KINETICS OF THE STEAM-CARBON REACTION (SECTION I). A KINETIC THEORY FOR THE OXIDATION OF GRAPHITE (SECTION II)

Abstract : A description is given of a more satisfactory type apparatus for the study of high temperature (1500 C), low pressure (1 to 100 microns) heterogeneous processes in which one or more products is a gas. The water-gas reaction has been studied in the 900 C to 1300 C temperature range. This is the first kinetic study of this reaction at high temperatures in which the oxidizing gases have been carefully preheated to the reaction temperature. A zero-order reaction with an activation energy of 60.3 kcal/mole is found in the 900 C to 1100 C range, changing to a first order process by 1300 C with a considerably lower value for the activation energy. Several possible mechanisms are discussed, including a surface rearrangement of adsorption sites and pre-dissociation of water vapor. A considerable amount of data on the carbon-oxygen reaction has been collected from the literature, evaluated, and expressed in such a manner that comparison can be made. A theory is proposed which applies to the complete temperature range in which data has been obtained, 350 C to 2000 C. In particular, the unusual maximum in the Arrhenius plot is explained on a theoretical basis although the model proposed is not readily adapted to the known structural features of graphite. (Author)