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Abstract: 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°C. The membrane performance gradually changes at a temperature of 80°C. After six months the water flux has increased from 1 to 1.4kgm2 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 γ-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°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°C, the thermal stability of the membranes is inadequate for most practical applications. [Copyright &y& Elsevier]

Abstract: Catalytic Amberlyst 15 layers have been deposited on composite ceramic/poly(vinyl)alcohol membranes by the dip-coat technique using Aculyn® as a rheology modifier. Tuning of the catalytic layer thickness is possible by varying the number of dip-coat steps. The obtained “dried-mud like” Amberlyst 15 layers are stable during pervaporation and reaction experiments. The catalytic activity of the Amberlyst-coated pervaporation membrane equals the activity of the unsupported catalyst. In the pervaporation-assisted esterification reaction between acetic acid and 1-butanol the catalytic membrane is able to couple catalytic activity and water removal. Due to the high activity of the Amberlyst catalyst the conversion of the esterification reaction is limited by the removal rate of water through the membrane. This is in contrast to zeolite-coated pervaporation membranes, for which the conversion of the esterification reaction between acetic acid and 1-butanol is limited by the catalytic activity. [Copyright &y& Elsevier]

Temperature polarization effects can considerably limit the overall performance of pervaporation modules. This study shows the measurement of temperatures in a pervaporation membrane module using ultrasonic computer tomography (U-CT). With this technique complete 2D-temperature distributions that occur in the module can be measured within seconds. Temperature distributions were also determined using computational fluid dynamics (CFD). Both temperature distributions are comparable and show that in the tubular pervaporation system studied, temperature segregation occurs. This segregation is a result of the occurring hydrodynamics in the system that is determined by mixed convection. Also, the measured water fluxes through the membrane show to be dependent of forced and natural convection. [Copyright &y& Elsevier]