Mn-based denitration catalyst for low-temperature flue gas as well as preparation method and application of Mn-based denitration catalyst

Abstract

The invention discloses a Mn-based denitration catalyst for low-temperature flue gas as well as a preparation method and application of the Mn-based denitration catalyst. The Mn-based denitration catalyst comprises the following components or consists of the following components: (a) delta-MnO2; and (b), phenylalanine. Wherein the amount of substance of phenylalanine accounts for 3.4%-35% of the total amount of the catalyst, and the amount of substance of delta-MnO2 accounts for 65%-96.6% of the total amount of the catalyst. The denitration catalyst has good catalytic activity, the NOx conversion rate at 75-210 DEG C reaches 90% or above, and the catalytic performance is remarkably superior to that of an existing commercial catalyst. Meanwhile, the catalyst is simple in preparation method, easy to synthesize, high in sulfur and water poisoning resistance, stable in long-period operation and very suitable for practical application, and can be widely applied to selective catalytic reduction removal of nitrogen oxides in low-temperature flue gas.

Description

Technical Field

[0001] This invention relates to a Mn-based denitrification catalyst for low-temperature flue gas, its preparation method and application, belonging to the fields of catalytic materials and flue gas denitrification technology for air pollution control. Background Technology

[0002] Among the many NOs x In the treatment technology, selective catalytic reduction of NH3 is used to remove NO. x NH3-SCR has received widespread attention and has been extensively applied in the treatment of industrial flue gas due to its economic efficiency and high efficiency. Currently, the main commercial NH3-SCR catalyst is the V2O5-WO3 / TiO2 catalyst, which operates at 300°C. o Catalysts exhibit good catalytic performance above a certain temperature (C) and are widely used in the treatment of high-temperature flue gas from coal-fired power plants. However, with increasingly stringent flue gas emission requirements, more low-temperature flue gas also needs treatment, and the high reaction temperatures of commercial catalysts cannot meet the requirements of low-temperature reactions. Therefore, there is an urgent need to develop novel catalysts for the efficient removal of nitrogen oxides from low-temperature flue gas. Summary of the Invention

[0003] The purpose of this invention is to provide a Mn-based denitrification catalyst for low-temperature flue gas, its preparation method, and its application. The Mn-based denitrification catalyst can remove NO from low-temperature flue gas. x The catalyst exhibits good catalytic activity and high stability during long-term operation, while also demonstrating strong resistance to sulfur and water. It can be widely used in the treatment of nitrogen oxides in low-temperature flue gas from industrial boilers in metallurgy and other industries.

[0004] The technical solution of the present invention is: a Mn-based denitrification catalyst for low-temperature flue gas, wherein the Mn-based catalyst is phenylalanine-modified δ-MnO2, comprising the following components: δ-MnO2 and phenylalanine, wherein the amount of δ-MnO2 accounts for 65-96.6% of the amount of Mn-based denitrification catalyst, and the remainder is phenylalanine.

[0005] A method for preparing a Mn-based denitrification catalyst for low-temperature flue gas, comprising the following steps:

[0006] Step (1): Dissolve potassium permanganate and manganese sulfate monohydrate in deionized water and stir continuously to obtain a clear and transparent solution A;

[0007] Step (2): Dissolve phenylalanine in deionized water and stir continuously to obtain a clear and transparent solution B;

[0008] Step (3): Slowly add the solution B obtained in step (2) to the solution A obtained in step (1) and continue stirring to form a mixed solution C;

[0009] Step (4): gradually adding hydrochloric acid into the mixed solution C obtained in step (3) to obtain a mixed solution D;

[0010] Step (5): placing the mixed solution D into a polytetrafluoroethylene reaction kettle and reacting at a reaction temperature of 100-160 o C for 8-24 hours; then cooling to room temperature, standing for 10-14 hours, centrifuging, washing and drying the precipitate to obtain the Mn-based denitration catalyst;

[0011] In the composition of the NH3-SCR denitration catalyst obtained in step (5), the amount of phenylalanine and Mn element is such that the amount of substance of δ-MnO2 accounts for 65-96.6% of the amount of substance of the Mn-based denitration catalyst, and the amount of substance of phenylalanine accounts for 3.4%-35% of the amount of substance of the Mn-based denitration catalyst.

[0012] In the composition of the NH3-SCR denitration catalyst obtained in step (5), the amount of phenylalanine and Mn element is such that the amount of substance of δ-MnO2 accounts for 65-96.6% of the amount of substance of the Mn-based denitration catalyst, and the amount of substance of phenylalanine accounts for 3.4%-35% of the amount of substance of the Mn-based denitration catalyst.

[0013] In the preparation method of the Mn-based denitration catalyst for low-temperature flue gas, the final pH of the mixed solution D is 2-4.

[0014] In the preparation method of the Mn-based denitration catalyst for low-temperature flue gas, the stirring time in step (4) is 2-6 hours.

[0015] In the preparation method of the Mn-based denitration catalyst for low-temperature flue gas, the drying temperature in step (5) is 80-110 o C.

[0016] In the preparation method of the Mn-based denitration catalyst for low-temperature flue gas, the reaction temperature in step (5) is 140 o C.

[0017] The application of the Mn-based denitration catalyst in the denitration reaction of low-temperature flue gas is as follows: mixing the low-temperature flue gas with the reducing agent NH3, and then passing the mixture into a device loaded with the catalyst to make the gas and the catalyst fully contact and react.

[0018] In the application, the temperature of the low-temperature flue gas is 50-260 o C.

[0019] The beneficial effects of the present application are as follows: compared with the prior art, the traditional commercial catalyst has the problem of high reaction temperature, and the removal effect of NO x from low-temperature flue gas is poor. However, the Mn-based composite catalyst has good oxidation-reduction capacity, thereby reducing the reaction temperature of NH3-SCR and improving the removal effect of NO xThe removal rate of NO. The application utilizes a hydrothermal method to synthesize a high-efficiency NH3-SCR catalyst, which is applied to the removal of NO in low-temperature flue gas x and achieves good catalytic effect, and has a wide operation temperature window. Meanwhile, the catalyst is easy to prepare, has excellent sulfur resistance and water resistance, is different from traditional vanadium-based catalysts, and has small harm to the environment. The application provides a new choice for the catalytic reaction of flue gas denitrification catalysts in the low-temperature region.

[0020] The application has the following advantages:

[0021] 1. The catalyst preparation method is simple, easy to synthesize, suitable for large-scale production and application to the removal of NO in actual industrial low-temperature flue gas. x

[0022] 2. The catalyst has good catalytic activity under the conditions of 50,000 h -1 high space velocity, 500 ppm NO, 500 ppm NH3 and 5% O2 simulated flue gas, and maintains more than 90% NO o conversion rate at 75-210 x C. Further increasing the NO concentration or space velocity, the catalyst still maintains high catalytic performance, and has strong sulfur resistance and water resistance, which can effectively meet the processing requirements of low-temperature flue gas. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a NO x conversion rate curve diagram of the Mn-based composite catalyst with different proportions. DETAILED DESCRIPTION

[0024] The application will be further described below in combination with the drawings and examples, but it is not used as the basis for limiting the application.

[0025] Comparative example

[0026] Preparation of the catalyst: 0.474 g of potassium permanganate and 0.084 g of manganese sulfate monohydrate were dissolved in deionized water and continuously stirred for 30 min to obtain a clear and transparent Mn-containing solution. Hydrochloric acid solution was slowly added to the Mn solution to make the pH reach 2-4 and continuously stirred for 6 to form a mixed solution, and the mixed solution was placed in a polytetrafluoroethylene reaction kettle and reacted at 140 o C for 12 h. Then, it was cooled to room temperature and placed for aging for 12 hours, the precipitate was centrifuged, washed for multiple times and treated by drying at 100 o C to obtain the catalyst, which is recorded as MnO x .

[0027] ​Catalyst performance testing: The catalyst prepared above was placed in a U-shaped quartz reactor for activity testing, simulating flue gas conditions of 500 ppm NO, 500 ppm NH3, and 5% O2, with a space velocity of 50,000 h⁻¹. -1 .like Figure 1 As shown, the results indicate that the test temperature is 50-260°C. o Within the C range, this MnO x The catalyst exhibited poor catalytic activity, achieving NO concentrations of less than 20% across the entire range. x Conversion rate.

[0028] Example 1

[0029] Catalyst preparation: 0.474 g of potassium permanganate and 0.084 g of manganese sulfate monohydrate were dissolved in deionized water and stirred continuously for 30 min to obtain a clear and transparent Mn-containing solution. 0.05 g of phenylalanine was dissolved in deionized water and stirred continuously for 30 min to obtain a clear and transparent phenylalanine solution. The obtained phenylalanine solution was slowly added to the Mn solution and stirred continuously for 30 min to form a mixed solution. Hydrochloric acid solution was slowly added to the Mn solution to adjust the pH to 2-4 and stirred continuously for 6 min to form a mixed solution. The mixed solution was placed in a polytetrafluoroethylene reactor and incubated at 140°C. o The reaction was carried out at C for 12 hours. Then it was cooled to room temperature and allowed to age for 12 hours. The precipitate was centrifuged, washed multiple times, and then... o The catalyst was obtained by drying at C, in which phenylalanine accounted for 8.6% of the total amount and δ-MnO2 accounted for 91.4% of the total amount, and was designated as MnO2. x -Phe-0.05.

[0030] Catalyst performance testing: The catalyst prepared above was placed in a U-shaped quartz reactor for activity testing, simulating flue gas conditions of 500 ppm NO, 500 ppm NH3, and 5% O2, with a space velocity of 50,000 h⁻¹. -1 .like Figure 1 As shown, the results indicate that the test temperature is 50-260°C. o Within the C range, this MnO x The -Phe-0.05 catalyst exhibited good catalytic activity at 110-200 °C. o NO within range C reaches less than 90% x Conversion rate.

[0031] Example 2

[0032] Catalyst preparation: 0.474 g of potassium permanganate and 0.084 g of manganese sulfate monohydrate were dissolved in deionized water and stirred continuously for 30 min to obtain a clear and transparent Mn-containing solution. 0.1 g of phenylalanine was dissolved in deionized water and stirred continuously for 30 min to obtain a clear and transparent phenylalanine solution. The obtained phenylalanine solution was slowly added to the Mn solution and stirred continuously for 30 min to form a mixed solution. Hydrochloric acid solution was slowly added to the Mn solution to adjust the pH to 2-4 and stirred continuously for 6 min to form a mixed solution. The mixed solution was placed in a polytetrafluoroethylene reactor and incubated at 140°C. o The reaction was carried out at C for 12 hours. Then it was cooled to room temperature and allowed to age for 12 hours. The precipitate was centrifuged, washed multiple times, and then... o The catalyst was obtained by drying at C, in which phenylalanine accounted for 17.2% of the total amount and δ-MnO2 accounted for 82.8% of the total amount, and was designated as MnO2. x -Phe-0.1.

[0033] Catalyst performance testing: The catalyst prepared above was placed in a U-shaped quartz reactor for activity testing, simulating flue gas conditions of 500 ppm NO, 500 ppm NH3, and 5% O2, with a space velocity of 50,000 h⁻¹. -1 .like Figure 1 As shown, the results indicate that the test temperature is 50-260°C. o Within the C range, this MnO x The -Phe-0.1 catalyst exhibited good catalytic activity in the range of 75-210 °C. o NO within range C reaches less than 90% x Conversion rate.

[0034] Example 3

[0035] Catalyst preparation: 0.474 g of potassium permanganate and 0.084 g of manganese sulfate monohydrate were dissolved in deionized water and stirred continuously for 30 min to obtain a clear and transparent Mn-containing solution. 0.2 g of phenylalanine was dissolved in deionized water and stirred continuously for 30 min to obtain a clear and transparent phenylalanine solution. The obtained phenylalanine solution was slowly added to the Mn solution and stirred continuously for 30 min to form a mixed solution. Hydrochloric acid solution was slowly added to the Mn solution to adjust the pH to 2-4 and stirred continuously for 6 min to form a mixed solution. The mixed solution was placed in a polytetrafluoroethylene reactor and incubated at 140°C. o The reaction was carried out at C for 12 hours. Then it was cooled to room temperature and allowed to age for 12 hours. The precipitate was centrifuged, washed multiple times, and then... oThe catalyst was obtained by drying at C, in which phenylalanine accounted for 34.6% of the total amount and δ-MnO2 accounted for 65.6% of the total amount, and was designated as MnO2. x -Phe-0.2.

[0036] Catalyst performance testing: The catalyst prepared above was placed in a U-shaped quartz reactor for activity testing, simulating flue gas conditions of 500 ppm NO, 500 ppm NH3, and 5% O2, with a space velocity of 50,000 h⁻¹. -1 .like Figure 1 As shown, the results indicate that the test temperature is 50-260°C. o Within the C range, this MnO x The Phe-0.2 catalyst exhibited certain catalytic activity at 200 °C. o C reaches less than 40% NO x Conversion rate, at 250 o NO levels below C can reach up to approximately 80%. x Conversion rate.

Claims

1. A Mn-based De-NOx catalyst for low-temperature flue gas, characterized by: The Mn-based catalyst is phenylalanine-modified δ-MnO2, comprising the following components: δ-MnO2 and phenylalanine, the amount of substance of δ-MnO2 accounting for 65-96.6% of the amount of substance of the Mn-based denitration catalyst, and the rest being phenylalanine.

2. The method for preparing the Mn-based denitration catalyst for low-temperature flue gas according to claim 1, characterized in that: The preparation method comprises the following steps: Step (1): dissolve potassium permanganate and manganese sulfate monohydrate in deionized water and continuously stir to obtain a clear and transparent solution A; Step (2): dissolve phenylalanine in deionized water and continuously stir to obtain a clear and transparent solution B; Step (3): slowly add the solution B obtained in step (2) to the solution A obtained in step (1) and continuously stir to form a mixed solution C; Step (4): gradually add hydrochloric acid to the mixed solution C obtained in step (3) and stir to obtain a mixed solution D; Step (5): The mixed solution D is placed in a polytetrafluoroethylene reactor at a reaction temperature of 100-160 o C for 8-24 hours; then cooled to room temperature, placed for aging for 10-14 hours, the precipitate is centrifuged, washed multiple times and subjected to drying treatment to obtain the Mn-based denitration catalyst; wherein the addition amount of phenylalanine and Mn element is such that the amount of substance of δ-MnO2 in the composition of the NH3-SCR denitration catalyst obtained in step (5) accounts for 65-96.6% of the amount of substance of the Mn-based denitration catalyst, and the amount of substance of phenylalanine accounts for 3.4%-35% of the amount of substance of the Mn-based denitration catalyst; wherein the molar ratio of potassium permanganate to manganese sulfate monohydrate is 6:

1.

3. The method for preparing a Mn-based denitration catalyst for low-temperature flue gas according to claim 2, characterized in that: The final pH of the mixed solution D is 2-4.

4. The method for preparing a Mn-based denitration catalyst for low-temperature flue gas according to claim 2, characterized in that: The stirring time in step (4) is 2-6 hours.

5. The method for preparing a Mn-based denitration catalyst for low-temperature flue gas according to claim 2, characterized by: The drying temperature in step (5) is 80-110 o C.

6. The method for preparing a Mn-based denitration catalyst for low-temperature flue gas according to claim 2, characterized in that: The reaction temperature in the step (5) is 140 o C.

7. The use of the Mn-based de-NOx catalyst according to claim 1 in a de-NOx reaction of low-temperature flue gas, characterized by: After mixing the low-temperature flue gas with the reducing agent NH3, the gas is introduced into a device loaded with a catalyst, so that the gas and the catalyst are fully contacted and reacted.

8. Use according to claim 7, characterized in that: The low-temperature flue gas temperature is 50-260 o C.

Images