Hybrid ceramic-supported thin PVA pervaporation membranes: Long-term performance and thermal stability in the dehydration of alcohols

The long-term performance and thermal stability of ceramic-supported cross-linked poly(vinyl)alcohol membranes has been examined over a period of six months up to a temperature of 100 degrees C. The membrane performance gradually changes at a temperature of 80 degrees C. After six months the water flux has increased from 1 to 1.4 kg m(2) h(-1), while the selectivity has decreased from 450 to 300. SEM analysis gives no indication that the decrease in performance is caused by defects in the membrane layers or a decreased adherence of the PVA layer to the gamma-Al2O3 support. It is more likely that observed higher water flux and lower selectivity are caused by a decrease in cross-linking of the PVA-chains due to removal of maleic acid. At a temperature of 100 degrees C the decline in performance is accelerated. At this temperature the selectivity drops from 300 to 25, over a period of two weeks. At 100 degrees C, the thermal stability of the membranes is inadequate for most practical applications. (C) 2008 Elsevier B.V. All rights reserved.