(585h) Kinetic Study of Thermal Degradation of 2-Amino-2-Methyl-1-Propanol to Cyclic 4,4-Dimethyl-1,3-Oxazolidin-2-One

Naser S. Matin¹, Jesse Thompson¹, Femke M. Onneweer¹, and Kunlei Liu^{1, 2}

1. Center for Applied Energy Research, University of Kentucky, 2540 Research Park Drive, Lexington, KY 40511, United States
2. Department of Mechanical Engineering, University of Kentucky, Lexington, KY 40506, United States

CO₂ capture through chemical absorption suffers from some disadvantages such as high energy penalty associated with this process and amine degradation through irreversible side reactions mostly with CO₂ and O₂. Amine degradation reactions can lead to many problems within the process including: solvent loss, formation of volatile compounds potentially dangerous for environment, solvent foaming, fouling and material corrosion [1-2]. Amine degradation increases total operating cost of CO₂ capture. Sterically hindered amines offer advantages over conventional amines for the CO₂ capture process, in terms of less energy for solvent regeneration and capability to reach higher loadings of mol of CO₂ /mol of amine. AMP as a sterically hindered amine is thought to be resistant to oxidative degradation, as it does not have an α-hydrogen. However, it may be susceptible to degradation at high temperature, e.g. in cross heat exchanger and stripper [3, 4]. Because of its perceived low carbamate stability, is thought that AMP to be less prone to thermal degradation than MEA. However, the AMP carbamate (AMPCOO^-) can be as stable as MEA carbamate (MEACOO^-) in an aqueous solutions [5].

In this study, using experimental kinetics data, an apparent power law rate equation for the thermal degradation of 2-amino-2-methyl-1-propanol (AMP) to 4,4-Dimethyl-1,3-oxazolidin-2-one (DMOZD) as a primary stable degradation product is introduced. The reaction rate model of the AMP degradation to DMOZD as a function of amine and CO₂ concentration in the solution is introduced. In order to simulate potential stripper and reboiler conditions, the rate measurement experiments were performed at temperatures of 120, 135 and 150 °C. Aqueous solutions of 1.12, 1.68, 2.24 and 3.36 mol/L AMP concentration were prepared with CO₂ loadings varying from 0.17 to 0.7, mol_CO2/mol_AMP. The powers with respect to AMP and CO₂ concentrations in the kinetic model, and activation energies and pre-exponential factors, were calculated and introduced in this work. Considering the reaction rate orders (i.e 0.45 and 1.18 for the CO₂ and AMP concentrations respectively) the DMOZD formation rate displayed more dependency to AMP concentration and less dependency towards CO₂. The temperature dependent reaction rate constants obtained in this work are in the same order of magnitude and consistent with the literature values despite using different forms of the rate equation and different rate constants units [6, 7].

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