Ultrasonic-assisted method for preparing MnOX low-temperature denitration catalyst

Abstract

The invention discloses an ultrasonic-assisted method for preparing a MnOx low-temperature denitration catalyst, belongs to the field of environmental protection, and particularly relates to a method for preparing a MnOx low-temperature denitration catalyst through an ultrasonic-assisted redox reaction. The method is characterized in that an oxidizing agent and a reducing agent are subjected to ultrasonic-assisted oxidation-reduction reaction, and then are washed and dried to obtain the catalyst. A sodium carbonate solution (5-15%, w / w) and a lactic acid diluent (1-10%, v / v) are sequentially added into a potassium permanganate solution (0.2-10%, w / w), the ratio of potassium permanganate to the lactic acid solution is 4-12 (v / v), the ratio of the lactic acid solution to the sodium carbonate solution is 1-4 (v / v), then ultrasonic treatment is carried out for a proper time (0.5-4 h), and the catalyst is obtained.

Description

Field of the Invention

[0001] The present invention relates to a method for preparing a low-temperature denitration catalyst by ultrasonic assistance, and particularly to a method for preparing a MnO low-temperature denitration catalyst by ultrasonic-assisted redox reaction. X X Background Art

[0002] Nitrogen oxides (NO, NO 2 and N 2 O) remain the main sources of air pollution. They can cause photochemical smog, acid rain, ozone depletion and the greenhouse effect. And they can cause respiratory problems, thus posing hazards to both the ecosystem and humans. Important human social activities such as industrial processes, transportation, and power production will inevitably use fossil fuels as important energy sources, resulting in a large amount of nitrogen oxide emissions. Therefore, the denitration process for treating nitrogen oxides in flue gas is particularly important.

[0003] In recent years, many methods have been used to reduce nitrogen oxide emissions. The catalytic process is attractive due to its low cost and high efficiency. Among them, the ammonia selective catalytic reduction (NH 3 -SCR) technology is one of the most effective methods and has been widely applied. It has high denitration efficiency, good selectivity, and a clean process. NO X reacts with the reducing agent under the action of the catalyst to generate nitrogen and water. However, NH 3 -SCR catalysts are generally sensitive to temperature and need to maintain high-temperature conditions to fully exert their denitration activity. The currently used V 2 O 5 -WO 3 / TiO 2 catalyst has an optimal reaction temperature range of 300 - 400 °C. It has a high operating temperature, a narrow operating temperature window, is biotoxic, and is easily oxidized by SO 2 and SO 3 . To meet the high-active temperature, the denitration device usually needs to adopt a high-dust layout, that is, the flue gas is first denitrified, and then dust removal and desulfurization are carried out. In this way, the dust and sulfur dioxide in the flue gas will easily cause the catalyst to be deactivated in advance. Catalysts with a low reaction temperature can be arranged under low dust and low temperature, which can reduce catalyst poisoning, extend its working life, avoid flue gas reheating, and save costs. Therefore, it is of great significance to develop high-performance NH 3 -SCR denitration catalysts at low temperatures.

[0004] Li et al. adopted the wet impregnation method, using Ce(NO 3 ) 2 ·6H 2 O, Co(NO 3 )2 ·6H 2 O and Mn(NO 3 ) 2 were dissolved in deionized water, and then anatase TiO 2 was added. The mixture was stirred at room temperature for 2 hours and then the excess deionized water was slowly evaporated at 70 °C. Subsequently, the sample was dried in an oven at 120 °C for 12 h and calcined in a muffle furnace at 400 °C for 4 h to prepare the CoMnCeO X / TiO 2 catalyst. It can maintain a NO X conversion rate greater than 95% when maintained at 100 - 225 °C, and within the temperature range of 50 - 175 °C, the N 2 selectivity is higher than 92%. Wang et al. developed an acid-etched mullite-type SmMn 3 O 2 catalyst for ultra-low temperature NH 5 -SCR. A solution of Sm(NO 3 ) 3 ·6H 2 O, Mn(NO 3 ) 2 ·4H 2 O and KMnO 4 was stirred at room temperature for 1 h, and then the pH was adjusted to 9 using 10 mol / L NaOH solution, and hydrothermal reaction was carried out at 180 °C for 16 h to prepare the catalyst, which can achieve a NO X conversion of more than 90% within the temperature window of 90 - 200 °C.

[0005] Che et al. loaded Mn(NO 3 ) 2 ·4H 2 O onto an amorphous ZrTiO X support prepared by the coprecipitation method through the impregnation method. It has a NO X conversion rate greater than 90% in the temperature window of 120 - 330 °C. The amorphous ZrTiO X support enables the N 2 selectivity of the catalyst to reach more than 80% within the temperature range of 90 - 330 °C.

[0006] Although new preparation technologies for low-temperature denitration catalysts have emerged continuously, these preparation methods still cannot get rid of problems such as numerous raw materials, cumbersome synthesis steps, and complex preparation processes, and the low-temperature properties of the catalysts are still not ideal. In the present invention, a manganese oxide catalyst was prepared by a simple reaction of potassium permanganate and lactic acid under ultrasonic conditions. The catalyst is active at 40 - 300 degrees Celsius and can maintain a catalytic activity close to 100% even at extremely low temperatures. Summary of the Invention

[0007] The object of the present invention is to develop a simple preparation process for a manganese-based low-temperature denitration catalyst. A method for preparing a MnO low-temperature denitration catalyst by ultrasonic assistance developed by the present invention, that is, under ultrasonic assistance conditions, through an oxidation-reduction reaction, and then washing and drying to obtain a MnO low-temperature denitration catalyst. X X Method for low-temperature denitration catalyst

[0008] The characteristics of this method are: the catalyst is a MnOX catalyst, the oxidant is potassium permanganate, the reducing agent is lactic acid, through ultrasonic-assisted oxidation-reduction reaction; then washing and drying to obtain a MnOX low-temperature denitration catalyst.

[0009] A method for preparing a MnOX low-temperature denitration catalyst by ultrasonic assistance provided by the present invention comprises the following steps:

[0010] 1) Prepare potassium permanganate solution (0.2 - 10%, w / w), lactic acid dilution (1 - 10%, v / v) and sodium carbonate solution (5 - 15%, w / w) with certain concentrations;

[0011] 2) Add sodium carbonate solution (5 - 15%, w / w) and lactic acid dilution (1 - 10%, v / v) to the potassium permanganate solution (0.2 - 10%, w / w) in sequence, with potassium permanganate : lactic acid solution = 4 - 12 (v / v), lactic acid solution : sodium carbonate solution = 1 - 4 (v / v), and then ultrasonic for an appropriate time (0.5 - 4 h);

[0012] 3) Wash with water and dry (generally at 60 - 100 °C) to obtain the catalyst.

[0013] Compared with the existing process, the characteristics and advantages of the present invention are:

[0014] Less raw materials, simple process and low cost. Detailed Embodiments

[0015] Embodiment 1:

[0016] 1) Add sodium carbonate solution (5 - 7%, w / w) and lactic acid dilution (3 - 4%, v / v) to the potassium permanganate solution (2 - 3%, w / w) in sequence, with potassium permanganate : lactic acid solution = 4 - 6 (v / v), lactic acid solution : sodium carbonate solution = 2 - 3 (v / v), and then ultrasonic for an appropriate time of 2 h;

[0017] 2) Wash with water and dry overnight at 80 °C in a forced-air drying oven to obtain the catalyst, and the catalyst has activity at 40 - 180 °C.

[0018] Embodiment 2:

[0019] ​1) Add a sodium carbonate solution (4 - 6%, w / w) and a lactic acid dilution (2 - 4%, v / v) to a potassium permanganate solution (3 - 5%, w / w) in sequence. The ratio of potassium permanganate to lactic acid solution is 3 - 5 (v / v), and the ratio of lactic acid solution to sodium carbonate solution is 2 - 1 (v / v). Then, perform ultrasonic treatment for an appropriate time of 3 h.

[0020] 2) Wash with water and dry overnight at 80 °C in a forced-air drying oven to obtain a catalyst. The catalyst is active at 40 - 180 degrees Celsius.

Claims

1. A method for preparing a low-temperature denitration catalyst of MnO assisted by ultrasound X ​ It is characterized in that An oxidant, a reductant, and ultrasonic assistance are used. After the redox reaction assisted by ultrasound, the catalyst is obtained after washing with water and drying. The specific preparation steps are as follows: 1) Prepare potassium permanganate solution, lactic acid dilution solution and sodium carbonate solution with certain concentrations; add the sodium carbonate solution and lactic acid dilution solution to the potassium permanganate solution in sequence according to the ratio; 2) After the above solutions are mixed evenly, place them in an ultrasonic reactor and ultrasonicate for an appropriate time (0.5 - 4 h); 3) Wash with water and dry (generally at 60 - 100 °C) to obtain the catalyst.

2. According to claim 1, It is characterized in that The concentration of the oxidant potassium permanganate solution is 0.2 - 10%, w / w.

3. According to claim 1, It is characterized in that The concentration of the lactic acid dilution solution is 1 - 10% (v / v), the concentration of the sodium carbonate solution is 5 - 15% (w / w), and the ratio of lactic acid solution to sodium carbonate solution is 1 - 4 (v / v).

4. According to claim 2, It is characterized in that The reaction in the ultrasonic reactor is carried out for an appropriate time, generally 0 - 4 h.