Influence of iron substitution on formation and structure of Cu-based mixed oxides derived from layered double hydroxides

Cu/Zn/Fe/Al mixed metal oxides were prepared by calcination of layered double hydroxides (LDHs) carbonate precursors. The iron content had significant influence on the crystallinity, purity and thermal stability of as-synthesized Cu/Zn/Fe/Al-LDHs as well as the structure and composition of resultant mixed oxides obtained at 773 K. The mixed oxide with the Fe/Al ratio of 0.3:0.7 exhibited highest catalytic activity for oxidation of phenol by hydrogen peroxide. Moreover, the Fe-containing mixed oxides had stronger oxidation abilities than the Fe-free ones. The difference of catalytic activity is probably related to the difference in the amounts and types of composite oxides containing Cu2+ and/or Fe3+ cations on the surface of calcined products depending on the pristine nature of the starting LDHs precursors.