Modification of KL zeolite by chemical vapour deposition (CVD) of Si(OEt)4 and (CH3)3SiOSi(CH3)3 was used to study the influence of zeoltie support on the aromatization of n-hexane over Pt/KL catalyst. The pore size and pore volume of zeolite were decreased by CVD. The acidic hydroxyl groups remaining on the surface of KL zeolite were removed and thus the selectivity of non-acidic catalyzed aromatization reaction was improved. Whereas the activity of aromatiztion reaction was decreased due to the destruction of some of active sites in KL zeolite for 1,6-cyclization. Becuase of the coverage of the framework of zeolite by CVD of SiO2, Pt particles became more electron-excess.Therefore, the silica-coated catalysts were easier to be poisoned by sulphur.
The influence of second metal component (Fc) on Pt/KL zeolie catalyst was investi-gated. The catalytic properties of Pt-Fe/KL zeolite varied as the amount of Fe. When the amount of Fe was 0.3 % (mass fraction), the catalyst was found to show both excellent n-hexane aromati-zation reactivity and higher ability for sulphur-resistance. The dispersion of Pt particles was also found to be better in this bimetallic catalyst, whereas the electron state of Pt particles as indicated by CO-FTIR was nlodified to be more electron-deficient than that of Pt/KL zeolite, which made the bimetallic Pt-Fe/KL more tolerant to sulphur poisoning.
