Facilitated transport of CO₂ through immobilized liquid membrane

Selective removal of acid gases from a contaminated gas stream was studied using four amines (diethylenetriamine (DETA), diaminoethane (DAE), diethylamine (DEYA), and bis(2-ethylhexyl)amine (BEHA)) as immobilized liquids in a facilitated transport membrane. The effect of amine concentration, CO ₂ partial pressure, and operating temperature on the permeance of CO₂ and CH4 was investigated for each aqueous amine solution. The observed CO₂ permeance decreased with increasing CO₂ feed pressure, whereas the permeance of CH₄ remained constant for all tested amines. The permeance of CO₂ and the selectivity were in the order DETA > DAE > BEHA & DEYA. This order is related to the number of nitrogen atoms per amine molecule, which can be correlated to loading capacity and consequently to amine reactivity with CO₂. The permeance of CO₂ in 2 M DETA increased with increasing temperature. The permeance of CO₂ using DETA was about 4 times that obtained using diethanolamine (DEA) and monoethanolamine (MEA), which are the most commonly used solvents in industrial applications.