Partial oxidation of methane was studied by pulsing O2 into a CH4 flow over Rh/Al2O3 in a sequence of in situ infrared (IR) cell and fixed bed reactor at 773 K. The results obtained from the sequence of an IR cell followed by a fixed bed reactor show that (i) adsorbed CO produced possesses a long residence time, indicating that adsorbed oxygen leading to the formation of CO is significantly different from those leading to CO2 and (ii) CO2 is not an intermediate species for the formation of CO. The results obtained from the reversed reactor sequence show the water–gas shift reaction as the dominant pathway in the downstream of the catalyst bed. Pulsing oxygen into varying partial pressure of methane revealed that H2 oxidation is more sensitive to the partial pressure of the reactant than CO oxidation. In situ IR of pulse reaction coupled with alternating reactor sequence is an effective approach to study the primary and secondary reactions as well as the nature of their adsorbed species.
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