from first principles PP-I-1

OP-III-6Self-Oscillations in the Methane Oxidation on Ni: Mathematical ModellingLashina E.A. 1,2 , Chumakova N.A. 1,2 , Kaichev V.V. 1,2 , Ustugov V.V. 1 ,Chumakov G.A. 2,3 , Bukhtiyarov V.I. 1,21 Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia2 Novosibirsk State University, Novosibirsk, Russia3 Sobolev Institute of Mathematics SB RAS, Novosibirsk, Russialashina@catalysis.ruStudying nonlinear dynamics of heterogeneous catalytic reactions attracts a great attention.One of the reasons is the possibility to study the reaction mechanism when the catalystactivity changes under the reaction conditions. There are many experimental datademonstrated oscillatory behaviour in the methane oxidation on Ni catalysts. The oscillationsare observed of both concentrations of products and reactants and catalyst temperature undercertain conditions. It is suggested that the oscillations appearance is related to the reversibleoxidation of Ni to NiO.In this work, we apply the methods of mathematical modelling to study the self-oscillations inthis reaction. We consider the reaction mechanism of Langmuir type, taking into account theCH 4 dissociative adsorption that lead to formation of different CH x species, carbon andhydrogen adsorbed on the Ni surface. Oxygen also adsorbs and dissociates on the Ni surfaceand then can transform into NiO. Adsorbed C, H, and O can react to form CO, CO 2 , H 2 , andH 2 O. Reduction of the Ni surface is considered to proceed mainly via the NiO interaction withadsorbed carbon. Using the method by Shustorovich [1], we specify the activation energies aswell as thermal effects of some steps corresponding to the species interactions on the metalsurface. The parameter values for the other steps are taken of [2].The developed mathematical model describes the dynamics of the concentrations of differentsurface species, partial pressures of methane and oxygen in the gas phase, and temperature.We show that the model predicts the oscillatory behaviour under isothermal conditions.Moreover, using the bifurcation theory and numerical methods, we specify the ranges of theinlet partial pressures and initial catalyst temperature, for which non-isothermal selfoscillationsoccur.This work was partially supported by the Russian Foundation for Basic Research (projectno.11-03-00498) and the Siberian Branch of the Russian Academy of Sciences(Interdisciplinary project no. 80).[1] Shustorovich E., Sellers H. // Surf. Sci. Rep. 1998. V. 31. No. 1-3. P. 1.[2] Ren X.-B., Li H.-Y., Guo X.-Y. // Surf. Sci. 2008. V. 602. No. 1. P. 300.49