Dehydration of water/t-butanol mixtures by pervaporation:: comparative study of commercially available polymeric, microporous silica and zeolite membranes

The performance of commercially available polymeric (PERVAP 2202, PERVAP 2510, Sulzer Chemtech GmbH), microporous silica (PERVAP SMS, Sulzer Chemtech GmbH) and zeolite pervaporation membranes (NaA type, SMART Chemical Company Ltd. (UK)) has been investigated with respect to the dehydration of binary mixtures of t-butanol (t-BuOH) and water. The range of concentrations investigated (C-H2O less than or equal to 20 wt.%) was selected according to existing industrial needs. Fluxes and selectivities were monitored as dehydration proceeded. In addition, the effect of temperature on these parameters was investigated. Over this range, both water and t-BuOH fluxes generally decreased with water concentration. The effect of temperature was investigated in the 60-100degreesC range. Increasing the operating temperature resulted, as expected, in larger water fluxes for both polymeric and silica membranes. Experimental work showed that at 60degreesC and with 10 wt.% initial water concentration, larger fluxes were obtained using the microporous silica unit (3.5 kg m(-2) h(-1)), followed by zeolites (1.5 kg m(-2) h(-1)) and finally by the polymeric membranes (0.5 kg m(-2) h-1). For this specific set of conditions, higher water selectivities were obtained with the zeolite (16,000), followed by the polymeric (3615) and finally by the microporous silica (144) membranes. In addition, studies performed for various temperatures in the vapour permeation regime showed that even if temperature was increased, water separation factors remained approximately constant for PERVAP 2510 polymeric membranes. Activation energies were calculated for each of the components using the microporous silica and polymeric membranes. (C) 2002 Elsevier Science B.V. All rights reserved.