Highly Perm-Selective Micro-Porous Hydrotalcite-Silica Membrane for Improved Carbon Dioxide-Methane Separation

A notable improvement of carbon dioxide (CO2) adsorption in meso- and micro-porous membranes was observed when hydrotalcite (HT) was incorporated in the membranes. For carbon dioxide in carbon dioxide-methane (CH4) mixture, HT-silica membrane successfully overcame the upper permeability/selectivity limitation for glassy and polymeric membranes, despite the absence of a solution-diffusion mechanism that is typically present in the glassy and polymeric membranes. The performance of HT-silica membrane was observed to exceed that of micro-porous silica and high performance zeolitic imidazolate framework (ZIF) membranes. Incorporating unnecessarily high HT content in silica membrane, however, caused the membrane to lose its molecular sieving capacity and resulted in reduced selectivity of the gas.