Defective hexagonal boron nitride supported palladium nanocluster catalysts, preparation and use thereof

Abstract

The present application belongs to the technical field of chemical synthesis, and particularly relates to a defective hexagonal boron nitride supported palladium nanocluster catalyst as well as preparation and application thereof. The defective hexagonal boron nitride supported palladium nanocluster catalyst comprises defective hexagonal boron nitride nanosheets as a carrier and palladium nanoclusters as an active component, the palladium nanoclusters are dispersed on the surface of the defective hexagonal boron nitride nanosheets, and the mass ratio of the palladium nanoclusters to the defective hexagonal boron nitride nanosheets is 0.08% to 0.12%:1. The present application uses defective hexagonal boron nitride as a carrier to support active site palladium nanoclusters, reduces the use amount of noble metal palladium, improves the catalyst activity, and enables 5-HMF to be converted into HMFCA under mild photocatalytic conditions with high conversion rate, high selectivity and high stability.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and particularly relates to a defective hexagonal boron nitride-supported palladium nanocluster catalyst and a preparation and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Fossil energy is the material foundation of human society and plays a vital role in social development. However, excessive fossil energy use can cause a series of ecological and environmental problems, such as air pollution and the greenhouse effect. Therefore, the development of clean, renewable energy is the future direction of development. Biomass, as the most abundant renewable resource on Earth, is the most attractive way to alleviate the energy crisis and environmental pollution by converting it into a series of high-value-added chemicals.

[0004] When 5-hydroxymethylfurfural (5-HMF) is used as a platform molecule to be converted into high-value-added chemicals through an oxidation reaction, a catalyst is usually required to promote the reaction. The catalysts commonly used in this reaction are divided into non-precious metal and precious metal catalysts. Non-precious metal catalysts usually require high temperature, high pressure, and long reaction conditions, and often face the dilemma of low conversion rate and low selectivity. Precious metal catalysts can achieve the goals of high conversion rate and high selectivity, but alkali needs to be added during the reaction to adjust the pH value, which increases the difficulty of the subsequent separation process. In addition, precious metal catalysts are expensive, resulting in increased preparation costs. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention provides a defective hexagonal boron nitride-supported palladium nanocluster catalyst, its preparation, and application. This invention uses defective hexagonal boron nitride as a carrier for active-site palladium nanoclusters, reducing the amount of precious metal palladium required while improving catalyst activity. This catalyst can convert 5-HMF to 5-hydroxymethyl-2-furoic acid (HMFCA) with high conversion efficiency, selectivity, and stability under mild photocatalytic conditions.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In the first aspect, the present invention provides a defective hexagonal boron nitride-supported palladium nanocluster catalyst, comprising defective hexagonal boron nitride nanosheets as a carrier and palladium nanoclusters as an active component, wherein the palladium nanoclusters are dispersed on the surface of the defective hexagonal boron nitride nanosheets, and the mass ratio of the palladium nanoclusters to the defective hexagonal boron nitride nanosheets is 0.08% to 0.12%:1.

[0008] Preferably, the defective hexagonal boron nitride is obtained by treating hexagonal boron nitride with nitrogen surface plasma.

[0009] Preferably, the size of the palladium nanoclusters is 5 to 10 nm.

[0010] In a second aspect, the present invention provides a method for preparing the defective hexagonal boron nitride-supported palladium nanocluster catalyst as described in the first aspect, comprising the following steps:

[0011] S1, mixing hexagonal boron nitride and isopropyl alcohol, stirring, ultrasonicating, standing and then centrifuging, washing and drying the precipitate to obtain few-layer hexagonal boron nitride nanosheets;

[0012] S2, treating the surface of the few-layer hexagonal boron nitride nanosheets with nitrogen plasma to obtain defective hexagonal boron nitride nanosheets;

[0013] S3, freezing a mixed solution of a palladium precursor and deionized water, and melting it under laser irradiation in the dark to obtain a palladium precursor solution;

[0014] S4. Dispersing the defective hexagonal boron nitride nanosheets in ethanol, adding the palladium precursor solution, stirring, collecting the precipitate by centrifugation, and drying to obtain the defective hexagonal boron nitride-supported palladium nanocluster catalyst.

[0015] Preferably, in step S1, the stirring temperature is 45-55°C, the time is 22-26 hours, the ultrasonic time is 18-22 hours, and the standing time is 22-26 hours.

[0016] Preferably, in step S2, the surface plasma treatment is specifically performed by using a nitrogen plasma surface treatment instrument with a power of 90-110 W for laser irradiation for 15-25 minutes.

[0017] Preferably, in step S3, the palladium precursor is palladium chloride or a palladium chloride solution; the laser irradiation time is 1-1.5 hours, and the temperature of the mixed solution is controlled at -30 to -20°C during laser irradiation.

[0018] Preferably, in step S4, the stirring temperature is room temperature and the stirring time is 1-1.5 h.

[0019] In a third aspect, the present invention provides the use of the defective hexagonal boron nitride-supported palladium nanocluster catalyst as described in the first aspect in the selective photocatalytic oxidation of 5-hydroxymethylfurfural to prepare 5-hydroxymethyl-furancarboxylic acid.

[0020] In a fourth aspect, the present invention provides a method for preparing 5-hydroxymethyl-furancarboxylic acid by selective photocatalytic oxidation of 5-hydroxymethylfurfural, comprising the following steps:

[0021] The defective hexagonal boron nitride-supported palladium nanocluster catalyst and 5-hydroxymethylfurfural as described in the first aspect are dispersed in acetonitrile and subjected to a photocatalytic reaction under light.

[0022] Preferably, the mass of the defective hexagonal boron nitride-supported palladium nanocluster catalyst is 9-11 mg, and the wavelength of the light is 300-400 nm.

[0023] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0024] (1) The catalyst of the present invention is defective hexagonal boron nitride-supported palladium nanoclusters. The composite photocatalyst uses defective hexagonal boron nitride as a carrier and disperses palladium nanoclusters as active sites on the carrier, so that the palladium nanoclusters are better exposed and can provide more active sites, so that the catalyst has higher reaction activity and selectivity while reducing the amount of palladium used.

[0025] (2) The defective hexagonal boron nitride-supported palladium nanocluster catalyst in the present invention can improve the conversion rate and selectivity of the 5-HMF photocatalytic oxidation reaction under mild conditions, providing a new solution for the further industrial application of the 5-HMF oxidation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 TEM image of defective hexagonal boron nitride nanosheets in Example 1;

[0028] Figure 2 This is a transmission electron microscopy image of defective hexagonal boron nitride-supported palladium nanoclusters in Example 1;

[0029] Figure 3 The electrochemical impedance spectroscopy (EIS) graphs of bulk h-BN, defective h-BN, and palladium nanoclusters supported on defective h-BN in Example 1 are shown.

[0030] Figure 4 These are the results of the conversion rate (a), selectivity (b) and cyclic stability experiment (c is conversion rate, d is selectivity) during the 5-HMF oxidation reaction catalyzed by the defective hexagonal boron nitride-supported palladium nanoclusters of Example 1. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments and comparative examples.

[0032] Example 1

[0033] Disperse 0.5 g of hexagonal boron nitride in 50 ml of isopropanol, stir at 50 ° C for 24 hours, then cool to room temperature, and perform low-power ultrasound for 20 hours. Then, place it at room temperature for 1 day, centrifuge, remove the supernatant, wash the lower milky white precipitate with acetone, and dry it in a vacuum drying oven at 50 ° C for 6 hours to obtain few-layer hexagonal boron nitride nanosheets.

[0034] The above few layers of hexagonal boron nitride were spread on a quartz boat and irradiated with a nitrogen plasma surface treatment instrument with a power of 100 W for 20 minutes to obtain defective hexagonal boron nitride nanosheets (Defective h-BN).

[0035] 60 μl of chloropalladic acid solution (10 mg ml -1 ) was mixed with 2 ml of deionized water, frozen in liquid nitrogen, irradiated with laser (355 nm) at -25 °C for 1 h, and melted in the dark to obtain a chloropalladic acid solution.

[0036] 100 mg of defective hexagonal boron nitride nanosheets were dispersed in an ethanol solution, and the above-mentioned chloropalladic acid solution was added to the mixed solution. The mixture was stirred at room temperature for 1 hour, centrifuged, and dried to obtain defective hexagonal boron nitride-supported palladium nanoclusters (Pd NCs / h-BN).

[0037] like Figure 1 As shown in Figure 2, the defective hexagonal boron nitride nanosheets are a small number of stacked nanosheets. Figure 2 As shown in Figure 3, the morphology of defective hexagonal boron nitride nanosheets in defective hexagonal boron nitride-loaded palladium nanoclusters did not change significantly, and the palladium nanoclusters were dispersed on the hexagonal boron nitride nanosheets. Figure 3 As shown, compared with hexagonal boron nitride and defective hexagonal boron nitride, the impedance of defective hexagonal boron nitride-loaded palladium nanoclusters is smaller, indicating that when it is used in the catalytic process, the active sites have less resistance to charge transfer and have stronger catalytic activity.

[0038] Example 2

[0039] 10 mg of defective hexagonal boron nitride-supported palladium nanoclusters of Example 1 and 0.1 mmol

[0040] 5-HMF was dispersed in 10 mL of acetonitrile and photocatalytic selective oxidation of 5-HMF was carried out at room temperature and a light wavelength of 355 nm. Figure 4 As shown in a, the conversion rate of 5-HMF is ≥95% after 20 hours of reaction. Figure 4 As shown in b, the selectivity of HMFCA is ≥75%. In order to test the cyclic stability of the catalyst, the defective hexagonal boron nitride supported palladium nanoclusters prepared in Example 1 were used for 5 consecutive catalytic reactions. Figure 4 As shown in Figures c and d, after 5 cycles, the conversion rate of the catalyst prepared in Example 1 remains above ≥80%, and the selectivity remains above ≥70%.

[0041] Example 3

[0042] Disperse 0.5 g of hexagonal boron nitride in 50 ml of isopropanol, stir at 50°C for 24 hours, then cool to room temperature, perform low-power ultrasound for 22 hours, and place at room temperature for 1 day. Centrifuge, remove the supernatant, wash the lower milky white precipitate with acetone, and dry in a vacuum drying oven at 50°C for 6 hours to obtain few-layer hexagonal boron nitride nanosheets.

[0043] The above few layers of hexagonal boron nitride were spread on a quartz boat and irradiated with a nitrogen plasma surface treatment instrument with a power of 100 W for 20 minutes to obtain defective hexagonal boron nitride nanosheets (Defective h-BN).

[0044] 40 μl of chloropalladic acid solution (10 mg ml -1 ) was mixed with 2 ml of deionized water, frozen in liquid nitrogen, irradiated with laser (355 nm) at -20 °C for 1 h, and melted in the dark to obtain a chloropalladic acid solution.

[0045] 100 mg of defective hexagonal boron nitride nanosheets were dispersed in an ethanol solution, and the above-mentioned chloropalladic acid solution was added to the mixed solution. The mixture was stirred at room temperature for 1 hour, centrifuged, and dried to obtain defective hexagonal boron nitride-supported palladium nanoclusters (Pd NCs / h-BN).

[0046] Example 4

[0047] Disperse 0.5 g of hexagonal boron nitride in 50 ml of isopropanol, stir at 50 ° C for 24 hours, then cool to room temperature, and perform low-power ultrasound for 20 hours. Then, place it at room temperature for 1 day, centrifuge, remove the supernatant, wash the lower milky white precipitate with acetone, and dry it in a vacuum drying oven at 50 ° C for 6 hours to obtain few-layer hexagonal boron nitride nanosheets.

[0048] The above few layers of hexagonal boron nitride were spread on a quartz boat and irradiated with a nitrogen plasma surface treatment instrument with a power of 100 W for 20 minutes to obtain defective hexagonal boron nitride nanosheets (Defective h-BN).

[0049] 50 μl of chloropalladic acid solution (10 mg ml -1 ) was mixed with 2 ml of deionized water, frozen in liquid nitrogen, irradiated with laser (355 nm) at -25 °C for 1 h, and melted in the dark to obtain a chloropalladic acid solution.

[0050] 100 mg of defective hexagonal boron nitride nanosheets were dispersed in an ethanol solution, and the above-mentioned chloropalladic acid solution was added to the mixed solution. The mixture was stirred at room temperature for 1 hour, centrifuged, and dried to obtain defective hexagonal boron nitride-supported palladium nanoclusters (Pd NCs / h-BN).

[0051] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a defective hexagonal boron nitride supported palladium nanocluster catalyst, characterized in that: The following steps are involved: S1, mixing hexagonal boron nitride and isopropyl alcohol, stirring, ultrasonicating, standing and then centrifuging, washing and drying the precipitate to obtain few-layer hexagonal boron nitride nanosheets; S2, treating the surface of the few-layer hexagonal boron nitride nanosheets with nitrogen plasma to obtain defective hexagonal boron nitride nanosheets; S3, freezing a mixed solution of a palladium precursor and deionized water, and melting it under laser irradiation in the dark to obtain a palladium precursor solution; S4, dispersing the defective hexagonal boron nitride nanosheets in ethanol, adding a palladium precursor solution, stirring, collecting the precipitate by centrifugation, and drying to obtain the defective hexagonal boron nitride-supported palladium nanocluster catalyst; The defective hexagonal boron nitride-supported palladium nanocluster catalyst comprises defective hexagonal boron nitride nanosheets as a carrier and palladium nanoclusters as an active component. The palladium nanoclusters are dispersed on the surface of the defective hexagonal boron nitride nanosheets, and the mass ratio of the palladium nanoclusters to the defective hexagonal boron nitride nanosheets is 0.08% to 0.12%.

2. The method for preparing the defective hexagonal boron nitride supported palladium nanocluster catalyst according to claim 1, wherein: The defective hexagonal boron nitride is obtained by treating hexagonal boron nitride with nitrogen surface plasma.

3. The method for preparing the defective hexagonal boron nitride supported palladium nanocluster catalyst according to claim 1, wherein: The size of the palladium nanoclusters is 5-10 nm.

4. The preparation method according to claim 1, wherein In step S1, the stirring temperature is 45-55° C., the time is 22-26 h; the ultrasonic time is 18-22 h; and the standing time is 22-26 h.

5. The preparation method according to claim 1, wherein In step S2, the surface plasma treatment is specifically performed by using a nitrogen plasma surface treatment instrument with a power of 90-110 W for laser irradiation for 15-25 min.

6. The preparation method according to claim 1, wherein In step S3, the palladium precursor is a palladium chloride solution; the laser irradiation time is 1-1.5 h, and the temperature of the mixed solution is controlled at -30~-20°C during laser irradiation.

7. The preparation method according to claim 1, wherein In step S4, the stirring temperature is room temperature and the stirring time is 1-1.5 h.

8. Use of the defective hexagonal boron nitride-supported palladium nanocluster catalyst obtained by the preparation method according to claim 1 in the preparation of 5-hydroxymethyl-2-furancarboxylic acid.

9. A method for preparing 5-hydroxymethyl-2-furancarboxylic acid by selective photocatalytic oxidation of 5-hydroxymethylfurfural, characterized in that: The following steps are involved: The defective hexagonal boron nitride-supported palladium nanocluster catalyst according to any one of claims 1 to 3 and 5-hydroxymethylfurfural are dispersed in acetonitrile and subjected to a photocatalytic reaction under light.

10. The method for preparing 5-hydroxymethyl-2-furancarboxylic acid by selective photocatalytic oxidation of 5-hydroxymethylfurfural according to claim 9, characterized in that: The mass of the defective hexagonal boron nitride-supported palladium nanocluster catalyst is 9-11 mg, and the illumination wavelength is 300-400 nm.

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