Catalytic Degradation of Rapeseed (<i>Brassica napus</i>) Oil to a Biofuel Using MgO: An Optimization and Kinetic Study

Abstract

A kinetic study of the catalytic degradation of rapeseed (Brassica napus) oil over MgO has been performed in a 70 cm3 batch reactor using a 2k factorial level experimental design. This study predicted the parameters that affected the liquid yield and the highest selectivity for naphtha. The optimal operating conditions were a temperature of 390 °C, a hydrogen gas pressure of 3 bars, a reaction time of 60 minutes and MgO catalyst content of 0.5 wt%. These conditions gave a yield of 85.33 wt% and 32.04 wt% liquid fuel and naphtha, respectively. From an analysis with a simulated distillation gas chromatograph and a gas chromatograph/mass spectrometer, the distribution of liquid fuel was found to be C5-C12 aliphatic hydrocarbon molecules, 9.49 wt% alkane and 50.62 wt% alkene. FT-IR analysis showed C-H (stretching) indicating the presence of aliphatic hydrocarbon compounds (among the main functional groups), represented by the obvious peak at 2850-3000 cm-1. The physicochemical parameters identified pyrolysis oil, which has an acidity of 1.49 mgKOH/mg and a heating value and kinematic viscosity of 44.93 MJkg-1 and 0.99 mm2s-1, respectively. The temperature contributed to the decomposition of triglyceride acid by secondary catalytic cracking, and the acid active sites on MgO produced a biofuel that was used as an alternative fuel. Furthermore, the kinetic parameters were also determined to be second order. The activation energy (Ea) and the pre-exponential factor (A) from an Arrhenius relationship were also defined as 71.134 KJ mol-1 and 18.21 s-1, respectively.