DEVELOPMENT OF A MIXED-MATRIX MEMBRANE FOR PERVAPORATION

In the production of pure alcohol, pervaporation is developing into an important technology. In this study, in order to improve the performa nce of the pervaporation process, a mixed-matrix polymer-zeolite membr ane is developed. In the preparation of these membranes, cellulose ace tate as base polymer, acetone or DMF as solvent, and 13X or 4A zeolite s as fillers were used. To test the performance of homogeneous and mix ed-matrix membranes, a laboratory-scale pervaporation setup was constr ucted. The effect of the following experimental parameters on the sele ctivity and flux were experimentally studied to determine the optimum values of operating conditions and to understand the separation mechan ism in the indicated ranges: feed concentration, 70-90 wt%; feed tempe rature, 30-70-degrees-C; feed flow rate, 32-76 L/h. It was observed th at the addition of zeolite to the membrane matrix improves the flux va lue twofold with respect to its homogeneous membranes with some loss i n their selectivity. For example, for a feed concentration of 74 wt% E tOH at 50-degrees-C and 1 mmHg, the flux value for the unfilled membra ne is 0.6 L/m2.h, and for a 30% zeolite-filled membrane, the flux is i ncreased to 1.33. For these cases, the selectivities are 7.76 and 5.0 for the unfilled and filled membranes, respectively. TEM micrographs o f the mixed-matrix membranes show a homogeneous distribution of zeolit e particles which produce a cave-like porous structure in the matrix. The combined effect of this modified morphology and zeolite selectivit y is the possible reason for the observed pervaporation performances o f mixed-matrix membranes.