Fractionation Behaviors of Walnut Shell Bio-Oil Components Under Atmospheric Distillation

In this study, walnut shell bio-oil was separated into aqueous phase and oil phase, which were subjected to atmospheric distillation, accompanied by changes of heating temperature and heat preservation time. The fractionation behaviors of various components were investigated by analyzing the distillate collected independently at each temperature in stages. In distillation experiments on oil phase bio-oil (OPB), phenols fractionated in large quantities in the temperature range of 280-320 °C were the main component of oil phase fraction, of which the overwhelming majority were phenol as well as its congeners and guaiacol as well as its congeners. Changing the temperature program had a significant effect on the separation of these two compounds, and the relative concentrations of both were increased by 468 wt. % and 139 wt. %, respectively, when comparing OPB. Experimental data on the distillation of aqueous phase bio-oil (APB) revealed that the fractions were enriched with compounds such as acetic acid and guaiacol in a directional manner, whereas the large amount of water distillation and heating temperature higher than 140°C were two necessary conditions for the coking of aqueous phase bio-oil. Summary of distillation behaviors for various high-value compounds provides guidance for process design and scale-up utilization.