RECOVERING OF THE CATALYTIC FUNCTIONS OF NAPHTHA REFORMING CATALYSTS BY PARTIAL COKE BURNING

The selective regeneration of the catalytic functions during coke burning on Pt/Al2O3 and Pt-Re/Al2O3 naphtha reforming catalysts was studied. Sulphided and unsulphided catalysts were coked in the laboratory and tested for benzene hydrogenation (metallic function) and n-pentane isomerisation (acid function). These test reactions and the temperature-programmed oxidation of the coke showed that only the metallic function is recovered by coke burning at low temperature and that at high temperature both functions are recovered. All this according on how coke was eliminated from the functions. Upon reduction with hydrogen at 773 K of catalysts whose coke was only eliminated from the metallic function, migration of part of the remaining coke to the metal occurred and resulted in metal deactivation. At the same time, the sulphur present on the support as sulphate ion is reduced to hydrogen sulphide at this temperature, thus deactivating the metallic function.