Behaviour of Smooth Catalyst at High Reaction Rates

SERGIO DARÍO KEEGAN; NÉSTOR JAVIER MARIANI; OSVALDO MIGUEL MARTÍNEZ; GUILLERMO FERNANDO BARRETO

CHEMICAL ENGINEERING JOURNAL

Elsevier Science Ltd.

Lugar: Oxford, Inglaterra; Año: 2005 vol. 110 p. 41 - 56

1385-8947

In evaluating effective reaction rates in catalysts subject to heat and mass transport limitations, the size of the catalytic body is best defined by the so-called characteristic length l, the ratio between catalyst volume and its external surface area, l=Vp/Sp. This result follows from the limiting behaviour at very high reaction rates, when the effective reaction rates are proportional to 1/l (e.g. Aris [1]) or, in dimensionless form, to the inverse of the Thiele modulus F. It is further known from simple geometrical shapes that a series solution can be written up in terms of powers of (1/F) and that the second order term [in (1/F)2] depends on the shape of the catalytic body. It is the aim of this paper to develop expressions of such second order term for 2D or 3D catalytic bodies showing arbitrary smooth external surfaces. In a similar way as the first order term allows to define the proper size of a catalyst, the second order term is expected to provide a significant description of catalyst shape. This and other potential applications are discussed in this contribution.