Extraction of Value-Added Chemicals from Bio-Oil Products
Bio-oils originating from the pyrolysis of lignocellulosic biomass are complex mixtures of monomeric and oligomeric organic molecules in the presence of water. Initially, it was intended to use the liquid products as fuel, but with the development of new biorefinery concepts for a future bio-based economy, bio-oils are also regarded as a source of valuable renewable chemicals. In contrast to crude petroleum oils with a relatively simple chemical composition, bio-oils exhibit a much more complicated chemcial composition due to the presence of oxygenated molecules with different chemical functionalites involving organic acids, carbonyl, phenols, and sugars. Moreover, bio-oils are sensitive to heat so that traditional separation methods known from petroleum cannot be transformed directly. Hence, separation processes for bio-oils must be carefully selected to avoid undesirable side-reactions. Basically, four principles for separation and enrichment of chemcials are described in literature: Distillation, liqud-liquid extraction, adorption/desorption, and fractional condensation. This chapter gives an overview of all methodologies applied to pyrolysis liquids, including one industrial example based on liquids from slow pyrolysis of wood.