Combustion Of Methane In Lean Mixtures Over Bulk Transition-metal Oxides: Evaluation Of The Activity Andself-deactivation

摘要

Different bulk transition-metal oxides (NiO, CuO, Mn_2O_3, Cr_2O_3, and CO_3O_4) were prepared, by precipitation from nitrate precursors, and tested for the combustion of methane-air lean mixtures (1000-5000 ppmv of CH_4). Catalyst performances were compared in terms of both intrinsic activity and resistance to self-deactivation. Methane combustion experiments were carried out at ambient pressure and a space velocity of 62 h~(-1) [weight hourly space velocity (WHSV)]. The activity of the studied catalysts (determined by the recording of light-off curves in the interval of 250-600℃) decreases in the order: Co_3O_4 > Mn_2O_2 > Cr_2O_3 > CuO > NiO. However, deactivation studies, carried out both at constant temperature (620 ℃) and in hysteresis experiments, reveal that Mn_2O_3 is the most stable catalyst.