Bimetal CO-SCR catalyst as well as preparation method and application thereof

Abstract

The invention discloses a bimetallic CO-SCR catalyst and a preparation method and application thereof, and belongs to the technical field of catalytic materials. The bimetallic CO-SCR catalyst comprises the following raw materials: an X metal precursor, a Y metal precursor, a ligand and a carrier, x metal in the X metal precursor is precious metal; y metal in the Y metal precursor is non-noble metal. According to the bimetal CO-SCR catalyst, coordination of bimetal X and Y is utilized, high oxygen resistance of the X-Y bimetal catalyst is achieved through the steric hindrance effect by means of the synergistic effect of ligands, the preparation method is simple, and an important reference basis is provided for preparation of the catalyst for CO selective catalytic reduction of NOx (CO-SCR) in the oxygen-containing environment.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic materials, and in particular to a bimetallic CO-SCR catalyst and a preparation method and application thereof. Background Art

[0002] NO x and CO are the main gaseous pollutants emitted by industries, posing a serious threat to the atmospheric environment and human health. Selective catalytic reduction (SCR) has been widely used in NO x The SCR method with CO as a reducing agent (CO-SCR) has great application potential. However, in an oxygen-containing environment, the design of catalysts faces challenges, especially avoiding excessive adsorption of O2 by the catalyst to improve NO x Precious metal-based catalysts have excellent catalytic performance and high efficiency in NO x The strong adsorption of O2 by noble metals has attracted wide attention due to their reducing ability, but the competitive adsorption effect caused by the strong adsorption of O2 by noble metals will significantly reduce their selectivity in the CO-SCR reaction, resulting in a decrease in catalyst activity. Therefore, how to design a catalyst that can inhibit the adsorption of O2 on noble metal sites has become a key issue in the current research on CO-SCR catalysts.

[0003] Traditional single metal catalysts have limitations in solving the above problems, so bimetallic catalysts have gradually become an important research direction. By rationally selecting a second metal Y (such as Cu metal) to coordinate with X, the competitive adsorption of O2 can be effectively inhibited through the steric hindrance effect, the antioxidant capacity of the catalyst can be enhanced, and the selectivity and stability of the catalyst can be improved. In addition, appropriate ligands can not only stabilize the metal center, but also improve the coordination efficiency and stability. By optimizing the synergistic effect of metal-ligand, the competitive adsorption of O2 can be more effectively inhibited, while maintaining the selectivity and stability of NO. x However, in practical applications, the oxygen content of industrial waste gas is usually high and complex, and the effect and stability of existing catalysts in high-oxygen environments are not ideal. The high oxygen content will cause the active sites to be over-occupied, thus affecting the CO and NO x adsorption and catalytic reaction, reducing denitrification efficiency and selectivity. In addition, the synthesis process of molecular sieves used in existing catalysts is complicated and has strict requirements on experimental conditions and operation, which undoubtedly increases the difficulty and cost of preparation and makes it difficult to produce on a large scale. Summary of the invention

[0004] The purpose of the present invention is to provide a bimetallic CO-SCR catalyst and a preparation method and application thereof, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: a bimetallic CO-SCR catalyst, the raw materials of which include an X metal precursor, a Y metal precursor, a ligand and a carrier;

[0007] The X metal in the X metal precursor is a noble metal;

[0008] The Y metal in the Y metal precursor is a non-noble metal.

[0009] In the technical solution of the present invention, the X metal in the X metal precursor and the Y metal in the Y metal precursor have a coordination effect, and the coordination effect of the X metal and the Y metal is stronger than the coordination effect of X-O2.

[0010] In the technical solution of the present invention, the X metal is selected from any one of Pt, Ir and Ag;

[0011] The Y metal is selected from any one of Cu, Co, W and Nb.

[0012] Preferably, the X metal is Pt and the Y metal is Cu.

[0013] In the technical solution of the present invention, the ligand includes ethylenediaminetetraacetic acid or triethanolamine.

[0014] Furthermore, the ligand is ethylenediaminetetraacetic acid.

[0015] The ligand used in the present invention has strong chelating ability and multi-coordination, and can make X metal and Y metal strongly coordinated.

[0016] In the technical solution of the present invention, the carrier is an inert carrier (the inert carrier will not interact with the metal active component, which is conducive to obtaining low-valent active species); the inert carrier includes SiO2 or all-silicon ZSM-5 molecular sieve.

[0017] Preferably, the inert carrier is SiO2; the specific surface area of ​​the SiO2 is 200 to 250 m 2 / g, preferably 200m 2 / g.

[0018] In the technical solution of the present invention, the loading amount of the X metal is 0.1 to 2.0 wt.% of the mass of the bimetallic CO-SCR catalyst.

[0019] Preferably, the loading amount of the X metal is 0.5 wt.% or 1 wt.% of the mass of the bimetallic CO-SCR catalyst.

[0020] Technical solution 2 of the present invention: A method for preparing the above-mentioned bimetallic CO-SCR catalyst comprises the following steps:

[0021] The X metal precursor, the Y metal precursor, the ligand and the carrier are dissolved in a solvent to obtain a mixed solution, and the solvent is removed after stirring for reaction, and the mixture is dried, calcined and activated to obtain the bimetallic CO-SCR catalyst (CO-SCR catalyst loaded with X metal and Y metal).

[0022] In the technical solution of the present invention, the calcination includes calcination in an air atmosphere or an inert atmosphere, the calcination temperature is 400 to 500° C., preferably 450° C., and the calcination time is 2 to 6 hours, preferably 3 hours;

[0023] And / or, the activation comprises activation in a reducing atmosphere, the activation heating rate is 6-10°C / min, the temperature is 200-400°C, and the time is 1-4h.

[0024] Preferably, the activation heating rate is 6°C / min, 8°C / min or 10°C / min, the temperature is 300°C, and the time is 1 hour.

[0025] More preferably, the activation heating rate is 10°C / min.

[0026] In the technical solution of the present invention, the molar amount of the ligand is 1.2 to 2 times, preferably 1.5 times, the molar amount of the M metal precursor.

[0027] Preferably, the X metal precursor is platinum acetate or chloroplatinic acid, more preferably chloroplatinic acid.

[0028] In the technical solution of the present invention, the Y metal precursor is selected from any one of copper nitrate, cobalt nitrate, ammonium metatungstate, and niobium oxalate.

[0029] Preferably, the Y metal precursor is copper nitrate.

[0030] Preferably, the loading ratio of the X metal to the Y metal in the bimetallic CO-SCR catalyst is 1:(5-10), preferably 1:5.

[0031] Preferably, the inert atmosphere includes at least one of N2, Ar and He; the reducing atmosphere includes at least one of H2, CO and NH3.

[0032] In the technical solution of the present invention, the solvent includes water and / or ethanol, preferably water.

[0033] In the technical solution of the present invention, the pH value of the mixed solution is 3-7, preferably 7.

[0034] In the technical solution of the present invention, the temperature of the stirring reaction is 25 to 80° C., preferably 60° C.; the time of the stirring reaction is 1 to 12 hours, preferably 6 hours.

[0035] In the technical solution of the present invention, the method for removing the solvent includes rotary evaporation, filtration or centrifugation.

[0036] In the technical solution of the present invention, the rotation speed of the rotary evaporation is 60-80 rpm, preferably 60 rpm, 70 rpm or 80 rpm, and more preferably 80 rpm.

[0037] In the technical solution of the present invention, the rotary evaporation is carried out by water bath heating, and the heating temperature is 60-80°C, preferably 80°C.

[0038] In the technical solution of the present invention, the filtering or centrifuging also includes washing with ethanol.

[0039] In the technical solution of the present invention, the drying method includes vacuum drying and / or air atmosphere drying, preferably air atmosphere drying.

[0040] Preferably, the drying temperature is 80-100°C, preferably 80°C.

[0041] The X metal in the bimetallic CO-SCR catalyst is in a highly dispersed state, providing sufficient active sites for the adsorption and activation of NO and CO; the Y metal coordinates with the X metal to prevent O2 from being adsorbed on the X metal site, thereby reducing competitive adsorption and improving the selectivity of the catalyst for ideal products under oxygen-containing conditions; the ligand can improve the coordination efficiency and stability of the XY bimetal, and improve the antioxidant capacity and selectivity of the catalyst through the steric effect; the carrier is an inert carrier and it is difficult to interact with the active component, which is conducive to obtaining low-valent active species.

[0042] The bimetallic CO-SCR catalyst of the present invention utilizes the coordination of bimetallic X and Y and, with the help of the synergistic effect of the ligands, realizes high oxygen resistance on the XY bimetallic catalyst by the steric hindrance effect. The preparation method is simple and can be used for selective catalytic reduction of NO by CO in an oxygen-containing environment. x It provides an important reference for the preparation of (CO-SCR) catalysts.

[0043] Technical solution 3 of the present invention: A bimetallic CO-SCR catalyst catalytically reduces NO x (Selective catalytic reduction of NO with CO x ), CO oxidation or photocatalytic methanol to hydrogen production.

[0044] In the technical solution of the present invention, the NO x Including NO xAutomobile exhaust or industrial waste gas.

[0045] Technical solution four of the present invention: an application of the above-mentioned bimetallic CO-SCR catalyst in the denitrification of industrial flue gas with high oxygen content.

[0046] In the technical solution of the present invention, the gas contained in the high oxygen content industrial flue gas includes NO x , CO, O2, wherein the concentration of oxygen is 10-15 vol.%, preferably 10 vol.%; NO x The concentration is 400-500 ppm, preferably 400 ppm (ppm refers to volume concentration, NO x If it is 400ppm, then in every 1 million volume units of feed gas, NO x The volume occupied by the gas is 400 volume units); the CO concentration is 400 to 8000 ppm, preferably 2000 ppm.

[0047] In the technical solution of the present invention, the temperature of the catalytic reduction is 200-350°C, preferably 200-300°C.

[0048] In the technical solution of the present invention, the space velocity of the catalytic reduction is 15000~40000h -1 , preferably 15000h -1 .

[0049] The present invention discloses the following technical effects:

[0050] (1) The bimetallic CO-SCR catalyst of the present invention is particularly suitable for selective catalytic reduction of NO by CO in an oxygen-containing environment. x (CO-SCR) reaction has important guiding significance and application value for industrial flue gas pollution control.

[0051] (2) The present invention uses an inert carrier to load the active component, and it is difficult for the carrier and the active component to interact with each other, which is conducive to obtaining low-valent active species and improving the low-temperature activity and stability of the catalyst.

[0052] (3) The bimetallic CO-SCR catalyst of the present invention achieves efficient CO-SCR denitrification in a high-oxygen environment, providing new ideas and references for the development of oxygen-containing flue gas denitrification technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] Figure 1 This is a schematic diagram of a bimetallic catalyst for denitrification of industrial flue gas with high oxygen content guided by the steric hindrance effect of the present invention.

[0055] Figure 2 The conversion rate of NO over Ir-Co / ZSM-5 catalysts with different Ir loadings at different temperatures.

[0056] Figure 3 The conversion rates of NO for the catalysts prepared in Example 3 and Comparative Example 1 at different temperatures.

[0057] Figure 4 The conversion rates of NO at different temperatures for 0.5% Ir-Co / ZSM-5 prepared in Example 3, 0.5% Ir-Co / SSZ-13 prepared in Comparative Example 2 and 0.5% Ir-Co / HY catalysts.

[0058] Figure 5 The conversion rates of NO and CO of the 0.5% Ir-Co / ZSM-5 catalyst prepared in Example 3 at different oxygen contents.

[0059] Figure 6 N2 selectivity and catalytic stability of the 0.5% Ir-Co / ZSM-5 catalyst prepared in Example 3. DETAILED DESCRIPTION

[0060] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0061] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0062] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0063] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0064] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0065] Example 1

[0066] A bimetallic CO-SCR catalyst for denitrification of industrial flue gas with high oxygen content:

[0067] 0.27 mL of H2PtCl6 aqueous solution (0.242 M), 0.476 g of Cu(NO3)2·3H2O and 0.0287 g of ligand (ethylenediaminetetraacetic acid) were dissolved in 250 mL of deionized water, and after sufficient stirring, a clear solution was formed. Subsequently, 2.500 g of SiO2 was added, and the resulting slurry was heated to 80°C and stirred for 6 h, and the temperature was maintained for rotary evaporation until the water was completely evaporated (the speed of the rotary evaporation was 80 rpm, and water bath heating was used). The collected solid was dried in a vacuum oven at 80°C, then calcined at 450°C for 3 h in an air atmosphere, cooled to room temperature, and reduced at 400°C for 2 h in a reducing atmosphere (5 vol.% H2 / Ar) (heating rate was 10°C / min) to obtain a Pt-Cu / SiO2 catalyst with a Pt loading of 0.5 wt.% and a Cu loading of 5 wt.%.

[0068] Example 2

[0069] 5.12 mL of H2IrCl6 (0.0203 M) aqueous solution was mixed with 0.268 g (NH4)6H2 12 O 40x(H2O) and 0.0456g ethylenediaminetetraacetic acid were dissolved in deionized water and stirred thoroughly to form a clear solution. Subsequently, 4g SiO2 was added, and the resulting slurry was heated to 80°C and stirred for 6h, and the temperature was maintained for rotary evaporation until the water was completely evaporated (the speed of the rotary evaporation was 80rpm, and the water bath was used for heating). The collected solid was dried in a vacuum oven at 80°C, then calcined at 450°C for 3h in an air atmosphere, cooled to room temperature, and reduced at 200°C for 1h in a reducing atmosphere (5vol.%H2 / Ar) (heating rate was 10°C / min) to obtain an Ir-W / SiO2 catalyst with an Ir loading of 0.5wt.% and a W loading of 5wt.%.

[0070] Example 3

[0071] 5.12 mL of H2IrCl6 (0.0203 M) aqueous solution, 0.99 g of Co(NO3)26H2O and 0.0456 g of ethylenediaminetetraacetic acid were dissolved in deionized water, and after sufficient stirring, a clear solution was formed. Subsequently, 4 g of all-silicon ZSM-5 molecular sieve was added, and the resulting slurry was heated to 80°C and stirred for 6 h, and the temperature was maintained for rotary evaporation until the water was completely evaporated (the speed of the rotary evaporation was 80 rpm, and water bath heating was used). The collected solid was dried in a vacuum oven at 80°C, then calcined at 450°C for 3 h in an air atmosphere, cooled to room temperature, and reduced at 200°C for 1 h (heating rate of 10°C / min) in a reducing atmosphere (5 vol.% H2 / Ar) to obtain an Ir-Co / ZSM-5 catalyst (0.5% Ir-Co / ZSM-5), with an Ir loading of 0.5 wt.% and a Co loading of 5 wt.%.

[0072] Example 4

[0073] The same as Example 3, except that the amount of H2IrCl6 was changed so that the Ir loading amounts were 0.1wt.%, 0.3wt.%, 0.7wt.%, and 1wt.%, respectively.

[0074] The conversion rate of NO by the catalysts prepared in Example 3 and Example 4 was determined as follows:

[0075] 0.35 g of Ir-Co / ZSM-5 catalyst (particle size of 40-60 mesh) was placed in a continuous flow fixed bed reactor (inner diameter 6 mm). The composition of the reaction gas was 400 ppm NO, 8000 ppm CO, 5 vol.% O2, nitrogen was used as the balance gas, the flow rate of the reaction gas was 100 mL / min, and the space velocity was 15000 h -1 The activity evaluation temperature range is 150~350℃. The conversion rate of NO reduction by the catalyst at different temperatures is shown in Table 2. Figure 2 .

[0076] Comparative Example 1

[0077] The same as Example 3, except that no ligand was added during the preparation of the 0.5% Ir-Co / ZSM-5 catalyst, and the obtained catalyst was named NO EDTA.

[0078] The conversion rate of NO by the catalysts prepared in Example 3 (EDTA) and Comparative Example 1 (NO EDTA) was determined using the same method as above. The results are shown in Figure 3 .

[0079] Comparative Example 2

[0080] The same as Example 3, except that the all-silicon ZSM-5 molecular sieve is replaced with an equal mass of SSZ-13 molecular sieve or HY molecular sieve to prepare 0.5% Ir-Co / SSZ-13 catalyst and 0.5% Ir-Co / HY catalyst.

[0081] The conversion rate of NO by the 0.5% Ir-Co / ZSM-5 catalyst prepared in Example 3 and the 0.5% Ir-Co / SSZ-13 catalyst and the 0.5% Ir-Co / HY catalyst prepared in Comparative Example 2 was determined as follows:

[0082] 0.35 g 0.5% Ir-Co / ZSM-5 catalyst, 0.4 g 0.5% Ir-Co / SSZ-13 catalyst or 0.55 g 0.5% Ir-Co / HY catalyst (all with a particle size of 40-60 mesh) was placed in a continuous flow fixed bed reactor (inner diameter 6 mm). The composition of the reaction gas was 400 ppm NO, 8000 ppm CO, 5 vol.% O2, nitrogen was used as the balance gas, the flow rate of the reaction gas was 100 mL / min, and the space velocity was 15000 h -1 The activity evaluation temperature range is 150~350℃. The conversion rate of NO reduction by the catalyst at different temperatures is shown in Table 2. Figure 4 .

[0083] Effect Example 1

[0084] The conversion rates of NO and CO of the 0.5% Ir-Co / ZSM-5 catalyst prepared in Example 3 at different oxygen contents were determined as follows:

[0085] 0.35 g of the 0.5% Ir-Co / ZSM-5 catalyst (particle size of 40-60 mesh) prepared in Example 3 was placed in a continuous flow fixed bed reactor (inner diameter 6 mm). The composition of the reaction gas was 400 ppm NO, 8000 ppm CO, 5-20 vol.% O2 (i.e., the O2 content was 5 vol.%, 10 vol.%, 15 vol.% or 20 vol.%), nitrogen was used as the balance gas, the flow rate of the reaction gas was 100 mL / min, and the space velocity was 15000 h -1 The activity evaluation temperature range is 150~350℃. The conversion rates of NO and CO at different temperatures are shown in Figure 5 .

[0086] Effect Example 2

[0087] The N2 selectivity of the 0.5% Ir-Co / ZSM-5 catalyst prepared in Example 3 and the catalytic stability of the catalyst for reducing NO were determined as follows:

[0088] 0.35 g of the 0.5% Ir-Co / ZSM-5 catalyst (particle size of 40-60 mesh) prepared in Example 3 was placed in a continuous flow fixed bed reactor (inner diameter 6 mm). The composition of the reaction gas was 400 ppm NO, 8000 ppm CO, 5-20 vol.% O2 (i.e., the O2 content was 5 vol.%, 10 vol.%, 15 vol.% or 20 vol.%), nitrogen was used as the balance gas, the flow rate of the reaction gas was 100 mL / min, and the space velocity was 15000 h -1 The activity evaluation temperature range is 150~350℃. The results of N2 selectivity (below 200℃, the conversion rate is not high, no statistics were conducted) and catalytic stability of catalyst for NO reduction (250℃) are shown in Figure 6 .

[0089] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A bimetallic CO-SCR catalyst, characterized in that: The raw materials include an X metal precursor, a Y metal precursor, a ligand and a carrier; The X metal in the X metal precursor is a noble metal; The Y metal in the Y metal precursor is a non-noble metal.

2. The bimetallic CO-SCR catalyst according to claim 1, characterized in that: The X metal in the X metal precursor and the Y metal in the Y metal precursor have a coordination effect, and the coordination effect between the X metal and the Y metal is stronger than the coordination effect of X-O2.

3. The bimetallic CO-SCR catalyst according to claim 2, characterized in that: The X metal is selected from any one of Pt, Ir and Ag; And / or, the Y metal is selected from any one of Cu, Co, W and Nb.

4. The bimetallic CO-SCR catalyst according to claim 1, characterized in that: The ligand includes ethylenediaminetetraacetic acid or triethanolamine.

5. The bimetallic CO-SCR catalyst according to claim 1, characterized in that: The loading amount of the X metal is 0.1-2.0 wt.% of the mass of the bimetallic CO-SCR catalyst.

6. A method for preparing a bimetallic CO-SCR catalyst according to any one of claims 1 to 5, characterized in that: The following steps are involved: The X metal precursor, the Y metal precursor, the ligand and the carrier are dissolved in a solvent, mixed and reacted, and then the solvent is removed, calcined and activated to obtain the bimetallic CO-SCR catalyst.

7. The preparation method according to claim 6, characterized in that: The calcination includes calcination in an air atmosphere or an inert atmosphere, the calcination temperature is 400 to 500° C., and the time is 2 to 6 hours; And / or, the activation includes activation in a reducing atmosphere, the activation temperature is 200-400° C., and the activation time is 1-4 hours.

8. The preparation method according to claim 6, characterized in that: The molar amount of the ligand is 1.2 to 2 times the molar amount of the X metal precursor.

9. A bimetallic CO-SCR catalyst according to any one of claims 1 to 5 for catalytic reduction of NO x , CO oxidation or photocatalytic methanol to hydrogen production.

10. Use of the bimetallic CO-SCR catalyst according to any one of claims 1 to 5 in denitrification of industrial flue gas with high oxygen content.

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