Nitric acid modified red mud-based VOCs catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of volatile organic compound treatment, and relates to a VOCs catalyst, in particular to a nitric acid modified red mud-based VOCs catalyst as well as a preparation method and application thereof. The method comprises the following steps: carrying out modification treatment on Bayer process red mud by using 2.5-3.5 mol / L nitric acid, uniformly mixing the modified red mud and manganese salt in a solution to obtain a modified red mud and manganese composite precursor, and calcining the precursor at 500-600 DEG C to obtain the red mud-manganese composite material. According to the invention, the Bayer process red mud is modified by nitric acid, and the modified red mud is used as a carrier to load the transition metal Mn, so that the catalytic efficiency on toluene is obviously improved, and the catalytic treatment on VOCs is expected to be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of volatile organic compounds (VOCs) treatment, and relates to a VOCs catalyst, and specifically to a nitric acid-modified red mud-based VOCs catalyst, and a preparation method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The emission of volatile organic compounds (VOCs) comes from a variety of sources, such as industrial processes, building materials, and automobile exhaust, which poses a major threat to public health and the ecological environment, and effective control strategies are urgently needed. Catalytic oxidation is an efficient, safe, and economical VOCs treatment technology that is valued for its excellent performance. Currently, common catalysts can be divided into two categories based on the materials: precious metal catalysts and non-precious metal catalysts. Precious metal catalysts generally show higher activity than non-precious metal catalysts, so they have higher VOCs conversion efficiency under certain specific catalytic conditions. However, the high material cost, catalytic stability, and generally poor anti-poisoning ability of precious metals limit the large-scale application of precious metal catalysts. On the contrary, catalysts containing non-precious metals such as manganese and iron have rich valence states, low acquisition costs, and little impact on environmental pollution. Therefore, many studies have focused on improving the VOCs catalytic activity of non-precious metal catalysts.

[0004] Red mud is a solid waste generated during the extraction of bauxite. Using red mud as a raw material for preparing catalysts not only solves the problem of low utilization rate of solid waste red mud and environmental pollution, but also effectively reduces the cost of catalysts. Red mud is divided into Bayer red mud, sintering red mud, and combined red mud according to the aluminum smelting process. Among them, the content of Fe2O3 in Bayer red mud is the highest, up to 50%, which can be used as an active ingredient of the catalyst; however, the redox performance of Fe2O3 when it exists alone is not very outstanding. Therefore, if red mud containing only Fe2O3 is directly used, it is difficult to quickly catalyze the oxidation reaction of toluene, which affects the further improvement of catalytic activity. Summary of the invention

[0005] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide a nitric acid-modified red mud-based VOCs catalyst, and a preparation method and application thereof. The present invention modifies the Bayer process red mud with nitric acid, and uses the modified red mud as a carrier to load the transition metal Mn, which significantly improves the catalytic efficiency of toluene and is expected to achieve catalytic treatment of VOCs.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] In the first aspect, a method for preparing a nitric acid-modified red mud-based VOCs catalyst is provided, wherein 2.5 to 3.5 mol / L nitric acid is used to modify Bayer process red mud, the modified red mud and a manganese salt are uniformly mixed in a solution to obtain a precursor of a modified red mud and manganese composite, and the precursor is calcined at 500 to 600°C to obtain the catalyst.

[0008] First, the present invention selects nitric acid as the acid for modifying Bayer red mud, which is not only acidic but also oxidizing, and has a better modification effect on Bayer red mud. At the same time, when optimizing the concentration of nitric acid, it is unexpectedly found that the Bayer red mud modified with nitric acid at a concentration of 2.5 to 3.5 mol / L can retain more Fe2O3, which is beneficial to improve the catalytic activity of the catalyst prepared therefrom. Secondly, the present invention selects Bayer red mud modified with 2.5 to 3.5 mol / L nitric acid as a carrier, adds new active ingredients to improve its catalytic activity, and studies have found that when compared with loading cerium, cobalt, chromium, or even loading multiple metals, the catalytic activity of the catalyst prepared by loading manganese is higher.

[0009] Further studies have shown that when the mass of manganese is 5-15% of the mass of the catalyst, the catalytic oxidation of toluene has an excellent catalytic effect, and when the mass of manganese is 14-15% of the mass of the catalyst, the catalytic effect is even better.

[0010] On the other hand, a nitric acid-modified red mud-based VOCs catalyst is obtained by the above preparation method.

[0011] In a third aspect, a red mud-based VOCs catalyst modified by nitric acid is used for removing VOCs.

[0012] Furthermore, the removal of VOCs includes catalytic oxidation of toluene.

[0013] The beneficial effects of the present invention are:

[0014] The present invention uses 2.5-3.5 mol / L nitric acid to modify the Bayer red mud, which can not only effectively increase the proportion of Fe in the red mud, but also increase the specific surface area of ​​the red mud, which is beneficial to the catalytic oxidation of toluene; further, experiments on loading various metals show that loading various metals can improve the catalytic effect of the catalyst on toluene to a certain extent, but the most obvious improvement is loading manganese on the nitric acid-modified Bayer red mud. Compared with commercially commonly used Al2O3 and TiO2 as catalyst carriers to load manganese, the catalyst prepared by the present invention has higher catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0016] Figure 1 XRD spectra of 15Mn / ARM, ARM and RM prepared in Example 3 of the present invention;

[0017] Figure 2 This is a schematic diagram of the structure of a detection device for detecting the activity of a 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 the present invention;

[0019] Figure 4 The toluene catalytic activity curves of the catalysts prepared in Example 1 and Comparative Examples 2 to 5 of the present invention;

[0020] Figure 5 The toluene catalytic activity curve of the catalyst prepared in Examples 1 to 3 of the present invention;

[0021] Figure 6 The toluene catalytic activity curves of the catalysts prepared in Example 1 and Comparative Examples 6-7 of the present invention. DETAILED DESCRIPTION

[0022] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] In view of the high content of Fe2O3 in Bayer process red mud, which makes it difficult to further improve its catalytic activity as a VOCs catalyst, the present invention proposes a nitric acid-modified red mud-based VOCs catalyst, a preparation method and an application thereof.

[0025] A typical embodiment of the present invention provides a method for preparing a nitric acid-modified red mud-based VOCs catalyst, wherein 2.5 to 3.5 mol / L nitric acid is used to modify Bayer process red mud, the modified red mud and manganese salt are evenly mixed in a solution to obtain a precursor of a modified red mud and manganese composite, and the precursor is calcined at 500 to 600°C to obtain the catalyst.

[0026] In some embodiments, the concentration of nitric acid is 2.8-3.2 mol / L.

[0027] In some embodiments, after the Bayer red mud is dried, nitric acid is added for treatment. Specifically, the amount of nitric acid added is: at least enough to cover the red mud, preferably the mass ratio of red mud to nitric acid solution is 1:5-15, preferably 1:8-12. Specifically, the treatment time is 0.5-1.5 hours.

[0028] In some embodiments, after the modification treatment, the red mud is washed until the pH is neutral, and then the modified red mud and the manganese salt are mixed evenly in the solution.

[0029] The manganese salt described in the present invention is a compound whose cation is a manganese ion, such as manganese sulfate, manganese nitrate, etc.

[0030] The method of compounding the modified red mud with manganese must be carried out in a solution. If mixed in a solid phase, such as grinding, it is not easy to mix manganese and the modified red mud evenly. The method can be impregnation, or precipitation by adding a precipitant (such as ammonia water) after mixing. In some embodiments, the modified red mud and the manganese salt are evenly mixed in a solution, and the solvent is evaporated to obtain a precursor of the modified red mud and manganese compound. That is, the use of the impregnation method can reduce the use of chemical reagents and reduce production costs.

[0031] In some embodiments, when the mass of manganese is 5-15% of the mass of the catalyst, the catalytic oxidation of toluene has an excellent catalytic effect, and when the mass of manganese is 14-15% of the mass of the catalyst, the catalytic effect is 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-mentioned preparation method.

[0035] In a third aspect, a red mud-based VOCs catalyst modified by nitric acid is used for removing VOCs.

[0036] Specifically, the removal of VOCs includes catalytic oxidation of toluene. More specifically, the temperature of the catalytic oxidation is 250-320°C.

[0037] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in combination with specific embodiments and comparative examples.

[0038] The red mud used in the following examples is Bayer red mud, which was purchased from China Aluminum Shandong Co., Ltd.

[0039] Example 1

[0040] The preparation method of the nitric acid-modified red mud-based VOCs catalyst comprises 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 dried red mud obtained 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 filtered and washed with deionized water until the pH value of the solution was 7. RM was then dried in a water bath at 80°C until the water was completely evaporated to obtain nitric acid-modified red mud, recorded as ARM.

[0043] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Mn / ARM):

[0044] ARM was ground to 200 mesh, then mixed with deionized water at a solid-liquid mass ratio of 1:3, and the solution was stirred in a water bath at 80°C for 20 minutes. Then a 50% Mn(NO3)2 solution was added (according to the mass percentage of Mn in the final prepared catalyst of 5%, that is, 3g red mud and 1.042g 50% Mn(NO3)2 solution were mixed), and the mixture was stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours. The rate at which the muffle furnace was heated from room temperature to 550°C was 5°C / minute. Finally, the calcined material was naturally cooled to room temperature, which was a red mud-based VOCs catalyst, recorded as 5Mn / ARM.

[0045] Example 2

[0046] The preparation method of the nitric acid-modified red mud-based VOCs catalyst comprises 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 dried red mud obtained 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 filtered and washed with deionized water until the pH value of the solution was 7. RM was then dried in a water bath at 80°C until the water was completely evaporated to obtain nitric acid-modified red mud, recorded as ARM.

[0049] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Mn / ARM):

[0050] ARM was ground to 200 mesh, then mixed with deionized water at a solid-liquid mass ratio of 1:3, and the solution was stirred in a water bath at 80°C for 20 minutes. Then a 50% Mn(NO3)2 solution was added (according to the mass percentage of Mn in the final prepared catalyst of 10%, that is, 3g red mud and 2.174g 50% Mn(NO3)2 solution were mixed), and the mixture was stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours. The rate at which the muffle furnace was heated from room temperature to 550°C was 5°C / minute. Finally, the calcined material was naturally cooled to room temperature, which was a red mud-based VOCs catalyst, recorded as 10Mn / ARM.

[0051] Example 3

[0052] The preparation method of the nitric acid-modified red mud-based VOCs catalyst comprises 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 dried red mud obtained 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 filtered and washed with deionized water until the pH value of the solution was 7. RM was then dried in a water bath at 80°C until the water was completely evaporated to obtain nitric acid-modified red mud, recorded as ARM.

[0055] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Mn / ARM):

[0056] ARM was ground to 200 mesh, then mixed with deionized water at a solid-liquid mass ratio of 1:3, and the solution was stirred in a water bath at 80°C for 20 minutes. Then a 50% Mn(NO3)2 solution was added (according to the mass percentage of Mn in the final prepared catalyst of 15%, that is, 3g red mud and 3.460g 50% Mn(NO3)2 solution were mixed), and stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours. The rate at which the muffle furnace was heated from room temperature to 550°C was 5°C / minute. Finally, the calcined material was naturally cooled to room temperature, which was a red mud-based VOCs catalyst, recorded as 15Mn / ARM.

[0057] Comparative Example 1

[0058] The preparation method of the nitric acid-modified red mud-based VOCs catalyst comprises 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 dried red mud obtained 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). The mixture of nitric acid and RM was then filtered and washed with deionized water until the pH value of the solution was 7. RM was then dried in a water bath at 80°C until the water was completely evaporated to obtain nitric acid-modified red mud, recorded as ARM-HCl.

[0061] Comparative Example 2

[0062] The preparation method of the nitric acid-modified red mud-based VOCs catalyst comprises 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 dried red mud obtained 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 filtered and washed with deionized water until the pH value of the solution was 7. RM was then dried in a water bath at 80°C until the water was completely evaporated to obtain nitric acid-modified red mud, recorded 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 a water bath at 80°C for 20 minutes. Then Ce(NO3)3·6H2O was added (according to the mass percentage of Ce in the final prepared catalyst of 5%, that is, 3g red mud and 0.489g Ce(NO3)3·6H2O were mixed) and stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours. The rate at which the muffle furnace was heated from room temperature to 550°C was 5°C / min. Finally, the calcined material was naturally cooled to room temperature, which was a red mud-based VOCs catalyst, recorded as 5Ce / ARM.

[0067] Comparative Example 3

[0068] The preparation method of the nitric acid-modified red mud-based VOCs catalyst comprises 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 dried red mud obtained 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 filtered and washed with deionized water until the pH value of the solution was 7. RM was then dried in a water bath at 80°C until the water was completely evaporated to obtain nitric acid-modified red mud, recorded 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, and the solution was stirred in a water bath at 80°C for 20 minutes. Then Co(NO3)2·6H2O was added (according to the mass percentage of Co in the final prepared catalyst of 5%, that is, 3g red mud and 0.790g Co(NO3)2·6H2O were mixed), and stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours. The rate at which the muffle furnace was heated from room temperature to 550°C was 5°C / minute. Finally, the calcined material was naturally cooled to room temperature, which was a red mud-based VOCs catalyst, recorded as 5Co / ARM.

[0073] Comparative Example 4

[0074] The preparation method of the nitric acid-modified red mud-based VOCs catalyst comprises 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 dried red mud obtained 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 filtered and washed with deionized water until the pH value of the solution was 7. RM was then dried in a water bath at 80°C until the water was completely evaporated to obtain nitric acid-modified red mud, recorded 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 a water bath at 80°C for 20 minutes. Then Cr(NO3)3·9H2O was added (according to the mass percentage of Cr in the final prepared catalyst of 5%, that is, 3g red mud and 1.246g Cr(NO3)3·9H2O were mixed) and stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours. The rate at which the muffle furnace was heated from room temperature to 550°C was 5°C / minute. Finally, the calcined material was naturally cooled to room temperature, which was a red mud-based VOCs catalyst, recorded as 5Cr / ARM.

[0079] Comparative Example 5

[0080] The preparation method of the nitric acid-modified red mud-based VOCs catalyst comprises 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 dried red mud obtained 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 filtered and washed with deionized water until the pH value of the solution was 7. RM was then dried in a water bath at 80°C until the water was completely evaporated to obtain nitric acid-modified red mud, recorded as ARM.

[0083] (2) Preparation of nitric acid-modified red mud-based VOCs catalyst (Mn-Ce / ARM):

[0084] ARM was ground to 200 mesh, then mixed with deionized water at a solid-liquid mass ratio of 1:3, and the solution was stirred in a water bath at 80°C for 20 minutes. Then, 50% Mn(NO3)2 solution and Ce(NO3)3·6H2O were added (according to the mass percentage of Mn and Ce in the final prepared catalyst of 2.5% and 2.5%, respectively, that is, 3g red mud and 0.514g 50% Mn(NO3)2 solution and 0.245g Ce(NO3)3·6H2O were mixed), and stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours, and the rate of heating the muffle furnace from room temperature to 550°C was 5°C / min. Finally, the calcined material was naturally cooled to room temperature to obtain a 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, then mixed with deionized water at a solid-liquid mass ratio of 1:3, and the solution was stirred in a water bath at 80°C for 20 minutes. Then a 50% Mn(NO3)2 solution was added (according to the mass percentage of Mn in the final prepared catalyst of 15%, that is, 3gAl2O3 and 3.460g 50% Mn(NO3)2 solution were mixed), and the mixture was stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours. The rate at which the muffle furnace was heated from room temperature to 550°C was 5°C / minute. Finally, the calcined material was naturally cooled to room temperature, which was a red mud-based VOCs catalyst, recorded as 15Mn / Al.

[0087] Comparative Example 7

[0088] Commercially available TiO2 was ground to 200 mesh, then mixed with deionized water at a solid-liquid mass ratio of 1:3, and the solution was stirred in a water bath at 80°C for 20 minutes. Then a 50% Mn(NO3)2 solution was added (according to the mass percentage of Mn in the final prepared catalyst of 15%, that is, 3gTiO2 and 3.460g 50% Mn(NO3)2 solution were mixed), and the mixture was stirred continuously in a water bath at 80°C until the water was completely evaporated. Subsequently, the sample was dried in a drying oven at 105°C overnight. The sample was taken out of the drying oven and calcined in a muffle furnace in an air environment at 550°C for 5 hours. The rate at which the muffle furnace was heated from room temperature to 550°C was 5°C / minute. Finally, the calcined material was naturally cooled to room temperature, which was a red mud-based VOCs catalyst, recorded as 15Mn / Ti.

[0089] The composition contents and physical structures of RM, ARM and 15Mn / ARM prepared in Example 3 are shown in Tables 1, 2 and Figure 1 shown.

[0090] Table 1 Component contents of RM and ARM prepared in Example 3

[0091]

[0092] Table 2 Physical structures of RM, ARM and 15Mn / ARM prepared in Example 3

[0093]

[0094]

[0095] Table 1 and Figure 1 The results show that red mud contains Fe2O3 before and after acid treatment, and nitric acid treatment can effectively increase the proportion of Fe in red mud, which is beneficial to the catalytic oxidation of toluene.

[0096] Table 2 shows that the specific surface area of ​​ARM after nitric acid treatment increased from 23.5m 2 / g increased to 45.7m 2 / g, and 15Mn / ARM was further increased to 58.2m 2 / g, the larger the specific surface area, the more active sites the catalyst has to adsorb toluene during the reaction. At the same time, the pore volume increases from 0.12m 3 / g increased to 0.15m for ARM and 15Mn / ARM 3 / g, the larger the pore volume, the stronger the catalyst's ability to accommodate toluene, which is beneficial to the catalytic oxidation of toluene.

[0097] The catalysts prepared in the examples and comparative examples were tested for activity using a testing device such as Figure 2 As shown, the detection process is as follows:

[0098] The simulated flue gas flow rate is 100mL / min, the toluene concentration is 1000ppm, the percentage of O2 is 21%, N2 is used as the balance gas, and the mass space velocity is 60000mL / (g·h). The temperature range of the catalytic test is 200~350℃. The results are as follows Figures 3 to 6 shown.

[0099] Figure 3 It shows that the catalytic effect of red mud modification using hydrochloric acid is weaker than that of red mud modification using nitric acid.

[0100] Figure 4It shows that loading various metals can improve the catalytic effect of the catalyst on toluene to a certain extent, but the most obvious improvement is when Mn is loaded on red mud ARM.

[0101] Figure 5 It shows that when the mass proportion of Mn increases to 15%, the T 90 (Temperature at which toluene conversion reaches 90%) compared to the T of the ARM catalyst 90 The improvement exceeded 100℃, showing good advantages.

[0102] Al2O3 and TiO2 are commonly used as catalyst carriers in the commercial industry. Here, 15Mn / Al catalyst and 15Mn / Ti catalyst were prepared by the same synthesis method. The T 90 Compared with 15Mn / Al catalyst and 15Mn / Ti catalyst, the temperature increased by 37℃ and 26℃ respectively, indicating that the red mud can be effectively used for catalytic oxidation of toluene by this method, and the effect is better than other catalysts, such as Figure 6 shown.

[0103] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a nitric acid-modified red mud-based VOCs catalyst, characterized in that: The Bayer red mud is modified by using 2.5-3.5 mol / L nitric acid, the modified red mud is evenly mixed with manganese salt in a solution to obtain a precursor of modified red mud and manganese composite, and the precursor is calcined at 500-600° C. to obtain the product.

2. The preparation method according to claim 1, characterized in that: The concentration of nitric acid is 2.8~3.2mol / L.

3. The preparation method according to claim 1, characterized in that: After the Bayer process red mud is dried, nitric acid is added for treatment.

4. The preparation method according to claim 1, characterized in that: After the modification treatment, the red mud is washed until the pH is neutral, and then the modified red mud and the manganese salt are mixed evenly in the solution.

5. The preparation method according to claim 1, characterized in that: The modified red mud and manganese salt are uniformly mixed in a solution, and the solvent is evaporated to obtain a precursor of the modified red mud and manganese composite.

6. The preparation method according to claim 1, characterized in that: The mass of manganese is 5-15% of the mass of the catalyst, preferably 14-15%.

7. The preparation method according to claim 1, characterized in that: The precursor is dried and then calcined at a drying temperature of 100 to 110° C.; Alternatively, the calcination time is 4 to 6 hours.

8. A nitric acid-modified red mud-based VOCs catalyst, characterized in that: Obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the nitric acid-modified red mud-based VOCs catalyst according to claim 8 in removing VOCs.

10. The use according to claim 9, characterized in that: The removal of VOCs includes catalytic oxidation of toluene; preferably, the temperature of the catalytic oxidation is 250-320°C.

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