Manganese-containing denitration catalyst and preparation method thereof

Abstract

The invention discloses a manganese-containing denitration catalyst and a preparation method thereof, and the preparation method comprises the following steps: 1) adding a manganese source precursor solution and a basic hydroxide solution into a potassium permanganate solution to obtain a mixed solution; continuously stirring the mixed solution at 20-80 DEG C for more than 0.5 h, and then carrying out solid-liquid separation to obtain an initial solid; drying the initial solid to obtain an active manganese oxide; and 2) mixing 30-70 parts by weight of active manganese oxide, 3-12 parts by weight of an active auxiliary agent, 0.5-8 parts by weight of a molding auxiliary agent and 1-6 parts by weight of a pore-forming agent, wetting, kneading, molding, and drying to obtain the manganese-containing denitration catalyst. The manganese-containing denitration catalyst prepared by the preparation method disclosed by the invention has NO low-temperature oxidation activity and relatively good water resistance and sulfur resistance.

Description

Technical Field

[0001] The invention relates to a manganese-containing denitration catalyst and a preparation method thereof. Background Art

[0002] Nitrogen oxides (NOx) are one of the main air pollutants. Under the background of the country's vigorous advocacy of ultra-low emissions, the ultra-low emission transformation of coal-fired power plants in my country has been basically completed, and the focus of air pollution control has gradually shifted to non-power industries such as the steel industry, coking industry, glass industry, and cement industry. At present, the most mature denitrification process in industrial application is SCR technology, but it has problems such as high catalyst cost and secondary pollution such as ammonia escape, and it cannot be directly applied to flue gas with a flue gas emission temperature of 120 to 200°C in industrial boiler (kiln) equipment in non-power industries. Among the oxidative denitrification methods, ozone oxidation and wet scrubbing are more widely used. The stability of ozone is greatly affected by temperature, and the cost of preparing ozone is relatively high.

[0003] CN106268855A discloses a low-temperature NO oxidation catalyst and its preparation method and use method. The catalyst includes a carrier and an active component, and the carrier is anatase-type nano-TiO 2 Or nano α-Al 2 O 3 The active components are oxides containing manganese, cerium and cobalt. The catalyst still needs to be in a relatively high temperature range of 180-250°C to obtain an NO oxidation efficiency of about 80%. The preparation of the catalyst still requires high-temperature calcination, which consumes slightly more energy.

[0004] CN104258872A discloses a method for preparing a denitration catalytic material, which includes adding a manganese acetate solution to a metatitanic acid suspension, adjusting the pH with urea, ammonia water, and hydrogen peroxide until the precipitation is complete, and then centrifuging, washing with water, washing with alcohol, drying, and roasting to obtain the denitration catalytic material. Although the denitration catalytic material has a wide active temperature window, its ability to resist sulfur poisoning still needs to be improved.

[0005] CN106732648A discloses a low-temperature flue gas oxidation denitration catalyst and a preparation method thereof, the preparation method comprising: using manganese acetate, polyethylene glycol, potassium permanganate, cobalt nitrate, and transition metal soluble salt as raw materials, aging, washing, drying, and roasting to prepare a denitration catalyst. When the denitration catalyst removes NO, the temperature only reaches above 200°C, the denitration efficiency is above 60%, and the denitration temperature is still high.

[0006] CN105833894A discloses a denitration catalyst with alkali resistance, sulfur resistance and water resistance, and its preparation method and application. The preparation method comprises: dissolving one or more of iron salt, vanadium salt and molybdenum salt and cerium salt in a certain amount of deionized water, ultrasonically dispersing to form a solution; adding a porous molecular sieve carrier to the above solution, adding a certain amount of precipitant under stirring, reacting, centrifugation washing, drying, and roasting to obtain a finished catalyst. The denitration temperature of the catalyst is still relatively high, basically at 200 to 500°C. Summary of the invention

[0007] In view of this, one object of the present invention is to provide a method for preparing a manganese-containing denitration catalyst, wherein the manganese-containing denitration catalyst prepared by the preparation method has low-temperature NO oxidation activity and good water and sulfur resistance. Another object of the present invention is to provide a manganese-containing denitration catalyst prepared according to the preparation method as described above.

[0008] The present invention adopts the following technical solutions to achieve the above-mentioned purpose.

[0009] In one aspect, the present invention provides a method for preparing a manganese-containing denitration catalyst, comprising the following steps:

[0010] 1) adding a manganese source precursor solution and an alkaline hydroxide solution to a potassium permanganate solution to obtain a mixed solution; stirring the mixed solution at 20 to 80° C. for more than 0.5 h,

[0011] Then the solid and liquid are separated to obtain an initial solid; the initial solid is dried to obtain an active manganese oxide;

[0012] 2) 30 to 70 parts by weight of active manganese oxide, 3 to 12 parts by weight of active auxiliary agent, 0.5 to 8 parts by weight of forming auxiliary agent and 1 to 6 parts by weight of pore former are mixed and wetted,

[0013] After kneading and molding, drying is performed to obtain a manganese-containing denitration catalyst;

[0014] Wherein, the manganese source precursor in the manganese source precursor solution is selected from one or more of manganese sulfate, manganese acetate, manganese nitrate and manganese chloride;

[0015] Wherein, the active auxiliary agent is selected from one or more of cerium-containing inorganic salts, molybdenum-containing inorganic salts, cerium oxide, molybdenum oxide and phosphate;

[0016] Wherein, the molding aid is selected from one or more of kaolin, attapulgite, gypsum, glycerin, titanium dioxide, sesbania powder, polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

[0017] According to the preparation method of the present invention, preferably, the concentration of the manganese source precursor solution is 20-60wt%; the concentration of the alkaline hydroxide solution is above 30wt%; and the concentration of the potassium permanganate solution is 10-40wt%.

[0018] According to the preparation method of the present invention, preferably, the concentration of the manganese source precursor solution is 25-55wt%; the concentration of the alkaline hydroxide solution is 35-70wt%; and the concentration of the potassium permanganate solution is 15-35wt%.

[0019] According to the preparation method of the present invention, preferably, the manganese source precursor in the manganese source precursor solution is selected from one of manganese nitrate and manganese acetate.

[0020] According to the preparation method of the present invention, preferably, the alkaline hydroxide in the alkaline hydroxide solution is selected from one of sodium hydroxide and potassium hydroxide.

[0021] According to the preparation method of the present invention, preferably, the mixed solution is stirred at 20-80° C. for 2-8 hours; and the initial solid is dried at 40-100° C. for 1-5 hours.

[0022] According to the preparation method of the present invention, preferably, the active auxiliary agent is selected from one of phosphates, cerium-containing inorganic salts, molybdenum-containing inorganic salts, molybdenum oxide and cerium oxide.

[0023] According to the preparation method of the present invention, preferably, the molding aid is selected from one of kaolin, attapulgite, sesbania powder, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

[0024] According to the preparation method of the present invention, preferably, the pore-forming agent is selected from one or more of sodium bicarbonate, starch, citric acid, chitosan and lignin.

[0025] On the other hand, the present invention also provides a manganese-containing denitration catalyst, which is prepared according to the preparation method as described above.

[0026] The manganese-containing denitration catalyst prepared by the preparation method of the manganese-containing denitration catalyst of the present invention has low-temperature NO oxidation activity and good water and sulfur resistance. The manganese-containing denitration catalyst can be used in the denitration of flue gas with a flue gas emission temperature within the range of 100 to 200° C. in industrial boiler (kiln) equipment in non-power industries. The preparation method of the present invention has a relatively simple process, does not require roasting, has low energy consumption, and is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The catalytic denitration test result curves of the manganese-containing denitration catalysts of the embodiments and comparative examples are shown. DETAILED DESCRIPTION

[0028] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0029] The manganese-containing denitration catalyst prepared by the present invention directly utilizes oxygen in flue gas to convert NO (nitric oxide) into NO in the temperature range of 100-200°C. 2 , no additional strong oxidant is required, and it has good anti-sulfur and water resistance, overcoming the flue gas temperature limitation and solving the problem that the existing NO catalytic oxidation catalyst is prone to produce SO 2 Poisoning problem or high denitrification temperature problem.

[0030] The method for preparing the manganese-containing denitration catalyst of the present invention comprises the following steps: (1) a step of preparing active manganese oxide; and (2) a step of forming the manganese-containing denitration catalyst.

[0031] <Active manganese oxide preparation steps>

[0032] A manganese source precursor solution and an alkaline hydroxide solution are added to a potassium permanganate solution to obtain a mixed solution; the mixed solution is stirred at 20 to 80°C for more than 0.5 hours, and then solid-liquid separation is performed to obtain an initial solid; the initial solid is dried to obtain an active manganese oxide. The present invention has found through extensive research and experiments that the method for preparing active manganese oxide of the present invention is an in-situ deposition method that can give full play to the advantages of manganese source-containing materials, and the synthesized active manganese oxide has a high catalytic activity for NO, and can complete the catalytic oxidation of NO at low temperatures. At the same time, the combination of cerium, phosphorus, molybdenum and other substances can improve the anti-sulfur poisoning performance of the catalyst material, and has a good NO catalytic oxidation effect.

[0033] In the present invention, the manganese source precursor solution is an aqueous solution. The manganese source precursor in the manganese source precursor solution can be selected from one or more of manganese sulfate, manganese acetate, manganese nitrate and manganese chloride, preferably selected from one of manganese sulfate, manganese acetate, manganese nitrate and manganese chloride, more preferably selected from one of manganese nitrate and manganese acetate.

[0034] In the present invention, the concentration of the manganese source precursor solution may be 20-60 wt %, preferably 25-55 wt %, more preferably 30-50 wt %. According to a specific embodiment of the present invention, the concentration of the manganese source precursor solution is 35-48 wt %.

[0035] In the present invention, the alkaline hydroxide in the alkaline hydroxide solution is selected from one of sodium hydroxide and potassium hydroxide, preferably potassium hydroxide. The concentration of the alkaline hydroxide solution can be 30wt% or more, preferably 35-70wt%, more preferably 40-60wt%. According to a specific embodiment of the present invention, the concentration of the alkaline hydroxide solution is 45-60wt%.

[0036] In the present invention, the potassium permanganate solution is an aqueous solution. The concentration of the potassium permanganate solution may be 10 to 40 wt %, preferably 15 to 35 wt %, and more preferably 15 to 20 wt %.

[0037] In the present invention, a manganese source precursor, an alkaline hydroxide, and potassium permanganate can be dissolved in water to obtain a manganese source precursor solution, an alkaline hydroxide solution, and a potassium permanganate solution, respectively. The solution can be stirred at 30 to 60° C., or dissolved in water at 30 to 60° C.

[0038] According to a preferred embodiment of the present invention, the manganese source precursor solution and the alkaline hydroxide solution are simultaneously added dropwise to the potassium permanganate solution to obtain a mixed solution.

[0039] In the present invention, the volume ratio of the manganese source precursor solution, the alkaline hydroxide solution and the potassium permanganate solution can be 1.5-4:0.3-1:2-8, preferably 2.5-3:0.5-0.8:5-7. Such as 3:0.5:6. The mixed solution is preferably stirred at 30-60°C, more preferably at 30-40°C. The stirring time can be more than 0.5h, preferably more than 1h, more preferably 2-8h, more preferably 2.5-6h, and more preferably 2.5-4h. The stirring speed can be 300-1000rpm, preferably 600-800rpm. Solid-liquid separation can be centrifuged or filtered. The temperature for drying the initial solid can be 40-110°C, preferably 50-100°C, and more preferably 60-80°C. The drying time can be 1-5h, preferably 2-4h, and more preferably 2-3h.

[0040] In certain embodiments, the mixed solution is stirred at 20-80° C. for 2-8 hours, then allowed to stand for 1-4 hours, and then solid-liquid separation is performed to obtain an initial solid; the initial solid is dried to obtain an active manganese oxide.

[0041] <Step of Forming a Manganese-Containing DeNOx Catalyst>

[0042] 30 to 70 parts by weight of active manganese oxide, 3 to 12 parts by weight of active auxiliary agent, 0.5 to 8 parts by weight of molding auxiliary agent and 1 to 6 parts by weight of pore-forming agent are mixed and moistened, kneaded and molded, and then dried to obtain a manganese-containing denitration catalyst. This is conducive to making the obtained manganese-containing denitration catalyst have a higher denitration efficiency at low temperature and better resistance to water and sulfur poisoning.

[0043] In the present invention, the active additive is selected from salt substances or oxides containing cerium, phosphorus or molybdenum. The active additive is beneficial to improving the sulfur resistance of the obtained manganese-containing denitration catalyst.

[0044] In the present invention, the source of the cerium element may be one of cerium sulfate, cerium nitrate, cerium chloride, cerium carbonate and cerium oxide. Preferably, cerium carbonate or cerium oxide. The source of the molybdenum element may be one of molybdenum oxide, ammonium molybdate, manganese molybdate and zinc molybdate, preferably ammonium molybdate. The source of the phosphorus element may be one of ammonium phosphate, sodium dihydrogen phosphate and potassium dihydrogen phosphate. Preferably, sodium dihydrogen phosphate and potassium dihydrogen phosphate.

[0045] In the present invention, the molding aid is selected from one or more of kaolin, attapulgite, gypsum, glycerol, titanium dioxide, sesbania powder, polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose, preferably selected from one of kaolin, attapulgite, sesbania powder, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose, more preferably kaolin. The molding aid is conducive to obtaining a molded and uniformly shaped manganese-containing denitration catalyst.

[0046] In the present invention, the pore-forming agent is selected from one or more of sodium bicarbonate, starch, citric acid, chitosan and lignin, preferably selected from one of sodium bicarbonate, starch, citric acid, chitosan and lignin, more preferably sodium bicarbonate.

[0047] In the present invention, the active manganese oxide may be 30 to 70 parts by weight, preferably 35 to 65 parts by weight, and more preferably 45 to 60 parts by weight. The active auxiliary agent may be 3 to 12 parts by weight, preferably 4 to 11 parts by weight, and more preferably 6 to 10 parts by weight. The molding auxiliary agent may be 0.5 to 8 parts by weight, preferably 1.5 to 6.5 parts by weight, and more preferably 2 to 5 parts by weight. The pore former may be 1 to 6 parts by weight, preferably 1.5 to 5.5 parts by weight, and more preferably 2 to 5 parts by weight.

[0048] According to one embodiment of the present invention, active manganese oxide, active auxiliary agent, molding auxiliary agent and pore-forming agent are mixed and wetted, and the mixing time can be 10 to 30 minutes; after kneading and molding, they are dried at 20 to 150° C. for 1 to 8 hours to obtain a manganese-containing denitration catalyst.

[0049] In the present invention, the amount of water used for wetting can be 20-45 wt% of the total weight of active manganese oxide, active auxiliary agent, molding auxiliary agent and pore-forming agent. The kneading molding can be performed by granulating with a granulator or tabletting with a tablet press.

[0050] The present invention also provides a manganese-containing denitration catalyst prepared according to the preparation method as described above, which has low-temperature NO oxidation activity and good water and sulfur resistance.

[0051] The manganese-containing denitration catalyst of the present invention is used at a denitration temperature of 120 to 200°C and at SO 2 In the presence of water vapor, the denitrification efficiency can reach more than 60%; when the denitrification temperature is 160-200℃ and in SO 2 In the presence of water vapor, the denitrification efficiency can reach more than 80%, preferably more than 90%.

[0052] Example 1

[0053] Manganese acetate is dissolved in water to form a manganese acetate precursor solution with a concentration of 48 wt%. Potassium hydroxide is dissolved in water to form a potassium hydroxide solution with a concentration of 52 wt%. Potassium permanganate is dissolved in water to form a potassium permanganate solution with a concentration of 20 wt%.

[0054] Slowly add the manganese acetate precursor solution and potassium hydroxide solution to the potassium permanganate solution to obtain a mixed solution. Continue stirring the mixed solution at 30°C for 3 hours, then let it stand for 2 hours, filter it, and obtain an initial solid. Dry the initial solid at 80°C for 3 hours to obtain active manganese oxide. The volume ratio of the manganese acetate precursor solution, potassium hydroxide solution, and potassium permanganate solution is 3:0.5:6.

[0055] 45 parts by weight of active manganese oxide, 10 parts by weight of cerium oxide, 6 parts by weight of kaolin and 3 parts by weight of sodium bicarbonate were mixed and moistened, kneaded into a mold and then dried to obtain a manganese-containing denitration catalyst.

[0056] Example 2

[0057] Except for the following parameter settings, the rest is the same as Example 1: the mixed solution is continuously stirred at 60°C.

[0058] Comparative Example 1

[0059] Except for the following parameter settings, the rest is the same as Example 1: In this comparative example, active manganese oxide is not prepared. The active manganese oxide is replaced by commercially available manganese dioxide.

[0060] The performance of the manganese-containing denitration catalysts of the examples and comparative examples was tested.

[0061] Catalyst performance evaluation method: A small laboratory fixed bed reactor was used for testing. The NO content in the combined gas was 500 mg / m 3 , SO 2 The content is 20mg / m 3 , oxygen content is 12vol%, water vapor content is 5vol%, reaction space velocity is 10000h -1 The test was carried out at 100℃, 120℃, 140℃, 160℃, 180℃ and 200℃ respectively, and each temperature section was stabilized for 30min. The NO conversion rate was calculated by detecting the NO inlet and outlet concentrations.

[0062]

[0063] Among them, C 出口NO2 Indicates NO in outlet gas 2 The concentration is in mg / m 3 ; C 入口NO Indicates the concentration of NO in the inlet gas, in mg / m 3 The results are shown in Figure 1 .

[0064] Depend on Figure 1 It can be seen that the embodiment using the manganese-containing denitration catalyst of the present invention can achieve high-efficiency oxidation of NO in the temperature range of 160-200°C, and the effect is better than the catalyst prepared by using commercially available manganese dioxide in Comparative Example 1. 2 In the presence of water vapor, the denitration efficiency of the manganese-containing denitration catalyst of the present invention at 160-200° C. is still above 85%, preferably above 90%. Therefore, the manganese-containing denitration catalyst prepared by the present invention has better NO low-temperature oxidation activity and better water and sulfur resistance.

[0065] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A method for preparing a manganese-containing denitration catalyst, characterized in that: The steps include: 1) adding a manganese source precursor solution and an alkaline hydroxide solution to a potassium permanganate solution to obtain a mixed solution; stirring the mixed solution at 20 to 80° C. for more than 0.5 h, and then performing solid-liquid separation to obtain an initial solid; drying the initial solid to obtain an active manganese oxide; 2) 30 to 70 parts by weight of active manganese oxide, 3 to 12 parts by weight of an active auxiliary agent, 0.5 to 8 parts by weight of a molding auxiliary agent and 1 to 6 parts by weight of a pore-forming agent are mixed and moistened, kneaded into a mold and then dried to obtain a manganese-containing denitration catalyst; Wherein, the manganese source precursor in the manganese source precursor solution is selected from one or more of manganese sulfate, manganese acetate, manganese nitrate and manganese chloride; Wherein, the active auxiliary agent is selected from one or more of cerium-containing inorganic salts, molybdenum-containing inorganic salts, cerium oxide, molybdenum oxide and phosphate; Wherein, the molding aid is selected from one or more of kaolin, attapulgite, gypsum, glycerin, titanium dioxide, sesbania powder, polyethylene oxide, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

2. The preparation method according to claim 1, characterized in that: The concentration of the manganese source precursor solution is 20-60 wt %; the concentration of the alkaline hydroxide solution is above 30 wt %; and the concentration of the potassium permanganate solution is 10-40 wt %.

3. The preparation method according to claim 1, characterized in that: The concentration of the manganese source precursor solution is 25-55 wt %; the concentration of the alkaline hydroxide solution is 35-70 wt %; and the concentration of the potassium permanganate solution is 15-35 wt %.

4. The preparation method according to claim 1, characterized in that: The manganese source precursor in the manganese source precursor solution is selected from one of manganese nitrate and manganese acetate.

5. The preparation method according to claim 1, characterized in that: The alkaline hydroxide in the alkaline hydroxide solution is selected from one of sodium hydroxide and potassium hydroxide.

6. The preparation method according to claim 1, characterized in that: The mixed solution is stirred at 20-80°C for 2-8 hours; the initial solid is dried at 40-100°C for 1-5 hours.

7. The preparation method according to claim 1, characterized in that: The active auxiliary agent is selected from one of phosphates, cerium-containing inorganic salts, molybdenum-containing inorganic salts, molybdenum oxide and cerium oxide.

8. The preparation method according to claim 1, characterized in that: The molding aid is selected from one of kaolin, attapulgite, sesbania powder, carboxymethyl cellulose, hydroxyethyl cellulose and hydroxypropyl methyl cellulose.

9. The preparation method according to claim 1, characterized in that: The pore-forming agent is selected from one or more of sodium bicarbonate, starch, citric acid, chitosan and lignin.

10. A manganese-containing denitration catalyst, characterized in that: It is prepared according to the preparation method according to any one of claims 1 to 9.

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