The use of a circulation-type reactor set-up for the modification of supported platinum catalysts with tin tetraethyl is described. All of the elementary steps of the modification were done in the same reactor. The new approach allowed to increase the amount of catalyst modified from a few grams to 250 g. The catalytic tests of Sn-Pt/Al2O3 catalysts prepared both in n-hexane reaction and naphtha reforming unambiguously demonstrated the applicability of the new approach.