Mean penetration depth of metals in hydrodemetallation catalysts

A descriptor has been proposed, the mean penetration depth, to characterize the deposit profiles of metals in hydrodemetallation catalysts. This mean penetration depth can be obtained from concentration maps or profiles of elements along catalyst cross sections using local characterization techniques. This descriptor is well suited even for very irregular shapes such as multilobed extrudates often encountered in industrial catalysts. Using a very simple model of metal deposit, the mean penetration depth can be analytically related to the Thiele modulus of the deposit reaction and consequently to the catalyst efficiency for trivial shapes (infinite slab, infinite cylinder and sphere). The mean distance to the surface of the catalyst pellet is found to be the convenient quantity to renormalize Thiele modulus and mean penetration depth to obtain an universal curve independent of the catalyst pellet shape. An example of application is given on a used hydrodemetallation catalyst of tetralobed shape. (C) 2016 Elsevier Ltd. All rights reserved.