Influence of strong metal–support interaction on exchange with deuterium and other reactions of hydrocarbons. Part 1.—Studies with Rh/TiO2 and Rh/SiO2

Abstract

The changes in the catalytic properties of Rh/TiO₂ caused by raising the reduction temperature from 473 to 773 K have been investigated for four reactions, the exchange with deuterium of methane and cyclopentane, and the hydrogenolysis of 2,2-dimethylpropane and methylcyclopentane.

The so-called strong metal–support interaction (SMSI) brought about by the high-temperature reduction had least effect on the exchange of methane but reduced the rate of hydrogenolysis of 2,2-dimethylpropane by factors of 10⁴ or 10⁵. The SMSI was reversible and its influence on each of the reactions was eliminated by oxidation of the catalyst followed by low-temperature reduction. No marked changes in the catalytic behaviour of Rh/SiO₂ resulted from increasing the reduction temperature.

The results provide further evidence for the existence of a number of kinds of catalytic sites on Rh/TiO₂. The sites for the more structure-sensitive reactions tend to be more seriously affected by SMSI and probably involve more metal atoms than the sites responsible for methane exchange.