Measuring the Absorption Rate of CO2 in Nonaqueous CO2-Binding Organic Liquid Solvents with a Wetted-Wall Apparatus

The kinetics of the absorption of CO2 into two nonaqueous CO2-binding organic liquid (CO2BOL) solvents were measured at T=35, 45, and 55 degrees C with a wetted-wall column. Selected CO2 loadings were run with a so-called first-generation CO2BOL, comprising an independent base and alcohol, and a second-generation CO2BOL, in which the base and alcohol were conjoined. Liquid-film mass-transfer coefficient (k(g)) values for both solvents were measured to be comparable to values for monoethanolamine and piperazine aqueous solvents under a comparable driving force, in spite of far higher solution viscosities. An inverse temperature dependence of the k(g) value was also observed, which suggests that the physical solubility of CO2 in organic liquids may be making CO2 mass transfer faster than expected. Aspen Plus software was used to model the kinetic data and compare the CO2 absorption behavior of nonaqueous solvents with that of aqueous solvent platforms. This work continues our development of the CO2BOL solvents. Previous work established the thermodynamic properties related to CO2 capture. The present paper quantitatively studies the kinetics of CO2 capture and develops a rate-based model.