The ranking of all amines in terms of the values of the three pKa s is presented in Table 4. It clearly shows that all the studied amines have a higher pKathan MEA. 2-MPMDA, with two primary amino groups, has the highest pKa1 and the second pKa 2. It should be an amine of great interest in carbon capture operations. DAOMDPA, with two primary and a tertiary amino group, also has a high pKavalue. The coefficient of determination (R2) of the linear regression for the Figure 1, 2, and 3 are presented in Table S5.
Table 4 pKa ranking at 298 K for all amines