NaY zeolite membranes with high performance prepared by a variable-temperature synthesis

• Preparation of NaY zeolite membranes by a variable-temperature synthesis.
• Higher membrane performances compared to the constant-temperature synthesis.
• Pervaporation of water/alcohol and alcohol/organic mixtures were investigated.
• High pervaporation performances in separation of alcohol/organic systems.

NaY zeolite membranes were synthesized by the secondary growth method on the surface of α-Al2O3 and mullite tubular supports. Influence of the different thermal profiles during the hydrothermal synthesis was investigated. In addition to the conventional constant temperature (CT) at 100 and 140 °C syntheses, a variable-temperature syntheses were applied where the temperature was increased from 100 to 140 °C (VT-LH) and decreased from 140 to 100 °C (VT-HL) during the hydrothermal syntheses. Synthesized membranes were characterized by XRD, SEM and EPMA. The pervaporation (PV) performance of the NaY zeolite membranes was examined with water/alcohol (ethanol or isopropanol) mixtures and alcohol/organic mixtures such as methanol/dimethly carbonate (DMC), /methyl methacrylate (MMA), /methyl tert-butyl ether (MTBE), /methyl isobutyrate (MIB), /methyl acrylate (MA), /methyl propionate (MP) and ethanol/ethyl tert-butyl ether (ETBE) mixtures. NaY zeolite membranes showed dehydration properties and alcohol selectivity from alcohol/organic mixtures. The highest PV results were obtained with membranes prepared on α-Al2O3 supports with the VT-HL thermal profile: separation factors over 5000 with fluxes over 3 kg m−2 h−1 were obtained in the separation of methanol/MMA (10/90 wt.%) and methanol/MA (10/90 wt.%) mixtures at 60 °C. The remarkably high perm-selectivity makes the NaY zeolite membrane an attractive candidate in alcohol/organic separations.

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