The catalytic activity for ethanol steam reforming of Na-Y zeolite supporting transition metals was compared with that of zeolite Y encapsulating transition metal cations. It was found that zeolite Y supporting Co or Ni, prepared by the incipient wetness impregnation process, produced mainly hydrogen at 300 degrees C. Acetaldehyde products indicated that hydrogen production was due to the dehydrogenation of ethanol molecules. On the other hand, for zeolite Y encapsulating cations such as Co(2+) or Ni(2+), prepared by an ion exchange process, the reforming reaction resulted in mainly ethylene production, which was considered to be due to the dehydration of ethanol molecules. The results indicate that the presence of cations in zeolite Y has a significant influence on the ethanol reforming reaction. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.