Aqueous Extractive Upgrading of Bio-Oils Created by Tail-Gas Reactive Pyrolysis To Produce Pure Hydrocarbons and Phenols
journal contributionposted on 02.11.2015, 00:00 by Yaseen 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.