Evaluating the Effectiveness of Piperazine on Carbon Dioxide Loading in N-Methyl Diethanolamine Aqueous Solutions and Water/Oil Microemulsions

This study investigated the chemical absorption of carbon dioxide gas from a carbon dioxide–nitrogen gas mixture at a low partial pressure of carbon dioxide (0.1–1.0 bar) using a water-in-oil microemulsion system. Gas chemisorption in the aqueous phase was examined using N-methyldiethanolamine (MDEA) at 3 mol kg–1 concentration and piperazine (PZ) at concentrations ranging from 0.3 to 0.9 mol kg–1. The first stage was to assess the effectiveness of the microemulsion system in comparison to that of the nonemulsion system for gas absorption. Then, the aim was to evaluate the effectiveness of PZ in combination with an amine. The results clearly validate the superior gas absorption performance of the microemulsion system compared to that of the nonemulsion system. Furthermore, concerning the effectiveness of PZ, the results indicate that PZ is more efficient at low partial pressures of carbon dioxide than at high pressures. An interesting observation is that in a solution with a constant concentration of MDEA and PZ, as the partial pressure of carbon dioxide gas changes, PZ performs optimally at a partial pressure of 0.3 bar. Additionally, the results obtained confirm the linearity of the relationship between the mole fraction of PZ in the MDEA/PZ solution and the carbon dioxide loading of the MDEA/PZ solution within this pressure range.