Experimental and modelling studies on the solvent assisted hydraulic pressing of dehulled rubber seeds

A systematic study on the expression of rubber seed oil from dehulled rubber seeds in a hydraulic press was performed in the presence and absence of ethanol. The effect of seed moisture content (0–6 wt%, w.b.), temperature (35–105 °C), pressure (15–25 MPa) and ethanol to seed ratio (0–21%v/w) on the oil recovery was investigated. An optimum oil recovery of 76 wt%, d.b. was obtained (1.6 wt% moisture content, 14%v/w ethanol, 20 MPa, 75 °C, 10 min pressing time). The experimental dataset was modeled using two approaches, viz (i) the Shirato model and (ii) an empirical model using multi-variable non-linear regression. Good agreement between models and experimental data was obtained. Relevant properties of the rubber seed oil obtained at optimum pressing conditions (free fatty acid content, viscosity, density, water and P-content, cold flow properties and flash point) were determined. The pressed rubber seed oil has a relatively low acid value (2.3 mg KOH/g) and is suitable for subsequent biodiesel synthesis.