CN114797841A - Mn (manganese) 4+ And Ce 3+ Preparation method of enhanced Mn-M-Ti-O ultralow-temperature denitration catalyst - Google Patents

Abstract

Mn (manganese) ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow temperature denitration catalyst is characterized in that the Mn-M-Ti-O (M ═ Ce, La and Gd) ultralow temperature denitration catalyst is TiO ₂ Loading denitration active component and auxiliary agent as carrier and oxidizing Mn with ozone ^x+ And hydrogen peroxide reduction of Ce ⁴⁺ Thus obtaining the product. The catalyst obtained by the invention has appropriate specific surface area (70-90 m) ² Per g), uniform particle size (1-5 μm), surface Mn ⁴⁺ High proportion (47-50%), surface Ce ³⁺ High ratio (19-25%), high surface activityThe method has the characteristics of large number of sexual oxygen species (45-50%), small average pore diameter (less than 13nm), high hydrothermal stability, wide low-temperature active temperature window (125-400 ℃), good denitration performance and the like, meets the requirements of the high-efficiency denitration SCR catalyst, has controllable product components, simple operation flow, low cost and good stability, and is easy to realize large-scale industrial production.

Description

A kind of preparation method of Mn4+ and Ce3+ enhanced Mn-M-Ti-O ultra-low temperature denitration catalyst

technical field

The invention belongs to the technical field of environmental protection, in particular to a preparation method of a Mn ⁴⁺ and Ce ³⁺ enhanced Mn-M-Ti-O ultra-low temperature denitration catalyst.

Background technique

Today, coal-fired power units, which account for 60-70% of the total power generation, are all planned to be withdrawn in 2060, and solar energy, wind energy, and biomass energy are mainly in the dominant position. Waste incineration, biomass energy and other industries are the way out for the entire environmental protection industry to turn waste into treasure, but the flue gas produced by it has the particularity of containing acidic substances and low temperature. At present, domestic catalysts are difficult to meet the temperature requirements of ultra-low temperature, and the exhaust gas must be After heating, the greenhouse effect is serious, and all kinds of ultra-low temperature catalysts have been monopolized by foreign countries. Therefore, it is urgent to develop ultra-low temperature denitration catalysts with high efficiency and strong anti-poisoning ability.

In recent years, transition metal oxides have been proved to be active for SCR reaction in various studies, especially Mn-based oxide catalysts have been widely studied for low-temperature _NH3 -SCR reaction due to their excellent catalytic performance. Its specific advantages are: outstanding stability and large specific surface area. Manganese oxides easily form a redox cycle, which reflects good low-temperature SCR denitration performance. Mn has five common valence states: MnO, Mn ₂ O ₃ , Mn ₃ O ₄ , Mn ₅ O ₈ , and MnO ₂ . Among them, MnO ₂ has better oxygen transfer ability than others and has the best catalytic performance. However, single _MnOx catalysts have disadvantages such as poor _N2 selectivity and easy deactivation. Therefore, it needs to be modified by doping other metal oxides to make it have higher redox ability and acid sites, so as to have better SCR performance.

The rare earth metal elements (M=Ce, La, Gd) in the denitration catalyst of the present invention mainly exist in the form of promoters, which mainly play the following roles: cause the surface electron imbalance of the catalyst, form unsaturated chemical bonds and oxygen vacancies, increase surface adsorption The concentration of oxygen can improve the oxidation capacity of the catalyst; in addition, it can provide more NH ₃ adsorption sites and increase the activity of the catalyst; at the same time, it can also reduce the thermal stability of sulfate and promote its decomposition, thereby improving the sulfur resistance of the catalyst. Poisoning ability. The synergistic effect of Mn and rare earth elements takes Ce as an example:

1. A redox shift occurs between Ce ⁴⁺ and Ce ³⁺ , which enhances the low-temperature activity of MnO _x , and the higher the Ce ⁴⁺ /Ce ³⁺ ratio, the better the oxygen storage between Ce ⁴⁺ and Ce ³⁺ . The stronger the release, the higher the SCR activity.

2. Provide more NH ₃ adsorption sites. The Mn-Ce sample has higher reducibility and can provide more NH 3 adsorption sites on Lewis acid sites.

3. Ce improves the stability of the Mn-based catalyst structure and makes it have a larger specific surface area.

In order to further increase the concentration of Mn ⁴⁺ to improve its redox performance, the Mn-Ce catalyst can be modified with hydrogen peroxide in the form of adding an oxidant, which can improve the surface Ce ³⁺ /(Ce ³⁺ +Ce ⁴⁺ ) of the catalyst surface. molar ratio, indicating that the hydrogen peroxide modification can increase the concentration of surface oxygen vacancies. At the same time, the dispersion of Ce species on the surface of the hydrogen peroxide-modified catalyst is enhanced, which helps to improve its NH ₃ -SCR activity.

Therefore, the present invention adopts the synergistic effect of rare earth metals and Mn groups and modifies the catalyst in a new redox form, and develops an ultra-low temperature Mn-based denitration catalyst, which is expected to solve the problems of large specific surface area, narrow temperature window, and few active oxygen species, and realize waste incineration. , Ultra-low emissions in the field of biomass energy.

SUMMARY OF THE INVENTION

The purpose of the present invention is to synthesize a Mn ⁴⁺ and Ce ³⁺ enhanced Mn-M-Ti-O (M=Ce, La, Gd) ultra-low temperature denitration catalyst.

In order to achieve the above object, the present invention adopts the following technical solutions:

A preparation method of a Mn ⁴⁺ and Ce ³⁺ enhanced Mn-M-Ti-O ultra-low temperature denitration catalyst, the denitration catalyst uses TiO ₂ as a carrier, supports denitration active components and rare earth metal auxiliaries, and is oxidized by ozone , hydrogen peroxide reduction, calcination obtained. After oxidation, the proportion of Mn ⁴⁺ on the surface of the active component increases, and the catalytic oxidation performance is enhanced; the reduction of hydrogen peroxide can promote the reduction of Ce ⁴⁺ to Ce ³⁺ , increase the proportion of Ce ³⁺ on the surface of the active component and the number of surface active oxygen species, and increase the oxygen deficiency. bit to facilitate electron transfer.

The active component is the transition metal element manganese; the auxiliary agent is one of the rare earth metal elements cerium, lanthanum and gadolinium, preferably cerium.

The denitration catalyst has a specific surface area of 70-90 m ² /g, a particle size of 1-5 μm, a surface Mn ⁴⁺ ratio of 47-50%, a surface Ce ³⁺ ratio of 19-25%, and the number of surface active oxygen species 45- 50%, the average pore diameter is less than 13nm; the catalytic activity temperature window with denitration efficiency over 97% is 125-400℃.

Specifically include the following steps:

(1) adding manganese nitrate solution and M(NO ₃ ) _x solid in distilled water and stirring to dissolve to obtain a mixed solution; M in the formula is Ce, La or Gd;

(2) adding the catalyst carrier TiO ₂ into the mixed solution, stirring evenly, to obtain a mixed slurry;

(3) adjust the pH value of the mixed slurry, continue stirring at room temperature to obtain a suspension;

(4) Pneumatic mixer is used to introduce ozone into the suspension while stirring to make it fully oxidized;

(5) after passing through, add hydrogen peroxide dropwise to the slurry after ozonation;

(6) after continuing to stir for a period of time, centrifugal washing several times;

(7) drying the catalyst after washing;

(8) temperature-programmed calcination is carried out to the dried product;

(9) Grind the calcined product into powder to obtain the required material.

The concentration of manganese nitrate solution is 50wt%, and the mass ratio of manganese nitrate solution, M(NO ₃ ) _x , distilled water and TiO ₂ is (5.94-6.31):(6.04-7.64):100:3.53.

In step (3), the pH is adjusted to 8-10 by using ammonia water with a concentration of 20-30 wt%.

In step (4), the concrete method of ozone oxidation is: adopt a pneumatic mixer with a convex or concave propeller and set a ventilation hole on the propeller shaft, place the suspension in the pneumatic mixer, and pass the ventilation hole to the suspension while stirring. Ozone is introduced into the turbid liquid; the speed of the propeller is 10-15r/min, and the ozone ventilation volume is 500mL/min.

In step (5), the concrete method of dripping hydrogen peroxide is: the dropper is stretched into the bottom of slurry and drip hydrogen peroxide, and the dripping speed is controlled at 10 seconds/drip.

In step (7), the drying method selects negative pressure drying or spray evaporation drying method: the negative pressure drying method is to form a negative pressure state with a vacuum pump, and dry through devices such as drying furnace, heating chamber, stirring, driving, steam, filtration, and condensation. ; The spray evaporation method is to pump the catalyst into the spray dryer, and spray it out from the bottom of the spray dryer after being atomized by the nozzle.

In step (8), the temperature-programmed rate is 10°C/min, the calcination temperature is 500-550°C, and the calcination time is 4 hours.

The beneficial effects of the present invention are:

In the present invention, Mn(NO ₃ ) ₂ is mixed with the precursor solution of M(NO ₃ ) _{x (} M=Ce, La, Gd), and then the pH value of the solution is adjusted by ammonia water to obtain a mixed solution, which is oxidized by ozone , The hydrogen peroxide is reduced, and then the solution is dried by negative pressure drying or spray evaporation, and then the material with the required particle size is obtained by calcination and ball milling. The preparation method of the invention has the advantages of simple operation, convenient equipment requirements and the like.

In the Mn ⁴⁺ and Ce ³⁺ enhanced Mn-M-Ti-O (M=Ce, La, Gd) ultra-low temperature denitration catalyst prepared by the invention, the mass fraction of manganese nitrate solution is adjusted in the range of 20%-30%, cerium nitrate The adjustment range of the mass fraction of (lanthanum, gadolinium) is 20%-30%. The composite powder has moderate specific surface area (70-90m ² /g), uniform particle size (1-5μm), high proportion of surface Mn ⁴⁺ (47-50%), and high proportion of surface Ce ³⁺ (19-25%). , the number of surface active oxygen species is large (45-50%), the average pore size is small (less than 13nm), the hydrothermal stability is high, the low temperature active temperature window is wide (125-400℃), and the denitration performance is good. demand.

A large number of studies have shown that rare earth metal elements such as cerium can provide acid sites to ensure SCR catalytic activity, but also reduce the stability of sulfate, promote its decomposition, and improve the ability of the catalyst to resist SO ₂ poisoning. In addition, rare-earth metal elements such as cerium can also bring a large number of lattice oxygen defects, which play a role in improving the oxygen storage ability and enhancing the reducibility of the catalyst. Therefore, the addition of rare earth metal elements such as cerium can improve the stability of the catalyst structure, make it have a larger specific surface area, and provide a large number of active centers for the SCR reaction.

Detailed ways

The present invention is further illustrated by the following examples (reagents used in the examples are chemically pure), it should be noted that the following examples are only used for illustration, and the content of the present invention is not limited thereto.

Example 1: Preparation of MnCeTi-O ultra-low temperature denitration catalyst with manganese content of 24wt% and cerium content of 24wt%.

Step 1: Dissolve 6.31 g of manganese nitrate solution and 7.64 g of solid cerium nitrate in 100 g of distilled water, and stir for 30 minutes to obtain a mixed solution.

Step 2: Add 3.53 g of catalyst carrier titanium dioxide into the mixed solution of step 1, and continue to stir for 1 hour to obtain a mixed slurry of manganese nitrate, cerium nitrate and titanium dioxide.

Step 3: Slowly add aqueous ammonia solution (analytical purity, concentration 20-30wt%) to the mixed slurry in Step 2, adjust the pH of the solution to 10, and continue stirring at room temperature for half an hour to obtain a manganese-cerium-titanium suspension.

Step 4: Use a pneumatic mixer with a convex or concave propeller and set a ventilation hole on the propeller; place the stirred manganese-cerium-titanium suspension in the pneumatic mixer, and while fully stirring the screw, pass the ventilation hole to the suspension. Ozone is introduced into the turbid liquid to make it fully oxidized, the speed of the propeller is 10-15r/min, and the ventilation rate is 500mL/min.

Step 5: Add hydrogen peroxide dropwise to the oxidized slurry in a dropwise manner by inserting a dropper into the bottom of the slurry and drop by dropwise, and control the dripping speed at 10 seconds/drop.

Step 6: After continuing to stir for a period of time, the slurry after oxidation and reduction is centrifuged and washed several times to obtain a relatively wet catalyst solid.

Step 7: The obtained catalyst solid is sprayed to dryness (that is, the catalyst is pumped into the spray dryer, and sprayed from the bottom of the spray dryer after being atomized by the nozzle), the particle size of the introduced slurry is 10-20 μm, and the spray temperature is controlled at 250 -300℃, effectively reduce drying time.

Step 8: Put the obtained dry material into a muffle furnace for temperature-programmed calcination. The calcination temperature was 550°C, the heating rate was 10°C/min, and the calcination time was 4 hours.

Step 9: put the calcined material into a ball mill for ball milling to obtain a MnCeTi-O ultra-low temperature denitration catalyst with a particle size of 1-5 μm.

Comparative Example 1

The MnCeTi denitration catalyst was prepared by the method of Example 1, except that the steps of ozone oxidation and hydrogen peroxide reduction were omitted.

The NH ₃ -SCR reaction activity of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 1. The denitration conversion rate of the catalyst is maintained at 100% in the temperature range of 125-350 °C, and it is always maintained at more than 98% below 400 °C. Denitrification performance.

Table 1 Characterization activity of MnCeTi-O catalyst for ultra-low temperature denitration

The XPS ion species ratio of the denitration catalyst prepared in Example 1 and Comparative Example 1 is shown in Table 2. It can be seen that the ratio of Mn ⁴⁺ , Ce ³⁺ , and active oxygen species is significantly increased after ozone oxidation and hydrogen peroxide reduction, which is conducive to low-temperature reduction.

Table 2 XPS ion species ratio of denitration catalyst

The hydrogen consumption of temperature-programmed reduction (H ₂ -TPR) of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 3. It can be seen that the catalysts reduced by ozone oxidation and hydrogen peroxide increase the area of the low temperature reduction peaks of MnO ₂ and surface CeO ₂ , indicating that Ozone oxidation increases Mn ⁴⁺ , and hydrogen peroxide reduction increases Ce ³⁺ , which is beneficial to low temperature reduction.

Table 3 Temperature-programmed reduction (H ₂ -TPR) hydrogen consumption of MnCeTi-O ultra-low temperature denitration catalysts

Example 2: Preparation of MnCeTi-O ultra-low temperature denitration catalyst with manganese content of 24wt% and cerium content of 24wt%.

Step 1: Dissolve 6.31 g of manganese nitrate solution and 7.64 g of solid cerium nitrate in 100 g of distilled water, and stir for 30 minutes to obtain a mixed solution.

Step 2: Add 3.53 g of catalyst carrier titanium dioxide into the mixed solution of step 1, and continue to stir for 1 hour to obtain a mixed slurry of manganese nitrate, cerium nitrate and titanium dioxide.

Step 3: Slowly add aqueous ammonia solution (analytical purity, concentration 20-30wt%) to the mixed slurry in step 2, adjust the pH of the solution to 8, and continue stirring at room temperature for half an hour to obtain a manganese-cerium-titanium suspension.

Step 4: Use a pneumatic mixer with a convex or concave propeller and set a ventilation hole on the propeller; place the stirred manganese-cerium-titanium suspension in the pneumatic mixer, and while fully stirring the screw, pass the ventilation hole to the suspension. Ozone is introduced into the turbid liquid to make it fully oxidized, the speed of the propeller is 10-15r/min, and the ventilation rate is 500mL/min.

Step 5: Add hydrogen peroxide dropwise to the oxidized slurry in a dropwise manner by inserting a dropper into the bottom of the slurry and drop by dropwise, and control the dripping speed at 10 seconds/drop.

Step 6: After continuing to stir for a period of time, the slurry after oxidation and reduction is centrifuged and washed several times to obtain a relatively wet catalyst solid.

Step 7: The obtained catalyst solid is dried by spray evaporation method, the particle size of the introduced slurry is 10-20 μm, and the spray temperature is controlled at 250-300° C. to effectively reduce the drying time.

Step 8: Put the obtained dry material into a muffle furnace for temperature-programmed calcination. The calcination temperature was 550°C, the heating rate was 10°C/min, and the calcination time was 4 hours.

Step 9: put the calcined material into a ball mill for ball milling to obtain a MnCeTi-O ultra-low temperature denitration catalyst with a particle size of 1-5 μm.

The NH ₃ -SCR reaction activity of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 4. The denitration conversion rate of the catalyst is maintained at 100% in the temperature range of 125-275 °C, and it is always maintained at more than 97% below 400 °C. Denitrification performance.

Table 4 Characterization activity of MnCeTi-O ultra-low temperature denitration catalyst

The XPS ion species ratio of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 5. Comparing Comparative Example 1 and Example 1, it can be seen that the ratio of Mn ⁴⁺ , Ce ³⁺ , and active oxygen species after ozone oxidation and hydrogen peroxide reduction is increased, and Compared with the catalyst prepared at pH=10, it is lower, indicating that pH=10 is the optimal pH value.

Table 5 XPS ion species and active oxygen species ratio of MnCeTi-O ultra-low temperature denitration catalyst

Example 3: Preparation of MnCeTi-O ultra-low temperature denitration catalyst with manganese content of 24wt% and cerium content of 24wt%.

Step 1: Dissolve 6.31 g of manganese nitrate solution and 7.64 g of solid cerium nitrate in 100 g of distilled water, and stir for 30 minutes to obtain a mixed solution.

Step 2: Add 3.53 g of catalyst carrier titanium dioxide into the mixed solution of step 1, and continue to stir for 1 hour to obtain a mixed slurry of manganese nitrate, cerium nitrate and titanium dioxide.

Step 3: Slowly add aqueous ammonia solution (analytical purity, concentration 20-30wt%) to the mixed slurry in Step 2, adjust the pH of the solution to 10, and continue stirring at room temperature for half an hour to obtain a manganese-cerium-titanium suspension.

Step 4: Use a pneumatic mixer with a convex or concave propeller and set a ventilation hole on the propeller; place the stirred manganese-cerium-titanium suspension in the pneumatic mixer, and while fully stirring the screw, pass the ventilation hole to the suspension. Ozone was introduced into the turbid liquid to make it fully oxidized. The speed of the propeller was 10-15r/min, and the ventilation rate was 300mL/min. During the oxidation process, it was found that the color of the solution did not become darker rapidly, which may be due to the fact that Mn ²⁺ It cannot be rapidly and completely oxidized to Mn ⁴⁺ , so the ventilation time should be appropriately prolonged.

Step 5: Add hydrogen peroxide dropwise to the oxidized slurry in a dropwise manner by inserting a dropper into the bottom of the slurry and drop by dropwise, and control the dripping speed at 10 seconds/drop.

Step 6: After continuing to stir for a period of time, the slurry after oxidation and reduction is centrifuged and washed several times to obtain a relatively wet catalyst solid.

Step 7: The obtained catalyst solid is dried by spray evaporation (that is, the catalyst is pumped into the spray dryer, and sprayed from the bottom of the spray dryer after being atomized by the nozzle), the particle size of the introduced slurry is 10-20 μm, and the spray temperature is controlled at 250-300℃, effectively reduce drying time.

Step 8: Put the obtained dry material into a muffle furnace for temperature-programmed calcination. The calcination temperature was 550°C, the heating rate was 10°C/min, and the calcination time was 4 hours.

Step 9: put the calcined material into a ball mill for ball milling to obtain a MnCeTi-O ultra-low temperature denitration catalyst with a particle size of 1-5 μm.

The NH ₃ -SCR reaction activity of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 6. The denitration conversion rate of the catalyst is maintained at 100% in the temperature range of 125-275 °C, and it is always maintained at more than 96% below 400 °C. Denitrification performance.

Table 6 Characterization activity of MnCeTi-O ultra-low temperature denitration catalyst

The XPS ion species ratio of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 7. Comparing Comparative Example 1 and Example 1, it can be seen that the ratio of Mn ⁴⁺ , Ce ³⁺ and active oxygen species after ozone oxidation and hydrogen peroxide reduction is increased, and compared to Ozone ventilation was reduced at 500 mL/min.

Table 7 XPS ion species ratio of MnCeTi-O ultra-low temperature denitration catalyst

Example 4: Preparation of MnCeTi-O ultra-low temperature denitration catalyst with manganese content of 24wt% and cerium content of 24wt%.

Step 1: Dissolve 6.31 g of manganese nitrate solution and 7.64 g of solid cerium nitrate in 100 g of distilled water, and stir for 30 minutes to obtain a mixed solution.

Step 2: Add 3.53 g of catalyst carrier titanium dioxide into the mixed solution of step 1, and continue to stir for 1 hour to obtain a mixed slurry of manganese nitrate, cerium nitrate and titanium dioxide.

Step 3: Slowly add aqueous ammonia solution (analytical purity, concentration 20-30wt%) to the mixed slurry in Step 2, adjust the pH of the solution to 10, and continue stirring at room temperature for half an hour to obtain a manganese-cerium-titanium suspension.

Step 4: Use a pneumatic mixer with a convex or concave propeller and set a ventilation hole on the propeller; place the stirred manganese-cerium-titanium suspension in the pneumatic mixer, and while fully stirring the screw, pass the ventilation hole to the suspension. Ozone is introduced into the turbid liquid to make it fully oxidized, the speed of the propeller is 10-15r/min, and the ventilation rate is 500mL/min.

Step 5: Add hydrogen peroxide dropwise to the oxidized slurry in a dropwise manner by inserting a dropper into the bottom of the slurry and drop by dropwise, and control the dripping speed at 10 seconds/drop.

Step 6: After continuing to stir for a period of time, the slurry after oxidation and reduction is centrifuged and washed several times to obtain a relatively wet catalyst solid.

Step 7: The obtained catalyst solid is dried by a negative pressure (that is, a negative pressure state is formed by a vacuum pump, and dried through devices such as a drying furnace, a heating chamber, stirring, driving, steam, filtration, and condensation), and the internal temperature is controlled in the negative pressure. in the range of 160-180°C.

Step 8: Put the obtained dry material into a muffle furnace for temperature-programmed calcination. The calcination temperature was 550°C, the heating rate was 10°C/min, and the calcination time was 4 hours.

Step 9: put the calcined material into a ball mill for ball milling to obtain a MnCeTi-O ultra-low temperature denitration catalyst with a particle size of 1-5 μm.

The NH ₃ -SCR reaction activity of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 8. The denitration conversion rate of the catalyst is maintained at 100% in the temperature range of 125-350 °C, and it is always maintained at more than 96% below 400 °C. Denitrification performance.

Table 8 Characterization activity of MnCeTi-O ultra-low temperature denitration catalyst

The XPS ion species ratio of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 9. Compared with Comparative Example 1, it can be seen that the ratio of Mn ⁴⁺ and Ce ³⁺ has increased after ozone oxidation and hydrogen peroxide reduction, which is conducive to low temperature reduction.

Table 9 XPS ion species ratio of MnCeTi-O ultra-low temperature denitration catalyst

Example 5: Preparation of MnCeTi-O ultra-low temperature denitration catalyst with manganese content of 24wt% and cerium content of 24wt%.

Step 1: Dissolve 6.31 g of manganese nitrate solution and 7.64 g of solid cerium nitrate in 100 g of distilled water, and stir for 30 minutes to obtain a mixed solution.

Step 2: Add 3.53 g of catalyst carrier titanium dioxide into the mixed solution of step 1, and continue to stir for 1 hour to obtain a mixed slurry of manganese nitrate, cerium nitrate and titanium dioxide.

Step 3: Slowly add aqueous ammonia solution (analytical purity, concentration 20-30wt%) to the mixed slurry in Step 2, adjust the pH of the solution to 10, and continue stirring at room temperature for half an hour to obtain a manganese-cerium-titanium suspension.

Step 4: Use a pneumatic mixer with a convex or concave propeller and set a ventilation hole on the propeller; place the stirred manganese-cerium-titanium suspension in the pneumatic mixer, and while fully stirring the screw, pass the ventilation hole to the suspension. Ozone is introduced into the turbid liquid to make it fully oxidized, the speed of the propeller is 10-15r/min, and the ventilation rate is 500mL/min.

Step 5: Add hydrogen peroxide dropwise to the oxidized slurry in a dropwise manner by inserting a dropper into the bottom of the slurry and drop by dropwise, and control the dripping speed at 10 seconds/drop.

Step 6: After continuing to stir for a period of time, the slurry after oxidation and reduction is centrifuged and washed several times to obtain a relatively wet catalyst solid.

Step 7: The obtained catalyst solid is evaporated to dryness by spray method, the particle size of the introduced slurry is 10-20 μm, and the spray temperature is controlled at 250-300° C. to effectively reduce the drying time.

Step 8: Put the obtained dry material into a muffle furnace for temperature-programmed calcination. The calcination temperature was 500°C, the heating rate was 10°C/min, and the calcination time was 4 hours.

Step 9: put the calcined material into a ball mill for ball milling to obtain a MnCeTi-O ultra-low temperature denitration catalyst with a particle size of 1-5 μm.

The NH ₃ -SCR reaction activity of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 10. The denitration conversion rate of the catalyst is maintained at 100% in the temperature range of 125-275 °C, and it is always maintained above 95% below 400 °C. Denitrification performance.

Table 10 Characterization activity of MnCeTi-O ultra-low temperature denitration catalyst

The XPS ion species ratio of the MnCeTi-O ultra-low temperature denitration catalyst is shown in Table 11. Comparing Comparative Example 1 and Example 1, it can be seen that the ratio of Mn ⁴⁺ and Ce ³⁺ increases after ozone oxidation and hydrogen peroxide reduction, and compared with 550 ℃ preparation The catalyst has decreased, indicating that the temperature has an influence on the denitration performance of the catalyst.

Table 11 Species ratio of XPS ions of MnCeTi-O ultra-low temperature denitration catalysts

Example 6: Preparation of MnLaTi-O ultra-low temperature denitration catalyst with manganese content of 24wt% and lanthanum content of 24wt%.

Step 1: Dissolve 5.94 g of manganese nitrate solution and 7.62 g of solid cerium nitrate in 100 g of distilled water, and stir for 30 minutes to obtain a mixed solution.

Step 2: Add 3.53 g of catalyst carrier titanium dioxide to the mixed solution of step 1, and continue to stir for 1 hour to obtain a mixed slurry of manganese nitrate, lanthanum nitrate and titanium dioxide.

Step 3: Slowly add aqueous ammonia solution (analytical purity, concentration 20-30wt%) to the mixed slurry in step 2, adjust the pH of the solution to 10, and continue stirring at room temperature for half an hour to obtain a manganese-lanthanum-titanium suspension.

Step 4: Use a pneumatic mixer with a convex or concave propeller and set ventilation holes on the propeller; place the stirred manganese-lanthanum-titanium suspension in the pneumatic mixer, while fully stirring the screw, pass the ventilation hole to the suspension. Ozone is introduced into the turbid liquid to make it fully oxidized, the speed of the propeller is 10-15r/min, and the ventilation rate is 500mL/min.

Step 5: Add hydrogen peroxide dropwise to the oxidized slurry in a dropwise manner by inserting a dropper into the bottom of the slurry and drop by dropwise, and control the dripping speed at 10 seconds/drop.

Step 6: After continuing to stir for a period of time, the slurry after oxidation and reduction is centrifuged and washed several times to obtain a relatively wet catalyst solid.

Step 7: The obtained catalyst solid is dried by spray evaporation (that is, the catalyst is pumped into the spray dryer, and sprayed from the bottom of the spray dryer after being atomized by the nozzle), the particle size of the introduced slurry is 10-20 μm, and the spray temperature is controlled at 250-300℃, effectively reducing drying time.

Step 8: Put the obtained dry material into a muffle furnace for temperature-programmed calcination. The calcination temperature was 550°C, the heating rate was 10°C/min, and the calcination time was 4 hours.

Step 9: put the calcined material into a ball mill for ball milling to obtain a MnLaTi-O ultra-low temperature denitration catalyst with a particle size of 1-5 μm.

Comparative Example 2

The denitration catalyst was prepared according to the method of Example 6, except that the steps of ozone oxidation and hydrogen peroxide reduction were omitted.

The NH ₃ -SCR reaction activity of the MnLaTi-O ultra-low temperature denitration catalyst is shown in Table 12. The denitration conversion rate of the catalyst is maintained at 100% in the temperature range of 100-350 °C, and it is always maintained above 97% below 400 °C. Denitrification performance.

Table 12 Characterization activity of MnLaTi-O ultra-low temperature denitration catalyst

The ratios of XPS ions of the denitration catalysts prepared in Comparative Example 6 and Comparative Example 1 are shown in Table 13. It can be seen that the ratio of Mn ⁴⁺ and La ³⁺ increases after ozone oxidation and hydrogen peroxide reduction, which is beneficial to low-temperature reduction.

Table 13 Species ratio of XPS ions of 1MnLaTi-O ultra-low temperature denitration catalyst

Example 7: Preparation of MnGdTi-O ultra-low temperature denitration catalyst with manganese content of 24wt% and gadolinium content of 24wt%.

Step 1: Dissolve 5.94g of manganese nitrate and 6.04g of gadolinium nitrate solid in 100g of distilled water, and stir for 30 minutes to obtain a mixed solution.

Step 2: Add 3.53 g of catalyst carrier titanium dioxide to the mixed solution of step 1, and continue stirring for 1 hour to obtain a mixed slurry of manganese nitrate, gadolinium nitrate and titanium dioxide.

Step 3: Slowly add aqueous ammonia solution (analytical purity, concentration 20-30wt%) to the mixed slurry in step 2, adjust the pH of the solution to 10, and continue stirring at room temperature for half an hour to obtain a manganese-gadolinium-titanium suspension.

Step 4: Use a pneumatic mixer with a convex or concave propeller and set a ventilation hole on the propeller; place the stirred manganese-gadolinium-titanium suspension in the pneumatic mixer, and while fully stirring the screw, pass the ventilation hole to the suspension. Ozone is introduced into the turbid liquid to make it fully oxidized, the speed of the propeller is 10-15r/min, and the ventilation rate is 500mL/min.

Step 5: Add hydrogen peroxide dropwise to the oxidized slurry in a dropwise manner by inserting a dropper into the bottom of the slurry and drop by dropwise, and control the dripping speed at 10 seconds/drop.

Step 6: After continuing to stir for a period of time, the slurry after oxidation and reduction is centrifuged and washed several times to obtain a relatively wet catalyst solid.

Step 7: The obtained catalyst solid is dried by spray evaporation (that is, the catalyst is pumped into the spray dryer, and sprayed from the bottom of the spray dryer after being atomized by the nozzle), the particle size of the introduced slurry is 10-20 μm, and the spray temperature is controlled at 250-300℃, effectively reduce drying time.

Step 8: Put the obtained dry material into a muffle furnace for temperature-programmed calcination. The calcination temperature was 550°C, the heating rate was 10°C/min, and the calcination time was 4 hours.

Step 9: put the calcined material into a ball mill for ball milling to obtain a MnGdTi-O ultra-low temperature denitration catalyst with a particle size of 1-5 μm.

Comparative Example 3

The denitration catalyst was prepared according to the method of Example 7, except that the steps of ozone oxidation and hydrogen peroxide reduction were omitted.

The NH ₃ -SCR reaction activity of the MnGdTi-O ultra-low temperature denitration catalyst is shown in Table 14. The denitration conversion rate of the catalyst is maintained at 100% in the temperature range of 100-350 °C, and it is always maintained at more than 97% below 400 °C, with good performance. Denitrification performance.

Table 14 Characterization activity of MnGdTi-O ultra-low temperature denitration catalyst

The XPS ion species ratios of the denitration catalysts prepared in Comparative Example 6 and Comparative Example 1 are shown in Table 15. It can be seen that the ratio of Mn ⁴⁺ and Gd ³⁺ increases after ozone oxidation and hydrogen peroxide reduction, which is beneficial to low-temperature reduction.

Table 15 Species ratio of XPS ions of MnCeTi-O ultra-low temperature denitration catalysts

The specific surface area and pore size of the MGdTi-O ultra-low temperature denitration catalysts prepared in Examples 1-7 are shown in Table 16.

Table 16 Specific surface area and pore size of MGdTi-O ultra-low temperature denitration catalysts

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 specific surface area 88 80 79 85 75 83 80 Aperture 11.43 12.2 10.6 12.32 12.94 12.14 12.08

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

Claims (10)

1. Mn (manganese) ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow temperature denitration catalyst is characterized in that the denitration catalyst is TiO ₂ The carrier is loaded with denitration active ingredients and rare earth metal element auxiliaries, and is prepared by ozone oxidation, hydrogen peroxide reduction and calcination.

2. A Mn as claimed in claim 1 ⁴⁺ And Ce ³⁺ Enhanced Mn-M-Ti-O ultralow temperature denitrationThe preparation method of the catalyst is characterized in that the active component is transition metal element manganese; the auxiliary agent is one of rare earth metal elements of cerium, lanthanum and gadolinium.

3. A Mn as claimed in claim 1 ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow-temperature denitration catalyst is characterized in that the specific surface area of the denitration catalyst is 70-90M ² Per g, particle size 1-5 μm, surface Mn ⁴⁺ 47-50% of surface Ce ³⁺ The proportion is 19-25%, the number of surface active oxygen species is 45-50%, and the average pore diameter is less than 13 nm; the temperature window of catalytic activity for denitration efficiency reaching more than 97 percent is 125-400 ℃.

4. A Mn as set forth in any one of claims 1 to 3 ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow-temperature denitration catalyst is characterized by comprising the following steps:

(1) mixing manganese nitrate solution with M (NO) ₃ ) _x Adding the solid into distilled water, stirring and dissolving to obtain a mixed solution; wherein M is Ce, La or Gd;

(2) making the catalyst carrier TiO ₂ Adding the mixture into the mixed solution, and uniformly stirring to obtain mixed slurry;

(3) adjusting the pH value of the mixed slurry, and continuously stirring at normal temperature to obtain a suspension;

(4) introducing ozone into the suspension while stirring by using a pneumatic stirrer to fully oxidize the suspension;

(5) after the introduction is finished, adding hydrogen peroxide dropwise into the slurry after the ozone oxidation;

(6) after continuously stirring for a period of time, centrifugally washing for a plurality of times;

(7) drying the washed catalyst;

(8) carrying out temperature programming calcination on the dried product;

(9) grinding the calcined product into powder to obtain the material meeting the requirement.

5. A compound of claim 4n ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow-temperature denitration catalyst is characterized in that the concentration of a manganese nitrate solution is 50 wt%, and the manganese nitrate solution and M (NO) are ₃ ) _x Distilled water, TiO ₂ The mass ratio of (5.94-6.31): (6.04-7.64): 100: 3.53.

6. a Mn according to claim 4 ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow-temperature denitration catalyst is characterized in that in the step (3), ammonia water with the concentration of 20-30 wt% is adopted to adjust the pH value to 8-10.

7. A Mn according to claim 4 ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow temperature denitration catalyst is characterized in that in the step (4), the specific method of ozone oxidation is as follows: adopting a pneumatic stirrer with a convex or concave propeller, arranging a vent hole on a propeller shaft, placing the suspension in the pneumatic stirrer, and introducing ozone into the suspension through the vent hole while stirring; the rotating speed of the propeller is 10-15r/min, and the ozone ventilation volume is 500 mL/min.

8. A Mn according to claim 4 ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow-temperature denitration catalyst is characterized in that in the step (5), the specific method for dropwise adding hydrogen peroxide is as follows: and (4) extending a dropper into the bottom of the slurry, and dropwise adding hydrogen peroxide, wherein the dropping speed is controlled to be 10 seconds per drop.

9. A Mn according to claim 4 ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow temperature denitration catalyst is characterized in that in the step (7), the drying method is negative pressure drying or spray evaporation: the negative pressure drying method is that a vacuum pump forms a negative pressure state, and the drying is carried out by a drying furnace, a heating chamber, stirring, driving, steam, filtering, condensing and other devices; the spray evaporation method is to pump the catalyst into a spray dryer, atomize the catalyst by a nozzle and spray the atomized catalyst out of the bottom of the spray dryer.

10. A Mn according to claim 4 ⁴⁺ And Ce ³⁺ The preparation method of the enhanced Mn-M-Ti-O ultralow temperature denitration catalyst is characterized in that in the step (8), the temperature programming rate is 10 ℃/min, the calcination temperature is 500-.