The operation of a modem refinery nowadays is becoming more and more complex. World-wide public concerns about the earth's environment and health considerations led into several new legislative actions all around the world. With the requirement to meet clean fuels challenge the processing configuration has to be adapted accordingly.Apart from this, modem isomerization technology based on state-of-the-art catalytic solutions provides a number of other substantial advantages to the refiner. Traditionally, users of paraffin isomerization technology had the choice between robust zeolite based catalysts and chlorided alumina based systems. While zeolite catalysts are characterized by their outstanding tolerance of feedstock poisons such as sulphur and water-this is particularly true for SUD-CHEMIE's HYSOPAR(R) catalyst that operates commercially at sulphur levels exceeding 100 ppm-the chlorinated catalysts suffer from extreme sensitivity to all kinds of feed contaminants. This intrinsic property often outweighs the superior activity of the Cl/Pt/Al2O3 system which is based on the more favourable equilibrium at lower operating temperatures. This scenario creates a desire for a catalyst that combines high activity with acceptable poison resistance. (C) 2003 Published by Elsevier Science B.V.