Nitrogen adsorption properties of cubic and orthorhombic Li-exchanged low silica X

Abstract The adsorption capacity of nitrogen on Li-exchanged low silica X zeolite (LiLSX) was measured at various temperatures. The isosteres for 100% Li-exchanged LSX (Li100%LSX), where the logarithm of pressure is plotted against the inverse of absolute temperature, are divided into two straight lines. The discontinuous temperature range of the isosteres corresponded to that of the cubic–orthorhombic symmetry change for Li100%LSX. The unexpected increase in nitrogen adsorption on Li100%LSX at low temperature is due to the increase in the number of main adsorption sites (Li ions at site III (′) ) caused by the cubic–orthorhombic symmetry change induced by temperature. The isosteric heat of adsorption on the orthorhombic phase agrees with that on the cubic phase.