posted on 2015-11-02, 00:00authored byYaseen Elkasabi, Charles A. Mullen, Akwasi A. Boateng
Tail-gas
reactive pyrolysis (TGRP) of biomass produces bio-oil
that is lower in oxygen (∼15 wt % total) and significantly
more hydrocarbon-rich than traditional bio-oils or even catalytic
fast pyrolysis bio-oils. TGRP bio-oils lend themselves toward mild
and inexpensive upgrading procedures. We isolated oxygen-free hydrocarbons
by extraction of TGRP bio-oil distillates. Extraction proceeded by
adding aqueous sodium hydroxide to distillates, resulting in a hydrocarbon
layer and a phenolic salts layer. The hydrocarbons consist primarily
of mono- and bicyclic aromatics, are essentially free of oxygen (<1.0
wt %), and possess low moisture (<1.0 wt %) and low acidity (TAN
< 5.0 mg KOH/g). The phenolic salts can be reacidified to produce
phenols with low moisture (∼2.5 wt %) and with narrow product
distribution. The aqueous phase byproduct contains organic acids and
precipitated sodium chloride. The hydrocarbon layer can be upgraded
via mild hydrogenation with a sponge nickel base metal catalyst in
water, producing naphtha compounds appropriate for direct use as drop-in
fuel and/or refinery blendstock. Furthermore, using only hydrogenation
eliminates CO and CO2 production that normally accompanies
hydrodeoxygenation.