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

In this study, nanoporous (pore size: 1.5 nm) and subnanopomus (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 degrees 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 (similar to 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 H2O/N-2 permeance ratio of several hundreds at 150 degrees 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, subnanopomus organosilica membranes showed similar high levels of water permeance for seven binary steam/non-condensable gas (He, H-2, CO2, N-2, CH4, CF4, SF6) mixtures.

Automated summary

Subnanoporous organosilica membranes outperform nanoporous membranes in steam recovery at high temperatures, exhibiting higher water permeance, H₂O/N₂ permeance ratio, and maximum water flux. They also demonstrate similar high levels of water permeance for various binary steam/non-condensable gas mixtures.