Scalable free fatty acid esterification for methyl esters production

Deacidification of raw oils is the first step towards a low-cost biodiesel (BD) production. The authors propose a method of deacidification based on the esterification of free fatty acids (FFA). Two acid resins, Amberlyst®46 (A46) and Purolite®D5081, and sulphated zirconias (SO4=/ZrO2) were used as catalysts. The outcome of this study shows that the two resins do not incur into chemical or mechanical deactivation giving a very stable performance over time. Differently, inorganic catalysts incur in fast deactivation due to active groups leaching [1]. The authors have moreover found that there is a linear correlation between the FFA concentration and the number of active acid sites on the catalyst’s surface. This finding was also possible thanks to the use of the software PROII (Simsci-Esscor’s) for the process simulations. The pseudohomogeneous model already reported in literature by the authors and hereinafter displayed was used [2]. Activities (a) are used instead of concentrations. The adopted kinetic parameters set is reported in Table 1. The absolute values of the pre-exponential factors of the Arrhenius equation (k0 i) were corrected so to take into account the presence of both a second liquid phase and a different type of catalyst. The adopted model resulted to be in good correlation with the experimental data and to estimate rather precisely the time needed for the complete conversion of FFA for different oils (as way of example in Fig. 1 the comparison is represented for a rapeseed oil with an initial FFA concentration of 6%wt).