Catalysis Today, Vol.307, 189-196, 2018
Plain and CeO2 - Supported LaxNiOy catalysts for partial oxidation of CH4
LaNiO3 and La2NiO4, as such and in combination with CeO2, were prepared by microwave assisted co-precipitation procedure and tested in the catalytic partial oxidation of methane (CPO). The materials were characterized by BET, TGA/DTG, XRD, TPR and TEM techniques. In the absence of CeO2, the microwave processing allowed obtaining perovskite and spinel phases in high percentage at milder conditions as compared to traditional methods. In the presence of CeO2, Ce1-xLaxO2-x/2 solid solutions and NiO formed. At high temperature (similar to 800 degrees C) all the catalysts exhibited high methane conversion with near 100% CO selectivity and good stability. Activation of the catalysts occurred during temperature cycling. At the temperature corresponding to similar to 60% conversion, the CeO2-free sample deactivated quickly, differently from the CeO2 containing sample being very stable during the 18 h of reaction. The temperature surface reaction (TPSR) of CH4 without O-2 confirmed the differences between the two systems, i.e. with and without CeO2. The LaNiO3-CeO2 activated the decomposition of methane with simultaneous CO/CO2 evolution in a large range of temperature contrary to LaNiO3 activating methane decomposition only in a narrow range of temperature, without any CO/CO2 evolution. As shown from TPR analyses, an intimate contact between nickel phases and ceria was required to promote CPO activity. According to TGA and as confirmed by TEM analyses, formation of carbon was inhibited over the CeO2 containing catalysts, whereas different types of carbons were formed over the spinel and the perovskites formulation samples.