In the model studied in [T.G. Mattos, F.D.A. Aarao Reis, J. Catal. 263 (2009) 67], the constant external reactant flux drives the system far from equilibrium, thus detailed balance conditions are expected to fail and chemical potentials are not useful to determine equilibrium conditions. This is similar to other far from equilibrium models, some of them also applied to catalysis. There is a nonzero net flux of reactants across the catalyst-sup port interface, but mass conservation is satisfied there, although the original solution of the model was based on a global mass conservation. Thus, the claim that the results of [T.G. Mattos, F.D.A. Aarao Reis, J. Catal. 263 (2009) 67] are wrong is unjustified, and the far from equilibrium conditions may be observed experimentally. (C) 2009 Elsevier Inc. All rights reserved.