(241c) High Temperature Dual-Phase Inorganic Membranes for Carbon Dioxide Separation

Electrical generation from fossil fuels results in emission of carbon dioxide into atmosphere causing global warming.  The challenge is how to effectively capture carbon dioxide before other alternative non-fossil energy resources are developed to replace the fossil fuels.  There are three strategies to capture carbon dioxide from power plants burning fossil fuels:  post-combustion carbon dioxide removal, pre-combustion carbon removal andoxyfuelcombustion processes.    High temperature CO₂ perm-selective inorganic membranes will play a critical role in these processes.  All microporous inorganic membranes showing high CO₂/N₂ selectivity at room temperature become non-selective for CO₂ separation at high temperatures due to low diffusion controlled selectivity for molecules of similar sizes. The talk will focus on new dual-phase membranes that permeate only carbon dioxide at high temperatures.  The dual-phase membranes consist of a metal or oxygen ionic conducting oxide phase and a molten carbonate phase which conduct respectively electrons or oxygen ions and carbonate ions.  When using metal as the solid phase, the membranes permeate both CO₂ and O₂ in 2:1 ratio.  Dual-phase membranes consisting of a mixed electronic and ionic conducting or oxygen ionic conducting ceramic solid phase permeate CO₂ with CO₂permeace upto 10^-7mol/m².s.Pa with CO₂/N₂ selectivity up to 3000 in temperature range from 500-900^oC.   The activation energy for CO2 permeation through these dual-phase membranes is in the range of 80-110 kJ/mol, depending on the ceramic phase. CO₂ permeation flux is controlled by oxygen ionic conductivity in the ceramic phase. Results will be presented showing improvement of CO₂permeance by using a ceramic phase with higher oxygen ionic conductivity or preparing membranes with small thickness.