A ru-based catalyst, its preparation method and use

Abstract

This invention relates to a Ru-based catalyst, its preparation method, and its uses. The Ru-based catalyst comprises a cerium-tin composite oxide support and an active component Ru supported on the support. Based on a total mass of 100 wt% of the Ru-based catalyst, the content of the active component Ru is 0.5-2 wt%, with the remainder being the cerium-tin composite oxide support. This invention uses a cerium-tin composite oxide as the support and Ru as the active component to prepare the catalyst. Ru has good dispersion, and the active component, even at a low content, enables the catalyst to exhibit good low-temperature activity, N2 selectivity, and thermal stability. Compared with conventional catalyst supports, the cerium-tin composite oxide support of this invention itself possesses certain catalytic activity. After Ru is loaded onto it, the number of oxygen vacancies and active sites increases, thereby further enhancing the catalytic activity.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a Ru-based catalyst, its preparation method, and its uses. Background Technology

[0002] Ammonia (NH3) in the environment mainly originates from agriculture, animal husbandry, industry, and transportation, and its emissions directly impact the environment and human health. Motor vehicle exhaust is considered a major source of ammonia in cities, including exhaust from gasoline vehicles equipped with three-way catalytic converters and diesel vehicles using urea selective catalytic reduction (NH3-SCR) denitrification technology. The latter, in particular, produces significantly higher levels of nitrogen oxides (NOx) in its exhaust. x During the process, NH3 escape is likely to occur, so an NH3 purification device needs to be added at the end of the NH3-SCR purification system.

[0003] Currently, NH3 pollution control technologies mainly include biological methods, adsorption methods, catalytic decomposition methods, photocatalysis, and selective ammonia oxidation (NH3-SCO). Among these, NH3-SCO is a highly efficient and environmentally friendly NH3 purification technology, its core being a highly efficient and stable NH3 oxidation catalyst. NH3 oxidation catalysts mainly include noble metal catalysts, modified zeolite catalysts, and transition metal oxide catalysts. Noble metal catalysts are generally considered the most effective NH3 oxidation catalysts because they possess excellent NH3 oxidation activity. For example, Pt / Al2O3 catalysts are currently commercially available NH3 oxidation catalysts. However, excessive oxidation of NH3 produces many byproducts, such as N2O and NO. x wait.

[0004] Therefore, there is an urgent need to develop an NH3-SCO catalyst with excellent low-temperature activity and high N2 selectivity. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a Ru-based catalyst, its preparation method, and its applications. The Ru-based catalyst exhibits good low-temperature activity, N2 selectivity, and thermal stability. The preparation method is simple, and it possesses excellent low-temperature activity and N2 selectivity, meeting current market demands and showing promising practical application prospects.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a Ru-based catalyst, the Ru-based catalyst comprising a cerium-tin composite oxide support and an active component Ru supported on the support; the content of the active component Ru is 0.5-2.0 wt% based on 100 wt% of the total mass of the Ru-based catalyst, for example, it may be 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or 2.0 wt%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable, the balance being the cerium-tin composite oxide support.

[0008] The Ru-based catalyst of the present invention uses a cerium-tin composite oxide as a support and Ru as an active component. Ru has good dispersibility, and the active component can enable the catalyst to have good low-temperature activity, N2 selectivity and thermal stability even at a low content. Compared with conventional catalyst supports, the cerium-tin composite oxide support of the present invention has certain catalytic activity itself. After Ru is loaded on it, the oxygen vacancies and active sites are increased, thereby further improving the catalytic activity of the catalyst.

[0009] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0010] Preferably, the cerium-tin composite oxide support has the chemical formula Ce. x Sn 1-x O2, where 0.20≤x≤0.90, can be, for example, 0.20, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85 or 0.90, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, with 0.55≤x≤0.65 being the preferred value.

[0011] The cerium-tin composite oxide support in this invention has the chemical formula Ce. x Sn 1-x O2, where the value of x affects the reaction activity of the catalyst.

[0012] Preferably, based on the total mass of the Ru-based catalyst of 100 wt%, the content of the active component Ru is 1.0-2.0 wt%, for example, it can be 1.0 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, 1.5 wt%, 1.6 wt%, 1.7 wt%, 1.8 wt%, 1.9 wt%, or 2.0 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, and the balance is a cerium-tin composite oxide support.

[0013] Preferably, the cerium-tin composite oxide support is a nanorod structure.

[0014] Preferably, the average diameter of the cerium-tin composite oxide carrier is 5-7 nm, for example, it can be 5 nm, 5.5 nm, 6 nm, 6.5 nm or 7 nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the average length of the cerium-tin composite oxide carrier is 40-50 nm, for example, it can be 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm or 50 nm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0016] Preferably, the specific surface area of ​​the cerium-tin composite oxide carrier is 100-130 m². 2 / g, for example, could be 100m 2 / g、102m 2 / g, 104m 2 / g, 106m 2 / g, 108m 2 / g、110m 2 / g、112m 2 / g、114m 2 / g、115m 2 / g、116m 2 / g、117m 2 / g、118m 2 / g, 120m 2 / g、121m 2 / g、122m 2 / g、124m 2 / g、126m 2 / g、128m 2 / g or 130m 2 / g, but not limited to the listed values, other unlisted values ​​within the range also apply.

[0017] The cerium-tin composite oxide support in this invention has a specific structure. This nanorod structure has a high specific surface area, which is beneficial for the loading and uniform dispersion of active components.

[0018] In a second aspect, the present invention provides a method for preparing a Ru-based catalyst as described in the first aspect, the method comprising the following steps:

[0019] A Ru source and water are mixed evenly to obtain a first mixture; a cerium-tin composite oxide support is mixed with the first mixture, impregnated, ultrasonicated, stirred, and then subjected to rotary evaporation, a first drying, and a first calcination to obtain the Ru-based catalyst.

[0020] This invention uses an impregnation method to prepare catalysts, which is low-cost and simple to synthesize. During the impregnation process, the Ru species generated by the Ru source can be uniformly dispersed on the surface of the cerium-tin composite oxide support, which is beneficial to the active components.

[0021] Preferably, the Ru source includes any one or a combination of at least two of ruthenium trichloride, ruthenium acetate, or ammonium ruthenate. Typical but non-limiting combinations include combinations of ruthenium trichloride and ruthenium acetate, combinations of ruthenium acetate and ammonium ruthenate, combinations of ruthenium trichloride and ammonium ruthenate, and combinations of ruthenium trichloride, ruthenium acetate, and ammonium ruthenate, with ruthenium trichloride being the most preferred.

[0022] Preferably, the mass ratio of Ru source to water is (6-10):1000, for example, it can be 6:1000, 7:1000, 8:1000, 9:1000 or 10:1000, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably (7-9):1000.

[0023] Preferably, the ultrasound duration is 15-60 minutes, for example, it can be 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the stirring time is 0.5-2 hours, for example, it can be 0.5 hours, 1 hour, 1.5 hours or 2 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the gauge pressure during rotary evaporation is -0.08 MPa or below, for example, it can be -0.098 MPa, -0.096 MPa, -0.094 MPa, -0.090 MPa, -0.088 MPa, -0.086 MPa, -0.084 MPa, -0.082 MPa or -0.08 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the temperature of the rotary evaporation is 50-70°C, for example, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the temperature of the first drying is 90-110°C, for example, it can be 90°C, 95°C, 100°C, 105°C or 110°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the first drying time is 12-24 hours, for example, it can be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the temperature of the first roasting is 500-600℃, for example, it can be 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0030] In this invention, the impregnated product is subjected to a first calcination at 500-600°C. The calcination process allows the active component Ru to bind tightly with the support. If the first calcination temperature is too low, the prepared catalyst will not form the target nanorod structure and the Ru distribution will be uneven. If the first calcination temperature is too high, the prepared catalyst nanorod structure will be destroyed and Ru will agglomerate, thereby affecting the catalytic activity of the catalyst.

[0031] Preferably, the first roasting time is 2-4 hours, for example, it can be 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the preparation method of the cerium-tin composite oxide support includes:

[0033] A second mixture is obtained by uniformly mixing a cerium source, a tin source, and water; a sodium hydroxide solution is then mixed with the second mixture and stirred until homogeneous before undergoing a hydrothermal reaction. After solid-liquid separation, washing, a second drying process, and a second calcination, the cerium-tin composite oxide carrier is obtained.

[0034] Preferably, the cerium source includes any one or a combination of at least two of cerium nitrate hexahydrate, cerium carbonate, or cerium oxalate. Typical but non-limiting combinations include combinations of cerium nitrate hexahydrate and cerium carbonate, combinations of cerium carbonate and cerium oxalate, combinations of cerium nitrate hexahydrate and cerium oxalate, and combinations of cerium nitrate hexahydrate, cerium carbonate, and cerium oxalate. Cerium nitrate hexahydrate is preferred.

[0035] Preferably, the tin source includes any one or a combination of at least two of tin tetrachloride pentahydrate, tin acetate, or tin iodide. Typical but non-limiting combinations include a combination of tin tetrachloride pentahydrate and tin acetate, a combination of tin acetate and tin iodide, a combination of tin tetrachloride pentahydrate and tin iodide, a combination of tin tetrachloride pentahydrate, tin acetate, and tin iodide, with tin tetrachloride pentahydrate being the most preferred.

[0036] Preferably, the molar ratio of the cerium source to the tin source is (0.25-9):1, for example, it can be 0.25:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, 4:1, 5:1, 5.7:1, 7:1, 8:1 or 9:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the total concentration of metal ions in the second mixture is 0.20-0.25 mol / L, for example, it can be 0.20 mol / L, 0.21 mol / L, 0.22 mol / L, 0.23 mol / L, 0.24 mol / L or 0.25 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, the concentration of the sodium hydroxide solution is 6-8 mol / L, for example, it can be 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L or 8 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0039] Preferably, the molar ratio of metal ions in the cerium source to solute in the sodium hydroxide solution is (0.004-0.017):1, for example, it can be 0.004:1, 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, 0.010:1, 0.011:1, 0.012:1, 0.013:1, 0.014:1, 0.015:1, 0.016:1 or 0.017:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the temperature of the hydrothermal reaction is 90-110℃, for example, it can be 90℃, 95℃, 100℃, 105℃ or 110℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] In this invention, the hydrothermal reaction during the preparation of the cerium-tin composite oxide support affects the morphology and structure of the support. When the temperature of the hydrothermal reaction is controlled within the range of 90-110℃, a support with a nanorod structure is obtained. If the temperature of the hydrothermal reaction is too low, the prepared cerium-tin composite oxide support will not be fully crystallized, thus affecting the activity of the catalyst. If the temperature of the hydrothermal reaction is too high, the pore structure of the prepared cerium-tin composite oxide support will be destroyed, thereby reducing the specific surface area of ​​the catalyst and hindering the loading of the active component.

[0042] Preferably, the hydrothermal reaction time is 10-14 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours or 14 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the washing endpoint is when the pH of the washing solution is 6-8, for example, it can be 6, 6.5, 7, 7.5 or 8, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the temperature of the second drying is 90-110°C, for example, it can be 90°C, 95°C, 100°C, 105°C or 110°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] Preferably, the second drying time is 12-24 hours, for example, it can be 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] Preferably, the second roasting temperature is 500-600℃, for example, it can be 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0047] Preferably, the second roasting time is 3-5 hours, for example, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0048] Preferably, the preparation method includes the following steps:

[0049] (1) A cerium source and a tin source are dissolved in water at a molar ratio of (0.3-3):1 to obtain a second mixture with a total metal ion concentration of 0.20-0.25 mol / L. A sodium hydroxide solution with a concentration of 6-8 mol / L is mixed and stirred evenly with the second mixture. The mixture is then subjected to a hydrothermal reaction at 90-110℃ for 10-14 h. After solid-liquid separation and washing until the washing liquid is neutral, the mixture is dried at 90-110℃ for 12-24 h. Finally, it is calcined at 500-600℃ for 3-5 h to obtain the cerium-tin composite oxide support.

[0050] The molar ratio of metal ions in the cerium source to solutes in the sodium hydroxide solution is (0.004-0.017):1;

[0051] (2) The Ru source and water are mixed evenly at a mass ratio of (6-10):1000 to obtain a first mixture. The cerium-tin composite oxide support obtained in step (1) is mixed with the first mixture, impregnated, sonicated for 15-60 min, stirred for 0.5-2 h, and then rotary evaporated under a pressure of -0.08 MPa or below and a temperature of 50-70 °C, dried for 12-24 h at 90-110 °C, and then calcined for 2-4 h at 500-600 °C to obtain the Ru-based catalyst.

[0052] Thirdly, the present invention provides the use of the Ru-based catalyst described in the first aspect for the selective catalytic oxidation of ammonia.

[0053] The Ru-based catalyst of this invention exhibits excellent low-temperature activity and N2 selectivity, demonstrating superior ammonia catalytic oxidation activity, meeting current market demands, and showing great promise for practical applications.

[0054] Preferably, the Ru-based catalyst operates at a temperature of 150-300°C for the selective catalytic oxidation of ammonia, for example, 150°C, 200°C, 250°C or 300°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0056] Compared with the prior art, the present invention has at least the following beneficial effects:

[0057] (1) The present invention uses cerium-tin composite oxide as a support and Ru as an active component to prepare a catalyst. The content of Ru is 0.5-2.0 wt%. Ru has good dispersion. The catalyst can have good low-temperature activity and thermal stability even when the content of the active component is very low.

[0058] (2) The present invention uses the impregnation method to prepare the catalyst, which is low in cost and simple in synthesis. During the impregnation process, the Ru species generated by the Ru source can be uniformly dispersed on the surface of the cerium-tin composite oxide support.

[0059] (3) The Ru-based catalyst of the present invention has excellent low-temperature activity and exhibits excellent ammonia catalytic oxidation activity, which meets the current market demand and has good practical application prospects. Attached Figure Description

[0060] Figure 1 This is a graph showing the conversion rate of NH3 of the catalysts prepared in Example 1 and Comparative Examples 3, 4 and 5 of the present invention.

[0061] Figure 2 This is a N2 selectivity curve of the catalysts prepared in Example 1 and Comparative Examples 3, 4 and 5 of the present invention. Detailed Implementation

[0062] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0063] In the following examples, unless otherwise specified, all reagents and consumables were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used are conventional methods and techniques in the art.

[0064] Example 1

[0065] This embodiment provides a Ru-based catalyst, wherein the content of the active component Ru is 1 wt% based on a total mass of 100 wt% of the Ru-based catalyst, and the balance is a cerium-tin composite oxide support; the chemical formula of the cerium-tin composite oxide support is Ce. 0.6 Sn 0.4 O2;

[0066] The cerium-tin composite oxide carrier has a diameter of 6 nm, a length of 45 nm, and a specific surface area of ​​115 m². 2 / g of nanorod-like structure;

[0067] The method for preparing the Ru-based catalyst provided in this embodiment includes the following steps:

[0068] (1) Cerium nitrate hexahydrate and tin tetrachloride pentahydrate were dissolved in water at a Ce:Sn molar ratio of 1.5:1. A 7 mol / L sodium hydroxide solution was added and stirred until homogeneous. The mixture was then subjected to a hydrothermal reaction at 100°C for 12 h. After solid-liquid separation and washing until the pH of the solution reached 7, the solution was dried at 100°C for 18 h and then calcined at 550°C for 4 h to obtain Ce. 0.6 Sn 0.4 O2 carrier;

[0069] The molar ratio of metal ions in the cerium source to solute in the sodium hydroxide solution is 0.011:1;

[0070] (2) Ruthenium trichloride and water are mixed evenly at a mass ratio of 7:1000 to obtain the first mixture. The Ce obtained in step (1) 0.6 Sn 0.4 The O2 support was added to the first mixture for impregnation, ultrasonicated for 30 min, stirred for 1 h, and then subjected to rotary evaporation at a pressure of -0.098 MPa and a temperature of 60 °C, followed by a first drying at 100 °C for 18 h, and then a first calcination at 550 °C for 3 h to obtain the Ru-based catalyst.

[0071] The conversion rate of NH3 obtained by the prepared Ru-based catalyst is as follows: Figure 1 As shown, from Figure 1 As can be seen, its conversion rate can reach over 96% at 250℃, and the selectivity of N2 is as follows: Figure 2 As shown.

[0072] Example 2

[0073] This embodiment provides a Ru-based catalyst, wherein the content of the active component Ru is 1.5 wt% based on a total mass of 100 wt% of the Ru-based catalyst, and the balance is a cerium-tin composite oxide support; the chemical formula of the cerium-tin composite oxide support is Ce. 0.7 Sn0.3 O2;

[0074] The cerium-tin composite oxide carrier has a diameter of 5.3 nm, a length of 41 nm, and a specific surface area of ​​104 m². 2 / g of nanorod-like structure;

[0075] The method for preparing the Ru-based catalyst provided in this embodiment includes the following steps:

[0076] (1) Cerium nitrate hexahydrate and tin tetrachloride pentahydrate were dissolved in water at a Ce:Sn molar ratio of 2.33:1. A 6 mol / L sodium hydroxide solution was added and stirred until homogeneous. The mixture was then subjected to a hydrothermal reaction at 110°C for 11 h. After solid-liquid separation and washing until the pH of the solution reached 7, the solution was dried at 110°C for 12 h and then calcined at 600°C for 3 h to obtain Ce. 0.7 Sn 0.3 O2 carrier;

[0077] The molar ratio of metal ions in the cerium source to solute in the sodium hydroxide solution is 0.004:1;

[0078] (2) Ruthenium acetate and water are mixed evenly at a mass ratio of 8:1000 to obtain the first mixture. The Ce obtained in step (1) 0.7 Sn 0.3 The O2 support was added to the first mixture for impregnation, ultrasonicated for 60 min, stirred for 0.5 h, and then subjected to rotary evaporation at a pressure of -0.095 MPa and a temperature of 50 °C, followed by a first drying at 110 °C for 12 h, and then a first calcination at 600 °C for 2 h to obtain the Ru-based catalyst.

[0079] Example 3

[0080] This embodiment provides a Ru-based catalyst, wherein the content of the active component Ru is 2 wt% based on a total mass of 100 wt% of the Ru-based catalyst, and the balance is a cerium-tin composite oxide support; the chemical formula of the cerium-tin composite oxide support is Ce. 0.5 Sn 0.5 O2;

[0081] The cerium-tin composite oxide carrier has a diameter of 6.7 nm, a length of 48 nm, and a specific surface area of ​​127 m². 2 / g of nanorod-like structure;

[0082] The method for preparing the Ru-based catalyst provided in this embodiment includes the following steps:

[0083] (1) Cerium nitrate hexahydrate and tin tetrachloride pentahydrate were dissolved in water at a molar ratio of Ce:Sn of 1:1. An 8 mol / L sodium hydroxide solution was added, and the mixture was stirred until homogeneous. The mixture was then subjected to a hydrothermal reaction at 90°C for 14 hours. After solid-liquid separation and washing until the pH of the solution reached 8, it was dried at 90°C for 24 hours, and then calcined at 500°C for 5 hours to obtain Ce. 0.5 Sn 0.5 O2 carrier;

[0084] The molar ratio of metal ions in the cerium source to solute in the sodium hydroxide solution is 0.017:1;

[0085] (2) Ruthenium trichloride and water are mixed evenly at a mass ratio of 10:1000 to obtain the first mixture. The Ce obtained in step (1) 0.5 Sn 0.5 The O2 support was added to the first mixture for impregnation, ultrasonicated for 15 min, stirred for 2 h, and then rotary evaporated at a pressure of -0.08 MPa and a temperature of 70 °C, dried at 90 °C for 24 h, and then calcined at 500 °C for 4 h to obtain the Ru-based catalyst.

[0086] Example 4

[0087] This embodiment provides a Ru-based catalyst, which differs from Example 1 only in that the hydrothermal reaction temperature in step (1) is 80°C when preparing the Ru-based catalyst.

[0088] Example 5

[0089] This embodiment provides a Ru-based catalyst, which differs from Example 1 only in that the hydrothermal reaction temperature in step (1) is 120°C when preparing the Ru-based catalyst.

[0090] Example 6

[0091] This embodiment provides a Ru-based catalyst, which differs from Example 1 only in that the first calcination temperature in step (2) is 700°C when preparing the Ru-based catalyst.

[0092] Example 7

[0093] This embodiment provides a Ru-based catalyst, which differs from Example 1 only in that the first calcination temperature in step (2) is 400°C when preparing the Ru-based catalyst.

[0094] Comparative Example 1

[0095] This comparative example provides a Ru-based catalyst, which differs from Example 1 only in that, based on a total mass of 100 wt% of the Ru-based catalyst, the content of the active component Ru is 0.1 wt%.

[0096] Comparative Example 2

[0097] This comparative example provides a catalyst, which differs from Example 1 only in that the catalyst is prepared using titanium oxide as the support, which was purchased from Aladdin.

[0098] Comparative Example 3

[0099] This comparative example provides a Ce 0.6 Sn 0.4 The O2 catalyst differs from that in Example 1 only in that the Ce obtained in step (1) is used instead. 0.6 Sn 0.4 The O2 support is used as a catalyst, that is, step (2) is not performed and the active component is not loaded.

[0100] Ce prepared 0.6 Sn 0.4 The conversion rate of NH3 by O2 catalyst is as follows: Figure 1 As shown, the selectivity of N2 is as follows Figure 2 As shown.

[0101] Comparative Example 4

[0102] This comparative example provides a Ru / CeO2 catalyst, which differs from Example 1 only in that the support used in preparing this catalyst is CeO2, that is, no tin source is added in step (1), and the remaining steps are the same as in Example 1.

[0103] The conversion rate of NH3 in the prepared Ru / CeO2 catalyst is as follows: Figure 1 As shown, the selectivity of N2 is as follows Figure 2 As shown.

[0104] Comparative Example 5

[0105] This comparative example provides a CeO2 catalyst, which differs from Comparative Example 4 only in that the CeO2 obtained in step (1) is used as the catalyst, i.e., it is not loaded with active components.

[0106] The conversion rate of NH3 obtained by the prepared CeO2 catalyst is as follows: Figure 1 As shown, the selectivity of N2 is as follows Figure 2 As shown.

[0107] Test method: 100 mg of the prepared Ru catalyst was sieved through a 40-60 mesh sieve and placed in a catalyst activity evaluation device (Antaris IGS, Thermo Fisher). The activity evaluation was carried out in a fixed-bed reactor. The test conditions were: 500 ppm NH3, 10% O2, N2 equilibrium, and a total flow rate of 200 mL / min. The test results are shown in Table 1.

[0108] Table 1

[0109]

[0110]

[0111] The test results show that:

[0112] (1) As can be seen from Examples 1-3, the present invention prepares a cerium-tin composite oxide support by a hydrothermal method, and loads the active component Ru with a mass fraction of 0.5-2 wt% onto the support using an impregnation method. The Ru-based catalyst prepared exhibits an NH3 conversion rate of over 85% and an N2 selectivity of less than 66% at 250℃, demonstrating excellent low-temperature ammonia catalytic oxidation activity. The chemical formula of the cerium-tin composite oxide support is Ce. 0.6 Sn 0.4 The catalyst exhibits the highest activity when O2 is used and the active component Ru is loaded at 1 wt%, with an NH3 conversion rate exceeding 96% at 250℃.

[0113] (2) By comparing Example 1 with Examples 4-5, it can be seen that the temperature of the hydrothermal reaction during the preparation of the cerium-tin composite oxide support in this invention will affect the reaction activity of the final catalyst. When the reaction temperature is too low, the cerium-tin composite oxide support will not be fully crystallized, which will affect the activity of the catalyst. If the reaction temperature is too high, the pore structure of the cerium-tin composite oxide support will be destroyed, reducing the specific surface area of ​​the catalyst, thereby affecting the loading of the active component, which will lead to a decrease in the activity of the catalyst.

[0114] (3) By comparing Example 1 with Examples 6-7, it can be seen that in this invention, the impregnated product is subjected to a first calcination at 500-600°C. During this process, the active component Ru is tightly bound to the support. If the temperature of the first calcination is too low, the catalyst prepared will not form the target nanorod structure and the Ru will be unevenly distributed. If the temperature of the first calcination is too high, the catalyst nanorod structure prepared will be destroyed and Ru will agglomerate.

[0115] (4) By comparing Example 1 with Comparative Example 1, it can be seen that by further controlling the content range of the active component Ru, the present invention can achieve better catalytic activity at a low loading. When the content of the active component Ru is too low, the catalytic efficiency is too low. When the content of the active component Ru is too high, it not only increases the manufacturing cost of the catalyst, but also causes the active component to agglomerate, so that the catalyst cannot play its full role.

[0116] (5) As can be seen from Example 1 and Comparative Example 2, when conventional titanium oxide is used as the support, the NH3 conversion rate of the prepared catalyst at 250°C is only about 63%. It can be seen that the present invention significantly improves the low-temperature NH3 conversion rate of the catalyst by loading Ru active component on the cerium-tin composite oxide support.

[0117] (6) As can be seen from Example 1 and Comparative Example 3, when no active component is loaded, the prepared Ce can be directly applied... 0.6 Sn 0.4 When O2 is used as a catalyst, its NH3 conversion rate is only 6.78% at 250℃. It can be seen that the present invention significantly improves the NH3 conversion rate of the catalyst by loading Ru active component on cerium-tin composite oxide support.

[0118] (7) As can be seen from Example 1 and Comparative Example 4, when CeO2 is used as the support, the NH3 conversion rate of the prepared catalyst is 57.85% at 250°C. It can be seen that the specific composition of the support of the present invention has a serious impact on the activity of the catalyst. Without Sn, the activity of the catalyst is very low. The present invention significantly improves the NH3 conversion rate of the catalyst by loading Ru active component on the cerium-tin composite oxide support.

[0119] (8) As can be seen from Comparative Examples 4 and 5, when CeO2 is directly used as a catalyst without loading the active component, the catalyst activity is very low. This invention significantly improves the NH3 conversion rate of the catalyst by loading Ru active component on the cerium-tin composite oxide support.

[0120] In summary, this invention uses cerium-tin composite oxide as a support and Ru as the active component to prepare the catalyst. Ru has good dispersibility, and the active component of the catalyst can achieve good low-temperature activity, N2 selectivity and thermal stability even at a low content.

[0121] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. The use of a Ru-based catalyst, characterized in that, The Ru-based catalyst is used for the selective catalytic oxidation of ammonia; The Ru-based catalyst comprises a cerium-tin composite oxide support and an active component Ru supported on the support; based on a total mass of 100 wt% of the Ru-based catalyst, the content of the active component Ru is 0.5-2 wt%, and the balance is the cerium-tin composite oxide support. The Ru-based catalyst is prepared by the following method, which includes the following steps: (1) A second mixture with a total metal ion concentration of 0.20-0.25 mol / L is obtained by dissolving a cerium source and a tin source in water at a molar ratio of (0.3-3):

1. The second mixture is then mixed with a sodium hydroxide solution with a concentration of 6-8 mol / L and stirred until homogeneous. The mixture is then subjected to a hydrothermal reaction at 90-110℃ for 10-14 h. After solid-liquid separation and washing until the washing solution is neutral, the mixture is dried at 90-110℃ for 12-24 h and then calcined at 500-600℃ for 3-5 h to obtain the cerium-tin composite oxide carrier. The molar ratio of metal ions in the cerium source to solutes in the sodium hydroxide solution is (0.004-0.017):1; (2) The Ru source and water are mixed evenly at a mass ratio of (6-10):1000 to obtain the first mixture. The cerium-tin composite oxide support obtained in step (1) is mixed with the first mixture, impregnated, sonicated for 15-60 min, stirred for 0.5-2 h, and then rotary evaporated at a gauge pressure of -0.08 MPa and below and a temperature of 50-70 °C, dried at 90-110 °C for 12-24 h, and then calcined at 500-600 °C for 2-4 h to obtain the Ru-based catalyst.

2. The use according to claim 1, characterized in that, The chemical formula of the cerium-tin composite oxide support is Ce. x Sn 1-x O2, where 0.55≤x≤0.

65.

3. The use according to claim 1, characterized in that, Based on a total mass of 100wt% for the Ru-based catalyst, the content of the active component Ru is 1.0-2.0wt%, with the balance being a cerium-tin composite oxide support.

4. The use according to claim 1, characterized in that, The cerium-tin composite oxide carrier has a nanorod structure.

5. The use according to claim 1, characterized in that, The cerium-tin composite oxide carrier has an average diameter of 5-7 nm, an average length of 40-50 nm, and a specific surface area of ​​100-130 m². 2 / g.

6. The use according to claim 1, characterized in that, The Ru-based catalyst operates at a temperature of 150-300℃ for the selective catalytic oxidation of ammonia.

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