Partial oxidation of methane over bimetallic copper- and nickel-actinide oxides (Th, U)

The study of partial oxidation of methane (POM) over bimetallic nickel- or copper-actinide oxides was undertaken. Binary intermetallic compounds of the type AnNi2 (An = Th, U) and ThCu2 were used as precursors and the products (2NiO·UO3, 2NiO·ThO2 and 2CuO·ThO2) characterized by means of X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy and temperature-programmed reduction. The catalysts were active and selective for the conversion of methane to H2 and CO and stable for a period of time of ≈18 h on stream. The nickel catalysts were more active and selective than the copper catalyst and, under the same conditions, show a catalytic behaviour comparable to that of a platinum commercial catalyst, 5 wt% Pt/Al2O3. The catalytic activity increases when uranium replaces thorium and the selectivity of this type of materials is clearly different from that of single metal oxides and/or mechanical mixtures. The good catalytic behaviour of the bimetallic copper- and nickel-actinide oxides was attributed to an unusual interaction between copper or nickel oxide and the actinide oxide phase as showed by H2-TPR, XPS and Raman analysis of the catalysts before and after reaction.