Catalyst for treating malodorous waste gas of sewage plant and preparation method of catalyst

Abstract

The invention relates to a catalyst for sewage plant malodorous waste gas treatment and a preparation method thereof, and the catalyst is prepared by loading a metal oxide as an active component on a carrier with a confinement structure through a chemical precipitation assisted in-situ loading method. The catalyst disclosed by the invention has the advantages of excellent performance, cheap and easily available raw materials, low requirements on synthesis equipment, extremely strong heavy metal ion poisoning resistance and the like, and can be used for catalytic removal treatment of nitrogen oxides and volatile organic pollutants in waste gas generated by a sewage treatment plant.

Description

Technical Field

[0001] This invention belongs to the field of waste gas treatment technology, and specifically relates to a catalyst for treating odorous waste gas from sewage treatment plants and its preparation method. Background Technology

[0002] Wastewater treatment plants, as crucial environmental infrastructure, play an irreplaceable role in improving regional water quality. However, the wastewater treatment process inevitably generates byproducts, primarily odorous gases produced by anaerobic reactions. Multiple process units within the wastewater treatment system can become sources of odor: screens in the pretreatment stage if screenings are not cleaned promptly; anaerobic-anoxic tanks in the biological treatment stage during biochemical reactions; and sludge tanks in the sludge treatment system where accumulated sludge undergoes anaerobic decomposition. These odorous substances not only have low threshold values, negatively impacting the lives of surrounding residents, but also harm the environment. NOx is a significant odor hazard. x Methanethiol is a major precursor to environmental problems such as acid rain, photochemical smog, and haze, seriously threatening ecosystems and human health. As a volatile organic compound (VOC), methanethiol is a typical sulfur-containing pollutant that can cause severe irritation to the eyes, skin, and respiratory system. Its delayed effects, strong irritation, wide-ranging impact, and high toxicity have drawn significant attention. Therefore, odor from wastewater treatment plants has been included as an important aspect of industrial waste gas pollution control. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a catalyst for the treatment of odorous waste gas in sewage treatment plants and a method for preparing the same, wherein the catalyst can maintain excellent activity under heavy metal poisoning.

[0004] This invention provides a catalyst for treating odorous waste gas from wastewater treatment plants. The catalyst is prepared by chemical precipitation-assisted in-situ loading of a metal oxide as the active component on a carrier with a confined structure.

[0005] Preferably, the carrier with the confined structure is a titanium dioxide nanotube.

[0006] Preferably, the metal oxide is an oxide of at least two of the following metal elements: copper, cerium, iron, manganese, cobalt, and nickel.

[0007] This invention also provides a method for preparing a catalyst for treating odorous waste gas from wastewater treatment plants, comprising the following steps:

[0008] (1) Titanium dioxide nanotubes were prepared by hydrothermal method as carriers with confined structures;

[0009] (2) Dissolve the soluble metal salt in water to form a metal salt solution, then mix and stir the metal salt solution, the carrier in step (1) and the molding aid B, dry and grind and then calcine to obtain a catalyst for the treatment of odorous waste gas in sewage treatment plants.

[0010] Preferably, the hydrothermal preparation in step (1) is as follows: titanium dioxide and molding aid A are mixed and stirred and then added to a polytetrafluoroethylene liner tube. A hydrothermal reaction is carried out at 130-150°C. The mixture is taken out and washed with deionized water until neutral. It is then acidified with an acid solution and washed again until neutral. Finally, it is diluted with an ethanol dispersion and dried and ground to obtain the carrier.

[0011] Preferably, the molding aid A is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonia, and urea; the molar ratio of titanium dioxide to molding aid A is 3-5:100.

[0012] Preferably, the acid solution is at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0013] Preferably, the hydrothermal reaction time is 24-48 h.

[0014] Preferably, the soluble metal salt in step (2) is at least two of copper salt, iron salt, manganese salt, cerium salt, cobalt salt, and chromium salt.

[0015] More preferably, the copper salt is any one of copper nitrate, copper acetate, and copper chloride; the iron salt is any one of ferric nitrate, ferric acetate, and ferric chloride; the manganese salt is any one of manganese nitrate, manganese acetate, and manganese chloride; the cerium salt is any one of cerium nitrate, cerium acetate, and cerium chloride; the cobalt salt is any one of cobalt nitrate, cobalt acetate, and cobalt chloride; and the chromium salt is any one of chromium nitrate, chromium acetate, and chromium chloride.

[0016] Preferably, the molding aid B in step (2) is at least one of ammonium carbonate, ammonium bicarbonate, and ammonia.

[0017] Preferably, the mixing and stirring in step (2) lasts for at least 0.5 h.

[0018] Preferably, the calcination in step (2) specifically involves calcining at 400-500℃ for 2-5 hours at a heating rate of 2-10℃ / min.

[0019] This invention constructs a support with a confined structure, which increases the specific surface area of ​​the catalyst, promotes the dispersion of active components and pollutants, and simultaneously confines the two active components inside and outside the support, thereby achieving efficient and synergistic catalytic purification of NO. x and volatile organic pollutants.

[0020] Beneficial effects

[0021] The catalyst of this invention has the advantages of excellent performance, inexpensive and readily available raw materials, low requirements for synthesis equipment, and strong resistance to heavy metal ion poisoning. It can be used for the catalytic removal of nitrogen oxides and volatile organic pollutants in the waste gas generated by sewage treatment plants. Attached Figure Description

[0022] Figure 1 This is a high-magnification TEM image of the catalyst in Example 2.

[0023] Figure 2 This is a synergistic activity diagram of the catalyst in Example 2.

[0024] Figure 3 The graph shows the resistance of the catalyst to heavy metal ion poisoning in Example 2. Detailed Implementation

[0025] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0026] The titanium dioxide used in the following examples is TiO2 P25.

[0027] Example 1

[0028] This embodiment provides a method for preparing a catalyst for treating odorous waste gas from a wastewater treatment plant, comprising the following steps:

[0029] a. Preparation of the support: 1 g of titanium dioxide was added to a polytetrafluoroethylene-lined tube, followed by 40 mL of 10 mol / L NaOH solution. After stirring for 30 min, the mixture was placed in a hydrothermal reactor and then placed in an oven at 130 ℃ for 24 h. After the reaction, the supernatant alkaline solution was poured into a waste liquid container. The remaining TiO2 nanotube precursor was diluted with deionized water and washed until neutral. Acidification was performed with 0.1 mol / L hydrochloric acid solution for 2 h. After acidification, the supernatant was poured off, and the TiO2 nanotubes were washed with deionized water until neutral. The aqueous component was then diluted five times with ethanol dispersion. The mixture was dried and ground to obtain the TiO2 NTs support.

[0030] b. Preparation of fresh catalyst: Catalyst was prepared by chemical precipitation-assisted in-situ loading: 0.5 g TiO2NTs were slowly stirred in 30 mL of deionized water to obtain solution A. 0.1265 g ferric nitrate and 0.0631 g cerium nitrate were dissolved in 15 mL of deionized water to obtain solution B. 0.5 mol / L (NH4)2CO3 solution was added dropwise to solution A until the pH of the solution reached 9. Then, solution B was added dropwise to solution A while stirring continuously. During this process, (NH4)2CO3 solution was continuously added to maintain the pH of the mixed solution at 9. The solutions were stirred for another 1 h after mixing. The mixed solution was then dried by vacuum rotary evaporation at 60 °C, dried in a vacuum drying oven at 80 °C, and calcined in a muffle furnace at 400 °C for 4 h at a heating rate of 2 °C / min.

[0031] Synergistic removal performance of the catalyst from nitrogen oxides and methanethiol: The catalyst prepared above was granulated to 40-60 mesh and placed in a reactor for activity, CO2 selectivity, and N2 selectivity tests. The reaction temperature was 180-330℃ and the space velocity was 50,000 h⁻¹. -1 Under these conditions, the synergistic removal efficiency remained stable at over 80%. The simulated waste gas contained 5% O2, 500 ppm methanethiol, 500 ppm NO, 500 ppm NH3, and N2 as a dilution gas.

[0032] Test on resistance to heavy metal poisoning:

[0033] A simulated poisoned catalyst was prepared by impregnation of 1 wt% PbO onto the catalyst and calcined at 400 °C for 4 h. Its synergistic removal performance of nitrogen oxides and methanethiols was then tested at reaction temperatures of 180–330 °C and a space velocity of 50,000 h⁻¹. -1 Under these conditions, the synergistic removal efficiency remains stable at over 85%.

[0034] A simulated poisoned catalyst was prepared by impregnation of 1 wt% ZnO onto the catalyst and calcined at 400 °C for 4 h. Its synergistic removal performance of nitrogen oxides and methanethiols was then tested at reaction temperatures of 180–330 °C and a space velocity of 50,000 h⁻¹. -1 Under these conditions, the synergistic removal efficiency remains stable at over 85%.

[0035] The catalyst in this embodiment is a high-performance catalyst capable of synergistically removing nitrogen oxides and methanethiols. This catalyst fully utilizes the structural characteristics of nanotubes, significantly reducing the impact of heavy metal poisoning on the catalyst's acidity and redox capacity, thereby improving the catalyst's heavy metal poisoning effect. While ensuring excellent synergistic catalytic purification, the catalyst's resistance to heavy metals is also enhanced.

[0036] Example 2

[0037] The difference from Example 1 is that 0.1265g of ferric nitrate and 0.0883g of cerium nitrate were dissolved in 15 mL of deionized water to obtain solution B, and the rest was the same as in Example 1. Figure 1 This is a high-magnification TEM image of the catalyst, from Figure 1 It can be seen that the presence of iron and cerium did not change the structure of TiO2 nanotubes, and Fe2O3 and CeO2 were highly dispersed inside and outside the TiO2 nanotubes.

[0038] Synergistic removal performance of the catalyst from nitrogen oxides and methanethiol: The catalyst prepared above was granulated to 40-60 mesh and placed in a reactor for activity, CO2 selectivity, and N2 selectivity tests. The reaction temperature was 180-330℃ and the space velocity was 50,000 h⁻¹. -1 Under the following conditions, such as Figure 2 As shown, the synergistic removal efficiency remained stable at over 85%. The simulated waste gas contained 5% O2, 500 ppm methanethiol, 500 ppm NO, 500 ppm NH3, and N2 as dilution gas.

[0039] Test on resistance to heavy metal poisoning:

[0040] A simulated poisoned catalyst was prepared by impregnation of 1 wt% PbO onto the catalyst and calcined at 400 °C for 4 h. Its synergistic removal performance of nitrogen oxides and methanethiols was then tested at reaction temperatures of 180–330 °C and a space velocity of 50,000 h⁻¹. -1 Under the following conditions, such as Figure 3 As shown, the synergistic removal efficiency remains stable at over 90%.

[0041] A simulated poisoned catalyst was prepared by impregnation of 1 wt% ZnO onto the catalyst and calcined at 400 °C for 4 h. Its synergistic removal performance of nitrogen oxides and methanethiols was then tested at reaction temperatures of 180–330 °C and a space velocity of 50,000 h⁻¹. -1 Under these conditions, the synergistic removal efficiency remains stable at over 90%.

[0042] Example 3

[0043] The difference from Example 1 is that 0.1265g of ferric nitrate and 0.1261g of cerium nitrate were dissolved in 15 mL of deionized water to obtain solution B, and the rest was the same as in Example 1.

[0044] Synergistic removal performance of the catalyst from nitrogen oxides and methanethiol: The catalyst prepared above was granulated to 40-60 mesh and placed in a reactor for activity, CO2 selectivity, and N2 selectivity tests. The reaction temperature was 180-330℃ and the space velocity was 50,000 h⁻¹. -1Under these conditions, the synergistic removal efficiency remained stable at over 75%. The simulated waste gas contained 5% O2, 500 ppm methanethiol, 500 ppm NO, 500 ppm NH3, and N2 as a dilution gas.

[0045] Test on resistance to heavy metal poisoning:

[0046] A simulated poisoned catalyst was prepared by impregnation of 1 wt% PbO onto the catalyst and calcined at 400 °C for 4 h. Its synergistic removal performance of nitrogen oxides and methanethiols was then tested at reaction temperatures of 180–330 °C and a space velocity of 50,000 h⁻¹. -1 Under these conditions, the synergistic removal efficiency remains stable at over 80%.

[0047] A simulated poisoned catalyst was prepared by impregnation of 1 wt% ZnO onto the catalyst and calcined at 400 °C for 4 h. Its synergistic removal performance of nitrogen oxides and methanethiols was then tested at reaction temperatures of 180–330 °C and a space velocity of 50,000 h⁻¹. -1 Under these conditions, the synergistic removal efficiency remains stable at over 80%.

Claims

1. A catalyst for the treatment of odorous waste gas from sewage plants, characterized in that: The catalyst is prepared by chemical precipitation assisted in-situ loading method, and the catalyst is loaded with a carrier with limited domain structure as an active component of metal oxide.

2. The catalyst of claim 1, wherein: The carrier with limited domain structure is titanium dioxide nanotube.

3. The catalyst of claim 1, wherein: The metal oxide is an oxide of at least two metal elements selected from copper, cerium, iron, manganese, cobalt and nickel.

4. A preparation method of a catalyst for sewage plant odor waste gas treatment, comprising the following steps: (1) preparing titanium dioxide nanotube as a carrier with limited domain structure by a hydrothermal method; (2) dissolving soluble metal salt in water to form a metal salt solution, then mixing and stirring the metal salt solution, the carrier in step (1) and a molding aid B, drying and grinding, and then calcining to obtain the catalyst for sewage plant odor waste gas treatment.

5. The method of claim 4, wherein: The hydrothermal method in step (1) is specifically as follows: mixing and stirring titanium dioxide and a molding aid A, then adding into a polytetrafluoroethylene lined tube, performing hydrothermal reaction at 130-150 ℃, taking out, washing with deionized water until neutral, acidizing with an acid solution, then washing until neutral, diluting with an ethanol dispersion, drying and grinding to obtain the carrier.

6. The method of claim 5, wherein: The molding aid A is at least one selected from sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonia and urea; and the molar ratio of the titanium dioxide to the molding aid A is 3-5:

100.

7. The method of claim 5, wherein: The acid solution is at least one selected from hydrochloric acid, sulfuric acid and nitric acid.

8. The method of claim 4, wherein: The soluble metal salt in step (2) is at least two selected from copper salt, iron salt, manganese salt, cerium salt, cobalt salt and chromium salt.

9. The method of claim 4, wherein: The molding aid B in step (2) is at least one selected from ammonium carbonate, ammonium bicarbonate and ammonia.

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