CdS-SH for photo-thermal catalytic lignin cracking x Photocatalyst

Abstract

A CdS-SHx photocatalyst for photothermal catalytic lignin degradation, its preparation method, and its application, comprising Cd(NO3)2·4H2O, TAA, and 3-mercaptopropionic acid, is prepared by a one-pot hydrothermal synthesis to obtain mercapto-modified cadmium sulfide (CdS-SHx). x This photothermal catalyst utilizes thiol groups chemically bonded to the CdS surface. Its electronic structure modifiers inhibit photogenerated electron-hole recombination and can specifically adsorb and activate centers to precisely regulate the C-O bond breaking pathway in lignin. The catalyst is prepared under mild conditions with a simple and controllable process. When applied to the photothermal catalytic pyrolysis of lignin, it significantly improves the conversion efficiency of both lignin model compounds and real lignin, exhibiting high selectivity for target aromatic monomers, few byproducts, and excellent catalyst stability and recyclability. This provides a highly efficient and environmentally friendly new method for the highly selective conversion of lignin, with broad industrial application prospects.

Description

Technical Field

[0001] This invention belongs to the field of photothermal catalytic materials and environmental protection technology, and specifically relates to a CdS-SH for photothermal catalytic degradation of lignin. X Photocatalysts, their preparation methods, and applications. Background Technology

[0002] Lignin is the only renewable aromatic resource in nature. Its molecule is rich in CO bonds (especially the β-O-4 structure), which are the core sites for depolymerization into high-value aromatic monomers such as phenol and acetophenone. The efficient pyrolysis and conversion of lignin is of great significance to the development of green chemistry. Traditional lignin depolymerization methods suffer from problems such as high energy consumption, poor selectivity, and low product yield. Photothermal catalysis technology, due to its mild reaction conditions and high efficiency, has become an important research direction for lignin pyrolysis and conversion.

[0003] Cadmium sulfide (CdS) has become a core catalyst for the photothermal catalytic cracking of lignin due to its excellent visible light response. However, single CdS catalysts suffer from drawbacks such as rapid recombination of photogenerated electron-hole pairs, weak adsorption and activation ability for lignin macromolecules, insufficient CO bond scission efficiency, low selectivity for target products, and easy catalyst deactivation. This study uses cadmium sulfide as a substrate and employs a simple one-pot hydrothermal preparation method to synthesize CdS-SH. X Photocatalyst. Thiol-modification of cadmium sulfide surfaces introduces abundant defect sites, which accelerate charge transfer and promote space charge separation. The CdS-SH photocatalyst can be optimized by loading different thiol contents. X The photothermal catalytic properties of the photocatalyst enhance its activity and stability during photothermal degradation. This work is significant for developing novel photothermal catalytic materials and their application in lignin degradation, as thiol modification can improve the stability, reusability, and efficiency of the photocatalyst. Summary of the Invention

[0004] Technical Problem Solved: This invention addresses the problems of rapid electron-hole recombination, weak adsorption and activation capacity, low product selectivity, and easy catalyst deactivation in the photothermal catalytic cracking of lignin by existing CdS catalysts. It provides a CdS-SH catalyst for photothermal catalytic lignin cracking. X Photocatalysts, their preparation methods, and applications: Through precise modification of thiol groups, the catalytic performance of CdS is comprehensively improved, enabling efficient and highly selective pyrolysis and conversion of lignin.

[0005] Technical solution: A CdS-SH X A method for preparing a photocatalyst, characterized in that it comprises a solution of Cd(NO3)2·4H2O, TAA, and 3-mercaptopropionic acid, and is prepared by a one-pot hydrothermal synthesis to obtain CdS-SH.X Photothermal catalyst, SH, based on mercapto content (μL) X (X = 10, 20, 40, 60). The preparation steps are as follows: (1) Cadmium nitrate tetrahydrate and trisodium citrate are placed in a beaker, deionized water and ethylene glycol are added, and the mixture is ultrasonically stirred magnetically to obtain phase A; (2) 3-mercaptopropionic acid is added to phase A and stirred continuously to obtain mixture B; (3) Thioacetamide is added to mixture B and stirred continuously to obtain mixture C; (4) Mixture C is subjected to hydrothermal reaction at a reaction temperature of 120℃-180℃ for 2-6 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, the product is centrifuged, and washed three times each with deionized water and anhydrous ethanol. After drying, CdS-SH is obtained. X Photothermal catalyst.

[0006] Preferred, CdS-SH X The method for preparing a photocatalyst is characterized in that, in step (1), 0.5-2.5 mmol of cadmium nitrate tetrahydrate and 0.5-2 mmol of trisodium citrate are added.

[0007] Preferred, CdS-SH X A method for preparing a photocatalyst, characterized in that, in step (2), SH X The amount added (X = 10, 20, 40, 60) is expressed in μL.

[0008] Preferred, CdS-SH X The method for preparing a photocatalyst is characterized in that 3.5-6 mmol of thioacetamide is added in step (3).

[0009] CdS-SH prepared by the above method X catalyst.

[0010] The above CdS-SH X Photocatalyst, characterized by being composed of Cd(NO3)2·4H2O, TAA and SH X The solution composition forms CdS-SH X Photocatalyst.

[0011] The above CdS-SH X Application of photocatalysts in the catalytic degradation of lignin.

[0012] The above CdS-SH X The application of photocatalyst in the catalytic degradation of lignin is characterized by a lignin concentration of ~0.1 mol / L, the reaction being carried out under visible light irradiation, and the reaction temperature being 25°C.

[0013] Beneficial effects: (1) The CdS-SH of the present invention XThe photothermal catalyst, through the chemical bonding modification of thiol groups, achieves the optimization of the electronic structure of CdS and the precise construction of surface-specific adsorption activation sites. It effectively inhibits the recombination of photogenerated electron-hole pairs, enhances the photothermal catalytic activity of the catalyst, and precisely controls the lignin CO bond breaking path, significantly improving the selectivity of the target aromatic monomers, while significantly reducing the generation of polymerization by-products; (2) The preparation method of the present invention adopts a one-pot hydrothermal synthesis, which is simple, convenient to operate, and has readily available and low-cost raw materials. The reaction conditions are mild, and the precise modification of thiol groups can be achieved by controlling the proportion of raw materials and hydrothermal parameters, making it suitable for industrial-scale preparation; (3) The CdS-SH of the present invention X The photocatalyst has excellent stability and can be recycled at least 5 times while maintaining good catalytic activity and selectivity. It solves the problem of easy deactivation of traditional CdS catalyst and greatly reduces the industrial cost of lignin conversion. (4) When the catalyst of the present invention is applied to the photothermal catalytic cracking of lignin, the reaction conditions are mild and no harsh reaction environment is required. It provides a new technical solution for the efficient and high-value utilization of lignin, meets the needs of green chemistry development, and has broad industrial application prospects. Attached Figure Description

[0014] Figure 1 CdS-SH with different thiol modification levels X The photothermal catalytic cracking performance of the catalyst on lignin CO bonds. The catalytic activity initially increases and then decreases with increasing thiol modification level, particularly in CSS. 20 To achieve optimal results, appropriate thiol modification can optimize catalyst surface properties, enhance the adsorption capacity for lignin substrates, improve the separation efficiency of photogenerated carriers, and thus improve pyrolysis performance; however, excessive thiol modification can block active sites and hinder light absorption, resulting in a decline in catalytic performance. Detailed Implementation

[0015] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0016] Example 1

[0017] A CdS-SH for photothermal catalytic degradation of lignin 20 Catalyst preparation method, SH 20The amount of 3-mercaptopropionic acid added was 20 μL. The preparation steps were as follows: (1) Cadmium nitrate tetrahydrate and trisodium citrate were placed in a beaker, and deionized water and ethylene glycol were added. After sonication, the mixture was magnetically stirred to obtain phase A; (2) 3-mercaptopropionic acid was added to phase A and stirred continuously to obtain mixture B; (3) Thioacetamide was added to mixture B and stirred continuously to obtain mixture C; (4) Mixture C was subjected to hydrothermal reaction at a reaction temperature of 120℃ for 2 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was centrifuged and washed three times each with deionized water and anhydrous ethanol. After drying, CdS-SH was obtained. X Photothermal catalyst.

[0018] Example 2

[0019] A CdS-SH for photothermal catalytic degradation of lignin 20 Catalyst preparation method, SH 20 The amount of 3-mercaptopropionic acid added was 20 μL. The preparation steps were as follows: (1) Cadmium nitrate tetrahydrate and trisodium citrate were placed in a beaker, and deionized water and ethylene glycol were added. After sonication, the mixture was magnetically stirred to obtain phase A; (2) 3-mercaptopropionic acid was added to phase A and stirred continuously to obtain mixture B; (3) Thioacetamide was added to mixture B and stirred continuously to obtain mixture C; (4) Mixture C was subjected to hydrothermal reaction at a reaction temperature of 140℃ for 4 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was centrifuged and washed three times each with deionized water and anhydrous ethanol. After drying, CdS-SH was obtained. X Photothermal catalyst.

[0020] Example 3

[0021] A CdS-SH for photothermal catalytic degradation of lignin 20 Catalyst preparation method, SH 20 The amount of 3-mercaptopropionic acid added was 20 μL. The preparation steps were as follows: (1) Cadmium nitrate tetrahydrate and trisodium citrate were placed in a beaker, and deionized water and ethylene glycol were added. After sonication, the mixture was magnetically stirred to obtain phase A; (2) 3-mercaptopropionic acid was added to phase A and stirred continuously to obtain mixture B; (3) Thioacetamide was added to mixture B and stirred continuously to obtain mixture C; (4) Mixture C was subjected to hydrothermal reaction at a reaction temperature of 160℃ for 4 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was centrifuged and washed three times each with deionized water and anhydrous ethanol. After drying, CdS-SH was obtained. X Photothermal catalyst.

[0022] Example 4

[0023] A CdS-SH for photothermal catalytic degradation of lignin10 Catalyst preparation method, SH 10 The amount of 3-mercaptopropionic acid added was 10 μL. The preparation steps were as follows: (1) Cadmium nitrate tetrahydrate and trisodium citrate were placed in a beaker, and deionized water and ethylene glycol were added. After sonication, the mixture was magnetically stirred to obtain phase A; (2) 3-mercaptopropionic acid was added to phase A and stirred continuously to obtain mixture B; (3) Thioacetamide was added to mixture B and stirred continuously to obtain mixture C; (4) Mixture C was subjected to hydrothermal reaction at a reaction temperature of 180℃ for 6 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was centrifuged and washed three times each with deionized water and anhydrous ethanol. After drying, CdS-SH was obtained. X Photothermal catalyst.

[0024] Comparative Example 1

[0025] Except for the absence of added thiol groups (see Table 1), the rest is the same as in Example 4.

[0026] Comparative Example 2

[0027] A CdS-SH for photothermal catalytic degradation of lignin 60 Catalyst preparation method, SH 60 The amount of 3-mercaptopropionic acid added was 60 μL. The preparation steps were as follows: (1) Cadmium nitrate tetrahydrate and trisodium citrate were placed in a beaker, and deionized water and ethylene glycol were added. After sonication, the mixture was magnetically stirred to obtain phase A; (2) 3-mercaptopropionic acid was added to phase A and stirred continuously to obtain mixture B; (3) Thioacetamide was added to mixture B and stirred continuously to obtain mixture C; (4) Mixture C was subjected to hydrothermal reaction at a reaction temperature of 160℃ for 6 hours. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was centrifuged and washed three times each with deionized water and anhydrous ethanol. After drying, CdS-SH was obtained. X Photothermal catalyst.

[0028] Example 5

[0029] This reaction uses a typical lignin model compound (2-phenoxy-1-acetophenone) as the reaction substrate. Specific steps: 10 mg of the catalyst prepared according to the methods described in Examples 1-4 and Comparative Examples 1-2, and the catalyst prepared according to the corresponding proportions in Table 1, were degassed under vacuum and then ultrasonically dispersed in 2 mL of a propanol solution containing 0.1 mmol of 2-phenoxy-1-acetophenone. Before illumination, nitrogen gas was purged through the entire reactor to ensure the reaction apparatus was filled with nitrogen, and the reactor pressure was maintained at 0.1 MPa. The mixture was then exposed to visible light, and the sample was kept suspended by a magnetic stirrer. After 60 min of illumination, the experiment was terminated, and the sample was detected using gas chromatography (Agilent 1680, FID).

[0030]

[0031] Table 1 CdS-SH X Catalyst activity evaluation results

[0032]

[0033] As can be seen from Table 1, the experimental results show that the CdS-SH prepared in this invention... X The catalyst exhibits excellent photothermal catalytic degradation effect on lignin, significantly improving lignin conversion rate and selectivity. Specifically, the catalyst in Example 3 achieved a lignin conversion rate of 84% and a selectivity of 97% within 60 minutes, demonstrating superior photocatalytic performance. (Unsupported SH) X When CdS is used to catalyze the conversion of lignin, the conversion rate is low and the selectivity is weak.

[0034] The foregoing description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a CdS-SHx photocatalyst, characterized in that, CdS-SHx photocatalysts were prepared by one-pot hydrothermal synthesis of Cd(NO3)2·4H2O, TAA, and 3-mercaptopropionic acid solution. The SHx values ​​were calculated as μL of mercapto content (X = 10, 20, 40, 60). The preparation steps were as follows: (1) Cadmium nitrate tetrahydrate and trisodium citrate were placed in a beaker, and deionized water and ethylene glycol were added. After sonication, the mixture was magnetically stirred to obtain phase A; (2) 3-mercaptopropionic acid was added to phase A and stirred continuously to obtain mixture B; (3) Thioacetamide was added to mixture B and stirred continuously to obtain mixture C; (4) Mixture C was subjected to hydrothermal reaction at a reaction temperature of 120℃-180℃ for 2-6 h. After the reaction was completed, the mixture was naturally cooled to room temperature. The product was centrifuged and washed three times each with deionized water and anhydrous ethanol. After drying, CdS-SHx photothermal catalysts were obtained.

2. The preparation method of the CdS-SHx photocatalyst according to claim 1, characterized in that, In step (1), 0.5-2.5 mmol of cadmium nitrate tetrahydrate and 0.5-2 mmol of trisodium citrate are added.

3. The preparation method of the CdS-SHx photocatalyst according to claim 1, characterized in that, The amount of SHx (X = 10, 20, 40, 60) added in step (2) is expressed in μL.

4. The preparation method of the CdS-SHx photocatalyst according to claim 1, characterized in that, In step (3), 3.5-6 mmol of thioacetamide is added.

5. The CdS-SHx catalyst prepared by any one of the preparation methods described in claims 1-4.

6. The CdS-SHx photocatalyst according to claim 5, characterized in that, A CdS-SHx photocatalyst is formed by combining Cd(NO3)2, 4H2O, TAA, and SHx solution.

7. The application of the CdS-SHx photocatalyst according to claim 6 in the catalytic degradation of lignin.

8. The application of the CdS-SHx photocatalyst in the catalytic degradation of lignin according to claim 7, characterized in that, The lignin concentration was ~0.1mol / L, and the reaction was carried out under visible light irradiation at a reaction temperature of 25℃.

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