Synthesis of MgO nanocatalyst in water-in-oil microemulsion for CO oxidation

Abstract

Periclase-like magnesia nanoparticles (MgO(μ) NPs) were obtained by calcination at ≥ 400 °C of brucite-like Mg(OH)2 NPs synthesized in water-in-n-heptane microemulsion system stabilized by a mixture of cationic and nonionic surfactants. The bulk and surface properties of the hydroxide NPs were characterized, before and/or after calcination at 400, 600 and 800 °C by means of thermogravimetry, X-ray powder diffractometry, X-ray photoelectron spectroscopy (XPS), electron microscopy (SEM/HRTEM) and N2 sorptiometry. The results obtained could help revealing that the yielding MgO(μ) NPs assume high-temperature stable (up to 800 °C) crystallite structure (cubic) and size (25–30 nm), and surface area (93–68 m2 g−1), mesopore size (15–21 nm), morphology (coalesced platelets) and microstructure ((100) and (200) faceted) XPS-implied moderate surface basicity, and ability to ionosorb O2 molecules and disproportionate CO molecules have rendered MgO(μ) NPs a catalyst that is capable of triggering the CO oxidation at a temperature as low as 50 °C, as well as undertaking 50% CO conversion at a temperature as low as 180 °C. To the best of our knowledge, no such a low CO oxidation light-off temperature has hitherto been reported for MgO bulk catalysts.