Biodiesel production from mixtures of waste fish oil, palm oil and waste frying oil: Optimization of fuel properties

• Biodiesel production from mixtures of waste fish oil, palm oil and waste frying oil
• A simplex centroid design and statistical modeling were performed.
• High biodiesel yield and FAME content were obtained for all the oil mixtures assayed.
• Fuel properties such as viscosity, oxidative stability and COM were optimized.
• A Pareto Front was generated using weighted-sum multi-objective optimization.

The present work studies the influence of waste fish oil, palm oil and waste frying oil as raw material on biodiesel properties. The experimental planning was executed through acid esterification (6:1 methanol to oil ratio, 1 wt.% sulfuric acid, at 60 °C, 1 h) followed by transesterification (9:1 methanol to oil ratio, 0.5 wt.% sodium hydroxide, at 60 °C for 1 h). Biodiesel samples showed yield higher than 82%, reaching 90% for palm oil (33.3 wt.%) and waste frying oil (66.7 wt.%) biodiesel. FAME content was higher than 92.3% and had a maximum of 98.5% for waste fish oil (33.3 wt.%) and palm oil (66.7 wt.%) biodiesel. Special cubic models were used to fit experimental data, and were optimized by response surface methodology and multi-objective optimization. Viscosity (4.3 mm2/s) and COM (2.5 °C) were minimized when pure fish oil was used as raw material, whereas IP maximum (22.0 h) was found for palm oil biodiesel. Multi-objective optimization evidenced that although the use of the pure oils as feedstock presented more advantages to biodiesel properties, the waste fish oil (42.1 wt.%) and waste frying oil (57.9 wt.%) mix is beneficial, if the aim is IP (20%) and COM (80%) improvement.