Green synthesis method and application of Pt monatomic catalyst

Abstract

The invention discloses a green synthesis method and application of a Pt monatomic catalyst, and belongs to the technical field of heterogeneous catalysis. The preparation method provided by the invention comprises the following steps: mixing PtO2 nanoparticles and CeO2 nanoparticles, grinding and uniformly mixing, and carrying out high-temperature calcination to obtain the CeO2 carrier loaded Pt monatomic catalyst. In the preparation process, the use of any solvent and metal precursor salt anions is not involved, so that any wastewater and atmospheric pollutants are not generated in the calcination process; meanwhile, the Pt monatomic catalyst prepared by the method shows excellent catalytic activity in a methane dry reforming reaction; more importantly, the preparation method disclosed by the invention is green and simple, and has a wide industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of heterogeneous catalysis, and specifically relates to a green synthesis method of a Pt single-atom catalyst and application thereof. Background Art

[0002] At present, my country's energy supply still relies on various fossil fuels, but the large-scale burning of fossil fuels will lead to the emission of a large amount of greenhouse gases, aggravating the greenhouse effect, causing global warming, melting glaciers, rising sea levels and other extreme weather conditions. Therefore, air pollution control is imminent. So far, my country has made phased progress in air pollution control, and governance awareness and governance standards are also 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 atmospheric concentrations of CO2 and CH4 in 2023 are 420.0±0.1 ppm and 1934±2 ppm, respectively. Dry reforming of methane (DRM) is one of the effective ways to eliminate CO2 and CH4, and can convert them into high value-added synthesis gas (H2 / CO). However, the reaction usually needs to be carried out at a higher temperature (700-1000 ℃), which limits the industrial application of methane dry reforming technology. The development of efficient catalysts is conducive to reducing the reaction temperature of methane dry reforming, thereby promoting the industrialization of methane dry reforming reaction.

[0004] In recent years, single-atom catalysts have been widely used in the field of heterogeneous catalysis due to their advantages such as high atomic utilization, excellent stability and easy regulation of coordination structure. Among them, Pt single-atom catalysts supported on cerium oxide materials with superior redox properties and thermal stability have received widespread attention from researchers. Common preparation methods for Pt single-atom catalysts include (initial) wet impregnation, vapor deposition and electrostatic adsorption. These methods are complicated to operate and are not suitable for large-scale industrial applications. They also generally involve the use of solvents and metal precursor salts, and the wastewater and waste gas generated will seriously harm the environment. Therefore, it is urgent to develop a green synthesis method for Pt single-atom catalysts. Summary of the invention

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

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A green synthesis method for a Pt single-atom catalyst comprises mixing PtO2 nanoparticles with CeO2 nanoparticles, grinding and mixing them evenly, and calcining them at high temperature to obtain a Pt single-atom catalyst supported by a CeO2 carrier.

[0008] Furthermore, the Pt loading is 0.25-2.00 wt.%.

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

[0010] Furthermore, the calcination temperature is 700-1000°C.

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

[0012] Furthermore, the calcination atmosphere is air or oxygen.

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

[0014] Furthermore, the Pt single-atom catalyst is used in methane dry reforming reaction.

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

[0016] Furthermore, the catalytic reaction temperature is 600-800°C.

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

[0018] 1) The raw materials used in the present invention are cheap, easy to obtain, and have abundant resources; the preparation process is simple, and a highly dispersed Pt single-atom catalyst can be obtained by only grinding and high-temperature calcination. No solvents and metal precursor salt anions (Cl - / NO3 - / SO4 2- ), can effectively avoid the generation of sewage and air pollutants, achieve 100% atomic utilization, and has environmentally friendly characteristics.

[0019] 2) The present invention has verified through experiments that the prepared catalyst has efficient catalytic performance, wherein the calcination technology (temperature, time) used in the preparation of each catalyst has a significant impact on the catalytic performance of the catalyst; the most ideal catalytic performance can be obtained by controlling the reasonable calcination temperature and time. BRIEF DESCRIPTION OF THE 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 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;

[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 The CO-TPR result graphs are 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 The methane dry reforming activity diagram is 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 invention is further illustrated below in conjunction with specific examples. The examples are implemented based on the technical solutions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0026] Example 1

[0027] Weigh 2 g of commercial CeO2 and 0.0237 g of PtO2 particles in an agate mortar (Pt mass fraction is 1.00wt.%), grind evenly for about 30 min, and obtain a mixed powder with uniform color, which is recorded as 1.00Pt-CeO2-30 sample. The mixed powder 1.00Pt-CeO2-30 sample was placed in a muffle furnace and calcined at 800 °C for 12 h, with a heating rate of 5 °C·min -1 The obtained sample was 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 adjusted to 0.25-2.00 wt.%, and the remaining steps are the same as in Example 1. The specific steps are as follows: weigh 2 g of commercial CeO2 and a certain amount of PtO2 particles in an agate mortar (assuming that the mass fraction of Pt is x wt.%, the mass of PtO2 weighed is 0.0237xg), grind evenly for about 30 min, and obtain a mixed powder with uniform color, which is the xPt-CeO2-30 sample. Further, the mixed powder is placed in a muffle furnace and calcined at 800 °C for 12 h, with a heating rate of 5 °C·min -1 The obtained sample is xPt-CeO2-30-800-12.

[0030] The typical samples prepared in this example (x = 0.25, 0.50, 2.00 wt.%) 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] Preparation of 1.00Pt-CeO2-m-800-12, the grinding time of CeO2 and PtO2 particles was adjusted to 2-30 min, and the remaining steps were the same as in Example 1. The specific steps are as follows: 2 g of commercial CeO2 and 0.0237 g of PtO2 particles were weighed in an agate mortar and evenly ground for about 2-30 min to obtain a mixed powder with uniform color, which is the 1.00Pt-CeO2-m sample (m is the grinding time, min). Further, the mixed powder was placed in a muffle furnace and calcined at 800 °C for 12 h, with a heating rate of 5 °C·min -1 The obtained sample was recorded as xPt-CeO2-m-800-12.

[0033] Example 4

[0034] Preparation of 1.00Pt-CeO2-30-n-12, the calcination temperature is adjusted to 700-1000 °C, and the remaining steps are the same as Example 1. The specific steps are as follows: weigh 2 g of commercial CeO2 and 0.0237 g of PtO2 particles in an agate mortar, grind evenly for about 30 min, and obtain a mixed powder with uniform color, which is the 1.00Pt-CeO2-30 sample. Further, the mixed powder is placed in a muffle furnace and calcined at 700-1000 °C for 12 h, with a heating rate of 5 °C·min -1 The obtained sample was recorded as 1.00Pt-CeO2-30-n-12 (n is the calcination temperature, ℃).

[0035] Example 5

[0036] Preparation of 1.00Pt-CeO2-30-800-p, the calcination time is adjusted to 2-12 h, and the remaining steps are the same as Example 1. The specific steps are as follows: weigh 2 g of commercial CeO2 and 0.0237 g of PtO2 particles in an agate mortar, grind evenly for about 30 minutes, and obtain a mixed powder with uniform color, which is the 1.00Pt-CeO2-30 sample. Further, the mixed powder is placed in a muffle furnace and calcined at 800 °C for 2-12 h, with a heating rate of 5 °C·min -1 The obtained sample was recorded as 1.00Pt-CeO2-30-800-p (p is the calcination time, h).

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

[0038] Comparative Example 1

[0039] Use a pipette to measure 0.065 mL of platinum nitrate solution (Pt(NO3)2, Pt content 18.02%, density 1.714 g·mL -1) and diluted it with water to 0.42 mL (the water absorption rate of commercial CeO2 is 0.21 mL g -1 ). Weigh 2 g of commercial CeO2 in a ceramic crucible, add Pt(NO3)2 solution drop by drop, and stir thoroughly with a glass rod. During the impregnation process, CeO2 always remains in a relatively loose powder state, and no obvious agglomerates appear. Then, the sample is placed in an oven and dried at 120 °C for 30 min. After being ground evenly, it is placed in a muffle furnace and calcined at 800 °C for 12 h, with a heating rate of 5 °C·min -1 , you can get 1.00Pt / CeO2-800-12 catalyst.

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

[0041] Figure 1 These are 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. The results show that all 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 CeO2 surface.

[0042] Figure 2 These are 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. The results show that simple mechanical grinding and high-temperature calcination can disperse the PtO2 particles, and a rich Pt-O-Ce structure can be formed between Pt and CeO2.

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

[0044] Figure 4 The 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 are shown. The results show that with the increase of Pt loading, calcination temperature and calcination time, the redox ability of the mechanically ground samples increases, and the redox ability of 1.00Pt-CeO2-30-800-12 is significantly better than that of 1.00Pt / CeO2-800-12.

[0045] Example 6

[0046] Application of Pt single atom catalyst in 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 were applied to methane dry reforming reaction. The results are as follows: Figure 5As shown. The results show that for the Pt-CeO2 catalyst prepared by mechanical grinding, with the increase of Pt loading, calcination temperature and calcination time, the methane dry reforming activity is significantly improved, indicating that the formation of more Pt-O-Ce structures or stronger Pt-CeO2 interactions is beneficial 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 Pt single atom coordination environment prepared by mechanical grinding is more conducive to the methane dry reforming reaction.

[0048] The specific reaction conditions are as follows: methane dry reforming reaction is carried out in a fixed bed continuous flow quartz reactor, the catalyst particle size is 40-60 mesh, the reaction gas composition is CH4 and CO2 ratio is 1:1, the mass space velocity of the test is 30000 mL·g cat -1 ·h -1 The catalytic reaction was carried out in the temperature range of 600-800 °C, and the catalytic performance data at each test temperature was collected after the reaction reached equilibrium. The products were analyzed by chromatographic detection, and the conversion rates of CH4 and CO2 were 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 is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A green synthesis method of Pt single-atom catalyst, characterized in that: The Pt single atom catalyst supported on the CeO2 carrier can be obtained by simply mixing the PtO2 nanoparticles with the CeO2 nanoparticles, grinding and mixing them evenly, and then calcining them at high temperature.

2. The green synthesis method of Pt single atom catalyst according to claim 1, characterized in that: The Pt loading amount is 0.25-2.00 wt.%.

3. The green synthesis method of Pt single atom catalyst according to claim 1, characterized in that: The grinding time is 2-30 min.

4. The green synthesis method of Pt single atom catalyst according to claim 1, characterized in that: The calcination temperature is 700-1000°C.

5. The green synthesis method of Pt single atom catalyst according to claim 1, characterized in that: The calcination time is 2-12 h.

6. The green synthesis method of Pt single atom catalyst according to claim 1, characterized in that: The calcination atmosphere is air and oxygen.

7. A Pt single-atom catalyst is prepared according to the green synthesis method of the Pt single-atom catalyst according to any one of claims 1 to 6.

8. Use of the Pt single atom catalyst according to claim 7 in methane dry reforming reaction.

9. The use of the Pt single atom catalyst in methane dry reforming reaction according to claim 8, characterized in that: The catalytic conditions of the methane dry reforming reaction are: the catalyst particle size is 40-60 mesh, the reaction gas composition CH4 and CO2 ratio is 1:1, and the mass space velocity of the test is 30000 mL·g cat -1 ·h -1 .

10. The use of the Pt single atom catalyst in methane dry reforming reaction according to claim 9, characterized in that: The catalytic reaction temperature is 600-800°C.

Images