Biodiesel from rapeseed oil (Brassica napus) by supported Li2O and MgO

Abstract

Vegetable oils are a vast triglyceride source for biodiesel production; i.e. fatty acid methyl esters (FAME), with methanol and a catalyst via transesterification reaction. The aim of this work was to study heterogeneously catalysed biodiesel production with solid oxides such as mayenite (Ca12Al14O33) and alumina (Al2O3) as catalyst carriers using edible rapeseed oil as feedstock. These oxides were impregnated to have Li2O and MgO concentrations of 5–10 and 5–30 wt% on each carrier, respectively. The catalysts were characterized using N2-physisorption (BET/BJH), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analyses. The synthesized catalysts were mesoporous ranging from 119 to 401 Å and their chemical phase composition was confirmed by the XRD. The catalyst coating (MgO/Li2O) was studied, along with the catalyst amount in the reactor and the assessment of the transesterification reaction kinetics. The reaction was studied at 60 °C, atmospheric pressure, agitation rate of 180 rpm, and a reaction time of 2 h in a 6:1 molar ratio of methanol to oil. For each catalyst, loadings of 2.5, 5, and 10 wt% relative to the oil weight were evaluated. The highest biodiesel yield was obtained by 5 wt% (relative to oil weight) impregnated mayenite catalyst coated with 10 wt% of Li2O. The kinetic data fits to a pseudo-first-order model having a reaction rate constant equal to 0.045 min−1 under these mild reaction conditions.