Degradation of Benzyl Phenyl Ether as Lignin Model Compound by Electrochemical Advanced Oxidation Process in a Microreactor

Abstract

As the world is shifting away from its reliance on fossil fuel, lignocellulosic biomass, which is low cost, renewable and abundant with cellulose, hemicellulose and lignin being its major components. Lignin has high potential to be converted into other value-added chemicals as an alternative to fossil fuel. This research focusses on systematic investigation of degradation of lignin by electrochemical advanced oxidation process (EAOP) in a microreactor, using benzyl phenyl ether (BPE) as a model compound for lignin. The first part of the research investigates the dissolution of BPE in various volume fraction of co-solvent system. The co-solvent system is used because water is needed to generate hydroxyl radicals to cleave the α-O-4 bond between two aromatic rings in BPE via EAOP, while an organic solvent is used to dissolve BPE as it is insoluble in pure water. The effect of organic solvent volume fraction in the co-solvent system, in the range of 0% to 100%, on solubility of BPE was investigated, while the concentration of BPE was fixed at 100 mg/L. The results indicated that the solubility of BPE decreases as the volume fraction of organic solvent decreased. Volume fraction of 30% organic solvent in the co-solvent system is chosen as a balance between solubility and conversion. The second part of the research focusses on the degradation kinetics of BPE in the co-solvent system where the influence of mean residence time (27.0 - 81.0 s), applied current (0.93 - 8.33 A/m2), concentration of solvent (30 - 50 vol% ethanol/water) and type of solvent (acetonitrile/water and ethanol/water). Intermediate products detected, partial pathways and partial mechanisms of the degradation of BPE are discussed at the final third section as well.