Highly efficient scallop seashell-derived catalyst for biodiesel production from sunflower and waste cooking oils: Reaction kinetics and effect of calcination temperature studies

The sustainable production of biodiesel from waste materials has become of utmost importance in recent years. In this study, cheap CaO catalysts were prepared by calcination of waste scallop seashells (Noble Pectin). The seashells were thermally treated at different temperatures (600–1000 °C) and then used in the transesterification of sunflower oil for biodiesel production. The catalysts were characterized using Fourier Transform Infrared Spectroscopy (FTIR) and simultaneous Thermal Gravimetric-Differential Scanning Calorimetry (TG-DSC) techniques. The highest Fatty Acid Methyl Esters (FAME) yield (97%) was obtained in the presence of the catalyst calcined at 700 °C under the following conditions: a methanol-to-oil molar ratio (MOMR) of 12:1, a catalyst-to-oil ratio (CTOR) of 10 wt%, a stirring rate of 700 rpm, a reaction temperature of 65 °C and a reaction time of 4 h. The seashell-derived catalyst was practically stable for at least 4 consecutive runs in the reusability study, maintaining a high FAME yield (>92%). The reaction followed pseudo-first order kinetics, with an activation energy (Ea) of 133.57 kJ/mol and a pre-exponential factor (A) of 4.025 × 10¹⁸ min⁻¹. This catalyst additionally exhibited a very high activity in the transesterification of waste cooking oil, with a similar FAME yield of 97%. This shows that this catalyst is promising for potential biodiesel production scale-up schemes and industrial applications.