Description of dehydration performance of amorphous silica pervaporation membranes

The dehydration performance of a ceramic pervaporation membrane is studied for the separation of isopropanol/water mixtures. The membranes are provided by ECN (The Netherlands) and consist of a water selective amorphous silica top layer and four alumina supporting layers. For the system investigated, these membranes appear to combine high selectivities with high permeabilities. This results in a very high pervaporation separation index (PSI up to 6000 kg/m2 h at 80°C). A generalized Maxwell–Stefan model has been set up to model the fluxes. From this analysis it follows, that the water flux is only proportional to its own driving force. It is experimentally demonstrated that this holds for a wide range of operating conditions and feed compositions. From these data, values of various Maxwell–Stefan diffusivities are estimated.