Synthesis of Ca–Fe-based heterogeneous catalyst from waste shells and their application for transesterification of Jatropha oil

Abstract

The depletion of fossil fuel reserves with increased fuel demand and global emissions has increased the search for eco-friendly renewable fuels with a low environmental impact. Biodiesel can be considered as mono-alkyl esters of long-chain fatty acids obtained from the transesterification of vegetable oils and animal fats. Economically low-cost biodiesel production has received considerable interest for blending with fossil-based diesel for a more sustainable future. Therefore, the current study focuses on synthesizing an efficient, low-cost heterogeneous CaO catalyst from waste egg and seashell using a solid-state method and applying it to the transesterification of Jatropha oil. The Ca2Fe2O5 solid catalyst was prepared by doping calcined CaO with iron in a 2:1 ratio using ferric oxide (Fe2O3). Furthermore, the catalyst was extruded and analytically characterized using XRD, FT IR, BET, and its basic strength was quantified by Hammett indicators. Later on, transesterification of Jatropha oil was optimized by varying reaction parameters, such as the molar ratio of methanol to Jatropha oil, reaction time, and catalyst loading. The maximum conversion yield was 96.3% at a 20:1 methanol-to-oil ratio and 80 bar N2 pressure using 5% (w/w) catalyst loading. Furthermore, the catalytic recycling study demonstrated that the Ca2Fe2O5 catalyst could retain > 70–80% of transesterification efficiency and stability up to 4 cycles under high acid value and moisture conditions.Graphical abstract