A dual-metal CO-SCR catalyst, its preparation method and application

Abstract

The present invention discloses a bimetallic CO-SCR catalyst, a preparation method thereof and an application thereof, belonging to the technical field of catalytic materials. The bimetallic CO-SCR catalyst of the present invention has raw materials including 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. The bimetallic CO-SCR catalyst of the present invention utilizes the coordination of bimetallic X and Y and, with the synergistic effect of the ligand, realizes high oxygen tolerance on the X-Y bimetallic catalyst by means of a steric hindrance effect. The preparation method is simple and provides an important reference basis for the preparation of a catalyst for selective catalytic reduction of NO x (CO-SCR) in an 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 using CO as a reducing agent (CO-SCR) has great application potential. However, in an oxygen-containing environment, the design of the catalyst faces challenges, especially avoiding excessive adsorption of O2 by the catalyst to improve NO x The selective reduction efficiency of NO is high. x While noble metals have attracted widespread attention due to their strong O2 reduction capabilities, the competitive adsorption effect caused by their strong adsorption of O2 can significantly reduce their selectivity in the CO-SCR reaction, leading to a decrease in catalytic activity. Therefore, how to design a catalyst that can inhibit O2 adsorption on noble metal sites has become a key issue in current CO-SCR catalyst research.

[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 suppressed through the steric 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 suppressed while maintaining the selectivity and stability of NO. x However, in actual 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 The adsorption and catalytic reaction of nitrates reduces the efficiency and selectivity of denitrification. In addition, the synthesis process of molecular sieves used in existing catalysts is complex and requires strict experimental conditions and operations, which undoubtedly increases the difficulty and cost of preparation and makes large-scale production more difficult. 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 including an X metal precursor, a Y metal precursor, a ligand and a support;

[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] Further, the ligand is ethylenediaminetetraacetic acid.

[0015] The ligand adopted by the present invention has strong chelating ability and multi-coordination, and can strongly coordinate the X metal and the Y metal.

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

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

[0018] In the technical solution of the present invention, the loading amount of the X metal is 0.1-2.0 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] The second technical solution of the present invention: A preparation method of the above-mentioned bimetallic CO-SCR catalyst, comprising the following steps:

[0021] Dissolve the X metal precursor, Y metal precursor, ligand and support in a solvent to obtain a mixed solution. After stirring and reacting, remove the solvent, dry, calcine, and activate to obtain the bimetallic CO-SCR catalyst (the 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 400-500 °C, preferably 450 °C, and the calcination time is 2-6 h, preferably 3 h;

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

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

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

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

[0027] Preferably, the X metal precursor is platinum acetate or chloroplatinic acid, and 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 ratio of the loading amounts of the X metal and 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 h, preferably 6 h.

[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 to 80 rpm, preferably 60 rpm, 70 rpm or 80 rpm, more preferably 80 rpm.

[0037] In the technical solution of the present invention, water bath heating is adopted during the rotary evaporation, and the heating temperature is 60 to 80 °C, preferably 80 °C.

[0038] In the technical solution of the present invention, during the filtration or centrifugation, washing with ethanol is further included.

[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 to 100 °C, preferably 80 °C.

[0041] In the bimetallic CO-SCR catalyst, the X metal 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 adsorbing on the X metal sites, thereby reducing competitive adsorption and improving the selectivity of the ideal product of the catalyst under oxygen-containing conditions; the ligand can enhance the coordination efficiency and stability of the X-Y bimetal, and improve the antioxidant capacity and selectivity of the catalyst through steric hindrance effects; the carrier is an inert carrier, which is difficult to interact with the active components, facilitating the formation of low-valence active species.

[0042] The bimetallic CO-SCR catalyst of the present invention utilizes the coordination of the bimetals X and Y and the synergistic effect of the ligand to achieve high oxygen tolerance on the X-Y bimetallic catalyst through steric hindrance effects. The preparation method is simple and provides an important reference for the preparation of a catalyst for the selective catalytic reduction of NO x (CO-SCR).

[0043] The third technical solution of the present invention: An application of the above bimetallic CO-SCR catalyst in the catalytic reduction of NO x (CO selective catalytic reduction of NO x )、CO oxidation or photocatalytic hydrogen production from methanol.

[0044] In the technical solution of the present invention, the NO x includes containing 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 denitrification of industrial flue gas with high oxygen content.

[0046] In the technical solution of the present invention, the gases contained in the industrial flue gas with high oxygen content include NO x , CO, O2. Among them, the concentration of oxygen is 10-15 vol.%, preferably 10 vol.%; NO x concentration is 400-500 ppm, preferably 400 ppm (ppm refers to volume concentration. When NO x is 400 ppm, it means that in every 1 million volume units of the feed gas, the volume of NO x gas accounts for 400 volume units); the CO concentration is 400-8000 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 15000-40000 h -1 , preferably 15000 h -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 the CO selective catalytic reduction of NO x (CO-SCR) reaction in an oxygen-containing environment, which has important guiding significance and application value for the treatment of industrial flue gas pollution.

[0051] (2) The present invention uses an inert carrier to support the active components, and it is difficult to generate an interaction between the carrier and the active components, which is beneficial to obtaining low-valence active species and improving the low-temperature activity and stability of the catalyst.

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

[0053] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

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

[0055] Figure 2 It is the conversion rate of NO by Ir-Co / ZSM-5 catalysts with different Ir loadings at different temperatures.

[0056] Figure 3 It is the conversion rate of NO by the catalysts prepared in Example 3 and Comparative Example 1 at different temperatures.

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

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

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

[0060] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

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

[0062] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0063] Without departing from the scope or spirit of this invention, various improvements and changes can be made to the specific embodiments of the specification of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the specification of this invention are obvious to those skilled in the art. The specification and examples of this invention are merely exemplary.

[0064] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all 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 an aqueous H2PtCl6 solution (0.242 M), 0.476 g of Cu(NO3)2·3H2O and 0.0287 g of a ligand (ethylenediaminetetraacetic acid) were dissolved in 250 mL of deionized water. After sufficient stirring, a clear solution was formed. Subsequently, 2.500 g of SiO2 was added. The obtained slurry was heated to 80 °C and stirred for reaction for 6 h, and rotary evaporation was carried out at this temperature until the water was completely evaporated (the rotation speed of 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 in an air atmosphere for 3 h, and reduced at 400 °C for 2 h in a reducing atmosphere (5 vol.% H2 / Ar) (the heating rate was 10 °C / min) after cooling to room temperature 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 an aqueous H2IrCl6 (0.0203 M) solution was mixed with 0.268 g of (NH4)6H2W 12 O 40· x(H2O) and 0.0456 g of ethylenediaminetetraacetic acid were dissolved in deionized water. After sufficient stirring, a clear solution was formed. Subsequently, 4 g of SiO2 was added, and the resulting slurry was heated to 80 °C and stirred for reaction for 6 h, and rotary evaporation was carried out at this temperature until the water was completely evaporated (the rotation speed of 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, and reduced at 200 °C for 1 h in a reducing atmosphere (5 vol.% H2 / Ar) (the heating rate was 10 °C / min) after cooling to room temperature to obtain the Ir-W / SiO2 catalyst with the Ir loading of 0.5 wt.% and the W loading of 5 wt.%.

[0070] Example 3

[0071] 5.12 mL of an aqueous solution of H2IrCl6 (0.0203 M) was dissolved in deionized water together with 0.99 g of Co(NO3)2·6H2O and 0.0456 g of ethylenediaminetetraacetic acid. After sufficient stirring, a clear solution was formed. Subsequently, 4 g of all-silica ZSM-5 molecular sieve was added, and the resulting slurry was heated to 80 °C and stirred for reaction for 6 h, and rotary evaporation was carried out at this temperature until the water was completely evaporated (the rotation speed of 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, and reduced at 200 °C for 1 h in a reducing atmosphere (5 vol.% H2 / Ar) (the heating rate was 10 °C / min) after cooling to room temperature to obtain the Ir-Co / ZSM-5 catalyst (0.5% Ir-Co / ZSM-5) with the Ir loading of 0.5 wt.% and the Co loading of 5 wt.%.

[0072] Example 4

[0073] Same as Example 3, the difference was only that the amount of H2IrCl6 was changed so that the Ir loadings were 0.1 wt.%, 0.3 wt.%, 0.7 wt.%, and 1 wt.% respectively.

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

[0075] 0.35 g of the Ir-Co / ZSM-5 catalyst (particle size 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, and 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 active evaluation temperature range was 150 - 350 °C. At different temperatures, the conversion rate of the catalyst for reducing NO is shown in Figure 2 .

[0076] Comparative Example 1

[0077] 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 rates of NO over the catalysts prepared in Example 3 (EDTA) and Comparative Example 1 (NO EDTA) were measured. The measurement method was the same as above, and the results are shown in Figure 3 。

[0079] Comparative Example 2

[0080] Same as Example 3, except that the all-silica ZSM-5 molecular sieve was 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 rates of NO over the 0.5% Ir-Co / ZSM-5 catalyst prepared in Example 3, the 0.5% Ir-Co / SSZ-13 catalyst and the 0.5% Ir-Co / HY catalyst prepared in Comparative Example 2 were measured. The measurement method was as follows:

[0082] 0.35 g of 0.5% Ir-Co / ZSM-5 catalyst, 0.4 g of 0.5% Ir-Co / SSZ-13 catalyst or 0.55 g of 0.5% Ir-Co / HY catalyst (particle size was 40 - 60 mesh) were 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, and 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 active evaluation temperature range was 150 - 350 °C. The conversion rates of the catalyst for reducing NO at different temperatures are shown in Figure 4 。

[0083] Effect Example 1

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

[0085] 0.35 g of the 0.5% Ir-Co / ZSM-5 catalyst prepared in Example 3 (particle size 40 - 60 mesh) was placed in a continuous flow fixed bed reactor (inner diameter 6 mm). The reaction gas composition was 400 ppm NO, 8000 ppm CO, 5 - 20 vol.% O2 (i.e., O2 contents of 5 vol.%, 10 vol.%, 15 vol.% or 20 vol.%), with nitrogen as the balance gas. The flow rate of the reaction gas was 100 mL / min and the space velocity was 15000 h -1 . The active evaluation temperature range was 150 - 350 °C. 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 measured. The measurement method was as follows:

[0088] 0.35 g of the 0.5% Ir-Co / ZSM-5 catalyst prepared in Example 3 (particle size 40 - 60 mesh) was placed in a continuous flow fixed bed reactor (inner diameter 6 mm). The reaction gas composition was 400 ppm NO, 8000 ppm CO, 5 - 20 vol.% O2 (i.e., O2 contents of 5 vol.%, 10 vol.%, 15 vol.% or 20 vol.%), with nitrogen as the balance gas. The flow rate of the reaction gas was 100 mL / min and the space velocity was 15000 h -1 . The active evaluation temperature range was 150 - 350 °C. The N2 selectivity (below 200 °C, the conversion rate was not high and not statistically analyzed) and the catalytic stability of the catalyst for reducing NO (250 °C) at different temperatures are shown in Figure 6 .

[0089] The above-described embodiments are only descriptions of the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A bimetallic CO-SCR catalyst for denitrification of industrial flue gas with high oxygen content, characterized in that, The raw materials include an X metal precursor, a Y metal precursor, a ligand, and a support; 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; 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; The X metal is selected from any one of Pt, Ir, and Ag; The Y metal is selected from any one of Cu, Co, W, and Nb; The ligand includes ethylenediaminetetraacetic acid or triethanolamine; The support includes SiO2 or all-silica ZSM-5 molecular sieve; The preparation method of the bimetallic CO-SCR catalyst includes the following steps: Dissolve the X metal precursor, the Y metal precursor, the ligand, and the support in a solvent, remove the solvent after mixing and reacting, and calcine and activate to obtain the bimetallic CO-SCR catalyst.

2. The bimetallic CO-SCR catalyst according to claim 1, wherein The loading amount of the X metal is 0.1-2.0 wt.% of the mass of the bimetallic CO-SCR catalyst.

3. The bimetallic CO-SCR catalyst according to claim 1, characterized in that, The calcination includes calcination in an air atmosphere or an inert atmosphere, the calcination temperature is 400-500 °C, and the time is 2-6 h; And / or, the activation includes activation in a reducing atmosphere, the activation temperature is 200-400 °C, and the time is 1-4 h.

4. The bimetallic CO-SCR catalyst according to claim 1, wherein The molar amount of the ligand is 1.2-2 times the molar amount of the X metal precursor.

5. Application of the bimetallic CO-SCR catalyst according to any one of claims 1 to 4 in denitrification of industrial flue gas with high oxygen content.

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