Co / CeO2-TDC catalyst applied to denitration of medium and low temperature flue gas as well as preparation method and application of Co / CeO2-TDC catalyst

Abstract

The invention discloses a Co / CeO2-TDC catalyst applied to denitration of medium and low temperature flue gas as well as a preparation method and application of the Co / CeO2-TDC catalyst, and belongs to the technical field of environmental protection. The preparation method comprises the following steps: taking ceric ammonium nitrate and 2, 5-thiophenedicarboxylic acid as raw materials, preparing Ce-TDC by adopting a one-step solvothermal method, then impregnating a cobalt nitrate solution into the Ce-TDC by adopting an initial wet impregnation method, and roasting to prepare the Co / CeO2-TDC catalyst. The Co / CeO2-TDC catalyst prepared by the invention has a smaller mesoporous structure and more acidic sites, and shows excellent denitration efficiency, nitrogen selectivity, thermal stability and resistance to SO2 and H2O at medium and low temperature of 200-300 DEG C, the preparation method is simple and pollution-free, large-scale mass production can be realized, and the Co / CeO2-TDC catalyst has good application value for high-efficiency low-consumption removal of NOx.

Description

Technical Field

[0001] The present invention belongs to the field of environmental protection technology, and more specifically, relates to a Co / CeO 2 -TDC catalyst and its preparation method and application. Background Art

[0002] With the development of economy, fossil fuels are one of the main energy sources used in human production processes such as industrial production and transportation. The combustion of fossil fuels will produce nitrogen oxides (NO x ), causing environmental pollution problems such as photochemical smog, acid rain, ozone layer depletion, global warming, etc. x The presence of nitrogen oxides can cause serious harm to the human body, causing lung infections and respiratory diseases. At present, my country's control technologies for nitrogen oxides are mainly divided into combustion control (low-nitrogen combustion, reburning, flue gas recirculation) and post-combustion control (selective catalytic reduction technology, selective non-catalytic reduction technology). Among them, ammonia selective catalytic reduction technology (NH 3 -SCR), using the reducing agent NH 3 Under the conditions of catalyst and appropriate reaction temperature, NO x Selective catalytic reduction to N 2 and H 2 O, with the advantages of good conversion efficiency and high selectivity, is one of the most effective NOx control technologies.

[0003] Although the conventional vanadium-titanium-based SCR catalysts currently used have advantages such as high activity and strong sulfur resistance, they have problems such as high toxicity of vanadium species and high operating temperature. Therefore, the research and development of non-vanadium-based SCR catalysts is very important. The outermost electron orbital structure of rare earth cerium (Ce) atoms is 4f 1 5d 1 6s 2 , the 4f and 5d orbitals with similar energies are favorable for Ce 3+ and Ce 4+ There is no energy barrier switching between CeO 2 With excellent redox properties and abundant oxygen vacancies, 3 -SCR reaction is widely used. However, pure CeO 2 There are some problems with the material, such as few acid sites, poor thermal stability, easy sintering, etc. Usually CeO 2 As a catalyst carrier, it loads other active components to improve the performance of the catalyst. Summary of the invention

[0004] In view of the above problems existing in the prior art, the technical problem to be solved by the present invention is to provide a Co / CeO 2-TDC catalyst preparation method, the method has the characteristics of simple process, green safety and environmental protection. Another technical problem to be solved by the present invention is to provide a Co / CeO prepared by the above method 2 -TDC catalyst, which has a smaller mesoporous structure and more acidic sites, exhibits excellent denitrification efficiency, nitrogen selectivity, thermal stability and SO 2 and H 2 O resistance. The present invention also solves a technical problem of providing the above-mentioned Co / CeO 2 -TDC catalyst in medium and low temperature NH 3 -Application in SCR catalytic denitrification.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A Co / CeO nanoparticle for denitrification of medium and low temperature flue gas 2 The preparation method of the -TDC catalyst is to use cerium ammonium nitrate and 2,5-thiophene dicarboxylic acid as raw materials, adopt a one-step solvent thermal method to prepare Ce-TDC, then impregnate the cobalt nitrate solution into Ce-TDC by the incipient wetness impregnation method, and calcine to prepare Co / CeO 2 -TDC catalyst.

[0007] Preferably, the specific process of the one-step solvothermal method is: cerium ammonium nitrate, deionized water, N-N-dimethylformamide, 2,5-thiophene dicarboxylic acid and formic acid are uniformly mixed and reacted to obtain Ce-TDC.

[0008] Preferably, the specific process of the incipient wetness impregnation method is: adding the cobalt nitrate solution dropwise to the Ce-TDC powder, and stirring continuously with a glass rod during the adding process to ensure that the solution can just wet the Ce-TDC powder without forming wet balls.

[0009] Preferably, the mol / mL / mL / mol / mol of the ammonium cerium nitrate, deionized water, N-N-dimethylformamide, 2,5-thiophenedicarboxylic acid and formic acid is 0.002:4:18:0.00298:0.273.

[0010] Preferably, in the one-step solvothermal method, the reaction temperature is 100° C. and the reaction time is 30 min.

[0011] Preferably, the calcination temperature is 400° C. and the calcination time is 3 h.

[0012] Preferably, the cobalt nitrate solution is impregnated into the Ce-TDC to make Co / CeO 2 -The Co content in the TDC catalyst is 1 wt%.

[0013] The Co / CeO used for medium and low temperature flue gas denitrification 2 -The preparation method of TDC catalyst specifically comprises the following steps:

[0014] 1) dissolving ammonium cerium nitrate in deionized water to obtain solution A; dissolving 2,5-thiophenedicarboxylic acid and formic acid in N-N-dimethylformamide to obtain solution B; dropping solution A into solution B, mixing evenly, and reacting to obtain a white precipitate;

[0015] 2) washing the white precipitate obtained in step 1) twice by centrifugation with N-dimethylformamide, then washing it three times by centrifugation with acetone, and drying it in an oven to obtain Ce-TDC powder;

[0016] 3) dissolving cobalt nitrate in deionized water to obtain a cobalt nitrate solution; adding the obtained cobalt nitrate solution dropwise to the Ce-TDC powder obtained in step 2), stirring continuously with a glass rod during the adding process to ensure that the solution can just wet the Ce-TDC powder without forming wet balls;

[0017] 4) The mixture obtained in step 3) is first placed in an oven for drying, and then placed in a muffle furnace for calcination to prepare Co / CeO 2 -TDC catalyst.

[0018] The Co / CeO used for medium and low temperature flue gas denitrification 2 -TDC catalyst preparation method, preparation of Co / CeO 2 -TDC catalyst.

[0019] The Co / CeO 2 -TDC catalyst in medium and low temperature NH 3 -Application in SCR catalytic denitrification.

[0020] As a preferred embodiment, the Co / CeO 2 -Application of TDC catalyst in 250-400℃ flue gas denitrification in coal-fired power plants.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention is based on cobalt oxide with good redox properties and 2,5-thiophenedicarboxylic acid (H 2 TDC) was used to introduce Co into the catalyst of cerium-based MOF materials by incipient wetness impregnation. Using Ce-TDC as a cerium precursor can significantly improve the Co / CeO 2 -TDC catalyst acid sites and redox properties, ultimately improving the low-temperature NH 3 -SCR reaction performance;

[0023] (2) The raw materials used in the preparation method of the present invention are cheap and readily available, the operation is simple and quick, the energy consumption is low, there is no special requirement for equipment, it is environmentally friendly, and it has potential application prospects in the field of flue gas denitrification in coal-fired power plants;

[0024] (3) Compared with Co / CeO prepared by conventional impregnation method 2 Materials, Co / CeO prepared by the present invention 2 -TDC catalyst has a smaller mesoporous structure and more acidic sites, and exhibits excellent denitrification efficiency, nitrogen selectivity, thermal stability and SO 2 and H 2 O resistance, and the preparation method is simple and pollution-free, can be mass-produced, and is effective for the efficient and low-cost removal of NO x Has good application value;

[0025] (4) Compared with the common cerium-cobalt composite catalyst, the Co / CeO 2 -TDC catalyst exhibits excellent catalytic performance in the medium and low temperature range, with high NO conversion rate and good nitrogen selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The Co / CeO prepared in Example 1 2 -TDC, Co / CeO prepared in Comparative Example 1 2 XRD pattern of

[0027] Figure 2 The Co / CeO prepared in Example 1 2 -TDC, Co / CeO prepared in Comparative Example 1 2 N 2 Adsorption-desorption isotherms and BJH pore size distribution results;

[0028] Figure 3 CeO 2 , Co / CeO prepared in Example 1 2 -TDC, Co / CeO prepared in Comparative Example 1 2 Ultraviolet visible diffuse reflectance spectrum (UV-vis DRS);

[0029] Figure 4 The Co / CeO prepared in Example 1 2 -TDC, Co / CeO prepared in Comparative Example 1 2 NH 3 -SCR reaction result diagram;

[0030] Figure 5 The Co / CeO prepared in Example 1 2-TDC at 300℃Co / CeO 2 -TDC Anti-SO 2 and H 2 OPerformance test result diagram;

[0031] Figure 6 The Co / CeO prepared in Example 1 2 -TDC, Co / CeO prepared in Comparative Example 1 2 The programmed temperature desorption (NH 3 -TPD) result graph;

[0032] Figure 7 The Co / CeO prepared in Example 1 2 -TDC, Co / CeO prepared in Comparative Example 1 2 H 2 -TPR result graph. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described below in conjunction with specific examples. In the following examples, unless otherwise specified, the technical means used are conventional means well known to those skilled in the art. If specific conditions are not specified in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0034] Example 1

[0035] A Co / CeO nanoparticle for denitrification of medium and low temperature flue gas 2 -The preparation method of TDC catalyst comprises the following steps:

[0036] 1) Dissolve 0.002 mol of ammonium cerium nitrate in 4 mL of deionized water to obtain solution A; dissolve 0.00298 mol of 2,5-thiophenedicarboxylic acid and 0.273 mol of formic acid in 18 mL of NN dimethylformamide to obtain solution B; drop solution A into solution B, mix well, and react at 100° C. for 30 min to obtain a white precipitate;

[0037] 2) The white precipitate obtained in step 1) was centrifugally washed twice with N-N-dimethylformamide, then centrifugally washed three times with acetone, and dried in an oven at 80° C. for 12 hours to obtain 0.4 g of Ce-TDC powder;

[0038] 3) Dissolve 0.049 g of cobalt nitrate in 0.16 mL of deionized water to obtain a 1.06 mol / L cobalt nitrate solution; add the obtained cobalt nitrate solution dropwise to the Ce-TDC powder to make Co / CeO 2- The Co content in the TDC catalyst was 1 wt%, and a glass rod was used to stir the solution during the addition process to ensure that the solution could just wet the Ce-TDC powder without the formation of wet balls;

[0039] 4) The mixture obtained in step 3) was first placed in an oven at 80°C for 3 h and then calcined in a muffle furnace at 400°C for 3 h to obtain 1 g Co / CeO 2 -TDC catalyst.

[0040] Comparative Example 1

[0041] Co / CeO 2 The method for preparing a catalyst comprises the following steps:

[0042] 1) Weigh a certain amount of ammonium cerium nitrate and place it in a muffle furnace and calcine it at 400℃ for 3h to obtain powdered CeO 2 ;

[0043] 2) Dissolve 0.049 g of cobalt nitrate in 0.16 mL of deionized water to obtain a 1.06 mol / L cobalt nitrate solution; add the obtained cobalt nitrate solution dropwise to 1 g CeO 2 Powder, making Co / CeO 2 -TDC catalyst has a Co content of 1wt%. During the addition process, a glass rod was used to stir continuously to ensure that the solution could just wet the CeO 2 Powder, no wet pellets formed;

[0044] 3) The mixture obtained in step 2) was first placed in an oven at 80°C for 3 h and then calcined in a muffle furnace at 400°C for 3 h to obtain 1 g Co / CeO 2 catalyst.

[0045] Depend on Figure 1 It can be seen that the Co / CeO prepared in Example 1 2 -TDC and Co / CeO prepared in Comparative Example 1 2 Both show CeO 2 Diffraction peaks of cubic fluorite structure, no Co detected 3 O 4 The diffraction peaks indicate that the cobalt species exist in CeO in a highly dispersed form or in clusters that are smaller than the detection limit of XRD and cannot be detected. 2 On the carrier.

[0046] Table 1 Specific surface area and pore size results of the catalysts prepared in Example 1 and Comparative Example 1

[0047] sample <![CDATA[Specific surface area (m 2 g -1 )]]> <![CDATA[Specific pore volume (m 3 g -1 )]]> Pore ​​size (nm) <![CDATA[Co / CeO 2 ]]> 23.8 0.08 16.3 <![CDATA[Co / CeO 2 -TDC]]> 4.0 0.01 12.21

[0048] From Table 1 and Figure 2 It can be seen that the Co / CeO prepared in Example 12 -TDC and Co / CeO prepared in Comparative Example 1 2 Both produced H 3 The type IV isotherm of the hysteresis loop indicates that Co / CeO 2 -TDC and Co / CeO 2 Both have mesoporous structures, Co / CeO 2 -TDC pore size distribution is more concentrated at 3.5nm, while Co / CeO 2 The pore size distribution is more concentrated at 30.6nm, Co / CeO 2 -TDC has a smaller mesoporous structure, indicating that Co / CeO 2 -TDC catalyst has a smaller particle size and can provide NH 3 -SCR reaction provides more exposed active sites. Co / CeO 2 -TDC has a smaller specific surface area than Co / CeO 2 , but the catalytic activity is much higher than that of Co / CeO 2 , indicating that the specific surface area is not the decisive factor affecting the catalytic performance.

[0049] Depend on Figure 3 It can be seen that CeO 2 The absorption edge appears at 462nm. After Co doping, Co / CeO 2 The absorption edge of Co / CeO prepared in Example 1 shows a red shift, indicating that the introduction of Co significantly increases the light absorption in the visible light region. 2 The light absorption performance of the -TDC catalyst becomes stronger. This red shift is due to the fact that Co doping makes the catalyst have small nanoparticles with rich surface defects, which causes the lattice symmetry to decrease.

[0050] Example 2

[0051] The catalysts prepared in Example 1 and Comparative Example 1 were applied to medium and low temperature NH 3 -SCR reaction, the experimental steps are as follows: the catalytic reaction test is carried out in a fixed bed continuous flow quartz reactor. The catalyst particle size is 40-60 mesh, and the dosage is 100 mg. The reaction gas composition is: 500ppm NO, 500ppm NH 3 , 5% O 2 , 5% H 2 O, 500ppm SO 2 (If used), Ar is used as the balance gas, and the gas space velocity in the reaction is 60000 mL g –1 ·h –1 The catalytic reaction was carried out at 100-400 °C. The activity data were collected after the catalyst was pre-adsorbed and saturated. The products were analyzed by Thermofisher IS10 FTIR. The NO conversion rate and N2 The selectivity is calculated by the following formula:

[0052]

[0053] In the formula: [NO x ] in and [NO x ] out Respectively represent the NO in the reactor inlet and outlet x Concentration (ppm); [NO] in and [NO] out Respectively represent the NO concentration (ppm) at the reactor inlet and outlet; [NH 3 ] in and [NH 3 ] out Represents the NH in the reactor inlet and outlet, respectively. 3 Concentration (ppm); [NO 2 ] out Indicates the NO in the reactor outlet 2 Concentration (ppm); [N 2 O] out Represents the N in the reactor outlet 2 O concentration (ppm).

[0054] NH of the catalysts prepared in Example 1 and Comparative Example 1 3 -SCR activity test results such as Figure 4 And as shown in Table 2.

[0055] Table 2 NH of the catalysts prepared in Example 1 and Comparative Example 1 3 -SCR activity test results

[0056]

[0057] From Table 2 and Figure 4 It can be seen that the Co / CeO prepared by the present invention 2 -TDC activity is significantly better than Co / CeO 2 , in the range of 250-400℃, Co / CeO 2 -TDC maintains high catalytic activity and high nitrogen selectivity over the entire temperature range tested, indicating that Co / CeO 2 Due to the fine particle size in the TDC catalyst, there is a strong synergistic effect between Co and Ce, which produces more active sites and significantly improves the NH 3 -SCR reaction performance.

[0058] Depend on Figure 5 It can be seen that when 200ppm SO is introduced 2After that, the NOx conversion rate of the catalyst decreased by about 10% and then stabilized. At this time, 5% H 2 O, in 5% HO 2 O and 200ppm SO 2 In the presence of Co / CeO 2 -TDC catalyst NO conversion rate decreased by only 4%, and remained stable at around 68% during the 8-hour test. 2 O and SO 2 The catalyst activity quickly recovered to about 76%, indicating that Co / CeO 2 -TDC catalyst can effectively inhibit the deposition of surface sulfate, thereby alleviating the deactivation of the catalyst.

[0059] Depend on Figure 6 It can be seen that Co / CeO 2 and Co / CeO 2 -TDC shows a broad peak at 100-300℃, compared with Co / CeO 2 , low temperature section Co / CeO 2 -TDC has a lower desorption peak area than Co / CeO 2 However, a new desorption peak appeared at 517 °C, indicating that the acidic groups in Ce-TDC were successfully introduced into the catalyst, forming new uniformly distributed medium-strong acid sites in situ, which was beneficial to the NH 3 The adsorption and activation of Co / CeO 2 -TDC has better denitrification performance in the low temperature section than Co / CeO 2 .

[0060] Depend on Figure 7 It can be seen that for Co / CeO 2 Catalyst, TPR spectrum can be divided into two regions, the reduction peak in the low temperature region is attributed to the surface CeO 2 The reduction peak at 789℃ in the high temperature zone belongs to the bulk CeO 2 Reduction; for Co / CeO 2 -TDC catalyst, no surface CeO 2 The strong reduction peaks at 529℃ and 565℃ are attributed to the reduction of sulfate species, and the reduction peak at 691℃ is attributed to the bulk CeO 2 The reduction of Co / CeO 2 -TDC catalyst bulk CeO 2 The reduction peak of the catalyst migrates to a lower temperature and effectively increases the number of reducible species in the catalyst, thereby improving the redox performance of the catalyst and helping to improve the denitrification performance of the catalyst.

[0061] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration, characterized in that: Ce-TDC was prepared by a one-step solvothermal method using cerium ammonium nitrate and 2,5-thiophenedicarboxylic acid as raw materials. Cobalt nitrate solution was then impregnated into Ce-TDC by the incipient wetness impregnation method and calcined to obtain Co / CeO2-TDC catalyst.

2. The method for preparing the Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration according to claim 1, characterized in that: The specific process of the one-step solvothermal method is: cerium ammonium nitrate, deionized water, N-N-dimethylformamide, 2,5-thiophene dicarboxylic acid and formic acid are uniformly mixed and reacted to obtain Ce-TDC.

3. The method for preparing the Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration according to claim 1, characterized in that: The specific process of the incipient wetness impregnation method is: adding the cobalt nitrate solution dropwise to the Ce-TDC powder, and stirring continuously with a glass rod during the adding process to ensure that the solution can just wet the Ce-TDC powder without forming wet balls.

4. The method for preparing the Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration according to claim 2, characterized in that: The mol / mL / mL / mol / mol of the ammonium cerium nitrate, deionized water, N-N-dimethylformamide, 2,5-thiophene dicarboxylic acid and formic acid is 0.002:4:18:0.00298:0.

273.

5. The method for preparing the Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration according to claim 2, characterized in that: In the one-step solvent thermal method, the reaction temperature is 100° C. and the reaction time is 30 min.

6. The method for preparing the Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration according to claim 1, characterized in that: The calcination temperature is 400° C. and the calcination time is 3 hours.

7. The method for preparing the Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration according to claim 1, characterized in that: The cobalt nitrate solution was impregnated into Ce-TDC so that the Co content in the Co / CeO2-TDC catalyst was 1 wt%.

8. The method for preparing the Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration according to claim 1, characterized in that: The specific steps include: 1) dissolving ammonium cerium nitrate in deionized water to obtain solution A; dissolving 2,5-thiophenedicarboxylic acid and formic acid in N-N-dimethylformamide to obtain solution B; dropping solution A into solution B, mixing evenly, and reacting to obtain a white precipitate; 2) washing the white precipitate obtained in step 1) twice by centrifugation with N-dimethylformamide, then washing it three times by centrifugation with acetone, and drying it in an oven to obtain Ce-TDC powder; 3) dissolving cobalt nitrate in deionized water to obtain a cobalt nitrate solution; dropping the obtained cobalt nitrate solution into the Ce-TDC powder, stirring continuously with a glass rod during the dropping process to ensure that the solution can just wet the Ce-TDC powder without forming wet balls; 4) The mixture obtained in step 3) is first placed in an oven for drying, and then placed in a muffle furnace for calcination to prepare a Co / CeO2-TDC catalyst.

9. The method for preparing the Co / CeO2-TDC catalyst for medium and low temperature flue gas denitration according to any one of claims 1 to 8, wherein the Co / CeO2-TDC catalyst is prepared.

10. Use of the Co / CeO2-TDC catalyst according to claim 9 in medium and low temperature NH3-SCR catalytic denitrification.

Images