High-Selectivity, High-Flux Gel-Based Membrane for the Separation of Carbon Dioxide

Much of the U.S. energy comes from fixed, large-scale fossil fuel power plants, which will remain the case for the foreseeable future. Therefore, in a carbon-constrained environment targeted at preventing the predicted 2°C warming by 2100, the implementation of carbon capture and storage technologies is critical. Several approaches are under development to capture carbon as flue gas emissions at the generation source, including a range of chemical and membrane separation processes. The point of use capture focuses on lowering the overall costs and parasitic energy requirements for the process. There is a need for an alternative high efficiency, high permeability membrane approach that simultaneously provides both very high selectivity and permeability. Membrane-based separations provide attractive low power routes to gas separation; however, for effective separation at low concentrations, the selectivity must be very high over 100. Additionally, to make the process economically attractive, the flux must also be high while retaining a high selectivity level. With conventional membranes, there is a tradeoff between selectivity and flux that makes this difficult to achieve. Mainstream is developing an innovative membrane separation approach that integrates combined selective chemical capture and a membrane where the adsorption on the feed side of the membrane and the release of the CO2 on the permeate or capture side is controlled by tailoring the electrochemistry of the carrier molecules at the membrane surface. Our process uses a low-voltage, low-current applied field, and we have shown that the selectivity and permeability can increase significantly. Mainstream’s electrochemically activated membrane separation process has been tested on the lab scale for a wide range of compositions, including standard room air. In Phase 1, Mainstream will scale up the membrane coating process and optimize the membrane chemistry to separate atmospheric and low concentration CO2 streams. The U.S. can increase the removal of CO2 from the environment as high purity carbon dioxide than can be readily utilized in a wide range of applications. The scalable, modular high selectivity, high permeability membrane-based separation modules, and systems being developed by Mainstream can be used in a wide range of locations to effectively remove the CO2, making it available for a wide range of CO2 reuse and storage applications.