Improved performance of organosilica membranes for steam recovery at moderate-to-high temperatures via the use of a hydrothermally stable intermediate layer

To examine the prospect of a future application of organosilica membranes to steam recovery under hydrothermal conditions, we proposed a novel concept that involved a hydrothermally stable intermediate layer derived from colloidal 1,2-bis(triethoxysilyl)ethane (BTESE) sols with a BTESE-derived separation top layer. In this work, a BTESE-derived nanoporous intermediate layer (i-BTESE) was prepared from a BTESE-derived colloidal sol without pinholes or cracks, and then a BTESE-derived sub-nanoporous separation layer was formed on the i-BTESE to obtain a BTESE/i-BTESE membrane. The BTESE/i-BTESE membrane showed excellent water permeance as high as 5 × 10-6 mol/(m2 s Pa), and a high level of permeance was maintained for as long as 361 h at 200°C under vapor pressure of 200 kPa (abs.). In addition, the membrane achieved an H2O/N2 permeance ratio that reached as high as 350 even after 361 h. On the other hand, the permeance of a conventional BTESE-derived membrane that used a silica-zirconia intermediate layer (BTESE/i-SiO2-ZrO2) decreased gradually, which suggested a degradation of the BTESE/i-SiO2-ZrO2 membrane. The high and stable performance of the BTESE/i-BTESE membrane confirmed the proposed concept whereby a hydrothermally stable intermediate layer could significantly improve the hydrothermal stability that is required in order to use organosilica membranes in steam recovery.