(696b) Pure Silica Sodalite as a Building Block for Hydrogen Separation Membranes

Hydrogen as a high-quality and clean energy carrier has attracted renewed and ever-increasing attention in recent years, mainly due to developments in fuel cells and environmental pressures including climate-change issues. Hydrogen separation from hydrogen-containing gas mixtures, e.g., syngas, at elevated temperatures is a critical component of the WGS membrane reactor technology. Ultra-microporous sodalite (SOD) is a highly desirable structure for the membrane separation of small gas molecules, such as hydrogen, due to the presence of small (~2.8 Å) six-membered ring openings of the sodalite cages. These openings are accessible only to small molecules such as H2, H2O and He, resulting in a superior membrane performance.

Pure-silica sodalite (Si/Al = ∞) framework is particularly attractive sodalite structure that is hydrophobic in nature, thereby reducing water adsorption and also displaying high chemical and thermal stability due to neutral framework. In this study, we investigated the effect of calcination of pure-silica sodalite crystals as a function of crystal size. IR, SEM/EDS, TGA/DSC, XRD and pore size analysis were performed to study the effects of removal of ethylene glycol occluded during synthesis from the beta cages of pure silica sodalite. The results of this study have important consequences with respect to conditions of seeded synthesis of sodalite membranes that are expected to produce thin, continuous and defect-free sodalite membranes for hydrogen separation at elevated temperatures.