Fabrication of SiO2–ZrO2 (50/50) membranes on the porous stainless steel-tube support for pervaporation

Abstract

The SiO2–ZrO2 membranes were fabricated with silica–zirconia sols on a porous stainless steel-tube support (O.D. = 10 mm, length = 20 mm, 316L SUS, Mott Corp. USA) by a dipping–rolling–freezing–fast drying (DRFF) and/or soaking–rolling–freezing–fast drying (SRFF) method. After coating of SiO2–ZrO2 sol, single gas permeation characteristics (He, H2, and N2) for SiO2–ZrO2 membranes were evaluated at room temperature, and the pervaporation experiments were performed at a specified feed isopropyl alcohol concentration of 90 wt% at 50°C with silica–zirconia membranes. The morphology of surface and the cross sections of the membrane were investigated with FE-SEM analysis. Judging from FE-SEM analysis, the surface of silica–zirconia membrane on the PSS tube support was denser, and the number of surface defects considerably reduced than DRFF method, and the additional modification via the SRFF significantly diminished surface defects, which could not be avoided during the DRFF step. The membrane the silica–zirconia membrane showed hydrogen permeability under 10−7 mol m−2 s−1 Pa−1 and low water selectivity in the range of 10–23. The silica–zirconia membranes with a smooth surface on the stainless steel tube supports, was quite well prepared by the DRFF and SRFF method in this study.