Radio-frequency thermal plasma preparation of nano-sized Ni catalysts supported on MgO nano-rods for partial oxidation of methane

Abstract

Nano-sized Ni catalysts supported on MgO nano-rods were prepared by RF thermal plasma treatment of Ni metal (~5μm) and MgO powders (~100nm). For this purpose, each powder was ball-milled at pre-set molar ratio of 5:5, and then, injected into RF thermal plasma generated at the power level of ~25.5kW. From FE-SEM (field emission scanning electron microscopy) and TEM-EDS (transmission electron microscopy-energy dispersive spectrometer) analyses, it is found that as-prepared catalysts mainly consist of very small Ni particles (<100nm) attached to MgO nano-rods with diameter of 10–20nm. In order to investigate their catalytic performance, methane partial oxidation experiment was also conducted at atmospheric pressure, 400°C<T<800°C and reaction mixture of CH4:O2=2:1mol% with Ar diluents. Test results revealed that as-prepared MgO nano-rods supported Ni catalysts showed thermodynamic equilibrium values of methane conversion rate (>99%) and high selectivity more than 90% and 80% for CO and H2 at T=750°C, respectively. In spite of relatively high Ni content of 50mol%, little carbon deposition is found in the TEM images and the derivative curves of TGA (thermogravimetry analysis) data for as-prepared catalysts after 24h test at 750°C, which are attributed to the structural features of Nano-sized Ni catalysts supported on MgO nano-rods prepared by RF thermal plasma.