Bifunctional mechanism of Pt-Rh catalysts investigated by a frequency response technique

The frequency response technique (Yasuda et al., 1995) is applied to investigate the bifunctional mechanism of the dissociation of H-2, (I), and the association of 2H to olefins (e.g. propene), (II), in a hydrogenation reaction over the bimetallic catalyst Pt-Rh by using a cell reactor composed of a proton-conducting membrane, on opposite sides of which the two metals were chemically deposited. Based on 'reaction rate spectra', the kinetic constants at several elementary steps involved in the rate process of (I) are evaluated; they were affected by the metal on the opposite side. The results reveal that microcells would be produced over actual bimetallic catalysts during the reaction and then the two processes, (I) and (II), become not individual but correlated. (C) 1997 Elsevier Science B.V.