CN110773153A - A supported manganese-based medium and low temperature denitration catalyst, preparation method and application thereof - Google Patents

Abstract

The invention discloses a supported manganese-based medium and low temperature denitration catalyst, preparation and application thereof, and belongs to the technical field of environmental protection catalytic materials. The catalyst is prepared by adding carrier titania or alumina into a divalent manganese salt solution, stirring, mixing, drying, and then adding potassium permanganate to conduct solid-phase interfacial reaction. The denitration catalyst provided by the invention is used for selective catalytic reduction and denitration reaction, has significantly enhanced low-temperature (100-200°C) or medium-low temperature (200-300°C) catalytic activity, and has excellent low-temperature denitration performance at high loadings , the typical sample has a space velocity of 30000ml/g h, 100 ℃, the NO conversion rate in the mixture reaches 98.7%, and the NO conversion rate at 200 ℃ is 98.9%; the typical sample has excellent medium-temperature denitrification performance at low loading. When the space velocity is 60000ml/g·h and 200℃, the NO conversion rate in the mixture reaches 99.0%. When the temperature rises to 300℃, the NO conversion rate is still 99.6%. The denitration catalyst provided by the invention has potential application value.

Description

A supported manganese-based medium and low temperature denitration catalyst, preparation method and application thereof

technical field

The invention relates to the technical field of environmental protection catalytic materials, in particular to a supported manganese-based medium and low temperature denitration catalyst, a preparation method and an application thereof.

Background technique

In recent years, the state has paid more attention and effect to environmental protection and environmental governance, and has tightened control over the discharge of pollutants. Among them, NOx is a type of air pollutant that produces great pollution. The main sources are boiler exhaust, nitrification plant exhaust, etc. In particular, coal-fired power generation still occupies an absolute dominant position in my country, producing a large amount of exhaust gas and containing NOx. Selective catalytic reduction (SCR), the most widely used denitration method at present, uses a reducing agent to reduce NOx to N ₂ which is harmless to the atmosphere. Common reducing agents are hydrocarbons, hydrogen (H ₂ ) and ammonia (NH ₃ ). With the development of ammonia synthesis technology, the cost of using NH ₃ is significantly reduced. Therefore, NH ₃ -SCR is currently the most commonly used catalytic denitration method.

The denitration catalyst is the core of the NH ₃ -SCR technology. The structure and composition of the catalyst have an extremely important influence on the catalytic denitration efficiency and the service life of the catalyst. According to the classification of catalyst active components, NH ₃ -SCR catalysts can be divided into noble metal catalysts, molecular sieve catalysts and transition metal oxide catalysts. Considering the cost, transition metal oxide-based catalysts are widely used at present, among which V ₂ O ₅ -based catalysts have the most extensive industrial applications. V ₂ O ₅ -based catalysts are usually used between 300 and 400°C, and have excellent catalytic denitration performance. In general, in addition to NOx, there are SO ₂ and dust in the exhaust gas. SO ₂ has a strong toxic effect on the catalyst. On the surface of the catalyst, SO ₂ can be oxidized to form SO ₃ , and SO ₃ combines with active metal oxides or NH ₃ to form sulfuric acid. Salt, covering the surface of the catalyst, causes the reduction of active components, and the catalytic performance drops significantly. Therefore, in the new exhaust gas purification process in recent years, desulfurization and dust removal are carried out first, and then denitrification is carried out to reduce the requirements for the catalyst's anti-sulfur performance. V ₂ O ₅ -based catalysts can no longer meet the requirements of new technology at medium and low temperature. At the same time, V ₂ O ₅ has the problem of easy volatilization and loss, which causes the denitration activity of the catalyst to decrease. At the same time, V ₂ O ₅ has great harm to the atmosphere and human health, resulting in secondary pollution.

For the denitration catalysts commonly used in reaction devices for medium-temperature denitration (200-300°C) and medium-low temperature denitration (100-300°C), the activity of manganese-based denitration catalysts currently used needs to be improved. When the temperature of the system decreases, the NO conversion rate in the exhaust gas also decreases, which affects the catalytic denitration effect.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a supported manganese-based medium and low temperature denitration catalyst, preparation method and application thereof, which have excellent low temperature catalytic denitration and medium and low temperature reaction performance, and a wide operating temperature window; can be applied to flue gas denitration, In order to solve the problem that the manganese-based denitration catalyst has poor activity at medium and low temperature in the existing flue gas SCR denitration catalyst technology.

The technical scheme that the present invention intends to solve the above problems is as follows:

A supported manganese-based medium and low temperature denitration catalyst is prepared by adding carrier titania or alumina into a divalent manganese salt solution, stirring, mixing, drying and then adding potassium permanganate through solid-phase interface reaction.

The supported manganese-based medium and low-temperature denitration catalyst of the present invention is prepared by an impregnation-mechanical method, using titanium dioxide or aluminum oxide as a carrier, firstly introducing a highly dispersed low-valent manganese salt through the impregnation method, and then adding a high-valent manganese salt potassium permanganate, Through grinding and mixing and solid-phase interface reaction, potassium permanganate and divalent manganese salt can be fully contacted, and then through aging, washing and roasting, potassium permanganate and divalent manganese salt are more fully reacted. In the present invention, the chemical reaction of the high-valent manganese salt and the divalent manganese salt only occurs at the interface of the solid contact, so that the crystal grains of the denitration catalyst formed in this way are smaller (larger specific surface area), and the crystal surface has more defect sites, more conducive to the catalytic reaction.

Further, in a preferred embodiment of the present invention, when the supported amount of the catalyst (the percentage by mass of manganese salt in the catalyst carrier) is 2% to 27%, it is a low-loaded denitration catalyst with excellent medium-temperature denitration performance , the typical sample has a space velocity of 60000ml/g·h, the NO conversion rate in the mixture at 200℃ is 99.0%, and the NO conversion rate at 300℃ is 99.6%.

Further, in a preferred embodiment of the present invention, when the loading of the above catalyst is 27% to 60%, it is a high-loading denitration catalyst, which has excellent low-temperature denitration performance. A typical sample has a space velocity of 30000ml/ g·h, the NO conversion rate at 100 °C reaches 98.7%, and the NO conversion rate at 200 °C is 98.9%.

The preparation method of the above-mentioned supported manganese-based medium-low temperature denitration catalyst, comprising the following steps:

(1) Impregnation: after adding the divalent manganese salt into the water to dissolve, and adding the carrier titanium dioxide or alumina, stirring and mixing, and drying to obtain the initial sample of the divalent manganese salt;

(2) grinding and mixing and solid-phase interfacial reaction: adding potassium permanganate solid to the initial sample of divalent manganese salt, and performing sufficient grinding and mixing and solid-phase interfacial reaction to obtain a manganese-containing precursor;

(3) Aging: aging the manganese-containing precursor at 50-150° C. for 2-8 hours to obtain an initial sample of the catalyst;

(4) Washing: For the initial catalyst sample after aging of the high-load manganese-containing precursor, wash it with deionized water until the filtrate is colorless; for the catalyst sample after the aging of the low-load manganese-containing precursor, no washing is required ;

(5) Roasting: Pre-calcining the catalyst initial sample treated in step (4) at a temperature of 150-250°C for 0.5-1.5h, then heating up to a temperature of 330-375°C for further calcination for 2-5h to obtain a supported Mn-based medium and low temperature denitration catalyst.

Compared with the traditional impregnation method, the present invention can make the potassium permanganate and the divalent manganese salt fully contacted by grinding, which effectively solves the problem that the low-valent manganese salt directly decomposes and agglomerates on the surface of the carrier during the roasting process in the traditional impregnation method to form a large The particles are not conducive to the effective progress of the reaction, and at the same time lead to poor dispersibility and few active sites of the generated denitration catalyst.

In addition, the present invention also carries out washing treatment for the catalyst initial sample after the aging of the high-loading manganese-containing precursor before calcination, and partially synthetic raw materials ( Potassium permanganate, divalent manganese salt) washing and removal, in the removed potassium permanganate raw material, the K ⁺ of its band is an important poison in the selective catalytic denitrification reaction, and it is easy to occupy the acid site and reduce the adsorption of NH ₃ performance, resulting in a decrease in catalytic denitration efficiency. Through washing, useless and toxic components in the aged manganese-containing precursor are removed to ensure the purity and catalytic activity of the denitration catalyst obtained by roasting. For samples with low loadings, no washing is required, and unreacted manganese salts can be converted into manganese oxides in the subsequent roasting process, which does not have toxic effects, reduces operation steps and saves water to avoid waste water.

In the present invention, potassium permanganate and manganese acetate that have not undergone redox reaction can be fully decomposed to form manganese oxides by roasting to form more active sites; meanwhile, the interaction between the carrier and the active components is enhanced by roasting, thereby enhancing the catalytic performance of the catalyst. stability. In addition, by controlling the roasting temperature, the present invention ensures that the potassium permanganate and the divalent manganese salt can fully react, and the surface lattice oxygen of the generated manganese-based denitration catalyst is more stable. This is because the temperature is too low, the potassium permanganate and divalent manganese salts cannot be completely decomposed, and it is easy to cover the active sites on the catalyst surface, reducing the catalytic reaction activity; if the temperature is too low, the surface lattice oxygen of the manganese-based denitration catalyst is easy to remove. , the average valence state of Mn decreases, which is not conducive to the selective catalytic denitration reaction.

Further, in a preferred embodiment of the present invention, the divalent manganese salt in the above step (1) is manganese acetate or manganese nitrate.

Further, in a preferred embodiment of the present invention, the titanium dioxide in the above step (1) is an anatase phase, and its specific surface area is 50-100 m ² /g.

Preferably, the above-mentioned titanium dioxide is an anatase phase, and its specific surface area is 80 m ² /g.

Further, in a preferred embodiment of the present invention, the alumina in the above step (1) is a γ phase, and its specific surface area is 120-180 m ² /g.

Preferably, the above-mentioned alumina is γ-phase, and its specific surface area is 140 m ² /g.

Further, in a preferred embodiment of the present invention, the Mn molar ratio of potassium permanganate and divalent manganese salt in the manganese-containing precursor in the above step (2) is 1:5 to 3:2.

Further, in a preferred embodiment of the present invention, the Mn molar ratio of potassium permanganate and divalent manganese salt in the above manganese-containing precursor is 2:3.

Further, in a preferred embodiment of the present invention, in the above-mentioned step (5), the initial sample of the catalyst is pre-calcined at 150-250 ℃, and the temperature is raised to 330-375 ℃ for further post-calcination, wherein the heating rate is 2-5 ℃. /minute.

Application of the above supported manganese-based medium and low temperature denitration catalyst in low temperature and medium and low temperature NH ₃ -SCR catalytic denitration reaction.

The present invention has the following beneficial effects:

The supported manganese-based medium and low temperature denitration catalyst provided by the present invention has significantly enhanced medium and low temperature catalytic activity, is used for selective catalytic reduction and denitration reaction, and has excellent low temperature denitration performance at high loading capacity, and has excellent low temperature denitration performance at 30000ml/g·h The NO conversion rate at 100 °C can reach 98.7%, and the NO conversion rate at 200 °C can reach 98.9%; it has excellent medium-temperature denitrification performance at low loading, the space velocity is 60000ml/g h, at 200 °C The NO conversion rate in the mixed gas can reach 99.0%, and the NO conversion rate is still 99.6% at 300 °C. The stability test and analysis of typical catalyst samples were carried out, the space velocity was 60000ml/g·h, and the reaction temperature was 200℃. When stable (120min) for 2h, NO conversion rate is 93.1%; when stable (720min) for 12h, NO conversion rate is 93.5%; when stable (1440min) for 24h, NO conversion rate is 97.5%; when stable (2880min) 48h, NO conversion rate The conversion rate was 98.1%, and the catalytic denitrification performance was not observed to decrease significantly with the increase of use time, and even slightly increased.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the following briefly introduces the accompanying drawings used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope, and for those of ordinary skill in the art, other related drawings can also be obtained according to these drawings without any creative effort.

Fig. 1 is OMTi-2 prepared in Example 2 of the present invention and the catalyst prepared in Comparative Examples 1 and 2 to test and analyze the denitration performance of the catalyst;

Fig. 2 is OMAl-3 prepared in Example 5 of the present invention and the catalyst prepared in Comparative Example 3 to carry out the test and analysis result diagram of catalyst denitration performance;

Fig. 3 shows the variation curve of NO conversion rate obtained by the stability test of OMAl-3 prepared in Example 5 of the present invention at a test space velocity of 60000ml/g·h and a reaction temperature of 200°C.

Detailed ways

The principles and features of the present invention will be described below with reference to the embodiments and accompanying drawings. The examples are only used to explain the present invention, but not to limit the scope of the present invention. If the specific conditions are not indicated in the examples, it is carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used without the manufacturer's indication are conventional products that can be purchased from the market.

It should be noted that, in the following embodiments of the present invention, the divalent manganese salt is preferably manganese acetate, which can be replaced by an equimolar amount of manganese nitrate.

In addition, the simulated flue gas conditions were NO (500ppm), NH ₃ (500ppm), O ₂ (5%), and argon was a mixture of equilibrium gas; the reaction space velocity was 60000ml/g·h; the reaction temperature was 100～300℃. The NO concentration is detected and analyzed by FGA-4100, and the NO conversion rate is calculated by the following formula:

Among them, [NO] _in refers to the NO concentration at the reactor inlet, and [NO] _out refers to the NO concentration at the reactor outlet.

Comparative Example 1

According to the literature, a 1% V ₂ O ₅ -4% MoO ₃ -TiO ₂ catalyst sample was prepared as Comparative Example 1, and its preparation included the following steps: weighing 0.15 g of ammonium molybdate tetrahydrate, dissolved in 10 ml of deionized water; weighing Amount of TiO ₂ 2.85g, stirred at room temperature for 6h; transferred to an oven at 80°C for drying for 12h; transferred to a tube furnace for calcination at 450°C for 3h in an air atmosphere; weighed 0.04g of ammonium metavanadate and dissolved in 10ml of deionized water; Add the above calcined samples, stir at room temperature for 6 hours; transfer to an oven at 80 °C for drying for 12 hours; transfer to a tube furnace for calcination at 450 °C for 3 hours in an air atmosphere to obtain a catalyst sample marked as 1% V ₂ O ₅ -4% MoO ₃ -TiO ₂ .

The 1%V ₂ O ₅ -4% MoO ₃ -TiO ₂ catalyst of Comparative Example 1 was subjected to denitration performance analysis. Under the test space velocity of 30000ml/g·h and the reaction temperature of 100°C, the NO conversion rate was 9.8%; the reaction When the temperature is 150°C, the NO conversion rate is 20.7%; when the reaction temperature is 200°C, the NO conversion rate is 67.2%.

Comparative Example 2

According to the literature, a 20% MnO ₂ /TiO ₂ catalyst sample was prepared by impregnation method as Comparative Example 2. The preparation included the following steps: weighing 1.69g of manganese acetate, dissolved in 8ml of deionized water; weighing 2.40g of TiO ₂ , at room temperature Stir for 6h; transfer to 80°C oven for drying for 12h; transfer to tube furnace for calcination at 200°C for 1h and 350°C for 3h in air atmosphere to obtain a catalyst sample marked as 20%MnO ₂ /TiO ₂ .

The denitration performance of the 20% MnO ₂ /TiO ₂ catalyst prepared in Comparative Example 2 was analyzed. Under the test space velocity of 30,000 ml/g·h, when the reaction temperature was 100 °C, the NO conversion rate was 26.8%; when the reaction temperature was 150 °C, the NO conversion rate was 26.8%. The NO conversion rate was 87.5%; when the reaction temperature was 200°C, the NO conversion rate was 99.6%.

The catalysts prepared in Comparative Examples 1 and 2 were tested and analyzed for catalytic denitration performance, wherein the simulated flue gas composition was: 500ppm NO, 500ppm NH ₃ , 5% O ₂ , argon was the balance gas, the gas flow rate was 100ml/min, and the space velocity 30000ml/g·h, test temperature 100～200℃.

Comparative Example 3

According to the literature, a 5% MnO ₂ /γ-Al ₂ O ₃ catalyst sample was prepared by impregnation method. As control example 3, its preparation included the following steps: weighing 0.42g manganese acetate, dissolved in 8ml deionized water; weighing γ -Al ₂ O ₃ 2.85g, stirred at room temperature for 6h; transferred to an oven at 80°C for drying for 12h; transferred to a tube furnace for calcination at 200°C for 1h and 350°C for 3h in an air atmosphere to obtain a catalyst sample marked as 5%MnO ₂ /γ-Al ₂ O ₃ .

The denitration performance of the 5% MnO ₂ /γ-Al ₂ O ₃ catalyst prepared in Comparative Example 3 was analyzed. Under the test space velocity of 60000ml/g·h and the reaction temperature of 150°C, the NO conversion rate was 85.0%; the reaction temperature was When the reaction temperature was 200°C, the NO conversion rate was 92.1%; when the reaction temperature was 250°C, the NO conversion rate was 92.7%; when the reaction temperature was 300°C, the NO conversion rate was 89.6%.

The catalyst prepared in Comparative Example 3 was tested and analyzed for catalyst denitration performance, wherein the simulated flue gas composition was: 500ppm NO, 500ppm NH ₃ , 5% O ₂ , argon was the balance gas, the flow rate was 100ml/min, and the space velocity was 60000ml/ g·h, the test temperature is 100～200℃.

Example 1:

The supported manganese-based low-temperature denitration catalyst sample of the present embodiment is prepared by the following steps:

(1) Impregnation: Weigh 1.01 g of manganese acetate and dissolve it into 8 mL of deionized water, add 2.4 g of carrier titanium dioxide, stir at room temperature for 6 hours, mix well, transfer to an oven at 80°C for 12 hours, and grind to powder to obtain divalent Initial sample of manganese salt;

(2) Grinding and mixing and solid-phase interface reaction: adding potassium permanganate solid to the initial sample of divalent manganese salt, and performing sufficient grinding and mixing and solid-phase interface reaction for 20 minutes to obtain a manganese-containing precursor; among them, potassium permanganate The molar ratio of Mn to divalent manganese salt is 1:5, and the total mass of divalent manganese salt and potassium permanganate is 27% of the carrier mass.

(3) Aging: aging the manganese-containing precursor at 50°C for 8 hours in an air atmosphere to obtain an initial sample of the catalyst;

(4) washing: wash with deionized water until the filtrate is colorless;

(5) Roasting: in an air atmosphere, pre-calcined at a temperature of 150 °C for 1.5 h, and then heated to a temperature of 300 °C at a heating rate of 2 °C/min for further post-roasting for 5 h to obtain a supported manganese-based medium and low temperature denitration catalyst.

The denitration catalyst prepared in Example 1 was marked as OMTi-1, and its denitration performance was analyzed. Under the test space velocity of 30000ml/g·h and the reaction temperature of 100℃, the NO conversion rate was 92.3%; When the temperature is 150°C, the NO conversion rate is 98.9%; when the reaction temperature is 200°C, the NO conversion rate is 98.9%.

Example 2:

The supported manganese-based low-temperature denitration catalyst sample of the present embodiment is prepared by the following steps:

(1) Impregnation: Weigh 0.51 g of manganese acetate and dissolve it into 8 mL of deionized water, add 2.7 g of carrier titanium dioxide, stir at room temperature for 6 hours, mix well, transfer to an oven at 80°C for 12 hours, and grind to powder to obtain bivalent Initial sample of manganese salt;

(2) Grinding and mixing and solid-phase interface reaction: adding potassium permanganate solid to the initial sample of divalent manganese salt, and performing sufficient grinding and mixing and solid-phase interface reaction for 20 minutes to obtain a manganese-containing precursor; among them, potassium permanganate The molar ratio of Mn to divalent manganese salt is 2:3, and the total mass of divalent manganese salt and potassium permanganate is 60% of the mass of the carrier.

(3) Aging: aging the manganese-containing precursor at 65°C for 5 hours in an air atmosphere to obtain a catalyst initial sample;

(4) washing: wash with deionized water until the filtrate is colorless;

(5) Roasting: in an air atmosphere, pre-calcined at a temperature of 200 °C for 1 h, and then heated up to a temperature of 350 °C at a heating rate of 3 °C/min for further post-calcination for 4 h to obtain a supported manganese-based medium and low temperature denitration catalyst.

The denitration catalyst prepared in Example 2 was marked as OMTi-2, and its denitration performance was analyzed. Under the test space velocity of 30,000 ml/g·h and the reaction temperature of 100 °C, the NO conversion rate was 95.2%; the reaction temperature When the temperature is 150°C, the NO conversion rate is 100.0%; when the reaction temperature is 200°C, the NO conversion rate is 100.0%.

In the test and analysis of the catalytic denitration performance of the catalyst prepared in Example 2, the simulated flue gas composition is consistent with the simulated flue gas composition in the test and analysis of the catalytic denitration performance of the catalyst prepared in Comparative Example 1-2, and is consistent with The catalysts prepared in Comparative Example 1-2 were compared for the catalytic performance of NH ₃ -SCR. The results are shown in Figure 1. Under the test space velocity of 30000 ml/g·h, the sample of Comparative Example 1 was a common commercial V-based denitration catalyst with 1% V ₂ O ₅ -4%MoO ₃ -TiO ₂ has extremely poor low temperature denitration performance, the NO conversion rate in the range of 100-200℃ is less than 70%, and the NO conversion rate at 100℃ is only 9.8%; Compared with commercial V-based catalysts, the supported manganese-based denitration catalyst 20%MnO ₂ /TiO ₂ synthesized by traditional impregnation method has relatively better low-temperature denitration performance, but the NO conversion rate is still less than 90% at 100-150 °C. The NO conversion rate at 100 °C is only 26.8%, and it is difficult to achieve efficient NO removal under low-temperature denitration conditions. The sample OMTi-2 in Example 2 uses anatase TiO2 as the carrier and adopts the solid-phase interface reaction method. It has excellent denitration performance in the process of low temperature denitration, and in the temperature range of 100 to 200 °C, the NO conversion rate in the mixture reaches more than 95%.

Example 3:

The supported manganese-based medium and low temperature denitration catalyst sample of the present embodiment is prepared by the following steps:

(1) Impregnation: Weigh 0.05 g of manganese acetate and dissolve it in 8 mL of deionized water, add 2.97 g of carrier γ-Al ₂ O ₃ , stir at room temperature for 6 hours, mix well, transfer to an oven at 80°C for 12 hours, and grind to powder form, to obtain the initial sample of divalent manganese salt;

(2) Grinding and mixing and solid-phase interface reaction: adding potassium permanganate solid to the initial sample of divalent manganese salt, and performing sufficient grinding and mixing and solid-phase interface reaction for 20 minutes to obtain a manganese-containing precursor; among them, potassium permanganate The molar ratio of Mn to divalent manganese salt is 2:3, and the total mass of divalent manganese salt and potassium permanganate is 2% of the mass of the carrier.

(3) Aging: The manganese-containing precursor was aged at 80°C for 4 hours in an air atmosphere to obtain an initial sample of the catalyst;

(4) Roasting: in an air atmosphere, pre-calcined at a temperature of 250 °C for 0.5 h, then heated to a temperature of 400 °C at a heating rate of 4 °C/min for further post-roasting for 3 h to obtain a supported manganese-based medium and low temperature denitration catalyst.

The denitration catalyst prepared in Example 3 was marked as OMAl-1, and its denitration performance was analyzed. Under the test space velocity of 60,000 ml/g·h and the reaction temperature of 150 °C, the NO conversion rate was 69.4%; the reaction temperature When the reaction temperature is 200°C, the NO conversion rate is 87.6%; when the reaction temperature is 250°C, the NO conversion rate is 97.0%; when the reaction temperature is 300°C, the NO conversion rate is 99.6%.

Example 4:

The supported manganese-based medium and low temperature denitration catalyst sample of the present embodiment is prepared by the following steps:

(1) Impregnation: Weigh 0.15 g of manganese acetate and dissolve it into 8 mL of deionized water, add 2.91 g of carrier γ-Al ₂ O ₃ , stir at room temperature for 6 hours, mix well, transfer to an oven at 80°C for 12 hours, and grind to powder form, to obtain the initial sample of divalent manganese salt;

(2) Grinding and mixing and solid-phase interface reaction: adding potassium permanganate solid to the initial sample of divalent manganese salt, and performing sufficient grinding and mixing and solid-phase interface reaction for 20 minutes to obtain a manganese-containing precursor; among them, potassium permanganate The molar ratio of Mn to divalent manganese salt is 2:3, and the total mass of divalent manganese salt and potassium permanganate is 15% of the mass of the carrier.

(3) Aging: The manganese-containing precursor was aged at 110 °C for 3 hours in an air atmosphere to obtain an initial sample of the catalyst;

(4) Roasting: in an air atmosphere, pre-calcined at a temperature of 220 °C for 1 h, and then heated to a temperature of 450 °C at a heating rate of 5 °C/min for further post-calcination for 2 h to obtain a supported manganese-based medium and low temperature denitration catalyst.

The denitration catalyst prepared in Example 4 was marked as OMAl-2, and its denitration performance was analyzed. Under the test space velocity of 60,000 ml/g·h and the reaction temperature of 150 °C, the NO conversion rate was 88.5%; the reaction temperature When the reaction temperature is 200°C, the NO conversion rate is 99.8%; when the reaction temperature is 250°C, the NO conversion rate is 97.0%; when the reaction temperature is 300°C, the NO conversion rate is 99.6%.

Example 5:

The supported manganese-based medium and low temperature denitration catalyst sample of the present embodiment is prepared by the following steps:

(1) Impregnation: Weigh 0.25 g of manganese acetate and dissolve it in 8 mL of deionized water, add 2.85 g of carrier γ-Al ₂ O ₃ , stir at room temperature for 6 hours, mix well, transfer to an oven at 80°C for 12 hours, and grind to powder form, to obtain the initial sample of divalent manganese salt;

(2) Grinding and mixing and solid-phase interface reaction: adding potassium permanganate solid to the initial sample of divalent manganese salt, and performing sufficient grinding and mixing and solid-phase interface reaction for 20 minutes to obtain a manganese-containing precursor; among them, potassium permanganate The molar ratio of Mn to divalent manganese salt is 2:3, and the total mass of divalent manganese salt and potassium permanganate is 27% of the mass of the carrier.

(3) Aging: The manganese-containing precursor was aged at 150°C for 2 hours in an air atmosphere to obtain a preliminary sample of the catalyst;

(4) Roasting: in an air atmosphere, pre-calcined at a temperature of 240 °C for 0.8 h, and then heated to a temperature of 420 °C at a heating rate of 3 °C/min for further post-calcination for 2.5 h to obtain a supported manganese-based medium and low temperature denitration catalyst. .

The denitration catalyst prepared in Example 5 was marked as OMAl-3, and its denitration performance was analyzed. Under the test space velocity of 60,000 ml/g·h and the reaction temperature of 150 °C, the NO conversion rate was 88.5%; the reaction temperature When the reaction temperature is 200°C, the NO conversion rate is 98.9%; when the reaction temperature is 250°C, the NO conversion rate is 99.4%; when the reaction temperature is 300°C, the NO conversion rate is 99.4%.

The NH ₃ -SCR catalytic performance was compared between the OMAl-3 prepared in Example 5 and the catalyst prepared in Comparative Example 3. The results are shown in Figure 2. Under the test space velocity of 60000 ml/g·h, the traditional impregnation method was adopted in Comparative Example 3. For the synthesized 5%MnO ₂ /γ-Al ₂ O ₃ , the NO conversion first increased and then decreased between 150 and 300°C, and the maximum NO conversion rate reached 92.7% within the temperature range (150 to 300°C).

Example 5 The sample OMAl-3, using γ-Al ₂ O ₃ as the carrier, was synthesized by the solid-phase interface method, and the maximum NO conversion rate reached 99.4% in the temperature range (150 ~ 300 ° C), and in 200 ~ 300 The NO conversion rate is maintained at about 99% in the range of ℃, that is, close to the complete removal of NO. In practical applications, if the NO concentration is higher or the space velocity is higher, the sample of this example will show a more obvious activity advantage for selective catalytic reduction and denitrification.

Example 6:

The supported manganese-based medium and low temperature denitration catalyst sample of the present embodiment is prepared by the following steps:

(1) Impregnation: Weigh 0.51 g of manganese acetate and dissolve it into 8 mL of deionized water, add 2.70 g of carrier γ-Al ₂ O ₃ , stir at room temperature for 6 hours, mix well, transfer to an oven at 80°C for 12 hours, and grind to powder form, to obtain the initial sample of divalent manganese salt;

(2) Grinding and mixing and solid-phase interface reaction: adding potassium permanganate solid to the initial sample of divalent manganese salt, and performing sufficient grinding and mixing and solid-phase interface reaction for 20 minutes to obtain a manganese-containing precursor; among them, potassium permanganate The molar ratio of Mn to divalent manganese salt is 3:2, and the total mass of divalent manganese salt and potassium permanganate is 7.5% of the mass of the carrier.

(3) Aging: The manganese-containing precursor was aged at 80°C for 4 hours in an air atmosphere to obtain an initial sample of the catalyst;

(4) Roasting: in an air atmosphere, pre-calcined at a temperature of 250 °C for 1.2 h, and then heated to a temperature of 450 °C at a heating rate of 4 °C/min for further post-roasting for 2.5 h to obtain a supported manganese-based medium and low temperature denitration catalyst. .

The denitration catalyst prepared in Example 6 was marked as OMAl-4, and its denitration performance was analyzed. Under the test space velocity of 60,000 ml/g·h and the reaction temperature of 150 °C, the NO conversion rate was 80.0%; the reaction temperature When the reaction temperature is 200°C, the NO conversion rate is 82.6%; when the reaction temperature is 250°C, the NO conversion rate is 77.0%; when the reaction temperature is 300°C, the NO conversion rate is 72.1%.

It can be seen from Figures 1 and 2 that the catalyst formulation and its application provided by the present invention can prepare low-temperature (100-200°C) and medium-temperature (200-300°C) denitration catalysts with excellent performance by adjusting the catalyst carrier and the loading amount. .

Test Example: Stability Analysis

On the basis of comparison and optimization, the stability test of the OMAl-3 catalyst sample prepared in Example 5 was carried out. The reaction process conditions were, the space velocity was 60000ml/g h, the reaction temperature was 200℃, and the catalytic process was continuously carried out for 2880min (48h). , the NO conversion rate change curve of Example 3 is obtained, as shown in FIG. 3 .

It can be seen from Figure 3 that the catalytic performance of the OMAl-3 sample prepared in Example 5 has no obvious decrease. At 720min (12h), the NO conversion rate was 93.5%; at 1440min (24h), the NO conversion rate was 97.5%; at 2160min (36h), the NO conversion rate was 98.1%; at 2880min (48h), the NO conversion rate 98.1%. Under laboratory conditions, at a high space velocity of 60,000 ml/g·h, and running at 200 °C for 2880 min (48 h), the catalytic performance did not decrease significantly.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

1. The supported manganese-based medium-low temperature denitration catalyst is characterized by being prepared by adding carrier titanium dioxide or aluminum oxide into a divalent manganese salt solution, stirring, mixing, drying, adding potassium permanganate and carrying out solid-phase interface reaction.

2. The supported manganese-based medium-low temperature denitration catalyst of claim 1, wherein when the supported amount of the catalyst (manganese salt accounts for 2-27% of the mass of the catalyst carrier), the catalyst is a low-supported denitration catalyst, and has excellent medium-temperature denitration performance, and typical samples have an airspeed of 60000 ml/g-h, the NO conversion rate in a mixed gas at 200 ℃ is 99.0%, and the NO conversion rate at 300 ℃ is 99.6%.

3. The supported manganese-based medium-low temperature denitration catalyst of claim 1, wherein the supported manganese-based medium-low temperature denitration catalyst is a high-supported denitration catalyst with an excellent low-temperature denitration performance when the supported amount of the catalyst is 27% to 60%, and the typical sample has an NO conversion rate of 98.7% at 100 ℃ and an NO conversion rate of 98.9% at 200 ℃ at an airspeed of 30000 ml/g-h.

4. The method for preparing the supported manganese-based medium and low temperature denitration catalyst according to any one of claims 1 to 3, comprising the steps of:

(1) dipping: adding divalent manganese salt into water for dissolving, adding carrier titanium dioxide or alumina, stirring and mixing uniformly, and drying to obtain a divalent manganese salt primary sample;

(2) grinding and mixing and solid phase interface reaction: adding potassium permanganate solid into a bivalent manganese salt initial sample, and carrying out full grinding and mixing and solid phase interface reaction to obtain a manganese-containing precursor;

(3) aging: aging the manganese-containing precursor at 50-150 ℃ for 2-8 h to obtain a primary catalyst sample;

(4) washing: washing the aged catalyst primary sample with high-load manganese-containing precursor with deionized water until the filtrate is colorless; the initial sample of the catalyst after the aging of the low-load manganese-containing precursor is not required to be washed;

(5) roasting: and (3) pre-roasting the catalyst primary sample treated in the step (4) at the temperature of 150-250 ℃ for 0.5-1.5 h, heating to 330-375 ℃, and further roasting for 2-5 h to prepare the supported manganese-based medium-low temperature denitration catalyst.

5. The preparation method of the supported manganese-based medium-low temperature denitration catalyst according to claim 4, wherein the manganous salt in the step (1) is manganese acetate or manganese nitrate.

6. The preparation method of the supported manganese-based medium-low temperature denitration catalyst according to claim 4, wherein the titanium dioxide in the step (1) is anatase phase, and the specific surface area of the titanium dioxide is 50-100 m ²/g。

7. The preparation method of the supported manganese-based medium-low temperature denitration catalyst according to claim 4, wherein the molar ratio of Mn in the potassium permanganate and the manganous salt in the manganese-containing precursor in the step (2) is 1: 5-3: 2.

8. the preparation method of the supported manganese-based medium-low temperature denitration catalyst according to claim 7, wherein the molar ratio of Mn of the potassium permanganate in the manganese-containing precursor to Mn of the manganous salt is 2: 3.

9. the preparation method of the supported manganese-based medium-low temperature denitration catalyst according to claim 4, characterized in that in the step (5), a catalyst initial sample is firstly pre-roasted at 150-250 ℃, and is further roasted after being heated to 330-375 ℃, wherein the heating rate is 2-5 ℃/min.

10. The supported manganese-based medium and low temperature denitration catalyst as set forth in any one of claims 1 to 3, NH being generated at low temperature and medium and low temperature ₃Application to SCR catalytic denitration reactions.

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