A catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming, its preparation method and application.

Abstract

This invention belongs to the field of catalysts and discloses a photocatalytic synthesis of H2O2 coupled with PLA reforming, its preparation method, and its application. The preparation method includes obtaining B-doped carbon nitride by introducing NaBH3-CN as a B source; subsequently, a noble metal precursor is photodeposited onto the B-doped carbon nitride to obtain the photocatalytic synthesis of H2O2 coupled with PLA reforming. The Au@BCN bifunctional photocatalyst prepared by this invention simultaneously synthesizes H2O2 and reforms PLA, fully utilizing electrons and holes, achieving an H2O2 production efficiency of 2.0 mmol g. ‑1 h ‑1 The AA production efficiency was 3.7 mmol g. ‑1 h ‑1 The selectivity exceeds 99.0%. This invention utilizes solar visible light to drive the catalytic reaction, effectively reducing energy consumption and environmental pollutant emissions. Furthermore, this invention can simultaneously synthesize H2O2 and high-value-added chemicals, resulting in significant environmental and economic benefits. The entire photocatalytic process does not produce harmful byproducts, conforming to the principles of green chemistry.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and specifically relates to a catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming, its preparation method, and its application. Background Technology

[0002] H₂O₂ is an important green oxidant with wide applications in wastewater treatment, disinfection, and environmental purification. However, its traditional industrial production mainly relies on the anthraquinone process, which has long faced problems such as high energy consumption, heavy pollution, high costs, and significant safety hazards. In recent years, solar-driven photocatalytic oxygen reduction reactions, especially those achieving H₂O₂ synthesis via single-electron or double-electron reduction pathways, have attracted widespread attention due to their greenness and sustainability. However, in these photocatalytic oxygen reduction processes, the water oxidation reaction coupled with the electron reduction half-reaction is kineticly slow, severely limiting the overall reaction efficiency. Therefore, developing an alternative half-oxidation reaction that is thermodynamically more favorable and has a lower reaction potential than the oxygen evolution reaction is of great significance for improving the overall performance of photocatalytic H₂O₂ production systems.

[0003] Currently, to improve H2O2 generation efficiency, traditional photocatalytic systems typically introduce sacrificial agents such as methanol and triethanolamine to capture photogenerated holes, thereby promoting electron participation in the oxygen reduction process. However, this strategy essentially wastes the oxidation capacity of photogenerated holes; at the same time, the sacrificial oxidation products have low added value, further weakening the economic viability and sustainability of the technology, and contradicting the principles of green chemistry and atom economy.

[0004] In recent years, the strategy of using waste plastic-derived organic matter as hole acceptors to achieve high-value selective oxidation has been preliminarily verified and is gradually becoming an important direction for building a sustainable energy conversion system. Simultaneously, the hole-driven oxidation process of organic substrates can achieve charge-balance coupling with the electron-driven O2 reduction to H2O2 process, providing a theoretical basis for constructing a solar-driven closed-loop photo-oxidation-reduction cycle of "H2O2 synthesis-waste plastic reforming". Among numerous plastic substrates, polylactic acid (PLA), as an important bio-based biodegradable polymer, accounts for approximately 67% of global bioplastic production. If its pretreatment hydrolysis product, lactic acid (LA), can be further selectively oxidized into high-value-added chemicals such as pyruvate (PA), acetic acid (AA), and formic acid (FA), it will provide a new pathway for the resource utilization of PLA. Although theoretically, H2O2 synthesis can be combined with high-value oxidation of PLA pretreatment solution to achieve synergistic enhancement of redox half-reaction and simultaneous improvement of product value, traditional photocatalysts often struggle to balance the band structure and surface reaction characteristics required for efficient O2 reduction and selective organic oxidation. Furthermore, photogenerated carriers are prone to rapid recombination, making efficient coupling of redox reactions a significant challenge.

[0005] Therefore, it is urgent to construct a highly efficient photocatalytic synthesis catalyst for H2O2 coupled with PLA reforming, so as to achieve the synergistic unity of green synthesis of H2O2 driven by solar energy and resource utilization of waste plastics. Summary of the Invention

[0006] The purpose of this invention is to construct a carbon nitride-based catalyst, using supported noble metal sites as electron-rich sites and doped boron atoms as hole-rich sites, to efficiently accelerate the separation of photogenerated carriers. Furthermore, it utilizes PLA pretreated solution from PLA hydrolysis as a sacrificial agent in the photocatalytic synthesis of H₂O₂ to consume holes, thereby improving carrier separation efficiency while simultaneously preparing high-value-added chemicals. This achieves full utilization of electrons and holes, thus enhancing reaction efficiency.

[0007] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0008] A method for preparing a catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming, comprising,

[0009] NaBH3-CN was introduced as a B source and mixed with carbon nitride and calcined to obtain B-doped carbon nitride.

[0010] Subsequently, the noble metal precursor was mixed with a B-doped carbon nitride dispersion, and the noble metal precursor was photodeposited onto B-doped carbon nitride.

[0011] The reaction yielded a catalyst for the photocatalytic synthesis of H2O2 coupled with PLA reforming.

[0012] It should be noted that the effective components of the noble metal precursor are not strictly limited in this invention. For example, they can be at least one of HAuCl4·3H2O, AgNO3, Cl4H8N2Pd, KPdCl4, H2PtCl6·6H2O, KRuCl6, etc., with HAuCl4·3H2O being the most preferred.

[0013] The noble metal precursor can be in a solid state or can be dissolved to form a solution, but the mass ratio of the effective component to boron-doped carbon nitride must be within a suitable range. The noble metal reduction method is not strictly limited and can be any common metal reduction method. For example, it can be at least one of photodeposition reduction, microwave-assisted reduction, or high-temperature atmosphere reduction.

[0014] Furthermore, the concentration of the B-doped carbon nitride is 0.5-1 mg / mL;

[0015] The mass ratio of the noble metal precursor to the B-doped carbon nitride dispersion is 0.01-0.1:1.

[0016] Furthermore, the B-doped carbon nitride is obtained by high-temperature calcination; the calcination temperature for preparing B-doped carbon nitride is 300~500℃, and the calcination time is 0.5~2h;

[0017] The mass ratio of NaBH3-CN to carbon nitride is 0.1-0.5:1.

[0018] Furthermore, the carbon nitride is obtained through a carbon nitride precursor calcination reaction; the calcination temperature for preparing carbon nitride is 400-600°C. o C, calcination time is 3-5 hours.

[0019] It should be noted that the carbon nitride precursor is not strictly limited in this invention. For example, it can be at least one of urea, dicyandiamine, melamine, etc., preferably urea.

[0020] The present invention also provides a catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming, which is obtained by the above-described method for preparing the catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming.

[0021] This invention also provides the application of the above-mentioned photocatalytic synthesis of H2O2 coupled with PLA reforming catalyst in the simultaneous reduction of O2 to prepare H2O2 and selective oxidation of PLA pretreatment solution under light irradiation.

[0022] Furthermore, applications of simultaneously reducing O2 to prepare H2O2 and selectively oxidizing PLA pretreatment solution under light irradiation include:

[0023] The catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming was mixed with PLA pretreatment liquid, and high-purity air was introduced to remove impurity gases to obtain the catalytic reaction system.

[0024] The catalytic reaction system is subjected to photocatalytic reaction under light irradiation.

[0025] Furthermore, the ratio of the catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming to the PLA pretreatment solution is 5-20 mg: 5-20 mL;

[0026] The concentration of the LA solution is 0.1-1 mg / mL.

[0027] Furthermore, the light source is at least one of xenon lamp, LED lamp, fluorescent lamp, or sunlight;

[0028] The photocatalytic temperature is 30-50°C. o C.

[0029] Furthermore, before carrying out the photocatalytic reaction under light, the catalytic reaction system is stirred at 400-600 rpm for 30-60 minutes in a dark environment to ensure that the catalytic reaction system reaches adsorption-desorption equilibrium.

[0030] Beneficial effects

[0031] The Au@BCN bifunctional photocatalyst prepared in this invention can simultaneously reduce O2 to produce H2O2 and selectively oxidize PLA pretreated solution, making full use of electrons and holes, and the H2O2 precipitation efficiency can reach 2.0 mmol g. -1 h -1 The production efficiency of AA reached 3.7 mmol g. -1 h -1 The selectivity exceeds 99.0%.

[0032] This invention utilizes visible light as an energy source to drive the reaction, reducing energy consumption and environmental pollution. Furthermore, this invention can simultaneously produce and synthesize H2O2 and high-value-added chemicals, offering significant environmental and economic benefits. The entire photocatalytic process does not produce harmful byproducts, conforming to the principles of green chemistry. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 The XRD patterns of the catalysts prepared in Example 1 and Comparative Example 1 are shown.

[0035] Figure 2 The graphs showing the H2O2 and AA production rates for different catalysts are presented.

[0036] Figure 3 The graph shows the H2O2 and AA production rates of catalysts with different Au loadings;

[0037] Figure 4 The graph shows the H2O2 and AA production rates in catalytic systems without Air or PLA pretreatment solution. Detailed Implementation

[0038] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0039] The technical solution of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise expressly stated, the technical or scientific terms used in the present invention should be understood as having the meaning commonly understood by those skilled in the art. The various embodiments and specific features of the present invention can be arbitrarily combined without contradiction. The embodiments listed below are only used to further illustrate the content of the present invention and are not intended to limit its scope of protection.

[0040] Example 1

[0041] A method for preparing a catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming includes the following steps:

[0042] (1) At room temperature, urea is placed in a N2 atmosphere at 550°C. o Carbon nitride was obtained by calcination at C for 4 hours.

[0043] (2) Grind the carbon nitride obtained in step (1) and NaBH3-CN thoroughly at a mass ratio of 1:0.1-0.5, and then further grind them in a N2 atmosphere at 400°C. o Calcination of C for 1 hour yields B-doped carbon nitride.

[0044] (3) The B-doped carbon nitride obtained in step (2) is mixed with deionized water at a concentration of 5 mg / mL to obtain a B-doped carbon nitride dispersion; HAuCl4·3H2O is mixed with the B-doped carbon nitride dispersion, wherein the mass ratio of HAuCl4·3H2O to the B-doped carbon nitride dispersion is 0.05:1; then the mixture is stirred to dissolve HAuCl4·3H2O to obtain a suspension.

[0045] (4) 0.1 mL of PLA pretreatment solution was introduced into 30 mL of suspension solution as a hole acceptor, and after being purged with argon gas, it was placed under xenon lamp irradiation and stirred for 2 hours.

[0046] (5) Centrifuge and wash the product obtained in step (4), and then heat it at 75°C. oAfter drying at C for 13 h, a catalyst for the photocatalytic synthesis of H2O2 coupled with PLA reforming was obtained and named Au. 0.05 @BCN photocatalyst.

[0047] Examples 2-4

[0048] Compared with Example 1, the difference lies in that: in step (3), the mass ratios of HAuCl4·3H2O to B-doped carbon nitride are 0.01:1, 0.02:1, and 0.1:1, respectively. Correspondingly, they are named Au... 0.01 @BCN、Au 0.02 @BCN、Au 0.1 @BCN.

[0049] Comparative Example 1

[0050] The catalyst is carbon nitride or B-doped carbon nitride. The preparation method is described in steps (1)-(2) of Example 1.

[0051] Test case

[0052] The crystal structures of the catalysts prepared in Example 1 and Comparative Example 1 were characterized by XRD, and the results are as follows: Figure 1 As shown, the introduction of Au and B species did not disrupt the intrinsic molecular structure of carbon nitride. The signal peak of the (002) crystal plane of carbon nitride shifted to a lower angle after B doping, indicating that B atom doping led to an increase in the interlayer packing distance and a decrease in structural order in the conjugated aromatic system. No Au species-related signal peaks were found in the figure.

[0053] The photocatalytic synthesis of H2O2 coupled with PLA reforming performance of the catalysts prepared in Examples 1-4 and Comparative Example 1 was evaluated. The specific steps were as follows:

[0054] S1. Mix 10 mg of the catalyst to be evaluated and 10 mL of PLA pretreatment solution with a LA concentration of 1 mg / mL (PLA pretreatment solution is obtained by hydrothermal treatment of PLA at 150 °C for 8 h, and the composition is lactic acid aqueous solution) and add it to a 220 mL quartz reactor.

[0055] S2. Pass 210 mL of high-purity air into the quartz reactor, then add a magnetic particle and seal it. Stir at 500 rpm for 30 min in the dark to ensure that the adsorption-desorption equilibrium is reached, and obtain the catalytic reaction system.

[0056] S3. The catalytic reaction system is subjected to light intensity of 300 mW·cm. -2 The xenon lamp light source, at 30 o Photocatalytic reaction was carried out under C irradiation for 1 hour, simultaneously achieving O2 reduction to prepare H2O2 and selective oxidation of PLA pretreated solution to AA; the reaction equation is as follows:

[0057]

[0058] S4. After the photocatalytic reaction is completed, the catalyst is removed by filtration, and the AA content of the filtrate is determined by high performance liquid chromatography; the H2O2 content is detected by micro-iodometric method in conjunction with ultraviolet spectrophotometer (355 nm).

[0059] Figure 2 The production efficiencies of H2O2 and AA with different catalysts are shown. It can be seen that under the same catalytic conditions, the catalyst of Example 1 has the highest production rate of H2O2 and AA.

[0060] The performance of the catalyst in Example 1 was tested under different Au loading levels. Figure 3 As shown, with the increase of Au loading, the production rates of H2O2 and AA show a trend of first increasing and then decreasing, which may be due to Au agglomeration caused by excessive Au loading.

[0061] By optimizing different Au loadings, the H2O2 production rate can reach 2.0 mmol g. -1 h -1 The AA production efficiency was 3.7 mmol g. -1 h -1 Meanwhile, high performance liquid chromatography (HPLC) tests showed that the selectivity of the product acetic acid exceeded 99.0%.

[0062] Furthermore, the formation of AA and H2O2 was evaluated using the catalyst from Example 1 in catalytic systems without O2 or LA. Figure 4 As shown, the results indicate that both the AA production efficiency and the H2O2 precipitation rate decreased. These results suggest that only by using PLA pretreated solution as a sacrificial agent to consume holes in the photocatalytic H2O2 generation can the electrons and holes of the Au@BCN photocatalyst be fully utilized and the reaction efficiency improved.

[0063] In summary, based on the reaction mechanism of photocatalytic O2 reduction to H2O2 synthesis and selective oxidation of PLA pretreatment solution, this invention designs and synthesizes Au@BCN photocatalyst. By utilizing Au and B sites as electron and hole enrichment centers, respectively, it simultaneously achieves efficient O2 reduction and highly selective oxidation of PLA pretreatment solution under visible light drive. This fully utilizes electrons and holes, effectively reduces energy consumption and environmental pollutant emissions, and realizes the simultaneous production of H2O2 and high-value-added chemicals, resulting in significant environmental and economic benefits.

[0064] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming, characterized in that, include, NaBH3-CN was introduced as a B source and mixed with carbon nitride and calcined to obtain B-doped carbon nitride; subsequently, the noble metal precursor was mixed with the B-doped carbon nitride dispersion and the noble metal precursor was photodeposited onto the B-doped carbon nitride. The reaction yielded a catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming.

2. The method for preparing the catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming according to claim 1, characterized in that, The noble metal precursor is at least one of HAuCl4·3H2O, AgNO3, Cl4H8N2Pd, KPdCl4, H2PtCl6·6H2O, and KRuCl6. The concentration of B-doped carbon nitride is 0.5-1 mg / mL; The mass ratio of the noble metal precursor to the B-doped carbon nitride dispersion is 0.01-0.1:

1.

3. The method for preparing the catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming according to claim 1, characterized in that, The mass ratio of NaBH3-CN to carbon nitride is 0.1-0.5:

1.

4. The method for preparing the catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming according to claim 1, characterized in that, The carbon nitride is obtained by calcination of a carbon nitride precursor; the carbon nitride precursor is at least one of urea, dicyandiamine, and melamine; the calcination temperature for preparing carbon nitride is 400-600°C. o C, calcination time is 3-5h; the calcination temperature for preparing B-doped carbon nitride is 300~500℃, and the calcination time is 0.5~2h.

5. A catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming, characterized in that, The catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming, as described in any one of claims 1-4, was obtained.

6. The application of the photocatalytic synthesis of H2O2 coupled with PLA reforming as described in claim 5 in the simultaneous reduction of O2 to prepare H2O2 and selective oxidation of PLA pretreatment solution under light irradiation.

7. The application according to claim 6, characterized in that, include: The catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming was mixed with PLA pretreatment liquid, and high-purity air was introduced to remove impurity gases to obtain the catalytic reaction system. The catalytic reaction system is subjected to photocatalytic reaction under light irradiation.

8. The application according to claim 7, characterized in that, The ratio of the catalyst for photocatalytic synthesis of H2O2 coupled with PLA reforming to the PLA pretreatment solution is 5-20 mg: 5-20 mL. The concentration of the PLA pretreatment solution is 0.1-1 mg / mL.

9. The application according to claim 7, characterized in that, The light source is at least one of xenon lamp, LED lamp, fluorescent lamp or sunlight; The photocatalytic temperature is 30-50℃.

10. The application according to any one of claims 6-9, characterized in that, Before carrying out the photocatalytic reaction under light, the catalytic reaction system is stirred at 400-600 rpm for 30-60 minutes in a dark environment to ensure that the catalytic reaction system reaches adsorption-desorption equilibrium.

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