Sorption properties of cation exchanged y zeolites

The sorption of nitrogen, benzene and water on a series of La3+, Ca2+ and NH4+ exchanged type Y zeolites are reported. The surface area and void volumes of modified zeolites are calculated from nitrogen sorption data. The type of the cation as well as the degree of Na+ replacement influenced the sorption characteristics. The decrease in nitrogen uptake in LaY zeolites is attributed to lattice distortion on account of larger hydroxy lanthanum cations [La(OH)2+] occupying screened sites in sodalite cage. Due to tighter bonding protons to the framework oxygen, the sorption capacity of HY zeolite for nitrogen is increased, however, in Ca(85)Y it was reduced due to hydroxy cations in the supercage. The sorption capacity for water increased upto 35% La3+ exchange and decreased with deeper exchange. On the contrary, benzene uptake decreased monotonically with the degree of Na+ replacement by La3+ and was lower in cation exchanged zeolites as compared to the NaY. (author)