High temperature solid-catalized transesterification for biodiesel production

Biodiesel has become more attractive recently because of its environmental benefits and the fact that it is made from renewable resources. Biodiesel is a mixture of monoalkyl esters of long chain fatty acids derived from renewable feed stock like vegetable oils and animal fats, mainly made of fatty acid glycerides. It is produced by transesterification processes in which oil or fat are reacted with a monohydric alcohol in the presence of a catalyst. The transesterification process is affected by reaction conditions, alcohol to oil molar ratio, type of alcohol, type and amount of catalysts, temperature and purity of reactants. Heterogeneous acid catalysts are quite efficient in promoting the transesterification reaction also in the presence of free fatty acids, which get esterificated under the same reaction conditions. They also allow a prompter separation of pure glycerol and a simplification of subsequent purification steps of this by-product. In the present paper, the performance of a titanium doped zirconia solid catalyst is presented, with attention to the effect of water in the reactant feed. Results show that the presence of water is well tolerated and even beneficial for the transesterification process.