Conventional DDR-type zeolite membranes are well suited for separating CO2 from different-sized molecules, such as methane, which is present in associated gas or natural gas. However, such membranes are not very efficient for separating CO2 from O2 or N2, which is common in many industrial exhaust-gas streams. Now, a new DDR-type zeolite membrane, developed by NGK Insulators, Ltd. (Tokyo, Japan; www.ngk-insulators.com) has been demonstrated to be five times more efficient than conventional DDR-type zeolite membranes for separating CO2 from such exhaust gases.
Unlike conventional zeolite membranes that perform the separation on the difference in molecule’s size, the new membrane makes use of the different adsorption characteristics (affinity) for molecules to separate CO2 from N2 and O2. Taking advantage of the stable properties of ceramics under harsh conditions, the company is working to increase the separation factor even further for applications involving high-temperature industrial exhaust gases. Following more testing and development, the company is targeting a commercial launch in 2030.