Iridium catalysts, hydrocarbon conversion

The attractive features of platinum-rhenium and platinum-iridium catalysts can be combined in a reforming operation. The data for the reactions of selected hydrocarbons considered earlier for platinum-rhenium and platinum-iridium catalysts indicate that the former catalyst is more selective for the conversion of cycloalkanes to aromatics, while the latter is more selective for the dehydrocyclization of alkanes. Since cycloalkane conversion occurs primarily in the initial part of a reforming system while dehydrocyclization is the predominant reaction after the cycloalkanes have reacted, it is reasonable to use a platinum-rhenium catalyst in the front of the system and to follow it with a platinum-iridium catalyst (32). 

The comparison (Fig. 1 and 6) between NO oxidation by oxygen in the absence of hydrocarbon and NO reduction in the presence of C10H22 and O2 shows that the oxidation and the reduction of NO are comparable and occur in the same temperature range with platinum or ruthenium catalysts, the conversion rates being very low with ruthenium. With rhodium or iridium and more particularly with palladium or copper NO oxidation is very limited at the temperature where NO reduction occurs. 

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