MEASUREMENT OF THE ABSORPTION RATE OF CARBON-DIOXIDE INTO AQUEOUS DIETHANOLAMINE

Absorption rates of gaseous CO2 into aqueous diethanolamine (DEA) solu tions were measured in a quiescent, inverted-tube diffusiometer by mon itoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO2 in solution but very sensitive to the diffusion rate of bicarbonate, protonated DEA and car bamate ions. Evidence also suggested that chemical reaction equilibriu m is rapid relative to diffusion. The diffusion coefficient of DEA in water was also measured using a Taylor dispersion apparatus. A numeric al model was developed and used to regress diffusion coefficients of b icarbonate, carbamate, and protonated amine from measured absorption r ates. CO2 absorption rates and diffusion coefficients of bicarbonate, carbamate, and protonated DEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % DEA in water.