PVA embedded hydrotalcite membranes as basic catalysts for biodiesel synthesis by soybean oil methanolysis

Biodiesel was produced by transesterification of soybean oil with methanol using poly(vinyl alcohol) membranes as solid base catalysts. The membranes were prepared dispersing hydrotalcite in the polymer solution. The reactions were carried out at 60 °C in a three-necked batch reactor using all the catalysts in the form of pellets. The effect of the hydrophobic/hydrophilic properties of the membranes on the catalytic activity was studied. Membranes with a poly(vinyl alcohol) matrix totally or partially acetylated, in order to increase hydrophobicity, or treated with succinic anhydride, in order to increase hydrophilicity, were prepared. The best results were obtained with the most hydrophilic membrane. In order to evaluate the catalyst stability a same sample of that membrane was used in seven consecutive runs. These catalysts are more active in the transesterification of soybean oil with methanol than the free hydrotalcite and can be reused for several runs without any further reactivation.A diffusion-kinetic model was developed in an attempt to explain the induction period observed in the kinetic curves.