Prediction of the Hydrodesulfurization (Hds) Performances of Catalysts Under Operating Conditions Relevant to Industrial Practice

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Abstract
Catalysts for the catalytic HDS process are still being improved, for instance by optimization of the particle geometry. They are generally tested in small‐scale trickle‐flow equipment, with heavy gas oil (HGO) serving as the feedstock. An analysis of this test procedure has shown that the most important factors which determine the HGO‐HDS performance are the intrinsic HGO‐HDS activity and the diffusion of the sulfur compounds through the catalyst pores. A study of the applicability of the dynamic oxygen chemisorption (DOC) technique has shown that can be estimated from the DOC capacity (DOCC). However, there are some limitations: the ‐DOCC correlations are restricted to narrowly defined groups of catalysts and must not exceed a critical level M, which is group‐dependent. The effect of pore diffusion can be described very precisely by a simple but physically substantiated multi‐component HDS computer model, which makes use of a statistical function for the distribution of the rate constants k over the individual sulfur compounds and assumes that they all have the same effective diffusion coefficient . It is illustrated by way of an example that the model, in combination with DOC, is able, on the basis of the measured HGO‐HDS performance of one catalyst geometry, to predict very accurately the performances of other geometries.