Influence of additives on the Pt metal activity of naphtha reforming catalysts

Abstract

Alumina supported bimetallic Pt-Re, Pt-Sn and Pt-Ge naphtha reforming catalysts were studied. The Pt concentration was kept constant at 0.3% (weight basis) while the concentration of the second metal was varied in order to assess its influence. The experimental results showed that the addition of a second metal (Re, Sn, Ge) to the Pt catalyst produces a modification of the metal and acid functions. Sn and Ge produce similar modifications of the metal function: a marked decrease of the dehydrogenation and hydrogenolytic capacity of Pt. The addition of Re modifies the dehydrogenation capacity to a lower extent than the addition of Sn or Ge. The hydrogenolytic capacity is increased upon Re addition. The changes on the acid function are different depending on which metal is added. Re and Ge modify the acid strength distribution; they favor the formation of sites of lower acid strength but they keep the total concentration of acid sites almost constant. Conversely Sn addition not only produces a change in the acid strength distribution but also a decrease of the total acidity of the catalyst.