Solid-Gas Carbonation Coupled with Solid Ionic Liquids for the Synthesis of CaCO3: Performance, Polymorphic Control, and Self-Catalytic Kinetics

The effect of temperature, pressure, time, solid ionic liquid (SIL) mass (here, the SIL used is tetra-n-heptyl-ammonium bromide, abbreviated as THepAmBr), reuse of THepAmBr, type of SIL, and additives on the solid-gas (Ca(OH)(2)-CO2) carbonation system was investigated. Results showed that conversion increased as the temperature increased from 25.0 degrees C up to 50.0 degrees C and then decreased thereafter; but increased consistently with increasing pressure. Similarly, conversion increased as the mass of THepAmBr increased, leading to complete conversion at a THepAmBr/Ca(OH)(2) mass ratio of 0.1:1 with the production of rhombohedral calcites. Stability tests revealed that THepAmBr was active and stable. The effect of BmimBr and BmimCl indicated that they gave conversions of >96%. Furthermore, studies on polymorphic control to aragonite gave interesting results: 30.2% aragonite was synthesized with MgCl2 and 54.7% with PEG6000. Moreover, time-dependent conversion showed that the reaction mechanism for the system was self-catalytic. Consequently, the reaction rate equation that was derived described the experimental conversion satisfactorily.