Binary gaseous diffusion coefficients in a nuclear graphite (H-451) along with the pore volume distribution were measured. The diffusion models of Johnson and Stewart and of Wakao and Smith were applied to this material. Diffusion coefficients predicted by the latter model were higher than the measured values at a ratio ranging from 1.2 to 1.6, whereas this ratio was about 4 to 5 with the former model. The models were also applied to other graphites whose diffusion and pore data were available in the literature. The predicted diffusion coefficients were all higher than the experimental data and the model by Wakao and Smith was consistently better. These results were compared with the literature data on commercial catalysts and inferences were drawn for the differences in the characteristics of diffusion in these two types of materials.

Gaseous Diffusion in Carbon with Particular Reference to Graphite. Yang, R.T., Liu, R.T.: Industrial and Engineering Chemistry Process Design and Development, 1979, 18[2], 245-9