Flash Distillation of Bio-Oils for Simultaneous Production of Hydrocarbons and Green Coke

Fast pyrolysis bio-oils from biomass can potentially integrate with petroleum refinery infrastructure for production of renewable fuels and chemicals. Besides hydro-deoxygenation, few feasible options exist for entry points. When considering advanced pyrolysis techniques such as catalytic and/or tail-gas reactive pyrolysis (TGRP), distillation for using both light and heavy ends becomes possible. Our goal was to demonstrate and optimize continuous production of liquid organic distillates and residual solids coke, both in appreciable yields for downstream conversion into renewable products. We fabricated a flash drum for continuous one-step distillations of four oils of varying oxygen content (ranging from 5 to 32 wt %). While a mesh demisting screen enhanced separation, removal of the screen ultimately improved overall yields. The flash drum proceeded to distill lower-oxygen oils (similar to 10 wt %) with 80 wt % time-on-stream yields over several hours; steady state was reached within 30-40 min. Bio-oils with moderate oxygen levels (20 wt %) took a noticeably longer time to attain steady state and gave 60 wt % yield. Under distillation conditions, oils from conventional pyrolysis (32 wt %) underwent condensation repolymerization due to reactive instabilities and produced only 6 wt % organic liquid yield. Solid coke residues were collected and converted into calcined coke, with Raman analysis indicating that catalytic and/or TGRP oil residues had higher molecular weight polyaromatics than those from traditional oil.