Effects of the aqueous phase recycling on bio-oil yield in hydrothermal liquefaction of Spirulina Platensis, α-cellulose, and lignin

The utilization of hydrothermal liquefaction (HTL), an efficient thermochemical conversion technology, can produce biofuels from biomass, but also a large amount of processing wastewater. In the present paper, the aqueous phase from the HTL of Spirulina Platensis was recycled as the intermediate reactant and its effects on the bio-oil yield from the HTL of Spirulina Platensis, alpha-Cellulose, and Lignin were investigated. The results revealed that the best bio-oil yields obtained from HTL of Spirulina Platensis and alpha-Cellulose in pure water were 30 and 7.03 wt% at the optimized operation conditions. Aqueous phase obtained from HTL of Spirulina Platensis could be introduced return into HTL system and result in an obvious increase in the bio-oil yield by 10 wt% and 6 wt% from HTL of Spirulina Platensis and alpha-Cellulose, respectively. Energy recovery rates from bio-oil were improved greatly by applying aqueous phase recycling during HTL. However, aqueous phase recycling inhibited generation of bio-oil, suggesting the presence of the antagonistic reaction between protein aqueous and Lignin. Based on the gas chromatography-mass spectrometer (GC-MS) and fourier transform infrared spectroscopy (FT-IR) analysis of the aqueous phase and bio-oil, the possible reaction pathways were deduced. (C) 2019 Published by Elsevier Ltd.