Photocatalyst CdS for efficient cleavage of lignin C O bonds in micellar aqueous medium

Photocatalytic cleavage of lignin CO bonds is a promising way to depolymerize lignin into aromatic value-added chemicals. However, the dispersibility of lignin in solvents and photocatalytic efficiency still face great challenges. Here, a micelle aqueous medium (CTAB-15) composed of hexadecyl trimethyl ammonium bromide and water was successfully prepared. 2-phenoxy-1-phenylethanol (lignin model compounds, PPol) and dioxanesolv poplar lignin have a good dispersion in CTAB-15. Compared to the previous reports, the highest photocatalytic efficiency can be obtained under optimal conditions by using the photocatalyst CdS. The main products formed by photocatalytic cleavage of lignin CO bonds are phenols and ketones. Mechanism studies show that CTAB-15 can provide sufficient hydrogen by photo-driven dissociation of water for photocatalytic cleavage of lignin CO bonds, which is critical to rapidly improving photocatalytic efficiency. The hydrogen, which is used to form acetophenone, comes from H2O and PPol. However, the hydrogen needed to form phenol comes only from PPol itself. In addition, the photocatalytic reaction follows a photogenerated electron-hole coupled redox process. This work develops a new direction for promoting the high-value utilization of lignin.