Antioxidant Activity of Lignocellulose Pyrolysis by-Products after Levoglucosan Separation

Abstract

Fast pyrolysis of pre-treated lignocellulose gives a high yield of levoglucosan and other anhydrosugars, which are considered as the main product. However, the chemical composition of the liquid pyrolysis products is a complex mixture of hundreds of individual compounds. To implement the biorefinery principles, it is important to find applications for the side-streams which arise during levoglucosan production. First, we separated the anhydrosugars by eluting the pyrolysis product water solution through an anion exchange resin column. The anhydrosugars were eluted, but the aromatic by-products were adsorbed on the resin. The by-products were desorbed from the resin with a mixture of methanol/water/acetic acid, and the chemical composition of the obtained by-products was analyzed by UHPLC-UV, and the Folin-Ciocalteu method. Alternatively, the pyrolysis products were separated by crystallization, which yielded levoglucosan with >90% purity, and a mother liquor enriched with aromatic chemical compounds. The antioxidant activity in all samples was evaluated by the DPPH method with corrections to compensate for the color of the by-product samples, which interfered with the UV/VIS spectrophotometry readings.