The doping effect of copper on the catalytic growth of carbon fibers from methane over a Ni/Al2O3 catalyst prepared from Feitknecht compound precursor

The doping effect of copper on the structure of a nickel-alumina catalyst, which was prepared from Feitknecht compound precursor with a hydrotalcite-like layered structure and on the catalytic growth of carbon fibers from methane have been investigated. An in-situ thermal balance was employed in the study of the carbon fiber growth process. It has been found that the addition of a small amount of copper into the nickel-alumina catalyst promotes the activity and that more than 36 wt% of CFs was produced when 2 mol% copper was added into a catalyst with a Ni/Al molar ratio of 3 : 1. Too much copper was found to decrease the activity of the catalyst toward solid carbon formation. The amount of carbon fibers produced on the catalyst, before its deactivation, decreases with the increase of the reaction temperature. When hydrogen instead of nitrogen was used as the dilution gas, the activity of the catalyst decreased and the reaction temperature had to be increased. The addition of copper lowers the effect of hydrogen. TEM micrographs showed that small particles are easier to activate than larger ones in the reaction. The possible effect of alloying between copper and nickel is discussed. (C) 1998 Academic Press.