REACTION KINETICS OF CARBON DIOXIDE WITH NONAQUEOUS SOLUTIONS OF STERICALLY HINDERED AMINES

Abstract

Due to existing energy intensive CO₂ capture processes and rising fuel costs, alternative and affordable solvents or technologies for CO₂ capture have gained importance in the research of reducing global warming. To that effect, sterically hindered amines have been introduced which have high CO₂ absorption capacities by means of the formation of unstable carbamate ions. Another factor leading to an affordable solvent for CO₂ capture could be using nonaqueous solvents instead of aqueous solvents in the process. This is important because nonaqueous solvents can eliminate some of the problems of aqueous solvents such as corrosion and high heat requirements. To that end, in this study we investigated the reaction kinetics of CO₂ and two sterically hindered amines; 2-amino-2-methyl-1,3-propanediol (AMPD) and 2-amino-2-ethyl-1,3-propanediol  (AEPD) in ethanol. The pseudo–first-order reaction rate constants of the reactions between CO₂ and sterically hindered amines were measured in ethanol at 288, 298 ve 308K by using direct stopped-flow technique. The measured rate constants were then analyzed by using the equations of termolecular reaction mechanism. The orders of the reactions (n) between CO₂-AMPD and CO₂-AEPD were found as 1 and 2, respectively. To our best knowledge, our study is the first in the literature showing that ethanol can be involved in a termolecular reaction just as the partaking of water in the reaction.  

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