A composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O, its preparation method and application

Abstract

The application belongs to the field of atmospheric pollution treatment and environmental protection catalytic materials, and particularly relates to a composite oxide catalyst for catalytic decomposition of N2O at medium and low temperatures and a preparation method and application thereof. z -CuO x , wherein the molar ratio of Sm to Cu is 0.01-0.5:1. z -CuO x The composite oxide catalyst provided by the application has good tolerance to impurity gases (including nitrogen oxides (NO x , x=1 and 2), O2 and H2O), and can efficiently catalytically decompose N2O at medium and low temperatures.

Description

Technical Field

[0001] This invention belongs to the field of air pollution control and environmental protection catalytic materials, specifically relating to a composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] As a greenhouse gas, nitrogen (N2O) has a stronger greenhouse effect potential than CO2 and CH4. Furthermore, it can remain stably in the troposphere, and once transported to the stratosphere, it has a significant destructive effect on the ozone layer. The main sources of N2O are human industrial production, including the production of nitric acid and adipic acid, as well as emissions from fuel combustion. Therefore, eliminating N2O emissions from industrial production has become one of the most pressing environmental issues to be addressed.

[0004] Researchers have developed various technologies for controlling N2O emissions, such as selective absorption, thermal decomposition, direct catalytic decomposition, and selective catalytic reduction with reducing agents. Among these, direct catalytic decomposition of N2O shows promising application prospects due to its simplicity, high efficiency, and ability to prevent secondary pollution. Catalysts used for catalytic decomposition of N2O can be broadly classified into three categories: supported noble metal catalysts, molecular sieve catalysts, and metal oxide catalysts. Among metal oxide catalysts, copper-based oxide catalysts have attracted researchers' attention due to their low cost and wide availability of raw materials. It has been reported that CuO-based catalysts contain Cu... + Species are active sites for N2O decomposition. The Advanced Materials Laboratory at Fudan University studied a series of Cu with different Cu / Ce molar ratios. x Ce 1-x O y Catalytic decomposition of N2O by mixed oxides. The synergistic effect of CeO2 and CuO mixed oxides was significant, and Cu was found to... 0.67 Ce 0.33 O y The catalyst has the most Cu + Ba-Ce-Cu catalysts exhibit high N2O decomposition activity in Cu-Ce-O mixed oxides. Dalian University of Technology has studied a series of Ba-Ce-Cu catalysts for the catalytic decomposition of N2O. The presence of Ba significantly enhances the activity of CuO-based catalysts, but NO impurity gases severely inhibit their activity. While the aforementioned copper-based oxide catalysts show good catalytic activity, they exhibit poor tolerance to impurity gases and water, and require relatively high catalytic activation temperatures. Summary of the Invention

[0005] To overcome the above problems, this invention provides a composite oxide catalyst for the medium-to-low temperature catalytic decomposition of N₂O, its preparation method, and its application. The composite oxide catalyst Sm provided by this invention... z -CuO x It has good impurity gases (including nitrogen oxides (NOx)). x It exhibits tolerance to (x=1 and 2), O2 and H2O), and can efficiently catalyze the decomposition of N2O under medium and low temperature conditions.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a composite oxide catalyst for the medium-to-low temperature catalytic decomposition of N₂O, wherein the composite oxide catalyst is Sm z -CuO x The molar ratio of Sm to Cu is 0.01 to 0.5:1.

[0008] A second aspect of the present invention provides a method for preparing the above-mentioned composite oxide catalyst for the catalytic decomposition of N2O at medium and low temperatures, comprising the following steps:

[0009] (1) Add copper nitrate and samarium nitrate to deionized water, add chelating agent, mix and stir, heat to 80-90℃, stir to react, and dry after the reaction is completed to obtain the precursor;

[0010] (2) The precursor is calcined at 350–550 °C for 4–8 h to obtain the composite oxide catalyst Sm. z -CuO x .

[0011] A third aspect of the present invention provides a method for catalytically decomposing N2O, which utilizes the above-mentioned composite oxide catalyst for catalytically decomposing N2O at medium and low temperatures.

[0012] The beneficial effects of this invention are as follows:

[0013] (1) Under the action of a chelating agent, rare earth element Sm is incorporated into CuO. During calcination, Sm induces the formation of a spinel phase, Sm₂CuO₄, on the surface of the CuO phase. By changing the molar ratio of Sm to Cu, different Sm phases can be synthesized. z -CuO x Catalyst. During catalyst preparation, the Sm₂CuO₄ spinel phase induced by Sm and Cu reacts with CuO. x An interface is formed between the phases, and the interaction between the two phases enhances the adsorption and desorption capacity of N2O, thereby greatly enhancing the N2O decomposition efficiency of the catalyst and its tolerance to impurity gases.

[0014] (2) The preferred Sm of the present invention 0.2 -CuO x The catalyst exhibits excellent N2O decomposition performance, with its T... 10 (Temperature at which N2O decomposition efficiency is 10%), T 50 and T 90 The temperatures were measured at 300℃, 350℃, and 400℃, respectively. Furthermore, the catalyst exhibits good tolerance to impurity gases; at 450℃, the decomposition rate decreased from 100% to approximately 90% after the introduction of O2, and decreased further after the introduction of NO. x Afterward, the decomposition rate remained at around 75%. After introducing H2O, the decomposition rate stabilized at around 68%. After stopping the introduction of impurity gas, the decomposition rate quickly recovered to 100%.

[0015] (3) The composite oxide catalyst preparation method provided by the present invention is simple, the raw materials are readily available and inexpensive, and it is suitable for industrial promotion. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0017] Figure 1 XRD images of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4;

[0018] Figure 2 The results show the test results of the catalytic activity of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 for the catalytic decomposition of N2O;

[0019] Figure 3 The results are the impurity gas tolerance test results of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4. Detailed Implementation

[0020] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] A first typical embodiment of the present invention provides a composite oxide catalyst for the medium-to-low temperature catalytic decomposition of N2O, wherein the composite oxide catalyst is Sm z -CuO x The molar ratio of Sm to Cu is 0.01 to 0.5:1.

[0023] A second typical embodiment of the present invention provides a method for preparing the above-mentioned composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O, comprising the following steps:

[0024] (1) Add copper nitrate and samarium nitrate to deionized water, add chelating agent, mix and stir, heat to 80-90℃, stir to react, and dry after the reaction is completed to obtain the precursor;

[0025] (2) The precursor is calcined at 350–550 °C for 4–8 h to obtain the composite oxide catalyst Sm. z -CuO x .

[0026] In one or more embodiments, in step (1), the molar ratio of copper nitrate to samarium nitrate is 0.01 to 0.5:1, preferably 0.2:1.

[0027] In one or more embodiments, in step (1), the mass fraction of the copper nitrate solute in deionized water is 4 to 7 mol / L, preferably 5.5 mol / L.

[0028] In one or more embodiments, in step (1), the molar ratio of copper nitrate to chelating agent is 1:0.15 to 0.25, preferably 1:0.2.

[0029] In one or more embodiments, in step (1), the chelating agent includes: ethylenediaminetetraacetic acid (EDTA), disodium ethylenediaminetetraacetic acid (EDTA-2Na), tetrasodium ethylenediaminetetraacetic acid (EDTA-4Na), disodium aminotriacetate (NTA), citric acid (CA), tartaric acid (TA), gluconic acid (GA), sodium tripolyphosphate, sodium tripolyphosphate and H-501, preferably citric acid.

[0030] In one or more embodiments, in step (1), a chelating agent is added and the mixture is stirred for 1.5 to 2.5 hours, preferably 2 hours.

[0031] In one or more embodiments, in step (1), the stirring reaction time is 4 to 6 hours, preferably 5 hours.

[0032] In one or more embodiments, in step (1), the drying temperature is 90-120°C and the drying time is 30-40 hours.

[0033] A third typical embodiment of the present invention provides a method for catalytic decomposition of N2O, which utilizes the above-mentioned composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O to catalytically decompose N2O.

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0035] Example 1

[0036] 0.3 mol of Cu(NO3)2·3H2O and 0.018 mol of Sm(NO3)3·6H2O were added to 54 mL of deionized water, followed by the addition of 0.06 mol of citric acid to form a metal complex. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and stirred for 5 h. After drying in an oven at 110 °C for 36 h, the precursor was obtained. The precursor was then calcined in a muffle furnace at 550 °C for 4 h to obtain Sm. 0.06 -CuO x .

[0037] Example 2

[0038] 0.3 mol of Cu(NO3)2·3H2O and 0.06 mol of Sm(NO3)3·6H2O were added to 54 mL of deionized water, followed by the addition of 0.06 mol of citric acid to form a metal complex. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and stirred for 5 h. After drying in an oven at 110 °C for 36 h, the precursor was obtained. The precursor was then calcined in a muffle furnace at 550 °C for 4 h to obtain Sm. 0.2 -CuO x .

[0039] Example 3

[0040] 0.3 mol of Cu(NO3)2·3H2O and 0.09 mol of Sm(NO3)3·6H2O were added to 54 mL of deionized water, followed by the addition of 0.06 mol of citric acid to form a metal complex. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and stirred for 5 h. After drying in an oven at 110 °C for 36 h, the precursor was obtained. The precursor was then calcined in a muffle furnace at 550 °C for 4 h to obtain Sm. 0.3 -CuO x .

[0041] Example 4

[0042] 0.3 mol of Cu(NO3)2·3H2O and 0.18 mol of Sm(NO3)3·6H2O were added to 54 mL of deionized water, followed by the addition of 0.06 mol of citric acid to form a metal complex. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and stirred for 5 h. After drying in an oven at 110 °C for 36 h, the precursor was obtained. The precursor was then calcined in a muffle furnace at 550 °C for 4 h to obtain Sm. 0.6 -CuO x .

[0043] Comparative Example 1

[0044] 0.3 mol of Cu(NO3)2·3H2O was added to 54 mL of deionized water, followed by the addition of 0.06 mol of citric acid to form a metal complex. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and stirred for 5 h. After that, it was dried in an oven at 110 °C for 36 h to obtain the precursor. The precursor was then calcined in a muffle furnace at 550 °C for 4 h to obtain CuO. x .

[0045] Comparative Example 2

[0046] 0.06 mol of Sm(NO3)3·6H2O was added to 54 mL of deionized water, followed by the addition of 0.06 mol of citric acid to form a metal complex. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and stirred for 5 h. After that, it was dried in an oven at 110 °C for 36 h to obtain the precursor. The precursor was then calcined in a muffle furnace at 550 °C for 4 h to obtain Sm2O3.

[0047] Comparative Example 3

[0048] 0.1 mol of Cu(NO3)2·3H2O and 0.2 mol of Sm(NO3)3·6H2O were added to 54 mL of deionized water, followed by the addition of 0.06 mol of citric acid to form a metal complex. The mixture was stirred at room temperature for 2 h, then heated to 90 °C and stirred for 5 h. After that, it was dried in an oven at 110 °C for 36 h to obtain the precursor. The precursor was then calcined in a muffle furnace at 550 °C for 4 h to obtain CuSm2O4.

[0049] Comparative Example 4

[0050] CuO prepared in Comparative Example 1 x CuO was prepared by mixing CuSm2O4 with CuSm2O4 prepared in Comparative Example 3 at a mass ratio of 1:0.3649. x / CuSm2O4.

[0051] XRD images of the catalysts prepared in Examples 1-4 and Comparative Examples 1-4 are shown below. Figure 1 As shown, CuO xThe XRD diffraction peaks of the catalyst showed a diffraction peak at 37.1° belonging to Cu₂O, corresponding to chalcopyrite (PDF number 48-1548). Sm z -CuO x The catalyst also showed diffraction peaks attributable to CuO, but no diffraction peaks of Sm2O3 were observed. Instead, characteristic peaks of Sm2CuO4 (PDF number 24-0998) were present. This indicates that the Sm2O3 phase was not formed during the catalyst preparation process, but rather the Sm2CuO4 phase was induced to form.

[0052] Experimental Example 1: Test of the catalyst's activity in the catalytic decomposition of N2O

[0053] The catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were respectively compressed and granulated (40-60 mesh size), and then filled on top of the quartz sand core of the fixed-bed reactor. A small amount of quartz wool was filled on top of the catalyst particles. The concentration of the N2O component of the reaction gas was adjusted to 1000 ppm, and the total gas flow rate was maintained at 100 mL·min. -1 The gas hourly space velocity (GHSV) is 60,000 mL·g⁻¹. -1 ·h -1 Before testing, the reactant gas was switched to bypass the sample tube and enter the detection system directly to ensure that the configured gas concentration reached the set value. Then, the reactant gas was switched back and passed through the catalyst to be tested in the fixed-bed reactor. Finally, a temperature control program was set, with a heating rate of 5°C / min. -1 The gas was kept at each temperature point for 0.5 hours, and the composition of the exhaust gas was detected in real time using infrared spectroscopy. The results are as follows: Figure 2 As shown, from Figure 2 As can be seen from this, the Sm provided by the present invention z -CuO x With increasing Sm content, the N2O decomposition performance of the catalyst exhibits a volcano-like trend, where Sm... 0.2 CuO x The catalyst exhibits the best catalytic performance, achieving a 90% N2O decomposition rate at 400℃, and its T... 90 More than pure CuO x The catalyst temperature was increased by approximately 150°C, resulting in a significant improvement.

[0054] Experiment Example 2 Impurity Gas Tolerance Test

[0055] The catalysts prepared in Examples 1-4 and Comparative Examples 1-4 were respectively pressed into tablets and granulated (40-60 mesh size), and then filled above the quartz sand core of the fixed-bed reactor. A small amount of quartz wool was filled above the catalyst particles. The reaction gas components N2O and NO were... x The concentrations of O2 and H2O were adjusted to 1000 ppm, 500 ppm, 5 vol%, and 5 vol%, respectively, while maintaining a total gas flow rate of 150 mL / min. -1 The gas hourly space velocity is 90,000 mL·g -1 ·h -1 The reaction temperature was set to 450℃. NO was introduced sequentially at test times of 15h, 30h, and 60h. x O2, H2O. Before testing, the reactant gas was switched to bypass the sample tube and enter the detection system directly to ensure that the configured gas concentration reached the set value. Subsequently, the reactant gas was switched back and passed through the catalyst under test in the fixed-bed reactor. The test duration was 150 hours. The results are as follows: Figure 3 As shown, the results indicate that Sm2CuO4 and CuO x It has the worst tolerance to impurity gases; when O2 is introduced, the decomposition rate of Sm2CuO4 drops directly to 0, and CuO... x The decomposition rate of CuO decreased to 15%. After passing H2O through it, CuO... x The decomposition rate also dropped to 0. In contrast, the catalyst's tolerance to impurity gases was significantly improved after incorporation of Sm, especially with Sm. 0.2 / CuO x The catalyst exhibits the best tolerance. When O2 is introduced, the decomposition rate drops from 100% to approximately 90%, while when NO is introduced... x Afterward, the decomposition rate remained at around 75%. After introducing H2O, the decomposition rate stabilized at around 68%. After stopping the introduction of impurity gas, the decomposition rate quickly recovered to 100%.

Claims

1. A composite oxide catalyst for the medium-to-low temperature catalytic decomposition of N₂O, characterized in that, The composite oxide catalyst is Sm z -CuO x The molar ratio of Sm to Cu is 0.01 to 0.5:

1. The preparation method of the composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O includes the following steps: (1) Add copper nitrate and samarium nitrate to deionized water, add chelating agent, mix and stir, heat to 80~90 ℃, stir to react, and dry after the reaction is completed to obtain the precursor; (2) The precursor is calcined at 550 °C for 4-8 h to obtain the composite oxide catalyst Sm z -CuO x ; In step (1), the chelating agent is citric acid; Under the action of chelating agents, rare earth element Sm will be doped into CuO. During the calcination process, rare earth element Sm induces the formation of Sm2CuO4 spinel phase on the surface of CuO phase.

2. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N₂O as described in claim 1, characterized in that, The molar ratio of Sm to Cu is 0.2:

1.

3. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N₂O as described in claim 1, characterized in that, In step (1), the mass fraction of the solute in the copper nitrate in the deionized water is 4~7 mol / L.

4. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O as described in claim 3, characterized in that, In step (1), the mass fraction of the copper nitrate solute in deionized water is 5.5 mol / L.

5. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N₂O as described in claim 1, characterized in that, In step (1), the molar ratio of copper nitrate to chelating agent is 1:0.15~0.

25.

6. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O as described in claim 5, characterized in that, In step (1), the molar ratio of copper nitrate to chelating agent is 1:0.

2.

7. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N₂O as described in claim 1, characterized in that, In step (1), a chelating agent is added and the mixture is stirred for 1.5 to 2.5 hours.

8. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O as described in claim 7, characterized in that, In step (1), a chelating agent is added and the mixture is stirred for 2 hours.

9. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N2O as described in claim 1, characterized in that, In step (1), the stirring reaction time is 4 to 6 hours.

10. The composite oxide catalyst for medium- and low-temperature catalytic decomposition of N₂O as described in claim 9, characterized in that, In step (1), the stirring reaction time is 5 h.

11. A method for the catalytic decomposition of N2O at medium and low temperatures, characterized in that, The composite oxide catalyst for the medium- and low-temperature catalytic decomposition of N2O as described in any one of claims 1 to 10 is used to catalytically decompose N2O.

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