A nanocube CeO2 catalyst supported with Pt nanoparticles for catalyzing direct decomposition of NO

Abstract

The application discloses a kind of supported Pt nanoparticles nano-cube CeO2 catalyst for catalyzing NO direct decomposition, which realizes the catalytic decomposition of nitric oxide (NO) in the temperature interval of 200-500 ℃ without using any reducing agent (for example: ammonia, methane, hydrogen, etc.). The catalyst (Pt / CeO2) is prepared by grinding, pre-burning and high-temperature calcination of noble metal platinum (Pt) salt and nano-cube ceria (CeO2) support. The high-temperature calcination atmosphere can be argon, hydrogen and oxygen. The application prepares a Pt / CeO2 catalyst suitable for NO direct decomposition. The preparation method of the Pt / CeO2 catalyst is simple, suitable for large-scale industrial production, and has a broad industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the fields of environmental protection technology and denitrification catalysis, specifically relating to a nanocube CeO2 catalyst loaded with Pt nanoparticles that catalyzes the direct decomposition of NO. Background Technology

[0002] Nitrogen oxides (NOx) are widely present in both stationary and mobile source exhaust gases, harming the natural environment in the form of acid rain, photochemical smog, and the greenhouse effect. In addition, the harm of NOx to human health cannot be ignored. Once inside the body, NO rapidly binds to hemoglobin, leading to hypoxia and myocardial damage.

[0003] To address the aforementioned issues, mobile sources such as automobiles employ three-way catalytic converters to reduce NO emissions, while stationary sources like coal-fired power plants typically use selective catalytic reduction (NH3-SCR) technology with ammonia as the reducing agent to remove NO. However, the use of reducing agents not only places a significant economic burden on plants but also easily leads to secondary pollution due to improper disposal. Therefore, a method for the direct decomposition of NO without a reducing agent has attracted considerable attention. While the direct decomposition of NO is thermodynamically feasible, it requires high kinetics due to the strong double bond between N and O. Therefore, it is necessary to find a suitable catalyst to lower the activation energy of the direct decomposition reaction of NO.

[0004] Catalysts for the direct decomposition of NO mainly include noble metals, simple metal oxides, perovskites, and molecular sieves. Noble metals were the earliest catalysts studied for the direct decomposition of NO. Although they have good high-temperature performance, they have almost no performance at low temperatures, thus limiting the further industrial application of the direct decomposition technology of NO. In the literature Haneda M, Kintaichi Y, Hamada H. Surface reactivity of prereduced rare earth oxides with nitric oxide: New approach for NO decomposition[J]. Physical Chemistry Chemical Physics, 2002, 4(13): 3146-3151, Haneda et al. found that among many catalytic materials, Pt / CeO2 catalyst can catalyze the direct decomposition of NO, but its catalytic activity is poor at low temperatures (200℃). How to adjust the state of Pt on CeO2 to regulate its activity in catalyzing the direct decomposition of NO, and how to prepare Pt / CeO2 catalysts through a simple process, has always been a research hotspot and difficulty. Furthermore, the design and development of supported noble metal catalysts suitable for the direct decomposition of NO under low-temperature conditions is of great significance for the practical industrial application of NO direct decomposition technology. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature catalytic direct decomposition of NO using a nanocubic CeO2 catalyst supported on Pt nanoparticles. Currently, ZrO2 and Al2O3 are commonly studied supports, while CeO2 is less frequently used for NO direct decomposition. CeO2 possesses excellent oxygen storage and release capabilities, making it highly suitable as a support for noble metals. However, the inventors have discovered that the presence state of Pt in Pt / CeO2 prepared under different atmospheres affects its catalytic performance. This invention, through grinding, pretreatment, and high-temperature calcination, prepares a Pt / CeO2 catalyst suitable for low-temperature catalytic direct decomposition of NO, achieving the direct decomposition of NO at low temperatures.

[0006] This invention is achieved using the following technical solution:

[0007] A nanocubic CeO2 catalyst loaded with Pt nanoparticles for the direct decomposition of NO can be used to achieve the direct catalytic decomposition of NO within a temperature range of 200℃-500℃ without the addition of any reducing agent.

[0008] The preparation method of the Pt / CeO2 catalyst includes the following process steps:

[0009] (1) Prepare an alkaline solution with a concentration of 2-20 mol / L, preferably a sodium hydroxide solution. Add cerium salt to the sodium hydroxide solution and continue stirring on a magnetic stirrer.

[0010] (2) Pour the mixed solution into a stainless steel hydrothermal reactor and place the reactor in a high-temperature oven for heating. The reaction time is 12-48 hours.

[0011] (3) After the reaction is complete, the solution is centrifuged, washed until neutral and dried. Finally, the dried solid is calcined at high temperature to obtain CeO2 nanocube carrier material.

[0012] (4) Weigh CeO2 nanocube carrier material and noble metal platinum salt in a mass ratio of 100:2-10 and put them into a mortar. Then mix and grind for 10 min-40 min to obtain a light yellow solid powder.

[0013] (5) The above light yellow solid powder is subjected to high-temperature calcination to obtain the Pt / CeO2 catalyst.

[0014] The method for directly decomposing NO using Pt / CeO2 according to the present invention also includes the following preferred embodiments.

[0015] In a preferred embodiment of the present invention, the cerium salt in step (1) is at least one of cerium nitrate, cerium chloride, or cerium carbonate.

[0016] In a preferred embodiment of the present invention, the heating temperature in step (2) is 100℃-250℃.

[0017] In a preferred embodiment of the present invention, the calcination temperature in step (3) is 300℃-800℃, the heating rate is 1℃ / min-10℃ / min, and the calcination time is 2-60h.

[0018] In a preferred embodiment of the present invention, the solid cerium salt particles in step (4) are at least one of cerium nitrate or cerium acetate.

[0019] In a preferred embodiment of the present invention, the noble metal platinum salt mentioned in step (4) is at least one of platinum acetylacetonate, platinum chloride, or platinum acetate.

[0020] In a preferred embodiment of the present invention, the high-temperature calcination in step (5) is carried out at a temperature of 300℃-550℃, a heating rate of 1℃ / min-10℃ / min, and a calcination time of 2-60h. The calcination atmosphere can be an inert atmosphere (e.g., argon, nitrogen, helium), a reducing atmosphere (e.g., hydrogen, carbon monoxide), or an oxidizing atmosphere (e.g., oxygen, air).

[0021] Compared with existing technologies, the beneficial effects of the present invention are as follows:

[0022] Compared with existing technologies, this invention obtains nanocube CeO2 (Pt / CeO2 catalyst) loaded with Pt nanoparticles by treating it with different atmospheres. The prepared Pt / CeO2 catalyst can achieve highly efficient direct decomposition of NO within the temperature range of 200℃-500℃ without the use of any reducing agent. The preparation of Pt / CeO2 is selective for the reaction atmosphere; the Pt / CeO2 catalysts obtained by different atmosphere treatments show a difference of nearly three times. Since the temperature of flue gas at the tail end of coal-fired power plants is often around 200℃, most current NO direct decomposition catalysts have no performance or poor performance at low temperatures. However, the catalyst prepared by this invention using an inert or reducing atmosphere exhibits excellent NO conversion rate at a low temperature of 200℃. Therefore, the catalyst of this invention can achieve true direct decomposition. The Pt / CeO2 prepared using the method of this invention not only maximizes the catalytic performance of the precious metal platinum, but also has a simple preparation process, is suitable for large-scale industrial production, and has promising industrial application prospects. Attached Figure Description

[0023] Figure 1 The image shows a TEM image of the catalyst prepared in Example 1.

[0024] Figure 2 The image shows a TEM image of the catalyst prepared in Example 2.

[0025] Figure 3 The image shows a TEM image of the catalyst prepared in Example 3.

[0026] Figure 4 The image shows a TEM image of the catalyst prepared in Example 4.

[0027] Figure 5 The graphs show the denitrification activity test results of the catalysts prepared in Examples 1-4. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] Example 1

[0030] A nanocube CeO2 catalyst loaded with Pt nanoparticles for direct decomposition of NO includes the following steps: (1) Prepare 140 ml of 10 mol / L sodium hydroxide solution, add 1 mol of cerium nitrate to the sodium hydroxide solution, and continue stirring on a magnetic stirrer. (2) Pour the mixed solution into a stainless steel hydrothermal reactor, place the reactor in a 200℃ oven and heat for 24 h. (3) After the reaction is complete, centrifuge the solution, wash it until neutral and dry it. Finally, calcine the dried solid at 500℃ to obtain CeO2 nanocube support material. (4) Weigh nanocube CeO2 and platinum acetylacetone in a mass ratio of 19:1 and place them in a mortar. Mix and grind for 30 min to obtain a light yellow solid powder. (5) Calcine the above light yellow solid powder at 500℃ under an argon atmosphere for 2 h to obtain a Pt / CeO2 catalyst (e.g., Figure 1 ).

[0031] Example 2

[0032] A nanocube CeO2 catalyst loaded with Pt nanoparticles for direct decomposition of NO includes the following steps: (1) Prepare 140 ml of a 10 mol / L sodium hydroxide solution, add 1 mol of cerium nitrate to the sodium hydroxide solution, and continue stirring on a magnetic stirrer. (2) Pour the mixed solution into a stainless steel hydrothermal reactor, place the reactor in a 200℃ oven and heat for 24 h. (3) After the reaction is complete, centrifuge the solution, wash it until neutral and dry it. Finally, calcine the dried solid at 500℃ to obtain the CeO2 nanocube support material. (4) Weigh the nanocube CeO2 and platinum acetylacetone in a mass ratio of 19:1 and place them in a mortar. Then mix and grind for 30 min to obtain a light yellow solid powder. (5) Calcine the above light yellow solid powder at 500℃ under a hydrogen atmosphere for 2 h to obtain the Pt / CeO2 catalyst (e.g., Figure 2 ).

[0033] Example 3

[0034] A nanocube CeO2 catalyst loaded with Pt nanoparticles for direct decomposition of NO includes the following steps: (1) Prepare 140 ml of 10 mol / L sodium hydroxide solution, add 1 mol of cerium nitrate to the sodium hydroxide solution, and continue stirring on a magnetic stirrer. (2) Pour the mixed solution into a stainless steel hydrothermal reactor, place the reactor in a 200℃ oven and heat for 24 h. (3) After the reaction is complete, centrifuge the solution, wash it until neutral and dry it. Finally, calcine the dried solid at 500℃ to obtain CeO2 nanocube support material. (4) Weigh nanocube CeO2 and platinum acetylacetone in a mass ratio of 19:1 and place them in a mortar, then mix and grind for 30 min to obtain a light yellow solid powder. (5) Calcine the above light yellow solid powder at 500℃ under an oxygen atmosphere for 2 h to obtain a Pt / CeO2 catalyst (e.g., Figure 3 ).

[0035] Example 4

[0036] A CeO2 cubic catalyst for the direct decomposition of NO comprises the following steps: (1) Prepare 140 ml of a 10 mol / L sodium hydroxide solution, add 1 mol of cerium nitrate to the sodium hydroxide solution, and continue stirring on a magnetic stirrer. (2) Pour the mixed solution into a stainless steel hydrothermal reactor, place the reactor in a 200℃ oven and heat for 24 h. (3) After the reaction is complete, centrifuge the solution, wash it until neutral and dry it. Finally, calcine the dried solid at 500℃ to obtain CeO2 nanocubic support material (e.g., Figure 4 ).

[0037] The denitrification performance of the catalysts prepared in Examples 1, 2, 3, and 4 was tested, specifically including the following steps: (1) 500 mg of the prepared catalyst was weighed and placed in a fixed-bed quartz reaction tube; (2) the inlet of the reaction tube contained 200 ppm NO, the carrier gas was N2, the total gas flow rate was 600 mL / min, the mass hourly space velocity was 72000 mg / mL / h, and the test reaction temperature was 200℃-500℃. The denitrification performance test results of the catalysts prepared in Examples 1-4 are as follows: Figure 5 As shown, compared with Example 1, the Pt / CeO2 catalysts prepared in Examples 2 and 3 exhibited relatively poor denitrification performance within the temperature range of 200℃-500℃. The corresponding TEM images show that, under the same Pt ​​loading, the form of Pt on the CeO2 support differed significantly after treatment in different atmospheres. After treatment under hydrogen, Pt exhibited higher dispersion and existed as a solid solution. After treatment under argon, it mainly existed as metallic Pt particles. After treatment under oxygen, it mainly existed as oxidized PtO. x The presence of particles indicates that selecting a suitable atmosphere is crucial for preparing catalysts with direct catalytic decomposition properties of NO.

[0038] Example 5

[0039] The only difference from Example 1 is that the mass ratio of nanocube CeO2 and platinum acetylacetonate in step (4) is 50:1.

[0040] Example 6

[0041] The only difference from Example 1 is that the mass ratio of nanocube CeO2 and platinum acetylacetonate in step (4) is 10:1.

[0042] Example 7

[0043] The only difference from Example 1 is that the calcination temperature in step (5) is 300°C.

[0044] Example 8

[0045] The only difference from Example 1 is that the calcination temperature in step (5) is 550°C.

[0046] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Use of a nanocubic CeO2 catalyst loaded with Pt nanoparticles for catalyzing the direct decomposition of NO, characterized in that, The catalyst can realize direct catalytic decomposition of NO in a temperature range of 200-500 DEG C without adding any reducing agent; The preparation method of the catalyst comprises the following steps: (1) taking nanometer cubic morphology CeO2 and noble metal platinum salt with a mass ratio of 100:2-10 into a mortar, then mixing and grinding for 10-40 min to obtain a light yellow solid powder; (2) carrying out high-temperature calcination treatment on the light yellow solid powder obtained in step (1) to obtain the Pt / CeO2 catalyst; the high-temperature calcination temperature is 300-550 DEG C, the calcination time is 2-60 h, and the calcination atmosphere is an inert atmosphere.

2. Use according to claim 1, characterized in that, The noble metal platinum salt in step (1) is at least one of platinum acetylacetone, platinum chloride or platinum acetate.

3. Use according to claim 1, characterized in that, The temperature rising speed of the high-temperature calcination in step (2) is 1-10 DEG C / min.

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