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

It was found that three crystalline Re-Sb-O compounds, SbOReO4. 2H(2)O, Sb4Re2O13 and SbRe2O6, were active for the selective catalytic oxidation of isobutane (773 K) and isobutylene (623-723 K). Among the three compounds, SbRe2O6 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). SbRe2O6 decomposed to Re2O7 and Sb4Re2O13 partly at the surface under isobutylene oxidation at 673 K, while Sb4Re2O13 was stable under the reaction conditions. Under isobutane oxidation conditions at 773 K, the three ReSb-O compounds underwent a progressive decomposition to Sb4Re2O13, Re2O7 and Sb2O4 The catalytic behavior and structural characterization of the new catalysts allowed us to refer the reactivity of the catalysts to surface Re2O7 species benefiting from a cooperation with Sb4Re2O13. (C) 2000 Elsevier Science B.V. All rights reserved.