Review of Kinetics for the Gas-Carbon Reactions

The value of 0 is a function of the magnitude of the individual rate constants for the formation of the surface complex and its conversion to a desorbable product and the pressure of the reacting gas. If the product of the rate constant for the formation of the surface-oxygen complex and the pressure of the reacting gas is large compared with the rate constant for 

Reaction temperature can also affect the order of a reaction. It is generally agreed that the rate constant for the conversion (or desorption) of the surface-oxygen complex has a higher activation energy than the rate constant for the formation of the complex. Therefore, a reaction which is zero order at low temperatures and a given pressure can become first order at the same pressure and a sufficiently high temperature. 

Unfortunately, insofar as a clear understanding of the true orders of gas-carbon reactions is concerned, the problem is made more difficult when the gasification rate is affected by product retardation and by the rate of mass transport of reactants to the surface of the solid. Product retardation can result in the obtaining of orders of reaction which are too low, while mass transport retardation can either raise or lower the apparent order depending upon the true order of reaction and the nature of the mass transport control. In Secs. V and VI, these complicating factors will be discussed in more detail. In the remainder of this Section, pertinent references on the orders of gas-carbon reactions will be given. 

Workers reporting orders of reaction for the carbon-carbon dioxide reaction include Graham (41), Strickland-Constable (48), Vulis and Vitman (60), Thring and Price (61), Armington (62), Vastola (63), Duval (64), and Karzhavina (65). As expected, they find reaction orders which vary from zero to one depending upon temperature, pressure, type of carbon reacted, purity of carbon, and geometric dimensions of the sample. 

Comparison of True Activation Energies in Reactions of Carbon with Oxygen-Containing Gases and the Dissociation Energy of an 0 Atom from the Reactant after Rossberg ) 

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