Supercritical carbon dioxide extraction of fast pyrolysis oil from softwood

Supercritical carbon dioxide (scCO(2)) was studied for separation of bio-oil applying different pressures (100, 200, 300 bar), temperatures (60, 80 degrees C), carriers (SiO2, activated carbon), and times (1-6 h). The maximum extraction yield (13-14 wt%) was obtained at 300 bar, 60 degrees C with SiO2 as carrier. The composition of the scCO(2) extracts was determined by GC MS/FID. The concentration progress of 32 typical compounds in the extracts at 200 bar was monitored in detail. At 200 bar pressure, the contents in the scCO(2) extracts of aldehydes, furanones, coniferyl alcohol, coniferyl aldehyde, and vanillin increased with extraction time. Acids, ketones and most of the guaiacols decreased while phenols and pyrans remained the same. More acids, ketones, and furaldehydes could be obtained at a lower temperature and more aromatic compounds could be extracted when SiO2 as the carrier was employed. The yields of individual components were mainly depending on the duration of extraction.