Novel Re–Sb–O catalysts for the selective oxidation of isobutane and isobutylene

Abstract

It was found that three crystalline Re–Sb–O compounds, SbOReO 4·2H 2O, Sb 4Re 2O 13 and SbRe 2O 6, were active for the selective catalytic oxidation of isobutane (773 K) and isobutylene (623–723 K). Among the three compounds, SbRe 2O 6 exhibited the highest catalytic activity for the selective oxidation of isobutane with a high selectivity of 83% to methacrolein (MAL)+isobutylene at the steady-state conversion of 7%. The Re–Sb–O catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and in situ laser Raman microscopy (LRM). SbRe 2O 6 decomposed to Re 2O 7 and Sb 4Re 2O 13 partly at the surface under isobutylene oxidation at 673 K, while Sb 4Re 2O 13 was stable under the reaction conditions. Under isobutane oxidation conditions at 773 K, the three Re–Sb–O compounds underwent a progressive decomposition to Sb 4Re 2O 13, Re 2O 7 and Sb 2O 4. The catalytic behavior and structural characterization of the new catalysts allowed us to refer the reactivity of the catalysts to surface Re 2O 7 species benefiting from a cooperation with Sb 4Re 2O 13.