Steam recovery via nanoporous and subnanoporous organosilica membranes: The effects of pore structure and operating conditions

Abstract

• Nanoporous and subnanoporous organosilica membranes were prepared for steam recovery. • The performances of membranes were compared under various operation conditions. • Subnanoporous membranes showed high water permeance with high permeance ratios. • High performance was obtained for various steam/non-condensable gas mixtures. In this study, nanoporous (pore size: 1.5 nm) and subnanoporous (pore size: 0.42–0.43 nm) organosilica membranes were prepared to accomplish steam recovery via vapor permeation (VP) at high temperatures. These membranes were evaluated under various operating conditions that included high temperatures (80–150 °C), various water mole fractions in the feed stream (0.1–0.9), and various pressures of the feed (130–140 kPa (abs.) or 400 kPa (abs.)) and permeate (~0 kPa (abs.) or 100 kPa (abs.)). A comparison of the performances of nanoporous and subnanoporous membranes clearly showed the advantage of the subnanoporous structure for steam recovery under high temperature. Subnanoporous organosilica membranes showed water permeance of several 10 −6 mol/(m 2 s Pa) and an H 2 O/N 2 permeance ratio of several hundreds at 150 °C, compared with the results from nanoporous organosilica membranes that were approximately 10 −5 mol/(m 2 s Pa) and below ten, respectively. Furthermore, subnanoporous organosilica membranes showed a maximum water flux as high as 73 kg/(m 2 h) at a transmembrane pressure of 300 kPa during VP. In addition, subnanoporous organosilica membranes showed similar high levels of water permeance for seven binary steam/non-condensable gas (He, H 2 , CO 2 , N 2 , CH 4 , CF 4 , SF 6 ) mixtures.