Hydrogen recovery using hollow fiber membranes in the ammonia cracking process

Abstract

This study investigates the separation performance of various hollow fiber membranes (HFMs) for hydrogen (H2) recovery from ammonia (NH3) cracking processes. Oxide-based (γ-Al2O3 and SiO2) and metal-based (Pd and Pd–Ag–Cu) thin films were deposited on α-Al2O3 HFM supports and exposed to H2, N2 and trace of NH3 gas at 450 °C and 0.5–2.0 bar. The separation factor was defined as the ratio of the H2 permeate flow rate to the N2 permeate flow rate (α H2/N2) and to the NH3 permeate flow rate (α H2/NH3). Results show that Pd-based HFMs have better H2 selectivity than oxide-based HFMs. The Pd–Ag–Cu/α-Al2O3 HFM had the highest H2-to-NH3 selectivity with a α H2/NH3 separation factor of 1.4 104 over the tested pressure range. Pressure dependence varied among HFM types, metal-based HFMs showed increased H2 selectivity at higher pressures. These results have big implications for developing advanced membrane-based gas-gas separation processes for H2 purification in proton exchange membrane (PEM) fuel cell (FC) applications. Pd-alloy HFMs, especially Pd–Ag–Cu, are shown to be good for high-selectivity H2 separation from NH3 cracking products. © 2025