Macroscopic diffusional anisotropy in porous media

An image analysis method, based on a lattice-based model projection technique, has been used to show that the structure of a porous catalyst support pellet may possess a fractal character over macroscopic lengthscales (0.01–1 mm). It has also been shown that a geometric method of obtaining tortuosity for lattice-based model structural representations (such as those used in the image analysis method) gives rise to a good prediction of the degree of anisotropy to be expected between the diffusion in the axial and radial planes of the cylindrical pellet.