New heterogeneous process for biodiesel production: A way to improve the quality and the value of the crude glycerin produced by biodiesel plants

With over 10 years of development and commercial use in Europe, biodiesel has now proved its value as a fuel for diesel engines. A sharp increase in the production of this kind of biofuel is expected in the near future. Biodiesel is obtained through transesterification reaction of vegetable oil by methanol. Several commercial processes to produce fatty acid methyl esters from vegetable oils have been developed and are available today. These processes use homogeneous basic catalysts such as caustic soda or sodium methylate which lead to waste products after neutralization with mineral acids. This paper provides a general description of a completely new continuous biodiesel production process, where the transesterification reaction is promoted by an heterogeneous catalyst. This process requires neither catalyst recovery nor aqueous treatment steps: the purification steps of products are then much more simplified and very high yields of methyl esters, close to the theoretical value, are obtained. Glycerin is directly produced with high purity levels (at least 98%) and is exempt from any salt contaminants. With all these features, this process can be considered as a green process. (c) 2005 Elsevier B.V. All rights reserved.