A series of dealuminated Y-type-zeolites was prepared by treating zeolites with SiCl₄, steam, and EDTA at elevated temperatures. Y-type zeolites can be dealuminated by reaction with SiCl₄ without collapse of the crystal structure as compared with the treatment of steam and EDTA. Regardless of preparation method, the infrared absorp-tion bands in frequency of the stretching O-(Si, Al)-O vibrations shifted in a linear manner as number almost linearly with an increasing Si/Al ratio of the zeolite, but beyond a ratio close to 5, the frequency remained virtually unchanged. Upon dealumination the ability of the zeolite to absorb water decreased due to the decrease of net electrostatic charge.