Rapid CO2 absorption into aqueous benzylamine (BZA) solutions and its formulations with monoethanolamine (MEA), and 2-amino-2-methyl-1-propanol (AMP) as components for post combustion capture processes

• Overall CO2 mass transfer coefficients in 0.5–5.0 M BZA and CO2 loadings from 0.0 to 0.4.
• Significantly larger CO2 mass transfer coefficients in BZA than in MEA at high concentrations.
• CO2 absorption into aqueous amine formulations containing BZA, MEA, and AMP as components.
• Substantially larger CO2 mass transfer coefficients in BZA formulations than in unblended MEA.
• Density and viscosity data for BZA and its formulations with MEA and AMP at different CO2 loadings.

Our recent studies have identified benzylamine (BZA) as a promising candidate for CO2 capture processes, however the formation of stable and insoluble BZA-carbamate salts in highly concentrated unblended BZA solutions, and at high CO2 loadings, severely restricts the working concentration of the unblended BZA solvent. Thus, BZA is ideally placed as a candidate for use in a formulated solvent to improve the overall amine concentration and CO2 loading which can be used.The current work focuses on the investigation of CO2 absorption into aqueous solutions of BZA as well as formulations of BZA incorporating MEA and AMP as the second amine components, respectively. Mass transfer/kinetic measurements using a wetted wall column (WWC) at 40 °C have been performed for a series of unblended BZA solutions as well as a series of amine concentrations and ratios in the formulations. Overall mass transfer coefficients as a function of total CO2 loading in the solutions (0.0–0.4 mol CO2/total mole amine in solution) have been determined for the unblended BZA solutions and formulations. CO2 absorption rates into unblended BZA solutions are significantly faster than in MEA solutions at similar concentrations and zero CO2 loading. The majority of the BZA formulations investigated here can be considered promising candidates for CO2 capture and possess larger or comparable mass transfer rates (up to 30% increase at low loadings) when compared to the corresponding unblended 5.0 and 6.0 M MEA solutions under similar conditions. Formulations containing BZA and MEA demonstrated the fastest CO2 absorption rates overall due to the presence of two fast reacting amines, both of which can actively and directly contribute to the absorption of CO2.