13C and14C kinetic isotope effects in the catalytic oxidation of CO over ZnO

摘要

13C and14C kinetic effects in the reaction CO+1/2 O2rarr;CO2over ZnO catalyst were experimentally determined. The k12/k13 and k12/k14 ratios were found to be temperature independent in the temperature range studied (200ndash;500thinsp;deg;C) and amounted to 1.0101plusmn;0.0010 and 1.0204plusmn;0.0019, respectively. Interpretation of the experimental values, following Bigeleisenrsquo;s formalism, reveals that (CO2)Dagger;with an interband angles of (90plusmn;10)deg; and planar (CO3)Dagger;with two interband angles in the range of (120plusmn;10)deg; may be considered as activated complexes of the rate determining and isotope effect fractionation governing step of the reaction mechanism.