Acid-catalyzed ethanol depolymerization of Chaenomeles sinensis lignin for enhanced phenolic antioxidants and biodiesel stabilization.

This study implemented an acid-catalyzed ethanol methodology for depolymerizing Chinese quince fruit (CQF) lignin, intending to enhance its antioxidant properties and lipophilicity to serve as a natural antioxidant for biodiesel. The results demonstrated that CQF lignin was effectively depolymerized at 200 °C, 220 °C, and 240 °C. A range of monophenols were identified in the depolymerization products, with desaspidinol being the most abundant compound. The total phenolic hydroxyl content in PL240 was as high as 5.79 mmol/g, and all three depolymerization products demonstrated ultra-high DPPH radical scavenging capacity. Lignin depolymerization products (400 ppm) led to the biodiesel kinematic viscosities within the standard range. Importantly, the lignin depolymerization products significantly enhanced the oxidative stability of different biodiesels, outperforming butylated hydroxytoluene. Among these, PL240 demonstrated the highest efficacy. This study is of significant importance for achieving the high-value utilization of CQF waste residues and advancing the development of lignin-based natural antioxidants.