(156c) Distillation and Isolation of Commodity Chemicals from Bio-Oil Made By Tail-Gas Reactive Pyrolysis

Mullen, C. A., USDA-ARS
Boateng, A. A., USDA-ARS

Owing to instabilities, very little has been accomplished with regards to simple cost-effective separations of fast-pyrolysis bio-oil. When heated, the resulting depletion of valuable compounds (already at low concentrations) renders bio-oil distillation as a futile effort. A recently developed pyrolysis process based upon tail-gas reactive pyrolysis (TGRP) significantly improves bio-oil quality through reduction of oxygen to < 10 wt%, reduction of viscosity, increased hydrocarbon concentrations, and increased thermal stability.

We used fractional distillation to isolate compounds from bio-oil produced by TGRP. All bio-oils produced from TGRP contained significantly less acid (0.2 – 4% total), trace amounts of aldehydes, and significantly higher concentrations of hydrocarbons and phenolics (5 – 20% each). Organic yields from distillation of TGRP bio-oil ranged from 55 – 65%. On a dry basis, organic yields were more than 3 times that from traditional bio-oil; discounting acetic acid and furfural, TGRP distillation yields jumped to 10-fold. We categorized distillates according to boiling temperature and chemical components: benzene-toluene-xylenes (BTX), styrene, indene, pyridine, phenols, naphthalenes, acetic acid, and fluorene/anthracene. The relatively narrow product distributions allowed for the isolation of pure naphthalene by recrystallization from a naphthalene-rich fraction. Using GC-MS compositions, a thermodynamic computation of the TGRP distillation profiles correctly predicted the experimental results when acid content was < 1%.