Low-temperature denitration catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of low-temperature flue gas denitration, in particular to a low-temperature denitration catalyst as well as a preparation method and application thereof. Comprising the following steps: 1, calcining an active component precursor in an air atmosphere to obtain a high-entropy oxide HEO; 2, under the H2 / Ar mixed atmosphere, the high-entropy oxide HEO is subjected to reduction treatment, and a high-entropy alloy FeCoNiCrMn, namely the low-temperature denitration catalyst is obtained; the low-temperature denitration catalyst is applied to treatment of nitrogen oxide in waste gas discharged by a gas turbine and a coal-fired boiler.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature flue gas denitration, and in particular to a low-temperature denitration catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Nitrogen oxides (NO x ) is one of the main air pollutants emitted by coal-fired power plants and is a key factor in the formation of acid rain and photochemical smog. x Emissions will drop from 24.0427 million tons in 2011 to 8.9574 million tons in 2022 (an average annual decrease of about 1.5 million tons). However, due to its huge emission base and long-term harm to the ecological environment and human health, further reduction of NO x Emissions remain an urgent environmental issue that needs to be addressed.

[0003] Selective catalytic reduction (SCR) technology is the most widely used NO x The core of the control method is to use NH3 as a reducing agent through the action of catalyst to reduce NO x Reducing to harmless N2 and H2O. While traditional SCR catalysts (such as V2O5-WO3 / TiO2) offer high activity and sulfur resistance, they must operate at temperatures above 623K (approximately 350°C). This limitation necessitates the placement of the SCR device before the air preheater, dust collector, and desulfurization unit. In this scenario, the catalyst is directly exposed to high concentrations of SO2 and dust, accelerating catalyst poisoning and shortening its service life and efficiency.

[0004] In summary, it is of great significance to solve the above problems, prepare a low-temperature denitrification catalyst and apply it in practice. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-temperature denitration catalyst and a preparation method and application thereof, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A low-temperature denitration catalyst comprising an active component; the active component is composed of F e , Co, Ni, Cr and Mn five metal elements; the molar ratio of Fe, Co, Ni, Cr and Mn in the metal elements is (0.8~1.2):(0.8~1.2):(0.8~1.2):(0.8~1.5):(0.8~1.5).

[0008] More optimally, a method for preparing a low-temperature denitration catalyst comprises the following steps:

[0009] Step 1: calcining the active component precursor under air atmosphere to obtain high entropy oxide HEO;

[0010] Step 2: Under a H2 / Ar mixed atmosphere, the high entropy oxide HEO is reduced to obtain a high entropy alloy FeCoNiCrMn, which is a low-temperature denitrification catalyst.

[0011] In a further embodiment, the high entropy oxide HEO is a product of calcining the active component precursor.

[0012] In a further solution, the high entropy alloy FeCoNiCrMn is a high entropy oxide HEO, and the multi-metal oxide is converted into a high entropy alloy FeCoNiCrMn, which is a low-temperature denitrification catalyst, through reduction treatment.

[0013] More optimally, the calcination temperature is 480-520°C, and the calcination time is 1.5-2.5 hours; the H2 content in the H2 / Ar mixed atmosphere is 5%-10%; the reduction treatment temperature is 480-520°C, and the time is 2-3 hours.

[0014] More optimally, the preparation process of the active component precursor is:

[0015] S1-1: Fe(NO3)3·9H2O, Co(NO3)3·6H2O, Ni(NO3)2·6H2O, Cr(NO3)3·9H2O, and Mn(NO3)2·4H2O were dissolved in diethylene glycol and stirred to obtain solution I;

[0016] S1-2: heating solution I, keeping it warm, and cooling it to obtain reactant II;

[0017] S1-3: The reactant II is washed with deionized water and ethanol, centrifuged, and dried to obtain an active component precursor.

[0018] More optimally, in S1-1, the stirring time is 4.5 to 5.5 hours.

[0019] More optimally, in S1-2, the heating rate is 4.5-5.5°C·min -1 , the heating temperature is 180-220°C; the insulation time is 11.5-12.5h; and the cooling temperature is 10-30°C.

[0020] More optimally, in S1-3, the drying temperature is 55-65°C, and the drying time is 11.5-12.5h.

[0021] More optimally, a low-temperature denitrification catalyst is used to treat nitrogen oxides in exhaust gases emitted by gas turbines and coal-fired boilers.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The low-temperature denitration catalyst prepared by the present invention can be used to treat nitrogen oxides in the exhaust gas discharged from gas turbines and coal-fired boilers, significantly improving the low-temperature denitration activity, nitrogen selectivity, and resistance to water vapor and sulfur dioxide. Compared with the prior art, the low-temperature denitration catalyst of the present invention exhibits excellent NO catalytic reduction activity under low-temperature conditions. When the denitration temperature is 250 °C, the NO conversion rate can exceed 95%. The preparation process of this low-temperature denitration catalyst is simple, environmentally friendly and pollution-free. The synergistic effect of multiple metals effectively overcomes the problem that traditional catalysts are susceptible to water vapor and SO2 due to the single active component, and has high industrial application value. In addition, within the range of 150-450 °C, especially below 300 °C, the low-temperature denitration catalyst of the present invention shows higher activity and stronger resistance to water and SO2 compared with ordinary catalysts. This characteristic makes the SCR denitration device more suitable for being arranged in the tail flue of thermal power plants, helping to reduce waste heat loss and improve the operating economy of thermal power plants. Description of the Drawings

[0024] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention, but do not constitute a limitation to the present invention. In the drawings:

[0025] Figure 1 is the XRD pattern of Example 1;

[0026] Figure 2 is the XPS pattern of the 2P orbital of cobalt element in Example 1;

[0027] Figure 3 is the XPS pattern of the 2P orbital of chromium element in Example 1;

[0028] Figure 4 is the XPS pattern of the 2P orbital of iron element in Example 1;

[0029] Figure 5 is the XPS pattern of the 2P orbital of manganese element in Example 1;

[0030] Figure 6 is the XPS pattern of the 2P orbital of nickel element in Example 1;

[0031] Figure 7 is the infrared spectrum of ammonia adsorption at different temperatures in Example 1;

[0032] Figure 8 is the infrared spectrum of nitrogen oxide adsorption at different temperatures in Example 1;

[0033] Figure 9The infrared spectra of nitrogen oxides and pre-adsorbed ammonia at different reaction times in Example 1;

[0034] Figure 10 1 is an infrared spectrum of ammonia and pre-adsorbed nitrogen oxides at different reaction times in Example 1. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] The fixed bed microreactor evaluation device used in the examples is a 4100 type fixed bed microreactor evaluation device produced by Zhejiang Pantai Instrument Co., Ltd. The reactor has an outer diameter of 16 mm and a length of 480 mm. The raw gas is preheated and enters the reactor. The reaction temperature is 150-450 ° C, the flow rate is 1000 ml / min, and the space velocity is 216000 h -1 The experiment was carried out under the conditions of .

[0037] The simulated flue gas composition in this example included 600 ppm NO, 600 ppm NH, and 5% O, with the remainder being Ar. Gas flow was controlled by a CS200 mass flowmeter manufactured by Beijing Qixing Huachuang Electronics Co., Ltd. NO and NH at a molar concentration of 1%, with the remainder being Ar, purchased from Shanghai Wei Chuang Standard Gas Co., Ltd. O and Ar were purchased from Jiangnan Mixed Gas Co., Ltd. at a purity of 99.99%.

[0038] All drugs used were purchased from Aladdin.

[0039] Example 1: A method for preparing and using a low-temperature denitration catalyst, comprising the following steps:

[0040] Step 1: Dissolve 0.1 mol Fe(NO3)3·9H2O, 0.1 mol Co(NO3)3·6H2O, 0.1 mol Ni(NO3)2·6H2O, 0.1 mol Cr(NO3)3·9H2O, and 0.1 mol Mn(NO3)2·4H2O in 60 mL of diethylene glycol and stir for 5 hours to obtain a clear and transparent solution, i.e., Solution I;

[0041] Step 2: Solution I was transferred to a 100 mL autoclave and heated at 5 °C·min -1 The mixture was heated to 200°C at a rate of 1000 ℃, then kept at this temperature for 12 hours and naturally cooled to 20°C to obtain reactant II;

[0042] Step 3: Wash the reactant II with deionized water and ethanol, centrifuge for 10 min, and then dry at 60 °C for 12 h to obtain the active substance precursor;

[0043] Step 4: Calcinate the active substance precursor at 500 °C for 2 h in an air atmosphere to obtain the high-entropy oxide HEO;

[0044] Step 5: Under a H2 / Ar mixed atmosphere (the content of H2 is 5%), reduce the high-entropy oxide HEO at 500 °C for 2 h to obtain the high-entropy alloy FeCoNiCrMn, which is the low-temperature denitration catalyst. The low-temperature denitration catalyst is used to treat nitrogen oxides in the exhaust gas discharged from gas turbines and coal-fired boilers.

[0045] In the above embodiments, the molar ratio of the metal elements Fe, Co, Ni, Cr, and Mn in the low-temperature denitration catalyst is 1:1:1:1:1.

[0046] Example 2: A preparation method and application of a low-temperature denitration catalyst, including the following steps:

[0047] Step 1: Dissolve 0.1 mol of Fe(NO3)3·9H2O, 0.1 mol of Co(NO3)3·6H2O, 0.1 mol of Ni(NO3)2·6H2O, 0.1 mol of Cr(NO3)3·9H2O, and 0.15 mol of Mn(NO3)2·4H2O in 60 mL of diethylene glycol and stir for 5 hours to obtain a clear and transparent solution, namely solution I;

[0048] Step 2: Transfer solution I to a 100 mL autoclave and heat it to 200 °C at a rate of 5 °C·min -1 and then keep it warm for 12 hours and naturally cool to 20 °C to obtain the reactant II;

[0049] Step 3: Wash the reactant II with deionized water and ethanol, centrifuge for 10 min, and then dry at 60 °C for 12 h to obtain the active substance precursor;

[0050] Step 4: Calcinate the active substance precursor at 500 °C for 2 h in an air atmosphere to obtain the high-entropy oxide HEO;

[0051] Step 5: Under a H2 / Ar mixed atmosphere (the content of H2 is 5%), reduce the high-entropy oxide HEO at 500 °C for 2 h to obtain the high-entropy alloy FeCoNiCrMn, which is the low-temperature denitration catalyst. The low-temperature denitration catalyst is used to treat nitrogen oxides in the exhaust gas discharged from gas turbines and coal-fired boilers.

[0052] In the above embodiments, the molar ratio of the metal elements Fe, Co, Ni, Cr, and Mn in the low-temperature denitration catalyst is 1:1:1:1:1.5.

[0053] Comparative Example 1: The low-temperature denitration catalyst was adjusted to a common denitration catalyst, specifically V2O5-WO3 / TiO2 (produced by Chengdu Dongfang Ketrui Co., Ltd., mainly composed of tungsten trioxide, nano-titanium dioxide, and vanadium pentoxide).

[0054] Comparative Example 2: The low-temperature denitration catalyst was adjusted to a high-entropy oxide catalyst (produced by Chengdu Dongfang Ketrui Co., Ltd., mainly composed of (FeCoNiCrMn)3O4).

[0055] Detection Experiment 1: The low-temperature denitration catalysts obtained in Examples 1-2 and Comparative Examples 1-2 were respectively subjected to denitration performance tests under different temperature conditions of 150 °C, 200 °C, 250 °C, 300 °C, and 350 °C. The specific procedure is as follows:

[0056] Step 1: Before the start of the experimental test, NO in the simulated flue gas was introduced into the fixed-bed micro-reactor evaluation device and continued for 0.5-1 hour to saturate the low-temperature denitration catalyst with NO, so as to eliminate the interference of the NO concentration decay caused by physical adsorption on the experimental results.

[0057] Step 2: The simulated flue gas was prepared using a gas mixing box: NO with a concentration of 600 ppm, NH3 with a concentration of 600 ppm, 5% O2, and the remaining gas being Ar (balance gas) were fully mixed at a flow rate of 1000 ml / min and then fed into the fixed-bed micro-reactor evaluation device.

[0058] Step 3: Flue gas denitration: At temperature gradients of 150 °C, 200 °C, 250 °C, 300 °C, and 350 °C, NH3 reduced NO to N2 under the action of 4 ml of the low-temperature denitration catalyst. After the reacted mixed gas absorbed the unreacted NH3 through a phosphoric acid solution, it was discharged into the atmosphere through the exhaust pipe.

[0059] Step 4: A Model 60i flue gas analyzer produced by Thermo Fisher Scientific Inc. was used to measure the inlet NO concentration and the outlet NO concentration, and the denitration efficiency was calculated from the above test results through the denitration efficiency calculation formula. The denitration efficiency calculation formula is as follows: Denitration efficiency (%) = [(inlet NO concentration - outlet NO concentration) / inlet NO concentration] × 100%.

[0060] The denitration efficiency results calculated above are shown in Table 1;

[0061]

[0062]

[0063] Table 1

[0064] Result analysis: According to the data analysis in Table 1, it can be seen that when performing flue gas denitrification under the same conditions, the low-temperature denitrification catalyst prepared by the present invention shows higher denitrification efficiency and a wider applicable temperature range in flue gas denitrification compared with Comparative Examples 1-2. Between 150 and 350 °C, its denitrification efficiency reaches 81-99.5%, far superior to the low-temperature denitrification catalyst in Comparative Example 1 (only 10% at 150 °C and 90.5% at 350 °C). In contrast, the denitrification efficiency of the low-temperature denitrification catalyst in Comparative Example 2 is 79.2-92.5%, slightly lower than that of the low-temperature denitrification catalysts in Examples 1-2.

[0065] By regulating the element ratio, the denitrification performance can be further improved. For example, the denitrification efficiency of the low-temperature denitrification catalyst in Example 2 reaches 99.4% at 300 °C. The excellent performance of the low-temperature denitrification catalyst in this solution can be attributed to the metal characteristics of the high-entropy alloy, which can provide more Lewis acid sites and enhance NH3 adsorption and activation. This is the reason for the higher denitrification efficiency compared with the ordinary catalyst in Comparative Example 1. In addition, the electronic effect brought by the multi-component alloy structure causes changes in the surface electron density, thereby optimizing the active sites of the catalyst and making the NO x reduction reaction more likely to occur and promoting NO x reduction. In contrast, the high-entropy oxide catalyst in Comparative Example 2, as an oxide, has a relatively stable surface and is difficult to efficiently activate NH3 and NO x at low temperatures.

[0066] In summary, the low-temperature denitrification catalyst prepared by the present invention shows excellent denitrification performance in the wide temperature range of 150-400 °C, especially having a relatively high denitrification efficiency under low-temperature conditions around 150 °C. And it has a wider activity window (150-400 °C) compared with the ordinary catalyst (Comparative Example 1) and the high-entropy oxide catalyst (Comparative Example 2), making the SCR denitrification device more suitable for being arranged in the tail flue of thermal power plants, thereby reducing waste heat loss and improving the operating economy of thermal power plants.

[0067] Detection experiment 2: The low-temperature denitrification catalyst prepared in Example 1 was subjected to XRD, BET, XPS, and DRIFT analyses. The low-temperature denitrification catalyst was analyzed by a MAX2200V X-ray diffractometer (Rigaku Corporation, Japan). The XRD analysis results are as Figure 1 shown; the BET analysis results are shown in Table 2; the XPS analysis results are as Figure 2 shown; the DRIFT analysis results are as Figure 3 shown;

[0068] Example <![CDATA[Specific surface area (m 2 / g)]]> Porosity (%) Example 1 9.7 4.8

[0069] Table 2

[0070] Result analysis: According to Figure 1 , and the analysis of Table 2 shows that XRD and BET analyses indicate that the diffraction peaks of the high-entropy alloy coating broaden near 2θ = 45°, and all elements are dissolved in the same lattice to form a single disordered solid solution phase. The synergistic effect of multiple metals can regulate the microstructure of the catalyst, endowing it with an ideal specific surface area and porosity, thereby enhancing the adsorption ability of NO x and NH3 on the surface of the low-temperature denitration catalyst;

[0071] According to Figure 2 analysis, XPS analysis shows that the presence of variable valence metals such as Fe 3+ / Fe 2+ , Co 3+ / Co 2+ , Cr 6+ / Cr 3+ enhances the redox cycling ability of the catalyst, which is beneficial to the generation of surface active oxygen (O2 - , O - , O2 2- ), improves the oxidation ability of NO, accelerates the conversion of NO to NO2, and promotes the "fast SCR" reaction;

[0072] According to Figure 3 analysis, the mechanism analysis by DRIFT shows that elements such as Fe, Cr, and Mn in the high-entropy catalyst can provide more NH4 + -Bronsted acid sites, enhancing the adsorption ability of NH3, which is consistent with the conclusion of XPS; in addition, the results show that the denitration catalyst mainly follows the L-H mechanism in the low-temperature range. The synergistic effect of Fe, Co, Ni, Cr, and Mn elements is beneficial to the chemisorption of NH3 on the catalyst surface, while promoting the generation of highly active nitrite (NO2 - ) and inhibiting the accumulation of nitrates (NO3 - ) with strong thermal stability, thereby accelerating the SCR reaction rate and improving the low-temperature denitration performance;

[0073] The introduction of Mn 4+ and Cr 6+ improves the sulfur resistance of the low-temperature denitration catalyst, reduces the occupation of active sites by SO2, and decreases the influence of sulfate deposition. The high-entropy effect enhances the anti-poisoning ability of the low-temperature denitration catalyst, enabling it to maintain a high NO x conversion rate in a humid environment, improving the anti-poisoning performance and long-term stability under actual working conditions.

[0074] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, in any regard, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Thus, all changes that fall within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A low-temperature denitration catalyst, characterized in that, It includes an active ingredient; the active ingredient is composed of five metal elements, namely Fe, Co, Ni, Cr, and Mn; the molar ratio of Fe, Co, Ni, Cr, and Mn in the metal elements is (0.8 - 1.2):(0.8 - 1.2):(0.8 - 1.2):(0.8 - 1.5):(0.8 - 1.5).

2. The preparation method of a low-temperature denitration catalyst according to claim 1, characterized in that: It includes the following steps: Step 1: Under an air atmosphere, calcine the active component precursor to obtain a high-entropy oxide HEO; Step 2: Under a H2 / Ar mixed atmosphere, perform reduction treatment on the high-entropy oxide HEO to obtain a high-entropy alloy FeCoNiCrMn, which is the low-temperature denitration catalyst.

3. The preparation method of a low-temperature denitration catalyst according to claim 2, characterized in that: The calcination temperature is 480 - 520 °C, and the calcination time is 1.5 - 2.5 h; in the H2 / Ar mixed atmosphere, the content of H2 is 5% - 10%; the reduction treatment temperature is 480 - 520 °C, and the time is 2 - 3 h.

4. The preparation method of a low-temperature denitration catalyst according to claim 2, characterized in that: The preparation process of the active component precursor is as follows: S1-1: Dissolve Fe(NO3)3·9H2O, Co(NO3)3·6H2O, Ni(NO3)2·6H2O, Cr(NO3)3·9H2O, and Mn(NO3)2·4H2O in diethylene glycol and stir to obtain Solution I; S1-2: Heat, keep warm, and then cool Solution I to obtain Reactant II; S1-3: Wash Reactant II with deionized water and ethanol, centrifuge, and dry to obtain the active component precursor.

5. The preparation method of a low-temperature denitration catalyst according to claim 4, characterized in that: In S1-1, the stirring time is 4.5 - 5.5 h.

6. The preparation method of a low-temperature denitration catalyst according to claim 4, characterized in that: In S1-2, the heating rate is 4.5 to 5.5 °C·min -1 , the heating temperature is 180 to 220 °C; the heat preservation time is 11.5 to 12.5 h; the cooling temperature is 10 to 30 °C.

7. The preparation method of a low-temperature denitration catalyst according to claim 4, characterized in that: In S1-3, the drying temperature is 55 - 65 °C, and the drying time is 11.5 - 12.5 h.

8. Application of a low-temperature denitration catalyst according to claim 1 in treating nitrogen oxides in the exhaust gas discharged from gas turbines and coal-fired boilers.

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