Two-step conversion of neem (azadirachta indica) seed oil into fatty methyl esters using a heterogeneous biomass-based catalyst: an example of cocoa pod husk

Abstract

In this study, the viability of using calcined cocoa pod husk ash (CCPHA) as a catalyst for the transesterification of neem seed oil (NSO) into biodiesel was investigated. Prior to transesterification to biodiesel, the oil was pretreated with Fe2(SO4)3 via esterification to reduce its high acid value content. The Box-Behnken design (BBD) and central composite design (CCD) of response surface methodology (RSM) were used to investigate the individual and interactive effects of the methanol/ oil ratio, catalyst amount, and reaction time on the acid value and biodiesel yield, respectively. Results of scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and elemental analysis showed that the catalytic action of the CCPHA produced was due to its K content and microstructural development when calcined at 700 °C for 4 h. The acid value of the NSO could be reduced from 11.57 to 1.80 mg of KOH/g of oil using optimum values of the methanol/oil ratio of 2.19 (v/v), catalyst amount of 6 wt %, and reaction time of 15 min while maintaining the reaction temperature constant at 65 °C. The results confirmed that neem seed oil methyl ester (NSOME), which satisfied ASTM D6751 and EN 14214 standards, could be produced at an optimum yield of 99.3 wt % using the methanol/oil ratio of 0.73 (v/v), catalyst amount of 0.65 wt %, and reaction time of 57 min while maintaining the reaction temperature constant at 65 °C. The results of this study demonstrated the prospect of developing an heterogeneous base catalyst from cocoa pod husk (CPH) for biodiesel production, which may reduce the total cost of production.