Zirconia and alumina supported MFI zeolite membranes: Effects of support materials on membrane properties

Good quality MFI type zeolite membranes were prepared on mesoporous Y₂O₃ doped ZrO₂ (YZ) support and macroporous α-Al₂O₃ support with pure SiO₂ precursor by hydrothermal process. Permeation of binary mixture H₂/n-C₄H₁₀ through zeolite membranes on YZ and α-Al₂O₃ supports was measured using a multi-component gas permeation set-up. YZ supported zeolite membrane had a much higher n-C₄H₁₀ permeance than the α-Al₂O₃ supported one in the lower temperature range. The maximum n-C₄H₁₀ to H₂ separation factor of YZ supported zeolite membrane was as high as 500. Pure p-xylene pervaporation through these zeolite membranes was also conducted to study the membranes separation property. The pervaporation flux declined significantly with time for the α- Al₂O₃supported zeolite membrane. Much less change in pervaporation flux was found for the YZ supported zeolite membrane. XRD was employed to analyze the phase structure of the zeolite membranes. The thermal stability of the YZ and α-Al₂O₃ supported MFI zeolite membranes was studied by comparing the phase structure of the zeolite films after heat-treatment at different temperatures. The zeolite membrane on the YZ support remained in the MFI structure up to 1000°C. The zeolite membrane on the α- Al₂O₃ support transformed completely to a quartz phase after heat-treatment at 950°C. Zirconia supported MFI type zeolite membrane is more hydrophobic, thermally stable and fouling resistant than the alumina supported one.