Large-scale synthesis of carbon nanofibers on Ni-Fe-Al hydrotalcite derived catalysts I. Preparation and characterization of the Ni-Fe-Al hydrotalcites and their derived catalysts

摘要

A series of Ni~(2+)-Fe~(2+)-Al~(3+) hydrotalcite (HT) catalysts with varying compositions have been prepared by coprecipitation from Fe~(2+). The structure and properties of the catalysts were carefully characterized by various methods such as XRD, EXAFS, TGA, TPR, N2 adsorption/ desorption, XPS and H2 chemisorption. It was shown that pure HT structures can only be prepared at low Fe~(2+) concentrations, while mixed oxide phases with spinel structure will form simultaneously at high Fe~(2+) concentrations. Pure HT structures are very important for small particle size, narrow size distribution and large surface area of the resulting catalysts. XPS study demonstrated Fe enrichment on the catalyst surfaces, which might have partly contributed to the low hydrogen chemisorption capacity for the Fe-containing catalysts.