Lipid-based biofuel synthesized from palm-olein oil by supercritical ethyl acetate in fixed-bed reactor

This study aimed to investigate the effects of temperature, ethyl acetate to palm oil molar ratio, residence time, and packing alumina balls on triglyceride conversion, ethyl ester, and acetin contents. The complete triglyceride conversion was observed at 1.35 +/- 0.05 times of the transition temperature. The packed alumina enhanced the ester content up to 20%; but it had no effect on the acetin content. Furthermore, this study also intended to determine the effects of the acetin content and thermal cracking on 19 fuel properties of lipid-based biofuel samples synthesized by supercritical ethyl acetate. The optimal condition was found at 380 degrees C, 20 MPa and ethyl acetate to oil molar ratio of 30:1. First, the density and kinematic viscosity of the biofuels were slightly higher than the maximum values specified by standards because of the presence of triacetin and polymerized products. Second, packing alumina balls increase the mixing intensity and thermal conductivity inside the tubular reactor resulted in higher contents of sulfated ash and carbon residue. Third, the acid values of the biofuel samples were considerably higher than the standard value of biodiesel. However, copper strip corrosion testing resulted in slight tarnishing (level 1A). The corrosiveness of fuels mainly originates from their sulfur compound content, neither biofuel sample was classified as a corrosive material. Furthermore, the high acid values of the samples interfered with the testing of oxidation stability. Finally, beneficial effects of triacetin on cold flow properties were revealed in this study. The cloud point and cold filter plugging point of lipid-based biofuels strongly depended on the thermal stress of the reaction conditions rather than the triacetin concentration.