Two-Stage Liquefaction of Oil Palm Shell in Alkali Supercritical Ethanol–Water for Enhanced Bio-Oil Production
Oil palm shell (OPS) was converted to bio-oil in supercritical ethanol–water via one- and two-stage liquefaction. In the 1st stage, the OPS liquefaction was performed using 5 or 10% by weight (wt%) NaOH or KOH as the catalyst at 330 °C and an initial hydrogen (H2) pressure of 4 MPa. In the 2nd stage, the solid residue (SR) from 1st stage was again liquefied using 5 wt% catalyst (NaOH or KOH) at otherwise the same conditions as before. For the one-stage liquefaction, 10 wt% KOH gave the maximum yield of bio-oil and SR (61.9% and 27.3%, respectively) and the highest energy equivalent ratio (1.012). In the two-stage liquefaction using 10 wt% KOH in the 1st stage, using 5 wt% KOH in the 2nd stage gave the maximum yield of bio-oil (18.8%), which was lower than in the 1st stage liquefaction using the same catalyst type. However, the total bio-oil production in the two-stages was higher than in the one-stage liquefaction. The heating value of the obtained bio-oil was in the range of 26.2–32.5 MJ/kg, with the main components, as analyzed by gas chromatography-mass spectrometry, being phenols, esters, alcohols and benzene derivatives.
KeywordsAlkali Oil palm shell Liquefaction Supercritical fluid Energy equivalent ratio
The financial support, equipment and all materials were provided by the Chemical Technology Department Research Fund and are greatly acknowledged. The authors also thank Mr. Somei Hayashi and Mr. Nutdanai Wannasuth for their assistance throughout this project.
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