Separation of organic compounds from water by pervaporation in the production of n-butyl acetate via esterification by reactive distillation

This study deals with the separation of n-butyl acetate, n-butanol and acetic acid from aqueous solutions by pervaporation using a poly(ether block amide) membrane. Initially the separations of binary (i.e., n-butyl acetate-water, n-butanol-water and acetic acid-water) mixtures were investigated, followed by separation studies of quaternary mixtures comprising of all the four components that are relevant to n-butyl acetate production by esterification via reactive distillation. The membrane permeability was found to follow the order of n-butyl acetate > n-butanol > acetic acid > water. The effects of feed composition and operating temperature on the separation performance were investigated. It is shown that the membrane is especially selective to n-butyl acetate permeation. For the separation of the quaternary mixtures, the concentration of n-butyl acetate in the permeate stream was so high (i.e., beyond its solubility limit) that the phase separation of the permeate occurred. This is of particular interest from an industrial application point of view in that the organic phase can be recycled to the distillation column for reprocessing, while the aqueous phase can be recycled to the pervaporation unit for further treatment.