(539f) Comparative Study of the Pervaporation of Methanol-Methyl Acetate Binary Mixtures with Hydrophilic and Organophilic Membranes

In recent years, there has been a significant rise in the number of pervaporation processes for industrial applications. The field of interest for the application of this unit operation has a span from dehydration processes to equilibrium limited reactions. Former applications conducted by pervaporation already represent the state of the art in the dehydration of organic solvents.  The main benefits of pervaporation are based on low operation temperatures, partial evaporation and the nature of the driving force. The outlined advantages may result in energy savings compared to conventional unit operations when dealing with thermodynamic limitations.

In this research activity we focus on the separation of azeotropic mixtures. The methyl acetate synthesis serves as a model reaction, since it forms two low boiling azeotropes with methanol and with water. The reverse reaction, the hydrolysis of methyl acetate, as well as transesterification reactions are facing the same issues. The azeotropic mixture of methyl acetate and methanol represents the bottleneck in all these reactions. The major focus of our investigations is to overcome this limitation by applying a pervaporation process. We conducted a screening of various commercially available hydrophilic and organophilic membranes. Hydrophilic membranes enhance the permeate flux of polar components. The active layer of the investigated hydrophilic membranes consists of crosslinked PVA. An increase in the degree of crosslinking leads to a significant improvement in selectivity. The maximum permeate flux of the investigated PVA-membranes ranges from 0.9 to 9.4 kg^.m^-2.h^-1. In the case of organophilic membranes a rise in the permeate flux up to values of 72 kg^.m^-2.h^-1 was observed. Organophilic membranes with an active layer consisting of POMS show a better separation performance than PDMS based layers Although the difference in permeate flux is not that pronounced. A model for the permeate flux based on an adapted solution-diffusion model was proposed.