Preparation method of FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants

Abstract

A preparation method of a FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants relates to a preparation method of a catalyst for treating pollutants such as flue gas, and the catalyst is obtained by loading Cu and Fe on a ZSM-5 molecular sieve carrier at the same time through an ion exchange method and roasting and activating. Compared with single-metal Cu / ZSM-5 and Fe / ZSM-5, FeCu / ZSM-5 shows remarkable advantages in catalysis of synchronous removal of multiple pollutants such as nitrogen oxides and chlorobenzene. The catalyst has the advantages of wider active temperature window (275-450 DEG C), higher conversion rate (the conversion rates of nitrogen oxide (NOx) and chlorobenzene (CB) both exceed 90%), better oxygen migration ability and more reasonable Lewis / Bronsted acid site proportion. The performance advantages mainly derive from the synergistic effect of Fe and Cu species, and the effect improves the electronic structure of the catalyst, inhibits agglomeration of metal species and enhances the content of surface adsorbed oxygen. The catalyst can be widely applied to multi-pollutant cooperative treatment of flue gas of coal-fired power plants, waste incineration, ferrous metallurgy and petrochemical devices.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a catalyst for treating flue gas and other pollutants, in particular to a preparation method of a FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants. BACKGROUND

[0002] 1. Challenges of air pollution control With the increase of energy consumption and industrial activities, the types of pollutants in industrial flue gas are becoming more and more complex. Nitrogen oxides (NO, NO2) and chlorinated organic compounds (such as chlorobenzene, chlorinated diphenyl ether, dioxin precursors) are considered to be two harmful components of air pollution.

[0003] (1) NO x : is an important precursor of acid rain, photochemical smog and ozone pollution.

[0004] (2) Chlorobenzene (CB): a class of volatile organic pollutants, high thermal stability, often as a precursor of dioxin and other persistent organic pollutants.

[0005] In waste incineration, coal-fired power plants, steel smelting, petrochemical cracking and chlorination processes, NO x and chlorinated organic compounds often exist at the same time. If the simultaneous removal of the two types of pollutants can be achieved in the same reaction unit, the process will be greatly simplified and the operating cost will be reduced.

[0006] 2. Deficiencies of existing technologies Currently, the mainstream SCR denitration process uses V2O5-WO3 / TiO2 catalyst, which has good performance for removing NO x , but has the following defects: (1) narrow active temperature window (300-400 ℃); (2) insufficient oxidation performance for chlorinated organic compounds; (3) V2O5 has secondary pollution and toxicity problems, which is not conducive to green and sustainable development.

[0007] In addition, single-metal-loaded ZSM-5 catalysts have been widely studied: (1) Cu / ZSM-5: has strong oxidation activity and certain Brønsted acid sites, and the conversion rate of CB can reach 90% at 250 ℃, but the stability is insufficient at high temperature (> 400 ℃), and the conversion rate of NO x decreases at high temperature.

[0008] (2) Fe / ZSM-5: shows good Lewis acidity and maintains high stability at 350-400 ℃, but the conversion rate of NO xPoor removal performance and low oxidation efficiency of CB (<60%).

[0009] Therefore, it is difficult for single-metal catalysts to meet the comprehensive requirements of low-temperature high activity, high-temperature high stability and simultaneous removal of multiple pollutants.

[0010] 3. Potential of bimetallic synergy Previous studies have shown that Cu species are good at providing oxidation ability, while Fe species are good at providing acidic sites. If Fe and Cu are combined, a synergistic effect is expected to be achieved, which realizes: (1) maintaining high catalytic performance in a wide temperature range; (2) simultaneous removal of NO x and organic chlorine pollutants; (3) improving oxygen migration rate and oxygen vacancy concentration; (4) maintaining structural stability to avoid agglomeration and deactivation of single-metal species.

[0011] Therefore, it is urgent to develop a bimetallic FeCu / ZSM-5 catalyst to achieve efficient, stable and wide-temperature-range removal of multiple pollutants. SUMMARY

[0012] The purpose of the present application is to provide a preparation method of FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants. The prepared FeCu / ZSM-5 bimetallic catalyst has wide-temperature-range activity, high conversion rate, chlorine poisoning resistance and high stability; Fe and Cu are highly dispersed in ZSM-5 to form a synergistic effect, realizing conversion rates of NO x and CB both exceeding 90%; the catalyst has significant application value in the simultaneous purification of multiple pollutants in industrial flue gas.

[0013] The purpose of the present application is achieved by the following technical solutions: A preparation method of FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants, the preparation steps of the method are as follows: (1) treating ZSM-5 molecular sieve with an ammonium nitrate solution to obtain NH4-ZSM-5; (2) dissolving Cu(NO3)2·3H2O and FeCl2·4H2O in deionized water, adding NH4-ZSM-5, stirring at 80°C for 6 h, and reacting under N2 protection; (3) after filtration and drying, calcining at 400°C for 2 h to obtain FeCu / ZSM-5.

[0014] The preparation method of FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants, the molar ratio of Fe to Cu is 1:1.

[0015] The application discloses a preparation method of an FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants. x Conversion of CB.

[0016] The application discloses a preparation method of an FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants. ads latt The FeCu / ZSM-5 has a high oxygen transfer capacity.

[0017] The application discloses a preparation method of an FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants.

[0018] The application discloses a preparation method of an FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants. x Synchronous removal of CB and other pollutants.

[0019] The application discloses a preparation method of an FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants. 1. The catalyst prepared by the application has a wide temperature window: 275-450 DEG C, and can keep the conversion rate of NO x Conversion rate of CB > 90%; Acid site optimization: Fe provides Lewis acid sites, Cu provides Brønsted acid sites, and the synergistic effect brings a more reasonable L / B acid ratio. 2. The catalyst prepared by the application has enhanced oxygen transfer: the O ads / O latt The ratio is increased to 0.98, which is higher than that of Cu / ZSM-5 (0.88) and Fe / ZSM-5 (0.70). 3. The catalyst prepared by the application has increased oxygen vacancies: EPR analysis shows that the FeCu / ZSM-5 contains more oxygen vacancies, which is beneficial to the activation of pollutants. 4. The catalyst prepared by the application has strong resistance to poisoning: the conversion rate is still high under the coexistence of H2O. 5. The catalyst prepared by the application has stable structure: XRD shows that the molecular sieve structure is kept intact, and the metal species are highly dispersed. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 Conversion rate of CB and NOx by the catalyst; Figure 2 ​Stability and water resistance of FeCu / ZSM-5 catalysts Figure 3 XRD pattern of the catalysts Figure 4 EPR pattern of the catalysts Figure 5 H2-TPR pattern of the catalysts Figure 6 NH3-TPD pattern of the catalysts Figure 7 N2 adsorption-desorption pattern of the catalysts Figure 8 XPS pattern of the catalysts: (A) Cu 2p, (B) Fe 2p, (C) O 1s. DETAILED DESCRIPTION

[0021] The application will be described in detail below with reference to the embodiments shown in the drawings.

[0022] Preparation method of FeCu / ZSM-5 bimetallic catalyst Step 1: carrier pretreatment Ion exchange ZSM-5 molecular sieve with 0.1 mol / L ammonium nitrate solution to obtain NH4-ZSM-5; Step 2: metal loading Dissolve Cu(NO3)2·3H2O and FeCl2·4H2O in deionized water according to the molar ratio of 1:1, add NH4-ZSM-5, stir at 80 ℃ for 6 h, and protect by passing N2; Step 3: calcination After suction filtration and drying, heat to 400 ℃ at 2 ℃ / min in a muffle furnace, and calcine at constant temperature for 2 h to obtain FeCu / ZSM-5.

[0023] Example 1 (preparation of NH4-ZSM-5) Weigh dry ammonium nitrate (NH4NO3) and dissolve it to prepare a 0.10 mol / L ammonium nitrate solution. According to the proportion of 1 g of molecular sieve corresponding to 50 mL of ammonium nitrate solution, weigh 10 g of dry ZSM-5 molecular sieve into a beaker, and add 500 mL of ammonium nitrate solution. Mix the ammonia water and deionized water at a volume ratio of 1:5 to prepare dilute ammonia water, and drop the mixed solution to pH 4, stir for 30 min, and transfer to a three-necked flask for constant temperature stirring at 80 ℃ in a water bath for 6 h. After the water bath is finished, take out the three-necked flask and let it stand until it cools to room temperature. Then wash and suction filter. After suction filtration, put the filter cake together with the filter paper into a drying oven at 60 ℃ for air drying for more than 12 h to obtain the NH4-ZSM-5 carrier.

[0024] Example 2 (Preparation of Cu / ZSM-5) 0.02 mol / L Cu(NO3)2·3H2O was dissolved in 100 mL of deionized water, and then 1 g of NH4-ZSM-5 molecular sieve was added. The mixture was stirred for 30 min, transferred to a three-necked flask, and stirred at an 80 °C water bath for 6 h under N2 protection. The filtered and dried molecular sieve powder was transferred to a ceramic boat and calcined in a muffle furnace, starting at 30 °C and increasing to 400 °C at a rate of 2 °C / min, for 2 h to obtain the 0.02Cu / ZSM-5 catalyst.

[0025] Example 3 (Preparation of Fe / ZSM-5) 0.02 mol / L FeCl2·4H2O was dissolved in 100 mL of deionized water, and then 1 g of NH4-ZSM-5 molecular sieve was added. The mixture was stirred for 30 min, transferred to a three-necked flask, and stirred at a constant temperature of 80 °C for 6 h under N2 protection. The filtered and dried molecular sieve powder was transferred to a ceramic boat and calcined in a muffle furnace, starting at 30 °C and increasing to 400 °C at a rate of 2 °C / min, for 2 h to obtain the 0.02Fe / ZSM-5 catalyst.

[0026] Example 4 (Preparation of FeCu / ZSM-5) 0.01 mol / L FeCl₂·4H₂O and 0.01 mol / L Cu(NO₃)₂·3H₂O were dissolved in 100 mL of deionized water, and then 1 g of NH₄-ZSM-5 molecular sieve was added. The mixture was stirred for 30 min, transferred to a three-necked flask, and stirred at an 80 °C water bath for 6 h under N₂ protection. The filtered and dried molecular sieve powder was transferred to a ceramic boat and calcined in a muffle furnace, starting at 30 °C and increasing to 400 °C at a rate of 2 °C / min, for 2 h to obtain the FeCu / ZSM-5 catalyst.

[0027] Example 5 (Industrial Simulated Flue Gas Test) Simulated flue gas from a coal-fired power plant: 600 ppm NO, 600 ppm NH3, 100 ppm CB, 5% O2 and 10% H2O; Test Example 1 100 mg of catalyst was placed in a quartz tube with an inner diameter of 8 mm and placed in a quartz fixed-bed reactor. The reaction atmosphere consisted of 600 ppm NO, 600 ppm NH3, 100 ppm CB (introduced via a bubble generator), 5 vol.% O2, and the balance being high-purity nitrogen. The total flow rate was controlled at 100 mL / min, corresponding to a gas hourly space velocity of approximately 60,000 h⁻¹.- ¹, the reaction temperature was increased from 150 ℃ to 450 ℃. The concentration of CB in the outlet gas was determined using a Fuli gas chromatograph (GC-9790Ⅱ type, equipped with a TCD / FID detector), and NO... x Measurements were taken using a flue gas analyzer. The results showed that the FeCu / ZSM-5 catalyst of this invention exhibits good performance in the temperature range of 275-450 °C in terms of reducing CB and NO. x The conversion rates remained above 90%, significantly better than the control samples of single-metal Cu / ZSM-5 and Fe / ZSM-5 (see...). Figure 1 Catalysts for CB and NO x (conversion rate).

[0028] Test Example 2 FeCu / ZSM-5 reacted continuously at 275 °C for 40 h, and even with the introduction of 5 vol% water vapor, NO... x The conversion rate can still be maintained at 100%; while the conversion rate of CB, although temporarily reduced due to the addition of water vapor, can gradually recover its activity after the water supply is stopped (see...). Figure 2 Stability and water resistance of FeCu / ZSM-5 catalyst.

[0029] Test Example 3 Powder XRD analysis of FeCu / ZSM-5, Cu / ZSM-5, Fe / ZSM-5, and ZSM-5 catalysts revealed typical ZSM-5 molecular sieve diffraction peaks. No diffraction signals from other metal oxides or impurity species were observed, indicating that the introduced Cu and Fe components are highly dispersed within the ZSM-5 molecular sieve framework or channels and do not precipitate as crystalline particles. This ensures the integrity of the molecular sieve structure and the effective utilization of the active metal components (see [link to article]). Figure 3 XRD pattern of the catalyst.

[0030] Test Example 4 The three catalysts were characterized using EPR. The results showed that FeCu / ZSM-5 exhibited a significant signal peak near g = 2.003, while the signals of single-metal Cu / ZSM-5 and Fe / ZSM-5 were relatively weak. This result indicates that bimetallic coexistence can effectively promote the dispersion and interaction of active sites, providing more transferable electrons for subsequent redox cycles (see...). Figure 4 EPR spectrum of the catalyst.

[0031] Test Example 5 H2-TPR testing of the three catalysts revealed that the reduction peak of FeCu / ZSM-5 shifted significantly to the low-temperature region, making it more easily reduced than single-metal Cu / ZSM-5 and Fe / ZSM-5. This indicates a synergistic effect between the bimetallic catalysts, which can reduce the energy required for reduction and accelerate the redox cycle. This is beneficial for NO. x Efficient conversion of CB is crucial (see Figure 5 H2-TPR spectrum of the catalyst.

[0032] Test Example 6 The surface acidity of the catalysts was determined by NH3-TPD. The results showed that all three exhibited a bimodal characteristic of weak and strong acids. Although the overall acidity of FeCu / ZSM-5 was lower than that of Fe / ZSM-5 but higher than that of Cu / ZSM-5, the distribution of medium and strong acid sites on the catalyst was more balanced. This is beneficial to the adsorption and activation of chlorobenzene molecules, thereby improving the synergistic reaction performance (see...). Figure 6 (NH3-TPD spectrum of the catalyst).

[0033] Test Example 7 Nitrogen adsorption-desorption tests were performed on FeCu / ZSM-5, Cu / ZSM-5, Fe / ZSM-5, and ZSM-5 catalysts. The results showed that all four maintained typical IUPAC type IV isotherms and H1 type hysteresis loops, indicating that they still possess microporous / mesoporous structures characteristic of molecular sieves. The specific surface area and pore volume of FeCu / ZSM-5 were slightly higher than those of the single-metal samples, indicating that the strong interaction between Cu and Fe species prevented the aggregation of Cu and Fe species, thereby reducing the clogging of the support micropores (see...). Figure 7 (N2 adsorption-desorption spectra of the catalyst).

[0034] Test Example 8 XPS analysis of the valence states of FeCu / ZSM-5 surface showed that Cu mainly exists as Cu. + / Cu 2+ It exists in a coexisting form, with Fe mainly existing as Fe. 2+ / Fe 3+ The presence of these substances, and the higher proportion of low-valence species in the bimetallic samples compared to monometallic samples, indicates electron transfer between the two, enhancing the activation ability of surface oxygen. Furthermore, O... ads / O latt The ratio increased to 0.98, higher than Cu / ZSM-5 (0.88) and Fe / ZSM-5 (0.70) (see...). Figure 8 XPS spectra of the catalyst: (A) Cu 2p, (B) Fe 2p, (C) O 1s.

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a FeCu / ZSM-5 bimetallic catalyst for cleaning flue gas pollutants, characterized in that, The preparation step of the method is as follows: (1) treating ZSM-5 molecular sieve with an ammonium nitrate solution to obtain NH4-ZSM-5; (2) dissolving Cu(NO3)2·3H2O and FeCl2·4H2O in deionized water, adding NH4-ZSM-5, stirring at 80 ℃ for 6 h, and reacting under N2 protection; (3) after suction filtration and drying, calcining at 400 ℃ for 2 h to obtain FeCu / ZSM-5.

2. The preparation method of FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants according to claim 1, characterized in that, The molar ratio of Fe to Cu is 1:

1.

3. The method for preparing FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants according to claim 1, characterized in that, The FeCu / ZSM-5 simultaneously removes NO x Conversion with CB.

4. The method for preparing FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants according to claim 1, characterized in that, The FeCu / ZSM-5 has high surface O ads / O latt proportion and high oxygen migration ability.

5. The method for preparing FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants according to claim 1, characterized in that, The FeCu / ZSM-5 catalyst is pressed into a honeycomb ceramic or metal module and applied to a fixed bed or moving bed reactor.

6. The method for preparing FeCu / ZSM-5 bimetallic catalyst for purifying flue gas pollutants according to claim 1, characterized in that, The FeCu / ZSM-5 catalyst is applied in industrial flue gas pollutant treatment, such as: used in flue gas of coal-fired power plant, waste incineration, steel smelting, petrochemical device, NO x Synchronous removal of CB type pollutants.

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