Red mud-based vocs catalyst modified by nitric acid, and preparation method and application thereof
Patent Information
- Application Number
- CN202411862563.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-17
- Publication Date
- 2026-09-25
- Estimated Expiration
- 2044-12-17
AI Technical Summary
赤泥按照炼铝工艺分为拜耳法赤泥、烧结法赤泥、联合法赤泥等，其中，拜耳法赤泥中的Fe2O3的含量最高，可达50％，其可以作为催化剂的活性成分；然而，Fe2O3单独存在时的氧化还原性能不是十分突出，因此只含有Fe2O3的赤泥若直接利用的话，难以快速发生催化甲苯的氧化反应，影响催化活性的进一步提高
[0014]本发明采用2.5～3.5mol/L硝酸改性拜耳法赤泥不仅能够有效提升赤泥中Fe的占比，而且能够提高赤泥的比表面积，利于催化氧化甲苯；进一步地，通过负载各种金属的实验表明负载各种金属都能够在一定程度上提升催化剂对甲苯的催化效果，但提升最为明显的是在硝酸改性拜耳法赤泥上负载锰。与商业上常用Al2O3、TiO2作为催化剂载体负载锰相比，本发明制备的催化剂的催化活性更高。
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of volatile organic compound (VOCs) treatment technology, and relates to VOCs catalysts, specifically to nitric acid-modified red mud-based VOCs catalysts, their preparation methods, and applications. Background Technology
[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.
[0003] Emissions of volatile organic compounds (VOCs) originate from various sources, such as industrial processes, building materials, and vehicle exhaust, posing a significant threat to public health and the ecological environment, thus urgently requiring effective control strategies. Catalytic oxidation is a highly efficient, safe, and economical VOCs treatment technology, gaining attention due to its superior performance. Currently, common catalysts can be classified into two categories based on their materials: noble metal catalysts and non-noble metal catalysts. Noble metal catalysts generally exhibit higher activity than non-noble metal catalysts, thus achieving higher VOCs conversion efficiencies under certain catalytic conditions. However, the high material cost, generally poor catalytic stability, and generally poor resistance to poisoning of noble metals limit their large-scale application. Conversely, catalysts containing non-noble metals such as manganese and iron, due to their diverse valence states, low acquisition cost, and minimal environmental impact, have attracted much research focus on improving their VOCs catalytic activity.
[0004] Red mud is a solid waste generated during bauxite extraction. Using red mud as a raw material for catalyst preparation not only solves the problems of low utilization rate and environmental pollution caused by solid waste red mud, but also effectively reduces catalyst costs. Red mud is classified into Bayer process red mud, sintering process red mud, and combined process red mud according to the aluminum smelting process. Among them, Bayer process red mud has the highest Fe2O3 content, reaching up to 50%, which can be used as the active component of catalysts. However, the redox performance of Fe2O3 alone is not very outstanding. Therefore, if red mud containing only Fe2O3 is used directly, it is difficult to quickly catalyze the oxidation reaction of toluene, affecting the further improvement of catalytic activity. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a red mud-based VOCs catalyst modified with nitric acid, its preparation method, and its application. The present invention modifies Bayer process red mud with nitric acid and uses the modified red mud as a support to load transition metal Mn, which significantly improves the catalytic efficiency for toluene and is expected to achieve catalytic treatment of VOCs.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] In the first aspect, a method for preparing a red mud-based VOCs catalyst modified with nitric acid is provided, wherein Bayer process red mud is modified with 2.5 to 3.5 mol / L nitric acid, the modified red mud is mixed with manganese salt in solution to obtain a precursor of modified red mud and manganese composite, and the precursor is calcined at 500 to 600°C to obtain the catalyst.
[0008] First, this invention selects nitric acid as the acid for modifying Bayer process red mud. Nitric acid not only possesses acidity but also oxidizing properties, resulting in better modification of Bayer process red mud. Furthermore, during optimization of the nitric acid concentration, it was unexpectedly discovered that using nitric acid at a concentration of 2.5–3.5 mol / L to modify Bayer process red mud retains more Fe₂O₃, which is beneficial for improving the catalytic activity of the prepared catalyst. Second, this invention selects Bayer process red mud modified with 2.5–3.5 mol / L nitric acid as a support, adding new active components to enhance its catalytic activity. Studies have shown that, compared to supporting cerium, cobalt, chromium, or even multiple metals, the catalyst prepared by supporting manganese exhibits higher catalytic activity.
[0009] Further research showed that when the mass of manganese was 5-15% of the mass of the catalyst, it had excellent catalytic effect on the catalytic oxidation of toluene, and the catalytic effect was even better when the mass of manganese was 14-15% of the mass of the catalyst.
[0010] On the other hand, a red mud-based VOCs catalyst modified with nitric acid was obtained by the above preparation method.
[0011] Thirdly, the application of the above-mentioned nitric acid-modified red mud-based VOCs catalyst in VOCs removal.
[0012] Furthermore, the removal of VOCs includes the catalytic oxidation of toluene.
[0013] The beneficial effects of this invention are as follows:
[0014] This invention utilizes 2.5–3.5 mol / L nitric acid to modify Bayer process red mud, which not only effectively increases the Fe content in the red mud but also enhances its specific surface area, thus facilitating the catalytic oxidation of toluene. Furthermore, experiments with various metal loadings demonstrate that loading different metals can improve the catalyst's catalytic effect on toluene to some extent, but the most significant improvement is observed with manganese loading on nitric acid-modified Bayer process red mud. Compared to commercially available Al₂O₃ and TiO₂ as catalyst supports for manganese, the catalyst prepared in this invention exhibits higher catalytic activity. Attached Figure Description
[0015] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.
[0016] Figure 1 The XRD patterns of 15Mn / ARM, ARM, and RM prepared in Example 3 of this invention are shown.
[0017] Figure 2 This is a schematic diagram of the detection device for detecting the activity of the catalyst in an embodiment of the present invention;
[0018] Figure 3 The toluene catalytic activity curves of ARM and ARM-HCl prepared in Example 1 and Comparative Example 1 of this invention are shown.
[0019] Figure 4 The toluene catalytic activity curves of the catalysts prepared in Example 1 and Comparative Examples 2-5 of this invention are shown.
[0020] Figure 5 The toluene catalytic activity curves of the catalysts prepared in Examples 1-3 of this invention are shown.
[0021] Figure 6 The toluene catalytic activity curves of the catalysts prepared in Example 1 and Comparative Examples 6-7 of this invention are shown. Detailed Implementation
[0022] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.
[0024] Given that the high Fe2O3 content in Bayer process red mud makes it difficult to further improve its catalytic activity as a VOCs catalyst, this invention proposes a red mud-based VOCs catalyst modified with nitric acid, its preparation method, and its application.
[0025] A typical embodiment of the present invention provides a method for preparing a red mud-based VOCs catalyst modified with nitric acid. The Bayer process red mud is modified with 2.5 to 3.5 mol / L nitric acid. The modified red mud is mixed with manganese salt in a solution to obtain a precursor of modified red mud and manganese composite. The precursor is calcined at 500 to 600°C to obtain the final product.
[0026] In some embodiments, the concentration of nitric acid is 2.8–3.2 mol / L.
[0027] In some embodiments, Bayer process red mud is dried and then treated with nitric acid. Specifically, the amount of nitric acid added is such that it at least covers the red mud, preferably with a mass ratio of red mud to nitric acid solution of 1:5 to 15, more preferably 1:8 to 12. Specifically, the treatment time is 0.5 to 1.5 hours.
[0028] In some embodiments, after modification, the red mud is washed until the pH is neutral, and then the modified red mud is mixed evenly with manganese salt in a solution.
[0029] The manganese salts described in this invention are compounds whose cations are manganese ions, such as manganese sulfate and manganese nitrate.
[0030] The method of compounding modified red mud with manganese must be carried out in solution. If mixed in a solid phase, such as through grinding, it is difficult to achieve a uniform mixture of manganese and modified red mud. Methods include impregnation or adding a precipitant (e.g., ammonia) after mixing. In some embodiments, the modified red mud and manganese salt are mixed uniformly in solution, and the solvent is removed by evaporation to obtain the precursor of the modified red mud-manganese composite. That is, using the impregnation method can reduce the use of chemical reagents and lower production costs.
[0031] In some embodiments, when the mass of manganese is 5-15% of the mass of the catalyst, it exhibits excellent catalytic oxidation of toluene, and when the mass of manganese is 14-15% of the mass of the catalyst, the catalytic effect is even better.
[0032] In some embodiments, the precursor is dried and then calcined. Specifically, the drying temperature is 100–110°C.
[0033] In some embodiments, the calcination time is 4 to 6 hours.
[0034] Another embodiment of the present invention provides a nitric acid-modified red mud-based VOCs catalyst, obtained by the above preparation method.
[0035] Thirdly, the application of the above-mentioned nitric acid-modified red mud-based VOCs catalyst in VOCs removal.
[0036] Specifically, the removal of VOCs includes the catalytic oxidation of toluene. More specifically, the catalytic oxidation temperature is 250–320°C.
[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.
[0038] The red mud used in the following examples is Bayer process red mud, which was purchased from Chinalco Shandong Co., Ltd.
[0039] Example 1
[0040] The preparation method of nitric acid-modified red mud-based VOCs catalyst includes the following steps:
[0041] (1) Preparation of nitric acid-modified red mud (ARM):
[0042] The red mud raw material was ground to 200 mesh and then dried overnight in a drying oven at 80°C. The resulting dried red mud was named RM. Subsequently, RM was treated with nitric acid (3 mol / L) for 1 hour (the mass ratio of red mud to nitric acid solution was 1:10). The mixture of nitric acid and RM was then washed with deionized water by vacuum filtration until the pH of the solution reached 7. RM was then dried in a water bath at 80°C until all the water evaporated, yielding nitric acid-modified red mud, denoted as ARM.
[0043] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Mn / ARM):
[0044] ARM was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, a 50% Mn(NO3)2 solution was added (based on a final Mn mass percentage of 5%, i.e., 3g of red mud and 1.042g of 50% Mn(NO3)2 solution were mixed), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. The sample was then dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace heating from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material was allowed to cool naturally to room temperature, yielding the red mud-based VOCs catalyst, denoted as 5Mn / ARM.
[0045] Example 2
[0046] The preparation method of nitric acid-modified red mud-based VOCs catalyst includes the following steps:
[0047] (1) Preparation of nitric acid-modified red mud (ARM):
[0048] The red mud raw material was ground to 200 mesh and then dried overnight in a drying oven at 80°C. The resulting dried red mud was named RM. Subsequently, RM was treated with nitric acid (3 mol / L) for 1 hour (the mass ratio of red mud to nitric acid solution was 1:10). The mixture of nitric acid and RM was then washed with deionized water by vacuum filtration until the pH of the solution reached 7. RM was then dried in a water bath at 80°C until all the water evaporated, yielding nitric acid-modified red mud, denoted as ARM.
[0049] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Mn / ARM):
[0050] ARM was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, a 50% Mn(NO3)2 solution was added (based on a 10% mass percentage of Mn in the final catalyst, i.e., 3g of red mud and 2.174g of 50% Mn(NO3)2 solution were mixed), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. The sample was then dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace heating from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material was allowed to cool naturally to room temperature, yielding the red mud-based VOCs catalyst, denoted as 10Mn / ARM.
[0051] Example 3
[0052] The preparation method of nitric acid-modified red mud-based VOCs catalyst includes the following steps:
[0053] (1) Preparation of nitric acid-modified red mud (ARM):
[0054] The red mud raw material was ground to 200 mesh and then dried overnight in a drying oven at 80°C. The resulting dried red mud was named RM. Subsequently, RM was treated with nitric acid (3 mol / L) for 1 hour (the mass ratio of red mud to nitric acid solution was 1:10). The mixture of nitric acid and RM was then washed with deionized water by vacuum filtration until the pH of the solution reached 7. RM was then dried in a water bath at 80°C until all the water evaporated, yielding nitric acid-modified red mud, denoted as ARM.
[0055] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Mn / ARM):
[0056] ARM was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, a 50% Mn(NO3)2 solution was added (based on a final Mn mass percentage of 15% in the prepared catalyst, i.e., 3 g of red mud and 3.460 g of 50% Mn(NO3)2 solution were mixed), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. The sample was then dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace heating from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material was allowed to cool naturally to room temperature, yielding the red mud-based VOCs catalyst, denoted as 15Mn / ARM.
[0057] Comparative Example 1
[0058] The preparation method of nitric acid-modified red mud-based VOCs catalyst includes the following steps:
[0059] (1) Preparation of nitric acid-modified red mud (ARM):
[0060] The red mud raw material was ground to 200 mesh and then dried overnight in a drying oven at 80°C. The resulting dried red mud was named RM. Subsequently, RM was treated with hydrochloric acid (3 mol / L) for 1 hour (the mass ratio of red mud to hydrochloric acid solution was 1:10). Then, the mixture of nitric acid and RM was washed with deionized water by vacuum filtration until the pH of the solution reached 7. RM was then dried in a water bath at 80°C until the water was completely evaporated, yielding nitric acid-modified red mud, denoted as ARM-HCl.
[0061] Comparative Example 2
[0062] The preparation method of nitric acid-modified red mud-based VOCs catalyst includes the following steps:
[0063] (1) Preparation of nitric acid-modified red mud (ARM):
[0064] The red mud raw material was ground to 200 mesh and then dried overnight in a drying oven at 80°C. The resulting dried red mud was named RM. Subsequently, RM was treated with nitric acid (3 mol / L) for 1 hour (the mass ratio of red mud to nitric acid solution was 1:10). The mixture of nitric acid and RM was then washed with deionized water by vacuum filtration until the pH of the solution reached 7. RM was then dried in a water bath at 80°C until all the water evaporated, yielding nitric acid-modified red mud, denoted as ARM.
[0065] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Ce / ARM):
[0066] ARM was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, Ce(NO3)3·6H2O was added (according to a Ce mass percentage of 5% in the final catalyst, i.e., 3g of red mud and 0.489g of Ce(NO3)3·6H2O mixed together), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. Subsequently, the sample was dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace heating from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material was allowed to cool naturally to room temperature, yielding the red mud-based VOCs catalyst, denoted as 5Ce / ARM.
[0067] Comparative Example 3
[0068] The preparation method of nitric acid-modified red mud-based VOCs catalyst includes the following steps:
[0069] (1) Preparation of nitric acid-modified red mud (ARM):
[0070] The red mud raw material was ground to 200 mesh and then dried overnight in a drying oven at 80°C. The resulting dried red mud was named RM. Subsequently, RM was treated with nitric acid (3 mol / L) for 1 hour (the mass ratio of red mud to nitric acid solution was 1:10). The mixture of nitric acid and RM was then washed with deionized water by vacuum filtration until the pH of the solution reached 7. RM was then dried in a water bath at 80°C until all the water evaporated, yielding nitric acid-modified red mud, denoted as ARM.
[0071] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Co / ARM):
[0072] ARM was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, Co(NO3)2·6H2O was added (according to a final catalyst mass percentage of 5%, i.e., 3g of red mud and 0.790g of Co(NO3)2·6H2O mixed together), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. Subsequently, the sample was dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace heating from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material was allowed to cool naturally to room temperature, yielding the red mud-based VOCs catalyst, denoted as 5Co / ARM.
[0073] Comparative Example 4
[0074] The preparation method of nitric acid-modified red mud-based VOCs catalyst includes the following steps:
[0075] (1) Preparation of nitric acid-modified red mud (ARM):
[0076] The red mud raw material was ground to 200 mesh and then dried overnight in a drying oven at 80°C. The resulting dried red mud was named RM. Subsequently, RM was treated with nitric acid (3 mol / L) for 1 hour (the mass ratio of red mud to nitric acid solution was 1:10). The mixture of nitric acid and RM was then washed with deionized water by vacuum filtration until the pH of the solution reached 7. RM was then dried in a water bath at 80°C until all the water evaporated, yielding nitric acid-modified red mud, denoted as ARM.
[0077] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Cr / ARM):
[0078] ARM was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, Cr(NO3)3·9H2O was added (according to the final catalyst mass percentage of 5%, i.e., 3g of red mud and 1.246g of Cr(NO3)3·9H2O were mixed), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. Subsequently, the sample was dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace heating from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material was allowed to cool naturally to room temperature, yielding the red mud-based VOCs catalyst, denoted as 5Cr / ARM.
[0079] Comparative Example 5
[0080] The preparation method of nitric acid-modified red mud-based VOCs catalyst includes the following steps:
[0081] (1) Preparation of nitric acid-modified red mud (ARM):
[0082] The red mud raw material was ground to 200 mesh and then dried overnight in a drying oven at 80°C. The resulting dried red mud was named RM. Subsequently, RM was treated with nitric acid (3 mol / L) for 1 hour (the mass ratio of red mud to nitric acid solution was 1:10). The mixture of nitric acid and RM was then washed with deionized water by vacuum filtration until the pH of the solution reached 7. RM was then dried in a water bath at 80°C until all the water evaporated, yielding nitric acid-modified red mud, denoted as ARM.
[0083] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Mn-Ce / ARM):
[0084] The ARM was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, a 50% Mn(NO3)2 solution and Ce(NO3)3·6H2O were added (according to the final catalyst mass percentages of 2.5% for Mn and 2.5% for Ce, i.e., 3g red mud, 0.514g of 50% Mn(NO3)2 solution, and 0.245g of Ce(NO3)3·6H2O were added), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. Subsequently, the sample was dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace temperature increased from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material is naturally cooled to room temperature, which is the red mud-based VOCs catalyst, denoted as 2.5Mn-2.5Ce / ARM.
[0085] Comparative Example 6
[0086] Commercially available Al₂O₃ was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, a 50% Mn(NO₃)₂ solution was added (according to the final catalyst, the mass percentage of Mn is 15%, i.e., 3g Al₂O₃ and 3.460g of 50% Mn(NO₃)₂ solution were mixed), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. The sample was then dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace heating from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material was allowed to cool naturally to room temperature, yielding the red mud-based VOCs catalyst, denoted as 15Mn / Al.
[0087] Comparative Example 7
[0088] Commercially available TiO2 was ground to 200 mesh and then mixed with deionized water at a solid-liquid mass ratio of 1:3. The solution was stirred in an 80°C water bath for 20 minutes. Then, a 50% Mn(NO3)2 solution was added (according to the final catalyst, the mass percentage of Mn was 15%, i.e., 3 g TiO2 and 3.460 g of 50% Mn(NO3)2 solution were mixed), and the mixture was stirred continuously in an 80°C water bath until the water was completely evaporated. The sample was then dried overnight in a 105°C drying oven. The sample was then removed from the drying oven and calcined in a muffle furnace at 550°C in air for 5 hours, with the muffle furnace heating from room temperature to 550°C at a rate of 5°C / min. Finally, the calcined material was allowed to cool naturally to room temperature, yielding the red mud-based VOCs catalyst, denoted as 15Mn / Ti.
[0089] The content and physical structure of RM, ARM, and 15Mn / ARM prepared in Example 3 are shown in Tables 1 and 2. Figure 1 As shown.
[0090] Table 1. Component content of RM and ARM prepared in Example 3
[0091]
[0092] Table 2 shows the physical structures of the RM, ARM, and 15Mn / ARM prepared in Example 3.
[0093]
[0094]
[0095] Table 1 and Figure 1 This indicates that both the red mud before and after acid treatment contain Fe2O3, and that nitric acid treatment can effectively increase the proportion of Fe in the red mud, which is beneficial for the catalytic oxidation of toluene.
[0096] Table 2 shows that the specific surface area of ARM decreased from 23.5 m² after nitric acid treatment. 2 / g increased to 45.7m 2 / g, further increased by 15Mn / ARM to 58.2m 2 A larger specific surface area ( / g) indicates that the catalyst has more active sites for toluene adsorption during the reaction. Simultaneously, the pore volume increases from 0.12 m² / g for ARM. 3 / g was increased to 0.15m for ARM and 15Mn / ARM. 3 A larger pore volume per g indicates that the catalyst has a stronger capacity to accommodate toluene, which is beneficial for the catalytic oxidation of toluene.
[0097] The catalysts prepared in each embodiment and comparative example were subjected to activity testing, using a testing device such as... Figure 2 As shown, the detection process is as follows:
[0098] The simulated flue gas flow rate was 100 mL / min, with a toluene concentration of 1000 ppm, an O2 content of 21%, and N2 as the equilibrium gas. The mass hourly space velocity (WHSV) was 60000 mL / (g·h). The catalytic testing temperature range was 200–350 °C. The results are as follows: Figures 3-6 As shown.
[0099] Figure 3 This indicates that the catalytic effect of hydrochloric acid on red mud modification is weaker than that of nitric acid on red mud modification.
[0100] Figure 4This indicates that loading various metals can improve the catalytic effect of catalysts on toluene to some extent, but the most significant improvement is achieved by loading Mn onto red mud ARM.
[0101] Figure 5 This indicates that when the mass percentage of Mn is increased to 15%, the T of the 15Mn / ARM catalyst... 90 (The temperature at which toluene conversion reaches 90%) compared to the T of the ARM catalyst. 90 The temperature increase exceeded 100°C, demonstrating a significant advantage.
[0102] Commercially, Al₂O₃ and TiO₂ are commonly used as catalyst supports. Here, 15Mn / Al and 15Mn / Ti catalysts were prepared using the same synthesis method. The T of the 15Mn / Al catalyst was also discussed. 90 Compared to 15Mn / Al and 15Mn / Ti catalysts, the temperature increases were 37℃ and 26℃ respectively, indicating that this method can effectively enhance the activity of red mud for the catalytic oxidation of toluene, and its effect is superior to other catalysts, such as... Figure 6 As shown.
[0103] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. The application of a nitric acid-modified red mud-based VOCs catalyst in VOCs removal, characterized in that, Preparation method of nitric acid modified red mud-based VOCs catalyst The process includes modifying Bayer red mud with 2.8-3.2 mol / L nitric acid, mixing the modified red mud with manganese salt in a solution to obtain a precursor of modified red mud and manganese composite, and calcining the precursor at 500-600 °C to obtain the final product. After modification, the red mud is washed until the pH is neutral, and then the modified red mud and manganese salt are mixed evenly in the solution. The mass of manganese is 14-15% of the mass of the catalyst.
2. The application as described in claim 1, characterized in that, After drying the Bayer red mud, nitric acid is added for treatment.
3. The application as described in claim 1, characterized in that, The modified red mud and manganese salt were mixed evenly in a solution, and the solvent was removed by evaporation to obtain the precursor of the modified red mud and manganese composite.
4. The application as described in claim 1, characterized in that, The precursor is dried and then calcined at a temperature of 100-110 °C.
5. The application as described in claim 4, characterized in that, The calcination time is 4-6 hours.
6. The application as described in claim 1, characterized in that, The removal of VOCs includes the catalytic oxidation of toluene.
7. The application as described in claim 6, characterized in that, The temperature for the catalytic oxidation is 250~320 ℃.