A review on catalytic biodiesel production

The industrialization of societies and as the result, the increase of demand for fuel in the world and speculations on the reduction of fossil fuels and on the other hand, the issue of world health emphasizes on the necessity of substituting renewable and clean energy, so biodiesel as the best substitute for diesel fuels is common. In general, three ways are used to produce biodiesel including pyrolysis, micro-emulsification and transesterification among which transesterification is known as the most usual and common way. The catalysts used in transesterification are divided into three groups of acidic, alkaline and enzymatic catalysts in which the acidic and alkaline catalysts in turn divide into two groups of heterogeneous and homogeneous. The Transesterification reaction using acidic catalysts involves more time for the reaction and high cost. The alkaline catalysts produce an appropriate amount of product in moderate operational conditions and show a better performance in comparison with the other catalysts. These catalysts have a limitation in use for raw material containing high free fatty acids. The way of using Lipase catalysts is the most viable method that can be applied, however it requires high costs. Given today's high total cost as the main obstacle for producing biodiesel, using animal fats and waste oils as raw material and using the heterogeneous catalysts and preferably renewable ones is suggested so as to reduce the total cost