Improvement of activity and stability of Ni-Mg-Al catalysts by Cu addition during hydrogen production by catalytic decomposition of methane
Résumé
Catalytic decomposition of methane is a potential alternative route for the production of hydrogen and carbon nanofilaments from natural gas and other feedstocks. In the present paper, we report the results of characterization and catalytic behaviour of Ni-Cu-Mg-Al catalysts. The effect of the Cu addition in the catalyst composition on activity and stability has been investigated. The influence of operating temperature and feed composition on carbon content and carbon formation rate has also been studied. It has been shown that H2 inhibits both the carbon filament formation and the encapsulation of metallic particles by coke. A higher reaction temperature increases both the deactivation rate and the growth rate of filaments. An increase in the methane concentration generates a rise of the rate of carbon filament formation. The size of metal particles and the carbon filaments as well as the nanofilament texture depends on the copper content of the catalyst. When the Cu content is 7.6 wt.%, the carbon nanofilaments are nanofibers with a platelet texture, and the particles and CNFs sizes are widely distributed (50-400 nm). © 2006 Elsevier B.V. All rights reserved.