(722f) Protic Ammonium Based ILs and Mn Frameworks for Facile Conversion of Lignin to Valuable Aromatic Ketones.

This study is centered on the development of a robust catalytic system utilizing protic ionic liquids (PILs) and coordinated metal frameworks to effectively break down lignin by cleaving C-O and C-C bonds. We devised a manganese-coordinated protic ionic liquid catalyst capable of depolymerizing lignin through rapid hydrogen atom and hydride transfer reactions. Through a systematic investigation, we assessed the impact of each catalyst component and optimized process conditions (such as temperature, time, and catalyst concentration) to enhance yield and selectivity. The resulting depolymerization products were analyzed and quantified using HSQC, GCMS, and HPLC techniques. Remarkably, under mild conditions (6 hours at 80 °C), 91% of the dealkaline lignin was transformed into valuable ketones, phenolics, aldehydes, and acids. Notably, the catalyst exhibited a 55% selectivity towards an acetoveratrone derivative, a sought-after compound in the cosmetics and oil industries. The depolymerization process followed pseudo-first-order kinetics according to the Wilkinson model. Additionally, we conducted studies to enrich the product by exploring the influence of different solvents, pH levels, and metal loadings for optimal yield and conversion. This investigation demonstrates that a multifunctional catalysts can efficiently produce valuable aromatic ketone products from dealkaline lignin under mild conditions.