A thin-felt Pd–MgO–Al₂O₃/Al-fiber catalyst for catalytic combustion of methane with resistance to water-vapor poisoning

Thin-sheet microfibrous-structured Pd–MgO–Al₂O₃/Al-fiber catalysts were developed for high-throughput catalytic methane combustion with 3–15 vol% water vapor in feed gas. The catalysts were obtained by hydrothermally growing Mg–Al mixed-oxide precursors (e.g., layered double hydroxides (LDHs) plus MgCO₃) on Al-fiber surfaces followed by placing 0.5 wt% Pd on the as-obtained substrates by impregnation. Transformation of Pd/MgAl-LDH–MgCO₃ mounted on the Al-fiber into Pd-MgO-Al₂O₃ via in situ reaction activation markedly enhances the catalyst basicity and electron density of metallic Pd, thus weakening support electrophilicity and stabilizing PdO against the formation of inactive Pd⁴⁺ species. This preferred catalyst with high intrinsic activity (turnover frequency 135 h⁻¹ at 290 °C and 3 vol% water vapor) achieves a very low E_a of only 57 kJ mol⁻¹, a third that (170 kJ mol⁻¹) for the Pd/AlOOH/Al-fiber. This catalyst can stably run for feed gases of 1 vol% methane and 3–15 vol% water vapor in air.