Solvent-Free LDH-Derived Nanocrystalline Ni–Mg–Al Mixed Oxides for Oxidative Steam Reforming of Ethanol

Abstract Ni–Mg–Al mixed oxides for oxidative steam reforming of ethanol (OSRE) were prepared from layered double hydroxide (LDH) precursors by a solvent-free route and compared with hydrothermal-LDH-derived, sol–gel, and impregnation-derived reference catalysts. The solvent-free NiMgAl-SF sample formed a nanocrystalline rock-salt-type mixed oxide with a high BET surface area of 234.4 m2 g–1 and a PXRD-derived crystallite size of 3.6 ± 0.5 nm. XPS and XANES showed a larger fraction of oxidized Ni surface species and higher nonlattice oxygen contribution, whereas EXAFS indicated reduced Ni–O and Ni–Ni coordination relative to bulk NiO, consistent with a distorted mixed-oxide environment. In OSRE, NiMgAl-SF reached complete ethanol conversion within experimental error at 450 °C and maintained stable H2 selectivity for 100 h at C/O = 0.6 and GHSV = 1.6 × 105 h–1. A matched comparison with Mg-free NiAl-SF showed that Mg incorporation improved structural retention and suppressed loss of oxidized surface character during long-term operation. These results show that the solvent-free LDH route provides a useful entry to nanocrystalline Ni–Mg–Al mixed oxides for durable ethanol reforming catalysis.