Biodiesel production from transesterified waste cooking oil by zinc-modified anthill catalyst: Parametric optimization and biodiesel properties improvement

Biodiesel, an unconventional fuel to substitute the existing fossil diesel, is non-toxic, biodegradable, possesses high lubricity and better combustion capacity. In this paper, a new eco-friendly solid catalyst was developed from anthill-zinc modification for methanolysis of low-grade feedstock (waste cooking oil, WCO) to make biodiesel. The zinc-modified anthill was prepared via the sol-gel technique and characterized by EDX, TGA/DTA, FTIR, XRD, SEM, BET and CO2-TPD. The optimum experimental conditions obtained by a central composite design were 17.99:1, 0.51 wt%, and 66.54 °C for the molar ratio of methanol to WCO, catalyst loading and reaction temperature, respectively. At these optimum values, the highest experimentally obtained biodiesel yield was 83.16%, which matched the predicted value (82.71%) reasonably well with R2 = 0.9914. According to gas chromatography analysis, the fatty acid methyl ester conversion under optimum conditions was 97.05%. While 20% blending of biodiesel on a volume basis with petroleum-based diesel showed remarkable fuel properties, the catalyst exhibited better stability after being regenerated and reused for six cycles. This study extends the frontier of knowledge in the economical production of biofuels from waste products.