Macroemulsions of Liquid and Supercritical CO2-in-Water and Water-in-Liquid CO2 Stabilized by Fine Particles

Liquid and supercritical carbon dioxide-in-water (C/W) and water-in-carbon dioxide (W/C) macroemulsions (Pickering emulsions) stabilized by fine particles were created in a high-pressure batch reactor. C/W macroemulsions form when hydrophilic particles, such as pulverized limestone, sand, flyash, shale, and lizardite, a rock rich in magnesium silicate, are used as stabilizers; W/C macroemulsions form when hydrophobic particles, such as Teflon powder, activated carbon, carbon black, and pulverized coal, are used as stabilizers. C/W macroemulsions form with both liquid and supercritical CO2. C/W macroemulsions consist of dispersed droplets of liquid or supercritical CO2 sheathed with particles in water; W/C macroemulsions consist of droplets of water sheathed with particles dispersed in liquid CO2. The sheathed droplets are called globules. The globule diameter is largely dependent on the shear force imparted by mixing the two fluids, CO2 and H2O. The particle size needs to be adjusted to the dispersed droplet diameter; a practical ratio was found to be 1:20. In a batch reactor with a magnetic stir bar rotating at 1300 rpm, liquid CO2 produced typical globule diameters in the 200-300 (mu)m range, whereas supercritical CO2 produced smaller globules, in the 100-150 (mu)m range.