%0 Journal Article
%T Heterogeneous Tin Catalysts Applied to the Esterification and Transesterification Reactions
%A M¨¢rcio Jos¨¦ da Silva
%A Abiney Lemos Cardoso
%J Journal of Catalysts
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/510509
%X The interest in the development of efficient and environmentally benign catalysts for esters synthesis has increased exponentially, mainly due to the demand for biodiesel. In general, fatty esters are used as bioadditive, cosmetic ingredients, polymers, and, more recently, biofuel. Nevertheless, most of the production processes use nonrecyclable and homogenous alkaline catalysts, which results in the reactors corrosion, large generation of effluents, and residues on the steps of separation and catalyst neutralization. Heterogeneous acid catalysts can answer these demands and are an environmentally benign alternative extensively explored. Remarkably, solid acid catalysts based on tin have been shown highly attractive for the biodiesel production, mainly via FFA esterification reactions. This review describes important features related to be the synthesis, stability to, and activity of heterogeneous tin catalysts in biodiesel production reactions. 1. Introduction The recent demand by alternative energy sources has made the biodiesel production a concern worldwide. Biodiesel is a renewable, biodegradable, and less polluting fuel than mineral diesel. It consists of ethyl (FAEE) or methyl esters of fatty acids (FAME), which are obtained from the triglycerides (TG) transesterification reactions present in vegetal oil (Figure 1), such as showed in Figure 1 [1]. Figure 1: Transesterification of triglycerides with methyl or ethyl alcohol. Currently, most of the processes used for biodiesel production from the vegetable oils transesterification operating under homogeneous alkaline catalysis conditions (i.e., NaOH, KOH, or NaOCH3) [1]. However, if a high content of FFA is present, homogeneous acid catalysts (i.e., H2SO4) are commonly applied on the steps of preesterification [1]. Both processes result in a large generation of wastewaters, residues, and salts formed during the catalyst neutralization and products recovery. Currently, the greater part of the biodiesel consumed is produced by transesterification of expensive edible vegetable oils, which are responsible for 65% of the final price [2]. Alternative routes for the production of biodiesel where inexpensive feedstock such as animal fats, waste frying, and highly acid vegetable oil are an attractive option [3]. Nevertheless, these low cost raw materials are incompatible with alkaline catalysts due the formation of soaps, which hinders the separation of the FAME or FAEE from the glycerol, reducing consequently the biodiesel yields [4]. For these reasons, developing active catalysts for the FFA esterification
%U http://www.hindawi.com/journals/jcat/2013/510509/