Catalyst for bioenergy conversion, preparation method and application

Abstract

The present invention discloses a catalyst, preparation method and application for bioenergy conversion. With g-C3N4 nanosheets as loading objects, CdS / rGO is loaded on g-C3N4 to obtain a g-C3N4 / rGO / CdS photocatalyst, wherein the mass fraction of CdS is 5%, the mass fraction of reduced graphene oxide nanosheets is 0.5% to 8%, and the remainder is g-C3N4. While enhancing visible light absorption and carrier separation, g-C3N4 and rGO, as oxidation reaction sites and reduction reaction sites, respectively, have π-π effects with lignin model objects, effectively improving charge utilization, and can achieve efficient C-C bond selective cracking in lignin. The catalyst raw materials prepared by the present invention are cheap and easy to obtain, the process is simple and safe, the requirements for equipment are relatively low, the reaction conditions are highly controllable, the lignin model object is low in cost, does not consume fossil resources, and has great advantages in the application of bioenergy conversion.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst preparation technology and biorefining, and particularly relates to a catalyst for bioenergy conversion, a preparation method and an application thereof. Background Art

[0002] Lignin, the most abundant renewable aromatic natural polymer on Earth, can provide high-value-added aromatic monomers, has the potential to replace fossil resources, and is an important bioenergy source. However, due to the defects and complex structure of lignin itself, it is difficult to achieve efficient bioenergy conversion. The aromatic groups in lignin are mainly connected by CC bonds and CO bonds. Therefore, selectively cleaving CC bonds and CO bonds while keeping the aromatic groups intact is the key to depolymerizing lignin. Since 2-phenoxy-1-phenylethanol (β-O-4 type) lignin accounts for 43-62% of natural lignin and has both CC bonds and CO bonds, β-O-4 type lignin is usually the focus of depolymerization research. Using semiconductor photocatalytic technology to selectively cleave CC / CO bonds in lignin model compounds under mild conditions to obtain valuable aromatic monomers has become a forward-looking technology for solving energy problems and has attracted great interest from scientists. Although there have been increasing reports in recent years on the successful selective cleavage of CO bonds by photocatalysts, suitable photocatalysts for breaking CC bonds remain scarce. This is because the dissociation energy of CC bonds (264.3 kJ / mol) is greater than that of CO bonds (247.9 kJ / mol), which has become a bottleneck restricting the development of depolymerized lignin. In addition, excellent photocatalytic effects require that the three cascade processes of light capture, photogenerated charge, and charge utilization are all at their optimal conditions. Therefore, the adsorption of lignin model compounds at the oxidation and reduction sites is the key to selective catalysis.

[0003] Graphitic carbon nitride (g-C3N4) has become a hot topic in the field of photocatalysis due to its low cost, ease of fabrication, environmental friendliness, and high stability. Previous studies have demonstrated that g-C3N4 exhibits a strong π-π conjugation effect with a β-O-4 model compound, promoting the cleavage of C-C bonds in the β-O-4 model compound. However, bare g-C3N4 exhibits inherent drawbacks, such as a wide band gap (2.7 eV), a narrow visible light absorption range, and enhanced carrier recombination due to its π-conjugated polymeric structure. These limitations result in low yields of aromatic monomers and require a strict ultraviolet (UV) light environment, which accounts for less than 5% of the solar spectrum. This severely limits its further application in the study of C-C bond cleavage in lignin.

[0004] In summary, in recent years, corresponding progress has been made in the study of CC bond cleavage in β-O-4 lignin model compounds, but the yield of depolymerization products of β-O-4 lignin model compounds under visible light is still low. Although coupling with CdS can overcome the inherent shortcomings of g-C3N4, the separation efficiency of photogenerated charges and the adsorption of lignin model compounds by reduction sites are still serious problems. Summary of the Invention

[0005] In response to the above-mentioned deficiencies in the prior art, the present invention provides a catalyst, preparation method, and application for bioenergy conversion, which effectively improves the light response range of the catalyst and inhibits the recombination of electron-hole pairs, provides optimal redox sites, and overcomes the problem in the prior art of low yield of aromatic monomers obtained by selectively breaking CC bonds of lignin under visible light.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve the technical problem is:

[0007] A catalyst for bioenergy conversion, comprising g-C3N4 nanosheets, on which CdS and reduced graphene oxide are loaded;

[0008] Reduction of graphene oxide into nanosheets;

[0009] The diameter of CdS is 2 to 3 μm.

[0010] Optionally, it is prepared by combining g-C3N4 nanosheets, reduced graphene oxide rGO and CdS nanoparticles;

[0011] Calculated by mass percentage, the mass fraction of CdS is 5%, the mass fraction of reduced graphene oxide nanosheets is 0.5% to 8%, and the balance is g-C3N4.

[0012] The preparation method of the catalyst for bioenergy conversion according to the present invention comprises:

[0013] Protonated CdS was prepared, and then CdS / rGO was prepared. The aqueous solution of CdS / rGO was mixed with the methanol solution of g-C3N4 nanosheets, dried and then heated to obtain g-C3N4 / rGO / CdS;

[0014] The mass of reduced graphene oxide accounts for 10% to 160% of the mass of CdS, the solid-liquid ratio of CdS / rGO to water is 1 g:1000 mL, the solid-liquid ratio of g-C3N4 nanosheets to methanol is 1 g:50 to 60 mL, and the solid-liquid ratio of g-C3N4 nanosheets to CdS / rGO aqueous solution is 1 g:50 mL.

[0015] Optionally, the preparation of protonated CdS includes:

[0016] CdS was added to a 0.5 mol / L HCl aqueous solution and sonicated, and the CdS stripped from the acid suspension was vigorously stirred at room temperature for further protonation. Protonated CdS was obtained after centrifugation, washing, and drying.

[0017] The solid-liquid ratio of CdS and HCl aqueous solution is 1 g:200-300 mL.

[0018] Optionally, the preparation of CdS / rGO includes:

[0019] Protonated CdS and reduced graphene oxide were added to water, ultrasonically treated, and stirred at room temperature to obtain a mixed solution. 0.1 g / mL NaBH4 solution was added to the mixed solution, and stirring was continued at 80°C. The mixed solution was cooled to room temperature, centrifuged, washed, and dried to obtain CdS / rGO; wherein the solid-liquid ratio of protonated CdS to water was 1 g:700-800 mL, the solid-liquid ratio of graphene oxide to water was 1 g:200-300 mL, and the volume ratio of NaBH4 solution to the mixed solution was 1:5.

[0020] Optionally, CdS is added to a 0.5 mol / L HCl aqueous solution and subjected to ultrasonic treatment, followed by stirring. The ultrasonic treatment time is 1 to 2 h, and the stirring time is 4 to 5 h.

[0021] Protonated CdS and reduced graphene oxide are added to water, ultrasonically treated for 1 to 3 hours, and then stirred at room temperature for 1 to 1.5 hours.

[0022] Optionally, the preparation of g-C3N4 / rGO / CdS includes:

[0023] The prepared CdS / rGO was added to water to obtain a CdS / rGO aqueous solution; g-C3N4 nanosheets were dispersed in methanol, and the CdS / rGO aqueous solution was added. After drying in a water bath at 80°C, the mixture was heated at 180°C to obtain g-C3N4 / rGO / CdS.

[0024] Optionally, after adding NaBH4 solution to the mixture, stirring time at 80°C is 3 to 4 hours, and heating time at 180°C is 2 to 3 hours.

[0025] Optionally, the preparation method of the g-C3N4 nanosheets includes:

[0026] Melamine was heated at 550°C in a muffle furnace at a heating rate of 2.3°C / min for 4 hours to obtain g-C3N4 blocks; the g-C3N4 blocks were ground into powder and placed in a muffle furnace at 520°C for 5 hours at a heating rate of 5°C / min to obtain g-C3N4 nanosheets.

[0027] The catalyst for bioenergy conversion of the present invention selectively breaks down lignin β-O-4 model compound C in photocatalysis. α -C β Application in key.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] 1) The catalyst for bioenergy conversion prepared by the present invention uses g-C3N4 nanosheets as a carrier and CdS as a photosensitizer. The synergistic effect of g-C3N4 and CdS improves the response ability of g-C3N4 to visible light in the photocatalytic reaction, while enhancing the anti-photocorrosion ability of CdS. In addition, the internal electric field formed between g-C3N4 and CdS can accelerate electron transfer and inhibit the recombination of photogenerated electron-hole pairs, thereby improving the photocatalytic performance.

[0030] 2) The catalyst for bioenergy conversion prepared by the present invention uses rGO as a solid electron medium, which further promotes charge transfer. g-C3N4 and rGO, as oxidation reaction sites and reduction reaction sites, respectively, have π-π interactions with the lignin model, effectively improving charge utilization. In addition, the π-π interaction between rGO and g-C3N4 helps to form a tightly structured ternary composite photocatalyst between g-C3N4, CdS and rGO, thereby enhancing the stability of the photocatalyst.

[0031] 3) The catalyst for bioenergy conversion prepared by the present invention has a relatively efficient depolymerization ability for the CC bonds in the β-O-4 lignin model. The operation method is simple, the reagents are cheap, and it can be used for large-scale low-cost preparation, which has great advantages in promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings:

[0033] Figure 1 XRD patterns of CdS and g-C3N4 prepared in the present invention and the composite catalyst prepared in Example 1;

[0034] Figure 2 is a SEM image of the g-C3N4 / rGO / CdS composite catalyst prepared in Example 1;

[0035] Figure 3 TEM image of the g-C3N4 / rGO / CdS composite catalyst prepared in Example 1;

[0036] Figure 4 This is the EDS spectrum of the g-C3N4 / rGO / CdS composite catalyst prepared in Example 1;

[0037] Figure 5 PL spectra of g-C3N4 prepared in the present invention and g-C3N4 / rGO / CdS composite catalyst prepared in Example 1;

[0038] Figure 6 A comparison chart showing the substrate conversion and target product yield of the CdS and g-C3N4 prepared in the present invention and the g-C3N4 / rGO / CdS composite catalyst prepared in Examples 1 to 5 for selectively cleaving CC bonds in a β-O-4 lignin model;

[0039] Figure 7 This is a graph showing the cycling experimental results of the g-C3N4 / rGO / CdS composite catalyst prepared in Example 1. DETAILED DESCRIPTION

[0040] rGO, reduced graphene oxide;

[0041] The present invention uses g-C3N4 nanosheets as the loading object, and loads CdS / rGO on g-C3N4 to obtain a g-C3N4 / rGO / CdS photocatalyst, wherein the mass fraction of CdS is 5%, the mass fraction of reduced graphene oxide nanosheets is 0.5% to 8%, and the balance is g-C3N4. While enhancing visible light absorption and carrier separation, g-C3N4 and rGO, as oxidation reaction sites and reduction reaction sites, respectively, have π-π interactions with the lignin model, effectively improving charge utilization and achieving efficient C-C bond selective cleavage in lignin. The catalyst prepared by the present invention has cheap and easily available raw materials, a simple and safe process, low equipment requirements, and highly controllable reaction conditions. The lignin model is low-cost and does not consume fossil resources, which has great advantages in the application of bioenergy conversion.

[0042] The catalyst for bioenergy conversion of the present invention is prepared by compositely preparing g-C3N4 nanosheets, reduced graphene oxide rGO and CdS nanoparticles, wherein the mass fraction of CdS is 5%, the mass fraction of reduced graphene oxide nanosheets is 0.5% to 8%, and the balance is g-C3N4.

[0043] The present invention also discloses a method for preparing the catalyst for bioenergy conversion, which comprises the following steps:

[0044] (1) Preparation of g-C3N4: Melamine was heated in a muffle furnace at a temperature of 550°C for 4 h at a heating rate of 2.3°C / min to obtain g-C3N4 bulk. The g-C3N4 bulk was then ground into powder and placed in a muffle furnace at a temperature of 520°C for 5 h at a heating rate of 5°C / min to obtain g-C3N4 nanosheets.

[0045] (2) Preparation of protonated CdS: CdS was added to a 0.5 mol / L HCl aqueous solution and sonicated. The CdS stripped from the acid suspension was vigorously stirred at room temperature for further protonation, washed by centrifugation, and dried to obtain protonated CdS; wherein the solid-to-liquid ratio of CdS to the HCl aqueous solution was 1 g:200-300 mL;

[0046] (3) Preparation of CdS / rGO: The protonated CdS and graphene oxide prepared in step (2) were added to deionized water, respectively, and ultrasonically treated. The two were then mixed and ultrasonicated, stirred at room temperature, and a 0.1 g / mL NaBH4 solution was added to the mixture. The mixture was stirred at 80°C, cooled to room temperature, centrifuged, washed, and dried to obtain CdS / rGO; wherein the solid-liquid ratio of protonated CdS to water was 1 g:700-800 mL, the solid-liquid ratio of graphene oxide to water was 1 g:200-300 mL, the volume ratio of NaBH4 solution to the mixed solution was 1:5, and the mass of graphene oxide accounted for 10%-160% of the mass of CdS;

[0047] (4) Preparation of g-C3N4 / rGO / CdS: CdS / rGO prepared in step (3) was added to deionized water to obtain a CdS / rGO aqueous solution; g-C3N4 prepared in step (1) was dispersed in methanol, the CdS / rGO aqueous solution was added, the mixture was dried in a water bath at 80°C, and then heated at 180°C to obtain g-C3N4 / rGO / CdS; wherein the solid-liquid ratio of CdS / rGO to deionized water was 1 g:1000 mL, the solid-liquid ratio of g-C3N4 to methanol was 1 g:50-60 mL, and the solid-liquid ratio of g-C3N4 to CdS / rGO solution was 1 g:50 mL.

[0048] Furthermore, the ultrasonic time in step (2) is 1 to 2 hours.

[0049] Furthermore, the stirring time in step (2) is 4 to 5 hours.

[0050] Furthermore, in step (3), the protonated CdS and graphene oxide are added to water respectively, and the ultrasonic treatment time is 1 to 2 hours.

[0051] Furthermore, in step (3), the protonated CdS and graphene oxide suspension are mixed and ultrasonically treated for 2 to 3 hours.

[0052] Furthermore, in step (3), NaBH4 solution is added to the mixture and stirred at 80°C for 3 to 4 hours.

[0053] Furthermore, the heating time at 180° C. in step (4) is 2 to 3 hours.

[0054] The invention also discloses the application of the catalyst for bioenergy conversion in photocatalytic selective cleavage of CC bonds in a β-O-4 lignin model compound.

[0055] The present invention loads a small amount of CdS and reduced graphene oxide (rGO) on g-C3N4 nanosheets, forming a heterojunction with g-C3N4, inhibiting the recombination of photogenerated electrons and holes, and allowing electrons and holes to better participate in the breakage reaction of the C-C bond in the β-O-4 model. The reduced graphene oxide (rGO) involved in the recombination acts as a conductive medium, transferring a large amount of charge to the rGO nanosheets, separating the electrons and holes, and further inhibiting the combination of the two. The g-C3N4 nanosheets and rGO nanosheets sandwich the CdS particles in the middle, allowing the heterojunction to be more tightly combined. As planar structures, the g-C3N4 nanosheets and rGO nanosheets can be better adsorbed by the β-O-4 model, increasing the reaction area; the composite material of the present invention is used for the first time in the field of depolymerization of lignin (or bioenergy conversion), and its ability to depolymerize lignin is indeed improved compared to g-C3N4.

[0056] The present invention will be further described in detail below with reference to specific embodiments, which are intended to explain the present invention rather than to limit it.

[0057] Example 1:

[0058] (1) Preparation of g-C3N4: Melamine was heated in a muffle furnace at 550°C for 4 h at a heating rate of 2.3°C / min to obtain g-C3N4 bulk. The g-C3N4 bulk was ground into powder and placed in a muffle furnace at 520°C for 5 h at a heating rate of 5°C / min to obtain g-C3N4 nanosheets.

[0059] (2) Preparation of protonated CdS: 0.2 g of CdS was added to 40 mL of 0.5 mol / L HCl aqueous solution, ultrasonicated for 1 h, stirred for 4 h, washed by centrifugation, and dried to obtain protonated CdS.

[0060] (3) Preparation of CdS / rGO: 0.1 g of protonated CdS and 0.06 g of graphene oxide prepared in step (2) were added to 80 mL and 20 mL of deionized water, respectively. After ultrasonic treatment for 1 h, the mixture was mixed and ultrasonicated for 2 h. The mixture was stirred for 1 h. 0.1 g / mL NaBH4 solution was added to the mixture. The mixture was stirred at 80°C for 3 h. The mixture was cooled to room temperature, centrifuged, washed, and dried to obtain CdS / rGO.

[0061] The present invention does not specifically limit the specific source of the GO, which can be commercially available or prepared by the Hummers oxidation method or other methods.

[0062] (4) Preparation of g-C3N4 / rGO / CdS: 0.2 g of g-C3N4 was dispersed in 10 mL of methanol, 5 mL of CdS / rGO (1 mg / mL) was added, and the mixture was dried in a water bath at 80 °C and heated at 180 °C for 2 h to obtain g-C3N4 / rGO / CdS.

[0063] The purity and crystal phase composition of the samples were determined by X-ray diffractometer (XRD). Figure 1 As shown in the figure, the g-C3N4 / rGO / CdS composite catalyst has four obvious diffraction peaks, corresponding to the (100) and (002) crystal planes of g-C3N4 and the (110) and (112) crystal planes of CdS, respectively, indicating that CdS nanoparticles have been successfully incorporated. No characteristic peaks of rGO were observed in the composite, which may be due to the low weight loading of rGO contained in the composite (<4%) and the low X-ray diffraction intensity.

[0064] The morphology of g-C3N4 / rGO / CdS composite catalyst was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Figure 2 As shown in Figure 2, it can be clearly seen that CdS and rGO are uniformly dispersed on the surface of g-C3N4. Figure 3 It can also be seen that g-C3N4, rGO, and CdS coexist in the g-C3N4 / rGO / CdS composite catalyst, and CdS and rGO are stacked on g-C3N4. This provides evidence for the successful synthesis of the g-C3N4 / rGO / CdS composite catalyst, and the close contact of the components is conducive to the formation of a dense heterojunction, thereby improving the photocatalytic activity of the composite catalyst.

[0065] The elemental composition of g-C3N4 / rGO / CdS composite catalyst was detected by EDS element scanning analysis, such as Figure 4 , the simultaneous appearance of C, N, O, S and Cd elements in the composite catalyst proves the successful preparation of g-C3N4 / rGO / CdS composite catalyst.

[0066] Steady-state fluorescence (PL) spectroscopy was used to study the separation efficiency of photogenerated carriers in g-C3N4 and g-C3N4 / rGO / CdS composite catalysts. Figure 5 As shown in the figure, g-C3N4 exhibits a very strong fluorescence emission peak intensity, which is a typical feature of a large number of carriers severely binding and releasing energy. The PL signal of the g-C3N4 / rGO / CdS composite catalyst is much weaker, indicating that the recombination of photogenerated charges and holes is effectively suppressed after loading CdS and rGO on g-C3N4, which is beneficial to improve the photocatalytic activity.

[0067] A quartz bottle was filled with 1 mg of lignin β-O-4 model, 10 mg of catalyst, and 1 mL of CH3CN solvent. O2 was then introduced, the quartz bottle was sealed, and placed under light. The reaction mixture was stirred at 500 r / min for 200 min. A condenser was used to cool the photocatalytic system. After the reaction, the product was analyzed using high-performance liquid chromatography.

[0068] After the above test, if Figure 6 As shown, the lignin β-O-4 model achieved a 95% conversion rate under the action of the photocatalyst, including a 71% benzaldehyde yield and a 69% phenyl formate yield.

[0069] After the photocatalytic test, the g-C3N4 / rGO / CdS composite catalyst was collected and washed and dried with CH3CN solvent. It was then used again for the depolymerization reaction of lignin β-O-4 model according to the test requirements. This cycle was repeated 5 times to evaluate the stability of the composite catalyst. Figure 7 As shown in the figure, the activity of the g-C3N4 / rGO / CdS ternary composite catalyst decreased slightly after 5 uses, but still maintained a high level of catalytic depolymerization, indicating that the g-C3N4 / rGO / CdS composite material has good stability.

[0070] The lignin β-O-4 model substance used in the present invention is 2-phenoxy-1-phenylethanol, which is purchased from Aladdin Chemical Reagent.

[0071] Example 2:

[0072] (1) Preparation of g-C3N4: Melamine was heated in a muffle furnace at 550°C for 4 h at a heating rate of 2.3°C / min to obtain g-C3N4 bulk. The g-C3N4 bulk was ground into powder and placed in a muffle furnace at 520°C for 5 h at a heating rate of 5°C / min to obtain g-C3N4 nanosheets.

[0073] (2) Preparation of protonated CdS: 0.2 g of CdS was added to 40 mL of 0.5 mol / L HCl aqueous solution, ultrasonicated for 1 h, stirred for 4 h, washed by centrifugation, and dried to obtain protonated CdS.

[0074] (3) Preparation of CdS / rGO: 0.1 g of protonated CdS and 0.01 g of graphene oxide prepared in step (2) were added to 80 mL and 20 mL of deionized water, respectively. After ultrasonic treatment for 1 h, the mixture was mixed and ultrasonicated for 2 h. The mixture was stirred for 1 h. 20 mL of 0.1 g / mL NaBH4 solution was added to the mixture. The mixture was stirred at 80°C for 3 h. The mixture was cooled to room temperature, centrifuged, washed, and dried to obtain CdS / rGO.

[0075] The present invention does not specifically limit the specific source of the GO, which can be commercially available or prepared by the Hummers oxidation method or other methods.

[0076] (4) Preparation of g-C3N4 / rGO / CdS: 0.2 g of g-C3N4 was dispersed in 10 mL of methanol, 5 mL of CdS / rGO (1 mg / mL) was added, and the mixture was dried in a water bath at 80 °C and heated at 180 °C for 2 h to obtain g-C3N4 / rGO / CdS.

[0077] A quartz bottle was filled with 1 mg of lignin β-O-4 model, 10 mg of catalyst, and 1 mL of CH3CN solvent. O2 was then introduced, the quartz bottle was sealed, and placed under light. The reaction mixture was stirred at 500 r / min for 200 min. A condenser was used to cool the photocatalytic system. After the reaction, the product was analyzed using high-performance liquid chromatography.

[0078] After the above test, if Figure 6 As shown, the lignin β-O-4 model achieved a 66% conversion rate under the action of the photocatalyst, including a 49% benzaldehyde yield and a 24% phenyl formate yield.

[0079] The lignin β-O-4 model substance used in the present invention is 2-phenoxy-1-phenylethanol, which is purchased from Aladdin Chemical Reagent.

[0080] Example 3:

[0081] (1) Preparation of g-C3N4: Melamine was heated in a muffle furnace at 550°C for 4 h at a heating rate of 2.3°C / min to obtain g-C3N4 bulk. The g-C3N4 bulk was ground into powder and placed in a muffle furnace at 520°C for 5 h at a heating rate of 5°C / min to obtain g-C3N4 nanosheets.

[0082] (2) Preparation of protonated CdS: 0.2 g of CdS was added to 40 mL of 0.5 mol / L HCl aqueous solution, ultrasonicated for 1 h, stirred for 4 h, washed by centrifugation, and dried to obtain protonated CdS.

[0083] (3) Preparation of CdS / rGO: 0.1 g of protonated CdS and 0.02 g of graphene oxide prepared in step (2) were added to 80 mL and 20 mL of deionized water, respectively. After ultrasonic treatment for 1 h, the mixture was mixed and ultrasonicated for 2 h. The mixture was stirred for 1 h. 0.1 g / mL NaBH4 solution was added to the mixture. The mixture was stirred at 80°C for 3 h. The mixture was cooled to room temperature, centrifuged, washed, and dried to obtain CdS / rGO.

[0084] The present invention does not specifically limit the specific source of the GO, which can be commercially available or prepared by the Hummers oxidation method or other methods.

[0085] (4) Preparation of g-C3N4 / rGO / CdS: 0.2 g of g-C3N4 was dispersed in 10 mL of methanol, 5 mL of CdS / rGO (1 mg / mL) was added, and the mixture was dried in a water bath at 80 °C and heated at 180 °C for 2 h to obtain g-C3N4 / rGO / CdS.

[0086] A quartz bottle was filled with 1 mg of lignin β-O-4 model, 10 mg of catalyst, and 1 mL of CH3CN solvent. O2 was then introduced, the quartz bottle was sealed, and placed under light. The reaction mixture was stirred at 500 r / min for 200 min. A condenser was used to cool the photocatalytic system. After the reaction, the product was analyzed using high-performance liquid chromatography.

[0087] After the above test, if Figure 6 As shown, the lignin β-O-4 model achieved a 93% conversion rate under the action of the photocatalyst, including a 62% benzaldehyde yield and a 37% phenyl formate yield.

[0088] The lignin β-O-4 model substance used in the present invention is 2-phenoxy-1-phenylethanol, which is purchased from Aladdin Chemical Reagent.

[0089] Example 4:

[0090] (1) Preparation of g-C3N4: Melamine was heated in a muffle furnace at 550°C for 4 h at a heating rate of 2.3°C / min to obtain g-C3N4 bulk. The g-C3N4 bulk was ground into powder and placed in a muffle furnace at 520°C for 5 h at a heating rate of 5°C / min to obtain g-C3N4 nanosheets.

[0091] (2) Preparation of protonated CdS: 0.2 g of CdS was added to 40 mL of 0.5 mol / L HCl aqueous solution, ultrasonicated for 1 h, stirred for 4 h, washed by centrifugation, and dried to obtain protonated CdS.

[0092] (3) Preparation of CdS / rGO: 0.1 g of protonated CdS and 0.1 g of graphene oxide prepared in step (2) were added to 80 mL and 20 mL of deionized water, respectively. After ultrasonic treatment for 1 h, the mixture was mixed and ultrasonicated for 2 h. The mixture was stirred for 1 h. 0.1 g / mL NaBH4 solution was added to the mixture. The mixture was stirred at 80°C for 3 h. The mixture was cooled to room temperature, centrifuged, washed, and dried to obtain CdS / rGO.

[0093] The present invention does not specifically limit the specific source of the GO, which can be commercially available or prepared by the Hummers oxidation method or other methods.

[0094] (4) Preparation of g-C3N4 / rGO / CdS: 0.2 g of g-C3N4 was dispersed in 10 mL of methanol, 5 mL of CdS / rGO (1 mg / mL) was added, and the mixture was dried in a water bath at 80 °C and heated at 180 °C for 2 h to obtain g-C3N4 / rGO / CdS.

[0095] A quartz bottle was filled with 1 mg of lignin β-O-4 model, 10 mg of catalyst, and 1 mL of CH3CN solvent. O2 was then introduced, the quartz bottle was sealed, and placed under light. The reaction mixture was stirred at 500 r / min for 200 min. A condenser was used to cool the photocatalytic system. After the reaction, the product was analyzed using high-performance liquid chromatography.

[0096] After the above test, if Figure 6 As shown, the lignin β-O-4 model achieved an 89% conversion rate under the action of the photocatalyst, including a 62% benzaldehyde yield and a 38% phenyl formate yield.

[0097] The lignin β-O-4 model substance used in the present invention is 2-phenoxy-1-phenylethanol, which is purchased from Aladdin Chemical Reagent.

[0098] Example 5:

[0099] (1) Preparation of g-C3N4: Melamine was heated in a muffle furnace at 550°C for 4 h at a heating rate of 2.3°C / min to obtain g-C3N4 bulk. The g-C3N4 bulk was ground into powder and placed in a muffle furnace at 520°C for 5 h at a heating rate of 5°C / min to obtain g-C3N4 nanosheets.

[0100] (2) Preparation of protonated CdS: 0.2 g of CdS was added to 40 mL of 0.5 mol / L HCl aqueous solution, ultrasonicated for 1 h, stirred for 4 h, washed by centrifugation, and dried to obtain protonated CdS.

[0101] (3) Preparation of CdS / rGO: 0.1 g of protonated CdS and 0.16 g of graphene oxide prepared in step (2) were added to 80 mL and 20 mL of deionized water, respectively. After ultrasonic treatment for 1 h, the mixture was mixed and ultrasonicated for 2 h. The mixture was stirred for 1 h. 0.1 g / mL NaBH4 solution was added to the mixture. The mixture was stirred at 80°C for 3 h. The mixture was cooled to room temperature, centrifuged, washed, and dried to obtain CdS / rGO.

[0102] The present invention does not specifically limit the specific source of the GO, which can be commercially available or prepared by the Hummers oxidation method or other methods.

[0103] (4) Preparation of g-C3N4 / rGO / CdS: 0.2 g of g-C3N4 was dispersed in 10 mL of methanol, 5 mL of CdS / rGO (1 mg / mL) was added, and the mixture was dried in a water bath at 80 °C and heated at 180 °C for 2 h to obtain g-C3N4 / rGO / CdS.

[0104] A quartz bottle was filled with 1 mg of lignin β-O-4 model, 10 mg of catalyst, and 1 mL of CH3CN solvent. O2 was then introduced, the quartz bottle was sealed, and placed under light. The reaction mixture was stirred at 500 r / min for 200 min. A condenser was used to cool the photocatalytic system. After the reaction, the product was analyzed using high-performance liquid chromatography.

[0105] After the above test, if Figure 6 As shown, the lignin β-O-4 model achieved a conversion rate of 79% under the action of the photocatalyst, including a benzaldehyde yield of 57% and a phenyl formate yield of 32%.

[0106] The lignin β-O-4 model substance used in the present invention is 2-phenoxy-1-phenylethanol, which is purchased from Aladdin Chemical Reagent.

[0107] The CdS used in the above examples can be purchased directly or prepared in-house. The CdS preparation method is as follows: Cd(NO₃)₂·4H₂O and Na₂S·9H₂O are added to deionized water separately and stirred evenly. The Na₂S·9H₂O solution is then added dropwise to the Cd(NO₃)₂·4H₂O solution, and stirring is continued for 0.5 h. The solution is then maintained at 180°C for 12 h. After the reaction is complete, the resulting sample is washed three times alternately with deionized water and ethanol, then dried in an oven at 80°C for 8 h to obtain CdS. The molar ratio of Cd(NO₃)₂·4H₂O to Na₂S·9H₂O is 1:1.

[0108] Examples 6-8:

[0109] In order to study whether the composite photocatalyst of the present invention is effective in depolymerizing other different lignin β-O-4 models, three other lignin β-O-4 models containing methoxy or hydroxyl substituents were selected for performance testing.

[0110] 1 mg of other lignin β-O-4 model, 10 mg of the catalyst prepared in Example 3, and 1 mL of CH3CN solvent were added to a quartz bottle, and O2 was filled in. The quartz bottle was sealed and placed under light. The reaction mixture was stirred at a speed of 500 r / min for 200 min. The photocatalytic system was cooled using a condenser. After the reaction was completed, the product was analyzed by high performance liquid chromatography. The results are shown in Table 1.

[0111] Table 1 Photocatalytic depolymerization of other different lignin β-O-4 models

[0112]

[0113] The following is the control group, which includes two groups of experiments:

[0114] Group 1:

[0115] Add 1 mg of lignin β-O-4 model, 10 mg of g-C3N4, and 1 mL of CH3CN solvent to a quartz bottle, fill it with O2, seal the quartz bottle and place it under light. Stir the reaction mixture at 500 r / min for 200 minutes. Use a condenser to cool the photocatalytic system. After the reaction is completed, use high-performance liquid chromatography to analyze the product.

[0116] After the above test, if Figure 6 As shown, the lignin β-O-4 model achieved a 25% conversion rate under the action of the photocatalyst, including a 23% benzaldehyde yield and a 19% phenyl formate yield.

[0117] The lignin β-O-4 model substance used in the present invention is 2-phenoxy-1-phenylethanol, which is purchased from Aladdin Chemical Reagent.

[0118] Group 2:

[0119] A quartz bottle was filled with 1 mg of lignin β-O-4 model, 10 mg of CdS, and 1 mL of CH3CN solvent. O2 was then introduced, the quartz bottle was sealed, and the reaction mixture was stirred at 500 r / min for 200 min. The photocatalytic system was cooled using a condenser. After the reaction, the product was analyzed using high-performance liquid chromatography.

[0120] After the above test, if Figure 6 As shown, the lignin β-O-4 model has no conversion rate under the action of this photocatalyst.

[0121] The lignin β-O-4 model substance used in the present invention is 2-phenoxy-1-phenylethanol, which is purchased from Aladdin Chemical Reagent.

[0122] In summary, the g-C3N4 / rGO / CdS composite photocatalyst prepared by the present invention has good depolymerization performance for the CC bond in the β-O-4 lignin model, and the preparation process is simple, which has great advantages in promotion and application.

[0123] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0124] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0125] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A catalyst for bioenergy conversion, characterized in that: The invention comprises g-C3N4 nanosheets, on which CdS and reduced graphene oxide are loaded; the reduced graphene oxide is a nanosheet; the diameter of the CdS is 2 to 3 μm; The composite is prepared by g-C3N4 nanosheets, reduced graphene oxide rGO and CdS nanoparticles; in terms of mass percentage, the mass fraction of CdS is 5%, the mass fraction of reduced graphene oxide nanosheets is 0.5% to 8%, and the balance is g-C3N4; CdS and reduced graphene oxide are loaded on g-C3N4 nanosheets to form a heterojunction with g-C3N4; The preparation method includes: preparing protonated CdS, then preparing CdS / rGO, adding the prepared CdS / rGO to water to obtain a CdS / rGO aqueous solution; dispersing g-C3N4 nanosheets in methanol, adding the CdS / rGO aqueous solution, drying in a water bath at 80°C, and heating at 180°C to obtain g-C3N4 / rGO / CdS; the preparation method of the g-C3N4 nanosheets includes: heating melamine in a muffle furnace at a heating rate of 2.3°C / min and maintaining it at 550°C for 4 hours to obtain a g-C3N4 block; grinding the g-C3N4 block into powder, placing it in a muffle furnace at a heating rate of 5°C / min and maintaining it at 520°C for 5 hours to obtain a g-C3N4 nanosheet; The preparation of protonated CdS comprises: adding CdS to a 0.5 mol / L HCl aqueous solution and ultrasonically treating it, then vigorously stirring the CdS stripped from the acid suspension at room temperature to further protonate it, and then centrifuging, washing, and drying to obtain the protonated CdS; The preparation of CdS / rGO comprises: adding protonated CdS and graphene oxide to water, ultrasonically treating, stirring at room temperature to obtain a mixed solution, adding 0.1 g / mL NaBH4 solution to the mixed solution, continuing stirring at 80°C, cooling to room temperature, centrifuging, washing and drying to obtain CdS / rGO.

2. A method for preparing a catalyst for bioenergy conversion according to claim 1, characterized in that: The preparation method comprises: Protonated CdS was prepared, followed by CdS / rGO, which was then added to water to obtain a CdS / rGO aqueous solution. g-C3N4 nanosheets were dispersed in methanol, the CdS / rGO aqueous solution was added, and the mixture was dried in a water bath at 80°C and then heated at 180°C to obtain g-C3N4 / rGO / CdS. The mass of reduced graphene oxide accounts for 10% to 160% of the mass of CdS, the solid-liquid ratio of CdS / rGO to water is 1 g:1000 mL, the solid-liquid ratio of g-C3N4 nanosheets to methanol is 1 g:50-60 mL, and the solid-liquid ratio of g-C3N4 nanosheets to CdS / rGO aqueous solution is 1 g:50 mL; The preparation method of g-C3N4 nanosheets comprises: heating melamine in a muffle furnace at a temperature of 550°C for 4 hours at a heating rate of 2.3°C / min to obtain a g-C3N4 block; grinding the g-C3N4 block into powder and placing the powder in a muffle furnace at a temperature of 5°C / min at a temperature of 520°C for 5 hours to obtain a g-C3N4 nanosheet; The preparation of protonated CdS comprises: adding CdS to a 0.5 mol / L HCl aqueous solution and ultrasonically treating it, then vigorously stirring the CdS stripped from the acid suspension at room temperature to further protonate it, and then centrifuging, washing, and drying to obtain the protonated CdS; The preparation of CdS / rGO comprises: adding protonated CdS and graphene oxide to water, ultrasonically treating, stirring at room temperature to obtain a mixed solution, adding 0.1 g / mL NaBH4 solution to the mixed solution, continuing stirring at 80°C, cooling to room temperature, centrifuging, washing and drying to obtain CdS / rGO.

3. The method for preparing a catalyst for bioenergy conversion according to claim 2, characterized in that: The solid-liquid ratio of the CdS and HCl aqueous solution is 1g:200-300mL.

4. The method for preparing a catalyst for bioenergy conversion according to claim 2, wherein: The solid-liquid ratio of the protonated CdS to water is 1g:700-800mL, the solid-liquid ratio of the graphene oxide to water is 1g:200-300mL, and the volume ratio of the NaBH4 solution to the mixed solution is 1:

5.

5. The method for preparing a catalyst for bioenergy conversion according to claim 4, characterized in that: CdS was added to a 0.5 mol / L HCl aqueous solution and ultrasonically treated, followed by stirring. The ultrasonic treatment time was 1 to 2 hours, and the stirring time was 4 to 5 hours. Protonated CdS and graphene oxide are added to water, ultrasonically treated for 1 to 3 hours, and stirred at room temperature for 1 to 1.5 hours.

6. The method for preparing a catalyst for bioenergy conversion according to claim 2, wherein: After adding NaBH4 solution to the mixed solution, stir at 80°C for 3 to 4 h; g-C3N4 / rGO / CdS was obtained by heating at 180℃ for 2 to 3h.

7. The catalyst for bioenergy conversion according to claim 1 selectively breaks down lignin β-O-4 model compound C in photocatalysis. α -C β Application in key.

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