Characterization of column chromatography separated bio-oil obtained from hydrothermal liquefaction of Spirulina

Bio-oil contained a large number of macromolecular compounds like asphalt, which made it difficult to obtain accurate results from direct test analysis. In this study, hydrothermal liquefaction (HTL) bio-oil of Spirulina (300 degrees C, 30 min, 10 MPa) was underwent column chromatography separation (CCS) process to retain the macromolecular substances in the column, which improved the accuracy of subsequent analysis results. The obtained fractions were characterized by Thermo-Gravimetric Analysis (TG), Gas Chromatography-Mass Spectrometry (GC-MS) analysis, Elemental Analysis, and Fourier Transform Infrared (FT-IR) Spectroscopy Analysis. TG analysis showed that a significant amount of components coexisting in high-boiling-range residue in bio-oil could be isolated into quasi-gasoline and quasi-kerosene species, so the low boiling-point fractions of bio-oil between 30250 degrees C increased. GC-MS proved that CCS could effectively separate bio-oil and the number of detected components in bio-oil increased from 25 to 109 after CCS. The results of elemental analysis and FT-IR indicated that the components of the bio-oil were separated according to the polarity, and the higher heating values(HHVs) of each distillate oil (38.32-42.19 MJ kg(-1)) was significantly higher than the bio-oil before CCS (31.83-36.04 MJ kg(-1)). Comprehensive results of multiple analysis could help determine the market application prospects of bio-oil. In addition, tert-hexadecanethiol was studied as a representative Sulphur-compound to surmise its generation mechanism. The speculation of the conversion pathway of sulphur (S) element could provide a basis for a better understanding of the HTL reaction mechanism.