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Hydrogen sensitivity of MCP ring opening on Ir/Al2O3 and that of n-hexane transformation on Pt black have been investigated. Comparison of the results on O2–H2-treated and ‘carbon’-precovered catalysts confirms that in the interpretation of the hydrogen effect on product distribution one has to regard the steric/electronic effect of trapped hydrocarbons on the surface metal atoms.

The adsorption and deuterium exchange of methane and ethane and the hydrogenolysis and isomerization of ethane, butanes and some C5 hydrocarbons have been investigated on Ru, Rh and Ir blacks. Product distribution patterns, together with data on chemisorption and deuterium exchange, suggest that surface transformations of hydrocarbons into strongly/multiply bonded species easily take place. The initial multiple rupture of hydrocarbons is a result of the slow product desorption, that seems to be the rate limiting step of the hydrogenolysis on these metals.

Hydrogen–deuterium exchange in methane, ethane and propane, hydrogenolysis of ethane, n-butane and isobutane and chemisorption of methane and ethane have been studied on rhenium powder catalysts.The kinetic isotope effect and the rate sequences of the exchange reactions mentioned above show that the rate limiting step is C—H bond dissociation.Ethane hydrogenolysis overlaps ethane exchange at 523 K. The hydrogenolysis reaction order with respect to hydrogen is slightly positive for ethane and greater than unity for butane. Methane is the main product of butane hydrogenolysis. Hydrogen assisted thermal desorption of methane produced from chemisorbed ethane evolves a peak with a maximum at 560–570 K, similar to the thermal desorption peak of methane. Therefore a strong, multiple metal–carbon bond is involved in rhenium–saturated hydrocarbon interaction, C—C bond breaking takes place easily but desorption of the reaction products is hindered.

Transformation of n-pentane, 2-methylbutane and 2,2-dimethylbutane has been investigated as a function of the H2/hydrocarbon ratio over a 10 wt % Ir/Al2O3 catalyst of 14 % dispersion. The selectivity of isomer formation has been observed to decrease with the increase of the H2/hydrocarbon ratio and follow the sequence n-pentane > 2-methylbutane 2,2-dimethylbutane. The effect of the experimental conditions on the product selectivity has been interpreted considering the actual surface state of the working catalyst.

The chemisorption and transformation of n-hexane have been investigated over Pt black in the presence of hydrogen between 450 and 600 K. Direct gravimetric measurements have confirmed that only 3–8% of the total hydrocarbon coverage can be removed by evacuation or by purging the system with an inert gas. Hydrogenation experiments have been used to separate reactive and irreversibly bound hydrocarbons; their coverages have been measured as a function of temperature and partial pressure of hydrogen. The variation of the product selectivity with the partial pressure of hydrogen has been interpreted considering the effect of the irreversibly bound hydrocarbons on ensemble size and on availability of hydrogen.

Chain lengthening homologation of propane,n-butane,2-methylpropane,2-methylbutane and 2,2-dimethylpropane has been investigated over Pt, Pd and Ni catalysts. With both Pd and Ni the chain lengthening selectivity was observed to be commensurable to the isomerisation one. Addition of CHx onto the β-carbon atom in n-butane and propane as well as chain lengthening of 2-methylpropane and 2-methylbutane were observed. The mechanism of the skeletal rearrangement is discussed in terms of CHx addition.

Deuterium exchange reactions of methane, ethane, propane and neopentane, and the hydrogenolysis and isomerization of ethane, propane, n-butane and isobutane on platinum black have been studied in the temperature range 363–743 K. There is a gap of 150 K between the temperature of deuterium exchange and that of hydrogenolysis and isomerization. Only at high hydrogen pressure (about 50 kN m–2) and at low catalytic activity is the hydrogenolysis characterized by selective loss of a terminal methyl group, except for n-butane in which there is an equal chance of any of the C—C bond rupturing. The selectivity for isomerization has a maximum at high hydrogen pressure. These values together with kinetic data suggest that the ability of platinum in an exchange reaction to convert weakly bonded intermediates into strongly bonded ones is much less than that of nickel. The phenomenon of π-olefin and π-allyl bond conversion is applied in part to explain the results obtained. Brief comparison is given between the catalytic properties of platinum and those of nickel for the reactions investigated.