Study on Degradation of Lignin by TiO2-based Photocatalyst Doped with Carbon Dots

Yu Tan,Mingyu He,Ying Li,Mamatjan Yimit

doi:10.37358/rc.22.1.8507

Abstract

The carbon dots were prepared by the microwave method, and then the TiO2 doped with carbon dots was successfully synthesized by the hydrothermal method. Its structure was investigated using TEM, XRD and XPS. The catalyst was applied to the degradation of lignin base solution (50 mg of lignin in 30 mL of sodium hydroxide solution pH = 12) under ultraviolet light. It was found that when the mass ratio of carbon point to TiO2 was 1.5:1, the dosage of catalyst was 0.75 g/L, and the degradation time was 6 h, the degradation rate could reach more than 45%. The degradation rate of more than 40% could be maintained after seven cycles, indicating that the catalyst had good photocatalytic cycle stability. The degradation products were analyzed by GC-MS, and the main products were n-butyl acetate, butyl phthalate and alkanes with long carbon chains.

Highlights

Lignin is the only natural polymer material with aromatic structure in nature, which is composed of sinapyl alcohol group, coniferyl alcohol group and p-coumary alcohol group connected by 4-O-5, α-O4, β-O-4, β-β, β-1, 5-5 and other bonds
The surface morphology of carbon dots (CDs)/TiO2 was observed by TEM, and the results show that CDs has been successfully compounded to the surface of TiO2
The crystal structure of CDs/TiO2 was investigated by XRD, and the results showed that the addition of CDs did not affect the crystal form of TiO2, and both TEM and XRD indicated that the TiO2 used was anatase type TiO2

Summary

1.Introduction

Lignin is the only natural polymer material with aromatic structure in nature, which is composed of sinapyl alcohol group, coniferyl alcohol group and p-coumary alcohol group connected by 4-O-5, α-O4, β-O-4, β-β, β-1, 5-5 and other bonds. The lignin can be degraded to obtain products such as low molecular weight phenols and organic acids [4, 5]. These degradation products are important chemical raw materials and can be converted into liquid fuels through hydrogenation and deoxygenation reactions. The results showed that the three-dimensional electron distribution of nickel was changed by carbon modification, and it had a high selectivity for the hydrolysis of C-O bonds of lignin to generate aromatic hydrocarbons, with a yield of up to 22%. Zhang Bo et al [25] used hydrothermal method to combine CDs and TiO2, and investigated the degradation effect of composite catalyst on pulping black liquor under visible light. Under the irradiation of ultraviolet light, the alkali-lignin was degraded to obtain n-butyl acetate, butyl phthalate and alkanes with longer carbon chains

Materials and methods

Degradation results

Findings

4.Conclusions