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Pore diffusion in silver catalysts
Author(s) -
Masamune Shinobu,
Smith J. M.
Publication year - 1962
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690080218
Subject(s) - macropore , microporous material , porosity , chemistry , diffusion , pellets , mass transfer , analytical chemistry (journal) , volume (thermodynamics) , void (composites) , volume fraction , thermodynamics , mineralogy , materials science , catalysis , chromatography , composite material , organic chemistry , mesoporous material , physics
Diffusion rates were measured at atmospheric pressure and room temperature for helium and nitrogen in pelleted silver catalysts. Pellets were prepared from three silver salts giving different micropore characteristics. The data showed that the diffusion was of the bulk type and that the micropores had no effect, indicating that mass transfer was predominantly in the macropore region. For each kind of material data were obtained for five pellet densities corresponding to macropore volume fractions from 0 up to 0.7. Effective diffusivities and labyrinth factors ψ were evaluated and found to increase with macropore porosity. The linear relationship between ψ and void fraction proposed by Buckingham for diffusion through soils fitted the data at high void fractions. A generalized form of the Maxwell equation containing three constants was derived. A single‐constant form of this expression agreed reasonably well with the measured results over the entire range of macropore volume fraction.