【Original Contribution】 High Gas Permselective MFI Zeolite Membranes Prepared on Novel Silica Substrates

Abstract

MFI membranes with high gas permselectivities were successfully prepared on a novel porous silica substrate. Procedures for coating of MFI seed crystals are important due to ζ-potential difference between the silica substrates and the seed crystals. Dense MFI membranes were obtained from the seed slurry of pH 2, because the isoelectric pH of silica is 2. MFI membranes were crystalized at 180 ℃ for 16 h. The parent gel compositions were SiO₂ : TPABr : Na₂O : H₂O=1 : 0.2 : 0.01 ∼ 0.6 : 150 ∼ 600 (mol/mol). Single gas permeation tests were performed by using N₂, SF₆, C₃H₆ and C₃H₈ at room temperature. N₂ permeance was 3.0 × 10^-6 mol m^-2 s^-1 Pa^-1 with high N₂/SF₆ permeance ratio of 108 through the membrane. This is one of the best results among the previously reported MFI membranes. This membrane showed the high hydrocarbon permeances. C₃H₆ permeance was 2.0 × 10^-6 mol m^-2 s^-1 Pa^-1 with C3H6/C3H8 permeance ratio of 6.16.