Aspects of Mg–Al mixed oxide activity in transesterification of rapeseed oil in a fixed-bed reactor

The performance of Mg–Al mixed oxides prepared from different types of precursors in transesterification of rapeseed oil was studied in a fixed-bed reactor. The structure and basicity of Mg–Al–K and Mg–Al–Na mixed oxides with 3.6 Mg/Al molar ratio were compared before and after the catalytic tests carried out at various reaction temperatures (115 and 140 °C) and residence times (0.7, 1.54 and 1.79 h). The maximum ester yield of 77% was obtained at 140 °C and residence time of 1.54 h. The ester yield was stable during 50 h of the experiment. It was associated with the negligible magnesium leaching from the solid catalyst into the liquid phases and the minimum change in the composition, structure and basicity of Mg–Al mixed oxides after the catalytic test.