Effect of solvent on the hydrothermal liquefaction of macro algae Ulva fasciata

Hydrothermal liquefaction is an attractive approach for the conversion of aquatic biomass like algae as it does not require the energy intensive drying steps. The objective of the study is to understand the effect of various solvents (H2O, CH3OH and C2H5OH) on product distribution and nature of products of hydrothermal liquefaction of macro algae Ulva fasciata (MAUF). Hydrothermal liquefaction of MAUF was performed using subcritical H2O (300 °C) as well as supercritical organic solvents CH3OH and C2H5OH (300 °C). The use of alcoholic solvents significantly increased the bio-oil yield. The bio-oil yield was 44% and 40% in case of liquefaction with CH3OH and C2H5OH respectively whereas the bio-oil yield was 11% with H2O. Use of alcoholic solvents converted the acids obtained in bio-oil to the corresponding methyl and ethyl esters. 1H NMR data showed that use of alcoholic solvents (C2H5OH and CH3OH) increased aliphatic content of bio-oil1 (ether/methanol/ethanol fraction). FTIR and SEM results showed the difference in the bio residue obtained using alcoholic solvents and H2O. The results showed that liquefaction with supercritical alcohols is an effective way to produce functional hydrocarbons for chemical feedstock.