Synthesization of metal based-HAP catalysts for enhanced biodiesel yield from palm fatty acid distillate (PFAD)

Biodiesel is a promising alternative fuel and one of the fundamental renewable energy resources due to its unique properties such as significant reduction in greenhouse gas emissions, non-sulfur emissions, non- particulate matter pollutants, low toxicity, and biodegradable. However, it is expensive to produce biodiesel compared to diesel fuel due to the expensive raw material. Heterogeneous catalyst was used because it low cost and easy to separate the product. In this study, biodiesel is studied using high free fatty acid (FFA) feedstock which is palm fatty acid distillate (PFAD) and using different metal-hydroxyapatite (HAP) catalysts; Mg/HAP, Na/HAP, and Cu/HAP. HAP has ion-exchange ability, acid base adjustability and non-toxicity. The catalysts were characterized via X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer-Emmett- Teller surface area measurement (BET), temperature-programmed desorption of ammonia (TPD-NH₃), and the biodiesel was identified using Fourier transform infrared spectroscopy (FTIR) and gas chromatography with flame-ionization detector (GC-FID). The optimum parameter used were molar ratio 10:1 methanol to PFAD within 2 h reaction time at 65 °C. The results showed that only Cu/HAP catalyst works on PFAD to convert to biodiesel due to mesoporous structure as observed in BET, and the biodiesel yield was 40.4%. This might due to presence of strong acid sites that been observed using TPD-NH₃.