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

Nano-sized Ni catalysts supported on MgO nano-rods were prepared by RF thermal plasma treatment of Ni metal (similar to 5 mu m) and MgO powders (similar to 100 nm). 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 similar to 25.5 kW. 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 (<100 nm) attached to MgO nano-rods with diameter of 10-20 nm. In order to investigate their catalytic performance, methane partial oxidation experiment was also conducted at atmospheric pressure, 400 degrees C<T<800 degrees C and reaction mixture of CH4:O-2=2:1 mol% 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 H-2 at T=750 degrees C, respectively. In spite of relatively high Ni content of 50 mol%, little carbon deposition is found in the TEM images and the derivative curves of TGA (thermogravimetry analysis) data for as-prepared catalysts after 24 h test at 750 degrees C, which are attributed to the structural features of Nano-sized Ni catalysts supported on MgO nano-rods prepared by RF thermal plasma. (C) 2012 Elsevier B.V. All rights reserved.