A flaky MnO2 / TiO2 composite denitration catalytic material and a preparation method thereof

Abstract

The application discloses flaky MnO2 / TiO2 composite denitration catalytic material and a preparation method thereof, and belongs to the technical field of environmental catalytic materials. The flaky MnO2 / TiO2 composite denitration catalytic material is prepared by using flaky biomass carbon prepared by using onion stems as a carrier, which is beneficial to the reaction of titanium powder and excessive biomass carbon material to form flaky TiC / C composite material, and TiC is finally formed into TiO2 under the action of strong oxidant potassium permanganate; the excessive biomass carbon oxidizes the excessive potassium permanganate (or potassium manganate) into MnO2 in a hydrothermal reaction process; the excessive biomass carbon and oxygen are reacted to generate CO2 gas, which can play a pore-forming agent function on the honeycomb catalytic material, so that the specific surface area and pore structure distribution of the MnO2 / TiO2 composite honeycomb denitration catalytic material are improved.

Description

Technical Field

[0001] This invention relates to a sheet-like MnO2 / TiO2 composite denitrification catalytic material and its preparation method, belonging to the field of environmental catalytic materials technology. Background Technology

[0002] MnO x Due to its unique low-temperature catalytic activity, MnO has shown promising application prospects in the field of low-temperature SCR denitrification in recent years. x Supported manganese-based denitration catalysts mounted on honeycomb carriers have attracted considerable attention. Titanium dioxide (TiO2) is commonly used as a catalyst support for flue gas denitration; however, honeycomb carriers formed by high-temperature calcination of TiO2 suffer from drawbacks such as small specific surface area, few acidic active centers, and poor mechanical properties. Chinese patent CN113398905A proposes a low-temperature denitration catalyst for MnO2 nanowires based on a network TiO2 support and its preparation method. The technical solution uses network nano-TiO2 as the support and microscopic linear MnO2 nanowires as the active material, with the network nano-TiO2 supported on the MnO2 nanowires to obtain the low-temperature denitration catalyst. However, the appendix to the specification of this invention patent... Figure 2 As can be seen, the network-like nano-TiO2 still exists in the form of aggregates, which makes it difficult to uniformly load onto MnO2 nanowires with a length of micrometers. Furthermore, although the network-like nano-TiO2 has advantages such as a large specific surface area and numerous pores, this patented technology still suffers from sintering and agglomeration problems during high-temperature calcination, thus reducing its specific surface area. It does not fundamentally solve the problem of the incompatibility between the specific surface area and mechanical strength of MnO2 / TiO2-type denitration catalysts. Summary of the Invention

[0003] To address the problems existing in the background technology, the present invention provides a sheet-like MnO2 / TiO2 composite denitration catalyst and its preparation method. The purpose is to solve the problem of incompatibility between specific surface area and mechanical strength in the high-temperature calcination process of MnO2 / TiO2 denitration catalysts, and to prepare a sheet-like MnO2 / TiO2 composite honeycomb denitration catalyst with large specific surface area and high strength, thereby further improving the denitration performance of MnO2 / TiO2 catalysts.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing a sheet-like MnO2 / TiO2 composite denitrification catalyst specifically includes the following steps:

[0006] 1. Under a nitrogen atmosphere, dried onion stems are carbonized at 300℃~350℃ for 2~4 hours to prepare flake-shaped biomass carbon (C). Then, the flake-shaped biomass carbon and titanium powder (100~300 mesh) are added together to anhydrous ethanol solvent and ultrasonically dispersed for 20~40 minutes. The mass ratio of titanium powder to biomass carbon is 0.05~0.25:1 (biomass carbon in excess), and the mass ratio of the total mass of titanium powder and biomass carbon to the mass of ethanol solvent is 0.2~0.6:1. The mixture is filtered and dried at 35℃~55℃. Finally, the resulting mixture of biomass carbon and titanium powder is calcined at 950℃~1150℃ for 1~3 hours under a nitrogen atmosphere to obtain a flake-shaped TiC / C composite powder.

[0007] 2. While stirring, add the TiC / C composite powder obtained in step 1 (based on theoretical values) to a potassium hydroxide solution with a mass percentage concentration of 5%~15%, wherein the mass ratio of TiC / C composite powder to potassium hydroxide solution is 0.05~0.1:1; then dissolve potassium permanganate in the resulting dispersion, wherein the molar ratio of potassium permanganate to TiC (based on theoretical values) is 8~10:1; finally, carry out a hydrothermal reaction at a temperature of 180℃~220℃ for 10~16 hours, filter, and wash successively with hydrochloric acid solution with a molar concentration of 1.0~3.0 mol / L and deionized water until the pH value of the filtrate is 6~7, thus obtaining a flake-like MnO2 / TiO2 / C wet filter cake composite.

[0008] 3. Place the flake-shaped MnO2 / TiO2 / C wet filter cake composite obtained in step 2 and glycerol in a kneader and knead for 30-90 minutes, wherein the mass ratio of glycerol to wet filter cake composite is 0.05-0.1:1; then add the mixture to a vacuum pumice machine and repeat pumice 4-6 times; finally, place the vacuum pumice mixture in a forming extruder and extrude it into shape, and microwave dry it at a temperature of 100℃-120℃ for 10-30 minutes; calcine the dried composite in air at a temperature of 650℃-850℃ for 4-8 hours to obtain a flake-shaped MnO2 / TiO2 composite honeycomb denitrification catalyst.

[0009] The beneficial effects of this invention are:

[0010] 1. This invention uses onion stalks with a sheet-like structure to prepare biomass carbon as a carrier. Its advantages are: ① The surface of the sheet-like biomass carbon material has a large number of active groups, which is conducive to the reaction of metallic titanium powder with biomass carbon material to form sheet-like TiC / C composite material. Then, TiC is finally converted into TiO2 under the action of strong oxidant potassium permanganate; ② On the one hand, the excess biomass carbon can act as a reducing agent in the hydrothermal reaction process, further oxidizing the excess potassium permanganate (or potassium manganate) to generate MnO2; on the other hand, in the high-temperature calcination and molding process of the honeycomb catalytic material, the excess biomass carbon reacts with oxygen to generate CO2 gas, which can act as a pore-forming agent for the honeycomb catalytic material, thereby improving the specific surface area and pore structure distribution of the MnO2 / TiO2 composite honeycomb denitrification catalytic material.

[0011] 2. The sheet-like MnO2 / TiO2 composite honeycomb denitrification catalyst prepared by this invention has a sheet-like-particle structure, which can effectively prevent sintering and agglomeration during high-temperature calcination. It can further maintain a high specific surface area of ​​the catalyst without affecting the strength of the honeycomb catalyst, thus solving the problem of incompatibility between specific surface area and mechanical strength of Mn-Ti denitrification catalysts in the high-temperature calcination process of traditional processes. Attached Figure Description

[0012] Figure 1 This is a photograph of a sheet-like MnO2 / TiO2 composite honeycomb denitrification catalyst prepared in Example 4.

[0013] Figure 2 The X-ray diffraction (XRD) spectrum of a sheet-like MnO2 / TiO2 composite honeycomb denitrification catalyst prepared in Example 4;

[0014] Figure 3 This is a transmission electron microscope (TEM) image of the sheet-like biocarbon carrier prepared in step 1 of Example 4;

[0015] Figure 4 This is a TEM image of the sheet-like MnO2 / TiO2 / C composite obtained in step 2 of Example 4;

[0016] Figure 5 This is a TEM image of the sheet-like MnO2 / TiO2 composite honeycomb denitrification catalyst material prepared in Example 4. Detailed Implementation

[0017] The present invention will be further described below with reference to embodiments and comparative examples, but in no way is it limited to the scope of application of the present invention. Example 1

[0018] 1. Under a nitrogen atmosphere, dried onion stems were carbonized at 300℃ for 4 hours to prepare flake-shaped biomass carbon (C). Then, 1.0 kg of flake-shaped biomass carbon (excess) and 0.25 kg of titanium powder (100 mesh) were added to 2.08 kg of anhydrous ethanol solvent and ultrasonically dispersed for 40 minutes. The mixture was filtered and dried at 35℃. Finally, the resulting biomass carbon and titanium powder mixture was calcined at 1150℃ for 1 hour under a nitrogen atmosphere to obtain a flake-shaped TiC / C composite powder.

[0019] 2. While stirring, add the TiC / C composite powder obtained in step 1 to 12.5 kg of potassium hydroxide solution with a mass percentage concentration of 15%, and then dissolve 6.60 kg of potassium permanganate in the resulting dispersion; finally, carry out a hydrothermal reaction at a temperature of 220℃ for 10 hours, filter, and wash with hydrochloric acid solution with a molar concentration of 3.0 mol / L and deionized water successively until the pH value of the filtrate is 6, thus obtaining a sheet-like MnO2 / TiO2 / C wet filter cake composite.

[0020] 3. Take 1.0 kg of the flake-shaped MnO2 / TiO2 / C wet filter cake composite obtained in step 2 and 0.1 kg of glycerol and place them in a kneader (NH-20 type, Rugao Kunhong Kneading Machinery Co., Ltd., the same below) and knead for 90 minutes. Then, add the mixture to a vacuum pumice machine (Yixing Jiuling Machinery Equipment Co., Ltd., the same below) and repeat pumice six times. Finally, place the vacuum pumice mixture in a forming extruder (equipped with a 28 mm diameter honeycomb circular mold, Yixing Jiuling Machinery Equipment Co., Ltd., the same below) and extrude it. Then, microwave dry it at 100℃ for 30 minutes. Calcine the dried composite at 650℃ for 8 hours in an air atmosphere to obtain a flake-shaped MnO2 / TiO2 composite honeycomb denitrification catalyst. Example 2

[0021] 1. Under a nitrogen atmosphere, dried onion stems were carbonized at 350℃ for 2 hours to prepare flake-shaped biomass carbon (C). Then, 1.0 kg of flake-shaped biomass carbon (excess) and 0.05 kg of titanium powder (300 mesh) were added to 5.25 kg of anhydrous ethanol solvent and ultrasonically dispersed for 20 minutes. The mixture was filtered and dried at 55℃. Finally, the resulting mixture of biomass carbon and titanium powder was calcined at 950℃ for 3 hours under a nitrogen atmosphere to obtain a flake-shaped TiC / C composite powder.

[0022] 2. While stirring, add the TiC / C composite powder obtained in step 1 to 21 kg of potassium hydroxide solution with a mass percentage concentration of 5%, and then dissolve 1.65 kg of potassium permanganate in the resulting dispersion; finally, carry out a hydrothermal reaction at a temperature of 180℃ for 16 hours, filter, and wash with hydrochloric acid solution with a molar concentration of 1.0 mol / L and deionized water successively until the pH value of the filtrate is 7, thus obtaining a sheet-like MnO2 / TiO2 / C wet filter cake composite.

[0023] 3. Take 1.0 kg of the flake-shaped MnO2 / TiO2 / C wet filter cake composite obtained in step 2 and 0.05 kg of glycerol and knead them in a kneader for 30 minutes. Then, add the mixture to a vacuum pumice machine and repeat the pumice process 4 times. Finally, place the vacuum-pumice mixture in a molding extruder for extrusion and microwave dry it at 120°C for 10 minutes. Calcinate the dried composite in air at 850°C for 4 hours to obtain a flake-shaped MnO2 / TiO2 composite honeycomb denitrification catalyst. Example 3

[0024] 1. Under a nitrogen atmosphere, dried onion stems were carbonized at 325℃ for 3 hours to prepare flake-shaped biomass carbon (C). Then, 1.0 kg of flake-shaped biomass carbon (excess) and 0.15 kg of titanium powder (200 mesh) were added to 2.88 kg of anhydrous ethanol solvent and ultrasonically dispersed for 30 minutes. The mixture was filtered and dried at 45℃. Finally, the biomass carbon and titanium powder mixture was calcined at 1050℃ for 2 hours under a nitrogen atmosphere to obtain a flake-shaped TiC / C composite powder.

[0025] 2. While stirring, add the TiC / C composite powder obtained in step 1 to 15.3 kg of a 10% potassium hydroxide solution, and then dissolve 4.46 kg of potassium permanganate in the resulting dispersion. Finally, carry out a hydrothermal reaction at 200℃ for 13 hours, filter, and wash with 2.0 mol / L hydrochloric acid solution and deionized water until the pH of the filtrate is 6.5, thus obtaining a sheet-like MnO2 / TiO2 / C wet filter cake composite.

[0026] 3. Take 1.0 kg of the flake-shaped MnO2 / TiO2 / C wet filter cake composite obtained in step 2 and 0.08 kg of glycerol and knead them in a kneader for 60 minutes. Then, add the mixture to a vacuum pumice machine and repeat the pumice process 5 times. Finally, place the vacuum-pumice mixture in a molding extruder for extrusion and microwave dry it at 110℃ for 20 minutes. Calcinate the dried composite in air at 750℃ for 6 hours to obtain a flake-shaped MnO2 / TiO2 composite honeycomb denitrification catalyst. Example 4

[0027] 1. Under a nitrogen atmosphere, dried onion stems were carbonized at 330℃ for 3 hours to prepare flake-shaped biomass carbon (C). Then, 1.0 kg of flake-shaped biomass carbon (excess) and 0.1 kg of titanium powder (200 mesh) were added to 2.2 kg of anhydrous ethanol solvent and ultrasonically dispersed for 30 minutes. The mixture was filtered and dried at 50℃. Finally, the biomass carbon and titanium powder mixture was calcined at 1100℃ for 2 hours under a nitrogen atmosphere to obtain a flake-shaped TiC / C composite powder.

[0028] 2. While stirring, add the TiC / C composite powder obtained in step 1 to 13.8 kg of potassium hydroxide solution with a mass percentage concentration of 12%, and then dissolve 2.64 kg of potassium permanganate in the resulting dispersion; finally, carry out a hydrothermal reaction at a temperature of 210℃ for 12 hours, filter, and wash with hydrochloric acid solution with a molar concentration of 2.0 mol / L and deionized water successively until the pH value of the filtrate is 6.0, thus obtaining a sheet-like MnO2 / TiO2 / C wet filter cake composite.

[0029] 3. Take 1.0 kg of the flake-shaped MnO2 / TiO2 / C wet filter cake composite obtained in step 2 and 0.06 kg of glycerol and knead them in a kneader for 45 minutes. Then, add the mixture to a vacuum pumice machine and repeat the pumice process 5 times. Finally, place the vacuum-pumice mixture in a molding extruder for extrusion and microwave dry it at 115℃ for 15 minutes. Calcinate the dried composite at 700℃ in air for 7 hours to obtain a flake-shaped MnO2 / TiO2 composite honeycomb denitrification catalyst. Comparative Example 1

[0030] Compared with Example 4, in Comparative Example 1, the "excess carbon" in step 1 of Example 4 was changed to "equal amount of carbon (the mass of carbon required to react with 0.1 kg of metallic titanium powder)", while other processes remained unchanged. The specific steps are as follows:

[0031] 1. Under a nitrogen atmosphere, dried onion stems were carbonized at 330℃ for 3 hours to prepare flake-shaped biomass carbon (C). Then, 0.025 kg of flake-shaped biomass carbon and 0.1 kg of titanium powder (200 mesh) were added to 2.2 kg of anhydrous ethanol solvent and ultrasonically dispersed for 30 minutes. The mixture was filtered and dried at 50℃. Finally, the resulting mixture of biomass carbon and titanium powder was calcined at 1100℃ for 2 hours under a nitrogen atmosphere to obtain a flake-shaped TiC powder.

[0032] 2. While stirring, add the TiC powder obtained in step 1 to 13.8 kg of potassium hydroxide solution with a mass percentage concentration of 12%, and then dissolve 2.64 kg of potassium permanganate in the resulting dispersion; finally, carry out a hydrothermal reaction at a temperature of 210℃ for 12 hours, filter, and wash with hydrochloric acid solution with a molar concentration of 2.0 mol / L and deionized water successively until the pH value of the filtrate is 6.0, thus obtaining a sheet-like MnO2 / TiO2 wet filter cake composite.

[0033] 3. Take 1.0 kg of the flake-shaped MnO2 / TiO2 wet filter cake composite obtained in step 2 and 0.06 kg of glycerol and knead them in a kneader for 45 minutes. Then, add the mixture to a vacuum pumice machine and repeat the pumice process 5 times. Finally, place the vacuum-pumice mixture in a molding extruder and extrude it into shape. Then, microwave dry it at 115℃ for 15 minutes. Calcinate the dried composite at 700℃ in air for 7 hours to obtain a flake-shaped MnO2 / TiO2 composite honeycomb denitrification catalyst.

[0034] Performance Evaluation

[0035] Denitrification performance testing: The activity of the catalytic material was tested on a fixed-bed reactor (Beijing TORCH Scientific Equipment Co., Ltd.). The reaction gas ratio was: 0.1% NH3, 0.1% NO, and 3 vol% O2, with N2 as the balance gas, and the space velocity was controlled at 15000 h⁻¹. -1 The total gas flow rate was maintained at 1.5 L / min. A flue gas analyzer (KM9106, Kane, UK) was used to analyze the NO content before the reaction. x The concentration of imported NO was detected to obtain accurate results. x Concentration, denoted as [NO x ] in The temperature was then gradually increased, and the NO at the outlet was measured at every temperature interval. x Concentration, denoted as [NO x ] out The reaction continues until the upper limit of the reaction temperature is reached. An NH3 sensor is needed to detect the concentration of NH3 at the inlet, denoted as [NH3]. in Simultaneously, the NH3 concentration at that temperature range at the outlet is detected and recorded as [NH3]. out Simultaneously, the concentrations of NO2 and N2O at the outlet are read and denoted as [NO2]. out and [N2O] out .

[0036] NO x The conversion rate formula is as follows:

[0037]

[0038] Compressive strength test: The compressive strength of the honeycomb catalytic material sample in this invention was determined according to the national standard GB / T5072-2008.

[0039] Specific surface area test: The honeycomb catalyst sample prepared in this invention was crushed, and a suitable small particle sample was placed in a rapid fully automatic specific surface area and pore size analyzer (model: Autosorb-iQ2-MP, CANTA Instruments, USA) to determine its specific surface area.

[0040] Table 1 Catalyst Performance Evaluation

[0041] Group <![CDATA[NO x Conversion rate η / % Maximum active temperature / °C Compressive strength / MPa <![CDATA[Specific surface area / m 2. g -1 > Example 1 98.3 205 4.53 38.6 Example 2 96.7 210 4.92 38.8 Example 3 97.2 197 4.85 38.9 Example 4 98.4 191 4.97 41.5 Comparative Example 1 92.1 243 4.21 17.8

Claims

1. A preparation method of a sheet-shaped MnO2 / TiO2 composite denitration catalytic material, characterized in that, Specifically comprising the following steps: (1) under a nitrogen atmosphere, excess flaky biomass carbon and titanium powder are added into anhydrous ethanol solvent and ultrasonically dispersed uniformly, a mixture of biomass carbon and titanium powder is collected by filtration and dried at a temperature of 35-55 DEG C; the dried mixture of biomass carbon and titanium powder is calcined at a temperature of 950-1150 DEG C for 1-3 hours under a nitrogen atmosphere, thereby obtaining flaky TiC / C composite powder; the mass ratio of titanium powder to biomass carbon is 0.05-0.25:1; (2) under stirring, the TiC / C composite powder prepared in step (1) is added into a 5-15% potassium hydroxide solution to obtain a dispersion; then potassium permanganate is dissolved in the obtained dispersion, and finally a hydrothermal reaction is carried out at a temperature of 180-220 DEG C for 10-16 hours, followed by filtration and washing until the pH value of the filtrate is 6-7, thereby obtaining a flaky MnO2 / TiO2 / C wet-cake composite; the theoretical molar ratio of potassium permanganate to TiC is 8-10:1; (3) the flaky MnO2 / TiO2 / C wet-cake composite obtained in step (2) is mixed with glycerol, and after kneading, pugging and extrusion molding, the mixture is dried; the dried composite is calcined at a temperature of 650-850 DEG C for 4-8 hours under an air atmosphere, thereby obtaining a flaky MnO2 / TiO2 composite denitration catalyst material; The flaky biomass carbon is an onion stem biomass carbon, which is prepared by carbonizing dried onion stems at a temperature of 300-350 DEG C for 2-4 hours.

2. The preparation method of the flaky MnO2 / TiO2 composite denitration catalytic material according to claim 1, characterized in that, In step (1), the mass ratio of the total mass of titanium powder and biomass carbon to the mass of anhydrous ethanol solvent is 0.2-0.6:

1.

3. The preparation method of the sheet-like MnO2 / TiO2 composite denitrification catalyst according to claim 1, characterized in that, In step (2), the mass ratio of the mass of TiC / C composite powder to the mass of potassium hydroxide solution is 0.05-0.1:

1.

4. The method according to claim 1, wherein the method comprises the steps of: 5 mixing manganese dioxide and titanium dioxide to form a mixture; 10 heating the mixture to a temperature of 400-800°C; and 15 calcining the mixture at a temperature of 400-800°C for 1-5 hours. In step (2), the washing is carried out with a 1.0-3.0 mol / L hydrochloric acid solution and deionized water in sequence until the pH value of the filtrate is 6-7.

5. The preparation method of the sheet-like MnO2 / TiO2 composite denitrification catalyst according to claim 1, characterized in that, In step (3), the mass ratio of glycerol to the flaky MnO2 / TiO2 / C wet-cake composite is 0.05-0.1:

1.

6. The preparation method of the sheet-like MnO2 / TiO2 composite denitrification catalyst according to claim 1, characterized in that, In step (3), the flaky MnO2 / TiO2 / C wet-cake composite obtained in step (2) and glycerol are put into a kneader and kneaded for 30-90 minutes; then the mixture is added into a vacuum pug mill and pugged repeatedly for 4-6 times, and finally the vacuum-pugged mixture is put into a molding extruder and extruded and molded, and then microwave dried at a temperature of 100-120 DEG C for 10-30 minutes.

7. A flaky MnO2 / TiO2 composite denitration catalytic material, characterized in that, Prepared by the method of any one of claims 1-6.

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