CN115709062A

CN115709062A - Denitration catalyst and preparation method thereof

Info

Publication number: CN115709062A
Application number: CN202211242621.1A
Authority: CN
Inventors: 禚玉群; 任雯; 王涛; 李亚斌; 郭谨玮; 贺文宇
Original assignee: Tsinghua University; Shanxi Research Institute for Clean Energy of Tsinghua University
Current assignee: Tsinghua University; Shanxi Research Institute for Clean Energy of Tsinghua University
Priority date: 2022-10-11
Filing date: 2022-10-11
Publication date: 2023-02-24
Anticipated expiration: 2042-10-11
Also published as: CN115709062B

Abstract

The invention discloses a denitration catalyst and a preparation method thereof, wherein the method comprises the following steps: (1) Mixing a titanium source with a first dispersant to obtain a first mixed solution; (2) Mixing a second dispersing agent with a complexing agent to obtain a second mixed solution; (3) Mixing the active component metal salt with the second mixed solution to obtain a third mixed solution; (4) Mixing the first mixed solution with the third mixed solution to obtain a fourth mixed solution; (5) And adding a precipitator into the fourth mixed solution, and then drying and roasting to obtain the denitration catalyst. Therefore, the denitration catalyst prepared by the method has high denitration efficiency under the conditions of low temperature and high airspeed, and has high water resistance and sulfur poisoning resistance.

Description

Denitration catalyst and preparation method thereof

Technical Field

The invention relates to the technical field of catalyst preparation, and particularly relates to a denitration catalyst and a preparation method thereof.

Background

Fossil energy (including petroleum, coal and natural gas) is still the main energy of the modern society, and the combustion of the fossil energy inevitably releases a large amount of nitrogen oxides, and the nitrogen oxides not only cause environmental problems such as photochemical smog, acid rain and the like, but also cause harm to human bodies and animals. When inhaled into the body, nitric oxide preferentially binds to hemoglobin, thereby preventing hemoglobin from binding with oxygen, and causing respiratory tract and lung diseases.

The low-temperature SCR denitration technology utilizes ammonia gas and NO _x The reaction generates nontoxic nitrogen and water, which is the most effective method for removing nitrogen oxide in flue gas at present, and the catalyst V is used ₂ O ₅ -WO ₃ /TiO ₂ Has been developed for higher flue gas temperatures (>300 ℃ C.) of power plant and the like NO _x And (4) removing. However, vanadium catalysts are not suitable for denitration applications in steel plants, cement plants, glass plants and other plants with low flue gas temperatures (180 to 250 ℃). In order to obtain an effective low-temperature catalyst, a great deal of research has been conducted, and it has been found that oxides of transition metal manganese react with NO under low-temperature conditions _x Has better removal effect, but because the residual sulfur dioxide in the flue gas can react with the active components in the manganese catalyst to generate sulfate, the catalyst is irreversibly inactivated, thereby reducing the activity of the manganese catalyst.

Therefore, improvement of the existing low-temperature denitration catalyst is urgently needed.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, one object of the present invention is to provide a denitration catalyst and a preparation method thereof, wherein the denitration catalyst prepared by the method has high denitration efficiency under low temperature and high space velocity conditions, and has high water resistance and sulfur poisoning resistance.

In one aspect of the present invention, a method of preparing a denitration catalyst is provided. According to an embodiment of the invention, the method comprises:

(1) Mixing a titanium source with a first dispersant to obtain a first mixed solution;

(2) Mixing a second dispersing agent with a complexing agent to obtain a second mixed solution;

(3) Mixing an active component metal salt with the second mixed solution so as to obtain a third mixed solution;

(4) Mixing the first mixed solution with the third mixed solution to obtain a fourth mixed solution;

(5) And adding a precipitator into the fourth mixed solution, and then drying and roasting to obtain the denitration catalyst.

According to the method for preparing the denitration catalyst provided by the embodiment of the invention, by adopting a sol-precipitation method, firstly, a titanium source is mixed with a first dispersing agent, so that the titanium source is uniformly dispersed in the first dispersing agent to obtain a first mixed solution, and meanwhile, a second dispersing agent is mixed with a complexing agent, so that the complexing agent is uniformly dispersed in the second dispersing agent to obtain a second mixed solution. And then mixing the active component metal salt with the second mixed solution, wherein the active component metal salt reacts with the complexing agent to generate a metal complex, so as to obtain a third mixed solution. Meanwhile, due to the addition of the catalytic assistant, acid sites are formed on the surface of the active component, the bond energy of ammonium radicals and sulfate ions is reduced, and ammonium sulfate or ammonium bisulfate generated by the reaction of reducing agent ammonia and sulfur dioxide is easier to decompose. And then mixing the first mixed solution and the third mixed solution to obtain sol, namely a fourth mixed solution, adding a precipitator into the fourth mixed solution, carrying out precipitation reaction on the metal complex and the precipitator, stopping adding the precipitator when no precipitate is generated in the fourth mixed solution, converting all active components into solid precipitates, and then drying and roasting to obtain the denitration catalyst. Compared with the impregnation method in the prior art, the denitration catalyst is prepared by adopting the sol-precipitation method, so that the active components in the active component metal salt and the titanium dioxide carrier are more uniformly distributed in the sol, and meanwhile, the active components in the active component metal salt can be directly and uniformly loaded on the titanium dioxide carrier, the agglomeration of the active components on the titanium dioxide carrier in the direct impregnation method is avoided, and the denitration catalyst has higher catalytic activity under the low-temperature condition. In conclusion, the denitration catalyst prepared by the method has high denitration efficiency under the conditions of low temperature and high airspeed, and has high water resistance and sulfur poisoning resistance.

In addition, the method for preparing a denitration catalyst according to the above embodiment of the present invention may further have the following additional technical features:

in some embodiments of the invention, in step (1), the molar ratio of the titanium source to the first dispersant is 1: (1-10). Thereby, the titanium source is advantageously uniformly dispersed in the first dispersant.

In some embodiments of the invention, in step (1), the titanium source comprises at least one of isopropyl titanate, titanyl sulfate, and tetrabutyl titanate.

In some embodiments of the invention, the molar ratio of the first dispersant to the second dispersant is 1: (1-2).

In some embodiments of the invention, the first dispersant and the second dispersant each independently comprise at least one of absolute ethanol, glycerol, and butanol.

In some embodiments of the invention, in step (2), the molar ratio of the second dispersant to the complexing agent is 1: (0.01-3).

In some embodiments of the invention, in step (2), the complexing agent comprises at least one of acetic acid, citric acid, and ethylenediaminetetraacetic acid.

In some embodiments of the invention, in step (2), the second dispersant is mixed with the complexing agent and water. Thereby, the active ingredient metal salt can be completely dissolved in the second dispersant.

In some embodiments of the invention, the molar ratio of the second dispersant to the complexing agent and the water is 1: (0.01-3): (0.5-2).

In some embodiments of the invention, in step (3), the active ingredient metal salt includes at least one of manganese nitrate, manganese acetate, manganese sulfate, ferric nitrate, ferric sulfate, ferric acetate, cerium nitrate, and cerium chloride.

In some embodiments of the invention, in step (3), the active component of the active component metal salt comprises at least one of manganese, iron, and cerium.

In some embodiments of the invention, the mass ratio of manganese, iron and cerium is 1: (0.5-2): (1-3). Therefore, the denitration catalyst can keep high activity in the presence of sulfur dioxide.

In some embodiments of the invention, the mass ratio of the active component in the active component metal salt to the titanium source is (3.53-22.5): 100.

in some embodiments of the present invention, in the step (5), the concentration of the precipitant is 0.5 to 2mol/L.

In some embodiments of the invention, in step (5), the precipitant comprises at least one of aqueous ammonia, ammonium bicarbonate, ammonium carbonate, and urea.

In a second aspect of the present invention, a denitration catalyst is provided. According to the embodiment of the invention, the denitration catalyst is prepared by adopting the method. Therefore, the denitration catalyst has high denitration efficiency under the conditions of low temperature and high airspeed, and has higher water resistance and sulfur poisoning resistance.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 is a schematic flow chart of a method for preparing a denitration catalyst according to an embodiment of the present invention.

Detailed Description

The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.

In one aspect of the present invention, a method of preparing a denitration catalyst is provided. According to an embodiment of the invention, with reference to fig. 1, the method comprises:

s100: mixing a titanium source with a first dispersant

In this step, a titanium source is mixed with a first dispersant to obtain a first mixed solution. Specifically, the titanium source and the first dispersant are mixed and then stirred to uniformly mix the two. Further, the molar ratio of the titanium source to the first dispersant is 1: (1-10). The inventors have found that if the first dispersant is added in an excessive amount, the particles are more agglomerated and sintered during firing, and hydrolysis of the titanium source is suppressed; if the addition amount of the first dispersant is too small, the particle size of the obtained colloid is large, the flocculation phenomenon of the system can occur, the stability is reduced, and even coagulation and emulsion breaking can occur.

It is to be noted that the specific types of the above-mentioned titanium source and the first dispersant are not particularly limited, and may be selected as needed by those skilled in the art, for example, the titanium source includes at least one of isopropyl titanate, titanyl sulfate, and tetrabutyl titanate; the first dispersant includes at least one of absolute ethyl alcohol, glycerol and butanol, and the stirring manner is not particularly limited, and may be, for example, mechanical stirring or magnetic stirring.

S200: mixing the second dispersant with the complexing agent

In this step, the second dispersant is mixed with the complexing agent to obtain a second mixed solution. Specifically, the second dispersing agent and the complexing agent are mixed and stirred so as to be uniformly mixed. Further, the molar ratio of the second dispersing agent to the complexing agent is 1: (0.01-3). The inventor finds that if the addition amount of the complexing agent is too much, a large amount of heat can be released in the subsequent roasting process, so that the active component in the active component metal salt is sintered, and a heterogeneous substance is generated; if the addition amount of the complexing agent is too small, the active component cannot completely form a complex with the complexing agent, and the complex still exists in a free state in the solution, so that a uniform precipitate cannot be formed, and the content of high-valence ions in the active component can be reduced.

In the specific embodiment of the invention, the second dispersing agent is mixed with the complexing agent and water, and the mixture of the second dispersing agent, the complexing agent and the water is stirred uniformly. Further, the molar ratio of the second dispersing agent to the complexing agent and water is 1: (0.01-3): (0.5-2). The inventors have found that if the amount of water added is too large, the titanium source hydrolyzes too quickly to form a homogeneous mass with the active ingredient; if the amount of water added is too small, the titanium source cannot be completely hydrolyzed, and the designed ratio of the carrier to the active ingredient cannot be formed.

Further, the molar ratio of the first dispersant to the second dispersant is 1: (1-2). The inventors found that if the amount of the second dispersant is too much, the colloidal particles may be agglomerated in the subsequent mixing step; if the amount of the second dispersant added is too small, the active ingredient cannot be dissolved.

It should be noted that the specific type of the complexing agent is not particularly limited, and may be selected by those skilled in the art according to the need, for example, the complexing agent includes at least one of acetic acid, citric acid, and ethylenediaminetetraacetic acid; the specific type of the second dispersant is the same as the first dispersant, and the stirring manner is the same as that described above, which is not repeated herein.

S300: mixing the metal salt of the active component with the second mixed solution

In this step, an active component metal salt is mixed with the second mixed solution to obtain a third mixed solution. The inventor finds that the active component metal salt reacts with the complexing agent in the second mixed solution, so that the active component and the complexing agent are combined to generate a metal complex, the metal complex is more stable in the solution, and thus, the active component metal ions are more difficult to deposit from the solution, and the metal active component can form finer grains subsequently.

It is to be noted that the specific type of the active ingredient metal salt is not particularly limited, and for example, the active ingredient metal salt includes at least one of manganese nitrate, manganese acetate, manganese sulfate, iron nitrate, iron sulfate, iron acetate, cerium nitrate, and cerium chloride.

Further, the active component in the active component metal salt includes at least one of manganese, iron, and cerium. Meanwhile, the mass ratio of manganese to iron to cerium is 1: (0.5-2): (1-3). The inventor finds that the deposition of sulfate ions and water molecules on the surface of the catalyst can be reduced by doping the element iron, and if the addition amount of the iron is too large, the catalyst is easy to sinter in the roasting process; if the addition amount of iron is too small, the deposition of sulfate ions and water molecules on the surface of the catalyst cannot be reduced; if the amount of cerium added is too large, the activity of the catalyst is lowered, and if the amount of cerium added is too small, the water resistance of the catalyst is lowered.

Further, the mass ratio of the active component in the active component metal salt to the titanium source is (3.53-22.5): 100. the inventors have found that if the amount of the active component added to the active component metal salt is too large, the solvent used cannot completely dissolve the active component, and if the amount of the active component added to the active component metal salt is too small, a relatively uniform distribution phase cannot be formed with the carrier, and the activity of the catalyst cannot be increased.

S400: mixing the first mixed solution with the third mixed solution

In this step, the first mixed solution is mixed with the third mixed solution to obtain a fourth mixed solution. Specifically, the first mixed solution and the third mixed solution are mixed under the ultrasonic condition, the ultrasonic time is 1-2 h, and the ultrasonic temperature is 20-40 ℃. The inventor finds that in the step, the first mixed solution and the third mixed solution are mixed to form the sol, the metal active components are distributed in the sol more uniformly, agglomeration does not occur, and sintering in the roasting process is avoided.

S500: adding the precipitant into the fourth mixed solution, drying, and calcining

In the step, a precipitant is added to the fourth mixed solution, and then drying and roasting are performed to obtain the denitration catalyst. Specifically, under the conditions of ultrasound and stirring, the precipitant is dripped into the fourth mixed solution, and after no precipitate is generated in the fourth mixed solution, the precipitant is stopped being added. The inventor finds that the precipitant reacts with the active components in the fourth mixed solution, and all the active components are converted into solid precipitates to be directly and uniformly loaded on the titanium dioxide carrier. Wherein the drying temperature is 100-130 ℃, and the drying time is 8-15 h; the roasting temperature is 250-550 ℃; the rate of temperature rise is 1-5 ℃/min, and the time of roasting is 3-6 h. Furthermore, the concentration of the precipitator is 0.5-2 mol/L. The concentration of the precipitant may be any value of 0.5 to 2mol/L, and may be, for example, 0.5mol/L, 1mol/L, or 2mol/L. While the specific type of the precipitant is not particularly limited and may be selected as needed by those skilled in the art, for example, the precipitant includes at least one of aqueous ammonia, ammonium bicarbonate, ammonium carbonate, and urea.

Further, the denitration catalyst obtained as described above may be ground and then subjected to secondary impregnation or kneading to be molded into a honeycomb-shaped or granular catalyst.

In a second aspect of the present invention, a denitration catalyst is provided. According to the embodiment of the invention, the denitration catalyst is prepared by adopting the method. Therefore, the denitration catalyst has high denitration efficiency under the conditions of low temperature and high airspeed, and has higher water resistance and sulfur poisoning resistance. It should be noted that the features and advantages described above for the method for preparing the denitration catalyst are also applicable to the denitration catalyst, and are not described herein again.

The following embodiments of the present invention are described in detail, and it should be noted that the following embodiments are exemplary only, and are not to be construed as limiting the present invention. In addition, all reagents used in the following examples are commercially available or can be synthesized according to methods herein or known, and are readily available to those skilled in the art for reaction conditions not listed, if not explicitly stated.

Example 1

(1) Weighing 35.5g of isopropyl titanate and 23g of glycerol, mixing the isopropyl titanate and the glycerol, and stirring for 20min to obtain a first mixed solution;

(2) Weighing 46g of glycerol, 16g of deionized water and 7.5g of acetic acid, mixing the three, and stirring for 10min to obtain a second mixed solution;

(3) Weighing 11.136g of manganese acetate and 4.4g of cerium chloride, dissolving the manganese acetate and the cerium chloride in the second mixed solution, and obtaining a third mixed solution after the manganese acetate and the cerium chloride are completely dissolved;

(4) And slowly adding the third mixed solution into the first mixed solution under the stirring condition, and continuously stirring for 90min to obtain a fourth mixed solution.

(5) And dropwise adding 1.5mol/L ammonium carbonate solution into the fourth mixed solution, drying at 120 ℃ for 9h after the solution is solidified, and roasting at 450 ℃ for 3.5h at the temperature rise rate of 2 ℃/min. Finally obtaining the low-temperature sulfur-resistant SCR denitration catalyst loaded on the titanium dioxide.

The denitration catalyst is used at the temperature of 175 ℃ and the space velocity of 60000h ^-1 1200ppm NO _x Under the condition, the denitration efficiency reaches more than 95 percent, and simultaneously 6 percent of water vapor and 80ppm of SO ₂ In the presence of the catalyst, the denitration catalytic efficiency of 82% is still maintained.

Example 2

(1) 42.5g of tetrabutyl titanate and 46.25g of n-butanol are weighed, mixed and stirred for 20min to obtain a first mixed solution.

(2) Weighing 46.25g of n-butanol, 8g of deionized water and 36.5g of ethylenediamine tetraacetic acid, mixing the n-butanol, the deionized water and the ethylenediamine tetraacetic acid, and stirring for 15min to obtain a second mixed solution;

(3) Weighing 13.015g of 50% manganese nitrate solution and 4.762g of ferric nitrate, dissolving the two into the second mixed solution, and obtaining a third mixed solution after the two are completely dissolved;

(4) Slowly adding the third mixed solution into the first mixed solution under the stirring condition, and continuously stirring for 60min under the ultrasonic condition of 25 ℃ to obtain a fourth mixed solution;

(5) Dropwise adding 1mol/L ammonium bicarbonate solution into the fourth mixed solution, drying at 110 ℃ for 10h after the solution is solidified, and then roasting at 400 ℃ for 4h at the heating rate of 2 ℃/min. Finally obtaining the low-temperature sulfur-resistant SCR denitration catalyst loaded on the titanium dioxide.

The denitration catalyst is used at 180 ℃ and the space velocity of 62000h ^-1 1100ppm of NO _x Under the condition, the denitration efficiency reaches more than 93 percent, and simultaneously, the denitration efficiency is controlled at the sum of 5 percent of water vapor and 1000ppm of SO ₂ In the presence of the catalyst, the denitration catalytic efficiency of 80 percent is still maintained.

Example 3

(1) Weighing 20g of titanyl sulfate and 28.75g of absolute ethyl alcohol, mixing the two, and stirring for 15min to obtain a first mixed solution;

(2) Weighing 28.75g of absolute ethyl alcohol, 15g of deionized water and 24g of citric acid, mixing the three, and stirring for 10min to obtain a second mixed solution;

(3) Weighing 13.364g of manganese acetate, 4.65g of cerium nitrate hexahydrate and 5.196g of ferric acetate, dissolving the manganese acetate, the cerium nitrate hexahydrate and the ferric acetate in a second solution, and obtaining a third mixed solution after all the manganese acetate, the cerium nitrate hexahydrate and the ferric acetate are dissolved;

(4) Slowly adding the third mixed solution into the first mixed solution under the stirring condition, and continuously stirring for 80min to obtain a fourth mixed solution;

(5) And dropwise adding 2mol/L ammonium carbonate solution into the mixed solution, drying at 100 ℃ for 12h after the solution is solidified, and then roasting at 350 ℃ for 5h at the heating rate of 3 ℃/min. Finally obtaining the low-temperature sulfur-resistant SCR denitration catalyst loaded on the titanium dioxide.

The denitration catalyst has the advantages of 180 ℃ and 65000h space velocity ^-1 1200ppm NO _x Under the condition, the denitration efficiency reaches more than 92 percent, and simultaneously, the denitration efficiency is controlled at 5 percent of water vapor and 100ppm of SO ₂ In the presence of the catalyst, the denitration catalytic efficiency of 82% is still maintained.

In the description of the specification, reference to the description of "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims

1. A method of preparing a denitration catalyst, comprising:

2. The method of claim 1, wherein in step (1), the molar ratio of the titanium source to the first dispersant is 1: (1-10);

optionally, in step (1), the titanium source comprises at least one of isopropyl titanate, titanyl sulfate, and tetrabutyl titanate.

3. The method of claim 1, wherein the molar ratio of the first dispersant to the second dispersant is 1: (1-2);

optionally, the first dispersant and the second dispersant each independently comprise at least one of absolute ethanol, glycerol, and butanol.

4. The method of claim 1, wherein in step (2), the molar ratio of the second dispersant to the complexing agent is 1: (0.01 to 3);

optionally, in step (2), the complexing agent comprises at least one of acetic acid, citric acid and ethylenediaminetetraacetic acid.

5. The method of claim 1 or 4, wherein in step (2), the second dispersant is mixed with the complexing agent and water;

optionally, the molar ratio of the second dispersant to the complexing agent and the water is 1: (0.01-3): (0.5-2).

6. The method according to claim 1, wherein in step (3), the active ingredient metal salt includes at least one of manganese nitrate, manganese acetate, manganese sulfate, iron nitrate, iron sulfate, iron acetate, cerium nitrate, and cerium chloride;

optionally, in step (3), the active component in the active component metal salt includes at least one of manganese, iron, and cerium.

7. The method according to claim 6, wherein the mass ratio of manganese, iron and cerium is 1: (0.5-2): (1-3).

8. The method according to claim 1, wherein the mass ratio of the active component in the active component metal salt to the titanium source is (3.53-22.5): 100.

9. the method according to claim 1, wherein in the step (5), the concentration of the precipitant is 0.5 to 2mol/L;

optionally, in step (5), the precipitant comprises at least one of aqueous ammonia, ammonium bicarbonate, ammonium carbonate, and urea.

10. A denitration catalyst, characterized in that the denitration catalyst is prepared by the method of any one of claims 1 to 9.