Acid heterogeneous catalysis for free fatty acids esterification

Deacidification of not refined, vegetable or waste oils is the first step towards a low-cost biodiesel production. The authors present a study on the esterification reaction of Free Fatty Acids (FFA) contained in different kinds of feedstock in presence of methanol. Two acid resins, Amberlyst®46 and Purolite®D5081, have been used as acid heterogeneous catalysts. The outcome of this study shows that these catalysts do not incur into chemical or mechanical deactivation and are stable in the adopted reaction conditions. This happens thanks to their particular configuration in which the sulphonic acid sites are located only on their surface, so to eliminate restrictions to the mass transfer and giving a very stable performance over time. The authors have found that there is a linear correlation between the FFA concentration in the oil and the number of active acid sites on the catalyst’s surface. This finding was also possible thanks to the use of the process simulation program PROII by Simsci-Esscor’s (Invensys). Different kinds of not refined feedstock have been selected as potential raw materials for biodiesel production. In particular the use of alternative oil crops like Brassicaceae and Nicotiana tabacum is investigated. The main objective of the work will be to assess the sustainability of biodiesel production from these innovative cultivations in crop rotation, following a life cycle thinking approach.