Optimization of oleaginous seeds liquefaction using response surface methodology

Bio-oil production from sunflower seeds, as model components, was carried out in supercritical hydrothermal liquefaction conditions. The effects of operating parameters such as temperature, time, and biomass/solvent mass ratio were investigated. Response surface methodology based on full factorial design was utilized to optimize the operating conditions using Design Expert software. From the analysis of variance, the most influential factor of each experimental design response was identified and a regression model was derived. The results show that the quadratic polynomial model provided accurate predictions for bio-oil yield and its viscosity, with a determination coefficient R2 of 0.9120 and 0.9351, respectively. The optimum condition was 286.21 °C, a reaction time of 12 min, and 20% of biomass/solvent mass ratio. These conditions led to obtain 79.96 wt.% of bio-oil with a viscosity of 18.09 mPa s. The produced bio-oil was subjected to different analyses and characterized by gas chromatography–mass spectrometry. Besides, ether esters were identified as major components. Bio-oil properties were evaluated according to standard norms, and the results suggest the need of further upgrading step to improve its quality.