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Effects of feed ratio on the product quality of SAME reactive distillation process

Abdulwahab Giwa and Saidat Olanipekun Giwa

This research work has been carried out to investigate the effects of volumetric feed ratio of stearic acid and methanol on the purity of the stearic acid methyl ester (SAME) obtained from a reactive distillation processaccomplished through an esterification reaction. The investigation was carried out by developing a model of the process with the aid of Aspen Plus using RadFrac column having 32 stages including the condenser and the reboiler. Wilson model was used as the property package of the simulation. The feeds (top – stearic acid and bottom – methanol) were passed into the column at a temperature and a pressure of 25 oC and 1 atm, respectively. The esterification reaction of the process was modelled as an equilibrium type, the equilibrium constant of which was estimated using Gibbs free energy. In the simulation of the developed Aspen Plus model of the reactive distillation process, the volumetric feed ratio of the column was varied from 3 to 11, and the results obtained showed that the trends of the mole fraction profiles of the components of the process were very similar to one another except those of the feed ratios of 9, 10 and 11 that were a little bit different from the others. Also obtained from the results was that increasing the volumetric feed ratio of the column made the mole fraction of the desired product, which was stearic acid methyl ester and also known as methyl stearate, to decrease. The results obtained have thus revealed that there was an inverseproportional, but not linear, relationship between the volumetric feed ratio of the process and the mole fraction of the desired product. Furthermore, it was discovered from the results that the feed ratio that gave the highest mole fraction of the desired product was 3