Influence of pKa on solvent performance of MAPA promoted tertiary amines

Abstract

In the present work, absorption and desorption performance of ten single tertiary amines and their blends with MAPA was studied using a screening apparatus. Absorption experiments were conducted at 40 °C and up to 9.5 kPa partial pressure of CO2, while desorption experiments were conducted at 80 °C and down to 1.0 kPa partial pressure of CO2. In addition, the pKa value of the studied amines was measured at 25 °C.

The results indicated that the optimal pKa of the tertiary amines, giving the highest absorption capacity and cyclic capacity, was in the range of 9.48–10.13. At a higher pKa value, the cyclic capacity was decreased. Further, addition of MAPA to the tertiary amines influenced the absorption performance by increasing the absorption capacity for tertiary amines with low pKa (7.79–9.03) and decreasing the absorption capacity for tertiary amines with high pKa (9.48–10.42). Also, the CO2 absorption rate was significant enhanced by addition of MAPA.