Kinetics of Aromatic Ring Hydrogenation

There are no recent comprehensive measurements of the relative activities of metals for benzene hydrogenation, and since most of the detailed work concerns only nickel, palladium and platinum a short summary of what is known about other metals is all that can be made. Quantitative measurements of seven of the metals of Groups 9 to 10 supported on silica were reported many years ago, and the low activity of the base metals has been confirmed by measurements on 

Before proceeding to consider kinetic equations and implied reaction mechanisms, we may note some other pertinent features of these reactions. (A) Benzene hydrogenation was subject to the influence of the Strong Metal-Support Interaction (Section 3.35) when titania and vanadium sesquioxide were used as supports for rhodium, platinum and iridium - even Pt/Si02 and Ni/Si02 when heated 

TABLE 10.1. Kinetics of the Hydrogenation of Benzene on Metals of Groups 8 and 11 

Metal Form Size Range/Dispersion Conclusion Reference 

No evidence was found of an effect of diluting Pt/A Os with more support, although in other work a four-fold increase was reported. Ir/A Os behaved as Pt/Al203 when reduced at low temperature, while with Ru/Si02 the rate passed through a maximum as dispersion was altered. Extreme care has therefore to be taken before any generalisations about structure-sensitivity are advanced. 

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