Low-temperature and highly efficient denitration catalyst and corresponding method of preparation

Abstract

The present invention relates to a field of control of nitrogen oxide pollution, and involves a high-efficient catalyst for denitration at low temperature and preparation method thereof, which comprises the steps: (1) preparing aqueous solution of cerium nitrate; (2) soaking mesoporous silica materials SBA-15 with aqueous solution from step (1), after stirring, filtrating, washing and drying; (3) calcining materials from step (2) to obtain evenly dispersed CeO.sub.2-SBA-15 materials; (4) preparing ethanol solution of manganese nitrate; (5) soaking CeO.sub.2-SBA-15 materials from step (3) with ethanol solution of manganese nitrate from step (4) and volatilizing ethanol, washing and drying; (6) calcining materials from step (5) to obtain evenly distributed Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalyst for denitration; The preparation method has simple process with lower cost, and the obtained Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalyst has uniform and ordered pores, large specific area, narrow pore size distribution, well dispersity of catalytic components, high catalytic activity, better effect of denitration at low temperature range and wider temperature range available for denitration.

Claims

1. A method for preparing catalyst for denitration, wherein the method comprises the following steps: (a) preparing an aqueous solution of cerium nitrate; (b) soaking mesoporous silica materials SBA-15 with the aqueous solution of cerium nitrate obtained from step (a), then stirring, filtrating, washing and drying; (c) calcining the materials obtained from step (b) to obtain CeO.sub.2-SBA-15 materials; (d) preparing an ethanol solution of manganese nitrate; (e) soaking the CeO.sub.2-SBA-15 materials from step (c) with the ethanol solution of manganese nitrate from step (d), then volatilizing ethanol, washing and drying; and (f) calcining the materials obtained from step (e) to obtain Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalyst for denitration.

2. The method according to claim 1, wherein in step (a) the concentration of the aqueous solution of cerium nitrateis 0.1 mol/L to 1 mol/L.

3. The method according to claim 1, wherein in step (b) dosage of mesoporous silica materials SBA-15 is 10 g/L to 40 g/L.

4. The method according to claim 1, wherein in step (b) soaking time is 4 to 8 hours.

5. The method according to claim 1, wherein in step (c) calcining temperature is 300 C. to 500 C. and calcining time is 4 hours to 8 hours.

6. The method according to claim 1, wherein in step (d) a mass of manganese in the ethanol solution of manganese nitrate accounts for 10% to 30% of dosage of the CeO.sub.2-SBA-15 materials.

7. The method according to claim 1, wherein in step (e) soaking time is 1 hour to 3 hours.

8. The method according to claim 1, wherein in step (f) calcining temperature is 300 C. to 500 C. and calcining time is 4 hours to 8 hours.

9. The method according to claim 1, wherein and Mn.sub.xO.sub.yis MnO.sub.2and Mn.sub.2O.sub.3.

10. The method according to claim 1, wherein pores of the catalyst have two-dimensional hexagonal structures, and sizes of the pores range from 6 nm to 7 nm, specific areas of the pores range from 300 m 2/g to 500 m 2/g, and volumes of the pores range from 0.3 cm 3/g to 0.5 cm 3/g.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a transmission electron microscopy image (TEM) of the catalyst obtained from Example 1 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(2) The following is a further explanation of the present invention in combination with the examples and figure.

EXAMPLE 1

(3) (1) At first, preparing 0.5 mol/L of ready-to-use aqueous solution of cerium nitrate.

(4) (2) And then, adding 2 g of SBA-15 into 100 mL of aforementioned aqueous solution of cerium nitrate (20 g/L), stirring for 6 h, then filtrating, washing and drying.

(5) (3) And next, placing the sample obtained from step (2) into a muffle furnace and calcining at 300 C. for 6 h to obtain uniformly dispersed CeO.sub.2-SBA-15 materials.

(6) (4) Afterwards, preparing an ethanol solution of manganese nitrate, wherein mass of manganese accounts for 20% of dosage of the CeO.sub.2-SBA-15.

(7) (5) Soaking the materials from step (3) with the solution from step (4), stirring for 2 h to volatilize ethanol, washing and drying.

(8) (6) Finally, placing the materials obtained from step (5) into muffle furnace, calcining at 300 C. for 6 h to obtain uniformly dispersed Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalyst for denitration, wherein Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 is a mixture of MnO.sub.2/CeO.sub.2-SBA-15 and Mn.sub.2O.sub.3/CeO.sub.2-SBA-15, the structural parameter of which is shown in Table 1.

(9) FIG. 1 is a TEM image of the catalyst obtained from Example 1, in which the shadowed area is active metal particles that have been successfully loaded onto SBA-15.

EXAMPLE 2

(10) (1) At first, preparing 0.1 mol/L of ready-to-use aqueous solution of cerium nitrate. (2) And then, adding 1 g of SBA-15 into 100 mL of aforementioned aqueous solution of cerium nitrate (10 g/L), stirring for 8 h, then filtrating, washing and drying. (3) And next, placing the sample obtained from step (2) into a muffle furnace and calcining at 500 C. for 4 h to obtain uniformly dispersed CeO.sub.2-SBA-15 materials. (4) Afterwards, preparing an ethanol solution of manganese nitrate, wherein mass of manganese accounts for 30% of dosage of the CeO.sub.2-SBA-15. (5) Soaking the materials from step (3) with the solution from step (4), stirring for 1 h to volatilize ethanol, washing and drying. (6) Finally, placing the materials obtained from step (5) into a muffle furnace, calcining at 40 C. for 4 h to obtain uniformly dispersed Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalyst for denitration, wherein Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 is a mixture of MnO.sub.2/CeO.sub.2-SBA-15 and Mn.sub.2O.sub.3/CeO.sub.2-SBA-15, the structural parameter of which is shown in table 1.

EXAMPLE 3

(11) (1) At first, preparing 1 mol/L of ready-to-use aqueous solution of cerium nitrate.

(12) (2) And then, adding 4 g of SBA-15 into 100 mL of aforementioned aqueous solution of cerium nitrate (40 g/L), stirring for 4 h, then filtrating, washing and drying.

(13) (3) And next, placing the sample obtained from step (2) into a muffle furnace and calcining at 400 C. for 8 h to obtain uniformly dispersed CeO.sub.2-SBA-15 materials;

(14) (4) Afterwards, preparing an ethanol solution of manganese nitrate, wherein mass of manganese accounts for 10% of dosage of the CeO.sub.2-SBA-15.

(15) (5) Soaking the materials from step (3) with the solution from step (4), stirring for 3 h to volatilize ethanol, washing and drying.

(16) (6) Finally, placing the materials obtained from step (5) into a muffle furnace, calcining at 500 C. for 8 h to obtain uniformly dispersed Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalyst for denitration, wherein Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 is a mixture of MnO.sub.2/CeO.sub.2-SBA-15 and Mn.sub.2O.sub.3/CeO.sub.2-SBA-15, the structural parameter of which is shown in Table 1.

(17) Table 1 shows the structural parameters of Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 for denitration that are prepared by the Example 1 to 3.

(18) TABLE-US-00001 TABLE 1 Specific area Examples Pore size (nm) Pore volume (cm.sup.3/g) (m.sup.2/g) Example 1 6.38 0.42 421 Example 2 6.27 0.35 397 Example3 6.39 0.47 435

(19) A small-scale laboratorial smoke denitration experiment is conducted towards the catalysts for denitration prepared by examples. The stimulated airspeed of smoke is 10000 h.sup.1, wherein concentration of NO is 1000 ppm, oxygen gas is 5%, carrier gas is N.sub.2, NH.sub.3 is sprayed as reductant with the volume ratio of NH.sub.3/NO being 1.2. The concentrations of NO before and after reaction are monitored by the use of EasyLine continuous gas analyzer. Reactor for denitration is electric heating tubular furnace to maintain the stability of reaction temperature. The denitration efficiency of the catalyst prepared in examples at 100 to 300 C. is shown in Table 2.

(20) Table 2 shows denitration efficiency of Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalysts for denitration at 100300 C. that are prepared in the Example 1 to 3.

(21) TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 100 C. 85% 87% 71% 140 C. 87% 89% 72% 180 C. 90% 90% 74% 220 C. 91% 89% 76% 260 C. 91% 88% 76% 300 C. 83% 80% 74%

(22) The above experimental results reveal that:

(23) (1) Under the above conditions of reactions, the Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalysts for denitration prepared by the present invention possess a wider available temperature scope and can reach 70% or above of dinitration efficiency at 100300 C.

(24) (2) Under the above conditions of reactions, the Mn.sub.xO.sub.y/CeO.sub.2-SBA-15 catalysts for denitration prepared by the present invention have higher catalytic activities at low temperature range, wherein the denitration efficiency of the catalysts with manganese content reaching 20% or above under the condition of 100200 C. can arrive at nearly 90%, which is obviously better than normal catalysts.

(25) The above descriptions of embodiments are conducive for ordinary technicians of the present technical field to understand and apply the invention. It is obvious that persons skilled in the art of the present field can easily make various amendments to the above embodiments and apply the general principle illustrated in here into other embodiments without the effort of inventive work. Therefore, the present invention is not confined to embodiments herein. Any improvements and modifications conducted by persons skilled in the art of the present field according to the instructions of the present invention and without going beyond the scope of the present invention shall be included in the extent of protection of the present invention.