Kinetic study by 1H nuclear magnetic resonance spectroscopy for biodiesel production from castor oil

In this work a highly profitable process to produce biodiesel from castor oil is being reported, which is convenient in equatorial climate countries where the higuerilla bush grows everywhere. It is not necessary to preheat the reactants, nor to use heat exchange systems in the reaction. The temperature and catalyst concentration effects in the reaction yield and the kinetic constants quantifications are determined by proton nuclear magnetic resonance spectroscopy (1H NMR). The benefit of using 1H-NMR system for monitoring the results and outcomes of the transesterification reaction is clearly obtained. An irreversible step followed by a reversible stage, both of pseudo-second-order are obtained in the best modeling of experimental data, the rate constant and equilibrium constant obtained k2 = 814.056 ml mol−1 min−1 and K = 17,190, respectively, are in agreement with previous experimental studies. A biodiesel demand of 3935 kg/month, requires to use two intermittent reactors producing two batches from 122.26 l/day. The first reactor must operate 14.42 min at 26 °C, stirring the reaction constantly at 700 rpm to produce this demand which improve its quality in the second reactor. The adequate molar ratio feeding of oil/methanol/sodium hydroxide is 1/6/0.20, respectively.

► Castor oil chemical characteristics give a highly rentable process at 26 °C.
► Conversion equation of oil to biodiesel is an original contribution of this work.
► Castor oil equilibrium constant value is bigger than the corresponding to other oils.
► Sample preparation procedure and the 1H NMR equipment handle in detail are reported.
► General methodology reported drives to adequate results reproducibility.