2024 AIChE Annual Meeting
(383y) A Novel ZIF-8 Membrane for Enhanced Thermal Stability and H2/CO2 Separation in Water Gas Shift Reactions
Zeolitic imidazolate framework-8 (ZIF-8) membranes have shown great potential as effective barriers in membrane reactors, particularly enhancing the water gas shift (WGS) reaction due to their outstanding thermal stability and hydrogen over carbon dioxide sieving properties. In this study, we introduce an innovative counter diffusion approach to create a novel, thermally robust ZIF-8 membrane. This process involves an initial application of a zinc precursor (zinc acetate dihydrate), followed by a solvothermal reaction with a methanolic 2-methylimidazole solution. The strategic pre-application and drying of the zinc precursor on a porous support significantly slow the zinc source's diffusion, ensuring initial interaction between the zinc and ligand molecules occurs within the porous medium. This technique likely facilitated the formation of a uniform ZIF-8 layer across the surface and more critically, at the porous support's grain interfaces, penetrating up to 80 μm in depth. This approach not only effectively seals the support's pores with ZIF-8 particles but also ensures their widespread distribution. The developed ZIF-8 membrane showcased an impressive hydrogen to carbon dioxide separation factor of about 8.7 at the WGS reaction condition of 300 °C. Contrary to traditional membrane designs, the ZIF-8 particles were compactly integrated into the porous support, minimizing the likelihood of mechanical damage. Additionally, the membrane's distinct structure contributed to its exceptional thermal stability, maintaining reliable and sustainable hydrogen/carbon dioxide separation at 300 °C over a period of 72 h.
