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, Sb4 Re2O13 and SbRe2O6, were active for the selective catalytic oxidation of is obutane (773 K) and isobutylene (623-723 K). Among the three compounds, SbR e2O6 exhibited the highest catalytic activity for the selective oxidation o f isobutane with a high selectivity of 83% to methacrolein (MAL)+isobutylen e at the steady-state conversion of 7%. The Re-Sb-O catalysts were characte rized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and in situ laser Raman microscopy (LRM). SbRe2O6 decomposed to Re2O7 and Sb4Re2O 13 partly at the surface under isobutylene oxidation at 673 K, while Sb4Re2 O13 was stable under the reaction conditions. Under isobutane oxidation con ditions at 773 K, the three ReSb-O compounds underwent a progressive decomp osition to Sb4Re2O13, Re2O7 and Sb2O4 The catalytic behavior and structural characterization of the new catalysts allowed us to refer the reactivity o f the catalysts to surface Re2O7 species benefiting from a cooperation with Sb4Re2O13. (C) 2000 Elsevier Science B.V. All rights reserved.