Hydrothermal Liquefaction of Mentha-Waste: Effects of Operating and Reaction Parameters on Product Yields

Abstract

The production of essential oils leads to the production of huge amounts of residual aromatic biomass after extraction.Hydrothermal Liquefaction of Mentha-waste was performed at different temperatures (220-300°C) using solvents such as water (H2 O), acetone (C3H6O), methanol (CH3OH) and ethanol (C2H5OH) at reaction times ranging from 15-60 min. There was a significant increase in bio-oil yield with the use of organic solvents as compared to water. It increased from 9.84 wt.% (water as a solvent) to 20.17-31 wt.% using C3 H6 O, CH3 OH and C2 H5 OH as solvents. The highest bio-oil yield (31wt.%) was when C2H5OH was used as a solvent. Maximum bio-oil yield at 220°C was obtained with water at a residence time of 45 min. At temperatures 240°C, 260°C and 280°C, maximum bio-oil was obtained at optimum reaction time of 30 min. The highest bio-oil yield i.e. 9.84 wt.%, was attained at 300°C with reaction time of 15 min. The bio-oil yield(s) increased discernibly with increasing temperature and decreasing reaction time. The organic solvent reactions were specifically performed at the reaction temperature and residence time which yielded the highest bio-oil (9.84 wt.%) under H2 O as a solvent i.e., 300°C and 15 min respectively. NMR and GC-MS analysis results show that use of organic solvents has a considerable effect on the decomposition of mentha-waste.