A method for efficient thermocatalytic degradation of acetone in waste gas

Abstract

This invention discloses a highly efficient thermocatalytic degradation method for acetone in waste gas. The method involves catalytically degrading acetone-containing waste gas in a fixed-bed reactor filled with activated carbon catalyst to remove acetone. The activated carbon catalyst is prepared by: preparing a mixed manganese and cerium precursor solution; impregnating an activated carbon support with the precursor solution to adsorb metal ions into the pores of the activated carbon; drying the activated carbon sample and then vacuum drying it; and finally calcining the vacuum-dried activated carbon sample at high temperature under nitrogen protection. This invention achieves high efficiency, low reaction temperature, rapid degradation rate, and good degradation effect for acetone in waste gas containing 714 mg / m³. 3 Acetone, at a temperature of 180-190℃, has a degradation rate of more than 90% within 15 minutes, which is significantly lower than the degradation temperature of similar catalysts, thus saving operating costs.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control technology, and in particular relates to a method for efficient thermocatalytic degradation of acetone in waste gas. Background Technology

[0002] Acetone is volatile, has a distinctive pungent odor, and is chemically reactive. It is primarily produced in the chemical, printing, pharmaceutical, and bio-fermentation industries. Excessive acetone intake can cause headaches, dizziness, and dermatitis; it can also irritate the eyes and respiratory system, damage the nervous system, and threaten human health. Therefore, finding efficient and economical methods to control acetone pollution is urgently needed.

[0003] Catalytic oxidation is one of the most efficient and cost-effective technologies for oxidizing acetone into carbon dioxide, water, and other relatively harmless compounds. The core technology for achieving efficient catalytic degradation of acetone in waste gas is to find catalysts with low mass transfer resistance and high active sites.

[0004] Chinese patents CN103962132A and CN101116810A disclose carbon-based catalysts prepared from activated carbon, which are used to catalyze the synthesis reaction of gluconic acid and acetals / ketones. Carbon-based catalysts are rarely used in the degradation of organic gaseous pollutants. In addition, the existing technology uses a large amount of precious metals or heavy metals as active components of carbon-based catalysts, which is not conducive to the dispersion of active components on the surface of the support. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, the present invention aims to provide a highly efficient thermocatalytic degradation method for acetone in waste gas. In this method, activated carbon catalyst is used for the catalytic oxidation degradation of acetone. This catalyst leverages the well-developed porous structure of activated carbon, along with the small size and uniform dispersion of the supported Ce / Mn particles, ensuring the catalytic degradation activity. The entire catalyst preparation process is simple and easy to implement, requiring no high-temperature reduction and generating no pollution. The catalyst exhibits high activity, low dosage, low pollution, low catalytic reaction temperature, and low energy consumption, meeting the requirements of green chemistry. This catalyst has broad industrial prospects in fields such as bio-fermentation, chemical engineering, and food processing. The catalyst of this invention, used for the catalytic degradation of acetone, requires a small dosage, has a fast degradation rate, good degradation effect, and high stability.

[0006] The technical solution of the present invention is described in detail below.

[0007] This invention provides a method for the efficient thermocatalytic degradation of acetone in waste gas. The acetone-containing waste gas undergoes a catalytic degradation reaction in a fixed-bed reactor packed with activated carbon catalyst to remove acetone. The reaction temperature is 160-280℃. The activated carbon catalyst is prepared by the following method:

[0008] (1) Prepare a mixed solution of manganese metal salt and cerium metal salt as a precursor solution;

[0009] (2) Impregnate the activated carbon support with a precursor solution so that metal ions are adsorbed into the pores of the activated carbon support;

[0010] (3) Take out the impregnated activated carbon sample, air dry it, and then vacuum dry it;

[0011] (4) Under an inert atmosphere, the vacuum-dried activated carbon sample is calcined at high temperature in a tube furnace to obtain the supported activated carbon catalyst.

[0012] In this invention, the reaction temperature in the catalytic degradation reaction is 170-225℃. More preferably, the reaction temperature is 180-190℃.

[0013] In this invention, the space velocity in the catalytic degradation reaction is 10000-20000 mL / g·h, and the concentration of acetone in the waste gas is 100-2000 mg / m³. 3 The exhaust gas flow rate is between 50-500 mL / min, and more preferably, the space velocity is 12000-15000 mL / g·h, and the acetone concentration in the exhaust gas is 238-714 mg / m³. 3 The exhaust gas flow rate is between 50-200 mL / min.

[0014] In this invention, in step (1), the manganese metal salt in the precursor solution is a divalent manganese salt, and the cerium metal salt is a trivalent cerium salt; the mass ratio of cerium to manganese is 0.2:1 to 1:1, and the mass fraction of manganese in the precursor solution is 1.5-2.5%. Most preferably, the mass ratio of cerium to manganese is 0.8:1.

[0015] In this invention, in step (1), the manganese metal salt is manganese sulfate, manganese nitrate or manganese chloride, and the cerium metal salt is cerium nitrate, cerium acetate or cerium chloride.

[0016] In this invention, in step (2), the activated carbon carrier is biomass activated carbon with a specific surface area of ​​900-1400 m². 2 / g, total pore volume ≥0.7cm³ 3 / g, micropore volume ≥0.15 cm³ 3 / g; The mass-to-volume ratio of activated carbon carrier and precursor solution is 1:5~1:20g / mL. First, ultrasonically impregnate at room temperature for 50min-2h, and then impregnate in a water bath at 50-70℃ for 3-5h.

[0017] In this invention, in step (2), the activated carbon carrier is citric acid fermentation waste residue-based biomass activated carbon.

[0018] In this invention, in step (3), the vacuum drying temperature is 100-120℃ and the vacuum drying time is 2-10h.

[0019] In this invention, in step (4), the calcination temperature is 350-450℃ and the calcination time is 2-5h.

[0020] The present invention also provides an activated carbon catalyst for the above-mentioned thermocatalytic degradation of acetone in waste gas, which is a supported activated carbon catalyst, and the active material includes MnO. x (X=1, 1.5, 2.0), CeO2, Ce2O3.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) The catalyst used in the catalytic degradation of this invention is calcined under high temperature conditions, which greatly enhances the interaction between manganese, cerium and activated carbon support, and increases the number of defects and vacancies on the surface of activated carbon, resulting in excellent dispersion of surface metal particles; at the same time, the particle size of active metal particles on the surface of activated carbon support is 5-20 nm, with an average spacing of more than 100 nm, which makes it less prone to agglomeration and more active in catalytic reaction.

[0023] 2) The catalyst used in the catalytic degradation of this invention has a simple preparation process, is easy to industrialize, can significantly save production costs, and has excellent practical application prospects.

[0024] 3) The catalyst provided by this invention has the characteristics of long service life and stable performance in the degradation of acetone, and can maintain a high degradation rate of acetone for a long time. It increases the utilization rate of the active component of the catalyst, which is beneficial to improving production efficiency and reducing production costs.

[0025] 4) This invention catalytically degrades acetone in waste gas at a low reaction temperature, with a rapid degradation rate and good degradation effect; it is effective against acetone concentrations of 714 mg / m³. 3 Acetone, at a temperature of 180-190℃, has a degradation rate of more than 90% within 15 minutes, which is significantly lower than the degradation temperature of similar catalysts, thus saving operating costs. Attached Figure Description

[0026] Figure 1 The process flow diagram for preparing the highly efficient acetone-degrading biochar supported catalyst in Example 1 is shown.

[0027] Figure 2 The N2 isotherm (a) and pore size distribution (b) of the highly efficient acetone-degrading biochar supported catalyst prepared in Example 1 are shown.

[0028] Figure 3 The image shown is a scanning electron microscope (SEM) image of the catalyst prepared in Example 1.

[0029] Figure 4 The image shows a transmission electron microscope (TEM) image of the catalyst prepared in Example 1.

[0030] Figure 5 The XRD characterization results are for catalysts with different ratios in Example 2.

[0031] Figure 6 The catalyst prepared in Example 1 and the biomass activated carbon without active metal showed a reaction concentration of 238 mg / m³. 3 Comparison of acetone degradation performance.

[0032] Figure 7 The graph shows the degradation performance of acetone by different Ce / Mn ratio catalysts prepared in Example 2.

[0033] Figure 8 This is a stability performance evaluation diagram of the catalyst prepared in Example 1. Detailed Implementation

[0034] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] Example 1: Preparation and physicochemical properties of a biochar-supported catalyst for efficient degradation of acetone.

[0036] The process flow diagram of the high-efficiency acetone degradation biochar supported catalyst is as follows: Figure 1 As shown. 16.9 g of MnSO4·H2O solid was weighed using an analytical balance and prepared into a 1 mol / L MnSO4 solution. 36.403 mL of this solution was measured, containing 2 g of Mn (denoted as solution A). 13.027 g of Ce(NO3)3·6H2O solid was weighed and prepared into a 0.3 mol / L Ce(NO3)3 solution. 38.063 mL of this solution was measured, containing 1.6 g of Ce (denoted as solution B). Solutions A and B were mixed, resulting in a Ce to Mn mass ratio of 0.8. Then, 10 g of biomass activated carbon was impregnated in the mixed solution, ultrasonically impregnated at room temperature for 1 h, and then heated in a water bath at 60 °C for 4 h. The activated carbon catalyst was then removed and dried under vacuum at 110 °C for 8 h, followed by high-temperature calcination under nitrogen protection at 400 °C for 3 h to increase the stability of the active components of the catalyst. The N2 isotherm adsorption lines and pore size distribution of the prepared catalyst material are shown in the figure below. Figure 2 As shown in the figure, the pore size of the catalyst material is mainly concentrated below 5 nm, exhibiting a highly developed microporous and mesoporous structure. The microscopic surface morphology of the catalyst material is shown in the figure. Figure 3 and Figure 4As shown in the figure, the active metal particles on the material surface have a particle size of 5-20 nm and an average spacing of over 100 nm, making them less prone to aggregation. The active components exhibit excellent dispersion on the support surface, ensuring good catalytic activity in the catalytic reaction.

[0037] Example 2: Test of active component morphology and surface content.

[0038] A Ce / Mn mixed impregnation solution was prepared using the controlled variable method, maintaining the mass fraction of Mn in the mixed solution at 2 wt%, and varying the Ce content to prepare six different Ce:Mn ratios of 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0. Subsequently, Ce was prepared using the preparation method described in this invention. 0.0 -Mn / AC、Ce 0.2 -Mn / AC、Ce 0.4 -Mn / AC、Ce 0.6 -Mn / AC、Ce 0.8 -Mn / AC and Ce 1.0 Six catalyst materials with different Ce / Mn ratios were prepared using Mn / AC. The structures of these catalyst materials prepared under different ratio conditions were characterized by X-ray diffraction (XRD), and the characterization results are shown below. Figure 5 As shown in the figure, the peak positions and shapes of the diffraction peaks of catalysts with different cerium-manganese ratios are basically consistent. Each sample exhibits sharp characteristic diffraction peaks at 2θ = 24.0° and 49.1°, corresponding to the positions on standard card JCPDS PDF#73-1361, indicating the presence of MnSO4 in the samples. Each sample also exhibits characteristic diffraction peaks at 2θ = 21.7° and 37.9°, corresponding to the positions on standard card JCPDS PDF#12-0141, indicating the presence of MnO in the samples. Furthermore, characteristic diffraction peaks for Mn2O3 and MnO2 were found on JCPDS PDF#41.1442 and JCPDS PDF#42-1169, respectively. These results indicate that metallic manganese has been successfully mounted on the granular activated carbon support. Moreover, during calcination at 400℃, a portion of MnSO4 is converted to MnO. x The desired effect before catalyst preparation was achieved; and the positions of each sample at 2θ=35.2° and 30.3° corresponded to standard cards PDF#04-0711 and PDF#44-1086, respectively, indicating the presence of CeO2 and Ce2O3 in the samples. The absence or undetectable presence of some characteristic peaks may be due to the presence of MnO. x CeO xThe dispersion of the Ce phase in activated carbon leads to a significant decrease in the intensity of the diffraction peaks of cerium oxide as the Ce ratio increases. This indicates that the doping of a small amount of Ce not only has high self-dispersion but also promotes the uniform dispersion of manganese oxide. Therefore, the addition of cerium can reduce the crystallinity of the active component. The surface elemental content test results of the above six catalyst materials are shown in Table 1. As can be seen from the table, the Ce content described in this invention... 0.8 The Mn / AC catalyst exhibits the highest Mn and Ce content on its surface among all six materials. This indicates that Ce... 0.8 The Mn / AC catalyst has the highest content of active components.

[0039] Table 1. Test results of elemental content of different catalysts

[0040]

[0041] Example 3: Experiment on the degradation of acetone by a biochar-supported catalyst with high efficiency in degrading acetone.

[0042] 500 mg of the catalyst material prepared in Example 1 was loaded into a fixed-bed catalytic reactor. Acetone waste gas was mixed and heated in the furnace. The total flow rate of the acetone waste gas was 100 mL / min, and the concentration was 238-714 mg / m³. 3 The reactor temperature range was 130℃~240℃, with a heating rate of 10℃. At each temperature point, the temperature was maintained for 30 min. Based on the acetone concentration at the inlet and outlet of the catalyst bed, the catalytic degradation efficiency of the catalyst for acetone was measured at different temperatures. The results are shown in Table 2. As can be seen from the figure, at a temperature of 180-190℃, the catalytic degradation efficiency of the catalyst for 714 mg / m³ was significantly higher than that for acetone. 3 The degradation rate of acetone can reach about 90%, which significantly reduces the degradation temperature of similar catalysts and saves operating costs.

[0043] Table 2 shows the degradation performance of the prepared catalysts on acetone of different concentrations.

[0044]

[0045] Example 4: Control experiment on the degradation of acetone before and after loading active components onto biomass activated carbon carrier.

[0046] 500 mg of biomass activated carbon carrier and 500 mg of the catalyst material prepared in Example 1 were respectively loaded into a fixed-bed catalytic reactor. Acetone waste gas was mixed and heated in the furnace. The total flow rate of acetone waste gas was 100 mL / min, and the concentration was 238 mg / m³. 3 The reactor temperature ranged from 120℃ to 300℃, with a heating rate of 10℃. Each temperature was held constant for 30 minutes, and the catalytic degradation efficiency of the catalyst for acetone was measured at different temperatures. The results are as follows: Figure 6 As shown, without the active component, acetone degradation on the biomass activated carbon support reaches a degradation temperature of 290 °C with a degradation rate of only about 80%. With the active component, the degradation temperature corresponding to an acetone degradation rate of 80% drops significantly to 170 °C, and above 180 °C, the degradation rate exceeds 90%. This demonstrates that the catalyst can significantly improve the degradation effect on acetone.

[0047] Example 5: Experiment on the rate of acetone degradation by a biochar-supported catalyst for high-efficiency acetone degradation

[0048] 500 mg of the catalyst material prepared in Example 1 was loaded into a fixed-bed catalytic reactor. Acetone waste gas was mixed and heated in the furnace. The total flow rate of the acetone waste gas was 100 mL / min, and the concentration was 238 mg / m³. 3 The reactor temperature was controlled at 180℃, and the relationship between the catalyst's catalytic degradation efficiency of acetone and time was measured. The results showed that when the catalyst concentration was 238 mg / m³, the catalytic degradation efficiency of acetone decreased over time. 3 After the acetone waste gas is introduced into the fixed-bed catalytic reactor, the degradation rate of acetone can reach more than 90% within 15 minutes. The good pore structure enables the rapid diffusion of acetone in the carrier, and the highly dispersed active components can fully contact the acetone, achieving rapid degradation of acetone.

[0049] Example 6: Experiments on the degradation of acetone by biochar-supported catalysts with different Ce / Mn ratios

[0050] Figure 7 The figure shows the result at an acetone concentration of 238 mg / m³. 3 In Example 2, Ce was prepared. 0.0 -Mn / AC、Ce 0.2 -Mn / AC、Ce 0.4 -Mn / AC、Ce 0.6 -Mn / AC and Ce 1.0 The degradation performance of five Mn / AC catalysts on acetone. Comparison. Figure 6 Under the same conditions, Ce 0.8 The degradation performance of acetone by -Mn / AC can be seen in Ce. 0.8 -Mn / AC achieved 50% and 90% degradation rates of acetone at temperatures of 160℃ and 180℃, respectively, significantly lower than the other five catalysts, indicating that Ce... 0.8 -Mn / AC exhibits significantly better catalytic degradation performance for acetone than other materials.

[0051] Example 7: Stability Experiment of Acetone Degradation by Biochar-Supported Catalyst for High-Efficiency Acetone Degradation

[0052] 500 mg of catalyst material was loaded into a fixed-bed catalytic reactor. Acetone waste gas was mixed and heated in the furnace. The total flow rate of the acetone waste gas was 100 mL / min, and the concentration was 238 mg / m³. 3 The reactor temperature was controlled at 180℃, and the catalytic degradation efficiency of the catalyst for acetone was continuously measured. The results are as follows: Figure 8 As shown in the figure, during approximately 1500 hours of continuous experimentation, the catalyst maintained a degradation rate of around 80% for acetone. This indicates that the catalyst has a long service life and stable performance in acetone degradation.

Claims

1. A method for efficient thermocatalytic degradation of acetone in waste gas, characterized in that, The process involves catalytically degrading acetone-containing waste gas in a fixed-bed reactor filled with activated carbon catalyst to remove acetone. The reaction temperature is 170-225℃, and the reaction time is 10-30 minutes. The active component of the activated carbon catalyst includes MnO. x X = 1, 1.5, or 2.0, CeO2 and Ce2O3; which are prepared by the following method: (1) Prepare a mixed solution of manganese metal salt and cerium metal salt as a precursor solution; (2) Impregnate the activated carbon support with a precursor solution so that metal ions are adsorbed into the pores of the activated carbon support; (3) Take out the impregnated activated carbon sample, air dry it, and then vacuum dry it; (4) Under an inert atmosphere, the vacuum-dried activated carbon sample is calcined at high temperature in a tube furnace to obtain the supported activated carbon catalyst; wherein: In step (1), the manganese metal salt in the precursor solution is a divalent manganese salt and the cerium metal salt is a trivalent cerium salt; the mass ratio of cerium to manganese is 0.2:1 to 1:

1.

2. The method according to claim 1, characterized in that, In the catalytic degradation reaction, the space velocity is 10000-20000 mL / g·h, and the concentration of acetone in the waste gas is 100-2000 mg / m³. 3 The exhaust gas flow rate is between 50-500 mL / min.

3. The method according to claim 1, characterized in that, In step (1), the mass fraction of manganese in the precursor solution is 1.5-2.5%.

4. The method according to claim 1, characterized in that, In step (1), the mass ratio of cerium to manganese in the precursor solution is 0.8:

1.

5. The method according to claim 1, characterized in that, In step (2), the activated carbon carrier is biomass activated carbon with a specific surface area of ​​900-1400 m². 2 / g, total pore volume ≥0.7cm³ 3 / g, micropore volume ≥0.15 cm³ 3 / g, the mass-volume ratio of activated carbon carrier and precursor solution is 1:5~1:20g / mL, first ultrasonically impregnate at room temperature for 50min-2h, and then heat at a water bath temperature of 50-70℃ for 3-5h.

6. The method according to claim 1, characterized in that, In step (3), the vacuum drying temperature is 100-120℃ and the vacuum drying time is 2-10h.

7. The method according to claim 1, characterized in that, In step (4), the roasting temperature is 350-450℃ and the roasting time is 2-5h.

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