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.