Research into the improvement of CO2 absorption rates in ammonia-based absorbents via addition of fast reacting primary/secondary amines are of great interest. In this work, a new substituted cyclic amine 4-amino-methyltetrahydropyran (4-AMTHP) was blended with aqueous ammonia to increase its reactivity toward CO2. Stopped flow spectrophotometry was employed to investigate the underlying reaction mechanism between dissolved CO2(aq) and a series of blended NH3/4-AMTHP solutions under homogeneous conditions. A comprehensive chemical model describing the blended 4-AMTHP NH3-CO2-H2O system, which involves a total of 11 kinetic reactions and 15 species, has been developed and further evaluated to explore the experimental kinetic and CO2 mass transfer data measured from a bench-scale wetted-wall column. From the resulting data, it was demonstrated here that the addition of a small quantity of similar to 0.3 M 4-AMTHP into the 3 M NH3/0.9 M CO2 solution can effectively increase the kinetic reactivity during CO2 absorption into aqueous ammonia solutions, resulting in a similar to 50% increase in mass transfer.