On the role of additives to platinum catalysts for reforming reactions

The effect of various additives to platinum catalysts has been compared under standard reaction conditions at which aromatization of n -hexane occurs. With the same catalysts, (Pt/SiO 2 , Pt K + /SiO 2 ,Pt Mg 2+ /SiO 2 , Pt KL zeolite, Pt Mg 2+ KL-zeolite, Pt/Al 2 O 3 , Pt K + /Al 2 O 3 ) dehydrogenation of cyclohexane to benzene has also been monitored. It has been established that the presence of K + - or Mg 2+ -additives can enhance the aromatization activity, but the condition is that the additive-free catalyst is monofunctional. A discussion of the data presented together with the relevant pieces of information from the literature leads to a conclusion that the effect of K + or Mg 2+ is of electrostatic nature, influencing the ring-closure.