Platinum monatomic catalyst and use in catalyzing propane combustion

Abstract

The present application relates to a kind of platinum monatomic catalyst and its preparation method and application.The catalyst is with WO3 and TiO2 composite material as carrier, and platinum is loaded by impregnation method.The preparation method includes the synthesis of WO3-TiO2 carrier and the loading of metal platinum monatomic atom.The obtained platinum / WO3-TiO2 catalyst in the present application can realize the low-temperature combustion of propane under the condition of photo-thermal synergy.The platinum exists in the form of monatomic atom, greatly reduces the amount of noble metal, reduces the cost of catalyst preparation, and has excellent reaction activity and stability.The preparation method of catalyst in the present application is simple, low in cost, easy to realize large-scale industrial production, and applied to the treatment of automobile exhaust.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a method for preparing a platinum single-atom catalyst and its application in the photothermal synergistic catalytic propane combustion reaction. The preparation method involves the composite of WO3 and TiO2 supports and the loading of platinum single atoms. Compared with previously reported methods for preparing platinum single-atom catalysts, the catalyst in this invention exhibits superior activity and good stability, and the preparation method is simple and mild. Background Technology

[0002] With the rapid development of human society, fossil fuels are burned in large quantities to meet energy demands, resulting in the emission of large amounts of volatile organic compounds (VOCs). As the most difficult VOCs to oxidize, low-carbon alkanes are widely present in petrochemical industry exhaust and vehicle emissions, and can lead to the formation of secondary pollutants, such as tropospheric ozone, peroxyacetyl nitrate (a major harmful substance in photochemical smog that irritates the eyes, a plant toxin, and a potential mutagen causing skin cancer), and secondary organic aerosols, the toxicity and carcinogenicity of which have been well-proven. Moreover, with the gradual increase in low-carbon alkanes emissions, the greenhouse effect they cause cannot be ignored. Propane is a typical VOC; therefore, using it as a model reactant to develop highly active and stable catalytic combustion catalysts has significant theoretical and practical value.

[0003] Single-atom catalysts, where the active metal component is dispersed and anchored on a support in the form of individual atoms, maximize atom utilization and can reduce production costs when applied to industrial production. Furthermore, single-atom catalysts maximize the metal-support interface, exhibiting superior catalytic performance in reactions where the metal and support interface are synergistically catalyzed. Moreover, when the metal exists in the form of individual atoms, the degree of unsaturated coordination on the metal surface increases, typically leading to a significant increase in catalyst activity. Traditional catalytic oxidation catalysts often use nanoparticles as active centers, which greatly increases the amount of precious metals required. However, these precious metals are very limited in reserves on Earth and are expensive, hindering industrial production. Additionally, photocatalysis can enable chemical reactions at room temperature or even lower temperatures, but is limited by low reaction rates. Therefore, developing a single-atom catalyst with both photocatalytic and thermal catalytic properties is of great significance, potentially enabling the low-temperature catalytic combustion of propane. On one hand, light can effectively modulate the electronic structure of the catalyst surface; on the other hand, single-atom dispersed platinum can more effectively activate reactants. This patent describes a method for preparing a platinum single-atom catalyst, which uses a photosensitive semiconductor TiO2 and WO3 composite material as a carrier and platinum single atoms as active centers, enabling efficient combustion of propane under photothermal conditions. Summary of the Invention

[0004] This invention provides a method for preparing a platinum single-atom catalyst and its low-temperature photothermal catalytic application. This catalyst enables efficient propane combustion at lower temperatures under synergistic photothermal conditions, solving the problems of poor propane catalytic combustion performance and excessive use of precious metals in existing catalysts at low temperatures.

[0005] In the low-temperature, high-activity platinum single-atom catalyst of the present invention, the content of the noble metal platinum is 0.01 to 0.05 wt%, and the molar ratio of TiO2 to WO3 is 1:5 to 5:1.

[0006] The preparation method of the platinum single-atom catalyst in this invention is specifically implemented according to the following steps:

[0007] I. Preparation of the support: Under stirring conditions of 400–800 rpm, the required mass of TiO2 powder was added to the aqueous solution of the W precursor to ensure thorough dispersion. The suspension was heated to 60–120°C and stirred continuously until the liquid evaporated to dryness. The solution was then dried in an oven at 60–120°C for 8–20 hours. The dried solid was ground and calcined at 500–800°C for 3–6 hours to obtain the WO3-TiO2 composite support.

[0008] II. Platinum loading: at concentrations of 0.1–1 mg Pt The desired proportion of WO3-TiO2 composite support is added to a platinum precursor solution of 1 mL / mL water. The mixture is stirred continuously at 20–60 °C until the liquid evaporates to dryness, and then dried in an oven at 60–120 °C for 8–20 h. The solid is then ground and calcined at 300–600 °C for 2–5 h. The resulting highly photothermal active platinum single-atom catalyst is thus prepared.

[0009] The catalyst has a simple preparation process, mild conditions, is suitable for large-scale production, and exhibits excellent low-temperature propane combustion performance under photothermal conditions.

[0010] The platinum / WO3-TiO2 catalyst obtained in this invention can achieve low-temperature combustion of propane under photothermal synergy. Platinum exists in single-atom form, significantly reducing the amount of precious metal used and lowering the cost of catalyst preparation, while exhibiting excellent reactivity and stability. The catalyst preparation method of this invention is simple, low-cost, and easily achievable for large-scale industrial production, and can be applied to the treatment of automotive exhaust gases. Attached Figure Description

[0011] Figure 1 Aberration-corrected scanning transmission electron microscopy image of 0.05% Pt / WO3-TiO2 catalyst;

[0012] Figure 2 Energy dispersive spectrum of 0.05% Pt / WO3-TiO2 catalyst;

[0013] Figure 3 Scanning transmission electron microscopy image of 0.05% Pt / TiO2 catalyst;

[0014] Figure 4 Graphs showing the conversion rate of platinum / WO3-TiO2 catalysts with different W-Ti ratios as a function of temperature in propane combustion;

[0015] Figure 5 A comparison of reaction rates between a single-atom catalyst with a Pt loading of 0.05 wt% and a nanoparticle catalyst with a Pt loading of 0.5 wt%.

[0016] Figure 6 0.05% Pt / WO under different light intensities 3- The curve of TiO2 catalyst conversion rate as a function of temperature in propane combustion;

[0017] Figure 7 . Curves showing the conversion rate of 0.05% Pt / WO3-Al2O3 catalyst in propane combustion as a function of temperature under different light intensities; Detailed Implementation

[0018] The technical solution of the present invention is not limited to the following specific embodiments.

[0019] Comparative Example 1

[0020] Platinum / WO3-Al2O3 catalyst

[0021] Preparation of platinum / WO3-Al2O3 catalyst by excess impregnation method: Ammonium metatungstate in the required proportion was dissolved in 50 mL of deionized water, 5 g of nano-Al2O3 was added and vigorously stirred to ensure thorough dispersion. The suspension was heated to 80 °C at 300 rpm and continuously heated until the solvent was completely evaporated. The resulting solid was transferred to an 80 °C oven and dried for 12 h. The dried solid was then ground and calcined in a muffle furnace at 550 °C for 4 h to obtain the WO3-Al2O3 composite support.

[0022] At a concentration of 0.1 mg in 2 mL Pt 1 g of the above composite support powder was added to a chloroplatinic acid solution of 1 mL water and dispersed thoroughly at 300 rpm. The dispersion was heated to 40 °C and continuously heated until all the liquid was evaporated, then transferred to a 60 °C oven to dry for 12 h. The resulting solid was ground and calcined in air at 400 °C for 2 h to obtain a platinum / WO3-Al2O3 catalyst with a theoretical platinum content of 0.05% (denoted as 0.05Pt / WO3-Al2O3 (Al-W molar ratio of 1:1)).

[0023] Comparative Example 2

[0024] Platinum / TiO2 catalyst

[0025] Preparation of platinum / TiO2 catalyst by excess impregnation method: In 2 mL of 0.1 mg platinum / TiO2 catalyst... Pt 1 g of commercial anatase powder was added to a chloroplatinic acid solution of 1 mL and dispersed thoroughly under stirring at 300 rpm. The mixture was heated to 40 °C and continuously heated until all liquid was evaporated, then dried in a 60 °C oven for 12 h. After grinding, it was calcined in air at 400 °C for 2 h to obtain a platinum / anatase catalyst with a theoretical platinum content of 0.05% (denoted as 0.05% Pt / TiO2).

[0026] Comparative Example 3

[0027] Platinum / WO3 catalyst

[0028] Preparation of platinum / WO3 catalyst by excess impregnation method: A certain amount of ammonium metatungstate was dissolved in 50 mL of deionized water. The suspension was heated to 80 °C at 300 rpm and heated continuously until the solvent was completely evaporated. The resulting solid was transferred to an 80 °C oven and dried for 12 h. The dried solid was ground and then calcined in a muffle furnace at 550 °C for 4 h to obtain the WO3 support.

[0029] At a concentration of 0.1 mg in 2 mL Pt 1 g of the above WO3 support powder was added to a chloroplatinic acid solution of 1 mL water and dispersed thoroughly at 300 rpm. The dispersion was heated to 40 °C and continuously heated until all the liquid was evaporated, then transferred to a 60 °C oven to dry for 12 h. The resulting solid was ground and calcined in air at 400 °C for 2 h to obtain a platinum / WO3 catalyst with a theoretical platinum content of 0.05% (denoted as 0.05% Pt / WO3).

[0030] Comparative Example 4

[0031] Platinum / WO3-TiO2 nanoparticle catalyst

[0032] Ammonium metatungstate in the required proportion was dissolved in 50 mL of deionized water. 5 g of commercial anatase powder was added and vigorously stirred to ensure thorough dispersion. The suspension was heated to 80 °C at 300 rpm and continued heating until the solvent was completely evaporated. The resulting solid was transferred to an 80 °C oven and dried for 12 h. The dried solid was then ground and calcined in a muffle furnace at 550 °C for 4 h to obtain the WO3-TiO2 composite support.

[0033] 1 g of the above composite support powder was added to 1 mL of chloroplatinic acid solution with a concentration of 5 mg Pt / mL water and dispersed thoroughly at 300 rpm. The dispersion was heated to 40 °C and continuously heated until all the liquid was evaporated, then transferred to a 60 °C oven to dry for 12 h. The resulting solid was ground and calcined in air at 400 °C for 2 h to obtain a platinum / WO3-TiO2 nanoparticle catalyst with a theoretical platinum content of 0.5% (denoted as 0.5% Pt / WO3-TiO2 (Ti-W molar ratio of 1:1)).

[0034] Example 1

[0035] Investigating the effect of the W-Ti molar ratio in the support on the catalytic performance of the platinum / WO3-TiO2 catalyst.

[0036] Carrier preparation: Ammonium metatungstate in the required proportion was dissolved in 10 mL of deionized water. 1 g of anatase powder was added while stirring at 300 rpm to ensure thorough dispersion. The suspension was heated to 80 °C and stirred continuously until the liquid evaporated to dryness. The solution was then dried in a 60 °C oven for 12 h. The dried solid was ground and calcined at 550 °C for 4 h to obtain WO3-TiO2 composite carriers with W-Ti molar ratios of 1:2, 1:1, and 2:1.

[0037] Platinum loading by impregnation: in 2 mL of solution at a concentration of 0.1 mg... Pt 1 g of WO3-TiO2 composite support with Ti-W molar ratios of 1:2, 1:1, and 2:1 was added to a chloroplatinic acid solution of 1 mL. The mixture was stirred continuously at 40 °C until the liquid evaporated to dryness, and then dried in an oven at 60 °C for 12 h. The solid was then ground and calcined at 400 °C for 2 h. After grinding, a platinum / WO3-TiO2 catalyst with a platinum mass loading of 0.05% was prepared. The prepared catalysts were designated as 0.05% Pt / WO3-TiO2 (1:2), 0.05% Pt / WO3-TiO2 (1:1), and 0.05% Pt / WO3-TiO2 (2:1), respectively.

[0038] The scanning transmission electron microscopy image of the 0.05% Pt / WO3-TiO2 (1:1) catalyst prepared in this embodiment is shown below. Figure 1 As shown in the figure, platinum is dispersed as single atoms.

[0039] The energy dispersive spectrum of the 0.05% Pt / WO3-TiO2 (1:1) catalyst prepared in this embodiment is shown in the figure below. Figure 2 As shown in the figure, the platinum, Ti, and W elements are uniformly distributed, indicating that the WO3-TiO2 support is uniformly composited and that platinum is uniformly dispersed on its surface. The composition of other catalysts is the same as that of the 0.05% Pt / WO3-TiO2 (1:1) catalyst.

[0040] In this embodiment, propane oxidation was used as the probe reaction in the catalyst activity test. Test conditions: A fixed-bed reactor with a light-transmitting window (1.5cm × 3cm) was used; 100mg of catalyst was evenly distributed in the reactor; feed gas composition (volume ratio): 1% C3H8, 20% O2, 79% He; gas flow rate: 50mL / min; the catalyst was irradiated through the light-transmitting window using a xenon lamp with an energy density of 500mW / cm³. 2 Samples were purged with He for 30 min before testing to remove impurities adsorbed on the catalyst surface. Catalytic products were analyzed online using a gas chromatograph (Panuo A91 Plus) equipped with a Poropak Q packed column. Figure 4 Platinum / WO at different W-Ti molar ratios 3- The curves showing the reaction rate of TiO2 and the catalysts obtained in Comparative Examples 2 and 3 in propane combustion as a function of temperature are shown in the figure. It can be seen from the figure that as the proportion of WO3 in the catalyst increases, the reaction rate of propane is significantly improved, indicating that a certain proportion of WO3 under light conditions is beneficial to the activation of platinum, thereby improving the propane combustion performance of the catalyst; however, when the support is only WO3, the catalytic activity decreases significantly, indicating that TiO2 is an essential support component under light irradiation.

[0041] Example 2

[0042] The influence of support type on the particle size and catalytic activity of platinum catalysts was studied.

[0043] The catalysts used in this example are those in Comparative Example 1, Comparative Example 2, Comparative Example 3, Example 1, and Comparative Example 4. The catalytic activity testing method is the same as that in Example 1, and the relevant parameters are summarized in Table 1.

[0044] Table 1. Forms of platinum in catalysts with different support types at the same loading and T 50

[0045]

[0046]

[0047] Comparing the particle size of platinum in platinum catalysts with different support types, platinum can only achieve single-atom dispersion when WO3 and TiO2 are present simultaneously. Furthermore, the catalytic performance of single-atom platinum catalysts is superior to that of nanoparticles. Under the same loading conditions, the To of the platinum / WO3-TiO2 catalyst is higher. 50 T compared to platinum / WO3 catalysts 50 At a low temperature of 320℃, with the same support, increasing the platinum loading to form nanoparticles is beneficial for improving the performance of propane oxidation in the low-temperature range, but T... 50There was no significant decrease. In contrast, the reaction rate was higher with platinum single-atom catalysts with lower loadings, such as... Figure 5 As shown.

[0048] Example 3

[0049] Investigating the effect of light intensity on the catalytic performance of platinum / TiO2-WO3 catalysts

[0050] The catalyst used in this example is the same as the 0.05% Pt / WO3-TiO2 (1:1) used in Comparative Example 1 and Example 1, and the catalyst activity testing method is the same as in Example 1. The difference is that the light intensity (0 mW / cm²) was adjusted. 2 500mW / cm 2 and 1000mW / cm 2 ) and the temperature at which 10% of propane is converted to CO2 (T) 10 To compare activity. Figure 6 and Figure 7 The conversion rates of 0.05% Pt / WO3-TiO2 and 0.05% Pt / WO3-Al2O3 catalysts in propane combustion under different light intensities are shown in Table 2. The relevant parameters are summarized in Table 2.

[0051] Table 2. Effects of different light intensities on the Ti of platinum / WO3-TiO2 and platinum / WO3-Al2O3 catalysts. 10 Impact

[0052]

[0053] As can be seen from Table 2, with the increase of light intensity, the corresponding T of the 0.05% Pt / WO3-TiO2 catalyst... 10 Significantly reduced. When the optical power density is 1000 mW / cm². 2 At that time, T 10 The value is 155°C lower than in the absence of light; when the light power density is 500 mW / cm² 2 At that time, T 10 The value is 105°C lower than that in the absence of light. Meanwhile, the power density of the 0.05% Pt / WO3-Al2O3 catalyst is 500 mW / cm³. 2 After the light T 10 The value changes very little, only from 220℃ to 182℃. These results indicate that the WO3-TiO2 support, as a light-absorbing semiconductor, can transfer electrons to the platinum surface under photoexcitation, thereby activating the active centers and effectively reducing the combustion temperature of propane. In contrast, the Al2O3 support does not possess light-absorbing properties, and the efficiency of photoactivation of platinum in the 0.05% Pt / WO3-Al2O3 catalyst decreases significantly, indicating that this catalyst is insensitive to changes in light intensity.

[0054] As can be seen from the above embodiments, the preparation of the TiO2-WO3 composite support can effectively enhance light absorption, thereby transferring photogenerated electrons to the active platinum center of the catalyst under photothermal conditions, further activating it, and thus improving its performance in catalytic combustion of propane. The results show that the performance of this catalyst under photothermal conditions is significantly better than that of traditional photo or thermal catalysts, and the preparation method is simple and mild, providing a new approach for the development of low-temperature catalytic combustion catalysts for propane.

Claims

1. A platinum single-atom catalyst, characterized in that: The structure is a Pt1 / WO3-TiO2 composite material with WO3 and TiO2 as the support, and the mass fraction of platinum is 0.01%~0.05%; the molar ratio of W to Ti in the composite support is 1:1; The platinum single-atom catalyst was prepared by the following method: Step 1: Dissolve the precursor of W in water and add TiO2 powder while stirring; Step 2: Heat the dispersion from Step 1 in a water bath at 60-120°C and stir until the solvent is completely evaporated. Dry the remaining solid in an oven at 60-120°C. Step 3: Grind the solid obtained after drying in Step 2 into powder, transfer it to a muffle furnace, and calcine it at 500~800℃ for 3~6 hours to obtain the composite carrier; Step 4: Add the composite support from Step 3 to the platinum precursor solution, and heat in a water bath at 30~90℃ with stirring until the solvent is completely evaporated. Dry the remaining solid in an oven at 60~120℃. Step 5: Grind the solid obtained in step 4 and transfer it to a muffle furnace, calcining it at 300~600℃ for 2~5 hours to obtain the platinum single-atom catalyst.

2. The platinum single-atom catalyst according to claim 1, characterized in that: Platinum single atoms are dispersed on the support, and the platinum single atoms serve as the active sites of the catalyst. TiO2 can effectively enhance the photoreactivity of the catalyst, while WO3 can improve the dispersion of platinum and stabilize the active components. The synergistic effect of the two can enable this single-atom catalyst to have excellent propane combustion performance.

3. The platinum single-atom catalyst according to claim 1, characterized in that: The precursor of W is one or more of ammonium metatungstate, ammonium paratungstate, or sodium tungstate. TiO2 is one or more of anatase, rutile, or P25.

4. The platinum single-atom catalyst according to claim 1, characterized in that: The platinum precursor is one or more of chloroplatinic acid, tetraammineplatinum chloride, or potassium chloroplatinate, and the concentration of the solution is 0.1~1 mg. Pt / mL water.

5. The application of a platinum single-atom catalyst according to any one of claims 1-4, characterized in that: The platinum single-atom catalyst is used in the photothermal synergistic catalytic combustion reaction of propane.

6. The application of the platinum single-atom catalyst according to claim 5, characterized in that: The required light power density for the reaction is 200~2000 mW / cm². 2 .

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