Process Optimization of Biodiesel Production Using Waste Snail Shell as a Highly Active Nanocatalyst

Abstract

In this work, we reported the transesterification of soybean oil (SO) to biodiesel using a basic CaO nanocatalyst produced by sequential calcination, hydration, and dehydration of waste snail shells. Response-surface methodology (RSM) and a central composite design (CCD) were used to predict several optimization parameters. 1H-NMR confirmed that 98.5% of the SO was transformed into methyl ester biodiesel. Under the optimal reaction parameters of catalyst loading of 6 wt. %, methanol to oil molar ratio of 8 : 1, reaction duration of 3 h, and temperature of 70°C, an excellent biodiesel yield of 96.1% was obtained. The transesterification of SO to biodiesel displayed a significantly low activation energy (30.45 kJ mol-1), whereas, the turnover frequency of the transesterification reaction was found to be 0.0063 mol g-1 h-1. The catalyst showed excellent stability and was consecutively used for six cycles without a significant decline in catalytic activity. Based on life cycle cost analysis (LCCA), the estimated cost for producing 1 kg of biodiesel in this study comes out to be just $0.935, signifying its strong potential for widespread commercial use.