CN-121988367-A - Catalytic system based on graphite-phase carbon nitride composite photocatalyst and preparation and application methods thereof

Abstract

The invention belongs to the technical field of green energy and biomass high-value conversion, and particularly relates to a catalytic system based on a graphite-phase carbon nitride composite photocatalyst and a preparation and application method thereof. The invention firstly prepares graphite-phase carbon nitride g-C 3 N 4 by secondary calcination of melamine, and then adds the g-C 3 N 4 dispersion liquid into tetrachloroauric acid aqueous solution containing sodium borohydride to react to prepare Au x /g-C 3 N 4 composite photocatalytic material. The plasma effect of Au enhances the capturing and utilizing of visible light and generates high-energy hot electrons to directly participate in oxidation reaction. The Schottky junction formed between the Au and the g-C 3 N 4 can rapidly transfer the photo-generated electrons from the g-C 3 N 4 conduction band to the Au, so that the efficient separation and migration of the photo-generated charges are realized. The selective oxidation of 5-hydroxymethylfurfural to 5-formyl-2-furancarboxylic acid can be carried out in aqueous medium under mild conditions.

Inventors

• HAN DONGXUE
• ZHONG ZHIMEI
• LIANG ZHISHAN
• HAN DONGFANG

Assignees

• 广州大学

Dates

Publication Date

20260508

Application Date

20260331

Claims (10)

1. 1. The preparation method of the graphite-phase-based carbon nitride composite photocatalyst is characterized by comprising the following steps of: s1, preparing g-C 3 N 4 photocatalytic materials, namely placing melamine into a sealed porcelain boat, calcining the melamine for the first time, taking out and grinding the melamine into powder, paving the powder into an open porcelain boat, and calcining the powder for the second time; And S2, preparing the Au x /g-C 3 N 4 composite photocatalytic material, namely adding tetrachloroauric acid trihydrate into a sodium citrate aqueous solution, stirring, then adding sodium borohydride under ice bath condition, stirring, finally adding g-C 3 N 4 dispersion, stirring, filtering, washing, and drying in vacuum to obtain the Au x /g-C 3 N 4 composite photocatalytic material.
2. 2. The method for preparing the graphite-phase-based carbon nitride composite photocatalyst according to claim 1, wherein in the step S1, the temperature of the first calcination is 500-600 ℃ and the time is 3-5 h.
3. 3. The method for preparing the graphite-phase-based carbon nitride composite photocatalyst according to claim 1, wherein in the step S1, the temperature of the second calcination is 450-550 ℃ and the time is 1-3 h.
4. 4. The method for preparing a graphite-phase-based carbon nitride composite photocatalyst according to claim 1, wherein in step S2, the g-C 3 N 4 dispersion is prepared by ultrasonically dispersing a g-C 3 N 4 photocatalytic material into deionized water.
5. 5. The method for preparing the graphite-phase-based carbon nitride composite photocatalyst according to claim 1, wherein in the step S2, the stirring time for adding the g-C 3 N 4 dispersion liquid and stirring is 4-8 hours.
6. 6. The method for preparing the graphite-phase-based carbon nitride composite photocatalyst according to claim 1, wherein in the step S2, the mass content of Au in the Au x /g-C 3 N 4 composite photocatalytic material is 7-9%.
7. 7. A graphite-phase-based carbon nitride composite photocatalyst prepared by the preparation method according to any one of claims 1 to 6.
8. 8. Use of a graphite-phase carbon nitride based composite photocatalyst according to claim 7 for the preparation of 5-formyl-2-furancarboxylic acid by selective oxidation of 5-hydroxymethylfurfural, characterized in that the use comprises the following steps: And (3) putting the Au x /g-C 3 N 4 composite photocatalytic material and 5-hydroxymethylfurfural into a photocatalytic reactor, adding sodium carbonate aqueous solution, performing ultrasonic treatment, continuously introducing oxygen, stirring in the dark, and starting a water-cooling circulation xenon lamp to start the visible photocatalytic reaction of the system to obtain the product 5-formyl-2-furancarboxylic acid.
9. 9. The application of the graphite-phase-based carbon nitride composite photocatalyst in preparing 5-formyl-2-furancarboxylic acid by selectively oxidizing 5-hydroxymethylfurfural, according to claim 8, wherein the flow rate of oxygen is 10-30 mL/min, the irradiation intensity of a xenon lamp is 400-600 mW/cm 2 , and the irradiation time is 4-8 h.
10. 10. The use of a graphite-phase-based carbon nitride composite photocatalyst for preparing 5-formyl-2-furancarboxylic acid by selectively oxidizing 5-hydroxymethylfurfural according to claim 8, wherein the concentration of Au x /g-C 3 N 4 composite photocatalytic material in the system is 2 mg/mL, the concentration of 5-hydroxymethylfurfural is 1.26 g/L, and the concentration of sodium carbonate is 1.6 g/L.

Description

Catalytic system based on graphite-phase carbon nitride composite photocatalyst and preparation and application methods thereof Technical Field The invention belongs to the technical field of green energy and biomass high-value conversion, and particularly relates to a catalytic system based on a graphite-phase carbon nitride composite photocatalyst and a preparation and application method thereof. Background In order to reduce the reliance on fossil resources and meet market demands for green chemicals, efficient technologies are being developed to convert renewable biomass to high value chemicals. Among a plurality of biomass platform molecules, 5-Hydroxymethylfurfural (HMF) integrates hydroxyl, aldehyde group, furan ring and other key functional groups, has a prominent chemical structure and is a platform molecule with great potential. The selective oxidation of HMF can produce a series of valuable derivatives including 5-Diformylfuran (DFF), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 5-formyl-2-furancarboxylic acid (FFCA) and 2, 5-furandicarboxylic acid (FDCA), which have wide application prospects in the fields of medicine, chemical industry and the like, so that the selective oxidation of HMF has great significance in science and industry. Conventional thermocatalytic and electrocatalytic processes for HMF oxidation generally achieve high yields but require harsh conditions, high pressure noble metal catalysts or expensive oxidants, which affect their sustainability and scalability. In contrast, photocatalysis provides a green and energy-efficient alternative by utilizing solar energy to drive selective redox reactions at ambient conditions. The semiconductor photocatalyst generates electron-hole pairs under the irradiation of light, so that molecular oxygen is activated into active oxygen substances such as superoxide radicals, hydroxyl radicals and the like, and selective organic conversion is promoted. Graphite phase carbon nitride (g-C 3N4) is a promising metal-free photocatalyst, which can be attributed to its response to visible light (about 2.7 eV), chemical stability, and energy band structure suitable for O 2 activation and selective oxidation. However, the original g-C 3N4 has a general DFF selectivity due to a fast electron-hole recombination rate and a limited active site. Although heterojunction engineering, such as g-C 3N4/NaNbO3、WO3/g-C3N4 and CoPz/g-C 3N4, can improve charge separation and achieve higher selectivity to DFF or FFCA, there is still a need for further improvement in activity and tunability. In the prior art, the method for realizing the catalytic conversion of the HMF based on a synergistic mechanism of plasma metal synergy and semiconductor photocatalysis has some economical and sustainable problems. For example, pt/TiO 2 composite catalytic system, pt is used as a high-efficiency promoter, and can promote the adsorption and activation of oxygen. TiO 2 generates holes and hydroxyl free radicals with strong oxidability under the excitation of ultraviolet light. The system has high catalytic activity and mature technology. But depending on ultraviolet light (only accounting for 5 percent of sunlight), a special light source is needed, the energy consumption is high, and Pt is noble metal which is more expensive and thinner than Au. In an Ag/AgX (x=cl, br, I) catalytic system, ag nanoparticles generate a strong visible light plasma resonance effect, hot electrons generated by excitation of the Ag nanoparticles can be injected into a conduction band of an adjacent silver halide (AgX) semiconductor to participate in a reduction reaction, and AgX itself can be used as a photocatalyst. However, ag + in AgX is easily reduced to Ag 0 under light, resulting in phase transition and deactivation of the catalyst structure. Meanwhile, cl - or Br - may leach out in the reaction, causing catalyst dissolution and environmental pollution. And a Covalent Organic Framework (COF) with a definite pore structure and an adjustable energy band is utilized as an all-organic, metal-free photocatalyst. The catalytically active sites are introduced into the framework by means of a pre-modification or post-synthetic modification. The principle is that the selective oxidation of HMF is realized under visible light by combining the shape selective adsorption of porous materials and the photocatalysis performance of organic semiconductors. However, the synthesis of COF generally requires high purity monomers, strict anaerobic and anhydrous conditions, and long-term reaction, and is costly to prepare and difficult to scale. Therefore, how to utilize the synergistic mechanism of plasma metal synergy and semiconductor photocatalysis to realize the selective preparation of FFCA by oxidizing HMF under the condition of water medium and mild condition is the technical problem to be solved by the invention. Disclosure of Invention Aiming at the problems in the prior art, the invention provides a catalytic