The conversion of FFA in the tobacco seed oil is lower compared
to canola oil (Figs. 3 and 4).One of the major differences is the initial FFA concentration, that is about 1% vs. the 4% for tobacco and
canola oil, respectively. However, this difference was insufficient
to account for the lower conversion. US enhances the mass transfer
rate considerably with the exception of the test with canola oil at
63C. In this case, the conversion reached 94% after a reaction time
of 6 h, whereas it only reached 91% with US. This lower conversion
must be due to equilibrium considerations – perhaps water contamination, lower temperature or MeOH might have preferentially
evaporated during this test, as already hypothesized by the authors
in a previous study[21]. All other tests show a significant improvement in the mass transfer rate with US – typically greater than 2X.
Table 4summarizes the relative improvement,km,US/km, and the
best fit parameters