Nonaqueous amine-based absorbent for energy-efficient CO2 capture: Effect of shifting solvent on kinetic behaviors

Nonaqueous absorbents have shown great potential in lowering regeneration energy for energy-efficient CO₂ capture. The effect of reaction media with varying solvent characteristics (polarity, solubility parameter and dielectric constant) on kinetic behaviors deserves to be discovered. In this work, CO₂ absorption flux against CO₂ partial pressure was determined in a stirred cell reactor at temperatures of 283.2–303.2 K with 1.0–5.0 mol L⁻¹ 2-(butylamino)ethanol (BAE) in nonaqueous 2-butoxyethanol (2-BE). Physicochemical properties and the physical mass transfer coefficients were also measured and represented by proposed correlations. The overall reaction rate constants were derived under the well-defined pseudo-first-order regime conditions. The partial reaction order with respect to BAE was found to be about 2.0 in 2-BE and 1.0–1.3 in water respectively, which reveals that the formation of ionic products may be highly depressed in solvent with low Hansen solubility parameter (HSP) resulting in the increasing reaction order. The overall third-order kinetic data can be well represented by termolecular mechanism model with AARD of 10.5 %. The findings will provide fundamental support for further pilot-scale performance demonstration.