Lattice representation, reaction rate

Figure 6. (a) Schematic representation of the proton-promoted dissolution process at a M203 surface site. Three preceding fast protonation steps are followed by a slow detachment of the metal from the lattice surface, (b) The reaction rate derived from individual experiments is proportional to the surface protonation to the third power. 

The model of the ODH of propane on NiMo04 catalyst, based on a simplified mechanism taking into account the formation of propene and its further oxidation to carbon oxides may be used both with transient and steady state results. In the first case, the evolution of partial pressures of propene and carbon oxides (lumped into COJ is reproduced. When applied to steady state results, the model gives a good representation of the reaction rate, but overestimates the propene selectivity. It should be stressed, that the mechanism proposed takes into account the participation of the lattice oxygen only, both in the formation of propene and in its destruction. Under steady state conditions, where the oxygen gas is present, its participation seems restricted to the propane destruction (but is not significant in the propane activation). 

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