A catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion, its preparation method and application

Abstract

This invention discloses a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion, its preparation method, and its application, belonging to the field of air pollution control. The catalyst is a composite catalyst composed of a catalytic combustion active component and a nitrogen oxide selective reduction component, used for the selective reduction of nitrogen-containing organic compounds through catalytic combustion. The catalytic combustion active component is a copper-manganese metal oxide; the nitrogen oxide selective reduction component is a copper molecular sieve. The catalytic combustion active component and the nitrogen oxide selective reduction component are mechanically mixed to obtain a composite catalyst capable of selectively treating nitrogen-containing organic compounds. This invention effectively solves the problem of excessive nitrogen oxide byproducts when conventional VOCs catalysts treat nitrogen-containing organic waste gas, and is applicable to the treatment of nitrogen-containing organic waste gas in industries such as leather making, PRA membranes, PU gloves, and lithium batteries.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control, and relates to a catalytic combustion catalyst, particularly a catalytic combustion selective reduction catalyst for nitrogen-containing organic compounds, its preparation method, and its application. Background Technology

[0002] Nitrogen oxides (NOx) are pollutants that have a significant impact on the environment and human health. Combustion of nitrogen-containing organic compounds is one of the main pathways for NOx generation. In the field of industrial VOCs treatment, important industries such as leather making, mobile phone plastic film production, polyurethane gloves, and lithium batteries use large amounts of nitrogen-containing organic compounds such as dimethylformamide (DMF), dimethylacetamide (DMAC), and N,N-dimethylpyrrolidone as solvents. Catalytic combustion is the mainstream treatment process for industrial volatile organic compounds. Conventional VOCs treatment catalysts can oxidize nitrogen-containing organic compounds, but the oxidation products contain a large amount of NOx byproducts, which has become an important factor restricting the achievement of emission standards.

[0003] While industrial methods for NOx treatment, such as SCR (Selective Catalytic Reduction) and SNCR (Selective Non-Catalytic Reduction), are relatively mature, they require auxiliary reducing agents such as NH3. Adding new NOx reprocessing equipment increases the complexity of the system process and raises environmental investment and operating costs. Developing catalysts for the selective reduction of nitrogen-containing organic compounds through catalytic combustion, based on conventional VOCs catalysts, to reduce NOx generation is a challenging problem in the treatment of nitrogen-containing organic waste gas. Summary of the Invention

[0004] To address the problem of NOx exceeding standards during the treatment of nitrogen-containing organic waste gas in the field of industrial VOCs treatment, this invention provides a catalyst for selective reduction of nitrogen-containing organic compounds through catalytic combustion, its preparation method, and its application. The catalyst has a simple synthesis method and exhibits excellent catalytic selectivity within the temperature range of 200–400°C. It is suitable for the catalytic combustion treatment of nitrogen-containing organic waste gas in industries such as leather making, PRA membranes, PU gloves, and lithium batteries.

[0005] To achieve the above objectives, the present invention provides a catalyst for the selective reduction of nitrogen-containing organic compounds by catalytic combustion, characterized in that: the catalyst is a composite catalyst composed of a catalytic combustion active component and a nitrogen oxide selective reduction component, used for the selective reduction of nitrogen-containing organic compounds by catalytic combustion; the catalytic combustion active component is a copper-manganese metal oxide; the nitrogen oxide selective reduction component is a copper molecular sieve; the catalytic combustion active component and the nitrogen oxide selective reduction component are mechanically mixed to obtain a composite catalyst capable of selectively treating nitrogen-containing organic compounds; the mass ratio of the catalytic combustion active component to the nitrogen oxide selective reduction component is 1:1 to 9.

[0006] Furthermore, the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion provided by the present invention may also have the following characteristics: wherein the copper-manganese metal oxide is prepared by co-precipitation method; and the copper molecular sieve is prepared by solid-phase ion exchange method.

[0007] Furthermore, the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion provided by the present invention may also have the following characteristics: wherein the preparation method of the copper-manganese metal oxide is as follows: dissolving a copper source and a manganese source in deionized water to obtain a solution, adjusting the pH of the solution to alkaline to obtain a suspension, filtering to obtain a solid, washing the solid to neutral, and then drying and calcining to obtain the copper-manganese metal oxide; wherein the copper source is copper nitrate trihydrate and the manganese source is manganese acetate tetrahydrate; the molar ratio of copper nitrate trihydrate to manganese acetate tetrahydrate is 5-30:10-40; the drying temperature is 90-130℃ and the time is 5-14h; the calcination temperature is 400-650℃ and the time is 2-8h.

[0008] Furthermore, the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion provided by the present invention may also have the following characteristics: wherein the preparation method of the copper molecular sieve includes the following steps: Step 1, pre-treating the molecular sieve by heating to obtain a white powder; grinding copper chloride or copper nitrate evenly to obtain uniform copper salt particles; Step 2, performing ion exchange between the molecular sieve and the copper salt by physical grinding to obtain a solid powder; Step 3, calcining the solid powder obtained in Step 2 in a first stage to obtain a solid with uniform color; and then performing a second stage of calcination to obtain the copper molecular sieve.

[0009] Furthermore, the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion provided by the present invention may also have the following characteristics: in step one of the copper molecular sieve preparation method, the silicon-to-aluminum ratio of the molecular sieve is 15-60:1, such as ZSM-5, Y, etc.; the temperature of the heating pretreatment is 400-600℃, and the calcination time is 4-8h.

[0010] Furthermore, the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion provided by the present invention may also have the following feature: wherein, in step two of the method for preparing copper molecular sieves, the percentage of copper salt in the total mass of molecular sieves and copper salts is 2-20 wt%.

[0011] Furthermore, the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion provided by the present invention may also have the following characteristics: in step three of the method for preparing copper molecular sieves, the calcination temperature in the first stage is 150-400℃ and the time is 1-3h; the calcination temperature in the second stage is 350-600℃ and the time is 3-5h.

[0012] The present invention also provides a method for preparing the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion, characterized in that: the catalytic combustion active component and the nitrogen oxide selective reduction component are placed in a shaker for mechanical and physical mixing, thereby obtaining the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion.

[0013] The present invention also provides the application of the catalyst in the catalytic combustion of nitrogen-containing organic waste gas.

[0014] Furthermore, the present invention provides the application of the catalyst in the catalytic combustion of nitrogen-containing organic waste gas, which may also have the following characteristics: the catalyst for selective reduction of nitrogen-containing organic matter by catalytic combustion is added to a fixed bed reactor, the nitrogen-containing organic waste gas to be treated is introduced, and catalytic combustion is carried out at 175-325°C.

[0015] The beneficial effects of this invention are as follows: This invention provides a catalyst for selective reduction of nitrogen-containing organic compounds through catalytic combustion, its preparation method, and its application. It combines VOCs catalytic oxidation and nitrogen oxide reduction technologies to prepare a composite catalyst that simultaneously contains active components for the oxidation of nitrogen-containing organic compounds and active components for the reduction of nitrogen-containing organic compounds. This catalyst achieves catalytic reduction of NOx during catalytic combustion, improves the N2 selectivity of the reaction, and can effectively solve the problem of NOx exceeding the standard during the catalytic combustion process of nitrogen-containing organic waste gas in the field of industrial VOCs treatment.

[0016] Specifically, the composite catalyst not only enables the catalytic combustion and degradation of nitrogen-containing organic matter at lower temperatures, but also utilizes the organic matter itself to catalytically reduce nitrogen oxides without the need for external reducing agents. The primary role of copper-manganese metal oxides is the catalytic combustion of nitrogen-containing organic matter, while the primary role of the copper molecular sieve catalyst is catalytic reduction. During combustion, the copper-manganese metal oxides first adsorb nitrogen-containing organic matter and, under the influence of oxygen vacancies, oxidize and decompose it. Within a certain temperature window, due to the presence of the copper molecular sieve (mainly cuprous ions), it interacts with the copper-manganese metal oxides, forming reducing substances such as CO, hydrocarbons, or some incompletely combusted organic matter during catalytic combustion. These substances synergistically interact with cuprous ions on the molecular sieve, reacting with the generated nitrogen oxides during catalytic combustion to reduce them to nitrogen gas. During the reduction process, these reducing substances are fully utilized to co-reduce with the cuprous ions, leaving only carbon dioxide, water, and nitrogen in the exhaust gas. Simultaneously, the presence of these reducing substances improves the durability of the cuprous ions, further extending the catalyst's lifespan. Furthermore, considering the differences in the silicon-to-aluminum ratio, particle size, copper salt exchange capacity, and temperature window of the molecular sieve, not just any metal oxide can achieve the same effect when combined with a copper molecular sieve. The catalyst of this invention is a composite metal oxide of copper and manganese, with strong interactions between these two metals, resulting in a synergistic effect with the cuprous ions in the molecular sieve. This composite catalyst exhibits high catalytic performance, long service life, completely solves the problem of excessive nitrogen oxide emissions, and has low investment and operating costs.

[0017] Furthermore, a copper-containing molecular sieve catalyst in the form of free cuprous ions was prepared using an improved solid-phase grinding method. It exhibits excellent selective reduction performance of nitrogen oxides generated during the combustion of nitrogen-containing organic waste gas. Compared with the conventional solid-phase method, the improved solid-phase method has no requirements on catalyst particle size and a larger temperature control window, which saves a lot of costs in actual production. It is also simple to operate and conducive to mass production. Attached Figure Description

[0018] Figure 1 This is the XRD pattern of the metal oxide from Example 1;

[0019] Figure 2 This is the XRD pattern of the copper molecular sieve from Example 1;

[0020] Figure 3 This is the XPS spectrum of the copper molecular sieve from Example 1.

[0021] Figure 4 These are schematic diagrams illustrating the degradation of DMAC by catalytic combustion of catalysts in various embodiments and comparative examples;

[0022] Figure 5 This is a schematic diagram illustrating the selectivity of the catalysts used to treat DMAC in the various embodiments and comparative examples for N2.

[0023] Figure 6 This is a schematic diagram of the selectivity of the catalyst for N2 when treating DMAC in Example 3;

[0024] Figure 7 This is a schematic diagram of the degradation of DMAC by catalytic combustion of catalysts in Comparative Examples 1, 3 and 4.

[0025] Figure 8 This is a schematic diagram illustrating the selectivity of catalysts 1, 3, and 4 for N2 when treating DMAC. Detailed Implementation

[0026] The present invention will be further described below with reference to specific embodiments.

[0027] Example 1

[0028] This embodiment provides a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion. It is a composite catalyst composed of copper-manganese metal oxides as the active component for catalytic combustion and copper molecular sieves as the selective reduction component for nitrogen oxides.

[0029] The copper-manganese metal oxide was prepared by a co-precipitation method. Specifically, manganese acetate tetrahydrate and copper nitrate trihydrate were dissolved in deionized water and stirred until homogeneous to obtain a nitrate solution. The molar ratio of copper nitrate trihydrate to manganese acetate tetrahydrate was 10:15. Anhydrous sodium carbonate was dissolved in deionized water to obtain a pH-adjusting buffer solution with a concentration of 1 mol / L. The anhydrous sodium carbonate solution was slowly added dropwise to the nitrate solution while continuously stirring to form a suspension. The pH was adjusted to 11 to obtain the desired suspension, which was then stirred for 40 min. The suspension was filtered and washed with deionized water until neutral to obtain a solid. The solid was then dried in an oven at 110℃ and calcined in a muffle furnace at 500℃ for 4 h to obtain the copper-manganese metal oxide. XRD analysis of the copper-manganese metal oxide yielded the following results: Figure 1 As shown.

[0030] Copper molecular sieves were prepared using a solid-phase ion exchange method, specifically including the following steps: Step 1: Commercially available hydrogen-form molecular sieve HZSM-5 (silicon-to-aluminum ratio 50:1) was pretreated in a muffle furnace at 600℃ for 4 hours to obtain a white powder; copper chloride was ground uniformly to obtain uniform copper salt particles. Step 2: The pretreated molecular sieve and copper chloride were physically ground to obtain a light green solid powder, wherein the copper salt accounted for 15% of the total mass of the molecular sieve and copper salt. Step 3: The ground solid powder was placed in a muffle furnace at 150℃ for the first stage of calcination for 2 hours to obtain a light green solid powder. Then, the obtained solid powder was placed in a muffle furnace at 450℃ for the second stage of calcination for 4 hours to obtain a grayish-white solid powder, which is the copper molecular sieve. XRD and XPS analyses were performed on the copper molecular sieve, and the results are shown in Figures [Figure Number 1] and [Figure Number 2]. Figure 3 As shown.

[0031] The catalyst for the selective reduction of nitrogen-containing organic compounds by catalytic combustion is prepared by mechanically and physically mixing copper manganese metal oxide and copper molecular sieve in a shaker. The mass ratio of copper manganese metal oxide to copper molecular sieve is 1:1.

[0032] Example 2

[0033] This embodiment provides a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion. This catalyst is a composite catalyst composed of copper-manganese metal oxide as the active component for catalytic combustion and copper molecular sieve as the selective reduction component for nitrogen oxides. The preparation methods for the copper-manganese metal oxide and copper molecular sieve are the same as in Example 1.

[0034] The catalyst for the selective reduction of nitrogen-containing organic compounds by catalytic combustion is prepared by mechanically and physically mixing copper manganese metal oxide and copper molecular sieve in a shaker. The mass ratio of copper manganese metal oxide to copper molecular sieve is 1:3.

[0035] Example 3

[0036] This embodiment provides a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion. This catalyst is a composite catalyst composed of copper-manganese metal oxide as the active component for catalytic combustion and copper molecular sieve as the selective reduction component for nitrogen oxides. The preparation methods for the copper-manganese metal oxide and copper molecular sieve are the same as in Example 1.

[0037] The catalyst for the selective reduction of nitrogen-containing organic compounds by catalytic combustion is prepared by mechanically and physically mixing copper manganese metal oxide and copper molecular sieve in a shaker. The mass ratio of copper manganese metal oxide to copper molecular sieve is 1:6.

[0038] Example 4

[0039] This embodiment provides a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion. This catalyst is a composite catalyst composed of copper-manganese metal oxide as the active component for catalytic combustion and copper molecular sieve as the selective reduction component for nitrogen oxides. The preparation methods for the copper-manganese metal oxide and copper molecular sieve are the same as in Example 1.

[0040] The catalyst for the selective reduction of nitrogen-containing organic compounds by catalytic combustion is prepared by mechanically and physically mixing copper manganese metal oxide and copper molecular sieve in a shaker. The mass ratio of copper manganese metal oxide to copper molecular sieve is 1:9.

[0041] Comparative Example 1

[0042] This comparative example provides a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion, specifically a copper-manganese metal oxide, prepared using the same method as in Example 1. Specifically, the mass ratio of the copper-manganese metal oxide to the copper molecular sieve is 1:0.

[0043] Comparative Example 2

[0044] This comparative example provides a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion, specifically a copper molecular sieve, prepared using the same method as in Example 1. That is, the mass ratio of copper manganese metal oxide to copper molecular sieve is 0:1.

[0045] Comparative Example 3

[0046] This comparative example provides a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion, specifically copper oxide. The preparation method is as follows: Copper nitrate trihydrate is dissolved in deionized water and stirred until homogeneous to obtain a copper nitrate solution. Anhydrous sodium carbonate is dissolved in deionized water to obtain a pH-adjusting buffer solution, wherein the concentration of anhydrous sodium carbonate is 1 mol / L. The anhydrous sodium carbonate solution is slowly added dropwise to the copper nitrate solution while continuously stirring to form a suspension. The pH value is adjusted to 11 to obtain the desired suspension, and stirring is continued for 40 min. The suspension is filtered and washed with deionized water until neutral to obtain a solid. The solid is then dried in an oven at 110℃ and calcined in a muffle furnace at 500℃ for 4 h to obtain copper oxide.

[0047] Comparative Example 4

[0048] This comparative example provides a catalyst for the selective reduction of nitrogen-containing organic compounds through catalytic combustion, specifically manganese oxide. The preparation method is as follows: Manganese acetate tetrahydrate is dissolved in deionized water and stirred until homogeneous to obtain a manganese nitrate solution. Anhydrous sodium carbonate is dissolved in deionized water to obtain a pH-adjusting buffer solution, wherein the concentration of anhydrous sodium carbonate is 1 mol / L. The anhydrous sodium carbonate solution is slowly added dropwise to the manganese nitrate solution while continuously stirring to form a suspension. The pH value is adjusted to 11 to obtain the desired suspension, and stirring is continued for 40 min. The suspension is filtered and washed with deionized water until neutral to obtain a solid. The solid is then dried in an oven at 110℃ and calcined in a muffle furnace at 500℃ for 4 h to obtain manganese oxide.

[0049] The catalytic combustion selective reduction catalyst for nitrogen-containing organic compounds provided by this invention is used for the catalytic combustion of nitrogen-containing organic waste gas. The specific method is as follows: the catalytic combustion selective reduction catalyst for nitrogen-containing organic compounds is added to a fixed-bed reactor, and the nitrogen-containing organic waste gas to be treated is introduced, followed by catalytic combustion at 200–400°C. To verify this effect, the degradation reaction of dimethylacetamide (DMAC) containing nitrogen-containing organic compounds was experimentally tested as follows:

[0050] The catalysts of each embodiment and comparative example were added to a fixed-bed microreactor, respectively. Then, a mixture of N2 and O2 (volume ratio 1:9) carrying 5000 ppm DMAC gas was passed through the fixed-bed microreactor at a flow rate of 40 mL / min, and catalytic combustion was carried out at 175–375 °C, wherein the space velocity of the mixed gas was 48000 h⁻¹. -1 The test results are as follows: Figures 4-8 As shown.

[0051] Figure 4 and 5 These are graphs showing the effects of catalytic combustion degradation of DMAC using the catalysts in the various embodiments and Comparative Examples 1 and 2. Figure 4 and 5 It can be seen that copper-manganese metal oxides have high catalytic combustion efficiency for DMAC, but also produce a large amount of nitrogen oxides. While copper-containing molecular sieves exhibit excellent selective reduction performance for nitrogen oxides, their catalytic combustion efficiency for DMAC is low. The composite catalyst formed by combining copper-manganese metal oxides and copper molecular sieves possesses both the ability to degrade nitrogen-containing organic compounds in DMAC and the ability to selectively reduce nitrogen oxides. Furthermore, it can be seen that the catalyst of this invention exhibits higher catalytic efficiency and N2 selectivity within the temperature range of 175–325℃.

[0052] Furthermore, to demonstrate the importance of the window temperature, the catalyst in Example 3 was further tested, and the results are as follows: Figure 6 As shown. From Figure 6It can be seen that when the temperature is further increased to above the window temperature, the N2 selectivity of the reaction decreases significantly. That is, during the window temperature period, the best removal effect on DMAC nitrogen-containing organic matter is achieved under the synergistic interaction of copper manganese metal oxide and copper-containing molecular sieve.

[0053] Figure 7 and 8 This is a graph showing the effect of catalysts in proportions 1, 3, and 4 on the catalytic combustion degradation of DMAC. From... Figure 7 and 8 It can be seen that the copper oxide catalyst and manganese oxide catalyst synthesized by the co-precipitation method under the same conditions are far inferior to the copper-manganese metal oxide catalyst in terms of DMAC degradation and N2 selectivity, which indicates that there is a synergistic effect between copper and manganese oxides.

[0054] The above experiments and results show that the catalytic combustion selective reduction catalyst for nitrogen-containing organic matter provided by this invention has a significant ability to catalytically combust nitrogen-containing organic matter and selectively reduce nitrogen oxides in DMAC waste gas at lower temperatures, which is far superior to commercial catalysts currently on the market. Moreover, this invention is simple to prepare, low in cost, and has huge market potential.

[0055] In this invention, unless otherwise stated, scientific and technical terms used herein have the meanings commonly understood by those skilled in the art. Furthermore, the reagents, materials, and procedures used herein are all widely used in the relevant fields.

[0056] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. The application of a catalyst for selective reduction of nitrogen-containing organic compounds in the catalytic combustion of nitrogen-containing organic waste gas, characterized in that: The catalyst is a composite catalyst composed of a catalytic combustion active component and a nitrogen oxide selective reduction component, used for the selective reduction of nitrogen-containing organic compounds by catalytic combustion; The active component for catalytic combustion is copper-manganese metal oxide; The selective reducing component for nitrogen oxides is a copper molecular sieve; A composite catalyst capable of selectively treating nitrogen-containing organic compounds is obtained by mechanically mixing catalytic combustion active components and nitrogen oxide selective reduction components. The mass ratio of the catalytic combustion active component to the nitrogen oxide selective reduction component is 1:1~9; The copper-manganese metal oxide was prepared by a co-precipitation method; The copper molecular sieve is prepared by a solid-phase ion exchange method, which includes the following steps: Step 1: Pre-treat the molecular sieve by heating to obtain a white powder; grind copper chloride or copper nitrate evenly to obtain uniform copper salt particles; the silicon-to-aluminum ratio of the molecular sieve is 15-60:1; the temperature of the pre-treatment is 400-600℃, and the calcination time is 4-8h. Step 2: The molecular sieve and copper salt are subjected to ion exchange through physical grinding to obtain a solid powder; Step 3: The solid powder obtained in Step 2 is subjected to a first-stage calcination to obtain a solid with uniform color; then a second-stage calcination is carried out to obtain copper molecular sieves; the temperature of the first-stage calcination is 150-400℃ and the time is 1-3h; the temperature of the second-stage calcination is 350-600℃ and the time is 3-5h.

2. The application of the catalyst according to claim 1 in the catalytic combustion of nitrogen-containing organic waste gas, characterized in that: in, The preparation method of the copper-manganese metal oxide is as follows: copper source and manganese source are dissolved in deionized water to obtain a solution, the pH value of the solution is adjusted to alkaline to obtain a suspension, the solid is obtained by filtration, the solid is washed to neutral and then dried and calcined to obtain copper-manganese metal oxide. The copper source is copper nitrate trihydrate, and the manganese source is manganese acetate tetrahydrate; the molar ratio of copper nitrate trihydrate to manganese acetate tetrahydrate is 5-30:10-40. The drying temperature is 90–130℃, and the time is 5–14 h; The calcination temperature is 400–650 °C, and the time is 2–8 h.

3. The application of the catalyst according to claim 1 in the catalytic combustion of nitrogen-containing organic waste gas, characterized in that: in, In step two of the copper molecular sieve preparation method, the percentage of copper salt in the total mass of the molecular sieve and copper salt is 2-20 wt%.

4. The application of the catalyst according to claim 1 in the catalytic combustion of nitrogen-containing organic waste gas, characterized in that: The preparation method of the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion is as follows: the active component for catalytic combustion and the selective reduction component for nitrogen oxides are placed in a shaker and mechanically mixed to obtain the catalyst for selective reduction of nitrogen-containing organic compounds by catalytic combustion.

5. The application of the catalyst according to claim 1 in the catalytic combustion of nitrogen-containing organic waste gas, characterized in that: The catalyst for selective reduction of nitrogen-containing organic matter through catalytic combustion is added to a fixed-bed reactor, and the nitrogen-containing organic waste gas to be treated is introduced and subjected to catalytic combustion at 175~325℃.

Images