A denitration catalyst against heavy metal poisoning, a preparation method and application thereof

Abstract

The application discloses an anti-heavy metal poisoning denitration catalyst and a preparation method thereof. The method adopts ZnO quantum dots as an anti-heavy metal poisoning additive, has the characteristics of high activity and high dispersibility, is easy to combine with heavy metals As and Pb in flue gas, thereby reducing the contact between an active component of the denitration catalyst and the heavy metals, enhancing the stability of the catalyst, and prolonging the service life of the catalyst. In addition, the ZnO quantum dots are highly dispersed on the catalyst, and have a smaller negative influence on the active component and the acidity of the catalyst. The denitration catalyst has a simple preparation process and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of selective catalytic reduction catalyst technology, and in particular to a denitrification catalyst resistant to heavy metal poisoning, its preparation method, and its application. Background Technology

[0002] Coal-fired power plants commonly employ selective catalytic reduction (SCR) technology to control nitrogen oxide (NOx) emissions from flue gas. In the SCR reactor, NOx in the flue gas reacts with injected NH3 under the action of a denitrification catalyst, producing harmless N2 and H2O. The design life of industrial denitrification catalysts is generally 24,000 hours. However, in actual operating conditions, due to the influence of toxic substances in the fly ash of coal-fired power plants, the denitrification activity of the catalyst gradually decreases with increasing reaction time, causing the catalyst's operating time to fall short of design requirements.

[0003] Common poisoning elements for denitration catalysts include alkali metals K and Na, alkaline earth metals Ca, non-metals P, and heavy metals As and Pb. Among these, heavy metals have a relatively strong poisoning effect on denitration catalysts. To extend the industrial application life of denitration catalysts, improving their resistance to heavy metal poisoning has become a research hotspot in recent years, and many related technologies have been published in this field. Chinese invention patent CN108435159B discloses a denitration catalyst with improved resistance to arsenic poisoning, its preparation method, and its application. This invention improves the chemical stability of the catalyst by introducing an arsenic-resistant additive during the preparation process. Chinese invention patent CN201710367686.1 discloses an arsenic-resistant SCR denitration catalyst and its preparation method. This invention uses bismuth or indium as an arsenic-resistant additive to improve the catalyst's resistance to arsenic poisoning.

[0004] However, existing reports show more research on improving the arsenic poisoning performance of catalysts, but fewer on improving the lead poisoning performance. Moreover, most of the reported preparation processes are quite complex and not suitable for industrial scale-up. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the background art by proposing a denitrification catalyst resistant to heavy metal poisoning, its preparation method, and its application. The denitrification catalyst prepared using the method of this invention also possesses strong resistance to As and Pb poisoning. It is suitable for the production of industrial denitrification catalysts.

[0006] The technical solution of this invention, a method for preparing a denitration catalyst resistant to heavy metal poisoning, includes the following specific steps:

[0007] S1. Weigh the zinc precursor salt, add it to the alcohol solvent, stir in a water bath at 60-80°C for 2-4 hours, and then cool to room temperature;

[0008] S2. Add KOH in an alcohol solvent solution, continue stirring for 5-10 hours, then evaporate by rotary evaporation, wash with water, and filter to obtain white ZnO quantum dots;

[0009] S3. Weigh anatase TiO2, place it in a kneader, add ammonium metavanadate and an aqueous solution of precursor salt, and knead for 2-4 hours.

[0010] S4. Add ZnO quantum dots, inorganic binder, organic extrusion aid and glass fiber, knead for 2-4 hours and then dry.

[0011] S5. The product obtained in S4 is calcined at 450-550℃ for 2-5 hours to obtain a denitrification catalyst resistant to heavy metal poisoning.

[0012] In S1, the zinc precursor salt is one of zinc nitrate, zinc acetate, or zinc chloride.

[0013] In S1, the alcohol solvent is one of methanol, ethanol, or isopropanol.

[0014] Preferably, the molar ratio of KOH to zinc precursor salt in S2 is 1.5:1 to 5:1.

[0015] In S3, the precursor salt of the auxiliary agent is either ammonium heptamolybdate or ammonium paratungstate.

[0016] Preferably, the inorganic binder in S4 is one of sepiolite, wollastonite, and kaolin, and the amount added is 5-10% of the mass of TiO2.

[0017] Preferably, the organic extrusion aid S4 is one of carboxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose, and the amount added is 1 to 5% of the mass of TiO2.

[0018] Preferably, the amount of glass fiber added in S4 is 1 to 5% of the mass of TiO2.

[0019] A denitration catalyst resistant to heavy metal poisoning was prepared using the above method;

[0020] Its molecular formula is V2O5-MoO3-ZnO / TiO2 or V2O5-WO3-ZnO / TiO2;

[0021] The mass percentage of V2O5 is 1–5%, the mass percentage of WO3 or MoO3 is 3–8%, and the mass percentage of ZnO is 1–5%.

[0022] An application of a denitrification catalyst resistant to heavy metal poisoning in the control of nitrogen oxides in flue gas by SCR was prepared using the above method.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] (1) The ZnO quantum dots prepared by this invention are small in size, with most of the atoms located on the surface of the quantum dots relative to the bulk material; therefore, the specific surface area of ​​the quantum dots increases continuously as the size decreases. Due to the large specific surface area of ​​the quantum dots, the coordination of the atoms on the surface of the quantum dots is insufficient, and the number of unsaturated bonds and dangling bonds increases. Therefore, the atoms on the surface of the quantum dots have high activity and can easily combine with other atoms. Thus, they have the characteristics of high activity and high dispersibility. Unlike conventional ZnO or other oxide additives, they are easier to disperse on denitrification catalysts and react more easily with As and Pb in flue gas, thereby protecting the active components of the denitrification catalyst from poisoning.

[0025] (2) In the denitration catalyst prepared by the present invention, ZnO quantum dots are highly dispersed on the denitration catalyst and will not have a negative impact on the active components of the denitration catalyst or the acidity of the catalyst.

[0026] (3) The anti-heavy metal poisoning denitrification catalyst of the present invention has a simple preparation process and is applicable to the production process of denitrification catalysts with different structures and types. Detailed Implementation

[0027] Comparative Example 1

[0028] Anatase TiO2 was weighed and placed in a kneader. An aqueous solution of ammonium metavanadate and ammonium heptamolybdate was added, and the mixture was kneaded for 2 hours. Then, sepiolite, carboxymethyl cellulose, and glass fiber were added. The amount of sepiolite added was 5% of the TiO2 mass, the amount of organic extrusion aid added was 1% of the TiO2 mass, and the amount of glass fiber added was 1% of the TiO2 mass. Kneading continued for 2 hours, followed by drying and calcination at 550℃ for 2 hours to obtain a denitrification catalyst resistant to heavy metal poisoning. The catalyst contained 1% V2O5 and 3% MoO3 by mass.

[0029] Comparative Example 2

[0030] Anatase TiO2 was weighed and placed in a kneader. An aqueous solution of ammonium metavanadate and ammonium paratungstate was added, and the mixture was kneaded for 2 hours. Then, wollastonite, an organic extrusion aid, and glass fiber were added. The amount of wollastonite added was 8% of the mass of TiO2, the amount of carboxymethyl cellulose added was 5% of the mass of TiO2, and the amount of glass fiber added was 5% of the mass of TiO2. Kneading continued for 2 hours, followed by drying and calcination at 450℃ for 5 hours to obtain a denitrification catalyst resistant to heavy metal poisoning. The catalyst contained 2% V2O5 and 5% WO3 by mass.

[0031] Example 1

[0032] Zinc acetate was weighed and added to ethanol. The mixture was stirred in an 80°C water bath for 2 hours, then cooled to room temperature. An ethanol solution of KOH was added, with a molar ratio of KOH to zinc acetate of 1.5:1. Stirring continued for 5 hours, followed by rotary evaporation, washing with water, and filtration to obtain white ZnO quantum dots. Anatase TiO2 was weighed and placed in a kneader. An aqueous solution of ammonium metavanadate and ammonium heptamolybdate was added, and the mixture was kneaded for 2 hours. ZnO quantum dots, sepiolite, carboxymethyl cellulose, and glass fiber were then added. The amount of sepiolite added was 5% of the mass of TiO2, the amount of organic extrusion aid added was 1% of the mass of TiO2, and the amount of glass fiber added was 1% of the mass of TiO2. Kneading continued for 2 hours, followed by drying and calcination at 550°C for 2 hours to obtain a denitrification catalyst resistant to heavy metal poisoning. The catalyst contained 1% V2O5, 3% MoO3, and 1% ZnO by mass.

[0033] Example 2

[0034] Zinc nitrate was weighed and added to isopropanol. The mixture was stirred in a water bath at 60°C for 4 hours, then cooled to room temperature. A KOH solution in isopropanol was added, with a molar ratio of KOH to zinc nitrate of 2:1. Stirring continued for 10 hours, followed by rotary evaporation, washing with water, and filtration to obtain white ZnO quantum dots. Anatase TiO2 was weighed and placed in a kneader. An aqueous solution of ammonium metavanadate and ammonium paratungstate was added, and the mixture was kneaded for 2 hours. ZnO quantum dots, wollastonite, an organic extrusion aid, and glass fiber were then added. The amount of wollastonite added was 8% of the mass of TiO2, the amount of carboxymethyl cellulose added was 5% of the mass of TiO2, and the amount of glass fiber added was 5% of the mass of TiO2. Kneading continued for 2 hours, followed by drying and calcination at 450°C for 5 hours to obtain a denitrification catalyst resistant to heavy metal poisoning. The catalyst contained 2% V2O5, 5% WO3, and 5% ZnO by mass.

[0035] Example 3

[0036] Zinc chloride was weighed and added to methanol. The mixture was stirred in an 80°C water bath for 3 hours, then cooled to room temperature. A methanol solution of KOH was added, with a molar ratio of KOH to zinc chloride of 5:1. Stirring continued for 5 hours, followed by rotary evaporation, washing with water, and filtration to obtain white ZnO quantum dots. Anatase TiO2 was weighed and placed in a kneader. An aqueous solution of ammonium metavanadate and ammonium heptamolybdate was added, and the mixture was kneaded for 4 hours. ZnO quantum dots, kaolin, hydroxyethyl cellulose, and glass fiber were then added. The amount of kaolin added was 10% of the mass of TiO2, the amount of hydroxyethyl cellulose added was 2% of the mass of TiO2, and the amount of glass fiber added was 2% of the mass of TiO2. Kneading continued for 4 hours, followed by drying and calcination at 500°C for 2 hours to obtain a denitrification catalyst resistant to heavy metal poisoning. The catalyst contained 5% V2O5, 8% MoO3, and 2% ZnO by mass.

[0037] Example 4

[0038] Zinc acetate was weighed and added to methanol. The mixture was stirred in a water bath at 70°C for 4 hours, then cooled to room temperature. A methanol solution of KOH was added, with a molar ratio of KOH to zinc acetate of 3:1. Stirring continued for 8 hours, followed by rotary evaporation, washing with water, and filtration to obtain white ZnO quantum dots. Anatase TiO2 was weighed and placed in a kneader. An aqueous solution of ammonium metavanadate and ammonium paratungstate was added, and the mixture was kneaded for 4 hours. ZnO quantum dots, sepiolite, hydroxypropyl cellulose, and glass fiber were then added. The amount of sepiolite added was 5% of the mass of TiO2, the amount of hydroxypropyl cellulose added was 3% of the mass of TiO2, and the amount of glass fiber added was 3% of the mass of TiO2. Kneading continued for 3 hours, followed by drying and calcination at 550°C for 3 hours to obtain a denitrification catalyst resistant to heavy metal poisoning. The catalyst contained 2% V2O5, 6% WO3, and 4% ZnO by mass.

[0039] Example 5

[0040] Zinc nitrate was weighed and added to ethanol. The mixture was stirred in an 80°C water bath for 2 hours, then cooled to room temperature. An ethanol solution of KOH was added, with a molar ratio of KOH to zinc nitrate of 2:1. Stirring continued for 6 hours, followed by rotary evaporation, washing with water, and filtration to obtain white ZnO quantum dots. Anatase TiO2 was weighed and placed in a kneader. An aqueous solution of ammonium metavanadate and ammonium paratungstate was added, and the mixture was kneaded for 3 hours. ZnO quantum dots, kaolin, hydroxyethyl cellulose, and glass fiber were then added. The amount of kaolin added was 7% of the mass of TiO2, the amount of hydroxyethyl cellulose added was 1% of the mass of TiO2, and the amount of glass fiber added was 4% of the mass of TiO2. Kneading continued for 2 hours, followed by drying and calcination at 480°C for 4 hours to obtain a denitrification catalyst resistant to heavy metal poisoning. The catalyst contained 2.5% V2O5, 4% WO3, and 2.5% ZnO by mass.

[0041] Example 6

[0042] The denitrification performance of the denitrification catalysts prepared in Comparative Examples 1-2 and Examples 1-5 was tested. The test conditions were: NO concentration 500 ppm, NH3 / NO = 1, SO2 concentration 200 ppm, H2O concentration 5 vol%, N2 as balance gas, GHSV = 120000 h⁻¹. -1 The test results are shown in Table 1.

[0043] Table 1. Denitrification efficiency of different denitrification catalysts

[0044]

[0045]

[0046] As can be seen from Table 1, the denitrification catalyst prepared by the method of the present invention has excellent denitrification performance under the test conditions.

[0047] Example 7

[0048] To verify the arsenic poisoning resistance of the denitrification catalysts prepared in the above examples, simulated arsenic poisoning was conducted on the denitrification catalysts in the above examples and comparative examples. 1% As2O3 was loaded onto the denitrification catalysts prepared in Comparative Examples 1-2 and Examples 1-5, respectively.

[0049] Furthermore, the denitrification performance of the catalyst after simulated arsenic poisoning was tested under the same conditions as in Example 6, and the test results are shown in Table 2.

[0050] Table 2. Denitrification efficiency of different denitrification catalysts

[0051]

[0052] As can be seen from Table 2, the denitrification efficiency of the anti-heavy metal poisoning denitrification catalyst prepared by the present invention, after loading 1 wt% As2O3, decreased significantly less than that of the conventional catalyst in the comparative example.

[0053] Example 8

[0054] To verify the lead poisoning resistance of the denitration catalysts prepared in the above examples, simulated arsenic poisoning was conducted on the denitration catalysts in the above examples and comparative examples. 1% PbO was loaded onto the denitration catalysts prepared in Comparative Examples 1-2 and Examples 1-5, respectively.

[0055] Furthermore, the denitrification performance of the catalyst after simulated arsenic poisoning was tested under the same conditions as in Example 6, and the test results are shown in Table 3.

[0056] Table 3. Denitrification efficiency of different denitrification catalysts

[0057]

[0058] As can be seen from Table 3, the denitrification efficiency of the anti-heavy metal poisoning denitrification catalyst prepared by the present invention, after loading 1 wt% PbO, decreased significantly less than that of the conventional catalyst in the comparative example.

[0059] The embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing a denitration catalyst resistant to heavy metal poisoning, characterized in that, The specific steps include the following: S1. Weigh the zinc precursor salt, add it to the alcohol solvent, stir in a water bath at 60~80℃ for 2~4 hours, and then cool to room temperature; S2. Add KOH in an alcohol solvent solution, continue stirring for 5-10 hours, then evaporate by rotary evaporation, wash with water, and filter to obtain white ZnO quantum dots; S3. Weigh anatase TiO2, place it in a kneader, add ammonium metavanadate and an aqueous solution of the precursor salt, and knead for 2-4 hours; the precursor salt in S3 is either ammonium heptamolybdate or ammonium paratungstate. S4. Add ZnO quantum dots, inorganic binder, organic extrusion aid and glass fiber, knead for 2-4 hours and then dry. S5. The product obtained in S4 is calcined at 450~550℃ for 2~5h to obtain a denitrification catalyst resistant to heavy metal poisoning.

2. The method for preparing a denitrification catalyst resistant to heavy metal poisoning according to claim 1, characterized in that, The zinc precursor salt in S1 is one of zinc nitrate, zinc acetate, or zinc chloride.

3. A method for preparing a denitrification catalyst resistant to heavy metal poisoning according to claim 1 or 2, characterized in that, The alcohol solvent in S1 is one of methanol, ethanol, or isopropanol.

4. The method for preparing a denitrification catalyst resistant to heavy metal poisoning according to claim 1, characterized in that, The molar ratio of KOH to zinc precursor salt in S2 is 1.5:1 to 5:

1.

5. The method for preparing a denitrification catalyst resistant to heavy metal poisoning according to claim 1, characterized in that, The inorganic binder in S4 is one of sepiolite, wollastonite, or kaolin, and its addition amount is 5-10% of the mass of TiO2.

6. The method for preparing a denitrification catalyst resistant to heavy metal poisoning according to claim 1, characterized in that, The organic extrusion aid S4 is one of carboxymethyl cellulose, hydroxyethyl cellulose, or hydroxypropyl cellulose, and the amount added is 1 to 5% of the mass of TiO2.

7. The method for preparing a denitrification catalyst resistant to heavy metal poisoning according to claim 1, characterized in that, The amount of glass fiber added in S4 is 1 to 5% of the mass of TiO2.

8. A denitration catalyst resistant to heavy metal poisoning, characterized in that, Prepared using the method as described in any one of claims 1-7; Its molecular formula is V2O5-MoO3-ZnO / TiO2 or V2O5-WO3-ZnO / TiO2; The mass percentage of V2O5 is 1-5%, the mass percentage of WO3 or MoO3 is 3-8%, and the mass percentage of ZnO is 1-5%.

9. The application of a denitrification catalyst resistant to heavy metal poisoning in SCR control of nitrogen oxides in flue gas, characterized in that, It is prepared using the method described in any one of claims 1-7.

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