Selective separation of CO2 by using novel facilitated transport membrane at elevated temperatures and pressures

A novel facilitated transport membrane consisting of 2,3-diaminopropionic acid (DAPA) as a selective carrier of CO2 and PVA/PAA gel as support was developed for the removal of CO2 from the water gas shift reactor in the hydrogen production plants. The membrane performance was tested by the experiments on the selective separation of CO2 from a mixture of 3.65% CO2, 32.9% N2 and 63.5% H2O at the temperature from 125 to 160 °C and the feed gas pressure from 100 to 650 kPa. Typical observed CO2 permeances were 3.14 × 10−4 mol/m2 s kPa at 125 °C and 300 kPa, 1.71 × 10−4 at 140 °C and the feed gas pressure of 450 kPa and 1.10 × 10−4 at 160 °C and 600 kPa, and the CO2/H2 selectivities at the respective conditions were 1070, 561 and 432, respectively. Obtained results showed that the water content in the membrane is one of the key factors, which determines the CO2 permeance and CO2/N2 selectivity. The CO2 permeance as well as the CO2/N2 selectivity increased with increasing the pressure, which might be mainly caused by increasing the water content in the membrane. It was also found that increasing the carrier concentration could significantly enhance the membrane performance, especially at elevated temperatures.