Immiscible Polymer Blend Membranes for High Pressure, High Temperature H2/CO2 Separation

High pressure and high temperature separation of H2/CO2 is of great interest for clean energy generation in processes such as coal gasification. Flat and tubular membranes of the polybenzimidazole (PBI)/6FDA-DAM immiscible blend containing colloidal ZIF-8 were prepared to test the gas separation performance of single gases and the H2/CO2 gas mixture at various pressures and temperatures. It was found that the amount of colloidal ZIF-8 in the blend has a remarkable effect on membrane morphology and gas separation. An increase of the loading for the colloidal ZIF-8 in the blend leads to a decrease in the size for the dispersed 6FDA-DAM domains. A higher experimental temperature resulted in higher gas permeance through the membrane, while the gas selectivity remained constant. At 30 atm and 300 °C, a 5% colloidal ZIF-8 PBI/6FDA-DAM membrane exhibited a H2 permeance of 29.52 GPU (approximately 472 Barrer), an ideal H2/CO2 selectivity of 17.4, and a H2/CO2 gas mixture selectivity of 12.8. In comparison to other membranes, this polymer blend membrane shows high gas permeance and high gas selectivity, and it surpasses the upper bound of the 2008 Robeson plot for H2/CO2.