Characterization and separation of wood tar by full temperature range fractional distillation

Abstract

Wood tar has been regarded as the most undesirable by-product of biomass carbonization. Fractional distillation of the wood tar at the full temperature range from the initial evaporating point to the coking point (110∼300 °C), was investigated. Characterization of the six typical distillates in the wood tar in terms of moisture content, elemental and chemical compositions was precisely analyzed to evaluate the effectiveness of the distillation process in separating the components. A life cycle assessment based on biomass converting to wood tar and further into distilled-oils was constructed to estimate the CO2 emission. Results showed high yields (∼15.4 wt%) of the heavy distillates (b.p. 250∼300 °C) and a significant reduction in water content (∼4.5 %) while high heating value (∼30 MJ/kg). The majority of the compounds presented in each fraction is phenolic, aromatic and oxygenated compounds especially phenols and their alkyl and methoxy derivatives. Phenolic compounds perform various distillation properties due to different functional groups and the hydrogen-bond interaction. LCA indicated that the distillation exerted advantages in reducing carbon emission and that it has a potential for future development of these processes for commercial and industrial use.