Vegetable Oil Deacidification by Amberlyst: Study of the Catalyst Lifetime and a Suitable Reactor Configuration

Abstract

Deacidification of crude vegetable oils containing high amounts of free fatty acids is the first step toward low-cost biodiesel production. In order to lower the acid content, the most popular method is based on an esterification process carried out with methanol and using Amberlysts as solid acid heterogeneous catalysts. This process was deeply investigated in recent years with good results. At the moment, the lifetime of the catalyst is the most crucial issue in industrial applications. With the aim of investigating this aspect, 90 consecutive batch deacidification runs, each lasting 6 h, were conducted using crude palm oil or soybean oil as a feedstock and Amberlyst 46 as a catalyst. At the end of the recycles, a decrease of activity of about 25% was observed, probably ascribed to some fragmentation of the catalyst's particles, with a loss of active material, caused by the mechanical stress occurring in the batch reactor. The same reaction was also conducted in both continuous and semicontinuous catalytic packed-bed reactors, in order to immobilize the catalyst so as to prevent mechanical stress. A catalytic packed-bed reactor needs to be fed with a homogeneous methanol/ vegetable oil emulsion: the results obtained with a traditional mechanical stirring and with an emulsificator were compared.

Ultrasonic enhancement of the acidity, surface area and free fatty acids esterification catalytic activity of sulphated ZrO 2 –TiO 2 systems

“…As already evidenced in previous studies of the authors [5,7], the experiment carried out in absence of the catalyst showed no FFA conversion.…”

“…FFA are highly sterically hindered molecules, which might not be able to penetrate inside the pores as narrow as those of the catalysts here synthesized. The importance of the location of the active sites on the outer surface of the catalyst has already been evidenced by the authors in a previous work for other kinds of materials [7]. Therefore, it is possible to assume that, in the present case, the active sites located on the catalyst's outer surface are the most responsible for the reaction to occur.…”

“…In recent years a great deal of attention has been focused on the study of the pre-esterification as a method to lower the acidity of the raw oils to be used for biodiesel production [5,[7][8][9][10]. The esterification reaction of FFA also allows to improve the final yield in biodiesel as the obtained products are FAME, i.e.…”

“…For liquid phase reactions, the latter approach is preferred as it brings benefits such as the easier separation of the catalyst from the products, thus facilitating catalyst recovery and re-use. Much attention has been focused on the use of ion exchange acid resins as catalysts for the FFA esterification reaction [5,[7][8][9][10]. A significant outcome of these studies lies in the correlation between the catalytic activity of the tested catalysts with the acidity present on the catalyst outer surface regardless of the nature of adopted catalysts [10].…”

Vegetable Oil Deacidification by Methanol Heterogeneously Catalyzed Esterification in (Monophasic Liquid)/Solid Batch and Continuous Reactors

“…In a previous paper 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 catalytic bed, the FFA esterification reached in fact the thermodynamic plateau, corresponding to FFA conversion greater than 90%. This means that the final FFA concentration in the oil was about 0.3% wt , lower than the set limit of 0.5% w for biodiesel processes production.…”