Development of Silica Sodalite With Enhanced Porosity via Topotactic Synthesis for Pre Combustion Co2 Capture

Abstract

Topotactic conversion of layered silicates is reported to yield sodalite with enhanced frameworks, chemical compositions and predictable outcomes. Traditional hydrothermal synthesis results in sodalite with occluded matter preventing the effective use of sodalite cages for adsorption and separation applications. However, the reproducibility of high quality silica sodalite depends on obtaining optimized synthesis conditions and investigating the effect these conditions is essential. A 23 factorial design was employed to investigate the effect of process variables (acid strength, acid treatment time and calcination temperature) on the quality of silica sodalite produced via topotactic conversion in this study. XRD, SEM and Nitrogen physisorption at 77K were used for physio-chemical characterization of the sodalite samples. The produced sodalite crystals were used in membrane synthesis, and the membrane was tested for CO2/H2/N2 separation. Sodalite of desirable crystallinity and plate-like morphology was produced with surface area and porosity of 79.44m2/g and 0.081cm3/g, respectively. An incomplete transformation of sodalite at low acid concentration and treatment time was experienced. A significant improvement on surface area and pore volume was reported on all samples as compared to that of the hydroxy sodalite. Analysis of the regression model obtained from the experimental data indicates acid treatment time as an insignificant variable. The preliminary investigation of the application for membrane synthesis indicates enhanced porosity of the HSOD improved the membrane H2 permeance by 178%.