CN115709062B

CN115709062B - Denitration catalyst and preparation method thereof

Info

Publication number: CN115709062B
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: 2024-02-13
Anticipated expiration: 2042-10-11
Also published as: CN115709062A

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 dispersant 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) Adding the precipitant 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 higher 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, in particular to a denitration catalyst and a preparation method thereof.

Background

Fossil energy sources (including petroleum, coal and natural gas) are still main energy sources in the society today, and combustion of the fossil energy sources inevitably releases a large amount of nitrogen oxides, which not only cause environmental problems such as photochemical smog and acid rain, but also cause harm to human bodies and animals. When the nitrogen oxides are inhaled into the body, the nitrogen oxides are preferentially combined with the hemoglobin, so that the combination of the hemoglobin and oxygen is blocked, and the respiratory tract and the lung are diseased.

Low-temperature SCR (selective catalytic reduction) denitration technology utilizes ammonia and NO _x The reaction produces nontoxic nitrogen and water, which are the most effective method for removing nitrogen oxides in flue gas at present, and the catalyst V is used ₂ O ₅ -WO ₃ /TiO ₂ Has been developed for use in high smoke exhaust temperatures>300 ℃ power plant and other places NO _x Is removed. However, the vanadium catalyst is not suitable for denitration applications in other factories such as iron and steel factories, cement factories and glass factories with low flue gas temperature (180-250 ℃). Numerous studies have been conducted to obtain an effective low temperature catalyst, and it has been found that oxides of transition metal manganese react with NO at low temperature conditions _x The catalyst has better removal effect, but the residual sulfur dioxide in the flue gas can react with active components in the manganese catalyst to generate sulfate, so that the catalyst is irreversibly deactivated, and the activity of the manganese catalyst is reduced.

Therefore, the existing low-temperature denitration catalyst needs to be improved.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems in the related art to some extent. Therefore, an 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 the conditions of low temperature and high airspeed, and simultaneously has high water resistance and sulfur poisoning resistance.

In one aspect of the 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 dispersant with a complexing agent to obtain a second mixed solution;

(3) Mixing an active ingredient 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) Adding a precipitant into the fourth mixed solution, and then drying and roasting to obtain the denitration catalyst.

According to the method for preparing the denitration catalyst, the titanium source and the first dispersing agent are mixed by adopting a sol-precipitation method, so that the titanium source is uniformly dispersed in the first dispersing agent to obtain a first mixed solution, and meanwhile, the second dispersing agent and the complexing agent are mixed, 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, the addition of the catalyst auxiliary agent enables the surface of the active component to form an acid site, reduces the bond energy of ammonium and sulfate ions, and enables ammonium sulfate or ammonium bisulfate generated by the reaction of the reducing agent ammonia and sulfur dioxide to be easier to decompose. And then mixing the first mixed solution with the third mixed solution to obtain sol, namely a fourth mixed solution, adding a precipitant into the fourth mixed solution, performing precipitation reaction on the metal complex and the precipitant, stopping adding the precipitant when no precipitation is generated in the fourth mixed solution, completely converting active components into solid precipitates at the moment, and drying and roasting to obtain the denitration catalyst. Compared with the impregnation method in the prior art, the preparation method of the denitration catalyst by adopting the sol-precipitation method ensures that the active components in the active component metal salt and the titanium dioxide carrier are distributed more uniformly in the sol, and simultaneously the active components in the active component metal salt can be directly and uniformly loaded on the titanium dioxide carrier, so that 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 higher 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 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 ethylenediamine tetraacetic 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 component metal salt comprises at least one of manganese nitrate, manganese acetate, manganese sulfate, iron nitrate, iron sulfate, iron acetate, cerium nitrate, and cerium chloride.

In some embodiments of the invention, in step (3), the active component in 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 still keep higher activity in the presence of sulfur dioxide.

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

in some embodiments of the invention, in 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 ammonia, ammonium bicarbonate, ammonium carbonate, and urea.

In a second aspect of the invention, the invention provides a denitration catalyst. 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 foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in 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 by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.

In one aspect of the invention, a method of preparing a denitration catalyst is provided. Referring to fig. 1, according to an embodiment of the present invention, the method includes:

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 dispersing agent are mixed and stirred so as to be uniformly mixed. Further, the molar ratio of the titanium source to the first dispersant is 1: (1-10). The inventors found that if the addition amount of the first dispersant is too large, the agglomeration of particles is aggravated, and sintering is performed during the calcination process, and meanwhile, the hydrolysis of the titanium source is suppressed; if the addition amount of the first dispersing agent is too small, the colloid particle size is larger, flocculation phenomenon can occur in the system, the stability is reduced, and even coagulation and demulsification can occur.

The specific types of the above titanium source and the first dispersant are not particularly limited, and those skilled in the art can select according to need, 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 ethanol, glycerol, and butanol, and the manner of stirring is also not particularly limited, and may be, for example, mechanical stirring or magnetic stirring.

S200: mixing a second dispersant with a complexing agent

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

In a specific embodiment of the invention, the second dispersant is mixed with the complexing agent and water, and the three are mixed and stirred uniformly. Further, the molar ratio of the second dispersant to the complexing agent and water was 1: (0.01-3): (0.5-2). The inventor finds that if the addition amount of water is too large, the titanium source is hydrolyzed too quickly, and a uniform substance cannot be formed with the active component; if the amount of water added is too small, the titanium source cannot be completely hydrolyzed, and the designed ratio of carrier to active component 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 added is excessive, the colloidal particles are 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 those skilled in the art can select the complexing agent according to need, for example, the complexing agent includes at least one of acetic acid, citric acid and ethylenediamine tetraacetic acid; the specific type of the second dispersant is the same as that of the first dispersant, and the stirring manner is the same as that described above, and will not be repeated here.

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

In this step, the active ingredient metal salt is mixed with the second mixed solution so as 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 form a metal complex, and the metal complex is more stable in the solution, so that the active component metal ions are more difficult to deposit out of the solution, and further, the metal active component can form finer grains later.

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 doped element iron can reduce the deposition of sulfate ions and water molecules on the surface of the catalyst, and if the addition amount of the iron is excessive, 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 found that if the addition amount of the active ingredient in the active ingredient metal salt is too large, the solvent used cannot completely dissolve the active ingredient, and if the addition amount of the active ingredient in the active ingredient 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 inventors found that in this step, the first mixed solution and the third mixed solution are mixed to form a sol, the metal active components are more uniformly distributed in the sol, agglomeration does not occur, and sintering during the firing process is avoided.

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

In this step, a precipitant is added to the fourth mixed solution, and then dried and calcined, so as to obtain a denitration catalyst. Specifically, under the conditions of ultrasound and stirring, the precipitant is dripped into the fourth mixed solution, and after no precipitation 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 the active components are completely converted into solid precipitate which is 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 temperature rising rate is 1-5 ℃/min, and the roasting time is 3-6 h. Further, the concentration of the precipitant is 0.5-2 mol/L. The concentration of the precipitant may be any value from 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, those skilled in the art may select as desired, and for example, the precipitant includes at least one of ammonia, ammonium bicarbonate, ammonium carbonate, and urea.

Further, the denitration catalyst obtained above may be ground and then subjected to secondary impregnation or kneading to form a honeycomb-like or particulate catalyst.

In a second aspect of the invention, the invention provides a denitration catalyst. 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 equally applicable to the denitration catalyst, and are not described here again.

The following detailed description of embodiments of the invention is provided for the purpose of illustration only and is not to be construed as limiting the invention. In addition, all reagents employed in the examples below are commercially available or may 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 two, 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 all the manganese acetate and the cerium chloride are 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) An ammonium carbonate solution of 1.5mol/L is added dropwise into the fourth mixed solution, and after the solution is solidified, the solution is dried for 9 hours at 120 ℃, and then baked for 3.5 hours at 450 ℃ at a heating rate of 2 ℃/min. Finally, the low-temperature sulfur-resistant SCR denitration catalyst loaded on the titanium dioxide is obtained.

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

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 three, 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 manganese nitrate solution and the ferric nitrate solution in the second mixed solution, and obtaining a third mixed solution after all the manganese nitrate solution and the ferric nitrate solution are 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 at 25 ℃ to obtain a fourth mixed solution;

(5) And (3) dripping 1mol/L ammonium bicarbonate solution into the fourth mixed solution, drying at 110 ℃ for 10 hours after the solution is solidified, and then roasting at 400 ℃ for 4 hours at a heating rate of 2 ℃/min. Finally, the low-temperature sulfur-resistant SCR denitration catalyst loaded on the titanium dioxide is obtained.

The denitration catalyst has the airspeed of 62000h at 180 DEG C ^-1 1100ppm NO _x Under the condition that the denitration efficiency reaches more than 93 percent, and simultaneously the sum of 5 percent of water vapor and 1000ppm of SO ₂ In the presence, the denitration catalytic efficiency is still maintained at 80%.

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) 28.75g of absolute ethyl alcohol, 15g of deionized water and 24g of citric acid are weighed, and the three are mixed and stirred 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 three in the second solution, and obtaining a third mixed solution after all the three 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) 2mol/L ammonium carbonate solution is used to be added into the mixed solution in a dropwise manner, after the solution is solidified, the mixed solution is dried for 12 hours at 100 ℃, and then baked for 5 hours at 350 ℃ at a heating rate of 3 ℃/min. Finally, the low-temperature sulfur-resistant SCR denitration catalyst loaded on the titanium dioxide is obtained.

The denitration catalyst has the airspeed of 65000h at 180 DEG C ^-1 NO of 1200ppm _x Under the condition that the denitration efficiency reaches more than 92 percent, and simultaneously, the denitration efficiency is improved by 5 percent of water vapor and 100ppm of SO ₂ In the presence of the catalyst, the denitration catalytic efficiency is still kept at 82%.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., 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 present invention. In this specification, schematic representations of the above terms are not necessarily directed 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, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.

Claims

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

(2) Mixing a second dispersant with a complexing agent and water to obtain a second mixed solution;

(5) Adding a precipitant into the fourth mixed solution, then drying and roasting to obtain a denitration catalyst,

wherein the molar ratio of the titanium source to the first dispersant is 1: (1-10), wherein the mole ratio of the first dispersing agent to the second dispersing agent is 1: (1-2), wherein the molar ratio of the second dispersant to the complexing agent to the water is 1: (0.01-3): (0.5-2), wherein the first dispersing agent and the second dispersing agent respectively and independently comprise at least one of absolute ethyl alcohol, glycerol and butanol, the complexing agent comprises at least one of acetic acid, citric acid and ethylenediamine tetraacetic acid, and the mass ratio of the active component in the active component metal salt to the titanium source is (3.53-22.5): 100, wherein the active component metal salt comprises at least one of manganese nitrate, manganese acetate, manganese sulfate, ferric nitrate, ferric sulfate, ferric acetate, cerium nitrate and cerium chloride, the active component in the active component metal salt comprises manganese, iron and cerium, and the mass ratio of manganese, iron and cerium is 1: (0.5-2): (1-3), wherein the precipitant comprises at least one of ammonia water, ammonium bicarbonate, ammonium carbonate and urea.

2. The method of claim 1, wherein in step (1), the titanium source comprises at least one of isopropyl titanate, titanyl sulfate, and tetrabutyl titanate.

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

4. A denitration catalyst, characterized in that it is prepared by the method according to any one of claims 1 to 3.