RSM Optimization of Used Engine Oil Recovery Using Coal-Based Activated Carbon in a Pyrolysis–Distillation Unit

Recovery of hydrocarbon compounds from waste lubricating oil has gained considerable attention because of its potential as an alternative liquid fuel source and its contribution to environmental protection. Besides containing valuable hydrocarbons, waste lubricating oil also contains sulfur compounds and heavy metals that may reduce fuel quality and cause environmental pollution. This study evaluates the recovery of waste lubricating oil through a pyrolysis–distillation process assisted by activated carbon derived from low-rank coal from East Kalimantan, Indonesia. The activated carbon was synthesized through carbonization and chemical activation and characterized using iodine number analysis to determine its adsorption capability. Response Surface Methodology (RSM) was applied to optimize pyrolysis temperature and activated carbon dosage in order to maximize liquid yield and contaminant removal efficiency. The synthesized activated carbon exhibited an iodine number of 1163.51 mg/g. Optimization predicted optimum conditions at 416.54 °C and 12.87 wt.% activated carbon dosage, producing 89.67% liquid yield and approximately 76% contaminant removal efficiency. Experimental validation confirmed the model prediction, resulting in 88% liquid yield with satisfactory fuel characteristics.