ADVANCED HYDROGEN TRANSPORT MEMBRANES FOR VISION 21 FOSSIL FUEL PLANTS

Abstract

Eltron Research Inc., and team members CoorsTek, McDermott Technology, Inc., Sued Chemie, Argonne National Laboratory, and Oak Ridge National Laboratory are developing an environmentally benign, inexpensive, and efficient method for separating hydrogen from gas mixtures produced during industrial processes, such as coal gasification. This objective is being pursued using dense membranes based in part on Eltron-patented ceramic materials with a demonstrated ability for proton and electron conduction. The technical goals are being addressed by modifying single-phase and composite membrane composition and microstructure to maximize proton and electron conductivity without loss of material stability. Ultimately, these materials must enable hydrogen separation at practical rates under ambient and high-pressure conditions, without deactivation in the presence of feedstream components such as carbon dioxide, water, and sulfur. This project was motivated by the National Energy Technology Laboratory (NETL) Vision 21 initiative which seeks to economically eliminate environmental concerns associated with the use of fossil fuels. The proposed technology addresses the DOE Vision 21 initiative in two ways. First, this process offers a relatively inexpensive solution for pure hydrogen separation that can be easily incorporated into Vision 21 fossil fuel plants. Second, this process could reduce the cost of hydrogen, which is a clean burning fuel under increasing demand as supporting technologies are developed for hydrogen utilization and storage. Additional motivation for this project arises from the potential of this technology for other applications. Membranes testing during this reporting period were greater than 1 mm thick and had the general perovskite composition AB{sub 1-x}B'{sub x}O{sub 3-{delta}}, where 0.05 {<=} x {<=} 0.3. These materials demonstrated hydrogen separation rates between 1 and 2 mL/min/cm{sup 2}, which represents roughly 20% of the target goal for membranes of this thickness. The sintered membranes were greater than 95% dense, but the phase purity decreased with increasing dopant concentration. The quantity of dopant incorporated into the perovskite phase was roughly constant, with excess dopant forming an additional phase. Composite materials with distinct ceramic and metallic phases, and thin film perovskites (100 {micro}m) also were successfully prepared, but have not yet been tested for hydrogen transport. Finally, porous platinum was identified as a excellent catalyst for evaluation of membrane materials, however, lower cost nickel catalyst systems are being developed.