The hydrogen-deuterium exchange reactions of methane in a deuterium stream were studied by a pulse experiment over a reduced nickel (Ni1373 prepared from nickel oxide calcined at 1373 K. and Ni773 prepared from nickel oxide calcined at 773 K) and K2O promoted reduced nickel (K-Ni1373 and K-Ni773). Ni1373 had a higher exchange activity than Ni773. The effects of the addition of K2O resulted in the decrease in the exchange activity due to the inhibition of step defect sites and/or the promotion of the change of nickel crystal structure. High activity of Ni1373 could be due to that the Ni1373 had the surface of a higher Ni(100)/Ni(111) ratio. (c) 2010 Elsevier B.V. All rights reserved.