Acetic Acid Recovery from Fast Pyrolysis Oil. An Exploratory Study on Liquid-Liquid Reactive Extraction using Aliphatic Tertiary Amines

Abstract: Flash pyrolysis oil or Bio-oil (BO), obtained by flash pyrolysis of ligno-cellulosic biomass, is very acidic in nature. Themajor component responsible for this acidity is acetic acid, present in levels up to 2–10wt%. Here, we report an exploratory study on BO upgrading by reactive extraction of acetic acid using long-chain tertiary amines in a batch set-up. Factors affecting the extraction efficiency, such as the type and concentration of tertiary amine and co-solvents, were investigated. More than 90wt % of the acetic acid could be extracted in a single equilibrium step (BO diluted in THF (26wt % BO), trioctylamine (TOA) in octane as the extractant phase, T 20C).However, the amine has considerable affinity for the BOphase and about 10wt % on initial intake was transferred to the BO.A considerable improvement was obtained when using the aqueous phase of a thermally treated BO containing 6wt% acid of acetic acid. In a single extraction step, acetic acid extraction efficiencies up to 75wt % were achieved without significant amine transfer to the aqueous phase