The catalytic oxidation of propylene I. Evidence for surface initiated homogeneous reactions

Abstract The catalytic oxidation of propylene over bismuth molybdate was studied in a flow reactor at atmospheric pressure and at 425 °C. Several reactor designs were utilized in an effort to define more clearly the nature and the importance of homogeneous reactions which may be occurring in the postcatalytic volume. Evidence is presented for a surface initiated homogeneous reaction which results in an enhanced conversion of propylene and the formation of propylene oxide. Allyl peroxide or allyl hydroperoxide species, formed on the surface, are suggested as possible initiators for this homogeneous reaction. A modified reaction mechanism is proposed which incorporates the surface initiated homogeneous reaction, as well as a surface reaction of the allyl peroxide or allyl hydroperoxide species. Four additional oxide catalysts, copper-molybdenum, iron-molybdenum, manganesemolybdenum, and zinc, are offered as other examples on which the surface initiated homogeneous reaction occurs.