Selective and simultaneous membrane separation of CO and H2 from N2 by protic chlorocuprate ionic liquids

Abstract

Efficient recovery of CO and H2 from offgas streams is environmentally and economically meaningful from the view point of the wide use of syngas (CO/H2) in the chemical industry. This work reports selective and simultaneous separation of CO and H2 from N2 using protic chlorocuprate ionic liquids (PCILs)-based membranes. The chemical structures of the prepared PCILs were characterized using FTIR, NMR and ESI-MS, and the thermal stability, melting points, viscosity and density of PCILs were determined. The morphology and elemental distribution of PCIL-based membranes were characterized by SEM and EDS. Facilitated transport of CO is observed in these membranes, and the CO permeability is up to 178.3 barrers (0.1 bar, 40 °C) in [TEAH][CuCl2], with a CO/N2 selectivity of 26.2. H2 permeability and H2/N2 selectivity are also found to reach 198.2 barrers (0.5 bar, 40 °C) and 29.1, respectively. The permeability of CO and the selectivity of CO/N2 can be further optimized to 405.9 barrers and 69.9 by altering the Cu(I) content, respectively. In addition, the selectivity of CO/H2 can be tuned drastically via varying the Cu(I) content (from 0.77 to 12.0) and the operating temperature (from 2.14 to 0.42), which may be applied to the composition adjustment of syngas. In a word, this work offers a new strategy for designing IL-based membranes that used for CO and H2 capture.