Green synthesis of pt single-atom catalyst and application thereof

Abstract

The application discloses a green synthesis method of a Pt monatomic catalyst and application thereof, and belongs to the technical field of heterogeneous catalysis. The preparation method of the application is that only PtO2 nanoparticles and CeO2 nanoparticles are mixed, grinded and uniformly mixed, and high-temperature calcination is performed, so that a CeO2 carrier loaded Pt monatomic catalyst can be obtained. In the preparation process, no solvent and metal precursor salt anion are used, so that no waste water and atmospheric pollutants are generated in the calcination process. Meanwhile, the Pt monatomic catalyst prepared by the method has excellent catalytic activity in a methane dry reforming reaction. More importantly, the preparation method of the application is green and simple, and has wide industrial application prospects.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of heterogeneous catalysis, and particularly relates to a green synthesis method of a Pt monatomic catalyst and application thereof. BACKGROUND

[0002] At present, China's energy supply still relies on various fossil fuels, but the massive combustion of fossil fuels will lead to the emission of a large amount of greenhouse gases, aggravate the greenhouse effect, and cause global climate warming, glacier melting, sea level rise and other extremely adverse weather conditions. Therefore, air pollution control is imminent. So far, China has made phased progress in air pollution control, and the awareness and standards of control are constantly improving.

[0003] Methane (CH4) and carbon dioxide (CO2) are the main components of greenhouse gases. According to the WTO Greenhouse Gas Bulletin (2023), the global average annual concentration of CO2 and CH4 in 2023 was 420.0±0.1 ppm and 1934±2 ppm, respectively. The dry reforming of methane (DRM) is one of the effective ways to eliminate CO2 and CH4, and can convert them into high-value synthesis gas (H2 / CO). However, this reaction usually needs to be carried out at a relatively high temperature (700-1000 ℃), which limits the industrial application of methane dry reforming technology. The development of efficient catalysts is conducive to reducing the methane dry reforming reaction temperature, thereby promoting the industrialization process of methane dry reforming reaction.

[0004] In recent years, monatomic catalysts have been widely used in the field of heterogeneous catalysis due to their high atom utilization rate, excellent stability and easy-to-control coordination structure. Among them, Pt monatomic catalysts supported by cerium oxide materials with superior redox performance and thermal stability have attracted widespread attention from researchers. Common methods for preparing Pt monatomic catalysts include (initial) wet impregnation, vapor deposition and electrostatic adsorption. These methods are complex and not suitable for large-scale industrial application, and generally involve the use of solvents and metal precursor salts, which can seriously harm the environment. Therefore, it is urgent to develop a green synthesis method for Pt monatomic catalysts. SUMMARY

[0005] The first technical problem to be solved by the present application is to provide a green synthesis method of a Pt monatomic catalyst, which has a simple preparation process and is environmentally friendly. The second technical problem to be solved by the present application is to provide a Pt monatomic catalyst, which has excellent methane dry reforming reaction performance. The third technical problem to be solved by the present application is to provide an application of a Pt monatomic catalyst for methane dry reforming reaction.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0007] A green synthesis method of a Pt single-atom catalyst, only PtO2 nanoparticles and CeO2 nanoparticles are mixed, ground uniformly, and high-temperature calcination is performed, so that a CeO2 carrier loaded Pt single-atom catalyst can be obtained.

[0008] Further, the loading amount of Pt is 0.25-2.00 wt.%.

[0009] Further, the grinding time is 2-30 min.

[0010] Further, the calcination temperature is 700-1000 ℃.

[0011] Further, the calcination time is 2-12 h.

[0012] Further, the calcination atmosphere is air, oxygen.

[0013] Further, the Pt single-atom catalyst is prepared by any of the green synthesis methods of the Pt single-atom catalyst.

[0014] Further, the Pt single-atom catalyst is applied in a methane dry reforming reaction.

[0015] Further, the catalytic conditions of the methane dry reforming reaction are as follows: the catalyst particle size is 40-60 mesh, the reaction gas composition CH4 and CO2 ratio is 1:1, and the test mass space velocity is 30000 mL·g cat -1 ·h -1 .

[0016] Further, the catalytic reaction temperature is 600-800 ℃.

[0017] Compared with the prior art, the present application has the following advantages:

[0018] 1) The raw materials adopted by the present application are cheap and easy to obtain, and the resources are abundant; the preparation process is simple, and only grinding and high-temperature calcination are used to obtain a highly dispersed Pt single-atom catalyst. In this preparation process, no solvent and metal precursor salt anion (Cl - / NO3 - / SO4 2- ) is introduced, which can effectively avoid the generation of wastewater and air pollutants, realize 100% atom utilization rate, and has the characteristics of environmental friendliness.

[0019] 2) The application is verified by experiments that the prepared catalyst has high catalytic performance, wherein the calcination technology (temperature, time) adopted in preparation of each catalyst has a significant influence on the catalytic performance of the catalyst; reasonable control of the calcination temperature and time can obtain the most ideal catalytic performance. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 XRD results of CeO2, 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12 and 1.00Pt / CeO2-800-12;

[0021] Figure 2 Raman results of PtO2, CeO2, 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12 and 1.00Pt / CeO2-800-12;

[0022] Figure 3 In situ DRIFTS of CO adsorption results of PtO2, 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12, 0.25Pt-CeO2-30-800-12, 0.50Pt-CeO2-30-800-12, 2.00Pt-CeO2-30-800-12 and 1.00Pt / CeO2-800-12;

[0023] Figure 4 CO-TPR results of CeO2, 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12, 0.25Pt-CeO2-30-800-12, 0.50Pt-CeO2-30-800-12, 2.00Pt-CeO2-30-800-12 and 1.00Pt / CeO2-800-12;

[0024] Figure 5 Methane dry reforming activity diagrams of 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12, 0.50Pt-CeO2-30-800-12, 2.00Pt-CeO2-30-800-12 and 1.00Pt / CeO2-800-12. DETAILED DESCRIPTION

[0025] The present application is further illustrated below in conjunction with specific examples, which are implemented on the premise of the technical solutions of the present application, and it should be understood that these examples are only used to illustrate the present application and not used to limit the scope of the present application.

[0026] Example 1

[0027] Take 2 g of commercial CeO2 and 0.0237 g of PtO2 particles in an agate mortar (mass fraction of Pt is 1.00 wt.%), uniformly grind for about 30 min, and obtain a mixed powder with uniform color, which is recorded as 1.00Pt-CeO2-30 sample. Put the mixed powder 1.00Pt-CeO2-30 sample into a muffle furnace and calcine at 800 ℃ for 12 h, the heating rate is 5 ℃·min -1 , and the obtained sample is recorded as 1.00Pt-CeO2-30-800-12.

[0028] Example 2

[0029] Preparation of xPt-CeO2-30-800-12: The mass fraction of Pt is controlled to be 0.25-2.00 wt.%, and the remaining steps are the same as Example 1. The specific steps are as follows: take 2 g of commercial CeO2 and a certain amount of PtO2 particles in an agate mortar (assuming the mass fraction of Pt is x wt.%, the mass of PtO2 taken is 0.0237x g), uniformly grind for about 30 min, and obtain a mixed powder with uniform color, which is xPt-CeO2-30 sample. Further, put the mixed powder into a muffle furnace and calcine at 800 ℃ for 12 h, the heating rate is 5 ℃·min -1 , and the obtained sample is xPt-CeO2-30-800-12.

[0030] The typical samples (x = 0.25, 0.50, 2.00 wt.%) prepared in this example are recorded as: 0.25Pt-CeO2-30-800-12, 0.50Pt-CeO2-30-800-12, 2.00Pt-CeO2-30-800-12.

[0031] Example 3

[0032] 1.00Pt-CeO2-m-800-12 was prepared by adjusting the grinding time of CeO2 and PtO2 particles to 2-30 min, and the rest of the steps were the same as Example 1. The specific steps were as follows: 2 g of commercial CeO2 and 0.0237 g of PtO2 particles were weighed in an agate mortar and uniformly ground for about 2-30 min to obtain a mixed powder with uniform color, which was 1.00Pt-CeO2-m sample (m was the grinding time, min). Further, the mixed powder was placed in a muffle furnace and calcined at 800 ℃ for 12 h, and the heating rate was 5 ℃·min -1 , and the obtained sample was recorded as xPt-CeO2-m-800-12.

[0033] Example 4

[0034] 1.00Pt-CeO2-30-n-12 was prepared by adjusting the calcination temperature to 700-1000 ℃, and the rest of the steps were the same as Example 1. The specific steps were as follows: 2 g of commercial CeO2 and 0.0237 g of PtO2 particles were weighed in an agate mortar and uniformly ground for about 30 min to obtain a mixed powder with uniform color, which was 1.00Pt-CeO2-30 sample. Further, the mixed powder was placed in a muffle furnace and calcined at 700-1000 ℃ for 12 h, and the heating rate was 5 ℃·min -1 , and the obtained sample was recorded as 1.00Pt-CeO2-30-n-12 (n was the calcination temperature, ℃).

[0035] Example 5

[0036] 1.00Pt-CeO2-30-800-p was prepared by adjusting the calcination time to 2-12 h, and the rest of the steps were the same as Example 1. The specific steps were as follows: 2 g of commercial CeO2 and 0.0237 g of PtO2 particles were weighed in an agate mortar and uniformly ground for about 30 min to obtain a mixed powder with uniform color, which was 1.00Pt-CeO2-30 sample. Further, the mixed powder was placed in a muffle furnace and calcined at 800 ℃ for 2-12 h, and the heating rate was 5 ℃·min -1 , and the obtained sample was recorded as 1.00Pt-CeO2-30-800-p (p was the calcination time, h).

[0037] The typical sample (p = 2 h) prepared in this example was recorded as: 1.00Pt-CeO2-30-800-2.

[0038] Comparative Example 1

[0039] 0.065 mL of platinum nitrate solution (Pt(NO3)2, Pt content 18.02%, density 1.714 g·mL -1), and diluted with water to 0.42 mL (water absorption of commercial CeO2 is 0.21 mL·g -1 ). 2 g of commercial CeO2 was weighed in a ceramic crucible, Pt(NO3)2 solution was added dropwise, and a glass rod was used for stirring. The CeO2 remained in a loose powder state during the impregnation process, and no obvious granular particles appeared. Then the sample was placed in an oven at 120 ℃ for 30 min, and after grinding, it was placed in a muffle furnace at 800 ℃ for 12 h, with a heating rate of 5 ℃·min -1 , and 1.00Pt / CeO2-800-12 catalyst was obtained.

[0040] The prepared catalysts were evaluated by X-ray diffraction (XRD), Raman spectra, in situ CO adsorption infrared (In situ DRIFTS of CO adsorption), CO temperature programmed reduction (CO-TPR), and methane dry reforming (DRM, CH4 + CO2 → 2CO + 2H2) performance testing methods for the structure and catalyst performance of the catalysts. The test results are shown in Figures 1-5 .

[0041] Figure 1 The XRD results of CeO2, 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12, and 1.00Pt / CeO2-800-12 are shown in the figure. The results show that all the Pt / CeO2 catalysts exhibit a cubic fluorite CeO2 structure, and no obvious crystal phase peak belonging to PtO2 appears, indicating that the Pt species is highly dispersed on the surface of CeO2.

[0042] Figure 2 The Raman results of PtO2, CeO2, 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12, and 1.00Pt / CeO2-800-12 are shown in the figure. The results show that simple mechanical grinding and high-temperature calcination can disperse PtO2 particles, and abundant Pt-O-Ce structures can be formed between Pt and CeO2.

[0043] Figure 3The results of the In situ DRIFTS of CO adsorption of PtO2, 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12, 0.25Pt-CeO2-30-800-12, 0.50Pt-CeO2-30-800-12, 2.00Pt-CeO2-30-800-12 and 1.00Pt / CeO2-800-12 show that simple mechanical grinding and high temperature calcination and traditional incipient wetness impregnation can both successfully prepare Pt single atom catalysts, and their coordination environments are obviously different, and the average valence of the Pt single atom on the surface of 1.00Pt-CeO2-30-800-12 is obviously higher than that of 1.00Pt / CeO2-800-12.

[0044] Figure 4 The results of the CO-TPR of CeO2, 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12, 0.25Pt-CeO2-30-800-12, 0.50Pt-CeO2-30-800-12, 2.00Pt-CeO2-30-800-12 and 1.00Pt / CeO2-800-12 show that the redox ability of the mechanically ground sample is enhanced with the increase of the Pt loading, the calcination temperature and the calcination time, and the redox ability of 1.00Pt-CeO2-30-800-12 is obviously superior to that of 1.00Pt / CeO2-800-12.

[0045] Example 6

[0046] Application of Pt single atom catalysts in the methane dry reforming reaction

[0047] The 1.00Pt-CeO2-30, 1.00Pt-CeO2-30-800-2, 1.00Pt-CeO2-30-800-12, 0.50Pt-CeO2-30-800-12, 2.00Pt-CeO2-30-800-12 and 1.00Pt / CeO2-800-12 catalysts prepared above are applied in the methane dry reforming reaction, and the results are as follows Figure 5The results show that for the Pt-CeO2 catalyst prepared by mechanical grinding, the methane dry reforming activity is significantly improved with the increase of Pt loading, calcination temperature and calcination time, indicating that the formation of more Pt-O-Ce structure or stronger Pt-CeO2 interaction is conducive to the methane dry reforming reaction. In addition, the methane dry reforming activity of 1.00Pt-CeO2-30-800-12 prepared by mechanical grinding is better than that of 1.00Pt / CeO2-800-12 prepared by incipient wetness impregnation, indicating that the coordination environment of Pt single atom prepared by mechanical grinding is more conducive to the methane dry reforming reaction.

[0048] The specific reaction conditions are as follows: the methane dry reforming reaction is carried out in a fixed bed continuous flow quartz reactor, and the catalyst particle size is 40-60 mesh. The reaction gas composition CH4 and CO2 ratio is 1:1, and the mass space velocity tested is 30000 mL·g cat -1 ·h -1 The catalytic reaction is carried out in the temperature range of 600-800 ℃, and the catalytic performance data at each test temperature is collected after the reaction reaches equilibrium. The products are analyzed by chromatography, and the conversion rates of CH4 and CO2 are calculated by the following formula:

[0049] CH4 conversion (%) = {([CH4] in - [CH4] out ) / [CH4] in} × 100%

[0050] CO2 conversion (%) = {([CO2] in - [CO2] out ) / [CO2] in} × 100%

[0051] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. Use of a Pt single-atom catalyst in a dry reforming of methane reaction, characterized in that: The synthesis method of the Pt monatomic catalyst is that only PtO2 nanoparticles and CeO2 nanoparticles are mixed, ground and mixed uniformly, high-temperature calcination is carried out, and the CeO2 carrier loaded Pt monatomic catalyst can be obtained; the loading amount of Pt is 1-2.00 wt.%; the calcination temperature is 700-1000 DEG C; and the calcination time is 12 h.

2. Use of the Pt single-atom catalyst according to claim 1 in the dry reforming of methane reaction, characterized by: The grinding time is 2-30 min.

3. Use of the Pt single-atom catalyst according to claim 1 in the dry reforming of methane reaction, characterized by: The calcination atmosphere is air or oxygen.

4. The use of the Pt single-atom catalyst according to claim 1 in the dry reforming of methane reaction, characterized by: The catalytic conditions of the methane dry reforming reaction are: catalyst particle size is 40-60 mesh, the composition of the reaction gas CH4 and CO2 ratio is 1:1, the mass space velocity tested is 30000 mL-g cat -1 ·h -1 .

5. Use of the Pt single-atom catalyst according to claim 4 in a dry reforming of methane reaction, characterized in that: The catalytic reaction temperature of the methane dry reforming reaction is 600-800 DEG C.

Images