Characterization and separation of corn stover bio-oil by fractional distillation

Fractional distillation of bio-oil derived from pyrolysis of corn stover was investigated under atmospheric and reduced pressure/vacuum conditions. Characterization of the fractions in terms of moisture, total acid number (TAN), energy content, elemental and chemical compositions was performed to evaluate the effectiveness of the distillation process in separating the components and rendering improved product properties. Results showed high yields (wt.%) of the heavy fractions (b.p. 180-250 °C at 1 bar; 160-230 °C at 0.5 bar) and significant reduction in moisture and TAN content. Water was obtained as a separate layer in the first (light) fraction (b.p.⩽100 °C at 1 bar; ⩽80 °C at 0.5 bar). The heating values increased, especially for the light distillates in both atmospheric and vacuum distillation and the heavy distillates in atmospheric distillation. Analysis of the chemical composition showed that aromatic and oxygenated compounds were distributed in the light and middle fractions (∼15-20%) while phenolic compounds were concentrated in the heavy fraction (∼53%). The distillation process was effective in separating the components and yielding a product (heavy fraction) with improved properties and composition and which can be further utilized as feedstock for future upgrading procedures or as a blending material with other liquid fuels.