No abstract

No abstract

A rigorous kinetic model was derived for the formation on a nickel catalyst of filamentous carbon by the Boudouard reaction and for the gasification of filamentous carbon by carbon dioxide, by hydrogen, and by steam. The experimental study was performed in an electrobalance unit. Carbon formation and gasification experiments were performed at temperatures ranging from 773 to 848 K. The partial pressures of the various components were chosen in the ranges encountered in industrial steam reformers. The influence of the carbon formation reaction on the subsequent gasification process was also investigated. The mode of experimentation ensured that the rates of growth or gasification of the carbon filaments were always based on the same number of carbon filaments. The same reaction mechanism was derived from the study both of methane cracking and the Boudouard reaction and of the reverse reactions, gasification by hydrogen and carbon dioxide. Using the results of the parameter estimation, energy diagrams were constructed for the Boudouard reaction and for gasification by carbon dioxide and by hydrogen.

No abstract

A rigorous kinetic model for the formation and gasification of filamentous carbon on a nickel steam-reforming catalyst is derived. Carbon formation and gasification experiments were performed in an electrobalance unit at temperatures ranging from 773 to 823 K and partial pressures of the various components in the range encountered in industrial steam reformers. The rates of growth or gasification of the carbon filaments were always based on the same number of carbon filaments. The gasification by carbon dioxide and by steam proceed through adsorbed oxygen, generated by the dissociation of steam and carbon dioxide. Relationships between the various carbon formation and gasification reactions are accounted for, to ensure that the kinetic model is thermodynamically sound. The lower net rate of carbon formation on an alkalized catalyst can be explained by a lower lumped forward rate coefficient for the methane cracking and an increased surface concentration of oxygen.