MultipleSteadyStatesSurfaceReactions

Nb v ris 3 15 i1 thus in general the normal component

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Unformatted text preview: us in general, the normal component of the molar average velocity is not zero at the interface when there is a surface reaction. The special case when moles are conserved so that i 1 Ris =0, the normal component of molar average velocity is zero. Limiting Case In the absence of diffusive effects and when v Cis t 0, the species jump condition becomes (16) Ris s Consider the active site CAZ , we have CAz k1 CA CZ k 1 CAZ t k2 CAz C2 Z (17) We can rewrite this balance in terms of the fractional coverage Θ k1 CA 1 Θ k 1 Θ k2 Θ 1 Θ 2 (18) t where k2 =k2 C2 . It is convenient to write this expression in terms of the following dimensionless T variables Τ k2 t, Α k1 CA k ,Γ 1 (19) k2 k2 Then Eq. (18) becomes Θ Α1Θ ΓΘ Θ 1 Θ 2 (20) t At steady state we have G Θ; Α, Γ Α 1 Θs Γ Θs Θs 1 Θs 2 0 (21) To visualize how the solutions for Θs depend on the parameters Α and Γ, we re-organize G(Θ; Α, Γ)=0 as follows 1 Θs Γ Θs Θs 1 Θ 2 Α Then by plotting the LHS and the RHS versus Θ on the same plot, the points of intersection are the desired steady sta...
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