Improvement of H2/CO2 selectivity at high pressure and temperature of benzimidazole-linked hybrid membranes via post treatment

Abstract

H₂-selective membranes with high performance at high pressure and temperature are required. Here, we prepared high performance membranes for H₂/CO₂ separation by post treatment (in terms of crosslinking and thermal treatment) of CP-2-BILP molecular-scale hybrid membranes. Post crosslinking with TMC generated new amide linkages and compacted the membranes. So, the CP-2-BILP-0.4 %TMC membranes had an improved H₂/CO₂ selectivity of 65.5 (corresponding H₂ permeance of 35.6 GPU) at 11 bar (423 K) and an improved H₂/CO₂ selectivity of 41.7 (corresponding H₂ permeance of 515 GPU) at 573 K (1 bar). Post thermal treatment promoted further reaction of monomers and further formation of benzimidazole rings, and also compacted the membranes. Given by the synergistic effect of post crosslinking and thermal treatment, the CP-2-BILP-0.4 %TMC-423K membranes demonstrated a good pressure resistance. When the feed pressure was increased from 1 bar to 11 bar, the H₂/CO₂ selectivity of the membranes only decreased 10.2 % (74.5–66.9) and the H₂ permeance only slightly dropped (48.3 GPU to 44.1 GPU). The good H₂/CO₂ separation performance at high pressure and temperature, as well as good stability, demonstrated their potential for H₂ purification under industrial relevant process.