Authors: REYYAN KOÇ, ERDOĞAN ALPER, ERIC CROISET, ALI ELKAMEL
Abstract: Methane cracking has the potential to produce high purity, carbon monoxide-free hydrogen suitable for application in PEM fuel cells. The 2 products of the reaction are molecular hydrogen and solid carbon. The carbon appears in the form of carbon filaments whose growth is hindered by carbon encapsulation leading to total deactivation of the catalyst. Several attempts have been made to regenerate the catalyst, mainly by gasifying the carbon filament in air or steam. Our work on 5-wt% Ni/\gamma-Al_2O_3 indicated that after complete gasification of the carbon the catalyst lost nearly all its activity toward methane cracking. However, if the gasification proceeds to only a certain extent, it is possible to recover significant activity of the catalyst. This technique, also known as partial regeneration, is a promising strategy to overcome the challenge of catalyst deactivation in catalytic decomposition of methane. Optimization of the partial regeneration method is presented here, in particular the extent to which the gasification should take place. Activity of the catalyst and the extent of gasification have been monitored through thermogravimetric analysis. Regeneration of catalyst is still a much-questioned field to maintain not only a continuous and also an economical process. That is why this experimental study focused on regeneration of nickel supported on alumina. As an overview of this study: The effects of percentage of nickel, application of reduction, reaction temperature, and the amount of gasified carbon on weight gain are stated as the rate of carbon formation per gram of nickel present in catalyst.
Keywords: Methane cracking, hydrogen, filamentous carbon, partial regeneration, Ni/\gamma-Al_2O_3 catalyst
Full Text: PDF