On the zeolitic imidazolate framework-8 (ZIF-8) membrane for hydrogen separation from simulated biomass-derived syngas

• ZIF-8 membranes were successfully prepared with post-treatments.
• ZIF-8 membranes gave good H2 separation performance in a simulated syngas environment.
• The hydrothermal stability of the ZIF-8 membrane was evaluated.

Hydrogen separation from biomass-derived syngas is a critical step in the utilization of gasification technology. Compared with the traditional methods, membrane technology provides an effective and low-cost solution for adjusting the gas composition and collecting H2 in syngas environments. In this study, a zeolitic imidazolate framework-8 (ZIF-8)-based membrane, which is a potential candidate for H2 separation from biomass-derived syngas, was successfully fabricated through the seeded (secondary) growth method and the subsequent post-treatments. The prepared ZIF-8 membrane exhibited a modest H2 separation performance for H2/CO2 and H2/CO, with separation factors of 4.95 and 6.08, respectively, and a H2 permeance of 7.81 × 10−8 mol m−2 s−1 Pa−1 at 200 °C in the simulated biomass-derived syngas environments (H2/CO2/CO) with the presence of steam. In particular, the H2/CO2 and H2/CO separation factors were increased by 36% and 97%, respectively, with respect to those obtained through bare supports. Despite the promising H2 perm-selectivity, the H2/CO2 and H2/CO separation factors of ZIF-8 membranes at 200 °C under water-containing syngas environments were maintained up to 10 h but the longer exposure led to the gradual degradation and eventual reduction toward those of bare supports after 15 h seemingly due to the water-involved membrane degradation. This study provides the availability and limitation of ZIF-8 membranes for H2 separations in stimulated biomass-derived syngas environments.

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