Synthesis of MCM-22 zeolite membranes and vapor permeation of water/acetic acid mixtures

MCM-22 membranes were prepared on a porous α-alumina tube using a secondary growth technique consisting of the deposition of seed crystals on a substrate followed by crystal growth under hydrothermal conditions. In this study, two types of seed crystals, MCM-22 and ITQ-2, were used. The MCM-22 membrane prepared using ITQ-2 seed crystals (MCM-22 (I) membrane) was composed of MCM-22 polycrystals with a thickness of 5 μm, which is much thinner than that of the MCM-22 membrane prepared using MCM-22 seed crystals (MCM-22 (M) membrane) (15–20 μm). Vapor permeation of water/acetic acid mixtures through the MCM-22 membranes was studied. The MCM-22 (I) membranes calcined at 400 °C showed a high separation factor of 78 with a water permeance of 4 × 10−8 mol m−2 s−1 Pa−1 at 120 °C. Elevating the calcination temperature to 500 °C resulted in a lower separation factor. The MCM-22 (I) membrane calcined at 400 °C has a hydrophilic internal surface due to the presence of silanol groups within the framework that contribute to the high selectivity to water permeation.

Research highlights
► MCM-22 membranes were prepared using a secondary growth technique.
► Two types of seed crystals (MCM-22 and ITQ-2) were used.
► We studied the effect of the seed on the thickness and the vapor permeation results.
► We studied the effect of calcination temperature on the separation factor.
► The MCM-22 membranes showed a separation factor of 78 for water/acetic acid vapors.