Volatility of amines for CO₂ capture

Volatility is a critical criterion for amine selection for CO₂ capture from low pressure gas streams. The Henry's law constant (H_am) in water of 24 novel amines, including 18 tertiary amines, 3 hindered amines, 2 ether amines, and 1 pyridine derivative was measured at 40 °C using a hot gas FTIR. 14 of them have a H_am less than 2-amino-2-methyl-1-propanol (AMP). A group contribution model that correlates H_am to molecular structure was developed based on the data from this work and data from literature. Non-cyclic groups and cyclic groups have significant effect on the volatility of the amine. The amine partial pressure (P_am) of tertiary and hindered amines was also measured in a blend with PZ at 40 °C and their normal CO₂ loading range for flue gas CO₂ capture. With increased pK_a, the P_am of tertiary and hindered amines becomes a stronger function of CO₂ loading. These results at nominal lean loading were correlated with H_am of the amine.