A manganese-based catalyst for simultaneous removal of nitrogen oxides and ethylene, and a preparation method and application thereof

Abstract

The application discloses a manganese-based catalyst for simultaneously removing nitrogen oxides and ethylene as well as a preparation method and application thereof. x As the base, another metal element is one of Cu, Fe, Co, Ce, Cr, V and W. The ethylene removal rate of the catalyst is greatly improved mainly through the interaction of Mn and other metals (Ce, Co, Cu, Fe, Cr, V and W), the catalyst can realize the synergistic control of 50-100 ppm of ethylene and 500-1000 ppm of nitrogen oxides at 240 DEG C, the effect is better than that of a traditional V-W-Ti denitration catalyst, and the catalyst is mainly used for simultaneously treating a series of nitrogen oxides and VOCs atmospheric pollutants mainly containing ethylene in coke oven flue gas and the like.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control technology, specifically relating to a manganese-based catalyst that efficiently removes nitrogen oxides and ethylene simultaneously in a medium-low temperature range, its preparation method, and its application. Background Technology

[0002] Nitrogen oxides (NOx) are currently the main air pollutant and are considered a major contributor to the greenhouse effect, ozone, smog, photochemical smog, and acid rain. Selective catalytic reduction (SCR) of NOx using NH3 is a method that addresses this issue. x This is the most widely used denitrification technology in industry. In this method, NH3 is used as a reducing agent, and NO is reduced under the action of a catalyst. x The nitrogen oxides are converted into environmentally harmless N2 and H2O. However, in actual flue gas production, the conditions are complex, with multiple pollutants coexisting. How to simultaneously remove nitrogen oxides and other volatile organic compounds (VOCs) from complex flue gas is a worthwhile research topic. For example, flue gas from coking, waste incineration, and steel sintering contains nitrogen oxides, dioxins, and VOCs, which not only affect the SCR catalytic activity but also pose toxic risks to the environment and humans. Volatile organic compounds (VOCs) such as benzene, toluene, and styrene not only threaten human health but also react with NO... x SO x Reactions with ammonia and other substances produce harmful substances such as ozone, secondary aerosols, photochemical smog, and greenhouse gases. Currently, there are many VOCs purification technologies available, and catalytic oxidation has proven to be a highly efficient and thorough VOCs purification technology. Its principle is to oxidize VOCs into pollution-free CO2 and H2O. Based on the principle of catalysis, developing catalytic systems that simultaneously remove nitrogen oxides and characteristic volatile organic compounds in the control of multiple pollutants in flue gas has become a research hotspot.

[0003] In recent years, many local standards for coke oven flue gas pollutants have proposed control targets for non-methane total hydrocarbons. In 2021, Shanxi Province issued the "Implementation Plan for Ultra-Low Emission Transformation of the Coking Industry in Shanxi Province," which requires that non-methane total hydrocarbons in coke oven flue gas be controlled at 60 mg / m³. 3 The Ministry of Ecology and Environment's draft for public comment on ultra-low emissions from coke ovens also proposes a non-methane total hydrocarbon limit of 100 mg / m³. 3In the field of simultaneous removal of nitrogen oxides and VOCs, the development of catalysts for removing VOCs mainly focuses on toluene and chlorobenzene. For example, patent CN112755991 discloses a preparation method of a catalyst for simultaneous removal of nitrogen oxides and VOCs, which is mainly aimed at flue gas from coal-fired power plants, and the main component of VOCs is toluene. Patent CN114308088 develops a catalyst for simultaneous removal of nitrogen oxides and Cl-VOCs, and patent CN113731417 develops a catalyst for simultaneous degradation of propylene and nitrogen oxides using olefins as reducing agents, but the catalytic efficiency cannot be applied to the field of low-temperature denitrification. According to the literature (Wang R, Wang X, Cheng S, et al. Science of The Total Environment. 2022, 809: 151134.)(Wang J, Li X, Wang B, et al. Environmental Pollution. 2022, 308: 119648.), the content of ethylene in coke oven flue gas accounts for more than half of the total VOCs, and the flue gas temperature is relatively low. At present, the mainstream flue gas treatment process in the coking industry is desulfurization → dust removal → denitrification. The temperature for desulfurization is generally 160-240°C for best results, and the temperature for denitrification is generally below 300°C, mostly in the range of 160-280°C. Therefore, compared with traditional V-W-Ti catalysts (active temperature window of 300-400°C, and V2O5 has strong biological toxicity), medium and low temperature catalysts have greater activity and low toxicity advantages. Therefore, the development of a non-V-based catalyst for simultaneous removal of nitrogen oxides and ethylene in medium and low temperature flue gas will have broad application prospects. The present invention develops a medium and low temperature modified Mn-based catalyst that can simultaneously remove ethylene and nitrogen oxides in flue gas in the range of 180-300°C. SUMMARY

[0004] In view of the shortcomings and deficiencies of the prior art, the primary purpose of the present invention is to develop a catalyst for simultaneous catalytic degradation of nitrogen oxides and ethylene at medium and low temperatures (180-300°C).

[0005] Another purpose of the present invention is to provide a manganese-based catalyst (MnO x -AO y for simultaneous removal of nitrogen oxides and ethylene prepared by the above method.

[0006] Still another purpose of the present invention is to provide a MnO x -AO y catalyst prepared by the above method for simultaneous removal of nitrogen oxides and ethylene.

[0007] To solve the existing problems, the technical solution adopted by the present invention is as follows:

[0008] A manganese-based catalyst for simultaneous removal of nitrogen oxides and ethylene, the catalyst is MnO x -AO y (x is 0.5-1, y is 1-x), wherein the MnO x is a base, and A represents another metal element, specifically one of Cu, Fe, Co, Ce, Cr, V, and W. The metal element A has a strong metal interaction with Mn to achieve the synergistic control of nitrogen oxides and ethylene.

[0009] The activity temperature range of the catalyst is 180-300℃.

[0010] A preparation method of a manganese-based catalyst for simultaneous removal of nitrogen oxides and ethylene, comprising the following steps:

[0011] (1) A certain amount of manganese salt and metal salt solid powder is weighed;

[0012] (2) The two metal salts are mixed and ground at room temperature;

[0013] (3) The mixture is dried at a certain temperature;

[0014] (4) MnO x -AO y Catalyst (x is 0.5-1, y is 1-x).

[0015] Further, the manganese salt in step (1) is at least one of manganese acetate, manganese chloride, manganese sulfate, and manganese nitrate.

[0016] Further, the metal salt in step (1) is at least one of a chloride salt, a sulfate salt, an ammonium salt, and a nitrate salt, wherein the metal element is one of Cu, Fe, Co, Ce, Cr, V, and W.

[0017] Further, the amount-of-substance ratio of the manganese salt and the metal salt in step (1) is (0.5-1):(1-x), and x is 0.5-1.

[0018] Further, the grinding time in step (2) is 5-60 min, preferably 15-60 min.

[0019] Further, the drying temperature in step (3) is set to 60-120℃, preferably 105℃; and the drying time is 6-12h.

[0020] Further, the calcination in step (4) refers to calcination at 200-800℃ for 2-6h.

[0021] The present application develops a manganese-based catalyst with strong metal interaction for VOCs and NOx Collaborative removal.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The preparation method is simple, and for the first time, ethylene gas can be controlled simultaneously in a temperature range with a conversion rate of more than 90% of nitrogen oxides by strong interaction between Mn and other metal elements; synergistic control of nitrogen oxides and ethylene is achieved, and good stability is maintained. Attached Figure Description

[0024] Figure 1 These are ethylene conversion graphs for Examples 1, 2, 3, 4, 5, 6, 7, and 8 of the present invention, and Comparative Example 1.

[0025] Figure 2 This is an activity diagram of ethylene conversion rate in Example 1 of the present invention, where the gases include SCR reaction gas (in use) and ethylene.

[0026] Figure 3 It is NO in Embodiment 1 of the present invention. x The conversion activity graph shows the gases being SCR reaction gas and ethylene (when in use).

[0027] Figure 4 NO is from Examples 1, 9, 10, 11, and 12. x The conversion rate diagram shows that the gases include SCR reaction gas and ethylene.

[0028] Figure 5 The graphs show the ethylene conversion rates for Examples 1, 9, 10, 11, and 12, where the gases include SCR reaction gas and ethylene.

[0029] Figure 6 It is NO in Examples 10, 13, and 14 x The conversion rate diagram shows that the gases include SCR reaction gas and ethylene.

[0030] Figure 7 The graphs show the ethylene conversion rates for Examples 10, 13, and 14, with the gases being SCR reaction gas and ethylene. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0032] The catalyst used in the following examples has a particle size of 40-60 mesh for activity evaluation, and the efficiency of the catalyst for the synergistic removal of ethylene and NO is tested at a temperature of 180-300°C. The test conditions are: the ethylene concentration is 50 ppm, the catalyst dosage is 0.8 g, the stabilization time is 40 min, the reaction flow rate is 400 ml / min, the space velocity is 60,000 ml / (g h), the reaction atmosphere is simulated coke oven flue gas, the NO concentration is 500 ppm, the NH3 concentration is 500 ppm, the O2 concentration is 5 vol%, and N2 is the balance gas; the concentrations of NO and NO2 are measured online by a flue gas analyzer (FGA10). The concentration of ethylene is detected by a gas chromatograph (Agilent 6890N gas chromatograph equipped with a thermal conductivity detector (TCD) and a hydrogen flame detector (FID)). As a control, we tested the ethylene removal performance of a conventional V-W-Ti catalyst, and the stability test was carried out at 245°C, with SCR gas and ethylene gas as the reaction gas.

[0033] Example 1

[0034] A strong metal interaction MnO x The preparation method of the strong metal interaction MnO-CuO composite catalyst is as follows:

[0035] (1) Take 0.05 mol of manganese acetate and 0.05 mol of copper nitrate mixture (molar ratio of 1:1) by mass, denoted as mixture A;

[0036] (2) Put A into a maroon mortar and grind for 30 min to fully mix the manganese acetate and copper nitrate;

[0037] (3) Dry the mixture at 105°C for 12 h;

[0038] (4) After drying the sample, calcine it at 500°C for 3 h to obtain MnO-CuO 0.5 -CuO 0.5 catalyst.

[0039] Example 2

[0040] This example is basically the same as Example 1, except that in this example, the copper nitrate in step (1) is replaced by iron nitrate.

[0041] Example 3

[0042] This example is basically the same as Example 1, except that in this example, the copper nitrate in step (1) is replaced by cobalt nitrate.

[0043] Example 4

[0044] This example is basically the same as Example 1, except that in this example, the copper nitrate in step (1) is replaced by chromium nitrate.

[0045] Example 5

[0046] This example is basically the same as Example 1, except that in this example, the copper nitrate in step (1) is replaced by cerium nitrate.

[0047] Example 6

[0048] This example is basically the same as Example 1, except that in this example, the copper nitrate in step (1) is replaced by ammonium metavanadate.

[0049] Example 7

[0050] This example is basically the same as Example 1, except that in this example, the copper nitrate in step (1) is replaced by ammonium metatungstate.

[0051] Example 8

[0052] This example is basically the same as Example 1, except that in this example, the copper nitrate in step (1) is not added.

[0053] Example 9

[0054] This example is basically the same as Example 1, except that in this example, the molar ratio of manganese acetate to copper nitrate in step (1) is 6:4.

[0055] Example 10

[0056] This example is basically the same as Example 1, except that in this example, the molar ratio of manganese acetate to copper nitrate in step (1) is 7:3.

[0057] Example 11

[0058] This example is basically the same as Example 1, except that in this example, the molar ratio of manganese acetate to copper nitrate in step (1) is 8:2.

[0059] Example 12

[0060] This example is basically the same as Example 1, except that in this example, the molar ratio of manganese acetate to copper nitrate in step (1) is 9:1.

[0061] Example 13

[0062] This example is basically the same as Example 10, except that the calcination temperature is set to 400 degrees Celsius.

[0063] Example 14

[0064] This example is basically the same as Example 10, except that the calcination temperature is set to 600 degrees Celsius.

[0065] Comparative Example 1

[0066] The present comparative example is a commercial V-W-Ti catalyst, 0.53wt% V2O5 and 7.7wt.% WO3 are loaded on TiO2 by impregnation method, the specific implementation method is as follows: a certain amount of ammonium metatungstate [(NH4) 10 H2(W2O7)6] and ammonium metavanadate (NH4VO3) are added to oxalic acid solution, ultrasonic for half an hour, magnetic stirring for 1 hour to make it completely dissolved, titanium dioxide (P25) is added to the precursor solution, ultrasonic for half an hour, to make it uniform impregnation, stand for 2h, put into the air drying oven at 120℃ for 12h, finally in the muffle furnace at 500℃ for 2h.

[0067] Experimental Example 1

[0068] In order to explore the promotion of strong metal interaction on ethylene oxidation performance, the catalysts prepared by examples 1, 2, 3, 4, 5, 6, 7, 8 and comparative example 1 are selected, the catalytic oxidation process between different metals and MnO x -AO y The specific experiment is as follows: under the conditions of 50ppm ethylene, 5% oxygen, nitrogen balance, total flow rate of 400ml / min, catalyst dosage of 0.4g, space velocity of 60000ml / (gh), the catalytic effect of single metal and double metal on ethylene is tested, and the oxidation effect of V-W-Ti catalyst on ethylene is also tested. The results show that MnO x -CuO can oxidize ethylene through strong metal interaction between Mn and Cu, which is much better than MnO x , and other metals, and the commercial V-W-Ti catalyst.

[0069] Experimental Example 2

[0070] In order to explore the influence of SCR gas (ammonia and nitric oxide) on ethylene oxidation on Mn-Cu catalyst, the experiment is carried out under the conditions of 50ppm ethylene, 500ppm NO concentration (when used), 500ppm NH3 (when used), 5% oxygen, nitrogen balance, the total flow rate is set to 400ml / min, the catalyst dosage is 0.4g, the space velocity is 60000ml / (gh), the influence of SCR gas on ethylene oxidation is tested, the results show that the SCR gas has a certain inhibitory effect on ethylene oxidation on the catalyst of example 1.

[0071] Experimental Example 3

[0072] In order to explore the influence of ethylene on the activity of SCR reaction, the influence of ethylene on the activity of SCR reaction was tested under the conditions of 50 ppm ethylene (when used), 500 ppm NO concentration, 500 ppm NH3, 5% oxygen, nitrogen balance, total flow rate of 400 ml / min, catalyst dosage of 0.4 g, and space velocity of 60000 mL / (g h), and the results showed that the denitration reaction on the catalyst of example 1 had good resistance to ethylene, and the catalyst could be used for simultaneous removal of ethylene and nitrogen oxides.

[0073] Experimental example 4

[0074] In order to explore the influence of different metal ratios on the synergistic catalysis, the catalysts prepared in examples 1, 9, 10, 11 and 12 were selected, and the conversion rates of NO x in the synergistic reaction of the catalysts with different ratios were compared, and the specific experiment was as follows: under the atmosphere of 50 ppm ethylene, 500 ppm NO, 500 ppm NH3, 5% oxygen, and nitrogen balance, the total flow rate was set to 400 ml / min, the catalyst dosage was 0.4 g, and the space velocity was 60000 ml / (g h), and the SCR denitration performance was tested, and the results showed that the denitration activity of example 10 was the best.

[0075] Experimental example 5

[0076] In order to explore the influence of different metal ratios on the synergistic catalysis, the catalysts prepared in examples 1, 9, 10, 11 and 12 were selected, and the conversion rates of NO x in the synergistic reaction of the catalysts with different ratios were compared, and the specific experiment was as follows: under the atmosphere of 50 ppm ethylene, 500 ppm NO, 500 ppm NH3, 5% oxygen, and nitrogen balance, the total flow rate was set to 400 ml / min, the catalyst dosage was 0.4 g, and the space velocity was 60000 ml / (g h), and the ethylene oxidation performance was tested, and the results showed that the oxidation activity of ethylene in example 10 was the best, and according to the data of experimental example 4, it was found that the metal ratio in example 10 had the best denitration performance and ethylene oxidation performance, and could remove ethylene and nitrogen oxides in the same activity temperature window.

[0077] Experimental example 6

[0078] In order to explore the influence of different calcination temperatures on the synergistic catalysis, the catalysts prepared in examples 10, 13 and 14 were selected, and the conversion rates of NO xThe conversion rate of SCR and the conversion rate of ethylene were compared in the following experiments: Under an atmosphere of 50 ppm ethylene, 500 ppm NO, 500 ppm NH3, 5% oxygen, and nitrogen balance, the total flow rate was set to 400 ml / min, the catalyst dosage was 0.4 g, and the space velocity was 60000 ml / (gh). The SCR denitrification performance was tested, and the results showed that the effect was best at 500℃.

[0079] Experimental Example 7

[0080] To investigate the effect of different calcination temperatures on co-catalysis, this experiment used catalysts prepared in Examples 10, 13, and 14, and compared the NO content in the co-catalytic reaction of catalysts calcined at different temperatures. x The conversion rate of ethylene was compared with that of nitrogen. Specific experiments were conducted as follows: Under an atmosphere of 50 ppm ethylene, 500 ppm NO, 500 ppm NH3, 5% oxygen, and nitrogen balance, with a total flow rate of 400 ml / min, a catalyst dosage of 0.4 g, and a space velocity of 60000 ml / (gh), the ethylene oxidation performance was tested. The results showed that 500℃ yielded the best results. Combined with Experiment 6, 500℃ is the optimal calcination temperature for the catalyst in Example 10.

Claims

1. Use of a manganese-based catalyst for the simultaneous removal of nitrogen oxides and ethylene, characterized in that, The manganese-based catalyst is MnO x -CuO y , x is 0.5-1, y is 1-x, wherein the MnO x is the base; the active temperature range of the catalyst is 180-300°C.

2. Use according to claim 1, characterized in that, The manganese-based catalyst is prepared by the following steps: (1) weighing manganese salt and metal salt solid powder; the metal salt is at least one of chloride, sulfate, ammonium salt and nitrate of Cu; the amount-of-substance ratio of the manganese salt and the metal salt is (0.5-1):(1-x), x is 0.5-1 (2) mixing and grinding the two metal salts; (3) drying the mixture; (4) roasting in a muffle furnace to obtain the manganese-based catalyst for simultaneously removing nitrogen oxides and ethylene.

3. Use according to claim 2, characterized in that, The manganese salt in step (1) is at least one of manganese acetate, manganese chloride, manganese sulfate and manganese nitrate.

4. Use according to claim 2, characterized in that, The grinding time in step (2) is 5-60 min.

5. Use according to claim 2, characterized in that, The drying temperature in step (3) is set to 60-120℃; the drying time is 6-12 h.

6. Use according to claim 2, characterized in that, The roasting in step (4) refers to roasting at 200-800℃ for 2-6 h.

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