Carbon formation and gasification on metals. Bulk diffusion mechanism: A reassessment

The mechanism for carbon formation from hydrocarbons on transition metals, proposed 40 years ago, is reassessed, evaluating the role of surface catalysis and bulk diffusion. Under steady-state conditions, solid state reactions, which are essential to start-up the process, will be confined to carbon growth. The dynamics of carbon mass transfer is discussed, together with the thermodynamic equilibria prevailing at the metal–gas and metal–graphite interfaces. The reverse process of carbon gasification is also addressed.