Pervaporation of organic/water mixtures through B-ZSM-5 zeolite membranes on monolith supports

High-quality, boron-substituted ZSM-5 zeolite membranes were prepared on Al2O3-coated SiC multi-channel monolith supports. Monoliths have larger surface to volume ratios than tubular supports and are more practical for large-scale applications. Two types of supports with 66 channels (2 mm×2 mm, 10.6 cm2 surface area cm−3) and 22 channels (4 mm×4 mm, 7.2 cm2 cm−3) were used. The membranes effectively removed alcohols and acetone from 5 wt.% organic/water binary feeds by pervaporation over a temperature range of 303–333 K. The membranes were selective because acetone and the alcohols preferentially adsorbed and inhibited water transport, but diffusion differences caused by different adsorption strengths and molecular sizes were also important. Methods for calculating molecular kinetic diameters for polar molecules are compared. The acetone/water separation factor was 330 at 303 K, and it decreased to 220 at 333 K. Methanol, ethanol, 2-propanol, and 1-propanol separation factors were 8.4, 31, 42, and 75, respectively, at 333 K and were relatively independent of temperature. With the exception of methanol, these separation factors are significantly higher than those reported for a B-ZSM-5 tubular membrane. The fluxes at 333 K were 0.90, 0.16, 0.047, 0.071, and 0.22 kg m−2 h−1 for methanol, ethanol, 1-propanol, 2-propanol, and acetone, respectively, and increased with temperature. The methanol and ethanol fluxes are comparable to those for the B-ZSM-5 tubular membrane.