A membrane-based reactive separation system for CO2 removal in a life support system

The capture and utilization of carbon dioxide have significant potential applications in the chemical and power generation industries, as well as in space applications. For the proper performance of space life-support systems, for example, the removal from the cabin atmosphere of the CO2 produced by the inhabitants is required. For short-term flights, CO2 can be controlled by sorption on metal hydroxide adsorbents. For long-term space applications, however, continuous regenerative approaches are required, including pressure-swing adsorption and membranes which, in addition to removing the CO2, may, potentially, also allow for the recovery of oxygen. One of the approaches proposed is the use of the methanation (Sabatier) reaction, in which the CO2 catalytically reacts with hydrogen to simultaneously produce methane and water. In space applications, one of the challenges the application of catalytic reactor technology faces is the dilute concentrations of CO2 which make its pre-concentration a required step, thus complicating the process train. In this study, we investigate the application of a reactive separation technology, in which the catalytic and separation steps are coupled in situ through the use of high-temperature membranes. Coupling reaction and separation provides added synergy, which enhances the performance of both steps. In the paper, we describe our current experimental and modeling efforts in this area aiming to establish the feasibility of the proposed reactive separation application for life-support systems.