Carbon dioxide is produced in large quantities in many industrial processes such as generation of electricity by burning coal. In many cases, it is highly desirable to separate carbon dioxide from industrial gas streams at high temperatures. A membrane process is generally more energy efficient and easier to operate than other separation processes. A large number of microporous inorganic membranes permselective for carbon dioxide at low temperatures have been reported, but these membranes do not offer high selectivity for carbon dioxide at high temperatures. This project is focused on the synthesis and property study of a new non-porous ceramic-carbonate dual-phase membrane fundamentally different from previous porous inorganic membranes used for carbon dioxide separation. The membrane consists of a carbonate ion conducting molten carbonate phase dispersed in an oxygen ion conducting ceramic phase as the support. The ceramic phase provides a pathway for oxygen ion conduction allowing permeation of carbon dioxide through the dual-phase membrane. The ceramic phase also offers physical affinity for the molten carbonate, ensuring good mechanical stability of the dual-phase membrane. The research is aimed at understanding and optimizing the synthesis and properties of the new carbon dioxide semi-permeable inorganic membrane for effective separation of carbon dioxide from various gas streams at high temperatures.
Synthesis and characterization experiments will be performed to optimize the support materials, synthesis conditions, and structure of the dual-phase membranes in order to maximize membrane stability, carbon dioxide permeance, and selectivity. Powders and membranes of four oxygen ionic conducting metal oxides with different crystal structure and ionic transference number will be synthesized, and their chemical stability, oxygen permeability, partial electrical conductivity and surface properties with respect to molten carbonate will be studied experimentally. Symmetrical, thick dual-phase membranes with different supports will be synthesized and characterized to identify the ionic conducting ceramic with the best properties as the support for the dual-phase membranes. The main experimental efforts will be focused on synthesis and characterization of an asymmetric membrane support consisting of a thick, large pore base and a thin, small pore top-layer, both being made of the same ionic conducting ceramic. The top-layer will be subsequently filled with the molten carbonate by a direct infiltration method to give an asymmetric dual-phase membrane with carbon dioxide permeance of about 10-6 mol/m2.s.Pa. Carbon dioxide permeation through the asymmetric dual phase membranes will be studied both experimentally and by modeling to understand the carbon dioxide transport mechanism through the new dual-phase membranes.
The ceramic-carbonate dual phase membrane represents a new concept of inorganic membranes which can be extended to other materials for dual-phase membranes perm-selective for other gases at high temperatures. The work will have a significant impact on carbon dioxide sequestration and inorganic membrane science. Undergraduate and graduate students working on the research will receive broad education and training in membrane science, separation processes, nanostructured materials, and environmental science. The PI will strive to target the large ASU undergraduate minority and women talent pool to join the project as research students. The results obtained in this project will be disseminated to the scientific community through journal publication and conference presentations and will be included in course materials and workshop lectures to benefit graduates students and other scientists and engineers with interest in membrane science. A workshop on carbon dioxide capture technology for high school students will improve the awareness of the young generation on global warming and environmental protection, and motivate their interest in pursuing science and technology as a career path.
