Isotopic GCMS Study of the Mechanism of Methane Partial Oxidation To Synthesis Gas

An isotopic pulse is combined with a gas chromatography−mass spectrum to investigate the mechanism of the partial oxidation of methane. For a pulse reaction of CH 4 /CD 4 /O 2 (1/1/1) at 600 °C over a reduced NiO/SiO 2 catalyst, besides CH 4 and CD 4, large amounts of CHD 3, CH 2 D 2, and CH 3 D were detected in the exit gas. This indicates that CH, CH 2, and CH 3 species are formed during the reaction, i.e., that CH 4 is activated via its dissociation before its oxidation. The amount of methane involved in the isotopic exchange reaction was larger than that converted to CO and CO 2 . Consequently, the dissociation of methane is not rate determining. Over an unreduced NiO/SiO 2 catalyst, CH 4 and CD 4, without any CH x D y ( x + y = 4), were detected in the exit gas, indicating that methane reacts directly with oxygen without its predissociation. For the reaction of CH 4 /CD 4 (1/1) with the lattice oxygen of the catalyst, CH 4 and CD 4, without any CH x D y ( x + y = 4), were detected in the exit gas, indicating that methane reacts directly with the lattice oxygen without predissociation. Moreover, the CH 4 / 16 O 2 reaction over an unreduced NiO 18 catalyst revealed that the lattice oxygen of the catalyst participates in the reaction of CH 4 /O 2 .