Glucosamine for CO2 Capture: Absorption Kinetics, Promoted Absorption Rate, and Comparison with Other Amino Sugars

Abstract

Amino sugars─sugars wherein the amine group substitutes the hydroxyl group─are renewable and ecofriendly CO2 separation solvents. In this work, the kinetics of CO2 absorption in the amino sugar glucosamine (GA) was studied. Absorption rates in aqueous GA solutions (0.1–1 M) were measured in a stirred cell reactor in the 303–313 K range. At T = 308 K, the value of the reaction rate constant for GA (0.1 M) was 27 M–1 s–1. The two-step zwitterion mechanism was employed for describing the reaction pathway. Some useful characteristics of GA solutions, such as density and viscosity, were measured. Using the modified Stokes law and the N2O analogy method, the diffusivity and solubility of CO2 in solutions were determined. The liquid-side mass-transfer coefficient was found to be 0.005 cm/s at 308 K. Three amine promoters were chosen to improve the reactivity of GA, viz., monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), and piperazine (PZ). Mixtures of GA/PZ (2.5/0.5 M) were the most reactive. The reactivity of two further amino sugars, N-acetyl-d-glucosamine (NAG) and N-methyl-d-glucamine (NMG), was also studied, and a comparison with GA was provided. NMG was the most reactive with CO2, whereas GA was the least reactive. This work will draw attention to this new category of CO2-capturing solvents.