Iron-doped manganite catalyst, method for preparing same, and use thereof
By using sulfuric acid aqueous solution to regulate the redox reaction in the preparation of iron-doped manganese oxide catalysts, uniform dispersion of Fe3+ in the MnO2 lattice was achieved, forming stable Fe-O-Mn bond bridges. This solved the problem of uneven Fe3+ dispersion and improved the low-temperature catalytic activity and energy consumption efficiency of the catalyst.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JILIN INST OF CHEM TECH
- Filing Date
- 2026-04-28
- Publication Date
- 2026-06-05
AI Technical Summary
In the preparation process of existing iron-doped manganese oxide catalysts, Fe3+ is difficult to be uniformly dispersed in the MnO2 lattice, resulting in insufficient concentration of surface active oxygen species, weak Fe-Mn synergistic effect, unsatisfactory low-temperature catalytic activity, high energy consumption during high-temperature calcination, and easy sintering of crystal grains.
Using sulfuric acid aqueous solution as the reaction medium, the redox reaction kinetics are regulated by the acidic environment, which promotes the uniform dispersion of Fe3+ in the MnO2 lattice and the formation of stable Fe-O-Mn bond bridges. Iron-doped manganese oxide catalysts are prepared by one-step water bath co-precipitation method and low-temperature calcination.
It significantly improves the low-temperature catalytic activity and high space velocity adaptability of the catalyst, and the toluene conversion rate can reach 100% in the range of 220℃~300℃. Compared with the traditional method, it saves more than 60% energy and has better catalytic activity than the unmodified catalyst.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of catalyst technology, specifically to an iron-doped manganese oxide catalyst, its preparation method, and its application. Background Technology
[0002] Volatile organic compounds (VOCs) are major contributors to smog and ozone pollution. Toluene is a typical aromatic VOC, primarily originating from the pharmaceutical and chemical industries. It is highly toxic and carcinogenic, posing a serious threat to human health and the atmospheric environment. Therefore, developing efficient toluene remediation technologies is of great significance.
[0003] Currently, toluene treatment technologies include adsorption, biodegradation, and catalytic oxidation. Among these, catalytic oxidation is considered the most effective and economical technology due to its high oxidation efficiency, low reaction temperature, and lack of secondary pollution. Commonly used catalysts in catalytic oxidation mainly include noble metal catalysts and transition metal oxide catalysts. Noble metal catalysts exhibit excellent catalytic performance at low temperatures, but they are expensive, prone to poisoning, and require high-temperature sintering. In contrast, manganese oxide (MnO4) in transition metal oxide catalysts... x Its low price, easy availability and adjustable oxygen vacancy have attracted widespread attention, and its catalytic performance can be further improved by iron doping.
[0004] Currently, iron-doped manganese oxide catalysts are mainly prepared using an aqueous co-precipitation method. This involves co-precipitating soluble iron and manganese salts under alkaline conditions, followed by aging, washing, drying, and calcination at 300℃–500℃. However, this method contains Fe... 3+ The catalyst has several problems: it is difficult to effectively embed into the MnO2 lattice and it is easy to agglomerate on the surface to form an independent phase; the high-temperature calcination process not only has high energy consumption, but also easily causes grain sintering and a decrease in specific surface area; in addition, the concentration of surface active oxygen species is insufficient and the Fe-Mn synergistic effect is weak, resulting in unsatisfactory low-temperature catalytic activity. Summary of the Invention
[0005] To address the above technical problems, this invention provides an iron-doped manganese oxide catalyst, its preparation method, and its applications. This invention uses an aqueous sulfuric acid solution as the reaction medium, which not only provides an acidic environment to regulate the redox reaction kinetics but also promotes Fe production through sulfuric acid modification. 3+ The iron-doped manganese oxide is uniformly dispersed in the MnO2 lattice, forming stable Fe-O-Mn bond bridges, thereby promoting the synergistic effect of iron and manganese. This invention prepares iron-doped manganese oxide via a one-step water bath co-precipitation method, increasing the number of oxygen species on the catalyst surface and improving the catalyst's catalytic oxidation activity for toluene, thus enhancing the low-temperature catalytic oxidation performance of toluene.
[0006] To achieve the above objectives, the technical solution of the present invention is as follows.
[0007] This invention provides a method for preparing an iron-doped manganese oxide catalyst, comprising the following steps: Manganese salt compounds were dissolved in an aqueous sulfuric acid solution and subjected to a redox reaction with ferrous sulfate and potassium permanganate in a water bath at 10°C–30°C. After the reaction was completed, Fe / MnO2 solid precursors were obtained by separation, washing, and drying. The Fe / MnO2 solid precursors were then calcined in a mixed atmosphere of O2 to obtain an iron-doped manganese oxide catalyst.
[0008] Preferably, the molar ratio of iron in the ferrous sulfate to manganese in the manganese salt compound is 1:1 to 5; and the mass ratio of potassium permanganate to ferrous sulfate is 2 to 3:1.
[0009] Preferably, the manganese salt compound is selected from manganese sulfate, manganese acetate, and manganese nitrate.
[0010] Preferably, the concentration of the sulfuric acid aqueous solution is 0.04 mol / L to 0.06 mol / L.
[0011] Preferably, the redox reaction takes 6 to 10 hours.
[0012] Preferably, the roasting temperature is 100℃~400℃.
[0013] Preferably, the O2-containing mixed atmosphere is a mixture of O2 and Ar, wherein the volume content of oxygen is 20%.
[0014] The second objective of this invention is to provide an iron-doped manganese oxide catalyst, wherein the iron-doped manganese oxide catalyst is prepared using the aforementioned method for preparing iron-doped manganese oxide catalysts.
[0015] A third objective of this invention is to provide an application of an iron-doped manganese oxide catalyst for the catalytic oxidation of toluene.
[0016] Preferably, the application method is as follows: a fixed-bed reactor is used, the catalyst loading is 0.1g (40-60 mesh), and the reaction gas composition is toluene 2000mg / m³. 3 (Nitrogen-carrying gas), 20% oxygen, nitrogen balance, total flow rate 100 mL / min, space velocity 60000 mL / (g·h). The reaction temperature range was 180℃~300℃. Toluene conversion was detected by gas chromatography-FID, and CO2 production was detected by TCD.
[0017] In this invention, the toluene concentration is 2000 mg / m³. 3Under a space velocity of 60,000 mL / (g·h), the prepared iron-doped manganese oxide catalyst can achieve a toluene conversion rate of ≥90% at 220℃~260℃.
[0018] The beneficial effects of this invention are: 1. The preparation method of the iron-doped manganese oxide catalyst provided by the present invention uses sulfuric acid aqueous solution as the reaction medium, and regulates the redox reaction kinetics through an acidic environment to promote Fe 3+ The catalyst is uniformly dispersed in the MnO2 lattice, forming stable Fe-O-Mn bond bridges, which significantly increases the content of adsorbed oxygen on the catalyst surface and lattice oxygen. Using this catalyst in the catalytic oxidation of toluene, under high space velocity conditions and a temperature range of 220℃ to 300℃, the conversion rate of toluene can reach up to 100%.
[0019] 2. The preparation method of this invention is simple, energy-saving, has few steps, and is easy to operate. This invention adopts a one-step water bath co-precipitation method, with a reaction temperature below 30℃ and a calcination temperature as low as 100℃~200℃, saving more than 60% energy compared to conventional methods (300℃~500℃).
[0020] 3. The catalyst prepared by this invention exhibits excellent low-temperature catalytic activity and strong adaptability to high space velocities. The catalyst prepared by this invention can withstand toluene concentrations of 2000 mg / m³. 3 Under test conditions of 60,000 mL / (g·h), the catalyst of this invention achieved a toluene conversion rate of 98% at 240℃ and 100% complete conversion at 250℃~260℃, which is significantly better than the unmodified catalyst (conversion rate of 71% at 260℃) and the pure MnO2 catalyst (conversion rate of 57% at 260℃). Detailed Implementation
[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0022] 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.
[0023] The technical solution of the present invention will be further described below through specific embodiments.
[0024] In the following embodiments, unless otherwise specified, the methods described are conventional methods; and unless otherwise specified, the reagents and materials described are commercially available.
[0025] Example 1 A method for preparing an iron-doped manganese oxide catalyst includes the following steps: S1. Prepare 100 mL of 0.05 mol / L sulfuric acid aqueous solution, add 0.45 g of MnSO4·H2O, stir and dissolve in a water bath, then slowly add 1.02 g of FeSO4·7H2O and continue stirring; dissolve 2.5 g of KMnO4 in 100 mL of deionized water, add it dropwise to the above solution, stir evenly to obtain a solid-liquid mixture.
[0026] S2. The solid-liquid mixture is stirred vigorously in a water bath at 25°C for 6 hours.
[0027] S3. The reaction product was centrifuged at 8000 r / min and washed repeatedly with deionized water and ethanol until the filtrate was neutral to obtain the Fe / MnO2 solid precursor.
[0028] S4. The Fe / MnO2 solid precursor is vacuum dried at 60°C for 12 hours, and then calcined in a muffle furnace at 100°C for 2 hours to obtain an iron-doped manganese oxide catalyst, denoted as Fe / MnO2 catalyst.
[0029] Example 2 A method for preparing an iron-doped manganese oxide catalyst includes the following steps: S1. Prepare 100 mL of 0.05 mol / L sulfuric acid aqueous solution, add 0.65 g of (CH3COO)2Mn·4H2O, stir and dissolve in a water bath, then slowly add 1.02 g of FeSO4·7H2O and continue stirring; dissolve 2.5 g of KMnO4 in 100 mL of deionized water, add it dropwise to the above solution, stir evenly to obtain a solid-liquid mixture.
[0030] S2. The solid-liquid mixture is stirred vigorously in a water bath at 25°C for 6 hours.
[0031] S3. The reaction product was centrifuged at 8000 r / min and washed repeatedly with deionized water and ethanol until the filtrate was neutral to obtain the Fe / MnO2 solid precursor.
[0032] S4. The Fe / MnO2 solid precursor is vacuum dried at 60°C for 12 hours, and then calcined in a muffle furnace at 100°C for 2 hours to obtain an iron-doped manganese oxide catalyst, denoted as Fe / MnO2 catalyst.
[0033] Example 3 A method for preparing an iron-doped manganese oxide catalyst includes the following steps: S1. Prepare 100 mL of 0.05 mol / L sulfuric acid aqueous solution, add 0.48 g of Mn(NO3)2, stir and dissolve in a water bath, then slowly add 1.02 g of FeSO4·7H2O and continue stirring; dissolve 2.5 g of KMnO4 in 100 mL of deionized water, add it dropwise to the above solution, stir evenly to obtain a solid-liquid mixture.
[0034] S2. The solid-liquid mixture is stirred vigorously in a water bath at 25°C for 6 hours.
[0035] S3. The reaction product was centrifuged at 8000 r / min and washed repeatedly with deionized water and ethanol until the filtrate was neutral to obtain the Fe / MnO2 solid precursor.
[0036] S4. The Fe / MnO2 solid precursor is vacuum dried at 60°C for 12 hours, and then calcined in a muffle furnace at 100°C for 2 hours to obtain an iron-doped manganese oxide catalyst, denoted as Fe / MnO2 catalyst.
[0037] Comparative Example 1 A method for preparing an iron-doped manganese oxide catalyst includes the following steps: S1. Dissolve 0.45g of MnSO4·H2O in 100mL of deionized water, add 1.02g of FeSO4·7H2O, and stir to dissolve; dissolve 2.5g of KMnO4 in 100mL of deionized water, add it dropwise to the above solution, and stir evenly to obtain a solid-liquid mixture.
[0038] S2. The solid-liquid mixture is stirred vigorously in a water bath at 25°C for 6 hours.
[0039] S3. The reaction product was centrifuged at 8000 r / min and washed repeatedly with deionized water and ethanol until the filtrate was neutral to obtain the Fe / MnO2 solid precursor.
[0040] S4. The Fe / MnO2 solid precursor is vacuum dried at 60°C for 12 hours, and then calcined in a muffle furnace at 100°C for 2 hours to obtain an iron-doped manganese oxide catalyst, denoted as Fe / MnO2 catalyst.
[0041] Comparative Example 2 A method for preparing a MnO2 catalyst includes the following steps: S1. Dissolve 0.45g of MnSO4·H2O in 100mL of deionized water; dissolve 2.5g of KMnO4 in 100mL of deionized water, add the solutions dropwise to the above solution, stir until homogeneous, and obtain a solid-liquid mixture.
[0042] S2. The solid-liquid mixture is stirred vigorously in a water bath at 25°C for 6 hours.
[0043] S3. The reaction product was centrifuged at 8000 r / min and washed repeatedly with deionized water and ethanol to obtain the MnO2 solid precursor.
[0044] S4. The MnO2 solid precursor is dried at 60°C for 12 hours and then calcined in a muffle furnace at 100°C for 2 hours to obtain the MnO2 catalyst.
[0045] The catalysts prepared in Examples 1 to 3, Comparative Examples 1 and 2 were used for the catalytic oxidation of toluene, and their catalytic oxidation performance was tested in the range of 220°C to 260°C.
[0046] Test method: The test apparatus consists of a VOC generation reaction device, a gas chromatograph, and a tail gas absorption device. The specific test steps are as follows:
[0047] The catalyst to be tested was compressed into tablets, crushed, and sieved to select particles with a particle size of 40-60 mesh for later use. 0.1 g of the pretreated catalyst was accurately weighed and packed into a fixed-bed quartz reaction tube, with both ends of the catalyst bed fixed with quartz wool. Using a static gas mixing method, nitrogen was used as the carrier gas, and toluene vapor was carried by a toluene bubbler. The flow rates of nitrogen, oxygen, and toluene vapor were adjusted to prepare a toluene concentration of 2000 mg / m³. 3 Simulated waste gas was used. The inlet gas components were: toluene 10 mL / min (carried by nitrogen), oxygen 20 mL / min, and nitrogen 70 mL / min, with a total flow rate of 100 mL / min. The reaction space velocity was 60,000 mL / (g·h). The reaction tube filled with catalyst was placed in a heating furnace, and the above simulated waste gas was introduced. Catalytic oxidation reaction was carried out at the set reaction temperature (e.g., various temperature points within the range of 180℃~300℃). After stabilizing the reaction at each temperature point for 30 min~60 min, outlet gas samples were collected. The outlet gas samples were analyzed online by gas chromatography. The residual concentration of toluene was determined using a flame ionization detector (FID), and the toluene conversion rate was calculated. The amount of CO2 generated was determined using a thermal conductivity detector (TCD). The test results are shown in Table 1.
[0048] Table 1. Conversion rate (%) of catalytic oxidation of toluene in Examples 1-3, Comparative Examples 1 and 2 at different temperatures. As shown in Table 1, Example 1 (sulfuric acid modification, manganese sulfate as the manganese source) exhibited the best catalytic oxidation activity for toluene, achieving a conversion rate of 100% at 260℃ and 98% at 240℃, significantly better than Comparative Example 1 (no sulfuric acid modification, 71% conversion rate at 260℃) and Comparative Example 2 (no iron doping, 57% conversion rate at 260℃). Examples 2 and 3 (manganese acetate and manganese nitrate as manganese sources) showed slightly lower activity than Example 1, but were still significantly better than the comparative examples, demonstrating that the sulfuric acid modification strategy is universally applicable to different manganese salts.
[0049] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing an iron-doped manganese oxide catalyst, characterized in that, Includes the following steps: Manganese salt compounds were dissolved in sulfuric acid aqueous solution and subjected to redox reaction with ferrous sulfate and potassium permanganate at 10℃~30℃. The pH of the solution was controlled at 1~2 during the reaction. After the reaction was completed, Fe / MnO2 solid precursor was obtained by separation, washing and drying. The Fe / MnO2 solid precursor was calcined in a mixed atmosphere containing O2 to obtain an iron-doped manganese oxide catalyst.
2. The method for preparing the iron-doped manganese oxide catalyst according to claim 1, characterized in that, The molar ratio of iron in the ferrous sulfate to manganese in the manganese salt compound is 1:1 to 5; the mass ratio of potassium permanganate to ferrous sulfate is 2 to 3:
1.
3. The method for preparing the iron-doped manganese oxide catalyst according to claim 1, characterized in that, The manganese salt compound is selected from manganese sulfate, manganese acetate, and manganese nitrate.
4. The method for preparing the iron-doped manganese oxide catalyst according to claim 1, characterized in that, The concentration of the sulfuric acid aqueous solution is 0.04 mol / L to 0.06 mol / L.
5. The method for preparing the iron-doped manganese oxide catalyst according to claim 1, characterized in that, The redox reaction takes 6 to 10 hours.
6. The method for preparing the iron-doped manganese oxide catalyst according to claim 1, characterized in that, The roasting temperature is 100℃~400℃.
7. The method for preparing the iron-doped manganese oxide catalyst according to claim 1, characterized in that, The O2-containing mixed atmosphere is a mixture of O2 and Ar, wherein the oxygen volume content is 20%.
8. An iron-doped manganese oxide catalyst, characterized in that, The iron-doped manganese oxide catalyst is prepared by the method described in any one of claims 1 to 6.
9. The application of the iron-doped manganese oxide catalyst of claim 8 as a catalyst in the catalytic oxidation treatment of toluene.