Solubility of carbon-dioxide (CO2) in piperazine-activated 2-amino-2-methyl-1-propanol (AMP) and N-methyldiethanolamine (MDEA) respectively

Alkanolamines have become very popular for the removal of acid gases such as hydrogen sulphide and carbon-dioxide. 2-amino-2-methyl-1-propanol (AMP) and N-methyldiethanolamine (MDEA) are two of those popular to investigate of late. In recent times, piperazine (PZ), another amine, has been discovered to have a positive effect on the absorption of CO2, in terms of both rate and capacity, in the former amines. The task is to find the best mix of the amines in order to maximise absorption, whilst also operating at higher pressures.
In this work the study is conducted at the temperatures 303.15 K and 333.15 K, and pressures from 4 to 16 bar. The piperazine mass fractions are 2 and 8 mass %, while the AMP and MDEA concentrations are 25 mass % and 50 mass%.
It is found that AMP has a higher CO2 loading than MDEA at the same pressure, and that the solubility increases almost exponentially with pressure increase.
The highest loading (4.6 mol gas/mol amine) is found at a 25 mass% AMP, 8 mass% PZ solution at 303.15K and 16 bar. The lowest loading (0.86 mol gas/mol amine) is at 50 mass% MDEA, 2 mass% PZ at 333.15K and 4 bar.