LaSrFeO Perovskite Oxide Nanoparticles for Low-Temperature Aerobic Oxidation of Isobutane to -Butyl Alcohol.

The development of reusable solid catalysts based on naturally abundant metal elements for the liquid-phase selective oxidation of light alkanes under mild conditions to obtain desired oxygenated products, such as alcohols and carbonyl compounds, remains a challenge. In this study, various perovskite oxide nanoparticles were synthesized by a sol-gel method using aspartic acid, and the effects of A- and B-site metal cations on the liquid-phase oxidation of isobutane to -butyl alcohol with molecular oxygen as the sole oxidant were investigated. Iron-based perovskite oxides containing Fe such as BaFeO, SrFeO, and LaSrFeO exhibited catalytic performance superior to those of other Fe- and Fe-based iron oxides and Mn-, Ni-, and Co-based perovskite oxides. The partial substitution of Sr for La in LaFeO significantly enhanced the catalytic performance and durability. In particular, the LaSrFeO catalyst could be recovered by simple filtration and reused several times without an obvious loss of its high catalytic performance, whereas the recovered BaFeO and SrFeO catalysts were almost inactive. LaSrFeO promoted the selective oxidation of isobutane even under mild conditions (60 °C), and the catalytic activity was comparable to that of homogeneous systems, including halogenated metalloporphyrin complexes. On the basis of mechanistic studies, including the effect of Sr substitution in LaSrFeO on surface redox reactions, the present oxidation proceeds via a radical-mediated oxidation mechanism, and the surface-mixed Fe/Fe valence states of LaSrFeO nanoparticles likely play an important role in promoting C-H activation of isobutane as well as decomposition of -butyl hydroperoxide.