Hydrothermal hydrolysis of grape seeds to produce bio-oil

Abstract

In the present work, the hydrothermal hydrolysis of grape seeds focused on the production of bio-oil was studied. The grape seeds composition in terms of lignin, sugars, ash, extractives and bio-oil was determined. The composition of grape seeds was: 17.0 wt% of extractives; 36.8 wt% of sugars (hemicellulose and cellulose); 43.8 wt% of lignin and 2.4 wt% of ash. The grape seeds were hydrothermally treated using three different temperatures: 250 °C, 300 °C and 340 °C employing a semi-continuous reactor. The solid residue varied from 25.6–35.8 wt% depending on the hydrolysis temperature. The maximum yields of light (15.7 wt%) and heavy bio-oil (16.2 wt%) were achieved at 340 °C. The Arrhenius parameters for the kinetics of grape seeds hydrolysis in our system were k₀ = 0.995 g min⁻¹ and E_a = 13.8 kJ mol⁻¹. The increment of the flow rate favoured the mass transfer in the system and so, the hydrolysis rate. However, the maximum hydrolysis rate was found at a water surface velocity of 2.3 cm min⁻¹.