HZSM-5 Zeolite Catalysts Modified by Zn, Ga and Cr

The aromatization of C_4 alkane/alkene hydrocarbons mixture, except i-butene,over Zn, Ga and Cr modified HZSM-5 zeolite catalysts was studied. The macro-structure,the crystal structure and the surface acidic properties of HZSM-5 catalyst and its modified form were investigated by BET method, X-ray diffraction, TPD of NH_3, and LR spectroscopy. Based on the experimental results, it was suggested that the activity of aromatization of modified HZSM-5 zeolites catalysts may be correlative to the chang of catalyst surface acidic properties. With the decrease of total acidity, the conversion of C_4 hydrocar-bons decreases, with the decrease of stronger Bronsted acid sites, the cracking reactions decrease. The Zn, Zn-Ga and Zn-Cr modified HZSM-5 catalysts exhibiting high aromatization activity may be correlative to L_(1.15) cm~(-1) absorption peak and the increase of stronger Lewis acid sites.