Liquid product formation during the aqueous catalytic reforming of ethylene glycol (EG) was studied up to 450 degrees C and 250 bar pressure. Methanol, ethanol, and acetic acid were the main liquid by-products during EG reforming in the presence of alumina-supported Pt and Pt-Ni catalysts. The effect of these by-products on selectivity and catalyst stability was further investigated by studying reforming of these components. Reforming of these products was shown to be responsible for the formation of alkanes. The high dehydrogenation activity of Pt-Ni catalysts leads to high H-2 yields during EG reforming by (i) suppressing the formation of methane during methanol reforming (a major by-product of EG reforming) and (ii) suppressing the formation of acetic acid. In addition, the decrease in acetic acid formation showed a positive effect on catalyst lifetime. Acetic acid was found to be responsible for hydroxylation of the Al2O3 support, leading to migration and coverage of the metal particles by Al(OH)(x) and resulting in deactivation of the Pt-based catalysts. (C) 2012 Elsevier Inc. All rights reserved.