Kinetics of Carbon Dioxide Absorption into Aqueous Solutions of4-(Diethylamino)-2-Butanol and Blended Monoethanolamine and 4-(Diethylamino)-2-Butanol

Abstract

Recently, global warming and climate change problems have begun to receive attention globally. One of the urgent policies is to control greenhouse gas emissions to the atmosphere. Among the greenhouse gases, CO2 is considered to be a major contributor due to its abundance. The absorption of CO2 into chemical solvents is one of the mostpromising technologies for capturing CO2 due to its capability of handling large amounts of exhaust stream. One of the key parameters for this technology is to use effective solvents. A newly developed amino alcohol solvent, 4-(diethylamino)-2-butanol (DEAB), is now being considered as a promising alternative solvent for capturing CO2 due to its energy efficiency for regeneration and high absorption capacity. The primary focus of this research is on developing comprehensive reaction rate/kinetics models that take into account the coupling between the chemical equilibrium, mass transfer, and chemical kinetics of all possible chemical reactions for the absorption of CO2 into aqueous solutions of DEAB and blended MEA-DEAB in order to explore the potential of these new formulated solvents for capturing CO2 in terms of reaction kinetics. The fundamental knowledge required for the kinetics study, such as the physical solubility of CO2 (Henry’s law constant), the physical diffusivity of CO2, the equilibrium solubility of CO2, and the CO2-amines equilibria, are also considered in this research. The physical solubility and physical diffusivity of CO2 in aqueous solutions of DEAB and blended MEA-DEAB were estimated via a N2O analogy, which consists of measuring the solubility and diffusivity of N2O instead of CO2. The developed predictive correlations for the solubility and diffusivity of N2O in these new formulated solvents provide good predictive results compared to the experimental results. The absorption capacity in terms of the equilibrium solubility of CO2 in aqueous solutions of DEAB was found to be very high (comparable with PZ) and higher than that of AMP, MDEA, MEA, and DEA. Furthermore, the equilibrium solubility of CO2 in an aqueous solution of blended MEA-DEAB was observed to be higher than that of MEA. This research also established the mathematical models for calculating the equilibrium solubility of CO2 in an aqueous solution of these new formulated solvents. The calculated CO2 equilibrium solubility results were found to fit well with the experimental results. Finally, the comprehensive reaction rate/kinetics models for CO2 absorption into aqueous solutions of DEAB and blended MEA-DEAB were successfully developed. The predicted CO2 absorption rates obtained from the models favourably fit with the experimental results. The reaction kinetics results show that: (i) the rate of CO2 absorption into DEAB is higher than that into MDEA, is comparable with that into AMP and DEA, and is lower than that into MEA and PZ, and (ii) the rate of CO2 absorption into blended MEA-DEAB is higher than that into MEA. Based on the results obtained from this research in terms of reaction kinetics and absorption capacity, it can be concluded that the aqueous solutions of DEAB and blended MEA-DEAB have good potential to be used as the alternative solvents for capturing CO2.