(210b) Semi-clathrate Hydrates for Carbon Dioxide Capture: Prospects and Challenges

Semiclathrate hydrates (sc) are non-stoichiometric crystalline compounds in which a part of the guest compound along with water molecules form the host framework and also occupy the cages of the structure. Semiclathrates also have the ability to accommodate small gas molecules like carbon dioxide, nitrogen, hydrogen etc into the structure. Quaternary ammonium/phosphonium salts such as tetra butyl ammonium bromide (TBAB), tetra butyl ammonium nitrate (TBANO₃) which form semi-clathrate hydrates have been extensively investigated for cold storage and secondary refrigeration applications. Recently, semi-clathrate hydrates have received attention as promoters for gas separation applications especially for CO₂ separation from power plants, coalmine gas, and land fill gas. In our kinetic work, we have identified several distinctive observations of the formation behavior of semi-clathrates applicable to CO₂ capture from pre-combustion streams. In this presentation, the distinctive advantages and the significant challenges associated with the use of quaternary ammonium salts for carbon dioxide capture based on our understanding of the kinetics of semi-clathrate hydrate formation will be highlighted.