A series of experiments was conducted to study the deactivation and regeneration of activated carbon catalyst used for methane thermocatalytic decomposition to produce hydrogen. The catalyst becomes deactivated due to carbon deposition and six decomposition cycles of methane at temperatures of 850 and 950 degrees C, and five cycles of regeneration by using CO(2) at temperatures of 900, 950 and 1000 degrees C were carried out to evaluate the stability of the catalyst. The experiment was conducted by using a thermobalance by monitoring the mass gain during decomposition or the mass lost during the regeneration with time. The initial activity and the ultimate mass gain of the catalyst decreased after each regeneration cycle at both reaction temperatures of 850 and 950 degrees C, but the amount is smaller under the more severe regenerating conditions. For the reaction at 950 degrees C, comparison between the first and sixth reaction cycles shows that the initial activity decreased by 69, 51 and 42%, while the ultimate mass gain decreased by 62%, 36% and 16% when CO(2) gasification carried out at 900, 950 and 1000 degrees C respectively. Temperature-programmed oxidation profiles for the deactivated catalyst at reaction temperature of 950 degrees C and after several cycles showed two peaks which are attributed to different carbon characteristics, while one peak was obtained when the experiment was carried out at 850 degrees C. In conclusion, conducting methane decomposition at 950 degrees C and regeneration at 1000 degrees C showed the lowest decrease in the mass gain with reaction cycles. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.