Shear Viscosity and Heterogeneous Structure of Alkylaminoethanol-Based CO₂ Absorbents

Shear viscosity of concentrated aqueous solutions of alkylaminoethanols was determined with changing the length of the alkyl chain and the concentration of dissolved CO₂. The viscosity increased with increasing the CO₂ loading, reflecting the strengthening of the intermolecular electrostatic interaction. The dependence of the viscosity on both temperature and CO₂ loading was described by a modified version of Vogel-Fulchar-Tammann equation. Compared at the same volume concentration of CO₂, the viscosity increased with increasing the alkyl chain lengths, and the dependence on the alkyl chain length increased with the CO₂ loading. At the same time, small-angle X-ray scattering profiles exhibited the presence of a prepeak when the alkyl chain was long, and the prepeak grew with the CO₂ loading. It suggests that the presence of the heterogeneous structure increases the shear viscosity of the CO₂ absorbents when the alkyl chain is long.