A theoretical model of the ethane/deuterium exchange reaction catalysed by platinum. The nature of the αβ process

Publisher Website
Google Scholar
Abstract
The bimodal initial product distributions in ethane exchange with deuterium observed using several transition-metal catalysts were quantitatively reproduced by a theoretical model in the classical work of Anderson and Kemball in 1954. They showed that the only mechanistic process required is the interconversion of adsorbed ethyl and 1,2-diadsorbed ethene (the αβ process) but two independent types of site seemed necessary. This important problem has now been re-examined in the light of many developments since the early fifties in organometallic chemistry, heterogeneous catalysis and surface science. Sets of steady-state equations are derived based on the original mathematical model, but much more sophisticated descriptions of the αβ process are employed using the following basic assumptions. A small concentration of defects of a fundamental type is responsible for alkane activation but only generates a limited αβ process. The main αβ process is now described as interconversion of σ-bonded alkyl and π-bonded alkene and is associated with numerous sites of a different kind which are populated by transfer of intermediates from the first type of site rather than by direct alkane activation. Using these postulates the U-shaped distributions reported in the literature including that for a Pt single crystal (111 face) are quantitatively modelled. The general philosophical importance of these basic concepts for an understanding of alkane reactions on transition-metal catalysts is discussed.

This publication has 0 references indexed in Scilit: