A Fe-NC ultra-low temperature SCR denitration catalyst and its preparation method and application

Abstract

The present invention belongs to the field of ultra-low temperature terminal denitration, and specifically relates to a Fe-N-C ultra-low temperature SCR denitration catalyst and its preparation method and application. The preparation of the catalyst includes: washing the carbon black with hydrochloric acid, washing to neutrality and drying, then condensing and refluxing in nitric acid, washing again to neutrality and drying to obtain purified carbon black; mixing and dissolving aniline, nitrogen source and iron salt in hydrochloric acid, adding ammonium persulfate solution and purified carbon black solution, stirring and reacting, filtering, washing and drying to obtain a catalyst precursor; calcining, acid washing, drying and re-calcining the catalyst precursor to obtain the catalyst. The preparation method of the catalyst of the present invention is simple, easy to operate, has good denitration efficiency at 30-120°C, has extremely high market prospects and practical utilization value, and is expected to further promote ultra-low emission transformation in non-electricity industries.

Description

Technical Field

[0001] The present invention belongs to the field of ultra-low temperature terminal denitration, and in particular relates to a Fe-NC ultra-low temperature SCR denitration catalyst and a preparation method and application thereof. Background Art

[0002] As one of the main air pollutants, nitrogen oxides (NO x ) will cause acid rain, photochemical smog, ozone layer depletion, etc., which seriously threatens human physical and mental health and environmental safety. In order to control the emission of nitrogen oxides, my country has clearly stated in the "14th Five-Year Plan" that the emission of nitrogen oxides in 2025 should be reduced by more than 10% compared with 2020. Selective catalytic reduction (SCR) technology is currently the most widely used flue gas denitrification method. At present, my country's thermal power plants have basically completed the ultra-low emission transformation using SCR technology. However, due to the narrow temperature window (300~400℃) of the mature SCR denitrification catalyst (V2O5-WO3(MoO3) / TiO2) of thermal power plants, it cannot be further extended to non-electric low temperature and ultra-low temperature sections. Therefore, the development of highly active (ultra-) low temperature SCR denitrification catalysts is an effective measure to promote ultra-low emissions in the non-electric industry.

[0003] In recent years, multifunctional carbon-based porous materials represented by activated carbon have been widely used in the field of environmental governance due to their developed pore structure, high specific surface area, rich surface functional groups and sources. Activated carbon dry flue gas desulfurization and denitrification technology has been applied to flue gas treatment in non-electricity industries. However, the relatively low low-temperature and ultra-low-temperature SCR activity limits its further industrial application. Therefore, it is urgent to develop new carbon-based catalysts with high SCR activity in order to further promote its industrial application.

[0004] Fe has become a hot topic in the research of low-temperature and ultra-low-temperature catalysts due to its strong low-temperature electron exchange capacity and wide sources. Patent CN103506121A discloses a carbon nanotube-loaded iron low-temperature denitration catalyst with good low-temperature denitration activity. In addition, doping N in the carbon atom skeleton can not only regulate the electronic structure and defects of the carbon material surface, improve the chemical properties of the carbon surface, and enhance the low-temperature denitration catalytic activity of the catalyst, but also form Fe-N x Coordination bonds enhance the interaction between the catalyst and the active components and improve the catalyst stability. Therefore, the development of new Fe-NC catalysts is expected to further improve the low-temperature and ultra-low-temperature SCR activity. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned prior art, the present invention provides a method for preparing a new Fe-NC low-temperature and ultra-low-temperature denitrification catalyst by in-situ synthesis. The developed catalyst has the characteristics of high SCR activity, high efficiency and stability, which is expected to promote the further industrial application of carbon-based materials and promote the ultra-low emission transformation of non-electric industries.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a Fe-NC ultra-low temperature SCR denitration catalyst, the method comprising the following steps:

[0008] Step 1: washing the carbon black with hydrochloric acid, washing it to neutrality and drying it, then condensing and refluxing it in nitric acid, washing it again to neutrality and drying it to obtain purified carbon black;

[0009] Step 2: dissolving aniline, nitrogen source and iron salt in hydrochloric acid, adding ammonium persulfate solution and purified carbon black suspension, stirring and reacting, filtering, washing and drying to obtain a catalyst precursor;

[0010] Step 3: calcining, acid-washing, drying and re-calcining the catalyst precursor to obtain the Fe-NC ultra-low temperature SCR denitration catalyst.

[0011] Preferably, in step 1, the concentration of hydrochloric acid is 0.5-1 mol / L, the condensation reflux temperature is 70-85° C., and the time is 6-12 h.

[0012] Preferably, the reaction temperature in step 2 is 5-10°C.

[0013] Preferably, in step 2, the concentration of hydrochloric acid is 1-2 mol / L, the concentration of ammonium persulfate solution is 200-300 mg / mL, and the concentration of purified carbon black suspension is 5-20 mg / mL.

[0014] Preferably, in step 2, the mass ratio of aniline to purified carbon black is 7.5-15, and the mass ratio of aniline to ammonium persulfate is 0.6.

[0015] Preferably, in step 2, the nitrogen source includes but is not limited to urea, melamine, cyanamide and nicarbazine, and the iron salt includes but is not limited to ferric chloride, ferric ammonium sulfate and ferric nitrate.

[0016] Preferably, in step 2, the mass ratio of aniline to nitrogen source is 0.15-0.43, and the mass ratio of aniline to iron salt is 0.21-0.36.

[0017] Preferably, the calcination conditions in step 3 are: a heating rate of 5-10°C / min, a temperature of 800-900°C, and a time of 1-2 h; and the pickling conditions are: condensing and refluxing with 1-2 mol / L sulfuric acid at 70-85°C for 6-12 h.

[0018] In a second aspect, the present invention provides a Fe-NC ultra-low temperature SCR denitration catalyst prepared by the aforementioned method.

[0019] In a third aspect, the present invention provides the use of the aforementioned desulfurization and denitrification activated carbon in denitrification.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention develops a novel ultra-low temperature SCR denitration catalyst, which uses cheap and readily available raw materials to obtain a Fe-NC ultra-low temperature SCR denitration catalyst in a simple preparation method, and is easy to realize industrial production. The metal active component in the catalyst of the present invention forms a coordination bond with the nitrogen element and is coated with a carbon structure, which is not easy to fall off and deactivate, has good denitration efficiency at 30-120°C, and has extremely high market prospects and practical utilization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The catalyst of Example 1 of the present invention is heated at a space velocity of 4000 h -1 The trend diagram of denitrification rate changing with increasing temperature.

[0023] Figure 2 The catalyst of Example 1 of the present invention is heated at a space velocity of 4000 h -1 , 30℃, 100 ppm SO2 conditions. DETAILED DESCRIPTION

[0024] To facilitate understanding of the present invention, the present invention will be described more fully below. Example 1

[0025] A method for preparing a Fe-NC ultra-low temperature SCR catalyst comprises the following steps:

[0026] 1. Preparation of polyaniline / carbon material composites:

[0027] The carbon black was acid-washed with 0.5 mol / L hydrochloric acid and then washed with deionized water until the pH was neutral, then filtered and dried, condensed and refluxed with nitric acid at 85°C for 8 h, and then the pH of the sample was washed to neutral, filtered and dried to obtain purified carbon black; the purified carbon black was ultrasonically dispersed in water to obtain a purified carbon black suspension with a concentration of 8 mg / mL;

[0028] 6 g of aniline, 16.6 g of ferric chloride, and 20 g of urea were mixed in 1 mol / L hydrochloric acid, and 50 mL of 200 mg / mL ammonium persulfate was added as an initiator. Then, 50 mL of purified carbon black suspension was added. After stirring and reacting for 48 h at 10°C, the mixture was washed with deionized water until the pH was neutral, and filtered and dried to obtain a polyaniline / carbon material composite.

[0029] 2. Preparation of catalyst:

[0030] The polyaniline / carbon material composite was calcined at 900°C for 1 h in a nitrogen atmosphere, pickled in 2 mol / L sulfuric acid at 80°C for 8 h, washed and dried, and then calcined for the second time (calcination conditions were the same as the first calcination) to obtain a Fe-NC ultra-low temperature SCR denitrification catalyst. Example 2

[0031] A method for preparing a Fe-NC ultra-low temperature SCR catalyst comprises the following steps:

[0032] 1. Preparation of polyaniline / carbon material composites:

[0033] The carbon black was acid-washed with 0.5 mol / L hydrochloric acid and then washed with deionized water until the pH was neutral, then filtered and dried, condensed and refluxed with nitric acid at 85°C for 8 h, and then the pH of the sample was washed to neutral, filtered and dried to obtain purified carbon black; the purified carbon black was ultrasonically dispersed in water to obtain a purified carbon black suspension with a concentration of 8 mg / mL;

[0034] 6 g of aniline, 22.4 g of ferric nitrate, and 14 g of cyanamide were mixed in 1 mol / L hydrochloric acid, and 50 mL of 200 mg / mL ammonium persulfate was added as an initiator. Then, 50 mL of purified carbon black suspension was added. After stirring and reacting for 48 h at 10°C, the mixture was washed with deionized water until the pH was neutral, and filtered and dried to obtain a polyaniline / carbon material composite.

[0035] 2. Preparation of catalyst:

[0036] The polyaniline / carbon material composite was calcined at 900°C for 1 h in a nitrogen atmosphere, pickled in 2 mol / L sulfuric acid at 80°C for 8 h, washed and dried, and then calcined for the second time (calcination conditions were the same as the first calcination) to obtain a Fe-NC ultra-low temperature SCR denitrification catalyst. Example 3

[0037] The catalyst prepared in Example 1 was placed in a vertical quartz tube and subjected to a denitration test under the following simulated atmosphere. The simulated atmosphere consisted of a. 500 ppm NO, 500 ppm NH3, 5 vol.% O2, and N2 as the balance gas. The air velocity was fixed at 4000 h -1 , the investigation temperature is 30~120℃; b. 500 ppm NO, 500 ppm NH3, 100 ppm SO2, 5 vol.% O2, N2 as the balance gas, and the space velocity is fixed at 4000 h -1 , the investigation temperature is 30℃.

[0038] The denitration rate of the catalyst at different temperatures is calculated by the following formula:

[0039] η = (C in -C out ) / C in ×100%, where C in , C out are the concentrations of NO at the inlet and outlet, respectively. In the present invention, when the denitration rate of the Fe-NC ultra-low temperature SCR catalyst sample reaches equilibrium, the denitration rate of the catalyst is calculated.

[0040] Depend on Figure 1 It can be seen that the denitrification activity of the Fe-NC ultra-low temperature SCR catalyst decreases with increasing temperature, from 99% at 30°C to 59.6% at 120°C and then to 28.6% (150°C), proving that the catalyst has a high denitrification activity (more than 50%) in the ultra-low temperature range. Figure 2 This indicates that the catalyst has good sulfur resistance at 30° C. In summary, the catalyst provided by the present invention has excellent ultra-low temperature denitration activity and good sulfur resistance.

[0041] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. Application of an Fe-NC ultra-low temperature SCR denitration catalyst in denitration, characterized in that: The preparation method of the catalyst comprises the following steps: Step 1: washing the carbon black with hydrochloric acid, washing it to neutrality and drying it, then condensing and refluxing it in nitric acid, washing it again to neutrality and drying it to obtain purified carbon black; Step 2: dissolving aniline, nitrogen source and iron salt in hydrochloric acid, adding ammonium persulfate solution and purified carbon black suspension, stirring and reacting, filtering, washing and drying to obtain a catalyst precursor; Step 3: calcining, acid-washing, drying and re-calcining the catalyst precursor to obtain the Fe-NC ultra-low temperature SCR denitration catalyst; The denitrification reaction temperature is 30~120℃.

2. The use of a Fe-NC ultra-low temperature SCR denitration catalyst according to claim 1, characterized in that: In step 1, the concentration of hydrochloric acid is 0.5-1 mol / L, the temperature of condensation reflux is 70-85° C., and the time is 6-12 h.

3. The use of a Fe-NC ultra-low temperature SCR denitration catalyst according to claim 1, characterized in that: The reaction temperature in step 2 is 5-10°C.

4. The use of a Fe-NC ultra-low temperature SCR denitration catalyst according to claim 1, characterized in that: In step 2, the concentration of hydrochloric acid is 1-2 mol / L, the concentration of ammonium persulfate solution is 200-300 mg / mL, and the concentration of purified carbon black suspension is 5-20 mg / mL.

5. The use of a Fe-NC ultra-low temperature SCR denitration catalyst according to claim 1, characterized in that: In the step 2, the mass ratio of aniline to purified carbon black is 7.5-15:1, and the mass ratio of aniline to ammonium persulfate is 0.6:

1.

6. The use of a Fe-NC ultra-low temperature SCR denitration catalyst according to claim 1, characterized in that: In step 2, the nitrogen source is urea, melamine, cyanamide or nicarbazine, and the iron salt is ferric chloride, ferric ammonium sulfate or ferric nitrate.

7. The use of a Fe-NC ultra-low temperature SCR denitration catalyst according to claim 1, characterized in that: In the step 2, the mass ratio of aniline to the nitrogen source is 0.15-0.43:1, and the mass ratio of aniline to the iron salt is 0.21-0.36:

1.

8. The use of a Fe-NC ultra-low temperature SCR denitration catalyst according to claim 1, characterized in that: The conditions for calcination and re-calcination in step 3 are: heating rate of 5-10°C / min, temperature of 800-900°C, and time of 1-2 h; the conditions for pickling are: condensation reflux with 1-2 mol / L sulfuric acid at 70-85°C for 6-12 h.

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