Selective Removal of Carbon Dioxide from Wet CO2/H2 Mixtures via Facilitated Transport Membranes containing Amine Blends as Carriers

The selective separation of carbon dioxide (CO₂) from a wet gaseous mixture of CO₂/H₂ through facilitated transport membranes containing immobilized aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), ethylenediamine (EDA) and monoprotonated ethylenediamine (EDAH⁺) and their blends was experimentally investigated. The effect of CO₂ partial pressure, amine concentration, feed side pressure and amine species on the CO₂ and H₂ permeances were studied. The CO₂ permeability through amine solution membranes decreased with increasing CO₂ feed partial pressure but the H₂ permeance was almost independent of the H₂ partial pressure. A comparison of experimental results showed that single or blended amines with low viscosity and a moderate equilibrium constant, i.e., large forward and reverse reaction rate of CO₂‐amine, are suitable for effective separation of CO₂. The permeability of CO₂ generally increased with an increase in amine concentration, although this increase may be compromised by the salting out effect and decrease in diffusivities of species. The results obtained indicated that CO₂ permeance across a variety of amines are in the order of DEA (2 M) > MD (2 M) > MD (1 M) > MEA (2 M) > MEA (4 M) > MD (4 M) > DEA (1 M) > DEA (4 M) > MEA (1 M) for various concentrations of MEA + DEA blend and are in the order of EDAH⁺ (2 M) > DEA (2 M) > MH (2 M) > DH (2 M) > ED (2 M) > EDA (2 M) > MEA (2 M) for various blends of amine.