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This paper presents a comparative experimental study of the oxidation of light alkanes (methane and ethane) and alkenes (ethylene and propylene) catalyzed by unsupported platinum (Pt) and palladium (Pd). The oxidation was studied under a wide range of reaction conditions, such as temperatures, residence times, and mixture equivalence ratios. Two different catalyst morphologies were investigated: a packed bed of nanoparticles and a wire coiled inside a tube reactor. The order of hydrocarbons in terms of their oxidation activity on the Pt and Pd was found to be consistent regardless of the wire/nanoparticle morphology, with propylene exhibiting the highest reactivity followed by ethylene, ethane, and then methane. The effects of residence time on the oxidation of hydrocarbons showed similar trends with the two types of catalysts, whereby a longer residence time leads to a higher oxidation activity. However, the degree of that activity enhancement was insignificant with the nanoparticles. On the other hand, the effects of the equivalence ratio, φ, were significantly different between the two catalyst configurations. In the near-adiabatic wire reactor, the oxidation activity increases with increasing φ due to the heat release and higher temperature ramp along the reactor. The reverse is true in the isothermal bed of nanoparticles. Analysis of the surface of the catalyst using X-ray diffraction revealed that for the palladium, palladium oxide was active in promoting the oxidation of all tested hydrocarbons at a lower temperature than platinum. That was not the case for nanoparticles, as the temperature was not sufficiently high to oxidize the surface. The obtained results help understand the catalytic oxidation of the tested hydrocarbons under different conditions and help optimize the operation parameters for catalysts.

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