Aromatic benzene and aliphatic n-hexane mixtures, along with the corresponding pure components, were partially oxidized in air over Pt and Rh coated monoliths in millisecond contact times. At carbon to oxygen ratios (C/O) > 1.0, the addition of the aromatic benzene increased the selectivity of the non-equilibrium products ethylene and propylene formed from the aliphatic n-hexane. When compared to the partial oxidation of the pure aliphatic, the addition of the aromatic to the aliphatic also increased the operating temperature and conversion of the aliphatic in the mixture. Higher conversions of the aromatic were observed on Rh than on Pt.

Benzene appears to competitively adsorb onto the catalyst, reducing the catalytic reactivity of the aliphatic. As a result, the aliphatic remains in the gas phase where homogeneous cracking to olefins occurs, and the aromatic is partially oxidized to synthesis gas which supplies heat to the endothermic cracking reactions. Higher temperatures increase the reforming and cracking rates in these millisecond reactors that result in increased conversion of the aliphatic.