X-ray study of the reduction and reoxidation of nickel(2+) ion in x-type zeolite in the presence of cerium(3+) ion

Microwave-Assisted Hydrothermal Synthesis of NiO-Ce1-XEuxO2-δ Powders for Fuel Cell Catalytic Anodes

“…With the presence of Ce 3+ cations, the maximum TPR peak for NiO observed at 370°C was divided into two peaks and the hydrogen consumption increased considerably. Peak division indicates that NiO reduction is accompanied by the reduction of cerium ions or interaction between these cerium ions in order to stabilize nickel during the reduction process (JEANJEAN et al , 1981). Figure 3 shows the XRD patterns of powders obtained in this work.…”

Catalytic properties of NiX zeolites in the presence of ceriumadditives

“…Apparently, a higher concentration of Ce3+ ions or a higher Ce3+-to-N?+ ratio correspond to a higher catalytic activity. The results might be ascribed to the intrinsic properties of Ce3+ cations as a catalyst promoter or the "chemical anchoring" ability of the highly polarizing Ce3+ cations to achieve a good dispersion of the metallic nickel particles on the zeolites, as suggested by Sauvion et al [ 51. The lower activity of 5-2.5 Ni-Cc/X might possibly occur because most of the Ce3+ cations go into Si sites in the hexagonal prism during the dehydration or reduction processes [9] prior to acting as the anchoring sites for the nickel and therefore, as a consequence, no Ce3+ cations would act as a catalyst promoter. According to the performance of the Ni-Cc/X samples, prepared by incipient-wetness impregnation, it seems clear that the Ce3+ ions acted not only as catalyst promoters but also probably as the "chemical anchors".…”