Nb2O5-catalyzed kinetics of fatty acids esterification for reactive distillation process simulation

• A kinetic model of niobium-oxide-catalyzed esterification of fatty acids is provided.
• Reactive distillation esterification of fatty acids or their mixtures was simulated.
• Results point out the different reactivity of the single acids.
• Tests with acid mixtures show how composition affects reaction rate and temperature.
• Some design guidelines for reactive distillation esterification are provided.

On the basis of kinetic data obtained for the first time in the presence of pelletized niobium oxide as a catalyst, the esterification with methanol of single fatty acids or their mixtures has been simulated in a reactive distillation unit, which is a promising intensification technique in the frame of biodiesel synthesis. The kinetic behaviour of the reversible esterification of capric, lauric, myristic, palmitic, stearic and oleic acid at different temperatures was fitted through a pseudo-homogeneous reversible model suitable for the process design. The simulations showed that the reactivity of the acids and the acid composition of the feed affect both the column temperature profile and conversion, and that the benefit of a methanol excess is limited by the temperature decrease in the reactive section. The simulations also provided some preliminary design guidelines about the role of the main parameters, such as top reflux ratio, column pressure, feed temperature and number of stages, on the process performance.