof. Background Art
[0002] The highly elastic CH bond in the methane molecule (bond energy is about 435 kJ / mol) makes its degradation very difficult. The traditional methane flame combustion temperature must be above 1500 °C, and it will also react with N in the air. 2 The reaction generates NO x Pollutants are extremely harmful to the environment. Moreover, the energy utilization rate of traditional flame combustion is very low, which is not suitable for energy-saving and environmentally friendly treatment. Therefore, changing the combustion method of methane is currently a key issue, and catalytic oxidation is an economical and effective technology to reduce unburned methane and CO emissions because of its moderate operating temperature and high removal efficiency. A key aspect of promoting this technology is to create efficient catalysts.
[0003] For commonly used catalytic oxidation technologies, the life of the catalyst is a priority factor in eliminating the adverse environmental impact of harmful exhaust gases. Sulfide is widely considered to be one of the toxic components that can poison catalysts. Under actual application conditions, despite the continuous improvement of desulfurization technology, trace amounts of sulfur species still remain in industrial exhaust gas, engine lubricating oil, commercial diesel, and blast furnace gas. Sulfur will inevitably be oxidized to SO 2 . SO 2 It is adsorbed on the active noble metal sites on the catalyst surface and preferentially discharged, thereby blocking the reaction pathway between the catalyst and the reactants, resulting in irreversible deactivation of the reaction. 2 The metal sulfates and sulfites produced by oxidation will not only lead to the accumulation of intermediates on the catalyst surface, inhibiting the catalytic performance, but also seriously affect the service life of the catalyst, hinder subsequent reactions, and ultimately deactivate the catalyst. 2 Tolerant catalysts are an issue that cannot be ignored for environmental sustainability.
[0004] For the catalytic combustion of methane, its catalysts can be divided into two categories: precious metal catalysts and non-precious metal catalysts. At present, researchers have made great progress in the study of precious metals, and have achieved certain research results in both preparation methods and reaction mechanisms. Although precious metal catalysts show significant activity, their widespread adoption is hindered by their high cost and easy poisoning. As for non-precious metal catalysts, especially transition metal oxide catalysts (TMOs), they have attracted great attention due to their low cost and good activity, and the advantages of variable valence states and adjustable occupied orbitals in redox reactions. However, the activity of transition metal oxide catalysts is still significantly different from that of precious metal catalysts. Therefore, improving the catalytic efficiency of transition metal oxide catalysts is crucial to promote the application of deep oxidation technology in mitigating light alkane emissions.
[0005] Among the reported non-precious metal catalysts, cobalt-based catalysts are considered as promising alternatives due to their excellent catalytic performance comparable to that of precious metal catalysts. Spinel-type Co-based oxides have unique electronic properties, with metal cations having multiple valence states in tetrahedral and octahedral interstices, surface lattice oxygen ions with different Lewis basicities, and low bond energies of Co-O bonds. In addition, the exposed (110) surface of Co-based spinel oxides provides a highly active surface for CH activation. However, Co-based catalysts are very susceptible to deactivation because they are prone to sintering at high temperatures, have poor water resistance, and are easily poisoned in sulfur-containing environments. Therefore, regulating the activity of oxygen on spinel oxides to improve their catalytic activity has always been a challenge for heterogeneous catalytic oxidation reactions; at the same time, due to the lack of appropriate metal-support interactions and anti-poisoning sites, the metal active components are easily oxidized by SO at low temperatures for a long time. 2 and H 2 O aggregation and poisoning lead to unsatisfactory catalytic stability.
[0006] According to existing literature reports, CeO 2 There are abundant surface oxygen vacancies, which can serve as SO 2 adsorption and activation sites, protecting the active components from being poisoned. 2 Under high temperature treatment, the surface area is significantly reduced and the degradation is rapid, so it cannot meet the requirements of practical use. However, after doping or surface modification, CeO 2 The structural properties of CeO can be improved. 2 Other metal ions are introduced into the lattice to form CeO-based 2 Solid solution can make the material have higher oxygen storage capacity, thermal stability and redox performance, thus having excellent catalytic performance. Compared with single oxides, most composite metal oxides have the advantages of larger specific surface area, better thermal stability and mechanical strength, and stronger surface acidity and alkalinity.
[0007] Therefore, how to develop a cobalt-based composite oxide catalyst is an urgent problem to be solved by those skilled in the art. Summary of the invention
[0008] In view of this, the object of the present invention is to provide a cobalt-cerium composite oxide catalyst and a preparation method and application thereof, so as to solve the deficiencies in the prior art.
[0009] In order to achieve the above object, the present invention adopts the following technical solution:
[0010] A method for preparing a cobalt-cerium composite oxide catalyst comprises the following steps:
[0011] (1) dissolving cerium nitrate hexahydrate and cobalt nitrate hexahydrate in water under ultrasonic conditions, and then adding anhydrous citric acid to obtain a mixed solution;
[0012] (2) The mixed solution is stirred and evaporated to dryness, and the obtained solid is dried overnight, calcined, and cooled to obtain a cobalt-cerium composite oxide catalyst.
[0013] Furthermore, in the above step (1), the ratio of the sum of the molar amount of cerium ions in cerium nitrate hexahydrate and the molar amount of cobalt ions in cobalt nitrate hexahydrate to the molar amount of anhydrous citric acid is 1:(0.5-1.5).
[0014] The above further beneficial effects are that the present invention uses anhydrous citric acid to:
[0015] (1) As a chelating agent: Citric acid can form stable complexes with cerium and cobalt metal ions, preventing their premature precipitation and ensuring uniform distribution of metal ions.
[0016] (2) As a pH regulator: By adjusting the pH value of the sol, the rates of hydrolysis and polycondensation reactions are affected, thereby controlling the formation and stability of the sol.
[0017] advantage:
[0018] (1) Improving uniformity: As a chelating agent, citric acid helps cerium and cobalt metal ions to be evenly distributed in the sol, thereby improving the uniformity of the cobalt-cerium composite oxide catalyst.
[0019] (2) Controlling reaction rate: By adjusting the pH, citric acid can effectively control the rates of hydrolysis and polycondensation reactions and optimize the sol formation process.
[0020] (3) Simplified process: The use of citric acid simplifies the operation steps of the sol-gel method and reduces the complexity of the process.
[0021] (4) Environmental protection: Citric acid is non-toxic and biodegradable, meeting the requirements of green chemistry.
[0022] Furthermore, in the above step (2), the stirring evaporation drying conditions are 50-90° C. water bath, stirring speed is 300-700 rpm, and stirring time is 1-4 h.
[0023] Furthermore, in the above step (2), the temperature for drying overnight is 70-120°C.
[0024] Furthermore, in the above step (2), the calcination atmosphere is air, the temperature is 400-700° C., and the time is 2-5 hours.
[0025] The further beneficial effect of adopting the above is that the present invention selects the effect of calcining in air at 400-700°C for 2-5h, including removing organic matter, promoting the formation of crystalline phase, increasing specific surface area and porosity, and enhancing thermal stability, as follows:
[0026] (1) Removal of organic matter: It can effectively remove the organic components (citric acid) in the sol to avoid its interference with the catalyst performance.
[0027] (2) Promote crystal phase formation: Appropriate calcination temperature helps the catalyst precursor to transform into the desired crystal phase structure and enhance the catalytic activity.
[0028] (3) Increase specific surface area and porosity: During the calcination process, pores are formed inside the material, increasing the specific surface area and porosity, thereby enhancing the active sites of the catalyst.
[0029] (4) Enhanced thermal stability: Calcination can improve the thermal stability of the catalyst, allowing it to maintain structural stability under high temperature reaction conditions.
[0030] Benefits include optimized catalytic performance, controlled grain size, energy savings and reduced sintering risk, as follows:
[0031] (1) Optimizing catalytic performance: Calcination temperatures of 400 to 700 °C can effectively remove organic matter and promote the formation of crystalline phases, thereby optimizing the activity and selectivity of the catalyst.
[0032] (2) Controlling grain size: This temperature range helps control grain size, avoid excessive grain growth caused by excessive temperature, and maintain a high specific surface area.
[0033] (3) Energy saving: Compared with higher temperatures, calcination temperatures of 400-700°C consume less energy and are more economical.
[0034] (4) Reduce sintering risk: This temperature range can reduce the sintering of catalyst particles and maintain a high specific surface area and porosity.
[0035] Furthermore, in the above step (2), the chemical formula of the cobalt-cerium composite oxide catalyst is Co 3-x Cex O 4 , where x=0~0.5.
[0036] The present invention also claims a cobalt-cerium composite oxide catalyst prepared by the above preparation method, the chemical formula of which is Co 3-x Ce x O 4 , where x=0~0.5.
[0037] The present invention also claims to protect the use of a cobalt-cerium composite oxide catalyst prepared by the above preparation method in catalytic combustion of methane.
[0038] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:
[0039] 1. In most methane catalytic oxidation reactions, SO 2 However, the present invention dissolves ultrafine CeO in situ on the surface by doping Ce into Co-based oxides. 2 The particles form a (Co-SO)-Ce structure, which is conducive to the adsorption and conversion of oxygen on the catalyst surface, and also promotes the adsorption of methane, resulting in better combustion performance of methane. In addition, this active structure can eliminate SO 2 The effect of metal sulfates and sulfites produced by the interaction with the catalyst on the service life of the catalyst offsets the accumulation of intermediates on the catalyst surface, leaving the catalytic performance uninhibited.
[0040] 2. The present invention doped Ce into Co-based oxides through interface engineering to obtain a high-performance methane combustion catalyst with excellent low-temperature activity and high heat and poisoning resistance, and SO 2 The poisoning effect on methane combustion catalyst turns into a promoting effect, which is the main reason for high SO 2 The rational design of chemical bonds of tolerant catalysts provides new ideas to improve the economic and environmental benefits of catalysts.
[0041] 3. Cobalt-cerium composite oxide Co of the present invention 3-x Ce x O 4 The catalyst exhibits excellent low-temperature activity during the catalytic combustion of methane, with a low-concentration methane (methane concentration of 0.5% to 1.5%) conversion rate of 90%, and has high stability against water and sulfur dioxide when the temperature drops below 400°C (383°C).
[0042] 4. Compared with the atmosphere without sulfur dioxide, the cobalt-cerium composite oxide Co 3-x Ce x O 4The catalyst has an improved conversion rate for methane catalytic combustion in a sulfur dioxide atmosphere, showing a high SO 2 Tolerance.
[0043] 5. The present invention prepares a Ce-doped Co 3 O 4 Cobalt-cerium composite oxide Co2-ceramic oxide with active interface structure of (cobalt-oxygen-cerium)-cerium oxide 3-x Ce x O 4 The catalyst is simple in process, green and efficient in preparation, and the catalyst obtained fully utilizes the synergistic effect between the non-precious metal Co-based solid solution catalyst and the carrier, significantly improving the low-temperature catalytic activity, selectivity, and high heat resistance and anti-poisoning stability, and the catalyst can be recycled and reused repeatedly, which is conducive to the recycling of resources and reduces costs. In addition, the catalyst is used for low-concentration methane combustion reaction, which is easy to operate and has a high conversion rate.
[0044] 6. Cobalt-cerium composite oxide Co of the present invention 3-x Ce x O 4 The catalyst can be used in coal mine gas ventilation and industrial flue gas treatment, and can be used for catalyst filling in tail gas purification devices. It exhibits high water resistance and sulfur dioxide resistance stability in low-temperature and low-concentration methane catalytic combustion, and sulfur dioxide exhibits an excellent promoting effect in methane catalytic oxidation. BRIEF DESCRIPTION OF THE DRAWINGS
[0045] Figure 1 The process flow chart of the preparation method of the cobalt-cerium composite oxide catalyst is as follows;
[0046] Figure 2 For Co 2.8 Ce 0.2 O 4 Catalyst and Co 2.8 Ce 0.2 O 4 -SO 2 Comparison of catalytic performance of catalysts;
[0047] Figure 3 For Co 2.7 Ce 0.3 O 4 Catalyst and Co 2.7 Ce 0.3 O 4 -SO 2 Comparison of catalytic performance of catalysts;
[0048] Figure 4 For Co 3 O 4 Catalyst and Co3 O 4 -SO 2 Comparison of catalytic performance of catalysts. DETAILED DESCRIPTION
[0049] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0050] Example 1
[0051] The preparation method of the cobalt-cerium composite oxide catalyst is as follows: Figure 1 As shown, the specific steps include:
[0052] (1) Under ultrasonic conditions, 0.9 g of cerium nitrate hexahydrate and 8.2 g of cobalt nitrate hexahydrate were dissolved in 100 mL of deionized water, and then 5.8 g of anhydrous citric acid was added, wherein the ratio of the sum of the molar amount of cerium ions in the cerium nitrate hexahydrate and the molar amount of cobalt ions in the cobalt nitrate hexahydrate to the molar amount of anhydrous citric acid was 1:0.5, to obtain a mixed solution;
[0053] (2) The mixed solution was stirred and evaporated to dryness at 300 rpm in a water bath at 70°C for 1 hour. The obtained solid was dried at 100°C overnight, then calcined in air at 500°C for 2 hours and cooled to obtain cobalt-cerium composite oxide Co 2.8 Ce 0.2 O 4 catalyst.
[0054] Example 2
[0055] The preparation method of the cobalt-cerium composite oxide catalyst is as follows: Figure 1 As shown, the specific steps include:
[0056] (1) Under ultrasonic conditions, 1.3 g of cerium nitrate hexahydrate and 7.8 g of cobalt nitrate hexahydrate were dissolved in 100 mL of deionized water, and then 8.6 g of anhydrous citric acid was added, wherein the ratio of the sum of the molar amount of cerium ions in the cerium nitrate hexahydrate and the molar amount of cobalt ions in the cobalt nitrate hexahydrate to the molar amount of anhydrous citric acid was 1:1.5, to obtain a mixed solution;
[0057] (2) The mixed solution was stirred and evaporated to dryness at 500 rpm in a water bath at 90°C for 4 h. The obtained solid was dried at 120°C overnight, then calcined in air at 700°C for 4 h and cooled to obtain cobalt-cerium composite oxide Co 2.7 Ce 0.3 O 4 catalyst.
[0058] Comparative Example
[0059] The preparation method of the cobalt-based oxide catalyst specifically comprises the following steps:
[0060] (1) Under ultrasonic conditions, 8.7 g of cerium nitrate hexahydrate was dissolved in 100 mL of deionized water, and then 5.76 g of anhydrous citric acid was added, wherein the ratio of the molar amount of cerium ions in the cerium nitrate hexahydrate to the molar amount of the anhydrous citric acid was 1:1, to obtain a mixed solution;
[0061] (2) The mixed solution was stirred and evaporated to dryness at 400 rpm in a water bath at 80°C for 4 h. The obtained solid was dried at 110°C overnight, calcined in air at 600°C for 3 h, and cooled to obtain the cobalt-based oxide Co 3 O 4 catalyst.
[0062] Performance Testing
[0063] 1. Co 2.8 Ce 0.2 O 4 Catalyst and Co 2.8 Ce 0.2 O 4 -SO 2 Comparison of catalytic performance of catalysts
[0064] The cobalt-cerium composite oxide Co prepared in Example 1 2.8 Ce 0.2 O 4 The catalyst is 1% methane + 20% oxygen + 100ppm SO 2 atmosphere for 24 h, marked as Co 2.8 Ce 0.2 O 4 -SO 2 Catalyst. In 1% methane + 20% oxygen + N 2 Next, Co 2.8 Ce 0.2 O 4 Catalyst and Co 2.8 Ce 0.2 O 4 -SO 2 The catalytic performance of the catalyst is Figure 2 shown.
[0065] Depend on Figure 2 It can be seen that Co 2.8 Ce 0.2 O 4 The catalytic performance of the catalyst for methane combustion in a sulfur-containing atmosphere is improved compared with that in a sulfur-free atmosphere, and the temperature at which the conversion rate reaches 90% is reduced by 20°C.
[0066] 2. Co 2.7 Ce 0.3 O 4 Catalyst and Co 2.7 Ce 0.3 O 4 -SO 2 Comparison of catalytic performance of catalysts
[0067] The cobalt-cerium composite oxide Co prepared in Example 2 2.7 Ce 0.3 O 4 The catalyst is 1% methane + 20% oxygen + 100ppm SO 2 atmosphere for 24 h, marked as Co 2.7 Ce 0.3 O 4 -SO 2 Catalyst. In 1% methane + 20% oxygen + N 2 Next, Co 2.7 Ce 0.3 O 4 Catalyst and Co 2.7 Ce 0.3 O 4 -SO 2 The catalytic performance of the catalyst is Figure 3 shown.
[0068] Depend on Figure 3 It can be seen that Co 2.7 Ce 0.3 O 4 The catalytic performance of the catalyst for methane combustion in a sulfur-containing atmosphere is improved compared with that in a sulfur-free atmosphere, and the temperature at which the conversion rate reaches 90% is reduced by 30°C.
[0069] 3. Co 3 O 4 Catalyst and Co 3 O 4 -SO 2 Comparison of catalytic performance of catalysts
[0070] The cobalt-based oxide Co prepared in the comparative example 3 O 4 The catalyst is 1% methane + 20% oxygen + 100ppm SO 2 atmosphere for 24 h, marked as Co 3 O 4 -SO 2 Catalyst. In 1% methane + 20% oxygen + N 2 Next, Co 3 O 4 Catalyst and Co 3 O 4 -SO 2The catalytic performance of the catalyst is Figure 4 shown.
[0071] Depend on Figure 4 It can be seen that Co 3 O 4 The catalytic performance of the catalyst for methane combustion in a sulfur-containing atmosphere is significantly lower than that in a sulfur-free atmosphere, and the temperature at which the conversion rate reaches 90% increases by 70°C.
[0072] The above experiments show that Ce doping into Co 3 O 4 It can eliminate the poisoning effect of sulfur dioxide on the catalyst and promote the catalytic performance. 3 O 4 In the process, a (Co-SO)-Ce structure can be formed on the surface in situ, which can eliminate the influence of sulfides produced by the catalyst and sulfur dioxide, making the cobalt-cerium composite oxide Co 3-x Ce x O 4 The catalyst has good sulfur dioxide tolerance.
[0073] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for preparing a cobalt-cerium composite oxide catalyst, characterized in that: The specific steps include: (1) dissolving cerium nitrate hexahydrate and cobalt nitrate hexahydrate in water under ultrasonic conditions, and then adding anhydrous citric acid to obtain a mixed solution; (2) stirring the mixed solution and evaporating to dryness, drying the obtained solid overnight, calcining, and cooling to obtain the cobalt-cerium composite oxide catalyst.
2. The method for preparing a cobalt-cerium composite oxide catalyst according to claim 1, characterized in that: In step (1), the ratio of the sum of the molar amount of cerium ions in the cerium nitrate hexahydrate and the molar amount of cobalt ions in the cobalt nitrate hexahydrate to the molar amount of anhydrous citric acid is 1:(0.5-1.5).
3. The method for preparing a cobalt-cerium composite oxide catalyst according to claim 1, characterized in that: In step (2), the stirring evaporation drying conditions are 50-90° C. water bath, stirring speed is 300-700 rpm, and stirring time is 1-4 h.
4. The method for preparing a cobalt-cerium composite oxide catalyst according to claim 1, characterized in that: In step (2), the temperature for drying overnight is 70-120°C.
5. The method for preparing a cobalt-cerium composite oxide catalyst according to claim 1, characterized in that: In step (2), the calcination atmosphere is air, the temperature is 400-700° C., and the time is 2-5 hours.
6. The method for preparing a cobalt-cerium composite oxide catalyst according to claim 1, characterized in that: In step (2), the chemical formula of the cobalt-cerium composite oxide catalyst is Co 3-x Ce x O4, where x = 0 to 0.
5.
7. A cobalt-cerium composite oxide catalyst prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The chemical formula is Co 3-x Ce x O4, where x = 0 to 0.
5.
8. Use of the cobalt-cerium composite oxide catalyst prepared by the preparation method according to any one of claims 1 to 6 in catalytic combustion of methane.