Long-Term Stability against H2S Poisoning on Pd Composite Membranes by Thin Zeolite Coatings

Parts per million levels of H2S can lead to fast deactivation of Pd-based membranes due to preferential adsorption on the membrane surface or the formation of metal sulfides. This study provides an effective approach to protect Pd-based membranes against sulfur poisoning by a thin zeolite layer of ca. 2 μm thickness coating on the Pd surface. Both NaA and KA zeolite layers act as barriers at 673–773 K under 5–15 ppm of H2S atmosphere, for the H2S cannot reach the Pd surface due to dissociation within the supercages and molecular sieving mechanism. The long-term stability in 10 ppm of H2S at 673 K demonstrates the capability of the zeolite layer to improve H2S resistance of Pd membranes and simultaneously maintain a relatively high H2 permeance (4.6 × 10–7 mol m–2 s–1 Pa–1 in this study) under practical operation conditions.