One factor at a time and two-factor optimization of transesterification parameters through central composite design (CCD) for the conversion of used peanut oil (UPNO) to biodiesel

Abstract

This present investigation has optimized the acid and base catalysed transesterification process parameters to enhance the conversion of used peanut oil (UPNO) into biodiesel through a central composite design. Of the different acid and alkali catalysts tested, KOH and H2SO4 were found to be efficient catalysts, which yielded 94.2% UPNO biodiesel. For one factor at a time approach, four reaction parameters such as catalyst dose, reaction time, methanol volume, reaction temperature, and speed of mixing were chosen and a catalyst dose of 1 g and reaction time of 60 min was found to be an independent influential factor to enhance UPNO yield. Therefore, KOH/ H2SO4 catalyst concentration and reaction time were selected to ascertain their synergistic effect on the UPNO biodiesel production through central composite design (CCD). Two factorial CCD design unveils that 1.5 g catalyst (acid and alkali) and 90 min reaction time are the optimal conditions along with 70 °C reaction temperature, 6 mL methanol volume, and 50 rpm stirring speed for high UPNO biodiesel yield of 95.9%. In addition, the fatty acid profile of UPNO biodiesel contains oleic acid and linoleic acid as dominant fatty acids in the range of 55–56 % and 25–27%, respectively in KOH and H2SO4 catalysis. Further, MUFAs, PUFAs, and SFAs levels of UPNO biodiesel produced by H2SO4 catalyst were 55.44, 25.66 and 16.43 %, respectively while they were 56.12, 26.32 and 14.53%, respectively for KOH catalysis. Based on the results of high UPNO biodiesel and MUFA levels, it is contemplated that UPNO biodiesel could be a promising alternative fuel from a commercialization perspective.