Elucidation of the Effect of Fast Pyrolysis and Hydrothermal Liquefaction on the Physico-Chemical Properties of Bio-Oil from Southern Yellow Pine Biomass As a Chemical Feedstock

Bio-oils obtained from southern yellow pine biomass from two thermochemical conversion processes, fast pyrolysis (FP) and hydrothermal liquefaction (HTL), were investigated. The effects of FP and HTL on the physical and chemical properties of the bio-oils were characterized. The HTL and FP bio-oil yields were 67 and 36 wt%, respectively. The results indicated that the physical properties of the HTL bio-oil and FP bio-oil were similar; however, there were variations in the composition of the bio-oils from the same biomass. The pH values of the FP and HTL bio-oils were 2.3 and 2.8, respectively. From the GC-MS (gas chromatography–mass spectrometry) analysis, esterified chemical compounds were prevalent in the HTL bio-oil, while phenols and phenolic derivatives were found in both bio-oils. The 31P-NMR (phosphorous nuclear magnetic resonance) analysis of the bio-oils further revealed that both FP and HTL bio-oils are rich in phenolic OH and aliphatic OH functionalities, which could serve as a potential bio-polyol.