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In this work, the characteristics of waste pig fat degradation using supercritical alcohols have been studied. Comparative analysis of the influence of supercritical methanol and supercritical ethanol as solvents on the transesterification was the primary focus of this research. The experiments were carried out with waste pig fat to alcohol weight ratios of 1:1.5 (molar ratio: 1:40.5 for methanol and 1:28 for ethanol), 1:2.0 (molar ratio: 1:54 for methanol and 1:37.5 for ethanol) and 1:2.5 (molar ratio: 1:67.5 for methanol and 1:47 for ethanol) at transesterification temperatures 250, 270 and 290 °C for holding time 0, 15, 30, 45 and 60 min. Increase in the transesterification and holding time increased the conversion while increase in alcohol amount from 1:1.5 to 1:2.0 and 1:2.5 had minimal effect on the conversion. Further, majority of the ester composition in using SCM as solvent falls in the carbon range of C17:0, C19:1 and C19:2 while that for SCE falls in the carbon range of C18:0, C20:1 and C20:2. Glycerol was only present while using SCM as solvent.

Comparative analysis of transesterification of virgin cooking oil (VCO) and waste cooking oil (WCO) in catalyzed and supercritical transesterification process using methanol and ethanol as solvents has been conducted in this study. The luminous point of this research was the direct comparison of catalytic and supercritical process using the ester composition obtained from virgin cooking oil and waste cooking oil transesterification. Oil to alcohol molar ratio of 1:6 and reaction condition of 65 °C and 1 bar pressure were considered for the catalytic process, while 260 °C and high pressure (65 and 75 bar for methanol and ethanol, respectively) were accounted for the supercritical process. Distinct layer separation was observed for both processes. Ester, fatty acid and glycerol composition was studied for both the upper and lower layers separately, from which 100% ester composition in the upper layer and a mixture of ester and other composition in the lower layer was obtained for the catalytic process owing to succeeding filtration and washing. However, mixture of ester (>75%) and other composition was obtained in both layers for the supercritical process where purification process was not implemented. The similarity in the result obtained demonstrates the superiority of waste cooking oil compared to virgin cooking oil, taking cost into consideration. [ABSTRACT FROM AUTHOR]