Mathematical modeling of the pervaporative separation of methanol-methylterbutyl ether mixtures

This work reports the kinetic modeling of the pervaporative separation of methanol-MTBE mixtures. Using a commercial membrane, Pervap 2256, that presented high selectivity toward methanol permeation, the influence of the operating variables feed composition in the range 1-20 wt % MeOH, feed temperature between 30 and 50 degreesC, and permeate pressure between 1 and 20 mmHg on the pervaporation flux was experimentally analyzed in a laboratory setup working under pseudo-steady-state conditions. A mathematical model based on the generalized Fick's law and the assumption that transport through the membrane is the rate-limiting step was developed in order to describe the PV flux of both components. The prediction of the flux of methanol needed of a concentration-dependent diffusion coefficient, whereas a simple model with concentration-independent diffusivity was sufficient for the description of the MTBE flux. Finally, the influence of the temperature on the partial fluxes was described through an Arrhenius-type expression that allowed for the determination of the apparent activation energies. This work contributes to the knowledge of pervaporation mechanisms of azeotropic mixtures; having selected the system MeOH-MTBE as a case of study, the mathematical model and parameters of the separation that are the necessary tools for process design and optimization are reported.