Formation of calcium carbonate particles by direct contact of Ca(OH)2 powders with supercritical CO2

A novel method to obtain a high conversion of Ca(OH)2 powder to CaCO3 is reported. The method uses supercritical CO2 containing water that is passed over the dry Ca(OH)2 powder. Conversions greater than 98% are obtained. The dominant crystal structure is calcite. The process has the advantages of the conventional solution based process in terms of high conversion and the advantages of a gas–solid based process in that dry, non-agglomerated particles are obtained by simple venting of the solvent.