from first principles PP-I-1

OY-III-6Concentration Hysteresis in the Oxidation of Methane over Pt/γ-Al 2 O 3Pakharukov I.Yu. 1,2 , Matrosova M.M. 1 , Bukhtiyarov V.I. 1,2 , Parmon V.N. 1,21 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia2 Novosibirsk State University, Novosibirsk, Russiailyapakharukov@yandex.ruCurrently, the reaction of methane deep oxidation is very intensively investigated. This is dueto the fact that natural gas, whose main component is methane (98%), is widely used asdomestic and industrial fuel, as well as motor fuel for automobiles. Another importantapplication field of the methane deep oxidation is the development of catalytic heat sources(catalytic combustion).It is known that the activity of platinum catalysts in the methane oxidation at low temperaturedepends on CH 4 :O 2 ratio. Some authors suppose that the reaction has zero order in oxygenunder fuel-lean conditions, whereas it has the order about unity under fuel-reach conditions.Others observed the zero-order reaction in oxygen in both cases. These data seemcontradictory only at first glance; because platinum has high redox lability and can easilychange the chemical state depending on the reaction composition. In our work [1], it wasshown that there is concentration hysteresis in the low-temperature oxidation of methane oversupported nano-sized particles of platinum. It was found that there are two stable stationarystates of the catalytic system with low and high catalytic activity, which are realized at thesame external conditions depending on the direction of change of CH 4 :O 2 ratio. Discoveredway for increase in activity allows improving the catalyst performance significantly withoutvariation of the reaction temperature, contact time and the composition of the catalyst. Forinstance, the increase in methane conversion from 11 to 80 % can be achieved only by changein the composition of initial reaction mixture. Study of concentration hysteresis may form anew basis for the control of the Pt catalyst activity.References:[1] I.Yu. Pakharukov, I.E.Beck, M.M. Matrosova, V.I. Bukhtiyarov, V.N. Parmon. Doklady PhysicalChemistry 439 1 (2011) 131.99