A Diffusion Cell Method for Studying Heterogeneous Kinetics in the Chemical Reaction/Diffusion Controlled Region. Kinetics of C + CO₂ → 2CO at 1200-1600°C

A technique utilizing a diffusion cell similar to that used by Stefan and by Lee and Wilke (1954) in vapor diffusivity measurements is developed to study the kinetics of heterogeneous chemical reactions at conditions where both diffusion and chemical reaction are important. Such conditions normally exist at high temperatures for gas-solid reactions. Theoretical treatments of the diffusion cell system, including a critical examination of the estimation methods of the high-temperature diffusion coefficients, are given. The technique is applied to a study of the reaction C + CO₂ → 2CO using a nuclear graphite at temperatures between 1200 and 1600 °C and total pressure of 1 atm. A chemical rate maximum which was observed by other methods (Rosner, 1972) over the temperature range is also observed. Advantages and possible applications of this technique are discussed.