Continuous production of biodiesel in a packed-bed reactor using shell–core structural Ca(C 3H 7O 3) 2/CaCO 3 catalyst

Abstract

The continuous production of biodiesel was studied by using a steady-state packed-bed reactor. The shell–core Ca(C 3H 7O 3) 2/CaCO 3 solid-base catalyst was prepared with a mechanical strong core of CaCO 3 for continuous transesterification of soybean oil in a packed-bed reactor. Alcohol–oil ratio, retention time and reaction temperature were evaluated to obtain optimum reaction conditions. The yield of fatty acid methyl esters (FAME, i.e. biodiesel) achieved 95% at the reaction temperature 60 °C, alcohol–oil molar ratio of 30:1 and retention time of 168 min. The reusability of catalyst was checked up to 5 cycles and found negligible decrease in the catalyst activity. Water in the oil can significantly decrease the yield due to the deactivation of Ca(C 3H 7O 3) 2 and hydrolysis of FAME. The transesterification of soybean oil, canola oil and sunflower oil also was compared with model compound, triolein, using powder Ca(C 3H 7O 3) 2 in the batch reactor. Although these oils contained different triglyceride mixtures, their FAME yields were comparable. A Langmuir–Hinshelwood rate equation was established for the transesterification of soybean oil with methanol. Regression of experimental data indicated that the transesterification was an endothermic reaction with the enthalpy change of 23,504 J/mol and the activation energy was 42,096 J/mol.