Moroccan sardine scales as a novel and renewable source of heterogeneous catalyst for biodiesel production using palm fatty acid distillate

The continued growth in energy consumption, in concert with the depleting resources of fossil fuels and their detrimental effects on the environment, has required the exploration of substitute, renewable, and sustainable sources of energy. Biodiesel is one such alternative. In this current study, a heterogeneous sulfated catalyst based on Sardine scales was developed to improve biodiesel synthesis from palm fatty acid distillate (PFAD) through esterification. The catalyst was synthesized via a clean flash pyrolysis method with a thermal shock (950 °C) followed by a sulfonation process. The prepared catalyst was characterized by utilizing diverse methods, including XRD, FTIR, TGA/DSC, SEM/EDX, DLS, BET, and the Hammett test. The sulfated hydroxyapatite (HAPSS-SO4) catalyst demonstrated a maximum conversion of PFAD to biodiesel of 96.75% under optimal reaction conditions such as 3 wt% catalyst loading and 15:1 MeOH/PFAD molar ratio for 3 h at 70 °C. Additionally, the catalyst proved excellent stability, with the ability to regenerate for three cycles. The properties of the produced biodiesel are within the limits stipulated by international standards. The results of the molecular simulation demonstrate that the Lewis acid sites (Ca) are very susceptible to attack through the free fatty acid (FFA). The study proved the effectiveness of a sardine scale-derived catalyst (HAPSS-SO4) as a heterogeneous catalyst for biodiesel production.