Microwave-assisted chemistry: parametric optimization for catalytic degradation of lignin model compounds in imidazolium-based ILs

Lignin, a readily available form of biomass with a potential source of aromatic chemical compounds, has not been fully utilized due to its complex structure. Hence, this study aims to elaborate and optimize the effects of parametric microwave conditions for the catalytic degradation of lignin model compounds. In addition to that, 41 types of imidazolium-based Ionic liquids were employed for the conversion of lignin model compounds such as guaiacol and benzyl phenyl ether. The microwave-assisted conversion of lignin model compounds in imidazolium-based ionic liquids was performed at optimum applied microwave power 700 W and 30-min irradiation time. The percentages conversion and yield were quantified using high-performance liquid chromatography (HPLC) analysis. Results revealed that the chloride anion-based ionic liquids exhibited better nucleophilic behavior and catalyzed the cleavage of ether-based compounds efficiently under microwave irradiation. Among the imidazolium-based ionic liquids, 1H-methylimidazolium chloride ([1H-MIM][Cl]) exhibited better performance with guaiacol conversion and catechol yield of 99% and 81%, respectively. Therefore, the microwave-assisted technique was found to be more promising than conventional methods for the ionic liquid-based catalytic degradation of lignin model compounds.