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<p>This study comprehensively investigates unrefined castor oil biodiesel production and its subsequent evaluation in a diesel engine. Cold pressing was selected over Soxhlet reflux for oil extraction, once its faster processing and superior preservation of oil quality were demonstrated. Biodiesel was synthesized and optimized through transesterification using both homogeneous (KOH) and heterogeneous (calcined Mg/Al hydrotalcite) catalysts. Optimization of key reaction variables was performed using response surface methodology. Optimized conditions for the homogeneous catalyzed reaction were 44.27&#xa0;°C, 20:1 methanol/oil molar ratio, 2% (w/w) KOH, after 30&#xa0;min. For the heterogeneously catalyzed reaction, the process was optimized at 65&#xa0;°C, 57.83:1 methanol:oil molar ratio, 14.17% (w/w) catalyst, after 240&#xa0;min. Both optimization processes achieved a maximum biodiesel yield above 76%, surpassing typical reported values for unrefined castor oil biodiesel production. Resulting biodiesel exhibited high kinematic viscosity (15.1 mm<sup>2</sup>/s at 40&#xa0;°C) and density (930&#xa0;kg/m<sup>3</sup> at 15&#xa0;°C). To comply with EN 590 fuel standards, a 10% biodiesel, 90% diesel fuel blend (B10) was formulated, successfully reducing viscosity to 3.38 mm<sup>2</sup>/s and density to 839.66&#xa0;kg/m<sup>3</sup>. Engine performance tests using B10 demonstrated significant environmental benefits, i.e., unburnt hydrocarbon and CO emissions decreased up to 67 and 41%, respectively, thus indicating improved combustion stability. While some emissions improved, minor variations in NOₓ emissions were observed. This area is targeted for future optimization. This work provides, as the main innovation, a comprehensive and complete analysis on the direct transformation of unrefined castor oil in biodiesel, a route that has received poor specific consideration in the existing literature. Through catalyst-based optimization and practical engine testing, this research demonstrates the high potential of this low-cost and underutilized raw material as a sustainable and economically viable substitute to biodiesel.</p>

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Optimization of biodiesel production from unrefined castor oil: homogeneous vs. heterogeneous catalysis and diesel engine performance

  • 期刊论文

  • 发表日期：

    2025年9月9日

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  • S. Jedidi,
  • D. Levia-Candia,
  • J. Tejada-Hernandez,
  • N. Nasri,
  • M. P. Dorado

摘要

This study comprehensively investigates unrefined castor oil biodiesel production and its subsequent evaluation in a diesel engine. Cold pressing was selected over Soxhlet reflux for oil extraction, once its faster processing and superior preservation of oil quality were demonstrated. Biodiesel was synthesized and optimized through transesterification using both homogeneous (KOH) and heterogeneous (calcined Mg/Al hydrotalcite) catalysts. Optimization of key reaction variables was performed using response surface methodology. Optimized conditions for the homogeneous catalyzed reaction were 44.27 °C, 20:1 methanol/oil molar ratio, 2% (w/w) KOH, after 30 min. For the heterogeneously catalyzed reaction, the process was optimized at 65 °C, 57.83:1 methanol:oil molar ratio, 14.17% (w/w) catalyst, after 240 min. Both optimization processes achieved a maximum biodiesel yield above 76%, surpassing typical reported values for unrefined castor oil biodiesel production. Resulting biodiesel exhibited high kinematic viscosity (15.1 mm2/s at 40 °C) and density (930 kg/m3 at 15 °C). To comply with EN 590 fuel standards, a 10% biodiesel, 90% diesel fuel blend (B10) was formulated, successfully reducing viscosity to 3.38 mm2/s and density to 839.66 kg/m3. Engine performance tests using B10 demonstrated significant environmental benefits, i.e., unburnt hydrocarbon and CO emissions decreased up to 67 and 41%, respectively, thus indicating improved combustion stability. While some emissions improved, minor variations in NOₓ emissions were observed. This area is targeted for future optimization. This work provides, as the main innovation, a comprehensive and complete analysis on the direct transformation of unrefined castor oil in biodiesel, a route that has received poor specific consideration in the existing literature. Through catalyst-based optimization and practical engine testing, this research demonstrates the high potential of this low-cost and underutilized raw material as a sustainable and economically viable substitute to biodiesel.