阅读说明：本技术 一种用于低温脱硝的整体型锰基催化剂的制备方法 (Preparation method of monolithic manganese-based catalyst for low-temperature denitration ) 是由 上官文峰 李咸伟 陶善龙 石洪志 石琎 张志翔 刘道清 于 2020-05-20 设计创作，主要内容包括：本发明公开了一种用于低温脱硝的整体型锰基催化剂的制备方法,涉及环境催化技术领域。包括如下步骤：A、将蜂窝陶瓷催化剂载体浸渍在氧化性溶剂中,洗涤至中性干燥；B、将锰盐、铁盐或锰盐、铈盐溶于溶剂中得到混合溶液,加入有机化合物,水浴加热搅拌；C、将催化剂前驱体溶液干燥并焙烧得到催化剂粉末,将催化剂粉末与去离子水、络合粘结剂混合涂覆至预处理载体上；或直接添加预处理载体至催化剂前驱体溶液中,将涂覆有催化剂前驱体溶液的预处理载体干燥、焙烧,即得用于低温脱硝的整体型锰基催化剂。本方法简单高效、无毒无害,制得产品分散均匀、结合牢固、活性高,NOx的去除效率可达70％-96％,烟气脱硝效果显著,有广阔应用前景。(The invention discloses a preparation method of an integral manganese-based catalyst for low-temperature denitration, and relates to the technical field of environmental catalysis. The method comprises the following steps: A. soaking the honeycomb ceramic catalyst carrier in an oxidizing solvent, washing to be neutral and drying; B. dissolving manganese salt, ferric salt or manganese salt and cerium salt in a solvent to obtain a mixed solution, adding an organic compound, and heating and stirring in a water bath; C. drying and roasting the catalyst precursor solution to obtain catalyst powder, mixing the catalyst powder with deionized water and a complexing binder, and coating the mixture on a pretreatment carrier; or directly adding the pretreatment carrier into the catalyst precursor solution, and drying and roasting the pretreatment carrier coated with the catalyst precursor solution to obtain the monolithic manganese-based catalyst for low-temperature denitration. The method is simple and efficient, nontoxic and harmless, the prepared product is uniform in dispersion, firm in combination and high in activity, the NOx removal efficiency can reach 70% -96%, the flue gas denitration effect is obvious, and the method has a wide application prospect.)

1. A preparation method of a monolithic manganese-based catalyst for low-temperature denitration is characterized by comprising the following steps: the method comprises the following steps:

A. pretreatment of the carrier: soaking the honeycomb ceramic catalyst carrier in an oxidizing solvent, washing until the honeycomb ceramic catalyst carrier is neutral, and drying for later use;

B. preparing a catalyst precursor solution: dissolving manganese salt, ferric salt or manganese salt and cerium salt in a solvent to obtain a mixed solution, adding an organic compound, and heating and stirring in a water bath;

C. preparation of monolithic catalyst: drying and roasting the catalyst precursor solution to obtain catalyst powder, mixing the catalyst powder with deionized water and a complexing binder, and coating the mixture on a pretreatment carrier; or directly adding a pretreatment carrier into the catalyst precursor solution, drying and roasting the pretreatment carrier coated with the catalyst precursor solution to obtain the monolithic manganese-based catalyst for low-temperature denitration, wherein the manganese-based active component loaded on the monolithic manganese-based catalyst for low-temperature denitration is 6-14% in mass percentage.

2. The method of claim 1, wherein the honeycomb ceramic catalyst support in step A comprises one or more of alumina ceramic and cordierite ceramic.

3. The method according to claim 1, wherein the oxidizing solvent in step A comprises a phosphoric acid solution with a concentration of 20-40% by mass or a hydrogen peroxide solution with a concentration of 15-30% by mass.

4. The method of claim 1, wherein the honeycomb ceramic catalyst carrier is immersed in the oxidizing solvent for 4 to 8 hours in step A, and the drying temperature is 80 to 120 ℃.

5. The method for preparing a monolithic manganese-based catalyst for low-temperature denitration according to claim 1, wherein said manganese salt in step B comprises one or more of manganese nitrate and manganese acetate; the ferric salt comprises one or more of ferric nitrate, ferric ammonium oxalate, ferric acetate and ferric citrate; the cerium salt comprises one or more of cerium nitrate and cerous ammonium oxalate; the solvent comprises one or more of deionized water, methanol and ethanol.

6. The method according to claim 1, wherein the organic compound in step B comprises one or more of urea, citric acid and glycine.

7. The method according to claim 1, wherein the molar ratio of manganese to iron in the mixed solution of step B is (0.5-1.5): 1; the molar ratio of the manganese element to the cerium element is (1-5): 5-9, and the molar ratio of the organic compound to the manganese element is (0.5-5): 1.

8. The method for preparing a monolithic manganese-based catalyst for low-temperature denitration according to claim 1, wherein the water bath in step B is heated at a temperature of 70 ℃ to 90 ℃ for a time of 1h to 4 h.

9. The method according to claim 1, wherein the step C comprises the following steps:

drying the catalyst precursor solution at 80-120 ℃ for 6-12 h and roasting at 450-650 ℃ for 4-6 h to obtain catalyst powder, mixing ionic water and a complexing binder, spraying the pretreated carrier by using a compressor spray gun for 1-5 min, drying at 80-120 ℃ for 1-3 h, and repeating for a plurality of times to obtain the monolithic manganese-based catalyst for low-temperature denitration, wherein the mass ratio of the pretreated carrier to the deionized water to the complexing binder is 1: (0.75-1.25): (0.05-0.2);

or adding the pretreatment carrier into a catalyst precursor solution, carrying out ultrasonic impregnation for 10-60 min, drying the pretreatment carrier coated with the catalyst precursor solution at 150-350 ℃ for 1h, and roasting at 450-650 ℃ for 5-6 h to obtain the monolithic manganese-based catalyst for low-temperature denitration.

10. The method of claim 9, wherein the complex binder comprises one or more of silica sol, aluminum sol, and methyl cellulose.

Technical Field

The invention relates to the technical field of environmental catalysis, in particular to a monolithic manganese-based catalyst for low-temperature denitration and a preparation method thereof, and specifically relates to a monolithic catalyst based on a manganese-based composite oxide and applied to low-temperature denitration of sintering flue gas and a preparation method thereof.

Background

With the development of the steel industry, the emission of nitrogen oxides in sintering flue gas becomes one of the main resistances which hinder the green development of steel enterprises. These pollutions not only cause damage to the atmospheric environment (ozone layer cavities, acid rain, photochemical smog, etc.), but also seriously harm human health. Using a suitable catalyst, at a temperature, using a nitrogenous reductant such as ammonia (NH)₃) The nitrogen oxide (NOx) in the flue gas is selectively catalytically reduced and converted into nitrogen, namelySelective Catalytic Reduction (SCR) is the main method for denitration of sintering flue gas at present.

The most mature catalyst system applied to the SCR process in the industry at present is a vanadium-tungsten-titanium catalyst, but because the activity temperature is higher, a denitration reactor needs to be arranged in front of a desulfurization device, an electrostatic precipitator and an air preheater, SO that fly ash is easy to block a catalyst bed layer and a catalyst SO is easy to cause₂Poisoning. In addition, the precursor of the vanadium oxide has high toxicity and is easy to cause environmental pollution. Therefore, the development of a novel low-temperature SCR catalyst is needed, and the activity temperature of the catalyst is reduced to 120-160 ℃, so that the denitration device is moved backwards.

Manganese-based catalysts are novel high efficiency catalysts currently used in SCR processes, e.g., Mn₃O₄Can realize the high-efficiency adsorption of NO and convert NO into adsorbed NO, and oxygen vacancies on the surface can effectively capture oxygen molecules and activate the oxygen molecules so as to complete the conversion of NO into NO₂The reaction process of (1). Thus more easily realizing NO₂1:1 "fast SCR reaction".

The Chinese patent with publication number 107126955A 'a carbon-based low-temperature sintering flue gas denitration catalyst and a preparation method thereof' discloses a modified biomass coke-supported MnO₂As active component, CeO₂The powdery catalyst serving as a promoter component shows excellent performance in a fixed bed denitration test, and the denitration rate can reach over 90 percent within the range of 100-200 ℃. In addition, the chinese invention patent with publication number 108671965a, "a semicoke low-temperature SCR denitration catalyst and a preparation method thereof" proposes that activated carbon carrier is prepared from semicoke, melamine is used as a reducing agent, and the denitration efficiency of the obtained catalyst can reach more than 90% within the range of 175-300 ℃ by impregnating and roasting the active component of the supported manganese oxide. However, in consideration of the fact that catalyst components need to be coated on a large-size molded carrier in practical application and the space velocity of practical working conditions is low, how to prepare the high-efficiency monolithic catalyst needs to be further explored.

The invention patent of China with the publication number of 105854874A discloses a low-temperature denitration catalyst prepared by a low-temperature self-propagating combustion coating method, and a preparation method and application thereof in flue gas denitration, wherein substances such as glycine, urea and the like are mainly used for igniting colloidal solution, so that active components such as Mn, Ce, Al and the like are uniformly loaded on a carrier, and the NO conversion rate of the obtained monolithic catalyst can reach about 80% at 250 ℃, but the current requirement can not be met.

The Chinese invention patent with the publication number of 101879452A, "a manganese-based low-temperature denitration catalyst and a preparation method thereof" discloses a low-temperature denitration catalyst containing four elements of manganese, iron, cerium and tin, and 200mg of the obtained powder sample is used for 30000h^-1The NO conversion rate in the range of 110-200 ℃ under the airspeed can reach more than 95 percent. The patent mainly adds ammonium salt solution into precursor solution drop by drop to precipitate manganese and other elements, and then calcines to obtain the manganese and other elements oxide compound. However, the combination of various active ingredients increases the manufacturing cost, and it is important to reduce the raw material cost and optimize the preparation process to further meet the actual production on the premise of reaching the emission reduction standard.

Disclosure of Invention

In view of the above, the present invention aims to overcome the defects of the prior art, and provides a preparation method of a monolithic manganese-based catalyst for low temperature denitration. The monolithic catalyst prepared by the invention can be applied to removing nitrogen oxides by ammonia selective catalytic reduction, thereby realizing denitration treatment of sintering flue gas.

The purpose of the invention is realized by the following technical scheme: a preparation method of a monolithic manganese-based catalyst for low-temperature denitration comprises the following steps:

A. pretreatment of the carrier: soaking the honeycomb ceramic catalyst carrier in an oxidizing solvent, washing until the honeycomb ceramic catalyst carrier is neutral, and drying for later use;

B. preparing a catalyst precursor solution: dissolving manganese salt, ferric salt or manganese salt and cerium salt in a solvent to obtain a mixed solution, adding an organic compound, and heating and stirring in a water bath;

C. preparation of monolithic catalyst: drying and roasting the catalyst precursor solution to obtain catalyst powder, mixing the catalyst powder with deionized water and a complexing binder, and coating the mixture on a pretreatment carrier; or directly adding a pretreatment carrier into the catalyst precursor solution, drying and roasting the pretreatment carrier coated with the catalyst precursor solution to obtain the monolithic manganese-based catalyst for low-temperature denitration, wherein the manganese-based active component loaded on the monolithic manganese-based catalyst for low-temperature denitration is 6-14% in mass percentage.

When the mass percentage content of the manganese-based active component loaded on the monolithic manganese-based catalyst for low-temperature denitration is lower than 6%, the excellent low-temperature denitration performance cannot be achieved due to less active components; when the mass percentage of the manganese-based active component loaded on the monolithic manganese-based catalyst for low-temperature denitration is higher than 14%, the manganese-based active component is agglomerated to form a large amount of oxide particles due to the excessively high content of the metal element, so that the gas phase diffusion resistance is increased, and the activity of the catalyst is reduced. At the same time, too high a content of active component also increases the production cost per unit volume of the monolithic catalyst.

Preferably, the honeycomb ceramic catalyst carrier in step a comprises one or more of alumina ceramic and cordierite ceramic.

Preferably, the oxidizing solvent in step a comprises a phosphoric acid solution with a mass percentage concentration of 20% -40% or a hydrogen peroxide solution with a mass percentage concentration of 15% -30%.

Preferably, the honeycomb ceramic catalyst carrier in the step A is soaked in the oxidizing solvent for 4-8h, and the drying temperature is 80-120 ℃.

Preferably, the manganese salt in step B comprises one or more of manganese nitrate and manganese acetate; the ferric salt comprises one or more of ferric nitrate, ferric ammonium oxalate, ferric acetate and ferric citrate; the cerium salt comprises one or more of cerium nitrate and cerous ammonium oxalate; the solvent comprises one or more of deionized water, methanol and ethanol.

More preferably, the manganese salt in step B is preferably manganese nitrate.

Preferably, the organic compound in step B comprises one or more of urea, citric acid and glycine.

Preferably, the molar ratio of the manganese element to the iron element in the mixed solution in the step B is (0.5-1.5): 1; the molar ratio of the manganese element to the cerium element is (1-5) to (5-9), and the molar ratio of the organic compound to the manganese element is (0.5-5) to 1; more preferably, the molar ratio of the urea to the manganese elements is (3-5): 1.

In the ferromanganese element ratio and the manganese-cerium element ratio, when the manganese element is too small and iron or cerium is too large, the activity is lowered. The nitrate is insufficiently oxidized due to too few organic matters, and the productivity and the activity of the catalyst are reduced; the excessive organic matters can cause the excessive oxidation and even sintering of nitrate, and the activity of the catalyst is reduced.

Preferably, the heating temperature of the water bath in the step B is 70-90 ℃, and the heating time is 1-4 h.

More preferably, TiO (NO) is further added before the organic compound is added in the step B₃) Precursor solution of said TiO (NO)₃) The molar weight of the precursor solution is 2 times of that of the manganese element; the TiO (NO)₃) The preparation method of the precursor solution comprises the following steps: taking tetrabutyl titanate with 2 times of the molar weight of manganese as a precursor of titanium dioxide, slowly dripping absolute ethyl alcohol into a beaker containing a proper amount of tetrabutyl titanate for alcoholysis, stirring the solution at room temperature by using magnetic force, dripping deionized water into the alcoholysis solution in the same way to hydrolyze the solution to generate TiO (OH)₂Precipitating, and then dripping a proper amount of nitric acid to dissolve the precipitate to obtain clear and transparent TiO (NO)₃) A precursor liquid.

Preferably, the step C specifically includes the following steps:

drying the catalyst precursor solution at 80-120 ℃ for 6-12 h and roasting at 450-650 ℃ for 4-6 h to obtain catalyst powder, mixing ionic water and a complexing binder, spraying the pretreated carrier by using a compressor spray gun for 1-5 min, drying at 80-120 ℃ for 1-3 h, and repeating for a plurality of times to obtain the monolithic manganese-based catalyst for low-temperature denitration, wherein the mass ratio of the pretreated carrier to the deionized water to the complexing binder is 1: (0.75-1.25): (0.05-0.2);

or adding the pretreated carrier into a catalyst precursor solution, carrying out ultrasonic impregnation for 10-60 min, drying the pretreated carrier coated with the catalyst precursor solution at 150-350 ℃ for 1h, and roasting at 450-650 ℃ for 5-6 h to obtain the monolithic manganese-based catalyst for low-temperature denitration; more preferably, the ultrasonic immersion time is 35-60 min.

When the roasting temperature is too high, excessive oxidation is caused, excessive catalyst lattice distortion is generated, and the activity is reduced; if the roasting temperature is too low, the oxidation of the nitrate of the precursor is insufficient, and the activity is also reduced.

Preferably, the complex binder comprises one or more of silica sol, aluminum sol, methyl cellulose.

In summary, compared with the prior art, the invention has the following beneficial effects:

(1) the catalyst is prepared by mainly utilizing the manganese-based oxide composite iron element or cerium element, the raw material components are simple, the catalyst is nontoxic and harmless, the preparation process is quick, and the large-scale production test can be further realized;

(2) the content range of the carrier coating active component in the catalyst loading method is mainly between 6 and 14 percent. Aiming at the same precursor, the monolithic catalyst loaded with low-content active components and prepared by the optimized process has higher specific activity. Therefore, the repeated utilization rate of the precursor solution can be improved, and the production cost is reduced;

(3) the invention realizes high-efficiency coating preparation on the basis of the powder catalyst and the honeycomb ceramic carrier, optimizes the dispersibility of active components on the honeycomb ceramic carrier, thereby improving the reactant diffusion condition in the gas-solid two-phase reaction and reducing the denitration reaction activity temperature, and ensuring that the catalyst can be used for 8000h^-1Under the condition of low space velocity, the NO conversion rate in the temperature range of 110-160 ℃ can reach more than 90 percent, and the performance is superior to that of the common forming and powder system manganese-based catalyst.

Drawings

Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:

FIG. 1 shows NH as catalyst for the monolithic manganese-based catalyst for low-temperature denitration in examples 1 to 7₃-a plot of NO conversion during SCR denitration.

Detailed Description

The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, which ranges of values are to be considered as specifically disclosed herein, the invention is described in detail below with reference to specific examples: