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Optimum effectiveness factors for porous catalysts
Author(s) -
Cunningham R. E.,
Smith J. M.
Publication year - 1963
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.690090328
Subject(s) - pellets , catalysis , pellet , porosity , reaction rate , diffusion , materials science , hydrogen , chemical engineering , volume (thermodynamics) , chemistry , thermodynamics , composite material , organic chemistry , physics , engineering
In the manufacture of catalyst pellets from particles of powder, for example alumina, one of the parameters is pellet density. The opposing effects of density on surface available for reaction and on pore diffusion result in a specific pellet density for maximum reaction rate per unit volume of reactor. The method for predicting the optimum density and rate is presented for a first‐order reaction. The data required are pore volumes and pore‐size distributions as a function of density, as well as kinetic measurements. Such data are available for the ortho‐para hydrogen reaction using a nickel oxide‐on‐alumina catalyst. Using this system as an illustration, it can be seen that the optimum effectiveness factors are less than unity and range from about 0.68 for 1/8‐in. diam. spherical catalyst pellets to 0.29 for 1‐in. pellets. Corresponding optimum densities are from about 1.3 to 0.6 g./cc The results demonstrate the possibility of a tailor‐made pelleted catalyst for optimum reaction rate.