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

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 catalysts 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.