Heterogeneous catalysis for free fatty acids esterification reaction as a first step towards biodiesel production
Different non-food-grade oils characterized by a high content of free fatty acids have been successfully deacidified with the use of commercial resins Amberlyst®46 (A46), Purolite®D5081and zirconium sulphate. Not refined or waste oils have been selected in order to reduce the biodiesel production costs, mostly depending on the raw material’s high price. Five sulphated, Zr-based, catalysts have been synthesized through different methods based on sol-gel or impregnation techniques and tested in the same reaction. The role played by the different catalysts’ features in affecting their catalytic activity in the studied reaction is discussed. The economic sustainability of the whole process is also assessed.
The EU directive 2009/28/EC has set the targets of achieving in each Member State, by 2020, a minimum share of 10 percent of energy consumption in transport sector from renewable sources. In this context special consideration is paid to the production of biofuels.
Biodiesel is a biofuel that is produced through triglycerides transesterification of food-grade oils with methanol, in the presence of an alkaline catalyst (1, 2). Food-grade oilseeds may be easily converted into biodiesel, but besides being in competition with the food requirements, this route results in a biofuel that is not competitive, cost-wise, with the petroleum-based diesel (3). On the other side the use of non-edible, raw oils results in saponification problems during the transesterification reaction due to their high content of free fatty acids (FFA) (4, 5). A process capable of reducing the feedstock’s acidity is not only necessary for practical reasons, but also to meet the EN14214 European standard for biodiesel, which requires a FFA maximum content of 0.5 percent per weight.
In this work, the esterification reaction of FFA in raw or waste greases is ...