PROBLEMS INVOLVED IN THE REDUCIBILITY OF THE NIO-MGO SYSTEM AS EVIDENCED BY X-RAY-DIFFRACTION, ELECTRON-PARAMAGNETIC RESONANCE, ELECTRON-SPECTROSCOPY FOR CHEMICAL-ANALYSIS AND ADSORPTION TECHNIQUES

Nickel oxide supported on high-surface-area magnesia (123 m2 g-1) containing 10 wt.% nickel was prepared in a systematic way by the impregnation method. The problems associated with the reduction of nickel oxide due to formation of an NiO-MgO solid solution are discussed. At 673 K the interaction between NiO and MgO starts and is further facilitated with increasing calcination temperature. In an attempt to reduce the interaction between NiO and MgO, magnesium hydroxide calcined at different temperatures was used as a support. Multiply impregnated catalysts on magnesia were also prepared for this purpose. Physical mixtures of NiO and MgO were compared with the impregnated catalysts for hydrogen and oxygen adsorption capacities. X-Ray diffraction (XRD), electron paramagnetic resonance (EPR) and electron spectroscopy for chemical analysis (ESCA) studies were performed in order to try to understand the NiO-MgO catalytic system.