Diffusion resistances in alumina and silica catalysts

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Abstract
Reaction‐rate measurements were made for the ortho‐para hydrogen conversion at −196°C. at 1 atm. pressure with nickel oxide catalysts using alumina and silica gel as carriers. Data were obtained for fine particles for which pore‐diffusion resistances were negligible, for large particles of silica catalysts containing only micropores, and for alumina pellets containing both micro‐ and macropores. From these data experimental effectiveness factors were evaluated.Theoretical effectiveness factors predicted by using a previous theory (7) agreed well with the experimental results. The application of the theory requires pore‐geometry data. The measurement of these data and their use in predicting diffusion resistances are illustrated by experimental data and calculations for the several catalysts. It is shown that a satisfactory method of predicting the significance of diffusion within porous catalysts requires information on the pore volume and pore sizes.