Iron-manganese metal catalyst for synergistically removing NOx and VOCs as well as preparation method and application of iron-manganese metal catalyst

Abstract

The embodiment of the invention provides an iron-manganese metal catalyst for synergistically removing NOx and VOCs as well as a preparation method and application of the iron-manganese metal catalyst, and belongs to the technical field of air pollution control. The preparation method comprises the following steps: preparing an iron-manganese metal salt solution from iron ions and manganese ions in a first molar ratio, wherein the first molar ratio comprises 3: 1, 2: 1, 1: 1, 1: 2 and 1: 3; preparing an oxalic acid precipitator from iron-manganese metal cations and oxalate in a second molar ratio, wherein the range of the second molar ratio is 1: 1.05-1: 1.25; adding an oxalic acid precipitant into the ferro-manganese metal salt solution, and stirring at room temperature to obtain an acidic precipitate; washing and filtering the acidic precipitate, and then calcining, wherein the calcining temperature range is 250-350 DEG C; and calcining to remove water adsorbed on the surface of the acidic precipitate and pyrolyzing the acidic precipitate into an oxide to obtain the iron-manganese metal catalyst with oxygen vacancies and acidic sites and high low-temperature catalytic activity. The iron-manganese metal catalyst disclosed by the invention can reach 90% of synergistic purification efficiency under a low-temperature flue gas condition.

Description

Technical Field

[0001] The present invention belongs to the technical field of air pollution control, and particularly relates to a method for collaboratively removing NO x and VOC s The invention discloses an iron-manganese metal catalyst and a preparation method and application thereof. Background Art

[0002] NO x and VOC s PM2.5 and ozone 3 With the help of the existing denitration equipment, the catalyst is optimized to remove VOC s The effect can not only effectively reduce costs but also save space. 3 -SCR and catalytic oxidation method are coupled to achieve NO x and VOC s The synergistic removal of PM2.5 and ozone can effectively inhibit PM2.5 and ozone from the source. 3 The production of.

[0003] The reaction temperature required by the common vanadium-tungsten-titanium denitrification catalyst is very high. When the flue gas temperature is low, such as in coking and waste incineration, additional heating is required to reach the effective reaction temperature range. In addition, the oxidizing property of the vanadium-tungsten-titanium catalyst is insufficient, and it is impossible to achieve the denitrification of VOC in the flue gas. s deep oxidation.

[0004] Usually single manganese oxide in NO x or VOC s It has good low-temperature reaction activity in the scene of single removal, but its reaction activity is obviously insufficient when facing multiple pollutants at the same time. Therefore, how to further activate the catalytic activity of manganese oxide to meet the efficient synergistic removal of multiple pollutants has gradually become an important research topic in this field.

[0005] In view of this, a new type of synergistic removal of NO is needed x and VOC s The iron-manganese metal catalyst and its preparation method and application are used to solve the above problems. Summary of the invention

[0006] In order to solve at least one aspect of the above-mentioned problems and defects in the prior art, the embodiment of the present invention provides a method for synergistically removing NO x and VOC s The iron-manganese metal catalyst and its preparation method and application are obtained by adjusting the ratio of iron ions to manganese ions and the ratio of precipitant to iron-manganese metal ions and using a specific precipitant to achieve 90% NO under low-temperature flue gas conditions of 100-200°C. xand VOC s The iron-manganese metal catalyst with high synergistic purification efficiency is as follows:

[0007] According to one aspect of the present invention, a method for synergistically removing NO x and VOC s A method for preparing an iron-manganese metal catalyst. The preparation method comprises:

[0008] Preparing an iron-manganese metal salt solution with a first molar ratio of iron ions to manganese ions, wherein the first molar ratio includes 3:1, 2:1, 1:1, 1:2 and 1:3;

[0009] An oxalic acid precipitant is prepared with a second molar ratio of iron and manganese metal cations to oxalate, wherein the second molar ratio ranges from 1:1.05 to 1:1.25;

[0010] adding an oxalic acid precipitant to the iron-manganese metal salt solution and stirring until the iron ions and the manganese ions are (e.g., completely) precipitated to obtain an acidic precipitate, which is an oxalic acid compound;

[0011] The acidic precipitate is washed and filtered and then calcined at a temperature ranging from 250 to 350°C;

[0012] After calcination, the adsorbed water on the surface of the acidic precipitate is removed and the oxalic acid compound is thermally decomposed into oxides, thereby obtaining an iron-manganese metal catalyst with oxygen vacancies and acidic sites and high low-temperature catalytic activity.

[0013] In some embodiments, specifically, Fe(SO 4 ) 2 7H 2 O and MnSO 4 ·H 2 O is added into ultrapure water to dissolve, and stirred at room temperature to obtain an iron-manganese metal salt solution, and the stirring time ranges from 10 to 60 minutes.

[0014] In some embodiments, specifically, the oxalic acid precipitant is oxalic acid solution, oxalic acid dihydrate solution or sodium oxalate solution; oxalic acid, oxalic acid dihydrate or sodium oxalate is weighed in a second molar ratio and added to ultrapure water to dissolve, and stirred at room temperature to obtain the oxalic acid precipitant, and the stirring time ranges from 10 to 60 minutes.

[0015] In some embodiments, specifically, ultrapure water and anhydrous ethanol are used to wash and filter the acidic precipitate, so that the pH value of the filtrate of the acidic precipitate reaches a range of 6.5 to 7.5.

[0016] In some embodiments, specifically, the acidic precipitate is placed in a drying oven for drying, the drying temperature range is 50-70°C, and the drying time range is 10-15 hours; the dried acidic precipitate is placed in a tubular furnace and calcined under flowing air, the calcination temperature is 300°C, the calcination time range is 1.5-4.5 hours, and the calcination heating rate range is 1-3°C / min.

[0017] In some embodiments, further, during the calcination process, the carbon dioxide generated by the pyrolysis of the acidic precipitate is detached from the surface to form a mesoporous structure, thereby increasing the oxygen vacancies and acidic sites on the surface of the iron-manganese metal catalyst; the acidic precipitate after calcination is amorphous or microcrystalline, and the crystallinity is reduced, thereby increasing the specific surface area of ​​the iron-manganese metal catalyst.

[0018] In some embodiments, further, the iron ions in the iron-manganese metal catalyst increase the valence of the manganese ions to obtain strong oxidizing properties; the increase in the acid sites on the surface of the iron-manganese metal catalyst and the strong oxidizing properties work together to obtain a synergistic removal of NO in flue gas in a low temperature range. x and VOC s The purification efficiency is greater than or equal to 90% of the catalytic activity, and the low temperature range is 100-200°C.

[0019] According to another aspect of the present invention, an iron-manganese metal catalyst is provided. The iron-manganese metal catalyst is prepared by the preparation method of the iron-manganese metal catalyst described in the above aspect.

[0020] In some embodiments, specifically, the iron-manganese metal catalyst is an oxalate metal compound, which has acid sites and oxygen vacancies for enhancing catalytic activity under low temperature conditions; the iron-manganese metal catalyst synergistically removes NO in flue gas at a low temperature range of 100 to 200°C. x and VOC s The purification efficiency reaches 90%.

[0021] According to another aspect of the present invention, an iron-manganese metal catalyst is provided for synergistically removing NO from flue gas. x and VOC s The application of the present invention is to use the preparation method of the iron-manganese metal catalyst described in the above aspects to obtain the iron-manganese metal catalyst and use the iron-manganese metal catalyst to synergistically remove NO in flue gas. x and VOC s .

[0022] In some embodiments, specifically, the smoke simulation atmosphere parameters are NO concentration range of 400-600 ppm, NH 3 Concentration range 400~600ppm, C 7 H 8Concentration range 80~120ppm, O 2 Volume fraction range 5~15vol%, nitrogen balance and decontamination gas temperature range 100~350℃, total gas flow range 180~220mL / min, reaction space velocity range 55000~65000mL / g -1 ·h -1 Under the test conditions: when the temperature of the gas to be decontaminated is 110°C, the purification efficiency of the iron-manganese metal catalyst for NO is 90%; when the temperature of the gas to be decontaminated is 150°C, the purification efficiency of the iron-manganese metal catalyst for C 7 H 8 The purification efficiency reaches 90%.

[0023] The embodiments of the present invention provide a synergistic removal of NO x and VOC s The iron-manganese metal catalyst and its preparation method and use have at least one of the following advantages or part of at least one advantage:

[0024] (1) Synergistic removal of NO provided by embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application increase the valence state of manganese ions by doping the second active metal iron in manganese oxide, further improving the strong oxidizing property of the manganese-based catalyst and achieving NO x and VOC s The collaborative removal of

[0025] (2) Synergistic removal of NO provided by embodiments of the present invention x and VOC s The iron-manganese metal catalyst with the best iron-manganese ratio screened out can achieve more than 90% NO in the low temperature range of 100-200°C. x and VOC s Synergistic removal and purification efficiency, showing extremely strong low-temperature pollutant removal performance and significantly better than most similar catalysts;

[0026] (3) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application are obtained in an amorphous or microcrystalline state, and its crystallinity is low, which helps to expose a large number of oxygen vacancies and acid sites on the surface of the iron-manganese metal catalyst, thereby obtaining a high degree of strong acidity and strong redox performance;

[0027] (4) Synergistic removal of NO provided by the embodiments of the present invention x and VOC sThe iron-manganese metal catalyst and its preparation method and application use common cheap metal iron and metal manganese, have low cost, high low-temperature purification efficiency, and have prospects for industrial application;

[0028] (5) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application obtain an acidic precipitate by using an oxalic acid precipitant, and a sufficient mesoporous structure is formed by pyrolysis during calcination, which is conducive to the formation of abundant oxygen vacancies and acidic sites on the surface of the iron-manganese metal catalyst. Compared with the alkaline precipitant, it is more effective in synergistically removing NO x and VOC s It has higher catalytic activity;

[0029] (6) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application. The acid sites formed by calcining the acidic precipitate can promote the strong oxidizing property of the iron-manganese metal catalyst, so that it has a high catalytic activity in a low temperature range to obtain a high purification efficiency;

[0030] (7) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application have simple preparation steps and processes, especially using common sodium oxalate as a precipitant to obtain an iron-manganese catalyst with high catalytic activity after washing, drying and calcination, thereby reducing the process and manufacturing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] These and / or other aspects and advantages of the present invention will become apparent and readily understood from the following description of preferred embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 The synergistic removal of NO by an iron-manganese metal catalyst according to one embodiment of the present invention x and VOC s The purification efficiency curve diagram of

[0033] Figure 2 The iron-manganese metal catalysts according to Examples 1 to 5 of the present invention are used to synergistically remove NO from experimental flue gas. x and VOC s The NO purification efficiency curve diagram;

[0034] Figure 3 The iron-manganese metal catalysts according to Examples 1 to 5 of the present invention are used to synergistically remove NO from experimental flue gas. x and VOC s C7 H 8 A graph of purification efficiency;

[0035] Figure 4 According to the present invention, the iron-manganese metal catalyst of Example 4 synergistically removes NO in the experimental flue gas at different reaction space velocities x and VOC s The NO purification efficiency curve diagram;

[0036] Figure 5 The iron-manganese metal catalyst according to Example 4 of the present invention synergistically removes NO in the experimental flue gas at different reaction space velocities. x and VOC s C 7 H 8 A graph of purification efficiency;

[0037] Figure 6 The results are as follows: the synergistic removal of NO in experimental flue gas by the iron-manganese metal catalysts according to Example 4, Comparative Example 1 and Comparative Example 2 of the present invention. x and VOC s The NO purification efficiency curve diagram;

[0038] Figure 7 The results are as follows: the synergistic removal of NO in experimental flue gas by the iron-manganese metal catalysts according to Example 4, Comparative Example 1 and Comparative Example 2 of the present invention. x and VOC s C 7 H 8 A graph of purification efficiency;

[0039] Figure 8 is the NH of the iron-manganese metal catalyst according to Example 4, Comparative Example 1 and Comparative Example 2 of the present invention. 3 Desorption amount curve diagram;

[0040] Fig. 9 is a graph of the X-ray photoelectron spectrum of O1s of the iron-manganese metal catalysts according to Example 4, Comparative Example 1 and Comparative Example 2 of the present invention;

[0041] Fig.10 It is a curve diagram of the X-ray photoelectron spectrum of Mn2p of the iron-manganese metal catalyst according to Example 4, Comparative Example 1 and Comparative Example 2 of the present invention;

[0042] Fig.11 It is a curve chart of the X-ray diffraction patterns of the iron-manganese metal catalysts according to Examples 1 to 5 and Comparative Examples 1 to 2 of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further specifically described below by examples and in conjunction with the accompanying drawings. In the specification, the same or similar reference numerals indicate the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the overall inventive concept of the present invention and should not be construed as a limitation of the present invention.

[0044] The currently used vanadium-tungsten-titanium catalyst for denitrification or a single manganese oxide catalyst has the problem of low catalytic activity when synergistically removing multiple pollutants, or requires a higher reaction temperature to activate its catalytic activity to a certain extent. Therefore, the present invention proposes a new type of iron-manganese metal catalyst and a preparation method thereof, which is formed by adding a second active metal to a single manganese oxide and using an acidic precipitant to form an acidic precipitate, and then calcining to form an iron-manganese metal catalyst. The iron-manganese metal catalyst can achieve 90% NO removal under low-temperature flue gas conditions of 100-200°C. x and VOC s The collaborative purification efficiency.

[0045] The preparation method of the iron-manganese metal catalyst mainly comprises the following steps:

[0046] Step S100: preparing an iron-manganese metal salt solution with a first molar ratio of iron ions to manganese ions, wherein optionally, the first molar ratio includes 3:1, 2:1, 1:1, 1:2 and 1:3;

[0047] Step S200: preparing an oxalic acid precipitant with a second molar ratio of iron and manganese metal cations to oxalate, wherein optionally, the second molar ratio ranges from 1:1.05 to 1:1.25;

[0048] Step S300: adding an oxalic acid precipitant to an iron-manganese metal salt solution and stirring until the iron ions and manganese ions are completely precipitated to obtain an acidic precipitate, wherein the acidic precipitate is an oxalic acid compound;

[0049] Step S400: washing and filtering the acidic precipitate and then calcining it at a temperature ranging from 250 to 350°C.

[0050] After calcination, the adsorbed water on the surface of the acidic precipitate is removed and the oxalic acid compound is thermally decomposed into oxides, thereby obtaining an iron-manganese metal catalyst with oxygen vacancies and acidic sites and high low-temperature catalytic activity.

[0051] In one example, see Figure 1 , showing that the iron-manganese metal catalyst (the iron-manganese metal catalyst obtained in Example 4 below) is used to purify the flue gas (experimental flue gas) as the flue gas temperature rises. x (NO in the experiment) and VOC s (In the experiment, C 7 H 8) purification efficiency curve. Specifically, the blue curve is the curve of NO purification efficiency as the flue gas temperature increases. It can be seen that it has a NO purification efficiency of more than 90% at 110°C. The red curve is C 7 H 8 The curve of purification efficiency changing with the increase of flue gas temperature shows that it has a C of more than 90% at 150℃. 7 H 8 Purification efficiency.

[0052] In one example, further, by precisely controlling the first molar ratio in step S100 and the second molar ratio in step S200, the catalytic activity of the iron-manganese metal catalyst can be effectively adjusted so that a higher synergistic removal of NO can be achieved under low temperature conditions (e.g., 100-200° C.). x and VOC s The optimal first molar ratio and the optimal second molar ratio are screened by the specific preparation parameters of Examples 1 to 5 and the characterization results of the catalytic activity of the iron-manganese metal catalysts obtained therefrom, so as to obtain the iron-manganese metal catalyst with the best or better purification effect.

[0053] Example 1

[0054] In Example 1, the first molar ratio is 3:1, and the iron oxide is Fe(SO 4 ) 2 7H 2 O, manganese oxide, MnSO 4 ·H 2 O. Then the second molar ratio is selected as 1:1.1, and the oxalic acid precipitant is sodium oxalate (Na 2 C 2 O 4 ) solution. For the convenience of comparative analysis and description, the molecular formula of the iron-manganese metal catalyst obtained in Example 1 is recorded as Fe 3 Mn 1 O x Then prepare Fe 3 Mn 1 O x The specific steps are as follows:

[0055] Step S101: prepare an iron-manganese metal salt solution with iron ions and manganese ions in a first molar ratio. Specifically, Fe(SO 4 ) 2 7H 2 O and MnSO 4 ·H 2 O and add ultrapure water to dissolve, and after stirring at room temperature for 30 minutes, an iron-manganese metal salt solution is obtained.

[0056] Step S201: prepare an oxalic acid precipitant with a second molar ratio of iron and manganese metal cations to oxalate. Specifically, according to n(Fe+Mn): n(C 2 O 4 )=1:1.1 Weigh Na 2 C 2 O 4 Add ultrapure water and stir at room temperature for 30 minutes to make Na 2 C 2 O 4 The oxalic acid precipitant is obtained after complete dissolution.

[0057] Step S301: adding an oxalic acid precipitant to an iron-manganese metal salt solution, wherein a precipitate is generated in the mixed solution, and stirring is continued at room temperature for 2 hours to precipitate the iron ions and manganese ions. Preferably, the iron ions and manganese ions are completely precipitated to obtain an acidic precipitate, which is an oxalic acid compound.

[0058] Step S401: The acidic precipitate is washed with ultrapure water and anhydrous ethanol and filtered to make the pH value of the filtrate reach 7 (the pH value floating range is generally 6.5-7.5), and then the acidic precipitate is dried in a drying device, preferably, placed in an electric blast drying oven for drying, and further preferably, the drying temperature is 60°C and the drying time is 12 hours; finally, it is placed in a tubular furnace and calcined under flowing air, preferably, the calcination temperature is 300°C, the calcination time is 2 hours, and the heating rate is maintained at 1°C / min.

[0059] After calcination, the iron-manganese metal catalyst Fe 3 Mn 1 O x .

[0060] Example 2

[0061] In Example 2, the first molar ratio is selected as 2:1, that is, n(Fe):n(Mn)=2:1, and the other parameters and preparation steps are completely consistent with those of Example 1. At the same time, the molecular formula of the iron-manganese metal catalyst obtained in Example 2 is recorded as Fe 2 Mn 1 O x Then prepare Fe 2 Mn 1 O x The specific steps are briefly described as follows:

[0062] Step S102: Weigh Fe(SO 4 ) 2 7H 2 O and MnSO4 ·H 2 O and add ultrapure water to dissolve, and after stirring at room temperature for 30 minutes, an iron-manganese metal salt solution is obtained.

[0063] Step S202: According to n(Fe+Mn): n(C 2 O 4 )=1:1.1 Weigh Na 2 C 2 O 4 Add ultrapure water and stir at room temperature for 30 minutes to make Na 2 C 2 O 4 The oxalic acid precipitant is obtained after complete dissolution.

[0064] Step S302: adding oxalic acid precipitant to the iron and manganese metal salt solution, and continuing to stir at room temperature for 2 hours to obtain an acidic precipitate.

[0065] Step S402: After the acidic precipitate is washed with ultrapure water and anhydrous ethanol and filtered to a pH value of 7, the acidic precipitate is placed in an electric blast drying oven for drying (the drying conditions are the same as those in Example 1), and finally placed in a tubular furnace for calcination under flowing air (the calcination conditions are the same as those in Example 1).

[0066] After calcination, the iron-manganese metal catalyst Fe 2 Mn 1 O x .

[0067] Example 3

[0068] In Example 3, the first molar ratio is selected as 1:1, that is, n(Fe):n(Mn)=1:1, and the other parameter conditions and preparation steps are completely consistent with those in Example 1. At the same time, the molecular formula of the iron-manganese metal catalyst obtained in Example 3 is recorded as Fe 1 Mn 1 O x The specific preparation steps can be referred to Example 1 and Example 2, which will not be repeated here.

[0069] Example 4

[0070] In Example 4, the first molar ratio is selected as 1:2, that is, n(Fe):n(Mn)=1:2, and the other parameter conditions and preparation steps are completely consistent with those in Example 1. At the same time, the molecular formula of the iron-manganese metal catalyst obtained in Example 4 is recorded as Fe 1 Mn 2 O x The specific preparation steps can be referred to Example 1 and Example 2, which will not be repeated here.

[0071] Example 5

[0072] In Example 5, the first molar ratio is selected to be 1:3, that is, n(Fe):n(Mn)=1:3, and the other parameter conditions and preparation steps are completely consistent with those in Example 1. At the same time, the molecular formula of the iron-manganese metal catalyst obtained in Example 4 is recorded as Fe 1 Mn 3 O x The specific preparation steps can be referred to Example 1 and Example 2, which will not be repeated here.

[0073] In one example, specifically, oxalic acid solution, dihydrate oxalic acid solution or sodium oxalate solution can be selected as the oxalic acid precipitant. Further, in the above-mentioned Examples 1 to 5, sodium oxalate (Na 2 C 2 O 4 ) solution.

[0074] In one example, the purpose of determining the amount of oxalic acid precipitant, that is, determining the second molar ratio, is to make the oxalic acid precipitant slightly excessive, usually 110% of the amount of iron and manganese metal ions, to ensure complete precipitation of iron ions and manganese ions during the mixed precipitation process.

[0075] At the same time, it is known through repeated experiments that continuing to increase the amount of oxalic acid precipitant does not affect the complete precipitation of iron-manganese metal ions on the one hand, and does not improve the catalytic activity and catalytic effect of the iron-manganese metal catalyst finally obtained on the other hand. Therefore, in Examples 1 to 5, the second molar ratio is determined to be 1:1.1. Of course, those skilled in the art can understand that the specific value of the second molar ratio can be adjusted according to the actual application environment of the iron-manganese metal catalyst. This example is only an illustrative example, and those skilled in the art should not be understood as a limitation of the present invention.

[0076] In one example, it was found through experiments that there was no significant difference in the catalytic activity of the iron-manganese metal catalyst obtained under the preparation conditions of Example 1 to Example 5 by changing the specific components of the oxalic acid precipitant. For example, when the sodium oxalate solution was replaced with the dihydrate oxalic acid solution in the experiment, the characterization results of the catalytic activity of the iron-manganese metal catalyst finally obtained were basically the same, except that the time for complete precipitation in the process of mixing the oxalic acid precipitant with the iron-manganese metal salt solution to produce the acidic precipitate was different, that is, the speed of precipitation was different.

[0077] Therefore, in Examples 1 to 5, the same oxalic acid precipitate is selected to be used, preferably sodium oxalate solution.

[0078] In one example, the iron-manganese metal catalysts obtained in Examples 1 to 5 were subjected to the same experimental flue gas conditions to synergistically remove NO x and VOCs The purification effect is tested. The specific test conditions are as follows:

[0079] The prepared iron-manganese metal catalyst is sieved to make its particle size reach 40-60 mesh;

[0080] Weigh an appropriate amount of sieved iron-manganese metal catalyst and fix it in a quartz tube with quartz wool and place it in an experimental fixed bed reactor;

[0081] The simulated atmosphere conditions of flue gas are: NO concentration range 400~600ppm, NH 3 Concentration range 400~600ppm, C 7 H 8 Concentration range 80~120ppm, O 2 Volume fraction range 5~15vol%, nitrogen balance, gas temperature range 100~350℃, total gas flow range 180~220mL / min, reaction space velocity range 55000~65000mL / g -1 ·h -1 The reaction space velocity refers to the amount of gas treated by a catalyst (such as the iron-manganese metal catalyst of each embodiment of the present invention) per unit volume per unit time under preset conditions (such as the simulated flue gas conditions described above).

[0082] More preferably, the NO concentration is 500 ppm, NH 3 Concentration 500ppm, C 7 H 8 Concentration 100ppm, O 2 Volume fraction 10vol%, nitrogen balance, gas temperature range for decontamination 100~350℃, total gas flow rate 200mL / min, reaction space velocity 60000mL / g -1 ·h -1 .

[0083] In one example, after the above smoke simulation atmosphere test, see Figure 2 , showing the iron-manganese metal catalyst (Fe 3 Mn 1 O x , Fe 2 Mn 1 O x , Fe 1 Mn 1 O x , Fe 1 Mn 2 O x , Fe 1 Mn 3 O x ) in the synergistic removal of NOx and VOC s The curve of NO purification efficiency in the flue gas temperature range of 100-350℃ during the process.

[0084] like Figure 2 As shown in the figure, when the flue gas temperature reaches 110°C, the iron-manganese metal catalyst that first reaches a NO purification efficiency of 90% is the Fe 1 Mn 2 O x , and when the flue gas temperature is within 200℃, the NO purification efficiency can always be maintained above 90%.

[0085] Further, from Figure 2 It can also be seen that the Fe obtained in Example 3 1 Mn 1 O x and Fe obtained in Example 5 1 Mn 3 O x All have the same Fe content as that obtained in Example 4 1 Mn 2 O x The catalytic effect curve is similar. When the flue gas temperature ranges from 110 to 200°C, the NO purification efficiency can always be maintained above 85%.

[0086] In one example, after the above smoke simulation atmosphere test, see Figure 3 , showing the iron-manganese metal catalyst (Fe 3 Mn 1 O x , Fe 2 Mn 1 O x , Fe 1 Mn 1 O x , Fe 1 Mn 2 O x , Fe 1 Mn 3 O x ) in the synergistic removal of NO x and VOC s In the process of flue gas temperature range of 100 ~ 350 ℃, C 7 H 8 The purification efficiency curve.

[0087] like Figure 3 As shown in the figure, similar to the case of NO removal, when the flue gas temperature reaches 150℃, C 7 H 8The iron-manganese metal catalyst with a purification efficiency of 90% is Fe 1 Mn 2 O x , and when the flue gas temperature is within 200℃, the C 7 H 8 The purification efficiency can always be maintained above 90%. At the same time, for Example 4, when the flue gas temperature reaches 110°C, the 7 H 8 The purification efficiency has reached 50%, and as the flue gas temperature rises to 150℃, its C 7 H 8 The growth rate of the purification efficiency is very fast, indicating that it has strong catalytic activity under low temperature conditions of 100-150°C.

[0088] Further, from Figure 3 It can also be seen that the Fe obtained in Example 3 1 Mn 1 O x and Fe obtained in Example 5 1 Mn 3 O x All have the same Fe content as that obtained in Example 4 1 Mn 2 O x The catalytic effect curve is similar. When the flue gas temperature ranges from 150 to 200°C, the NO purification efficiency can always be maintained above 85%.

[0089] Combination Figure 2 and Figure 3 Analysis shows that the ratio of manganese to iron mainly affects the redox performance and acid sites of the iron-manganese metal catalyst. Among them, manganese is the main metal ion component of the iron-manganese metal catalyst with strong oxidizing properties. Iron, as the second active metal, works together with manganese to bring two improvements. On the one hand, iron ions can increase the valence of manganese ions, so that the strong oxidizing properties of manganese ions are further improved with the increase of their ion valence; on the other hand, the addition of iron helps to form abundant acid sites on the surface of the iron-manganese metal catalyst, thereby stimulating the catalytic activity of the iron-manganese metal catalyst under low temperature conditions.

[0090] At the same time, there is a coupling relationship between the strong oxidizing property and the abundant acidic sites of the iron-manganese metal catalyst. When the coupling relationship reaches a balanced state, the optimal synergistic effect can be formed, thereby achieving the synergistic removal of NO as in Example 4. x and VOC s Therefore, in the actual synergistic removal of NO x and VOC sIn the application, it is necessary to balance the redox performance and acid sites by adjusting the ratio of iron and manganese to achieve the best synergistic removal of NO. x and VOC s purification efficiency.

[0091] According to Examples 1 to 5, the method for synergistically removing NO in flue gas provided by the present invention x and VOC s The catalyst is an iron-manganese metal catalyst, which is obtained by the preparation method of each of the above embodiments. Preferably, under the experimental flue gas conditions provided in each embodiment of the present invention, the iron-manganese metal catalyst uses the Fe obtained in Example 4. 1 Mn 2 O x .

[0092] Specifically, in the preferred iron-manganese metal catalyst, the first molar ratio is 1:2, that is, n(Fe):n(Mn)=1:2, wherein the iron oxide is Fe(SO 4 ) 2 7H 2 O, manganese oxide, MnSO 4 ·H 2 O. Oxalic acid precipitant selected Na 2 C 2 O 4 The solution has a second molar ratio of 1:1.1. Then, when the acidic precipitate obtained by the preparation methods and steps of the above embodiments is calcined under flowing air, the calcination temperature is controlled to be 300°C, the calcination time is 2 hours, and the heating rate is maintained at 1°C / min.

[0093] In order to further verify the effectiveness of the iron-manganese metal catalysts in the synergistic removal of NO in flue gas, x and VOC s To achieve the best purification effect, the conditions of the simulated flue gas atmosphere, especially the reaction space velocity, were adjusted. See the following Examples 6 and 7 for details. The iron-manganese metal catalysts used in Examples 6 and 7 are all Fe obtained from Example 4 with the best purification effect. 1 Mn 2 O x .

[0094] Example 6

[0095] First, the iron-manganese metal catalyst Fe was prepared according to Example 4. 1 Mn 2 O x .

[0096] Then the prepared Fe 1 Mn2 O x Sieve until the particle size reaches 40-60 mesh.

[0097] Finally, weigh an appropriate amount of sieved Fe 1 Mn 2 O x The simulated flue gas atmosphere conditions of Example 6 were: NO concentration 500 ppm, NH 3 Concentration 500ppm, C 7 H 8 Concentration 100ppm, O 2 Volume fraction 10vol%, nitrogen balance, gas temperature range 100~350℃, total gas flow 200mL / min, increase reaction space velocity to 120000mL / g -1 ·h -1 .

[0098] Example 7

[0099] The only difference from Example 6 is that the reaction space velocity is increased to 180000 mL / g in the simulated atmosphere of flue gas. -1 ·h -1 .

[0100] In one example, see Figure 4 , showing the reaction time of the iron-manganese metal catalyst Fe at different reaction space velocities (Example 4, Example 6 and Example 7). 1 Mn 2 O x In synergistic removal of NO x and VOC s (Specifically, to remove NO and C in the experimental flue gas 7 H 8 ) process in the flue gas temperature range of 100 ~ 350 ℃ for NO purification efficiency.

[0101] like Figure 4 As shown, when the reaction space velocity of the experimental flue gas is greatly increased, although Fe 1 Mn 2 O x The catalysis is completed, but with the increase of the reaction space velocity, the NO purification efficiency shows a downward trend as a whole, especially in the low temperature range of 100-150° C. Of course, with the increase of the flue gas temperature and the continuous catalytic reaction, in the temperature range of 150-200° C., Example 4, Example 6 and Example 7 all achieve a NO purification efficiency of 90%.

[0102] In one example, see Figure 5, showing the reaction time of the iron-manganese metal catalyst Fe at different reaction space velocities (Example 4, Example 6 and Example 7). 1 Mn 2 O x In synergistic removal of NO x and VOC s (Specifically, to remove NO and C in the experimental flue gas 7 H 8 ) in the flue gas temperature range of 100 ~ 350 ℃ 7 H 8 The purification efficiency curve.

[0103] like Figure 5 As shown in the figure, similar to the case of NO removal, with the significant increase in reaction space velocity, C 7 H 8 The overall purification efficiency shows a downward trend. 7 H 8 The active temperature range of NO removal is higher than that of NO removal. Figure 5 It can be seen that after removing C 7 H 8 In the active temperature range (e.g. 150-200°C), the faster reaction space velocity has an effect on C 7 H 8 The purification efficiency has a significant impact. For example, when the reaction space velocity is increased from 60000mL / g -1 ·h -1 Increased to 180000mL / g -1 ·h -1 Later, when the flue gas temperature is 150℃, C 7 H 8 Purification efficiency dropped from 90% to 50%.

[0104] Combination Figure 4 and Figure 5 Analysis shows that the change in the reaction space velocity of the experimental flue gas mainly affects the contact time between the flue gas and the iron-manganese metal catalyst. The increase in the reaction space velocity will shorten the contact time between the flue gas and the iron-manganese metal catalyst, thereby affecting the degree of activation of the catalytic activity, that is, the catalytic activity decreases.

[0105] At the same time, due to the synergistic removal of NO x and VOC s In the process of catalytic reaction, it is more difficult to carry out catalytic reaction under low temperature conditions than under high temperature conditions. Therefore, at low temperatures, such as 150°C, the catalytic activity decreases particularly significantly. Later, as the flue gas temperature increases, the catalytic activity can be improved to a certain extent to compensate for the insufficient catalytic activity at low temperatures.

[0106] Comprehensive analysis shows that although different reaction space velocities have little effect on the catalytic activity of the iron-manganese metal catalyst to a certain extent, increasing the reaction space velocity (such as accelerating the flue gas flow rate, etc.) itself will bring about system energy consumption, resulting in unnecessary power consumption and energy waste. Therefore, those skilled in the art can understand that the reaction space velocity of the flue gas can be controlled within an optimal range according to the actual application conditions of the iron-manganese metal catalyst, which can not only meet the full contact between the iron-manganese metal catalyst and the flue gas but also control the system energy consumption. This example only provides some illustrative examples, and those skilled in the art should not be understood as a limitation of the present invention.

[0107] In order to further verify the role of the oxalic acid precipitant in providing sufficient acid sites in the preparation of the iron-manganese metal catalysts of each embodiment of the present invention, a comparative experiment was also conducted using a common alkaline precipitant. 1 Mn 2 Ox is used as the iron-manganese metal catalyst in the control group. Meanwhile, except for using an alkaline precipitant, the other preparation steps and processes of the comparative example are consistent with those of Examples 1 to 5. The following is a detailed description of Comparative Example 1 and Comparative Example 2.

[0108] Comparative Example 1

[0109] In Comparative Example 1, the first molar ratio is 1:2, and the iron oxide is Fe(SO 4 ) 2 7H 2 O, manganese oxide, MnSO 4 ·H 2 O. Then, an alkaline precipitant is selected, and the alkaline precipitant is a NaOH solution with a concentration of 1 mol / L. For the convenience of comparative analysis and description, the molecular formula of the iron-manganese metal catalyst obtained in Comparative Example 1 is recorded as Fe 1 Mn 2 O x -N. Then prepare Fe 1 Mn 2 O x The specific steps of -N are as follows:

[0110] Step S103: Weigh Fe(SO 4 ) 2 7H 2 O and MnSO 4 ·H 2 O and add ultrapure water to dissolve, and after stirring at room temperature for 30 minutes, an iron-manganese metal salt solution is obtained.

[0111] Step S203: prepare 1 mol / L NaOH solution as an alkaline precipitant.

[0112] Step S303: Under vigorous stirring, slowly add 1 mol / L NaOH solution to the iron-manganese metal salt solution until the pH value of the mixed solution reaches 10, and continue stirring at room temperature for 2 hours, so that the iron ions and manganese ions are completely precipitated to obtain an alkaline precipitate.

[0113] Step S403: The alkaline precipitate is washed with ultrapure water and anhydrous ethanol and filtered until the pH value of the filtrate reaches 7, and then the alkaline precipitate is placed in an electric blast drying oven for drying at a temperature of 60°C for 12 hours; finally, the alkaline precipitate is placed in a tubular furnace for calcination under flowing air at a temperature of 300°C for 2 hours, and the heating rate is maintained at 1°C / min.

[0114] After calcination, the iron-manganese metal catalyst Fe 1 Mn 2 O x -N.

[0115] Comparative Example 2

[0116] The only difference between Comparative Example 2 and Comparative Example 1 is the alkaline precipitant selected. Specifically, in Comparative Example 2, 25 wt% of ammonia water is added. In order to facilitate comparative analysis and description, the molecular formula of the iron-manganese metal catalyst obtained in Comparative Example 2 is recorded as Fe 1 Mn 2 O x -A.

[0117] Corresponding to step S303 of comparative example 1, when ammonia water is added to the iron-manganese metal salt solution of comparative example 2, the specific operation process is: under vigorous stirring, slowly dropwise add ammonia water with a mass fraction of 25wt% to the iron-manganese metal salt solution until the pH value of the mixed solution reaches 10, continue stirring at room temperature for 2 hours, and the iron ions and manganese ions are completely precipitated to obtain an alkaline precipitate. The remaining steps and processes are consistent with comparative example 1 and are not repeated here.

[0118] In one example, the iron-manganese metal catalysts obtained in Example 4, Comparative Example 1 and Comparative Example 2 were subjected to the same experimental flue gas conditions to synergistically remove NO x and VOC s The purification effect was tested. The experimental parameters used in the above-mentioned experimental parameters for obtaining the best purification efficiency and purification effect in Examples 1 to 5 are as follows:

[0119] The prepared iron-manganese metal catalyst is sieved to make its particle size reach 40-60 mesh;

[0120] Weigh an appropriate amount of sieved iron-manganese metal catalyst and fix it in a quartz tube with quartz wool and place it in an experimental fixed bed reactor;

[0121] The simulated atmosphere conditions of the flue gas are: NO concentration 500ppm, NH 3 Concentration 500ppm, C 7 H 8 Concentration 100ppm, O 2 Volume fraction 10vol%, nitrogen balance, gas temperature range for decontamination 100~350℃, total gas flow rate 200mL / min, reaction space velocity 60000mL / g -1 ·h -1 .

[0122] In one example, after the above smoke simulation atmosphere test, see Figure 6 , showing the iron-manganese metal catalyst (Fe 1 Mn 2 O x , Fe 1 Mn 2 O x -N, Fe 1 Mn 2 O x -A) Synergistic removal of NO x and VOC s In the process (i.e., synergistic removal of NO and C in the experimental flue gas) 7 H 8 ) is the curve of NO purification efficiency in the flue gas temperature range of 100 to 350°C.

[0123] like Figure 6 As shown in Figure 2, the catalytic activity of using oxalic acid precipitant is significantly better than that of using alkaline precipitant. When the flue gas temperature is between 100 and 125 °C, Fe 1 Mn 2 O x The purification efficiency of NO has reached or even exceeded 90%, showing very high low-temperature catalytic activity. 1 Mn 2 O x -N and Fe 1 Mn 2 O x -A purification efficiency of NO is less than 50%. When the flue gas temperature exceeds 175℃, Fe 1 Mn 2 O x -N can achieve a purification efficiency of 90% for NO, while Fe 1 Mn 2 O x-A requires the flue gas temperature to exceed 230°C to achieve a NOx purification efficiency of 90%.

[0124] Further, from Figure 6 It can also be analyzed that the high purification efficiency at low temperature is produced by the strong oxidizing property of iron-manganese metal ions and the large number of acid sites provided by the acidic precipitant. When the acidic precipitate is obtained using the acidic precipitant and calcined, under suitable calcination temperature parameters (for example, the preferred calcination temperature of 300°C in each embodiment, the calcination heating rate is controlled at 1°C / min, and calcined for 2 hours), the oxalic acid precipitant, such as sodium oxalate, interacts with the iron-manganese metal salt to produce a mixture with very low crystallinity, which is in a non-crystalline state or a microcrystalline state. This low crystallinity structure allows the specific surface area of ​​the iron-manganese metal catalyst after calcination to be increased to a large extent.

[0125] At the same time, during the calcination process, the oxalic acid precipitant (such as sodium oxalate) will undergo a pyrolysis reaction, and the pyrolysis process will produce a large number of defects on the surface of the acidic precipitate and the iron-manganese metal catalyst finally formed, thereby exposing abundant acid sites. The acid sites work together with the strong oxidizing properties of the iron-manganese metal ions themselves to stimulate the catalytic activity of the iron-manganese metal catalyst in a low temperature range, thereby obtaining a very high NO conversion rate in a low temperature range and achieving a very high NO purification efficiency.

[0126] In one example, after the above smoke simulation atmosphere test, see Figure 7 , showing the iron-manganese metal catalyst (Fe 1 Mn 2 O x , Fe 1 Mn 2 O x -N, Fe 1 Mn 2 O x -A) Synergistic removal of NO x and VOC s In the process (i.e., synergistic removal of NO and C in the experimental flue gas) 7 H 8 ) In the flue gas temperature range of 100 ~ 350 ℃, C 7 H 8 The purification efficiency curve.

[0127] like Figure 7 As shown in Figure 2, the catalytic activity of using oxalic acid precipitant is significantly better than that of using alkaline precipitant. When the flue gas temperature is 150℃, Fe 1 Mn 2 O x C 7 H 8The purification efficiency has reached or even exceeded 90%, and its catalytic reaction is very active in the early stage at a lower temperature (100-150°C), which is reflected in its 7 H 8 The purification efficiency of Fe 1 Mn 2 O x -N and Fe 1 Mn 2 O x -A vs. C 7 H 8 The purification efficiency is less than 20%, and it is always in a catalytically inactive state within a relatively large low temperature range (100-250°C). When the flue gas temperature exceeds 250°C, Fe 1 Mn 2 O x -N and Fe 1 Mn 2 O x The catalytic reaction of -A begins to become active gradually until the flue gas temperature exceeds 300℃. 7 H 8 The purification efficiency can be close to 90%.

[0128] Furthermore, combined with Figure 6 and Figure 7 It can also be analyzed that the use of oxalic acid precipitant can reduce the C 7 H 8 The improvement in purification efficiency is particularly significant, indicating that the use of acidic precipitants to prepare iron-manganese metal catalysts in low-temperature flue gas can effectively improve the synergistic removal of NO x and VOC s purification effect.

[0129] At the same time, the iron-manganese metal catalyst prepared by using an acidic precipitant has a positive effect on NO x and VOC s The removal principle is the same, for example, the principle of improved catalytic activity generated by the balance between acidic sites and strong oxidizing properties is the same. Especially for the removal of VOC s Compared with the catalyst obtained by using alkaline precipitant or other commonly used metal doping methods, the iron-manganese metal catalyst has better low-temperature catalytic activity, that is, when it enters the flue gas for catalytic reaction, the reaction temperature, especially the reaction temperature range with high catalytic activity, is advanced, that is, the effective reaction temperature is reduced.

[0130] In one example, the catalytic properties of the iron-manganese metal catalysts of Example 4, Comparative Example 1 and Comparative Example 2 can be further characterized by means of a detection device. Figure 8 , Fig. 9 and Fig.10 , respectively show the NH 3 Desorption curve (NH 3 -TPD), X-ray photoelectron spectrum of O1s (O1s-XPS) and X-ray photoelectron spectrum of Mn2p (Mn2p-XPS) obtained by photoelectron spectrometer.

[0131] like Figure 8 As shown, by comparing the Fe 1 Mn 2 O x , Fe 1 Mn 2 O x -N and Fe 1 Mn 2 O x -NH of A 3 The desorption amount shows that the Fe 1 Mn 2 O x With the highest NH 3 The desorption amount is significantly higher than that of Fe obtained by using alkaline precipitants. 1 Mn 2 O x -N and Fe 1 Mn 2 O x -NH of A 3 Although the redox performance, specific surface area, and pore structure of Fe-Mn metal catalysts are also key factors affecting their catalytic activity, the acidic sites are the main factors affecting NO x and VOC s An essential active site in the synergistic removal process that can effectively activate NO x and VOC s , thereby promoting NO x and VOC s Catalytic oxidation reaction. 3 The desorption amount can also verify this point well, NH 3 The more desorption, the stronger the acidity or the more acid sites. Figure 8 As shown in the figure, the peak before 300°C can be attributed to the acidic sites of Lewis acid (Lewis acid is an ion, ion group, molecule or molecular group that is more likely to accept electron pairs). This Lewis acidic site has a better effect of promoting catalytic activity at low temperatures. 1 Mn 2 O x NH4+ appeared at around 150℃ 3The desorption peak indicates that the use of acidic precipitant is more conducive to the iron-manganese metal catalyst to exhibit stronger catalytic activity at low temperature.

[0132] like Fig. 9 As shown, Fe 1 Mn 2 O x O β The content of (i.e. chemically adsorbed oxygen) is 46.70%, much higher than that of Fe 1 Mn 2 O x -N and Fe 1 Mn 2 O x -A of O β Usually, chemisorbed oxygen is adsorbed on oxygen vacancies, so more chemisorbed oxygen proves that Fe 1 Mn 2 O x There are high content of oxygen vacancies on the surface, which makes it have strong redox properties.

[0133] Furthermore, the formation of oxygen vacancies is mainly related to the precipitation pathway, where oxalate precipitation produces oxalic acid compounds, which, upon further calcination, will adsorb water and pyrolyzed CO on the surface. 2 The surface of the acidic precipitate is separated, resulting in more surface defects and pore structures. Oxygen vacancies are a type of surface defect and are formed in this process. In contrast, when an alkaline precipitate is used, a hydroxide precipitate is produced. During calcination, the alkaline precipitate will only pyrolyze to produce water, so very few surface defects can be produced, and the quality change is also smaller, that is, no obvious pore structure or surface defects that are beneficial to catalysis will be produced.

[0134] like Fig.10 As shown, Fe 1 Mn 2 O x High valence Mn 4+ The content is higher than Fe 1 Mn 2 O x -N and Fe 1 Mn 2 O x -A high valence Mn 4+ The use of acidic precipitants makes the strong interaction between iron and manganese more active, thereby increasing the valence of manganese and producing more Mn 4+ When the single manganese metal catalyst or the mixed metal manganese catalyst has more Mn 4+ When NO is oxidized to NO 2The process promotes the selective catalytic reduction reaction (SCR), thereby improving the NO purification efficiency and achieving efficient removal of NO x At the same time, Mn 4+ It is also beneficial to VOC s mineralization, promoting VOC s Completely decomposed into CO 2 .

[0135] In one example, see Fig.11 , shows the X-ray diffraction patterns (XRD) of the iron-manganese metal catalysts of Examples 1 to 5 and Comparative Examples 1 and 2 obtained by means of detection equipment such as an X-ray diffractometer.

[0136] like Fig.11 As shown, compared with the alkaline precipitants such as the traditional sodium hydroxide precipitant and the ammonia precipitant, the iron-manganese metal catalyst prepared using the acidic precipitant such as sodium oxalate exhibits a lower crystallinity. In the XRD diffraction pattern, no obvious characteristic peaks of iron and manganese oxides were observed for Examples 1-5, and only two wider non-crystalline peaks were shown. The advantage of amorphous or microcrystalline materials compared to higher crystalline materials is that low crystallinity is conducive to the exposure of active sites and defect sites inside the material. Therefore, it is conducive to the formation of more oxygen vacancies and acidic sites on the surface of the iron-manganese metal catalyst.

[0137] Furthermore, there are two main reasons why the iron-manganese metal catalyst obtained by the acidic precipitant has a lower crystallinity. On the one hand, the metal ions are converted into oxalic acid compounds using oxalate ions. During the subsequent calcination, the oxalic acid compounds will experience two stages of weight loss, which correspond to the removal of surface adsorbed water and the pyrolysis of oxalic acid compounds into oxides. At the same time, the mass change of oxalic acid compounds during the entire calcination process exceeds 50%, and the removal of adsorbed water and the CO generated during pyrolysis are 2 When the catalyst is separated from the surface of the iron-manganese metal catalyst, the crystallization of the iron-manganese metal catalyst is affected, and the mesoporous structure is more conducive to the formation. On the other hand, the calcination temperature parameter is controlled and adjusted. Generally, the higher the calcination temperature, the easier it is to crystallize. Therefore, in Examples 1 to 5, the calcination temperature is reduced to 300° C. or within a controllable calcination temperature range of, for example, 250 to 350° C., so that the formation of the crystal phase of the iron-manganese metal catalyst can be effectively controlled.

[0138] In addition, it can be seen from the XRD diffraction pattern that the effect of adjusting the ratio of iron to manganese on the crystallinity of the final iron-manganese metal catalyst is not obvious. However, when sodium hydroxide and ammonia water are used as precipitants, the crystallinity of the iron-manganese metal catalyst obtained by calcining at the same temperature (e.g., 300° C.) is significantly higher than that of Examples 1 to 5, further indicating that the improvement in crystallinity mainly comes from the influence of the precipitant.

[0139] The embodiments of the present invention provide a synergistic removal of NO x and VOC s The iron-manganese metal catalyst and its preparation method and use have at least one of the following advantages or part of at least one advantage:

[0140] (1) Synergistic removal of NO provided by embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application increase the valence state of manganese ions by doping the second active metal iron in manganese oxide, further improving the strong oxidizing property of the manganese-based catalyst and achieving NO x and VOC s The collaborative removal of

[0141] (2) Synergistic removal of NO provided by embodiments of the present invention x and VOC s The iron-manganese metal catalyst with the best iron-manganese ratio screened out can achieve more than 90% NO in the low temperature range of 100-200°C. x and VOC s Synergistic removal and purification efficiency, showing extremely strong low-temperature pollutant removal performance and significantly better than most similar catalysts;

[0142] (3) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application are obtained in an amorphous or microcrystalline state, and its crystallinity is low, which helps to expose a large number of oxygen vacancies and acid sites on the surface of the iron-manganese metal catalyst, thereby obtaining a high degree of strong acidity and strong redox performance;

[0143] (4) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application use common cheap metal iron and metal manganese, have low cost, high low-temperature purification efficiency, and have prospects for industrial application;

[0144] (5) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application obtain an acidic precipitate by using an oxalic acid precipitant, and a sufficient mesoporous structure is formed by pyrolysis during calcination, which is conducive to the formation of abundant oxygen vacancies and acidic sites on the surface of the iron-manganese metal catalyst. Compared with the alkaline precipitant, it is more effective in synergistically removing NO x and VOC s It has higher catalytic activity;

[0145] (6) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application. The acid sites formed by calcining the acidic precipitate can promote the strong oxidizing property of the iron-manganese metal catalyst, so that it has a high catalytic activity in a low temperature range to obtain a high purification efficiency;

[0146] (7) Synergistic removal of NO provided by the embodiments of the present invention x and VOC s The iron-manganese metal catalyst and its preparation method and application have simple preparation steps and processes, especially using common sodium oxalate as a precipitant to obtain an iron-manganese catalyst with high catalytic activity after washing, drying and calcination, thereby reducing the process and manufacturing costs.

[0147] Although some embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made to these embodiments without departing from the principles and spirit of the present general inventive concept, the scope of which is defined by the claims and their equivalents.

Claims

1. A synergistic removal of NO x and VOC s The preparation method of the iron-manganese metal catalyst is characterized in that the preparation method comprises: preparing an iron-manganese metal salt solution with a first molar ratio of iron ions to manganese ions, wherein the first molar ratio includes 3:1, 2:1, 1:1, 1:2 and 1:3; The oxalic acid precipitant is prepared with a second molar ratio of iron and manganese metal cations to oxalate, wherein the second molar ratio is in the range of 1: 1.05～1：1.25； adding the oxalic acid precipitant to the iron-manganese metal salt solution and stirring until the iron ions and manganese ions are precipitated to obtain an acidic precipitate, wherein the acidic precipitate is an oxalic acid compound; The acidic precipitate is washed and filtered and then calcined at a temperature ranging from 250 to 350° C.; After calcination, the adsorbed water on the surface of the acidic precipitate is removed and the oxalic acid compound is thermally decomposed into oxides, thereby obtaining an iron-manganese metal catalyst with oxygen vacancies and acidic sites and high low-temperature catalytic activity.

2. The preparation method according to claim 1, characterized in that: Fe(SO4)2·7H2O and MnSO4·H2O are weighed in the first molar ratio, added into ultrapure water to dissolve, and stirred at room temperature to obtain an iron-manganese metal salt solution, and the stirring time ranges from 10 to 60 minutes.

3. The preparation method according to claim 1, characterized in that: The oxalic acid precipitant is oxalic acid solution, dihydrate oxalic acid solution or sodium oxalate solution; Oxalic acid, oxalic acid dihydrate or sodium oxalate is weighed in the second molar ratio, added into ultrapure water to dissolve, and stirred at room temperature to obtain an oxalic acid precipitant, and the stirring time ranges from 10 to 60 minutes.

4. The preparation method according to claim 1, characterized in that: The acidic precipitate is washed and filtered using ultrapure water and anhydrous ethanol, so that the pH value of the filtrate of the acidic precipitate reaches a range of 6.5 to 7.

5.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The acidic precipitate is placed in a drying oven for drying at a temperature of 50 to 70° C. and a drying time of 10 to 15 hours; The dried acidic precipitate is placed in a tube furnace and calcined under flowing air. The calcination temperature is 300° C., the calcination time ranges from 1.5 to 4.5 hours, and the calcination heating rate ranges from 1 to 3° C. / min.

6. The preparation method according to claim 5, characterized in that: During the calcination process, the carbon dioxide generated by the pyrolysis of the acidic precipitate is separated from the surface to form a mesoporous structure, which increases the oxygen vacancies and acid sites on the surface of the iron-manganese metal catalyst. The acidic precipitate after calcination is in an amorphous or microcrystalline state, and the decrease in crystallinity increases the specific surface area of ​​the iron-manganese metal catalyst.

7. The preparation method according to claim 6, characterized in that: The iron ions in the iron-manganese metal catalyst increase the valence of the manganese ions to obtain strong oxidizing properties; The increased acid sites on the surface of the iron-manganese metal catalyst and the strong oxidizing property work together to obtain a catalyst having the synergistic effect of removing NO in flue gas in a low temperature range. x and VOC s The purification efficiency is greater than or equal to 90% of the catalytic activity, and the low temperature range is 100 to 200°C.

8. An iron-manganese metal catalyst obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The iron-manganese metal catalyst is a metal oxalate compound having acid sites and oxygen vacancies for enhancing catalytic activity under low temperature conditions; The iron-manganese metal catalyst can synergistically remove NO in flue gas at a low temperature range of 100-200°C. x and VOC s The purification efficiency reaches 90%.

9. An iron-manganese metal catalyst according to claim 8 for synergistically removing NO from flue gas x and VOC s application.

10. The use according to claim 9, characterized in that: The parameters of the flue gas simulation atmosphere are NO concentration range 400 ~ 600ppm, NH3 concentration range 400 ~ 600ppm, C7H8 concentration range 80 ~ 120ppm, O2 volume fraction range 5 ~ 15vol%, nitrogen balance and the temperature range of the gas to be decontaminated is 100 ~ 350℃, the total gas flow range is 180 ~ 220mL / min, and the reaction space velocity range is 55000 ~ 65000mL / g -1 ·h -1 Under the test conditions, When the temperature of the gas to be decontaminated is 110°C, the purification efficiency of the iron-manganese metal catalyst for NO reaches 90%; When the temperature of the gas to be decontaminated is 150° C., the purification efficiency of the iron-manganese metal catalyst for C7H8 reaches 90%.

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