Nickel monatomic / platinum group metal nanoparticle bimetallic catalyst as well as preparation method and application thereof

Abstract

The invention relates to a nickel monatomic / platinum group metal nanoparticle bimetallic catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts. The preparation method comprises the following steps: S1, under an alkaline condition, performing a hydrothermal reaction on cerium salt and nickel salt in a first solvent, and performing centrifugation, washing, drying and heat treatment to obtain a cerium oxide supported nickel monatomic catalyst; and S2, under a protective atmosphere, carrying out a heating reaction on the cerium oxide loaded nickel monatomic catalyst and a platinum group metal salt in a second solvent, and carrying out centrifugation, washing, drying and roasting to obtain the nickel monatomic / platinum group metal nanoparticle bimetallic catalyst. According to the technical scheme, the platinum group metal nanoparticles are effectively stabilized by constructing high-load nickel monatomic isolation sites, and the catalyst shows excellent high-temperature stability (the activity is basically kept unchanged after the catalyst is aged at 600-800 DEG C) and excellent catalytic activity (the methane conversion rate gt; 90% of the reaction temperature is 300 DEG C).

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a nickel single atom / platinum group metal nanoparticle bimetallic catalyst and a preparation method and application thereof. Background Art

[0002] In the next few decades, fossil energy (oil, coal, natural gas) will still play an important role in the global energy supply. -1 ), low pollutant emissions (such as SO x 、NO x and particulate matter) and has low toxicity, making it an important choice for the transition from traditional internal combustion engines to clean energy. However, unburned methane from natural gas vehicles has become a new environmental problem, because the greenhouse effect caused by methane is 25 times that of CO2, which puts higher demands on automobile exhaust purification technology. Precious metal catalysts have been widely used in methane combustion reactions, and their active components are mainly composed of Pt, Pd, Rh, Ru or Au precious metals. Among them, Pd is the most widely used precious metal due to its excellent activity. Faced with the current stringent emission requirements, there are three core challenges: first, the catalytic activity needs to be further improved to achieve ignition below 300°C and conversion below 500°C; second, the stability of the catalyst under complex working conditions (such as lean and rich oxygen switching, high-temperature hydrothermal environment) needs to be enhanced; finally, the high price of precious metals significantly increases the cost of the catalyst.

[0003] Therefore, it is crucial to develop efficient and stable natural gas vehicle exhaust purification catalysts, which will not only help promote the application of clean energy, but also make important contributions to reducing the greenhouse effect. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problem in the prior art that the noble metal nanoparticles in the catalyst have poor activity below 300°C and are easily agglomerated and deactivated at high temperatures.

[0005] In order to solve the above technical problems, the present invention provides a nickel single atom / platinum group metal nanoparticle bimetallic catalyst and its preparation method and application.

[0006] The first object of the present invention is to provide a method for preparing a nickel single atom / platinum group metal nanoparticle bimetallic catalyst, comprising the following steps:

[0007] S1. Under alkaline conditions, a cerium salt and a nickel salt are hydrothermally reacted in a first solvent, and a cerium oxide-supported nickel single-atom catalyst is obtained by centrifugation, washing, drying, and heat treatment;

[0008] S2. Under a protective atmosphere, the cerium oxide-supported nickel single atom catalyst and the platinum group metal salt described in S1 are heated to react in a second solvent, and the nickel single atom / platinum group metal nanoparticle bimetallic catalyst is obtained through centrifugation, washing, drying and calcination.

[0009] In one embodiment of the present invention, in S1, the cerium salt is selected from one or more of cerium nitrate, cerium sulfate, cerium acetate and cerium oxalate, and the amount of the cerium salt is 15 mg / mL-28 mg / mL;

[0010] The nickel salt is selected from one or more of nickel nitrate, nickel sulfate, nickel acetate and nickel oxalate, and the amount of the nickel salt is 1.5 mg / mL-2.5 mg / mL.

[0011] In one embodiment of the present invention, in S1, the hydrothermal reaction is carried out at a pH of 10-12, heating to 100-200°C at a rate of 2°C / min-5°C / min, and keeping the temperature for 12h-48h;

[0012] The number of centrifugation is 3-5 times;

[0013] The washing step is to first wash with ethanol for 2-3 times, and then wash with deionized water for 2-3 times;

[0014] The drying is carried out under vacuum conditions at 40°C-100°C for 6h-24h;

[0015] The heat treatment is carried out in an air atmosphere, heating to 500-800°C at a rate of 2-5°C / min and keeping the temperature for 2-10 hours; this rate is conducive to uniform dispersion of nickel on the surface of cerium oxide to form high-density nickel single atoms.

[0016] In one embodiment of the present invention, in S1, the first solvent is selected from one or more of water, ethanol, ethylene glycol, diethylene glycol dimethyl ether and N,N-dimethylformamide.

[0017] In one embodiment of the present invention, in S2, the platinum group noble metal salt is selected from palladium salt, platinum salt, rhodium salt, iridium salt, ruthenium salt or gold salt.

[0018] In one embodiment of the present invention, in S2, the molar ratio of the cerium oxide-supported nickel single-atom catalyst and the platinum group metal salt is (3.5-35):1.

[0019] In one embodiment of the present invention, in S2, the pH of the heating reaction is 8-10, the temperature is 40°C-130°C, and the time is 0.5h-5h; under these conditions, platinum group metal nanoparticles can be grown in situ on the surface of the cerium oxide-supported nickel single-atom catalyst.

[0020] The number of centrifugation is 3-5 times;

[0021] The washing step is to first wash with ethanol for 2-3 times, and then wash with deionized water for 2-3 times;

[0022] The drying is carried out under vacuum conditions at 40°C-100°C for 6h-24h;

[0023] The calcination is carried out in an air atmosphere, heating to 300-800°C at a rate of 2-5°C / min and keeping the temperature for 2-5 hours; this rate is conducive to uniform dispersion of platinum group metal nanoparticles on the surface of the cerium oxide-supported nickel single-atom catalyst.

[0024] In one embodiment of the present invention, in S2, the second solvent is selected from one or more of water, ethanol, ethylene glycol, diethylene glycol dimethyl ether and N,N-dimethylformamide.

[0025] A second object of the present invention is to provide a nickel single atom / platinum group metal nanoparticle bimetallic catalyst prepared by the method, wherein the molar ratio of cerium, nickel, and platinum group metal in the nickel single atom / platinum group metal nanoparticle bimetallic catalyst is 61.5:(1.8-9.0):(0.5-1.0). By varying the mass ratio of nickel to platinum group metal to regulate the loading of the nickel single atom, the platinum group metal nanoparticles are shielded and isolated, while the synergistic effect of the platinum group metal nanoparticles and the nickel single atom is simultaneously utilized to enhance catalyst activity. Furthermore, the steric hindrance effect of the high-density nickel single atoms effectively suppresses the aggregation and deactivation of the platinum group metal nanoparticles under high temperature conditions, significantly enhancing the thermal stability of the catalyst.

[0026] In one embodiment of the present invention, the nickel single atom in the nickel single atom / platinum group metal nanoparticle bimetallic catalyst strongly interacts with the ceria support to form stable isolation sites, stabilize the platinum group metal nanoparticles, and still maintain good thermal stability and catalytic activity after high-temperature aging.

[0027] In one embodiment of the present invention, the high temperature aging is performed at 500° C.-800° C. for 1 h-10 h.

[0028] The third object of the present invention is to provide an application of the nickel single atom / platinum group metal nanoparticle bimetallic catalyst in the catalytic oxidation of methane to produce carbon dioxide, which specifically includes the following steps: under a protective atmosphere, methane and oxygen are introduced into a reactor containing the nickel single atom / platinum group metal nanoparticle bimetallic catalyst to react to obtain carbon dioxide.

[0029] In one embodiment of the present invention, the space velocity of methane and oxygen is independently 40000 mL·g -1 ·h -1-80000mL·g -1 ·h -1 .

[0030] In one embodiment of the present invention, the concentration of methane is 0.5 vol.%-5 vol.%, and the concentration of oxygen is 10 vol.%-50 vol.%.

[0031] The technical solution of the present invention has the following advantages over the prior art:

[0032] (1) The nickel single atom / platinum group metal nanoparticle bimetallic catalyst described in the present invention has excellent catalytic activity. This is because there is a synergistic effect between nickel single atoms and platinum group metal nanoparticles. Taking palladium nanoparticles as an example, the work function of nickel is about 5.0eV, and the work function of palladium is about 5.6eV. Nickel acts as an electron donor to regulate the center position of the d band of palladium, optimize the electronic structure of the active center, reduce the energy barrier for the activation of the CH bond of methane, and significantly improve the catalyst's ability to adsorb and activate methane molecules, so that the catalyst exhibits excellent ignition activity in the low temperature range of 100℃-200℃. In addition, the introduction of high-density nickel single atoms also enhances the mobility of lattice oxygen on the catalyst surface, providing sufficient active oxygen species for the deep oxidation of methane.

[0033] (2) The nickel single atom / platinum group metal nanoparticle bimetallic catalyst of the present invention has excellent high temperature stability and catalytic activity under oxygen-rich conditions. This is because the high-density nickel single atoms form stable isolation sites on the surface of the ceria support through strong metal-support interaction (SMSI), and their steric hindrance effect effectively inhibits the migration and agglomeration of platinum group metal nanoparticles under high temperature conditions. In addition, in an oxygen-rich environment, the nickel single atoms react with the ceria support through a reversible redox cycle (Ni 2+ / Ni 3+ ) maintains a dynamic balance of surface oxygen vacancies, promoting the Mars-van Krevelen mechanism in which lattice oxygen participates in the reaction, thereby maintaining stable catalytic performance at high temperatures of 600°C-800°C. This ensures that the catalyst exhibits both high-temperature stability and excellent light-off activity under oxygen-rich conditions.

[0034] (3) The nickel single atom / platinum group metal nanoparticle bimetallic catalyst of the present invention is heated at a space velocity of 60000 mL·g -1 ·h -1Under the reaction conditions of 1 vol.% CH4+20 vol.% O2+N2, CH4 ignition was achieved below 100°C and complete CH4 oxidation was achieved below 400°C, completing the technical challenges of CH4 ignition below 300°C and complete CH4 conversion at 500°C. After high-temperature air aging, the catalyst's CH4 complete conversion temperature and precious metal nanoparticle size remained basically unchanged.

[0035] (4) The nickel single atom / platinum group metal nanoparticle bimetallic catalyst described in the present invention achieves effective stabilization of platinum group metal nanoparticles by constructing high-load nickel single atom isolation sites as a technical solution. It exhibits excellent high-temperature stability (activity remains basically unchanged after aging at 600℃-800℃) and excellent catalytic activity (methane conversion rate>90% reaction temperature at 300℃) under oxygen-rich conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0037] Figure 1 This is the X-ray photoelectron spectrum of Ni1 / CeO2 of Example 1 of the present invention;

[0038] Figure 2 is Pd in ​​Example 1 of the present invention NP -X-ray photoelectron spectrum of Ni1 / CeO2;

[0039] Figure 3 is Pd in ​​Example 1 of the present invention NP -Transmission electron microscopy images of Ni1 / CeO2 before and after aging; (a)-(b) are Pd NP -Transmission electron microscopy images of Ni1 / CeO2, (c)-(d) are Pd after aging NP - Transmission electron microscopy image of Ni1 / CeO2;

[0040] Figure 4 is Pd in ​​Example 1 of the present invention NP -Diffuse reflectance infrared Fourier transform spectra of Ni1 / CeO2 before and after aging;

[0041] Figure 5 This is a graph showing the reaction performance of methane catalyzed by the catalysts of Example 1 and Comparative Examples 1-3 in Application Example 1 of the present invention;

[0042] Figure 6 This is a graph showing the reaction performance of methane catalyzed by the catalysts of Example 1 and Comparative Examples 4-6 in Application Example 1 of the present invention;

[0043] Figure 7This is a graph showing the reaction performance of methane catalyzed by catalysts with different Ni contents in Application Example 2 of the present invention;

[0044] Figure 8 The Pd after aging at different temperatures in Application Example 3 of the present invention NP -Ni1 / CeO2、Pd NP / CeO2 catalytic methane reaction performance diagram;

[0045] Figure 9 The Pd prepared at different calcination temperatures in Application Example 4 of the present invention NP -Chart of methane catalytic reaction performance of Ni1 / CeO2 catalyst;

[0046] Figure 10 The Pd before and after hydrothermal aging in Application Example 5 of the present invention NP -Ni1 / CeO2、Pd NP / CeO2 catalytic methane reaction performance diagram. DETAILED DESCRIPTION

[0047] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0048] In the present invention, unless otherwise specified, the washing involved in the embodiments of the present invention is first washing with ethanol twice and then washing with deionized water twice.

[0049] In the present invention, unless otherwise stated, all catalytic tests involved in the examples of the present invention were carried out in a fixed bed reactor.

[0050] Example 1

[0051] The nickel single atom / palladium nanoparticle bimetallic catalyst and its preparation method of this embodiment specifically include the following steps:

[0052] S1. Preparation of Cerium Oxide Supported Nickel Single Atom Catalyst

[0053] S11. Disperse 1.61 g of cerium nitrate and 95.2 mg of nickel nitrate in 60 mL of deionized water. Ultrasonic vibration is used to evenly disperse the cerium nitrate and nickel nitrate. The pH is adjusted to 12 with sodium hydroxide. The mixture is heated to 120°C at a rate of 5°C / min and subjected to hydrothermal reaction for 25 h. The mixture is then centrifuged four times and washed to obtain a solid intermediate, which is designated as Ni / CeO. x ;

[0054] S12, the solid intermediate was vacuum dried at 60 ° C for 12 h, and then heat treated at 800 ° C at a rate of 5 ° C / min for 4 h in an air atmosphere to obtain a cerium oxide-supported nickel single atom catalyst, denoted as Ni1 / CeO2;

[0055] S2. Preparation of nickel single atom / palladium nanoparticle bimetallic catalyst

[0056] S21, dissolving 30 mg of palladium chloride in a mixed solution of 1 mL of water and 0.1 mL of hydrochloric acid to obtain a chloropalladic acid solution with a concentration of 27.3 mg / mL;

[0057] 200 mg of cerium oxide-supported nickel single-atom catalyst was added to 50 mL of ethylene glycol to form a dispersion;

[0058] S22. Use a peristaltic pump to dropwise add 0.72 mL of chloropalladic acid solution into the dispersion, and adjust the pH to 8 with a 12 mg / mL sodium ethoxide solution; then stir at 40 ° C for 0.5 h under nitrogen protection, centrifuge 4 times, wash, and vacuum dry at 60 ° C for 12 h; finally, heat the temperature to 400 ° C in an air atmosphere at a rate of 5 ° C / min and calcine for 2 h to obtain a nickel single atom / palladium nanoparticle bimetallic catalyst, denoted as Pd NP -Ni1 / CeO2(1%Pd NP -3%Ni1 / CeO2).

[0059] (1) Ni1 / CeO2 and Pd NP -X-ray photoelectron spectrum of Ni1 / CeO2 Figure 1-Figure 2 As shown, from Figure 1 It can be seen that Ni 2p 3 / 2 The binding energies are located at 853.2 eV and 855.6 eV, corresponding to Ni 2+ (NiO species) and Ni 3+ (Ni2O3 or Ni-O-Ce interface species), no metallic nickel (Ni 0 ,~852.6eV) characteristic peak, indicating that nickel is highly dispersed on the surface of CeO2 support in an oxidized state. Ni is mainly in the form of Ni 2+ (NiO species) and Ni 3+ (Ni2O3 or Ni-O-Ce interface species) and no metallic nickel was detected. Figure 2 It can be seen that the binding energy of Ni moves to higher binding energy after the simultaneous introduction of Pd, indicating that Ni species moves to the adjacent Pd nanoparticles (Pd NP) undergoes significant electron transfer, inducing a redistribution of electronic states on the surface of Pd nanoparticles and forming electron-rich Pd active centers. This metal-metal electronic synergistic effect optimizes the adsorption and activation ability of the catalyst surface for reactant molecules (such as CH4), thereby significantly improving the catalytic efficiency of the methane oxidation reaction.

[0060] (2)Pd NP -Ni1 / CeO2 was heated to 800℃ at a rate of 10℃ / min in air atmosphere and aged for 2h. NP -Ni1 / CeO2 was characterized by transmission electron microscopy, and the results were as follows Figure 3 As shown. Figure 3 It can be seen that the particle size of palladium nanoparticles is maintained at about 3 nm, indicating that the introduction of Ni can effectively sinter and agglomerate Pd particles at high temperature.

[0061] (3) Pd before and after aging NP -Diffuse reflectance infrared Fourier transform spectroscopy of Ni1 / CeO2, with CO as the probe molecule, the results are as follows Figure 4 As shown. Figure 4 It can be seen that Pd NP -Ni1 / CeO2 after high temperature aging in air has a linear adsorption peak of Pd from 2090 cm -1 becomes 2100cm -1 and 2089cm -1 , indicating that higher valence Pd species were formed after high temperature aging in air; Pd NP -Ni1 / CeO2 showed a bridge adsorption peak before and after aging, and the bridge adsorption peak was maintained at 1985cm -1 Around, indicating Pd NP -Pd in ​​Ni1 / CeO2 always exists in the form of nanoparticles. This is because the strong interaction between nickel atoms and the support forms stable isolation sites, which inhibits the migration, agglomeration / redispersion of Pd species at high temperatures, stabilizes the platinum group metal nanoparticles, and improves the high temperature stability of the platinum group metal nanoparticle catalyst. Figure 3 It is further shown that the introduction of Ni can effectively sinter and agglomerate Pd particles at high temperatures and redisperse them at high temperatures.

[0062] Comparative Example 1

[0063] The method is basically the same as Example 1, except that nickel single atoms and palladium nanoparticles are not loaded, and CeO2 is obtained.

[0064] Comparative Example 2

[0065] Basically the same as Example 1, except that palladium nanoparticles are not loaded, and Ni1 / CeO2 is obtained.

[0066] Comparative Example 3

[0067] The same as Example 1, except that nickel single atom loading is not performed, and Pd NP / CeO2.

[0068] Comparative Example 4

[0069] The same as Example 1, except that the nickel single atom support is replaced by cobalt single atom support, to obtain a cobalt single atom / palladium nanoparticle bimetallic catalyst, denoted as Pd NP -Co1 / CeO2.

[0070] Comparative Example 5

[0071] The same as Example 1, except that the nickel single atom support is replaced by manganese single atom support to obtain a manganese single atom / palladium nanoparticle bimetallic catalyst, denoted as Pd NP -Mn1 / CeO2.

[0072] Comparative Example 6

[0073] The same as Example 1, except that the nickel single atom support is replaced by copper single atom support to obtain a copper single atom / palladium nanoparticle bimetallic catalyst, denoted as Pd NP -Cu1 / CeO2.

[0074] Application Example 1

[0075] 100 mg of the catalysts of Example 1 and Comparative Examples 1-6 were mixed with 100 mg of quartz sand and loaded into a fixed bed reactor at a temperature of 60000 mL·g -1 ·h -1 A gas mixture of 1 vol.% CH4 + 20 vol.% O2 + N2 was introduced at a space velocity of 1.5 % and the temperature was raised according to a temperature program to carry out the reaction; the reactants (CH4) and products (CO2) were analyzed by a gas chromatograph (Agilent GC-2060) equipped with a methane reformer, and the CH4 conversion rate was calculated. The results are shown in FIG. Figure 5-Figure 6 As shown. Figure 5-Figure 6 It can be seen that Pd NP -Ni1 / CeO2 catalyzes the complete conversion of CH4 at 400℃. NP / CeO2、Pd NP -Co1 / CeO2、Pd NP -Mn1 / CeO2、Pd NP -Cu1 / CeO2 catalyzes complete conversion of CH4 at 900℃, 600℃, 750℃, 550℃, 800℃, and 750℃. This indicates that under oxygen-rich conditions, Pd NP-Ni1 / CeO2 has excellent ignition conversion activity and complete conversion activity for catalyzing the complete conversion of CH4. This is because the strong interaction between Ni single atoms and CeO2 carriers forms stable isolation sites, while significantly enhancing the lattice oxygen mobility. In addition, nickel acts as an electron donor, regulating the d-band center position of palladium, optimizing the electronic structure of the active center, reducing the energy barrier for methane C-H bond activation, and significantly improving the catalyst's adsorption and activation ability for methane molecules. Therefore, it has excellent ignition conversion activity and complete conversion activity, and presents significant advantages in the application of catalytic natural gas vehicle exhaust treatment.

[0076] Application Example 2

[0077] Based on Example 1, the effect of different Ni contents (mass ratio of Ni1 to CeO2 was 1:100, 2:100, 3:100, 4:100, and 5:100) on the catalytic performance was studied; 100 mg of catalysts with different Ni contents were mixed with 100 mg of quartz sand and loaded into a fixed bed reactor at a temperature of 60000 mL·g -1 ·h -1 A gas mixture of 1 vol.% CH4 + 20 vol.% O2 + N2 was introduced at a space velocity of 1.5 % and the temperature was raised according to a temperature program to carry out the reaction; the reactants (CH4) and products (CO2) were analyzed by a gas chromatograph (Agilent GC-2060) equipped with a methane reformer, and the CH4 conversion rate was calculated. The results are shown in FIG. Figure 7 As shown. Figure 7 It can be seen that 1% Pd NP -1% Ni1 / CeO2 catalyzes complete conversion of CH4 at 500℃; 1% Pd NP -3% Ni1 / CeO2 catalyzes complete conversion of CH4 at 400℃; 1% Pd NP -5% Ni1 / CeO2 catalyzes complete conversion of CH4 at 450°C. A high Ni content easily forms a metallic state and loses the ability to activate oxygen, while a low Ni content makes it difficult to produce a synergistic effect with Pd particles and cannot effectively inhibit the high-temperature migration of Pd particles. Therefore, by adjusting the Ni content, the catalytic activity and stability of the catalyst can be improved.

[0078] Application Example 3

[0079] Based on Example 1 and Comparative Example 3, the effects of different aging temperatures on catalytic performance were studied. The temperatures were raised to 200°C, 400°C, 600°C, and 800°C at a rate of 10°C / min in an air atmosphere and aged for 1 h. 100 mg of the catalyst aged at different aging temperatures was mixed with 100 mg of quartz sand and loaded into a fixed bed reactor. The mixture was heated at 60000 mL·g -1 ·h -1A gas mixture of 1 vol.% CH4 + 20 vol.% O2 + N2 was introduced at a space velocity of 1.5 % and the temperature was raised according to a temperature program to carry out the reaction; the reactants (CH4) and products (CO2) were analyzed by a gas chromatograph (Agilent GC-2060) equipped with a methane reformer, and the CH4 conversion rate was calculated. The results are shown in FIG. Figure 8 As shown. Figure 8 It can be seen that Pd NP -Ni1 / CeO2 and Pd aged in air at 800℃ for 1h NP -Ni1 / CeO2, both catalyzed complete conversion of CH4 at 400℃.

[0080] Application Example 4

[0081] Based on Example 1, the effects of different calcination temperatures (400°C, 600°C, 700°C, and 800°C) on the catalytic performance were studied. 100 mg of the catalysts prepared at different calcination temperatures were mixed with 100 mg of quartz sand and loaded into a fixed bed reactor at a temperature of 60,000 mL·g -1 ·h -1 A gas mixture of 1 vol.% CH4 + 20 vol.% O2 + N2 was introduced at a space velocity of 1.5 % and the temperature was raised according to a temperature program to carry out the reaction; the reactants (CH4) and products (CO2) were analyzed by a gas chromatograph (Agilent GC-2060) equipped with a methane reformer, and the CH4 conversion rate was calculated. The results are shown in FIG. Figure 9 As shown. Figure 9 It can be seen that the catalyst calcined at 400°C completely catalyzes CH4 conversion at 400°C, with a conversion rate of 10% at 125°C. The catalyst calcined at 600°C completely catalyzes CH4 conversion at 400°C, with a conversion rate of 10% at 150°C. The catalyst calcined at 800°C completely catalyzes CH4 conversion at 400°C, with a conversion rate of 10% at 200°C. This indicates that calcination temperature does not affect the catalyst's high-temperature activity for complete CH4 conversion, but does affect its low-temperature activity for complete CH4 conversion.

[0082] Application Example 5

[0083] Based on Example 1 and Comparative Example 3, the effect of hydrothermal aging on catalytic performance was studied. The catalyst was heated to 800°C at a rate of 10°C / min for 2h and then hydrothermally aged at 700°C for 10h. 100mg of catalyst and 100mg of quartz sand were mixed and loaded into a fixed bed reactor. The mixture was heated to 60000mL·g -1 ·h -1A gas mixture of 1 vol.% CH4 + 20 vol.% O2 + N2 + 10% H2O was introduced at a space velocity of 1.5 % and the temperature was raised according to a temperature program to carry out the reaction; the reactants (CH4) and products (CO2) were analyzed by a gas chromatograph (Agilent GC-2060) equipped with a methane reformer, and the CH4 conversion rate was calculated. The results are shown in FIG. Figure 10 As shown. Figure 10 It can be seen that the Pd NP -Ni1 / CeO2 catalyzed the complete conversion of CH4 at 400℃, while Pd NP The catalytic CH4 conversion rate of / CeO2 decreased from complete at 750℃ to ~80% at 900℃, indicating that Ni atoms stabilize oxygen vacancies through strong interactions with the support, reducing the effect of hydroxyl coverage on oxygen migration and improving the hydrothermal stability of the catalyst.

[0084] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a nickel single atom / platinum group metal nanoparticle bimetallic catalyst, characterized in that: The following steps are involved: S1. Under alkaline conditions, a cerium salt and a nickel salt are hydrothermally reacted in a first solvent, and a cerium oxide-supported nickel single-atom catalyst is obtained by centrifugation, washing, drying, and heat treatment; S2. Under a protective atmosphere, the cerium oxide-supported nickel single atom catalyst and the platinum group metal salt described in S1 are heated and reacted in a second solvent, and the nickel single atom / platinum group metal nanoparticle bimetallic catalyst is obtained through centrifugation, washing, drying and calcination.

2. The method for preparing the nickel single atom / platinum group metal nanoparticle bimetallic catalyst according to claim 1, characterized in that: In S1, the cerium salt is selected from one or more of cerium nitrate, cerium sulfate, cerium acetate and cerium oxalate, and the amount of the cerium salt is 15 mg / mL-28 mg / mL; The nickel salt is selected from one or more of nickel nitrate, nickel sulfate, nickel acetate and nickel oxalate, and the amount of the nickel salt is 1.5 mg / mL-2.5 mg / mL.

3. The method for preparing the nickel single atom / platinum group metal nanoparticle bimetallic catalyst according to claim 1, characterized in that: In S1, the hydrothermal reaction is carried out at a pH of 10-12, heating to 100-200°C at a rate of 2°C / min-5°C / min, and keeping the temperature for 12h-48h; The heat treatment is carried out in an air atmosphere, heating the temperature to 500° C.-800° C. at a rate of 2° C. / min-5° C. / min, and keeping the temperature for 2 h-10 h.

4. The method for preparing the nickel single atom / platinum group metal nanoparticle bimetallic catalyst according to claim 1, characterized in that: In S2, the platinum group noble metal salt is selected from palladium salt, platinum salt, rhodium salt, iridium salt, ruthenium salt or gold salt.

5. The method for preparing the nickel single atom / platinum group metal nanoparticle bimetallic catalyst according to claim 1, characterized in that: In S2, the molar ratio of the cerium oxide-supported nickel single-atom catalyst and the platinum group metal salt is (3.5-35):

1.

6. The method for preparing the nickel single atom / platinum group metal nanoparticle bimetallic catalyst according to claim 1, characterized in that: In S2, the pH of the heating reaction is 8-10, the temperature is 40°C-130°C, and the time is 0.5h-5h; The calcination is carried out in an air atmosphere, heating the temperature to 300-800° C. at a rate of 2-5° C. / min and keeping the temperature for 2-5 hours.

7. A nickel single atom / platinum group metal nanoparticle bimetallic catalyst prepared by the method according to any one of claims 1 to 6, characterized in that: The molar ratio of cerium, nickel and platinum group metal in the nickel single atom / platinum group metal nanoparticle bimetallic catalyst is 61.5:(1.8-9.0):(0.5-1.0).

8. Use of the nickel single atom / platinum group metal nanoparticle bimetallic catalyst according to claim 7 in catalytic oxidation of methane to produce carbon dioxide, characterized in that: The specific steps include: Under a protective atmosphere, methane and oxygen are introduced into a reactor equipped with a nickel single atom / platinum group metal nanoparticle bimetallic catalyst to react and produce carbon dioxide.

9. The use according to claim 8, wherein the space velocity of methane and oxygen is independently 40000 mL·g -1 ·h -1 -80000mL·g -1 ·h -1 .

10. The use according to claim 8, wherein the concentration of methane is 0.5 vol.%-5 vol.%, and the concentration of oxygen is 10 vol.%-50 vol.%.

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