Regularity in Catalytic Properties of Various Promoted 61203 for the Vapor-Phase Oxidative Dehydrogenation of Isobutylaldehyde

Abstract

Vapor-phase oxidative dehydrogenation of isobutylaldehyde over various B403 catalysts promoted with alkali metal oxides or alkaline earth metal oxides has been investigated to the reaction mechanism of methacrylaldehyde formation and the effect of addition of these oxides on the catalytic activity of Bi₂O₃. Almost selective formation of methacrylaldehyde was observed during the reaction of isobutylaldehyde with these promoted Bi₂O₃ in the absence of gaseous oxygen; the Bi₂O₃ containing these oxides at 10-15 atm% was most effective for methacryl- aldehyde formation. Furthermore, the conversion of isobutylaldehyde and the yield of methacrylaldehyde at zero reaction time increased with the decrease in the electronegativity of metal ion added to Bi₂O₃. Similar regularity was also observed in the catalytic oxidative dehydrogenation of isobutylaldehyde and the catalytic oxidation of carbon monoxide over these oxides. In the catalytic oxidative dehydrogenation over Cs₂0-Bi₂O₃ (Cs=15 atm %), the yield of methacryl- aldehyde was 47.1%, the selectivity being 65.5% at 450°C. Formations of carbon dioxide and of methacrylaldehyde were kinetically discussed on the basis of the regularity observed, and participation of lattice oxygen rather than oxygen species adsorbed in the oxidative dehydrogenation was proposed. Metal oxides added probably control the strength of Bi-O bond according to the electronegativities of metal ions.