An hc-scr catalyst, its preparation method and use

Abstract

This application provides an HC-SCR catalyst, its preparation method, and its application. The HC-SCR catalyst includes a support and an active component supported on the support. The support is a ZSM-5 support, and the active component is MnCeOx. The beneficial effects of this application include: the catalyst introduces a second active element, Ce, into the manganese-based molecular sieve catalyst, further improving the conversion rate of the HC-SCR catalyst at low temperatures and widening the temperature window. The introduction of Ce can also lower the reduction temperature and promote the redox performance of the catalyst; it provides more sites for propylene activation, promoting further reactions of active intermediates; the active component of the catalyst is prepared using the MOF derivatization method, which produces an active component with uniform particle size and improves the valence state of Mn ions, promoting MnOx activation. 3+ The formation of the catalyst; and the active components of the catalyst prepared by solid-phase grinding are highly dispersed on the catalyst surface, which largely ensures the loading of the active components.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to an HC-SCR catalyst and a preparation method and application thereof. BACKGROUND

[0002] Coking industry, as an important part of the steel industry, produces a large amount of pollutants in the production process, especially in the coking process, the coke oven flue gas discharged contains NO x , SO2, volatile organic compounds (VOCs) and particulate matter and other pollutants. The traditional ammonia selective catalytic reduction (NH3-SCR) process for removing NO x requires a large amount of reducing agent NH3 in the denitrification process, which increases the additional cost of purchase and storage. At the same time, VOCs in the coking process are usually removed by combustion. Therefore, HC-SCR derived from the use of original VOCs in flue gas as reducing agent for the removal of NO x has become a research focus, and the preparation and selection of high-performance catalysts in the HC-SCR process have become the focus of research.

[0003] In practice, HC-SCR catalysts are mainly used to remove NO x and C3H6 in flue gas. However, such catalysts have the problems of low catalytic efficiency and narrow temperature window in application, which leads to the inability to be used in specific working conditions. SUMMARY

[0004] The application aims to provide an HC-SCR catalyst and a preparation method and application thereof, and aims to solve the problems of low catalytic efficiency and narrow temperature window of the existing HC-SCR catalyst.

[0005] To achieve the above application purposes, the technical solutions adopted by the application are as follows:

[0006] In a first aspect of the application, an HC-SCR catalyst is provided, comprising a carrier and an active component loaded on the carrier, the carrier is a ZSM-5 carrier, and the active component is MnCeO x . Wherein, X can be 2, 3, 4, 5, 6 or 7.

[0007] The application introduces a second active element Ce on the basis of the manganese-based molecular sieve catalyst, further improves the conversion rate of the HC-SCR catalyst at low temperature, and widens the temperature window. Specifically, the introduction of the Ce element increases the content of adsorbed oxygen on the surface of the catalyst, accelerates the migration of oxygen on the surface of the catalyst, and is beneficial to the oxidation reaction of HC. The introduction of Ce can also reduce the reduction temperature and promote the redox performance on the catalyst. At the same time, the double active metal catalyst has higher surface acidity, especially weak Bronsted acid sites, which provides more abundant sites for the activation of propylene and promotes the further reaction of active intermediates.

[0008] According to some embodiments of the HC-SCR catalyst described in the application, the active component is Mn 0.32 Ce 0.08 O X , wherein 0.5≤X≤7. For example, X is 2, 3, 4, 5, 6 or 7.

[0009] According to some embodiments of the HC-SCR catalyst described in the application, the molar ratio of the carrier and the active component is (4-10):2, for example 4:2, 5:2, 6:2, 7:2, 8:2, 10:2, etc.

[0010] In a second aspect of the application, a composition for preparing the HC-SCR catalyst of the first aspect of the application is provided, which includes a manganese source, a cerium source, terephthalic acid, ZSM-5 molecular sieve and a solvent.

[0011] According to some embodiments of the composition described in the application, the manganese source includes a 50wt% manganese nitrate solution.

[0012] According to some embodiments of the composition described in the application, the cerium source includes cerium nitrate hexahydrate with a purity of 99.5%.

[0013] According to some embodiments of the composition described in the application, the purity of the terephthalic acid is 99%.

[0014] According to some embodiments of the composition described in the application, the solvent includes one or both of N,N-dimethylformamide and anhydrous ethanol.

[0015] According to some embodiments of the composition described in the application, the molar ratio of the manganese source and the cerium source is (1-7):1, for example 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, etc.

[0016] According to some embodiments of the composition described in the application, the total molar amount of the manganese element and the cerium element and the molar ratio of the terephthalic acid is 1:(1.0-1.4), for example 1:1, 1:1.2, 1:1.3, 1:1.4, etc.

[0017] According to some embodiments of the composition of the present application, the molar ratio of the manganese source and the ZSM-5 molecular sieve is (2-6): 10, such as 2:10, 3:10, 4:10, 6:10, etc.

[0018] According to some embodiments of the composition of the present application, the molar ratio of the manganese source and the solvent is 1:(120-170), such as 1:120, 1:130, 1:150, 1:160, 1:170, etc.

[0019] According to some embodiments of the composition of the present application, the solvent is a mixture of N,N-dimethylformamide and anhydrous ethanol, preferably, the molar ratio of the N,N-dimethylformamide and the anhydrous ethanol is 125:41.

[0020] In a third aspect of the present application, a preparation method of the HC-SCR catalyst of the first aspect of the present application is provided, which is prepared by using the composition of the second aspect of the present application.

[0021] According to some embodiments of the preparation method of the present application, the method comprises the following steps:

[0022] (1) mixing the manganese source, the cerium source, the terephthalic acid and the solvent, and performing a reaction, and performing a calcination treatment on the reaction product to obtain an active component MnCeO X , 0.5≤X≤7.

[0023] (2) mixing the active component and the ZSM-5 molecular sieve and performing a grinding to obtain the HC-SCR catalyst.

[0024] The active component of the present application is prepared by using a MOF derivation method. The active component prepared by using this method has a uniform particle size, and the valence state of Mn ions is improved, which promotes the formation of Mn 3+ . Mn 3+ is not only an active site for NO oxidation, but also has a certain reduction performance.

[0025] The active component of the present application and the carrier are combined by using a solid-phase grinding method. The active component of the catalyst prepared by using the solid-phase grinding method is highly dispersed on the surface of the catalyst, which greatly ensures the loading amount of the active component.

[0026] Mn 3+ is an active site that plays a leading role in the HC-SCR reaction, that is, an active site for NO oxidation, and also has a certain reduction performance. The abundant Mn 3+ active sites are beneficial to the generation and reaction of a large amount of intermediate products, promote the HC-SCR reaction, and the surface active oxygen is generated by oxygen defects (oxygen vacancies), including peroxide (O- ) and superoxide (O 2- ) species, which are beneficial to the process of NO oxidation to NO2 on the catalyst surface and the oxidation process of -C x H y O z At the same time, the surface active oxygen has a higher oxygen mobility than other oxygen species, and is more active in the redox reaction, which is beneficial to improve the conversion rate of the catalyst and broaden the temperature window of the catalyst.

[0027] The application utilizes the MOF derived method to prepare the active component, which improves the valence state of Mn ions and promotes the formation of Mn 3+ At the same time, the active component is loaded on the carrier to a large extent by solid phase grinding, which avoids the loss of the active component. The introduction of Ce increases the adsorbed oxygen content on the catalyst surface, accelerates the oxygen migration on the catalyst surface, and is beneficial to the oxidation reaction of HC. Ce can also reduce the reduction temperature, improve the surface acidity of the catalyst, provide more abundant sites for the activation of propylene, and promote the further reaction of the active intermediate.

[0028] According to some embodiments of the preparation method, in step (1), the temperature of the reaction is 95-120℃, such as 95℃, 100℃, 105℃, 110℃, 120℃, etc., and the reaction time is 10-14h, such as 10h, 12h, 13h, 14h, etc.

[0029] According to some embodiments of the preparation method, the calcination includes first stage calcination and second stage calcination. The first stage calcination is calcination under a nitrogen atmosphere at a temperature of 300-400℃, such as 300℃, 320℃, 340℃, 360℃, 400℃, etc., for 2-4h, such as 2h, 3h, 4h, etc. The second stage calcination is calcination under an air atmosphere at a temperature of 300-400℃, such as 300℃, 320℃, 340℃, 360℃, 400℃, etc., for 2-4h, such as 2h, 3h, 4h, etc.

[0030] According to some embodiments of the preparation method, the second stage calcination is performed after the first stage calcination is completed and cooled to room temperature.

[0031] According to some embodiments of the preparation method, the heating rate of the first stage calcination is 5℃ / min.

[0032] According to some embodiments of the preparation method, the heating rate of the second stage calcination is 2℃ / min.

[0033] According to some embodiments of the preparation method, the grinding is performed in an agate mortar.

[0034] According to some embodiments of the preparation method of the application, the grinding time is 30-60 min, such as 30 min, 35 min, 40 min, 45 min, 50 min, 60 min, etc.

[0035] According to a fourth aspect of the application, a method for treating coke oven flue gas is provided, which is reacted under the action of the HC-SCR catalyst of the first aspect of the application or the HC-SCR catalyst prepared by the preparation method of the third aspect of the application.

[0036] According to some embodiments of the method for treating coke oven flue gas of the application, the coke oven flue gas comprises one or more of NO, NO2 and C3H6.

[0037] According to some embodiments of the method for treating coke oven flue gas of the application, the reaction temperature is 150-350℃, such as 150℃, 180℃, 200℃, 250℃, 300℃, 250℃. The temperature range of the reaction of the application conforms to the flue gas temperature of 180-250℃ in the coke oven flue gas of a coking plant, and the catalyst of the application has a wider temperature window, further making the catalyst have better adaptability.

[0038] According to some embodiments of the method for treating coke oven flue gas of the application, the volume space velocity of the coke oven flue gas is 25000-35000 / h, such as 25000 / h, 28000 / h, 30000 / h, 32000 / h, 35000 / h, etc.

[0039] The beneficial effects of the application include:

[0040] (1) The catalyst of the application introduces a second active element Ce on the basis of a manganese-based molecular sieve catalyst, further improving the conversion rate of the HC-SCR catalyst at low temperature and widening the temperature window. Specifically, the introduction of Ce element increases the adsorbed oxygen content on the surface of the catalyst, accelerates the oxygen migration on the surface of the catalyst, and is conducive to the oxidation reaction of HC. The introduction of Ce can also reduce the reduction temperature and promote the redox performance on the catalyst. At the same time, the double active metal catalyst has higher surface acidity, especially weak Bronsted acid sites, which provides more abundant sites for the activation of propylene and promotes the further reaction of active intermediates.

[0041] (2) The active component of the catalyst of the application is prepared by a MOF derivation method, which has uniform particle size and improves the valence state of Mn 3+ ions and promotes the formation of Mn 3+It serves as both an active site for NO oxidation and possesses certain reducing properties. Furthermore, the active components of the catalyst described in this application are combined with ZSM-5 molecular sieves through solid-phase grinding. The active components of the catalyst prepared by solid-phase grinding are highly dispersed on the catalyst surface, which largely ensures the loading of the active components.

[0042] (3) The optimal temperature range of HC-SCR in this application is consistent with the flue gas temperature of 180-250℃ in the coke oven flue gas of coking plant. The higher HC-SCR performance and wider temperature window make the catalyst in this invention have better adaptability. Attached Figure Description

[0043] Figure 1 The catalysts described in Examples 1, 1, 4, and 5 of this application catalyze NO. x The conversion efficiency diagram;

[0044] Figure 2 This is a graph showing the conversion efficiency of CH4 catalyzed by the catalysts described in Examples 1, 1, 4 and 5 of this application.

[0045] Figure 3 The catalysts described in Comparative Examples 1 and 2 of this application catalyze NO. x The conversion efficiency diagram;

[0046] Figure 4 The conversion efficiency of CH4 catalyzed by the catalysts described in Comparative Examples 1 and 2 of this application is shown in the graph.

[0047] Figure 5 The active components of the catalyst described in Comparative Example 1 of this application and the active components of the catalyst described in Comparative Example 2 and the XRD patterns of the catalyst described in Comparative Example 2 are shown.

[0048] Figure 6 (a) XPS spectra of Mn2P of the catalyst described in Comparative Example 1 and Comparative Example 2 of this application;

[0049] Figure 6 (b) XPS spectra of the catalyst described in Comparative Example 1 and Comparative Example 2 of this application for O 1s;

[0050] Figure 7 (a) Catalysis of NO by the catalysts described in Comparative Examples 1 and 3 of this application. x The conversion efficiency diagram;

[0051] Figure 7 (b) is a graph showing the conversion efficiency of CH by the catalysts described in Comparative Examples 1 and 3 of this application;

[0052] Figure 8(a) SEM images of Mn0.4-MOF / ZSM-5-deposited precipitation catalyst prepared as Comparative Example 1 of the present application 0.4 - SEM images of MOF / ZSM-5-solid phase grinding catalysts;

[0053] Figure 8 (b) SEM images of Mn0.4-MOF / ZSM-5-deposited precipitation catalyst prepared as Comparative Example 3 of the present application

[0054] Figure 8 (c) and Figure 8 (d) SEM images of Mn0.4-MOF / ZSM-5-deposited precipitation catalyst prepared as Comparative Example 1 of the present application 0.4 - EDS spectra of MOF / ZSM-5-solid phase grinding catalysts;

[0055] Figure 8 (e) and Figure 8 (f) EDS spectra of Mn0.4-MOF / ZSM-5-deposited precipitation catalyst prepared as Comparative Example 3 of the present application 0.4 - EDS spectra of MOF / ZSM-5-solid phase grinding catalysts;

[0056] Figure 8 (g) and Figure 8 (h) SEM images of Mn0.4-MOF / ZSM-5-solid phase grinding catalyst and Mn0.4-MOF / ZSM-5-deposited precipitation catalyst prepared as Comparative Example 1 and Example 3 of the present application, respectively 0.4 - EDS spectra of MOF / ZSM-5-solid phase grinding catalyst and Mn0.4-MOF / ZSM-5-deposited precipitation catalyst; 0.4 - SEM + EDS spectra of MOF / ZSM-5-solid phase grinding catalyst and Mn0.4-MOF / ZSM-5-deposited precipitation catalyst;

[0057] Figure 9 (a) Conversion efficiency graphs of NOxby the catalysts described in Examples 1-5 of the present application x

[0058] Figure 9 (b) Conversion efficiency graphs of CH4by the catalysts described in Examples 1-5 of the present application

[0059] Figure 10 (a) Conversion efficiency graphs of NOxby the catalysts described in Examples 6-9 of the present application x

[0060] Figure 10 (b) Conversion efficiency graphs of CH4by the catalysts described in Examples 6-9 of the present application DETAILED DESCRIPTION

[0061] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below by reference to the drawings are exemplary and are intended to explain the present application, and are not to be understood as limiting the present application.

[0062] ​​The technical solutions of the present application will be described in detail below with reference to specific embodiments and drawings.

[0063] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0064] The embodiment of the present application provides an HC-SCR catalyst. The catalyst is composed of the following components: Mn 0.32 Ce 0.08 O X The active component is loaded on the ZSM-5 carrier by a solid phase grinding method. That is, the HC-SCR catalyst provided by the present application is composed of MnCe-MOF / ZSM-5. 0.32 Ce 0.08 O X The active component is prepared by a MOF derivation method. The active component is loaded on the molecular sieve carrier by a solid phase grinding method. That is, the HC-SCR catalyst provided by the present application is composed of MnCe-MOF / ZSM-5.

[0065] Mn 3+ is the active site that plays a leading role in the HC-SCR reaction, which is not only the active site for NO oxidation, but also has certain reduction performance. Abundant Mn 3+ Active sites are beneficial to the generation and reaction of a large number of intermediate products, and promote the HC-SCR reaction. Surface active oxygen is generated by oxygen defects (oxygen vacancies), including peroxide (O - ) and superoxide (O 2- ) species, which is beneficial to the process of oxidizing NO on the surface of the catalyst into NO2 and the oxidation process of -C x H y O z At the same time, the surface active oxygen has a higher oxygen mobility than other oxygen species, so it is more active in the oxidation-reduction reaction, which is beneficial to improve the conversion rate of the catalyst and broaden the temperature window of the catalyst. Specifically, the preparation of the active component by the MOF derivation method in the present application can improve the valence state of Mn ions, promote the generation of surface active oxygen, and improve the catalytic activity of the catalyst. In addition, the MOF derivation method can improve the dispersion of the active component on the carrier, which is beneficial to the generation of surface active oxygen. 3+The active component can be loaded on the carrier to a large extent by solid phase grinding, avoiding loss of the active component. The introduction of Ce increases the content of adsorbed oxygen on the surface of the catalyst, accelerates the migration of oxygen on the surface of the catalyst, and is beneficial to the oxidation reaction of HC. Ce can also reduce the reduction temperature and increase the surface acidity of the catalyst, providing more abundant sites for the activation of propylene and promoting the further reaction of active intermediates.

[0066] Some embodiments of the present application compare the HC-SCR efficiency of the MnOx active component supported molecular sieve catalyst prepared by the MOF derived method and the precipitation method, highlighting the superiority of the active component prepared by the MOF derived method. For example: the NO x conversion rate of the Mn-MOF / ZSM-5 catalyst is higher than that of the Mn-C / ZSM-5 catalyst. The NO x conversion rate of the Mn-MOF / ZSM-5 catalyst is the highest, reaching 90.37%, which is much higher than the highest conversion rate of 76.63% of the Mn-C / ZSM-5 catalyst at 250°C. Higher conversion efficiency and a wider temperature window indicate that the Mn-MOF / ZSM-5 catalyst has better low-temperature HC-SCR performance. At the same time, the HC conversion rate of the Mn-MOF / ZSM-5 catalyst is almost 100% at 225°C.

[0067] Some embodiments of the present application compare the HC-SCR efficiency of the active component supported molecular sieve catalyst prepared by the solid phase grinding method and the deposition precipitation method, highlighting the superiority of the active component supported by the solid phase grinding method. For example: within the entire temperature range of 150-350°C, the catalyst prepared by the solid phase grinding method is better than that prepared by the deposition precipitation method.

[0068] Some embodiments of the present application compare the preparation of bimetallic active components by using Ce, La, and Pr as the second active metal element through the MOF derived method, and then loading them on the ZSM-5 carrier by solid phase grinding. The prepared catalysts have a temperature range of 150-350°C, NO x = 500 ppm, O2= 6%, and GHSV = 30000 / h. Among them, the NO x conversion rate of the MnCe-MOF / ZSM-5 catalyst reaches the highest conversion rate of 97.26% at 225°C, and the HC conversion rate is greater than 90% within the entire temperature range.

[0069] Some embodiments of the present application compare the preparation of MnCe-MOF / ZSM-5 catalysts with different Mn and Ce ratios, and the prepared catalysts have a temperature range of 150-350°C, NO xThe HC-SCR performance test was carried out under the conditions of C3H6= 500 ppm, O2= 6%, and GHSV = 30000 / h. When the molar ratio of Mn:Ce was 4:1, the catalyst had the best catalytic performance, and the highest conversion rate of 97.26% was reached at 225°C. The HC conversion rate was greater than 90% in the entire temperature range.

[0070] Some embodiments of the present application compared the preparation of MnCe-MOF / ZSM-5 catalysts with different active components and molecular sieve carriers. The NO x The HC-SCR performance test was carried out under the conditions of C3H6= 500 ppm, O2= 6%, and GHSV = 30000 / h. When the molar ratio of Mn:Ce was 4:1, the catalyst had the best catalytic performance, and the highest conversion rate of 97.26% was reached at 225°C. The HC conversion rate was greater than 90% in the entire temperature range. Specific embodiments: Example 1

[0072] A MOF-derived method was used to prepare a bimetallic active component, and a solid-phase grinding method was used to load the active component. The second active metal element Ce was introduced into the Mn-based catalyst.

[0073] A total of 10 mmol of Mn(NO3)3 aqueous solution (50%) and 99.5% pure Ce(NO3)3·6H2O were added to 96 ml of N,N-dimethylformamide and 24 ml of anhydrous ethanol in a beaker and stirred for 1 h to fully disperse the solution. The resulting mixed solution was placed in a 250 ml reaction kettle and crystallized at 100°C in an oven for 12 h under high temperature and high pressure to obtain light yellow solid particles. The obtained solid was centrifuged in a centrifuge tube for 2-3 times, and the lower layer was taken out, washed, and filtered, and the process was repeated 3 times. The obtained precipitate was dried in a 100°C oven for 12 h, then calcined at 350°C for 3 h in a tube furnace with N2 at a temperature rising rate of 5°C / min, and the tube furnace was allowed to cool to room temperature. Then, it was calcined at 350°C for 3 h with air at a temperature rising rate of 2°C / min. The final sample was recorded as MnCe-MOF.

[0074] MnCe-MOF and ZSM-5 molecular sieve were ground in a 2:5 molar ratio in an agate mortar for 40 min to obtain an HC-SCR catalyst MnCe-MOF / ZSM-5.

[0075] Example 2

[0076] Example 2 differs from Example 1 in that the molar ratio of Mn(NO3)3 aqueous solution and Ce(NO3)3·6H2O is 1:1, and the rest of the operations are the same as Example 1, and the obtained catalyst is Mn 0.2 Ce 0.2 -MOF / ZSM-5.

[0077] Example 3

[0078] Example 3 differs from Example 1 only in that the molar ratio of Mn(NO3)3 aqueous solution and Ce(NO3)3·6H2O is 2:1, and the rest of the operations are the same as Example 1, and the obtained catalyst is Mn 0.26 Ce 0.13 -MOF / ZSM-5.

[0079] Example 4

[0080] Example 4 differs from Example 1 only in that the molar ratio of Mn(NO3)3 aqueous solution and Ce(NO3)3·6H2O is 3:1, and the rest of the operations are the same as Example 1, and the obtained catalyst is Mn 0.3 Ce 0.1 -MOF / ZSM-5.

[0081] Example 5

[0082] Example 5 differs from Example 1 only in that the molar ratio of Mn(NO3)3 aqueous solution and Ce(NO3)3·6H2O is 5.6:1, and the rest of the operations are the same as Example 1, and the obtained catalyst is Mn 0.34 Ce 0.06 -MOF / ZSM-5.

[0083] Example 6

[0084] Example 6 differs from Example 1 only in that the molar ratio of Mn(NO3)3 aqueous solution and Ce(NO3)3·6H2O is 7:1, and the rest of the operations are the same as Example 1, and the obtained catalyst is Mn 0.35 Ce 0.05 -MOF / ZSM-5.

[0085] Example 7

[0086] Example 7 differs from Example 1 only in that the molar ratio of MnCe-MOF and ZSM-5 molecular sieve is 2:10, and the rest of the operations are the same as Example 1, and the obtained catalyst is Mn 0.16 Ce 0.04 -MOF / ZSM-5.

[0087] Example 8

[0088] Example 8 differs from Example 1 only in that the molar ratio of MnCe-MOF to ZSM-5 molecular sieve is 3:10, and the rest of the operations are the same as those of Example 1, and the obtained catalyst is Mn 0.24 Ce 0.06 -MOF / ZSM-5.

[0089] Example 9

[0090] Example 9 differs from Example 1 only in that the molar ratio of MnCe-MOF to ZSM-5 molecular sieve is 5:10, and the rest of the operations are the same as those of Example 1, and the obtained catalyst is Mn 0.4 Ce 0.1 -MOF / ZSM-5.

[0091] Example 10

[0092] Example 10 differs from Example 1 only in that the molar ratio of MnCe-MOF to ZSM-5 molecular sieve is 6:10, and the rest of the operations are the same as those of Example 1, and the obtained catalyst is Mn 0.48 Ce 0.12 -MOF / ZSM-5.

[0093] Comparative Example 1

[0094] Comparative Example 1 differs from Example 1 only in that the raw material for preparing the active component in Comparative Example 1 contains only Mn(NO3)3 aqueous solution (50%) without Ce(NO3)3·6H2O.

[0095] The specific operation is as follows:

[0096] The active component MnO x of the HC-SCR catalyst with a single active component prepared by the MOF derivation method is prepared as follows: 10 mmol of Mn(NO3)3 aqueous solution (50%) and 12.8 mmol of H2BDC (terephthalic acid) are added to 96 ml of N,N-dimethylformamide and 24 ml of anhydrous ethanol in a beaker and stirred for 1 h to make the solution fully dispersed. The obtained mixed solution is placed in a 250 ml reaction kettle, and crystallized at high temperature and high pressure in an oven at 100℃ for 12 h to obtain light yellow solid particles. The obtained solid is centrifuged in a centrifuge tube for 2-3 times, and the lower precipitate is taken out, washed, and filtered, and the operation is repeated for 3 times. The obtained precipitate is dried in an oven at 100℃ for 12 h, and then calcined at 350℃ for 3 h with N2 at a temperature rising rate of 5℃ / min in a tube furnace, and the tube furnace is allowed to cool to room temperature. Then, the temperature is raised to 350℃ at a temperature rising rate of 2℃ / min, and calcined for 3 h with air. The finally obtained sample is recorded as Mn-MOF.

[0097] The active component Mn-MOF prepared by MOF derived method was ground with ZSM-5 molecular sieve carrier in a 2:5 molar ratio in an agate mortar for 40 min by solid phase grinding method to obtain HC-SCR catalyst Mn 0.4 -MOF / ZSM-5 solid phase grinding catalyst.

[0098] Comparative Example 2

[0099] Comparative Example 2 is different from Comparative Example 1 in that the active component MnO x of the HC-SCR catalyst with single active component prepared by the precipitation method.

[0100] The specific operation is as follows:

[0101] The active component MnO x of the HC-SCR catalyst with single active component prepared by the precipitation method is prepared as follows: 10 mmol of Mn(NO3)3 aqueous solution (50%) is added to excess NaOH, and the pH is adjusted to 10. The obtained mixed solution is placed in a 250 ml reaction kettle, and high-temperature and high-pressure crystallization is carried out in a 100℃ oven for 12 h to obtain purple-black solid particles. The obtained solid is centrifuged in a centrifuge tube for 2-3 times, and the lower precipitate is taken out, washed, filtered, and repeated for 3 times. The obtained precipitate is dried in a 100℃ oven for 12 h, then calcined in a tube furnace at a temperature rising rate of 5℃ / min to 350℃ for 3 h with N2, and the tube furnace is cooled to room temperature. Then, it is calcined at a temperature rising rate of 2℃ / min to 350℃ for 3 h with air. The finally obtained sample is recorded as Mn-C.

[0102] The Mn-C is ground with ZSM-5 molecular sieve carrier in a 2:5 molar ratio in an agate mortar for 40 min by solid phase grinding method to obtain HC-SCR catalyst Mn 0.4 -C / ZSM-5 solid phase grinding catalyst.

[0103] Comparative Example 3

[0104] Comparative Example 3 is different from Comparative Example 1 only in that the active component Mn-MOF is generated on the ZSM-5 molecular sieve by the precipitation method.

[0105] The specific operation is: 10 mmol of Mn(NO3)3 aqueous solution (50%), 12.8 mmol of H2BDC (terephthalic acid) and 25 mmol of ZSM-5 molecular sieve are added into 96 ml of N,N-dimethylformamide and 24 ml of anhydrous ethanol in a beaker and stirred for 1 h to make the solution fully dispersed. The obtained mixed solution is placed in a 250 ml reaction kettle, and high-temperature and high-pressure crystallization is carried out at 100°C in an oven for 12 h. The obtained solid is centrifuged in a centrifuge tube for 2-3 times, and the lower precipitate is taken out, washed, filtered, and repeated for 3 times. The obtained precipitate is dried in an oven at 100°C for 12 h, then calcined with N2 at a temperature rising rate of 5°C / min to 350°C in a tube furnace for 3 h, and the tube furnace is allowed to cool to room temperature. Then, the temperature is raised to 350°C at a temperature rising rate of 2°C / min, and calcination is carried out with air for 3 h. The finally obtained sample is recorded as Mn-MOF / ZSM-5-deposition precipitated catalyst.

[0106] Comparative Example 4

[0107] Comparative Example 4 differs from Example 1 only in that LaN3O9·6H2O is used to replace Ce(NO3)3·6H2O, and the rest of the operations are the same as those of Example 1. The obtained catalyst is recorded as Mn 0.32 La 0.08 -MOF / ZSM-5.

[0108] Comparative Example 5

[0109] Comparative Example 5 differs from Example 1 only in that Pr(NO3)3·6H2O is used to replace Ce(NO3)3·6H2O, and the rest of the operations are the same as those of Example 1. The obtained catalyst is recorded as: Mn 0.32 Pr 0.08 -MOF / ZSM-5.

[0110] Performance research of the catalysts described in Examples 1-10 and the catalysts described in Comparative Examples 1-5:

[0111] 0.5 mL of each of the catalysts described in Examples 1-10 and the catalysts described in Comparative Examples 1-5 is respectively placed in a quartz tube, and then the quartz tube is placed in a tube furnace, and a temperature rising program is set, the reaction temperature is 150-350°C, a simulated atmosphere is introduced, NO x =C3H6=500ppm, O2=6%, N2 is the balance gas, the volume space velocity GHSV=30000 / h, and the mixed gas flow rate is 250 ml / min. The concentrations of NO x and C3H6 in the outlet gas are respectively determined by using a flue gas analyzer at 150°C, 200°C, 225°C, 250°C, 275°C, 300°C and 350°C for 30 minutes, and the removal rates of the two pollutants are calculated. The catalytic activity of the catalyst is expressed by the removal rate of NO xThe removal rate of C3H6 is used as an evaluation indicator.

[0112] 1. The effect of adding different rare earth metals on the performance of the catalyst.

[0113] The catalysts described in Example 1 and Comparative Examples 1 and 4-5 catalyze NO x Conversion efficiency such as Figure 1 As shown, the catalytic conversion efficiency of CH is as follows: Figure 2 As shown.

[0114] from Figure 1 and Figure 2 As can be seen, the catalyst described in Example 1 of this application exhibits higher conversion efficiency. Within the entire temperature range of 150-350℃, the conversion rate of MnCe-MOF / ZSM-5 is higher than that of the Mn-MOF / ZSM-5 (Comparative Example 1) catalyst. The highest conversion rate of 97.26% was achieved at 225℃, which is higher than that of NO when Mn is used as the single metal active component. x The conversion rate was 90.37%. Furthermore, the HC conversion rates of both catalysts were greater than 90% across the entire temperature range, with little difference in trend. This indicates that the introduction of Ce can enhance the NO conversion of the Mn-based molecular sieve catalyst. x The conversion rate may be attributed to the higher reduction performance of MnCe-MOF / ZSM-5.

[0115] When the active metal component La is introduced, the maximum temperature range of MnLa-MOF / ZSM-5 is advanced to 175℃, NO x The conversion rate reached 89.84%, but its temperature window was narrow; when the temperature exceeded 175℃, its NO content decreased. x The conversion rate drops rapidly. This may be because the interaction between La and Mn helps to shift the reaction towards a lower temperature range, but it shortens the temperature range.

[0116] The conversion rate of MnPr-MOF / ZSM-5 decreased significantly after the introduction of Pr as an active component, reaching a maximum of only 62.44% at 250℃. This indicates that the interaction between Pr doping and Mn weakens the HC-SCR reaction. Furthermore, the low-temperature HC conversion rates of both MnLa-MOF / ZSM-5 and MnPr-MOF / ZSM-5 catalysts were lower than those of Mn-MOF / ZSM-5. Therefore, introducing rare earth metal Ce as a second active component into the Mn-MOF / ZSM-5 catalyst improves its redox performance, increasing the conversion rate while broadening the temperature window.

[0117] 2. Effects of derivatization and precipitation methods on catalyst performance

[0118] The catalysts described in Comparative Examples 1 and 2 catalyze NOx Conversion efficiency such as Figure 3 As shown, the catalytic conversion efficiency of CH is as follows: Figure 4 As shown.

[0119] from Figure 3 and Figure 4 It can be seen that within the temperature range of 225-275℃, the NO content of the Mn-MOF / ZSM-5 catalyst is... x The conversion rate is higher than that of the Mn-C / ZSM-5 catalyst. Furthermore, the Mn-MOF / ZSM-5 catalyst exhibits better conversion efficiency at 225 °C for NO. x The highest conversion rate was achieved at 90.37%, significantly higher than the 76.63% maximum conversion rate of the Mn-C / ZSM-5 catalyst at 250 °C. This higher conversion efficiency and wider temperature window indicate that the Mn-MOF / ZSM-5 catalyst exhibits superior low-temperature HC-SCR performance. Furthermore, the HC conversion rate of the Mn-MOF / ZSM-5 catalyst reached almost 100% at 225 °C, a lower temperature than that of Mn-C / ZSM-5, suggesting stronger HC oxidation capacity and more efficient utilization of C3H6 at low temperatures.

[0120] The manganese oxides prepared by the MOF derivatization method are mainly in the oxidized state of trivalent manganese, while those prepared by the precipitation method are in a mixed state of trivalent and tetravalent manganese. Catalysts with the Mn₂O₃ crystalline phase as the main component exhibit better low-temperature redox performance, which is beneficial for the HC-SCR reaction. 0.4 Mn-MOF / ZSM-5 catalyst 3+ The relative content of [agent] (79.18%) is much greater than that of Mn. 0.4 -C / ZSM-5 catalyst (58.96%). Higher Mn content. 3+ / Mn 4+ A higher ratio means the catalyst has a higher oxygen vacancy density (Ov), which is beneficial for improving the catalytic oxidation efficiency of HC. Mn 0.4 -High Mn of MOF / ZSM-5 catalyst 3+ / Mn 4+ This ratio generates more oxygen vacancies (Ov). More oxygen vacancies lead to faster oxygen migration, thus improving the catalyst's catalytic performance. Therefore, the active component prepared using the MOF derivatization method is more conducive to the HC-SCR reaction.

[0121] The active components Mn-MOF and Mn obtained in Comparative Example 1 0.4 XRD pattern of MOF / ZSM-5 catalyst and Mn of active component Mn-C obtained in Comparative Example 2 0.4 The XRD pattern of the -C / ZSM-5 catalyst is shown below. Figure 5 As shown.

[0122] Mn obtained from Comparative Example 1 0.4 XPS spectra of Mn2P for the MOF / ZSM-5 catalyst and the catalyst obtained in Comparative Example 2 are as follows: Figure 6 As shown in (a).

[0123] Mn obtained from Comparative Example 1 0.4 -MOF / ZSM-5 catalyst and Mn obtained from Comparative Example 2 0.4 XPS spectra of O1s of the -C / ZSM-5 catalyst are as follows: Figure 6 As shown in (b).

[0124] from Figure 5 It can be seen that the manganese oxide prepared by the MOF derivatization method mainly has the oxidized state of trivalent manganese, while the manganese oxide prepared by the precipitation method has a mixed state of trivalent and tetravalent manganese. Considering the catalytic effect of HC-SCR, the catalyst with the Mn2O3 crystalline phase as the main component has better low-temperature redox performance, which is beneficial to the HC-SCR reaction.

[0125] from Figure 6 (a) It can be seen that in Mn-MOF / ZSM-5 and Mn-C / ZSM-5 catalysts, Mn element is mainly distributed as Mn 3+ (641.9 eV) and Mn 4+ MnO exists in the form of (643.8 eV) and may be highly dispersed on the catalyst surface. Higher Mn content... 3+ / (Mn 3 + + Mn 4+ The ratio of ) means that the catalyst has a higher oxygen vacancy density (O) v This accelerates oxygen migration, which is beneficial for improving the catalytic oxidation efficiency of HC.

[0126] from Figure 6 (b) It can be seen that: Mn prepared by MOF derivatization 0.4 -MOF / ZSM-5 catalyst surface active oxygen O α The proportion is higher than that of Mn 0.4 -C / ZSM-5. This may be due to Mn 0.4 -High Mn of MOF / ZSM-5 catalyst 3+ / (Mn 3+ + Mn 4+ The ratio of oxygen vacancies (O) produces more oxygen vacancies. v This improves the catalytic performance of the catalyst.

[0127] 3. Effects of solid-state grinding and precipitation methods on catalyst performance.

[0128] The catalysts described in Comparative Examples 1 and 3 catalyze NO x Conversion efficiency such as Figure 7 As shown in (a), the catalytic conversion efficiency of CH is as follows: Figure 7 As shown in (b).

[0129] from Figure 7 It can be seen from the data that: throughout the entire temperature testing range, the Mn prepared by solid-state grinding method... 0.4 The activity of the MOF / ZSM-5 catalyst is much greater than that of the catalyst prepared by the deposition-precipitation method. This may be because the catalyst prepared by the deposition-precipitation method suffers from excessive loss of active components and uneven distribution, resulting in low catalytic efficiency.

[0130] To further analyze the loading and dispersion of Mn-MOF on molecular sieves, the microstructure and structure of molecular sieve catalysts with different loading methods were analyzed by SEM and EDS.

[0131] Mn prepared in Comparative Example 1 0.4 SEM image of the MOF / ZSM-5 solid-phase milling catalyst is shown below. Figure 8 As shown in (a), the Mn prepared in Comparative Example 3 0.4 SEM image of the MOF / ZSM-5 deposited catalyst is shown below. Figure 8 As shown in (b).

[0132] from Figure 8 (a) shows that in Mn 0.4 In the MOF / ZSM-5 solid-phase milling catalyst, large ZSM-5 molecular sieves with uniformly dispersed MnO can be clearly seen. x Small particles; from Figure 8 (b) shows that Mn 0.4 A smooth ZSM-5 molecular sieve surface was observed on the MOF / ZSM-5- deposited catalyst, with no obvious particulate growth on the catalyst surface. This may be due to the presence of Mn. 0.4 - The MOF was not loaded onto the molecular sieve or entered the pores of the molecular sieve.

[0133] Mn prepared in Comparative Example 1 0.4 EDS spectra of the MOF / ZSM-5 solid-phase milling catalyst, as shown Figure 8 (c) and Figure 8 As shown in (d).

[0134] from Figure 8 (c) and Figure 8 As can be seen from (d), the distribution of Mn and O atoms on the catalyst is relatively uniform, indicating that the active component Mn-MOF has good dispersion on the catalyst.

[0135] Mn 0.4 -MOF / ZSM-5- deposited precipitation catalysts, as shown in Figure 8 (e) and Figure 8 (f).

[0136] From Figure 8 (e) and Figure 8 (f) can be seen: the distribution of O atoms on the catalyst is uneven, and only a small part of the Mn atoms on the catalyst.

[0137] From Figure 8 (g) and Figure 8 (h) can be seen: the O distribution on the surface of the Mn0.4-MOF / ZSM-5- solid phase grinding catalyst is uniform, while the O on the surface of the Mn0.4-MOF / ZSM-5- deposited precipitation catalyst is aggregated and unevenly distributed.

[0138] In addition, the mass percentage of Mn 0.4 -MOF / ZSM-5- solid phase grinding catalyst prepared by Comparative Example 1 is 9.67%, and the mass percentage of Mn 0.4 -MOF / ZSM-5- deposited precipitation catalyst prepared by Comparative Example 3 is 5.07%, which indicates that the method of loading Mn-MOF by deposition precipitation method will cause too much loss of active components, which also directly leads to Mn 0.4 -MOF / ZSM-5- deposited precipitation catalyst is lower than that of Mn 0.4 -MOF / ZSM-5- solid phase grinding catalyst.

[0139] 4. The effect of different Mn, Ce ratios on the performance of Mn x Ce y -MOF / ZSM-5 catalyst (x:y is the mole ratio of Mn, Ce)

[0140] The conversion efficiency of NO x catalyzed by the catalysts described in Examples 1-6 is shown in Figure 9 (a), and the conversion efficiency of CH4catalyzed is shown in Figure 9 (b).

[0141] From Figure 9 (a) and Figure 9 (b) can be seen: with the increase of the relative content of Mn, the activity of the catalyst first increases, and when Mn:Ce = 4:1, the activity of the catalyst reaches the maximum. This may be due to the active component Mn 3+The content of Mn increased with the increase of the proportion of Mn, providing more active sites for HC-SCR reaction. When the relative content of Mn continued to increase, the activity decreased. This may be because the relative proportion of Ce increased, causing more Ce 4+ + Mn 3+ → Ce 3+ + Mn 4+ oxidation reaction, resulting in a decrease in the content of Mn 3+ . At the same time, the conversion rate of HC also remained at a relatively high low-temperature removal rate and tended to be stable after Mn:Ce = 4:1 and higher proportions. This may be because the relative proportion of Ce increased, causing more Ce 3+ was generated, which was beneficial to the generation of more oxygen vacancies, accelerating the oxygen migration, and was beneficial to the oxidation reaction of HC.

[0142] 5. The effect of different proportions of active ingredients and carriers on the performance of the catalyst.

[0143] The conversion efficiency of NO x catalyzed by the catalysts described in Examples 7-10 is shown in Figure 10 (a), and the conversion efficiency of CH catalyzed is shown in Figure 10 (b).

[0144] As can be seen from Figure 10 (a) and Figure 10 (b), with the increase of the active component, the catalyst activity also gradually increased. And the growth rate was obvious at first and then slow. When the active component accounted for 4:10, although the activity and temperature zone were still improved, the relative growth was not obvious compared with the previous one, and the catalytic activity almost reached a peak. This may be because the large specific surface area of the molecular sieve can provide a large amount of active component loading, and when a certain content is reached, the reaction activity of the catalyst also almost reaches a certain peak. Because more active components cannot bring higher conversion rate and wider temperature window, the proportion of active component:molecular sieve is 4:10, which is more economical and environmentally friendly.

[0145] Although the above examples have been shown and described, it can be understood that the above examples are exemplary and cannot be understood as limiting the present application, and the changes, modifications, replacements and variations of the above examples made by those of ordinary skill in the art are within the protection scope of the present application.

Claims

1. A composition for preparing an HC-SCR catalyst, characterized in that, Including manganese source, cerium source, terephthalic acid, ZSM-5 molecular sieve and solvent; The manganese source comprises a 50 wt% manganese nitrate solution; the cerium source comprises cerium nitrate hexahydrate with a purity of 99.5%; the terephthalic acid has a purity of 99%; the solvent comprises one or both of N,N-dimethylformamide and anhydrous ethanol. The molar ratio of the manganese source to the cerium source is (1-7):1; And / or, the total molar number of manganese and cerium elements to the molar ratio of the terephthalic acid is 1:(1.0-1.4). And / or, the molar ratio of the manganese source to the ZSM-5 molecular sieve is (2-6):10; And / or, the molar ratio of the manganese source to the solvent is 1:(120-170).

2. A method for preparing an HC-SCR catalyst, characterized in that the HC-SCR catalyst comprises a support and an active component supported on the support, wherein the support is a ZSM-5 support and the active component is MnCeOx; and / or, the molar ratio of the support to the active component is (4-10):

2. Prepared using the composition according to claim 1.

3. The preparation method according to claim 2, characterized in that, Includes the following steps: (1) The manganese source, the cerium source, the terephthalic acid and the solvent are mixed and reacted. The reaction product is then calcined to obtain the active component MnCeO. X ; (2) The active component and ZSM-5 molecular sieve are mixed and ground to obtain the HC-SCR catalyst.

4. The preparation method according to claim 3, characterized in that, In step (1), the reaction temperature is 95-120℃ and the reaction time is 10-14h; And / or, the calcination includes a first stage calcination and a second stage calcination. The first stage calcination is carried out under a nitrogen atmosphere at a temperature of 300-400°C for 2-4 hours. The second stage calcination is carried out under an air atmosphere at a temperature of 300-400°C for 2-4 hours. The second stage calcination is carried out after the first stage calcination is completed and cooled to room temperature.

5. The preparation method according to claim 3, characterized in that, The grinding was carried out in an agate mortar; And / or, the grinding time is 30-60 min.

6. A method for treating coke oven flue gas, characterized in that, The reaction is carried out under the action of the HC-SCR catalyst obtained by the preparation method according to any one of claims 2-5.

7. The method according to claim 6, characterized in that, The coke oven flue gas includes one or more of NO, NO2, and C3H6; And / or, the temperature of the reaction is 150-350°C; And / or, the volumetric space velocity of the coke oven flue gas is 25,000-35,000 / h.

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