abstracts - Институт катализа им. Г.К. Борескова

OP-III-332r. 2[Ni 0 -O] → O 2 + 2[Ni 0 ]3. [Ni 0 -C] + [Ni 0 -O] → [Ni 0 -CO] + [Ni 0 ]4. [Ni 0 -CO] → [Ni 0 ] + CO5. 2[Ni 0 -H] → H 2 + 2[Ni 0 ]6. [Ni 0 -O] + 2[Ni 0 -H] → 3[Ni 0 ] + H 2 O7. [Ni 0 -O] → NiO4[NiO] + CH 4 → CO 2 + 2H 2 O + 4[Ni 0 ]2[NiO] + [Ni 0 -C] → CO 2 + 3[Ni 0 ][NiO] + 2[Ni 0 -H] → 3[Ni 0 ] + H 2 OTo simulate the surface phase transitions the variable s, 0 ≤ s ≤ 1, indicating the fractionof the reduced surface was introduced. Correspondingly, s o = 1−s denotes the fraction of theoxidized surface. The variables x 1 , x 2 , x 3 , x 4 , indicate the average coverages of C, O, CO, andH on the reduced surface. The relation with respecting coverage on the whole surface X i is thefollowing: X i = x i s. The equations for the evolution of x i consider the fact that x i can changenot only due to the surface reactions, but also due to the variation of the area of the reducedsurface. In this case the mathematical model, corresponding to the mechanism (1) anddescribing the dynamic behaviour of the surface coverages, catalyst temperature, partialpressures of reactants can be formulated as follows:s′= −Rx′= R1234T′= α(Tp′= τ121x′= R37x′= 2R2x′= 4R1−1−1+ 4R− R− 2R− 2R03− R− T ) + β s( P4p′= τ ( PCH 4O28− R5+ 2R9−2− x3( f s),− 2R− p219s − x− Rs+ R3110( f s)− R6− 2 R6 106q Ri=1 i i∑1) − γ s(R2≡,− R7− p ) − γ sR − γ Rsfs,s − x+ β− Rs − x8,−2).2( f s),( f s)4 s107 i∑s;q R .Here P CH4 , P O2 , and T 0 , indicate the partial pressures of CH 4 and O 2 in the inlet gasmixture and initial gas phase temperature. p 1 and p 2 denote the partial pressures of CH 4 andO 2 in reactor, and T – the catalyst surface temperature. α = (hS)/(WC p ); β = (SN)/(WC p );γ = (SNRT 0 )/V; τ = V/F, where: h is the heat transfer coefficient, S – the catalyst surface area,W – the catalyst weight, C p – the catalyst heat capacity; N – the adsorption capacity of Ni;R – the universal gas constant, V – the reactor volume; F – the flow rate of the reactantmixture, q i – the heat effects of the corresponding studies of the reaction mechanism.The results of mathematic modelling are demonstrated in Figures 1a, 1b. The modelproduces oscillatory behaviour at realistic experimental conditions and values of parameters.395i(1)