Aj. Colussi et Vt. Amorebieta, ARRESTED FORMATION OF CARBON OXIDES IN PROGRAMMED OXIDATION OF METHANE ON NONSTOICHIOMETRIC SAMARIA, Journal of physical chemistry, 99(38), 1995, pp. 13921-13925
COx species evolved during transient exposure of Sm2O3 catalysts to ve
ry low pressure CH4/O-2 mixtures are monitored in real time by molecul
ar beam mass spectrometry at 1100 K. The rise of m/z = 28 and 44 signa
ls is significantly delayed relative to the onset of CH4 decay only on
substoichiometric Sm2O3-y samples. This observation rules out CO and
CO2 as primary products of methane heterogeneous oxidation and implies
that their immediate precursor, most probably CH3(g), is slowly oxidi
zed during the initial stages of Sm2O3-y surface reconstruction. Prese
nt results suggest the possibility of suppressing carbon oxides in the
oxidative dimerization of methane by dynamic control of selective sit
e populations.