Vanadium oxide-based supported platinum catalyst as well as preparation method and application thereof

Abstract

The invention discloses a vanadium oxide-based supported platinum catalyst and a preparation method and application thereof, and the preparation method comprises the following steps: a) carrying out high-temperature heat treatment on a V precursor to obtain orange V2O5 carrier powder; b) adding V2O5 powder, a Pt metal precursor and a sacrificial reagent into the solution, carrying out ultrasonic treatment, stirring, and reacting under the irradiation of a xenon lamp to obtain a dark brown suspension; c) centrifuging, washing, drying, grinding and roasting the dark brown suspension to obtain dark brown powder; and d) carrying out three times of high-temperature heat treatment on the dark brown powder under different protective gases, and sequentially carrying out three processes of oxidation, reduction and partial oxidation to obtain the vanadium oxide-based platinum-loaded catalyst. The catalyst prepared according to the invention is applied to a carbon monoxide oxidation reaction, and has the advantages of excellent catalytic performance, long-time stability and good recycling stability at a high space velocity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of catalysts, in particular to a vanadium oxide supported platinum catalyst and a preparation method and application thereof. BACKGROUND

[0002] Carbon monoxide (CO) is one of the important sources of pollution in today's environment, mainly due to incomplete combustion of fossil fuels and direct emission into the atmosphere. Effective removal of CO pollution in the atmosphere is an important direction of environmental governance. Removing CO in the atmosphere by catalytic oxidation is considered an effective method. Rare earth cerium oxide supported platinum catalysts have been widely concerned due to their excellent catalytic activity in promoting CO oxidation reactions. However, rare earth and platinum resources are limited and expensive, and under this background, how to improve the utilization of Pt and design and synthesize high-activity and high-stability supported Pt catalysts for complete oxidation of CO has always been a research hotspot.

[0003] Compared with ceria support materials, 3D transition metals such as iron, cobalt and nickel, which are relatively low in price, have been widely studied as support materials, while reports on vanadium are still very rare. Vanadium, as a 3D transition metal element with variable oxidation state and coordination number, has shown great potential in photocatalytic synthesis. In addition, during high-temperature or long-term CO oxidation, platinum species supported on the carrier tend to agglomerate, leading to a sharp decline in CO oxidation activity. Therefore, improving the utilization of noble metal Pt, exploring other carriers and preparation methods to establish strong metal and carrier interactions to improve the performance and stability of catalytic CO oxidation reactions is still a research direction.

[0004] In view of this, the present application is proposed. SUMMARY

[0005] The present application aims to provide a vanadium oxide supported platinum catalyst and a preparation method and application thereof, thereby solving the problem that the application of noble metal platinum catalysts is limited due to the limited and expensive rare earth and platinum resources in the prior art.

[0006] In order to solve the above problems, the present application adopts the following technical solutions:

[0007] According to a first aspect of the present application, there is provided a method for preparing a vanadium oxide supported platinum catalyst, comprising the following steps: a) high-temperature heat treatment of a V precursor to obtain an orange V2O5 support powder; b) adding the V2O5 powder, a Pt metal precursor and a sacrificial reagent to a solution, stirring after ultrasonic treatment, and reacting under xenon lamp irradiation to obtain a dark brown suspension; c) centrifuging, washing, drying and grinding the dark brown suspension to obtain a dark brown powder; and d) high-temperature heat treatment of the dark brown powder under different protective atmospheres to obtain the vanadium oxide supported platinum catalyst.

[0008] Preferably, in step a), the V precursor is ammonium vanadate (NH4VO3).

[0009] Preferably, in step a), the heat treatment is to raise the temperature to 500°C at a rate of 5°C / min and maintain for 4-8 h.

[0010] Preferably, in step b), the Pt metal precursor is tetraammine platinum nitrate (K2Pt(NH3)4(NO3)2), the sacrificial reagent is a small amount of ethanol solution, and the solution is deionized water. 12 N6O6Pt), the sacrificial reagent is a small amount of ethanol solution, and the solution is deionized water.

[0011] Preferably, in step b), the ultrasonic treatment time is 0.1-0.5 h, the stirring rate is 400-600 r / min, the reaction temperature is constant at 20-40°C, and the reaction time is 2-3 h.

[0012] Preferably, in step b), the mass ratio of the mass of Pt to the total mass of Pt and V2O5 (Pt / (Pt+V2O5)) is (0.25-1):100, the concentration of Pt in the system is 0.125-0.5 mmol / L, the deionized water is 100 mL, and the ethanol is 5 mL.

[0013] Preferably, in step c), the centrifugation speed is 6000-8000 rpm, and the centrifugation time is 5-10 min.

[0014] Preferably, in step c), the drying conditions are 60-80°C for 10-20 h.

[0015] Preferably, in step d), the different protective atmospheres are air, H2 / N2 mixed gas and CO / O2 / He mixed gas in sequence, the heat treatment temperatures are 400°C, 200°C and 250-350°C in sequence, the heat treatment times are 4-8 h, 0.5-1 h and 0.5-1 h in sequence, and the heating rates are all 5-10°C / min. More preferably, the heat treatment temperatures are 400°C, 200°C and 300°C in sequence, the heat treatment times are 4 h, 0.5 h and 0.5 h in sequence, and the heating rates are all 5°C / min.

[0016] According to a second aspect of the present application, there is provided a platinum catalyst supported on vanadium oxide, wherein the support is a semiconductor material V2O5, and the metal Pt is the active metal, and the catalyst is prepared by the preparation method described above.

[0017] According to a third aspect of the present application, there is provided a use of the platinum catalyst supported on vanadium oxide in a CO oxidation reaction.

[0018] The present application uses ammonium vanadate high-temperature pyrolysis to prepare a V2O5 support material, uses ethanol as a sacrificial reagent to obtain a deep brown suspension by a photodeposition method, and then performs centrifugation, washing, drying, and grinding to prepare a Pt-V2O5 catalyst precursor, and then performs high-temperature air oxidation, hydrogen reduction, and mixed gas partial oxidation in sequence to obtain a platinum nanocatalyst supported on vanadium oxide. In the preparation method provided by the present application, step b) is used to preliminarily load Pt on V2O5, and step d) is used to optimize the CO oxidation catalytic activity of the sample after the three processes of oxidation, reduction, and partial oxidation in sequence. The key points of the present application are mainly these two steps, i.e., the synthesis of Pt / V2O5 by the photodeposition method and the three-step treatment of Pt / V2O5 before the catalytic reaction, so that the Pt / V2O5 has high catalytic activity in the CO oxidation reaction.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] 1) The present application combines the synthesis of a Pt-V2O5 precursor by a photodeposition method with a process for regulating the morphology or structure of a supported nanocatalyst by three-step high-temperature heat treatment to prepare a novel platinum nanocatalyst supported on vanadium oxide. The preparation method is simple and controllable, has low cost, and can be produced on a large scale.

[0021] 2) Unlike traditional preparation methods of supported catalysts, the addition of an ethanol sacrificial agent in the photodeposition process effectively suppresses the recombination of electron-hole pairs, improves the photodeposition efficiency, and obtains a Pt-V2O5 precursor. The Pt-V2O5 precursor is then subjected to high-temperature heat treatment in different atmospheres to undergo three processes of oxidation-reduction-partial oxidation, the interaction between the metal Pt and the support is effectively regulated, the sintering or agglomeration of the active components in the traditional catalysts during high-temperature calcination or long-time high-temperature reaction is suppressed, the utilization rate of the noble metal Pt is improved, and the stability of the structure of the catalyst itself is improved. Therefore, the prepared catalyst can be applied to a CO oxidation reaction, has excellent catalytic performance at a high space velocity, and has long-time reaction and recycling stability.

[0022] In summary, this invention provides a vanadium oxide-supported platinum catalyst, its preparation method, and its application. The V2O5 nanosheet semiconductor material prepared according to the method of this invention is used to uniformly disperse metallic Pt on the V2O5 surface through photodeposition, followed by a three-step high-temperature heat treatment of oxidation-reduction-partial oxidation to obtain Pt nanocatalytic material that can be used as a CO oxidation catalyst. It has the advantages of excellent catalytic performance at high space velocities, long-term stability, and good cyclic stability. Attached Figure Description

[0023] Figure 1 This is a transmission electron microscope (TEM) image of the vanadium oxide-supported platinum catalyst prepared in Example 1 of this invention.

[0024] Figure 2 This is a transmission electron microscope (TEM) image of the vanadium oxide-supported platinum catalyst prepared in Example 1 of this invention after the CO oxidation reaction.

[0025] Figure 3 This is a cyclic test curve of the vanadium oxide-supported platinum catalyst prepared in Example 1 of the present invention in the CO oxidation reaction;

[0026] Figure 4 This is a long-term stability test curve of the vanadium oxide-supported platinum catalyst prepared in Example 1 of the present invention in the CO oxidation reaction;

[0027] Figure 5 This is a transmission electron microscope image of the vanadium oxide-supported Pt nanocatalyst prepared in Example 2 of the present invention.

[0028] Figure 6 This is a transmission electron microscope image of the vanadium oxide-supported Pt nanocatalyst prepared in Example 3 of the present invention.

[0029] Figure 7 The image shows the CO oxidation test curve of the vanadium oxide-supported Pt nanocatalyst prepared in Comparative Example 1 of this invention.

[0030] Figure 8 This is a test curve of CO oxidation based on vanadium oxide-supported Pt nanocatalyst prepared in Comparative Example 2 of this invention. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. The raw materials and instruments used in the following embodiments are all commercially available; unless otherwise specified, the equipment and preparation processes used are conventional equipment and conventional processes.

[0032] Example 1

[0033] This embodiment describes a method for preparing Pt nanocatalysts supported on vanadium oxide, which includes the following steps:

[0034] (a) 5.0 g of ammonium vanadate was heated to 500 °C in a muffle furnace at a programmed temperature of 5 °C / min and maintained for 4 h, and then cooled naturally to room temperature to obtain orange-red V2O5 carrier powder.

[0035] (b) 0.995 g V2O5 powder, 0.01 g tetraammine nitrate platinum and 5 mL ethanol reagent were added to 100 mL deionized water and ultrasonically treated for 0.5 h. The mixture was then stirred at room temperature at a stirring rate of 400 r / min and then reacted under xenon lamp irradiation for 2 h to obtain a dark brown suspension.

[0036] (c) The dark brown suspension was centrifuged at 8000 rpm for 5 min, washed three times with deionized water, dried at 80 °C for 10 h, and then ground to obtain dark brown powder.

[0037] (d) The dark brown powder was first heated to 400°C in air at a heating rate of 5°C / min, held for 4 hours, and then cooled to room temperature. Then the atmosphere was switched to H2 / N2 mixed gas and heated to 200°C at a heating rate of 5°C / min, held for 1 hour, and then cooled to room temperature. Finally, the atmosphere was switched to CO / O2 / He mixed gas and heated to 300°C at a heating rate of 5°C / min, held for 0.5 hours, and then cooled to room temperature to obtain the above-mentioned vanadium oxide-supported Pt nanocatalyst.

[0038] Example 2

[0039] This embodiment describes a method for preparing a vanadium oxide-supported Pt sub-nano cluster catalyst, which includes the following steps:

[0040] (a) 5.0 g of ammonium vanadate was heated to 500 °C in a muffle furnace at a programmed temperature of 5 °C / min and maintained for 4 h, and then cooled naturally to room temperature to obtain orange-red V2O5 carrier powder.

[0041] (b) 0.9975 g V2O5 powder, 0.005 g tetraammine nitrate platinum and 5 mL ethanol reagent were added to 100 mL deionized water and ultrasonically treated for 0.5 h. The mixture was then stirred at room temperature at a stirring rate of 400 r / min and then reacted under xenon lamp irradiation for 2 h to obtain a dark brown suspension.

[0042] (c) The dark brown suspension was centrifuged at 8000 rpm for 5 min, washed three times with deionized water, dried at 80 °C for 10 h, and then ground to obtain dark brown powder.

[0043] (d) The dark brown powder was first heated to 400°C in air at a heating rate of 5°C / min, held for 4 hours, and then cooled to room temperature. Then the atmosphere was switched to H2 / N2 mixed gas and heated to 200°C at a heating rate of 5°C / min, held for 1 hour, and then cooled to room temperature. Finally, the atmosphere was switched to CO / O2 / He mixed gas and heated to 300°C at a heating rate of 5°C / min, held for 0.5 hours, and then cooled to room temperature to obtain the above-mentioned vanadium oxide-supported Pt nanocatalyst.

[0044] Example 3

[0045] This embodiment describes a method for preparing Pt nanocatalysts supported on vanadium oxide, which includes the following steps:

[0046] (a) 5.0 g of ammonium vanadate was heated to 500 °C in a muffle furnace at a programmed temperature of 5 °C / min and maintained for 4 h, and then cooled naturally to room temperature to obtain orange-red V2O5 carrier powder.

[0047] (b) 0.99 g V2O5 powder, 0.02 g tetraammine nitrate platinum and 10 mL ethanol reagent were added to 100 mL deionized water and ultrasonically treated for 0.5 h. The mixture was then stirred at room temperature at a stirring rate of 400 r / min and then reacted under xenon lamp irradiation for 2 h to obtain a dark brown suspension.

[0048] (c) The dark brown suspension was centrifuged at 8000 rpm for 5 min, washed three times with deionized water, dried at 80 °C for 10 h, and then ground to obtain dark brown powder.

[0049] (d) The dark brown powder was first heated to 400°C in air at a heating rate of 5°C / min, held for 4 hours, and then cooled to room temperature. Then the atmosphere was switched to H2 / N2 mixed gas and heated to 200°C at a heating rate of 5°C / min, held for 1 hour, and then cooled to room temperature. Finally, the atmosphere was switched to CO / O2 / He mixed gas and heated to 300°C at a heating rate of 5°C / min, held for 0.5 hours, and then cooled to room temperature to obtain the above-mentioned vanadium oxide-supported Pt nanocatalyst.

[0050] Comparative Example 1

[0051] In this comparative example, He gas treated at 200℃ and CO / O2 / He mixed gas treated at 300℃ were selected as comparisons:

[0052] (a) 5.0 g of ammonium vanadate was heated to 500 °C in a muffle furnace at a programmed temperature of 5 °C / min and maintained for 4 h, and then cooled naturally to room temperature to obtain orange-red V2O5 carrier powder.

[0053] (b) 0.995 g V2O5 powder, 0.01 g tetraammine nitrate platinum and 5 mL ethanol reagent were added to 100 mL deionized water and ultrasonically treated for 0.5 h. The mixture was then stirred at room temperature at a stirring rate of 400 r / min and then reacted under xenon lamp irradiation for 2 h to obtain a dark brown suspension.

[0054] (c) The dark brown suspension was centrifuged at 8000 rpm for 5 min, washed three times with deionized water, dried at 80 °C for 10 h, and then ground to obtain dark brown powder.

[0055] (d) The dark brown powder was first heated to 400°C in air at a heating rate of 5°C / min, held for 4 hours, and then cooled to room temperature. Then the atmosphere was switched to He gas and heated to 200°C at a heating rate of 5°C / min, held for 0.5 hours, and then cooled to room temperature. Finally, the atmosphere was switched to a CO / O2 / He mixed gas and heated to 300°C at a heating rate of 5°C / min, held for 0.5 hours, and then cooled to room temperature to obtain the above-mentioned vanadium oxide-supported Pt nanocatalyst.

[0056] Comparative Example 2

[0057] In this comparative example, a gas mixture without CO / O2 / He treatment at 300℃ was selected as the control:

[0058] (a) 5.0 g of ammonium vanadate was heated to 500 °C in a muffle furnace at a programmed temperature of 5 °C / min and maintained for 4 h, and then cooled naturally to room temperature to obtain orange-red V2O5 carrier powder.

[0059] (b) 0.995 g V2O5 powder, 0.01 g tetraammine nitrate platinum and 5 mL ethanol reagent were added to 100 mL deionized water and ultrasonically treated for 0.5 h. The mixture was then stirred at room temperature at a stirring rate of 400 r / min and then reacted under xenon lamp irradiation for 2 h to obtain a dark brown suspension.

[0060] (c) The dark brown suspension was centrifuged at 8000 rpm for 5 min, washed three times with deionized water, dried at 80 °C for 10 h, and then ground to obtain dark brown powder.

[0061] (d) The dark brown powder was first heated to 400°C in air at a heating rate of 5°C / min, held for 4 hours and then cooled to room temperature; then the atmosphere was switched to H2 / N2 mixed gas and heated to 200°C at a heating rate of 5°C / min, held for 1 hour and then cooled to room temperature to obtain the above-mentioned vanadium oxide-supported Pt nanocatalyst.

[0062] The microstructure of the vanadium oxide-supported Pt nanocatalyst prepared in Example 1 was observed by transmission electron microscopy (TEM). The TEM image is shown below. Figure 1 As shown;

[0063] The Pt nanoparticles obtained by photodeposition and three-step high-temperature heat treatment are uniformly dispersed on vanadium oxide sheets and are relatively uniform in size. The average size of the Pt nanoparticles is 2.8 nm, indicating that the nano-Pt catalyst was successfully prepared in Example 1.

[0064] The CO oxidation reaction sample prepared above based on vanadium oxide-supported Pt nanocatalyst was observed by transmission electron microscopy. The observation results are as follows: Figure 2 As shown;

[0065] Depend on Figure 2 It can be seen that Pt nanoparticles with an average diameter of 3.0 nm can be observed on the surface of vanadium oxide after the CO oxidation reaction. Compared with the pre-reaction, the size of the nanoparticles is not significantly larger and the dispersion is good. In addition, the vanadium oxide support structure does not undergo obvious structural changes such as collapse after the reaction, indicating that the prepared vanadium oxide-supported Pt nanocatalyst has good stability in the CO oxidation process.

[0066] The vanadium oxide-supported Pt nanocatalyst prepared in Example 1 was used to evaluate the CO oxidation catalytic performance by connecting it to a gas analyzer manufactured by Ruiyi Automation Co., Ltd. in a fixed-bed reactor to measure the CO and CO2 contents. Evaluation conditions: reaction temperature room temperature to 250℃, atmospheric pressure, CO to O2 ratio in the feed gas of 1:20, total inlet flow rate of 60 mL / min, catalyst loading of 30 mg, and space velocity of 120,000 mL / h / g. cat Catalytic cycle reaction test results Figure 3 As shown;

[0067] Depend on Figure 3 It can be seen that, under the above-mentioned CO oxidation evaluation conditions, the vanadium oxide-supported Pt nanocatalyst can achieve a 50% conversion rate at 135℃ and complete conversion at 165℃, indicating that the catalyst has good CO oxidation catalytic activity. After one round of "Light-Off" testing, the catalyst was cooled to room temperature and then subjected to a second temperature-programmed activity test. As can be seen from the figure, the curves of the two rounds of "Light-Off" testing almost overlapped, and both achieved complete CO conversion at 165℃, indicating that the catalyst has excellent cycling performance in the CO oxidation reaction.

[0068] The stability of the vanadium oxide-supported Pt nanocatalyst prepared in Example 1 was tested over a long period of time, and the test results are as follows: Figure 4 As shown;

[0069] The CO oxidation reaction temperature was adjusted to 150℃, at which point the CO conversion rate was approximately 80%. A stability test was then conducted for 48 hours. Figure 4It can be seen that under the test conditions, the vanadium oxide-supported Pt nanocatalyst of Example 1 can maintain almost no catalytic activity decay within 48 hours, indicating that the catalyst has excellent long-term reaction stability. Combined with the above-mentioned excellent cycling stability, this shows that the catalyst has excellent potential for practical application.

[0070] Vanadium oxide-supported Pt nanocatalysts were prepared according to the methods of Examples 2 and 3.

[0071] The microstructure of the vanadium oxide-supported Pt nanocatalysts prepared in Examples 2 and 3 above was observed by transmission electron microscopy (TEM). The TEM images are shown below. Figure 5 and 6 As shown;

[0072] After adjusting the ratio of Pt metal to V2O5 support, the Pt catalyst obtained by photodeposition and three-step high-temperature heat treatment has Pt nanoparticles uniformly dispersed on vanadium oxide sheets with relatively uniform size. The average size of the Pt nanoparticles is 2.8 nm, indicating that nano Pt catalysts can be successfully prepared in both Examples 2 and 3.

[0073] The CO oxidation of the vanadium oxide-supported Pt nanocatalysts in Comparative Examples 1 and 2 was evaluated, as follows: Figure 7 and Figure 8 It was found that the initial conversion temperature of CO was significantly higher than 150℃, and complete conversion was only achieved at temperatures above 200℃, which fully demonstrates the promoting effect of the three-step heat treatment on the catalyst in the catalytic CO oxidation process.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. All simple and equivalent changes and modifications made in accordance with the claims and description of this application fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for preparing a platinum catalyst supported on vanadium oxide, characterized in that, Includes the following steps: a) The V precursor was heat-treated at high temperature to obtain orange-red V2O5 carrier powder; b) V2O5 carrier powder, Pt metal precursor and sacrificial reagent were added to the solution, ultrasonicated and stirred, and reacted under xenon lamp irradiation to obtain a dark brown suspension. c) The dark brown suspension was centrifuged, washed, dried, ground, and calcined to obtain a dark brown powder; d) By subjecting the dark brown powder to three high-temperature heat treatments under different protective gases, successively undergoing oxidation, reduction, and partial oxidation processes, a vanadium oxide-supported platinum catalyst can be obtained.

2. The preparation method according to claim 1, characterized in that, In step a), the V precursor is ammonium vanadate.

3. The preparation method according to claim 1, characterized in that, In step a), the heat treatment involves raising the temperature to 500℃-600℃ at a rate of 5℃ / min and maintaining it for 4-8 hours.

4. The preparation method according to claim 1, characterized in that, In step b), the Pt metal precursor is tetraammineplatinum nitrate, the sacrificial reagent is a small amount of ethanol solution, and the solution is deionized water.

5. The preparation method according to claim 1, characterized in that, In step b), the ultrasonic treatment time is 0.1 to 0.5 hours; the stirring rate is 400 to 600 r / min; the reaction temperature is constant at 20 to 40°C; and the reaction time is 2 to 3 hours.

6. The preparation method according to claim 1, characterized in that, In step b), the mass ratio of Pt to the total mass of Pt and V2O5 is (0.25-1):100, the concentration of Pt in the system is 0.125-0.5 mmol / L, 100 mL of deionized water and 5 mL of ethanol are used.

7. The preparation method according to claim 1, characterized in that, In step c), the centrifugation speed is 6000-8000 rpm, the centrifugation time is 5-10 min, the drying conditions are 60-80℃, and the drying time is 10-20 hours.

8. The preparation method according to claim 1, characterized in that, In step d), the different protective atmospheres are air, H2 / N2 mixture and CO / O2 / He mixture, respectively; the heat treatment temperatures are 400℃, 200℃ and 250~350℃, respectively; the heat treatment times are 4~8h, 0.5~1h and 0.5~1h, respectively; and the heating rate is 5~10℃ / min.

9. A vanadium oxide-supported platinum catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the vanadium oxide-supported platinum catalyst according to claim 9 in the CO oxidation reaction.

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