Preparation method and application of Mn-based composite oxide oxygen storage catalyst
Through the preparation of Mn-based composite oxide oxygen storage catalyst, the problems of insufficient activity of ethylene and formaldehyde catalysts under low temperature and high humidity conditions and high cost of precious metals in the prior art are solved, and the effect of efficient removal of low temperature and reducing the Production cost.
Patent Information
- Application Number
- CN202410756635.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-12
- Publication Date
- 2024-12-13
Smart Images
Figure CN119114056A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of environmental catalysis, and in particular to a preparation method and application of a Mn-based composite oxide oxygen storage catalyst. Background Art
[0002] Although ethylene has a simple structure, as an important endogenous hormone in plants, it regulates plant metabolism, stimulates the respiration intensity of fruits and vegetables after harvest, accelerates the development and completion of the ripening process of fruits and vegetables, and ultimately affects the physiological activities and nutritional quality of fruits and vegetables during storage. At the same time, ethylene, as a signal molecule, participates in regulating the ripening and aging of fruits and vegetables, inducing the expression of defense genes, and mediating the formation of plant disease and injury responses. Therefore, controlling or reducing the ethylene content is very beneficial to delaying the ripening of fruits and vegetables. Storage in controlled atmosphere cold storage can control the ethylene content in the storage environment within a certain limit according to the sensitivity of different fruits and vegetables to ethylene, so as to ensure the storage quality of fruits and vegetables, especially those fruits and vegetables that are sensitive to ethylene (such as kiwis and tomatoes), and the ethylene in the storage environment should be completely removed.
[0003] In recent years, a variety of exogenous ethylene removal technologies have emerged to control ethylene in the post-harvest environment of fruits and vegetables, mainly including physical adsorption, chemical oxidation, photocatalysis and catalytic oxidation. Among them, the catalytic combustion method has the advantages of fast ethylene removal, high efficiency, continuous operation, low operating cost, and no secondary pollution, and has high commercial application value. Catalytic combustion removal technology has strong adaptability to the preservation environment, whether it is bagged preservatives, cling paper or atmosphere treatment of large rooms. Therefore, it has great development potential in the preservation of fruits and vegetables and is considered to be a sustainable, practical and economical method.
[0004] In recent years, researchers have developed a variety of powder catalysts for catalytic removal of trace ethylene, such as Pt / MCM-41 (Angew.Chem.Int.Ed., 2013, 52, 6265), Au / meso-Co3O4 (J.Am.Chem.Soc, 2010, 132, 2608), Pt / SBA-15 (ACS Sustainable Chemistry & Engineering, 2018, 6, 11480), etc., which show high trace ethylene removal activity at lower temperatures or even room temperature. Of course, the high activity of these catalysts is based on high loading of Au and Pt noble metals, and the stability of the catalysts needs to be improved. In order to reduce the cost of expensive metals such as Au and Pt, some researchers have turned their attention to relatively cheap but highly active noble metal elements (such as Ag). The effects of 5wt% Ag / ZSM-5 and 5wt% Ag / Beta (ACS. Cata l., 2018, 8, 1248) catalysts on the catalytic combustion performance of ethylene (100ppm) showed that the complete conversion of ethylene could be achieved under the conditions of GHSV of 7500mL / (g·h) and 25°C, but it quickly deactivated after stabilization for 6h. Although the noble metal-metal oxide composite has a good catalytic degradation effect on ethylene, the cost of noble metals is high and the economic applicability is low in practical applications. The development of non-noble metal ethylene removal catalysts suitable for post-harvest transportation and storage environments of fruits and vegetables has important academic significance and application value.
[0005] Ethylene waste gas in the fruit and vegetable storage environment has the characteristics of low temperature, high humidity and low concentration, so the catalyst must not only have high low-temperature activity but also strong water vapor resistance. However, at present, to achieve efficient low-temperature ethylene removal, a breakthrough increase in the active oxygen load in the oxygen storage body is the key. The effective lattice oxygen of existing ethylene removal catalysts is very limited, and non-precious metal oxide systems based on oxygen storage bodies are rarely reported. Therefore, it is crucial to improve the oxygen storage and release capacity of the oxygen storage body by adjusting the composition and structure of the composite oxide, and to improve the catalyst's catalytic combustion activity and stability for ethylene under water vapor conditions.
[0006] At the same time, formaldehyde is a harmful volatile organic compound that is widely present in industrial emissions and daily life. It is not only mutagenic, carcinogenic and teratogenic to the human body, but also has a negative impact on air quality. Catalytic oxidation is an effective method for removing formaldehyde. At present, supported Pt and Pd catalysts can completely convert formaldehyde at room temperature, but their application is limited due to their high cost. Transition metal oxide catalytic systems such as manganese and cobalt oxides have better catalytic activity in formaldehyde oxidation than traditional MnO2, Co3O4 or other metal oxides. Therefore, the development of non-precious metal oxide catalysts for low-temperature and efficient formaldehyde removal has important academic significance and application value. Summary of the invention
[0007] In view of the shortcomings of the prior art, the present invention provides a method for preparing and applying a Mn-based composite oxide oxygen storage catalyst, which increases oxygen vacancies by lattice expansion or electronic modulation, and regulates the distribution of surface and lattice oxygen species, so that it exhibits the advantages of high activity, water vapor resistance and good stability in the catalytic combustion removal of trace ethylene and formaldehyde.
[0008] To achieve the above object, the present invention is implemented by the following technical scheme: a Mn-based composite oxide oxygen storage catalyst, the catalyst is an oxygen storage catalyst composed of manganese oxide doped, substituted or composited with another metal oxide, and has the following general formula: aMO-bMnO x , a represents the mass percentage of another metal oxide in the oxygen storage catalyst, b represents the mass percentage of manganese oxide in the oxygen storage catalyst; and a is 0 to 90%, and b is 0 to 100%.
[0009] Preferably, the manganese oxide is selected from at least one of manganese monoxide, manganese dioxide, manganese trioxide, manganese tetraoxide, manganous anhydride, manganic anhydride, and permanganic anhydride; and the other metal oxide is selected from at least one of lanthanide rare earth metals, cobalt, zirconium, iron, copper, titanium, aluminum, and zinc oxide.
[0010] Preferably, the catalyst has a micro-mesoporous structure.
[0011] Preferably, the catalyst has a specific surface area of 50 to 400 m 2 / g.
[0012] A method for preparing a Mn-based composite oxide oxygen storage catalyst, applied to the above-mentioned Mn-based composite oxide oxygen storage catalyst, comprises the following steps:
[0013] S1. Weigh the manganese source and MO precursor, dissolve them in deionized water, and mix them evenly to form solution A; weigh potassium permanganate and dissolve it in deionized water to form solution B; drop solution B into solution A, stir evenly to form an emulsion;
[0014] S2. The obtained emulsion is transferred to a stainless steel hydrothermal kettle for hydrothermal treatment at a certain temperature. After cooling to room temperature, the sample is filtered, washed and dried, and then placed in a muffle furnace for roasting. The obtained sample is the Mn-based composite oxide oxygen storage body aMO-bMnO x catalyst.
[0015] Preferably, in the step S1, the manganese source is selected from manganese acetate, manganese nitrate, manganese sulfate, manganese carbonate, manganese chloride or potassium permanganate, preferably manganese nitrate; the MO precursor is selected from nitrate, acetate, sulfate, carbonate or chloride; the concentrations of the manganese source and MO precursor aqueous solutions are 0-5 mol / L and 0-2 mol / L, respectively, the concentration of the potassium permanganate aqueous solution is 0.5-2 mol / L, and the stirring time required for dripping the B solution into the A solution is 5-30 min.
[0016] Preferably, in the step S2, the hydrothermal treatment temperature is 80-180°C, the hydrothermal treatment time is 0.5-3h, the drying temperature is 50-100°C, the drying time is 6-12h, the roasting temperature is 300-600°C, and the roasting time is 1-6h.
[0017] Preferably, in the step S2, the chemical reactions involved include:
[0018] 2MnO 4- +3Mn 2+ +2H2O→5MnO2+4H +
[0019] MnO 4- +M x+ +H2O→M(OH) x ↓+MnO2+H + .
[0020] Preferably, the Mn-based composite oxide catalyst is used in the low-temperature catalytic combustion reaction of trace amounts of ethylene and formaldehyde.
[0021] The present invention provides a method for preparing a Mn-based composite oxide oxygen storage catalyst and its application, which has the following beneficial effects:
[0022] Compared with the prior art, the Mn-based composite oxide oxygen storage catalyst provided by the present invention has abundant oxygen vacancies and oxygen storage / release capacity, and exhibits the advantages of high low-temperature activity, good water vapor resistance and stability in the process of catalytic combustion removal of trace amounts of ethylene and formaldehyde. In addition, the preparation method is simple, the raw materials are readily available, large-scale production is facilitated, and the cost is low. The present invention is an excellent catalyst for the low-temperature catalytic combustion removal of trace amounts of ethylene and formaldehyde, and has significant industrial application value. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 The 10CeO2-90MnO prepared in Example 1 x SEM images of the composite oxide catalysts;
[0024] Figure 2 The 10CeO2-90MnO prepared in Example 1 xFigure 2 shows nitrogen absorption and desorption of composite oxide catalysts;
[0025] Figure 3 The 10CeO2-90MnO prepared in Example 1 x X-ray diffraction pattern of the composite oxide catalyst;
[0026] Figure 4 The 10CeO2-90MnO prepared in Example 1 x O2-TPD spectrum of composite oxide catalyst;
[0027] Figure 5 80Co3O4-20MnO prepared in Example 2 x Scanning electron microscopy image of the composite oxide catalyst.
[0028] Figure 6 80Co3O4-20MnO prepared in Example 2 x Figure 2 shows nitrogen absorption and desorption of composite oxide catalysts;
[0029] Figure 7 The 10CeO2-90MnO prepared in Example 1 x Schematic diagram of the effect of composite oxide catalysts on ethylene exhaust gas catalytic activity at different hydrothermal temperatures;
[0030] Figure 8 The 10CeO2-90MnO prepared in Example 1 x Schematic diagram of the effect of composite oxide catalyst catalytic activity on ethylene exhaust gas under dry / water vapor conditions;
[0031] Fig. 9 The 10CeO2-90MnO prepared in Example 1 x Schematic diagram of the stability test of the catalytic activity of the composite oxide catalyst on ethylene exhaust gas under dry and water vapor conditions;
[0032] Fig.10 The 20CeO2-80MnO prepared in Example 1 x Schematic diagram of the conversion rate of composite oxide catalysts in the catalytic combustion of trace formaldehyde;
[0033] Fig.11 80Co3O4-20MnO prepared in Example 2 x Schematic diagram of the effect of different hydrothermal temperatures of composite oxide catalysts on the catalytic activity of ethylene exhaust gas;
[0034] Fig.12 80Co3O4-20MnO prepared in Example 2 x Schematic diagram of the effect of different calcination temperatures of composite oxide catalysts on the catalytic activity of ethylene exhaust gas;
[0035] Fig.13 80Co3O4-20MnO prepared in Example 2 x Schematic diagram of the effect of different temperatures on the catalytic activity of trace formaldehyde in composite oxide catalysts. DETAILED DESCRIPTION
[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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.
[0037] Embodiment 1:
[0038] This embodiment provides a Mn-based composite oxide oxygen storage catalyst, and the preparation method thereof is as follows:
[0039] S1. Weigh 3.5g Ce(NO3)3·6H2O and 2.0g Mn(NO3)2·4H2O and add them to 80mL deionized water. After stirring for 1h, drop the resulting mixed solution into the solution containing 1.2g KMnO4. After the dropwise addition, continue stirring for 60min to form an emulsion.
[0040] S2. The obtained emulsion was transferred to a 100 mL stainless steel reactor and hydrothermaled at 180 ° C for 3 h. After cooling, the precipitate was taken out, filtered, and washed, and dried at 50 ° C for 12 h. The obtained sample was put into a muffle furnace, heated to 600 ° C at a rate of 2 ° C / min, and calcined for 4 h. The obtained sample is CeO2-MnO x Composite oxide catalysts.
[0041] According to ICP-AES test, the actual composition of the composite oxide is 10CeO2-90MnO x .
[0042] Please see attached Figure 1 , which is 10CeO2-90MnO prepared in Example 1 x Scanning electron microscopy image of the composite oxide catalyst.
[0043] Figure 2 This is a nitrogen absorption and desorption diagram of the 10CeO2-90MnOx composite oxide catalyst prepared in Example 1. The specific surface area is 204.7 m 2 / g, micropore volume 0.12cm 3 / g, mesopore volume 0.49cm 3 / g, belonging to micro-mesoporous material.
[0044] In step 1 of this embodiment, the hydrothermal treatment temperature is 80-180°C, the hydrothermal treatment time is 0.5-3h, the drying temperature is 50-100°C, the drying time is 6-12h, the roasting temperature is 300-600°C, the roasting time is 1-6h, and the rest is the same as this embodiment.
[0045] In step 1 of this embodiment, the cerium source can be cerium acetate or cerium sulfate, the manganese source can be manganese acetate or manganese sulfate, the ratio of the cerium source to the manganese source can vary within different ranges, and the rest is the same as in this embodiment.
[0046] Please refer to the attached Figure 3 , which are CeO2-MnO with different ratios prepared in Example 1 x From the X-ray diffraction pattern of the composite oxide catalyst, it can be seen that the composite oxide exists in the amorphous form of a solid solution.
[0047] Figure 4 The 10CeO2-90MnO prepared in Example 1 with different calcination temperatures x From the O2-TPD spectrum of the composite oxide catalyst, it can be seen that the composite oxide catalyst not only has abundant low-temperature active oxygen species (desorption peak at 150-300°C) to promote the oxidation reaction, but also has active surface lattice oxygen (desorption peak at 300-450°C) to ensure the efficient cycle of the oxidation-reduction reaction and enhance the hydrothermal stability.
[0048] Embodiment 2:
[0049] This embodiment provides a Mn-based composite oxide oxygen storage catalyst, and the preparation method thereof is as follows:
[0050] S1. Weigh an appropriate amount of 3.5g Co(NO3)2·6H2O and 2.0g Mn(NO3)2·4H2O and add them to 80mL deionized water. After stirring for 1h, drop the resulting mixed solution into the solution containing 1.2g KMnO4. After the dropwise addition, continue stirring for 60min to form an emulsion.
[0051] S2. The obtained emulsion was transferred to a 100 mL stainless steel reactor and hydrothermaled at 160 ° C for 5 h. After the hydrothermal was completed, the precipitate was taken out, filtered, and washed to obtain the precipitate. The precipitate was dried at 100 ° C for 12 h, ground and sieved, and the obtained sample was placed in a muffle furnace, heated to 550 ° C at a rate of 2 ° C / min, and calcined for 4 h. The obtained sample was Co3O4-MnO x Composite oxide catalysts.
[0052] According to I CP-AES test, the actual composition of the composite oxide is 80Co3O4-20MnO x .
[0053] Please see attached Figure 5 , which is 80Co3O4-20MnO prepared in Example 2 x Scanning electron microscope image of the composite oxide catalyst, the composite oxide has a flaky crystal structure.
[0054] Figure 6 80Co3O4-20MnO prepared in Example 2 x Figure 1 shows the nitrogen absorption and desorption of the composite oxide catalyst. The specific surface area is 58.5 m 2 / g, micropore volume 0.02cm 3 / g, mesopore volume 0.35cm 3 / g, with obvious mesoporous distribution at around 12nm, belonging to micro-mesoporous material.
[0055] In step 2 of this embodiment, the hydrothermal treatment temperature is 80-180° C., the hydrothermal treatment time is 0.5-3 h, the drying temperature is 50-100° C., the drying time is 6-12 h, the roasting temperature is 300-600° C., the roasting atmosphere is air, and the roasting time is 1-6 h. The rest is the same as in this embodiment.
[0056] In step 1 of this embodiment, the cobalt source may be cobalt acetate or cobalt sulfate, and the manganese source may be manganese acetate or manganese sulfate. The ratio of the cobalt source to the manganese source may vary within different ranges. The rest is the same as in this embodiment.
[0057] Application Example 1:
[0058] The CeO2-MnO prepared in Example 1 was investigated in a fixed bed reactor. x The catalytic performance of the composite oxide catalyst in the catalytic combustion removal of trace ethylene and formaldehyde is as follows:
[0059] The reactants are a mixture of ethylene and air or a mixture of formaldehyde and air; the fixed bed reactor is a quartz tube with an inner diameter of 8mm and a length of 600mm. The catalyst is loaded in the constant temperature section. The raw gas enters the catalyst bed to react, and the tail gas enters the gas chromatograph for online analysis, which is analyzed by a hydrogen flame detector (FID). A nickel converter is installed before the FID detector to convert the reaction products carbon dioxide and carbon monoxide into methane, which is then quantitatively analyzed by the FID detector. After testing, only the completely oxidized product carbon dioxide is found in the product.
[0060] Reaction conditions: catalyst dosage 0.2 g, gas hourly space velocity 15000 mL·h -1 ·g -1 The gas composition is 100 ppm ethylene in the air or 250 ppm formaldehyde in the air. The water vapor condition is achieved by constant temperature bubbling to maintain a relative humidity of 95%.
[0061] Under the above conditions, the 10CeO2-90MnO x The effects of hydrothermal temperature and drying / steam preparation conditions on the catalytic combustion performance of ethylene are shown in the experimental results. Figure 7 and 8 As shown. It can be seen that 10CeO2-90MnO prepared under 100℃ hydrothermal conditions x The composite oxide catalyst has high activity, and too high hydrothermal temperature is not conducive to improving the catalyst activity. x The composite oxide can achieve complete conversion of ethylene at 150°C, while water vapor conditions will have a certain inhibitory effect on the activity of the catalyst, and complete conversion can be achieved at 195°C. Fig. 9 The stability test was carried out under dry (reaction temperature 140°C) and water vapor conditions (reaction temperature 170°C). There was no sign of deactivation after running for 43 hours, indicating that the catalyst has good stability and hydrothermal stability.
[0062] Under the above conditions, the 20CeO2-80MnO x The effect of reaction temperature on the catalytic combustion performance of trace formaldehyde on the catalyst is shown in the experimental results. Fig.10 As shown, complete conversion of formaldehyde can be achieved at 100°C.
[0063] Application Example 2:
[0064] The 80Co3O4-20MnO prepared in Example 2 was investigated in a fixed bed reactor. x Catalytic performance of composite oxide catalyst in the process of catalytic combustion removal of trace ethylene and formaldehyde: The reactant is a mixture of ethylene and air; the fixed bed reactor is a quartz tube with an inner diameter of 8mm and a length of 600mm. The catalyst is loaded in the constant temperature section. The raw gas enters the catalyst bed to react, and the tail gas enters the gas chromatography online analysis, which is analyzed by hydrogen flame detector (FID). A nickel converter is installed before the FID detector to convert the reaction products carbon dioxide and carbon monoxide into methane, which is then analyzed quantitatively by the FID detector. After testing, only the completely oxidized product carbon dioxide is included in the product.
[0065] Reaction conditions: catalyst dosage 0.2 g, gas hourly space velocity 15000 mL·h -1 ·g -1 The gas composition is 100 ppm ethylene in the air or 250 ppm formaldehyde in the air. The water vapor condition is achieved by constant temperature bubbling to maintain a relative humidity of 95%.
[0066] Under the above conditions, the effects of preparation conditions such as hydrothermal temperature and calcination temperature on the catalytic combustion performance of trace ethylene containing water vapor were investigated. The experimental results are as follows Fig.11 and 12 As shown. It can be seen that 80Co3O4-20MnO prepared under 90℃ hydrothermal conditions x The composite oxide catalyst has high activity, and too high a hydrothermal temperature is not conducive to improving the catalyst activity. The 80Co3O4-20MnO prepared at a calcination temperature of 300°C x The composite oxide has the highest activity and can achieve complete conversion of ethylene at 175°C.
[0067] Under the above conditions, the effect of reaction temperature on the catalytic combustion performance of trace formaldehyde was investigated. The experimental results are as follows Fig.13 As shown. 80Co3O4-20MnO x The composite oxide can achieve complete conversion of formaldehyde at 120°C.
[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A Mn-based composite oxide oxygen storage catalyst, characterized in that: The catalyst is an oxygen storage catalyst composed of manganese oxide doped, substituted or compounded with another metal oxide and has the following general formula: aMO-bMnO x , a represents the mass percentage of another metal oxide in the oxygen storage catalyst, b represents the mass percentage of manganese oxide in the oxygen storage catalyst; and a is 0 to 90%, and b is 0 to 100%.
2. A Mn-based composite oxide oxygen storage catalyst according to claim 1, characterized in that: The manganese oxide is selected from at least one of manganese monoxide, manganese dioxide, manganese trioxide, manganese tetraoxide, manganous anhydride, manganic anhydride, and permanganic anhydride; the other metal oxide is selected from at least one of lanthanide rare earth metals, cobalt, zirconium, iron, copper, titanium, aluminum, and zinc oxide.
3. A Mn-based composite oxide oxygen storage catalyst according to claim 1, characterized in that: The catalyst has a micro-mesoporous structure.
4. A Mn-based composite oxide oxygen storage catalyst according to claim 1, characterized in that: The specific surface area of the catalyst is 50 to 400 m 2 / g.
5. A method for preparing a Mn-based composite oxide oxygen storage catalyst, applied to a Mn-based composite oxide oxygen storage catalyst according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1. Weigh the manganese source and MO precursor, dissolve them in deionized water, and mix them evenly to form solution A; weigh potassium permanganate and dissolve it in deionized water to form solution B; drop solution B into solution A, stir evenly to form an emulsion; S2. The obtained emulsion is transferred to a stainless steel hydrothermal kettle for hydrothermal treatment at a certain temperature. After cooling to room temperature, the sample is filtered, washed and dried, and then placed in a muffle furnace for roasting. The obtained sample is the Mn-based composite oxide oxygen storage body aMO-bMnO x catalyst.
6. The method for preparing a Mn-based composite oxide oxygen storage catalyst according to claim 5, characterized in that: In the step S1, the manganese source is selected from manganese acetate, manganese nitrate, manganese sulfate, manganese carbonate, manganese chloride or potassium permanganate, preferably manganese nitrate; the MO precursor is selected from nitrate, acetate, sulfate, carbonate or chloride; the concentrations of the manganese source and MO precursor aqueous solutions are 0-5 mol / L and 0-2 mol / L respectively, the concentration of the potassium permanganate aqueous solution is 0.5-2 mol / L, and the stirring time required for dripping the B solution into the A solution is 5-30 min.
7. The method for preparing a Mn-based composite oxide oxygen storage catalyst according to claim 5, characterized in that: In the step S2, the hydrothermal treatment temperature is 80-180°C, the hydrothermal treatment time is 0.5-3h, the drying temperature is 50-100°C, the drying time is 6-12h, the roasting temperature is 300-600°C, and the roasting time is 1-6h.
8. The method for preparing a Mn-based composite oxide oxygen storage catalyst according to claim 5, characterized in that: In the step S2, the chemical reactions involved include: 2MnO 4- +3Mn 2+ +2H2O→5MnO2+4H + MnO 4- +M x+ +H2O→M(OH) x ↓+MnO2+H + 。 9. Use of the Mn-based composite oxide catalyst as claimed in any one of claims 1 to 4 in the low-temperature catalytic combustion reaction of trace amounts of ethylene and formaldehyde.