Recovery of carbon monoxide from flue gases by reactive absorption in ionic liquid imidazolium chlorocuprate(I): mass transfer coefficients

Abstract

Recovery of carbon monoxide from flue gases by selective absorption of carbon monoxide in an imidazolium chlorocuprate(I) ionic liquid is considered in this work as an alternative to the use of molecular volatile solvents such as aromatic hydrocarbons. The present work evaluates the CO mass transfer rates from the gas phase to the ionic liquid solutions in the absence of chemical reaction. To that end, carbon dioxide was employed as an inert model gas and absorption experiments were performed to assess the influence of different process variables in a batch reactor with flat gas–liquid interface. The experimental mass transfer coefficients showed significant variation with temperature, (3.4–10.9) × 10- 7 m·s- 1 between 293 and 313 K; stirring speed, (10.2–33.1) × 10- 7 m·s- 1 between 100 and 300 r·min- 1; and concentration of copper(I), (6.6–10.2) × 10- 7 m·s- 1 between 0.25 and 2 mol·L- 1. In addition, the mass transfer coefficients were eventually found to follow a potential proportionality of the type kL ? µ- 0.5 and the dimensionless correlation that makes the estimation of the mass transfer coefficients possible in the studied range of process variables was obtained: Sh = 10- 2.64 · Re1.07 · Sc0.75. These results constitute the first step in the kinetic analysis of the reaction between CO and imidazolium chlorocuprate(I) ionic liquid that determines the design of the separation units.