Carbon molecular-sieve membranes developed from a Tröger's base polymer and possessing superior gas-separation performance

Abstract

Carbon molecular-sieve membranes possess tremendous practical advantages over unary polymer membranes by providing high gas-separation performance levels, coupled with excellent mechanical and chemical stability. Improving their overall effectiveness greatly expands the competitiveness of this class of membranes. In the present study, carbon membranes are fabricated from a Tröger’s base polymer as the precursor. By optimizing the carbonization conditions, the gas-separation performance of the resultant membranes are significantly enhanced. Under optimized conditions, a H2 permeability of up to 1135 Barrer is achieved, with a corresponding H2/CH4 selectivity of 1170 and a CO2/CH4 selectivity of 238. While increasing the operating temperature slightly reduces the selectivity, it still remains in the high-separation region. Overall, the measured separation performance levels for H2-related separations, i.e., H2/CH4, H2/N2 and H2/CO2, all substantially exceed the Robeson upper bound. Moreover, the CO2/CH4 separation efficacy also lies above the 2019 upper bound, indicating that the carbon membranes developed in the present work are versatile and promising for many different gas-separation applications.