A low-temperature denitration catalyst resistant to water, sulfur and alkali and a preparation method thereof

Abstract

The application discloses a kind of low-temperature denitration catalysts of water resistance, sulfur resistance and alkali resistance and a preparation method thereof, and belongs to the technical field of catalyst materials.The preparation method comprises the following steps: ammonium metavanadate and ammonium dihydrogen phosphate are added to monoethanolamine and a small amount of water to stir and dissolve, obtaining solution 1; cerium nitrate is added to deionized water to dissolve, obtaining solution 2; solutions 1 and 2 are mixed uniformly to obtain solution 3; ammonium metatungstate and ammonium heptamolybdate are added to deionized water to dissolve and then added to solution 3, obtaining solution 4; titanium white, zirconium nitrate and silicon dioxide powder are mixed uniformly and added to solution 4 to stir uniformly, while a certain amount of lactic acid, glass fiber and boric acid are added, obtaining uniform slurry; drying; calcination, and the process is completed.The beneficial effects are as follows: the prepared catalyst can achieve a denitration efficiency of more than 90% in a low-temperature range of 160-220°C, and the catalyst has high strength, resistance to 6% water poisoning, 3% alkali poisoning and 400ppm sulfur poisoning.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalyst materials, in particular to a low-temperature denitration catalyst resistant to water, sulfur and alkali and a preparation method thereof. BACKGROUND

[0002] With the acceleration of industrialization in recent years, environmental pollution is getting worse, and air pollution has become an environmental problem that cannot be ignored. Nitrogen oxides (NOx) produced by the combustion of fossil fuels have become one of the main pollutants in the atmosphere, which has seriously restricted the development of the power, steel, building materials and other industries.

[0003] At present, the relatively mature and widely used technology for removing nitrogen oxides in waste gas is NH3-SCR denitration. The medium-high temperature SCR denitration technology is relatively mature, and can effectively reduce NOx under the condition of a reaction temperature of 320-450℃. However, for the coking, cement, glass and other low-temperature industries, the flue gas temperature is usually below 300℃, and the energy consumption for heating the flue gas is large. In addition, in the denitration process, SO2 will generate sticky ammonium sulfate substances such as ammonium bisulfate with NH3 in the reducing agent under low-temperature conditions, which will adhere to the surface of the catalyst and enter the pores of the catalyst. H2O will compete with NH3 for adsorption under low-temperature conditions, which will reduce the adsorption amount of NH3 on the catalyst, thereby reducing the denitration capacity of the catalyst. In addition, alkali poisoning occupies the acidic active sites of the catalyst, which reduces the catalytic efficiency. Therefore, it is of great significance to prepare a low-temperature denitration catalyst resistant to water, sulfur and alkali.

[0004] A Chinese patent application document with publication number CN107088433A discloses a low-temperature denitration catalyst with strong resistance to sulfur and water and a preparation method thereof. The catalyst uses anatase TiO2 as a carrier and loads vanadyl phosphate active components. The molar ratio of V and P in the vanadyl phosphate active components is 1-6:1. The mass of the vanadyl phosphate active components in the catalyst accounts for 5%-15% of the total mass of the catalyst. V2O5 is used as an active precursor, isobutyl alcohol is used as a reducing agent, and benzyl alcohol is used as a solvent. The reaction is refluxed at a temperature of 150℃, and then phosphoric acid is added in proportion and heated to reflux. Next, the reaction mixture is filtered, dried and calcined to obtain vanadyl phosphate active components. Finally, the prepared vanadyl phosphate active components are mixed with anatase TiO2 with a specific surface area of not less than 250m2 / g as a carrier in proportion, stirred, mixed with distilled water, dried in a water bath and calcined to obtain the catalyst. The catalyst has high low-temperature denitration activity and strong resistance to SO2 and water vapor poisoning. However, the denitration efficiency of the catalyst is low, and the catalyst does not have alkali resistance. Therefore, further improvement is needed. 2 / g as a carrier in proportion, stirred, mixed with distilled water, dried in a water bath and calcined to obtain the catalyst. The catalyst has high low-temperature denitration activity and strong resistance to SO2 and water vapor poisoning. However, the denitration efficiency of the catalyst is low, and the catalyst does not have alkali resistance. Therefore, further improvement is needed. SUMMARY

[0005] The technical problem to be solved by the present application is how to solve the problems of poor water resistance, poor sulfur resistance and poor low-temperature denitration efficiency of the catalyst in the prior art.

[0006] The present application solves the above technical problems by the following technical means:

[0007] The first aspect of the present application provides a preparation method of a water-resistant, sulfur-resistant and alkali-resistant low-temperature denitration catalyst, comprising the following steps:

[0008] (1) A certain amount of ammonium metavanadate and ammonium dihydrogen phosphate are weighed, and single ethanolamine and water are added to stir and dissolve to obtain solution 1;

[0009] (2) A certain amount of cerium nitrate is weighed and dissolved in deionized water to obtain solution 2; solution 1 and 2 are mixed uniformly to obtain solution 3; a certain amount of ammonium metatungstate and ammonium heptamolybdate are weighed, dissolved in deionized water and then added to solution 3 to obtain solution 4;

[0010] (3) The titanium white powder, zirconium nitrate and silicon dioxide powder are mixed uniformly, added to solution 4 and stirred uniformly, and a certain amount of lactic acid, glass fiber and boric acid are added to obtain a uniform mass slurry;

[0011] (4) The uniform mass slurry of step (3) is dried;

[0012] (5) The dried material of step (4) is calcined, and the water-resistant, sulfur-resistant and alkali-resistant low-temperature denitration catalyst is obtained.

[0013] Beneficial effects: The preparation method of the water-resistant, sulfur-resistant and alkali-resistant denitration catalyst provided by the present application uses phosphorus-modified V2O5 as the active component, and phosphorus-doped V2O5 improves the specific surface area and acidity of the catalyst, and improves the alkali metal poisoning resistance and sulfur poisoning resistance of the catalyst; zirconium dioxide, boric acid and titanium dioxide are used as the mixed carrier, TiO2-SiO2 can improve the vanadium surface acidity and dispersion, inhibit the crystal transformation and specific surface loss of the carrier at high temperature, and TiO2-ZrO2 composite oxide can change the dispersion state and active structure of the active component through interaction with the active component; lactic acid is used as a defoaming agent to remove bubbles during the mixing of the powder; glass fiber and boric acid are used as strength aids, and the synergistic effect of glass fiber and boric acid can improve the strength and compression resistance; MoO3, WO3 and CeO2 are used as active aids, WO3 and CeO2 have rich surface oxygen vacancies and strong oxidation-reduction capacity, and have certain water poisoning resistance, and the denitration efficiency in the low-temperature range of 160-220 DEG C is more than 90%.

[0014] 2NH4VO3 (calcined) = V2O5 + H2O + 2NH3↑

[0015] Preferably, the mass ratio of ammonium metavanadate to ammonium dihydrogen phosphate in step (1) is 1:1-3, and the mass of ammonium metavanadate accounts for 3-5% of the total mass of the catalyst.

[0016] Preferably, the mass of cerium nitrate in step (2) accounts for 1-2% of the total mass of the catalyst.

[0017] Preferably, the mass of ammonium metatungstate and ammonium heptamolybdate in step (2) accounts for 2-10% and 1-4% of the total mass of the catalyst, respectively.

[0018] Preferably, the mass of zirconium nitrate in step (3) is 5-10% of the total mass of the catalyst, and the mass of silicon dioxide is 7-10% of the total mass of the catalyst.

[0019] Preferably, the mass of lactic acid in step (3) is 0.5-2% of the total mass of the catalyst, the mass of glass fiber is 2-5% of the total mass of the catalyst, and the mass of boric acid is 7-15% of the total mass of the catalyst.

[0020] Preferably, the temperature of drying in step (4) is 90-130℃, and the drying time is 1-6h.

[0021] Preferably, the temperature of drying in step (4) is 110℃, and the drying time is 2-4h.

[0022] Preferably, the temperature of calcination in step (5) is 400-600℃, and the calcination time is 2-8h.

[0023] Preferably, the temperature of calcination in step (5) is 500℃, and the calcination time is 4-6h.

[0024] The second aspect of the present application proposes a water-resistant, sulfur-resistant, alkali-resistant, and low-temperature denitration catalyst prepared by the above method.

[0025] The present application has the following advantages:

[0026] 1. The preparation method of the anti-water, sulfur-resistant and alkali-resistant denitration catalyst provided by the application, in which phosphorus-modified V2O5 is used as the active component, the specific surface area and acidity of the catalyst are improved by phosphorus-doped V2O5, the resistance to alkali metal poisoning and sulfur poisoning of the catalyst is improved, zirconium dioxide, boric acid and titanium dioxide are used as the mixed carrier, TiO2-SiO2 can improve the surface acidity and dispersity of vanadium, inhibit the crystal transformation and specific surface loss of the carrier at high temperature, TiO2-ZrO2 composite oxide can change the dispersion state and active structure of the active component through the interaction with the active component, lactic acid is used as the defoaming agent to remove the bubbles in the powder mixing process, glass fiber and boric acid are used as the strength aids, the strength and pressure resistance can be improved through the synergistic effect of the glass fiber and boric acid, and MoO3, WO3 and CeO2 are used as the active aids, WO3 and CeO2 have rich surface oxygen vacancies and strong oxidation-reduction capacity, and have certain water poisoning resistance.

[0027] 2. The catalyst prepared by the method has the advantages that the active components are mixed to obtain a solution, then the carrier is uniformly mixed with the solution, V2O5 is converted into a crystal state through ammonium metavanadate dissolution to improve the active space, the specific surface area and acidity of the catalyst are improved by phosphorus-modified V2O5, the resistance to alkali metal poisoning and sulfur poisoning of the catalyst is improved, cerium nitrate, ammonium heptamolybdate and ammonium metatungstate with strong oxidation activity are used as low-temperature active aids and active temperature window broadening aids, the denitration efficiency of the prepared catalyst can reach more than 90% in the low-temperature range of 160-220 DEG C, the catalyst has high strength, has the resistance to 6% water poisoning, 3% alkali poisoning and 400 ppm sulfur poisoning, and has the advantages of simple preparation process, wide application range and low energy consumption loss. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described below in a clear and complete manner in combination with the embodiments of the application. Obviously, the described embodiments are some but not all of the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0029] Embodiment 1

[0030] A preparation method of an anti-water, sulfur-resistant and alkali-resistant low-temperature denitration catalyst, comprising the following steps:

[0031] (1) 3 g of ammonium metavanadate and 3 g of ammonium dihydrogen phosphate are weighed, and then single ethanol amine and deionized water are added and stirred uniformly to obtain solution 1;

[0032] (2) take 1.3 g of cerium nitrate, add 5 ml of deionized water to dissolve, get solution 2, mix solution 1 and 2 uniformly, then take 2.8 g of ammonium metatungstate and 2 g of ammonium heptamolybdate, add deionized water to dissolve and then add to solution 3 to get solution 4;

[0033] (3) mix 5 g of zirconium nitrate, 7 g of silicon dioxide and 66.4 g of titanium white uniformly, then add to solution 4 and stir uniformly, at the same time, add 0.5 g of lactic acid, 2 g of glass fiber and 7 g of boric acid, mix and stir uniformly to get uniform slurry;

[0034] (4) place the uniform slurry of step (3) in an oven and dry at 110℃ for 2 h;

[0035] (5) place the catalyst dried in step (4) in a muffle furnace and calcine at 500℃ for 4 h to get the catalyst sample.

[0036] Example 2:

[0037] A preparation method of a water-resistant sulfur-resistant alkali-resistant low-temperature denitration catalyst, comprising the following steps:

[0038] (1) take 2 g of ammonium metavanadate and 4 g of ammonium dihydrogen phosphate, add monoethanolamine and deionized water to stir uniformly to get solution 1;

[0039] (2) take 1.5 g of cerium nitrate, add 5 ml of deionized water to dissolve, get solution 2, mix solution 1 and 2 uniformly to get solution 3, then take 4 g of ammonium metatungstate and 2 g of ammonium heptamolybdate, add deionized water to dissolve and then add to solution 3 to get solution 4;

[0040] (3) mix 6 g of zirconium nitrate, 8 g of silicon dioxide and 60.9 g of titanium white uniformly, then add to solution 4 and stir uniformly, at the same time, add 0.6 g of lactic acid, 3 glass fibers and 8 g of boric acid, mix and stir uniformly to get uniform slurry;

[0041] (4) place the uniform slurry of step (3) in an oven and dry at 110℃ for 3 h;

[0042] (5) place the catalyst dried in step (4) in a muffle furnace and calcine at 500℃ for 5 h to get the catalyst sample.

[0043] Example 3:

[0044] A preparation method of a water-resistant sulfur-resistant alkali-resistant low-temperature denitration catalyst, comprising the following steps:

[0045] (1) take 4 g of ammonium metavanadate and 6 g of ammonium dihydrogen phosphate, add monoethanolamine and deionized water to stir uniformly to get solution 1;

[0046] (2) Take 2 g of cerium nitrate, add 5 ml of deionized water to dissolve, get solution 2, mix solution 1 and 2 uniformly to get solution 3, continue to take 8 g of ammonium metatungstate and 3 g of ammonium heptamolybdate, add deionized water to dissolve and then add to solution 3 to get solution 4;

[0047] (3) Mix 8 g of zirconium nitrate, 9 g of silicon dioxide and 43 g of titanium white powder uniformly, then add to solution 4 and stir uniformly, at the same time, add 1 g of lactic acid, 4 g of glass fiber and 12 g of boric acid, mix and stir uniformly to get uniform slurry;

[0048] (4) Put the uniform slurry of step (3) into an oven and dry at 110℃ for 4 h;

[0049] (5) Put the dried catalyst of step (4) into a muffle furnace and calcine at 500℃ for 6 h to get the catalyst sample.

[0050] Comparative Example 1:

[0051] (1) Take 2 g of ammonium metavanadate and add to monoethanolamine to stir uniformly to get solution 1;

[0052] (2) Take 1.5 g of cerium nitrate, add 5 ml of deionized water to dissolve to get solution 2, mix solution 1 and 2 uniformly to get solution 3, continue to take 4 g of ammonium heptamolybdate, add deionized water to dissolve and then add to solution 3 to get solution 4;

[0053] (3) Mix 6 g of zirconium nitrate, 8 g of silicon dioxide and 60.9 g of titanium white powder uniformly, then add to solution 4 and stir uniformly, at the same time, add 0.6 g of lactic acid, 3 glass fiber and 8 g of boric acid, mix and stir uniformly to get uniform slurry;

[0054] (4) Put the uniform slurry of step (3) into an oven and dry at 110℃ for 3 h;

[0055] (5) Put the dried catalyst of step (4) into a muffle furnace and calcine at 500℃ for 4 h to get the catalyst sample.

[0056] Comparative Example 2:

[0057] (1) Take 2 g of ammonium metavanadate and 4 g of ammonium dihydrogen phosphate, add to monoethanolamine and deionized water to stir uniformly to get solution 1;

[0058] (2) Take 1.5 g of cerium nitrate, add 5 ml of deionized water to dissolve to get solution 2, mix solution 1 and 2 uniformly to get solution 3, continue to take 4 g of ammonium metatungstate and 2 g of ammonium heptamolybdate, add deionized water to dissolve and then add to solution 3 to get solution 4;

[0059] (3) 60.9 g titanium white powder was added into solution 4 and stirred uniformly, while 0.6 g lactic acid, 3 g glass fiber and 8 g boric acid were added and stirred uniformly to obtain a uniform slurry;

[0060] (4) The uniform slurry of step (3) was placed in an oven and dried at 110°C for 3 h;

[0061] (5) The catalyst dried in step (4) was placed in a muffle furnace and calcined at 500°C for 4 h to obtain a catalyst sample.

[0062] Experimental Example

[0063] Examples 1-3 and Comparative Examples 1-2 in the present application were tested for catalyst denitration efficiency by using a laboratory denitration small test evaluation device, and the test conditions were as follows: the catalyst was ground to 40-60 mesh, the catalyst dosage was 5 mL, T = 160-200°C, GSHV = 10000 h -1 , 400 ppm SO2, 3% CaO, 6% H2O. The test results of the catalyst denitration efficiency are shown in Table 1 below:

[0064] Table 1: Test results of denitration catalytic activity of the catalyst prepared in Examples 1-3 and Comparative Examples 1-2

[0065]

[0066]

[0067] Table 1

[0068] Example 4:

[0069] The difference between this example and Example 1 is that "3 g ammonium metavanadate, 3 g ammonium dihydrogen phosphate and 66.4 g titanium white powder" in Example 1 is replaced by "5 g ammonium metavanadate, 15 g ammonium dihydrogen phosphate and 52.4 g titanium white powder", and the other steps are the same as those in Example 1.

[0070] Example 5:

[0071] The difference between this example and Example 1 is that "110°C drying for 2 h, 500°C calcination for 4 h" in Example 1 is replaced by "90°C drying for 6 h, 600°C calcination for 2 h", and the other steps are the same as those in Example 1.

[0072] Example 6:

[0073] The difference between this example and Example 1 is that "110°C drying for 2 h, 500°C calcination for 4 h" in Example 1 is replaced by "130°C drying for 1 h, 400°C calcination for 6 h", and the other steps are the same as those in Example 1.

[0074] The catalysts prepared in Examples 4-6 have similar performance to the catalyst prepared in Example 1.

[0075] As seen from Table 1, the catalysts of Examples 1-3 have catalytic activity of over 90% at the temperature range of 160-220℃ after 6% H2O, 400ppm SO2 and 3% CaO are passed through, and no obvious change is observed, indicating that the synergistic effect of the phosphorus-modified V2O5 and one or two of ammonium heptamolybdate, ammonium metatungstate and cerium nitrate has certain water resistance, alkali resistance and sulfur resistance, and the activity of the catalysts of Comparative Examples 1-2 is obviously lower, indicating that the phosphorus-modified V2O5 and the active component do not form a synergistic effect, do not form a composite oxide carrier, cannot change the dispersion state and active structure of the active component through the interaction with the active component, and cannot improve the water resistance, sulfur resistance and alkali resistance of the catalyst and the denitration efficiency.

[0076] The application converts V2O5 into a crystal state by dissolving ammonium metavanadate to improve the active space, improves the specific surface area and acidity of the catalyst by phosphorus-modifying V2O5, improves the alkali metal poisoning resistance and sulfur poisoning resistance of the catalyst, and synergistically uses cerium nitrate, ammonium heptamolybdate and ammonium metatungstate as low-temperature active additives and active temperature window broadening additives, so that the prepared catalyst has a denitration efficiency of over 90% in the low-temperature range of 160-220℃, and has high strength, 6% H2O resistance, 3% alkali poisoning resistance and 400ppm sulfur poisoning resistance.

[0077] The above examples are only used to illustrate the technical solutions of the application, but not to limit the application; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the application.

Claims

1. A method for preparing a water-resistant, sulfur-resistant, and alkali-resistant low-temperature denitrification catalyst, characterized in that, It comprises the following steps: (1) A certain amount of ammonium metavanadate and ammonium dihydrogen phosphate are weighed, and monoethanolamine and water are added to stir and dissolve to obtain solution 1; the mass ratio of ammonium metavanadate to ammonium dihydrogen phosphate is 1:1-3; the mass of ammonium metavanadate accounts for 3-5% of the total mass of the catalyst; (2) A certain amount of cerium nitrate is weighed and dissolved in deionized water to obtain solution 2; solutions 1 and 2 are mixed uniformly to obtain solution 3; a certain amount of ammonium metatungstate and ammonium heptamolybdate are dissolved in deionized water and then added to solution 3 to obtain solution 4; the mass of cerium nitrate accounts for 1-2% of the total mass of the catalyst; ammonium metatungstate and ammonium heptamolybdate account for 2-10% and 1-4% of the total mass of the catalyst, respectively; (3) Titanium dioxide, zirconium nitrate and silicon dioxide powder are mixed uniformly and added to solution 4 to stir uniformly, and a certain amount of lactic acid, glass fiber and boric acid are added to obtain a uniform slurry; the mass of zirconium nitrate, silicon dioxide, lactic acid, glass fiber and boric acid is 5-10%, 7-10%, 0.5-2%, 2-5% and 7-15% of the total mass of the catalyst, respectively; (4) The uniform slurry of step (3) is dried; (5) The dried material of step (4) is calcined to obtain.

2. The preparation method of the water-resistant, sulfur-resistant, alkali-resistant, low-temperature denitrification catalyst according to claim 1, characterized in that, In step (1), the mass ratio of ammonium metavanadate to ammonium dihydrogen phosphate is 1:1; the mass of ammonium metavanadate accounts for 3% of the total mass of the catalyst.

3. The method of claim 1 or 2, wherein the method is characterized by, In step (2), the mass of cerium nitrate accounts for 1% of the total mass of the catalyst; ammonium metatungstate and ammonium heptamolybdate account for 2% and 1% of the total mass of the catalyst, respectively.

4. The preparation method of the water-resistant, sulfur-resistant, alkali-resistant, low-temperature denitrification catalyst according to claim 3, characterized in that, In step (3), the mass of zirconium nitrate is 10% of the total mass of the catalyst, and the mass of silicon dioxide is 10% of the total mass of the catalyst.

5. The preparation method of the water-resistant, sulfur-resistant, alkali-resistant, low-temperature denitrification catalyst according to claim 4, characterized in that, In step (3), the mass of lactic acid is 2% of the total mass of the catalyst, the mass of glass fiber is 5% of the total mass of the catalyst, and the mass of boric acid is 15% of the total mass of the catalyst.

6. The preparation method of the water-resistant, sulfur-resistant, alkali-resistant, low-temperature denitrification catalyst according to claim 1, characterized in that, In step (4), the drying temperature is 90-130°C, and the drying time is 1-6h.

7. The preparation method of the water-resistant, sulfur-resistant, alkali-resistant, low-temperature denitrification catalyst according to claim 6, characterized in that, In step (4), the drying temperature is 110°C, and the drying time is 2-4h.

8. The preparation method of the water-resistant, sulfur-resistant, alkali-resistant, low-temperature denitrification catalyst according to claim 1, characterized in that, In step (5), the calcination temperature is 400-600°C, and the calcination time is 2-8h.

9. The preparation method of the water-resistant, sulfur-resistant, alkali-resistant, low-temperature denitrification catalyst according to claim 8, characterized in that, In step (5), the calcination temperature is 500°C, and the calcination time is 4-6h.

10. The water-resistant, sulfur-resistant, alkali-resistant and low-temperature denitration catalyst prepared by the preparation method of any one of claims 1-9.

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