Guanidine catalysts for biodiesel production: Activity, process modelling and optimization

Since conventional catalysts for biodiesel production have problems with saponification, ten guanidine de-rivatives were investigated in this study for their catalytic activity in the production of biodiesel from rapeseed oil and methanol. The most active catalyst was selected for process optimization. The influence of process pa-rameters (reaction time, mass percent of catalyst and alcohol to oil ratio) on the transesterification process was evaluated using a design of experiments following a 33 factorial Box-Behnken design of experiments in conjunction with response surface methodology. An accurate quadratic model was developed (p-value < 0.001, F-value 65.90, R2 0.990) and used for process optimization. The resulting optimal conditions were 1.8 wt% of catalyst, methanol to oil ratio of 6.2:1, and a reaction time of 80 min with a predicted yield of 99.2 mol%. The optimal conditions were verified on a larger scale (1 kg), obtaining a yield of 96.5 mol%, confirming the accuracy of the quadratic model. In addition, the obtained biodiesel was characterized with respect to the main physi-cochemical and application properties.