On the properties of surface complexes formed upon the adsorption of NOx, C3H6, and their mixtures with oxygen on ZrO2 according to EPR, TPD, and fourier transform IR spectroscopy data

Abstract

The adsorption of reactant mixtures is quantitatively and qualitatively different from the adsorption of the individual reactants. Thus, O₂ is almost not adsorbed on ZrO₂; however, a considerable concentration of molecular oxygen was detected among the products of desorption after the adsorption of a mixture of NO + O₂ and the total amount of desorbed molecules was greater by a factor of 10 than their total amount after the individual adsorption of NO and O₂. Among the qualitative differences is the formation of the O₂^- radical anion on the surface only upon the adsorption of the mixture of NO + O₂. Similarly, the number of desorbed molecules upon the simultaneous adsorption of C₃H₆, NO, and O₂ was much greater than that upon their individual adsorption; this is related to the formation of paramagnetic and nonparamagnetic NO₂–hydrocarbon complexes on the surface, which contained the NO₂ group and a hydrocarbon fragment.