Secondary metals have different properties. For example, rhe- nium and iridium are active metals for hydrogenolysis reactions, thus Pt–Re/Al2O3 and Pt–Ir/Al2O3 catalysts are usually presulfided in situ during commercial practice to passivate their initial hyper- activity for exothermic demethylation reactions. In contrast, Pt– Ge/Al2O3 and Pt–Sn/Al2O3 catalysts are not presulfided because germanium and tin are inactive metals for naphtha reforming reac- tions. Therefore, Pt–Ge and Pt–Sn catalysts are good candidates for use in novel low pressure naphtha reforming processes employing continuous catalyst regeneration because these catalysts do not re- quire complex activation procedures [40].
The addition of alternative component to the metal function re- sults in different effects such as:
modifying the electronic state of the metal,
changing the geometry of adjacent Pt atom clusters,
changing the final Pt particle size.
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