COMPARISON BETWEEN BETA-ZEOLITES AND L-ZEOLITES SUPPORTED PLATINUM FOR N-HEXANE AROMATIZATION

The performance of zeolite KP supported platinum as a bifunctional cat alyst for the reforming of n-hexane has been examined using pulse and continuous flow microreaction methods. A comparison under the same con ditions with zeolite KL supported platinum was carried out. It is foun d that due to the stronger acidity of zeolite beta, Pt/K beta exhibits more skeletal isomerization and cracking than does Pt/KL zeolite, whi le the latter shows superior aromatization activity. Ion exchange of b eta zeolite with alkali cations as Cs+ can reduce the acidity and incr ease benzene selectivity. Ba2+ exchange also can lead to better disper sion of platinum and so can improve the aromatization activity. In con trast to the high sensitivity to sulphur poisoning of Pt/KL, Pt/K beta is relatively stable to sulphur poisoning and regains to some extent its initial activity. All these observations are explained in terms of support acidity, the electron state and the dispersion of platinum.