Two commercial Cu catalysts, Cu/Zn and Cu/Cr, were pretreated to produce calcined, partially reduced and completely reduced catalysts, and tested for methanol decomposition. The pretreatments resulted in different initial Cu states based on extended X-ray absorption fine structure (EXAFS) morphological analysis, but only metallic Cu was found after methanol decomposition tests. Pretreatment was found to affect catalytic activity only during the initial transient period, when atom balance analysis showed the presence of excess oxygen in the effluent. The excess oxygen is attributed to the participation of lattice oxygen in the reaction leading to CO2 and H2O formation. When there was no excess oxygen present in the effluent, a steady state was achieved and a similar catalytic performance was obtained regardless of catalyst pretreatment conditions. (c) 2009 Elsevier B.V. All rights reserved.