Storage stability of bio-oils derived from the catatytic conversion of kraft lignin in subcritical water

Paper in proceeding, 2016

In the efforts of replacing fossil raw material with renewable resources, most attention has been on carbohydrates (e.g. 2nd generation ethanol). However, during the last period of time the interest in lignin has raised due to its aromatic nature and that it now has started to be more abundant. The conversion of lignin in subcritical water into smaller aromatic units is a promising process because of the relatively mild operating temperatures, which allows the aromatic structures to be retained. In this work, we have investigated the storage stability of lignin-derived bio-oil obtained from the continuous process at subcritical conditions of water (25 MPa, 350oC). The bio-oil was stored at an ambient temperature for 1–2 years. The changes in water concentration (Karl Fischer measurement), chemical composition (GC-MS and elemental analysis) and molecular weight (GPC analysis) of bio-oils were evaluated before and after the storage. The bio-oil was fractionated into: light oil (a low Mw fraction), heavy oil and solids (the high Mw fractions) and all three fractions were analyzed in order to obtain a better understanding about the stability of monomeric as well as oligomeric structures.