Effect of metallic impurities on the gasification of graphite in water vapor and hydrogen

• Published in: Carbon (New York) 1974-01, Vol.12 (4), p.453-464
• Main Author: McKee, Douglas W.
• Format: Article
• Language: English
• ISSN: 0008-6223; 1873-3891
• DOI: 10.1016/0008-6223(74)90011-6

The catalytic effects of metallic impurities on the reactivity of graphite towards water vapor and hydrogen in the temperature range 25° to 1100°C have been investigated as a function of the oxidation state of the impurity. Iron, cobalt and nickel are active catalysts for the former reaction between 600° and 1000°C when the metal is kept in the reduced state by means of added hydrogen. Motion of the metallic particles on the basal plane surface of the graphite during the reaction leads to the formation of channels which with the smallest catalyst particles are oriented mostly in the 〈112̄0〉 directions. Vanadium and molybdenum are weak catalysts under these conditions, whereas copper, zinc, cadmium, silver, chromium, manganese and lead are inactive. When hydrogen is absent so that the metal remains in the oxidized state, the catalytic activity of all these impurities is low or negligible. The reaction of graphite with dry hydrogen occurs less readily but is again strongly catalyzed by metallic iron, cobalt and nickel. Manganese, chromium, molybdenum and vanadium show a slight catalytic effect in the hydrogenation reaction at temperatures around 1000°C, whereas copper, zinc, cadmium, silver and lead are inactive.