Internal mass-transfer limitations on the transesterification of coconut oil using an anionic ion exchange resin in a packed bed reactor

In this study, a strongly basic anion-exchange resin was used for the transesterification of coconut oil and methanol using a continuous-flow packed-bed reactor. Statistical analysis shows that the observed conversion and apparent bulk reaction rate are insensitive to temperature. This suggests that mass transfer is the rate-determining step. Analysis of the Wagner–Weisz–Wheeler (WWW) modulus shows that the observed reaction rate is strongly influenced by internal mass-transfer resistances (WWW > 4) under most of the experimental conditions used. However, in some tests, the overall reaction rate can be said to be in the transition regime between reaction control and internal mass-transfer control (0.15 < WWW < 4). Extended continuous flow experiments showed no noticeable decline in the catalyst activity even after almost 400 reactor bed void volumes of biodiesel had been produced. These results suggest that the catalyst and thus the overall reactor performance may be further improved by increasing the porosity.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (143 K)Download as PowerPoint slideHighlights► The reaction rate of the transesterification of coconut oil on an anion-exchange resin is insensitive to temperature. ► Many of the Weisz–Wheeler–Wagner moduli computed for the reaction conditions are above 4. ► Results suggest that transesterification of coconut oil to biodiesel using anion-exchange resin may be internal mass-transfer limited.