A co-removal of NO x and CO catalyst and its preparation method and application

Abstract

This invention relates to a method for co-removing NO x A CO catalyst, its preparation method, and its application are disclosed. The catalyst comprises activated carbon as a support, and metallic manganese, metallic cerium, and metallic cobalt supported on the support. The preparation method includes the following steps: dissolving manganese-containing inorganic salts, cerium-containing inorganic salts, and cobalt-containing inorganic salts in water according to atomic ratio to obtain a precursor solution; completely impregnating the activated carbon in the precursor solution, then removing and drying it; and heat-treating the dried support under an inert gas atmosphere to obtain a co-removing NO catalyst. x And a CO catalyst. This catalyst is used for flue gas treatment. Compared with the prior art, this invention does not contain precious metals and balances CO oxidation and NO oxidation. x Reduce NO x Removing heat can help remove harmful pollutants from flue gas.

Description

Technical Field

[0001] This invention relates to the field of flue gas purification, specifically to a method for co-removing NO. x CO catalysts, their preparation methods, and applications. Background Technology

[0002] With the acceleration of industrialization, air pollution has become a major environmental problem. Human factors are the main cause of air pollution, including fuel combustion, industrial production, transportation, and agricultural activities. Among many air pollutants, nitrogen oxides (NOx) are... x Nitrogen oxides (NOx) are among the major air pollutants that cause a range of environmental problems, such as photochemical smog, acid rain, and ozone layer depletion. Global source attribute studies indicate that the petrochemical industry is a major contributor to NOx emissions.

[0003] More importantly, nitrogen oxides can enter the human body through inhalation, skin contact, and ingestion, seriously endangering human health. Exposure to nitrogen dioxide (NO2) for approximately 30-60 minutes can lead to chronic pulmonary edema and worsen respiratory symptoms in asthmatic individuals. Due to the multiple hazards of nitrogen oxides to human health and the environment, controlling nitrogen oxide emissions has become one of the major problems urgently needing to be solved in human societal development. Currently, NO... x Control technologies mainly include combustion control technology and combustion aftertreatment technology. Among combustion aftertreatment technologies, selective catalytic reduction (SCR) technology has been widely used and recognized by many experts and scholars.

[0004] Most currently used CO oxidation catalysts are based on noble metals (Pt, Pd, and Rh), which exhibit high activity for flue gas oxidation but are expensive. Therefore, developing noble metal-free CO oxidation catalysts is of great significance.

[0005] Manganese-based catalysts exhibit good activity at low temperatures below 160 °C and have a wider operating temperature window. Ce-based catalysts significantly improve the NH3-SCR performance of NO due to their large oxygen storage capacity and unique redox coupling of Ce. 3+ / Ce 4+ It exhibits significant SO2 tolerance and N2 selectivity. Carbon-supported Mn-Ce mixed oxide catalysts have been reported to possess good low-temperature denitrification activity. Activated carbon, due to its porous nature, has a large surface area and pore volume. The excellent pore structure is considered beneficial for the uniform dispersion of active components on the catalyst.

[0006] Patent 114669286A discloses a platinum-based catalyst for CO oxidation, its preparation method, and its application. This catalyst comprises a TiO2-SiO2 composite oxide support and Pt, fully leveraging the synergistic effect between the support and the active component. This increases the size of the active component and improves sulfur resistance. Due to the presence of TiO2 in the support, the platinum-based catalyst exhibits good catalytic performance under aqueous conditions. The active component Pt is loaded onto the support via an impregnation method, which is simple, easy to operate, and has good reproducibility. However, this catalyst still uses the precious metal Pt, resulting in a relatively high price, which is not conducive to large-scale application.

[0007] Patent CN114192158A discloses a CO and NO x A method for preparing a synergistic removal catalyst involves loading copper, manganese, iron, and cerium ions onto the surface of a vanadium-tungsten-titanium catalyst via a spraying process. Utilizing the reducing properties of NH3 and CO, the catalyst effectively removes NO. x At the same time, it also has a strong effect on removing CO from flue gas and lowers the reaction temperature range. However, the volatilization of vanadium-tungsten catalysts at high temperatures is harmful to human health, so it is not suitable for modern green chemical enterprises.

[0008] In engineering practice, not only is denitrification necessary, but a large amount of CO also needs to be removed from sintering machines or coke oven gas. Therefore, the preparation of a bifunctional catalyst has become a technology with broad application prospects. Summary of the Invention

[0009] The purpose of this invention is to overcome at least one of the defects of the prior art and provide a method that is free of precious metals and simultaneously addresses CO oxidation and NO oxidation. x Reduce NO x Co-removal of NO at removal temperature x CO catalysts, their preparation methods, and applications. They can synergistically remove harmful pollutants from flue gas.

[0010] The objective of this invention can be achieved through the following technical solutions:

[0011] The inventors understand that precious metal catalysts are commonly used as the main catalysts for CO oxidation, but their high production cost hinders large-scale industrial applications. Based on their experience in denitrification catalysts, this invention provides an activated carbon catalyst that does not contain precious metals. Further testing revealed that this catalyst exhibits excellent co-removal of CO and NO. x Performance-wise, the specific solution is as follows:

[0012] A co-removal of NO xThe catalyst comprises activated carbon as a support, and manganese, cerium, and cobalt supported on the support. The activated carbon support used is typically obtained industrially through simple extrusion molding, possessing a good pore structure and a simple preparation process.

[0013] Furthermore, the atomic ratios of manganese, cerium, and cobalt are Mn:Ce = (0.5-4):1 and Mn:Co = (0.5-4):1, respectively. The mass of manganese oxide accounts for 2-5% of the activated carbon mass. This mixed oxide of the above metal combination has a very good effect on CO oxidation and can also lower the temperature range of NO removal reaction.

[0014] Manganese-based metals are known to have attracted widespread attention in the field of catalysis due to their excellent activity. They possess abundant Lewis acidic centers and multiple oxidation states, making them excellent electron donors in the CO oxidation reaction. Furthermore, the addition of rare earth metals can promote the dispersion of manganese-based metals on the catalyst surface, and the strong interaction between rare earth metals and manganese-based metals enhances electron transfer activity, thereby lowering the temperature range for NO removal.

[0015] A method for co-removing NO as described above x A method for preparing a CO catalyst, the method comprising the following steps:

[0016] According to the atomic ratio, manganese-containing inorganic salts, cerium-containing inorganic salts, and cobalt-containing inorganic salts are dissolved in water to obtain precursor solutions;

[0017] The activated carbon was completely immersed in the precursor solution, then removed and dried.

[0018] The dried support was heat-treated in an inert gas atmosphere to obtain a co-removed NO. x and CO catalyst.

[0019] Furthermore, the manganese-containing inorganic salts include manganese acetate, manganese nitrate, or manganese sulfate; the cerium-containing inorganic salts include cerium nitrate, cerium sulfate, or cerium chloride; and the cobalt-containing inorganic salts include cobalt acetate, cobalt chloride, or cobalt nitrate.

[0020] Furthermore, the manganese ion mass concentration in the precursor solution is 2.5-3.5%.

[0021] Furthermore, the carrier is dried in an oven or in a freezer after impregnation.

[0022] Furthermore, the specific process of heat treatment is as follows: the dried carrier is heated to 300-500℃ and kept at a constant temperature in an inert gas atmosphere, and then cooled to a constant temperature below 120-200℃ in an air atmosphere.

[0023] A method for co-removing NO as described abovex And the application of CO catalysts, which are used for flue gas treatment of sintering machines or coke oven gas.

[0024] Furthermore, the temperature range for flue gas treatment is 60-170℃.

[0025] Furthermore, the temperature range for flue gas treatment is 120-170℃, preferably 160-170℃.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The catalyst used in this invention is an activated carbon catalyst, which is simple to prepare and the impregnation method for loading active metals is simple and conducive to large-scale industrial production.

[0028] (2) The metals used in this invention do not contain precious metals, are inexpensive, and are pollution-free;

[0029] (3) This invention takes into account both CO oxidation and NO oxidation. x The restoration achieves effective removal with dual functions, reducing the actual cost of industrial equipment;

[0030] (4) This invention can be used for flue gas removal in power plant boilers, industrial boilers, gas boilers, internal combustion engines, chemical plants and steel mills, etc., and has the characteristics of wide application range, broad market and high economic benefits. Attached Figure Description

[0031] Figure 1 The NO removal efficiency of the catalyst in Example 3 is shown.

[0032] Figure 2 The CO removal efficiency of the catalyst in Example 3 is shown. Detailed Implementation

[0033] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0034] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation 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.

[0035] 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 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.

[0036] 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.

[0037] A co-removal of NO x This paper describes a CO catalyst, its preparation method, and its application. The catalyst uses activated carbon as a support. A precursor mixture is prepared by uniformly mixing manganese-containing, cerium-containing, and cobalt-containing inorganic salts in deionized water. The support is then impregnated with the mixture, removed, dried, and subsequently calcined. The metal ion ratio is Mn:Ce = 0.5-4 and Mn:Co = 0.5-4.

[0038] The specific steps for preparing the catalyst through impregnation are as follows:

[0039] (1) The mass of manganese-containing inorganic salts, such as manganese acetate, manganese nitrate, or manganese sulfate, converted to manganese oxide accounts for 2-5% of the mass of activated carbon; a certain amount of cerium-containing inorganic salts, such as cerium nitrate, cerium sulfate, or cerium chloride, and a certain amount of cobalt-containing inorganic salts, such as cobalt acetate, cobalt chloride, or cobalt nitrate, are dissolved in 20-40 ml of deionized water and stirred at room temperature to obtain a uniformly mixed precursor solution; in the metal salt solution, the mass concentration of manganese ions is about 3%, and cerium and cobalt are mixed in the corresponding proportion.

[0040] (2) The activated carbon is completely immersed in the precursor solution and then removed. The sample is then dried in an oven or freezer. The carrier is dried in an oven or freezer after immersion. The above immersion and drying operations ensure that the metal ions are uniformly and fully distributed on the surface of the activated carbon.

[0041] (3) After drying, the carrier is kept at a constant temperature of 300-500℃ in an inert gas atmosphere with a certain heating rate, and then kept at a constant temperature below 200℃ in an air atmosphere with a certain heating rate to obtain a co-removed NO. x And CO catalyst. This catalyst is used in flue gas treatment, including but not limited to the treatment of flue gas from sintering machines or coke ovens. It removes NO. x The CO catalyst was placed separately in NO xFlue gas removal tests were conducted in a CO removal and oxidation reactor. Through the examination of flue gas removal efficiency, this invention confirms that the catalyst prepared by the above method can effectively reduce NO. x It has a high removal temperature and also has a good catalytic effect on CO oxidation.

[0042] Example 1

[0043] A co-removal of NO x CO catalysts, their preparation methods, and applications are detailed below:

[0044] (1) Take the inorganic salts of manganese, cerium, and cobalt, and mix them evenly in deionized water in a certain proportion. Cut the purchased activated carbon into shapes that are easy to test the volume, and dry it overnight in an oven or freezer to fully remove its original water absorption.

[0045] (2) Using the equal volume impregnation method, the precursor solution was taken with a dropper and added to the activated carbon until the activated carbon was saturated with water, and then dried to constant weight.

[0046] (3) After drying, the carrier is kept at 500°C under an inert gas atmosphere with a certain heating rate, and then kept at 120°C under an air atmosphere with a certain heating rate to obtain the co-removed NO. x and CO catalyst.

[0047] The catalysts were placed in the CO removal and NO removal processes, respectively. x In the removal reaction apparatus, the concentrations of various gases in the bypass and reaction paths at different temperatures were tested, and the catalytic efficiency was calculated.

[0048] Example 2

[0049] A co-removal of NO x CO catalysts, their preparation methods, and applications are detailed below:

[0050] (1) Take the inorganic salts of manganese and cerium and mix them evenly in deionized water in a certain proportion.

[0051] (2) The activated carbon support was immersed in the precursor solution, removed and dried to constant weight. The dried support was then immersed in a cobalt ion-containing solution with a cobalt mass fraction of 5%, removed and dried to constant weight.

[0052] (3) After drying, the carrier is kept at 400°C under an inert gas atmosphere with a certain heating rate, and then kept at 140°C under an air atmosphere with a certain heating rate to obtain the co-removed NO. x and CO catalyst.

[0053] The catalysts were placed in the CO removal and NO removal processes, respectively.x In the removal reaction apparatus, the concentrations of various gases in the bypass and reaction paths at different temperatures were tested, and the catalytic efficiency was calculated.

[0054] Example 3

[0055] A co-removal of NO x CO catalysts, their preparation methods, and applications are detailed below:

[0056] (1) Take 5.7g of manganese nitrate, cerium chloride and cobalt nitrate and mix them evenly in 30ml of deionized water with an atomic ratio of manganese:cerium:cobalt = 2:2:0.5.

[0057] (2) Activated carbon (specific surface area > 1200 m²) 2 Cut 6g of the sample into a shape suitable for testing volume and dry it overnight in an oven or freezer to fully remove its original water absorption.

[0058] (3) The activated carbon carrier dried in an oven at 100℃ is immersed in the precursor solution, and then dried in an oven at 100℃ for 6 hours.

[0059] (4) After drying, the carrier is heated to 400°C at a rate of 2°C per minute in an inert gas atmosphere, and held at 400°C until it cools to room temperature. Then, the atmosphere is switched to air, and the temperature is raised to 140°C at a rate of 2°C per minute and held for 2 hours to obtain the co-removed NO. x And CO catalyst. This heat treatment method facilitates the full distribution of metal on the catalyst surface, and the metal is transformed into metal oxides with different valence states during the process. Metals with different valence states will play an important role in electron transfer in the gas removal reaction.

[0060] The catalysts were placed in the CO removal and NO removal processes, respectively. x In the removal reaction apparatus, the concentrations of various gases in the bypass and reaction paths at different temperatures were tested, and the catalytic efficiency was calculated.

[0061] In the CO removal unit, the gas composition is CO and air, with a total flow rate of 100 ml / min, and the CO concentration is 2600 ppm. In the NO removal unit, the gas composition is nitric oxide, ammonia, air, and nitrogen, with a total flow rate of 500 ml, and the concentrations of NO and NH3 are both 500 ppm. The inlet and outlet CO and NO concentrations are continuously monitored online using a VARIOPLUS enhanced flue gas analyzer (MRU). The catalytic efficiency is calculated from the gas conversion rate, specifically as follows:

[0062]

[0063] In the formula, CO in This indicates the CO concentration at the reactor inlet, in ppmv; CO outThis indicates the CO concentration at the reactor outlet, in ppmv.

[0064]

[0065] In the formula, NO in This indicates the NO concentration at the reactor inlet, in ppmv; NO out This indicates the NO concentration at the reactor outlet, in ppmv.

[0066] The gas removal efficiency of the catalyst described in this embodiment is as follows: Figure 1 , Figure 2 ,Depend on Figure 1 It can be seen that the catalyst's NO catalytic efficiency reaches over 90% at 160℃, achieving low-temperature NO removal; and from Figure 2 It can be seen that at 170℃, the catalyst has a CO removal efficiency of over 50%, indicating that the catalyst has good CO catalytic oxidation ability.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for co-removing NO x The method for preparing CO catalyst is characterized by, The catalyst comprises activated carbon as a support, and manganese, cerium, and cobalt supported on the support; the atomic ratio of manganese, cerium, and cobalt is Mn:Ce=(0.5-4):1, Mn:Co=(0.5-4):1, and the mass of manganese, converted to manganese oxide, accounts for 2-5% of the mass of activated carbon. The method includes the following steps: According to the atomic ratio, manganese-containing inorganic salts, cerium-containing inorganic salts, and cobalt-containing inorganic salts are dissolved in water to obtain precursor solutions; The activated carbon was completely immersed in the precursor solution, then removed and dried. The dried support was heated to 300-500℃ and held at that temperature under an inert gas atmosphere, then cooled to below 200℃ and held at that temperature under an air atmosphere to obtain a nitrogen-removed substrate. x and CO catalyst.

2. A method for co-removing NO according to claim 1 x The method for preparing CO catalyst is characterized by, The manganese-containing inorganic salts include manganese nitrate or manganese sulfate, the cerium-containing inorganic salts include cerium nitrate, cerium sulfate or cerium chloride, and the cobalt-containing inorganic salts include cobalt chloride or cobalt nitrate.

3. A method for co-removing NO according to claim 1 x The method for preparing CO catalyst is characterized by, The precursor solution contains 2.5-3.5% manganese ions by mass.

4. A method for co-removing NO according to claim 1 x The method for preparing CO catalyst is characterized by, The carrier is dried in an oven or in a freezer after impregnation.

5. A co-removing NO preparation according to any one of claims 1 to 4 x The application of CO catalysts is characterized by, This catalyst is used for flue gas treatment.

6. The application according to claim 5, characterized in that, This catalyst is used for flue gas treatment of sintering machines or coke oven gas.

7. The application according to claim 5, characterized in that, The temperature range for flue gas treatment is 60-170℃.

8. The application according to claim 7, characterized in that, The temperature range for flue gas treatment is 120-170℃.

9. The application according to claim 7, characterized in that, The temperature range for flue gas treatment is 160-170℃.

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