Marble slurry derived hydroxyapatite as heterogeneous catalyst for biodiesel production from soybean oil

Abstract In this study, utilization of waste marble slurry (MS) as an eco‐friendly and low‐cost heterogeneous catalyst is introduced for biodiesel production from soybean oil. Catalytic transesterification reaction was done to convert biodiesel from soybean oil using Marble slurry (MS) derived calcined marble slurry (CMS), and hydroxyapatite (HAP) as a heterogeneous catalyst. Marble slurry derived catalysts were characterized by XRD, FTIR, SEM, and TGA with elemental analysis. Hammett indicator method and ion exchange method were also used to verify catalytic activities of the catalysts. The HAP provided the better biodiesel yield of 94 ± 1 % with the highest basicity (13.30 mmol/g) and basic strength than CMS under optimized reaction conditions: reaction temperature 65 °C; reaction time 3 h; methanol/oil molar ratio 9:1; and catalyst concentration 6 wt%. Reusability tests provide confirmation about the stability of the catalyst and slight fluctuations in catalytic activity and biodiesel yield when used up to five runs.