A supported pt2 cluster catalyst, its preparation method and application

Abstract

The application relates to a supported Pt2 cluster catalyst, wherein Pt is uniformly supported on a MnO2 carrier in the form of Pt2 clusters, and the loading of Pt is 0.2-1%. The supported Pt2 cluster catalyst has the following advantages: the catalytic active center exists in the form of Pt2 clusters, the strong electron transfer from the Pt2 clusters to the MnO2 improves the activity of the surface lattice oxygen, promotes the generation of benzoic acid and the mineralization of toluene, the Pt atom accelerates the generation of superoxide free radicals, promotes the ring-opening and deep oxidation of toluene, and thus has excellent catalytic performance for removing benzene series volatile organic compounds in cooperation with low-temperature plasma, and can keep good catalytic activity for a long time.

Description

Technical Field

[0001] This invention belongs to the technical field of catalyst technology, specifically relating to a supported Pt2 cluster catalyst, its preparation method, and its application. Background Technology

[0002] Benzene-based volatile organic compounds (VOCs) are significant air pollutants, primarily including benzene derivatives such as toluene, ethylbenzene, o-xylene, styrene, and cumene. Current methods for removing benzene-based VOCs from the atmosphere include adsorption, membrane separation, catalysis, and low-temperature plasma methods. Among these, low-temperature plasma methods show promise for industrial applications due to their simplicity, low cost, and small footprint. However, they currently suffer from low energy efficiency and low catalytic activity. There are reports of combining catalysis and low-temperature plasma methods. The introduction of a catalyst can improve energy efficiency and increase the conversion rate of VOCs. For example, the literature (Applied catalysis B: environmental, 2014, 150:167-178) reports that introducing Cu into MnO2 to form a Cu-O-Mn interface improves the catalyst's reducibility, and Cu-doped MnO2 exhibits enhanced degradation activity for benzene-based VOCs.

[0003] CN113368897A discloses a highly active alumina-supported platinum catalyst, its preparation method, and its application. The preparation method includes: pretreating an alumina support with organic atmosphere dielectric barrier discharge plasma to obtain an alumina support grafted with organic groups; and loading platinum onto the organic alumina support by impregnation to obtain a highly active alumina-supported platinum catalyst. However, its catalytic ability for the degradation of benzene-based VOCs is insufficient.

[0004] CN115400762A discloses a catalyst for synergistic low-temperature plasma catalysis of xylene, its preparation method, and its application. The catalyst comprises manganese oxide, rare earth metal oxide, and a support, wherein the manganese oxide and rare earth metal oxide are both supported on the support. The active components of the catalyst are Mn, Co, La, and Ce, with an atomic molar ratio of Mn:Co:La:Ce = 1–2:1:1:1–2. The catalyst obtained by this patent exhibits good scavenging effect on xylene through synergistic low-temperature plasma treatment; however, its activity remains relatively low, requiring a high discharge voltage to achieve good degradation efficiency. Furthermore, the catalyst has poor stability and cannot maintain its catalytic function for an extended period. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies that combine catalysts and low-temperature plasma for the combined treatment of benzene-based volatile organic compounds, which lack sufficient catalytic activity and / or stability to meet the requirements of industrial-scale air pollution treatment, this invention proposes a supported Pt2 cluster catalyst, its preparation method, and its application. This invention involves the reaction of a platinum source with a ligand (tris(4-chlorophenyl)phosphine) to obtain Pt2(CO)4(C 18 H 12 Cl3P)3Br3 cluster, Pt2(CO)4(C 18 H 12 Cl3P)3Br3 clusters are supported on MnO2 and annealed to obtain a supported Pt2 catalyst. The supported Pt2 catalyst prepared by this invention, when used in conjunction with low-temperature plasma technology, exhibits high removal efficiency for benzene-based volatile organic compounds and a long catalyst lifetime, maintaining high catalytic activity for an extended period, thus showing promising industrial applications in the removal of benzene-based volatile organic compounds. Specifically, this invention achieves the above objectives through the following technical solutions:

[0006] A supported Pt2 cluster catalyst is provided, wherein Pt is uniformly supported on a MnO2 support in the form of Pt2 clusters, and the Pt loading is 0.2-1%; and the supported Pt2 cluster catalyst has at least one of the following physicochemical parameters:

[0007] (1) The XRD pattern has characteristic peaks of 22.4±0.1°, 37.5±0.1°, and 50.6±1°;

[0008] (2) The XPS spectrum of Pt has characteristic peaks of 72.6±0.2eV and 75.9±0.2eV.

[0009] Furthermore, the loading of Pt is 0.3-0.61%.

[0010] This invention also provides a method for preparing the above-mentioned supported Pt2 cluster catalyst, comprising the following steps:

[0011] (S1) An aqueous solution of platinum source was added to an organic solvent containing a quaternary ammonium salt phase transfer catalyst. After purging with carbon monoxide gas, the reaction was sealed. Tris(4-chlorophenyl)phosphine ligand was added, and the reaction continued. A reducing agent was then added for reduction to obtain Pt₂(CO)₄(C 18 H 12 Cl3P)3X3 clusters; X is Br or Cl;

[0012] (S2) Pt2(CO)4(C 18 H 12 Cl3P)3X3 clusters were dispersed in an alcohol solvent, added to a MnO2 suspension, stirred, and washed to obtain Pt2(CO)4(C 18 H12 The Cl3P)3X3 / MnO2 composite material was dried and sintered under an inert atmosphere to obtain a Pt2 / MnO2 catalyst, namely a supported Pt2 cluster catalyst.

[0013] Further, in step (S1), the platinum source is selected from at least one of chloroplatinic acid, platinum chloride, potassium chloroplatinate, potassium chloroplatinate, sodium chloroplatinate, sodium chloroplatinate, and ammonium chloroplatinate; the quaternary ammonium salt phase transfer catalyst is selected from at least one of tetraoctylammonium bromide, tri-n-butylammonium chloride, tri-n-butylammonium bromide, benzyltriethylammonium chloride, tetrabutylammonium hydrogen sulfate, and hexadecyltrimethylammonium bromide; the organic solvent is selected from at least one of dichloromethane, chloroform, acetone, and tetrahydrofuran; and the reducing agent is selected from at least one of sodium borohydride, ascorbic acid, and hydrazine hydrate.

[0014] Further, in step (S1), the concentration of Pt in the aqueous solution of the platinum source is 0.05-0.2 mol / L, for example 0.1 mol / L, the concentration of the quaternary ammonium salt phase transfer catalyst is 0.3-0.5 mol / L, and the amounts of the aqueous solution of the platinum source, the quaternary ammonium salt phase transfer catalyst solution, and the tris(4-chlorophenyl)phosphine ligand satisfy the molar ratio of Pt:phase transfer catalyst:ligand:reducing agent as 1:2-3:3-5:3-5.

[0015] Furthermore, in step (S1), the carbon monoxide aeration rate is 50-70 times the molar amount of Pt in the system, and the closed reaction time is 1-3 hours; the reaction time is 1-3 hours after the addition of the ligand, and 3-5 hours after the addition of the reducing agent.

[0016] Further, in step (S1), after obtaining the cluster solution, the post-processing steps are well known in the art. In one specific embodiment of the present invention, it involves first washing with water, and then washing with a mixture of petroleum ether and dichloromethane in a ratio of 3-5:1 to obtain pure Pt2(CO)4(C 18 H 12 Cl3P)3X3 clusters.

[0017] Further, in step (S2), the alcohol solvent is selected from at least one of methanol, ethanol, and isopropanol; the amount of alcohol solvent added is such that Pt2(CO)4(C 18 H 12 The concentration of Cl3P)3X3 clusters was 1-5 mg / mL. The concentration of MnO2 suspension was 1-20 mg / mL, and the amount added was such that Pt2(CO)4(C 18 H 12 The mass ratio of Cl3P)3X3 clusters to MnO2 is 1:50-100.

[0018] Further, in step (S2), the stirring time is 10-20 h, washing is done with deionized water, and drying is done under vacuum; the inert atmosphere is nitrogen and / or argon; the sintering temperature is 400-500℃, and the sintering time is 1-3 h. The purpose of sintering is to remove ligands. The sintering temperature is crucial and needs to be controlled at 400-500℃; otherwise, a Pt2 supported catalyst cannot be successfully obtained, but rather platinum particle nanoaggregates (Pt NPs) will form.

[0019] Furthermore, in step (S2), the surface area of ​​MnO2 is 40-60 m². 2 / g, pore volume 0.2-0.3cm 3 / g, with a pore size of 6-10nm, has a large specific surface area and many defect structures, which is beneficial for catalyst anchoring.

[0020] Further, in step (S2), MnO2 is prepared by a method including the following steps: potassium permanganate solution is added to a colloid mill, formamide solution is added to the colloid mill, and the mixture is stirred at 5000-10000 rpm for 3-5 minutes to allow nucleation, at which point the color of the system changes from purple to brown; the solution after nucleation reaction is allowed to stand to isolate crystals, and after natural aging, the supernatant is removed, the lower solution is centrifuged, the precipitate is washed with water and ethanol, dried, and ball-milled to obtain MnO2.

[0021] The inventors discovered that the supported Pt2 cluster catalyst prepared by the above method has Pt as the catalytic active center in the form of Pt2 clusters. The strong electron transfer from the Pt2 clusters to MnO2 enhances the activity of surface lattice oxygen, promoting the formation of benzoic acid and the mineralization of toluene. Pt atoms accelerate the generation of superoxide radicals, promoting ring-opening and deep oxidation of toluene. Therefore, it exhibits excellent catalytic performance in synergistic removal of benzene-based volatile organic compounds with low-temperature plasma, and can maintain good catalytic activity for a long period.

[0022] The present invention also provides a Pt2(CO)4(C) 18 H 12 Application of Cl3P)3X3 cluster in preparing supported Pt2 cluster catalysts; further, the catalyst is used in conjunction with low-temperature plasma for the removal of benzene-based volatile organic compounds.

[0023] The present invention also provides a method for removing benzene-based volatile organic compounds by catalyst-assisted low-temperature plasma, comprising the following steps: filling the above-mentioned supported Pt2 cluster catalyst into a dielectric barrier discharge plasma reactor, and introducing a gas containing benzene-based volatile organic compounds under high-voltage power supply conditions.

[0024] Furthermore, the ratio of the amount of supported Pt2 cluster catalyst to the reactor volume is 100-300 mg: 1 L; the high-voltage power supply conditions are 5-20 kV; the content of benzene-based volatile organic compounds in the gas is 100-10000 ppm, and oxygen accounts for 15-30%; preferably, air is used as the carrier gas; the gas flow rate is 0.5-2 L / min. Attached Figure Description

[0025] Figure 1 This is a SEM image of the MnO2 obtained in Preparation Example 1.

[0026] Figure 2 This is the XRD pattern of MnO2 obtained in Preparation Example 1.

[0027] Figure 3 The N2 adsorption-desorption isotherm of MnO2 obtained in Preparation Example 1 is shown.

[0028] Figure 4 Pt2(CO)4(C) was prepared in step (S1) of Example 1. 18 H 12 Cl3 P UV-vis image of 3Br3 cluster.

[0029] Figure 5 Pt2(CO)4(C) was prepared in step (S1) of Example 1. 18 H 12 Cl3 P ESI-MS image of 3Br3 cluster.

[0030] Figure 6 Pt2(CO)4(C) was prepared in step (S1) of Example 1. 18 H 12 Infrared spectrum of Cl3P)3Br3 cluster.

[0031] Figure 7 This is a SEM image of the Pt2 / MnO2 catalyst prepared in Example 1.

[0032] Figure 8 This is the XRD pattern of the Pt2 / MnO2 catalyst prepared in Example 1.

[0033] Figure 9 This is the XPS diagram of Pt elemental composition of the Pt2 / MnO2 catalyst prepared in Example 1.

[0034] Figure 10 This is a SEM image of the catalyst prepared in Comparative Example 1. Detailed Implementation

[0035] Preparation Example 1

[0036] (1) Dissolve 200g of potassium permanganate in 3L of water and label the solution as solution A; label 500mL of formamide solution as solution B.

[0037] (2) Nucleation reaction: Add liquid A to the colloid mill, then quickly add liquid B to the colloid mill, and stir continuously at 6000 rpm for 4 minutes to enable rapid nucleation. The color of the system changes from purple to brown.

[0038] (3) Crystallization and isolation: Take out the solution after the reaction and let it stand for 8 hours to allow it to be isolated and crystallized.

[0039] (4) Centrifugation and washing: After natural sedimentation, remove the supernatant, transfer the lower solution to a centrifuge for centrifugation, and wash with water and ethanol in sequence to obtain the wet product.

[0040] (5) Drying: The wet product is placed in an oven and dried at 30°C to obtain the product, which is then ground into powder using a ball mill to obtain MnO2.

[0041] Figure 1 This is a SEM image of the MnO2 obtained in Preparation Example 1. Figure 2 This is the XRD pattern of MnO2 obtained in Preparation Example 1. Its two strong characteristic peaks (26.62°, 36.86°) indicate that the main component is tetragonal MnO2. Figure 3 The table shows the N2 adsorption-desorption isotherm of MnO2 obtained in Preparation Example 1. It can be seen that the isotherm is close to a type IV adsorption isotherm and contains an H3 type hysteresis loop, indicating the presence of an irregular pore structure. The table shows that its specific surface area, pore volume, and pore size are relatively large. The effective surface area and suitable pore structure are beneficial for catalyst anchoring, providing abundant active sites and facilitating the catalytic oxidation of toluene. Calculations show that the specific surface area of ​​MnO2 obtained in Preparation Example 1 is 49.7 m². 2 / g, pore volume 0.24cm 3 / g, pore size 8.58nm.

[0042] Example 1

[0043] (S1) In an ice-water bath environment, 1 mL of a 1 mol / L aqueous solution of chloroplatinic acid hexahydrate was added to dichloromethane containing 1 mL of a 3 mol / L solution of tetraoctylammonium bromide (TOAB). Carbon monoxide gas was then introduced at a flow rate of 0.1 L / min for 1.5 min. The solution was stirred and bubbled for 1-5 minutes, then sealed for 1 hour. Next, 3 mmol of the ligand (tris(4-chlorophenyl)phosphine) was added and the reaction was continued for 1 hour. Finally, 0.5 mmol of the reducing agent sodium borohydride (NaBH4) was added and the reaction was continued for 3 hours to obtain a reduction product solution. The reduction product was Pt₂(CO)₄(C 18 H 12 Cl3P)3Br3 cluster.

[0044] (S2) Take 10 mg of Pt2(CO)4(C 18 H 12 The Cl3P)3Br3 cluster was dispersed in 10 mL of methanol and added dropwise to a suspension containing 100 mL of 10 mg / mL MnO2 (MnO2 mass 1 g). The mixture was stirred at room temperature for 12 h, centrifuged and washed, and Pt2(CO)4(C)3Br3 was collected. 18 H 12 The Cl3P)3Br3 composite material was vacuum dried overnight and then annealed at 400℃ for 2 h under an argon atmosphere to obtain a Pt2 / MnO2 catalyst. ICP analysis showed that the Pt loading was 0.31 wt%.

[0045] Figure 4 Pt2(CO)4(C) was prepared in step (S1) of Example 1. 18 H 12 UV-vis image of Cl3P)3Br3 cluster Figure 5 Pt2(CO)4(C) was prepared in step (S1) of Example 1. 18 H 12 ESI-MS image of Cl3P)3Br3 cluster. Figure 6 Pt2(CO)4(C) was prepared in step (S1) of Example 1. 18 H 12 The infrared spectrum of the Cl3P)3Br3 cluster shows that the OH peak is attributed to water, and the Pt2 cluster contains CP, C-Cl, CO, CH, and C=C. This indicates that the target product Pt2(CO)4(C) was successfully prepared. 18 H 12 Cl3P)3Br3 cluster.

[0046] Example 2

[0047] Other conditions are the same as in Example 1, the difference being that in step (S2) 10 mg Pt2(CO)4(C 18 H 12 The amount of Cl3P)3Br3 cluster was changed to 15mg, and the Pt content in the Pt2 / MnO2 catalyst obtained in Example 2 was 0.46% according to ICP test.

[0048] Example 3

[0049] Other conditions are the same as in Example 1, the difference being that in step (S2) 10 mg Pt2(CO)4(C 18 H 12 The amount of Cl3P)3Br3 cluster was changed to 20mg, and the Pt content in the Pt2 / MnO2 catalyst obtained in Example 3 was 0.61% according to ICP test.

[0050] Example 4

[0051] Other conditions are the same as in Example 1, the difference being that in step (S2) 10 mg Pt2(CO)4(C 18 H 12 The amount of Cl3P)3Br3 cluster was changed to 30mg, and the Pt content in the Pt2 / MnO2 catalyst obtained in Example 3 was 0.91% according to ICP test.

[0052] Comparative Example 1

[0053] Other conditions were the same as in Example 1, except that the annealing temperature in step (S2) was 700°C. A Pt NPs / MnO2 catalyst was obtained.

[0054] Figure 7 This is a SEM image of the Pt2 / MnO2 catalyst prepared in Example 1. A and B are SEM images at different magnifications. From B, it can be clearly seen that Pt is supported on MnO2 in the form of Pt2 clusters. Figure 8 The image shows an SEM image of the catalyst prepared in Comparative Example 1. As can be seen, unlike Example 1, when the annealing temperature is increased to 700°C, Pt is loaded onto MnO2 in the form of nano-aggregates. Figure 9 The image shows the XRD pattern of the Pt2 / MnO2 catalyst prepared in Example 1. The absence of characteristic diffraction peaks of Pt nanoparticles indicates that the prepared Pt2 clusters are small in size and have not agglomerated. Figure 10 The image shows the XPS plot of Pt in the Pt2 / MnO2 catalyst prepared in Example 1. The valence state of the prepared Pt2 clusters is close to +2, indicating that Pt has been reduced.

[0055] Application examples

[0056] The catalysts from the above examples and comparative examples were used in conjunction with low-temperature plasma to remove benzene-based volatile organic compounds (VOCs). Specifically, 300 mg of the catalysts prepared in the examples / comparative examples were packed into a quartz low-temperature plasma generator with a length of 300 mm and an inner diameter of 30 mm. Air was used as the carrier gas, the concentration of the VOCs to be removed was 1000 ppm, the gas flow rate was set to 1 L / min, the reaction temperature was room temperature, the discharge frequency was 500 Hz, and the discharge voltage was 10 kV. Air containing VOCs was passed through the low-temperature plasma generator, and the VOCs in the outlet gas were detected by gas chromatograph. The degradation rate was calculated, and the degradation rate after 48 hours of continuous operation is shown in Table 1 below.

[0057] Table 1

[0058]

[0059]

Claims

1. A supported Pt2 cluster catalyst characterized in that, Pt is uniformly supported on a MnO2 support in the form of Pt2 clusters, with a Pt loading of 0.2-1%; and the supported Pt2 cluster catalyst has at least one of the following physicochemical parameters: (1) The XRD pattern has characteristic peaks of 22.4±0.1°, 37.5±0.1°, and 50.6±1°; (2) The XPS spectrum of Pt has characteristic peaks of 72.6±0.2eV and 75.9±0.2eV; The preparation method of the supported Pt2 cluster catalyst includes the following steps: (S1) An aqueous solution of platinum source was added to an organic solvent containing a quaternary ammonium salt phase transfer catalyst. After purging with carbon monoxide gas, the reaction was sealed. Tris(4-chlorophenyl)phosphine ligand was added, and the reaction continued. A reducing agent was then added for reduction to obtain Pt₂(CO)₄(C 18 H 12 Cl3P)3X3 clusters; X is Br or Cl; (S2) Pt2(CO)4(C 18 H 12 Cl3P)3X3 clusters were dispersed in an alcohol solvent, added to a MnO2 suspension, stirred, and washed to obtain Pt2(CO)4(C 18 H 12 The Cl3P)3X3 / MnO2 composite material was dried and sintered under an inert atmosphere to obtain a Pt2 / MnO2 catalyst, namely a supported Pt2 cluster catalyst.

2. The supported Pt2 cluster catalyst of claim 1, wherein, The load on Pt is 0.3-0.61%.

3. The supported Pt2 cluster catalyst of claim 1, wherein, In step (S1), the platinum source is selected from at least one of chloroplatinic acid, platinum chloride, potassium chloroplatinate, potassium chloroplatinate, sodium chloroplatinate, sodium chloroplatinate, and ammonium chloroplatinate; the quaternary ammonium salt phase transfer catalyst is selected from at least one of tetraoctylammonium bromide, tri-n-butylammonium chloride, tri-n-butylammonium bromide, benzyltriethylammonium chloride, tetrabutylammonium hydrogen sulfate, and hexadecyltrimethylammonium bromide; the organic solvent is selected from at least one of dichloromethane, chloroform, acetone, and tetrahydrofuran; and the reducing agent is selected from at least one of sodium borohydride, ascorbic acid, and hydrazine hydrate.

4. The supported Pt2 cluster catalyst according to claim 1, characterized in that, In step (S1), the Pt concentration in the aqueous solution of the platinum source is 0.05-0.2 mol / L, the concentration of the quaternary ammonium salt phase transfer catalyst is 0.3-0.5 mol / L, and the amounts of the aqueous solution of the platinum source, the quaternary ammonium salt phase transfer catalyst solution, and the tris(4-chlorophenyl)phosphine ligand satisfy the following ratio: Pt: phase transfer catalyst: The molar ratio of ligand to reducing agent is 1:2-3:3-5:3-5.

5. The supported Pt2 cluster catalyst of claim 4, wherein, The concentration of Pt in the aqueous solution of the platinum source is 0.1 mol / L.

6. The supported Pt2 cluster catalyst of claim 1, wherein, In step (S1), the carbon monoxide aeration rate is 50-70 times the molar amount of Pt in the system, and the closed reaction time is 1-3 hours; the reaction time is 1-3 hours after the addition of the ligand, and 3-5 hours after the addition of the reducing agent.

7. The supported Pt2 cluster catalyst according to claim 1, characterized in that, In step (S1), after obtaining the cluster solution, the post-processing steps are to first wash with water, and then wash with a mixture of petroleum ether and dichloromethane in a ratio of 3-5:1 to obtain pure Pt2(CO)4(C 18 H 12 Cl3P)3X3 clusters.

8. The supported Pt2 cluster catalyst of claim 1, wherein, In step (S2), the alcohol solvent is selected from at least one of methanol, ethanol, and isopropanol; the amount of alcohol solvent added is such that Pt2(CO)4(C 18 H 12 The concentration of Cl3P)3X3 clusters was 1-5 mg / mL; the concentration of MnO2 suspension was 1-20 mg / mL, and the amount added was such that Pt2(CO)4(C 18 H 12 The mass ratio of Cl3P)3X3 clusters to MnO2 is 1:50-100.

9. The supported Pt2 cluster catalyst of claim 1, wherein, In step (S2), the stirring time is 10-20 h, the washing is done with deionized water, and the drying is done under vacuum; the inert atmosphere is nitrogen and / or argon; the sintering temperature is 400-500℃, and the sintering time is 1-3 h. The surface area of ​​MnO2 is 40-60m² 2 / g, pore volume 0.2-0.3 cm³ 3 / g, pore size 6-10nm.

10. A method for removing benzene-based volatile organic compounds using catalyst-assisted low-temperature plasma, comprising the following steps: A dielectric barrier discharge plasma reactor is filled with the supported Pt2 cluster catalyst as described in any one of claims 1-9, and a gas containing benzene-based volatile organic compounds is introduced under high-voltage power supply conditions.

11. The method of claim 10, wherein, The ratio of supported Pt2 cluster catalyst dosage to reactor volume is 100-300 mg: 1 L; the high-voltage power supply conditions are 5-20 kV; the content of benzene series volatile organic compounds in the gas is 100-10000 ppm, and oxygen accounts for 15-30%.

12. The method of claim 11, wherein, Air is used as the carrier gas; gas flow rate is 0.5-2 L / min.

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