Electro-catalytic oxidative cleavage of lignin in a protic ionic liquid.

Lignin is a component of lignocellulosic biomass and a promising matrix for recovering important renewable aromatic compounds. We present a new approach of electro-oxidative cleavage of lignin, dissolved in a special protic ionic liquid, using an anode with particular electro-catalytic activity. As appropriate ionic liquid triethylammonium methanesulfonate was identified, synthesised, explored for dissolution of alkali-lignin and used for electrolysis of 5 wt.% lignin solutions. As appropriate anode material, oxidation-stable ruthenium-vanadium-titanium mixed oxide electrodes were prepared and explored for their electro-catalytic activity. The electrolysis was performed at several potentials in the range from 1.0 V to 1.5 V (vs. an Ag pseudo reference electrode). A wide range of aromatic fragments was identified as cleavage products by means of GC-MS and HPLC measurements.