Separation of carbon dioxide from nitrogen using diethanolamine-impregnated poly(vinyl alcohol) membranes

This work is a continuation of our efforts to develop CO₂ separation membranes based on facilitated transport, and it deals with the separation of CO₂/N₂ mixtures using DEA-impregnated membranes at various operating conditions (i.e., temperature, feed composition and pressure). The idea was to exploit the favourable interaction between CO₂ and DEA in the membrane to facilitate CO₂ transport. The effects of DEA content in the membrane on the separation performance were examined, and the membrane containing 20 wt% DEA exhibited the best performance among all the membranes (containing 0-50 wt% DEA) studied. Consistent with pure gas permeation, the facilitation in CO₂ transport was more pronounced at lower CO₂ partial pressures. The membrane exhibited a higher permselectivity at higher temperatures and lower CO₂ partial pressures. At a feed pressure of 308 kPa, a CO₂ permeance of 9.7 GPU and a CO₂/N₂ selectivity of 112 were achieved at ambient temperature in separating CO₂ from a CO₂/N₂ mixture containing 15.6 mol% CO₂. The membrane was shown to be stable; no deterioration in the separation performance was observed during the course of continuous operation over a period of over 5 weeks.