Mass Transfer with Chemical Reactions in Porous Catalysts: A Discussion on the Criteria for the Internal and External Diffusion Limitations

Abstract:

In this study, criteria for internal mass transfer given in the literature were investigated by considering tortuosity (τ) in the porous catalysts. Uncertainties in τ, which may have values between 2 to 7, have a big impact on the effective diffusivity (D_eff) which also affects the Thiele Modulus (Φ). Since effectiveness factor (η) is function of Φ, then the criteria given for limitations are questionable. The value of D_eff, and in turn the value of Φ calculated for the τ=2 to 7. At low Φ the effects are very small, but when the Φ increases the effect becomes more pronounced. As a result, when using internal mass transfer limitations, one has to be very careful not to get trapped by the disguised kinetics, results of which may end up with disaster.

• Periodical: Defect and Diffusion Forum (Volumes 334-335)
• Pages: 279-283
• DOI: https://doi.org/10.4028/www.scientific.net/DDF.334-335.279
• Online since: February 2013
• Authors: S. Gültekin

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