Preparation and Characterization of Several High-Area NiAl₂O₄Spinels. Study of Their Reducibility

A rigorous study was made of the different experimental conditions that affect the obtention of high-area spinels. Some of the key factors in the preparation of NiAl 2 O 4, such as precipitation and calcination temperatures, have been carefully studied and correlated to the reducibility of the final spinel. All the samples were characterized by X-ray diffraction, nitrogen physisorption, scanning electron microscopy, temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS) techniques. Spinels were obtained with high area (110−220 m 2 /g) compared with those usually reported. XPS showed that these spinels can be surface reduced. The largest amount of metallic nickel phase was found in the spinel prepared by precipitation at 348 K and calcination at 773 K. This spinel also had the lowest initial temperature of reduction (TPR).