Heterogeneous alkaline earth metal–transition metal bimetallic catalysts for synthesis of biodiesel from low grade unrefined feedstock†
A bimetallic alkaline earth metal–transition metal oxide, synthesized through a method of direct low-temperature decomposition of the bimetallic complex, is reported for the synthesis of biodiesel. Due to the high phase purity of the Ca/Fe catalytic system and its catalytic stability and robustness, the Ca/Fe catalyst was selected for further investigation. A transesterification conversion of 99.5% could be achieved in 1 h under the optimal conditions: feedstock to methanol, 1 : 20; catalyst loading, 6 wt%; temperature, 120 °C. ANOVA tests suggested that the reaction temperature was discerned as the most prominent factor which contributed 82.84% to the overall catalytic feedstock conversion. In addition, the Ca/Fe catalytic system demonstrated a high FFA tolerance of 2 wt% and a water tolerance of 1 wt% with remarkable catalytic activity in one-step biodiesel synthesis.