Colloidal Silicalite Coating for Improving Ionic Liquid Membrane Loading on Macroporous Ceramic Substrate for Gas Separation
Pages 25-37
Zishu Cao, Shaowei Yang, Xinhui Sun, Antonios Arvanitis and Junhang Dong

DOI: http://dx.doi.org/10.6000/1929-6037.2016.05.01.3

Published: 06 April 2016

Abstract: Athin layer of colloidal silicalite was coated on a macroporous alumina substrate to improve the effectiveness in loading and supporting ionic liquid (IL) membrane on macroporous ceramic substrate. The [bmim][BF₄] IL and CO₂ gas separation were used as the model system in this research. The colloidal silicalite top layer enabled the formation of a pinhole-free IL membrane with significantly reduced load of IL as compared to the bare alumina substrate because the former had a smaller and more uniform inter-particle pore size than the latter. The supported IL membrane was extensively studied for CO₂ separation in conditions relevant to coal combustion flue gases. The silicalite-supported IL membrane achieved a CO₂/N₂ permselectivity of ~24 with CO₂ permeance of ~1.0×10^-8 mol/m²·s·Pa in dry conditions at 26˚C and reached a CO₂/N₂ separation factor of ~18 with CO₂ permeance of ~1.56×10^-8 mol/m²·s·Pa for a feed mixture containing ~11% CO₂ and ~9% water vapor at 50^oC. This supported IL membrane exhibited excellent stability under a 5-bar transmembrane pressure at 103˚C and chemical resistance to H₂O, SO₂, and air (O₂). Results of this study also indicated that, in order to fully realize the advantages of using the colloidal silicalite support for IL membranes, it is necessary to develop macroporous ceramic supports with optimized pore size distribution so that the IL film can be retained in the micron-thin silicalite layer without penetrating into the base substrate.

Keywords: Colloidal silicalite, ionic liquid, membrane, carbon dioxide, separation.