Denitration and decarburization catalyst, preparation method and application

Abstract

The invention relates to the technical field of flue gas multi-pollutant synergistic purification, in particular to a preparation method of an ultralow-temperature denitration and decarbonization catalyst and application of the ultralow-temperature denitration and decarbonization catalyst to synchronous removal of nitrogen oxides and carbon monoxide in industrial flue gas. The catalyst is prepared by a two-step method comprising the following steps: S1, dispersing a cerium source and a platinum source in absolute ethyl alcohol, and synthesizing a Pt / CeO2 monatomic catalyst by a hydrogen combustion method; s2, compounding an iron source and Pt / CeO2 through a coprecipitation method, drying and calcining in a nitrogen atmosphere to obtain the Fe-Pt / CeO2 composite catalyst. The key process parameters comprise hydrogen / oxygen flow velocity, calcination temperature and mass ratio of the iron source to the carrier. The synergistic removal efficiency of the catalyst on NOx and CO at the ultralow temperature of 50-120 DEG C reaches 85% or above, and the bottleneck that the low-temperature activity of a traditional catalyst is insufficient is broken through; sulfur resistance and water resistance are remarkably improved through the porous structure and the oxygen storage capacity of CeO2, and the activity retention rate is larger than 90% when SO2 and H2O are contained; the device is suitable for high-efficiency purification of complex flue gas of steel, waste incineration and the like, and meets the policy requirements of pollution reduction, carbon reduction and synergistic interaction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flue gas multi-pollutant simultaneous removal, and particularly relates to a preparation method of a denitration and decarbonization catalyst and application of the catalyst in simultaneous removal of nitrogen oxides (NO x ) and carbon monoxide (CO) in industrial flue gas. BACKGROUND

[0002] In recent years, with the acceleration of global industrialization and the continuous growth of energy consumption, air pollution problems have become increasingly serious, especially the emission of nitrogen oxides (NO x ) and carbon monoxide (CO) has become a key factor affecting air quality. These pollutants not only exacerbate the generation of PM2.5 and ozone (O3), but also pose a serious threat to human health and the ecological environment.

[0003] To address this challenge, a series of environmental protection policies have been introduced in China in recent years. However, existing pollution control technologies are difficult to meet the demand of new policies for multi-pollutant simultaneous treatment. For example, the mainstream selective catalytic reduction (SCR) technology relies on vanadium-based or tungsten-titanium catalysts, which requires high temperature (300-400℃) operation, high energy consumption and cannot handle CO; while low-temperature SCR technology can reduce energy consumption, but it faces problems such as low catalyst activity, poor sulfur and water resistance, and is difficult to adapt to complex and variable industrial flue gas environments.

[0004] Under this background, CO-SCR technology has attracted widespread attention due to its "waste treatment" characteristics. This technology uses CO naturally present in flue gas as a reducing agent to reduce NO x to N2 under the action of a catalyst, while simultaneously removing CO. However, existing CO-SCR catalysts still have significant defects:

[0005] Firstly, the active temperature window is narrow, with most research focusing on the 150-250℃ interval, and below 100℃ the denitration efficiency drops to below 50%;

[0006] Secondly, the oxidation reaction of CO and the reduction reaction of NO x exist competitive adsorption, resulting in low simultaneous removal efficiency;

[0007] In addition, the widespread presence of SO2 (200-1000ppm) and water vapor (5-15vol%) in industrial flue gas will poison the active sites of the catalyst, causing rapid deactivation.

[0008] In existing technologies, noble metal catalysts (such as Pt, Pd) are highly expected due to their excellent low-temperature activity, but their high cost and sintering problems limit their large-scale application. Developing a catalyst with ultra-low temperature activity, multi-pollutant simultaneous removal capability and strong anti-interference performance still faces great challenges.

[0009] In addition, the temperature of the flue gas of industrial furnaces fluctuates in a large range (50-300℃), and the composition is complex (containing dust, heavy metals, etc.), which further increases the design difficulty of the catalyst. For example, the typical temperature of the sintering flue gas in the steel industry is 80-150℃, but it contains high concentration of SO2 (300-800 ppm) and humidity (8-12%), and the traditional catalyst is prone to sulfate plugging or loss of active components in this environment. Therefore, how to construct a multifunctional catalyst system with high stability and high resistance to poisoning in the ultra-low temperature range (50-120℃) has become the key to breaking through the bottleneck of industrial flue gas purification technology.

[0010] In summary, the existing technology has significant deficiencies in the aspects of multi-pollutant simultaneous removal, low-temperature activity improvement, and environmental adaptability. In view of the above problems, the present application proposes a Fe-Pt / CeO2 composite catalyst suitable for ultra-low temperature working conditions through innovative material design and process optimization, aiming to realize the efficient simultaneous removal of NO x and CO, and at the same time solve the technical problems of poor sulfur resistance and water resistance, providing a more competitive solution for industrial flue gas purification. SUMMARY

[0011] The present application aims to improve the denitration and decarburization efficiency of the catalyst at low temperature, the sulfur resistance and water resistance, and realize the simultaneous removal of NOx and CO. In order to achieve the above purpose, the present application provides a preparation method of a denitration and decarburization catalyst, comprising the following steps:

[0012] S1. Preparation of Pt / CeO2 single-atom catalyst: disperse cerium source and platinum source in anhydrous ethanol to form a precursor solution, inject the solution into a tubular combustion furnace with hydrogen as fuel, and completely burn and evaporate under the condition of oxygen inlet to obtain a solid Pt / CeO2 single-atom catalyst;

[0013] S2. Preparation of Fe-Pt / CeO2 composite catalyst: dissolve iron source in deionized water to form a mixed solution, add the Pt / CeO2 single-atom catalyst obtained in step S1 to the mixed solution, add a precipitating agent for co-precipitation, and after drying and calcination, the Fe-Pt / CeO2 composite catalyst is obtained.

[0014] In one embodiment, in step S1, the cerium source is cerium nitrate, and the platinum source is chloroplatinic acid or platinum nitrate.

[0015] In one embodiment, in step S1, the flow rate of hydrogen is 1.0-2.0 L / min, and the pressure of oxygen is 1.5 bar and the flow rate is 10.0-12.0 L / min.

[0016] In one of the embodiments, in step S2, the iron source is selected from ferric nitrate, ferric sulfate or ferric carbonate.

[0017] In one of the embodiments, in step S2, the precipitant is ammonia water or urea solution.

[0018] In one of the embodiments, in step S2, the drying temperature is 20-120℃, and the time is 6-12 hours.

[0019] The calcination is carried out under nitrogen atmosphere, at a temperature of 350-450℃, and for a time of 24-36 hours.

[0020] In one of the embodiments, in step S1, the molar ratio of the cerium source to the platinum source is 1:0.01-0.1.

[0021] In one of the embodiments, in step S2, the mass ratio of the iron source to the Pt / CeO2 monatomic catalyst is 1:10-1:2.

[0022] The denitration and decarbonization catalyst is prepared by the above-mentioned method for preparing a denitration and decarbonization catalyst.

[0023] The denitration and decarbonization catalyst is used for simultaneously removing nitrogen oxides and carbon monoxide in flue gas in the application of the denitration and decarbonization catalyst in industrial flue gas purification.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1. Traditional denitration catalysts (such as vanadium-based SCR) need to be operated at a high temperature of 300℃ or above, which consumes a large amount of energy and cannot handle low-temperature flue gas. The Fe-Pt / CeO2 composite catalyst constructed by the two-step method of the present application significantly reduces the reaction activation energy by relying on the unique electronic structure of the monatomic Pt / CeO2 support. The strong metal-support interaction (SMSI effect) between the monatomic Pt and CeO2 not only improves the dispersion of the noble metal, but also promotes the adsorption and activation of the reactants through the surface oxygen vacancies.

[0026] Experiments show that, in the medium and low temperature range of 50-120℃, the removal efficiency of the catalyst for NO x and CO is stably above 85%, and in the optimal embodiment (Cat-1), the NO x conversion rate is 88.2% and the CO conversion rate is 86.5% at 80℃. This performance breaks through the bottleneck of the insufficient low-temperature activity of traditional catalysts, and provides an efficient solution for the low-temperature purification of industrial flue gas.

[0027] 2. The prior art focuses on a single pollutant (such as NO xThe present invention realizes the removal of NO through the synergistic catalytic mechanism of Fe and Pt / CeO2. x Simultaneous and efficient removal of CO. Fe species undergo redox cycles (Fe 2+ / Fe 3+ ) promotes the adsorption and reduction of NO to N2, while single-atom Pt accelerates the oxidation reaction of CO to generate CO2. The synergistic effect of the two at the catalytic interface avoids the problem of competitive adsorption. In addition, CO is directly used as a reducing agent for NO x The conversion of waste into fuel has realized the resource utilization of “waste treatment with waste”, reducing the consumption of reducing agents (such as NH3) by about 30% compared with traditional SCR technology, significantly reducing operating costs.

[0028] 3. High concentrations of SO₂ (200-1000 ppm) and humidity (5-15%) in industrial flue gas are the primary factors contributing to catalyst deactivation. The Fe-Pt / CeO₂ catalyst of this invention effectively suppresses the poisoning effects of sulfides and water vapor through its multi-level pore structure and the oxygen storage capacity of CeO₂. Dynamically generated oxygen vacancies on the CeO₂ surface preferentially adsorb SO₂ and oxidize it to sulfate, reducing its occupation of active sites. Furthermore, the porous structure provides a physical barrier, slowing the condensation of H₂O molecules on the catalyst surface. In simulated flue gas containing SO₂ (200 ppm) and H₂O (10 vol%), Cat-1 maintained over 90% activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for describing the embodiments or the prior art.

[0030] Figure 1 The catalyst product prepared by the preparation method of the present invention under different iron sources has a significant effect on NO X Comparison of removal rates;

[0031] Figure 2 The figure shows a comparison of the CO removal rates of catalyst products prepared by the preparation method of the present invention under different iron sources. DETAILED DESCRIPTION

[0032] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0033] Example 1: Preparation of Fe-Pt / CeO2 Catalyst (Using Ferric Nitrate as Iron Source)

[0034] Step 1: Preparation of Pt / CeO2 single-atom catalyst

[0035] (1) Take cerium nitrate (Ce(N03)3-6H20) 10.0 g and chloroplatinic acid (H2PtCl6-6H20) 0.5 g, mix according to the molar ratio of cerium source to platinum source 1:0.05, dissolve in 200 mL of anhydrous ethanol, magnetically stir for 2 hours until completely dissolved, form a homogeneous precursor solution;

[0036] (2) The precursor solution is injected through the atomizing nozzle into a tube furnace with an inner diameter of 50 mm and a length of 1 m at a rate of 0.5 mL / min, the combustion furnace uses hydrogen as fuel, the flow rate is set to 1.5 L / min, and oxygen is introduced at a pressure of 1.5 bar and a flow rate of 11.0 L / min;

[0037] (3) The temperature of the combustion furnace is maintained at 800°C, the precursor solution is completely combusted and evaporated in the furnace to generate off-white solid powder, which is collected after natural cooling to obtain Pt / Ce02 single-atom catalyst, marked as Pt / Ce02-SAC.

[0038] Step 2: Preparation of Fe-Pt / Ce02 composite catalyst

[0039] (1) Take iron nitrate (Fe(N03)3-9H20) 2.0 g, dissolve in 500 mL of deionized water, and ultrasonic disperse for 30 minutes until the solution is clear;

[0040] (2) Add 10.0 g of Pt / Ce02-SAC prepared in step 1 to the above solution, magnetically stir for 1 hour to form a uniform suspension;

[0041] (3) Adjust the pH to 9.0 by adding 25% ammonia water dropwise, continue to stir for 4 hours to generate red-brown precipitate;

[0042] (4) Centrifuge the precipitate at 8000 rpm for 10 minutes, wash with deionized water 3 times, and dry in an oven at 80°C for 10 hours;

[0043] (5) Place the dried material in a tube furnace and calcine at 400°C for 30 hours under a nitrogen atmosphere, ensure the heating rate is 5°C / min, cool naturally, grind through a 200 mesh sieve to obtain Fe-Pt / Ce02 composite catalyst, marked as Cat-1.

[0044] Example 2: Preparation of catalyst using iron sulfate as iron source

[0045] Step 1: Same as Example 1.

[0046] Step 2:

[0047] (1) Iron sulfate (Fe2(S04)3) was used to replace ferric nitrate, the mass ratio of Fe to Pt / Ce02-SAC was 1:5, and 7.16 g of Fe2(S04)3 was weighed according to the Fe content of 2.0 g.

[0048] (2) The remaining steps were exactly the same as in Example 1, and the final product was labeled as Cat-2.

[0049] Example 3: Preparation of catalyst with iron carbonate as iron source

[0050] Step 1: Same as Example 1.

[0051] Step 2:

[0052] (1) Iron carbonate (FeC03) was used to replace ferric nitrate, the mass ratio of Fe to Pt / Ce02-SAC was 1:5, and 4.15 g of FeC03 was weighed according to the Fe content of 2.0 g;

[0053] (2) FeC03 was pre-dissolved in 100 mL of dilute hydrochloric acid (concentration 0.1 mol / L), and after stirring to complete dissolution, it was mixed with Pt / Ce02-SAC;

[0054] (3) The remaining steps were the same as in Example 1, and the final product was labeled as Cat-3.

[0055] Example 4: Preparation of catalyst with platinum nitrate as platinum source

[0056] Step 1: Preparation of Pt / Ce02 monatomic catalyst

[0057] (1) Cerium nitrate (Ce(N03)3-6H20) 10.0 g and platinum nitrate (Pt(N03)2) 0.6 g (molar ratio of Ce:Pt 1:0.05) were dissolved in 200 mL of anhydrous ethanol;

[0058] (2) The flow rates of hydrogen and oxygen were adjusted to 1.2 L / min and 10.5 L / min respectively, and the remaining conditions were the same as in Example 1, and Pt / Ce02-SAC was prepared, labeled as Pt / Ce02-SAC-PtN.

[0059] Step 2: Preparation of Fe-Pt / Ce02 composite catalyst

[0060] According to Step 2 of Example 1, Pt / Ce02-SAC-PtN was used with ferric nitrate to prepare a composite catalyst, labeled as Cat-4.

[0061] Example 5: Optimization of different hydrogen / oxygen flow rates

[0062] Step 1: Preparation of Pt / Ce02 monatomic catalyst

[0063] (1) The fixed hydrogen flow rate is 1.0 L / min, the oxygen flow rate is 10.0 L / min, and the remaining conditions are the same as those in Example 1 to prepare Pt / CeO2-SAC-LowGas;

[0064] (2) Another hydrogen flow rate is 2.0 L / min, and the oxygen flow rate is 12.0 L / min to prepare Pt / CeO2-SAC-HighGas.

[0065] Step 2: Preparation of Fe-Pt / CeO2 composite catalyst

[0066] The above two kinds of Pt / CeO2 carriers are used to prepare composite catalysts according to Step 2 of Example 1, which are marked as Cat-5 (low flow rate) and Cat-6 (high flow rate).

[0067] Example 6: Combination of different calcination temperatures and times

[0068] Step 1: The same as Example 1.

[0069] Step 2:

[0070] (1) The calcination temperature is adjusted to 350℃, and the calcination time is extended to 36 hours to prepare catalyst Cat-7;

[0071] (2) The calcination temperature is adjusted to 450℃, and the calcination time is shortened to 24 hours to prepare catalyst Cat-8;

[0072] (3) The remaining steps are the same as those in Example 1.

[0073] Example 7: Optimization of different iron sources and carrier mass ratios

[0074] Step 1: The same as Example 1.

[0075] Step 2:

[0076] (1) Iron nitrate 1.0 g and Pt / CeO2-SAC 10.0 g are weighed according to the mass ratio of Fe to Pt / CeO2-SAC 1:10 to prepare catalyst Cat-9;

[0077] (2) Iron nitrate 5.0 g and Pt / CeO2-SAC 10.0 g are weighed according to the mass ratio of 1:2 to prepare catalyst Cat-10.

[0078] Example 8: Effect of different precipitants

[0079] Step 1: The same as Example 1.

[0080] Step 2:

[0081] (1) The precipitant was changed from ammonia water to urea solution (20% concentration), and was added according to the molar ratio of urea to Fe of 3:1;

[0082] (2) The mixed solution was stirred in a water bath at 80°C for 6 hours to allow the urea to decompose slowly to produce NH3, inducing co-precipitation;

[0083] (3) The remaining steps were the same as in Example 1, and the final product was labeled as Cat-11.

[0084] Example 9: Optimization of calcination atmosphere (air vs. nitrogen)

[0085] Step 1: The same as in Example 1.

[0086] Step 2:

[0087] (1) The calcination atmosphere was changed from nitrogen to air, and the catalyst Cat-12 was prepared by calcination at 400°C for 30 hours;

[0088] (2) The remaining steps were the same as in Example 1.

[0089] The catalysts prepared in Examples 1-9 above were tested in a fixed bed reactor, simulating a flue gas composition of: NO 500 ppm, CO 1000 ppm, O2 5%, SO2 200 ppm, H2O 10 vol%, space velocity 30000 h-1, and a temperature range of 50-200°C. -1

[0090] The test results are shown in Table 1 below:

[0091] Catalyst Optimum temperature (°C) NO x Conversion (%)]] CO conversion (%) Sulfur resistance retention (%) Water resistance retention (%) Cat-1 80 88.2 86.5 92.3 91.7 Cat-2 90 85.7 84.1 89.4 88.2 Cat-3 100 83.2 82.6 85.1 84.5 Cat-4 80 87.5 85.9 91.8 90.3 Cat-5 85 84.6 83.2 87.6 86.1 Cat-6 75 86.1 84.7 90.5 89.0 Cat-7 95 82.4 80.9 83.2 82.0 Cat-8 70 85.3 83.8 88.7 87.4 Cat-9 100 80.1 78.5 81.5 80.3 Cat-10 60 89.0 87.2 93.5 92.0 Cat-11 85 84.8 83.4 88.1 86.9 Cat-12 110 79.5 77.8 80.2 79.0

[0092] Table 1: Test results of catalysts prepared in Examples 1-9, respectively

[0093] As shown in Table 1 above, the Fe-Pt / CeO2 composite catalyst prepared by the two-step process of the present application exhibits excellent catalytic performance and stability at ultra-low temperatures (50-120°C). The key example data show that the Cat-1 catalyst, with ferric nitrate as the iron source, hydrogen / oxygen flow rates of 1.5 L / min and 11.0 L / min, and a calcination temperature of 400°C, has NO x and CO conversion rates of 88.2% and 86.5%, respectively, at 80°C, and the activity retention rate is >90% in complex flue gas containing SO2 (200 ppm) and H2O (10 vol%). Comparing the experimental results of different iron sources (ferric nitrate, ferric sulfate, ferric carbonate) and process parameters (hydrogen flow rate, calcination temperature, iron loading ratio), ferric nitrate is the best choice due to its high dispersibility and compatibility with the carrier, and a moderate iron loading ratio (1:5) and calcination conditions (400°C, 30h) effectively balance the active site density and structural stability.​

[0094] In summary, by analyzing the test data of each embodiment, the Fe-Pt / CeO2 catalyst of the present application has significant advantages in low-temperature activity, multi-pollutant simultaneous removal, and environmental adaptability. The precise control of process parameters such as hydrogen combustion and coprecipitation, and the innovation of material design such as single-atom Pt support and porous Fe composite structure, jointly support its high-efficiency performance, and it has broad industrial application prospects.

[0095] Although the present application has been described in detail with general description and specific embodiments above, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of protection required by the present application.

Claims

1. A method for preparing a denitration and decarbonization catalyst, characterized in that: The following steps are involved: S1. Preparation of Pt / CeO2 single-atom catalyst: A cerium source and a platinum source are dispersed in anhydrous ethanol to form a precursor solution. This solution is injected into a tubular combustion furnace fueled by hydrogen. The solution is completely burned and evaporated under the condition of oxygen flow to obtain a solid Pt / CeO2 single-atom catalyst. S2. Preparation of Fe-Pt / CeO2 composite catalyst: dissolving the iron source in deionized water to form a mixed solution, adding the Pt / CeO2 single-atom catalyst obtained in step S1 to the mixed solution, adding a precipitant for co-precipitation, and obtaining the Fe-Pt / CeO2 composite catalyst after drying and calcination.

2. The method for preparing a denitration and decarbonization catalyst according to claim 1, wherein: In step S1, the cerium source is cerium nitrate, and the platinum source is chloroplatinic acid or platinum nitrate.

3. The method for preparing a denitration and decarbonization catalyst according to claim 1, wherein: In step S1, the flow rate of hydrogen is 1.0-2.0 L / min, the pressure of oxygen is 1.5 bar, and the flow rate is 10.0-12.0 L / min.

4. The method for preparing a denitration and decarbonization catalyst according to claim 1, wherein: In step S2, the iron source is selected from ferric nitrate, ferric sulfate or ferric carbonate.

5. The method for preparing a denitration and decarbonization catalyst according to claim 1, wherein: In step S2, the precipitant is ammonia water or urea solution.

6. The method for preparing a denitration and decarbonization catalyst according to claim 1, wherein: In step S2, the drying temperature is 20-120° C. and the drying time is 6-12 hours; The calcination is carried out in a nitrogen atmosphere at a temperature of 350-450° C. for 24-36 hours.

7. The method for preparing a denitration and decarbonization catalyst according to claim 1, wherein: In step S1, the molar ratio of the cerium source to the platinum source is 1:0.01-0.

1.

8. The method for preparing a denitration and decarbonization catalyst according to claim 1, wherein: In step S2, the mass ratio of the iron source to the Pt / CeO2 single-atom catalyst is 1:10-1:

2.

9. Denitrification and decarbonization catalyst, characterized in that: The denitration and decarbonization catalyst is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the denitrification and decarbonization catalyst according to claim 9 in industrial flue gas purification, characterized in that: The application includes using the denitration and decarbonization catalyst to simultaneously remove nitrogen oxides and carbon monoxide from flue gas.

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