Semi-hollow LTA zeolite membrane for water permeation in simulated CO2 hydrogenation to methanol

Abstract

Linde Type A (LTA) zeolite is an effective inorganic water permeable membrane material due to its inherent Na+-gated water-conducting mechanism. Although dense LTA membranes show excellent water selective permeability, the water permeability rate still needs to be improved to drive the CO2 hydrogenation reaction towards methanol production. In this work, we prepared a water-conducting LTA membrane with well-distributed non-penetrative macroholes, resulting in a cheese-like structure that combines the advantages of micro-nanochannels for high water selective permeability and macroholes for quick water diffusion. These semi-hollow (SH)-LTA membranes with different thicknesses and number of macroholes were fabricated via a steam-assisted method by adjusting the amount of water in the precursor solution. The optimized SH-LTA membranes presented an average water permeance of 8.57 × 10−7 mol m−2 s−1 Pa−1 at 200 °C along with CH3OH, H2, and CO2 permeances of 3.24 × 10−9, 7.92 × 10−12, and 4.32 × 10−12 mol m−2 s−1 Pa−1, respectively. The membrane stability was verified under continuous mixture gas permeation tests for 10 h between 200 and 300 °C. The dissolution-recrystallization route of the SH morphology was confirmed following comprehensive characterizations and complemented by molecular dynamics simulations to elucidate the superior water separation behavior in SH-LTA membrane in comparison with pristine LTA membrane.