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Gas diffusion with chemical reaction in porous solids
Author(s) -
Scott D. S.
Publication year - 1962
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450400411
Subject(s) - diffusion , isothermal process , effective diffusion coefficient , thermodynamics , anomalous diffusion , diffusion layer , chemistry , molecular diffusion , grain boundary diffusion coefficient , materials science , physics , innovation diffusion , medicine , knowledge management , electrode , computer science , magnetic resonance imaging , radiology , metric (unit) , operations management , economics
The nature of the diffusive mechanisms in the pore spaces of catalytic solids is briefly reviewed, and the effective diffusion coefficient is discussed. Binary diffusion equations, including a general expression covering all modes of diffusion, are given. Using the general diffusion equation together with first order reaction, a solution for isothermal conditions and slab type geometry is found, applicable to all modes of diffusion, with or without volume change on reaction. The extension of this solution to other pellet shapes and to second order reactions is discussed. The measurement of diffusion rates in porous solids is considered, and the interpretation of such measurements in terms of effective diffusion coefficients is clarified by means of the general diffusion equation. Methods of determining effective diffusion coefficients other than by direct diffusion measurements are discussed, and, in particular, a forced flow technique is reviewed.