US-China Clean Energy Research Center Advanced Coal Technology Consortium

To mitigate CO2 emissions and meet the DOE's costs goals (NETL, 2009)), significant improvements and breakthroughs in cost-effective techniques for capture are needed. We propose a broad research effort covering (1) membrane barrier material development and system integration; (2) a hybrid process consisting of catalyzed solvents and post-scrubbing carbon enrichment for the post-combustion CO2 capture process. Membrane: Researcher at LLNL are have used novel fabrication technologies (first applied to national security missions) to create high permeability, high selectivity membranes for CO2 separation. The approach involves nano-engineered fabrication of membranes with deposition of polymers (such as polyimides) through a vapor to fabricate uniform, extremely thin membranes. Bench-scale tests have shown that the resulting composite membranes exhibit a high CO2 permeability combined with high CO2/N2 selectivity (~20:1). This indicates the feasibility of using LLNL's composite membranes to capture CO2 from coal-derived flue gas stream. Post-Combustion: Carbonic anhydrase enzyme, as a homogeneous catalyst, is a very fast catalyst for CO2 hydration and several organizations are exploring it for post-combustion CO2 capture (CO2 Solutions, 2008; Bao, 2006). Questions remain regarding the enzyme's utility in harsh industrial conditions (excess O2, NOx, and SO2; pH?9.7). In order to overcome these disadvantages, organo-metallic enzyme mimics are proposed with simpler, more robust structures than the enzyme. LLNL has conducted extensive analysis of cyclen and other small-molecule catalysts for CO2 hydration and has a well-developed calculational ability to evaluate the kinetics of proposed catalyst structures upon the combination of transition state theory (Laidler, 1983) and quantum mechanical calculations (Gaussian 03). This ability can calculate the transition state energy and determine if a particular design feature will improve the catalytic activity or longevity in this program. Furthermore, a series of metal cyclen complexes have been synthesized and tested at CAER. More than a 15% rate increase has been observed in a wetted wall column for 30% MEA with zinc catalyst versus solvent alone.