Delonix regia heterogeneous catalyzed two-step biodiesel production from Pongamia pinnata oil using methanol and 2-propanol

Abstract

The study described here was focussed on preparing heterogeneous catalysts (acid and base) by H2SO4 and KOH wet impregnation technique from raw Delonix regia pods after carbonization and steam activation, which was used in converting free fatty acids and glycerides in karanja oil into fuel-grade esters. Resistance to thermal degradation of the precursor material was evaluated by TGA analysis, while catalyst characterization was done through BET, EDAX, FT-IR, SEM and XRD. These helped in estimating efficient surface modification and efficient doping of functional groups. Optimization of both esterification and transesterification steps is done through L16 Taguchi matrices, with the following process parameters: agitation speed, alcohol to oil ratio, catalyst concentration, reaction duration, reaction temperature. With a maximum FFA conversion of 99.86%, the biodiesel yield was 99.39%. Fuel characterization tests and GC analyses for residual glycerides showed that the fuel has acceptable physico-chemical properties according to ASTM standards with low residual glycerides. Catalysts show significant reusability with sulfonated (H2SO4 impregnated) catalyst retaining efficiency up to 3 uses and base catalyst (KOH doped) up to 7 uses. A cost analysis of catalyst preparation shows that the indigenously developed catalysts reduce production costs by a significant margin, proving to be lucrative for commercialization.