(709a) Methyl Stearate Transesterification with n-Butanol: Process Intensification Using Distillation with External Side Reactors

Fatty acid butyl esters (FABE) are commercially important chemicals used in a wide range of applications such as lubricants, emulsifiers, detergents, and as biofuel constituents. An alternate approach to direct esterification of fatty acids for producing higher alcohol esters is to first make the fatty acid methyl esters (FAME) via traditional base catalysis and then transesterify FAME with other alcohols using heterogeneous catalysts to produce the desired esters.  In previous work, we have characterized kinetics of methyl stearate transesterification with n-butanol using Amberlyst 15; this reaction is slow at 90^oC even with a very large excess of butanol. Above 90°C or at high catalyst loadings, ether formation takes place, liberating water which leads to hydrolysis of the esters.

Conventional reactive distillation will likely be uneconomical for this reaction system because of the slow reaction rate and temperature limitations.  We present here a study that evaluates the potential of carrying out reactive distillation in a column with external side reactors for continuous transesterification of FAME with n-butanol. Process simulation using AspenPlus describes column performance as a function of operating conditions, the number of side reactors utilized, and location of side draws and re-entry points in the column.  The column configuration that maximizes conversion of the methyl ester to its butyl counterpart is described.